title: Time response of carboplatin-induced hearing loss in rat.
abstract: Carboplatin is currently being used as an anticancer drug against human cancers. However, high dose of carboplatin chemotherapy resulted in hearing loss in cancer patients. We have shown that carboplatin-induced hearing loss was related to dose-dependent oxidative injury to the cochlea in rat model. However, the time response of ototoxic dose of carboplatin on hearing loss and oxidative injury to cochlea has not been explored. The aim of the study was to evaluate the time response of carboplatin-induced hearing loss and oxidative injury to the cochlea of the rat. Male Wistar rats were divided into two groups of 30 animals each and treated as follows: (1) control (normal saline, i.p.) and (2) carboplatin (256 mg/kg, a single i.p. bolus injection). Auditory brain-evoked responses (ABRs) were recorded before and 1-5 days after treatments. The animals (n = 6) from each group were sacrificed on day 1, 2, 3, 4, and 5 and cochleae were isolated and analyzed. Carboplatin significantly elevated the hearing thresholds to clicks and to 2, 4, 8, 16, and 32 kHz tone burst stimuli only 3-5 days post-treatment. Carboplatin significantly increased nitric oxide (NO), malondialdehyde (MDA) levels and manganese superoxide dismutase (Mn-SOD) activity in the cochlea 4-5 and 3-5 days post-treatment, respectively, indicating enhanced influx of free radicals and oxidative injury to the cochlea. Carboplatin significantly depressed the reduced to oxidized glutathione (GSH/GSSG) ratio, antioxidant enzyme activities such as copper/zinc-superoxide dismutase (CuZn-SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) as well as enzyme protein expressions in the cochlea 3-5 days after treatment. The data suggest that carboplatin-induced hearing loss involves oxidative injury to the cochlea of the rat in a time-dependent manner.
authors.affiliation: Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL 62794, USA. khusain@psm.edu
authors.forename: K
authors.initials: K
authors.lastname: Husain
authors.forename: B
authors.initials: B
authors.lastname: Scott
authors.forename: C
authors.initials: C
authors.lastname: Whitworth
authors.forename: L P
authors.initials: LP
authors.lastname: Rybak
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000633:toxicity*; D016190:Carboplatin / Q000008:administration & dosage / Q000633:toxicity*; D016022:Case-Control Studies; D003051:Cochlea / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D016057:Evoked Potentials, Auditory, Brain Stem; D005978:Glutathione / Q000032:analysis; D019803:Glutathione Disulfide / Q000032:analysis; D006319:Hearing Loss, Sensorineural / Q000139:chemically induced*; D006801:Humans; D008297:Male; D008315:Malondialdehyde / Q000032:analysis; D023421:Models, Animal; D009569:Nitric Oxide / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000032:analysis
chemical_list: D000970:Antineoplastic Agents; D009569:Nitric Oxide; D008315:Malondialdehyde; D016190:Carboplatin; D013482:Superoxide Dismutase; D005978:Glutathione; D019803:Glutathione Disulfide