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Purification and characterization of sheep platelet cyclo-oxygenase. Acetylation by aspirin prevents haemin binding to the enzyme.

ABSTRACT: Arachidonate cyclo-oxygenase (prostaglandin synthetase; prostaglandin endoperoxide synthetase; EC 1.14.99.1) was purified from sheep platelets. The purification procedure involved hydrophobic column chromatography using either Ibuprofen-Sepharose, phenyl-Sepharose or arachidic acid-Sepharose as the first step followed by metal-chelate Sepharose and haemin-Sepharose affinity chromatography. The purified enzyme (Mr approximately 65,000) was homogeneous as observed by SDS/polyacrylamide-gel electrophoresis and silver staining. The enzyme was a glycoprotein with mannose as the neutral sugar. Haemin or haemoglobin was essential for activity. The purified enzyme could bind haemin exhibiting a characteristic absorption maximum at 410 nm. The enzyme after metal-chelate column chromatography could undergo acetylation by [acetyl-3H]aspirin. The labelled acetylated enzyme could not bind to haemin-Sepharose, presumably due to acetylation of a serine residue involved in the binding to haemin. The acetylated enzyme also failed to show its characteristic absorption maximum at 410 nm when allowed to bind haemin.

SUBMITTER: Boopathy R

PROVIDER: S-EPMC1147290 | biostudies-other | 1986 Oct

REPOSITORIES: biostudies-other

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The inhibition of platelet cyclo-oxygenase by aspirin is associated with the acetylation of a 72kDa polypeptide in the intracellular membranes.

Project description:Previous studies by Roth & Majerus [J. Clin. Invest. (1975) 56, 624-632] showed that exposure of platelets to [acetyl-14C]aspirin resulted in the radioactive labelling of three polypeptides, two of which were in the cytosol and not saturable, whilst the third was located in particulate material, and was saturated at 30 microM-aspirin. By using high voltage free flow electrophoresis to separate a platelet mixed membrane fraction into highly purified surface and intracellular membrane subfractions, we have confirmed that the major polypeptide acetylated after exposing whole platelets to [acetyl-14C]aspirin is almost exclusively associated with intracellular membrane structures. We have shown previously that these intracellular membranes are the major site for prostanoid biosynthesis [Carey, Menashi & Crawford (1982) Biochem. J. 204, 847-851] and in the present study the extent of the radioactive labelling correlated well with inhibition of the cyclo-oxygenase activity in these intracellular membranes. In sodium dodecyl sulphate/polyacrylamide-gel electrophoresis the [14C]acetylated component, which appears to be a dimer, migrates with a mobility corresponding to 72kDa. Although cyclo-oxygenase is inhibited, there is no discernible radioactive labelling when the platelets are exposed to aromatic-ring-labelled [14C]aspirin. We suggest that the site or sites for aspirin acetylation and cyclo-oxygenase activity are structurally associated in the platelet's intracellular membranes referred to by electron microscopists as the dense tubular membrane system.

| S-EPMC1144270 | biostudies-other

Differential impairment of aspirin-dependent platelet cyclooxygenase acetylation by nonsteroidal antiinflammatory drugs.

Project description:The cardiovascular safety of nonsteroidal antiinflammatory drugs (NSAIDs) may be influenced by interactions with antiplatelet doses of aspirin. We sought to quantitate precisely the propensity of commonly consumed NSAIDs—ibuprofen, naproxen, and celecoxib—to cause a drug-drug interaction with aspirin in vivo by measuring the target engagement of aspirin directly by MS. We developed a novel assay of cyclooxygenase-1 (COX-1) acetylation in platelets isolated from volunteers who were administered aspirin and used conventional and microfluidic assays to evaluate platelet function. Although ibuprofen, naproxen, and celecoxib all had the potential to compete with the access of aspirin to the substrate binding channel of COX-1 in vitro, exposure of volunteers to a single therapeutic dose of each NSAID followed by 325 mg aspirin revealed a potent drug-drug interaction between ibuprofen and aspirin and between naproxen and aspirin but not between celecoxib and aspirin. The imprecision of estimates of aspirin consumption and the differential impact on the ability of aspirin to inactivate platelet COX-1 will confound head-to-head comparisons of distinct NSAIDs in ongoing clinical studies designed to measure their cardiovascular risk.

| S-EPMC4250103 | biostudies-literature

Aspirin inhibits expression of sFLT1 from human cytotrophoblasts induced by hypoxia, via cyclo-oxygenase 1.

Project description:IntroductionElevated circulating soluble FLT1 (sFLT1) levels seen in preeclampsia may play a role in its development. Aspirin is recommended for prevention of preeclampsia. We hypothesized that aspirin may inhibit the production of sFlt1.MethodsPlacentas from women with and without preeclampsia were collected. Primary cytotrophoblasts (CTBs) were cultured from normal placentas and treated with aspirin, sc-560, a COX1 inhibitor or celecoxib, a COX2 inhibitor. The expression of sFLT1, FLT1, COX1 and COX2 was studied. The effect of aspirin on sFlt1 expression was also studied in HEK293 cells and in HTR-8/SVNeo cells.ResultsThe expression of sFLT1 was increased in preeclamptic placentas compared to control placentas and the expression and release of sFLT1 increased in CTBs exposed to 2% O2 compared to controls. Aspirin at 3 and 12 mM concentration reduced the expression and release of sFLT1 in CTBs. Aspirin also inhibited sFlt1 expression from HTR-8/SVNeo and HEK293 cells. Sc-560, but not celecoxib, reduced sFLT1 expression and release from CTBs. Aspirin and sc-560 also reduced hypoxia-induced FLT1 mRNA expression and inhibited COX1 mRNA in CTBs.DiscussionThis study confirms that sFLT1 expression is increased in preeclamptic placentas and in CTBs exposed to hypoxia. Aspirin inhibits the production sFLT1 in CTBs and in HTR-8/SVNeo. Sc-560 recapitulated the effects of aspirin on sFLT1 expression and release in CTBs suggesting that the aspirin effect may be mediated via inhibition of COX1. The study increases our understanding of the mechanisms regulating sFlt1 expression and provides a plausible explanation for the effect of aspirin to prevent preeclampsia.

| S-EPMC4359945 | biostudies-literature

Haemin-enhanced expression of haem oxygenase-1 stabilizes erythrocyte-induced vulnerable atherosclerotic plaques.

Project description:Previous studies demonstrated that intraplaque haemorrhage increased the contents of cholesterol and oxidants in atherosclerotic plaques. The present study was aimed to test the hypothesis that enhanced expression of haem oxygenase-1 (HO-1) may stabilize vulnerable plaques.Intravascular ultrasound (IVUS) was performed to identify three similar abdominal aortic plaques in each of 58 fat-fed New Zealand rabbits after aortic balloon injury. With the guidance of IVUS, 50 microL autologous erythrocytes (RBC) or normal saline (NS) were injected from adventitia into two of the pre-selected plaques, respectively, whereas the third plaque served as a blank control. All rabbits were randomly divided into two groups, receiving intraperitoneal injection of haemin and saline respectively.Compared with NS or control plaques, RBC plaques had more macrophage infiltration and lipid content, thinner plaque fibrous cap, and higher expression of inflammatory factors and incidence of plaque rupture. RBC plaques in the haemin group had about a 50% lower incidence of plaque rupture than those in the control group.Haem oxygenase-1 may eliminate haem or other oxidants, exert unexpected anti-oxidative and anti-inflammatory effects and serve as a promising approach to the direct inhibition of erythrocyte-induced plaque instability.

| S-EPMC2938819 | biostudies-literature

Shotgun proteomics data on the impact of hyperglycaemia on platelet protein acetylation by aspirin.

Project description:This data article associated with the manuscript "A high glucose levels is associated with decreased aspirin-mediated acetylation of platelet cyclooxygenase (COX)-1 at serine 529: a pilot study" (Finamore et al., 2018) refers to the shotgun proteomics approach carried out on platelet protein extracts from diabetic patients and healthy controls. Platelet proteins were in vitro incubated with 500 µM aspirin for 30 min at 37 °C to enhance the acetylation process. After protein digestion with trypsin, DDA data were acquired on a Thermo QExactive plus using 3 technical replicate injections per sample. Here, we were able to elucidate the preferential sites of aspirin-induced acetylation on a significant fraction of the platelet proteome and to quantify the impact of diabetes on the effect of aspirin on several platelet proteins. Data are available via ProteomeXchange with identifier PXD011582.

| S-EPMC6288982 | biostudies-literature

Risk of upper gastrointestinal ulcer bleeding associated with selective cyclo-oxygenase-2 inhibitors, traditional non-aspirin non-steroidal anti-inflammatory drugs, aspirin and combinations.

Project description:BackgroundThe risks and benefits of coxibs, non-steroidal anti-inflammatory drugs (NSAIDs), and aspirin treatment are under intense debate.ObjectiveTo determine the risk of peptic ulcer upper gastrointestinal bleeding (UGIB) associated with the use of coxibs, traditional NSAIDs, aspirin or combinations of these drugs in clinical practice.MethodsA hospital-based, case-control study in the general community of patients from the National Health System in Spain. The study included 2777 consecutive patients with endoscopy-proved major UGIB because of the peptic lesions and 5532 controls matched by age, hospital and month of admission. Adjusted relative risk (adj RR) of UGIB determined by conditional logistic regression analysis is provided.ResultsUse of non-aspirin-NSAIDs increased the risk of UGIB (adj RR 5.3; 95% confidence interval (CI) 4.5 to 6.2). Among non-aspirin-NSAIDs, aceclofenac (adj RR 3.1; 95% CI 2.3 to 4.2) had the lowest RR, whereas ketorolac (adj RR 14.4; 95% CI 5.2 to 39.9) had the highest. Rofecoxib treatment increased the risk of UGIB (adj RR 2.1; 95% CI 1.1 to 4.0), whereas celecoxib, paracetamol or concomitant use of a proton pump inhibitor with an NSAID presented no increased risk. Non-aspirin antiplatelet treatment (clopidogrel/ticlopidine) had a similar risk of UGIB (adj RR 2.8; 95% CI 1.9 to 4.2) to cardioprotective aspirin at a dose of 100 mg/day (adj RR 2.7; 95% CI 2.0 to 3.6) or anticoagulants (adj RR 2.8; 95% CI 2.1 to 3.7). An apparent interaction was found between low-dose aspirin and use of non-aspirin-NSAIDs, coxibs or thienopyridines, which increased further the risk of UGIB in a similar way.ConclusionsCoxib use presents a lower RR of UGIB than non-selective NSAIDs. However, when combined with low-dose aspirin, the differences between non-selective NSAIDs and coxibs tend to disappear. Treatment with either non-aspirin antiplatelet or cardioprotective aspirin has a similar risk of UGIB.

| S-EPMC1856452 | biostudies-literature

Platelet Carbonic Anhydrase II, a Forgotten Enzyme, May Be Responsible for Aspirin Resistance.

Project description:Thromboembolic events constitute a major health problem, despite the steadily expanding arsenal of antiplatelet drugs. Hence, there is still a need to optimize the antiplatelet therapy.The aim of our study was to verify a hypothesis that there are no differences in platelet proteome between two groups of healthy people representing different acetylsalicylic acid (aspirin) responses as assessed by the liquid chromatography/mass spectrometry (LC/MS) technique.A total of 61 healthy volunteers were recruited for the study. Physical examination and blood collection were followed by platelet-rich plasma aggregation assays and platelet separation for proteomic LC/MS analysis. Arachidonic acid- (AA-) induced aggregation (in the presence of aspirin) allowed to divide study participants into two groups aspirin-resistant (AR) and aspirin-sensitive (AS) ones. Subsequently, platelet proteome was compared in groups using the LC/MS analysis.The LC/MS analysis of platelet proteome between groups revealed that out of all identified proteins, the only discriminatory protein, affecting aspirin responsiveness, is platelet carbonic anhydrase II (CA II).CA II is a platelet function modulator and should be taken into consideration as a cardiovascular event risk factor or therapeutic target.

| S-EPMC5635279 | biostudies-literature

Localization of cyclo-oxygenase and thromboxane synthetase in human platelet intracellular membranes.

Project description:Platelet mixed membrane fractions can be separated into discrete vesicle subpopulations of surface and intracellular origin. Intracellular membrane vesicles are the predominant site of phospholipid-modifying enzymes that liberate arachidonic acid. We report the selective enrichment in intracellular membranes of cyclo-oxygenase and thromboxane synthetase activities. Surface membrane fractions show no such enrichment. These results suggest that a sequence of activities leading to the biosynthesis of thromboxane from arachidonate is associated with the intracellular membrane elements known as dense tubular membranes.

| S-EPMC1158429 | biostudies-other

Low concentrations of lipid hydroperoxides prime human platelet aggregation specifically via cyclo-oxygenase activation.

Project description:There is mounting evidence that lipid peroxides contribute to pathophysiological processes and can modulate cellular functions. The aim of the present study was to investigate the effects of lipid hydroperoxides on platelet aggregation and arachidonic acid (AA) metabolism. Human platelets, isolated from plasma, were incubated with subthreshold (i.e. non-aggregating) concentrations of AA in the absence or presence of hydroperoxyeicosatetraenoic acids (HPETEs). Although HPETEs alone had no effect on platelet function, HPETEs induced the aggregation of platelets co-incubated with non-aggregating concentrations of AA, HPETEs being more potent than non-eicosanoid peroxides. The priming effect of HPETEs on platelet aggregation was associated with an increased formation of cyclo-oxygenase metabolites, in particular thromboxane A2, and was abolished by aspirin, suggesting an activation of cyclo-oxygenase by HPETEs. It was not receptor-mediated because the 12-HPETE-induced enhancement of AA metabolism was sustained in the presence of SQ29, 548 or RGDS, which blocked the aggregation. These results indicate that physiologically relevant concentrations of HPETEs potentiate platelet aggregation, which appears to be mediated via a stimulation of cyclo-oxygenase activity.

| S-EPMC1218587 | biostudies-other

MZe786, a hydrogen sulfide-releasing aspirin prevents preeclampsia in heme oxygenase-1 haplodeficient pregnancy under high soluble flt-1 environment.

Project description:Preeclampsia affects one in twelve of the 130 million pregnancies a year. The lack of an effective therapeutic to prevent or treat it is responsible for an annual global cost burden of 100 billion US dollars. Preeclampsia also affects these women later in life as it is a recognised risk factor for cardiovascular disease, stroke and vascular dementia. Our laboratory demonstrated that preeclampsia is associated with high soluble fms-like tyrosine kinase 1 (sFlt-1) and low heme oxygenase-1 (HO1/Hmox1) expression. Here we sought to determine the therapeutic value of a novel H2S-releasing aspirin (MZe786) in HO-1 haploid deficient (Hmox1+/-) pregnant mice in a high sFlt-1 environment. Pregnant Hmox1+/- mice were injected with adenovirus encoding sFlt-1 or control virus at gestation day E11.5. Subsequently, Hmox1+/- dams were treated daily with a number of treatment regimens until E17.5, when maternal and fetal outcomes were assessed. Here we show that HO-1 compromised mice in a high sFlt-1 environment during pregnancy exhibit severe preeclampsia signs and a reduction in antioxidant genes. MZe786 ameliorates preeclampsia by reducing hypertension and renal damage possibly by stimulating antioxidant genes. MZe786 also improved fetal outcome in comparison with aspirin alone and appears to be a better therapeutic agent at preventing preeclampsia than aspirin alone.

| S-EPMC7610044 | biostudies-literature

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