Interaction between resident luminal bacteria and the host: can a healthy relationship turn sour?

Epoxy Triglyceride Enhances Intestinal Permeability via Caspase-1/NLRP3/GSDMD and cGAS-STING Pathways in Dextran Sulfate Sodium-Induced Colitis Mice

Oxidized triglyceride monomers are the main cytotoxic products of deep-frying oil. However, its impact on the intestinal barrier, the first health guardian, remains unknown. In this study, HPLC-MS/MS analysis revealed that the epoxy group is the main oxidation product, indicating that it may be the main cytotoxic factor. Therefore, 1-9,10-epoxystearic ester, 2,3-dioleic acid (EGT) and glycerol trioleate (GT) were used to reveal the effect of the epoxy group on the intestinal barrier of dextran sulfate sodium-induced colitis. Characteristics analysis showed that EGT could aggravate intestinal damage. The relative mRNA expression analysis suggested that EGT could activate Caspase-1/NLRP3/GSDMD, thereby inducing pyroptosis. The proinflammatory cytokines activated by pyroptosis and the cGAS-STING pathway were released through the pores, thus inducing the disintegration of the tight junction between the intestinal epithelial cells and enhancing intestinal permeability. Metabonomics further confirmed that EGT can change the composition and content of phospholipids on the cell membrane, indicating the morphological changes of the intestinal epithelial cell membrane. In conclusion, this study highlights that EGT induced intestinal dysfunction via Caspase-1/NLRP3/GSDMD and cGAS-STING pathways.

Village-Indigenous Chicken Bacterial Carriage after the Heavy Rains of 2018, Kenya: Indicator on Environmental Contamination with Pathogenic/Zoonotic Bacteria

Food borne diseases are one of the major human disease conditions worldwide. Most of them are of bacterial origin and chickens are a major source of such bacteria; they are consumed at high rate worldwide and tend to harbor the zoonotic bacteria without showing signs of illness. Running rain water tends to increase environmental contamination, since it carries various substances from one area to another; this results in village-indigenous chickens picking more bacteria from the environment as they roam/scavenge around for food. Thus, after the rain, the chickens' intestinal contents may contain more bacteria quantity-wise and type-wise. This study was carried-out to determine whether that was the case after heavy rains of 2018.120 intestine samples were collected from indigenous chickens from three slaughterhouses in Nairobi for bacterial quantification using the Miles and Misra technique; bacterial isolation and identification were carried out using standard bacteriological procedures. Intestines from the slaughterhouses had different mean bacterial counts: Kangemi had the highest (1.3 × 10¹² colony-forming units per ml), followed by Burma (5.6 × 10¹¹), then Kariokor (4.7 × 10¹¹). E. coli was the most isolated at 85.8%, followed by genera Staphylococcus (55%), Streptococcus (43.3%), Bacillus (41.66%), Listeria (38.3%), Proteus (24.16%), Klebsiella (7.5%), Campylobacter (2.5%), Pseudomonas (6%), and Streptobacillus (0.83%). The study showed that the indigenous chickens carry a variety of bacteria in types and numbers, some of them being zoonotic. Apart from picking more bacteria as a result of environmental contamination during rainy season, the weather and bird-handling further stress the birds, thus contributing to higher bacterial multiplication and higher bacterial carriage. If slaughter is not done right, these intestinal bacteria can easily cause contamination of respective chicken meat; thus, if pathogenic, it can cause food poisoning to consumers of the meat. Therefore, it is recommended that precaution be taken while slaughtering chickens for consumption. In addition, where possible, free-range indigenous chickens be confined during rainy seasons to reduce their exposure to contaminated environment.

Synergistic Protective Effect of Konjac Mannan Oligosaccharides and Bacillus subtilis on Intestinal Epithelial Barrier Dysfunction in Caco-2 Cell Model and Mice Model of Lipopolysaccharide Stimulation

As the first line of defense against intestinal bacteria and toxins, intestinal epithelial cells are always exposed to bacteria or lipopolysaccharide (LPS), whereas pathogenic bacteria or LPS can cause intestinal epithelial cell damage. Previous studies have shown that konjac mannan oligosaccharides (KMOS) have a positive effect on maintaining intestinal integrity, and Bacillus subtilis (BS) can promote the barrier effect of the intestine. However, it is still unknown whether KMOS and BS have a synergistic protective effect on the intestines. In this study, we used the LPS-induced Caco-2 cell injury model and mouse intestinal injury model to study the synergistic effects of KMOS and BS. Compared with KMOS or BS alone, co-treatment with KMOS and BS significantly enhanced the activity and antioxidant capacity of Caco-2 cell, protected mouse liver and ileum from LPS-induced oxidative damage, and repaired tight junction and mucus barrier damage by up-regulating the expression of Claudin-1, ZO-1 and MUC-2. Our results demonstrate that the combination of KMOS and BS has a synergistic repair effect on inflammatory and oxidative damage of Caco-2 cells and aIIeviates LPS-induced acute intestinal injury in mice.

'Layered immunity' and the 'neonatal window of opportunity' - timed succession of non-redundant phases to establish mucosal host-microbial homeostasis after birth

The intricate host–microbial interaction and the overwhelming complexity of the mucosal immune system in the adult host raise the question of how this system is initially established. Here, we propose the implementation of the concept of the ‘postnatal window of opportunity’ into the model of a ‘layered immunity’ to explain how the newborn's mucosal immune system matures and how host–microbial immune homeostasis is established after birth. We outline the concept of a timed succession of non‐redundant phases during postnatal immune development and discuss the possible influence of external factors and conditions.

Mechanisms of angiogenesis in microbe-regulated inflammatory and neoplastic conditions

Commensal microbiota inhabit all the mucosal surfaces of the human body. It plays significant roles during homeostatic conditions, and perturbations in numbers and/or products are associated with several pathological disorders. Angiogenesis, the process of new vessel formation, promotes embryonic development and critically modulates several biological processes during adulthood. Indeed, deregulated angiogenesis can induce or augment several pathological conditions. Accumulating evidence has implicated the angiogenic process in various microbiota-associated human diseases. Herein, we critically review diseases that are regulated by microbiota and are affected by angiogenesis, aiming to provide a broad understanding of how angiogenesis is involved and how microbiota regulate angiogenesis in microbiota-associated human conditions.

Enteric glial cells: Powerful guardian of intestinal epithelial barrier in inflammatory bowel disease

The intestinal epithelium constitutes a physical and functional barrier between the external environment and the host organism. Once the integrity of this barrier is disrupted, inflammatory disorders and tissue injury are initiated and perpetuated. Beneath the intestinal epithelial cells lies a population of astrocyte-like cells that are known as enteric glia cells (EGCs). They play a key role in maintaining the homeostasis and integrity of intestinal epithelial barrier by secretion of some mediators and modulation of enteric neuronal activities. In this review, we will describe the functional roles of enteric glia cells in the intestinal barrier, and highlight the protective action of EGCs in inflammatory bowel disease.

Intestinal anti-inflammatory activity of lentinan: influence on IL-8 and TNFR1 expression in intestinal epithelial cells

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the gastrointestinal tract. It is unknown whether β-1,3;1,6-glucan can induce immune suppressive effects. Here, we study intestinal anti-inflammatory activity of Lentinula edodes-derived β-1,3;1,6-glucan, which is known as lentinan. Dextran sulfate sodium (DSS)-induced colitis mice were used to elucidate effects of lentinan in vivo. In the cellular level assessment, lentinan was added into a co-culture model consisting of intestinal epithelial Caco-2 cells and LPS-stimulated macrophage RAW264.7 cells. Ligated intestinal loop assay was performed for assessing effects of lentinan on intestinal epithelial cells (IECs) in vivo. Oral administration of lentinan (100 µg/mouse) significantly ameliorated DSS-induced colitis in body weight loss, shortening of colon lengths, histological score, and inflammatory cytokine mRNA expression in inflamed tissues. Lentinan reduced interleukin (IL)-8 mRNA expression and nuclear factor (NF)-κB activation in Caco-2 cells without decreasing of tumor necrosis factor (TNF)-α production from RAW264.7 cells. Flow cytometric analysis revealed that surface levels of TNF receptor (TNFR) 1 were decreased by lentinan treatment. A clathrin-mediated endocytosis inhibitor, monodansylcadaverine, canceled lentinan inhibition of IL-8 mRNA expression. Moreover, lentinan inhibited TNFR1 expression in Caco-2 cells in both protein and mRNA level. Lentinan also inhibited TNFR1 mRNA expression in mouse IECs. These results suggest that lentinan exhibits intestinal anti-inflammatory activity through inhibition of IL-8 mRNA expression associated with the inhibition of NF-κB activation which is triggered by TNFR1 endocytosis and lowering of their expression in IECs. Lentinan may be effective for the treatment of gut inflammation including IBD.

Bacterial mediated gastrointestinal inflammation

Mouse models have proven to be a key approach in our understanding of the etiology and physiology underlying bacterial mediated gastrointestinal inflammation. Generally, these models are based on the inoculation of genetically susceptible mice with either commensal or pathogenic bacteria to elicit an inflammatory response. Here, we describe models of acute and chronic gastrointestinal inflammation using interleukin 10-deficient (Il10 (-/-)) mice colonized with the pathogenic Campylobacter jejuni strain 81-176 or the commensal Escherichia coli strain NC 101.

Expression of Toll-like receptor 4, CD14, and NF-κB in Chinese patients with ulcerative colitis

This study elucidates the significance of Toll-like receptor 4 (TLR4), CD14, and nuclear factor (NF)-κB on the pathogenesis of ulcerative colitis (UC). Colonic biopsy specimens were collected from active UC and controls. The expression of TLR4, CD14, and NF-κBp 65 was analyzed by immunohistochemistry (IHC) and reverse-transcription polymerase chain reaction (RT-PCR). In UC, disease activity index (DAI) and pathological grade were classified according to the Powell-Tuck grade system and Truelove-Richards system, respectively. Fifty-six UC cases and 56 controls entered the investigation. IHC and RT-PCR revealed a significant increase of TLR4, CD14, and NF-κBp 65 antigen expression in colonic mucosa of UC compared with colonic mucosa of controls (p < .001). In UC, TLR4, CD14, and NF-κBp 65 expression were positively related to DAI (r = .873, p < .001; r = .576, p < .001; r = .747, p < .001 receptively). NF-κBp65 significantly correlated with TLR4 and CD14 (r = .669, p < .001; r = .576, p < .001, receptively). TLR4, CD14, and NF-κBp65 were positively related to pathological classification in UC (p < .01). Thus, TLR4, CD14, and NF-κBp65 were upregulated significantly in UC, to an extent that reflects the degree of inflammation and thereby might contribute to the occurrence and development of UC.

Peroxisome proliferator-activated receptor γ 2 mutation may cause a subset of ulcerative colitis

AIM

Previous studies suggest the homeostasis between acquisition of tolerance to the indigenous microflora and protective immune responses appears to be disrupted in inflammatory bowel disease (IBD). Some experimental studies indicate peroxisome proliferator-activated receptor γ (PPARγ) has been implicated as a regulator of intestinal inflammatory responses. In addition, the toll-like receptor (TLR)-4 can regulate expression of PPARγ in colonic epithelial cells. We attempted to demonstrate whether the functional imbalance between TLRs and PPARγ could lead to the onset and some polymorphisms of those genes could contribute to susceptibility to IBD.

METHODS

RT-PCR analysis were performed to detect TLR4 and PPARγ mRNA associated with those of P65 of NFκB, TNFα, MyD88, NOD2/CARD15, TLR-2,5,9, in the diseased colonic mucosa in ulcerative colitis (UC; n = 13) and Crohn's disease (CD; n = 7) compared with normal controls (n = 18). Consequently, we genotyped UC (n = 29) and CD (n = 10) compared with normal controls (n = 134) for the prevalence of suspicious mutations.

RESULTS

In a subset of UC patients who were revealed to carry PPARγ Pro12Ala mutation later, impaired expression of normal PPARγ mRNA was noted in the diseased mucosa accompanied with upregulations of MyD88 TLR-4, 5, 9, P65 and TNFα in mRNA levels. The prevalence of PPARγ Pro12Ala mutation was more frequently found in UC patients compared with CD patients and normal controls (P < 0.05).

CONCLUSIONS

These findings suggested that imbalances between TLRs and PPARγ in response to luminal bacteria could lead to colonic inflammation in some UC patients. Alternative explanations will be needed for the onset of the rest of UC and CD.

Human gut microbiome: the second genome of human body

The human body is actually a super-organism that is composed of 10 times more microbial cells than our body cells. Metagenomic study of the human microbiome has demonstrated that there are 3.3 million unique genes in human gut, 150 times more genes than our own genome, and the bacterial diversity analysis showed that about 1000 bacterial species are living in our gut and a majority of them belongs to the divisions of Firmicutes and Bacteriodetes. In addition, most people share a core microbiota that comprises 50-100 bacterial species when the frequency of abundance at phylotype level is not considered, and a core microbiome harboring more than 6000 functional gene groups is present in the majority of human gut surveyed till now. Gut bacteria are not only critical for regulating gut metabolism, but also important for host immune system as revealed by animal studies.

Astragalus mongholicus polysaccharide inhibits lipopolysaccharide-induced production of TNF-α and interleukin-8

AIM: To explore the effect of Astragalus mongholicus polysaccharide (APS) on gene expression and mitogen-activated protein kinase (MAPK) transcriptional activity in intestinal epithelial cells (IEC).

METHODS: IEC were divided into control group, lipopolysaccharide (LPS) group, LPS+ 50 &mgr;g/mL APS group, LPS+ 100 &mgr;g/mL APS group, LPS+ 200 &mgr;g/mL APS group, and LPS+ 500 &mgr;g/mL APS group. Levels of mRNAs in LPS-induced inflammatory factors, tumor necrosis factor (TNF)-α and interleukin (IL)-8, were measured by reverse transcription-polymerase chain reaction. MAPK protein level was measured by Western blotting.

RESULTS: The levels of TNF-α and IL-8 mRNAs were significantly higher in IEC with LPS-induced damage than in control cells. APS significantly abrogated the LPS-induced expression of the TNF-α and IL-8 genes. APS did not block the activation of extracellular signal-regulated kinase or c Jun amino-terminal kinase, but inhibited the activation of p38, suggesting that APS inhibits LPS-induced production of TNF-α and IL-8 mRNAs, possibly by suppressing the p38 signaling pathway.

CONCLUSION: APS-modulated bacterial product-mediated p38 signaling represents an attractive strategy for prevention and treatment of intestinal inflammation.

Modulation of the intestinal microbiota alters colitis-associated colorectal cancer susceptibility

It is well established that the intestinal microbiota plays a key role in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) collectively referred to as inflammatory bowel disease (IBD). Epidemiological studies have provided strong evidence that IBD patients bear increased risk for the development of colorectal cancer (CRC). However, the impact of the microbiota on the development of colitis-associated cancer (CAC) remains largely unknown. In this study, we established a new model of CAC using azoxymethane (AOM)-exposed, conventionalized-Il10^−/− mice and have explored the contribution of the host intestinal microbiota and MyD88 signaling to the development of CAC. We show that 8/13 (62%) of AOM-Il10^−/− mice developed colon tumors compared to only 3/15 (20%) of AOM- wild-type (WT) mice. Conventionalized AOM-Il10^−/− mice developed spontaneous colitis and colorectal carcinomas while AOM-WT mice were colitis-free and developed only rare adenomas. Importantly, tumor multiplicity directly correlated with the presence of colitis. Il10^−/− mice mono-associated with the mildly colitogenic bacterium Bacteroides vulgatus displayed significantly reduced colitis and colorectal tumor multiplicity compared to Il10^−/− mice. Germ-free AOM-treated Il10^−/− mice showed normal colon histology and were devoid of tumors. Il10^−/−; Myd88^−/− mice treated with AOM displayed reduced expression of Il12p40 and Tnfα mRNA and showed no signs of tumor development. We present the first direct demonstration that manipulation of the intestinal microbiota alters the development of CAC. The TLR/MyD88 pathway is essential for microbiota-induced development of CAC. Unlike findings obtained using the AOM/DSS model, we demonstrate that the severity of chronic colitis directly correlates to colorectal tumor development and that bacterial-induced inflammation drives progression from adenoma to invasive carcinoma.

Host-microbe communication within the GI tract

The gastrointestinal tract is a biologically diverse and complicated system which carries out essential physiological functions that support human health, while at the same time maintaining itself as an isolated environment to prevent infection and systemic disease. To maintain homeostasis in the gut, communication between the host and residing microbial communities must occur to identify and eliminate potential pathogens which could colonize and cause damage through aggressive pro-inflammatory responses by the mucosal immune system. To prevent such events, a number of host and bacterial-mediated mechanisms are utilized to monitor the environment and initiate appropriate immune responses to invading pathogens. An essential component of this communication process between gastrointestinal microflora and the host involves distinguishing indigenous species from pathogens through ligand-receptor interactions which lead to various signaling events in host cells. Such events generally result in the development of mucosal immunity and immunological tolerance. While these signaling pathways provide a highly effective means of communication between the gut microflora and the host, pathogens have developed mechanisms to manipulate these pathways to evade detection by the immune system to persist and cause disease. These adaptations include cell surface modifications and the expression of various virulence factors in response to different immunological and hormonal components produced by the host.

Impaired Bcl3 up-regulation leads to enhanced lipopolysaccharide-induced interleukin (IL)-23P19 gene expression in IL-10(-/-) mice

Genetic and biochemical analyses show that IL-23p19 plays a central role in mediating bacteria-induced colitis in interleukin-10-deficient (IL-10(-/-)) mice. The molecular mechanisms responsible for the dysregulated innate host response leading to enhanced IL-23 gene expression in IL-10(-/-) mice are poorly understood. In this study, we investigated the role of Bcl3 in controlling LPS-induced IL-23p19 gene expression in bone marrow-derived dendritic cells (BMDC) isolated from IL-10(-/-) mice. We report higher IL-23p19 mRNA accumulation and protein secretion in LPS-stimulated BMDC isolated from IL-10(-/-) compared with WT mice. Lipopolysaccharide (LPS)-induced B cell leukemia 3 (Bcl3) expression was strongly impaired (90% decrease) in IL-10(-/-) BMDC compared with WT BMDC. Chromatin immunoprecipitation demonstrated enhanced RelA binding to the IL-23p19 promoter in IL-10(-/-) compared with WT BMDC. Bcl3 overexpression decreased LPS-induced IL-23p19 gene expression in IL-10(-/-) BMDC, which correlated with enhanced NF-kappaB p50 binding and decreased RelA binding to the gene promoter. Conversely, Bcl3 knockdown enhanced LPS-induced IL-23p19 gene expression in WT BMDC. Moreover, LPS-induced IL-23p19 gene expression was significantly enhanced in Bcl3(-/-) BMDC compared with WT BMDC. In conclusion, enhanced LPS-induced IL-23p19 gene expression in IL-10(-/-) mice is due to impaired Bcl3 expression leading to diminished p50 and enhanced RelA recruitment to the IL-23p19 promoter.

Commensal bacteria and epithelial cross talk in the developing intestine

Indigenous intestinal microbes have co-evolved with the intestinal immune system to form a symbiotic ecosystem. In the postnatal period, intestinal microbes provide the developing gut with stimuli that are necessary for healthy maturation of the intestinal immune system. Cross talk between the host and commensal microbes is an essential component of gut homeostasis mechanisms also in later life. During recent years, innovative research has shed light on the molecular mechanisms of these interactions.

NF-kappaB and the intestine: friend or foe?

The biological impact of the NF-kappaB transcriptional system in various intestinal biological processes such as cellular proliferation, differentiation and survival, inflammation, and carcinogenesis is a relatively young field of research. Less than a decade ago, reviews addressing NF-kappaB regulation and function in the intestine had to borrow concepts and hypotheses from other bodily systems such as the joints (rheumatoid arthritis), the lungs (asthma), or the cardiovascular system (systemic inflammatory states, sepsis). Since then, important progress has been made in defining the various functional aspects of NF-kappaB signaling in intestinal homeostasis and diseases, and exciting new paradigms have emerged from this research. This review will discuss the function of NF-kappaB in intestinal homeostasis and diseases in relation to injury responses and microbial colonization/infection.

UDN glycoprotein regulates activities of manganese-superoxide dismutase, activator protein-1, and nuclear factor-κB stimulated by reactive oxygen radicals in lipopolysaccharide-stimulated HCT-116 cells

This study was carried out to investigate the anti-inflammatory effects of glycoprotein (UDN glycoprotein, 116-kDa) isolated from Ulmus davidiana Nakai, which has been used to heal inflammatory diseases in Korean herbal medicine. We found that UDN glycoprotein has strong scavenging effect on the production of intracellular superoxide anion (O(2)(-)), hydrogen peroxides (H(2)O(2)), and nitric oxide (NO) without any cytotoxicity, and that the glycoprotein also selectively normalizes the aberrant activation of manganese-superoxide dismutases (Mn-SOD) activity in lipopolysaccaride (LPS)-treated cancerous human colon epithelial cells (HCT-116 cells). The results obtained from electrophoretic mobility shift assay (EMSA) and Western blot analysis showed that UDN glycoprotein blocks the DNA binding activities of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), and attenuates the activities of NF-kappaB subunits (p50 and p65), and AP-1 subunits (c-Jun and c-Fos), respectively. To further verify the anti-inflammatory effect of UDN glycoprotein, we investigated the activity of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and matrix metalloproteinases-9 (MMP-9) in LPS-treated HCT-116 cells, using Western blot analysis and gelatin zymographic assay. Results in this study indicated that 200mug/ml of UDN glycoprotein has inhibitory effects on the activations of iNOS, COX-2, and MMP-9. Therefore, UDN glycoprotein, a natural antioxidant, is a potential modulator of inflammatory signal pathways in LPS-treated HCT-116 cells.

Focus on infantile colic

Infantile colic is a widespread clinical condition in the first 3 months of life, which is easily recognized, but incompletely understood and difficult to solve. The available evidence suggests that infantile colic might have several independent causes. The medical hypotheses include food hypersensitivity or allergy, immaturity of gut function and dysmotility, and the behavioural hypotheses include inadequate maternal-infant interaction, anxiety in the mother and difficult infant temperament. Other recent hypotheses, such as hormone alterations and maternal smoking, still need confirmation, whereas the new concept of alterations in the gut microflora, have been reported. A number of interventions, including pharmacological agents, are discussed, but it is probable that infants with colic require a graded strategy.

CONCLUSION

Considering the favourable clinical course and the wide range of manifestations, a safe approach should be adopted, which is proportional to the intensity of the infantile colic. However, further research and guidelines are still needed.

Increased mucosal expression of Toll-like receptor (TLR)2 and TLR4 in coeliac disease

OBJECTIVES

The dysregulation of adaptive immunity is extensively investigated in celiac disease (CD). Recent data also suggest, however, the implication of innate immunity in CD. Toll-like receptors (TLRs) play a central role in the initiation or maintenance of innate immune responses. The aim of this study was to characterise the expression of TLR2, TLR3, and TLR4 in duodenal biopsy samples taken from children with CD and from controls.

PATIENTS AND METHODS

Duodenal biopsy specimens were collected from 16 children with untreated CD, 9 children with treated CD, and 10 controls. The mRNA expression of TLR2, TLR3, and TLR4 was determined by semiquantitative reverse transcription-polymerase chain reaction. Protein levels of TLRs were determined by Western blot.

RESULTS

We found higher TLR2 and TLR4 mRNA expression and protein levels in the duodenal mucosa of children with treated CD and untreated CD compared with controls. TLR2 and TLR4 mRNA expression and protein levels were even higher in the duodenal mucosa of children with treated CD than in untreated CD. TLR3 mRNA expression was increased in the duodenal mucosa of children with treated CD compared with untreated CD and controls. We were able to detect TLR3 protein only in the biopsy specimens of treated patients with CD.

CONCLUSIONS

The alteration of TLR2 and TLR4 expression in the duodenal mucosa of patients with CD supports the potential implication of innate immune system in the pathomechanism of this disease.

The flavonoid luteolin worsens chemical-induced colitis in NF-kappaB(EGFP) transgenic mice through blockade of NF-kappaB-dependent protective molecules

Background

The flavonoid luteolin has anti-inflammatory properties both in vivo and in vitro. However, the impact of luteolin on experimental models of colitis is unknown.

Methodology/Principal Findings

To address the therapeutic impact of luteolin, NF-κB^EGFP transgenic mice were fed a chow diet containing 2% luteolin- or isoflavone-free control chow (AIN-76), and acute colitis was induced using 3% dextran sodium sulfate (DSS). Additionally, development of spontaneous colitis was evaluated in IL-10^−/−;NF-κB^EGFP transgenic mice fed 2% luteolin chow diet or control chow diet. Interestingly, NF-κB^EGFP transgenic mice exposed to luteolin showed worse DSS-induced colitis (weight loss, histological scores) compared to control-fed mice, whereas spontaneous colitis in IL-10^−/−;NF-κB^EGFP mice was significantly attenuated. Macroscopic imaging of live resected colon showed enhanced EGFP expression (NF-κB activity) in luteolin-fed mice as compared to control-fed animals after DSS exposure, while cecal EGFP expression was attenuated in luteolin-fed IL-10^−/− mice. Interestingly, confocal microscopy showed that EGFP positive cells were mostly located in the lamina propria and not in the epithelium. Caspase 3 activation was significantly enhanced whereas COX-2 gene expression was reduced in luteolin-fed, DSS-exposed NF-κB^EGFP transgenic mice as assessed by Western blot and immunohistochemical analysis. In vitro, luteolin sensitized colonic epithelial HT29 cells to TNFα-induced apoptosis, caspase 3 activation, DNA fragmentation and reduced TNFα-induced C-IAP1, C-IAP2 and COX-2 gene expression.

Conclusions/Significance

We conclude that while luteolin shows beneficial effects on spontaneous colitis, it aggravates DSS-induced experimental colitis by blocking NF-κB-dependent protective molecules in enterocytes.

Gnotobiotic IL-10-/-;NF-kappa B(EGFP) mice reveal the critical role of TLR/NF-kappa B signaling in commensal bacteria-induced colitis

Commensal bacteria and TLR signaling have been associated with the maintenance of intestinal homeostasis in dextran sodium sulfate-induced intestinal injury. The aim of this study was to determine the in vivo role of TLR/NF-kappaB activation in a model of commensal bacteria-induced T cell-mediated colitis. A NF-kappaB reporter gene mouse (NF-kappaBEGFP) (EGFP, enhanced GFP) was crossed to the colitogenic susceptible strain IL-10-/- and derived into germfree conditions using embryo-transfer technology. Germfree IL-10wt/wt;NF-kappaBEGFP and IL-10-/-;NF-kappaBEGFP mice (wt, wild type) were dual associated with the nonpathogenic commensal bacteria strains Enterococcus faecalis and Escherichia coli. EGFP was detected using macroimaging, confocal microscopy, and flow cytometry. IL-10-/-;MyD88-/- mice were used to assess E. faecalis/E. coli-induced TLR-dependent signaling and IL-23 gene expression. Dual-associated IL-10-/-;NF-kappaBEGFP mice developed severe inflammation by 7 wk. Macroscopic analysis showed elevated EGFP expression throughout the colon of bacteria-associated IL-10-/-;NF-kappaBEGFP mice. Confocal microscopy analysis revealed EGFP-positive enterocytes during the early phase of bacterial colonization (1 wk) in both IL-10wt/wt and IL-10-/- mice, while the signal shifted toward lamina propria T cells, dendritic cells, neutrophils, and macrophages in IL-10-/- mice during colitis (7 wk). The NF-kappaB inhibitor BAY 11-7085 attenuated E. faecalis/E. coli-induced EGFP expression and development of colitis. Additionally, E. faecalis/E. coli-induced NF-kappaB signaling and IL-23 gene expression were blocked in bone marrow-derived dendritic cells derived from IL-10-/-;MyD88-/- mice. We conclude that bacteria-induced experimental colitis involves the activation of TLR-induced NF-kappaB signaling derived mostly from mucosal immune cells. Blocking TLR-induced NF-kappaB activity may represent an attractive strategy to treat immune-mediated intestinal inflammation.

Intestinal epithelial cell signalling and chronic inflammation: From the proteome to specific molecular mechanisms

Advancing knowledge regarding the cellular mechanisms of intestinal inflammation has led to a better understanding of the disease pathology in patients with inflammatory bowel disease (IBD) including Crohn's disease and ulcerative colitis. It has become clear from numerous studies that enteric bacteria are a critical component in the development and prevention/treatment of chronic intestinal inflammation. An emerging new paradigm suggests that changes in the homeostasis of bacteria- and host-derived signal transduction at the intestinal epithelial cell (IEC) level may lead to a break in barrier function and the development of adaptive immune disturbances. The functional loss of anti-inflammatory host-derived signals in the gut including the immunosuppressive cytokines Interleukin 10 (IL-10) and transforming growth factor (TGF)-beta are of high relevance to the pathogenesis of IBD. The development of analytical tools including two-dimensional (2D) high-resolution protein separation techniques and peptide mass fingerprinting via high-sensitivity mass-spectrometers (MS) allows the quantitative assessment of protein expression changes in disease-relevant cell types. By using these advanced methods, the characterization of the epithelial cell proteome from murine models of experimental colitis and human IBD patients identified novel disease-related mechanisms with respect to the regulation of the glucose-regulated endoplasmic reticulum stress response protein 78 (grp-78). In conclusion, the identification and functional analysis of differentially expressed proteins in purified intestinal target cell types will help to add important insights to the understanding of the molecular pathogenesis of these immune-mediated chronic intestinal disorders.

Quercetin inhibits TNF-induced NF-kappaB transcription factor recruitment to proinflammatory gene promoters in murine intestinal epithelial cells

Flavonoids may play an important role for adjunct nutritional therapy of chronic intestinal inflammation. In this study, we characterized the molecular mechanisms by which quercetin and its enteric bacterial metabolites, taxifolin, alphitonin, and 3, 4-dihydroxy-phenylacetic acid, inhibit tumor necrosis factor alpha (TNF)-induced proinflammatory gene expression in the murine small intestinal epithelial cell (IEC) line Mode-K as well as in heterozygous TNFDeltaARE/WT mice, a murine model of experimental ileitis. Quercetin inhibited TNF-induced interferon-gamma-inducible protein 10 (IP-10) and macrophage inflammatory protein 2 (MIP-2) gene expression in Mode-K cells with effective inhibitory concentration of 40 and 44 micromol/L, respectively. Interestingly, taxifolin, alphitonin, and 3,4-dihydroxy-phenylacetic acid did not inhibit TNF responses in IEC, suggesting that microbial transformation of quercetin completely abolished its anti-inflammatory effect. At the molecular level, quercetin inhibited Akt phosphorylation but did not inhibit TNF-induced RelA/I-kappaB phosphorylation and IkappaB degradation or TNF-alpha-induced nuclear factor-kappaB transcriptional activity. Most important for understanding the mechanism involved, chromatin immunoprecipitation analysis revealed inhibitory effects of quercetin on phospho-RelA recruitment to the IP-10 and MIP-2 gene promoters. In addition, and consistent with the lack of cAMP response element binding protein (CBP)/p300 recruitment and phosphorylation/acetylation of histone 3 at the promoter binding site, quercetin inhibited histone acetyl transferase activity. The oral application of quercetin to heterozygous TNFDeltaARE/WT mice [10 mg/(d x kg body wt)] significantly inhibited IP-10 and MIP-2 gene expression in primary ileal epithelial cells but did not affect tissue pathology. These studies support an anti-inflammatory effect of quercetin in epithelial cells through mechanisms that inhibit cofactor recruitment at the chromatin of proinflammatory genes.

UDN glycoprotein inhibits activator protein-1 and matrix metalloproteinase-9 via blocking of oxygen radicals in HT-29 cells

The present study was performed to investigate the anti-inflammatory potential of a 116-kDa glycoprotein isolated from Ulmus davidiana Nakai (UDN glycoprotein) in lipopolysaccaride (LPS)-treated cancerous human colon epithelial cells (HT-29 cells). UDN glycoprotein inhibited the production of intracellular superoxide anion (O (2) (.-) ), hydrogen peroxides (H(2)O(2)), and nitric oxide (NO), whereas normalized the activity of anti-oxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX)], accompanying the inhibition of manganese-superoxide dismutases (Mn-SOD) activity in LPS-treated HT-29 cells. In addition, UDN glycoprotein blocked the DNA binding activity of activator protein-1 (AP-1) through suppression of c-Jun and c-Fos activities, respectively. We also evaluated the anti-inflammatory potential of UDN glycoprotein based on the activity of the pro-inflammatory signal mediators [inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and matrix metalloproteinases-9 (MMP-9)]. The results showed that UDN glycoprotein (200 mug/ml) has an inhibitory effect on the activation of iNOS, COX-2, and MMP-9 proteins in the LPS-treated HT-29 cells. From these results, we suggest that UDN glycoprotein is one of the potential anti-inflammatory agents that blocks LPS-mediated inflammatory signal pathway in HT-29 cells. Here, we speculate that UDN glycoprotein could be used as an antioxidative agent for inflammatory gastrointestinal cancers.

Lactobacillus reuteri (American Type Culture Collection Strain 55730) versus simethicone in the treatment of infantile colic: a prospective randomized study

OBJECTIVE

The goal was to test the hypothesis that oral administration of Lactobacillus reuteri in a prospective randomized study would improve symptoms of infantile colic.

METHODS

Ninety breastfed colicky infants were assigned randomly to receive either the probiotic L. reuteri (10(8) live bacteria per day) or simethicone (60 mg/day) each day for 28 days. The mothers avoided cow's milk in their diet. Parents monitored daily crying times and adverse effects by using a questionnaire.

RESULTS

Eighty-three infants completed the trial: 41 in the probiotic group and 42 in the simethicone group. The infants were similar regarding gestational age, birth weight, gender, and crying time at baseline. Daily median crying times in the probiotic and simethicone groups were 159 minutes/day and 177 minutes/day, respectively, on the seventh day and 51 minutes/day and 145 minutes/day on the 28th day. On day 28, 39 patients (95%) were responders in the probiotic group and 3 patients (7%) were responders in the simethicone group. No adverse effects were reported.

CONCLUSIONS

In our cohort, L. reuteri improved colicky symptoms in breastfed infants within 1 week of treatment, compared with simethicone, which suggests that probiotics may have a role in the treatment of infantile colic.

IL-10 gene-deficient mice lack TGF-beta/Smad-mediated TLR2 degradation and fail to inhibit proinflammatory gene expression in intestinal epithelial cells under conditions of chronic inflammation

Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in interleukin-10 geneeficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to distinguish because of the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared to wild-type mice fail to inhibit pro-inflammatory gene expression in native intestinal epithelial cells after the colonization with colitogenic Gram-positive Enterococcus faecalis. Of interest, pro-inflammatory gene expression was transient after 1 week of E. faecalis monoassociation in IECs from wild-type mice but persisted after 14 weeks of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IECs expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10(-/-) mice triggered persistent RelA but no Smad2 phosphorylation in IECs at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and pro-inflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice but persisted in IL-10(-/-) IECs. Of note, TGF-beta-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappa Bependent gene expression in E. faecalis-stimulated IEC lines. In conclusion, E. faecalis-monoassociated IL-10(-/-) but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated pro-inflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria.

Safety and Tolerance of a Probiotic Formula in Early Infancy Comparing Two Probiotic Agents: A Pilot Study

OBJECTIVE

To compare the safety and tolerance of two formulas, supplemented with different probiotic agents, in early infancy.

DESIGN

Prospective randomized placebo-controlled trial.

SETTING

Clinics of a University Medical Center.

SUBJECTS

Full-term healthy infants aged less than 4 months.

INTERVENTION

Infants were randomly assigned for 4 weeks to a standard milk-based formula supplemented with either Bifidobacterium lactis (BB-12), Lactobacillus reuteri (ATCC 55730) or a probiotics-free formula.

MEASURES OF OUTCOME

Growth parameters, daily characteristics of feeding, stooling and behavior, and side effects.

RESULTS

Fifty-nine infants, aged 3-65 days, were included. Subjects in all three groups were similar at entry in terms of gestational age, birth weight, sex, growth parameters and breast feeding rate prior to the study. The supplemented formulas were well accepted and did not reveal any adverse effects. A comparison of growth parameters, and variables of feeding, stooling and crying and irritability did not reveal any significant differences between groups.

CONCLUSIONS

The use of formula supplemented with either Lactobacillus reuteri or Bifidobacterium lactis in early infancy, was safe, well tolerated and did not adversely affect growth, stooling habits or infant behavior.

Lipopolysaccharide induces CXCL2/macrophage inflammatory protein-2 gene expression in enterocytes via NF-kappaB activation: independence from endogenous TNF-alpha and platelet-activating factor

CXCL2 (macrophage inflammatory protein-2 (MIP-2)), a critical chemokine for neutrophils, has been shown to be produced in the rat intestine in response to platelet-activating factor (PAF) and to mediate intestinal inflammation and injury. The intestinal epithelium, constantly exposed to bacterial products, is the first line of defence against micro-organisms. It has been reported that enterocytes produce proinflammatory mediators, including tumour necrosis factor (TNF) and PAF, and we showed that lipopolysaccharide (LPS) and TNF activate nuclear factor (NF)-kappaB in enterocytes. However, it remains elusive whether enterocytes release CXCL2 in response to LPS and TNF via a NF-kappaB-dependent pathway and whether this involves the endogenous production of TNF and PAF. In this study, we found that TNF and LPS markedly induced CXCL2 gene expression in IEC-6 cells, TNF within 30 min, peaking at 45 min, while LPS more slowly, peaking after 2 hr. TNF- and LPS- induced CXCL2 gene expression and protein release were completely blocked by pyrrolidine dithiocarbamate (PDTC) and helenalin, two potent NF-kappaB inhibitors. NEMO-binding domain peptide, a specific inhibitor of inhibitor protein kappaB kinase (IKK) activation, a major upstream kinase mediating NF-kappaB activation, significantly blocked CXCL2 gene expression and protein release induced by LPS. WEB2170 (PAF antagonist) and anti-TNF antibodies had no effect on LPS-induced CXCL2 expression. In conclusion, CXCL2 gene is expressed in enterocytes in response to both TNF and LPS. LPS-induced CXCL2 expression is dependent on NF-kappaB activation via the IKK pathway. The effect of LPS is independent of endogenous TNF and PAF.

The front line of enteric host defense against unwelcome intrusion of harmful microorganisms: mucins, antimicrobial peptides, and microbiota

The intestinal tract is a complex ecosystem that combines resident microbiota and the cells of various phenotypes with complex metabolic activities that line the epithelial wall. The intestinal cells that make up the epithelium provide physical and chemical barriers that protect the host against the unwanted intrusion of microorganisms that hijack the cellular molecules and signaling pathways of the host and become pathogenic. Some of the organisms making up the intestinal microbiota also have microbicidal effects that contribute to the barrier against enteric pathogens. This review describes the two cell lineages present in the intestinal epithelium: the goblet cells and the Paneth cells, both of which play a pivotal role in the first line of enteric defense by producing mucus and antimicrobial peptides, respectively. We also analyze recent insights into the intestinal microbiota and the mechanisms by which some resident species act as a barrier to enteric pathogens. Moreover, this review examines whether the cells producing mucins or antimicrobial peptides and the resident microbiota act in partnership and whether they function individually and/or synergistically to provide the host with an effective front line of defense against harmful enteric pathogens.

Reduction of crying episodes owing to infantile colic: a randomized controlled study on the efficacy of a new infant formula

OBJECTIVES

The aim of this study was to evaluate the efficacy on crying episodes owing to infantile colic of a new infant formula containing partially hydrolysed whey proteins, prebiotic oligosaccharides (OS), with a high beta-palmitic acid content.

DESIGN

Prospective randomized controlled study.

SETTING

Italy.

SUBJECTS

Two hundred and sixty-seven formula-fed infants, aged less than 4 months, with infantile colic, were randomized to receive either the new infant formula (study treatment (ST)) or a standard formula and simethicone (6 mg/kg twice a day) (control treatment (CT)). A questionnaire was given to parents to evaluate for 14 days the daily number of colic episodes and crying time.

RESULTS

Out of the 199 infants who completed the study, 96 were treated with the new formula and 103 were not treated. Infants receiving the new formula had a significant decrease in colic episodes after 1 week (2.47+/-1.94 at day 7 vs 5.99+/-1.84 at the study entry) compared to infants receiving the CT (3.72+/-1.98 at day 7 vs 5.41+/-1.88 at the study entry) (P < 0.0001). Also at day 14, the crying episodes were significantly different between the two groups of infants (1.76+/-1.60 in ST vs 3.32+/-2.06 in CT) (P < 0.0001).

CONCLUSIONS

The use of a partially hydrolysed formula supplemented with fructo- and galacto-OS induces a reduction of crying episodes in infants with colic after 7 and 14 days when compared with a standard formula and simethicone.

Intestinal epithelial cell signalling and host-derived negative regulators under chronic inflammation: to be or not to be activated determines the balance towards commensal bacteria

Advancing knowledge regarding the cellular mechanisms of intestinal inflammation has led to a better understanding of the disease pathology in patients with chronic disorders of the gut including inflammatory bowel disease, coeliac disease, lymphocytic colitis and irritable bowel syndrome. An emerging new paradigm suggests that changes in the homeostasis of bacteria- and host-derived signal transduction at the epithelial cell level may lead to functional and immune disturbances of the intestinal epithelium. It has become clear from numerous studies that enteric bacteria are a critical component in the development and prevention/treatment of chronic intestinal inflammation. Signal-specific activation of mitogen-activated protein kinases (MAPK), interferon-regulated factors (IRF) and the transcription factor NF-kappaB through pattern recognition receptor signalling effectively induce inflammatory defence mechanisms. Unbalanced activation of these innate signalling pathways because of host genetic predispositions and/or the lack of adequate anti-inflammatory feedback mechanisms may turn a physiological response into a pathological situation including failure of bacterial clearance and development of chronic inflammation. Host-derived regulators from the immune and enteric nerve system crosstalk to the innate signalling network of the intestinal epithelium in order to shape the extent and duration of inflammatory processes.

Functional diversity of flavonoids in the inhibition of the proinflammatory NF-kappaB, IRF, and Akt signaling pathways in murine intestinal epithelial cells

The molecular understanding of nutritional factors in the process of host factor-mediated activation of the intestinal epithelium may play an important role in the assessment of adjunct nutritional therapy for chronic intestinal inflammation. We characterized the molecular mechanisms of flavonoids including apigenin, luteolin, genistein, 3'-hydroxy-flavone, and flavone in inhibiting tumor necrosis factor-alpha (TNF)-induced interferon-induced protein (IP)-10 gene expression in the murine intestinal epithelial cell (IEC) line Mode-K. We demonstrated that 3'-hydroxy-flavone but not the chemical core structure flavone blocked TNF-alpha-induced nuclear factor (NF)-kappaB transcriptional activity and IP-10 expression at the level of NF-kappaB/IkappaBalpha phosphorylation/degradation by inhibiting IkappaB kinase activity. Although 3'-hydroxy-flavone effectively triggered p38 mitogen-activated protein kinase signaling and late caspase-3 cleavage, the induction of apoptotic cell death in TNF-activated IEC was not the primary mechanism inhibiting NF-kappaB transcriptional activity and IP-10 expression. In addition to the compound-specific inhibition of TNF-induced NF-kappaB DNA binding and NF-kappaB transcriptional activity, apigenin and luteolin selectively blocked Akt phosphorylation/activity. The ability of these polyphenolic compounds to target various signal transduction pathways was further supported by the observation that luteolin and 3'-hydroxy-flavone selectively induced interferon regulatory factor (IRF)-1 degradation. Finally, we showed that genistein blocked IP-10 but not IL-6 expression through NF-kappaB, IRF, and Akt independent mechanisms, demonstrating the functional diversity of flavonoids in inhibiting proinflammatory processes in IEC. In conclusion, we provide molecular evidence for the presence of characteristic inhibition patterns of these polyphenolic compounds to inhibit proinflammatory gene expression in IEC through the specific modulation of the NF-kappaB, IRF and Akt signaling pathways.

Interaction of mucosal microbiota with the innate immune system

Organisms live in continuos interaction with their environment; this interaction is of vital importance but at the same time can be life threatening. The largest and most important interface between the organism and its environment is represented by surfaces covered with epithelial cells. Of these surfaces, mucosae comprise in humans approximately 300 m2, and the skin covers approximately 1.8 m2 surface of the human body. Mucosal tissues contain two effector arms of the immune system, innate and adaptive, which operate in synergy. Interaction with commensal bacteria, which outnumber the nucleated cells of our body, occurs physiologically on epithelial surfaces; this interaction could pose the risk of inflammation. The mucosal immune system has developed a complex network of regulatory signalling cascades that is a prerequisite for proper activation but also for a timely inactivation of the pathway. As demonstrated in gnotobiotic animal models of human diseases, impaired regulation of mucosal responses to commensal bacteria plays an important role in the development of several inflammatory and autoimmune diseases.

Salvia miltiorrhiza water-soluble extract, but not its constituent salvianolic acid B, abrogates LPS-induced NF-kappaB signalling in intestinal epithelial cells

Herbal medicine has become an increasing popular therapeutic alternative among patients suffering from various inflammatory disorders. The Salvia miltiorrhizae water-soluble extract (SME) have been shown to possess antioxidant and anti-inflammatory properties in vitro. However, the mechanism of action and impact of SME on LPS-induced gene expression is still unknown. We report that SME significantly abrogated LPS-induced IkappaB phosphorylation/degradation, NF-kappaB transcriptional activity and ICAM-1 gene expression in rat IEC-18 cells. Chromatin immunoprecipitation assay demonstrated that LPS-induced RelA recruitment to the ICAM-1 gene promoter was inhibited by SME. Moreover, in vitro kinase assay showed that SME directly inhibits LPS induced IkappaB kinase (IKK) activity in IEC-18 cells. To investigate the physiological relevance of SME inhibitory activity on NF-kappaB signalling, we used small intestinal explants and primary intestinal epithelial cells derived from a transgenic mouse expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-kappaB cis-elements (cis-NF-kappaB(EGFP)). SME significantly blocked LPS-induced EGFP expression and IkappaBalpha phosphorylation in intestinal explants and primary IECs, respectively. However, salvianolic acid B, an activate component of SME did not inhibit NF-kappaB transcriptional activity and IkappaB phosphorylation/degradation in IEC-18 cells. These results indicate that SME blocks LPS-induced NF-kappaB signalling pathway by targeting the IKK complex in intestinal epithelial cells. Modulation of bacterial product-mediated NF-kappaB signalling by natural plant extracts may represent an attractive strategy towards the prevention and treatment of intestinal inflammation.

Innate mechanisms for Bifidobacterium lactis to activate transient pro-inflammatory host responses in intestinal epithelial cells after the colonization of germ-free rats

Bifidobacteria comprise a dominant microbial population group in the human intestinal tract with purported beneficial health effects on the host. In this study, we characterized the molecular mechanisms for the initial interaction of probiotic Bifidobacterium lactis strain BB12 with native and intestinal epithelial cell (IEC) lines. We showed that B. lactis-monoassociated Fisher F344 rats transiently induce phosphorylation/activation of the NF-kappaB transcriptionally active subunit RelA and the mitogen-activated protein kinase (MAPK) p38 in native IEC at day 5 after initial bacterial colonization. In addition, Interleukin 6 (IL-6) gene expression was significantly increased at day 5, demonstrating the physiological relevance of transient transcription factor activation in IEC. In contrast, Bacteroides vulgatus-monoassociated Fisher rats revealed RelA but not p38 MAPK phosphorylation and failed to trigger significant IL-6 gene expression in native IEC. Moreover, we demonstrated that B. lactis triggers NF-kappaB RelA and p38 MAPK phosphorylation in IEC lines. Adenoviral delivery of mutant IKK-beta (Ad5dnIKKbeta) and inhibition of the p38 MAPK pathway through the pharmacological inhibitor SB203580 significantly blocked B. lactis-induced IL-6 gene expression in IEC, suggesting that B. lactis triggers NF-kappaB and MAPK signaling to induce gene expression in the intestinal epithelium. Regarding the mechanisms of bacteria epithelial cell cross-talk, B. lactis-induced IL-6 gene expression was completely inhibited in TLR2 deficient mouse embryogenic fibroblasts (MEF TLR2-/-) as well as TLR2DeltaTIR transfected Mode-K cells. In conclusion, we demonstrated that probiotic bacteria transiently trigger innate signal transduction and pro-inflammatory gene expression in the intestinal epithelium at early stages of bacterial colonization.

Salvia miltiorrhiza water-soluble extract, but not its constituent salvianolic acid B, abrogates LPS-induced NF-kappaB signalling in intestinal epithelial cells

Herbal medicine has become an increasing popular therapeutic alternative among patients suffering from various inflammatory disorders. The Salvia miltiorrhizae water-soluble extract (SME) have been shown to possess antioxidant and anti-inflammatory properties in vitro. However, the mechanism of action and impact of SME on LPS-induced gene expression is still unknown. We report that SME significantly abrogated LPS-induced IkappaB phosphorylation/degradation, NF-kappaB transcriptional activity and ICAM-1 gene expression in rat IEC-18 cells. Chromatin immunoprecipitation assay demonstrated that LPS-induced RelA recruitment to the ICAM-1 gene promoter was inhibited by SME. Moreover, in vitro kinase assay showed that SME directly inhibits LPS induced IkappaB kinase (IKK) activity in IEC-18 cells. To investigate the physiological relevance of SME inhibitory activity on NF-kappaB signalling, we used small intestinal explants and primary intestinal epithelial cells derived from a transgenic mouse expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-kappaB cis-elements (cis-NF-kappaB(EGFP)). SME significantly blocked LPS-induced EGFP expression and IkappaBalpha phosphorylation in intestinal explants and primary IECs, respectively. However, salvianolic acid B, an activate component of SME did not inhibit NF-kappaB transcriptional activity and IkappaB phosphorylation/degradation in IEC-18 cells. These results indicate that SME blocks LPS-induced NF-kappaB signalling pathway by targeting the IKK complex in intestinal epithelial cells. Modulation of bacterial product-mediated NF-kappaB signalling by natural plant extracts may represent an attractive strategy towards the prevention and treatment of intestinal inflammation.

The flavonoid luteolin prevents lipopolysaccharide-induced NF-kappaB signalling and gene expression by blocking IkappaB kinase activity in intestinal epithelial cells and bone-marrow derived dendritic cells

The nuclear factor (NF)-kappaB transcriptional system is a major effector pathway involved in inflammation and innate immune responses. The flavonoid luteolin is found in various herbal extracts and has shown anti-inflammatory properties. However, the mechanism of action and impact of luteolin on innate immunity is still unknown. We report that luteolin significantly blocks lipopolysaccharide (LPS)-induced IkappaB phosphorylation/degradation, NF-kappaB transcriptional activity and intercellular adhesion molecule-1 (ICAM-1) gene expression in rat IEC-18 cells. Using chromatin immunoprecipitation, we demonstrate that LPS-induced RelA recruitment to the ICAM-1 gene promoter is significantly reduced in luteolin-treated cells. Moreover, in vitro kinase assays show that luteolin directly inhibits LPS-induced IkappaB kinase (IKK) activity in IEC-18 cells. Using bone-marrow derived dendritic cells (BMDCs) isolated from interleukin (IL)-10(-/-) mice or from recently engineered transgenic mice expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-kappaB cis-elements (cis-NF-kappaB(EGFP)), we found that luteolin blocks LPS-induced IkappaB phosphorylation and IKK activity, and decreases EGFP, IL-12 and tumour necrosis factor-alpha gene expression. Moreover, intraperitoneal administration of luteolin significantly inhibited LPS-induced EGFP expression in both peripheral blood mononuclear cells and splenocytes isolated from cis-NF-kappaB(EGFP) mice. These results indicate that luteolin blocks LPS-induced NF-kappaB signalling and proinflammatory gene expression in intestinal epithelial cells and dendritic cells. Modulation of innate immunity by natural plant products may represent an attractive strategy to prevent intestinal inflammation associated with dysregulated innate immune responses.

Dysregulated innate immune responses in young children with autism spectrum disorders: their relationship to gastrointestinal symptoms and dietary intervention

OBJECTIVE

Our previous study indicated an association between cellular immune reactivity to common dietary proteins (DPs) and excessive proinflammatory cytokine production with endotoxin (lipopolysaccharide, LPS), a major stimulant of innate immunity in the gut mucosa, in a subset of autism spectrum disorder (ASD) children. However, it is unclear whether such abnormal LPS responses are intrinsic in these ASD children or the results of chronic gastrointestinal (GI) inflammation secondary to immune reactivity to DPs. This study further explored possible dysregulated production of proinflammatory and counter-regulatory cytokines with LPS in ASD children and its relationship to GI symptoms and the effects of dietary intervention measures.

METHODS

This study includes ASD children (median age 4.8 years) on the unrestricted (n = 100) or elimination (n = 77) diet appropriate with their immune reactivity. Controls include children with non-allergic food hypersensitivity (NFH; median age 2.9 years) on the unrestricted (n = 14) or elimination (n = 16) diet, and typically developing children (median age 4.5 years, n = 13). The innate immune responses were assessed by measuring production of proinflammatory (TNF-alpha, IL-1beta, IL-6, and IL-12) and counter-regulatory (IL-1ra, IL-10, and sTNFRII) cytokines by peripheral blood mononuclear cells (PBMCs) with LPS. The results were also compared to T-cell responses with common DPs and control T-cell mitogens assessed by measuring T-cell cytokine production.

RESULTS

ASD and NFH PBMCs produced higher levels of TNF-alpha with LPS than controls regardless of dietary interventions. However, only in PBMCs from ASD children with positive gastrointestinal (GI(+)) symptoms, did we find a positive association between TNF-alpha levels produced with LPS and those with cow's milk protein (CMP) and its major components regardless of dietary interventions. In the unrestricted diet group, GI(+) ASD PBMCs produced higher IL-12 than controls and less IL-10 than GI(-) ASD PBMCs with LPS. GI(+) ASD but not GI(-) ASD or NFH PBMCs produced less counter-regulatory cytokines with LPS in the unrestricted diet group than in the elimination diet group. There was no significant difference among the study groups with regard to cytokine production in responses to T-cell mitogens and other recall antigens.

CONCLUSION

Our results revealed that there are findings limited to GI(+) ASD PBMCs in both the unrestricted and elimination diet groups. Thus our findings indicate intrinsic defects of innate immune responses in GI(+) ASD children but not in NFH or GI(-) ASD children, suggesting a possible link between GI and behavioral symptoms mediated by innate immune abnormalities.

IL-10 gene-deficient mice lack TGF-beta/Smad signaling and fail to inhibit proinflammatory gene expression in intestinal epithelial cells after the colonization with colitogenic Enterococcus faecalis

Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in IL-10 gene-deficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to dissect due to the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared with wild-type mice fail to inhibit proinflammatory gene expression in native intestinal epithelial cells (IEC) after the colonization with colitogenic Gram-positive Enterococcus faecalis. Interestingly, proinflammatory gene expression was transient after 1 wk of E. faecalis monoassociation in IEC from wild-type mice, but persisted after 14 wk of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IEC expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10(-/-) mice triggered persistent RelA, but no Smad2 phosphorylation in IEC at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and proinflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice, but persisted in IL-10(-/-) IEC. Of note, TGF-beta1-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappaB-dependent gene expression in IEC lines. In conclusion, E. faecalis-monoassociated IL-10(-/-), but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated proinflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria.

A polymorphism in the TNF-alpha promoter gene is associated with pediatric onset and colonic location of Crohn's disease

OBJECTIVES

Studies suggest that pediatric onset of Crohn's disease (CD) may demonstrate more frequent upper intestinal and colonic location and in male gender, in comparison to adults. Variability in age of onset (AOO) and location of disease have not been adequately explained to date. NOD2/CARD15 is highly expressed in the ileum, while TNF-alpha expression is distributed throughout the gastrointestinal tract. We hypothesized that polymorphisms that affect TNF-alpha function may influence variability of disease location and AOO of CD.

METHODS

We evaluated two CD cohorts based on AOO (pediatric and adult onset) and 100 ethnically matched healthy controls. Patients were evaluated for AOO, disease location, and genotyped for the presence of polymorphisms in NOD2/CARD15 and in the TNF-alpha promoter region.

RESULTS

Early AOO was associated with male gender, upper intestinal involvement, and a polymorphism in the binding site for NF-kappaB (TNF-863A polymorphism). NOD2 mutations and TNF-863A polymorphism had equivalent but opposite effects on disease location, with a strong combined effect (p= 0.004 corrected for multiple testing). NOD2/CARD15 was associated with ileal involvement, while presence of TNF-863A was inversely associated with ileal disease (OR = 0.42, p= 0.008) and positively associated with isolated colitis (OR = 2.16, p= 0.008, OR = 2.12, p= 0.03 corrected) and familial disease (p= 0.004).

CONCLUSIONS

Pediatric onset of CD in our population was associated with a frequent polymorphism in the binding site for NF-kappaB in TNF-alpha promoter but not to defined NOD2/CARD15 disease-associated mutations. This polymorphism is associated with colitis and familial disease. NOD2/CARD15 mutations and the TNF-863C/A polymorphism have equivalent but opposite effects on disease location. These findings may help explain differences in CD phenotype.

Bacterial counts of intestinal Lactobacillus species in infants with colic

Intestinal colonization by lactobacilli is suggested to be a prerequisite to normal mucosal immune functions. An inadequate level of lactobacilli may be involved in appearance of allergic disease of which, infantile colic, is often considered an early clinical manifestation. The aim of the study is to evaluate intestinal lactobacilli in breast-fed infants with infantile colic and healthy infants. Fifty-six breast-fed infants, aged 15-60 days were enrolled in the study and divided into two groups: colicky (30 cases) and healthy (26 cases) according to Wessel's criteria. Stool samples were collected, diluted and cultured on selective media. The colonies were counted, reported as colony forming unit (cfu) per gram of faeces and identified by biochemical methods. Different colonization patterns of lactobacilli were found among colicky and healthy infants. Lactobacillus brevis (4.34 x 10(8) cfu/g) and L. lactis lactis (2.51 x 10(7) cfu/g) were found only in colicky infants while L. acidophilus (2.41 x 10(7) cfu/g) was found only in healthy infants. Lactobacillus brevis and L. lactis lactis might be involved in the pathogenesis of infantile colic increasing meteorism and abdominal distension. Further studies are required to understand how the observed differences may be involved in the pathogenesis of this common disorder.