Extracellular vesicle-mediated transfer of BACH1 from macrophage promotes vascular smooth muscle cell proliferation via suppressing FNDC5 expression

Abstract Objectives: Extracellular vesicles (EVs) derived from macrophages play crucial roles in the proliferation of vascular smooth muscle cells (VSMCs) and hypertensive vascular remodeling. However, the role of BTB and CNC homology 1 (BACH1) in the EVs regulates VSMC proliferation and vascular remodeling is still unclear. Methods: Normotensive Wistar-Kyoto rat (WKY) and spontaneously hypertensive (SHR) rat were used as animal models. Primary macrophages and VSMCs were used to study the molecular mechanism. Ultracentrifugation was performed to isolate EVs from macrophages collected from WKY rats (WKY-EVs) and SHR rats (SHR-EVs). Results: The level of BACH1 in SHR-EVs was significantly higher than that in WKY-EVs. Compared with WKYs, the expression of fibronectin type III domain (FNDC5) in SHR VSMCs decreased, while the content of BACH1 increased. Double luciferase reporter analysis showed that FNDC5 was the target gene of BACH1. FNDC5 improved the proliferation-promoting effect of SHR-EVs in VSMCs. Moreover, SHR-EVs inhibited the expression of FNDC5, but promoted proliferation in VSMCs, and these effects were reversed by the treatment with SHR-EVs from the BACH1 knockdown-treated macrophages. Knockdown of BACH1 reversed the down-regulation of FNDC5, hypertension, VSMC proliferation and vascular remodeling in SHR. Repeated intravenous injection of SHR-EVs increased blood pressure and vascular BACH1 contents, and promoted vascular remodeling of WKYs and SHRs, while WKY-EVs decreased vascular BACH1 and weakened hypertension and vascular remodeling of SHR. Conclusion: Increased BACH1 in the SHR-EVs enhances VSMC proliferation in SHR by inhibiting FNDC5 expression, and that intervening EV-mediated transfer of BACH1 and inhibition of BACH1 expression in macrophages or up-regulation of FNDC5 may be effective therapeutic strategies in attenuating VSMC proliferation in hypertensive vascular remodeling.