Abstract 263: Role of Micro RNA-21 in Atherosclerosis
Micro RNAs (miR) are short non-coding RNAs that regulate several genes under pathophysiological conditions. Accumulating evidence suggest the involvement of miR in atherogenesis. However, limited information is available about atherogenic miR and the underling mechanisms by which miR affect atherogenesis. Our data shows that 12 weeks of western diet (WD) in LDL receptor-knockout (LDLR-KO) mice upregulated 99 and downregulated 50 miR in the aorta. Among the 41 differentially expressed miR associated with macrophage inflammation and apoptosis, expression of micro RNA-21 (miR-21) was increased by 1.4-fold (P<0.05). WD also increased the expression of miR-21 by 1.5-fold in bone marrow derived macrophages (BMDM). In vitro , LDL, oxidized LDL, acetylated LDL and LPS induced miR-21 by 2-3-fold (P<0.05) and down regulated its target protein PDCD4 in BMDM. Basally, miR-21 deficient BMDM showed increased secretion of IL-6, IL-9 and CXCL-2,-3,-4, and -10 (P<0.05)); and increased early and late apoptosis (2-3-fold, P<0.05). We also observed 40% decrease in the survival of F4/80+ cells during differentiation of bone marrow derived cells isolated from miR-21-KO mice. Stimulation of miR-21-KO BMDM with LPS significantly increased the activation of NF-κB and enhanced the secretion of several pro-inflammatory cytokines including TNFα, IL-6, IL-12 and CXCL-2 (2-10 fold; P<0.05); interferon gamma+LPS polarized the macrophages to pro-inflammatory M1 phenotype (increased expression of CD11c and CD86). Staurosporin and oxidized lipids derived aldehyde 4-hydroxynonenal significantly increased both early and late apoptosis of miR-21-KO BMDM (2-4-fold, P<0.05). This was accompanied by increased cleavage of caspase -3, -7 and -9. Transplantation of bone marrow cells from miR-21-KO into LDLR-KO mice, followed by 12 weeks of WD increased the lesion formation (1.7-fold, P<0.05), apoptosis (3-fold, P<0.05) and necrosis (1.6-fold, P<0.05) in the aortic valve of the chimeric mice. Collectively, these data suggest that miR-21 prevents atherosclerosis, at least in parts, by preventing macrophage apoptosis and inflammation.