Resolving neutrophils through genetic deletion of TRAM attenuate atherosclerosis pathogenesis

Summary: Systemic neutrophil dysregulation contributes to atherosclerosis pathogenesis, and restoring neutrophil homeostasis may be beneficial for treating atherosclerosis. Herein, we report that a homeostatic resolving subset of neutrophils exists in mice and humans characterized by the low expression of TRAM, correlated with reduced expression of inflammatory mediators (leukotriene B4 [LTB4] and elastase) and elevated expression of anti-inflammatory resolving mediators (resolvin D1 [RvD1] and CD200R). TRAM-deficient neutrophils can potently improve vascular integrity and suppress atherosclerosis pathogenesis when adoptively transfused into recipient atherosclerotic animals. Mechanistically, we show that TRAM deficiency correlates with reduced expression of 5-lipoxygenase (LOX5) activating protein (LOX5AP), dislodges nuclear localization of LOX5, and switches the lipid mediator secretion from pro-inflammatory LTB4 to pro-resolving RvD1. TRAM also serves as a stress sensor of oxidized low-density lipoprotein (oxLDL) and/or free cholesterol and triggers inflammatory signaling processes that facilitate elastase release. Together, our study defines a unique neutrophil population characterized by reduced TRAM, capable of homeostatic resolution and treatment of atherosclerosis.