Abstract 089: Role of LncRNA Snhg18 in Diabetes Induced Macrophage Dysfunction and Atherosclerosis

Abstract

Atherosclerotic vascular disease is the major cause of mortality in diabetic patients. Evidence from our laboratory and others showed that long non-coding RNAs (lncRNAs) play important roles in diabetic vascular complications. Here we investigated role of lncRNAs in hyperglycemia-induced macrophage dysfunction and accelerated atherosclerosis in diabetes. Hyperglycemia (~300-400 mg/dl) was induced in atherosclerosis-prone ApoE -/- mice by low dose Streptozotocin injections (50mg/kg/day i.p., 5 days) and were sacrificed at 20 weeks’ post diabetes. Aortic root F4/80 immunohistochemistry and morphometric analysis showed increased macrophage infiltration and enhanced atherosclerosis respectively in diabetic vs non-diabetic ApoE -/- mice. RNA-seq analysis identified ~45 up-regulated lncRNAs in bone marrow macrophages (BMM) from diabetic versus non-diabetic ApoE -/- mice. Among these, one of the robustly induced (~7.5 log 2 fold) lncRNA candidate was small nucleolar RNA host gene 18 ( Snhg18) located on mouse chromosome 15. Gene expression analysis by RT-qPCR validated Snhg18 upregulation in BMM from diabetic ApoE -/- mice and in peritoneal macrophages from type 2 diabetic db/db vs control db/+ mice. Moreover, diabetic-ApoE -/- aortic tissue also demonstrated increased expression of Snhg18 as compared to non-diabetic ApoE -/- s . Additionally, Snhg18 was significantly increased in high glucose (HG) (25mM) treated RAW mouse macrophages in vitro . A human ortholog, SNHG18 , located on chromosome 5 was also significantly increased in HG treated human THP1 monocytes. Cellular fractionation of RAW macrophages demonstrated that Snhg18 was localized in both cytoplasmic and nuclear compartments. Overexpression of Snhg18 in RAW macrophages significantly increased expression of proinflammatory ( Il1b , Il6 , and Tnf) and proatherogenic ( Thbs1 ) genes but downregulated a nearby gene, Semaphorin 5A ( Sema5a). These results suggest that diabetes induced lncRNA Snhg18 upregulates macrophage inflammatory phenotype to modulate diabetes induced accelerated macrophage dysfunction and atherosclerosis development.