Dextran sulphate sodium induces acute colitis and alters hepatic function in hamsters

Milk Fat Globule Membrane Attenuates Acute Colitis and Secondary Liver Injury by Improving the Mucus Barrier and Regulating the Gut Microbiota

Objective

Inflammatory bowel disease (IBD) often occurs along with extraintestinal manifestations, including hepatic injury. Milk fat globule membrane (MFGM) is an active substance with a potential anti-inflammation activity. However, its alleviated effect and mechanisms in IBD as well as the IBD-induced secondary liver injury are still unclear.

Methods

C57BL/6J mice were administered with a 21-day oral gavage of MFGM, followed by 7 days of drinking water with 4% dextran sulfate sodium (DSS). Disease activity index (DAI), histological features, and cytokines of the colon and liver were evaluated. Then, RNA-seq of the colon and liver was conducted. The gut microbiota was assessed by analyzing 16S rRNA gene sequences, and finally the integrity and the function of the mucus barrier were evaluated by Alcian blue staining, real-time quantitative PCR, and ELISA.

Results

Prophylactic MFGM treatment was effective against colitis to include effects in body weight loss, DAI score, colonic length, intestinal pathology, and histological score. Additionally, prophylactic MFGM decreased the levels of interleukin (IL)-1β, IL-6, and myeloperoxidase in colonic tissue, while it increased the IL-10 level. Moreover, the gene expressions of MUC2, MUC4, Reg3b, and Reg3g associated with the production of the molecular mediator of immune response, membrane invagination, and response to protozoan were strikingly upregulated when administered with MFGM. On the other hand, the beneficial effects of MFGM were related to the enriched abundance of genera such as Faccalibacumum and Roseburia in feces samples. Consistently, the administration of MFGM was also found to alleviate DSS-induced hepatic injury. Furthermore, the glutathione transferase activity pathway was enriched in the liver of MFGM-treated mice after DSS administration. Mechanistically, prophylactic MFGM enhanced the mucosal barrier by increasing the gene levels of Reg3b and Reg3g. Meanwhile, the alleviation of MFGM on liver injury was dependent on the reduced hepatic oxidative stress.

Conclusions

MFGM attenuated colitis and hepatic injury by maintaining the mucosal barrier and bacterial community while inhibiting oxidative stress, which might be an effective therapy of hepatic injury secondary to IBD.

Mechanism of Ulcerative Colitis-Aggravated Liver Fibrosis: The Activation of Hepatic Stellate Cells and TLR4 Signaling Through Gut-Liver Axis

Background: The progression of liver disorders is frequently associated with inflammatory bowel disease through the gut-liver axis. However, no direct evidence showed the mechanisms of ulcerative colitis (UC) in the development of liver fibrosis per se. Thus, this study aimed to evaluate the effects of UC on liver fibrosis and its potential mechanism in the experimental model. Methods: Male C57BL/6 mice were allocated into five groups (n = 10 per group) to receive either drinking water (control), 2% dextran sulfate sodium (DSS), olive oil, carbon tetrachloride (CCl₄) or DSS + CCl₄ for 4 cycles. Blood was collected for biochemical analysis. Colons were excised for the evaluation of colon length and morphological score. Liver, colon, and mesenteric lymph nodes (MLNs) were collected for histopathological staining, expression analysis, and bacterial translocation assay to evaluate the inflammation, fibrosis, the activation of hepatic stellate cells (HSCs), and gut barrier function. Results: DSS caused severe colitis in mice treated or treated with CCl₄, as evident from the elevation of disease activity index (DAI), histological abnormalities, and increased pro-inflammatory cytokines (TNF-α, IFN-γ, and IL-17A). Histopathological staining revealed that DSS treatment aggravated the CCl₄-induced extracellular matrix deposition, liver fibrosis, and inflammation in mice. Additionally, biochemical and expression analysis indicated the DSS treatment caused the increase of hydroxyproline and pro-inflammatory cytokines, as well as the abnormal liver function indexes in CCl₄-induced mice. Gut barrier function was impaired in DSS- and DSS + CCl₄-treated mice, manifesting as the increase in bacterial translocation and lipopolysaccharide level, and the reduction in tight junction proteins (occluding, claudin-1 and ZO-1) expression. Further, the activations of HSCs and TLR4 signaling pathway were observed after DSS + CCl₄ treatment, presenting with the increase in expression of α-SMA, vimentin, TGF-β, collagen type I, collagen type II, TIMP-2, TLR4, TRAF6, and NF-κB p65, and a decrease in GFAP and MMP-2 expression. Conclusion: The present study verified that UC aggravated CCl₄-induced liver injury, inflammation, and fibrosis in mice through the gut-liver axis. Gut barrier dysfunction in UC leads to bacterial translocation and elevated lipopolysaccharide, which may promote the activation of TLR4 signaling and HSCs in the liver.

Extracellular Matrix Fragments of the Basement Membrane and the Interstitial Matrix Are Serological Markers of Intestinal Tissue Remodeling and Disease Activity in Dextran Sulfate Sodium Colitis

BACKGROUND

Chronic intestinal inflammation results in tissue damage partly caused by an increase in matrix metalloproteinases (MMP) activity causing degradation of extracellular matrix (ECM) proteins. We studied intestinal tissue remodeling by quantifying ECM protein fragments in serum in dextran sulfate sodium (DSS)-induced colitis, to investigate ECM protein fragments as serological biomarkers of intestinal tissue remodeling and disease activity.

METHODS

Male Sprague-Dawley rats received 5% DSS in drinking water for 5 days followed by 11 days with regular water. Disease activity index (DAI) was scored daily. Serum was collected on day 0, 6, 7, and 16. ELISAs were used to quantify MMP-derived remodeling fragments of basement membrane type IV collagen (C4M and PRO-C4) and interstitial matrix type III collagen (C3M and rPRO-C3).

RESULTS

In DSS rats, serum levels relative to baseline of C4M, PRO-C4, and C3M were elevated (P < 0.01; P < 0.001; P < 0.001) at day 7, which declined at day 16. Levels of rPRO-C3 were lower in DSS rats at day 7 and increased to normal levels at day 16. The ratio between C3M and rPRO-C3 showed an overall degradation (P < 0.0001) of collagen type III in DSS rats at day 7, which correlated to the DAI (r² = 0.5588, P < 0.0001).

CONCLUSION

Our data suggest that remodeling of the basement membrane (C4M and PRO-C4) and the interstitial matrix (C3M and rPRO-C3) increased during DSS-induced colitis and declined with reversal of the disease. Thus, serological biochemical biomarkers of the ECM reflect tissue remodeling and could be studied as markers of disease activity in IBD.

Impact of phytosterols on liver and distal colon metabolome in experimental murine colitis model: an explorative study

Phytosterols are known to reduce plasma cholesterol levels and thereby reduce cardiovascular risk. Studies conducted on human and animal models have demonstrated that these compounds have also anti-inflammatory effects. Recently, an experimental colitis model (dextran sulphate sodium-induced) has shown that pre-treatment with phytosterols decreases infiltration of inflammatory cells and accelerates mucosal healing. This study aims to understand the mechanism underlying the colitis by analysing the end-products of the metabolism in distal colon and liver excised from the same mice used in the previous work. In particular, an unsupervised gas chromatography-mass spectrometry (GC-MS) and NMR based metabolomics approach was employed to identify the metabolic pathways perturbed by the dextran sodium sulphate (DSS) insult (i.e. Krebs cycle, carbohydrate, amino acids, and nucleotide metabolism). Interestingly, phytosterols were able to restore the homeostatic equilibrium of the hepatic and colonic metabolome.

Polysaccharides From Chrysanthemum morifolium Ramat Ameliorate Colitis Rats via Regulation of the Metabolic Profiling and NF-κ B/TLR4 and IL-6/JAK2/STAT3 Signaling Pathways

Studies have indicated that Chrysanthemum polysaccharides (CP) could prominently ameliorate colitis rats, but its possible mechanism remains unclear. In this study, the underlying mechanism of CP was explored by the metabolic profiling analysis and correlated signaling pathways. TNBS/ethanol induced colitis was used to investigate the intervention efficacy following oral administration of CP. The levels of cytokines such as TNF-α, IL-6, IFN-γ and IL-1β, and the activities of SOD, MPO, and MDA were determined. We also performed western-blot for p65, TLR4, p-JAK2, and STAT3 protein expression in the colon tissue to probe their mechanisms of correlated signaling pathways. What’s more, the metabolic changes in plasma and urine from colitis rats were investigated based on UPLC-Q-TOF/MS combined with Metabolynx^TM software. The potential biomarkers and metabolic pathways were also tentatively confirmed. The metabolic profiles of plasma and urine were clearly improved in model rats after oral administration of CP. Thirty-two (17 in serum and 15 in urine) potential biomarkers were identified. The endogenous metabolites were mainly involved in linoleic acid, retinol, arachidonic acid, glycerophospholipid and primary bile acid metabolism in plasma, and nicotinate and nicotinamide, ascorbate and aldarate, histidine and β-alanine metabolism in urine. After polysaccharides intervention, these markers turned back to normal level at some extent. Meanwhile, the elevated expression levels of pp65, TLR4, p-STAT3, and p-JAK2 were significantly decreased after treatment. Results suggested that CP would be a potential prebiotics for alleviation of TNBS-induced colitis. The study paved the way for the further exploration of the pathogenesis, early diagnosis and curative drug development of the colitis.

The enhanced susceptibility of ADAM-17 hypomorphic mice to DSS-induced colitis is not ameliorated by loss of RIPK3, revealing an unexpected function of ADAM-17 in necroptosis

The disintegrin metalloprotease ADAM17 has a critical role in intestinal inflammation and regeneration in mice, as illustrated by the dramatically increased susceptibility of ADAM17 hypomorphic (ADAM17^ex/ex) mice to dextran sulfate sodium (DSS)-induced colitis. Similarly, necroptosis has been implicated in inflammatory responses in the intestine. In this study, we have investigated the contribution of necroptosis to ADAM17-regulated intestinal inflammation in vivo by crossing ADAM17^ex/ex mice with mice that lack the necroptotic core protein RIPK3. Despite the loss of RIPK3, ADAM17^ex/ex/RIPK3^−/− mice showed the same increased susceptibility as ADAM17^ex/ex mice in both acute and chronic models of DSS-induced colitis. Mice of both genotypes revealed comparable results with regard to weight loss, disease activity index and colitis-associated changes of inner organs. Histopathological analyses confirmed similar tissue destruction, loss of barrier integrity, immune cell infiltration, and cell death; serum analyses revealed similar levels of the pro-inflammatory cytokine KC. Resolving these unexpected findings, ADAM17^ex/ex mice did not show phosphorylation of RIPK3 and its necroptotic interaction partner MLKL during DSS-induced colitis, although both proteins were clearly expressed. Consistent with these findings, murine embryonic fibroblasts derived from ADAM17^ex/ex mice were protected from tumor necrosis factor (TNF)-induced necroptosis and failed to show phosphorylation of MLKL and RIPK3 after induction of necroptosis by TNF, revealing a novel, undescribed role of the protease ADAM17 in necroptosis.

Dual effects of a high-protein diet on DSS-treated mice during colitis resolution phase

The impact of the dietary protein level on the process of colonic mucosal inflammation and subsequent recovery remains largely unknown. In this study, we fed DSS-treated mice with either a normoproteic (NP) or a high-protein (HP) isocaloric diet from the beginning of the 5-day dextran sulfate sodium (DSS) treatment to 14 days later. Measurements of colitis indicators (colon weight:length ratio, myeloperoxidase activity, cytokine expressions) showed a similar level of colonic inflammation in both DSS groups during the colitis induction phase. However, during the colitis resolution phase, inflammation intensity was higher in the DSS-HP group than in the DSS-NP group as evidenced by higher inflammatory score and body weight loss. This coincided with a higher mortality rate. In surviving animals, an increase in colonic crypt height associated with a higher number of colon epithelial cells per crypt, and TGF-β3 content was observed in the DSS-HP vs. DSS-NP group. Moreover, colonic expression patterns of tight junction proteins and E-cadherin were also different according to the diet. Altogether, our results indicate that the HP diet, when given during both the induction and resolution periods of DSS-induced colitis, showed deleterious effects during the post-induction phase. However, HP diet ingestion was also associated with morphological and biochemical differences compatible with higher colonic epithelium restoration in surviving animals, indicating an effect of the dietary protein level on colonic crypt repair after acute inflammation. These data highlight the potential impact of the dietary protein amount during the colitis course.

Protective effects of heat-killed Lactococcus lactis subsp. lactis BF3, isolated from the intestine of chum salmon, in a murine model of DSS-induced inflammatory bowel disease

Oxidative stress is considered an etiological factor responsible for several symptoms of inflammatory bowel disease (IBD). In vitro anti-inflammatory activities of heat-killed Lactococcus lactis subsp. lactis BF3 have been reported. In this study, the anti-inflammatory effect of these cells was examined using a dextran sodium sulphate (DSS)-induced murine IBD model. Administration of heat-killed L. lactis BF3 via drinking water suppressed the IBD symptoms, such as shortening of colon length, damage to the colon mucosa as observed under the microscope, and spleen enlargement. This result suggests that heat-killed L. lactis BF3 has the potential to treat IBD.

Anti-inflammatory properties of fermented soy milk with Lactococcus lactis subsp. lactis S-SU2 in murine macrophage RAW264.7 cells and DSS-induced IBD model mice

Six lactic acid bacteria strains (four Lactobacillus plantarum strains and one each of Lactococcus lactis subsp. lactis and Pediococcus pentosaceus) have been isolated and shown to possess anti-oxidant activity. In this study, we determined their acid, bile, salt resistance, and adhesion activity on human enterocyte-like HT-29-Luc and Caco-2 cells. An isolate Lc. lactis S-SU2 showed highest bile resistance and adhesion activity compared to type strains. S-SU2 could ferment both 10% skimmed milk and soy milk while the type strain could not ferment soy milk. Soy milk fermented with S-SU2 showed an increased nitric oxide (NO) secretion in the mouse macrophage RAW264.7 cells without bacterial lipopolysaccharide (LPS). Furthermore, the inhibitory effects of the fermented soy milk on Escherichia coli O111 LPS-induced NO secretion were higher than those of fresh soy milk. Inflammatory bowel disease (IBD) was induced in mice fed either 5% (w/v) dextran sodium sulfate (DSS) in drinking water or 50% soy milk in drinking water. Shortening of colon length, breaking of epithelial cells, lowering liver and thymus weights, and enlargement of spleen are some of the characteristics observed in the IBD, which were prevented by the use of soy milk fermented with Lc. lactis S-SU2.

Garcinol suppresses inflammation-associated colon carcinogenesis in mice

SCOPE

Garcinol is a polyisoprenylated benzophenone derivative isolated from the fruit rind of Garcinia indica and has exhibited chemopreventive effects on azoxymethane)-induced colonic aberrant crypt foci in mice. In this study, we investigated whether garcinol protects against dextran sulfate sodium (DSS) induced colitis/inflammation and azoxymethane/DSS-induced inflammation-related colon tumorigenesis in male ICR mice. We also aimed to delineate the possible molecular mechanisms responsible for these effects.

METHODS AND RESULTS

Treatment with garcinol prevented shortening of the colon length and the formation of aberrant crypt foci and improved the inflammation score in the mouse colon stimulated by DSS. Moreover, administration of garcinol markedly decreased DSS-induced inducible nitric oxide synthase, cyclooxygenase-2, and proliferating cell nuclear antigen protein expression. The dietary administration of garcinol effectively reduced the tumor size and incidence in the mouse colon. Western blot and immunohistochemical analysis revealed that administration of garcinol significantly downregulated cyclooxygenase-2, cyclin D1, and vascular endothelial growth factor expression via inhibition of the extracellular signal-regulated protein kinase 1/2, phosphatidylinositol 3 kinase/Akt/p70 ribosomal S6 kinase, and Wnt/β-catenin signaling pathways.

CONCLUSION

Our results suggest that garcinol may merit further clinical investigation as a chemoprophylactic food that helps prevent colitis-associated colon cancer.

Dietary flaxseed intake exacerbates acute colonic mucosal injury and inflammation induced by dextran sodium sulfate

Flaxseed (FS), a dietary oilseed, contains a variety of anti-inflammatory bioactives, including fermentable fiber, phenolic compounds (lignans), and the n-3 polyunsaturated fatty acid (PUFA) α-linolenic acid. The objective of this study was to determine the effects of FS and its n-3 PUFA-rich kernel or lignan- and soluble fiber-rich hull on colitis severity in a mouse model of acute colonic inflammation. C57BL/6 male mice were fed a basal diet (negative control) or a basal diet supplemented with 10% FS, 6% kernel, or 4% hull for 3 wk prior to and during colitis induction via 5 days of 2% (wt/vol) dextran sodium sulfate (DSS) in their drinking water (n = 12/group). An increase in anti-inflammatory metabolites (hepatic n-3 PUFAs, serum mammalian lignans, and cecal short-chain fatty acids) was associated with consumption of all FS-based diets, but not with anti-inflammatory effects in DSS-exposed mice. Dietary FS exacerbated DSS-induced acute colitis, as indicated by a heightened disease activity index and an increase in colonic injury and inflammatory biomarkers [histological damage, apoptosis, myeloperoxidase, inflammatory cytokines (IL-6 and IL-1β), and NF-κB signaling-related genes (Nfkb1, Ccl5, Bcl2a1a, Egfr, Relb, Birc3, and Atf1)]. Additionally, the adverse effect of the FS diet was extended systemically, as serum cytokines (IL-6, IFNγ, and IL-1β) and hepatic cholesterol levels were increased. The adverse effects of FS were not associated with alterations in fecal microbial load or systemic bacterial translocation (endotoxemia). Collectively, this study demonstrates that although consumption of a 10% FS diet enhanced the levels of n-3 PUFAs, short-chain polyunsaturated fatty acids, and lignans in mice, it exacerbated DSS-induced colonic injury and inflammation.

Systemic responses of mice to dextran sulfate sodium-induced acute ulcerative colitis using 1H NMR spectroscopy

The interplay between genetic mutation and environmental factors is believed to contribute to the etiology of inflammatory bowel disease (IBD). While focused attention has been paid to the aforementioned research, time-specific and organ-specific metabolic changes associated with IBD are still lacking. Here, we induced acute ulcerative colitis in mice by providing water containing 3% dextran sulfate sodium (DSS) for 7 days and investigated the metabolic changes of plasma, urine, and a range of biological tissues by employing a (1)H nuclear magnetic resonance (NMR)-based metabonomics approach with complementary information on serum clinical chemistry and histopathology. We found that DSS-induced acute ulcerative colitis leads to significant elevations in the levels of amino acids in plasma and decreased levels in the membrane-related metabolites and a range of nucleotides, nucleobases, and nucleosides in the colon. In addition, acute-colitis-induced elevations in the levels of nucleotides in the liver were observed, accompanied by reduced levels of glucose. DSS-induced acute colitis also resulted in increased levels of oxidized glutathione and attenuated levels of taurine in the spleen. Furthermore, acute colitis resulted in depletion in the levels of gut microbial cometabolites in urine along with an increase in citric acid cycle intermediates. These findings suggest that DSS-induced acute colitis causes a disturbance of lipid and energy metabolism, damage to the colon and liver, a promoted antioxidative and anti-inflammatory response, and perturbed gut microbiotal communities. The information obtained here provided details of the time-dependent and holistic metabolic changes in the development of the DSS-induced acute ulcerative colitis, which could be useful in discovery of novel therapeutic targets for management of IBD.

Ulcerative colitis-induced hepatic damage in mice: studies on inflammation, fibrosis, oxidative DNA damage and GST-P expression

There exists a close relationship between ulcerative colitis and various hepatic disorders. The present study was aimed to evaluate the hepatocellular damage in experimental colitis model. Ulcerative colitis was induced in Swiss mice by cyclic treatment with 3% w/v dextran sulfate sodium in drinking water. The severity of colitis was assessed on the basis of disease activity index and colon histology. The effect of ulcerative colitis on the liver was assessed using various biochemical parameters, histological evaluation, sirius red staining, immunohistochemical staining with peroxisome proliferator-activated receptor γ, 8-oxo-7,8-dihydro-2'-deoxyguanosine and placental glutathione S-transferase, comet assay (alkaline and modified), Terminal Deoxynucleotidyl Transferase-mediated dUTP Nick End Labeling assay and western blot analysis to detect the protein expression of nuclear factor kappa B, cyclooxygenase-2, nuclear erythroid 2-related factor 2 and NADPH: quinone oxidoreductase-1. Dextran sulfate sodium induced severe colitis in mice as evident from an elevated disease activity index and histological abnormalities. Ulcerative colitis increased the permeability of colon as apparent from a significant reduction in the expression of tight junction protein, occludin. Further, the bacterial translocation assay as well as the analysis of lipopolysaccharide level revealed the existence of various bacterial species in the liver of ulcerative colitis-induced mice. There was a significant increase in the plasma alanine and aspartate transaminases and liver triglyceride levels, expression of peroxisome proliferator-activated receptor γ, inflammatory markers, oxidative stress, fibrosis, oxidative DNA damage and apoptosis in the liver of mice. Moreover, there was an increase in the expression of nuclear factor kappa B and cyclooxygenase-2 and a reduction in the expression of nuclear erythroid 2-related factor 2 and NADPH: quinone oxidoreductase-1 in the liver of severe ulcerative colitis-induced mice. The results of the present study provide evidence that ulcerative colitis is accompanied with hepatic damage in mice.

Effects of Bifidobacterium breve on inflammatory gene expression in neonatal and weaning rat intestine

INTRODUCTION

To examine the immune-modulatory effects of probiotics during early infancy, Bifidobacterium breve M-16V (B. breve) was administered to rat pups during the newborn or weaning period, and the expression of inflammatory genes was investigated using a cDNA microarray and real-time PCR.

RESULTS

After B. breve administration, significant increases in the numbers of Bifidobacterium in both the cecum and colon were confirmed during the newborn period. The numbers of upregulated and downregulated genes were greater during the weaning period than in the newborn period and were greatest in the colon, with fewer genes altered in the small intestine and the fewest in the spleen. The expression of inflammation-related genes, including lipoprotein lipase (Lpl), glutathione peroxidase 2 (Gpx2), and lipopolysaccharide-binding protein (Lbp), was significantly reduced in the colon during the newborn period. In weaning rat pups, the expression of CD3d, a cell surface receptor-linked signaling molecule, was significantly enhanced in the colon; however, the expression of co-stimulatory molecules was not enhanced.

DISCUSSION

Our findings support a possible role for B. breve in mediating anti-inflammatory and antiallergic reactions by modulating the expression of inflammatory molecules during the newborn period and by regulating the expression of co-stimulatory molecules during the weaning period.

METHODS

Gene expression in the intestine was investigated after feeding 5 × 10(8) cfu of B. breve every day to the F344/Du rat from days 1 to 14 (newborn group) and from days 21 to 34 (weaning group). mRNA was extracted from intestine, and the expression of inflammatory gene was analyzed by microarray and real-time PCR.

Factors influencing the development of animal models of dextran sulphate sodium-induced colitis

The animal models of dextran sulphate sodium (DSS)-induced colitis have demonstrated several correlations with human ulcerative colitis (UC) since the first report of DSS-induced colitis in hamsters in 1985. These animal models have similarities to human UC in etiology, pathology, pathogenesis and therapeutic response, and are deemed suitable for investigating the pathogenesis and therapeutic options of UC and UC-related dysplasia-adenocarcinoma sequence. Although induction of colitis with DSS is relatively cheap and simple, the development of this model is influenced by many factors, such as DSS concentration, administration duration, DSS molecular weight and animal species. These factors are important for successful development of DSS-induced colitis. In this paper we summarize factors influencing the development of animal models of DSS-induced colitis.

DSS induced colitis increases portal LPS levels and enhances hepatic inflammation and fibrogenesis in experimental NASH

BACKGROUND & AIMS

Intestinal bacterial overgrowth and increased permeability are features of non alcoholic steatohepatitis (NASH). Bacterial endotoxin has been shown to promote NASH progression. Application of dextran sulfate sodium (DSS) is a colitis model in mice characterized by damage of the intestinal barrier. This study was designed to investigate if application of DSS aggravates experimental NASH.

METHODS

Male C57bl/6 mice were allocated into four experimental groups receiving either (I) standard chow (SC), (II) a high fat (HF) diet, (III) SC+DSS (1% in the drinking water), and (IV) HF+DSS for 12 weeks.

RESULTS

DSS treatment caused inflammation and proinflammatory gene expression (IL-1β, IL-17, TNF) in the colon. Expression of colonic antimicrobial peptide Cramp was significantly induced in SC+DSS mice, whereas expression was blocked in the HF+DSS group. Endotoxin levels were elevated in SC+DSS and HF mice but further augmented in the HF+DSS group. In line with this, increased hepatic TLR4 and TLR9 mRNA levels were detected in HF+DSS mice. The histological analysis revealed hepatic steatosis in both HF groups. Hepatic inflammation was more severe in HF+DSS mice, reflected by histology and analysis of proinflammatory gene expression (TNF and MCP-1). HF+DSS mice showed increased hepatic fibrosis by sirius red staining, hepatic collagen I expression, and α-SMA positive cells accompanied by higher p47(phox), TIMP-1, TGF-β, Pai-1, and α-SMA mRNA expression.

CONCLUSIONS

Induction of an intestinal inflammation in experimental NASH promotes LPS translocation, hepatic inflammation, and fibrogenesis probably due to inhibition of intestinal antimicrobial peptides. These findings underscore the pathophysiological role of the gut-liver axis in the progression of NASH.

A novel Toll-like receptor 4 antagonist antibody ameliorates inflammation but impairs mucosal healing in murine colitis

Dysregulated innate immune responses to commensal bacteria contribute to the development of inflammatory bowel disease (IBD). TLR4 is overexpressed in the intestinal mucosa of IBD patients and may contribute to uncontrolled inflammation. However, TLR4 is also an important mediator of intestinal repair. The aim of this study is to examine the effect of a TLR4 antagonist on inflammation and intestinal repair in two murine models of IBD. Colitis was induced in C57BL/6J mice with dextran sodium sulfate (DSS) or by transferring CD45Rb(hi) T cells into RAG1-/- mice. An antibody (Ab) against the TLR4/MD-2 complex or isotype control Ab was administered intraperitoneally during DSS treatment, recovery from DSS colitis, or induction of colitis in RAG1-/- mice. Colitis severity was assessed by disease activity index (DAI) and histology. The effect of the Ab on the inflammatory infiltrate was determined by cell isolation and immunohistochemistry. Mucosal expression of inflammatory mediators was analyzed by real-time PCR and ELISA. Blocking TLR4 at the beginning of DSS administration delayed the development of colitis with significantly lower DAI scores. Anti-TLR4 Ab treatment decreased macrophage and dendritic cell infiltrate and reduced mucosal expression of CCL2, CCL20, TNF-alpha, and IL-6. Anti-TLR4 Ab treatment during recovery from DSS colitis resulted in defective mucosal healing with lower expression of COX-2, PGE(2), and amphiregulin. In contrast, TLR4 blockade had minimal efficacy in ameliorating inflammation in the adoptive transfer model of chronic colitis. Our findings suggest that anti-TLR4 therapy may decrease inflammation in IBD but may also interfere with colonic mucosal healing.

Dextran sodium sulfate-induced colitis causes rapid bone loss in mice

INTRODUCTION

Osteopenia is a common complication of human inflammatory bowel disease (IBD). We evaluated the contribution of colonic inflammation to osteopenia and its mechanism in a murine colitis model.

METHODS

Colitis was induced by adding dextran sodium sulfate (DSS) to the drinking water for 2 weeks to nine-week-old Balb/C male mice. 5% DSS was added on the first week and was reduced to 2.5% on the second week. Age- and sex-matched Balb/C mice served as the control group. Indices of femoral bone mass and architecture were determined by micro computed tomography (muCT). Bone formation parameters and osteoclast number were determined by dynamic histomorphometry. The degree of colonic inflammation was assessed by a clinical disease activity index, and colonic mucosal myeloperoxidase activity.

RESULTS

DSS-treated mice exhibited a significantly lower bone mass compared to controls as indicated by decreased trabecular bone volume (BV/TV) of 32%. This reduction was accompanied by decreased trabecular number (23%) and connectivity density (37%) compared to the controls. No changes were observed in cortical bone indices. Osteopenia resulted from suppressed bone formation, as indicated by decreased trabecular double-labeled surface (dL%) of 90%, mineralizing surface (MS) of 62%, and bone formation rate (BFR) of 67%, and increased bone resorption as indicated by a 34% increase in osteoclast number in DSS-treated mice compared to the controls. Myeloperoxidase activity inversely correlated with trabecular BV/TV (r=-0.67, p=0.02), trabecular number (r=-0.86, p=0.0008) and connectivity density (r=-0.63, p=0.03). Myeloperoxidase activity inversely correlated with the bone formation indices: dL%, MS, and BFR (r=-0.79, p=0.007, r=-0.84, p=0.002, r=-0.83, p=0.003, respectively).

CONCLUSIONS

DSS-induced colitis is associated with reduced femoral bone mass and altered micro architecture, which results from suppressed bone formation and increased bone resorption. The decrease in indices of bone mass, structure and formation are directly linked to the degree of colonic mucosal inflammation. DSS-induced colitis can be used to study pharmacological interventions for bone loss in colitis.