Carnosic acid protects against doxorubicin-induced cardiotoxicity through enhancing the Nrf2/HO-1 pathway

Doxorubicin (DOX) is used extensively in anticancer therapy, but its clinical application is limited due to its cardiotoxicity. Carnosic acid (CA) is a bioactive compound found in rosemary. It has been shown to reduce inflammation and reactive oxygen species. The purpose of this study was to investigate the potential cardioprotective effects of CA in response to DOX-induced cardiotoxicity. Here, C57BL/6 mice were administered an intraperitoneal injection of DOX (5 mg kg^-1, ip) once a week for three consecutive weeks and treated with CA (40 mg kg^-1, ig) for a three-week experimental period. For in vitro study, neonatal rat ventricular cardiomyocytes were used to validate the protective effects of CA (20 μM) in response to DOX-induced cardiotoxicity. CA markedly suppressed oxidative stress, apoptosis, and pyroptosis responses in the mouse hearts, eventually improving cardiac function. CA showed its antioxidant effect by activating nuclear factor erythroid 2-related factor (Nrf2) and its downstream heme oxygenase-1 (HO-1); CA also reduced oxidative stress by lowering the MDA and lipid ROS levels and raising the SOD and GSH-px levels. Additionally, CA treatment significantly increased Bcl-2 and inhibited Bax and Caspase-3 cleavage in DOX-induced cardiotoxicity. Moreover, CA suppressed the NOD-like receptor protein 3 (NLRP3) pathway to mitigate pyroptosis, as evidenced by lowered caspase1, interleukin-18, and interleukin-1β. Consistently, the transfection of Nrf2-siRNA eliminated the protective effects of CA on cardiomyocytes. Altogether, our findings demonstrated that CA inhibited NLRP3 inflammasomes via activating the Nrf2-related cytoprotective system and protected the heart from oxidative damage, apoptosis, and pyroptosis, implying that the use of CA could be a potential therapeutic strategy in the prevention of DOX-associated myocardiopathy.