Atorvastatin ameliorates sildenafil-induced penile erections in experimental diabetes by inhibiting diabetes-induced RhoA/Rho-kinase signaling hyperactivation.

INTRODUCTION

One of the proposed mechanisms responsible for diabetes-related erectile dysfunction (ED) is overactivity of RhoA/ROCK signaling, as seen in experimental models of chemical diabetes.

AIM: Because statins may interfere with RhoA/Rho-kinase (ROCK) signaling through the reduction of geranyl-geranyl pyrophosphate (GGPP), required for RhoA activation, we investigated whether atorvastatin ameliorated diabetes-related ED.

METHODS

Streptozotocin-induced (8 weeks) diabetic rats and alloxan-induced (8 weeks) diabetic rabbits received atorvastatin (5 mg/kg daily) for the last 2 weeks. In vitro contractility studies were conducted in the rabbit model. In the rat model, sildenafil effect on electrical stimulation (ES)-induced erection was investigated. Atorvastatin action was also analyzed using human fetal penile smooth muscle cells (hfPSMCs) exposed to low (5 mM), high (22 mM), and very high (40 mM) glucose.

MAIN OUTCOME MEASURES: Atorvastatin effect on hyperglycemia-induced RhoA/ROCK signaling was evaluated using the ROCK inhibitor Y-27632 in both animal models and by analyzing functional effects downstream to RhoA activation in hfPSMCs.

RESULTS

In both diabetic models, atorvastatin did not affect glycemia, lipid plasma levels, and the hypogonadal state. In diabetic rats, atorvastatin ameliorated the erectile response to the ES of the cavernous nerve and normalized sildenafil effect on erectile function, strongly decreased by diabetes. In penile tissue from diabetic animals, atorvastatin completely restored the diabetes-induced hypersensitivity to Y-27632 and prevented RhoA membrane translocation/activation. In hfPSMCs, high glucose significantly increased not only membrane RhoA expression, but also ROCK activity (increased phosphorylation of the ROCK substrate myosin phosphatase target subunit 1) and several RhoA-dependent functions such as proliferation, migration, and smooth muscle-related gene expression. Atorvastatin restored all the high-glucose-induced effects, an action specifically reverted by GGPP.

CONCLUSION

Atorvastatin improves diabetes-related ED and restores sildenafil responsiveness, most probably by inhibiting RhoA/ROCK signaling, which underlies several high-glucose-induced derangements in penile smooth muscle cell commitment.