Grant: Travel Awards - Institute Community Support

Nitric oxide (NO) is a main regulatory determinant of vascular homeostasis. Endothelial NO synthase (eNOS), the main NO-producing enzyme in the vascular walls, can be regulated by posttranslational modifications, such as phosphorylation and S-nitrosylation. In the present study, we found that H2S stimulates NO production via S-sulfhydration modification of eNOS. Treatment with dithiothreitol abolished H2S-mediated eNOS S-sulfhydration and NO production in endothelial cells. GSNO (NO-donor) reduced the S-sulfhydration effect of H2S on eNOS, while GSNO alone had little effect on eNOS S-sulfhydration. Treatment with NaHS and GSNO has divergent effect on S-sulfhydration and S-nitrosylation of eNOS. Furthermore, incubation of endothelial cell lysates with NO donor decreased eNOS dimer stability but increased the monomer formation. Inhibition of H2S production by DL-propargylglycine decreased the dimer formation of eNOS in endothelial cells. The ratio of eNOS monomer to functional dimer in aortic tissue was significantly higher in wild type mice than in CSE-knockout which has a targeted deletion of the CSE gene, the major H2S- producing enzyme in vascular tissues. In addition, incubation of endothelial cell lysates with NO and H2S together restored the stability of the eNOS dimer. Mutation of eNOS protein at cysteine 443 eliminated eNOS S-sulfhydration and S-nitrosylation as well as dimer formation. In summary, H2S induces eNOS S-sulfhydration and causes eNOS dimer stabilization in endothelial cells. H2S may be a valuable therapeutic agent for endothelial dysfunction and increases the functional eNOS stability in vascular tissues.