Significant impairment in endothelial-derived nitric oxide is present in the diabetic corpus cavernosum. RhoA͞Rho-kinase may suppress endothelial nitric oxide synthase (eNOS). Here, we tested the hypothesis that RhoA͞Rho-kinase contributes to diabetesrelated erectile dysfunction and down-regulation of eNOS in the streptozotocin (STZ)-diabetic rat penis. Colocalization of Rhokinase and eNOS protein was present in the endothelium of the corpus cavernosum. RhoA͞Rho-kinase protein abundance and MYPT-1 phosphorylation at Thr-696 were elevated in the STZdiabetic rat penis. In addition, eNOS protein expression, cavernosal constitutive NOS activity, and cGMP levels were reduced in the STZ-diabetic penis. To assess the functional role of RhoA͞Rho-kinase in the penis, we evaluated the effects of an adenoassociated virus encoding the dominant-negative RhoA mutant (AAVTCMV19NRhoA) on RhoA͞Rho-kinase and eNOS and erectile function in vivo in the STZ-diabetic rat. STZ-diabetic rats transfected with AAVCMVT19NRhoA had a reduction in RhoA͞Rho-kinase and MYPT-1 phosphorylation at a time when cavernosal eNOS protein, constitutive NOS activity, and cGMP levels were restored to levels found in the control rats. There was a significant decrease in erectile response to cavernosal nerve stimulation in the STZ-diabetic rat. AAVT19NRhoA gene transfer improved erectile responses in the STZ-diabetic rat to values similar to control. These data demonstrate a previously undescribed mechanism for the down-regulation of penile eNOS in diabetes mediated by activation of the RhoA͞Rho-kinase pathway. Importantly, these data imply that inhibition of RhoA͞Rho-kinase improves eNOS protein content and activity thus restoring erectile function in diabetes.gene therapy ͉ neuronal NO synthase ͉ endothelium R elaxation of corporal smooth muscle is essential for normal erectile function, and evidence exists to implicate neuronaland endothelial-derived nitric oxide (NO) as the principal mediator of corporal smooth muscle relaxation (1-3). Impairments in neurogenic and endothelium-dependent corporal smooth muscle relaxation is observed in diabetes mellitus and is responsible for erectile impairment in diabetic patients (4, 5).Contraction of smooth muscle is primarily mediated by phosphorylation of the regulatory myosin light chain (MLC) by the Ca 2ϩ ͞calmodulin-dependent activation of MLC kinase and actin͞myosin cross-bridge formation (6). Relaxation is mediated by the dephosphorylation of MLC by smooth muscle myosin phosphatase. Recent evidence has established the importance of Ca 2ϩ -sensitization through the Ca 2ϩ -independent stimulation of MLC kinase or the attenuation of MLC phosphatase activity (7). A principle regulator of MLC phosphatase is the serine͞ threonine kinase, Rho-kinase. Data from peripheral arteries suggest that RhoA, a GTP-binding protein, mediates agonistinduced activation of Rho-kinase (8). The exchange of GDP for GTP on RhoA and translocation of RhoA from the cytosol to the membrane are markers of activation, and enable the downstr...

The etiologies of erectile dysfunction (ED) after nerve-sparing radical prostatectomy have not been clearly elucidated. The aim of this study was to evaluate the effects of cavernous nerve injury on cavernous fibrosis, and to consider measures to prevent irreversible damage to the cavernous tissues. Twenty male Sprague-Dawley rats constituted the study population. The animals were divided into 2 groups; group 1 consisted of sham-operated rats (n = 10), and group 2 consisted of rats that underwent incision of both cavernous nerves (n = 10). Three months later, all rats underwent intracavernous papaverine injection (300 and 600 mg), and intracorporal pressures were recorded. Transforming growth factor-beta(1) (TGF-beta(1)) messenger RNA (mRNA) expression from rat penile tissue was measured using reverse transcriptase-polymerase chain reaction. Hypoxia-inducible factor-1alpha (HIF-1alpha), TGF-beta(1), and collagen I and III protein expressions were determined by Western blot analysis and immunohistochemical staining. Erectile function as studied with intracavernosal papaverine injection and histological analysis of penile cross-sections at 3 months was similar in both groups. TGF-beta(1) mRNA expression, HIF-1alpha, TGF-beta(1), and collagen I and III protein expressions were significantly greater in the neurotomy group. Immunohistochemical staining for TGF-beta(1), HIF-1alpha, and collagen III were qualitatively more positive in the neurotomy group, whereas collagen I staining was similar. This study demonstrates an increase in TGF-beta(1), HIF-1alpha, and collagen III synthesis in rat cavernosal smooth musculature after cavernous neurotomies. In theory, cavernous fibrosis may be reduced by employing various vasoactive agents or interventions that increase oxygenation to the corporal tissues during the postoperative period.

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