Hydrogen sulfide suppresses endoplasmic reticulum stress-induced endothelial-to-mesenchymal transition through Src pathway.

Aims: Hydrogen sulfide (H2S) ameliorates cardiac fibrosis in several models by suppressing endoplasmic reticulum (ER) stress. Endothelial-to-mesenchymal transition (EndMT) is implicated in the development of cardiac fibrosis. Therefore, we investigated whether H2S could attenuate EndMT by suppressing ER stress.
Main Methods: ER stress was induced by tunicamycin (TM) and thapsigargin (TG) and inhibited by 4-phenylbutyrate (4-PBA) in human umbilical vein endothelial cells (HUVECs). ER stress and EndMT were measured by Western blot, Real-Time PCR and immunofluorescence staining. Inhibition Smad2 and Src pathway were performed by specific inhibitors and siRNA. Ultrastructural examination was detected by transmission electron microscope. The functions of HUVECs were investigated by cell migration assay and tube formation in vitro.
Key Findings: Under ER stress, the expression of endothelial marker CD31 significantly decreased while mesenchymal markers α-SMA, vimentin and collagen 1 increased which could be inhibited by 4-PBA. Moreover, HUVECs changed into a fibroblast-like appearance with the activation of Smad2 and Src kinase pathway. After inhibiting Src pathway, EndMT would be significantly inhibited. TM reduced H2S levels in cell lysate and H2S pretreatment could preserve endothelial cell appearance with decreased ER stress and ameliorated dilation of ER. H2S could also downregulate the mesenchymal marker expression, and upregulate the endothelial markers expression, accompanied with the suppression of Src pathway. Moreover, H2S partially restored the capacity of migration and tube formation in HUVECs.
Significance: These results revealed that H2S could protect against ER stress-induced EndMT through Src pathway, which may be a novel role for the cardioprotection of H2S.
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