Nitric oxide in inflammatory bowel disease

Combined glutamine and arginine decrease proinflammatory cytokine production by biopsies from Crohn's patients in association with changes in nuclear factor-kappaB and p38 mitogen-activated protein kinase pathways

Glutamine (Gln) and arginine (Arg) are conditionally essential amino acids with immunomodulatory properties. The aim of the study was to assess the effects of Gln and Arg alone or in combination on cytokine release by cultured colonic biopsies from patients with active Crohn's disease (CD). Ten consecutive patients [mean (range) age 26 (18-39) y] with active colonic CD (mean CD activity index: 383.7 +/- 129.8) were prospectively included in the study. Eight colonic biopsies were obtained via a colonoscopy and incubated during 18 h with low (physiological) or high (pharmacological) doses of Arg (0.1 or 2 mmol/L designated as Arg(low) or Arg(high), respectively) and Gln (0.6 or 10 mmol/L designated as Gln(low) or Gln(high), respectively). The concentrations of cytokines [interleukin (IL)-4, IL-10, IL-8, IL-6, tumor necrosis factor-alpha (TNFalpha), IL-1beta, interferon-gamma) were assessed by ELISA, and nitric oxide (NO) production was evaluated by Griess assay. Nuclear factor (NF)-kappaB p65 subunit, inhibitor of NFkappaB-alpha, and p38 mitogen-activated protein kinase (MAPK) were assessed by immunoblotting. Arg(high)/Gln(high) decreased the production of TNFalpha, IL-1beta, IL-8, and IL-6 (each P < 0.01). Arg(low)/Gln(high) decreased IL-6 and IL-8 production (both P < 0.01), whereas Arg(high)/Gln(low) did not affect cytokine and NO production. Arg(low)/Gln(high) and Arg(high)/Gln(high) decreased NF-kappaB p65 subunit expression, whereas p38 MAPK was decreased only by Arg(high)/Gln(high). Combined pharmacological doses of Arg and Gln decreased TNFalpha and the main proinflammatory cytokines release in active colonic CD biopsies via NF-kappaB and p38 MAPK pathways. These results could be the basis of prospective studies evaluating the effects of enteral supply of combined Arg and Gln during active CD.

Teupolioside, a phenylpropanoid glycosides of Ajuga reptans, biotechnologically produced by IRBN22 plant cell line, exerts beneficial effects on a rodent model of colitis

The aim of the present study was to examine the effects of phenylpropanoid glycoside, teupolioside, biotechnologically produced by IRBN22 Ajuga reptans cell line, in rats subjected to experimental colitis. Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulfonic acid (DNBS). Teupolioside was administered daily orally (0.2 or 2mgkg(-1)). On Day 4, animals were sacrificed and tissues were taken for histological and biochemical analysis. Four days after DNBS administration, colon TNF-alpha and IL-1beta productions were increased, associated with colon damage. Neutrophil infiltration, by myeloperoxidase activity, in the mucosa was associated with up-regulation of ICAM-1 and P-selectin and high levels of malondialdehyde. Immunohistochemistry for nitrotyrosine and poly (ADP-ribose) polymerase (PARP) showed an intense staining in the inflamed colon. Biochemical methods and zymography were used to analyze MMP-9 and -2 activities in colon tissues from DNBS-injured rats. Treatment with teupolioside significantly reduced the appearance of diarrhoea and the loss of body weight. This was associated with a remarkable amelioration in the disruption of the colonic architecture and a significant reduction in colonic myeloperoxidase activity and malondialdehyde levels. Teupolioside also reduced the pro-inflammatory cytokines release, the appearance of nitrotyrosine and PARP immunoreactivity in the colon and reduced the up-regulation of ICAM-1 and the expression of P-selectin. Therefore, teupolioside also reduced proMMP-9 and -2 activity induced in the colon by DNBS administration. The results of this study suggested that administration of teupolioside may be beneficial for treatment of inflammatory bowel disease.

Helminth antigen-based strategy to ameliorate inflammation in an experimental model of colitis

Inflammatory bowel disease (IBD) is the most common and serious chronic inflammatory condition of the gut. Among the distinct T helper (Th) cell subsets, a Th1 type response is associated predominantly with Crohn's disease (CD) while helminth infections generate a strong Th2 type response. IBD is most prevalent in developed countries but rare in countries where infections with helminths are common. Thus, it has been hypothesized that infection with helminth infection influence the development of CD and recent clinical and experimental studies suggest strongly a beneficial role of helminth infection in IBD. In the present study we examined the effects of rectal submucosal administration of helminth antigens on subsequent experimental colitis. Mice were treated with Trichinella spiralis antigens prior to the induction of dinitrobenzenesulphonic acid (DNBS)-induced colitis and were killed 3 days post-DNBS to assess colonic damage macroscopically, histologically and by myeloperoxidase (MPO) activity, inducible nitric oxide synthase (iNOS) and cytokine levels. Previous treatment with T. spiralis antigens reduced the severity of colitis significantly, as assessed macroscopically and histologically, and reduced the mortality rate. This benefit was correlated with a down-regulation of MPO activity, interleukin (IL)-1beta production and iNOS expression and an up-regulation of IL-13 and transforming growth factor-beta production in colon. These results clearly show a beneficial role of local treatment with helminth antigens for experimental colitis and prompt consideration of helminth antigen-based therapy for IBD instead of infection with live parasites.

Piceatannol, a stilbene present in grapes, attenuates dextran sulfate sodium-induced colitis

Piceatannol (3,5,3',4'-tetrahydroxy-trans-stilbene; PIC) is a polyphenol found in grapes. It is known as a protein kinase inhibitor that modifies multiple cellular targets, exerting immunosuppressive and antitumorigenic activities in several cell lines. The purpose of the present work was to evaluate the anti-inflammatory effect of PIC on dextran sulfate sodium (DSS)-induced colitis. Experimental colitis was induced in BALB/c mice by dissolving 5% DSS in their drinking water for 7 days. PIC (1, 2.5, 5, or 10 mg/kg body weight) was administrated daily per oral route for 7 days. A significant blunting of weight loss and clinical signs was observed in DSS-exposed, PIC-treated mice when compared to vehicle-treated mice. This was associated with a remarkable amelioration of the disruption of the colonic architecture, a significant reduction in colonic myeloperoxidase (MPO) activity, and a decrease in production of inflammatory mediators such as nitric oxide (NO), prostaglandin (PG) E2, and pro-inflammatory cytokines. The present data indicate that further evaluation of the potential of PIC as an agent for the prevention and/or treatment of inflammatory bowel diseases in human clinical studies is warranted.

The apolipoprotein E-mimetic peptide COG112 inhibits the inflammatory response to Citrobacter rodentium in colonic epithelial cells by preventing NF-kappaB activation

Inflammatory bowel disease arises from the interplay between luminal bacteria and the colonic mucosa. Targeted inhibition of pro-inflammatory pathways without global immunosuppression is highly desirable. Apolipoprotein (apo) E has immunomodulatory effects and synthetically derived apoE-mimetic peptides are beneficial in models of sepsis and neuroinflammation. Citrobacter rodentium is the rodent equivalent of enteropathogenic Escherichia coli, and it causes colitis in mice by colonizing the surface of colonic epithelial cells and inducing signaling events. We have reported that mice deficient in inducible nitric-oxide (NO) synthase (iNOS) have attenuated C. rodentium-induced colitis. We used young adult mouse colon (YAMC) cells that mimic primary colonic epithelial cells to study effects of an antennapedia-linked apoE-mimetic peptide, COG112, on C. rodentium-activated cells. COG112 significantly attenuated induction of NO production, and iNOS mRNA and protein expression, in a concentration-dependent manner. COG112 inhibited the C. rodentium-stimulated induction of iNOS and the CXC chemokines KC and MIP-2 to the same degree as the NF-kappaB inhibitors MG132 or BAY 11-7082, and there was no additive effect when COG112 and these inhibitors were combined. COG112 significantly reduced nuclear translocation of NF-kappaB, when assessed by electromobility shift assay, immunoblotting, and immunofluorescence for p65. This correlated with inhibition of both C. rodentium-stimulated IkappaB-alpha phosphorylation and degradation, and IkappaB kinase activity, which occurred by inhibition of IkappaB kinase complex formation rather than by a direct effect on the enzyme itself. These studies indicate that apoE-mimetic peptides may have novel therapeutic potential by inhibiting NF-kappaB-driven proinflammatory epithelial responses to pathogenic colonic bacteria.

Targeting NOX, INOS and COX-2 in inflammatory cells: chemoprevention using food phytochemicals

Biological, biochemical and physical stimuli activate inflammatory leukocytes, such as macrophages, resulting in induction and synthesis of proinflammatory proteins and enzymes, together with free radicals, as innate immune responses. On the other hand, chronic and dysregulated activation of some inducible enzymes, including NADPH oxidase (NOX), inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, have been shown to play pivotal roles in the development of certain inflammatory diseases such as oncogenesis. While the use of synthetic agents, especially those targeting molecules, is an attractive and reasonable approach to prevent carcinogenesis, it should be noted that traditional herbs and spices also exist along with their active constituents, which have been demonstrated to disrupt inflammatory signal transduction pathways. In this mini-review, the molecular mechanisms of activation or induction of NOX, iNOS and COX-2, as well as some food phytochemicals with marked potential to regulate those key inflammatory molecules, are highlighted. For example, 1'-acetoxychavicol acetate, which occurs in the rhizomes of the subtropical Zingiberaceae plant, has been shown to attenuate NOX-derived superoxide generation in macrophages, as well as lipopolysaccharide-induced nitric oxide and prostaglandin E(2) production through the suppression of iNOS and COX-2 synthesis, respectively. Notably, this phytochemical has exhibited a wide range of cancer prevention activities in several rodent models of inflammation-associated carcinogenesis. Herein, the cancer preventive potentials of several food phytochemicals targeting the induction of NOX, iNOS and COX-2 are described.

Biochemical aspects of inflammation

This review considers biochemical aspects of inflammation. The international literature until December 2006 has been analyzed, with the principal attention paid to the most dynamic problems: enzymology of inflammation, its regulation by hormones and signal transducers, and negative feedbacks, which underlie intensive current studies on pathogenesis, diagnostics, and therapy of inflammation. Such achievements as discoveries of defensins, toll-like receptors, interconnections of inflammation and iron metabolism, the roles of oxidative stress and antioxidant defense, lipoxins, inflammatory components of "non-inflammatory" diseases, and action mechanisms of effective drugs are discussed.

Glabridin, a functional compound of liquorice, attenuates colonic inflammation in mice with dextran sulphate sodium-induced colitis

Inflammatory bowel disease (IBD) is characterized by detrimental immune reactivity in the gut, and the imbalance between proinflammatory and anti-inflammatory reactivity. The aims of this study were to determine whether oral administration of glabridin, a functional component of liquorice, could ameliorate dextran sulphate sodium (DSS)-induced colitis, as well as to understand the possible underlying mechanisms. Acute experimental colitis was induced in BALB/c mice by treatment with 5% DSS for 7 days. Glabridin (10 or 50 mg/kg/day) was given for 7 days. Treatment with glabridin significantly attenuated mortality, loss of body weight, shortening of the colon and severe clinical symptoms. This was associated with a remarkable amelioration of the disruption of the colonic architecture, a significant reduction in colonic myeloperoxidase (MPO) activity and the production of inflammatory mediators such as nitric oxide (NO), prostaglandin (PG) E2, and proinflammatory cytokines. These results suggest that glabridin-mediated anti-inflammatory action on colorectal sites may be a useful therapeutic approach to IBD.

Polyamines and the intestinal tract

Owing to their high turnover, the intestinal mucosal cells have a particularly high requirement for polyamines. Therefore, they are an excellent charcol for the study of polyamine function in rapid physiological growth and differentiation. After a cursory introduction to the major aspects of polyamine metabolism, regulation, and mode of action, we discuss the contribution of the polyamines to the maintenance of normal gut function, the maturation of the intestinal mucosa, and its repair after injuries. Repletion of cellular polyamine pools with (D,L)-2-(difluoromethyl)ornithine has considerably improved our understanding of how the polyamines are involved in the regulation of normal and neoplastic growth. Unfortunately, the attempts to exploit polyamine metabolism as a cancer therapeutic target have not yet been successful. However, the selective inactivation of ornithine decarboxylase appears to be a promising chemopreventive method in familial adenomatous polyposis. Presumably, it relies on the fact that ornithine decarboxylase is a critical regulator of the proliferative response of the protooncogene c-myc, but not of its apoptotic response.

Oxidative DNA damage and antioxidant activity in patients with inflammatory bowel disease

Chronic inflammation may contribute to cancer risk through the accumulation of specific products as a result of DNA damage. Endogenous antioxidant enzymes prevent the formation of these harmful products. Oxidative DNA damage and endogenous antioxidant defense were determined in patients with inflammatory bowel disease (IBD). Plasma levels of 8-hydroxydeoxyguanosine (8-OHdG) and nitric oxide (NO) and plasma activities of glutathione peroxidase (G-Px) and superoxide dismutase (SOD) were determined in patients with IBD by ELISA and spectrophotometric assay, respectively. Plasma levels of 8-OHdG, SOD, and G-Px activity were found to be increased in the patient group compared to the control group (P < 0.02, P < 0.001, and P < 0.001, respectively), whereas NO was unchanged. 8-OHdG level was found to be weakly correlated with age, NO, and SOD. The results show increased DNA damage in patients with IBD. This may explain the increased risk of developing colon cancer in these patients.

L-arginine availability regulates inducible nitric oxide synthase-dependent host defense against Helicobacter pylori

Helicobacter pylori infection of the stomach causes an active immune response that includes stimulation of inducible nitric oxide (NO) synthase (iNOS) expression. Although NO can kill H. pylori, the bacterium persists indefinitely, suggesting that NO production is inadequate. We determined if the NO derived from iNOS in macrophages was dependent on the availability of its substrate, L-arginine (L-Arg). Production of NO by H. pylori-stimulated RAW 264.7 cells was dependent on the L-Arg concentration in the culture medium, and the 50% effective dose for L-Arg was 220 microM, which is above reported plasma L-Arg levels. While iNOS mRNA induction was L-Arg independent, iNOS protein increased in an L-Arg-dependent manner that did not involve changes in iNOS protein degradation. L-lysine, an inhibitor of L-Arg uptake, attenuated H. pylori-stimulated iNOS protein expression, translation, NO levels, and killing of H. pylori. While L-Arg starvation suppressed global protein translation, at concentrations of L-Arg at which iNOS protein was only minimally expressed in response to H. pylori, global translation was fully restored and eukaryotic translation initiation factor alpha was dephosphorylated. H. pylori lacking the gene rocF, which codes for a bacterial arginase, induced higher levels of NO production by increasing iNOS protein levels. When murine gastric macrophages were activated with H. pylori, supraphysiologic levels of L-Arg were required to permit iNOS protein expression and NO production. These findings indicate that L-Arg is rate limiting for iNOS translation and suggest that the levels of L-Arg that occur in vivo do not permit sufficient NO generation by the host to kill H. pylori.

Role of blood- and tissue-associated inducible nitric-oxide synthase in colonic inflammation

There is evidence that inducible nitric-oxide synthase (iNOS)-derived NO contributes to the pathophysiology of intestinal inflammation. The aims of this study were to assess the role of iNOS in the development of dextran sodium sulfate (DSS)-induced colonic inflammation and to define the contribution of tissue-specific iNOS expression to this inflammatory response. Study groups included: 1) wild-type (WT) mice; 2) WT=>WT bone marrow chimeras with normal iNOS function; 3) WT=>iNOS-/- chimeras (with functional blood cell iNOS, but iNOS-deficient tissue); 4) iNOS-/-=>WT chimeras (with iNOS-deficient blood cells, but normal tissue iNOS activity); and 5) iNOS-deficient mice. In WT mice and WT=>WT chimeras, DSS-induced colonic inflammation was characterized by bloody diarrhea and a high disease activity index. However, WT=>iNOS-/- and iNOS-/-=>WT chimeras and iNOS-/- mice exhibited an attenuated disease activity index, with parallel changes in histopathology. Colonic myeloperoxidase (MPO) was comparably elevated in DSS-treated WT mice (30.1+/-1.7) and WT=>WT chimeras (29.0+/-1), whereas MPO was significantly reduced in iNOS-/- mice and iNOS-/-=>WT chimeras (9.5+/-1.7 and 15.6+/-2.2, respectively). WT=>iNOS-/- chimeras exhibited the lowest MPO activity (3.7+/-0.6). Our findings implicate both blood cell- and tissue-derived iNOS in DSS-induced colonic inflammation, with tissue-associated iNOS making a larger contribution to the recruitment of inflammatory cells.

Deoxycholate-induced colitis is markedly attenuated in Nos2 knockout mice in association with modulation of gene expression profiles

Nos2 knockout mice were compared to wild-type mice for susceptibility to colitis in response to a diet supplemented with deoxycholate, a bile acid increased in the colon of individuals on a high-fat diet. Wild-type mice fed a fat-related diet, supplemented with 0.2% DOC, develop colonic inflammation associated with increases in nitrosative stress, proliferation, oxidative DNA/RNA damage, and angiogenesis, as well as altered expression of numerous genes. However, Nos2 knockout mice fed a diet supplemented with deoxycholate were resistant to these alterations. In particular, 35 genes were identified whose expression was significantly altered at the mRNA level in deoxycholate-fed Nos2(+/+) mice but not in deoxycholate-fed Nos2(-/-) mice. Some of these alterations in NOS2-dependent gene expression correspond to those reported in human inflammatory bowel disease. Overall, our results indicate that NOS2 expression is necessary for the development of deoxycholate-induced colitis in mice, a unique dietary-related model of colitis.

Study on the Correlations among Disease Activity Index and Salivary Transforming Growth Factor-beta1 and Nitric Oxide in Ulcerative Colitis Patients

Growth factors and nitric oxide (NO) play a major role in dysregulated immune response in ulcerative colitis (UC). Recent evidence has shown increased levels of transforming growth factor-beta(1) (TGF-beta(1)) in UC and suggested an anti-inflammatory effect for this factor. Based on our recent study, dysfunctional immunoregulation is present in saliva of UC patients, we hypothesized that salivary level of NO and TGF-beta(1) may differ by severity of UC and be useful to determine the activity of the disease. Thirty-seven UC patients and 15 healthy controls were enrolled and saliva samples were obtained. Truelove-Witts severity index and modified Truelove-Witts severity index were used to determine the severity of the disease. NO and TGF-beta(1) levels were detected in saliva of all patients and control subjects using enzyme-linked immunosorbent assay. A total of 21 patients had mild disease while 8 had moderate and 8 had severe colitis. Adjusted for baseline characteristics, the levels of NO and TGF-beta(1) in different groups were compared. Salivary NO and TGF-beta(1) levels were higher in UC patients comparing to controls (P < 0.00005 and P = 0.005, respectively). The levels of NO and TGF-beta(1) showed no significant differences among the severity groups (P = 0.46 and P = 0.23, respectively). NO levels linearly increased by age (Coeff = 1.5, r = 0.38, P = 0.02). Gender, extension of disease, and medical treatment did not affect NO and TGF-beta(1) levels. Although UC patients have abnormal amounts of NO and TGF-beta(1) in their saliva, their disease activity cannot be predicted by these factors, which may indicate a pathophysiologic role rather than being nonspecific inflammatory markers for TGF-beta(1) and NO.

Modulatory effect of nitric oxide on mast cells during induction of dextran sulfate sodium colitis

Nitric oxide (NO) is implicated in the pathophysiology of intestinal inflammation. Intestinal mast cells may amplify inflammatory response and mucosal injury in inflammatory bowel disease. Our aim was to examine the role of NO and intestinal mast cells by investigating the effects of NO synthase (NOS) inhibitors and a mast cell stabilizer during induction of dextran sulfate sodium (DSS) colitis. Colitis was induced by 4% DSS in drinking water, in rats pretreated with L-NAME or aminoguanidine. In another set of experiments, we investigated the effect of ketotifen in this setting. Inhibition of NO by L-NAME worsened DSS-induced inflammation, however, aminoguanidine had no effect. On the other hand, ketotifen abolished the deleterious effects of L-NAME on colonic inflammation, suggesting that hyperactivation of mast cells by NOS inhibition amplifies mucosal injury induced by DSS. Our results suggest that constitutive isoforms of NOS prevent mast cell activation.

Effects of timed administration of doxycycline or methylprednisolone on post-myocardial infarction inflammation and left ventricular remodeling in the rat heart

The development of strategies to ameliorate post-myocardial infarction (MI) remodeling and improve function continues to be an area of clinical importance. Use of steroids for this purpose is controversial since the effects of timed treatment on relevant inflammatory, biochemical and structure/function endpoints are unclear. In a previous report, we demonstrated that use of doxycycline pre-treatment improves post-MI remodeling and passive left ventricular (LV) function. However, the effects of timed doxycycline post-MI treatment are unknown. To examine these issues, we performed a study using a rat MI model. Animals were administered one of the following: doxycycline (DOX), the corticosteroid methylprednisolone (MP), or aqueous vehicle. Treatment was given early, short-term (at time of MI to 24 h post-MI) or late, long term (2-7 days post-MI). Animals were sacrificed at 3, 7 or 42 days post-surgery. We assessed LV hemodynamics, pressure-volume, and pressure-scar strains, histomorphometry, inflammation via measurements of myeloperoxidase activity, and matrix metalloproteinase (MMP) activity. Late MP treatment yielded a robust right-shifted pressure-volume curve, which was accompanied by increased scar strains. Late DOX treatment yielded reduced average heart weight and size and preserved scar thickness. DOX treatment did not suppress inflammation, which contrasts with the suppressive effects of MP. Use of early or late MP yielded increased MMP activity in infarcted and non-infarcted regions. Early and late treatment with DOX yielded infarct-associated MMP activity levels comparable to those of vehicle-treated animals. In conclusion, results indicate that late use of MP yields adverse post-MI structure/function outcomes that correlate with suppression of inflammation and increased MMP activity. These observations contrast with those of DOX, in particular, late treatment where improved outcomes were observed in LV structure and were accompanied by the lack of suppression of inflammation.

Alterations in Salivary Antioxidants, Nitric Oxide, and Transforming Growth Factor-β1in Relation to Disease Activity in Crohn's Disease Patients

It has been postulated that oxidative stress, nitric oxide (NO), and transforming growth factor beta(1) (TGF- beta(1)) have major roles in the pathophysiology of Crohn's disease (CD). The aim of this study was to determine the salivary levels of total antioxidant capacity (TAC), specific antioxidants (i.e., uric acid, albumin, transferrin, and thiol molecules), lipid peroxidation (LPO), NO, and TGF- beta(1) in CD patients and control subjects and to also investigate their correlation with activity of the disease. Twenty-eight patients with confirmed diagnosis of CD were enrolled and whole saliva samples were obtained. Smokers, diabetics, those who suffered from periodontitis, and those who were consuming antioxidant supplements were excluded from the study. The Crohn's Disease Activity Index (CDAI) was used to determine the severity of the disease. Twenty healthy subjects were also recruited. In CD patients significant reductions in salivary levels of TAC (0.248 +/- 0.145 vs. 0.342 +/- 0.110 mmol/L), albumin (1.79 +/- 0.42 vs. 2.3 +/- 0.2 microg/mL), and uric acid (3.1 +/- 1.4 vs. 4.1 +/- 2.0 mg/dL) were found. TGF-beta(1) was significantly increased in CD patients compared to healthy subjects (3.02 +/- 1.54 vs. 2.36 +/- 0.52 ng/mL). A fourfold increase in NO levels (198.8 +/- 39.9 vs. 50.2 +/- 21.3 micromol/L) along with a fivefold increase in LPO concentration (0.146 +/- 0.064 vs. 0.027 +/- 0.019 micromol/L) was documented in CD patients in comparison to the control group. CDAI significantly correlated with the TAC, LPO, and the interaction between TAC and LPO (r(2) = 0.625, r(2) = 0.8, F-test's P < 0.00005). Saliva of CD patients exhibits an abnormal feature with respect to oxidative stress, NO, and TGF-beta(1). TAC and LPO modify the effect of each other in determination of CD severity, which underlines the importance of oxidative stress in the pathogenesis of CD.

Budesonide treatment and expression of inducible nitric oxide synthase mRNA in colonic mucosa in collagenous colitis

OBJECTIVE

In collagenous colitis, the production of nitric oxide in the colon is found to be 50 to 100-fold higher than in healthy controls. The role of nitric oxide in collagenous colitis is debated and it has been suggested that nitric oxide has a causative role in diarrhoea. The aim of this study was to examine the possible effect of budesonide treatment on the level of inducible nitric oxide synthase mRNA.

METHODS

In 20 patients with collagenous colitis, clinical activity was assessed by registration of the daily stool frequency and stool weight. Sigmoidoscopy was performed and biopsies for histological examination and one biopsy for determination of inducible nitric oxide synthase mRNA was obtained in 16 patients.

RESULTS

Budesonide treatment was followed by a significant reduction of inducible nitric oxide synthase mRNA (P<0.01) whereas no change was observed after placebo treatment. Significant correlations between inducible nitric oxide synthase mRNA and the grade of inflammation (rho=0.47; P<0.01), the daily stool weight (rho=0.51; P<0.005) and the daily stool frequency (rho=0.49; P<0.005) were observed. No significant association was observed between inducible nitric oxide synthase mRNA and the thickness of the collagen layer.

CONCLUSIONS

In patients with collagenous colitis, treatment with budesonide results in a reduction of inducible nitric oxide synthase mRNA. The level of inducible nitric oxide synthase mRNA in colonic mucosa correlates with the inflammatory and clinical activity. The results support that nitric oxide is a central factor in the pathogenesis of collagenous colitis.

Consequences of Citrobacter rodentium infection on enteroendocrine cells and the enteric nervous system in the mouse colon

We tested the hypothesis that Citrobacter rodentium infection leads to changes in the mucosal enteroendocrine signalling and the enteric nervous system and that the host's immune response contributes to these changes. Enteroendocrine cells, serotonin (5-HT) reuptake transporter (SERT), 5-HT release, and inducible nitric oxide synthase (iNOS) expression were assessed in the colon of infected wild-type or severe combined immunodeficient (SCID) mice. Immunoreactivity for iNOS and neuropeptides were examined in the submucosal and myenteric plexuses. Mice were orogastrically infected with C. rodentium and experiments were conducted during the injury phase (10 days) and the recovery phase (30 days). 5-HT and somatostatin enteroendocrine cells and SERT were significantly reduced 10 days after infection, with numbers returning to control values at 30 days. 5-HT release was increased at 10 days. Changes to the mucosal serotonin signalling system were not observed in SCID mice. iNOS immunoreactivity was increased in the submucosa and mucosa at 10 days and returned to baseline levels by 30 days. No differences were observed in neuropeptide or iNOS immunoreactivity in the enteric plexuses following infection. The host's immune response underlies changes to enteroendocrine cells, SERT expression and 5-HT release in C. rodentium infection. These changes could contribute to disturbances in gut function arising from enteric infection.

Cancer-preventive anti-oxidants that attenuate free radical generation by inflammatory cells

Active inflammatory leukocytes are a major endogenous source of reactive oxygen and nitrogen oxide species (RONS). We have recently established novel bioassay systems, in which either phorbol ester-stimulated, differentiated HL-60 human leukemia cells or lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages were co-cultured with AS52 Chinese hamster ovary cells. Extensive screening of extracts from Asian vegetables and fruits led to the identification of 1′-acetoxychavicol acetate (ACA), auraptene, nobiletin, and zerumbone, all of which were found to be highly anti-mutagenic in the above co-culture systems. Pretreatment of RAW264.7 macrophages with LPS led to the activation of mitogen-activated protein kinases (MAPKs) and Akt, together with the degradation of IκB-α protein, and the resultant activation of the AP-1, NF-κB, and CREB transcription factors. ACA abrogated ERK1/2 and JNK1/2, but not p38 activation, as well as the activation and transcriptional activation of NF-κB and CREB, whereas nobiletin allowed phosphorylation of these MAPKs, while it suppressed AP-1, NF-κB, and CREB activation. Interestingly, zerumbone did not have any effects on the latter transcription factors, although it did attenuate iNOS mRNA expression. In addition, auraptene suppressed iNOS protein production, but not mRNA expression, implying that it targets the translation step. Our model systems may be useful for identifying potentially anti-carcinogenic inhibitors of RONS generation.

Nitric oxide-modulating agents for gastrointestinal disorders

Almost 20 years after the identification of the biological role of nitric oxide (NO), the full therapeutic potential of novel agents that mimic the activity of NO or interfere with its synthesis has yet to be realised for utilities involving the gastrointestinal tract. New utilities for classical NO donors, which were used as vasodilators for decades, in the treatment of motility disorders have been explored and a product for treating anal fissure was recently launched. New classes of compounds incorporating a NO-donating moiety into standard non-steroidal anti-inflammatory drugs, the NO-non-steroidal anti-inflammatory drugs (NO-NSAIDs) or COX-inhibiting nitric oxide donors (CINODs) have also been developed. These have been shown to exhibit reduced gastrointestinal injury in experimental models, and reports on their efficacy and safety in Phase I and II studies are now available. Modulation of the inducible NO synthase isoform that generates excessive NO that can lead to subsequent cytotoxic moieties, such as peroxynitrite, may have therapeutic possibilities in a range of inflammatory diseases of the gut. Likewise, agents that promote the decomposition of peroxynitrite or removal of its other component, superoxide, may also prove to be of use. Further targets for pharmaceutical exploitation are likely to come from both genomic and molecular insights into the processes that regulate the NO system.

Anti-inflammatory mechanisms of phenanthroindolizidine alkaloids

The molecular mechanisms for the anti-inflammatory activity of phenanthroindolizidine alkaloids were examined in an in vitro system mimicking acute inflammation by studying the suppression of lipopolysaccharide (LPS)/interferon-gamma (IFNgamma)-induced nitric oxide production in RAW264.7 cells. Two of the phenanthroindolizidine alkaloids, NSTP0G01 (tylophorine) and NSTP0G07 (ficuseptine-A), exhibited potent suppression of nitric oxide production and did not show significant cytotoxicity to the LPS/IFNgamma-stimulated RAW264.7 cells, in contrast to their respective cytotoxic effects on cancer cells. Tylophorine was studied further to investigate the responsible mechanisms. It was found to inhibit the induced protein levels of tumor necrosis factor-alpha, inducible nitric-oxide synthase (iNOS), and cyclooxygenase (COX)-II. It also inhibited the activation of murine iNOS and COX-II promoter activity. However, of the two common responsive elements of iNOS and COX-II promoters, nuclear factor-kappaB (NF-kappaB) and adaptor protein (AP)1, only AP1 activation was inhibited by tylophorine in the LPS/IFNgamma-stimulated RAW264.7 cells. Further studies showed that the tylophorine enhanced the phosphorylation of Akt and thus decreased the expression and phosphorylation levels of c-Jun protein, thereby causing the subsequent inhibition of AP1 activity. Furthermore, the tylophorine was able to block mitogen-activated protein/extracellular signal-regulated kinase kinase 1 activity and its downstream signaling activation of NF-kappaB and AP1. Thus, NSTP0G01 exerts its anti-inflammatory effects by inhibiting expression of the proinflammatory factors and related signaling pathways.

Pitavastatin Prevents Bacterial Translocation after Nonpulsatile/Low-Pressure Blood Flow in Early Atherosclerotic Rat: Inhibition of Small Intestine Inducible Nitric Oxide Synthase

BACKGROUND

Cardiopulmonary bypass decreases intestinal mucosal blood flow because of nonpulsatile and low-pressure blood flow resulting in bacterial translocation (BT) and atherosclerosis also has peripheral blood flow deficiency. The risk of nonpulsatile and low-pressure blood flow for atherosclerotic animals and the effect of statin administration, which has pleiotropic effects, were studied.

METHODS

Wistar rats were divided into four groups: group N (normal diet), group C (high-cholesterol diet), group S (group C plus pitavastatin therapy), and group I [group C plus inducible nitric oxide (iNOS) inhibitor therapy]. First of all, vascular responses were measured. Then the rats underwent nonpulsatile/low-pressure blood flow in the intestine, and the serum peptidoglycan concentration as a parameter of BT, the small intestinal PO(2) ratio (intestinal PO(2)/PaO(2)) as a parameter of mucosal blood flow, and NO concentrations were measured before surgery (T0), at the end of 90 min of stenosis (T1), and 90 min after the release of stenosis (T2). Immunostaining for nitrotyrosine was also performed at T2.

RESULTS

Group C had vascular endothelial dysfunction without histological changes, which indicated early atherosclerosis. The serum peptidoglycan concentration increased significantly at T2 only in group C. The intestinal PO(2) ratio was decreased at T1 in all the groups, and retuned to baseline at T2 in group N and group S, but not in group C or group I. Jejunal NO only in group C was significantly higher at all time points and ileal NO production at T1 and T2. There tended to be a positive stain for nitrotyrosine along the mucosal epithelium in group C.

CONCLUSION

In the setting of early atherosclerosis, intestinal blood flow does not only improve after nonpulsatile/low-pressure blood flow but causes BT because of a large amount of NO from high enzymatic intestinal iNOS activity, and pitavastatin treatment can prevent BT by improving both issues.

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.

Disruption of the p53-p53r2 DNA repair system in ulcerative colitis contributes to colon tumorigenesis

With ulcerative colitis (UC)-associated tumorigenesis, p53 gene alteration is considered to be a key event. To clarify whether the p53-checkpoint is operating in foci of inflammation and that its disruption is a feature of UC-associated neoplasms, the present immunohistochemical study was conducted. Since accumulation of butyric acid with active UC is associated with apoptosis, effects of in vitro exposure of newly established UC-cancer derived cell lines to organic acids were also assessed. The regulatory subunit of ribonucleotide reductase, p53R2, was found to be localized with p53 in situ, and levels of p53, phospho-p53, p53R2 and inducible nitric oxide synthase were significantly intercorrelated. However, p53R2 expression was clearly reduced with progression through UC-associated dysplasia to carcinoma, demonstrating an inverse relation with p53 overexpression. In vitro treatment with butyrate or propionic acid, but not succinic acid, elicited a positive response in the p53-p53R2 system. Moreover, p53-dependent DNA repair, investigated by radioactive nucleotide incorporation, was induced by butyric acid and inhibited by short-interfering p53 and p53R2 RNAs. Therefore, it was concluded that the p53-p53R2-dependent DNA repair system is constitutively stimulated by butyric acid, which accumulates in UC inflammatory lesions. Since failure of the p53-G(1) checkpoint may cause dysfunction of repair under the influence of butyrate, gene alterations may increase and spread through the genome, leading to tumorigenesis.

Changes in the expression and distribution of the inducible and endothelial nitric oxide synthase in mucosal biopsy specimens of inflammatory bowel disease

OBJECTIVE

The role of nitric oxide (NO) in the pathophysiology of inflammatory bowel disease (IBD) is controversial. The aim of this study was to investigate the expression and localization of nitric oxide synthase isoforms (iNOS, eNOS) in IBD colonic mucosa.

MATERIAL AND METHODS

Forty-four patients with IBD (24 ulcerative colitis (UC), 20 Crohn's disease (CD) and 16 controls) were investigated by colonoscopy. iNOS and eNOS in tissue sections was demonstrated by histochemistry (NADPH-diaphorase reaction) and immunohistochemistry. Cell type analysis and quantitative assessment of the iNOS immunoreactive (IR) cells and densitometry of iNOS in immunoblots were also performed.

RESULTS

iNOS-IR cells were significantly numerous in inflamed mucosa of UC (64+/-4 cells/mm2) than in CD (4+/-2 cells/mm2). iNOS-IR/CD15-IR cells showed significant elevation in inflamed (i) versus uninflamed (u) UC mucosa (UCu 8+/-3%, UCi 85+/-10%) In CD, the percentage of iNOS-IR/CD68-IR cells was lower in inflamed sites (CDu 23+/-8%, CDi 4+/-3%). Immunoblot of biopsies revealed significant elevation of iNOS in active UC compared with uninflamed sites, whereas in CD no significant changes were detected. Differences were observed in eNOS and endothelial marker CD31 immunoreactivity. In patients with UC and in controls the ratios of eNOS/CD31-IR vessels were 82.3% and 92.0% respectively, whereas in CD the ratio was 8.3% with a concomitantly significant increase of CD31-IR vessels. The distribution and morphological characteristics of the NOS-IR inflammatory cells and endothelia were similar to those showing NADPH-diaphorase reactivity.

CONCLUSIONS

Differences observed in the expression and distribution of NOS isoforms in immune and endothelial cells may contribute to better understanding of the structural and physiological changes in UC and CD.

Development and validation of a novel IL-10 deficient cell transfer model for colitis

A number of rodent models for inflammatory bowel disease (IBD) have been developed, but most cannot be used to develop and validate new therapies for IBD. From the models developed, the IL-10 deficient mouse model is the one that results in a disease similar to human IBD; however, in this model, colitis occurs with variable incidence taking 3-4 months to develop. These are serious problems with the model when evaluating a new therapy because of the large-scale experiments required and the difficulty in performing an accurate pharmacological analysis. In this study, the IL-10 deficient mouse model was modified by transferring whole spleen and mesenteric lymph node cells from IL-10 deficient mice to CB-17 SCID mice. In this IL-10 deficient cell transfer model, chronic intestinal inflammation developed in all recipients within 2-3 weeks, which was far earlier than in donor IL-10 deficient mice. The pathological phenotypes were similar to those of IL-10 deficient mice and CD45RBhi T cell-transfer models. In addition, we assessed several agents for inflammatory bowel disease to validate the general utility of this cell transfer model. It is worth noting that TNFR-Ig or prednisolone, which is effective for treatment of patients with severe-fulminant Crohn's disease, markedly attenuated pathological clinical indices in this colitis model, whereas the immunosuppressive agents, azathioprine, tacrolimus, and cyclosporine A produced no significant effect. These results suggest that the IL-10 deficient cell transfer model is a good experimental model to use for developing new and effective therapies for active IBD.

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Protective role of arginase in a mouse model of colitis

Arginase is the endogenous inhibitor of inducible NO synthase (iNOS), because both enzymes use the same substrate, l-arginine (Arg). Importantly, arginase synthesizes ornithine, which is metabolized by the enzyme ornithine decarboxylase (ODC) to produce polyamines. We investigated the role of these enzymes in the Citrobacter rodentium model of colitis. Arginase I, iNOS, and ODC were induced in the colon during the infection, while arginase II was not up-regulated. l-Arg supplementation of wild-type mice or iNOS deletion significantly improved colitis, and l-Arg treatment of iNOS(-/-) mice led to an additive improvement. There was a significant induction of IFN-gamma, IL-1, and TNF-alpha mRNA expression in colitis tissues that was markedly attenuated with l-Arg treatment or iNOS deletion. Treatment with the arginase inhibitor S-(2-boronoethyl)-l-cysteine worsened colitis in both wild-type and iNOS(-/-) mice. Polyamine levels were increased in colitis tissues, and were further increased by l-Arg. In addition, in vivo inhibition of ODC with alpha-difluoromethylornithine also exacerbated the colitis. Taken together, these data indicate that arginase is protective in C. rodentium colitis by enhancing the generation of polyamines in addition to competitive inhibition of iNOS. Modulation of the balance of iNOS and arginase, and of the arginase-ODC metabolic pathway may represent a new strategy for regulating intestinal inflammation.

Alterations in antioxidant power and levels of epidermal growth factor and nitric oxide in saliva of patients with inflammatory bowel diseases

Despite extensive investigation, the pathophysiology of human inflammatory bowel disease (IBD) remains incompletely understood. We examined the existence of oxidative and nitrosative stress and also alterations in epidermal growth factor (EGF) secretion in saliva of IBD patients. Saliva samples were obtained from 30 nonsmoking IBD patients including 16 Crohn's disease (CD) patients and 16 ulcerative colitis (UC) patients and 16 age- and sex-matched controls. Samples were analyzed for thiobarbituric reactive substances (TBARS) as a marker of lipid peroxidation, ferric reducing ability (antioxidant power), and EGF and nitric oxide (NO) levels. Saliva TBARS levels increased significantly (P < 0.01) in CD patients but not in UC patients. Analysis of antioxidant power revealed that saliva of CD patients has lower antioxidant power (P < 0.01) than saliva of the healthy control population. The concentration of EGF was found to be increased (P < 0.01) in saliva of CD patients in comparison to that of healthy subjects. NO levels increased in saliva of both CD and UC patients in comparison to that of healthy subjects. It is concluded that excessive NO production is present in saliva of both CD and UC patients but only saliva of CD patients is oxidatively stressed. EGF secretion is normal in UC patients, although CD patients show a significant increase in salivary EGF levels.

Relative contributions of NOS isoforms during experimental colitis: endothelial-derived NOS maintains mucosal integrity

The role of nitric oxide (NO) in inflammatory bowel diseases has traditionally focused on the inducible form of NO synthase (iNOS). However, the constitutive endothelial (eNOS) and neuronal (nNOS) isoforms may also impact on colitis, either by contributing to the inflammation or by regulating mucosal integrity in response to noxious stimuli. To date, studies examining the roles of the NOS isoforms in experimental colitis have been conflicting, and the mechanisms by which these enzymes exert their effects remain unclear. To investigate and clarify the roles of the NOS isoforms in gut inflammation, we induced trinitrobenzenesulfonic acid colitis in eNOS, nNOS, and iNOS knockout (KO) mice, assessing the course of colitis at early and late times. Both eNOS and iNOS KO mice developed a more severe colitis compared with wild-type mice. During colitis, iNOS expression dramatically increased on epithelial and lamina propria mononuclear cells, whereas eNOS expression remained localized to endothelial cells. Electron and fluorescence microscopy identified bacteria in the ulcerated colonic mucosa of eNOS KO mice, but not in wild-type, iNOS, or nNOS KO mice. Furthermore, eNOS KO mice had fewer colonic goblet cells, impaired mucin production, and exhibited increased susceptibility to an inflammatory stimulus that was subthreshold to other mice. This susceptibility was reversible, because the NO donor isosorbide dinitrate normalized goblet cell numbers and ameliorated subsequent colitis in eNOS KO mice. These results identify a protective role for both iNOS and eNOS during colitis, with eNOS deficiency resulting in impaired intestinal defense against lumenal bacteria and increased susceptibility to colitis.

Arginine and cancer

Arginine is a dibasic, cationic, semiessential amino acid with numerous roles in cellular metabolism. It serves as an intermediate in the urea cycle and as a precursor for protein, polyamine, creatine and nitric oxide (NO) biosynthesis. Arginine is conditionally essential since it becomes necessary under periods of growth and after recovery after injury. Arginine also promotes wound healing and functions as a secretagogue stimulating the release of growth hormone, insulin-like growth factor 1, insulin, and prolactin. Furthermore, arginine has several immunomodulatory effects such as stimulating T- and natural killer cell activity and influencing pro-inflammatory cytokine levels. The discover that l-arginine is the sole precursor for the multifunctional messenger molecule nitric oxide (NO) led to investigation into the role of arginine in numerous physiologic and pathophysiologic phenomena including cancer. Although NO was first identified in endothelial cells, it is now recognized to be generated by a variety of cell types, including several tumor cell lines and solid human tumors. Unfortunately, the precise role of NO in cancer is poorly understood but it may influence tumor initiation, promotion, and progression, tumor-cell adhesion, apoptosis angiogenesis, differentiation, chemosensitivity, radiosensitivity, and tumor-induced immunosuppression. The biological effects of NO are complex and dependent upon numerous regulatory factors. Further research is necessary to enhance our understanding of the complex mechanisms that regulate NO's role in tumor biology. A better understanding of the role of arginine-derived NO in cancer may lead to novel antineoplastic and chemopreventative strategies.

Microsomal prostaglandin E synthase-1 is overexpressed in inflammatory bowel disease. Evidence for involvement of the transcription factor Egr-1

Microsomal prostaglandin E synthase-1 (mPGES-1) catalyzes the conversion of cyclooxygenase-derived prostaglandin (PG) H(2) to PGE(2). Increased amounts of mPGES-1 were detected in inflamed intestinal mucosa from patients with inflammatory bowel disease (IBD). Treatment with tumor necrosis factor (TNF)-alpha stimulated mPGES-1 transcription in human colonocytes, resulting in increased amounts of mPGES-1 mRNA and protein. The inductive effect of TNF-alpha localized to the GC box region of the mPGES-1 promoter. Binding of Egr-1 to the GC box region of the mPGES-1 promoter was enhanced by treatment with TNF-alpha. Notably, increased Egr-1 expression and binding activity were also detected in inflamed mucosa from IBD patients. Treatment with TNF-alpha induced the activities of phosphatidylcholine-phospholipase C (PC-PLC) and protein kinase (PK) C and enhanced NO production. A pharmacological approach was used to implicate PC-PLC --> PKC --> NO signaling as being important for the induction of mPGES-1 by TNF-alpha. TNF-alpha also enhanced guanylate cyclase activity and inhibitors of guanylate cyclase activity blocked the induction of mPGES-1 by TNF-alpha. YC-1, an activator of guanylate cyclase, induced mPGES-1. Overexpressing a dominant negative form of PKG blocked TNF-alpha-mediated stimulation of the mPGES-1 promoter. Taken together, these results suggest that overexpression of mPGES-1 in IBD is the result of Egr-1-mediated activation of transcription. Moreover, TNF-alpha induced mPGES-1 by stimulating PC-PLC --> PKC --> NO --> cGMP --> PKG signal transduction pathway.