Intracellular L-PGDS–Derived 15d-PGJ2 Inhibits CaMKII Through Lipoxidation to Alleviate Cardiac Ischemia/Reperfusion Injury

BACKGROUND: Myocardial ischemia/reperfusion (I/R) injury is a substantial challenge to the management of ischemic heart disease, the leading cause of mortality worldwide. Arachidonic acid (AA) is a prominent polyunsaturated fatty acid in the human body and plays an important role in various physiological and pathological conditions. AA metabolic enzymes determine AA levels; however, currently there is no comprehensive analysis of AA enzymes in cardiac I/R injury. METHODS: The profiling of AA metabolic enzymes was analyzed with the RNA sequencing transcriptome data from the mouse heart tissues with I/R injury. Cultured neonatal and adult rat ventricular myocytes, human embryonic stem cell–derived cardiomyocytes, and in vivo mouse I/R models were used to confirm the role of L-PGDS (lipocalin-type prostaglandin D2 synthase)/15d-PGJ2 in I/R injury. A biotin-tagged 15d-PGJ2 analog combined with liquid chromatography–tandem mass spectrometry was used to identify the downstream signaling of L-PGDS/15d-PGJ2. RESULTS: Based on the transcriptome data and experimental validations, L-PGDS, together with its downstream metabolite 15d-PGJ2, was downregulated in cardiac tissue with I/R injury. Functionally, L-PGDS overexpression mitigates myocardial I/R injury, whereas knockdown exacerbates the damage. Supplementation of 15d-PGJ2 alleviated I/R injury. Mechanistically, 15d-PGJ2 covalently bound to the Ca 2+ /CaMKII (calmodulin protein kinase II) and induced lipoxidation of its cysteine 495 (CaMKII-δ9) to dampen the formation of CaMKII oligomers and alleviate its overactivation, consequently ameliorating cardiomyocyte death and cardiac injury. CONCLUSIONS: Our study uncovered L-PGDS/15d-PGJ2/CaMKII signaling as a new mechanism underlying I/R-induced cardiomyocyte death. This provides new mechanistic insights and therapeutic targets for myocardial I/R injury and subsequent heart failure. We also showed that lipoxidation is a new post-translational modification type for CaMKII, deepening our understanding of the regulation of its activity.