Mitochondrial transcription factor A overexpression and base excision repair deficiency in the inner ear of rats with d-galactose-induced aging

• Published in: The FEBS journal Vol. 278; no. 14; pp. 2500 - 2510
• Main Authors: Zhong, Yi, Hu, Yu-Juan, Chen, Bei, Peng, Wei, Sun, Yu, Yang, Yang, Zhao, Xue-Yan, Fan, Guo-run, Huang, Xiang, Kong, Wei-Jia
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.2011
• Subjects: age‐related hearing loss; Aging - drug effects; Aging - genetics; Aging - metabolism; Animals; DNA Glycosylases - genetics; DNA Glycosylases - metabolism; DNA Polymerase gamma; DNA repair; DNA Repair - drug effects; DNA Replication - drug effects; DNA, Mitochondrial - genetics; DNA, Mitochondrial - metabolism; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; DNA-Directed DNA Polymerase - genetics; DNA-Directed DNA Polymerase - metabolism; Ear, Inner - drug effects; Ear, Inner - metabolism; Ear, Inner - pathology; ears; Galactose - toxicity; Gene Deletion; Gene Dosage - drug effects; Gene Expression Regulation, Developmental - drug effects; gene overexpression; Hair Cells, Auditory - drug effects; Hair Cells, Auditory - metabolism; Hair Cells, Auditory - pathology; hearing disorders; humans; Male; mitochondrial common deletion; mitochondrial DNA; Mitochondrial Proteins - biosynthesis; Mitochondrial Proteins - genetics; Mitochondrial Proteins - metabolism; mitochondrial transcription factor A; mutation; oxidative damage; Oxidative Stress - drug effects; Presbycusis - genetics; Presbycusis - metabolism; Presbycusis - pathology; Random Allocation; Rats; Rats, Sprague-Dawley; reactive oxygen species; RNA - metabolism; transcription factors; Transcription Factors - biosynthesis; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 1742-464X; 1742-4658; 1742-4658
• DOI: 10.1111/j.1742-4658.2011.08176.x

Oxidative damage to mtDNA is associated with excessive reactive oxygen species production. The mitochondrial common deletion (mtDNA 4977-bp and 4834-bp deletion in humans and rats, respectively) is the most typical and frequent form of mtDNA damage associated with aging and degenerative diseases. The accumulation of the mitochondrial common deletion has been proposed to play a crucial role in age-related hearing loss (presbycusis). However, the mechanisms underlying the formation and accumulation of mtDNA deletions are still obscure. In the present study, a rat mimetic aging model induced by d-Gal was used to explore the origin of deletion mutations and how mtDNA repair systems modulate this process in the inner ear during aging. We found that the mitochondrial common deletion was greatly increased and mitochondrial base excision repair capacity was significantly reduced in the inner ear in d-Gal-treated rats as compared with controls. The overexpression of mitochondrial transcription factor A induced by d-Gal significantly stimulated mtDNA replication, resulting in an increase in mtDNA copy number. In addition, an age-related loss of auditory sensory cells in the inner ear was observed in d-Gal-treated rats. Taken together, our data suggest that mitochondrial base excision repair capacity deficiency and an increase in mtDNA replication resulting from mitochondrial transcription factor A overexpression may contribute to the accumulation of mtDNA deletions in the inner ear during aging. This study also provides new insights into the development of presbycusis.