1
|
Osaki LH, Gama P. MAPKs and signal transduction in the control of gastrointestinal epithelial cell proliferation and differentiation. Int J Mol Sci 2013; 14:10143-61. [PMID: 23670595 PMCID: PMC3676833 DOI: 10.3390/ijms140510143] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/19/2013] [Accepted: 04/22/2013] [Indexed: 02/06/2023] Open
Abstract
Mitogen-activated protein kinase (MAPK) pathways are activated by several stimuli and transduce the signal inside cells, generating diverse responses including cell proliferation, differentiation, migration and apoptosis. Each MAPK cascade comprises a series of molecules, and regulation takes place at different levels. They communicate with each other and with additional pathways, creating a signaling network that is important for cell fate determination. In this review, we focus on ERK, JNK, p38 and ERK5, the major MAPKs, and their interactions with PI3K-Akt, TGFβ/Smad and Wnt/β-catenin pathways. More importantly, we describe how MAPKs regulate cell proliferation and differentiation in the rapidly renewing epithelia that lines the gastrointestinal tract and, finally, we highlight the recent findings on nutritional aspects that affect MAPK transduction cascades.
Collapse
Affiliation(s)
- Luciana H Osaki
- Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, SP 05508-000, Brazil.
| | | |
Collapse
|
2
|
Gagnon J, Anini Y. Insulin and norepinephrine regulate ghrelin secretion from a rat primary stomach cell culture. Endocrinology 2012; 153:3646-56. [PMID: 22691550 DOI: 10.1210/en.2012-1040] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Ghrelin is a peptide hormone primarily produced in the previously unidentified X/A endocrine cells of the stomach. Extensive studies have focused on the effects of ghrelin on growth hormone release and appetite regulation. However, the mechanisms regulating ghrelin secretion are less understood. In the present study, we developed a primary culture of newborn rat stomach cells to investigate the mechanisms regulating ghrelin synthesis and secretion. We demonstrated that this cell preparation secretes ghrelin in a regulated manner through the increase of cAMP, intracellular calcium, and activation of protein kinase C. Norepinephrine (NE) (0.1-10 μm) stimulated ghrelin secretion through the β1-adrenergic receptor via increased cAMP and protein kinase A activity, whereas acetylcholine had no effect. Because circulating ghrelin levels were previously shown to be inversely correlated with insulin levels, we investigated the effect of insulin on ghrelin secretion. We first demonstrated that ghrelin cells express the insulin receptor α- and β-subunits. Next, we determined that insulin (1-10 nm) inhibited both basal and NE-stimulated ghrelin secretion, caused an increase in phosphorylated serine-threonine kinase (AKT) and a reduction in intracellular cAMP, but did not alter proghrelin mRNA levels. The inhibitory effect of insulin was blocked by inhibiting phospho-inositol-3 kinase and AKT but not MAPK. Higher dose insulin (100 nm) did not suppress ghrelin secretion, which prompted the investigation of cellular insulin resistance by pretreating the cells with 100 nm insulin for 24 h. This caused a reduction in insulin receptor expression and prevented the insulin-mediated AKT activation and the suppression of ghrelin secretion with no impact on NE-stimulated ghrelin secretion. Our findings highlight the role of the sympathetic nervous system, insulin, and insulin resistance in the regulation of ghrelin secretion.
Collapse
Affiliation(s)
- Jeffrey Gagnon
- Department of Obstetrics, Faculty of Medicine,Dalhousie University, Halifax, Nova Scotia, Canada
| | | |
Collapse
|
3
|
Rubach M, Lang R, Seebach E, Somoza MM, Hofmann T, Somoza V. Multi-parametric approach to identify coffee components that regulate mechanisms of gastric acid secretion. Mol Nutr Food Res 2011; 56:325-35. [PMID: 22147653 DOI: 10.1002/mnfr.201100453] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 09/07/2011] [Accepted: 09/15/2011] [Indexed: 12/18/2022]
Abstract
SCOPE Chlorogenic acid (CA), caffeine (CAFF), pyrogallol (PYR), catechol (CAT), (β)N-alkanoyl-hydroxytryptamides (C5HT) and N-methylpyridinium (N-MP) were evaluated for their influence on mechanisms of gastric acid secretion as single compounds and in biomimetic mixtures. METHODS AND RESULTS Compounds were tested in coffee representative concentrations. Human gastric cancer cells (HGT-1) were used to study the proton secretory activity by Ussing chamber experiments and FACS analysis. For activation of EGFr, Akt1, ERK1/2, ATF-2 and cAMP levels, we performed pathway screening assays. Time-dependent expression of related genes were determined by real-time PCR. Part of the data was used for neural network modeling to identify the most relevant compounds. N-MP increased the expression of the anti-secretory somatostatin receptor by 114%, whereas C5HT decreased its expression by 52%. N-MP down-regulated the pro-secretory CHRM3 receptor by 36% and the H⁺,K⁺-ATPase by 36%. CAFF stimulated the secretory activity in the functional assays, whereas N-MP and CA decreased proton secretion. After applying a pathway analysis, we were able to discriminate between CAFF, CA, CAT, C5HT, PYR and histamine-activating EGFr signaling and N-MP-associated ERK1/2 signaling. CONCLUSION By applying a multi-parametric approach, N-MP was shown to effectively down-regulate mechanisms of gastric acid secretion in human parietal gastric cells.
Collapse
Affiliation(s)
- Malte Rubach
- German Research Center for Food Chemistry, Freising, Germany
| | | | | | | | | | | |
Collapse
|
4
|
Rubach M, Lang R, Skupin C, Hofmann T, Somoza V. Activity-guided fractionation to characterize a coffee beverage that effectively down-regulates mechanisms of gastric acid secretion as compared to regular coffee. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:4153-4161. [PMID: 20235536 DOI: 10.1021/jf904493f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In some individuals, the consumption of coffee beverages is related to symptoms of gastric irritation. Hot water steam-treatment of raw coffee beans is hypothesized to reduce the contents of stomach irritating compounds, and products to which this technology is applied are launched as stomach-friendly coffee. However, data on the effect of steam-treated coffee on gastric acid secretion are conflicting and it has not been proven yet as to which coffee components act as pro- or antisecretory stimulants. The work presented here aimed at the characterization of a coffee beverage that effectively down-regulates mechanisms of proton secretion in human gastric cells (HGT-1). At first, a regular coffee beverage was fractionated by using solvents of different polarity: water, ethylacetate, dichloromethane, and pentane. Functional assays on the proton secretory activity (PSA) of these solvent fractions revealed the least pronounced effect for the water fraction, for which quantitative analyses demonstrated the highest distribution of chlorogenic acid (95%), (beta)N-alkanoyl-5-hydroxytryptamides (55%), and N-methylpyridinium (N-MP, >99%) among all fractions. Following experiments demonstrated that HGT-1 cells treated with regular coffee fortified with N-MP at a concentration of about 20 mg/mL N-MP showed a significantly decreased PSA as compared to cells which were exposed to coffee beverages containing higher (32-34 mg/L) or lower (5 mg/L) N-MP concentrations. Results from cellular pathway analyses of transcription (ATF-1 and Akt1) and signaling (cAMP and EGFr) factors and kinases (ERK1/2), and experiments on the gene expression of pro (histamine-HRH2 and acetylcholine-CHRM3)- and anti (somatostatin-SSTR1)-secretory receptors and H(+),K(+)-ATPase verified this antisecretory activity of N-MP in coffee beverages.
Collapse
Affiliation(s)
- Malte Rubach
- German Research Center for Food Chemistry, Garching, Germany
| | | | | | | | | |
Collapse
|
5
|
Saha A, Hammond CE, Gooz M, Smolka AJ. The role of Sp1 in IL-1beta and H. pylori-mediated regulation of H,K-ATPase gene transcription. Am J Physiol Gastrointest Liver Physiol 2008; 295:G977-86. [PMID: 18772363 PMCID: PMC2584829 DOI: 10.1152/ajpgi.90338.2008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Helicobacter pylori infection of the gastric body induces transient hypochlorhydria and contributes to mucosal progression toward gastric carcinoma. Acid secretion is mediated by parietal cell H,K-ATPase, in which the catalytic alpha-subunit (HKalpha) promoter activity in transfected gastric epithelial [gastric adenocarcinoma (AGS)] cells is repressed by H. pylori through NF-kappaB p50 homodimer binding to the promoter. IL-1beta, an acid secretory inhibitor whose mucosal level is increased by H. pylori, upregulates HKalpha promoter activity in AGS cells. Because IL-1beta also activates NF-kappaB signaling, we investigated disparate HKalpha regulation by H. pylori and IL-1beta, testing the hypothesis that IL-1beta-induced HKalpha promoter activation is mediated by the transcription factor Sp1. DNase I footprinting revealed Sp1 binding to the HKalpha promoter at -56 to -39 bp. IL-1beta stimulated the activity of three HKalpha promoter constructs containing NF-kappaB and Sp1 sites transfected into AGS cells and also stimulated a construct containing only an Sp1 site. This stimulation was abrogated by mutating the HKalpha promoter Sp1 binding site. Gelshift assays showed that IL-1beta increased Sp1 but not p50 binding to cognate HKalpha probes and that Sp1 also interacts with an HKalpha NF-kappaB site when bound to its cognate HKalpha cis-response element. H. pylori did not augment Sp1 binding to an HKalpha Sp1 probe, and small interfering RNA-mediated knockdown of Sp1 expression abrogated IL-1beta-induced HKalpha promoter stimulation. We conclude that IL-1beta upregulates HKalpha gene transcription by inducing Sp1 binding to HKalpha Sp1 and NF-kappaB sites and that the H. pylori perturbation of HKalpha gene expression is independent of Sp1-mediated basal HKalpha transcription.
Collapse
Affiliation(s)
- Arindam Saha
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Charles E. Hammond
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Monika Gooz
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Adam J. Smolka
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| |
Collapse
|
6
|
Epithelial cell expression of BCL-2 family proteins predicts mechanisms that regulate Helicobacter pylori-induced pathology in the mouse stomach. J Transl Med 2008; 88:1227-44. [PMID: 18779780 PMCID: PMC2766781 DOI: 10.1038/labinvest.2008.84] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Corpus-predominant infection with Helicobacter pylori (HP) results in the activation of programmed cell death pathways in surface, parietal, and chief cells. At present, mechanisms that regulate these pathways to result in HP-associated pathology are not fully understood. Because it is not known which survival and death pathways are present in gastric epithelial cells, we used an antibody panel to evaluate the expression of BCL-2 family prosurvival proteins or multi-Bcl-2 homology (BH)-domains (group 1) or BH3-only (group-2) proapoptotic proteins in the stomachs of uninfected or HP-infected C57BL/6 mice. This strategy identified BCL-2, BAK, and BAD as the major prosurvival and proapoptotic proteins, in surface cells and BAD as the only BCL-2 family protein expressed in parietal cells. Chief cells express altogether different effectors, including BCL-X(L)/BCL-2, for survival but have no constitutively expressed proapoptotic proteins. In model chief cells, however, the group 1 proapoptotic protein BCL-X(S) was expressed after exposure to proinflammatory cytokines concomitant with reduced viability, demonstrating that chief cells can transcriptionally regulate the induction of proapoptotic proteins to execute apoptosis. During HP infection, no additional BCL-2 family proteins were expressed in epithelial cells, whereas those present either remained unchanged or were reduced as cell deletion occurred over time. Additional studies demonstrated that the posttranslational regulation of BAD in surface and parietal cells was negatively affected by HP infection, a result that may be directly related to an increase in apoptosis during infection. Thus, gastric epithelial cells express cell-specific prosurvival and proapoptotic pathways. From the results presented here, mechanisms that regulate HP-related changes in the survival and death profile of gastric epithelial cells can be predicted and then tested, with the ultimate goal of elucidating important therapeutic targets to inhibit the progression of HP-related pathology in the stomach.
Collapse
|
7
|
Rubach M, Lang R, Hofmann T, Somoza V. Time-dependent Component-specific Regulation of Gastric Acid Secretion-related Proteins by Roasted Coffee Constituents. Ann N Y Acad Sci 2008; 1126:310-4. [DOI: 10.1196/annals.1433.061] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
8
|
Mettler SE, Ghayouri S, Christensen GP, Forte JG. Modulatory role of phosphoinositide 3-kinase in gastric acid secretion. Am J Physiol Gastrointest Liver Physiol 2007; 293:G532-43. [PMID: 17569740 DOI: 10.1152/ajpgi.00138.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The gastric parietal cell is responsible for the secretion of HCl into the lumen of the stomach mainly due to stimulation by histamine via the cAMP pathway. However, the participation of several other receptors and pathways have been discovered to influence both stimulation and inhibition of acid secretion (e.g., cholinergic). Here we examine the role of phosphoinositide 3-kinase (PI3K) in the modulation of acid secretion. Treatment of isolated gastric glands and parietal cells with the PI3K inhibitor, LY294002 (LY), potentiated acid secretion in response to histamine to nearly the maximal secretion obtained with histamine plus phosphodiesterase inhibitors. As cAMP levels were elevated in response to histamine plus LY, but other means of elevating cAMP (e.g., forskolin, dbcAMP) were not influenced by LY, we posited that the effect might require activation of G-protein-coupled histamine H(2) receptors, possibly through the protein kinase B pathway (also known as Akt). Study of downstream effectors of PI3K showed that histaminergic stimulation increased Akt phosphorylation, which in turn was blocked by inhibition of PI3K. Expression studies showed that high expression of active Akt decreased acid secretion, whereas dominant-negative Akt increased acid secretion. Taken together, these data suggest stimulation with histamine increases the activity of PI3K leading to increased activity of Akt and decreased levels of cAMP in the parietal cell.
Collapse
Affiliation(s)
- S E Mettler
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720-3200, USA
| | | | | | | |
Collapse
|
9
|
Nitsche H, Ramamoorthy S, Sareban M, Pausawasdi N, Todisco A. Functional role of bone morphogenetic protein-4 in isolated canine parietal cells. Am J Physiol Gastrointest Liver Physiol 2007; 293:G607-14. [PMID: 17600042 DOI: 10.1152/ajpgi.00194.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Bone morphogenetic protein (BMP)-4 is an important regulator of cellular growth and differentiation. Expression of BMP-4 has been documented in the gastric mucosa. We reported that incubation of canine parietal cells with EGF for 72 h induced both parietal cell morphological transformation and inhibition of H(+)/K(+)-ATPase gene expression through MAPK-dependent mechanisms. We explored the role of BMP-4 in parietal cell maturation and differentiation. Moreover, we investigated if BMP-4 modulates the actions of EGF in parietal cells. H(+)/K(+)-ATPase gene expression was examined by Northern blots and quantitative RT-PCR. Acid production was assessed by measuring the uptake of [(14)C]aminopyrine. Parietal cell apoptosis was quantitated by Western blots with anti-cleaved caspase 3 antibodies and by counting the numbers of fragmented, propidium iodide-stained nuclei. MAPK activation and Smad1 phosphorylation were measured by Western blots with anti-phospho-MAPK and anti-phospho-Smad1 antibodies. Parietal cell morphology was examined by immunohistochemical staining of cells with anti-H(+)/K(+)-ATPase alpha-subunit antibodies. BMP-4 stimulated Smad1 phosphorylation and induced H(+)/K(+)-ATPase gene expression. BMP-4 attenuated EGF-mediated inhibition of H(+)/K(+)-ATPase gene expression and blocked EGF induction of both parietal cell morphological transformation and MAPK activation. Incubation of cells with BMP-4 enhanced histamine-stimulated [(14)C]aminopyrine uptake. BMP-4 had no effect on parietal cell apoptosis, whereas TGF-beta stimulated caspase-3 activation and nuclear fragmentation. In conclusion, BMP-4 promotes the induction and maintenance of a differentiated parietal cell phenotype. These findings may provide new clues for a better understanding of the mechanisms that regulate gastric epithelial cell growth and differentiation.
Collapse
Affiliation(s)
- Hildegard Nitsche
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI 48109-0682, USA
| | | | | | | | | |
Collapse
|
10
|
Watson SA, Grabowska AM, El-Zaatari M, Takhar A. Gastrin - active participant or bystander in gastric carcinogenesis? Nat Rev Cancer 2006; 6:936-46. [PMID: 17128210 DOI: 10.1038/nrc2014] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Gastrin is a pro-proliferative, anti-apoptotic hormone with a central role in acid secretion in the gastric mucosa and a long-standing association with malignant progression in transgenic mouse models. However, its exact role in human gastric malignancy requires further validation. Gastrin expression is tightly regulated by two closely associated hormones, somatostatin and gastrin-releasing peptide, and aspects of their interaction may be deregulated during progression to gastric adenocarcinoma. Furthermore, agonists and antagonists of the receptors for all three hormones have shown modest clinical efficacy against gastric adenocarcinoma, which might provide useful information on the future combined use of these agents.
Collapse
Affiliation(s)
- Susan A Watson
- Academic Unit of Cancer Studies, University of Nottingham, Nottingham, NG7 2UH, UK.
| | | | | | | |
Collapse
|
11
|
Ancha HR, Ancha HB, Tedesco DS, Ward AR, Harty RF. Inhibition of epidermal growth factor receptor activation enhances in vivo histamine-stimulated gastric acid secretion in the rat. Dig Dis Sci 2006; 51:274-81. [PMID: 16534669 DOI: 10.1007/s10620-006-3125-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Accepted: 05/16/2005] [Indexed: 12/09/2022]
Abstract
Epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) have been shown to inhibit gastric acid secretion through stimulation of the EGF receptor (EGFR). In this study we examined in vivo the effects of inhibition of the EGFR on histamine-stimulated acid secretion in the rat. Submaximal (1.5 mg/kg/hr) histamine-stimulated acid secretion was measured (microEq H(+)/2 hr) during infusion of EGFRtk inhibitors and ranitidine in anesthetized rats. EGFR phosphorylation in gastric mucosal tissue lysates was measured by Western blot analysis. Submaximal histamine-stimulated acid secretion was increased significantly by the EGFR inhibitors tyrphostin (Tyr) A46 and Tyr AG1478. Tyr A46 prevented TGFalpha (10 microg/kg/hr)-mediated inhibition of maximal (5.0 microg/kg/hr) histamine-stimulated acid output. Histamine caused a fourfold increase in EGFR phosphorylation which was inhibited by both Tyr and ranitidine. We conclude that the EGFRtk inhibitors, Tyr A46 and Tyr AG1478, significantly increased submaximal histamine-stimulated acid output and Tyr A46 prevented TGFalpha inhibition of histamine-stimulated acid secretion. These observations suggest that the EGFR is involved, in vivo, in the regulation of gastric acid secretion.
Collapse
Affiliation(s)
- Hanumantha R Ancha
- Section of Gastroenterology, Department of Internal Medicine, University of Oklahoma Health Sciences Center and Oklahoma City VA Medical Center, Oklahoma City, 73126, USA
| | | | | | | | | |
Collapse
|
12
|
Stepan V, Ramamoorthy S, Nitsche H, Zavros Y, Merchant JL, Todisco A. Regulation and function of the sonic hedgehog signal transduction pathway in isolated gastric parietal cells. J Biol Chem 2005; 280:15700-8. [PMID: 15691835 DOI: 10.1074/jbc.m413037200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Shh (Sonic hedgehog) regulates gastric epithelial cell differentiation. We reported that incubation of purified canine parietal cells with epidermal growth factor (EGF) for 6-16 h, stimulates H(+)/K(+)-ATPase alpha-subunit gene expression through the activation of Akt. We explored if Shh mediates some of the actions of EGF in the parietal cells. EGF induced a 6-fold increase in Shh expression, measured by Western blots, after 5 h of incubation. This effect was inhibited by both the phosphatidylinositol 3-kinase inhibitor LY294002 and by transduction of the cells with an adenoviral vector expressing dominant negative Akt. EGF stimulated the release of Shh-like immunoreactivity from the parietal cells, after 16 h of incubation. Shh induced H(+)/K(+)-ATPase alpha-subunit gene expression, assessed by Northern blots, it stimulated a luciferase reporter plasmid containing the EGF-responsive sequence (ERE) of the canine H(+)/K(+)-ATPase alpha-subunit gene promoter, and it induced parietal cell nuclear protein binding to the ERE. Gli transcription factors mediate the intracellular actions of Shh. Co-transfection of the parietal cells with the H(+)/K(+)-luc plasmid together with one expressing Gli2, induced H(+)/K(+)-luciferase activity 5-fold, whereas co-transfection of the cells with the H(+)/K(+)-luc plasmid together with one expressing dominant negative Gli2, inhibited EGF induction of H(+)/K(+)-luciferase activity. Identical results were observed in the presence of the Shh signal transduction pathway inhibitor, cyclopamine. Transfection of the cells with dominant negative Akt inhibited EGF, but not Shh stimulation of H(+)/K(+)-ATPase-luciferase activity. Thus, EGF but not Shh signals through Akt. Preincubation of the cells for 16 h with either Shh or EGF enhanced histamine-stimulated [(14)C]aminopyrine uptake by 50%. In conclusions, some of the actions of EGF in the parietal cells are mediated by the sequential activation of the Akt and the Shh signal transduction pathways. These effects might represent novel mechanisms mediating the actions of growth factors on gastric epithelial cell differentiation.
Collapse
Affiliation(s)
- Vinzenz Stepan
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA
| | | | | | | | | | | |
Collapse
|
13
|
Stepan V, Pausawasdi N, Ramamoorthy S, Todisco A. The Akt and MAPK signal-transduction pathways regulate growth factor actions in isolated gastric parietal cells. Gastroenterology 2004; 127:1150-61. [PMID: 15480993 DOI: 10.1053/j.gastro.2004.06.059] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Incubation of purified (>95%) canine parietal cells in primary culture with epidermal growth factor for 7-16 hours stimulates H(+)K(+)-adenosine triphosphatase gene expression. In this study, we examined the effect of prolonged stimulation (72 hours) of the parietal cells with epidermal growth factor. METHODS H(+)K(+)-adenosine triphosphatase protein and gene expression were assessed by immunohistochemistry and Northern blots. Mitogen-activated protein kinase and Akt activation were quantitated by kinase assays and Western blots with specific antiphospho antibodies. Akt overexpression was achieved by adenovirus-mediated gene transfer of a constitutively active Akt gene. RESULTS Epidermal growth factor changed the morphology of the cultured cells, which acquired the appearance of fusiform cells, and it inhibited H(+)K(+)-adenosine triphosphatase gene expression. Staining of the cells both with anti-H(+)K(+)-adenosine triphosphatase antibodies and with Texas Red-labeled Dolichos biflorus lectin confirmed that the fusiform cells expressed markers of parietal cell differentiation. Epidermal growth factor stimulated mitogen-activated protein kinase with 2 peaks of activation, observed after 5 minutes and 72 hours, whereas it activated Akt after 5 minutes but not 72 hours of incubation. Overexpression of Akt blocked both epidermal growth factor-induced morphological transformation and inhibition of H + K + -adenosine triphosphatase gene expression. Identical results were observed in the presence of the mitogen-activated protein kinase inhibitor PD98059. CONCLUSIONS Activation of the Akt signal-transduction pathway seems to be a crucial event for the induction of parietal cell maturation and differentiation.
Collapse
Affiliation(s)
- Vinzenz Stepan
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor 48109-0682, USA
| | | | | | | |
Collapse
|
14
|
Xin X, Hou YT, Li L, Schmiedlin-Ren P, Christman GM, Cheng HL, Bitar KN, Zimmermann EM. IGF-I increases IGFBP-5 and collagen alpha1(I) mRNAs by the MAPK pathway in rat intestinal smooth muscle cells. Am J Physiol Gastrointest Liver Physiol 2004; 286:G777-83. [PMID: 15068962 DOI: 10.1152/ajpgi.00293.2003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
IGF-I is a potent fibrogenic growth factor that stimulates proliferation of intestinal smooth muscle cells and increases synthesis of collagen and IGF-I-binding proteins by the cells. These processes contribute to intestinal fibrosis that develops in patients with Crohn's disease and in Lewis-strain rats with experimental Crohn's disease. The aim of this study was to determine which early docking proteins are associated with IGF-I receptor signal transduction and which transduction pathway is involved in IGF-I-mediated gene regulation in intestinal smooth muscle cells. Primary cultures of smooth muscle cells isolated from the muscularis externa of the distal colon of Lewis rats were treated with IGF-I (100 ng/ml). Immunoprecipitation studies demonstrated that IGF-I stimulation resulted in tyrosine phosphorylation of IRS-1, IRS-2, and Shc. Coimmunoprecipitation demonstrated a close association between the IGF-I receptor and these three early docking proteins. Concurrent treatment with the MAPK inhibitor PD98059 (10 microM) resulted in an inhibition of the IGF-I-mediated increase in IGFBP-5 and collagen alpha(1)(I) mRNAs, while concurrent treatment with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin (100 nM) had no effect. In additional experiments, cells were transiently transfected with adenoviral vectors dominantly expressing inactive mutant Akt or constitutively expressing wild-type Akt. In both cases, the IGF-I-mediated increase in collagen I protein did not differ from that observed in control cultures that had been transfected with an adenoviral vector carrying the LacZ reporter gene. These results suggest that the MAPK pathway is key to IGF-I-mediated gene regulation in intestinal smooth muscle cells, whereas data do not suggest a role for the Akt-dependent pathway in our system.
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport/metabolism
- Animals
- Cells, Cultured
- Collagen Type I/genetics
- Collagen Type I/metabolism
- Crohn Disease/metabolism
- Crohn Disease/pathology
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Female
- Flavonoids/pharmacology
- Insulin Receptor Substrate Proteins
- Insulin-Like Growth Factor Binding Protein 5/genetics
- Insulin-Like Growth Factor Binding Protein 5/metabolism
- Insulin-Like Growth Factor I/administration & dosage
- Insulin-Like Growth Factor I/pharmacology
- Insulin-Like Growth Factor I/physiology
- Intestinal Mucosa/metabolism
- Intestines/drug effects
- Intracellular Signaling Peptides and Proteins
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Mitogen-Activated Protein Kinases/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Phosphoproteins/metabolism
- Phosphorylation/drug effects
- RNA, Messenger/antagonists & inhibitors
- RNA, Messenger/metabolism
- Rats
- Rats, Inbred Lew
- Receptor, IGF Type 1/metabolism
- Shc Signaling Adaptor Proteins
- Src Homology 2 Domain-Containing, Transforming Protein 1
- Time Factors
- Tyrosine/metabolism
Collapse
Affiliation(s)
- Xiping Xin
- Univ. of Michigan Medical School, Rm. 6520 MSRB I, 1150 West Medical Center Dr., Ann Arbor, MI 48109-0682, USA
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
Acid secretion by the gastric parietal cell is regulated by paracrine, endocrine, and neural pathways. The physiological stimuli include histamine, acetylcholine, and gastrin via their receptors located on the basolateral plasma membranes. Stimulation of acid secretion typically involves an initial elevation of intracellular calcium and/or cAMP followed by activation of a cAMP-dependent protein kinase cascade that triggers the translocation and insertion of the proton pump enzyme, H,K-ATPase, into the apical plasma membrane of parietal cells. Whereas the H,K-ATPase contains a plasma membrane targeting motif, the stimulation-mediated relocation of the H,K-ATPase from the cytoplasmic membrane compartment to the apical plasma membrane is mediated by a SNARE protein complex and its regulatory proteins. This review summarizes the progress made toward an understanding of the cell biology of gastric acid secretion. In particular we have reviewed the early signaling events following histaminergic and cholinergic activation, the identification of multiple factors participating in the trafficking and recycling of the proton pump, and the role of the cytoskeleton in supporting the apical pole remodeling, which appears to be necessary for active acid secretion by the parietal cell. Emphasis is placed on identifying protein factors that serve as effectors for the mechanistic changes associated with cellular activation and the secretory response.
Collapse
Affiliation(s)
- Xuebiao Yao
- Department of Molecular and Cell Biology University of California, Berkeley, California 94720, USA.
| | | |
Collapse
|
16
|
Abstract
Overlapping neural, hormonal, and paracrine pathways finely regulate gastric acid secretion. In rats and guinea pigs, most of the intrinsic neural innervation to the gastric mucosa originates in the myenteric plexus. In contrast, human stomachs have a clearly defined submucosal plexus that contains a variety of transmitters including nitric oxide, vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP), substance P, and calcitonin gene-related peptide (CGRP). Although GRP is known to participate in meal-stimulated acid secretion by releasing gastrin in a variety of laboratory animals, recent studies were unable to demonstrate a role for endogenous GRP in meal-stimulated gastrin secretion in humans. Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin-glucagon-VIP family, has been localized to gastric mucosal neurons and may participate in vagally mediated acid secretion. Two novel peptides, ghrelin and leptin, have been localized to the stomach. Peripheral administration of ghrelin stimulates and of leptin inhibits acid secretion. The binding of secretagogues to parietal cells generates changes in second messengers that regulate the translocation and activation of the proton pump, HK-ATPase. In resting cells, HK-ATPase is contained within cytoplasmic tubulovesicles in an inactive form. At stimulation, the tubulovesicles fuse with the apical canaliculi and the HK-ATPase is incorporated into the apical membrane where it actively pumps H ions in exchange for K. Acute infection with Helicobacter pylori results in hypochlorhydria, whereas chronic infection can cause either hypo- or hyperchlorhydria, depending on the distribution of the infection and the degree of corpus gastritis. Recent studies suggest that inflammatory cytokines, produced in response to the organism, can play a role in the perturbations in acid and gastrin secretion induced by H. pylori.
Collapse
Affiliation(s)
- Mitchell L Schubert
- Department of Medicine, Division of Gastroenterology, Medical College of Virginia and McGuire VAMC Richmond, Virginia 23249, USA.
| |
Collapse
|
17
|
Pausawasdi N, Ramamoorthy S, Crofford LJ, Askari FK, Todisco A. Regulation and function of COX-2 gene expression in isolated gastric parietal cells. Am J Physiol Gastrointest Liver Physiol 2002; 282:G1069-78. [PMID: 12016133 DOI: 10.1152/ajpgi.00164.2001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We examined expression, function, and regulation of the cyclooxygenase (COX)-2 gene in gastric parietal cells. COX-2-specific mRNA was isolated from purified (>95%) canine gastric parietal cells in primary culture and measured by Northern blots using a human COX-2 cDNA probe. Carbachol was the most potent inducer of COX-2 gene expression. Gastrin and histamine exhibited minor stimulatory effects. Carbachol-stimulated expression was inhibited by intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM (90%), protein kinase C (PKC) inhibitor GF-109203X (48%), and p38 kinase inhibitor SB-203580 (48%). Nuclear factor (NF)-kappaB inhibitor 1-pyrrolidinecarbodithioic acid inhibited carbachol-stimulated expression by 80%. Similar results were observed in the presence of adenoviral vector Ad.dom.neg.IkappaB, which expresses a repressor of NF-kappaB. Addition of SB-203580 with Ad.dom.neg.IkappaB almost completely blocked carbachol stimulation of COX-2 gene expression. We examined the effect of carbachol on PGE(2) release by enzyme-linked immunoassay. Carbachol induced PGE(2) release. Ad.dom.neg.IkappaB, alone or with SB-203580, produced, respectively, partial (70%) and almost complete (>80%) inhibition of carbachol-stimulated PGE(2) production. Selective COX-2 inhibitor NS-398 blocked carbachol-stimulated PGE(2) release without affecting basal PGE(2) production. In contrast, indomethacin inhibited both basal and carbachol-stimulated PGE(2) release. Carbachol induces COX-2 gene expression in the parietal cells through signaling pathways that involve intracellular Ca(2+), PKC, p38 kinase, and activation of NF-kappaB. The functional significance of these effects seems to be stimulation of PGE(2) release.
Collapse
Affiliation(s)
- Nonthalee Pausawasdi
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 47109-0682, USA
| | | | | | | | | |
Collapse
|