Background and Aims. Vascular smooth muscle cells (VSMCs) are central components of atherosclerotic plaque. Loss of VSMCs through apoptotic cell death can cause fibrous cap thinning, necrotic core formation, and calcification that may destabilize plaque. Elevated glucocorticoid levels caused by psychological stress promote VSMC apoptosis and can exacerbate atherosclerosis in mice and humans. Changes in the levels of antiapoptosis microRNA-25 (miR-25) have been linked with heart disease, inflammation, VSMC phenotype, oxidative stress, and apoptosis. Here, we investigated the pathways and mechanisms of glucocorticoid-induced apoptosis of mouse VSMCs and the protective role of miR-25. Methods. Primary mouse VSMCs were cultured +/- corticosterone for 48 h. Apoptosis, ROS, apoptotic protein activities, miR-25, MOAP1, a miR-25 target, and p70S6 kinase were quantified at intervals. The roles of miR-25 were assessed by treating cells with lenti-pre-miR-25 and anti-miR-25. Results. VSMC apoptosis, caspase-3 activity, and Bax were increased by corticosterone, and cell death was paralleled by marked loss of miR-25. Protection was conferred by pre-miR-25 and exacerbated by anti-miR-25. Pre-miR-25 conferred reduced expression of the proapoptotic protein MOAP1, and the protective effects of pre-miR-25 were abrogated by overexpressing MOAP1. The antiapoptotic effects of miR-25 were paralleled by inhibition of the p70S6K pathway, a convergence target for the survival signaling pathways, and protection by pre-miR-25 was abrogated by the p70S6k inhibitor rapamycin. Conclusions. MicroRNA-25 blocks corticosterone-induced VSMC apoptosis by targeting MOAP1 and the p70S6k pathway. Therapeutic manipulation of miR-25 may reduce atherosclerosis and unstable plaque formation associated with chronic stress.

Chemokine ligand 25 (CCL25) and chemokine receptor 9 (CCR9) are important regulators of migration, proliferation and apoptosis in leukocytes and cancer cells. Blocking of the CCR9/CCL25 signal has been demonstrated to be a potential novel cancer therapy. Research into CCR9 and CCL25 has revealed their associated upstream and downstream signaling pathways; CCR9 is regulated by several immunological factors, including NOTCH, interleukin 2, interleukin 4 and retinoic acid. NOTCH in particular, has been revealed to be a crucial upstream regulator of CCR9. Furthermore, proteins including matrix metalloproteinases, P‑glycoprotein, Ezrin/Radixin/Moesin and Livin are regulated via phosphatidylinositol‑3 kinase/ protein kinase B, which are in turn stimulated by CCR9/CCL25. This is a review of the current literature on the functions and signaling pathways of CCR9/CCL25.

EPCs play important roles in the maintenance of vascular repair and health. Aging is associated with both reduced numbers and functional impairment of EPCs, leading to diminished angiogenic capacity, impaired cardiac repair, and increased risk for cardiovascular disease (CVD). The molecular mechanisms that govern EPC function in cardiovascular health are not fully understood, but there is increasing evidence that microRNAs (miRNAs) play key roles in modulating EPC functionality, endothelial homeostasis, and vascular repair. We aimed to determine how aging alters endothelial progenitor (EPC) health and functionality by altering key miRNA-mRNA pathways. To identify key miRNA-mRNA pathways contributing to diminished EPC functionality associated with aging, microRNA and mRNA profiling were conducted in EPCs from young and aged C57BL/6 mice. We identified a complex aging-associated regulatory network involving two miRNAs—miR-29c-3p and -126a—that acted in tandem to impair vascular endothelial growth factor signaling through targeting Klf2 and Spred1, respectively. The modulation of components of the miR-29c-3p–Klf2–miR-126a–Spred-1–Vegf signaling pathway altered EPC self-renewal capacity, vascular tube formation, and migration in vitro, as well as cardiac repair in vivo. The miR-29c-3p–Klf2–miR-126a–Spred1–Vegf signaling axis plays a critical role in regulating the aging-associated deficits in EPC-mediated vascular repair and CVD risk.