Oxidative stress in bladder outlet obstruction: a narrative review

Introduction

Background

Partial bladder outlet obstruction (pBOO) is a urological disease characterized by incomplete obstruction that occurs from the bladder outlet to any part of the external orifice of the urethra. Urodynamic evaluation usually reveals the high-pressure and low-flow urination patterns of affected individuals (1,2). Clinically, pBOO is mainly manifested as lower urinary tract symptoms (LUTS), such as frequent urination and urgency. As the disease progresses, pBOO can lead to structural changes and bladder dysfunction (BD), which seriously affects the quality of life of patients (3). The common causes of pBOO include benign prostatic hyperplasia (BPH), urethral stricture and urethral valve hypertrophy, especially in elderly male BPH patients (4). Epidemiological study has shown that about 21.5% of the global population was affected by pBOO/LUTS in 2008, and this number was expected to reach 18.5 % by 2018, equivalent to about 1.1 billion patients worldwide. The proportion of male patients is relatively high, and the incidence rate has increased significantly in developing regions such as Asia, with a reported increase of 19.7–24.4% (5). The increasing prevalence of pBOO highlights the enormous and increasing clinical and economic burden worldwide.

Rationale and knowledge gap

Accumulating evidence indicates that bladder hypoxia acts as a pivotal pathophysiological factor driving the progression of pBOO. Different from BD caused by other disorders, pBOO-induced bladder impairment is characterized by unique mechanical and hemodynamic changes within the obstructed bladder. Physiologically, the bladder undergoes cyclic filling and emptying with mild fluctuations in wall tension and blood perfusion. In pBOO, however, structural adaptive alterations of the bladder further exacerbate the ischemia-reperfusion (I/R) process (6). Elevated intravesical pressure during micturition compresses submucosal vessels and triggers intermittent ischemia, followed by rapid reperfusion during bladder relaxation. This recurrent I/R injury pattern is distinctly different from the persistent hypoxia observed in most other organs. Each micturition cycle constitutes an independent I/R episode, and the high frequency of such episodes induces cumulative oxidative damage that is far more severe than that caused by static hypoxia (7). This unique cyclic I/R mechanism explains why hypoxia serves as a core pathogenic driver rather than the sole contributor to pBOO-mediated BD. In patients with pBOO, this mechanism is closely associated with secondary pathological changes, including tissue fibrosis, abnormal smooth muscle metabolism, and impaired contractile function (8). Over time, these pathological alterations may further damage neural pathways, alter neural responsiveness, reduce bladder compliance, and ultimately lead to severe voiding dysfunction (9).

The pathogenesis of BOO-induced BD involves multiple interrelated mechanisms, including oxidative stress (OS), bladder tissue fibrosis, transient receptor potential (TRP) channel dysfunction, cyclic nucleotide signaling, adenosine signaling, and other multi-factor pathways (10). Among them, OS is widely considered as the key mechanism of pBOO-related BD. Reactive oxygen species (ROS)-mediated OS can not only induce peroxidation damage of biological macromolecules such as proteins, lipids and DNA, but also promote inflammatory activation. In addition, the upstream signaling molecule ROS in cells can regulate the operation of various pathway networks, which plays a central regulatory role in the response of cells to OS.

Among the various sources and targets of OS, mitochondria represent a unique nexus. They are simultaneously a primary site of ROS generation and a vulnerable target of oxidative damage. In the obstructed bladder, cyclical I/R injury directly compromises mitochondrial electron transport chain function, leading to electron leakage and superoxide production. Damaged mitochondria, in turn, release pro-apoptotic factors and trigger further ROS generation through the ‘ROS-induced ROS release’ (RIRR) mechanism, creating a self-amplifying cycle of oxidative injury that drives the progression from compensated hypertrophy to decompensated bladder failure.

Objective

Recent studies have found that ROS-related signaling network is involved in the whole process of BOO-induced BD disease from initiation to progression. Taking these ROS-related signaling pathways as a therapeutic target is likely to bring some new therapeutic ideas to the disease. The purpose of this review is to sort out the mechanism of OS in pBOO-induced BD, and to clarify the regulatory function of the signal network driven by ROS. In this way, it can provide a theoretical basis for the treatment of BD induced by BOO, and can also find some potential therapeutic targets. We present this article in accordance with the Narrative Review reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0358/rc).

Methods

This study first determined the core search terms, covering five major thematic words: Urinary Bladder Neck Obstruction, Reperfusion Injury, Oxidative Stress, Hypoxia, and Reactive Oxygen Species. On this basis, the search terms were expanded by including synonyms, subject terms, and free words. Taking “Urinary Bladder Neck Obstruction” as an example, the search formula was constructed as: (“Urinary Bladder Neck Obstruction” [Mesh]) OR ((Bladder Neck Obstruction [Title/Abstract]) OR (Bladder Outlet Obstruction [Title/Abstract])). The search terms other than “Urinary Bladder Neck Obstruction” were paired with the “Urinary Bladder Neck Obstruction” group and the intersection was retrieved, for example: ((“Urinary Bladder Neck Obstruction”[Mesh]) OR ((Bladder Neck Obstruction[Title/Abstract]) OR (Bladder Outlet Obstruction[Title/Abstract]))) AND ((“Hypoxia”[Mesh]) OR (((((((Deficiency, Oxygen[Title/Abstract]) OR (Deficiencies, Oxygen[Title/Abstract])) OR (Oxygen Deficiencies[Title/Abstract])) OR (Oxygen Deficiency[Title/Abstract])) OR (Anoxemia[Title/Abstract])) OR (Hypoxemia[Title/Abstract])) OR (Anoxia[Title/Abstract]))). The initial screening yielded relevant literature concerning bladder outlet obstruction (BOO) and oxidative stress (OS).

This study selected PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI) as the literature search databases and set strict inclusion and exclusion criteria. Clear inclusion criteria: original research articles, in English or Chinese, with the research subjects being the oxidative mechanism in pBOO, published between October 1990 and April 2026; exclusion criteria: literature involving other urinary system diseases or systemic diseases, literature related to pBOO but not the mechanism related to OS, case reports, conference abstracts, reviews, and studies focusing only on surgical techniques without mechanism data.

To improve the discussion system of OS-related mechanisms and ensure the completeness of the review content, this study additionally supplemented several specialized literatures solely focused on the regulatory mechanism of OS. The article first conducts a preliminary screening through the abstract, and then reads and summarizes the selected literature. After cross-rechecking and joint discussion by all the authors, the complete list of references for this study was finally determined (Table 1).

OS and BOO-induced BD

BOO pathophysiology

The pathophysiological process of bladder injury induced by pBOO is widely believed to progress through three different stages: hypertrophy, compensation and decompensation (3). In the early stage of hypertrophy, pBOO leads to urinary retention and increased bladder pressure. Cyclic mechanical compression of the bladder wall activates hypertrophy-related signal pathways (11). Related signal pathways cause smooth muscle hyperplasia and hypertrophy to adapt to the increased stress. At the same time, vascular compression leads to focal hypoxia, which stimulates angiogenesis. These changes are accompanied by a significant increase in bladder wall thickness and weight (12). However, due to the abnormal proliferation and hypertrophy of smooth muscle, the uneven distribution of new blood vessels, and the periodic bladder contractions, the bladder tissue is in a state of insufficient oxygen supply for a long time, and repeated I/R injury occurs. This pathological process will lead to the gradual damage of bladder structure and function. Study has shown that its mechanism is closely related to the increase of OS level (13). If the obstruction persists, the bladder will enter the decompensation period, which is characterized by prolonged urination cycle. Compared with physiological conditions, the I/R stage is prolonged and more severe, exceeding the body’s ability to adapt (6), and leading to BD deterioration and morphological deterioration (14).

More and more evidence shows that OS plays a crucial role in BOO-related BD. Reperfusion after chronic ischemia and hypoxia can trigger a large amount of ROS production, and the oxidative damage induced by reperfusion exceeds the oxidative damage caused by hypoxia alone (7). In the continuous BOO state, the production of ROS may exceed the endogenous antioxidant defense, leading to obvious oxidative damage, and prolonged OS promotes the structural remodeling of the bladder and the functional transformation from compensation to decompensation (15). Clinical and experimental studies have shown that BOO-related BD has elevated OS markers, inflammatory infiltration, enhanced apoptosis, extracellular matrix deposition, fibrosis, and decreased systemic antioxidant capacity. The negative correlation between OS level and bladder function capacity further underscores the pathogenic significance of OS in this case (Figure 1).

Figure 1 Pathophysiological mechanism of bladder dysfunction induced by partial bladder outlet obstruction and the central role of oxidative stress. This schematic illustrates the progressive stages of bladder injury following pBOO, emphasizing the critical role of OS. The process begins with [1] initial trigger: pBOO causes urinary retention and increased bladder pressure. This leads to [2] three stages of pathophysiology: initially, the bladder undergoes hypertrophy (stage 1) with smooth muscle hyperplasia and angiogenesis. Persistent obstruction leads to compensation (stage 2), characterized by chronic hypoxia and repeated I/R injury. If obstruction continues, the bladder enters decompensation (stage 3), with prolonged voiding cycles and overwhelmed adaptive capacity. [3] Core mechanism: the repeated I/R injury during the compensation stage is the primary driver of OS. Excessive production of ROS and RNS exceeds the endogenous antioxidant defense, causing DNA damage, protein carbonylation, and lipid peroxidation. This triggers downstream events including apoptosis, autophagy, and inflammatory infiltration. [4] Final outcome: these OS-mediated cellular injuries collectively lead to denervation, smooth muscle cell apoptosis, and tissue fibrosis, culminating in significant bladder dysfunction characterized by decreased bladder functional capacity. ECM, extracellular matrix; I/R, ischemia/reperfusion; OS, oxidative stress; RNS, reactive nitrogen species; ROS, reactive oxygen species.

OS in BOO

OS is a pathological state characterized by a systemic imbalance between oxidation and antioxidation, leading to elevated levels of oxidation and subsequent potential damage to tissues and cells (16). Under OS, a series of characteristic biomarkers can be detected, including DNA base damage, protein oxidation products and lipid peroxidation derivatives (17).

The oxidation reaction mainly involves two key active substances: ROS and reactive nitrogen (RNS). ROS is a heterogeneous group composed of highly active molecules and ions derived from molecular oxygen (O₂), such as superoxide anion (O₂⁻), hydroxyl radical, hydrogen peroxide, hypochlorous acid and singlet oxygen. Among them, hydrogen peroxide (H₂O₂) plays a particularly important role in regulating cell function due to its stability and ability to diffuse freely across the membrane (18). As another powerful oxidant, RNS is also involved in many physiological and pathological regulation processes (19).

Under physiological conditions, ROS and RNS act as signaling molecules that regulate the basic processes of cells, including proliferation, differentiation, apoptosis, migration and metabolism, thereby helping to maintain normal cell function (20). However, under pathological conditions, excessive production of ROS/RNS triggers a series of oxidative damage events, such as DNA damage, protein carbonylation, lipid peroxidation and biofilm rupture, eventually leading to structural and functional damage of target organs (17). In addition, elevated ROS/RNS levels activate a variety of signaling pathways, leading to OS-mediated cell damage, including apoptosis and autophagy, which will be discussed later. In summary, in the context of BD, these processes contribute to pathological changes such as denervation, smooth muscle cell apoptosis, and tissue fibrosis (21). Therefore, the biological results of physiological regulation or pathological damage are determined by ROS/RNS levels.

ROS generation

The increase of ROS levels in tissues is considered to be a hallmark of OS damage in BOO-induced BD. Under physiological conditions, the production of endogenous ROS occurs through a variety of pathways, including nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase (NOX) system, xanthine oxidase pathway, nitric oxide synthase (NOS) pathway, mitochondrial electron transport chain and inflammatory response. When these pathways are over-activated, they jointly promote pathological ROS accumulation, leading to OS-mediated tissue damage. This cascade reaction ultimately drives the structural and functional damage characteristics of BD induced by BOO (Figure 2).

Figure 2 The generation and elimination of reactive oxygen species in bladder outlet obstruction-induced bladder dysfunction. BOO-associated stimuli, including mechanical stretch, AngII, and I/R, initiate ROS overproduction from three interactive cellular sources with distinct functional roles. (I) Enzymatic ROS generation (initiator): bladder NOX2/NOX4 and AngII are rapidly activated to produce the initial superoxide burst. (II) Mitochondria-derived ROS (dominant and sustained source): enzymatic-derived ROS trigger the RIRR mechanism; under chronic obstruction, the dysfunctional mitochondrial ETC (damaged Complexes I and III) becomes the predominant source of ROS, accompanied by mPTP opening, membrane depolarization, cytochrome c release, lipid peroxidation, and impaired ATP synthesis. (III) Inflammation-derived ROS (secondary amplifier): NOX and mitochondria-derived ROS activate NF-κB and the NLRP3 inflammasome, promoting pro-inflammatory gene transcription and neutrophil/macrophage infiltration; recruited inflammatory cells further express NOX2 and iNOS, generating secondary ROS/RNS. Intensive crosstalk among the three sources forms a positive feedback loop that sustains persistent OS independent of the initial obstructive insult. Concurrently, the antioxidant defense system is compromised: enzymatic scavengers (SOD, CAT, GSH-Px) are downregulated, while activation of the KEAP1-NRF2-ARE pathway—in which ROS-modified KEAP1 releases NRF2 to translocate into the nucleus and drive transcription of SOD, CAT and GSH-Px—is insufficient to counteract the overwhelming ROS burden. Collectively, the self-sustaining OS culminates in apoptosis, ATP depletion, detrusor contractile dysfunction, and bladder remodeling, hallmarks of BOO-induced BD. Red arrows indicate activation/damaging events; blunt-ended lines indicate inhibition; green elements denote antioxidant defenses. AngII, angiotensin II; ARE, antioxidant response element; ATP, adenosine triphosphate; BD, bladder dysfunction; BOO, bladder outlet obstruction; CAT, catalase; ETC, electron transport chain; GSH-Px, glutathione peroxidase; I/R, ischemia/reperfusion; iNOS, inducible nitric oxide synthase; KEAP1, Kelch-like ECH-associated protein 1; NF-κB, nuclear factor kappa-B; NOX, nicotinamide adenine dinucleotide phosphate hydrogen oxidase; NRF2, nuclear factor erythroid 2-related factor 2; OS, oxidative stress; RIRR, ROS-induced ROS release; RNS, reactive nitrogen species; ROS, reactive oxygen species; SOD, superoxide dismutase.

Enzymatic ROS generation

At present, it is generally believed that most enzymes produce ROS mainly under the condition of enzymatic coupling or as a catalytic by-product (22). For example, xanthine oxidase produces ROS in the process of catalyzing the conversion of hypoxanthine to uric acid, thereby inducing OS damage (23). Study has shown that long-term exposure to hypoxanthine can increase OS markers in bladder tissue, reduce nicotinamide adenine dinucleotide⁺ (NAD⁺) levels, destroy cell energy metabolism, and promote bladder remodeling and urinary dysfunction (24). The NOX family is a key enzyme system responsible for intracellular ROS production. It is composed of seven isoforms of NOX1–NOX5 and DUOX1/2-NOX enzymes, which have unique special ability to produce ROS and play a central role in enzymatic ROS production (25). Under physiological conditions, NOX-derived ROS is involved in the regulation of bladder smooth muscle (BSM) contraction (26). In addition, NOX2-mediated oxidative damage in the urinary center is related to the pathogenesis of BD (27). However, the distribution pattern of specific NOX subtypes in bladder tissue is still poorly understood. In addition, under the condition of BOO, the mechanism of NOX activation promoting BD through ROS-dependent signaling pathway needs further study.

Mitochondria-derived ROS production

In addition to enzyme-derived ROS, mitochondria are also an important source of intracellular ROS. Mitochondria, as the main place of cell energy metabolism, are prone to OS injury under ischemic and hypoxic conditions. Study has shown that with the aggravation of BOO in male patients, mitochondria in detrusor cells can appear swelling and structural damage, suggesting that there is serious oxidative damage (28). It is currently believed that when the level of ROS in mitochondria exceeds a specific threshold, it can induce the opening of mitochondrial membrane permeability transition pores, causing membrane potential collapse and electron transport chain dysfunction, which in turn triggers a large amount of ROS production, forming a vicious cycle mechanism of ‘ROS-induced ROS release’ (RIRR) (29). ROS released from damaged mitochondria can spread oxidative damage to adjacent mitochondria, resulting in a wave of cellular injury (30). In addition, elevated ROS levels lead to rapid depolarization of the mitochondrial inner membrane and inhibition of oxidative phosphorylation, significantly impairing cell energy production (31,32). In the case of BOO, the accumulation of ROS directly damages the integrity of the mitochondrial membrane, initiates the lipid peroxidation cascade, and further amplifies the production of ROS. This self-sustaining cycle of oxidative damage ultimately impairs adenosine triphosphate (ATP) synthesis and disrupts detrusor contractile function (33).

Inflammation-derived ROS production

Inflammation is an important source of ROS in PBOO. Chronic pBOO is often accompanied by inflammatory cell infiltration, and the release of pro-inflammatory factors further stimulates ROS production. In addition, nuclear factor kappa-B (NF-κB) is a key transcription factor family that plays a central role in inflammation and immune regulation. Study has shown that NF-κB regulates inflammation and immune intensity by regulating intracellular ROS levels, while ROS affects the inflammatory process by activating or inhibiting the NF-κB signaling pathway. Through this interaction, NF-κB and ROS together regulate inflammation and immune homeostasis, thus playing an important role in the pathogenesis of the disease (34). Available evidence suggests that ROS enhances NF-κB activation during I/R injury, which in turn promotes the transcription of inflammation-related genes and may promote neutrophil aggregation (35). Consistently, Sezginer et al. reported a significant increase in NF-κB activity in severe pBOO rat models, suggesting that OS-induced NF-κB signaling contributes to BOO-induced BD (36). However, the exact mechanism of ROS-NF-κB crosstalk in pBOO and its specific role in inflammation regulation need to be further elucidated.

Discussion

In pBOO-induced bladder I/R injury, ROS overproduction originates from three interactive cellular sources with distinct functional roles.

As the initiating factor, bladder NOX2 and NOX4 are rapidly activated by mechanical stretch, angiotensin II and acute I/R stimuli, producing the initial ROS burst and upstream-triggered mitochondrial ROS release. Under chronic obstruction, dysfunctional mitochondrial electron transport chain (ETC) becomes the predominant and sustained source of ROS. Damaged complexes I and III mediate constitutive superoxide generation and RIRR-dependent self-amplifying oxidative cascades. This suggests that mitochondria may be the main source of ROS within the cells during reperfusion

Inflammatory cells act as a secondary amplifier, whereby NOX and mitochondrial ROS activate NF-κB and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome signaling to induce neutrophil and macrophage infiltration. Recruited inflammatory cells further express NOX2 and inducible NOS (iNOS), generating secondary ROS/RNS to aggravate tissue injury.

Notably, intensive crosstalk among these sources forms a positive feedback loop: NOX-derived ROS triggers mitochondrial RIRR, while mitochondrial ROS facilitates inflammatory infiltration and NOX upregulation, ultimately sustaining persistent OS independent of the initial obstructive insult. Collectively, current evidence from pBOO and I/R mechanistic studies demonstrates that mitochondrial ETC dysfunction serves as the quantitatively dominant and therapeutically targetable source of ROS in chronic pBOO.

ROS scavenging

OS is mainly due to the imbalance between cell oxidation and antioxidant systems, resulting in excessive accumulation of ROS/RNS. The antioxidant defense system consists of two main components: (I) enzymatic antioxidants, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), which directly neutralize ROS; (II) gene regulation mechanisms, such as nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway, coordinate the expression of antioxidant proteins. When the function of these antioxidant systems is impaired or inhibited, the ability to scavenge ROS is weakened, resulting in ROS-mediated oxidative damage.

Enzyme-catalyzed ROS neutralization

SOD is a key enzyme in the body’s antioxidant defense system by catalyzing the disproportionation of O₂•⁻ to H₂O₂ and O₂ (12). In the human body, there are three major isoforms of SOD: Cu/Zn-SOD (SOD1) located in the cytoplasm and mitochondrial membrane space, Mn-SOD (SOD2) located in the mitochondrial matrix, and extracellular SOD (SOD3) distributed in the extracellular matrix and cell membrane (37). Among them, Mn-SOD plays a vital role in maintaining mitochondrial function. As confirmed by Macmillan-Crow et al. (38), Mn-SOD is synthesized in the cytoplasm and then transported to mitochondria, which are assembled into biologically active homotetramers, responsible for scavenging O₂•⁻ produced during aerobic metabolism. Study using acute BOO and I/R animal models has shown that long-term ischemic injury leads to a significant decrease in Mn-SOD expression in bladder tissue, accompanied by an increase in apoptosis (39). These results indicate that the down-regulation of Mn-SOD contributes to the accumulation of superoxide in mitochondria. As mentioned above, OS induces mitochondrial membrane depolarization and increased permeability, triggers the release of pro-apoptotic factors such as cytochrome c, activates the caspase cascade, and ultimately leads to apoptosis.

The antioxidant system also includes other enzymes involved in scavenging ROS. CAT catalyzes the decomposition of H₂O₂ into water and O₂, preventing the accumulation of cytotoxic H₂O₂ and its conversion into highly reactive hydroxyl radicals (40). At the same time, GSH-Px uses reduced glutathione (GSH) to reduce H₂O₂ and organic peroxides to water or corresponding alcohols, thereby protecting cell membranes and lipids from oxidative damage (41).

Other enzyme components include glutathione S-transferase (GST), paraoxonase (PON1), thioredoxin reductase, heme oxygenase and acetaldehyde dehydrogenase, which are involved in scavenging free radicals, oxidative damage repair and redox homeostasis (12).

In pBOO-induced BD, the expression and activity of various antioxidant enzymes are reduced, accompanied by an increase in OS. Targeted regulation of these antioxidant enzymes can enhance the removal of ROS under pathological conditions and reduce intracellular OS, thereby improving BOO-related BD. This approach provides a promising treatment strategy for this condition.

Gene expression-regulated ROS scavenging

The Kelch-like ECH-associated protein 1 (KEAP1)—Nrf2-ARE pathway is a key defense mechanism for cells to resist oxidative and electrophilic stress. By regulating the expression of various antioxidant genes, it is beneficial to the removal of ROS and electrophilic compounds, thereby enhancing the antioxidant capacity of cells (42).

Under normal conditions, KEAP1, as an adaptor protein of E3 ubiquitin ligase, promotes Nrf2 ubiquitination and degradation by proteasome by binding to the Neh2 domain of Nrf2, thereby maintaining low-level expression of Nrf2 (43). Under oxidative or electrophilic stress, the key cysteine residues of KEAP1 are modified, resulting in its conformational change and loss of ubiquitination ability to Nrf2. Consequently, Nrf2 accumulates and translocates to the nucleus, where it binds to ARE and activates the transcription of enzymes such as SOD, CAT, GSH-Px and oxygenase-1 (HO-1), bolstering the cellular antioxidant response (44).

The KEAP1-Nrf2 system does not operate independently, but interacts with multiple signaling pathways including PI3K-AKT and autophagy to form a broad regulatory network. This makes Nrf2 a key node in the regulation of OS in various diseases. In addition, relevant studies have confirmed that nitric oxide (NO) plays an important regulatory role in this pathway, which will be discussed in detail later.

In summary, the KEAP1-Nrf2-ARE pathway plays a central role in antioxidant defense, and its activation can significantly enhance the antioxidant capacity of cells. Current studies have found that activation of this pathway during PBOO can reduce OS damage. Future research should focus on identifying the optimal strategy for targeted regulation of Nrf2 to expand its therapeutic application in pBOO-induced BD.

Mechanisms of OS in BOO-induced BD

In general, the regulation mechanism of OS in BOO is very complex and involves multiple processes. These processes include the denaturation of biological macromolecules by ROS, ROS-mediated apoptosis and autophagy, the dual role of NO, the regulation of smooth muscle contractility by ROS, and ROS-mediated fibrosis (Figure 3).

Figure 3 Oxidative stress-mediated signal pathway in bladder outlet obstruction-induced bladder dysfunction. The accumulation of ROS and RNS drives OS and activates seven downstream pathological mechanisms. [1] Macromolecular oxidation: ROS/RNS directly oxidize proteins (protein carbonyls, nitrotyrosine), lipids (MDA, 4-HNE, F2-isoprostanes), and DNA (8-OHdG), generating established OS biomarkers for bladder injury. [2] RIRR-cytochrome c-caspase apoptosis: mitochondrial ROS damage increases membrane permeability, releasing cytochrome c into the cytoplasm, which activates caspase-9 and downstream caspase-3/7, leading to bladder cell apoptosis. Besides, ROS/RNS upregulates Bax, and downregulates Bcl-2, increasing the Bax/Bcl-2 ratio, promoting bladder cell apoptosis. [3] Autophagy/mitophagy: OS or energy deficiency activates AMPK, which inhibits mTOR and phosphorylates ULK1, initiating autophagy and mitophagy to clear damaged mitochondria and limit RIRR. Mitophagy serves as a protective mechanism, though its role remains context-dependent. [4] Dual role of nitric oxide: NO exerts protective effects via the sGC-cGMP-PKG pathway (smooth muscle relaxation, antioxidant response) and Keap1/Nrf2 pathway (antioxidant gene upregulation). However, excessive NO reacts with O₂•⁻ to form ONOO⁻, causing nitrative damage, and pathological eNOS uncoupling generates O₂•⁻ instead of NO, amplifying ROS production. [5] ROS-mediated fibrosis: ROS promote fibrosis through two interacting pathways: (I) HIF-1α-NLRP3 inflammasome-IL-1β signaling (inflammation/pyroptosis) and (II) TGF-β2-EMT-ECM signaling (extracellular matrix deposition and collagen accumulation). [6] ROS-mediated smooth muscle contractility regulation: The AngII-AT1-Nox-ROS signal pathway regulates BSM contraction in a concentration-dependent manner: low ROS maintain normal contraction via Ca²⁺ signaling and MLCK activation, while excessive ROS oxidize actin and myosin, impairing detrusor contractility. [7] ROS and NF-κB exhibit mutual regulatory interactions, which can further exacerbate OS injury. These converging mechanisms ultimately lead to bladder remodeling, reduced compliance, impaired detrusor contractility, fibrosis, and bladder dysfunction. 4-HNE, 4-hydroxynonenal; 8-OHdG, 8-hydroxy-2'-deoxyguanosine; AMPK, 5'-monophosphate-activated protein kinase; BSM, bladder smooth muscle; cGMP, cyclic guanosine monophosphate; ECM, extracellular matrix; eNOS, endothelial nitric oxide synthase; HIF-1α, hypoxia-inducible factor 1-α; IL-1β, interleukin-1β; MDA, malondialdehyde; mTOR, mammalian target of rapamycin; NO, nitric oxide; OS, oxidative stress; PKG, protein kinase G; RIRR, ROS-induced ROS release; RNS, reactive nitrogen species; ROS, reactive oxygen species; sGC, soluble guanylate cyclase; TGF, transforming growth factor; ULK, Unc-51 like autophagy activating kinase.

ROS-mediated denaturation of biological macromolecules

ROS is extremely unstable in biological systems and is prone to oxidative reactions with macromolecules such as proteins, lipids, and DNA. Study on pBOO has shown that there is obvious OS damage in bladder tissue, accompanied by increased levels of characteristic oxidation products: protein carbonyl and protein-oxidized nitrotyrosine (45); lipid peroxidation markers such as malondialdehyde (MDA) (46) and F2-isoprostanes (F2-IsoPs) (14); and DNA oxidation products include 8-hydroxy-2’-deoxyguanosine (8-OHdG) (11). Therefore, the current research mainly evaluates the oxidative damage of tissues by detecting these stable OS end-products. The established biomarkers include 8-OHdG, MDA/4-hydroxynonenal (4-HNE) and F2-Iso Ps (47). A number of studies have consistently shown that these biomarkers are significantly increased in BOO-induced BD animal models, confirming that BOO induces OS damage.

In summary, under BOO conditions, circulatory I/R injury exceeds the body’s compensatory capacity, resulting in pathological accumulation of ROS/RNS. These excessive ROS react with various biomolecules, resulting in elevated oxidative biomarkers. By detecting oxidative biomarkers, it can reflect the level of systemic OS.

In studies related to OS, MDA and 4-HNE can effectively reflect the level of lipid oxidation damage in cell membranes (11). They can be used for the early screening of BSM dysfunction, but existing studies have confirmed that their application in clinical efficacy assessment has significant limitations (48). Currently, F2-isoprostane and 8-OHdG are recognized as the most promising non-invasive biomarkers for detecting bladder OS damage. Among them, the related research on 8-OHdG is mostly concentrated in animal models, and the clinical verification data is relatively scarce (47). Previous studies regarded F2-isoprostane as the gold standard for evaluating bladder OS, but this indicator lacks mature urine detection technology and relies on invasive tissue biopsy, making its clinical application and implementation difficult (14). And 8-isoprostane, as an important subtype of F2-isoprostane, has currently been established as a new gold standard for detecting OS damage in the bladder (49).

It is worth noting that currently, no OS biomarker has been proven to be applicable for clinical diagnosis and treatment decisions in pBOO. The existing research evidence is all cross-sectional studies, lacking longitudinal dynamic monitoring data, making it difficult to support the clinical translation of the biomarkers. Compared with single indicator detection, the combined detection mode of OS biomarkers and biomarkers related to the OS activation pathway is expected to become the core research direction in this field in the future. This study systematically reviews and summarizes the currently reported high-value bladder OS-related biomarkers, and the specific results are shown in Table 2.

ROS-mediated apoptosis

RIRR-cytochrome c-caspase cascade reaction

Cysteine aspartic proteases (Caspase) family proteins play a central role in the regulation mechanism of apoptosis. Caspase-8 and caspase-9 act as the starting factors of cysteine aspartic proteases, and activate the downstream effectors caspase-3 and caspase-7. These effector Caspases perform the final step of apoptosis through mechanisms such as cytochrome c release (50). Studies have shown that mitochondrial OS damage is particularly prominent in pBOO-induced BD. Due to the RIRR mechanism, this damage exhibits a cascade amplification effect. In this process, excessive ROS production is accompanied by the leakage of mitochondrial contents, which in turn activates multiple downstream signaling pathways, eventually leading to serious consequences such as cell damage and apoptosis. Specifically, mitochondrial OS damage increases membrane permeability and promotes the release of pro-apoptotic factors such as cytochrome c into the cytoplasm (51).

A number of studies have confirmed that bladder cell apoptosis can be observed as early as the acute phase of BOO, accompanied by a significant increase in caspase-3 (39). Similarly, elevated caspase-3 levels were also detected in the bladder I/R injury model (35). It is worth noting that cytochrome c in the cytoplasm activates the caspase cascade, and activated caspase-3 induces apoptosis by degrading various key proteins, including homeostasis proteins, repair proteins, and cytoskeleton components (51).

In summary, in BOO-induced BD, high levels of ROS in bladder tissue trigger mitochondrial OS damage and activate the RIRR mechanism. This leads to a large amount of ROS production and mitochondrial content leakage, followed by activation of various signaling pathways, including the caspase pathway, eventually causing cell damage and apoptosis. These findings suggest that targeting mitochondrial-derived ROS and its downstream signaling pathways may be a new therapeutic strategy for BOO-induced BD.

ROS-MAPK-Bax/Bcl pathway

Another key regulatory mechanism of apoptosis involves B-cell lymphoma (Bcl-2) family proteins, especially pro-apoptotic proteins Bcl-2 antagonist/killer 1 (Bak) and Bcl-2-related X protein (Bax). When these proteins are activated, they increase mitochondrial outer membrane permeability, change membrane potential, and increase ROS levels, ultimately triggering apoptosis (50). Several studies have elucidated the role of this mechanism in BOO-related injury. Li et al. observed time-dependent bladder tissue apoptosis in acute BOO and subsequent voiding models, accompanied by significant down-regulation of Bcl-2, up-regulation of Bax, increased OS and impaired antioxidant function. These findings suggest that Bax/Bcl-2 imbalance is a key factor in BOO-induced apoptosis in I/R injury (39).

Mitogen-activated protein kinase (MAPK) signaling pathway includes a series of cascade reactions, including extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 kinase. Previous study has shown that ROS can directly or indirectly induce or regulate MAPK signaling (18). Park et al. (52) demonstrated in the pBOO model that after the obstruction was relieved, the expression of Bax, caspase-3, p38 and JNK was up-regulated, and the expression of ERK and Bcl-2 was down-regulated. This indicates that pBOO-induced apoptosis of urothelial cells is related to MAPK signaling and Bax/Bcl-2 regulation, and the ERK cascade may play a key role in bladder repair after ischemia. In addition, in the bladder I/R injury model (35), elevated ROS levels were associated with increased JNK/p38 expression and Bax/Bcl-2 ratio, and metformin/sildenafil treatment reversed this effect. These results suggest that the activation of MAPK pathway may inhibit apoptosis by reducing the ratio of Bax/Bcl-2.

In summary, in the period of bladder I/R injury, ROS levels were significantly increased, MAPK-related signaling pathways were activated, Bax/Bcl-2 balance was regulated, apoptosis was promoted, and ROS production was further amplified, ultimately promoting the occurrence of BD.

ROS-mediated autophagy

Autophagy is a ubiquitous degradation or recycling mechanism in eukaryotic cells. Its main function is to remove microorganisms, damaged organelles and abnormal proteins, so as to realize the renewal and recycling of organelles and macromolecular substances (53). More and more evidence shows that OS regulates autophagy through adenosine 5’-monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) to reduce oxidative damage.

Unc-51 like autophagy activating kinase 1 (ULK1) acts as a central regulator of autophagy initiation. Under physiological conditions, activated mTOR inhibits autophagy by phosphorylating ULK1 (54). However, during OS, AMPK relieves mTOR-mediated inhibition and triggers autophagy by phosphorylating Ser555 of ULK1 (55).

Zhu et al. (56) proved that astragaloside IV (AS-IV) alleviates BOO-induced bladder injury by reducing bladder weight gain, reducing OS and reducing smooth muscle cell apoptosis. This study proposes that AS-IV enhances mitophagy, restores mitochondrial function, and improves detrusor contractility through an AMPK-dependent mechanism. This process eliminates damaged mitochondria, prevents RIRR, and reduces excessive ROS accumulation.

However, conflicting evidence suggests that the mTOR/AMPK signaling pathway may not be the main pathway for ULK1 activation. Li et al. (57) found that the activity of lysine demethylase 5C (KDM5C) was inhibited under hypoxia. This promotes the methylation of ULK1 mediated by arginine methyltransferase 5 (PRMT5). The oxygen-sensitive dimethylation at Arg170 of ULK1 increases, and induces the activation of ULK1 and the phosphorylation of ULK1 substrates Atg13 and Beclin 1, which ultimately promotes the formation of autophagosomes.

In summary, energy deficiency or OS activates AMPK. Then, AMPK phosphorylates ULK1 to initiate autophagy and remove damaged mitochondria, thereby reducing oxidative damage. However, the AMPK-ULK1 pathway remains controversial and further studies are needed to verify its role in mitophagy-mediated OS protection.

The dual role of NO

NO and its related signal network play a key role in the regulation of BOO-induced OS damage in BD. As an important signaling molecule, NO is involved in a variety of physiological processes, including the regulation of vascular tension, free radical metabolism, and oxidative modification of biological macromolecules.

In mammals, NO is mainly synthesized by the NOS family, including iNOS and constitutive NOS, which are divided into endothelial NOS (eNOS) and neuronal NOS (nNOS). Studies have shown that pBOO changes the expression profile of NOS subtypes, thereby affecting NO levels and the activity of downstream signaling pathways. In addition, existing studies suggest that NO has a dual role in pBOO.

Lemack et al. (58) reported that iNOS expression was significantly up-regulated in a mouse model 1 week after pBOO, suggesting that iNOS-derived NO may participate in early compensatory vasodilation by regulating local blood flow to reduce occlusion-induced ischemia. In contrast, Juan et al. (45) observed in the pBOO rabbit model that early application of the non-specific NOS inhibitor N-Nitro-L-arginine methylester (L-NAME) exacerbated tissue hypoxia, while prolonged administration attenuated protein nitration. In addition, excessive NO during reperfusion may promote the formation of RNS through uncoupling reaction and aggravate tissue damage (59). Conners et al. (60) further demonstrated that L-NAME improved bladder contractility and reduced denervation by inhibiting NO-mediated oxygen free radical burst during reperfusion. These findings suggest that early NO-mediated vasodilation may aggravate I/R injury, leading to ROS/RNS accumulation, which in turn leads to bladder injury.

Yuan et al. (61) emphasized the protective effect of eNOS: in the pBOO model, bladder wall hypertrophy and dysfunction were accompanied by increased MDA, decreased SOD activity, and down-regulated eNOS expression. This suggests that eNOS-derived NO may play a protective role through anti-oxidation and anti-fibrosis mechanisms. It is worth noting that under pathological conditions, eNOS may undergo uncoupling, from generating NO to generating O₂⁻—a mechanism that has been verified in diseases such as hypertension, indicating that eNOS uncoupling may be one of the important molecular mechanisms of bladder tissue remodeling (62).

At the molecular level, NO may achieve its antioxidant effect through the Keap1/Nrf2 signaling pathway and the cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) signaling pathway. Lin et al. (63) showed that in the model of metabolic syndrome with ovarian hormone deficiency, L-arginine as a precursor of NO activates the Nrf2/hypoxia-inducible factor 1-α (HIF-1α) pathway, up-regulates antioxidant genes, promotes angiogenesis, thereby reducing oxidative damage and improving bladder function. This indicates that elevated NO may promote the dissociation of Keap1-Nrf2, inhibit Nrf2 ubiquitination, and activate the antioxidant transcription program. Typically, NO activates soluble guanylate cyclases (sGC) to generate cGMP, while phosphodiesterases (PDEs) regulate their intracellular concentration by degrading cGMP. The above mechanisms can be involved in the regulation of the second messenger in the intracellular level, thus affecting a variety of physiological processes. Current studies suggest that NO-sGC-cGMP-PKG signaling pathway contributes to smooth muscle relaxation, neurotransmitter inhibition and antioxidant response. This will be further discussed in the treatment section.

In summary, NOS-derived NO plays a dual role in BOO-induced BD. On the one hand, it may activate Keap1/Nrf2 and cGMP/PKG pathways to exert antioxidant effects. On the other hand, however, the theory that relaxing blood vessels and alleviating bladder ischemia to reduce OS is still controversial. NO may react with ROS to form RNS or aggravate oxidative damage during reperfusion. In addition, pathological eNOS uncoupling may also promote ROS production and aggravate OS. The dual role of NO may be affected by NOS subtypes and pathological environment, and its exact mechanism needs further study.

ROS-mediated regulation of smooth muscle contractility

Previous study has shown that angiotensin II (AngII)-angiotensin II type 1 receptor (AT1) signaling pathway plays a crucial role in the molecular regulation of BD induced by BOO (4). AngII affects the contractility of BSM through a variety of mechanisms, including promoting the overexpression of heparin-binding epidermal growth factor (HB-EGF), activating nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase to induce the production of O₂⁻, and regulating the biosynthesis, release and reuptake of neurotransmitters.

Nox enzyme is the main source of intracellular ROS. Frara et al. (26) found that in the electric field stimulation (EFS)-induced bladder strip contraction experiment, the Nox inhibitor apocynin could significantly reduce the contraction force, while exogenous Ang II could partially restore the contraction force. This indicates that AngII-AT1-Nox-ROS signaling regulates BSM contraction by enhancing ROS production.

Studies have shown that the effect of ROS on BSM function is concentration-dependent. At the physiological level, low ROS concentration may enhance EFS-induced contraction by regulating calcium channels or oxidizing Ca²⁺-signaling proteins, thereby increasing intracellular Ca²⁺ (64,65). On the contrary, pathological elevated ROS impairs contractility. For example, high concentrations of H₂O₂ gradually inhibited EFS-induced contraction of rabbit bladder strips, indicating that excessive ROS destroyed the function of BSM (66).

This biphasic regulation may be due to ROS-mediated effects on contractile proteins. Moderate ROS levels enhance myosin light chain kinase (MLCK) activity and increase Ca²⁺ sensitivity, while excessive ROS oxidize actin, myosin and other contractile proteins, resulting in structural damage and functional damage (67).

In summary, the AngII-AT1-Nox-ROS signaling pathway regulates BSM contraction in a ROS-dependent manner: physiological ROS levels maintain normal contractility, while pathological ROS accumulation leads to dysfunction and BOO-related bladder injury.

ROS-mediated fibrosis

Recent studies have shown that OS promotes bladder tissue fibrosis through a variety of signaling pathways, including transforming growth factor-β (TGF-β), NLRP3 inflammasome and HIF-1α-mediated signaling pathways, which can interact with each other.

Hughes et al. (68,69) demonstrated that BOO activates NLRP3 inflammasome, triggers inflammatory response and interleukin-1β (IL-1β), release, promotes bladder fibrosis, and ultimately leads to BD. Under the condition of bladder tissue hypoxia, the increase of ROS level may be involved in this process. Study has shown that hypoxia-induced mitochondrial OS increases ROS production, up-regulates G protein-coupled receptor kinase 2 (GRK2) expression, and promotes HIF-1α synthesis (70). HIF signaling pathway can regulate the activation of NLRP3 inflammasome. In the neurogenic BD model, hypoxia-induced upregulation of HIF-1α promoted epithelial-mesenchymal transition (EMT) and pyroptosis of bladder epithelial cells, and HIF-1α knockout improved these pathological changes (71). These findings highlight that the ROS-HIF-NLRP3 signaling pathway may be involved in BOO-induced BD.

In addition, TGF-β is considered to be a key regulator of tissue fibrosis. Geng et al. (72) reported that BOO significantly up-regulated the expression of TGF-β2 in bladder tissue and activated EMT. In vitro, H₂O₂ induced TGF-β expression in primary BSM cells, suggesting that OS drives EMT through the ROS-TGF-β2 signaling pathway. EMT-transformed cells have the characteristics of migration and invasion, which can accelerate the deposition of extracellular matrix (ECM), and ultimately lead to bladder wall fibrosis and contraction dysfunction.

Treatment

At present, the clinical treatment of pBOO caused by BPH mainly includes drug treatment and surgical intervention. However, detrusor injury induced by pBOO is a progressive pathological process. It is worth noting that even after successful relief of obstruction, a considerable proportion of patients still show persistent BD or LUTS, which highlights the limitations of simple relief of obstruction in achieving complete functional recovery. Therefore, how to effectively promote the comprehensive recovery of bladder function has become a key scientific problem to be solved in the field of urology.

Studies have shown that ROS plays a central role in the pathogenesis of pBOO-induced BD. The potential mechanisms include: (I) oxidative damage to biological macromolecules; (II) persistent inflammatory cascade; (III) activate a variety of ROS-related signaling pathways, leading to significant oxidative damage in bladder tissue; (IV) mitochondria-targeted therapeutic strategies.

Both clinical observation and animal experiments confirmed that pBOO leads to a significant increase in ROS levels in bladder tissues (73). Study has further confirmed that targeted regulation of OS signaling pathway and its downstream effector molecules can effectively improve pBOO-induced BD (10). The majority of therapeutic evidence discussed in this section derives from preclinical studies in rodent, rabbit, and canine pBOO models. Clinical validation of these interventions in human pBOO patients remains limited to a small number of agents. These findings provide an important theoretical basis for the development of new treatment methods, which will be systematically discussed below (Table 3).

Antioxidants

A large number of studies have shown that the use of free radical scavengers can effectively neutralize excessive ROS by activating the antioxidant system and inhibiting the inflammatory response, thereby alleviating OS-induced BD. Related therapeutic drugs include epigallocatechin-3-gallate (EGCG), coenzyme Q10 (CoQ10), melatonin, omega-3 fatty acids, eviprostat, hydrogen-rich water, among others.

EGCG

EGCG is the main polyphenol component found in green tea, which has the characteristics of anti-oxidation, anti-inflammation and anti-cancer. A number of studies have shown that EGCG intervention in rodent pBOO models, BSM injury, collagen deposition, tissue fibrosis and other bladder structural abnormalities have been alleviated. EGCG significantly improves bladder function by increasing bladder capacity and improving bladder compliance.

Hsieh et al. (74) first used EGCG to treat rodent pBOO models. The results showed that after EGCG was given to female SD rats with pBOO, EGCG reduced the expression of cyclooxygenase-2 (COX-2) and inhibited the inflammatory response, thereby reducing tissue damage and improving bladder function. In addition, EGCG reduced the expression of C/EBP-homologous protein (CHOP) and caspase-12 and inhibited endoplasmic reticulum (ER) stress-mediated apoptosis. Studies suggest that EGCG alleviates pBOO-induced bladder injury by inhibiting ER stress-mediated apoptosis and inflammatory response, and long-term treatment can improve bladder function.

Gu et al. administered EGCG via intraperitoneal injection to rodent pBOO models (75). It was found that EGCG could increase the activities of antioxidant enzymes such as total superoxide dismutase (t-SOD), GSH-Px and CAT in tissues, especially the activity of CAT was significantly increased. Moreover, EGCG inhibited bladder cell apoptosis and promoted bladder cell proliferation in BOO rats by reducing caspase-3 expression. In addition, EGCG promoted the translocation of Nrf2 to the nucleus and increased the expression of Nrf2 in the nucleus. Activation of Nrf2-ARE pathway leads to increased expression of Nrf2 downstream target proteins heme HO-1 and NADPH quinone oxidoreductase 1 (NOQ1), resulting in corresponding antioxidant damage effects. Under the combined action of the above mechanisms, the OS injury of BOO rats was significantly improved.

In conclusion, EGCG alleviates pBOO-induced OS-induced bladder injury and dysfunction by inhibiting inflammation, ER stress-related apoptosis, increasing the activity of antioxidant enzyme system in the body, and activating Nrf-2/ARE antioxidant damage pathway.

CoQ10

CoQ10 is a soluble endogenous vitamin precursor present in mitochondria. CoQ10 is involved in the formation of mitochondrial electron transport chain and drives ATP synthesis. In addition, it is also involved in the transport of electrons and protons, and has the functions of scavenging free radicals in the body and protecting cells from oxidative damage.

Juan et al. (76) gave CoQ10 and lipoic acid supplements to rabbits with partial urethral ligation. The results showed that this therapy reduced protein nitration and carbonylation by regulating mitochondrial and neuronal activity, improved bladder tissue hypertrophy, and restored bladder contraction dysfunction. In addition, Juan et al. also found that in the rabbit model with bladder I/R injury, CoQ10 can improve the protection of bladder nerve and reduce the apoptosis of detrusor cells by increasing the activity of SOD and CAT (77).

Eviprostat

Eviprostat is a plant medicine, its main components include Chimaphila umbellata, Populus tremula, Pulsatilla pratensis, Equisetum arvense and other plant extracts. These plant extracts were mixed with wheat germ oil to form the final preparation of Eviprostat.

Unlike most agents, eviprostat has been tested in both pBOO animal models and BPH patients. Matsumoto et al. (78) gave eviprostat to pBOO-treated rabbit models and men with BPH-related pBOO. The results showed that Eviprostat significantly reduced the level of 8-OHdG in the urine of animals and patients, and reduced the OS damage of DNA. At the same time, the international prostate symptom score (IPSS) and quality of life score also improved. Oka et al. also gave eviprostat to rodent pBOO models (79). The experimental results also showed that bladder hypertrophy, OS level, inflammatory response were reduced, and BSM contraction function was improved. The results above suggest that the antioxidant activity of Eviprostat is the reason for its effective treatment of BPH, but the related molecular mechanism is still unclear.

Herbal preparation, WSY-1075

WSY-1075 is a mixed herbal health product with antioxidant and anti-inflammatory effects. Its main components are dogwood, wolfberry, angelica, cassia seed skin, ginseng. Kim et al. gave WSY-1075 to pBOO-induced detrusor overactivity (DO) female rodent model (80). The results showed that WSY-1075 significantly reduced the level of OS in tissues by increasing SOD expression. WSY-1075 can also inhibit inflammation and improve bladder function. This study has shown that WSY-1075 improves the continuous DO after BOO remission through antioxidant and anti-inflammatory effects.

Melatonin

Melatonin is a potent antioxidant. It can participate in a variety of physiological processes and protect tissues from oxidative damage mediated by abnormal NOS.

Onur et al. used melatonin or terazosin alone or in combination in pBOO-treated rabbit models (81). They found that the use of terazosin or melatonin alone only partially improved systolic function. However, the combination of the two drugs can increase the activity of antioxidant enzymes, reduce the level of lipid peroxidation, and restore the contractility of the bladder. Studies have shown that melatonin, as a potent antioxidant, can effectively antagonize pBOO-induced OS. Moreover, the combined use of α-receptor blocker terazosin can further restore bladder contraction function.

Hydrogen water

Hydrogen molecule (H₂) is an effective antioxidant. It can be made by dissolving H₂ gas in ordinary drinking water through a hydrogen water generating device. Miyazaki et al. used hydrogen water to intervene in rodent pBOO models (82). The results showed that hydrogen water could reduce DO caused by BOO and improve bladder function. It can prevent bladder structural remodeling and dysfunction caused by OS injury induced by pBOO.

Inosine

Inosine is an endogenous purine nucleoside produced by the decomposition of adenosine. Recent studies have found that it has anti-inflammatory effects, exerts cytoprotective effects both in vivo and in vitro, and enhances endogenous antioxidant defense systems. Inosine can produce urate after metabolism. The latter is involved in scavenging oxygen free radicals and peroxynitrite, thereby reducing oxidative damage.

Liu et al. used inosine in the treatment of rodent pBOO models (83). The results showed that inosine improved bladder contraction function in a dose-dependent manner, reduced residual urine volume, and increased nerve density in bladder tissue. In addition, inosine intervention significantly enhanced the activity of SOD and reduced the level of thiobarbituric acid reactive substance.

Inhibitors targeting ROS-associated signaling pathway

In addition to using free radical scavengers to reduce ROS levels, other studies have shown that blocking key targets in the ROS signaling network to inhibit ROS-mediated OS damage can also achieve better therapeutic effects.

Astragalus membranaceus

Astragalus membranaceus is a traditional Chinese medicine. Its main active ingredients include astragalus polysaccharides (APS) and AS-IV. ROS can regulate HIF-1α and its downstream signaling pathways in a variety of ways. Under hypoxic conditions, mitochondrial OS leads to excessive ROS production. ROS promotes HIF-1α synthesis by up-regulating GRK2 expression. ROS may also promote HIF-1α accumulation by inhibiting the activity of related enzymes, activate downstream signaling pathways and aggravate tissue damage (84). It has been found that in rodent pBOO models hypoxia can lead to changes in the structure and function of bladder detrusor, accompanied by increased expression of connexin 43 (CX43) (85). APS has been shown to reduce the expression of CX43 in BSM cells by inhibiting the HIF-1α signal pathway in rodent pBOO models (86). However, other study suggests that under hypoxic conditions, a part of HIF-1α (mito HIF-1α) can be translocated to mitochondria. Mito HIF-1α reduces OS-induced apoptosis by regulating mitochondrial DNA-encoded mRNA expression to reduce ROS production and maintain mitochondrial membrane potential in rodent model of liver fibrosis (87). At present, the exact role of HIF-1α in bladder hypoxia response is not fully understood, and further research is needed to elucidate the therapeutic mechanism of APS.

In addition, AS-IV alleviated ROS-mediated OS damage in pBOO through a variety of ways. Dong et al. reported that AS-IV improved chronic intermittent hypoxia-induced enuresis in rodent pBOO models by inhibiting Toll-like receptor 4 (TLR4)-mediated p38 MAPK signal pathway in a dose-dependent manner (88). Zhu et al. found that in rodent pBOO models AS-IV intervention activated mitophagy and AMPK-dependent pathways, significantly enhanced detrusor contractility, reduced bladder wall remodeling, and reduced OS damage. The effects above are related to the improvement of mitochondrial function through AMPK-ULK signaling pathway (56).

Recent study has found that Huang ‘e Capsule, with Astragalus as the main active ingredient, can reduce the expression of Rho/Rho kinase signaling pathway, reduce OS and inflammation levels, and improve overactive bladder (OAB) in rodent pBOO models (89).

In summary, the active components of Astragalus membranaceus alleviate BOO-induced OS and improve BD through different mechanisms.

MicroRNA, miR-101b

H₂O₂ has been shown to induce TGF-β expression in BSM cells, activate downstream signaling pathways and promote EMT, eventually leading to bladder fibrosis, decreased compliance and impaired urination. Wang et al. found that in rodent pBOO models miR-101b significantly inhibited the expression of hypoxia-induced TGF-β receptor 1 (TGF-β R1) and its downstream effector molecule Smad2/3 (90). The study above suggests that miR-101b is a potential anti-fibrotic strategy to reduce bladder structural remodeling after pBOO.

The combined application of PDE inhibitors and antioxidants

The NO•/sGC/cGMP signal pathway is a key therapeutic target for urological research. Exogenous administration of NO, up-regulation of sGC activity, or inhibition of PDE5 can increase cGMP levels. In turn, it activates this pathway and produces effects such as promoting smooth muscle relaxation, inhibiting neurotransmitter release, and anti-fibrosis in pBOO rat models (92). Filippi et al. explored the expression and activity of PDE5 in human bladder tissue from pBOO patients undergoing prostatectomy, and found that PDE5 inhibitors (PDE5i) can alleviate irritating LUTS. This may provide a new direction for the treatment of BD (91).

However, sGC activity depends on the maintenance of cytochrome b5-reductase 3 (CYB5R3) in the reduced state (Fe²⁺) of the heme cofactor. Under OS, heme oxidation (Fe³⁺) made sGC insensitive to NO• in aged rat models (92), supporting the potential benefits of antioxidant binding to PDE5 inhibitors. Yilmaz-Oral et al. evaluated the effects of hydrogen sulfide donor (H₂S), hydrogen sulfide (NaHS) and PDE5i inhibitor tadalafil alone and in combination in rodent pBOO models (93). The results showed that the combined treatment was more effective than single drug in improving bladder hypertrophy, dysfunction and detrusor contractility.

Therefore, sGC direct activators such as cinaciguat may be more effective under OS conditions. Related study has shown that cinaciguat is significantly superior to PDE5 inhibitors such as tadalafil and sildenafil in the treatment of BPH-related LUTs (94).

In addition, PDE5i sildenafil also has the effect of scavenging ROS. In a bladder I/R injury model, Park et al. reported that sildenafil combined with metformin restored SOD activity and tissue OS (35). It may be achieved through the ROS-MAPK signaling pathway, but the exact mechanism is not clear. In addition, sildenafil can also inhibit NF-κB by activating AMPK to exert anti-inflammatory effects. Metformin alone showed stronger efficacy, and no synergistic effect was observed in combination.

Metformin

Metformin is a commonly used hypoglycemic drug for type 2 diabetes. It has been shown to activate AMPK which is a central regulator of cellular energy metabolism. The drug effectively alleviates OS, inhibits inflammatory response, and regulates autophagy to jointly fight the development of organ fibrosis and functional damage.

In the model of bladder I/R injury in rats, Park et al. found that metformin inhibited the production of ROS and reduced the inflammatory response of bladder tissue, thus protecting against I/R injury (35). These findings suggest that metformin effectively disrupts the pathophysiological processes from OS and inflammation to apoptosis, and inhibits bladder structural remodeling and dysfunction.

In a study of partial urethral ligation in rats, Chen et al. reported that metformin intervention initially alleviated inflammation by inhibiting the NLRP3 inflammasome pathway (95). As treatment time increased, metformin further activates AMPK, up-regulates microtubule-associated protein light chain 3 BII (LC3BII) to enhance autophagy, and inhibits TGF-β1/Smad3 pathway to reduce fibrosis, ultimately ameliorating bladder fibrosis and improving BD. This study showed that metformin effectively blocked the transition from inflammatory activation to fibrotic remodeling in pBOO and delayed loss of bladder function.

Other treatments

Nebivolol

Nebivolol is a third-generation β-blocker, which is widely used in the treatment of cardiovascular diseases. It not only has β-adrenergic receptor blocking effect, but also has significant antioxidant and anti-inflammatory effects, as well as potential organ protection. In a study by Altunkaynak-Camca et al., rats with bladder I/R injury were given nebivolol before OS injury (96). Bladder tissue assessment showed that nebivolol pretreatment could attenuate OS levels and reduce interleukin-6 (IL-6) levels to improve I/R-induced systolic dysfunction.

Mirabegron

Mirabegron is a new clinical drug for the treatment of OAB. In a study by Pan et al., rodent pBOO models were given mirabegron (97). The results showed that mirabegron improved bladder hemodynamics and reduced OS levels and alleviated OAB-related symptoms in rats with obstruction. These effects are related to the regulation of matrix metalloproteinases 1 (MMP1), matrix metalloproteinases 2 (MMP2) and tissue inhibitors of metalloproteinases (TIMP1) expression in bladder tissue.

Blueberry powder

Blueberry is a widely consumed health food. It contains a variety of bioactive components, including anthocyanins, phenolic acids, ascorbic acid, flavonols and tannins, and has antioxidant, anti-inflammatory and anti-cancer properties. In a study by Miyazaki et al., dietary supplementation of blueberry powder was given to rodent pBOO models (13). The results showed that blueberry powder intake improved BOO-induced urinary dysfunction, reduced bladder hypertrophy and fibrosis, and reduced OS levels. These findings suggest that blueberry powder may prevent BOO-related BD through its antioxidant activity and ability to inhibit bladder structural remodeling.

Flavonoid-rich diet

Flavonoids have significant anti-inflammatory and antioxidant properties, and reduce OS damage by scavenging ROS and free radicals. A number of studies have shown that a flavonoid-rich diet can reduce the risk of BOO-induced BD, showing considerable potential in prevention and treatment.

In rodent pBOO models, Bisogni et al. (15) administered a diet rich in flavonoids galangin and observed a decrease in tissue OS levels and improvement in BOO-related BD symptoms. This study demonstrated for the first time that supplementation of antioxidants before and after the onset of chronic obstruction can prevent the injury of detrusor muscle cells. In addition, in a cross-sectional clinical study, Lin et al. (98) believed that a diet high in anthocyanins and flavonoids may help reduce the risk of OAB.

The study of Miyazaki et al. (99) showed that equol, a metabolite of soybean isoflavones, protected bladder nerves by reducing lipid peroxidation and smooth muscle layer fibrosis, thereby alleviating BOO-induced BD symptoms in rodent pBOO models. These findings highlight their potential applications in the prevention and management of BOO-related OABs.

Another flavonoid with significant antioxidant and anti-inflammatory activity, flavanthin, was studied by Akbaş et al. (100) in a cyclophosphamide-induced rat cystitis model. Study has reported that the total oxidation state (TOS) and oxidative stress index (OSI) in bladder tissue were significantly increased, as well as reduced glutathione (tGSH) and total antioxidant status (TAS). Taxifolin intervention reduced these oxidative and inflammatory markers and alleviated pathological damage, suggesting its role in regulating tissue oxidation-antioxidation balance to combat OS damage.

Mitochondria-targeted therapeutic strategies

Mitochondrial dysfunction plays a pivotal role in OS, and multiple mitochondria-targeted therapeutic strategies have been validated to exert therapeutic effects (101). Four categories of agents—including mitochondria-targeted antioxidants, mitochondrial biogenesis activators, mitophagy modulators, and mitochondrial permeability transition pore (mPTP) inhibitors—will be discussed to offer novel insights into mitochondria-targeted therapy for pBOO.

Mitochondria-targeted antioxidants

Mitochondria-targeted antioxidants accumulate specifically in mitochondria via targeted carriers, which eliminate ROS in mitochondria, repair oxidative damage, and interrupt the vicious cycle of OS. Previous studies have shown that CoQ10 can restore the mitochondrial dysfunction caused by pBOO (76). MitoQ is a mitochondrial-targeted derivative of CoQ10. It can accumulate in the mitochondrial matrix and may exert a more effective antioxidant effect. A study demonstrated that MitoQ could reverse age-related physical dysfunction by eliminating excess mitochondrial reactive oxygen species (mitoROS) (102). As another mitochondria-targeted antioxidant, MitoTEMPO has also been reported to alleviate OS injury in degenerative joint diseases (103). In addition, SS-31 (elamipretide) specifically binds to cardiolipin on the inner mitochondrial membrane, exerting multiple biological effects including antioxidation, mitochondrial structural restoration, and suppression of apoptosis and inflammatory responses. Existing evidence has verified that SS-31 ameliorates mitochondrial dysfunction in cardiac and skeletal muscle tissues under OS conditions (104). Notably, although the aforementioned agents have demonstrated therapeutic efficacy in I/R injury models of the heart, skeletal muscle and nervous system, their therapeutic effects have not yet been investigated in pBOO models, which creates significant opportunities for translational research.

Mitochondrial biogenesis activators

Existing research indicates that mitochondrial biogenesis activators such as AICAR can not only restore impaired cellular energy metabolism and improve mitochondrial function, but also suppress inflammatory signaling pathways by activating the AMPK pathway to alleviate I/R injury (105). This mechanism may contribute to the recovery of mitochondrial dysfunction induced by I/R in pBOO (95). Metformin has also been shown to activate the AMPK pathway, restore mitochondrial homeostasis and block apoptotic signaling pathways in necrotic neurological lesions (106).

Mitophagy modulators

Mitophagy is considered to be critically involved in OS injury under pBOO conditions. Mitophagy modulators facilitate mitophagy to eliminate damaged mitochondria and break the RIRR cycle, which may alleviate OS injury in pBOO. Current research suggests that AS-IV may exert its effects by activating the AMPK pathway to regulate mitochondrial autophagy, and thereby improving BD caused by pBOO (56). Among other diseases, reports have identified urolithin A (107) and NAD⁺ (108) precursors as mitophagy-promoting agents. Spermidine has also been documented to possess the capacity to induce mitophagy (109).

mPTP inhibitors

As mentioned above, the opening of the mPTP serves as a core event in mitochondria-mediated cell death. Cyclosporin A (110) and TRO40303 (111) are capable of reversing this pathological opening to a certain extent. Cyclosporin A has already entered clinical trials for cardiac I/R injury (110). This provides a potential translational therapeutic strategy for pBOO treatment.

Discussion

Although most mitochondria-targeted pharmaceuticals have not been tested in pBOO models, their therapeutic efficacy has been validated in other I/R injury and OS-related models. Combined with the well-established central role of mitochondrial dysfunction in the pathogenesis of pBOO, mitochondria-targeted therapy stands as a priority direction for future translational research.

Conclusions

BOO caused by diseases such as BPH is a common urinary system problem. As the obstruction persists, it will lead to BD and produce a series of LUTS, affecting the quality of life of a large number of patients around the world. BD caused by BOO may be caused by many reasons, but recent studies have shown that OS plays a crucial role in BD caused by BOO. Ischemia and hypoxia are common in the bladder of BOO, and I/R is a key pathophysiological step in the progression of BOO. In the process of I/R, a large amount of ROS/RNS will be produced, which often exceeds the scavenging ability of the body’s antioxidant system, resulting in the accumulation of a large amount of ROS, eventually leading to the continuous OS state of the bladder, resulting in a series of OS damage and bladder structure remodeling, and ultimately leading to BD. The occurrence and clearance of OS and its pathogenic mechanism in BOO have aroused great interest.

At present, traditional surgery and drugs are used for treatment. While BD still exists in some patients after relieving obstruction. Therefore, it is important to develop therapeutic strategies to target OS in pBOO to reverse and prevent more oxidative damage to restore bladder function. Although OS is well known for BD caused by BOO, the exact molecular pathways behind these effects are still not fully understood. Existing studies suggest that specific therapies such as targeting ROS-related signaling pathways and antioxidants may restore BOO-induced BD, but the efficacy of single-target drugs is suboptimal. Therefore, the development of targeted treatments depends on elucidating the molecular connections and signaling pathways that lead to BOO-induced BD.

Further research should focus on clarifying. (I) Quantify the relative contributions of NOX, mitochondria, and inflammatory cells in pBOO at different stages, as well as their temporal dynamic changes. Future studies should employ time-series analysis and combine the use of inhibitors targeting specific sources and genetically modified animal models. (II) The precise molecular mechanisms underlying fibrosis and inflammation mediated by ROS, including the interaction patterns between TGF-β, NLRP3 inflammasome and HIF-1α pathways, as well as the factors regulating the protective or harmful effects of ROS-induced autophagy. Future research should integrate multi-omics analysis and single-cell RNA sequencing. (III) Identify clinically applicable biomarkers for disease staging and monitoring. This includes whether a group of OS biomarkers can distinguish compensated pBOO from decompensated pBOO, and whether the biomarker concentrations can predict the therapeutic response to antioxidant intervention. Future research should include prospective clinical analyses to correlate the biomarker levels with urodynamic indicators and treatment outcomes. (IV) Determine the therapeutic window period for antioxidant intervention. This includes the disease stage at which antioxidant treatment achieves the best therapeutic effect and whether there is an irreversible pathological threshold. Future research should include preclinical trials of administering antioxidants at specific time points, and a comprehensive evaluation of the experimental results. (V) Search for multi-target treatment strategies and explore whether single-drug intervention is sufficient to address the multi-source and multi-pathway characteristics of OS. Future research should evaluate the reasonably designed combined therapy through preclinical model systems. (VI) There is still a gap in the translation between preclinical models and clinical applications. Although antioxidant therapies have shown efficacy in preclinical studies, only a few have progressed to clinical trials. It is necessary to determine whether the currently available animal models are sufficient to fully simulate the BOO associated with BPH in humans. Future research should establish large animal models with clinical relevance and conducting well-designed randomized controlled trials.

In summary, solving the problem of OS and BD caused by BOO and exploring new research approaches will generate important knowledge about possible processes, diagnostic methods, and treatment strategies. By overcoming these obstacles, we can restore the bladder function of patients who have received traditional treatment but have a poor prognosis, thereby improving the quality of life of patients.

Acknowledgments

Special thanks go to Dr. Miaoyong Ye for his guidance and support on figure illustration.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0358/rc

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0358/prf

Funding: This work was supported by Young Elite Scientists Sponsorship Program by CACM (No. CACM-2023-QNRC2-B21); Foundation of National Flagship Construction Department (Urology) of Collaboration between Traditional Chinese Medicine and Western Medicine ([2024]No. 221); and National Natural Science Foundation of China (No. 82560938).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0358/coif). The authors have no conflicts of interest to declare.

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