Data suggest that RhoA/rho kinase up-regulation in response to cavernous nerve injury contributes to penile vasculature dysfunction after cavernous nerve injury. Thus, the RhoA/rho kinase pathway may be a suitable target for treating post-radical prostatectomy erectile dysfunction.

Purpose We determined the effect of passive secondhand cigarette smoke on 1) erectile function in vivo, 2) molecular mechanisms involved in penile vascular function, and 3) erectile function and penile molecular signaling in the presence of phosphodiesterase type 5 inhibitor therapy. Materials and Methods Four groups of mice were used, including group 1—controls, group 2—mice exposed to 3 weeks of secondhand smoke (5 hours per day for 5 days per week), group 3—control plus sildenafil (100 mg/kg per day) and group 4—smoke exposed plus sildenafil (100 mg/kg per day). Cavernous nerve electrical stimulation and intracavernous injection of acetylcholine were done to assess erectile function. Constitutive and inducible nitric oxide synthase activity, reactive oxygen species generation, nitrotyrosine formation and superoxide anion levels were assessed. Results Decreased erectile responses to cavernous nerve electrical stimulation and impaired endothelium dependent erectile responses to ACh in mice exposed to secondhand smoke were observed. Superoxide anion was increased in endothelial and corporeal smooth muscle cells of smoking mouse penises. In mice exposed to secondhand smoke constitutive nitric oxide synthase activity was decreased, and inducible nitric oxide synthase activity, reactive oxygen species generation and nitrotyrosine formation increased. Sildenafil therapy restored constitutive nitric oxide synthase activity in the penis of smoking mice, decreased inducible nitric oxide synthase activity, reactive oxygen species generation and nitrotyrosine formation, and improved erectile responses to cavernous nerve electrical stimulation and acetylcholine. Conclusions Short-term exposure to secondhand smoke impairs erectile function through excessive penile reactive oxygen species signaling and inducible nitric oxide synthase activity. Decreased penile constitutive nitric oxide synthase activity may be attributable to the decreased endothelial nitric oxide synthase activity resulting from increased oxidative stress. Sildenafil therapy restored nitric oxide synthase activity and decreased reactive oxygen species signaling, resulting in improved erectile function.

Objectives RhoA and its main downstream effector, Rho-kinase (ROCK) are important in maintaining the penis in the flaccid state. The pathophysiology of Sickle cell disease-associated priapism is not well defined. We hypothesize that RhoA/ROCK vasoconstrictive pathways may be involved in the development of priapism. Therefore, the objective of this study was to evaluate molecular changes in RhoA and ROCK in an established transgenic sickle cell mouse model of priapism. Methods Two groups of mice were utilized: 1) wild type (WT; C57BL/6), and 2) transgenic Sickle cell mice (Sickle). We evaluated RhoA GTPase and total ROCK activities as well as ROCK1 and ROCK2 protein expression in WT and Sickle mice penes. We also evaluated in vivo erectile responses to cavernous nerve stimulation (CNS) and the frequency and duration of spontaneous erections both pre- and post-CNS. Results Sickle mice demonstrated significantly (p<0.05) enhanced erectile responses to CNS and frequency of spontaneous erections both pre- and post-CNS when compared to WT. Sickle mice penes had a significant decline in RhoA GTPase (p<0.01) and total ROCK activities (p<0.05) when compared to WT mice. There was a significant (p<0.05) reduction in ROCK2 protein expression in Sickle mice penes when compared to WT mice protein expression. No change in ROCK1 protein expression was observed in both cohort’s of mice penes. Conclusion These data suggest that Sickle cell disease associated-priapism may be contributed by a lack of RhoA/ROCK mediated vasoconstriction and highlight a novel molecular mechanism in the pathophysiology of priapism.

Erectile dysfunction (ED) commonly results from endothelial dysfunction of the systemic vasculature. Although phosphodiesterase type 5 (PDE-5) inhibitors are effective at treating most cases of ED, they must be taken routinely and are ineffectual for a meaningful number of men. In recent years gene and stem cell-based therapies targeted at the penile endothelium have been gaining momentum in preclinical studies. These early studies reveal that gene and stem cell-based therapies may be both enduring and efficacious, and may eventually lead to a cure for ED. The following review will highlight our current understanding of endothelial-specific gene and stem cell-based therapies performed to date in a number of experimental animal models.

Objective We tested the hypothesis that endothelial proliferator-activated receptor-gamma (PPARγ) protects against vascular thrombosis using a transgenic mouse model expressing a PPARγ mutant (E-V290M) selectively in endothelium. Approach and Results The time to occlusive thrombosis of the carotid artery was significantly shortened in E-V290M mice compared with non-transgenic (non-Tg) littermates after either chemical injury with ferric chloride (5.1±0.2 vs. 10.1±3.3 minutes; P = 0.01) or photochemical injury with rose bengal (48±9 vs. 74±9 minutes; P = 0.04). Gene Set Enrichment Analysis demonstrated upregulation of NF-κB target genes, including P-selectin, in aortic endothelial cells from E-V290M mice (P < 0.001). Plasma P-selectin and carotid artery P-selectin mRNA were elevated in E-V290M mice (P < 0.05). P-selectin-dependent leukocyte rolling on mesenteric venules was increased in E-V290M mice compared with non-Tg mice (53±8 vs. 25±7 per minute; P = 0.02). The shortened time to arterial occlusion in E-V290M mice was reversed by administration of P-selectin blocking antibodies or neutrophil-depleting antibodies (P = 0.04 and P = 0.02, respectively) prior to photochemical injury. Conclusions Endothelial PPARγ protects against thrombosis through a mechanism that involves downregulation of P-selectin expression and diminished P-selectin-mediated leukocyte-endothelial interactions.