Hydrogen sulfide-mediated vasodilation requires heme oxygenase-derived carbon monoxide

Background Hydrogen sulfide (H 2 S) is an important endothelial-derived vasodilator, but the signaling mechanism remains incompletely understood. We previously demonstrated that H 2 S-mediated vasodilation requires transient receptor potential vanilloid type 4 (TRPV4) channels. Because H 2 S has been reported to enhance heme oxygenase (HO) activity and HO-derived carbon monoxide (CO) regulates endothelial signaling, we hypothesized that H 2 S-mediated vasodilation requires HO-2-derived CO. Methods Pressure myography was performed in isolated rat mesenteric arteries to determine the contribution of HO, TRPV4, eBK, and SK/IK channels to H 2 S-mediated vasodilation. We assessed HO-2 persulfidation using a maleimide assay and examined the spatial association between HO-2 and TRPV4 using proximity ligation assays in human aortic endothelial cells. Results H 2 S elicited concentration-dependent vasodilation that was abolished by HO inhibition. Repletion of CO restored H 2 S-mediated vasodilation in the presence of HO inhibition. CO-mediated vasodilation was abolished by TRPV4 and SK/IK inhibition but was unaffected by eBK inhibition. H 2 S increased HO-2 persulfidation and enhanced HO activity. In endothelial cells, HO-2 and TRPV4 exhibited close spatial association. Conclusions These findings support a model in which H 2 S stimulates HO-2-derived CO production, leading to TRPV4-dependent endothelial signaling, SK/IK activation, and vasodilation. Together, the data support an endothelial HO-2/TRPV4/SK/IK signaling domain that contributes to H 2 S-mediated vascular reactivity.