Zinc-finger protein A20 protects hair cells from damage made by high-power microwave

Abstract

Abstract Inner ear hair cells are important for maintaining hearing. Irreversible damage to hair cells is an important cause of sensorineural deafness. Electromagnetic radiation, especially high-power microwave, is an important threat to human health in modern society and war. However, it is not clear whether high-power microwave has an effect on cochlea hair cells. This study aimed to assess the effects of high-power microwave on cochlear hair cells in guinea pigs, and investigate the potential protection of these cells against high-power microwave-induced damage by recombinant adenovirus A20. Based on experimental results, a 65 W/cm2 irradiation density applied to guinea pigs in this study to establish a high-power microwave inner ear injury model. In addition, pAdEeay-1/A20 was injected via a round window into experimental guinea pig cochlea, whereas artificial perilymph was injected into the control group. Auditory function was assessed by testing the auditory brainstem response threshold, and damage to cochlear hair cells was investigated by cell counting and scanning electron microscopy observations of the basilar membrane. Inner ear injury was observed 6hours after 65 W/cm2 of irradiation and the auditory brainstem response threshold was significantly higher in the irradiation group (P < 0.05) compared with other groups. Propidium iodide staining and scanning electron microscopy results indicated that significant morphological changes occurred after radiation, especially to inner hair cells, which exhibited remarkable damage and the presence of several unknown spherical substances. Auditory brainstem response threshold was decreased in the pAdEeay-1/A20 group compared with the artificial perilymph group; moreover, damage to hair cells was milder in the pAdEeay-1/A20 group compared with the control group (P < 0.01). Thus, high-power microwave can cause damage to cochlear hair cells, as well as hearing loss with prolonged exposure and/or high dosage. In this regard, 65 W/cm2 of irradiation for 6hours is a reliable target dose for observation of damage. The zinc finger protein A20 can protect cochlear hair cells from high-power microwave-induced damage and prevent further hearing loss. This study was approved by the Laboratory Animal Welfare and Ethics Committee of the Third Military Medical University, China on April 18, 2017.