OP1-10 RHO-KINASE INHIBITION PREVENTS NNOS UNCOUPLING IN THE MPG, ERECTILE DYSFUNCTION AND INCREASES NEURONAL OUTGROWTH FOLLOWING CAVERNOUS NERVE INJURY

Abstract

INTRODUCTION AND OBJECTIVES: RhoA and Rho-kinase (ROCK) are implicated in the inhibition axonal growth/neurite sprouting, and neurodegeneration via regulation of inflammation and apoptosis following peripheral nerve injury. We hypothesize that degeneration of the cavernous nerve (CN) after injury is due to increased RhoA/ROCK signaling in the major pelvic ganglion (MPG) leading to neuronal nitric oxide synthase (nNOS) uncoupling and nerve degeneration. This study aimed to characterize the role of ROCK inhibition in preserving erectile responses, penile contractions, nNOS uncoupling and neurite outgrowth following bilateral cavernous nerve injury (BCNI). METHODS: Male Sprague-Dawleys rats (12 wks) were separated into sham, BCNI and BCNI treated with Y-27632 (ROCK inhibitor, 5 mg/kg twice daily; n1⁄48/group). 14 days after BCNI, groups underwent CN stimulation to determine erectile function. Penes were dissected and contractile responses to phenylephrine (PE) and electrical field stimulation (EFS) were assessed. MPGs were excised and protein (Western blots) and gene expression (q-PCR) of nNOS and growth associated protein 43 (GAP43) were assessed. Additional MPGs (n1⁄43/ group) were cultured in reduced growth factor matrigel for 48h and neurite growth was measured. RESULTS: While erectile function was severely decreased in BCNI rats, daily administration of Y-27632 improved erections 2-fold (p<0.05). nNOS MPG gene expression was decreased by 50% after BCNI and recovered to sham levels with Y-27632 (p<0.05). nNOS uncoupling was increased in BCNI MPGs and completely prevented in y-27632 treated rats (p<0.05). Cavernous contractile responses to PE were unchanged. EFS-mediated penile contractions were significantly lower following BCNI and treatment with Y-27632 increased EFSmediated contractions 2-fold compared to sham and BCNI penes (p<0.05). MPG neurite outgrowth was unchanged in sham and BCNI; however, BCNI+Y MPGs had significantly increased growth (S:328 9mm; BCNI:349 14mm; BCNI+Y:405 11mm, p<0.05). GAP43, a growth protein highly expressed during axonal regeneration, was increased 25% following BCNI and 30% with Y-27632 treatment indicating treatment increased axonal growth. CONCLUSIONS: Inhibition of ROCK preserved erections, prevented nNOS uncoupling, mediated increased neurite growth and increased nerve-mediated penile contractions in BCNI rats. Preventing the activation of RhoA/ROCK signaling in the MPG and CN after injury may inhibit neurodegeneration and post-radical prostatectomy erectile dysfunction.