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

• Published in: PloS one Vol. 10; no. 4; p. e0124301
• Main Authors: Mutai, Hideki, Miya, Fuyuki, Fujii, Masato, Tsunoda, Tatsuhiko, Matsunaga, Tatsuo
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.04.2015; Public Library of Science (PLoS)
• Subjects: Acids; Age; Analysis; Animals; Attenuation; Auditory system; Brain research; Brain stem; Catechin - analogs & derivatives; Catechin - pharmacology; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; Cochlea; Cochlea - drug effects; Cochlea - metabolism; Cyanocobalamin; Deoxyribonucleic acid; DNA; DNA methylation; DNA methyltransferase; DNA microarrays; DNA probes; Down-Regulation - drug effects; Environmental factors; Epigenesis, Genetic; Epigenetic inheritance; Epigenetics; Epithelium; Evoked Potentials, Auditory, Brain Stem - drug effects; Folic acid; Gene expression; Hearing loss; Hearing Loss - chemically induced; Hearing Loss - metabolism; Hearing Loss - pathology; Hearing protection; Histone deacetylase; Immunohistochemistry; Investigations; Laboratories; Medical research; Methionine; Methionine - toxicity; Mice; Mice, Inbred DBA; Microscopy, Fluorescence; Oligonucleotide Array Sequence Analysis; Organ of Corti; Organ of Corti - metabolism; Polymerase chain reaction; Proteins; Reagents; Real-Time Polymerase Chain Reaction; Serum levels; Spiral ganglion; Spiral Ganglion - metabolism; Stem cells; Transferases; Up-regulation; Up-Regulation - drug effects; Valproic acid; Valproic Acid - toxicity; Vitamin B12; Zinc; Japan
• DOI: 10.1371/journal.pone.0124301
• ISSN: 1932-6203

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: L-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 L-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.