Differential Effects of Cystathionine-γ-lyase-Dependent Vasodilatory H2S in Periadventitial Vasoregulation of Rat and Mouse Aortas

Background: Hydrogen sulfide (H2S) is a potent vasodilator. However, the complex mechanisms of vasoregulation by H2S are not fully understood. We tested the hypotheses that (1) H2S exerts vasodilatory effects by opening KCNQ-type voltage-dependent (K-v) K+ channels and (2) that H2S-producing cystathionine-gamma-lyase (CSE) in perivascular adipose tissue plays a major role in this pathway. Methodology/Principal Findings: Wire myography of rat and mouse aortas was used. NaHS and 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (ADTOH) were used as H2S donors. KCNQ-type K-v channels were blocked by XE991. 4-Propargylglycine (PPG) and beta-cyano-l-alanine (BCA), or 2-(aminooxy)-acetic acid (AOAA) were used as inhibitors of CSE or cystathionine-beta-synthase (CBS), respectively. NaHS and ADTOH produced strong vasorelaxation in rat and mouse aortas, which were abolished by KCNQ channel inhibition with XE991. Perivascular adipose tissue (PVAT) exerted an anticontractile effect in these arteries. CSE inhibition by PPG and BCA reduced this effect in aortas from rats but not from mice. CBS inhibition with AOAA did not inhibit the anticontractile effects of PVAT. XE991, however, almost completely suppressed the anticontractile effects of PVAT in both species. Exogenous l-cysteine, substrate for the endogenous production of H2S, induced vasorelaxation only at concentrations >5 mmol/l, an effect unchanged by CSE inhibition. Conclusions/Signficance: Our results demonstrate potent vasorelaxant effects of H2S donors in large arteries of both rats and mice, in which XE991-sensitive KCNQ-type channel opening play a pivotal role. CSE-H2S seems to modulate the effect of adipocyte-derived relaxing factor in rat but not in mouse aorta. The present study provides novel insight into the interaction of CSE-H2S and perivascular adipose tissue. Furthermore, with additional technical advances, a future clinical approach targeting vascular H2S/KCNQ pathways to influence states of vascular dysfunction may be possible.