Imbalance of Homocysteine and H 2 S: Significance, Mechanisms, and Therapeutic Promise in Vascular Injury

While the role of hyperhomocysteinemia in cardiovascular pathogenesis continuously draws attention, deficiency of hydrogen sulfide (H 2 S) has been growingly implicated in cardiovascular diseases. Generation of H 2 S is closely associated with the metabolism of homocysteine via key enzymes such as cystathionine β -synthase (CBS) and cystathionine γ -lyase (CSE). The level of homocysteine and H 2 S is regulated by each other. Metabolic switch in the activity of CBS and CSE may occur with a resultant operating preference change of these enzymes in homocysteine and H 2 S metabolism. This paper presented an overview regarding (1) linkage between the metabolism of homocysteine and H 2 S, (2) mutual regulation of homocysteine and H 2 S, (3) imbalance of homocysteine and H 2 S in cardiovascular disorders, (4) mechanisms underlying the protective effect of H 2 S against homocysteine-induced vascular injury, and (5) the current status of homocysteine-lowering and H 2 S-based therapies for cardiovascular disease. The metabolic imbalance of homocysteine and H 2 S renders H 2 S/homocysteine ratio a potentially reliable biomarker for cardiovascular disease and development of drugs or interventions targeting the interplay between homocysteine and H 2 S to maintain the endogenous balance of these two molecules may hold an even bigger promise for management of vascular disorders than targeting homocysteine or H 2 S alone.