Stress and survival pathways in the mammalian cochlea

Studies conducted over the last few years demonstrated that signaling pathways that operate in the organs of Corti (OC) play a central role in survival and death of hair cells. An important goal of molecular otology is to characterize these signaling pathways in normal inner ears and inner ears exposed to a variety of different forms of stress, such as ototoxic substances and noise overexposure. In this study, we used high-performance reverse protein microarray technology and phospho-specific antibodies to examine the activation status of defined molecules involved in cellular signaling. We demonstrate that reverse protein microarrays based on the highly sensitive planar-waveguide technology provide an effective and high-throughput means to assess the activation state of key molecules involved in apoptotic and prosurvival signaling in microdissected OC explants over time. In this study, we show that gentamicin and a specific NF-kappaB inhibitor increase the ratio of phospho-c-Jun/c-Jun in OC explants of postnatal rats soon after exposure to these drugs. In addition, we found a decrease in the phospho-Akt/Akt ratio in OC explants early after NF-kappaB inhibition. Finally, we observed an early and consistent decrease in the phospho-p38/p38 ratio in OC explants exposed to the NF-kappaB inhibitor and only a transient decrease in this ratio in OC examples after gentamicin exposure.