Cell death signalling is competitively but coordinately regulated by repressor-type and activator-type ethylene response factors in tobacco (Nicotiana tabacum) plants

Ethylene response factors (ERFs) comprise one of the largest transcription factor families in many plant species. Tobacco (Nicotiana tabacum) ERF3 (NtERF3) and other ERF-associated amphiphilic repression (EAR) motif-containing ERFs are known to function as transcriptional repressors. NtERF3 and several repressor-type ERFs induce cell death in tobacco leaves and are also associated with a defence response against tobacco mosaic virus (TMV). We investigated whether transcriptional activator-type NtERFs function together with NtERF3 in the defence response against TMV infection by performing transient ectopic expression, together with gene expression, chromatin immunoprecipitation (ChIP) and promoter analyses. Transient overexpression of NtERF2 and NtERF4 induced cell death in tobacco leaves, albeit later than that induced by NtERF3. Fusion of the EAR motif to the C-terminal end of NtERF2 and NtERF4 abolished their cell death-inducing ability. The expression of NtERF2 and NtERF4 was upregulated at the early phase of N gene-triggered hypersensitive response (HR) against TMV infection. The cell death phenotype induced by overexpression of wild-type NtERF2 and NtERF4 was suppressed by co-expression of an EAR motif-deficient form of NtERF3. Furthermore, ChIP and promoter analyses suggested that NtERF2, NtERF3 and NtERF4 positively or negatively regulate the expression of NtERF3 by binding to its promoter region. Overall, our results revealed the cell death-inducing abilities of genes encoding activator-type NtERFs, including NtERF2 and NtERF4, suggesting that the HR-cell death signalling via the repressor-type NtERF3 is competitively but coordinately regulated by these NtERFs.

Uptake through glycoprotein 2 of FimH(+) bacteria by M cells initiates mucosal immune response

The mucosal immune system forms the largest part of the entire immune system, containing about three-quarters of all lymphocytes and producing grams of secretory IgA daily to protect the mucosal surface from pathogens. To evoke the mucosal immune response, antigens on the mucosal surface must be transported across the epithelial barrier into organized lymphoid structures such as Peyer's patches. This function, called antigen transcytosis, is mediated by specialized epithelial M cells. The molecular mechanisms promoting this antigen uptake, however, are largely unknown. Here we report that glycoprotein 2 (GP2), specifically expressed on the apical plasma membrane of M cells among enterocytes, serves as a transcytotic receptor for mucosal antigens. Recombinant GP2 protein selectively bound a subset of commensal and pathogenic enterobacteria, including Escherichia coli and Salmonella enterica serovar Typhimurium (S. Typhimurium), by recognizing FimH, a component of type I pili on the bacterial outer membrane. Consistently, these bacteria were colocalized with endogenous GP2 on the apical plasma membrane as well as in cytoplasmic vesicles in M cells. Moreover, deficiency of bacterial FimH or host GP2 led to defects in transcytosis of type-I-piliated bacteria through M cells, resulting in an attenuation of antigen-specific immune responses in Peyer's patches. GP2 is therefore a previously unrecognized transcytotic receptor on M cells for type-I-piliated bacteria and is a prerequisite for the mucosal immune response to these bacteria. Given that M cells are considered a promising target for oral vaccination against various infectious diseases, the GP2-dependent transcytotic pathway could provide a new target for the development of M-cell-targeted mucosal vaccines.

IL-6-dependent mucosal protection prevents establishment of a microbial niche for attaching/effacing lesion-forming enteric bacterial pathogens

Enteric infections with attaching/effacing lesion-inducing bacterial pathogens are a worldwide health problem. A murine infection model with one such pathogen, Citrobacter rodentium, was used to elucidate the importance of the pleiotropic immune regulator, IL-6, in the pathogenesis of infection. IL-6 was strongly induced in colonic epithelial cells and macrophages upon C. rodentium infection and was required for effective host defense, because mice lacking IL-6 failed to control bacterial numbers 2-3 wk after infection and exhibited increased mortality. IL-6 was not needed for mounting effective T and B cell responses to the pathogens, nor was it important for induction of IFN-gamma or TNF-alpha, cytokines involved in host defense against the bacteria, or the antibacterial effector, NO. Instead, IL-6 played a key role in mucosal protection, since its absence was associated with marked infection-induced apoptosis in the colonic epithelium and subsequent ulcerations. Cell culture studies confirmed that IL-6 protected colon epithelial cells directly against inducible apoptosis, which was accompanied by increased expression of an array of genes encoding antiapoptotic proteins, including Bcl-x(L), Mcl-1, cIAP-2, and Bcl-3. Ulcerations appeared to be pathogenetically important, because bacteria localized preferentially to those regions, and chemically induced colonic ulcerations promoted bacterial colonization. Furthermore, blood components likely present in ulcer exudates, particularly alanine, asparagine, and glycine, promoted bacterial growth. Thus, IL-6 is an important regulator of host defense against C. rodentium by protecting the mucosa against ulcerations which can act as a microbial niche for the bacteria.

[A case of Turner syndrome complicated with Crohn's disease, erythema nodosum and Hashimoto disease]

A 26-year-old woman, who had had Turner syndrome from age 10 years old, had diarrhea, fever, joint pain, and erythema in the lower left leg. She was given a diagnosis of Crohn's disease, erythema nodosum, and Hashimoto disease. Systemic steroid therapy was very effective for both intestinal and skin lesions. It has been reported that half of inflammatory bowel disease patients with Turner syndrome have 46XiX (q) type chromosome abnormality, and this case also has this type of abnormality.

Role of Shiga toxin versus H7 flagellin in enterohaemorrhagic Escherichia coli signalling of human colon epithelium in vivo

Enterohaemorrhagic Escherichia coli O157:H7 (EHEC) is a clinically important foodborne pathogen that colonizes human colon epithelium and induces acute colonic inflammation, but does not invade the epithelial cells. Whereas Shiga toxin (Stx) and bacterial flagellin have been studied for their ability to upregulate the production of proinflammatory chemokines by cultured human colon cancer cell lines, the relevance of studies in colon cancer cell lines to the production of proinflammatory signals by normal epithelial cells in EHEC-infected human colon is not known. We show herein that Stx does not bind to human colon epithelium in vivo. Moreover, globotriaosylceramide (Gb3/CD77) synthase, the enzyme required for synthesis of the Gb3/CD77 receptor for Stx, was not expressed by normal or inflamed human colon epithelium in vivo. In contrast, Toll-like receptor (TLR) 5, the receptor for bacterial flagellin, was expressed by normal human colon epithelium and by colon epithelium in human intestinal xenografts. EHEC H7 flagellin instilled in the lumen of human colon xenografts that contain an intact human epithelium upregulated the expression of epithelial cell proinflammatory chemokines, which was accompanied by a subepithelial influx of neutrophils. Isogenic mutants of EHEC that lacked flagellin did not significantly upregulate prototypic neutrophil and dendritic cell chemoattractants by model human colon epithelia, irrespective of Stx production. We conclude that EHEC H7 flagellin and not Stx is the major EHEC factor that directly upregulates proinflammatory chemokine production by human colon epithelium in vivo.

The membrane-bound chemokine CXCL16 expressed on follicle-associated epithelium and M cells mediates lympho-epithelial interaction in GALT

The recently identified CXCL16 has dual functions as a transmembrane adhesion molecule and a soluble chemokine. In this study we found that CXCL16 mRNA and protein were expressed constitutively on the follicle-associated epithelium covering Peyer's patches (PPs), isolated lymphoid follicles, and cecal patches, but minimally on the villous epithelium in the murine gastrointestinal tract. The CXCL16 receptor CXCR6/Bonzo was constitutively expressed on subpopulations of CD4+ and CD8+ T cells isolated from PPs. The expression of CXCR6/Bonzo on the PP T cells was up-regulated after stimulation with anti-CD3 and anti-CD28 mAbs. The activated PP T cells showed chemotactic migration in response to the soluble N-terminal chemokine domain of CXCL16. Furthermore, the activated PP T cells selectively adhered to cells expressing murine CXCL16. To determine the physiological role of CXCL16 in GALT, we first carefully analyzed T cell distribution in PPs. T cells localized not only in the interfollicular region but also at a lesser frequency in the subepithelial dome (SED) and in the germinal center of lymphoid follicles. Consistently, the majority of the adoptive transferred activated T cells migrated into the SED and the interfollicular region. However, the neutralization of CXCL16 specifically reduced the migration of the adoptive, transferred, activated T cells into the SED of PPs. These data suggest that CXCL16 expressed on the follicle-associated epithelium plays an important role in the recruitment and retention of activated T cells in the SED and should, at least partially, be responsible for lymphocyte compartmentalization in GALT.

Cathelicidin mediates innate intestinal defense against colonization with epithelial adherent bacterial pathogens

Cathelicidin-related antimicrobial peptide (mCRAMP), the sole murine cathelicidin, is encoded by the gene Cnlp. We show that mCRAMP expression in the intestinal tract is largely restricted to surface epithelial cells in the colon. Synthetic mCRAMP had antimicrobial activity against the murine enteric pathogen Citrobacter rodentium, which like the related clinically important human pathogens enteropathogenic Escherichia coli and enterohemorrhagic E. coli, adheres to the apical membrane of intestinal epithelial cells. Colon epithelial cell extracts from Cnlp+/+ mice had significantly greater antimicrobial activity against C. rodentium than those of mutant Cnlp-/- mice that lack mCRAMP. Cnlp-/- mice developed significantly greater colon surface and crypt epithelial cell colonization, surface epithelial cell damage, and systemic dissemination of infection than Cnlp+/+ mice after oral infection with C. rodentium. Moreover, Cnlp+/+ mice were protected from oral infections with C. rodentium inocula that infected the majority of Cnlp-/- mice. These results establish cathelicidin as an important component of innate antimicrobial defense in the colon.

Nod2 mutation in Crohn's disease potentiates NF-kappaB activity and IL-1beta processing

Variants of NOD2, an intracellular sensor of bacteria-derived muramyl dipeptide (MDP), increase susceptibility to Crohn's disease (CD). These variants are thought to be defective in activation of nuclear factor kappaB (NF-kappaB) and antibacterial defenses, but CD clinical specimens display elevated NF-kappaB activity. To illuminate the pathophysiological function of NOD2, we introduced such a variant to the mouse Nod2 locus. Mutant mice exhibited elevated NF-kappaB activation in response to MDP and more efficient processing and secretion of the cytokine interleukin-1beta (IL-1beta). These effects are linked to increased susceptibility to bacterial-induced intestinal inflammation and identify NOD2 as a positive regulator of NF-kappaB activation and IL-1beta secretion.

Regulated production of the chemokine CCL28 in human colon epithelium

The chemokine CCL28 is constitutively expressed by epithelial cells at several mucosal sites and is thought to function as a homeostatic chemoattractant of subpopulations of T cells and IgA B cells and to mediate antimicrobial activity. We report herein on the regulation of CCL28 in human colon epithelium by the proinflammatory cytokine IL-1, bacterial flagellin, and n-butyrate, a product of microbial metabolism. In vivo, CCL28 was markedly increased in the epithelium of pathologically inflamed compared with normal human colon. Human colon and small intestinal xenografts were used to model human intestinal epithelium in vivo. Xenografts constitutively expressed little, if any, CCL28 mRNA or protein. After stimulation with the proinflammatory cytokine IL-1, CCL28 mRNA and protein were significantly increased in the epithelium of colon but not small intestinal xenografts, although both upregulated the expression of another prototypic chemokine, CXCL8, in response to the identical stimulus. In studies of CCL28 regulation using human colon epithelial cell lines, proinflammatory stimuli, including IL-1, bacterial flagellin, and bacterial infection, significantly upregulated CCL28 mRNA expression and protein production. In addition, CCL28 mRNA expression and protein secretion by those cells were significantly increased by the short-chain fatty acid n-butyrate, and IL-1- or flagellin-stimulated upregulation of CCL28 by colon epithelial cells was synergistically increased by pretreatment of cells with n-butyrate. Consistent with its upregulated expression by proinflammatory stimuli, CCL28 mRNA expression was attenuated by pharmacological inhibitors of NF-kappaB activation. These findings indicate that CCL28 functions as an "inflammatory" chemokine in human colon epithelium and suggest the notion that CCL28 may act to counterregulate colonic inflammation.

Clearance of Citrobacter rodentium requires B cells but not secretory immunoglobulin A (IgA) or IgM antibodies

Citrobacter rodentium, a murine model pathogen for human enteropathogenic Escherichia coli, predominantly colonizes the lumen and mucosal surface of the colon and cecum and causes crypt hyperplasia and mucosal inflammation. Mice infected with C. rodentium develop a secretory immunoglobulin A (IgA) response, but the role of B cells or secretory antibodies in host defense is unknown. To address this question, we conducted oral C. rodentium infections in mice lacking B cells, IgA, secreted IgM, polymeric Ig receptor (pIgR), or J chain. Normal mice showed peak bacterial numbers in colon and feces at 1 week and bacterial eradication after 3 to 4 weeks. B-cell-deficient mice were equally susceptible initially but could not control infection subsequently. Tissue responses showed marked differences, as infection of normal mice was accompanied by transient crypt hyperplasia and mucosal inflammation in the colon and cecum at 2 but not 6 weeks, whereas B-cell-deficient mice had few mucosal changes at 2 weeks but severe epithelial hyperplasia with ulcerations and mucosal inflammation at 6 weeks. The functions of B cells were not mediated by secretory antibodies, since mice lacking IgA or secreted IgM or proteins required for their transport into the lumen, pIgR or J chain, cleared C. rodentium normally. Nonetheless, systemic administration of immune sera reduced bacterial numbers significantly in normal and pIgR-deficient mice, and depletion of IgG abrogated this effect. These results indicate that host defense against C. rodentium depends on B cells and IgG antibodies but does not require production or transepithelial transport of IgA or secreted IgM.

Expression of LL-37 by human gastric epithelial cells as a potential host defense mechanism against Helicobacter pylori

BACKGROUND & AIMS

LL-37/human cationic antimicrobial peptide 18 (hCAP18) is a human cathelicidin with broad-spectrum antimicrobial, lipopolysaccharide binding, and chemotactic activities. This study examined the role of LL-37/hCAP18 in gastric innate immune defense by characterizing its constitutive and regulated expression by human gastric mucosa and its bactericidal activity against the gastric pathogen Helicobacter pylori.

METHODS

LL-37/hCAP18 messenger RNA expression in normal and H. pylori -infected gastric mucosa and gastric epithelial cells was determined by in situ hybridization, real-time polymerase chain reaction, immunostaining, and immunoblot analysis. Bactericidal activity was measured by using a colony-forming unit assay.

RESULTS

LL-37/hCAP18 messenger RNA and protein were expressed in a distinct distribution by surface epithelial cells as well as chief and parietal cells in the fundic glands of normal gastric mucosa. LL-37/hCAP18 was significantly increased in the epithelium and gastric secretions of H. pylori -infected patients, but not in individuals with non-H. pylori -induced gastric inflammation. Infection of cultured gastric epithelial cells with a wild-type but not an isogenic Delta cagE mutant strain of H. pylori increased LL-37/hCAP18 expression, indicating that H. pylori -induced regulation of LL-37/hCAP18 production required an intact type IV secretion system. LL-37, the C-terminal peptide of LL-37/hCAP18, alone or in synergy with human beta-defensin 1, was bactericidal for several H. pylori strains.

CONCLUSIONS

These data indicate that H. pylori up-regulates production of LL-37/hCAP18 by gastric epithelium and suggest this cathelicidin contributes to determining the balance between host mucosal defense and H. pylori survival mechanisms that govern chronic infection with this gastric pathogen.

Cytokine profile in colonic mucosa of ulcerative colitis correlates with disease activity and response to granulocytapheresis

OBJECTIVE

The aim of this study was to clarify the correlation between cytokine profile in colonic mucosa with disease activity and response to granulocytapheresis (GCAP) in patients with ulcerative colitis (UC), using a reliable, reproducible quantitative method.

METHODS

Colonoscopic biopsies of inflamed colonic mucosa (16 patients, 21 cases) and uninflamed colonic mucosa (25 patients, 33 cases) were obtained from UC patients. Messenger (m)RNA was extracted and subjected to realtime polymerase chain reaction for quantitative measurement of interleukin (IL)-12, interferon-gamma, tumor necrosis factor-alpha, IL-4, IL-8, and IL-18 mRNAs. In seven patients with high disease activity despite prednisolone (PSL) treatment (> or = 20 mg/day), one course of GCAP was conducted, and pre- and post-GCAP cytokine profiles were determined.

RESULTS

In inflamed colonic mucosa of UC patients, three cytokine profiles were observed: 1) high expression of interferon-gamma, tumor necrosis factor-alpha, and IL-4 mRNAs but low expression of IL-8 mRNA; 2) high expression of IL-8 mRNA and low expression of others; and 3) low expression of all cytokines examined. Inflamed colonic mucosa of patients with high disease activity showed the second pattern. Inflamed colonic mucosa of patients who were not treated with PSL and who had low disease activity showed the first pattern, whereas those on high-dose PSL exhibited the second pattern. IL-8 mRNA was significantly higher in inflamed UC samples than in uninflamed samples. GCAP was effective in five of seven PSL-resistant patients (71.4%). IL-8 was the only cytokine that correlated with effectiveness of GCAP. Compared with GCAP nonresponders, responders had significantly higher IL-8 mRNA before GCAP and showed marked reduction of IL-8 mRNA after GCAP.

CONCLUSIONS

IL-8 mRNA was significantly increased in inflamed mucosa of UC. Patients with high IL-8 mRNA expression in colonic mucosa despite PSL treatment were responsive to GCAP. Therefore, quantitative measurement of mucosal IL-8 mRNA may be useful in predicting the response to GCAP.

Upregulation of Reg 1alpha and GW112 in the epithelium of inflamed colonic mucosa

BACKGROUND AND AIMS

Colonic epithelium is involved in the regulation of intestinal function and mucosal immune responses, and its function is altered in inflammatory bowel disease (IBD). However, a comprehensive analysis of the genetic alterations in inflamed colonic epithelium is not available at present. The aim of our study was to detect genes that are preferentially expressed in inflamed colonic epithelia and clarify the biochemical responses of epithelial cells in inflamed colonic mucosa.

METHODS

cDNA representation difference analysis was used to identify candidate genes selectively expressed in inflamed colonic epithelia. Selective expression of these genes in the epithelium of inflamed colonic mucosa, including IBD and non-IBD tissues, was examined by real time polymerase chain reaction and in situ hybridisation. The effect of cell confluence and inflammatory mediators on Reg 1alpha gene expression was examined using a colon cancer cell line (HT29).

RESULTS

We identified seven candidate genes that were presumed to be upregulated in the inflamed colonic epithelium. Of these, Reg 1alpha and GW112 were the dominant species and expression of these genes was confined to the crypt epithelium. In vitro studies using a colonic epithelial cell line suggested that cell confluence regulates Reg 1alpha gene expression.

CONCLUSIONS

Selective expression of Reg 1alpha and GW112 genes in the crypt epithelium of inflamed colonic mucosa suggests the important regulatory functions of these genes.

Bax is downregulated in inflamed colonic mucosa of ulcerative colitis

BACKGROUND AND AIMS

One form of epithelial cell injury in inflamed colonic mucosa in ulcerative colitis (UC) is reported to involve apoptosis of these cells. Bcl-2 family proteins Bax and Bcl-2 are the major regulators of apoptosis. The aim of this study was to elucidate the involvement of the Bax/Bcl-2 system in induction of apoptosis of the inflamed colonic epithelium in UC.

METHODS

Colonic epithelium was isolated from colonic biopsy specimens. Expression of CD95, Bax, Bcl-xL, and Bcl-2 proteins was determined by western blotting. Bax gene expression was assessed by both reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern hybridisation and a real time PCR assay.

RESULTS

Equal levels of expression of CD95, Bcl-xL, and Bcl-2 proteins were noted in normal and UC colonic epithelia. Equal levels of expression of Bax protein and mRNA were noted in epithelia of normal colon and inactive UC. Levels of expression of Bax protein and mRNA were markedly reduced in inflamed UC colonic epithelium.

CONCLUSIONS

Our study showed for the first time downregulation of Bax in inflamed colonic epithelium of UC. The Bax/Bcl-2 system did not seem to be involved in induction of apoptosis of epithelial cells in the inflamed colonic mucosa of UC.

Effects of ethyl all-cis-5,8,11,14,17-icosapentaenoate on the physical properties of arterial walls in high cholesterol diet-fed rabbits

The effects of ethyl all-cis-5,8,11,14,17-icosapentaenoate (EPA-E) on in vivo physical properties of arteriosclerotic aorta and femoral artery in high cholesterol diet (HCD)-fed rabbits were studied. The aortic pulse wave velocity (PWV) of rabbits fed HCD for 12 weeks (control group) tended to be higher than that of rabbits fed a normal diet (normal group). Because the PWVs in HCD-fed rabbits administered orally with 30 and 300 mg/kg/day EPA-E were significantly lower than the PWV of the control group, the distensibility of arteriosclerotic aorta was improved with administration of EPA-E. The stiffness parameter (beta) value as an in vivo indicator of arteriosclerosis was significantly higher in the control group than in the normal group and improved with administration of EPA-E to almost the same level as that of the normal group. The beta-values were in significant negative correlation with medial elastin content and medial smooth muscle cell (SMC) density in thoracic aorta and in positive correlation with the free cholesterol content in abdominal aortic SMC. On the other hand, they were not correlated with either the cross-sectional area of intimal thickening lesions or the plasma lipid levels measured simultaneously. The femoral PWVs were, like those in the aorta, higher in the control group as compared with the normal group, and the changes were improved with administration of EPA-E. These results show that EPA-E improved the in vivo distensibility of arteriosclerotic arteries in HCD-fed rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)