HS protects from oxidative stress-driven ACE2 expression and cardiac aging.

Cystathionine gamma-lyase (CSE)-derived hydrogen sulfide (HS) plays an essential role in preserving cardiac functions. Angiotensin-converting enzyme 2 (ACE2) acts as the negative regulator of the renin-angiotensin system, exerting anti-oxidative stress and anti-inflammatory properties within the body. The interplays of CSE/HS signaling and ACE2 in cardiac aging are unclear. In this study, the regulatory roles of HS on ACE2 expression in mouse heart tissue and rat cardiomyocytes under different stress conditions were investigated. It was found that ACE2 protein level was lower in heart tissues from old mice (56-week-old) than young mice (8-week-old), and the knockout of CSE (CSE KO) induced moderate oxidative stress and further inhibited ACE2 protein level in mouse hearts at both young and old age. Incubation of rat cardiac cells (H9C2) with a low dose of HO (50 µM) suppressed ACE2 protein level and induced cellular senescence, which was completely reversed by co-incubation with 30 µM NaHS (a HS donor). Prolonged nutrient excess is an increased risk of heart disorders by causing metabolic dysfunction and cardiac remodeling. We further found high-fat diet feeding stimulated ACE2 expression and induced severe oxidative stress in CSE KO heart in comparison with wild-type heart. Lipid overload in H9C2 cells to mimic a status of nutrient excess also enhanced the expression of ACE2 protein and induced severe oxidative stress and cell senescence, which were significantly attenuated by the supplementation of exogenous HS. Furthermore, the manipulation of ACE2 expression partially abolished the protective role of HS against cellular senescence. These results demonstrate the dynamic roles of HS in the maintenance of ACE2 levels under different levels of oxidative stress, pointing to the potential implications in targeting the CSE/HS system for the interruption of aging and diabetes-related heart disorders.