SREBP1 deficiency aggravates vascular calcification via iASPP-triggered ferroptosis of vascular smooth muscle cells

Vascular calcification (VC) is frequently observed in patients with chronic kidney disease (CKD), which seriously affects the structure and function of blood vessels. Ferroptosis, a type of cell death caused by iron-catalyzed reactive oxygen species (ROS) and lipid peroxidation, has been implicated in cardiovascular diseases, including VC. However, the underlying molecular mechanisms of ferroptosis in VSMCs remain poorly understood. Bioinformatics analysis was employed to mine the dataset and screen sterol regulatory element-binding protein 1 (SREBP1) related to ferroptosis and VC. Quantitative real-time polymerase chain reaction, western blotting, immunofluorescence, and immunohistochemistry were used to analyze gene expression. Functional experiments were conducted to comprehensively investigate the effects of SREBP1 on ferroptosis and VC. Chromatin immunoprecipitation (ChIP) analysis and dual-luciferase reporter assays were utilized to further elucidate the regulatory effects of SREBP1 on the inhibitor of apoptosis-stimulating protein of p53 (iASPP). We identified that liproxstatin-1 (Lip-1), as a ferroptosis-specific inhibitor, dose-dependently impeded calcification progression, highlighting the pivotal roles of lipid peroxidation. Furthermore, we obtained clues that SREBP1, a lipid-regulating transcription factor, was associated with calcification and ferroptosis by investigating the GEO and FerrDB databases. Subsequently, we observed that SREBP1 was significantly downregulated in serum and calcified radial arteries of CKD patients, in calcified aortas from CKD mice, and in calcified VSMCs. The low SREBP1 expression was inversely correlated with ferroptosis in vivo and in vitro, respectively. Overexpression of SREBP1 remarkably attenuated osteogenic differentiation and calcium deposition of VSMCs by suppressing ferroptosis. Mechanistically, we demonstrated that SREBP1 bound to the promoter region of iASPP and directly promoted the expression of iASPP. Moreover, iASPP silencing exacerbated ferroptosis and calcification of VSMCs. Rescue experiments revealed that SREBP1 exerted the protective effects on VC that were achieved in part by regulating the activation of iASPP. In vivo experiments further elucidated that artery-specific SREBP1 overexpression alleviated ferroptosis and calcification via the SREBP1/iASPP axis in CKD mice. These findings report that targeting SREBP1 or iASPP may represent an attractive interventional strategy for VC in CKD.