Reactive oxygen species are formed internally through cellular metabolism and through external sources including radiation and pollutants. They play an important role in physiologic functions; however, when reactive oxygen species exceed our body’s antioxidant defense system, oxidative stress can occur. Oxidative stress has been implicated in aging and aging-related diseases including cancer and cardiovascular disease. Numerous oxidative stress genes produce antioxidative enzymes to mitigate the effects of reactive oxygen species. Single nucleotide polymorphisms within these genes may impact the functionality of antioxidant enzymes produced leaving the body more susceptible to damage from oxidative stress. The Iowa 65+ Rural Health Study was one of the four study populations in the Established Population for Epidemiologic Studies of the Elderly (EPESE) project initiated by the intramural Epidemiology, Demography and Biometry Program of the National Institute on Aging in 1980. The Iowa cohort was comprised of Iowa county and Washington county residents aged 65 and older at the time of the baseline interview in 1982. Participants completed three in-person interviews and five telephone interviews over eight years which collected data on habits, lifestyle and disease. During the in-person Year 06 interview participants were asked to donate a blood sample. The DNA extracted from the samples was used in each of the three aims of this project. The first aim evaluated single nucleotide polymorphisms in selected oxidative stress genes and their association with lifespan while controlling for aging-associated risk factors such as body mass index, comorbidity, alcohol consumption, smoking, and physical activity. Multivariable linear regression models were fit in the framework of the co-dominant genetic model. The oxidative stress genes selected for this project included the sirtuin family of genes (SIRT1-7), two of the forkhead box genes (FOXO1 and FOXO3), superoxide dismutase 2 and 3 (SOD2 and SOD3), glutathione peroxidase (GPX1), AKT, TP53, and CAMK4. A model was fitted with the risk factors before assessing the impact of each single nucleotide polymorphism. The q-value was used to control for the multiple hypothesis tests. Significant associations were detected between human lifespan and SNPs in genes SIRT3, SIRT5, SIRT6, FOXO3, and SOD3; gender modified the effect of SNPs in SIRT3, SIRT5, and AKT1. The second aim of this project evaluated single nucleotide polymorphisms in selected oxidative stress genes and their association with blood pressure measures while controlling for known risk factors including body mass index, alcohol consumption, smoking, and physical activity. Blood pressure was measured at the baseline and Year 06 interviews. Systolic pressure and diastolic pressure were used to calculate mean arterial pressure and pulse pressure at baseline and Year 06. Multivariable linear regression was used within the co-dominant genetic framework to determine if single nucleotide polymorphisms in SIRT1-7, FOXO1, FOXO3, SOD2-3, GPX1, AKT, TP53, and CAMK4 were associated with systolic, diastolic, mean arterial, or pulse pressure at baseline or Year 06. To examine longitudinal effects, the difference between each measure (i.e., Year 06 systolic – baseline systolic) was calculated for each individual and used to evaluate if any of the single polymorphisms was associated with change in blood pressure measures over time. Significant associations were detected between SIRT1 and SIRT3 and for males in SIRT1 and various blood pressure measures for females. Gender modified the effect of SIRT1, SIRT3, SIRT6, and FOXO1 variants. The third aim of this project evaluated if these genetic variants were associated with incident stroke while controlling for known risk factors including blood pressure, diabetes, body mass index, alcohol consumption, smoking, and physical activity. Multivariable logistic regression within the framework of the co-dominant genetic model was used. Individuals with the GPX1 genotype TT had 2.76 times the risk of an incident stroke compared to the CC genotype. This project identified several associations between single nucleotide polymorphisms within oxidative stress genes and lifespan, blood pressure measures, and incident stroke. Gender modified the association of several single nucleotide polymorphisms and lifespan as well as blood pressure measures. These results suggest genetic variation within oxidative stress genes may play a role in aging, blood pressure and incident stroke.

帕金森氏症 (Parkinson’s disease，PD) 為目前最普遍的神經退化性疾病之一，該病因主要是由於中腦黑質區的多巴胺細胞的死亡造成運動系統的失能。環境常用農藥百草枯 (Paraquat，PQ) 目前已知是導致帕金森氏症的環境因子之一。它主要作用在粒線體上，阻斷粒線體的功能、造成大量氧化自由基生成、並誘導細胞凋亡的發生。沉默調節因子蛋白Sirtuin家族 (Sirtuin Family，Sirt1-Sirt7) 是一群 Nicotinamide adenine dinucleotide (NAD+) 依賴性去乙醯化酶，具有抗老化、以及預防神經退化性疾病等能力。SRT1720是根據天然植物酚類白藜蘆醇製造出來的化學衍生物，具有活化Sirtuin的能力。先前研究也顯示SRT1720具有增加糖尿病小鼠的存活率、抗腫瘤、抗發炎等功能，但SRT1720對於神經退化性疾病的保護性並不清楚。為了解SRT1720是否具有對抗PQ的細胞毒性，用以評估SRT1720是否具有治療帕金森氏症的潛力，本研究使用人類神經瘤母細胞株 (SH-SY5Y) 作為帕金森氏症的離體外實驗模式，來探討SRT1720及PQ對於細胞的作用及影響。實驗結果顯示，PQ造成細胞存活率呈劑量反應地下降，而SRT1720可以回復因PQ所造成細胞存活率的下降、細胞凋亡的產生、粒線體的型態變化，以及降低氧化自由基的生成等。這證明SRT1720對細胞具有神經保護的效果。本研究也利用西方點墨法證實了當細胞暴露在PQ下，SRT1720會回復因PQ所導致Sirt1-Sirt7蛋白含量的下降。其中，大量表現Sirt1可以對抗PQ造成細胞的死亡。本研究也發現SRT1720可回復PQ自噬小體在細胞中的堆積情形，利用西方點墨法觀察SRT1720可以回復LC3-I/II的蛋白質再細胞間的堆積。此外，在對於20週大的C57BL/6小鼠注射PQ (10 mg/kg) 及SRT1720 (0.1mg/kg或1 mg/kg)，並利用滾輪及獨木橋試驗觀察其運動行為。結果顯示，SRT1720可以回復PQ所造成運動能力上的下降，並且減緩PQ所造成中腦區多巴胺神經元的傷害。綜觀以上結果，在細胞暴露在PQ時，SRT1720或許可以經由保護粒線體功能，使ROS生成量達到回復及降低細胞凋亡的發生。同時SRT1720也能保持自噬作用的平衡，降低自噬小體在細胞中的堆積。這些機轉也許與SRT1720可以保護多巴胺神經元有關。另一方面，由於Peroxisomal proliferator-activated receptor-coactivator 1α (PGC-1α) 與粒線體的生合成與神經保護有關，本實驗也發現SRT1720可改變PGC-1α去乙醯化的程度，但SRT1720對於Sirtuin蛋白以及Sirt1下游PGC-1α的活化與否還需做進一步的調查及研究。此研究顯示SRT1720對於保護細胞免於受到PQ所引發氧化壓力以及粒線體損傷之神經退化模型提供了一個具有潛力的治療方法。 / Parkinson’s disease (PD) is one of the most common neurodegenerative disorder and mainly affecting the motor system because of the dopamine neuronal death in the substantia nigra. The exposure to environmental neurotoxin paraquat (PQ) is a widely used herbicide. It induces the increase of ROS stress, leads to mitochondrial dysfunction, and results in apoptotic cell death. Epidemiologically, it could be the risk for PD incidence. Mammalian silent information regulator 2 Sirtuin Family (Sirt1-Sirt7) is a NAD+ dependent deacetylase enzyme and it protects against such as anti-aging and neurodegenerative disease. SRT1720 which derives from resveratrol is able to activate Sirt1. SRT1720 has been reported to improve survival in obese mice, anti-tumor, and anti-inflammatory, but the effect in the neurodegenerative disease it still unknown. We thus proposed if SRT1720 could have neuron- protective effect in PQ-induced toxicity. We used SH-SY5Y cell to evaluate the effect of SRT1720 and PQ. First, we confirmed that PQ could dose- and time-dependently decrease SH-SY5Y cell viability, increase ROS formation, and induce mitochondrial dysfunction. However, SRT1720 pretreatment improved cell viability, decreased apoptosis and ROS formation, and prevented mitochondrial dysfunction in PQ-treated SH-SY5Y cells. By Western blot analysis, SRT1720 pretreatment could preserve Sirt1-Sirt7 protein contents during PQ intoxication. In autophagy studies, we also found that SRT1720 could reduce PQ-induce autophagic vacuoles accumulation. Furthermore, we also found that intraperitoneally injection of 10 mg/kg PQ once a week in mice can decrease the level of motor activity after 6 weeks treatment. However, SRT1720 (0.1 mg/kg or 1mg/kg) treatment, reversed PQ- induced motor defect. Taken together, SRT1720 could protect mitochondrial function and improve cell survival during PQ intoxication. This work provided a promising therapeutic way for treating aging-related neurodegenerations, such as PD.