Exercise and Kidney Dopamine Receptor Function in Aging

描述(由申请人提供)： 项目摘要：我们报告了老年(24个月)大鼠与成年(6个月)大鼠相比，多巴胺促进钠排泄的能力明显减弱。这是由于D_1受体的过度磷酸化及其与G蛋白的解偶联导致D_1受体激动剂不能抑制钠转运体(Na，K-ATPase，Na，H-交换器)和产生钠尿。老年大鼠近端小管(PTS)氧化应激的增加是导致D1R磷酸化并通过PKC/GRK-2途径与G蛋白解偶联的原因。据报道，有规律的体育锻炼可以减缓细胞损伤和生理功能障碍，这是衰老过程的特征。在初步研究中，我们发现，与久坐不动的老年大鼠相比，老年大鼠6周的跑步机运动降低了PTS中丙二醛(氧化应激的标志)的水平，增加了超氧化物歧化酶(一种抗氧化酶)的表达和活性。此外，与久坐不动的老年大鼠相比，运动后PTS的血浆IL-10(一种抗炎标记物)水平和Nrf2(一种负责转录抗氧化防御基因的转录因子)的核水平都有所增加。此外，与久坐不动的老年大鼠相比，运动后PTS膜上的D1受体数目增加，且D1受体激动剂SKF38393增加了钠的排泄。这项应用将检验这样一种假设，即老年大鼠的运动导致抗炎细胞因子的产生增加，肾脏PTS的Nrf2激活和抗氧化能力增强。抗氧化能力的增强降低了氧化应激，降低了PKC活性/GRK-2易位，从而恢复了运动老年大鼠肾小管近端D_1受体G蛋白偶联和对多巴胺的利钠反应。为了验证我们的假设，老年大鼠将进行为期6周的跑步机运动，随后测量氧化应激、抗氧化防御、细胞因子、D1受体/G蛋白偶联和功能的标记物。将使用生化、免疫学、分子生物学和肾脏功能研究方法来完成拟议的研究。这些研究将使我们能够确定运动的有益效果，并为确定抗炎细胞因子介导的增加抗氧化防御、降低氧化应激、恢复D_1受体G-蛋白偶联和功能的分子机制奠定基础。项目简介：未来几十年，人口中老年人口的数量预计将大幅增加，因此与年龄相关的疾病也将大幅增加。我们的研究将有助于确定运动是一种干预措施，可以逆转一些与年龄相关的异常，如氧化应激增加、炎症和药物反应性丧失。这一结果将对证明运动中增加抗炎细胞因子和抗氧化防御系统产生有益效果具有深远的意义。也许以后可以证明，定期锻炼是预防一些与年龄相关的心血管和肾脏疾病的有效干预措施。

DESCRIPTION (provided by applicant): Project Summary: We reported that the ability of dopamine to promote sodium excretion is markedly diminished in old (24-month) compared to adult (6-month) rats. This is due to the hyperphosphorylation of D1 receptors and their uncoupling from G-proteins resulting in the failure of D1 receptor agonist to inhibit the sodium transporters (Na,K-ATPase, Na,H-exchanger) and to produce natriuresis. Age-related increase in oxidative stress in the proximal tubules (PTs) of old rats is responsible for causing D1 receptor phosphorylation and it's uncoupling from G-proteins via PKC/GRK-2 pathway. Regular physical exercise is reported to slow down cell damage and physiological dysfunction that is characteristic of the aging process. In preliminary studies, we found that 6-week treadmill exercise in old rats decreased levels of malondialdehyde (a marker of oxidative stress) and increased expression and activity of superoxide dismutase (an anti-oxidant enzyme) in PTs compared to PTs of sedentary old rats. Further, the plasma levels of IL-10 (an anti-inflammatory marker) and the nuclear levels of Nrf2 (a transcription factor responsible for transcription of anti-oxidant defense genes) in PTs were increased in exercised compared to sedentary old rats. Moreover, D1 receptor numbers increased in the PTs membranes, and D1 receptor agonist SKF38393 increased sodium excretion in exercised compared to sedentary old rats. This application will test the hypothesis that exercise in old rats leads to increased production of anti-inflammatory cytokines, activation of Nrf2 and increased anti-oxidant capacity in renal PTs. The increased anti-oxidant capacity lowers oxidative stress, reduces PKC activity/GRK-2 translocation, and thus restores proximal tubular D1 receptor G-protein coupling and the natriuretic response to dopamine in exercised old rats. In order to test our hypothesis, old rats will be placed on treadmill exercise for 6-week followed by measurement of markers of oxidative stress, anti-oxidant defenses, cytokines, D1 receptor/G- protein coupling and function. Biochemical, immunological, molecular biology and renal functional studies methodologies will be employed to accomplish the proposed studies. These studies will allow us to determine beneficial effects of exercise and form the basis to identify molecular mechanism of anti-inflammatory cytokines-mediated increase in anti-oxidant defenses and in lowering oxidative stress and restoring D1 receptor G-protein coupling and function in old rats. Project Narrative: The number of elderly in the population and therefore age-related disorders is predicted to increase dramatically over the next few decades. Our research will help identify exercise as an intervention to reverse some of the age-associated abnormalities such as increases in oxidative stress, inflammation and loss of drug responsiveness. The results obtained will have far reaching significance in terms of demonstrating that increasing anti-inflammatory cytokines and anti-oxidant defenses with exercise leads to beneficial effects. Perhaps regular exercise can later on be demonstrated as an effective intervention to prevent some of the age- associated cardiovascular and kidney diseases.