Probiotics:Potential Therapeutic Roles in Diarrhea

描述（由申请人提供）：益生菌微生物对人体健康有益。这些包括促进肠道屏障功能，抑制病原体感染，维持肠道稳态和免疫调节。益生菌已被用于治疗各种胃肠道疾病，包括肠易激综合症、肠易激综合症、袋炎和几种腹泻。腹泻可能是由于氯化物分泌增加，NaCl吸收受损，或两者兼而有之。最近的研究表明，乳酸杆菌可以抑制病原菌诱导的氯化物分泌。然而，迄今为止，益生菌对肠道NaCl吸收过程的影响尚未得到研究。回肠和结肠的电中性NaCl吸收涉及腔内Na+/H+交换和Cl-/OH-(HCO3-)交换活性的耦合。我们假设，在腹泻疾病中，益生菌除了抑制氯离子分泌增加外，益生菌的有益作用也可能来自于刺激NaCl的吸收。我们利用Caco-2细胞单层作为人类肠道的实验模型进行的初步研究表明，乳酸杆菌及其培养上清对Cl-/OH-(HCO3-)和Na+/H+交换活性的急性处理显著增强，表明细菌分泌的可溶性因子参与了介导这些促进吸收的作用。我们的初步研究进一步表明，乳酸菌诱导的信号通路和运输事件的参与，需要对所涉及的机制进行详细的调查。目前的建议集中在阐明在体外和体内模型中乳酸杆菌治疗对腔内Cl-吸收调节的细胞和分子机制。设计了三个具体目标：1。研究正常情况下和肠致病性大肠杆菌（EPEC）感染时，乳酸杆菌及其分泌的可溶性因子对Caco-2和T-84（模型人结肠）细胞中氯离子运输的急性影响；2. 揭示DRA和PAT1在乳酸杆菌激活Cl-/OH-(HCO3-)交换活性中的作用，阐明刺激Cl-吸收的信号传导和分子运输机制；和3。观察口服乳酸杆菌对正常小鼠肠内和右旋糖酐硫酸钠（DSS）或EPEC感染引起的腹泻情况下NaCl吸收的影响。我们提出的研究对益生菌在正常和病理生理条件下调节肠道电解质吸收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。公共卫生相关性：益生菌是一种对人体健康有益的细菌。近年来，益生菌已被用于治疗多种胃肠道疾病，包括炎症性肠病和几种腹泻。然而，益生菌有益作用的详细机制尚不清楚。本研究对益生菌在正常和疾病条件下调节肠道盐和水吸收的作用提供了新的见解，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.