Probiotics:Potential Therapeutic Roles in Diarrhea

说明(申请人提供)：益生菌对人体健康有益。这些包括促进肠道屏障功能，抑制病原体感染，维持肠道内环境平衡，以及免疫调节。益生菌已被用于治疗各种胃肠道疾病，包括IBD、IBS、膀胱炎和几种类型的腹泻。腹泻可能是由于氯化物分泌增加或氯化钠吸收障碍，或两者兼而有之。最近的研究表明，乳杆菌能抑制病原菌诱导的氯离子分泌。然而，到目前为止，益生菌对肠道盐吸收过程的影响还没有被研究过。人回肠和结肠对氯化钠的电子中和吸收包括腔内Na/H交换和Cl-/OH-(HCO3-)交换活动的耦合。我们推测，除了抑制腹泻疾病中益生菌增加的氯分泌外，益生菌的有益作用也可能来自于促进盐的吸收。我们利用Caco-2细胞单层作为人体肠道实验模型的初步研究表明，乳酸杆菌及其培养上清液对急性处理的人肠道的Cl-/OH-(HCO3-)和Na/H交换活性显著增强，提示细菌分泌的可溶性因子参与了这些前吸收效应的调节。我们的初步研究进一步表明，乳杆菌诱导的信号通路和转运事件参与其中，因此有必要对相关机制进行详细研究。目前的建议集中在阐明在体外和体内模型中乳杆菌对鲁米那氯离子吸收的调节的细胞和分子机制。1.检测乳杆菌菌种及其分泌的可溶性因子对Caco-2和T-84(模型人结肠)细胞在正常条件下和肠道致病性大肠杆菌(EPEC)感染后氯离子转运的急性影响；2.研究DRA和PAT1在乳杆菌激活Cl-/OH-(HCO3-)交换活性中的作用，阐明刺激氯吸收的信号和分子转运机制；3.检测口服乳杆菌对正常小鼠肠道和由葡聚糖硫酸钠(DSS)或EPEC感染的腹泻条件下氯化钠吸收的影响。我们提出的研究对于在正常和病理生理条件下益生菌在调节肠道电解质吸收中的作用提供了新的见解，并可能为预防和治疗腹泻和炎症性疾病提供更好的策略。与公共健康相关：益生菌是对人类健康有益的细菌。近年来，益生菌已被用于治疗各种胃肠道疾病，包括炎症性肠病和几种类型的腹泻。然而，益生菌有益作用的详细机制尚不清楚。拟议的研究对于了解益生菌在正常和疾病条件下调节肠道盐分和水分吸收的作用至关重要，并可能为腹泻和炎症性疾病的预防和治疗提供更好的策略。

DESCRIPTION (provided by applicant): Probiotic microorganisms confer beneficial effects on human health. These include promotion of gut barrier function, inhibition of pathogen infection, maintenance of intestinal homeostasis, and immune modulation. Probiotics have been used to treat a variety of gastrointestinal ailments including IBD, IBS, pouchitis, and several types of diarrhea. Diarrhea may result from increased chloride secretion, impairment of NaCl absorption, or both. Recent studies showed inhibition of pathogen-induced chloride secretion by Lactobacillus species. To date, however, the effects of probiotics on intestinal NaCl absorptive processes have not been investigated. Electroneutral NaCl absorption in the human ileum and colon involves coupling of luminal Na+/H+ exchange and Cl-/OH-(HCO3-) exchange activities. We hypothesized that, in addition to inhibition of increased chloride secretion by probiotics in diarrheal disorders, the beneficial effects of probiotics may also arise from stimulation of NaCl absorption as well. Our preliminary studies utilizing Caco-2 cell monolayers as an experimental model for human intestine, demonstrated significant enhancement of Cl-/OH-(HCO3-) and Na+/H+ exchange activities in response to acute treatment with Lactobacilli, and also their culture supernatant, suggesting that bacteria-secreted soluble factors are involved in mediating these proabsorptive effects. Our preliminary studies further indicated involvement of Lactobacillus-induced signaling pathways and trafficking events warranting a detailed investigation of the mechanisms involved. The current proposal is focused at elucidating the cellular and molecular mechanisms underlying the modulation of luminal Cl- absorption in response to treatments with Lactobacilli in in vitro and in vivo models. Three specific aims have been designed: 1. Examine the acute effects of Lactobacillus species and their secreted soluble factors on chloride transport in Caco-2 and T-84 (model human colonic) cells under normal conditions and in response to infection with enteropathogenic E. coli (EPEC); 2. Dissect out the role of DRA and PAT1 in activation of Cl-/OH-(HCO3-) exchange activity by Lactobacilli and elucidate signaling and molecular trafficking mechanisms involved in stimulation of Cl- absorption; and 3. Examine the effects of oral administration of Lactobacilli on NaCl absorption in normal mouse intestine and under diarrheal conditions, induced by dextran sodium sulfate (DSS) or EPEC infection. Our proposed studies are critical for providing novel insights into the role of probiotics in regulating intestinal electrolyte absorption under normal and pathophysiological conditions and may provide better strategies for the prevention and treatment of diarrheal and inflammatory disorders. PUBLIC HEALTH RELEVANCE: Probiotica are bacteria that confer beneficial effects on human health. In recent years, probiotics have been used to treat a variety of gastrointestinal diseases including inflammatory bowel diseases and several types of diarrhea. However, the detailed mechanisms underlying the beneficial effects of probiotics are not known. The proposed studies are critical to provide novel insights into role of probiotics in regulating intestinal salt and water absorption under normal and disease conditions and may provide better strategies for the prevention and treatment of diarrheal and inflammatory diseases.