Hydrogen sulfide inhibits calcification of heart valves; implications for calcific aortic valve disease.

Calcification of heart valves is a frequent pathological finding in chronic kidney disease and in elderly patients. Hydrogen sulfide (H₂ S) may exert anti-calcific actions. Here we investigated H₂ S as an inhibitor of valvular calcification and to identify its targets in the pathogenesis.

Effects of H₂ S on osteoblastic transdifferentiation of valvular interstitial cells (VIC) isolated from samples of human aortic valves were studied using immunohistochemistry and western blots. We also assessed H2S on valvular calcification in apolipoprotein E-deficient (ApoE^-/- ) mice.

In human VIC, H₂ S from donor compounds (NaSH, Na₂ S, GYY4137, AP67, and AP72) inhibited mineralization/osteoblastic transdifferentiation, dose-dependently in response to phosphate. Accumulation of calcium in the extracellular matrix and expression of osteocalcin and alkaline phosphatase was also inhibited. RUNX2 was not translocated to the nucleus and phosphate uptake was decreased. Pyrophosphate generation was increased via up-regulating ENPP2 and ANK1. Lowering endogenous production of H₂ S by concomitant silencing of cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) favoured VIC calcification. analysis of human specimens revealed higher Expression of CSE in aorta stenosis valves with calcification (AS) was higher than in valves of aortic insufficiency (AI). In contrast, tissue H₂ S generation was lower in AS valves compared to AI valves. Valvular calcification in ApoE^-/- mice on a high-fat diet was inhibited by H₂ S.

The endogenous CSE-CBS/H₂ S system exerts anti-calcification effects in heart valves providing a novel therapeutic approach to prevent hardening of valves.