Host-microbe interaction in Drosophila gut

描述（由申请人提供）：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，研究肠道内的宿主-微生物相互作用和先天免疫反应可以为治疗提供新的策略。本研究旨在建立一个新的遗传模型系统来研究肠道上皮对化学物质和微生物的反应。黑腹果蝇，一种常见的果蝇，已经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保守的机制来对抗感染。事实上，哺乳动物Toll样受体的研究最初是基于果蝇Toll。向果蝇注射微生物可引起脂肪体和血细胞的全身免疫反应，但向野生型果蝇喂食微生物很少引起致命。果蝇肠道上皮作为一个强大的屏障，具有组成性和诱导性抗菌防御。构成性防御涉及活性氧（ROS），当苍蝇摄入包括大肠杆菌在内的常见细菌时，这种机制的取消会导致显著的致命性。果蝇的肠道细胞如何对微生物作出反应并建立诱导防御机制尚不清楚。我们通过基因表达谱证明，成年果蝇肠道在喂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，喂食葡聚糖硫酸钠（DSS）（一种广泛使用的化学物质，可诱发哺乳动物的溃疡性结肠炎）会导致剂量依赖性致死，而共同摄入致病菌会增强这种致死性。我们还观察到，饲喂DSS会引起肠道的病理变化，包括肠道干细胞行为异常。因此，果蝇肠道与环境刺激相互作用并产生可检测的反应。本研究的具体目的是研究果蝇肠道对微生物的反应，了解DSS如何改变上皮细胞和干细胞的行为，并对肠道中自卫所必需的宿主基因进行初步基因筛选。从R21探索性研究中获得的数据将用于未来的R01申请，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侵害。

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.