Age-related increase in PKC gamma expression in the cochlear nucleus of hearing impaired C57BL/6J and BALB/c mice

Age-dependent alteration in cellular signaling is implicated in the onset of age-related hearing loss (presbycusis). The gamma subtype of protein kinase C (PKCγ) is a PKC isoenzyme exclusively expressed in central nervous system but its potential role in the presbycusis remains unclear. Using two presbycusis-like animal models (C57BL/6J strain and BALB/c strain), the auditory thresholds were assessed by auditory brainstem response (ABR) in young (2-month-old), adult (8-month-old) and old (24-month-old) groups, and the localization and expression of PKCγ in the cochlear nucleus (CN) was examined by immunohistochemistry, Western blotting and Real-Time PCR. The results showed that PKCγ immmunoreactive (-ir) neurons were mainly concentrated in the molecular layer and fusiform layer of the dorsal CN (DCN) and their number was increased significantly with aging (p < 0.05). Moreover, compared with 2-month-old mice, PKCγ expression in the CN at both protein and mRNA levels was significantly increased in the 8-month-old mice and 24-month-old mice (p < 0.05). Thus our findings demonstrate a potential link between the increased PKCγ expression and the age-related hearing loss in these mice, suggesting novel strategies for the prevention and therapy of age-associated auditory disorders.

Research highlights▶ Our findings indicate that PKCγ-ir neurons distribute in the cartwheel cells of the superficial layer of the DCN. ▶ There are potential links between the elevation of PKCγ and the age-related hearing loss in C57 mice and BALB/c mice. ▶ The neuroplasticity in PKCγ at mRNA and protein levels in the CN might be associated with the Ca2+ related neuronal degeneration. ▶ The changes in PKCγ suggest that it could provide insights into protection and therapy of auditory degeneration.