Host-microbe interaction in Drosophila gut

描述(申请人提供)：食物和水传播的病原体构成了人类历史上持续存在的健康问题，炎症性肠病在我们的社会中有增加的趋势。因此，研究肠道内宿主-微生物的相互作用和天然免疫反应可以为治疗提供新的策略。这项提议旨在建立一种新的遗传模型系统，以研究肠道上皮对化学物质和微生物的反应。果蝇是一种常见的果蝇，已成为分析人类疾病基因和研究先天免疫的有力工具。果蝇的先天免疫使用进化上保守的机制来对抗感染。事实上，对哺乳动物Toll样受体的研究最初是基于果蝇的Toll。给果蝇注射微生物可以诱导脂肪体和血细胞的全身免疫反应，但给野生型果蝇喂食微生物几乎不会导致死亡。果蝇的肠道上皮起着强大的屏障作用，具有结构性和诱导性的抗菌防御。这种结构性防御涉及到活性氧物种(ROS)，当苍蝇摄入包括大肠杆菌在内的常见细菌时，这一机制的取消会导致显著的致命性。果蝇肠道细胞如何对微生物做出反应并建立诱导防御机制还不是很清楚。我们通过基因表达谱证明，成年果蝇的肠道在摄食细菌后有广泛的反应。我们还发现了对肠道病原体易感性增加的基因突变。此外，喂养葡聚糖硫酸钠(DSS)，一种广泛使用的化学物质，可导致哺乳动物溃疡性结肠炎，导致剂量依赖性死亡，而共同摄入病原菌会增加这种诱导的致死率。我们还观察到，喂食DSS会导致肠道的病理变化，包括肠道干细胞行为异常。因此，果蝇的肠道与环境刺激相互作用，并产生可检测到的反应。这项建议的具体目的是调查果蝇肠道对微生物的反应，了解DSS如何改变上皮和干细胞行为，并对肠道中对自卫至关重要的宿主基因进行试点遗传筛选。从这项R21探索性研究获得的数据将用于未来R01赠款的提交，并将提供新的诊断和治疗策略，以保护公众免受肠道病原体和炎症性疾病的影响。

DESCRIPTION (provided by applicant): Food- and water-borne pathogens constitute a continuing health problem in human history, and inflammatory bowel disease in our society has an increasing trend. Thus, the study of host- microbe interaction and innate immune response in the intestine can provide novel strategies for therapy. This proposal aims at establishing a new genetic model system to study how the gut epithelium reacts to chemicals and microbes. Drosophila melanogaster, the common fruit fly, has emerged as a powerful tool for analyzing human disease genes and studying innate immunity. Drosophila innate immunity uses evolutionarily conserved mechanisms to fight infections. Indeed, the study of mammalian Toll-like receptors is originally based on the Drosophila Toll. Injection of microbes to Drosophila can induce systemic immune responses in fat bodies and hemocytes but feeding of microbes to wild type flies rarely causes lethality. The Drosophila gut epithelium acts as a strong barrier and has both constitutive and inducible antimicrobial defense. The constitutive defense involves reactive oxygen species (ROS) and annulment of this mechanism causes significant lethality when flies ingest common bacteria including E. coli. How Drosophila gut cells respond to microbes and mount an inducibe defense is not well understood. We demonstrate by gene expression profiling that the adult Drosophila gut has an extensive response after feeding with bacteria. We have also identified genetic mutants that have increased susceptibility to gut pathogens. Moreover, feeding of dextran sulfate sodium (DSS), a widely used chemical that can induce ulcerative colitis in mammals, causes dose dependent lethality, and co-ingestion of pathogenic bacteria enhances this induced lethality. We also observe that feeding of DSS causes pathological changes in the gut including abnormal intestinal stem cell behavior. Thus, Drosophila gut interacts with environmental stimuli and generates detectable responses. The specific aims of this proposal are to investigate the Drosophila gut response to microbes, to understand how DSS changes epithelial and stem cell behavior, and to perform a pilot genetic screen for host genes essential for self-defense in the gut. Data obtained from this R21 exploratory study will be used for future R01 grant submission and will provide novel diagnostic and therapeutic strategies to protect the public against pathogens and inflammatory diseases in the intestine.