Proteins In Intestinal Epithelial Cells Research Articles

Effect of corticotropin-releasing factor on expression of tight junction proteins in intestinal epithelial cells

Effect of corticotropin-releasing factor on expression of tight junction proteins in intestinal epithelial cells

Changes in the intestinal microenvironment during development of alcoholic fatty liver disease and related effects of probiotic therapy

To investigate the initial changes in the gut microenvironment that accompany intestinal endotoxemia related to alcoholic fatty liver disease (ALD) in order to explore the potential initiating factors and to observe the effect of probiotic therapy on these factors. Fifty Sprague-Dawley male rats were randomly divided into an ALD model group (alcoholic intragastric administration), an intervention group (ALD with probiotic intragastric administration), and a control group (physiological saline intragastric administration). Histological changes of the liver were evaluated using hematoxylin-eosin staining and light microscopy. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and triglycerides (TG), and plasma endotoxin and coli bacillus were determined. The structural integrity of intestinal mucosa and tight junctions were observed by transmission electron microscopy. Occludin protein expression in intestinal epithelial cells was detected by immunohistochemistry. After four weeks, the three groups showed significant differences in the plasma endotoxin levels [control: (0.67+/-0.14) pg/ml, model: (4.42+/-1.28) pg/ml, and intervention: (2.88+/-0.83) pg/ml; F = 27.288, P = 0.000] and numbers of Escherichia coli [control: (2.31+/-0.39) lg3/ml, model: (3.23+/-0.41) lg3/ml, and intervention: (2.24+/-0.44) lg3/ml; F = 10.692, P = 0.001]. The plasma endotoxin level and E. coli number were significantly higher in the model group than in the control group and the intervention group (all P less than 0.05). The three groups showed no significant differences in the levels of ALT, AST, and TG at four weeks. After eight weeks, however, all three serum markers were significantly different between the three groups [ALT: control: (62.33+/-7.12) U/L, model: (95.50+/-8.73) U/L, and intervention: (81.33+/-6.19) U/L; F = 18.051, P = 0.000]; [AST: control: (90.50+/-10.67) U/L, model: (130.00+/-14.91) U/L, and intervention: (110.33+/-7.26) U/L; F = 30.170, P = 0.000]; [TG: control: (0.84+/-0.84) mmol/L, model: (1.40+/-0.17) mmol/L, and intervention: (1.10+/-0.17) mmol/L; F = 10.592, P = 0.001]. In addition, the three groups showed significant differences in E. coli number [control: (2.23+/-0.46) lg3/ml, model: (4.81+/-0.29) lg3/ml, and intervention: (3.61+/-0.50) lg3/ml; F = 23.579, P = 0.000] and plasma endotoxin level [control: (0.52+/-0.21) pg/ml, model: (12.46+/-2.61) pg/ml, intervention: (6.83+/-1.74) pg/ml; F = 30.731, P = 0.000]. The levels of ALT, AST, TG and endotoxin, and the number of E. coli were all significantly higher in the model group than in the control group and the intervention group (all P less than 0.05). Small intestinal epithelial cell structural failure was more apparent and intercellular gaps more broad after eight weeks than after four weeks for all three groups. However, the intervention group showed clearer cell connection structures and less extensive cell gap broadening than the model group at eight weeks. After eight weeks, the occludin protein had become significantly down-regulated and distributed in a non-continuous pattern in the model group, as compared with the control group. However, the occludin protein expression was higher in intervention group than in the model group. Intestinal endotoxemia related to perturbations in the microenvironment occurs in the early phase of ALD, and the increased intestinal permeability appears to be the initial factor of elevated plasma endotoxin, which may lead to liver damage. Probiotic therapy can reduced plasma endotoxin levels and postpone ALD progression by altering the composition of the gut microbiota and up-regulating expression of the occludin protein in intestinal epithelial cells.

High-tailing it to the apical surface. Focus on “Apical targeting of the P2Y4 receptor is directed by hydrophobic and basic residues in the cytoplasmic tail”

epithelial cell function requires the generation and maintenance of polarized apical and basolateral membrane domains with distinct protein and lipid compositions. This asymmetry in membrane composition is essential for myriad cell functions that include substratum adhesion, cell-cell communication

A novel role of intestine epithelial GABAergic signaling in regulating intestinal fluid secretion

γ-Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system, and it is produced via the enzymatic activity of glutamic acid decarboxylase (GAD). GABA generates fast biological signaling through type A receptors (GABA(A)R), an anionic channel. Intriguingly, GABA is found in the jejunum epithelium of rats. The present study intended to determine whether a functional GABA signaling system exists in the intestinal epithelium and if so whether the GABA signaling regulates intestinal epithelial functions. RT-PCR, Western blot, and immunohistochemical assays of small intestinal tissues of various species were performed to determine the expression of GABA-signaling proteins in intestinal epithelial cells. Perforated patch-clamp recording was used to measure GABA-induced transmembrane current in the small intestine epithelial cell line IEC-18. The fluid weight-to-intestine length ratio was measured in mice that were treated with GABA(A)R agonist and antagonist. The effect of GABA(A)R antagonist on allergic diarrhea was examined using a mouse model. GABA, GAD, and GABA(A)R subunits were identified in small intestine epithelial cells of mice, rats, pigs, and humans. GABA(A)R agonist induced an inward current and depolarized IEC-18. Both GABA and the GABA(A)R agonist muscimol increased intestinal fluid secretion of rats. The increased intestinal secretion was largely decreased by the GABA(A)R antagonist picrotoxin or gabazine, but not by tetrodotoxin. The expression levels of GABA-signaling proteins were increased in the intestinal epithelium of mice that were sensitized and challenged with ovalbumin (OVA). The OVA-treated mice exhibited diarrhea, which was alleviated by oral administration of gabazine or picrotoxin. An endogenous autocrine GABAergic signaling exists in the mammalian intestinal epithelium, which upregulates intestinal fluid secretion. The intestinal GABAergic signaling becomes intensified in allergic diarrhea, and inhibition of this GABA-signal system alleviates the allergic diarrhea.

630 Expression of C/EBP Homologous Protein in Intestinal Epithelial Cells is Not Associated With the Development of Chronic Inflammation: A Transgenic Approach

630 Expression of C/EBP Homologous Protein in Intestinal Epithelial Cells is Not Associated With the Development of Chronic Inflammation: A Transgenic Approach

Proteomic analysis of Trichinella spiralis proteins in intestinal epithelial cells after culture with their larvae by shotgun LC–MS/MS approach

Although it has been known for many years that Trichinella spiralis initiates infection by invading intestinal epithelium, the mechanisms by which the parasite invades the intestinal epithelium are unknown. The purpose of this study was to screen the invasion-related proteins among the increased proteins of intestinal epithelial cells after culture with T. spiralis and to study their molecular functions. The proteins of HCT-8 cells which cultured with T. spiralis infective larvae were analyzed by SDS-PAGE and Western blot. Results showed that compared with proteins of normal HCT-8 cells, four additional protein bands (115, 61, 35 and 24 kDa) of HCT-8 cells cultured with the infective larvae were recognized by sera of the mice infected with T. spiralis, which may be the invasion-related proteins released by the infective larvae. Three bands (61, 35 and 24 kDa) were studied employing shotgun LC-MS/MS. Total 64 proteins of T. spiralis were identified from T. spiralis protein database by using SEQUEST searches, of which 43 (67.2%) proteins were distributed in a range of 10-70 kDa, and 26 proteins (40.6%) were in the range of pI 5-6. Fifty-four proteins were annotated according to Gene Ontology Annotation in terms of molecular function, biological process, and cellular localization. Out of 54 annotated proteins, 43 proteins (79.6%) had binding activity and 23 proteins (42.6%) had catalytic activity (e.g. hydrolase, transferase, etc.), which might be related to the invasion of intestinal epithelial cells by T. spiralis. The protein profile provides a valuable basis for further studies of the invasion-related proteins of T. spiralis.

Luminal-Applied Flagellin Is Internalized by Polarized Intestinal Epithelial Cells and Elicits Immune Responses via the TLR5 Dependent Mechanism

Bacteria release flagellin that elicits innate responses via Toll-like receptor 5 (TLR5). Here, we investigated the fate of apically administrated full length flagellin from virulent and avirulent bacteria, along with truncated recombinant flagellin proteins in intestinal epithelial cells and cellular responses. Flagellin was internalized by intestinal epithelial cell (IEC) monolayers of IEC-18. Additionally, apically applied flagellin was internalized by polarized human Caco-2BBe and T-84 cells in a TLR5 dependent mechanism. More, flagellin exposure did not affect the integrity of intestinal monolayers. With immunofluorescent staining, internalized flagellin was detected in both early endosomes as well as lysosomes. We found that apical exposure of polarized Caco-2BBe and T-84 to flagellin from purified Salmonella, Escherichia coli O83:H1 (isolate from Crohn’s lesion) or avirulent E. coli K12 induced comparable levels of basolateral IL-8 secretion. A recombinant protein representing the conserved amino (N) and carboxyl (C) domains (D) of the flagellin protein (ND1/2ECHCD2/1) induced IL-8 secretion from IEC similar to levels elicited by full-length flagellins. However, a recombinant flagellin protein containing only the D3 hypervariable region elicited no IL-8 secretion in both cell lines compared to un-stimulated controls. Silencing or blocking TLR5 in Caco-2BBe cells resulted in a lack of flagellin internalization and decreased IL-8 secretion. Furthermore, apical exposure to flagellin stimulated transepithelial migration of neutrophils and dendritic cells. The novel findings in this study show that luminal-applied flagellin is internalized by normal IEC via TLR5 and co-localizes to endosomal and lysosomal compartments where it is likely degraded as flagellin was not detected on the basolateral side of IEC cultures.

Abstract 5324: Ablation of IL-17A abrogates progression of spontaneous intestinal tumorigenesis

Abstract The intestinal tract is subject to constant stimulation of immune cells and intestinal epithelial cells either by noninfectious antigens or infection. Recent studies identified the role of IL-17A in chronic inflammation in intestinal epithelium. Yet the intrinsic role of endogenous IL-17A in spontaneous intestinal tumorigenesis has not been addressed previously. Ablation of IL-17A significantly reduced tumor development in mice bearing a heterozygote mutation in the APC (adenomatous polyposis coli) gene (ApcMin/+ mice). There was a marked decrease in IL-6 and IL-23 (p19), as well as a decrease in IL-1β, suggesting that the inflammatory microenvironment was significantly changed by ablating IL-17A. We also found a significant decrease in CD44 and proinflammatory mediators such as KC (Keratinocyte Chemoattractant) and Cox-2. There was also a reduced infiltration of lymphocytes including T cells and preservation of intestinal architecture and the presence of APC protein in intestinal epithelial cells in IL-17AKO ApcMin/+ mice. Interestingly, IL-17A ablation also corrected immunological abnormalities such as splenomegaly and thymic atrophy in ApcMin/+ mice. We tested whether CD4 T cells from ApcMin/+ mice are more proliferative based on its role as a tumor suppressor gene, thereby regulating cell cycle. We observed that CD4 T cells from ApcMin/+ mice were hyperproliferative when compared with their wildtype littermate controls upon TcR (T cell receptor) stimulation. This hyperproliferation was more obvious following stronger stimulation through the TcR. Next, we tested whether the effector CD4 T cells are more refractory to regulatory T cell (Treg)-mediated suppression. Upon co-culture with wildtype Treg cells, ApcMin/+ CD4 effector T cells were more resistant to Treg-mediated suppression especially at a high ratio of effectors to Treg, suggesting that the suppression on ApcMin/+ CD4 effector T cells are not as efficient as for wildtype CD4 effector T cells. Finally, these CD4 T cells from ApcMin/+ mice induced colitis in immunodeficient mice upon adoptive transfer, while the ablation of IL-17A in CD4 T cells in ApcMin/+ mice (IL-17A KO ApcMin/+ mice) completely abolished this pathogenic potential in vivo, clearly showing that ablation of IL-17A abrogated hyperproliferation and colitogenic potential in immunodeficient mice. This was consistent with our observation of the phenotypic changes in intestinal tumorigenesis. Taken together, our results suggest an important proinflammatory role of IL-17A and its correction of immune abnormalities in spontaneous intestinal tumorigenesis. We demonstrate altered CD4 T cell functions from ApcMin/+ mice which favors intestinal tumorigenesis and the ablation of IL-17A can abolish these altered function, suggesting the importance of T-cell mediated IL-17A in spontaneous intestinal tumorigenesis Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5324.

Ablation of IL-17A abrogates progression of spontaneous intestinal tumorigenesis

The intrinsic role of endogenous IL-17A in spontaneous intestinal tumorigenesis has not been addressed previously to our knowledge. Ablation of IL-17A significantly reduced tumor development in mice bearing a heterozygote mutation in the adenomatous polyposis coli (APC) gene (Apc(Min/+) mice). There was also a decrease in inflammatory cytokines and proinflammatory mediators, reduced infiltration of lymphocytes including T cells, and preservation of intestinal architecture and the presence of APC protein in intestinal epithelial cells. Interestingly, IL-17A ablation also corrected immunological abnormalities such as splenomegaly and thymic atrophy in Apc(Min/+) mice. CD4 T cells from Apc(Min/+) mice showed hyperproliferative potential in vitro and in vivo and increased levels of IL-17A and IL-10. The effector CD4 T cells from Apc(Min/+) mice were more resistant to regulatory T cell-mediated suppression. Finally, these CD4 T cells induced colitis in immunodeficient mice upon adoptive transfer, whereas the ablation of IL-17A in CD4 T cells in Apc(Min/+) mice completely abolished this pathogenic potential in vivo. Taken together, our results show that CD4 T cell-derived IL-17A promotes spontaneous intestinal tumorigenesis with altered functions of CD4 T cells in Apc(Min/+) mice.

Flagellin is required for salmonella-induced expression of heat shock protein Hsp25 in intestinal epithelium

Flagellin is a bacterial protein responsible for activation of Toll-like receptor 5 (TLR5), which we hypothesize is involved in Salmonella's induction of cytoprotective heat shock proteins in intestinal epithelial cells. Flagellin induces the cytoprotective heat shock protein Hsp25 in different intestinal epithelial cell lines and in mouse intestine. Flagellin induces Hsp25 expression in a time-dependent manner in vitro. This effect is transcriptional, as confirmed by luciferase reporter assays and actinomycin D treatment. In addition, Hsp25 induction requires p38 MAPK activation and is only observed when flagellin is added to the basolateral side of polarized intestinal epithelial cells, consistent with the known location of TLR5. Flagellin-mediated Hsp25 induction is associated with increased protective effects against oxidant stress, an effect that is at least partially mediated by p38 MAPK. Use of small interfering RNA against Hsp25 demonstrates that flagellin-mediated protection against oxidant stress is to some degree mediated through Hsp25 induction. This suggests that, by protecting against oxidant injury, the induction of Hsp25 expression by flagellin may contribute to intestinal homeostasis. In a coculture cell model and in a mouse model of Salmonella enterica Serovar Typhimurium infection, not only does infection with wild-type and a flagellin-deletion mutant strain of Salmonella show that flagellin induces Hsp25 in vivo, but it also demonstrates that in the case of live Salmonella infection, flagellin serves as a major stimulus for the induction of Hsp25 expression. These data provide evidence that flagellin is required for Salmonella-mediated induction of Hsp25 expression in intestinal epithelium.

Binding of the hop (Humulus lupulus L.) chalcone xanthohumol to cytosolic proteins in Caco‐2 intestinal epithelial cells

Used in the brewing of beer, hops (Humulus lupulus L.) contain the prenylated chalcone xanthohumol, which is under investigation as a cancer chemoprevention agent and as a precursor for the estrogenic flavanones isoxanthohumol and 8-prenylnaringenin. The uptake, transport and accumulation of xanthohumol were studied using the human intestinal epithelial cell line Caco-2 to help understand the poor bioavailability of this chalcone. Studies were carried out using Caco-2 cell monolayers 18-21 days after seeding. The apparent K(m) and V(max) values of xanthohumol accumulation in Caco-2 cells were determined, and the protein binding of xanthohumol in sub-cellular fractions of Caco-2 cells was investigated. Approximately 70% of xanthohumol added to the apical side of Caco-2 cells accumulated inside the cells, while 93% of the intracellular xanthohumol was localized in the cytosol. Xanthohumol accumulation was temperature dependent and saturable with an apparent K(m )value of 26.5 +/- 4.66 muM and an apparent V(max) of 0.215 +/- 0.018 nmol/mg protein/min. Facilitated transport was not responsible for the uptake of xanthohumol, instead, accumulation inside the Caco-2 cells was apparently the result of specific binding to cytosolic proteins. These data suggest that specific binding of xanthohumol to cytosolic proteins in intestinal epithelial cells contributes to the poor oral bioavailability observed previously in vivo.

The Rab8 GTPase regulates apical protein localization in intestinal cells

A number of proteins are known to be involved in apical/basolateral transport of proteins in polarized epithelial cells. The small GTP-binding protein Rab8 was thought to regulate basolateral transport in polarized kidney epithelial cells through the AP1B-complex-mediated pathway. However, the role of Rab8 (Rab8A) in cell polarity in vivo remains unknown. Here we show that Rab8 is responsible for the localization of apical proteins in intestinal epithelial cells. We found that apical peptidases and transporters localized to lysosomes in the small intestine of Rab8-deficient mice. Their mislocalization and degradation in lysosomes led to a marked reduction in the absorption rate of nutrients in the small intestine, and ultimately to death. Ultrastructurally, a shortening of apical microvilli, an increased number of enlarged lysosomes, and microvillus inclusions in the enterocytes were also observed. One microvillus inclusion disease patient who shows an identical phenotype to Rab8-deficient mice expresses a reduced amount of RAB8 (RAB8A; NM_005370). Our results demonstrate that Rab8 is necessary for the proper localization of apical proteins and the absorption and digestion of various nutrients in the small intestine.

STAT1-independent inhibition of cyclooxygenase-2 expression by IFNγ; a common pathway of IFNγ-mediated gene repression but not gene activation

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme in the synthesis of prostaglandins, promotes the development of colorectal cancer, and is a key molecular target of non-steroidal anti-inflammatory drugs, compounds that reduce the relative risk of developing colon cancer. In this study, we showed that interferon gamma (IFNgamma) inhibits the expression of COX-2 protein in intestinal epithelial cells (IECs) through a pathway that requires Janus-activated kinase (JAK) activity. In contrast, we demonstrated that transcriptional inhibition of COX-2 by IFNbeta or IFNgamma occurs in cells with silenced signal transducer and activator of transcription 1 (STAT1) expression and that IFNs retained the ability to inhibit COX-2 transcription in cells with activated RasV12, in which IFNgamma failed to induce STAT1. Thus, unlike the activity of JAK, STAT1 is not required for the inhibition of COX-2 expression by IFNgamma. In contrast to COX-2, the activation of genes in response to IFNgamma, such as interferon regulatory factor-1, was severely impaired by both STAT1 silencing and by constitutive Ras signaling. To determine whether there is a general differential requirement for STAT1 in gene activation and gene repression in response to IFNgamma in intestinal cells, we performed genome-wide analysis of IFNgamma target genes in an IEC line in which STAT1 expression was silenced by small interfering RNA. The results confirmed that the activation of the majority of genes by IFNgamma required STAT1. In contrast, the repression of several genes, as we showed for COX-2 specifically, was largely unaffected in cells with silenced STAT1. Our results therefore demonstrate that in general gene activation by IFNgamma is more sensitive to STAT1 deficiency than gene repression, and suggest that IFNgamma activates and represses gene expression via distinct pathways that can be distinguished, at least in part, by their requirement for STAT1.

Soluble factors from Lactobacillus GG activate MAPKs and induce cytoprotective heat shock proteins in intestinal epithelial cells

Conditioned media from the probiotic Lactobacillus GG (LGG-CM) induce heat shock protein (Hsp) expression in intestinal epithelial cells. LGG-CM induces both Hsp25 and Hsp72 in a time- and concentration-dependent manner. These effects are mediated by a low-molecular-weight peptide that is acid and heat stable. DNA microarray experiments demonstrate that Hsp72 is one of the most highly upregulated genes in response to LGG-CM treatment. Real-time PCR and electrophoretic mobility shift assay confirm that regulation of Hsp induction is at least in part transcriptional in nature, involving heat shock factor-1. Although Hsps are not induced for hours after exposure, transient exposure to LGG-CM is sufficient to initiate the signal for Hsp induction, suggesting that signal transduction pathways may be involved. Experiments confirm that LGG-CM modulates the activity of certain signaling pathways in intestinal epithelial cells by activating MAP kinases. Inhibitors of p38 and JNK block the expression of Hsp72 normally induced by LGG-CM. Functional studies indicate that LGG-CM treatment of gut epithelial cells protects them from oxidant stress, perhaps by preserving cytoskeletal integrity. By inducing the expression of cytoprotective Hsps in gut epithelial cells, and by activating signal transduction pathways, the peptide product(s) secreted by LGG may contribute to the beneficial clinical effects attributed to this probiotic.

TFF3 modulates NF-κB and a novel negative regulatory molecule of NF-κB in intestinal epithelial cells via a mechanism distinct from TNF-α

Trefoil factor 3 (intestinal trefoil factor) is a cytoprotective factor in the gut. Herein we compared the effect of trefoil factor 3 with tumor necrosis factor-α on 1) activation of NF-κB in intestinal epithelial cells; 2) expression of Twist protein (a molecule essential for downregulation of nuclear factor-κB activity in vivo); and 3) production of interleukin-8. We showed that Twist protein is constitutively expressed in intestinal epithelial cells. Tumor necrosis factor-α induced persistent degradation of Twist protein in intestinal epithelial cells via a signaling pathway linked to proteasome, which was associated with prolonged activation of NF-κB. In contrast to tumor necrosis factor, trefoil factor 3 triggered transient activation of NF-κB and prolonged upregulation of Twist protein in intestinal epithelial cells via an ERK kinase-mediated pathway. Unlike tumor necrosis factor-α, transient activation of NF-κB by trefoil factor 3 is not associated with induction of IL-8 in cells. To examine the role of Twist protein in intestinal epithelial cells, we silenced the Twist expression by siRNA. Our data showed that trefoil factor 3 induced interleukin-8 production after silencing Twist in intestinal epithelial cells. Together, these observations indicated that 1) trefoil factor 3 triggers a diverse signal from tumor necrosis factor-α on the activation of NF-κB and its associated molecules in intestinal epithelial cells; and 2) trefoil factor 3-induced Twist protein plays an important role in the modulation of inflammatory cytokine production in intestinal epithelial cells.

Polyamines are necessary for synthesis and stability of occludin protein in intestinal epithelial cells

Occludin is an integral membrane protein that forms the sealing element of tight junctions and is critical for epithelial barrier function. Polyamines are implicated in multiple signaling pathways driving different biological functions of intestinal epithelial cells (IEC). The present study determined whether polyamines are involved in expression of occludin and play a role in intestinal epithelial barrier function. Studies were conducted in stable Cdx2-transfected IEC-6 cells (IEC-Cdx2L1) associated with a highly differentiated phenotype. Polyamine depletion by alpha-difluoromethylornithine (DFMO) decreased levels of occludin protein but failed to affect expression of its mRNA. Other tight junction proteins, zonula occludens (ZO)-1, ZO-2, claudin-2, and claudin-3, were also decreased in polyamine-deficient cells. Decreased levels of tight junction proteins in DFMO-treated cells were associated with dysfunction of the epithelial barrier, which was overcome by exogenous polyamine spermidine. Decreased levels of occludin in polyamine-deficient cells was not due to the reduction of intracellular-free Ca(2+) concentration ([Ca(2+)](cyt)), because either increased or decreased [Ca(2+)](cyt) did not alter levels of occludin in the presence or absence of polyamines. The level of newly synthesized occludin protein was decreased by approximately 70% following polyamine depletion, whereas its protein half-life was reduced from approximately 120 min in control cells to approximately 75 min in polyamine-deficient cells. These findings indicate that polyamines are necessary for the synthesis and stability of occludin protein and that polyamine depletion disrupts the epithelial barrier function, at least partially, by decreasing occludin.

Laminin isoforms: biological roles and effects on the intracellular distribution of nuclear proteins in intestinal epithelial cells

Laminins are structurally and functionally major components of the extracellular matrix. Four isoforms of laminins (laminin-1, -2, -5 and -10) are expressed in a specific pattern along the crypt–villus axis of the intestine. Previous works indicated that expression of these isoforms is developmentally regulated and that laminins could modulate the behaviour of intestinal cells, but the exact role of each isoform remained unclear. Here, we report the first systematic analysis of the cellular functions of the four isoforms using the human colon adenocarcinoma Caco2/TC7 cell line as a model. We compared the respective abilities of each isoform to modulate adhesion, proliferation and differentiation of intestinal epithelial cells. We found that the isoforms were functionally distinct, with laminin-10 being the most adhesive substratum, laminin-2, laminin-5 and laminin-10 enhancing cellular proliferation and at the opposite, laminin-1 stimulating intestinal cell differentiation. To begin to characterise the molecular events induced by the different isoforms, we examined by immunofluorescence the intracellular distribution of several nuclear proteins, recently highlighted by a nuclear proteomic approach. We observed clear nucleocytoplasmic redistribution of these proteins, which depended on the laminin isoform. These results provide evidence for a distinct functional role of laminins in intestinal cell functions characterised by specific localisation of nuclear proteins.

Modulation of nuclear speckles and SR proteins in intestinal epithelial cells by

Modulation of nuclear speckles and SR proteins in intestinal epithelial cells by

Proinflammatory cytokines cause NO*-dependent and -independent changes in expression and localization of tight junction proteins in intestinal epithelial cells.

Intestinal epithelial barrier function is impaired after the exposure of enterocytes to proinflammatory cytokines. The mechanism(s) responsible for this phenomenon remain incompletely understood. We used cultured monolayers of Caco-2 enterocyte-like cells to characterize the effect of cytomix, a mixture of interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta, on the expression and localization of several tight junctions proteins. Cells were stimulated with cytomix in the presence or absence of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1 -oxyl-3-oxide (cPTIO), an NO* scavenger. Some cells were treated with (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate] (DETA-NONOate), an NO* donor. Tight junction protein expression was measured in cellular extracts by Western blotting and localized in cells using immunofluorescence. Steady-state mRNA levels were determined using semi-quantitative reverse-transcription polymerase chain reaction. Incubation of cells with DETA-NONOate or cytomix decreased epithelial barrier function, decreased expression of ZO-1 mRNA, decreased expression of ZO-1, ZO-3, and occludin protein, and increased expression of claudin-1 protein. The effects of cytomix on barrier function and tight junction protein expression were modulated by cPTIO. Cytomix caused incorrect subcellular localization of ZO-1, occludin, and claudin-1, and this was modulated by co-incubation with cPTIO. DETA-NONOate caused similar protein mislocalization as observed with cytomix. The effectiveness of cPTIO in maintaining tight junction protein expression and correct subcellular localization was less apparent at early time points (12 h) compared with later points, suggesting an NO*-independent effect of cytokines on barrier function. Thus, cytomix appears to increase the permeability of Caco-2 monolayers through NO*-dependent and -independent mechanisms that are associated with changes in the expression and/or targeting of proteins involved in tight junction function.

Shiga toxins induce, superinduce, and stabilize a variety of C-X-C chemokine mRNAs in intestinal epithelial cells, resulting in increased chemokine expression.

Exposure of humans to Shiga toxins (Stxs) is a risk factor for hemolytic-uremic syndrome (HUS). Because Stx-producing Escherichia coli (STEC) is a noninvasive enteric pathogen, the extent to which Stxs can cross the host intestinal epithelium may affect the risk of developing HUS. We have previously shown that Stxs can induce and superinduce IL-8 mRNA and protein in intestinal epithelial cells (IECs) in vitro via a ribotoxic stress response. We used cytokine expression arrays to determine the effect of Stx1 on various C-X-C chemokine genes in IECs. We observed that Stx1 induces multiple C-X-C chemokines at the mRNA level, including interleukin-8 (IL-8), GRO-alpha, GRO-beta, GRO-gamma, and ENA-78. Like that of IL-8, GRO-alpha and ENA-78 mRNAs are both induced and superinduced by Stx1. Furthermore, Stx1 induces both IL-8 and GRO-alpha protein in a dose-response fashion, despite an overall inhibition in host cell protein synthesis. Stx1 treatment stabilizes both IL-8 and GRO-alpha mRNA. We conclude that Stxs are able to increase mRNA and protein levels of multiple C-X-C chemokines in IECs, with increased mRNA stability at least one mechanism involved. We hypothesize that ribotoxic stress is a pathway by which Stxs can alter host signal transduction in IECs, resulting in the production of multiple chemokine mRNAs, leading to increased expression of specific proteins. Taken together, these data suggest that exposing IECs to Stxs may stimulate a proinflammatory response, resulting in influx of acute inflammatory cells and thus contributing to the intestinal tissue damage seen in STEC infection.