iRhom2 promotes atherosclerosis through macrophage inflammation and induction of oxidative stress

Atherosclerosis is a complex chronic inflammatory disease that is characterized by the formation of lipid-rich plaques on the inner walls of the arteries. Inactive rhomboid protein 2 (iRhom2) was recently determined as a necessary regulator for the shedding of tumor necrosis factor-alpha (TNF-α) in immune cells. In the present study, we aimed to explore the effects of iRhom2 on the inflammatory response and oxidative stress induced by low-density lipoprotein (ox-LDL) in RAW264.7 and THP-1-derived macrophages. The expression levels of iRhom2 were also investigated in apolipoprotein E knockout (ApoE^-/-) mice fed a high-fat diet (HFD). iRhom2 was significantly induced by ox-LDL in macrophages, as confirmed by Western blotting and RT-qPCR analysis. Furthermore, iRhom2 knockdown showed significant suppressive effects on the activation of ox-LDL-induced RAW264.7 and THP-1-derived macrophages through reducing TACE and TNFR2 expressions, and the inactivation of the IκBα/NF-κB signaling pathway. A reduction in reactive oxygen species (ROS) generation, malondialdehyde (MDA) levels, and nitric oxide (NOX) activity and an increase in glutathione peroxidase (GSH-Px) activity were determined in the absence of iRhom2 expression. In addition, the NF-E2 related factor-2 (Nrf-2)/heme oxygenase-1 (HO-1) pathway was also upregulated in ox-LDL-treated macrophages subjected to iRhom2 inhibition. Moreover, suppression of iRhom2 expression inactivated PI3K/AKT pathway activation, contributing to ROS reduction in ox-LDL-stimulated macrophages. iRhom2 was also significantly expressed in ApoE^-/- mice fed HFD. Finally, we observed increased serum levels of TNF-α, TNFR1, and TNFR2 in patients with coronary artery atherosclerosis as compared to healthy volunteers. In conclusion, our findings suggested that iRhom2 played a key role in the pathogenesis of atherosclerosis, and that iRhom2 might be a potential therapeutic target against atherosclerosis.