Aporphine and bisaporphine alkaloids from Aristolochia lagesiana var. intermedia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Induction of macrophage nitric oxide production by interferon-gamma and tumor necrosis factor-alpha is enhanced by interleukin-10.

Interleukin-10 (IL-10) has been reported to inhibit nitric oxide (NO) synthesis and microbicidal activity of interferon-gamma (IFN-gamma)-stimulated macrophages (M phi) by preventing the secretion of tumor necrosis factor-alpha (TNF-alpha) which serves as an autocrine activating signal. We have examined the effects of recombinant IL-10 on the capacity of IFN-gamma together with exogenous TNF-alpha to induce NO synthesis by bone marrow-derived M phi. Under these conditions and in contrast to its reported deactivating potential, IL-10 strongly enhanced NO synthesis measured as nitrite (NO2-) release (half maximal stimulation at approximately 10 U/ml). IL-10 further increased NO2- production by M phi stimulated in the presence of optimal concentrations of prostaglandin E2, a positive modulator of M phi activation by IFN-gamma/TNF-alpha. Increased steady state levels of NO synthase mRNA were observed in 4-h IFN-gamma/TNF-alpha cultures and enhanced NO2(-)-release was evident 24 h but not 48 h after stimulation. These results suggest that the effects of IL-10 on M phi function are more complex than previously recognized.

Insulin resistance in mice lacking neuronal nitric oxide synthase is related to an alpha-adrenergic mechanism

Rapport de synthèse : Le monoxyde d'azote (NO) joue un rôle important dans la régulation de l'homéostasie du système cardiovasculaire et du glucose. Les souris déficientes pour le gène codant l'isoforme neuronale de la synthase de monoxyde d'azote (nNOS) sont résistantes à l'insuline, mais les mécanismes sous-jacents sont inconnus. Le manque de NO produit par la nNOS pourrait être à l'origine d'une diminution de la perfusion du muscle squelettique et ainsi d'une diminution de l'apport de substrat. Alternativement, le déficit de nNOS normalement hautement exprimé dans le tissu musculaire squelettique pourrait directement y perturber la consommation de glucose. Finalement l'absence de l'action sympatholytique du NO neuronal pourrait diminuer la sensibilité à l'insuline. Afin de tester ces hypothèses nous avons étudié, chez des souris déficientes en nNOS et des souris-contrôle, la consommation corporelle totale de glucose et le flux musculaire squelettique pendant des clamps hyperinsulinémiques euglycémiques in vivo, ainsi que la consommation de glucose dans le muscle squelettique in vitro. De plus nous avons analysé les effets d'une inhibition alpha-adrénergique sur la consommation de glucose pendant les clamps hyperinsulinémiques euglycémiques in vivo. Le taux de perfusion de glucose pendant les clamps était grossièrement 15 pourcent plus bas (P<0.001) chez les souris déficientes en nNOS que chez les souris-contrôle. Cette résistance à l'insuline chez les souris déficientes en nNOS n'était due ni à une stimulation déficiente du flux sanguin musculaire par l'insuline ni à un défaut intrinsèque de la consommation de glucose du muscle (qui étaient comparables dans les deux groupes), mais à un mécanisme alpha-adrénergique, car l'administration de phentolamine rétablissait la sensibilité à l'insuline chez les souris déficientes en nNOS. Ces résultats suggèrent qu'une hyperactivité sympathique, potentiellement due à la perte de l'inhibition neuronale centrale du flux sympathique par le NO provenant de nNOS, contribue à la résistance à l'insuline des souris déficientes en nNOS. Par ailleurs ces résultats tendent à prouver qu'un défaut de production de NO provoquerait une résistance à l'insuline par des mécanismes différents selon l'isoforme de NO synthase déficiente (par exemple chez les souris déficientes pour la forme endothéliale de NO synthase, il a été montré que la résistance à l'insuline est due à un défaut de stimulation de la perfusion musculaire par l'insuline et à un défaut du signalling de l'insuline dans la cellule musculaire squelettique). Chez l'être humain il est établi que les états de résistance à l'insuline sont associés à une synthèse défectueuse et/ou une mauvaise biodisponibilité du NO, ainsi qu'à une hyperactivité sympathique. Nous spéculons que la perte d'inhibition centrale du flux sympathique représente un mécanisme contribuant à la résistance à l'insuline et ses complications cardiovasculaires chez l'être humain.

Inducible nitric oxide synthase and tumor necrosis factor-alpha in delayed gastric emptying and gastrointestinal transit induced by lipopolysaccharide in mice

Gastrointestinal motility disturbances during endotoxemia are probably caused by lipopolysaccharide (LPS)-induced factors: candidates include nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), interleukin-1ß, and interleukin-6. Flow cytometry was used to determine the effects of LPS and these factors on gastric emptying (evaluated indirectly by determining percent gastric retention; %GR) and gastrointestinal transit (GIT) in male BALB/c mice (23-28 g). NO (300 µg/mouse, N = 8) and TNF-alpha (2 µg/mouse, N = 7) increased (P < 0.01) GR and delayed GIT, mimicking the effect of LPS (50 µg/mouse). During early endotoxemia (1.5 h after LPS), inhibition of inducible NO synthase (iNOS) by a selective inhibitor, 1400 W (150 µg/mouse, N = 11), but not antibody neutralization of TNF-alpha (200 µg/mouse, N = 11), reversed the increase of GR (%GR 78.8 ± 3.3 vs 47.2 ± 7.5%) and the delay of GIT (geometric center 3.7 ± 0.4 vs 5.6 ± 0.2). During late endotoxemia (8 h after LPS), both iNOS inhibition (N = 9) and TNF-alpha neutralization (N = 9) reversed the increase of GR (%GR 33.7 ± 2.0 vs 19.1 ± 2.6% (1400 W) and 20.1 ± 2.0% (anti-TNF-alpha)), but only TNF-alpha neutralization reversed the delay of GIT (geometric center 3.9 ± 0.4 vs 5.9 ± 0.2). These findings suggest that iNOS, but not TNF-alpha, is associated with delayed gastric emptying and GIT during early endotoxemia and that during late endotoxemia, both factors are associated with delayed gastric emptying, but only TNF-alpha is associated with delayed GIT.

Sporothrix schenckii lipid inhibits macrophage phagocytosis: Involvement of nitric oxide and tumour necrosis factor-alpha

The role of cell-wall compounds in the immune response to sporotrichosis is unknown. The effect of cell-wall compounds and exoantigen obtained from Sporothrix schenckii in macrophage/fungus interaction was analysed with respect to nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha). The lipid compound of the cell wall plays an important role in the pathogenesis of this mycosis and was found to inhibit the phagocytic process and to induce high liberation of NO and TNF-alpha in macrophage cultures in the present study. This is a very interesting result because it is the first report about one compound of the fungus S. schenckii that presents this activity.

Influence of Yersinia pseudotuberculosis outer proteins (Yops) on interleukin-12, tumor necrosis factor alpha and nitric oxide production by peritoneal macrophages

An essential key to pathogenicity in Yersinia is the presence of a 70 kb plasmid (pYV) which encodes a type-III secretion system and several virulence outer proteins whose main function is to enable the bacteria to survive in the host. Thus, a specific immune response is needed in which cytokines are engaged. The aim of this study was to assess the influence of Yersinia outer proteins (Yops) released by Yersinia pseudotuberculosis on the production of the proinflammatory cytokines, interleukin-12 (IL-12), and tumor necrosis factor alpha (TNF-alpha), and nitric oxide (NO) by murine peritoneal macrophages. To this end, female Swiss mice were infected intravenously with wild-type Y pseudotuberculosis or with mutant strains unable to secrete specific Yops (YopE, YopH, YopJ, YopM, and YpkA). on the 7th, 14th, 21st, and 28th days after infection, the animals were sacrificed and the cytokines and NO were assayed in the peritoneal macrophages culture supernatants. A fall in NO production was observed during the course of infection with all the strains tested, though during the infection with the strains that did not secrete YopE and YopH, the suppression occurred later. There was, in general, an unchanged or sometimes increased production of TNF-alpha between the 7th and the 21st day after infection, compared to the control group, followed by an abrupt decrease on the last day of infection. The IL-12 production was also suppressed during the infection, with most of the strains tested, except with those that did not secrete YopJ and YopE. The results suggest that Yops may suppress IL-12, TNF-alpha, and NO production and that the most important proteins involved in this suppression are YopE and YopH. (C) 2004 Elsevier B.V. All rights reserved.

Tumor Necrosis Factor alpha and Interleukin-1 beta Modulate Calcium and Nitric Oxide Signaling in Mechanically Stimulated Osteocytes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Inhibition of hydrogen peroxide, nitric oxide and TNF-alpha production in peritoneal macrophages by ethyl acetate fraction from Alchornea glandulosa

The effects of Alchornea glandulosa ethyl acetate fraction (AGF) on hydrogen peroxide (H2O2), nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) production in peritoneal macrophages activated with lipopolysaccharide (LPS) or phorbol myristate acetate (PMA) were investigated. Analysis by thin layer chromatography (TLC) of AGF showed several constituents, including flavonoids, which may have anti-inflammatory activity. Inhibitory effects of the fraction in H2O2 and NO production ranged from 8.59 +/- 7.84% to 70.56 +/- 4.16% and from 16.06 +/- 3.65% to 38.73 +/- 3.90%, respectively. The TNF-alpha production was only partially inhibited in the tested concentrations (12.21 +/- 6.23%-15.16 +/- 0.96%). According to these results, it is suggested that AGF has anti-inflammatory activity. This medicinal plant may have therapeutic potential in the control of inflammatory disorders.

Study of the thermal resistance of alpha-phase aluminum oxide (alpha-Al2O3) films deposited on the paper substrate

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Inhibition of Nitric Oxide and Tumour Necrosis Factor-alpha Production in Peritoneal Macrophages by Aspergillus nidulans Melanin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Insulin resistance in mice lacking neuronal nitric oxide synthase is related to an alpha-adrenergic mechanism

BACKGROUND: nitric oxide (NO) plays an important role in the regulation of cardiovascular and glucose homeostasis. Mice lacking the gene encoding the neuronal isoform of nitric oxide synthase (nNOS) are insulin-resistant, but the underlying mechanism is unknown. nNOS is expressed in skeletal muscle tissue where it may regulate glucose uptake. Alternatively, nNOS driven NO synthesis may facilitate skeletal muscle perfusion and substrate delivery. Finally, nNOS dependent NO in the central nervous system may facilitate glucose disposal by decreasing sympathetic nerve activity. METHODS: in nNOS null and control mice, we studied whole body glucose uptake and skeletal muscle blood flow during hyperinsulinaemic clamp studies in vivo and glucose uptake in skeletal muscle preparations in vitro. We also examined the effects of alpha-adrenergic blockade (phentolamine) on glucose uptake during the clamp studies. RESULTS: as expected, the glucose infusion rate during clamping was roughly 15 percent lower in nNOS null than in control mice (89 (17) vs 101 (12) [-22 to -2]). Insulin stimulation of muscle blood flow in vivo, and intrinsic muscle glucose uptake in vitro, were comparable in the two groups. Phentolamine, which had no effect in the wild-type mice, normalised the insulin sensitivity in the mice lacking the nNOS gene. CONCLUSIONS: insulin resistance in nNOS null mice was not related to defective insulin stimulation of skeletal muscle perfusion and substrate delivery or insulin signaling in the skeletal muscle cell, but to a sympathetic alpha-adrenergic mechanism.

Evidence of autocrine modulation of macrophage nitric oxide synthase by alpha-melanocyte-stimulating hormone.

alpha-Melanocyte-stimulating hormone (alpha-MSH) is a potent inhibitory agent in all major forms of inflammation. To identify a potential mechanism of antiinflammatory action of alpha-MSH, we tested its effects on production of nitric oxide (NO), believed to be a mediator common to all forms of inflammation. We measured NO and alpha-MSH production in RAW 264.7 cultured murine macrophages stimulated with bacterial lipopolysaccharide and interferon gamma. alpha-MSH inhibited production of NO, as estimated from nitrite production and nitration of endogenous macrophage proteins. This occurred through inhibition of production of NO synthase II protein; steady-state NO synthase II mRNA abundance was also reduced. alpha-MSH increased cAMP accumulation in RAW cells, characteristic of alpha-MSH receptors in other cell types. RAW cells also expressed mRNA for the primary alpha-MSH receptor (melanocortin 1). mRNA for proopiomelanocortin, the precursor molecular of alpha-MSH, was expressed in RAW cells, and tumor necrosis factor alpha increased production and release of alpha-MSH. These results suggest that the proinflammatory cytokine tumor necrosis factor alpha can induce macrophages to increase production of alpha-MSH, which then becomes available to act upon melanocortin receptors on the same cells. Such stimulation of melanocortin receptors could modulate inflammation by inhibiting the production of NO. The results suggest that alpha-MSH is an autocrine factor in macrophages which modulates inflammation by counteracting the effects of proinflammatory cytokines.