Influence of endoplasmic reticulum stress in degeneration of cochlear hair cells in type 2 diabetic mice / 吉林大学学报(医学版)

ABSTRACT

Objective: To investigate the influence of endoplasmic reticulum stress (ERS) in the degeneration of cochlear hair cells in the type 2 diabetic mice∗ and to clarify its mechanism. Methods: Twenty clean Kun Ming male mice aged one month were selected and randomly divided into control group and model group (n= 10). The mice in model group were injected with STZ (40 mg • kg ) to establish the type 2 diabetic models. The fasting blood glucose levels of the mice were measured through collecting the vena caudalis blood of the mice. Auditory brain stem response (ABR) was used to detect the ABR threshold of the mice. Otoacoustic emission (OAE) test was used to detect the OAE threshold of mice. The defect rate of mouse cochlear outer hair cells was calculated by the mouse cochlear spreading technique. The expression levels of GRP78, caspase-12, p-ERK and Nrf2 proteins were detected by Western blotting method. Results: Compared with control group, the fasting blood glucose levels of the mice in model group at the 7th and the 14th days had no significant differences ( P>0. 05) , but the levels were increased significantly at the 21th,28th and 35th days and the level reached the highest value at the 35th day. The ABR thresholds of the mice in model group at 8, 12, and 24 kHZ were increased significantly compared with control group ( P0. 05). The expression levels of p-ERK and Nrf2 in the cochlear hair cells of the mice in model group were lower than those in control group (P<0.05), and the expression levels of GRP78 and caspase-12 were higher than those in control group (P<0. 05). Conclusion: ERS can result in the increase of defect rate of cochlear outer hair cells and ABR brainstem hearing threshold of the diabetic mice and decrease the expression levels of p-ERK and Nrf2 proteins, suggesting that ERS can promote the degenerative lesions of cochlear hair cells in the type 2 diabetic mice.