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

• 批准号: 10347178
• 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
• 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/10347178
• 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' s disease; Data; Defect; Dexamethasone; Diarrhea; Digestive System Disorders; Disease; Disease remission; Dose; Down-Regulation; Electrolytes; Epithelial; 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; 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; 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

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.

腹泻不仅是炎症性肠病（IBD）的标志症状，而且是反复发作的腹泻。 炎症性肠病 相关的腹泻是由于管腔氯化钠和水吸收的减少以及肠道菌群紊乱造成的。 屏障完整性。 人体肠道吸收 NaCl 的主要途径涉及 Na+/H+ 的协同作用。 Cl-/HCO3- 交换器或 DRA（腺瘤中下调）是参与此过程的关键转运蛋白。 DRA 敲除小鼠的肠道 Cl- 吸收已被证明表现出类似于人类的腹泻表型。 CLD（先天性氯化物腹泻）和最近的全基因组关联研究 (GWAS) 将 DRA 表达失调与 IBD 发病机制有关。此外，我们最近还证明了 DRA 缺陷。 在小鼠中，DRA 会增强肠道通透性并损害屏障完整性。 腹泻病和 IBD 干预的重要新靶标因此，表征至关重要。 参与健康和疾病 DRA 调节的分子机制，并确定可以激活的药物 DRA 和/或抵消其下调 在这方面，糖皮质激素 (GC) 具有重要的抗炎作用。 GC 是诱导 IBD 缓解的一线治疗药物。GC 已被证明具有稳定作用。 通过恢复电解质和水的吸收来发挥上皮屏障功能并发挥止泻作用 然而，迄今为止，GC 对 DRA 表达和氯的直接影响。 我们目前的初步数据提供了合成气相色谱的有力证据。 例如地塞米松 (DEX) 通过糖皮质激素受体 (GR) 可以通过转录增加 DRA 表达 DEX 治疗也增加了小鼠肠道中的 DRA 表达。 DEX 通过上调 DRA 表达和氯化物吸收发挥止泻作用。 我们的初步数据证明了 DRA 在肠道屏障完整性中的关键作用，我们进一步探索 DEX 介导的 DRA 上调不仅可以改善腹泻，还可以恢复上皮细胞 因此，当前的应用旨在研究调节机制。 DEX 的 DRA 基因表达、GR 受体的作用以及正常和正常情况下相关的共激活因子 利用体外细胞培养、离体人类心尖出肠和体内小鼠的炎症条件 模型包括 DRA-KO 小鼠和肠道特异性删除 GR 的小鼠。具体目标是： 1. 阐明DEX诱导DRA表达和功能的转录调控机制及其作用 抵消 TNF-α 对 DRA 基因表达的抑制作用 2. 阐明其潜在机制； 利用野生型和肠道特异性 GR 敲除小鼠体内 DEX 上调 DRA；以及 3. 检查 DEX 在 DRA 上调中的作用作为逆转腹泻和恢复肠道菌群的新治疗方法 我们提出的研究将产生对于实验性结肠炎小鼠的屏障完整性至关重要的机制信息。 更好地了解 DEX 等 GC 调节 DRA 功能和表达的机制 对于提高我们的知识以开发更新更好的治疗工具至关重要 改善退伍军人的健康。