PT  - JOURNAL ARTICLE
AU  - Bo Hua Hu
AU  - Qunfeng Cai
AU  - Zihua Hu
AU  - Minal Patel
AU  - Jonathan Bard
AU  - Jennifer Jamison
AU  - Donald Coling
TI  - Metalloproteinases and Their Associated Genes Contribute to the Functional Integrity and Noise-Induced Damage in the Cochlear Sensory Epithelium
AID  - 10.1523/JNEUROSCI.1588-12.2012
DP  - 2012 Oct 24
TA  - The Journal of Neuroscience
PG  - 14927--14941
VI  - 32
IP  - 43
4099  - http://www.jneurosci.org/content/32/43/14927.short
4100  - http://www.jneurosci.org/content/32/43/14927.full
SO  - J. Neurosci.2012 Oct 24; 32
AB  - Matrix metalloproteinases (MMPs) and their related gene products regulate essential cellular functions. An imbalance in MMPs has been implicated in various neurological disorders, including traumatic injuries. Here, we report a role for MMPs and their related gene products in the modulation of cochlear responses to acoustic trauma in rats. The normal cochlea was shown to be enriched in MMP enzymatic activity, and this activity was reduced in a time-dependent manner after traumatic noise injury. The analysis of gene expression by RNA sequencing and qRT-PCR revealed the differential expression of MMPs and their related genes between functionally specialized regions of the sensory epithelium. The expression of these genes was dynamically regulated between the acute and chronic phases of noise-induced hearing loss. Moreover, noise-induced expression changes in two endogenous MMP inhibitors, Timp1 and Timp2, in sensory cells were dependent on the stage of nuclear condensation, suggesting a specific role for MMP activity in sensory cell apoptosis. A short-term application of doxycycline, a broad-spectrum inhibitor of MMPs, before noise exposure reduced noise-induced hearing loss and sensory cell death. In contrast, a 7 d treatment compromised hearing sensitivity and potentiated noise-induced hearing loss. This detrimental effect of the long-term inhibition of MMPs on noise-induced hearing loss was further confirmed using targeted Mmp7 knock-out mice. Together, these observations suggest that MMPs and their related genes participate in the regulation of cochlear responses to acoustic overstimulation and that the modulation of MMP activity can serve as a novel therapeutic target for the reduction of noise-induced cochlear damage.