ADENOVIRUS-MEDIATED FKBP12.6 OVEREXPRESSION INDUCES HYPERTROPHY AND APOPTOSIS IN CULTURED NEONATAL CARDIOMYOCYTES

Punicalagin Protects Against Diabetic Cardiomyopathy by Promoting Opa1-Mediated Mitochondrial Fusion via Regulating PTP1B-Stat3 Pathway

Aims: This study aims to explore the efficacy of punicalagin (PG) on diabetic cardiomyopathy (DCM), with a specific focus on the mechanisms underlying the effects of PG on mitochondrial fusion/fission dynamics. Results: Cardiac structural and functional abnormalities were ameliorated in diabetic rats receiving PG administration as evidenced by increased ejection fraction, and attenuated myocardial fibrosis and hypertrophy. PG enhanced mitochondrial function and inhibited mitochondria-derived oxidative stress by promoting Opa1-mediated mitochondrial fusion. The benefits of PG could be abrogated by knockdown of Opa1 in vivo and in vitro. Inhibitor screening and chromatin immunoprecipitation analysis showed that Stat3 directly regulated the transcriptional expression of Opa1 by binding to its promoter and was responsible for PG-induced Opa1-mediated mitochondrial fusion. Moreover, pharmmapper screening and molecular docking studies revealed that PG embedded into the activity pocket of PTP1B and inhibited the activity of PTP1B. Overexpression of PTP1B blocked the promoting effect of PG on Stat3 phosphorylation and Opa1-mediated mitochondrial fusion, whereas knockdown of PTP1B mimicked the benefits of PG in high-glucose-treated cardiomyocytes. Innovation: Our study is the first to identify PG as a novel mitochondrial fusion promoter against hyperglycemia-induced mitochondrial oxidative injury and cardiomyopathy by upregulating Opa1 via regulating PTP1B-Stat3 pathway. Conclusion: PG protects against DCM by promoting Opa1-mediated mitochondrial fusion, a process in which PG interacts with PTP1B and inhibits its activity, which in turn increases Stat3 phosphorylation and then enhances the transcriptional expression of Opa1. These results suggest that PG might be a promising new therapeutic approach against diabetic cardiac complication. Antioxid. Redox Signal. 35, 618-641.

FKBP12.6 protects heart from AngII-induced hypertrophy through inhibiting Ca2+ /calmodulin-mediated signalling pathways in vivo and in vitro

We previously observed that disruption of FK506‐binding protein 12.6 (FKBP12.6) gene resulted in cardiac hypertrophy in male mice. Studies showed that overexpression of FKBP12.6 attenuated thoracic aortic constriction (TAC)‐induced cardiac hypertrophy in mice, whereas the adenovirus‐mediated overexpression of FKBP12.6 induced hypertrophy and apoptosis in cultured neonatal cardiomyocytes, indicating that the role of FKBP12.6 in cardiac hypertrophy is still controversial. In this study, we aimed to investigate the roles and mechanisms of FKBP12.6 in angiotensin II (AngII)‐induced cardiac hypertrophy using various transgenic mouse models in vivo and in vitro. FKBP12.6 knockout (FKBP12.6^−/−) mice and cardiac‐specific FKBP12.6 overexpressing (FKBP12.6 TG) mice were infused with AngII (1500 ng/kg/min) for 14 days subcutaneously by implantation of an osmotic mini‐pump. The results showed that FKBP12.6 deficiency aggravated AngII‐induced cardiac hypertrophy, while cardiac‐specific overexpression of FKBP12.6 prevented hearts from the hypertrophic response to AngII stimulation in mice. Consistent with the results in vivo, overexpression of FKBP12.6 in H9c2 cells significantly repressed the AngII‐induced cardiomyocyte hypertrophy, seen as reductions in the cell sizes and the expressions of hypertrophic genes. Furthermore, we demonstrated that the protection of FKBP12.6 on AngII‐induced cardiac hypertrophy was involved in reducing the concentration of intracellular Ca²⁺ ([Ca²⁺]i), in which the protein significantly inhibited the key Ca²⁺/calmodulin‐dependent signalling pathways such as calcineurin/cardiac form of nuclear factor of activated T cells 4 (NFATc4), calmodulin kinaseII (CaMKII)/MEF‐2, AKT/Glycogen synthase kinase 3β (GSK3β)/NFATc4 and AKT/mTOR signalling pathways. Our study demonstrated that FKBP12.6 protects heart from AngII‐induced cardiac hypertrophy through inhibiting Ca²⁺/calmodulin‐mediated signalling pathways.