No abstract

Background/Aims: Cardiovascular disease is a growing major global public health problem. Necrosis is one of the main forms of cardiomyocyte death in heart disease. Oxidative stress is regarded as one of the key regulators of cardiac necrosis, which eventually leads to cardiovascular disease. Many pharmacological and in vitro studies have suggested that FGF-2 can act directly on cardiomyocytes to maintain the integrity and function of the myocardium and prevent damage during oxidative stress. However, the mechanisms by which FGF-2 rescues the myocardium from oxidative stress damage in cardiovascular disease remain unclear. The present study explored the protective effects of FGF-2 in the H₂O₂-induced necrosis of H9C2 cardiomyocytes as well as the possible signaling pathways involved. Methods: Necrosis of H9c2 cardiomyocytes was induced by H₂O₂ and assessed using a Cell Counting Kit-8 (CCK8) assay and flow cytometry analysis. The cells were pretreated with the PI3K/Akt inhibitor Wortmannin to investigate the possible involvement of the PI3K/Akt pathway in the protection by FGF-2. The levels of Akt, p-Akt, FoxO3a, p-FoxO3a, and BNIP3L were detected by Western blot. Chromatin immuno-precipitation (ChIP) analysis was used to test whether FoxO3a binds directly to the BNIP3L promoter region. A luciferase assay was used to study the effects of FoxO3a on BNIP3L gene promoter activity. Mitochondrial ΔΨM was quantified using tetramethylrhodamine methyl ester perchlorate (TMRM). The mitochondrial oxygen consumption rate (OCR) was assessed with a Seahorse XF24 Analyzer. Results: Treatment with H₂O₂ decreased the phosphorylation of Akt and FoxO3a, and it induced the nuclear localization of FoxO3a and the necrosis of H9c2 cells. These effects of H₂O₂ were abrogated by pretreatment with FGF-2. Furthermore, the protective effects of FGF-2 were abolished by the PI3K/Akt inhibitor Wortmannin. ChIP analyses indicated that FoxO3a binds directly to the BNIP3L promoter region. Using a luciferase assay, we further observed that FoxO3a increased BNIP3L gene promoter activity. As expected, overexpression of BNIP3L in H9C2 cardiomyoblast cells reduced the cardioprotection of FGF-2 in H₂O₂-induced necrosis and mitochondrial dysfunction. Conclusions: The present data suggest that FGF-2 protects against H₂O₂-induced necrosis of H9C2 cardiomyocytes via the activation of the PI3K/Akt/FoxO3a pathway. Moreover, the present results demonstrate that FoxO3a is an important transcription factor that acts by binding to the promoter and promoting the transcription of BNIP3L, and it contributes to the necrosis and mitochondrial dysfunction induced by H₂O₂ in H9c2 cardiomyoblast cells.