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Mechanisms of Regulation of Intestinal Cl Absorption in IBD Associated Diarrhea

IBD 相关腹泻肠道 Cl 吸收的调节机制

基本信息

批准号：
10620145
负责人：
Pradeep K Dudeja
金额：
--
依托单位：
JESSE BROWN VA MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-01-01 至 2025-03-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10620145
关键词：
3-Dimensional Affect Animal Model Anions Anti-Inflammatory Agents Antidiarrheals Antiinflammatory Effect Apical Bicarbonates Binding Biopsy Caco-2 Cells Cell Culture Techniques Chlorides Chronic Colitis Crohn&apos s disease Data Defect Dexamethasone Diarrhea Digestive System Disorders Disease Disease remission Dose Down-Regulation Electrolytes Epithelium Exhibits Functional disorder Gene Expression Genetic Transcription Glucocorticoid Receptor Glucocorticoids Health Healthcare Human Impairment In Vitro Inflammation Inflammatory Inflammatory Bowel Diseases Intervention Intestinal permeability Intestines Investigation Knockout Mice Knowledge Light Link Liquid substance Maintenance Measurement Mediating Messenger RNA Molecular Morbidity - disease rate Mucositis Mus NF-kappa B Outcome Study Pathogenesis Pathway interactions Patients Phenotype Physiological Play Proteins Quality of life Recurrence Regulation Regulatory Element Remission Induction Role Route SLC26A3 gene Sodium Symptoms T cell therapy TNF gene Therapeutic Therapeutic Agents Time Transcriptional Activation Transcriptional Regulation Ulcerative Colitis Up-Regulation Veterans Water Water Movements absorption apical membrane care burden cohort design dextran sulfate sodium induced colitis disabling symptom genome wide association study gut dysbiosis gut inflammation immunoregulation improved in vivo interest intestinal barrier monolayer mouse model new therapeutic target novel novel therapeutic intervention operation patient population promoter protein expression receptor response restoration tool

项目摘要

Diarrhea is the hallmark symptom of inflammatory bowel diseases (IBD). Recurring diarrheal episodes not only significantly affect treatment options, but also the quality of life of the US veteran patients with IBD. IBD associated diarrhea results from a decrease in luminal NaCl and water absorption as well as derangements in barrier integrity. Major route of NaCl absorption in the human intestine involves concerted operation of Na+/H+ and Cl-/HCO3- exchangers. SLC26A3 or DRA (Down-Regulated in Adenoma) is the key transporter involved in intestinal Cl- absorption. DRA knockout mice have been shown to exhibit diarrheal phenotype resembling human CLD (congenital chloride diarrhea) and recent genome-wide association studies (GWAS) have linked the dysregulated DRA expression to IBD pathogenesis. Further, we have recently demonstrated that DRA deficiency in mice enhances intestinal permeability and compromises barrier integrity. Thus, DRA has emerged as an important novel target for intervention in diarrheal disorders and IBD. Therefore, it is vital to characterize molecular mechanisms involved in DRA regulation in health and disease and to identify agents that can activate DRA and/or counteract its downregulation. In this regard, glucocorticoids (GCs) are important anti-inflammatory agents and are first line therapeutics for the induction of remission in IBD. Also, GCs have been shown to stabilize epithelial barrier function and exert antidiarrheal effects by restoring electrolyte and water absorption in chronically inflamed epithelium. However, to date, the direct effects of GCs on DRA expression and chloride absorption have not been investigated. Our current preliminary data provide strong evidence that synthetic GC such as Dexamethasone (DEX) via glucocorticoid receptor (GR) can increase DRA expression via transcriptional activation. DEX treatment also increased DRA expression in mouse intestine. Therefore, we hypothesized that DEX exerts antidiarrheal effects by upregulating DRA expression and chloride absorption. Also, in light of our preliminary data demonstrating a key role of DRA in intestinal barrier integrity, we further hypothesized that DEX mediated upregulation of DRA will not only ameliorate diarrhea but will also restore epithelial barrier integrity. The current application is, therefore, designed to investigate the mechanisms of regulation of DRA gene expression by DEX, role of GR receptor and the associated co-activators under normal and inflammatory conditions utilizing both in-vitro cell culture, ex-vivo human apical-out enteroids, and in-vivo mouse models including DRA-KO mice and mice with intestine specific deletion of GR. The Specific Aims are: 1. Elucidate the mechanisms of DEX-induced transcriptional regulation of DRA expression and function and its role in counteracting inhibitory effects of TNF- on DRA gene expression; 2. Elucidate the mechanisms underlying DRA up-regulation by DEX in-vivo utilizing wild type and intestine specific GR knockout mice; and 3. Examine the role of DEX in DRA upregulation as a novel therapeutic approach in reversal of diarrhea and restoration of barrier integrity in mice with experimental colitis. Our proposed studies will yield mechanistic information vital for a better understanding of the mechanisms of regulation of DRA function and expression by GCs such as DEX and are of critical importance in advancing our knowledge to develop newer and better therapeutic tools to improve the health of veterans.

腹泻是炎症性肠病(IBD)的显著症状。反复发作的腹泻不仅显著影响治疗选择，也影响美国退伍军人IBD患者的生活质量。IBD 相关腹泻的原因是管腔内氯化钠和水分吸收减少，以及屏障完整性。人体肠道吸收氯化钠的主要途径与Na+/H+的协同作用有关和Cl-/HCO3-交换剂。SLC26A3或DRA(腺瘤中下调)是参与肠道氯离子吸收。DRA基因敲除小鼠表现出与人类类似的腹泻表型 CLD(先天性氯化物腹泻)和最近的全基因组关联研究(GWAS)将 DRA表达异常在IBD发病机制中的作用此外，我们最近证明了DRA缺乏在小鼠体内，提高肠道通透性，损害屏障完整性。因此，DRA已经成为一种腹泻疾病和IBD干预的重要新靶点。因此，至关重要的是要刻画出参与DRA调节的分子机制在健康和疾病中的作用以及识别能够激活DRA的因素 DRA和/或抵消其下调监管。在这方面，糖皮质激素(GC)是重要的抗炎药物这些药物是诱导IBD缓解的一线治疗药物。此外，GC已被证明是稳定的大鼠上皮屏障功能及通过恢复电解质和水分吸收发挥止泻作用慢性发炎的上皮细胞。然而，到目前为止，GC对DRA表达和氯离子的直接影响吸收还没有被研究过。我们目前的初步数据提供了强有力的证据，证明合成GC 如地塞米松(DEX)通过糖皮质激素受体(GR)可通过转录增加DRA的表达激活。地塞米松还可增加小鼠肠道DRA的表达。因此，我们假设地塞米松通过上调DRA表达和氯离子吸收发挥止泻作用。此外，在光线下根据我们的初步数据显示DRA在肠道屏障完整性中的关键作用，我们进一步假设地塞米松介导的DRA上调不仅能缓解腹泻，还能修复上皮细胞屏障完整性。因此，目前的应用被设计为研究 DEX对DRA基因的表达、GR受体及其相关共激活因子在正常和利用体外细胞培养、体外人类根尖外肠样体和体内小鼠的炎症条件模型包括DRA-KO小鼠和肠道特异性GR缺失小鼠。具体目标是：1. 地塞米松诱导DRA表达和功能的转录调控机制及其作用对抗肿瘤坏死因子-对DRA基因表达的抑制作用；2.阐明其作用机制利用野生型和肠道特异性GR基因敲除小鼠体内DEX上调DRA；以及3.检查地塞米松作为一种新的治疗途径在DRA上调中的作用实验性结肠炎小鼠的屏障完整性。我们提议的研究将产生对以下方面至关重要的机械信息更好地理解DEX等GC对DRA功能和表达的调节机制在发展我们的知识以开发更新和更好的治疗工具方面具有至关重要的作用改善退伍军人健康状况。