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Richard W. Gross - One of the best experts on this subject based on the ideXlab platform.
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expression purification and kinetic characterization of a recombinant 80 kda intracellular calcium independent Phospholipase A2
1996Co-Authors: Matthew J Wolf, Richard W. GrossAbstract:Abstract A CHO cell-derived 80-kDa recombinant polypeptide (GenBank number I15470[GenBank]) putatively encoding a calcium-independent Phospholipase A2 was expressed in S. frugiperda cells resulting in over a 15-fold increase in a calcium-independent Phospholipase A1/A2 activity which was entirely inhibitable by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one. The recombinant polypeptide was purified from cytosol by sequential tandem affinity chromatographies employing ATP-agarose and calmodulin-Sepharose stationary phases. This strategy resulted in the rapid purification (36 h) of recombinant Phospholipase A2 activity in 56% overall yield to a single intense 80-kDa protein band on SDS-polyacrylamide gel electrophoresis after silver staining. The purified protein possessed Phospholipase A1, Phospholipase A2, and lysoPhospholipase activities. Microbore anion exchange chromatography demonstrated that the 80-kDa protein band was comprised of multiple distinct isoforms including an anionic isoform which possessed over a 5-fold higher specific activity (5 μmol/mg·min) than earlier eluting isoforms. Collectively, these results unambiguously demonstrate that: 1) the 80-kDa polypeptide catalyzes Phospholipase A1/A2 and lysoPhospholipase activities with distinct kinetic parameters; 2) calmodulin and ATP both interact with the catalytic polypeptide independent of regulatory proteins; and 3) distinct isoforms of this polypeptide exist which possess markedly different specific activities.
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isolation of a human myocardial cytosolic Phospholipase A2 isoform fast atom bombardment mass spectroscopic and reverse phase high pressure liquid chromatography identification of choline and ethanolamine glycerophospholipid substrates
1993Co-Authors: Stanley A Hazen, David A Ford, Curtis R Hall, Richard W. GrossAbstract:Recent studies have demonstrated the existence of a novel family of calcium-independent plasmalogen-selective Phospholipases A2 in canine myocardium that have been implicated as enzymic mediators of ischemic membrane damage. We now report that human myocardium contains two functionally distinct isoforms of cytosolic calcium-independent Phospholipase A2. The major cytosolic Phospholipase A2 isoform preferentially hydrolyzes plasmalogen substrate, possesses a pH optimum of 7.0, and is chromatographically resolvable from a minor cytosolic calcium-independent Phospholipase A2 isoform that hydrolyzes plasmenylcholine and phosphatidylcholine substrates at similar rates and possesses a pH optimum of 8.5. The major cytosolic calcium-independent Phospholipase A2 isoform was identified as a 40-kD polypeptide after its 182,000-fold purification by sequential column chromatographies to a final specific activity of 67 mumol/mg.min. The purified 40-kD human myocardial Phospholipase A2 preferentially hydrolyzes plasmalogens containing arachidonic acid at the sn-2 position. Both reverse-phase HPLC and fast atom bombardment mass spectroscopic analysis of human myocardial ethanolamine and choline glycerophospholipids demonstrated that plasmenylethanolamine and plasmenylcholine molecular species containing arachidonic acid at the sn-2 position are prominent constituents of human myocardium. Collectively, these results identify and characterize the major human myocardial cytosolic calcium-independent Phospholipase A2 activity, demonstrate the presence of functionally distinct human myocardial cytosolic calcium-independent Phospholipase A2 isoforms, and document the abundance of arachidonoylated plasmalogen molecular species in human myocardium that serve as substrates.
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the rapid and reversible activation of a calcium independent plasmalogen selective Phospholipase A2 during myocardial ischemia
1991Co-Authors: David A Ford, Stanley L Hazen, Jeffrey E Saffitz, Richard W. GrossAbstract:Abstract Recent studies have demonstrated the existence of two members of a novel family of calcium-independent plasmalogen-selective Phospholipases A2 in mammalian myocardium (Wolf, R. A., and R. W. Gross. 1985. J. Biol. Chem. 260:7295-7303; and Hazen, S. L., D. A. Ford, and R. W. Gross. 1991. J. Biol. Chem. 266:5629-5633). To examine the potential role of these calcium-independent Phospholipases A2 in mediating membrane dysfunction during early myocardial ischemia, the temporal course of alterations in Phospholipase A2 activity during global ischemia in Langendorf perfused rabbit hearts was quantified and compared with traditionally accepted markers of myocytic ischemic injury and anaerobic metabolism. We now report that membrane-associated calcium-independent plasmalogen-selective Phospholipase A2 activity increased over 400% during 2 min of global ischemia (P less than 0.01), was near maximally activated (greater than 10-fold) after only 5 min of ischemia, and remained activated throughout the entire ischemic interval examined (2-60 min). Activation of membrane-associated plasmalogen-selective Phospholipase A2 after 5 min of myocardial ischemia was rapidly reversible during reperfusion of ischemic tissue. Both the activation of Phospholipase A2 and its reversibility during reperfusion were temporally correlated to alterations in myocytic anaerobic metabolism. Furthermore, activation of membrane-associated Phospholipase A2 was essentially complete before electron microscopic evidence of cellular damage. Collectively, these results identify dynamic alterations in calcium-independent plasmalogen-selective Phospholipase A2 activity during myocardial ischemia which precede irreversible cellular injury and demonstrate that activation of plasmalogen-selective Phospholipase A2 is amongst the earliest biochemical alterations in ischemic myocardium.
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suicide inhibition of canine myocardial cytosolic calcium independent Phospholipase A2 mechanism based discrimination between calcium dependent and independent Phospholipases A2
1991Co-Authors: Stanley L Hazen, Lori A Zupan, Randy H Weiss, Daniel P Getman, Richard W. GrossAbstract:The majority of Phospholipase A2 activity in myocardium is calcium-independent and selective for hydrolysis of plasmalogen substrate (Wolf, R. A., and Gross, R. W. (1985) J. Biol. Chem. 260, 7295-7303; Hazen, S. L., Stuppy, R. J., and Gross, R. W. (1990) J. Biol. Chem. 265, 10622-10630). Accordingly, identification of an inhibitor which selectively targets calcium-independent Phospholipases A2 would facilitate elucidation of the biologic significance of this class of intracellular Phospholipases. We now report that the haloenol lactone, (E)-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one (Compound 1), is a potent, irreversible, mechanism-based inhibitor of myocardial calcium-independent Phospholipase A2 which is greater than 1000-fold specific for inhibition of myocardial calcium-independent Phospholipase A2 in comparisons with multiple calcium-dependent Phospholipases A2. Mechanism-based inhibition of myocardial cytosolic calcium-independent Phospholipase A2 by Compound 1 was established by demonstrating: 1) time-dependent irreversible inactivation; 2) covalent binding of [3H]Compound 1 to the purified Phospholipase A2; 3) ablation of covalent binding of [3H]Compound 1 after chemical inactivation of Phospholipase A2 enzymic activity; 4) identical inhibition of myocardial Phospholipase A2 by Compound 1 in the absence or presence of nucleophilic scavengers; 5) Compound 1 is a substrate for myocardial calcium-independent Phospholipase A2 resulting in the generation of the electrophilic alpha-bromomethyl ketone; 6) Phospholipase A2 inhibition requires the in situ generation of the reactive electrophile (i.e. neither the alpha-bromomethyl ketone nor the diproteoenol lactone analog are inhibitory); and 7) concomitant attenuation of the inhibitory potency and the extent of covalent adduct formation in the presence of saturating substrate. Collectively, these results demonstrate that the haloenol lactone, Compound 1, is a substrate for, covalently binds to, and irreversibly inhibits canine myocardial cytosolic calcium-independent Phospholipase A2.
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activation of a membrane associated Phospholipase A2 during rabbit myocardial ischemia which is highly selective for plasmalogen substrate
1991Co-Authors: Stanley L Hazen, David A Ford, Richard W. GrossAbstract:Abstract Recently, the prototype of a novel class of calcium-independent plasmalogen-selective Phospholipase A2 activities was identified in the cytosolic fraction of canine myocardium (Wolf, R.A., and Gross, R.W. (1985) J. Biol. Chem. 260, 7295-7303) and subsequently purified and characterized (Hazen, S.L., Stuppy, R.J., and Gross, R.W. (1990) J. Biol. Chem. 265, 10622-10630). We now demonstrate that 15 min of myocardial ischemia utilizing a rabbit Langendorf perfused heart model results in a 10-fold increase in membrane-associated calcium-independent Phospholipase A2 activity whose detection is entirely dependent upon utilization of plasmalogen substrate. Ischemia-induced Phospholipase activity was identified as a membrane bound member of this class of Phospholipases A2 by demonstration of: 1) concomitant production of lysoplasmenylcholine and sn-2 fatty acid from plasmenylcholine substrate; 2) maximal enzymatic activity in the absence of calcium ion; and 3) a 16-fold higher maximum reaction velocity utilizing plasmenylcholine compared to phosphatidylcholine substrate at multiple surface concentrations. Ischemia-induced Phospholipase A2 activity was specifically localized to the microsomal fraction and could not be solubilized by sonication, salt treatment, exposure to chelators, or utilization of submicellar concentrations of detergent. The appearance of microsomal Phospholipase A2 activity did not require ischemia-induced transcription or translation since identical increases in enzymic activity were obtained in hearts previously treated with actinomycin D and cycloheximide. Collectively, these results demonstrate that a membrane-associated calcium-independent Phospholipase A2 that selectively hydrolyzes plasmalogen molecular species is the likely enzymic mediator of accelerated phospholipid catabolism during early myocardial ischemia.
Edward A. Dennis - One of the best experts on this subject based on the ideXlab platform.
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Phospholipase A2 catalysis and lipid mediator lipidomics
2019Co-Authors: Varnavas D Mouchlis, Edward A. DennisAbstract:Phospholipase A2 (PLA2) enzymes are the upstream regulators of the eicosanoid pathway liberating free arachidonic acid from the sn-2 position of membrane phospholipids. Free intracellular arachidonic acid serves as a substrate for the eicosanoid biosynthetic enzymes including cyclooxygenases, lipoxygenases, and cytochrome P450s that lead to inflammation. The Group IVA cytosolic (cPLA2), Group VIA calcium-independent (iPLA2), and Group V secreted (sPLA2) are three well-characterized human enzymes that have been implicated in eicosanoid formation. In this review, we will introduce and summarize the regulation of catalytic activity and cellular localization, structural characteristics, interfacial activation and kinetics, substrate specificity, inhibitor binding and interactions, and the downstream implications for eicosanoid biosynthesis of these three important PLA2 enzymes.
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cytosolic group iva Phospholipase A2 inhibitors avx001 and avx002 ameliorate collagen induced arthritis
2019Co-Authors: Astrid Jullumstro Feuerherm, Edward A. Dennis, Berit JohansenAbstract:Background Cytosolic Phospholipase A2 group IVA (cPLA2α)-deficient mice are resistant to collagen-induced arthritis, suggesting that cPLA2α is an important therapeutic target. Here, the anti-inflammatory effects of the AVX001 and AVX002 cPLA2α inhibitors were investigated.
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Phospholipase A2 structure function mechanism and signaling
2009Co-Authors: Edward A. Dennis, John E BurkeAbstract:Tremendous advances in understanding the structure and function of the superfamily of Phospholipase A2 (PLA2) enzymes has occurred in the twenty-first century. The superfamily includes 15 groups comprising four main types including the secreted sPLA2, cytosolic cPLA2, calcium-independent iPLA2, and platelet activating factor (PAF) acetyl hydrolase/oxidized lipid lipoprotein associated (Lp)PLA2. We review herein our current understanding of the structure and interaction with substrate phospholipids, which resides in membranes for a representative of each of these main types of PLA2. We will also briefly review the development of inhibitors of these enzymes and their roles in lipid signaling.
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Phospholipase A2 biochemistry
2009Co-Authors: John E Burke, Edward A. DennisAbstract:The Phospholipase A2 (PLA2) superfamily consists of many different groups of enzymes that catalyze the hydrolysis of the sn-2 ester bond in a variety of different phospholipids. The products of this reaction, a free fatty acid, and lysophospholipid have many different important physiological roles. There are five main types of PLA2: the secreted sPLA2’s, the cytosolic cPLA2’s, the CA2+independent iPLA2’s, the PAF acetylhydrolases, and the lysosomal PLA2’s. This review focuses on the superfamily of PLA2 enzymes, and then uses three specific examples of these enzymes to examine the differing biochemistry of the three main types of these enzymes. These three examples are the GIA cobra venom PLA2, the GIVA cytosolic cPLA2, and the GVIA CA2+-independent iPLA2.
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functional coupling between secretory Phospholipase A2 and cyclooxygenase 2 and its regulation by cytosolic group iv Phospholipase A2
1998Co-Authors: Jesus Balsinde, Maria A Balboa, Edward A. DennisAbstract:Secretory Phospholipase A2 (sPLA2) is the major effector involved in arachidonic acid (AA) mobilization and prostaglandin E2 (PGE2) production during stimulation of P388D1 macrophages with the inflammatory stimuli bacterial lipopolysaccharide and platelet-activating factor. We herein demonstrate that PGE2 in stimulated P388D1 cells is accounted for by the inducible cyclooxygenase (COX)-2. COX-1, though present, appears not to participate significantly in stimulus-induced PGE2 production in P388D1 macrophages. Reconstitution experiments utilizing exogenous recombinant sPLA2 demonstrate that activation of the sPLA2 at the plasma membrane is highly dependent on previous activation of the cytosolic Phospholipase A2 (cPLA2). Collectively these results demonstrate (i) that functional coupling exists between sPLA2 and COX-2 in activated cells, (ii) the critical role that cPLA2 plays in lipid mediator production, and (iii) that there is crosstalk between cPLA2 and sPLA2 in the cell.
Hitoshi Arita - One of the best experts on this subject based on the ideXlab platform.
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resistance to endotoxic shock in Phospholipase A2 receptor deficient mice
1997Co-Authors: Kohji Hanasaki, Yasunori Yokota, Jun Ishizaki, Takeshi Itoh, Hitoshi AritaAbstract:Abstract Mammals possess various types of secretory Phospholipase A2, which differ in the primary structure and tissue distribution. The phosholipase A2receptor (PLA2R) recognizes group IB Phospholipase A2 (PLA2-IB) and mediates the PLA2-IB-induced biological responses in non-digestive organs, including eicosanoid production and contraction of airway smooth muscles. In this study, we generated PLA2R-deficient mice to define its biological roles further. These mice are viable, fertile, and without evident histopathological abnormalities. There was no difference in the clearance of circulating PLA2-IB between wild-type and mutant mice. After challenge with bacterial lipopolysaccharide (LPS), PLA2R-deficient mice exhibited longer survival than wild-type mice. The mutant mice were also resistant to lethal effects of exogenous PLA2-IB after sensitization with sublethal dose of LPS. The plasma levels of tumor necrosis factor-α and interleukin-1β elevated after LPS treatment were significantly reduced in mutant mice compared with wild-type mice. These findings suggest a potential role of PLA2R in the progression of endotoxic shock.
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pancreatic type Phospholipase A2 induces group ii Phospholipase A2 expression and prostaglandin biosynthesis in rat mesangial cells
1994Co-Authors: Junji Kishino, Osamu Ohara, Koji Nomura, R M Kramer, Hitoshi AritaAbstract:The effect of pancreatic group I Phospholipase A2 (PLA2-I) on receptor-mediated expression of arthritic group II Phospholipase A2 (PLA2-II) and its correlation with prostaglandin E2 (PGE2) synthesis were examined in cultured rat mesangial cells. Scatchard analysis using 125I-PLA2-I revealed the existence of a single class of specific binding sites for PLA2-I in rat mesangial cells with an equilibrium dissociation constant (Kd) of 1.6 nM and a maximum binding capacity of 10.1 fmol/10(6) cells. The mammalian mature type of PLA2-I specifically recognized this binding site, whereas its inactive zymogen and mammalian PLA2-II showed much lower affinities. PLA2-I markedly increased PLA2-II mRNA levels as well as PLA2-II secretion from the cells in a time- and dose-dependent manner that was closely correlated with PGE2 production. Both PLA2-II expression and PGE2 synthesis were completely suppressed by pretreatment of the cells with actinomycin D, cycloheximide, or dexamethasone. These results strongly suggest that there may be crosstalk between PLA2-I and PLA2-II via the specific PLA2-I receptor that elicits PGE2 synthesis.
Stanley L Hazen - One of the best experts on this subject based on the ideXlab platform.
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the rapid and reversible activation of a calcium independent plasmalogen selective Phospholipase A2 during myocardial ischemia
1991Co-Authors: David A Ford, Stanley L Hazen, Jeffrey E Saffitz, Richard W. GrossAbstract:Abstract Recent studies have demonstrated the existence of two members of a novel family of calcium-independent plasmalogen-selective Phospholipases A2 in mammalian myocardium (Wolf, R. A., and R. W. Gross. 1985. J. Biol. Chem. 260:7295-7303; and Hazen, S. L., D. A. Ford, and R. W. Gross. 1991. J. Biol. Chem. 266:5629-5633). To examine the potential role of these calcium-independent Phospholipases A2 in mediating membrane dysfunction during early myocardial ischemia, the temporal course of alterations in Phospholipase A2 activity during global ischemia in Langendorf perfused rabbit hearts was quantified and compared with traditionally accepted markers of myocytic ischemic injury and anaerobic metabolism. We now report that membrane-associated calcium-independent plasmalogen-selective Phospholipase A2 activity increased over 400% during 2 min of global ischemia (P less than 0.01), was near maximally activated (greater than 10-fold) after only 5 min of ischemia, and remained activated throughout the entire ischemic interval examined (2-60 min). Activation of membrane-associated plasmalogen-selective Phospholipase A2 after 5 min of myocardial ischemia was rapidly reversible during reperfusion of ischemic tissue. Both the activation of Phospholipase A2 and its reversibility during reperfusion were temporally correlated to alterations in myocytic anaerobic metabolism. Furthermore, activation of membrane-associated Phospholipase A2 was essentially complete before electron microscopic evidence of cellular damage. Collectively, these results identify dynamic alterations in calcium-independent plasmalogen-selective Phospholipase A2 activity during myocardial ischemia which precede irreversible cellular injury and demonstrate that activation of plasmalogen-selective Phospholipase A2 is amongst the earliest biochemical alterations in ischemic myocardium.
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suicide inhibition of canine myocardial cytosolic calcium independent Phospholipase A2 mechanism based discrimination between calcium dependent and independent Phospholipases A2
1991Co-Authors: Stanley L Hazen, Lori A Zupan, Randy H Weiss, Daniel P Getman, Richard W. GrossAbstract:The majority of Phospholipase A2 activity in myocardium is calcium-independent and selective for hydrolysis of plasmalogen substrate (Wolf, R. A., and Gross, R. W. (1985) J. Biol. Chem. 260, 7295-7303; Hazen, S. L., Stuppy, R. J., and Gross, R. W. (1990) J. Biol. Chem. 265, 10622-10630). Accordingly, identification of an inhibitor which selectively targets calcium-independent Phospholipases A2 would facilitate elucidation of the biologic significance of this class of intracellular Phospholipases. We now report that the haloenol lactone, (E)-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one (Compound 1), is a potent, irreversible, mechanism-based inhibitor of myocardial calcium-independent Phospholipase A2 which is greater than 1000-fold specific for inhibition of myocardial calcium-independent Phospholipase A2 in comparisons with multiple calcium-dependent Phospholipases A2. Mechanism-based inhibition of myocardial cytosolic calcium-independent Phospholipase A2 by Compound 1 was established by demonstrating: 1) time-dependent irreversible inactivation; 2) covalent binding of [3H]Compound 1 to the purified Phospholipase A2; 3) ablation of covalent binding of [3H]Compound 1 after chemical inactivation of Phospholipase A2 enzymic activity; 4) identical inhibition of myocardial Phospholipase A2 by Compound 1 in the absence or presence of nucleophilic scavengers; 5) Compound 1 is a substrate for myocardial calcium-independent Phospholipase A2 resulting in the generation of the electrophilic alpha-bromomethyl ketone; 6) Phospholipase A2 inhibition requires the in situ generation of the reactive electrophile (i.e. neither the alpha-bromomethyl ketone nor the diproteoenol lactone analog are inhibitory); and 7) concomitant attenuation of the inhibitory potency and the extent of covalent adduct formation in the presence of saturating substrate. Collectively, these results demonstrate that the haloenol lactone, Compound 1, is a substrate for, covalently binds to, and irreversibly inhibits canine myocardial cytosolic calcium-independent Phospholipase A2.
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activation of a membrane associated Phospholipase A2 during rabbit myocardial ischemia which is highly selective for plasmalogen substrate
1991Co-Authors: Stanley L Hazen, David A Ford, Richard W. GrossAbstract:Abstract Recently, the prototype of a novel class of calcium-independent plasmalogen-selective Phospholipase A2 activities was identified in the cytosolic fraction of canine myocardium (Wolf, R.A., and Gross, R.W. (1985) J. Biol. Chem. 260, 7295-7303) and subsequently purified and characterized (Hazen, S.L., Stuppy, R.J., and Gross, R.W. (1990) J. Biol. Chem. 265, 10622-10630). We now demonstrate that 15 min of myocardial ischemia utilizing a rabbit Langendorf perfused heart model results in a 10-fold increase in membrane-associated calcium-independent Phospholipase A2 activity whose detection is entirely dependent upon utilization of plasmalogen substrate. Ischemia-induced Phospholipase activity was identified as a membrane bound member of this class of Phospholipases A2 by demonstration of: 1) concomitant production of lysoplasmenylcholine and sn-2 fatty acid from plasmenylcholine substrate; 2) maximal enzymatic activity in the absence of calcium ion; and 3) a 16-fold higher maximum reaction velocity utilizing plasmenylcholine compared to phosphatidylcholine substrate at multiple surface concentrations. Ischemia-induced Phospholipase A2 activity was specifically localized to the microsomal fraction and could not be solubilized by sonication, salt treatment, exposure to chelators, or utilization of submicellar concentrations of detergent. The appearance of microsomal Phospholipase A2 activity did not require ischemia-induced transcription or translation since identical increases in enzymic activity were obtained in hearts previously treated with actinomycin D and cycloheximide. Collectively, these results demonstrate that a membrane-associated calcium-independent Phospholipase A2 that selectively hydrolyzes plasmalogen molecular species is the likely enzymic mediator of accelerated phospholipid catabolism during early myocardial ischemia.
Colin H Macphee - One of the best experts on this subject based on the ideXlab platform.
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Effect of Darapladib Treatment on Endarterectomy Carotid Plaque Lipoprotein-Associated Phospholipase A2 Activity: A Randomized, Controlled Trial
2016Co-Authors: Joel L. Johnson, Rose Snipes, Salim Janmohamed, Timothy E. Rolfe, Bill Davis, Anthony D. Postle, Yi Shi, Colin H MacpheeAbstract:Background: The aim of this study was to assess the effects of darapladib, a selective oral investigational lipoprotein-associated Phospholipase A2 inhibitor, on both plasma and plaque lipoprotein-associated Phospholipase A2 activity. Methods: Patients undergoing elective carotid endarterectomy were randomized to darapladib 40 mg (n = 34), 80 mg (n = 34), or placebo (n = 34) for 14 days, followed by carotid endarterectomy 24 hours after the last dose of study medication. Results: Darapladib 40 mg and 80 mg reduced plasma lipoprotein-associated Phospholipase A2 activity by 52 % and 81%, respectively, versus placebo (both P,0.001). Significant reductions in plaque lipoprotein-associated Phospholipase A2 activity were also observed compared with placebo (P,0.0001), which equated to a 52 % and 80 % decrease compared with placebo. No significant differences were observed between groups in plaque lysophosphatidylcholine content or other biomarkers, although a dose-dependent decrease in plaque matrix metalloproteinase-9 mRNA expression was observed with darapladib 80 mg (P = 0.053 vs placebo). In a post-hoc analysis, plaque caspase-3 (P,0.001) and caspase-8 (P,0.05) activity were found to be significantly lower in the darapladib 80-mg group versus placebo. No major safety concerns were identified in the study. Conclusions: Short-term treatment (1464 days) with darapladib produced a robust, dose-dependent reduction in plasm
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Effect of darapladib treatment on endarterectomy carotid plaque lipoprotein-associated Phospholipase A2 activity: a randomized, controlled trial.
2014Co-Authors: Joel L. Johnson, Rose Snipes, Salim Janmohamed, Timothy E. Rolfe, Bill Davis, Anthony D. Postle, Colin H MacpheeAbstract:Background The aim of this study was to assess the effects of darapladib, a selective oral investigational lipoprotein-associated Phospholipase A2 inhibitor, on both plasma and plaque lipoprotein-associated Phospholipase A2 activity. Methods Patients undergoing elective carotid endarterectomy were randomized to darapladib 40 mg (n = 34), 80 mg (n = 34), or placebo (n = 34) for 14 days, followed by carotid endarterectomy 24 hours after the last dose of study medication. Results Darapladib 40 mg and 80 mg reduced plasma lipoprotein-associated Phospholipase A2 activity by 52% and 81%, respectively, versus placebo (both P
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effect of darapladib treatment on endarterectomy carotid plaque lipoprotein associated Phospholipase A2 activity a randomized controlled trial
2014Co-Authors: Joel L. Johnson, Rose Snipes, Salim Janmohamed, Timothy E. Rolfe, Bill Davis, Anthony D. Postle, Yi Shi, Colin H MacpheeAbstract:Background The aim of this study was to assess the effects of darapladib, a selective oral investigational lipoprotein-associated Phospholipase A2 inhibitor, on both plasma and plaque lipoprotein-associated Phospholipase A2 activity. Methods Patients undergoing elective carotid endarterectomy were randomized to darapladib 40 mg (n = 34), 80 mg (n = 34), or placebo (n = 34) for 14 days, followed by carotid endarterectomy 24 hours after the last dose of study medication. Results Darapladib 40 mg and 80 mg reduced plasma lipoprotein-associated Phospholipase A2 activity by 52% and 81%, respectively, versus placebo (both P<0.001). Significant reductions in plaque lipoprotein-associated Phospholipase A2 activity were also observed compared with placebo (P<0.0001), which equated to a 52% and 80% decrease compared with placebo. No significant differences were observed between groups in plaque lysophosphatidylcholine content or other biomarkers, although a dose-dependent decrease in plaque matrix metalloproteinase-9 mRNA expression was observed with darapladib 80 mg (P = 0.053 vs placebo). In a post-hoc analysis, plaque caspase-3 (P<0.001) and caspase-8 (P<0.05) activity were found to be significantly lower in the darapladib 80-mg group versus placebo. No major safety concerns were identified in the study. Conclusions Short-term treatment (14±4 days) with darapladib produced a robust, dose-dependent reduction in plasma lipoprotein-associated Phospholipase A2 activity. More importantly, darapladib demonstrated placebo-corrected reductions in carotid plaque lipoprotein-associated Phospholipase A2 activity of similar magnitude. Darapladib was generally well tolerated and no safety concerns were identified. Additional studies of longer duration are needed to explore whether these pharmacodynamic effects are associated with improved clinical outcomes, as might be hypothesized. Trial Registration Information Name of Registry 1: ClinicalTrials.gov Registry Number 1: NCT01916720 Trial URL in Registry Database 1: www.clinicaltrials.gov/ct2/show/NCT01916720 Name of Registry 2: GSK Clinical Study Register Registry Number 2∶480848/010 Trial URL in Registry Database 2: www.gsk-clinicalstudyregister.com/result_detail.jsp?protocolId=480848%2F010&studyId=74F5DB65-4661-4FA8-91D4-EBF78D769F24&compound=darapladib&type=Compound&letterrange=A-F