Association of gene polymorphisms with coronary artery disease in individuals with or without nonfamilial hypercholesterolemia

Association of single nucleotide polymorphisms in the CYBA gene with coal workers' pneumoconiosis in the Han Chinese population

Coal workers' pneumoconiosis (CWP) is caused by long-term exposure to inhaled coal dust; it is likely influenced by the interaction between environmental factors and multiple susceptibility genes, such as the CYBA (cytochrome b-245α polypeptide) gene that has recently been identified to be involved in the genetic susceptibility for several pulmonary diseases. The aim of this case-control study was to explore the association between CYBA gene polymorphisms and the development of CWP in coal miners belonging to the Han ethnic group in China. Single nucleotide polymorphisms (SNPs) rs7195830, rs13306296, rs4673, rs9932581, and rs16966671 of the CYBA gene were analyzed in CWP patients (n = 652) and dust-exposed control subjects (n = 648) using the matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) on the Sequenom MassARRAY® platform (Sequenom, San Diego, CA, USA). Results from the present study showed a strong allele association between CWP patients and the CYBA SNP rs7195830 polymorphism (p < .001, OR = 1.550). Using the additive and the dominant model, the CYBA SNP rs7195830 polymorphism also showed significant associations with CWP patients (p < .001, OR = 1.621; p = .003, OR = 1.711, respectively). No statistically significant difference was demonstrated in either the allele or genotype frequencies of the other four examined SNPs (rs13306296, rs4673, rs9932581, and rs16966671) between the CWP group and dust-exposed control group (all p > .05). The present study is the first to have demonstrated an association between CYBA (rs7195830) polymorphism and the risk of developing CWP in subjects belong to the Han ethnic group in China and provides further clues for research into the pathogenesis of CWP.

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.

Pharmacogenetic meta-analysis of baseline risk factors, pharmacodynamic, efficacy and tolerability endpoints from two large global cardiovascular outcomes trials for darapladib

Darapladib, a lipoprotein-associated phospholipase A2 (Lp-PLA₂) inhibitor, failed to demonstrate efficacy for the primary endpoints in two large phase III cardiovascular outcomes trials, one in stable coronary heart disease patients (STABILITY) and one in acute coronary syndrome (SOLID-TIMI 52). No major safety signals were observed but tolerability issues of diarrhea and odor were common (up to 13%). We hypothesized that genetic variants associated with Lp-PLA₂ activity may influence efficacy and tolerability and therefore performed a comprehensive pharmacogenetic analysis of both trials. We genotyped patients within the STABILITY and SOLID-TIMI 52 trials who provided a DNA sample and consent (n = 13,577 and 10,404 respectively, representing 86% and 82% of the trial participants) using genome-wide arrays with exome content and performed imputation using a 1000 Genomes reference panel. We investigated baseline and change from baseline in Lp-PLA₂ activity, two efficacy endpoints (major coronary events and myocardial infarction) as well as tolerability parameters at genome-wide and candidate gene level using a meta-analytic approach. We replicated associations of published loci on baseline Lp-PLA₂ activity (APOE, CELSR2, LPA, PLA2G7, LDLR and SCARB1) and identified three novel loci (TOMM5, FRMD5 and LPL) using the GWAS-significance threshold P≤5E-08. Review of the PLA2G7 gene (encoding Lp-PLA₂) within these datasets identified V279F null allele carriers as well as three other rare exonic null alleles within various ethnic groups, however none of these variants nor any other loci associated with Lp-PLA₂ activity at baseline were associated with any of the drug response endpoints. The analysis of darapladib efficacy endpoints, despite low power, identified six low frequency loci with main genotype effect (though with borderline imputation scores) and one common locus (minor allele frequency 0.24) with genotype by treatment interaction effect passing the GWAS-significance threshold. This locus conferred risk in placebo subjects, hazard ratio (HR) 1.22 with 95% confidence interval (CI) 1.11–1.33, but was protective in darapladib subjects, HR 0.79 (95% CI 0.71–0.88). No major loci for tolerability were found. Thus, genetic analysis confirmed and extended the influence of lipoprotein loci on Lp-PLA₂ levels, identified some novel null alleles in the PLA2G7 gene, and only identified one potentially efficacious subgroup within these two large clinical trials.

Roles of Vascular Oxidative Stress and Nitric Oxide in the Pathogenesis of Atherosclerosis

Major reactive oxygen species (ROS)–producing systems in vascular wall include NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase, xanthine oxidase, the mitochondrial electron transport chain, and uncoupled endothelial nitric oxide (NO) synthase. ROS at moderate concentrations have important signaling roles under physiological conditions. Excessive or sustained ROS production, however, when exceeding the available antioxidant defense systems, leads to oxidative stress. Animal studies have provided compelling evidence demonstrating the roles of vascular oxidative stress and NO in atherosclerosis. All established cardiovascular risk factors such as hypercholesterolemia, hypertension, diabetes mellitus, and smoking enhance ROS generation and decrease endothelial NO production. Key molecular events in atherogenesis such as oxidative modification of lipoproteins and phospholipids, endothelial cell activation, and macrophage infiltration/activation are facilitated by vascular oxidative stress and inhibited by endothelial NO. Atherosclerosis develops preferentially in vascular regions with disturbed blood flow (arches, branches, and bifurcations). The fact that these sites are associated with enhanced oxidative stress and reduced endothelial NO production is a further indication for the roles of ROS and NO in atherosclerosis. Therefore, prevention of vascular oxidative stress and improvement of endothelial NO production represent reasonable therapeutic strategies in addition to the treatment of established risk factors (hypercholesterolemia, hypertension, and diabetes mellitus).

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.

[Lp-PLA2, a biomarker of vascular inflammation and vulnerability of atherosclerosis plaques]

A chronic inflammation is involved in various stages of development of the atherosclerotic plaques. Among the emerging biomarkers of atherogenesis, the lipoprotein-associated phospholipase A2 (Lp-PLA2), formerly known as PAF-acetylhydrolase (McIntyre et al., 2009), hydrolyses the oxidized short chain phospholipids of low-density lipoproteins (LDL), thereby releasing pro-inflammatory mediators (lysophospholipids and oxidized fatty acids). Lp-PLA2, produced by monocytes/macrophages and T-lymphocytes, and mainly associated with LDL (Gazi et al., 2005), is predominantly expressed in the necrotic center of the atherosclerotic plaques and in the macrophage-rich areas (Kolodgie et al., 2006). It would have a predictive role of cardiovascular (CV) events in relation to the vulnerability of atherosclerotic plaques. Determination of Lp-PLA2 has been proposed in the assessment of the CV risk, to ensure a better stratification of populations at intermediate risk for targeted therapy (Davidson et al., 2008). Its proatherogenic role suggested that inhibition of its activity could ensure a better vascular protection in combination with cholesterol-lowering agents. Nevertheless, Lp-PLA2 is not yet a fully validated marker for use in daily clinical practice, especially since the studies using an inhibitor of Lp-PLA2 (darapladib) (STABILITY Investigators et al., 2014; O'Donoghue et al., 2014) did not show any reduction in coronary events. Lp-PLA2 could have a site-specific role in plaque inflammation and development (Fenning et al., 2015). High Lp-PLA2 activity could reflect a response to pro-inflammatory stress characteristic of atherosclerosis (Marathe et al., 2014). This presentation aims at clarifying the involvement of Lp-PLA2 in the pathophysiology of atherosclerosis, and at assessing its interest both as a biomarker for the onset of CV events and as a therapeutic target.

Association of the p22phox polymorphism C242T with the risk of late-onset Alzheimer's disease in a northern Han Chinese population

The C242T polymorphism of the CYBA gene that encodes p22phox, a component of nicotinamide adenine dinucleotide phosphate oxidase, has been found to modulate reactive oxygen species (ROS) production. Oxidative stress is thought to play a pivotal role in the pathophysiology of Alzheimer's disease (AD), which is manifested as increased availability of ROS because of an imbalanced redox state. Therefore, the aim of this study was to investigate potential associations of the p22phox C242T polymorphism with the risk of late-onset AD (LOAD) in a northern Han Chinese population. Patients with LOAD (n = 276) and 320 control subjects were recruited for the study. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the genotypes. No significant differences were found between LOAD and p22phox C242T polymorphism, but a significant association was obtained in the genotype and allele distributions of p22phox C242T between LOAD patients and controls in apolipoprotein E (ApoE) ϵ4 carriers. These results suggested that p22phox C242T polymorphism has a possible role in changing the genetic susceptibility to LOAD in ApoE ϵ4 carriers of this northern Han Chinese population.

Nonsynonymous polymorphisms in PLA2G7 gene are associated with the risk of coronary heart disease in a southern Chinese population

Lipoprotein-associated phospholipase A2 (Lp-PLA2) plays an important role in coronary heart disease (CHD). This study was aimed to investigate the associations of polymorphisms (R92H, V279F, I198T, and A379V) in PLA2G7 with CHD. A total of 322 patients with CHD and 414 CHD-free controls were included in the study. Polymorphisms in PLA2G7 were sequenced by DNA Sequencer and statistical analyses were performed to study the associations between polymorphisms and CHD. RH + HH genotype, RH genotype, and H allele of R92H were significantly associated with an increased risk of CHD (P = 0.005, P = 0.009, and P = 0.003, respectively), while no associations were observed between V279F and I198T and CHD (A379V was not analyzed because of deviation from Hardy-Weinberg equilibrium). Correlations between R92H and CHD still existed after adjustment for confounding risk factors of CHD (P = 0.001). Furthermore, stratified analyses showed subgroups of the senior, hypertension, non-smoking, non-diabetics, and male subjects brought a higher risk for CHD (P = 0.015, P = 0.001, P = 0.001, P = 0.002, and P = 0.004, respectively). We also observed a lower level of protective factor HDL-C in CHD patients carrying genotype RH + HH than patients with RR (P = 0.047). Furthermore, we conducted haplotype analysis and detected more harmful effects of haplotypes HVI and RVT as compared with other haplotypes (P = 2.538 × 10(-3) and P = 0.031). These findings indicated that R92H variant in PLA2G7 gene might contribute to CHD susceptibility in a southern Chinese population.

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.

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.

Relationship of the p22phox (CYBA) gene polymorphism C242T with risk of coronary artery disease: a meta-analysis

Background

Observational and experimental studies have thus far been unable to resolve whether the CYBA C242T polymorphism is associated with coronary artery disease (CAD). Therefore, we undertook a comprehensive meta-analysis to more precisely evaluate the influence of this polymorphism on CAD and potential biases.

Methods

We screened MEDLINE, Embase, CNKI, Wanfang and CBM up to January 2013 and extracted data from 22 studies with 9,279 CAD patients and 9,349 controls. A random-effects model was exploited to synthesize the inconsistent outcomes of the individual studies, while addressing between-study heterogeneity and publication bias.

Results

The CYBA C242T polymorphism conformed to Hard-Weinberg Equilibrium for all studies (P>0.05). Overall comparison of the T allele with the C allele produced a non-significant risk estimate for CAD but with striking heterogeneity (T versus C: P = 0.87, OR = 0.99, 95%CI 0.89–1.11, P_{heterogeneity}<0.0001, I² = 67.8%). However, subgroup analysis by ethnicity documented that the T allele carriers had a marginal risk increase (21%) of CAD among Caucasians (recessive genetic model: P = 0.05, 95%CI 1.00–1.46, P_{heterogeneity} = 0.15, I² = 29.1%). Then data were divided into study design, the significance of CAD risk increase was substantially strengthened in matched case-control studies (allele comparison: P = 0.02, OR = 1.13, 95%CI 1.02–1.26, P_{heterogeneity} = 0.24, I² = 21.6%).Further meta-regression analysis identified that a large proportion of heterogeneity was explained by body mass index (BMI) (P = 0.03, OR = 1.07, 95%CI 1.01–1.15) and study design (P = 0.03, OR = 1.30, 95%CI 1.02–1.64).There was no obvious publication bias as verified by funnel plot and Egger's linear regression test (t = −0.25, P = 0.81 for allele comparison).

Conclusion

Taken together, our results suggested the CYBA C242T polymorphism might be a risk-conferring factor on developing CAD and BMI and study design were probable sources of between-study heterogeneity.

Association between NADPH oxidase p22(phox) C242T polymorphism and ischemic cerebrovascular disease: a meta-analysis

Background

Epidemiological studies have evaluated the association between nicotinamide adenine dinucleotide phosphate (NADPH) oxidase p22^phox C242T polymorphism and risk of ischemic cerebrovascular disease (ICVD), but the results remain inconclusive. This meta-analysis was therefore designed to clarify these controversies.

Methodology/Principal Findings

Systematic searches of electronic databases Embase, PubMed and Web of Science, as well as hand searching of the references of identified articles and the meeting abstracts were performed. Statistical analyses were performed using software Review Manager (Version 5.1.7) and Stata (Version 11.0). The pooled odds ratios (ORs) with 95% confidence intervals (95%CIs) were performed. Fixed or random effects model was separately used depending on the heterogeneity between studies. Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 6 studies including 1,948 cases and 2,357 controls were combined showing no statistical evidence of association between NADPH oxidase p22^phox C242T polymorphism and overall ICVD (allelic model: OR = 1.08, 95%CI = 0.93–1.26; additive model: OR = 1.33, 95%CI = 0.81–2.17; dominant model: OR = 1.00, 95%CI = 0.86–1.15; recessive model: OR = 1.06, 95%CI = 0.77–1.45). Significant association was found in large-artery atherosclerotic stroke subgroup (allelic model: OR = 1.12, 95%CI = 0.88–1.41; additive model: OR = 1.36, 95%CI = 0.60–3.09; dominant model: OR = 1.25, 95%CI = 0.74–2.11; recessive model: OR = 2.17, 95%CI = 1.11–4.23). No statistical evidence of significant association was observed for small-vessel occlusive stroke, as well as Asian subgroup and Caucasian subgroup. Statistical powers on the combined sample size (total and subgroup) were all lower than 80%.

Conclusions/Significance

This meta-analysis indicates that NADPH oxidase p22^phox C242T polymorphism is more associated with large-artery atherosclerotic stroke than small-vessel occlusive stroke. However, this conclusion should be interpreted with caution due to the small sample size. Larger sample-size studies with homogeneous ICVD patients and well-matched controls are required.

Selective inhibitors and tailored activity probes for lipoprotein-associated phospholipase A(2)

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2) or PLA(2)G7) binds to low-density lipoprotein (LDL) particles, where it is thought to hydrolyze oxidatively truncated phospholipids. Lp-PLA(2) has also been implicated as a pro-tumorigenic enzyme in human prostate cancer. Several inhibitors of Lp-PLA(2) have been described, including darapladib, which is currently in phase 3 clinical development for the treatment of atherosclerosis. The selectivity that darapladib and other Lp-PLA(2) inhibitors display across the larger serine hydrolase family has not, however, been reported. Here, we describe the use of both general and tailored activity-based probes for profiling Lp-PLA(2) and inhibitors of this enzyme in native biological systems. We show that both darapladib and a novel class of structurally distinct carbamate inhibitors inactivate Lp-PLA(2) in mouse tissues and human cell lines with high selectivity. Our findings thus identify both inhibitors and chemoproteomic probes that are suitable for investigating Lp-PLA(2) function in biological systems.

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.

CYBA and GSTP1 variants associate with oxidative stress under hypobaric hypoxia as observed in high-altitude pulmonary oedema

HAPE (high-altitude pulmonary oedema) is characterized by pulmonary hypertension, vasoconstriction and an imbalance in oxygen-sensing redox switches. Excess ROS (reactive oxygen species) contribute to endothelial damage under hypobaric hypoxia, hence the oxidative-stress-related genes CYBA (cytochrome b-245 α polypeptide) and GSTP1 (glutathione transferase Pi 1) are potential candidate genes for HAPE. In the present study, we investigated the polymorphisms -930A/G and H72Y (C/T) of CYBA and I105V (A/G) and A114V (C/T) of GSTP1, individually and in combination, in 150 HAPE-p (HAPE patients), 180 HAPE-r (HAPE-resistant lowland natives) and 180 HLs (healthy highland natives). 8-Iso-PGF2α (8-iso-prostaglandin F2α) levels were determined in plasma and were correlated with individual alleles, genotype, haplotype and gene-gene interactions. The relative expression of CYBA and GSTP1 were determined in peripheral blood leucocytes. The genotype distribution of -930A/G, H72Y (C/T) and I105V (A/G) differed significantly in HAPE-p compared with HAPE-r and HLs (P≤0.01). The haplotypes G-C of -930A/G and H72Y (C/T) in CYBA and G-C and G-T of I105V (A/G) and A114V (C/T) in GSTP1 were over-represented in HAPE-p; in contrast, haplotypes A-T of -930A/G and H72Y (C/T) in CYBA and A-C of I105V (A/G) and A114V (C/T) in GSTP1 were over-represented in HAPE-r and HLs. 8-Iso-PGF2α levels were significantly higher in HAPE-p and in HLs than in HAPE-r (P=2.2×10(-16) and 1.2×10(-14) respectively) and the expression of CYBA and GSTP1 varied differentially (P<0.05). Regression analysis showed that the risk alleles G, C, G and T of -930A/G, H72Y (C/T), I105V (A/G) and A114V (C/T) were associated with increased 8-iso-PGF2α levels (P<0.05). Interaction between the two genes revealed over-representation of most of the risk-allele-associated genotype combinations in HAPE-p and protective-allele-associated genotype combinations in HLs. In conclusion, the risk alleles of CYBA and GSTP1, their haplotypes and gene-gene interactions are associated with imbalanced oxidative stress and, thereby, with high-altitude adaptation and mal-adaptation.

Association between lipoprotein-associated phospholipase A2 gene polymorphism and coronary artery disease in the Chinese Han population

The role of the lipoprotein-associated phospholipase A(2) gene (PLA2G7) in atherosclerosis remains controversial. We investigated the frequency of single-nucleotide polymorphisms (SNPs) of PLA2G7 (rs16874954 and rs1051931) and their association with coronary artery disease (CAD) in a cohort of CAD patients (n= 806) and age-matched healthy controls (n= 482) in the Chinese Han population. The VF and FF genotype of rs16874954 was significantly more frequent in the CAD patients (13.5%) than in the controls (9.3%, P= 0.024). The association remained after adjustment for age, gender, body mass index, smoking status, history of diabetes, positive family history of CAD, high-density lipoprotein cholesterol, and triglyceride (OR = 1.922; 95% CI [1.146-3.224]; P= 0.013). There was no significant difference in the frequency of any genotype of rs1051931 between the two groups. However, the frequency of the allele V379 was significantly greater in CAD patients with a history of myocardial infarction (MI) than in those without a history of MI (18.7% and 14.8%, P= 0.038). We conclude that there is significant association between the rs16874954 mutation and CAD in the Chinese Han population. The expression of rs1051931 variant in CAD patients may entail increased risk of MI.

Carriage of the V279F null allele within the gene encoding Lp-PLA₂ is protective from coronary artery disease in South Korean males

Background

The Asia-specific PLA2G7 994G-T transversion leads to V279F substitution within the lipoprotein-associated phospholipase-A2 (Lp-PLA₂) and to absence of enzyme activity in plasma. This variant offers a unique natural experiment to assess the role of Lp-PLA₂ in the pathogenesis of coronary artery disease (CAD) in humans. Given conflicting results from mostly small studies, a large two-stage case-control study was warranted.

Methodology/Principal Findings

PLA2G7 V279F genotypes were initially compared in 2890 male cases diagnosed with CAD before age 60 with 3128 male controls without CAD at age 50 and above and subsequently in a second independent male dataset of 877 CAD cases and 1230 controls. In the first dataset, the prevalence of the 279F null allele was 11.5% in cases and 12.8% in controls. After adjustment for age, body mass index, diabetes, smoking, glucose and lipid levels, the OR (95% CI) for CAD for this allele was 0.80 (0.66–0.97, p = 0.02). The results were very similar in the second dataset, despite lower power, with an allele frequency of 11.2% in cases and 12.5% in controls, leading to a combined OR of 0.80 (0.69–0.92), p = 0.002. The magnitude and direction of this genetic effect were fully consistent with large epidemiological studies on plasma Lp-PLA₂ activity and CAD risk.

Conclusions

Natural deficiency in Lp-PLA₂ activity due to carriage of PLA2G7 279F allele protects from CAD in Korean men. These results provide evidence for a causal relationship between Lp-PLA₂ and CAD, and support pharmacological inhibition of this enzyme as an innovative way to prevent CAD.

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.

Effect of dietary saturated fatty acids on HNF-4α DNA binding activity and ApoCIII mRNA in sedentary rat liver

Hind limb-suspended rats represent a sedentary-hyperinsulinemic model with a liver dyslipidemia mainly related to changes in sterol regulatory element-binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor-α (PPARα) expression and activity. To assess the effects of dietary fatty acids on hepatic lipid homeostasis, the hepatic expression and activity of PPARα, SREBP-1, and hepatocyte nuclear factor-4α (HNF-4α) were investigated in this animal model. In control and sedentary rats, diets enriched with saturated, monounsaturated, and polyunsaturated fatty acids (PUFA) enhanced the expression of the PPARα target genes carnitine palmitoyltransferase 1 and acyl-CoA oxidase, the highest effect being exerted by ω-3. The same diets reduced SREBP-1 mRNA and target lipogenic gene expression, as indicated by the reduction in fatty acid synthase and acetyl-CoA carboxylase mRNA content. Effects were greater in sedentary rat liver than in controls on the same diet. Only the ω-3 enriched diet decreased liver triglyceride content as well as plasma cholesterol and triglyceride levels in sedentary rats. This effect may be mainly related to the enhanced mitochondrial and peroxisomal β-oxidation genes expression. On the other hand, saturated fatty acid-enriched diet induced an increase in liver triglyceride content and enhanced plasma cholesterol and triglyceride levels, both in control and immobilized rats. This detrimental effect may be ascribed to the induced HNF-4α binding activity on ApoCIII promoter and to the enhanced ApoCIII mRNA levels both in control and in sedentary rat livers. In conclusion, we can speculate that dietary saturated fats, acting at apolipoprotein transcriptional level, may impact on the close relationship existing among high ApoCIII plasma level, dyslipidemia, and atherosclerosis.

Lipoprotein-associated phospholipase A₂ activity and mass in relation to vascular disease and nonvascular mortality

OBJECTIVES

To assess whether associations of circulating lipoprotein-associated phospholipase A₂ (Lp-PLA₂) with vascular disease are independent of other risk factors.

METHODS

Lp-PLA₂ activity and mass, lipids and other characteristics were measured at baseline in 19,037 individuals at high risk of vascular disease in a randomized trial of simvastatin with 5-year average follow-up.

RESULTS

Lp-PLA₂ activity and mass were correlated with each other (r = 0.56), lipids and other vascular risk factors. The moderate association of Lp-PLA₂ activity with occlusive coronary events (n = 2531) in analyses adjusted for nonlipid factors (hazard ratio per 1 SD [HR] 1.11, 95% CI 1.06-1.15) became nonsignificant after further adjustment for apolipoproteins (HR 1.02, 0.97-1.06). Such adjustment also attenuated HRs with Lp-PLA₂ mass from 1.08 (1.03-1.12) to 1.05 (1.01-1.09). By contrast, the HR with apolipoprotein-B100 of 1.15 (1.10-1.19) was only slightly attenuated to 1.14 (1.09-1.19) after further adjustment for apolipoprotein A₁ and Lp-PLA₂. Age- and sex-adjusted HRs for other cardiac events (n = 1007) with either Lp-PLA₂ activity or mass were about 1.20, but HRs reduced after adjustment for nonlipid factors (activity: 1.11, 1.04-1.18; mass: 1.08, 1.02-1.15). Adjusted HRs for ischaemic stroke (n = 900) were weak and nonsignificant and for nonvascular mortality (n = 1040) were 1.01 (0.94-1.09) with activity and 1.12 (1.05-1.19) with mass. Simvastatin reduced Lp-PLA₂ levels by about one-quarter, but simvastatin's vascular protection did not vary with baseline Lp-PLA₂ concentration.

CONCLUSIONS

Associations of Lp-PLA₂ with occlusive coronary events depend considerably on lipid levels, whereas those with other cardiac events appear to reflect confounding from cardiovascular medication and prior vascular disease.

Oxidative risk for atherothrombotic cardiovascular disease

In the vasculature, reactive oxidant species, including reactive oxygen, nitrogen, or halogenating species, and thiyl, tyrosyl, or protein radicals may oxidatively modify lipids and proteins with deleterious consequences for vascular function. These biologically active free radical and nonradical species may be produced by increased activation of oxidant-generating sources and/or decreased cellular antioxidant capacity. Once formed, these species may engage in reactions to yield more potent oxidants that promote transition of the homeostatic vascular phenotype to a pathobiological state that is permissive for atherothrombogenesis. This dysfunctional vasculature is characterized by lipid peroxidation and aberrant lipid deposition, inflammation, immune cell activation, platelet activation, thrombus formation, and disturbed hemodynamic flow. Each of these pathobiological states is associated with an increase in the vascular burden of free radical species-derived oxidation products and, thereby, implicates increased oxidant stress in the pathogenesis of atherothrombotic vascular disease.

NADPH oxidase CYBA polymorphisms, oxidative stress and cardiovascular diseases

Oxidative stress plays a key role in the pathophysiology of several major cardiovascular diseases, including atherosclerosis, hypertension, heart failure, stroke and diabetes. ROS (reactive oxygen species) affect multiple tissues either directly or through NO depletion. ROS induce cardiovascular dysfunction by modulating cell contraction/dilation, migration, growth/apoptosis and extracellular matrix protein turnover, which contribute to vascular and cardiac remodelling. Of the several sources of ROS within the cardiovascular system, a family of multisubunit NADPH oxidases appears to be a predominant contributor of superoxide anion. Recent findings suggest a significant role of the genetic background in NADPH oxidase regulation. Common genetic polymorphisms within the promoter and exonic sequences of CYBA, the gene that encodes the p22(phox) subunit of NADPH oxidase, have been characterized in the context of cardiovascular diseases. This review aims to present the current state of research into these polymorphisms in their relationship to cardiovascular diseases.

NAD(P)H oxidase p22phoxC242T polymorphism and ischemic stroke in Japan: the Fukuoka Stroke Registry and the Hisayama study

The C242T polymorphism of p22phox, a component of NAD(P)H oxidase, may have an impact on cardiovascular diseases; however, the association between this polymorphism and brain infarction is not fully understood. Here, we investigate the relationship between the C242T polymorphism and brain infarction in Japan. We recruited 1055 patients with brain infarction and 1055 control subjects. A chi-squared test revealed that the T-allele frequency was lower in patients with cardioembolic infarction (5.6%) than in control subjects (11.0%, P < 0.001); however, allele frequencies in patients with lacunar and atherothrombotic infarction (11.2%) were not significantly different from those in control subjects (11.0%). A multivariate-adjusted conditional logistic regression analysis also revealed no association between CT + TT genotype, and lacunar and atherothrombotic infarction (odds ratio = 0.97, 95% confidence interval: 0.72-1.32). To investigate the functional effects of the C242T polymorphism, we examined superoxide production in COS-7 cells cotransfected with Nox4 and p22phox of each genotype. The superoxide-producing activity in those cells expressing p22phox with the T allele was not significantly different from that in cells expressing p22phox with the C allele. The present results suggest that the p22phox C242T polymorphism may have a protective effect against cardioembolic infarction, but is not related to lacunar and atherothrombotic infarction in Japan.

The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology

For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the phagocyte NADPH oxidase itself (NOX2/gp91(phox)), the homologs are now referred to as the NOX family of NADPH oxidases. These enzymes share the capacity to transport electrons across the plasma membrane and to generate superoxide and other downstream reactive oxygen species (ROS). Activation mechanisms and tissue distribution of the different members of the family are markedly different. The physiological functions of NOX family enzymes include host defense, posttranlational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. NOX enzymes also contribute to a wide range of pathological processes. NOX deficiency may lead to immunosuppresion, lack of otoconogenesis, or hypothyroidism. Increased NOX activity also contributes to a large number or pathologies, in particular cardiovascular diseases and neurodegeneration. This review summarizes the current state of knowledge of the functions of NOX enzymes in physiology and pathology.

NAD(P)H oxidase polymorphism (C242T) and high HDL cholesterol associate with recurrent coronary events in postinfarction patients

We recently identified a subgroup of postinfarction patients at high-risk for recurrent coronary events defined by inflammation (high C-reactive protein) (CRP) and hypercholesterolemia. Within this subgroup, only elevated high-density lipoprotein cholesterol (HDL-C) from a set of metabolic, inflammatory and thrombogenic blood markers was associated with additional risk. To investigate the role of oxidative stress in this high-risk subgroup, we examined effects on risk of a polymorphism known to affect functional activity of NAD(P)H oxidase, an oxidative enzyme associated with generation of reactive oxygen species. The study population comprised non-diabetic patients of thrombogenic factors and recurrent coronary events (THROMBO) postinfarction study having complete blood marker and genotyping results (N=663) for C242T polymorphism of p22phox subunit (T allele associated with decreased activity). Cox multivariable regression, adjusted for significant clinical covariates, was used to assess within-subgroup risk associated with blood markers and polymorphism. In addition to elevated HDL-C (hazard ratio, 95% CI and p-value; 2.62, 1.05-6.55 and 0.039), significant independent risk was found for C242T (CC versus CT plus TT: 3.14, 1.34-7.35 and 0.0084). We conclude that oxidative stress plays a significant role in establishment of risk for recurrent coronary events in a high-risk subgroup of postinfarction patients defined by inflammation and hypercholesterolemia.

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.

Combined effects of apoE-CI-CII cluster and LDL-R gene polymorphisms on chromosome 19 and coronary artery disease risk

OBJECTIVE

To investigate associations of gene polymorphisms of the apoE-CI-CII gene cluster and the LDL-R gene on coronary artery disease (CAD) and their interactions with alcohol drinking and smoking in the Chinese Han population.

METHODS

A questionnaire survey of the behaviors of smoking and drinking, dietary patterns and anamnesis was conducted among 203 patients of CAD, aged 65.0 +/- 11.1 years, and 365 controls, aged 63.6 +/- 12.0 years. Peripheral blood samples were colleted and the total DNA was extracted. The apoE genotypes were identified by multiplex amplification refractory mutation system (multi-AMRS), the apoCI promoter polymorphisms and AvaII polymorphisms of the apoCII and LDL-R gene were detected by using PCR-RFLP. Pairwise linkage disequilibrium coefficients (D, D') were estimated by the LINKAGE program. The interactions between genes with alcohol drinking and smoking were analyzed by using multivariate logistic regression models.

RESULTS

The differences of systolic/diastolic blood pressure, total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) concentrations, smoking and drinking were significant between subjects with CAD and controls. The frequencies of apoE gene epsilon 3/4 genotype (25.9%) and epsilon 4 (13.9%) in CAD were significantly higher than those in controls (12.5% and 6.9%, respectively, p < 0.05). A significant difference was also found for the apoCI locus, the frequencies of H2 allele were 20.5% in the CAD and 11.3% in the control. Linkage disequilibrium coefficient D' was 0.672 (p < 0.01) between apoE and apoCI genes. Significant differences for a deficit of epsilon 3-H1-T1 and excess of epsilon 4-H2-T1 was found in CAD by estimation of the haplotype frequencies. After control for possible confounding factors, the multivariate logistic analysis showed that epsilon 4, H2 allele, smoking and drinking were risk factors of CAD. A significant interaction among epsilon 4, H2 and smoking was observed (OR 18.3, 95% CI: 2.35-150.81, p < 0.05), it was a multiplicative model. An additive model was shown among epsilon 4, H2 and drinking (OR12.7, 95% CI: 2.8-58.6, p < 0.05).

CONCLUSION

The results suggested that both apoE and apoCI on chromosome 19 were the susceptibility locus for CAD, their linkage disequilibrium should be responsible for the development of CAD. Drinking and smoking enhance the genetic predisposition to CAD.

Identification of Genetic Factors and Development of Genetic Risk Diagnosis Systems for Cardiovascular Diseases and Stroke

BACKGROUND

Polymorphisms of GJA4 and CYBA and of PAI1 and MMP3 are associated with myocardial infarction (MI) in men and women, respectively. In addition, several polymorphisms associated with restenosis after percutaneous coronary intervention, coronary artery spasm, or hypertension have been identified. More recently, a large genetic epidemiological study was performed to identify additional gene polymorphisms that confer susceptibility to cardiovascular diseases, stroke, and other complex diseases.

METHODS AND RESULTS

The relationship of 202 polymorphisms in 152 candidate genes to MI, hypertension, ischemic or hemorrhagic stroke, metabolic syndrome, type 2 diabetes mellitus, obesity, or in-stent restenosis were examined in 5,000 unrelated Japanese individuals. Of these, 14 polymorphisms related to MI, 8 to atherothrombotic cerebral infarction, 9 to intracerebral hemorrhage, and 10 to subarachnoid hemorrhage were identified. This information was then used to develop risk diagnosis systems to predict the future risk for development of each disease in a given individual.

CONCLUSIONS

Identification of gene polymorphisms that confer susceptibility to cardiovascular diseases or stroke and the development of genetic risk diagnosis systems may contribute to the personalized prevention of these conditions.

Release of free F2-isoprostanes from esterified phospholipids is catalyzed by intracellular and plasma platelet-activating factor acetylhydrolases

F2-isoprostanes are produced in vivo by nonenzymatic peroxidation of arachidonic acid esterified in phospholipids. Increased urinary and plasma F2-isoprostane levels are associated with a number of human diseases. These metabolites are regarded as excellent markers of oxidant stress in vivo. Isoprostanes are initially generated in situ, i.e. when the arachidonate precursor is esterified in phospholipids, and they are subsequently released in free form. Although the mechanism(s) responsible for the release of free isoprostanes after in situ generation in membrane phospholipids is, for the most part, unknown, this process is likely mediated by phospholipase A2 activity(ies). Here we reported that human plasma contains an enzymatic activity that catalyzes this reaction. The activity associates with high density and low density lipoprotein and comigrates with platelet-activating factor (PAF) acetylhydrolase on KBr density gradients. Plasma samples from subjects deficient in PAF acetylhydrolase do not release F2-isoprostanes from esterified precursors. The intracellular PAF acetylhydrolase II, which shares homology to the plasma enzyme, also catalyzes this reaction. We found that both the intracellular and plasma PAF acetylhydrolases have high affinity for esterified F2-isoprostanes. However, the rate of esterified F2-isoprostane hydrolysis is much slower compared with the rate of hydrolysis of other substrates utilized by these enzymes. Studies using PAF acetylhydrolase transgenic mice indicated that these animals have a higher capacity to release F2-isoprostanes compared with nontransgenic littermates. Our results suggested that PAF acetylhydrolases play key roles in the hydrolysis of F2-isoprostanes esterified on phospholipids in vivo.

Mechanism and effect of thrombospondin-4 polymorphisms on neutrophil function

High-throughput genomic technology identified an association between a single nucleotide polymorphism (SNP), a proline (P387) rather than the predominant alanine (A387) at position 387 in thrombospondin-4 (TSP-4) and premature myocardial infarction. The inflammatory hypothesis of atherosclerosis invokes a prominent role of leukocytes and cytokines in pathogenesis. As the expression of TSP-4 by vascular cells permits its exposure to circulating leukocytes, the interactions of human neutrophils (polymorphonuclear leukocytes [PMNs]) with both TSP-4 variants were investigated. Phorbol 12-myristate 13-acetate (PMA)-stimulated PMNs adhered and migrated well and equally on the TSP-4 variants. Integrin alpha(M)beta2 was identified as the TSP-4 receptor mediating these responses, and the 3 epidermal growth factor (EGF)-like domains of TSP-4 harboring the SNPs interacted with the alpha(M)I-domain. Despite the similarity in these responses, the P387 variant induced more robust tyrosine phosphorylation of the stress-related mitogen-activated protein kinases (MAPKs): p38MAPK and c-Jun NH2-terminal kinase (JNK), as well as signal transducer and activator of transcription-1 (STAT1) and heat shock protein 27 (HSP27) than the A387 variant. Additionally, cells adherent to P387 TSP-4 variant released 4-fold more H2O2 and secreted 2-fold more interleukin 8 (IL-8) as compared with the A387. H2O2 release and p38MAPK activation were totally inhibited by blockade of alpha(M)beta2. Thus, alpha(M)beta2 plays a central role in proinflammatory activities of TSP-4 (P387) and may contribute to the prothrombotic phenotype associated with this variant.