NF-kappa B in Murine Sepsis

尽管在心肺支持的同时使用了有效的抗生素，但在过去的三十年里，败血症和感染性休克的死亡率仍然很高(29%)。此外，败血症和感染性休克的发生率似乎在增加。需要具有广泛临床适用性的新的治疗方法来降低这种综合征的高死亡率。 炎症介质的过度释放直接导致严重感染并发脓毒症和感染性休克时器官损伤和死亡的发生。核因子kappaB是一种核转录调节蛋白，参与多种不同基因的激活，编码与脓毒症时的炎症反应相关的蛋白。正常情况下，在其胞质抑制物(I-(B)蛋白的控制下，核因子-KB仍以非活性状态被隔离在细胞质中。然而，不同种类的刺激包括内毒素(革兰氏阴性菌的毒性部分)和细胞因子(如肿瘤坏死因子α和白介素6)导致I-KB蛋白的磷酸化、泛素化和随后的降解，进而导致NF-KB的激活。然后，核因子-kB的DNA结合亚基迁移到细胞核并激活靶基因的表达，这些基因编码了炎症和免疫反应中的蛋白质，如趋化因子、细胞因子、诱导型一氧化氮合酶(INOS)和黏附分子。其中许多基因产物与脓毒症和感染性休克时血流动力学不稳定和器官损伤的发病机制密切相关。因此，抑制核因子-KB的药物可能具有广泛的抗炎作用，这在脓毒症期间可能是有益的。然而，许多与炎症反应相关的宿主介质也参与了天然免疫和清除细菌感染。因此，在脓毒症期间抑制核因子-KB也可能加重潜在感染。 本方案在一种脓毒症小鼠模型中测试了单边旗内酯对核因子-kB的调节作用。白菊内酯是一种从菊科植物中提取的倍半萜内酯。据报道，在分别用腹腔或静脉注射脂多糖攻击的小鼠或大鼠中，在静脉注射脂多糖刺激后长达3小时的时间内给药可提高存活率。然而，在迄今为止在该方案下流体支持的小鼠模型中完成的研究中，用巴马内酯抑制核因子-kB对内毒素的攻击是有害的。这些结果强调了核因子-KB在宿主防御微生物毒素方面的潜在保护作用。 这个项目的工作现在集中在研究在脂多糖攻击后一段时间内组织中核因子-KB的表达。到目前为止，在肺内的研究表明，核因子-kB的表达与内毒素攻击的剂量有关。此外，菊内酯、S对核因子-KB表达的影响似乎具有时间依赖性。虽然早期水平下降，但在内酯内酯攻击后后期水平升高。与Parthenolide类似的变化在血浆细胞因子水平上也被注意到。 总体而言，这些研究表明，在脓毒症动物模型中抑制核因子-KB的作用可能是不同的。在对患者进行研究之前，必须很好地了解在脓毒症期间抑制这种中枢介质在炎症和宿主反应中的作用。

Despite the use of effective antibiotics in combination with cardiopulmonary support, the mortality rate from sepsis and septic shock for the last three decades has remained high (29%. Furthermore, the incidence of sepsis and septic shock appear to be increasing. New therapeutic approaches with wide clinical applicability are needed to lower the high mortality rate of this syndrome. Excessive release of inflammatory mediators contributes directly to the pathogenesis of organ injury and death occurring during severe infection complicated by sepsis and septic shock. Nuclear factor kappa B (NF-KB) is a nuclear transcription regulatory protein central to the activation of several different genes encoding proteins associated with the inflammatory response during sepsis. Under normal conditions, NF-KB remains sequestered in an inactive state in the cytoplasm under the control of its cytoplasmic inhibitor (I-(B) proteins. However, differing kinds of stimuli including LPS (the toxic moiety of gram-negative bacteria) and cytokines (e.g. TNF alpha and interleukin-6) cause the phosphorylation, ubiquitinylation, and the subsequent degradation of I-KB proteins in turn resulting in the activation of NF-KB. Then the DNA-binding subunits of NF-KB migrate into the nucleus and activate expression of target genes that code for proteins in the inflammatory and immune responses, such as chemokines, cytokines, inducible nitric oxide synthase (iNOS), and adhesion molecules. Many of these gene products have been closely associated with the pathogenesis of the hemodynamic instability and organ injury occurring during sepsis and septic shock. Therefore, agents designed to inhibit NF-KB may have broad antiinflammmatory effects that could be beneficial during sepsis. However, many of the host mediators associated with the inflammatory response and under the control of NF-KB also contribute to innate immunity and the clearance of bacterial infection. Suppression of NF-KB during sepsis could therefore also worsen underlying infection. The present protocol tested the effects of of modulating NF-KB with parthenolide in a murine model of sepsis. Parthenolide is a sesquiterpene lactone derived from Asteraceae plants. Parthenolide has been reported to improve survival when administered up to 3 hours following intravenous LPS stimulation in mice or rats challenged with intraperitoneal or intravenous LPS respectively. However in the investigations that have thus far been completed in a fluid supported mouse model under this protocol, inhibition of NF-KB with parthenolide has been harmful with LPS challenge. These results emphasize the potential protective effect NF-KB has in host defense against microbial toxins. Work in this project is now centered on investigating tissue expression of NF-KB over the time following LPS challenge. Thus far, studies in the lung have shown that NF-KB expression is related to the dose of LPS challenge. Furthermore, parthenolide?s effects on NF-KB expression appear to be time dependent. Although levels are decreased early, they are increased late after LPS challenge with parthenolide. Similar changes with parthenolide were noted with plasma cytokine levels. Overall, these studies suggest that the effects of NF-KB inhibition in animal models of sepsis may be variable. Understanding the effects of inhibiting such a central mediator in the inflammatory and host responses during sepsis must be well defined before this is explored in patients.