Cyclooxygenase-2 promotes early atherosclerotic lesion formation in LDL receptor-deficient mice

Altered gene expression in early atherosclerosis is blocked by low level apolipoprotein E

BACKGROUND

Mice deficient in apolipoprotein E (apoE(-/-)) develop atherosclerosis. The possible linkage between expression of adhesion molecules/cofactors and atherosclerosis was probed at the level of mRNA and protein expression. The hypothesis of a linkage between changes of adhesion molecules/cofactors and atherosclerosis was tested further by suppression of aortic lesion formation in apoE(-/-) mice by expression of very low levels of transgenic apolipoprotein E.

METHODOLOGY/PRINCIPAL FINDINGS

We show that at 8.5 months of age, the apoE(-/-) mice display elevated expression of mRNA for LFA-1, MAC-1, VCAM-1, ICAM-1, and for CD44, as well as MCP-1, cathepsin B, and COX-2 (but not that for eNOS) in atherosclerotic aortic arches. At earlier age, (10-13 week old) apoE(-/-) mice already display elevated expression of mRNA of CD44, LFA-1, MAC-1, VCAM-1, ICAM-1, cathepsin, and of COX-2 in lesioned aortic arches. Expressing very low levels of transgenic apolipoprotein E suppresses both aortic lesions and the expression of mRNA of LFA-1, VCAM-1, MCP-1, cathepsin B, and of ICAM-1 in ApoE(-/-) mice. We tested at the level of protein, the observations obtained for mRNA expression. CD11a (a component of LFA-1), VCAM-1 and cathepsin B expression was found to be elevated in apoE(-/-) aortas at 8-9 months; low level expression of transgenic apolipoprotein E rectifies these changes.

CONCLUSIONS/SIGNIFICANCE

Atherosclerotic lesions in apoE(-/-) mice are detected as early as 4 weeks of age. Expression of low levels of apoE is shown to be both atheroprotective and to suppress these changes in key adhesion and inflammatory molecules observed in early atherosclerotic lesions.

Selective cyclooxygenase inhibitors prevent the growth of Chlamydia pneumoniae in HL cells

The effects of the selective cyclooxygenase (COX) inhibitors SC-560 and PTPBS were studied in Chlamydia pneumoniae-infected HL cell cultures. Chlamydia pneumoniae growth and viability were assessed by quantifying inclusions and re-passages. COX-1 and COX-2 mRNA expression in HL cells during chlamydial infection was quantified with real-time polymerase chain reaction. SC-560 (10 microg/mL) and PTPBS (18 microg/mL) completely inhibited the growth of C. pneumoniae and the effect was dose-dependent between 4-9 microg/mL and 2-16 microg/mL, respectively. Inclusion size was reduced from 11.5+/-1.3 microm to 1.9+/-0.7 microm in the presence of the drugs. Removing the drugs returned the size to normal and increased the number of inclusions. Selective COX inhibitors appear to have a chlamydiostatic but not chlamydiacidic effect; they inhibit the growth of C. pneumoniae in vitro but do not prevent infection or eradicate C. pneumoniae from host cells.

The David Y. Graham lecture: use of nonsteroidal antiinflammatory drugs in a COX-2 restricted environment

Recent evidence suggests that both cyclooxygenase-2 (COX-2) inhibitors and nonselective NSAIDs, with the possible exception of naproxen, increase cardiovascular (CV) hazard. Clinicians should assess not only patients' GI risk but also their CV risk before prescribing these drugs. Patients with low CV risk can be managed according to their GI risk-low-risk patients (without risk factors) receive nonselective NSAIDs, medium risk patients (1-2 risk factors) receive COX-2 inhibitors or nonselective NSAIDs plus a proton pump inhibitor (PPI) or misoprostol, whereas high-risk patients (multiple risk factors, previous ulcer complications, or concomitant anticoagulants) receive a COX-2 inhibitor plus a PPI or misoprostol. Among patients with high CV risk (e.g., prior cardiothrombotic events) who require NSAIDs, naproxen is preferred. These patients should receive a prophylactic PPI or misoprostol because the risk of ulcer bleeding is substantially increased with concomitant use of naproxen and low-dose aspirin. Substitution of clopidogrel for aspirin is not recommended in patients at risk for upper GI bleeding who require antiplatelet therapy. Patients with high GI and high CV risk should avoid NSAIDs and COX-2 inhibitors. If antiinflammatory analgesics are required, the choice of therapy depends on the relative importance of GI and CV risks of individual patients. Combination of naproxen, low-dose aspirin, and a PPI or misoprostol is recommended if CV risk is the major concern (e.g., recent myocardial infarction). In contrast, combination of low-dose COX-2 inhibitor, low-dose aspirin, and a PPI or misoprostol is preferred if GI risk outweighs CV risk (e.g., recent ulcer bleeding and stable CV disease).

An improved LC-MS/MS method for the quantification of prostaglandins E(2) and D(2) production in biological fluids

We report an improved liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay that accurately measures prostaglandins D(2) (PGD(2)) and E(2) (PGE(2)) in cell culture supernatants and other biological fluids. The limit of detection for each prostaglandin was 20 pg/ml (0.20 pg, 0.55 fmol on-column), and the interday and intraday coefficients of variation were less than 5%. Both d(4)-PGE(2) and d(4)-PGD(2) were used as surrogate standards to control for differential loss and degradation of the analytes. Stability studies indicated that sample preparation time should be less than 8h to measure PGD(2) accurately, whereas preparation time did not affect PGE(2) measurement due to its greater stability in biological samples. As an application of the method, PGD(2) and PGE(2) were measured in culture supernatants from A549 cells and RAW 264.7 cells. The human lung alveolar cell line A549 was found to produce PGE(2) but no PGD(2), whereas the murine macrophage cell line RAW 264.7 produced PGD(2) and only trace amounts of PGE(2). This direct comparison showed that COX-2 gene expression can lead to differential production of PGD(2) and PGE(2) by epithelial cells and macrophages. Because PGE(2) is antiasthmatic and PGD(2) is proasthmatic, we speculate that the balance of production of these eicosanoids by epithelial cells and macrophages in the lung contributes to the pathogenesis of chronic obstructive pulmonary disease (COPD), bronchiectasis, asthma, and lung cancer.

PPARalpha ligands reduce PCB-induced endothelial activation: possible interactions in inflammation and atherosclerosis

Exposure to polychlorinated biphenyls (PCBs) can activate inflammatory responses in vascular endothelial cells. Activation of peroxisome proliferator-activated receptors (PPARs) by nutrients or synthetic agonists has been shown to block pro-inflammatory responses both in vitro and in vivo. Here we demonstrate that activation of PPARalpha by synthetic agonists can reduce 3,3'4,4'-tetrachlorobiphenyl (PCB77)-induced endothelial cell activation. Primary vascular endothelial cells were pretreated with the PPARalpha ligands fenofibrate or WY14643 followed by exposure to PCB77. PPARalpha activation protected endothelial cells against PCB77-induced expression of the pro-inflammatory proteins vascular cell adhesion molecule-1 (VCAM-1), cycloxygenase-2 (COX-2), and PCB77-induced expression and activity of the aryl hydrocarbon receptor (AHR) responsive cytochrome P450 1A1 (CYP1A1). Furthermore, basal AHR expression was downregulated by fenofibrate and WY14643. We also investigated the possible interactions between PCBs, and basal PPAR activity and protein expression. Treatment with PCB77 significantly reduced basal mRNA expression of PPARalpha and the PPAR responsive gene CYP4A1, as well as PPARalpha protein expression. Also, PCB77 exposure caused a significant decrease in basal PPAR-dependent reporter gene expression in MCF-7 cells. Overall, these findings suggest that PPARalpha agonists can reduce PCB77 induction of endothelial cell activation by inhibition of the AHR pathway, and that coplanar PCB induced pro-inflammatory effects could be mediated, in part, by inhibition of PPARalpha expression and function.

The select cyclooxygenase-2 inhibitor celecoxib reduced the extent of atherosclerosis in apo E-/- mice

Many investigators have suggested that immune activation may trigger the atherosclerotic process. The benefits of aspirin in preventing myocardial infarction have been attributed, in part, to its anti-inflammatory effects. Several reports have documented that cyclooxygenase (COX)-2 is up-regulated in human and mouse atherosclerotic lesions. To clarify the role of COX-2 in atherosclerosis, we conducted a study to test whether the COX-2 inhibitor, celecoxib, prevents the development and progression of the atherosclerotic process. We have used the apo E-/- mouse, a relevant animal model of atherosclerosis that develops fibrofatty lesions similar to human atherosclerosis. Treatment of 4-wk old apo E-/- mice with a standard rodent no. 5020 diet supplemented with 900 ppm of celecoxib for 16 wk led to an 81% reduction in lesion size. The mean lesion area per section (mean +/- SD) of proximal aorta from the apo E-/- mice fed the diet with celecoxib (33,991 +/- 7863 microm2, P < 0.001) was significantly less than that of the untreated apo E-/- mice (183,401 +/- 36,212 microm2). There were no lesions detected in the C57B1/6 mice. Immunohistochemistry of the ileum revealed that there was 80% reduction in staining for intercellular adhesion molecule and 60% reduction in staining for vascular cell adhesion molecule in the celecoxib treated mice. The protective effect of celecoxib was not maintained when the mice were switched after feeding the celecoxib-supplemented diet to the control 5020 diet for an additional 10 wk. These findings demonstrate that selective inhibition of the COX-2 enzyme with celecoxib prevented the development of atherosclerotic lesions in the proximal aortas from apo E-/- mice. One of the possible mechanisms is reduction in expression of the endothelial cell adhesion cell molecules intercellular adhesion molecule and vascular cell adhesion molecule, which plays a key role in the recruitment of inflammatory cells during the early stages of atherogenesis.

Platelet-derived growth factor-induced stabilization of cyclooxygenase 2 mRNA in rat smooth muscle cells requires the c-Src family of protein-tyrosine kinases

Cyclooxygenases (COXs) are crucial rate-limiting enzymes required for the biosynthesis of prostaglandins. COX-2 is an inducible isoform of this enzyme, which is believed to play important roles in the development of atherosclerotic vascular disease. We found that COX-2 expression rapidly increases in response to various signaling events, including activation of the platelet-derived growth factor (PDGF) pathway. Activation of PDGF receptor (PDGFR) in rat aortic vascular smooth muscle cells leads to c-Src-dependent stabilization of COX-2 mRNA requiring an AU-rich region within the 3'-untranslated region of this transcript. This regulation correlates with tyrosine phosphorylation of the RNA-associated protein, CUG-binding protein 2 (CUGBP2), which appears to enhance its interaction with COX-2 mRNA. Site-directed mutagenesis of putative tyrosine phosphorylation sites in CUGBP2 identified tyrosine 39 as a c-Src target, and a CUGBP2 with a mutated tyrosine 39 displayed an attenuated ability to bind COX-2 mRNA. We further show that silencing of CUGBP2 with specific small interference RNAs significantly reduces PDGF-dependent induction of COX-2 at both mRNA and protein levels. Furthermore, forced expression of CUGBP2 or constitutively active c-Src leads to stabilization of co-expressed COX-2 mRNA. Finally, in vitro RNA decay assay demonstrates that CUGBP2 is functionally required for the stabilization of COX-2 mRNA. Therefore, our data suggest that tyrosine phosphorylation of CUGBP2 is an important underlying mechanism for the ability of PDGFR/c-Src signaling to control the stability of COX-2 mRNA.

A novel anti-atherogenic role for COX-2--potential mechanism for the cardiovascular side effects of COX-2 inhibitors

Atherosclerosis, the underlying cause of cardiovascular disease, is characterized by lipid accumulation, lipoprotein oxidation, and inflammation. Products of the cyclooxygenase (COX) pathway participate in acute and chronic inflammation. The inducible form of COX, COX-2, generates lipid mediators of inflammation that are pro-inflammatory and COX-2-selective inhibitors are potent anti-inflammatory agents. However, clinical data suggest an increased risk of cardiovascular side effects in patients using COX-2-selective inhibitors. In this paper, we sought to determine the effect of COX-2 deficiency on atherosclerosis-related lipoprotein metabolism in mice. We demonstrate that COX-2 deficiency resulted in (i) accumulation of lipids in circulation and liver, (ii) pro-inflammatory properties of HDL as measured by HDL's increased reactive oxygen species (ROS) content, decreased paraoxonase 1 (PON1) activity, decreased serum apoA-1, reduced ability to efflux cholesterol and to prevent LDL oxidizability, and (iii) increased TXB(2) in circulation. Moreover, when placed on an atherogenic diet, COX-2 deficiency resulted in (i) increased lipid deposition in the aorta, (ii) a further dramatic imbalance in circulating eicosanoids, i.e. decreased serum PGI(2) coupled with increased PGE(2) and TXB(2), and (iii) a marked elevation of pro-inflammatory cytokines, TNF and IL-6. Our results suggest, for the first time, that COX-2 deficiency contributes to the pro-atherogenic properties of HDL in mice.

The cycloxygenase 2 (COX-2) story: it's time to explain, not inflame

Despite initial promising reports that anti-inflammatory properties of cycloxygenase-2 (COX-2) inhibitors may confer anti-atherosclerosis effects and stabilize the atherosclerotic plaque, subsequent data from long-term clinical trials have shown that selective COX-2 inhibitors are associated with increased risk of cardiovascular events. The commonly cited explanation is that selective inhibition of COX-2 leads to depletion of prostacyclin, whereas the production of pro-thrombotic thromboxane by means of cycloxygenase-1 (COX-1) is unopposed. This hypothesis seems unlikely as the overall explanation, because low-dose aspirin does not decrease the increased risk associated with COX-2 inhibitors. Moreover, the risk associated with nonselective COX inhibitors may be similar to selective COX-2 inhibitors. Alternative hypotheses include (1) elevated blood pressure, (2) abnormal vascular remodeling, (3) inhibition of protective mechanisms against ischemia-reperfusion injury, and (4) inhibition of 15-epi-lipoxin production. Varying results in different experimental models may be related to the fact that COX-2 is involved in numerous cellular functions. Inhibiting COX-2 in inflammatory cells may have favorable effects, whereas in organs such as the heart and brain and/or blood vessels may have deleterious effects. Currently, the "selective COX-2 inhibitors" are not selective in the sense that they inhibit COX-2 in all tissues without predilection to inflammatory cells and, as a result, may summate to increase the risk of cardiovascular events.

Cyclooxygenase-2 inhibitors and coronary occlusion--exploring dose-response relationships

AIMS

To investigate the relationship between acute coronary syndrome (ACS) and ingested doses of selective cyclooxygenase-2 (COX-2) inhibitors and other nonsteroidal anti-inflammatory drugs (NSAIDs).

METHODS

Case-control study, commenced August 2003. Cases were patients admitted to hospital with ACS (myocardial infarction/unstable angina). Controls were hospital patients admitted for reasons other than acute vascular ischaemia or conditions that are believed to be complications of treatment with COX-2 inhibitors or NSAIDs. Structured interviews were undertaken within 7 days of admission, collecting information on cardiovascular events and risk factors and all ingested drugs, including the doses of COX-2 inhibitors and NSAID consumed in the previous week and month.

RESULTS

An interim analysis of the data was conducted in late 2004 to inform a review of the COX-2 inhibitors by the Australian drug regulatory agency. Between August 2003 and October 2004, we recruited 328 ACS cases and 478 controls. With non-use of COX-2 inhibitors or NSAIDs as the reference the adjusted odds ratios (OR) for ACS were: celecoxib 1.11 (95% confidence interval 0.59, 2.11), rofecoxib 0.63 (0.31, 1.28) and other NSAIDs 0.67 (0.41, 1.09). Among control subjects, median daily ingested doses of celecoxib and rofecoxib were 200 mg and 13.4 mg, respectively. Using these to stratify risk, adjusted ORs for ACS were: 'low' dose (< median) 0.44 (0.19, 1.03); 'high' dose (>/= median) 1.22 (0.67, 2.21). A test for interaction across doses was statistically significant, OR 2.8 (1.0, 7.7), suggesting that at low doses, COX-2 inhibitors may be protective, becoming risk-inducing only at higher doses.

CONCLUSION

The possibility that the gradient of cardiovascular risk with COX-2 inhibitors runs from protective to risk-inducing has biological plausibility and merits further investigation.

Up-regulation of cyclooxygenase-2 in different grades of acute human renal allograft rejection

BACKGROUND

Cyclooxygenase-2 (COX-2) is up-regulated by a variety of stimuli that are associated with tissue injury and inflammation.

METHODS

The purpose of this study was to analyze COX-2 detection during different grades of acute human renal allograft rejection. COX-2 expressions were analyzed by immunohistochemistry in 74 samples obtained from biopsies with acute rejection of different grades (n= 48), tubular changes (n=13) and from kidney allografts with stable function (n=13).

RESULTS

In interstitial area, there was a significant correlation of COX-2 induction in acute rejection in comparison to tubular changes (1.67 vs. 0.76, p=0.02) and stable function (vs. 0.07, p<0.001), as well as in vessels in the group with acute rejection in relation to stable function (1.1 vs. 0, p=0.04). When the group with acute rejection was analyzed in subgroups, there was a clear increase of COX-2 expression from acute rejection grade IB to III in vessels, in inflammatory infiltrating cells in interstitial area and in glomeruli, while borderline and IA grades were intermediate.

CONCLUSION

COX-2 is up-regulated during acute human renal allograft rejection according to the severity of acute rejection and could be used as a marker of inflammation in kidney transplantation.

Drug-induced immunomodulation to affect the development and progression of atherosclerosis: a new opportunity?

Inflammation and cytokine pathways are crucial for the development and progression of atherosclerotic lesions. In this review, the hypothesis that immunomodulatory drugs provide a possible therapeutic modality for cardiovascular disease is evaluated. Therefore, after a short overview of the specific inflammatory pathways involved in atherosclerosis, literature on the effect of several immunomodulatory drugs, such as nonsteroidal anti-inflammatory drugs, specific cyclooxygenase inhibitors and immunosuppressive drugs, used currently in the prevention of rejection after organ transplant, on the development and progression of atherosclerosis is reviewed. In addition, the pleiotropic immunomodulatory effect of two established cardiovascular drugs (angiotensin-converting enzyme inhibitors and statins) is discussed.

Developing Strategies to Link Basic Cardiovascular Sciences with Clinical Drug Development: Another Opportunity for Translational Sciences

Driven, at least in part, by the National Institutes of Health roadmap, an increasing number of studies has bridged the chasm between observations in the basic research laboratory and the clinical bedside. These studies have been an integral part in "translating" new discoveries into therapeutic initiatives. However, "translational medicine" has been used less frequently in the development of cardiovascular drugs or in predicting the potential cardiovascular toxicity of non-cardiac agents. Studies in animal models can provide important clues as to the potential cardiotoxicity of new therapeutic agents, as well as providing a template for the rational design of clinical trials. Three examples of drug development programs that might have been altered by clues available from laboratory studies include the development programs for the anti-cancer drug trastuzumab, the cyclooxygenase inhibitors, and the adenosine-receptor agonists and antagonists. Although mouse models may not always represent the physiology of humans, they provide important information that clinical scientists can utilize in designing safe programs for the evaluation of new pharmacologic agents.

The effects of COX-2 selective and non-selective NSAIDs on the initiation and progression of atherosclerosis in ApoE−/− mice

In this study, we investigated the effects of prolonged administration of the selective COX-2 inhibitors celecoxib and rofecoxib and the non-selective NSAID naproxen on the initiation and progression of atherosclerosis. ApoE(-/-) mice, as well as corresponding wild-type mice, were fed either a normal chow or a high fat Western diet with or without addition of the respective drugs over a period of 16 weeks. Thereafter, aortic lesion size, plasma lipid levels, and COX-2 expression in the plaques were determined. The results showed that neither the COX-2 selective inhibitors nor naproxen had a significant impact on the initiation and progression of atherosclerosis in diet-fed ApoE(-/-) mice, although both celecoxib and rofecoxib showed a tendency to reduce plaque size. This slight effect may be due to selective inhibition of COX-2 activity because the COX-2 expression was not altered in the plaque. Plasma lipid levels were also not significantly influenced by these drugs. Interestingly, in ApoE(-/-) mice that have been fed with normal chow, we found an increased incidence of plaque formation after treatment with celecoxib and rofecoxib, indicating that coxibs may promote the initiation of atherosclerosis. This effect was probably masked in diet-fed mice by the more pronounced effects of the high cholesterol diet. In conclusion, the reduction in diet-induced plaque size in animals fed a high fat diet and the promotion of atherosclerosis in mice on a normal diet indicate a dual role of the coxibs. In advanced stages of atherosclerosis, they may exert antithrombotic properties due to their COX-2 inhibiting activity, whereas in very early stages they may favor the initiation of atherogenesis. However, because these results were only observed in ApoE(-/-) and not in wild-type animals, coxibs may increase the risk of thrombosis in patients with a predisposition for thrombotic complications.

Cyclooxygenase-2 Inhibition Increases Mortality, Enhances Left Ventricular Remodeling, and Impairs Systolic Function After Myocardial Infarction in the Pig

BACKGROUND

Cyclooxygenase (COX)-2 expression in the heart increases after myocardial infarction (MI). In murine models of MI, COX-2 inhibition preserves left ventricular dimensions and function. We studied the effect of selective COX-2 inhibition on left ventricular remodeling and function after MI in a pig model.

METHODS AND RESULTS

Twenty-two pigs were assigned to COX-2 inhibition with a COX-2 inhibitor (COX-2i; celecoxib 400 mg twice daily; n=14) or a control group (n=8). MI was induced by left circumflex coronary artery ligation, and the animals were euthanized 6 weeks later. Cardiac dimensions and function were assessed with echocardiography and conductance catheters. Infarct size and collagen density were analyzed with triphenyltetrazolium chloride staining and picrosirius red staining, respectively. COX-2 inhibition increased mortality compared with controls (50% versus 0%, P=0.022), whereas infarct size was similar (13.1+/-0.7% versus 14.1+/-0.1%, P=0.536). The decrease in thickness of the infarcted myocardial wall was more pronounced in the COX-2i group (60.6+/-9.6% versus 36.2+/-5.7%, P=0.001). End-diastolic volume was higher in the COX-2i group (133.9+/-33.5 versus 91.1+/-24.0 mL; P=0.021), as was the end-systolic volume at 100 mm Hg (81.7+/-27.8 versus 56.3+/-21.1 mL; P=0.037), which indicates that systolic function was more severely impaired. Infarct collagen density was lower after COX-2i treatment (25.3+/-3.9 versus 56.1+/-23.8 gray value/mm2; P=0.005).

CONCLUSIONS

In pigs, COX-2 inhibition after MI is associated with increased mortality, enhanced left ventricular remodeling, and impaired systolic function, probably due to decreased infarct collagen fiber density.

Double-label expression studies of prostacyclin synthase, thromboxane synthase and COX isoforms in normal aortic endothelium

We have performed double-label immunofluorescence microscopy studies to evaluate the extent of co-localization of prostacyclin synthase (PGIS) and thromboxane synthase (TXS) with cyclooxygenase (COX)-1 and COX-2 in normal aortic endothelium. In dogs, COX-2 expression was found to be restricted to small foci of endothelial cells while COX-1, PGIS and TXS were widely distributed throughout the endothelium. Quantification of the total cross-sectioned aortic endothelium revealed a 6- to 7-fold greater expression of COX-1 relative to COX-2 (55 vs. 8%) and greater co-distribution of PGIS with COX-1 compared to COX-2 (19 vs. 3%). These results are in contrast to the extensive co-localization of PGIS and COX-2 in bronchiolar epithelium. In rat and human aortas, immunofluorescence studies also showed significant COX-1 and PGIS co-localization in the endothelium. Only minor focal COX-2 expression was detected in rat endothelium, similar to the dog, while COX-2 was not detected in human specimens. Inhibition studies in rats showed that selective COX-1 inhibition caused a marked reduction of 6-keto-PGF(1alpha) and TXB(2) aortic tissue levels, while COX-2 inhibition had no significant effect, providing further evidence for a functionally larger contribution of COX-1 to the synthesis of prostacyclin and thromboxane in aortic tissue. The data suggest a major role for COX-1 in the production of both prostacyclin and thromboxane in normal aortic tissue. The extensive co-localization of PGIS and COX-2 in the lung also indicates significant tissue differences in the co-expression patterns of these two enzymes.

Distribution Profiles of Membrane Type-1 Matrix Metalloproteinase (MT1-MMP), Matrix Metalloproteinase-2 (MMP-2) and Cyclooxygenase-2 (COX-2) in Rabbit Atherosclerosis: Comparison with Plaque Instability Analysis

BACKGROUND

Despite increasing evidence that membrane type 1 matrix metalloproteinase (MT1-MMP), matrix metalloproteinase-2 (MMP-2), and cyclooxygenase-2 (COX-2) are involved in the pathogenesis of atherosclerosis, the possible links among these enzymes remain unclear. Accordingly, we investigated the distribution of MT1-MMP, MMP-2, and COX-2 immunohistologically in the atherosclerotic lesions of hypercholesterolemic (WHHLMI) rabbits.

METHODS AND RESULTS

Distribution of MT1-MMP, MMP-2, and COX-2 was examined by immunohistochemical staining using sixty cross sections of the ascending-arch and thoracic aortas prepared from 4 WHHLMI rabbits. MT1-MMP and MMP-2 staining was prominently observed in the macrophage-rich regions of the atheromatous lesions, and was positively correlated with morphological vulnerability (r=0.63 for MT1-MMP; r=0.60 for MMP-2; p<0.0001). MT1-MMP staining was positively correlated with MMP-2 staining (r=0.61, p<0.0001). COX-2 staining was also the highest in the macrophage-rich regions of the atheromatous lesions, with relatively high staining levels in other more stable lesions.

CONCLUSIONS

Co-distribution of MT1-MMP, MMP-2, and COX-2 was demonstrated in grade IV atheroma, indicating a possible link among these enzymes in the destabilization of atherosclerotic plaques. The relatively high COX-2 distribution in other more stable lesions may indicate its additional roles in the stabilization of atherosclerotic lesions. The present findings in hypercholesterolemic rabbits should help advance our understanding of the pathophysiology of atherosclerosis and provide useful information for the development of new therapeutic and diagnostic (imaging) agents that target MMPs and COX-2 in atherosclerosis.

Peroxisome proliferator-activated receptor-gamma agonists for management and prevention of vascular disease in patients with and without diabetes mellitus

Inflammation is known to have a pathogenic role in atherosclerosis and the genesis of acute coronary syndromes. The peroxisome proliferator-activated receptor (PPAR)-gamma, which is expressed in many constituent cells of atheromatous plaques, inhibits the activation of several proinflammatory genes responsible for atheromatous plaque development and maturation. Agonists of this receptor, such as rosiglitazone and pioglitazone, are currently available for the treatment of type 2 diabetes mellitus, and several lines of evidence have shown that these drugs have antiatherogenic effects. Insulin resistance is associated with inflammation and has a key role in atherogenesis. The antiatherogenic and insulin sensitizing effects of the thiazolidinediones in patients with type 2 diabetes mellitus may be associated with this action. However, in recent years there has been growing evidence that the antiatherogenic effects of PPAR-gamma agonists are not confined to patients with diabetes mellitus. PPAR-gamma agonists have been shown to downregulate the expression of endothelial activation markers, reduce circulating platelet activity, improve flow-mediated dilatation and attenuate atheromatous plaque progression in patients without diabetes mellitus. These effects of PPAR-gamma agonists appear to result from both insulin sensitization and a direct modulation of transcriptional activity in the vessel wall. This review summarizes the current understanding of the role of PPAR-gamma agonists in atherogenesis and discusses their potential role in the treatment of coronary artery disease in patients with type 2 diabetes mellitus and in nondiabetic patients.

Age-related changes in monocyte and platelet cyclooxygenase expression in healthy male humans and rats

Cyclooxygenase (COX) catalyses the formation of prostanoids that are crucial in maintaining hemostasis and important in inflammation. Animal studies reveal that COX-1 and COX-2 expression increase in some cell types during aging. This study determined age-related changes in COX expression in platelets and monocytes. Platelets and mononuclear cells were isolated from healthy male human volunteers from 18 to 28 and from 55 to 65 years of age, as well as male rats 8 and 54 weeks old for comparison. Western blot analysis was performed using selective antibodies against COX-1 and COX-2, followed by densitometrical analysis. In humans, an age-related increase in COX-2 expression in mononuclear cells was observed, with a 70% increase in the older age group. In rat studies, a 50% increase of COX-2 protein occurred in mononuclear cells of 54-week-old rats, compared with 8-week-old rats. For COX-1, an age-related increase of 50% occurred in rat platelets, but no difference occurred in the platelets' COX-1 levels between young and elderly human age groups. The increased COX-2 in monocytes of older humans, which is mirrored in rats, may have downstream implications in atherosclerosis and cardiovascular risk as mononuclear prostanoids are implicated in atherosclerotic plaque stability.

Safety and efficacy of short-term celecoxib before elective percutaneous coronary intervention for stable angina pectoris

Fifty patients with stable angina pectoris entered a randomized, double-blind study and were assigned to receive celecoxib (200 mg 2 times daily) or placebo 7 days before percutaneous coronary intervention (PCI). Results showed that detection of markers of myocardial injury above the upper normal limit was significantly lower in the celecoxib than in the placebo group: 12% versus 35% for creatine kinase-MB (CK-MB; p = 0.001), 20% versus 48% for troponin I (p = 0.0004), and 22% versus 51% for myoglobin (p = 0.0005). Myocardial infarction by CK-MB determination was less commonly seen after PCI in the celecoxib than in the placebo group (5% vs 18%, p = 0.025). Postprocedural peak levels of CK-MB (2.9 +/- 18 vs 7.5 +/- 18 ng/ml, p = 0.0002) were also significantly lower in the celecoxib than in the placebo group. No significant side effect was reported by the 2 groups of patients. In conclusion, pretreatment with celecoxib 200 mg 2 times daily for 7 days significantly decreased procedural myocardial injury in elective PCI. These findings indicate that the antiphlogistic action of cyclo-oxygenase-2 inhibition may provide a friendly protection to ischemic cardiomyocytes.

Cyclooxygenase-2 inhibition and coagulation

Selective inhibitors of cyclooxygenase-2 (COX-2) have come under scrutiny because of a possibly increased thrombotic risk observed in retrospective studies and comparatively small cancer trials. Indeed, inhibition of COX-2 may favor a prothrombotic environment by suppressing endothelial prostacyclin synthesis while leaving COX-1-dependent platelet thromboxane (TX) A2 synthesis unopposed. However, in vitro studies have shown that the effect of coxibs on coagulation is dependent on several variables; for example, the coxib celecoxib reduces endothelial tissue factor expression, a key initiator of the coagulation cascade. Furthermore, animal studies are inconclusive as some studies investigating the effect of COX-2 inhibition in atherosclerosis imply a detrimental effect of coxibs, whereas others suggest a beneficial effect on plaque progression and stability. In healthy human subjects and in patients with atherosclerotic vascular diseases, the effect of COX-2 inhibition on coagulation is equally unclear as no prospective, randomized, double-blinded studies sufficiently powered to investigate cardiovascular endpoints have been performed to directly investigate a potentially cardiotoxic effect of coxibs. Here, we review the effect of COX-2 inhibition on the coagulation system; we discuss the molecular mechanisms involved and summarize important clinical trials in which an increased frequency of thrombotic complications coxibs was observed.

Infiltration of inflammatory cells plays an important role in matrix metalloproteinase expression and activation in the heart during sepsis

Septicemia is an emerging pathological condition involving, among other effects, refractory hypotension and heart dysfunction. Here we have investigated the contribution of resident nonmyocytic cells to heart alterations after lipopolysaccharide administration. These cells contributed to the rapid infiltration of additional inflammatory cells that enhance the onset of heart disease through the release of inflammatory mediators. Early activation of resident monocytic cells played a relevant role on the infiltration process, mainly of major histocompatibility complex class II- and CD11b-positive cells. This infiltration was significantly impaired in animals lacking the nitric-oxide synthase-2 (NOS-2) gene or after pharmacological in-hibition of NOS-2 or cylooxygenase-2, suggesting a significant contribution of nitric oxide and prostanoids to the infiltration process. Under these conditions, the expression of NOS-2 and cylooxygenase-2 in the whole organ was attenuated because cardiomyocytes failed to express these enzymes. However, cardiomyocytes expressed and activated matrix metalloproteinase-9 through mechanisms regulated, at least in part, by nitric oxide and prostaglandins in an additive way. These results directly link the inflammatory response in the heart and extracellular matrix remodeling by the matrix metalloproteinases released by the cardiomyocytes, suggesting that activation and recruitment of inflammatory cells to the heart is a major early event in cardiac dysfunction promoted by septicemia.

The omega-3 fatty acid docosahexaenoate attenuates endothelial cyclooxygenase-2 induction through both NADP(H) oxidase and PKC epsilon inhibition

A high intake of the omega-3 fatty acid docosahexaenoate [docosahexaenoic acid (DHA)] has been associated with systemic antiinflammatory effects and cardiovascular protection. Cyclooxygenase (COX)-2 is responsible for the overproduction of prostaglandins (PG) at inflammatory sites, and its expression is increased in atheroma. We studied the effects of DHA on COX-2 expression and activity in human saphenous vein endothelial cells challenged with proinflammatory stimuli. A>or=24-h exposure to DHA reduced COX-2 expression and activity induced by IL-1, without affecting COX-1 expression. DHA effect depended on the NF-kappaB-binding site in the COX-2 promoter. EMSAs confirmed that DHA attenuated NF-kappaB activation. Because MAPK, PKC, and NAD(P)H oxidase all participate in IL-1-mediated COX-2 expression, we also tested whether these enzymes were involved in DHA effects. Western blots showed that DHA blocked nuclear p65 NF-kappaB subunit translocation by decreasing cytokine-stimulated reactive oxygen species and ERK1/2 activation by effects on both NAD(P)H oxidase and PKCepsilon activities. Finally, to address the question whether DHA itself or DHA-derived products were responsible for these effects, we inhibited the most important enzymes involved in polyunsaturated fatty acid metabolism, showing that 15-lipoxygenase-1 products mediate part of DHA effects. These studies provide a mechanistic basis for antiinflammatory and possibly plaque-stabilizing effects of DHA.

Divergent effects of rofecoxib on endothelial function and inflammation in acute coronary syndromes

BACKGROUND

The safe use of selective inhibitors of cyclooxygenase-2 in patients with cardiovascular disease has been questioned because of studies showing an increased risk of cardiac events. We examined the short-term effect of rofecoxib, a selective cyclooxygenase-2 inhibitor, on endothelial function, oxidative damage and inflammation in patients with acute coronary syndromes without ST-segment elevation.

METHODS

Forty-three patients with acute coronary syndromes without ST-segment elevation participated in the study. Flow-mediated dilatation (FMD), nitrate-mediated dilatation (NMD) of the brachial artery, malondialdehyde, a marker of lipid peroxidation, C-reactive protein, an acute phase marker of inflammation, and interleukin-6, a proinflammatory cytokine, were measured within 24 h of admission and a week later. Patients were randomized to receive for a week 100 mg aspirin daily with either 25 mg of rofecoxib (n=21) or placebo (n=22) orally once daily.

RESULTS

Malondialdehyde, C-reactive protein and interleukin-6 levels were reduced in the rofecoxib group (p=0.04, p=0.003 and p=0.02 respectively) while they remained unchanged in the placebo group after 1 week of treatment. FMD and NMD changes in both groups were not statistically different.

CONCLUSIONS

Co-administration of rofecoxib with low-dose aspirin decreases inflammatory and oxidative indices but does not improve endothelial function. The lack of improvement in FMD despite the improvement in inflammation and oxidative stress could be viewed in association to the recent observations on the adverse effects of COX-2 inhibition on the cardiovascular system.

Aging associated with mild dyslipidemia reveals that COX-2 preserves dilation despite endothelial dysfunction

The endothelial function declines with age, and dyslipidemia (DL) has been shown to hasten this process by favoring the generation of reactive oxygen species (ROS). Cyclooxygenase-2 (COX-2) can be induced by ROS, but its contribution to the regulation of the endothelial function is unknown. Since COX-2 inhibitors may be deleterious to the cardiovascular system, we hypothesized that DL leads to ROS-dependent endothelial damage and a protective upregulation of COX-2. Dilations to acetylcholine (ACh) of renal arteries isolated from 3-, 6-, and 12-mo-old wild-type (WT) and DL mice expressing the human ApoB-100 were recorded with or without COX inhibitors and the antioxidant N-acetyl-l-cystein (NAC). Nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) were inhibited using N(omega)-nitro-l-arginine (l-NNA) and a depolarizing solution, respectively. In WT mice, the dilation to ACh declined at 12 mo but was insensitive to COX-1/2 inhibition alone or with NAC. DL led to an early endothelial dysfunction at 6 mo, normalized, however, by NAC. At 12 mo, vascular sensitivity to ACh was further reduced by DL. At this age, selective COX-2 inhibition reduced the dilation, whereas addition of NAC improved it. In 3- and 6-mo-old WT mice, l-NNA significantly reduced the dilation, whereas it limited the dilation only in 3-mo-old DL mice. EDHF-dependent dilation remains identical in both groups. These data suggest that COX-2 activity confers endothelium-dependent vasodilatory function in aged DL mice in the face of a pro-oxidative environment. Upregulation of this pathway compensates for the early loss of the contribution of NO in DL mice.

Deletion of microsomal prostaglandin E synthase-1 augments prostacyclin and retards atherogenesis

Prostaglandin (PG) E(2) is formed from PGH(2) by a series of PGE synthase (PGES) enzymes. Microsomal PGES-1(-/-) (mPGES-1(-/-)) mice were crossed into low-density lipoprotein receptor knockout (LDLR(-/-)) mice to generate mPGES-1(-/-) LDLR(-/-)s. Urinary 11alpha-hydroxy-9, 15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M) was depressed by mPGES-1 deletion. Vascular mPGES-1 was augmented during atherogenesis in LDLR(-/-)s. Deletion of mPGES-1 reduced plaque burden in fat-fed LDLR(-/-)s but did not alter blood pressure. mPGES-1(-/-) LDLR(-/-) plaques were enriched with fibrillar collagens relative to LDLR(-/-), which also contained small and intermediate-sized collagens. Macrophage foam cells were depleted in mPGES-1(-/-) LDLR(-/-) lesions, whereas the total areas rich in vascular smooth muscle cell (VSMC) and matrix were unaltered. mPGES-1 deletion augmented expression of both prostacyclin (PGI(2)) and thromboxane (Tx) synthases in endothelial cells, and VSMCs expressing PGI synthase were enriched in mPGES-1(-/-) LDLR(-/-) lesions. Stimulation of mPGES-1(-/-) VSMC and macrophages with bacterial LPS increased PGI(2) and thromboxane A(2) to varied extents. Urinary PGE-M was depressed, whereas urinary 2,3-dinor 6-keto PGF(1alpha), but not 2,3-dinor-TxB(2), was increased in mPGES-1(-/-) LDLR(-/-)s. mPGES-1-derived PGE(2) accelerates atherogenesis in LDLR(-/-) mice. Disruption of this enzyme retards atherogenesis, without an attendant impact on blood pressure. This may reflect, in part, rediversion of accumulated PGH(2) to augment formation of PGI(2). Inhibitors of mPGES-1 may be less likely than those selective for cyclooxygenase 2 to result in cardiovascular complications because of a divergent impact on the biosynthesis of PGI(2).

Enhanced proatherogenic responses in macrophages and vascular smooth muscle cells derived from diabetic db/db mice

Diabetes is associated with enhanced inflammatory responses and cardiovascular complications such as atherosclerosis. However, it is unclear whether similar responses are present in cells derived from experimental animal models of diabetes. We examined our hypothesis that macrophages and short-term cultured vascular smooth muscle cells (VSMCs) derived from obese, insulin-resistant, and diabetic db/db mice would exhibit increased proatherogenic responses relative to those from control db/+ mice. We observed that macrophages from db/db mice exhibit significantly increased expression of key inflammatory cytokines and chemokines as well as arachidonic acid-metabolizing enzymes cyclooxygenase-2 and 12/15-lipoxygenase that generate inflammatory lipids. Furthermore, VSMCs derived from db/db mice also showed similar enhanced expression of inflammatory genes. Expression of inflammatory genes was also significantly increased in aortas derived from db/db mice. Both macrophages and VSMCs from db/db mice demonstrated significantly increased oxidant stress, activation of key signaling kinases, and transcription factors cAMP response element-binding protein and nuclear factor-kappaB, involved in the regulation of atherogenic and inflammatory genes. Interestingly, VSMCs from db/db mice displayed enhanced migration as well as adhesion to WEHI mouse monocytes relative to db/+. Thus, the diabetic milieu and a potential hyperglycemic memory can induce aberrant behavior of vascular cells. These new results demonstrate that monocyte/macrophages and VSMCs derived from db/db mice display a "preactivated" and proinflammatory phenotype associated with the pathogenesis of diabetic vascular dysfunction and atherosclerosis.

Procyanidin dimer B2 [epicatechin-(4β-8)-epicatechin] suppresses the expression of cyclooxygenase-2 in endotoxin-treated monocytic cells

The anti-inflammatory activity of the predominant procyanidin dimer in cocoa, dimer B2, was investigated in this study. Pretreatment of the procyanidin dimer B2 reduced COX-2 expression induced by the endotoxin lipopolysaccharide (LPS) in differentiated human monocytic cells (THP-1) in culture. To further elucidate the underlying mechanism of COX-2 inhibition by procyanidin, we examined their effects on the activation of extracellular signal-regulated protein kinase (ERK), Jun-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK), which are upstream enzymes known to regulate COX-2 expression in many cell types. Pretreatment with procyanidin dimer B2 decreased the activation of ERK, JNK, and p38 MAPK. In addition, procyanidin dimer B2 suppressed the NF-kappaB activation through stabilization of IkappaB proteins, suggesting that these signal-transducing enzymes could be potential targets for procyanidin dimer B2. By affecting the expression rather than the activity of COX-2, these in vitro data reported herein give further evidence on the anti-inflammatory protection by procyanidins.

Adventures in vascular biology: a tale of two mediators

I would like to thank the Royal Society for inviting me to deliver the Croonian Lecture. In so doing, the Society is adding my name to a list of very distinguished scientists who, since 1738, have preceded me in this task. This is, indeed, a great honour. For most of my research career my main interest has been the understanding of the normal functioning of the blood vessel wall and the way this is affected in pathology. During this time, our knowledge of these subjects has grown to such an extent that many people now believe that the conquering of vascular disease is a real possibility in the foreseeable future. My lecture concerns the discovery of two substances, prostacyclin and nitric oxide. I would like to describe the moments of insight and some of the critical experiments that contributed significantly to the uncovering of their roles in vascular biology. The process was often adventurous, hence the title of this lecture. It is the excitement of the adventure that I would like to convey in the text that follows.

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.

Cyclooxygenase-2 inhibition: Vascular inflammation and cardiovascular risk

The inducible isoform of cyclooxygenase-2 (COX-2) plays a role in pathophysiologic processes like inflammation and pain but is also constitutively expressed in tissues such as the kidney or vascular endothelium, where it exerts important physiologic functions. Although much evidence exists that implicates COX-2 in atherosclerosis, its role in this setting remains substantially uncertain. This observation is also confirmed by the results of clinical trials of selective COX-2 inhibitors. Treatment with these drugs, developed with the assumption that they would be as effective as nonselective COX inhibitors but without their gastrointestinal side effects, has been reported to be associated with an increased cardiovascular risk. In this article, we review the pattern of expression of COX-2 in the cellular players of atherothrombosis, its role as a determinant of plaque vulnerability, and the vascular effects on prostanoid inhibition by COX-2 inhibitors.

Melatonin suppresses macrophage cyclooxygenase-2 and inducible nitric oxide synthase expression by inhibiting p52 acetylation and binding

Melatonin has been shown to be produced by nonpineal cells and possess anti-inflammatory actions in animal models. In the present study, we tested the hypothesis that melatonin suppresses the expression of proinflammatory genes such as cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (INOS) by a common transcriptional mechanism. Melatonin but not tryptophan or serotonin inhibited lipopolysaccharide (LPS)-induced COX-2 and iNOS protein levels and promoter activities in RAW 264.7 cells in a time- and concentration-dependent manner. LPS or LPS plus interferon-gamma (IFNgamma) increased binding of all 5 isoforms of NF-kappaB to COX-2 and iNOS promoters. Melatonin selectively inhibited p52 binding without affecting p100 expression, p52 generation from p100, or p52 nuclear translocation. p52 acetylation was enhanced by LPS, which was abrogated by melatonin. Melatonin inhibited p300 histone acetyltransferase (HAT) activity and abrogated p300-augmented COX-2 and iNOS expression. HAT inhibitors suppressed LPS-induced p52 binding and acetylation to an extent similar to melatonin, and melatonin did not potentiate the effect of HAT inhibitors. These results suggest that melatonin inhibits COX-2 and iNOS transcriptional activation by inhibiting p300 HAT activity, thereby suppressing p52 acetylation, binding, and transactivation.

RUTI: a new chance to shorten the treatment of latent tuberculosis infection

Treatment of latent tuberculosis infection (LTBI) requires a long period of chemotherapy (9 months), which makes treatment-compliance extremely difficult. Current knowledge of latent bacilli and of the lesions with which they are associated suggests that these bacilli survive in granulomas with a central necrotic core and an outermost layer of foamy macrophages (FM) that represent an important immunosuppressive barrier. The presence of FM, which is especially strong in mice, explains not only the kinetics of the drainage of dead bacilli, debris and surfactant, but also how latent bacilli can escape from the granuloma and re-grow in the periphery, particularly in the alveolar spaces where they can disseminate easily. RUTI, a therapeutic vaccine made of detoxified, fragmented Mycobacterium tuberculosis cells, delivered in liposomes, was used to assess its effectiveness in a short period of chemotherapy (1 month). The rationale of this therapy was first to take advantage of the bactericidal properties of chemotherapy to kill active growing bacilli, eliminate the outermost layer of FM and reduce local inflammatory responses so as to avoid the predictable Koch phenomenon caused by M. tuberculosis antigens when given therapeutically. After chemotherapy, RUTI can be inoculated to reduce the probability of regrowth of the remaining latent bacilli. RUTI has already demonstrated its efficacy in controlling LTBI in experimental models of mice and guinea-pigs after a short period of chemotherapy; these experiments in animals showed the induction of a mixed Th1/Th2/Th3, polyantigenic response with no local or systemic toxicity. Local accumulation of specific CD8 T cells and a strong humoral response are characteristic features of RUTI that explain its protective properties; these are particular improvements when compared with BCG, although the regulatory response to RUTI may also be an important advantage. Further experiments using bigger animals (goats and mini-pigs) will provide more data on the efficacy of RUTI before starting phase I clinical trials.

Selective cyclooxygenase-2 inhibition with celecoxib decreases angiotensin II-induced abdominal aortic aneurysm formation in mice

OBJECTIVE

Inflammation plays an integral role in the development of abdominal aortic aneurysms (AAAs), and the expression of cyclooxygenase (COX)-2 is increased in aneurysmal tissue compared with normal aorta. Nonsteroidal anti-inflammatory drugs, which inhibit the activity of COX-1 and COX-2, decrease AAA expansion in humans and animal models of the disease. In the current study, we investigated the effectiveness of selective inhibition of COX-1 or COX-2 in attenuating AAA formation.

METHODS AND RESULTS

Eight-week-old male apolipoprotein E-deficient mice were treated with selective inhibitors of COX-1 or COX-2, SC-560 (approximately 25 mg.kg(-1).day(-1)), or celecoxib (approximately 125 mg.kg(-1).day(-1)), respectively. COX inhibitors were administered 1 week before angiotensin II (Ang II; 1000 ng.kg(-1).min(-1)) or saline infusion and throughout the time course of the experiment. COX-1 inhibition had no effect on incidence (control: 90% [9:10] versus SC-560: 89% [8:9]) or severity of Ang II-induced AAA formation. In contrast, celecoxib decreased the incidence (control: 74% [22:30] versus celecoxib: 11% [2:19]; P<0.001) and severity (P=0.001) of AAA formation. Celecoxib also decreased the incidence and severity of AAAs in nonhyperlipidemic mice.

CONCLUSIONS

COX-2-derived prostanoids play a fundamental role in the development of Ang II-induced AAAs in both hyperlipidemic and nonhyperlipidemic mice.

Update on cyclooxygenase-2 inhibitors

Nonsteroidal anti-inflammatory drugs represent the most commonly used medications for the treatment of pain and inflammation, but numerous well-described side effects can limit their use. Cyclooxygenase-2 (COX-2) inhibitors were initially touted as a therapeutic strategy to avoid not only the gastrointestinal but also the renal and cardiovascular side effects of nonspecific nonsteroidal anti-inflammatory drugs. However, in the kidney, COX-2 is constitutively expressed and is highly regulated in response to alterations in intravascular volume. COX-2 metabolites have been implicated in mediation of renin release, regulation of sodium excretion, and maintenance of renal blood flow. This review summarizes the current state of knowledge about both renal and cardiovascular side effects that are attributed to COX-2 selective inhibitors.

Atorvastatin Reduces the Expression of COX-2 mRNA in Peripheral Blood Monocytes from Patients with Acute Myocardial Infarction and Modulates the Early Inflammatory Response

Background: We examined the effect of atorvastatin on the expression of COX-2 in peripheral blood monocytes from patients with early stage of acute myocardial infarction (AMI), and the plasma C-reactive protein (CRP) concentrations were also examined.

Methods: Patients with AMI (n = 40) and with stable coronary heart disease (CHD; n = 18) were registered, and patients with AMI were randomly separated to a group that received routine therapy (group A, n = 20) or to a group that received routine therapy plus atorvastatin at 20 mg/day (group B, n = 20) for a week. Peripheral blood monocytes from patients with AMI both before and after treatment and from patients with stable CHD were isolated and cultured for 24 h. COX-2 mRNA expression was analyzed by reverse transcription-PCR. We measured concentrations of CRP in plasma by ELISA.

Results: COX-2 expression was activated in peripheral blood monocytes from patients with AMI [0.92 (0.13)] compared with patients with stable CHD [0.19 (0.08)]; after a week of treatment, COX-2 expression in group B (reduced by 66%) was obviously lower than in group A (reduced by 24%; P &lt;0.05). Plasma concentrations of CRP from patients with AMI [43.3 (14.9) mg/L] were increased compared with those from patients with stable CHD [1.65 (0.78) mg/L; P &lt;0.05]; after a week of treatment, CRP concentrations in group B (reduced by 62%) were lower than in group A (reduced by 35%; P &lt;0.05). COX-2 expression in peripheral blood monocytes from patients with AMI was positively correlated with plasma CRP concentration (r = 0.662; P &lt;0.05).

Conclusions: COX-2 may promote acute inflammatory process after AMI. Atorvastatin may improve the antiinflammatory effects through the COX-2 pathway.

Role of angiotensin II receptor blockers in atherosclerotic plaque stability

Several clinical trials have shown that agents blocking the renin-angiotensin system reduce the incidence of acute ischaemic events. This effect was independent from blood pressure reduction and was presumably related to plaque stabilisation. With the aim of investigating potential mechanisms underlying this effect, carotid plaques were analysed in a recent study from patients randomised to treatment with the angiotensin receptor blocker irbesartan, or the diuretic chlorthalidone for 4 months before carotid endarterectomy. It was found that irbesartan decreased inflammatory infiltration, increased collagen content and downregulated prostaglandin E2-dependent metalloproteases as a consequence of suppression of inducible COX-2/prostaglandin E synthase. This article reviews the results of this study and the most recent evidence that supports the possibility that angiotensin II receptor blockers represent a novel therapy for plaque stabilisation.

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.

Salvianolic acid B attenuates cyclooxygenase-2 expression in vitro in LPS-treated human aortic smooth muscle cells and in vivo in the apolipoprotein-E-deficient mouse aorta

Inflammation plays an essential role in atherosclerosis and post-angioplasty restenosis and the synthesis and release of inflammatory cytokines from vascular smooth muscle cells is an important contributor to these pathologies. It is assumed that drugs that prevent the overproduction of inflammatory cytokines may inhibit cardiovascular disorders. In the present study, the effects of a water-soluble antioxidant, salvianolic acid B (Sal B), derived from a Chinese herb, on the expression of cyclooxygenase (COX) in lipopolysaccharide (LPS)-treated human aortic smooth muscle cells (HASMCs) and in the aortas of cholesterol-fed apoE deficient mice were investigated. In unstimulated HASMCs, COX-2 mRNA and protein were almost undetectable, but were strongly upregulated in response to LPS. In contrast, HASMCs with or without LPS treatment showed constitutive expression of COX-1 mRNA and protein. The activation of COX-2 protein synthesis in LPS-stimulated HASMCs was shown to involve the activation of the extracellular-signal-regulated kinase 1/2 (ERK1/2), c-Jun NH(2)-terminal kinase (JNK), and p38 mitogen-activated protein kinase pathway. Incubation of HASMCs with Sal B before LPS stimulation resulted in pronounced downregulation of COX-2 expression. Sal B treatment suppressed ERK1/2 and JNK phosphorylation and attenuated the increase in prostaglandin E(2) production and NADPH oxidase activity in LPS-treated HASMCs. When apoE-deficient mice were fed a 0.15% cholesterol diet with or without supplementation with 0.3% Sal B for 12 weeks, the intima/media area ratio in the thoracic aortas was significantly reduced in the Sal B group (0.010 +/- 0.009%) compared to the apoE-deficient group (0.114 +/- 0.043%) and there was a significant reduction in COX-2 protein expression in the thickened intima. These results demonstrate that Sal B has anti-inflammatory properties and may explain its anti-atherosclerotic properties. This new mechanism of action of Sal B, in addition to its previously reported inhibition of LDL oxidation, may help explain its efficacy in the treatment of atherosclerosis.