Noise-induced trauma produces a temporal pattern of change in blood levels of the outer hair cell biomarker prestin.

Biomarkers in easy-to-access body fluid compartments, such as blood, are commonly used to assess health of various organ systems in clinical medicine. At present, no such biomarkers are available to inform on the health of the inner ear. Previously, we proposed the outer-hair-cell-specific protein prestin, as a possible biomarker and provided proof of concept in noise- and cisplatin-induced hearing loss. Our ototoxicity data suggest that circulatory prestin changes after inner ear injury are not static and that there is a temporal pattern of change that needs to be further characterized before practical information can be extracted. To achieve this goal, we set out to 1) describe the time course of change in prestin after intense noise exposure, and 2) determine if the temporal patterns and prestin levels are sensitive to severity of injury. After assessing auditory brainstem thresholds and distortion product otoacoustic emission levels, rats were exposed to intense octave band noise for 2 h at either 110 or 120 dB SPL. Auditory function was re-assessed 1 and 14 days later. Blood samples were collected at baseline, 4, 24, 48, 72 h and 7 and 14 days post exposure and prestin concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Functional measures showed temporary hearing loss 1 day after exposure in the 110 dB SPL group, but permanent loss through Day 14 in the 120 dB SPL group. Prestin levels temporarily increased 5% at 4 h after 120 dB SPL exposure, but not in the 110 dB SPL group. There was a gradual decline in prestin levels in both groups thereafter, with prestin being below baseline on Day 14 by 5% in the 110 dB group (NS) and more than 10% in the 120 dB SPL group (p = 0.043). These results suggest that there is a temporal pattern of change in serum prestin level after noise-induced hearing loss that is related to severity of hearing loss. Circulatory levels of prestin may be able to act as surrogate biomarker for hearing loss involving OHC loss.