Showing papers by "Garret A. FitzGerald published in 2001"

The coxibs, selective inhibitors of cyclooxygenase-2.

Abstract: Nonsteroidal antiinflammatory drugs (NSAIDs) are widely used to treat arthritis, menstrual pain, and headache. Although they are effective, their long-term use is limited by gastrointestinal effects such as dyspepsia and abdominal pain and, less often, gastric or duodenal perforation or bleeding. Development of the coxibs, a new group of antiinflammatory drugs, represents a response to the unsatisfactory therapeutic profile of NSAIDs. Both groups of drugs inhibit prostaglandin G/H synthase, the enzyme that catalyzes the transformation of arachidonic acid to a range of lipid mediators, termed prostaglandins and thromboxanes (Figure 1). However, whereas NSAIDs inhibit the two recognized forms of the . . .

Cyclooxygenase Inhibitors and the Antiplatelet Effects of Aspirin

Abstract: Background Patients with arthritis and vascular disease may receive both low-dose aspirin and other nonsteroidal antiinflammatory drugs. We therefore investigated potential interactions between aspirin and commonly prescribed arthritis therapies. Methods We administered the following combinations of drugs for six days: aspirin (81 mg every morning) two hours before ibuprofen (400 mg every morning) and the same medications in the reverse order; aspirin two hours before acetaminophen (1000 mg every morning) and the same medications in the reverse order; aspirin two hours before the cyclooxygenase-2 inhibitor rofecoxib (25 mg every morning) and the same medications in the reverse order; enteric-coated aspirin two hours before ibuprofen (400 mg three times a day); and enteric-coated aspirin two hours before delayed-release diclofenac (75 mg twice daily). Results Serum thromboxane B2 levels (an index of cyclooxygenase-1 activity in platelets) and platelet aggregation were maximally inhibited 24 hours after the...

Effects of vitamin E on lipid peroxidation in healthy persons.

Abstract: ContextOxidative stress may play a role in the development or exacerbation of many common diseases. However, results of prospective controlled trials of the effects of antioxidants such as vitamin E are contradictory.ObjectiveTo assess the effects of supplemental vitamin E on lipid peroxidation in vivo in healthy adults.DesignRandomized, double-blind, placebo-controlled trial conducted March 1999 to June 2000.SettingA general clinical research center in a tertiary referral academic medical center.ParticipantsThirty healthy men and women aged 18 to 60 years.InterventionsParticipants were randomly assigned to receive placebo or α-tocopherol dosages of 200, 400, 800, 1200, or 2000 IU/d for 8 weeks (n = 5 in each group), followed by an 8-week washout period.Main Outcome MeasuresThree indices of lipid peroxidation, urinary 4-hydroxynonenal (4-HNE) and 2 isoprostanes, iPF2α-III and iPF2α-VI, measured by gas chromatography/mass spectrometry and compared among the 6 groups at baseline, 2, 4, 6, and 8 weeks, and 1, 3, and 8 weeks after discontinuation.ResultsCirculating vitamin E levels increased in a dose-dependent manner during the study. No significant effect of vitamin E on levels of urinary 4-HNE or either isoprostane was observed. Mean (SEM) baseline vs week 8 levels of iPF2α-III were 154 (20.1) vs 168 (22.3) pg/mg of creatinine for subjects taking placebo; 165 (19.6) vs 234 (30.1) pg/mg for those taking 200 IU/d of vitamin E; and 195 (26.7) vs 213 (40.6) pg/mg for subjects taking 2000 IU/d. Corresponding iPF2α-VI levels were 1.43 (0.6) vs 1.62 (0.4) ng/mg of creatinine for subjects taking placebo; 1.64 (0.3) vs 1.24 (0.8) ng/mg for those taking 200 IU/d of vitamin E; and 1.83 (0.3) vs 1.94 (0.9) ng/mg for those taking 2000 IU/d. Baseline vs week 8 levels of 4-HNE were 0.5 (0.04) vs 0.4 (0.05) ng/mg of creatinine for subjects taking placebo; 0.4 (0.06) vs 0.5 (0.02) ng/mg with 200 IU/d of vitamin E; and 0.2 (0.02) vs 0.2 (0.1) ng/mg with 2000 IU/d.ConclusionsOur results question the rationale for vitamin E supplementation in healthy individuals. Specific quantitative indices of oxidative stress in vivo should be considered as entry criteria and for dose selection in clinical trials of antioxidant drugs and vitamins in human disease.

Absence of 12/15-Lipoxygenase Expression Decreases Lipid Peroxidation and Atherogenesis in Apolipoprotein E–Deficient Mice

Abstract: Background—The enzyme 12/15-lipoxygenase (12/15-LO) has been implicated in the oxidative modification of LDL. In a murine model, we tested the hypothesis that deletion of 12/15-LO decreases atherogenesis by reducing oxidant stress, as measured by 2 indices of lipid peroxidation: isoprostane generation and autoantibody formation to malondialdehyde (MDA)-LDL, an epitope of LDL formed as a result of oxidative modification. Methods and Results—12/15-LO–deficient (12/15-LO−/−) mice were crossed with apolipoprotein E–deficient (apoE−/−) mice. At 10 weeks of age, atherosclerotic lesion initiation was significantly delayed in the double-knockout mice. The rate of lesion progression was diminished at 8 and 12 months, and even at 15 months, lesion size was reduced 50% (P<0.0005) compared with control apoE−/− mice. The urinary and plasma levels of the specific isoprostane 8,12-iso-iPF2α-VI, as well as IgG autoantibodies against MDA-LDL, were significantly reduced in the double-deficient mice in parallel with decreas...

Acceleration of atherogenesis by COX-1-dependent prostanoid formation in low density lipoprotein receptor knockout mice

Abstract: The cyclooxygenase (COX) product, prostacyclin (PGI(2)), inhibits platelet activation and vascular smooth-muscle cell migration and proliferation. Biochemically selective inhibition of COX-2 reduces PGI(2) biosynthesis substantially in humans. Because deletion of the PGI(2) receptor accelerates atherogenesis in the fat-fed low density lipoprotein receptor knockout mouse, we wished to determine whether selective inhibition of COX-2 would accelerate atherogenesis in this model. To address this hypothesis, we used dosing with nimesulide, which inhibited COX-2 ex vivo, depressed urinary 2,3 dinor 6-keto PGF(1alpha) by approximately 60% but had no effect on thromboxane formation by platelets, which only express COX-1. By contrast, the isoform nonspecific inhibitor, indomethacin, suppressed platelet function and thromboxane formation ex vivo and in vivo, coincident with effects on PGI(2) biosynthesis indistinguishable from nimesulide. Indomethacin reduced the extent of atherosclerosis by 55 +/- 4%, whereas nimesulide failed to increase the rate of atherogenesis. Despite their divergent effects on atherogenesis, both drugs depressed two indices of systemic inflammation, soluble intracellular adhesion molecule-1, and monocyte chemoattractant protein-1 to a similar but incomplete degree. Neither drug altered serum lipids and the marked increase in vascular expression of COX-2 during atherogenesis. Accelerated progression of atherosclerosis is unlikely during chronic intake of specific COX-2 inhibitors. Furthermore, evidence that COX-1-derived prostanoids contribute to atherogenesis suggests that controlled evaluation of the effects of nonsteroidal anti-inflammatory drugs and/or aspirin on plaque progression in humans is timely.

The isoprostanes in biology and medicine

Abstract: Isoprostanes are a new class of lipids, isomers of the conventional enzymatically derived prostaglandins, which are produced in vivo primarily by a free radical-catalyzed peroxidation of polyunsaturated fatty acids. F 2 -isoprostanes, isomers of the enzyme-derived prostaglandin F 2α , are the most studied species, but analogous isomers of other prostaglandins and leukotrienes have been described. Because of their mechanism of formation, specific structural features that distinguish them from other free radical-generated products and chemical stability, they can provide a reliable index for the oxidant component of several diseases in vivo . Consistent data suggest that formation of F 2 -isoprostanes is altered in a variety of clinical settings putatively associated with oxidant stress. Moreover, measurement of F 2 -isoprostanes might provide a sensitive biochemical basis for dose-selection in studies of natural and synthetic antioxidants. Finally, some F 2 -isoprostanes possess potent biological activities in vitro and in vivo , suggesting that they may also act as mediators of the cellular effects of oxidative stress.

Activation of the murine EP3 receptor for PGE2 inhibits cAMP production and promotes platelet aggregation

Abstract: The importance of arachidonic acid metabolites (termed eicosanoids), particularly those derived from the COX-1 and COX-2 pathways (termed prostanoids), in platelet homeostasis has long been recognized. Thromboxane is a potent agonist, whereas prostacyclin is an inhibitor of platelet aggregation. In contrast, the effect of prostaglandin E2 (PGE2) on platelet aggregation varies significantly depending on its concentration. Low concentrations of PGE2 enhance platelet aggregation, whereas high PGE2 levels inhibit aggregation. The mechanism for this dual action of PGE2 is not clear. This study shows that among the four PGE2 receptors (EP1–EP4), activation of EP3 is sufficient to mediate the proaggregatory actions of low PGE2 concentration. In contrast, the prostacyclin receptor (IP) mediates the inhibitory effect of higher PGE2 concentrations. Furthermore, the relative activation of these two receptors, EP3 and IP, regulates the intracellular level of cAMP and in this way conditions the response of the platelet to aggregating agents. Consistent with these findings, loss of the EP3 receptor in a model of venous inflammation protects against formation of intravascular clots. Our results suggest that local production of PGE2 during an inflammatory process can modulate ensuing platelet responses.

Series Introduction: COX in a crystal ball: current status and future promise of prostaglandin research

Abstract: Prostaglandins were first discovered by von Euler in the late 1940s to be active principles in semen that induced uterine contractility. Since then, interest in the field has waxed and waned. Indeed, through much of the 50s and 60s, prostaglandin research remained the arcane preserve of the dedicated few. It maintained a continuing emphasis on reproductive biology but was eclipsed in the popular vision by those other stepchildren of von Euler’s creativity, the catecholamines.

Characterization of a novel hemoglobin-glutathione adduct that is elevated in diabetic patients.

Abstract: Typically, a diagnosis of diabetes mellitus is based on elevated circulating blood glucose levels. In an attempt to discover additional markers for the disease and predictors of prognosis, we undertook the characterization of HbA1d3 in diabetic and normal patients. PolyCAT A cation exchange chromatography and liquid chromatography-mass spectroscopy was utilized to separate the α- and β-globin chains of HbA1d3 and characterize their presence in normal and diabetic patients. We report the characterization of HbA1d3 as a glutathionylated, minor hemoglobin subfraction that occurs in higher levels in diabetic patients (2.26 ± 0.29 %) than in normal individuals (1.21 ± 0.14%, p < 0.001). The α-chain spectrum displayed a molecular ion of m/z 15126 Da, which is consistent with the predicted native mass of the HbA0 α-globin chain. By contrast, the mass spectrum of the β-chain showed a mass excess of 307 Da (m/z = 16173 Da) versus that of the native HbA0 β-globin chain (m/z = 15866 Da). The native molecular weight of the modified β-globin chain HbA0 was regenerated by treatment of HbA1d3 with dithiothreitol, consistent with a glutathionylated adduct. We propose that HbA1d3 (HbSSG) forms normally in vivo, and may provide a useful marker of oxidative stress in diabetes mellitus and potentially other pathologic situations.

Twenty-First Century Phox: Not Yet Ready for Widespread Screening

Abstract: Unstable forms of oxygen are highly reactive and have been widely implicated in disease pathogenesis. Indeed, interest in detecting their formation extends beyond this planet.1 Given their intrinsic evanescence, the generation of reactive oxygen species (ROS) in vivo has been inferred by the quantitation of products of their reaction with lipids,2 proteins,3 and DNA.4 Such data have implicated ROS in cardiovascular diseases such as atherosclerosis5 6 7 8 and ischemia-reperfusion syndromes.9 10 Evidence consistent with increased ROS generation based on such methodology has emerged in individuals with cardiovascular risk factors such as hypercholesterolemia,11 12 cigarette smoking,13 14 and alcoholism.15 Despite this, the outcome of trials of antioxidants as protective agents in cardiovascular diseases have been contradictory.16 17 18 However, a limitation of these trials is that none of them have included an assessment of ROS generation, either as an entry criterion or as a basis for dose selection. As in model systems in vitro,19 the response of humans to exogenous antioxidants is highly conditioned by the extent to which endogenous antioxidant defenses are depleted.20 21 Thus, inclusion of phenotypically inappropriate patients in such trials may have undermined sample size calculations and, consequently, the basis of statistical inference. If the functional competence of the diverse enzymes that comprise our defense against ROS is a critical determinant of our capacity to respond to exogenous antioxidants, genetic variations in the activity or expression of such enzymes may contribute to interindividual differences in susceptibility to ROS-mediated diseases. Reduced activity of the superoxide dismutase expressed in endothelial cells has been reported in patients with coronary artery disease (CAD) and correlates with their degree of endothelial dysfunction.22 Similarly, serum levels of paraoxonase (PON) 1, an enzyme that protects low density lipoprotein from oxidative …

Prostaglandin F2α Receptor-Dependent Regulation of Prostaglandin Transport

Abstract: Prostaglandin (PG) F(2alpha) may act on its G protein-coupled receptor (FP) or be imported intracellularly via a transporter, which has high affinity for PGF(2alpha) and PGE(2), but not prostacyclin (PGI(2)). In cells overexpressing the epitope-tagged FP together with the human prostaglandin transporter (hPGT), stimulation of the FP with PGF(2alpha) (1 nM-1 microM), or the less potent FP agonist, the isoprostane 8,12-iso-iPF(2alpha)-III, inhibited prostaglandin uptake via the hPGT. This effect was abolished by pretreatment of the cells with cholera toxin, but not with pertussis toxin. Furthermore, two dominant negative constructs directed against Galpha(s) partially blocked FP-mediated regulation of hPGT function, also suggesting Galpha(s) involvement in this phenomenon. Surprisingly, neither an activator (dibutyryl cyclic AMP) nor an inhibitor (H89) of cyclic AMP-dependent protein kinase had any effect on FP-mediated inhibition of hPGT activity. Furthermore, although PGF(2alpha) increases intracellular cyclic AMP via Galpha(s) activation, it does not induce phosphorylation of the transporter, excluding a role of cyclic AMP-dependent protein kinase in hPGT regulation. Activation of the PGI(2) receptor, which is also coupled to Galpha(s), does not regulate hPGT activity, despite markedly augmenting adenylate cyclase activation. In conclusion, activation of the FP reduces intracellular import of prostaglandins for metabolic inactivation, increasing prostanoid availability for membrane receptor activation. This effect seems to be mediated via Galpha(s), independent of adenylate cyclase and cyclic AMP-dependent protein kinase activation.

Smoking-induced vascular disease: a new twist on an old theme.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are recognized widely as potential environmental procarcinogens and have attracted their share of attention from both funding agencies and scientists interested in biomedical research. Curiously, their potential relevance to cardiovascular disease, rather than cancer, has stirred less emotion. This imbalance of attention is reflected also in society’s response to that most intimate form of self-pollution with PAHs (and much else), cigarette smoking. While the States have chosen to allocate varying proportions of their Tobacco Settlements to research, cancer tends to dominate the agenda. Yet, tobacco-related cardiovascular disease yields an even more striking burden on the public health than cancer. It has been estimated that cardiovascular morbidity and mortality are increased 4-fold in smokers and by one third in passive smokers.1 One might think that such daunting figures would prompt advocacy groups, such as the American Heart Association, to lobby vigorously at the State level for an appropriate allocation of the Tobacco Settlements to cardiovascular research. Our understanding of the mechanisms by which smoking mediates cardiovascular injury and the factors that determine interindividual susceptibility to smoking-induced tissue injury is remarkably limited. In this issue of Circulation Research , Kerzee and Ramos2 draw our attention to a mechanism of potential relevance to acceleration of atherogenesis by PAHs, including those in cigarette smoke. The aryl hydrocarbon receptor (Ahr) is a member of the family of basic helix loop helix proteins (bHLHs) that contain PAS domains. This family includes proteins related to differentiation, such as MyoD, the response to hypoxia, such as Hif1α, and circadian rhythms, such as CLOCK, …

Oral glycoprotein IIb/IIIa antagonism in patients with coronary artery disease

Abstract: Dose-finding studies and trials of interaction of oral glycoprotein IIb/IIIa antagonists with other antiplatelet agents have been limited. We hypothesized that these detailed assessments could be first performed in patients with stable coronary artery disease (CAD) and then extrapolated to the target population. To this end, we performed 2 sequential studies. The first study examined the dose-related effects on indexes of platelet and vascular function induced by the oral inhibitor RPR 109891, when given alone and in combination with aspirin, in patients (n = 100) with stable CAD. The second study (the Antagonism of the FIbrinogen Receptor after Myocardial Events trial) assessed the pharmacodynamics and safety of derived regimens in patients (n = 320) with unstable coronary syndromes. In patients with stable CAD, platelet aggregation was dose dependently inhibited by RPR 109891, and the dose-response relation was shifted to the right by the concomitant administration of aspirin (p = 0.0001). The degree of platelet inhibition induced by 3 doses of RPR 109891 (plus aspirin) was lower in patients with unstable than stable CAD. No drug-related major bleeding occurred in either study. RPR 109891 treatment was associated with acute and delayed thrombocytopenia. In conclusion, chronic treatment with an oral glycoprotein IIb/IIIa antagonist (1) induces antiplatelet effects that are potentiated by concomitant administration of aspirin, (2) may require dose adjustment in syndromes of platelet activation, (3) is associated with a low rate of clinically significant bleeding when doses inducing incomplete inhibition of platelet aggregation are used, and (4) requires frequent monitoring of platelet count unless reliable predictors of delayed thrombocytopenia become available.