TrxR2 Lactylation Facilitates Mitochondrial Protection and Endothelial Ferroptosis Resistance in Diabetic Cardiomyopathy

Thioredoxin reductase 2 (TrxR2), a radical-trapping antioxidant, plays a critical role in cardiac defense. However, the mechanisms underlying its benefits remain unclear. In this study, we aimed to investigate whether endothelial TrxR2 prevents cardiac microvascular dysfunction in diabetic cardiomyopathy (DCM). Key genes in the thioredoxin family and those involved in ferroptosis were analyzed using bulk RNA-sequencing assay. Diabetic injury was induced in multiple transgenic mouse models, including endothelial cell-specific knockout mice for TrxR2, sterol carrier protein 2 (SCP2), and Tu translation elongation factor, mitochondrial (TUFM). The TrxR2 lactylation site was identified by mass spectrometry and verified by a custom-made lactylation antibody. Mitochondrial thioredoxin reductase (mitoTrxR) activity and lipid peroxyl radicals were detected using fluorescence staining. Endothelial TrxR2 deficiency significantly suppressed mitoTrxR activity, exacerbated cardiac microvascular dysfunction, and accelerated DCM progression. In contrast, TrxR2 overexpression and Kukoamine B (TrxR2 agonist) treatment inhibited mitochondria-associated ferroptosis by facilitating SCP2 degradation and blocking the mitochondrial translocation of acyl-CoA synthetase long-chain family member 4 (ACSL4) via mitophagy. Mechanistically, TrxR2 maintained TUFM expression by scavenging oxygen radicals, thereby facilitating the mitochondrial translocation of AMPK for mitophagy activation. TrxR2 undergoes lactylation at lysine 340. This process is mediated by mitochondrial alanyl-tRNA synthetase 2 (AARS2) and lactate accumulation in both human and mouse diabetic hearts. This modification and sodium lactate administration compensatorily enhanced mitoTrxR activity, promoted mitophagy, and conferred ferroptosis resistance in cardiac microcirculation in DCM. Our findings demonstrate that TrxR2 and its lactylation modification promote mitophagy, enhance ferroptosis resistance, and improve cardiac microvascular function in DCM. Thus, this study provides a promising therapeutic approach for the management of diabetic complications.