Metformin and Sildenafil Attenuate Inflammation and Suppress Apoptosis After Ischemia/Reperfusion Injuries in Rat Urinary Bladder

Although metformin and sildenafil can protect various organs against ischemia/reperfusion (I/R) injuries, their effects and mechanisms of action in bladder I/R injuries remain unknown. This study investigated the effects and mechanisms of action of metformin and sildenafil against bladder I/R insults in rats. One hundred male Sprague-Dawley rats were randomly divided into 5 groups, each of which contained 20 rats: a sham-operated group, a bladder I/R group, and bladder I/R groups treated with metformin, sildenafil, or both agents. Ischemia was induced by clamping the bilateral common iliac arteries with atraumatic vascular clamps for 2 hours, followed by reperfusion for 7 days. During this period, rats were injected once daily with 4-mg/kg metformin and/or 1-mg/kg sildenafil. I/R injuries induced increased malondialdehyde levels and myeloperoxidase activity and decreased superoxide dismutase activity. These changes were attenuated by treatment with metformin and/or sildenafil. The I/R group had significantly higher Jun N-terminal kinase, p38 mitogen-activated protein kinase (MAPK), Bax, caspase-3, and nuclear factor-kappa B (NF-κB) levels, and lower extracellular signal-regulated kinase, and Bcl-2 levels in the bladder than the sham-operated group; these changes were significantly ameliorated by metformin and/or sildenafil treatment. No differences in the levels of these markers were observed between rats coadministered metformin and sildenafil and those treated with either agent alone. Metformin and sildenafil protected the rat bladder against I/R injuries. This effect may have been due to the inhibition of reactive oxygen species production through MAPK, Bax, and Bcl-2 activation, and the restoration of inflammation through NF-κB inhibition. However, the combination of metformin and sildenafil was not more effective than either agent alone.