<scp>ANXA4</scp> Alleviates Cardiomyocyte Injury Associated With Ischemia–Reperfusion by Interfering With <scp>NFκB</scp> p50's Transcriptional Activation of <scp>RAGE</scp>

Myocardial ischemia/reperfusion injury (MI/R) remains a major challenge in cardiac transplantation, leading to early graft dysfunction or primary nonfunction, and eventually death. This study explores the role of annexin A4 (ANXA4), a calcium-dependent phospholipid-binding protein, in MI/R pathogenesis and investigates its underlying mechanisms. In C57BL/6J mice, ANXA4 expression was moderately increased following MI/R (induced by 45-min occlusion/24 h reperfusion) (mRNA: sham vs. MI/R = 1.00 vs. 2.42, p < 0.01; protein: 1.00 vs. 2.39, p < 0.05). To assess its functional role, AAV9 particles (1 × 10¹¹ viral genomes per mouse) carrying ANXA4 encoding fragments were intravenously injected into mice 4 weeks before the surgery. The forced elevation of ANXA4 reduced IR-induced myocardial infarction from 41.22% to 18.23%, lowered the ventricular arrhythmias score from 10.83 to 6.00, and creatinine kinase-myocardial band (CK-MB) activity from 450 to 268 U/L. ANXA4 overexpression also inhibited cardiomyocyte apoptosis, inflammation, and oxidative stress. In vitro, ANXA4 overexpression mediated by pcDNA3.1 vector protected HL-1 mouse cardiomyocytes against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced cell damage. Further high-throughput transcriptomics illustrated that ANXA4 upregulation significantly suppressed the expression of the receptor for advanced glycosylation end products (RAGE; Log2 Fold change = -3.19, p < 0.05). Mechanistically, ANXA4 repressed the transcription of RAGE by dampening the nuclear translocation of NFκB p50. Collectively, this study demonstrates that ANXA4 is upregulated in the mouse myocardium post MI/R as a compensatory response, and its overexpression alleviates MI/R- and OGD/R-induced cardiomyocyte injury by preventing NFκB p50 from binding to and initiating transcription of RAGE.