scholarly journals A Lipidomic Perspective of the Action of Group IIA Secreted Phospholipase A2 on Human Monocytes: Lipid Droplet Biogenesis and Activation of Cytosolic Phospholipase A2α

Biomolecules ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 891 ◽  
Author(s):  
Juan P. Rodríguez ◽  
Elbio Leiguez ◽  
Carlos Guijas ◽  
Bruno Lomonte ◽  
José M. Gutiérrez ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Lipid Droplet ◽  
Human Peripheral Blood ◽  
Fatty Acid Content ◽  
Blood Monocytes ◽  
Membrane Phospholipids ◽  
Cytosolic Phospholipase ◽  
Secreted Phospholipase A2 ◽  
Cytosolic Phospholipase A2α

Phospholipase A2s constitute a wide group of lipid-modifying enzymes which display a variety of functions in innate immune responses. In this work, we utilized mass spectrometry-based lipidomic approaches to investigate the action of Asp-49 Ca2+-dependent secreted phospholipase A2 (sPLA2) (MT-III) and Lys-49 sPLA2 (MT-II), two group IIA phospholipase A2s isolated from the venom of the snake Bothrops asper, on human peripheral blood monocytes. MT-III is catalytically active, whereas MT-II lacks enzyme activity. A large decrease in the fatty acid content of membrane phospholipids was detected in MT III-treated monocytes. The significant diminution of the cellular content of phospholipid-bound arachidonic acid seemed to be mediated, in part, by the activation of the endogenous group IVA cytosolic phospholipase A2α. MT-III triggered the formation of triacylglycerol and cholesterol enriched in palmitic, stearic, and oleic acids, but not arachidonic acid, along with an increase in lipid droplet synthesis. Additionally, it was shown that the increased availability of arachidonic acid arising from phospholipid hydrolysis promoted abundant eicosanoid synthesis. The inactive form, MT-II, failed to produce any of the effects described above. These studies provide a complete lipidomic characterization of the monocyte response to snake venom group IIA phospholipase A2, and reveal significant connections among lipid droplet biogenesis, cell signaling and biochemical pathways that contribute to initiating the inflammatory response.

scholarly journals Cellular Plasmalogen Content Does Not Influence Arachidonic Acid Levels or Distribution in Macrophages: A Role for Cytosolic Phospholipase A2γ in Phospholipid Remodeling

Cells ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 799 ◽  
Author(s):  
Patricia Lebrero ◽  
Alma M. Astudillo ◽  
Julio M. Rubio ◽  
Lidia Fernández-Caballero ◽  
George Kokotos ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipid Composition ◽  
Limiting Factor ◽  
Membrane Phospholipids ◽  
Cytosolic Phospholipase ◽  
Rich Media ◽  
Plasmalogen Content ◽  
Free Arachidonic Acid ◽  
Ethanolamine Plasmalogens

Availability of free arachidonic acid (AA) constitutes a rate limiting factor for cellular eicosanoid synthesis. AA distributes differentially across membrane phospholipids, which is largely due to the action of coenzyme A-independent transacylase (CoA-IT), an enzyme that moves the fatty acid primarily from diacyl phospholipid species to ether-containing species, particularly the ethanolamine plasmalogens. In this work, we examined the dependence of AA remodeling on plasmalogen content using the murine macrophage cell line RAW264.7 and its plasmalogen-deficient variants RAW.12 and RAW.108. All three strains remodeled AA between phospholipids with similar magnitude and kinetics, thus demonstrating that cellular plasmalogen content does not influence the process. Cell stimulation with yeast-derived zymosan also had no effect on AA remodeling, but incubating the cells in AA-rich media markedly slowed down the process. Further, knockdown of cytosolic-group IVC phospholipase A2γ (cPLA2γ) by RNA silencing significantly reduced AA remodeling, while inhibition of other major phospholipase A2 forms such as cytosolic phospholipase A2α, calcium-independent phospholipase A2β, or secreted phospholipase A2 had no effect. These results uncover new regulatory features of CoA-IT-mediated transacylation reactions in cellular AA homeostasis and suggest a hitherto unrecognized role for cPLA2γ in maintaining membrane phospholipid composition via regulation of AA remodeling.

scholarly journals Acute Nicotine Reduces Brain Arachidonic Acid Signaling in Unanesthetized Rats

2009 ◽  
Vol 29 (3) ◽  
pp. 648-658 ◽  
Author(s):  
Lisa Chang ◽  
Stanley I Rapoport ◽  
Henry N Nguyen ◽  
Dede Greenstein ◽  
Mei Chen ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Brain Regions ◽  
Membrane Phospholipids ◽  
Dose Equivalent ◽  
Central Effects ◽  
Postsynaptic Receptors ◽  
Cytosolic Phospholipase ◽  
Presynaptic Release

Nicotine exerts its central effects by activating pre- and postsynaptic nicotinic acetylcholine receptors (nAChRs). Presynaptic nAChRs modulate the release of many neurotransmitters that bind to postsynaptic receptors. These may be coupled to the activation of cytosolic phospholipase A2 (cPLA2), which hydrolyzes arachidonic acid (AA) from membrane phospholipids. We hypothesized that nicotine would modify brain signaling involving AA by binding to nAChRs. Nicotine (0.1 mg/kg, subcutaneously) or saline was injected 2 or 10 mins before infusing [1-14C]AA in unanesthetized rats. The AA incorporation coefficient k∗ (a marker of the AA signal) was measured in 80 brain regions by quantitative autoradiography. Nicotine, compared to saline, when administrated 2 mins before [1-14C]AA infusion, significantly decreased k∗ for AA in 26 regions, including cerebral cortex, thalamus, and habenula—interpeduncular regions, by 13% to 45%. These decreases could be entirely prevented by pretreatment with mecamylamine (1.0 mg/kg, subcutaneously). When administered 10 mins before [1-14C]AA infusion, nicotine did not alter any value of k∗. In summary, nicotine given to unanesthetized rats rapidly reduces signaling involving AA in brain regions containing nAChRs, likely by modulating the presynaptic release of neurotransmitters. The effect shows rapid desensitization and is produced at a nicotine dose equivalent to smoking one cigarette in humans.

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.

scholarly journals Role of Phosphorylation Sites and the C2 Domain in Regulation of Cytosolic Phospholipase A2

1999 ◽  
Vol 145 (6) ◽  
pp. 1219-1232 ◽  
Author(s):  
Miguel A. Gijón ◽  
Diane M. Spencer ◽  
Alan L. Kaiser ◽  
Christina C. Leslie
Keyword(s):  
Arachidonic Acid ◽  
Nuclear Envelope ◽  
Phospholipase A2 ◽  
Okadaic Acid ◽  
Cytosolic Phospholipase A2 ◽  
Phosphorylation Sites ◽  
C2 Domain ◽  
Arachidonic Acid Release ◽  
Cytosolic Phospholipase ◽  
Acid Release

Cytosolic phospholipase A2 (cPLA2) mediates agonist-induced arachidonic acid release, the first step in eicosanoid production. cPLA2 is regulated by phosphorylation and by calcium, which binds to a C2 domain and induces its translocation to membrane. The functional roles of phosphorylation sites and the C2 domain of cPLA2 were investigated. In Sf9 insect cells expressing cPLA2, okadaic acid, and the calcium-mobilizing agonists A23187 and CryIC toxin induce arachidonic acid release and translocation of green fluorescent protein (GFP)-cPLA2 to the nuclear envelope. cPLA2 is phosphorylated on multiple sites in Sf9 cells; however, only S505 phosphorylation partially contributes to cPLA2 activation. Although okadaic acid does not increase calcium, mutating the calcium-binding residues D43 and D93 prevents arachidonic acid release and translocation of cPLA2, demonstrating the requirement for a functional C2 domain. However, the D93N mutant is fully functional with A23187, whereas the D43N mutant is nearly inactive. The C2 domain of cPLA2 linked to GFP translocates to the nuclear envelope with calcium-mobilizing agonists but not with okadaic acid. Consequently, the C2 domain is necessary and sufficient for translocation of cPLA2 to the nuclear envelope when calcium is increased; however, it is required but not sufficient with okadaic acid.

Evidence for a Role for Phospholipase C, but not Phospholipase A2, in Platelet Activation in Response to Low Concentrations of Collagen

2001 ◽  
Vol 85 (05) ◽  
pp. 882-889 ◽  
Author(s):  
Leslie Lockhart ◽  
Caroline Pampolina ◽  
Brent Nickolaychuk ◽  
Archibald McNicol
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Platelet Activation ◽  
Cytosolic Phospholipase A2 ◽  
Arachidonic Acid Release ◽  
Cytosolic Phospholipase ◽  
Low Concentrations ◽  
Acid Release ◽  
Induced Aggregation

SummaryThe release of arachidonic acid is a key component in platelet activation in response to low concentrations (1-20 g/ml) of collagen. The precise mechanism remains elusive although a variety of pathways have been implicated. In the present study the effects of inhibitors of several potentially key enzymes in these pathways have been examined. Collagen (1-10 g/ml) caused maximal platelet aggregation which was accompanied by the release of arachidonic acid, the synthesis of thromboxane A2, and p38MAPK phosphorylation. Preincubation with the dual cyclooxygenase/lipoxygenase inhibitor BW755C inhibited aggregation and thromboxane production, and reduced p38MAPK phosphorylation. A phospholipase C inhibitor, U73122, blocked collagen-induced aggregation and reduced arachidonic acid release, thromboxane synthesis and p38MAPK phosphorylation. Pretreatment with a cytosolic phospholipase A2 inhibitor, AACOCF3, blocked collagen-induced aggregation, reduced the levels of thromboxane formation and p38MAPK phosphorylation but had no significant effect on arachidonic acid release. In contrast inhibition of PKC by Rö31-8220 inhibited collagen-induced aggregation, did not affect p38MAPK phosphorylation but significantly potentiated arachidonic acid release and thromboxane formation. Collagen caused the tyrosine phosphorylation of phospholipase C 2 which was inhibited by pretreatment with U73122, unaffected by AACOCF3 and enhanced by Rö31-8220. These results suggest that cytosolic phospholipase A2 plays no role in the arachidonic acid release in response to collagen. In contrast, the data are consistent with phospholipase C 2 playing a role in an intricately controlled pathway, or multiple pathways, mediating the release of arachidonic acid in collagen-stimulated platelets.

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