Endotoxin preconditioning as a model to uncover protective pathways in sepsis-induced renal injury

脓毒症所致的急性肾损伤仍然是一个主要的临床问题，目前还没有建立有效的治疗方法 约会。尽管已经确定了潜在的治疗靶点并在临床试验中进行了测试，但还没有一个 事实证明是有效的，强调了脓毒症病理生理学的复杂性。我们实验室的工作 细胞间通讯障碍被认为是复杂病理生理学的主要特征 脓毒症引起的肾损伤。例如，从S1小管到下游S2/S3的病理信号 肾小管是脓毒症时肾脏损伤的主要途径。事实上，我们确定了S1近端肾小管片段为 过滤内毒素的主要传感器和水槽。这种摄取内毒素的S1导致严重的氧化应激 以及对下游S2/S3节段的破坏。靶向S1转录和组织代谢组学揭示 在败血症的S1近端小管中，嘌呤代谢明显改变。这种转变是由黄嘌呤催化的。 氧化还原酶，嘌呤降解途径中的关键酶。这种酶起脱氢酶的作用。 (Xdh)天然形式，但很容易通过巯基氧化或蛋白分解转化为氧化酶(Xo) 修改。而XDH的催化不会产生自由基，而XO是一种强烈的促氧化剂， 产生有害的活性物质。此外，促氧化剂XO被分泌到尿腔和 因此可能会对下游管段造成损害。相反，巨噬细胞中XO的表达可能是 有益的是因为它通过产生活性物质来刺激这些细胞的杀菌潜力。 本研究的目的之一是确定XO和XDH在脓毒症的S1和巨噬细胞中的相对作用 肾脏。此外，由于XO/XdH参与了嘌呤的最终降解，因此XO/XdH的变化 活性不仅会影响活性物种的生成，还会对上游的大小产生影响 关于嘌呤池的。这项提议的第二个目标是确定嘌呤代谢物和 它们在脓毒症中对嘌呤稳态的贡献。

Sepsis-induced acute kidney injury remains a major clinical problem with no effective therapy established to date. Although potential therapeutic targets have been identified and tested in clinical trials, none of them has proven to be effective, underscoring the complexity of sepsis pathophysiology. Work from our laboratory identified disturbances in cell-cell communication as a major feature underlying the complex pathophysiology of sepsis-induced kidney damage. For example, pathologic signaling from S1 tubules to downstream S2/S3 tubules was a major pathway of renal injury in sepsis. Indeed, we identified the S1 proximal tubular segment as a major sensor and sink for filtered endotoxin. This S1 uptake of endotoxin resulted in severe oxidative stress and damage to downstream S2/S3 segments. Targeted S1 transcriptomics and tissue metabolomics revealed that purine metabolism is markedly altered in septic S1 proximal tubules. This shift is catalyzed by xanthine oxidoreductase, a key enzyme in the purine degradation pathway. This enzyme functions as a dehydrogenase (XDH) in its native form but is readily converted to an oxidase (XO) through sulfhydryl oxidation or proteolytic modification. Whereas catalysis by XDH does not generate free radicals, XO is a strong pro-oxidant that generates deleterious reactive species. Furthermore, the pro-oxidant XO is secreted into the urinary lumen and can therefore cause damage to downstream segments. In contrast, XO expression in macrophages may be beneficial because it stimulates the bactericidal potential of these cells through generation of reactive species. It is one goal of this proposal to establish the relative roles of XO versus XDH in S1 and macrophages in septic kidneys. Moreover, because XO/XDH is involved in the final degradation of purines, the changes in XO/XDH activity will not only affect the generation of reactive species but will also have an upstream impact on the size of purine pools. It is the second goal of this proposal to determine the overall flux of purine metabolites and their contributions to purine homeostasis in sepsis.