Role of Red Blood Cell Released ATP in Disturbed Blood Flow‐Initiated Vascular Inflammation and Atherosclerosis

Abstract

Vascular inflammation and atherosclerosis are implicated in many cardiovascular diseases. While systemic risk factors such as hyperlipidemia and/or hyperglycemia circulate throughout the vasculature, inflammatory cell infiltration and atherosclerotic plaque formation preferentially occur at sites of disturbed blood flow, indicating a role of hemodynamic forces in the pathogenesis of vascular diseases. For decades, endothelial cell (EC) responses to the changes in fluid‐generated wall shear stress (WSS) have been the main or sole focus of flow dynamics related studies, which consider circulating blood as a cell‐free fluid, completely overlooking the impact of mechanical force‐activated blood cells on the vascular walls. Our previous studies found that changes in blood flow alter vascular EC function through both WSS and SS exerted on RBCs, and that the released ATP via RBC pannexin 1 (Panx1) channels alters EC barrier integrity and vascular permeability. These observations led us to hypothesize that the RBC released ATP in response to changes in blood flow plays a significant role in site‐specific vascular vulnerability, and synergistically contributes to the initiation and progression of vascular inflammation and atherosclerosis along with local WSS and systemic risk factors. To investigate the role of RBC released ATP in atherogenesis, we developed a new mouse model with blood cell specific Panx1 deletion that abolishes SS‐induced ATP release from RBCs, and two hypercholesterolemia models with RBC Panx1−/−: ApoE−/−/RBC‐Panx1−/− and AAV‐mediated gene transfer of mutant PCSK9 (AAV‐PCSK9DY) in RBC‐Panx1−/− mice fed with high‐fat diet (HFD). We observed extensive atherosclerotic plaques in mouse aorta after HFD feeding for 12–16 weeks, which were preferentially located at regions with disturbed flow. In contrast, under identical hyperlipidemia conditions, mice with RBC‐Panx1−/− showed a 40–60% decrease in atherosclerotic plaque burden, as well as reduced numbers of damaged ECs at bifurcations and macrophage infiltration within the plaques. We also observed a 40–50% higher plaque formation in male mice compared to females of the same strain. However, the percent of plaque reduction in RBC Panx−/− mice are similar in both genders. HFD fed ApoE−/− mice also showed elevated plasma levels of IL‐1β and IFN‐γ, but these elevations were significantly reduced in ApoE−/−/RBC‐Panx1−/− mice under identical hyperlipidemic conditions. In conclusion, our results indicated that RBC released ATP contributes significantly to disturbed blood flow‐induced site‐specific vascular vulnerability and atherosclerosis. In addition to its local effect, the reduced levels of inflammatory cytokines found in RBC Panx1−/− mice indicate an important role of RBC released ATP in immune cell activation and cytokine production, contributing to immune system‐involved initiation and progression of atherosclerosis. The results that female mice had less atherosclerotic plaque burden than males indicate a substantial female protection under hyperlipidemia conditions.Support or Funding InformationSupported by HL130363 and DK097391.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.