Noise-induced hearing loss

Abstract

Purpose of the review This article presents research findings from two invertebrate model systems with potential to advance both the understanding of noise-induced hearing loss mechanisms and the development of putative therapies to reduce human noise damage. Recent findings Work on sea anemone hair bundles, which resemble auditory hair cells, has revealed secretions that exhibit astonishing healing properties not only for damaged hair bundles, but also for vertebrate lateral line neuromasts. We present progress on identifying functional components of the secretions, and their mechanisms of repair. The second model, the Johnston's organ in Drosophila, is also genetically homologous to hair cells and shows noise-induced hearing loss similar to vertebrates. Drosophila offers genetic and molecular insight into noise sensitivity and pathways that can be manipulated to reduce stress and damage from noise. Summary Using the comparative approach is a productive avenue to understanding basic mechanisms, in this case cellular responses to noise trauma. Expanding study of these systems may accelerate identification of strategies to reduce or prevent noise damage in the human ear.

Physiological basis of noise-induced hearing loss in a tympanal ear

“…We found that the number of sound-elicited nerve potentials was mildly decreased and their peak response was strongly decreased in noise-exposed locust ears. In addition, the latency to first spike was significantly increased in noise-exposed locusts compared to controls which reflects increased latencies of CAPs measured in other noise-exposed auditory systems (Christie & Eberl, 2014;Sendowski et al, 2004;Pettigrew et al, 1984;;Van Heusden & Smoorenburg, 1981). Is it not known what changes take place in the auditory receptors to decrease spiking responses increase spike latency.…”

“…An increased sound amplitude elicited an increase in the nerve potentials (Figure 2Ci,ii,iii). Across hearing models hearing impairment is characterised by an increase in the latency of toneevoked electrical signals (Christie & Eberl, 2014;Coomber et al, 2014;Van Heusden & Smoorenburg, 1981;Salvi et al, 1980).…”

“…The health of an auditory system -its ability to transduce sound into electrical signals -has been assayed from the summated electrical activity of the auditory nerve (Compound Action Potentials (CAPs)) and hierarchical auditory processing areas through the brain (Auditory Brainstem Responses (ABRs)). After acoustic overstimulation there is an increase in the minimum sound level to get a sound-evoked electrical signal from the auditory nerve -the so-called auditory threshold (Coyat, et al, 2018;Christie & Eberl, 2014;Housley et al, 2013;Pilati et al, 2012;Telang et al, 2010;Sendowski et al, 2004;Ma et al, 1995;Dolan & Mills, 1989;Pettigrew et al, 1984;Van Heusden & Smoorenburg, 1981). This increased auditory threshold is mirrored by a decrease in the sound-evoked CAP amplitude after noise exposure (Christie & Eberl, 2014;Sendowski et al, 2004;Wang et al ., 1992;Dolan & Mills, 1989;Pettigrew et al, 1984;Van Heusden & Smoorenburg, 1981).…”

“…A decrease in ionic gradient and potential in the receptor lymph could result from damage in the supporting cells that pump ions. Indeed, in the fruit fly, knocked down expression of the sodium pump (Na + /K + ATPase) in the supporting scolopale cells that enclose the receptor lymph result in deafness and anatomical pathologies in the receptor lymph space and sensitisation to acoustic trauma (Christie & Eberl, 2014;Roy et al, 2013). A similar result is found in mammals where the supporting cells (in the stria vasculairs) are oxidatively damaged (Shi et al, 2015) after noise exposure and, in mammals, there is a concurrent decrease in the endocochlear potential (Hirose & Liberman, 2003) and normal concentrations of potassium and calcium ions (Li et al, 1997;Ma et al, 1995;Vassout, 1984).…”

Ion pumps in Drosophila hearing

“…Most work on the scolopidium has focused on development of the general structure and the ciliated nature of the dendrite (Caldwell & Eberl, 2002;Ebacher, et al, 2007;Jarman & Groves, 2013). More recent work on traumatized flies has developed flies as a model of hearing loss, validating the fruitfly as a meaningful model for hearing (Christie & Eberl, 2014;Christie et al, 2013). Only recently has work been done on the Johnston's Organ to understand the actual physiology of the structures and ion homeostasis (Roy et al, 2013).…”