Mechanisms of susceptibility to sepsis after acute kidney injury

 描述(由申请人提供)：急性肾损伤(AKI)很常见，会增加死亡率。AKI使高达20%的医院入院和30%至50%的ICU入院复杂化。AKI确诊后，40%-45%的患者会发生脓毒症，并使死亡率翻一番。目前还没有治疗AKI或预防其并发症的疗法。到目前为止，将BASE研究转化为AKI的治疗方法完全不成功，因为所有在动物模型中有效的治疗方法在AKI患者中都失败了。对于成功的最关键障碍，人们给出了许多解释，但一致程度各不相同。AKI社区中一个值得注意的共识是，临床试验中的疗法实施得太晚，或者在AKI的不适当阶段，无法奏效。在这项资助中，我们调查了AKI易患肺炎败血症的机制。由于脓毒症是在AKI确诊后发生的(根据AKI的血肌酐定义)，我们认为这一并发症是高度可预见和预防的。因此，如果这项建议的目标得以实现，将确定一个立即适用的目标，以提高AKI患者的存活率。我们的总体假设是，AKI使肺泡巨噬细胞在暴露于内毒素或革兰氏阴性细菌时产生旺盛的炎症反应。我们认为，活跃的炎症反应介导了肺部炎症、紧密连接蛋白的丢失和上皮通透性的增加，这有助于细菌移位到循环中，导致菌血症和败血症。我们有三个具体的目标：1)确定急性肾损伤(AKI)是否导致肺泡巨噬细胞的免疫启动；2)确定AKI诱导的肺泡巨噬细胞是否介导肺上皮损伤；3)确定肺炎期间AKI诱导的肺泡巨噬细胞的肺上皮损伤是否介导细菌移位到循环中。肺泡巨噬细胞的免疫启动将在体内确定，并在体外通过内毒素暴露后AKI产生过多的肿瘤坏死因子-α来判断。在体内和体外，通过在AKI和内毒素的情况下将IL-6暴露于肺泡巨噬细胞，研究IL-6的抗炎信号作用。AKI诱导的肺泡巨噬细胞紧密连接蛋白丢失和肺上皮损伤将通过靶向抑制肺泡巨噬细胞肿瘤坏死因子-α或给予IL-6来研究。通过靶向抑制肺泡巨噬细胞肿瘤坏死因子-α或IL-6来预防细菌易位的方法将被研究。细菌移位将通过活体内评估 共聚焦显微镜追踪绿色荧光蛋白标记的铜绿假单胞菌细菌从肺泡进入循环。这笔赠款中的实验将为开发预防脓毒症和提高AKI患者存活率的干预措施提供有用的指导。

 DESCRIPTION (provided by applicant): Acute kidney injury (AKI) is common and increases mortality. AKI complicates up to 20% of hospital admissions and 30 to 50% of ICU admissions. Sepsis occurs in 40-45% of patients after AKI diagnosis and doubles mortality. No therapy is available to treat AKI or prevent its complications. To date, translation of bench research into therapies for AKI has been completely unsuccessful, as all of the trials examining therapies that were effective in animal models failed in patients with AKI. Numerous explanations have been offered, with variable degree of agreement on the most critical barriers to success. One notable area of agreement in the AKI community is that therapies in clinical trials were administered too late, or in the inappropriate phase of AKI, to be effective. In this grant, we investigate the mechanisms by which AKI predisposes to sepsis from pneumonia. Since sepsis occurs after the diagnosis of AKI (based on a serum creatinine definition of AKI), we believe that this complication is highly amenable to anticipation and prevention. Thus, if the aims of this proposal are achieved, an immediately applicable target to improve survival in patients with AKI will be identified. Our overall hypothesis is that AKI primes alveolar macrophages to exert an exuberant inflammatory response when exposed to endotoxin or gram negative bacteria. We propose that exuberant inflammatory response mediates lung inflammation, loss of tight junction proteins, and increased epithelial permeability which facilitates translocation of bacteria into the circulation resulting in bacteremia and sepsis. We have three Specific Aims: 1) Determine if acute kidney injury (AKI) causes immune priming of alveolar macrophages; 2) Determine if AKI-primed alveolar macrophages mediate lung epithelial injury; 3) Determine if lung epithelial injury from AKI-primed alveolar macrophages mediates translocation of bacteria into the circulation during pneumonia. Immune priming of alveolar macrophages will be ascertained in vivo, and in vitro as judged by excessive TNF-a production in AKI after endotoxin exposure. Anti-inflammatory signaling effects of IL-6 will be investigated in AKI-primed alveolar macrophages, in vivo and in vitro, by exposing alveolar macrophages to IL-6 in the setting of AKI and endotoxin. Tight junction protein loss and lung epithelial injury due to AKI-primed alveolar macrophages will be studied via targeted alveolar macrophage TNF-a inhibition or IL-6 administration. Methods to prevent bacterial translocation via targeted alveolar macrophage TNF-a inhibition or IT IL-6 will be studied. Bacterial translocation will be assessed by intravital confocal microscopy to track GFP-labeled Pseudomonas aeruginosa bacteria from the alveoli into the circulation. The experiments in this grant will provide useful leads into the development of interventions to prevent sepsis and improve survival in patients with AKI.