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.

scholarly journals Regulation of the electrogenic H+ channel in the plasma membrane of neutrophils: possible role of phospholipase A2, internal and external protons

1993 ◽  
Vol 292 (2) ◽  
pp. 445-450 ◽  
Author(s):  
A Kapus ◽  
K Suszták ◽  
E Ligeti
Keyword(s):  
Plasma Membrane ◽  
Phospholipase A2 ◽  
Neutrophil Granulocytes ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Conducting Pathway ◽  
External Ph ◽  
Force Relationship ◽  
Stimulation Of

Possible factors regulating the opening of and the rate of H+ flux through a recently described, Cd(2+)-sensitive, phorbol ester- and arachidonic acid (AA)-activatable H(+)-conducting pathway in the plasma membrane of neutrophil granulocytes were investigated. (1) The phospholipase A2 blocker p-bromophenacyl bromide (BPB) inhibited the phorbol 12-myristate 13-acetate (PMA)-induced activation of this channel in a concentration-dependent manner (IC50, 4 microM). (2) Neither BPB nor the protein kinase C (PKC) inhibitor staurosporine influenced the AA-elicited stimulation of this route. (3) Intracellular acidification (cytoplasmic pH below 6.9) itself is capable of activating an electrogenic, Cd(2+)-sensitive H+ efflux indicating that protons can open up this route in the absence of any other stimulator. (4) PMA significantly decreases the intracellular H+ concentration ([H+]i) threshold for the opening of the channel, thus providing a conductive state at resting pH values, and elevates the rate of H+ efflux at any [H+]i. (5) Changes in external pH also modify the operation of the channel: above an extracellular pH (pH(o)) value of 7.4, the H(+)-flux/driving force relationship is approx. 5-fold greater than below this value. Our results suggest a multifactorial regulation of the electrogenic H+ channel: most probably PKC activates the channel indirectly, via stimulation of phospholipase A2 that subsequently liberates AA. In addition to this, the channel conductance seems to be promoted by internal H+ and inhibited by external H+.

scholarly journals Influence of arachidonic acid on indices of phospholipase A2 activity in the human neutrophil

1993 ◽  
Vol 291 (3) ◽  
pp. 825-831 ◽  
Author(s):  
J D Winkler ◽  
C M Sung ◽  
W C Hubbard ◽  
F H Chilton
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Human Neutrophils ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Pla2 Activity ◽  
Tetraenoic Acid ◽  
Stimulation Of

The present studies were conducted to understand better the regulation of phospholipase A2 (PLA2)-dependent mobilization of lipid mediators by arachidonic acid (C20:4). After stimulation of human neutrophils, g.l.c./m.s. analysis of non-esterified fatty acids indicated that the quantity of C20:4 increased as a function of time after stimulation, from undetectable quantities to > 800 pmol/10(7) cells. In contrast with C20:4, the quantities of other free fatty acids such as oleic and linoleic were high in resting cells and did not change after stimulation. Some 15% of the C20:4 released from cellular lipids remained cell-associated. To examine the effect of C20:4 on its own release, neutrophils were exposed to [2H8]C20:4, to differentiate it by g.l.c./m.s. from naturally occurring C20:4. In A23187-stimulated neutrophils, low concentrations (5-10 microM) of [2H8]C20:4 added just before A23187 increased the quantity of C20:4 produced by the cell, whereas higher concentrations (30-50 microM) decreased the quantity of C20:4 released from phospholipids. As other measures of PLA2 activity, the effects of C20:4 on production of platelet-activity factor (PAF) and leukotriene B4 (LTB4) were assessed. C20:4 treatment just before stimulation of neutrophils blocked PAF and LTB4 production in a concentration-dependent manner (IC50 10-20 microM). The effect of C20:4 was not blocked by the cyclo-oxygenase inhibitor naproxine (10 microM), nor could it be mimicked by 1 microM LTB4, 5-hydroxyeicosa-6,8,11,14-tetraenoic acid (5HETE), 5-hydroperoxyeicosa-6,8,11,14-tetraenoic acid (5HPETE) or 15-hydroxyeicosa-5,8,11,13-tetraenoic acid (15HETE). The 5-lipoxygenase (5LO) inhibitor zileuton induced a concentration-dependent decrease in PAF, with a maximal effect of a 50% decrease at 10-50 microM. The decrease in PAF by the 5LO inhibitor could not be circumvented by addition of 1 microM 5HETE, 5HPETE and LTB4, and may be attributed to the capacity of zileuton to increase the quantity of C20:4 in A23187-treated neutrophils. The inhibitory effect of C20:4 (20-40 microM) on PAF production could be antagonized by the protein kinase C inhibitor staurosporine (30 nM), but not by inhibitors of protein kinase A, tyrosine kinase or calmodulin kinase II. Taken together, these data demonstrate that C20:4 is selectively released from membrane phospholipids of A23187-stimulated neutrophils, and this C20:4 may play an important role in regulating the mobilization of C20:4 by altering PLA2 activity.

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.

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.

Endothelium and mechanical responses of isolated monkey pulmonary veins to histamine

1990 ◽  
Vol 259 (4) ◽  
pp. H1032-H1037 ◽  
Author(s):  
T. Matsuki ◽  
T. Ohhashi
Keyword(s):  
Pulmonary Veins ◽  
Dependent Manner ◽  
High Concentration ◽  
Concentration Dependent Manner ◽  
Mechanical Responses ◽  
Relaxing Factor ◽  
Prostaglandin F2 Alpha ◽  
H2 Receptors ◽  
Endothelium Derived Relaxing Factor ◽  
Stimulation Of

Ring strips of monkey pulmonary veins precontracted with a high concentration of prostaglandin F2 alpha (PGF2 alpha) relaxed in a concentration-dependent manner in response to histamine. Treatment with mepyramine and/or famotidine attenuated the relaxation. 2-Pyridylethylamine (2PEA) and dimaprit caused relaxations in the precontracted preparations, which were inhibited by pretreatment with mepyramine and famotidine, respectively. Removal of endothelium reversed the histamine- and 2PEA-induced relaxations to dose-related contractions. On the other hand, the removal had no effect on the dimaprit-induced relaxations, which were significantly reduced by pretreatment with famotidine. Histamine-induced relaxations in the precontracted strips with endothelium in the presence and absence of famotidine were suppressed or abolished by treatment with methylene blue or hemoglobin but were unaffected by aspirin. It may be concluded that histamine-induced relaxation in monkey pulmonary veins precontracted with PGF2 alpha is mediated by H2-receptors in smooth muscle and H1-receptors in endothelium. Also, stimulation of the endothelial H1-receptors liberates an endothelium-derived relaxing factor.

scholarly journals Inhibition of HepG-2 Cells (Liver Cancer Cell Line) Viability by 3-Hydroxypyridine-2-Carboxaldehyde N(4)-Methylthiosemicarbazone

2021 ◽  
Vol 8 (2) ◽  
pp. 88-97
Author(s):  
Edrees Khan Rahmatzada ◽  
Prof. Paras Nath Yadav ◽  
Dr. Yuba Raj Pokharel
Keyword(s):  
Cancer Cell Line ◽  
Mapk Signaling ◽  
In Vivo Model ◽  
Dependent Manner ◽  
Dapi Staining ◽  
Concentration Dependent Manner ◽  
Anticancer Effects ◽  
Ic50 Value ◽  
Colony Number

Thiosemicarbazone have the antiviral, antibacterial, antifungal, and anticancer effects. 3-OH-Me-TSC inhibited the cell viability of HepG-2 cells by CV assay in a concentration dependent manner (control, 1μM, 3μM, 10μM, 30μM, and 100μM) with IC50 value of 9.587622μM. Further colony formation assay demonstrated that 3-OH-Me-TSC inhibits colony number and size of HepG-2. Wound healing assay exhibited that 3-OH-Me-TSC inhibit the migration of HepG-2 cells. DAPI staining showed that 3-OH-Me-TSC inhibited proliferation of HepG-2 cells in 30μM and 100μM concentrations respectively. 3-OH-Me-TSC inhibited VEGF, p38 alpha, C-JUN, BECN-1, ERK, NF-KB, in HepG-2 cells. We found that 3-OH-Me-TSC inhibit proliferation of HepG-2 cells by inhibiting MAPK signaling pathway, 3-OH-Me-TSC can be developed as future chemotherapeutic agent for treatment of hepatocellular carcinoma after the evaluation of this compounds in more cancer cells an in vivo model.

scholarly journals Adrenaline Stimulation of Phospholipid Metabolism in Adipocyte Ghosts

1987 ◽  
Vol 40 (4) ◽  
pp. 405
Author(s):  
David Mann ◽  
Audrey M Bersten
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Adenylate Cyclase ◽  
Phospholipid Metabolism ◽  
Dependent Manner ◽  
Long Chain Fatty Acids ◽  
Membrane Phospholipids ◽  
Dose Dependent ◽  
Stimulation Of

The incorporation of long-chain fatty acids into phospholipids has been detected in adipocyte ghosts that were incubated with [1_14 C] stearic, [1_14 C] linoleic or [l_14C] arachidonic acid. Adrenaline and adenosine activated this incorporation within 15 s of exposure of the ghosts to the hormones and the response was dose dependent. Maximum incorporation of labelled linoleic acid occurred at 10-5 M adrenaline and 10-7 M adenosine. The a-agonist phenylephrine and the ~-agonist isoproterenol were also shown to stimulate the incorporation of fatty acid in a dose dependent manner. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were each labelled preferentially with linoleic or arachidonic acid. p-Bromophenacylbromide, quinacrine and centrophenoxine inhibited the adrenaline-stimulated incorporation of fatty acids into ghost membrane phospholipids, and p-bromophenacylbromide also reduced the activation of adenylate cyclase by adrenaline. NaF, an activator of adenylate cyclase, like adrenaline, stimulated the incorporation of linoleic acid into ghost membrane phospholipids.

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