Age-Related Expression Of KCNQ1 And NKCC1 Protein In Stria Vascularis Of The Cochlea Of C57BL/6J Mice

Objective To investigate the age-related expression of KCNQ1 and NKCC1 protein in stria vascularis of the cochlea of C57BL/6J mice, and to analyze the relationship between the two channels and age-related hearing loss (AHL).Methods Auditory function of C57BL/6J mice was measured by auditory brainstem response (ABR) at the ages of 4, 8, 14, 24, 40 weeks old respectively. The location of KCNQ1 and NKCC1 protein in the cochlea of C57BL/6J mice was detected by immunohistochemistry. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the level of KCNQ1 and NKCC1 mRNA in cochlea of C57BL/6J mice at different ages.Results The mean value for ABR thresholds in response to click, 4KHz and 8KHz sound stimulus of C57BL/6J mice gradually increased with age. From the mice of 8 weeks old, ABR thresholds were significantly elevated(P<0.05). In the lateral wall of C57BL/6J mice cochlea, the KCNQ1 protein was mainly expressed at the apical membrane of the strial marginal cells. The localization of NKCC1 protein was mainly present at the basolateral membrane of the stria marginal cells, spiral ligament and the fibrocytes in the inferior portion of spiral limbus. Expression of KCNQ1 and NKCC1 protein in cochlea of C57BL/6J mice showed age-related decreasing. The level of KCNQ1 and NKCC1 mRNA in cochlea of C57BL/6J also showed a age-related decreasing trend. There was a significant reducing of KCNQ1 mRNA level between C57BL/6J mice of 40 and 4 weeks old(P <0.05). Compared with the C57BL/6J mice of 4 weeks old, the NKCC1 mRNA level of 24 and 40 weeks old also showed a clearly reducing(P <0.05).Conclusion Expression of KCNQ1 and NKCC1 protein in stria vascularis of C57BL/6J mice decreases with age. The level of KCNQ1 and NKCC1 mRNA in cochlea of C57BL/6J showed a age-related reducing trend. Regulating after post-translation may also participate in the adjusting of the age-related decreasing of KCNQ1 and NKCC1 protein in cochlea C57BL/6J mice. KCNQ1 and NKCC1 channels may play a critical role in maintaining normal hearing function of inner ear.