Attenuation of progressive hearing loss in DBA/2J mice by reagents that affect epigenetic modifications is associated with up-regulation of the zinc importer Zip4

PLoS One. 2015 Apr 14;10(4):e0124301. doi: 10.1371/journal.pone.0124301. eCollection 2015.

Abstract

Various factors that are important for proper hearing have been identified, including serum levels of zinc. Here we investigated whether epigenetic regulatory pathways, which can be modified by environmental factors, could modulate hearing. RT-PCR detected expression of genes encoding DNA methyltransferase and histone deacetylase (Hdac) in the postnatal as well as adult mouse auditory epithelium. DBA/2J mice, which are a model for progressive hearing loss, were injected subcutaneously with one or a combination of the following reagents: <smallcaps>L</smallcaps>-methionine as a methyl donor, valproic acid as a pan-Hdac inhibitor, and folic acid and vitamin B12 as putative factors involved in age-related hearing loss. The mice were treated from ages 4 to 12 weeks (N ≥ 5), and auditory brainstem response (ABR) thresholds were measured at 8, 16, and 32 kHz. Treatment of the mice with a combination of <smallcaps>L</smallcaps>-methionine and valproic acid (M+V) significantly reduced the increase in the ABR threshold at 32 kHz. Treatment with any of these reagents individually produced no such effect. Microarray analyses detected 299 gene probes that were significantly up- or down-regulated in the cochleae of mice treated with M+V compared with the control vehicle-treated mice. Quantitative RT-PCR confirmed significant up-regulation of a zinc importer gene, Zip4, in the cochleae of mice treated with M+V. Immunohistochemistry demonstrated an intense Zip4 signal in cochlear tissues such as the lateral wall, organ of Corti, and spiral ganglion. Finally, mice treated with the Zip4 inducer (-)-epigallocatechin-3-O-gallate showed a significant reduction in the increase of the ABR threshold at 32 kHz and up-regulation of Zip4 expression in the cochlea. This study suggests that epigenetic regulatory pathways can modify auditory function and that zinc intake in the cochlea via Zip4 mediates maintenance of mammalian hearing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Catechin / analogs & derivatives
  • Catechin / pharmacology
  • Cation Transport Proteins / genetics*
  • Cation Transport Proteins / metabolism
  • Cochlea / drug effects
  • Cochlea / metabolism
  • Down-Regulation / drug effects
  • Epigenesis, Genetic*
  • Evoked Potentials, Auditory, Brain Stem / drug effects
  • Hearing Loss / chemically induced
  • Hearing Loss / metabolism
  • Hearing Loss / pathology*
  • Immunohistochemistry
  • Methionine / toxicity*
  • Mice
  • Mice, Inbred DBA
  • Microscopy, Fluorescence
  • Oligonucleotide Array Sequence Analysis
  • Organ of Corti / metabolism
  • Real-Time Polymerase Chain Reaction
  • Spiral Ganglion / metabolism
  • Up-Regulation / drug effects*
  • Valproic Acid / toxicity*

Substances

  • Cation Transport Proteins
  • Slc39a4 protein, mouse
  • Valproic Acid
  • Catechin
  • Methionine
  • epigallocatechin gallate

Associated data

  • GEO/GSE62173

Grant support

Funding for this work came from Japan Society for the Promotion of Science KAKENHI (http://www.jsps.go.jp/j-grantsinaid/) grant numbers 21791659 and 24592573 to HM and 24390391 to TM. Grant numbers 21791659 and 24592573 supported study design, data collection, analysis, and preparation of the manuscript. Grant 24390391 supported data analysis.