Nitric oxide supplementation ameliorates dextran sulfate sodium-induced colitis in mice

O-GlcNAc modification in endothelial cells modulates adiposity via fat absorption from the intestine in mice

Introduction

Endothelial cells have a crucial function in transporting and exchanging various nutrients. O-GlcNAcylation, mediated by O-GlcNAc transferase (OGT), involves the addition of N-acetylglucosamine to proteins and serves as an intracellular nutrient sensing mechanism. However, the role of O-GlcNAcylation in endothelial cells remains poorly understood.

Objective

This study investigated the role of O-GlcNAcylation in endothelial cells.

Methods

Endothelial-cell-specific Ogt -knockout mice (Ogt-ECKO) were generated by crossing Ogt-floxed mice (Ogt-flox) with VE-Cadherin Cre ERT2 mice. Ogt-ECKO mice and Ogt-flox control mice were subjected to a normal or high-fat diet, and their body weight, glucose metabolism, and lipid metabolism were examined.

Results

Ogt-ECKO mice exhibited reduced body weight compared with Ogt-flox control mice under a high-fat diet. Lipid absorption was significantly impaired in Ogt-ECKO mice. Changes in the intercellular junctions of small intestinal lacteal endothelial cells from a button-like to a zipper-like configuration were observed. Furthermore, Ogt-ECKO mice showed decreased expression of VEGFR3. The administration of a nitric oxide donor restored lipid absorption and reversed the morphological alterations in Ogt-ECKO mice.

Conclusions

These findings demonstrate the critical role of O-GlcNAcylation in endothelial cells in lipid absorption in the intestine through the modulation of lacteal junction morphology. These results provide novel insight into the metabolic regulatory mechanisms under physiological conditions and have implications for the development of new therapeutic strategies for obesity.

Ameliorative effect of nodakenin in combating TNBS-induced ulcerative colitis by suppressing NFƙB-mediated NLRP3 inflammasome pathway

Ulcerative colitis (UC) is an enduring and complex inflammatory bowel disease that is clinically prevalent, progressive, and debilitating. As of now, the few effective medical treatments for UC have unacceptably high side effects. It is crucial to find safer and more effective UC treatments. Nodakenin possesses anti-inflammatory and antioxidant activity by suppressing several pro-inflammatory mediators. In the present study, we aimed to evaluate the colonoprotective effect of nodakenin in combating colitis through the NFƙB-mediated NLRP3 inflammasome pathway. In mice, UC was induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). Nodakenin (10, 20, and 40 mg/kg) was introduced intragastrically, and disease activity index (DAI) score was calculated. Malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD), nitric oxide (NO) levels, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) concentration were evaluated in colon homogenate. Colon samples were used for histopathological investigation and mRNA expression studies involving nuclear factor kappa B (NFƙB), cyclooxygenase-2 (COX-2), inducible nitric oxide (iNOS), nucleotide-binding receptor domain 3 (NLRP3), interleukin-1β (IL-1β), and interleukin-18 (IL-18). Nodakenin treatment was found effective in lowering the DAI score, histological score, MPO, MDA, and NO levels while elevating SOD levels as compared to the model control group, showcasing its anti-inflammatory and antioxidant properties. Nodakenin (40 mg/kg) significantly downregulated the expression of TNF-α, IL-6, NFƙB (1.24-fold), iNOS (1.2-fold), COX-2 (1.98-fold), NLRP3 (1.78-fold), IL-1β (1.29-fold), and IL-18 (1.17-fold) conferring its great anti-inflammatory potential in combating colitis. Taking together, nodakenin presumably alleviated TNBS-induced colitis by NFƙB-mediated NLRP3 inflammasome pathway and reduced colon damage by downregulating various transcriptional genes and pro-inflammatory mediators.

Tetramerization of STAT5 regulates monocyte differentiation and the dextran sulfate sodium-induced colitis in mice

In response to external stimuli during immune responses, monocytes can have multifaceted roles such as pathogen clearance and tissue repair. However, aberrant control of monocyte activation can result in chronic inflammation and subsequent tissue damage. Granulocyte-macrophage colony-stimulating factor (GM-CSF) induces monocyte differentiation into a heterogenous population of monocyte-derived dendritic cells (moDCs) and macrophages. However, the downstream molecular signals that dictate the differentiation of monocytes under pathological conditions is incompletely understood. We report here that the GM-CSF-induced STAT5 tetramerization is a critical determinate of monocyte fate and function. Monocytes require STAT5 tetramers to differentiate into moDCs. Conversely, the absence of STAT5 tetramers results in a switch to a functionally distinct monocyte-derived macrophage population. In the dextran sulfate sodium (DSS) model of colitis, STAT5 tetramer-deficient monocytes exacerbate disease severity. Mechanistically, GM-CSF signaling in STAT5 tetramer-deficient monocytes results in the overexpression of arginase I and a reduction in nitric oxide synthesis following stimulation with lipopolysaccharide. Correspondingly, the inhibition of arginase I activity and sustained supplementation of nitric oxide ameliorates the worsened colitis in STAT5 tetramer-deficient mice. This study suggests that STAT5 tetramers protect against severe intestinal inflammation through the regulation of arginine metabolism.

L-citrulline enriched fermented milk with Lactobacillus helveticus attenuates dextran sulfate sodium (DSS) induced colitis in mice

Inflammatory bowel disease (IBD) is a group of chronic inflammatory gastrointestinal diseases that causes worldwide suffering. L. helveticus is a probiotic that can enhance intestinal barrier function via alleviation of excessive inflammatory response. Citrulline, a functional amino acid, has been reported to stimulate muscle synthesis and to function with a prebiotic-like action with certain Lactobacillus strains. The aim of this study was to investigate the potential synergistic effect of combining L. helveticus and citrulline on protection against damage induced by dextran sulfate sodium (DSS) in a mouse model. 6-week-old male C57BL/6J mice were fed with DSS water and randomly divided for administering with different milk treatments: 1) plain milk (control or DSS control), 2) 1% (w/v) citrulline enriched milk (Cit_milk), 3) milk fermented with L. helveticus (LHFM) and 4) DSS+milk fermented with L. helveticus with 1% (w/v) citrulline (Cit_LHFM). The treatment effects on the survival and macroscopic and microscopic signs were examined. All treatments presented different degrees of protective effects on attenuating the damages induced by DSS. All treatments reduced the body weight loss, disease activity index (DAI), histological scores, pro-inflammatory cytokine expression (IL-6, TNF-α and IFN-γ) and production (IL-4) (all P <0.05) and the tight junction (TJ) protein (zonula occluden-1 (ZO-1) expression. LHFM and Cit_LHFM improved survival rate (both at P<0.05). Particularly, Cit_LHFM showed greater effects on protecting the damages induced by DSS, especially in ameliorating colonic permeability, TJ protein (ZO-1, occludin and claudin-1) expression and distribution as well as in reducing IL-4 and IL-17 expression (all P <0.05). Our findings suggested that the combination of and citrulline had significant synergistic effect on protecting against injury from DSS-induced colitis. Therefore, citrulline enriched L. helveticus fermented milk is suggested to be a potential therapy for treating IBD.

Temporal inhibition of mouse mammary gland cancer metastasis by CORM-A1 and DETA/NO combination therapy

Carbon monoxide and nitric oxide are two of the most important vasoprotective mediators. Their downregulation observed during vascular dysfunction, which is associated with cancer progression, leads to uncontrolled platelet activation. Therefore, the aim of our studies was to improve vasoprotection and to decrease platelet activation during progression of mouse mammary gland cancer by concurrent use of CO and NO donors (CORM-A1 and DETA/NO, respectively). Methods: Mice injected intravenously with 4T1-luc2-tdTomato or orthotopically with 4T1 mouse mammary gland cancer cells were treated with CORM-A1 and DETA/NO. Ex vivo aggregation and activation of platelets were assessed in the blood of healthy donors and breast cancer patients. Moreover, we analyzed the compounds' direct effect on 4T1 mouse and MDA-MB-231 human breast cancer cells proliferation, adhesion and migration in vitro. Results: We have observed antimetastatic effect of combination therapy, which was only transient in orthotopic model. During early stages of tumor progression concurrent use of CORM-A1 and DETA/NO demonstrated vasoprotective ability (decreased endothelin-1, sICAM and sE-selectin plasma level) and downregulated platelets activation (decreased bound of fibrinogen and vWf to platelets) as well as inhibited EMT process. Combined treatment with CO and NO donors diminished adhesion and migration of breast cancer cells in vitro and inhibited aggregation as well as TGF-β release from breast cancer patients' platelets ex vivo. However, antimetastatic effect was not observed at a later stage of tumor progression which was accompanied by increased platelets activation and endothelial dysfunction related to a decrease of VASP level. Conclusion: The therapy was shown to have antimetastatic action and resulted in normalization of endothelial metabolism, diminution of platelet activation and inhibition of EMT process. The effect was more prominent during early stages of tumor dissemination. Such treatment could be applied to inhibit metastasis during the first stages of this process.

Gasotransmitters and the immune system: Mode of action and novel therapeutic targets

Gasotransmitters are a group of gaseous molecules, with pleiotropic biological functions. These molecules include nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO). Abnormal production and metabolism of these molecules have been observed in several pathological conditions. The understanding of the role of gasotransmitters in the immune system has grown significantly in the past years, and independent studies have shed light on the effect of exogenous and endogenous gasotransmitters on immune responses. Moreover, encouraging results come from the efficacy of NO-, CO- and H₂S -donors in preclinical animal models of autoimmune, acute and chronic inflammatory diseases. To date, data on the influence of gasotransmitters in immunity and immunopathology are often scattered and partial, and the scarcity of clinical trials using NO-, CO- and H₂S -donors, reveals that more effort is warranted. This review focuses on the role of gasotransmitters in the immune system and covers the evidences on the possible use of gasotransmitters for the treatment of inflammatory conditions.

Goat whey ameliorates intestinal inflammation on acetic acid-induced colitis in rats

Complementary or alternative medicine is of great interest for the treatment of inflammatory bowel disease, with the aim of ameliorating the side effects of the drugs commonly used or improving their efficacy. In this study, we evaluated the ability of goat whey to prevent intestinal inflammation in the experimental model of acetic acid-induced rats and compared it to sulfasalazine. Pretreatment with goat whey (1, 2, and 4g/kg) and sulfasalazine (250mg/kg) on colitic rats improved colonic inflammatory markers, including myeloperoxidase activity, leukotriene B₄ levels, as well as the production of proinflammatory cytokines IL-1β and tumor necrosis factor-α. Furthermore, the administration of goat whey significantly reduced the colonic oxidative stress by reducing malondialdehyde levels and increased total glutathione content, a potent antioxidant peptide. The histological evaluation of the colonic specimens from colitic rats confirmed these beneficial effects, as goat whey preserved the colonic tissue, especially in those rats treated with the highest dose of goat whey or with sulfasalazine. The immunohistochemistry analysis of the colonic tissue evaluation also revealed a reduction in the expression of cyclooxygenase-2, inducible nitric oxide synthase, and matrix metalloproteinase-9, together with an increased expression of suppressor of cytokine signaling-1. These results suggest that goat whey exerted a preventive effect against the intestinal damage induced by acetic acid, showing a similar efficacy to that shown by sulfasalazine, therefore making it a potential treatment for human inflammatory bowel disease.

Temporal and spatial dependence of inflammatory biomarkers and suppression by fluvastatin in dextran sodium sulfate-induced rat colitis model

BACKGROUND

Dextran sodium sulfate (DSS)-induced colitis in rats is widely used as an experimental model for elucidating the etiology of ulcerative colitis (UC) and developing its novel remedy. We investigated the temporal and spatial changes in inflammatory mediators such as tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) in the regions of rectum and distal colon and examined whether statins, which were designed to lower plasma cholesterol levels, influenced those mediators.

METHODS

Colitis was induced in rats by oral administration of 5 % DSS for 5 days, followed by 2 % DSS for 10 days. 5 % DSS rats were treated with fluvastatin (20 mg/kg) concomitantly for 5 days. The expression of inflammatory mediators of a sequence of four regions in rectum (R) and distal colon (D0, D1, and D2) was determined by quantitative RT-PCR.

RESULTS

The peak of colitic damage, which was confirmed clinically and histopathologically, was found on days 4-6. The expression of TNF-α, iNOS, cytokine-induced neutrophil chemoattractant-1, interleukin (IL)-1β, and IL-6 mRNA increased in R time dependently, showing the peak on days 4-6, and then decreased thereafter. The levels of mRNAs reduced from R to D0, D1, and D2 region dependently. Fluvastatin decreased the expression of these markers in addition to the prevention of DSS-induced damage.

CONCLUSIONS

Results demonstrated that the expression of inflammatory biomarkers had time and region specificity and was markedly inhibited by fluvastatin. To obtain a precise drug effect for UC, it is important to elucidate the temporal and spatial dependence of inflammatory biomarkers in DSS colitis model.

Involvement of nitric oxide with activation of Toll-like receptor 4 signaling in mice with dextran sodium sulfate-induced colitis

Ulcerative colitis is an inflammatory bowel disease characterized by acute inflammation, ulceration, and bleeding of the colonic mucosa. Its cause remains unknown. Increases in adhesion molecules in vascular endothelium, and activated neutrophils releasing injurious molecules such as reactive oxygen species, are reportedly associated with the pathogenesis of dextran sodium sulfate (DSS)-induced colitis. Nitric oxide (NO) production derived from inducible NO synthase (iNOS) via activation of nuclear factor κB (NF-κB) has been reported. It is also reported that stimulation of Toll-like receptor 4 (TLR4) by lipopolysaccharide can activate NF-κB. In this study, we investigated the involvement of NO production in activation of the TLR4/NF-κB signaling pathway in mice with DSS-induced colitis. The addition of 5% DSS to the drinking water of male ICR mice resulted in increases in TLR4 protein in colon tissue and NF-κB p65 subunit in the nuclear fraction on day 3, increases in colonic tumor necrosis factor-α on day 4, and increases in P-selectin, intercellular adhesion molecule-1, NO2(-)/NO3(-), and nitrotyrosine in colonic mucosa on day 5. These activated inflammatory mediators and pathology of colitis were completely suppressed by treatment with a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, as well as an iNOS inhibitor, aminoguanidine. Conversely, a NO-releasing compound, NOC-18, increased TLR4 levels and nuclear translocation of NF-κB p65 and exacerbated mucosal damage induced by DSS challenge. These data suggest that increases in TLR4 expression induced by drinking DSS-treated water might be directly or indirectly associated with NO overproduction.

Concentrated grape juice (G8000™) reduces immunoexpression of iNOS, TNF-alpha, COX-2 and DNA damage on 2,4,6-trinitrobenzene sulfonic acid-induced-colitis

Inflammatory bowel disease (IBD) is a common chronic gastrointestinal disorder characterized by alternating periods of remission and active intestinal inflammation. Flavonoids exert several biological activities, which are mainly related to their ability to inhibit inflammatory process and/or to their antioxidant properties, and are able to regulate the immune response. The aim of this study was to evaluate whether phenolic compounds present in grape juice could reduce the inflammatory effects induced by experimental colitis. A total of 41 male Wistar rats were randomized into seven groups, as follows: G1--Sham group: sham induced-colitis rats; G2--(2,4,6-rinitrobenzenesulfonic acid) TNBS group: nontreated induced-colitis; G3--2% grape juice control group; G4--1% grape juice 24h after TNBS colitis induction; G5--1% grape juice on day 7 after colitis induction; G6--2% grape juice 24h after colitis induction; G7--2% grape juice on day 7 after colitis induction. Genotoxicity was evaluated by comet assay. Immunohistochemistry was determined using the streptavidin-biotin-peroxidase method being analyzed in control (normal tissue) and "hot spot" areas i.e., presenting inflammatory process being graded as 1 (weak), 2 (moderate), or 3 (strong). Both parameters were evaluated in the cytoplasm of epithelial or inflammatory cells. TNF-immunoexpression and iNOS were reduced after drinking grape juice 24 h or after 7 days for all doses tested. COX-2 was reduced in the groups exposed to 1% grape juice 24 h or 7 days of exposure. The grape juice at 1% dose in the last 7 days of treatment as well as grape juice at 2% dose decreased the peripheral blood genotoxicity. Taken together, the grape juice mainly at 1% dose exerts anti-inflammatory effects in chronic colitis caused by TNBS as a result of down regulation in the expression of pro-inflammatory cytokines and reduction of genotoxicity in peripheral blood cells.

The anti-inflammatory potential of phenolic compounds in grape juice concentrate (G8000™) on 2,4,6-trinitrobenzene sulphonic acid-induced colitis

Chronic inflammatory bowel disease is characterised by an up-regulation of the synthesis and release of a variety of pro-inflammatory mediators leading to excessive tissue injury. Flavonoids are able to inhibit enzymes and/or due to their antioxidant properties regulate the immune response. The goal of the present study was to evaluate the mechanisms of action of phenolic compounds present in grape juice on 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis. A total of forty-one male Wistar rats were randomised into seven groups: negative control group; TNBS non-treated induced colitis; 2 % grape juice control group; 1 % grape juice 24 h after TNBS colitis induction; 1 % grape juice on day 7 after colitis induction; 2 % grape juice 24 h after colitis induction; 2 % grape juice on day 7 after colitis induction. The 1 % grape juice-treated induced colitis group showed marked clinical improvement when compared with the TNBS-induced colitis group. Rats that received 1 % grape juice, on day 7 after colitis induction, presented reduced intensity of macroscopic and histological scores. Statistically significant differences (P< 0·05) of TNF-α and inducible NO synthase mRNA expression were detected in the groups treated with grape juice at the 1 % dose after inducing experimental colitis when compared with the TNBS group. Grape juice reduced the noxious effects induced by colitis caused by TNBS, especially at the 1 % dose.

Anti-inflammatory Effect of Oyster Shell Extract in LPS-stimulated Raw 264.7 Cells

This study was designed to investigate the anti-inflammatory effect of oyster shell extract on the production of pro-inflammatory factors [NO, reactive oxygen species (ROS), nuclear factor-kappa B (NF-κB), inducible nitric oxide synthase (iNOS) and cycloxygenase-2 (COX-2)] and pro-inflammatory cytokines [Interleukin-1β (IL-1β), Interleukin-6 (IL-6) and TNF-α] in the lipopolysaccharide (LPS)-stimulated Raw 264.7 cells. Cell viability, as measured by the MTT assay, showed that oyster shell extract had no significant cytotoxicity in Raw 264.7 cells. The treatment with oyster shell extract decreased the generation of intracellular reactive oxygen species dose dependently and increased antioxidant enzyme activities, such as SOD, catalase, GSH-px in LPS-stimulated macrophage cells. Oyster shell extract significantly suppressed the production of NO and also decreased the expressions of iNOS, COX-2 and NF-κB. Additionally, oyster shell extract significantly inhibited the production of IL-1β, IL-6, and TNF-α in LPS-stimulated Raw 264.7 cells. Thus, these results showed that the oyster shell extract had an anti-inflammatory effect on LPS-stimulated Raw 264.7 cells.

Epicatechin used in the treatment of intestinal inflammatory disease: an analysis by experimental models

Background. This study was pathway of (−)-epicatechin (EC) in the prevention and treatment of intestine inflammation in acute and chronic rat models. Methods. Intestine inflammation was induced in rats using TNBS. The morphological, inflammatory, immunohistochemical, and immunoblotting characteristics of colon samples were examined. The effects of EC were evaluated in an acute model at doses of 5, 10, 25, and 50 mg/kg by gavage for 5 days. The chronic colitis model was induced 1st day, and treated for 21 days. For the colitis relapse model, the induction was repeated on 14th. Results. EC10 and EC50 effectively reduced the lesion size, as assessed macroscopically; and confirmed by microscopy for EC10. The glutathione levels were higher in EC10 group but decreased COX-2 expression and increased cell proliferation (PC) were observed, indicating an anti-inflammatory activity and a proliferation-stimulating effect. In the chronic colitis model, EC10 showed lower macroscopic and microscopic lesion scores and increase in glutathione levels. As in the acute model, a decrease in COX-2 expression and an increase in PC in EC10, the chronic model this increase maybe by the pathway EGF expression. Conclusion. These results confirm the activity of EC as an antioxidant that reduces of the lesion and that has the potential to stimulate tissue healing, indicating useful for preventing and treating intestine inflammation.

Inorganic nitrite therapy: historical perspective and future directions

Over the past several years, investigators studying nitric oxide (NO) biology and metabolism have come to learn that the one-electron oxidation product of NO, nitrite anion, serves as a unique player in modulating tissue NO bioavailability. Numerous studies have examined how this oxidized metabolite of NO can act as a salvage pathway for maintaining NO equivalents through multiple reduction mechanisms in permissive tissue environments. Moreover, it is now clear that nitrite anion production and distribution throughout the body can act in an endocrine manner to augment NO bioavailability, which is important for physiological and pathological processes. These discoveries have led to renewed hope and efforts for an effective NO-based therapeutic agent through the unique action of sodium nitrite as an NO prodrug. More recent studies also indicate that sodium nitrate may also increase plasma nitrite levels via the enterosalivary circulatory system resulting in nitrate reduction to nitrite by microorganisms found within the oral cavity. In this review, we discuss the importance of nitrite anion in several disease models along with an appraisal of sodium nitrite therapy in the clinic, potential caveats of such clinical uses, and future possibilities for nitrite-based therapies.

Advances in understanding the effect of sinomenine on intestinal immune inflammation in inflammatory bowel disease

Intestinal immune inflammatory response is abnormal in patients with inflammatory bowel disease (IBD). Control of intestinal immune inflammatory response represents one of the methods for treatment of IBD. It has been proved that sinomenine (SN) can inhibit lymphocyte proliferation, regulate immune cell function, reduce inflammation mediator production, modulate cytokine secretion, and thereby suppress the immune inflammatory response. This article gives an overview of the role of the immune response in the pathogenesis of IBD and summarizes the recent advances in understanding the effect of SN on intestinal immune inflammation in IBD, seeking to provide a new reference for the treatment of IBD.

Oral nitrite ameliorates dextran sulfate sodium-induced acute experimental colitis in mice

Inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis are chronic inflammatory disorders of the intestinal tract with excessive production of cytokines, adhesion molecules, and reactive oxygen species. Although nitric oxide (NO) is reported to be involved in the onset and progression of IBDs, it remains controversial as to whether NO is toxic or protective in experimental colitis. We investigated the effects of oral nitrite as a NO donor on dextran sulfate sodium (DSS)-induced acute colitis in mice. Mice were fed DSS in their drinking water with or without nitrite for up to 7days. The severity of colitis was assessed by disease activity index (DAI) observed over the experimental period, as well as by the other parameters, including colon lengths, hematocrit levels, and histological scores at day 7. DSS treatment induced severe colitis by day 7 with exacerbation in DAI and histological scores. We first observed a significant decrease in colonic nitrite levels and increase in colonic TNF-alpha expression at day 3 after DSS treatment, followed by increased colonic myeloperoxidase (MPO) activity and increased colonic expressions of both inducible NO synthase (iNOS) and heme oxygenase-1 (HO-1) at day 7. Oral nitrite supplementation to colitis mice reversed colonic nitrite levels and TNF-alpha expression to that of normal control mice at day 3, resulting in the reduction of MPO activity as well as iNOS and HO-1 expressions in colonic tissues with clinical and histological improvements at day 7. These results suggest that oral nitrite inhibits inflammatory process of DSS-induced experimental colitis by supplying nitrite-derived NO instead of impaired colonic NOS activity.

Expression of MAdCAM-1 and nuclear factor kappa B and the intervention effect of nitric oxide donor in oxazolone-induced colitis

AIM: To investigate the expression of MAdCAM-1 and nuclear factor kappa B (NF-κB) as well as the intervention of nitric oxide (NO) donor DETA NONOate and GTN in oxazolone-induced colitis.

METHODS: Thirty two C57BL/6 mice were randomly divided into 4 groups: group A, B, C and D. The oxazolone experimental colitis model was established in group B, C and D. Mice of group C were treated with GTN and group D with DETA NONOate. The disease activity index (DAI), macroscopic score and histological score in each group were evaluated. The expression of MAdCAM-1 and NF-κB were determined by immunohistochemical staining. The plasma nitric oxide (NO) levels and the MPO activity in colonic tissues were also analyzed.

RESULTS: The DAI in group B and C increased since oxazolone was administered rectally, but it did not changed obviously in group D. The macroscopic score, the histological score, the expression of NF-κB, the expression of MAdCAM-1 and the MPO activity in group B (3.13 ± 0.84, 20.31 ± 2.63, 30.29 ± 8.68, 17.60 ± 6.53, 3.83 ± 0.60), which were significantly higher than those in group A, respectively (0.38 ± 0.52, 0.88 ± 0.83, 7.38 ± 2.29, 4.08 ± 1.30, 1.75 ± 0.25, P < 0.01) and group D (1.38 ± 0.52, 11.13 ± 1.48, 12.60 ± 3.54, 8.42 ± 2.16, 2.76 ± 0.48, P < 0.01), but similar to those of group C. The level of plasma NO in group B was significantly higher than that of group A (54.51 ± 22.28 vs 32.17 ± 14.88, P < 0.05), but significantly lower than that of group D and C (54.51 ± 22.28 vs 88.53 ± 24.77, 80.12 ± 19.79, all P < 0.05). There were significant positive correlations between the expression of MAdCAM-1 and the histological score, the MPO activity and IA of NF-κB (r = 0.786, r = 0.833, r = 0.833, P < 0.05).

CONCLUSION: The expression of MAdCAM-1 increases significantly in lumina propria of colonic tissues in oxazolone-induced colitis of mice. According to these results, DETA NONOate may serve as a valuable biological agent for UC treatment.

The intestinal anti-inflammatory effects of the novel agent UR-1505 in the TNBS model of rat colitis are mediated by T-lymphocyte inhibition

UR-1505 is a novel pentafluoropropoxy derivative of salicylic acid, selected from a series of salicylate derivatives, according to their activity as inhibitors of T-lymphocyte activation. This study describes the anti-inflammatory activity of UR-1505 on trinitrobenzenesulphonic acid-induced colitis in rat, an experimental model that resembles to Crohn's disease (CD), as well as its in vitro effects on T-cells and bone marrow-derived macrophages (BMDM) activation. UR-1505 showed intestinal anti-inflammatory effect, associated with reduced colonic levels of TNFalpha and LTB(4), inhibition of the expression of IFNgamma and iNOS, and lower colonic leukocyte infiltration. The in vitro assays revealed that UR-1505 also inhibited T-lymphocyte proliferation and IL-12/IFNgamma production, two of the main pro-inflammatory cytokines involved in the pathogenesis of CD. However, UR-1505 did not modify LPS- nor IFNgamma-induced activation in BMDM. Thus, UR-1505 specifically affects T-cells without modifying the activation of BMDM. In conclusion, the intestinal anti-inflammatory activity of UR-1505 seems to be mediated by a reduction in the recruitment of immune cells to the inflammatory foci, together with the inhibition of T-cell activation. These results suggest that UR-1505 may be an interesting candidate to be explored for the treatment of CD.

Effects of intestinal trefoil, factor on colonic mucosa in experimental colitis of rats

In order to investigate the protective effects of intestinal trefoil factor (ITF) on colonic mucosa in experimental colitis of rats, ITF was detected by RT-PCR and immunohistochemistry at different time points. Three days after colitis induction, rats were treated with either 0.9% saline solution or rhITF. Pathological changes and the expression of iNOS mRNA, NO, MDA and SOD were measured respectively. It was found that ITF was mainly located in goblet cells, significantly higher in model group than in normal group (P<0.05). rhITF could increase the iNOS mRNA expression and NO contents, and there was statistically significant difference between rhITF group and model group (P<0.05). rhITF also caused an increase of MDA and a decrease of SOD, but there was no significant difference between two groups. These results indicated that ITF has apparent therapeutic effects in ulcerative colitis, which may be associated with iNOS and NO.

Down-regulation of endothelial adhesion molecules and leukocyte adhesion by treatment with superoxide dismutase is beneficial in chronic immune experimental colitis

Modulation of adhesion molecule expression that govern trafficking of leukocytes into the inflamed intestine is envisioned as a new strategy for treatment of inflammatory bowel disease (IBD). This study was designed to determine the impact of reducing oxidative stress on adhesion molecules expression and leukocyte recruitment in experimental chronic colitis. For that purpose, colitic interleukin-10 knockout and wild-type mice were studied. Groups of animals were treated with Cu/Zn superoxide dismutase (SOD1) 13 mg/kg/d or vehicle for either 7 or 14 days. Expression of vascular cell adhesion molecule-1 and mucosal addressin cell adhesion molecule-1 were determined; leukocyte-endothelial cell interactions in colonic venules were studied with intravital microscopy; and changes in colon pathology and biomarkers of colitis severity were determined. Development of colitis was associated with a marked increase in endothelial vascular cell adhesion molecule-1 and mucosal addressin cell adhesion molecule-1 expression, which were significantly reduced by treatment with SOD1. The increase in leukocyte rolling and adhesion in colonic venules of colitic mice were significantly reduced by administration of SOD1. This treatment markedly reduced colonic lipid hydroperoxidation, myeoloperoxidase activity, and plasma levels of serum amyloid A protein and resulted in significant, although modest, reductions in histologic damage score. The therapeutic value of SOD1 when administered prophylactically was assessed in the dextran sulfate sodium model of colitis with similar positive results. These results indicate that SOD1 affords significant amelioration of colonic inflammatory changes in experimental colitis. Down-regulation of adhesion molecule expression, reduction of lipid hydroperoxidation, and recruitment of leukocytes into the inflamed intestine contribute to this beneficial effect.

Different sensitivity of lamina propria T-cell subsets to nitric oxide-induced apoptosis explains immunomodulatory activity of a nitric oxide-releasing derivative of mesalamine in rodent colitis

BACKGROUND & AIMS

Uncontrolled T-cell activation plays a critical role in the pathogenesis of inflammatory bowel diseases. Therefore, pharmacological strategies directed toward restoring the normal responsiveness of the immune system could be effective in the treatment of these pathologic conditions. The addition of a nitric oxide-releasing moiety to conventional drugs, such as aspirin and other anti-inflammatory analgesic drugs, results in new chemical entities with potent immunomodulatory activities. The aim of this study was to investigate the immunomodulatory activity of a nitric oxide-releasing derivative of mesalamine (NCX-456), as compared with standard mesalamine, in 2,4,6-trinitrobenzene sulfonic acid-induced colitis in mice.

METHODS

Cells and tissues from mice with 2,4,6-trinitrobenzene sulfonic acid-induced colitis and from interleukin 10-deficient mice with spontaneous chronic colitis receiving treatment with several doses of NCX-456 or mesalamine were analyzed for morphology, cytokine production, and apoptosis.

RESULTS

NCX-456, but not mesalamine, administration resulted in a marked reduction in clinical, histological, and immunologic signs of colitis in both models. NCX-456 inhibited the release of T-helper type 1-derived cytokines and increased the release of the regulatory T cell-derived cytokines interleukin 10 and transforming growth factor beta. In vitro analyses showed that NCX-456 inhibited proliferation and caused selective apoptosis of the subset of activated lamina propria T-helper type 1 cells, whereas it was ineffective for regulatory T-cell function and survival.

CONCLUSIONS

Collectively, these data show that NCX-456 inhibits lamina propria T-helper type 1 function and stimulates the activity of interleukin 10- and transforming growth factor beta-secreting cells, thus restoring mucosal immune homeostasis and suppressing intestinal inflammation.

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Nitric oxide in inflammatory bowel disease: a universal messenger in an unsolved puzzle

In recent years, nitric oxide (NO), a gas previously considered to be a potentially toxic chemical, has been established as a diffusible universal messenger that mediates cell-cell communication throughout the body. Constitutive and inducible NO production regulate numerous essential functions of the gastrointestinal mucosa, such as maintenance of adequate perfusion, regulation of microvascular and epithelial permeability, and regulation of the immune response. Up-regulation of the production of NO via expression of inducible nitric oxide synthase (iNOS) represents part of a prompt intestinal antibacterial response; however, NO has also been associated with the initiation and maintenance of inflammation in human inflammatory bowel disease (IBD). Recent studies on animal models of experimental IBD have shown that constitutive and inducible NO production seems to be beneficial during acute colitis, but sustained up-regulation of NO is detrimental. This fact is also supported by studies on mice genetically deficient in various NOS isoforms. However, the mechanism by which NO proceeds from being an indispensable homeostatic regulator to a harmful destructor remains unknown. Furthermore, extrapolation of data from animal colitis models to human IBD is questionable. The purpose of this review is to update our knowledge about the role of this universal mediator and the enzymes that generate it in the pathogenesis of IBD.

The intestinal anti-inflammatory effect of quercitrin is associated with an inhibition in iNOS expression

Quercitrin, 3-rhamnosylquercetin, is a bioflavonoid with antioxidant properties, which exerts anti-inflammatory activity in experimental colitis. In the present study, different in vivo experiments were performed in order to evaluate the mechanisms of action involved in this effect, with special attention to its effects on proinflammatory mediators, including nitric oxide (NO). Experimental colitis was induced in female Wistar rats by incorporation of dextran sodium sulfate (DSS) in drinking water. Oral treatment of quercitrin (1 or 5 mg kg(-1) day(-1)) to colitic rats ameliorated the evolution of the inflammatory process induced when administered in a preventative dosing protocol. When quercitrin (1 mg kg(-1) day(-1)) was administered on established colitis, it facilitated the recovery of the inflamed mucosa. The beneficial effects exerted by quercitrin were evidenced both histologically and biochemically, and were associated with an improvement in the colonic oxidative status, altered as a consequence of the colonic insult induced by DSS. In addition, a reduction of colonic NO synthase activity was observed, probably related to a decreased expression in the inducible form of the enzyme via downregulation in the colonic activity of the nuclear factor-kappaB. Immunohistochemical studies showed that quercitrin treatment reduced macrophage and granulocyte infiltration in the inflamed tissue.

L-arginine polymers enhance coronary flow and reduce oxidative stress following cardiac transplantation in rats

BACKGROUND

Hearts treated with l-arginine polymers have demonstrated upregulated production of nitric oxide. The current study examined whether these polymers improved coronary flow and reduced myocardial oxidative stress after rat heart transplantation.

METHODS

PVG donor hearts were incubated ex vivo with either 100 mumol/L l-arginine polymers 9 amino acids in length (R9) (n = 7) or phosphate-buffered saline (n = 7) for 30 minutes after arrest and then transplanted heterotopically into the abdomen of ACI recipient rats. Coronary flows were assessed using fluorescent microspheres both at baseline (30 minutes after reperfusion) and at 6 hours and compared using the paired Student t test. Evidence of oxidative stress was assessed in a separate cohort of similarly treated animals by enzyme-linked imunosorbent assay for rat tumor necrosis factor-alpha at 6 hours.

RESULTS

Histochemistry with biotinylated l-arginine polymers demonstrated uptake of R9 into the vascular walls of treated allografts. Although all hearts experienced deterioration in coronary flow between baseline and 6 hours, the R9-treated group had a smaller reduction (29.9%, P =.10) than the phosphate-buffered saline control group (58.0%, P =.003). Tumor necrosis factor-alpha levels were also significantly reduced in the R9 treatment group compared with the phosphate-buffered saline category (160 +/- 30 versus 205 +/- 38, P =.007).

CONCLUSION

Rat cardiac allografts treated with R9 at the time of procurement exhibited less deterioration in coronary flow and a reduction in myocardial oxidative stress than the phosphate-buffered saline control group in the perioperative period. The use of arginine polymers may thus provide important myocardial protection against ischemia-reperfusion injury in both transplant and routine cardiac surgery cases.

Neurogenic and non-neurogenic mechanisms in response of rat distal colon muscle to dextran sulphate sodium treatment

We studied, by organ bath methodology, how experimental colitis in rat, induced by the administration of dextran sulphate sodium (DSS) in the drinking water (3% for 3 or 7 days, or 5% for 7 days; Controls received ordinary tap water), may influence spontaneous, contractile activity of the longitudinal muscle layer. DSS treatment caused a dose-dependent increase in phasic contractile activity of the colon muscle. This effect needed an optimal preload of the tissues to be evident, and was non-neurogenic (i.e. myogenic and/or paracrine) in nature. Moreover, the DSS treatment appeared to impair a neurogenic, nitric oxide (NO)-dependent, relaxant response to the stretch (i.e. preload) applied to the tissues. Inducible NO synthase was localized by immunohistochemistry to infiltrating mononuclear cells in the colon wall. We propose that NO, via the inducible pathway, exerts marked effects on the neuromuscular apparatus in the DSS model of experimental colitis.

Nitric oxide in inflammatory bowel disease

Nitric oxide (NO) is a pleiotropic free radical messenger molecule. There is a large body of evidence that the inducible form of the NO synthase enzyme (iNOS) that is responsible for high-output production of NO from l-arginine is up-regulated in various forms of mucosal inflammation. Consistent with this, multiple detection strategies have demonstrated that iNOS expression, enzymatic activity, and NO production are increased in human inflammatory bowel disease tissues. There is also evidence that the level of iNOS-derived NO correlates well with disease activity in ulcerative colitis, while for Crohn's disease, the results are more variable. A substantial number of animal studies have assessed the role of inducible NO production. While the majority of studies have shown improvement in experimental inflammatory bowel disease with iNOS inhibition, there are also a significant number of reports of exacerbation of disease with inhibitors. Similarly, studies using iNOS-deficient mice in colitis models have shown improvement, worsening, or no effect on disease. The authors suggest that additional studies to assess the role of the competing biochemical pathway, namely the conversion of l-arginine to polyamines via the actions of arginase and ornithine decarboxylase, may provide important new insights into understanding the regulation of mucosal inflammation and inflammatory bowel disease.

Enhanced intestinal inflammation induced by dextran sulfate sodium in tumor necrosis factor-alpha deficient mice

BACKGROUND AND AIMS

Tumor necrosis factor-alpha (TNF-alpha) is a potent pro-inflammatory cytokine thought to be involved in the pathogenesis of inflammatory bowel disease. To further define the role of TNF-alpha in intestinal inflammation, we studied the effects of dextran sulfate sodium (DSS) administration in mice with targeted deletions of TNF-alpha gene.

METHODS

Acute colitis was induced in female TNF-alpha-/- and TNF-alpha+/+ mice by administering 4.5% DSS orally in drinking water for seven days. The colonic mucosal injury and inflammation was evaluated based on body weight changes, total colon length, luminal hemoglobin, and histological findings. Colonic mRNA expression for inducible nitric oxide synthase (iNOS), TNF-alpha, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) were measured by reverse transcription polymerase chain reaction (RT-PCR), and nuclear factor kappaB (NF-kappaB) activation was evaluated by electrophoretic mobility shift assay.

RESULTS

In each assessment, colonic injury was significantly aggravated in DSS-treated TNF-alpha-/- mice compared with DSS-treated TNF-alpha+/+ mice. The survival rate of TNF-alpha-/- mice on day seven was 40%; in contrast, all TNF-alpha+/+ mice were alive. Histological study also showed an enhanced infiltration of inflammatory cells, especially neutrophils, and mucosal cell disruption in DSS-treated TNF-alpha-/- mice compared with DSS-treated TNF-alpha+/+ mice. On day seven, mRNA levels of IFN-gamma and IL-4 in the colons of TNF-alpha-/- mice were faint or not detected; in contrast, those of TNF-alpha+/+ mice were detected. Although the expression of iNOS mRNA and luminal nitrite levels were similarly increased in both mice on day seven, this induction was delayed in TNF-alpha-/- mice during the early phase. The degree of NF-kappaB binding activity seemed to be similar between the two types of mice on day seven.

CONCLUSION

DSS-induced inflammation is significantly enhanced in TNF-alpha-/- mice compared to TNF-alpha+/+ mice. These data suggest that persistent and marked blockage of TNF-alpha bioactivity may provide a detrimental effect on acute intestinal inflammation.