Regulation of induction of nitric oxide synthase and the inhibitory actions of dexamethasone in the human intestinal epithelial cell line, Caco-2: influence of cell differentiation

Pre-clinical evidence for the therapeutic effect of Pitaya (Hylocereus lemairei) on diabetic intestinal microenvironment

Intestinal glucose absorption plays a central role in the regulation of glucose plasmatic; however, current clinical management does not target the gut for treating diabetes. This study evaluated the effects of peel and pulp aqueous extract from Hylocereus lemairei on human enterocytes under high glucose concentration. Anti-hyperglycemic and antiobesity activities in vitro were also evaluated. Extracts did not cause cytotoxicity at 1 to 500 μg/mL. Moreover, they were effective in attenuating oxidative stress (DCFH-DA assay) and inflammation (^•ON production) caused by high glucose. Intestinal enzymes (α- glucosidase and pancreatic lipase) were inhibited by pulp and peel extracts (>60% and >95%, respectively). Extracts exhibited a redox capacity superior to ascorbic and chlorogenic acids, presenting high phenolic content, mainly anthocyanins. The main compounds for both extracts were chlorogenic acid and naringin, and peel stood both qualitatively and quantitatively. Data suggest red Pitaya has potential as a new medicine for diabetes.

Elucidation of the chemical structure and determination of the production conditions for a bioactive Maillard reaction product, [5-(5,6-dihydro-4H-pyridin-3-ylidenemethyl)furan-2-yl]methanol, isolated from a glucose-lysine heated mixture

We previously isolated a bioactive molecule, named F3-A, from an aqueous glucose (Glc) and lysine (Lys) Maillard reaction (MR) model system. Herein, F3-A was verified as [5-(5,6-dihydro-4H-pyridin-3-ylidenemethyl)furan-2-yl]methanol (5) and was subsequently synthesized for confirmation of bioactivity. Using Taguchi and factorial designs, we determined that the conditions which best increased the yield of F3-A were at pH 6 with a sugar:amino acid ratio of 2:1 and heating time of 12 h at 100 °C. The MR mixtures containing glucose produced highest yield, compared to fructose, lactose, and sucrose. Both the F3-A recovered from Glc-Lys MR mixture and the synthesized product exhibited significant (P < 0.05), dose dependent, nitric oxide (NO) inhibitory activity in Caco-2 cells that was comparable to aminoguanidine (AG) and pyrrolidine dithiocarbamate (PDTC), respectively. Finally, an additional inhibitory effect of F3-A was determined when coincubated with AG in cytokine-induced Caco-2 cells. This bioactivity points to a potential role in preventing intestinal inflammation.

DNA methylation is required for the control of stem cell differentiation in the small intestine

There is a tight correlation between the epigenetic status of genes and expression changes during differentiation. Sheaffer et al. used acute deletion of Dnmt1 to reduce DNA methylation maintenance in the intestinal epithelium. This caused crypt expansion and decreased differentiation. DNA methylation was dynamic at enhancers during the rapid transition from stem to differentiated epithelial cells. These findings reveal that the loss of DNA methylation at intestinal stem cell gene enhancers causes inappropriate gene expression and delayed differentiation.

The mammalian intestinal epithelium has a unique organization in which crypts harboring stem cells produce progenitors and finally clonal populations of differentiated cells. Remarkably, the epithelium is replaced every 3–5 d throughout adult life. Disrupted maintenance of the intricate balance of proliferation and differentiation leads to loss of epithelial integrity or barrier function or to cancer. There is a tight correlation between the epigenetic status of genes and expression changes during differentiation; however, the mechanism of how changes in DNA methylation direct gene expression and the progression from stem cells to their differentiated descendants is unclear. Using conditional gene ablation of the maintenance methyltransferase Dnmt1, we demonstrate that reducing DNA methylation causes intestinal crypt expansion in vivo. Determination of the base-resolution DNA methylome in intestinal stem cells and their differentiated descendants shows that DNA methylation is dynamic at enhancers, which are often associated with genes important for both stem cell maintenance and differentiation. We establish that the loss of DNA methylation at intestinal stem cell gene enhancers causes inappropriate gene expression and delayed differentiation.

Kiwifruit extracts inhibit cytokine production by lipopolysaccharide-activated macrophages, and intestinal epithelial cells isolated from IL10 gene deficient mice

Inflammatory bowel disease (IBD) is a chronic, inflammatory disorder of the gastrointestinal tract involving an inappropriate immune response to commensal microorganisms in a genetically susceptible host. This study examined the effects of aqueous and ethyl acetate extracts of gold kiwifruit (Actinidia chinensis) or green kiwifruit (Actinidia deliciosa) using in vitro models of IBD. These models comprised primary macrophages and intestinal epithelial cells isolated from C57BL/5J and interleukin-10 gene deficient (Il10(-/-)) mice and RAW 264.7, a murine macrophage-like cell line. All four kiwifruit extracts reduced the activation of these models after lipopolysaccharide stimulation, decreasing nitric oxide and cytokine secretion by both Il10(-/-) and wild-type cells. The ethyl acetate extracts exhibited the highest anti-inflammatory activity, with almost complete suppression of lipopolysaccharide-stimulated macrophage activation. These results suggest that kiwifruit extracts have significant anti-inflammatory activity relevant to IBD. We suggest that the Il10(-/-) mouse is a suitable model for further study of these compounds.

Nitric oxide blocks cellular heme insertion into a broad range of heme proteins

Although the insertion of heme into proteins enables their function in bioenergetics, metabolism, and signaling, the mechanisms and regulation of this process are not fully understood. We developed a means to study cellular heme insertion into apo-protein targets over a 3-h period and then investigated how nitric oxide (NO) released from a chemical donor (NOC-18) might influence heme (protoporphyrin IX) insertion into seven targets that present a range of protein structures, heme ligation states, and functions (three NO synthases, two cytochrome P450's, catalase, and hemoglobin). NO blocked cellular heme insertion into all seven apo-protein targets. The inhibition occurred at relatively low (nM/min) fluxes of NO, was reversible, and did not involve changes in intracellular heme levels, activation of guanylate cyclase, or inhibition of mitochondrial ATP production. These aspects and the range of protein targets suggest that NO can act as a global inhibitor of heme insertion, possibly by inhibiting a common step in the process.

Determining conditions for nitric oxide synthesis in Caco-2 cells using Taguchi and factorial experimental designs

Intestinal inflammation correlates well with the increased synthesis of nitric oxide (NO), which is attributed mainly to the up-regulation of inducible nitric oxide synthase (iNOS). We optimized the use of interferon gamma (IFN-gamma), tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), lipopolysaccharide (LPS), and phorbol myristate acetate (PMA) as inducers to stimulate NO synthesis in Caco-2 cells using a Taguchi design. The results indicated that IFN-gamma was the most important inducer of iNOS in Caco-2 cells. Treating Caco-2 cells with both IFN-gamma and PMA using an optimal mixture of 8000 U/ml IFN-gamma and 0.1 microg/ml of PMA resulted in a synergistic induction of NO synthesis. Further experiments using a 5-factor/2-level factorial design including Caco-2 growth conditions such as cell passage, culture medium composition, cell seeding time and density, and stimulation time were also performed. Cell seeding and stimulation times significantly (P<0.05) affected NO synthesis, whereas culture medium and seeding density did not appreciably affect NO synthesis in Caco-2 cells. Western blotting and RT-PCR findings confirmed that the optimal mixture of IFN-gamma and PMA effectively up-regulated iNOS mRNA and protein. The induced NO, iNOS mRNA, and protein were all inhibited by the iNOS selective inhibitor, aminoguanidine (AG).

Methylprednisolone treatment delays remote cell death after focal brain lesion

Glucocorticoids have a prominent role in the treatment of CNS injuries. However, the cellular consequences of glucocorticoid treatment on remote degenerative responses after focal brain lesions have been poorly investigated. Here we examine the effectiveness of a high dose (50 mg/kg) of methylprednisolone sodium succinate (MPSS) in reducing neuronal loss, glial response and glial-derived inflammatory mediators in inferior olive and pontine nuclei after lesion of the contralateral cerebellar hemisphere using immunohistochemistry and Western blot techniques. Quantitative analysis demonstrated that MPSS treatment significantly improved the survival of neurons in remote precerebellar stations. This survival was accompanied by reduction in the postlesional activation of microglia, astrocytes and interleukin-1 beta (IL-1beta). Cell death resumed after suspension of MPSS treatment and this delayed wave of cell loss was paralleled by reactivation of the inflammatory markers analyzed. The present study confirms the importance of inflammatory events in inducing remote cell death and that this type of degeneration can be delayed by MPSS treatment. Furthermore, the sustained effect of MPSS treatment, up to 28 days postlesion, and the reactivation of the degenerative phenomena after its suspension, support the hypothesis that glucocorticoid treatment, although capable of delaying cell death mechanisms, is not effective in blocking the cascade of remote degenerative events started by the primary lesion.

Biphasic effect of IL-1β on the activity of argininosuccinate synthetase in Caco-2 cells. Involvement of nitric oxide production

The expression of the argininosuccinate synthetase gene (ASS), the limiting enzyme of arginine synthesis, was previously shown to be rapidly induced by a short-term (4 h) exposure to IL-1beta in Caco-2 cells [Biochimie, 2005, 403-409]. The present report shows that, by contrast, a long-term (24 h) exposure to IL-1beta inhibited the ASS activity despite an increase in both specific mRNA level and protein amount, demonstrating a post-translational effect. Concerning the mechanism involved, we demonstrate that the inhibiting effect is linked to the production of nitric oxide (NO) induced by IL-1beta. Indeed, the inhibiting effect of IL-1beta was totally blocked in the presence of l-NMMA, an inhibitor of the inducible nitric oxide synthase, or by culturing the cells in an arginine-deprived medium. Moreover, a decrease in the ASS activity was induced by culturing the cells in the presence of SNAP, a NO donor. Conversely, blocking the action of NO by antioxidant agents, the stimulatory effect of IL-1beta on ASS activity was restored, as measured at 24 h. Finally, such an inhibiting effect of NO on ASS activity may be related, at least in part, to S-nitrosylation of the protein. The physiological relevance of the antagonistic effects of IL-1beta and NO on ASS is discussed.

Enteropathogenic Escherichia coli (EPEC) effector-mediated suppression of antimicrobial nitric oxide production in a small intestinal epithelial model system

In vivo studies with the mouse-specific member of the attaching and effacing (A/E) family of pathogens raised the possibility that these non-invasive enteric pathogens can specifically inhibit inducible nitric oxide synthase (iNOS) expression to prevent the production of antimicrobial nitric oxide (NO). In this study we use polarized Caco-2 cells, a model of human small intestinal epithelia, to (i) demonstrate conclusively that an A/E member, human specific enteropathogenic Escherichia coli (EPEC), can inhibit cytokine-induced iNOS expression, (ii) show that this activity is dependent on the delivery of effector molecules into host cells and (iii) investigate the mechanism of inhibition. Analysis of the level of iNOS-related mRNA, protein and NO production demonstrated that EPEC can inhibit iNOS expression at the transcriptional, by direct and indirect mechanisms, and post-transcriptional levels. This transcriptional block was linked to the failure of the iNOS-related transcriptional factor NF-kappaB, but not STAT1, to undergo phosphorylation-associated activation. A selective pressure to prevent iNOS production was evidenced by the finding that iNOS activity had a potent antimicrobial effect on adherent but not non-adherent bacteria. Moreover, given the central role NF-kappaB plays in transcribing genes associated with early host immune responses, this inhibitory mechanism presumably represents an important role in pathogenesis. Our study also provides insights into the nature of NO production in response to bacterial infection as well as the role of the locus of enterocyte effacement (LEE)-encoded effector molecules in inhibiting iNOS expression.

L-Arginine modulates CXC chemokines in the human intestinal epithelial cell line HCT-8 by the NO pathway

Arginine has immunomodulating properties in different animal models but its effects in human intestine remain unknown. This study examined whether arginine modulates inflammatory mediators as chemokines and nitric oxide (NO) in the human intestinal epithelial cell line HCT-8 induced by cytokines. Under basal conditions, arginine did not influence iNOS protein expression, NO and chemokine production and mRNA levels (P>0.05 for all). Stimulation with cytokines-induced a significant increase of NO and chemokine production, iNOS and chemokine mRNA level and iNOS protein expression. Under inflammatory conditions, arginine increased 30% NO production (P<0.05) but did not influence iNOS mRNA level or iNOS protein expression. Under stimulated conditions, arginine decreased IL-8 and Mig mRNA level (57% and 39%, for 0.1 vs. 2 mmol/l l-arginine, P<0.05, respectively), and production (respectively, 28 and 23%, both P<0.05). IP-10 and I-TAC mRNA level and production were not significantly influenced by arginine. Under inflammatory conditions, l-arginine as well as a NO donor (sodium nitroprusside (SNP)) increased NO production, which was inversely correlated with IL-8 production (r'=-0.66, P=0.007 for arginine; r'=-0.79, P<0.0001 for SNP). Use of NG-Methyl-l-arginine acetate, a NOS inhibitor which prevents arginine-induced NO production, suppressed the arginine-induced IL-8 inhibition (P<0.05). In HCT-8 cells, arginine enhanced cytokine-induced NO production, reduced IL-8 and Mig production and mRNA level and had no effects on other assessed chemokines. In conclusion, arginine-induced IL-8 inhibition in HCT-8 cells involves NO pathway under inflammatory conditions. These data suggest that arginine-enriched enteral nutrition may have significant influence on inflammatory response in human intestine.

Actinodaphnine induces apoptosis through increased nitric oxide, reactive oxygen species and down-regulation of NF-kappaB signaling in human hepatoma Mahlavu cells

Actinodaphnine, extracted from Cinnamomum insularimontanum (Lauraceae), possesses cytotoxicity in some cancers, but the mechanism by which actinodaphnine induces apoptosis in human hepatoma cells remains poorly understood. In this study, we investigated the mechanisms of apoptosis induced by actinodaphnine in human hepatoma Mahlavu cells. Treatment with actinodaphnine dose-dependently induced apoptosis in Mahlavu cells that correlated with increased intracellular nitric oxide (NO) and reactive oxygen species (ROS), disruptive mitochondrial transmembrane potential (DeltaPsi(m)), and activation of caspase 3/7. Our data also demonstrated that actinodaphnine down-regulated activity of nuclear factor kappaB (NF-kappaB). The apoptotic response to actinodaphnine was markedly decreased in Mahlavu cells pretreated with dexsamethasone, a NO inhibitor, N-acetylcysteine (NAC), an antioxidant, and Boc-Asp(OMe)-fmk, a broad caspases inhibitor. These results suggested that actinodaphnine-induced apoptosis is initially mediated through the NO and/or ROS increase and caspases-dependent pathway. In conclusion, our results indicate that an increase of ROS and/or NO is the initial essential event that results in the decrease of DeltaPsi(m) and the activation of caspases that commits the cells to the apoptotic pathway in actinodaphnine-treated hepatoma Mahlavu cells.

Nitro-arginine methyl ester, a non-selective inhibitor of nitric oxide synthase reduces ibuprofen-induced gastric mucosal injury in the rat

Ibuprofen is a commonly used non-steroidal anti-inflammatory drug. Gastrointestinal adverse drug reactions from ibuprofen usage include gastric mucosal ulcers and bleeding. The mechanism by which ibuprofen induces gastric mucosal damage is not clear. The present study is an attempt to examine the role of nitric oxide in the pathogenesis of ibuprofen-induced gastric mucosal damage. Ibuprofen administered orally at the dose of 100 mg/kg body weight for 6 days to the rats resulted in gastric mucosal injury. Serum nitrite and nitrosothiol were increased significantly as compared with the controls, which were treated with the vehicle alone. In the gastric mucosa, lipid peroxidation and protein thiols were increased, and the activity of glyceraldehyde 3-phosphate dehydrogenase, a nitric oxide sensitive enzyme was decreased significantly. Pretreatment of the rats daily with nitric oxide synthase inhibitor, nitro-arginine methyl ester (30 mg/kg body weight) 1 hr before treatment with ibuprofen reduced the gastric mucosal injury. Biochemically, it prevented the rise in serum nitrite levels and the increase in lipid peroxidation and protein thiol levels and the loss of glyceraldehyde 3-phosphate dehydrogenase activity in the gastric mucosa. The results of the present study suggest that increased nitric oxide production may be one of the mechanisms by which ibuprofen produces gastric mucosal injury and that inhibition of nitric oxide synthase reduces gastric mucosal injury.

Acute effects of glucocorticoids on ATP-induced Ca2+ mobilization and nitric oxide production in cochlear spiral ganglion neurons

Rapid, non-genomic effects of glucocorticoids on extracellular adenosine 5'-triphosphate (ATP)-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) changes and nitric oxide (NO) production were investigated in type I spiral ganglion neurons (SGNs) of the guinea-pig cochlea using the Ca(2+)-sensitive dye fura-2 and the NO-sensitive dye 4,5-diaminofluorescein (DAF-2). Pretreatment of SGNs with 1 microM dexamethasone for 10 min, a synthetic glucocorticoid hormone, enhanced the ATP-induced [Ca(2+)](i) increase in SGNs. RU 38486, a competitive glucocorticoid receptor antagonist eliminated the effects of dexamethasone on the ATP-induced [Ca(2+)](i) increase in SGNs. These acute effects of dexamethasone were dependent on the presence of extracellular Ca(2+), thereby suggesting that dexamethasone may rapidly enhance the Ca(2+) influx through the activation of ionotropic P2X receptors which may interact with glucocorticoid-mediated membrane receptors. Extracellular ATP increased the intensity of DAF-2 fluorescence, indicating NO production in SGNs. The ATP-induced NO production was mainly due to the Ca(2+) influx through the activation of P2 receptors. S-nitroso-N-acetylpenicillamine, a NO donor, enhanced the ATP-induced [Ca(2+)](i) increase in SGNs while L-N(G)-nitroarginine methyl ester (L-NAME), a NO synthesis inhibitor, inhibited it. Dexamethasone enhanced the ATP-induced NO production in SGNs. The augmentation of dexamethasone on ATP-induced NO production was abolished in the presence of l-NAME. It is concluded that the ATP-induced [Ca(2+)](i) increase induces NO production which enhances a [Ca(2+)](i) increase in SGNs by a positive-feedback mechanism. Dexamethasone enhances the ATP-induced [Ca(2+)](i) increase in SGNs which results in the augmentation of NO production. The present study suggests that NO may play an important role in auditory signal transduction. Our results also indicate that glucocorticoids may rapidly affect auditory neurotransmission due to a novel non-genomic mechanism.

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.

Green tea inhibits human inducible nitric-oxide synthase expression by down-regulating signal transducer and activator of transcription-1alpha activation

Green tea has been reported to show anti-inflammatory properties because of its inhibitory effects on the expression of several pro-inflammatory genes. Because the inducible nitricoxide synthase (iNOS) plays an important role in chronic inflammatory diseases, we have focused our attention on the regulation of iNOS expression by green tea in two different human epithelial cell lines, alveolar A549/8 and colon DLD-1 cells. With the use of electrophoretic mobility shift assays, we found a green tea-mediated down-regulation of the DNA binding activity of the transcription factor signal transducer and activator of transcription-1alpha (STAT-1alpha), but not of nuclear factor-kappaB. This down-regulation of the STAT-1alpha DNA binding was shown to result from reduced tyrosine phosphorylation of the STAT-1alpha protein and not from antioxidative effects of the green tea extract. Green tea extract inhibited human iNOS expression in a concentration-dependent manner, quantified in terms of iNOS mRNA, iNOS protein, and nitric oxide production in both cell lines. This inhibitory effect of green tea resulted from transcriptional inhibition as shown in reporter gene experiments. These data suggest that green tea extracts may be promising at least as an auxiliary anti-inflammatory principle in chronic inflammatory diseases.

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Cytokine-stimulated nitric oxide production and inducible NO-synthase mRNA level in human intestinal cells: lack of modulation by glutamine

BACKGROUND & AIMS

Excess NO production has been reported during intestinal inflammation. Modulation of the inflammatory response with nutrients in critically ill patients has gained increasing interest. Glutamine has beneficial effects on gut mucosa but its effects on human intestinal NO production during an inflammatory response are not known.

METHODS

Caco-2/TC7 and HCT-8 cells were stimulated with a cytokine mixture (IL-1 beta, TNF alpha, IFN gamma) and duodenal biopsies from human healthy volunteers in organ culture were stimulated with IL-1 beta. All cultures were performed in the presence of 2-10 mmol/l glutamine. NO release in culture supernatant and iNOS mRNA level in cultured cells or biopsies were assessed by nitrate reduction and Griess assay and RT-PCR, respectively.

RESULTS

In Caco-2, HCT-8 cells and duodenal biopsies, cytokine stimulation increased iNOS mRNA level 1.2-fold (ns), 3.8-fold (P=0.02), 4.7-fold (P=0.03) and NO production 1.4-fold (ns), 9.1 (P=0.01) and 1.7-fold (P=0.01), respectively. Increasing glutamine concentration had no significant effect on NO production and iNOS mRNA in any type of culture, stimulated or not by cytokines. In various models of human intestinal cells, glutamine does not further increase NO production induced by pro-inflammatory cytokines.

Nitric oxide suppresses apoptosis in human colon cancer cells by scavenging mitochondrial superoxide anions

In cells lacking a functional p53 tumor suppressor protein, the endogenous free radical nitric oxide (NO) appears to inhibit apoptosis, and thereby promotes growth of cancer cells. In order to elucidate the underlying mechanisms on a molecular basis, we used HT-29 human colon carcinoma cells, carrying a p53 loss-of-function mutation, and examined the effects of NO on apoptosis when induced either by the flavonoid flavone or by the chemotherapeutic drug camptothecin (CPT), which is able to scavenge NO by superoxide anion production. Caspase-3 activation as well as nuclear fragmentation, both indicative of apoptosis, were dose dependently inhibited by the NO-liberating agents sodium nitroprusside (SNP) or S-nitroso-N-acetyl-D,L-penicillamine (SNAP) when apoptosis was initiated by flavone with only minor effects on apoptosis when initiated by camptothecin. The transcript levels of 9 apoptosis-related genes were assessed and NO liberation was shown to completely and specifically prevent the flavone-induced but not camptothecin-induced decrease in bcl-X(L) mRNA levels. These results were also confirmed at the protein level. The effects of NO on the mitochondrial apoptosis pathway were further evidenced by the scavenging of superoxide anions as produced in mitochondria of cells undergoing apoptosis. Scavenging of mitochondrial superoxide anions by NO prevents the downregulation of bcl-X(L), the depolarization of the mitochondrial membrane potential, the cytochrome c release and finally the activation of caspase-3. In conclusion, NO effectively inhibits apoptosis by scavenging superoxide anions generated in the mitochondria of p53 mutant cells and thereby prevents the downregulation of the antiapoptotic factor bcl-X(L), which controls the mitochondrial apoptosis pathway.

Proteome analysis reveals novel proteins associated with proliferation and differentiation of the colorectal cancer cell line Caco-2

Here, we describe a proteomics approach to study protein expression changes in differentiating Caco-2 cells. Caco-2 is a colorectal carcinoma cell line, which upon differentiation loses its tumorigenic phenotype and displays characteristics of mature enterocytes, including brush borders with microvilli. Cells were grown in culture flasks and harvested at different stages of differentiation (days post-confluence: -3, 0, 3, 7, 10, 14, and 18). Two-dimensional gel electrophoresis was used to analyse proteome changes. Approximately 1400 protein spots were detected within the Caco-2 proteome, within the pH 4-7 range. Two-dimensional gel electrophoresis allowed for the detection of 18 proteins from which the levels of expression were found to be associated with differentiation. Of these proteins, 11 were identified by means of MALDI-TOF or NANO-ESI-MS/MS mass spectrometry and include liver fatty acid binding protein (FABL), three forms of alpha-enolase (ENOA), nucleoside diphosphate kinase A (NDKA), cofilin-1 (COF1), translationally controlled tumour protein (TCTP), mitochondrial 60-kDa heat shock protein (CH60), probable protein disulfide isomerase (ER60), creatine kinase B (KCRB), and glutathione S-transferase alpha (GTA1). Thus, proteomics revealed that the differentiation-related change in phenotype of Caco-2 involves changes in a variety of distinct biochemical pathways. Some of these proteins have not been shown before to be associated with Caco-2 differentiation (ER60; COF1; CH60; NDKA; TCTP and ENOA). Therefore, processes related to protein folding and disulfide bridge formation, cytoskeleton formation and maintenance, nucleotide metabolism, glycolysis as well as tumorigenesis-associated proteins may be involved in Caco-2 differentiation. Changes in the expression of CH60, TCTP, GTA1, NDKA, and FABL have also been reported to be associated with in vivo colon carcinogenesis. These findings illustrate that a combination of proteomics and cell culture is a useful approach to find markers for Caco-2 differentiation, which could contribute to the comprehension of the process of colon carcinogenesis.

Interleukin-4 and transforming growth factor beta have opposing regulatory effects on gamma interferon-mediated inhibition of Cryptosporidium parvum reproduction

It was shown previously that enterocytes activated by gamma interferon (IFN-gamma) are efficient effector cells in the killing of Cryptosporidium parvum. How this function is regulated is not clearly understood, but transforming growth factor beta (TGF-beta) and the Th2 regulatory cytokines may play a role. Using an in vitro cell culture system, we investigated how the key regulatory cytokines interleukin-4 (IL-4), IL-10, IL-13, and TGF-beta might modulate the effect of IFN-gamma in inducing resistance to infection in enterocyte cell lines. The results showed that TGF-beta can abolish the inhibitory effect on C. parvum development and that neither IL-13 nor IL-10 influenced the action of IFN-gamma. In contrast, IL-4 cooperated with low concentrations of IFN-gamma (1 and 10 U/ml) to enhance parasite killing. One mechanism that appeared to be involved in the combined activity of IFN-gamma and IL-4 was intracellular Fe(2+) deprivation, but induction of nitric oxide production was not involved. In one cell line, the extents and durations of phosphorylation of STAT1, a transcription factor involved in IFN-gamma signaling, were similar when cells were stimulated with IFN-gamma alone and with IFN-gamma and IL-4 gamma, suggesting that the cooperative effect of the cytokines was not related to STAT1 activation. The effects of the presence of TGF-beta and IL-4 on IFN-gamma function did not appear to involve any alteration in the level of expression of IFN-gamma receptors.

Ethyl pyruvate ameliorates intestinal epithelial barrier dysfunction in endotoxemic mice and immunostimulated caco-2 enterocytic monolayers

Ethyl pyruvate (EP) solution ameliorates ileal mucosal hyperpermeability and decreases the expression of several proinflammatory genes in ileal and/or colonic mucosa when it is used instead of Ringer's lactate solution (RLS) to resuscitate mice from hemorrhagic shock. To test the hypothesis that EP can ameliorate gut barrier dysfunction induced by other forms of inflammation, we incubated Caco-2 monolayers for 24 to 48 h with cytomix (a mixture of interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta) in the presence or absence of graded concentrations of EP or sodium pyruvate. Cytomix increased the permeability of Caco-2 monolayers to fluorescein isothiocyanate-labeled dextran (FD4; average molecular mass 4 kDa), but this effect was inhibited by adding 0.1 to 10 mM EP (but not similar concentrations of sodium pyruvate) to the culture medium. EP inhibited several other cytomix-induced phenomena, including nuclear factor-kappaB activation, inducible nitric oxide synthase mRNA expression, and nitric oxide production. Cytomix altered the expression and localization of the tight junctional proteins, ZO-1 and occludin, but this effect was prevented by EP. Delayed treatment with EP solution instead of RLS ameliorated ileal mucosal hyperpermeability to FD4 and bacterial translocation to mesenteric lymph nodes in mice challenged with lipopolysaccharide (LPS). These data support the view that EP ameliorates cytokine- and/or LPS-induced derangements in intestinal epithelial barrier function.

Mechanisms involved in protection afforded by L-arginine in ibuprofen-induced gastric damage: role of nitric oxide and prostaglandins

L-Arginine (L-arg) exhibits multiple biological properties and plays an important role in the regulation of different functions in pathological conditions. Many of these effects could be achieved on this amino acid serving as a substrate for the enzyme nitric oxide synthase (NOS). At the gastrointestinal level, recent reports revealed its protective activities involving a hyperemic response increasing the gastric blood flow. The aim of this study was to characterize the relationship between NOS activity/expression and prostaglandin changes (PGs) in rats gastric mucosa, with L-arg associated resistance to the nonsteroidal anti-inflammatory drug (NSAID) ibuprofen (IBP). The protective effect of oral L-arg (100 mg/kg body wt), administerred together with IBP (100 mg/kg body wt, per os), was evident enough 90 min after drug administration, although a significant protection persisted for more than 6 hr. Pretreatment with N(G)-nitro-L-arginine (L-NNA) (40 mg/kg body wt, intraperitoneally), a competitive inhibitor of constitutive NOS, partly altered the protection afforded by the amino acid. In contrast, no changes could be observed after inducible NOS inhibition [aminoguanidine (AG) 50 mg/Kg body wt, intraperitoneally). L-arg, plus IBP, produced a significant increase of the cyclic GMP (cGMP) response in tissue samples from rat stomach, 90 min and 6 h after drug administration. iNOS activity and mRNA expression were higher in IBP-treated rats, and no differences were observed in inducible responses in the L-arg plus IBP group. No variations in the cNOS activity and expression were found among the different groups of animals assayed. The measurement of mucosal PGE2 content confirmed that biosynthesis of the eicosanoid is maintained by L-arg for over 90 min after IBP, while a total inhibition was observed 6 hr later. The mechanisms of the L-arg protective effect on the damaged induced by IBP could be explained by the different period after drug administration. The early phase is mediated by cyclooxygenase/prostaglandins pathway (COX/PGs) although NO liberated by cNOS and the guanylate cyclase/cGMP pathway could be also relevant. The later phase implicates inhibition of the iNOS/NO response.

An essential role of the JAK-STAT pathway in ischemic preconditioning

The goal of this study was to determine the role of the Janus tyrosine kinase (JAK)-signal transducers and activators of transcription (STAT) pathway in the late phase of ischemic preconditioning (PC). A total of 230 mice were used. At 5 min after ischemic PC (induced with six cycles of 4-min coronary occlusion/4-min reperfusion), immunoprecipitation with anti-phosphotyrosine (anti-pTyr) antibodies followed by immunoblotting with anti-JAK antibodies revealed increased tyrosine phosphorylation of JAK1 (+257 +/- 53%) and JAK2 (+238 +/- 35%), indicating rapid activation of these two kinases. Similar results were obtained by immunoblotting with anti-pTyr-JAK1 and anti-pTyr-JAK2 antibodies. Western analysis with anti-pTyr-STAT antibodies demonstrated a marked increase in nuclear pTyr-STAT1 (+301 +/- 61%) and pTyr-STAT3 (+253 +/- 60%) 30 min after ischemic PC, which was associated with redistribution of STAT1 and STAT3 from the cytosolic to the nuclear fraction and with an increase in STAT1 and STAT3 gamma-IFN activation site DNA-binding activity (+606 +/- 64%), indicating activation of STAT1 and STAT3. No nuclear translocation or tyrosine phosphorylation of STAT2, STAT4, STAT5A, STAT5B, or STAT6 was observed. Pretreatment with the JAK inhibitor AG-490 20 min before the six occlusion/reperfusion cycles blocked the enhanced tyrosine phosphorylation of JAK1 and JAK2 and the increased tyrosine phosphorylation, nuclear translocation, and enhanced DNA-binding activity of STAT1 and STAT3. The same dose of AG-490 abrogated the protection against myocardial infarction and the concomitant up-regulation of inducible NO synthase (iNOS) protein and activity observed 24 h after ischemic PC. Taken together, these results demonstrate that ischemic PC induces isoform-selective activation of JAK1, JAK2, STAT1, and STAT3, and that ablation of this response impedes the up-regulation of iNOS and the concurrent acquisition of ischemic tolerance. This study demonstrates that the JAK-STAT pathway plays an essential role in the development of late PC. The results reveal a signaling mechanism that underlies the transcriptional up-regulation of the cardiac iNOS gene and the adaptation of the heart to ischemic stress.

Increase in cyclooxygenase-2 and nitric oxide-synthase-2 mRNAs in pouchitis without modification of inducible isoenzyme heme-oxygenase-1

OBJECTIVES

The pathophysiology of pouchitis occurring after ileal pouch-anal anastomosis remains controversial. Prostaglandins and nitric oxide synthesized in excess by cyclooxygenase-2 and nitric oxide synthase-2 are thought to be involved in the inflammatory process. Because heme oxygenase-1, by its antioxidant properties, could modulate inflammatory reaction, we analyzed mRNAs of the three enzymes (cyclooxygenase-2, nitric oxide synthase-2, and heme oxygenase-1) in patients with ileal pouch-anal anastomosis.

METHODS

Endoscopic biopsies were obtained in eight patients with normal ileal pouch-anal anastomosis, in eight patients with pouchitis, and in normal ileum of six healthy subjects. A relative quantitative RT-PCR was performed to determine the levels of cyclooxygenase-2, nitric oxide synthase-2, and heme oxygenase-1 mRNAs.

RESULTS

Cyclooxygenase-2 and nitric oxide synthase-2 mRNAs were increased both in normal ileal pouch-anal anastomosis and in pouchitis, compared with healthy subjects. Pouchitis disease activity index was correlated with mRNA levels of cyclooxygenase-2 (r = 0.71; p < 0.01) and nitric oxide synthase-2 (r = 0.51; p < 0.05). Heme oxygenase-1 mRNA levels were not significantly different in patients versus healthy subjects.

CONCLUSIONS

The increase in cyclooxygenase-2 and nitric oxide synthase-2 mRNA levels both in pouchitis and normal ileal pouch-anal anastomosis demonstrates that a latent inflammatory process occurs in the ileal pouch mucosa. This inflammatory process was not found to be associated with an induction of heme oxygenase mRNA, a possible regulator of the inflammatory response.

LPS induction of I kappa B-alpha degradation and iNOS expression in a skin dendritic cell line is prevented by the janus kinase 2 inhibitor, Tyrphostin b42

The Janus kinase (JAK) family of protein tyrosine kinases are activated in response to a wide variety of external stimuli. Here we have investigated whether the janus kinase 2 (JAK2) is involved in the induction of nitric oxide synthase type II (iNOS) expression in a mouse fetal skin dendritic cell line (FSDC). In FSDC the expression of iNOS protein and nitric oxide production, in response to the lipopolysaccharide (LPS) stimulus (5 microg/ml), is inhibited by the specific inhibitor of the JAK2, tyrphostin B42 with an half maximal inhibitory concentration (IC(50)) of 9.65 microM. The antioxidant compound pyrrolidinedithiocarbamate (PDTC) inhibits both the nitrite production with an IC(50) of 16.6 microM and the iNOS protein expression in FSDC. In addition, LPS induces the activation of NF-kappa B, and tyrphostin B42 prevents the degradation of the cytosolic factor I kappa B-alpha and blocks the translocation of the NF-kappa B p65 protein subunit into the nucleus. These results indicate that the JAK family of protein kinases and the transcription factor NF-kappa B are involved in the induction of iNOS protein expression in FSDC stimulated with LPS.