Cyclooxygenase-2 Expression and Inhibition in Atherothrombosis

Novel strategies in antithrombotic therapy: targeting thrombosis while preserving hemostasis

Antithrombotic therapy is a delicate balance between the benefits of preventing a thrombotic event and the risks of inducing a major bleed. Traditional approaches have included antiplatelet and anticoagulant medications, require careful dosing and monitoring, and all carry some risk of bleeding. In recent years, several new targets have been identified, both in the platelet and coagulation systems, which may mitigate this bleeding risk. In this review, we briefly describe the current state of antithrombotic therapy, and then present a detailed discussion of the new generation of drugs that are being developed to target more safely existing or newly identified pathways, alongside the strategies to reverse direct oral anticoagulants, showcasing the breadth of approaches. Combined, these exciting advances in antithrombotic therapy bring us closer than we have ever been to the "holy grail" of the field, a treatment that separates the hemostatic and thrombotic systems, preventing clots without any concurrent bleeding risk.

Disconnect between COX-2 selective inhibition and cardiovascular risk in preclinical models

INTRODUCTION

Secondary pharmacology profiling is routinely applied in pharmaceutical drug discovery to investigate the pharmaceutical effects of a drug at molecular targets distinct from (off-target) the intended therapeutic molecular target (on-target). Data from a randomized, placebo-controlled clinical trial, the APPROVe (Adenomatous Polyp Prevention on VIOXX, rofecoxib) trial, raised significant concerns about COX-2 inhibition as a primary or secondary target, shaping the screening and decision-making processes of some pharmaceutical companies. COX-2 is often included in off-target screens due to cardiovascular (CV) safety concerns about secondary interactions with this target. Several potential mechanisms of COX-2-mediated myocardial infarctions have been considered including, effects on platelet stickiness/aggregation, vasal tone and blood pressure, and endothelial cell activation. In the present study, we focused on each of these mechanisms as potential effects of COX-2 inhibitors, to find evidence of mechanism using various in vitro and in vivo preclinical models.

METHODS

Compounds tested in the study, with a range of COX-2 selectivity, included rofecoxib, celecoxib, etodolac, and meloxicam. Compounds were screened for inhibition of COX-2 vs COX-1 enzymatic activity, ex vivo platelet aggregation (using whole blood from multiple species), ex vivo canine femoral vascular ring model, in vitro human endothelial cell activation (with and without COX-2 induction), and in vivo cardiovascular assessment (anesthetized dog).

RESULTS

The COX-2 binding assessment generally confirmed the COX-2 selectivity previously reported. COX-2 inhibitors did not have effects on platelet function (spontaneous aggregation or inhibition of aggregation), cardiovascular parameters (mean arterial pressure, heart rate, and left ventricular contractility), or endothelial cell activation. However, rofecoxib uniquely produced an endothelial mediated constriction response in canine femoral arteries.

CONCLUSION

Our data suggest that rofecoxib-related cardiovascular events in humans are not predicted by COX-2 potency or selectivity. In addition, the vascular ring model suggested possible adverse cardiovascular effects by COX-2 inhibitors, although these effects were not seen in vivo studies. These results may also suggest that COX-2 inhibition alone is not responsible for rofecoxib-mediated adverse cardiovascular outcomes.

Papain ameliorates monocyte-platelet aggregate formation-mediated inflammatory responses in monocytes by upregulating miRNA-146a transcription

BACKGROUND

MicroRNA-146a (miRNA-146a) is a nuclear factor κB (NF-κB)-inducible and inflammation-sensitive miRNA, while papain elicits anti-inflammatory effects by inhibiting monocyte-platelet aggregate (MPA)-mediated NF-κB pathway activation in monocytes. This study aimed to demonstrate the underlying effects of papain on MPA formation-initiated miRNA-146a expression and subsequent action in monocytes.

METHODS

THP-1 cells were exposed to papain, miRNA-146a mimic and inhibitor, NF-κB inhibitor (BAY11-7082), and platelets. Flow cytometry was used to measure the MPA formation-initiated monocyte activation. Levels of miRNA-146a, cyclooxygenase 2 (COX-2) mRNA and protein, and monocyte chemoattractant protein 1 (MCP-1) were analyzed in monocytes by RT-PCR, western blot, and ELISA.

RESULTS

The NF-κB inhibitor and miRNA-146a mimics upregulated miRNA-146a expression but suppressed subsequent monocyte activation and expression of COX-2 and MCP-1. Following exposure to papain, the enhanced miRNA-146a transcription induced by MPA-formation was found along with significant inhibition of monocyte activation in a dose-dependent manner. However, the inhibitory tendency was significantly reversed by miRNA-146a inhibitors. Expression of COX-2 mRNA and protein, as well as MCP-1, was inhibited in monocytes by papain, whereas miRNA-146a inhibitors promoted COX-2 and MCP-1 expression.

CONCLUSION

Our findings suggest that papain can inhibit MPA formation-mediated expression of inflammatory mediators in activated monocytes by upregulating miRNA-146a transcription.

POTENTIAL CARDIOPROTECTIVE EFFECT OF GENIPIN VIA CYCLOOXIDASE 2 SUPPRESSION AND P53 SIGNAL PATHWAY ATTENUATION IN INDUCED MYOCARDIAL INFARCTION IN RATS

ABSTRACT

Background and aims: Genipin, an iridoid derived from geniposide by β-glucosidase hydrolysis, has shown potential benefit in the treatment of heart function insufficiency despite its unclear therapeutic mechanism. This study aimed to investigate the primary cardioprotective mechanism of genipin. We hypothesized that genipin demonstrated the antiapoptosis and anti-inflammation for cardiac protection by inhibiting the cyclooxidase 2 (COX2)-prostaglandin D2 (PGD2) and murine double minute 2 (MDM2)-p53 pathways. Methods: The normal Sprague-Dawley rats were made into myocardial infarction models by conventional methods. Animals were treated with genipin for 5 weeks after myocardial infarction (MI). Morphometric and hemodynamic measurements were performed 5 weeks post-MI. Biological and molecular experiments were performed after the termination. Results: Both morphometry and hemodynamics in systole and diastole were significantly impaired in the model group but restored close to basal level after treatment with genipin. Genipin also restored the post-MI upregulated expressions of cytochrome c, p53, COX2, and PGD2 and downregulated expression of MDM2 to the approximate baseline. Genipin inhibited apoptotic and inflammatory pathways to prevent post-MI structure-function remodeling. Conclusions: This study showed the cardioprotective mechanism of genipin and implied its potential clinical application for the treatment of ischemic heart failure.

Current and Novel Antiplatelet Therapies for the Treatment of Cardiovascular Diseases

Over the last decades, antiplatelet agents, mainly aspirin and P2Y₁₂ receptor antagonists, have significantly reduced morbidity and mortality associated with arterial thrombosis. Their pharmacological characteristics, including pharmacokinetic/pharmacodynamics profiles, have been extensively studied, and a significant number of clinical trials assessing their efficacy and safety in various clinical settings have established antithrombotic efficacy. Notwithstanding, antiplatelet agents carry an inherent risk of bleeding. Given that bleeding is associated with adverse cardiovascular outcomes and mortality, there is an unmet clinical need to develop novel antiplatelet therapies that inhibit thrombosis while maintaining hemostasis. In this review, we present the currently available antiplatelet agents, with a particular focus on their targets, pharmacological characteristics, and patterns of use. We will further discuss the novel antiplatelet therapies in the pipeline, with the goal of improved clinical outcomes among patients with atherothrombotic diseases.

Is it safe to take Radix Salvia Miltiorrhiza - Radix Pueraria Lobate product with warfarin and aspirin? A pilot study in healthy human subjects

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Salvia Miltiorrhiza (Danshen) and Radix Pueraria Lobate (Gegen) are officially listed in the Chinese Pharmacopoeia and have long been used together as a Compound Chinese Traditional Medicine (CCTM) for treatment of coronary heart diseases, which are often co-administered with aspirin or warfarin to patients suffering from cardiovascular diseases.

AIM OF STUDY

Since significant pharmacokinetic and pharmacodynamic interactions between Danshen-Gegen (DG) formula and aspirin/warfarin have been observed in our previous rat studies, the current study was proposed aiming to further verify such pharmacokinetic and pharmacodynamic interactions in healthy human subjects and explore related mechanisms.

MATERIALS AND METHODS

A 5-day, multiple dose, five-session clinical trial has been carried out (n = 14) with 2-week washout periods between sessions, during which the subjects would receive different combinations of the medications. Plasma samples were collected for pharmacokinetic evaluation, and whole blood samples were collected for pharmacodynamic evaluation. In addition, an in-vitro mechanistic study is conducted to investigate the role of danshensu on the anti-thrombotic and anti-platelet aggregation effects of warfarin and aspirin respectively.

RESULTS

Significant pharmacokinetic and pharmacodynamic herb-drug interactions were observed in healthy human subjects. pharmacokinetically, co-administration of DG with aspirin or warfarin could lead to a moderately increased AUC_0→t of aspirin and a decreased AUC_0→t of 7-hydroxyl warfarin respectively. The systemic exposure of danshensu (DSS, the marker component of DG) would be significantly increased after co-administration with warfarin. Pharmacodynamically, a reduction in systemic thromboxane B2 concentration was noticed after administration of DG with aspirin, which could be associated with the increased systemic exposure of aspirin and the synergistic effect of danshensu, aspirin and salicylic acid on cyclooxygenase (COX) inhibition. An offset on the warfarin induced soluble thrombomodulin induction was observed after its co-administration with DG, which could be partially attributed to the COX-2 inhibition effect of danshensu.

CONCLUSION

Our results indicated that co-administration of DG with aspirin/warfarin would lead to significant pharmacokinetic and pharmacodynamic herb-drug interactions in healthy human subjects.

Prophylactic effect of Biochanin A in lipopolysaccharide-stimulated BV2 microglial cells

Aim/Purpose of the study:Inhibition of microglial activation using phytochemicals may be a potential candidate for the prevention of neurodegenerative diseases caused by neuroinflammation and oxidative stress. The goal of this study was to investigate the protective role of Biochanin A on lipopolysaccharide (LPS)-stimulated BV2 microglial cells. BV2 microglial cells were treated with LPS in the presence and absence of Biochanin A. Materials and methods: For this aim, nitric oxide production, nuclear factor kappa B (NF-κB), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, Prostaglandin E2 (PGE2), and reactive oxygen species (ROS) levels, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), myeloid differentiation factor-88 (MyD88), and toll like receptor-4 (TLR-4) protein expressions, Akt and ERK1/2 phosphorylation levels were measured. Results:Biochanin A pretreatment resulted in significant and concentration-dependently reduced the LPS-induced production of nitric oxide, NF-κB p65, TNF-α, IL-1β, IL-6, PGE2, and ROS compared to the untreated group. Biochanin A prophylaxis exerted an anti-inflammatory effect by suppressing iNOS, COX-2, MyD88, and TLR-4 protein expressions and Akt and ERK1/2 pathway activation. Conclusion:Taken together, these results show that Biochanin A exerts antioxidant and anti-inflammatory activities, thus may be beneficial for preventing neurodegenerative diseases mediated by microglial cells.

From Endothelium to Lipids, Through microRNAs and PCSK9: A Fascinating Travel Across Atherosclerosis

Lipids and endothelium are pivotal players on the scene of atherosclerosis and their interaction is crucial for the establishment of the pathological processes. The endothelium is not only the border of the arterial wall: it plays a key role in regulating circulating fatty acids and lipoproteins and vice versa it is regulated by these lipidic molecules thereby promoting atherosclerosis. Inflammation is another important element in the relationship between lipids and endothelium. Recently, proprotein convertase subtilisin/kexin type 9 (PCSK9) has been recognized as a fundamental regulator of LDL-C and anti-PCSK9 monoclonal antibodies have been approved for therapeutic use in hypercholesterolemia, with the promise to subvert the natural history of the disease. Moreover, growing experimental and clinical evidence is enlarging our understanding of the mechanisms through which this protein may facilitate the genesis of atherosclerosis, independently of its impact on lipid metabolism. In addition, environmental stimuli may affect the post-transcriptional regulation of genes through micro-RNAs, which in turn play a key role in orchestrating the crosstalk between endothelium and cholesterol. Advances in experimental research, with development of high throughput techniques, have led, over the last century, to a tremendous progress in the understanding and fine tuning of the molecular mechanisms leading to atherosclerosis. Identification of pivotal keystone molecules bridging lipid metabolism, endothelial dysfunction and atherogenesis will provide the mechanistic substrate to test valuable targets for prediction, prevention and treatment of atherosclerosis-related disease.

Predicting significance of COX-2 expression of peripheral blood monocyte in patients with coronary artery disease

Background

Cyclooxygenase-2 (COX-2) plays an important role in the monocyte-platelet aggregate (MPA)-medicated inflammatory response and possible coronary artery disease (CAD). This study aimed to assess the predicting significance of COX-2 expression in peripheral blood monocyte for CAD.

Methods

A total of 66 patients with CAD including stable angina (SA) and unstable angina (UA) were enrolled. The inflammatory indexes including white blood cell (WBC) count, high-sensitive C reactive protein (hs-CRP), serum monocyte chemoattractant protein-1 (MCP-1) and MPA levels were measured. The western-blotting assay and reverse transcription-polymerase chain reaction (RT-PCR) analysis were used to detect the COX-2 expression in peripheral blood monocytes. Furthermore, the correlation between COX-2 expression and MPA levels, and the association of COX-2 expression with CAD risk were assessed.

Results

The UA patients demonstrated higher levels of inflammatory indexes than the SA patients (P<0.001). Simultaneously, higher MPA levels and enhanced COX-2 expression were observed in the UA patients (P<0.01). The patients with enhanced COX-2 expression exhibited higher MPA than those without (P<0.01), and patients with increased MPA also demonstrated enhanced COX-2 expression (P<0.001). Moreover, the levels of COX-2 protein expression was positively related to the MPA formation rates (R²=0.4933, P<0.01), and enhanced COX-2 expression was independently associated with CAD risk [odds ratio (OR): 6.322, 95% confidence interval (CI): 4.544-8.978 ].

Conclusions

The COX-2 expression of peripheral blood monocytes can be used as an independent predictor for CAD.

Dose-Effect of Irbesartan on Cyclooxygenase-2 and Matrix Metalloproteinase-9 Expression in Rabbit Atherosclerosis

Irbesartan has previously shown antiatherosclerotic effects on human carotid atherosclerotic plaques. Our study aimed to assess the dose-effect of irbesartan on cyclooxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) in rabbit atherosclerotic aorta. New Zealand rabbits were randomly divided into 6 groups: normal control (NC), high cholesterol (HC), low-dose (10 mg·kg·day), medium-dose (20 mg·kg·d), and high-dose (30 mg·kg·d) irbesartan and celecoxib (20 mg·kg·d). Except for the NCs, rabbits were fed a HC diet for 14 weeks to induce atherosclerosis. Aortic atherosclerotic lesions and messenger RNA and protein expression of COX-2, MMP-9, and nuclear factor-κB (NF-κB) were subsequently measured. The surface area of aortic atherosclerotic lesions was visibly larger in the HC group than in NCs (P < 0.01), but showed considerable reduction with medium- and high-dosage irbesartan and celecoxib treatments (P < 0.01). In medium- and high-dosage irbesartan and celecoxib groups, COX-2 and MMP-9 expression and NF-κB activity were significantly lower than in the high-cholesterol group (P < 0.01). No significant differences in treatment effects were observed between the high-dosage irbesartan and celecoxib groups (P > 0.05). Our results indicate that medium and high doses of irbesartan and celecoxib have antiatherosclerotic effects in aortic plaques via inhibition of COX-2 and MMP-9 by suppressing NF-κB activation. High-dose irbesartan has effects similar to celecoxib.

Angiotensin II and vascular damage in hypertension: Role of oxidative stress and sympathetic activation

Reactive oxygen species (ROS) are oxygen derivates and play an active role in vascular biology. These compounds are generated within the vascular wall, at the level of endothelial and vascular smooth muscle cells, as well as by adventitial fibroblasts. Physiologically, ROS generation is counteracted effectively by the rate of elimination. In hypertension, a ROS excess occurs, which is not counterbalanced by the endogenous antioxidant mechanisms, leading to a state of oxidative stress. Angiotensin II, the active peptide of the renin-angiotensin-system (RAS), is a significant stimulus for ROS generation within the vasculature. It was also documented that at the level of subfornical cerebral regions an inappropriate RAS stimulation may lead to an increased vascular sympathetic activity. More recently, in conditions of fetal undernutrition, it was also proposed an increased vascular sympathetic activity secondary to inappropriate RAS activation, leading to the development of hypertension in adult life. The present review will discuss the complex interaction between RAS activation, vascular ROS generation and increased sympathetic outflow in hypertension.

Up-regulation of COX-2 and mPGES-1 by 27-hydroxycholesterol and 4-hydroxynonenal: A crucial role in atherosclerotic plaque instability

Atherosclerosis is currently understood to be mainly the consequence of a complicated inflammatory process at the different stages of plaque development. Among the several inflammatory molecules involved, up-regulation of the functional cyclooxygenase 2/membrane-bound prostaglandin E synthase 1 (COX-2/mPGES-1) axis plays a key role in plaque development. Excessive production of oxidized lipids, following low-density lipoprotein (LDL) oxidation, is a characteristic feature of atherosclerosis. Among the oxidized lipids of LDLs, the oxysterol 27-hydroxycholesterol (27-OH) and the aldehyde 4-hydroxynonenal (HNE) substantially accumulate in the atherosclerotic plaque, contributing to its progression and instability through a variety of processes. This study shows that 27-OH and HNE promote up-regulation of both the inducible enzymes COX-2 and mPGES-1, leading to increased production of prostaglandin (PG) E₂ and inducible nitric oxide synthase, and the subsequent release of nitric oxide in human promonocytic U937 cells. The study also examined the potential involvement of the functionally coupled COX-2/mPGES-1 in enhancing the production of certain pro-inflammatory cytokines and of matrix metalloproteinase 9 by U937 cells. This enhancement is presumably due to the induction of PGE₂ synthesis, as a result of the up-regulation of the COX-2/mPGES-1, stimulated by the two oxidized lipids, 27-OH and HNE. Induction of PGE₂ synthesis might thus be a mechanism of plaque instability and eventual rupture, contributing to matrix metalloproteinase production by activated macrophages.

The genetic basis of antiplatelet and anticoagulant therapy: A pharmacogenetic review of newer antiplatelets (clopidogrel, prasugrel and ticagrelor) and anticoagulants (dabigatran, rivaroxaban, apixaban and edoxaban)

INTRODUCTION

The study of pharmacogenomics presents the possibility of individualised optimisation of drug therapy tailored to each patients' unique physiological traits. Both antiplatelet and anticoagulant drugs play a key role in the management of cardiovascular disease. Despite their importance, there is a substantial volume of literature to suggest marked person-to-person variability in their effect. Areas covered: This article reviews the data available for the genetic cause for this inter-patient variability of antiplatelet and anticoagulant drugs. The genetic basis for traditional antiplatelets (i.e. aspirin) is compared with the newly available antiplatelet medicines (clopidogrel, prasugrel and ticagrelor). Similarly, the pharmacogenetics of warfarin is compared with the newer direct oral anticoagulants (DOACs) in detail. Expert Opinion: We identify strengths and weaknesses in the research thus far; including shortcomings in trial design and a review of newer analytical techniques. The direction of this research and its real-world implications are discussed.

Saikosaponin a inhibits lipopolysaccharide-oxidative stress and inflammation in Human umbilical vein endothelial cells via preventing TLR4 translocation into lipid rafts

Saikosaponin a (SSa), the major triterpenoid saponin derivatives from Radix bupleuri (RB), has been reported to have anti-inflammatory effects. The aim of this study was to investigate the effects of SSa on lipopolysaccharide (LPS)-induced oxidative stress and inflammatory response in human umbilical vein endothelial cells (HUVECs). HUVECs were stimulated with LPS in the presence or absence of SSa. The levels of TNF-α and IL-8 were detected by ELISA. The expression of COX-2 and iNOS, NF-κB and IκB protein were determined by Western blotting. To investigate the protective mechanisms of SSa, TLR4 expression was detected by Western blotting and membrane lipid rafts were separated by density gradient ultracentrifugation and analyzed by immunoblotting with anti-TLR4 antibody. The results showed that SSa dose-dependently inhibited the production of ROS, TNF-α, IL-8, COX-2 and iNOS in LPS-stimulated HUVECs. Western blot analysis showed that SSa suppressed LPS-induced NF-κB activation. SSa did not affect the expression of TLR4 induced by LPS. However, translocation of TLR4 into lipid rafts and oligomerization of TLR4 induce by LPS was inhibited by SSa. Furthermore, SSa disrupted the formation of lipid rafts by depleting cholesterol. Moreover, SSa activated LXRα-ABCA1 signaling pathway, which could induce cholesterol efflux from lipid rafts. Knockdown of LXRα abrogated the anti-inflammatory effects of SSa. In conclusion, the effects of SSa is associated with activating LXRα-ABCA1 signaling pathway which results in disrupting lipid rafts by depleting cholesterol and reducing translocation of TLR4 to lipid rafts and oligomerization of TLR4, thereby attenuating LPS mediated oxidative and inflammatory responses.

Predictors of high on-aspirin platelet reactivity in high-risk vascular patients treated with single or dual antiplatelet therapy

Aspirin is the key treatment in the secondary prevention of atherothrombosis. Interindividual variability of response has been linked to a higher risk for ischemic events. The aim of this study was to identify clinical and biologic factors predicting high on-aspirin platelet reactivity (HPR) in a high-risk, "real-world" population of vascular patients. All platelet testing performed from 2011 to 2013 in consecutive patients receiving long-term treatment with aspirin for coronary or cerebrovascular disease was retrospectively analyzed. Indications for platelet testing were recurrent ischemic events or high-risk angioplasty. HPR was defined as aggregation intensity≥20% using light-transmission aggregometry with arachidonic acid 0.5 mg/ml. Collagen-epinephrine platelet function analysis was also performed (threshold<165 seconds). Cardiovascular risk factors, usual biologic parameters, and antiplatelet treatment were recorded. A total of 1,508 patients were included (mean age 63 years, 71% men, 23% with diabetes). Antiplatelet treatment was aspirin alone in 333 patients and dual-antiplatelet therapy in 1,175 patients. HPR was found in 11.1% of patients. In multivariate analysis, independent predictive factors of HPR on light-transmission aggregometry with arachidonic acid were diabetes mellitus (odds ratio [OR] 2.10, 95% confidence interval [CI] 1.39 to 3.16), age (OR 1.25, 95% CI 1.06 to 1.47), fibrinogen level (OR 1.20, 95% CI 1.02 to 1.42), and von Willebrand factor level (OR 1.06, 95% CI 1.03 to 1.09). On light-transmission aggregometry with arachidonic acid and collagen-epinephrine platelet function analysis, fibrinogen remained the main factor associated with HPR (OR 1.33, 95% CI 1.19 to 1.61). Similar results were found in patients treated with aspirin alone or dual-antiplatelet therapy. A fibrinogen level>4.0 g/L was associated with a 3.9-fold increased risk for HPR in patients aged <75 years. In conclusion, fibrinogen level was the major predictor of HPR on aspirin in this large population of high-risk vascular patients.

Acetylsalicylic acid resistance risk factors in patients with myocardial infarction

BACKGROUND

Despite its commonly recognized benefits in the cardiovascular disease setting, an issue of resistance to this drug has lately emerged. The aim of this research was assessment of the phenomenon of acetylsalicylic acid (ASA) resistance and its risk factors in patients treated for myocardial infarction.

METHODS

This study is a post-hoc analysis of a previous prospective study with approximately 200 patients treated for myocardial infarction with a coated formulation of ASA. The population was divided into two subgroups according to the response to ASA. ASA responsiveness was assessed using the arachidonic acid-dependent platelet aggregation (ASPI-test). The measurements were performed using the technique of impedance aggregometry.

RESULTS

The prevalence of aspirin resistance among the study population was 6.2%. All analyzed aggregometric parameters (including ASPI-test, adenosine diphosphate dependent platelet aggregation - ADP-test, bleeding time measurement) showed significant differences between both subgroups. ASA resistant patients had higher concentrations of brain natriuretic peptide (BNP), high-sensitivity C-reactive protein (hs-CRP), leukocytes (WBC) and platelets (PLT) but lower concentrations of hemoglobin (HGB). The temporal point analysis for both subgroups showed aspirin resistance incidence peak in patients at 9 months after myocardial infarction.

CONCLUSIONS

The prevalence of aspirin resistance in our study population is comparable with rates reported in literature among patients with cardiovascular diseases. There is a possible relation between aspirin resistance and clopidogrel resistance. Presence did not affect the incidence of the clinical end-points.

High on-treatment platelet reactivity in peripheral endovascular procedures

The use of aspirin is considered the "gold standard" for the decrease of major adverse cardiovascular events in patients with atherosclerosis, including peripheral arterial disease (PAD), whereas a dual-antiplatelet regimen with aspirin and clopidogrel is usually indicated for such patients after angioplasty and stent deployment. However, a substantial number of subsequent adverse events still occur, even in patients who receive double-antiplatelet therapy. The "high on-treatment platelet reactivity" (HTPR) phenomenon has been lately recognized and plays a major role in the management of patients with PAD. Greater and more rapid inhibition of platelet aggregation has become the goal for new antiplatelet agents with the expectation of further improving outcomes for percutaneous intervention for PAD. The purpose of this review article is to highlight current evidence regarding the prevalence, aetiology, and clinical implications of HTPR in PAD as well as to discuss the possibilities of novel alternative antiplatelet regiments.

The safety and efficacy of aspirin intake in photoselective vaporization laser treatment of benign prostate hyperplasia

Endoscopic surgical treatment has become an option to treat benign prostate hyperplasia. We evaluated the safety and effectiveness of photoselective vaporization of the prostate (PVP) in patients. We evaluated preoperative and perioperative parameters, functional outcomes, and adverse events up to 12 months postoperatively of patients on oral anticoagulation therapy undergoing PVP, and compared the results with patients who did not take anticoagulation therapy. A total of 89 patients who received photoselective vaporization laser for benign prostate hyperplasia from May 2006 to February 2011 in our hospital were enrolled in our study. The patients were divided into two groups based on whether or not they were taking oral aspirin; 23 (25.8%) patients were taking aspirin derivatives (aspirin group), and 66 (74.2%) were not taking aspirin derivatives (control group). The mean prostate volume (58.8 mL vs 51 mL; P = 0.16) and mean energy consumption (235,268 J vs 289,793 J; P = 0.097) were comparable between the aspirin group and control group. The average postoperative results of hemoglobin were 13.4 mg/ dL for the aspirin group versus 13.9 mg/dL for the control group (P = 0.327). A significantly higher maximum flow rates and 80% improved post-void residual urine were noted during the followup. Postoperatively all variable showed significant improvement starting at month 1 of followup and remained improved for the 12 month followup. Postoperative complications were low and comparable between groups. PVP was characterized by excellent hemostatic properties and a very low intraoperative complication rate, even in the patients who were taking aspirin. On the basis of our perioperative results, we recommend PVP as a safe and effective procedure for patients with symptomatic benign prostate hyperplasia when taking an aspirin derivative.

Lumiracoxib Does Not Affect the Ex Vivo Antiplatelet Aggregation Activity of Low-Dose Aspirin in Healthy Subjects

This randomized, double-blind, placebo-controlled study evaluated the pharmacodynamic effects of concomitant low-dose aspirin and lumiracoxib in healthy subjects. Participants received lumiracoxib 400 mg once daily (n = 14) or placebo (n = 14) for 11 days, with concomitant low-dose aspirin (75 mg once daily) from days 5 to 11. Ex vivo pharmacodynamic assessments included assays of platelet aggregation and urinary thromboxane and prostacyclin metabolite profile. Arachidonic acid-stimulated platelet aggregation was reduced from 76.3% on day 4 to 4.8% on day 11 in the placebo group and from 75.8% on day 4 to 5.1% on day 11 in the lumiracoxib group. Collagen-induced platelet aggregation was reduced from 77.5% on day 4 to 52.8% on day 11 in the placebo group and from 79.5% on day 4 to 55.9% on day 11 in the lumiracoxib group. Urinary thromboxane and prostacyclin were unaffected by lumiracoxib. In conclusion, concomitant lumiracoxib did not interfere with the cyclooxygenase-1-mediated antiplatelet effects of low-dose aspirin.

Antiplatelet drug resistance in patients with coronary heart disease

Coronary angioplasty is an important component of coronary heart disease (CHD) management. There is a substantial evidence of the need for dual antiaggregant therapy (clopidogrel and aspirin) in this clinical group, both before and after the intervention. The development of thrombotic complications during antiaggregant therapy suggests the antiplatelet drug resistance. The prevalence of this condition varies from 5% to 45% for aspirin, and from 20% to 45% for clopidogrel, depending on the assessment method and the specific clinical group. For dual antiplatelet therapy, the resistance prevalence is 6-8%. Presently, the gold standard method of the platelet functional activity assessment is optical aggregometry. To assess the resistance to aspirin, arachidonic acid is used as an aggregation inductor, with the calculation of absolute aggregation levels. To assess the resistance to clopidogrel, ADP is used as an aggregation inductor, and the relative aggregation parameters are calculated. The development of aspirin resistance is influenced by biological, clinical, and genetic factors. The clopidogrel resistance is associated with certain medications, hyperglycemia, atherosclerosis, and CYP2C19*2 gene polymorphism. Identification of the patients resistant to antiplatelet drugs enables the clinicians to adjust the antiplatelet treatment reasonably early and to reduce the risk of cardiovascular events. The possible methods of overcoming antiplatelet drug resistance are to double the loading and maintenance doses of clopidogrel and to use new agents.

Exposure to diesel exhaust upregulates COX-2 expression in ApoE knockout mice

INTRODUCTION

We have shown that diesel exhaust (DE) inhalation caused progression of atherosclerosis; however, the mechanisms are not fully understood. We hypothesize that exposure to DE upregulates cyclooxygenase (COX) expression and activity, which could play a role in DE-induced atherosclerosis.

METHODS

ApoE knockout mice (30-week old) fed with regular chow were exposed to DE (at 200 µg/m(3) of particulate matter) or filtered air (control) for 7 weeks (6 h/day, 5 days/week). The protein and mRNA expression of COX-1 and COX-2 were evaluated by immunohistochemistry analysis and quantitative real-time PCR, respectively. To examine COX activity, thoracic aortae were mounted in a wire myograph, and phenylephrine (PE)-stimulated vasoconstriction was measured with and without the presence of COX antagonists (indomethacin). COX-2 activity was further assessed by urine 2,3-dinor-6-keto PGF(1α) level, a major metabolite of prostacyclin I(2) (PGI(2)).

RESULTS

Immunohistochemistry analysis demonstrates that DE exposure enhanced COX-2 expression in both thoracic aorta (p < 0.01) and aortic root (p < 0.03), with no modification of COX-1 expression. The increased COX-2 expression was positively correlated with smooth muscle cell content in aortic lesions (R(2) = 0.4081, p < 0.008). The fractional changes of maximal vasoconstriction in the presence of indomethacin was attenuated by 3-fold after DE exposure (p < 0.02). Urine 2,3-dinor-6-keto PGF(1α) level was 15-fold higher in DE group than the control (p < 0.007). The mRNA expression of COX-2 (p < 0.006) and PGI synthase (p < 0.02), but not COX-1, was significantly augmented after DE exposure.

CONCLUSION

We show that DE inhalation enhanced COX-2 expression, which is also associated with phenotypic changes of aortic lesion.

Defining the COX inhibitor selectivity of NSAIDs: implications for understanding toxicity

The hypothesis that the anti-inflammatory activity of NSAIDs derives from COX inhibition is well established. It also underpins the accepted mechanism of the gastrointestinal and renal toxicity of NSAIDs. However, in terms of NSAID-induced cardiovascular toxicity, is COX inhibition then guilty by association? Multiple experimental models of COX-1/COX-2 inhibition have enabled ranking of the relative inhibitory activity of NSAIDs. Inhibition is expressed as an IC(50) value and the index of COX selectivity as the ratio of the IC(50) value for COX-2 and COX-1. These data informed the 'imbalance hypothesis' that the cardiovascular risk of NSAIDs results from an imbalance in the detrimental actions of COX-1-derived thromboxane A(2) and the beneficial actions of COX-2-derived prostacyclin (PGI(2)). Data derived from in vitro models used to generate NSAID IC(50) values are discussed in the context of the difficulties in defining COX selectivity and hence understanding the toxicity of NSAIDs in current clinical use.

Prostaglandins: modulators of inflammation and cardiovascular risk

Cyclooxygenase (COX)-2-specific drugs such as rofecoxib and celecoxib and the newer agents, etoricoxib and valdecoxib, were developed to provide a safer alternative to traditional nonsteroidal antiinflammatory drugs (tNSAIDs). These drugs have been shown significantly to reduce endoscopically visualized gastrointestinal ulcers, and one of them, rofecoxib, has demonstrated a 50% reduction in clinically important gastrointestinal outcomes compared with a tNSAID. However, COX-derived prostaglandins also have complex interactions with the cardiovascular system. This article briefly reviews our current understanding of the interactions between prostaglandins and cardiovascular physiology, and addresses some of the concerns that recently have been raised regarding coxibs and the risk of cardiovascular events.

Impact of maternal dexamethasone on coronary PGE(2) production and prostaglandin-dependent coronary reactivity

Intrauterine growth restriction is associated with increased fetal glucocorticoid exposure and an increased risk of adult coronary artery disease. Coronary arteries from sheep exposed to early gestation dexamethasone (Dex) have increased constriction to angiotensin II (ANG II). Prostaglandin E(2) (PGE(2)) helps maintain coronary dilation, but PGE(2) production is acutely decreased by Dex administration. We hypothesized early gestation Dex exposure impairs adult coronary PGE(2) production with subsequent increases in coronary reactivity. Dex was administered to ewes at 27-28 days gestation (term 145 days). Coronary reactivity was assessed by wire myography in offspring at 4 mo of age (N = 5 to 7). Coronary smooth muscle cells were cultured and prostaglandin production was measured after 90 min incubation with radiolabeled arachidonate. Coronary myocytes from Dex-exposed lambs had a significant decrease in PGE(2) production that was reversed with ANG II incubation. Dex-exposed coronary arteries had increased constriction to ANG II and attenuated dilatation to arachidonic acid, with the greatest difference seen after the endothelium was inactivated by rubbing. Preincubation with the cyclooxygenase (COX) inhibitor indomethacin altered control responses and recapitulated the heightened coronary tone seen following Dex exposure. We conclude that impaired coronary smooth muscle COX-mediated PGE(2) production contributes to the coronary dysfunction elicited by early gestation Dex. Programmed inhibition of vasodilatory prostanoid production may link an adverse intrauterine environment with adult coronary artery disease.

Monocyte-platelet interaction induces a pro-inflammatory phenotype in circulating monocytes

Background

Activated platelets exert a pro-inflammatory action that can be largely ascribed to their ability to interact with leukocytes and modulate their activity. We hypothesized that platelet activation and consequent formation of monocyte-platelet aggregates (MPA) induces a pro-inflammatory phenotype in circulating monocytes.

Methodology/Principal Findings

CD62P⁺ platelets and MPA were measured, and monocytes characterized, by whole blood flow cytometry in healthy subjects, before and two days after receiving influenza immunization. Three monocytic subsets were identified: CD14⁺CD16⁻, CD14^highCD16⁺and CD14^lowCD16⁺. The increase in high sensitivity C-reactive protein post-immunization was accompanied by increased platelet activation and MPA formation (25.02±12.57 vs 41.48±16.81; p = 0.01), along with enhancement of circulating CD14^highCD16⁺ cells (4.7±3.6 vs 10.4±4.8; p = 0.003), their percentage being linearly related to levels of CD62P⁺-platelets (r² = 0.4347; p = 0.0008). In separate in vitro experiments, co-incubation of CD14⁺CD16⁻ cells, isolated from healthy donor subjects, with autologous platelets gave rise to up-regulation of CD16 on monocytes as compared with those maintained in medium alone (% change in CD14⁺CD16⁺ cells following 48 h co-incubation of monocytes with platelets was +106±51% vs monocytes in medium alone; p<0.001). This effect correlated directly with degree of MPA formation (r² = 0.7731; p<0.0001) and was associated with increased monocyte adhesion to endothelial cells. P-selectin glycoprotein ligand-1 (PSGL-1) blocking antibody, which abrogates MPA formation, abolished these effects, as did the cyclooxygenase (COX)-2 selective inhibitor NS-398, aspirin and the EP1/EP2-selective antagonist AH6809.

Conclusions/Significance

These data suggest that MPA formation, as occurs in the blood under pro-inflammatory conditions, expands the pool of circulating CD14^highCD16⁺ monocytes in a COX-2 dependent manner, and these monocytes exhibit increased adhesion to endothelium. Our findings delineate a novel mechanism underlying the pro-inflammatory effect of platelet activation.

Oxidative Stress and Vascular Damage in Hypertension: Role of Angiotensin II

Reactive oxygen species are oxygen derivates and play an active role in vascular biology. These compounds are generated within the vascular wall, at the level of endothelial and vascular smooth muscle cells, as well as by adventitial fibroblasts. In healthy conditions, ROS are produced in a controlled manner at low concentrations and function as signaling molecules regulating vascular contraction-relaxation and cell growth. Physiologically, the rate of ROS generation is counterbalanced by the rate of elimination. In hypertension, an enhanced ROS generation occurs, which is not counterbalanced by the endogenous antioxidant mechanisms, leading to a state of oxidative stress. In the present paper, major angiotensin II-induced vascular ROS generation within the vasculature, and relative sources, will be discussed. Recent development of signalling pathways whereby angiotensin II-driven vascular ROS induce and accelerate functional and structural vascular injury will be also considered.

Antiplatelet drug therapy: role of pharmacodynamic and genetic testing

Antiplatelet therapy represents the cornerstone of treatment for the short- and long-term prevention of atherothrombotic disease processes, in particular in high-risk settings such as in patients with acute coronary syndrome and those undergoing percutaneous coronary intervention. Currently, dual antiplatelet therapy with aspirin and clopidogrel represents the most commonly used treatment regimen in these settings. However, a considerable number of patients continue to experience adverse outcomes, including both bleeding and recurrent ischemic events. Numerous investigations have demonstrated that this phenomenon may be, in part, attributed to the broad variability in individual response profiles to this standard antiplatelet treatment regimen, as identified by various assays of platelet function testing. In addition, recent studies have demonstrated that genetic polymorphisms may also have an important role in determining levels of platelet inhibition and may be considered as a tool to identify patients at risk of adverse events. This article provides an overview on antiplatelet drug response variability, an update on definitions, including the role of pharmacodynamic testing, underlying mechanisms – with emphasis on recent understandings on pharmacogenetics and drug–drug interactions – and current and future perspectives on individualized antiplatelet therapy.

Long-chain acyl-CoA synthetase 4 modulates prostaglandin E₂ release from human arterial smooth muscle cells

Long-chain acyl-CoA synthetases (ACSLs) catalyze the thioesterification of long-chain FAs into their acyl-CoA derivatives. Purified ACSL4 is an arachidonic acid (20:4)-preferring ACSL isoform, and ACSL4 is therefore a probable regulator of lipid mediator production in intact cells. Eicosanoids play important roles in vascular homeostasis and disease, yet the role of ACSL4 in vascular cells is largely unknown. In the present study, the ACSL4 splice variant expressed in human arterial smooth muscle cells (SMCs) was identified as variant 1. To investigate the function of ACSL4 in SMCs, ACSL4 variant 1 was overexpressed, knocked-down by small interfering RNA, or its enzymatic activity acutely inhibited in these cells. Overexpression of ACSL4 resulted in a markedly increased synthesis of arachidonoyl-CoA, increased 20:4 incorporation into phosphatidylethanolamine, phosphatidylinositol, and triacylglycerol, and reduced cellular levels of unesterified 20:4. Accordingly, secretion of prostaglandin E₂ (PGE₂) was blunted in ACSL4-overexpressing SMCs compared with controls. Conversely, acute pharmacological inhibition of ACSL4 activity resulted in increased release of PGE₂. However, long-term downregulation of ACSL4 resulted in markedly reduced PGE₂ secretion. Thus, ACSL4 modulates PGE₂ release from human SMCs. ACSL4 may regulate a number of processes dependent on the release of arachidonic acid-derived lipid mediators in the arterial wall.

Genes and abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a multifactorial disease with a strong genetic component. Since the first candidate gene studies were published 20 years ago, approximately 100 genetic association studies using single nucleotide polymorphisms (SNPs) in biologically relevant genes have been reported on AAA. These studies investigated SNPs in genes of the extracellular matrix, the cardiovascular system, the immune system, and signaling pathways. Very few studies were large enough to draw firm conclusions and very few results could be replicated in another sample set. The more recent unbiased approaches are family-based DNA linkage studies and genome-wide genetic association studies, which have the potential of identifying the genetic basis for AAA, only when appropriately powered and well-characterized large AAA cohorts are used. SNPs associated with AAA have already been identified in these large multicenter studies. One significant association was of a variant in a gene called contactin-3, which is located on chromosome 3p12.3. However, two follow-up studies could not replicate this association. Two other SNPs, which are located on chromosome 9p21 and 9q33, were replicated in other samples. The two genes with the strongest supporting evidence of contribution to the genetic risk for AAA are the CDKN2BAS gene, also known as ANRIL, which encodes an antisense ribonucleic acid that regulates expression of the cyclin-dependent kinase inhibitors CDKN2A and CDKN2B, and DAB2IP, which encodes an inhibitor of cell growth and survival. Functional studies are now needed to establish the mechanisms by which these genes contribute toward AAA pathogenesis.

Use of nonsteroidal anti-inflammatory drugs in patients with cardiovascular disease: a cautionary tale

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit production of prostaglandins by acting on cyclooxygenase (COX) isoenzymes 1 and 2. Nonselective NSAIDs inhibit both COX 1 and 2 isoenzymes (eg, ibuprofen and naproxen). Selective NSAIDs act on COX-1 (eg, aspirin) or COX-2 (eg, celecoxib) isoenzymes, respectively. Prostaglandins are produced in platelets and gastric mucosal cells through constitutively expressed COX-1 isoenzyme. They are involved in the regulation of hemostasis, functional integrity of the gastrointestinal and renal tracts, platelet function, and macrophage differentiation. Inhibition of COX-1 isoenzymes impedes platelet aggregation, impairs maintenance of protective gastric mucosal barrier, and affects renal function. Prostaglandin production in inflamed tissue results from de novo induction of COX-2 expression by inflammatory cytokines and other noxious stimuli. Thus, COX-2 isoenzyme inhibition either selectively or nonselectively helps in reducing inflammation in the setting of musculoskeletal disorders. Safety and efficacy of NSAIDs are related to their relative actions on COX-1 or COX-2 inhibition. Given the multisystem (gastrointestinal, hematopoietic, and renal) adverse effect profile of COX-1 inhibition, formulation of NSAIDs with relative COX-2 selectivity became a highly desirable target during the 90's. However, studies in the first half of this decade revealed adverse effects of COX-2 inhibition on the cardiovascular system, including increased risks of myocardial infarction, exacerbation of stable congestive heart failure, and worsening high blood pressure. Randomized trials and meta-analyses confirmed these findings, which led to withdrawal of some of the COX-2 inhibitors from the market by the federal Food and Drug Administration a few years ago. Here, we review the effects of COX-2 isoenzyme inhibitors on the cardiovascular system to provide a safe strategy for prescribing these agents in patients with existing cardiovascular disease. We did not find adequate long-term randomized controlled trials appropriately powered to evaluate cardiovascular outcomes. Potentially, all NSAIDs possess a fair risk of adverse effects on gastrointestinal, cardiovascular, and renal systems. Until more evidence for safety via randomized trials is available, we recommend caution in prescribing COX-1 and 2 inhibitors for musculoskeletal disorders in patients with existing gastrointestinal or cardiovascular conditions.

The effect of the expression of angiotensin II on extracellular matrix metalloproteinase inducer (EMMPRIN) in macrophages is mediated via the AT1/COX-2/PGE2 pathway

AIM

To explore the expression of extracellular matrix metalloproteinase inducer (EMMPRIN) in THP-1 macrophages induced by angiotensin II (Ang II) and the mechanism of EMMPRIN expression.

METHODS

THP-1 cells were cultured and induced into macrophages, then stimulated with 10(-6) mol/L Ang II. Levels of EMMPRIN gene and its protein were measured by real-time polymerase chain reaction and western blotting. Prostaglandin E(2) (PGE(2)) expression was assayed by enzyme-linked immunosorbent assay. Antagonists of the angiotensin type-1 receptor (AT(1)R) and angiotensin type-2 receptor (AT(2)R) were used to inhibit the effect of Ang II, and PGE(2) added to detail the mechanism of Ang II-induced EMMPRIN expression.

RESULTS

Ang II clearly induced the expression of EMMPRIN mRNA and protein in macrophages; this expression peaked at 12 h and declined after 24 h. The tendency of enhancement of the levels of cyclooxygenase-2 (COX-2) and PGE(2) was coincident with EMMPRIN expression. AT(1)-receptor antagonists and COX-2 inhibitors inhibited the effect of Ang II, but AT(2)-receptor antagonists did not.

CONCLUSION

Ang II can up-regulate EMMPRIN expression in THP-1 macrophages via the AT(1)/COX-2/PGE(2) signal transduction pathway, and the effect can be inhibited by losartan and NS-398.

Celecoxib combined with atorvastatin prevents progression of atherosclerosis

BACKGROUND

Increased expression of cyclooxygenase (COX-2) contributes to atherosclerosis. Recent studies suggest that COX-2 inhibitors prevent early plaque development but their effects on established lesions are less clear, while the statins promote plaque stability. The purpose of this study is to investigate whether administering a combination of a COX-2 inhibitor with a statin drug alters plaque progression in apo E-/- mice.

MATERIALS AND METHODS

Apo E-/- mice were fed a Western diet from 6 to 26 wk of age. At 26 wk, the Western diets supplemented with atorvastatin, celecoxib, or atorvastatin plus celecoxib were given for an additional 12 wk.

RESULTS

When the mice were 38 wk of age, the total area occupied by the atherosclerotic lesion was 53% less in the mice fed the combination of atorvastatin + celecoxib P ≤ 0.05) than that of the apo E-/- mice fed the Western diet alone, atorvastatin alone, or celecoxib alone. The decreased extent of atherosclerosis observed in the apo E-/- mice fed the combination of drugs was associated with reduced levels of prostaglandin (PG) E(2,) decreased protein expression of metalloproteinase (MMP)-9, macrophage chemotactic protein (MCP-1), and COX 2, and decreased staining for MMP-9, F4-80 (a marker for macrophages), and vascular cell adhesion molecule (VCAM).

CONCLUSION

This study indicates that using statins with a COX-2 inhibitor reduced the extent of atherosclerosis and inflammatory/cell adhesion molecule levels in the apo E-/- mouse model.

Prevention of NSAID-related upper gastrointestinal toxicity: a meta-analysis of traditional NSAIDs with gastroprotection and COX-2 inhibitors

Background:

Traditional NSAIDs (tNSAIDs) and COX-2 inhibitors (COX-2s) are important agents for the treatment of a variety or arthritic conditions. The purpose of this study was to systematically review the effectiveness of misoprostol, H2-receptor antagonists (H2RAs), and proton pump inhibitors (PPIs) for the prevention of tNSAID related upper gastrointestinal (GI) toxicity, and to review the upper gastrointestinal (GI) safety of COX-2s.

Methods:

An extensive literature search was performed to identify randomized controlled trials (RCTs) of prophylactic agents used for the prevention of upper GI toxicity, and RCTs that assessed the GI safety of the newer COX-2s. Meta-analysis was performed in accordance with accepted techniques.

Results:

39 gastroprotection and 69 COX-2 RCTs met inclusion criteria. Misoprostol, PPIs, and double doses of H2RAs are effective at reducing the risk of both endoscopic gastric and duodenal tNSAID-induced ulcers. Standard doses of H2RAs are not effective at reducing the risk of tNSAID-induced gastric ulcers, but reduce the risk of duodenal ulcers. Misoprostol is associated with greater adverse effects than the other agents, particularly at higher doses. COX-2s are associated with fewer endoscopic ulcers and clinically important ulcer complications, and have fewer treatment withdrawals due to GI symptoms than tNSAIDS. Acetylsalicylic acid appears to diminish the benefit of COX-2s over tNSAIDs. In high risk GI patients, tNSAID with a PPI or a COX-2 alone appear to offer similar GI safety, but a strategy of a COX-2 with a PPI appears to offer the greatest GI safety.

Conclusion:

Several strategies are available to reduce the risk of upper GI toxicity with tNSAIDs. The choice between these strategies needs to consider patients’ underlying GI and cardiovascular risk.

The influence of COX-2 single nucleotide polymorphisms on abdominal aortic aneurysm development and the associated inflammation

INTRODUCTION

Cyclooxygenase (COX)-2 influences cardiovascular disease and serum concentration of high-sensitivity C-reactive protein (hsCRP). The study purpose was to determine the influence of single nucleotide polymorphisms (SNPs) of the COX-2 gene on abdominal aortic aneurysm (AAA) development and serum hsCRP concentrations.

PATIENTS AND METHODS

Patients with AAA and disease-free controls were recruited. High-sensitivity C-reactive protein was measured by an enzyme-linked immunosorbent assay (ELISA) test. The distributions of COX-2 SNPs were investigated (rs20417 and rs4648307). The influence of the COX-2 SNPs on the hsCRP serum concentration was assessed.

RESULTS

A total of 230 patients with AAA and 279 controls were included. No difference was found in the genotype distribution of the COX-2 SNPs rs20417 (P = .26) and rs4648307 (P = .90). They did not influence the hsCRP concentration (P = .24 and P = .61, respectively). Haplotype analysis of COX-2 SNPs revealed no difference.

CONCLUSION

These COX-2 SNPs do not play any role in AAA development and do not influence serum hsCRP. These results differentiate AAA development from atherosclerotic diseases.

Prospective, observational study of antiplatelet and coagulation biomarkers as predictors of thromboembolic events after implantation of ventricular assist devices

BACKGROUND

Long-term success in ventricular assist device (VAD) recipients is limited by thromboembolic events, the prediction of which remains elusive. We evaluated the predictive value of aspirin hyporesponsiveness and markers of coagulation and fibrinolysis.

METHODS

We prospectively enrolled patients scheduled to undergo VAD implantation between June 2004 and March 2006. Once before surgery, daily during hospitalization, and weekly after discharge we assessed platelet function, measured prothrombin activation fragment 1.2 (F1.2) and plasminogen activator inhibitor-1 (PAI-1) concentrations, and evaluated aspirin hyporesponsiveness by whole-blood aggregometry and thromboelastography. All patients received 325 mg oral aspirin daily from at least 7 days before VAD implantation. Follow-up continued until heart transplantation, death or closure of the database.

RESULTS

We included 26 patients (median follow-up 315 days, range 9-833 days). In eight (31%) patients, 14 thromboembolic events occurred at a median of 42 (interquartile range 26-131) days. Only six (43%) events based on whole-blood aggregometry and one (7%) based on thromboelastography coincided with aspirin hyporesponsiveness. Within-patient variability was high for both tests (59% and 567%, respectively). Compared with levels before surgery, PAI-1 concentrations were raised for up to 45 days (P <0.0001) and those of F1.2 for up to 3 days (P = 0.0001) after VAD implantation. PAI-1 and F1.2 levels did not rise significantly further before thromboembolic events.

CONCLUSIONS

Aspirin hyporesponsiveness was not associated with raised risk of future clinical thromboembolic events after VAD implantation. Impaired fibrinolysis, demonstrated by raised PAI-1 concentrations, might, however, indicate a predisposition to such events early after surgery.

Angiotensin II modulates CD40 expression in vascular smooth muscle cells

The signalling pathway CD40/CD40L (CD40 ligand) plays an important role in atherosclerotic plaque formation and rupture. AngII (angiotensin II), which induces oxidative stress and inflammation, is also implicated in the progression of atherosclerosis. In the present study, we tested the hypothesis that AngII increases CD40/CD40L activity in vascular cells and that ROS (reactive oxygen species) are part of the signalling cascade that controls CD40/CD40L expression. Human CASMCs (coronary artery smooth muscle cells) in culture exposed to IL (interleukin)-1β or TNF-α (tumour necrosis factor-α) had increased superoxide generation and enhanced CD40 expression, detected by EPR (electron paramagnetic resonance) and immunoblotting respectively. Both phenomena were abolished by previous incubation with membrane-permeant antioxidants or cell transfection with p22phoxantisense. AngII (50–200 nmol/l) induced an early and sustained increase in CD40 mRNA and protein expression in CASMCs, which was blocked by treatment with antioxidants. Increased CD40 expression led to enhanced activity of the pathway, as AngII-treated cells stimulated with recombinant CD40L released higher amounts of IL-8 and had increased COX-2 (cyclo-oxygenase-2) expression. We conclude that AngII stimulation of vascular cells leads to a ROS-dependent increase in CD40/CD40L signalling pathway activity. This phenomenon may be an important mechanism modulating the arterial injury observed in atherosclerosis-related vasculopathy.

[Variable platelet response to aspirin and new therapeutic targets]

Aspirin is the first-line oral antiplatelet drug to prevent thromboembolic arterial occlusions. Aspirin irreversibly inhibits cyclooxygenase (COX) 1 involved in the platelet production of thromboxane (TX) A(2), an inducer of vasoconstriction and a platelet activating agent. Recurrent vascular events despite aspirin intake, combined with laboratory evidence of poor antiplatelet effect, suggested what has been called "aspirin resistance". For clarity's sake a real aspirin resistance would be the absence of COX1 inhibition due to intrinsic platelet factors (which has never been reported). What has been described is (expected) variability. COX1 inhibition can be insufficient to modify TX-dependent platelet behaviour. Other agonists, the production of which does not involve COX1, can stimulate TX-receptors. The antiplatelet effect of aspirin can be insufficient for pharmacokinetic or pharmacodynamic reasons, the latter being further classified as TX-dependent or not. If platelets are so reactive that responses are more TX-independent than normally, then neither aspirin nor any drugs acting on this pathway can do the job. These mechanisms should be better understood and diagnosed, and this is the prerequisite for the development of newer antiplatelet agents.

Aspirin resistance in atherosclerosis

Clinically, aspirin resistance is defined as the failure of aspirin therapy to prevent an acute vascular thrombotic event despite regular intake of appropriate doses. In the laboratory, aspirin resistance encompasses the drug's failure to attain a particular level of platelet inhibition. From a clinical standpoint, the inability of aspirin to prevent a thrombotic event, despite appropriate cyclooxygenase-1 inhibition, implies the involvement of other factors. Evidence is emerging that aspirin resistance, as defined by residual platelet activity, merely reflects an individual's enhanced basal platelet function and suggests a hereditary component. Due to the multifactorial nature of cardiovascular disease, it is likely that a single therapy like aspirin cannot fully treat and prevent all thrombotic complications in the setting of atherosclerosis.