ABSTRACT
Rho-kinase activity is a key regulator in the maintenance of corporal vasoconstriction and penile detumescense. Also, importance of l-cysteine/H2S pathway in erectile tissue has been shown; however it is currently unknown the role RhoA/Rho-kinase pathway in H2S-induced inhibition in cavernosal tissue. We investigated the role of RhoA/Rho-kinase pathway in the inhibitory effect of l-cysteine and NaHS, as endogenous and exogenous H2S, respectively, on phenylephrine-induced contractions of mouse cavernosal strips. Phenylephrine, α1 receptor agonist, (10â¯nM-100⯵M) induced a concentration-dependent contraction in CC. l-cysteine (endogenous H2S substrate; 10â¯mM) and exogenous H2S (NaHS; 1â¯mM) significantly inhibited the contractile response to phenylephrine (Pâ¯<â¯0.05). Inhibition of CSE and CBS enzymes by PAG (10â¯mM) and AOAA (1â¯mM), respectively, significantly reversed the inhibitory effects of l-cysteine on phenylephrine-induced contraction (Pâ¯<â¯0.05). Y-27632 (1⯵M), a specific Rho-kinase inhibitor, significantly augmented the inhibitory effect of l-cysteine and NaHS on phenylephrine-induced contraction, and this inhibition was reversed by PAG and AOAA (Pâ¯<â¯0.05). In addition, the formation of H2S was increased by approximately 1.8 fold over basal values after incubation of tissue homogenates with l-cysteine. Y-27632 significantly increased both basal and l-cysteine-induced H2S formation and this augmentation diminished by PAG and AOAA (Pâ¯<â¯0.05). Furthermore, the pMYPT-1 expression was significantly decreased by l-cysteine, NaHS or Y-27632 alone. Also, pMYPT-1 expression was completely abolished by the l-cysteine/NaHS plus Y-27632 combination, and this inhibition was reversed by PAG and AOAA (Pâ¯<â¯0.05). These results suggest that there is an interaction between Rho-kinase and H2S pathways. Rho-kinase may be, at least in part, inhibits CSE/CBS enzymes in mouse corpus cavernosal tissue; however, it is not excluded the other kinases such as PKC and Zip-kinase.
