Leukemia inhibitory factor receptor inhibition reduces stenosis grade and total serum cholesterol levels in a mouse model for atherosclerosis

Abstract

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Dutch Heart Foundation Atherosclerosis is characterized by the accumulation of lipids and immune cells in the arterial wall and it is the main underlying pathology causing cardiovascular diseases (CVD). Cytokines are involved in all stages of atherosclerosis and most cytokines contribute to disease progression. For instance, IL-6 cytokine family members, such as IL-6, oncostatin-M and cardiotrophin-1, are closely related to CVDs. However, the role of leukemia inhibitory factor (LIF), a member of the IL-6 cytokine family, and its receptor (LIFR) in atherosclerosis remains unknown. Therefore, the aim of this study is to assess the contribution of LIFR signaling to atherosclerosis development by systemically inhibiting LIFR in an atherosclerotic mouse model. First, the expression of LIF and LIFR was examined using single-cell RNA sequencing data of human carotid artery plaques. Mast cells highly and exclusively express LIF, whereas LIFR was specifically expressed by activated endothelial cells. To validate LIFR signaling in vivo, female western-type diet fed Ldlr-/- mice were treated with LIFR inhibitor EC359 (5 mg/kg s.c., n=15) or control solvent (n=15) three times per week for eight weeks. During the experiment, weights of the mice did not differ between groups, whereas total serum cholesterol levels were significantly reduced in EC359 treated mice (p=0.03). In particular, EC359 treatment reduced VLDL levels. Additionally, EC359 treatment significantly reduced Sr1, Abca1 and Lrp1 expression in the liver, suggesting an altered lipid metabolism in EC359 treated mice. Furthermore, LIFR inhibition affected innate immunity, both systemically and locally in the plaque. Neutrophil numbers were significantly increased in the circulation (ctrl 18.7±1.7%; EC359 28.0±2.0%; p=0.002) and aortic plaques (ctrl 3.9±0.8%; EC359 9.9±1.9%; p=0.003) of mice treated with EC359 compared to control mice. Moreover, LIFR inhibition affected circulating monocytes resulting in less inflammatory monocytes. The adaptive immune cells, such as T and B cells, remained largely unaffected. Collectively, the reduction of serum total cholesterol and increase in neutrophil numbers in EC359 treated mice resulted in a trend towards reduced atherosclerotic stenosis grade compared to control mice (39.8±1.4% versus 34.9±1.9%; p=0.054), but it did not affect plaque collagen and monocyte/macrophage content in the aortic root. Conclusively, LIFR signaling inhibition reduces atherosclerotic stenosis grade, lowers plasma total cholesterol levels and affects innate immunity.