Synthesis of Prostacyclin from Platelet-derived Endoperoxides by Cultured Human Endothelial Cells

Marcus, Aaron J.; Weksler, Babette B.; Jaffe, Eric; Broekman, M. Johan

doi:10.1172/jci109967

Cited by 376 publications

(108 citation statements)

References 20 publications

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“…2). It is possible that in addition to the platelet/ leukocyte ratio, the cell concentration in the incubation medium also is an important parameter, which has been observed in studies of platelet-derived endoperoxides as substrates for endothelial cell prostacyclin synthetase (15). The observation that platelets lost their stimulatory effect, upon short preincubation with arachidonic acid prior to the addition of leukocytes, favored the involvement of a short-lived factor as the activator ofthe leukocyte C-5 lipoxygenase.…”

Section: Resultsmentioning

confidence: 99%

Stimulation of leukotriene biosynthesis in human blood leukocytes by platelet-derived 12-hydroperoxy-icosatetraenoic acid.

Maclouf¹,

Laclos²,

Borgeat³

1982

Proc. Natl. Acad. Sci. U.S.A.

155

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Addition of arachidonic acid to suspensions of human blood leukocytes induces the synthesis of small amounts only of the C-5 lipoxygenase products as demonstrated by HPLC. However, the coincubation of blood platelets with the leukocytes always resulted in an activation of the C-5 lipoxygenase and formation of (5S)-5-hydroxy-6,8,11,14-icosatetraenoic acid, (5S,12S)-5,12-dihydroxy-6,8,10,14-icosatetraenoic acid, and leukotriene B4 from exogenous arachidonic acid. It was found that the activation ofarachidonic acid metabolism in leukocytes was caused by a labile compound because the synthesis of the C-5 lipoxygenase products did not occur when platelets were preincubated for 1 min or more with the substrate prior to the addition of the leukocytes. The use of cyclooxygenase inhibitors did not suppress the activation of the leukocytes by the platelets. However, the addition of 5,8,11,14-icosatetraynoic acid, an inhibitor of cyclooxygenase and C-12 and C-15 lipoxygenases, completely suppressed the formation of leukotrienes, although this substance is not an inhibitor of the C-5 lipoxygenase in human leukocytes. This indicated that a product ofthe C-12 lipoxygenase was likely the mediator ofthe stimulatory effect of platelets on leukocyte arachidonic acid metabolism. The finding that the direct addition of(12S)-12-hydroperoxy-5,8,10,14-icosatetraenoic acid, but not of the corresponding hydroxy derivative, could activate the leukocyte's C-5 lipoxygenase confirmed this hypothesis. These data demonstrate that an interaction between C-12 and C-5 lipoxygenases can promote the formation of leukotrienes and support the possibility of a cooperation between platelets and leukocytes in inflammation and hypersensitivity reactions. Furthermore, the finding provides a new interest for the platelet C-12 lipoxygenase.The existence of a mammalian lipoxygenase was first demonstrated in human platelets, where arachidonic acid is converted to (12S)-12-hydroperoxy-5,8,10,14-icosatetraenoic acid (12-HPETE) and subsequently to the corresponding (12S)-12-hydroxy acid (12-HETE) (1). More recently, the discovery of leukotrienes (LTs) (2-4), a new family of bioactive metabolites formed in a lipoxygenase-type reaction (involving the C-5 of arachidonic acid), and the detection of a C-15 lipoxygenase in leukocytes (5, 6) have indicated the existence of several lipoxygenases in blood cells. In addition to differences in positional specificities, the heterogeneity of these enzymes is further emphasized by different reactivities. For instance, it has been shown that, in contrast to platelet suspensions which efficiently transform exogenous arachidonic acid into 12-HETE (and cyclooxygenase products), the addition of the fatty acid to preparations of human polymorphonuclear leukocytes (PMNL) was followed by only minor transformation ofthe substrate (5); however, the metabolism ofarachidonic acid was strongly enhanced when leukocytes were incubated in the presence ofarachidonic acid and of the divalent cation ionophore A23187, indicating clearl...

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Section: Resultsmentioning

confidence: 99%

Stimulation of leukotriene biosynthesis in human blood leukocytes by platelet-derived 12-hydroperoxy-icosatetraenoic acid.

Maclouf¹,

Laclos²,

Borgeat³

1982

Proc. Natl. Acad. Sci. U.S.A.

155

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“…31,32) The perinuclear region is the primary target of cPLA 2 a translocation, but there are some reports indicating unique subcellular localization of cPLA 2 a under certain conditions. First, in subconfluent endothelial cells, the truncated form of cPLA 2 a is prominently located in the nucleoplasm 33) and stimulation with histamine causes rapid transport of intranu- binding to the C2 domain promotes cPLA 2 a translocation from the cytosol to the membrane containing phosphatidylcholine.…”

Section: -1 Subcellular Localizationmentioning

confidence: 99%

Regulatory Mechanism and Physiological Role of Cytosolic Phospholipase A2

Hirabayashi

Murayama

Shimizu

2004

Biological & Pharmaceutical Bulletin

216

184

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Cytosolic phospholipase A 2 a a (cPLA 2 a a) preferentially hydrolyzes phospholipids containing arachidonic acid and plays a key role in the biosynthesis of eicosanoids. This review discusses the essential features of cPLA 2 a a regulation and addresses new insights into the functional properties of this enzyme. Full activation of the enzyme requires Ca 2؉ binding to an N-terminal C2 domain and phosphorylation on serine residues. Ca 2؉ binding induces translocation of cPLA 2 a a from the cytosol to the perinuclear membranes. Serine phosphorylation is mediated by mitogen-activated protein kinases (MAPKs), Ca 2؉ /calmodulin-dependent protein kinase II, and MAPK-interacting kinase Mnk1. Interaction with proteins and lipids, which include vimentin, annexins, NADPH oxidase, phosphatidylcholine, phosphatidylinositol 4,5-bisphosphate (PIP 2 ), and ceramide-1-phosphate, can also modulate the activity of cPLA 2 a a. Recent evidence has established the physiological and pathological roles of cPLA 2 a a using cPLA 2 a a knockout mice. This enzyme has been implicated in fertility, striated muscle growth, renal concentration, postischemic brain injury, arthritis, inflammatory bone resorption, intestinal polyposis, pulmonary fibrosis, acute respiratory distress syndrome, and autoimmune encephalomyelitis. Now novel three paralogs, cPLA 2 b b, cPLA 2 g g, and cPLA 2 d d, have been identified in humans. cPLA 2 g g is distinct from others in that it is farnesylated and lacks the C2 domain. Biological roles for these new enzymes have not yet been defined.

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“…Expanding on this concept, we define thromboregulation as a process or group of processes by which circulating hematologic cells and cells of the vessel wall interact to regulate or inhibit thrombus formation. Essentially, all thromboregulatory reactions are biochemical in nature and result in formation of biologically active metabolites that could have only arisen through interactions between heterogeneous cell types in the vasculature (Marcus et al, 1980(Marcus et al, , 1982(Marcus et al, , 1988Valles et al, 1993Valles et al, , 2002Serhan and Oliw, 2001). Thromboregulation is accomplished by biological compounds that are either cellassociated or released from the cell into the fluid-phase microenvironment.…”

Section: Hemostasis and Thrombosis As Models Of Cell-cell Interactionsmentioning

confidence: 99%

Metabolic Control of Excessive Extracellular Nucleotide Accumulation by CD39/Ecto-Nucleotidase-1: Implications for Ischemic Vascular Diseases

Marcus

Broekman

Drosopoulos

et al. 2003

J Pharmacol Exp Ther

Self Cite

122

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Platelets are responsible for maintaining vascular integrity. In thrombocytopenic states, vascular permeability and fragility increase, presumably due to the absence of this platelet function. Chemical or physical injury to a blood vessel induces platelet activation and platelet recruitment. This is beneficial for the arrest of bleeding (hemostasis), but when an atherosclerotic plaque is ulcerated or fissured, it becomes an agonist for vascular occlusion (thrombosis). Experiments in the late 1980s cumulatively indicated that endothelial cell CD39 -an ecto-ADPase-reduced platelet reactivity to most agonists, even in the absence of prostacyclin or nitric oxide. As discussed herein, CD39 rapidly and preferentially metabolizes ATP and ADP released from activated platelets to AMP, thereby drastically reducing or even abolishing platelet aggregation and recruitment. Since ADP is the final common agonist for platelet recruitment and thrombus formation, this finding highlights the significance of CD39. A recombinant, soluble form of human CD39, solCD39, has enzymatic and biological properties identical to the full-length form of the molecule and strongly inhibits human platelet aggregation induced by ADP, collagen, arachidonate, or TRAP (thrombin receptor agonist peptide). In sympathetic nerve endings isolated from guinea pig hearts, where neuronal ATP enhances norepinephrine exocytosis, solCD39 markedly attenuated norepinephrine release. This suggests that NTPDase (nucleoside triphosphate diphosphohydrolase) could exert a cardioprotective action by reducing ATP-mediated norepinephrine release, thereby offering a novel therapeutic approach to myocardial ischemia and its consequences. In a murine model of stroke, driven by excessive platelet recruitment, solCD39 reduced the sequelae of stroke, without an increase in intracerebral hemorrhage. CD39 null mice, generated by deletion of apyrase-conserved regions 2 to 4, exhibited a decrease in postischemic perfusion and an increase in cerebral infarct volume when compared with controls. "Reconstitution" of CD39 null mice with solCD39 reversed these changes. We hypothesize that solCD39 has potential as a novel therapeutic agent for thrombotic diatheses. The Hemostatic MechanismThe hemostatic process consists of a series of physiologic and biochemical reactions that culminate in the arrest of bleeding from blood vessels that have been severed or traumatized physically or chemically. Hemostasis is accomplished via the interaction of three biological systems: 1) components of the vasculature per se, including endothelial cells; 2) blood platelets; and 3) plasma proteins comprising the intrinsic and extrinsic coagulation pathways (Marcus, 1999). Qualitative or quantitative deficiencies in any one of these systems result in a defect of hemostasis, coagulation, or both. These abnormalities can lead to a hemorrhagic diathesis that is clinically mild, moderate, or severe. -methyladenosine-3Ј,5Ј-diphosphate; NTPDase, nucleoside triphosphate diphosphohydrolase.

show abstract

Synthesis of Prostacyclin from Platelet-derived Endoperoxides by Cultured Human Endothelial Cells

Cited by 376 publications

References 20 publications

Stimulation of leukotriene biosynthesis in human blood leukocytes by platelet-derived 12-hydroperoxy-icosatetraenoic acid.

Stimulation of leukotriene biosynthesis in human blood leukocytes by platelet-derived 12-hydroperoxy-icosatetraenoic acid.

Regulatory Mechanism and Physiological Role of Cytosolic Phospholipase A2

Metabolic Control of Excessive Extracellular Nucleotide Accumulation by CD39/Ecto-Nucleotidase-1: Implications for Ischemic Vascular Diseases

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