No abstract

Vascular endothelial cells (ECs) at arterial branches and curvatures experience disturbed blood flow and induce a quiescent-to-activated phenotypic transition of the adjacent smooth muscle cells (SMCs) and a subsequent smooth muscle hyperplasia. However, the mechanism underlying the flow pattern-specific initiation of EC-to-SMC signaling remains elusive. Our previous study demonstrated that endothelial microRNA-126-3p (miR-126-3p) acts as a key intercellular molecule to increase turnover of the recipient SMCs, and that its release is reduced by atheroprotective laminar shear (12 dynes/cm 2 ) to ECs. Here we provide evidence that atherogenic oscillatory shear (0.5 ± 4 dynes/cm 2 ), but not atheroprotective pulsatile shear (12 ± 4 dynes/cm 2 ), increases the endothelial secretion of nonmembrane-bound miR-126-3p and other microRNAs (miRNAs) via the activation of SNAREs, vesicleassociated membrane protein 3 (VAMP3) and synaptosomalassociated protein 23 (SNAP23). Knockdown of VAMP3 and SNAP23 reduces endothelial secretion of miR-126-3p and miR-200a-3p, as well as the proliferation, migration, and suppression of contractile markers in SMCs caused by EC-coculture. Pharmacological intervention of mammalian target of rapamycin complex 1 in ECs blocks endothelial secretion and EC-to-SMC transfer of miR-126-3p through transcriptional inhibition of VAMP3 and SNAP23. Systemic inhibition of VAMP3 and SNAP23 by rapamycin or periadventitial application of the endocytosis inhibitor dynasore ameliorates the disturbed flow-induced neointimal formation, whereas intraluminal overexpression of SNAP23 aggravates it. Our findings demonstrate the flow-pattern-specificity of SNARE activation and its contribution to the miRNA-mediated EC-SMC communication. T he interaction between hemodynamics and vascular endothelium is an important determinant of vascular homeostasis (1). In the straight part of the arteries, endothelial cells (ECs) are exposed to laminar blood flow with high shear stress that protects these parts of the vessels from atherogenesis, whereas in the branches and curvatures, the ECs experiencing disturbed flow with reciprocating and low shear stress stimulate the smooth muscle cells (SMCs) within the tunica media to become proliferative and migratory. The activated SMCs migrate into the intima, where they come into close contact with ECs and undergo phenotypic changes to lead to atherosclerosis (2). We recently demonstrated that vascular ECs repress expressions of forkhead box O3, B-cell lymphoma 2, and insulin receptor substrate 1 in the adjacent SMCs by producing microRNA-126-3p (miR-126-3p), and hence induce SMC turnover, and that the application of atheroprotective laminar shear (LS) at 12 dynes/cm 2 to ECs inhibits this paracrine effect (3). Although extracellular microRNAs (miRNAs) have been shown to convey messages from donor cells to recipient cells, how fluid shear stress regulates endothelial miRNA secretion remains to be elucidated.Emerging evidence has suggested that extracellular miRNAs can serve as not only pu...