Objectives: Cisplatin, a widely used chemotherapeutic agent, has serious side effects, including nephrotoxicity and ototoxicity. Minocycline is a semisynthetic second-generation tetracycline that exerts anti-inflammatory and neuroprotective effects. The purpose of this study was to elucidate the protective effect of minocycline against cisplatin-induced ototoxicity in the auditory hair cell.
Methods: The House Ear Institute-Organ of Corti 1 (HEI-OC1) cell line and guinea pigs were used for in vitro and in vivo experiments. Cells were exposed to cisplatin with or without pre-treatment with minocycline. Cell survival was analyzed using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). Whole-cell lysates were collected and immunoblotted with antibodies against Bcl-2, p-c-Jun, active caspase-3, cleaved poly (ADP-ribose) polymerase (PARP), and apoptosis-inducing factor (AIF). The guinea pigs received intraperitoneal injections of cisplatin alone or following minocycline pretreatment. The auditory brainstem response was tested and the cochleae were harvested and evaluated using scanning electron microscopy.
Results: Survival significantly increased in cells pretreated with minocycline compared with cells exposed to cisplatin alone. Cisplatin treatment increased the expression of active caspase 3, p-c Jun, PARP, and AIF, and pretreatment with minocycline attenuated this response. In animal study, the threshold shift by cisplatin injection in the auditory brainstem response was less pronounced in animals pretreated with minocycline. Scanning electron microscopy revealed more severe damage to the outer hair cells at the basal and middle turns than the apical turn.
Conclusion: Minocycline partially protects against cisplatin-induced ototoxicity via both caspase-dependent and independent apoptosis pathways.
Keywords: Apoptosis; Caspase; Hair cell; Minocycline.