Inhibition of PCSK9 protects against myocardial ischemia-reperfusion injury by suppressing ferroptosis via negative regulation of the P65/MMP9 pathway

Ferroptosis is a critical driver of cardiomyocyte death during myocardial ischemia-reperfusion (I/R) injury. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is well-established as a key regulator of cholesterol metabolism; however, its role in modulating cardiomyocyte death, particularly ferroptosis, in the context of I/R injury remains poorly defined. Plasma PCSK9 level was determined by ELISA in patients with acute myocardial infarction 12 h after PCI. Left anterior descending coronary artery ligation was established to induce myocardial I/R injury in male SD rats. Alirocumab or vehicle was administered immediately after reperfusion. Cardiac function was evaluated by transthoracic echocardiography, and myocardial injury was assessed by histological staining. GSH/GSSG levels, MDA content, SOD activity, and Fe²⁺ concentration were measured to evaluate ferroptosis. Furthermore, myocardial RNA sequencing (RNA-seq) was performed to explore the molecular mechanisms by which PCSK9 inhibition attenuates cardiomyocyte ferroptosis. Circulating PCSK9 levels were significantly elevated in patients with acute myocardial infarction after PCI and were positively correlated with myocardial injury biomarkers, including LDH, CK-MB, and cTnI. In vivo, pharmacological inhibition of PCSK9 improved cardiac function and attenuated myocardial pathological injury. Transcriptomic analysis revealed that differentially expressed genes in the PCSK9 inhibitor group were enriched in lipid metabolism, oxidative stress, and iron-related pathways. PCSK9 inhibition reduced iron accumulation and lipid peroxidation, restored antioxidant capacity, and reversed the dysregulated expression of GPX4, ACSL4, and TFR in the I/R injury SD rats. MMP9 was identified as one of the most significantly altered genes in the transcriptomic analysis, and its overexpression abolished the protective effects of PCSK9 silencing. Mechanistically, PCSK9 interacted with NF-κB p65 and promoted its nuclear translocation, thereby enhancing MMP9 transcription. Our findings unveil a novel non-canonical role of PCSK9 in myocardial ischemia-reperfusion injury. PCSK9 functions as a critical upstream regulator of the NF-κB p65/MMP9 signaling axis, thereby exacerbating ferroptosis in cardiomyocytes. Targeting the PCSK9-NF-κB p65-MMP9 axis may represent a promising therapeutic strategy for myocardial ischemia-reperfusion injury.