Yang Weiping, Hu Bohua, Chen Guangdi, Bielefeld Eric C, Henderson Donald
Institute of Otolaryngology, Chinese General Hospital of PLA, Beijing, 100853, China.
Lin Chuang Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2011 Feb;25(4):176-9.
To observe the effects of N-acetyl-L-cysteine (L-NAC) protect hair cells in the rat cochlea from injury of exposure to styrene.
Seventeen adult Long Evans rats were used in present study. The animals were randomly assigned into test group (n=9) and control group (n=8). The animals were exposed to styrene by gavage at 400 mg/kg (2 g styrene was mixed with 1 ml olive oil). Test group animals received styrene exposure plus L-NAC 325 mg/kg (L-NAC was dissolved in physiological saline solution) by intraperitoneal injection. Treatment was performed once a day, 5 days per week for 3 weeks. Control group animals received the same volume of saline injection on an identical time schedule used for the test group. The auditory brainstem response (ABR) thresholds of both ears elicited with clicks were measured before and at the end of the 3-week styrene or styrene plus L-NAC treatment. After hearing was re-assessed, animals were sacrificed and cochleae were quickly removed from the skull. Following fixation, whole specimens comprising the basilar membrane with Corti's organ were separated from the modiolus. The organs of Corti were stained with propidium iodide (PI) and the TUNEL assay to visualize the morphologic viability of hair cell nuclei, FITC-labeled phalloidin, a F-actin intercalating fluorescent probe used to visualize the morphologic viability of cuticular plate and the stereocilia in the hair cells. Each organ of Corti was thoroughly examined using fluorescence microscopy. The numbers of damaged OHCs (apoptotic, necrotic and missing OHCs) were documented.
There was a statistically significant decrease in ABR threshold shift (P<0.05) in the styrene-plus-L-NAC treated animals. The average percentage of damaged OHCs in the styrene-treated animals was 28.3%. In contrast, the average percentage of OHC damage in the styrene-plus-L-NAC treated group was only 10.6% (P<0.01). The percentage of reduction in the number of apoptotic cells in styrene-plus-L-NAC treated group was 78% (P<0.01). However, the mean reduction of necrotic cells was only 23% (P>0.05).
The results indicate that the treatment with L-NAC may effectively protect against the styrene-induced hair cells damage and preferably reduce the number of apoptotic OHCs.
观察N-乙酰-L-半胱氨酸（L-NAC）对大鼠耳蜗毛细胞免受苯乙烯暴露损伤的保护作用。
本研究使用17只成年Long Evans大鼠。动物被随机分为试验组（n = 9）和对照组（n = 8）。通过灌胃给予动物400 mg/kg苯乙烯（2 g苯乙烯与1 ml橄榄油混合）。试验组动物在接受苯乙烯暴露的同时，通过腹腔注射给予325 mg/kg L-NAC（L-NAC溶解于生理盐水中）。每天治疗1次，每周5天，共3周。对照组动物在与试验组相同的时间安排下接受相同体积的生理盐水注射。在3周苯乙烯或苯乙烯加L-NAC治疗前及治疗结束时，测量双耳点击诱发的听性脑干反应（ABR）阈值。听力重新评估后，处死动物并迅速从颅骨中取出耳蜗。固定后，将包含基底膜和柯蒂氏器的整个标本从蜗轴分离。用碘化丙啶（PI）和TUNEL法对柯蒂氏器进行染色，以观察毛细胞核的形态活力，用FITC标记的鬼笔环肽（一种F-肌动蛋白嵌入荧光探针）观察毛细胞表皮板和静纤毛的形态活力。使用荧光显微镜对每个柯蒂氏器进行全面检查。记录受损外毛细胞（凋亡、坏死和缺失的外毛细胞）的数量。
苯乙烯加L-NAC治疗的动物ABR阈值变化有统计学显著降低（P<0.05）。苯乙烯治疗动物中外毛细胞受损的平均百分比为28.3%。相比之下，苯乙烯加L-NAC治疗组中外毛细胞损伤的平均百分比仅为10.6%（P<0.01）。苯乙烯加L-NAC治疗组凋亡细胞数量减少的百分比为78%（P<0.01）。然而，坏死细胞的平均减少率仅为23%（P>0.05）。
结果表明，L-NAC治疗可有效预防苯乙烯诱导的毛细胞损伤，并优先减少凋亡外毛细胞的数量。
