Gut microbiota maturation during early human life induces enterocyte proliferation via microbial metabolites.

BACKGROUND: The intestinal tract undergoes a period of cellular maturation during early life, primarily characterized by the organization of epithelial cells into specialized crypt and villus structures. These processes are in part mediated by the acquisition of microbes. Infants delivered at term typically harbor a stable, low diversity microbiota characterized by an overrepresentation of various Bacilli spp., while pre-term infants are colonized by an assortment of bacteria during the first several weeks after delivery. However, the functional effects of these changes on intestinal epithelium homeostasis and maturation remain unclear. To study these effects, human neonate feces were obtained from term and pre-term infants. Fecal 16S rDNA sequencing and global untargeted LC-MS were performed to characterize microbial composition and metabolites from each population. Murine enteral organoids (enteroids) were cultured with 0.22 µm filtered stool supernatant pooled from term or pre-term infants. RESULTS: Term and pre-term microbial communities differed significantly from each other by principle components analysis (PCoA, PERMANOVA p < 0.001), with the pre-term microbiome characterized by increased OTU diversity (Wilcox test p < 0.01). Term communities were less diverse and dominated by Bacilli (81.54%). Pre-term stools had an increased abundance of vitamins, amino acid derivatives and unconjugated bile acids. Pathway analysis revealed a significant increase in multiple metabolic pathways in pre-term samples mapped to E. coli using the KEGG database related to the fermentation of various amino acids and vitamin biosynthesis. Enteroids cultured with supernatant from pre-term stools proliferated at a higher rate than those cultured with supernatant from term stools (cell viability: 207% vs. 147.7%, p < 0.01), grew larger (area: 81,189µm2 vs. 41,777µm2, p < 0.001), and bud at a higher rate (6.5 vs. 4, p < 0.01). Additionally, genes involved in stem cell proliferation were upregulated in pre-term stool treated enteroid cultures (Lgr5, Ephb2, Ascl2 Sox9) but not term stool treated enteroids. CONCLUSIONS: Our findings indicate that microbial metabolites from the more diverse gut microbiome associated with pre-term infants facilitate stem cell proliferation. Therefore, perturbations of the pre-term microbiota may impair intestinal homeostasis.

Ahr-Foxp3-RORγt axis controls gut homing of CD4+ T cells by regulating GPR15.

The orphan chemoattractant receptor GPR15 is important for homing T lymphocytes to the large intestine, thereby maintaining intestinal immune homeostasis. However, the molecular mechanisms underlying the regulation of GPR15 expression remain elusive. Here, we show a central role of the aryl hydrocarbon receptor (Ahr) in promoting GPR15 expression in both mice and human, thus gut homing of T lymphocytes. Mechanistically, Ahr directly binds to open chromatin regions of the Gpr15 locus to enhance its expression. Ahr transcriptional activity in directing GPR15 expression was modulated by two transcription factors, Foxp3 and RORγt, both of which are expressed preferentially by gut regulatory T cells (Tregs) in vivo. Specifically, Foxp3 interacted with Ahr and enhanced Ahr DNA binding at the Gpr15 locus, thereby promoting GPR15 expression. In contrast, RORγt plays an inhibitory role, at least in part, by competing with Ahr binding to the Gpr15 locus. Our findings thus demonstrate a key role for Ahr in regulating Treg intestinal homing under the steady state and during inflammation and the importance of Ahr-RORγt-Foxp3 axis in regulating gut homing receptor GPR15 expression by lymphocytes.

Human colon mucosal biofilms from healthy or colon cancer hosts are carcinogenic.

Mucus-invasive bacterial biofilms are identified on the colon mucosa of approximately 50% of colorectal cancer (CRC) patients and approximately 13% of healthy subjects. Here, we test the hypothesis that human colon biofilms comprise microbial communities that are carcinogenic in CRC mouse models. Homogenates of human biofilm-positive colon mucosa were prepared from tumor patients (tumor and paired normal tissues from surgical resections) or biofilm-positive biopsies from healthy individuals undergoing screening colonoscopy; homogenates of biofilm-negative colon biopsies from healthy individuals undergoing screening colonoscopy served as controls. After 12 weeks, biofilm-positive, but not biofilm-negative, human colon mucosal homogenates induced colon tumor formation in 3 mouse colon tumor models (germ-free ApcMinΔ850/+;Il10-/- or ApcMinΔ850/+ and specific pathogen-free ApcMinΔ716/+ mice). Remarkably, biofilm-positive communities from healthy colonoscopy biopsies induced colon inflammation and tumors similarly to biofilm-positive tumor tissues. By 1 week, biofilm-positive human tumor homogenates, but not healthy biopsies, displayed consistent bacterial mucus invasion and biofilm formation in mouse colons. 16S rRNA gene sequencing and RNA-Seq analyses identified compositional and functional microbiota differences between mice colonized with biofilm-positive and biofilm-negative communities. These results suggest human colon mucosal biofilms, whether from tumor hosts or healthy individuals undergoing screening colonoscopy, are carcinogenic in murine models of CRC.

Locoregional Effects of Microbiota in a Preclinical Model of Colon Carcinogenesis.

Inflammation and microbiota are critical components of intestinal tumorigenesis. To dissect how the microbiota contributes to tumor distribution, we generated germ-free (GF) ApcMin/+ and ApcMin/+ ;Il10-/- mice and exposed them to specific-pathogen-free (SPF) or colorectal cancer-associated bacteria. We found that colon tumorigenesis significantly correlated with inflammation in SPF-housed ApcMin/+ ;Il10-/- , but not in ApcMin/+ mice. In contrast, small intestinal neoplasia development significantly correlated with age in both ApcMin/+ ;Il10-/- and ApcMin/+ mice. GF ApcMin/+ ;Il10-/- mice conventionalized by an SPF microbiota had significantly more colon tumors compared with GF mice. Gnotobiotic studies revealed that while Fusobacterium nucleatum clinical isolates with FadA and Fap2 adhesins failed to induce inflammation and tumorigenesis, pks+Escherichia coli promoted tumorigenesis in the ApcMin/+ ;Il10-/- model in a colibactin-dependent manner, suggesting colibactin is a driver of carcinogenesis. Our results suggest a distinct etiology of cancers in different locations of the gut, where colon cancer is primarily driven by inflammation and the microbiome, while age is a driving force for small intestine cancer. Cancer Res; 77(10); 2620-32. ©2017 AACR.

Altered intestinal microbiota-host mitochondria crosstalk in new onset Crohn's disease.

Intestinal microbial dysbiosis is associated with Crohn's disease (CD). However, the mechanisms leading to the chronic mucosal inflammation that characterizes this disease remain unclear. In this report, we use systems-level approaches to study the interactions between the gut microbiota and host in new-onset paediatric patients to evaluate causality and mechanisms of disease. We report an altered host proteome in CD patients indicative of impaired mitochondrial functions. In particular, mitochondrial proteins implicated in H2S detoxification are downregulated, while the relative abundance of H2S microbial producers is increased. Network correlation analysis reveals that Atopobium parvulum controls the central hub of H2S producers. A. parvulum induces pancolitis in colitis-susceptible interleukin-10-deficient mice and this phenotype requires the presence of the intestinal microbiota. Administrating the H2S scavenger bismuth mitigates A. parvulum-induced colitis in vivo. This study reveals that host-microbiota interactions are disturbed in CD and thus provides mechanistic insights into CD pathogenesis.

The Innate Immune Receptor NLRX1 Functions as a Tumor Suppressor by Reducing Colon Tumorigenesis and Key Tumor-Promoting Signals.

NOD-like receptor (NLR) proteins are intracellular innate immune sensors/receptors that regulate immunity. This work shows that NLRX1 serves as a tumor suppressor in colitis-associated cancer (CAC) and sporadic colon cancer by keeping key tumor promoting pathways in check. Nlrx1(-/-) mice were highly susceptible to CAC, showing increases in key cancer-promoting pathways including nuclear factor κB (NF-κB), mitogen-activated protein kinase (MAPK), signal transducer and activator of transcription 3 (STAT3), and interleukin 6 (IL-6). The tumor-suppressive function of NLRX1 originated primarily from the non-hematopoietic compartment. This prompted an analysis of NLRX1 function in the Apc(min/+) genetic model of sporadic gastrointestinal cancer. NLRX1 attenuated Apc(min/+) colon tumorigenesis, cellular proliferation, NF-κB, MAPK, STAT3 activation, and IL-6 levels. Application of anti-interleukin 6 receptor (IL6R) antibody therapy reduced tumor burden, increased survival, and reduced STAT3 activation in Nlrx1(-/-)Apc(min/+) mice. As an important clinical correlate, human colon cancer samples expressed lower levels of NLRX1 than healthy controls in multiple patient cohorts. These data implicate anti-IL6R as a potential personalized therapy for colon cancers with reduced NLRX1.

Inflammasome-independent role of AIM2 in suppressing colon tumorigenesis via DNA-PK and Akt.

The inflammasome activates caspase-1 and the release of interleukin-1ß (IL-1ß) and IL-18, and several inflammasomes protect against intestinal inflammation and colitis-associated colon cancer (CAC) in animal models. The absent in melanoma 2 (AIM2) inflammasome is activated by double-stranded DNA, and AIM2 expression is reduced in several types of cancer, but the mechanism by which AIM2 restricts tumor growth remains unclear. We found that Aim2-deficient mice had greater tumor load than Asc-deficient mice in the azoxymethane/dextran sodium sulfate (AOM/DSS) model of colorectal cancer. Tumor burden was also higher in Aim2(-/-)/Apc(Min/+) than in APC(Min/+) mice. The effects of AIM2 on CAC were independent of inflammasome activation and IL-1ß and were primarily mediated by a non-bone marrow source of AIM2. In resting cells, AIM2 physically interacted with and limited activation of DNA-dependent protein kinase (DNA-PK), a PI3K-related family member that promotes Akt phosphorylation, whereas loss of AIM2 promoted DNA-PK-mediated Akt activation. AIM2 reduced Akt activation and tumor burden in colorectal cancer models, while an Akt inhibitor reduced tumor load in Aim2(-/-) mice. These findings suggest that Akt inhibitors could be used to treat AIM2-deficient human cancers.

Microbial genomic analysis reveals the essential role of inflammation in bacteria-induced colorectal cancer.

Enterobacteria, especially Escherichia coli, are abundant in patients with inflammatory bowel disease or colorectal cancer (CRC). However, it is unclear whether cancer is promoted by inflammation-induced expansion of E. coli and/or changes in expression of specific microbial genes. Here we use longitudinal (2, 12 and 20 weeks) 16S rRNA sequencing of luminal microbiota from ex-germ-free mice to show that inflamed Il10(-/-) mice maintain a higher abundance of Enterobacteriaceae than healthy wild-type mice. Experiments with mono-colonized Il10(-/-) mice reveal that host inflammation is necessary for E. coli cancer-promoting activity. RNA-sequence analysis indicates significant changes in E. coli gene catalogue in Il10(-/-) mice, with changes mostly driven by adaptation to the intestinal environment. Expression of specific genes present in the tumour-promoting E. coli pks island are modulated by inflammation/CRC development. Thus, progression of inflammation in Il10(-/-) mice supports Enterobacteriaceae and alters a small subset of microbial genes important for tumour development.

The microbiota protects against ischemia/reperfusion-induced intestinal injury through nucleotide-binding oligomerization domain-containing protein 2 (NOD2) signaling.

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2), an intracellular pattern recognition receptor, induces autophagy on detection of muramyl dipeptide (MDP), a component of microbial cell walls. The role of bacteria and NOD2 signaling toward ischemia/reperfusion (I/R)-induced intestinal injury response is unknown. Herein, we report that I/R-induced intestinal injury in germ-free (GF) C57BL/6 wild-type (WT) mice is worse than in conventionally derived mice. More important, microbiota-mediated protection against I/R-induced intestinal injury is abrogated in conventionally derived Nod2(-/-) mice and GF Nod2(-/-) mice. Also, WT mice raised in specific pathogen-free (SPF) conditions fared better against I/R-induced injury than SPF Nod2(-/-) mice. Moreover, SPF WT mice i.p. administered 10 mg/kg MDP were protected against injury compared with mice administered the inactive enantiomer, l-MDP, an effect lost in Nod2(-/-) mice. However, MDP administration failed to protect GF mice from I/R-induced intestinal injury compared with control, a phenomenon correlating with undetectable Nod2 mRNA level in the epithelium of GF mice. More important, the autophagy-inducer rapamycin protected Nod2(-/-) mice against I/R-induced injury and increased the levels of LC3(+) puncta in injured tissue of Nod2(-/-) mice. These findings demonstrate that NOD2 protects against I/R and promotes wound healing, likely through the induction of the autophagy response.

Glass Microparticulate Ingestion: An Unusual and Difficult-to-Diagnose Cause of Chronic Abdominal Pain.

In the absence of overt structural abnormalities, the diagnostic approach to chronic abdominal pain can be challenging. Occupational particulate inhalation causing injury to an organ other than the lung is rare. We report a case of inadvertent glass microparticulate ingestion causing chronic abdominal pain with altered local and systemic inflammatory responses.

Epithelial cell-specific MyD88 signaling mediates ischemia/reperfusion-induced intestinal injury independent of microbial status.

The Toll-like receptor/MyD88 signaling pathway has been shown to mediate protective functions during intestinal exposure to various noxious events. The goal of this study was to define the role of bacteria and MyD88 signaling in intestinal response to damage using an ischemia-reperfusion (I/R)-induced injury model. We showed that conventionalized mice displayed a better outcome to I/R-induced injury than germ-free mice (3.8 ± 1.98 vs. 11.8 ± 1.83, P < 0.05). However, mice with intestinal epithelial cell (IEC)-specific deletion of Myd88 (Myd88) were protected from I/R-induced injury compared with Myd88 control mice. Myd88 mice also displayed a significantly reduced bacterial translocation (∼85%) into lymph nodes compared with Myd88 mice. Expression of ccl2 and cxcl1 mRNA was significantly reduced (85% and 62%, respectively) in intestinal tissue of Myd88 mice compared with Myd88 mice, which associated with a reduced number of myeloperoxidase-positive cells in intestinal tissues of I/R-exposed Myd88 mice. Immunohistochemistry analysis showed a reduced IgA deposition and complement staining in ischemic tissue of Myd88 mice compared with Myd88 mice. These findings suggest that I/R-induced intestinal injury involves IEC-derived MyD88 signaling leading to increased IgA deposition/degradation, and complement activation in conjunction with an influx of neutrophils mediated by chemokine production.

VSL#3 probiotic modifies mucosal microbial composition but does not reduce colitis-associated colorectal cancer.

Although probiotics have shown success in preventing the development of experimental colitis-associated colorectal cancer (CRC), beneficial effects of interventional treatment are relatively unknown. Here we show that interventional treatment with VSL#3 probiotic alters the luminal and mucosally-adherent microbiota, but does not protect against inflammation or tumorigenesis in the azoxymethane (AOM)/Il10⁻/⁻ mouse model of colitis-associated CRC. VSL#3 (109 CFU/animal/day) significantly enhanced tumor penetrance, multiplicity, histologic dysplasia scores, and adenocarcinoma invasion relative to VSL#3-untreated mice. Illumina 16S sequencing demonstrated that VSL#3 significantly decreased (16-fold) the abundance of a bacterial taxon assigned to genus Clostridium in the mucosally-adherent microbiota. Mediation analysis by linear models suggested that this taxon was a contributing factor to increased tumorigenesis in VSL#3-fed mice. We conclude that VSL#3 interventional therapy can alter microbial community composition and enhance tumorigenesis in the AOM/Il10⁻/⁻ model.

Stochastic changes over time and not founder effects drive cage effects in microbial community assembly in a mouse model.

Maternal transmission and cage effects are powerful confounding factors in microbiome studies. To assess the consequences of cage microenvironment on the mouse gut microbiome, two groups of germ-free (GF) wild-type (WT) mice, one gavaged with a microbiota harvested from adult WT mice and another allowed to acquire the microbiome from the cage microenvironment, were monitored using Illumina 16S rRNA sequencing over a period of 8 weeks. Our results revealed that cage effects in WT mice moved from GF to specific pathogen free (SPF) conditions take several weeks to develop and are not eliminated by the initial gavage treatment. Initial gavage influenced, but did not eliminate a successional pattern in which Proteobacteria became less abundant over time. An analysis in which 16S rRNA sequences are mapped to the closest sequenced whole genome suggests that the functional potential of microbial genomes changes significantly over time shifting from an emphasis on pathogenesis and motility early in community assembly to metabolic processes at later time points. Functionally, mice allowed to naturally acquire a microbial community from their cage, but not mice gavaged with a common biome, exhibit a cage effect in Dextran Sulfate Sodium-induced inflammation. Our results argue that while there are long-term effects of the founding community, these effects are mitigated by cage microenvironment and successional community assembly over time, which must both be explicitly considered in the interpretation of microbiome mouse experiments.

Oxymatrine prevents NF-κB nuclear translocation and ameliorates acute intestinal inflammation.

Oxymatrine is a traditional Chinese herbal product that exhibits anti-inflammatory effects in models of heart, brain and liver injury. We investigated the impact of oxymatrine in an acute model of intestinal injury and inflammation. Oxymatrine significantly decreased LPS-induced NF-κB-driven luciferase activity, correlating with diminished induction of Cxcl2, Tnfα and Il6 mRNA expression in rat IEC-6 and murine BMDC. Although oxymatrine decreased LPS-induced p65 nuclear translocation and binding to the Cxcl2 gene promoter, this effect was independent of IκBα degradation/phosphorylation. DSS-induced weight loss and histological damage were ameliorated in oxymatrine-treated C57BL/6-WT-mice. While this effect correlated with reduced colonic Il6 and Il1ß mRNA accumulation, global NF-κB activity as measured in NF-κB(EGFP) mice was unaffected. Our data demonstrate that oxymatrine reduces LPS-induced NF-κB nuclear translocation and activity independently of IκBα status, prevents intestinal inflammation through blockade of inflammatory signaling and ameliorates overall intestinal inflammation in vivo.

Intestinal inflammation targets cancer-inducing activity of the microbiota.

Inflammation alters host physiology to promote cancer, as seen in colitis-associated colorectal cancer (CRC). Here, we identify the intestinal microbiota as a target of inflammation that affects the progression of CRC. High-throughput sequencing revealed that inflammation modifies gut microbial composition in colitis-susceptible interleukin-10-deficient (Il10(-/-)) mice. Monocolonization with the commensal Escherichia coli NC101 promoted invasive carcinoma in azoxymethane (AOM)-treated Il10(-/-) mice. Deletion of the polyketide synthase (pks) genotoxic island from E. coli NC101 decreased tumor multiplicity and invasion in AOM/Il10(-/-) mice, without altering intestinal inflammation. Mucosa-associated pks(+) E. coli were found in a significantly high percentage of inflammatory bowel disease and CRC patients. This suggests that in mice, colitis can promote tumorigenesis by altering microbial composition and inducing the expansion of microorganisms with genotoxic capabilities.

A cell permeable peptide inhibitor of NFAT inhibits macrophage cytokine expression and ameliorates experimental colitis.

Nuclear factor of activated T cells (NFAT) plays a critical role in the development and function of immune and non-immune cells. Although NFAT is a central transcriptional regulator of T cell cytokines, its role in macrophage specific gene expression is less defined. Previous work from our group demonstrated that NFAT regulates Il12b gene expression in macrophages. Here, we further investigate NFAT function in murine macrophages and determined the effects of a cell permeable NFAT inhibitor peptide 11R-VIVIT on experimental colitis in mice. Treatment of bone marrow derived macrophages (BMDMs) with tacrolimus or 11R-VIVIT significantly inhibited LPS and LPS plus IFN-γ induced IL-12 p40 mRNA and protein expression. IL-12 p70 and IL-23 secretion were also decreased. NFAT nuclear translocation and binding to the IL-12 p40 promoter was reduced by NFAT inhibition. Experiments in BMDMs from IL-10 deficient (Il10(-/-)) mice demonstrate that inhibition of IL-12 expression by 11R-VIVIT was independent of IL-10 expression. To test its therapeutic potential, 11R-VIVIT was administered systemically to Il10(-/-) mice with piroxicam-induced colitis. 11R-VIVIT treated mice demonstrated significant improvement in colitis compared to mice treated with an inactive peptide. Moreover, decreased spontaneous secretion of IL-12 p40 and TNF in supernatants from colon explant cultures was demonstrated. In summary, NFAT, widely recognized for its role in T cell biology, also regulates important innate inflammatory pathways in macrophages. Selective blocking of NFAT via a cell permeable inhibitory peptide is a promising therapeutic strategy for the treatment of inflammatory bowel diseases.

Microbial colonization induces dynamic temporal and spatial patterns of NF-κB activation in the zebrafish digestive tract.

BACKGROUND & AIMS: The nuclear factor κ-light-chain enhancer of activated B cells (NF-κB) transcription factor pathway is activated in response to diverse microbial stimuli to regulate expression of genes involved in immune responses and tissue homeostasis. However, the temporal and spatial activation of NF-κB in response to microbial signals have not been determined in whole living organisms, and the molecular and cellular details of these responses are not well understood. We used in vivo imaging and molecular approaches to analyze NF-κB activation in response to the commensal microbiota in transparent gnotobiotic zebrafish. METHODS: We used DNA microarrays, in situ hybridization, and quantitative reverse transcription polymerase chain reaction analyses to study the effects of the commensal microbiota on gene expression in gnotobiotic zebrafish. Zebrafish PAC2 and ZFL cells were used to study the NF-κB signaling pathway in response to bacterial stimuli. We generated transgenic zebrafish that express enhanced green fluorescent protein under transcriptional control of NF-κB, and used them to study patterns of NF-κB activation during development and microbial colonization. RESULTS: Bacterial stimulation induced canonical activation of the NF-κB pathway in zebrafish cells. Colonization of germ-free transgenic zebrafish with a commensal microbiota activated NF-κB and led to up-regulation of its target genes in intestinal and extraintestinal tissues of the digestive tract. Colonization with the bacterium Pseudomonas aeruginosa was sufficient to activate NF-κB, and this activation required a functional flagellar apparatus. CONCLUSIONS: In zebrafish, transcriptional activity of NF-κB is spatially and temporally regulated by specific microbial factors. The observed patterns of NF-κB-dependent responses to microbial colonization indicate that cells in the gastrointestinal tract respond robustly to the microbial environment.

Reduced expression of fibroblast growth factor receptor 2IIIb in hepatocellular carcinoma induces a more aggressive growth.

Fibroblast growth factor receptor 2 isoform b (FGFR2-IIIb) is highly expressed in hepatocytes and plays an important role in liver homeostasis and regeneration. Here, we analyzed the expression and function of FGFR2-IIIb in hepatocellular carcinoma (HCC). FGFR2-IIIb expression in HCC tissues and cell lines was lower than in primary human hepatocytes and nontumorous tissue. FGFR2-IIIb-negative HCCs showed a significantly higher Ki-67 labeling index, and loss of FGFR2-IIIb expression correlated significantly with vascular invasion and more advanced tumor stages. A decrease in FGFR-2IIIb expression in HCC cell lines was not related to promoter hypermethylation. However, PCR analysis indicated that chromosomal deletion at 10q accounted for the loss of FGFR2 expression in a subset of HCC cells. FGFR2-IIIb re-expression in stable transfected HCC cell lines induced a higher basal apoptosis rate and a significantly reduced proliferation and migratory potential in vitro. In nude mice, FGFR2-IIIb re-expressing HCC cells grew significantly slower, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay revealed higher apoptosis rates. The antitumorigenic effects of FGFR2-IIIb expression in HCC cells were not affected by keratinocyte growth factor or an inhibitor of FGFR-phosphorylation, indicating that they are independent of tyrosine kinase activation. In conclusion, our data indicate that FGFR2-IIIb inhibits tumorigenicity of HCC cells. Identification of the molecular mechanisms promoting regeneration in normal tissue while suppressing malignancy may lead to novel therapeutic targets of this highly aggressive tumor.

Tumor necrosis factor and interferon-gamma down-regulate Klotho in mice with colitis.

BACKGROUND & AIMS: Klotho (KL) is an anti-inflammatory protein that protects the endothelium from nitric oxide (NO)-induced dysfunction, reduces the expression of endothelial adhesion molecules, and potentially regulates T-cell functions. KL deficiency leads to premature senescence and impaired Ca2+/Pi homeostasis, which can lead to inflammatory bowel disease (IBD)-associated osteopenia/osteoporosis. We investigated the changes in renal expression of Kl as a consequence of colitis. METHODS: We studied 3 mouse models of IBD: colitis induced by trinitrobenzene sulfonic acid, colitis induced by microflora (in gnotobiotic interleukin-10(-/-)), and colitis induced by adoptive transfer of CD4(+)CD45RB(high) T cells. Effects of the tumor necrosis factor (TNF) and interferon (IFN)-gamma on Kl expression and the activity of its promoter were examined in renal epithelial cells (mpkDCT4 and mIMCD3). RESULTS: Renal expression of Kl messenger RNA (mRNA) and protein was reduced in all 3 models of IBD. Reduced level of KL correlated with the severity of colitis; the effect was reversed by neutralizing antibodies against TNF. In vitro, TNF inhibited Kl expression, an effect potentiated by IFN-gamma. The combination of TNF and IFN-gamma increased expression of inducible nitric oxide synthase (iNOS) and increased NO production. The effect of IFN-gamma was reproduced by exposure to an NO donor and reversed by the iNOS inhibitor. In cells incubated with TNF and/or IFN-gamma, Kl mRNA stability was unaffected, whereas Kl promoter activity was reduced, indicating that these cytokines regulate Kl at the transcriptional level. CONCLUSIONS: The down-regulation of KL that occurs during inflammation might account for the extraintestinal complications such as abnormalities in bone homeostasis that occur in patients with IBD.

Analysis of monocyte chemotactic protein-1 gene polymorphism in patients with spontaneous bacterial peritonitis.

AIM: To investigate a genetic polymorphism of the monocyte chemotactic protein-1 (MCP-1) gene in patients with spontaneous bacterial peritonitis (SBP). METHODS: MCP-1 genotyping was performed in 23 patients with SBP and 83 cirrhotic control patients with non-infected ascites. RESULTS: The frequency of carriers of the G-allele was lower in SBP patients but this difference did not reach statistical significance. However, in the subgroup of patients with alcoholic cirrhosis (n = 80), carriers of the G-allele were significantly less frequent in SBP-patients (38.1%) than in cirrhotic controls (67.8%, P = 0.021). CONCLUSION: In patients with alcoholic liver cirrhosis, the -2518 MCP-1 genotype AA is a risk factor for the development of SBP.