ABSTRACT Cisplatin‐induced ototoxicity is a detrimental side effect of chemotherapy leading to hearing loss, for which no treatments are currently available. Despite the growing recognition of the endocannabinoid (eCB) system (ECS) as a significant contributor to different physiological and pathological processes, its role in hearing remains poorly investigated. To fill this knowledge gap, we performed a molecular profiling of the ECS in auditory hair cell (HC)‐like UB/OC1 cells derived from the mouse organ of Corti (OC), demonstrating the presence of the main eCBs‐binding receptors and metabolic enzymes along with the major eCBs ( N ‐arachidonoylethanolamine, AEA, and 2‐arachidonoylglycerol, 2‐AG) and additional eCB‐like compounds. Subsequently, we established an in vitro model of cisplatin‐induced ototoxicity, which was characterized by the downregulation of the HC marker myosin 7a (Myo 7a), and activation of nuclear factor kappa‐light‐chain‐enhancer of activated B‐cells (NF‐κB) associated with caspase‐3‐mediated cell death. In this model, we observed a downregulation of cannabinoid receptor 2 (CB 2 R), diacylglycerol lipase β (DAGLβ), and α/β hydrolase domain‐containing protein 6 (ABHD6), indicating a perturbation of the 2‐AG metabolic pathway. Furthermore, we validated the observed in vitro alterations in the OC of an in vivo model of cisplatin‐induced ototoxicity, thereby strengthening the physiological relevance of our findings. Finally, we demonstrated that pharmacological blockade of CB 2 R through SR144528 mitigates cisplatin‐induced HC damage via inhibition of caspase‐3 cleavage in UB/OC1 HC‐like cells, thereby providing novel mechanistic insights into the role of CB 2 R in ototoxicity. Overall, our study demonstrates the involvement of selective elements of the ECS in cisplatin‐induced ototoxicity, hence identifying novel potential biomolecular targets for chemotherapy‐related side effects.
Palaniappan et al. (Tue,) studied this question.