Renin-Angiotensin System Activation Accelerates Atherosclerosis In Experimental Renal Failure By Promoting Endoplasmic Reticulum Stress-Related Inflammation

In this study, we investigated the association between the renin-angiotensin system (RAS), endoplasmic reticulum (ER) stress and atherosclerosis (AS) in uremic apolipoprotein E knockout (apoE(-/-)) mice. Mild uremia was induced by a 5/6 nephrectomy (5/6 Nx) in 10-week-old apoE(-/-) mice. Four weeks after nephrectomy, the mice received losartan or no treatment for 16 weeks. Sham-operated mice served as the controls. We found that uremia accelerated AS at the aortic root. The activation of ER stress and the significant upregulation of pro-inflammatory cytokines and chemokines were observed in the uremic mice. Phosphorylated inositol-requiring 1 alpha (p-IRE1 alpha), an ER stress marker protein, was mainly expressed in macrophages in the atherosclerotic lesions. Treatment with losartan significantly attenuated aortic AS, inhibited ER stress and reduced aortic inflammation. In in vitro experiments, angiotensin II (Ang II) increased the levels of the common ER stress maker, glucose regulated protein 78 (GRP78) and the phosphorylation of IRE1 alpha in RAW264.7 macrophages. Treatment with losartan inhibited the activation of ER stress and the upregulation of GRP78, and enhanced the expression of nuclear factor-kappa B (NF-kappa B) inhibitor (I kappa B) in Ang II-stimulated RAW264.7 macrophages. IRE1 alpha-siRNA suppressed inflammation and downregulated I kappa B expression and I kappa B kinase (IKK) phosphorylation, which inhibited I kappa B degradation and NF-kappa B p65 nuclear translocation in Ang II-treated RAW264.7 macrophages. These findings suggest that RAS activation accelerates AS by promoting ER stress-related inflammation in uremic mice.