Hydrogen Sulfide Protects Hyperhomocysteinemia-Induced Renal Damage by Modulation of Caveolin and eNOS Interaction

The accumulation of homocysteine (Hcy) during chronic kidney failure (CKD) can exert toxic effects on the glomeruli and tubulo-interstitial region. Among the potential mechanisms, the formation of highly reactive metabolite, Hcy thiolactone, is known to modify proteins by N-homocysteinylation, leading to protein degradation, stress and impaired function. Previous studies documented impaired nitric oxide production and altered caveolin expression in hyperhomocysteinemia (HHcy), leading to endothelial dysfunction. The aim of this study was to determine whether Hhcy homocysteinylates endothelial nitric oxide synthase (eNOS) and alters caveolin-1 expression to decrease nitric oxide bioavailability, causing hypertension and renal dysfunction. We also examined whether hydrogen sulfide (H₂S) could dehomocysteinylate eNOS to protect the kidney. WT and Cystathionine β-Synthase deficient (CBS+/-) mice representing HHcy were treated without or with sodium hydrogen sulfide (NaHS), a H₂S donor (30 µM), in drinking water for 8 weeks. Hhcy mice (CBS+/-) showed low levels of plasma H₂S, elevated systolic blood pressure (SBP) and renal dysfunction. H₂S treatment reduced SBP and improved renal function. Hhcy was associated with homocysteinylation of eNOS, reduced enzyme activity and upregulation of caveolin-1 expression. Further, Hhcy increased extracellular matrix (ECM) protein deposition and disruption of gap junction proteins, connexins. H₂S treatment reversed the changes above and transfection of triple genes producing H₂S (CBS, CSE and 3MST) showed reduction of vascular smooth muscle cell proliferation. We conclude that during Hhcy, homocysteinylation of eNOS and disruption of caveolin-mediated regulation leads to ECM remodeling and hypertension, and H₂S treatment attenuates renovascular damage.