NPC1L1, stabilized by PABPC1/IGF2BP1, accelerates atherosclerosis by enhancing CYP11A1-mediated mitophagy and...

In our previous study, we identified Niemann-Pick C1 like intracellular cholesterol transporter 1 (NPC1L1) as a key contributor in lipid oxidative stress during atherosclerosis (AS) progression. However, the regulation mode of its expression and the specific approaches by which it functions in lipid oxidative stress are still unclear. HUVECs and macrophages were treated with oxidized low-density lipoprotein (ox-LDL) to induce endothelial cell injury. First, the effects of the RNA binding proteins IGF2BP1 and poly (A) binding protein cytoplasmic 1 (PABPC1) on the stability of NPC1L1 mRNA was evaluated. The interaction between NPC1L1 and cytochrome P450 family 11 subfamily A member 1 (CYP11A1) was analyzed using Co-IP, and the co-localization of the two was detected using immunofluorescence. Combined with qPCR, Western blotting, CCK8, ferroptosis-related index and mitophagy-related index determination were performed to evaluate the expression of CYP11A1 in ox-LDL-treated HUVECs and its role of ferroptosis and mitophagy. Subsequently, pcDNA-NPC1L1 or CYP11A1 siRNA were individually or altogether transfected into ox-LDL-treated HUVECs to verify the involvement of CYP11A1 in NPC1L1-mediated ferroptosis and mitochondrial oxidative stress. Finally, ApoE-/- mice were fed with high-fat diet to establish an AS model in vivo and sh-NPC1L1 and/or Ad-CYP11A1 were injected via tail vein to verify the therapeutic effect of NPC1L1 knockdown on AS and reversal effect of CYP11A1. Either knockdown of IGF2BP1 or PABPC1 reduced NPC1L1 mRNA stability. Mechanistically, NPC1L1 interacted with CYP11A1 and promoted CYP11A1 protein expression. CYP11A1 was upregulated in ox-LDL-treated HUVECs and overexpression of CYP11A1 induced ferroptosis by activating excessive mitophagy, and knockdown of CYP11A1 reversed the promotion of NPC1L1 on mitophagy and ferroptosis in ox-LDL treated HUVECs. In vivo, injection of the sh-NPC1L1 lentiviral vector inhibited AS progression, while injection of the LV-CYP11A1 lentiviral vector attenuated the protective effect of sh-NPC1L1 on AS. PABPC1 and IGF2BP1 synergistically stabilized NPC1L1 mRNA, and NPC1L1 interacted with CYP11A1 to induce endothelial mitophagy and ferroptosis during AS.