Expression of tumor necrosis factor-alpha and interleukin-1beta genes in the cochlea and inferior colliculus in salicylate-induced tinnitus (Journal of Neuroinflammation)

Background: Changes in the gene expressions for tumor necrosis factor-alpha (TNF-alpha) and/or interleukin-1beta (IL-1beta) during tinnitus have not been previously reported. We evaluated tinnitus and mRNA expression levels of TNF-alpha, IL-1beta, and N-methyl D-aspartate receptor subunit 2B (NR2B) genes in cochlea and inferior colliculus (IC) of mice after intraperitoneal injections of salicylate. Methods: 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-alpha, IL-1beta, and NR2B genes in cochlea and IC at day 10. Results: Tinnitus scores increased in response to daily salicylate treatments. The mRNA expression levels of TNF-alpha 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