AIMS: Doxorubicin (DOX), an effective and commonly used chemotherapeutic agent, often triggers dosage-dependent and potentially lethal cardiotoxicity, which heavily limits its clinical application in cancer survivors. However, no actual pharmacological therapeutics for this adverse effect are available. Tirzepatide (TZP), a novel GIP/GLP-1 receptor agonist, exhibits efficacy in controlling glycaemia and has very recently been approved for the treatment of type 2 diabetes. Several clinical trials provided evidence that TZP treatment contributed to a substantial reduction in HbA1c levels, body weight, and cardiovascular risk factors through the involvement of biochemical and molecular mechanisms that needed to be deeply explored. Here, we aimed to investigate the role of TZP in DOX-induced cardiotoxicity and to clarify the underlying mechanisms.
METHODS AND RESULTS: Male C57BL/6 mice were exposed to subcutaneous injections of TZP or an equal volume of vehicle once a day for 14 consecutive days. To generate DOX-induced cardiotoxicity, the mice received a single intraperitoneal injection of DOX (15 mg/kg). In vitro studies were performed on the H9c2 cell line in exposure to DOX alone or combined with TZP incubation. Echocardiographic measurement, histological assessment, and molecular analysis were obtained to determine the impact of TZP treatment on cardiotoxicity induced by DOX insult. To explore the underlying mechanisms, we performed RNA sequencing of murine heart tissue to screen for the potential targets. Moreover, Ad-Hrd1 and siNrf2 were utilized to further confirm the involvement of HRD1 and Nrf2 in this process. Mice with TZP administration were protected from myocardial injury, cardiac dysfunction, and fatality in response to DOX. A significant reduction in both oxidative stress and cardiomyocyte apoptosis induced by DOX injection was also observed in the presence of TZP. Consistently, results obtained from in vitro studies revealed that DOX challenge impaired cell viability and led to elevated oxidative damage and cellular apoptosis, which were significantly alleviated in TZP-treated H9c2 cells. Mechanistically, we provided direct evidence that the cardioprotective effect of TZP was mediated by the transcription factor Nrf2 in an HRD1-dependent manner. Upon DOX treatment, TZP incubation could prevent ER stress-induced HRD1 upregulation in cardiomyocytes and subsequently decrease the ubiquitylation and degradation of Nrf2, thus enhancing its protein expression level, nuclear translocation, and transcription activity, ultimately contributing to the decreased oxidative stress and cardiomyocyte apoptosis.
CONCLUSION: Our study suggested that TZP attenuated oxidative stress and cardiomyocyte apoptosis by modulating HRD1-mediated Nrf2 expression and activity, thereby protecting against the cardiotoxic effects exerted by DOX. These results supported that TZP might be a promising therapeutic option for reducing chemotherapy-related cardiotoxicity.
