噪声对耳蜗边缘细胞及螺旋神经节细胞乙酰化组蛋白H2B的影响

Noise-induced acetyl-histone H2B expression alteration in marginal cell of stria vascularis and spiral ganglion cell of cochlear

目的观察噪声性聋豚鼠耳蜗侧壁血管纹边缘细胞及蜗轴螺旋神经节细胞乙酰化组蛋白H2B表达水平的变化。方法成年雄性白色红目豚鼠50只随机分为噪声组和对照组,通过听性脑干反应检测两组豚鼠噪声前听力,噪声组给予高强度窄带噪声(122 dB SPL,3 h)暴露,于暴露后1 h行ABR检测噪声后听力,并通过免疫荧光染色和Western blot方法检测暴露后2 h两组豚鼠耳蜗血管纹边缘细胞及蜗轴螺旋神经节细胞中乙酰化组蛋白H2B的表达水平。结果两组豚鼠噪声暴露前听力在4、8、16与32 kHz频率的反应阈比较,差异无统计学意义。噪声组在噪声刺激1 h后ABR阈值在4、8、16与32 kHz频率的最大输出90 dB无反应。免疫荧光染色显示在噪声刺激2 h后血管纹边缘细胞中乙酰化组蛋白H2B荧光强度明显下降,Western blot显示噪声组豚鼠侧壁中乙酰化组蛋白H2B表达(H2B-AcK5/β-actin的比值为0.3471±0.0843)较对照组(0.6114±0.0207)明显下调,两组比较差异有统计学意义(t=5.268,P<0.01)。耳蜗蜗轴组织中乙酰化组蛋白H2B表达在噪声组和对照组中分别为(0.4993±0.0994)和(0.5139±0.0132),两组比较差异无统计学意义(P>0.05)。结论噪声可导致豚鼠耳蜗血管纹边缘细胞组蛋白乙酰化水平显著下降,螺旋神经节细胞中组蛋白乙酰化水平无明显改变,血管纹边缘细胞组蛋白乙酰化失衡有可能参与噪声性聋的发生发展。

OBJECTIVE Aimed to observe the changes of acetylated histone H2B in the marginal cells of stria vascularis and spiral ganglion cells from the noise- induced hearing loss model（NIHL）. METHODS Fifty guinea pigs were randomly divided into control and noise- exposure group. Auditory brainstem response threshold shift was examined before noise exposure and at lh after noise exposure（122 dB SPL, 3 h）. Immunofluorescence staining and western blot were used to observe the expression of acetyl-histone H2B both in the marginal cells of stria vascularis and spiral ganglion cells ofmodiolus 2 h after noise expose in two groups. RESULTS There was no significant difference in hearing threshold of 4, 8, 16, 32 kHz for the two groups before noise exposure. The hearing threshold was beyond 90dB（the maximum output） at 4, 8, 16 and 32 kHz lh after noise exposure. The expression of acetylated histone H2B significantly decreased with immunofluorescence staining in the marginal cells after noise stimulation. Accordingly, the protein level of acetylated histone H2B in the lateral wall of cochlear decreased obviously in the noise group compared to the control, the ratios of H2B- AcK5/13-actin were 0.3471 ± 0.0843 and 0.6114 ± 0.0207 respectively（t=5.268, P〈 0.01）. There was no obvious difference for the expression of acetylated histone H2B in the modiolar tissue between two groups, the ratio of H2B- AcK5/β-actin was 0.4993 ± 0.0994 for the noise group and 0.5139 ± 0.0132 for the control（P〉 0.05）. CONCLUSION Noise exposure significantly decreased histone acetylation expression in the nuclei of stria/marginal cells, whereas the level in the spiral ganglion cells remained stable. Histone acetylation imbalance in the marginal cells of stria vascularis may contributed to the occurrence of NIHL.