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Histone deacetylase inhibition protects hearing against acute ototoxicity by activating the Nf-κB pathway.

Layman WS, Williams DM, Dearman JA, Sauceda MA, Zuo J - Cell Death Discov (2015)

Bottom Line: We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic Atoh1 induction) hair cell regeneration.In addition, we also detected increased expression of pro-survival genes Cdkn1a (p21) and Hspa1a (Hsp70), and decreased expression of the pro-apoptosis gene Bcl2l11 (Bim).These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.

ABSTRACT

Auditory hair cells have repeatedly been shown to be susceptible to ototoxicity from a multitude of drugs including aminoglycoside antibiotics. Here, we found that systemic HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) on adult mice offers almost complete protection against hair cell loss and hearing threshold shifts from acute ototoxic insult from kanamycin potentiated with furosemide. We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic Atoh1 induction) hair cell regeneration. Rather, SAHA treatment correlated with RelA acetylation (K310) and subsequent activation of the Nf-κB pro-survival pathway leading to expression of pro-survival genes such as Cflar (cFLIP) and Bcl2l1 (Bcl-xL). In addition, we also detected increased expression of pro-survival genes Cdkn1a (p21) and Hspa1a (Hsp70), and decreased expression of the pro-apoptosis gene Bcl2l11 (Bim). These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.

No MeSH data available.


Related in: MedlinePlus

Systemically delivered SAHA penetrates the mouse inner ear. Mice were administered either vehicle (DMSO; a and a′) or SAHA at 50 mg/kg (b and b′), 100 mg/kg (d and d′), or 150 mg/kg (d and d′) by intraperitoneal injection at P28 and analyzed at P29. Immunofluorescence of organ of Corti sections was performed using antibodies against H4ac (red), Pvalb (green), and Hoechst (blue). (a and a′) The mature organ of Corti normally has very low levels of H4ac staining, similar to previous studies.7 (b–d′) Systemic SAHA mildly increases histone acetylation levels at 50 mg/kg, whereas both the 100 mg/kg and 150 mg/kg doses markedly increased the levels of histone H4 acetylation. (e) SAHA delivered systemically daily for 2 weeks did not adversely affect hearing thresholds tested by ABR. Confocal laser intensity and gain were kept consistent between samples. All representative images were taken from the middle turn of the cochlea. Scale bar is 20 μm.
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Figure 1: Systemically delivered SAHA penetrates the mouse inner ear. Mice were administered either vehicle (DMSO; a and a′) or SAHA at 50 mg/kg (b and b′), 100 mg/kg (d and d′), or 150 mg/kg (d and d′) by intraperitoneal injection at P28 and analyzed at P29. Immunofluorescence of organ of Corti sections was performed using antibodies against H4ac (red), Pvalb (green), and Hoechst (blue). (a and a′) The mature organ of Corti normally has very low levels of H4ac staining, similar to previous studies.7 (b–d′) Systemic SAHA mildly increases histone acetylation levels at 50 mg/kg, whereas both the 100 mg/kg and 150 mg/kg doses markedly increased the levels of histone H4 acetylation. (e) SAHA delivered systemically daily for 2 weeks did not adversely affect hearing thresholds tested by ABR. Confocal laser intensity and gain were kept consistent between samples. All representative images were taken from the middle turn of the cochlea. Scale bar is 20 μm.

Mentions: The adult mammalian inner ear has a remarkably stable homeostatic mechanism to maintain its functional integrity. Many regulatory mechanisms are involved in maintaining this homeostasis including ion transport, constant blood supply, and a blood–labyrinth barrier.6 Any disturbance in one of these mechanisms by free radicals, stress hormones, noise exposure, or aminoglycoside antibiotics may induce short- and long-term effects on cellular function.6 To determine whether systemic SAHA is able to both permeate the blood–labyrinth barrier and not perturb the inner ear's homeostasis, we administered SAHA to adult C57BL/6J (B6) and FVB/NJ (FVB) wild-type mice via intraperitoneal injection using 50 mg/kg, 100 mg/kg, or 150 mg/kg SAHA dissolved in DMSO compared with vehicle-treated controls (FVB n = 3; B6 n = 3; for each dosage group). Since the mature mammalian inner ear normally has low levels of histone acetylation (Figure 1a),7 we used immunofluorescence to detect changes in histone H4 acetylation levels using an antibody against histone H4 pan-acetylation (H4ac). We found that 100 mg/kg SAHA caused an increase in histone H4 acetylation staining (Figure 1c), whereas 50 mg/kg had very little affect (Figure 1b). Although 150 mg/kg SAHA also dramatically increased histone H4 acetylation staining (Figure 1d), we chose to further pursue the 100 mg/kg dose for this study as higher doses of SAHA can cause cytotoxicity.8,9


Histone deacetylase inhibition protects hearing against acute ototoxicity by activating the Nf-κB pathway.

Layman WS, Williams DM, Dearman JA, Sauceda MA, Zuo J - Cell Death Discov (2015)

Systemically delivered SAHA penetrates the mouse inner ear. Mice were administered either vehicle (DMSO; a and a′) or SAHA at 50 mg/kg (b and b′), 100 mg/kg (d and d′), or 150 mg/kg (d and d′) by intraperitoneal injection at P28 and analyzed at P29. Immunofluorescence of organ of Corti sections was performed using antibodies against H4ac (red), Pvalb (green), and Hoechst (blue). (a and a′) The mature organ of Corti normally has very low levels of H4ac staining, similar to previous studies.7 (b–d′) Systemic SAHA mildly increases histone acetylation levels at 50 mg/kg, whereas both the 100 mg/kg and 150 mg/kg doses markedly increased the levels of histone H4 acetylation. (e) SAHA delivered systemically daily for 2 weeks did not adversely affect hearing thresholds tested by ABR. Confocal laser intensity and gain were kept consistent between samples. All representative images were taken from the middle turn of the cochlea. Scale bar is 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 1: Systemically delivered SAHA penetrates the mouse inner ear. Mice were administered either vehicle (DMSO; a and a′) or SAHA at 50 mg/kg (b and b′), 100 mg/kg (d and d′), or 150 mg/kg (d and d′) by intraperitoneal injection at P28 and analyzed at P29. Immunofluorescence of organ of Corti sections was performed using antibodies against H4ac (red), Pvalb (green), and Hoechst (blue). (a and a′) The mature organ of Corti normally has very low levels of H4ac staining, similar to previous studies.7 (b–d′) Systemic SAHA mildly increases histone acetylation levels at 50 mg/kg, whereas both the 100 mg/kg and 150 mg/kg doses markedly increased the levels of histone H4 acetylation. (e) SAHA delivered systemically daily for 2 weeks did not adversely affect hearing thresholds tested by ABR. Confocal laser intensity and gain were kept consistent between samples. All representative images were taken from the middle turn of the cochlea. Scale bar is 20 μm.
Mentions: The adult mammalian inner ear has a remarkably stable homeostatic mechanism to maintain its functional integrity. Many regulatory mechanisms are involved in maintaining this homeostasis including ion transport, constant blood supply, and a blood–labyrinth barrier.6 Any disturbance in one of these mechanisms by free radicals, stress hormones, noise exposure, or aminoglycoside antibiotics may induce short- and long-term effects on cellular function.6 To determine whether systemic SAHA is able to both permeate the blood–labyrinth barrier and not perturb the inner ear's homeostasis, we administered SAHA to adult C57BL/6J (B6) and FVB/NJ (FVB) wild-type mice via intraperitoneal injection using 50 mg/kg, 100 mg/kg, or 150 mg/kg SAHA dissolved in DMSO compared with vehicle-treated controls (FVB n = 3; B6 n = 3; for each dosage group). Since the mature mammalian inner ear normally has low levels of histone acetylation (Figure 1a),7 we used immunofluorescence to detect changes in histone H4 acetylation levels using an antibody against histone H4 pan-acetylation (H4ac). We found that 100 mg/kg SAHA caused an increase in histone H4 acetylation staining (Figure 1c), whereas 50 mg/kg had very little affect (Figure 1b). Although 150 mg/kg SAHA also dramatically increased histone H4 acetylation staining (Figure 1d), we chose to further pursue the 100 mg/kg dose for this study as higher doses of SAHA can cause cytotoxicity.8,9

Bottom Line: We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic Atoh1 induction) hair cell regeneration.In addition, we also detected increased expression of pro-survival genes Cdkn1a (p21) and Hspa1a (Hsp70), and decreased expression of the pro-apoptosis gene Bcl2l11 (Bim).These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.

ABSTRACT

Auditory hair cells have repeatedly been shown to be susceptible to ototoxicity from a multitude of drugs including aminoglycoside antibiotics. Here, we found that systemic HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) on adult mice offers almost complete protection against hair cell loss and hearing threshold shifts from acute ototoxic insult from kanamycin potentiated with furosemide. We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic Atoh1 induction) hair cell regeneration. Rather, SAHA treatment correlated with RelA acetylation (K310) and subsequent activation of the Nf-κB pro-survival pathway leading to expression of pro-survival genes such as Cflar (cFLIP) and Bcl2l1 (Bcl-xL). In addition, we also detected increased expression of pro-survival genes Cdkn1a (p21) and Hspa1a (Hsp70), and decreased expression of the pro-apoptosis gene Bcl2l11 (Bim). These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.

No MeSH data available.


Related in: MedlinePlus