Yansong Xue

Dietary grape seed extract ameliorates symptoms of inflammatory bowel disease in IL10-deficient mice

Grape seed extract (GSE) is a by-product of the wine industry, with abundant polyphenolic compounds known for their anti-inflammatory and anti-oxidative effects. Using IL10-deficient mice (IL10KO), here we showed that GSE (1% of dry feed weight) ameliorated inflammatory bowel disease indices, increased colonic goblet cell numbers and decreased myeloperoxidase levels in the large intestine. Concomitantly, GSE supplementation attenuated inflammation, decreased the expression of pore forming tight junction protein claudin2, and increased levels of Lactobacilli and Bacteroides in the gut microbiota of IL10KO mice. In summary, our study shows that GSE has protective roles on inflammatory bowel disease through altering gut inflammation, tight junction protein expression, and gut microbiota composition.

Host Inflammatory Response Inhibits Escherichia coli O157:H7 Adhesion to Gut Epithelium through Augmentation of Mucin Expression

ABSTRACT Escherichia coli O157:H7, a major Shiga toxin-producing pathogen, has a low infectious dose and causes serious illness in humans. The gastrointestinal tract of cattle is the primary reservoir of E. coli O157:H7, and thus, it is critical to eliminate or reduce E. coli O157:H7 gut colonization. Given that E. coli O157:H7 produces effectors that attenuate inflammatory signaling, we hypothesized that the host inflammatory response acts to perturb E. coli O157:H7 intestinal colonization. Tumor necrosis factor alpha (TNF-α) treatment of HT-29 cells resulted in increased expression of inflammatory cytokine interleukin 1β (IL-1β), IL-8, and TNF-α genes and increased IL-8 protein and resulted in decreased adhesion of E. coli O157:H7. Similarly, E. coli O157:H7 adhesion to cattle colonic explants was reduced by TNF-α treatment. Irrespective of the presence of E. coli O157:H7, TNF-α enhanced activation of p65, the key mediator of NF-κB inflammatory signaling, whereas E. coli O157:H7 infection suppressed this pathway by inhibiting p65 activation in HT-29 cells. To further explore the mechanisms linking the inflammatory response to attenuated E. coli O157:H7 adhesion, mucin 2 (MUC2) expression was analyzed, considering that the intestinal mucus layer is the first defense against enteric pathogens and MUC2 is the major secretory mucin in the intestine. MUC2 expression in HT-29 cells was increased by TNF-α treatment and by E. coli O157:H7 infection. However, reducing mucin expression by blocking mitogen-activated protein kinase (MAPK) extracellular signal-regulated protein kinases 1/2 (ERK1/2) and/or phosphatidylinositol 3-kinase (PI3K)/Akt signaling increased E. coli O157:H7 adherence to HT-29 cells. These data suggest that the inflammatory cytokine response acts to protect host epithelial cells against E. coli O157:H7 colonization, at least in part, by promoting mucin production.

Maternal obesity induces gut inflammation and impairs gut epithelial barrier function in nonobese diabetic mice

Impairment of gut epithelial barrier function is a key predisposing factor for inflammatory bowel disease, type 1 diabetes (T1D) and related autoimmune diseases. We hypothesized that maternal obesity induces gut inflammation and impairs epithelial barrier function in the offspring of nonobese diabetic (NOD) mice. Four-week-old female NOD/ShiLtJ mice were fed with a control diet (CON; 10% energy from fat) or a high-fat diet (HFD; 60% energy from fat) for 8 weeks to induce obesity and then mated. During pregnancy and lactation, mice were maintained in their respective diets. After weaning, all offspring were fed the CON diet. At 16 weeks of age, female offspring were subjected to in vivo intestinal permeability test, and then ileum was sampled for biochemical analyses. Inflammasome mediators, activated caspase-1 and mature forms of interleukin (IL)-1β and IL-18 were enhanced in offspring of obese mothers, which was associated with elevated serum tumor necrosis factor α level and inflammatory mediators. Consistently, abundance of oxidative stress markers including catalase, peroxiredoxin-4 and superoxide dismutase 1 was heightened in offspring ileum (P<.05). Furthermore, offspring from obese mothers had a higher intestinal permeability. Morphologically, maternal obesity reduced villi/crypt ratio in the ileum of offspring gut. In conclusion, maternal obesity induced inflammation and impaired gut barrier function in offspring of NOD mice. The enhanced gut permeability in HFD offspring might predispose them to the development of T1D and other gut permeability-associated diseases.

Favourable effects of grape seed extract on intestinal epithelial differentiation and barrier function in IL10-deficient mice

The impairment in the rate of cell proliferation and differentiation leads to a negative consequence on the renewal of the intestinal epithelium, which is the aetiological factor of a number of digestive diseases. Grape seed extract (GSE), a rich source of proanthocyanidins, is known for its beneficial health effects. The present study evaluated the beneficial effects of GSE on colonic cell differentiation and barrier function in IL10-deficient mice. Female mice aged 6 weeks were randomised into two groups and given drinking-water containing 0 or 0.1 % GSE (w/v) for 12 weeks. GSE supplementation decreased serum TNF-α level and intestinal permeability, and increased the colonic goblet cell density that was associated with increased mRNA expression of mucin (Muc)-2. Immunohistochemical analyses showed lower accumulation of β-catenin in the crypts of colon tissues of the GSE-supplemented mice, which was associated with a decreased mRNA expression of two downstream effectors of Wingless and Int (Wnt)/catenin signalling, myelocytomatosis oncogene protein (Myc) and cyclin D1 (Ccnd1). Consistently, GSE supplementation decreased the number of colonic proliferating cell nuclear antigen-positive cells, a well-known cell proliferation marker, and a weakened extracellular signal-regulated kinases 1 and 2 (ERK1/2) signalling. In summary, these data indicate that supplementation of 0.1 % GSE for 12 weeks improved gut barrier function and colonic cell differentiation in the IL10-deficient mice probably via inhibiting Wnt/β-catenin pathway.

Mast cell deficiency exacerbates inflammatory bowel symptoms in interleukin-10-deficient mice

AIM To test the role of mast cells in gut inflammation and colitis using interleukin (IL)-10-deficient mice as an experimental model. METHODS Mast cell-deficient (Kit (W-sh/W-sh) ) mice were crossbred with IL-10-deficient mice to obtain double knockout (DKO) mice. The growth, mucosal damage and colitis status of DKO mice were compared with their IL-10-deficient littermates. RESULTS DKO mice exhibited exacerbated colitis compared with their IL-10-deficient littermates, as shown by increased pathological score, higher myeloperoxidase content, enhanced Th1 type pro-inflammatory cytokines and inflammatory signaling, elevated oxidative stress, as well as pronounced goblet cell loss. In addition, deficiency in mast cells resulted in enhanced mucosal damage, increased gut permeability, and impaired epithelial tight junctions. Mast cell deficiency was also linked to systemic inflammation, as demonstrated by higher serum levels of tumor necrosis factor α and interferon γ in DKO mice than that in IL-10-deficient mice. CONCLUSION Mast cell deficiency in IL-10-deficient mice resulted in systematic and gut inflammation, impaired gut barrier function, and severer Th1-mediated colitis when compared to mice with only IL-10-deficiency. Inflammation and impaired gut epithelial barrier function likely form a vicious cycle to worsen colitis in the DKO mice.

Preventive effects of Goji berry on dextran-sulfate-sodium-induced colitis in mice

Goji berry (Lycium barbarum) exerts immune modulation and suppresses inflammation in vitro and in vivo. We hypothesized that Goji berry had beneficial effects on dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice through suppressing inflammation. Six-week-old male C57BL/6 mice were supplemented with a standard AIN-93G diet with or without 1% (w/w) Goji berry for 4 weeks. Then, colitis was induced by supplementing 3% DSS in drinking water for 7 days, followed by 7 days of remission period to mimic ulcerative colitis symptoms. Goji berry supplementation ameliorated DSS-induced body weight loss, diminished diarrhea and gross bleeding, and resulted in a significantly decreased disease activity index, as well as DSS-associated colon shortening. Moreover, 30% mortality rate caused by DSS-induced colitis was avoided because of Goji berry supplementation. Histologically, Goji berry ameliorated colonic edema, mucosal damage and neutrophil infiltration into colonic intestinal tissue in response to DSS challenge, which was associated with decreased expression of chemokine (C-X-C motif) ligand 1 and monocyte chemoattractant protein-1, as well as inflammatory mediators interleukin-6 and cyclooxygenase-2. In conclusion, Goji supplementation confers protective effects against DSS-induced colitis, which is associated with decreased neutrophil infiltration and suppressed inflammation. Thus, dietary Goji is likely beneficial to inflammatory bowel disease patients as a complementary therapeutic strategy.

Metformin Improves Ileal Epithelial Barrier Function in Interleukin-10 Deficient Mice

Background and aims The impairment of intestinal epithelial barrier is the main etiologic factor of inflammatory bowel disease. The proper intestinal epithelial proliferation and differentiation is crucial for maintaining intestinal integrity. Metformin is a common anti-diabetic drug. The objective is to evaluate the protective effects of metformin on ileal epithelial barrier integrity using interleukin-10 deficient (IL10KO) mice. Methods Wild-type and IL10KO mice were fed with/without metformin for 6 weeks and then ileum was collected for analyses. The mediatory role of AMP-activated protein kinase (AMPK) was further examined by gain and loss of function study in vitro. Results Compared to wild-type mice, IL10KO mice had increased proliferation, reduced goblet cell and Paneth cell lineage differentiation in the ileum tissue, which was accompanied with increased crypt expansion. Metformin supplementation mitigated intestinal cell proliferation, restored villus/crypt ratio, increased goblet cell and Paneth cell differentiation and improved barrier function. In addition, metformin supplementation in IL10KO mice suppressed macrophage pro-inflammatory activity as indicated by reduced M1 macrophage abundance and decreased pro-inflammatory cytokine IL-1β, TNF-α and IFN-γ expressions. As a target of metformin, AMPK phosphorylation was enhanced in mice treated with metformin, regardless of mouse genotypes. In correlation, the mRNA level of differentiation regulator including bmp4, bmpr2 and math1 were also increased in IL10KO mice supplemented with metformin, which likely explains the enhanced epithelial differentiation in IL10KO mice with metformin. Consistently, in Caco-2 cells, metformin promoted claudin-3 and E-cadherin assembly and mitigated TNF-α-induced fragmentation of tight junction proteins. Gain and loss of function assay also demonstrated AMPK was correlated with epithelial differentiation and proliferation. Conclusions Metformin supplementation promotes secretory cell lineage differentiation, suppresses inflammation and improves epithelial barrier function in IL10KO mice likely through activation of AMPK, showing its beneficial effects on gut epithelial.

Quercetin suppresses NLRP3 inflammasome activation in epithelial cells triggered by Escherichia coli O157:H7

Abstract Inflammatory responses elicited by LRR and PYD domains‐containing protein 3 (NLRP3) inflammasome is induced by a wide variety of stress signals including infectious agents and cellular disorders. E. coli O157:H7 causes serious gastrointestinal diseases that results in severe inflammation and oxidative stress, causing host cell damage. In this study, we found that E. coli O157:H7 infection induced NLRP3 assembly, caspase‐1 activation and interleukin (IL)‐1&bgr; and IL‐18 release in Caco‐2 cells. Infection also resulted in mitochondrial dysfunction with disrupted mitochondrial potential and mitochondrial complex‐I activity, as well as the cytosolic release of cytochrome c and altered mitochondrial respiratory chain. The damage of mitochondria led to increased production of reactive oxygen species (ROS) and cytosolic release of mitochondrial DNA. Moreover, ROS was required for E. coli O157:H7 induced NLRP3 assembly as inhibiting mitochondrial ROS release by ROS scavengers Mito‐TEMPO and N‐acetylcysteine abrogated NLRP3 inflammasome activation in Caco‐2 cells in response to E. coli O157:H7. Quercetin, one of the most important flavonoids in plant origin foods, had a protective role in inhibiting NLRP3 activation upon E. coli O157:H7 infection by protecting mitochondrial integrity and inhibiting mitochondrial ROS release. In addition, E. coli O157:H7 infection inhibited the host autophagy while quercetin treatment augmented autophagy activation, which further blocked ROS generation and IL‐1&bgr; and IL‐18 release. In summary, E. coli O157:H7 infection induced mitochondrial ROS release and NLRP3 assembly in host cells, while quercetin exerted a preventive role in host cells upon E. coli O157:H7 infection partially due to prevention of ROS production and activation of autophagy. Graphical abstract Figure. No Caption available. HighlightsEscherichia coli O157:H7 induces NLRP3 inflammasome in epithelial cells.ROS is required for E. coli O157:H7 induced NLRP3 activation.Quercetin prevents mitochondrial damage caused by E. coli O157:H7 infection.Quercetin restores autophagy, suppresses ROS, and inhibits infection‐induced inflammasome.

Maternal obesity exacerbates insulitis and type 1 diabetes in non-obese diabetic mice.

Accompanying the dramatic increase in maternal obesity, the incidence of type 1 diabetes (T1D) in children is also rapidly increasing. The objective of this study was to explore the effects of maternal obesity on the incidence of T1D in offspring using non-obese diabetic (NOD) mice, a common model for TID. Four-week-old female NOD mice were fed either a control diet (10% energy from fat, CON) or a high-fat diet (60% energy from fat) for 8 weeks before mating. Mice were maintained in their respective diets during pregnancy and lactation. All offspring mice were fed the CON to 16 weeks. Female offspring (16-week-old) born to obese dams showed more severe islet lymphocyte infiltration (major manifestation of insulitis) (P<0.01), concomitant with elevated nuclear factor kappa-light-chain-enhancer of activated B cells p65 signaling (P<0.01) and tumor necrosis factor alpha protein level (P<0.05) in the pancreas. In addition, maternal obesity resulted in impaired (P<0.05) glucose tolerance and lower (P<0.05) serum insulin levels in offspring. In conclusion, maternal obesity resulted in exacerbated insulitis and inflammation in the pancreas of NOD offspring mice, providing a possible explanation for the increased incidence of T1D in children.

Red raspberries suppress NLRP3 inflammasome and attenuate metabolic abnormalities in diet-induced obese mice

The NLR family pyrin domain containing 3 (NLRP3) inflammasome plays a critical role in insulin resistance and the pathogenesis of type 2 diabetes. Red raspberry (RB) contains high amounts of dietary fibers and polyphenolic compounds, which are known for their anti-oxidative and anti-inflammatory effects. This study evaluated the preventive effects of RB supplementation on the NLRP3 inflammasome activation and associated metabolic abnormalities induced by high fat diet (HFD). Wild-type male mice (six weeks old) were randomized into 4 groups receiving a control or typical western HFD supplemented with or without 5% freeze-dried RB for 12 weeks, when mice were sacrificed for tissue collection. HFD feeding substantially increased body weight, which was alleviated by RB supplementation towards the end of the feeding trial. Dietary RB restored the baseline blood glucose level, ameliorating glucose intolerance and insulin resistance, which were aggravated by HFD. Additionally, HFD reduced O2 expenditure and CO2 production, which were ameliorated by RB consumption. The liver is the key site for energy metabolism and a key peripheral tissue responsive to insulin. RB supplementation reduced hepatic lipid accumulation in HFD mice. In agreement, RB consumption suppressed hepatic NLRP3 inflammasome activation and reduced interleukin (IL)-1β and IL-18 production in HFD mice, accompanied with normalized mitochondriogenesis. These results suggest that RB consumption improves insulin resistance and metabolic dysfunction in diet-induced obesity, which is concomitant with suppression of NLRP3 inflammasome elicited by HFD. Thus, dietary RB intake is a promising strategy for ameliorating diet-induced metabolic abnormalities.