Maria G. Sciulli

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-PGF1&agr; 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.

Effects of Vitamin E Supplementation on F2-Isoprostane and Thromboxane Biosynthesis in Healthy Cigarette Smokers

BACKGROUND Increased formation of 8-iso-prostaglandin (PG) F(2alpha) and thromboxane (TX) A(2), potent agonists of platelet and vascular thromboxane (TH)/PGH(2) receptors, has been detected in cigarette smokers. We performed a randomized, double-blind, placebo-controlled study of the effects of vitamin E (300, 600, and 1200 mg/d, each dose for 3 consecutive weeks) on 8-iso-PGF(2alpha) and TXA(2) biosynthesis in 46 moderate cigarette smokers. METHODS AND RESULTS Urinary immunoreactive 8-iso-PGF(2alpha) and 11-dehydro-TXB(2), plasma vitamin E, and serum TXB(2) were measured by previously validated techniques. Baseline urinary 8-iso-PGF(2alpha) and 11-dehydro-TXB(2) excretion averaged 241+/-78 and 430+/-293 pg/mg creatinine, respectively. Urinary 8-iso-PGF(2alpha) was significantly correlated with 11-dehydro-TXB(2) (r=0.360, n=138, P<0.0001). Baseline plasma vitamin E levels averaged 20.6+/-4.9 micromol/L and were inversely correlated with urinary 11-dehydro-TXB(2) (r=-0.304, P=0.039) but not with 8-iso-PGF(2alpha) (r=-0.227, P=0.129). Vitamin E supplementation caused a dose-dependent increase in its plasma levels that reached a plateau at 600 mg (42.3+/-11.2 micromol/L, P<0. 001). This was not associated with any statistically significant change in urinary 8-iso-PGF(2alpha) or 11-dehydro-TXB(2) excretion. CONCLUSIONS Supplementation with pharmacological doses of vitamin E has no detectable effects on lipid peroxidation and thromboxane biosynthesis in vivo in healthy subjects with a mild degree of oxidant stress. These findings are consistent with the hypothesis that the basal rate of lipid peroxidation is a major determinant of the response to vitamin E supplementation and have implications for the use of vitamin E in healthy subjects as well as for the design and interpretation of clinical trials of antioxidant intervention.

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

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.

Effects of the novel anti-inflammatory compounds, N-[2-(cyclohexyloxy)-4-nitrophenyl] methanesulphonamide (NS-398) and 5-methanesulphonamido-6-(2,4-difluorothiophenyl)-1-indanone (L-745,337), on the cyclo-oxygenase activity of human blood prostaglandin endoperoxide synthases

1 We have evaluated the selectivity of ketoprofen and two novel nonsteroidal anti‐inflammatory drugs, N‐[2‐(cyclohexyloxy)‐4‐nitrophenyl]methanesulphonamide (NS‐398) and 5‐methanesulphonamido‐6‐(2, 4‐difluorothiophenyl)‐1‐indanone (L‐745, 337), in inhibiting the cyclo‐oxygenase activity of prostaglandin endoperoxide synthase‐2 (PGHS‐2) vs PGHS‐1 in human blood monocytes and platelets, respectively. 2 Heparinized whole blood samples were drawn from healthy volunteers pretreated with aspirin, 300 mg 48 h before sampling, to suppress the activity of platelet PGHS‐1 and incubated at 37°C for 24 h with increasing concentrations of the test compounds in the presence of lipopolysaccharide (LPS, 10 μg ml−1). Immunoreactive PGE2 levels were measured in plasma by a specific radioimmunoassay as an index of the cyclo‐oxygenase activity of LPS‐induced monocyte PGHS‐2. 3 The effects of the same inhibitors on platelet PGHS‐1 activity were assessed by allowing whole blood samples, drawn from the same subjects in aspirin‐free periods, to clot at 37°C for 1 h in the presence of the compounds and measuring immunoreactive thromboxane B2 (TXB2) levels in serum by a specific radioimmunoassay. 4 Under these experimental conditions, ketoprofen enantioselectively inhibited the cyclo‐oxygenase activity of both PGHS‐1 and PGHS‐2 with equal potency (IC50 ratio: approx. 0.5 for both enantiomers), while L‐745, 337 and NS‐398 achieved selective inhibition of monocyte PGHS‐2 (IC50 ratio: > 150). L‐745, 337 and NS‐398 did not affect LPS‐induced monocyte PGHS‐2 biosynthesis to any detectable extent. 5 We conclude that L‐745, 337 and NS‐398 are selective inhibitors of the cyclo‐oxygenase activity of human monocyte PGHS‐2. These compounds may provide adequate tools to test the contribution of this novel pathway of arachidonate metabolism to human inflammatory disease.

Expression of COX-2, mPGE-synthase1, MDR-1 (P-gp), and Bcl-xL: a molecular pathway of H pylori-related gastric carcinogenesis.

Helicobacter pylori up‐regulates cyclo‐oxygenase‐2 (COX‐2) expression, which in turn is involved in tumourigenesis. Recently, a causal link between COX‐2 and multidrug resistance 1 (MDR‐1) gene expression, implicated in cancer chemoresistance, has been demonstrated. Thus, the expression of COX‐2 and the downstream enzyme involved in PGE2 biosynthesis, microsomal PGE‐synthase1 (mPGES1), was correlated with P‐gp, the product of MDR‐1, and the anti‐apoptotic protein, Bcl‐xL, in gastric biopsies from patients with H pylori infection and in patients with gastric cancer. In a retrospective analysis of endoscopic and pathology files, 40 H pylori‐negative patients (Hp−), 50 H pylori‐positive patients who responded to eradication therapy (Hp+R), 84 H pylori‐positive patients who did not respond to eradication therapy (Hp+NR), and 30 patients with gastric cancer (18 intestinal and 12 diffuse types) were selected. COX‐2, mPGES1, P‐gp, and Bcl‐xL were detected by immunohistochemistry. COX‐2, mPGES1, P‐gp, and Bcl‐xL expression was undetectable in gastric mucosa from Hp− patients. By contrast, COX‐2 and mPGES1 expression was detected in 42% and 44% of Hp+R patients, respectively, and in up to 66% (range 63–66%) of Hp+NR patients (p < 0.05). The expression of COX‐2 and mPGES1 correlated significantly (p < 0.0001) with that of P‐gp and Bcl‐xL. High levels of COX‐2, mPGES1, P‐gp, and Bcl‐xL expression were found in intestinal‐type gastric cancer samples. In conclusion, H pylori‐dependent induction of COX‐2 and mPGES1 is associated with enhanced production of P‐gp and Bcl‐xL that may contribute to gastric tumourigenesis and resistance to therapy. Copyright

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

Summary 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°C, or stimulated with lipopolysaccharide (10|ig/ml) for 24 h at 37°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 visà-vis celecoxib and rofecoxib remains to be established.

Induction of prostaglandin endoperoxide synthase-2 in human monocytes associated with cyclo-oxygenase-dependent F2-isoprostane formation

1 The isoprostane 8‐epi‐prostaglandin (PG)F2α is produced by free radical‐catalyzed peroxidation of arachidonic acid. It may also be formed as a minor product of the cyclo‐oxygenase activity of platelet PGH synthase (PGHS)‐1. We investigated 8‐epi‐PGF2α production associated with induction of the human monocyte PGHS‐2 and its pharmacological modulation. 2 Heparinized whole blood samples were drawn from healthy volunteers, 48 h following oral dosing with aspirin 300 mg to suppress platelet cyclo‐oxygenase activity. One ml aliquots were incubated with lipopolysaccharide (LPS: 0.1–50 μg ml−1) for 0–24 h at 37°C. PGE2 and 8‐epi‐PGF2α were measured in separated plasma by radioimmunoassay and enzyme immunoassay techniques. 3 Levels of both eicosanoids were undetectable (i.e. < 60 pg ml−1) at time 0. LPS induced the formation of PGE2 and 8‐epi‐PGF2α in a time‐ and concentration‐dependent fashion, coincident with the induction of PGHS‐2 detected by Western blot analysis of monocyte lysates. After 24 h at 10 μg ml−1 LPS, immunoreactive PGE2 and 8‐epi‐PGF2α averaged 10,480 ± 4,643 and 295 ± 140 pg ml−1 (mean ± s.d., n = 6), respectively. 4 Dexamethasone and 5‐methanesulphonamido‐6‐(2, 4‐difluorothiophenyl)‐1‐indanone (L‐745,337), a selective inhibitor of the cyclo‐oxygenase activity of PGHS‐2, reduced PGE2 and 8‐epi‐PGF2α production in response to LPS. 5 Isolated monocytes produced PGE2 and 8‐epi‐PGF2α in response to LPS (10 μg ml−1) in a time‐dependent fashion. Monocyte PGE2 and 8‐epi‐PGF2α production was largely prevented by dexamethasone (2 μm) and cycloheximide (10 μg ml−1) in association with suppression of PGHS‐2 but not of PGHS‐1 expression. 6 We conclude that the induction of PGHS‐2 in human monocytes is associated with cyclo‐oxygenase‐dependent generation of the vasoconstrictor and platelet‐agonist 8‐epi‐PGF2α.

Human Pharmacology of Naproxen Sodium

We compared the variability in degree and recovery from steady-state inhibition of cyclooxygenase (COX)-1 and COX-2 ex vivo and in vivo and platelet aggregation by naproxen sodium at 220 versus 440 mg b.i.d. and low-dose aspirin in healthy subjects. Six healthy subjects received consecutively naproxen sodium (220 and 440 mg b.i.d.) and aspirin (100 mg daily) for 6 days, separated by washout periods of 2 weeks. COX-1 and COX-2 inhibition was determined using ex vivo and in vivo indices of enzymatic activity: 1) the measurement of serum thromboxane (TX)B2 levels and whole-blood lipopolysaccharide-stimulated prostaglandin (PG)E2 levels, markers of COX-1 in platelets and COX-2 in monocytes, respectively; 2) the measurement of urinary 11-dehydro-TXB2 and 2,3-dinor-6-keto-PGF1α levels, markers of systemic TXA2 biosynthesis (mostly COX-1-derived) and prostacyclin biosynthesis (mostly COX-2-derived), respectively. Arachidonic acid (AA)-induced platelet aggregation was also studied. The maximal inhibition of platelet COX-1 (95.9 ± 5.1 and 99.2 ± 0.4%) and AA-induced platelet aggregation (92 ± 3.5 and 93.7 ± 1.5%) obtained at 2 h after dosing with naproxen sodium at 220 and 440 mg b.i.d., respectively, was indistinguishable from aspirin, but at 12 and 24 h after dosing, we detected marked variability, which was higher with naproxen sodium at 220 mg than at 440 mg b.i.d. Assessment of the ratio of inhibition of urinary 11-dehydro-TXB2 versus 2,3-dinor-6-keto-PGF1α showed that the treatments caused a more profound inhibition of TXA2 than prostacyclin biosynthesis in vivo throughout dosing interval. In conclusion, neither of the two naproxen doses mimed the persistent and complete inhibition of platelet COX-1 activity obtained by aspirin, but marked heterogeneity was mitigated by the higher dose of the drug.

Effects of nimesulide on constitutive and inducible prostanoid biosynthesis in human beings

The aim of this study was to test the hypothesis that nimesulide, a nonsteroidal antiinflammatory drug, or its principal metabolite 4‐hydroxynimesulide, is a selective inhibitor of prostaglandin H synthase‐2 in human beings.

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

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. 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 PGE2 and thromboxane (TX) B2 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. Acetaminophen inhibited LPS‐induced whole blood PGE2 and TXB2 production, in a concentration‐dependent fashion [IC50 μM (95% confidence intervals): 44 (27–70) and 94 (79–112), respectively]. Therapeutic plasma concentrations (100 and 300 μM) of the drug more profoundly reduced PGE2 than TXB2 (71±3 vs 54±4 and 95±0.8 vs 78±2%, respectively, mean±s.e.mean, n=6, P<0.01). Differently, in isolated monocytes stimulated with LPS, both PGE2 and TXB2 production was maximally reduced by only 60%. At 100 and 300 μM, the drug caused a similar and incomplete inhibition of platelet PGE2 and TXB2 production during whole blood clotting (45±4 vs 54±4 and 75±2 vs 75±1%, respectively, mean±s.e.mean, n=4). 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 PGE2 biosynthesis through its inhibitory effects on both COX‐2 and inducible PGES.