Mitochondrial DNA Variations And Susceptibility To Oxidative Injury In The RPE
Jiyang Cai
Neurologyvanderbilt University
Grant 1R21EY018715-01A1 from National Eye Institute, IRG: ZRG1
Abstract: Our recent studies have identified a novel genetic variation associated with age-related macular degeneration (AMD). The 4917G allele of mitochondrial DNA (mtDNA) was independently associated with AMD (OR=3.30, 95% CI 1.25 - 7.17, p=0.01) following adjustment for known risk factors including complement factor H, LOC387715 gene on chromosome 10q26, age, gender and smoking status. The 4917G polymorphism is a common variation in haplogroup T mitochondria and results in a non-synonomous change, asparagine for aspartic acid, in the ND2 subunit of Complex I. Mitochondria play essential roles in controlling cellular energy production, apoptosis and redox homeostasis. Mutations and polymorphisms of the mitochondrial genome often lead to pathological lesions in tissues with high energy demand, such as the retina. The retinal pigment epithelium (RPE) is a primary site of lesion in AMD. Accumulating evidence indicates that oxidative stress induced dysfunction of the RPE contributes to the development and progression of AMD. We hypothesize that specific polymorphisms in the mitochondrial genome control susceptibility to oxidative injury in the RPE. The hypothesis will be tested in the following two specific aims using cultured human fetal RPE cells which do not carry somatic damage to the mtDNA seen with aging. Specific Aim 1 will determine whether specific mitochondrial DNA polymorphisms are associated with increased susceptibility to oxidant-induced apoptosis in cultured fetal RPE cells and whether the sensitivity is associated with mitochondrial genetic variations. Specific Aim 2 will determine whether variations in the mitochondrial genome affect responses to agents that induce the antioxidant responses in the RPE. Results from these studies will support the use of mtDNA haplotypes as a genetic biomarker in identifying people with increased risk of AMD and may lead to predictors of the outcome of clinical treatment with antioxidant supplementation or other agents that augment the antioxidant defense of the retina. Age-related macular degeneration (AMD) is the leading cause of blindness in elderly people. Recent studies have identified that the risk of developing AMD is associated with a novel genetic variation in the mitochondrial genome. Characterization of the functional consequences of such variation will be the focus of the current proposal
Project start date: 2008-08-01
Project end date: 2010-07-31
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Grants awarded to Jiyang Cai
Mitochondrial Oxidative Stress And Protection In Pesticide-induced Neurotoxicity
Jiyang Cai
Vanderbilt University Medical Center Nashville, Tn 372036869
Grant 1R21ES014668-01A1 from National Institute Of Environmental Health Sciences, IRG: NAL
Abstract: The etiology of Parkinson s disease (PD) involves gene/environment interaction. While most of the identified genetic mutations affect the ubiquitin-proteasome system (UPS), epidemiological studies and clinical case reports have strongly suggested the association between pesticide exposure and increased incidence of PD. In animal models, selective toxicities to the nigrostriatal dopaminergic neurons occur after systemic exposure to rotenone and paraquat. Oxidative stress is a common mediator of pesticide-induced neurotoxicity. It contributes to PD-related pathological changes such as formation of a-synuclein aggregates and inhibition of proteasomal function. However, the molecular targets of oxidative damage have not been clearly defined and the mechanistic link between mitochondria! and proteasomal dysfunction remains to be determined. In our preliminary studies, we have shown that mitochondrial thioredoxin (mtTrx; Trx2) is particularly susceptible to oxidation induced by a variety of environmental toxicants, including peroxides, rotenone, MPP+ and paraquat. Submicromolar concentrations of rotenone induced persistent oxidation of mtTrx and redistribution of mtTrx to the cytoplasm. Chronic exposure to nanomolar concentrations of rotenone resulted in decreased mtTrx protein. Overexpression of mtTrx protected cells from oxidant-induced apoptosis and inhibited a-synuclein aggregation caused by chronic rotenone toxicity. Downregulation of the mitochondrial thioredoxin reductase (TrxR 2) led to decreased mature mtTrx while increased its precursor form. Furthermore, we identified that mtTrx interacted with mitochondrial heat shock protein 60 which is a key component of the mitochondrial protein processing machinery. Based on these findings, we hypothesize that selective targeting of mtTrx by pesticides and the ensuring oxidation of mtTrx lead to impaired mitochondrial protein import. The hypothesis will be tested with two specific aims. Specific aim 1 is to determine whether the redox status and expression level of mtTrx control the sensitivity to pesticide-induced toxicity in cultured neuronal cells. Specific aim 2 is to determine whether the pesticide-induced oxidation inhibits the import of mtTrx and other nuclear DMA-encoded mitochondrial proteins. Results from these studies will define novel protein targets of oxidative injury and will facilitate our understanding towards the molecular mechanisms of environmental toxicities associated with PD.
Keywords: Parkinson s disease, disease /disorder etiology, mitochondria, neuroprotectant, neurotoxicology, oxidative stress, paraquat, pesticide biological effect, plant insecticide, NAD(P)H oxidoreductase, cytochrome c, gene expression, heat shock protein, molecular dynamics, proteasome, protein transport, superoxide dismutase, cell line, neoplastic cell, small interfering RNA
Project start date: 2006-12-01
Project end date: 2008-11-30
1R21ES014668-01A1 (2007): $215186
Mitochondrial DNA Variations And Susceptibility To Oxidative Injury In The RPE
Jiyang Cai
Neurologyvanderbilt University
Grant 1R21EY018715-01A1 from National Eye Institute, IRG: ZRG1
Abstract: Our recent studies have identified a novel genetic variation associated with age-related macular degeneration (AMD). The 4917G allele of mitochondrial DNA (mtDNA) was independently associated with AMD (OR=3.30, 95% CI 1.25 - 7.17, p=0.01) following adjustment for known risk factors including complement factor H, LOC387715 gene on chromosome 10q26, age, gender and smoking status. The 4917G polymorphism is a common variation in haplogroup T mitochondria and results in a non-synonomous change, asparagine for aspartic acid, in the ND2 subunit of Complex I. Mitochondria play essential roles in controlling cellular energy production, apoptosis and redox homeostasis. Mutations and polymorphisms of the mitochondrial genome often lead to pathological lesions in tissues with high energy demand, such as the retina. The retinal pigment epithelium (RPE) is a primary site of lesion in AMD. Accumulating evidence indicates that oxidative stress induced dysfunction of the RPE contributes to the development and progression of AMD. We hypothesize that specific polymorphisms in the mitochondrial genome control susceptibility to oxidative injury in the RPE. The hypothesis will be tested in the following two specific aims using cultured human fetal RPE cells which do not carry somatic damage to the mtDNA seen with aging. Specific Aim 1 will determine whether specific mitochondrial DNA polymorphisms are associated with increased susceptibility to oxidant-induced apoptosis in cultured fetal RPE cells and whether the sensitivity is associated with mitochondrial genetic variations. Specific Aim 2 will determine whether variations in the mitochondrial genome affect responses to agents that induce the antioxidant responses in the RPE. Results from these studies will support the use of mtDNA haplotypes as a genetic biomarker in identifying people with increased risk of AMD and may lead to predictors of the outcome of clinical treatment with antioxidant supplementation or other agents that augment the antioxidant defense of the retina. Age-related macular degeneration (AMD) is the leading cause of blindness in elderly people. Recent studies have identified that the risk of developing AMD is associated with a novel genetic variation in the mitochondrial genome. Characterization of the functional consequences of such variation will be the focus of the current proposal
Project start date: 2008-08-01
Project end date: 2010-07-31
Mitochondrial Oxidative Stress And Protection In Pesticide-induced Neurotoxicity
Jiyang Cai
Ophthalmology And Visual Scisvanderbilt University
medical Center
nashville, Tn 372036869
Grant 5R21ES014668-02 from National Institute Of Environmental Health Sciences, IRG: NAL
Project start date: 2006-12-01
Project end date: 2008-11-30
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