Free Radic Biol Med. 2026 Sep 30:S0891-5849(26)01179-2. doi: 10.1016/j.freeradbiomed.2026.09.029. Online ahead of print.
ABSTRACT
Postoperative atrial fibrillation (POAF) is strongly linked to mitochondrial oxidative stress, yet the upstream post-translational mechanisms that couple redox imbalance to atrial vulnerability remain unclear. We investigated atrial lysine 2-hydroxyisobutyrylation (Khib) remodeling and tested whether site-specific Khib regulates mitochondrial energy-redox signaling in POAF. Quantitative Khib proteomics was performed in right atrial appendage tissue from coronary artery bypass grafting patients. Differentially modified proteins were analyzed by functional enrichment and protein-interaction networks. Mitochondrial transcription factor A (TFAM) K76 Khib was validated by immunoprecipitation and western blotting. Site-directed mutagenesis in atrial cardiomyocytes was combined with measurements of cytochrome c oxidase (COX) activity, ATP, mitochondrial reactive oxygen species (mtROS), and AMPK phosphorylation, together with structural modeling and ultrastructural analysis. POAF atria exhibited extensive Khib remodeling enriched in mitochondrial metabolism, contractile regulation, and stress-response networks. Khib at TFAM Lys76 was markedly increased in POAF. Enhanced K76 modification impaired COX activity and ATP production, reduced AMPK phosphorylation, and increased mtROS accumulation. In silico structural modeling predicted that K76 Khib would weaken the interaction between TFAM and mtDNA. Electron microscopy demonstrated mitochondrial swelling and cristae disruption in POAF atria. These findings identify coordinated bioenergetic failure and oxidative stress downstream of aberrant TFAM K76 modification. TFAM K76 Khib affects a TFAM-COX/ATP/ROS-AMPK axis that couples mitochondrial bioenergetic dysfunction and redox imbalance in POAF. This Khib-induced alteration of the energy-redox pathway provides a mechanistic framework and a potential biomarker and therapeutic target for POAF.
PMID:42815861 | DOI:10.1016/j.freeradbiomed.2026.09.029