Interleukin-6 and its receptor are expressed in human intestinal epithelial cells

Irradiated Non-replicative Lactic Acid Bacteria Preserve Metabolic Activity While Exhibiting Diverse Immune Modulation

In the recent years, safety concerns regarding the administration of probiotics led to an increased interest in developing inactivated probiotics, also called “paraprobiotics”. Gamma irradiation represents a promising tool that can be used to produce safe paraprobiotics by inhibiting replication while preserving the structure, the metabolic activity, and the immunogenicity of bacteria. In this study, we evaluated the ability of four strains of lactic acid bacteria (LAB: Lacticaseibacillus casei, Lactobacillus acidophilus, Lactiplantibacillus plantarum, and Lacticaseibacillus paracasei) in preserving the metabolic activity and the immune modulation of swine porcine peripheral blood mononuclear cells, after gamma irradiation or heat inactivation. Our results show that all four strains retained the metabolic activity following gamma irradiation but not after heat inactivation. In terms of immune-modulatory capacity, irradiated L. acidophilus and Lc. paracasei were able to maintain an overall gene expression pattern similar to their live state, as heat inactivation did with Lc. casei. Moreover, we show that the two inactivation methods applied to the same strain can induce an opposed expression of key genes involved in pro-inflammatory response (e.g., IFNα and interleukin-6 for Lc. casei), whereas gamma irradiation of L. acidophilus and Lc. paracasei was able to induce a downregulation of the anti-inflammatory TGFβ. Taken together, our data show that immune modulation can be impacted not only by different inactivation methods but also by the strain of LAB selected. This study highlights that gamma irradiation harbors the potential to produce safe non-replicative metabolically active LAB and identifies immunomodulatory capacities that may be applied as vaccine adjuvants.

In Vitro Effects of Live and Heat-Inactivated Bifidobacterium animalis Subsp. Lactis, BB-12 and Lactobacillus rhamnosus GG on Caco-2 Cells

Probiotic–host interaction can be cell-to-cell or through metabolite production. Dead (inactive) organisms could interact with the host, leading to local effects and possible health benefits. This research examined the effects of live and heat-inactivated Bifidobacterium animalis subsp. lactis, BB-12 (BB-12) and Lactobacillus rhamnosus GG (LGG) on cultured Caco-2 cells focusing on epithelial integrity and production of inflammatory mediators. Live organisms increased transepithelial electrical resistance (TEER), a barrier-integrity marker, with LGG having a greater effect than BB-12. When mildly heat-treated, both organisms had a more modest effect on TEER than when alive. When they were heat-inactivated, both organisms had only a limited effect on TEER. Neither live nor heat-inactivated organisms affected production of six inflammatory mediators produced by Caco-2 cells compared to control conditions. Pre-treatment with heat-inactivated LGG or BB-12 did not alter the decline in TEER caused by exposure to an inflammatory cocktail of cytokines. However, pre-treatment of Caco-2 cells with heat-inactivated organisms alone or their combination decreased the production of interleukin (IL)-6, IL-18, and vascular endothelial growth factor. To conclude, while the live organisms improve the epithelial barrier using this model, neither live nor heat-inactivated organisms directly elicit an inflammatory response by the epithelium. Pre-treatment with heat-inactivated BB-12 or LGG can reduce some components of the response induced by an inflammatory stimulus.

Effects of Anti-Cytokine Antibodies on Gut Barrier Function

Anti-cytokine antibodies are used in treating chronic inflammatory diseases and autoimmune diseases such as inflammatory bowel disease and rheumatic diseases. Patients with these diseases often have a compromised gut barrier function, suggesting that anti-cytokine antibodies may contribute to the re-establishment of gut barrier integrity, in addition to their immunomodulatory effects. This paper reviews the effects of anti-cytokine antibodies on gut barrier function and their mechanisms.

Commensal Microbiota Regulate Vertebrate Innate Immunity-Insights From the Zebrafish

Microbial communities populate the mucosal surfaces of all animals. Metazoans have co-evolved with these microorganisms, forming symbioses that affect the molecular and cellular underpinnings of animal physiology. These microorganisms, collectively referred to as the microbiota, are found on many distinct body sites (including the skin, nasal cavity, and urogenital tract), however the most densely colonized host tissue is the intestinal tract. Although spatially confined within the intestinal lumen, the microbiota and associated products shape the development and function of the host immune system. Studies comparing gnotobiotic animals devoid of any microbes (germ free) with counterparts colonized with selected microbial communities have demonstrated that commensal microorganisms are required for the proper development and function of the immune system at homeostasis and following infectious challenge or injury. Animal model systems have been essential for defining microbiota-dependent shifts in innate immune cell function and intestinal physiology during infection and disease. In particular, the zebrafish has emerged as a powerful vertebrate model organism with unparalleled capacity for in vivo imaging, a full complement of genetic approaches, and facile methods to experimentally manipulate microbial communities. Here we review key insights afforded by the zebrafish into the impact of microbiota on innate immunity, including evidence that the perception of and response to the microbiota is evolutionarily conserved. We also highlight opportunities to strengthen the zebrafish model system, and to gain new insights into microbiota-innate immune interactions that would be difficult to achieve in mammalian models.

PMA treated THP-1-derived-IL-6 promotes EMT of SW48 through STAT3/ERK-dependent activation of Wnt/β-catenin signaling pathway

Colon cancer is one of the most common digestive malignant tumors that leads to high mortality worldwide, and metastasis is the primary cause of cancer-related death. It is well accepted that the epithelial-mesenchymal transition (EMT) plays a key role in the process of metastasis. As a cytokine that macrophage secretes, IL-6 is involved in the progression of tumors, including the invasion and metastasis via kinds of signaling pathways. However, the mechanism of interactions between IL-6, macrophage, EMT and colon cancer is not fully understood. Increased CD68⁺ macrophages and IL-6 level were found in colon tumor as compared to normal colon tissue. Metastatic lymph node showed even more CD68⁺ macrophages and higher IL-6 level than the primary tumor. These results suggested that macrophages and IL-6 play an important role in EMT of colon cancer. In order to investigate the effect of macrophage and IL-6 on EMT of colon cancer, we cultured human colon carcinoma cell line SW48 with conditioned medium (CM) from PMA-stimulated monocyte THP-1 cells and tested for IL-6 dependent EMT pathways. Wound healing assay and Transwell assay were used to analyze cell migration and invasion. Results showed that CM-treated SW48 cells increased IL-6 production and displayed elevated capacity of migration and invasion compared to untreated cells. Increased expressions of EMT markers (N-cadherin, Vimentin and β-catenin) and decreased expression of EMT marker(E-cadherin) were found in CM-treated SW48 cells by Western Blot. The addition of an anti-IL-6 antibody significantly inhibited the increase of EMT markers (Vimentin and β-catenin) as well as cell migration and invasion, suggesting that IL-6 played a critical role in promoting EMT of CM-treated SW48 cells. In addition, we found that the levels of p-STAT3 and p-ERK increased in CM-treated SW48 compared to untreated cells, which can be reversed by AG490, an inhibitor of JAK. In the meantime, the suppression of JAK-associated signaling pathways caused a decrease of β-catenin. In summary, our study suggested that macrophage-induced IL-6 promotes migration and invasion of colon cancer cell via Wnt/β-catenin pathway in STAT3/ERK-dependent way.

Could signal transducer and activator of transcription 3 be a therapeutic target in obesity-related gastrointestinal malignancy?

INTRODUCTION

A large body of evidence has implicated the signal transducer and activator of transcription (STAT) family and particularly the ubiquitously expressed STAT3 protein in the pathogenesis of colorectal, hepatocellular, gastric and pancreatic carcinoma.

DISCUSSION

Concomitantly, an increasing body of epidemiological evidence has linked obesity and its associated pro-inflammatory state with the development of gastrointestinal cancers. Visceral adipose tissue is no longer considered inert and is known to secrete a number of adipocytokines such as leptin, interleukin (IL)-6, IL-8, IL-1β and tumour necrosis factor-alpha (TNF-α) into the surrounding environment. Interestingly, these adipocytokines are strongly linked with the Janus kinase (JAK)/STAT pathway of signal transduction and there is experimental evidence linking IL-1β, IL-8 and TNF-α to JAK/STAT signaling in other tissues. The result is an up-regulation of a wide range of anti-apoptotic, pro-metastatic and pro-angiogenic genes and processes. This is particularly relevant for gastrointestinal malignancy as these factors have the potential to signal adjacent endothelial cells in a paracrine manner.

CONCLUSION

This review examines the potential role of the STAT3 signaling pathway in the pathogenesis of obesity-related gastrointestinal malignancy and the potential therapeutic role of STAT3 blockade given its status as a signaling hub for a number of inflammatory adipocytokines.

Clinical characteristics and the expression profiles of inflammatory cytokines/cytokine regulatory factors in asymptomatic patients with nodular gastritis

BACKGROUND

Nodular gastritis (NG) has been reported in adult dyspeptic patients, whereas information on NG in asymptomatic patients is limited.

AIMS

To evaluate the prevalence, clinico-epidemiological characteristics, and expression profiles of inflammatory cytokines or cytokine regulatory factors of NG in asymptomatic adults.

METHODS

A cross-sectional study was conducted prospectively using 2,579 consecutive asymptomatic subjects who underwent screening esophagogastroduodenoscopy. The expression of inflammatory cytokines or cytokine regulatory factors in the gastric mucosa of NG patients was evaluated using immunofluorescence staining.

RESULTS

NG was diagnosed in 52 patients (2.0%) and showed a predilection for females (M:F = 1:1.89) and young adults (median age: 34 years; range: 25-51 years). All NG patients were positive for Helicobacter pylori infection. Based on multivariate analysis, the risk of NG was increased in patients younger than 40 years (OR, 7.57; 95% CI, 3.76-15.24) and of the female gender (OR, 2.12; 95% CI; 1.05-4.28). Immunofluorescent staining for interleukin (IL)-1β, IL-10, IL-18, IL-18 binding protein, IL-32, IL-33, and neutrophil proteinase 3 (PR3) was performed on cryosections of gastric mucosa. Interestingly, the expression of PR3 was highly increased in the gastric biopsies from asymptomatic NG patients but was expressed infrequently in the controls.

CONCLUSIONS

Asymptomatic NG is associated with H. pylori infection, and a predilection for this condition exists in young females. The PR3 expression of gastric mucosa might play an important role in the pathogenesis of NG.

Interferon-γ modulates intestinal epithelial cell function in-vitro through a TGFβ-dependent mechanism

INTRODUCTION

Interferon γ (IFNγ) has been originally identified by its anti-viral activity and has been demonstrated to act as potent modulator of the immune system with a range of target cells limited largely to immune cell populations. Although IFNγ has been shown to directly affect the barrier function of intestinal epithelial cells, only limited information is available about other functional effects of IFNγ on intestinal epithelial cells.

METHODS

The effects on intestinal epithelial cell migration were studied using a previously described in-vitro model of epithelial restitution in confluent IEC-6 cell monolayers. Intestinal epithelial cell proliferation rates were assessed in various human and rat intestinal and colon epithelial cell lines using colorimetric MTT assays. Apoptosis of IEC-6 cells exposed to IFNγ was assessed by flow cytometry. In addition, transforming growth factor β mRNA expression after IFNγ treatment of IEC-6 cells was assessed by Northern blot analysis.

RESULTS

IFNγ significantly stimulated intestinal epithelial cell migration in an in-vitro wounding model. Furthermore, IFNγ caused a significant dose-dependent inhibition of epithelial cell proliferation in non-transformed small intestinal IEC-6 cells and human colon cancer-derived HT-29 cells and no significant rates of apoptosis were detected in the exposed epithelial cells. The effect of IFNγ on epithelial cell migration and proliferation could be completely blocked by neutralizing antibodies against TGFβ indicating that these effects are mediated through a TGFβ dependent pathway. In addition, increased expression of TGFβ1 mRNA by IEC-6 cells after treatment with IFNγ supports the hypothesis that IFNγ modulates intestinal epithelial cell function through a TGFβ-dependent pathway.

CONCLUSION

These studies suggest that IFNγ produced by constituents of the mucosal immune system modulates epithelial cell functions with relevance for intestinal wound healing and may play a role in preserving the integrity of the intestinal epithelium following various forms of injuries.

Clinical relevance of serum vascular endothelial growth factor and interleukin-6 in patients with colorectal cancer

BACKGROUND/AIM

Some biological factors play a role in stimulation of malignant growth, metastasis and angiogenesis; however, their clinical relevance has not yet been well established for most of them. This work was aimed at studying the clinical relevance of serum vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6), in patients with colorectal cancer (CRC).

MATERIALS AND METHODS

Preoperative serum levels of VEGF and IL-6 were measured by enzyme-linked immuno-assay in 35 CRC patients and in 30 healthy controls.

RESULTS

CRC patients with or without metastasis had significantly higher VEGF and IL-6 levels than healthy controls (all P < 0.001). Patients with advanced clinical stage had significantly higher levels of VEGF and IL-6 than those with early clinical stage (all P < 0.001). Also, patients with metastatic disease had significantly higher VEGF and IL-6 levels than those with localized disease (all P < 0.001). The diagnostic accuracy for invasiveness was 83% for VEGF (cut off value = 240 pg/ml) and 66% for IL-6 (cut off value = 6.7 pg/ml), with sensitivity 79% and 74% and specificity 68% and 59%, respectively.

CONCLUSION

In CRC patients, preoperative measurement of serum VEGF and Il-6 may prove useful non-invasive diagnostic indicators associated with advanced clinical stage and tumor metastasis that warrants further investigations.

Soluble gp130 promotes intestinal epithelial hyperplasia during reovirus infection

Soluble gp130 (sgp130) has been shown to suppress the inflammatory response of autoimmune pathologies; however, its effects on virus infection are not known. Here, we report that intraperitoneal treatment of mice with sgp130-Fc fusion protein at the time of oral reovirus serotype 3 infection resulted in altered morphopathological changes that were evident by less shortening of intestinal villi length and crypt depth after infection. That the effect mediated by sgp130 treatment was due to an increase in intestinal crypt cell proliferation was demonstrated by an increase in the number of crypt mitotic figures. This was further confirmed by increased immunoreactivity to the Cdc47 proliferation-associated antigen in crypts of sgp130-treated virus-infected mice compared to infected non-treated mice. These findings suggest that sgp130 may have a beneficial effect during intestinal virus infection by disrupting interleukin-6 trans-signalling, thereby reducing the local inflammatory response.

Interaction of early diet and the development of the immune system

The present review focuses on the specific effects of nutrients on the development of the immune system in early life. There is a big gap regarding the specific mechanisms that regulate immunity at the intestinal level and their impact in the systemic immune function. For this reason, during the last few years there has been great interest in ascertaining the mechanisms that regulate the intestinal immune function, as well as to understand how specific nutrients interact with the gut-associated lymphoid tissue. We have reviewed this topic with special emphasis on how human milk, and its components, influence the early development of intestinal immunity in breast-fed infants compared with formula-fed infants. Interactions between nutrients and intestinal microbiota have also been reviewed. Some micronutrients such as nucleotides and gangliosides, which are present in human milk and also in most foods, are able to influence immune functionality at very low concentrations. The specific action of these micronutrients on some parameters of immunity, as well as their potential mechanisms of action, have been considered in detail. However, there are limited data on how other specific nutrients, namely protein and non-protein N-containing compounds, lipids, carbohydrates, and others, such as minerals, vitamins, fibre, non-nutritional dietary compounds (flavonoids, carotenoids, phyto-oestrogens, etc), influence immunity. In the present review we have provided data regarding the potential effects of these compounds on the immune response in early life. The increasing use of functional foods by the public to improve their general health and prevent the incidence of chronic diseases has become a major area of interest within the nutrition community. Of the many functional foods available, probiotics have been most studied in infancy and childhood, particularly with regard to the prevention of allergic diseases. Infant formulae and fermented milks containing large quantities of probiotics are produced and consumed by Europeans and in other industrialized countries. In the present review we cover the clinical effects of probiotics in preventing disease during early life, as well as the potential mechanisms of interaction between probiotics and the gastrointestinal tract.

Bifidobacterium bifidum improves intestinal integrity in a rat model of necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is a major cause of morbidity and mortality in premature infants. Oral administration of probiotics has been suggested as a promising strategy for prevention of NEC. However, little is known about the mechanism(s) of probiotic-mediated protection against NEC. The aim of this study was to evaluate the effects of Bifidobacterium bifidum treatment on development of NEC, cytokine regulation, and intestinal integrity in a rat model of NEC. Premature rats were divided into three groups: dam fed (DF), hand fed with formula (NEC), or hand fed with formula supplemented with 5 x 10(6) CFU B. bifidum per day (B. bifidum). All groups were exposed to asphyxia and cold stress to develop NEC. Intestinal injury, mucin and trefoil factor 3 (Tff3) production, cytokine levels, and composition of tight junction (TJ) and adherens junction (AJ) proteins were evaluated in the terminal ileum. B. bifidum decreased the incidence of NEC from 57 to 17%. Increased levels of IL-6, mucin-3, and Tff3 in the ileum of NEC rats was normalized in B. bifidum treated rats. Reduced mucin-2 production in the NEC rats was not affected by B. bifidum. Administration of B. bifidum normalized the expression and localization of TJ and AJ proteins in the ileum compared with animals with NEC. In conclusion, administration of B. bifidum protects against NEC in the neonatal rat model. This protective effect is associated with reduction of inflammatory reaction in the ileum, regulation of main components of mucus layer, and improvement of intestinal integrity.

STAT1 expression is not required for polyp formation in Min mice

Recent studies have suggested the importance of interleukin (IL)-6 signaling in the development of colon cancer. Expression of IL-6 and the IL-6 receptor have been found to be elevated in colorectal carcinoma tissue, and IL-6 has been found to be critical for tumor formation in mouse models of colon cancer. IL-6 mediated activation of the transcription factor STAT1 has been shown to be important in protection of colorectal carcinoma cells from apoptotic signals. To test the hypothesis that the IL-6-STAT1 axis plays a role in early stages of colon cancer development, we examined the role of this pathway in the mouse multiple intestinal neoplasia (Min) model of intestinal tumorigenesis. Due to low fecundity, we were unable to generate Min mice lacking expression of IL-6. We then focused on the role of STAT1 in intestinal polyp formation in these animals. Min mice lacking STAT1 or heterozygous for STAT1 developed polyps in similar numbers as those expressing STAT1. Furthermore, the anatomic distribution and histological characteristics of these polyps did not vary among these populations. These results indicate that STAT1 does not play a role in the pathogenesis of the Min model for colon cancer. However, they do not rule out the possibility that STAT1 plays a role in other stages of colon cancer development.

Clone-specific expression, transcriptional regulation, and action of interleukin-6 in human colon carcinoma cells

Background

Many cancer cells produce interleukin-6 (IL-6), a cytokine that plays a role in growth stimulation, metastasis, and angiogenesis of secondary tumours in a variety of malignancies, including colorectal cancer. Effectiveness of IL-6 in this respect may depend on the quantity of basal and inducible IL-6 expressed as the tumour progresses through stages of malignancy. We therefore have evaluated the effect of IL-6 modulators, i.e. IL-1β, prostaglandin E₂, 17β-estradiol, and 1,25-dihydroxyvitamin D₃, on expression and synthesis of the cytokine at different stages of tumour progression.

Methods

We utilized cultures of the human colon carcinoma cell clones Caco-2/AQ, COGA-1A and COGA-13, all of which expressed differentiation and proliferation markers typical of distinct stages of tumour progression. IL-6 mRNA and protein levels were assayed by RT-PCR and ELISA, respectively. DNA sequencing was utilized to detect polymorphisms in the IL-6 gene promoter.

Results

IL-6 mRNA and protein concentrations were low in well and moderately differentiated Caco-2/AQ and COGA-1A cells, but were high in poorly differentiated COGA-13 cells. Addition of IL-1β (5 ng/ml) to a COGA-13 culture raised IL-6 production approximately thousandfold via a prostaglandin-independent mechanism. Addition of 17β-estradiol (10^-7 M) reduced basal IL-6 production by one-third, but IL-1β-inducible IL-6 was unaffected. Search for polymorphisms in the IL-6 promoter revealed the presence of a single haplotype, i.e., -597A/-572G/-174C, in COGA-13 cells, which is associated with a high degree of transcriptional activity of the IL-6 gene. IL-6 blocked differentiation only in Caco-2/AQ cells and stimulated mitosis through up-regulation of c-myc proto-oncogene expression. These effects were inhibited by 10^-8 M 1,25-dihydroxyvitamin D₃.

Conclusion

In human colon carcinoma cells derived from well and moderately differentiated tumours, IL-6 expression is low and only marginally affected, if at all, by PGE₂, 1,25-dihydroxyvitamin D₃, and 17β-estradiol. However, IL-6 is highly abundant in undifferentiated tumour cells and is effectively stimulated by IL-1β. In case of overexpression of an IL-6 gene variant with extreme sensitivity to IL-1β, massive release of the cytokine from undifferentiated tumour cells may accelerate progression towards malignancy by paracrine action on more differentiated tumour cells with a still functioning proliferative IL-6 signalling pathway.

The IL-6/sIL-6R complex as a novel target for therapeutic approaches

IL-6 plays a pivotal role in immune responses and certain oncologic conditions. The intense investigation of its biological activity and function led to the discovery of two different IL-6-driven signalling pathways. Binding to the membrane-bound IL-6 receptor (mIL-6R, CD126) causes the recruitment of two gp130 co-receptor molecules (CD130) and the activation of intracellular signalling cascades via gp130. Although this classical pathway is mainly limited to hepatocytes, neutrophils, monocytes/macrophages and certain other leukocyte populations, which express IL-6R on their surface, an alternative mechanism has also been described. Proteolytic cleavage of the mIL-6R protein or translation from alternatively spliced mRNA leads to the generation of a soluble form of the IL-6R (sIL-6R), which is likewise able to bind to IL-6. The resulting IL-6/sIL-6R complex is also capable of binding to gp130 and inducing intracellular signalling. Through this so-called 'trans-signalling' mechanism, IL-6 is able to stimulate cells that lack an endogenous mIL-6R. High levels of IL-6 and sIL-6R have been reported in several chronic inflammatory and autoimmune diseases as well as in cancer. Preclinical animal disease models have provided strong evidence that specific blockade of IL-6-regulated signalling pathways represents a promising approach for the therapy of these diseases. An optimised variant of the recently described fusion protein sgp30Fc is now heading towards its clinical evaluation.

IL-6 protects enterocytes from hypoxia-induced apoptosis by induction of bcl-2 mRNA and reduction of fas mRNA

Interleukin-6 (IL-6) has been shown to rescue enterocytes from hypoxia-induced apoptosis when given orally following hemorrhagic shock. In vitro models using an intestinal epithelial cell line (IEC-6) cultured with lipopolysaccharide (LPS) under low O2 conditions, to mimic intestinal conditions, show that these cells also undergo apoptosis, which can be reduced by subsequent culture with IL-6. To examine further the mechanisms of rescue, we cultured normal rat intestinal epithelial cells (IEC-6) under both normoxic and hypoxic conditions and analyzed their responses to LPS and IL-6. We showed that IEC-6 expressed IL-6 receptor on its surface. Further, IEC-6 cells could be rescued from hypoxia-induced apoptosis by co-culture with IL-6. RNase protection assay (RPA) examination revealed that under hypoxic conditions, IEC-6 cells that were resistant to apoptosis showed reduced fas expression and increased bcl-2 expression after co-culture with LPS+IL-6.

Role of interleukin-6 in hypoxic regulation of intestinal iron absorption

The regulation of intestinal iron absorption is not fully understood. Hepcidin, a liver-produced peptide, has recently been identified as a negative regulator of iron absorption in various conditions associated with altered iron metabolism (e.g. inflammation, anaemia, hypoxia). It is not clear whether these perturbants share a common signalling pathway. In this study, the importance of the cytokine interleukin-6 (IL-6) was investigated in the hypoxic mouse model. Hypoxia was associated with increased levels of circulating IL-6, decreased liver hepcidin mRNA and increased iron absorption (especially MT). A significant positive correlation existed between the total iron uptake and IL-6 levels in circulation. IL-6 per se, though inducing hepcidin mRNA, failed to affect basal iron absorption. The adaptive response to absorption following the hypoxic exposure was, however, more prominent if mice had been treated concurrently with IL-6. This enhancement in absorption occurred even though hepcidin mRNA was not significantly changed. Similar prominent responses were seen with both human and mouse IL-6. Anti-IL-6 antiserum normalised iron absorption in mice exposed to hypoxia, because of a reduction in the MT. These data indicate that IL-6 can influence iron absorption (especially MT) during the hypoxic exposure, but via a mechanism independent of hepcidin.

Differentiation-dependent expression and mitogenic action of interleukin-6 in human colon carcinoma cells: relevance for tumour progression

Interleukin (IL)-6 mRNA expression in general is low in normal, adenomatous and cancerous human colon mucosa, except in rather undifferentiated lesions, in which IL-6 is overexpressed. Cytokeratin (CK) 8-positive carcinoma cells were identified by double immunostaining as almost exclusive source of IL-6. Likewise, in five (sub)clones of primary culture COGA-1 and COGA-13 human colon carcinoma cells, and in three established cell lines (Caco-2/AQ, Caco-2/15 and HT-29), efficient translation of IL-6 mRNA into protein was observed only in the least differentiated COGA-13 cells. Notably, IL-1beta (5 ng/ml) enhanced IL-6 release in COGA-13 cultures by three orders of magnitude. Although all cell clones studied expressed the IL-6 receptor (IL-6R), rhIL-6 (1-100 ng/ml) had a significant effect on cellular proliferation only in highly differentiated Caco-2 cells. Our data imply that IL-6, when released from rather undifferentiated carcinoma cells, particularly in response to IL-1beta, can advance tumour progression through paracrine growth stimulation of normal or highly differentiated colon tumour cells with intact STAT-3-mediated IL-6 signalling.

Enhanced production of interleukin 6 in peripheral blood monocytes stimulated with mucins secreted into the bloodstream

PURPOSE

It has been reported that tumor progression is correlated with the serum level of interleukin 6 (IL-6). The purpose of this study was to investigate by what mechanism, other than production from tumor cell, the serum level of IL-6 is elevated in the tumor-bearing state.

EXPERIMENTAL DESIGN

Monocytes from healthy donors were cultured in the presence of sera from colon cancer patients, and the activity to elevate IL-6 production was estimated. This activity of serum was also examined after various biochemical treatments.

RESULTS

When monocytes from healthy donors were cultured in the presence of sera from patients with colon cancer, secretion of IL-6 from the cells was markedly elevated. Serum proteins were fractionated on Sepharose 4B and the activity to elevate IL-6 production was found in the excluded fractions. Sialyl Tn antigen was detected in these same fractions. By excluding some mucins from the serum, the inducing activity was reduced to 40% of the original level. Furthermore, we purified mucins from the conditioned medium of colon cancer cells. Production of IL-6 was effectively elevated by a small amount of purified mucins in a dose-dependent manner. When the inducing activity was examined in the presence of binding or competitive inhibitors to the scavenger receptor, the effect was remarkably reduced.

CONCLUSIONS

Mucins secreted from colon cancer cells into the bloodstream induce production of IL-6 in peripheral blood monocytes through the scavenger receptor, which may be responsible for the high level of serum IL-6 in colon cancer patients.

Variability of bacterial translocation in the absence of intestinal mucosal damage following injury and the influence of interleukin-6

Bacterial translocation and intestinal mucosal damage have been reported as potentially clinically important sequelae of injury. Evidence that endogenous interleukin-6 (IL-6) is able to protect against infection, and that orally administered IL-6 could prevent bacterial translocation and mucosal damage following haemorrhage, led us to evaluate the impact of injury on the intestinal mucosa and the role of endogenous IL-6. Normal and IL-6-deficient (IL-6-/-) mice were subjected to haemorrhage of increasing severity, hind limb ischaemia, or both. Mucosal integrity and bacterial translocation to the liver, spleen and mesenteric lymph nodes (MLN) were examined after 16 h. Bacterial translocation to each of these tissues was observed in unoperated animals. The more severe haemorrhage procedures, and hind limb ischaemia, increased bacterial translocation to the liver significantly in most experiments with normal mice. The IL-6-/- mice survived the most severe haemorrhage procedure less well (p = 0.0015), although increased bacterial translocation was not seen. There was no clear evidence of mucosal damage, or bacterial translocation to spleen and mesenteric lymph nodes, in either normal or IL-6-/- mice. Intestinal IgA concentrations were the same in IL-6-/- mice and controls. These data demonstrate that increased bacterial translocation can be observed following severe injury, but that neither bacterial translocation nor severe injury are inevitably associated with morphological damage to the intestinal mucosa, and endogenous IL-6 is more likely to promote bacterial translocation than protect the gut.

Tumor necrosis factor alpha reduces butyrate oxidation in vitro in human colonic mucosa: a link from inflammatory process to mucosal damage?

BACKGROUND

Butyrate produced by colonic bacterial fermentation is the main fuel for colonocytes, glucose being an alternative fuel. During inflammatory bowel disease, butyrate oxidation by colonocytes is impaired, and increased production of proinflammatory cytokines is detected in the colonic mucosa. We hypothesized that proinflammatory cytokines might reduce butyrate oxidation, and we assessed the in vitro effects of 3 proinflammatory cytokines on butyrate and glucose oxidation in colonic mucosa.

METHODS

Colonic biopsies were obtained from normal mucosa in 42 patients who underwent a colonoscopy. Biopsies were incubated in RPMI 1640 with [1-14C]-butyrate or [U-14C]-glucose with or without 1 of the 3 following proinflammatory cytokines: tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1beta, and IL-6. For each cytokine, 4 different concentrations were tested in 8 subjects. Concentrations overlapped those commonly found in inflamed mucosa and had no cytotoxicity as assessed in preliminary experiments using both the trypan blue exclusion test and lactate dehydrogenase release. Production of 14CO2 (picomoles per microgram dry weight per hour) was measured after a 2-hour incubation and expressed as a percentage of the control [14C]-substrate oxidation without cytokines.

RESULTS

Whereas glucose oxidation was not affected, butyrate oxidation was reduced significantly (P < 0.05) by TNFalpha at concentrations of 100 (-26 +/- 6%), 1000 (-32 +/- 7%), and 5000 pg/mL (-34 +/- 5%). IL-1beta (0, 500, 5000, and 25,000 pg/mL) and IL-6 (0, 100, 1000, and 5000 pg/mL) did not affect either substrate oxidation.

CONCLUSIONS

TNFalpha at concentrations found in inflamed mucosa reduces butyrate oxidation in vitro in mucosa from healthy controls. This result is not caused by a cytotoxic effect of TNFalpha and is not balanced by an increased oxidation of glucose. Reduced butyrate oxidation results in a decreased energy supply to colonocytes and may explain, in part, mucosal damage occurring during attacks of inflammatory bowel disease.

Increased Expression and Secretion of Interleukin-6 in Patients with Barrett’s Esophagus

Purpose: Barrett’s esophagus (BE) is a common premalignant lesion of the distal part of the esophagus that arises as a consequence of chronic duodenogastroesophageal reflux. Interleukin (IL)-6 is a pleiotropic cytokine that regulates immune defense mechanisms and hematopoiesis. In addition, IL-6 may also be involved in malignant transformation and tumor progression. IL-6 has been shown to inhibit apoptosis. The major aim of this study was to evaluate expression of IL-6 in BE at the protein and mRNA levels. In addition, we tested whether proteins that are associated with IL-6 signaling, phosphorylated signal transducer and activator of transcription 3 and two antiapoptotic proteins, Bcl-xL and Mcl-1, are also expressed in the same tissues.

Experimental Design: Biopsies of duodenum, BE, and squamous epithelium were evaluated by using a human cytokine protein array, ELISA, real-time PCR, and immunohistochemistry.

Results: Increased IL-6 levels were found to be secreted from BE tissue compared with duodenum or squamous epithelium from sites adjacent or 5 cm away from the BE lesion. IL-6 mRNA was also elevated in BE compared with duodenum or squamous epithelium in five of seven patients. Immunohistochemical studies confirmed IL-6 expression in intestinal glandular epithelium in BE tissue. Activated signal transducer and activator of transcription 3, Mcl-1, and Bcl-xL are present at higher levels in BE glands, with lower levels being found in duodenum or squamous epithelium

Conclusions: These data, taken together, suggest that elevated IL-6 levels in BE may contribute to the development of apoptosis resistance, thereby placing this epithelium at higher risk of developing malignancy.

IL-6 signal transduction and its physiological roles: the signal orchestration model

Interleukin (IL)-6 is a pleiotropic cytokine that not only affects the immune system, but also acts in other biological systems and many physiological events in various organs. In a target cell, IL-6 can simultaneously generate functionally distinct or sometimes contradictory signals through its receptor complex, IL-6Ralpha and gp130. One good illustration is derived from the in vitro observations that IL-6 promotes the growth arrest and differentiation of M1 cells through gp130-mediated STAT3 activation, whereas the Y759/SHP-2-mediated cascade by gp130 stimulation has growth-enhancing effects. The final physiological output can be thought of as a consequence of the orchestration of the diverse signaling pathways generated by a given ligand. This concept, the signal orchestration model, may explain how IL-6 can elicit proinflammatory or anti-inflammatory effects, depending on the in vivo environmental circumstances. Elucidation of the molecular mechanisms underlying this issue is a challenging subject for future research. Intriguingly, recent in vivo studies indicated that the SHP-2-binding site- and YXXQ-mediated pathways through gp130 are not mutually exclusive but affect each other: a mutation at the SHP-2-binding site prolongs STAT3 activation, and a loss of STAT activation by gp130 truncation leads to sustained SHP-2/ERK MAPK phosphorylation. Although IL-6/gp130 signaling is a promising target for drug discovery for many human diseases, the interdependence of each signaling pathway may be an obstacle to the development of a nonpeptide orally active small molecule to inhibit one of these IL-6 signaling cascades, because it would disturb the signal orchestration. In mice, a consequence of the imbalanced signals causes unexpected results such as gastrointestinal disorders, autoimmune diseases, and/or chronic inflammatory proliferative diseases. However, lessons learned from IL-6 KO mice indicate that IL-6 is not essential for vital biological processes, but a significant impact on disease progression in many experimental models for human disorders. Thus, IL-6/gp130 signaling will become a more attractive therapeutic target for human inflammatory diseases when a better understanding of IL-6 signaling, including the identification of the conductor for gp130 signal transduction, is achieved.

Differential expression and upregulation of interleukin-1alpha, interleukin-1beta and interleukin-6 by freshly isolated human small intestinal epithelial cells

BACKGROUND

Small intestinal epithelial cells (SIEC) may contribute to local immune regulation.

AIM

To examine production of interleukin (IL)-1alpha, IL-1beta and IL-6 by freshly isolated human SIEC.

METHODS

IL-1alpha and IL-1beta mRNA in epithelial layers (EL) prepared from small intestine and in intestinal epithelial cell (EC) lines were examined by reverse transcription-polymerase chain reaction. IL-1alpha, IL-1beta and IL-6 protein expression by SIEC was examined by flow cytometry before and after activation with lipopolysaccharide and epithelial growth factor.

RESULTS

IL-1alpha and IL-1beta mRNA was detected in EL and EC lines. Background expression of IL-1alpha and IL-1beta protein by SIEC was observed, which did not increase even following activation. IL-6 protein was expressed by SIEC, in a proportion that increased in two out of three samples following activation.

CONCLUSIONS

IL-6 expression and the presence of IL-1alpha and IL-1beta mRNA suggest a role for SIEC in the regulation of local inflammation.

Up-regulation of IL-18 and IL-12 in the ileum of neonatal rats with necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease of premature infants. Because the proinflammatory cytokines IL-18, IL-12, and interferon (IFN)-gamma have been implicated in other diseases of the small intestine, we hypothesized that these cytokines would play an important role in NEC pathogenesis. NEC was induced in newborn rats via enteral feeding with rat milk substitute and asphyxia and cold stress (RMS). Dam-fed, asphyxia- and cold-stressed littermates were used as controls (DF). After 96 h, the distal ileum was removed from all animals and processed to determine expression and localization of IL-18, IL-12, and IFN-gamma using real-time reverse transcriptase PCR and immunohistology. IL-18 and IL-12 mRNA from the RMS group were increased (p < or = 0.05) compared with DF controls, and there was a correlation between increasing IL-18 and IL-12 mRNA levels and progression of tissue damage (r = 0.629 and 0.588, respectively; p < or = 0.05). Immunohistology revealed IL-18 in the cytoplasm of villi and crypt enterocytes and IL-12-positive monocytes/macrophages were increased with disease progression (r = 0.503, p < or = 0.05). No differences in the number of IFN-gamma-positive cells were observed between groups. These data demonstrate up-regulation of IL-18 and IL-12 in experimental NEC and a correlation between production of these proinflammatory cytokines and progression of tissue damage.

Intra-tumoral interleukin-6 down-regulation system and genetic mutations of tumor suppressor genes in colorectal carcinoma

BACKGROUND

The interleukin (IL)-1-IL-6 network, the most potent cascade of pro-inflammatory cytokines, plays an autocrine role in tumor growth. The IL-1-IL-6 network is down-regulated by a phased cytokine inhibitor IL-1 receptor antagonist (ra) and an anti-inflammatory cytokine IL-10. The current study evaluated this down-regulation system in colorectal carcinoma and its relation to the genetic alteration of tumor suppressor genes.

METHODS

Seventy-four specimens of primary colorectal carcinoma and normal mucosa were collected to measure tissue concentrations of cytokines. Polymerase chain reaction amplification was performed to investigate the loss of heterozygosity of the microsatellite markers on chromosomes 17p and 18q.

RESULTS

The IL-1ra/IL-6 ratio in the carcinoma specimens was lower than ratios in adenomas and normal mucosae and decreased with disease progression. The IL-1ra/IL-6 ratio in early cancers tended to be lower than that in adenomas and normal mucosae. However, the tissue concentrations of IL-1beta and IL-10 were not associated with any clinicopathologic parameters. The tissue IL-1ra concentration correlated with that of IL-6 only in adenomas and early cancers. Immunohistochemically, IL-1ra and IL-6 were localized in the tumor cytoplasm. A reduced tissue IL-1ra/IL-6 ratio in the carcinomas correlated with poor prognosis and was associated with the loss of heterozygosity of the microsatellite markers on chromosomes 18q.

CONCLUSIONS

There is an IL-6-IL-1ra network system in colorectal tumors, but this system deteriorates with carcinogenesis and tumor growth. The deterioration of this network system was associated with the allelic loss of a portion of chromosome 18q, reflecting the genetic alteration of tumor suppressor genes.

Bacterial lipopolysaccharide induces transforming growth factor beta and hepatocyte growth factor through toll-like receptor 2 in cultured human colon cancer cells

This study examined, in human cancer lines, the pattern of cytokine production stimulated by lipopolysaccharide (LPS), a major component of outer surface of gram-negative bacteria, and characterized the expression pattern of CD14, cell surface LPS receptor antigen, and toll-like receptors (TLRs), which appear to be key regulators of the innate immune response system. Two colon cancer cell lines (DLD and LoVo), a hepatocellular carcinoma cell line and a myelomonocytic cell line were incubated with LPS for 0-72 h, and transforming growth factor (TGF) beta1 and beta2, hepatocyte growth factor (HGF) and interleukins 6, 8 and 15 were assayed. The only changes induced by incubation with LPS were significant increases in TGFbeta1 production at 12 h, and in HGF production at 72 h, in LPS-stimulated DLD cells, and significant increases in TGFbeta2 production after 12 h and in HGF after 72 h in LoVo cells. Using reverse transcriptase-polymerase chain reaction analysis, expression of CD14 and TLR-2 mRNA was detected in DLD and LoVo cells, and expression of TLR-4 mRNA was detected in PLC/PRF/5 and KG-1 cells. These results suggest that LPS induces TGFbeta and HGF production mediated by CD14/TLR-2 in cultured human colon cancer cell lines.

Expression of interleukin-6, leukemia inhibitory factor and their receptors by colonic epithelium and pericryptal fibroblasts

BACKGROUND AND AIM

The cellular configuration of the human colon suggests a predetermined organization that creates specific microenvironments. The role of pericryptal fibroblasts in this microenvironment has been the subject of considerable speculation. This study examined the expression of growth factors and their receptors by colonic crypt epithelium and pericryptal fibroblasts.

METHODS AND RESULTS

Pericryptal fibroblast cells were isolated and cultured from decrypted human colonic mucosa. The pericryptal fibroblast cells expressed messenger RNA (mRNA) for interleukin-6 (IL-6), leukemia inhibitory factor (LIF), LIF receptor alpha, and the common coreceptor glycoprotein 130 (GP130), but not the IL-6 receptor alpha. Interleukin-6 protein expression was confirmed by the analysis of conditioned medium and immunohistochemistry. In comparison, normal colonic epithelial cells express mRNA for LIF but not IL-6 as well as the receptors for GP-130, IL-6 receptor alpha but not LIF receptor alpha. As cultures of normal human colonic epithelial cells were not available, the conditioned medium was assayed from established colon carcinoma cell lines and demonstrated a secretion of LIF but not IL-6 protein.

CONCLUSION

The expression of reciprocal cytokine and receptor expression suggest that there is a paracrine relationship between pericryptal fibroblasts and colonic epithelium.

Flow cytometric measurement of intracellular migration inhibition factor and tumour necrosis factor alpha in the mucosa of patients with coeliac disease

There is increasing evidence that proinflammatory cytokines contribute to many of the small intestinal features in coeliac disease. The aim of the study was to investigate the expression of two proinflammatory cytokines, migration inhibition factor (MIF) and tumour necrosis factor alpha (TNF-alpha) in duodenal biopsy specimens from patients with coeliac disease on a gluten-free diet and normal control subjects. A flow cytometric system was used to analyse intracellular protein levels of MIF and TNF-alpha in freshly isolated cells from duodenal biopsies taken from 12 patients with treated coeliac disease and 10 healthy control subjects. From the biopsy specimens, single cell suspensions of the epithelium and lamina propria were prepared using EDTA/DTT and enzymes. Intracellular cytokine expression was studied in intraepithelial lymphocytes (IELs), lamina propria T cells (LP T) and intestinal epithelial cells using different surface labelling antibodies. MIF protein was constitutively expressed in IELs, LP T cells and epithelial cells from normal intestinal mucosa. In contrast, although TNF-alpha was found in LP T cells, this cytokine was virtually undetectable in either IELs or epithelial cells. In coeliac disease, intracellular levels of MIF were significantly higher in epithelial cells compared with control subjects (P = 0.005). Raised levels of TNF-alpha were found in epithelial cells (P = 0.03) as well as IELs (P = 0.045) from coeliac patients compared with controls. The findings from this study show up-regulated expression of MIF and TNF-alpha in IELs and epithelial cells of histologically normal mucosa in patients with coeliac disease. Increased expression of proinflammatory cytokines in cells occupying the epithelial layer could help explain the rapidity with which the coeliac mucosa may respond to gluten challenge.

Mitogenic action of tumour necrosis factor-alpha and interleukin-8 on explants of human duodenal mucosa

Our aim is to examine whether tumour necrosis factor-alpha (TNF-alpha) and interleukin affect the mitotic activity in explants of human duodenal mucosa and to estimate the release of cytokines from explants incubated with TNF-alpha. Biopsy specimens of normal duodenal mucosa were taken from 19 subjects that underwent upper endoscopy for investigation of dyspeptic symptoms or chronic gastrointestinal bleeding. The specimens were processed following guidelines for organ culture technique. Paired biopsy specimens from 12 subjects were cultured for 23 h to achieve steady state and thereafter the explants were incubated 25 h with 10(-13)-10(-9) M of TNF-alpha or IL-8. Mitoses were arrested in the metaphase by adding vincristine sulphate for the last three hours. The explants were then fixed and processed for microdissection. Fifteen crypts were microdissected and the total number of metaphases was determined using the whole crypt as reference volume. The number of metaphases per crypt was also estimated in explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies. Additional duodenal explants from seven subjects were incubated with 10(-10) M TNF-alpha for 25 h. Thereafter the release of IL-1-beta, IL-6, IL-8 and interferon gamma (IFN-gamma) into the culture medium was measured by enzyme immunoassay and expressed as pg/mg protein. TNF-alpha and IL-8 significantly increased the number of metaphases/crypts (P<0.0001). The addition of anti-IL-8 slightly reduced the number of metaphases/crypt compared to the values observed in the explants incubated with 10(-10) M TNF-alpha alone (P<0.0001). The number of metaphases/crypt in the explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies was, however, markedly and significantly higher than that of the controls (P<0.000). TNF-alpha induced the release of IL-8 (P<0.01) and IL-6 (P<0.05) from the duodenal explants. TNF-alpha and IL-8 are potent mitogens to human small intestinal crypts. The mitogenic action of TNF-alpha is primarily a direct effect of the cytokine and only to a minor extent mediated by a secondary production of IL-8 in the duodenal explant. Our findings indicate that TNF-alpha and IL-8 may participate in the regulation of cell proliferation in the human small intestinal epithelium.

Neutrophil-epithelial crosstalk at the intestinal lumenal surface mediated by reciprocal secretion of adenosine and IL-6

Adenosine is formed in the intestinal lumen during active inflammation from neutrophil-derived 5' AMP. Using intestinal epithelial cell line T84, we studied the effect of adenosine on the secretion of IL-6, a proinflammatory cytokine involved in neutrophil degranulation and lymphocyte differentiation. Stimulation of T84 monolayers with either apical or basolateral adenosine induces A2b receptor-mediated increase in IL-6 secretion, which is polarized to the apical (luminal) compartment. In addition, Salmonella typhimurium, TNF-alpha, and forskolin, known inducers of IL-6 secretion in intestinal epithelial cells, also stimulate IL-6 secretion into the apical compartment. We show that IL6 promoter induction by adenosine occurs through cAMP-mediated activation of nuclear cAMP-responsive element-binding protein (CREB). We also show that IL-6 released in the luminal (apical) compartment achieves a sufficient concentration to activate neutrophils (from which the adenosine signal originates), since such IL-6 is found to induce an intracellular [Ca(++)] flux in neutrophils. We conclude that adenosine released in the intestinal lumen during active inflammation may induce IL-6 secretion, which is mediated by cAMP/CREB activation and occurs in an apically polarized fashion. This would allow sequential activation of neutrophil degranulation in the lumen -- a flow of events that would, in an epithelium-dependent fashion, enhance microbicidal activity of neutrophils as they arrive in the intestinal lumen.

Dietary regulation of intestinal gene expression

We are becoming increasingly aware of inherited genetic abnormalities as causes of disease. However, alterations in gene expression can also contribute to other disease processes. Recently it has been suggested that our environment may alter such genes and thus be a direct influence on disease. Diet is a potent mechanism for altering the environment of cells of most organs, particularly the gastrointestinal tract. This review addresses the influence of nutritional factors on intestinal gene regulation. These influences include insulin, which is not a dietary component but responds to dietary changes, and butyrate, a short chain fatty acid produced by normal intestinal flora. Manipulation of diet may be a means of treating intestinal disorders. Nutritional treatment therefore is also discussed in the light of its effect on gene expression.

Necrotizing enterocolitis and hematopoietic cytokines

The names of the hematopoietic cytokines are misleading because in addition to their effects on bone marrow and bone marrow-derived cells, they have many diverse effects, including effects on the gastrointestinal tract. These effects may be directly mediated by interaction with specific receptors on gastrointestinal epithelial cells, or they may result from their effects on circulating or bowel wall leukocytes and the cytokines these cells produce. As might be expected of factors largely defined by their effects on inflammatory cells, the hematopoietic cytokines are intimately involved in the processes of bowel injury. Further investigations are needed to define the role of hematopoietic cytokines in the human neonate's balance between local gastrointestinal host defense and bowel wall injury. This could lead to effective strategies for the treatment and prevention of NEC.

Cellular localization of complement C3 and C4 transcripts in intestinal specimens from patients with Crohn's disease

It has been suggested that the increase in C3 and C4 levels in jejunal perfusates of patients with Crohn's disease (CD) results from local intestinal synthesis of complement. The present study evaluated the expression of these complement genes in inflamed tissues from patients with CD. Surgically resected specimens from patients with CD and control tissue obtained from subjects with adenocarcinoma of the colon were evaluated for C3 and C4 gene expression by the use of 35S-labelled anti-sense RNA probes. All tissue samples, diseased and normal tissue, expressed C4 mRNA throughout in the intestinal epithelium. C3 mRNA was not detected in epithelial cells in histologically normal tissue, but in diseased specimens there was a focal distribution of C3 mRNA in epithelial cells of the crypts, but not in villous epithelium. Focal C3 gene expression correlated with crypt abscess formation and the presence of polymorphonuclear leucocytes in the lumen of the crypts. In addition, C3 mRNA was also found in macrophages of the submucosa. These macrophages were CD68+, fusiform with faint cytoplasm and morphologically different from the large rounded lamina propria macrophages, which do not express C3 mRNA. Multinucleated giant cells did not express either C3 or C4 genes. In addition to its presence in intestinal epithelium, C4 mRNA was also expressed in mast cells, which however did not express C3 mRNA. These observations identify cells in the intestinal wall expressing complement genes and support the hypothesis that there is local regulated production of complement in the intestine of patients with CD, and subsequent complement activation may contribute to the inflammatory process.

Tumor necrosis factor-alpha and interleukin-1beta inhibit apolipoprotein B secretion in CaCo-2 cells via the epidermal growth factor receptor signaling pathway

In inflammatory conditions of the gut, cytokines are released into the mucosa and submucosa propagating and sustaining the inflammatory response. In CaCo-2 cells, we have shown that various inflammatory cytokines interfere with the secretion of lipids, an effect that is likely caused by the release of a ligand to the epidermal growth factor (EGF) receptor. In the present study, the role of the EGF receptor signaling pathway and the effects of the cytokines tumor necrosis factor-alpha (TNF-alpha) and and interleukin 1beta (IL-1beta) on triacylglycerol-rich lipoprotein secretion were investigated. CaCo-2 cells were incubated with oleic acid to enhance triacylglycerol-rich lipoprotein secretion. TNF-alpha and IL-1beta significantly decreased the basolateral secretion of apolipoprotein B (apoB) mass, with IL-1beta being more potent. Tyrphostin, an inhibitor of the EGF receptor intrinsic tryosine kinase, prevented or markedly attenuated the decrease in apoB secretion by TNF-alpha or IL-1beta. Both cytokines increased the phosphorylation of the EGF receptor by 30 min. Moreover, phosphotyrosine immunoblots of the EGF receptor demonstrated an increase in tyrosine residues phosphorylated by 0.5 and 6.5 h. At both these time points, TNF-alpha and IL-1beta also decreased the binding of EGF to its cell surface receptor. At 6.5 h, activation of the EGF receptor was sustained. In contrast, the early activation of the receptor was only transient as receptor phosphorylation and binding of EGF to its receptor returned to basal levels by 2 h. Preventing ligand binding to the EGF receptor by a receptor-blocking antibody attenuated receptor activation observed after 6.5 h. This did not occur at 0.5 h, suggesting that early activation of the EGF receptor was non-ligand-mediated. Similarly, apoB secretion was inhibited by an early non-ligand-mediated process; whereas at the later time, inhibition of apoB secretion was ligand-mediated. Thus, the inflammatory cytokines TNF-alpha and IL-1beta interfere with the secretion of triacylglycerol-rich lipoproteins by both early and delayed signaling events mediated by the EGF receptor signaling pathway.

Cell surface molecules and their prognostic values in assessing colorectal carcinomas

OBJECTIVE

Carcinomas of the colon and rectum are the third leading cause of cancer-related deaths. Although advances in the surgical treatment of primary colorectal cancers have lead to improvements in patient survival at early tumor stages, treatment of more progressive cancers has not resulted in dramatic improvements in patient survival. However, the selection of patient subgroups based on their prognosis and other characteristics could result in improved outcomes from adjuvant therapies in patients with Dukes B and C carcinomas.

METHODS

The authors reviewed the available data on the value of cell surface molecules in assessing the prognosis of colorectal carcinomas, paying specific attention to the evaluation of statistical analysis and multivariate procedures.

RESULTS

Cell surface molecules have been identified on colorectal carcinoma cells whose expression appears to be related to malignant transformation, tumor progression, or patient prognosis. Among these cell surface molecules, various cell adhesion molecules, growth factor receptors, proteinases, and their receptors and inhibitors have been identified as potentially useful prognostic markers.

CONCLUSIONS

Although data exist on the prognostic values of certain cell surface markers, the use of multivariate analysis for the identification of valuable prognostic factors remains uncommon. Using reproducible and standardized multivariate analysis procedures, new tumor markers should be carefully examined for their biologic and prognostic relevance before being considered as potentially useful in the management of colorectal cancers.

Serum interleukin-6 level reflects the tumor proliferative activity in patients with colorectal carcinoma

BACKGROUND

Interleukin (IL)-6 plays a central role as a differentiation and growth factor of tumor cells. It may be hypothesized that increased serum IL-6 derives from the tumor tissue, and that serum IL-6 levels consequently reflect the biologic characteristics of the tumor. The authors investigated the association between the serum levels of IL-6 in colorectal carcinoma patients and the biologic characteristics of the tumor as well as clinicopathologic status of the patients.

METHODS

Serum and tissue levels of IL-6 in 70 patients were determined using an immunoradiometric assay. Expression of IL-6 and IL-6 receptor were evaluated immunohistochemically. The proliferative activity of the tumor was assessed by nuclear Ki-67 labeling index.

RESULTS

The concentration of serum IL-6 in the patients was significantly higher than that in normal controls. The tissue concentration of IL-6 in tumor tissue was significantly higher than that in normal mucosa, and was correlated strongly with the serum IL-6 concentration. The serum IL-6 concentration was correlated with clinicopathologic parameters, including liver metastases and tumor size, and with proliferative activity of the tumor as assessed by the Ki-67 labeling index. In the patients with Stage I or II tumors, the preoperative serum IL-6 concentration was reduced significantly 3 months after surgery. Immunohistochemically, tumor tissues that expressed IL-6 immunoreactivity had a higher incidence of expression of IL-6 receptor immunoreactivity. CONCLUSIONS. Serum IL-6 concentration reflects IL-6 concentration in the tumor component and may reflect the proliferative activity of the tumor in patients with colorectal carcinoma.

Expression of functional immunomodulatory and anti-inflammatory factors in human milk

In addition to well-recognized antimicrobial substances, a growing body of evidence has accrued during the last decade regarding the presence and function of immunomodulatory and anti-inflammatory factors present in human milk and their role in protecting the mature newborn as well as the premature infant against infections. In addition, it is now appreciated that a number of these factors present in human milk may actively modulate the synthesis and maturation of the recipient immune system. This complex and interactive system of bioactive substances in human milk appears ideally to be designed to function by noninflammatory mechanisms, to operate often in a complementary or synergistic manner, to resist the digestive process in the recipient gastrointestinal tract, and to supplement developmentally delayed immune factors of the infant. The in vivo fate and effects of these immune factors in human milk, however, are still poorly understood. Clinical studies in conjunction with a broader use of experimental animal models and basic research are needed in the future to address these questions.

Colitis in transgenic and knockout animals as models of human inflammatory bowel disease

Spontaneous colitis in knockout (KO) and transgenic rodents provides experimental models to study the development of mucosal inflammation and inflammatory bowel disease (Crohn's disease and ulcerative colitis). Genetic and environmental factors, particularly the normal enteric flora, are important factors in the development of mucosal inflammation. The normal mucosal homeostasis is disrupted when there is either cytokine imbalance, abrogation of oral tolerance, alteration of epithelial barrier and function or loss of immunoregulatory cells. Some but not all immunodeficiencies, in the appropriate setting, lead to colitis. CD4+ T cells have been identified as the pathogenic T cells in colitis, which mediate inflammation by either the Th1 or the Th2 pathway. The Th1 pathway dominates most colitis models and in Crohn's disease. In contrast, the colitis in TCR alpha KO mice shares many features of ulcerative colitis including the dominance of Th2 pathway in colonic inflammation. A major benefit of these models is in the development of therapeutic strategies for the treatment of inflammatory bowel disease.

Preferential enhancement of B cell IgA secretion by intestinal epithelial cell-derived cytokines and interleukin-2

Intestinal epithelial cells (IEC) are known to secrete a number of important cytokines. Recently, we determined that IEC-derived IL-6 and TGF-beta could enhance IgA secretion and suppress IgM secretion by isolated mucosal B cells. However, since the IEC-derived cytokines must function in the context of locally produced T cell cytokines, the effect of IEC- and T cell-derived cytokines on mucosal B cell immunoglobulin secretion was determined. Using 4 day culture supernatants (IEC-SN) from the rat IEC-6 intestinal epithelial cell line and lipopolysaccharide (LPS) stimulated Peyer's patch or mesenteric lymph node B cells, the IEC- SN was found to act with IL-2 to greatly enhance IgA secretion but limit or suppress IgM secretion as compared to cultures of LPS stimulated B cells alone. However, neither IL-4, IL- 5, nor IFN-gamma affected IgA secretion with the IEC-SN. Depletion of the IEC-SN with specific anti-cytokine antibodies suggested that IEC-derived TGF-beta and IL-6 were both responsible for the enhancing effect along with IL-2 on IgA secretion, whereas IEC-derived TGF-beta alone limited or suppressed IgM secretion. These results suggest that cytokines derived from local IEC and T cells may create an environment which may contribute to the preferential enhancement of IgA secretion seen in mucosal tissues.

The mechanisms of action of interleukin-1 on rabbit intestinal epithelial cells

Interleukin-1 (IL-1) is an inflammatory mediator that increases Cl- secretion in intestinal epithelial cells. To identify the signal transduction pathway(s) involved in IL-1's action, cells were treated with IL-1 and the levels of cyclooxygenase (COX) enzymes, prostaglandin E2 (PGE2) and phospholipase A2-activating protein (PLAP), and the activity of phospholipase A2 (PLA2) were measured. IL-1 caused concentration- and time-dependent increases in the levels of PLA2 activity, and/or in the levels of PLAP, COX-2 and PGE2. The IL-induced increase in PGE2 levels was biphasic, with the first peak due to the increase in PLAP levels, and the second peak due to the increase in COX-2 levels. This increase in PGE2 levels may provide a mechanism for acute and chronic inflammation in the intestine.

Effect of pentoxifylline on survival and intestinal cytokine messenger RNA transcription in a rat model of ongoing peritoneal sepsis

OBJECTIVE

Septic animals receiving high-protein liquid diets have increased mortality and increased production of cytokines by the gut compared with animals receiving low-protein diets. The purpose of this study was to evaluate the ability of pentoxifylline to alter gut cytokine production in a rat model of prolonged acute peritonitis, to determine its effect on survival in such animals, and to determine whether alteration of gut cytokine production was associated with survival.

DESIGN

Prospective, randomized animal study.

SETTING

Research laboratory.

SUBJECTS

Male Lewis rats weighing between 250 and 300 g.

INTERVENTIONS

Anesthetized rats had placement of a gastrostomy, followed 1 wk later by implantation of a bacteria-filled osmotic minipump into the peritoneal cavity. Rats were fed a high-protein (20% total energy) enteral diet. Saline or pentoxifylline (5 or 20 mg/kg im) was administered daily beginning at the time of pump implantation.

MEASUREMENTS AND MAIN RESULTS

Septic rats fed the high-protein liquid diet and given pentoxifylline in a dose of 5 mg/kg/day demonstrated improved survival compared with saline-treated animals or animals given the high dose (20 mg/kg/day) of pentoxifylline (p< .05). Administration of pentoxifylline at 5 mg/kg/day also down regulated the production of IL-6 messenger RNA (mRNA) in liver and lipopolysaccharide binding protein mRNA in the liver and intestine of septic animals given the high-protein liquid diet.

CONCLUSION

Low-dose (but not high-dose) pentoxifylline administration reduced production of some, but not all, cytokines studied in the gut and liver in a rat model of acute peritonitis and this reduced production was associated with an improved survival in such animals.

Local cytokine response in Helicobacter pylori-infected subjects

The host immune response to Helicobacter pylori infection might be of importance with regard to the outcome of infection by this organism, e.g., to explain why only a proportion of infected subjects develop peptic ulcers. In this study we have analyzed the local response of different cytokines-i.e., the proinflammatory interleukin-1beta, (IL-1beta), IL-6, tumor necrosis factor alpha, and IL-8; the immunoregulatory gamma interferon (IFN-gamma); and IL-4; and the anti-inflammatory transforming growth factor beta (TGF-beta)-in antral biopsy specimens from H. pylori-infected duodenal ulcer (DU) patients and asymptomatic (AS) carriers (i.e., with chronic gastritis only). For comparison, biopsy specimens from uninfected healthy individuals were also analyzed. An immunohistochemical technique was used to allow quantification of the cytokine responses as well as identification of the cell types associated with the cytokine expression. We found that the levels of all of the studied cytokines except IL-4 were increased in the H. pylori-infected subjects compared to the levels in the healthy individuals. Our results indicate that the antral cytokine response is of the Th1 type since IFN-gamma, but not IL-4, was up-regulated both in H. pylori-infected DU patients and in AS carriers. However, there were no significant differences in either proinflammatory or immunoregulatory cytokine levels when H. pylori-infected subjects with and without peptic ulcers were compared. Some of the cytokines, particularly IL-1beta and TGF-beta, were also found in the gastric mucosae of healthy, uninfected subjects. We also showed that the gastric epithelium contributes substantially to the antral cytokine response of the proinflammatory cytokines IL-1beta and IL-6 in addition to IL-8.