Stress Pathways in the Rat Cochlea and Potential for Protection from Acquired Deafness

Abstract

Noise overstimulation will induce or influence intracellular molecular pathways in the cochlea. One of these is the ‘classical’ stress response pathway involving heat shock proteins. Hsp70 is induced in the cochlea by a wide variety of stresses including noise, hyperthermia and ototoxic drugs. When a stress that induces Hsp70 is applied to the cochlea, there is protection from a subsequent noise that would normally cause a permanent hearing loss. An upstream regulator of heat shock protein transcription, heat shock factor 1, is expressed in the cochlea and activated by stress. Mice lacking this heat shock factor have reduced recovery from noise-induced hearing loss. The same noise exposure that induces Hsp70 also increases the level of glial cell line-derived neurotrophic factor in the cochlea. Moreover, when this neurotrophic factor is applied into the perilymph of scala tympani prior to a noise exposure there is a significant reduction in hair cell loss and hearing loss. With the potential for activation of multiple pathways in the response to noise, gene microarrays can be useful to examine global gene expression. Initial studies examined differential gene expression immediately following a mild noise exposure (from which there is complete recovery) versus an intense noise (giving profound permanent deafness). Differential expression of several immediate early genes was found following the intense but not the mild noise exposure.

Frequency-specific association of antibodies against heat shock proteins 60 and 70 with noise-induced hearing loss in Chinese workers

“…Moreover, Hsps, when induced in response to moderate nontraumatic sound levels, can condition the ear to withstand effects of loud noise and protect from hearing loss, although there is individual variability (Yoshida et al 1999;Altschuler et al 2002). In addition, several lines of evidence suggest that antibody to Hsp70 may be closely associated with the pathogenesis or prognosis (or both) of sensorineural deafness Veldman 1997).…”

Association of Heat Shock Protein 60 With Noise-Induced Hearing Impairment and Electrocardiographic Abnormalities Among Workers Occupationally-Exposed to Noise

“…Statistical differences were based on the significance level of P < 0.05. Table ( 1) shows that the workers occupationally-exposed to noise are matched with the control group as regards age and smoking habit showing no statistically significant difference. On the other hand, the exposed and control groups showed statistically significant differences as regards NIHL in low and high frequencies, ECG abnormalities, and serum heat shock protein 60 (HSP60) levels.…”

“…HSPs protect from hearing loss by conditioning the ear to withstand consequences of severe noise exposure (Altschuler et al, 2002). Some HSPs play an important role in protecting cardiac cells against ischemic injury, and antibodies against these HSPs (anti-HSPs) are associated with the development and prognosis of atherogenesis, coronary heart disease and hypertension (Yuan et al, 2005 andMandal et al, 2004).…”

Heat shock response: hsp70 in environmental monitoring

“…In Drosophila, mammals, and other model organisms studied, Hsps are broadly classified according to the apparent molecular weight, amino acid sequence homologies, and their functional aspects into five major families: Hsp100 family (100-104 kDa), Hsp90 family (82-90 kDa), Hsp70 family (68-75 kDa), Hsp60 family (58-65 kDa), and the small Hsp family (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). The Hsp70 family is the most highly conserved and largest of all the stress protein families; it has also been most extensively studied [16][17][18][19][20][21][22].…”

“…The hsp70 family of proteins is present in the subcellular compartments and primarily they bind to target proteins to modulate protein folding, transport, and repair. Under adverse environmental conditions, the synthesis of Hsp70 increases and it takes on new but related roles to protect the cells from proteotoxicity [17,[23][24][25][26][27][28][29]. The understanding of stress proteins is still incomplete.…”