Noise-induced changes in gene expression in the cochleae of mice differing in their susceptibility to noise damage

The molecular mechanisms underlying the vast differences between individuals in their susceptibility to noise-induced hearing loss (NIHL) are unknown. The present study demonstrated that the effects of noise over-exposure on the expression of molecules likely to be important in the development of NIHL differ among inbred mouse strains having distinct susceptibilities to NIHL including B6 (B6.CAST) and 129 (129X1/SvJ and 129S1/SvImJ) mice. The noise-exposure protocol produced a loss of 40 dB in hearing sensitivity in susceptible B6 mice, but no loss for the two resistant 129 substrains. Analysis of gene expression in the membranous labyrinth 6 h following noise exposure revealed upregulation of transcription factors in both the susceptible and resistant strains. However, a significant induction of genes involved in cell-survival pathways such as the heat shock proteins HSP70 and HSP40, growth arrest and DNA-damage-inducible protein 45β (GADD45β), and CDK-interacting protein 1 (p21(Cip1)) was detected only in the resistant mice. Moreover, in 129 mice significant upregulation of HSP70, GADD45β, and p21(Cip1) was confirmed at the protein level. Since the functions of these proteins include roles in potent anti-apoptotic cellular pathways, their upregulation may contribute to protection from NIHL in the resistant 129 mice.