Search PubMed⌕ Search

Biomedical subjects

J Pfeilschifter

Publications and source records attributed to J Pfeilschifter.

At least 199 records · Page 11Linked to original sources
PubMed1993

A role for protein kinase C-alpha in zymosan-stimulated eicosanoid synthesis in mouse peritoneal macrophages.

A possible regulatory function of protein kinase C (PKC) isoenzymes in zymosan-stimulated eicosanoid synthesis was studied in mouse peritoneal macrophages in culture. The addition of zymosan to intact cells labelled with [3H]arachidonic acid stimulated a time-dependent and concentration-dependent release of the fatty acid. There was a simultaneous marked increase in the synthesis of prostaglandin E2 and leukotriene C4. The protein-kinase inhibitor K-252a and the selective PKC inhibitor CGP41251 completely blocked zymosan-triggered arachidonic acid release as well as prostaglandin E2 and leukotriene C4 synthesis. In contrast, an inactive staurosporine derivative, CGP42700, failed to inhibit any of the zymosan-induced responses. The down-regulation of PKC by long-term treatment with phorbol 12-myristate 13-acetate eliminated zymosan-stimulated arachidonic acid release and eicosanoid synthesis (after 4-6 h treatment). By using specific antibodies it was observed that mouse macrophages express five PKC isoenzymes, PKC-alpha, -beta, -delta, -epsilon and -zeta. No PKC-gamma isoenzyme was detected. After exposure to phorbol 12-myristate 13-acetate, a complete depletion of PKC-beta was observed within 1 h and the complete depletion of PKC-alpha and PKC-delta isotypes was observed within 4 h. In contrast, PKC-epsilon was only partially down-regulated after a 24-h treatment with phorbol 12-myristate 13-acetate and PKC-zeta was not affected at all. These data indicate that PKC-alpha and PKC-delta isoenzymes are candidates for regulating prostaglandin and leukotriene production. From the potent inhibitory activities of K-252a and CGP41251, two compounds that reportedly display a higher selectivity for PKC-alpha compared to PKC-delta, it is suggested that PKC-alpha triggers arachidonic acid mobilization and eicosanoid synthesis in peritoneal macrophages.

Alkaloids↗
PubMed1993

Angiotensin II binding sites on micro-organisms contaminating cell cultures.

An angiotensin II (Ang II) binding site, distinct from AT1 and AT2, has been found in cell cultures of rat aortic smooth muscle and rat glomerular mesangium. It is characterized by a high affinity for Ang II (Kd 0.75 +/- 0.13 nM) and Ang I (Ki 0.72 +/- 0.12 nM), but a very low affinity for Ang III (Ki 31 +/- 5 microM). Ang(1-7) (Ki 1.01 +/- 0.26 nM) and Ang(1-6) (Ki 4.54 +/- 0.24 nM) are very selective for this site, with affinities more than 150- and 10,000-fold greater, respectively, than for AT1 or AT2. The selective angiotensin receptor subtype ligands losartan and L-158,809 (AT1), PD 123319 and CGP 42112A (AT2) were inactive. Binding to this site was abolished after the cells had been treated with the antibiotic mixture BM-Cyclin, suggesting that the site is located not on the cells, but on a cell culture contaminant. This has been identified as Acholeplasma laidlawii. Caution should therefore be exercised when interpreting Ang II-related data obtained from cells that have not been checked for Mollicute contamination.

Acholeplasma laidlawii↗
PubMed1993

Protein kinase C inhibitors potentiate angiotensin II-induced phosphoinositide hydrolysis and intracellular Ca2+ mobilization in renal mesangial cells.

Stimulation of mesangial cells with angiotensin II leads to rapid phosphoinositide hydrolysis and subsequent mobilization of intracellular Ca2+. Previous studies indicated that activation of protein kinase C (PKC) triggers a negative-feedback signal, which limits phosphoinositide turnover. By comparing the relative susceptibility of PKC isoenzymes to phorbol ester-induced down-regulation with the down-regulation of the functional cell response, i.e. feedback inhibition of inositol trisphosphate production, we inferred that PKC-alpha and PKC-delta are candidates for regulating phosphoinositide hydrolysis in mesangial cells. To test this hypothesis further, we examined the effects of inhibitors of PKC, that are reportedly not active on PKC-delta, on angiotensin II-stimulated phosphoinositide degradation and Ca2+ mobilization. Pretreatment of mesangial cells with the PKC inhibitors staurosporine and K252a potently augmented inositol trisphosphate and 1,2-diacylglycerol formation as well as Ca2+ mobilization in response to angiotensin II. These results suggest that PKC-alpha, but not PKC-delta, is the most likely candidate mediating feedback inhibition of angiotensin II-stimulated phosphoinositide turnover in mesangial cells.

Alkaloids↗
PubMed1993

Mitogenic responsiveness of human bone cells in vitro to hormones and growth factors decreases with age.

Bone loss with aging may at least in part be due to inadequate bone formation. In this study, we examined whether the proliferation of osteoblast-like cells in vitro in response to local and systemic factors might be attenuated with age. A total of 36 cultures of osteoblast-like cells were obtained from outgrowths of human trabecular bone. Parathyroid hormone, growth hormone, calcitonin, transforming growth factor beta, insulin-like growth factor I, and platelet-derived growth factor BB dose dependently increased DNA synthesis in all cultures. Increases in DNA synthesis with each of these factors were significantly negatively correlated with donor age in cultures obtained from the iliac crest bone of 50- to 70-year-old women. Cells from 61- to 70-year-old donors required approximately 10-fold higher concentrations of growth factors and hormones to yield comparable increases in DNA synthesis than cells from 51- to 60-year-old donors. A significant negative correlation between age and mitogenic responsiveness to platelet-derived growth factor and growth hormone, but not toward the other factors, was also observed in cultures from the femoral head trabecular bone of 60- to 90-year-old women. Our findings suggest that bone loss with aging may be partially due to a decreased capacity of osteoblasts to proliferate in response to systemic or locally released osteotropic factors.

Aged↗
PubMed1993

Cytokine regulation of group II phospholipase A2 expression in glomerular mesangial cells.

Phospholipase A2 (PLA2) is believed to play an essential role in inflammatory processes by releasing arachidonic acid from membrane phospholipids for synthesis of important lipid mediators, such as prostaglandins, leukotrienes and platelet activating factor. We have used glomerular mesangial cells as a model system to study the regulation of PLA2 under inflammatory conditions. Potent pro-inflammatory cytokines, such as interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF alpha), as well as agents that increase cellular cAMP levels have been found to increase Group II PLA2 gene expression in a time- and dose-dependent manner. In all cases cytokine-induced synthesis of PLA2 occurred in parallel with cytokine-stimulated prostaglandin (PG) E2 synthesis. Three important classes of compounds that potently antagonise the stimulatory effect of IL-1, TNF alpha and cAMP on Group II PLA2 expression in mesangial cells have been identified, namely, glucocorticoids, transforming growth factors (TGF) type-beta and platelet-derived growth factor (PDGF). Those agents may act sequentially to protect the kidney from damage resulting from cytokine-stimulated mediator release and the subsequent inflammatory reactions.

Animals↗
PubMed1993

Effect of extracellular ATP on contraction, cytosolic calcium activity, membrane voltage and ion currents of rat mesangial cells in primary culture.

1. The effects of extracellular ATP on contraction, membrane voltage (Vm), ion currents and intracellular calcium activity [Ca2+]i were studied in rat mesangial cells (MC) in primary culture. 2. Addition of extracellular ATP (10(-5) and 10(-4) M) to MC led to a cell contraction which was independent of extracellular calcium. 3. Membrane voltage (Vm) and ion currents were measured with the nystatin patch clamp technique. ATP induced a concentration-dependent transient depolarization of Vm (ED50: 2 x 10(-6) M). During the transient depolarization ion currents were monitored simultaneously and showed an increase of the inward- and outward current. 4. In a buffer with a reduced extracellular chloride concentration (from 145 to 30 mM) ATP induced a depolarization augmented to -4 +/- 4 mV. 5. ATP-gamma-S and 2-methylthio-ATP depolarized Vm to the same extent as ATP, whereas alpha,beta-methylene-ATP (all 10(-5) M) had no effect on Vm. 6. The Ca2+ ionophore, A23187, depolarized Vm transiently from -51 +/- 2 to -28 +/- 4 mV and caused an increase of the inward current. 7. The intracellular calcium activity [Ca2+]i was measured with the fura-2 technique. ATP stimulated a concentration-dependent increase of [Ca2+]i (ED50: 5 x 10(-6) M). The increase of [Ca2+]i was biphasic with an initial peak followed by a sustained plateau. 8. The [Ca2+]i peak was still present in an extracellular Ca(2+)-free buffer, whereas the plateau was abolished. Verapamil (10(-4) M) did not inhibit the [Ca2+]i increase induced by ATP. 9. The data indicate that extracellular ATP contracts MC and is able to increase [Ca2+]i by the release of Ca2+ from intracellular stores and recruitment from the extracellular space. In addition ATP depolarizes Vm of MC by activating a Cl- conductance. The ATP-induced depolarization is mediated by a P2y receptor.

Adenosine Triphosphate↗
PubMed1993

Extracellular ATP and UTP activation of phospholipase D is mediated by protein kinase C-epsilon in rat renal mesangial cells.

1. We have studied whether a nucleotide receptor mediates the effects of extracellular ATP and UTP on phosphatidylcholine metabolism in rat cultured glomerular mesangial cells. 2. ATP and UTP stimulated a biphasic 1,2-diacylglycerol (DAG) formation in [3H]-arachidonic acid-labelled mesangial cells. In contrast, in cells labelled with [3H]-myristic acid, a tracer that preferentially marks phosphatidylcholine, both nucleotides induced a delayed monophasic production of DAG with a concomitant increase in phosphatidic acid and choline formation. 3. A phospholipase D-mediated phosphatidylcholine hydrolysis was further suggested by the observation that ATP and UTP stimulate the accumulation of phosphatidylethanol, when ethanol was added to mesangial cells. 4. The rank order of potency of a series of nucleotide analogues for stimulation of phosphatidylethanol formation was UTP = ATP > ITP > ATP gamma S > beta gamma-imido-ATP = ADP > 2-methylthio-ATP = beta gamma-methylene-ATP = ADP beta S, while AMP, adenosine, CTP and GTP were inactive, indicating the presence of a nucleotide receptor. 5. Elevation of cytosolic free Ca2+ by the calcium ionophore A23187 (1 microM) or the Ca(2+)-ATPase inhibitor, thapsigargin (200 nM) slightly increased phosphatidylethanol formation. However, chelation of cytosolic Ca2+ with high concentrations of Quin 2 did not attenuate ATP- and UTP-induced phosphatidylethanol production, thus suggesting that Ca2+ is not crucially involved in agonist-stimulated phospholipase D activation. 6. The protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA), but not the biologically inactive 4 alpha-phorbol 12,13-didecanoate, increased phospholipase D activity in mesangial cells, suggesting that PKC may mediate nucleotide-induced phosphatidylcholine hydrolysis. 7. Down-regulation of PKC-alpha and -delta isoenzymes by 8 h PMA treatment still resulted in full phospholipase D activation. In contrast, a 24 h treatment of mesangial cells with PMA, a regimen that also causes depletion of PKC-epsilon, markedly attenuated nucleotide-evoked phosphatidylethanol formation. In addition, the selective PKC inhibitor, calphostin C attenuated ATP- and UTP-induced phosphatidylethanol production.8. In summary, these data suggest that extracellular ATP and UTP use a common nucleotide receptor to activate phospholipase D-mediated phosphatidylcholine hydrolysis. Stimulation of phospholipase D appears to involve the PKC-epsilon isoenzyme, activated by DAG derived from phosphoinositide hydrolysis by phospholipase C.

Adenosine Triphosphate↗
PubMed1993

Cytokine-stimulated secretion of group II phospholipase A2 by rat mesangial cells. Its contribution to arachidonic acid release and prostaglandin synthesis by cultured rat glomerular cells.

Potent pro-inflammatory cytokines, such as interleukin 1 (IL-1) or tumor necrosis factor (TNF) alpha have been found to increase group II phospholipase A2 (PLA2) synthesis and secretion by mesangial cells. In all cases 85-90% of the enzyme is secreted from the cells and a parallel increase in prostaglandin (PG)E2 synthesis is observed. We report here that co-incubation with a monoclonal antibody that specifically binds and neutralizes rat group II PLA2 attenuates IL-1 beta and TNF alpha-stimulated PGE2 production by 45% and 52%, respectively. CGP43182, a specific inhibitor of group II PLA2, potently blocks mesangial cell group II PLA2 in vitro with a half-maximal inhibitory concentration (IC50) of 1.5 microM, while only slightly affecting mesangial cell high molecular weight PLA2. CGP 43182 markedly attenuates IL-1 beta- and TNF alpha-stimulated PGE2 synthesis in intact mesangial cells with IC50's of 1.3 and 1.0 microM, respectively. PLA2 secreted from cytokine-stimulated mesangial cells was purified to homogeneity. Addition of the purified enzyme to unstimulated mesangial cells causes a marked release of arachidonic acid and a subsequent increased synthesis of PGE2. Moreover, addition of purified PLA2 to a cloned rat glomerular epithelial cell line and cultured bovine glomerular endothelial cells augmented both arachidonic acid release and PGE2 synthesis, with the endothelial cells being especially sensitive. Thus, cytokine-triggered synthesis and secretion of group II PLA2 by mesangial cells contributes, at least in part, to the observed synthesis of PGE2 that occurs in parallel to the enzyme secretion. Furthermore, extracellular PLA2 secreted by mesangial cells is able to stimulate arachidonic acid release and PGE2 synthesis by the adjacent endothelial and epithelial cells. These data suggest that expression and secretion of group II PLA2 triggered by pro-inflammatory cytokines may crucially participate in the pathogenesis of inflammatory processes within the glomerulus.

Animals↗
PubMed1993

Light evoked inositol trisphosphate release in the rat retina in vitro.

Light exposure not only elicits a photic response but may also alter the metabolism and functional properties of the retina. This may be evoked by the stimulation of phospholipid derived second messenger systems. In this study, we investigated the light-evoked release of inositol 1,4,5-triphosphate in the isolated rat retina in vitro by means of high performance liquid chromatography (HPLC) detection. After prelabelling of isolated retinae with tritiated myo-inositol in darkness, they were exposed to no light or to white fluorescent light of 10,000 lux illuminance for 3,5 and 10 sec, respectively. We observed a 200% increase in the release of inositol 1,4,5-trisphosphate compared to basal values in darkness after 3 sec of light exposure with a decline after 5 sec and a return to basal values after 10 sec indicating a rapid breakdown of inositol 1,4,5-trisphosphate. Our data confirm previous studies in the amphibian retina and photoreceptors and demonstrate for the first time a light evoked inositol 1,4,5-trisphosphate release in the mammalian retina.

Animals↗
PubMed1992

Interleukin-1 beta and transforming growth factor-beta 2 enhance cytosolic high-molecular-mass phospholipase A2 activity and induce prostaglandin E2 formation in rat mesangial cells.

Interleukin-1 beta induces gene expression and secretion of group-II phospholipase A2 and release of prostaglandin E2 from rat mesangial cells. The interleukin-1 beta-induced synthesis of group-II phospholipase A2 is prevented by transforming growth factor-beta 2, whereas transforming growth factor-beta 2 potentiated the interleukin-1 beta-evoked prostaglandin E2 production. Transforming growth factor-beta 2 itself did not induce synthesis of group-II phospholipase A2, although it stimulated prostaglandin E2 formation. Here we describe the effect of interleukin-1 beta and transforming growth factor-beta 2 on a cytosolic phospholipase A2 activity and prostaglandin E2 formation in rat mesangial cells. Based on the resistance to dithiothreitol and migration profiles on a Mono-Q anion-exchange column and a Superose 12 gel-filtration column, the cytosolic phospholipase A2 activity was assigned to a high-molecular-mass phospholipase A2. Measured with 1-stearoyl-2-[1-14C]arachidonoylglycero-phosphocholine as substrate, both interleukin-1 beta and transforming growth factor-beta 2 enhanced the high-molecular-mass phospholipase A2 activity. The stimulation of rat mesangial cells with interleukin-1 beta and transforming growth factor-beta 2 was time- and dose-dependent with maximal cytosolic phospholipase A2 activities at 10 nM and at 10 ng/ml respectively, after 24 h of stimulation. Under these conditions, interleukin-1 beta and transforming growth factor-beta 2 enhanced the cytosolic phospholipase A2 activity 2.2 +/- 0.6-fold and 2.5 +/- 0.6-fold, respectively. These results strongly suggest that an enhanced cytosolic high-molecular-mass phospholipase A2 activity is involved in the formation of prostaglandin E2 mediated by transforming growth factor-beta 2. Whether interleukin-1 beta induced group-II phospholipase A2 and/or interleukin-1 beta-enhanced cytosolic phospholipase A2 activity is involved in prostaglandin E2 formation in rat mesangial cells is discussed.

Animals↗
PubMed1992

Interleukin-1 beta- and forskolin-induced synthesis and secretion of group II phospholipase A2 and prostaglandin E2 in rat mesangial cells is prevented by transforming growth factor-beta 2.

Interleukin-1 beta and forskolin induce prostaglandin E2 release as well as 14-kDa group II phospholipase A2 gene expression and secretion of the enzyme from rat glomerular mesangial cells. We now report that pretreatment of mesangial cells with transforming growth factor-beta 2 prior to stimulation with interleukin-1 beta or forskolin inhibits the induced release of prostaglandin E2. At the same time the secretion of group II phospholipase A2, measured both as enzyme activity with sn-2-labeled phosphatidylethanolamine as substrate and as enzyme protein in immunoblot experiments, is dose-dependently inhibited by pretreatment of the cells with transforming growth factor-beta 2. Analyses of enzyme activity and enzyme protein levels in the cells indicated that this is not due to inhibition of enzyme secretion with a concomitant increase in cellular levels of the enzyme. Rather, pretreatment of the cells with transforming growth factor-beta 2 largely prevented both the interleukin-1 beta- and the forskolin-induced synthesis of phospholipase A2. This is the first report indicating an inhibition of group II phospholipase A2 gene expression by transforming growth factor-beta 2. In line with those results, transforming growth factor-beta 2 did not induce the synthesis and secretion of group II phospholipase A2. However, under conditions where the interleukin-1 beta-induced expression of group II phospholipase A2 is fully suppressed by transforming growth factor-beta 2, the growth factor itself stimulated prostaglandin E2 synthesis by a mechanism apparently not involving group II phospholipase A2. The immunochemical identification of the inducible and secretable phospholipase A2 from rat mesangial cells as a group II enzyme was confirmed by purification and N-terminal amino acid sequence determination.

Amino Acid Sequence↗
PubMed1992

Transforming growth factors type-beta and dexamethasone attenuate group II phospholipase A2 gene expression by interleukin-1 and forskolin in rat mesangial cells.

Treatment of rat mesangial cells with interleukin-1 beta (IL-1 beta) and forskolin induced, in a synergistic fashion, the expression of group II phospholipase A2 (PLA2) mRNA, with subsequent increased synthesis and secretion of PLA2. In contrast, interleukin-6 did not increase PLA2 mRNA levels of PLA2 activity. Transforming growth factor (TGF) beta 1, TGF beta 2 and TGF beta 3 equipotently attenuated the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, as well as PLA2 synthesis and secretion. The glucocorticoid dexamethasone only partially suppressed the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, but totally inhibited PLA2 synthesis and secretion.

Animals↗
PubMed1992

Immunocharacterization of delta- and zeta-isoenzymes of protein kinase C in rat renal mesangial cells.

The isoforms of protein kinase C (PKC) present in rat mesangial cells were identified by immunoblot analysis with antibody raised against isotype-specific peptides. In addition to the previously observed alpha- and epsilon-subspecies, mesangial cells also express the delta- and zeta-isoenzymes of PKC. On exposure to phorbol 12,13-dibutyrate (PDB) a complete depletion of PKC-delta is observed within 8 h. Removal of PDB results in a recovery of PKC-delta. In contrast, PKC-zeta is unaffected by addition or removal of PDB.

Amino Acid Sequence↗
PubMed1992

Tumor necrosis factor alpha inhibits the stimulatory effect of the parathyroid hormone-related protein on cyclic AMP formation in osteoblast-like cells via protein kinase C+.

Tumor necrosis factor alpha (TNF alpha) and parathyroid hormone-related protein (PTHrP) are both factors that have been implicated in the mechanism of hypercalcemia of malignancy. In this study we investigated the effect of TNF alpha on the PTHrP-stimulated accumulation of intracellular cyclic AMP in osteoblast-like cells. In the clonal cell line Saos-2 and in primary cell cultures from fetal rat calvaria, PTHrP-stimulated accumulation of cAMP was time- and dose-dependently inhibited by exposure to TNF alpha. Significant inhibition occurred at concentrations as low as 2 x 10(-12) M and was maximal at 1 x 10(-9) M. Inhibition was observed after 6 h and was maximal after 18 h. Inhibition by TNF alpha was probably mediated by protein kinase C, since the phorbol ester PMA mimicked the effect of TNF alpha, and the protein kinase C inhibitor H-7 completely abolished the effect of TNF alpha. In conclusion, these observations suggest a possible mechanism by which TNF alpha may modulate the effect of PTHrP on osteoblast function in the syndrome of humoral hypercalcemia of malignancy.

Animals↗
PubMed1992

Interleukin 1 beta and tumour necrosis factor alpha induce a macrophage-type of nitric oxide synthase in rat renal mesangial cells.

Treatment of mesangial cells with interleukin 1 beta (IL-1 beta) or tumour necrosis factor alpha (TNF alpha) has been shown to increase cGMP formation, most probably due to induction of nitric oxide synthase. Here we report that maximum stimulation of cGMP formation over a 24-h period required the presence of IL-1 beta or TNF alpha during the first 18 h of induction. N4-monomethyl-L-arginine (L-NMMA) was a potent inhibitor of cytokine-induced cGMP formation while N4-nitro-L-arginine (L-NNA) was less active. Formation of nitric oxide was detected in the cytosol of cytokine-treated mesangial cells by activation of purified soluble guanylate cyclase and was stimulated by tetrahydrobiopterin, but not by calcium calmodulin. Treatment of cells with IL-1 beta or TNF alpha markedly attenuated the contractile response to a subsequent challenge with angiotensin II. Furthermore, conditioned medium from IL-1 beta-treated cells increased cGMP in untreated control cells.

Amino Acid Oxidoreductases↗
PubMed1992

Angiotensin II stimulation of phospholipase D in rat renal mesangial cells is mediated by the AT1 receptor subtype.

Angiotensin II stimulated a biphasic 1,2-diacylglycerol formation in [3H]arachidonic acid-labelled mesangial cells. In contrast, in cells labelled with [3H]myristic acid, a tracer that preferentially marks phosphatidylcholine, angiotensin II induced a delayed monophasic production of 1,2-diacylglycerol. This delayed peak of 1,2-diacylglycerol generation was associated with a concomitant increase in choline formation, suggesting that stimulation of mesangial cells with angiotensin II causes a phospholipase D-mediated phosphatidylcholine hydrolysis. This conclusion is supported by the observation that angiotensin II stimulated the accumulation of phosphatidylethanol, when ethanol was added to mesangial cells. The production of choline and phosphatidylethanol stimulated by angiotensin II was completely blocked by the angiotensin II AT1 receptor-selective antagonist DuP 753 with an IC50 value of 8 nM, but not by the angiotensin II AT2 receptor selective ligand CGP 42112A. Furthermore, angiotensin(1-7) and angiotensin(1-6) had only weak effects on choline generation. These data clearly indicate that angiotensin II AT1 receptors trigger phospholipase D-mediated phosphatidylcholine hydrolysis in rat mesangial cells.

Angiotensin II↗
PubMed1992

The induction of cellular group II phospholipase A2 by cytokines and its prevention by dexamethasone.

Treatment of rat glomerular mesangial cells with interleukin-1 beta, tumor necrosis factor or forskolin resulted in the secretion of phospholipase A2 activity into the culture medium. Essentially all of this secreted phospholipase A2 activity was recognized by monoclonal antibodies elicited against rat liver mitochondrial 14 kDa group II phospholipase A2. Immunoblot analysis and gel filtration confirmed the presence of only 14 kDa phospholipase A2 in the culture supernatant. This enzyme could hardly be detected in unstimulated mesangial cells and after a lag period of 6 to 8 hours becomes detectable in both cells and culture medium. The results indicate that the increased phospholipase A2 activity upon treatment of the cells with cytokines is not due to activation of an existing cellular pool of enzyme but is caused by induced synthesis of group II phospholipase A2. Pretreatment of the cells with dexamethasone, a known inhibitor of prostaglandin synthesis, dose-dependently inhibits cytokine-induced phospholipase A2 activity. Western immunoblot analysis of cells and culture medium demonstrates that this is not due to inhibition of existing phospholipase A2 but because dexamethasone prevents the cytokine-induced synthesis of phospholipase A2 protein.

Animals↗