Skeletal Muscle-derived FSTL1 Starting up Angiogenesis by Regulating Endothelial Junction via Activating Src Pathway Can be Upregulated by Hydrogen Sulfide

Hydrogen sulfide (H₂S) promotes microangiogenesis and revascularization after ischemia. Neovascularization starts with the destruction of intercellular junctions and is accompanied by various endothelial cell angiogenic behaviors. Follistatin-like 1 (FSTL1) is a cardiovascular-protective myokine that works against ischemic injury. The present study examined whether FSTL1 was involved in H₂S-induced angiogenesis and explored the underlying molecular mechanism. We observed that H₂S accelerated blood perfusion after ischemia in the mouse hindlimb ischemia model. Western blot analysis showed that H₂S stabilized FSTL1 transcript and increased FSTL1 and Human antigen R (HuR) levels in skeletal muscle. RNA interference HuR significantly inhibited the H₂S-promoted increase in FSTL1 levels. Exogenous FSTL1 promoted the wound healing migration of human umbilical vein endothelial cell (HUVEC) and increased monolayer endothelial barrier permeability. Immunostaining showed that FSTL1 increased inter-endothelial gap formation and decreased VE-Cadherin, Occludin, Connexin-43, and Claudin-5 expression. In addition, FSTL1 significantly increased the phosphorylation of Src and VEGFR2/KDR/Flk-1. However, that the Src Inhibitor, not the VEGFR2/KDR/Flk-1 inhibitor, could block FSTL1-induced effects in angiogenesis. In conclusion, we demonstrated that H₂S could upregulate the expression of FSTL1 by increasing the HuR levels in skeletal muscle, and paracrine FSTL1 could initiate angiogenesis by opening intercellular junctions via the Src signaling pathway.

Angiogenesis; Endothelial function; FSTL1; H2S; Src tyrosine phosphorylation.