Cyclooxygenase-2 is widely expressed in atherosclerotic lesions affecting native and transplanted human coronary arteries and colocalizes with inducible nitric oxide synthase and nitrotyrosine particularly in macrophages

The PGH-synthase system and isozyme-selective inhibition

Virtually all human cell types can express both cyclooxygenase (COX)-1 and COX-2 under appropriate circumstances. Both isoforms can subserve physiologic and pathophysiologic roles when coupled with the appropriate stimuli and downstream prostaglandin (PG)H2-isomerases and prostanoid receptors. Although the ratio of maximal biosynthetic capacity of human platelets to the basal rate of production of thromboxane A2 is approximately 5000, this ratio is much lower in the case of PGI2, thus dictating quite different requirements for the extent and duration of COX inhibition in human platelets and vascular endothelial cells to detect functional and clinical effects. The development of low-dose aspirin as an antiplatelet agent has been instrumental in characterizing the role of platelet COX-1 in atherothrombosis. Similarly, though quite unexpectedly, the development of coxibs as anti-inflammatory agents has been instrumental in elucidating the role of endothelial COX-2 in vascular occlusion. Because of differential requirements for the inhibition of thromboxane A2 versus PGI2 biosynthesis in vivo, most traditional nonsteroidal anti-inflammatory drugs tend to mimic the effects of coxibs, rather than aspirin, on prostanoid-dependent cardiovascular homeostasis.

Expression of COX-2 in platelet-monocyte interactions occurs via combinatorial regulation involving adhesion and cytokine signaling

Tight regulation of COX-2 expression is a key feature controlling eicosanoid production in atherosclerosis and other inflammatory syndromes. Adhesive interactions between platelets and monocytes occur in these conditions and deliver specific signals that trigger inflammatory gene expression. Using a cellular model of monocyte signaling induced by activated human platelets, we identified the central posttranscriptional mechanisms that regulate timing and magnitude of COX-2 expression. Tethering of monocytes to platelets and to purified P-selectin, a key adhesion molecule displayed by activated platelets, induces NF-kappaB activation and COX-2 promoter activity. Nevertheless, COX-2 mRNA is rapidly degraded, leading to aborted protein synthesis. Time-dependent signaling of monocytes induces a second phase of transcript accumulation accompanied by COX-2 enzyme synthesis and eicosanoid production. Here, generation of IL-1beta, a proinflammatory cytokine, promoted stabilization of COX-2 mRNA by silencing of the AU-rich mRNA decay element (ARE) in the 3'-untranslated region (3'UTR) of the mRNA. Consistent with observed mRNA stabilization, activated platelets or IL-1beta treatment induced cytoplasmic accumulation and enhanced ARE binding of the mRNA stability factor HuR in monocytes. These findings demonstrate that activated platelets induce COX-2 synthesis in monocytes by combinatorial signaling to transcriptional and posttranscriptional checkpoints. These checkpoints may be altered in disease and therefore useful as targets for antiinflammatory intervention.

Oxidative alterations of cyclooxygenase during atherogenesis

Nitric oxide (*NO) and eicosanoids are critical mediators of physiological and pathophysiological processes. They include inflammation and atherosclerosis. *NO production and eicosanoid synthesis become disrupted during atherosclerosis and thus, it is important to understand the mechanisms that may contribute to this outcome. We, and others, have shown that nitrogen oxide (NO(x)) species modulate cyclooxygenase (COX; also known as prostaglandin H(2) synthase) activity and alter eicosanoid production. We have determined that peroxynitrite (ONOO(-)) has multiple effects on COX activity. ONOO(-) can provide the peroxide tone necessary for COX activation, such that simultaneous exposure of COX to its arachidonic acid substrate and ONOO(-) results in increased eicosanoid production. Alternatively, in the absence of arachidonic acid, ONOO(-) can modify COX through nitration of an essential tyrosine residue (Tyr385) such that it is incapable of catalysis. In this regard, we have shown that COX nitration occurs in human atherosclerotic tissue and in aortic lesions from ApoE(-/-) mice kept on a high fat diet. Additionally, we have demonstrated that Tyr nitration in ApoE(-/-) mice is dependent on the inducible form of NO synthase (iNOS). Under conditions where ONOO(-) persists and arachidonic acid is not immediately available, the cell may try to correct the situation by responding to ONOO(-) and releasing arachidonic acid via a signaling pathway to favor COX activation. Other post-translational modifications of COX by NO(x) species include S-nitrosation of cysteine (Cys) residues (which may have an activating effect) and Cys oxidation. The central focus of this review will include a discussion of how NO(x) species alter COX activity at the molecular level and how these modifications may contribute to altered eicosanoid output during atherosclerosis and lesion development.

Protective effect of the G-765C COX-2 polymorphism on subclinical atherosclerosis and inflammatory markers in asymptomatic subjects with cardiovascular risk factors

BACKGROUND

Cyclooxygenase (COX)-2, a key regulatory enzyme in prostanoid synthesis, plays an important role in inflammatory processes. The -765G>C COX-2 polymorphism has been associated with lower promoter activity in vitro and reduced levels of C-reactive protein (CRP) in atherosclerotic carriers of the C allele. However, its pathophysiological relevance in vivo has not been fully elucidated.

METHODS AND RESULTS

We assessed the -765G>C polymorphism and COX-2 expression in 220 asymptomatic subjects free of cardiovascular disease, in relation to global vascular risk, carotid intima-media thickness (IMT), and inflammatory markers (fibrinogen, C-reactive protein [CRP], von Willebrand factor [vWF] and interleukin-6 [IL-6]). Genotype frequencies were: CC (7.7%), CG (34.5%), GG (57.7%). Among hypercholesterolemic subjects (n=140), C allele carriers had lower COX-2 expression (p<0.05), reduced carotid IMT (p<0.01) and diminished levels of inflammatory markers CRP, vWF and IL-6 (p<0.05), as compared to GG homozygous subjects. The association between carotid IMT and COX-2 polymorphism remained significant after adjusting for cardiovascular risk factors and inflammatory markers (p=0.008).

CONCLUSIONS

In asymptomatic hypercholesterolemic subjects the C allele of -765G>C COX-2 polymorphism was associated with lower COX-2 expression, and reduced subclinical atherosclerosis and systemic inflammation compared with GG homozygous, thus conferring atherosclerosis protection in this cardiovascular risk population.

Vitamin A deficiency induces prooxidant environment and inflammation in rat aorta

We evaluated whether nutritional vitamin A deficiency generates oxidative stress and inflammation in aorta. Wistar male rats (21 days old) were given free access to a control (8 mg retinol as retinyl palmitate/kg) or a vitamin A- deficient diet for three months. One group of deficient animals was fed with the control diet fifteen days before sacrifice. Thiobarbituric acid-reactive substances (TBARS) and nitrite concentration where both analyzed in serum and aorta. Aorta Copper-Zinc Superoxide dismutase (CuZnSOD), Glutathion peroxidase (GPx) and Catalase (CAT) activities were measured. In addition, binding activity of the nuclear factor- kB (NF-kB), inducible and endothelial Nitric Oxide synthase (iNOS and eNOS, respectively) and Ciclooxygenase-2 (COX-2) expressions were determinated in aorta. Rats fed the vitamin A- deficient diet were characterized by sub-clinical plasma retinol concentration and showed increased serum and aorta concentrations of TBARS compared to controls. Lower than control activities of CuZnSOD, GPx, and CAT were observed in aorta of the vitamin A- deficient group. The binding activity of NF- kB was higher in vitamin A- deficient animals than controls. In addition, NO production evaluated as nitrite concentration increased in aorta and serum, associated with a higher expression of iNOS, eNOS and COX-2 in aorta of vitamin A-deficient rats. The incorporation of vitamin A into the diet of vitamin A-deficient rats reverted the changes observed in TBARS level, CuZnSOD and GPx activities, nitrite concentration and also, iNOS, eNOS and COX-2 expression. Prooxidant environment and inflammation are induced by vitamin A deficiency in rat aorta.

Ciclooxigenasa 2: ¿una nueva diana terapéutica en la aterosclerosis?

It is now widely accepted that atherosclerosis is a complex chronic inflammatory disorder of the arterial tree associated with several risk factors. From the initial phases to eventual rupture of vulnerable atherosclerotic plaques, a low-grade inflammation, also termed microinflammation, appears to play a key pathogenetic role. Systemic inflammatory markers (C reactive protein, cytokines adhesion molecules) also play a role in this process. Experimental and clinical evidence suggests that cyclooxygenase-2 (COX-2), an enzyme which catalyzes the generation of prostaglandins from arachidonic acid, also contributes to lesion formation. Recent reports by our group have demonstrated increased monocyte COX-2 activity and the production of prostaglandin E2 in relation to cardiovascular risk factors and subclinical atherosclerosis in asymptomatic subjects. Our findings support the notion that the COX-2/prostaglandin E2 axis may have a role, raising the question as to whether its selective inhibition might be an attractive therapeutic target in atherosclerosis. COX-2 inhibitors, collectively called "coxibs" (celecoxib, rofecoxib, valdecoxib, lumiracoxib, etc), held a promise as anti-inflammatory drugs without the some of the side effects of aspirin or non steroidal antiinflammatory agents. However, clinical studies raise several clinically relevant questions as to their beneficial role in atherosclerosis prevention, because of increased thrombogenicity and cardiovascular risk, and therefore coxibs should be restricted in atherosclerosis-prone patients.

Nitric oxide and atherosclerosis: an update

Nitric oxide (NO) is a molecule that has gained recognition as a crucial modulator of vascular disease. NO has a number of intracellular effects that lead to vasorelaxation, endothelial regeneration, inhibition of leukocyte chemotaxis, and platelet adhesion. Endothelium damage induced by atherosclerosis leads to the reduction in bioactivity of endothelial NO synthase (eNOS) with subsequent impaired release of NO together with a local enhanced degradation of NO by increased generation of reactive oxygen species with subsequent cascade of oxidation-sensitive mechanisms in the arterial wall. Many commonly used vasculoprotective agents have their therapeutic actions through the production of NO. L-Arginine, the precursor of NO, has demonstrated beneficial effects in atherosclerosis and disturbed shear stress. Finally, eNOS gene polymorphism might be an additional risk factor that may contribute to predict cardiovascular events. However, further studies are needed to understand the possible clinical implications of these correlations.

Inducible nitric oxide synthase mediates prostaglandin h2 synthase nitration and suppresses eicosanoid production

Nitric oxide (NO) modulates the biological levels of arachidonate-derived cell signaling molecules by either enhancing or suppressing the activity of prostaglandin H(2) isoforms (PGHS-1 and PGHS-2). Whether NO activates or suppresses PGHS activity is determined by alternative protein modifications mediated by NO and NO-derived species. Here, we show that inducible NO synthase (iNOS) and PGHS-1 co-localize in atherosclerotic lesions of ApoE(-/-) mouse aortae. Immunoblotting and immunohistochemistry revealed Tyr nitration in PGHS-1 in aortic lesions but markedly less in adjacent nonlesion tissue. PGHS-2 was also found in lesions, but 3-nitrotyrosine incorporation was not detected. 3-Nitrotyrosine formation in proteins is considered a hallmark reaction of peroxynitrite, which can form via NO-superoxide reactions in an inflammatory setting. That iNOS-derived NO is essential for 3-nitrotyrosine modification of PGHS-1 was confirmed by the absence of 3-nitrotyrosine in lesions from ApoE(-/-)iNOS(-/-) mice. Mass spectrometric studies specifically identified the active site residue Tyr385 as a 3-nitrotyrosine modification site in purified PGHS-1 exposed to peroxynitrite. PGHS-mediated eicosanoid (PGE(2)) synthesis was more than fivefold accelerated in cultured iNOS(-/-) versus iNOS-expressing mouse aortic smooth muscle cells, suggesting that iNOS-derived NO markedly suppresses PGHS activity in vascular cells. These results further suggest a regulatory role of iNOS in eicosanoid biosynthesis in human atherosclerotic lesions.

COX isoforms in the cardiovascular system: understanding the activities of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the formation of prostanoids by the enzyme cyclooxygenase (COX). Work in the past 15 years has shown that COX exists in two forms: COX1, which is largely associated with physiological functions, and COX2, which is largely associated with pathological functions. Heated debate followed the introduction of selective COX2 inhibitors around 5 years ago: do these drugs offer any advantages over the traditional NSAIDs theywere meant to replace, particularly in regard to gastrointestinal and cardiovascular side effects? Here we discuss the evidence and the latest recommendations for the use of selective inhibitors of COX2 as well as the traditional NSAIDs.

Expression of cyclooxygenase-1 and cyclooxygenase-2 in human renal allograft rejection - a prospective study

Cyclooxygenases (COX) are known to be involved in inflammatory kidney diseases. However, there are no data available about the expression of COX-1 and only preliminary reports about the expression of COX-2 in biopsies of patients undergoing acute renal allograft rejection. We conducted this prospective study to analyze the expression, distribution, and cellular localization of COX-1 and -2 and thus to elucidate the role of COX in human kidney transplantation. One hundred forty-four biopsies were included from patients without rejection and unaltered morphology (n = 60), with acute interstitial rejection (n = 7), with acute vascular rejection (n = 21), with chronic allograft nephropathy (n = 16), without rejection but with various other lesions (n = 40). COX-1 and -2 expression was localized in each biopsy by immunohistochemistry. We found a highly significant up-regulation of COX-1 in vessels and in infiltrating interstitial cells of patients with acute allograft rejection compared with biopsies with well-preserved tissue. Also, COX-2 expression was significantly elevated in infiltrating interstitial cells of biopsies with acute rejection. This is the first prospective study demonstrating a significant induction of both COX-1 and -2 in human allograft biopsies with acute rejection after renal transplantation.

Anthocyanins from soybean seed coat inhibit the expression of TNF-alpha-induced genes associated with ischemia/reperfusion in endothelial cell by NF-kappaB-dependent pathway and reduce rat myocardial damages incurred by ischemia and reperfusion in vivo

We examined the inhibition of the expression of some inflammatory genes associated with ischemia-reperfusion (I/R) injury by anthocyanins isolated from black soybean seed coat in tumor necrosis factor-alpha (TNF-alpha)-treated bovine aortic endothelial cells. In addition, its potential use on I/R-injury was investigated using rats subjected to 30-min occlusion of left descending coronary artery followed by 24-h reperfusion. Western blot analysis and luciferase activity assay showed that anthocyanins inhibited TNF-alpha-induced vascular cell adhesion molecule-1, intracellular adhesion molecule-1, and cyclooxygenase-2 levels, which is through NF-kappaB-dependent pathway. Further, anthocyanins protected myocardiac injury from I/R in rats. It is suggested that anthocyanins from black soybean seed coat can be used as a useful drug to modulate cardiovascular disorder.

Prévention de la thrombose et de l’inflammation vasculaire : place des inhibiteurs mixtes des cyclooxygénases et de la 5-lipoxygénase

Aspirin, a standard non-steroidal anti-inflammatory drug (NSAID) is currently used in antithrombotic treatment. However, its use is limited by largely recognized gastrotoxicity and recommended doses are low. The major side effect of aspirin is related to its ability to suppress prostaglandin (PG) synthesis by constitutive cyclooxygenase-1 (COX-1). Specific inhibitors of COX-2, the inducible isoform of COX which was more recently described, have potent antiinflammatory effects. They are associated with minor risk of gastric tractus toxicity and reduced inflammatory leukocyte components known for their proatherothrombotic properties. Nevertheless, recent findings attributed a significant cardiovascular risk to some of them. 5-lipoxygenase (5-LOX), an enzyme mainly expressed by leukocytes, is responsible for the generation of leukotrienes, the major lipidic proinflammatory mediators. Development of combined inhibitors of 5-LOX and COX isoforms 1 and 2 inaugurate an interesting new therapeutic pathway. Indeed, such inhibitors suppress not only the activation of platelets, leukocytes and endothelial cells but also prevent their metabolic and functional interactions. In addition to their broad spectrum inhibition, they may be associated with the minor gastrotoxic effect. Thus, platelet-leukocyte interactions which dominate the underlying inflammatory process particularly in atherosclerosis, might reinforce the benefits of such inhibitors.

Cyclooxygenase-2 induction by bradykinin in aortic vascular smooth muscle cells

Vascular smooth muscle cell proliferation and migration play an important role in the pathophysiology of several vascular diseases, including atherosclerosis. Prostaglandins that have been implicated in this process are synthesized by two isoforms of cyclooxygenase (COX), with the expression of the regulated COX-2 isoform increased in atherosclerotic plaques. Bradykinin (BK), a vasoactive peptide increased in inflammation, induces the formation of prostaglandins through specific receptor activation. We hypothesized that BK plays an important role in the regulation of COX-2, contributing to the increase in production of prostaglandins in vascular smooth muscle cells. Herein we examined the signaling pathways that participate in the BK regulation of COX-2 protein levels in primary cultured aortic vascular smooth muscle cells. We observed an increase in COX-2 protein levels induced by BK that was maximal at 24 h. This increase was blocked by a B2 kinin receptor antagonist but not a B1 receptor antagonist, suggesting that the B2 receptor is involved in this pathway. In addition, we conclude that the activation of mitogen-activated protein kinases p42/p44, protein kinase C, and nitric oxide synthase is necessary for the increase in COX-2 levels induced by BK because either of the specific inhibitors for these enzymes blocked the effect of BK. Using a similar approach, we further demonstrated that reactive oxygen species and cAMP were not mediators on this pathway. These results suggest that BK activates several intracellular pathways that act in combination to increase COX-2 protein levels. This study suggests a role for BK on the evolution of the atheromatous plaque by virtue of controlling the levels of COX-2.

Oxidative stress augments the production of matrix metalloproteinase-1, cyclooxygenase-2, and prostaglandin E2 through enhancement of NF-kappa B activity in lipopolysaccharide-activated human primary monocytes

The excessive production of reactive oxidative species (ROS) associated with inflammation leads to a condition of oxidative stress. Cyclooxygenase-2 (COX-2), PGE(2), and matrix metalloproteinases (MMPs) are important mediators during the process of inflammation. In this paper we report on studies examining how the ROS hydrogen peroxide (H(2)O(2)) affects the production of MMP-1, COX-2, and PGE(2). Addition of H(2)O(2) to LPS-activated monocytes, but not naive monocytes, caused a significant enhancement of the LPS-induced production of MMP-1, COX-2, and PGE(2). The mechanism by which H(2)O(2) increased these mediators was through enhancement of IkappaBalpha degradation, with subsequent increases in NF-kappaB activation and NF-kappaB p50 translocation to the nucleus. The effects of H(2)O(2) on IkappaBalpha degradation, NF-kappaB activation, and NF-kappaB p50 localization to the nucleus were demonstrated through studies of coimmunoprecipitation of IkappaBalpha with p50, ELISA of NF-kappaB p65 activity, and Western blot analysis of the nuclear fraction extract for p50. The key role for NF-kappaB in this process was demonstrated by the ability of MG-132 or lactacystin (proteasome inhibitors) to block the enhanced production of MMP-1, COX-2, and PGE(2). In contrast, indomethacin, which inhibited PGE(2) production, partially blocked the enhanced MMP-1 production. Moreover, although PGE(2) restored MMP-1 production in indomethacin-treated monocyte cultures; it failed to significantly restore MMP-1 production in proteasome inhibitor-treated cultures. Thus, in the presence of LPS and H(2)O(2), NF-kappaB plays a dominate role in the regulation of MMP-1, COX-2, and PGE(2) expression.

Targeting prostaglandin E2 receptors as an alternative strategy to block cyclooxygenase-2-dependent extracellular matrix-induced matrix metalloproteinase-9 expression by macrophages

COX-2-dependent prostaglandin (PG) E2 synthesis regulates macrophage MMP expression, which is thought to destabilize atherosclerotic plaques. However, the administration of selective COX-2 inhibitors paradoxically increases the frequency of adverse cardiovascular events potentially through the loss of anti-inflammatory prostanoids and/or disturbance in the balance of pro- and anti-thrombotic prostanoids. To avoid these collateral effects of COX-2 inhibition, a strategy to identify and block specific prostanoid-receptor interactions may be required. We previously reported that macrophage engagement of vascular extracellular matrix (ECM) triggers proteinase expression through a MAPKerk1/2-dependent increase in COX-2 expression and PGE2 synthesis. Here we demonstrate that elicited macrophages express the PGE2 receptors EP1-4. When plated on ECM, their expression of EP2 and EP4, receptors linked to PGE2-induced activation of adenylyl cyclase, is strongly stimulated. Forskolin and dibutryl cyclic-AMP stimulate macrophage matrix metalloproteinase (MMP)-9 expression in a dose-dependent manner. However, an EP2 agonist (butaprost) has no effect on MMP-9 expression, and macrophages from EP2 null mice exhibited enhanced COX-2 and MMP-9 expression when plated on ECM. In contrast, the EP4 agonist (PGE1-OH) stimulated macrophage MMP-9 expression, which was inhibited by the EP4 antagonist ONO-AE3-208. When compared with COX-2 silencing by small interfering RNA or inhibition by celecoxib, the EP4 antagonist was as effective in inhibiting ECM-induced proteinase expression. In addition, ECM-induced MMP-9 expression was blocked in macrophages in which EP4 was silenced by small interfering RNA. Thus, COX-2-dependent ECM-induced proteinase expression is effectively blocked by selective inhibition of EP4, a member of the PGE2 family of receptors.

Induction of endothelial cell apoptosis by lipid hydroperoxide-derived bifunctional electrophiles

Endothelial dysfunction is considered to be the earliest event in atherogenesis. Oxidative stress, inflammation, and apoptosis play critical roles in its progression and onset. Lipid peroxidation, which occurs during oxidative stress, results in the formation of lipid hydroperoxide-derived bifunctional electrophiles such as 4-hydroxy-2(E)-nonenal that induce apoptosis. In this study, recently identified lipid hydroperoxide-derived bifunctional electrophiles 4-oxo-2(E)-nonenal (ONE; 5-30 microm) and 4,5-epoxy-2(E)-decenal (EDE; 10-20 microM) were shown to cause a dose- and time-dependent apoptosis in EA.hy 926 endothelial cells. This was manifest by morphological changes, caspase-3 activation, and poly(ADP-ribose) polymerase cleavage. Bifunctional electrophiles caused cytochrome c release from mitochondria into the cytosol, implicating a mitochondrial pathway of apoptosis in the endothelial cells. The novel carboxylate-containing lipid hydroperoxide-derived bifunctional electrophile 9,12-dioxo-10(E)-dodecenoic acid was inactive because it could not translocate across the plasma membrane. However, its less polar methyl ester derivative (2-10 microM) was the most potent inducer of apoptosis of any bifunctional electrophile that has been tested. An acute decrease in intracellular glutathione (GSH) preceded the onset of apoptosis in bifunctional electrophile-treated cells. The ability of ONE and EDE to deplete GSH was directly correlated with their predicted reactivity toward nucleophilic amino acids. Liquid chromatography/mass spectrometry methodology was developed in order to examine the intracellular and extracellular concentrations of bifunctional electrophile-derived GSH adducts. Relative intracellular/extracellular ratios of the GSH adducts were identical with the rank order of potency for inducing caspase 3 activation. This suggests that there may be a role for the bifunctional electrophile-derived GSH adducts in the apoptotic response. N-Acetylcysteine rescued bifunctional electrophile-treated cells from apoptosis, whereas the GSH biosynthesis inhibitor d,l-buthionine-(R,S)-sulfoximine sensitized the cells to apoptosis. These data suggest that lipid hydroperoxide-derived bifunctional electrophiles may play an important role in cardiovascular pathology through their ability to induce endothelial cell apoptosis.

Colocalization of oxidized low-density lipoprotein, caspase-3, cyclooxygenase-2, and macrophage migration inhibitory factor in arteriosclerotic human carotid arteries

Apoptotic and inflammatory processes occur in human arteriosclerotic lesions. We examined the hypothesis whether both processes are possibly associated by studying the colocalization of corresponding markers. In 11 human arteriosclerotic carotid arteries, proapoptotic markers (CPP32 (caspase-3), poly(ADP-ribose) polymerase, apoptosis-inducing factor, c-Jun/AP-1, and p53) and proinflammatory markers (macrophage migration inhibitory factor (MIF) and cyclooxygenase-2) were found in macrophages (MPhi) evaluated by computer-assisted immunohistomorphometry. Double-labeling studies demonstrated a colocalization of, both, proapoptotic and proinflammatory markers in these MPhi. Moreover, these MPhi also contained oxidized low-density lipoproteins (oxLDL). Exposure of cultured human MPhi to oxLDL, C6-ceramide, and tumor necrosis factor-alpha or H2O2 resulted in a significant increase of the apoptosis rate as well as of the MIF protein expression. Our study of MPhi in arteriosclerotic carotid arteries and in vitro experiments provide evidence that markers of apoptosis and inflammation are not only significantly increased but are also coexpressed. We conclude there are reciprocal modulatory interactions between apoptotic and inflammatory pathways in human plaque MPhi, which might importantly modify plaque progression or stability.

A Critical Appraisal of the Phenomenon of Aspirin Resistance

Aspirin is the mainstay antiplatelet treatment in patients with high risk of cardiovascular atherothrombotic events, and its beneficial effect is documented in several clinical trials. Nevertheless, the effectiveness of aspirin has been questioned by the emergence of the concept of 'aspirin resistance' (AR). This phenomenon, although lacking a precise definition, covers the fact that some patients do not exhibit the expected platelet inhibition by use of various techniques for measuring platelet function. In this critical review, we evaluate the methods used for measuring AR. We will discuss the available data regarding the prevalence and the clinical importance of the phenomenon. Finally, the potential mechanisms underlying AR are considered.

Inhibition of cyclooxygenase with indomethacin phenethylamide reduces atherosclerosis in apoE-null mice

Non-selective inhibition of cyclooxygenase (COX) has been reported to reduce atherosclerosis in both rabbit and murine models. In contrast, selective inhibition of COX-2 has been shown to suppress early atherosclerosis in LDL-receptor null mice but not more advanced lesions in apoE deficient (apoE(-/-)) mice. We investigated the efficacy of the novel COX inhibitor indomethacin phenethylamide (INDO-PA) on the development of different stages of atherosclerotic lesion formation in female apoE(-/-) mice. INDO-PA, which is highly selective for COX-2 in vitro, reduced platelet thromboxane production by 61% in vivo, indicating partial inhibition of COX-1 in vivo. Treatment of female apoE(-/-) mice with 5mg/kg INDO-PA significantly reduced early to intermediate aortic atherosclerotic lesion formation (44 and 53%, respectively) in both the aortic sinus and aorta en face compared to controls. Interestingly, there was no difference in the extent of atherosclerosis in the proximal aorta in apoE(-/-) mice treated from 11 to 21 weeks of age with INDO-PA, yet there was a striking (76%) reduction in lesion size by en face analysis in these mice. These studies demonstrate the ability of non-selective COX inhibition with INDO-PA to reduce early to intermediate atherosclerotic lesion formation in apoE(-/-) mice, supporting a role for anti-inflammatory approaches in the prevention of atherosclerosis.

Depletion of iNOS-derived nitric oxide by prostaglandin H synthase-2 in inflammation-activated J774.2 macrophages through lipohydroperoxidase turnover

PGHS-2 (prostaglandin H synthase-2) is induced in mammalian cells by pro-inflammatory cytokines in tandem with iNOS [high-output ('inducible') nitric oxide synthase], and is co-localized with iNOS and nitrotyrosine in human atheroma macrophages. Herein, murine J774.2 macrophages incubated with lipopolysaccharide and interferon gamma showed induction of PGHS-2 and generated NO using iNOS that could be completely depleted by 12(S)-HPETE [12(S)-hydroperoxyeicosatetraenoic acid; 2.4 muM] or hydrogen peroxide (500 microM) (0.42+/-0.084 and 0.38+/-0.02 nmol x min(-1) x 10(6) cells(-1) for HPETE and H2O2 respectively). COS-7 cells transiently transfected with human PGHS-2 also showed HPETE- or H2O2-dependent NO decay (0.44+/-0.016 and 0.20+/-0.04 nmol x min(-1) x 10(6) cells(-1) for 2.4 microM HPETE and 500 microM H2O2 respectively). Finally, purified PGHS-2 consumed NO in the presence of HPETE or H2O2 (168 and 140 microM x min(-1) x microM enzyme(-1) for HPETE and H2O2 respectively), in a haem-dependent manner, with 20 nM enzyme consuming up to 4 microM NO. K(m) (app) values for NO and 15(S)-HPETE were 1.7+/-0.2 and 0.45+/-0.16 microM respectively. These data indicate that PGHS-2 catalytically consumes NO during peroxidase turnover and that pro-inflammatory cytokines simultaneously upregulate NO synthesis and degradation pathways in murine macrophages. Catalytic NO consumption by PGHS-2 represents a novel interaction between NO and PGHS-2 that may impact on the biological effects of NO in vascular signalling and inflammation.

Suppression of experimental aortic aneurysms: comparison of inducible nitric oxide synthase and cyclooxygenase inhibitors

The rat model of abdominal aortic aneurysm (AAA) is associated with inflammation, destruction of extracellular matrix, and production of both inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-9 (MMP-9). Indomethacin, a nonselective cyclooxygenase inhibitor, may prevent AAA formation by inhibiting cyclooxygenase-2 (COX-2) activity. We hypothesized that indomethacin, rofecoxib (selective COX-2 inhibitor), and 1400 W (selective iNOS activity inhibitor) would decrease aneurysm formation in the rat model. Forty-six male Wistar rats underwent intraaortic elastase infusion in two parallel studies based on medication delivery route. Sixteen rats were randomized to rofecoxib or water by gastric lavage. Thirty rats were randomized to subcutaneous saline, indomethacin, or 1400 W. Heart rate, blood pressure and aortic diameters were measured. Western Blot and mRNA analysis for MMP-9 and iNOS was performed on postoperative day 7 aortic segments. Elastin degradation and inflammation were evaluated by immunohistochemistry. Elastase infusion produced AAA in all rats. 1400 W significantly limited aneurysm expansion (p = 0.01) whereas treatment with indomethacin and rofecoxib did not. Only 1400 W significantly increased blood pressure (p < 0.001). Indomethacin alone statistically decreased MMP-9 (p < 0.011). 1400 W resulted in greater conservation of aortic elastin than indomethacin (p = 0.025). All groups demonstrated statistically similar expression of iNOS. In conclusion, selective iNOS activity inhibitor, 1400 W, significantly decreased aneurysm size and preserved aortic elastin without altering MMP-9 levels. Indomethacin significantly decreased MMP-9 expression without decreasing aneurysm size. Rofecoxib did not significantly decrease MMP-9 expression or aneurysm size. Inhibition of iNOS limits aneurysmal expansion by mechanisms other than MMP-9 inhibition. MMP-9 inhibition by indomethacin is not sufficient to limit aneurysm expansion in our model.

Reduced Cyclooxygenase Involvement in Vascular Endothelial Function in Rat Renal Transplantation

BACKGROUND

Cardiovascular disease is a major cause of death following renal transplantation. Mechanisms leading to vascular dysfunction outside the transplanted organ involve common risk factors such as hypertension, hypercholesterolemia, proteinuria, but immune-mediated factors may also be involved. We hypothesized that transplantation-associated risk factors are involved in the development of vascular dysfunction following renal transplantation.

METHODS

Vascular function was studied in Fisher to Lewis allografts. Lewis to Lewis syngrafted rats served as controls. All rats received cyclosporin A for 10 days. Allografts were treated with ACE inhibition or AT1 receptor blockade or left untreated. After 34 weeks, aorta rings were studied for contractile and dilator responses in the presence or absence of L-NMMA and/or indomethacin. Tissue sections were immunostained for COX-1 and COX-2.

RESULTS

In contrast to syngrafts and treated allografts, untreated allografts developed proteinuria and hypercholesterolemia. In aortic rings, NOS inhibition similarly increased contractile responses and decreased dilator responses in syngrafts and allografts, indicating comparable NO pathways. In contrast, indomethacin affected contractile and dilator responses in syngrafts, but not in treated and untreated allografts, indicating absence of COX-derived prostanoids in control over vascular tone in allografts. This was in line with immunohistologic analysis demonstrating reduced aortic COX-2 expression in allografts. COX-1 expression was unaltered. Interestingly, RAS blockade quantitatively increased endothelium-dependent dilation without qualitatively altering COX function and expression.

CONCLUSION

Involvement of COX-derived prostaglandins in vascular endothelial function outside the transplanted organ is strongly diminished after allogeneic renal transplantation. RAS blockade improves common cardiovascular risk factors and endothelium-dependent dilation, but fails to restore prostaglandin function.

17-Beta estradiol enhances prostaglandin E2 production in human U937-derived macrophages

Prostaglandins (PGs) are potent eicosanoid lipid mediators that have been implicated in numerous homeostatic functions and inflammation. Estrogens have been shown to regulate the expression of genes in lipid metabolism in many cellular systems. In this study, the activation of macrophages and the modulation of PG release by estrogens were examined. The effects of 17-alpha and 17-beta estradiols, phytoestrogen Genistein and several selective estrogen receptor modulators on the release of PGE2 were investigated in human U937-derived macrophages. 17-Beta estradiol caused an enhancement of PGE2 production in a time- and dose-dependent manner. Treatment of macrophages with 17-beta estradiol elicited an increased arachidonic acid (AA) release and an up-regulation of both cyclooxygenesis-1 and cyclooxygenesis-2 enzymes at both the transcript and protein levels. In addition, immunostaining of nuclear estrogen receptor alpha and the observation of ICI182 780 blockade of PGE2 production indicated that 17-beta estradiol-induced PGE2 release was mainly through nuclear estrogen receptor alpha.

Resveratrol: Preventing properties against vascular alterations and ageing

Cardiovascular diseases are the leading cause of death in developed countries where the common pathological substrate underlying this process is atherosclerosis. Several new concepts have emerged in relation to mechanisms that contribute to the regulation of the vascular diseases and associated inflammatory effects. Recently, potential antioxidants (vitamin E, polyphenols) have received much attention as potential anti-atherosclerotic agents. Among the polyphenols with health benefic properties, resveratrol, a phytoalexin of grape, seem to be a good candidate protecting the vascular walls from oxidation, inflammation, platelet aggregation, and thrombus formation. In this review, we focus on the mechanism of resveratrol cardiovascular benefic effects. We analyze, in relation with the different steps of atherosclerotic process, the resveratrol properties at multiple levels, such as cellular signaling, enzymatic pathways, apoptosis, and gene expression. We show and discuss the relationship with reactive oxygen species, regulation of pro-inflammatory genes including cycloxygenases and cytokines in molecular inflammatory and aging processes, and how the regulation of these activites by resveratrol can lead to a prevention of vascular diseases.

CD40-ligand-dependent induction of COX-2 gene expression in endothelial cells by activated platelets: inhibitory effects of atorvastatin

Increasing evidence shows the importance of platelet-endothelial cell interactions in the progression of atherosclerosis. Platelets contribute to coronary events both as major components of thrombi and as a triggering factor in inflammation that leads to plaque vulnerability. Recent data suggest that statins, besides their lipid-lowering properties, exert pleiotropic effects that may be beneficial in atherosclerosis. Whether activated platelets influence cyclooxygenase-2 (COX-2) expression in human umbilical vein endothelial cells (HUVEC), the effect of atorvastatin, and possible mechanisms were investigated. COX-2 gene expression in HUVEC was studied using real-time polymerase chain reaction. CD40 ligand surface expression of platelets was tested by fluorescence-activated cell sorting analyses. Activated platelets significantly up-regulated COX-2 gene expression in HUVEC. Co-incubation of platelets with atorvastatin was shown to reverse this up-regulation via reduction of CD40 ligand surface expression on platelets. Data suggest that atorvastatin influences CD40-CD40-ligand-dependent platelet-endothelial interaction and that this influence affects platelet-induced COX-2 expression in HUVEC.

Novel features of nitric oxide, endothelial nitric oxide synthase, and atherosclerosis

There is a complex pathophysiologic scenario involving nitric oxide (NO), endothelial nitric oxide synthase (eNOS), and the development of atherosclerosis and unstable atheroma. Endothelial damage induced by atherosclerosis leads to the reduction in bioactivity of eNOS with subsequent impaired release of NO. An important mechanism is local enhanced degradation of NO by increased generation of reactive oxygen species and other free radicals, with subsequent cascade of oxidation-sensitive mechanisms in the arterial wall. Novel molecular approaches have resulted in the development of new strains of mice lacking eNOS. These experimental models will help to understand how to implement NO-based therapies against atherosclerosis. L-arginine, the precursor of NO, has demonstrated beneficial effects in atherosclerosis and disturbed shear stress. The target or goal for new drugs should be the complete restoration of NO-mediated signaling pathways in atherosclerotic arteries.

Drug therapies to prevent coronary plaque rupture and erosion: present and future

Patients at high risk for coronary heart disease usually have a number of atherosclerotic plaques in their coronary arteries. Some plaques grow inward and, once they have caused a critical degree of luminal stenosis, lead to chronic anginal symptoms. Other plaques grow outward and remain silent unless they disrupt and trigger an acute coronary event. Either type of plaque may become vulnerable to rupture or erosion once they have reached an advanced stage. Typically, a highly stenotic fibrotic plaque is prone to erosion, whereas an advanced lipid-rich thin-cap fibroatheroma is prone to rupture. Because of the multitude and complex nature of the coronary lesions and our inability to detect silent rupture-prone plaques, the best practical approach to prevent acute coronary events is to treat the vulnerable patient, i.e., to eliminate the risk factors of coronary disease. Despite such preventive measures, a sizable number of patients still experience acute coronary events due to plaque erosion or rupture. Thus, there is room for new avenues to pharmacologically stabilize vulnerable plaques. The development of new noninvasive tools to detect the progression and regression of individual non-stenotic rupture-prone plaques will allow testing of such novel pharmacotherapies. Because no specific plaque-targeted therapies are available at present, we give an overview of the current pharmacotherapy to treat the vulnerable patient and also discuss potential novel therapies to prevent acute coronary events.

Celecoxib, a Selective Cyclooxygenase-2 Inhibitor, Decreases Monocyte Chemoattractant Protein-1 Expression and Neointimal Hyperplasia in the Rabbit Atherosclerotic Balloon Injury Model

The inflammation in response to vascular injury is becoming increasingly recognized as a potential contributor to restenosis. Cyclooxygenase-2 (COX-2) is the inducible form of cyclooxygenase and has been shown to be involved in the proinflammatory response of vascular tissue. Bilateral femoral artery lesions were induced by air desiccation in New Zealand White rabbits followed by high cholesterol diet feeding for 28 days. Balloon injury and stent implantation were performed at the preinjured vessel segments. Immunostaining showed that uninjured vessel segments stained positive only for COX-1 but not for COX-2. Injured vessel segments showed, in addition to COX-1, significant positive staining for COX-2. In the efficacy study, celecoxib (75 mg/kg/d) was administered orally beginning 3 hours before balloon injury or stent implantation on day 28 and daily for 21 days. Monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-2 and -9 (MMPs) expression were quantified in arterial extracts 4 days after balloon injury by Western blot and gelatin zymography. Morphometric analysis and immunostaining for macrophages were performed 21 days after balloon injury. Celecoxib treatment significantly decreased MCP-1 expression (P < 0.01). Neointimal hyperplasia was significantly inhibited by celecoxib in both balloon injury and stent models (0.49 +/- 0.20 versus 0.70 +/- 0.35 mm2 from balloon injury model, P < 0.05, and 0.81 +/- 0.25 versus 1.69 +/- 0.43 mm2 from stent model, P < 0.05), accompanied by reduced macrophage infiltration. We conclude that celecoxib decreases the inflammatory response and intimal hyperplasia following vascular injury, possibly through inhibition of MCP-1 expression, implying a pivotal role of inflammation in the pathogenesis of restenosis.

Cyclooxygenase- and lipoxygenase-dependent relaxation to arachidonic acid in rabbit small mesenteric arteries

We recently reported that the lipoxygenase product 11,12,15-trihydroxyeicosatrienoic acid (THETA) mediates arachidonic acid (AA)-induced relaxation in the rabbit aorta. This study was designed to determine whether this lipoxygenase metabolite is involved in relaxation responses to AA in rabbit small mesenteric arteries. AA (10−9–10−4 M) produced potent relaxations in isolated phenylephrine-preconstricted arteries, with a maximal relaxation of 99 ± 0.5% and EC50 of 50 nM. The cyclooxygenase (COX) inhibitors indomethacin (10 μM), NS-398 (10 μM, selective for COX-2), and SC-560 (100 nM, selective for COX-1) caused a marked rightward shift of concentration responses to AA. With the use of immunohistochemical analysis, both COX-1 and COX-2 were detected in endothelium and smooth muscle of small mesenteric arteries. Indomethacin-resistant relaxations were further reduced by the lipoxygenase inhibitors cinnamyl-3,4-dihydroxy-cyanocinnamate (CDC; 1 μM), nordihydroguaiaretic acid (NDGA; 1 μM), and ebselen (1 μM). HPLC analysis showed that [14C]AA was metabolized by mesenteric arteries to PGI2, PGE2, THETAs, hydroxyepoxyeicosatrienoic acids (HEETAs), and 15-hydroxyeicosatetraenoic acid (15-HETE). The production of PGI2 and PGE2 was blocked by indomethacin, and the production of THETAs, HEETAs, and 15-HETE was inhibited by CDC and NDGA. Column fractions corresponding to THETAs were further purified, analyzed by gas chromatography/mass spectrometry, and identified as 11,12,15- and 11,14,15-THETA. PGI2, PGE2, and purified THETA fractions relaxed mesenteric arteries precontracted with phenylephrine. The AA- and THETA-induced relaxations were blocked by high K+ (60 mM). These findings provide functional and biochemical evidence that AA-induced relaxation in rabbit small mesenteric arteries is mediated through both COX and lipoxygenase pathways.

Effects of COX-2 inhibitors on ROS produced by Chlamydia pneumoniae-primed human promonocytic cells (THP-1)

Chronic inflammation through foam cells and macrophages is important in atherosclerosis development, and can be considered as therapeutic targets. Cyclooxygenase and NADPH-oxidase were expressed within atherosclerotic lesions. Reactive oxygen species produced by NADPH oxidase were found to trigger the cyclooxygenase-2 expression. The effects of preferential COX-2 inhibitors on ROS produced by Chlamydia-primed human monocytes (THP-1 cells) were evaluated by fluorescence, chemiluminescence, oxymetry, and EPR spin trapping. Fluorescence assays showed an increased production of ROS with Chlamydia versus cells primed by 10(-8)M PMA. COX-2 inhibitors inhibited in a dose-dependent manner the luminol-enhanced CL while ibuprofen and diclofenac increased the chemiluminescence response. By EPR spin trapping, COX-2 inhibitors, ibuprofen, and diclofenac, exhibited a dose-dependent inhibiting effect (10 and 100muM) on the EPR signal appearance. Our cell model combining EPR, chemiluminescence, and oxymetry appeared relevant to study the modulating effects of preferential COX-2 inhibitors on the cell oxidant activity and chronic inflammatory diseases.

Sulfone COX-2 inhibitors increase susceptibility of human LDL and plasma to oxidative modification: comparison to sulfonamide COX-2 inhibitors and NSAIDs

Clinical investigations have demonstrated a link between use of the sulfone cyclooxygenase-2 (COX-2) inhibitor, rofecoxib, and increased risk for atherothrombotic events. This increased risk was not observed for a sulfonamide COX-2 inhibitor (celecoxib), indicating a potential non-enzymatic mechanism for rofexocib. To test this hypothesis, we compared the independent effects of COX-2 inhibitors on human LDL oxidation, an important contributor to atherosclerotic cardiovascular disease. The results showed that rofecoxib (100 nM) significantly decreased (>40%, p<0.001) the lag time for LDL conjugated diene formation and increased levels of thiobarbituric-acid-reactive-substances (TBARS) in vitro. The pro-oxidant activity of rofecoxib was dose-dependent and attenuated by 70% (p<0.001) with the antioxidant, Trolox. Rofecoxib and etoricoxib (100 nM) also caused a marked increase (>35%, p<0.001) in non-enzymatic generation of isoprostanes, as measured by mass spectroscopy. Addition of rofecoxib to fresh human plasma reduced the oxygen radical antioxidant capacity (ORAC) by 34% (p<0.0001). By contrast, other selective (celecoxib, valdecoxib, meloxicam) and non-selective COX inhibitors (ibuprofen, naproxen, diclofenac) had no significant effect on LDL oxidation rates or plasma ORAC values, even at suprapharmacologic levels. X-ray diffraction analysis showed that sulfone COX-2 inhibitors interact differently with membrane phospholipids, suggesting a physico-chemical basis for the pro-oxidant activity. These results demonstrate that sulfone COX-2 inhibitors increase the susceptibility of biological lipids to oxidative modification through a non-enzymatic process. These findings may provide mechanistic insight into reported differences in cardiovascular risk for COX-2 inhibitors.

Monocyte cyclooxygenase-2 overactivity: a new marker of subclinical atherosclerosis in asymptomatic subjects with cardiovascular risk factors?

AIMS

Cyclooxygenase-2 (COX-2)-mediated prostaglandin production by activated macrophages is associated with inflammation and atherosclerosis. We investigated the relationship between COX-2-mediated prostaglandin-E2 (PGE2) release, cardiovascular risk factors, and carotid atherosclerosis in apparently healthy subjects.

METHODS AND RESULTS

PGE2 release by lipopolysaccharide-stimulated blood monocytes was measured by ELISA in 291 subjects (76.5% men, mean age 58) who underwent global vascular risk assessment and carotid ultrasonography. COX-2 expression (real-time RT-PCR) was analysed in a subgroup of 100 subjects (76% men, mean age 59). Inducible PGE2 production was associated with smoking and diabetes (P<0.05), but not with arterial hypertension, dyslipidaemia, or obesity. Subjects in the highest tertile of PGE2 (>8.1 ng/mL) had significantly higher mean carotid intima-media thickness (IMT) than those in the lowest tertile (P<0.01). No significant differences among tertiles were observed in the levels of inflammatory markers (C-reactive protein, fibrinogen, and von Willebrand factor). The association between PGE2 and carotid IMT remained statistically significant (P=0.012) after adjustment for a number of cardiovascular and inflammatory risk factors. A correlation between COX-2 expression and PGE2 production was observed (P<0.005).

CONCLUSIONS

COX-2-mediated PGE2 overproduction by stimulated monocytes might provide a new marker of subclinical atherosclerosis in asymptomatic subjects exposed to cardiovascular risk factors.

Novel features of nitric oxide, endothelial nitric oxide synthase, and atherosclerosis

There is a complex pathophysiologic scenario involving nitric oxide (NO), endothelial nitric oxide synthase (eNOS), and the development of atherosclerosis and unstable atheroma. Endothelial damage induced by atherosclerosis leads to the reduction in bioactivity of ENOS with subsequent impaired release of NO. An important mechanism is local enhanced degradation of NO by increased generation of reactive oxygen species and other free radicals, with subsequent cascade of oxidation-sensitive mechanisms in the arterial wall. Novel molecular approaches have resulted in the development of new strains of mice lacking eNOS. These experimental models will help to understand how to implement NO-based therapies against atherosclerosis. L-arginine, the precursor of NO, has demonstrated beneficial effects in atherosclerosis and disturbed shear stress. The target or goal for new drugs should be the complete restoration of NO-mediated signaling pathways in atherosclerotic arteries.

Cyclooxygenase-2 expression in experimental post-transplant obliterative bronchiolitis

Epithelial cell injury, inflammation, progressive fibrosis, and airway obliteration are histological features of post-transplant obliterative bronchiolitis (OB). Cyclooxygenase (COX)-2 is expressed in acute and chronic inflammatory responses. Our aim was to elucidate the possible role of COX-2 in post-transplant OB by using a heterotopic bronchial porcine model. Bronchial allografts from non-related donors were transplanted subcutaneously into 24 random-bred domestic pigs, each weighing about 20 kg. Groups studied had grafts, non-treated allografts, allografts given cyclosporine A (CsA), methylprednisolone (MP), and azathioprine (Aza), and allografts given CsA, MP, and everolimus. Grafts were serially harvested during a follow-up period of 21 days for histology (H&E) and immunohistochemistry. Immunostaining was performed with monoclonal IgG against human COX-2 peptide, and histological alterations and immunohistochemical positivity were graded on a scale from 0 to 5. Epithelial COX-2 index was calculated by multiplying the percentage of positive cells by grade of epithelial COX-2 intensity. Ischaemic epithelial loss, evident in all implants, recovered rapidly in autografts, and bronchi remained patent. Epithelial loss in non-treated allografts preceded fibroblast proliferation, resulting in total luminal obliteration. In CsA-, MP-, and Aza-treated allografts epithelial destruction and luminal obliteration were delayed, and these were prevented in CsA-, MP-, and everolimus-treated allografts. COX-2 expression due to operative ischaemia was evident in all implants on day 2. Thereafter, the epithelial COX-2 index preceded epithelial injury and obliteration. During the inflammatory response and fibroblast proliferation, COX-2 expression occurred in macrophages and fibroblasts. In conclusion, in the early stage of OB development, COX-2 induction occurred in airway epithelial cells prior to luminal obliteration. In addition, the observation that COX-2 expression in macrophages and fibroblasts paralleled the onset of inflammation and fibroblast proliferation indicates a role in OB development, but the causal relationships need further study.

Hypothesis: a potential role for the vasa vasorum in the maintenance of vein graft patency

Autologous saphenous vein is the most commonly used conduit for coronary artery bypass surgery with more than 50% grafts occluding within 10 years. In conventional preparation the vein undergoes considerable surgical trauma with damage to the outer layers during harvesting. Within these regions are situated the vasa vasorum and small vessels providing oxygen and nutrients to the vessel wall. Certain vasa vasorum terminate in the vessel lumen where it is suggested that they have a physiological role. Preservation of the vasa vasorum of saphenous veins used as bypass conduits may play an important role in the maintenance of graft patency.

Do some inhibitors of COX-2 increase the risk of thromboembolic events?: Linking pharmacology with pharmacoepidemiology

Inhibitors of the cyclo-oxygenase (COX)-2 isoenzyme were developed with the expectation that their use would be accompanied by a reduction in adverse reactions thought to be mediated through COX-1 compared with conventional nonselective NSAIDs. However, the results of some clinical studies and other evidence have led to the hypothesis that use of COX-2 inhibitors may contribute to an increased risk of adverse thromboembolic (TE) events. In this review, we have evaluated the evidence from small-scale in vitro and in vivo pharmacological studies, clinical trials and large-scale pharmacoepidemiological studies and commented on the relationship between the pharmacological characteristics related to thromboembolic events and the clinical effects in large-scale clinical trials and pharmacoepidemiological studies. Overall, the pharmacological evidence suggests that a prothrombotic effect of COX-2 selective inhibitors is plausible. To date, despite the results from the Vioxx Gastrointestinal Outcome Research (VIGOR) study from which the clinical concern regarding cardiovascular TE risk arose, the published data from other randomised controlled trials (RCTs), retrospective observational studies and spontaneous reporting schemes provide a conflicting body of evidence on the TE risk with COX-2 inhibitors. Concerns that COX-2 inhibitors may be associated with prothrombotic effects remain and these need to be addressed in large scale, RCTs designed specifically to investigate the possibility of an excess of adverse cardiovascular outcomes in users of some or all selective COX-2 inhibitors, both with and without concomitant low-dose aspirin (acetylsalicylic acid). Consideration must also be given to other pathophysiological mechanisms for potential cardiovascular risk linked with inhibition of COX-2. In view of the evidence reviewed, it is recommended that selective COX-2 inhibitors should be prescribed with caution, only in patients with conditions for which these drugs have proven efficacy and with careful monitoring of outcomes and adverse events. This is particularly important in the elderly, in patients with cardiovascular/renal disease and in patients with other risk factors that might predispose them to adverse events.

15-Deoxy-Delta12,14-prostaglandin J(2) protects against nitrosative PC12 cell death through up-regulation of intracellular glutathione synthesis

Nitrosative stress with subsequent inflammatory cell death has been associated with many neurodegenerative disorders. Expression of inducible nitric-oxide synthase and production of nitric oxide (NO) have been frequently elevated in many inflammatory disorders. NO can rapidly react with superoxide anion, producing more reactive peroxynitrite. In the present study, exposure of rat pheochromocytoma (PC12) cells to the peroxynitrite donor 3-morpholinosydnonimine hydrochloride (SIN-1) induced apoptosis, which accompanied depletion of intracellular glutathione (GSH), c-Jun N-terminal kinase activation, mitochondrial membrane depolarization, the cleavage of poly(ADP-ribose)polymerase, and DNA fragmentation. During SIN-1-induced apoptotic cell death, expression of inducible cyclooxygenase (COX-2), and peroxisome proliferator-activated receptor-gamma (PPARgamma) was elevated. SIN-1 treatment resulted in elevated production of 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), an endogenous PPARgamma activator. Preincubation with 15d-PGJ(2) rendered PC12 cells resistant to nitrosative stress induced by SIN-1. 15d-PGJ(2) fortified an intracellular GSH pool through up-regulation of glutamylcysteine ligase, thereby preventing cells from SIN-1-induced GSH depletion. The above findings suggest that 15d-PGJ(2) may act as a survival mediator capable of augmenting cellular thiol antioxidant capacity through up-regulation of the intracellular GSH synthesis in response to the nitrosative insult.

Benefit-risk assessment of rofecoxib in the treatment of osteoarthritis

NSAIDs are widely used to treat pain and inflammation in osteoarthritis. Their use in this indication is generally intermittent and fluctuates with the intensity of the disease. Nonetheless, success of the therapy is frequently limited by injury to the gastrointestinal mucosa and complications such as bleeding, ulceration and perforation. A careful and detailed evaluation of these aspects in regard to the newly introduced NSAIDs is of considerable clinical importance. This review focuses on the NSAID rofecoxib, one of the selective cyclo-oxygenase (COX)-2 inhibitors, which are claimed to be as effective as nonselective NSAIDs with better gastrointestinal tolerability. Indeed, phase II, phase III and epidemiological studies have revealed that the efficacy of rofecoxib is comparable to that of conventional NSAIDs but with lower gastrointestinal toxicity, although this advantage may not be demonstrable in every patient. In patients treated with low-dose aspirin (acetylsalicylic acid) for cardiovascular prophylaxis, celecoxib (another selective COX-2 inhibitor) seems to have no obvious advantages over conventional NSAIDs, and similar conclusions may be applied to rofecoxib. A comparison of NSAID therapy +/- concomitant low-dose aspirin was not a primary outcome in this trial with celecoxib and there is thus a need for further studies which compare the gastrointestinal risk of a selective COX-2 inhibitor plus aspirin versus a conventional NSAID. Recent debate has emerged regarding the cardiovascular safety of rofecoxib. Although there is evidence both for and against higher cardiovascular risk with rofecoxib, a retrospective cohort study recently published suggested that there is no increased risk of acute myocardial infarction in the short-term when compared with non-selective NSAIDs. The renal toxicity of rofecoxib has been thoroughly investigated. Clinical studies revealed renal effects of rofecoxib similar to those of conventional NSAIDs. Since adverse effects increase with the degree of renal impairment, monitoring of renal function should be carried out in patients at risk. Although there are still insufficient data concerning certain important adverse effects of rofecoxib, this drug is becoming an important alternative in the therapy of osteoarthritis, especially in high-risk patients. Clinicians need to weigh up the benefits and risks of rofecoxib on a case-by-base basis.

Simvastatin potenciates PGI2 release induced by HDL in human VSMC: effect on Cox-2 up-regulation and MAPK signalling pathways activated by HDL

High density lipoproteins (HDL) induce prostacyclin (PGI(2)) release in vascular smooth muscle cells (VSMC) by up-regulation of cyclooxygenase-2 (Cox-2). Our goal was to analyse the mechanisms underlying this effect, and its potential modulation by HMG-CoA reductase inhibition in human VSMC. The contribution of mitogen-activated protein kinase (MAPK) signalling pathways was assessed by Western blot analysis and using specific inhibitors [PD098059 for p42/44 MAPK kinase (MEK); SB203580 for p38 MAPK or L-JNKI1 for c-Jun N-terminal kinase-1 (JNK-1)]. HDL-induced PGI(2) release was inhibited by rofecoxib (a specific Cox-2 inhibitor, 5 microM). HDL induced the early activation of p42 MAPK, p38 MAPK and JNK-1. p42/44 MAPK was the major pathway involved in both Cox-2 up-regulation and PGI(2) synthesis; p38 MAPK was also involved in both processes while JNK inhibition only affected PGI(2) synthesis. Pertussis toxin (an inhibitor of Galphai/Galphao proteins) prevented MAPK activation and inhibited both Cox-2 up-regulation and PGI(2) release. Genistein (a tyrosine kinase inhibitor) inhibited PGI(2) release without affecting MAPK activation or Cox-2 up-regulation. Simvastatin (0.1-1 microM) increased HDL-induced PGI(2) release ( approximately 45% at 1 microM) but did not significantly modify early MAPK activation or Cox-2 expression. Simvastatin alone did not significantly affect PGI(2) release. Our results suggest that mechanisms associated with G protein-coupled receptor activation, trigger Cox-2 up-regulation and PGI(2) release via multiple MAPK signalling pathways in VSMC. The mechanism is independent of tyrosine kinase receptors, although cytosolic tyrosine kinases could activate Cox-2 post-translationally. The potential contribution of HDL to vascular homeostasis, via increases in PGI(2) synthesis, could be enhanced by HMG-CoA reductase inhibitors.

Extracellular Matrix-induced Cyclooxygenase-2 Regulates Macrophage Proteinase Expression

Chronic inflammatory diseases are characterized by the persistent presence of macrophages and other mononuclear cells, tissue destruction, cell proliferation, and the deposition of extracellular matrix (ECM). The tissue degradation is mediated, in part, by enhanced proteinase expression by macrophages. It has been demonstrated recently that macrophage proteinase expression can be stimulated or inhibited by purified ECM components. However, in an intact ECM the biologically active domains of matrix components may be masked either by tertiary conformation or by complex association with other matrix molecules. In an effort to determine whether a complex ECM produced by vascular smooth muscle cells (SMC) regulates macrophage degradative phenotype, we prepared insoluble SMC matrices and examined their ability to regulate proteinase expression by RAW264.7 and thioglycollate-elicited peritoneal macrophages. Here we demonstrate that macrophage engagement of SMC-ECM triggers PKC-dependent activation of MAPK(erk1/2) leading to increased expression of cyclooxygenase (COX)-2 and prostaglandin (PG) E(2) synthesis. The addition of PGE(2) to macrophage cultures stimulates their expression of both urokinase-type plasminogen activator and MMP-9, and the selective COX-2 inhibitor NS-398 blocks ECM-induced proteinase expression. Moreover, ECM-induced PGE(2) and MMP-9 expression by elicited COX-2(-/-) macrophages is markedly reduced when compared with the response of either COX-2(+/-) or COX-2(+/+) macrophages. These data clearly demonstrate that SMC-ECM exerts a regulatory role on the degradative phenotype of macrophages via enhanced urokinase-type plasminogen activator and MMP-9 expression, and identify COX-2 as a targetable component of the signaling pathway leading to increased proteinase expression.

Resveratrol protects myocardial ischemia-reperfusion injury through both NO-dependent and NO-independent mechanisms

We previously showed that resveratrol (3,4',5-trihydroxystilbene) stimulates NO production and is cardioprotective in rat heart subjected to ischemia-reperfusion (I/R rat heart). We now show that in I/R rat heart, inducible nitric oxide synthase (iNOS) expression is markedly induced, while expression of endothelial nitric oxide synthase (eNOS) and nueronal nitric oxide synthase (nNOS) is unchanged. In animals preconditioned with resveratrol (0.5 to 1 mg/kg body wt), I/R-induced iNOS induction is abrogated; however, expression of eNOS and nNOS is greatly upregulated. The protective effects of resveratrol on I/R rat heart include reduced rhythm disturbances, reduced cardiac infarct size, and decreased plasma levels of lactate dehydrogenase (LDH) and creatine kinase (CK). Among these, the reductions in LDH/CK levels and infarct size are NO-dependent as the coadministration of N(omega)-nitro-L-arginine methyl ester (L-NAME, 1 mg/kg body wt) with resveratrol abolishes the resveratrol effect. In contrast, the reductions in the severity of ventricular arrhythmia and mortality rate are not affected by L-NAME coadministration, suggesting that a NO-independent mechanism is involved.

Pro-thrombotic State Induced by Post-translational Modification of Fibrinogen by Reactive Nitrogen Species

Formation of nitric oxide-derived oxidants has been linked to development of atherosclerosis and associated thrombotic complications. Although systemic levels of protein nitrotyrosine predict risk for coronary artery disease, neither specific proteins targeted for modification nor functional consequences that might contribute to disease pathogenesis have been defined. Here we report a selective increase in circulating levels of nitrated fibrinogen in patients with coronary artery disease. Exposure of fibrinogen to nitrating oxidants, including those produced by the myeloperoxidase-hydrogen peroxide-nitrite system, significantly accelerates clot formation and factor XIII cross-linking, whereas exposure of fibrinogen to non-nitrating oxidants decelerates clot formation. Clots formed with fibrinogen exposed to nitrating oxidants are composed of large bundles made from twisted thin fibrin fibers with increased permeation and a decrease in storage modulus G' value, suggesting that these clots could be easily deformed by mechanical stresses. In contrast, clots formed with fibrinogen exposed to non-nitrating oxidants showed decreased permeation with normal architecture. Fibrinogen modified by exposure to physiologic nitration systems demonstrated no difference in the rate of plasmin-induced clot lysis, platelet aggregation, or binding. Thus, increased levels of fibrinogen nitration may lead to a pro-thrombotic state via acceleration in formation of fibrin clots. The present results may account, in part, for the association between nitrative stress and risk for coronary artery disease.

Optimal suppression of thromboxane a2formation by aspirin during percutaneous transluminal coronary angioplasty: no additional effect of a selective cyclooxygenase-2 inhibitor

OBJECTIVES

We examined the contribution of cyclooxygenase (COX)-1 and -2 to the generation of prostacyclin, thromboxane (Tx) A(2), and 8-epi prostaglandin (PG) F(2alpha) during percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

Both TxA(2) and 8-epi PGF(2alpha) activate platelets and are mitogenic, whereas prostacyclin is a platelet inhibitor, and therefore may influence the outcome of PTCA.

METHODS

Twenty-one patients undergoing PTCA while receiving aspirin 300 mg daily or aspirin plus the selective COX-2 inhibitor nimesulide were compared with 13 patients treated only with fradafiban, a glycoprotein IIb/IIIa antagonist. Urine was analyzed for the metabolites of TxA(2) (Tx-M) and prostacyclin (PGI-M) and for the isoprostane, 8-epi PGF(2alpha).

RESULTS

In the fradafiban group, there was a marked increase in Tx-M during PTCA (mean, 1973; 95% confidence interval [CI] 112 to 3834 rising to mean 7645; 95% CI 2,009 to 13281 pg/mg creatinine, p = 0.018). The Tx-M excretion was similarly reduced by aspirin and the combination of aspirin and nimesulide. In contrast, the combination of nimesulide and aspirin inhibited PGI-M excretion to a greater extent than aspirin (p = 0.001). Urinary 8-epi PGF(2alpha) excretion was elevated following PTCA compared with normal subjects (p = 0.002) and appeared to be unaffected by any of the treatments.

CONCLUSIONS

The increase in TxA(2) during PTCA is primarily COX-1 dependent, and aspirin alone is effective in suppressing its formation. In contrast, prostacyclin generation is both COX-1 and COX-2 dependent. The inhibition of COX-1 and COX-2 did not prevent the production of 8-epi PGF(2alpha), suggesting that this is not enzymatically derived. The persistent generation of 8-epi PGF(2alpha) may contribute to the thrombosis and restenosis that complicate PTCA.

Potential cardiovascular effects of COX-2 selective nonsteroidal antiinflammatory drugs

The newly developed nonsteroidal antiinflammatory drugs (NSAIDs) that selectively inhibit cyclooxygenase-2 (COX-2), are effective against pain and inflammation and appear to have less gastrointestinal toxicity than conventional NSAIDs. Their COX-2 selectivity, however, has raised concerns regarding their cardiovascular safety, since they do not inhibit COX-1, the isoform of the enzyme that is active in thrombosis and vasoconstriction. At this point there is no conclusive evidence that COX-2 inhibitors cause ischemic vascular events, because retrospective post hoc analyses conflict one another, and no specific randomized trials have yet been done. Renal effects, edema and hypertension appear to be similar between conventional NSAIDs and COX-2-selective inhibitors. Aspirin is still required for patients with cardiovascular risk who are prescribed a COX-2-selective inhibitor.

Effect of cyclooxygenase-2 inhibition with rofecoxib on endothelial dysfunction and inflammatory markers in patients with coronary artery disease

OBJECTIVES

The aim of this study was to determine whether selective cyclooxygenase-2 (COX-2) inhibition with rofecoxib can modulate endothelial dysfunction and levels of circulating inflammatory markers in patients with established coronary artery disease (CAD).

BACKGROUND

Expression of COX-2 is upregulated in atherosclerosis. Thus, it has been hypothesized that COX-2 may contribute to atherogenesis by producing eicosanoids, which mediate vascular inflammation and endothelial dysfunction.

METHODS

In a randomized, double-blind, placebo-controlled, parallel-design trial, we studied the vascular effects of rofecoxib on brachial artery vasoreactivity and inflammatory markers in 60 patients with angiographically proven CAD who were taking concomitant low-dose aspirin. Patients were randomly assigned to receive either rofecoxib (25 mg/day; n = 30) or placebo (n = 30) for eight weeks. Brachial artery endothelium-dependent flow-mediated dilation (FMD), endothelium-independent nitroglycerin-mediated dilation (NMD), and inflammatory markers (i.e., high-sensitivity C-reactive protein [CRP], soluble intercellular adhesion molecule-1 [sICAM-1], and soluble interleukin-6 receptor [sIL-6r]) were measured at baseline and after eight-week follow-up.

RESULTS

Baseline clinical characteristics were similar in the two groups. After eight weeks of treatment, FMD did not significantly change in either the rofecoxib or placebo group (4.0 +/- 3.0% to 4.0 +/- 3.8% vs. 2.7 +/- 2.7% to 3.1 +/- 2.7%, respectively; p = 0.6 by two-way analysis of variance). Similarly, NMD remained unchanged in both groups. Levels of CRP, sICAM-1, and sIL-6r were not significantly altered in either the rofecoxib or placebo group.

CONCLUSIONS

The addition of selective COX-2 inhibition with rofecoxib did not appear to have any favorable or adverse effects on endothelial dysfunction or vascular inflammation in patients with CAD using concomitant low-dose aspirin.

Selective COX-2 inhibition and cardiovascular effects: a review of the rofecoxib development program

See related Editorials on pages 561 and 563. Cyclo-oxygenase-2 (COX-2) inhibitors appear to alter the balance of vasoactive eicosanoids (prostacyclin and thromboxane) and to suppress the inflammatory mediators implicated in the progression of atherogenesis and ischemic myocardial injury. Neutral, harmful, and beneficial cardiovascular (CV) effects have all been postulated to result from these changes. Investigations conducted with rofecoxib, a selective COX-2 inhibitor, have substantially contributed to our understanding of this scientific area. Rofecoxib had little or no effect on platelet aggregation or platelet-derived thromboxane synthesis but reduced systemic prostacyclin synthesis by 50% to 60%. These findings prompted extensive analyses of CV thrombotic events within the rofecoxib development program. Among 5435 osteoarthritis trial participants, similar rates of CV thrombotic events were reported with rofecoxib, placebo, and comparator, nonselective NSAIDs (ibuprofen, diclofenac, and nabumetone). In the VIGOR gastrointestinal outcomes trial of >8000 patients, naproxen (an NSAID with aspirin-like sustained antiplatelet effects throughout its dosing interval) was associated with a significantly lower risk of CV events than was rofecoxib. A subsequent pooled analysis from 23 studies (including VIGOR) encompassing multiple disease states and including more than 14,000 patient-years at risk also demonstrated that rofecoxib was not associated with excess CV thrombotic events compared with either placebo or nonnaproxen NSAIDs. Again, naproxen appeared to be the outlier, suggesting a cardioprotective benefit of naproxen. Finally, among the predominantly elderly, male population participating in Alzheimer trials, both rofecoxib- and placebo-treated patients had similar rates of CV thrombotic events. The totality of data is not consistent with an increased CV risk among patients taking rofecoxib.

Selective cyclo-oxygenase-2 inhibition with parecoxib acutely impairs endothelium-dependent vasodilatation in patients with essential hypertension

BACKGROUND

Cyclo-oxygenase (COX)-2 isoform appears to be a major source of the vasodilator, prostacyclin. Both prostacyclin and nitric oxide may contribute to the regulation of vascular tone and endothelial-mediated homeostasis.

OBJECTIVE

To evaluate the effects of acute COX-2 inhibition on endothelial function in the forearm circulation of patients with essential hypertension.

METHODS

Forty patients with essential hypertension as the only risk factor were studied. Forearm blood flow was measured by venous occlusion phlethysmography. Vascular responses were measured after intra-arterial infusion of the endothelium-dependent agonist acetylcholine (15, 30, or 40 microg/min) and the endothelium-independent agonist nitroprusside (1.6, 3.2, or 4.0 microg/min). Patients were allocated randomly to groups to receive the non-selective COX-inhibitor, acetylsalicylate-lysin (500 mg intravenously), or the selective COX-2 inhibitor, parecoxib, an injectable prodrug of valdecoxib (20 mg intravenously). The infusion procedure was repeated 30 min later.

RESULTS

Acetylcholine increased concentration-dependent forearm blood flow. This increase was significantly augmented by acetylsalicylate-lysin, but significantly diminished by parecoxib. Neither acetylsalicylate-lysin nor parecoxib modified the vasodilator responses to nitroprusside.

CONCLUSION

COX-2 inhibition with the prodrug, parecoxib, diminishes the acetylcholine-induced vasodilatation in the forearm circulation of patients with essential hypertension. It is speculated that the production of vasodilator prostaglandins may be important in pathological states with endothelial dysfunction, at least in patients with essential hypertension.

Synergism between platelet-activating factor-like phospholipids and peroxisome proliferator-activated receptor gamma agonists generated during low density lipoprotein oxidation that induces lipid body formation in leukocytes

Oxidized low density lipoprotein (LDL) has an important proinflammatory role in atherogenesis. In this study, we investigated the ability of oxidized LDL (oxLDL) and its phospholipid components to induce lipid body formation in leukocytes. Incubation of mouse peritoneal macrophages with oxidized, but not with native LDL led to lipid body formation within 1 h. This was blocked by platelet-activating factor (PAF) receptor antagonists or by preincubation of oxLDL with rPAF acetylhydrolase. HPLC fractions of phospholipids purified from oxLDL induced calcium flux in neutrophils as well as lipid body formation in macrophages. Injection of the bioactive phospholipid fractions or butanoyl and butenoyl PAF, a phospholipid previously shown to be present in oxLDL, into the pleural cavity of mice induced lipid body formation in leukocytes recovered after 3 h. The 5-lipoxygenase and cyclooxygenase-2 colocalized within lipid bodies formed after stimulation with oxLDL, bioactive phospholipid fractions, or butanoyl and butenoyl PAF. Lipid body formation was inhibited by 5-lipoxygenase antagonists, but not by cyclooxygenase-2 inhibitors. Azelaoyl-phosphatidylcholine, a peroxisome proliferator-activated receptor-gamma agonist in oxLDL phospholipid fractions, induced formation of lipid bodies at late time points (6 h) and synergized with suboptimal concentrations of oxLDL. We conclude that lipid body formation is an important proinflammatory effect of oxLDL and that PAF-like phospholipids and peroxisome proliferator-activated receptor-gamma agonists generated during LDL oxidation are important mediators in this phenomenon.