Cinchonine and cinchonidine alleviate cisplatin‐induced ototoxicity by regulating PI3K‐AKT signaling.

Aim: Cinchonine (CN) and its isomer cinchonidine (CD), two of the common cinchona alkaloids, are wildly used as antimalarial drugs. However, the effects of CN and CD on the auditory system are unknown. Methods: Molecular docking and molecular dynamics (MD) simulation were used for predicting effective drugs. The CCK‐8 assay was conducted for assessing cell viability in House Ear Institute‐Organ of Corti 1 (HEI‐OC1) cells. MitoSox Red staining revealed reactive oxygen species (ROS) amounts. TMRM staining was used to assess the mitochondrial membrane potential (ΔΨm). Immunofluorescence staining of myosin 7a was used to examine hair cells (HCs) in cisplatin‐treated neonatal mouse cochlear explants, while TUJ‐1 immunostaining was used for the detection of spiral ganglion neurons (SGNs). Cleaved caspase‐3 and TUNEL immunostaining were utilized for apoptosis assessment. Immunoblot was carried out to detect PI3K‐AKT signaling effectors. Results: Pretreatment with CN or CD significantly increased cell viability and reduced mitochondrial dysfunction and ROS accumulation in cisplatin‐treated HEI‐OC1 cells. Immunofluorescent staining of cochlear explants showed that CN and CD attenuated cisplatin‐induced damage to SGNs and HCs. Immunoblot revealed that CN and CD downregulated the expression of cleaved caspase‐3 and activated PI3K‐AKT signaling in cisplatin‐injured HEI‐OC1 cells. Conclusion: CD and CN can reduce ototoxicity caused by cisplatin and might help treat cisplatin‐associated hearing loss. [ABSTRACT FROM AUTHOR]