Hydrogen Sulfide Preserves Endothelial Nitric Oxide Synthase Function by Inhibiting Proline-Rich Kinase 2: Implications for Cardiomyocyte Survival and Cardioprotection

Hydrogen sulfide (H 2 S) exhibits beneficial effects in the cardiovascular system, many of which depend on nitric oxide (NO). Proline-rich tyrosine kinase 2 (PYK2), a redox-sensitive tyrosine kinase, directly phosphorylates and inhibits endothelial NO synthase (eNOS). We investigated the ability of H 2 S to relieve PYK2-mediated eNOS inhibition and evaluated the importance of the H 2 S/PYK2/eNOS axis on cardiomyocyte injury in vitro and in vivo. Exposure of H9c2 cardiomyocytes to H 2 O 2 or pharmacologic inhibition of H 2 S production increased PYK2 (Y402) and eNOS (Y656) phosphorylation. These effects were blocked by treatment with Na 2 S or by overexpression of cystathionine γ -lyase (CSE). In addition, PYK2 overexpression reduced eNOS activity in a H 2 S-reversible manner. The viability of cardiomyocytes exposed to Η 2 Ο 2 was reduced and declined further after the inhibition of H 2 S production. PYK2 downregulation, l-cysteine supplementation, or CSE overexpression alleviated the effects of H 2 O 2 on H9c2 cardiomyocyte survival. Moreover, H 2 S promoted PYK2 sulfhydration and inhibited its activity. In vivo, H 2 S administration reduced reactive oxygen species levels, as well as PYK2 (Y402) and eNOS (Y656) phosphorylation. Pharmacologic blockade of PYK2 or inhibition of PYK2 activation by Na 2 S reduced myocardial infarct size in mice. Coadministration of a PYK2 inhibitor and Na 2 S did not result in additive effects on infarct size. We conclude that H 2 S relieves the inhibitory effect of PYK2 on eNOS, allowing the latter to produce greater amounts of NO, thereby affording cardioprotection. Our results unravel the existence of a novel H 2 S-NO interaction and identify PYK2 as a crucial target for the protective effects of H 2 S under conditions of oxidative stress.