β 3 adrenergic receptor activation relaxes human corpus cavernosum and penile artery through a hydrogen sulfide/cGMP-dependent mechanism.

Erectile function is a widely accepted indicator of systemic endothelial activity since from a clinical standpoint erectile dysfunction (ED) often precedes cardiovascular events. Recently it has been described a potential role for β3 adrenoceptor in cardiovascular diseases emphasizing a possible development of new drugs. β3 adrenoceptor stimulation relaxes human corpus cavernosum (HCC) strips in cyclic guanosine monophosphate (cGMP)-dependent and endothelium/nitric oxide (NO)-independent manner. Hydrogen sulfide (H2 S), along with NO, is another gaseous molecule involved in cardiovascular system and as a consequence also in penile erection. Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), the enzymes mainly responsible for H2 S biosynthesis, are constitutively expressed in HCC. CSE rather than CBS is more abundant in human penile tissue. Herein we investigated the involvement of H2 S pathway in β3 adrenoceptor-induced relaxation in HCC and penile artery. Penile artery expresses both CSE and β3 adrenoceptor. BRL37344, a β3 selective agonist, relaxed HCC strips and penile artery rings and this effect was significantly reduced by CSE inhibition. Incubation of HCC and penile artery homogenate with BRL37344 significantly increased H2 S production. This effect was significantly reduced by the inhibition of either CSE or β3 adrenoceptor. Finally, the BRL37344-induced increase in cGMP was reduced by CSE inhibition in both tissues. Thus, BRL37344-induced relaxation in HCC and penile artery occurs in a H2 S/cGMP-dependent manner. In conclusion, β3 /H2 S/cGMP pathway can act as an alternative to NO. Since about 15% of patients do not respond to phosphodiesterase-5 inhibitors, β3 agonists could represent a therapeutic alternative or a useful adjuvant therapy to treat these patients.