Neuroendocrine Stress Response in Inflammatory/Behavior

神经内分泌免疫学和行为科（SNIB）的研究重点是（1）近交系大鼠下丘脑垂体肾上腺（HPA）轴调节差异的分子基础及其与炎症性疾病易感性的关系，以及（2）糖皮质激素受体（GR）在自身免疫性/炎症性疾病中的作用，包括炭疽杆菌（炭疽）致死毒素（LeTx）对糖皮质激素和其它核激素受体的抑制。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HPA轴反应差异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，与炎症抵抗性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）。这些发现与成年大鼠中的新体内研究一致，该研究显示，与F344/N大鼠相比，LEW/N大鼠暴露于细菌脂多糖后IL-1 β mRNA的表达更高（项目1，参考文献3）。表达微阵列和实时RT-PCR分析下丘脑组织的前和后在体内腹腔内细菌脂多糖（LPS）治疗显示差异甲状腺素运载蛋白（TTR）和胆囊收缩素（CCK）mRNA的表达，提示甲状腺激素在差异神经内分泌表型中可能发挥作用，因为TTR是一种主要的甲状腺激素转运蛋白。事实上，甲状腺轴的进一步分析表明，在这些菌株中的差异甲状腺释放激素（TRH）的表达。多发性硬化患者的临床研究也与动物研究一致，将糖皮质激素失调与CNS自身免疫性疾病的病程和严重程度联系起来。因此，我们已经确定了MS患者的一个亚群，在离体试验中显示皮质类固醇耐药（项目1，参考文献4）。在项目2中，我们对初步研究进行了随访，这些研究表明纳摩尔浓度的炭疽杆菌LeTx（致死因子+保护性抗原）选择性抑制核激素受体活性，包括GR、孕酮受体（PR）和雌激素受体（ER）α，但不抑制盐皮质激素受体（MR）或ER β（项目2，参考文献1）。这种抑制是非竞争性的，不通过受体发生？的配体结合或DNA结合域，最有可能的结果从LeTx选择性相互作用与核激素受体辅因子。在体外瞬时转染系统和糖皮质激素调节酶（肝细胞酪氨酸氨基转移酶，达特）的活性水平以及体内（肝达特活化的抑制）中均观察到抑制。目前的研究进一步分析了这种效应的精确分子机制，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.