Cytokines in Crohn's colitis

Anti-Inflammatory Activity and Mechanism of Isookanin, Isolated by Bioassay-Guided Fractionation from Bidens pilosa L

Bidens pilosa L. (Asteraceae) has been used historically in traditional Asian medicine and is known to have a variety of biological effects. However, the specific active compounds responsible for the individual pharmacological effects of Bidens pilosa L. (B. pilosa) extract have not yet been made clear. This study aimed to investigate the anti-inflammatory phytochemicals obtained from B. pilosa. We isolated a flavonoids-type phytochemical, isookanin, from B. pilosa through bioassay-guided fractionation based on its capacity to inhibit inflammation. Some of isookanin’s biological properties have been reported; however, the anti-inflammatory mechanism of isookanin has not yet been studied. In the present study, we evaluated the anti-inflammatory activities of isookanin using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. We have shown that isookanin reduces the production of proinflammatory mediators (nitric oxide, prostaglandin E₂) by inhibiting the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-stimulated macrophages. Isookanin also inhibited the expression of activator protein 1 (AP-1) and downregulated the LPS-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-jun NH₂-terminal kinase (JNK) in the MAPK signaling pathway. Additionally, isookanin inhibited proinflammatory cytokines (tumor necrosis factor-a (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), and interleukin-1β (IL-1β)) in LPS-induced THP-1 cells. These results demonstrate that isookanin could be a potential therapeutic candidate for inflammatory disease.

NLRP1 variant M1184V decreases inflammasome activation in the context of DPP9 inhibition and asthma severity

Background

NLRP1 is an innate immune sensor that can form cytoplasmic inflammasome complexes. Polymorphisms in NLRP1 are linked to asthma; however, there is currently no functional or mechanistic explanation for this.

Objective

We sought to clarify the role of NLRP1 in asthma pathogenesis.

Methods

Results from the GALA II cohort study were used to identify a link between NLRP1 and asthma in Mexican Americans. In vitro and in vivo models for NLRP1 activation were applied to investigate the role of this inflammasome in asthma at the molecular level.

Results

We document the association of an NLRP1 haplotype with asthma for which the single nucleotide polymorphism rs11651270 (M1184V) individually is the most significant. Surprisingly, M1184V increases NLRP1 activation in the context of N-terminal destabilization, but decreases NLRP1 activation on dipeptidyl peptidase 9 inhibition. In vitro studies demonstrate that M1184V increases binding to dipeptidyl peptidase 9, which can account for its inhibitory role in this context. In addition, in vivo data from a mouse model of airway inflammation reveal a protective role for NLRP1 inflammasome activation reducing eosinophilia in this setting.

Conclusions

Linking our in vitro and in vivo results, we found that the NLRP1 variant M1184V reduces inflammasome activation in the context of dipeptidyl peptidase 9 inhibition and could thereby increase asthma severity. Our studies may have implications for the treatment of asthma in patients carrying this variant of NLRP1.

Robustaflavone Isolated from Nandina domestica Using Bioactivity-Guided Fractionation Downregulates Inflammatory Mediators

Nandina domestica (Berberidaceae) has been used in traditional medicine for the treatment of cough. This plant is distributed in Korea, Japan, China, and India This study aimed to investigate the anti-inflammatory phytochemicals obtained from the N. domestica fruits. We isolated a biflavonoid-type phytochemical, robustaflavone (R), from N. domestica fruits through bioactivity-guided fractionation based on its capacity to inhibit inflammation. The anti-inflammatory mechanism of R isolated from N. domestica has not yet been studied. In the present study, we evaluated the anti-inflammatory activities of R using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. We have shown that R reduces the production of nitric oxide (NO), pro-inflammatory cytokine interleukin-1 beta (IL-1β), and IL-6. Western blot analysis showed that R suppresses the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and downregulates the expression of LPS-induced nuclear factor-kappa B (NF-κB) and the phosphorylation of extracellular-regulated kinases (pERK 1/2). Moreover, R inhibited IL-8 release in LPS-induced human colonic epithelial cells (HT-29). These results suggest that R could be a potential therapeutic candidate for inflammatory bowel disease (IBD).

Role of epithelial ion transports in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with a complex pathogenesis. Diarrhea is a highly prevalent and often debilitating symptom of IBD patients that results, at least in part, from an intestinal hydroelectrolytic imbalance. Evidence suggests that reduced electrolyte absorption is more relevant than increased secretion to this disequilibrium. This systematic review analyses and integrates the current evidence on the roles of epithelial Na(+)-K(+)-ATPase (NKA), Na(+)/H(+) exchangers (NHEs), epithelial Na(+) channels (ENaC), and K(+) channels (KC) in IBD-associated diarrhea. NKA is the key driving force of the transepithelial ionic transport and its activity is decreased in IBD. In addition, the downregulation of apical NHE and ENaC and the upregulation of apical large-conductance KC all contribute to the IBD-associated diarrhea by lowering sodium absorption and/or increasing potassium secretion.

Cytokines in inflammatory bowel disease

Over the past decade, much has been learned regarding the role of various cytokines in the pathogenesis of inflammatory bowel disease. Several cytokine ‘knockout’ models in mice have been shown to develop colitis, while alterations in the production of various cytokines has been documented in human Crohn's disease and ulcerative colitis. In recent years, attempts have been made to treat these diseases through modulation of cytokine production or action. This review focuses on the cytokines that have been implicated in the pathogenesis of inflammatory bowel disease. The evidence for and against a role for particular cytokines in intestinal inflammation is reviewed, as is the experimental and clinical data suggesting that cytokines are rational targets for the development of new therapies.

Relationships between Helicobacter pylori infection status, endoscopic, histopathological findings, and cytokine production in the duodenum of Crohn's disease patients

BACKGROUND

The chronic inflammatory process in patients with Crohn's disease (CD) may affect any part of the gastrointestinal (GI) tract. The pathogenesis of CD involves immunological abnormalities, including deficient or excessive expression of cytokines. We examined Helicobacter pylori infection status, endoscopic and histopathological findings, and cytokine production in the duodenum of CD patients in comparison with controls.

METHODS

Thirty-eight CD patients underwent diagnostic upper GI endoscopy. Twelve age- and sex-matched health checkup examinees were used as controls. H. pylori infection status was assessed by the (13)C-urea breath test. At the time of endoscopy, two biopsy specimens each were obtained from the second portion of the duodenum, one for hematoxylin-eosin staining and immunohistochemical analysis with anti-CD68 antibody, and one for in vitro organ culture. Interleukin (IL)-6 and -8 levels were measured in organ culture supernatant by enzyme-linked immunosorbent assay.

RESULTS

H. pylori infection was significantly (P<0.05) more frequent in controls (42%) than in CD patients (8%). In the duodenum, erosions or ulcers were more frequent in CD patients (53%) than in controls (8%). Mononuclear cell infiltration in the duodenum was more severe in CD patients than in controls and IL-6 production was higher, whereas IL-8 production showed no significant difference. CD68+ cells in the duodenum were more prominent in CD patients than in controls.

CONCLUSIONS

H. pylori infection is unlikely in CD patients, but they show immunological abnormalities in the duodenum, possibly from innate immune responses.

Interleukin (IL) 1beta induction of IL-6 is mediated by a novel phosphatidylinositol 3-kinase-dependent AKT/IkappaB kinase alpha pathway targeting activator protein-1

Here we describe a novel role for the phosphatidylinositol 3-kinase/AKT pathway in mediating induction of interleukin-6 (IL-6) in response to IL-1. Pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K) inhibited IL-6 mRNA and protein production. Overexpression of either dominant-negative AKT or IkappaB kinase alpha mutant, IKKalphaT23A, containing a mutation in a functional AKT phosphorylation site, shown previously to be important for NFkappaB activation, completely abrogated IL-6 promoter activation in response to IL-1. However, mutation of the consensus NFkappaB site on the IL-6 promoter did not abrogate promoter activation by IL-1 in contrast to the AP-1 site mutation. IL-1 induces phosphorylation of IKKalpha on the NFkappaB inducing kinase (NIK) phosphorylation sites Ser(176)/Ser(180) and on the Thr(23) site, and although phosphorylation of IKKalphaT23 is inhibited both by LY294002 and wortmannin, phosphorylation of Ser(176)/Ser(180) is not. Neither inhibition of PI 3-kinase/AKT nor IKKalphaT23A overexpression affected IkappaBalpha degradation in response to IL-1. Only partial inhibition by dominant-negative AKT and no inhibitory effect of IKKalphaT23A was observed on an IL-6 promoter-specific NFkappaB site in contrast to significant inhibitory effects on the AP-1 site. Taken together, we have discovered a novel PI 3-kinase/AKT-dependent pathway in response to IL-1, encompassing PI 3-kinase/AKT/IKKalphaT23 upstream of AP-1. This novel pathway is a parallel pathway to the PI 3-kinase/AKT upstream of NFkappaB and both are involved in IL-6 gene transcription in response to IL-1.

Human intestinal epithelial and smooth muscle cells are potent producers of IL-6

BACKGROUND

Interleukin-6 (IL-6), a pluripotent cytokine, has traditionally been considered the product of proinflammatory cells. However, many other cell types have been shown to produce IL-6. Since intestinal inflammation is commonly associated with a vigorous systemic inflammatory response, we hypothesized that intestinal epithelial and smooth muscle cells might contribute to that response by producing IL-6. We therefore studied the capacity of differentiated human intestinal epithelial and smooth muscle cell lines to produce IL-6 in response to various proinflammatory stimuli.

MATERIALS AND METHODS

CCL-241, a human intestinal epithelial cell line, and HISM, a human intestinal muscle cell line, were grown to confluency and then treated for 24 h with various concentrations of lipopolysaccharide, Clostridium difficile culture extract containing both toxin A and toxin B, recombinant human tumor necrosis factor-alpha (TNF-alpha), or recombinant human interleukin-1 beta (IL-1beta). Supernatants were then collected for IL-6 determination using an enzyme-linked immunosorbent assay. Cell numbers were determined using a Coulter counter. For comparison, parallel studies were performed using phorbol ester-primed U-937 and THP-1 human macrophage cell lines.

RESULTS

Both human intestinal epithelial and smooth muscle cells produced IL-6 under basal conditions. In HISM cells, but not in CCL-241 cells, IL-6 release was increased slightly by treatment with C. difficile culture extract containing both toxin A and toxin B and with lipopolysaccharide. In both cell lines, IL-6 production was profoundly stimulated by treatment with IL-1beta and less so with TNF-alpha. Combinations of high-dose TNF-alpha and IL-1beta may have a slightly additive, but not synergistic, effect on IL-6 release. The amount of IL-6 produced by IL-1-stimulated intestinal cell lines was 70-fold higher than that produced by stimulated macrophage cell lines. CONCLUSIONS; Both intestinal epithelial and smooth muscle cells demonstrate the ability to release significant amounts of IL-6. The profound response to IL-1beta and TNF-alpha stimulation by both cell lines suggests that human intestinal parenchymal cells, influenced by paracrine mediators liberated from proinflammatory cells, might significantly contribute to the overall systemic inflammatory response by producing IL-6.

The insulin-like growth factor axis in children with inflammatory bowel disease

BACKGROUND

The insulin-like growth factor (IGF) axis consists of two IGFs and six IGF-binding proteins (IGFBPs) that regulate proliferation and differentiation of many cell types. Malnutrition and inflammation alter the IGF axis. The authors evaluated circulating IGFs and IGFBPs in patients with inflammatory bowel disease (IBD) at the time of presentation and compared them with values obtained during remission.

METHODS

Seventeen newly diagnosed pediatric IBD patients were studied on presentation and during remission. Nutritional status was assessed by body mass index (BMI) and serum protein assay. The Lloyd-Still and Green IBD clinical scoring system was used. IGF-I and IGF-II levels were measured by radioimmunoassay, and IGFBP-3 levels were measured by immunoradiometric assay. IGFBPs were quantified on ligand blots with a PhosphorImager.

RESULTS

Body mass index and IBD clinical scores improved after treatment: 18.7 +/- 3.0 versus 21.3 +/- 3.0 kg/m (P = 0.023) and 74.6 +/- 16.7 versus 93.1 +/- 7.4 (P< 0.001), respectively. Protein changes were insignificant. IGFBP-3 levels increased from time of first evaluation to remission: 3,470 +/- 850 versus 4,700 +/- 473 ng/mL (P< 0.001). The ratio of IGFBP-3 to IGFBP-2 increased from first evaluation to remission: 1.7 +/- 1.9 versus 3.9 +/- 1.9 (P= 0.003). IGF-I and IGF-II levels also increased: 139 +/- 167 versus 223 +/- 118 ng/mL (P= 0.011) and 307 +/- 111 versus 386 +/- 73 ng/mL (P= 0.007), respectively.

CONCLUSIONS

Circulating IGFBP-3 levels were low during active IBD and increased at remission in parallel with the IGF-I levels. The IGFBP-3 to IGFBP-2 ratio was altered in the presence of active disease in a manner that would reduce IGF-I action. This abnormality improved after treatment.

Chemokine expression in IBD. Mucosal chemokine expression is unselectively increased in both ulcerative colitis and Crohn's disease

Mucosal changes in inflammatory bowel disease (IBD) are characterized by ulcerative lesions accompanied by prominent cellular infiltrates in the bowel wall. Chemokines are chemotactic cytokines that are able to promote leukocyte migration to areas of inflammation and are also able to initiate cell activation events. They have recently been implicated in the pathophysiology of many disease states. The aim of this study was to detail the degree and distribution of specific chemokines, interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1, -2, and -3, and macrophage inflammatory protein (MIP)-1alpha and -1beta, in IBD mucosa. Thirty-nine patients were included, ten controls, 20 ulcerative colitis (UC), and nine Crohn's disease (CD), with a range of disease activity. Colonic mucosal biopsies were collected from UC, CD, and control patients and embedded in glycol methacrylate. Two-micrometre-thick sections were cut and stained using immunohistochemistry for chemokine protein expression. Sections were analysed using a light microscope. Expression of all types of chemokine protein was detected in colonic mucosa from both control and IBD patients. Patterns of staining between IBD patients and controls differed significantly, but CD and UC patients demonstrated similar patterns of staining. Individual chemokine expression was found to be significantly up-regulated in IBD when patients were compared with the non-diseased group in all areas of the mucosal sections. Up-regulated chemokine expression correlated with increasing activity of the disease. It is concluded that human colonic chemokine expression is non-selectively up-regulated in IBD. The results supported the hypothesis that the degree of local inflammation and tissue damage in UC and CD is dependent on local expression of specific chemokines within IBD tissues.

VEGF, basic-FGF, and TGF-beta in Crohn's disease and ulcerative colitis: a novel mechanism of chronic intestinal inflammation

OBJECTIVE

Inflammatory bowel disease (IBD), the precise etiology of which remains unknown, is comprised of two forms of chronic intestinal inflammation; ulcerative colitis (UC) and Crohn's disease (CD). Recent evidence increasingly suggests that IBD is the result of dysfunctional immunoregulation manifested by inappropriate production of mucosal cytokines. An abnormal microcirculatory system has also been implicated in its pathogenesis. To elucidate the mechanism of ischemic change in IBD, we assesse serum concentration levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF), and plasma level of endothelin-1 (ET-1). We also investigated the expression of VEGF, b-FGF, and transforming growth factor-beta1,2,3 (TGF-beta1,2,3) in tissue by immunostaining.

METHODS

Blood samples were obtained from 11 patients with UC, 11 patients with CD, and 10 patients as controls. Paraffin-embedded samples were used for an immunohistochemical study.

RESULTS

The concentration levels (in picograms per milliliter) were as follows: for ET-1, UC: 127+/-47.0, CD: 167.3+/-35.1, and controls (asthma: 38.5+/-23.8, p < 0.01; diverticulitis: 40.5+/-25.6, p < 0.01), for b-FGF, UC: 9.2+/-1.9, CD: 9.1+/-1.5, and controls (asthma: 5.0+/-0, p < 0.01; diverticulitis: 5.0+/-0, p < 0.01), for VEGF, UC: 659.8+/-181.0, CD: 740.0+/-182.3, and controls (asthma: 193.7+/-58.7, p < 0.01; diverticulitis: 199.6+/-59.7, p < 0.01). The levels of VEGF and b-FGF were significantly higher in active IBD than those in the controls. There was a significant positive correlation among the serum levels of VEGF and b-FGF and the plasma level of ET-1; that is, elevated VEGF, b-FGF, and ET-1 levels correlated well with each other. Immunohistochemical studies showed increased venula in the submucosa and lamina propria. Overexpression of VEGF and b-FGF in endothelial cells was revealed and TGF-beta2 and TGF-beta3 were found in inflammatory cells of active IBD, but no change was observed around the vessels in the controls.

CONCLUSIONS

It is suggested that the reciprocal reaction of these cytokines may contribute to angiogenesis in IBD b inducing intestinal ischemia through vasoconstriction.

Augmenting effect of methionine-enkephalin on interleukin-6 production by cytokine-stimulated murine macrophages

The effects of methionine-enkephalin on the production of interleukin-6 by activated peritoneal murine macrophages were studied. Macrophage were activated with interleukin-1beta or interferon-gamma in the presence or absence of graded concentrations of methionine-enkephalin. Methionine-enkephalin combined with interleukin-1beta or interferon-gamma caused an increase in IL-6 release from cultured macrophages. The opioid receptor antagonist naloxone did not change the stimulatory effect of methionine-enkephalin on IL-6 production by stimulated macrophages. Methionine-enkephalin added to the culture medium of resting macrophages increased IL-6 release from macrophages which were later induced with interleukin-1beta or interferon-gamma. The results of this study suggest that methionine-enkephalin can modulate the proinflammatory cytokine response by controlling, via non-opioid receptor mechanism, the production of IL-6.

Jejunal brush border microvillous alterations in Giardia muris-infected mice: role of T lymphocytes and interleukin-6

Intestinal colonization with the protozoan Giardia causes diffuse brush border microvillous alterations and disaccharidase deficiencies, which in turn are responsible for intestinal malabsorption and maldigestion. The role of T cells and/or cytokines in the pathogenesis of Giardia-induced microvillous injury remains unclear. The aim of this study was to assess the role of T cells and interleukin-6 (IL-6) in the brush border pathophysiology of acute murine giardiasis in vivo. Athymic nude (nu(-)/nu(-)) CD-1 mice and isogenic immunocompetent (nu(+)/nu(+)) CD-1 mice (4 weeks old) received an axenic Giardia muris trophozoite inoculum or vehicle (control) via orogastric gavage. Weight gain and food intake were assessed daily. On day 6, segments of jejunum were assessed for parasite load, brush border ultrastructure, IL-6 content, maltase and sucrase activities, villus-crypt architecture, and intraepithelial lymphocyte (IEL) infiltration. Despite similar parasitic loads on day 6, infected immunocompetent animals, but not infected nude mice, showed a diffuse loss of brush border microvillous surface area, which was correlated with a significant reduction in maltase and sucrase activities and a decrease in jejunal IL-6 concentration. In both athymic control and infected mice, jejunal brush border surface area and disaccharidases were high, but levels of tissue IL-6 were low and comparable to the concentration measured in immunocompetent infected animals. In both immunocompetent and nude mice, infection caused a small but significant increase in the numbers of IELs. These findings suggest that the enterocyte brush border injury and malfunction seen in giardiasis is, at least in part, mediated by thymus-derived T lymphocytes and that suppressed jejunal IL-6 does not necessarily accompany microvillous shortening.

Granulocyte elastase and systemic cytokine response after laparoscopic-assisted and open resections in Crohn's disease

PURPOSE

The aim of this study was to assess whether systemic proinflammatory cytokines (IL-6), anti-inflammatory cytokines (IL-4, IL-10), acute phase proteins (C-reactive protein), or granulocyte elastase are valuable indicators for determining the degree of surgical trauma after open vs. laparoscopic-assisted resections in Crohn's disease.

METHOD

Eleven patients in each group (open and laparoscopic-assisted surgery) were matched for indication, surgical procedure, and Crohn's disease activity index. Serum IL-4, IL-6, and IL-10 were measured using enzyme-linked immunosorbent assay. Serum C-reactive protein was determined by immunoturbidimetric assay. Plasma granulocyte elastase was determined by immunoactivation immunoassay. Blood was sampled preoperatively, six hours after the operation, and at postoperative Days 1 to 5.

RESULTS

IL-4 was not detectable in any sample analyzed. Serum IL-6 and IL-10 levels peaked postoperatively in both groups without significant differences between laparoscopic-assisted (185.6 +/-54.1 pg/ml and 112.1 +/- 19.4 pg/ml, respectively; mean +/-standard error of the mean) and open surgery (431.1 +/-240.4 pg/ml and 196.7 +/- 56.5 pg/ml, respectively). Serum C-reactive protein levels also rose postoperatively, with a peak on the second day, but showed similar values after laparoscopic-assisted (107.1 +/- 12.1 mg/l) and open (128.3 +/- 17.5 mg/l) surgery. Plasma granulocyte elastase levels peaked on the first and second postoperative day and were found elevated almost throughout the five-day observation period. Comparison between the groups revealed significantly (P < 0.02) lower values after laparoscopic-assisted (Day 1, 46.5 +/- 8.9 microg/l; Day 2, 41.9 +/- 5.9 microg/l) when compared with open surgery (Day 1, 89.7 +/- 13.8 microg/l; Day 2, 91.4 +/- 14).

CONCLUSIONS

Serum IL-6 and IL-10 may not be ideal measures for evaluation of the degree of tissue trauma in laparoscopic-assisted and open resections in Crohn's disease, probably because of interference with disease-specific cytokine interactions. In contrast, granulocyte elastase has to be considered a strong marker discriminating the different severity of surgical trauma induced by laparoscopic-assisted vs. open resection in Crohn's disease.

Review article: targeting TNF alpha as a key cytokine in the inflammatory processes of Crohn's disease--the mechanisms of action of infliximab

Crohn's disease is a chronic, debilitating gastrointestinal disorder in which a variety of cellular processes and pro-inflammatory mediators influence the pathogenesis of the disease. Although the potential roles and functions of the pro-inflammatory mediators continue to be debated, several mediators, specifically tumour necrosis factor-alpha, have been clearly identified as having a pivotal role in the inflammation of the bowel mucosa of these patients. Therapies specifically focusing on the inflammatory process underlying Crohn's disease have the potential for providing disease modification and prolonged remission. Infliximab, an antitumour necrosis factor-alpha monoclonal antibody, has been demonstrated to neutralize tumour necrosis factor-alpha and restore and reset the immunological dysbalance of the inflamed mucosa. Preliminary studies with infliximab suggested that treatment resulted in a rapid and almost complete inhibition of multiple inflammatory pathways. In clinical studies of infliximab, patients with Crohn's disease achieved rapid reduction in clinical signs and symptoms, substantiated by both endoscopic and microscopic evaluation.

The influence of cigarette smoking on cytokine levels in patients with inflammatory bowel disease

Anecdotal reports suggest that smoking may be beneficial for patients with inflammatory bowel disease (IBD) as nicotine may act through inflammatory mediators within the colonic mucosa. Furthermore, there is increasing evidence that cytokines play a pathologic role in IBD. Our aim was to determine the effects of cigarette smoking on cytokine levels in the colonic mucosa of patients with and without IBD. Mucosal biopsies were obtained from 10 patients with Crohn's disease (CD), 10 with ulcerative colitis (UC), and 10 healthy controls. Five of 10 patients in each of the three groups were smokers and five were nonsmokers. Concentrations of interleukin (IL)-1beta, IL-2, IL-6, and IL-8 were determined using enzyme-linked immunosorbent assay (ELISA). Cytokine levels of smokers were compared with nonsmokers in each group and with controls. Results were analyzed using the Mann-Whitney test; significance was set at p<0.05. The concentration of IL-8 was significantly higher in healthy controls who smoke compared with nonsmokers and significantly reduced in smokers with CD compared with nonsmokers with CD. Moreover, concentrations of IL-1beta and IL-8 were significantly reduced in smokers with UC compared with nonsmokers with UC. Smokers had significantly elevated levels of IL-8 in the colonic mucosa. Smokers with IBD had a significant reduction in cytokine levels; specifically, IL-1beta and IL-8 for patients with UC and IL-8 for patients with CD. Further studies are warranted to determine if this reduction in cytokine levels is histologically and clinically significant.

Identification of a human enterocyte lipoxin A4 receptor that is regulated by interleukin (IL)-13 and interferon gamma and inhibits tumor necrosis factor alpha-induced IL-8 release

Epithelial cells of the alimentary tract play a central role in mucosal immunophysiology. Pathogens and/or agonists that interact with mucosal surfaces often elicit epithelial responses that upregulate inflammation. Therefore, it was of interest to explore potential epithelial targeted antiinflammatory signals. Here we identified and sequenced a human enterocyte lipoxin (LX) A4 [5(S), 6(R),15(S)-trihydroxy-7,9,13-trans-11-cis eicosatetraenoic acid] receptor, and demonstrate that transcription of this receptor was controlled by cytokines, of which lymphocyte-derived interleukin (IL)-13 and interferon gamma were the most potent. When lipoxins and LXA4 stable analogs were evaluated for enterocyte functional as well as immune responses, lipoxins sharply inhibited TNF-alpha-induced IL-8 release but did not alter either barrier function or agonist-stimulated chloride secretion. 15R/S-methyl-LXA4 and 16-phenoxy-LXA4 each attenuated (IC50 approximately 10 nM) IL-8 release. Cyclooxygenase (COX) II is emerging as an important component in wound healing and proliferation in intestinal epithelia and when acetylated by acetylsalicylic acid (aspirin) initiates the biosynthesis of a LXA4 receptor ligand. We therefore determined whether colonic cell lines (HT-29 Cl.19A, Caco-2, or T84) express the COX II isozyme. Results for RT-PCR and Western blot analysis showed that COX I as well as an IL-1beta- and TNF-alpha-inducible COX II are expressed in HT-29 Cl.19A. In addition, aspirin-treated enterocytes generated 15R-HETE, a precursor of 15-epi-LXA4 biosynthesis, whose potent bioactions were mimicked by the stable analog 15R/S-methyl-LXA4. Taken together, these results identify an endogenous pathway for downregulating mucosal inflammatory events and suggest a potential therapeutic benefit for LXA4 stable analogs.

The role of cyclooxygenase-1 and cyclooxygenase-2 in lipopolysaccharide and interleukin-1 stimulated enterocyte prostanoid formation

Lipopolysaccharide is an inflammatory agent and interleukin-1 is a cytokine. Their pro-inflammatory effects may be mediated by prostanoids produced by inducible cyclooxygenase-2. The aim of this study was to determine the prostanoids produced by lipopolysaccharide and interleukin-1 stimulated enterocytes through the cyclooxygenase-1 and 2 pathways. Cultured enterocytes were stimulated with lipopolysaccharide or interleukin-1beta with and without cyclooxygenase inhibitors. Low concentrations of indomethacin and valerylsalicylic acid (VSA) were evaluated as cyclooxygenase-1 inhibitors and their effects compared with the effects of a specific cyclooxygenase-2 inhibitor, SC-58125. Prostaglandin E2, 6-keto prostaglandin F1alpha, prostaglandin D2 and leukotriene B4 levels were determined by radioimmunoassay. Immunoblot analysis using isoform-specific antibodies showed that the inducible cyclooxygenase enzyme (COX-2) was expressed by 4 h in LPS and IL-1beta treated cells while the constitutive COX-1 remained unaltered in its expression. Interleukin-1beta and lipopolysaccharide stimulated the formation of all prostanoids compared with untreated cells, but failed to stimulate leukotriene B4. Indomethacin at 20 microM concentration, and VSA inhibited lipopolysaccharide and interleukin 1beta stimulated prostaglandin E2, but not 6-keto prostaglandin F1alpha formation. SC-58125 inhibited lipopolysaccharide and interleukin-1beta stimulated 6-keto prostaglandin F1alpha but not prostaglandin E2 release. The specific cyclooxygenase-2 inhibitor also inhibited lipopolysaccharide produced prostaglandin D2 but not interleukin-1beta stimulated prostaglandin D2. While SC-58125 inhibited basal 6-keto prostaglandin-F1alpha formation it significantly increased basal prostaglandin E2 and prostaglandin D2 formation. As SC-58125 inhibited lipopolysaccharide and interleukin-1beta induced 6-keto prostaglandin F1alpha production but not prostaglandin E2 production, it suggests that these agents stimulate prostacyclin production through a cyclooxygenase-2 mediated mechanism and prostaglandin E2 production occurs through a cyclooxygenase-1 mediated mechanism. Prostaglandin D2 production appeared to be variably produced by cyclooxygenase-1 or cyclooxygenase-2, depending on the stimulus.

Intestinal interleukin-8 concentration and gene expression in inflammatory bowel disease

BACKGROUND

Interleukin-8 (IL-8) is an important cytokine for recruitment and activation of polymorphonuclear neutrophils (PMNs), cells that are abundant in the intestinal lesions of ulcerative colitis (UC) and Crohn's disease (CD). The present investigation was conducted to evaluate intestinal IL-8 concentration and IL-8 gene expression in parallel in inflammatory bowel disease (IBD) patients and a non-inflammatory control group.

METHODS

The intestinal concentration of IL-8 was measured with a sandwich enzyme-linked immunosorbent assay (ELISA) technique (detection limit, 17.4 pg/mg protein), and relative quantitation of IL-8 mRNA transcript levels was done with a reverse transcription polymerase chain reaction (RT-PCR)-based method. Biopsy specimens from 66 humans who underwent colonoscopy--28 with UC, 18 with CD and colonic involvement, and 20 non-inflammatory disease-specific controls who subsequently were found to fulfill the diagnostic criteria for irritable bowel syndrome (IBS)--were included. None had received glucocorticoids within 3 months.

RESULTS

Using a one-tailed variance analysis, a significant concordance between increasing IL-8 protein concentrations and disease activity was found both in UC and CD (P < 0.001), and only trace amounts were detected in IBS biopsy specimens. No differences were found between the two groups of UC and CD patients (P > 0.05), and no differences were found between quiescent IBD and IBS (P > 0.05). However, the PCR method showed IL-8 mRNA in 8 of 18 CD patients (44.4%; 95% confidence limits, 21.5-69.2%) and 7 of 28 UC patients (25.9%; 95% confidence limits, 11.1-46.3%), as compared with 0 of 20 IBS (P < 0.005). Increased IL-8 mRNA levels were found only in active CD, which was not the case in UC. No correlation was found between intestinal IL-8 ELISA and IL-8-mRNA levels (r = 0.24, P > 0.05).

CONCLUSIONS

The observed correlation between disease activity and expression of the IL-8 gene in active CD colitis but not in UC and the increased IL-8 protein concentrations in affected intestinal segments of IBD as compared with the non-inflamed IBS indicate a possible transient IL-8 gene expression or altered mRNA stability in UC and CD, as is well known for other cytokines, such as IL-2. If so, it may form the basis of new therapeutic regimens for IBD like IL-10.

Increased production of tumour necrosis factor-alpha interleukin-1 beta, and interleukin-6 by morphologically normal intestinal biopsies from patients with Crohn's disease

BACKGROUND

Increasing evidence points to a important role for inflammatory cytokines for the pathogenesis of Crohn's disease.

AIM

To compare the secretion rate of tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) by morphologically normal and inflamed intestinal mucosa from patients with Crohn's disease.

RESULTS

Organ cultures of intestinal biopsy specimens taken from areas of affected mucosa from patients with Crohn's disease spontaneously produced increased amounts of TNF-alpha, IL-1 beta, and IL-6 compared with controls but also biopsy specimens taken in macroscopically and microscopically unaffected areas in the same patients. Concentrations of IL-1 beta and IL-6 measured in the supernatant fluid of biopsy cultures were positively correlated with the degree of tissue involvement measured by both endoscopic and histological grading. By contrast, TNF-alpha concentrations were not correlated to endoscopic and histological grading.

CONCLUSIONS

These consistently raised TNF-alpha, IL-1 beta and IL-6 secretions by normal appearing mucosa from patients with Crohn's disease provide evidence for a sustained immune stimulation in Crohn's disease even in the absence of patent inflammation. The results shed a new light on the role of inflammatory cytokines in the onset of intestinal tissue damage in Crohn's disease and suggest that the range of intestinal lesions in Crohn's disease may be wider than suspected on the basis of regular endoscopic and histological examinations.

Is a histologically normal appendix following emergency appendicectomy alway normal?

BACKGROUND

Appendixes removed from patients with suspected appendicitis often appear normal on histological examination. We examined appendix specimens for expression of abnormal amounts of cytokines, an indicator of an inflammatory response.

METHODS

Tumour necrosis factor alpha (TNFalpha) and interleukin-2 (IL-2) expression was measured by in-situ hybridisation in ten specimens from patients with acute appendicitis, 12 normal appendix specimens removed from patients undergoing elective abdominal surgery, and 31 appendix specimens from patients with a clinical diagnosis of appendicitis but an appendix histologically classified as normal. Cytokine-specific RNA antisense probes were prepared by in-vitro transcription and digoxigenin (DIG) labelled. In-situ hybridisation was done on 5 micrometer paraffin sections. Tissue sections hybridised by sense probes acted as negative control for each cytokine. Following hybridisation, the probes were detected by alkaline phosphatase labelled anti-DIG monoclonal antibody and visualised by nitroblue tetrazolium staining.

FINDINGS

All histologically proven acute appendicitis specimens demonstrated intense cellular TNFalpha mRNA expression in germinal centres and moderate levels of expression throughout the mucosa. IL-2 mRNA was strongly expressed in the lamina propria and only moderately expressed in germinal centres. Normal appendixes all showed almost complete absence of TNFalpha and IL-2 mRNA expression. Seven of the 31 histologically classified normal appendix specimens from patients with a clinical diagnosis of appendicitis demonstrated TNFalpha and IL-2 mRNA expression similar to acute appendicitis specimens in germinal centres, submucosa, and lamina propria layers.

INTERPRETATION

TNFalpha and IL-2 mRNA expression is a sensitive marker of inflammation in appendicitis. A substantial proportion of histologically normal appendixes showed clear evidence of an inflammatory response in the form of increased cytokine expression.

Role of cytokines and platelet-activating factor in inflammatory bowel disease. Implications for therapy

BACKGROUND

Platelet-activating factor (PAF) and cytokines, such as interleukins, tumor necrosis factor, and others, are thought to play a role in the inflammatory process involving gastrointestinal disorders such as Crohn's disease, ulcerative colitis, ischemic colitis, or antibiotic-associated colitis.

PURPOSE

This study was undertaken to review the latest literature on the role of PAF and cytokines in the genesis of inflammatory bowel disease and implications for therapy and management.

RESULTS

PAF is an endogenous phospholipid involved in hypersensitivity and inflammatory reactions such as platelet and neutrophil aggregation, vasodilation, increased vascular permeability, and leukocyte adhesion, which have been associated with inflammatory processes. Cytokines are peptides that regulate and coordinate inflammatory and immunologic responses. Increased production of cytokines has been reported during Crohn's disease and ulcerative colitis and is correlated with disease activity.

CONCLUSIONS

Because PAF and cytokines may have an important role in the pathogenesis of inflammatory bowel disease, their inhibition by specific antagonists, mediators, or other agents such as steroids may have a potential therapeutic benefit in treatment and management of these inflammatory diseases in the near future.