ALDH2 regulates 4‐HNE accumulation and ferroptosis in MI/R. A) Protein expression of 4‐HNE in ALDH2flox/flox (F/F) and cardiomyocyte‐specific ALDH2‐knockout (cKO) mice hearts subjected to MI/R (30‐min ischemia/24‐h reperfusion, n = 4). B,C) Representative immunohistochemical staining results indicating 4‐HNE expression in F/F and cKO mice heart tissues 24 h after MI/R surgery (n = 4). Scale bar:50 µm. D) Representative photographs and statistical analysis of infarct size (IF) and area at risk (AAR) in mice hearts stained with Evans blue dye (EBD) and triphenyl tetrazolium chloride (TTC) (n = 6). The hearts were collected 24 h after MI/R surgery. Scale bar: 1 mm. E,F) Serum levels of CK‐MB and LDH in F/F and cKO mice with sham or MI/R injury (30‐min ischemia/24‐h reperfusion, n = 8). G‐J) Iron content, MDA, GSH, and GPX4 activity in F/F and cKO mice 24 h after MI/R surgery (n = 6–8). K) Western blotting of the ferroptosis marker protein (ACSL4, TfR1, FTH1, and GPX4) in F/F and cKO mice hearts subjected to MI/R (30‐min ischemia/24‐h reperfusion, n = 4). L) Representative western blotting of 4‐HNE in WT mice subjected to MI/R (30‐min ischemia/24‐h reperfusion). The mice were treated with DXZ (50 mg/kg), Alda‐1 (25 mg kg−1) or vehicle (solvent control) (n = 4). M) EBD/TTC staining of heart sections collected from the DXZ (50 mg kg−1), Alda‐1 (25 mg kg−1), and vehicle groups(n = 6). The hearts were collected 24 hours after MI/R surgery, and the infarct area and at‐risk area were evaluated. Scale bar: 1 mm. N,O) Serum levels of CK‐MB and LDH in mice treated with DXZ (50 mg kg−1), Alda‐1 (25 mg kg−1) and vehicle 24 h after MI/R surgery (n = 8). P,Q) Iron content, and GSH levels in WT mice with DXZ (50 mg/kg) or Alda‐1 (25 mg/kg) subjected to MI/R (30‐min ischemia/24‐h reperfusion, n = 6–8). R) Protein levels of ACSL4, TfR1, FTH1, and GPX4 in WT mice heart tissues from DXZ (50 mg kg−1), Alda‐1 (25 mg kg−1) and vehicle groups. The hearts were collected from 24 hours after MI/R surgery (n = 4). Data are expressed as mean ± SEM. Unpaired two‐tailed Student's t‐test (analysis in AAR/LV) and Mann‐Whitney test (analysis in IF/AAR) were used for the analysis in (D). One‐way analysis of variance (ANOVA) was used for the analysis in E–J,M–Q).