Exercise and Kidney Dopamine Receptor Function in Aging

描述（由申请人提供）： 项目概要：我们报道了多巴胺促进钠排泄的能力在老年（24个月）与成年（6个月）大鼠相比显著降低。这是由于D1受体的过度磷酸化及其与G蛋白的解偶联导致D1受体激动剂不能抑制钠转运蛋白（Na，K-ATP酶，Na，H-交换剂）和产生尿钠排泄。老年大鼠近曲小管（PT）氧化应激的增加是导致D1受体磷酸化并通过PKC/GRK-2途径与G蛋白解偶联的原因。据报道，定期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，6周的跑步机运动在老年大鼠降低水平的丙二醛（氧化应激的标志物）和增加的表达和活性的超氧化物歧化酶（抗氧化酶）的PT相比，PT的久坐不动的老年大鼠。此外，与久坐的老年大鼠相比，运动后PT中IL-10（抗炎标志物）的血浆水平和Nrf 2（负责抗氧化防御基因转录的转录因子）的核水平增加。此外，D1受体数量增加的PT膜，和D1受体激动剂SKF 38393增加钠排泄运动相比，久坐不动的老年大鼠。本申请将检验老年大鼠运动导致抗炎细胞因子产生增加、Nrf 2活化和肾脏PT抗氧化能力增加的假设。增加抗氧化能力降低氧化应激，减少PKC活性/GRK-2易位，从而恢复近端肾小管D1受体G蛋白偶联和利钠反应，多巴胺在运动老年大鼠。为了验证我们的假设，老年大鼠将被放置在跑步机上运动6周，然后测量氧化应激、抗氧化防御、细胞因子、D1受体/G-蛋白偶联和功能的标志物。将采用生化、免疫学、分子生物学和肾功能研究方法完成拟定研究。这些研究将使我们能够确定运动的有益作用，并为确定抗炎细胞因子介导的抗氧化防御增加的分子机制以及降低氧化应激和恢复老年大鼠D1受体G蛋白偶联和功能奠定基础。项目叙述：人口中老年人的数量以及因此与年龄有关的疾病预计在未来几十年内将急剧增加。我们的研究将有助于确定运动作为一种干预措施，以逆转一些与年龄相关的异常，如氧化应激，炎症和药物反应性丧失的增加。所获得的结果将具有深远的意义，证明增加抗炎细胞因子和抗氧化防御与运动导致有益的影响。也许规律的锻炼可以在以后被证明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.