Neuroendocrine Stress Response in Inflammatory/Behavior

神经内分泌免疫学和行为科（SNIB）的研究主要集中在(1)大鼠自交系下丘脑垂体肾上腺（HPA）轴差异调节的分子基础及其与炎性疾病易感性的关系；(2)糖皮质激素受体（GR）在自身免疫性/炎性疾病中的作用，包括炭疽芽孢杆菌（炭疽）致死毒素（LeTx）对糖皮质激素和其他核激素受体的抑制。在Project 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，将HPA轴反应差异与炎症易感性联系起来。近年来的研究主要集中在培养大鼠胎儿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（Project 1，参考文献1,2）表明，即使在发育的早期阶段，LEW/N下丘脑细胞表达的促炎细胞因子和相关分子（mRNA和蛋白质）的基础和刺激水平高于炎性抵抗的F344/N大鼠。这些发现与新的成年大鼠体内研究一致，研究显示暴露于细菌脂多糖后，与F344/N大鼠相比，LEW/N中il -1 β mRNA的表达更高（Project 1, ref 3）。下丘脑组织在体内腹腔内细菌脂多糖（LPS）处理前后的表达芯片和实时RT-PCR分析显示甲状腺转甲状腺素（TTR）和胆囊收缩素（CCK） mRNA表达差异，提示甲状腺激素可能在差异神经内分泌表型中起作用，因为TTR是甲状腺激素的主要转运体。事实上，进一步的甲状腺轴分析显示，这些菌株的甲状腺释放激素（TRH）表达存在差异。多发性硬化症患者的临床研究也与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有关的动物研究相一致。因此，我们在离体实验中确定了一个MS患者亚群，显示出皮质类固醇耐药性（项目1，参考文献4）。在项目2中，我们对最初的研究进行了后续研究，发现纳米摩尔浓度的炭疽芽孢杆菌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，而不是矿化皮质激素受体（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。并且很可能是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，TAT）的活性水平以及体内（肝脏TAT激活的抑制）中都可以看到。目前的研究进一步分析了这种作用的精确分子机制，并探讨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.