Protective effect of N-acetylcysteine against cisplatin ototoxicity in rats: a study with hearing tests and scanning electron microscopy

Abstract Introduction Ototoxicity is a health problem appearing after powerful treatments in serious health conditions. It is sometimes inevitable when treatment of the serious disease is required. Cisplatin is an antineoplastic agent which was investigated previously to reveal increased nitrogen and reactive oxygen radicals that damages hair cells, resulting in ototoxicity. N-acetylcysteine, previously shown to decrease ototoxicity caused by different agents, is known to be a powerful in vitro antioxidant. Probably N-acetylcysteine, in addition to its antioxidant effect, blocks a cascade where reactive oxygen species result in apoptosis in the cochlea. Objectives The possible preventive effect of N-acetylcysteine in cisplatin ototoxicity was studied with auditory brain stem responses, otoacoustic emissions, and histopathological investigation of the cochlea in a scanning electron microscopy. Methods This study was conducted on 21 Wistar Albino rats in four groups. 1 mL/kg/day three times in total intraperitoneal (i.p.) Saline (n = 5), 500 mg/kg/day i.p. three times in total N-acetylcysteine (n = 5), i.p. 15 mg/kg cisplatin alone (single dose) (n = 5) and i.p. 15 mg/kg cisplatin plus 500 mg/kg/day N-acetylcysteine (n = 6) were administered. The rats were anesthetized to study the hearing tests before and after the experiment. The rats were sacrificed to investigate the cochleas by scanning electron microscopy. Results Auditory brain stem responses and otoacoustic emissions values were attenuated in the cisplatin group. The group that received N-acetylcysteine in addition to cisplatin had better auditory brain stem responses thresholds and otoacoustic emissions. The samples obtained from the cisplatin group showed surface irregularities, degeneration areas, and total or partial severe stereocilia losses. The changes were milder in the cisplatin + N-acetylcysteine group. Conclusion Cisplatin ototoxicity can be detected by auditory brain stem responses and otoacoustic emissions testing in rats. N-acetylcysteine may protect the cochlear cells from histopathological changes. We concluded that N-acetylcysteine given 4 h after cisplatin injection has a potential otoprotective effect against cisplatin ototoxicity. which suggests it could be used in clinical trials.

摘要 引言
耳毒性是重症患者接受强效治疗后出现的健康问题，在需针对重症疾病开展治疗的场景下，耳毒性有时难以避免。顺铂是一种抗肿瘤药物，既往研究显示其可升高体内氮及活性氧自由基水平，损伤耳蜗毛细胞，进而引发耳毒性。N-乙酰半胱氨酸此前被证实可减轻多种药物所致的耳毒性，且作为一种强效体外抗氧化剂被广泛研究。除抗氧化作用外，N-乙酰半胱氨酸或可阻断活性氧诱导耳蜗细胞凋亡的级联反应。
研究目的
本研究通过听觉脑干反应、耳声发射检测及扫描电子显微镜下的耳蜗组织病理学检查，探讨N-乙酰半胱氨酸对顺铂诱导耳毒性的预防作用。
研究方法
本研究纳入21只Wistar白化大鼠，分为4组：腹腔注射生理盐水组（1 mL/kg/次，每日3次，n=5）、腹腔注射N-乙酰半胱氨酸组（500 mg/kg/次，每日3次，n=5）、单纯腹腔注射顺铂组（单次给药15 mg/kg，n=5）以及顺铂联合N-乙酰半胱氨酸组（15 mg/kg顺铂+500 mg/kg/次N-乙酰半胱氨酸，每日3次，n=6）。实验前后均对大鼠实施麻醉以完成听力检测，实验结束后处死大鼠，通过扫描电子显微镜观察耳蜗组织。
研究结果
顺铂组大鼠的听觉脑干反应及耳声发射幅值出现明显衰减。相较于顺铂单药组，联合使用N-乙酰半胱氨酸的大鼠听觉脑干反应阈值及耳声发射指标更优。顺铂组大鼠的耳蜗标本可见组织表面不规则、变性区域以及静纤毛完全或部分严重缺失；而顺铂联合N-乙酰半胱氨酸组的组织病理改变相对轻微。
研究结论
可通过听觉脑干反应及耳声发射检测大鼠顺铂诱导的耳毒性。N-乙酰半胱氨酸可减轻耳蜗细胞的组织病理学损伤。本研究证实，顺铂注射4小时后给予N-乙酰半胱氨酸，对顺铂诱导的耳毒性具有潜在的耳保护作用，提示其可用于后续临床试验。