Experimental ulcerative colitis impairs antioxidant defense system in rat intestine

Immunomodulatory and therapeutic properties of the Nigella sativa L. seed

A larger number of medicinal plants and their purified constituents have been shown beneficial therapeutic potentials. Seeds of Nigella sativa, a dicotyledon of the Ranunculaceae family, have been employed for thousands of years as a spice and food preservative. The oil and seed constituents, in particular thymoquinine (TQ), have shown potential medicinal properties in traditional medicine. In view of the recent literature, this article lists and discusses different immunomodulatory and immunotherapeutic potentials for the crude oil of N. sativa seeds and its active ingredients. The published findings provide clear evidence that both the oil and its active ingredients, in particular TQ, possess reproducible anti-oxidant effects through enhancing the oxidant scavenger system, which as a consequence lead to antitoxic effects induced by several insults. The oil and TQ have shown also potent anti-inflammatory effects on several inflammation-based models including experimental encephalomyelitis, colitis, peritonitis, oedama, and arthritis through suppression of the inflammatory mediators prostaglandins and leukotriens. The oil and certain active ingredients showed beneficial immunomodulatory properties, augmenting the T cell- and natural killer cell-mediated immune responses. Most importantly, both the oil and its active ingredients expressed anti-microbial and anti-tumor properties toward different microbes and cancers. Coupling these beneficial effects with its use in folk medicine, N. sativa seed is a promising source for active ingredients that would be with potential therapeutic modalities in different clinical settings. The efficacy of the active ingredients, however, should be measured by the nature of the disease. Given their potent immunomodulatory effects, further studies are urgently required to explore bystander effects of TQ on the professional antigen presenting cells, including macrophages and dendritic cells, as well as its modulatory effects upon Th1- and Th2-mediated inflammatory immune diseases. Ultimately, results emerging from such studies will substantially improve the immunotherapeutic application of TQ in clinical settings.

Selective expression of detoxifying glutathione transferases in mouse colon: effect of experimental colitis and the presence of bacteria

Glutathione transferases (GSTs) play a central role in the cellular defense against harmful endogenous compounds and xenobiotics in mouse and man. The gastrointestinal channel is constantly exposed to bacteria, bacterial products, and xenobiotics. In the present study the distribution of alpha, mu, and pi class GSTs was examined immunohistologically in the colon of conventional and germ-free (GF) mice subjected to experimental colitis. The tissues samples were from conventional mice with and without colitis induced by dextran sulfate sodium (DSS); GF mice treated with DSS or carrageenan; and GF mice inoculated with normal mouse bacterial flora as well as with Lactobacillus GG. In conventional as well as in GF mice the mu and pi class GSTs showed reduced intestinal expression when colitis was induced. In con-rast, the level of GSTs reacting with antibodies directed against the alpha class, in particular mGST A4-4, was elevated after induction of inflammation. Of special interest is mGST A4-4 because of its high catalytic activity with toxic products of lipid peroxidation. In the colon of conventionalized GF mice that were given mouse intestinal flora, the mGST A4-4 expression was increased with time for several weeks, but then showed a decrease to a normal level. Additionally, the inoculation of GF mice with Lactobacillus GG induced all the intestinal GSTs studied.

Glycosaminoglycans reduce oxidative damage induced by copper (Cu+2), iron (Fe+2) and hydrogen peroxide (H2O2) in human fibroblast cultures

Acid glycosaminoglycans (GAGs) antioxidant activity was assessed in a fibroblast culture system by evaluating reduction of oxidative system-induced damage. Three different methods to induce oxidative stress in human skin fibroblast cultures were used. In the first protocol cells were treated with CuSO4 plus ascorbate. In the second experiment fibroblasts were exposed to FeSO4 plus ascorbate. In the third system H2O2 was utilised. The exposition of fibroblasts to each one of the three oxidant systems caused inhibition of cell growth and cell death, increase of lipid peroxidation evaluated by the analysis of malondialdehyde (MDA), decrease of reduced glutathione (GSH) and superoxide dismutase (SOD) levels, and rise of lactate dehydrogenase activity (LDH). The treatment with commercial GAGs at different doses showed beneficial effects in all oxidative models. Hyaluronic acid (HA) and chondroitin-4-sulphate (C4S) exhibited the highest protection. However, the cells exposed to CuSO4 plus ascorbate and FeSO4 plus ascorbate were better protected by GAGs compared to those exposed to H2O2. These outcomes confirm the antioxidant properties of GAGs and further support the hypothesis that these molecules may function as metal chelators.

Suppression of dextran sodium sulfate-induced colitis in mice by zerumbone, a subtropical ginger sesquiterpene, and nimesulide: separately and in combination

Ulcerative colitis (UC) and Crohn's disease are inflammatory disorders of unknown cause and difficult to treat, though some synthetic chemicals, including ligands for peroxisome proliferator-activated receptors (PPARs), are anticipated to be useful drugs. In contrast, few food phytochemicals have been reported to suppress colitis in animal models. The present study was undertaken to explore the suppressive efficacy of zerumbone (ZER), a sesquiterpenoid present in the rhizome of Zingiber zerumbet Smith that is used as a condiment in Southeast Asian countries and known to be a potent suppressant of cyclooxygenase (COX)-2 and inducible nitric oxide synthase expression in cell culture systems. Acute colitis was induced by exposing female ICR mice to 5% DSS in drinking water for 1 week. One week prior to DSS administration, the experimental mice were fed ZER alone, nimesulide (NIM, a selective COX-2 inhibitor) alone, or both in combination (1000 ppm each) for a total of 2 weeks. Inflammatory biomarkers, i.e. interleukin (IL)-1alpha and IL-1beta, tumor necrosis factor (TNF)-alpha, and prostaglandin (PG)E(2) and PGF(2alpha) in colonic mucosa were quantified by an enzyme-linked immunosorbent assay in conjunction with histological alterations. Oral feeding of ZER significantly lowered the levels of IL-1beta [inhibitory rate (IR)=34%], TNF-alpha (IR=29%), and PGE(2) (IR=73%) and suppressed DSS-induced colitis, whereas NIM suppressed the histological changes induced by DSS without affecting inflammatory biomarkers. However, their treatment in combination was most effective for suppressing these biomarkers. Our results suggest that ZER is a novel food factor for mitigating experimental UC and that use of a combination of agents, with different modes of actions, may be an effective anti-inflammatory strategy.

Glutathione supplementation improves oxidative damage in experimental colitis

BACKGROUND

The pathogenesis of inflammatory bowel disease is due, in part, to enhanced free-radical production and reduced antioxidant potential in mucosa cells.

AIM

We evaluated in a rat model of trinitrobenzensulphonic acid (TNBS) colitis to see whether parenteral administration of glutathione is able to improve mucosal oxidative damage at onset (study A) and during chronic phases of colitis (study B).

METHODS

In study A, the rats were injected with a single dose of glutathione (200 mg/kg, i.p.) or saline (0,2 ml, i.p.) 1 h before colitis induction and killed 1 h later. In study B, rats with induced colitis were treated with daily injection of glutathione (50 mg/kg, i.p.) or saline (0,2 ml, i.p.), and killed at 1, 2, 4 and 8 weeks. We evaluated on mucosal samples the macroscopic and histological damage and the oxidative stress assessed by the mucosal levels of lipoperoxides, malonyldialdehyde, glutathione and cysteine.

RESULTS

In study A, colitis induction caused a significant increase to the total histological score (p<0.05), lipoperoxide and malonyldialdehyde levels (p<0.001), but did not affect glutathione and cysteine content. Glutathione pre-treatment decreased both total histological score (p<0.05) and lipoperoxide and malonyldialdehyde values (p<0.001). In study B, the extensive macroscopic and histological colonic damage induced by TNBS was accompanied by a reduction of glutathione and cysteine mucosal levels (p<0.01) and increased lipid peroxidation. Glutathione supplementation significantly improved colonic damage (p<0.01), restored glutathione and cysteine levels, and decreased, and even, if not totally, abolished lipid peroxidation (p<0.001).

CONCLUSION

This paper further supports the pathogenic role of the imbalance in oxidant/antioxidant content in inducing mucosal colonic damage.

Glutathione

Glutathione (GSH) is an ubiquitous thiol-containing tripeptide that plays a key role in cell biology. It modulates cell response to redox changes associated with the reactive oxygen species, detoxifies the metabolites of drugs; regulates gene expression and apoptosis, and is involved in the transmembrane transport of organic solutes. Polymorphism has been observed in key enzymes of GSH metabolism and some alleles have been associated with an impaired redox buffer system downsteam diseases, and susceptibility to ischaemia. These varied activities make GSH an attractive target for a more reductionist approach to the prevention and management of many conditions of interest to surgeons.

Evidence for oxidative stress in NSAID-induced colitis in IL10-/- mice

The goal of this study was to evaluate for evidence of oxidative stress in colonic inflammation in a novel model of inflammatory bowel disease, nonsteroidal anti-inflammatory drug- (NSAID-) treated interleukin-10-deficient (IL10(-/-)) mice. IL10(-/-) and wild-type (wt) mice were treated with a nonselective NSAID (piroxicam, 200 ppm in the diet) for 2 weeks to induce colitis, and parameters for oxidative stress in the colonic tissues were evaluated. Mean chemiluminescence enhanced with lucigenin in the colons from IL10(-/-) mice treated with piroxicam was more than 5-fold higher than that of the control wt group. Chemiluminescence was inhibited with diphenylethylene iodinium, but not allopurinol, indomethacin, or N-omega-nitro-L-arginine, indicating that flavin-containing enzymes were the source of the reactive oxygen species. Colonic aconitase activity in NSAID-treated IL10(-/-) mice decreased to 50% of the activity of control mice. There was no difference in the total glutathione levels in the colonic mucosa among the groups; however, glutathione disulfide levels were approximately 2-fold greater in the colon of NSAID-treated IL10(-/-) mice as compared with control groups. Immunohistochemistry studies of colons from NSAID-treated IL10(-/-) mice demonstrated intense staining with two antibodies that recognize advanced glycation endproducts formed through glycation and oxidation: anticarboxymethylysine and antipentosidine. The epithelial cells and lamina propria cells in the colons of NSAID-treated IL10(-/-) mice showed immunostaining with antinitrotyrosine, indicating the presence of reactive nitrogen species. Colonic epithelium of IL10(-/-) mice with colitis showed moderate immunostaining for 8-hydroxy-2'-deoxyguanosine in the nuclei. NSAID-treated IL10(-/-) mice treated with diphenylene idodonium chloride (DPI), an irreversible inhibitor of flavoprotein enzymes, experienced significantly reduced inflammation. Taken together, these results strongly indicate the presence of oxidative stress in the inflammatory bowel disease in NSAID-treated IL10(-/-) mice and suggests a role for oxidative stress in the pathophysiology of this model of inflammatory bowel disease.

Synergistic suppression of superoxide and nitric oxide generation from inflammatory cells by combined food factors

In contrast to chemopreventive strategies using individual agents, a combination of specified compounds may be effectual to achieve desirable results with higher efficacy and lower toxicity. In the present in vitro study, we examined combinations of agents and assessed which concentrations were appropriate to yield notable synergism. L-N(G)-Monomethyl-L-arginine (L-NMMA), a synthetic inducible nitric oxide synthase (iNOS) inhibitor, and zerumbone, a natural sesquiterpene that suppresses iNOS de novo synthesis, were combined at various concentrations, with the aim to diminish combined lipopolysaccharide- and interferon-gamma-induced nitric oxide generation in a murine macrophage line, RAW264.7. Although the combinatorial effects (CEs) were antagonistic or additive at higher concentrations, significant synergism was obtained at lower concentrations where each agent alone did not cause significant inhibition. Similarly, the CEs were synergistic when (-)-epigallocatechin gallate (EGCG) and genistein were combined at lower concentrations, whereas those of two iNOS inhibitors, L-NMMA and L-N(G)-aminoethyl-L-ornithine, were either additive or antagonistic at all concentrations tested, suggesting that a combination of given agents with different action mechanisms is a prerequisite for synergistic effects. For suppression of phorbol ester-induced superoxide anion radical (O(2)*(-)) generation in differentiated HL-60 cells, the CEs of 1'-acetoxycahvicol acetate (ACA), a phenyl propanoid that suppresses O(2)*(-) generation, and O(2)*(-) dismutase were also synergistic, though only at lower concentrations. The CEs of ACA/EGCG were antagonistic or additive, even at low concentrations, suggesting that the signal transduction pathways triggered by these agents are antagonistic. The present findings suggest that individual food phytochemicals have complex interactions that can be antagonistic, additive, and/or synergistic in biological systems, depending upon certain environmental factors including concentrations. Further, these results support and emphasize the concept that combinations of different types of chemicals at low concentrations are one of the essential areas of study for chemopreventive strategies.

The protective and healing effects of a natural antioxidant formulation based on ubiquinol and Aloe vera against dextran sulfate-induced ulcerative colitis in rats

Oxygen/nitrogen reactive species (ROS/RNS) are currently implicated in the pathogenesis of ulcerative colitis, drawing attention on the potential prophylactic and healing properties of antioxidants, scavengers, chelators. We evaluated the possible protective/curative effects of a natural antioxidant preparation based on Aloe vera and ubiquinol, against intestinal inflammation, lesions, and pathological alterations of the intestinal electrophysiological activity and motility, in a rat model of DSS-induced colitis. 5% dextrane sulfate (DDS) (3 days), followed by 1% DSS (4 days) was administered in drinking water. The antioxidant formulation (25 mg/kg) was delivered with a pre-treatment protocol, or simultaneously or post-colitis induction. Spontaneous and acetylcholine-stimulated electrical activity were impaired in the small intestine and in distal colon, upon exposure to DSS only. Severe inflammation occurred, with increased myeloperoxidase activity, and significant alterations of the oxidant/antioxidant status in colonic tissue and peritoneal cells. Lipoperoxidation, superoxide production, glutathione peroxidase and glutathione-S-transferase activities, and reduced glutathione content increased, whilst superoxide dismutase and catalase activities were sharply suppressed in colon tissue. ROS/RNS formation in peritoneal cells was strongly inhibited. Inflammation, electrical/mechanical impairment in the gut, and a great majority of oxidative stress parameters were improved substantially by pre-treatment with the antioxidant preparation, but not by simultaneous administration or post-treatment.

Vitamin A deficiency exacerbates inflammation in a rat model of colitis through activation of nuclear factor-kappaB and collagen formation

Inflammatory bowel disease is characterized by oxidative stress, inflammation and tissue damage. Vitamin A is an antioxidant, a regulator of epithelial proliferation and differentiation and vital for optimal immune function. To investigate the effect of vitamin A on the course of colitis, it was induced by administration of trinitrobenzene sulfonic acid (TNBS) into the colons of rats fed for 7 wk vitamin A-deficient (VAD), sufficient (VAS) or supplemented (VASUP) diet, or VAS pair-fed (PF) to the VAD rats. Inflammation and fibrosis were examined by hematoxin and eosin, and Sirius red staining. Activation of nuclear factor-kappaB (NF-kappaB) and oxidative stress were determined by electrophoretic mobility shift and plasma malondialdehyde (MDA) and RBC Cu/Zn-superoxide dismutase activity, respectively. Vitamin A deficiency in the noncolitic rats impaired food consumption and weight gain (P < 0.05) and increased plasma MDA, (P = 0.01) activity of NF-kappaB (P < 0.05) and deposition of collagen in the colon. Our data suggest that vitamin A deficiency induces colonic inflammation. Colitis is amplified by deficiency and ameliorated by supplementation of the vitamin. These findings have implications for the management of inflammatory bowel disease.

Role of reactive metabolites of oxygen and nitrogen in inflammatory bowel disease

The inflammatory bowel diseases (IBD; Crohn's disease, ulcerative colitis) are a collection of chronic idiopathic inflammatory disorders of the intestine and/or colon. Although the pathophysiology of IBD is not known with certainty, a growing body of experimental and clinical data suggests that chronic gut inflammation may result from a dysregulated immune response to normal bacterial antigens. This uncontrolled immune system activation results in the sustained overproduction of reactive metabolites of oxygen and nitrogen. It is thought that some of the intestinal and/or colonic injury and dysfunction observed in IBD is due to elaboration of these reactive species. This review summarizes the current state-of-knowledge of the role of reactive oxygen species and nitric oxide in the pathophysiology of IBD.

The conversion of redox status of peritoneal macrophages during pathological progression of spontaneous inflammatory bowel disease in Janus family tyrosine kinase 3(-/-) and IL-2 receptor gamma(-/-) mice

The distinct thiol redox status in macrophages, either elevated or reduced intracellular content of glutathione (GSH), was confirmed during aging in IL-2 receptor (IL-2R)gamma and Janus family tyrosine kinase (JAK)3 gene-disrupted mice. Oxidative macrophages (OMp) with reduced GSH dominated initially at a younger age in both mice. OMp-dominated JAK3 or IL-2R gamma chain-deficient mice showed shortened life longevity compared with wild-type littermates. These mice elicited spontaneous onsets of inflammatory bowel disease (IBD)-like symptoms accompanied with the conversion of the redox status of macrophages to reductive phenotypes with elevated intracellular GSH. Conversion of OMp to the reductive phenotype by GSH monoethyl ester or by a beta-(1-3)-glucan accelerated the disease onset, concomitant with the skewing from T(h)2 to T(h)1 responses. On the contrary, N,N'-diacetyl cystine dimethylester, which is capable of inducing OMp, delayed the incidence of IBD-like symptoms and improved the survival rate. This implies that the conversion of OMp/T(h)2 to reductive macrophages/T(h)1 may be critical for the disease progression. The study of these mice may provide insight into the mechanisms underlying Crohn's disease and ulcerative colitis.

Beneficial effect of a novel non-steroidal anti-inflammatory agent with basic character and antioxidant properties on experimental colitis in rats

Ulcerative colitis is a chronic disorder of unknown etiology. Conservative treatment remains empirical, even today. The aim of this study was to test the efficacy of a novel non-steroidal anti-inflammatory agent [5-(2-hydroxy-ethylamino)-1-cyclohexyl-2-pentanone] (compound A), with basic character and antioxidant properties on an experimental model of ulcerative colitis in rats. The effect of this compound was compared with that of methylprednisolone on the histological abnormalities and serum levels of tumor necrosis factor-alpha (TNF-alpha) in experimental colitis produced by 2,4,6-trinitrobenzenesulfonic acid (TNB). A total number of 24 rats were randomly assigned to one of four groups of six rats each. Group 1: colitis without treatment (disease control), group 2: normal animals (control), group 3: induction of experimental colitis treated with methylprednisolone (5.3 x 10(-3) mmol/kg i.v. every day for 7 days) and group 4: induction of experimental colitis plus administration of compound A (0.6 mmol/kg i.v. every day for 7 days). The administration of compound A resulted in a statistically significant reduction of the extent of tissue damage and of certain histological features (edema, inflammatory infiltration) (P<0.05). Compound A also resulted in a statistically significant reduction of the levels of serum TNF-alpha, compared to those of controls (P<0.005). The beneficial effect of this compound was probably due to the combination, on a single molecule, of anti-inflammatory and antioxidant properties as well as to its basic character. The reduction of the serum TNF-alpha levels could be one of the possible mechanism(s) of action of the compound. Further studies are necessary to establish the direct mechanism of action(s) of the drug and to evaluate its long-term efficacy and safety.

Dietary polyunsaturated fatty acids improve histological and biochemical alterations in rats with experimental ulcerative colitis

The aim of the present study was to determine whether dietary intake of monounsaturated (MUFA) and/or polyunsaturated fatty acids (PUFA) of the (n- 3) and (n-6) series could improve intestinal damage and reduce inflammation in experimental ulcerative colitis (UC). Rats were treated with 80 mg/kg body of 2,4,6-trinitrobenzenesulfonic acid and fed for 1 or 2 wk diets enriched in olive oil (OO), fish oil (FO), or purified pig brain phospholipids (BPL), as sources of monounsaturated and PUFA of the (n-3) and (n-3) + (n-6) series. Evaluation of macroscopic and microscopic colonic damage was assessed. Ultrastructural and histologic changes were analyzed as well as plasma and colonic mucosa fatty acid profiles and some biochemical markers of injury and inflammation [alkaline phosphatase (AP), mieloperoxidase (MPO), prostaglandin E(2) (PGE(2)) and leukotriene B(4)]. Fatty acid profiles of both plasma and mucosa mostly reflected the dietary fatty acid composition. Plasma MUFA proportions were higher in UC animals fed the OO diet compared with FO or BPL groups 1 and 2 wk and (n-3) long chain PUFA (LC-PUFA) were higher in the FO than in the OO and BPL groups. At 1 wk, UC led to lower MUFA mucosa levels and (n-3)LC-PUFA were higher in the FO group compared with the OO and BPL groups. Rats with UC fed FO at 1 wk showed significantly less macroscopic and microscopic colonic damage. They also have lower AP and MPO activities and PGE(2) levels compared with the OO and BPL groups and showed enhanced histological repair, less necrotic areas within the mucosa, and more goblet cells with mature mucin granules. These results suggest that the use of balanced diets containing (n-3) LC-PUFA could ameliorate the inflammation and mucosal damage in UC.