Expression of tumor necrosis factor-α and interleukin-1β genes in the cochlea and inferior colliculus in salicylate-induced tinnitus

• Published in: Journal of neuroinflammation 2011-04, Vol.8 (1), p.30-30, Article 30
• Main Authors: Hwang, Juen-Haur, Chen, Jin-Cherng, Yang, Shan-Ying, Wang, Ming-Fu, Chan, Yin-Ching
• Format: Article
• Language: English
• Subjects: Animals; Behavior, Animal; Cochlea - physiology; Conditioning (Psychology); Gene Expression - drug effects; Humans; Inferior Colliculi - physiology; Interleukin-1beta - genetics; Interleukin-1beta - metabolism; Male; Mice; Motor Activity - drug effects; Random Allocation; Receptors, N-Methyl-D-Aspartate - genetics; Receptors, N-Methyl-D-Aspartate - metabolism; RNA, Messenger - metabolism; Salicylates - pharmacology; Salicylates - toxicity; Tinnitus - chemically induced; Tinnitus - physiopathology; Tumor Necrosis Factor-alpha - genetics; Tumor Necrosis Factor-alpha - metabolism
• ISSN: 1742-2094; 1742-2094
• DOI: 10.1186/1742-2094-8-30

Changes in the gene expressions for tumor necrosis factor-α (TNF-α) and/or interleukin-1β (IL-1β) during tinnitus have not been previously reported. We evaluated tinnitus and mRNA expression levels of TNF-α, IL-1β, and N-methyl D-aspartate receptor subunit 2B (NR2B) genes in cochlea and inferior colliculus (IC) of mice after intraperitoneal injections of salicylate. Forty-eight 3-month-old male SAMP8 mice were randomly and equally divided into two groups: salicylate-treated and saline-treated. All mice were trained to perform an active avoidance task for 5 days. Once conditioned, an active avoidance task was performed 2 hours after daily intraperitoneal injections of saline, either alone or containing 300 mg/kg sodium salicylate. Total numbers of times (tinnitus score) the mice climbed during the inter-trial silent period for 10 trials were recorded daily for 4 days (days 7 to 10), and then mice were euthanized for determination of mRNA expression levels of TNF-α, IL-1β, and NR2B genes in cochlea and IC at day 10. Tinnitus scores increased in response to daily salicylate treatments. The mRNA expression levels of TNF-α increased significantly for the salicylate-treated group compared to the control group in both cochlea (1.89 ± 0.22 vs. 0.87 ± 0.07, P < 0.0001) and IC (2.12 ± 0.23 vs. 1.73 ± 0.22, p = 0.0040). mRNA expression levels for the IL-1β gene also increased significantly in the salicylate group compared to the control group in both cochlea (3.50 ± 1.05 vs. 2.80 ± 0.28, p < 0.0001) and IC (2.94 ± 0.51 versus 1.24 ± 0.52, p = 0.0013). Linear regression analysis revealed a significant positive association between tinnitus scores and expression levels of TNF-α, IL-1β, and NR2B genes in cochlea and IC. In addition, expression levels of the TNF-α gene were positively correlated with those of the NR2B gene in both cochlea and IC; whereas, the expression levels of the IL-1β gene was positively correlated with that of the NR2B gene in IC, but not in cochlea. We conclude that salicylate treatment resulting in tinnitus augments expression of the TNF-α and IL-1β genes in cochlea and IC of mice, and we suggest that these proinflammatory cytokines might lead to tinnitus directly or via modulating the NMDA receptor.