GI Nematodes and Gut Functional Responses to Inflammation

描述（由申请人提供）：宿主防御的进化以对抗多种病原体为特征，部分是通过向Th1或Th2细胞因子谱极化。众所周知，病原体诱导的Th1和Th2细胞因子的上调会诱导肠道平滑肌和上皮细胞反应的刻板变化，有时甚至是相反的变化，这对宿主耐药性很重要。Th1/Th2细胞因子的失衡以及Th1细胞因子的过度表达与肠道功能失调有关，并且是包括炎症性肠病（IBD）在内的许多肠道粘膜炎症的特征。我们研究的长期目标是了解特异性细胞因子谱的上调如何影响肠道功能并有助于宿主抵抗肠道病原体。在之前的研究中，我们确定了1)线虫诱导的Th2细胞因子上调在平滑肌和上皮细胞反应中诱导了刻板的stat6依赖性变化，这对宿主抗性很重要；2) IL-4和IL-13能够与结构细胞上的受体结合，激活STAT6信号通路；3) STAT6信号的激活导致影响功能的基因上调；4)细胞因子受体在小肠和结肠中的表达不同，并因感染而改变。我们还发现Th1细胞因子对平滑肌产生STAT4依赖性作用，这与Th2细胞因子诱导的作用相反。此外，先前的线虫感染提供了免疫介导的对结肠炎的保护，并改善了结肠功能。我们的初步数据使我们将重点放在肠道感染改变肠道功能的具体机制上。拟议的研究包含3个特定目的，旨在验证以下两个中心假设：1)感染诱导的肠道功能变化的发展和持续时间是由细胞因子对结构细胞的直接作用以及结构细胞和免疫细胞之间的相互作用介导的（特定目的1和2）；2) IL-17细胞因子家族的成员在调节与Th1或Th2基因相关的功能效应中起重要作用（Specific Aim 3）。建议的方法将使用感染天然啮齿动物病原体的小鼠，进行体内和体外粘膜和平滑肌功能研究，免疫细胞的原代培养以及分子和免疫组织化学分析。这些研究将帮助我们了解宿主如何利用生理机制来防御病原体，从而产生促进驱逐的刻板功能反应。这些研究的影响是显而易见的，因为这些功能变化的失调显著损害了宿主的抵抗力和维持足够的屏障功能和营养吸收。这些研究还将深入了解线虫感染预防自身免疫性疾病发展的机制，其中许多疾病的特征是肠道屏障功能受损。

DESCRIPTION (provided by applicant): The evolution of host defense to combat a multitude of pathogens is characterized, in part, by polarization towards either the Th1 or Th2 cytokine profile. It is known that pathogen-induced up-regulation of Th1 versus Th2 cytokines induces stereotypic and sometimes opposing changes in gut smooth muscle and epithelial cell responses that are important for host resistance. The imbalance of Th1/Th2 cytokines, with over-expression of Th1 cytokines, is associated with dysregulated gut function and is a characteristic of a number of mucosal inflammatory conditions of the gut including inflammatory bowel disease (IBD). The long term objective of our studies is to understand how up-regulation of specific cytokine profiles impacts gut function and contributes to host resistance against enteric pathogens. In the previous grant period we determined that 1) nematode- induced up-regulation of Th2 cytokines induced stereotypic STAT6-dependent changes in smooth muscle and epithelial cell responses that were important for host resistance; 2) IL-4 and IL-13, were able to bind to receptors on structural cells and activate STAT6 signaling pathways; 3) activation of STAT6 signaling resulted in up-regulation of genes that affect function; and 4) cytokine receptor expression was different in the small intestine and colon and is altered by infection. We also showed that the Th1 cytokines exert STAT4- dependent effects on smooth muscle that were opposite to those induced by Th2 cytokines. Moreover, prior nematode infection provided an immune-mediated protection against colitis along with improved colonic function. Our preliminary data led us to focus our efforts in this proposal on the specific mechanisms by which enteric infection alters gut function. The proposed studies contain 3 specific aims that are designed to test the following two central hypotheses: 1) infection-induced development and duration of changes in gut function are mediated by direct effects of cytokines on structural cells and on the interaction between structural and immune cells (Specific Aims 1 and 2); and 2) members of the IL-17 cytokine family are important in regulation of the functional effects associated with the Th1 or Th2 profiles (Specific Aim 3). The proposed approach will use mice infected with natural rodent pathogens, in vivo and in vitro studies of mucosal and smooth muscle function, primary cultures of immune cells, and molecular and immunohistochemical analyses. These studies will help us to understand how the host exploits physiological mechanisms in its defense against pathogens that allow for the stereotypic functional responses that promote expulsion. The impact of these studies is evident in that dysregulation of these functional changes significantly impairs host resistance and the maintenance of adequate barrier function and nutrient absorption. These studies also will provide insight on the mechanisms involved in the ability of nematode infection to protect against the development of autoimmune diseases, many of which are characterized by impaired intestinal barrier function. Project Narrative The rising prevalence of IBD is mirrored by the decreasing incidence of helminth infection, suggesting a relationship between the epidemiology of these diseases based, in part, on the polarity of Th cell responses. As one of the major regulatory mechanisms in the immune system is control of the balance of cytokines, both enteric infection and IBD are considered excellent targets for immunomodulatory therapies. Some nematodes induce an elevation of Th2 cytokines, including IL-4 and IL-13, which are linked to protective immunity against worm infection. Although a current therapeutic target in IBD is reduction of Th1 cytokine activity, an alternate approach is to rectify the Th1/Th2 cytokine imbalance by increasing Th2 cytokines. The recent clinical success of therapies directed at targeting Th2 cytokines provides a more specific therapeutic approach to the treatment of IBD than that offered by the standard anti-inflammatory and anti-immune regimens. Infection- induced up-regulation of Th2 and Th1 cytokines have a significant impact on gut function that is important to host resistance. The significance of the proposed studies is that they address how immune and structural cells interact to regulate gut function. The impact of these studies is based on identification potential therapeutic targets of benefit to pathologies associated with dysregulation of Th1 or Th2 responses.