Renal Oxygenation in the Pathophysiology of Kidney Disease

描述(由申请人提供)： 在慢性肾脏疾病(CKD)中，肾内缺氧已被确认为疾病进展的主要因素。因此，了解在健康和疾病中调节肾脏氧合的途径是非常必要的。在最初阶段，功能性氧供需不匹配会造成低氧环境。肾单位氧耗量高而供氧不增加是导致氧供需不匹配的最早病理生理变化。降低肾单位耗氧量可改善肾脏功能和形态。本研究旨在研究慢性肾脏病啮齿动物模型肾大部切除术早期的氧耗调节机制。其策略和总体目标是在疾病发生不可逆转的结构变化之前，在疾病进程的早期调查关键的病理生理事件及其调节，并确定可以预防或减缓CKD进展的新的治疗靶点。肾脏中的大部分能量是由线粒体氧化磷酸化提供的。初步数据显示，在早期肾大部切除术中，线粒体功能和形态发生了几个变化，表明线粒体处于应激状态。低氧诱导因子(HIF)转录复合体是氧稳态的主要氧感受器/调节器，可诱导多种靶基因影响氧的输送和消耗。它对线粒体功能也有几个有益的影响。AMP激活的蛋白激酶(AMPK)是另一个重要的能量感受器，在缺乏ATP的条件下调节细胞的代谢适应，越来越多地被认为是肾脏病理生理学中的主要参与者。HIF和AMPK也正在成为钠转运的调节者，钠转运是肾单位氧气消耗的主要驱动因素。根据初步数据，总体假设是早期肾小管缺氧，由于肾单位氧耗增加，导致线粒体功能障碍和ROS生成，从而导致组织损伤和肾功能障碍。这是由于AMPK活性被抑制而导致的异常细胞应激适应而持久存在的。HIF-1通过影响肾脏血流动力学、盐分转运和细胞效应，包括改善线粒体形态和功能，恢复AMPK活性，从而降低氧耗，增加供氧，从而改善肾脏氧合功能。研究的具体目的是确定早期CKD时HIF-1激活改善肾脏氧合作用的亚细胞、细胞和血流动力学机制，并通过检测AMPK通路在早期CKD肾小管运输和代谢中的作用，确定AMPK通路在肾功能和氧合中的意义。这些研究不仅将为疾病进展的早期机制提供重要和新颖的见解，并确定可以早期采用的治疗策略，以防止通常的疾病进展，而且基础广泛的方法还将成为未来关于HIF和AMPK在细胞和亚细胞水平上调节能量代谢和运输的协调作用的具体机制途径的建议的跳板。考虑到线粒体功能障碍在各种病理生理条件下的普遍含义，以及HIF和AMPK在几个器官中几乎无处不在的细胞表达，从这些研究中获得的理解将比所研究的模型更有价值。

DESCRIPTION (provided by applicant): In chronic kidney disease (CKD), intrarenal hypoxia has been identified as a major contributor to disease progression. Hence, it is imperative to understand the pathways that regulate kidney oxygenation in health and disease. At the earliest stages, a functional oxygen supply-demand mismatch creates a hypoxic environment. High nephron oxygen consumption without an increase in oxygen supply is the earliest pathophysiological change that leads to oxygen supply-demand mismatch. Lowering nephron oxygen consumption improves kidney function and morphology. This proposal is aimed at investigating the regulators of oxygen consumption at the earliest stages in subtotal nephrectomy, a rodent model of CKD. The strategy and overall objective is to investigate key pathophysiological events and their regulation early in the course of disease before irreversible structural changes set in and to identify novel therapeutic targets which can prevent or slow the progression of CKD. The majority of the energy in the kidney is provided by oxidative phosphorylation by the mitochondria. Preliminary data demonstrates several alterations in mitochondrial function and morphology in early subtotal nephrectomy indicating mitochondrial stress. Hypoxia inducible factor (HIF) transcription complex is a primary oxygen sensor/regulator of oxygen homeostasis and induces several target genes that impact oxygen delivery and consumption. It also has several beneficial effects on mitochondrial function. AMP-activated protein kinase (AMPK) is another important energy sensor that regulates cellular metabolic adaptations under ATP-deprived conditions and is increasingly being identified as a major player in renal pathophysiology. HIF and AMPK are also emerging as regulators of sodium transport, which is a primary driver of nephron oxygen consumption. Based on the preliminary data, the overall hypothesis is that hypoxia in early subtotal kidney, due to increased nephron oxygen consumption, leads to mitochondrial dysfunction and ROS generation, resulting in tissue injury and renal dysfunction. This is perpetuated by abnormal cellular stress adaptation due to suppressed AMPK activation. HIF-1 induction improves renal oxygenation by lowering oxygen consumption and increasing oxygen supply via effects on renal hemodynamics, salt transport and cellular effects including improvements in mitochondrial morphology and function and restoration of AMPK activation. The specific aims are to determine the subcellular, cellular and hemodynamic mechanisms whereby HIF-1 activation improves renal oxygenation in early CKD and to determine the significance of the AMPK pathway in renal function and oxygenation by examining its role in tubular transport and metabolism in early CKD. These investigations will not only provide important and novel insights into the early mechanisms of disease progression and identify treatment strategies that can be employed early to prevent the usual course of disease progression, but the broad-based approach will also serve as a spring-board for future proposals on specific mechanistic pathways underlying the coordinated actions of HIF and AMPK in the regulation of energy metabolism and transport at a cellular and subcellular level. The understanding obtained from these investigations will be valuable beyond the model studied given the universal implications of mitochondrial dysfunction in various pathophysiological conditions and the nearly ubiquitous cellular expression of HIF and AMPK in several organs.