Diarrhea associated with inflammatory bowel diseases (IBD) or infections by food-borne pathogens remains a major health problem in our veteran patient population. Despite major medical advances, diarrheal diseases still result in very high morbidity and mortality worldwide. Therefore, a better understanding of the pathophysiology of diarrhea associated with these diseases is critical for designing novel and superior strategies for intervention. Diarrhea results from increased intestinal secretion and/or decreased absorption. A major route of electrolyte absorption in the human intestine involves coupled operation of Na+/H+ and Cl-/HCO3- exchangers. The gene Slc26a3, whose mutations are associated with congenital chloride diarrhea, encodes DRA (Down-Regulated in Adenoma), a protein known to play a critical role in mediating intestinal chloride absorption. Recently, significant reduction of DRA expression has been shown to be one of the major mechanisms responsible for diarrhea in IBD patients. To date, however, very little is known about the molecular mechanisms involved in decreasing DRA expression in diarrheal diseases. In order to elucidate the mechanisms underlying the downregulation of DRA expression in IBD, our studies focused on the role of hepatic nuclear factors (HNFs, transcription factors essential for the expression of many transport proteins) and miRNAs (known to be upregulated in IBD patients and animal models of IBD). Our extensive preliminary data provided strong evidence for the regulation of DRA expression by both HNFs and their activators dexamenthasone (DEX) and conjugated linoleic acids (CLAs), as well as miRNAs. Based on these data, we hypothesize that a down-regulation of HNFs and upregulation of certain miRNAs in inflamed gut may underlie the decrease in DRA expression via transcriptional and post-transcriptional mechanisms, respectively. The current application is, therefore, designed to investigate the regulation of DRA by HNFs and miRNAs utilizing both in vitro (Aims 1 &2) and in vivo models (Aim 3) as follows:
Aim 1. Elucidate detailed mechanisms underlying basal regulation of DRA promoter by HNFs, in decreased DRA expression in IBD and to establish the molecular basis for the upregulation of DRA by DEX and CLAs;
Aim 2 : Extensively analyze the mechanisms underlying post-transcriptional regulation of DRA by miRNAs;
and Aim 3 : Analyze the regulation of DRA by HNFs and miRs in wild type and IL-10 knock out mouse model for IBD. The outcome of these studies should define the role of HNFs in basal, inflammatory or CLA/DEX-mediated upregulation of DRA, and will also establish for the first time, the role of miRs in the modulation of intestinal NaCl absorption under normal and inflammatory conditions. These studies should also identify novel targets for intervention in IBD associated diarrhea.
Diarrhea associated with inflammatory bowel diseases (IBD) and food-borne bacterial infections is a major health care problem in our veterans. Therefore, an understanding of the mechanisms of diarrheal diseases is extremely important for developing novel and superior drugs. The proposed studies are focused at understanding the mechanisms of a decrease in the levels of the key transporter involved in chloride absorption in the intestine in models of intestinal inflammation. The molecular biology approaches outlined in this application are likely to increase our knowledge of regulation of this transporter and identify novel targets for therapies of diarrheal diseases and IBD.
|Manzella, Christopher; Singhal, Megha; Alrefai, Waddah A et al. (2018) Serotonin is an endogenous regulator of intestinal CYP1A1 via AhR. Sci Rep 8:6103|
|Kumar, Anoop; Chatterjee, Ishita; Anbazhagan, Arivarasu N et al. (2018) Cryptosporidium parvum disrupts intestinal epithelial barrier function via altering expression of key tight junction and adherens junction proteins. Cell Microbiol 20:e12830|
|Engevik, Amy C; Kaji, Izumi; Engevik, Melinda A et al. (2018) Loss of MYO5B Leads to Reductions in Na+ Absorption With Maintenance of CFTR-Dependent Cl- Secretion in Enterocytes. Gastroenterology 155:1883-1897.e10|
|Priyadarshini, Medha; Kotlo, Kumar U; Dudeja, Pradeep K et al. (2018) Role of Short Chain Fatty Acid Receptors in Intestinal Physiology and Pathophysiology. Compr Physiol 8:1091-1115|
|Kumar, Anoop; Malhotra, Pooja; Coffing, Hayley et al. (2018) Epigenetic modulation of intestinal Na+/H+ exchanger-3 expression. Am J Physiol Gastrointest Liver Physiol 314:G309-G318|
|Zhang, Yong-Guo; Singhal, Megha; Lin, Zhijie et al. (2018) Infection with enteric pathogens Salmonella typhimurium and Citrobacter rodentium modulate TGF-beta/Smad signaling pathways in the intestine. Gut Microbes 9:326-337|
|Coffing, Hayley; Priyamvada, Shubha; Anbazhagan, Arivarasu N et al. (2018) Clostridium difficile toxins A and B decrease intestinal SLC26A3 protein expression. Am J Physiol Gastrointest Liver Physiol 315:G43-G52|
|Anbazhagan, Arivarasu N; Priyamvada, Shubha; Alrefai, Waddah A et al. (2018) Pathophysiology of IBD associated diarrhea. Tissue Barriers 6:e1463897|
|Muthusamy, Saminathan; Jeong, Jong Jin; Cheng, Ming et al. (2018) Hepatocyte nuclear factor 4? regulates the expression of intestinal epithelial Na+/H+ exchanger isoform 3. Am J Physiol Gastrointest Liver Physiol 314:G14-G21|
|Jayawardena, Dulari; Guzman, Grace; Gill, Ravinder K et al. (2017) Expression and localization of VPAC1, the major receptor of vasoactive intestinal peptide along the length of the intestine. Am J Physiol Gastrointest Liver Physiol 313:G16-G25|
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