HT-29 Human Colonic Epithelial Cells Research Articles

UNC‐45A is a novel regulator of the intestinal epithelial cell migration

Intestinal epithelial cell migration is a fundamental homeostatic process that regulates establishment of the epithelial architecture in healthy gut and drives mucosal wound healing during intestinal inflammation. Epithelial cell migration depends on remodeling of the cytoskeleton, most notably actin filament turnover and activity of nonmuscle myosin II (NM II) motors. The mechanisms that regulate remodeling of the actomyosin cytoskeleton in migrating intestinal epithelial cells remain poorly understood. UNC-45A is a highly conserved member of the UNC45/CRO1/She4p family proteins and it acts as a chaperone facilitating NM II folding and self-assembly. While previous studies implicated this molecular chaperon in controlling motility of fibroblastic and some tumor cells, its roles in regulating intestinal epithelial cell migration remain unexplored. In the present study, CRISPR/Cas9 mediated gene editing was used to downregulate UNC-45A expression in HT29 and SK-CO15 human colonic epithelial cells. Loss of UNC-45A significantly decreased cell contractility in the collagen contraction assay, thereby indicating impaired activity of NM II motors. Importantly, knockout of UNC-45A significantly decreased both collective epithelial cell migration in a wound heling assay and individual cell migration in the Boyden chamber. The attenuated migration of UNC-45A-depleted epithelial cells was accompanied by their increased adhesion to the collagen matrix, disassembly of basal actin stress fibers and inhibited membrane protrusion at the migrating cell edge. Interestingly, UNC-45A expression was significantly downregulated in isolated intestinal epithelial cells and tissue sections obtained from the colonic mucosa of ulcerative colitis patients. Our results signify UNC-45A as a novel cytoskeletal regulator of intestinal epithelial cell migration, which functions could be inhibited in chronic inflammatory disorders.

Anti-Inflammatory Effects of Fermented Products with Avena sativa on RAW264.7 and HT-29 Cells via Inhibition of Inflammatory Mediators

This study investigated therapeutic candidates with anti-inflammatory potential among traditional dietary ingredients targeting inflammatory bowel disease (IBD). Both Avena sativa and traditional fermented products, such as Korean soy paste, are popular health foods. We investigated the anti-inflammatory effects of soy paste combined with A. sativa (KDA), compared with soy paste without A. sativa (KD) by evaluating the expression of pro-inflammatory cytokines in lipopolysaccharide-stimulated RAW264.7 mouse macrophages and HT-29 human colon epithelial cells. KDA significantly inhibited the production of nitric oxide (NO) and downregulated the pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in lipopolysaccharide (LPS)-induced RAW264.7 cells. In another in vitro experiment involving LPS-stimulated HT- 29 cells, KDA suppressed the levels of IL-8, which is the chemokine elevated in IBD. In addition, KDA exhibited anti-oxidative properties, such as 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2''-azino-bis(3- ethylbenz-thiazoline-6-sulfonic acid) (ABTS) radical scavenging activity. Our findings revealed that A. sativa combined with soy paste exhibits a synergistic anti-inflammatory and anti-oxidant effect following fermentation. These results suggest that KDA may be used as a potential anti-inflammatory therapy against IBD.

Sudachinoid- and Ichangensin-Type Limonoids from Citrus junos Downregulate Pro-Inflammatory Cytokines.

Limonoids, a dominant group of phytochemicals in the Rutaceae family, are known to exhibit several pharmacological activities. To identify natural products having efficacy against inflammatory bowel disease (IBD), we isolated 13 limonoids including a new compound, methyl sudachinoid A, from the seeds of Citrus junos and investigated their anti-inflammatory effects by assessing the expression of pro-inflammatory cytokines in lipopolysaccharide-stimulated RAW 264.7 mouse macrophages and HT-29 human colon epithelial cells. Our findings revealed that limonoids significantly downregulated the pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α, and nuclear transcription factor κB. In particular, sudachinoid-type compounds, methyl sudachinoid A and sudachinoid B, and ichangensin-type compound, 1-O-methyichangensin downregulated the expression of pro-inflammatory cytokines more potently than other limonoids, nomilin and limonin, which have been previously reported to exhibit anti-inflammatory activities in other cells; nomilin and limonin were therefore employed as positive controls in this study. Herein, we reveal that the anti-inflammatory activities of limonoids including a new compound methyl sudachinoid A from C. junos were mediated via the downregulation of pro-inflammatory cytokines and these limonoids can be employed as potential therapeutic phytochemicals for IBD.

Astragalin Inhibits Nuclear Factor-κB Signaling in Human Colonic Epithelial Cells and Attenuates Experimental Colitis in Mice.

Background/AimsAstragalin (kaempferol-3-O-β-D-glucoside) is a flavonoid isolated from the leaves of persimmon or Rosa agrestis. Astragalin exhibits various anti-inflammatory properties; however, little is known about its therapeutic potential for inflammatory bowel disease (IBD). This study aims to investigate the anti-inflammatory effect of astragalin via blockade of the nuclear factor κB (NF-κB) signaling pathway in human colonic epithelial cells and a murine colitis model.MethodsHCT-116 and HT-29 human colonic epithelial cells were pretreated with astragalin and stimulated with tumor necrosis factor-α (TNF-α). Cell viability was assessed by the MTS assay. Real-time reverse transcription polymerase chain reaction was used to analyze the messenger RNA expression of the inflammatory cytokines interleukin (IL)-6 and IL-8. The effect of astragalin on the NF-κB pathway was evaluated by Western blot analysis of inhibitor of NF-κB alpha (IκBα) phosphorylation/degradation and by electrophoretic mobility shift assay. Dextran sulfate sodium (DSS)-induced acute murine colitis model was used for in vivo experiments.ResultsAstragalin strongly suppressed the expression of proinflammatory cytokines in human colonic epithelial cells in a dose-dependent manner. Western blot analysis showed that astragalin inhibited IκBα phosphorylation/degradation. Additionally, astragalin reduced the DNA binding activity of NF-κB. Astragalin alleviated colon shortening and improved the pathologic scores in DSS-induced acute murine colitis model. Furthermore, astragalin reduced the level of phosphorylated IκBα and decreased the production of the inflammatory cytokines IL-6, IL-8, and TNF-α in the DSS-treated colon mucosa.ConclusionsAstragalin exerted an anti-inflammatory effect through NF-κB pathway inhibition and attenuated murine colitis. Astragalin is thus a potential therapeutic agent for IBD.

Potent Inhibitory Effect of BJ-3105, a 6-Alkoxypyridin-3-ol Derivative, on Murine Colitis Is Mediated by Activating AMPK and Inhibiting NOX.

Inflammatory bowel disease (IBD) is a chronic relapsing inflammation in the gastrointestinal tract. Biological therapeutics and orally available small molecules like tofacitinib (a JAK inhibitor) have been developed to treat IBD, but half of the patients treated with these drugs fail to achieve sustained remission. In the present study, we compared the therapeutic effects of BJ-3105 (a 6-alkoxypyridin-3-ol derivative) and tofacitinib in IBD. BJ-3105 induced activation of AMP-activated protein kinase (AMPK) in the kinase activity measurement and recovery from cytokine-induced AMPK deactivation in HT-29 human colonic epithelial cells. Similar to tofacitinib and D942 (an AMPK activator), BJ-3105 inhibited IL-6-induced JAK2/STAT3 phosphorylation and TNF-α-stimulated activation of IKK/NF-κB, and consequently, stimulus-induced upregulations of inflammatory cytokines and inflammasome components. In addition, unlike tofacitinib or D942, BJ-3105 inhibited NADPH oxidase (NOX) activation and consequent superoxide production induced by activators (mevalonate and geranylgeranyl pyrophosphate) of the NOX cytosolic component Rac. In mice, oral administration with BJ-3105 ameliorated dextran sulfate sodium (DSS)-induced colitis and azoxymethane/DSS-induced colitis-associated tumor formation (CAT) much more potently than that with tofacitinib. Moreover, BJ-3105 suppressed the more severe form of colitis and CAT formation in mice with AMPK knocked-out in macrophages (AMPKαfl/fl-Lyz2-Cre mice) with much greater efficacy than tofacitinib. Taken together, our findings suggest BJ-3105, which exerted a much better anti-colitis effect than tofacitinib through AMPK activation and NOX inhibition, is a promising candidate for the treatment of IBD.

Expression of human REG family genes in inflammatory bowel disease and their molecular mechanism.

The pathophysiology of inflammatory bowel disease (IBD) reflects a balance between mucosal injury and reparative mechanisms. Some regenerating gene (Reg) family members have been reported to be expressed in Crohn's disease (CD) and ulcerative colitis (UC) and to be involved as proliferative mucosal factors in IBD. However, expression of all the REG family genes in IBD is still unclear. Here, we analyzed expression of all the REG family genes (REGIα, REGIβ, REG III, HIP/PAP, and REG IV) in biopsy specimens of UC and CD by real-time RT-PCR. REG Iα, REG Iβ, and REG IV genes were overexpressed in CD samples. REG IV gene was also overexpressed in UC samples. We further analyzed the expression mechanisms of REG Iα, REG Iβ, and REG IV genes in LS-174T and HT-29 human colonic epithelial cells. The expression of REG Iα was significantly induced by IL-6 or IL-22, and REG Iβ was induced by IL-22. Deletion analyses revealed that three regions (- 220~- 211, - 179~- 156, and - 146~- 130) in REG Iα and the region (- 274~- 260) in REG Iβ promoter were responsible for the activation by IL-22/IL-6. The promoters contain consensus transcription factor binding sequences for MZF1, RTEF1/TEAD4, and STAT3 in REG Iα, and HLTF/FOXN2F in REG Iβ, respectively. The introduction of siRNA for MZF1, RTEF1/TEAD4, STAT3, and HLTF/FOXN2F abolished the transcription of REG Iα and REG Iβ. The gene activation mechanisms of REG Iα/REG Iβ may play a role in colon mucosal regeneration in IBD.

Inhibition of Protein Translation Initiation and Disruption of the Intestinal Epithelial Barrier in Mucosal Inflammation

Integrity of the intestinal epithelial barrier is regulated by two types of adhesive structures: intercellular junctions and focal adhesions (FA) that control epithelial cell attachment to each other and to the extracellular matrix (ECM), respectively. Disassembly of adherens junctions (AJ) and tight junctions (TJ) plays key roles in the breakdown of the intestinal epithelial barrier during mucosal inflammation. Abnormal architecture and functions of FA significantly contribute to attenuated restitution of the inflamed intestinal mucosa. Proinflammatory cytokines such as interferon (IFN)‐γ and tumor necrosis factor (TNF)‐α, are known to trigger AJ/TJ disassembly and attenuate wound healing in model intestinal epithelial cell monolayers. We hypothesized that inhibition of protein translation factors eIF4G1 and eIF4G2 could mediate cytokine‐induced disruption of the gut barrier and attenuation of epithelial restitution.Immunoblotting analysis of IFNγ and IFNγ/TNFα‐treated HT29 and T84 human colonic epithelial cells demonstrated significant downregulation of expression AJ proteins, E‐cadherin, p120 catenin, β‐catenin, and the TJ protein, occludin. By contrast quantitative RT‐PCR analysis did not reveal changes in mRNA levels of selected junctional proteins. Furthermore, expression of translation initiation factors eIF4G1 and eIF4G2 was downregulated by these proinflammatory cytokines in vitro, and eIF4G2 level was decreased in colonic mucosa of IBD patients. In order to examine functional roles of these translation initiation factors, eIF4G1 or eIF4G2 were selectively downregulated in well‐differentiated SK‐CO15 and HT29cF8 human colonic epithelial cell lines, as well as in stem‐cell like human intestinal epithelial cells (HIEC) by using either siRNA‐mediated or shRNA‐mediated knock‐down. Downregulation of either eIF4G1, or eIF4G2 increased permeability of SK‐CO15 epithelial cell monolayers and decreased expression of different adherens junction and tight junction proteins. Furthermore, depletion of these translation initiating factors inhibited collective wound healing and individual transfilter migration of both stem‐cell like and well‐differentiated intestinal epithelial cells. Interestingly, immunolabeling of newly‐translated proteins identified the epithelial leading edge as the hot‐spot site of active translation during wound healing. Finally, we observed a robust epithelial to myofibroblast transition in HIEC cells upon depletion of eIF4G1. The described results reveal a novel role for protein translation initiation in regulating intestinal epithelial barrier and epithelial restitution and suggest that this important homeostatic mechanism could be impaired during mucosal inflammation and IBD.Support or Funding InformationSupported by the Crohn's and Colitis Foundation of America grant 380973 to NGN and NIH grant DK108278 to AII.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

MicroRNA-15 Activates NF-κB Pathway via Down Regulating Expression of Adenosine A2 Receptor in Ulcerative Colitis

Background/Aims: The role of miR-15 in ulcerative colitis (UC) is unclear. In this study, we found that miR-15 downregulated the expression of adenosine A2a receptor (A2aAR) in the colonic tissues of patients with UC and in HT-29 human colonic epithelial cells. Methods: The study population comprised patients with UC (n=23), irritable bowel syndrome (IBS, n=22), and healthy subjects (n = 20). The levels of miR-15, A2aAR, and protein in colon tissue biopsies were determined by real-time quantitative reverse transcription polymerase chain reaction, immunofluorescence staining, and Western blotting. The TargetScan prediction algorithm was used to identify the miR-15 binding site in the 3′-UTR of A2aAR. To assess the effects of miR-15 on A2aAR levels, HT-29 cells were transfected with miR-15 mimics. Results: Relative to expression in healthy subjects, A2aAR expression was decreased in UC patients and was similar in IBS patients. MiR-15 levels were higher in UC patients than in IBS patients or healthy subjects. A2aAR was the target of miR-15 in HT-29 cells, which downregulated A2aAR mRNA levels. MiR-15 mimics induced nuclear translocation of NF-κB p65 and upregulated the expression of IL-8 and IFN-γ in colonic epithelial cells; these effects were reversed by an miR-15 inhibitor. A2aAR knockdown confirmed that miR-15 activated the NF-κB cascade. Conclusion: Our data suggest that miR-15 modulates inflammatory and immune responses by suppressing the expression of A2aAR and regulating the NF-κB cascade.

Cranberry Xyloglucan Structure and Inhibition of Escherichia coli Adhesion to Epithelial Cells.

Cranberry juice has been recognized as a treatment for urinary tract infections on the basis of scientific reports of proanthocyanidin anti-adhesion activity against Escherichia coli as well as from folklore. Xyloglucan oligosaccharides were detected in cranberry juice and the residue remaining following commercial juice extraction that included pectinase maceration of the pulp. A novel xyloglucan was detected through tandem mass spectrometry analysis of an ion at m/z 1055 that was determined to be a branched, three hexose, four pentose oligosaccharide consistent with an arabino-xyloglucan structure. Two-dimensional nuclear magnetic resonance spectroscopy analysis provided through-bond correlations for the α-L-Araf (1→2) α-D-Xylp (1→6) β-D-Glcp sequence, proving the S-type cranberry xyloglucan structure. Cranberry xyloglucan-rich fractions inhibited the adhesion of E. coli CFT073 and UTI89 strains to T24 human bladder epithelial cells and that of E. coli O157:H7 to HT29 human colonic epithelial cells. SSGG xyloglucan oligosaccharides represent a new cranberry bioactive component with E. coli anti-adhesion activity and high affinity for type 1 fimbriae.

Increased Expression of Colonic Wnt9A through Sp1-mediated Transcriptional Effects involving Arylsulfatase B, Chondroitin 4-Sulfate, and Galectin-3

In cultured human colonic epithelial cells and mouse colonic tissue, exposure to the common food additive carrageenan leads to inflammation, activation of Wnt signaling, increased Wnt9A expression, and decline in the activity of the enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase). In this study, the novel transcriptional mechanism by which carrageenan and decline in ARSB increase Wnt9A expression in NCM460 and HT-29 human colonic epithelial cells and in mouse colon is presented. Increased expression of Wnt9A has been associated with multiple malignancies, including colon carcinoma, and with ectodermal and mesoendodermal morphogenesis. When ARSB activity was reduced by siRNA or by exposure to carrageenan (1 μg/ml for 24 h), degradation of chondroitin 4-sulfate (C4S) was inhibited, leading to accumulation of more highly sulfated C4S, which binds less galectin-3, a β-galactoside-binding protein. Nuclear galectin-3 increased and mediated increased binding of Sp1 to the Sp1 consensus sequence in the Wnt9A promoter, shown by oligonucleotide-binding assay and by chromatin immunoprecipitation assay. When galectin-3 was silenced, the increases in Sp1 binding to the Wnt9A promoter and in Wnt9A expression, which followed carrageenan or ARSB silencing, were inhibited. Mithramycin A, a specific inhibitor of Sp1 oligonucleotide binding, and Sp1 siRNA blocked the carrageenan- and ARSB siRNA-induced increases in Wnt9A expression. These studies reveal how carrageenan exposure can lead to transcriptional events in colonic epithelial cells through decline in arylsulfatase B activity, with subsequent impact on C4S, galectin-3, Sp1, and Wnt9A and can exert significant effects on Wnt-initiated signaling and related vital cell processes.

Protective effects of Pogostemon cablin Bentham water extract on inflammatory cytokine expression in TNBS-induced colitis in rats

In inflammatory bowel disease (IBD), colon epithelial cells express a variety of inflammatory mediators, including chemokines, which perpetuate inflammatory response. In the current study, we report that water extract of Pogostemon cablin Bentham aerial parts (PCW), which has traditionally been used for treatment of the common cold and infectious disease, suppressed colon inflammation. Treatment with PCW resulted in effective inhibition of tumor necrosis factor (TNF)-α-induced adhesion of monocytes to HT-29 human colonic epithelial cells. In a trinitrobenzene sulfonic acid (TNBS)-induced rat model of IBD, PCW suppressed clinical signs of colitis, including weight loss, colon tissue myeloperoxidase activity, a marker for inflammatory cell infiltration, and cyclooxygenase-2 expression in a dose-dependent manner. In addition, PCW suppressed TNBS-induced mRNA expression of IL-8, MCP-1, and IL-6 in rat colon. The nuclear level of NF-κB in TNBS-treated rat colon and NF-κB luciferase reporter gene activity in TNF-α-treated HT-29 cells were significantly inhibited by PCW. Taken together, the results of this study suggest that PCW suppressed colon inflammation via suppression of NF-κB-dependent expression of pro-inflammatory cytokines.

1,3-Diphenylpropenone ameliorates TNBS-induced rat colitis through suppression of NF-κB activation and IL-8 induction

In the present study, we examined whether newly synthesized phenylpropenone derivatives, by inhibiting NF-κB activity, would inhibit IL-8 expression, inflammation and abnormal angiogenesis, resulting in amelioration of disease conditions. The phenylpropenone derivatives inhibited NF-κB transcriptional activity, which correlated with their suppressive activity against TNF-α-induced adhesion of U937 human monocytic cells to HT-29 human colonic epithelial cells, an in vitro model of IBD. Among the derivatives, 1,3-diphenylpropenone (DPhP) was most efficacious, and it significantly suppressed TNF-α-induced production of IL-8 which is a proinflammatory and proangiogenic cytokine. The anti-inflammatory activity of DPhP was also confirmed in the trinitrobenzene sulfonic acid (TNBS)-induced rat colitis model. DPhP was protective against the TNBS-induced inflammatory responses, which included weight loss, increased myeloperoxidase activity and mucosal damage. In the colon tissue, DPhP inhibited TNBS-induced NF-κB nuclear translocation, IL-8 and TNF-α expressions, and abnormal angiogenesis. In addition, DPhP also suppressed IL-8-induced angiogenesis, which was revealed by an in vivo assay using chick chorioallantoic membrane. Furthermore, the level of IL-6, a pleiotropic cytokine which is implicated in the pathogenesis of IBD and colitis-associated cancer, was suppressed by DPhP in rat colon tissue and serum. In conclusion, the results suggest that DPhP is a potential dual-acting IBD drug candidate targeting both inflammation and abnormal angiogenesis, possibly through the NF-κB and IL-8 signaling pathway.

Anti-inflammatory action of mollugin and its synthetic derivatives in HT-29 human colonic epithelial cells is mediated through inhibition of NF-κB activation

Mollugin is the active compound of Rubia cordifolia, which has been used as a traditional Chinese medicine for the treatment of various inflammatory diseases including arthritis and uteritis. In the present study, we investigated for the first time the inhibitory effects and the mechanisms of action of mollugin (M1) and its synthetic derivatives (M2–M4) on tumor necrosis factor (TNF)-α-induced inflammatory responses in HT-29 human colon epithelial cells. Treatment with M1 and its derivatives M2–M4 significantly inhibited TNF-α-induced attachment of U937 monocytic cells to HT-29 cells, which mimics the initial phase of colon inflammation. TNF-α-induced mRNA induction of the chemokines, monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8, and the intercellular cell adhesion molecule (ICAM)-1, which are involved in adhesion between leukocytes and epithelial cells, was suppressed by M1–M4, and M1 was the most efficacious. In addition, M1–M4 significantly suppressed TNF-α-induced NF-κB transcriptional activity. Such NF-κB inhibitory activity of M1–M4 (20 µM) correlated with their ability to suppress TNF-α-induced chemokine expression and U937 monocytic cell adhesion to HT-29 colonic epithelial cells. Treatment of HT-29 cells with M1 and PDTC, a NF-κB inhibitor, synergistically suppressed both TNF-α-induced NF-κB activation and monocytic cell adhesion to HT-29 cells. These results suggest that M1–M4 inhibit TNF-α-induced expression of inflammatory molecules via NF-κB, and that M1, a potent NF-κB inhibitor, may be a valuable new drug candidate for the treatment of colon inflammation.

Glycoproteomics and glycomics investigation of membrane N‐glycosylproteins from human colon carcinoma cells

Aberrant glycosylation of proteins is known to profoundly affect cellular adhesion or motility of tumoral cells. In this study, we used HT-29 human colon epithelial cancer cells as a cellular model of cancer progression, as they can either proliferate or differentiate into enterocyte phenotype. A glycoproteomic approach based on Con A lectin-affinity chromatography, SDS-PAGE and MS analysis, allowed the identification of membrane N-glycoproteins from Triton X-100-solubilized proteins from membrane preparation. Among them, 65% were membrane proteins, and 45% were known to be N-glycosylated, such as alpha chains integrin and dipeptidyl isomerase IV. By lectin-blot analysis, significant changes of alpha-2,3- and alpha-2,6-sialylation of membrane glycoproteins were observed between proliferating and differentiated HT-29 cells. From these results, nano-LC-MS/MS analysis of the tryptic digests of the corresponding bands was performed and led to the identification of several transmembrane glycoproteins, like members of the solute carrier family and adhesion proteins. Finally, we compared N-glycans profiles and monosaccharide composition of proliferating and enterocyte-like HT-29 cells using MALDI-MS and GC-MS analyses of permethylated derivatives. This glycomic approach allowed to underscore significant changes in N-glycans structure, in particular the expression of atypical N-acetylglucosamine (GlcNAc)-ended N-glycans in enterocyte-like HT-29 cells.

Involvement of NF-κB in the inhibitory actions of Platycarya strobilacea on the TNF-α-induced monocyte adhesion to colon epithelial cells and chemokine expression

Oxidative stress and the activation of nuclear factor (NF)-kappaB play crucial roles in the pathogenesis of inflammatory bowel disease (IBD). In the present study, we examined the effects of the ethanol extract of Platycarya strobilacea Sieb. stem (EPS) on TNF-alpha-induced monocyte adhesion to HT29 human colon epithelial cells, an initial step of colon inflammation. EPS contained high amount of polyphenols (0.241+/-0.017 mg of catechin equivalent/g of extract) and showed substantial DPPH radical scavenging activity. In addition, EPS significantly suppressed TNF-alpha-induced reactive oxygen species (ROS) increase. Moreover, TNF-alpha-induced monocyte adhesion to HT29 colon epithelial cells was significantly suppressed by EPS in a concentration-dependent manner. The reduced adhesion by EPS was correlated with suppressed expression of MCP-1 and IL-8, the major chemokines in IBD. EPS also prevented the TNF-alpha-induced nuclear translocation of NF-kappaB, one of the redox-sensitive transcription factors, in a concentration-dependent manner. Taken together, our results suggest that the anti-oxidant components of EPS prevent TNF-alpha-induced NF-kappaB activation, chemokine induction, and monocyte adhesion at the site of intestinal inflammation.

Gp96 Is a Human Colonocyte Plasma Membrane Binding Protein for Clostridium difficile Toxin A

Clostridium difficile toxin A (TxA), a key mediator of antibiotic-associated colitis, requires binding to a cell surface receptor prior to internalization. Our aim was to identify novel plasma membrane TxA binding proteins on human colonocytes. TxA was coupled with biotin and cross-linked to the surface of HT29 human colonic epithelial cells. The main colonocyte binding protein for TxA was identified as glycoprotein 96 (gp96) by coimmunoprecipitation and mass spectrum analysis. gp96 is a member of the heat shock protein family, which is expressed on human colonocyte apical membranes as well as in the cytoplasm. TxA binding to gp96 was confirmed by fluorescence immunostaining and in vitro coimmunoprecipitation. Following TxA binding, the TxA-gp96 complex was translocated from the cell membrane to the cytoplasm. Pretreatment with gp96 antibody decreased TxA binding to colonocytes and inhibited TxA-induced cell rounding. Small interfering RNA directed against gp96 reduced gp96 expression and cytotoxicity in colonocytes. TxA-induced inflammatory signaling via p38 and apoptosis as measured by activation of BAK (Bcl-2 homologous antagonist/killer) and DNA fragmentation were decreased in gp96-deficient B cells. We conclude that human colonocyte gp96 serves as a plasma membrane binding protein that enhances cellular entry of TxA, participates in cellular signaling events in the inflammatory cascade, and facilitates cytotoxicity.

Grifola frondosa inhibits TNF‐α‐induced intestinal inflammation via suppression of MCP‐1 and IL‐8 expressions in HT‐29 human colon epithelial cells

Grifola frondosa (GF), a king‐size edible mushroom, has been used as a health food for centuries in China and Japan. In the present study, we investigated an anti‐inflammatory action of GF in inflammatory bowel disease (IBD) by using HT‐29 human colon epithelial cells stimulated with TNF‐α to induce intestinal inflammatory condition in vitro. Treatment with GF significantly prevented the attachment of leukocytes to HT29 colon epithelial cells, one of the pathologic hallmarks in colon inflammation. The effect of GF was comparable to that of 5‐aminosalicylic acid, a commonly used drug in the treatment of IBD. In addition, pretreatment with GF inhibited TNF‐α‐induced MCP‐1 mRNA expression and protein secretion. Furthermore, GF reduced the TNF‐α‐induced interleukin‐8 mRNA expression. These results demonstrate that GF modulates intestinal inflammation via suppressing the expression of inflammatory cytokines, and suggest that GF may be a valuable medicinal food for prevention and/or attenuation of IBD.

Inhibitory effect of berberine on the TNF‐α‐induced Expression of IL‐8 and MCP‐1 is mediated through suppression of NF‐κB activation in HT29 Human Colon Epithelial Cells

Berberine, an isoquinoline alkaloid, has a wide range of pharmacological effects, including anti‐inflammation. In this study, we examined the effects of berberine on the TNF‐α‐induced chemokine expression in HT29 human colon adenocarcinoma cells that were used as an in vitro model of inflammatory bowel disease (IBD). Since the activation and recruitment of leukocytes to the inflamed tissue is an important step initiating IBD, we evaluated the effect of berberine on the adhesion of U937 monocytic cells to HT29 colon epithelial cells. Berberine significantly inhibited the TNF‐α‐induced monocyte adhesion to HT29 cells in a concentration‐dependent manner. Co‐treatment of the TNF‐α‐stimulated HT29 cells with berberine concentration‐dependently inhibited the mRNA expression of IL‐8 and MCP‐1, important mediators involved in the pathologic process of IBD. In addition, the ratio of the firefly and renilla luciferase activities (F/R) was used as an indicator of the NF‐κB activity in the cells. TNF‐α significantly increased the F/R ratio in the cells, and this was significantly inhibited by berberine in a concentration‐dependent manner. The results suggest that berberine may be a potential candidate to suppress the colon inflammation by inhibiting TNF‐α‐induced pro‐inflammatory cytokines.

NF-κB-dependent synergistic regulation of CXCL10 gene expression by IL-1β and IFN-γ in human intestinal epithelial cell lines

Background and aimsLittle is known about the intestinal epithelial expression and secretion of CXCL10 (IP-10), a chemokine involved in recruiting T cells and monocytes. We aimed to study CXCL10 gene expression and regulation by the pro-inflammatory cytokines interleukin (IL)-1β, interferon (IFN)-γ and tumour necrosis factor (TNF)-α in intestinal epithelial cell lines.Materials and methodsCXCL10 expression and secretion kinetics were assessed in Caco-2, HT-29 and DLD1 human colon epithelial cells, treated with IL-1β, TNF-α, IFN-γ alone or in combination with each other by real-time polymerase chain reaction (PCR), Northern blotting and enzyme-linked immunoabsorbent assay (ELISA). Transient transfections with TGL-IP10 (CXCL10 promoter) and TGL-IP10-κB2 mutant promoter and gelshifts and supershifts for nuclear factor (NF)-κB were also performed.ResultsReal-time PCRs and ELISA experiments revealed that IL-1β was the strongest and earliest inducer of CXCL10 messenger ribonucleic acid (mRNA) expression and protein secretion in Caco-2 cell line, whereas INF-γ had a delayed kinetics. There was a strong synergistic effect of either TNF-α or IL-1β with IFN-γ both on CXCL10 mRNA expression and protein secretion in all three cell lines. Real-time PCR and ELISA experiments using a specific NF-κB inhibitor and transfection experiments with a NF-κB-binding defective CXCL10 promoter construct revealed that the induction of CXCL10 by IL-1β and its synergism with IFN-γ is NF-κB dependent.ConclusionThese data demonstrate that in colonic epithelial cells, depending on the cellular context and utilizing the NF-κB pathway, IL-1β alone and/or in synergism with IFN-γ may play a major role in the induction of CXCL10.

Further characterization of a type III secretion system (T3SS) and of a new effector protein from a clinical isolate of Aeromonas hydrophila—Part I

A type III secretion system (T3SS)-associated cytotoxin, AexT, with ADP-ribosyltransferase activity and homology to Pseudomonas aeruginosa bifuncational toxins ExoT/S, was recently identified from a fish pathogen Aeromonas salmonicida. In this study, we reported the molecular characterization of an aexT-like toxin gene (designated as aexU) from a diarrheal isolate SSU of A. hydrophila. The aexU gene was 1539 bp in length and encoded a protein of 512 amino acid (aa) residues. The NH 2-terminus of AexU (aa residues 1–231) exhibited a 67% homology with the NH 2-terminus of AexT from A. salmonicida. Importantly, its COOH-terminus (aa residues 232–512) had no homology with any known functional proteins in the database; however, the full-length AexU retained ADP-ribosyltransferase activity. The expression and subsequent secretion of AexU was T3SS dependent, as inactivation of the ascV gene that codes for an inner-membrane component of the T3SS channel from the wild-type (WT) bacterium, blocked translocation of AexU in HT-29 human colonic epithelial cells. We provided evidence that inactivation of acrV and axsE genes (homologs of lcrV and exsE in Yersinia species and P. aeruginosa, respectively) from A. hydrophila SSU, altered expression and/or secretion of AexU. We deleted an aexU gene from the WT, as well as from the Δ aopB mutant, of A. hydrophila, generating a single knockout (Δ aexU) and a double knockout mutant, Δ aopB/Δ aexU. Increased phagocytosis was observed in RAW264.7 murine macrophages infected with the Δ aopB/Δ aexU mutant, as compared to macrophages when infected with the parental Δ aopB strain. Further, mice infected with the Δ aexU mutant had a 60% survival rate, compared to animals infected with the WT or the Δ aexU-complemented strain that caused 90–100% of the animals to die at a 2–3 LD 50s dose. Immunization of mice with the recombinant AexU protected them from subsequent lethal challenge dose by the WT bacterium. Finally, we detected specific anti-AexU antibodies in the sera of mice that survived challenge by the WT bacterium, which may indicate that AexU plays an important role in the pathogenesis of Aeromonas infections.