Expression of inducible nitric oxide synthase activity in human colon epithelial cells: modulation by T lymphocyte derived cytokines

The Complexity of Interferon Signaling in Host Defense against Protozoan Parasite Infection

Protozoan parasites, such as Plasmodium, Leishmania, Toxoplasma, Cryptosporidium, and Trypanosoma, are causative agents of health-threatening diseases in both humans and animals, leading to significant health risks and socioeconomic losses globally. The development of effective therapeutic and prevention strategies for protozoan-caused diseases requires a full understanding of the pathogenesis and protective events occurring in infected hosts. Interferons (IFNs) are a family of cytokines with diverse biological effects in host antimicrobial defense and disease pathogenesis, including protozoan parasite infection. Type II IFN (IFN-γ) has been widely recognized as the essential defense cytokine in intracellular protozoan parasite infection, whereas recent studies also revealed the production and distinct function of type I and III IFNs in host defense against these parasites. Decoding the complex network of the IFN family in host-parasite interaction is critical for exploring potential new therapeutic strategies against intracellular protozoan parasite infection. Here, we review the complex effects of IFNs on the host defense against intracellular protozoan parasites and the crosstalk between distinct types of IFN signaling during infections.

Involvement of nitrergic neurons in colonic motility in a rat model of ulcerative colitis

BACKGROUND

The mechanisms underlying gastrointestinal (GI) dysmotility with ulcerative colitis (UC) have not been fully elucidated. The enteric nervous system (ENS) plays an essential role in the GI motility. As a vital neurotransmitter in the ENS, the gas neurotransmitter nitric oxide (NO) may impact the colonic motility. In this study, dextran sulfate sodium (DSS)-induced UC rat model was used for investigating the effects of NO by examining the effects of rate-limiting enzyme nitric oxide synthase (NOS) changes on the colonic motility as well as the role of the ENS in the colonic motility during UC.

AIM

To reveal the relationship between the effects of NOS expression changes in NOS-containing nitrergic neurons and the colonic motility in a rat UC model.

METHODS

Male rats (n = 8/each group) were randomly divided into a control (CG), a UC group (EG1), a UC + thrombin derived polypeptide 508 trifluoroacetic acid (TP508TFA; an NOS agonist) group (EG2), and a UC + NG-monomethyl-L-arginine monoacetate (L-NMMA; an NOS inhibitor) group (EG3). UC was induced by administering 5.5% DSS in drinking water without any other treatment (EG1), while the EG2 and EG3 were gavaged with TP508 TFA and L-NMMA, respectively. The disease activity index (DAI) and histological assessment were recorded for each group, whereas the changes in the proportion of colonic nitrergic neurons were counted using immunofluorescence histochemical staining, Western blot, and enzyme linked immunosorbent assay, respectively. In addition, the contractile tension changes in the circular and longitudinal muscles of the rat colon were investigated in vitro using an organ bath system.

RESULTS

The proportion of NOS-positive neurons within the colonic myenteric plexus (MP), the relative expression of NOS, and the NOS concentration in serum and colonic tissues were significantly elevated in EG1, EG2, and EG3 compared with CG rats. In UC rats, stimulation with agonists and inhibitors led to variable degrees of increase or decrease for each indicator in the EG2 and EG3. When the rats in EGs developed UC, the mean contraction tension of the colonic smooth muscle detected in vitro was higher in the EG1, EG2, and EG3 than in the CG group. Compared with the EG1, the contraction amplitude and mean contraction tension of the circular and longitudinal muscles of the colon in the EG2 and EG3 were enhanced and attenuated, respectively. Thus, during UC, regulation of the expression of NOS within the MP improved the intestinal motility, thereby favoring the recovery of intestinal functions.

CONCLUSION

In UC rats, an increased number of nitrergic neurons in the colonic MP leads to the attenuation of colonic motor function. To intervene NOS activity might modulate the function of nitrergic neurons in the colonic MP and prevent colonic motor dysfunction. These results might provide clues for a novel approach to alleviate diarrhea symptoms of UC patients.

Bile acid-sensitive tuft cells regulate biliary neutrophil influx

Inflammation and dysfunction of the extrahepatic biliary tree are common causes of human pathology, including gallstones and cholangiocarcinoma. Despite this, we know little about the local regulation of biliary inflammation. Tuft cells, rare sensory epithelial cells, are particularly prevalent in the mucosa of the gallbladder and extrahepatic bile ducts. Here, we show that biliary tuft cells express a core genetic tuft cell program in addition to a tissue-specific gene signature and, in contrast to small intestinal tuft cells, decreased postnatally, coincident with maturation of bile acid production. Manipulation of enterohepatic bile acid recirculation revealed that tuft cell abundance is negatively regulated by bile acids, including in a model of obstructive cholestasis in which inflammatory infiltration of the biliary tree correlated with loss of tuft cells. Unexpectedly, tuft cell-deficient mice spontaneously displayed an increased gallbladder epithelial inflammatory gene signature accompanied by neutrophil infiltration that was modulated by the microbiome. We propose that biliary tuft cells function as bile acid-sensitive negative regulators of inflammation in biliary tissues and serve to limit inflammation under homeostatic conditions.

Stressor-Induced Increases in Circulating, but Not Colonic, Cytokines Are Related to Anxiety-like Behavior and Hippocampal Inflammation in a Murine Colitis Model

Stressor exposure increases colonic inflammation. Because inflammation leads to anxiety-like behavior, we tested whether stressor exposure in mice recovering from dextran-sulfate-sodium (DSS)-induced colitis enhances anxiety-like behavior. Mice received 2% DSS for five consecutive days prior to being exposed to a social-disruption (SDR) stressor (or being left undisturbed). After stressor exposure, their behavior was tested and colitis was assessed via histopathology and via inflammatory-cytokine measurement in the serum and colon. Cytokine and chemokine mRNA levels in the colon, mesenteric lymph nodes (MLNs), hippocampus, and amygdala were measured with RT-PCR. SDR increased anxiety-like behaviors, which correlated with serum and hippocampal IL-17A. The stressor also reduced IL-1β, CCL2, and iNOS in the colonic tissue, but increased iNOS, IFNγ, IL-17A, and TNFα in the MLNs. A network analysis indicated that reductions in colonic iNOS were related to elevated MLN iNOS and IFNγ. These inflammatory markers were related to serum and hippocampal IL-17A and associated with anxiety-like behavior. Our data suggest that iNOS may protect against extra-colonic inflammation, and when suppressed during stress it is associated with elevated MLN IFNγ, which may coordinate gut-to-brain inflammation. Our data point to hippocampal IL-17A as a key correlate of anxiety-like behavior.

Efficacy of a functional food ingredient from Ensete superbum Roxb Cheesman peel in reducing the severity of ulcerative colitis in murine model

Ulcerative colitis is a recurrent inflammatory illness of the colon with an elevated risk of developing colon cancer. The drugs presently used to treat UC cause adverse effects and are...

Cancer-protective effect of a synbiotic combination between Lactobacillus gasseri 505 and a Cudrania tricuspidata leaf extract on colitis-associated colorectal cancer

Previously, a synbiotic combination of probiotic Lactobacillus gasseri 505 (LG) and a new prebiotic, Cudrania tricuspidata leaf extract (CT) in fermented milk, designated FCT, showed an in vitro immunomodulatory effect and antioxidant activity. Although synbiotic combination might have cancer-protective effects, these activities have not been fully validated in vivo. Ten-week treatment of LG, CT, or FCT to azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colitis-associated colorectal cancer (CAC) mouse model reduced both the incidence of colonic tumors and damage to the colonic mucosa effectively, suggesting a cancer-protective effect. To understand these, biomarkers associated with inflammation, colon barrier, apoptosis, and cancer cell proliferation were monitored in AOM/DSS group versus LG/CT/FCT groups. A synbiotic combination (FCT) down-regulated pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, and IL-6) and inflammation-associated enzymes (iNOS and COX-2), and up-regulated anti-inflammatory cytokines (IL-4 and IL-10). In addition, colon barrier experiment revealed that biomarkers of mucus layer (MUC-2 and TFF3) and tight junction (occludin and ZO-1) were up-regulated. Subsequent apoptosis experiment showed that pro-apoptotic factors (p53, p21, and Bax) were up-regulated and anti-apoptotic factors (Bcl-2 and Bcl-xL) were down-regulated. Furthermore, comparative metagenome analysis of gut microbiota revealed that Staphylococcus decreased but Lactobacillus, Bifidobacterium, and Akkermansia increased, supporting their protective effects, accompanied by increased short-chain fatty acids (SCFAs). Taken together, the FCT administration showed cancer-protective effects by reducing the risk of colitis-associated colon cancer via regulation of inflammation, carcinogenesis, and compositional change of gut microbiota. Consequently, the synbiotic combination (FCT) could be a novel potential health-protective natural agent against CAC.

Selective chemiluminescent TURN-ON quantitative bioassay and imaging of intracellular hydrogen peroxide in human living cells

Hydrogen peroxide is an unavoidable by-product of cell metabolism, but when it is not properly managed by the body it can lead to several pathologies (e.g., premature aging, cardiovascular and neurodegenerative diseases, cancer). Several methods have been proposed for the measurement of intracellular H₂O₂ but none of them has proven to be selective. We developed a rapid all-in-one chemiluminescent bioassay for the quantification of H₂O₂ in living cells with a low limit of detection (0.15 μM). The method relies on an adamantylidene-1,2-dioxetane lipophilic probe containing an arylboronate moiety; upon reaction with H₂O₂ the arylboronate moiety is converted to the correspondent phenol and the molecule decomposes leading to an excited-state fragment that emits light. The probe has been successfully employed for quantifying intracellular H₂O₂ in living human endothelial, colon and keratinocyte cells exposed to different pro-oxidant stimuli (i.e., menadione, phorbol myristate acetate and lipopolysaccharide). Imaging experiments clearly localize the chemiluminescence emission inside the cells. Treatment of cells with antioxidant molecules leads to a dose-dependent decrease of intracellular H₂O₂ levels. As a proof of concept, the bioassay has been used to measure the antioxidant activity of extracts from Brassica juncea wastes, which contain glucosinolates, isothiocyanates and other antioxidant molecules.

Fleszar M, Bednarz-Misa I, Lewandowski Ł, Szczuka I, Kempiński R, Neubauer K. Transcriptional and Metabolomic Analysis of L-Arginine/Nitric Oxide Pathway in Inflammatory Bowel Disease and Its Association with Local Inflammatory and Angiogenic Response: Preliminary Findings

L-arginine/nitric oxide pathway in Crohn's disease (CD) and ulcerative colitis (UC) is poorly investigated. The aim of current study is to quantify pathway serum metabolites in 52 CD (40 active), 48 UC (33 active), and 18 irritable bowel syndrome patients and 40 controls using mass spectrometry and at determining mRNA expression of pathway-associated enzymes in 91 bowel samples. Arginine and symmetric dimethylarginine decreased (p < 0.05) in active-CD (129 and 0.437 µM) compared to controls (157 and 0.494 µM) and active-UC (164 and 0.52 µM). Citrulline and dimethylamine increased (p < 0.05) in active-CD (68.7 and 70.9 µM) and active-UC (65.9 and 73.9 µM) compared to controls (42.7 and 50.4 µM). Compared to normal, CD-inflamed small bowel had downregulated (p < 0.05) arginase-2 by 2.4-fold and upregulated dimethylarginine dimethylaminohydrolase (DDAH)-2 (1.5-fold) and arginine N-methyltransferase (PRMT)-2 (1.6-fold). Quiescent-CD small bowel had upregulated (p < 0.05) arginase-2 (1.8-fold), DDAH1 (2.9-fold), DDAH2 (1.5-fold), PRMT1 (1.5-fold), PRMT2 (1.7-fold), and PRMT5 (1.4-fold). Pathway enzymes were upregulated in CD-inflamed/quiescent and UC-inflamed colon as compared to normal. Compared to inflamed, quiescent CD-colon had upregulated DDAH1 (5.7-fold) and ornithine decarboxylase (1.6-fold). Concluding, the pathway is deregulated in CD and UC, also in quiescent bowel, reflecting inflammation severity and angiogenic potential. Functional analysis of PRMTs and DDAHs as potential targets for therapy is warranted.

Somatic inflammatory gene mutations in human ulcerative colitis epithelium

With ageing, normal human tissues experience an expansion of somatic clones that carry cancer mutations^1-7. However, whether such clonal expansion exists in the non-neoplastic intestine remains unknown. Here, using whole-exome sequencing data from 76 clonal human colon organoids, we identify a unique pattern of somatic mutagenesis in the inflamed epithelium of patients with ulcerative colitis. The affected epithelium accumulates somatic mutations in multiple genes that are related to IL-17 signalling-including NFKBIZ, ZC3H12A and PIGR, which are genes that are rarely affected in colon cancer. Targeted sequencing validates the pervasive spread of mutations that are related to IL-17 signalling. Unbiased CRISPR-based knockout screening in colon organoids reveals that the mutations confer resistance to the pro-apoptotic response that is induced by IL-17A. Some of these genetic mutations are known to exacerbate experimental colitis in mice^8-11, and somatic mutagenesis in human colon epithelium may be causally linked to the inflammatory process. Our findings highlight a genetic landscape that adapts to a hostile microenvironment, and demonstrate its potential contribution to the pathogenesis of ulcerative colitis.

PD123319, angiotensin II type II receptor antagonist, inhibits oxidative stress and inflammation in 2, 4-dinitrobenzene sulfonic acid-induced colitis in rat and ameliorates colonic contractility

Angiotensin II, the main effector of renin angiotensin system, plays an important role in the inflammatory process and most of its effects are mediated through the AT1 receptor activation. However, the knowledge about the AT2 receptor involvement in this process is still evolving. We previously found that in an experimental model of colitis, AT2 receptor activation can contribute to the impairment of the muscle contractility in vitro in the course of inflammation. Here, we investigated the potential alleviating effects of the in vivo treatment of PD123319 (1-[[4-(Dimethylamino)-3-methylphenyl]methyl]-5-(diphenylacetyl)-4,5,6,7- tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid ditrifluoroacetate), AT2 receptor antagonist, in 2,4-dinitrobenzene sulfonic acid (DNBS)-induced rat model of colitis. The effects of i.p PD123319 (0.3, 3 and 10 mg/kg) administration to rats subjected to intra-rectal DNBS instillation were investigated. The study revealed that the colon injury and the inflammatory signs were ameliorated by PD123319 when visualized by the histopathological examination. The colon shortening, myeloperoxidase activity, and colonic expression of IL-1β, IL-6 and iNOS were downregulated in a dose-dependent manner in DNBS-induced colitis rats treated with PD123319 and the anti-oxidant defense machinery was also improved. The mechanism of these beneficial effects was found in the ability of PD123319 to inhibit NF-κB activation induced by DNBS. The colonic contractility in inflamed tissues was also improved by PD123319 treatment. In conclusion, our data have demonstrated previously that undescribed proinflammatory effects for the AT2 receptors in DNBS-induced colitis in rats in which they are mediated likely by NF-κB activation and reactive oxygen species generation. Moreover, when the inflammatory process is mitigated by the AT2 receptor antagonist treatment, the smooth muscle is able to recover its functionality.

Inducible nitric oxide synthase-derived nitric oxide reduces vagal satiety signalling in obese mice

KEY POINTS

Obesity is associated with disrupted satiety regulation. Mice with diet-induced obesity have reduced vagal afferent neuronal excitability and a decreased afferent response to satiety signals. A low grade inflammation occurs in obesity with increased expression of inducible nitric oxide synthase (iNOS). Inhibition of iNOS in diet-induced obese mice restored vagal afferent neuronal excitability, increased the afferent response to satiety mediators and distention of the gut, and reduced short-term energy intake. A prolonged inhibition of iNOS reduced energy intake and body weight gain during the first week, and reduced amounts of epididymal fat after 3 weeks. We identified a novel pathway underlying disrupted satiety regulation in obesity. Blocking of this pathway might be clinically useful for the management of obesity.

ABSTRACT

Vagal afferents regulate feeding by transmitting satiety signals to the brain. Mice with diet-induced obesity have reduced vagal afferent sensitivity to satiety signals. We investigated whether inducible nitric oxide synthase (iNOS)-derived NO contributed to this reduction. C57BL/6J mice were fed a high- or low-fat diet for 6-8 weeks. Nodose ganglia and jejunum were analysed by immunoblotting for iNOS expression; NO production was measured using a fluorometric assay. Nodose neuron excitability and intestinal afferent sensitivity were evaluated by whole-cell patch clamp and in vitro afferent recording, respectively. Expression of iNOS and production of NO were increased in nodose ganglia and the small intestine in obese mice. Inhibition of iNOS in obese mice by pre-treatment with an iNOS inhibitor increased nodose neuron excitability via 2-pore-domain K⁺ channel leak currents, restored afferent sensitivity to satiety signals and reduced short-term energy intake. Obese mice given the iNOS inhibitor daily for 3 weeks had reduced energy intake and decreased body weight gain during the first week, compared to mice given saline, and lower amounts of epididymal fat at the end of 3 weeks. Inhibition of iNOS or blocking the action of iNOS-derived NO on vagal afferent pathways might comprise therapeutic strategies for hyperphagia and obesity.

Antibiotics suppress colon tumorigenesis through inhibition of aberrant DNA methylation in an azoxymethane and dextran sulfate sodium colitis model

Chronic inflammation is involved in the development of colon cancer by inducing mutations and aberrant DNA methylation in colon epithelial cells. Furthermore, there is growing evidence that colonic microbiota modulates the inflammation response in the host and influences colon tumorigenesis. However, the influence of colonic microbiota on aberrant DNA methylation remains unknown. Here, we show the effect of colonic microbes on DNA methylation and tumorigenicity using a mouse model of human ulcerative colitis. Mice treated with azoxymethane (AOM) and dextran sulfate sodium (DSS) showed an increase in degree of colitis, as estimated by body weight, occult blood, and stool consistency/diarrhea at 2 weeks after treatment, but treatment with antibiotics markedly reduced the severity of the colitis. Although mucosal hyperplasia and increased inflammation‐related genes were observed in the colonic epithelial cells of the AOM/DSS‐treated mice, treatment with antibiotics abrogated these changes. In addition, treatment with antibiotics significantly decreased the number of mucosal nodules from 5.9 ± 5.3 to 0.2 ± 0.6 (P < .01) and area of occupancy from 50.1 ± 57.4 to 0.5 ± 1.4 mm² (P < .01). Aberrant DNA methylation of three marker CpG islands (Cbln4, Fosb, and Msx1) was induced by AOM/DSS treatment in colonic mucosae, but this increase was suppressed by 50%‐92% (P < .05) with antibiotic treatment. Microbiome analysis showed that this change was associated with a decrease of the Clostridium leptum subgroup. These data indicate that antibiotics suppressed tumorigenesis through inhibition of aberrant DNA methylation induced by chronic inflammation.

Black rice anthocyanin-rich extract and rosmarinic acid, alone and in combination, protect against DSS-induced colitis in mice

The aim of this study was to investigate the effect of black rice anthocyanin-rich extract (BRAE) and rosmarinic acid (RA), alone and in combination, on dextran sulfate sodium (DSS)-induced colitis in mice. Results showed that administration of BRAE and RA, alone and in combination, significantly decreased the disease activity index (DAI) and the histological score of colons in DSS-induced colitis mice. Moreover, the administration of BRAE and RA, alone and in combination, not only reduced myeloperoxidase (MPO) and nitric oxide (NO) levels, but also inhibited the expression of pro-inflammatory mediators including interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2. Our results showed that BRAE decreased the histological score and TNF-α mRNA expression in a dose-dependent manner, while BRAE + RA dose-dependently attenuated the histological score and mRNA expression of IL-6. However, the benefits of RA were not dose-dependent within the dose range of 25-100 mg kg-1. The combination of BRAE and RA showed better inhibitory effect on the NO content and iNOS mRNA expression than BRAE or RA given alone, and was the most effective in ameliorating DSS-induced colitis at 100 mg kg-1. Notably, the BRAE and RA combination exhibited additive interactions in reducing MPO and NO levels, as well as the expression of some pro-inflammatory mediators (IL-6, IL-1β and iNOS), especially at 100 mg kg-1. In conclusion, dietary BRAE and RA, alone and in combination, alleviate the symptoms and inflammation of DSS-induced colitis in mice, and may provide a promising dietary approach for the management of inflammatory bowel disease.

Tumor necrosis factor α decreases aquaporin 3 expression in intestinal epithelial cells through inhibition of constitutive transcription

Inflammatory diseases of the gut are associated with altered electrolyte and water transport, leading to the development of diarrhea. Epithelially expressed aquaporins (AQPs) are downregulated in inflammation, although the mechanisms involved are not known. We hypothesized that AQP3 expression in intestinal epithelial cells is altered in intestinal inflammation and that these changes are driven by tumor necrosis factor (TNF) α. Human colonic adenocarcinoma (HT‐29) cells were treated with TNFα to investigate signaling mechanisms in vitro. AQP3 expression was assessed by real‐time PCR and radiolabeled glycerol uptake, with select inhibitors and a luciferase reporter construct used to further elucidate intracellular signaling. AQP3 expression was downregulated in HT‐29 cells treated with TNFα. Luciferase reporter construct experiments revealed that TNFα downregulated constitutive transcriptional activity of the AQP3 promoter, and inhibition of MEK/ERK and nuclear factor κB (NF‐κB) signaling prevented the decrease in AQP3 mRNA expression. Constitutive AQP3 expression was suppressed by specificity protein (Sp) 3, and knockdown of this transcription factor bound to the AQP3 promoter was able to partially prevent the TNFα‐induced downregulation of AQP3. TNFα signals through MEK/ERK and NF‐κB to enhance the negative transcriptional control of AQP3 expression exerted by Sp3. Similar mechanisms regulate numerous ion channels, suggesting a common mechanism by which both ion and water transport are altered in inflammation.

Arginine Metabolism in Myeloid Cells Shapes Innate and Adaptive Immunity

Arginine metabolism has been a key catabolic and anabolic process throughout the evolution of the immune response. Accruing evidence indicates that arginine-catabolizing enzymes, mainly nitric oxide synthases and arginases, are closely integrated with the control of immune response under physiological and pathological conditions. Myeloid cells are major players that exploit the regulators of arginine metabolism to mediate diverse, although often opposing, immunological and functional consequences. In this article, we focus on the importance of arginine catabolism by myeloid cells in regulating innate and adaptive immunity. Revisiting this matter could result in novel therapeutic approaches by which the immunoregulatory nodes instructed by arginine metabolism can be targeted.

Molecular topology: a strategy to identify novel compounds against ulcerative colitis

In the present paper, a strategy to identify novel compounds against ulcerative colitis (UC) by molecular topology (MT) is presented. Several quantitative structure-activity relationship (QSAR) models based on molecular topology have been developed to predict inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha ([Formula: see text]) mediated anti-ulcerative colitis (UC) activity and protective activity against a dextran sulfate sodium (DSS)-induced UC model. Each one has been used for the screening of four previously selected compounds as potential therapeutic agents for UC: alizarin-3-methyliminodiacetic acid (AMA), Calcein, (+)-dibenzyl-L-tartrate, and Ro 41-0960. These four compounds were then tested in vitro and in vivo and confirmed AMA and Ro 41-0960 as the best lead candidates for further development against UC.

Roles of nitric oxide and intestinal microbiota in the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis remains one of the most vexing problems in the neonatal intensive care unit. Risk factors for NEC include prematurity, formula feeding, and inappropriate microbial colonization of the GI tract. The pathogenesis of NEC is believed to involve weakening of the intestinal barrier by perinatal insults, translocation of luminal bacteria across the weakened barrier, an exuberant inflammatory response, and exacerbation of the barrier damage by inflammatory factors, leading to a vicious cycle of inflammation-inflicted epithelial damage. Nitric oxide (NO), produced by inducible NO synthase (iNOS) and reactive NO oxidation intermediates play a prominent role in the intestinal barrier damage by inducing enterocyte apoptosis and inhibiting the epithelial restitution processes, namely enterocyte proliferation and migration. The factors that govern iNOS upregulation in the intestine are not well understood, which hampers efforts in developing NO/iNOS-targeted therapies. Similarly, efforts to identify bacteria or bacterial colonization patterns associated with NEC have met with limited success, because the same bacterial species can be found in NEC and in non-NEC subjects. However, microbiome studies have identified the three important characteristics of early bacterial populations of the GI tract: high diversity, low complexity, and fluidity. Whether NEC is caused by specific bacteria remains a matter of debate, but data from hospital outbreaks of NEC strongly argue in favor of the infectious nature of this disease. Studies in Cronobacter muytjensii have established that the ability to induce NEC is the property of specific strains rather than the species as a whole. Progress in our understanding of the roles of bacteria in NEC will require microbiological experiments and genome-wide analysis of virulence factors.

Splanchnic Hemodynamics and Intestinal Vascularity in Crohn's Disease: An In Vivo Evaluation Using Doppler and Contrast-Enhanced Ultrasound and Biochemical Parameters

Crohn's disease (CD) is characterized by inflammation and angiogenesis of affected bowel. We evaluated the correlation among vascularity of intestinal wall in CD, splanchnic hemodynamics, clinical activity and biochemical parameters of inflammation and angiogenesis. Sixteen patients with ileal CD and 10 healthy controls were investigated by means of Doppler ultrasound of the superior mesenteric artery and color Doppler and contrast-enhanced ultrasound of the ileal wall. In parallel, serum levels of vascular endothelial growth factor, tumor necrosis factor-α (TNF-α) and nitric oxide, before and 30 min after a standard meal, were evaluated. In CD patients, there was a significant post-prandial reduction in the resistance index and pulsatility index of the superior mesenteric artery, associated with increased levels of nitric oxide and decreased amounts of TNF-α. A correlation was observed between vascular endothelial growth factor and contrast-enhanced ultrasound parameters of intestinal wall vascularity (r = 0.63-0.71, p < 0.05) and between these parameters and superior mesenteric artery blood flow after fasting (resistance and pulsatility indexes: r = -0.64 and -0.72, p < 0.05). Our results revealed a post-prandial increase in nitric oxide and decrease in TNF-α in CD patients in vivo. They also confirm the role of vascular endothelial growth factor in angiogenesis and in pathologic vascular remodeling of CD and its effect on splanchnic blood flow.

Probiotic bacteria lactobacillus and bifidobacterium attenuate inflammation in dextran sulfate sodium-induced experimental colitis in mice

It is widely accepted that inflammatory Bowel disease (IBD) arises from a dysregulated mucosal immune response to the enteric microbiota in the gut of a genetically susceptible individual. No definitive therapies are available for this inflammatory disorder. Therefore it became imperative to develop new strategies for treating this disease. Probiotics have emerged as a potential new therapeutic strategy for IBD, however their exact mechanisms of action is still poorly defined. In this study, we address the potential effect of a probiotic cocktail (Ultrabiotique®) composed of four live bacterial strains (L. acidophilus, L. plantarum, B. lactis and B.breve) to promote recovery from acute colitis. Probiotic was given to mice by oral gavage after the onset of colitis and the establishment of dextran sulfate sodium (DSS)-induced intestinal injury. Clinical parameters were monitored daily, histological scores of colitis and the production of nitric oxide (NO) and interferon-&#947; (IFN-&#947;) were determined. In addition, TLR4, NF-&#954;B and iNOS colonic expression were examined. Probiotic treatment ameliorated clinical symptoms and histological scores. NO and IFN-&#947; production in plasma were decreased by probiotic. These results were associated with reduced TLR4, iNOS and NF-&#1082;B expression in colonic tissue. In conclusion, probiotic exerted anti-inflammatory effects and contributed to a rapid recovery of DSS-induced acute colitis.

Susceptibility to Salmonella carrier-state: a possible Th2 response in susceptible chicks

Infection of chicken with Salmonella may lead to a carrier-state characterized by the persistence of bacteria in the ceca for a long period of time and result in their excretion in feces. This excretion is the source of contamination of their congeners and food. During infection, enterocytes are the primary target cells for Salmonella, the producers of soluble factors which launch immune response and cells which are reciprocally responsive to surrounding immune cells. This study used microarrays to compare the gene expression profile during carrier-state of enterocytes purified from infected and control chicks which are either resistant or susceptible to Salmonella Enteritidis carrier-state. In total, we identified 271 genes significantly differentially expressed with an absolute fold change greater than 1.5. A global analysis determined interaction networks between differentially regulated genes. Using an a priori approach, our analyses focused on differentially expressed genes which were transcriptionally linked to cytokines playing a major role in the fate of the immune response. The expression of genes transcriptionally linked to type I interferon and TGF-β was down-regulated in infected chicks from both lines. Gene expression linked to the Th1 axis suggests the latter is inhibited in both lines. Finally, the expression of genes linked to IL-4, IL-5 and IL-13 indicates that susceptibility to carrier-state could be associated with a Th2 bias. Overall, these results highlight that the response to Salmonella during the acute phase and carrier-state is different and that enterocytes play a central role in this response.

Clinical presentation, diagnosis, pathogenesis and treatment options for lymphocytic colitis (Review)

Lymphocytic colitis (LC) is characterized by chronic or relapsing non-bloody watery diarrhea and a macroscopically normal colon. However, histopathological examination of colonic biopsy samples reveals an increased intraepithelial infiltration of lymphocytes (≥20/100 enterocytes), and increased inflammatory cells within the lamina propria, but with a normal mucosal architecture. The reported prevalence of LC varies from 14.2 to 45 per 100,000 individuals, while its reported incidence is between 0.6 and 16 per 100,000 individuals. LC has a high rate of spontaneous symptomatic remission and is not associated with an increased risk of colon cancer or inflammatory bowel disease. The diagnosis is based on the histopathological findings. The density of colonic chromogranin A-positive cells provides an effective diagnostic tool with high sensitivity and specificity in both the right and left colon. Gastrointestinal infections, drugs, and/or autoimmunity may trigger chronic colonic low-grade inflammation. Colonic nitric oxide, serotonin and peptide YY (PYY) cell densities are markedly increased in patients with LC. It has been hypothesized that the low-grade inflammation in LC through the endocrine-immune axis causes this increase. It has been postulated further that these abnormalities in the neuroendocrine system of the colon are responsible for the diarrhea observed in patients with LC. The benign course and rate of spontaneous remission of LC denotes that drugs with severe side-effects should be avoided if possible. The drug cost and drug coverage may also be limiting factors for some patients. These aspects should be taken into account when making decisions regarding treatment options.

Intestinal myofibroblasts produce nitric oxide in response to combinatorial cytokine stimulation

Inflammatory bowel disease (IBD) patients display elevated levels of intraluminal nitric oxide (NO). NO can react with other molecules to form toxic compounds, which has led to the idea that NO may be an important mediator of IBD. However, the cellular source of NO and how its production is regulated in the intestine are unclear. In this study we aimed to determine if intestinal myofibroblasts produce NO in response to the IBD-associated cytokines IL-1β, TNFα, and IFNγ. Intestinal myofibroblasts were isolated from mice and found to express inducible nitric oxide synthase (iNOS) mRNA, but not endothelial NOS or neuronal NOS. Individual treatment of myofibroblasts with IL-1β, TNFα, or IFNγ had no effect on NO production, but stimulation with combinations of these cytokines synergistically increased iNOS mRNA and protein expression. Treatment with TNFα or IFNγ increased cell surface expression of IFNγRI or TNFRII, respectively, suggesting that these cytokines act in concert to prime NO production by myofibroblasts. Impairment of NF-κB activity with a small molecule inhibitor was sufficient to prevent increased expression of IFNγRI or TNFRII, and inhibition of Akt, JAK/STAT, or NF-κB blocked nearly all NO production induced by combinatorial cytokine treatment. These data indicate that intestinal myofibroblasts require stimulation by multiple cytokines to produce NO and that these cytokines act through a novel pathway involving reciprocal cytokine receptor regulation and signaling by Akt, JAK/STAT, and NF-κB.

Results of the 2nd scientific workshop of the ECCO (III): basic mechanisms of intestinal healing

The second scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on the relevance of intestinal healing for the disease course of inflammatory bowel disease (IBD). The objective was to better understand basic mechanisms, markers for disease prediction, detection and monitoring of intestinal healing, impact of intestinal healing on the disease course of IBD as well as therapeutic strategies. The results of this workshop are presented in four separate manuscripts. This section describes basic mechanisms of intestinal healing, identifies open questions in the field and provides a framework for future studies.

Thrombospondin-1 and VEGF in inflammatory bowel disease

Background and aim

Angiogenesis is an important process in the pathogenesis of chronic inflammation. We aimed to study the angiogeneic balance in inflammatory bowel disease (IBD) by evaluating the expression of vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1) on colonic epithelial cells, together with the expression of inducible nitric oxide synthase (iNOS).

Methods

Twenty-one ulcerative colitis (UC), 14 Crohn's disease (CD), 11 colorectal cancer patients, and 11 healthy controls colonic biopsy samples were evaluated immunohistochemically.

Results

The expressions of TSP-1, VEGF, and iNOS in UC and CD groups were higher than expression in healthy control group, all with statistical significance. However, in colorectal cancer group, VEGF and iNOS expressions were increased importantly, but TSP-1 expression was not statistically different from healthy control group's expression. Both TSP-1 and VEGF expressions were correlated with iNOS expression distinctly but did not correlate with each other.

Conclusions

Both pro-angiogeneic VEGF and antiangiogeneic TSP-1 expressions were found increased in our IBD groups, but in colorectal cancer group, only VEGF expression was increased. TSP-1 increases in IBD patients as a response to inflammatory condition, but this increase was not enough to suppress pathologic angiogenesis and inflammation in IBD.

Involvement of interferon-γ in bowel disease pathogenesis by nitric oxide pathway: a study in Algerian patients

The pathogenesis of inflammatory bowel disease (IBD) is complex, involving a wide range of molecules including cytokines. Abnormalities in the expression of immunoregulatory cytokines such as interferon-γ (IFN-γ) and interleukin-12 (IL-12) may indicate a dysregulation of intestinal immunity probably associated with pathogenic events. The aim of this work was to study the implication of IFN-γ and nitric oxide (NO) in bowel disease pathogenesis. In this study, we investigated the circulating IFN-γ and IL-12 production in 2 groups of Algerian patients with IBD (Crohn's disease and ulcerative colitis). Moreover, systemic NO concentrations and NO generation by colonic mucosa were determined in these patients. Finally, we examined the effect of IFN-γ on NO production by peripheral blood mononuclear cells (PBMCs) of these patients. Our results indicate that IFN-γ/IL-12 production in IBD patients was increased in comparison to healthy donors. This strong production correlates with high levels of NO in sera and colonic mucosa culture. Interestingly, NO production was related to the clinical stage of IBD patients (inactive or active stage). The relationship between IFN-γ and NO production in IBD patients were confirmed by in vitro experiments and the role of IFN-γ in NO synthase induction in patients' PBMC culture was suggested. Collectively, our results show that IFN-γ plays a pivotal role in IBD pathogenesis through NO pathway.

Inducible NO synthase and antibacterial host defence in times of Th17/Th22/T22 immunity

During the last two decades nitric oxide (NO) produced by inducible NO synthase (iNOS or NOS2) has been characterized as immunoregulatory and antimicrobial principle displaying the potential to determine course of disease in a range of infections. Being an enzyme primarily regulated on expressional level, cytokine-driven iNOS appears to be connected in particular with activation of Th1-type immunity. However, with the recent advent of additional, partly overlapping CD4(+) T cell effector subsets, namely Th17 and Th22 cells, a further layer of complexity has been added to immunoregulatory networks determining inflammatory gene expression in the context of microbial infections. Here, we review current knowledge on activation of iNOS function by interleukin (IL)-17 and IL-22 with focus on Th17/Th22-directed antibacterial immunity.

Increased expression of chemokine receptor CCR3 and its ligands in ulcerative colitis: the role of colonic epithelial cells in in vitro studies

Human colonic epithelial cells express T helper type 1 (Th1)-associated chemoattractants, yet little is known about the production of Th2-associated chemoattractants. CCL11/eotaxin-1, CCL24/eotaxin-2 and CCL26/eotaxin-3 are known to attract CCR3-expressing, Th2-polarized lymphocytes. We studied constitutive and inflammation-induced expression and production of CCR3 together with its ligands in the colon and peripheral blood of patients with inflammatory bowel disease (IBD) by flow cytometry, reverse transcription–polymerase chain reaction (RT–PCR) and enzyme-linked immunosorbent assay (ELISA). We further defined the regulated expression of these chemokines by RT–PCR and ELISA using cultured human epithelial cell lines. A higher fraction of peripheral T lymphocytes were found to be positive for CCR3 in patients with ulcerative colitis (UC) compared to Crohn’s disease (CD), while almost no CCR3(+) T cells were found in normal controls (NC). Similarly, higher and more frequent expression of CCR3 was observed in colonic biopsies from patients with UC, regardless of the disease activity, when compared to CD or NCs. Serum CCL11/eotaxin-1 was increased significantly in UC (306 ± 87 pg/ml) and less so in CD (257 ± 43 pg/ml), whereas CCL24/eotaxin-2, and CCL26/eotaxin-3 were increased only in UC. Colonic expression of the three chemokines was minimal in NCs but high in inflammatory bowel diseases (especially UC) and was independent of disease activity. Th2, and to a lesser extent Th1, cytokines were able to induce expression and production of all three eotaxins from colonic epithelial cells in culture. CCR3 and ligands over-expression would appear to be a characteristic of UC. The production of CCR3 ligands by human colonic epithelial cells suggests further that epithelium can play a role in modulating pathological T cell-mediated mucosal inflammation.

ROS, Hsp27, and IKKbeta mediate dextran sodium sulfate (DSS) activation of IkappaBa, NFkappaB, and IL-8

BACKGROUND

Dextran sodium sulfate (DSS) is a sulfated polysaccharide that has been very widely used to induce inflammation in experimental models of inflammatory bowel disease in which the effects of pharmacologic and biologic therapies are tested. However, the precise mechanisms by which DSS induces inflammation have not been elucidated.

METHODS

DSS-induced increases in phospho-IkappaBalpha, nuclear NFkappaB (p65), and IL-8 secretion in human colonic epithelial cells in tissue culture are attributable to a reactive oxygen species (ROS)-induced pathway of inflammation, and do not require TLR4, MyD88, or Bcl10, which are associated with the innate immune pathway of NFkappaB-IL-8 activation.

RESULTS

DSS-induced increases were inhibited by the ROS scavengers Tempol and Tiron, were associated with decreased phosphorylation of MAPK12 (p38gamma), MAPK 13 (p38delta), and Hsp27, and required the IkappaB kinase (IKK) signalosome component IKKbeta. In ex vivo colonic tissue from TLR4-deficient mice, or following knockdown of MyD88 or Bcl10 or exposure to an IRAK 1/4 inhibitor, DSS effects were not suppressed. Data demonstrated that DSS activates IkappaBalpha, NFkappaB, and IL-8 through an ROS-Hsp27-IKKbeta-mediated pathway, and not through an innate immune cascade.

CONCLUSIONS

These results suggest that DSS models of inflammation may not be optimal for evaluation of interventions that involve mechanisms of innate immunity.

Nitric oxide-mediated intestinal injury is required for alcohol-induced gut leakiness and liver damage

BACKGROUND

Alcoholic liver disease (ALD) requires endotoxemia and is commonly associated with intestinal barrier leakiness. Using monolayers of intestinal epithelial cells as an in vitro barrier model, we showed that ethanol-induced intestinal barrier disruption is mediated by inducible nitric oxide synthase (iNOS) upregulation, nitric oxide (NO) overproduction, and oxidation/nitration of cytoskeletal proteins. We hypothesized that iNOS inhibitors [NG-nitro-l-arginine methyl ester (l-NAME), l-N(6)-(1-iminoethyl)-lysine (l-NIL)] in vivo will inhibit the above cascade and liver injury in an animal model of alcoholic steatohepatitis (ASH).

METHODS

Male Sprague-Dawley rats were gavaged daily with alcohol (6 g/kg/d) or dextrose for 10 weeks +/- l-NAME, l-NIL, or vehicle. Systemic and intestinal NO levels were measured by nitrites and nitrates in urine and tissue samples, oxidative damage to the intestinal mucosa by protein carbonyl and nitrotyrosine, intestinal permeability by urinary sugar tests, and liver injury by histological inflammation scores, liver fat, and myeloperoxidase activity.

RESULTS

Alcohol caused tissue oxidation, gut leakiness, endotoxemia, and ASH. l-NIL and l-NAME, but not the d-enantiomers, attenuated all steps in the alcohol-induced cascade including NO overproduction, oxidative tissue damage, gut leakiness, endotoxemia, hepatic inflammation, and liver injury.

CONCLUSIONS

The mechanism we reported for alcohol-induced intestinal barrier disruption in vitro - NO overproduction, oxidative tissue damage, leaky gut, endotoxemia, and liver injury - appears to be relevant in vivo in an animal model of alcohol-induced liver injury. That iNOS inhibitors attenuated all steps of this cascade suggests that prevention of this cascade in alcoholics will protect the liver against the injurious effects of chronic alcohol and that iNOS may be a useful target for prevention of ALD.

Expression of a splice variant of CXCR3 in Crohn's disease patients; indication for a lymphocyte--epithelial cell interaction

BACKGROUND AND AIM

T-lymphocyte migration is implicated in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC). CXC chemokines MIG, IP-10, and I-TAC act by binding to CXCR3 receptor on T-lymphocytes. We investigated the role of these chemokines and their receptor in patients with UC, CD, and normal controls (NC).

METHODS

Chemokine expression and serum levels were examined in colonic biopsies from patients and NC using reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. HT-29 and Caco2 colonic epithelial cells were studied following in vitro stimulation with proinflammatory (Th1) and Th2-derived cytokines. CXCR3 receptor expression was assessed in CD3+ peripheral blood lymphocytes (PBL) from patients and NC and in stimulated Jurkat leukaemia cells, using RT-PCR and flow cytometry.

RESULTS

Full size CXCR3 mRNA (FS) expression was found in CD3+ PBL from controls and UC, but not from CD patients. In contrast, CD3+ PBL from CD patients showed a marked mRNA expression of the spliced variant CXCR3 (TV). This finding explains the high expression of CXCR3 on CD3+ PBL from CD patients in flow cytometry. Increased chemokine expression and production was found in colonic biopsies and serum from CD compared to UC patients and controls. Stimulation of epithelial cells with proinflammatory cytokines significantly induced chemokine production. The addition of Th2 cytokines had an inhibitory effect. Stimulation of Jurkat cells with cytokines and supernatant conditioned media from epithelial cells induced CXCR3TV expression.

CONCLUSIONS

These data demonstrate that PBL from CD patients express a spliced variant of the CXCR3 receptor and suggest a role for the colonic epithelial cells in T-lymphocyte migration in intestinal inflammation.

Arginine stimulates cdx2-transformed intestinal epithelial cell migration via a mechanism requiring both nitric oxide and phosphorylation of p70 S6 kinase

In intestinal cells, arginine (Arg) is 1 of the 2 most potent amino acid activators of p70(s6k), a key regulator of 5'- terminal oligopyrimidine mRNA translation, a necessary condition for increased cell migration. To investigate the mechanism of response to Arg, we used the rat crypt cell line cdx2-transformed IEC-6 cells (cdx2-IEC) and measured cell migration, immunocytochemical analysis of p70(s6k) activation in response to Arg, and production of nitric oxide (NO). When treated with Arg, cdx2-IEC increased in phosphorylation on Thr-389 of p70(s6k) (pp70(s6k)) compared with control (P < 0.01). Phospho-Thr-421/Ser-424-p70(s6k) was located in the nucleus shortly after Arg treatment. Arg enhanced pp70(s6k), cell migration (55% wound coverage), and NO production. In comparison, the branched-chain amino acid leucine (Leu) activated pp70(s6k), was a weaker stimulator of migration (23% coverage), and did not increase NO. A total of 25 micromol/L DETA-NONOate (DETA/NO) did not significantly enhance phosphorylation of p70(s6k) but enhanced the rate of cell migration by approximately 25%. Wound coverage with Leu plus DETA/NO (25 micromol/L) was greater than coverage with DETA/NO alone (P < 0.01). These and our previous studies lead to a model in which Arg must stimulate both pp70(s6k) (in the nucleus) and NO release to enhance intestinal epithelial cell migration, which may be relevant to diseases that involve intestinal villous injury.

IL-13 attenuates vascular tube formation via JAK2-STAT6 pathway

BACKGROUND

Interleukin (IL)-13, which is a cytokine produced by type 2 helper T cells, has pathophysiological roles in allergic inflammation and fibrosis formation. IL-13 shares many functional properties with IL-4, which is known to inhibit angiogenesis.

METHODS AND RESULTS

The effects of IL-13 on angiogenesis were examined using human coronary artery endothelial cells (HCAECs), in addition to investigating the mechanism(s) of this action. Using an in vitro assay of angiogenesis it was demonstrated that IL-13, as well as IL-4, significantly inhibited capillary-like tube formation. Migration of HCAECs, considered to be a process of new capillary tube formation, was also significantly inhibited by IL-13. IL-13 activated signal transduction and transcription 6 (STAT6) as a result of the activation of Janus kinase 2 (JAK2). The inhibitory effect of IL-13 on angiogenesis was abolished by depletion of JAK2 and STAT6 by RNA interference.

CONCLUSION

IL-13 has anti-angiogenic activity as a result of activation of JAK2 and subsequent activation of STAT6.

Intrauterine nitric oxide in pelvic inflammatory disease

OBJECTIVE

To measure nitric oxide gas directly in the uterus of healthy women and patients with suspected pelvic inflammatory disease.

DESIGN

Pilot case-control study.

SETTING

The emergency department of a university hospital.

PATIENT(S)

Twenty premenopausal, nonpregnant women from 18 to 48 years of age with lower abdominal pain and nine healthy women with regular menstrual cycles were included.

INTERVENTION(S)

We measured nitric oxide levels in air incubated for 5 minutes in a catheter balloon in the uterine cavity.

MAIN OUTCOME MEASURE(S)

Intrauterine nitric oxide concentration in controls and patients.

RESULT(S)

In patients with lower abdominal pain, nitric oxide was almost 100-fold increased in those in whom pelvic inflammatory disease had been diagnosed compared with those in whom appendicitis had been diagnosed with no individual overlap. Uterine nitric oxide levels were uniformly low in healthy women throughout the menstrual cycle, compared with those with pelvic inflammatory disease.

CONCLUSION(S)

Nitric oxide gas can be measured directly in the uterine cavity with a fast, simple, and safe method. The levels of nitric oxide are increased in patients with pelvic inflammatory disease.

Increased interleukin-13 levels in patients with chronic heart failure

A great number of basic and clinical studies have demonstrated that inflammatory cytokines play an important role in development and progress of heart failure. However, there is limited information about allergic cytokine interleukin-13 (IL-13). The inflammatory responses mediated by allergic cytokines can cause significant morbidity and mortality when they become chronic. Therefore, we elucidated the role of IL-13 in the pathophysiology of chronic heart failure. We measured plasma IL-13 levels by enzyme-linked immunosorbent assay in 110 patients with chronic heart failure and 20 control subjects. Plasma IL-13 levels were increased in heart failure patients, compared with the controls, in association with NYHA functional class. In addition, IL-13 levels were correlated positively with plasma levels of brain natriuretic peptide and C-reactive protein, and negatively with left ventricular ejection fraction. Plasma IL-13 levels may be useful for evaluating disease severity in chronic heart failure.

Rectal nitric oxide and fecal calprotectin in inflammatory bowel disease

OBJECTIVE

The assessment of intestinal inflammation in patients with inflammatory bowel disease (IBD) remains a difficult challenge. Both rectal nitric oxide (NO) and fecal calprotectin can be measured using non-invasive methods and are emerging as promising inflammatory markers in IBD. In this study the aim was to compare calprotectin and NO levels in IBD patients.

MATERIAL AND METHODS

Rectal NO was measured tonometrically in 23 healthy volunteers and 32 patients with IBD. In addition, we collected stool samples from all subjects for measurement of fecal calprotectin and nitrate/nitrite (NO metabolites).

RESULTS

Patients with IBD had greatly increased NO and calprotectin levels compared to healthy volunteers (p <0.001). In addition, the nitrate levels were slightly increased in IBD patients. A weak correlation was found between rectal NO levels, disease activity and number of loose stools in IBD patients (Spearman's rho 0.37 and 0.51, respectively; p <0.05). Fecal calprotectin correlated only with age (Spearman's rho 0.51; p <0.01). However, no correlation was found between NO and calprotectin.

CONCLUSIONS

Both rectal NO and fecal calprotectin are greatly increased during bowel inflammation, but they may reflect different parts of the inflammatory process. Future studies will elucidate the clinical usefulness of these two markers.

Nitric oxide, antioxidant capacity, nitric oxide synthase and xanthine oxidase plasma levels in a cohort of burn patients

BACKGROUND

Nitric oxide (NO) is an important signal molecule in many types of cells and tissues. Efficiently balanced NO production was noted to play an important role in the healing of burns. However, the exact pathophysiological role of NO in burns and its potent relation with clinical and laboratory parameters has not been elucidated.

METHODS

A cohort of 23 burn patients followed for 5 days were enrolled. NO, antioxidant capacity (AC), NO synthase (NOS) activity and xanthine oxidase (XO) activity were indirectly determined by fluorophotometer. Multiple regression against total burn surface area (TBSA), age, weight, height, proximity of septic episode, hemoglobin, white blood cells, percent of neutrophils, platelets, glucose, urea, potassium, sodium and albumin was performed.

RESULTS

Elevation of NO, XO and AC levels is observed from day 2 (p<0.00001), day 4 (p=0.005) and day 6 (p=0.036), respectively. At the end of follow-up period (day 6), NO production was found to independently correlate with TBSA, glucose levels and percent of neutrophils (p=0.0004), AC with age, hemoglobin and glucose levels (p=0.012), and NOS with proximity of septic episode and glucose levels (p=0.027).

CONCLUSIONS

NO production exerts its prophylactic effect from the first 24h after burn, and is independently correlated with severe injury, enhanced neutrophil motivation and augmented glucose levels, thus possibly representing a response to stress. This need might trigger induction of XO and salvage of antioxidants, as suggested by their rise at a later stage. These data underline that an effort to compromise stress and to administer antioxidants could be a priority in the treatment of these patients.

Effects of amino acid-derived luminal metabolites on the colonic epithelium and physiopathological consequences

Depending on the amount of alimentary proteins, between 6 and 18 g nitrogenous material per day enter the large intestine lumen through the ileocaecal junction. This material is used as substrates by the flora resulting eventually in the presence of a complex mixture of metabolites including ammonia, hydrogen sulfide, short and branched-chain fatty acids, amines; phenolic, indolic and N-nitroso compounds. The beneficial versus deleterious effects of these compounds on the colonic epithelium depend on parameters such as their luminal concentrations, the duration of the colonic stasis, the detoxication capacity of epithelial cells in response to increase of metabolite concentrations, the cellular metabolic utilization of these metabolites as well as their effects on colonocyte intermediary and oxidative metabolism. Furthermore, the effects of metabolites on electrolyte movements through the colonic epithelium must as well be taken into consideration for such an evaluation. The situation is further complicated by the fact that other non-nitrogenous compounds are believed to interfere with these various phenomenons. Finally, the pathological consequences of the presence of excessive concentrations of these compounds are related to the short- and, most important, long-term effects of these compounds on the rapid colonic epithelium renewing and homeostasis.

Ciprofloxacin inhibits cytokine-induced nitric oxide production in human colonic epithelium

BACKGROUND

The fluoroquinolone ciprofloxacin is a broad-spectrum antibiotic that has been used in the treatment of inflammatory bowel diseases. There is evidence that quinolones have immunomodulating activities via the regulation of cytokine production.

MATERIALS AND METHODS

We investigated the effect of ciprofloxacin on the nitric oxide (NO) production by colonic epithelium. HT-29 cells and colonic biopsies from patients (n = 4) with ulcerative colitis (UC) and normal controls (n = 4) were cultured with various concentrations of ciprofloxacin (10-100 microg mL(-1)) in the presence and absence of pro-inflammatory cytokines. The production of NO was measured in culture supernatants with a spectrophotometric method and inducible nitric oxide synthase (iNOS) mRNA expression was examined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Ciprofloxacin did not have any effect on the basal NO production by HT-29 cells. In contrast, ciprofloxacin significantly (P < 0.001) inhibited the pro-inflammatory cytokines (interleukin-1alpha + tumour necrosis factor-alpha + interferon-gamma)-induced NO production in HT-29, in a concentration-dependent manner, via the inhibition of the cytokine-induced iNOS mRNA expression. Wortmannin produced a concentration related reversal of the inhibitory effect of ciprofloxacin at both iNOS mRNA expression and NO production in HT-29 cells. A similar inhibitory effect of ciprofloxacin on the cytokine-induced NO production and iNOS mRNA expression was detected in vitro in cultures of normal colonic tissue. In addition, ciprofloxacin significantly inhibited the NO production and iNOS mRNA expression in cultures of colonic tissue from ulcerative colitis patients, in a concentration-dependent manner.

CONCLUSIONS

These data suggest that ciprofloxacin, in addition to its antimicrobial role, might have an immunoregulatory effect on intestinal inflammation, via the modulation of inflammatory mediators.

Interaction between enteric epithelial cells and Peyer’s patch lymphocytes in response to Shigella lipopolysaccharide: Effect on nitric oxide and IL-6 release

AIM: To investigate the effect of interaction between enteric epithelial cells and lymphocytes of Peyer’s patch on the release of nitric oxide (NO) and IL-6 in response to Shigella lipopolysaccharide (LPS).

METHODS: Human colonic epithelial cells (Caco-2) were mixed cocultured with lymphocytes of Peyer’s patch from wild-type (C57 mice) and inducible NO synthase knockout mice, and challenged with Shigella F2a-12 LPS. Release of NO and mIL-6 was measured by Griess colorimetric assay and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS: In the absence of LPS challenge, NO was detected in the culture medium of Caco-2 epithelial cells but not in lymphocytes of Peyer’s patch, and the NO release was further up-regulated in both cocultures with lymphocytes from either the wild-type or iNOS knockout mice, with a significantly higher level observed in the coculture with iNOS knockout lymphocytes. After Shigella F2a-12 LPS challenge for 24-h, NO production was significantly increased in both Caco-2 alone and the coculture with lymphocytes of Peyer’s patch from the wild-type mice but not from iNOS knockout mice. LPS was found to stimulate the release of mIL-6 from lymphocytes, which was suppressed by coculture with Caco-2 epithelial cells. The LPS-induced mIL-6 production in lymphocytes from iNOS knockout mice was significantly greater than that from the wild-type mice.

CONCLUSION: Lymphocytes of Peyer’s patch maintain a constitutive basal level of NO production from the enteric epithelial cell Caco-2. LPS-induced mIL-6 release from lymphocytes of Peyer’s patch is suppressed by the cocultured epithelial cells. While no changes are detectable in NO production in lymphocytes from both wild-type and iNOS knockout mice before and after LPS challenge, NO from lymphocytes appears to play an inhibitory role in epithelial NO release and their own mIL-6 release in response to LPS.

Rectal nitric oxide as biomarker in the treatment of inflammatory bowel disease: Responders versus nonresponders

AIM: To explore rectal nitric oxide (NO) as biomarker of treatment response in ulcerative colitis (UC) and Crohn’s disease (CD), and examine relationships between rectal NO, mucosal expression of NO synthases (NOS), and pro-inflammatory cytokines.

METHODS: Twenty-two patients with UC and 24 with CD were monitored during steroid treatment. Rectal NO levels were measured and clinical activities were assessed on days 1, 3, 7 and 28. Mucosal presence of NOS and pro-inflammatory cytokines were analyzed by immunohistochemistry and RT-PCR.

RESULTS: Active UC and CD displayed markedly increased rectal NO levels (10 950 ± 7610 and 5 040 ± 1 280 parts per billion (ppb), respectively) as compared with the controls (154 ± 71 ppb, P < 0.001). Rectal NO correlated weakly with disease activity in both UC and CD (r = 0.34 for UC and r = 0.48 for CD, P < 0.01). In 12 patients, a steroid-refractory course led to colectomy. These patients had only slightly increased NO levels (UC: 620 ± 270 ppb; CD: 1260 ± 550 ppb) compared to those with a therapeutic response (UC: 18 860 ± 530 ppb, P < 0.001; CD: 10 060 ± 3200 ppb, P < 0.05).

CONCLUSION: Rectal NO level is a useful biomarker of treatment response in IBD as low NO levels predicts a poor clinical response to steroid treatment.

Change of nitric oxide in experimental colitis and its inhibition by melatonin in vivo and in vitro

AIM

To investigate the change of nitric oxide (NO) in rat colitis and its inhibition by melatonin in vivo and in vitro.

METHODS

In vivo, rat colitis was established intracolonically with trinitrobenzenesulphonic acid (TNBS) and ethanol. The animals were randomised into five groups: control group, model group, melatonin group (2.5, 5.0, 10.0 mg/kg), and treated intracolonically with saline, saline and melatonin respectively (once a day, from day 7 after colitis was established to day 28). After the end of the experiment, the mucosal damage index (CMDI) and histology score (HS) were evaluated and the level of myeloperoxidase (MPO) and malondiadehyde (MDA) and NO in the colon tissue were measured. In vitro, the co-culture model of the inflamed colon mucosa (from the colitis) with lipopolysaccharide (LPS), and the colonocytes oxidative injury model by hydroxyl radical, were designed respectively to elucidate the inhibition of NO by melatonin.

RESULTS

After treated with TNBS/ethanol, the extent of CMDI and HS, the levels of MPO, MDA, and NO in the model group, were higher than that in the control group; melatonin ameliorated these parameters effectively. The stimulation of LPS increased the level of NO and MPO and MDA in the co-culture model of inflamed colon mucosa, and melatonin significantly reduced the level of MPO, MDA, and NO. In the coloncyte oxidative injury model by hydroxyl radical, the contents of LDH, MDA, and NO were increased; melatonin reversed this oxidative injury considerably.

CONCLUSION

This study showed that TNBS/ethanol induced colitis was pharmacologically controlled by melatonin in vivo and in vitro.

Neuronal nitric oxide synthase is necessary for elimination of Giardia lamblia infections in mice

NO produced by inducible NO synthase (NOS2) is important for the control of numerous infections. In vitro, NO inhibits replication and differentiation of the intestinal protozoan parasite Giardia lamblia. However, the role of NO against this parasite has not been tested in vivo. IL-6-deficient mice fail to control Giardia infections, and these mice have reduced levels of NOS2 mRNA in the small intestine after infection compared with wild-type mice. However, NOS2 gene-targeted mice and wild-type mice treated with the NOS2 inhibitor N-iminoethyl-L-lysine eliminated parasites as well as control mice. In contrast, neuronal NOS (NOS1)-deficient mice and wild-type mice treated with the nonspecific NOS inhibitor NG-nitro-L-arginine methyl ester and the NOS1-specific inhibitor 7-nitroindazole all had delayed parasite clearance. Finally, Giardia infection increased gastrointestinal motility in wild-type mice, but not in SCID mice. Furthermore, treatment of wild-type mice with NG-nitro-L-arginine methyl ester or loperamide prevented both the increased motility and the elimination of parasites. Together, these data show that NOS1, but not NOS2, is necessary for clearance of Giardia infection. They also suggest that increased gastrointestinal motility contributes to elimination of the parasite and may also contribute to parasite-induced diarrhea. Importantly, this is the first example of NOS1 being involved in the elimination of an infection.

Production of IL-1β, hydrogen peroxide, and nitric oxide by colonic mucosa decreases sigmoid smooth muscle contractility in ulcerative colitis

We have previously shown that sigmoid circular muscle cells from patients with ulcerative colitis (UC) exhibit reduced contraction and Ca2+signaling in response to the neurotransmitter neurokinin A (NKA) and that IL-1β and H2O2may contribute to these reduced responses in UC. In addition, we have found that nitric oxide (NO) levels were significantly increased in UC circular muscle. To establish the site of origin for IL-1β, H2O2, and NO, we assembled an in vitro system in which normal or UC mucosa were sealed between two chambers filled with oxygenated Krebs solution. Because the mucosa consists of full-thickness mucosa and submucosa, it is expected that whatever is released into the undernatant from the submucosal side may diffuse to the circular muscle layer in the intact colon. Treatment of normal sigmoid circular muscle cells for 2 h with undernatants collected from the UC submucosal side (UCS) significantly decreased contraction induced by NKA and thapsigargin and the NKA- and caffeine-induced Ca2+signal in Ca2+-free medium. In addition, UC mucosa released into the undernatant on its submucosal side significantly more H2O2, IL-1β, and NO than normal mucosa. The reduction in contraction and Ca2+signal induced by UCS was partially reversed by pretreatment with an IL-1β antibody or with catalase. The NO scavenger hemoglobin partially prevented UCS-induced reduction in contraction and Ca2+signaling in response to NKA but not the reduced response to thapsigargin or caffeine. Sodium nitroprusside inhibited NKA but not the caffeine-induced Ca2+signal. We conclude that in UC the mucosa releases IL-1β, H2O2, and NO, which may contribute to the impaired Ca2+release and altered sigmoid muscle contractility.

Expression of inducible nitric oxide synthase and effects of L-arginine on colonic nitric oxide production and fluid transport in patients with "minimal colitis"

OBJECTIVE

Some patients with idiopathic, chronic diarrhoea have minimal, non-specific colonic inflammation. As nitric oxide (NO) acts as a secretagogue in the colon, we studied the expression of inducible NO synthase (iNOS) in mucosal biopsies and the effects of NOS stimulation on colonic transfer of fluid and output of NO in patients with "minimal colitis".

MATERIAL AND METHODS

Twelve patients with idiopathic, chronic diarrhoea and "minimal colitis" and 6 healthy volunteers were included in the study. Expression of iNOS in colonic mucosal biopsies was quantified by Western blot analysis and localized by immunohistochemistry. The effects of topical L-arginine or placebo on colonic net fluid transfer and nitrite/nitrate (NOx) output were assessed during "steady state" perfusion of the whole colon. Concentrations of NOx were measured by Griess' assay.

RESULTS

The expression of iNOS was increased 10-fold (p<0.01) in patients with "minimal colitis" compared with that in healthy volunteers and localized to the colonic epithelium. Colonic absorption of fluid was impaired (mean (SEM) 1.5 (0.2) versus 3.0 (0.2) ml/min, p<0.001) and the output of NOx was increased (47 (4) nmol/min versus <37 nmol/min, p<0.05) in patients with "minimal colitis" compared with that in healthy volunteers. Luminal L-arginine (20 mM) reduced colonic absorption of fluid in both groups (95% confidence intervals (CIs) 21-50% in patients with "minimal colitis" versus 4-18% in healthy volunteers), but an increase in NOx output was detectable only in the group of patients (8-106%). In time control experiments, colonic net transfer rates of fluid and outputs of NOx were unaffected by placebo.

CONCLUSIONS

In patients with idiopathic, chronic diarrhoea and histopathological evidence of "minimal colitis", colonic absorption of fluid is impaired, while epithelial expression of iNOS and mucosal production of NO is enhanced. It could be speculated that NO in excess contributes to the diarrhoea observed in "minimal colitis".

The effect of hydrodynamics-based delivery of an IL-13-Ig fusion gene for experimental autoimmune myocarditis in rats and its possible mechanism

Interleukin (IL)-13 is a pleiotropic cytokine secreted by activated Th2 T lymphocytes. Th1 cytokines are assumed to exacerbate and Th2 cytokines to ameliorate rat experimental autoimmune myocarditis (EAM). Here, we examined the effect of IL-13 on EAM, using a hydrodynamics-based delivery of an IL-13-Ig fusion gene, as well as the possible mechanism of its effect. Rats were immunized on day 0, and IL-13-Ig-treated rats were injected with pCAGGS-IL-13-Ig, and control rats with pCAGGS-Ig, on day 1 or 7. On day 17, the IL-13-Ig gene therapy was effective in controlling EAM as monitored by a decreased heart weight/body weight ratio, by reduced myocarditis and by reduced atrial natriuretic peptide mRNA in the heart, as a heart failure marker. On the basis of IL-13 receptor mRNA expression in separated cells from EAM hearts, we proposed that IL-13-Ig target cells were CD11b(+) cells and non-cardiomyocytic noninflammatory (NCNI) cells, such as fibroblasts, smooth muscle or endothelial cells. IL-13-Ig inhibited expression of the genes for prostaglandin E synthase, cyclooxygenase-2, inducible nitric oxide synthase, IL-1beta and TNF-alpha in cultivated cells from EAM hearts, while it enhanced expression of the IL-1 receptor antagonist gene. We conclude that IL-13-Ig ameliorates EAM and suppose that its effectiveness may be due to the influence on these immunologic molecules in CD11b(+) and NCNI cells.

Nitric oxide mediates increased P-glycoprotein activity in interferon-{gamma}-stimulated human intestinal cells

Patients with refractory inflammatory bowel disease (IBD) exhibit increased expression of intestinal P-glycoprotein (P-gp) as well as elevated luminal IFN-gamma and nitric oxide (NO) levels. Using the in vitro Caco-2 cell culture model, we investigated whether these pathological mediators associated with the etiology of IBD affect functional activity of intestinal efflux systems. IFN-gamma reduced cellular uptake of cyclosporin A (CysA) but not methotrexate (MTX) in a time- and concentration-dependent manner. Simultaneously, P-gp expression increased by approximately twofold. Coincubation with the inducible NO synthase inhibitor l-N(6)-(1-iminoethyl)lysine (l-NIL) dramatically reduced production of intracellular NO in response to IFN-gamma stimulus. The presence of l-NIL also abrogated the cytokine-mediated increase in P-gp expression and function suggesting that NO is required for IFN-gamma-mediated activation of this efflux system. Exposure of Caco-2 cells to the chemical NO donor S-nitroso-N-acetylpenicillamine (SNAP) produced a concentration-dependent decrease in intracellular CysA accumulation that was paralleled by an increase in P-gp expression. Both IFN-gamma and SNAP enhanced DNA binding of NF-kappaB, whereas inclusion of l-NIL dramatically decreased this cytokine-induced effect on NF-kappaB binding. These results suggest that NO mediates IFN-gamma-induced increase in expression and function of intestinal P-gp in the human Caco-2 cell culture model by altering DNA binding of NF-kappaB, which may enhance transcription of the ABCB1 gene encoding for this efflux system.