Alcohol, hedgehog signal, and HSC dysfunction in host defense against septicemia

描述（由申请人提供）：酒精滥用者易受细菌感染。酒精中毒患者严重感染，特别是败血症，经常出现粒细胞减少症，这是死亡率增加的指标。我们最近的研究表明，在细菌感染的反应中，谱系（lin）-干细胞因子受体（ckit）+干细胞抗原-1（Sca 1）+细胞（LKS细胞，富含造血干细胞的细胞群）的骨髓池在小鼠中迅速增加。LKS细胞群的紧急扩增与这些原始前体的重编程有关，以增强其对粒细胞谱系发育的承诺。酒精损害了粒细胞生成反应的这一关键步骤。目前，潜在的细胞信号传导机制仍不清楚。hedgehog信号转导通路在胚胎发育和成年期的正常状态下参与了某些干/祖细胞功能的调节。在初步的实验中，我们观察到，在败血症小鼠骨髓中，Sonic hedgehog（SHH）的表达显著上调。Toll样受体（TLR）4-细胞外信号调节激酶（ERK）1/2-特异性蛋白1（Sp1）信号级联提供了骨髓细胞上调SHH表达的必要信号。LKS细胞是对SHH反应最活跃的细胞。SHH-神经胶质瘤锌指转录因子1（Gli 1）-细胞周期蛋白D1信号的激活促进LKS细胞增殖，而SHH-Gli 1-PU.1（一种由SPI 1基因编码的ETS结构域转录因子）信号的激活介导LKS细胞重编程以增强粒细胞谱系发育。酒精暴露破坏了这个信号系统。因此，我们建议系统地研究酒精对SHH信号在原始造血前体细胞调控中的作用 在对败血症的粒细胞生成反应期间激活。我们的中心假设是，酒精损害原始造血前体细胞的功能，在粒细胞系统感染的反应，通过破坏SHH信号。三个具体目标是：1）测试酒精抑制LKS细胞中响应于败血症的SHH信号通路的活化的预测; 2）测试酒精通过损害GLI 1-细胞周期蛋白D1通路来抑制LKS细胞响应于败血症的增殖的预测;和3）检验酒精通过损害Gli 1 - 1蛋白抑制LKS细胞重编程以增强败血症期间粒细胞谱系定型的预测。PU.1信号级联。从这项调查中获得的结果将大大推进我们的知识损害的主机防御严重感染酗酒者。它还将确定开发新型治疗干预措施的关键目标，以治疗这些免疫功能低下宿主的致命感染。

DESCRIPTION (provided by applicant): Alcohol abusers are susceptible to bacterial infection. Alcoholic patients with serious infection, particularly septicemia, frequently present with granulocytopenia which is an indicator for increased mortality. Our recent studies have revealed that in response to bacterial infection, bone marrow pool of lineage(lin)-stem cell factor receptor(ckit)+stem cell antigen-1(Sca1)+ cells (LKS cells, a cell population enriched with hematopoietic stem cells) is rapidly increased in mice. The emergency expansion of LKS cell population is associated with reprogramming of these primitive precursors to enhance their commitment to granulocyte lineage development. Alcohol impairs this critical step of the granulopoietic response. At the present time, the underlying cell signaling mechanisms remain unclear. The hedgehog signal transduction pathway has been reported to participate in the regulation of certain stem/progenitor cell functions in normal state during embryogenesis and in adulthood. In preliminary experiments, we observed that Sonic hedgehog (SHH) expression was significantly up-regulated in the bone marrow of mice with septicemia. The Toll-like receptor (TLR)4-extracellular signal-regulated kinases (ERK)1/2-specificity protein 1(Sp1) signal cascade provided the essential signal for up-regulation of SHH expression by marrow cells. LKS cells were the most active cells responding to SHH. Activation of SHH-glioma zinc finger transcription factor 1 (Gli1)-cyclin D1 signaling promoted LKS cell proliferation, whereas activation of SHH-Gli1-PU.1 (an ETS-domain transcription factor encoded by the SPI1 gene) signaling mediated LKS cell reprogramming for enhanced commitment to granulocyte lineage development. Alcohol exposure disrupted this signaling system. Therefore, we propose to systematically investigate the effects of alcohol on SHH signaling in the regulation of primitive hematopoietic precursor cell activation during the granulopoietic response to septicemia. Our central hypothesis is that alcohol impairs primitive hematopoietic precursor cell function during the granulopoietic response to systemic infection by disrupting SHH signaling. Three specific aims are: 1) to test the prediction that alcohol inhibits activation of the SHH signal pathway in LKS cells in response to septicemia; 2) to test the prediction that alcohol inhibits LKS cell proliferation in response t septicemia via impairing the GLI1-cyclin D1 pathway; and 3) to test the prediction that alcohol inhibits LKS cell reprogramming for enhancing granulocyte lineage commitment during septicemia via impairing the Gli1-PU.1 signal cascade. Results obtained from this investigation will greatly advance our knowledge about the impairment of host defense against serious infections in alcohol abusers. It will also identify key targets for developing novel therapeutic interventions to treat fatal infections in these immunocompromised hosts.