A uro-protective agent with restorative actions on urethral and striated muscle morphology.

PURPOSE: Aging increases oxidative stress, which can have delirious effects on smooth and striated muscle resulting in bladder dysfunction. Consequently, in women aged over 60 years, urinary incontinence (UI) is a prevalent health problem. Despite the prevalence and consequences, UI continues to be undertreated simply because there are few therapeutic options. METHODS: Here we investigated whether 8-aminoguanine (8-AG), a purine nucleoside phosphorylase (PNPase inhibitor), would restore urethra and external sphincter (EUS) muscle morphology in the aged rat. Aged (> 25 months) female Fischer 344 rats were randomized to oral treatment with 8-AG (6 weeks) or placebo, and the urethra and EUS were evaluated by electron microscopy and protein expression (western immunoblotting). RESULTS: Aging was associated with mitochondrial degeneration in smooth and striated muscle cells as compared to young rats. We also observed a significant increase in biomarkers such as PARP, a downstream activator of oxidative/nitrosative stress. Treatment of aged rats with 8-AG normalized all abnormalities to that of a younger state. CONCLUSIONS: 8-AG, a potent inhibitor of PNPase, reverses age-related lower urinary tract morphological and biochemical changes. Our observations support the concept that 8-AG will reverse age-induced lower urinary tract disorders such as UI. These initial findings could have therapeutic implications for the prevention and treatment of age-related UI.

Purine nucleoside phosphorylase inhibition ameliorates age-associated lower urinary tract dysfunctions.

In the aging population, lower urinary tract (LUT) dysfunction is common and often leads to storage and voiding difficulties classified into overlapping symptom syndromes. Despite prevalence and consequences of these syndromes, LUT disorders continue to be undertreated simply because there are few therapeutic options. LUT function and structure were assessed in aged (>25 months) male and female Fischer 344 rats randomized to oral treatment with a purine nucleoside phosphorylase (PNPase inhibitor) 8-aminoguanine (8-AG) or vehicle for 6 weeks. The bladders of aged rats exhibited multiple abnormalities: tactile insensitivity, vascular remodeling, reduced collagen-fiber tortuosity, increased bladder stiffness, abnormal smooth muscle morphology, swelling of mitochondria, and increases in urodamaging purine metabolites. Treatment of aged rats with 8-AG restored all evaluated histological, ultrastructural, and physiological abnormalities toward that of a younger state. 8-AG is an effective treatment that ameliorates key age-related structural and physiologic bladder abnormalities. Because PNPase inhibition blocks metabolism of inosine to hypoxanthine and guanosine to guanine, likely uroprotective effects of 8-AG are mediated by increased bladder levels of uroprotective inosine and guanosine and reductions in urodamaging hypoxanthine and xanthine. These findings demonstrate that 8-AG has translational potential for treating age-associated LUT dysfunctions and resultant syndromes in humans.