A mutation in plasma platelet-activating factor acetylhydrolase (Val279-->Phe) is a genetic risk factor for stroke

Intracerebral Hemorrhage Genetics

Intracerebral hemorrhage (ICH) is a devastating type of stroke, frequently resulting in unfavorable functional outcomes. Up to 15% of stroke patients experience ICH and approximately half of those have a lethal outcome within a year. Considering the huge burden of ICH, timely prevention and optimized treatment strategies are particularly relevant. Nevertheless, ICH management options are quite limited, despite thorough research. More and more trials highlight the importance of the genetic component in the pathogenesis of ICH. Apart from distinct monogenic disorders of familial character, mostly occurring in younger subjects, there are numerous polygenic risk factors, such as hypertension, neurovascular inflammation, disorders of lipid metabolism and coagulation cascade, and small vessel disease. In this paper we describe gene-related ICH types and underlying mechanisms. We also briefly discuss the emerging treatment options and possible clinical relevance of the genetic findings in ICH management. Although existing data seems of more theoretical and scientific value so far, a growing body of evidence, combined with rapidly evolving experimental research, will probably serve clinicians in the future.

Human Secretary Phospholipase A2 Mutations and Their Clinical Implications

Phospholipases A2 (PLA₂s) belong to a superfamily of enzymes responsible for hydrolysis of the sn-2 fatty acids of membrane phospholipids to release arachidonic acid. PLA₂s are the rate limiting enzyme for the downstream synthesis of prostaglandins and leukotrienes that are the main mediators of inflammation. The extracellular forms of this enzyme are also called the secretary phospholipase A2 (sPLA₂) and are distributed extensively in most of the tissues in the human body. Their integral role in inflammatory pathways has been the primary reason for the extensive research on this molecule. The catalytic mechanism of sPLA₂ is initiated by a histidine/aspartic acid/calcium complex within the active site. Though they are known to have certain housekeeping functions, certain mutations of sPLA₂ are known to be implicated in causation of certain pathologies leading to diseases such as atherosclerosis, cardiovascular diseases, benign fleck retina, neurodegeneration, and asthma. We present an overview of human sPLA₂ and a comprehensive compilation of the mutations that result in various disease phenotypes. The study not only helps to have a holistic understanding of human sPLA₂ mutations and their clinical implications, but is also a useful platform to initiate research pertaining to structure–function relationship of the mutations to develop effective therapies for management of these diseases.

Phospholipase A2 is an Inflammatory Predictor in Cardiovascular Diseases: Is there any Spacious Room to Prove the Causation?

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an enzyme family of phospholipase A2 produced by the inflammatory cell in atherosclerotic plaque. It is transported in the circulation, attached mainly to low-density lipoprotein-cholesterol (LDL-C). It hydrolyzes glycerophospholipids particularly fatty acids at the sn-2 position and produces numerous bioactive lipids; and leads to endothelial dysfunction, atherosclerotic plaque inflammation, and development of the necrotic core in plaques. There are two kinds of phospholipase A2, namely: secretory phospholipase A2 (sPLA2) and Lp- PLA2. They are deemed as evolving predictors of cardiovascular disease (CVD) risk in hospitaland population-based studies, including healthy subjects, acute coronary syndromes (ACS) and patients with CVD. Unfortunately, Lp-PLA2 inhibitor (darapladib) and s-PLA2 inhibitor (varespladib methyl) failed to prove to lower the risk of composite CVD mortality, myocardial infarction and stroke in those with stable CVD and ACS. Herein, we describe the explanation based on the existing data why there is still a discrepancy among them. So, it highlights the opinion that phospholipase A2 is merely the inflammatory biomarkers of CVD and playing an important role in atherosclerosis. Further, there is more spacious room to prove the causation.

Platelet-activating factor acetylhydrolases: An overview and update

Platelet-activating factor acetylhydrolases (PAF-AHs) are unique members of the phospholipase A₂ family that can hydrolyze the acetyl group of PAF, a signaling phospholipid that has roles in diverse (patho)physiological processes. Three types of PAF-AH have been identified in mammals, one plasma type and two intracellular types [PAF-AH (I) and PAF-AH (II)]. Plasma PAF-AH and PAF-AH (II) are monomeric enzymes that are structurally similar, while PAF-AH (I) is a multimeric enzyme with no homology to other PAF-AHs. PAF-AH (I) shows a strong preference for an acetyl group, whereas plasma PAF-AH and PAF-AH (II) also hydrolyze phospholipids with oxidatively modified fatty acids. Plasma PAF-AH has been implicated in several diseases including cardiovascular disease. PAF-AH (I) is required for spermatogenesis and is increasingly recognized as an oncogenic factor. PAF-AH (II) was recently shown to act as a bioactive lipid-producing enzyme in mast cells and thus could be a drug target for allergic diseases. This article is part of a Special Issue entitled Novel functions of phospholipase A2 Guest Editors: Makoto Murakami and Gerard Lambeau.

Association of Lp-PLA2 G994T gene polymorphism with risk of ischemic stroke in Chinese population

The association between lipoprotein-associated phospholipase A2 (Lp-PLA2) G994T gene polymorphism and the risk of ischemic stroke is unclear. The aim of this study is to investigate the influence of Lp-PLA2 G994T genetic variant on the pathogenesis of ischemic stroke in Chinese population. A total of 348 patients with a clinical diagnosis of ischemic stroke and 260 gender-matched control subjects under physical examination were recruited from hospitals and genotyped for G994T gene polymorphism. The results showed that there was a significant difference in the genotype distribution between the two groups and people with GT or TT genotype were associated with the higher risk of ischemic stroke even after adjusting the effects of potential confounding factors. In addition, both ischemic stroke patients and control subjects carrying T allele showed relatively lower Lp-PLA2 activity and higher oxLDL level. Therefore, Lp-PLA2 G994T gene polymorphism may be an independent risk factor of ischemic stroke in Chinese population.

Investigation of a Bicyclo[1.1.1]pentane as a Phenyl Replacement within an LpPLA2 Inhibitor

We describe the incorporation of a bicyclo[1.1.1]pentane moiety within two known LpPLA₂ inhibitors to act as bioisosteric phenyl replacements. An efficient synthesis to the target compounds was enabled with a dichlorocarbene insertion into a bicyclo[1.1.0]butane system being the key transformation. Potency, physicochemical, and X-ray crystallographic data were obtained to compare the known inhibitors to their bioisosteric counterparts, which showed the isostere was well tolerated and positively impacted on the physicochemical profile.

A phenome-wide association study of a lipoprotein-associated phospholipase A2 loss-of-function variant in 90 000 Chinese adults

Background: Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) has been implicated in development of atherosclerosis; however, recent randomized trials of Lp-PLA₂ inhibition reported no beneficial effects on vascular diseases. In East Asians, a loss-of-function variant in the PLA2G7 gene can be used to assess the effects of genetically determined lower Lp-PLA₂.

Methods:PLA2G7 V279F (rs76863441) was genotyped in 91 428 individuals randomly selected from the China Kadoorie Biobank of 0.5 M participants recruited in 2004–08 from 10 regions of China, with 7 years’ follow-up. Linear regression was used to assess effects of V279F on baseline traits. Logistic regression was conducted for a range of vascular and non-vascular diseases, including 41 ICD-10 coded disease categories.

Results:PLA2G7 V279F frequency was 5% overall (range 3–7% by region), and 9691 (11%) participants had at least one loss-of-function variant. V279F was not associated with baseline blood pressure, adiposity, blood glucose or lung function. V279F was not associated with major vascular events [7141 events; odds ratio (OR) = 0.98 per F variant, 95% confidence interval (CI) 0.90-1.06] or other vascular outcomes, including major coronary events (922 events; 0.96, 0.79-1.18) and stroke (5967 events; 1.00, 0.92-1.09). Individuals with V279F had lower risks of diabetes (7031 events; 0.91, 0.84-0.98) and asthma (182 events; 0.53, 0.28-0.98), but there was no association after adjustment for multiple testing.

Conclusions: Lifelong lower Lp-PLA₂ activity was not associated with major risks of vascular or non-vascular diseases in Chinese adults. Using functional genetic variants in large-scale prospective studies with linkage to a range of health outcomes is a valuable approach to inform drug development and repositioning.

Associations of platelet-activating factor acetylhydrolase gene polymorphisms with risk of ischemic stroke

Platelet-activating factor acetylhydrolase (PAF-AH) has an important function in the pathogenesis of ischemic stroke. The aim of the present study was to investigate the correlation between the variation of polymorphisms (R92H and V279F) in PAF-AH and ischemic stroke. A total of 375 patients with ischemic stroke and 370 healthy controls were recruited into the study. Polymorphisms of V279F and R92H in PAF-AH were detected by polymerase chain reaction and DNA direct sequencing method. No significant association was observed between V279F and ischemic stroke. However, the RH+HH genotype, RH genotype and H allele of R92H were significantly associated with an increased risk of ischemic stroke (P=0.02, P=0.03 and P=0.02, respectively), In addition, these correlations remained following adjustment for confounding risk factors of stroke. Furthermore, subgroup analysis showed that a significant association with R92H was identified in the large-artery atherosclerotic stroke subgroup. These findings indicated that variation of R92H in the PAF-AH gene may contribute to ischemic stroke susceptibility in the population studied.

Lipoprotein-associated phospholipase A2 single-nucleotide polymorphisms and cardiovascular events in patients with coronary artery disease

AIMS

We tested the hypothesis that variations in the PLA2G7 gene encoding the lipoprotein-associated phospholipase A2 (Lp-PLA2), an enzyme deemed to have proatherogenic activity, affect the Lp-PLA2 levels and predicts cardiovascular events.

METHODS

Using a prospective cohort study design, we investigated incident cardiovascular events as a function of the PLA2G7 gene for rs1805017, rs1805018, and rs1051931 single-nucleotide polymorphisms (SNPs) in 643 randomly selected white patients from the GENICA Study, who at baseline underwent coronary angiography, measurement of Lp-PLA2 mass and activity. Cardiovascular event-free survival was compared across the genotypes by Cox regression, propensity score matching, and haplotype analysis.

RESULTS

The rs1805018 SNP did not follow the Hardy-Weinberg equilibrium and was not further explored. The rs1805017 GG genotype had a lower Lp-PLA2 mass and a higher Lp-PLA2 activity, thus suggesting that this SNP is functional. Long-term follow-up (median 7.8 years) was obtained in 75% of the cohort and allowed recording of incident cardiovascular events in 25.8% of the patients. On Cox regression analysis, the common rs1805017 GG genotype predicted acute myocardial infarction (AMI) [hazard ratio 1.75, 95% confidence interval (CI) 1.03-2.99, P = 0.041]; this finding was confirmed on propensity score matching (82.6% AMI-free survival in GG vs. 94.4% in GA + AA, P = 0.003). The rs1805017 and rs1051931 G/G haplotype was also associated with AMI (52.7 vs. 42.2%, P = 0.026) and cardiovascular event incidence (49.5 vs. 41.7%, P = 0.025).

CONCLUSION

In high-risk coronary artery disease patients of European ancestry, the PLA2G7 rs1805017 GG genotype is associated with increased Lp-PLA2 plasma activity and AMI.

Naturally Occurring Missense Mutation in Plasma PAF-AH Among the Japanese Population

A single nucleotide polymorphism in the plasma PAF-AH enzyme, i.e., G994T, which causes the substitution of Val at amino acid 279 with Phe (V279F), has been found in the Japanese population. This enzyme preferentially degrades oxidatively modulated or truncated phospholipids; therefore, it has been suggested that this enzyme may prevent the accumulation of proinflammatory and proatherogenic oxidized phospholipids. This hypothesis is supported by the higher prevalence of the V279F mutation in patients with asthmatic and atherosclerotic diseases, as compared with healthy controls. This mutation is rare in the Caucasian population. The plasma PAF-AH mass and enzyme activity are distributed over a wide range in the plasma and they are positively correlated with low-density lipoprotein (LDL) cholesterol. However, several clinical studies in the Caucasian population have suggested that this enzyme has the opposite role. This enzyme plays an active role in the development and progression of atherosclerosis via proinflammatory and proatherogenic lysophosphatidylcholine and oxidized fatty acids produced through the oxidation of LDL by this enzyme. Thus, plasma PAF-AH is a unique enzyme with dual roles in human inflammatory diseases. In this chapter, on the basis of recent findings we describe the association between a naturally occurring missense mutation in plasma PAF-AH and human diseases especially including atherosclerosis and asthma.

Lipoprotein-associated phospholipase A2 regulates macrophage apoptosis via the Akt and caspase-7 pathways

AIM

Mutations in lipoprotein-associated phospholipase A2 (Lp-PLA2) are related to atherosclerosis. However, the molecular effects of Lp-PLA2 on atherosclerosis have not been fully investigated. Therefore, this study attempted to elucidate this issue.

METHODS

Monocytes were isolated from randomly selected healthy male volunteers according to each Lp-PLA2 genotype (wild-type Lp-PLA2 [Lp-PLA2 (V/V)], the heterozygous V279F mutation [LpPLA2 (V/F)] and the homozygous V279F mutation [Lp-PLA2 (F/F)]) and differentiated into macrophages. The level of apoptosis in the macrophages following incubation without serum was measured using the annexin V/propidium iodide double staining method, and the underlying mechanisms were further examined using a culture cell line.

RESULTS

The average plasma Lp-PLA2 concentration [Lp-PLA2 (V/V): 129.4 ng/mL, Lp-PLA2 (V/F): 70.7 ng/mL, Lp-PLA2 (F/F): 0.4 ng/mL] and activity [Lp-PLA2 (V/V): 164.3 nmol/min/mL, LpPLA2 (V/F): 100.9 nmol/min/mL, Lp-PLA2 (F/F): 11.6 nmol/min/mL] were significantly different between each genotype, although the basic clinical characteristics were similar. The percentage of apoptotic cells was significantly higher among the Lp-PLA2 (F/F) macrophages compared with that observed in the Lp-PLA2 (V/V) macrophages. This induction of apoptosis was independent of the actions of acetylated low-density lipoproteins. In addition, the transfection of the expression plasmid of V279F mutant Lp-PLA2 into Cos-7 cells or monocyte/macrophage-like U937 cells promoted apoptosis. The knockdown of Lp-PLA2 also increased the number of apoptotic cells. Among the cells expressing mutant Lp-PLA2, the caspase-7 activity was increased, while the activated Akt level was decreased.

CONCLUSIONS

The V279F mutation of Lp-PLA2 positively regulates the induction of apoptosis in macrophages and Cos-7 cells. An increase in the caspase-7 activity and a reduction in the activated Akt level are likely to be involved in this phenomenon.

Association of PLA2G7 gene polymorphisms with ischemic stroke in northern Chinese Han population

OBJECTIVE

Human lipoprotein-associated phospholipase A2 (Lp-PLA2), encoded by the PLA2G7 gene, plays an important role in the pathophysiology of inflammation. This study is aimed at evaluating the potential association of V279F and A379V in PLA2G7 gene with ischemic stroke where inflammatory process is involved.

DESIGN AND METHODS

A total of 386 patients with ischemic stroke and 386 healthy controls were included in the study. The single nucleotide polymorphisms, V279F and A379V, were analyzed by the polymerase chain reaction-ligation detection reaction method.

RESULTS

The frequencies of VV+AV genotype, AV genotype and V allele of A379V in the patients with ischemic stroke were significantly higher than those in the controls (P=0.02, P=0.03, P=0.02, respectively). These correlations still remained after adjusting for confounding risk factors of stroke. Furthermore, subgroup analysis showed that a significant association with A379V was found in large-artery atherosclerotic stroke subgroup. In addition, no significant association was observed between V279F and ischemic stroke.

CONCLUSION

The study indicated that the A379V variant in PLA2G7 gene might contribute to ischemic stroke susceptibility in northern Chinese Han population.

PLAC™ test for identification of individuals at increased risk for coronary heart disease

Recent advances in cardiovascular research point to a critical role of inflammatory processes in the etiology of cardiovascular disease. This has led to the discovery of novel inflammatory biomarkers, which may be useful as additional screening tools for the identification of individuals at increased risk of coronary heart disease. One such novel inflammatory biomarker is lipoprotein-associated phospholipase A(2). This review discusses the recent development of a US Food and Drug Administration-approved blood test for lipoprotein-associated phospholipase A(2) (PLAC test, diaDexus, Inc.) and its efficacy as a predictive biomarker of risk for cardiovascular disease. More specifically, the article addresses the potential target group most likely to benefit from this new screening test and provides a prospective scenario for its implementation.

The prevalence of platelet activating factor acetylhydrolase single nucleotide polymorphisms in relationship to necrotizing enterocolitis in Northwest Louisiana infants

PURPOSE

Studies documented that platelet activating factor (PAF) and the enzyme platelet activating factor acetylhydrolase (PAFAH) play a very important role in the pathogenesis of neonatal necrotizing enterocolitis (NEC). In this retrospective, case-controlled pilot study, the authors investigated the prevalence of single nucleotide polymorphisms (Ile198Thr and Ala379Val) of the PAFAH gene.

SUBJECTS AND METHODS

We screened 570 blood samples from both Caucasian and African-American preterm infants in the Northwest Louisiana population for the above mentioned PAFAH gene polymorphisms. Out of 570 infants, 36 had stage I or II NEC based on diagnostic coding, the International Classification of Diseases, 9th revision, Clinical Modification, 2009 (ICD-9-CM). The remaining infants without an ICD-9-CM diagnosis of NEC were recruited as control population. The DNA was isolated and restriction fragment length polymorphism microplate polymerase chain reaction assay was performed.

RESULTS

Variants of the PAFAH gene polymorphism (Ile198Thr and Ala379Val) frequencies were not significantly different between the infants with NEC and the control group (P value of 0.26 by either multiple logistic regression analysis or the Cochran-Mantel-Haenszel test).

CONCLUSIONS

This is the first study of its kind in exploring the relationship between NEC and single nucleotide polymorphisms in the coding genes of the enzyme PAFAH. Our preliminary data demonstrated that adjusted for the effect of race, PAFAH polymorphisms (Ile198Thr and Ala379Val) have no significant effect on NEC.

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.

Lipoprotein-associated phospholipase A2 gene V279F polymorphisms and coronary heart disease: a meta-analysis

Lipoprotein-associated phospholipase A2 (LP-PLA2) may play an important role in the pathophysiology of coronary heart disease (CHD). The polymorphism of LP-PLA2 gene caused LP-PLA2 enzyme activity depressing or lost. But there is not a definite conclusion for the association of between the LP-PLA2 gene polymorphism and CHD risk. To assess the relationship between LP-PLA2 gene V279F polymorphism and CHD, a comprehensive Meta-analysis was performed. All the case-control studies evaluating the association of between the LP-PLA2 gene V279F polymorphism and CHD risk were identified. Seven case-control studies involving 3,614 patients with CHD and 4,334 controls were included. The crude odds ratios (ORs) of meta-analysis under the different gene model were not significant. But in the stratified analysis by study size, ethnicity, cases definition, and source of controls under the additive model, the association was evident in ethnicity for Japanese group (OR=1.38, 95%CI=1.22-1.56), cases definition for MI (OR=1.22, 95%CI=1.01-1.49), source of controls for the based-hospital (OR=1.42, 95%CI=1.24-1.59). These data suggested that the V279F polymorphism in LP-PLA2 gene may contribute to CHD development. But there is necessary that more well-designed large studies are required for the validation of this association.

Association of Lp-PLA(2) activity with allele-specific Lp(a) levels in a bi-ethnic population

OBJECTIVES

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) and lipoprotein(a) [Lp(a)] have been implicated as cardiovascular disease risk factors, and are differentially regulated across ethnicity. We investigated the association between Lp-PLA(2) activity and allele-specific apolipoprotein(a) [apo(a)] levels in a bi-ethnic population.

METHODS

Lp-PLA(2) activity, Lp(a) and allele-specific apo(a) levels were determined in 224 African Americans and 336 Caucasians.

RESULTS

Lp-PLA(2) activity level was higher among Caucasians compared to African Americans (173 + or - 41 nmol/min/ml vs. 141 + or - 39 nmol/min/ml, P<0.001), and positively associated with Lp(a), total and LDL cholesterol, triglyceride, apolipoprotein B-100, and negatively with HDL cholesterol levels in both ethnic groups. The association between Lp-PLA(2) activity and Lp(a) was stronger among African Americans compared to Caucasians (R=0.238, beta(1)=3.48, vs. R=0.111, beta(1)=1.93, respectively). The Lp-PLA(2) activity level was significantly associated with allele-specific apo(a) levels for smaller (<26 K4 repeats) apo(a) sizes in both ethnic groups (P=0.015 for African Americans, P=0.038 for Caucasians). In contrast, for larger (>26 K4 repeats) apo(a) sizes, high Lp-PLA(2) activity levels were associated with higher allele-specific apo(a) levels in African Americans (P=0.009), but not in Caucasians.

CONCLUSION

The association between Lp-PLA(2) activity and allele-specific apo(a) levels differs across African American-Caucasian ethnicity.

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.

Identification of the G994T polymorphism in exon 9 of plasma platelet-activating factor acetylhydrolase gene as a risk factor for polycystic ovary syndrome

BACKGROUND

Low-grade chronic inflammation and greater risks of cardiovascular diseases are often present in patients with polycystic ovary syndrome (PCOS). Platelet-activating factor (PAF) acetylhydrolase (PAF-AH) hydrolyzes and inactivates PAF and PAF-like oxidized phospholipids that are potent lipid mediators involved in inflammation and atherosclerosis. Deficiency of this enzyme is caused by a missense mutation (G994 --> T) in exon 9 of the plasma PAF-AH gene. The aim of the study was to investigate a possible association of this polymorphism with the risk of PCOS and to evaluate the effects of the genotype on the activity and distribution of PAFAH in Chinese patients.

METHODS

A total of 661 subjects (346 patients with PCOS and 315 healthy control women) from a population of Chinese Han nationality in Chengdu area were included in this study. PAFAH G994T genotype was studied using PCR and restriction fragment length polymorphism analysis. Total plasma PAF-AH, high-density lipoprotein (HDL)-associated PAF-AH (H-PAF-AH) and low-density lipoprotein (LDL)-associated PAF-AH (L-PAF-AH) activities were measured by the trichloroacetic acid precipitation procedure using [(3)H-acetyl] PAF and PAF C-16 as a substrate.

RESULTS

The prevalence of the mutant genotype (GT + TT) was significantly more frequent in patients with PCOS than in control subjects (12.7 versus 6.0%, P = 0.003). Genotype (GT + TT) remained a significant predictor for PCOS (P = 0.020) in prognostic models including age, body mass index, insulin resistance index, triglyceride, HDL and LDL as covariates. There was a significant difference in plasma PAF-AH, L-PAF-AH and H-PAF-AH activities between GG and GT genotypes in both the patient and control groups. The ratio of L-PAF-AH to H-PAF-AH activities was significantly higher after adjustment for multiple variables in patients with GT genotype compared with patients with GG genotype (P = 0.003). There were no significant differences in clinical, biochemical and metabolic parameters according to PAFAH G994T genotyping in patients with PCOS and control women.

CONCLUSIONS

The G994T polymorphism in PAFAH gene may be one of the genetic determinants for PCOS in Chinese Han women.

Effects of V279F in the Lp-PLA(2) gene on markers of oxidative stress and inflammation in Koreans

BACKGROUND

A single nucleotide polymorphism (SNP), V279F, in the lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) gene is known to influence enzyme activity. It is unclear whether Lp-PLA(2) exerts pro- or antiatherogenic effects in humans. We investigated the interplay between V279F, Lp-PLA(2) activity, oxidative stress and inflammation.

METHODS

We genotyped 2914 healthy Koreans (43-79years) for the Lp-PLA(2) V279F and measured anthropometric parameters, lipid profile, fatty acid composition, lipid peroxides, inflammatory markers and Lp-PLA(2) levels.

RESULTS

Lp-PLA(2) activity was 24% lower in V/F subjects (n=641) than in those with the V/V genotype (n=2227). Enzyme activity was undetectable in F/F subjects. Lp-PLA(2) activity was positively correlated with LDL-cholesterol (r=0.134, P<0.001), ox-LDL (r=0.064, P<0.01), 8-epi-PGF(2alpha) (r=0.198, P<0.001), free fatty acid (r=0.082, P<0.001), and fibrinogen (r=0.112, P<0.01) levels. Additionally, ox-LDL, 8-epi-PGF(2alpha), free fatty acid, and fibrinogen levels were positively correlated with hs-CRP. V279F was associated with LDL-cholesterol and arachidonic acid (AA) in serum phospholipid. F/F subjects had lower LDL-cholesterol than V/V subjects (V/V: 120.9+/-0.69, V/F: 119.4+/-1.26, F/F: 109.2+/-4.84mg/dl, P=0.025). A significant association between the F/F genotype and increasing AA in serum phospholipids was found in subjects with high LDL-cholesterol (> or =130mg/dl) (P=0.003) but not in those with low LDL-cholesterol (<130mg/dl). F/F subjects in the high LDL-cholesterol group had CRP concentrations about three times higher than those with V/V or V/F genotypes (V/V: 1.25+/-0.09, V/F: 0.97+/-0.12, F/F: 3.20+/-0.88mg/dl, P<0.001).

CONCLUSIONS

The recessive effects of Lp-PLA(2) V279F on LDL-cholesterol and significant correlations between Lp-PLA(2) activity and LDL-cholesterol, 8-epi-PGF(2alpha) and fibrinogen support a pro-oxidative or pro-atherogenic role for this enzyme. Paradoxically, the combination of the complete deficiency of Lp-PLA(2) activity and high LDL-cholesterol enhanced lipid peroxidation and inflammation.

Functional Consequences of Mutations and Polymorphisms in the Coding Region of the PAF Acetylhydrolase (PAF-AH) Gene

In the past several years a number of alterations in the PAF-AH/PLA₂G7/LpPLA₂ gene have been described. These include inactivating mutations, polymorphisms in the coding region, and other genetic changes located in promoter and intronic regions of the gene. The consequences associated with these genetic variations have been evaluated from different perspectives, including in vitro biochemical and molecular studies and clinical analyses in human subjects. This review highlights the current state of the field and suggests new approaches that can be used to evaluate functional consequences associated with mutations and polymorphisms in the PAF-AH gene.

Inter-individual variability of plasma PAF-acetylhydrolase activity in ARDS patients and PAFAH genotype

BACKGROUND

Platelet activating factor (PAF), a pro-inflammatory phospholipid, stimulates cytokine secretion from polymorphonuclear leukocytes expressing the transmembrane G-protein coupled PAF receptor. Elevated PAF levels are associated with acute respiratory distress syndrome (ARDS) and sepsis severity. The pro-inflammatory effects of PAF are terminated by PAF acetylhydrolase (PAF-AH).

OBJECTIVE

We sought to determine whether allelic variants in the human PAFAH gene (Arg92His, Ile198Thr, and Ala379Val) contribute to variability in PAF-AH activity in patient plasma obtained within 72 h of ARDS diagnosis.

RESULTS

Plasma PAF-AH activity (mean +/- SD) was higher in patients homozygous for the Arg92 allele compared to His92 allele carriers (2.21 +/- 0.77 vs. 1.64 +/- 0.68 U/min; P < 0.01; n = 31 and 21 respectively). Baseline plasma PAF-AH activity was higher among day 7 survivors vs. day 7 non-survivors (2.05 +/- 0.75 vs. 1.27 +/- 0.63, P = 0.05).

CONCLUSION

These data demonstrate an association between PAF-AH allelic variation, plasma activity, and outcome in ARDS.

Effects of G994T in the Lp-PLA2 gene on the plasma oxidized LDL level and carotid intima-media thickness in Japanese: the Shimane study

BACKGROUND

A single-nucleotide polymorphism (SNP), G994T, in the lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) gene is known to have a potent influence on the activity of the enzyme. As this enzyme hydrolyzes oxidized low-density lipoprotein (oxLDL), which is an important player in atherogenesis, the present study evaluated effects of the G994T genotype on the oxLDL level as well as on intima media thickness (IMT) in vivo.

METHODS

Participants of a health examination (1,307 in total) were recruited from two rural communities in Shimane, Japan. Genotyping was performed by an allele-specific PCR and the TaqMan method. The oxLDL level was determined by an enzyme immunoassay.

RESULTS

The minor allele (994T) frequency (0.19) in the studied populations was consistent with previous reports on Japanese. The 994T allele increased the plasma oxLDL/LDL ratio in a recessive manner, whereas 994T had a codominant effect on the Lp-PLA(2) activity. A multivariate analysis revealed that age and the G994T genotype had independent effects on the oxLDL/LDL level. By contrast, the G994T genotype was not associated with IMT. All of these results were reproducible in the two independent populations studied.

CONCLUSIONS

G994T influenced plasma LDL oxidation. Further studies on the effect of this polymorphism in cardiovascular diseases are warranted.

Current and emerging paradigms in the therapeutic management of atherosclerosis

BACKGROUND

The pathogenesis of atherosclerosis lies in abnormalities in lipoprotein metabolism leading to pathological interactions with vessel walls and the release of inflammatory components, which further aggravate the disease condition.

OBJECTIVE

To elucidate current and emerging trends in drug discovery towards the development of new entities regulating lipoprotein metabolism and inflammatory components to combat the progression of atherosclerosis.

METHODS

Research/review articles in the public domain and press releases were employed.

RESULTS/CONCLUSION

With the recent failure of torcetrapib and succinobucol, drug discovery and development efforts towards the treatment of atherosclerosis have received a big jolt and have been slowed down to a certain extent [corrected]. But this could be a starting point for several new mechanisms that are emerging to discover new drugs to combat the disease.

Associations of PLA2G7 gene polymorphisms with plasma lipoprotein-associated phospholipase A2 activity and coronary heart disease in a Chinese Han population: the Beijing atherosclerosis study

The human PLA2G7 gene encodes lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), an emerging risk factor for cardiovascular diseases. In the present study, seven single nucleotide polymorphisms (SNPs) in the PLA2G7 gene were genotyped in 827 patients with coronary heart disease (CHD), of which 512 were patients with myocardial infarction (MI), and 947 age- and gender-matched controls in a Chinese Han population. Plasma Lp-PLA(2) activity was measured in 416 randomly selected controls and 689 randomly selected CHD patients, including 423 MI patients. Lp-PLA(2) activity in CHD and MI cases was significantly higher (233.42+/-57.66 and 234.27+/-59.51 nmol ml(-1) min(-1), respectively) than in controls (211.47+/-58.61 nmol ml(-1) min(-1)). After adjusting for traditional risk factors by logistic regression, the odds ratios for CHD and MI per 1 standard deviation increment of Lp-PLA(2) activity were 1.27 (95% CI, 1.07-1.50) and 1.27 (95% CI, 1.05-1.54), respectively. Both single SNP analysis and haplotype analysis showed that the V279F and I198T polymorphisms were significantly associated with the reduced Lp-PLA(2) activity, but neither was associated with increased CHD risk. Both univariate and multivariate analyses, adjusting effects of conventional factors, indicated that the rs13210554 T allele increased the risk of MI in this Chinese Han population. In summary, an independent association of increased plasma Lp-PLA(2) activity with CHD and MI existed in this Chinese Han Population. Although V279F and I198T mutations significantly decreased the activity of Lp-PLA(2), only the promoter rs13210554 polymorphism was associated with MI. Lp-PLA(2) activity appears to influence the CHD and MI risk in Chinese Han population.

A twin study of heritability of plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) mass and activity

OBJECTIVE

We investigated heritability of plasma levels (mass) and activity of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)).

MATERIALS AND METHODS

In 54 healthy twins pairs we estimated genetic variance and heritability of Lp-PLA(2) mass and activity using maximum likelihood and least squares methods. We estimated intra-class correlation (ICC) and proportion of additive genetic variance from a model comprising additive genetic influence (A), environmental effect common to cotwins (C) and individually unique environmental (E) influence (ACE) model.

RESULTS

Twenty-six twin pairs were monozygotic (MZ) and 28 dizygotic (DZ). The Lp-PLA(2) mass and activity showed a significant correlation (r=0.87, p<0.001) and the mean values were similar in MZ and DZ. ICC estimates of heritability for Lp-PLA(2) were 0.27 (mass) and 0.28 (activity); ACE model-based estimates of heritability were 0.37 (mass) and 0.54 (activity). Heritability estimates were not significant for Lp-PLA(2) mass, but significant for Lp-PLA(2) activity.

CONCLUSIONS

These results suggest heritability for activity, but not for mass, in healthy Caucasians.

Biology of platelet-activating factor acetylhydrolase (PAF-AH, lipoprotein associated phospholipase A2)

INTRODUCTION

This article is focused on platelet-activating factor acetylhydrolase (PAF-AH), a lipoprotein bound, calcium-independent phospholipase A(2) activity also referred to as lipoprotein-associated phospholipase A(2) or PLA(2)G7. PAF-AH catalyzes the removal of the acyl group at the sn-2 position of PAF and truncated phospholipids generated in settings of inflammation and oxidant stress.

DISCUSSION

Here, I discuss current knowledge related to the structural features of this enzyme, including the molecular basis for association with lipoproteins and susceptibility to oxidative inactivation. The circulating form of PAF-AH is constitutively active and its expression is upregulated by mediators of inflammation at the transcriptional level. This mechanism is likely responsible for the observed up-regulation of PAF-AH during atherosclerosis and suggests that increased expression of this enzyme is a physiological response to inflammatory stimuli. Administration of recombinant forms of PAF-AH attenuate inflammation in a variety of experimental models. Conversely, genetic deficiency of PAF-AH in defined human populations increases the severity of atherosclerosis and other syndromes. Recent advances pointing to an interplay among oxidized phospholipid substrates, Lp(a), and PAF-AH could hold the key to a number of unanswered questions.

Lipoprotein-associated phospholipase A2 and risk of venous thrombosis in older adults

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an enzyme involved in inflammation and platelet function. Inherited deficiency and elevated levels are associated with atherosclerosis. Given potential common etiologies of atherosclerosis and venous thrombosis (VT), we hypothesized that low and high Lp-PLA2 would be associated with VT risk. Lp-PLA(2) mass and activity were measured in baseline samples of Cardiovascular Health Study participants (5,888 men and women age > or =65), excluding 354 reporting pre-baseline VT. The study endpoint was VT unrelated to cancer after 11.6 years follow-up. Hazard ratios were estimated using Cox proportional hazard models, adjusting for age, race, sex, and body-mass index. With 129 cases of VT, there was no association of Lp-PLA2 activity with risk. Adjusted hazard ratios were 1.19 (CI 0.62, 2.29) and 0.87 (CI 0.43, 1.76) for the lowest and highest decile, respectively, compared to the 10-25th percentile. Corresponding hazard ratios for Lp-PLA2 mass were 1.63 (CI 0.79, 3.34) and 1.33 (CI 0.61, 2.87). Results were robust to several definitions of low or high Lp-PLA2. While the association of Lp-PLA(2) levels with arterial disease events implies a role for this enzyme in atherogenesis, our findings suggest that it is not prothrombotic.

Platelet activating factor-acetylhydrolase (PAF-AH) activity and HDL levels, but not PAF-AH gene polymorphisms, are associated with successful aging in Sicilian octogenarians

BACKGROUND AND AIMS

Aging is associated with an increased risk of developing atherosclerosis. Subjects over 80 years of age without cardiovascular disease provide a model to investigate the protective factors increasing their resistance to atherosclerotic disease. Platelet-activating factor acetylhydrolase (PAF-AH) is an enzyme associated with low density lipoprotein (LDL) and high density lipoprotein (HDL) inactivating platelet-activating factor (PAF) and preventing LDL oxidation by hydrolysis of oxidized phospholipids. The aim of the present study was to evaluate the contribution of the PAFAH gene Arg92His, Ile198Thr and Ala379Val polymorphisms to resistance toward developing cardiovascular events in healthy Sicilian octogenarians.

METHODS

Distribution of PAF-AH genotypes and activity, and biochemical parameters, were compared between 100 octogenarians and 200 healthy adults.

RESULTS

The individuals in the elderly group displayed significantly higher levels of HDL-C (p<0.001) and plasma (p<0.001) and HDL (p<0.001) PAF-AH activity. Analysis of PAFAH genotype distributions showed no significant differences between octogenarians and controls. No differences among PAF-AH genotypes with respect to plasma and HDL PAF-AH activity were found in either group.

CONCLUSIONS

Our results provide no evidence of a significant association between the PAF-AH gene Arg92His, Ile198Thr and Ala379Val polymorphisms and successful aging in Sicilians. They also emphasize that, in these subjects, aging is characterized by increased levels of PAF-AH activity and HDL-C.

Association of lipoprotein-associated phospholipase A2 with coronary calcification among American and Japanese men

BACKGROUND

We have previously reported that the prevalence of coronary artery calcification (CAC) was substantially lower among Japanese than American men despite a less favorable profile of many traditional risk factors in Japanese men. To determine whether lipoprotein-associated phospholipase A2 (Lp-PLA2) levels are related to the difference in the prevalence of CAC between the two populations.

METHODS

A total of 200 men aged 40-49 years were examined: 100 residents in Allegheny County, Pennsylvania, United States, and 100 residents in Kusatsu City, Shiga, Japan. Coronary calcium score (CCS) was evaluated by electron-beam tomography, Lp-PLA2 levels, nuclear magnetic resonance (NMR) lipoprotein subclasses, and other factors were assessed in 2001-2002.

RESULTS

Lp-PLA2 levels were higher among American than Japanese men (Mean ± standard deviation 301.7 ± 82.6 versus 275.9 ± 104.7 ng/mL, respectively, p=0.06). Among all Japanese men and those with low density lipoprotein (LDL) cholesterol >130 mg/dL, there was an inverse association of the prevalence of CCS>0 with the fertile groups of Lp-PLA2 levels (p=0.08 and p=0.03, respectively). American men did not have any association between CCS>0 with the fertile groups of Lp-PLA2 (p=0.62). Although Lp-PLA2 among both populations correlated positively with LDL and total cholesterol, American and Japanese men had different correlations with NMR lipoprotein subclasses. Reported high odds ratio for CCS>0 among American compared to Japanese men was not reduced after adjusting for Lp-PLA2 levels.

CONCLUSION

Lp-PLA2 may have different mechanisms of action among American and Japanese men. Lp-PLA2 levels can not explain the observed CAC differences between the two populations.

Influence of race and sex on lipoprotein-associated phospholipase A2 levels: observations from the Dallas Heart Study

AIMS

Most lipoprotein-associated phospholipase A2 (Lp-PLA2) studies included mainly white men. We sought to determine whether Lp-PLA2 levels differ according to race and sex.

METHODS

Lp-PLA2 mass and activity were measured in 3332 subjects age 30-65 participating in the Dallas Heart Study, a multiethnic, population-based, probability sample. Lp-PLA2 levels were compared between different race and sex groups.

RESULTS

Mean age was 45+/-9 years and 44% were men; 30% were white, 17% hispanic, and 53% black. Mean Lp-PLA2 activity and mass were 146+/-40 nmol/min/mL and 191+/-60 ng/mL, respectively. Lp-PLA2 activity was lower in women compared with men (134+/-35 vs. 161+/-40, p=0.001) and was lowest in black (136+/-38), intermediate in hispanic (151+/-36), and highest in white subjects (161+/-39) (trend p=0.0001). In multivariable linear regression models, after adjusting for age, body mass index (BMI), smoking, total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, triglycerides and high sensitivity C-reactive protein (hsCRP), Lp-PLA2 activity was 19 nmol/min/mL higher in men vs. women (p<0.001); compared with black subjects, adjusted Lp-PLA2 activity was 11 and 20 nmol/min/mL higher in white and hispanic subjects, respectively (both p<0.001). Similar race and sex differences were observed for Lp-PLA2 mass.

CONCLUSION

Race and sex independently influence Lp-PLA2 activity and mass. Thresholds to define Lp-PLA2 elevation may need to be sex and race specific.

Protection against oxidative stress-induced hepatic injury by intracellular type II platelet-activating factor acetylhydrolase by metabolism of oxidized phospholipids in vivo

Membrane phospholipids are susceptible to oxidation, which is involved in various pathological processes such as inflammation, atherogenesis, neurodegeneration, and aging. One enzyme that may help to remove oxidized phospholipids from cells is intracellular type II platelet-activating factor acetylhydrolase (PAF-AH (II)), which hydrolyzes oxidatively fragmented fatty acyl chains attached to phospholipids. Overexpression of PAF-AH (II) in cells or tissues was previously shown to suppress oxidative stress-induced cell death. In this study we investigated the functions of PAF-AH (II) by generating PAF-AH (II)-deficient (Pafah2(-/-)) mice. PAF-AH (II) was predominantly expressed in epithelial cells such as kidney proximal and distal tubules, intestinal column epithelium, and hepatocytes. Although PAF-AH activity was almost abolished in the liver and kidney of Pafah2(-/-) mice, Pafah2(-/-) mice developed normally and were phenotypically indistinguishable from wild-type mice. However, mouse embryonic fibroblasts derived from Pafah2(-/-) mice were more sensitive to tert-butylhydroperoxide treatment than those derived from wild-type mice. When carbon tetrachloride (CCl(4)) was injected into mice, Pafah2(-/-) mice showed a delay in hepatic injury recovery. Moreover, after CCl(4) administration, liver levels of the esterified form of 8-iso-PGF(2alpha), a known in vitro substrate of PAF-AH (II), were higher in Pafah2(-/-) mice than in wild-type mice. These results indicate that PAF-AH (II) is involved in the metabolism of esterified 8-isoprostaglandin F(2alpha) and protects tissue from oxidative stress-induced injury.

Comprehensive evaluation of genetic and environmental factors influencing the plasma lipoprotein-associated phospholipase A2 activity in a Japanese population

The lipoprotein-associated phospholipase A2 (Lp-PLA2) metabolizes oxidized phospholipids, generating lysophosphatidylcholine. The activity of the enzyme is known to be influenced largely by a single-nucleotide polymorphism, G994T, in the Lp-PLA2 gene. Interestingly, this polymorphism is much more prevalent in Japanese than Caucasians. The purpose of the current study was to evaluate the effects of the G994T, several environmental factors, and their interactions on the Lp-PLA2 activity in a large Japanese cohort. Participants (1,110 males and 908 females) of a health-screening examination were recruited for this study. Genotyping of the G994T was done using allele-specific polymerase chain reaction (PCR). The Lp-PLA2 activity was measured using commercial kits. The minor allele (994T) frequency of the polymorphism was 0.17 in this study, which was consistent with previous reports. According to the multivariate linear regression analysis, the G994T was the most potent factor influencing the enzyme activity (standardized beta=0.76), followed by the low-density lipoprotein cholesterol (LDL-C) level (standardized beta=0.32) and the sex (standardized beta=0.13). The LDL-C level showed a significant interaction with the G994T genotype. By contrast, no significant interaction was observed between the LDL-C level and the sex. These observations should provide useful information for future clinical and epidemiological evaluations of the Lp-PLA2 activity in cardiovascular diseases in Japanese.

The role of lipoprotein-associated phospholipase A2 as a marker for atherosclerosis

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an enzyme that belongs to the superfamily of phospholipase A2 enzymes. Although initial studies showed that Lp-PLA2 might be protective against atherosclerosis, emerging data seem to suggest that Lp-PLA2 may be proatherogenic, which is an effect thought to be mediated by lysophosphatidylcholine and oxidized nonesterified fatty acids, two mediators generated by Lp-PLA2. This article reviews the potential mechanisms by which Lp-PLA2 may participate in the pathogenesis of atherosclerosis and its clinical manifestations, namely, coronary artery disease and stroke.

Impact of atorvastatin treatment on platelet-activating factor acetylhydrolase and 15-F(2trans)-isoprostane in hypercholesterolaemic patients

AIMS

Isoprostanes are the product of free radical oxidation of arachidonic acid, whose hydrolysis from phospholipids is presumably catalysed by phospholipases A(2) (PLA(2)s) such as group IIA or V PLA(2)s, or group VII PLA(2)[platelet-activating factor acetylhydrolase (PAF-AH), lipoprotein-associated phospholipase]. Atorvastatin reduces concentrations of low-density lipoprotein (LDL), with which PAF-AH is associated, and PLA(2)s' protein concentrations. We investigated the effect of atorvastatin on PLA(2)s and PAF-AH activity and the urinary excretion of 15-F(2trans)-isoprostane (15-F(2t)-IsoP, 8-iso-PGF(2alpha), iPF(2alpha)-III).

METHODS

Twenty-four hypercholesterolaemic individuals naive to lipid-lowering therapy were randomized to atorvastatin 40 mg or placebo for 6 weeks. The 15-F(2t)-isoP urinary excretion (gas chromatography/mass spectrometry), PAF-AH and group IIA and V PLA(2) activities (photometry) were assessed at baseline and end-point.

RESULTS

At end-point, 15-F(2t)-isoP urinary excretion concentrations as well as PLA(2)s' activity were unchanged under atorvastatin (mean change 0.21 +/- 1.79 ng h(-1), 95% confidence interval -0.92, 1.35 and 0.33 +/- 0.94 nmol min(-1) ml(-1), -0.27, 0.93) and under placebo (mean change 0.69 +/- 1.69 ng h(-1), -0.52, 1.90 and 1.29 +/- 2.16 nmol min(-1) ml(-1), -0.25, 2.84). Atorvastatin treatment decreased total (P < 0.001) and LDL-cholesterol (P < 0.001) but had no effect on high-density lipoprotein. PAF-AH activity was lowered in the atorvastatin group (mean change - 5.27+/- 1.96 nmol min(-1) ml(-1), -6.51, -4.03, P < 0.001) but not in the placebo group (mean change 1.02 +/- 1.64 nmol min(-1) ml(-1), 0.15, 2.20), and the change in PAF-AH activity was correlated with that in total (P = 0.03) and LDL-cholesterol (P = 0.03).

CONCLUSION

Our results show a lowering effect of atorvastatin on PAF-AH activity associated with its lipid-lowering effect and exclude a key role of PAF-AH in the liberation of 15-F(2t)-isoP from phospholipids.

Association of gene polymorphism with genetic susceptibility to stroke in Asian populations: a meta-analysis

Stroke is a heterogeneous multifactorial disease and is thought to have a polygenic basis. Case-control studies on gene sequence variations have identified a number of potential genetic predisposition factors, but due to the conflicting results, uncertainty remains on the effect of these polymorphisms on risk for the development of stroke. To qualitatively and quantitatively assess the risk associated with different gene polymorphisms for stroke in Asian populations, we comprehensively searched and identified all the studies of association. Clinically overt case-control studies were selected only if neuroimaging had been used as the confirmatory measure for diagnosis of stroke. We performed a meta-analysis of the three most investigated genes, viz., methylenetetrahydrofolate reductase (MTHFR), apolipoprotein E (ApoE) and angiotensin-converting enzyme (ACE). Statistically significant association with stroke were identified for C677T polymorphism of MTHFR [random effects odds ratio (OR) = 1.47, 95% confidence interval (95% CI) 1.19, 1.82; P = 0.0004] and marginally significant association was detected with allele epsilon 4 of ApoE (random effects OR = 1.47, 95% CI 1.00, 2.15; P = 0.049). The sensitivity analysis (exclusion of studies with controls not in Hardy-Weinberg equilibrium) revealed a significant association of stroke with the MTHFR C677T and ApoE epsilon 4 alleles but showed no association with ACE gene insertion/deletion polymorphism.

The proinflammatory mediator Platelet Activating Factor is an effective substrate for human group X secreted phospholipase A2

Platelet Activating Factor (PAF) is a potent mediator of inflammation whose biological activity depends on the acetyl group esterified at the sn-2 position of the molecule. PAF-acetylhydrolase (PAF-AH), a secreted calcium-independent phospholipase A(2), is known to inactivate PAF by formation of lyso-PAF and acetate. However, PAF-AH deficient patients are not susceptible to the biological effects of inhaled PAF in airway inflammation, suggesting that other enzymes may regulate extracellular levels of PAF. We therefore examined the hydrolytic activity of the recently described human group X secreted phospholipase A(2) (hGX sPLA(2)) towards PAF. Among different sPLA(2)s, hGX sPLA(2) has the highest affinity towards phosphatidylcholine (PC), the major phospholipid of cellular membranes and plasma lipoproteins. Our results show that unlike group IIA, group V, and the pancreatic group IB sPLA(2), recombinant hGX sPLA(2) can efficiently hydrolyze PAF. The hydrolysis of PAF by hGX sPLA(2) rises abruptly when the concentration of PAF passes through its critical micelle concentration suggesting that the enzyme undergoes interfacial binding and activation to PAF. In conclusion, our study shows that hGX sPLA(2) may be a novel player in PAF regulation during inflammatory processes.

Clinical aspects of plasma platelet-activating factor-acetylhydrolase

Plasma platelet-activating factor (PAF)-acetylhydrolase (PAF-AH), which is characterized by tight association with plasma lipoproteins, degrades not only PAF but also phospholipids with oxidatively modified short fatty acyl chain esterified at the sn-2 position. Production and accumulation of these phospholipids are associated with the onset of inflammatory diseases and preventive role of this enzyme has been evidenced by many recent studies including prevalence of the genetic deficiency of the enzyme in the patients and therapeutic effects of treatment with recombinant protein or gene transfer. With respect to the atherosclerosis, however, it is not fully cleared whether this enzyme plays an anti-atherogenic role or pro-atherogenic role because plasma PAF-AH also might produce lysophosphatidylcholine (LysoPC) and oxidatively modified nonesterified fatty acids with potent pro-inflammatory and pro-atherogenic bioactivities. These dual roles of plasma PAF-AH might be regulated by the altered distribution of the enzyme between low density lipoprotein (LDL) and high density lipoprotein (HDL) particles because HDL-associated enzymes are considered to contribute to the protection of LDL from oxidative modification. This review focuses on the recent findings which address the role of this enzyme in the human diseases especially including asthma, septic shock and atherosclerosis.

The Val279Phe variant of the lipoprotein-associated phospholipase A2 gene is associated with catalytic activities and cardiovascular disease in Korean men

CONTEXT AND OBJECTIVE

It is unclear whether lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) exerts a pro- or antiatherogenic effect on cardiovascular disease (CVD). We investigated the association between Lp-PLA(2) variant (V279F and A379V) and CVD in Korean men.

DESIGN

CVD patients (n = 532) and healthy controls (n = 670) were genotyped for the Lp-PLA(2) polymorphism (V279F and A379V).

MAIN OUTCOME MEASURES

We calculated odds ratio (OR) on CVD risk and measured anthropometries, lipid profiles, low-density lipoprotein (LDL) particle size, oxidized LDL, lipid peroxides, and Lp-PLA(2) activity.

RESULTS

The presence of the 279F allele was associated with a lower risk of CVD [OR 0.646 (95% confidence interval 0.490-0.850), P = 0.002], and the association still remained after adjustments for age, body mass index, waist circumference, waist to hip ratio, cigarette smoking, and alcohol consumption [OR 0.683 (95% confidence interval 0.512-0.911), P = 0.009]. Lp-PLA(2) activity was lower in CVD patients taking a lipid-lowering drug (31%), those not taking a lipid-lowering drug (26%), and control subjects (23%) with the V/F genotype, compared with those with the V/V genotype. Subjects with the F/F genotype in controls and two CVD patients groups showed no appreciable enzymatic activity. Control subjects with the V/F genotype had larger LDL particle size than those with the V/V genotype. In addition, control subjects carrying the F allele showed lower malondialdehyde concentrations. On the other hand, we found no significant relationship between A379V genotype and CVD risk.

CONCLUSIONS

The association of the F279 loss of function variant with the reduced risk of CVD supports the concept that Lp-PLA(2) plays a proatherogenic and causative role in CVD.

Lipoprotein-associated phospholipase A2: Pathogenic mechanisms and clinical utility for predicting cardiovascular events

Lipoprotein-associated phospholipase A(2 )(Lp-PLA(2)), a member of the phospholipase superfamily, circulates primarily bound to low-density lipoprotein and has been associated with cardiovascular disease risk in epidemiologic studies. However, it has not been established whether Lp-PLA(2) is a risk marker or a risk factor. Identification of individuals with elevated Lp-PLA(2) may improve risk assessment, and Lp-PLA(2) may also provide an additional target of therapy. Statin therapy has been shown to reduce Lp-PLA(2), and selective inhibitors of Lp-PLA(2) are under development. Additional research is needed to further determine the role of Lp-PLA(2) in atherogenesis and atherothrombotic events.

Lipoprotein-Associated Phospholipase A2

Lipoprotein-associated phospholipase A2 (LP-PLA2) is an emerging inflammatory marker that is used to assess the risk for cardiovascular disease (CVD) and associated events. Several epidemiologic studies have demonstrated an independent association between plasma Lp-PLA2 concentration and risk for cardiovascular events. HMG-CoA reductase inhibitors (statins) and fenofibrates can reduce Lp-PLA2 concentrations in plasma, and orally active, specific Lp-PLA2 inhibitors have been developed and are in clinical trials to evaluate the potential of Lp-PLA2 as a therapeutic target. This article reviews recent studies of Lp-PLA2 in the setting of CVD, discusses the proposed mechanisms of action of Lp-PLA2, and describes methods for measurement and their clinical application. Recent evidence that suggests Lp-PLA2's potential usefulness as a therapeutic target also is reviewed.