Oxidized phospholipids and lipoprotein-associated phospholipase A_2 as important determinants of Lp(a) functionality and pathophysiological role

Lipoprotein（a） [Lp（a）] is composed of a low density lipoprotein（LDL）-like particle to which apolipoprotein（a）[apo（a）] is linked by a single disulfide bridge. Lp（a） is considered a causal risk factor for ischemic cardiovascular disease（CVD） and calcific aortic valve stenosis（CAVS）. The evidence for a causal role of Lp（a） in CVD and CAVS is based on data from large epidemiological databases, mendelian randomization studies, and genome-wide association studies. Despite the well-established role of Lp（a） as a causal risk factor for CVD and CAVS, the underlying mechanisms are not well understood. A key role in the Lp（a） functionality may be played by its oxidized phospholipids（OxPL） content. Importantly, most of circulating OxPL are associated with Lp（a）; however, the underlying mechanisms leading to this preferential sequestration of OxPL on Lp（a） over the other lipoproteins,are mostly unknown. Several studies support the hypothesis that the risk of Lp（a） is primarily driven by its OxPL content.An important role in Lp（a） functionality may be played by the lipoprotein-associated phospholipase A_2（Lp-PLA_2）,an enzyme that catalyzes the degradation of OxPL and is bound to plasma lipoproteins including Lp（a）. The present review article discusses new data on the pathophysiological role of Lp（a） and particularly focuses on the functional role of OxPL and Lp-PLA_2 associated with Lp（a）.

Lipoprotein-associated phospholipase A2 prognostic role in atherosclerotic complications

Atherosclerosis manifests itself clinically at advanced stages when plaques undergo hemorrhage and/or rupture with superimposed thrombosis, thus abruptly stopping blood supply. Identification of markers of plaque destabilization at a pre-clinical stage is, therefore, a major goal of cardiovascular research. Promising results along this line were provided by studies investigating the lipoprotein-associated phospholipase A2(Lp-PLA2), a member of phospholipase A2 proteins family that plays a key role in the metabolism of pro-inflammatory phospholipids, as oxidized low-density lipoproteins, and in the generation of pro-atherogenic metabolites, including lysophosphatidylcholine and oxidized free fatty acids. We herein review the experimental and clinical studies supporting use of Lp-PLA2 activity for predicting cardiovascular events. To his end we considered not only Lp-PLA2 activity and mass, but also Lp-PLA2 gene variations and their association with incident coronary artery disease, stroke, and cardiovascular mortality. Based on these evidences the major scientific societies have included in their guidelines the measurement of Lp-PLA2 activity among the biomarkers that are useful in risk stratification of adult asymptomatic patients at intermediate cardiovascular risk. The results of two recently published major clinical trials with the LpPLA2 inhibitor darapladib, which seem to challenge the pathogenic role of Lp-PLA2, will also be discussed.

The Use of Lipoprotein-Associated Phospholipase A2 in a Chinese Population to Predict Cardiovascular Events

Objective To explore associations between lipoprotein-associated phospholipase A2(Lp-PLA2)and the risk of cardiovascular events in a Chinese population,with a long-term follow-up.Methods A random sample of 2,031 participants(73.6%males,mean age=60.4 years)was derived from the Asymptomatic Polyvascular Abnormalities Community study(APAC)from 2010 to 2011.Serum Lp-PLA2 levels were determined by enzyme-linked immunosorbent assay(ELISA).The composite endpoint was a combination of first-ever stroke,myocardial infarction(MI)or all-cause death.Lp-PLA2 associations with outcomes were assessed using Cox models.Results The median Lp-PLA2 level was 141.0 ng/m L.Over a median follow-up of 9.1 years,we identified 389 events(19.2%),including 137 stroke incidents,43 MIs,and 244 all-cause deaths.Using multivariate Cox regression,when compared with the lowest Lp-PLA2 quartile,the hazard ratios with95%confidence intervals for developing composite endpoints,stroke,major adverse cardiovascular events,and all-cause death were 1.77(1.24–2.54),1.92(1.03–3.60),1.69(1.003–2.84),and 1.94(1.18–3.18)in the highest quartile,respectively.Composite endpoints in 145(28.6%)patients occurred in the highest quartile where Lp-PLA2(159.0 ng/m L)was much lower than the American Association of Clinical Endocrinologists recommended cut-off point,200 ng/m L.Conclusion Higher Lp-PLA2 levels were associated with an increased risk of cardiovascular event/death in a middle-aged Chinese population.The Lp-PLA2 cut-off point may be lower in the Chinese population when predicting cardiovascular events.

Research Advance of Chinese Medicine in Treating Atherosclerosis:Focus on Lipoprotein-Associated Phospholipase A2

As a serious cardiovascular disease,atherosclerosis(AS)causes chronic inflammation and oxidative stress in the body and poses a threat to human health.Lipoprotein-associated phospholipase A2(Lp-PLA2)is a member of the phospholipase A2(PLA2)family,and its elevated levels have been shown to contribute to AS.Lp-PLA2 is closely related to a variety of lipoproteins,and its role in promoting inflammatory responses and oxidative stress in AS is mainly achieved by hydrolyzing oxidized phosphatidylcholine(ox PC)to produce lysophosphatidylcholine(lyso PC).Moreover,macrophage apoptosis within plaque is promoted by localized Lp-PLA2 which also promotes plaque instability.This paper reviews those researches of Chinese medicine in treating AS via reducing Lp-PLA2 levels to guide future experimental studies and clinical applications related to AS.

表观健康人群血清脂蛋白相关磷脂酶A_2参考区间的建立

目的建立上海地区表观健康人群血清脂蛋白相关磷脂酶A_2(Lp-PLA_2)的参考区间。方法检测800名健康体检者(男、女性各400名)血清Lp-PLA_2活性,根据美国临床实验室标准化协会(CLSI)C28-A3文件的相关要求,以百分位数法确定Lp-PLA_2的95%参考区间[第2.5百分位数(P2.5)~第97.5百分位数(P97.5),可信区间为90%]。结果表观健康人群血清Lp-PLA_2活性呈正态分布。男性Lp-PLA_2活性为(479±126)U/L,女性为(433±118)U/L,二者间差异有统计学意义(t=5.311,P<0.01)。男性血清LpPLA_2活性保持恒定,女性血清Lp-PLA_2活性随年龄的增加而呈升高趋势,各年龄段Lp-PLA_2活性比较差异有统计学意义(F=2.017,P<0.05)。进一步分析显示<50岁的各年龄组之间和≥50岁的各年龄组之间Lp-PLA_2活性差异均无统计学意义(P>0.05),因此将女性各年龄组合并为18~49岁组和50~89岁组。由此得出上海地区表观健康人群血清Lp-PLA_2的参考区间男性为219~694 U/L,女性18~49岁为204~651 U/L、50~89岁为217~686 U/L。结论初步建立了上海地区表观健康人群血清Lp-PLA_2的参考区间,为临床应用Lp-PLA_2作为心血管疾病风险评估指标提供依据。

Correlation study of serum Lp-PLA2 and NSE levels with nerve injury degree and lipid metabolism change in patients with acute cerebral infarction

Objective:To study the correlation of serum Lp-PLA2 and NSE levels with nerve injury degree and lipid metabolism change in patients with acute cerebral infarction.Methods: Patients diagnosed with acute cerebral infarction in our hospital between March 2014 and October 2016 were selected as the cerebral infarction group of the study, and healthy subjects receiving physical examination during the same period were selected as control group. Serum was collected to determine the levels of Lp-PLA2 and NSE as well as the content of nerve injury molecules and lipid metabolism molecules.Results:Serum Lp-PLA2, NSE, NO, MDA, LPO, 8-OHdG, ox-LDL, LDL-C and ApoB levels of cerebral infarction group were significantly higher than those of control group while HDL-C and ApoA1 content were significantly lower than those of control group;serum NO, MDA, LPO and 8-OHdG content of patients with NSE>Q3 were significantly higher than those of patients with<Q1, Q1-Q2 and Q2-Q3, serum NO, MDA, LPO and 8-OHdG content of patients with Q2-Q3 were significantly higher than those of patients with<Q1 and Q1-Q2, and serum NO, MDA, LPO and 8-OHdG content of patients with Q1-Q2 were significantly higher than those of patients with<Q1;serum ox-LDL, LDL-C and ApoB content of patients with Lp-PLA2>Q3 were significantly higher than those of patients with<Q1, Q1-Q2 and Q2-Q3 while HDL-C and ApoA1 content were significantly lower than those of patients with<Q1, Q1-Q2 and Q2-Q3;serum ox-LDL, LDL-C and ApoB content of patients with Q2-Q3 were significantly higher than those of patients with <Q1 and Q1-Q2 while HDL-C and ApoA1 content were significantly lower than those of patients with<Q1 and Q1-Q2;serum ox-LDL, LDL-C and ApoB content of patients with Q1-Q2 were significantly higher than those of patients with<Q1 while HDL-C and ApoA1 content were significantly lower than those of patients with<Q1.Conclusion: Serum Lp-PLA2 and NSE levels increase significantly in patients with acute cerebral infarction, the increase of Lp-PLA2 is associated with abnormal lipid metabolism, and the increase of NSE is associated with neural oxidative damage.

Elevated plasma lipoprotein-associated phospholipase A2 activity is associated with plaque rupture in patients with coronary artery disease

Background Lipoprotein-associated phospholipase A2 （Lp-PLA2） has recently been shown to be positively related to coronary events in patients with coronary artery disease （CAD）. However, direct evidence about the relationship between circulation Lp-PLA2 activity and vulnerable plaque in patients with CAD remains lacking. Methods Plasma Lp-PLA2 activity was determined in 146 consecutive patients with CAD who underwent clinically-indicated coronary angiography and preinterventional intravascular ultrasound （IVUS）. Results Eighty-three patients were included in the final analysis after the initial screening. Sixty （72.3%） were acute coronary syndrome （ACS） patients and 23 （27.7%） were stable angina pectoris （SAP） patients. Plaque rupture occurred in 39 （47.0%） patients, and 34 （87.2%） were from ACS patients and 5 （12.8%） from SAP patients. There were no significant differences in clinical and angiographic characteristics between patients with plaque rupture and those without plaque rupture, except for smoking, high-sensitive C-reactive protein （hs-CRP） level and Lp-PLA2 activity （all P 〈0.05）. IVUS measurement uncovered that patients with plaque rupture had more frequent positive remodeling （74.4% vs. 43.2%, P=0.004）, soft plaques （64.1% vs. 36.4%, P=-0.012） and higher remodeling index （1.13~0.16 vs. 0.99＋_0.11, P=0.041） as compared with those without plaque rupture. Multivariate Logistic regression analysis showed that plasma Lp-PLA2 activity was independently associated with plaque rupture after adjusting for smoking, positive remodeling and soft plaque （Model 1： odds ratio （OR） 1.13, 95% confidence interval （CO ： 1.06-1.20） or adjusting for smoking, hs-CRP level, positive remodeling and soft plaque （Model 2： OR 1.11,95%C1： 1.04-1.19）. Conclusions Plasma Lp-PLA2 activity is associated with plaque rupture in patients with CAD, independently of traditional CAD risk factors, hs-CRP level and IVUS parameters. Lp-PLA2 may be a risk marker for vulnerable plaques.

Study on the correlation between the concentration of plasma lipoprotein-associated phospholipase A2 and coronary heart disease

Objective: This study explores the correlation between plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) and coronary heart disease (CHD) by comparing the level of plasma Lp-PLA2 in the plasma of patients with different types of CHD. Methods: Blood samples were collected from 56 patients diagnosed with CHD by the Department of Cardiology of the First People's Hospital of Foshan and 34 healthy subjects from February 2013 to January 2014. We measured the concentration of plasma Lp-PLA2 and determined the levels of total cholesterol (Tch), triglyceride (TG), apolipoprotein A1 (Apo-A1), apolipoprotein B (Apo-B), high density lipoprotein-cholesterol (HDL-c), low density lipoprotein-cholesterol (LDL-c), lipoprotein a (Lp(a)), glucose (Glu), and high-sensitivity C-reactive protein (hs-CRP). The concentration of plasma Lp-PLA2 in the healthy control group and each subgroup of CHD patients were compared and analyzed for correlations of plasma Lp-PLA2 between the patients in different CHD subgroups and several laboratory indicators. Results: The concentration of plasma Lp-PLA2 in each subgroup of CHD was significantly higher than in the control group (P<0.05). The concentration of Lp-PLA2 in the unstable angina pectoris (UAP) group and acute myocardial infarction (AMI) group were significantly higher than in the stable angina pectoris (SAP) group (P<0.05), and the concentration of plasma Lp-PLA2 in the AMI group was significantly higher than in the UAP group (P<0.05). The concentration of plasma Lp-PLA2 in the CHD group merely showed a positive correlation (r ? 0.493, P<0.05) with the hs-CRP group, but the levels of Tch, TG, Apo-A1, Apo-B, HDL-c, LDL-c, Lp(a) and Glu did not. Conclusions: The concentration of plasma Lp-PLA2 in patients with CHD was higher than that in the control group. The concentration of plasma Lp-PLA2 in the subgroups of CHD patients varied greatly from each other. The inflammatory response of atherosclerosis might be resulted from the synergy of plasma Lp-PLA2 and hs-CRP. Copyright ? 2015, Chinese Medical Association Production. Production and hosting by Elsevier B.V. on behalf of KeAi Com-munications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

糖尿病冠状动脉粥样硬化性心脏病患者测定血清脂蛋白相关磷脂酶A2和血脂水平的临床价值

目的：探讨糖尿病冠状动脉粥样硬化性心脏病（简称糖尿病冠心病）患者血清脂蛋白相关磷脂酶A2（Lp-PLA2）和血脂（TG、HDL-C、LDL-C、Lp（a）、ApoA1、ApoB和ApoB/ApoA1比值）水平的临床价值。方法采用酶联免疫分析、生化法和免疫比浊分析测定157例糖尿病冠心病患者血清Lp-PLA2和血脂水平，并与60名健康对照组进行比较性分析。受试者工作曲线（ROC曲线）分析血清Lp-PLA2、TG、HDL-C、LDL-C、Lp（a）、ApoA1、ApoB水平，并进行预测冠状动脉粥样硬化性心血管疾病（CVD）的性能评估。结果糖尿病冠心病患者血清Lp-PLA2、TG、LDL-C、Lp（a）、ApoB和ApoB/ApoA1比值水平明显增高，而血清HLD-C、ApoA1水平稍降低。ROC曲线分析表明：血清Lp-PLA2、LDL-C、ApoA1和ApoB水平具有预测冠状动脉硬化性CVD性能的价值，并以血清Lp-PLA2为最佳。结论糖尿病冠心病的特点是血糖和血脂代谢紊乱，胰岛素抵抗和高尿酸血症，血清Lp-PLA2、LDL-C、ApoA1、ApoB和ApoB/ApoA1比值测定具有早期诊断的临床价值，血清Lp-PLA2、LDL-C、ApoA1和ApoB水平是预测冠心病心血管事件的有价值指标。

High density lipoprotein suppresses lipoprotein associated phospholipase A2 in human monocytes-derived macrophages through peroxisome proliferator-activated receptor-γ pathway

Background Lipoprotein-associated phospholipase A2 （Lp-PLA2） is mainly secreted by macrophages, serving as a specific marker of atherosclerotic plaque and exerting pro-atherogenic effects. It is known that high-density lipoprotein （HDL） plays an important role against atherosclerosis by inhibiting pro-inflammatory factors, however, the relationship between HDL and Lp-PLA2 remains elusive. Methods In this study, reverse transcription-polymerase chain reaction （RT-PCR）, Western blotting, and a platelet-activating factor （PAF） acetylhydrolase assay were performed to determine the Lp-PLA2 mRNA level, protein expression and activity in human monocyte-derived macrophages upon HDL treatment of different concentrations and durations. To investigate the underlying mechanism of HDL-induced Lp-PLA2 action, pioglitazone, a peroxisome proliferator-activated receptor-γ （PPARy） ligand, was introduced to human monocyte-derived macrophages and mRNA and protein levels of Lp-PLA2, as well as its activity, were determined. Results Lp-PLA2 mRNA levels, protein expression and activity were significantly inhibited in response to HDL treatment in a dose and time dependent manner in human monocyte-derived macrophages. Pioglitazone treatment （1-10 ng/ml） upregulated the Lp-PLA2 mRNA level, protein expression and activity in human monocyte-derived macrophages, while the effects were markedly reversed by HDL. In addition, pioglitazone resulted in a significant increase in PPARy phosphorylation in human monocyte-derived macrophages, which could be inhibited by HDL. Conclusion These findings indicate that HDL suppresses the expression and activity of Lp-PLA2 in human monocyte-derived macrophages, and the underlying mechanisms may be mediated through the PPARγ pathway.

Relationship of plasma level of Lp-PLA_2 and pulse wave velocity and carotid intima-media thickness

Background Increased plasma level of Lp-PLA2 is a potential risk factor for atherosclerosis. Nevertheless, whether Lp-PLA2 has effects on both vascular function and structure changes is still unclear. Method One hundred and eighty-six outpatient subjects without overt cardiovascular disease were enrolled and anthropomet- ric data, plasma level of Lp-PLA2 and other related laboratory parameters were collected. Measurements of pulse wave velocity （PWV） and carotid intima-media thickness （CIMT） were performed by an experienced investigator. According to plasma level of Lp-PLA2, all the subjects were divided into two groups as follows： 〈 200 ng/mL （n = 96） and ≥200 ng/mL （n = 90）. Result Body mass index, smoking, diabetic mellitus, systolic blood pressure, and LDL-C level were positive correlation with plasma level of Lp-PLA2, while use of statins was negatively correlative. Both PWV and CIMT positively correlated with smoking, systolic blood pressure, LDL-C level and plasma level of Lp-PLA2, while negatively correlated with HDL-C level and usage of statins. CIMT in the group with plasma level of Lp-PLA2 〈 200 ng/mL （0.9 ± 0.2 mm, n = 96） was sig- nificantly less than that with plasma level of Lp-PLA2≥200 ng/mL （1.2 ±0.4 mm, n = 90, P = 0.32）, and similar finding was also observed in PWV （9.1± 0.5 m/s vs 12.7 ± 0.4 m/s, P = 0.38）. Conclusion Our present study shows that in subjects without overt CVD, increased plasma level of Lp-PLA2 is associated with vascular function （PWV） and structure （CIMT） deterioration.

Design and Synthesis of Novel Pyrazole-based Lp-PLA2 Inhibitors

A series of novel pyrazole-based lipoprotein-associated phospholipase A2 （Lp-PLA2） inhibitors have been de- signed and synthetized by a variety of acetophenones via a 10-step convergent approach. The synthetic approach is carefully optimized, and an unsuccessful alternative route is also discussed. The in vitro biological activity reveals that all the synthesized compounds are potent Lp-PLA2 inhibitors with compound 13b being the most potent one （Lp-PLA2, IC50= 1.5 nmol/L）.

Why does a high-fat diet induce preeclampsia-like symptoms in pregnant rats?

Changes in neurotransmitter levels in the brain play an important role in epilepsy-like attacks after pregnancy-induced preeclampsia-eclampsia. Metabotropic glutamate receptor 1 participates in the onset of lipid metabolism disorder-induced preeclampsia. Pregnant rats were fed with a high-fat diet for 20 days. Thus, these pregnant rats experienced preeclampsia-like syndromes such as hyper-tension and proteinuria. Simultaneously, metabotropic glutamate receptor 1 mRNA and protein ex-pressions were upregulated in the rat hippocampus. These findings indicate that increased expres-sion of metabotropic glutamate receptor 1 promotes the occurrence of high-fat diet-induced pree-clampsia in pregnant rats.

Change of Inflammatory Factors in Patients with Acute Coronary Syndrome

Background： Acute coronary syndrome （ACS） is closely related to unstable plaques and secondary thrombosis. The inflammatory cells in plaques and their inflammatory products may be the cause for plaque instability and ruptures. The study aimed to disclose the changes of inflammatory factors including serum intracellular adhesion molecule-1（ICAM-1 ）, chitinase-3-like protein I （YKL-40）, and lipoprotein-associated phospholipase A2 （Lp-PLA2） in patients with ACS and its clinical significance. Methods： A total of 120 patients with coronary heart disease （CHD） were categorized into 2 groups： 69 with ACS and 51 with stable angina pectoris （SAP）： 20 patients with chest pain and normal angiography served as a control group. The 120 patients with CHD were categorized into single-vessel disease group, double-vessel disease group, and three-vessel disease group based on the number of coronary artery stenosis. The severity of coronary artery stenosis was quantified based on coronary angiography using Gensini score. They were further divided into mild CHD group with its Gensini score 〈26 （n = 36）, moderate CHD group with its Gensini score being 26-54 （n = 48） and severe CHD group with its Gensini score 〉54 （n = 36）. Serum levels of ICAM-1, YKL-40, and Lp-PLA2 of different groups were determined by enzyme-linked immunosorbent assay. Correlation between ICAM-1, YKL-40, Lp-PLA2, and Gensini score was analyzed. Results： The levels of serum inflammatory factors ICAM-1, YKL-40, and Lp-PLA2 were significantly higher in the ACS group than those in control group and SAP group （all P 〈 0.05）： and compared with control group, no significant difference was observed in terms of the serum ICAM-1, YKL-40, and Lp-PLA2 levels in the SAP group （P 〉 0.05）.The levels of serum ICAM-1, YKL-40, and Lp-PLA2 were not significantly different among control group, single-vessel disease group, double-vessel disease group, and three-vessel disease group （all P 〉 0.05）. The levels of serum ICAM-1, YKL-40, and Lp-PLA2 were not significantly different among control group, mild CHD group （Gensini score 〈26）, moderate CHD group （Gensini score 26-54）, and severe CHD group （Gensini score 〉54） （all P 〉 0.05）. Nonparametric Spearman correlation analysis showed that the levels of serum ICAM-1, YKL-40, and Lp-PLA2 were not correlated with the Gensini score in CHD patients （r=0.093, r=-0.149, and r= -0.085, all P 〉 0.05; respectively）. Conclusions： The serum levels of ICAM-1, YKL-40, and Lp-PLA2 were correlated with different clinical types of CHD, but not well correlated the severity and extent of artery stenosis, suggesting that ICAM-1, YKL-40, and Lp-PLA2 rnight be involved in occurrence of instability of atherosclerotic plaque, and might reflect the severity of CHD mostly through reflecting the plaque stability.

Relationship between Two Blood Stasis Syndromes and Inflammatory Factors in Patients with Acute Coronary Syndrome

Objective： To investigate the relationship between inflammatory factors and two Chinese medicine（CM） syndrome types of qi stagnation and blood stasis（QSBS） and qi deficiency and blood stasis（QDBS） in patients with acute coronary syndrome（ACS）. Methods： Sixty subjects with ACS, whose pathogenesis changes belongs to qi disturbance blood stasis syndrome, were divided into 2 groups： 30 in the QSBS group and 30 in the QDBS group. The comparative analysis on them was carried out through comparing general information, coronary angiography and inflammatory factors including intracellular adhesion molecule-1（ICAM-1）, chitinase-3-like protein 1（YKL-40） and lipoprotein-associated phospholipase A2（Lp-PLA2）. Results： Compared with the QSBS group, Lp-PLA2 and YKL-40 levels in the QDBS group showed no-significant difference（P〉0.05）; ICAM-1 was significantly higher in the QDBS group than in the QSBS group in the pathological processes of qi disturbance and blood stasis syndrome of ACS（P〈0.05）. Conclusion： Inflammatory factor ICAM-1 may be an objective basis for syndrome typing of QSBS and QDBS, which provides a research direction for standardization research of CM syndrome types.