Akt modulation by miR-145 during exercise-induced VSMC phenotypic switching in hypertension

Aims: This study investigated whether long-term exercise can influence vascular smooth muscle cells (VSMCs) phenotypic switching in mesenteric arteries of hypertensive rats, with a focus on the modulation of protein kinase B (PKB/Akt) signaling by microRNA-145 (miR-145). Main methods: In the exercise intervention experiment, mesenteric arteries from 3-month-old spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were isolated for histological observation, phenotypic marker analysis, Akt phosphorylation quantification, and miR-145 evaluation after being subjected to moderate-intensity treadmill training (E) or being sedentary (C) for 8 weeks. In the transfection experiment, VSMCs were harvested to determine Akt phosphorylation and mRNA expressions of the upstream and downstream signaling molecules. Key findings: Calponin, a VSMC contractile marker, was significantly up-regulated in SHR-E relative to SHR-C (P < 0.05); while osteopontin (OPN), a dedifferentiation marker, was down-regulated in SHR-E relative to SHR-C (P < 0.05). Exercise significantly normalized the expression of miR-145 and significantly enhanced Akt phosphorylation (P < 0.05). In VSMCs over-expressing miR-145, Akt phosphorylation was significantly decreased (P < 0.05) with inhibited mRNA of both insulin-like growth factor 1 receptor (IGF-1R) and insulin receptor substrate 1 (IRS-1). In VSMCs transfected with miR-145 inhibitor, Akt phosphorylation and mRNA of IGF-1R and IRS-1 were all down-regulated. miR-145 did not exhibit a clear effect on p70 ribosomal kinase (p70(S6K)), the downstream of Akt, following the transfections. Significance: Overall, exercise remodels arterioles in hypertension and induces VSMCs maintaining contractile phenotype, in which miR-145 appears to be involved by inversely regulating Akt signaling via its upstream signals.