A novel VCP modulator, KUS121, attenuates atherosclerosis progression by maintaining intracellular ATP and mitigating ER stress in endothelial cells

Background: Endoplasmic reticulum (ER) stress signaling pathways have pivotal roles in atherosclerosis progression. Recently, we have developed Kyoto University Substance (KUS) 121, which selectively inhibits ATPase activities of valosin-containing protein (VCP) and consequently saves intracellular ATP consumption and mitigates ER stress. Methods and Results: We assessed the efficacy of KUS121 against atherosclerosis by its daily injection into Apoe-/- mice fed with Western Diet (WD) for 8 weeks. Consequently, KUS121 treatment reduced atherosclerosis progression by approximately 40% in atherosclerotic plaques. Interestingly, we found that C/EBP homologous protein (CHOP), an established ER stress marker, was mainly expressed in plaque endothelium. Therefore, we assessed the action of KUS121 in endothelial cells using the human endothelial cell line (EA.hy926 cells). As a result, KUS121 prevented ER stress-induced apoptosis and downregulated the IRE1 (Inositol-requiring enzyme) α-associated inflammatory pathways. Consistent with these in vitro findings, KUS121 treatment also significantly reduced endothelial apoptosis assessed by TUNEL staining and inflammation examined by immunostaining of Nuclear factor kappa B (NF-κB) and Intercellular adhesion molecule (ICAM) 1 at plaque endothelium. We also demonstrated that KUS121 maintained ATP levels in EA.hy926 cells and atherosclerotic plaque lesions using the single-wavelength or the FRET-based fluorescent ATP sensor. Supplementation of intracellular ATP by Methyl pyruvate (MePyr) attenuated ER stress-induced apoptotic and inflammatory pathways in endothelial cells, which could be the main mechanism how KUS121 reduces ER stress. Conclusions: KUS121 can be a new therapeutic option for atherosclerotic diseases by maintaining intracellular ATP levels and attenuating ER stress-induced apoptosis and inflammation in plaque endothelium.