Hydrogen sulfide lowers hyperhomocysteinemia dependent on cystathionine γ lyase S-sulfhydration in ApoE-knockout atherosclerotic mice

Background and Purpose Hydrogen sulfide donors can block the cardiovascular injury of hyperhomocysteinemia. H2S also lowers serum homocysteine in rats with mild hyperhomocysteinemia, but the pharmacological mechanism is unknown. The present study investigated the mechanism(s) involved. Experimental Approach ApoE-knockout mice were fed a Paigen diet and L-methionine in drinking water for 16 weeks to create a mouse model of atherosclerosis with hyperhomocysteinemia. H2S donors (NaHS and GYY4137) were administered by intraperitoneal injection. We also assayed the H2S produced (by methylene blue assay and mito-HS [H2S fluorescence probe]), cystathionine gamma lyase (CSE) mRNA and protein expression, and CSE sulfhydration and nitrosylation and its activity. Key Results H2S donor treatment significantly lowered atherosclerotic plaque area, macrophage infiltration, and serum homocysteine level in the mouse model of atherosclerosis with co-existing hyperhomocysteinemia. mRNA and protein levels of CSE, a key enzyme catalyzing homocysteine trans-sulfuration, were down-regulated with hyperhomocysteinemia, and CSE catalytic activity was inhibited. All these effects were reversed with H2S donor treatment. Hyperhomocysteinemia induced CSE nitrosylation, whereas H2S sulfhydrated CSE at the same cysteine residues. Nitrosylated CSE decreased and sulfhydrated CSE increased its catalytic and binding activities towards L-homocysteine. Mutation of C252, C255, C307, and C310 residues in CSE abolished CSE nitrosylation or sulfhydration and prevented its binding to L-homocysteine. Conclusions and Implications Sulfhydration or nitrosylation of CSE represents a yin/yang regulation of catalysis or binding to L-homocysteine. H2S donor treatment enhanced CSE sulfhydration, thus lowering serum L-homocysteine, which contributed in part to the anti-atherosclerosis effects in ApoE-knockout mice with hyperhomocysteinemia.