Inhibition of RhoA/Rho kinase pathway and smooth muscle contraction by hydrogen sulfide

Abstract

Hydrogen sulfide (H2S) plays an important role in smooth muscle relaxation. Here, we investigated the expression of enzymes in H2S synthesis and the mechanism regulating colonic smooth muscle function by H2S. Expression of cystathionine‐γ‐lyase (CSE), but not cystathionine‐β‐synthase (CBS), was identified in the colonic smooth muscle of rabbit, mouse, and human. Carbachol (CCh)‐induced contraction in rabbit muscle strips and isolated muscle cells was inhibited by l‐cysteine (substrate of CSE) and NaHS (an exogenous H2S donor) in a concentration‐dependent fashion. H2S induced S‐sulfhydration of RhoA that was associated with inhibition of RhoA activity. CCh‐induced Rho kinase activity also was inhibited by l‐cysteine and NaHS in a concentration‐dependent fashion. Inhibition of CCh‐induced contraction by l‐cysteine was blocked by the CSE inhibitor, dl‐propargylglycine (DL‐PPG) in dispersed muscle cells. Inhibition of CCh‐induced Rho kinase activity by l‐cysteine was blocked by CSE siRNA in cultured cells and DL‐PPG in dispersed muscle cells. Stimulation of Rho kinase activity and muscle contraction in response to CCh was also inhibited by l‐cysteine or NaHS in colonic muscle cells from mouse and human. Collectively, our studies identified the expression of CSE in colonic smooth muscle and determined that sulfhydration of RhoA by H2S leads to inhibition of RhoA and Rho kinase activities and muscle contraction. The mechanism identified may provide novel therapeutic approaches to mitigate gastrointestinal motility disorders.

Cytoskeletal Arrest: An Anoxia Tolerance Mechanism

“…Effects of gasotransmitters are induced, in part, through post-translational modifications: S-sulfhydration by H 2 S, S-nitrosylation by NO, and carbonylation by CO [ 216 ]. H 2 S inhibits RhoA actomyosin contraction [ 217 , 218 ], seemingly through S-sulfhydration [ 219 ]. In neurons, H 2 S can inhibit RhoA through an unknown mechanism of RhoA phosphorylation, and this modification confers increased resistance to hypoxic/reoxygenation injury [ 220 ].…”

The role of gasotransmitters in neonatal physiology

“…Metabolism of H 2 S in the GI tract.-Due to the presence of mainly sulfate-reducing bacteria, which reduce inorganic sulfate (SO 4 2− ) to H 2 S, and other bacteria that reduce cysteine and methionine to H 2 S, the adult human gastrointestinal tract, especially the colon, is a site of significant H 2 S metabolism and bioactivity [254][255][256]. The GI tract also contains the CSE and CBS, which produce H 2 S from cysteine, especially in the colonic epithelial, smooth muscle, and neuronal cells, and interstitial cells of Cajal, in both animals and humans [257][258][259][260]. Similar to both NO and CO, H 2 S was historically regarded as a toxin in the GI tract.…”

“…where it has mainly been implicated in the modulation of gastric motility through its hyperpolarization and relaxation of enteric smooth muscle cells [261,262], involving the Ssulfhydration and activation of K ATP channels, inhibition of Rho/RhoA, [258], inhibition of both L-type Ca 2+ and BK channels [263], or through crosstalk with NO [264,265]. Similar to NOS and HO-2, expression of CSE and CBS is reduced in Hirschsprung's disease [257], demonstrating the possible importance of H 2 S to normal GI motility function in a neonatal or pediatric population group.…”

Regulation of vascular tone homeostasis by NO and H2S: Implications in hypertension

“…Inhibition of ROK activity by S -sulfhydration following NaSH administration has been reported in colonic smooth muscle [301]; which can give insight into the mechanism of action of H 2 S on Rho kinase activity in VSM. H 2 S promotes PDE 5 sulfhydration, inhibits its dimerization and activity, giving rise to cGMP levels in vascular tissues [196].…”