Role of Toll-Like Receptor 4 Signaling in Stress-Induced Lymphocyte Apoptosis

描述（由申请人提供）：我们这些研究的总体目标是阐明应激期间Toll样受体（TLR）介导的免疫抑制的潜在机制。身体和心理压力可以改变人类和动物的免疫系统。压力也是许多人类疾病的已知风险因素。TLR介导的信号通路在诱导免疫应答中起关键作用。TLR介导应激的免疫反应;然而，其机制仍有待阐明。为了研究应激诱导免疫应答的机制和设计治疗策略，我们建立了束缚应激动物模型来研究免疫抑制。使用这个模型，我们已经揭示了小鼠的束缚应激通过细胞凋亡机制调节免疫系统。我们发现TLR 4缺陷小鼠对应激诱导的脾细胞减少有抵抗力。TLR 4通常与高迁移率族蛋白-1（HMGB 1）相互作用。我们的初步数据表明，应激通过TLR 4增强血浆HMGB 1水平。磷脂酰肌醇3-激酶（PI 3 K）及其下游底物Akt可以通过减少炎症和抑制凋亡来调节TLR介导的反应。我们已经表明，小鼠中的TLR 4缺陷诱导脾细胞数量的保护，这是通过PI 3 K介导的。总的来说，我们的数据表明，TLR 4和PI 3 K/Akt信号在应激期间的免疫反应中发挥作用。目前，我们还不了解TLR 4介导的信号传导在应激诱导的淋巴细胞凋亡中的确切作用，也不了解TLR 4在应激期间免疫抑制中PI 3 K/Akt信号传导负调节中的确切作用。我们的假设是TLR 4和PI 3 K/Akt信号通路的调节决定了淋巴细胞对应激反应的命运。我们提出以下目标来检验这一假设。目的1将确定TLR 4介导的细胞凋亡信号通路的作用后的压力。为了阐明TLR 4是否在应激过程中激活凋亡信号通路，我们将首先研究TLR 4介导的信号对淋巴细胞凋亡的影响，包括CD 4+和CD 8 + T细胞凋亡。然后，我们将研究TLR 4缺陷是否激活PI 3 K/Akt信号在应激诱导的淋巴细胞凋亡。目的2：阐明TLR 4对PI 3 K/Akt信号通路的负调控在应激诱导的免疫抑制中的作用。为了检查TLR 4缺陷是否激活PI 3 K/Akt信号传导，导致免疫保护，将向TLR 4敲除小鼠和野生型小鼠施用PI 3 K抑制剂，然后使其经受不同时间段的应激。我们将确定TLR 4介导的信号转导在应激诱导的免疫抑制中的作用，然后确定TLR 4缺乏是否导致PI 3 K/Akt信号转导的激活。此外，我们将确定HMGB 1和多功能接头2-arrestin 2在应激后TLR 4介导的PI 3 K/Akt信号转导中的作用。我们的研究将使我们了解TLR 4介导的信号通路对免疫系统的影响，为开发免疫抑制的新策略和疗法提供机会。 公共卫生相关性：心理和身体压力会对免疫系统产生明显影响。从历史上看，这种影响归因于压力激素的释放，尽管其他因素似乎也起着重要作用。使用小鼠模型的物理约束压力，我们已经调查了一些分子介质，这可能占压力和免疫系统之间的联系。这项研究将研究免疫系统受压力影响的机制，希望能够开发出特定的治疗方法或药物，从而改善这种有时有害的相互作用。

DESCRIPTION (provided by applicant): Our overall goal of these studies is to elucidate the mechanism(s) underlying Toll-like receptor (TLR) mediated immune suppression during stress. Physical and psychological stress can alter the immune system in both humans and animals. Stress is also a known risk factor for numerous human diseases. TLR mediated signaling pathways play a critical role in the induction of immune response. TLRs mediate the immune response to stress; however, the mechanisms remain to be elucidated. In order to study the mechanisms of stress-induced immune responses and to design strategies for therapeutics, we established an animal model for restraint stress to study immune suppression. Using this model we have revealed that restraint stress of mice modulates the immune system through a cell apoptotic mechanism. We found that TLR4 deficient mice are resistant to stress-induced splenocyte reduction. TLR4 typically interacts with high mobility group box-1 protein (HMGB1). Our preliminary data indicate that stress enhances plasma HMGB1 levels through TLR4. The phosphoinositide 3-kinases (PI3K) and their downstream substrate Akt can modulate TLR-mediated responses by decreasing inflammation and inhibiting apoptosis. We have shown that TLR4 deficiency in mice induces protection in splenocyte numbers which is mediated through PI3K. Collectively, our data suggest that TLR4 and PI3K/Akt signaling play a role in immune responses during stress. At present, we do not understand the precise role of TLR4-mediated signaling in stress-induced lymphocyte apoptosis, nor do we understand the precise role of TLR4 in negative regulation of the PI3K/Akt signaling in immune suppression during stress. Our hypothesis is that modulation of TLR4 and the PI3K/Akt signaling pathways determines the fate of lymphocytes in response to stress. We propose the following aims to test this hypothesis. Aim 1 will define the role of TLR4-mediated apoptotic signaling pathways following stress. To elucidate whether TLR4 activates apoptotic signaling pathways during stress, we will first investigate the effects of TLR4-mediated signaling on lymphocyte apoptosis, including CD4+ and CD8+ T cell apoptosis. We will then examine whether TLR4 deficiency activates PI3K/Akt signaling in stress-induced lymphocyte apoptosis. Aim 2 will define the role TLR4 negative regulation of PI3K/Akt signaling in stress-induced immune suppression. To examine whether TLR4 deficiency activates PI3K/Akt signaling, resulting in immune protection, TLR4 knockout mice and wild type mice will be administered PI3K inhibitors, and then subjected to stress for different time periods. We will define the role of TLR4 mediated signaling in stress-induced immune suppression, and then determine whether TLR4 deficiency results in activation of PI3K/Akt signaling. In addition, we will determine the role of HMGB1 and a multifunctional adaptor 2-arrestin 2 in TLR4-mediated PI3K/Akt signaling following stress. Our studies should lead to our understanding of the effects of TLR4-mediated signaling pathways on the immune system, providing the opportunity to develop novel strategies and therapeutics for immune suppression. PUBLIC HEALTH RELEVANCE: Psychological and physical stress can have pronounced effects on the immune system. Historically this affect was attributed to the release of stress hormones although other factors appear to play an important role. Using a mouse model of physical restraint stress we have investigated some of the molecular mediators which may account for the connection between stress and the immune system. This research will examine the mechanisms whereby the immune system is influenced by stress with the hope of leading to the development of specific treatments or drugs which in turn may ameliorate this sometimes deleterious interaction.