Department of Pharmacology, College of Pharmacy, Army Medical University, Chongqing 400038, China
Rationale: Forkhead/winged helix transcriptional factor P3 (FoxP3) is a well-studied transcription factor that maintains the activity of T cells, but whether cardiomyocytic FoxP3 participates in cardiac remodeling (CR) remains unclear. The present study was to investigate the role of cardiomyocytic FoxP3 in CR from the perspective of mitophagy.
Methods: CR was induced by angiotensin II (AngII) in vitro, or by isoproterenol (Iso) in vivo using male C57 mice or FoxP3DTR mice. Histological changes were observed by hematoxylin-eosin and Masson staining. Molecular changes were detected by immunohistochemistry, immunofluorescence, immunoblotting, and real-time PCR. Mitophagy was shaped by transmission electron microscopy and co-localization. The mRNA expression was operated by siRNA or adeno associated virus (AAV). Molecular interactions were detected by co-localization, immunoprecipitation (IP), and chromatin IP.
Results: The expression and nuclear translocation of cardiomyocytic FoxP3 were downregulated in CR, while they were upregulated after triptolide (TP) treatment. In left ventricle (LV) remodeling in mice, autophagy was activated continuously in the myocardium, and TP significantly attenuated it. AngII induced massive mitophagy characterized by the activation of autophagy regulatory protein 5 (Atg5)-dependent autophagic flux. Critically, Parkin was identified as the main adaptor mediated myocardial mitophagy and was responsible for the effect of TP. Moreover, FoxP3 was responsible for the downregulation of Parkin and inhibited AngII-induced cardiac mitophagy. We found that mitophagy increased significantly and the inhibition of TP treatment reversed completely in FoxP3-deficient LVs. Mechanistically, FoxP3 interacted with a motif located downstream of the activating transcription 4 (ATF4)-binding motif involved in the promoter of Parkin and hijacked free nuclear ATF4 to decrease Parkin mRNA expression in CR.
Conclusion: Cardiomyocytic FoxP3 could negatively regulate Parkin-mediated mitophagy in CR, and restoring cardiomyocytic FoxP3 activity provided a cardioprotective strategy by inhibiting excessive cardiac mitophagy.
Keywords: cardiac remodeling, mitophagy, Parkin, FoxP3, triptolide