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A protective mechanism against antibiotic-induced ototoxicity: role of prestin.

Yu L, Jiang XH, Zhou Z, Tsang LL, Yu MK, Chung YW, Zhang XH, Wang AM, Tang H, Chan HC - PLoS ONE (2011)

Bottom Line: Hearing loss or ototoxicity is one of the major side effects associated with the use of the antibiotics, particularly aminoglycosides (AGs), which are the most commonly used antibiotics worldwide.In the present study, we test the possibility that prestin, the motor protein specifically expressed in the basolateral membrane of outer hair cells (OHCs) in the cochlea with electromotility responsible for sound amplification, may be involved in the process of AG-induced apoptosis in OHCs.Our results from both mice model and cultured cell line indicate a previously unexpected role of prestin, in mediating antibiotic-induced apoptosis, the effect of which is associated with its anion-transporting capacity.

View Article: PubMed Central - PubMed

Affiliation: Epithelial Cells Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, ShaTin, Hong Kong.

ABSTRACT
Hearing loss or ototoxicity is one of the major side effects associated with the use of the antibiotics, particularly aminoglycosides (AGs), which are the most commonly used antibiotics worldwide. However, the molecular and cellular events involved in the antibiotic-induced ototoxicity remains unclear. In the present study, we test the possibility that prestin, the motor protein specifically expressed in the basolateral membrane of outer hair cells (OHCs) in the cochlea with electromotility responsible for sound amplification, may be involved in the process of AG-induced apoptosis in OHCs. Our results from both mice model and cultured cell line indicate a previously unexpected role of prestin, in mediating antibiotic-induced apoptosis, the effect of which is associated with its anion-transporting capacity. The observed downregulation of prestin mRNA prior to detectable apoptosis in OHCs and hearing loss in the antibiotic-treated mice is interesting, which may serve as a protective mechanism against hearing loss induced by AGs in the early stage.

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Kanamycin induces hearing damage, apoptosis and down-regulation of prestin in OHC.4 week old BALB/c male mice were injected with 750 mg/kg kanamycin subcutaneously twice daily for the time indicated. (A): FITC-conjugated phalloidin (green) staining on cross section of OHC. a, normal control; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 20 µm. (B): TUNEL assay of cochlear sections. Cochlear sections were stained with TUNEL (green) and propidium iodide (red). a, Normal morphology and no TUNEL-positive staining was found in inner ear cells in saline-treated control animals; b–d, 7, 14 and 21 days of kanamycin treatment. The sections shown are representative of three individual animals at each time point. Scale bar = 25 µm. Green arrow head: OHC cells. (C): Rhodamine-conjugated prestin staining on cross section of OHC. a, Normal, normal staining of prestin with three rows of rings; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 15 µm. (D): Prestin immunofluorescence staining of cochlear sections. Cochlear sections of control, 7, 14 and 21 days after kanamycin treatment were stained with prestin at 1∶100 dilutions. Scale bar = 50 µm. Left column: immunostaining merged with bright field image; Middle column: PI (red) merged with Prestin (green); white rectangle indicated enlarged area shown in right column. Three OHC cells. (E): Q-RT-PCR analysis of prestin expression in kanamycin- treated mouse cochlea. Q-RT- PCR was performed using validated Taqman™ Gene Expression Assays as described in Materials and Methods. Kanamycin significantly down-regulated prestin expression. *, p<0.05; ***, p<0.01.
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pone-0017322-g002: Kanamycin induces hearing damage, apoptosis and down-regulation of prestin in OHC.4 week old BALB/c male mice were injected with 750 mg/kg kanamycin subcutaneously twice daily for the time indicated. (A): FITC-conjugated phalloidin (green) staining on cross section of OHC. a, normal control; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 20 µm. (B): TUNEL assay of cochlear sections. Cochlear sections were stained with TUNEL (green) and propidium iodide (red). a, Normal morphology and no TUNEL-positive staining was found in inner ear cells in saline-treated control animals; b–d, 7, 14 and 21 days of kanamycin treatment. The sections shown are representative of three individual animals at each time point. Scale bar = 25 µm. Green arrow head: OHC cells. (C): Rhodamine-conjugated prestin staining on cross section of OHC. a, Normal, normal staining of prestin with three rows of rings; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 15 µm. (D): Prestin immunofluorescence staining of cochlear sections. Cochlear sections of control, 7, 14 and 21 days after kanamycin treatment were stained with prestin at 1∶100 dilutions. Scale bar = 50 µm. Left column: immunostaining merged with bright field image; Middle column: PI (red) merged with Prestin (green); white rectangle indicated enlarged area shown in right column. Three OHC cells. (E): Q-RT-PCR analysis of prestin expression in kanamycin- treated mouse cochlea. Q-RT- PCR was performed using validated Taqman™ Gene Expression Assays as described in Materials and Methods. Kanamycin significantly down-regulated prestin expression. *, p<0.05; ***, p<0.01.

Mentions: It has been previously shown that ototoxicity induced by AGs is a result of irreversible damage in OHC [18]. To correlate the time-dependent changes in auditory threshold shift with structural changes induced by kanamycin in OHCs, we examined structural integrity on cochlear sections from animals treated with kanamycin at the same time points as that for ABR experiments. In saline-treated mice, FITC-phalloidin staining for F-actin showed the well-defined outline of OHCs (Fig. 2Aa). After treatment with kanamycin for 7 days, there was no apparent loss of OHC (Fig. 2Ab), whereas continued injections resulted in some initial death of OHC after 14 days (Fig. 2Ac). 21 days after kanamycin administration, normal structure of basilar membrane collapsed, almost all OHCs disappeared, and the space at which OHCs were located was filled with scarred structure (Fig. 2Ad). These results are consistent with the time-dependent functional deficits determined by the ABR measurements.


A protective mechanism against antibiotic-induced ototoxicity: role of prestin.

Yu L, Jiang XH, Zhou Z, Tsang LL, Yu MK, Chung YW, Zhang XH, Wang AM, Tang H, Chan HC - PLoS ONE (2011)

Kanamycin induces hearing damage, apoptosis and down-regulation of prestin in OHC.4 week old BALB/c male mice were injected with 750 mg/kg kanamycin subcutaneously twice daily for the time indicated. (A): FITC-conjugated phalloidin (green) staining on cross section of OHC. a, normal control; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 20 µm. (B): TUNEL assay of cochlear sections. Cochlear sections were stained with TUNEL (green) and propidium iodide (red). a, Normal morphology and no TUNEL-positive staining was found in inner ear cells in saline-treated control animals; b–d, 7, 14 and 21 days of kanamycin treatment. The sections shown are representative of three individual animals at each time point. Scale bar = 25 µm. Green arrow head: OHC cells. (C): Rhodamine-conjugated prestin staining on cross section of OHC. a, Normal, normal staining of prestin with three rows of rings; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 15 µm. (D): Prestin immunofluorescence staining of cochlear sections. Cochlear sections of control, 7, 14 and 21 days after kanamycin treatment were stained with prestin at 1∶100 dilutions. Scale bar = 50 µm. Left column: immunostaining merged with bright field image; Middle column: PI (red) merged with Prestin (green); white rectangle indicated enlarged area shown in right column. Three OHC cells. (E): Q-RT-PCR analysis of prestin expression in kanamycin- treated mouse cochlea. Q-RT- PCR was performed using validated Taqman™ Gene Expression Assays as described in Materials and Methods. Kanamycin significantly down-regulated prestin expression. *, p<0.05; ***, p<0.01.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3045444&req=5

pone-0017322-g002: Kanamycin induces hearing damage, apoptosis and down-regulation of prestin in OHC.4 week old BALB/c male mice were injected with 750 mg/kg kanamycin subcutaneously twice daily for the time indicated. (A): FITC-conjugated phalloidin (green) staining on cross section of OHC. a, normal control; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 20 µm. (B): TUNEL assay of cochlear sections. Cochlear sections were stained with TUNEL (green) and propidium iodide (red). a, Normal morphology and no TUNEL-positive staining was found in inner ear cells in saline-treated control animals; b–d, 7, 14 and 21 days of kanamycin treatment. The sections shown are representative of three individual animals at each time point. Scale bar = 25 µm. Green arrow head: OHC cells. (C): Rhodamine-conjugated prestin staining on cross section of OHC. a, Normal, normal staining of prestin with three rows of rings; b, ka-7d; c, ka-14d; d, ka-21d. Scale bar = 15 µm. (D): Prestin immunofluorescence staining of cochlear sections. Cochlear sections of control, 7, 14 and 21 days after kanamycin treatment were stained with prestin at 1∶100 dilutions. Scale bar = 50 µm. Left column: immunostaining merged with bright field image; Middle column: PI (red) merged with Prestin (green); white rectangle indicated enlarged area shown in right column. Three OHC cells. (E): Q-RT-PCR analysis of prestin expression in kanamycin- treated mouse cochlea. Q-RT- PCR was performed using validated Taqman™ Gene Expression Assays as described in Materials and Methods. Kanamycin significantly down-regulated prestin expression. *, p<0.05; ***, p<0.01.
Mentions: It has been previously shown that ototoxicity induced by AGs is a result of irreversible damage in OHC [18]. To correlate the time-dependent changes in auditory threshold shift with structural changes induced by kanamycin in OHCs, we examined structural integrity on cochlear sections from animals treated with kanamycin at the same time points as that for ABR experiments. In saline-treated mice, FITC-phalloidin staining for F-actin showed the well-defined outline of OHCs (Fig. 2Aa). After treatment with kanamycin for 7 days, there was no apparent loss of OHC (Fig. 2Ab), whereas continued injections resulted in some initial death of OHC after 14 days (Fig. 2Ac). 21 days after kanamycin administration, normal structure of basilar membrane collapsed, almost all OHCs disappeared, and the space at which OHCs were located was filled with scarred structure (Fig. 2Ad). These results are consistent with the time-dependent functional deficits determined by the ABR measurements.

Bottom Line: Hearing loss or ototoxicity is one of the major side effects associated with the use of the antibiotics, particularly aminoglycosides (AGs), which are the most commonly used antibiotics worldwide.In the present study, we test the possibility that prestin, the motor protein specifically expressed in the basolateral membrane of outer hair cells (OHCs) in the cochlea with electromotility responsible for sound amplification, may be involved in the process of AG-induced apoptosis in OHCs.Our results from both mice model and cultured cell line indicate a previously unexpected role of prestin, in mediating antibiotic-induced apoptosis, the effect of which is associated with its anion-transporting capacity.

View Article: PubMed Central - PubMed

Affiliation: Epithelial Cells Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, ShaTin, Hong Kong.

ABSTRACT
Hearing loss or ototoxicity is one of the major side effects associated with the use of the antibiotics, particularly aminoglycosides (AGs), which are the most commonly used antibiotics worldwide. However, the molecular and cellular events involved in the antibiotic-induced ototoxicity remains unclear. In the present study, we test the possibility that prestin, the motor protein specifically expressed in the basolateral membrane of outer hair cells (OHCs) in the cochlea with electromotility responsible for sound amplification, may be involved in the process of AG-induced apoptosis in OHCs. Our results from both mice model and cultured cell line indicate a previously unexpected role of prestin, in mediating antibiotic-induced apoptosis, the effect of which is associated with its anion-transporting capacity. The observed downregulation of prestin mRNA prior to detectable apoptosis in OHCs and hearing loss in the antibiotic-treated mice is interesting, which may serve as a protective mechanism against hearing loss induced by AGs in the early stage.

Show MeSH
Related in: MedlinePlus