Superoxide Anion Production by NADPH Oxidase Plays a Major Role in Erectile Dysfunction in Middle-Aged Rats: Prevention by Antioxidant Therapy

Introduction. Prevalence of erectile dysfunction (ED) increases progressively with aging, but the ED pathophysiology at its early stages is still poorly investigated. Aim. This study aimed to evaluate the functional and molecular alterations of erectile function at middle age, focusing on the contribution of oxidative stress in erectile tissue for the ED. Methods. Young (3.5-month) and middle-aged (10-month) male Wistar rats were used. Rat corpus cavernosum (RCC) was dissected free and mounted in 10-mL organ baths containing Krebs solution. Intracavernosal pressure (ICP) in anesthetized rats was evaluated. Main Outcome Measures. Concentrationresponse curves to endothelium-dependent and endothelium-independent agents, as well as to electrical field stimulation (EFS), were obtained in RCC strips. Measurement of cyclic guanosine monophosphate (cGMP) and expressions of neuronal nitric oxide synthase (nNOS) and endothelial NOS (eNOS), gp91phox and superoxide dismutase-1 (SOD-1) expressions in RCC were evaluated. Results. ICP was significantly reduced in middle-aged compared with young rats. RCC relaxations to acetylcholine (108 to 102M), sodium nitroprusside (108 to 102M), sildenafil (109 to 105M), BAY 41-2272 (109 to 105M), and EFS (432Hz) were decreased in middle-aged group, which were nearly normalized by apocynin (NADPH oxidase inhibitor; 104M) or SOD (75U/mL). Prolonged treatment with apocynin (85mg/rat/day, 4 weeks) also restored the impaired relaxations in middle-aged rats. Relaxations to 8-bromoguanosine 3,5-cyclic monophosphate sodium salt (8-Br-cGMP; 108 to 3x104M) remained unchanged between groups. Basal and stimulated cGMP production were lower in middle-aged group, an effect fully restored by apocynin and SOD. Protein expression of nNOS and phosphorylated eNOS (p-eNOS) (Ser-1177) reduced, whereas gp91phox mRNA expression increased in RCC from middle-aged rats. Conclusions. ED in middle-aged rats is associated with decreased NO bioavailability in erectile tissue due to upregulation of NADPH oxidase subunit gp91phox and downregulation of nNOS/p-eNOS. Antioxidant therapies may be a good pharmacological approach to prevent ED at its early stages. Silva FH, Monica FZ, Bau FR, Brugnerotto AF, Priviero FBM, Toque HA, and Antunes E. Superoxide anion production by NADPH oxidase plays a major role in erectile dysfunction in middle-aged rats: Prevention by antioxidant therapy. J Sex Med 2013; 10: 960-971.