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Han Y, Srinivasan S, Yun CC. Inhibition of protein kinase C-α and activation of ezrin by Lactobacillus acidophilus restore Na +/H + exchange activity and fluid absorption in db/db mice. Am J Physiol Endocrinol Metab 2023; 325:E214-E226. [PMID: 37467022 PMCID: PMC10511175 DOI: 10.1152/ajpendo.00145.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 07/03/2023] [Accepted: 07/03/2023] [Indexed: 07/20/2023]
Abstract
Gastrointestinal (GI) complications, including diarrhea, constipation, and gastroparesis, are common in patients with diabetes. Dysregulation of the Na+/H+ exchanger NHE3 in the intestine is linked to diarrhea and constipation, and recent studies showed that NHE3 expression is reduced in type 1 diabetes and metformin causes diarrhea in the db/db mouse model of type 2 diabetes (T2D) via inhibition of NHE3. In this study, we investigated whether NHE3 expression is altered in type 2 diabetic intestine and the underlying mechanism that dysregulates NHE3. NHE3 expression in the brush border membrane (BBM) of the intestine of diabetic mice and humans was decreased. Protein kinase C (PKC) activation is associated with pathologies of diabetes, and immunofluorescence (IF) analysis revealed increased BBM PKCα abundance. Inhibition of PKCα increased NHE3 BBM abundance and NHE3-mediated intestinal fluid absorption in db/db mice. Previous studies have shown that Lactobacillus acidophilus (LA) stimulates intestinal ion transporters. LA increased NHE3 BBM expression and mitigated metformin-mediated inhibition of NHE3 in vitro and in vivo. To understand the underlying mechanism of LA-mediated stimulation of NHE3, we used Caco-2bbe cells overexpressing PKCα that mimic the elevated state of PKCα in T2D. LA diminished PKCα BBM expression, increased phosphorylation of ezrin, and the interaction of NHE3 with NHE regulatory factor 2 (NHERF2). In addition, inhibition of PKCι blocked phosphorylation of ezrin and activation of NHE3 by LA. These findings demonstrate that NHE3 is downregulated in T2D, and LA restores NHE3 expression via regulation of PKCα, PKCι, and ezrin.NEW & NOTEWORTHY We used mouse models of type 2 diabetes (T2D) and human patient-derived samples to show that Na+/H+ exchanger 3 (NHE3) expression is decreased in T2D. We show that protein kinase C-α (PKCα) is activated in diabetes and inhibition of PKCα increased NHE3 expression and mitigates diarrhea. We show that Lactobacillus acidophilus (LA) stimulates NHE3 via inhibition of PKCα and phosphorylation of ezrin.
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Affiliation(s)
- Yiran Han
- Gastroenterology Research, Atlanta Veterans Administration Medical Center, Decatur, Georgia, United States
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Shanthi Srinivasan
- Gastroenterology Research, Atlanta Veterans Administration Medical Center, Decatur, Georgia, United States
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - C Chris Yun
- Gastroenterology Research, Atlanta Veterans Administration Medical Center, Decatur, Georgia, United States
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia, United States
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Cumhur Cure M, Cure E. Severe acute respiratory syndrome coronavirus 2 may cause liver injury via Na +/H + exchanger. World J Virol 2023; 12:12-21. [PMID: 36743661 PMCID: PMC9896593 DOI: 10.5501/wjv.v12.i1.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 10/03/2022] [Accepted: 11/22/2022] [Indexed: 01/18/2023] Open
Abstract
The liver has many significant functions, such as detoxification, the urea cycle, gluconeogenesis, and protein synthesis. Systemic diseases, hypoxia, infections, drugs, and toxins can easily affect the liver, which is extremely sensitive to injury. Systemic infection of severe acute respiratory syndrome coronavirus 2 can cause liver damage. The primary regulator of intracellular pH in the liver is the Na+/H+ exchanger (NHE). Physiologically, NHE protects hepatocytes from apoptosis by making the intracellular pH alkaline. Severe acute respiratory syndrome coronavirus 2 increases local angiotensin II levels by binding to angiotensin-converting enzyme 2. In severe cases of coronavirus disease 2019, high angi-otensin II levels may cause NHE overstimulation and lipid accumulation in the liver. NHE overstimulation can lead to hepatocyte death. NHE overstimulation may trigger a cytokine storm by increasing proinflammatory cytokines in the liver. Since the release of proinflammatory cytokines such as interleukin-6 increases with NHE activation, the virus may indirectly cause an increase in fibrinogen and D-dimer levels. NHE overstimulation may cause thrombotic events and systemic damage by increasing fibrinogen levels and cytokine release. Also, NHE overstimulation causes an increase in the urea cycle while inhibiting vitamin D synthesis and gluconeogenesis in the liver. Increasing NHE3 activity leads to Na+ loading, which impairs the containment and fluidity of bile acid. NHE overstimulation can change the gut microbiota composition by disrupting the structure and fluidity of bile acid, thus triggering systemic damage. Unlike other tissues, tumor necrosis factor-alpha and angiotensin II decrease NHE3 activity in the intestine. Thus, increased luminal Na+ leads to diarrhea and cytokine release. Severe acute respiratory syndrome coronavirus 2-induced local and systemic damage can be improved by preventing virus-induced NHE overstimulation in the liver.
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Affiliation(s)
- Medine Cumhur Cure
- Department of Biochemistry, Private Tanfer Hospital, Istanbul 34394, Turkey
| | - Erkan Cure
- Department of Internal Medicine, Bagcilar Medilife Hospital, Istanbul 34200, Turkey
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Zhao C, Jiang Y, Yin H, Jin Z, Yuan J, Shang H, Song H. Hericium caput-medusae (Bull.: Fr.) Pers. Fermentation concentrate polysaccharide ameliorate diarrhea in DSS-induced early colitis by modulating ion channel. J Funct Foods 2023. [DOI: 10.1016/j.jff.2022.105390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Nikolovska K, Seidler UE, Stock C. The Role of Plasma Membrane Sodium/Hydrogen Exchangers in Gastrointestinal Functions: Proliferation and Differentiation, Fluid/Electrolyte Transport and Barrier Integrity. Front Physiol 2022; 13:899286. [PMID: 35665228 PMCID: PMC9159811 DOI: 10.3389/fphys.2022.899286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 04/19/2022] [Indexed: 12/11/2022] Open
Abstract
The five plasma membrane Na+/H+ exchanger (NHE) isoforms in the gastrointestinal tract are characterized by distinct cellular localization, tissue distribution, inhibitor sensitivities, and physiological regulation. NHE1 (Slc9a1) is ubiquitously expressed along the gastrointestinal tract in the basolateral membrane of enterocytes, but so far, an exclusive role for NHE1 in enterocyte physiology has remained elusive. NHE2 (Slc9a2) and NHE8 (Slc9a8) are apically expressed isoforms with ubiquitous distribution along the colonic crypt axis. They are involved in pHi regulation of intestinal epithelial cells. Combined use of a knockout mouse model, intestinal organoid technology, and specific inhibitors revealed previously unrecognized actions of NHE2 and NHE8 in enterocyte proliferation and differentiation. NHE3 (Slc9a3), expressed in the apical membrane of differentiated intestinal epithelial cells, functions as the predominant nutrient-independent Na+ absorptive mechanism in the gut. The new selective NHE3 inhibitor (Tenapanor) allowed discovery of novel pathophysiological and drug-targetable NHE3 functions in cystic-fibrosis associated intestinal obstructions. NHE4, expressed in the basolateral membrane of parietal cells, is essential for parietal cell integrity and acid secretory function, through its role in cell volume regulation. This review focuses on the expression, regulation and activity of the five plasma membrane Na+/H+ exchangers in the gastrointestinal tract, emphasizing their role in maintaining intestinal homeostasis, or their impact on disease pathogenesis. We point to major open questions in identifying NHE interacting partners in central cellular pathways and processes and the necessity of determining their physiological role in a system where their endogenous expression/activity is maintained, such as organoids derived from different parts of the gastrointestinal tract.
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Prasad H, Mathew JKK, Visweswariah SS. Receptor Guanylyl Cyclase C and Cyclic GMP in Health and Disease: Perspectives and Therapeutic Opportunities. Front Endocrinol (Lausanne) 2022; 13:911459. [PMID: 35846281 PMCID: PMC9276936 DOI: 10.3389/fendo.2022.911459] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 05/26/2022] [Indexed: 11/13/2022] Open
Abstract
Receptor Guanylyl Cyclase C (GC-C) was initially characterized as an important regulator of intestinal fluid and ion homeostasis. Recent findings demonstrate that GC-C is also causally linked to intestinal inflammation, dysbiosis, and tumorigenesis. These advances have been fueled in part by identifying mutations or changes in gene expression in GC-C or its ligands, that disrupt the delicate balance of intracellular cGMP levels and are associated with a wide range of clinical phenotypes. In this review, we highlight aspects of the current knowledge of the GC-C signaling pathway in homeostasis and disease, emphasizing recent advances in the field. The review summarizes extra gastrointestinal functions for GC-C signaling, such as appetite control, energy expenditure, visceral nociception, and behavioral processes. Recent research has expanded the homeostatic role of GC-C and implicated it in regulating the ion-microbiome-immune axis, which acts as a mechanistic driver in inflammatory bowel disease. The development of transgenic and knockout mouse models allowed for in-depth studies of GC-C and its relationship to whole-animal physiology. A deeper understanding of the various aspects of GC-C biology and their relationships with pathologies such as inflammatory bowel disease, colorectal cancer, and obesity can be leveraged to devise novel therapeutics.
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Affiliation(s)
- Hari Prasad
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bengaluru, India
| | | | - Sandhya S. Visweswariah
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bengaluru, India
- Centre for Biosystems Science and Engineering, Indian Institute of Science, Bengaluru, India
- *Correspondence: Sandhya S. Visweswariah,
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Cure MC, Cure E. Prolonged NHE Activation may be both Cause and Outcome of Cytokine Release Syndrome in COVID-19. Curr Pharm Des 2022; 28:1815-1822. [PMID: 35838211 DOI: 10.2174/1381612828666220713121741] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 06/27/2022] [Indexed: 02/06/2023]
Abstract
The release of cytokines and chemokines such as IL-1β, IL-2, IL-6, IL-7, IL-10, TNF-α, IFN-γ, CCL2, CCL3, and CXCL10 is increased in critically ill patients with COVID-19. Excessive cytokine release during COVID-19 is related to increased morbidity and mortality. Several mechanisms are put forward for cytokine release syndrome during COVID-19. Here we have mentioned novel pathways. SARS-CoV-2 increases angiotensin II levels by rendering ACE2 nonfunctional. Angiotensin II causes cytokine release via AT1 and AT2 receptors. Moreover, angiotensin II potently stimulates the Na+/H+ exchanger (NHE). It is a pump found in the membranes of many cells that pumps Na+ inward and H+ outward. NHE has nine isoforms. NHE1 is the most common isoform found in endothelial cells and many cells. NHE is involved in keeping the intracellular pH within physiological limits. When the intracellular pH is acidic, NHE is activated, bringing the intracellular pH to physiological levels, ending its activity. Sustained NHE activity is highly pathological and causes many problems. Prolonged NHE activation in COVID-19 may cause a decrease in intracellular pH through H+ ion accumulation in the extracellular area and subsequent redox reactions. The activation reduces the intracellular K+ concentration and leads to Na+ and Ca2+ overload. Increased ROS can cause intense cytokine release by stimulating NF-κB and NLRP3 inflammasomes. Cytokines also cause overstimulation of NHE. As the intracellular pH decreases, SARS-CoV-2 rapidly infects new cells, increasing the viral load. This vicious circle increases morbidity and mortality in patients with COVID-19. On the other hand, SARS-CoV-2 interaction with NHE3 in intestinal tissue is different from other tissues. SARS-CoV-2 can trigger CRS via NHE3 inhibition by disrupting the intestinal microbiota. This review aimed to help develop new treatment models against SARS-CoV-2- induced CRS by revealing the possible effects of SARS-CoV-2 on the NHE.
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Affiliation(s)
| | - Erkan Cure
- Department of Internal Medicine, Bagcilar Medilife Hospital, Istanbul, Turkey
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Kovesdy CP, Adebiyi A, Rosenbaum D, Jacobs JW, Quarles LD. Novel Treatments from Inhibition of the Intestinal Sodium-Hydrogen Exchanger 3. Int J Nephrol Renovasc Dis 2021; 14:411-420. [PMID: 34880650 PMCID: PMC8646223 DOI: 10.2147/ijnrd.s334024] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 11/11/2021] [Indexed: 12/31/2022] Open
Abstract
Plasma membrane sodium–hydrogen exchangers (NHE) transport Na+ into cells in exchange for H+. While there are nine isoforms of NHE in humans, this review focuses on the NHE3 isoform, which is abundantly expressed in the gastrointestinal tract, where it plays a key role in acid–base balance and water homeostasis. NHE3 inhibition in the small intestine results in luminal sodium and water retention, leading to a general decrease in paracellular water flux and diffusional driving force, reduced intestinal sodium absorption, and increased stool sodium excretion. The resulting softer and more frequent stools are the rationale for the development of tenapanor as a novel, first-in-class NHE3 inhibitor to treat irritable bowel syndrome with constipation. NHE3 also has additional therapeutic implications in nephrology. Inhibition of intestinal NHE3 also lowers blood pressure by reducing intestinal sodium absorption. Perhaps, the most novel effect is its ability to decrease intestinal phosphate absorption by inhibiting the paracellular phosphate absorption pathway. Therefore, selective pharmacological inhibition of NHE3 could be a potential therapeutic strategy to treat not only heart failure and hypertension but also hyperphosphatemia. This review presents an overview of the molecular and physiological functions of NHE3 and discusses how these functions translate to potential clinical applications in nephrology.
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Affiliation(s)
- Csaba P Kovesdy
- Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Adebowale Adebiyi
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | | | | | - L Darryl Quarles
- Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA
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Jenkin KA, Han Y, Lin S, He P, Yun CC. Nedd4-2-dependent Ubiquitination Potentiates the Inhibition of Human NHE3 by Cholera Toxin and Enteropathogenic Escherichia coli. Cell Mol Gastroenterol Hepatol 2021; 13:695-716. [PMID: 34823064 PMCID: PMC8789535 DOI: 10.1016/j.jcmgh.2021.11.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/12/2021] [Accepted: 11/15/2021] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS Diarrhea is one of the most common illnesses and is often caused by bacterial infection. Recently, we have shown that human Na+/H+ exchanger NHE3 (hNHE3), but not non-human NHE3s, interacts with the E3 ubiquitin ligase Nedd4-2. We hypothesize that this property of hNHE3 contributes to the increased severity of diarrhea in humans. METHODS We used humanized mice expressing hNHE3 in the intestine (hNHE3int) to compare the contribution of hNHE3 and mouse NHE3 to diarrhea induced by cholera toxin (CTX) and enteropathogenic Escherichia coli (EPEC). We measured Na+/H+ exchange activity and fluid absorption. The role of Nedd4-2 on hNHE3 activity and ubiquitination was determined by knockdown in Caco-2bbe cells. The effects of protein kinase A (PKA), the primary mediator of CTX-induced diarrhea, on Nedd4-2 and hNHE3 phosphorylation and their interaction were determined. RESULTS The effects of CTX and EPEC were greater in hNHE3int mice than in control wild-type (WT) mice, resulting in greater inhibition of NHE3 activity and increased fluid accumulation in the intestine, the hallmark of diarrhea. Activation of PKA increased ubiquitination of hNHE3 and enhanced interaction of Nedd4-2 with hNHE3 via phosphorylation of Nedd4-2 at S342. S342A mutation mitigated the Nedd4-2-hNHE3 interaction and blocked PKA-induced inhibition of hNHE3. Unlike non-human NHE3s, inhibition of hNHE3 by PKA is independent of NHE3 phosphorylation, suggesting a distinct mechanism of hNHE3 regulation. CONCLUSIONS The effects of CTX and EPEC on hNHE3 are amplified, and the unique properties of hNHE3 may contribute to diarrheal symptoms occurring in humans.
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Affiliation(s)
- Kayte A. Jenkin
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,School of Science, Western Sydney University, Campbelltown, NSW 2560, Australia
| | - Yiran Han
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,Atlanta VA Medical Center, Decatur, Georgia
| | - Songbai Lin
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,Atlanta VA Medical Center, Decatur, Georgia
| | - Peijian He
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - C. Chris Yun
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia,Atlanta VA Medical Center, Decatur, Georgia,Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia,Correspondence Address correspondence to: Chris Yun, PhD, Division of Digestive Diseases, Emory University School of Medicine, Atlanta, Georgia 30324. fax: (404) 727-5767.
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Na +/H +-Exchanger Family as Novel Prognostic Biomarkers in Colorectal Cancer. JOURNAL OF ONCOLOGY 2021; 2021:3241351. [PMID: 34759967 PMCID: PMC8575632 DOI: 10.1155/2021/3241351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 10/05/2021] [Indexed: 11/17/2022]
Abstract
Background The acidic characteristics of the tumor microenvironment (TME) are attributed to cancer cells' needs of metabolism which produce a large amount of H+. In order not to affect its own life activities, it needs to release H+ into the intercellular space through an efficient Na+/H+ exchanger. On account of the intestine whose physiological function is highly dependent on intestinal pH value, NHE family members may play a critical role in the occurrence and development of colorectal cancer (CRC). Methods TCGA, GEPIA2, ONCOMINE, UALCAN, STRING, TIMER, Cytoscape, TargetScan, ENCORI, LncBase v.2, DNMIVD, HPA, and CellMinerTM databases were used in our study. Results The mRNA expressions of SLC9A1, SLC9A2, SLC9A3, and SLC9A9 were evidently lower in COAD than in normal samples; however, the mRNA expressions of SLC9A5, SLC9A8, and SLC9B2 were higher. Besides, mRNA expressions of NHE family were extremely associated with clinicopathological features, tumor immune microenvironment and stemness score, DNA methylation, and patient prognosis in COAD. Moreover, we conjectured that NHE family may play a role through MAPK or ErbB signaling pathway according to the results of GO/KEGG enrichment analysis. At last, we found that NHE family members were key factors of various kinds of cancers. Conclusion Our study indicated that NHE family represented new diagnostic and therapeutic targets for CRC, which could have important significance for the clinical treatment of CRC.
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Impaired Intestinal Sodium Transport in Inflammatory Bowel Disease: From the Passenger to the Driver's Seat. Cell Mol Gastroenterol Hepatol 2021; 12:277-292. [PMID: 33744482 PMCID: PMC8165433 DOI: 10.1016/j.jcmgh.2021.03.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 03/09/2021] [Accepted: 03/09/2021] [Indexed: 12/22/2022]
Abstract
Although impaired intestinal sodium transport has been described for decades as a ubiquitous feature of inflammatory bowel disease (IBD), whether and how it plays a pivotal role in the ailment has remained uncertain. Our identification of dominant mutations in receptor guanylyl cyclase 2C as a cause of IBD-associated familial diarrhea syndrome brought a shift in the way we envision impaired sodium transport. Is this just a passive collateral effect resulting from intestinal inflammation, or is it a crucial regulator of IBD pathogenesis? This review summarizes the mutational spectrum and underlying mechanisms of monogenic IBD associated with congenital sodium diarrhea. We constructed a model proposing that impaired sodium transport is an upstream pathogenic factor in IBD. The review also synthesized emerging insights from microbiome and animal studies to suggest how sodium malabsorption can serve as a unifying mediator of downstream pathophysiology. Further investigations into the mechanisms underlying salt and water transport in the intestine will provide newer approaches for understanding the ion-microbiome-immune cross-talk that serves as a driver of IBD. Model systems, such as patient-derived enteroids or induced pluripotent stem cell models, are warranted to unravel the role of individual genes regulating sodium transport and to develop more effective epithelial rescue and repair therapies.
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Ion Transport Basis of Diarrhea in a Mouse Model of Adoptive T Cell Transfer Colitis. Dig Dis Sci 2020; 65:1700-1709. [PMID: 31741140 PMCID: PMC7230007 DOI: 10.1007/s10620-019-05945-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 11/06/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Diarrhea, a major pathological hallmark of inflammatory bowel disease, is characterized by a significant reduction in the expression and function of key intestinal ion transporters. The adoptive naïve CD4+ T cell transfer colitis is an immune-based, chronic colitis mouse model which resembles human Crohn's disease. Although mice with T cell transfer colitis demonstrate diarrhea, the ion transporter basis of this phenotype has not been explored. AIMS/METHODS In the current studies, we aimed to determine the mRNA and protein levels of the key NaCl transporters DRA and NHE3 along with the mRNA expression of other transporters in the inflamed intestine. RESULTS Naïve CD4+ T cells, transferred to Rag2 knockout mice, induced severe colonic inflammation characterized by histological damage and increased mRNA levels of cytokines in the colon with no effect in the ileum. Diarrheal phenotype was a key feature of the excised colons of mice where loose stools were evident. Our results demonstrated that the key chloride transporter DRA, mRNA, and protein levels were significantly reduced in the inflamed colon. However, expression of the key sodium hydrogen exchanger NHE3 was unaffected. The mRNA expression of other important transporters was also determined; in this regard, the sodium channel ENACα and the monocarboxylate transporters MCT1 and SMCT1 mRNA levels were also significantly lower compared to control mice. However, CFTR mRNA was not altered in the colon or ileum. CONCLUSIONS The studies conducted herein for the first time demonstrate the downregulation of important intestinal ion transporters in proximal and distal colon in T cell transfer colitis mouse model, providing valuable evidence for the ion transporter basis of diarrhea in this chronic model of inflammation.
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Enns CB, Keith BA, Challa N, Harding JCS, Loewen ME. Impairment of electroneutral Na + transport and associated downregulation of NHE3 contributes to the development of diarrhea following in vivo challenge with Brachyspira spp. Am J Physiol Gastrointest Liver Physiol 2020; 318:G288-G297. [PMID: 31760765 PMCID: PMC7052572 DOI: 10.1152/ajpgi.00011.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The effect of Brachyspira hyodysenteriae and Brachyspira hampsonii spirochetosis on Na+ transport was assessed in the colon to determine its contribution to diarrheal disease in pigs following experimental infection. Electrogenic and electroneutral Na+ absorption was assessed in Ussing chambers by radiolabeled 22Na flux and pharmacological inhibitory studies. Basal radiolabeled 22Na flux experiments revealed that mucosal-to-serosal flux (Jms) was significantly impaired in B. hyodysenteriae and B. hampsonii-diseased pigs. Inhibition of epithelial sodium channel via amiloride did not significantly reduce electrogenic short-circuit current (Isc) in the proximal, apex, and distal colonic segments of diseased pigs over control pigs, suggesting that a loss of electroneutral Na+ absorption is responsible for diarrheal development. These findings were further supported by significant downregulation of Na+/H+ exchanger (NHE1, NHE2, and NHE3) mRNA expression in the proximal, apex, and distal colonic segments paired with decreased protein expression of the critical NHE3 isoform. The decrease in NHE3 mRNA expression appears not to be attributed to the host's cytokine response as human IL-1α did not modify NHE3 mRNA expression in Caco-2 cells. However, a whole cell B. hampsonii lysate significantly downregulated NHE3 mRNA expression and significantly increased p38 phosphorylation in Caco-2 cells. Together these findings provide a likely mechanism for the spirochete-induced malabsorptive diarrhea, indicated by a decrease in electroneutral Na+ absorption in the porcine colon due to Brachyspira's ability to inhibit NHE3 transcription, resulting in diarrheal disease.NEW & NOTEWORTHY This research demonstrates that diarrheal disease caused by two infectious spirochete spp. is a result of impaired electroneutral Na+ absorption via Na+/H+ exchanger 3 (NHE3) in the porcine colon. Our findings suggest that the decrease in NHE3 mRNA and protein is not likely a result of the host's cytokine response. Rather, it appears that these two Brachyspira spp. directly inhibit the transcription and translation of NHE3, resulting in the development of diarrhea.
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Affiliation(s)
- Cole B. Enns
- 1Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Brandon A. Keith
- 1Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Nitin Challa
- 1Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - John C. S. Harding
- 2Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Matthew E. Loewen
- 1Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Cao L, Yuan Z, Liu M, Stock C. (Patho-)Physiology of Na +/H + Exchangers (NHEs) in the Digestive System. Front Physiol 2020; 10:1566. [PMID: 32009977 PMCID: PMC6974801 DOI: 10.3389/fphys.2019.01566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 12/12/2019] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers (NHEs) are expressed in virtually all human tissues and organs. Two major tasks of those NHE isoforms that are located in plasma membranes are cell volume control by Na+-uptake and cellular pH regulation by H+-extrusion. Several NHEs, particularly NHE 1–4 and 8, are involved in the pathogenesis of diseases of the digestive system such as inflammatory bowel disease (ulcerative colitis, Crohn’s disease) and gastric and colorectal tumorigenesis. In the present review, we describe the physiological purposes, possible malfunctions and pathophysiological effects of the different NHE isoforms along the alimentary canal from esophagus to colon, including pancreas, liver and gallbladder. Particular attention is paid to the functions of NHEs in injury repair and to the role of NHE1 in Barrett’s esophagus. The impact of NHEs on gut microbiota and intestinal mucosal integrity is also dealt with. As the hitherto existing findings are not always consistent, sometimes even controversial, they are compared and critically discussed.
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Affiliation(s)
- Li Cao
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhenglin Yuan
- Department of Stomatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Mei Liu
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Christian Stock
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hanover, Germany
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Zeng C, Vanoni S, Wu D, Caldwell JM, Wheeler JC, Arora K, Noah TK, Waggoner L, Besse JA, Yamani AN, Uddin J, Rochman M, Wen T, Chehade M, Collins MH, Mukkada VA, Putnam PE, Naren AP, Rothenberg ME, Hogan SP. Solute carrier family 9, subfamily A, member 3 (SLC9A3)/sodium-hydrogen exchanger member 3 (NHE3) dysregulation and dilated intercellular spaces in patients with eosinophilic esophagitis. J Allergy Clin Immunol 2018; 142:1843-1855. [PMID: 29729938 PMCID: PMC6448407 DOI: 10.1016/j.jaci.2018.03.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 03/15/2018] [Accepted: 03/26/2018] [Indexed: 12/17/2022]
Abstract
BACKGROUND Eosinophilic esophagitis (EoE) is characterized by histopathologic modifications of esophageal tissue, including eosinophil-rich inflammation, basal zone hyperplasia, and dilated intercellular spaces (DIS). The underlying molecular processes that drive the histopathologic features of EoE remain largely unexplored. OBJECTIVE We sought to investigate the involvement of solute carrier family 9, subfamily A, member 3 (SLC9A3) in esophageal epithelial intracellular pH (pHi) and DIS formation and the histopathologic features of EoE. METHODS We examined expression of esophageal epithelial gene networks associated with regulation of pHi in the EoE transcriptome of primary esophageal epithelial cells and an in vitro esophageal epithelial 3-dimensional model system (EPC2-ALI). Molecular and cellular analyses and ion transport assays were used to evaluate the expression and function of SLC9A3. RESULTS We identified altered expression of gene networks associated with regulation of pHi and acid-protective mechanisms in esophageal biopsy specimens from pediatric patients with EoE (healthy subjects, n = 6; patients with EoE, n = 10). The most dysregulated gene central to regulating pHi was SLC9A3. SLC9A3 expression was increased within the basal layer of esophageal biopsy specimens from patients with EoE, and expression positively correlated with disease severity (eosinophils/high-power field) and DIS (healthy subjects, n = 10; patients with EoE, n = 10). Analyses of esophageal epithelial cells revealed IL-13-induced, signal transducer and activator of transcription 6-dependent SLC9A3 expression and Na+-dependent proton secretion and that SLC9A3 activity correlated positively with DIS formation. Finally, we showed that IL-13-mediated, Na+-dependent proton secretion was the primary intracellular acid-protective mechanism within the esophageal epithelium and that blockade of SLC9A3 transport abrogated IL-13-induced DIS formation. CONCLUSIONS SLC9A3 plays a functional role in DIS formation, and pharmacologic interventions targeting SLC9A3 function may suppress the histopathologic manifestations in patients with EoE.
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Affiliation(s)
- Chang Zeng
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Simone Vanoni
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - David Wu
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Julie M Caldwell
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Justin C Wheeler
- Division of Pathology and Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Kavisha Arora
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Taeko K Noah
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Lisa Waggoner
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - John A Besse
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Amnah N Yamani
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Jazib Uddin
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Mark Rochman
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Ting Wen
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Mirna Chehade
- Mount Sinai Center for Eosinophilic Disorders, Jaffe Food Allergy Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Margaret H Collins
- Division of Pathology and Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Vincent A Mukkada
- Division of Gastroenterology, Nutrition and Hepatology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Philip E Putnam
- Division of Gastroenterology, Nutrition and Hepatology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Anjaparavanda P Naren
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Marc E Rothenberg
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Simon P Hogan
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Pathology, Mary H Weiser Food Allergy Center, Michigan Medicine, University of Michigan, Ann Arbor, Mich.
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15
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Harrison CA, Laubitz D, Ohland CL, Midura-Kiela MT, Patil K, Besselsen DG, Jamwal DR, Jobin C, Ghishan FK, Kiela PR. Microbial dysbiosis associated with impaired intestinal Na +/H + exchange accelerates and exacerbates colitis in ex-germ free mice. Mucosal Immunol 2018; 11:1329-1341. [PMID: 29875400 PMCID: PMC6162102 DOI: 10.1038/s41385-018-0035-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 03/29/2018] [Accepted: 04/15/2018] [Indexed: 02/04/2023]
Abstract
Intestinal epithelial Na+/H+ exchange facilitated by the apical NHE3 (Slc9a3) is a highly regulated process inhibited by intestinal pathogens and in inflammatory bowel diseases. NHE3-/- mice develop spontaneous, bacterially mediated colitis, and IBD-like dysbiosis. Disruption of epithelial Na+/H+ exchange in IBD may thus represent a host response contributing to the altered gut microbial ecology, and may play a pivotal role in modulating the severity of inflammation in a microbiome-dependent manner. To test whether microbiome fostered in an NHE3-deficient environment is able to drive mucosal immune responses affecting the onset or severity of colitis, we performed a series of cohousing experiments and fecal microbiome transplants into germ-free Rag-deficient or IL-10-/- mice. We determined that in the settings where the microbiome of NHE3-deficient mice was stably engrafted in the recipient host, it was able accelerate the onset and amplify severity of experimental colitis. NHE3-deficiency was characterized by the reduction in pH-sensitive butyrate-producing Firmicutes families Lachnospiraceae and Ruminococcaceae (Clostridia clusters IV and XIVa), with an expansion of inflammation-associated Bacteroidaceae. We conclude that the microbiome fostered by impaired epithelial Na+/H+ exchange enhances the onset and severity of colitis through disruption of the gut microbial ecology.
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Affiliation(s)
- Christy A Harrison
- Department of Pediatrics, Steele Children's Research Center, Tucson, AZ, USA
- Department of Immunobiology, University of Arizona College of Medicine, Tucson, AZ, USA
| | - Daniel Laubitz
- Department of Pediatrics, Steele Children's Research Center, Tucson, AZ, USA
| | | | | | - Karuna Patil
- University Animal Care, University of Arizona, Tucson, AZ, USA
| | | | - Deepa R Jamwal
- Department of Pediatrics, Steele Children's Research Center, Tucson, AZ, USA
| | - Christian Jobin
- Division of Gastroenterology, Department of Medicine, University of Florida College of Medicine, Gainesville, FL, USA
| | - Fayez K Ghishan
- Department of Pediatrics, Steele Children's Research Center, Tucson, AZ, USA
| | - Pawel R Kiela
- Department of Pediatrics, Steele Children's Research Center, Tucson, AZ, USA.
- Department of Immunobiology, University of Arizona College of Medicine, Tucson, AZ, USA.
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16
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Peplowski MA, Dicay M, Baggio CH, Wysokinski F, Renaux B, Hollenberg MD, Proud D, MacNaughton WK. Interferon gamma decreases intestinal epithelial aquaporin 3 expression through downregulation of constitutive transcription. J Mol Med (Berl) 2018; 96:1081-1093. [DOI: 10.1007/s00109-018-1681-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 07/30/2018] [Accepted: 08/01/2018] [Indexed: 12/15/2022]
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17
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Abstract
Inflammatory bowel diseases broadly categorized into Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory disorders of the gastrointestinal tract with increasing prevalence worldwide. The etiology of the disease is complex and involves a combination of genetic, environmental, immunological and gut microbial factors. Recurring and bloody diarrhea is the most prevalent and debilitating symptom in IBD. The pathogenesis of IBD-associated diarrhea is multifactorial and is essentially an outcome of mucosal damage caused by persistent inflammation resulting in dysregulated intestinal ion transport, impaired epithelial barrier function and increased accessibility of the pathogens to the intestinal mucosa. Altered expression and/or function of epithelial ion transporters and channels is the principle cause of electrolyte retention and water accumulation in the intestinal lumen leading to diarrhea in IBD. Aberrant barrier function further contributes to diarrhea via leak-flux mechanism. Mucosal penetration of enteric pathogens promotes dysbiosis and exacerbates the underlying immune system further perpetuating IBD associated-tissue damage and diarrhea. Here, we review the mechanisms of impaired ion transport and loss of epithelial barrier function contributing to diarrhea associated with IBD.
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Affiliation(s)
- Arivarasu N Anbazhagan
- a Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago , IL , USA
| | - Shubha Priyamvada
- a Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago , IL , USA
| | - Waddah A Alrefai
- a Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago , IL , USA.,b Jesse Brown VA Medical Center , Chicago , IL , USA
| | - Pradeep K Dudeja
- a Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago , IL , USA.,b Jesse Brown VA Medical Center , Chicago , IL , USA
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18
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Kumar A, Malhotra P, Coffing H, Priyamvada S, Anbazhagan AN, Krishnan HR, Gill RK, Alrefai WA, Gavin DP, Pandey SC, Dudeja PK, Saksena S. Epigenetic modulation of intestinal Na +/H + exchanger-3 expression. Am J Physiol Gastrointest Liver Physiol 2018; 314:G309-G318. [PMID: 29167115 PMCID: PMC5899241 DOI: 10.1152/ajpgi.00293.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 11/01/2017] [Accepted: 11/09/2017] [Indexed: 01/31/2023]
Abstract
Na+/H+ exchanger-3 (NHE3) is crucial for intestinal Na+ absorption, and its reduction has been implicated in infectious and inflammatory bowel diseases (IBD)-associated diarrhea. Epigenetic mechanisms such as DNA methylation are involved in the pathophysiology of IBD. Whether changes in DNA methylation are involved in modulating intestinal NHE3 gene expression is not known. Caco-2 and HuTu 80 cells were used as models of human intestinal epithelial cells. Normal C57/BL6, wild-type, or growth arrest and DNA damage-inducible 45b (GADD45b) knockout (KO) mice were used as in vivo models. NHE3 gene DNA methylation levels were assessed by MBDCap (MethyMiner) assays. Results demonstrated that in vitro methylation of NHE3 promoter construct (p-1509/+127) cloned into a cytosine guanine dinucleotide-free lucia vector decreased the promoter activity in Caco-2 cells. DNA methyltransferase inhibitor 5-azacytidine (10 μM, 24 h) caused a significant decrease in DNA methylation of the NHE3 gene and concomitantly increased NHE3 expression in Caco-2 cells. Similarly, 5-azacytidine treatment increased NHE3 mRNA levels in HuTu 80 cells. 5-Azacytidine treatment for 3 wk (10 mg/kg body wt ip, 3 times/wk) also resulted in an increase in NHE3 expression in the mouse ileum and colon. Small-interfering RNA knockdown of GADD45b (protein involved in DNA demethylation) in Caco-2 cells decreased NHE3 mRNA expression. Furthermore, there was a significant decrease in NHE3 mRNA and protein expression in the ileum and colon of GADD45b KO mice. Our findings demonstrate that NHE3 gene expression is regulated by changes in its DNA methylation. NEW & NOTEWORTHY Our studies for the first time demonstrate that Na+/H+ exchanger-3 gene expression is regulated by an epigenetic mechanism involving DNA methylation.
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Affiliation(s)
- Anoop Kumar
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Pooja Malhotra
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Hayley Coffing
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Shubha Priyamvada
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Arivarasu N Anbazhagan
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Harish R Krishnan
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, University of Illinois at Chicago , Chicago, Illinois
| | - Ravinder K Gill
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Waddah A Alrefai
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
| | - David P Gavin
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
| | - Subhash C Pandey
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
| | - Pradeep K Dudeja
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
| | - Seema Saksena
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
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19
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Muthusamy S, Jeong JJ, Cheng M, Bonzo JA, Kumar A, Gonzalez FJ, Borthakur A, Dudeja PK, Saksena S, Malakooti J. Hepatocyte nuclear factor 4α regulates the expression of intestinal epithelial Na +/H + exchanger isoform 3. Am J Physiol Gastrointest Liver Physiol 2018; 314:G14-G21. [PMID: 28882825 PMCID: PMC5866373 DOI: 10.1152/ajpgi.00225.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 08/28/2017] [Accepted: 08/31/2017] [Indexed: 01/31/2023]
Abstract
Na+/H+ exchanger isoform 3 (NHE3) plays a key role in coupled electroneutral NaCl absorption in the mammalian intestine. Reduced NHE3 expression or function has been implicated in the pathogenesis of diarrhea associated with inflammatory bowel disease (IBD) or enteric infections. Our previous studies revealed transcriptional regulation of NHE3 by various agents such as TNF-α, IFN-γ, and butyrate involving transcription factors Sp1 and Sp3. In silico analysis revealed that the NHE3 core promoter also contains a hepatocyte nuclear factor 4α (HNF-4α) binding site that is evolutionarily conserved in several species suggesting that HNF-4α has a role in NHE3 regulation. Nhe3 mRNA levels were reduced in intestine-specific Hnf4α-null mice. However, detailed mechanisms of NHE3 regulation by HNF-4α are not known. We investigated the regulation of NHE3 gene expression by HNF-4α in vitro in the human intestinal epithelial cell line C2BBe1 and in vivo in intestine-specific Hnf4α-null ( Hnf4αΔIEpC) and control ( Hnf4αfl/fl) mice. HNF-4α knockdown by short interfering RNA in C2BBe1 cells significantly decreased NHE3 mRNA and NHE3 protein levels. Gel mobility shift and chromatin immunoprecipitation assays revealed that HNF-4α directly interacts with the HNF-4α motif in the NHE3 core promoter. Site-specific mutagenesis on the HNF-4α motif decreased, whereas ectopic overexpression of HNF-4α increased, NHE3 promoter activity. Furthermore, loss of HNF-4α in Hnf4αΔIEpC mice decreased colonic Nhe3 mRNA and NHE3 protein levels. Our results demonstrate a novel role for HNF-4α in basal regulation of NHE3 expression. These studies represent an important and novel target for therapeutic intervention in IBD-associated diarrhea. NEW & NOTEWORTHY Our studies for the first time show that hepatocyte nuclear factor 4α directly regulates NHE3 promoter activity and its basal expression in the intestine.
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Affiliation(s)
- Saminathan Muthusamy
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Jong Jin Jeong
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Ming Cheng
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Jessica A Bonzo
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland
| | - Anoop Kumar
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Frank J Gonzalez
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland
| | - Alip Borthakur
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
| | - Pradeep K Dudeja
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
| | - Seema Saksena
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago , Chicago, Illinois
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
| | - Jaleh Malakooti
- Jesse Brown Veterans Affairs Medical Center , Chicago, Illinois
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20
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Peplowski MA, Vegso AJ, Iablokov V, Dicay M, Zaheer RS, Renaux B, Proud D, Hollenberg MD, Beck PL, MacNaughton WK. Tumor necrosis factor α decreases aquaporin 3 expression in intestinal epithelial cells through inhibition of constitutive transcription. Physiol Rep 2017; 5:5/19/e13451. [PMID: 29038361 PMCID: PMC5641937 DOI: 10.14814/phy2.13451] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 08/21/2017] [Accepted: 08/24/2017] [Indexed: 01/08/2023] Open
Abstract
Inflammatory diseases of the gut are associated with altered electrolyte and water transport, leading to the development of diarrhea. Epithelially expressed aquaporins (AQPs) are downregulated in inflammation, although the mechanisms involved are not known. We hypothesized that AQP3 expression in intestinal epithelial cells is altered in intestinal inflammation and that these changes are driven by tumor necrosis factor (TNF) α. Human colonic adenocarcinoma (HT‐29) cells were treated with TNFα to investigate signaling mechanisms in vitro. AQP3 expression was assessed by real‐time PCR and radiolabeled glycerol uptake, with select inhibitors and a luciferase reporter construct used to further elucidate intracellular signaling. AQP3 expression was downregulated in HT‐29 cells treated with TNFα. Luciferase reporter construct experiments revealed that TNFα downregulated constitutive transcriptional activity of the AQP3 promoter, and inhibition of MEK/ERK and nuclear factor κB (NF‐κB) signaling prevented the decrease in AQP3 mRNA expression. Constitutive AQP3 expression was suppressed by specificity protein (Sp) 3, and knockdown of this transcription factor bound to the AQP3 promoter was able to partially prevent the TNFα‐induced downregulation of AQP3. TNFα signals through MEK/ERK and NF‐κB to enhance the negative transcriptional control of AQP3 expression exerted by Sp3. Similar mechanisms regulate numerous ion channels, suggesting a common mechanism by which both ion and water transport are altered in inflammation.
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Affiliation(s)
- Michael A Peplowski
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Andrew J Vegso
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Vadim Iablokov
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Michael Dicay
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Raza S Zaheer
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Bernard Renaux
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - David Proud
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Morley D Hollenberg
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.,Department of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Paul L Beck
- Department of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Wallace K MacNaughton
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
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21
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Dominguez Rieg JA, de la Mora Chavez S, Rieg T. Novel developments in differentiating the role of renal and intestinal sodium hydrogen exchanger 3. Am J Physiol Regul Integr Comp Physiol 2016; 311:R1186-R1191. [PMID: 27733387 DOI: 10.1152/ajpregu.00372.2016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 09/22/2016] [Accepted: 10/05/2016] [Indexed: 11/22/2022]
Abstract
The Na+/H+ exchanger isoform 3 (NHE3) facilitates Na+ absorption and H+ secretion and is expressed in the intestine, proximal tubule, and thick ascending limb of the kidney. While the function of NHE3 for Na+ and [Formula: see text](re)absorption has been defined using conventional NHE3 knockout mice (NHE3-/-), the recent generation of conditional NHE3 knockout mice started to give critical new insight into the role of this protein by allowing for temporal and spatial control of NHE3 expression. For example, in contrast to NHE3-/- mice, knockout of NHE3 in the S1 and S2 segments of the proximal tubule or along the entire tubule/collecting duct does not cause any lethality. Nonabsorbable NHE3 inhibitors have been developed, and preclinical as well as clinical trials indicate possible pharmacological use in fluid overload, hypertension, chronic kidney disease, hyperphosphatemia, and constipation. Some of the therapeutic considerations seem to be directly related to the pharmacodynamic properties of these drugs; however, little is known about the effects of these nonabsorbable NHE3 inhibitors on intestinal phosphate transport and the mechanisms so far remain elusive. This review focuses on novel findings of NHE3 in the intestine and the kidney as well as novel drug developments targeting NHE3.
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Affiliation(s)
- Jessica A Dominguez Rieg
- Department of Basic Sciences, Bastyr University California, San Diego, California.,Veterans Affairs San Diego Healthcare System, San Diego, California; and
| | | | - Timo Rieg
- Veterans Affairs San Diego Healthcare System, San Diego, California; and .,Division of Nephrology-Hypertension, Department of Medicine, University of California San Diego, La Jolla, California
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22
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TNFα/IFNγ Mediated Intestinal Epithelial Barrier Dysfunction Is Attenuated by MicroRNA-93 Downregulation of PTK6 in Mouse Colonic Epithelial Cells. PLoS One 2016; 11:e0154351. [PMID: 27119373 PMCID: PMC4847919 DOI: 10.1371/journal.pone.0154351] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 04/12/2016] [Indexed: 12/17/2022] Open
Abstract
Since inflammatory bowel diseases (IBD) represent significant morbidity and mortality in the US, the need for defining novel drug targets and inflammatory mechanisms would be of considerable benefit. Although protein tyrosine kinase 6 (PTK6, also known as breast tumor kinase BRK) has been primarily studied in an oncogenic context, it was noted that PTK6 null mice exhibited significantly enhanced colonic epithelial barrier function. Considering that the inflammatory functions of PTK6 have not yet been explored, we hypothesized that cytokines responsible for mediating IBD, such as TNFα/IFNγ, may solicit the action of PTK6 to alter barrier function. After first assessing critical mediators of TNFα/IFNγ driven epithelial barrier dysfunction, we further explored the possibility of PTK6 in this inflammatory context. In this report, we showed that PTK6 siRNA and PTK6 null young adult mouse colonic epithelial cells (YAMC) exhibited significant attenuation of TNFα/IFNγ induced barrier dysfunction as measured by electric cell-substrate impedance sensing (ECIS) assay and permeability assays. In addition, PTK6 null cells transfected with PTK6 cDNA displayed restored barrier dysfunction in response to TNFα/IFNγ, while the cells transfected with vector alone showed similar attenuation of barrier dysfunction. Furthermore, using subcellular fractionation and immunocytochemistry experiments, we found that PTK6 plays a role in FoxO1 nuclear accumulation leading to down-regulation of claudin-3, a tight junction protein. Moreover, we searched for relevant miRNA candidates putative for targeting PTK6 in order to identify and assess the impact of microRNA that target PTK6 with respect to TNFα/IFNγ induced barrier dysfunction. Subsequently, we assayed likely targets and determined their effectiveness in attenuating PTK6 expression as well as cytokine induced barrier dysfunction. Results showed that miR-93 reduced PTK6 expression and attenuated TNFα/IFNγ imposed decrease in transepithelial electrical resistance (TER), as well as excluded FoxO1 from the nucleus. Our results indicate that PTK6 may act as a novel mediator of intestinal epithelial permeability during inflammatory injury, and miR-93 may protect intestinal epithelial barrier function, at least in part, by targeting PTK6.
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23
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Magalhães D, Cabral JM, Soares-da-Silva P, Magro F. Role of epithelial ion transports in inflammatory bowel disease. Am J Physiol Gastrointest Liver Physiol 2016; 310:G460-76. [PMID: 26744474 DOI: 10.1152/ajpgi.00369.2015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 01/02/2016] [Indexed: 02/06/2023]
Abstract
Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with a complex pathogenesis. Diarrhea is a highly prevalent and often debilitating symptom of IBD patients that results, at least in part, from an intestinal hydroelectrolytic imbalance. Evidence suggests that reduced electrolyte absorption is more relevant than increased secretion to this disequilibrium. This systematic review analyses and integrates the current evidence on the roles of epithelial Na(+)-K(+)-ATPase (NKA), Na(+)/H(+) exchangers (NHEs), epithelial Na(+) channels (ENaC), and K(+) channels (KC) in IBD-associated diarrhea. NKA is the key driving force of the transepithelial ionic transport and its activity is decreased in IBD. In addition, the downregulation of apical NHE and ENaC and the upregulation of apical large-conductance KC all contribute to the IBD-associated diarrhea by lowering sodium absorption and/or increasing potassium secretion.
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Affiliation(s)
- Diogo Magalhães
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal; and MedInUP-Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal
| | - José Miguel Cabral
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal; and MedInUP-Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal
| | - Patrício Soares-da-Silva
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal; and MedInUP-Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal
| | - Fernando Magro
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal; and MedInUP-Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal
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24
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Priyamvada S, Gomes R, Gill RK, Saksena S, Alrefai WA, Dudeja PK. Mechanisms Underlying Dysregulation of Electrolyte Absorption in Inflammatory Bowel Disease-Associated Diarrhea. Inflamm Bowel Dis 2015; 21:2926-35. [PMID: 26595422 PMCID: PMC4662046 DOI: 10.1097/mib.0000000000000504] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Inflammatory bowel diseases (IBDs), including Crohn's disease and ulcerative colitis, are chronic relapsing inflammatory disorders of the gastrointestinal tract. Chronic inflammation of the intestine affects the normal fluid and electrolyte absorption leading to diarrhea, the hallmark symptom of IBD. The management of IBD-associated diarrhea still remains to be a challenge, and extensive studies over the last 2 decades have focused on investigating the molecular mechanisms underlying IBD-associated diarrhea. These studies have shown that the predominant mechanism of diarrhea in IBD involves impairment of electroneutral NaCl absorption, with very little role if any played by anion secretion. The electroneutral NaCl absorption involves coupled operation of Na/H exchanger 3 (NHE3 or SLC9A3) and Cl/HCO3 exchanger DRA (Down Regulated in Adenoma, or SLC26A3). Increasing evidence now supports the critical role of a marked decrease in NHE3 and DRA function and/or expression in IBD-associated diarrhea. This review provides a detailed analysis of the current knowledge related to alterations in NHE3 and DRA function and expression in IBD including the mechanisms underlying these observations and highlights the potential of these transporters as important and novel therapeutic targets.
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Affiliation(s)
- Shubha Priyamvada
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Rochelle Gomes
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Ravinder K. Gill
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Seema Saksena
- Jesse Brown VA Medical Center, University of Illinois at Chicago, Chicago, IL
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Waddah A. Alrefai
- Jesse Brown VA Medical Center, University of Illinois at Chicago, Chicago, IL
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Pradeep K. Dudeja
- Jesse Brown VA Medical Center, University of Illinois at Chicago, Chicago, IL
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, IL
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He P, Zhao L, Zhu L, Weinman EJ, De Giorgio R, Koval M, Srinivasan S, Yun CC. Restoration of Na+/H+ exchanger NHE3-containing macrocomplexes ameliorates diabetes-associated fluid loss. J Clin Invest 2015; 125:3519-31. [PMID: 26258413 DOI: 10.1172/jci79552] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 06/25/2015] [Indexed: 01/19/2023] Open
Abstract
Diarrhea is one of the troublesome complications of diabetes, and the underlying causes of this problem are complex. Here, we investigated whether altered electrolyte transport contributes to diabetic diarrhea. We found that the expression of Na+/H+ exchanger NHE3 and several scaffold proteins, including NHE3 regulatory factors (NHERFs), inositol trisphosphate (IP₃) receptor-binding protein released with IP₃ (IRBIT), and ezrin, was decreased in the intestinal brush border membrane (BBM) of mice with streptozotocin-induced diabetes. Treatment of diabetic mice with insulin restored intestinal NHE3 activity and fluid absorption. Molecular analysis revealed that NHE3, NHERF1, IRBIT, and ezrin form macrocomplexes, which are perturbed under diabetic conditions, and insulin administration reconstituted these macrocomplexes and restored NHE3 expression in the BBM. Silencing of NHERF1 or IRBIT prevented NHE3 trafficking to the BBM and insulin-dependent NHE3 activation. IRBIT facilitated the interaction of NHE3 with NHERF1 via protein kinase D2-dependent phosphorylation. Insulin stimulated ezrin phosphorylation, which enhanced the interaction of ezrin with NHERF1, IRBIT, and NHE3. Additionally, oral administration of lysophosphatidic acid (LPA) increased NHE3 activity and fluid absorption in diabetic mice via an insulin-independent pathway. Together, these findings indicate the importance of NHE3 in diabetic diarrhea and suggest LPA administration as a potential therapeutic strategy for management of diabetic diarrhea.
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Ghosal A, Jellbauer S, Kapadia R, Raffatellu M, Said HM. Salmonella infection inhibits intestinal biotin transport: cellular and molecular mechanisms. Am J Physiol Gastrointest Liver Physiol 2015; 309:G123-31. [PMID: 25999427 PMCID: PMC4504957 DOI: 10.1152/ajpgi.00112.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 05/13/2015] [Indexed: 01/31/2023]
Abstract
Infection with the nontyphoidal Salmonella is a common cause of food-borne disease that leads to acute gastroenteritis/diarrhea. Severe/prolonged cases of Salmonella infection could also impact host nutritional status, but little is known about its effect on intestinal absorption of vitamins, including biotin. We examined the effect of Salmonella enterica serovar Typhimurium (S. typhimurium) infection on intestinal biotin uptake using in vivo (streptomycin-pretreated mice) and in vitro [mouse (YAMC) and human (NCM460) colonic epithelial cells, and human intestinal epithelial Caco-2 cells] models. The results showed that infecting mice with wild-type S. typhimurium, but not with its nonpathogenic isogenic invA spiB mutant, leads to a significant inhibition in jejunal/colonic biotin uptake and in level of expression of the biotin transporter, sodium-dependent multivitamin transporter. In contrast, infecting YAMC, NCM460, and Caco-2 cells with S. typhimurium did not affect biotin uptake. These findings suggest that the effect of S. typhimurium infection is indirect and is likely mediated by proinflammatory cytokines, the levels of which were markedly induced in the intestine of S. typhimurium-infected mice. Consistent with this hypothesis, exposure of NCM460 cells to the proinflammatory cytokines TNF-α and IFN-γ led to a significant inhibition of biotin uptake, sodium-dependent multivitamin transporter expression, and activity of the SLC5A6 promoter. The latter effects appear to be mediated, at least in part, via the NF-κB signaling pathway. These results demonstrate that S. typhimurium infection inhibits intestinal biotin uptake, and that the inhibition is mediated via the action of proinflammatory cytokines.
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Affiliation(s)
- Abhisek Ghosal
- 1Departments of Medicine and Physiology/Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California;
| | - Stefan Jellbauer
- 3Department of Microbiology and Molecular Genetics, University of California, Irvine, California; and ,4Institute for Immunology, University of California, Irvine, California
| | - Rubina Kapadia
- 1Departments of Medicine and Physiology/Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California;
| | - Manuela Raffatellu
- 3Department of Microbiology and Molecular Genetics, University of California, Irvine, California; and ,4Institute for Immunology, University of California, Irvine, California
| | - Hamid M. Said
- 1Departments of Medicine and Physiology/Biophysics, University of California, Irvine, California; ,2Department of Veterans Affairs Medical Center, Long Beach, California;
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Parathyroid hormone inhibition of Na+/H+ exchanger 3 transcription: Intracellular signaling pathways and transcription factor expression. Biochem Biophys Res Commun 2015; 461:582-8. [DOI: 10.1016/j.bbrc.2015.04.049] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 04/07/2015] [Indexed: 11/18/2022]
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Singh V, Kumar A, Raheja G, Anbazhagan AN, Priyamvada S, Saksena S, Jhandier MN, Gill RK, Alrefai WA, Borthakur A, Dudeja PK. Lactobacillus acidophilus attenuates downregulation of DRA function and expression in inflammatory models. Am J Physiol Gastrointest Liver Physiol 2014; 307:G623-31. [PMID: 25059823 PMCID: PMC4166720 DOI: 10.1152/ajpgi.00104.2014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Probiotics, including Lactobacilli, are commensal bacteria that have been used in clinical trials and experimental models for the prevention and treatment of diarrheal disorders. Our previous studies have shown that Lactobacillus acidophilus (LA) and its culture supernatant (CS) stimulated Cl(-)/HCO3 (-) exchange activity, acutely via an increase in the surface levels of downregulated in adenoma (DRA, SLC26A3) and in long-term treatments via increasing its expression involving transcriptional mechanisms. However, the role of LA in modulating DRA activity under inflammatory conditions is not known. Current in vitro studies using human intestinal epithelial Caco-2 cells examined the efficacy of LA or its CS in counteracting the inhibitory effects of interferon-γ (IFN-γ) on Cl(-)/HCO3 (-) exchange activity. Pretreatment of cells with LA or LA-CS for 1 h followed by coincubation with IFN-γ significantly alleviated the inhibitory effects of IFN-γ on Cl(-)/HCO3 (-) exchange activity. In the in vivo model of dextran sulfate sodium-induced experimental colitis (3% in drinking water for 7 days) in C57BL/6J mice, administration of live LA (3 × 10(9) colony-forming units) via oral gavage attenuated colonic inflammation. LA administration also counteracted the colitis-induced decrease in DRA mRNA and protein levels. Efficacy of LA or its secreted soluble factors in alleviating inflammation and inflammation-associated dysregulation of DRA activity could justify their therapeutic potential in inflammatory diarrheal diseases.
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Affiliation(s)
- Varsha Singh
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Anoop Kumar
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and ,2Singhania University, Pacheri Bari, Rajasthan, India
| | - Geetu Raheja
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Arivarasu N. Anbazhagan
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Shubha Priyamvada
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Seema Saksena
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Muhammad Nauman Jhandier
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Ravinder K. Gill
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Waddah A. Alrefai
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Alip Borthakur
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Pradeep K. Dudeja
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
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Fuster DG, Alexander RT. Traditional and emerging roles for the SLC9 Na+/H+ exchangers. Pflugers Arch 2013; 466:61-76. [PMID: 24337822 DOI: 10.1007/s00424-013-1408-8] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 11/14/2013] [Accepted: 11/20/2013] [Indexed: 10/25/2022]
Abstract
The SLC9 gene family encodes Na(+)/H(+) exchangers (NHEs). These transmembrane proteins transport ions across lipid bilayers in a diverse array of species from prokaryotes to eukaryotes, including plants, fungi, and animals. They utilize the electrochemical gradient of one ion to transport another ion against its electrochemical gradient. Currently, 13 evolutionarily conserved NHE isoforms are known in mammals [22, 46, 128]. The SLC9 gene family (solute carrier classification of transporters: www.bioparadigms.org) is divided into three subgroups [46]. The SLC9A subgroup encompasses plasmalemmal isoforms NHE1-5 (SLC9A1-5) and the predominantly intracellular isoforms NHE6-9 (SLC9A6-9). The SLC9B subgroup consists of two recently cloned isoforms, NHA1 and NHA2 (SLC9B1 and SLC9B2, respectively). The SLC9C subgroup consist of a sperm specific plasmalemmal NHE (SLC9C1) and a putative NHE, SLC9C2, for which there is currently no functional data [46]. NHEs participate in the regulation of cytosolic and organellar pH as well as cell volume. In the intestine and kidney, NHEs are critical for transepithelial movement of Na(+) and HCO3(-) and thus for whole body volume and acid-base homeostasis [46]. Mutations in the NHE6 or NHE9 genes cause neurological disease in humans and are currently the only NHEs directly linked to human disease. However, it is becoming increasingly apparent that members of this gene family contribute to the pathophysiology of multiple human diseases.
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Affiliation(s)
- Daniel G Fuster
- Division of Nephrology, Hypertension and Clinical Pharmacology and Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland,
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Dietrich V, Szpilbarg N, Damiano A. Reduced expression of Na(+)/H(+) exchanger isoform 3 (NHE-3) in preeclamptic placentas. Placenta 2013; 34:828-30. [DOI: 10.1016/j.placenta.2013.06.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 05/22/2013] [Accepted: 06/08/2013] [Indexed: 01/17/2023]
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Khan I, Batinic-Haberle I, Benov LT. Effect of potent redox-modulating manganese porphyrin, MnTM-2-PyP, on the Na+/H+exchangers NHE-1 and NHE-3 in the diabetic rat. Redox Rep 2013; 14:236-42. [DOI: 10.1179/135100009x12525712409698] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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Transcriptional regulation by post-transcriptional modification—Role of phosphorylation in Sp1 transcriptional activity. Gene 2012; 508:1-8. [DOI: 10.1016/j.gene.2012.07.022] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 05/22/2012] [Accepted: 07/16/2012] [Indexed: 01/05/2023]
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Girardi ACC, Di Sole F. Deciphering the mechanisms of the Na+/H+ exchanger-3 regulation in organ dysfunction. Am J Physiol Cell Physiol 2012; 302:C1569-87. [DOI: 10.1152/ajpcell.00017.2012] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The Na+/H+ exchanger-3 (NHE3) belongs to the mammalian NHE protein family and catalyzes the electro-neutral exchange of extracellular sodium for intracellular proton across cellular membranes. Its transport function is of essential importance for the maintenance of the body's salt and water homeostasis as well as acid-base balance. Indeed, NHE3 activity is finely regulated by a variety of stimuli, both acutely and chronically, and its transport function is fundamental for a multiplicity of severe and world-wide infection-pathological conditions. This review aims to provide a concise overview of NHE3 physiology and discusses the role of NHE3 in clinical conditions of prominent importance, specifically in hypertension, diabetic nephropathy, heart failure, acute kidney injury, and diarrhea. Study of NHE3 function in models of these diseases has contributed to the deciphering of mechanisms that control the delicate ion balance disrupted in these disorders. The majority of the findings indicate that NHE3 transport function is activated before the onset of hypertension and inhibited thereafter; NHE3 transport function is also upregulated in diabetic nephropathy and heart failure, while it is reported to be downregulated in acute kidney injury and in diarrhea. The molecular mechanisms activated during these pathological conditions to regulate NHE3 transport function are examined with the aim of linking NHE3 dysfunction to the analyzed clinical disorders.
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Affiliation(s)
| | - Francesca Di Sole
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and
- Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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Silva PHI, Girardi ACC, Neri EA, Rebouças NA. Distinct mechanisms underlie adaptation of proximal tubule Na+/H+ exchanger isoform 3 in response to chronic metabolic and respiratory acidosis. Pflugers Arch 2012; 463:703-14. [PMID: 22419175 DOI: 10.1007/s00424-012-1092-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 02/03/2012] [Accepted: 02/22/2012] [Indexed: 12/11/2022]
Abstract
The Na(+/)H(+) exchanger isoform 3 (NHE3) is essential for HCO(3)(-) reabsorption in renal proximal tubules. The expression and function of NHE3 must adapt to acid-base conditions. The goal of this study was to elucidate the mechanisms responsible for higher proton secretion in proximal tubules during acidosis and to evaluate whether there are differences between metabolic and respiratory acidosis with regard to NHE3 modulation and, if so, to identify the relevant parameters that may trigger these distinct adaptive responses. We achieved metabolic acidosis by lowering HCO(3)(-) concentration in the cell culture medium and respiratory acidosis by increasing CO(2) tension in the incubator chamber. We found that cell-surface NHE3 expression was increased in response to both forms of acidosis. Mild (pH 7.21 ± 0.02) and severe (6.95 ± 0.07) metabolic acidosis increased mRNA levels, at least in part due to up-regulation of transcription, whilst mild (7.11 ± 0.03) and severe (6.86 ± 0.01) respiratory acidosis did not up-regulate NHE3 expression. Analyses of the Nhe3 promoter region suggested that the regulatory elements sensitive to metabolic acidosis are located between -466 and -153 bp, where two consensus binding sites for SP1, a transcription factor up-regulated in metabolic acidosis, were localised. We conclude that metabolic acidosis induces Nhe3 promoter activation, which results in higher mRNA and total protein level. At the plasma membrane surface, NHE3 expression was increased in metabolic and respiratory acidosis alike, suggesting that low pH is responsible for NHE3 displacement to the cell surface.
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Affiliation(s)
- Pedro Henrique Imenez Silva
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 1524, sala 222, Cidade Universitária, São Paulo, SP, Brazil.
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Muthusamy S, Shukla S, Amin MR, Cheng M, Orenuga T, Dudeja PK, Malakooti J. PKCδ-dependent activation of ERK1/2 leads to upregulation of the human NHE2 transcriptional activity in intestinal epithelial cell line C2BBe1. Am J Physiol Gastrointest Liver Physiol 2012; 302:G317-25. [PMID: 22052014 PMCID: PMC3287399 DOI: 10.1152/ajpgi.00363.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The apical Na+/H+ exchanger (NHE) isoform NHE2 is involved in transepithelial Na+ absorption in the intestine. Our earlier studies have shown that mitogenic agent phorbol 12-myristate 13-acetate (PMA) induces the expression of NHE2 through activation of transcription factor early growth response-1 (Egr-1) and its interactions with the NHE2 promoter. However, the signaling pathways involved in transcriptional stimulation of NHE2 in response to PMA in the intestinal epithelial cells are not known. Chemical inhibitors and genetic approaches were used to investigate the signaling pathways responsible for the stimulation of NHE2 expression by PMA via Egr-1 induction. We show that, in response to PMA, PKCδ, a member of novel PKC isozymes, and MEK-ERK1/2 pathway of mitogen-activated protein kinases stimulate the NHE2 expression in C2BBe1 intestinal epithelial cells. PMA rapidly and transiently induced activation of PKCδ. Small inhibitory RNA-mediated knockdown of PKCδ blocked the stimulatory effect of PMA on the NHE2 promoter activity. In addition, blockade of PKCδ by rottlerin, a PKCδ-specific inhibitor, and ERK1/2 by U0126, a MEK-ERK inhibitor, abrogated PMA-induced Egr-1 expression. Immunofluorescence studies revealed that inhibition of ERK1/2 activation prevents translocation of PMA-induced Egr-1 into the nucleus. Consistent with these data, PMA-induced Egr-1 interaction with the NHE2 promoter region was prevented in nuclear extracts from U0126-pretreated cells. In conclusion, our data provide the first evidence that the stimulatory effect of PMA on NHE2 expression is mediated through the initial activation of PKCδ, subsequent PKCδ-dependent activation of MEK-ERK1/2 signaling pathway, and stimulation of Egr-1 expression. Furthermore, we show that transcription factor Egr-1 acts as an intermediate effector molecule that links the upstream signaling cues to the long-term stimulation of NHE2 expression by PMA in C2BBe1 cells.
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Affiliation(s)
- Saminathan Muthusamy
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Sagar Shukla
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Md. Ruhul Amin
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Ming Cheng
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Temitope Orenuga
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Pradeep K. Dudeja
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Jaleh Malakooti
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
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Xiao F, Juric M, Li J, Riederer B, Yeruva S, Singh AK, Zheng L, Glage S, Kollias G, Dudeja P, Tian DA, Xu G, Zhu J, Bachmann O, Seidler U. Loss of downregulated in adenoma (DRA) impairs mucosal HCO3(-) secretion in murine ileocolonic inflammation. Inflamm Bowel Dis 2012; 18:101-11. [PMID: 21557395 PMCID: PMC5426909 DOI: 10.1002/ibd.21744] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Accepted: 03/28/2011] [Indexed: 12/12/2022]
Abstract
BACKGROUND Ileocolonic luminal pH has been reported to be abnormally low in inflammatory bowel disease (IBD) patients, and one of the causative factors may be reduced epithelial HCO(3)(-) secretory rate (J(HCO3)(-)). Disturbances in J(HCO3)(-) may occur due to inflammation-induced changes in the crypt and villous architecture, or due to the effect of proinflammatory cytokines on epithelial ion transporters. METHODS To discriminate between these possibilities, the tumor necrosis factor alpha (TNF-α) overexpressing (TNF(+/ΔARE)) mouse model was chosen, which displays high proinflammatory cytokine levels in both ileum and colon, but develops only mild colonic histopathology and diarrhea. HCO(3)(-) secretion, mRNA expression, immunohistochemistry, and fluid absorptive capacity were measured in ileal and mid-colonic mucosa of TNF(+/ΔARE) and wildtype (WT) (TNF(+/+)) mice in Ussing chambers, and in anesthetized mice in vivo. RESULTS The high basal J(HCO3)(-) observed in WT ileal and mid-colonic mucosa were luminal Cl(-) -dependent and strongly decreased in TNF(+/ΔARE) mice. Downregulated in adenoma (DRA) mRNA and protein expression was strongly decreased in TNF(+/ΔARE) ileocolon, whereas cystic fibrosis transmembrane conductance regulator (CFTR), Na(+) /H(+) exchanger 3 (NHE3), Na(+) /HCO(3)(-) cotransporter (NBC), and epithelial sodium channel (ENaC) expression was not significantly altered. This indicates that the severe defect in ileocolonic J(HCO3)(-) was due to DRA downregulation. Fluid absorption was severely depressed in the ileum but only mildly affected in the mid-distal colon, preventing the development of overt diarrhea. CONCLUSIONS Even mild ileocolonic inflammation may result in a decrease of epithelial HCO(3)(-) secretion, which may contribute to alterations in surface pH, intestinal flora, and mucus barrier properties.
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Affiliation(s)
- Fang Xiao
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Marina Juric
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Junhua Li
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany,Department of Nephrology, Tongji Hospital, Huazhong University of Science & Technology, China
| | - Brigitte Riederer
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Sunil Yeruva
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Anurag Kumar Singh
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Lifei Zheng
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany,Department of Physiology, Capital Medical University, China
| | - Silke Glage
- Institute of Laboratory Animal Science, Hannover Medical School, Hannover, Germany
| | - George Kollias
- Biomedical Sciences Research Center Alexander Fleming, Greece
| | - Pradeep Dudeja
- Department of Medicine, University of Illinois, Champaign, Illinois
| | - De-An Tian
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science & Technology, China
| | - Gang Xu
- Department of Nephrology, Tongji Hospital, Huazhong University of Science & Technology, China
| | - Jinxia Zhu
- Department of Physiology, Capital Medical University, China
| | - Oliver Bachmann
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Ursula Seidler
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
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Abstract
Diarrhoea is a hallmark of intestinal inflammation. The mechanisms operating in acute inflammation of the intestine are well characterized and are related to regulatory changes induced by inflammatory mediators such as prostaglandins, cytokines or reactive oxygen species, along with leakage due to epithelial injury and changes in permeability. In chronic colitis, however, the mechanisms are less well known, but it is generally accepted that both secretory and absorptive processes are inhibited. These disturbances in ionic transport may be viewed as an adaptation to protracted inflammation of the intestine, since prolonged intense secretion may be physiologically unacceptable in the long term. Mechanistically, the changes in transport may be due to adjustments in the regulation of the different processes involved, to broader epithelial alterations or frank damage, or to modulation of the transportome in terms of expression. In the present review, we offer a summary of the existing evidence on the status of the transportome in chronic intestinal inflammation.
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Abstract
The epithelial apical membrane Na+/H+ exchangers [NHE (sodium hydrogen exchanger)2 and NHE3] and Cl-/HCO3- exchangers [DRA (down-regulated in adenoma) and PAT-1 (putative anion transporter 1)] are key luminal membrane transporters involved in electroneutral NaCl absorption in the mammalian intestine. During the last decade, there has been a surge of studies focusing on the short-term regulation of these electrolyte transporters, particularly for NHE3 regulation. However, the long-term regulation of the electrolyte transporters, involving transcriptional mechanisms and transcription factors that govern their basal regulation or dysregulation in diseased states, has only now started to unfold with the cloning and characterization of their gene promoters. The present review provides a detailed analysis of the core promoters of NHE2, NHE3, DRA and PAT-1 and outlines the transcription factors involved in their basal regulation as well as in response to both physiological (butyrate, protein kinases and probiotics) and pathophysiological (cytokines and high levels of serotonin) stimuli. The information available on the transcriptional regulation of the recently identified NHE8 isoform is also highlighted. Therefore the present review bridges a gap in our knowledge of the transcriptional mechanisms underlying the alterations in the gene expression of intestinal epithelial luminal membrane Na+ and Cl- transporters involved in electroneutral NaCl absorption. An understanding of the mechanisms of the modulation of gene expression of these transporters is important for a better assessment of the pathophysiology of diarrhoea associated with inflammatory and infectious diseases and may aid in designing better management protocols.
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Larmonier CB, Laubitz D, Thurston RD, Bucknam AL, Hill FM, Midura-Kiela M, Ramalingam R, Kiela PR, Ghishan FK. NHE3 modulates the severity of colitis in IL-10-deficient mice. Am J Physiol Gastrointest Liver Physiol 2011; 300:G998-G1009. [PMID: 21415416 PMCID: PMC3119112 DOI: 10.1152/ajpgi.00073.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
NHE3, the major intestinal Na(+)/H(+) exchanger, was shown to be downregulated and/or inhibited in patients with inflammatory bowel disease (IBD), a phenomenon believed to contribute to inflammation-associated diarrhea. NHE3(-/-) mice spontaneously develop colitis and demonstrate high susceptibility to dextran sulfate-induced mucosal injury. We investigated the effects of NHE3 deficiency on the development of chronic colitis in an IL-10 knockout (KO) mouse model of Crohn's disease. NHE3(-/-) mice were first backcrossed to 129/SvEv mice for >10 generations, with no apparent changes in their survival or phenotype. These mice were crossed with IL-10(-/-) mice on the same genetic background, and the phenotypes of 10-wk-old wild-type (WT), IL-10(-/-), NHE3(-/-), and IL-10(-/-)/NHE3(-/-) (double-KO) mice were studied. Histological and immunohistochemical examination of the colon established important architectural alterations, including increased neutrophilic and mononuclear cell infiltration in double- compared with single-KO mice. Double-KO mice demonstrated increased colonic expression of neutrophil collagenase matrix metalloproteinase-8 and the chemokines macrophage inflammatory protein-2, CXCL1, CXCL10, and CXCL11. Colonic IFNγ, IL-17, and IL-12/23 p40 protein secretion was significantly increased in double- compared with single-KO mice. IL-10(-/-)/NHE3(-/-) mouse colonic epithelium exhibited increased hallmarks of apoptosis, including a significantly increased number of cleaved caspase-3-positive surface epithelial cells. These results highlight the importance of NHE3 in the maintenance of intestinal barrier integrity and in modulating the inflammatory process in IL-10-deficient mice. Chronic NHE3 inhibition or underexpression observed in IBD may therefore contribute to the pathogenesis of IBD by influencing the extent of the epithelial barrier defect and affect the ultimate degree of inflammation.
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Affiliation(s)
- C. B. Larmonier
- 1Department of Pediatrics, Steele Children's Research Center,
| | - D. Laubitz
- 1Department of Pediatrics, Steele Children's Research Center, ,3Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - R. D. Thurston
- 1Department of Pediatrics, Steele Children's Research Center,
| | - A. L. Bucknam
- 2Department of Immunobiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - F. M. Hill
- 1Department of Pediatrics, Steele Children's Research Center,
| | - M. Midura-Kiela
- 1Department of Pediatrics, Steele Children's Research Center,
| | - R. Ramalingam
- 1Department of Pediatrics, Steele Children's Research Center,
| | - P. R. Kiela
- 1Department of Pediatrics, Steele Children's Research Center, ,2Department of Immunobiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - F. K. Ghishan
- 1Department of Pediatrics, Steele Children's Research Center,
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Queiroz-Leite GD, Peruzzetto MC, Neri EA, Rebouças NA. Transcriptional regulation of the Na⁺/H⁺ exchanger NHE3 by chronic exposure to angiotensin II in renal epithelial cells. Biochem Biophys Res Commun 2011; 409:470-6. [PMID: 21600882 DOI: 10.1016/j.bbrc.2011.05.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 05/04/2011] [Indexed: 11/27/2022]
Abstract
Angiotensin II (Ang II) exerts an acute bimodal effect on proximal tubule NHE3: while low doses stimulate the exchanger, high doses inhibit it. In the present study, we have investigated the chronic effects of Ang II on NHE3 expression and transcriptional regulation. Treatment of a tubular epithelial cell line, OKP, with Ang II 10(-11)M significantly increased NHE protein expression and mRNA levels, without evidence of bimodal effect. No change in mRNA half-life was detected, but transient transfection studies showed a significant increase in NHE3 promoter activity. Binding sites for Sp1/Egr-1 and AP2 transcription factors of the NHE3 proximal promoter were mutated and we observed that the Sp1/Egr-1 binding site integrity is necessary for Ang II stimulatory effects. Inhibition of cytochrome P450, PI3K, PKA and MAPK pathways prevented the Ang II stimulatory effect on the NHE3 promoter activity. Taking all the results together, our data reveal that chronic Ang II treatment exerts a stimulatory effect on NHE3 expression and promoter activity. The Ang II up-regulation of the NHE3 promoter activity appears to involve the Sp1/Egr-1 binding site and the interplay of several intracellular signaling pathways.
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Affiliation(s)
- Gabriella D Queiroz-Leite
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
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Neri EA, Bezerra CNA, Rebouças NA. Essential regulatory elements for NHE3 gene transcription in renal proximal tubule cells. Braz J Med Biol Res 2011; 44:514-23. [PMID: 21537610 DOI: 10.1590/s0100-879x2011007500054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Accepted: 04/11/2011] [Indexed: 11/21/2022] Open
Abstract
The objectives of the present study were to identify the cis-elements of the promoter absolutely required for the efficient rat NHE3 gene transcription and to locate positive and negative regulatory elements in the 5'-flanking sequence (5'FS), which might modulate the gene expression in proximal tubules, and to compare this result to those reported for intestinal cell lines. We analyzed the promoter activity of different 5'FS segments of the rat NHE3 gene, in the OKP renal proximal tubule cell line by measuring the activity of the reporter gene luciferase. Because the segment spanning the first 157 bp of 5'FS was the most active it was studied in more detail by sequential deletions, point mutations, and gel shift assays. The essential elements for gene transcription are in the region -85 to -33, where we can identify consensual binding sites for Sp1 and EGR-1, which are relevant to NHE3 gene basal transcription. Although a low level of transcription is still possible when the first 25 bp of the 5'FS are used as promoter, efficient transcription only occurs with 44 bp of 5'FS. There are negative regulatory elements in the segments spanning -1196 to -889 and -467 to -152, and positive enhancers between -889 and -479 bp of 5'FS. Transcription factors in the OKP cell nuclear extract efficiently bound to DNA elements of rat NHE3 promoter as demonstrated by gel shift assays, suggesting a high level of similarity between transcription factors of both species, including Sp1 and EGR-1.
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Affiliation(s)
- E A Neri
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brazil
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Horita S, Seki G, Yamada H, Suzuki M, Koike K, Fujita T. Insulin resistance, obesity, hypertension, and renal sodium transport. Int J Hypertens 2011; 2011:391762. [PMID: 21629870 PMCID: PMC3095959 DOI: 10.4061/2011/391762] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 02/16/2011] [Indexed: 12/12/2022] Open
Abstract
Sodium transport through various nephron segments is quite important in regulating sodium reabsorption and blood pressure. Among several regulators of this process, insulin acts on almost all the nephron segments and is a strong enhancer of sodium reabsorption. Sodium-proton exchanger type 3 (NHE3) is a main regulator of sodium reabsorption in the luminal side of proximal tubule. In the basolateral side of the proximal tubule, sodium-bicarbonate cotransporter (NBCe1) mediates sodium and bicarbonate exit from tubular cells. In the distal nephron and the connecting tubule, epithelial sodium channel (ENaC) is of great importance to sodium reabsorption. NHE3, NBCe1, and ENaC are all regulated by insulin. Recently with-no-lysine (WNK) kinases, responsible for familial hypertension, stimulating sodium reabsorption in the distal nephron, have been found to be also regulated by insulin. We will discuss the regulation of renal sodium transport by insulin and its roles in the pathogenesis of hypertension in insulin resistance.
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Affiliation(s)
- Shoko Horita
- Department of Internal Medicine, Faculty of Medicine, The University of Tokyo 7-3-1 Hongo, Bunkyo, Tokyo 113-8655, Japan
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Amin MR, Orenuga T, Tyagi S, Dudeja PK, Ramaswamy K, Malakooti J. Tumor necrosis factor-α represses the expression of NHE2 through NF-κB activation in intestinal epithelial cell model, C2BBe1. Inflamm Bowel Dis 2011; 17:720-31. [PMID: 20722069 PMCID: PMC2990806 DOI: 10.1002/ibd.21419] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 06/09/2010] [Indexed: 12/15/2022]
Abstract
BACKGROUND High levels of proinflammatory cytokines are linked to pathogenesis of diarrhea in inflammatory bowel disease (IBD). Na(+) absorption is compromised in IBD. The studies were designed to determine the effect of tumor necrosis factor-α (TNF-α) on the expression and activity of NHE2, a Na(+) /H(+) exchanger (NHE) that is involved in transepithelial Na(+) absorption in intestinal epithelial cells. METHODS NHE2 regulation was examined in TNF-α-treated C2BBe1 cells by reverse-transcription polymerase chain reaction (RT-PCR), reporter gene assays, and Western blot analysis. NHE isoform activities were measured as ethyl-isopropyl-amiloride- and HOE694-sensitive (22) Na-uptake. In vitro and in vivo protein-DNA interactions were assessed by gel mobility shift assays and chromatin immunoprecipitation studies. RESULTS TNF-α treatment of C2BBe1 cells led to repression of NHE2 promoter activity, mRNA, and protein levels; and inhibited both NHE2 and NHE3 mediated (22) Na-uptake. 5'-deletion analysis of the NHE2 promoter-reporter constructs identified basepair -621 to -471 as the TNF-α-responsive region (TNF-RE). TNF-α activated NF-κB subunits, p50 and p65, and their DNA-binding to a putative NF-κB motif within TNF-RE. Mutations in the NF-κB motif abolished NF-κB-DNA interactions and abrogated TNF-α-induced repression. Ectopic overexpression of NF-κB resulted in repression of NHE2 expression. Two functionally distinct inhibitors of NF-κB blocked the inhibitory effect of TNF-α. CONCLUSIONS The human NHE2 isoform is a direct target of transcription factor NF-κB. TNF-α-mediated activation of NF-κB decreases the expression and activity of NHE2 in the intestinal epithelial cell line, C2BBe1. These findings implicate NF-κB in the modulation of Na(+) absorption during intestinal inflammatory conditions such as IBD where a high level of TNF-α is detected.
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Affiliation(s)
- Md Ruhul Amin
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, USA
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Xu H, Zhang B, Li J, Chen H, Tooley J, Ghishan FK. Epidermal growth factor inhibits intestinal NHE8 expression via reducing its basal transcription. Am J Physiol Cell Physiol 2010; 299:C51-7. [PMID: 20375273 DOI: 10.1152/ajpcell.00081.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Sodium/hydrogen exchangers (NHEs) play a major role in Na(+) absorption, cell volume regulation, and intracellular pH regulation. Of the nine identified mammalian NHEs, three (NHE2, NHE3, and NHE8) are localized on the apical membrane of epithelial cells in the small intestine and the kidney. Although the regulation of NHE2 and NHE3 expression has been extensively studied in the past decade, little is known about the regulation of NHE8 gene expression under physiological conditions. The current studies were performed to explore the role of epidermal growth factor (EGF) on NHE8 expression during intestinal maturation. Brush-border membrane vesicles (BBMV) were isolated from intestinal epithelia, and Western blot analysis was performed to determine NHE8 protein expression of sucking male rats treated with EGF. Real-time PCR was used to quantitate NHE8 mRNA expression in rats and Caco-2 cells. Human NHE8 promoter activity was characterized through transfection of Caco-2 cells. Gel mobility shift assays (GMSAs) were used to identify the promoter sequences and the transcriptional factors involved in EGF-mediated regulation. Our results showed that intestinal NHE8 mRNA expression was decreased in EGF-treated rats and Caco-2 cells, and NHE8 protein abundance was also decreased in EGF-treated rats. The activity of the human NHE8 gene promoter transfected in Caco-2 cells was also reduced by EGF treatment. This could be explained by reduced binding of transcription factor Sp3 on the NHE8 basal promoter region in the presence of EGF. Pretreatment with MEK1/2 inhibitor UO-126 could prevent EGF-mediated inhibition of NHE8 gene expression. In conclusion, this study showed that EGF inhibits NHE8 gene expression through reducing its basal transcription, suggesting an important role of EGF in regulating NHE expression during intestinal maturation.
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Affiliation(s)
- Hua Xu
- University of Arizona Health Sciences Center, Tucson, Arizona 85724, USA
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Alex P, Ye M, Zachos NC, Sipes J, Nguyen T, Suhodrev M, Gonzales L, Arora Z, Zhang T, Centola M, Guggino SE, Li X. Clcn5 knockout mice exhibit novel immunomodulatory effects and are more susceptible to dextran sulfate sodium-induced colitis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 184:3988-96. [PMID: 20181886 PMCID: PMC4460988 DOI: 10.4049/jimmunol.0901657] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Although the intracellular Cl(-)/H(+) exchanger Clc-5 is expressed in apical intestinal endocytic compartments, its pathophysiological role in the gastrointestinal tract is unknown. In light of recent findings that CLC-5 is downregulated in active ulcerative colitis (UC), we tested the hypothesis that loss of CLC-5 modulates the immune response, thereby inducing susceptibility to UC. Acute dextran sulfate sodium (DSS) colitis was induced in Clcn5 knockout (KO) and wild-type (WT) mice. Colitis, monitored by disease activity index, histological activity index, and myeloperoxidase activity were significantly elevated in DSS-induced Clcn5 KO mice compared with those in WT mice. Comprehensive serum multiplex cytokine profiling demonstrated a heightened Th1-Th17 profile (increased TNF-alpha, IL-6, and IL-17) in DSS-induced Clcn5 KO mice compared with that in WT DSS colitis mice. Interestingly, Clcn5 KO mice maintained on a high vitamin D diet attenuated DSS-induced colitis. Immunofluorescence and Western blot analyses of colonic mucosa validated the systemic cytokine patterns and further revealed enhanced activation of the NF-kappaB pathway in DSS-induced Clcn5 KO mice compared with those in WT mice. Intriguingly, high baseline levels of IL-6 and phospho-IkappaB were observed in Clcn5 KO mice, suggesting a novel immunopathogenic role for the functional defects that result from the loss of Clc-5. Our studies demonstrate that the loss of Clc-5 1) exhibits IL-6-mediated immunopathogenesis, 2) significantly exacerbated DSS-induced colitis, which is influenced by dietary factors, including vitamin D, and 3) portrays distinct NF-kappaB-modulated Th1-Th17 immune dysregulation, implying a role for CLC-5 in the immunopathogenesis of UC.
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Affiliation(s)
- Philip Alex
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Mei Ye
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Department of Internal Medicine and Geriatrics, Zhongnan Hospital, Wuhan University, Wuhan, China
| | - Nicholas C. Zachos
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Jennifer Sipes
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Thuan Nguyen
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Maxim Suhodrev
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Liberty Gonzales
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Zubin Arora
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Ting Zhang
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Michael Centola
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Sandra E. Guggino
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Xuhang Li
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
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Zhang CZY, Chen GG, Lai PBS. Transcription factor ZBP-89 in cancer growth and apoptosis. Biochim Biophys Acta Rev Cancer 2010; 1806:36-41. [PMID: 20230874 DOI: 10.1016/j.bbcan.2010.03.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 02/25/2010] [Accepted: 03/08/2010] [Indexed: 11/30/2022]
Abstract
ZBP-89, a Krüppel-type zinc-finger transcription factor that binds to GC-rich sequences, is involved in the regulation of cell growth and cell death. It maps to chromosome 3q21 and is composed of 794 residues. Having bifunctional regulatory domains, ZBP-89 may function as a transcriptional activator or repressor of variety of genes such as p16 and vimentin. ZBP-89 arrests cell proliferation through its interactions with p53 and p21(waf1). It is able to stabilize p53 through directly binding and enhance p53 transcriptional activity by retaining it in the nucleus. In addition, ZBP-89 potentiates in butyrate-induced endogenous p21(waf1) up-regulation. ZBP-89 is usually over-expressed in human cancer cells, where it can efficiently induce apoptosis through p53-dependent and -independent mechanisms. Moreover, ZBP-89 is capable of enhancing killing effects of several anti-cancer drugs. Therefore, ZBP-89 may be served as a potential target in cancer therapy.
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Affiliation(s)
- Chris Z Y Zhang
- Department of Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, N.T., Hong Kong
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Mechanisms of the regulation of the intestinal Na+/H+ exchanger NHE3. J Biomed Biotechnol 2010; 2010:238080. [PMID: 20011065 PMCID: PMC2789519 DOI: 10.1155/2010/238080] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 09/11/2009] [Indexed: 01/25/2023] Open
Abstract
A major of Na+ absorptive process in the proximal part of intestine and kidney is electroneutral exchange of Na+ and H+ by Na+/H+ exchanger type 3 (NHE3). During the past decade, significant advance has been achieved in the mechanisms of NHE3 regulation. A bulk of the current knowledge on Na+/H+ exchanger regulation is based on heterologous expression of mammalian Na+/H+ exchangers in Na+/H+ exchanger deficient fibroblasts, renal epithelial, and intestinal epithelial cells. Based on the reductionist's approach, an understanding of NHE3 regulation has been greatly advanced. More recently, confirmations of in vitro studies have been made using animals deficient in one or more proteins but in some cases unexpected findings have emerged. The purpose of this paper is to provide a brief overview of recent progress in the regulation and functions of NHE3 present in the luminal membrane of the intestinal tract.
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Saksena S, Singla A, Goyal S, Katyal S, Bansal N, Gill RK, Alrefai WA, Ramaswamy K, Dudeja PK. Mechanisms of transcriptional modulation of the human anion exchanger SLC26A3 gene expression by IFN-{gamma}. Am J Physiol Gastrointest Liver Physiol 2010; 298:G159-66. [PMID: 19940027 PMCID: PMC2822505 DOI: 10.1152/ajpgi.00374.2009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Two members of the SLC26 gene family, SLC26A3 or DRA (downregulated in adenoma) and SLC26A6 (putative anion transporter 1, PAT1), are known to play a major role in apical Cl(-)/OH(-) (HCO(3)(-)) exchange process in the human intestine. We have previously shown the inhibitory effects of IFN-gamma (30 ng/ml, 24 h) on both SLC26A3 and A6 expression and promoter activity. We also demonstrated that the effects of IFN-gamma on SLC26A6 gene expression were mediated via IRF-1 transcription factor. However, the molecular mechanisms underlying the transcriptional modulation of SLC26A3 gene expression by IFN-gamma in the intestine are not known. The present studies were, therefore, designed to elucidate the signaling mechanisms and transcription factor(s) involved in mediating the inhibitory effects of IFN-gamma on DRA promoter (p--1183/+114) activity. Deletion analysis indicated that the IFN-gamma response element is located within the -1183 to -790 region, and sequence analysis of this region revealed the presence of potential gamma-activated site (GAS), a binding site (-933/-925 bp) for signal transducer and activator of transcription factor 1 (STAT1). Mutations in the potential GAS element abrogated the inhibitory effects of IFN-gamma. These studies provide evidence for the involvement of STAT1 in the inhibition of SLC26A3 gene expression by IFN-gamma in the human intestine.
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Affiliation(s)
- Seema Saksena
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Amika Singla
- 2Department of Physiology and Biophysics, University of Illinois at Chicago and
| | - Sonia Goyal
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and
| | - Shivani Katyal
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and
| | - Nikhil Bansal
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and
| | - Ravinder K. Gill
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and
| | - Waddah A. Alrefai
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and ,3Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Krishnamurthy Ramaswamy
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and ,3Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Pradeep K. Dudeja
- 1Section of Digestive Diseases and Nutrition, Department of Medicine and ,3Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
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49
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Kiela PR, Laubitz D, Larmonier CB, Midura-Kiela MT, Lipko MA, Janikashvili N, Bai A, Thurston R, Ghishan FK. Changes in mucosal homeostasis predispose NHE3 knockout mice to increased susceptibility to DSS-induced epithelial injury. Gastroenterology 2009; 137:965-75, 975.e1-10. [PMID: 19450596 PMCID: PMC3454522 DOI: 10.1053/j.gastro.2009.05.043] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 05/04/2009] [Accepted: 05/14/2009] [Indexed: 12/27/2022]
Abstract
BACKGROUND & AIMS NHE3 is a target of inhibition by proinflammatory cytokines and pathogenic bacteria, an event contributing to diarrhea in infectious and idiopathic colitis. In mice, NHE3 deficiency leads to mild diarrhea, increased intestinal expression of interferon (IFN)-gamma, and distal colitis, suggesting its role in epithelial barrier homeostasis. Our aim was to investigate the role of NHE3 in maintaining mucosal integrity. METHODS Control or dextran sulfate sodium (DSS)-treated, 6- to 8-week-old wild-type (WT) and NHE3(-/-) mice were used for the experiments. Small intestines were dissected for further analysis. RESULTS NHE3(-/-) mice have elevated numbers of CD8alpha(+) T and natural killer cells in the intraepithelial lymphocytes and lamina propria lymphocytes compartments, representing the source of IFN-gamma. NHE3(-/-) mice display alterations in epithelial gene and protein expression patterns that predispose them to a high susceptibility to DSS, with accelerated mortality resulting from intestinal bleeding, hypovolemic shock, and sepsis, even at a very low DSS concentration. Microarray analysis and intestinal hemorrhage indicate that NHE3 deficiency predisposes mice to DSS-induced small intestinal injury, a segment never reported as affected by DSS, and demonstrate major differences in the colonic response to DSS challenge in WT and NHE3(-/-) mice. In NHE3(-/-) mice, broad-spectrum oral antibiotics or anti-asialo GM1 antibodies reduce the expression of IFN-gamma and iNOS to basal levels and delay but do not prevent severe mortality in response to DSS treatment. CONCLUSIONS These results suggest that NHE3 participates in mucosal responses to epithelial damage, acting as a modifier gene determining the extent of the gut inflammatory responses in the face of intestinal injury.
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Affiliation(s)
- Pawel R. Kiela
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
- Department of Immunobiology, University of Arizona Health Sciences Center, 1656 E. Mabel Street, Tucson, Arizona, 85724
| | - Daniel Laubitz
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Claire B. Larmonier
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Monica T. Midura-Kiela
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Maciej A. Lipko
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Nona Janikashvili
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Aiping Bai
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Robert Thurston
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Fayez K. Ghishan
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
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50
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Amin MR, Ghannad L, Othman A, Gill RK, Dudeja PK, Ramaswamy K, Malakooti J. Transcriptional regulation of the human Na+/H+ exchanger NHE3 by serotonin in intestinal epithelial cells. Biochem Biophys Res Commun 2009; 382:620-5. [PMID: 19303862 DOI: 10.1016/j.bbrc.2009.03.087] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 03/14/2009] [Indexed: 11/15/2022]
Abstract
Serotonin (5-HT) decreases NHE2 and NHE3 activities under acute conditions in human intestinal epithelial cells. Here, we have investigated the effects of 5-HT on expression of the human NHE3 gene and the mechanisms underlying its transcriptional regulation in differentiated C2BBe1 cells. Treatment of the human intestinal epithelial cell line, C2BBe1, with 5-HT (20 microM) resulted in a significant decrease in NHE3 mRNA and protein expression. In transient transfection studies, 5-HT repressed the NHE3 promoter activity by approximately 55%. The repression of the NHE3 promoter activity in response to 5-HT was accompanied by reduced DNA-binding activity of transcription factors Sp1 and Sp3 to the NHE3 promoter without alteration in their nuclear levels. Pharmacological inhibitors of protein kinase C reversed the inhibitory effect of 5-HT on the promoter activity. Our data indicate that 5-HT suppresses the transcriptional activity of the NHE3 promoter and this effect may be mediated by PKCalpha and modulation of DNA-binding affinities of Sp1 and Sp3.
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Affiliation(s)
- Md Ruhul Amin
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
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