Bosentan confers cardioprotection against cisplatin toxicity: Involvement of β-arrestin-linked ETA receptor signaling

The endothelin system, primarily through activation of the endothelin A (ET_A) receptor, mediates vasoconstriction and triggers inflammatory and proliferative responses, positioning it as a key mediator and promising therapeutic target in cardiovascular injury. Bosentan, a dual ET_A/ET_B receptor antagonist, has been reported to act as a biased ligand at the ET_A receptor. This study investigated whether bosentan protects H9c2 cardiomyoblasts against cisplatin-induced cardiotoxicity by preferentially modulating β-arrestin-related signaling of ET_A receptor. Bosentan treatment suppressed cellular injury by attenuating Reactive Oxygen Species (ROS) production, early Apoptosis, and Caspase-3/7 activity following cisplatin exposure. Bosentan preserved mitochondrial function by improving cellular respiration and glycolysis, as well as upregulating mitochondrial regulators OPA1 and ATP5A and anti-apoptotic BCL2, while downregulating mitochondrial fission-related DNM1 and pro-apoptotic Bax. Co-treatment with endothelin-1 (ET-1) synergistically aggravated cisplatin-induced cellular injury and diminished bosentan-mediated cardioprotection, supporting the involvement of ET receptors. ET_A receptor blockade (BQ-123) enhanced bosentan-mediated protection more effectively than ET_B receptor inhibition (BQ-788), suggesting ET_A receptor dominance. Inhibition of β-arrestin (barbadin) reduced bosentan's efficacy to a greater extent than G_αq protein inhibition (FR900359), highlighting a greater contribution of β-arrestin-mediated pathways. In addition, ERK1/2 and PI3K/Akt inhibition each impaired bosentan-enhanced pro-survival response, indicating the parallel involvement of both survival cascades. Although bosentan antagonizes both ET_A and ET_B receptors and modulates β-arrestin and G_αq signaling, its protective effect appears primarily mediated by ET_A receptor antagonism and β-arrestin-linked pro-survival signaling. This potential mechanism of bosentan may provide a basis for further investigation into therapeutic strategies for chemotherapy-induced cardiotoxicity.