Cystathionine γ Lyase Sulfhydrates the RNA Binding Protein Human Antigen R to Preserve Endothelial Cell Function and Delay Atherogenesis

Abstract

-Hydrogen sulfide (HS), generated by cystathionine γ lyase (CSE), is an important endogenous regulator of vascular function. The aim of the present study was to investigate the control and consequences of CSE activity in endothelial cells under physiological and pro-atherogenic conditions. -Endothelial cell CSE knock out mice were generated and lung endothelial cells were studied (gene expression, protein sulfhydration and monocyte adhesion). Mice were crossed onto the ApoE background and atherogenesis (partial carotid artery ligation) was monitored over 21 days. CSE expression, HS bioavailability and amino acid profiling were also performed using human material. -The endothelial cell-specific deletion of CSE selectively increased the expression of CD62E and elevated monocyte adherence in the absence of an inflammatory stimulus. Mechanistically, CD62E mRNA was more stable in endothelial cells from CSE-deficient mice, an effect attributed to the attenuated sulfhydration and dimerization of the RNA-binding protein HuR. CSE expression was upregulated in mice following partial carotid artery ligation as well as in atheromas from human subjects. Despite the increase in CSE protein, circulating and intra-plaque HS levels were reduced, a phenomenon that could be attributed to the serine phosphorylation (on Ser377) and inhibition of the enzyme, most likely due to increased IL-1β. Consistent with the loss of HS, HuR sulfhydration was attenuated in atherosclerosis, and resulted in the stabilization of HuR-target mRNAs e.g. CD62E and cathepsin S, both of which are linked with endothelial cell activation and atherosclerosis. The deletion of CSE from endothelial cells was associated with the accelerated development of endothelial dysfunction and atherosclerosis, effects that were reversed upon treatment with a HS donor. Finally, in mice and humans, plasma levels of the CSE substrate; L-cystathionine, negatively correlated with vascular reactivity and HS levels indicating its potential use as a biomarker for vascular disease. -The constitutive S-sulfhydration of HuR (on Cys13) by CSE-derived HS prevents its homo-dimerization and activity which attenuates the expression of target proteins such as CD62E and cathepsin S. However, as a consequence of vascular inflammation the beneficial actions of CSE-derived HS are lost due to the phosphorylation and inhibition of the enzyme.

From primordial gas to the medicine cabinet

“…Interestingly, aortic valves with calcification expressed more CSE but produced less H 2 S. Although not directly tested in the study, it is possible that CSE in calcified tissue is hyperphosphorylated on S377, leading to reduced activity. A similar finding has been recently reported for CSE in atheromas (Bibli et al, ). Based on their findings, the authors proposed that H 2 S donors might be useful in the treatment of valve calcification.…”

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

“…In keeping with our hypothesis that CAVD is a condition of perturbed H 2 S bioavailability, we found a deficiency in the generation of H 2 S in human AS valves in spite of the elevated expression of CSE. This contradiction can be resolved by the observations of Bibli et al, (2019), who found a markedly decreased H 2 S production after phosphorylation of Ser 377 of CSE, resulting in enzyme inactivation. As such, therapeutic supplementation of H 2 S using H 2 S donor molecules such as AP72 or other novel compounds that are currently under preclinical or clinical investigation by us and others may offer a novel approach to prevent valvular calcification in CAVD and related conditions.…”

Role of Endothelial Dysfunction in Cardiovascular Diseases: The Link Between Inflammation and Hydrogen Sulfide

“…However, in recent years, more studies support that H 2 S could inhibit the process of endothelial cell inflammation (Wen et al, 2018). For instance, specific endothelial deletion of CSE is associated with the development of endothelial inflammation and atherosclerosis, effects that are reversed on treatment with a polysulfide donor (Bibli et al, 2019). H 2 S treatment reduces the increases in inflammatory mediators such as vascular cell adhesionmolecule-1 (VCAM-1), intercellular adhesionmolecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) in endothelial cell induced by tumour necrosis factor-a (TNF-a), and the underlying mechanism of this protective effect is primarily mediated by inhibition of soluble TNF-a shedding and its relevant MCP-1 release (Perna et al, 2013).…”