Neuroendocrine Stress Response in Inflammatory/Behavior

神经内分泌免疫和行为(SNIB)部分的研究集中在(1)近交系大鼠下丘脑-垂体-肾上腺(HPA)轴差异性调节的分子基础及其与炎症性疾病易感性的关系；(2)糖皮质激素受体(GR)在自身免疫/炎症性疾病中的作用，包括炭疽杆菌(Bt)、致命毒素(LeTx)对糖皮质激素和其他核激素受体的抑制。在项目1中，我们继续在啮齿动物模型中探索下丘脑CRH和HPA轴反应差异的分子基础，该模型将不同的HPA轴反应与炎症易感性联系起来。最近的研究集中在培养的大鼠胚胎下丘脑细胞中免疫和神经内分泌分子的表达和分泌的发育差异。这些研究(项目1，参考文献1，2)表明，即使在发育的最早阶段，与炎症抵抗的F344/N大鼠相比，LEW/N下丘脑细胞表达更高的基础和刺激水平的促炎细胞因子和相关分子(mRNA和蛋白质)。这些发现与新的成年大鼠体内研究一致，该研究表明，与F344/N大鼠相比，LEW/N大鼠在暴露于细菌脂多糖后IL-1βmRNA的表达更高(项目1，参考文献3)。细菌脂多糖(LPS)处理前后下丘脑组织的表达谱芯片和实时定量RT-PCR分析显示，转甲状腺激素(TTR)和胆囊收缩素(CCK)的mRNA表达存在差异，提示甲状腺激素可能在不同的神经内分泌表型中起作用，因为TTR是主要的甲状腺激素转运体。事实上，对甲状腺轴的进一步分析表明，这些菌株中甲状腺释放激素(TRH)的表达存在差异。多发性硬化症患者的临床研究也与动物研究一致，将糖皮质激素失调与中枢神经系统自身免疫性疾病的病程和严重程度联系起来。因此，我们在体外试验中确定了MS患者中表现出皮质类固醇耐药的亚群(项目1，参考文献4)。在项目2中，我们跟进了初步研究表明，纳米分子浓度的炭疽杆菌LeTx(致死因子+保护性抗原)选择性地抑制核激素受体的活性，包括GR、孕激素受体(PR)和雌激素受体(ER)α，但不抑制盐皮质激素受体(MR)或ERβ(项目2，参考文献1)。这种抑制是非竞争性的，不是通过受体？S配体结合区域或脱氧核糖核酸结合区域发生的，很可能是LeTx与核激素受体辅助因子选择性相互作用的结果。这种抑制在体外的瞬时转基因系统中和糖皮质激素调节的酶(肝细胞酪氨酸氨基转移酶，TAT)的活性水平上都可以看到，在体内(抑制肝脏TAT的激活)中也可以看到。目前的研究进一步分析了这种效应的确切分子机制，并解决了核激素受体抑制在炭疽毒性中的作用。

The research of the Section on Neuroendocrine Immunology and Behavior (SNIB) focuses on (1) molecular basis of differential hypothalamic pituitary adrenal (HPA) axis regulation in inbred rat strains and its relationship to inflammatory disease susceptibility and (2) role of the glucocorticoid receptor (GR) in autoimmune/inflammatory disease, including Bacillus anthracis (anthrax) lethal toxin (LeTx) repression of the glucocorticoid and other nuclear hormone receptors. In Project 1, we have continued to explore the molecular basis for differential hypothalamic CRH and HPA axis responses in a rodent model linking differential HPA axis responsiveness and inflammatory susceptibility. Recent studies focused on developmental differences of expression and secretion of immune and neuroendocrine molecules in rat fetal hypothalamic cells in culture. These studies (Project 1, refs 1, 2) indicate that even at the earliest stages of development, LEW/N hypothalamic cells express higher basal and stimulated levels of pro-inflammatory cytokines and related molecules (both mRNA and protein) compared to inflammatory resistant F344/N rats. These findings are consistent with new in vivo studies in adult rats showing a greater expression of IL-1beta mRNA in LEW/N compared to F344/N rats after exposure to bacterial lipopolysaccharides (Project 1, ref 3). Expression microarray and real-time RT-PCR analyses of hypothalamic tissue pre- and post in vivo intraperitoneal bacterial lipopolysaccharide (LPS) treatment showed differential transthyretin (TTR) and cholecystokinin (CCK) mRNA expression, suggesting a possible role for thyroid hormone in the differential neuroendocrine phenotypes, since TTR is a major thyroid hormone transporter. Indeed, further analysis of the thyroid axis showed differential thyroid releasing hormone (TRH) expression in these strains. Clinical studies in patients with multiple sclerosis were also consistent with animal studies linking glucocorticoid dysregulation and course and severity of CNS autoimmune disease. Thus we have identified a sub-population of MS patients showing corticosteroid resistance in an ex vivo assay (Project 1, ref 4). In Project 2, we have followed up on initial studies showing that nanomolar concentrations of Bacillus anthracis LeTx (lethal factor + protective antigen) selectively repress nuclear hormone receptor activity, including GR, the progesterone receptor (PR) and the estrogen receptor (ER) alpha but not the mineralocorticoid receptor (MR) or ER beta (Project 2, ref 1). This repression is non-competitive, and does not occur through the receptor?s ligand binding or DNA binding domains, and most likely results from LeTx selective interaction with nuclear hormone receptor co-factors. The repression is seen in vitro both in a transient transfection system and at the level of activity of a glucocorticoid regulated enzyme (hepatocyte tyrosine amino transferase, TAT), and in vivo (repression of hepatic TAT activation). Current studies further analyze the precise molecular mechanism of this effect and address the role of nuclear hormone receptor repression in anthrax toxicity.