Future Role for Selective Phospholipase A2 Inhibitors in the Prevention of Atherosclerotic Cardiovascular Disease

iPLA2β Contributes to ER Stress-Induced Apoptosis during Myocardial Ischemia/Reperfusion Injury

Both calcium-independent phospholipase A2 beta (iPLA2β) and endoplasmic reticulum (ER) stress regulate important pathophysiological processes including inflammation, calcium homeostasis and apoptosis. However, their roles in ischemic heart disease are poorly understood. Here, we show that the expression of iPLA2β is increased during myocardial ischemia/reperfusion (I/R) injury, concomitant with the induction of ER stress and the upregulation of cell death. We further show that the levels of iPLA2β in serum collected from acute myocardial infarction (AMI) patients and in samples collected from both in vivo and in vitro I/R injury models are significantly elevated. Further, iPLA2β knockout mice and siRNA mediated iPLA2β knockdown are employed to evaluate the ER stress and cell apoptosis during I/R injury. Additionally, cell surface protein biotinylation and immunofluorescence assays are used to trace and locate iPLA2β. Our data demonstrate the increase of iPLA2β augments ER stress and enhances cardiomyocyte apoptosis during I/R injury in vitro and in vivo. Inhibition of iPLA2β ameliorates ER stress and decreases cell death. Mechanistically, iPLA2β promotes ER stress and apoptosis by translocating to ER upon myocardial I/R injury. Together, our study suggests iPLA2β contributes to ER stress-induced apoptosis during myocardial I/R injury, which may serve as a potential therapeutic target against ischemic heart disease.

Combined Lipidomics and Network Pharmacology Study of Protective Effects of Salvia miltiorrhiza against Blood Stasis Syndrome

Blood stasis syndrome (BSS) is one of the most common symptoms of cardiovascular diseases (CVDs) in traditional Chinese medicine (TCM) theory. Previous studies have identified that Salvia miltiorrhiza (Danshen) has beneficial effects on BSS, but there is no relevant research from the perspective of lipidomics to study the mechanism of Danshen against BSS since hyperlipidemia has been the widely accepted risk factor of CVDs. In this study, lipidomics technology combined with network pharmacology was applied to investigate the pathological mechanism of BSS and the protective effects of Danshen. The lipidomics profiling based on the UPLC-QTOF-MS analysis method was applied to identify the differential metabolites in the plasma of blood stasis rats. The related pathway and potential targets involved in the anti-BSS effects of Danshen were predicted by pathway analysis and network pharmacology. The biochemical results showed that Danshen intervention significantly reduced whole blood viscosity (WBV) at all the shear rates and fibrinogen concentration (FIB) (p < 0.01) and increased activated partial thromboplastin time (APTT) effectively (p < 0.01). We also found that 52 lipid metabolites, including glycerophospholipid, sphingolipid, glycerolipid, plasmalogen, cholesterol ester, and testosterone, were associated with blood stasis. Moreover, Dgka, Hsd17b3, Hsd3b1, Inppl1, Lpl, Pik3ca, Pik3r1, Pla2g1b, Pla2g2a, Soat1, and Soat2 were predicted as potential targets, while glycerophospholipid metabolism, glycerolipid metabolism, steroid and steroid hormone biosynthesis, phosphatidylinositol signaling system, and ether lipid metabolism were involved as shared critical pathways of lipidomics analysis and network pharmacology. Collectively, this study offered a new understanding of the protection mechanism of Danshen against BSS, which provided new insight to explore the protective effects of Danshen.

Tracking of secretory phospholipase A2 enzyme activity levels from childhood to adulthood: a 21-year cohort

OBJECTIVE

Secretory phospholipase A2 (sPLA2) enzyme activity is a potential inflammatory biomarker for cardiovascular disease. We examined the tracking, or persistence, of sPLA2 enzyme activity levels from childhood to adulthood, and identify potentially modifiable factors affecting tracking.

METHOD

Prospective cohort of 1735 children (45% females) who had serum sPLA2 enzyme activity levels and other cardiovascular disease risk factors measured in 1980 that were followed-up in 2001.

RESULTS

sPLA2 activity tracked from childhood to adulthood for males (r=0.39) and females (r=0.45). Those who decreased body mass index relative to their peers were more likely to resolve elevated childhood sPLA2 levels than have persistent elevated sPLA2 levels in childhood and adulthood. Those who consumed less fruit, and gained more body mass index relative to their peers, began smoking or were a persistent smoker between childhood and adulthood were more likely to develop incident elevated sPLA2 levels than those with persistent not elevated sPLA2 levels.

CONCLUSIONS

Childhood sPLA2 enzyme activity levels associate with adult sPLA2 levels 21 years later. Healthful changes in modifiable risk factors that occur between childhood and adulthood might prevent children from developing elevated sPLA2 levels in adulthood.

The associations of stroke, transient ischemic attack, and/or stroke-related recurrent vascular events with Lipoprotein-associated phospholipase A2: A systematic review and meta-analysis

BACKGROUND

Studies on stroke and lipoprotein-associated phospholipase A2 (Lp-PLA2) have produced conflicting results.

OBJECTIVE

The aim of the study was to assess the associations of Lp-PLA2 levels (mass and activity) with recurrent vascular events in patients with transient ischemic attack (TIA) and/or first ischemic stroke and with stroke in the general population.

METHODS

The MEDLINE, Embase, the Cochrane Library, Web of Science, Science Direct, China National Knowledge Infrastructure, China Biology Medical Disc (CBMdisc), and WanFang were searched for prospective observational studies reported until January 2017. Eligible studies reported Lp-PLA2 levels and adjusted risk estimates of recurrent vascular events and/or stroke. Risk ratio (RR) with corresponding 95% confidence intervals (CIs) were used to express the pooled data in a random-effects model.

RESULTS

A total of 11 studies that comprised 20,284 participants (4,045 were TIA and/or first ischemic stroke patients and 16,239 were residents in general population) were identified, which reported either Lp-PLA2 mass levels (4 studies) or Lp-PLA2 activity levels (10 studies). The pooled RR of recurrent vascular events (467 cases) in TIA and/or first ischemic group was 2.24 (95% CI, 1.33-3.78), whereas the pooled RR of stroke (1604 cases) in the general population was 1.47 (95% CI, 1.10-1.97). The pooled RRs of Lp-PLA2 mass and activity levels with the risk of stroke in the general population were 1.69 (95% CI, 1.03-2.79) and 1.28 (95% CI, 0.88-1.85), respectively.

CONCLUSIONS

In patients with TIA and first ischemic stroke, elevated Lp-PLA2 activity levels were associated with recurrent vascular events. And in the general population elevated Lp-PLA2 levels were associated with the risk of stroke, although the association between Lp-PLA2 activity levels and the risk of stroke was less profound compared with the corresponding association of stroke risk with the Lp-PLA2 mass levels.

Mendelian Randomization Analyses for Selection of Therapeutic Targets for Cardiovascular Disease Prevention: a Note of Circumspection

Genetic factors identified from genome-wide association studies have been used to understand causative variants for complex diseases. Studies conducted on large populations of individuals from many geographical regions have provided insights into genetic pathways involved in the causal pathway for atherosclerotic cardiovascular disease. A single genetic trait may ineffectively evaluate the pathway of interest, and it may not account for other complementary genetic pathways that may be activated at various stages of the disease process or evidence-based therapies that alter the molecular and cellular milieu.

Carboxyethylpyrroles: From Hypothesis to the Discovery of Biologically Active Natural Products

Our research on the roles of lipid oxidation in human disease is guided by chemical intuition. For example, we postulated that 2-(ω-carboxyethyl)pyrrole (CEP) derivatives of primary amines would be produced through covalent adduction of a γ-hydroxyalkenal generated, in turn, through oxidative fragmentation of docosahexaenoates. Our studies confirmed the natural occurrence of this chemistry, and the biological activities of these natural products and their extensive involvements in human physiology (wound healing) and pathology (age-related macular degeneration, autism, atherosclerosis, sickle cell disease, and tumor growth) continue to emerge. This perspective recounts these discoveries and proposes new frontiers where further developments are likely. Perhaps more significantly, it depicts an effective chemistry-based approach to the discovery of novel biochemistry.

Evaluation of anti-inflammatory activity of selected medicinal plants used in Indian traditional medication system in vitro as well as in vivo

The present study was carried out to evaluate in vivo and in vitro anti-inflammatory potential of selected medicinal plants used in Indian traditional medication. The sequentially extracted plant samples as, Cissus quadrangularis, Plumbago zeylanica, Terminalia bellarica and Terminalia chebula in water, ethanol and hexane were evaluated in-vitro for COX-1 and 2 inhibitory and antioxidant activities. The in vivo anti-inflammatory activity of selected samples showing promising COX-2 inhibition was assessed using carrageenan and Phorbol Myristate Acetate (PMA) induced mice edema animal model. The results obtained reveals that most of the plants were found to inhibit COX-2 activity as compared to COX-1. It was observed that the extracts of T. bellarica (73.34 %) and T. chebula (74.81 %) showed significant COX-2 selective inhibition as compared to other samples. The ethanol extract of the selected plants demonstrated effective DPPH, OH and superoxide radical scavenging activity. In vivo anti-inflammatory study shows that, T. bellarica and T. chebulla had a significant impact on inhibition of edema formation. The cytotoxicity evaluation study of ethanolic fraction of selected medicinal plants indicates that the selected samples have no effect on cell viability. HPTLC fingerprint of flavonoids of the selected samples was also prepared as a measure of quality control. The results obtained may be useful in strengthening the standardization of the selected botanicals. Moreover the selected plants can be considered as a resource for searching novel anti-inflammatory agents possessing COX-2 inhibition.

The role of inflammatory biomarkers in developing targeted cardiovascular therapies: lessons from the cardiovascular inflammation reduction trials

Anti-inflammatory add-on therapy to conventional cardiovascular prophylaxis has been proposed as a novel therapeutic approach to potentially reduce residual cardiovascular risk. This hypothesis has been challenged by a series of unsuccessful Phase III studies testing the impact on clinical outcomes of novel agents with immunomodulatory actions. Specifically, the apparent ability of phospholipase A2 (PLA2) inhibitors and of antioxidants to ameliorate inflammation and to reduce coronary disease in Phase II trials did not translate into improved secondary cardiovascular prevention in larger population-based studies. Other anti-inflammatory agents are still under scrutiny. However, studies to date have lacked information on the inflammatory profile of the participants, both at baseline and at follow-up, thereby limiting the possibility of identifying subgroups of patients in whom 'residual inflammation' can be detected despite optimal conventional therapy, and who could therefore benefit from a cardiovascular prevention strategy specifically targeting inflammation. This has also rendered it difficult to interpret the results as a conclusive demonstration of inefficacy of the tested anti-inflammatory strategies in the treatment of atherosclerosis. We here discuss the importance of better patient characterization to minimize heterogeneity of the study population, so that effectiveness of different anti-inflammatory strategies can be evaluated in targeted subgroups of patients. We also illustrate how specific inflammatory biomarkers could assist in this process, with particular emphasis on the roles of high-sensitivity C-reactive protein and circulating monocyte phenotype.

Anti-inflammatory and antioxidant properties of Eriobotrya japonica leaves extracts

BACKGROUND

In the present work we determined phenolic and flavonoids content of Eriobotrya japonica leaves extracts and fractions and their antioxidant and anti-inflammatory properties.

OBJECTIVES

To evaluate the inhibition of inflammatory PLA2 and antioxidant effects of extracts and fractions from Eriobotrya japonica leaves.

METHODS

Antioxidant activity was evaluated with DPPH radical scavenging assay and anti-inflammatory effect of fractions was measured by their inhibition potency on the human pro-inflammatory phospholipase A2 (group IIA).

RESULTS

The EtOH/EtOAc 2:1 extract exhibited a potent inhibition of the hG-IIA with an IC50 values of 8 µg/ml. It also shows an antioxidant activity measured on DPPH with an IC50 of 42 µg/ml. Fractionation shows that CH2Cl2/MeOH 0:1 fraction was the rich one on flavonoids compounds (4.3 mg/g dry weight) and demonstrates a high antioxidant activity with an IC50 of 12 µg/ml. The anti-inflammatory evaluation demonstrates that the same fraction was the best one to inhibit the pro-inflammatory phospholipase A2 group IIA with an IC50 of 4 µg/ml.

CONCLUSION

Study conducted on Eriobotrya japonica shows that CH2Cl2/MeOH 0:1 fraction inhibits efficiently the hG-IIA phospholipase. which is considered as pro-inflammatory enzyme.

Lipoproteins as biomarkers and therapeutic targets in the setting of acute coronary syndrome

The period following an acute coronary syndrome (ACS) represents a critical time frame with a high risk for recurrent events and death. The pathogenesis of this increase in clinical cardiovascular disease events after ACS is complex, with molecular mechanisms including increased thrombosis and inflammation. Dyslipoproteinemia is common in patients with ACS and predictive of recurrent cardiovascular disease events after presentation with an ACS event. Although randomized clinical trials have provided fairly convincing evidence that high-dose statins reduce the risk of recurrent cardiovascular events after ACS, there remain questions about how aggressively to reduce low-density lipoprotein cholesterol levels in ACS. Furthermore, no other lipid-related interventions have yet been proven to be effective in reducing major cardiovascular events after ACS. Here, we review the relationship of lipoproteins as biomarkers to cardiovascular risk after ACS, the evidence for lipid-targeted interventions, and the potential for novel therapeutic approaches in this arena.

Can lipoprotein-associated phospholipase A2 be used as a predictor of long-term outcome in patients with acute coronary syndrome?

Studies indicate that elevated plasma concentrations of lipoprotein-associated phospholipase A2 (Lp-PLA2) is associated with increased risk of cardiovascular disease. Lp-PLA2 seems to play a crucial role in the formation of plaques and acute inflammation, and plasma Lp-PLA2 could therefore potentially be used as a predictor of long-term outcome in ACS patients. To evaluate this, data concerning Lp-PLA2 as a predictor in ACS patients was gathered through a systematic literature review, and studies on this issue were extracted from relevant databases, incl. PubMed and Cochrane. A total of 14 articles were retrieved, but after thorough evaluation and elimination of irrelevant articles only seven studies were eligible for the literature review. All studies except two showed significant correlation between Lp-PLA2 and CV events in ACS patients. Only one study found an independent value to predict CV events 30 days after ACS. Altogether, there was inconsistency in the findings regarding the potential use of Lp-PLA2 and a lack of knowledge on several issues. Lp-PLA2 seems to give valuable information on which ACS patients are prone to new events and also provides important information on plaque size. However, more focused studies concerning genetic variations, time-window impact, patients with and without CV risk factors (e.g. diabetes), and treatment effects are needed. In conclusion, Lp-PLA2 offers new insight in the pathophysiological development of ACS, but until the aforementioned issues are addressed the biomarker will mainly be of interest in a research setting, not as a predictive parameter in a clinical setting.

Targeting inflammation: impact on atherothrombosis

Atherothrombosis is a worldwide epidemic accounting for an unacceptable toll of deaths and disabilities. Its pathophysiology is complex and hardly referable to a specific mechanism; however, in the last 20 years, a growing amount of evidence has demonstrated that inflammatory processes play a major role from the very beginning to the ultimate complication of atherothrombosis. These evidences are addressing a growing interest toward anti-inflammatory agents as preventive or curative treatments of atherothrombosis. At present, accumulated data are not conclusive, but strong evidence exists in favor of an anti-inflammatory positive effect for several drugs as statins or renin-angiotensin inhibitors. More conclusive data are expected from ongoing trials directly exploring the role of specific cytokines antagonists.

The biological role of inflammation in atherosclerosis

The concept of the involvement of inflammation in the pathogenesis of atherosclerosis has existed since the 1800s, stemming from sentinel pathologic observations made by Rudolf Virchow, Karl Rokitansky, and others. Our understanding of the complex role played by immune and inflammatory mediators in the initiation and progression of atherosclerosis has evolved considerably in the intervening years, and today, a dramatically evolved understanding of these processes has led to advances in both diagnostic and prognostic approaches, as well as novel treatment modalities targeting inflammatory and immune mediators. Therapeutic interventions working through multiple mechanisms involved in atheroma pathogenesis, such as statins, which both lower lipids and alter the inflammatory milieu in the vessel wall, hold promise for the future. In this brief review, we explore the biological role of inflammation in atherosclerosis, with a focus on cellular involvement in both acute and chronic inflammation, and outline novel biomarkers of inflammation and atherosclerosis with a particular focus on the potential application of these novel approaches in improving strategies for disease diagnosis and management.

Niacin: another look at an underutilized lipid-lowering medication

Niacin, or water-soluble vitamin B(3), when given at pharmacologic doses, is a powerful lipid-altering agent. This drug, which lowers the levels of atherogenic, apolipoprotein-B-containing lipoproteins, is one of few medications that can raise the levels of atheroprotective HDL cholesterol. Niacin also has beneficial effects on other cardiovascular risk factors, including lipoprotein(a), C-reactive protein, platelet-activating factor acetylhydrolase, plasminogen activator inhibitor 1 and fibrinogen. Many clinical trials have confirmed the lipid effects of niacin treatment; however, its effects on cardiovascular outcomes have been called into question owing to the AIM-HIGH trial, which showed no benefit of niacin therapy on cardiovascular endpoints. Furthermore, use of niacin has historically been limited by tolerability issues. In addition to flushing, worsened hyperglycaemia among patients with diabetes mellitus has also been a concern with niacin therapy. This article reviews the utility of niacin including its mechanism of action, clinical trial data regarding cardiovascular outcomes, adverse effect profile and strategies to address these effects and improve compliance.

Modulation of oxidative stress, inflammation, and atherosclerosis by lipoprotein-associated phospholipase A2

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), also known as platelet-activating factor acetylhydrolase (PAF-AH), is a unique member of the phospholipase A(2) superfamily. This enzyme is characterized by its ability to specifically hydrolyze PAF as well as glycerophospholipids containing short, truncated, and/or oxidized fatty acyl groups at the sn-2 position of the glycerol backbone. In humans, Lp-PLA(2) circulates in active form as a complex with low- and high-density lipoproteins. Clinical studies have reported that plasma Lp-PLA(2) activity and mass are strongly associated with atherogenic lipids and vascular risk. These observations led to the hypothesis that Lp-PLA(2) activity and/or mass levels could be used as biomarkers of cardiovascular disease and that inhibition of the activity could offer an attractive therapeutic strategy. Darapladib, a compound that inhibits Lp-PLA(2) activity, is anti-atherogenic in mice and other animals, and it decreases atherosclerotic plaque expansion in humans. However, disagreement continues to exist regarding the validity of Lp-PLA(2) as an independent marker of atherosclerosis and a scientifically justified target for intervention. Circulating Lp-PLA(2) mass and activity are associated with vascular risk, but the strength of the association is reduced after adjustment for basal concentrations of the lipoprotein carriers with which the enzyme associates. Genetic studies in humans harboring an inactivating mutation at this locus indicate that loss of Lp-PLA(2) function is a risk factor for inflammatory and vascular conditions in Japanese cohorts. Consistently, overexpression of Lp-PLA(2) has anti-inflammatory and anti-atherogenic properties in animal models. This thematic review critically discusses results from laboratory and animal studies, analyzes genetic evidence, reviews clinical work demonstrating associations between Lp-PLA(2) and vascular disease, and summarizes results from animal and human clinical trials in which administration of darapladib was tested as a strategy for the management of atherosclerosis.

Phospholipase A2 enzymes, high-dose atorvastatin, and prediction of ischemic events after acute coronary syndromes

BACKGROUND

Secretory phospholipase A2 (sPLA(2)) and lipoprotein-associated phospholipase A2 (Lp-PLA(2)) are enzyme biomarkers of increased cardiovascular risk and targets of emerging therapeutic agents. Their relationship to cardiovascular events in the setting of high-dose statin therapy compared with placebo in patients with acute coronary syndrome is not known.

METHODS AND RESULTS

sPLA(2) and Lp-PLA(2) mass and activity were measured in 2587 patients in the Myocardial Ischemia Reduction With Acute Cholesterol Lowering (MIRACL) trial at baseline and after 16 weeks of treatment with atorvastatin 80 mg/d or placebo. Baseline levels of sPLA(2) and Lp-PLA(2) mass and activity were not associated with the primary efficacy measure of the trial of death, myocardial infarction, or unstable angina. However, in the overall cohort, baseline sPLA(2) mass predicted risk of death after multivariable adjustment (hazard ratio for 2-fold increase, 1.30; 95% confidence interval, 1.09-1.56; P=0.004). This association remained significant when examined separately in the placebo group but not in the atorvastatin group. Compared with placebo, atorvastatin reduced median sPLA(2) mass (-32.1% versus -23.1%), sPLA(2) activity (-29.5% versus -19.2%), Lp-PLA(2) mass (-35.8% versus -6.2%), and Lp-PLA(2) activity (-24.3% versus 5.4%; P<0.001 for all). Atorvastatin reduced the hazard of death associated with elevated sPLA(2) mass and activity by ≈50%.

CONCLUSIONS

sPLA(2) mass independently predicts death during a 16-week period after acute coronary syndrome. High-dose atorvastatin significantly reduces sPLA(2) and Lp-PLA(2) mass and activity after acute coronary syndrome and mitigates the risk of death associated with sPLA(2) mass. Atorvastatin may exert antiinflammatory effects on phospholipases that contribute to its therapeutic benefit after acute coronary syndrome.

Type II secretory phospholipase A2 and prognosis in patients with stable coronary heart disease: mendelian randomization study

Background

Serum type II secretory phospholipase A₂ (sPLA₂-IIa) has been found to be predictive of adverse outcomes in patients with stable coronary heart disease. Compounds targeting sPLA₂-IIa are already under development. This study investigated if an association of sPLA₂-IIa with secondary cardiovascular disease (CVD) events may be of causal nature or mainly a matter of confounding by correlated cardiovascular risk markers.

Methodology/Principal Findings

Eight-year follow-up data of a prospective cohort study (KAROLA) of patients who underwent in-patient rehabilitation after an acute cardiovascular event were analysed. Associations of polymorphisms (SNP) in the sPLA₂-IIa-coding gene PLA2G2A with serum sPLA₂-IIa and secondary fatal or non-fatal CVD events were examined by multiple regression. Hazard ratios (HR) were compared with those expected if the association between sPLA₂-IIa and CVD were causal. The strongest determinants of sPLA₂-IIa (rs4744 and rs10732279) were associated with an increase of serum concentrations by 81% and 73% per variant allele. HRs (95% confidence intervals) estimating the associations of the SNPs with secondary CVD events were increased, but not statistically significant (1.16 [0.89–1.51] and 1.18 [0.91–1.52] per variant allele, respectively). However, these estimates were very similar to those expected when assuming causality (1.18 and 1.17), based on an association of natural log-transformed sPLA₂-IIa concentration with secondary events with HR = 1.33 per unit.

Conclusion

The present findings regarding genetic polymorphisms, determination of serum sPLA₂-IIa, and prognosis in CVD patients are consistent with a genuine causal relationship and thus might point to a valid drug target for prevention of secondary CVD events.

Anti-inflammatory therapeutics for the treatment of atherosclerosis

Atherosclerosis is the primary cause of heart disease and stroke and is thus the underlying pathology of the leading causes of death in the western world. Although risk can be reduced by lowering lipid levels, the equally important contribution of inflammation to the development of cardiovascular disease is not adequately addressed by existing therapies. Here, we summarize the evidence supporting a role for inflammation in the pathogenesis of atherosclerosis, discuss agents that are currently in the clinic and provide a perspective on the challenges faced in the development of drugs that target vascular inflammation.

Lipoprotein-associated phospholipase A2 testing usefulness among patients with symptomatic intracranial atherosclerotic disease

BACKGROUND AND PURPOSE

Circulating lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) has emerged as a novel biomarker for cardiovascular diseases. Our aim was to determine Lp-PLA(2) mass and activity in a selected cohort of first-ever transient ischemic attack (TIA) or ischemic stroke patients with intracranial atherosclerotic disease (ICAD) and to investigate its relationship with the presence of classical vascular risk factors, response to secondary prevention treatments and risk of recurrent vascular events.

METHODS

Lp-PLA(2) mass and activity were measured 3 months after TIA or stroke by means of the PLAC test and CAM-assay (diaDexus, Inc.) respectively in 75 patients. Classic vascular risk factors, preventive treatments and clinical characteristics at the time of the index event were recorded. Follow-up transcranial Doppler ultrasonography (TCD) was performed and the presence of a new vascular event was assessed every 6 months.

RESULTS

Several preventive treatments (statins and clopidogrel) were significantly associated with lower Lp-PLA(2) mass and activity. During follow-up (median time 23 months), eighteen patients (24%) suffered a new vascular event. Baseline factors associated with new vascular events were: history of coronary artery disease, number of intracranial stenoses detected by TCD and also Lp-PLA(2) activity, which was the only independent predictor for new vascular events (hazard ratio 2.89; 95% CI 1.029 to 8.096; p=0.044) after multivariate analysis (Cox regression).

CONCLUSIONS

Lp-PLA(2) activity might be a useful tool to identify intracranial large-artery occlusive disease patients at higher risk of suffering new vascular events.

After FRANCIS: next steps in the clinical evaluation of varespladib methyl

Secretory phospholipase A2 (sPLA2) represents a family of isoenzymes that participate in lipoprotein and inflammatory pathways, mediate atherosclerosis and enhance myocardial ischemic injury. The Fewer Recurrent Acute Coronary Events with Near-term Cardiovascular Inflammatory Suppression (FRANCIS) trial (NCT00743925) was a Phase II trial designed to examine the effects of varespladib methyl, a small-molecule inhibitor of sPLA2, on plasma biomarkers in patients with acute coronary syndrome (ACS) who were treated with atorvastatin 80 mg and standard-of-care daily. Varespladib methyl significantly reduced low-density lipoprotein cholesterol and inflammatory biomarkers in ACS subjects treated with standard-of-care and atorvastatin 80 mg daily. There was a nonsignificant reduction in major adverse cardiovascular events at study completion; however, positive trends remained for unstable angina and myocardial infarction. In order to achieve the widespread use of varespladib methyl in ACS patients, completion of a prospective, randomized placebo-controlled trial in ACS patients and stable coronary artery disease patients with increased sPLA2 activity will be required.

Recent progress in phospholipase A₂ research: from cells to animals to humans

Mammalian genomes encode genes for more than 30 phospholipase A₂s (PLA₂s) or related enzymes, which are subdivided into several classes including low-molecular-weight secreted PLA₂s (sPLA₂s), Ca²+-dependent cytosolic PLA₂s (cPLA₂s), Ca²+-independent PLA₂s (iPLA₂s), platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA₂s, and a recently identified adipose-specific PLA. Of these, the intracellular cPLA₂ and iPLA₂ families and the extracellular sPLA₂ family are recognized as the "big three". From a general viewpoint, cPLA₂α (the prototypic cPLA₂ plays a major role in the initiation of arachidonic acid metabolism, the iPLA₂ family contributes to membrane homeostasis and energy metabolism, and the sPLA₂ family affects various biological events by modulating the extracellular phospholipid milieus. The cPLA₂ family evolved along with eicosanoid receptors when vertebrates first appeared, whereas the diverse branching of the iPLA₂ and sPLA₂ families during earlier eukaryote development suggests that they play fundamental roles in life-related processes. During the past decade, data concerning the unexplored roles of various PLA₂ enzymes in pathophysiology have emerged on the basis of studies using knockout and transgenic mice, the use of specific inhibitors, and information obtained from analysis of human diseases caused by mutations in PLA₂ genes. This review focuses on current understanding of the emerging biological functions of PLA₂s and related enzymes.

Inhibition of secreted phospholipases A₂ by 2-oxoamides based on α-amino acids: Synthesis, in vitro evaluation and molecular docking calculations

Group IIA secreted phospholipase A₂ (GIIA sPLA₂) is a member of the mammalian sPLA₂ enzyme family and is associated with various inflammatory conditions. In this study, the synthesis of 2-oxoamides based on α-amino acids and the in vitro evaluation against three secreted sPLA₂s (GIIA, GV and GX) are described. The long chain 2-oxoamide GK126 based on the amino acid (S)-leucine displayed inhibition of human and mouse GIIA sPLA₂s (IC₅₀ 300nM and 180nM, respectively). It also inhibited human GV sPLA₂ with similar potency, while it did not inhibit human GX sPLA₂. The elucidation of the stereoelectronic characteristics that affect the in vitro activity of these compounds was achieved by using a combination of simulated annealing to sample low-energy conformations before the docking procedure, and molecular docking calculations.

Phospholipase A2 inhibition and atherosclerotic vascular disease: prospects for targeting secretory and lipoprotein-associated phospholipase A2 enzymes

PURPOSE OF REVIEW

Selective inhibitors of secretory phospholipase A2 and lipoprotein-associated phospholipase A2 are potential candidates for reducing recurrent cardiovascular events in patients with established coronary heart disease (CHD). With the active enrollment of CHD patients into phase III clinical trials with both classes of inhibitors, this article reviews the available experimental animal and human trial evidence that provides the rationale for the development of the phospholipase A2 inhibitors varespladib methyl and darapladib as preventive therapy.

RECENT FINDINGS

Recently completed experimental animal studies, human biomarker data, and vascular imaging studies provide support for proceeding with clinical outcome trials secretory phospholipase A2 and lipoprotein-associated phospholipase A2 inhibition.

SUMMARY

Both secretory phospholipase A2 and lipoprotein-associated phospholipase A2 inhibitors hold promise for the reduction of recurrent cardiovascular events in patients treated with current standards of care. The completion of the ongoing clinical event trials has the potential to provide a new dimension to secondary preventive therapy.

Randomized trial of an inhibitor of secretory phospholipase A2 on atherogenic lipoprotein subclasses in statin-treated patients with coronary heart disease

AIMS

To investigate the effects of secretory phospholipase A2 (sPLA(2)) inhibition on plasma lipoproteins. Secretory phospholipase A2 isoenzymes promote atherosclerosis by mechanisms that include lipoprotein modification, retention, and oxidation.

METHODS AND RESULTS

Phospholipase Levels And Serological Markers of Atherosclerosis II (PLASMA II) is a Phase II, randomized, double-blind, placebo-controlled parallel-arm study of two once-daily doses of the novel sPLA(2) inhibitor, 1-H-indole-3-glyoxamide or varespladib methyl (Anthera Pharmaceuticals, Hayward, CA, USA). One hundred and thirty-five stable coronary heart disease patients were treated with either varespladib methyl 250 mg once daily, varespladib methyl 500 mg once daily, or placebo for 8 weeks. Varespladib methyl treatment resulted in statistically significant dose-dependent reductions that were different from placebo in sPLA(2) concentration, low-density lipoprotein (LDL) cholesterol, and non-high-density lipoprotein (HDL) cholesterol. When compared with placebo, varespladib methyl 500 mg once daily reduced LDL cholesterol by 15% (P < 0.001), non-HDL cholesterol by 15% (P < 0.001), total very LDL (VLDL) particle concentration by 14% (P = 0.022), and small VLDL particle concentration by 24% (P = 0.030). Relative to baseline, varespladib methyl 500 mg once daily reduced total LDL particle concentration (7%, P = 0.002) and small LDL particle concentration (11%, P = 0.014).

CONCLUSION

Reductions in atherogenic lipoproteins suggest that varespladib methyl 500 mg once daily may be an effective anti-atherosclerotic agent. Trial registered at ClinicalTrials.gov, identifier: NCT00525954.

Lysophosphatidylcholine is generated by spontaneous deacylation of oxidized phospholipids

Elevated levels of lysophosphatidylcholine (lysoPC), present in oxidatively damaged low-density lipoprotein (oxLDL), are implicated in cardiovascular complications. LysoPC is generated by free radical-catalyzed oxidation of polyunsaturated PCs to oxidatively truncated phosphophatidylcholines (oxPCs). It is known that oxPCs are especially susceptible to hydrolysis by platelet-activating factor acetylhydrolase, a phospholipase (PL) A(2) that exists in plasma largely in association with LDL. Drugs that aim to prevent the generation of lysoPC by inhibiting this PLA(2)-catalyzed hydrolysis are in advanced clinical trials. We now report that spontaneous deacylation oxPCs, such as 1-palmityl-2-(4-hydroxy-7-oxo-5-heptenoyl)-sn-glycero-3-phosphocholine, occurs readily under physiological conditions of temperature and pH (t(1/2) = 30 min at 37 °C and pH 7.4). We also show that this reaction proceeds through an intramolecular transesterification mechanism. Because antiphospholipase drugs cannot block this nonenzymatic pathway to lysoPC, additional therapeutic measures may be needed to avoid the pathological consequences of the newly discovered biomolecular chemistry of oxPCs.

Effects of varespladib methyl on biomarkers and major cardiovascular events in acute coronary syndrome patients

OBJECTIVES

The purpose of this study was to investigate the effects of varespladib on cardiovascular biomarkers in acute coronary syndrome patients.

BACKGROUND

Secretory phospholipase A(2) (sPLA(2)) represents a family of proatherogenic enzymes that hydrolyze lipoprotein phospholipids, increasing their affinity for intimal proteoglycans; contribute to cholesterol loading of macrophages by nonscavenger receptor mediated pathways; and activate inflammatory pathways. In prospective studies, high sPLA(2)-IIA levels predicted major adverse cardiovascular events in acute coronary syndrome (ACS) and stable coronary heart disease patients.

METHODS

This randomized, double-blind, prospective controlled clinical trial (phase 2B) was designed to investigate the effects of sPLA(2) inhibition with varespladib 500 mg daily versus placebo as adjunctive therapy to atorvastatin 80 mg daily on biomarkers (low-density lipoprotein cholesterol [LDL-C], high-sensitivity C-reactive protein [hsCRP], and sPLA(2)-IIA levels), major adverse cardiovascular events (unstable angina, myocardial infarction, death), and safety. In all, 625 ACS subjects were randomized within 96 h of the index event and treated for a minimum of 6 months.

RESULTS

After 8 weeks (primary efficacy end point), varespladib/atorvastatin reduced mean LDL-C levels from baseline by 49.6% compared with 43.4% with placebo/atorvastatin (p = 0.002). Respective 8-week median reductions in sPLA(2)-IIA levels were 82.4% and 15.6% (p < 0.0001), and hsCRP levels were lowered by 75.0% and 71.0% (p = 0.097). At 24 weeks, respective reductions with varespladib and placebo were as follows: LDL-C 43.5% versus 37.6% (p < 0.05), hsCRP 79.8% versus 77.0% (p = 0.02), and sPLA(2)-IIA 78.5% versus 6.4% (p < 0.0001). Major adverse cardiovascular events were not different from placebo 6 months post-randomization (7.3% varespladib vs. 7.7% placebo). No treatment differences in elevated liver function studies on >1 occasion were observed.

CONCLUSIONS

Varespladib therapy effectively reduced LDL-C and inflammatory biomarkers in ACS patients treated with conventional therapy including atorvastatin 80 mg daily. There were no treatment differences in clinical cardiovascular events. (FRANCIS [Fewer Recurrent Acute Coronary Events With Near-Term Cardiovascular Inflammation Suppression]-ACS Trial: A Study of the Safety and Efficacy of A 002 in Subjects With Acute Coronary Syndromes; NCT00743925).

New technologies personalize diagnostics and therapeutics

Atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality in industrialized societies [10]. Efforts to reduce cardiovascular events in "high-risk" individuals or recurrent events in patients with established atherosclerotic cardiovascular disease emphasize broad-based implementation of guideline-directed therapeutic lifestyle changes and pharmacotherapy. Despite successful implementation of these evidence-based strategies, many individuals are not properly identified before their first event or they continue to experience cardiovascular events despite "optimal" levels of biomarkers. The application of genomics, proteomics, and metabolomics provides opportunities to improve our understanding of the complex process of atherosclerosis and enables personalized diagnostic and therapeutic approaches.

High plasma phospholipase A2 activity, inflammation markers, and LDL alterations in obesity with or without type 2 diabetes

Plasma phospholipases A(2) (PLA(2)) hydrolyze phospholipids of circulating lipoproteins or deposited in arteries producing bioactive lipids believed to contribute to the atherosclerotic inflammatory response. PLA(2)(s) are elevated in obesity and type 2 diabetes (T2D) but it is not clear which of these conditions is the cause since they frequently coexist. This study attempts to evaluate if high plasma PLA(2)(s) activities and markers of their effects in lipoproteins are associated with obesity or T2D diabetes, or with both. Total PLA(2) and Ca(2+)-dependent and -independent activities, lipids, lipoproteins, apoAI, and apoB apolipoproteins and affinity of apoB-lipoproteins for arterial proteoglycans were measured, as well as Inflammation markers. These parameters were evaluated in plasma samples of four groups: (i) apparently healthy controls with normal BMI (nBMI), (ii) obese subjects with no T2D, (iii) patients with T2D but with nBMI, and (iv) obese patients with T2D. PLA(2) activities were measured in the presence and absence of Ca(2+) and in the presence of specific inhibitors. Obese subjects, with or without T2D, had high activities of total PLA(2) and of Ca(2+)-dependent and Ca(2+)-independent enzymes. The activities were correlated with inflammation markers in obese subjects with and without diabetes and with alterations of low-density lipoproteins (LDLs) that increased their affinity for arterial proteoglycans. Ca(2+)-dependent secretory (sPLA(2)) enzymes were the main responsible of the obesity-associated high activity. We speculate that augmented PLA(2)(s) activity that increases affinity of circulating LDL for arterial intima proteoglycans could be another atherogenic component of obesity.

Group X secretory phospholipase A(2) augments angiotensin II-induced inflammatory responses and abdominal aortic aneurysm formation in apoE-deficient mice

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a complex vascular disease characterized by matrix degradation and inflammation and is a major cause of mortality in older men. Specific interventions that prevent AAA progression remain to be identified. In this study, we tested the hypothesis that Group X secretory phospholipase A(2) (GX sPLA(2)), an enzyme implicated in inflammatory processes, mediates AAA.

METHODS AND RESULTS

GX sPLA(2) was detected by immunostaining in human aneurysmal tissue and in angiotensin II (Ang II)-induced AAAs in apolipoprotein E-deficient (apoE(-/-)) mice. GX sPLA(2) mRNA was increased significantly (11-fold) in abdominal aortas of apoE(-/-) mice in response to Ang II infusion. To define the role of GX sPLA(2) in experimental AAAs, apoE(-/-) and apoE(-/-) x GX sPLA(2)(-/-) (GX DKO) mice were infused with Ang II for either 10 (n=7) or 28 (n=24-26) days. Deficiency of GX sPLA(2) significantly reduced the incidence and severity of AAAs, as assessed by ultrasound measurements in vivo of aortic lumens and by computer-assisted morphometric analyses ex vivo of external diameter. Results from gene expression profiling indicated that the expression of specific matrix metalloproteinases and inflammatory mediators was blunted in aortas from GX DKO mice compared to apoE(-/-) mice after 10-day Ang II infusion. Ang II induction of cyclooxygenase-2, interleukin-6, matrix metalloproteinase (MMP)-2, MMP-13 and MMP-14 was reduced significantly in GX DKO mice compared to apoE(-/-) mice.

CONCLUSION

GX sPLA(2) promotes Ang II-induced pathological responses leading to AAA formation.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): Progress in Small Molecule Drug Development

Ever since the discovery of aspirin, small molecule therapeutics have been widely prescribed to treat inflammation and pain. Aspirin and several small molecule NSAIDs are known to inhibit the enzymes cyclooxygenase-1 (COX-1) and -2 (COX-2). Despite the success of NSAIDs to treat inflammatory disorders, the development of a clinically useful small molecule NSAIDs with decreased side effect profiles is an ongoing effort. The recent discovery and development of selective COX-2 inhibitors was a step toward this direction. Emerging trends are represented by the progress in the development of hybrid agents such as nitric oxide donor-NSAIDs (NO-NSAIDs) and dual COX/lipoxygenase (LOX) inhibitors. This review focuses on the recent advances in the rational design of small molecule NSAIDs in therapy.

Lipid levels in sickle-cell disease associated with haemolytic severity, vascular dysfunction and pulmonary hypertension

Pulmonary hypertension (PH) in sickle cell disease (SCD) is an emerging and important clinical problem. In a single-institution adult cohort of 365 patients, we investigated lipid and lipoprotein levels and their relationship to markers of intravascular haemolysis, vascular dysfunction and PH. In agreement with prior studies, we confirm significantly decreased plasma levels of total cholesterol, high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) in SCD versus ethnically-matched healthy controls. Several cholesterol parameters correlated significantly with markers of anaemia, but not endothelial activation or PH. More importantly, serum triglyceride levels were significantly elevated in SCD compared to controls. Elevated triglyceride levels correlated significantly with markers of haemolysis (lactate dehydrogenase and arginase; both P < 0.0005), endothelial activation (soluble E-selectin, P < 0.0001; soluble P-selectin, P = 0.02; soluble vascular cell adhesion molecule-1, P = 0.01), inflammation (leucocyte count, P = 0.0004; erythrocyte sedimentation rate, P = 0.02) and PH (amino-terminal brain natriuretic peptide, P = 0.002; prevalence of elevated tricuspid regurgitant velocity (TRV), P < 0.001). In a multivariate analysis, triglyceride levels correlated independently with elevated TRV (P = 0.002). Finally, forearm blood flow studies in adult patients with SCD demonstrated a significant association between increased triglyceride/HDL-C ratio and endothelial dysfunction (P < 0.05). These results characterize elevated plasma triglyceride levels as a potential risk factor for PH in SCD.

Lp-PLA2 Inhibition-The Atherosclerosis Panacea?

Based on the complex pathophysiology of atherosclerosis, a large number of biomarkers that relate to lipids, inflammation, immunity, thrombosis and hemostasis, have been investigated experimentally, in epidemiologic studies and in clinical trials. Interest focuses on their potential role to aid in risk stratification, as possible surrogate markers of atherosclerosis, and potential targets for therapy. More recently, one lipid associated biomarker, lipoprotein-associated phospholipase A2 (Lp-PLA₂), has gained considerable interest. In addition to a plausible pathophysiological role by generating pro-inflammatory and pro-atherogenic compounds from oxidized LDL in the vessel wall, there is a large, fairly consistent epidemiological database indicating that increased levels of Lp-PLA₂ mass or activity are associated with increased risk for cardiovascular outcomes; such data further suggest that it might improve risk stratification. In addition, clinical studies indicate that increased Lp-PLA₂ levels are associated with endothelial dysfunction. Moreover, it may also serve as an interesting therapeutic target, since a specific inhibitor of the enzyme is available with promising animal data and initial positive data in humans. Recent experimental data from a hyperlipidemic diabetic pig model strongly suggest that increased Lp-PLA₂ in the vessel wall is associated with a more vulnerable plaque phenotype which can be modulated by inhibiting Lp-PLA₂ activity. A biomarker study in more than 1,000 patients with CHD over three months has demonstrated a positive effect on various inflammatory molecules. In addition, an imaging study using IVUS based modalities (greyscale, virtual histology, and palpography) together with a panel of biomarkers (IBIS-2) has been done in more than 300 patients with CHD treated over 12 months and results indicate that the progression of the necrotic core of the plaque can be retarded. Inhibition of the pro-atherogenic and pro-inflammatory effects of Lp-PLA₂ may therefore contribute to decrease the residual risk in high risk patients already on polypharmacotherapy. This hypothesis is now being tested in two large phase 3 clinical trials. Thus, Lp-PLA₂ indeed may represent a biomarker and a promising target for intervention.

Emerging roles of secreted phospholipase A2 enzymes: Lessons from transgenic and knockout mice

Among the emerging phospholipase A(2) (PLA(2)) superfamily, the secreted PLA(2) (sPLA(2)) family consists of low-molecular-mass, Ca(2+)-requiring extracellular enzymes with a His-Asp catalytic dyad. To date, more than 10 sPLA(2) enzymes have been identified in mammals. Individual sPLA(2)s exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Despite numerous enzymatic and cell biological studies on this enzyme family in the past two decades, their precise in vivo functions still remain largely obscure. Recent studies using transgenic and knockout mice for several sPLA(2) enzymes, in combination with lipidomics approaches, have opened new insights into their distinct contributions to various biological events such as food digestion, host defense, inflammation, asthma and atherosclerosis. In this article, we overview the latest understanding of the pathophysiological functions of individual sPLA(2) isoforms fueled by studies employing transgenic and knockout mice for several sPLA(2)s.

Darapladib

IMPORTANCE OF THE FIELD

Atherosclerosis is an inflammatory-immune mediated disease process. Plaque rupture is responsible for the clinical events of ischemic death, myocardial infarction, acute coronary syndromes and ischemic strokes. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) seems to play a major role in the development of such high-risk lesions, in both the coronary and carotid arteries. Darapladib is a selective inhibitor of Lp-PLA(2).

AREAS COVERED IN THIS REVIEW

An overview of darapladib by reviewing the studies (1990 - 2009) that have provided the rationale for the development of darapladib; and a discussion of its potential merit as a new therapeutic drug to target high-risk atherosclerosis.

WHAT THE READER WILL GAIN

The reader should gain an understanding of the importance of inflammation during atherogenesis as well as of the biology of Lp-PLA(2) and its proatherogenic role. Additional insights will be gained into the role of selective inhibitors of Lp-PLA(2) as new therapeutic agents.

TAKE HOME MESSAGE

Darapladib is a selective inhibitor of Lp-PLA(2) and represents a new class of therapeutic agents that target inflammation to treat high-risk atherosclerosis.