Induction of inactive TGF-β1 monomer formation by hydrogen sulfide contributes to its suppressive effects on Ang II- and TGF-β1-induced EMT in renal tubular epithelial cells

Highlights: • H₂S has anti-fibrotic actions with little information available about its mechanisms. • Ang II induced EMT in renal tubular epithelial cells via TGF-β. • H₂S inhibited Ang II- and TGF-β-induced EMT. • H₂S suppressed Ang II-induced activation of TGF-β. • H₂S inactivated TGF-β via cleavage of the disulfide bonds. Hydrogen sulfide (H₂S), an endogenous gas mediator with multifaced biological functions, has been shown to be effective in the prevention and treatment of renal sclerosis in several models of chronic renal diseases. The mechanisms involved are still unclear. Given that Ang II- and TGF-β-induced renal tubular epithelial-mesenchymal transition (EMT) is a pivotal cellular event leading to renal sclerosis, we examined whether and how H₂S intervened the processes of EMT. Ang II stimulated EMT in renal tubular epithelial cells, as indicated by the increased level of α-smooth muscle actin and a decreased level of E-cadherin. This effect of Ang II was blocked by a TGF-β receptor kinase inhibitor, indicative of a mediating role of TGF-β. Consistently, Ang II stimulated TGF-β activation and addition of the exogenous TGF-β1 also induced EMT. In the presence of H₂S donor NaHS, the EMT-promoting actions of Ang II and TGF-β1 were abolished, which was associated with a reduced TGF-β activity. Further analysis using a human recombinant active TGF-β1 revealed that H₂S cleaved the disulfide bond in the dimeric active TGF-β1 and promoted the formation of inactive TGF-β1 monomer. Collectively, these results indicate that H₂S counteracted Ang II- and TGF-β1-induced EMT through mechanisms involving direct inactivation of TGF-β1. Our study thus provides novel mechanistic insight into the anti-fibrotic actions of H₂S and suggest that H₂S could be used to treat renal sclerotic diseases.