Pathogenesis of infection in pancreatitis: from sterile inflammation to sepsis

项目总结： 急性胰腺炎(AP)在美国每年影响275,000人。AP突然和不可预测地开始无菌 炎症，但在严重的情况下，可被感染，导致败血症，延长住院时间，有时 死亡。在美国，脓毒症本身每年影响150万人，花费200亿美元，导致12%-18%的死亡率 和美联社有很多共同之处。虽然被定义为对感染的压倒性反应，但很大一部分 败血症始于AP等无菌疾病。AP已经模拟了无菌疾病向感染和 脓毒症是自1992年首次定义以来的败血症。这两种疾病都知之甚少，而且都没有特定的 靶向治疗。这两种疾病在严重时都会出现远端器官衰竭，我们已经证明这是由于 AP期间不饱和脂肪酸的过度和不受调节的脂解释放。游离脂肪酸(UFA) 指不与其主要载体，即白蛋白结合的一小部分(1%)游离脂肪酸，它是 重症急性胰腺炎时常为低水平。我们的初步数据显示，胰腺脂肪酶产生UFA，而UFA 在严重脓毒症患者的血清中升高。此外，UFA可以快速地融入膜中 炎症细胞，引发损伤，损害其功能。在此基础上，我们假设乌法 胰腺脂肪酶产生的脂肪会导致炎症细胞损伤，破坏细菌清除，导致脓毒症。 在AP期间。我们建议研究脂毒性炎症细胞损伤引起的分子机制。 通过使用细胞、动物模型(目标2)感染，并测试这在人类AP中的相关性，从而提供 支持临床AP管理变革的证据(目标1)。在目标1中，我们将确定临床 通过测定血清UFA的预后价值探讨脂毒性炎症细胞损伤在临床AP中的意义 AP入院时与感染时的炎性细胞损伤，以及两者之间的关系 UFA型之间，炎性损伤的性质与感染型有关。在目标2中，我们继续确定 用细胞和动物模型研究急性胰腺炎时脂毒性炎症细胞损伤的机制和后果。至 为此，我们将研究炎性细胞损伤对胰腺脂肪酶和脂质环境的依赖， 确定细菌清除受损的作用，并探索脂毒性的机制 会发生炎性细胞损伤。通过这样做，我们希望提供一个广泛相关的、机械上健全的、 治疗上顺从的，对脓毒症的新解释。这项工作将建立一个概念框架，以 了解无菌疾病中感染的发病机制(即通过UFA介导的炎症细胞损伤)， 这在临床上是相关的--即解释了为什么白细胞计数的下降可能预示着感染这种疾病的风险增加 作为医院感染，因此可能并不总是有利的。它还可以提供改进的诊断工具 基于流式细胞术来解释白细胞计数、损伤和感染风险，并提出治疗方案 如早期白蛋白替代，谨慎预防性使用抗生素，以及以胰腺脂肪酶为靶点 避免无菌AP发展为严重脓毒症和死亡的方法。

PROJECT SUMMARY: Acute pancreatitis (AP) affects @ 275,000/ year in the USA. AP starts suddenly and unpredictably as sterile inflammation but in severe cases can get infected, resulting in sepsis, prolonged hospitalization and sometimes death. Sepsis itself affects 1.5 million people /year in the USA, costs > $20 billion, results in 12-18% mortality and has a lot in common with AP. While defined as an overwhelming response to infection, a large portion of sepsis starts in sterile diseases like AP. AP has modelled the progression of sterile diseases to infection and sepsis since sepsis was first defined in 1992. Both diseases are poorly understood, and neither has a specific targeted therapy. Both diseases, when severe have distant organ failure, which we have shown to be due to the excessive and unregulated lipolytic release of unsaturated fatty acids during AP. Unbound fatty acids (uFA) refers to the small pool (<1%) of free fatty acids that are not bound to their main carrier, i.e. albumin, which is frequently low in severe AP. Our preliminary data show that pancreatic lipases generate uFA which are increased in the sera of severely septic patients. Additionally, uFA can rapidly incorporate into the membranes of inflammatory cells, trigger injury and impair their function. Based on these we hypothesize that uFA generated by pancreatic lipases cause inflammatory cell injury, impair bacterial clearance and result in sepsis during AP. We propose to study the molecular mechanisms of how lipotoxic inflammatory cell injury causes infections by using cell, animal models (Aim 2), and test the relevance of this in human AP, thus providing evidence to support changes in clinical AP management (Aim 1).In Aim 1 we will determine the clinical significance of lipotoxic inflammatory cell injury in clinical AP by determining the prognostic value of serum uFA and inflammatory cell injury at admission for AP vs. at time of infection, along with studying the relationship between type of uFA, nature of inflammatory injury with the type of infection. In Aim 2, we go on to determine the mechanisms and consequences of lipotoxic inflammatory cell injury in AP using cell and animal models. To do so we will study the dependence of inflammatory cell injury on pancreatic lipases and the lipid environment, determine the role of impaired bacterial clearance, and explore the mechanisms by which lipotoxic inflammatory cell injury occurs. By doing so, we hope to provide a broadly relevant, mechanistically sound, therapeutically amenable, novel explanation for sepsis. This work would set a conceptual framework to understand the pathogenesis of infection in sterile diseases (i.e. via uFA mediated inflammatory cell injury), which is clinically relevant- i.e. explains why a drop in white counts may signal increased risk of infection such as nosocomial infections and thus may not be always favorable. It can also provide improved diagnostic tools based on flow-cytometry to interpret WBC counts, injury and risk of infection, and suggest therapeutic options like the early replacement of albumin, prudent prophylactic antibiotic use, and targeting pancreatic lipases as an approach to avert the progression of sterile AP to severe sepsis and death.