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R J Flower

Publications and source records attributed to R J Flower.

At least 73 records · Page 4Linked to original sources
PubMed1997

Subacute treatment of rats with dexamethasone reduces ICAM-1 levels on circulating monocytes.

We report for the first time that in vivo treatment with dexamethasone (DEX) reduces levels of intercellular adhesion molecule-1 (ICAM-1) expression on rat circulating unstimulated monocytes (-55%) and peritoneal macrophages (-26%). This effect was present following sub-acute (5 days) treatment with a low dose (0.1 mg/kg per day), but not after single administration of a high dose (1 mg/kg, -2 h), of the steroid. Both acute and sub-acute treatment with DEX failed to modify either basal or up-regulated CD11b expression on peripheral blood monocytes and neutrophils, elastase release from neutrophils, and beta-glucuronidase release from cultured macrophages. The lack of alteration of CD11b expression on circulating leukocytes suggests that the effect of DEX on ICAM-1 expression is secondary to gene repression rather than a non-specific blockade of cell differentiation. These data promote the concept that different dose-regimens with glucocorticoids affect distinct molecular targets and indicate that clinically-related protocols of DEX may reveal new mechanism(s) of action.

Animals↗
PubMed1997

Dexamethasone inhibits leukocyte emigration in rat mesenteric post-capillary venules: an intravital microscopy study.

The effect of subcutaneous administration of dexamethasone (DEX) on interleukin-1beta(IL-1beta, 20 ng i.p., - 2 h) and platelet-activating factor (PAF, 100 nM in superfusion) -induced leukocyte interaction with the endothelium of rat mesenteric post-capillary venules was studied. DEX produced a dose-dependent inhibition of IL-1beta-induced leukocyte extravasation in the rat mesenteric vascular bed, with a calculated ED5o of 40 microg/kg and a maximal effect of 80-100% inhibition at 0.1 mg/kg. IL-1beta-induced cell adhesion to post-capillary venules was only partially inhibited by the steroid, with a calculated ED50 of 480 microg/kg and a maximal effect of 40-60% inhibition. Furthermore, the steroid inhibited leukocyte emigration, but not adhesion, caused by superfusion of the mesenteric vascular bed with PAF. A doubling of leukocyte emigration time (from 226 to 552 s) was observed after treatment of rats with DEX. Administration for 5 days of a dose of 10 microg/kg DEX (which was inactive when given as a single injection) resulted again in a selective inhibition of IL-1beta-induced leukocyte emigration, without effect on cell adhesion. These data demonstrate a preferential susceptibility of the leukocyte emigration process to the inhibitory action of DEX.

Animals↗
PubMed1997

Lipocortin 1: a second messenger of glucocorticoid action in the hypothalamo-pituitary-adrenocortical axis.

The secretion of hydrocortisone by the adrenal cortex is crucial in balancing the reaction of the body to injury or stress. In the periphery, hydrocortisone inhibits inflammation, downregulates the immune system and produces many other crucial physiological and metabolic changes. Within the neuroendocrine system, hydrocortisone inhibits the release of adrenocorticotrophic hormone (and other pituitary hormones), thereby governing its own secretion. The manifold actions of hydrocortisone are mediated through induction or repression of many genes but one pathway, mediated by the inducible protein lipocortin 1 (LC-1, also known as annexin 1), mediates several important effects both within the hypothalamo-pituitary-adrenocortical axis itself and in the periphery.

Animals↗
PubMed1997

Inhibition of neutrophil and monocyte recruitment by endogenous and exogenous lipocortin 1.

1. The role played by endogenous lipocortin 1 in the anti-migratory action exerted by dexamethasone (Dex) on monocyte recruitment in an in vivo model of acute inflammation was investigated by use of several neutralizing polyclonal antibodies raised against lipocortin 1 or a lipocortin 1-derived N-terminus peptide (peptide Ac2-26). The efficacy of peptide Ac2-26 in inhibiting monocyte and polymorphonuclear leucocyte (PMN) recruitment was also tested. 2. Intraperitoneal (i.p.) injection of zymosan A (1 mg) produced a time-dependent cell accumulation into mouse peritoneal cavities which followed a typical profile of acute inflammation: PMN influx was maximal at 4 h post-zymosan (between 15 and 20 x 10(6) cells per mouse), and this was followed by an accumulation of monocytes which peaked at the 24 h time-point (between 10 and 15 x 10(6) cells per mouse). 3. Dex administration to mice reduced zymosan-induced 4 h PMN infiltration and 24 h monocyte accumulation with similar efficacy: approximately 50% of inhibition of recruitment of both cell types was achieved at the dose of 30 micrograms per mouse (approximately 1 mg kg-1, subcutaneously (s.c.)). Maximal inhibitions of 64% and 67% on PMN and monocyte recruitment, respectively, were measured after a dose of 100 micrograms per mouse (approximately 3 mg kg-1, s.c.). 4. Dex (30 micrograms s.c.) inhibited monocyte (53%) and PMN (69%) accumulation in response to zymosan application in mice which had been treated with a non-immune sheep serum (50 microliters s.c.). In contrast, the steroid was no longer active in reducing cell accumulation in mice which had been passively immunized against full length human recombinant lipocortin 1 (serum LCS3), or against lipocortin 1 N-terminus peptide. 5. Treatment of mice with vinblastine (1 mg kg-1, intravenously (i.v.)) produced a remarkable leucopenia as assessed 24 h after administration. This was accompanied by a 60% reduction in 4 h-PMN influx, and by a 27% reduction in 24 h-monocyte accumulation, measured after zymosan administration. The inhibitory effect of Dex on monocyte recruitment was not significantly modified in vinblastine-treated mice, with 36% and 57% of inhibition calculated at the dose of 30 micrograms Dex, and 70% and 60% of inhibition at 100 micrograms Dex, in vehicle- and vinblastine-treated mice, respectively. 6. Treatment of mice with peptide Ac2-26 dose-dependently attenuated PMN influx at 4 h post-zymosan with a significant effect at 100 micrograms per mouse (45% of inhibition, n-9, P < 0.05) and a maximal effect of 61% inhibition at the highest dose tested of 200 micrograms s.c. (n = 14, P < 0.05). No effect of peptide Ac2-26 (200 micrograms s.c.) was seen on zymosan-induced 24 h monocyte recruitment. In contrast, administration of 200 micrograms peptide Ac2-26 every 6 h was effective in reducing the number of monocytes harvested from the inflamed peritoneal cavities at 24 h post-zymosan: 9.40 +/- 0.58 x 10(6) monocytes per mouse (n = 13) and 5.74 +/- 0.34 monocytes per mouse (n = 14) in vehicle- and peptide Ac2-26-treated mice, respectively (P < 0.05). 7. Finally, peptide Ac2-26 produced a concentration-dependent inhibition of the rate of phagocytosis of mouse resident peritoneal macrophages as measured by flow cytometry, with a maximal reduction of 34% at the highest concentration tested of 100 micrograms ml-1 (n = 8 experiments performed in duplicate; P < 0.05). 8. In conclusion, this study suggests that in vivo monocyte recruitment during acute inflammation is, at least in part, under the negative modulatory control of endogenous lipocortin 1 (as seen after administration of Dex by using the specific antisera) and exogenous lipocortin 1 mimetics (as observed with peptide Ac2-26. In addition to the neutrophil, we can now propose that the monocyte also can be a target for the in vivo anti-inflammatory action of lipocortin 1.

Animals↗
PubMed1997

A novel murine model of allergic inflammation to study the effect of dexamethasone on eosinophil recruitment.

1. We have developed a novel model of allergen-induced eosinophil into mouse air-pouches following sensitization and challenge with ovalbumin (Ova). This model was used to investigate the mechanism(s) underlying the anti-inflammatory action of the glucocorticoid hormone dexamethasone (Dex). 2. Injection of 10 micrograms Ova into 6-day-old dorsal air-pouches of mice sensitized to the same antigen provoked an intense cell accumulation as early as 6 h post-challenge (0.08 +/- 0.03 and 4.0 +/- 1.0 x 10(5) leucocytes in saline and Ova-treated air-pouches, respectively), maximal at 24 h (0.02 +/- 0.01 and 6.0 +/- 0.8 x 10(5) leucocytes in saline and Ova-treated air-pouches, respectively) and persisted up to 48 h. At the 24 h time-point, the cellular infiltrate consisted of 37% eosinophils, 18% neutrophils and 45% mononuclear cells, as assessed by histological examination. The same ratio of eosinophil/neutrophil was obtained by fluorescence-activated cell sorting (FACS) analysis, since 72% of the polymorphonuclear (PMN) population was positive for very-late antigen-4 (VLA-4) expression. 3. Subcutaneous (s.c.) administration of Dex (50 or 100 micrograms per mouse, -1 h) inhibited eosinophil accumulation into Ova challenged air-pouches by about 70% (P < 0.05) and 75% (P < 0.05), respectively, when compared to controls. Cell accumulation measured at 48 h after Ova injection was also significantly reduced (-75%) by Dex administration at the 24 h time-point (n = 12, P < 0.05). 4. Eosinophil numbers in the bone marrow and blood were quantitated. We found that the sensitization protocol induced a 3 fold increase in eosinophil numbers in the bone marrow (naive mice: 2.7 +/- 0.3 x 10(5); sensitized mice: 8.7 +/- 1.7 x 10(5), P < 0.05) and blood (naive mice: 0.5 +/- 0.2 x 10(5); sensitized mice: 1.5 +/- 0.3 x 10(5), P < 0.01). However, 24 h following Ova challenge, the eosinophil numbers in the bone marrow had dropped (3.7 +/- 0.8 x 10(5) with no change in the circulating pool, suggesting an equilibrium within the eosinophil pools had been reached. 5. Dex administration provoked a profound eosinopaenia in the blood of naive (5.2 +/- 1.5 to 0.9 +/- 0.6 x 10(4)) and sensitized mice (1.5 +/- 0.3 to 0.08 +/- 0.02 x 10(5)) at 4 h. This effect was reversed within 24 h. Dex also inhibited the release of eosinophils from the bone marrow in response to Ova challenge. 6. We show for the first time that express the steroid-inducible protein lipocortin 1 (LC1). FACS analysis of eosinophils emigrated into the Ova challenged air-pouches revealed detectable LC1-like immunoreactivity (373 x 10(3)). These data were also substantiated by LC1 detection in circulating eosinophils of interleukin-5 transgenic mice (strain: CBA/Ca). However, s.c. injection of Dex (50 micrograms) did not alter LC1 levels in blood eosinophils, such that 235 +/- 21 x 10(3) LC1-like molecules per cell were measured after vehicle treatment (n = 5), and 224 +/- 8 x 10(3) LC1-like molecules per cell were associated with this cell type 1 h after steroid treatment (n = 5, not significant). Finally, resident eosinophils (in the pleural cavity) were found to have much higher LC1 levels than that found in the blood circulation (2 fold increase, P < 0.05). 7. Passive immunization of mice against LC1 with a validated antiserum (termed LCS3) and protocol failed to modify the anti-migratory activity exerted by Dex towards eosinophil extravasation into Ova-challenged air-pouches. The steroid (50 micrograms s.c., -1 h) produced a similar degree of inhibition of eosinophil accumulation both in control animals (treated with a non-immune sheep serum) the LCS3-treated mice (-56% and 59%, respectively, n = 15-21, not significant). 8. In conclusion, the air-pouch provides a novel and convenient cavity to study allergen-induced cell recruitment which is sensitive to glucocorticoid hormone treatment. The effect of Dex on eosinophil distribution in these experimental conditions has been studied in detail and

Animals↗
PubMed1997

Role of lipocortin-1 in the anti-hyperalgesic actions of dexamethasone.

1. The effect of dexamethasone, lipocorton-1(2-26) and an antiserum to lipocortin-1(2-26) (LCPS1) upon the hyperalgesic activities in rats of carrageenin, bradykinin, tumour necrosis factor alpha (TNF alpha), interleukin-1(2), interleukin-6 (IL-6), interleukin-8 (IL-8), prostaglandin E beta (PGE2) and dopamine were investigated in a model of mechanical hyperalgesia. 2. Hyperalgesic responses to intraplantar (i.pl.) injections of carrageenin (100 micrograms), bradykinin (500 ng), TNF alpha (2.5 pg), IL-1 beta (0.5 pg), and IL-6 (1.0 ng), but not responses to IL-8 (0.1 ng), PGE2 (100 ng) and dopamine (10 micrograms), were inhibited by pretreatment with dexamethasone (0.5 mg kg-1, subcutaneously, s.c., or 0.04-5.0 micrograms/paw). 3. Inhibition of hyperalgesic responses to injections (i.pl.) of bradykinin (500 ng) and IL-1 beta (0.5 pg) by dexamethasone (0.5 mg kg-1, s.c.) was reversed by LCPS1 (0.5 ml kg-1, injected s.c., 24 h and 1 h before hyperalgesic substances) and hyperalgesic responses to injections (i.pl.) of bradykinin (500 ng), TNF alpha (2.5 pg) and IL-1 beta (0.5 pg), but not responses to PGE2 (100 ng), were inhibited by pretreatment with lipocortin-1(2-26) (100 micrograms/paw). Also, lipocortin-1(2-26) (30 and 100 micrograms ml-1 and dexamethasone (10 micrograms ml-1) inhibited TNF alpha release by cells of the J774 (murine macrophage-like) cell-line stimulated with LPS (3 micrograms ml-1), and LCPS1 partially reversed the inhibition by dexamethasone. These data are consistent with an important role for endogenous lipocortin-1(2-26) in mediating the anti-hyperalgesic effect of dexamethasone, with inhibiton of TNF alpha production by lipocortin-1(2-26) contributing, in part, to this role. 4. Although arachidonic acid by itself was not hyperalgesic, the hyperalgesic response to IL-1 beta (0.25 pg, i.pl.) was potentiated by arachidonic acid (50 micrograms) and the potentiated response was inhibited by dexamethasone (50 micrograms, i.pl.) and lipocortin-1(2-26) (100 micrograms, i.pl.). Also, lipocortin-1(2-26) (30 and 100 micrograms ml-1) inhibited/abolished PGE2 release by J774 cells stimulated with LPS (3 micrograms ml-1). These data suggest that, in inflammatory hyperalgesia, inhibition of the induction of cyclo-oxygenase 2 (COX-2), rather than phospholipase A2, by dexamethasone and lipocortin-1(2-26) accounts for the anti-hyperalgesic effects of these agents. 5. The above data support the notion that induction of lipocortin by dexamethasone plays a major role in the inhibition by dexamethasone of inflammatory hyperalgesia evoked by carrageenin, bradykinin and the cytokines TNF alpha, IL-1 beta and IL-6, and provides additional evidence that the biological activity of lipocortin resides within the peptide lipocortin-1(2-26). Further, the data suggest that inhibition of lipocortin-1(2-26) of eicosanoid production by COX-2 also contributes to the anti-hyperalgesic effect of lipocortin-1.

Animals↗
PubMed1997

Effects of dexamethasone and phorbol ester on P2 receptor-coupled Ca2+ signalling and lipocortin 1 presentation in U937 cells.

1. Cell surface bound lipocortin 1 (LC1) is a putative mediator of the antiproliferative and anti-inflammatory effects of glucocorticoids. This study assessed the hypothesis that the glucocorticoid, dexamethasone-phosphate (dex-p), might exert the above effects via an LC1-mediated downregulation of receptor-coupled Ca2+ signalling, using P2-receptor mediated intracellular Ca2+ accumulation in U937 cells as an appropriate model. 2. Addition of ATP (1-100 microM) to cells resulted in a transient increase in cytosolic Ca2+ ([Ca2+]i). Prior treatment of cells with dex-p (3-24 h) increased the magnitude of this Ca2+ transient at high, but not low concentrations of ATP, and increased thapsigargin (Tg)-induced Ca2+ influx, indicating that store-operated Ca2+ influx was potentiated in these cells. For cells treated with dex-p for 24 h, cell surface levels of LC1 were significantly reduced by 63%. 3. Differentiation of cells with 1 nM phorbol ester (PMA) for 24 h resulted in a 2.4 fold increase in the cell surface level of LC1 and inhibition of the ATP-induced Ca2+ response. However, the Tg-induced Ca2+ response was unaffected by long-term PMA treatment, and incubating cells with LC1 did not alter Tg-induced Ca2+ mobilization and influx, or the ATP-mediated Ca2+ response. 4. Data from this study suggest that: (1) dex-p does not inhibit P2-receptor-coupled Ca2+ signalling in this cell line, (2) the observed modulation of the ATP-induced increase in [Ca2+]i by dex-p and PMA, and store-operated Ca2+ influx by dex-p, is not linked to an increase in the cell surface level of LC1, and (3) differentiation of U937 cells with PMA downregulates the ATP-induced Ca2+ response, but does not affect the thapsigargin-sensitive Ca2+ pool or store-operated Ca2+ influx of these cells.

Adenosine Triphosphate↗
PubMed1997

Characterization and localization of lipocortin 1-binding sites on rat anterior pituitary cells by fluorescence-activated cell analysis/sorting and electron microscopy.

Lipocortin 1 (LC1) is an important mediator of glucocorticoid action in the anterior pituitary gland, where it appears to act via cell surface binding sites to suppress peptide release. We have exploited a combination of fluorescence-activated cell (FAC) analysis/sorting and electron microscopy to detect, characterize, and localize LC1-binding sites on the surface of dispersed rat anterior pituitary cells, using human recombinant LC1 (hu-r-LC1) as a probe. High affinity (Kd = 14 +/- 3 nM) hu-r-LC1-binding sites were detected on approximately 80% of anterior pituitary cells dispersed with collagenase. The binding characteristics of the ligand resembled those observed in leukocytes, in that it was saturable; concentration, Ca2+, and temperature dependent; and abolished by trypsin. Functional studies demonstrated an excellent correlation between the presence of the cell surface binding protein and the capacity of an anti-LC1 monoclonal antibody to abrogate the inhibitory actions of dexamethasone (10 nM) on the release of ACTH initiated in vitro by CRH-41 (1 nM). Morphological analysis of cells harvested by FAC sorting showed that 1) somatotrophs, corticotrophs, lactotrophs, thyrotrophs, and gonadotrophs were all included in the population expressing LC1 binding sites; and 2) the LC1-binding sites assume a punctate distribution across the cell surface. These data show that anterior pituitary cells express high affinity surface LC1-binding protein(s); they thus provide further evidence for a specific membrane mechanism of action of LC1 in regulating the endocrine function of the anterior pituitary.

Adrenocorticotropic Hormone↗
PubMed1997

An antisense oligodeoxynucleotide to lipocortin 1 reverses the inhibitory actions of dexamethasone on the release of adrenocorticotropin from rat pituitary tissue in vitro.

Our previous studies have demonstrated that lipocortin 1 (LC1, also called annexin 1) is an important mediator of glucocorticoid action in the neuroendocrine system, particularly with regard to the powerful inhibitory actions of the steroids on the secretion of ACTH and its hypothalamic releasing hormones. In the present study, we have used an antisense oligodeoxynucleotide (ODN) unique to LC1 to investigate further the role of this protein in the regulatory effects of dexamethasone on ACTH release in vitro from rat anterior pituitary cells. Pituitary cells dispersed with collagenase retained their functional and morphological integrity in vitro and sequestered ODNs in a time-dependent manner from the incubation medium. LC1 was readily detected in the cells by Western blot analysis or by immunoprecipitation/autoradiography after preloading with 35S-methionine/cysteine; the bulk of the protein was contained within an intracellular pool but a small amount was attached to the outer cell surface (pericellular). Dexamethasone (100 nm, 2.5 h) initiated de novo synthesis of LC1; it also increased the amount of LC1 in the pericellular pool detected by either method and caused a concomitant decrease in intracellular LC1. The responses to the steroid were prevented by the inclusion in the medium of an LC1 antisense ODN (50 nM, 3.5 h) but the corresponding sense and scrambled ODN sequences were inert. None of the ODN sequences tested influence the expression of annexin 5 in the pituitary tissue. CRH-41 (100 pM-1 mM), forskolin (1 nM-1 mM) and an L-Ca2+-channel opener BAY K8644 (100 pM-1 microM) initiated concentration dependent increases in immunoreactive- (ir-) ACTH release from the pituitary cells that were reduced (P < 0.01) by preincubation with dexamethasone (100 nM, 2.5 h). The inhibitory effects of the steroid were reversed by the LC1 antisense ODN (50 nM, P < 0.01), whereas the LC1 sense and scrambled control sequences (50 nM) were both ineffective in this respect (P > 0.05). The results add further support to the view that the acute inhibitory effects of glucocorticoids on the secretion of ACTH by the pituitary gland are dependent on the generation of lipocortin 1.

Adrenocorticotropic Hormone↗
PubMed1997

Molecular determinants of monosodium urate crystal-induced murine peritonitis: a role for endogenous mast cells and a distinct requirement for endothelial-derived selectins.

Injection of monosodium urate (MSU) crystals, the etiological cause of gouty arthritis, into murine peritoneal cavities produced an intense recruitment of polymorphonuclear leukocytes (PMN). After 3 mg MSU crystal injection, cell influx was maximal (approximately 10 x 10[6] cells per mouse) at 6 hr postinjection and sustained up to the 24 hr time-point. In mice depleted of mast cells by administration of compound 48/80 72 hr before challenge with MSU crystals a lower PMN influx was measured (58% reduction). The occurrence of endogenous mast cell activation, in the MSU response, was validated by the observation that MSU challenge reduced by more than 90% the number of intact mast cells recovered in the peritoneal washes. Pretreatment of mice with a histamine H1 antagonist (tripolidine; 0.5 mg/kg) or a platelet-activating factor receptor antagonist (WEB2086; 10 mg/kg) significantly reduced by 50 to 60% the number of PMN recovered from the peritoneal cavities. The molecular determinants of this process of leukocyte recruitment were also investigated. Treatment of mice with an anti-CD62P or anti-CD62E monoclonal antibody (mAb; 100 microg i.v.) produced a distinct inhibition of PMN recruitment measured at 6 hr, whereas only a combined administration of both monoclonal antibodies was effective in reducing by 60% the influx of PMN caused by the MSU crystals within 24 hr. In conclusion, these data highlight a role for endogenous mast cells and for endothelial-derived selectins in MSU crystal-induced PMN recruitment into the peritoneal cavity, and may be useful to dissect molecular mechanism(s) which may be operating in gouty arthritis.

Animals↗
PubMed1996

Functional importance of the dihydropyridine-sensitive, yet voltage-insensitive store-operated Ca2+ influx of U937 cells.

The Ca2+ current activated by Ca2+ store depletion in non-excitable cells is classically regarded as being dihydropyridine-insensitive, suggesting that store-operated Ca2+ channels (SOCs) are dissimilar to voltage-gated Ca2+ channels (VGCs) of excitable-cells. Here, we demonstrate dihydropyridine-sensitivity for the store-operated Ca2+ influx induced by ATP and thapsigargin (Tg) in the non-excitable U937 cell-line. Ca2+ store depletion by prior treatment of cells with either Tg or ATP, stimulated a Ca2+ entry mechanism that was inhibited by nicardipine, nifedipine, and the specific L-type Ca2+ channel blocker, calciseptine. A functional requirement for this Ca2+ influx mechanism in agonist-induced mitogenesis seemed likely, since nicardipine, a particularly potent inhibitor of store-operated Ca2+ influx in these cells, suppressed ATP- and Tg-stimulated cell proliferation. Depolarisation of cells with KCl, or gramicidin failed to elicit an increase in cytosolic Ca2+, suggesting that while the store-operated Ca2+ influx channel of U937 cells shares pharmacologic properties with the L-type Ca2+ channel, it is voltage-insensitive and therefore may resemble an L-type Ca2+ channel lacking a voltage sensor.

Adenosine Triphosphate↗
PubMed1996

Lipocortin 1 and the control of cPLA2 activity in A549 cells. Glucocorticoids block EGF stimulation of cPLA2 phosphorylation.

Epidermal growth factor (EGF) rapidly stimulates the release of arachidonic acid in A549 cells by a mechanism that is sensitive to pertussis toxin [1]. We show that EGF treatment of A549 cells stimulates phosphorylation of cytosolic phospholipase A2 (cPLA2) through a mechanism that is similarly inhibited by pertussis toxin. The level of cPLA2 expression is, apparently, not changed during this period. Pretreatment of cells with dexamethasone (10-100 nM) for 3 hr prevents this activation of cPLA2 by EFG, without changing the level of cPLA21 expression. The effect of dexamethasone is reversed in the presence of the neutralizing antilipocortin Mab 1A but not by the nonneutralizing antilipocortin 1 control Mab 1B. This strongly suggests that lipocortin 1 mediates the effect of dexamethasone by inhibiting activation of cPLA2. This concept is supported by the fact that a peptide Lc13-25 (10-200 micrograms/mL), derived from the N-terminus of lipocortin 1, also inhibits activation of cPLA2 by EGF in these cells.

Adenocarcinoma↗
PubMed1996

Modulation of ICAM-1 levels on U-937 cells and mouse macrophages by interleukin-1 beta and dexamethasone.

Differentiation of U-937 cells with phorbol ester (10 nM) induced a time-dependent (24 h or 48 h) increase of adhesion molecules and lipocortin 1 expression on the cell surface. Stimulation with interleukin-1 beta for a further 16 h increased the levels of intercellular adhesion molecule-1, and this effect was inhibited by co-incubation with 0.1-1 microM dexamethasone. The effect of the glucocorticoid was not modified by addition of a specific anti-lipocortin 1 monoclonal antibody (mAb 1A, 5 micrograms/ml). This opposite modulatory role of interleukin-1 and dexamethasone on intercellular adhesion molecule-1 expression was also, for the first time, observed in vivo using mouse peritoneal macrophages: a four-fold increase in intercellular adhesion molecule-1 expression was measured after local administration of the cytokine (5 micrograms/kg) and this effect was greatly inhibited (> 70%) by co-injection with 1 microgram dexamethasone. In conclusion, modulation of intercellular adhesion molecule-1 expression by glucocorticoids is an effect independent endogenous lipocortin 1, and it is an in vivo feature of these potent anti-inflammatory drugs.

Animals↗
PubMed1996

Relative contribution of the selectins in the neutrophil recruitment caused by the chemokine cytokine-induced neutrophil chemoattractant (CINC).

Rat CINC induced a dose- and time-dependent accumulation of neurophils into murine air-pouches, a response which was inhibited by two selective H1-antagonists, mepyramine and triprolidine (approximately 60%). As pretreatment with fucoidin abolished CINC effect, the relative time-related contribution of selectins on this process was then investigated by using specific monoclonal antibodies (mAb). Anti-CD62L mAb gave a similar degree of inhibition of CINC-induced cell accumulation both at the 2h and 4h time-point (approximately 75%). Anti-CD62P mAb, but not the anti-CD62E mAb, inhibited PMN accumulation at 2h (65%), but only co-administration of these two mAbs inhibited the cell response to CINC at the 4h time-point (90%). Thus endogenous histamine, CD62L, CD62P, and CD62E, though to a different degree, are required for PMN extravasation observed in response to CINC administration.

Animals↗
PubMed1996

Effect of interleukin-1 beta on the release of substance P from rat isolated spinal cord.

Superfusion of rat spinal cord slices with rat interleukin-1 beta resulted in a significant enhancement of electrically evoked substance P-like immunoreactivity with a maximal effect (> 2-fold increase) at 0.1 ng/ml, whereas higher concentration (10-50 ng/ml) of the cytokine inhibited (approximately 50%) the release of the neuropeptide. Interleukin-1 beta (0.1 ng/ml) potentiation of substance P-like immunoreactivity release was abrogated by co-perfusion with interleukin-1 receptor antagonist (10-100 ng/ml) or with indomethacin (1 microM). Superfusion of spinal cord with interleukin-1 beta inhibited electrically evoked calcitonin gene-related peptide-like immunoreactivity release. Modulation of substance P-like immunoreactivity release from the spinal cord by interleukin-1 beta may represent a mechanism responsible for the hyperalgesic action of the cytokine characteristic of the inflammatory response.

Animals↗
PubMed1996

The concerted regulation of cPLA2, COX2, and lipocortin 1 expression by IL-1beta in A549 cells.

The pro-inflammatory effects of IL-1beta have been linked to the induction of the enzyme COX-2. We now show that in addition to increasing the expression of COX-2, IL-1beta concomittantly decreased the expression of lipocortin 1 on the surface of A549 cells. Furthermore, cytosolic PLA2 is concomittantly activated by phosphorylation-resulting in a stimulation of arachidonic acid and PGE2 release. All of these effects appear to be mediated via a common pathway of PLC and PKC activation. Activation of cPLA2 is inhibited by dexamethasone in a lipocortin 1-dependent mechanism. We present a novel hypothesis whereby the effects of IL-1beta are not only due to activation of enzymes necessary for generation of eicosanoids but also to an inhibition of mechanisms that regulate the supply of arachidonic acid.

Adenocarcinoma↗