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.

腹泻是炎症性肠病（IBD）的标志性症状。反复出现的腹泻情节不仅 显着影响治疗方案，也影响美国资深患者IBD的生活质量。 相关的腹泻是由于腔内NaCl和吸水的降低以及在 障碍完整性。人类肠道中NACL滥用的主要途径涉及NA+/H+的协同操作 和cl-/hco3-交换器。 SLC26A3或DRA（在腺瘤中下调）是参与的关键转运蛋白 肠道吸收。 DRA敲除小鼠已显示出类似于人类的腹泻表型 CLD（先天性氯化腹泻）和最近全基因组关联研究（GWAS）已将 对IBD发病机理的DRA表达失调。此外，我们最近证明了DRA缺陷 在小鼠中，可以增强肠道通透性并损害屏障完整性。那是DRA作为一个 干预腹泻疾病和IBD的重要新颖目标。因此，表征至关重要 涉及健康和疾病中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）是重要的抗炎 代理，是IBD诱导缓解的第一线治疗。另外，GC已显示出稳定 上皮屏障功能和通过恢复电解质和水滥用在 长期发炎的上皮。但是，迄今为止，GC对DRA表达和氯化物的直接影响 尚未研究抽象。我们当前的初步数据提供了合成GC的有力证据 例如，通过糖皮质激素受体（GR）的地塞米松（DEX）可以通过转录增加DRA表达 激活。 DEX处理还增加了小鼠肠中的DRA表达。因此，我们假设 DEX通过上调DRA表达和氯化物滥用，发挥抗动脉炎作用。另外，光线 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，我们进一步假设 DEX介导的DRA上调不仅会改善腹泻，还可以恢复上皮 障碍完整性。因此，当前的应用旨在研究调节机制 DEX的DRA基因表达，GR接收器的作用和相关的共激活因子在正常和 利用体外细胞培养，前体顶肠和体内小鼠的炎症状况 包括DRA-KO小鼠和具有GR肠特异性缺失的小鼠在内的模型。具体目的是：1。 阐明DEX诱导的DRA表达和功能的转录调控的机制及其作用 在抵消TNF-对DRA基因表达的抑制作用时； 2。阐明基础机制 DEX在体内使用野生型和肠道特异性GR敲除小鼠的DRA上调；和3。检查 DEX在DRA上调中的作用是一种新型的治疗方法，在腹泻和恢复的逆转中 实验性结肠炎小鼠的屏障完整性。我们提出的研究将产生对机械信息至关重要 更好地理解GC（例如DEX）的DRA功能和表达调节机制 并且对于促进我们的知识来开发更新，更好的治疗工具至关重要 改善退伍军人的健康。