Redox regulation of intestinal T cells

描述（由申请人提供）：外源性细胞因子、细胞-细胞接触和内源性代谢物可介导T细胞受体发出的信号转导的调节，从而对抗原刺激产生特异性功能反应。尽管肠道的免疫环境恶劣，但粘膜固有层T细胞（LPT）对来源于“安全”管腔蛋白的抗原仍反应迟钝;但仍保留其对病原体产生强烈免疫反应的能力。因此，我们建议调查的机制，调节维持低反应性粘膜T细胞和环境信号，使这个正常静止的粘膜T细胞响应时，需要的。从T细胞受体（TCR）发出的信号转导对于所有功能性应答（例如增殖、免疫介质（例如Fas配体、受体和粘附蛋白）的表面表达、分化、活化诱导的细胞死亡和细胞因子基因表达）是关键的。在这个建议中，我们将集中在活性氧（ROS）来自不完全还原的氧，如过氧化氢，作为第二信使，因此内源性调节剂的信号转导发出的TCR。我们最近报道，LPT响应TCR交联的能力减弱，如通过弱增殖所测量的，反映在它们从TCR启动信号转导的能力的急剧丧失。为了理解LPT信号传导能力的这种降低，我们研究了与TCR的α链和ω链直接相关的酶途径，重点关注与TCR/CD 3复合物相关的酪氨酸激酶和磷酸酶之间的潜在不平衡。由于质膜容易渗透过氧化氢，外源性给予低，无毒浓度的H2 O2刺激酪氨酸磷酸化模式，反映TCR的参与。与TCR交联所观察到的相似，LPT中H2 O2诱导的酪氨酸磷酸化显著减弱。因此，我们假设，然后报告说，低反应性LPT的氧化还原状态是倾向于增加还原能力。此外，克罗恩病衍生的（一种形式的炎性肠病）LPT对TCR连接（例如，增殖，IFN-？产生），并且这种发炎的T细胞中的氧化还原状态是氧化的，这使得TCR接合后的强信号转导成为可能。与我们的研究结果一致，最近有报道称，在正常肠道中，固有层巨噬细胞不分泌半胱氨酸，这是LPT调节其胞质氧化还原电位所必需的。这些结果支持以下中心假设：粘膜T细胞的细胞内还原能力，调节细胞产生细胞内活性氧的能力，改变T细胞受体的参与在正常肠粘膜中启动免疫应答的阈值。这一假设将在以下两个具体目标中得到解决：目标1。定义TCR激活LPT中产生的活性氧物质的合成和/或稳定性的内在缺陷。目标2.确定胞质氧化还原电位为LPT反应设定阈值。 相关性：为了保护我们免受感染，我们有一个复杂的白色血细胞系统，其中的主要细胞被称为T淋巴细胞，它为宿主防御做出战略决策。与从血液中分离的T细胞相比，从结肠或小肠中分离的T细胞通常反应非常弱，而从患有感染或肠痉挛和慢性炎症引起的肠病的患者中的发炎的肠区域中分离的T细胞反应具有另一种独特的特征。该提案将定义粘膜T细胞的内在特性，使其能够在这些响应和无响应状态之间切换。我们最近发现，T细胞内的化学平衡（称为氧化还原电位）调节它是否可以对外界做出微弱或强烈的反应。我们还表明，通过将粘膜T细胞内的平衡转换为替代类型，这种治疗过的肠T细胞现在的行为更像正常的血液来源的T细胞。该项目将确定T细胞中导致这种不平衡的确切分子。然后，我们可以靶向这种分子进行“校正”，并在未来确定这种类型的治疗是否是粘膜感染，疫苗开发或粘膜自身免疫样疾病的有效疗法。

DESCRIPTION (provided by applicant): Modulation of signal transduction emanating from the T cell receptor can be mediated by exogenous cytokines, cell-cell contact, and endogenous metabolites, yielding a specialized functional response to antigenic stimulation. Despite the hostile immunological neighborhood of the intestinal tract, mucosal lamina propria T cells (LPT) remain hyporesponsive to antigens derived from "safe" luminal proteins; yet retain their capacity to mount a vigorous immune response to pathogens. We therefore propose to investigate the mechanisms regulating the maintenance of hyporesponsiveness in mucosal T cells and the environmental signals that enable this normally quiescent mucosal T cell to respond when needed. Signal transduction emanating from the T cell receptor (TCR) is critical for all functional responses, such as proliferation, surface expression of immune mediators such as Fas Ligand, receptors, and adhesion proteins, differentiation, activation induced cell death, and cytokine gene expression. In this proposal we will focus on reactive oxygen species (ROS) derived from incomplete reduction of oxygen, such as hydrogen peroxide, acting as second messengers and thus endogenous modulators of signal transduction emanating from the TCR. We recently reported that the diminished capability of LPT to respond to TCR cross-linking, as measured by weak proliferation, is mirrored by a dramatic loss in their ability to initiate signal transduction from the TCR. To understand this decrease in LPT signaling capacity we investigated the enzymatic pathway directly linked to the a and ¿ chains of the TCR, focusing on a potential imbalance between tyrosine kinases and phosphatases associated with the TCR/CD3 complex. Since the plasma membrane is readily permeable to hydrogen peroxide, exogenous administration of low, non-toxic concentrations of H2O2 stimulates a tyrosine phosphorylation pattern that reflects TCR engagement. Similar to what is observed with TCR cross-linking, H2O2-induced tyrosine phosphorylation in LPT is significantly muted. We therefore hypothesized and then reported that the redox status of the hyporesponsive LPT is tilted toward increased reductive capability. In addition, the Crohn's disease-derived (a form of inflammatory bowel disease) LPT responds robustly to TCR ligation (e.g., proliferation, IFN-? production), and the redox status in this inflamed T cell is oxidative, which enables strong signal transduction after TCR engagement. Consistent with our findings it was recently reported that in the normal intestine, lamina propria macrophages do not secrete cysteine, which is required by the LPT to regulate their cytosolic redox potential. These results support the following central hypothesis: The intracellular reducing capacity of the mucosal T cell, which modulates that cell's ability to generate intracellular reactive oxygen species, alters the threshold at which engagement of the T cell receptor initiates an immune response in the normal intestinal mucosa. This hypothesis will be addressed in the following two specific aims: Aim 1. Define the intrinsic defect in the synthesis and/or stability of reactive oxygen species generated in TCR-activated LPT. Aim 2. Establish that cytosolic redox potential sets the threshold for an LPT response. RELEVANCE: To protect us from infections we have a complex system of white blood cells, the principal of these is called the T lymphocyte, which makes strategic decisions for host defense. T cells isolated from the colon or small bowel normally respond very weakly when compared to T cells isolated from blood, while T cells isolated from inflamed intestinal areas in patients with an infection or intestinal cramping and bowel disease due to chronic inflammation respond with still yet another distinct character. This proposal will define those intrinsic properties of the mucosal T cell that enables it to toggle between these responsive and unresponsive states. We recently identified that a chemical balance (called the redox potential) within the T cell regulates whether it can respond weakly or strongly to the outside world. We also showed that by switching the balance within a mucosal T cell to the alternate type this treated intestinal T cell now behaves more like a normal blood-derived T cell. This project will define the exact molecules in the T cell that causes this imbalance. We can then target this molecule for 'correction' and in the future determine whether this type of treatment is an effective therapy for mucosal infections, vaccine development, or mucosal autoimmune-like diseases.