IR-780 Improves Urination Function and Complications in Rats with Partial Bladder Outlet Obstruction by Protecting Bladder Smooth Muscle Cell Mitochondria from Oxidative Stress

Feng Pi¹Benhuang Yan²Min Jia²Yuan Liu³Shuang Tang²Zhihong Huang²Qiang Fang²Chunmeng Shi⁴Weibing Li^2*

• ¹Third Affiliated Hospital of Chongqing Medical University, Chongqing, China
• ²The Third Affiliated Hospital of Chongqing Medical University, Chongqing, China
• ³The Southwest Hospital of AMU, Chongqing, China
• ⁴Institute of Rocket Force Medicine, Third Military Medical University, Chongqing, China

Introduction: Partial bladder outlet obstruction (pBOO) is the most common cause of lower urinary tract symptoms (LUTS). Prolonged BOO induces bladder remodeling, which can lead to severe bladder dysfunction and refractory LUTS in some patients, even after obstruction resolution. This condition significantly impairs patients' quality of life, and no effective treatment is currently available. This study investigated a pBOO rat model using IR-780, a novel near-infrared lipophilic dye with potential targeted antioxidant effects. Methods: A partial ligation of the rat bladder neck was performed to establish a pBOO model. After confirming successful modeling, the rats were randomly divided into sham, sham+IR-780, pBOO, and pBOO+IR-780 groups (eight rats per group). One week post-surgery, rats received intraperitoneal injections of IR-780 (0.667 mg/kg) or an equivalent volume of phosphate buffered saline solution twice weekly for 3 weeks. Before evaluating efficacy using the bladder filling manometry method, we examined the distribution of IR-780 in tissues and subcellular compartments via confocal fluorescence imaging. Results: IR-780 accumulated at high levels in the bladders of rats with pBOO, where it was primarily taken up by bladder smooth muscle cells (BSMCs) and localized within the mitochondria. Bladder pressure measurements revealed that IR-780 significantly improved bladder function in rats with pBOO. IR-780 effectively mitigated pathological changes in bladder smooth muscle tissue and concurrently alleviated pBOO-induced reflux nephropathy. In vitro and in vivo experiments confirmed that IR-780 significantly reduced apoptosis in BSMCs. Moreover, cryosection staining and transmission electron microscopy results demonstrated that IR-780 markedly decreased reactive oxygen species levels in BSMCs from rats with pBOO, prevented mitochondrial mass and morphological damage, and significantly reduced the levels of mitochondrial apoptosis pathway-related proteins (Bcl-2, Bcl-2-associated X, cytochrome C, and Caspase-9). We found that IR-780 upregulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its associated antioxidant proteins in the bladder tissue of rats with pBOO. Conclusion: IR-780 improved urinary function and complications in rats with pBOO by protecting BSMC mitochondria from oxidative stress, which was potentially mediated through the activation of the Nrf2 pathway.