Olfactory Receptor 2 Signaling in Monocytes Facilitates Chemotactic Migration to Atherosclerotic Aorta Due to Octanal from Dysfunctional Endothelium 2259390

Abstract Introduction Atherosclerosis is a chronic inflammatory disease of the arterial wall initiated by monocyte recruitment and foamy macrophage accumulation. Human and mouse vascular macrophages, mouse bone marrow-derived macrophages (BMDMs), and monocytes express several Olfactory Receptors (ORs), including Olfr2 and its human orthologue OR6A2. Although, its role in monocytes is unknown. Ligation of Olfr2/OR6A2 with their ligand, Octanal, activates the NLRP3 inflammasome pathway and exacerbates atherosclerosis, while Olfr2 KO mice reduces atherosclerosis progression in vivo. Additionally, the original source of Octanal is not yet defined. Due to Endothelial Dysfunction (ED) being one of the first major steps in atherosclerosis initiation, we propose that Octanal is produced by lipid peroxidation by a dysfunctional endothelium, specifically through the ferroptosis pathway. Methods We employed Bulk RNAseq to characterize the potential functions of Olfr2 which revealed that Olfr2 may behave as a chemotactic receptor for monocytes. Thus, migration assays were conducted using mouse monocytes isolated from the bone marrow to test migration significance with and without Olfr2. To test if Octanal is derived from ED, we treated Human Aortic Endothelial Cells (HAECs) with Palmitic Acid, which is a major fatty acid precursor, and used that supernatant to test if monocytes would migrate. Results Bulk RNAseq identified Olfr2/OR6A2 protein expression in about 20% of monocytes, with expression increasing with disease in humans and mice. It also may enhance the chemotactic function of monocytes. Migration assays revealed that monocytes significantly migrate in response to Octanal, a response ablated in Olfr2 KO monocytes. We verified further with human monocytic cell lines, THP1 and Mono-Mac 6. Conclusion These experiments suggest that Octanal derived from ED could drive Olfr2-mediated chemotaxis of monocytes and macrophages, highlighting Olfr2 as a possible previously unrecognized chemotactic receptor and therapeutic target. Funding Source n/a Topic Categories Cellular Adhesion, Migration, and Inflammation (CAM)