Low-dose naproxen interferes with the antiplatelet effects of aspirin in healthy subjects: recommendations to minimize the functional consequences.

OBJECTIVE: To investigate whether low-dose naproxen sodium (220 mg twice a day) interferes with aspirin's antiplatelet effect in healthy subjects. METHODS: We performed a crossover, open-label study in 9 healthy volunteers. They received for 6 days 3 different treatments separated by 14 days of washout: 1) naproxen 2 hours before aspirin, 2) aspirin 2 hours before naproxen, and 3) aspirin alone. The primary end point was the assessment of serum thromboxane B(2) (TXB(2)) 24 hours after the administration of naproxen 2 hours before aspirin on day 6 of treatment. In 5 volunteers, the rate of recovery of TXB(2) generation (up to 72 hours after drug discontinuation) was assessed in serum and in platelet-rich plasma stimulated with arachidonic acid (AA) or collagen. RESULTS: Twenty-four hours after the last dosing on day 6 in volunteers receiving aspirin alone or aspirin before naproxen, serum TXB(2) was almost completely inhibited (median [range] 99.1% [97.4-99.4%] and 99.1% [98.0-99.7%], respectively). Naproxen given before aspirin caused a slightly lower inhibition of serum TXB(2) (median [range] 98.0% [90.6-99.4%]) than aspirin alone (P = 0.0007) or aspirin before naproxen (P = 0.0045). All treatments produced a maximal inhibition of AA-induced platelet aggregation. At 24 hours, compared with baseline, collagen-induced platelet aggregation was still inhibited by aspirin alone (P = 0.0003), but not by aspirin given 2 hours before or after naproxen. Compared with administration of aspirin alone, the sequential administration of naproxen and aspirin caused a significant parallel upward shift of the regression lines describing the recovery of platelet TXB(2). CONCLUSION: Sequential administration of 220 mg naproxen twice a day and low-dose aspirin interferes with the irreversible inhibition of platelet cyclooxygenase 1 afforded by aspirin. The interaction was smaller when giving naproxen 2 hours after aspirin. The clinical consequences of these 2 schedules of administration of aspirin with naproxen remain to be studied in randomized clinical trials.

De novo synthesis of cyclooxygenase-1 counteracts the suppression of platelet thromboxane biosynthesis by aspirin.

Aspirin affords cardioprotection through the acetylation of serine529 in human cyclooxygenase-1 (COX-1) of anucleated platelets, inducing a permanent defect in thromboxane A2 (TXA2)-dependent platelet function. However, heterogeneity of COX-1 suppression by aspirin has been detected in cardiovascular disease and may contribute to failure to prevent clinical events. The recent recognized capacity of platelets to make proteins de novo paves the way to identify new mechanisms involved in the variable response to aspirin. We found that in washed human platelets, the complete suppression of TXA2 biosynthesis by aspirin, in vitro, recovered in response to thrombin and fibrinogen in a time-dependent fashion (at 0.5 and 24 hours, TXB2 averaged 0.1+/-0.03 and 3+/-0.8 ng/mL; in the presence of arachidonic acid [10 micromol/L], it was 2+/-0.7 and 25+/-7 ng/mL, respectively), and it was blocked by translational inhibitors, by rapamycin, and by inhibitors of phosphatidylinositol 3-kinase. The results that COX-1 mRNA was readily detected in resting platelets and that [35S]-methionine was incorporated into COX-1 protein after stimulation strongly support the occurrence of de novo COX-1 synthesis in platelets. This process may interfere with the complete and persistent suppression of TXA2 biosynthesis by aspirin necessary for cardioprotection.

Reduced Variability to Aspirin Antiplatelet Effect by the Coadministration of Statins in High-Risk Patients for Cardiovascular Disease.

We studied the influence of cardiovascular (CV) risk factors, previous CV events, and cotreatments with preventive medicines, on residual platelet thromboxane (TX)B2 production in 182 patients chronically treated with enteric coated (EC)-aspirin (100 mg/day). The response to aspirin was also verified by assessing arachidonic acid-induced platelet aggregation and urinary 11-dehydro-TXB2 levels. Residual serum TXB2 levels exceeded the upper limit value for an adequate aspirin response in 14% of individuals. This phenomenon was detected at 12 hours after dosing with aspirin. The coadministration of statins (mostly atorvastatin) was an independent predictor of residual serum TXB2 levels, and the percentage of patients with enhanced values was significantly lower in statin users vs. nonusers. We provide evidence in vitro that atorvastatin reduced residual TXB2 generation by increasing the extent of acetylation of platelet COX-1 by aspirin. In conclusion, the coadministration of statins may counter the mechanisms associated with reduced bioavailability of aspirin detected in some individuals with CV disease.

Pharmacodynamic of cyclooxygenase inhibitors in humans.

We provide comprehensive knowledge on the differential regulation of expression and catalysis of cyclooxygenase (COX)-1 and COX-2 in health and disease which represents an essential requirement to read out the clinical consequences of selective and nonselective inhibition of COX-isozymes in humans. Furthermore, we describe the pharmacodynamic and pharmacokinetic characteristics of major traditional nonsteroidal anti-inflammatory drugs (tNSAIDs) and coxibs (selective COX-2 inhibitors) which play a prime role in their efficacy and toxicity. Important information derived from our pharmacological studies has clarified that nonselective COX inhibitors should be considered the tNSAIDs with a balanced inhibitory effect on both COX-isozymes (exemplified by ibuprofen and naproxen). In contrast, the tNSAIDs meloxicam, nimesulide and diclofenac (which are from 18- to 29-fold more potent towards COX-2 in vitro) and coxibs (i.e. celecoxib, valdecoxib, rofecoxib, etoricoxib and lumiracoxib, which are from 30- to 433-fold more potent towards COX-2 in vitro) should be comprised into the cluster of COX-2 inhibitors. However, the dose and frequency of administration together with individual responses will drive the degree of COX-2 inhibition and selectivity achieved in vivo. The results of clinical pharmacology of COX inhibitors support the concept that the inhibition of platelet COX-1 may translate into an increased incidence of serious upper gastrointestinal bleeding but this effect on platelet COX-1 may mitigate the cardiovascular hazard associated with the profound inhibition of COX-2-dependent prostacyclin (PGI2).

Heterogeneity in the suppression of platelet cyclooxygenase-1 activity by aspirin in coronary heart disease.

BACKGROUND AND OBJECTIVES: Complete and persistent suppression of platelet thromboxane (TX) A(2) biosynthesis by aspirin is mandatory to fulfill its cardioprotection. We explored the determinants of heterogeneity of TXB2 generation in clotting whole blood, a capacity index of platelet cyclooxygenase (COX) activity, in patients with coronary heart disease (CHD) versus healthy subjects treated with low-dose aspirin on a long-term basis. METHODS: We studied 30 patients with CHD (ie, chronic stable angina, unstable angina, and acute myocardial infarction) and 10 healthy subjects, who were treated with low-dose aspirin (100 mg daily) on a long-term basis, 12 hours after the administration of 160 mg aspirin to ensure saturation of platelet COX-1 activity. Serum TXB2 levels were assessed. The contribution of blood COX-2 to TXA2 biosynthesis was explored by evaluation of the effect of a selective COX-2 inhibitor (L-745,337) added to heparinized whole blood stimulated with Ca++ ionophore A23187 (20 micromol/L) for 1 hour or lipopolysaccharide (0.1 microg/mL) for 4 hours. RESULTS: In healthy subjects serum TXB2 levels ranged from 0.6 to 7.9 ng/mL (median, 2.1 ng/mL; mean +/- SD, 3.2 +/- 2.6 ng/mL). In CHD patients we detected enhanced variability in serum TXB2 generation (median, 3.1 ng/mL [range, 0.15-47 ng/mL]; mean, 8.5 +/- 12.3 ng/mL), which in 8 patients (27%) exceeded the mean value + 2 SDs detected in healthy subjects (ie, 8.4 ng/mL), set as the limit value for an adequate inhibition of platelet COX-1 by aspirin. Elevated whole-blood TXB2 generation was not dependent on leukocyte count, COX-2 activity, or cigarette smoking but was plausibly a result of defective suppression of platelet COX-1 activity. CONCLUSIONS: Heterogeneity in the suppression of platelet COX-1 activity by aspirin occurred in CHD patients. The measurement of the serum TXB2 level seems to be an appropriate biomarker to identify patients who have an inadequate inhibition of platelet COX-1 activity by aspirin.

Celecoxib, ibuprofen, and the antiplatelet effect of aspirin in patients with osteoarthritis and ischemic heart disease.

BACKGROUND AND OBJECTIVE: We performed a placebo-controlled, randomized study to address whether celecoxib or ibuprofen undermines the functional range of inhibition of platelet cyclooxygenase (COX)-1 activity by aspirin in patients with osteoarthritis and stable ischemic heart disease. METHODS: Twenty-four patients who were undergoing long-term treatment with aspirin (100 mg daily) for cardioprotection were coadministered celecoxib, 200 mg twice daily, ibuprofen, 600 mg 3 times daily, or placebo for 7 days. RESULTS: The coadministration of placebo or celecoxib did not undermine the aspirin-related inhibition of platelet COX-1 activity, as assessed by measurements of serum thromboxane B(2) (TXB(2)) levels, as well as platelet function. In contrast, a significant (P < .001) increase in serum TXB(2) level was detected on day 7 before drug administration (median, 19.13 ng/mL [range, 1-47.5 ng/mL]) and at 24 hours after the coadministration of aspirin and ibuprofen (median, 22.28 ng/mL [range, 4.9-44.4 ng/mL]) versus baseline (median, 1.65 ng/mL [range, 0.55-79.8 ng/mL]); this was associated with a significant increase in arachidonic acid-induced platelet aggregation (P < .01) and adenosine diphosphate-induced platelet aggregation (P < .05) and a decrease in the time to form an occlusive thrombus in the platelet function analyzer (P < .01). The urinary excretion of 11-dehydro-TXB(2), an index of systemic thromboxane biosynthesis, was not significantly affected by the coadministration of treatment drugs. At steady state, a comparable and persistent inhibition of lipopolysaccharide-stimulated prostaglandin E(2) generation, a marker of COX-2 activity ex vivo, was caused by ibuprofen (>or=80%) or celecoxib (>or=70%) but not placebo. CONCLUSIONS: Unlike ibuprofen, celecoxib did not interfere with the inhibition of platelet COX-1 activity and function by aspirin despite a comparable suppression of COX-2 ex vivo in patients with osteoarthritis and stable ischemic heart disease.

Pharmacodynamic interaction of naproxen with low-dose aspirin in healthy subjects.

OBJECTIVES: We investigated the occurrence of pharmacodynamic interaction between low-dose aspirin and naproxen. BACKGROUND: The uncertainty of cardioprotection by naproxen has encouraged its combination with aspirin in patients with arthritis and cardiovascular disease. METHODS: The incubation of washed platelets with naproxen for 5 min before the addition of aspirin reduced the irreversible inhibition of thromboxane (TX)B(2) production by aspirin. The pharmacodynamic interaction between the two drugs was then investigated in four healthy volunteers who received aspirin (100 mg daily) for 6 days and then the combination of aspirin and naproxen for further 6 days: aspirin 2 h before naproxen (500 mg, twice-daily dosing). After 14 days of washout, naproxen was given 2 h before aspirin for further 6 days. RESULTS: The inhibition of serum TXB(2) production (index of platelet cyclooxygenase [COX]-1 activity) and platelet aggregation ex vivo and urinary 11-dehydro-TXB(2) levels (index of TXB(2) biosynthesis in vivo) by aspirin alone (99 +/- 0.2%, 95 +/- 0.6%, and 81 +/- 4%, respectively) was not significantly altered by the co-administration of naproxen, given either 2 h after aspirin or in reverse order. In a second study, the concurrent administration of a single dose of aspirin and naproxen did not affect platelet TXB(2) production and aggregation at 1 h after dosing, when aspirin alone causes maximal inhibitory effect. Moreover, the rapid recovery of platelet COX-1 activity and function supports the occurrence of a pharmacodynamic interaction between naproxen and aspirin. CONCLUSIONS: Naproxen interfered with the inhibitory effect of aspirin on platelet COX-1 activity and function. This pharmacodynamic interaction might undermine the sustained inhibition of platelet COX-1 that is necessary for aspirin's cardioprotective effects.

Clinical pharmacology of platelet, monocyte, and vascular cyclooxygenase inhibition by naproxen and low-dose aspirin in healthy subjects.

BACKGROUND: The current controversy on the potential cardioprotective effect of naproxen prompted us to evaluate the extent and duration of platelet, monocyte, and vascular cyclooxygenase (COX) inhibition by naproxen compared with low-dose aspirin. METHODS AND RESULTS: We performed a crossover, open-label study of low-dose aspirin (100 mg/d) or naproxen (500 mg BID) administered to 9 healthy subjects for 6 days. The effects on thromboxane (TX) and prostacyclin biosynthesis were assessed up to 24 hours after oral dosing. Serum TXB2, plasma prostaglandin (PG) E2, and urinary 11-dehydro-TXB2 and 2,3-dinor-6-keto-PGF(1alpha) were measured by previously validated radioimmunoassays. The administration of naproxen or aspirin caused a similar suppression of whole-blood TXB2 production, an index of platelet COX-1 activity ex vivo, by 94+/-3% and 99+/-0.3% (mean+/-SD), respectively, and of the urinary excretion of 11-dehydro-TXB2, an index of systemic biosynthesis of TXA2 in vivo, by 85+/-8% and 78+/-7%, respectively, that persisted throughout the dosing interval. Naproxen, in contrast to aspirin, significantly reduced systemic prostacyclin biosynthesis by 77+/-19%, consistent with differential inhibition of monocyte COX-2 activity measured ex vivo. CONCLUSIONS: The regular administration of naproxen 500 mg BID can mimic the antiplatelet COX-1 effect of low-dose aspirin. Naproxen, unlike aspirin, decreased prostacyclin biosynthesis in vivo.

Increased oxidative stress and platelet activation in patients with hypertension and renovascular disease.

BACKGROUND: Hypertensive patients with renovascular disease (RVD) may be exposed to increased oxidative stress, possibly related to activation of the renin-angiotensin system. METHODS AND RESULTS: We measured the urinary excretion of 8-iso-prostaglandin (PG) F2alpha and 11-dehydro-thromboxane (TX) B2 as indexes of in vivo lipid peroxidation and platelet activation, respectively, in 25 patients with RVD, 25 patients with essential hypertension, and 25 healthy subjects. Plasma renin activity in peripheral and renal veins, angiotensin II in renal veins, cholesterol, glucose, triglycerides, homocysteine, and antioxidant vitamins A, C, and E were also determined. Patients were also studied 6 months after a technically successful angioplasty of the stenotic renal arteries. Urinary 8-iso-PGF2alpha was significantly higher in patients with RVD (median, 305 pg/mg creatinine; range, 124 to 1224 pg/mg creatinine) than in patients with essential hypertension (median, 176 pg/mg creatinine; range, 48 to 384 pg/mg creatinine) or in healthy subjects (median, 123 pg/mg creatinine; range, 58 to 385 pg/mg creatinine). Urinary 11-dehydro-TXB2 was also significantly higher in RVD patients compared with healthy subjects. In RVD patients, urinary 8-iso-PGF2alpha correlated with 11-dehydro-TXB2 (r(s)=0.48; P<0.05) and renal vein renin (r(s)=0.67; P<0.005) and angiotensin II (r(s)=0.65; P=0.005) ratios. A reduction in 8-iso-PGF2alpha after angioplasty was observed in RVD patients with high baseline levels of lipid peroxidation. Changes in 8-iso-PGF2alpha were related to baseline lipid peroxidation (r(s)=-0.73; P<0.001), renal vein angiotensin II (r(s)=-0.70; P<0.01) and renin (r(s)=-0.63; P<0.05) ratios. CONCLUSIONS: Lipid peroxidation is markedly enhanced in hypertensive patients with RVD and is related to activation of the renin-angiotensin system. Moreover, persistent platelet activation triggered or amplified by bioactive isoprostanes may contribute to the progression of cardiovascular and renal damage in this setting.

Clinical pharmacology of etoricoxib.

Etoricoxib is a highly selective COX-2 inhibitor (coxib) approved in Europe for the treatment of osteoarthritis (OA), rheumatoid arthritis and acute gouty arthritis. Etoricoxib is an effective analgesic drug that has shown some improved efficacy versus traditional NSAIDs and it is the only coxib approved for the treatment of acute gouty arthritis. Moreover, recent studies evidence its efficacy in patients with ankylosing spondylitis. In the Etoricoxib Diclofenac Gastrointestinal Evaluation study performed in patients with OA, etoricoxib significantly reduced the rate of discontinuation by 50% due to gastrointestinal adverse events versus diclofenac. Comparable rates of thrombotic cardiovascular events were detected. Rates of discontinuation due to hypertension-related adverse effects were higher on etoricoxib than diclofenac. Similarly to other selective COX-2 inhibitors, etoricoxib is contraindicated in patients with ischaemic heart disease or stroke and it should be used with caution in patients with risk factors for heart disease. The European Medicines Agency has contraindicated the use of etoricoxib in patients with uncontrolled hypertension. Selective COX-2 inhibitors remain an appropriate choice in patients at low cardiovascular risk, but with increased risk of gastrointestinal complications.

Effects of acetaminophen on constitutive and inducible prostanoid biosynthesis in human blood cells.

1. Acetaminophen, an analgesic and antipyretic drug with weak antiinflammatory properties, has been suggested to act as a tissue-selective inhibitor of prostaglandin H synthases (PGHSs) (e.g. COX-1 and COX-2) through its reducing activity, that is influenced by the different cellular levels of peroxides. 2. We have studied the effects of acetaminophen on inducible and constitutive prostanoid biosynthesis in monocytes and platelets in vitro. To discriminate between the inhibitory effect of the drug on PGHS-isozymes vs PGE-synthases (PGESs), parallel measurements of PGE(2) and thromboxane (TX) B(2) were carried out. Since antioxidant enzymes and cofactors, present in plasma, may affect acetaminophen-dependent inhibition of prostanoids, comparative experiments in whole blood vs isolated monocytes were performed. 3. Acetaminophen inhibited LPS-induced whole blood PGE(2) and TXB(2) production, in a concentration-dependent fashion [IC(50) microM (95% confidence intervals): 44 (27-70) and 94 (79-112), respectively]. Therapeutic plasma concentrations (100 and 300 microM) of the drug more profoundly reduced PGE(2) than TXB(2) (71 +/- 3 vs 54 +/- 4 and 95 +/- 0.8 vs 78 +/- 2%, respectively, mean +/- s.e.mean, n = 6, P < 0.01). 4. Differently, in isolated monocytes stimulated with LPS, both PGE(2) and TXB(2) production was maximally reduced by only 60%. 5 At 100 and 300 microM, the drug caused a similar and incomplete inhibition of platelet PGE(2) and TXB(2) production during whole blood clotting (45 +/- 4 vs 54 +/- 4 and 75 +/- 2 vs 75 +/- 1%, respectively, mean +/- s.e.mean, n = 4). 6 In conclusion, therapeutic concentrations of acetaminophen caused an incomplete inhibition of platelet COX-1 and monocyte COX-2 but in the presence of plasma, the drug almost completely suppressed inducible PGE(2) biosynthesis through its inhibitory effects on both COX-2 and inducible PGES.

The biochemical selectivity of novel COX-2 inhibitors in whole blood assays of COX-isozyme activity.

We have evaluated the biochemical selectivity of novel cyclo-oxygenase (COX)-2 inhibitors, etoricoxib, valdecoxib, DFU and DFP, vs rofecoxib and celecoxib, using the human whole blood assays of COX-isozyme activity, in vitro. Compounds were incubated with human whole blood samples, allowed to clot for 1 h at 37 degrees C, or stimulated with lipopolysaccharide (10 microg/ml) for 24 h at 37 degrees C. Serum thromboxane (TX) B2 and plasma prostaglandin (PG) E2 levels were measured by specific radioimmunoassays as indices of platelet COX-1 and monocyte COX-2 activity, respectively. Valdecoxib, etoricoxib, DFU and DFP inhibited platelet COX-1 and monocyte COX-2 with the following COX-1/COX-2 IC50 ratios: 61.5, 344, 660 and 1918, respectively. The reference compounds, celecoxib and rofecoxib had corresponding values of 29.6 and 272. In conclusion, a second wave of COX-2 inhibitors with higher biochemical selectivity than the existing coxibs has been developed. Whether their administration will be associated with improved clinical efficacy and/or safety vis-à-vis celecoxib and rofecoxib remains to be established.

Clinical pharmacology of etoricoxib: a novel selective COX2 inhibitor.

The development of COX2 inhibitors with improved biochemical selectivity (such as etoricoxib and valdecoxib) over that of commercially available coxibs has been driven by the potential advantage of safety using higher coxib doses for increased efficacy. Etoricoxib has been approved in the UK as a once-daily medicine for symptomatic relief in the treatment of osteoarthritis (OA), rheumatoid arthritis (RA) and acute gouty arthritis. It is currently approved with additional indications (i.e., for relief of acute pain associated with dental surgery, for primary dysmenorrhoea and for chronic musculo-skeletal pain, including chronic lower-back pain) in Mexico, Brazil and Peru. Etoricoxib has an in vitro COX1/COX2 IC(50) ratio of 344, the highest of any coxib. The administration of therapeutic doses of etoricoxib to healthy subjects does not affect COX1 activity in circulating platelets and gastric biopsies. The profound inhibition of monocyte COX2 activity at 24 h after dosing, as predicted by a pharmacological half-life of approximately 22 h, supports a once-daily dosing regimen of etoricoxib. In randomised, well-controlled clinical trials, etoricoxib has been shown to have a comparable clinical efficacy with traditional NSAIDs. Combined analysis of efficacy trials with etoricoxib versus non-selective NSAIDs has shown that the drug halves both investigator-reported upper gastrointestinal perforation, ulcers and bleeds (PUBs) and confirmed PUBs, and reduces the need for gastroprotective agents and gastrointestinal comedications by approximately 40%. The risk of lower extremity oedema and hypertension adverse experiences with etoricoxib was low and generally similar to comparator NSAIDs in a combined analysis of eight Phase III studies in OA, RA, chronic low-back pain and surveillance endoscopy. Large, randomised clinical trials have been planned to confirm the renal, gastrointestinal and cardiovascular safety of etoricoxib.

Glucose and collagen regulate human platelet activity through aldose reductase induction of thromboxane.

Diabetes mellitus is associated with platelet hyperactivity, which leads to increased morbidity and mortality from cardiovascular disease. This is coupled with enhanced levels of thromboxane (TX), an eicosanoid that facilitates platelet aggregation. Although intensely studied, the mechanism underlying the relationship among hyperglycemia, TX generation, and platelet hyperactivity remains unclear. We sought to identify key signaling components that connect high levels of glucose to TX generation and to examine their clinical relevance. In human platelets, aldose reductase synergistically modulated platelet response to both hyperglycemia and collagen exposure through a pathway involving ROS/PLCγ2/PKC/p38α MAPK. In clinical patients with platelet activation (deep vein thrombosis; saphenous vein graft occlusion after coronary bypass surgery), and particularly those with diabetes, urinary levels of a major enzymatic metabolite of TX (11-dehydro-TXB2 [TX-M]) were substantially increased. Elevated TX-M persisted in diabetic patients taking low-dose aspirin (acetylsalicylic acid, ASA), suggesting that such patients may have underlying endothelial damage, collagen exposure, and thrombovascular disease. Thus, our study has identified multiple potential signaling targets for designing combination chemotherapies that could inhibit the synergistic activation of platelets by hyperglycemia and collagen exposure.

Measurement of 8-iso-prostaglandin F2alpha in biological fluids as a measure of lipid peroxidation.

Several lines of evidence suggest that reactive oxygen species are implicated in human disease, including atherosclerosis, hypertension, and restenosis after angioplasty. The measurement of F(2)-isoprostanes (F(2)-iPs), formed nonenzymatically through free radical catalyzed attack on esterified arachidonate, provides a reliable tool for identifying populations with enhanced rates of lipid peroxidation. Among F(2)-isoPs, 8-iso-PGF(2alpha) (also referred to IPF(2alpha)-III) and IPF(2alpha)-VI are the most frequently measured in biological fluids. A variety of methods have been proposed to measure F(2)-isoprostanes in urine and plasma. Mass spectrometry has been developed for the measurement of both F(2)-isoprostanes but its use is limited as it is time-consuming and highly expensive. We have developed validated enzyme immunoassay (EIA) and radioimmunoassay (RIA) techniques using highly specific antisera for the measurement of 8-iso-PGF(2alpha). In contrast, the commercially available immunoassay kits are limited for their poor specificity. The measurement of specific isoprostanes, such as 8-iso-PGF(2alpha), in urine is a reliable, noninvasive index of lipid peroxidation that is of valuable help in dose-finding studies of natural and synthetic antioxidant agents.

NSAIDs and cardiovascular disease: transducing human pharmacology results into clinical read-outs in the general population.

Traditional (t) non-steroidal anti-inflammatory drugs (NSAIDs) and selective cyclooxygenase (COX)-2 inhibitors (coxibs) are important and efficacious drugs for the management of musculoskeletal symptoms. These drugs have both beneficial and adverse effects due to the inhibition of prostanoids. Although the tNSAID and coxib inhibition of COX-2-dependent prostaglandin (PG)E(2) production is effective in ameliorating symptoms of inflammation and pain, a small but consistent increased risk of myocardial infarction has been detected in association with their use. Convincing evidence suggests that cardiovascular toxicity associated with the administration of these compounds occurs through a common mechanism involving inhibition of COX-2-dependent prostacyclin. The development of biomarkers that predict the impact of NSAIDs on COX-1 and COX-2 activities in vitro, ex vivo and in vivo has been essential to read-out the clinical consequences of the varying degrees of inhibition of the two COX-isozymes in humans. Whole blood assays for COX-1 and COX-2 might be candidates as surrogate end-points of toxicity and efficacy of NSAIDs. Using a biomarker strategy, we have shown that the degree of inhibition of COX-2 and the functional selectivity with which it is achieved are relevant to the level of cardiovascular hazard from NSAIDs and relate to drug potency (exposure). We propose that the assessment of COX-2 in whole blood ex vivo, either alone or in combination with urinary levels of 2,3-dinor-6-keto-PGF(1 alpha) a biomarker of prostacyclin biosynthesis in vivo, may represent a valid surrogate end-point to predict cardiovascular risk for functionally selective COX-2 inhibitors.

Effects of AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide], a novel inhibitor of human microsomal prostaglandin E synthase-1, on prostanoid biosynthesis in human monocytes in vitro.

Inhibitors of microsomal prostaglandin (PG) E synthase-1 (mPGES-1) are being developed for the relief of pain. Redirection of the PGH(2) substrate to other PG synthases, found both in vitro and in vivo, in mPGES-1 knockout mice, may influence their efficacy and safety. We characterized the contribution of mPGES-1 to PGH(2) metabolism in lipopolysaccharide (LPS)-stimulated isolated human monocytes and whole blood by studying the synthesis of prostanoids [PGE(2), thromboxane (TX)B(2), PGF(2alpha) and 6-keto-PGF(1alpha)] and expression of cyclooxygenase (COX)-isozymes and down-stream synthases in the presence of pharmacological inhibition by the novel mPGES-1 inhibitor AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide]. AF3442 caused a concentration-dependent inhibition of PGE(2) in human recombinant mPGES-1 with an IC(50) of 0.06microM. In LPS-stimulated monocytes, AF3442 caused a concentration-dependent reduction of PGE(2) biosynthesis with an IC(50) of 0.41microM. At 1microM, AF3442 caused maximal selective inhibitory effect of PGE(2) biosynthesis by 61+/-3.3% (mean+/-SEM, P<0.01 versus DMSO vehicle) without significantly affecting other prostanoids (i.e. TXB(2), PGF(2alpha) and 6-keto-PGF(1alpha)). In LPS-stimulated whole blood, AF3442 inhibited in a concentration-dependent fashion inducible PGE(2) biosynthesis with an IC(50) of 29microM. A statistically significant inhibition of mPGES-1 activity was detected at 10 and 100microM (38+/-14%, P<0.05, and 69+/-5%, P<0.01, respectively). Up to 100microM, the other prostanoids were not significantly affected. In conclusion, AF3442 is a selective mPGES-1 inhibitor which reduced monocyte PGE(2) generation also in the presence of plasma proteins. Pharmacological inhibition of mPGES-1 did not translate into redirection of PGH(2) metabolism towards other terminal PG synthases in monocytes. The functional relevance of this observation deserves to be investigated in vivo.

Risk management profile of etoricoxib: an example of personalized medicine.

The development of nonsteroidal anti-inflammatory drugs (NSAIDs) selective for cyclooxygenase (COX)-2 (named coxibs) has been driven by the aim of reducing the incidence of serious gastrointestinal (GI) adverse events associated with the administration of traditional (t) NSAIDs - mainly dependent on the inhibition of COX-1 in GI tract and platelets. However, their use has unravelled the important protective role of COX-2 for the cardiovascular (CV) system, mainly through the generation of prostacyclin. In a recent nested-case control study, we found that patients taking NSAIDs (both coxibs and tNSAIDs) had a 35% increase risk of myocardial infarction. The increased incidence of thrombotic events associated with profound inhibition of COX-2-dependent prostacyclin by coxibs and tNSAIDs can be mitigated, even if not obliterated, by a complete suppression of platelet COX-1 activity. However, most tNSAIDs and coxibs are functional COX-2 selective for the platelet (ie, they cause a profound suppression of COX-2 associated with insufficient inhibition of platelet COX-1 to translate into inhibition of platelet function), which explains their shared CV toxicity. The development of genetic and biochemical markers will help to identify the responders to NSAIDs or who are uniquely susceptible at developing thrombotic or GI events by COX inhibition. We will describe possible strategies to reduce the side effects of etoricoxib by using biochemical markers of COX inhibition, such as whole blood COX-2 and the assessment of prostacyclin biosynthesis in vivo.

Cardiovascular effects of valdecoxib: transducing human pharmacology results into clinical read-outs.

Valdecoxib is an NSAID that is selective for COX-2 (commonly named coxibs). It exhibits anti-inflammatory, analgesic and antipyretic properties in animal models and humans due to inhibition of prostanoid synthesis primarily by affecting COX-2. In this review, the clinical results of cardiovascular effects of valdecoxib and its prodrug parecoxib were analyzed and the information from animal models and clinical pharmacology was exploited, that is, pharmacodynamic and pharmacokinetic data, to give a mechanistic interpretation. Similarly to other coxibs and some traditional (t)NSAIDs less selective for COX-2, such as diclofenac, valdecoxib may increase the risk of thrombotic events through a prostacyclin-based mechanism. The rapid and elevated thrombotic risk detected in two coronary artery bypass graft surgery trials with parecoxib and valdecoxib is coherent with almost complete suppression of COX-2 by supratherapeutic doses (particularly parecoxib), which plausibly translates into a deep suppression of prostacyclin. Drug potency, that is, the degree of suppression of COX-2-dependent prostacyclin, is proposed to represent a strong determinant in the increased incidence of thrombotic events associated with the use of COX-2 inhibitors and some tNSAIDs.

Differential association between human prostacyclin receptor polymorphisms and the development of venous thrombosis and intimal hyperplasia: a clinical biomarker study.

OBJECTIVE AND METHODS: The role of prostacyclin in the development of venous thrombosis and vascular dysfunction in humans is unclear. In patients with deep vein thrombosis (DVT, n=34) and controls (matched for age, sex, indexes of systemic inflammation and metabolic status, n=20), we studied (i) differences on systemic markers of vascular disease and platelet activation and (ii) the influence of prostacyclin receptor gene (PTGIR) polymorphisms. MAIN RESULTS: Enhanced levels of urinary 11-dehydro-thromboxane (TX)B2 and plasma [soluble(s)] P-selectin, mostly platelet derived, were detected in DVT patients, whereas plasma von Willebrand factor levels and intima-media thickness of the common carotid arteries were not significantly different. In all patients' cohorts, we identified five PTGIR polymorphisms (three nonsynonymous: P226T, R212C, V196L; two synonymous: V53V, S328S). In the four individuals carriers of R212C polymorphism (three in DVT, one in controls), intima-media thickness values were significantly (P=0.0043) higher than those detected in individuals of all cohorts [1.68+/-0.38, 1.55 (1.4-2.2) vs. 1.05+/-0.33, 1.08 (0.01-1.68) mm, respectively, mean+/-SD, median (range)]. Moreover, enhanced sP-selectin and 11-dehydro-TXB2, in DVT versus controls, were statistically significant only in carriers of both synonymous PTGIR polymorphisms V53V/S328S. Only the PTGIR mutant R212C was dysfunctional when examined in an in vitro overexpression system. CONCLUSION: Our results suggest a propensity of enhanced platelet activation in DVT patients with PTGIR polymorphisms V53V/S328S. Moreover, we identified a dysfunctional PTGIR polymorphism (R212C) associated with intimal hyperplasia.