ABSTRACT
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 1h 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 of modiolus 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 1h 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/p-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/p-actin was 0. 4993 ± 0. 0994 for the noise group and 0. 5139±0. 0132 for the controI (P＞0. 05). CONCLUSION Noise exposure significantly decreased histone acetylation expression in the nuclei of strial 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 ofNIHL.
ABSTRACT
Objective To study the changes of acetyl-histone H2B in the cochlear hair cells of the guinea pig model of noise-induced hearing loss (NIHL).Methods Sixty guinea pigs were randomly divided into control and noise-exposure group.Thirty guinea pigs in the noise-exposure group were exposed to narrowband noise at 122 dB SPL for 3 hours , while thirty guinea pigs in the control group were not exposed to noise.Auditory thresholds were assessed by auditory brainstem response (ABR), prior to noise in two groups and 3, 7,14 and 21 days after noise exposure in the noise group.Then we investigated the expression of acetyl-histone H2B levels in the sensory cells of basilar membrane after noise expose by immunofluorescence staining and western blot.Results Compared with pre-exposure hearing, ABR thresholds were increased at 1h, 3, 7, 14 and 21 days after noise exposure, and recovered gradually with time and reached a permanent threshold shift at 14 days.The expression of acetyl-histone H2B was down-regulated in the hair cells and Hensen''s cells of the guinea pig cochlea after the noise expose , The ratio of H2B-AcK5 / β-actin was 0.6179±0.1260 in the control group and 0.3102±0.0839 in the noise group, and the difference was statistically significant (P<0.01).Conclusion Noise decreased the inner ear sensory cells histone acetylation level and histone acetylation imbalance may be involved in the occurrence of NIHL.
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OBJECTIVE To investigate the features of somatic mutations of the hypervariable region (HV) of mitochondrial DNA (mtDNA) D-loop in laryngeal squamous cell carcinoma (LSCC) and the relationship with clinicopathological characteristics. METHODS Microdissected cancerous tissues, paracancerous tissues and peripheral vein blood were obtained from 40 patients with LSCC and total DNA was extracted. HVⅠ and HVⅡ fragments were amplified by PCR and purified. Mutations were determined by DNA sequencing. The mutations of HVⅠand HVⅡ and their relationship with clinicopathological characteristics were analyzed. RESULTS ①In 40 LSCC samples, 86 polymorphisms were found, 21 (52.5 %) tumors presented somatic mtDNA mutations with a total of 34 mutations. Among them, 28 (82.4 %) and 6 (17.6 %) were located in HVⅠ and HVⅡ respectively. ②Tumor D-loop mutation showed significant correlation with tumor differentiation(P=0.028) and p53 mutation (P=0.041), respectively. CONCLUSION Mitochondrial DNA D-loop in LSCC is an unstable region with high frequency of somatic mutation and high polymorphism and might play a potential role in the carcinogenesis of the larynx.