Cannabinoid modulation of microglial response to the HIV protein Tat

描述(申请人提供)：本项目的目标是确定外源性大麻素在调节小胶质细胞对人类免疫缺陷病毒-1(HIV-1)反式激活(TAT)蛋白的反应中的功能相关性。小胶质细胞是中枢神经系统(CNS)的驻留巨噬细胞，是HIV-1的主要靶细胞。这些细胞是HIV-1的高效宿主，并在感染时产生过多的细胞因子、单因子和神经毒性因子。其中包括病毒包膜糖蛋白gp120和病毒特异性基因产物Tat。虽然这两种蛋白都可以激活中枢神经系统中未感染的小胶质细胞和免疫细胞，导致炎症和神经毒性因子的大量释放，但艾滋病毒感染细胞产生的TAT不受目前可用的抗逆转录病毒药物的影响，因为这些药物针对的是艾滋病毒的逆转录酶和蛋白酶。这一观察结果与TAT在细胞外释放的事实相结合，阐明了在当前高效抗逆转录病毒治疗时代评估其在艾滋病毒神经发病中的作用的理论基础。TAT具有强大的趋化特性，可将未感染的小胶质细胞和其他免疫细胞招募到HIV-1感染的局部区域。趋化作用驱动的免疫细胞在感染灶区聚集和炎症因子的激发的共同作用可能是HIV相关性神经认知障碍(HAND)发生的主要因素。大麻类化合物已被证明可以调节免疫细胞的功能活动，包括小胶质细胞的功能活动。这些作用的优势是抑制的，并通过CB2大麻素受体(CB2R)介导。由于该受体在神经炎症的不同状态下由小胶质细胞表达，因此它有可能作为细胞选择性分子靶点来消融不良免疫反应，包括TAT引起的免疫反应。因此，CB2R可以作为一个模板，用于产生不具有精神药物特性的特定配体，并根据与其相互作用的受体的关键特征进行合理的设计。在这项拟议的研究中，我们将检验这样一种假设，即选择外源性大麻素通过CB2R和可能的其他大麻素受体发挥作用，以抑制小胶质细胞对TAT的炎症反应。以下具体目标将作为研究的指导方针：(1)确定外源性大麻素对人小胶质细胞对HIV蛋白TAT的反应性的体外影响，(2)建立外源性大麻素改变小胶质细胞对HIV蛋白TAT的反应性的作用模式，以及(3)在人脑胶质细胞混合培养和小鼠脑切片培养的背景下，建立外源性大麻素对小胶质细胞对TAT的反应性的相关性。 公共卫生相关性：这项研究的目标是评估大麻类物质是否有可能下调小胶质细胞对人类免疫缺陷病毒(HIV-1)的Tat蛋白的高炎症反应。Tat蛋白在大脑中引起炎症，并在艾滋病毒相关的神经炎症中发挥重要作用。了解大麻素在TAT诱导的大脑炎症反应中的作用，大麻素是否选择性地针对作为HIV-1宿主的小胶质细胞，以及这些化合物是否专门针对小胶质细胞上的受体，应该为管理艾滋病毒诱导的神经炎症和相关损害的辅助治疗方法带来新的见解。

DESCRIPTION (provided by applicant): The goal of this project is to establish the functional relevance of exogenous cannabinoids in modulating responsiveness of microglia to the human immunodeficiency virus-1 (HIV-1) trans-activating (Tat) protein. Microglia are resident macrophages of the central nervous system (CNS) that serve as principal targets for HIV-1. These cells are productive hosts for HIV-1 and elicit a plethora of cytokines, monokines, and neurotoxic factors in response to infection. Included among these are the virus envelope glycoprotein gp120 and the virus-specified gene product Tat. While both proteins can activate uninfected microglia and immunocytes in the CNS resulting in an expansive release of inflammatory and neurotoxic factors, the production of Tat by HIV- infected cells is not affected by currently available anti-retroviral drugs since these target the reverse transcriptase and protease enzymes of HIV. This observation, taken together with the fact that Tat is released extracellularly, articulates a rationale for assessment of its role in HIV neuropathogenesis in the current highly- active antiretroviral therapy era. Tat exerts robust chemotactic properties and may recruit uninfected microglia and other immunocytes to focal areas of HIV-1 infection. The combined action of chemotaxis-driven aggregation of immunocytes at focal areas of infection and elicitation of inflammatory factors may be a major contributive factor in the development of HIV-associated neurocognitive disorder (HAND). Cannabinoids have been shown to modulate the functional activities of immune cells, including those of microglia. The preponderance of these effects has been inhibitory and mediated through the CB2 cannabinoid receptor (CB2R). Since this receptor is expressed by microglia during various states of neuroinflammation, it has the potential to serve as a cell-selective molecular target for ablating untoward immune responses, including those engendered by Tat. Thus, the CB2R may serve as a template for the generation of specific ligands devoid of psychotropic properties and rationally designed based on the critical features of the receptors with which they interact. In the proposed study we will test the hypothesis that select exogenous cannabinoids act through the CB2R, and possibly other cannabinoid receptors, to dampen microglial inflammatory responses to Tat. The following specific aims will serve as guidelines to the research: (1) to define the in vitro effects of exogenous cannabinoids on human microglial responsiveness to the HIV protein Tat, (2) to establish the mode of action through which exogenous cannabinoid alters microglial responsiveness to the HIV protein Tat, and (3) to establish the relevance of the effects of exogenous cannabinoid on microglial responsiveness to Tat in the context of human mixed glial cultures and mouse brain slice cultures. PUBLIC HEALTH RELEVANCE: The goal of this study is to assess the potential of cannabinoids to down-regulate hyper- inflammatory responses of microglia, resident macrophages in the brain, to the Tat protein of the human immunodeficiency virus (HIV-1). The Tat protein causes inflammation in the brain and plays an important role in HIV-associated neuroinflammation. Understanding the role of cannabinoids in the Tat-induced inflammatory response in the brain, whether cannabinoids selectively target microglia that serve as hosts for the HIV-1, and whether these compounds specifically target receptors on microglia should yield novel insights into adjunct therapeutic approaches for management of HIV-induced neuroinflammation and associated damage.