scholarly journals Role of a membrane-associated serine esterase in the oxidant activation of phospholipase A2 by t-butyl hydroperoxide

1993 ◽  
Vol 292 (2) ◽  
pp. 585-589 ◽  
Author(s):  
S Chakraborti ◽  
J R Michael ◽  
G H Gurtner ◽  
S S Ghosh ◽  
G Dutta ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Membrane ◽  
Phospholipase A2 ◽  
Antioxidant Vitamin ◽  
Serine Esterase ◽  
Pla2 Activity ◽  
Butyl Hydroperoxide ◽  
Synthetic Substrate ◽  
Esterase Inhibitors ◽  
Membrane Bound

Exposure of bovine pulmonary-arterial endothelial cells to the oxidant lipid t-butyl hydroperoxide (t-Bu-OOH) increases cell-membrane-associated phospholipase A2 (PLA2) activity and stimulates arachidonic acid (AA) release. To test the hypothesis that a membrane-associated serine esterase plays an important role in activating PLA2, the present study was undertaken. In addition to increasing PLA2 activity and AA release, t-Bu-OOH also enhances the activity of a membrane-associated serine esterase that cleaves the synthetic substrate N alpha-p-tosyl-L-arginine methyl ester (TAME). Changes in the activity of this membrane-bound serine esterase correlate directly with changes in the activity of PLA2. Serine esterase inhibitors such as phenylmethanesulphonyl fluoride, di-isopropyl fluorophosphate and alpha 1-proteinase inhibitor, and TAME, a synthetic substrate for serine esterase, prevent the increase in serine esterase activity, PLA2 activity and AA release caused by t-Bu-OOH. Pretreatment of the endothelial cells with the antioxidant vitamin E prevents t-Bu-OOH-induced stimulation of AA release and the cell-membrane-associated serine esterase and PLA2 activities. Adding t-Bu-OOH or the serine esterase trypsin to the endothelial-cell membrane fraction also significantly augments PLA2 activity, implying that these treatments activate latent PLA2. These results suggest that t-Bu-OOH stimulates a membrane-associated serine esterase that plays a crucial role in activating PLA2 and releasing AA.

Role of serine esterase in A23187-mediated activation of phospholipase A2 in pulmonary endothelium

1993 ◽  
Vol 264 (6) ◽  
pp. L538-L542 ◽  
Author(s):  
S. Chakraborti ◽  
J. R. Michael
Keyword(s):  
Endothelial Cell ◽  
Cell Membrane ◽  
Phospholipase A2 ◽  
Esterase Activity ◽  
Calcium Ionophore ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Serine Esterase ◽  
Pla2 Activity ◽  
Pulmonary Endothelium

To test the hypothesis that an endothelial cell membrane-associated serine esterase is involved in regulating phospholipase A2 (PLA2), we studied the effect of the calcium ionophore A23187 on intracellular PLA2 activity and arachidonic acid (AA) release in bovine pulmonary arterial endothelial cells. Exposure of these cells to A23187 causes a concentration-dependent increase in PLA2 activity and [14C]AA release. In addition to increasing PLA2 activity and AA release, A23187 enhances the activity of endothelial cell membrane-associated serine esterase that acts on the synthetic substrate N alpha-p-tosyl-L-arginine methyl ester. Serine esterase inhibitors, such as phenylmethylsulfonyl fluoride and diisopropyl fluorophosphate, prevent the A23187-mediated increase in serine esterase activity, PLA2 activity, and AA release. Pretreatment of the cells with actinomycin D or cycloheximide does not prevent the A23187-mediated increase in AA release, serine esterase activity, or PLA2 activity. The membrane-associated serine esterase activity directly correlates with membrane PLA2 activity. These results suggest that a membrane-associated serine esterase plays a pivotal role in regulating PLA2 activity after exposure to A23187.

ISOLATION OF A SOLUBLE PHOSPHOLIPASE A2 FROM HUMAN PLATELETS ACTIVE AGAINST 1-ACYL-2-ARACHIDONOYL GLYCEROPHOSPHOCHOLINE

1987 ◽  
Author(s):  
A D Purdon ◽  
J B Smith
Keyword(s):  
Phospholipase A2 ◽  
Specific Activity ◽  
Deae Cellulose ◽  
Human Platelets ◽  
Phospholipid Bilayer ◽  
Ionophore A23187 ◽  
Pla2 Activity ◽  
Enzyme Substrate ◽  
Membrane Bound ◽  
Layer Chromatography

Previously, we have shown that 1-acyl-2-arachidonoyl glycero-phosphocholine (GPC) is the main source of arachidonic acid in thrombin-stimulated (5 U/ml) human platelets. Thus 1-acyl-2-3H-arachidonoyl GPC was dispersed in Tris buffer, 0.01 M, pH 7.5, 0.01 M CaCl2 for use a substrate for the assay of phospholipase A2 activity in human platelets. The released 3H-arachidonate(AA) was isolated by thin layer chromatography following Bligh and Dyer extraction of the enzyme-substrate incubate. Phospholipase A2 (PLA2) specific for this phospholipid was thought to be membrane bound and of low activity when solubilized, however, we have found, that provided resting platelets are gently sonicated while suspended in tyrode's buffer in the presence of suitable concentrations of protease inhibitors and metal chelators (EGTA, EDTA), a large amount of soluble PLA2 activity can be isolated following centrifugation to remove membranes. The enzyme required calcium for activity and was inactive in the presence of EGTA. No activity was found in the secretate from thrombin-stimulated cells, indicating that the PLA2 assayed at pH 7.5 was not lysosomal. PLA2 was further purified by DEAE cellulose chromatography where a 5 times increase in specific activity was achieved. It is known that OAG (1-oleoyl-2-acetyle-glycerol) augments deacylation of 1,2 diradyl GPC in platelets stimulated with suboptimal levels of ionophore A23187. Thus the effect of OAG stimulation of platelets on the distribution of soluble PLA2 was studied. Platelets (109 cells/ml) suspended in tyrode's buffer and stimulated with 100 ug/ml OAG or 5 U/ml thrombin (10 min, 37°C., 10 min, without stirring), showed a considerable decrease in soluble PLA2 activity suggesting a partitioning of soluble PLA2 into the membrane bilayer. Thus a model for PLA2 action is suggested in which binding of the cytosolic enzyme to its site of hydrolysis is induced by diglyceride-perturbation of the membrane, phospholipid, bilayer phase.

Phospholipase A2 (PLA2) activity in bovine pulmonary artery endothelial cells

1991 ◽  
Vol 34 (1-2) ◽  
pp. 113-116 ◽  
Author(s):  
R. Goodman ◽  
T. M. Stevens ◽  
L. R. Mantegna ◽  
P. R. Kidd ◽  
R. R. Harris ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Pulmonary Artery ◽  
Phospholipase A2 ◽  
Pla2 Activity

The Increased Sensitivity of Platelets to Prostacyclin in Marathon Runners

1984 ◽  
Vol 51 (03) ◽  
pp. 385-387 ◽  
Author(s):  
Clive J Dix ◽  
David G Hassall ◽  
K Richard Bruckdorfer
Keyword(s):  
Cardiovascular Disease ◽  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Platelet Rich Plasma ◽  
Marathon Runners ◽  
Inhibition Of Platelet Aggregation ◽  
Increased Sensitivity ◽  
Membrane Bound

SummaryPlatelet-rich plasma was obtained 24 hr after the race ended from athletes who ran in the London marathon. The platelets were only marginally less sensitive to adrenaline than were those of non-runners using conventional aggregation tests. However, the runners’ platelets were much more sensitive to inhibition by prostacyclin, a prostaglandin synthesized by endothelial cells. It appeared that this effect was due to a greater activity in the platelets of the membrane-bound adenylate cyclase enzyme which generates intracellular cyclic AMP. Cyclic AMP production is known to be stimulated by prostacyclin and to cause the inhibition of platelet aggregation. The results indicate another possible protective effect of exercise against cardiovascular disease which is independent of the known changes in lipoprotein concentrations previously observed in athletes.

Study of phospholipase A2 activity in umbilical endothelial cells in toxemia of pregnancy.

1987 ◽  
Vol 18 (6) ◽  
pp. 582-588
Author(s):  
Hiroyuki SEKI ◽  
Toshiharu JIMBO ◽  
Kazuo SATOH
Keyword(s):  
Endothelial Cells ◽  
Phospholipase A2 ◽  
Phospholipase A2 Activity

Antiangiogenic effects of phospholipase A2 Lys49 BnSP-7 from Bothrops pauloensis snake venom on endothelial cells: An in vitro and ex vivo approach

2021 ◽  
Vol 72 ◽  
pp. 105099
Author(s):  
Lorena Polloni ◽  
Fernanda Van Petten Vasconcelos Azevedo ◽  
Samuel Cota Teixeira ◽  
Eloá Moura ◽  
Tassia Rafaela Costa ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Phospholipase A2 ◽  
Snake Venom ◽  
Ex Vivo ◽  
Ex Vivo Approach

scholarly journals Orai–vascular endothelial-cadherin signaling complex regulates high-glucose exposure-induced increased permeability of mouse aortic endothelial cells

2021 ◽  
Vol 9 (1) ◽  
pp. e002085
Author(s):  
Yuan Wei ◽  
Suwen Bai ◽  
YanHeng Yao ◽  
Wenxuan Hou ◽  
Junwei Zhu ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Membrane ◽  
High Glucose ◽  
Expression Level ◽  
Vascular Endothelial ◽  
Aortic Endothelial Cells ◽  
Downstream Signaling ◽  
Signaling Complex ◽  
Aortic Endothelium ◽  
Aortic Endothelial

IntroductionDiabetes-associated endothelial barrier function impairment might be linked to disturbances in Ca2+ homeostasis. To study the role and molecular mechanism of Orais–vascular endothelial (VE)-cadherin signaling complex and its downstream signaling pathway in diabetic endothelial injury using mouse aortic endothelial cells (MAECs).Research design and methodsThe activity of store-operated Ca2+ entry (SOCE) was detected by calcium imaging after 7 days of high-glucose (HG) or normal-glucose (NG) exposure, the expression levels of Orais after HG treatment was detected by western blot analysis. The effect of HG exposure on the expression of phosphorylated (p)-VE-cadherin and VE-cadherin on cell membrane was observed by immunofluorescence assay. HG-induced transendothelial electrical resistance was examined in vitro after MAECs were cultured in HG medium. FD-20 permeability was tested in monolayer aortic endothelial cells through transwell permeability assay. The interactions between Orais and VE-cadherin were detected by co-immunoprecipitation and immunofluorescence technologies. Immunohistochemical experiment was used to detect the expression changes of Orais, VE-cadherin and p-VE-cadherin in aortic endothelium of mice with diabetes.Results(1) The expression levels of Orais and activity of SOCE were significantly increased in MAECs cultured in HG for 7 days. (2) In MAECs cultured in HG for 7 days, the ratio of p-VE-cadherin to VE-cadherin expressed on the cell membrane and the FD-20 permeability in monolayer endothelial cells increased, indicating that intercellular permeability increased. (3) Orais and VE-cadherin can interact and enhance the interaction ratio through HG stimulation. (4) In MAECs cultured with HG, the SOCE activator ATP enhanced the expression level of p-VE-cadherin, and the SOCE inhibitor BTP2 decreased the expression level of p-VE-cadherin. (5) Significantly increased expression of p-VE-cadherin and Orais in the aortic endothelium of mice with diabetes.ConclusionHG exposure stimulated increased expression of Orais in endothelial cells, and increased VE-cadherin phosphorylation through Orais–VE-cadherin complex and a series of downstream signaling pathways, resulting in disruption of endothelial cell junctions and initiation of atherosclerosis.

scholarly journals Modulation of phospholipase A2 activity by the tumour promoters phorbol esters and teleocidin

1990 ◽  
Vol 268 (1) ◽  
pp. 169-173 ◽  
Author(s):  
K Y Nam ◽  
A Morino ◽  
S Kimura ◽  
H Fujiki ◽  
Y Imanishi
Keyword(s):  
Phospholipase A2 ◽  
Membrane Structure ◽  
Phorbol Esters ◽  
Hydrolytic Activity ◽  
Phospholipid Bilayer ◽  
Structural Defects ◽  
Moderate Degree ◽  
Pla2 Activity ◽  
Tumour Promoters ◽  
High Concentrations

The effects of tumour promoters, namely phorbol esters and teleocidin, on the activity of porcine pancreatic phospholipase A2 (PLA2) was investigated by using a system of small unilamellar vesicles composed of dipalmitoyl-phosphatidylcholine (DPPC). DPPC vesicles encapsulating Quin 2 (Quin 2/DPPC vesicles) were suspended in a medium containing Ca2+. The addition of PLA2 to Quin 2/DPPC vesicles increased the fluorescence intensity of Quin 2. This increase was due to chelation of Quin 2 with Ca2+, which resulted from an increase in the permeability of the phospholipid bilayer caused by the hydrolytic activity of PLA2. The tumour promoters phorbol 12-myristate 13-acetate (PMA) and teleocidin, at low concentrations, enhanced PLA2 activity at temperatures below the phase-transition temperature of the membrane, but, in contrast, high concentrations of the tumour promoters suppressed PLA2 activity. Phorbol 12-myristate (PM) also had a similar effect on PLA2 activity. PMA and PM disturbed the membrane structure markedly, which was indicated by the enhanced leakage of carboxyfluorescein (CF) from DPPC vesicles encapsulating CF. On the other hand, phorbol 12,13-didecanoate and 4 alpha-phorbol 12,13-didecanoate, which did not disturb the membrane structure to the same extent, had an insignificant effect on PLA2 activity. It is therefore concluded that PLA2 catalyses the hydrolysis of phospholipids in bilayer vesicles which contain a moderate degree of structural defects. However, the effects of tumour promoters on PLA2 activity was not related to their potencies as inflammatory and tumour-promoting agents.

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