Abstract P1109: Cholesterol Regulation of Hydrogen Sulfide-Mediated Vasodilation

Abstract

Hydrogen sulfide (H 2 S) is produced within the vascular wall by cystathionine γ-lyase (CSE). CSE is expressed throughout the vascular tree however, the sensitivity to H 2 S-induced dilation in small resistance size arteries (<100 μm) is greater than the dilation sensitivity in large arteries (>300 μm). Although H 2 S can induce vasodilation in different size arteries, it is not clear how H 2 S signaling mechanisms differ in large and small arteries, garnering H 2 S-induced dilation prominent and important in small resistance arteries. We previously demonstrated that within endothelial cells, H 2 S-mediated vasodilation involves activation of transient receptor potential cation channel subfamily V member 4 (TRPV4)-dependent Ca 2+ influx and large conductance Ca 2+ -activated potassium (BK) channel. Based on previous reports that membrane cholesterol negatively regulates TRPV4 mobility and BK activity, we hypothesized that H 2 S-mediated vasodilation is diminished by membrane cholesterol and that lower sensitivity in large arteries might be due to higher levels of membrane cholesterol in endothelial cells. Isolated pressurized mesenteric arteries (300-380 μm) were treated luminally with vehicle (HEPES) or the cholesterol-depleting agent, methyl β cyclodextran (MBCD, 100 μM) and exposed to H 2 S donor, NaHS (10 μM). Analysis of H 2 S-induced dilation (expressed as % Ca 2+ free diameter) showed that MBCD treatment significantly enhanced H 2 S-mediated vasodilation (vehicle: 1.2% ± 1.2, MBCD: 8.9% ± 2.3, p = 0.012, n = 5 animals/group). Additionally, mesenteric arteries of different orders were luminally loaded with the fluorescent cholesterol-binding agent, filipin III (20 μg/ml, ex/em: 405/461 nm) the endothelial glycocalyx marker DyLight 594-tomato lectin (20 μg/ml, ex/em: 561/613 nm) and the nuclei stain SYTOX green (ex/em: 488/518 nm). Analysis of endothelial membrane cholesterol content (filipin III /tomato lectin fluorescence) was significantly greater in larger arteries (2 nd order: 1.019 ± 0.158, 5 th order: 0.344 ± 0.179, p = 0.0054, n = 3-5 animals/group). These studies suggest that higher membrane cholesterol decreases H 2 S-mediated vasodilation.