ENDOTOXIN-MEDIATED DISTURBANCE OF HEPATIC CYTOCHROME P450 FUNCTION AND DEVELOPMENT OF ENDOTOXIN TOLERANCE IN THE RAT MODEL OF DEXTRAN SULFATE SODIUM-INDUCED EXPERIMENTAL COLITIS

Impact of Oral Probiotics in Amelioration of Immunological and Inflammatory Responses on Experimentally Induced Acute Diverticulitis

Acute diverticulitis is inflammation of a colon diverticulum; it represents a major cause of morbidity and mortality. The alteration of gut microbiota contributes to the promotion of inflammation and the development of acute diverticulitis disease. Probiotics can modify the gut microbiota, so they are considered a promising option for managing diverticulitis disease. This study aimed to investigate the potential protective effect of probiotics, alone or in combination with amoxicillin, on the experimentally induced model of acute diverticulitis disease. Forty-two rats were divided into seven groups as follows: control group: received water and food only; DSS group: received 3% dextran sulfate sodium (DSS) daily for 7 days; LPS group: injected with lipopolysaccharide (LPS) enema at the dose of (4 mg/kg); probiotics group: treated with probiotics (Lactobacillus acidophilus and Bifidobacterium lactis) each of which (4 × 108 CFU suspended in 2 ml distilled water) orally for 7 days; DSS/LPS group: received DSS and LPS; DSS/LPS treated with probiotics group; DSS/LPS treated with probiotics and amoxicillin group. The results revealed that both treatments (probiotics and probiotics-amoxicillin) attenuated DSS/LPS-induced diverticulitis, by restoring the colonic antioxidant status, ameliorating inflammation (significantly reduced TNF-α, interleukins, interferon-γ, myeloperoxidase activity, and C-reactive protein), decreasing apoptosis (through downregulating caspase-3), and reduction of the colon aerobic bacterial count. These probiotic strains were effective in preventing the development of the experimentally induced acute diverticulitis through the anti-inflammatory and immunomodulatory effects and have affected gut microbiota, so they can be considered a potential option in treating acute diverticulitis disease.

Protective effects of amoxicillin and probiotics on colon disorders in an experimental model of acute diverticulitis disease

Acute diverticulitis disease is associated with inflammation and infection in the colon diverticula and may lead to severe morbidity. This study aimed to evaluate and compare the protective effects of amoxicillin antibiotic, either alone or in combination with probiotics (Lactobacillus acidophilus and Bifidobacterium lactis), in a rat model of acute diverticulitis disease. Acute diverticulitis was induced, in albino rats, by adding 3% weight/volume of dextran sulfate sodium (DSS) to the rats’ drinking water; daily for 7 days, in addition to injecting lipopolysaccharide (LPS) enema (4 mg/kg). The impact of treatments was assessed by measuring the physiological and immunological parameters and evaluating colon macroscopic and microscopic lesions. The results showed that both treatments (especially probiotics with amoxicillin) alleviated the adverse effects of DSS and LPS. This was obvious through the modulation of the rats’ body weight and the colon weight-to-length ratio. Also, there was a significant (p < 0.001) decrease in the colon macroscopic lesion score. The pro-inflammatory cytokines [(TNF)-α, (IL)-1β, (IFN)-γ, and (IL)-18]; in the colon tissue; were significantly (p < 0.001) decreased. Also, both treatments significantly ameliorated the elevation of myeloperoxidase activity and C-reactive protein levels, in addition to improving the histopathological alterations in the colon tissue. In conclusion, amoxicillin and probiotics–amoxicillin were effective in preventing the development of experimentally induced acute diverticulitis, through their anti-inflammatory and immunomodulatory effects. Furthermore, this study has explored the role of probiotics in preventing DSS/LPS-induced acute diverticulitis, so it can be applied as a promising treatment option for acute diverticulitis disease.

Effects of Dextran Sulfate Sodium-Induced Ulcerative Colitis on the Disposition of Tofacitinib in Rats

Tofacitinib, a Janus kinase 1 and 3 inhibitor, is mainly metabolized by CYP3A1/2 and CYP2C11 in the liver. The drug has been approved for the chronic treatment of severe ulcerative colitis, a chronic inflammatory bowel disease. This study investigated the pharmacokinetics of tofacitinib in rats with dextran sulfate sodium (DSS)-induced ulcerative colitis. After 1-min of intravenous infusion of tofacitinib (10 mg/kg), the area under the plasma concentration-time curves from time zero to time infinity (AUC) of tofacitinib significantly increased by 92.3%. The time-averaged total body clearance decreased significantly by 47.7% in DSS rats compared with control rats. After the oral administration of tofacitinib (20 mg/kg), the AUC increased by 85.5% in DSS rats. These results could be due to decreased intrinsic clearance of the drug caused by the reduction of CYP3A1/2 and CYP2C11 in the liver and intestine of DSS rats. In conclusion, ulcerative colitis inhibited CYP3A1/2 and CYP2C11 in the liver and intestines of DSS rats and slowed the metabolism of tofacitinib, resulting in increased plasma concentrations of tofacitinib in DSS rats.

Gallic Acid Protects from Acute Multiorgan Injury Induced by Lipopolysaccharide and D-galactosamine

BACKGROUND

Secondary metabolites of plants, the polyphenols, play a vital role in protection from many health problems in human beings. Structurally favored phytochemicals may be studied to protect multiorgan injury. At pharmacological doses, gallic acid is nontoxic to mammals and is generally absorbed in the intestine.

AIMS

In this present study, gallic acid was evaluated for its protective efficacy against Lipo Polysaccharide (LPS) and d-Galactosamine (D-GalN) induced multiorgan injury, i.e., liver, kidney and brain.

METHODS

Three different doses of gallic acid (5, 10 and 20 mg/kg p.o.) were administered to the experimental animals for 6 consecutive days, followed by exposure to LPS (50 μg/kg I.P.) and D-GalN (300 mg/kg I.P.) on the 6th day.

RESULTS

Exposure to LPS and D-GalN resulted in increased oxidative stress and proinflammatory cytokines. Altered hematology and serology due to LPS and D-GalN were restored towards control by gallic acid. Declined antioxidants such as reduced glutathione, superoxide dismutase and catalase due to injurious effects of LPS and D-GalN were rejuvenated by gallic acid.

DISCUSSION

Exposure to LPS and D-GalN severely increased lipid peroxidation, CYP2E1 activity and tissue lipids while lowered protein content. Gallic acid restored all these parameters towards control in dose dependent manner and 20 mg/kg dose provided the best protection. Histological study showed improved histoarchitecture of liver, kidney and brain that supported biochemical endpoints.

CONCLUSION

Gallic acid minimized oxidative stress and provided best protection at 20 mg/kg dose against LPS and D-GalN induced multi organ acute injury.

Pharmacokinetics of omeprazole in rats with dextran sulfate sodium-induced ulcerative colitis

Omeprazole is a commonly used drug in patients with ulcerative colitis (UC). This study investigated the pharmacokinetics of omeprazole in rats with UC induced by dextran sulfate sodium (DSS). The pharmacokinetics of intravenously administered omeprazole (20 mg/kg) was investigated in normal and UC rats using LC-MS/MS. The formation of 5-OH omeprazole, a main metabolite of omeprazole, in rat liver microsomes (RLMs) from normal and UC rats was compared. The protein levels of CYP1A2, CYP2D1, and CYP3A1 in the liver were measured by Western blot. Compared with normal rats, UC rats had increased plasma concentrations of omeprazole, resulting in an increased AUC_0-240 min and decreased CL. DSS treatment decreased the formation rate of 5-OH omeprazole in RLMs but did not change the affinity of the enzymes. The V_max and CL_int of RLMs from UC rats were 62% and 48% those of RLMs from normal rats, respectively. The hepatic CYP1A2 and CYP3A1 protein levels in UC rats were 42.6 and 45.2% lower than those in normal rats, respectively; however, the protein levels of CYP2D1 in the two groups were similar. The activity and expression of some hepatic CYP450 isoforms were decreased by UC, leading to changes in the pharmacokinetics of omeprazole.

Gut-Liver Axis and Inflammasome Activation in Cholangiocyte Pathophysiology

The Nlrp3 inflammasome is a multiprotein complex activated by a number of bacterial products or danger signals and is involved in the regulation of inflammatory processes through caspase-1 activation. The Nlrp3 is expressed in immune cells but also in hepatocytes and cholangiocytes, where it appears to be involved in regulation of biliary damage, epithelial barrier integrity and development of fibrosis. Activation of the pathways of innate immunity is crucial in the pathophysiology of hepatobiliary diseases, given the strong link between the gut and the liver. The liver secretes bile acids, which influence the bacterial composition of the gut microbiota and, in turn, are heavily modified by microbial metabolism. Alterations of this balance, as for the development of dysbiosis, may deeply influence the composition of the bacterial products that reach the liver and are able to activate a number of intracellular pathways. This alteration may be particularly important in the pathogenesis of cholangiopathies and, in particular, of primary sclerosing cholangitis, given its strong association with inflammatory bowel disease. In the present review, we summarize current knowledge on the gut–liver axis in cholangiopathies and discuss the role of Nlrp3 inflammasome activation in cholestatic conditions.

The regulation of drug-metabolizing enzymes and membrane transporters by inflammation: Evidences in inflammatory diseases and age-related disorders

Drug-metabolizing enzymes (DMEs) and membrane transporters play important roles in the absorption, distribution, metabolism, and excretion processes that determine the pharmacokinetics of drugs. Inflammation has been shown to regulate the expression and function of these drug-processing proteins. Given that inflammation is a common feature of many diseases, in this review, the general mechanisms for inflammation-mediated regulation of DMEs and transporters are described. Also, evidences regarding the aberrant expression of these drug-processing proteins in several inflammatory diseases and age-related disorders are provided.

Inflammation and the Gut-Liver Axis in the Pathophysiology of Cholangiopathies

Cholangiocytes, the epithelial cells lining the bile ducts, represent the unique target of a group of progressive diseases known as cholangiopathies whose pathogenesis remain largely unknown. In normal conditions, cholangiocytes are quiescent and participate to the final bile volume and composition. Following exogenous or endogenous stimuli, cholangiocytes undergo extensive modifications of their phenotype. Reactive cholangiocytes actively proliferate and release a set of proinflammatory molecules, which act in autocrine/paracrine manner mediating the cross-talk with other liver cell types and innate and adaptive immune cells. Cholangiocytes themselves activate innate immune responses against gut-derived microorganisms or bacterial products that reach the liver via enterohepatic circulation. Gut microbiota has been implicated in the development and progression of the two most common cholangiopathies, i.e., primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC), which have distinctive microbiota composition compared to healthy individuals. The impairment of intestinal barrier functions or gut dysbiosis expose cholangiocytes to an increasing amount of microorganisms and may exacerbate inflammatory responses thus leading to fibrotic remodeling of the organ. The present review focuses on the complex interactions between the activation of innate immune responses in reactive cholangiocytes, dysbiosis, and gut permeability to bacterial products in the pathogenesis of PSC and PBC.

Changes in the Pharmacokinetics of Phenytoin in Dextran Sulfate Sodium–Induced Ulcerative Colitis in Mice

We previously demonstrated that the expression levels of drug-metabolizing enzymes, cytochrome P450 (CYP) enzymes, in the liver are significantly decreased in a murine model of ulcerative colitis (UC). In this study, we investigated changes in the pharmacokinetics of phenytoin, a CYP2C substrate drug, in the presence of UC. Colitis was induced by feeding male mice 3.5% dextran sulfate sodium (DSS) dissolved in drinking water for 10 days. The messenger RNA (mRNA) expression of CYP2C29 and CYP2C37 and the protein expression of CYP2C in the liver were evaluated via real-time reverse transcription–polymerase chain reaction and Western blotting, respectively. In DSS-treated animals, both mRNA and protein expression levels of CYP2C in the liver were significantly reduced relative to those in control animals (by 20%-40%). Phenytoin (30 mg/kg) was administered orally in a single dose to mice, and plasma concentrations were measured. Plasma concentrations of phenytoin were higher in the DSS-treated group than in the control group at 12, 24, and 36 hours after administration. Animals given DSS also exhibited a higher area under the plasma concentration–time curve extrapolated to infinity (AUCinf, 315 μg·h/mL), a delayed elimination half-life ( T1/2, 8.1 hours), and a decreased body clearance (CL/F, 3.52 mL/h) compared with that of control animals (AUCinf, 215 μg·h/mL; T1/2, 3.6 h; CL/F, 5.58 mL/h). This study indicated that the presence of UC decreases CYP2C expression levels in the liver, thereby delaying the metabolism of CYP2C substrates, including phenytoin, and increasing blood concentrations of these substrates.

Effects of dextran sulfate sodium induced experimental colitis on cytochrome P450 activities in rat liver, kidney and intestine

Dextran sulfate sodium (DSS) induced experimental colitis presents a histologic resemblance to human ulcerative colitis (UC). Altered cytochrome P450s (CYPs) have been reported in this model and patients with UC. In this study, six CYPs activities were quantitatively determined in microsomes of liver (RLMs), kidney (RRMs) and intestine (RIMs) from rats with colitis at acute (5% DSS for 7 days, UCA) and remission (7-day DSS treatment followed by 7-day cessation, UCR) phases and compared with normal rats. Generally, CYPs activities varied with isoform, organ, and disease status. Hepatic CYP1A2, 2B1, 2C6/11, 2E1 and 3A1/2 activities were reduced by acute colitis and completely or partially restored after DSS was halted. Although DSS treatment decreased the V_max of renal CYP2C6/11 and increased that of CYP2D2, their CL_{int, in vitro} were comparable among normal, acute and remission stages. DSS treatment changed the kinetics of CYP3A1/2-mediated nifedipine metabolism in RRMs from biphasic to classical kinetics. Notably, CYP2D2 activity was elevated in liver and kidney in acute UC, while enhanced in liver and decreased in kidney in remission. In intestine, CYP3A1/2 activity was increased in UCA and further enhanced after DSS withdrawal. These findings highlight the necessity of quantifying enzyme activity for precision drug therapy.

Downregulation of CYP3A and P-glycoprotein in the secondary inflammatory response of mice with dextran sulfate sodium-induced colitis and its contribution to cyclosporine A blood concentrations

CYP3A and P-glycoprotein (P-gp) play important roles in drug metabolism and excretion; however, their functions in pathological conditions remain unclear. Hepatobiliary abnormalities have been described in patients with ulcerative colitis, which may affect drug metabolism and excretion in the liver and small intestine. We examined the functions of CYP3A and P-gp in the liver and small intestine of mice with dextran sodium sulfate (DSS)-induced colitis. Up to day 7, inflammatory markers were significantly increased in the livers of DSS-treated mice, accompanied by decreased CYP3A. Additionally hepatobiliary transporters and Pregnane X receptor, which regulates the transcriptional activation of CYP3A, were reduced. Both CYP3A and P-gp were significantly decreased in the upper small intestine of DSS-treated mice on day 7. This was associated with the increased expression of inducible nitric oxide synthase, but not changes in nuclear receptor expression. On day 7 of DSS treatment, the concentrations of cyclosporine A (CsA), a substrate of both CYP3A and P-gp, were significantly higher than controls. These results indicated the existence of a second inflammatory response in the liver and upper small intestine of mice with DSS-induced colitis, and bioavailability of CsA was increased by the dysfunction of CYP3A and P-gp in these organs.

Hepatic early inflammation induces downregulation of hepatic cytochrome P450 expression and metabolic activity in the dextran sulfate sodium-induced murine colitis

Ulcerative colitis (UC) patients may have increased concentrations of drugs in their blood. We hypothesized that this response is mainly due to a decrease in the expression and activity of the drug-metabolizing enzyme, cytochrome P450 (CYP), in the liver. In this study, we have tried to demonstrate the hypothesis. UC was induced in mice by treatment with dextran sulfate sodium (DSS) solution. The mRNA and protein expression levels of CYP, inflammatory cytokine levels, and the metabolic activity of CYP3A in the liver were measured. The nuclear translocations of nuclear factor kappa B (NF-κB), pregnane X receptor (PXR), and constitutive androstane receptor (CAR) were analyzed. The levels of hepatic inflammatory cytokines increased in the DSS-treated group. The hepatic mRNA and protein expression of CYP (CYP1A, CYP2C, CYP2D, CYP2E, and CYP3A) and the CYP3A metabolic activity significantly decreased compared to the control group. Hepatic NF-κB nuclear translocation significantly increased in the DSS-treated group. In contrast, the nuclear translocations of PXR and CAR were decreased. Lipopolysaccharides from inflammatory sites in the colon induce hepatic inflammation in DSS-induced murine colitis. This inflammation then causes an increase in the nuclear translocation of hepatic NF-κB and a decrease in the nuclear translocation of PXR and CAR, resulting in the decreased expression and activities of CYP. The results of this study indicated that at the onset of UC, the decreased activity of hepatic CYP causes an increase in the concentrations of drugs in the blood, leading to an increase in the incidence of adverse reactions.

Nuclear receptors in the cross-talk of drug metabolism and inflammation

Inflammation and infection have long been known to affect the activity and expression of enzymes involved in hepatic and extrahepatic drug clearance. Significant advances have been made to elucidate the molecular mechanisms underlying the complex cross-talk between inflammation and drug-metabolism alterations. The emergent role of ligand-activated transcriptional regulators, belonging to the nuclear receptor (NR) superfamily, is now well established. The NRs, pregnane X receptor, constitutive androstane receptor, retinoic X receptor, glucocorticoid receptor, and hepatocyte nuclear factor 4, and the basic helix-loop-helix/Per-ARNT-Sim family member, aryl hydrocarbon receptor, are the main regulators of the detoxification function. According to the panel of mediators secreted during inflammation, a cascade of numerous signaling pathways is activated, including nuclear factor kappa B, mitogen-activated protein kinase, and the Janus kinase/signal transducer and activator of transcription pathways. Complex cross-talk is established between these signaling pathways regulating either constitutive or induced gene expression. In most cases, a mutual antagonism between xenosensor and inflammation signaling occurs. This review focuses on the molecular and cellular mechanisms implicated in this cross-talk.

Prevention of preneoplastic lesions by dietary vitamin D in a mouse model of colorectal carcinogenesis

Colorectal cancer (CRC) is one of the leading causes of cancer morbidity and mortality in Western countries. One of the risk factors for colorectal tumorigenesis is vitamin D insufficiency. The aim of this study was to establish whether increasing dietary vitamin D intake can prevent or delay development of chemically induced preneoplastic lesions in the colon of mice. We fed six weeks old female C57BL/6J mice (n=28) with increasing vitamin D3 concentrations (100, 400, 1000, 2500, 5000IU/kg diet). To induce dysplasia, a preneoplastic lesion, we injected mice with the carcinogen azoxymethane (10mg/kg) intraperitoneally, followed by three cycles of 2% dextran sodium sulfate salt, a tumor promoter, in the drinking water. To test our hypothesis that high vitamin D intake prevents formation of preneoplastic lesions, we have investigated the effect of increasing dietary vitamin D on development of premalignant colorectal lesions, serum 25-hydroxyvitamin D3 (25-D3) levels, and expression of renal vitamin D system genes. Dietary vitamin D concentration correlated inversely with dysplasia score (Spearman's correlation coefficient, ρ: -0.579, p=0.002) and positively with serum 25-D3 levels (ρ: 0.752, p=0.001). Increasing dietary vitamin D concentration beyond 1000IU/kg led to no further increase in circulating 25-D3 levels, while the dysplasia score leveled out at ≥2500IU/kg vitamin D. High dietary vitamin D intake led to increased renal mRNA expression of the vitamin D catabolizing enzyme cyp24a1 (ρ: 0.518, p=0.005) and decreased expression of the vitamin D activating enzyme cyp27b1 (ρ: -0.452, p=0.016), protecting the body from toxic serum levels of the active vitamin D metabolite 1,25-dihydroxyvitamin D3 (1,25-D3). Our data showed that increasing dietary vitamin D intake is able to prevent chemically induced preneoplastic lesions. The maximum impact was achieved when the mice consumed more than 2500IU vitamin D/kg diet. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Protective effect of naringenin against experimental colitis via suppression of Toll-like receptor 4/NF-κB signalling

Naringenin, one of the most abundant flavonoids in citrus, grapefruits and tomatoes, has been used as a traditional anti-inflammatory agent for centuries. However, the molecular mechanism of naringenin in intestinal inflammation remains unknown so far. The present study investigated a molecular basis for the protective effect of naringenin in dextran sulphate sodium-induced murine colitis. Pre-administration of naringenin significantly reduced the severity of colitis and resulted in down-regulation of pro-inflammatory mediators (inducible NO synthase (iNOS), intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), cyclo-oxygenase-2 (Cox2), TNF-α and IL-6 mRNA) in the colon mucosa. The decline in the production of pro-inflammatory cytokines, specifically TNF-α and IL-6, correlated with a decrease in mucosal Toll-like receptor 4 (TLR4) mRNA and protein. Phospho-NF-κB p65 protein was significantly decreased, which correlated with a similar decrease in phospho-IκBα protein. Consistent with the in vivo results, naringenin exposure blocked lipopolysaccharide-stimulated nuclear translocation of NF-κB p65 in mouse macrophage RAW264.7 cells. In addition, in vitro NF-κB reporter assays performed on human colonic HT-29 cells exposed to naringenin demonstrated a significant inhibition of TNF-α-induced NF-κB luciferase expression. Thus, for the first time, the present study indicates that targeted inhibition of the TLR4/NF-κB signalling pathway might be an important mechanism for naringenin in abrogating experimental colitis.

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.

N-acetylcysteine improves redox status, mitochondrial dysfunction, mucin-depleted crypts and epithelial hyperplasia in dextran sulfate sodium-induced oxidative colitis in mice

The effect of N-acetylcysteine (NAC), a pharmacological antioxidant was investigated in a murine model of chronic colitis. Male NMRI mice were given 5% dextran sulfate sodium (DSS) in drinking water for 5 days followed by 10 days of water, three times. Compared to control mice given water, DSS-treated mice displayed severe imbalanced redox status with decreased glutathione and catalase, but increased malondialdehyde, protein carbonyls, nitric oxide and myeloperoxidase levels, at days 35th (active colitis) and 45th (recovery period). It also resulted in mitochondrial dysfunction, mucosal ulcers, mucin-depleted crypts and epithelial cell apoptosis. Crypt abscesses and glandular hyperplasia occurred selectively in distal colon. NAC (150 mg/kg) given in drinking water for 45 days along with 3 DSS cycles improved the hallmarks of DSS-colitis. Interestingly, the moderate impact of NAC on lipids and proteins oxidation correlated with myeloperoxidase and nitric oxide levels.NAC as a mucoregulator and a thiol restoring agent is protective on oxidative crypt alterations, mucin depletion, epithelial cell hyperplasia and apoptosis. Taken together, our results highlight the role of NAC as a scavenger of phagocytes-derived reactive oxygen species in mice DDS-colitis, suggesting that a long term NAC diet might be beneficial in inflammatory bowel diseases and colorectal cancer.

Blueberry husks and probiotics attenuate colorectal inflammation and oncogenesis, and liver injuries in rats exposed to cycling DSS-treatment

Long-term colonic inflammation promotes carcinogenesis and histological abnormalities of the liver, and colorectal tumours frequently arise in a background of dysplasia, a precursor of adenomas. Altered colonic microbiota with an increased proportion of bacteria with pro-inflammatory characteristics, have been implicated in neoplastic progression. The composition of the microbiota can be modified by dietary components such as probiotics, polyphenols and dietary fibres. In the present study, the influence of probiotics in combination with blueberry husks on colorectal carcinogenesis and subsequent liver damage was evaluated.

Colorectal tumours were induced in rats by cyclic treatment with dextran sulphate sodium (DSS). Blueberry husks and a mixture of three probiotic strains (Bifidobacterium infantis DSM 15159, Lactobacillus gasseri, DSM 16737 and Lactobacillus plantarum DSM 15313) supplemented a basic diet fortified with oats. The condition of the rats was monitored using a disease activity index (DAI). A qualitative and quantitative histological judgement was performed on segments of distal colon and rectum and the caudate lobe of the liver. The formation of short-chain fatty acids, bacterial translocation, the inflammatory reaction and viable count of lactobacilli and Enterobaceriaceae were addressed.

Blueberry husks with or without probiotics significantly decreased DAI, and significantly reduced the number of colonic ulcers and dysplastic lesions. With a decreased proportion of blueberry husk in the diet, the probiotic supplement was needed to achieve a significant decrease in numbers of dysplastic lesions. Probiotics decreased faecal viable count of Enterobacteriaceae and increased that of lactobacilli. Blueberry husks with or without probiotics lowered the proportion of butyric acid in distal colon, and decreased the haptoglobin levels. Probiotics mitigated hepatic injuries by decreasing parenchymal infiltration and the incidence of stasis and translocation. The results demonstrate a dietary option for use of blueberry husks and probiotics to delay colonic carcinogenesis and hepatic injuries in the rat model.

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.

Colorectal Oncogenesis and Inflammation in a Rat Model Based on Chronic Inflammation due to Cycling DSS Treatments

Inflammation is known to be linked with development of colorectal cancer, and the aim was to assess the malignant potential and degree of inflammation in a dextran-sulphate-sodium-(DSS-) induced cyclic colonic tumour model (CTM) in rats and to compare it with the azoxymethane-(AOM-) induced CTM model. Tumours developed in both groups, although, in the DSS group, the colonic mucosa appeared edematous and the number of haemorrhagic erosions and quantity of dysplastic lesions were higher as well as the mucosal concentration of myeloperoxidase and faecal viable count of Enterobacteriaceae. The livers were affected as evaluated by steatosis, parenchymal loss, haemorrhage, and inflammatory infiltrations, and higher proportions of acetate and lower proportions of butyrate in colonic content were found. The DSS model seems to mimic the clinical situation and may be valuable for investigation of inflammation-related dysplasia and colon cancer, as well as for altered liver function by endogenous inflammatory mediators.

Gut microbiota and inflammation

Systemic and local inflammation in relation to the resident microbiota of the human gastro-intestinal (GI) tract and administration of probiotics are the main themes of the present review. The dominating taxa of the human GI tract and their potential for aggravating or suppressing inflammation are described. The review focuses on human trials with probiotics and does not include in vitro studies and animal experimental models. The applications of probiotics considered are systemic immune-modulation, the metabolic syndrome, liver injury, inflammatory bowel disease, colorectal cancer and radiation-induced enteritis. When the major genomic differences between different types of probiotics are taken into account, it is to be expected that the human body can respond differently to the different species and strains of probiotics. This fact is often neglected in discussions of the outcome of clinical trials with probiotics.

Marginal zinc deficiency exacerbates experimental colitis induced by dextran sulfate sodium in rats

We investigated the impact of Zn status on the maintenance of mucosal homeostasis. Rats were fed diets containing different amounts of Zn (30, 10, 5, <1 mg Zn/kg diet) for 21 d. Serum Zn concentrations were lower in rats fed marginally Zn-deficient (MZD; 5 mg Zn/kg diet) and severely Zn-deficient (<1 mg/kg) diets but not in those fed the marginally Zn-adequate diet (10 mg/kg) or the Zn-adequate (ZA; 30 mg/kg) group (P < 0.05). However, organ weights, colonic epithelial cell proliferation, and crypt fission did not differ between the MZD and ZA groups. We then evaluated whether MZD modulated dextran sulfate sodium (DSS)-induced colonic inflammation by administering 2% DSS to the MZD and ZA groups for 7 d. Myeloperoxidase activity and TNFα production increased in response to DSS in the MZD group (P < 0.03). Colonic permeability in the 2 groups did not differ after DSS administration. In a culture experiment using isolated mesenteric leukocytes, TNFα production was higher (P < 0.05) and TNF receptor type I (TNFR1) expression was detected in culture medium containing 20 and 30 μmol/L of Zn compared with culture medium lacking Zn supplementation. These results suggest that MZD exacerbated colitis by modulating the immune response through the impairment of TNFα production and TNFR1 expression rather than through the impairment of epithelial barrier function.

Protective effect of Gö6976, a PKD inhibitor, on LPS/D: -GalN-induced acute liver injury in mice

OBJECTIVE

Protein kinase D (PKD) is a newly described serine/threonine protein kinase that plays a pivotal role in inflammatory response. In the present study, we examined the protective effect of Gö6976, a PKD inhibitor, on lipopolysaccharide (LPS) and D: -galactosamine (D: -GalN)-induced acute liver injury in mice.

MATERIALS AND METHODS

Mice were pretreated intraperitoneally with Gö6976 30 min before LPS/D: -GalN administration . The mortality and degree of hepatic injury was subsequently assessed.

RESULTS

The results indicated that LPS/D: -GalN administration markedly induced hepatic PKD activation, lethality and liver injury, while pretreatment of the PKD inhibitor Gö6976 significantly inhibited LPS-induced PKD activation, improved the survival of LPS/D: -GalN-administered mice and attenuated LPS/D: -GalN-induced liver injury, as evidenced by reduced levels of serum aminotransferases as well as reduced histopathological changes. In addition, the protective effects of Gö6976 were paralleled by suppressed activation of mitogen-activated protein kinases (MAPKs), decreased expression of tumor necrosis factor-α (TNF-α) and adhesion molecules, and reduced apoptosis and myeloperoxidase (MPO) activity in liver.

CONCLUSIONS

Our experimental data indicated that Gö6976, a PKD inhibitor, could effectively prevent LPS/D: -GalN-induced acute liver injury by inhibition of MAPKs activation to reduce TNF-α production. This suggests the potential pharmacological value of PKD inhibitors in the intervention of inflammation-based liver diseases.

Salvage effect of E5564, Toll-like receptor 4 antagonist on d-galactosamine and lipopolysaccharide-induced acute liver failure in rats

BACKGROUND AND AIMS

The transmembrane protein Toll-like receptor 4 (TLR4), which exists mainly in macrophages such as Kupffer cells of the liver, plays an important role in recognizing and mediating macrophage activation and pro-inflammatory cytokine release. Activation of the pro-inflammatory cytokine cascade, including tumor necrosis factor-alpha (TNF-alpha), has a pivotal role in the progression of severe liver injury. D-galactosamine (GalN) and lipopolysaccharide (LPS)-induced liver injury in rats is an experimental model of fulminant hepatic failure, where TNF-alpha plays a central role in the progression of liver injury. E5564, a synthetic analogue of the lipid A component of endotoxin, inhibits endotoxin-stimulated inflammation and is under study for patients with sepsis. In the present study, we sought to explore the salvage effect of TLR4 antagonist E5564 on GalN+LPS-induced acute liver failure (ALF) in rats.

METHODS

ALF was induced in male Wistar rats by the intraperitoneal injection of GalN (500 mg/kg) and LPS (50 microg/kg). Immediately after GalN+LPS injection, rats were treated with intravenous injection of E5564 (3 mg/kg). The cumulative survival rates of GalN+LPS-induced ALF rats were compared between those with and without E5564 treatment.

RESULTS

The intravenous injection of E5564 reduced the elevation of serum total bilirubin, aspartate aminotransferase, alanine aminotransferase and TNF-alpha levels in rats at 3 h after GalN+LPS injection, and improved the survival rate of GalN+LPS-induced ALF rats at 24 h (8% vs 43%).

CONCLUSIONS

TLR4 antagonist E5564 reduced GalN+LPS-induced acute liver injury in rats and improved the overall survival rate of GalN+LPS-induced ALF rats. It may contribute to the treatment of ALF through blocking endotoxin-induced TNF-alpha overproduction of macrophages.

Increased susceptibility to dextran sulfate sodium induced colitis in the T cell protein tyrosine phosphatase heterozygous mouse

T cell protein tyrosine phosphatase (TC-PTP / PTPN2) is an enzyme that is essential for the proper functioning of the immune system and that participates in the control of cell proliferation, and inflammation. We previously observed that TC-PTP^−/− mice display various immunodeficiencies, hypersensitivity to LPS and die within three weeks of birth due to anemia and widespread inflammation. A recent analysis of the Wellcome Trust Case Control Consortium (WTCC) genome wide scan data, reported in 2007, indicated a potential role for TC-PTP in inflammatory bowel disease (IBD). To further investigate the potential role of TC-PTP in IBD, we studied heterozygous TC-PTP mutant mice challenged with dextran sulfate sodium (DSS) in their drinking water. In comparison to control animals, we observed significant changes in the colon mucosa of DSS-treated TC-PTP^+/− mice, in the ratio of colon to body weight, as well as an up-regulation of mRNA transcripts for IL-6, IL-23, 1L-12β, IFN-γ, TNF-α. Moreover, up-regulation of serum IL-6 levels in DSS-treated TC-PTP^+/− mice confirms that mice with a single copy of the TC-PTP gene display increased susceptibility to systemic inflammation due to bowel epithelial erosion resulting from DSS challenge. Our findings support the lack of modulation of Janus kinases 1 and 3 (Jak1, Jak3), and the downstream signal transducer and activator of transcription 1,3 and 5 (Stat1, Stat3, Stat 5) by PTPN2 in the development of IBD like condition. Pathological and molecular analysis reveal that the deficiency of TC-PTP results in pro-inflammatory condition in the bowel of heterozygous TC-PTP^+/− mice. These novel findings in TC-PTP hemi-deficiency support the hypothesis that TC-PTP is an important regulator of inflammatory cytokine signaling and that it may be implicated in the pathophysiology of IBD.

Genome-wide transcriptional response of Silurana (Xenopus) tropicalis to infection with the deadly chytrid fungus

Emerging infectious diseases are of great concern for both wildlife and humans. Several highly virulent fungal pathogens have recently been discovered in natural populations, highlighting the need for a better understanding of fungal-vertebrate host-pathogen interactions. Because most fungal pathogens are not fatal in the absence of other predisposing conditions, host-pathogen dynamics for deadly fungal pathogens are of particular interest. The chytrid fungus Batrachochytrium dendrobatidis (hereafter Bd) infects hundreds of species of frogs in the wild. It is found worldwide and is a significant contributor to the current global amphibian decline. However, the mechanism by which Bd causes death in amphibians, and the response of the host to Bd infection, remain largely unknown. Here we use whole-genome microarrays to monitor the transcriptional responses to Bd infection in the model frog species, Silurana (Xenopus) tropicalis, which is susceptible to chytridiomycosis. To elucidate the immune response to Bd and evaluate the physiological effects of chytridiomycosis, we measured gene expression changes in several tissues (liver, skin, spleen) following exposure to Bd. We detected a strong transcriptional response for genes involved in physiological processes that can help explain some clinical symptoms of chytridiomycosis at the organismal level. However, we detected surprisingly little evidence of an immune response to Bd exposure, suggesting that this susceptible species may not be mounting efficient innate and adaptive immune responses against Bd. The weak immune response may be partially explained by the thermal conditions of the experiment, which were optimal for Bd growth. However, many immune genes exhibited decreased expression in Bd-exposed frogs compared to control frogs, suggesting a more complex effect of Bd on the immune system than simple temperature-mediated immune suppression. This study generates important baseline data for ongoing efforts to understand differences in response to Bd between susceptible and resistant frog species and the effects of chytridiomycosis in natural populations.

Therapeutic approach to regulate innate immune response by Toll-like receptor 4 antagonist E5564 in rats with D-galactosamine-induced acute severe liver injury

BACKGROUND AND AIMS

Toll-like receptor 4 (TLR4) is a transmembrane protein, existing mainly in macrophages, such as Kupffer cells of the liver. It plays an important role in recognizing and mediating macrophage activation and pro-inflammatory cytokine release. Activation of pro-inflammatory cytokines, including tumor necrosis factor (TNF)-alpha is pivotal in the progression of liver injury. Gut-derived endotoxin has been considered to play an important role in the development and progression of a D-galactosamine (GalN)-induced acute severe liver injury (ALI) model. E5564, a synthetic analog of the lipid A component of endotoxin, inhibits endotoxin-stimulated inflammation and is under study for patients with sepsis. In this study, we seek to explore the effect of TLR4 antagonist E5564 on GalN-induced ALI in rats.

METHODS

ALI was induced in male Wistar rats by the i.p. injection of 1 g/kg bodyweight of GalN and immediately after GalN injection they were treated with an i.v. injection of 3 mg/kg bodyweight of E5564. At 24 h after GalN injection with or without E5564, serum levels of total bilirubin (T.Bil), alanine aminotransferase (ALT) and TNF-alpha were analyzed. Expression levels of TNF-alpha, TLR4 and CD14 mRNA in the whole liver of rats was detected by reverse transcription polymerase chain reaction analysis.

RESULTS

The i.v. injection of E5564 reduced the elevation of serum T.Bil, ALT and TNF-alpha levels in rats treated with GalN. The expression level of TNF-alpha mRNA in the whole liver, which was increased at 24 h after GalN injection, was also reduced by i.v. injection of E5564.

CONCLUSION

TLR4 antagonist E5564 reduced GalN-induced ALI in rats. It may contribute to the treatment of acute liver failure through blocking endotoxin-induced TNF-alpha overproduction of macrophages.

Intestinal flora induces the expression of Cyp3a in the mouse liver

In order to determine the effects of intestinal flora on the expression of cytochrome P450 (CYP), the mRNA expression of CYP was compared between specific pathogen-free (SPF) and germ-free (GF) mice. Most of the major CYP isozymes showed higher expression in the livers of SPF mice compared with GF mice. Nuclear factors such as pregnane X receptor (PXR) and constitutive androstane receptor (CAR), as well as transporters and conjugation enzymes involved in the detoxification of lithocholic acid (LCA), also showed higher expression in SPF mice. The findings suggest that in the livers of SPF mice, LCA produced by intestinal flora increases the expression of CYPs via activation of PXR and CAR. Drugs such as antibiotics, some diseases and ageing, etc. are known to alter intestinal flora. The present findings suggest that such changes also affect CYP and are one of the factors responsible for individual differences in pharmacokinetics.

Intestinal inflammation in rats induces metallothionein in colonic submucosa

The aim of the current study was to determine if induction of metallothionein (MT) via acute or chronic dietary zinc supplementation attenuates intestinal inflammation, and to investigate the relationship with site-specific intestinal MT determined by immunolocalization. Growing rats were assigned to zinc-deficient (ZD), acute zinc-treated (ZT), pair-fed, control or chronic Zn-supplemented (ZS) groups. Half the rats in each dietary group received 5% dextran sulphate sodium (DSS) in their drinking water for 4 days. DSS treatment produced acute intestinal inflammation in the colon only, however, dietary zinc deficiency, acute zinc treatment or chronic zinc supplementation did not alter the severity of ulceration. Serum zinc concentrations were attenuated in the DSS-challenged ZT and ZS groups suggesting that zinc was being utilized in some capacity in response to inflammation. DSS-challenge induced MT immunostaining in the colonic submucosa, however, MT was not associated with histological improvements in the present study. The site-specific MT induction in colonic submucosa during intestinal inflammation requires further clarification as a component of the host defense.

Hepatic flavin-containing monooxygenase gene regulation in different mouse inflammation models

The objective of the study was to investigate the regulation of hepatic flavin-containing monooxygenases (Fmo) Fmo1, Fmo3, Fmo4, and Fmo5 in three different mouse models of inflammation, including treatment with Citrobacter rodentium, lipopolysaccharide (LPS), and dextran sulfate sodium (DSS). Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to evaluate the steady-state mRNA levels for the various Fmo isoforms in these mouse models of inflammation during different treatment time courses. Fmo3 mRNA was most significantly down-regulated in C. rodentium-treated female mice. Fmo1, Fmo3, and Fmo5 mRNAs were also found to be down-regulated in LPS models of inflammation. The significant down-regulation of hepatic FMO3 protein during C. rodentium treatment was confirmed with Western blot analysis of liver microsomes from treated animals. Toll-like receptor (TLR) 4 is known to be responsible for LPS signaling in association with several proteins. To investigate whether TLR4 was responsible for regulation of Fmo genes in both LPS and C. rodentium animal models, Fmo mRNA levels in female wild-type (C3H/HeOuJ) and TLR4 mutant (C3H/HeJ) mice were compared in both inflammatory models by real-time RT-PCR. The results showed that Fmo3 down-regulation during C. rodentium infection is independent of TLR4. Whereas TLR4 is likely to play only a partial role in Fmo1 gene regulation in LPS-treated animals, our results show that the down-regulation of Fmo3 and Fmo5 in this model is TLR4-dependent. Unlike cytochrome P450 regulation measured in the same mouse strains, Fmo3 expression was largely refractory to down-regulation in the DSS model of inflammatory colitis.

TLR4-dependent and -independent regulation of hepatic cytochrome P450 in mice with chemically induced inflammatory bowel disease

The transcription and protein expression of many cytochrome P450 (P450) genes are down-regulated in animal models of inflammation and infection. We determined previously that hepatic P450 mRNAs are selectively regulated in a mouse model of enteropathogenic bacterial infection, and that this regulation was not dependent on the lipopolysaccharide (LPS) receptor protein toll-like receptor 4 (TLR4). In the dextran sulfate sodium (DSS) model of chemically induced inflammatory bowel disease (IBD), the reduction in activities of several hepatic P450 enzymes were concluded to be partially dependent on LPS from commensal bacteria [Masubuchi Y, Horie T. Endotoxin-mediated disturbance of hepatic cytochrome P450 function and development of endotoxin tolerance in the rat model of dextran sulfate sodium-induced experimental colitis. Drug Metab Dispos 2004;32:437-441]. In the present study, we sought to determine whether colitis induced by LPS regulates hepatic P450 mRNA and protein expression similarly to infectious colitis, and to determine the role of TLR4 in the response to DSS colitis. The role of LPS in the response to DSS was further examined by comparison with the effects of injected LPS. We demonstrate that administration of DSS results in the down-regulation of multiple P450 enzymes in mouse liver. However, there are discernable differences in the pattern of P450 expression in the two models. Some effects of DSS-induced colitis are TLR4-dependent, and others are not. In contrast, the effects of injected LPS on hepatic P450 mRNA expression are entirely TLR4-dependent. Thus, our results indicate that the pattern of hepatic P450 expression, and the mechanism of regulation, during inflammation of the bowel depend on the etiology of the disease.

Interaction of Muc2 and Apc on Wnt signaling and in intestinal tumorigenesis: potential role of chronic inflammation

Somatic mutations of the adenomatous polyposis coli (APC) gene are initiating events in the majority of sporadic colon cancers. A common characteristic of such tumors is reduction in the number of goblet cells that produce the mucin MUC2, the principal component of intestinal mucus. Consistent with these observations, we showed that Muc2 deficiency results in the spontaneous development of tumors along the entire gastrointestinal tract, independently of deregulated Wnt signaling. To dissect the complex interaction between Muc2 and Apc in intestinal tumorigenesis and to elucidate the mechanisms of tumor formation in Muc2(-/-) mice, we crossed the Muc2(-/-) mouse with two mouse models, Apc(1638N/+) and Apc(Min/+), each of which carries an inactivated Apc allele. The introduction of mutant Muc2 into Apc(1638N/+) and Apc(Min/+) mice greatly increased transformation induced by the Apc mutation and significantly shifted tumor development toward the colon as a function of Muc2 gene dosage. Furthermore, we showed that in compound double mutant mice, deregulation of Wnt signaling was the dominant mechanism of tumor formation. The increased tumor burden in the distal colon of Muc2/Apc double mutant mice was similar to the phenotype observed in Apc(Min/+) mice that are challenged to mount an inflammatory response, and consistent with this, gene expression profiles of epithelial cells from flat mucosa of Muc2-deficient mice suggested that Muc2 deficiency was associated with low levels of subclinical chronic inflammation. We hypothesize that Muc2(-/-) tumors develop through an inflammation-related pathway that is distinct from and can complement mechanisms of tumorigenesis in Apc(+/-) mice.

Expression of Toll-like receptor 4 in various organs in rats with D-galactosamine-induced acute hepatic failure

BACKGROUND AND AIMS

Activation of the pro-inflammatory cytokine cascade, including tumor necrosis factor alpha (TNF-alpha) is considered to play an important role in the pathophysiology and clinical outcome of severe liver injury. Kupffer cells, resident macrophages of the liver, have a transmembrane protein Toll-like receptor 4 (TLR4), which recognizes endotoxin (lipopolysaccharide; LPS) or LPS-CD14 complex and mediates macrophage activation and pro-inflammatory cytokine release. D-Galactosamine (GalN), a hepatocyte-specific inhibitor of RNA synthesis, is known to sensitize animals to the lethal effects of LPS and TNF-alpha. In the present study we seek to address TLR4-signaling in the development of GalN-induced acute hepatic failure (AHF) and explore the expression of TLR4 mRNA as compared to TNF-alpha mRNA and CD14 mRNA in the liver, spleen and lung of rats with GalN-induced hepatitis.

METHODS

AHF was induced in male Wistar rats by the intraperitoneal injection of 1 g/kg bodyweight GalN. Expression levels of TNF-alpha, TLR4 and CD14 mRNA in the whole liver, spleen and lung of rats were detected by reverse transcription-polymerase chain reaction analysis.

RESULTS

Expression level of TLR4 mRNA in the liver of rats with GalN-induced AHF was increased parallel with that of TNF-alpha and CD14 mRNA as compared to the control rats. However, expression levels of TNF-alpha, TLR4 and CD14 mRNA in the whole spleen and lung were not different between rats with AHF and control.

CONCLUSIONS

There may be a difference of stimulatory effects of endotoxin on the innate immunity between the liver and other organs of rats with GalN-induced AHF.

N-Demethylation is a major route of 2-amino-3-methylimidazo[4,5-f]quinoline metabolism in mouse

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) metabolism was evaluated in mouse to better understand its tumorigenicity. Urinary metabolites from mice orally administered 40 mg/kg [(14)C]IQ were compared with those from similarly treated rats. The recovery of radioactivity was significantly greater in mouse urine. The relative proportion of metabolites was significantly different, and a new rodent metabolite was detected. For rat, the proportion of previously identified metabolites excreted was 5-O-glucuronide > sulfamate > 5-sulfate > N-glucuronide. In mouse urine, a new metabolite, demethyl-IQ, represented approximately 26% of IQ metabolism with the proportion of metabolites as follows: 5-O-glucuronide > demethyl-IQ > sulfamate > N-glucuronide > 5-sulfate. Mouse metabolites were identified by electrospray ionization mass spectrometry. Demethyl-IQ was shown to be 2-aminoimidazo[4,5-f]quinoline. N-Acetyl-2-amino-3-methylimidazo[4,5-f]quinoline was not detected with mice. Mouse liver slices produced 5-O-glucuronide, demethyl-IQ, and sulfamate with the former two being significantly reduced by ellipticine. Liver microsomes only produced demethyl-IQ. Ellipticine, a cytochrome P450 1A inhibitor, but not furafylline, an 1A2 selective inhibitor, prevented microsomal N-demethylation. Inhibitors had similar effects on 7-ethoxyresorufin O-deethylation activity. Demethyl-IQ was not further metabolized by an intact mouse or liver microsomes. Thus, mouse IQ metabolism is significantly different from that in rat, and these differences may affect IQ tumorigenicity. N-Demethylation of IQ-like heterocyclic amines occurs in mouse, monkey, and human but not in rat.

Metabolomics reveals that hepatic stearoyl-CoA desaturase 1 downregulation exacerbates inflammation and acute colitis

To investigate the pathogenic mechanism of ulcerative colitis, a dextran sulfate sodium (DSS)-induced acute colitis model was examined by serum metabolomic analysis. Higher levels of stearoyl lysophosphatidylcholine and lower levels of oleoyl lysophosphatidylcholine in DSS-treated mice compared to controls led to the identification of DSS-elicited inhibition of stearoyl-CoA desaturase 1 (SCD1) expression in liver. This decrease occurred prior to the symptoms of acute colitis and was well correlated with elevated expression of proinflammatory cytokines. Furthermore, Citrobacter rodentium-induced colitis and lipopolysaccharide treatment also suppressed SCD1 expression in liver. Scd1 null mice were more susceptible to DSS treatment than wild-type mice, while oleic acid feeding and in vivo SCD1 rescue with SCD1 adenovirus alleviated the DSS-induced phenotype. This study reveals that inhibition of SCD1-mediated oleic acid biogenesis exacerbates proinflammatory responses to exogenous challenges, suggesting that SCD1 and its related lipid species may serve as potential targets for intervention or treatment of inflammatory diseases.

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

Dextran sulphate sodium (DSS)-induced colitis in rodents is an experimental model for human inflammatory bowel disease (IBD). The aim of this study was to characterize the effect of DSS in hamster colon and liver. DSS (2-5%) was administrated in the drinking water for 4-6 days. Clinical symptoms were recorded daily, inflammatory and fatty acid-related metabolic markers were assessed in plasma, colon and liver. Six days of 3 or 5% DSS induced a severe wasting disease, whereas 2.5% DSS induced a colonic inflammation without severe systemic adverse effects. The systemic inflammatory response was characterized by an inverse production of albumin and the acute phase protein haptoglobin. The colonic inflammatory response was confined to the proximal colon, manifested by a high macroscopic inflammatory score, increased colon weight and expression of IL-1beta, IL-6 and iNOS, infiltration of inflammatory cells and epithelial disruption. In contrast, only a low/mild inflammatory response was observed in the distal colon of DSS-exposed hamsters. Significant hepatic-related metabolic alterations were also observed, with elevation of plasma triglycerides and increased liver expression of lipoprotein lipase and reduced expression of acyl-CoA oxidase and cytochrome P450A. Although liver weight was significantly reduced, no histopathological signs of inflammation or tissue damage were observed. In summary, hamsters exposed to 2.5% DSS for 6 days develop acute colitis resembling murine DSS-induced colitis. In addition, DSS-exposed hamster showed alterations in hepatic fatty acids metabolism resembling human IBD, suggesting that the model can potentially be used for target discovery and validation of hepatic-related metabolic alterations.

Vitamin D and the vitamin D receptor are critical for control of the innate immune response to colonic injury

Background

The active form of vitamin D (1,25(OH)₂D₃) has been shown to inhibit development of inflammatory bowel disease (IBD) in IL-10 KO mice. Here, the role of the vitamin D receptor (VDR) and 1,25(OH)₂D₃ in acute experimental IBD was probed.

Results

VDR KO mice were extremely sensitive to dextran sodium sulfate (DSS) and there was increased mortality of the VDR KO mice at doses of DSS that only caused a mild form of colitis in wildtype (WT) mice. DSS colitis in the VDR KO mice was accompanied by high colonic expression of TNF-α, IL-1 α, IL-1β, IL-12, IFN-γ, IL-10, MIP-1α and KC. DSS concentrations as low as 0.5% were enough to induce bleeding, ulceration and weight loss in VDR KO mice. VDR KO mice failed to recover following the removal of DSS, while WT mice showed signs of recovery within 5 days of DSS removal. The early mortality of DSS treated VDR KO mice was likely due to perforation of the bowel and resulting endotoxemia. VDR KO mice were hyper-responsive to exogenously injected LPS and cultures of the peritoneal exudates of moribund DSS treated VDR KO mice were positive for bacterial growth. 1,25(OH)₂D₃ in the diet or rectally decreased the severity and extent of DSS-induced inflammation in WT mice.

Conclusion

The data point to a critical role for the VDR and 1,25(OH)₂D₃ in control of innate immunity and the response of the colon to chemical injury.

Possible implication of macrophages in the regulation of cytochrome P450 activities in carp (Cyprinus carpio)

Macrophages play a key role in the regulation of cytochrome P450 activity induced by immunostimulants in mammals. We investigated the effects of immunostimulants (LPS, dextran sulfate and tilorone) on biotransformation and macrophage activities in carp. The major effect of LPS was its capacity to inhibit 3-MC-induced cytochrome P450 activities in the liver and head kidney. Basal phase I activities were reduced by tilorone and dextran sulfate in immune organs. Tilorone and dextran sulfate differently modulated total cytochrome P450 contents and P4501A activities suggesting differential sensitivity for P450 classes. In immune organs, tilorone and dextran sulfate inhibited basal EROD activity. Tilorone inhibited 3-MC-induced EROD activity whereas dextran sulfate enhanced this activity. LPS and dextran sulfate increased ROS production by macrophages and all the immunostimulants induced macrophage activating factor (MAF) production. This study demonstrates for the first time in fish the capacity of CYP-regulated immunostimulants to activate macrophages and provides initial insight into the capacity of macrophages to regulate CYP activity induced by immunostimulants in fish.

Regulation of drug-metabolizing enzymes and transporters in inflammation

Inflammation and infection have long been known to downregulate the activity and expression of cytochrome P450 (CYP) enzymes involved in hepatic drug clearance. This can result in elevated plasma drug levels and increased adverse effects. Recent information on regulation of human CYP enzymes is presented, as are new developments in our understanding of the mechanisms of regulation. Experiments to study the effects of modulating CYP activities on the inflammatory response have yielded possible insights into the physiological consequences, if not the purpose, of the downregulation. Regulation of hepatic flavin monooxygenases, UDP-glucuronosyltransferases, sulfotransferases, glutathione S-transferases, as well as of hepatic transporters during the inflammatory response, exhibits similarities and differences with regulation of CYPs.

Down-regulation of hepatic cytochrome P450 enzymes associated with cisplatin-induced acute renal failure in male rats

Hepatic drug metabolism is impaired in experimental animals and humans with renal diseases. An anticancer drug, cisplatin induces acute renal failure (ARF) in rats. Under the same experimental conditions, cisplatin causes down-regulation of hepatic cytochrome P450 (P450) enzymes in an isozyme selective manner. The present study examined the pathological role of ARF in the down-regulation of hepatic P450 enzymes in the cisplatin-treated rats. Male rats with single dose of intraperitoneally cisplatin (5 mg/kg) caused marked changes in renal parameters, BUN and serum creatinine but not hepatic parameters, serum alanine aminotransferase or aspartate aminotransferase. The rats also suffered from down-regulation of hepatic microsomal CYP2C11 and CYP3A2, male specific P450 isozymes, but not CYP1A2, CYP2E1, or CYP2D2. The decrease in serum testosterone level was also observed in injured rats, which was consistent with the selective effects on male specific P450 enzymes. Protection of rats against cisplatin-induced ARF by dimethylthiourea, a hydroxyl radical scavenger, also protected rats against the decrease in serum testosterone levels and the down-regulation of CYP2C11 and CYP3A2. Carboplatin, an analogue to cisplatin but no ARF inducer, did not cause decrease in serum testosterone levels and down-regulation of hepatic male specific P450 enzymes. These results suggest that down-regulation of hepatic P450 enzymes in male rats given cisplatin is closely related to the cisplatin-induced ARF and the resultant impairment of testis function.

Hepatic and renal cytochrome p450 gene regulation during citrobacter rodentium infection in wild-type and toll-like receptor 4 mutant mice

Citrobacter rodentium is the rodent equivalent of human enteropathogenic Escherichia coli infection. This study investigated regulation of hepatic and renal cytochrome P450 (P450) mRNAs, hepatic P450 proteins, cytokines, and acute phase proteins during C. rodentium infection. Female C3H/HeOuJ (HeOu) and C3H/HeJ (HeJ) mice [which lack functional toll-like receptor 4 (TLR4)] were infected with C. rodentium by oral gavage and sacrificed 6 days later. Hepatic CYP4A10 and 4A14 mRNAs were decreased in HeOu mice (<4% of control). CYP3A11, 2C29, 4F14, and 4F15 mRNAs were reduced to 16 to 55% of control levels, whereas CYP2A5, 4F16, and 4F18 mRNAs were induced (180, 190, and 600% of control, respectively). The pattern of P450 regulation in HeJ mice was similar to that in HeOu mice for most P450s, with the exception of the TLR4 dependence of CYP4F15. Hepatic CYP2C, 3A, and 4A proteins in both groups were decreased, whereas CYP2E protein was not. Renal CYP4A10 and 4A14 mRNAs were significantly down-regulated in HeOu mice, whereas other P450s were unaffected. Most renal P450 mRNAs in infected HeJ mice were increased, notably CYP4A10, 4A14, 4F18, 2A5, and 3A13. Hepatic levels of interleukin (IL)-1beta, IL-6, and tumor necrosis factor alpha (TNFalpha) mRNAs were significantly increased in infected HeOu mice, whereas only TNFalpha mRNA was significantly increased in HeJ mice. Hepatic alpha1-acid glycoprotein was induced in both groups, whereas alpha-fibrinogen and angiotensinogen were unchanged. These data indicate that hepatic inflammation induced by C. rodentium infection is mainly TLR4-independent and suggest that hepatic P450 down-regulation in this model may be cytokine-mediated.