Reducing caloric intake extends the lifespan of a variety of laboratory animals and delays the progression of age-associated diseases such as age-related hearing loss (AHL) (1-9), a common feature of aging that affects more than 40% of people over 65 years of age in the US (13). Evidence indicates that caloric restriction (CR) leads to a reduction in the production of reactive oxygen species (ROS) in multiple tissues, while long-lived species produce higher levels of antioxidant enzymes (1-4). Consistent with these reports, overexpressing the antioxidant enzyme catalase localized to mitochondria increases lifespan (16), reduces oxidative damage in the cochlea, and delays the onset of AHL in mice (10). Thus, CR is thought to reduce oxidative stress through enhanced mitochondrial antioxidant defenses. The overall goal of our research proposal is to provide new basic knowledge of the mechanism underlying the efficacy of CR - the most reproducible intervention for increasing lifespan in mammals - to delay the development of AHL. A growing body of evidence indicates that reactive oxygen species (ROS) play a central role in AHL. There are two major antioxidant defense systems in mitochondria protecting cells from ROS: the glutathione (GSH) and thioredoxin (TXN) systems (11). Thioredoxin is an oxidoreductase enzyme and an essential component of the mitochondrial antioxidant defense system (11-12). Currently, the role of the TXN antioxidant defense system in protecting the inner ear cells from oxidative stress during aging or under CR conditions is not known. The central hypothesis of our proposal is that during aging, the mitochondrial TXN antioxidant defense system declines in the cochlea, leading to AHL, while under calorie restricted conditions, there is an up-regulation of the TXN system which in turn protects the inner ear cells from oxidative stress, thereby slowing the development of AHL in mammals. To test this hypothesis, we will explore the roles of two major components, Txn2 (thioredoxin 2) and Txnrd2 (thioredoxin reductase 2), in the mitochondrial TXN antioxidant defense system in AHL under standard and calorie restricted diet conditions. Currently there is no treatment for AHL. The results of our proposal will provide the opportunity to identify interventions that will delay presbycusis in humans.
Reducing caloric intake extends the lifespan of a variety of species and delays the progression of age- associated diseases such as age-related hearing loss (AHL) (1-9), a common feature of aging that affects more than 40% of people over 65 years of age in the US (13). The overall goal of our research proposal is to provide new basic knowledge of the mechanism underlying the efficacy of CR - the most reproducible intervention for increasing lifespan in mammals - to delay the development of AHL in mammals. The results of our proposal will provide an enhanced understanding of the fundamental mechanisms underlying AHL, and the opportunity to identify interventions that will delay presbycusis in humans.
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|Yu, Hong; Vikhe Patil, Kim; Han, Chul et al. (2016) GLAST Deficiency in Mice Exacerbates Gap Detection Deficits in a Model of Salicylate-Induced Tinnitus. Front Behav Neurosci 10:158|
|Han, Chul; Ding, Dalian; Lopez, Maria-Cecilia et al. (2016) Effects of Long-Term Exercise on Age-Related Hearing Loss in Mice. J Neurosci 36:11308-11319|
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|Ding, Dalian; Qi, Weidong; Yu, Dongzhen et al. (2013) Addition of exogenous NAD+ prevents mefloquine-induced neuroaxonal and hair cell degeneration through reduction of caspase-3-mediated apoptosis in cochlear organotypic cultures. PLoS One 8:e79817|
|Dalian, Ding; Haiyan, Jiang; Yong, Fu et al. (2013) Ototoxic Model of Oxaliplatin and Protection from Nicotinamide Adenine Dinucleotide. J Otol 8:63-71|
|Yamasoba, Tatsuya; Lin, Frank R; Someya, Shinichi et al. (2013) Current concepts in age-related hearing loss: epidemiology and mechanistic pathways. Hear Res 303:30-8|
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