Biomedical subjects

W Falk

Publications and source records attributed to W Falk.

At least 37 records · Page 2Linked to original sources

PubMed2002

Regulation of migration of human colonic myofibroblasts.

BACKGROUND AND AIM: The migration of mesenchymal cells to areas of mucosal or submucosal tissue damage is an essential factor for wound healing in the intestine. Thus far, neither migration inducing factors nor signal transduction cascades involved in the migration of colonic myofibroblasts (CMF) have been studied in detail. METHODS: Primary CMF were isolated from the mucosa of surgical specimens or endoscopic biopsies. Migration assays of CMF were performed in the modified 48-well Boyden chamber. Secreted growth factors were quantified by ELISA. RESULTS: CMF secrete autocrine or paracrine migration stimulating factors. Culture supernatant of CMF collected after 24, 48, and 72 h ( = conditioned media) stimulated the migration of CMF (48.9+/-4.5; 60.3+/-5.3 and 67.8+/-6.4 cells/hpf, respectively). Heating of conditioned media to 95 degrees C or addition of cycloheximide during the conditioning period abolished migration. Addition of PDGF-AB (2.5-50 ng/ml) or IGF-I (10-300 ng/ml) to CMF conditioned media further increased the migration of CMF to a maximum of 177 and 160%, respectively, when compared to the migration induced by conditioned medium alone. Addition of EGF (2.5-50 ng/ml) or TGF-beta1 (1-50 microg/ml) caused an increased CMF migration up to 139 and 128%, respectively. MCP-1 (5-50 ng/ml) and bFGF (10-200 ng/ml) had no effect on CMF migration. CONCLUSION: The growth factors PDGF-AB, IGF-I, EGF and TGF-beta1 stimulate the migration of CMF. However, factors secreted by CMF are essential for their ability to migrate in response to these growth factors. The identification of physiologically relevant migration inducing factors may help to elucidate the network of interactions and the complex mechanisms involved in intestinal wound healing or fibrosis.

Cell Movement↗

PubMed2001

A primary tumor promotes dormancy of solitary tumor cells before inhibiting angiogenesis.

Mechanisms that regulate the transition of micrometastases from clinically undetectable and dormant to progressively growing are critically important but poorly understood in cancer biology. Here we examined the effect of a primary tumor on the growth of solitary tumor cells in the mouse liver, as well as on the development of tumor angiogenesis in a dorsal skin-fold chamber. s.c. placement of a CT-26 (BALB/c-derived mouse colon carcinoma) primary tumor markedly inhibited development of liver metastasis in BALB/c mice after subsequent intraportal injection of tumor cells. Dorsal skin-fold chamber experiments showed that this growth inhibition paralleled a strong antiangiogenic effect by the primary tumor. Furthermore, intravital microscopy of the liver after intraportal injection of green fluorescent protein-expressing tumor cells showed that primary tumors promoted dormancy of single tumor cells for up to 7 days. Immunohistological staining for Ki-67 confirmed that these solitary cells were indeed dormant. In contrast, in the absence of a primary tumor, GFP-expressing tumor cells quickly developed into micrometastases. Thus, primary CT-26 tumor implants nearly abrogated tumor metastasis by inhibition of angiogenesis and by promoting a state of single-cell dormancy. Knowledge of the mechanism underlying this dormancy state could result in the development of new therapeutic tools to fight cancer.

Animals↗

PubMed2001

Therapeutic neutralization of CD95-ligand and TNF attenuates brain damage in stroke.

Stroke is the third most common cause of death in the Western world. The mechanisms of brain damage in the affected areas are largely unknown. Hence, rational treatment strategies are limited. Previous experimental evidence suggested that cerebral lesions were less prominent in CD95 (APO-1/Fas)-deficient (lpr) than in wild-type mice. Additional results strongly suggested that the CD95-ligand (CD95L) was a major cause of neuronal autocrine suicide in the penumbra. These data and the assumption that death-receptor systems might determine stroke-related damage in the brain prompted us to examine these systems in in vitro and in vivo models of ischemia. We showed that hybrids of TNF-deficient and gld mice were strongly resistant towards stroke-induced damage. To determine the mechanism of action of TNF and CD95L, we separately investigated their influence on primary ischemic death and secondary inflammatory injury. Inhibition of both TNF and CD95L in vitro prevented death of primary neurons induced by oxygen-glucose deprivation and reperfusion. The recruitment of inflammatory cells to the ischemic hemisphere was abrogated in the absence of both TNF and CD95L. Significantly, mice injected with a mixture of neutralizing anti-TNF and anti-CD95L antibodies 30 min after induction of stroke showed a marked decrease in both infarct volumes and mortality. Accordingly, the locomotor performance of these animals was not significantly impaired in comparison to sham-operated animals. These data reveal that inhibition of TNF and CD95L blocks stroke-related damage at two levels, the primary ischemic and the secondary inflammatory injury. These results offer new approaches in stroke treatment.

Animals↗

PubMed2001

Subtractive screening reveals up-regulation of NADPH oxidase expression in Crohn's disease intestinal macrophages.

Macrophages play a central role during the pathogenesis of inflammation. In normal intestinal mucosa surface expression of typical macrophage markers such as CD14, CD16, CD11b or T-cell co-stimulatory molecules such as CD80 or CD86 is low indicating anergy and low pro-inflammatory activity of these cells. During inflammatory bowel disease (IBD) the mucosa is invaded by a population of macrophages displaying these markers, secreting higher cytokine levels and representing an activated cell population. CD33(+) cells (macrophages) were isolated from normal and Crohn's disease mucosa and mRNA was isolated by polyT magnetic beads. A subtractive screening was performed subtracting mRNA from normal macrophages from those of Crohn's disease macrophages. Oxidative burst activity was determined by flow cytometry. Seventy clones were obtained by the subtractive mRNA screening. Sequencing showed > 99% homology to mRNA of monocyte chemoattractant protein-1 (MCP-1) for three clones. Five clones obtained by subtraction revealed > 99% homology to mRNA of cytochrome b (subunit gp91). Differential expression of the cytochrome b subunit gp91 and the cytosolic NADPH oxidase subunit p67 was confirmed by RT-PCR and 'virtual' Northern blots. The fluorescence ratio of stimulated versus unstimulated cells was 0.9 +/- 0.16 in control macrophages indicating a lack of oxidative burst activity. In Crohn's disease this ratio was significantly increased to 1.80 +/- 0.8 (P = 0.004) confirming the molecular data. In conclusion NADPH oxidase mRNA is down-regulated or absent in macrophages from normal mucosa correlating with a lack of oxidative burst activity. In IBD macrophage-oxidative burst activity is increased and NADPH oxidase mRNA induced. Inhibition of NADPH oxidase could be a new therapeutical target in IBD and reduce mucosal tissue damage in active IBD.

Chemokine CCL2↗

PubMed2001

Differential activation of cytokine secretion in primary human colonic fibroblast/myofibroblast cultures.

BACKGROUND: Fibroblasts and myofibroblasts are known to secrete a wide spectrum of cytokines, but the individual spectrum is tissue-specific. We investigated the effect of cell activation on cytokine secretion of isolated human colonic fibroblasts/myofibroblasts from control patients and patients with mucosal inflammation. METHODS: Primary cultures of human colonic submucosal fibroblasts/myofibroblasts were incubated with IL-1alpha (100 U/ml), IL-Ibeta (10 ng/ml), IL-10 (10 ng/ml), TNF (10 ng/ml), PMA (10 ng/ml), LPS (50 ng/ml), IL-4 (10 ng/ml), or a combination of IL-1 and TNF. Secreted cytokines were determined by ELISA. NF-kappaB activation was demonstrated by electrophoretic mobility-shift assays (EMSA). RESULTS: Incubation of colonic fibroblasts/myofibroblasts with IL-1, LPS, TNF and PMA induced secretion of IL-6, IL-8, M-CSF and GM-CSF. IL-8 and IL-6 secretion could be stimulated by IL-1alpha, IL-1beta, TNF, PMA and LPS within 6 h of incubation. IL-6 secretion was stimulated from 0.5 +/- 0.01 pg/h x microg fibroblast protein to 18.5 +/- 2.6 pg/h x microg fibroblast protein with IL-1beta (P < 0.01). IL-8 secretion was stimulated from 1.0 +/- 0.1 pg/h x microg fibroblast protein to 41.1 +/- 3.6 pg/h x microg (P < 0.005). IL-4 and IL-10 did not change cytokine secretion significantly. No significant differences between cultures from normal and inflamed mucosa were observed. TNF and IL-1 induced NF-kappaB activation. ALLN, a proteasome and NF-kappaB activation inhibitor, reduced TNF-mediated IL-8, GM-CSF and M-CSF induction significantly, whereas induction of IL-6 secretion remained unchanged. CONCLUSION: Human colonic myofibroblasts can secrete large amounts of IL-6, IL-8, M-CSF and GM-CSF upon stimulation. The induction of IL-8, M-CSF and GM-CSF, but not of IL-6 secretion, is mediated mainly by NF-kappaB activation. The cytokine profile and the total amounts of cytokines released suggest that colonic myofibroblasts can play a role in leukocyte recruitment and during mucosal inflammation. They therefore have to be regarded as an important part of the mucosal immune system.

Adult↗

PubMed2001

Monocyte differentiation in intestine-like macrophage phenotype induced by epithelial cells.

Macrophages in normal colonic mucosa show a specific and distinct phenotype with low expression of the typical monocyte/macrophage surface antigens CD14, CD16, and CD11b and T-cell costimulatory molecules. A method for the in vitro induction of a macrophage phenotype similar to this intestinal phenotype is presented. Multicellular spheroids (MCSs) of intestinal epithelial cell (IEC) and control cell lines were cocultured with elutriated monocytes. Surface antigen expression was analyzed by immunohistochemistry and flow cytometry. Interleukin (IL)-1beta mRNA was measured by quantitative PCR. Monocytes adhered and infiltrated the MCSs within 24 h. In the MCSs of all IEC lines, the typical monocyte/macrophage surface antigens CD14, CD16, CD11b, and CD11c, which are detectable after 24 h of coculture by immunohistochemistry and flow cytometry, were down-regulated after 7 days (e.g., for CD14 at 24 h, expression was 86% of CD33+ cells; at day 7, it was 11%). A clear decrease of lipopolysaccharide (LPS)-stimulated IL-1beta transcription in monocytes cocultured with IEC MCSs could be observed during the 7-day period. For the first time an intestine-like macrophage-phenotype could be induced in vitro. Interactions with IECs play an essential role during this differentiation, which is of functional relevance, e.g., for LPS-induced cytokine secretion.

Antigens, CD↗

PubMed2000

Treatment of murine colitis by Lactococcus lactis secreting interleukin-10.

The cytokine interleukin-10 (IL-10) has shown promise in clinical trials for treatment of inflammatory bowel disease (IBD). Using two mouse models, we show that the therapeutic dose of IL-10 can be reduced by localized delivery of a bacterium genetically engineered to secrete the cytokine. Intragastric administration of IL-10-secreting Lactococcus lactis caused a 50% reduction in colitis in mice treated with dextran sulfate sodium and prevented the onset of colitis in IL-10(-/-) mice. This approach may lead to better methods for cost-effective and long-term management of IBD in humans.

Animals↗

PubMed2000

Neurotransmitters of the sympathetic nerve terminal are powerful chemoattractants for monocytes.

Macrophages in lymphoid organs are in close contact to nerve terminals of the sympathetic nervous system. Hence, these cells could be targets of neuronal modulation. We studied sympathetic neurotransmitters as chemoattractants enabling the aggregation of macrophages and nerve terminals. Norepinephrine (NE), neuropeptide Y (NPY), isoproterenol (beta-adrenergic), p-aminoclonidine (alpha2-adrenergic), methoxamine (alpha1-adrenergic), and adenosine triphosphate (ATP) were used to study human monocyte and macrophage migration in 48-well Boyden chambers. NE stimulated chemotaxis of monocytes and macrophages at an optimal concentration of 10-(10) M (P < 0.025). Isoproterenol, but not p-aminoclonidine or methoxamine, induced chemotaxis of monocytes (10(-10) M, P < 0.05). In these studies, elevation of cAMP is a critical step in NE-induced chemotaxis of monocytes. NPY (10(-11) M, P < 0.05) stimulated monocyte chemotaxis as well. ATP at 10(-4) and 10(-5) M stimulated undirected cell mobility (P < 0.05). All tested neurotransmitters of the sympathetic nerve terminal were potent chemoattractants. These findings may explain the close association of nerves and macrophages in tissue and lymphoid organs and may thus be of functional relevance in neuroimmunomodulation.

Chemotactic Factors↗

PubMed2000

Modulation of IL-6 production during the menstrual cycle in vivo and in vitro.

During the menstrual cycle (MC), premenopausal women experience changes in basal temperature and their physical condition and well-being. Premenopausal female patients with chronic inflammatory diseases demonstrate changes in disease activity during the MC. The study was initiated to explore reasons for these phenomena. The sex hormone-modulated lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) secretion in a whole blood assay, serum IL-6 concentration, and serum sex hormone concentrations were studied throughout the MC in five healthy female subjects (median, 28 years; mean, 31.2+/-2.2 years, 26-38 years). Serum IL-6 concentration demonstrated a significant increase in the luteal phase of the MC and was elevated when serum dehydroepiandrosterone (DHEA) was low and vice versa. DHEA decreased LPS-induced IL-6 secretion at six of seven time points during the MC (DHEA, p = .047). In contrast, beta-estradiol and testosterone increased LPS-induced IL-6 secretion in six of seven time points during the MC (significant for testosterone, p = .005). The study demonstrates oscillation of serum IL-6 concentration during the MC and the marked MC-dependent modulation of IL-6 secretion by sex hormones. These mechanisms may be involved in the changes in the basal temperature, the general condition, and, in patients with chronic inflammatory diseases, of disease activity during the MC.

Adult↗

PubMed2000

Nuclear factor-kappa B activity and intestinal inflammation in dextran sulphate sodium (DSS)-induced colitis in mice is suppressed by gliotoxin.

In acute DSS-induced colitis nuclear factor (NF)-kappaB-dependent inflammatory cytokines including IL-1 and tumour necrosis factor-alpha (TNF-alpha) are up-regulated. Here we examined the effects of gliotoxin, a fungal metabolite known to inhibit NF-kappaB activity, on cytokine production by a mouse cell system in vitro and on intestinal inflammation and NF-kappaB activation in vivo. In vitro gliotoxin decreased TNF-alpha gene expression and protein production by RAW-264.7 mouse macrophage-like cells stimulated with lipopolysaccharide. In vivo, gliotoxin treatment of mice was begun on day 3 of 5% DSS application dissolved in the drinking water and continued until day 8. Gliotoxin treatment dose-dependently down-regulated colonic inflammation as assessed histologically and in parallel there was a suppression of colonic TNF-alpha and IL-1alpha mRNA expression on day 8 as analysed by semiquantitative reverse transcriptase-polymerase chain reaction (P < 0.01). Furthermore, colonic NF-kappaB DNA-binding activity was increased in DSS-induced colitis and was suppressed by gliotoxin. These results demonstrate the essential role of NF-kappaB in DSS-induced colitis and indicate a molecular approach to the treatment of intestinal inflammatory disorders.

Animals↗

PubMed2000

Neuropeptide Y cotransmission with norepinephrine in the sympathetic nerve-macrophage interplay.

The CNS modulates immune cells by direct synaptic-like contacts in the brain and at peripheral sites, such as lymphoid organs. To study the nerve-macrophage communication, a superfusion method was used to investigate cotransmission of neuropeptide Y (NPY) with norepinephrine (NE), with interleukin (IL)-6 secretion used as the macrophage read-out parameter. Spleen tissue slices spontaneously released NE, NPY, and IL-6 leading to a superfusate concentration at 3-4 h of 1 nM:, 10 pM:, and 120 pg/ml, respectively. Under these conditions, NPY dose-dependently inhibited IL-6 secretion with a maximum effect at 10(-10) M: (p = 0.012) and 10(-9) M: (p < 0.001). Simultaneous addition of NPY at 10(-9) M: and the alpha-2-adrenergic agonist p-aminoclonidine further inhibited IL-6 secretion (p < 0.05). However, simultaneous administration of NPY at 10(-9) M: and the beta-adrenergic agonist isoproterenol at 10(-6) M: or NE at 10(-6) M: significantly increased IL-6 secretion (p < 0.005). To objectify these differential effects of NPY, electrical field stimulation of spleen slices was applied to release endogenous NPY and NE. Electrical field stimulation markedly reduced IL-6 secretion, which was attenuated by the NPY Y1 receptor antagonist BIBP 3226 (10(-7) M, p = 0.039; 10(-8) M, p = 0.035). This indicates that NPY increases the inhibitory effect of endogenous NE, which is mediated at low NE concentrations via alpha-adrenoceptors. Blockade of alpha-adrenoceptors attenuated electrically induced inhibition of IL-6 secretion (p < 0.001), which was dose-dependently abrogated by BIBP 3226. This indicates that under blockade of alpha-adrenoceptors endogenous NPY supports the stimulating effect of endogenous NE via beta-adrenoceptors. These experiments demonstrate the ambiguity of NPY, which functions as a cotransmitter of NE in the nerve-macrophage interplay.

Adrenergic Agonists↗

PubMed2000

A bacteria-induced switch of sympathetic effector mechanisms augments local inhibition of TNF-alpha and IL-6 secretion in the spleen.

It is believed that an inflammation-induced activation of the CNS leads to an inhibition of overshooting immune responses to prevent extensive local cytokine secretion. However, immunosuppression by the sympathetic nervous system may be unfavorable when bacteria are present locally and when TNF-alpha is necessary to overcome infection. We now report in a superfusion model, using mouse spleen slices, that although local Pseudomonas aeruginosa increased splenic TNF-alpha and IL-6 secretion severalfold over basal levels, electrically released neurotransmitters attenuated cytokine secretion to similar basal level as under bacteria-free conditions. Bacteria reversed noradrenergic inhibitory effector mechanisms: Under bacteria-free conditions, TNF-alpha secretion was very low and IL-6 secretion was mainly inhibited by alpha2-adrenoreceptor ligation. In the presence of bacteria, TNF-alpha and IL-6 secretion were high and IL-6 secretion was mainly inhibited by beta-adrenoreceptor ligation. The alpha- to beta-adrenoswitch of IL-6 inhibition in the presence of bacteria was mediated by the prior adrenergic regulation of TNF-alpha. In vivo, chemical abrogation of sympathetic inhibition reduced accumulation of bacteria in the spleen, which depended at least in part on TNF-alpha. This suggests that activation of the sympathetic nervous system may be a forerunner for accumulation of bacteria in tissue and consecutively sepsis due to intensified inhibition of TNF-alpha secretion.

Animals↗

PubMed2000

The role of the resident intestinal flora in acute and chronic dextran sulfate sodium-induced colitis in mice.

OBJECTIVE: There is increasing evidence that the intestinal microflora plays an important role in the pathogenesis of inflammatory bowel disease. In the present study, we examined the role of the resident intestinal flora in our model of dextran sulfate sodium (DSS)-induced acute and chronic colitis in mice. METHODS: Acute colitis was induced in BALB/c mice with 5% DSS in their drinking water for 7 days. Chronic colitis was established after four cycles of feeding 5% DSS for 7 days and water for 10 days. For eliminating intestinal bacteria, mice were injected intraperitoneally with metronidazole and ciprofloxacin. We analysed four parameters: (1) body weight, (2) length of the colon, (3) histological score, and (4) myeloperoxidase activity. RESULTS: In acute DSS colitis treatment with antibiotics led to an improvement of the histological parameters (epithelial damage, P< 0.05; inflammatory infiltrate, P< 0.05) and colon length (P < 0.0028). A significant reduction in granulocyte infiltration was indicated by a 52.6% reduced myeloperoxidase activity in colonic biopsies. By contrast, in chronic colitis, treatment of mice with antibiotics failed to show significant effects. CONCLUSION: In acute DSS-induced colitis bacteria and/or bacterial products play a major role in initiation of inflammation but not in chronic DSS colitis.

Acute Disease↗

PubMed2000

Human intestinal epithelial cells secrete interleukin-1 receptor antagonist and interleukin-8 but not interleukin-1 or interleukin-6.

BACKGROUND: There is growing evidence that intestinal epithelial cells (IECs) are involved in the mucosal immune system. AIM: To assess the pattern of cytokines secreted by IECs and lamina propria mononuclear cells (LPMNCs). To achieve this, the expression and secretion of interleukin (IL)-1, IL-1 receptor antagonist (IL-1ra), IL-6, and IL-8 in human primary colonic and ileal IECs and LPMNCs from the same patient were studied. METHODS: IECs and LPMNCs were isolated from surgical specimens or endoscopic biopsy samples. mRNA expression was investigated by northern blot analysis. Secretion of IL-1beta, IL-6, IL-8, and IL-1ra was measured by enzyme linked immunosorbent assay. RESULTS: IL-1ra mRNA levels were higher in IECs than in LPMNCs in all probands. IL-8 mRNA was only present in low amounts in the IECs from two controls. In none of the specimens were IL-1beta and IL-6 mRNA present in IECs. Transcripts encoding IL-1beta, IL-1ra, IL-6, and IL-8 were identified in LPMNC preparations of all specimens. IECs from normal mucosa produced no detectable amounts of IL-1beta or IL-6, whereas LPMNCs did. IECs secreted some IL-8 (65 (9) pg/10(5) cells) but significantly more was generated by LPMNCs (408 (43) pg/10(5) cells, p<0.0001). However, IECs secreted more IL-1ra than did LPMNCs (120 (12) v 94 (11) pg/10(5) cells). In acute inflammation, IEC IL-1ra secretion was significantly increased. A correlation between secreted IL-1ra and the macroscopical degree of inflammation was found in Crohn's disease (r = 0.64, p<0.0001, n = 36) and ulcerative colitis (r = 0. 76, p<0.0001, n = 24). CONCLUSIONS: IECs from normal mucosa express and secrete IL-1ra and low amounts of IL-8, but no IL-1 or IL-6. In inflamed mucosa the secretion of IL-1ra by IECs is slightly increased but may be not sufficient to antagonise the greatly increased production of proinflammatory cytokines by LPMNCs and the IECs themselves.

Epithelial Cells↗

PubMed2000

Interleukin-12 induced interferon-gamma increases inflammation in acute dextran sulfate sodium induced colitis in mice.

There is increasing evidence that IL-12 and Th1-cytokines play an important role in intestinal inflammation. We therefore examined the role of IL-12 and interferon-gamma (IFN-gamma) in our model of dextran sulfate-induced acute colitis in mice. Treatment of mice with rmIL-12 during colitis induction resulted in severe aggravation as demonstrated by a greater loss of body weight, an increase of the histological parameters, and reduction of myeloperoxidase activity in colonic biopsies. Depletion of neutrophils in mice also led to aggravation of colitis. Neutralization of IFN-gamma in IL-12-treated mice with colitis inhibited these effects of IL-12. Neutralization of endogenous IFN-gamma or IL-12 with specific antibodies in DSS-treated mice, however, had only weak ameliorating effects. Since IL-12 and IFN-gamma have been shown to mediate experimental chronic colitis we conclude that the transition from a macrophage/neutrophil determined response to a Th-cell response promotes chronic intestinal inflammation.

Animals↗

PubMed1999

In vitro superfusion method to study nerve-immune cell interactions in human synovial membrane in long-standing rheumatoid arthritis or osteoarthritis.

Reports on patients with hemiparalysis indicate the importance of the nervous system for the pathophysiology of rheumatoid arthritis (RA) or osteoarthritis (OA). Norepinephrine (NE) and opioids seem to be more antiinflammatory neurotransmitters whereas substance P is proinflammatory. The study aimed to investigate the direct noradrenergic nerve-immune cell interaction in human synovial membrane. We used a recently developed superfusion technique with electrical stimulation of synovial membrane to elicit local NE from synovial membrane slices. The readout parameter of synovial immune cells was interleukin-6 (IL-6). IL-6 was spontaneously secreted from RA and OA synovial membranes. Electrical field stimulation intensively reduced IL-6 secretion. In patients with OA or RA, this electrically induced reduction of IL-6 secretion was not significantly changed by alpha- or beta-adrenergic antagonists. The study demonstrates that local endogenous NE seem to play a minor role, which may be due to a depletion of NE or loss of noradrenergic fibers during chronic RA and OA.

Aged↗

PubMed1999

Interleukin-1 production by mouse macrophages is regulated in a feedback fashion by nitric oxide.

The pleiotropic cytokine interleukin-1 (IL-1) is an inducer of the inducible nitric oxide synthase (iNOS). It was surprising to find that treatment of normal mice with an iNOS inhibitor resulted in detectable IL-1beta mRNA in colon and spleen, suggesting feedback regulation. When mouse peritoneal exudate cells (PEC) or RAW 264.7 cells were stimulated with lipopolysaccharide (LPS), concomitant inhibition of iNOS resulted in an increase of IL-1beta and IL-1alpha protein secretion. Conversely, after addition of the NO-generating compound NOC-18, IL-1beta and IL-1alpha concentrations in supernatants were dose-dependently reduced. Costimulation with interferon-gamma (IFN-gamma) reversed the NOC-18-mediated suppression of IL-1alpha protein concentration into an almost fivefold increase in RAW 264.7 cells. This effect was specific for IL-1alpha and was also seen in PEC. The mRNA expression for IL-1beta and IL-1alpha in RAW 264.7 cells correlated with the protein levels, suggesting transcriptional regulation by NO. Dysregulated IL-1/NO cross-regulation may play a role in inflammatory diseases.

Animals↗

PubMed1999

Interferon-gamma (IFN-gamma)- and tumour necrosis factor (TNF)-induced nitric oxide as toxic effector molecule in chronic dextran sulphate sodium (DSS)-induced colitis in mice.

Excess nitric oxide formation caused by the activity of the inducible nitric oxide synthase has been implicated as a toxic effector molecule in the pathogenesis of experimental colitis and inflammatory bowel disease. It was therefore investigated whether inhibition of this synthase or the cytokines TNF and IFN-gamma, inducers of nitric oxide synthase, had effects on chronic colitis in mice. Chronic colitis was induced in mice by repeated feeding of DSS. Cytokines were neutralized by treatment with MoAbs and nitric oxide synthase was inhibited by aminoguanidine. The degree of colonic inflammation was assessed by a histological score and colon length. Aminoguanidine treatment reduced nitric oxide activity by 60% (P = 0. 0004), the histological score by 31% (P = 0.005) and increased colon length by 1.4 cm (P = 0.002). Neutralization of TNF and IFN-gamma resulted in increased colon length (0.7 cm, P = 0.07 and 0.8 cm, P = 0.03), improved histological score (19%, P = 0.045 and 25%, P = 0. 013), and reduced nitric oxide activity (31%, P = 0.07 and 54%, P = 0.004) compared with controls. The combination of anti-cytokine treatments had additive effects. TNF and IFN-gamma are involved in perpetuation of chronic DSS-induced colitis, and induction of excessive nitric oxide activity could be their common effector mechanism.

Animals↗