Abstract 13202: LncRNA-MAP3K4 Regulates Vascular Inflammation Through a P38 MAPK Signaling Pathway and Cis -modulation of MAP3K4

Introduction: Long non-coding RNAs (lncRNAs) are emerging regulators of biological processes in the vessel wall; however, their role in vascular inflammation remains poorly understood. Hypothesis: Identification of inflammation-responsive lncRNAs expressed in the aortic intima may provide novel mechanistic insights in vascular inflammation. Methods: Using RNA-Seq profiling to identify a lncRNA derived specifically from the aortic intima of atherosclerotic mice, we discovered an inflammation-responsive lncRNA, lncRNA-MAP3K4, and evaluated its role in the mechanisms mediating vascular cell inflammation. Results: Aortic expression of lncRNA-MAP3K4 , an intima-enriched and polyadenylated lncRNA , was reduced by 50% with atherosclerotic progression and by 75% following LPS-induced endotoxemia in mice. GapmeR-mediated silencing of lncRNA-MAP3K4 potently reduced mRNA and protein expression of adhesion molecules or chemokines (e.g. ICAM-1, E-selectin, MCP-1) in endothelial cells via a p38-MAPK pathway, and decreased PBMC adhesion to endothelium by 40%. Moreover, lncRNA-MAP3K4 knockdown also reduced inflammatory markers in vascular smooth muscle cells and macrophages. Analyzing the lncRNA-MAP3K4 locus, we found MAP3K4, an upstream kinase of the MAPK cascade, shared the promoter region with lncRNA-MAP3K4. In vitro and in vivo, lncRNA-MAP3K4 and MAP3K4 showed parallel inflammation-responsive expression patterns. lncRNA-MAP3K4 knockdown reduced mRNA and protein expression of MAP3K4 in cis in vessel wall cell types. ChIP-seq data showed chromatin modifications and bidirectional promoter characteristics in the lncRNA-MAP3K4/ MAP3K4 promoter region. MAP3K4 knockdown showed a similar anti-inflammation phenotype as lncRNA-MAP3K4 via a p38-MAPK pathway and cooperativity with lncRNA-MAP3K4 . Conclusions: Deficiency of lncRNA-MAP3K4 markedly reduced inflammation in vascular cells via a p38-MAPK pathway and cis -regulation of MAP3K4 from a shared bidirectional promoter. This study illustrated a divergently transcribed lncRNA/protein-coding gene pair involved in vascular inflammation and more broadly informs a better understanding of mammalian genome regulatory mechanisms in vascular disease states.