A three-step kinetic mechanism for selective inhibition of cyclo-oxygenase-2 by diarylheterocyclic inhibitors.
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ABSTRACT:
SUBMITTER: Walker MC
PROVIDER: S-EPMC1222000 | biostudies-other | 2001 Aug
REPOSITORIES: biostudies-other
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Project description:Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the formation of prostaglandins by cyclo-oxygenases (COX). The discovery of a second COX isoform (COX-2) associated with inflammation led to agents that selectively inhibit COX-2, e.g. celecoxib. We evaluated the kinetics of inhibition of celecoxib and several NSAIDs. Celecoxib displays classic competitive kinetics on COX-1 (Ki=10-16 microM). An initial competitive interaction with COX-2 can also be discerned with celecoxib (Ki=11-15 microM), followed by a time-dependent interaction leading to potent inhibition, characterized as inactivation (Kinact=0.03-0.5 s-1). Half-maximal inhibition (IC50) using end-point assays reflects the competitive component on COX-1 (IC50=4-19 microM) and the inactivation component on COX-2 (IC50=0.003-0.006 microM). NSAIDs exhibit four distinct modes of COX inhibition based on kinetic behaviour: (1) competitive, e.g. ibuprofen; (2) weak binding, time-dependent, e.g. naproxen, oxicams; (3) tight binding, time-dependent, e.g. indomethacin; (4) covalent, e.g. aspirin. In addition, most NSAIDs display different kinetic behaviour for each isoform. Weakly binding inhibitors show variable behaviour in enzyme assays, with apparent inhibitory activity being markedly influenced by experimental conditions; determination of kinetic constants with this class is unreliable and IC50 values are strongly dependent on assay conditions. Although IC50 determinations are useful for structure/activity analyses, the complex and distinct mechanisms of enzyme inhibition of each COX isoform by the NSAIDs renders comparison of inhibitory activity on COX-1 and COX-2 using IC50 ratios of questionable validity.
| S-EPMC1220196 | biostudies-other
Project description:BackgroundDifferences between gastrointestinal and cardiovascular effects of traditional NSAID or cyclooxygenase-2 selective inhibitor (coxib) are affected by drug, dose, duration, outcome definition, and patient gastrointestinal and cardiovascular risk factors. We calculated the absolute risk for each effect.MethodsWe sought studies with large amounts of information to calculate annualised rates for clearly defined gastrointestinal (complicated upper gastrointestinal perforations, ulcers, or bleeds, but not symptomatic or endoscopic ulcers) and serious cardiovascular outcomes (antiplatelet trial collaborators - APTC - outcome of fatal or nonfatal myocardial infarction or stroke, or vascular death).ResultsMeta-analyses and large randomised trials specifically analysing serious gastrointestinal bleeding or cardiovascular events occurring with five different coxibs had appropriate data. In total there were 439 complicated upper gastrointestinal events in 49,006 patient years of exposure and 948 serious cardiovascular events in 99,400 patient years of exposure. Complicated gastrointestinal events occurred less frequently with coxibs than NSAIDs; serious cardiovascular events occurred at approximately equal rates. For each coxib, the reduction in complicated upper gastrointestinal events was numerically greater than any increase in APTC events. In the overall comparison, for every 1000 patients treated for a year with coxib rather than NSAID, there would be eight fewer complicated upper gastrointestinal events, but one more fatal or nonfatal heart attack or stroke. Three coxib-NSAID comparisons had sufficient numbers of events for individual comparisons. For every 1000 patients treated for a year with celecoxib rather than an NSAID there would be 12 fewer upper gastrointestinal complications, and two fewer fatal or nonfatal heart attacks or strokes. For rofecoxib there would be six fewer upper gastrointestinal complications, but three more fatal or nonfatal heart attacks or strokes. For lumiracoxib there would be eight fewer upper gastrointestinal complications, but one more fatal or nonfatal heart attack or stroke.ConclusionCalculating annualised event rates for gastrointestinal and cardiovascular harm shows that while complicated gastrointestinal events occur more frequently with NSAIDs than coxibs, serious cardiovascular events occur at approximately equal rates. For each coxib, the reduction in complicated upper gastrointestinal events was numerically greater than any increase in APTC events.
| S-EPMC2001315 | biostudies-literature
Project description:In the title compound, 5-(4-chloro-phen-yl)-1-(4-methoxy-phen-yl)-3-(trifluoro-meth-yl)-1H-pyrazole (SC-560), C(17)H(12)ClF(3)N(2)O, a COX-1-selective inhibitor, the dihedral angles between the heterocycle and the chlorobenzene and methoxybenzene rings are 41.66?(6) and 43.08?(7)°, respectively. The dihedral angle between the two phenyl rings is 59.94?(6)°. No classic hydrogen bonds are possible in the crystal, and intermolecular interactions must be mainly of the dispersion type. This information may aid the identification of dosage formulations with improved oral bioavailability.
| S-EPMC2968361 | biostudies-other
Project description:Carbamates are a widely used class of insecticides and herbicides. They were tested for their ability to affect human blood platelet aggregation and arachidonic acid metabolism in platelets. (1) The herbicides of the carbamate type have no, or only little, influence up to a concentration of 100 microM; the carbamate insecticides, however, inhibit both aggregation and arachidonic acid metabolism in a dose- and time-dependent manner. (2) Carbaryl, the most effective compound, inhibits platelet aggregation and cyclo-oxygenase activity completely at 10 microM. The liberation of arachidonic acid from phospholipids and the lipoxygenase pathway are not affected, whereas the products of the cyclo-oxygenase pathway are drastically decreased. (3) By using [14C]carbaryl labelled in the carbamyl or in the ring moiety, it could be proved that the carbamyl residue binds covalently to platelet proteins. In contrast with acetylsalicylic acid, which acetylates only one protein, carbaryl carbamylates a multitude of platelet proteins. (4) One of the carbamylated proteins was found to be the platelet cyclo-oxygenase, indicating that carbaryl resembles in this respect acetylsalicylic acid, which is known to inhibit this enzyme specifically by acetylation.
| S-EPMC1148821 | biostudies-other
Project description:The enzyme cyclo-oxygenase catalyses the oxygenation of arachidonic acid, leading to the formation of prostaglandins. Recently two forms of cyclo-oxygenase have been described: a constitutive (COX-1) enzyme present in most cells and tissues, and an inducible (COX-2) isoenzyme observed in many cells in response to pro-inflammatory cytokines. Constitutive and inducible forms of human cyclo-oxygenase (hCOX-1 and hCOX-2) were cloned and expressed in insect cells, utilizing a baculovirus expression system. hCOX-1 had a specific activity of 18.8 mumol of O2/mg with a Km of 13.8 microM for arachidonate and Vmax. of 1500 nmol of O2/nmol of enzyme, whereas hCOX-2 had a specific activity of 12.2 mumol of O2/mg with a Km of 8.7 microM for arachidonate and a Vmax. of 1090 nmol of O2/nmol of enzyme. Indomethacin inhibited both hCOX-1 and hCOX-2, whereas NS-398 and Dup-697 selectively inhibited hCOX-2. Both NS-398 and Dup-697 exhibited time-dependent inactivation of hCOX-2, as did indomethacin on both enzymes. The competitive inhibitor of hCOX-1, mefenamic acid, also displayed competitive inhibition of hCOX-2. These results demonstrate the ability to generate selective non-steroidal anti-inflammatory drugs (NSAIDs), which could provide useful improvement therapeutically in the treatment of chronic inflammatory disease.
| S-EPMC1136387 | biostudies-other
Project description:ObjectiveTo assess the comparative efficacy of traditional non-steroidal anti-inflammatory drugs (NSAIDs) and selective cyclo-oxygenase-2 inhibitors in patients with acute gout.DesignSystematic review and meta-analysis.Data sourcesMedline, Web of Science, China National Knowledge Infrastructure and Wanfang Data published as of 4 April 2020.MethodsWe performed meta-analysis of randomised controlled trials (RCTs) of traditional non-selective NSAIDs versus cyclo-oxygenase-2 inhibitors and RCTs of various cyclo-oxygenase-2 inhibitors in patients with acute gout. The main outcome measures were mean change in pain Visual Analogue Scale (VAS) score and 5-point Likert scale score on days 2-8.ResultsTwenty-four trials involving five drugs were evaluated. For pain Likert scale, etoricoxib was comparable to indomethacin (standardised mean difference (SMD): -0.09, 95% CI: -0.27 to 0.08) but better than diclofenac 50 mg three times a day (SMD: -0.53, 95% CI: -0.98 to 0.09). Regarding pain VAS score, etoricoxib was comparable to diclofenac 75 mg two times per day (SMD: -1.63, 95% CI: -4.60 to 1.34) and diclofenac 75 mg four times a day (SMD: -1.82, 95% CI: -5.18 to 1.53), while celecoxib was comparable to diclofenac 100 mg four times a day (SMD: -2.41, 95% CI: -5.91 to 1.09). Etoricoxib showed similar patients' global assessment of response (SMD: -0.10, 95% CI: -0.27 to 0.07) and swollen joint count (SMD: -0.25, 95% CI: -0.74 to 0.24), but better investigator's global assessment of response (SMD: -0.29, 95% CI: -0.46 to 0.11) compared with indomethacin. Etoricoxib showed more favourable pain VAS score than celecoxib (SMD: -2.36, 95% CI: -3.36 to 1.37), but was comparable to meloxicam (SMD: -4.02, 95% CI: -10.28 to 2.24). Etoricoxib showed more favourable pain Likert scale than meloxicam (SMD: -0.56, 95% CI: -1.10 to 0.02). Etoricoxib 120 mg four times a day was more likely to achieve clinical improvement than celecoxib 200 mg two times per day (OR: 4.84, 95% CI: 2.19 to 10.72).ConclusionAlthough cyclo-oxygenase-2 inhibitors and traditional non-selective NSAIDs may be equally beneficial in terms of pain relief, cyclo-oxygenase-2 inhibitors (especially etoricoxib) may confer a greater benefit.
| S-EPMC7485255 | biostudies-literature
Project description:AIMS: To investigate whether polymorphisms of the cyclo-oxygenase-2 (COX-2) gene modify the adverse cardiovascular effects of COX-2 inhibitors. METHODS: A case control study was conducted in the Hunter Region of New South Wales, Australia. Cases (n= 460) were hospitalized with acute coronary syndrome (ACS). Controls (n= 640) were recruited from the electoral rolls. Structured interviews gathered information on variables including recent ingestion of non-steroidal anti-inflammatory drugs (NSAIDs). Targeted genotyping of rs 20417(G > C) and rs5275 (T > C) polymorphisms was performed by real-time polymerase chain reaction using allele-specific probes. RESULTS: Ingestion of any NSAID in the week prior to interview was associated with an elevated risk for ACS: adjusted odds ratio 1.8 (1.2, 2.5). The rs 20417 and rs 5275 polymorphisms were not singly associated with risk for ACS: adjusted odds ratios 1.1 (0.80, 1.5) and 1.2 (0.88, 1.5), respectively. Individually, the polymorphisms did not modify the risk of ACS with the drugs. When analyses were conducted by haplotype, the adjusted odds ratio with celecoxib or rofecoxib in individuals who had one or two copies of the 'low risk' haplotype (no GT) was 1.2 (0.29, 5.0), compared with 2.1 (1.1, 4.0) with the 'high risk' haplotype (one or two copies of GT). CONCLUSIONS: We found little evidence of a gene/drug interaction. We found a statistically non-significant trend toward a lower risk of coronary events with NSAIDs in the presence of the 'low risk' haplotype. Even if confirmed, the clinical utility of the finding would be limited as this haplotype is carried by a minority of the population.
| S-EPMC3195745 | biostudies-literature
Project description:BackgroundLeukotriene (LT) B4 concentrations are increased and prostaglandin (PG) E2 concentrations are decreased in exhaled breath condensate (EBC) in patients with chronic obstructive pulmonary disease (COPD). A study was undertaken to investigate the short term effects of cyclo-oxygenase (COX) inhibition on exhaled LTB4 and PGE2 concentrations in patients with COPD and to identify the COX isoform responsible for exhaled PGE2 production.MethodsTwo studies were performed. A double blind, crossover, randomised, placebo controlled study with ibuprofen (400 mg qid for 2 days), a non-selective COX inhibitor, was undertaken in 14 patients with stable COPD, and an open label study with oral rofecoxib (25 mg once a day for 5 days), a selective COX-2 inhibitor, was undertaken in a different group of 16 COPD patients. EBC was collected before and after drug treatment. Exhaled LTB4 and PGE2 concentrations were measured with specific immunoassays.ResultsAll patients complied with treatment as indicated by a reduction in ex vivo serum thromboxane B2 concentrations (ibuprofen) and a reduction in lipopolysaccharide induced increase in ex vivo plasma PGE2 values (rofecoxib) of more than 80%. Exhaled LTB4 was increased after ibuprofen (median 175.5 (interquartile range 128.8-231.5) pg/ml v 84.0 (70.0-98.5) pg/ml, p < 0.001) and exhaled PGE2 was reduced (93.5 (84.0-105-5) pg/ml v 22.0 (15.0-25.5) pg/ml, p < 0.0001). Rofecoxib had no effect on exhaled LTB4 (p = 0.53) or PGE2 (p = 0.23).ConclusionsNon-selective COX inhibition decreases PGE2 and increases LTB4 in EBC, whereas selective COX-2 inhibition has no effect on these eicosanoids. PGE2 in EBC is primarily derived from COX-1 activity, and COX inhibition may redirect arachidonic acid metabolism towards the 5-lipoxygenase pathway.
| S-EPMC1747215 | biostudies-literature
Project description:ObjectiveTo assess the effects of selective cyclo-oxygenase-2 (COX 2) inhibitors and traditional non-steroidal anti-inflammatory drugs (NSAIDs) on the risk of vascular events.DesignMeta-analysis of published and unpublished tabular data from randomised trials, with indirect estimation of the effects of traditional NSAIDs.Data sourcesMedline and Embase (January 1966 to April 2005); Food and Drug Administration records; and data on file from Novartis, Pfizer, and Merck.Review methodsEligible studies were randomised trials that included a comparison of a selective COX 2 inhibitor versus placebo or a selective COX 2 inhibitor versus a traditional NSAID, of at least four weeks' duration, with information on serious vascular events (defined as myocardial infarction, stroke, or vascular death). Individual investigators and manufacturers provided information on the number of patients randomised, numbers of vascular events, and the person time of follow-up for each randomised group.ResultsIn placebo comparisons, allocation to a selective COX 2 inhibitor was associated with a 42% relative increase in the incidence of serious vascular events (1.2%/year v 0.9%/year; rate ratio 1.42, 95% confidence interval 1.13 to 1.78; P = 0.003), with no significant heterogeneity among the different selective COX 2 inhibitors. This was chiefly attributable to an increased risk of myocardial infarction (0.6%/year v 0.3%/year; 1.86, 1.33 to 2.59; P = 0.0003), with little apparent difference in other vascular outcomes. Among trials of at least one year's duration (mean 2.7 years), the rate ratio for vascular events was 1.45 (1.12 to 1.89; P = 0.005). Overall, the incidence of serious vascular events was similar between a selective COX 2 inhibitor and any traditional NSAID (1.0%/year v 0.9%/year; 1.16, 0.97 to 1.38; P = 0.1). However, statistical heterogeneity (P = 0.001) was found between trials of a selective COX 2 inhibitor versus naproxen (1.57, 1.21 to 2.03) and of a selective COX 2 inhibitor versus non-naproxen NSAIDs (0.88, 0.69 to 1.12). The summary rate ratio for vascular events, compared with placebo, was 0.92 (0.67 to 1.26) for naproxen, 1.51 (0.96 to 2.37) for ibuprofen, and 1.63 (1.12 to 2.37) for diclofenac.ConclusionsSelective COX 2 inhibitors are associated with a moderate increase in the risk of vascular events, as are high dose regimens of ibuprofen and diclofenac, but high dose naproxen is not associated with such an excess.
| S-EPMC1473048 | biostudies-literature
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