Hsp70 inhibits aminoglycoside-induced hair cell death and is necessary for the protective effect of heat shock.

Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29403, USA.
Journal of the Association for Research in Otolaryngology (Impact Factor: 2.55). 06/2008; 9(3):277-89. DOI: 10.1007/s10162-008-0122-2
Source: PubMed

ABSTRACT Sensory hair cells of the inner ear are sensitive to death from aging, noise trauma, and ototoxic drugs. Ototoxic drugs include the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Exposure to aminoglycosides results in hair cell death that is mediated by specific apoptotic proteins, including c-Jun N-terminal kinase (JNK) and caspases. Induction of heat shock proteins (Hsps) is a highly conserved stress response that can inhibit JNK- and caspase-dependent apoptosis in a variety of systems. We have previously shown that heat shock results in a robust upregulation of Hsps in the hair cells of the adult mouse utricle in vitro. In addition, heat shock results in significant inhibition of both cisplatin- and aminoglycoside-induced hair cell death. In our system, Hsp70 is the most strongly induced Hsp, which is upregulated over 250-fold at the level of mRNA 2 h after heat shock. Therefore, we have begun to examine the role of Hsp70 in mediating the protective effect of heat shock. To determine whether Hsp70 is necessary for the protective effect of heat shock against aminoglycoside-induced hair cell death, we utilized utricles from Hsp70.1/3 (-/-) mice. While heat shock inhibited gentamicin-induced hair cell death in wild-type utricles, utricles from Hsp70.1/3 (-/-) mice were not protected. In addition, we have examined the role of the major heat shock transcription factor, Hsf1, in mediating the protective effect of heat shock. Utricles from Hsf1 (-/-) mice and wild-type littermates were exposed to heat shock followed by gentamicin. The protective effect of heat shock on aminoglycoside-induced hair cell death was only observed in wild-type mice and not in Hsf1 (-/-) mice. To determine whether Hsp70 is sufficient to protect hair cells, we have utilized transgenic mice that constitutively overexpress Hsp70. Utricles from Hsp70-overexpressing mice and wild-type littermates were cultured in the presence of varying neomycin concentrations for 24 h. The Hsp70-overexpressing utricles were significantly protected against neomycin-induced hair cell death at moderate to high doses of neomycin. This protective effect was achieved without a heat shock. Taken together, these data indicate that Hsp70 and Hsf1 are each necessary for the protective effect of heat shock against aminoglycoside-induced death. Furthermore, overexpression of Hsp70 alone significantly inhibits aminoglycoside-induced hair cell death.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Tetramethylpyrazine has been suggested to have a therapeutic effect on impaired hearing that is induced by aminoglycoside antibiotics. However, its effectiveness on streptomycin ototoxicity and its cellular mechanisms are relatively unknown. Here we investigate the protective effect of tetramethylpyrazine on streptomycin-induced ototoxicity in guinea pig cochlea. Prospective randomized laboratory study. Hearing Research Laboratory of China Medical University. Adult guinea pigs were randomized to 4 groups. Hearing sensitivity of guinea pigs was tested by auditory brainstem response measurements before streptomycin exposure and again 10 days later. The cochlear tissues were prepared for electron microscopy and immunohistochemical staining of heat shock protein 70 (HSP70). The effect of tetramethylpyrazine on streptomycin-induced activation of caspase-3 was evaluated by Western blotting. Co-therapy with tetramethylpyrazine reduced a profound streptomycin-induced auditory threshold shift compared with streptomycin treatment alone (P = .0002 or P = .00008). Tetramethylpyrazine also attenuated the structural disruption in streptomycin-treated outer hair cells and marginal cells of vascular stria by transmission electronic microscopy and scanning electronic microscopy, respectively. Moreover, tetramethylpyrazine decreased the streptomycin-stimulated expressions of HSP70 and caspase-3. The correlation analysis demonstrated that HSP70 expression had a positive correlation with auditory brainstem response thresholds (|R| = 0.6-0.9, P = .0073 or P = .0169). Our data suggest that the protective effect of tetramethylpyrazine on hearing function is associated with the reduction of stress response and inhibition of apoptosis. Tetramethylpyrazine may have therapeutic potential for patients with ototoxicity diseases. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2015.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Effects of melamine (MEL) and its analogue, cyanuric acid (CYA) at various doses on Asian seabass (Lates calcarifer Bloch) are described. Diet 1 (a basal diet without MEL and CYA); diets 2–5 (with MEL and CYA at inclusion levels 2.5, 5, 7.5, 10 g/kg diet, each); diet 6 (with only MEL at 10 g/kg diet); and diet 7 (with CYA alone added at 10 g/kg diet) were examined. It is obvious that those fish that received combined MEL–CYA as follows had low growth and feed conversion ratio (FCR) (P < 0.05): 7.5:7.5, 10:10 or MEL alone diets. Abnormalities were observed in the liver and kidney of fish with combined MEL and CYA supplementation. The renal tubules of fish that were fed with diets 2–5 had golden-brown melamine–cyanurate crystals. Fish given only one type of supplementation did not have such crystals in the kidneys. The highest MEL residue in fillet was detected in the fish that ingested MEL alone (10 g/kg diet). Levels of heat shock protein (Hsp) 70 were elevated in the liver of fish that had ingested MEL/CYA, in combination or alone (diets 2–7) (P < 0.05). There were no significant differences between the treatments (P > 0.05) in the level of Hsp70 in the kidneys of the fish. High dosages of MEL–CYA induced the activities of catalase and glutathione peroxidase in liver and kidneys.
    Aquaculture 01/2015; 435:336–346. DOI:10.1016/j.aquaculture.2014.10.009 · 1.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Heat shock protein 70 (Hsp70) has been known to be able to play a protective role in the cochlea. The aim of this study was to investigate whether geldanamycin hydrosoluble derivative 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG) has the ability to induce Hsp70 up-regulation to protect hair cells from kanamycin-induced ototoxicity in vitro. The organ of Corti (OC) explants were isolated from mice at postnatal days 3-5. Then, the explants were exposed to kanamycin with or without pre-incubation with 17-DMAG. The expression of Hsp70 was assessed by reverse transcription-quantitative polymerase chain reaction, ELISA, and immunofluorescent staining. The surviving hair cells were examined by phalloidin labeling and were counted. We found that Hsp70 expression in the explants after pre-incubation with 17-DMAG was significantly increased at both mRNA and protein levels. Immunofluorescent staining showed that Hsp70 was mainly located in the auditory hair cells. Compared with kanamycin group, the loss of hair cells was inhibited significantly in 17-DMAG+kanamycin group. Our study demonstrated that 17-DMAG induces Hsp70 in the hair cells, and has a significant protective effect against kanamycin ototoxicity in vitro. 17-DMAG has the possibility to be a safe and effective anti-ototoxic drug. Copyright © 2014. Published by Elsevier Ireland Ltd.
    Neuroscience Letters 12/2014; 588. DOI:10.1016/j.neulet.2014.12.060 · 2.06 Impact Factor


Available from