Mechanism of Hypoxia‐Induced HMGB1 Regulating NLRP3 Inflammasome/Caspase‐1 Pathway‐Mediated Pyroptosis in Myocardial Ischemia Reperfusion Injury Through the Nrf2/ HO ‐1 Pathway

ABSTRACT Objective Myocardial ischemia–reperfusion injury (MIRI) represents an inevitable risk event for acute myocardial infarction. We explored the mechanism of hypoxia‐induced high‐mobility group box 1 (HMGB1) promoting MIRI by modulating the NLRP3 inflammasome/Caspase‐1 pathway‐mediated pyroptosis via the Nrf2/HO‐1 pathway. Methods In vitro cultured mouse cardiomyocytes were exposed to hypoxia/reoxygenation (H/R) to establish an MIRI cell model, then treated with short hairpin‐HMGB1, a NLRP3 agonist (Nigericin), and a Nrf2 inhibitor (ML385). Cell viability and injury were assessed via MTT and LDH assays. HMGB1 (nuclear/cytoplasm), Nrf2 (nuclear/cytoplasm), HO‐1, NLRP3, ASC, cleaved Caspase‐1, and GSDMD‐N protein levels, and IL‐1β and IL‐18 levels in cell supernatants were determined by western blot and ELISA. HMGB1 and Nrf2 distribution were analyzed by immunofluorescence, with their interaction verified by co‐immunoprecipitation. An MIRI mouse model was developed and treated with HMGB1 Box A for in vivo verification. Results H/R induction declined the nuclear HMGB1 protein level and cell viability, and intensified the cytoplasmic HMGB1 protein level, cell damage, and pyroptosis‐related protein and inflammatory cytokine levels, which were averted by HMGB1 knockdown. NLRP3 activation partially reversed HMGB1 knockdown's effect on improving cardiomyocyte pyroptosis. Hypoxia‐induced HMGB1 inhibited Nrf2/HO‐1 activation by interacting with Nrf2. Nrf2/HO‐1 suppression partly counteracted HMGB1 knockdown's suppressive effects on NLRP3 inflammasome activation and pyroptosis. HMGB1 suppressed the Nrf2/HO‐1 axis to enhance NLRP3 inflammasome/Caspase‐1 pathway‐mediated pyroptosis, thereby exacerbating MIRI in vivo. Conclusion Hypoxia induces HMGB1's nucleus‐to‐cytoplasm translocation, which binds to Nrf2 to repress Nrf2 nuclear translocation to suppress Nrf2/HO‐1 activation to promote NLRP3 inflammasome/Caspase‐1‐mediated pyroptosis, thereby exacerbating MIRI.