scholarly journals Inhibitors of phospholipase A2 block the stimulation of protein synthesis by insulin in L6 myoblasts

1990 ◽  
Vol 270 (3) ◽  
pp. 737-739 ◽  
Author(s):  
B G Southorn ◽  
R M Palmer
Keyword(s):  
Protein Synthesis ◽  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Insulin Action ◽  
Alternative Pathway ◽  
Physiological Range ◽  
Prostaglandin F2 Alpha ◽  
Pre Treatment ◽  
Phospholipase A2 Inhibitors ◽  
Stimulation Of

Insulin at a concentration close to the physiological range (100 mu-units/ml) stimulated protein synthesis in L6 myoblasts by 17%. Pre-treatment with the phospholipase A2 inhibitors mepacrine or dexamethasone prevented this stimulation and decreased the release of prostaglandin F2 alpha, implicating the action of phospholipase A2 and the subsequent metabolism of arachidonic acid to prostaglandins in the stimulation of protein synthesis by physiological doses of insulin. Higher concentrations of insulin (500-1000 mu-units/ml) stimulated protein synthesis in the presence of mepacrine or dexamethasone, suggesting that an alternative pathway may become important in insulin action when phospholipase A2 is inhibited.

scholarly journals Superoxide generation is inhibited by phospholipase A2 inhibitors. Role for phospholipase A2 in the activation of the NADPH oxidase

1989 ◽  
Vol 264 (1) ◽  
pp. 249-255 ◽  
Author(s):  
L M Henderson ◽  
J B Chappell ◽  
O T G Jones
Keyword(s):  
Arachidonic Acid ◽  
Nadph Oxidase ◽  
Phospholipase A2 ◽  
Potent Inhibitor ◽  
Dependent Manner ◽  
Superoxide Generation ◽  
Concentration Dependent Manner ◽  
Ic50 Value ◽  
Phospholipase A2 Inhibitors ◽  
Stimulation Of

The stimulation of O2.- generation by phorbol 12-myristate 13-acetate (PMA) in human neutrophil-derived cytoplasts was inhibited by a variety of phospholipase A2 inhibitors in a concentration-dependent manner. Inhibition was found to be independent of the order of addition of the inhibitor and PMA. The most potent inhibitor, RO 31-4639, inhibited O2.- generation with an IC50 value (concentration causing 50% inhibition) of 1.5 microM. The addition of either arachidonic acid or SDS, in the presence of the inhibitors, was able to restore O2.- generation. The results suggest that arachidonic acid, released by phospholipase A2, is necessary for both the activation and the maintenance of O2.- generation by the NADPH oxidase.

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

scholarly journals The immediate phase of c-kit ligand stimulation of mouse bone marrow-derived mast cells elicits rapid leukotriene C4 generation through posttranslational activation of cytosolic phospholipase A2 and 5-lipoxygenase.

1995 ◽  
Vol 182 (1) ◽  
pp. 197-206 ◽  
Author(s):  
M Murakami ◽  
K F Austen ◽  
J P Arm
Keyword(s):  
Bone Marrow ◽  
Arachidonic Acid ◽  
Mast Cells ◽  
Cell Membrane ◽  
Phospholipase A2 ◽  
Mouse Bone Marrow ◽  
Kit Ligand ◽  
Cytosolic Phospholipase ◽  
Delayed Phase ◽  
Stimulation Of

c-kit ligand (KL) activated mouse bone marrow-derived mast cells (BMMC) for the dose- and time-dependent release of arachidonic acid from cell membrane phospholipids, with generation of leukotriene (LT) C4 in preference to prostaglandin (PG)D2. KL at concentrations of 10 ng/ml elicited half-maximal eicosanoid generation and at concentrations of > 50 ng/ml elicited a maximal generation of approximately 15 ng LTC4 and 1 ng PGD2 per 10(6) cells, with 20% net beta-hexosaminidase release 10 min after stimulation. Of the other cytokines tested, none, either alone or in combination with KL, elicited or modulated the immediate phase of mediator release by BMMC, indicating strict specificity for KL. Activation of BMMC in response to KL was accompanied by transient phosphorylation of cytosolic phospholipase A2 and reversible translocation of 5-lipoxygenase to a cell membrane fraction 2-5 min after stimulation, when the rate of arachidonic acid release and LTC4 production were maximal. BMMC continuously exposed to KL in the presence of IL-10 and IL-1 beta generated LTC4 in marked preference to PGD2 over the first 10 min followed by delayed generation of PGD2 with no LTC4 over several hours. Pharmacologic studies revealed that PGD2 generation in the immediate phase depended on prostaglandin endoperoxide synthase (PGHS)-1 and in the delayed phase on PGHS-2. Thus, KL provided a nonallergic stimulus for biphasic eicosanoid generation by mast cells. The immediate phase is dominated by LTC4 generation with kinetics and postreceptor biosynthetic events similar to those observed after cell activation through the high affinity IgE receptor, whereas the delayed phase of slow and selective PGD2 production is mediated by induction of PGHS-2.

A role for p38 MAP kinase in platelet activation by von Willebrand Factor

2004 ◽  
Vol 91 (01) ◽  
pp. 102-110 ◽  
Author(s):  
Ilaria Canobbio ◽  
Stefania Reineri ◽  
Fabiola Sinigaglia ◽  
Cesare Balduini ◽  
Mauro Torti
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Map Kinase ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
P38 Map Kinase ◽  
Cyclooxygenase Inhibitors ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Stimulation Of

SummaryPlatelet activation induced by von Willebrand factor (VWF) binding to the membrane GPIb-IX-V receptor involves multiple signal transduction pathways. Among these, recruitment and activation of the FcγRIIA and stimulation of phospholipase A2 represent independent events equally essential to support a complete platelet response. Phospholipase A2 is activated by calcium and by phosphorylation through MAP kinases. In this work, we found that VWF stimulated the rapid and sustained phosphorylation of p38 MAP kinase (p38MAPK). In vitro kinase assay revealed that VWF-stimulated phosphorylation of p38MAPK was associated with increased kinase activity. Binding of VWF to GPIb-IX-V, but not to integrin αIIbβ3, was required to support phosphorylation of p38MAPK. Neither the blockade of the membrane FcγRIIA by a specific monoclonal antibody or the prevention of thromboxane A2 synthesis by cyclooxygenase inhibitors affected VWF-induced p38MAPK activation. However, phosphorylation of p38MAPK was prevented by the tyrosine kinase Syk inhibitor piceatannol. Treatment of platelets with the p38MAPK inhibitor SB203580 totally prevented VWFstimulated platelet aggregation. Moreover, release of arachidonic acid induced by VWF was strongly impaired by inhibition of p38MAPK. We also found thatVWF induced phosphorylation of cytosolic phospholipase A2, and that this process was prevented by the p38MAPK inhibitor SB203580.These results demonstrate that p38MAPK is a key element in the FcγRIIA-independent pathway for VWF-induced platelet activation, and is involved in the stimulation of phospholipase A2 and arachidonic acid release.

A role for G-proteins in the epidermal growth factor stimulation of phospholipase A2 in rat kidney mesangial cells

1990 ◽  
Vol 10 (4) ◽  
pp. 353-362 ◽  
Author(s):  
Nashrudeen Hack ◽  
Paula Clayman ◽  
Karl Skorecki
Keyword(s):  
Arachidonic Acid ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Phospholipase A2 ◽  
G Protein ◽  
Mesangial Cells ◽  
Rat Kidney ◽  
Glomerular Mesangial Cells ◽  
Epidermal Growth ◽  
Stimulation Of

We have previously demonstrated phospholipase C (PLC) independent activation of phospholipase A2(PLA2) by epidermal growth factor (EGF) in glomerular mesangial cells in culture. In the current study using glass beads to permeabilize [3H]- or [14C]-arachidonate labelled mesangial cells we demonstrate that guanine nucleotides modulate the EGF-mediated stimulation of arachidonic acid release (75% inhibition with 100 μM GDPβS and 108% augmentation with 100 μM GTPγS). GTPγS alone stimulated both the release of free arachidonic acid and production of diacylglycerol (DAG), while EGF itself neither stimulated DAG nor augmented the DAG response to GTPγS. These findings suggest the intermediacy of a G-protein in PLC-independent stimulation of PLA2 by a growth factor, and provide a model system for determining the relationship between G-protein intermediacy and the intrinsic tyrosine kinase activity of the growth factor receptor.

scholarly journals Insulin and TSH promote growth in size of PC Cl3 rat thyroid cells, possibly via a pathway different from DNA synthesis: comparison with FRTL-5 cells

1999 ◽  
pp. 94-103 ◽  
Author(s):  
T Kimura ◽  
JE Dumont ◽  
A Fusco ◽  
J Golstein
Keyword(s):  
Protein Synthesis ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Cell Lines ◽  
Insulin Action ◽  
Cell Mass ◽  
Thyroid Cell ◽  
Thyroid Cells ◽  
Rat Thyroid ◽  
Stimulation Of

In the rat thyroid cell lines PC Cl3, FRTL- 5 and WRT, proliferation is mainly regulated by insulin or IGF, and TSH. However, the mechanism regulating cell mass doubling prior to division is still unknown. Our laboratory has shown that in dog thyroid cells insulin promotes growth in size while TSH in the presence of insulin triggers DNA replication. In the absence of insulin, TSH has no effect on cell growth. In this report we investigated insulin action on both cell mass and DNA synthesis and its modulation by TSH and insulin in PC Cl3 and FRTL-5 cells. In PC Cl3 cells, insulin activated not only DNA synthesis but also protein synthesis and accumulation. Although TSH potentiated the stimulation of DNA synthesis induced by insulin, enhancement of protein synthesis by both agents was additive. All TSH effects were reproduced by forskolin. Similar effects were also obtained in FRTL-5 cells. This suggests that insulin and TSH, via cAMP, modulate both growth in size and DNA replication in these cell lines. Lovastatin, which blocks 3-hydroxy-3-methylglutaryl coenzyme A reductase, decreased the induction of DNA synthesis, but not of protein synthesis induced by insulin or TSH in PC Cl3 cells. In FRTL-5 cells, lovastatin reduced protein and DNA synthesis stimulated by insulin but not TSH-induced protein synthesis. Taking these data together, we propose that insulin and/or TSH both modulate cell mass doubling and DNA synthesis in these cell lines, presumably via different pathways, and that there are at least two pathways which regulate growth in size in FRTL-5 thyroid cells: one triggered by insulin, which is lovastatin sensitive, and the other activated by TSH, which is not sensitive to lovastatin.

Prostaglandins do not mediate arteriolar oxygen reactivity

1986 ◽  
Vol 250 (6) ◽  
pp. H1102-H1108 ◽  
Author(s):  
W. F. Jackson
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Intravital Microscopy ◽  
Cheek Pouch ◽  
Cyclooxygenase Inhibitor ◽  
Cremaster Muscle ◽  
Hamster Cheek Pouch ◽  
Nonspecific Effects ◽  
Oxygen Reactivity ◽  
Phospholipase A2 Inhibitors

The hypothesis that prostaglandins mediate arteriolar O2 reactivity was tested by assessing the effects of cyclooxygenase and phospholipase A2 inhibitors on the O2 responses of arterioles in superfused hamster cheek pouch and hamster and rat cremaster muscle preparations by use of intravital microscopy. Superfusion of these three preparations with the cyclooxygenase inhibitor indomethacin (50 microM) completely inhibited the response of the vessels to exogenous arachidonic acid but had no effect on the arteriolar constriction induced by elevation of superfusion solution PO2 from 15 to 150 mmHg. Similar results were obtained in the hamster cheek pouch with another cyclooxygenase inhibitor, meclofenamate, or when indomethacin (5-50 mg/kg) was administered systemically. Dexamethasone (12.7 microM) and quinacrine (10 microM), two reported inhibitors of phospholipase A2, also had no significant effect on arteriolar O2 reactivity in the cheek pouch. At 50 microM, quinacrine significantly depressed arteriolar reactivity to O2, adenosine, methacholine, and phenylephrine, suggesting nonspecific effects. These data do not support the hypothesis that prostaglandins mediate arteriolar O2 reactivity.

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