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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined the effect of cytokines on basal and agonist-stimulated release of von Willebrand factor (vWf) by human endothelial cells. Treatment of endothelial cells for up to 48 hours with human recombinant or purified interleukin 1 (IL-1) or human recombinant tumor necrosis factor-alpha (TNF-alpha) did not significantly affect constitutive secretion of vWf or intracellular levels of vWf, although basal prostacyclin (PGI2) production was markedly enhanced. In contrast, both IL-1 and TNF-alpha modulated vWf release in response to thrombin or phorbol ester. Pretreatment of endothelial cells for 2 hours with either cytokine enhanced by up to threefold the stimulatory effect of a subsequent 60-minute exposure to thrombin. Addition of cycloheximide (5 micrograms/mL) during the preincubation abolished this enhancement. Moreover, if the cytokine pretreatment time was extended to 24 hours, agonist-stimulated vWf release was significantly suppressed. Cytokine treatment for 2 or 24 hours had no detectable effect on levels of vWf messenger RNA. The effects of cytokines were not the result of contamination with bacterial lipopolysaccharide and were not attributable to endothelial cell injury. These results show that cytokines have little or no direct effect on vWf release from endothelial cells but can significantly modulate its acute release in response to other stimuli in a complex time- and dose-dependent manner.
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PMID:Differential regulation by cytokines of constitutive and stimulated secretion of von Willebrand factor from endothelial cells. 210 7

The vasodilator prostaglandin E2 has been proposed as a mediator of erythema in a variety of cutaneous inflammatory reactions and prostacyclin levels have been found to be elevated in ultraviolet induced erythema. Human recombinant interleukin 1 alpha and lipopolysaccharide induced a concentration- and time-dependent release of prostaglandin E2, but not prostacyclin, from cultured neonatal and adult human dermal microvascular endothelial cells. Prostaglandin E2 was measurable at 2 h after stimulation with 1 U/ml interleukin 1 alpha, levels increased rapidly up to 6 h and more slowly up to 24 h. Lipopolysaccharide (20 micrograms/ml) induced measurable release of prostaglandin E2 between 2 and 4 h after stimulation and release continued up to 24 h when incubation was terminated. With both agonists, release of prostaglandin E2 was inhibited by indomethacin and significantly reduced by cycloheximide. The sensitivity and magnitude of responses of the cutaneous endothelial cells to these pro-inflammatory stimuli appeared to be dependent on their derivation.
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PMID:Pro-inflammatory mediators induce sustained release of prostaglandin E2 from human dermal microvascular endothelial cells. 210 66

Direct effects of endotoxin (lipopolysaccharide [LPS]) on equine WBC are known to stimulate the release of a variety of mediators including thromboxane, prostacyclin, and leukotrienes. In this study, 0.1 microgram of LPS/ml stimulated an early increase in tumor necrosis factor, succeeded by an increase in interleukin-1, but concentrations of LPS up to 5.0 micrograms/ml caused no significant increase in superoxide anion release. The concentration of LPS (0.1 microgram/ml) used in this experiment was in the range of concentrations measured in plasma of some horses with gastrointestinal problems. These results indicate that mediators released in response to low concentrations of LPS may be responsible for many of the LPS-induced pathophysiologic effects. This is indicated because concentrations of LPS detected in plasma of some horses with severe gastrointestinal problems are approximately 0.1 microgram/ml, a concentration that will stimulate cells to produce tumor necrosis factor, but will not stimulate any other measurable cytotoxic effect.
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PMID:Characterization of release of tumor necrosis factor, interleukin-1, and superoxide anion from equine white blood cells in response to endotoxin. 216 32

Probucol, 4,4'-(isopropylidenedithio)bis(2,6-di-tert-butyl-phenol), has been shown to inhibit atherogenesis in genetically hypercholesterolemic (Watanabe) rabbits. Since atherosclerotic lesions contain macrophages capable of screting interleukin 1 (IL 1) and other cytokines that could contribute to the pathogenesis of the disease, we have investigated whether probucol affects IL 1 secretion. Resident peritoneal macrophages from mice dosed with probucol secreted 40-80% less IL 1 than macrophages from control animals when stimulated in vitro with lipopolysaccharide (LPS). The inhibitory effect of probucol was observed when IL 1 was assayed by the standard bioassay, the thymocyte proliferation assay, or a competitive IL 1 receptor binding assay. Probucol treatment had no effect on LPS-induced membrane IL 1 expression; secretion of tumor necrosis factor (TNF); Con A-induced splenic interleukin 2 (IL 2) and interleukin 3 (IL 3) release; and prostaglandin- or zymosan-induced secretion of prostacyclin, leukotriene C4, acid phosphatase, or superoxide anion. In contrast to the effect of oral administration, direct addition of probucol to macrophage cultures did not inhibit IL 1 release. Probucol administration did, however, inhibit the fall in serum zinc level induced by intravenous injection of LPS in zymosan-primed mice but had no effect on the LPS-induced increase in serum triglyceride levels, which indirectly confirms that probucol administration inhibits IL 1 but not TNF secretion. Paw granuloma induced in mice by heat-killed mycobacteria was inhibited by oral administration of probucol, an effect that may be attributable to inhibition of IL 1 secretion. Probucol neither reduced zymosan-induced liver granulomata in mice nor inhibited adjuvant-induced arthritis in rats. We suggest that inhibition of IL 1 secretion from macrophages by probucol contributes to its therapeutic effects in atherosclerosis and may also result in beneficial activity in some chronic inflammatory diseases.
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PMID:Ex vivo lipopolysaccharide-induced interleukin-1 secretion from murine peritoneal macrophages inhibited by probucol, a hypocholesterolemic agent with antioxidant properties. 231 80

Exposure of cultured bovine pulmonary endothelial cells to endotoxin (lipopolysaccharide, LPS) causes cytotoxicity and increased prostacyclin production. Since cyclic nucleotides have been proposed as modulators of inflammation, we wondered whether they were involved in LPS-induced endothelial damage. Bovine pulmonary endothelial cells were exposed for 24 h to LPS and the effects of 1-methyl-3-isobutylxanthine (MIX), a phosphodiesterase inhibitor, dibutyryl cyclic AMP (db-cAMP), forskolin (an adenylate cyclase activator), and sodium nitroprusside (an agent known to stimulate intracellular cyclic GMP generation) on LPS-induced injury were determined. Injury was assessed by measurement of lactate dehydrogenase (LDH) (activity) and prostacyclin (6-keto-PGF1 alpha) in the bathing medium. Incubation with MIX attenuated LPS-induced endothelial cytotoxicity and prostacyclin production in a dose-dependent manner (ANOVA, p less than 0.001). Dibutyryl cyclic AMP also inhibited LPS-stimulated LDH release from the endothelial cells but did not suppress increased prostacyclin production. The combinations of MIX and dibutyryl cyclic AMP produced protection similar to that of MIX alone. Neither nitroprusside nor forskolin affected LPS-induced endothelial injury. Measurements of intracellular cyclic nucleotide concentrations showed that MIX caused marked increases in both cyclic AMP and cyclic GMP within 30 min of incubation, while forskolin and nitroprusside failed to cause such early elevations. Thus, phosphodiesterase inhibition protects endothelial cells from the effects of LPS. Increased intracellular concentrations of cyclic AMP also protect endothelial cells from LPS-induced cytotoxicity but do not alter the prostanoid response. We conclude that increased intracellular concentrations of cyclic AMP protect against LPS-induced endothelial cytotoxicity if present early in the exposure. We further conclude that LPS-mediated endothelial cytotoxicity can be separated from increased prostacyclin production.
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PMID:Attenuation of endotoxin-induced cytotoxicity and prostacyclin production in cultured bovine pulmonary artery endothelial cells by phosphodiesterase inhibition. 246 43

Both cyclosporine and bacterial lipopolysaccharide enhance prostanoid synthesis and regulate the immune response. This study was designed to establish whether these agents affect prostanoid synthesis by common or different mechanisms. CsA and LPS stimulate prostanoid synthesis both in human monocytes and smooth muscle cells from guinea pig aorta. Only LPS stimulates synthesis in the presence of exogenous arachidonic acid. Dexamethasone totally blocks CsA but only partially inhibits LPS. CsA and LPS both enhance the release of labeled metabolites from cells labeled with arachidonic acid, but indomethacin only blocks the effect of LPS. CsA and the releasing agent calcium ionophore (A23187) both increase PGE2 and PGI2 synthesis without changing their relative concentrations, cause the release of free arachidonic acid, and lead to the formation of new metabolites that are not products of cyclooxygenase activity. Preincubation with either CsA or A23187 and a subsequent wash deplete the arachidonic acid pool available for prostanoid synthesis. Thus, A23187 and CsA have very similar effects on arachidonic acid metabolism. In contrast, LPS increases PGE2 and PGI2 synthesis and alters their relative concentrations, diminishes the relative concentration of free arachidonic acid, and enhances the formation of new metabolites that are products of cyclooxygenase activity. These differences are explained by mechanisms in which CsA promotes prostanoid synthesis through arachidonic acid release, and LPS promotes prostanoid synthesis through increased cyclooxygenase activity.
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PMID:Mechanisms for the stimulation of prostanoid synthesis by cyclosporine and bacterial lipopolysaccharide. 249 71

Rabbit alveolar macrophages were found to produce extraordinary amounts of prostaglandin E2 and F2 alpha with the stimulation of lipopolysaccharide or lipid A. Exogenous prostaglandin E2 greatly enhanced the lipopolysaccharide action on rabbit alveolar macrophages for the induction of prostaglandin F2 alpha release (3-5 fold), while prostaglandin E2 alone did not cause any effect. The enhancement expressed was especially strong when prostaglandin E2 was administered to the cells simultaneously with lipopolysaccharide. The effect of prostaglandin E2 was observed neither with a nonstimulating dose of lipopolysaccharide nor with a stimulating dose of zymosan. This phenomenon was even more pronounced when prostaglandin I2 was used instead of prostaglandin E2, while no sensitization was demonstrated by prostaglandin F2 alpha. These observations suggest that prostaglandins can modulate the activation of the cyclooxygenase pathway of arachidonate metabolism in the activated macrophages by lipopolysaccharide.
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PMID:Sensitization of alveolar macrophages to lipopolysaccharide-induced prostaglandin synthesis by exogenous prostaglandins. 251 48

The effects of OKY-046, a selective thromboxane A2 (TXA2) synthetase inhibitor, and ONO-3708, a novel TXA2 receptor antagonist, on liver disease were investigated in mice. The liver injury was induced by either an injection of antibasic liver protein (BLP) antibody into DBA/2 mice that had been previously immunized with rabbit IgG or by an injection of bacterial lipopolysaccharide (LPS) into Corynebacterium parvum (C. parvum) pretreated DDY mice. 1) In both injury models, clear elevation of glutamate transaminase (GOT and GPT) activity due to extensive liver parenchymal cell damage was observed; this was confirmed by significant histopathological changes in the liver. 2) Typical histopathological changes in the liver were submassive hepatocellular necrosis in the anti-BLP antibody-induced injury model and focal necrosis in the LPS-induced model. Inflammation and increased cell infiltration in portal connective tissue were observed in both cases. 3) Administration of OKY-046 (50 mg/kg) and ONO-3708 (0.5, 1.0 and 2.0 mg/kg) suppressed the elevation of serum GOT and GPT levels and histopathological changes in both experimental liver injury models. 4) Indomethacin inhibited the development of liver disease caused by anti-BLP antibody but not by bacterial LPS. Prostaglandin I2 inhibited the elevation of serum GOT and GPT levels and histopathological changes of the liver in the mice treated with anti-BLP antibody and showed the tendency to inhibit the development of liver injury caused by bacterial LPS.
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PMID:Effect of OKY-046 and ONO-3708 on liver injury in mice. 251 4

Pulp was experimentally inflamed by applying bacterial lipopolysaccharide (LPS). Changes in arachidonic acid (AA) metabolites were determined by measuring the conversion of exogenously added AA in pulp homogenates. The inflamed pulp produced 12-hydroxy-eicosatetraenoic acid (12-HETE), 6-keto-prostaglandin (PG) F1 alpha greater than PGE2, thromboxane B2 and 11-HETE, which was further identified with high-performance liquid chromatography. The LPS treatment caused a 2.0-fold increase in 12-HETE production at 1 h, a 3.8-fold increase in 6-keto-PGF1 alpha production at 12 h and increases in PGE2 and 11-HETE production of 8.8- and 5.5-fold, respectively, at 24 h. Vascular permeability in the inflamed pulp was measured by quantifying the amount of an extravasated dye; it increased markedly from 6 h and reached a peak at 12 h after the LPS application. When indomethacin (0.3-30 mg/kg, s.c.) was given before LPS, both the production of 6-keto-PGF1 alpha and PGE2 and the increase in vascular permeability were inhibited dose dependently. Exogenously applied PGE2 and PGI2 methyl ester reduced the inhibition of the increase in vascular permeability caused by indomethacin. Thus PGE2 and PGI2 may be involved in increases in vascular permeability in pulpal inflammation.
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PMID:Involvement of arachidonic acid metabolites in increases in vascular permeability in experimental dental pulpal inflammation in the rat. 251 1

The xanthine derivative pentoxifylline (POF, Trental) and its metabolically more stable structural analogues, HWA 138 and HWA 448, were compared for their capacity to prevent leukopenia provoked in mice by injection of bacterial lipopolysaccharide (LPS). It was found that HWA 138 and HWA 448 counteracted LPS-induced leukopenia more effectively than POF. Indomethacin diminished the action of HWA 138 and HWA 448, and the stable prostacyclin analogue CG-4203 (Taprosten) mimicked the effect of the xanthine derivatives. Since pentoxifylline and its structural analogues induced synthesis of PGI2 in endothelial cell cultures, it is suggested that its effect on LPS leukopenia is mediated by endogenous prostacyclin production. All of the xanthine derivatives tested and CG-4203 blocked the leukopenia induced by recombinant tumor necrosis factor, which is a major endogenous mediator for endotoxin toxicity.
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PMID:The role of prostacyclin in the protective effects of pentoxifylline and other xanthine derivatives in endotoxin action in mice. 251 31


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