Mechanisms of carrageenan injury of IEC18 small intestinal epithelial cell monolayers

Evidence and hypotheses on adverse effects of the food additives carrageenan (E 407)/processed Eucheuma seaweed (E 407a) and carboxymethylcellulose (E 466) on the intestines: a scoping review

This scoping review provides an overview of publications reporting adverse effects on the intestines of the food additives carrageenan (CGN) (E 407)/processed Eucheuma seaweed (PES) (E 407a) and carboxymethylcellulose (CMC) (E 466). It includes evidence from human, experimental mammal and in vitro research publications, and other evidence. The databases Medline, Embase, Scopus, Web of Science Core Collection, Cochrane Database of Systematic Reviews and Epistemonikos were searched without time limits, in addition to grey literature. The publications retrieved were screened against predefined criteria. From two literature searches, 2572 records were screened, of which 224 records were included, as well as 38 records from grey literature, making a total of 262 included publications, 196 on CGN and 101 on CMC. These publications were coded and analyzed in Eppi-Reviewer and data gaps presented in interactive maps. For CGN, five, 69 and 33 research publications on humans, experimental mammals and in vitro experiments were found, further separated as degraded or native (non-degraded) CGN. For CMC, three human, 20 animal and 14 in vitro research publications were obtained. The most studied adverse effects on the intestines were for both additives inflammation, the gut microbiome, including fermentation, intestinal permeability, and cancer and metabolic effects, and immune effects for CGN. Further studies should focus on native CGN, in the form and molecular weight used as food additive. For both additives, randomized controlled trials of sufficient power and with realistic dietary exposure levels of single additives, performed in persons of all ages, including potentially vulnerable groups, are needed.

Modulatory effect of eugenol on arginase, nucleotidase, and adenosine deaminase activities of platelets in a carrageenan-induced arthritis rat model: A possible anti-arthritic mechanism of eugenol

This study investigated the effect of eugenol on arginase, nucleotidase and adenosine deaminase activities in platelets of carrageenan-induced arthritic rat model to explain a possible anti-arthritic mechanism of eugenol. Fifty adult female rats (140-250 g) were divided into ten (10) groups (n = 5). Group I received oral administration of corn oil, group II received 2.50 mg/kg of eugenol, group III and IV rats received oral administration of 5.0 and 10.0 mg/kg of eugenol respectively, group V received 0.20 mg/kg of dexamethasone orally, group VI rats was injected with 1% carrageenan (arthritic rats) and received saline solution orally (arthritic control rat group), group VII, VIII and IX: arthritic rats received 2.50, 5.0 or 10 mg/kg of eugenol orally respectively, group X: arthritic rats was administered with 0.20 mg/kg of dexamethasone orally. The animals were treated for 21 days, thereafter, tibiofemoral histological examination, thiobabituric acid reactive substances level, arginase, nucleoside triphosphate diphosphohydrolase, 5´-nucleotidase and adenosine deaminase activities were assessed. Tibiofemoral histological examination result showed that infiltration of inflammatory cells was significantly decreased with an increase in eugenol dose. Activities of arginase, adenosine triphosphate and adenosine monophosphate hydrolyses were significantly decreased while adenosine diphosphate hydrolysis and adenosine deaminase activities were significantly increased in arthritic rat groups administered with different doses of eugenol. Therefore, eugenol might be a natural complement and alternative promising anti-arthritic agent. These possible anti-arthritic mechanisms may be partly through the modulation of arginase and adenosine nucleotides hydrolyzing enzyme activities as well as the antioxidative action of eugenol.

Pro-apoptotic action of macrophage inhibitory cytokine 1 and counteraction of activating transcription factor 3 in carrageenan-exposed enterocytes

Carrageenan (CGN), a widely used food additive, has been shown to injure the epithelial barrier in animal models. This type of damage is a clinical feature of inflammatory bowel disease (IBD) in humans. In the present study, the effects of CGN on pro-apoptotic responses associated with macrophage inhibitory cytokine 1 (MIC-1) regulation in human enterocytes were evaluated. CGN up-regulated the expression of MIC-1 that promoted epithelial cell apoptosis. Although MIC-1 induction was dependent on pro-apoptotic p53 protein, the pro-survival protein activating transcription factor 3 (ATF3) was negatively regulated by p53 expression. However, MIC-1 enhanced the expression of the pro-survival protein ATF3 in enterocytes exposed to CGN. Functionally, MIC-1-mediated epithelial cell apoptosis was counteracted by the pro-survival action of ATF3 in response to CGN exposure. These findings demonstrated that the counterbalance between MIC-1 and ATF3 is critical for deciding the fate of enterocytes under the food chemical stress.

Dextran sulfate sodium administered orally is depolymerized in the stomach and induces cell cycle arrest plus apoptosis in the colon in early mouse colitis

The mechanisms responsible for human inflammatory bowel disease remain poorly understood. The pathogenic factors for dextran sulfate sodium (DSS)-induced colitis, one of the experimental animal colitis models, also remain unknown. Furthermore, detailed studies on DSS metabolism in the gut lumen have not been reported. Therefore, we investigated DSS metabolism in the mouse gut lumen and report the mechanisms which induce colitis. DSS was labeled with 2-aminopyridine (pyridylamino-DSS, PA-DSS). PA-DSS was administered orally to male BALB/cA Jcl mice. The metabolites and histological findings were observed using HPLC and light or fluorescence microscopy. PA-DSS with Mr 5000 was depolymerized rapidly in the gastric lumen, and the depolymerized PA-DSS was absorbed in the small intestine. Therefore, the majority of the PA-DSS in the cecal contents returned to Mr 5000 PA-DSS, escaping absorption in the small intestine. Mr 5000 DSS induced severe colitis, and immunostaining using an anti-mouse Ki-67 antibody and the TUNEL assay showed that DSS arrested the cell cycle at the G0 phase and induced apoptosis of the colonic epithelium. Mr 2500 PA-DSS, however, induced these same effects weakly. During these processes, we observed that the epithelial cells can depolymerize DSS themselves. An in vitro study using Caco-2 cells also showed similar effects. Mr 5000 DSS was depolymerized in the gut lumen and epithelial cells. Therefore, the molecular mass distribution of the DSS differed between each part in the lumen. As an early stage event, DSS induced colitis through cell cycle arrest and apoptosis according to its molecular mass.

Pro-inflammatory NF-κB and early growth response gene 1 regulate epithelial barrier disruption by food additive carrageenan in human intestinal epithelial cells

The widely used food additive carrageenan (CGN) has been shown to induce intestinal inflammation, ulcerative colitis-like symptoms, or neoplasm in the gut epithelia in animal models, which are also clinical features of human inflammatory bowel disease. In this study, the effects of CGN on pro-inflammatory transcription factors NF-κB and early growth response gene 1 product (EGR-1) were evaluated in terms of human intestinal epithelial barrier integrity. Both pro-inflammatory transcription factors were elevated by CGN and only NF-κB activation was shown to be involved in the induction of pro-inflammatory cytokine interleukin-8. Moreover, the integrity of the in vitro epithelial monolayer under the CGN insult was maintained by both activated pro-inflammatory transcription factors NF-κB and EGR-1. Suppression of NF-κB or EGR-1 aggravated barrier disruption by CGN, which was associated with the reduced gene expression of tight junction component zonula occludens 1 and its irregular localization in the epithelial monolayer.

The role of transient receptor potential vanilloid 1 (TRPV1) receptors in dextran sulfate-induced colitis in mice

The aim of this study was to investigate the involvement of transient receptor potential vanilloid 1 (TRPV1) receptors in oral dextran sulfate sodium-induced (DSS) colitis using TRPV1 knockout mice and their wild-type C57BL/6 counterparts. DSS (2% or 5%) was administered orally ad libitum for 7 days; the controls received tap water. Animal weight, stool consistency, and blood content were scored every day to calculate the disease activity index (DAI). After sacrificing the mice on day 7, the colons were cut into three equal segments (proximal, intermediate, and distal) for histology, myeloperoxidase (MPO), and cytokine measurements. In the 2% DSS-treated group, the lack of TRPV1 receptors decreased the DAI. Each colon segment of wild-type animals showed more than two-fold increase of MPO activity and more severe histological changes compared to the knockouts. This difference was not observed in case of 5% DSS, when extremely severe inflammation occurred in both groups. IL-1beta production was not altered by the absence of TRPV1. In conclusion, activation of TRPV1 channels enhances the clinical symptoms, histopathological changes, and neutrophil accumulation induced by 2% DSS. Elucidating the modulator role of TRPV1 channels in inflammatory bowel diseases may contribute to the development of novel anti-inflammatory drugs for their therapy.

Degraded carrageenan causing colitis in rats induces TNF secretion and ICAM-1 upregulation in monocytes through NF-kappaB activation

Carrageenan (CGN) is a high molecular weight sulphated polysaccharide derived from red seaweeds. In rodents, its degraded forms (dCGN) can induce intestinal inflammation associated with macrophage recruitment and activation. The aim of this study was: 1) to analyze the size-dependent effects of dCGN on colon inflammation in vivo, and 2) to correlate these effects with monocyte/macrophage proliferation, cytokine production and expression of various cell surface antigens including ICAM-1 adhesion molecule. Peripheral blood monocytes (PBM) and THP-1 monocytic cells were cultured in the presence of either 10 or 40 kDa, dCGN. The 40 kDa, but not the 10 kDa dCGN, induced colitis in in vivo. Degraded CGN inhibited THP-1 cell proliferation in vitro, arresting the cells in G1 phase. In addition, dCGN increased ICAM-1 expression in both PBM and THP-1 cells with a major effect seen after 40 kDa dCGN exposure. Also, dCGN stimulated monocyte aggregation in vitro that was prevented by incubation with anti-ICAM-1 antibody. Finally, dCGN stimulated TNF-α expression and secretion by both PBM and THP-1 cells. All these effects were linked to NF-κB activation. These data strongly suggest that the degraded forms of CGN have a pronounced effect on monocytes, characteristic of an inflammatory phenotype.

DMBT1 functions as pattern-recognition molecule for poly-sulfated and poly-phosphorylated ligands

Deleted in malignant brain tumors 1 (DMBT1) is a secreted glycoprotein displaying a broad bacterial-binding spectrum. Recent functional and genetic studies linked DMBT1 to the suppression of LPS-induced TLR4-mediated NF-kappaB activation and to the pathogenesis of Crohn's disease. Here, we aimed at unraveling the molecular basis of its function in mucosal protection and of its broad pathogen-binding specificity. We report that DMBT1 directly interacts with dextran sulfate sodium (DSS) and carrageenan, a structurally similar sulfated polysaccharide, which is used as a texturizer and thickener in human dietary products. However, binding of DMBT1 does not reduce the cytotoxic effects of these agents to intestinal epithelial cells in vitro. DSS and carrageenan compete for DMBT1-mediated bacterial aggregation via interaction with its bacterial-recognition motif. Competition and ELISA studies identify poly-sulfated and poly-phosphorylated structures as ligands for this recognition motif, such as heparansulfate, LPS, and lipoteichoic acid. Dose-response studies in Dmbt1(-/-) and Dmbt1(+/+) mice utilizing the DSS-induced colitis model demonstrate a differential response only to low but not to high DSS doses. We propose that DMBT1 functions as pattern-recognition molecule for poly-sulfated and poly-phosphorylated ligands providing a molecular basis for its broad bacterial-binding specificity and its inhibitory effects on LPS-induced TLR4-mediated NF-kappaB activation.

Expression of apoptotic epithelial cells within lamina propria beneath the basement membrane triggers dextran sulfate sodium-induced colitis

We postulated that nuclear dust within the lamina propria beneath the basement membrane of the epithelium in colonic mucosa is a form of apoptotic epithelial cells and that its expression triggers dextran sulfate sodium-induced colitis. The aim was to determine the origin of nuclear dust and to explore the correlation between nuclear dust expression and clinicopathologic parameters of colitis. Rats were treated with 3% dextran sulfate sodium. Cells showing double positive staining with cytokeratin and TdT-mediated uUTP-biotin nick-end labeling technique were apoptotic cells derived from epithelial cells. Nuclear dust expression on day 5 correlated with bloody stools and a decrease of mitotic colonic cells just before ulceration. Examination of cultures under light and fluorescent microscopy showed that dextran sulfate sodium caused early apoptosis and late apoptosis or necrosis. Our results suggest that interventions directed toward the apoptotic process may be beneficial in the treatment of ulcerative colitis.

Cysteine-rich domains of muc3 intestinal mucin promote cell migration, inhibit apoptosis, and accelerate wound healing

BACKGROUND & AIMS

Muc3 intestinal mucin contains an extracellular cysteine-rich domain with 2 epidermal growth factor (EGF)-like motifs. The aim of this study was to determine the functional properties of Muc3 proteins.

METHODS

Glutathione S-transferase-fusion proteins containing both Muc3 EGF-like domains (m3EGF1,2) or truncated versions (m3EGF1 and m3EGF2) were purified from Escherichia coli. Mouse colon (young adult mouse colon) and human A431 and LoVo cells were examined for migration and tyrosine phosphorylation in response to recombinant proteins. LoVo cells were transfected with a human MUC3A transmembrane-EGF1,2 construct and a stable clone was isolated (LhM3c14). Endogenous MUC3A in LoVo was inhibited by specific small interfering RNA transfection. Apoptosis was quantitated by nuclear morphology or terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick-end labeling assay. Colitis was induced in mice by oral 5% dextran sodium sulfate or rectal 5% acetic acid, followed by enema treatments.

RESULTS

m3EGF1,2 stimulated cell migration in all cell lines, but did not induce proliferation. Migration was inhibited by a tyrosine phosphorylation inhibitor, genistein, but not by the EGF receptor inhibitor, tyrphostin (AG1478). Inhibition of endogenous MUC3A in LoVo reduced baseline migration. Tyrosine phosphorylation of ErbB receptors was not observed after treatment of cells with m3EGF1,2. LoVo cells pretreated with m3EGF1,2 and transfected LhM3c14 cells showed reduced apoptosis in response to tumor necrosis factor alpha or Fas-receptor stimulation. Administration of m3EGF1,2 per rectum significantly reduced mucosal ulceration and apoptosis in experimental acute colitis. Truncated proteins m3EGF1 and m3EGF2 had no effect.

CONCLUSIONS

The Muc3 mucin cysteine-rich domain plays an active role in epithelial restitution, and represents a potential novel therapeutic agent for intestinal wound healing.

Review of harmful gastrointestinal effects of carrageenan in animal experiments

In this article I review the association between exposure to carrageenan and the occurrence of colonic ulcerations and gastrointestinal neoplasms in animal models. Although the International Agency for Research on Cancer in 1982 identified sufficient evidence for the carcinogenicity of degraded carrageenan in animals to regard it as posing a carcinogenic risk to humans, carrageenan is still used widely as a thickener, stabilizer, and texturizer in a variety of processed foods prevalent in the Western diet. I reviewed experimental data pertaining to carrageenan's effects with particular attention to the occurrence of ulcerations and neoplasms in association with exposure to carrageenan. In addition, I reviewed from established sources mechanisms for production of degraded carrageenan from undegraded or native carrageenan and data with regard to carrageenan intake. Review of these data demonstrated that exposure to undegraded as well as to degraded carrageenan was associated with the occurrence of intestinal ulcerations and neoplasms. This association may be attributed to contamination of undegraded carrageenan by components of low molecular weight, spontaneous metabolism of undegraded carrageenan by acid hydrolysis under conditions of normal digestion, or the interactions with intestinal bacteria. Although in 1972, the U.S. Food and Drug Administration considered restricting dietary carrageenan to an average molecular weight > 100,000, this resolution did not prevail, and no subsequent regulation has restricted use. Because of the acknowledged carcinogenic properties of degraded carrageenan in animal models and the cancer-promoting effects of undegraded carrageenan in experimental models, the widespread use of carrageenan in the Western diet should be reconsidered.

Lambda-carrageenan-induced inhibition of gap-junctional intercellular communication in rat liver epithelial cells

lambda-Carrageenan, a food additive extracted from red seaweed, is widely used as an emulsifier, stabilizer, or thickener. Previously, it has been shown that carrageenan could play a role in carcinogenesis. However, the mechanism by which it might influence the multimechanism, multistep process of carcinogenesis is not known. Gap-junctional intercellular communication (GJIC) has been associated with maintaining homeostatic regulation of cell proliferation and differentiation. Most cancer cells have dysfunctional GJIC, and many tumor-promoting chemicals, growth factors, and oncogenes can downregulate GJIC. The experiments in this study were designed to test the hypothesis that carrageenan might function as a tumor-promoting chemical by inhibiting GJIC. To test this hypothesis, nontumorigenic rat liver epithelial cells were exposed to carrageenan, and GJIC was measured. Western blot analysis and immunofluorescent staining were used to monitor the phosphorylation and localization of connexin 43. The data revealed inhibition of GJIC by carrageenan similar to that by the well-documented tumor promoter phorbol ester. However, the phosphorylation and localization of connexin 43 were not altered. Although the mechanism by which carrageenan inhibits GJIC is unknown, carrageenan's influence on the carcinogenic process might be via its ability to be a tumor promoter.

Effect of D-002 on the pre-ulcerative phase of carrageenan-induced colonic ulceration in the guinea-pig

D-002 is a natural mixture of higher aliphatic primary alcohols, isolated and purified from beeswax which has anti-inflammatory properties, reduces leukotrienes (LTB4) and thromboxane B2 (TXB2) in exudated carrageenan-induced pleurisy, and has anti-ulcer activity in different experimental models. This study was conducted to determine the effect of D-002 on the pre-ulcerative phase of carrageenan-induced colonic ulceration in guinea-pigs. Animals were randomly distributed among a negative control, a positive control group treated with the vehicle Tween 20 in H2O and two experimental groups receiving D-002 at 25 and 50 mg kg(-1). All treated animals received degraded carrageenan for three days for induction of colonic ulceration. Significant reductions in wet weight, wall thickness, counts of infiltrating polymorphonuclear neutrophils and of macrophages, and histological index were observed in colonic mucosa of D-002-treated animals compared with controls. It is concluded that D-002 has a protective effect on the pre-ulcerative phase of carrageenan-induced colonic ulceration in the guinea-pig.

Dextran sulfate sodium-induced colitis occurs in severe combined immunodeficient mice

BACKGROUND/AIMS

Oral administration of dextran sulfate sodium (DSS) has been reported to induce colitis in mice. The purpose of this study was to determine whether the possible pathogenic mechanism involved the acquired immune system.

METHODS

Normal BALB/c and related C.B17 severe combined immunodeficient mice were fed 5% DSS (40 kilodaltons) in their drinking water for 7 days; controls were fed only water. Colons were scored for histological activity at various times. Cytokine production by cultures of colon and of draining lymph node cell was measured. The effect of DSS on the proliferation of the MCA-38 colonic epithelial cell line was assessed.

RESULTS

DSS feeding resulted in a very reproducible acute distal colitis in both BALB/c and C.B17 severe combined immunodeficient mice. The lesions of BALB/c mice had an increased production of macrophage-derived cytokines, such as interleukin (IL) 1 beta, IL-6, tumor necrosis factor, and granulocyte-macrophage colony-stimulating factor, but not the T-cell cytokines IL-3 or interferon gamma. Draining lymph node cells produced these cytokines plus interferon gamma and IL-3. DSS inhibited MCA-38 cells at doses that would be easily achieved in the distal colon.

CONCLUSIONS

Acute DSS-induced colitis does not require the presence of T cells or B cells because it occurred in C.B17 severe combined immunodeficient mice that lack these cells. Its induction may result from a toxicity of DSS for colonic epithelial cells.

Experimental colitis in animal models

Colitis may be induced in animals by oral administration of sulfated polysaccharides (carrageenan, amylopectin sulfate, dextran sulfate), chemical irritation by rectal instillation of diluted acetic acid, delayed hypersensitivity reaction after sensitization to DNCB or after one single administration of TNBS, and Arthus reaction induced by intravenous injection of immune complexes after chemical irritation of the colon, and by chemoattractant peptides such as FMLP. It appears that all models of colon inflammation in the rat, mouse, or rabbit produce increased amounts of eicosanoids similar to that found in human colitis. Thus, animal studies provide useful information on the origin, regulation, and function of inflammatory mediators. However, with the possible exception of the cotton-top tamarin, no animal model of induced or spontaneous inflammation of the colon is analogous to human ulcerative colitis in etiology, course of disease activity, or histology (114). The observation that two different immune-mediated models gave similar results suggests that the colitis is not a specific response to delayed-type hypersensitivity or immune-complex-mediated reactions but rather an unspecific, stereotype response (125). The original disturbance may not determine the nature of the lesions ultimately produced but may instead serve as an initiator of a final common immunologic pathway.

Oxygen free radical injury of IEC-18 small intestinal epithelial cell monolayers

Oxygen radicals can cause endothelial and epithelial permeability changes and mucosal injury of the small intestine. There is no clear consensus concerning the relative injurious potential of individual oxygen radicals. In this study, the small intestinal cell line IEC-18 was used as an in vitro model to study the relative injurious effects of reactive oxygen metabolites. By introducing different combinations of oxygen metabolite-producing enzymes, xanthine oxidase, superoxide dismutase, and catalase, and an iron chelator, deferoxamine, to the fully confluent monolayers and to proliferating IEC-18 cells, the differential injurious effects of the oxygen metabolites O2-, H2O2, and OH. could be evaluated. The extent of cellular injury was assessed using [3H]thymidine uptake, 51Cr release, and morphological evaluations. Our results suggest that OH. produced as a by-product of O2- and H2O2 via the Haber-Weiss reaction was the most injurious oxygen species involved in cellular injury of IEC-18 monolayers induced by xanthine oxidase. O2- produced by xanthine oxidase appeared to be only minimally injurious, and H2O2 produced by xanthine oxidase and as a result of conversion of O2- by superoxide dismutase was moderately injurious. Superoxide dismutase and deferoxamine at appropriate concentrations were protective against xanthine/xanthine oxidase-induced monolayer injury. H2O2 added directly or produced indirectly by glucose oxidase was very injurious to the intestinal monolayers, and this injury was mitigated by catalase.

The effects of carrageenan on drug-metabolizing enzyme system activities in the guinea-pig

Carrageenans are seaweed extracts comprising high molecular weight sulphated polygalactosides. They are used in foods at concentrations of up to 2.5% as thickening and gelling agents. When degraded to lower molecular weight forms, they have been shown to induce ulcerative colitis and colon cancer in laboratory animals. Furthermore, undegraded carrageenan (CG) has been shown to promote azoxymethane and methylnitrosourea initiated carcinogenesis, but the promotion mechanism is unclear. To determine if this mechanism involves alterations of tissue drug-metabolizing enzyme system (DMES) activities, six groups of five guinea-pigs each were administered 0.2% kappa undegraded, 0.2% i undegraded, 1% kappa degraded or 1% i degraded CG, or control solutions in the drinking-water for 8 wk. Microsomal and cytosolic DMES activities of the liver, small intestine and colon were determined. The kappa undegraded CG group exhibited significant (P less than 0.05) increases in small intestine cytochrome P-450 levels and benzo[a]pyrene hydroxylase activities. These data suggest that undegraded CG may selectively induce DMES activities in the small intestine mucosa.

A novel method in the induction of reliable experimental acute and chronic ulcerative colitis in mice

Acute and chronic experimental ulcerative colitis models were produced in mice by providing them with drinking water containing synthetic dextran sulfate sodium. Mice that developed acute colitis showed signs of diarrhea, gross rectal bleeding, and weight loss within 6-10 days after ingesting 3%-10% dextran sulfate sodium. On postmortem examination, multiple erosions and inflammatory changes including crypt abscesses were found on the left side of the large intestine. Mice that developed chronic colitis showed signs of erosions, prominent regenerations of the colonic mucosa including dysplasia, shortening of the large intestine, and frequent formation of lymphoid follicles after 5 administration cycles, where each cycle was composed of 7 days' consumption of drinking water containing 5% dextran sulfate sodium followed by 10 days' consumption of distilled water. The population of intestinal microflora, Bacteroides distasonis and Clostridium spp., increased significantly in mice with acute and chronic ulcerative colitis. Further, morphological studies suggest that the administered dextran sulfate sodium was partially phagocytized by macrophages in the colonic mucosa.