Objectives
To evaluate nNOS phosphorylation, nNOS uncoupling, and oxidative stress in the penis and major pelvic ganglia (MPG), before and after the administration of the cAMP-dependent protein kinase A (PKA) agonist colforsin in a rat model of bilateral cavernous nerve injury (BCNI) which mimics nerve injury following prostatectomy.
Materials and Methods
Adult male Sprague–Dawley rats were divided into BCNI and sham groups. Each group included 2 subgroups: vehicle and colforsin (0.1 mg/kg/day i.p.). After 3 days, erectile function (intracavernosal pressure) was measured and penes and MPG were collected for molecular analyses of phospho(P)-nNOS (Ser-1412 and Ser-847), total nNOS, nNOS uncoupling, binding of neuronal nitric oxide synthase (PIN) to nNOS, gp91phox subunit of NADPH oxidase, active caspase 3, PKA catalytic subunit alpha (PKA-Cα) (by Western blot) and oxidative stress (hydrogen peroxide [H2O2] and superoxide by Western blot and microdialysis method).
Results
Erectile function was decreased 3 days after BCNI and normalized by colforsin. nNOS phosphorylation on both positive (Ser-1412) and negative (Ser-847) regulatory sites, and nNOS uncoupling, were increased after BCNI in the penis and MPG and normalized by colforsin. Hydrogen peroxide and total ROS productions were increased in the penis after BCNI and normalized by colforsin. Protein expression of gp91phox was increased in the MPG after BCNI and was normalized by colforsin treatment. Binding of PIN to nNOS was increased in the penis after BCNI and was normalized by colforsin treatment. Protein expression of active Caspase 3 was increased in the MPG after BCNI and was normalized by colforsin treatment. Protein expression of PKA-Cα was decreased in the penis after BCNI and normalized by colforsin.
Conclusion
Collectively, BCNI impairs nNOS function in the penis and MPG by mechanisms involving its phosphorylation and uncoupling in association with increased oxidative stress, resulting in erectile dysfunction. PKA activation by colforsin reverses these molecular changes and preserves penile erection in the face of BCNI.