Rybak L P, Husain K, Morris C, Whitworth C, Somani S
Department of Surgery and Pharmacology, Southern Illinois University School of Medicine, Springfield 62794-1312, USA.
Am J Otol. 2000 Jul;21(4):513-20.
The goals of this investigation were to compare the efficacy of three protective agents against cisplatin-induced elevation of auditory brainstem response (ABR) thresholds and to examine whether these protective agents prevent cisplatin-induced alterations of the antioxidant defense system in the cochlea of the rat.
Cisplatin is an ototoxic antitumor agent. Previous animal studies have shown that cisplatin administration causes an elevation of ABR thresholds. These auditory changes are accompanied by alterations in the concentration of glutathione and the antioxidant enzymes in the cochlea. The authors' previous work has indicated that the protective agent diethyldithiocarbamate (DDTC) prevents decrease in glutathione (GSH), alteration of antioxidant enzyme activity, and disruption of cochlear function with cisplatin administration.
Wistar rats were sedated and underwent pretreatment ABR testing using clicks and tone burst stimuli at 8, 16, and 32 kHz. Control rats received saline by intraperitoneal (i.p.) injection. Positive control rats were administered cisplatin 16 mg/kg i.p. Three groups of rats received protective agents in combination with cisplatin. The DDTC-protected rats were given 600 mg/kg of DDTC subcutaneously 1 hour after cisplatin. Animals protected by 4-methylthiobenzoic acid (MTBA) were given 250 mg/kg of this agent i.p. 30 minutes before cisplatin. Animals protected with ebselen were given 16 mg/kg i.p. one hour before cisplatin. The ABR thresholds were recorded 72 hours after cisplatin administration in all groups. Cochleas were removed, and extracts of the tissues were analyzed for GSH, activities of antioxidant enzymes (superoxide dismutase [SOD], catalase, glutathione peroxidase, and glutathione reductase) and malondialdehyde (MDA) (as an index of lipid peroxidation).
Cisplatin-treated rats had significant ABR threshold shifts, ranging from 27 to 40 dB. Rats administered each of the three protective agents in combination with cisplatin had ABR threshold shifts of <10 dB. The cochleae of rats administered cisplatin alone had nearly a 50% depletion of glutathione and about a 50% reduction in the activities of SOD, glutathione peroxidase, and glutathione reductase, while catalase activity was reduced to 70% of control values. These changes were accompanied by a reciprocal elevation of MDA of 165%. These changes, namely, the depletion of GSH and antioxidant enzyme activity and the elevation of MDA in the cochlea, were largely attenuated by the administration of the protective agents tested.
These findings suggest that cisplatin ototoxicity is related to lipid peroxidation and that the use of protective agents prevents hearing loss and lipid peroxidation by sparing the antioxidant system in the cochlea. These results suggest the possibility that the clinical use of protective agents could effectively reduce or prevent damage to the inner ear of patients receiving cisplatin chemotherapy, provided that the antitumor effect is not altered.
本研究的目的是比较三种保护剂对顺铂诱导的听性脑干反应（ABR）阈值升高的疗效，并研究这些保护剂是否能预防顺铂诱导的大鼠耳蜗抗氧化防御系统的改变。
顺铂是一种耳毒性抗肿瘤药物。先前的动物研究表明，给予顺铂会导致ABR阈值升高。这些听觉变化伴随着耳蜗中谷胱甘肽浓度和抗氧化酶的改变。作者之前的研究表明，保护剂二乙基二硫代氨基甲酸盐（DDTC）可预防顺铂给药导致的谷胱甘肽（GSH）减少、抗氧化酶活性改变以及耳蜗功能破坏。
将Wistar大鼠麻醉，使用8、16和32kHz的短声和短纯音刺激进行预处理ABR测试。对照大鼠腹腔内（i.p.）注射生理盐水。阳性对照大鼠腹腔内注射16mg/kg顺铂。三组大鼠接受保护剂与顺铂联合给药。DDTC保护组的大鼠在顺铂给药后1小时皮下注射600mg/kg DDTC。4-甲基硫代苯甲酸（MTBA）保护的动物在顺铂给药前30分钟腹腔内注射250mg/kg该药物。用依布硒啉保护的动物在顺铂给药前1小时腹腔内注射16mg/kg。在所有组中，于顺铂给药72小时后记录ABR阈值。取出耳蜗，分析组织提取物中的GSH、抗氧化酶（超氧化物歧化酶[SOD]、过氧化氢酶、谷胱甘肽过氧化物酶和谷胱甘肽还原酶）活性以及丙二醛（MDA）（作为脂质过氧化指标）。
顺铂处理的大鼠ABR阈值有显著变化，范围为27至40dB。三种保护剂与顺铂联合给药的大鼠ABR阈值变化<10dB。单独给予顺铂的大鼠耳蜗中谷胱甘肽消耗近50%，SOD、谷胱甘肽过氧化物酶和谷胱甘肽还原酶活性降低约50%，而过氧化氢酶活性降至对照值的70%。这些变化伴随着MDA升高165%。所测试的保护剂给药在很大程度上减轻了耳蜗中GSH消耗、抗氧化酶活性改变以及MDA升高这些变化。
这些发现表明顺铂耳毒性与脂质过氧化有关，并且使用保护剂通过保护耳蜗中的抗氧化系统来预防听力损失和脂质过氧化。这些结果提示，只要不改变抗肿瘤效果，保护剂的临床应用有可能有效减少或预防接受顺铂化疗患者的内耳损伤。
