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，是婴儿肠衰竭的主要原因，目前没有特定的治疗方法。阐明导致NEC的机制是必不可少的，因此将来可以设计出改善疾病结果的策略。我们有证据表明核因素？B (NF - ?B)和IKK？(NF-？(我吗?B)激酶（kinase），激活NF-？B，介导新生大鼠NEC模型的肠损伤。然而，NF-？肠损伤发生在单个细胞类型中的B活化尚不清楚。我们的实验室最近开发并描述了NEC小鼠模型，这将使我们能够利用转基因小鼠来解剖NF-？体内NEC b依赖性肠损伤。用IKK？在肠上皮细胞（IEC）或骨髓细胞（MC）中，我们有初步证据表明NF-？MC中的B介导急性肠损伤模型中的肠损伤。此外，我们还发现NF-？MC中的B介导新生小鼠NEC模型的肠损伤。我们认为，在早产儿中，围产期应激和细菌定植至少在一定程度上通过激活NF-？B和下游细胞因子的产生。然而，最初的上皮细胞NF-？单独激活B并不会导致肠道损伤。我们假设细菌产物易位到固有层（LP）导致IKK？(NF-？B激酶)和NF-？B在LP MC和随后的生产大量的促炎细胞因子和趋化因子（如CXCL2）。这反过来又导致中性粒细胞的招募和活性氧的产生。结果，肠上皮进一步受损，包括细胞凋亡和粘膜坏死，以及NEC。因此,NF - ?肠MC中B的活化对NEC的发展至关重要。因此，为了使用我们在实验室开发的NEC新生小鼠模型来验证这一假设，我们建议：1)验证IKK？和NF - ?NEC的发展需要B活化；2)确定MC IKK的要求？引起肠道炎症和损伤的激活；3)确定IEC IKK的作用？激活肠通透性的增加和次级粘膜细胞因子和趋化因子的表达。通过了解NF-？B在个体细胞类型（如IEC和MC）中引起体内肠道损伤，我们将推进我们对NEC的了解，这将有可能导致新的治疗策略。

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.