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Background: Previous studies have suggested that exogenous hydrogen sulfide can alleviate the development of diabetic cardiomyopathy (DCM) by inhibiting oxidative stress, inflammation, and apoptosis. However, the underlying mechanism is not fully understood. Nuclear expression and function of the transcription factor Forkhead box protein O (FoxO1) have been associated with cardiovascular diseases, and thus, the importance of FoxO1 in DCM has gained increasing attention. This study was designed to investigate the interactions between hydrogen sulfide (H2S) and nuclear FoxO1 in DCM. Methods: Diabetes was induced in adult male C57BL/6J mice by intraperitoneal injection of streptozotocin and was treated with H2S donor sodium hydrosulfide for 12 weeks. The H9C2 cardiomyoblast cell line and neonatal rat cardiomyocytes (NRCMs) were treated with the slow‐releasing H2S donor GYY4137 before high‐glucose (HG) exposure with or without pretreatment with the Akt inhibitor MK‐2206 2HCl. Changes in FoxO1 protein phosphorylation and subcellular localization were determined in H9C2 cells, NRCMs, and cardiac tissues from normal and diabetic mice. Cardiac structure and function in the diabetic mice were evaluated by echocardiography and histological analysis and compared with those in control animals. Results: The echocardiographic and histopathological data indicated that exogenous H2S improved cardiac function and attenuated cardiac hypertrophy and myocardial fibrosis in diabetic mice. H2S also improved HG‐induced oxidative stress and apoptosis in cardiac tissue and NRCMs. In addition, H2S induced FoxO1 phosphorylation and nuclear exclusion in vitro and in vivo, and this function was not inhibited by MK‐2206 2HCl. Alanine substitution mutation of three sites in FoxO1‐enhanced FoxO1 transcriptional activity, and subsequent treatment with exogenous H2S could not prevent HG‐induced nuclear retention. Conclusions: Our data indicate that H2S is a novel regulator of FoxO1 in cardiac cells and provide evidence supporting the potential of H2S in inhibiting the progression of DCM. Our data indicate that hydrogen sulfide (H2S) is a novel regulator of Forkhead box protein O in cardiac cells and provide evidence supporting the potential of H2S in inhibiting the progression of diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Doxorubicin (Dox) is a potent antineoplastic agent, but its use is curtailed by severe cardiotoxicity, known as Dox-induced cardiomyopathy (DIC). The molecular mechanism underlying this cardiotoxicity remains unclear. Our current study investigates the role of Ubiquitin-Specific Protease 36 (USP36), a nucleolar deubiquitinating enzyme (DUB), in the progression of DIC and its mechanism. We found increased USP36 expression in neonatal rat cardiomyocytes and H9C2 cells exposed to Dox. Silencing USP36 significantly mitigated Dox-induced oxidative stress injury and apoptosis in vitro. Mechanistically, USP36 upregulation positively correlated with Poly (ADP-ribose) polymerase 1 (PARP1) expression, and its knockdown led to a reduction in PARP1 levels. Further investigation revealed that USP36 could bind to and mediate the deubiquitination of PARP1, thereby increasing its protein stability in cardiomyocytes upon Dox exposure. Moreover, overexpression of wild-type (WT) USP36 plasmid, but not its catalytically inactive mutant (C131A), stabilized PARP1 in HEK293T cells. We also established a DIC model in mice and observed significant upregulation of USP36 in the heart. Cardiac knockdown of USP36 in mice using a type 9 recombinant adeno-associated virus (rAAV9)-shUSP36 significantly preserved cardiac function after Dox treatment and protected against Dox-induced structural changes within the myocardium. In conclusion, these findings suggest that Dox promotes DIC progression by activating USP36-mediated PARP1 deubiquitination. This novel USP36/PARP1 axis may play a significant regulatory role in the pathogenesis of DIC. • Deficiency in USP36 provides a protective effect against cardiac oxidative stress injury and apoptosis induced by Dox. • USP36 interacts with PARP1, and it is through this interaction that USP36 influences the regulation of cardiac injury. • This research broadens our understanding of the USP family's role in cardiovascular diseases. [ABSTRACT FROM AUTHOR]