Cell-specific role of NF-KB in necrotizing enterocolitis

描述（由申请人提供）：坏死性小肠结肠炎（NEC）仍然是影响早产儿的最具破坏性的疾病之一，是婴儿期肠衰竭的主要原因，目前没有具体的治疗方法。阐明导致NEC的机制至关重要，因此未来可以设计改善疾病结局的策略。我们有证据表明核因子-？B（NF-？B）和IKK？(the NF-？B（I？B）激酶），关键的上游激酶激活NF-？B介导NEC新生大鼠模型中的肠损伤。然而，NF-？B激活在个别细胞类型的肠损伤发生是未知的。我们的实验室最近开发和特点的NEC小鼠模型，这将使我们能够利用转基因小鼠解剖NF-？NEC体内B依赖性肠损伤。使用IKK基因缺失的小鼠？在肠上皮细胞（IEC）或髓样细胞（MC），我们有初步的证据表明，NF-？MC中的B介导急性肠损伤模型的肠损伤。此外，我们还发现NF-？MC中的B介导了我们的NEC新生小鼠模型中的肠损伤。我们认为，在早产儿，围产期应激和细菌定植启动增加肠粘膜通透性至少部分通过激活NF-？B和IEC中下游细胞因子的产生。然而，最初的上皮NF-？单独的B激活不会导致肠损伤。我们推测，易位的细菌产物的固有层（LP）的原因持续激活IKK？（NF-？B激酶）和NF-？B和随后产生大量促炎细胞因子和趋化因子（例如，CXCL 2）。这反过来又导致中性粒细胞的募集和活性氧的产生。结果，存在进一步的肠上皮损伤，包括细胞凋亡和粘膜坏死，以及NEC。因此，NF-？肠MC中B的活化在NEC的发生发展中起关键作用。因此，为了验证这一假设，我们已经在我们的实验室开发的新生小鼠模型NEC，我们建议：1）测试的假设，IKK？而NF-？NEC的发展需要B激活; 2）确定MC IKK？激活引起肠道炎症和损伤; 3）确定IEC IKK的作用？肠通透性增加和继发性粘膜细胞因子和趋化因子表达的激活。通过了解NF-？B在个别细胞类型，如IEC和MC在体内引起肠损伤，我们将推进我们的知识NEC，这将可能导致新的治疗策略。 公共卫生相关性：这项建议旨在剖析坏死性小肠结肠炎的发病机制，这种疾病影响早产儿，发病率和死亡率很高。它使用基因操作的小鼠来研究调节炎症物质基因转录并导致肠道损伤的因子的作用。

DESCRIPTION (provided by applicant): Necrotizing enterocolitis (NEC) remains one of the most devastating diseases affecting premature babies and is the leading cause of intestinal failure in infancy, with currently no specific treatment available. Elucidating the mechanisms leading to NEC is essential so strategies that will improve the disease outcome can be designed in the future. We have evidence suggesting that nuclear factor-?B (NF-?B) and IKK? (the inhibitor of NF-?B (I?B) kinase), the critical upstream kinase activating NF-?B, mediate the bowel injury in a neonatal rat model of NEC. However, the specific requirement of NF-?B activation in individual cell types for bowel injury to occur is unknown. Our laboratory has recently developed and characterized a mouse model of NEC that will allow us to utilize transgenic mice to dissect the mechanism of NF-?B-dependent bowel injury in NEC in vivo. Using mice with deletion of IKK? in intestinal epithelial cells (IEC) or myeloid cells (MC), we have preliminary evidence that NF-?B in MC mediates the intestinal damage in a model of acute bowel injury. Furthermore, we also found that NF-?B in MC mediates the bowel injury in our neonatal mouse model of NEC. We believe that, in premature infants, perinatal stress and bacterial colonization initiate an increase in intestinal mucosal permeability at least in part through activation of NF-?B and production of downstream cytokines in IEC. However, the initial epithelial NF-?B activation alone does not lead to intestinal injury. We hypothesize that translocation of bacterial products to the lamina propria (LP) causes sustained activation of IKK? (inhibitor of NF-?B kinase) and NF-?B in the LP MC and subsequent production of large amounts of pro- inflammatory cytokines and chemokines (e.g., CXCL2). This in turn leads to the recruitment of neutrophils and production of reactive oxygen species. As a result, there is further intestinal epithelial damage, including apoptosis and mucosal necrosis, and NEC. Thus, NF-?B activation in intestinal MC is pivotal for the development of NEC. Therefore, to test this hypothesis using the neonatal mouse model of NEC that we have developed in our laboratory, we propose to: 1) Test the hypothesis that IKK? and NF-?B activation is required for NEC to develop; 2) determine the requirement for MC IKK? activation in causing intestinal inflammation and injury; 3) determine the role for IEC IKK? activation in the increase in intestinal permeability and in secondary mucosal cytokine and chemokine expression. By understanding the specific role of NF-?B in individual cell types such as IEC and MC in causing bowel injury in vivo, we will advance our knowledge of NEC, which will potentially lead to new therapeutic strategies. PUBLIC HEALTH RELEVANCE: This proposal aims at dissecting the mechanisms leading to necrotizing enterocolitis, a disease affecting premature babies with great morbidity and mortality. It uses genetically manipulated mice to study the role of a factor that regulates the gene transcription of inflammatory substances and contributes to intestinal injury.