TNF-α And IL-6 Expression In Cochlea Of Model Of Presbycusis During Aging

Object To study the alternation of proinflammatory cytokines TNF-αand IL-6 in the process of ageing in the C57BL/6J mice.Methods1. Eighteen C57BL/6J mice were divided into three groups : 4- , 20- ,36-40-week-old .2. In our study, RT-PCR were employed to show different expression among three groups of C57BL/6J mice.3. Immunohistochemistry were employed to show different expression and distribution among three groups of C57BL/6J mice.4. Otherwise,we use conventional hematoxylin and eosin (H&E) staining to display morphology of cochlea of different groups.Results1.Conventional hematoxylin and eosin (H&E) staining showed normal morphology of cochlea in the 4-w-group and 20-w-group C57BL/6J mice.But abnormal structure were detected in the 36-40-group:disorganization of the organ of Corti, a decrease in the number of spiral ganglion cells, and atrophy of the stria vascularis.2.RT-PCR showed that TNF-αmRNA concentration was weak in the 4-w-group,but in the 20- and 36-40-w-group,expression of TNF-αwas apparently increased. The statistic results for gel electrophoresis:4-w-group:0.107±0.014;20-w-group:0.364±0.061;36-40-group:0.584±0.042.All comparison between any two groups has statistics significance(P<0.001).3.RT-PCR showed that IL-6 mRNA concentration was faint in the 4-w-group,but in the 20- and 36-40-w-group,expression of TNF-αwas apparently increased. The statistic results for gel electrophoresis:4-w-group:0.015±0.009; 20-w-group: 0.358±0.027;36-40-w-group:0.528±0.061.All comparison between any two groups has statistics significance(P<0.001).4.Immunohitochemistry showed that the expression of TNF-αwas weakly positive in the cochleae of the 4-w-group C57BL/6J mice,but significant positive cells were observed in both 20- and 36-40-w-group,and positive cells distributed in the spiral ganglion cells, stria vasculari and the organ of Corti. The statistical analysis of OD values:4-w-group:0.0034±0.0009;20-w-group:0.1362±0.0241;36-40-group : 0.1920±0.0328.All comparison between any two groups has statistics significance(P<0.01).5.Immunohitochemistry showed that the expression of IL-6 was almost negative in the cochleae of the 4-w-group C57BL/6J mice,but significant positive cells were observed in both 20-w- and 36-40-w-group,and positive cells distribution was concurrent with TNF-α. The statistical analysis of OD values:4-w-group:0.0008±0.0002;20-w-group:0.1459±0.0273;36-40-group:0.1868±0.0356.All comparison between any two groups has statistics significance(P<0.05).Conclusions:1. Comparing to 4-w- and 20-w-group mice, cochlea sections stained with H&E showing atrophy of stria vascularis,a decreased number of spiral ganglion cells,and disorganization of the organ of Corti with loss of hair cell in the 36-40-w-group.2. Expression of TNF-αand IL-6 mRNAs were apparently increased in the 20-w - and 36-40-w-group C57/BL6 mice comparing to 4-w one and the positive cells distributed in the spiral ganglion cells, stria vasculari and the organ of Corti.3. Our study indicates that inflammaging would have intense relationship with presbycusis,and proinflammatory cytokines TNF-αand IL-6 may play some role in the mechanism of presbycusis.