Geldanamycin induces production of heat shock protein 70 and partially attenuates ototoxicity caused by gentamicin in the organ of Corti explants.
BACKGROUND
Heat shock protein 70 (HSP70) protects inner ear cells from damage and death induced by e.g. heat or toxins. Benzoquinone ansamycin antibiotic geldanamycin (GA) was demonstrated to induce the expression of HSP70 in various animal cell types. The aim of our study was to investigate whether GA induces HSP70 in the organ of Corti (OC), which contains the auditory sensory cells, and whether GA can protect these cells from toxicity caused by a common aminoglycoside antibiotic gentamicin.


METHODS
To address these questions, we used the OC explants isolated from p3-p5 rats. As a read-out, we used RT-PCR, ELISA and immunofluorescence.


RESULTS
We found that GA at the concentration of 2 microM efficiently induced HSP70 expression on mRNA and protein level in the OC explants. Confocal microscopy revealed that HSP70 induced by GA is expressed by hair cells and interdental cells of spiral limbus. Preincubation of explants with 2 muM GA prior to adding gentamicin (500 microM) significantly reduced the loss of outer but not inner hair cells, suggesting different mechanisms of otoprotection needed for these two cell types.


CONCLUSIONS
GA induced HSP70 in the auditory sensory cells and partially protected them from toxicity of gentamicin. Understanding the molecular mechanisms of GA otoprotection may provide insights for preventative therapy of the hearing loss caused by aminoglycoside antibiotics.
Yu
Yang
Y
Molecular Biology Research Laboratory and Tinnitus Center, Department of Otorhinolaryngology, Charité-Universitätsmedizin Berlin, Campus Charité Mitte, Charitéplatz 1, 10117 Berlin, Germany. dryangyu@yahoo.com
Szczepek
Agnieszka J
AJ
Haupt
Heidemarie
H
Mazurek
Birgit
B
D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology / Q000627:therapeutic use*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects; D005839:Gentamicins / Q000633:toxicity*; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects*; D006319:Hearing Loss, Sensorineural / Q000517:prevention & control*; D047029:Lactams, Macrocyclic / Q000494:pharmacology / Q000627:therapeutic use*; D018613:Microscopy, Confocal; D009924:Organ Culture Techniques; D009925:Organ of Corti / Q000187:drug effects*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016227:Benzoquinones; D005839:Gentamicins; D018840:HSP70 Heat-Shock Proteins; C490435:Hspa2 protein, rat; D047029:Lactams, Macrocyclic; D012333:RNA, Messenger; C001277:geldanamycin