Lipoprotein-associated phospholipase A2 as a biomarker for coronary disease and stroke

B. Comparison of Different Vascular Biomarkers for Predicting In-Hospital Mortality in Severe SARS-CoV-2 Infection

Severe SARS-CoV-2 elicits a hyper-inflammatory response that results in intravascular inflammation with endothelial injury, which contributes to increased mortality in COVID-19. To predict the outcome of severe SARS-CoV-2 infection, we analyzed the baseline level of different biomarkers of vascular disorders in COVID-19 subjects upon intensive care unit (ICU) admission and prior to any vaccination. A total of 70 severe COVID-19 patients (37 survivors and 33 non-survivors) were included with 16 age- and sex-matched controls. Vascular dysfunction was monitored via soluble VCAM-1, E-selectin, ACE2 and Lp-PLA2, while abnormal platelet activation was evaluated by soluble P-selectin and CD40L in parallel. These results were correlated with routine laboratory parameters and disease outcomes. Among these parameters, VCAM-1 and ACE2 showed significantly higher serum levels in COVID-19 patients with early death vs. convalescent subjects. VCAM-1 was significantly correlated with the Horowitz index (r = 0.3115) and IL-6 (r = 0.4599), while ACE2 was related to E-selectin (r = 0.4143) and CD40L (r = 0.2948). Lp-PLA2 was altered in none of these COVID-19 subcohorts and showed no relationship with the other parameters. Finally, the pre-treatment level of VCAM-1 (≥1420 ng/mL) and ACE2 activity (≥45.2 μU/mL) predicted a larger risk for mortality (Log-Rank p = 0.0031 and p = 0.0117, respectively). Vascular dysfunction with endothelial cell activation is linked to lethal COVID-19, and highly elevated soluble VCAM-1 and ACE2 at admission to ICU may predict unfavorable outcomes.

Lp-PLA2 as a biomarker and its possible associations with SARS-CoV-2 infection

Lp-PLA2 is an enzyme encoded by the PLA2G7 gene located at chromosome 6p12-21, which is included in different signal transduction pathways. The potential of serum levels of Lp-PLA2 as a marker of inflammation quantifying cardio-metabolic risk, renal impairment and oxidative stress has been explored in earlier studies. It has also been used in chronic obstructive pulmonary disease, hepatic disease, metabolic conditions and exercise tolerance. Additionally, it shows promising evidence for the assessment of risk for certain cardiovascular conditions in otherwise seemingly healthy individuals. COVID-19 has affected life and the economy globally. The identification of biomarkers to assess the sickness and treatment plan is the need of the hour. This review summarizes the pathophysiological inter-relationship between serum levels of Lp-PLA2 and COVID-19. The authors hypothesize that the estimation of Lp-PLA2 levels may help in the early identification of risk and thus may play a beneficial role in the proactive management of COVID-19.

Serum levels of sLOX-1 and Lp-PLA2 can predict the prognosis of acute cerebral infarction with a high specificity

Soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1) and lipoprotein-associated phospholipase A2 (Lp-PLA2) plays an important role in acute cerebral infarction (ACI), whereas its clinical value in predicting the prognosis is unclear. Thus, this study aimed to explore this issue. A total of 127 ACI patients were included in this prospective observational study. The concentrations of sLOX-1 and Lp-PLA2 in serum were measured and their relationship with a poor prognosis 90 days after the onset of ACI was analyzed. We found that patients with poor prognosis had higher mean serum levels of sLOX-1 and Lp-PLA2. The level of sLOX-1 and Lp-PLA2 could predict the functional outcome of ACI. At the optimal cut off value of sLOX-1 level (1257.92 ng/ml), the sensitivity and specificity for the poor functional outcome were 0.69 and 0.753, respectively, and the area under ROC curve (AUC) was 0.727. Similarly, the optimal value for Lp-PLA2 level was 160.9 ng/ml, at which the sensitivity and specificity were 0.643 and 0.835, respectively; and the AUC was 0.758. When the two biomarkers were used in combination, the AUC was 0.855, and the sensitivity and specificity were 0.643 and 0.976, respectively, indicating a significant improvement of the diagnostic specificity. The level of sLOX-1 or Lp-PLA2 could thus serve as useful biomarkers to predict the functional outcome of ACI. Combined use of both indicators is better than the use of either single indicator, and provides the highest specificity in predicting poor prognosis.

Clinical Utility of the Serum Level of Lipoprotein-Related Phospholipase A2 in Acute Ischemic Stroke With Cerebral Artery Stenosis

We aimed to study the clinical utility of serum lipoprotein-associated phospholipase A2 (Lp-PLA2) in acute ischemic stroke (AIS) with cerebral artery stenosis (CAS). We included 200 AIS patients and 90 healthy controls in this study. AIS patients were classified into three subgroups depending on the severity of CAS. They were also classified based on the stability of the carotid plaques. Spearman correlation analysis was performed to determine the correlation relationship between the level of Lp-PLA2 and neurologic injury. Binary logistic regression analysis was performed to determine the independent risk factors for AIS. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic value of Lp-PLA2 for AIS and for the degree of CAS. We found that the serum level of Lp-PLA2 in AIS patients was significantly higher than that in the control group. Lp-PLA2 was further identified as an independent risk factor for AIS (p = 0.001, OR = 1.057). In addition, serum Lp-PLA2 level was the highest in AIS patients with severe CAS or occlusion. Lp-PLA2 level was higher in AIS patients with unstable plaques and in AIS patients with moderate to severe neurological injury. Lp-PLA2 level was positively correlated with National Institutes of Health Stroke Scale (NIHSS) score (r = 0.335, p = 0.001). We found that the optimal cut-off value for Lp-PLA2 level was 123.365 ng/ml, at which the sensitivity and specificity for the diagnosis of ACI were 74.5 and 86.7%, respectively, and the area under ROC curve (AUC) was 0.892. Similarly, the optimal value for Lp-PLA2 level was 136.46 ng/ml, at which the sensitivity and specificity for the diagnosis of the presence of moderate to severe artery stenosis or occlusion were 79.6 and 95.2%, respectively, and the AUC was 0.938. The ROC curve indicated that serum Lp-PLA2 level has an excellent diagnostic value for AIS and severe stenosis. Based on these results we conclude that Lp-PLA2 could be a potential biomarker to complement the current imaging methods in the prediction and diagnosis of AIS. An elevated Lp-PLA2 level is also correlated with carotid plaque instability, severe neurological injury and cerebrovascular stenosis. Future longitudinal studies are needed to determine whether there is a causative relationship between Lp-PLA2 and AIS.

Modulatory properties of cardiac and quercetin glycosides from Dacryodes edulis seeds during L-NAME-induced vascular perturbation

Background Numerous food wastes have been identified to possess potent bioactive compounds used for the treatment of several diseases. Therefore this study evaluated the potentials of cardiac and quercetin glycosides extracted from Dacryodes edulis seeds to reverse vascular and endothelial damage (VAED). Methods The glycoside composition of the seeds was extracted using standard methods and characterized by gas chromatography. We then recruited rats with L-NAME-induced VAED based on confirmatory biomarkers cardiac troponin (CnT), cellular adhesion molecule (VCAM-1), lipoprotein associated phospholipase A2 (Lp-PLA2), RAAS, VWF, endothelin, eNOx, and homocysteine. Only rats that showed total alterations of all biomarkers were recruited into the respective experimental groups and treated with either metaprolol succinate (met.su) + losartan or glycoside extracts of D. edulis seeds (NPSG). Results Chromatographic isolation of glycosides in the seed showed predominance of artemetin (1.59 mg/100 g), amygdalin (3.68 mg/100 g), digitoxin (19.21 mg/100 g), digoxin (27.23 mg/100 g), avicularin (133.59 mg/100 g), and hyperoside (481.76 mg/100 g). We observed decreased water intake and higher heart beats under vascular damage as the experiment progressed up to the fourth week. The met.su + losartan and H.D NPSG proved effective in restoring troponin, but both doses of NPSG normalized the VCAM-1 and RAAS activities excluding aldosterone and Lp-PLA2. Among the endothelial dysfunction biomarkers, H.D NPSG produced equivalent effects to met.su + losartan towards restoring the eNOx and VWF activities, but showed higher potency in normalizing the endothelin and Hcy levels. Conclusions We thus propose that the synergistic effect of the isolated glycosides from D. edulis shown in our study proved potent enough at high doses in treatment of vascular and endothelial dysfunction.

Resveratrol Treatment Is Associated with Lipid Regulation and Inhibition of Lipoprotein-Associated Phospholipase A2 (Lp-PLA2) in Rabbits Fed a High-Fat Diet

The effects of resveratrol on various conditions have been widely studied previously. This paper aimed to investigate the influence of resveratrol on atherosclerosis (AS). Twenty-four New Zealand male rabbits were randomly and equally assigned to the normal diet group (NDG), fat diet group (FDG), and fat diet with resveratrol group (80 mg/kg/d, RFG). Biochemical indicators from blood samples were analyzed at baseline and 3 months to investigate the effects of resveratrol on blood lipid, lipoprotein-associated phospholipase A2 (Lp-PLA2), liver, and renal function. The indicators including alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CREA), triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and Lp-PLA2. At 3 months, arteries were stained with hematoxylin and eosin to study the influence of resveratrol on the aortic intima, smooth muscle layer, and the intima/media ratio. Comparisons of weight, ALT, AST, CREA, TG, TC, HDL-C, LDL-C, and Lp-PLA2 among the three groups showed no significant difference at baseline. However, at the end of 3 months, significant differences were observed in AST, CREA, TC, HDL-C, LDL-C, and Lp-PLA2 between the three groups (P < 0.05). In pairwise comparison, CREA, TC, LDL-C, and Lp-PLA2 had significant differences between any two groups (P < 0.05). In addition, there were significant differences in the AST and HDL-C levels between RFG and NDG groups (P < 0.05). Meanwhile, the HDL-C levels were also significantly different between the FDG and NDG groups (P < 0.01). The histologic analysis also showed that the thickness of the aortic intima and the ratio of the intima and aortic tunica media (P < 0.05) significantly decreased in RFG compared to FDG. Resveratrol may have an antiatherosclerosis effect on a rabbit model of AS.

Association of Serum Lipoprotein-Associated Phospholipase A2 and A379V Gene Polymorphisms with Carotid Plaques

Objective: Lipoprotein-associated phospholipase A2 (LP-PLA2) is closely related to the development of atherosclerosis. The A379V gene polymorphism, located in exon 11 of the PLA2G7 gene, can affect LP-PLA2 levels and the inflammatory response. However, the association between the A379V polymorphism and formation of carotid plaques is unclear. Materials and Methods: A total of 516 ischemic stroke patients were classified according to carotid intima-media thickness as measured by ultrasound into the plaque group (n = 375, including 258 and 117 cases having vulnerable and stable plaques, respectively) and the nonplaque group (n = 141). The LP-PLA2 gene A379V polymorphism was determined by DNA sequencing, and Lp-PLA2 serum protein levels were determined simultaneously. Results: The serum Lp-PLA2 levels (p < 0.0005), CT+TT genotype frequency (odds ratio [OR]: 1.730, 95% confidence interval [CI]: 1.114-2.686, p = 0.014), and T allele frequency (OR: 1.592, 95% CI: 1.082-2.342, p = 0.018) in the plaque group were significantly higher than those in the nonplaque group. Lp-PLA2 serum levels in the vulnerable plaque subgroup were significantly higher than those in the stable plaque subgroup (p = 0.003). However, there were no significant differences in the frequency of the A379V polymorphism between the vulnerable and stable plaque subgroups. For all subjects, Lp-PLA2 serum levels for patients having a CC genotype were significantly lower than those for patients having a CT (p = 0.003), TT (p = 0.014), or CC+TT genotype (p = 0.001). Logistic regression showed that the Lp-PLA2 level was a risk factor for carotid plaque formation (OR: 1.024, 95% CI: 1.011-1.030, p = 0.001), but the A379V gene polymorphism was not (OR: 1.037, 95% CI: 0.357-3.012, p = 0.947). Conclusion: The A379V gene polymorphism might be associated with serum Lp-PLA2 levels and carotid plaque formation, but not with plaque vulnerability in a Chinese Han population. Serum Lp-PLA2 level was shown to be a risk factor for carotid plaque formation.

The elevated lipoprotein-associated phospholipase A2 activity is associated with the occurrence and recurrence of acute cerebral infarction

There is a strong association between lipoprotein-associated phospholipase A2 (Lp-PLA2) levels and atherosclerosis-related diseases. The aim of this study was to investigate the role of Lp-PLA2 in the ischemic stroke and further offer clinical evidence that measuring Lp-PLA2 helps predict the risk of stroke occurrence and recurrence. A total of 328 hospitalized patients were recruited, including 179 cases of acute cerebral infarction (ACI) and 149 non-ACI controls. The serum level of Lp-PLA2 in ACI was significantly higher than non-ACI. The serum level of Lp-PLA2 in the recurrence of ACI was significantly higher than the nonrecurrence. The serum levels of Lp-PLA2 in large-artery atherosclerosis subtype were the highest among the subtypes of the Trial of Org 10172 in Acute Stroke Treatment and non-ACI controls. The level of Lp-PLA2 in large-artery atherosclerosis and the cardioembolism group was statistically significantly higher than that of the control cases. There was no statistically significant difference between the small-vessel occlusion group and the control cases. The present study confirmed that the elevated Lp-PLA2 level can be a risk factor for ischemic stroke in the Chinese population. The serum level of Lp-PLA2 may be a predictive factor for the recurrence of ACI.

The Association between Periodontal Status, Serum Lipid Levels, Lipoprotein Associated Phosholipase A2 (Lp-PLA2) in Chronic Periodontitis Subjects and Healthy Controls

INTRODUCTION

Lipoprotein associated phospholipase A2 (Lp-PLA2) has been explored as a potential biomarker for Cardiovascular Disease (CVD). The human Lp-PLA2 is a serine-dependent, Ca2+- independent enzyme. It gives way to oxidised free fatty acids and lysophosphatidyl choline by hydrolysing oxidised phospholipids, that leads to smooth muscle cell apoptosis, inflammatory cell chemotaxis and endothelial cell dysfunction in CVD. Owing to its role in inflammation, it may influence the development and progression of periodontitis as well.

AIM

To compare the demographic variables, Gingival Index(GI), Bleeding On Probing (BOP), Probing Pocket Depth (PPD), and Clinical Attachment Level (CAL) with serum lipid profile and Lp-PLA2 level in Chronic Periodontitis (CP) subjects.

MATERIALS AND METHODS

A total of 75 subjects were selected and divided into three groups; based on the inclusion and exclusion criteria: Group I - 25 subjects with severe generalized CP with CAL ≥ 5 mm in more than 30% of sites. Group II -25 subjects with moderate generalized CD with clinical CAL 3 mm-4 mm in more than 30% of sites. Group III- 25 systemically and periodontally healthy volunteers who served as control. Clinical parameters such as Plaque Index (PI), BOP, Probing Depth (PD) and CAL, lipid profile such as Total Cholesterol (TC), Triglyceride (TG), High density Lipoprotein (HDL), Low Density Lipoprotein (LDL), Very Low Density Lipoprotein (VLDL) as well as Lp-PLA2 were assessed. One-way ANOVA and Tukey's Post-hoc test were used for data analysis.

RESULTS

Age was higher in Group I and II when compared to Group III. Group II showed a significant correlation between PI and LDL. In Group III, lower PI was significantly correlated with high HDL and low LDL and BOP was positively correlated with TG and HDL. A significant association of Lp-PLA2 was found to be higher with increase in the TG and VLDL level in Group I and Group II when compared to Group III.

CONCLUSION

The study concluded that Lp-PLA2, TG and VLDL already being a predictor biomarker for atherosclerotic disease can be an inflammatory marker for periodontitis.

Serum lipoprotein-associated phospholipase A2 predicts the formation of carotid artery plaque and its vulnerability in anterior circulation cerebral infarction

OBJECTIVE

Circulation inflammation markers such as high-sensitive C-reactive protein (hsCRP) and lipoprotein-associated phospholipase A2 (Lp-PLA2) are considered as predictors of cerebral and cardiac vascular diseases. However, the role of hsCRP and Lp-PLA2 in the anterior circulation cerebral infarction (ACI) is to be elaborated.

PATIENTS AND METHODS

We included 100 patients with acute anterior circulation cerebral infarction (AaCI group) and 50 non-infarction subjects (control group). Carotid artery was detected by color Doppler ultrasound. Subjects were grouped based on carotid intima-media thickness (IMT) and degree of stability of carotid atherosclerotic plaque. The levels of hsCRP and Lp-PLA2 were measured in corresponding groups and the association was analyzed.

RESULTS

hsCRP and Lp-PLA2 levels were the risk factors for AaCI. With the increment of carotid IMT and degree of plaque instability, the level of hsCRP and Lp-PLA2 showed an elevating tendency. hsCRP and Lp-PLA2 levels were significantly higher in plaque formation group than in IMT normal group (P=0.002 and P=0.001, respectively). hsCRP and Lp-PLA2 levels were significantly higher in vulnerable plaque group than in mixed plaque group and stable plaque group (P=0.003, P<0.001 for hsCRP and P<0.001, P<0.001 for Lp-PLA2). Lp-PLA2 was finally included in the atherosclerotic plaque model (OR=1.019, 95% confidence interval (CI): 1.003-1.035, P=0.020) and vulnerable plaque model (OR=1.041, 95%CI: 1.017-1.065, P=0.001) by performing multivariate logistic regression analysis. The area under the ROC curve (AUC) of Lp-PLA2 levels for atherosclerotic plaque was 0.746 (95% CI: 0.628-0.865, P<0.001). The optimal cut-off value for Lp-PLA2 level was 267.5ng/ml, and its sensitivity and specificity for diagnosis of atherosclerotic plaque were 70.8% and 67.1%, respectively.

CONCLUSIONS

The current study demonstrates that hsCRP and Lp-PLA2 are among the risk factors for AaCI. Elevated hsCRP and Lp-PLA2 are associated with carotid plaque formation. Univariate and multivariate logistic regression analysis suggests that elevated Lp-PLA2 is the independent risk factor for carotid plaque and its vulnerability.

Cellphone Monitoring of Multi-Qubit Emission Enhancements from Pd-Carbon Plasmonic Nanocavities in Tunable Coupling Regimes with Attomolar Sensitivity

We demonstrate for the first time the tuning of qubit emission based on cavity engineering on plasmonic silver thin films. This tunable transition from weak to strong coupling regime in plasmon-coupled fluorescence platform was achieved with the use of palladium nanocomposites. In addition to our recently established correlation between Purcell factor and surface plasmon-coupled emission enhancements, we now show that the qubit-cavity environment experiences the Purcell effect, Casimir force, internal fano resonance, and Rabi splitting. Finite-difference time-domain simulations and time correlated single photon counting studies helped probe the molecular structure of the radiating dipole, rhodamine-6G, in palladium-based nanocavities. The sensitivity of the qubit-cavity mode helped attain a DNA detection limit of 1 aM (attomolar) and multianalyte sensing at picomolar concentration with the use of a smartphone camera and CIE color space. We believe that this low-cost technology will lay the groundwork for mobile phone-based next-gen plasmonic sensing devices.

Lipoprotein-associated phospholipase A2 distribution among lipoproteins differs in type 1 diabetes

BACKGROUND

LpPLA2 mass and activity have been variably related to cardiovascular disease risk, and the distribution of LpPLA2 in patients with type 1 diabetes (T1D), wherein cardiovascular disease risk is high despite normal or higher levels of high-density lipoprotein (HDL) cholesterol, is unknown.

OBJECTIVE

To determine whether there are differences in the distribution of LpPLA2 mass and activity across lipoproteins and their association with coronary artery calcium (CAC) in patients with T1D.

METHODS

Men with T1D (n = 19) not on statins, with and without CAC progression, and men without diabetes matched for HDL cholesterol (n = 25) had lipoproteins separated by fast protein liquid chromatography.

RESULTS

Both LpPLA2 mass and activity were found within low-density lipoprotein (LDL) and HDL pools with more LpPLA2 mass being associated with HDL (54% vs 44%; P-value <.001) and more LpPLA2 activity being associated with LDL (56% vs 40%; P value = .02). In T1D, more LpPLA2 activity was associated with large- or less-dense LDL compared to those without diabetes. However, no difference in LpPLA2 activity or mass between lipoprotein subfractions was observed between all groups, and there was no relationship between LpPLA2 activity or mass and its distribution and CAC score progression in healthy or T1D men.

CONCLUSION

LpPLA2 is found in both LDL and HDL and is distributed differently in men with T1D without any relationship to CAC score progression.

Increased Lipoprotein-associated phospholipase A2 activity portends an increased risk of resistant hypertension

BACKGROUND

To investigate the relationship between plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) activity and incidence of resistant hypertension (RH).

METHODS

This was a cross-sectional research. In essential, it was an observational design and collecting data on a population at a single point in time to evaluate the associations of studied variables. Totally 208 patients with arterial hypertension were enrolled. Baseline characteristics were collected and fasting venous blood were drawn for plasma Lp-PLA2 activity assessment. Twenty-four hour ambulatory blood pressure ambulatory (ABPM) was performed to diagnose RH. Initially, based on ABPM examination, all participants were divided into two groups, namely RH group and without RH group. And thereafter, in order to evaluate the effects of Lp-PLA2 activity on blood pressure, all participants were divided into low (< 225 nm/min/ml) and high (≥ 225 nm/min/ml) Lp-PLA2 activity groups based on the cut-off value of Lp-PLA2 activity. Comparisons were conducted between groups.

RESULTS

Forty two patients were diagnosed as RH. Compared to patients without RH, patients with RH were more elderly, had more males, smokers, longer duration of hypertension, higher plasma C-reactive protein (CRP) level and Lp-PLA2 activity (P < 0.05 for all comparisons). More RH patients treated with calcium channel blocker and diuretic, while less treated with angiotensin converting enzyme inhibitor, angiotensin receptor blocker and statins (P < 0.05 for all comparisons). Compared to low Lp-PLA2 group, the rate of RH was significantly higher in high Lp-PLA2 group (26.7 % versus 6.1 %, P < 0.05). Multivariate regression analysis revealed that after adjusted for age, gender, smoking, body mass index, hypertension duration, CRP, and anti-hypertensive drugs, association between Lp-PLA2 activity and RH remained significant, with odds ratio (OD) of 2.02 (95 % confidence interval, CI 1.85-2.06, P < 0.05). Nonetheless, the association was attenuated when further adjusted for statins, with OR of 1.81 (95 % CI 1.74-1.93, P < 0.05).

CONCLUSION

Increased plasma Lp-PLA2 activity portends increased risk of RH, and statins may be beneficial to reduce incidence of RH in subjects with increased plasma Lp-PLA2 activity.

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.

Elevated circulating levels of lipoprotein-associated phospholipase A2 in obese children

Obesity and cardiovascular disease (CVD) often co-exist, but the pathophysiologic mechanisms that link the two are not fully understood. Lipoprotein-associated phospholipase A

Sixty-seven lean [39 boys and 28 girls, mean body mass index (BMI) z-score –0.2±0.8] and 66 obese (32 boys and 34 girls, mean BMI z-score 4.4±1.2) age-matched (p=0.251) children, aged 6–12 years, were studied. BMI z-score was calculated based on the Greek BMI growth curves, and children were categorized as obese according to the Cole criteria. All children underwent physical examination and a fasting morning blood sample was obtained for glucose, insulin, lipid profile, and Lp-PLA2 assessment. Plasma concentrations of Lp-PLA2 were determined by a commercially available Lp-PLA2 enzyme-linked immunosorbent assay kit (PLAC Test), while other measurements were performed using standard methods.

Plasma Lp-PLA2 levels were significantly higher in obese children (322.5±77.8 ng/mL) compared with normal-weight ones (278.0±64.4 ng/mL, p<0.001). Lp-PLA2 concentrations were significantly correlated with the BMI z-score (p=0.004). Receiver operating characteristic analysis on Lp-PLA2 values resulted in significant areas under the curve (AUC) for distinguishing between obese and normal-weight groups of children (AUC, 0.726; p<0.001).

We found significantly higher Lp-PLA2 levels in obese children than lean controls. Interestingly, they all had levels >200 ng/mL, which are considered to correlate with atherosclerosis and a high thromboembolic risk in adults. The positive correlation of Lp-PLA2 with BMI suggests that Lp-PLA2 might be the link between obesity and increased cardiovascular risk, which can be elevated even at a very young age. Measurement of Lp-PLA2 in plasma could therefore represent a further biomarker for assessing increased CVD risk in obese children and adolescents.

Low-dimensional carbon spacers in surface plasmon-coupled emission with femtomolar sensitivity and 1000-fold fluorescence enhancements

We present low-dimensional carbon spacer engineering technology in surface plasmon-coupled emission for femtomolar sensitivity and fluorescence enhancements exceeding 1000 fold.

Lipid peroxidation generates biologically active phospholipids including oxidatively N-modified phospholipids

Peroxidation of membranes and lipoproteins converts "inert" phospholipids into a plethora of oxidatively modified phospholipids (oxPL) that can act as signaling molecules. In this review, we will discuss four major classes of oxPL: mildly oxygenated phospholipids, phospholipids with oxidatively truncated acyl chains, phospholipids with cyclized acyl chains, and phospholipids that have been oxidatively N-modified on their headgroups by reactive lipid species. For each class of oxPL we will review the chemical mechanisms of their formation, the evidence for their formation in biological samples, the biological activities and signaling pathways associated with them, and the catabolic pathways for their elimination. We will end by briefly highlighting some of the critical questions that remain about the role of oxPL in physiology and disease.

Intensive lifestyle modification reduces Lp-PLA2 in dyslipidemic HIV/HAART patients

PURPOSE

Patients with dyslipidemia associated with HIV-1 infection and highly active antiretroviral therapy (HAART) have elevated levels of Lp-PLA2 and CCL5/regulated on activation, normal T-cell expressed and secreted (RANTES), which may increase the risk of cardiovascular disease.

PURPOSE

This study aimed to determine whether an intensive diet and exercise (D/E) program, independently or combined with fenofibrate or niacin, could reduce Lp-PLA2 or RANTES.

METHODS

Patients with hypertriglyceridemic HIV on stable HAART (n = 107) were randomized to one of five interventions: 1) usual care, 2) D/E with placebos, 3) D/E with fenofibrate and placebo, 4) D/E with niacin and placebo, or 5) D/E with fenofibrate and niacin for 24 wk. Lp-PLA2 and RANTES concentrations were measured in fasting plasma samples at baseline and postintervention. General linear models were used to compare Lp-PLA2 and RANTES levels between the five groups postintervention, controlling for baseline levels, age, body mass index, CD4 T-cell count, viral load, duration of infection, and HAART.

RESULTS

At baseline, fasting plasma Lp-PLA2 (388.5 ± 127.5 ng·mL) and RANTES (43.8 ± 25.5 ng·mL) levels were elevated when compared with healthy controls. Posttreatment Lp-PLA2 mass was lower in patients who received D/E only (323.0 ± 27.2 ng·mL), D/E plus fenofibrate (327.2 ± 25.9 ng·mL), and D/E plus niacin (311.1 ± 27.8 ng·mL) when compared with patients receiving usual care (402.2 ± 25.3 ng·mL). RANTES concentrations were not significantly affected by any intervention.

CONCLUSIONS

Elevated plasma Lp-PLA2 mass can be reduced by an intensive D/E program in patients with HIV/HAART-associated dyslipidemia. RANTES is elevated but is not reduced by lifestyle modification, fenofibrate, or niacin.

Inflammatory biomarkers for predicting cardiovascular disease

The pathology of cardiovascular disease (CVD) is complex; multiple biological pathways have been implicated, including, but not limited to, inflammation and oxidative stress. Biomarkers of inflammation and oxidative stress may serve to help identify patients at risk for CVD, to monitor the efficacy of treatments, and to develop new pharmacological tools. However, due to the complexities of CVD pathogenesis there is no single biomarker available to estimate absolute risk of future cardiovascular events. Furthermore, not all biomarkers are equal; the functions of many biomarkers overlap, some offer better prognostic information than others, and some are better suited to identify/predict the pathogenesis of particular cardiovascular events. The identification of the most appropriate set of biomarkers can provide a detailed picture of the specific nature of the cardiovascular event. The following review provides an overview of existing and emerging inflammatory biomarkers, pro-inflammatory cytokines, anti-inflammatory cytokines, chemokines, oxidative stress biomarkers, and antioxidant biomarkers. The functions of each biomarker are discussed, and prognostic data are provided where available.

Plasma Lp-PLA(2) mass and apoB-lipoproteins that carry Lp-PLA(2) decrease after sodium

BACKGROUND

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2) ) is a novel cardiovascular risk marker, which is predominantly complexed to apolipoprotein (apo) B-containing lipoproteins in human plasma. As increasing dietary sodium intake may decrease plasma apoB-containing lipoproteins, we tested whether a sodium challenge lowers plasma Lp-PLA(2) mass, as well as the levels of apoB-containing lipoprotein particles carrying Lp-PLA(2) (apoB-Lp-PLA(2) ), employing a newly developed enzyme-linked immunosorbent assay.

MATERIALS AND METHODS

In 45 women and 31 men (mean age 44 ± 14 years), plasma Lp-PLA(2) mass (turbidimetric immunoassay), the level of apoB-Lp-PLA(2) , expressed in apoB concentration and lipoproteins were measured in response to a 3-day challenge with 9 g sodium chloride tablets daily.

RESULTS

Urinary sodium excretion increased from 165 ± 60 to 321 ± 70 mmol/24 h (P<0.001) after salt loading. Plasma Lp-PLA(2) mass decreased from 618 (493-719) to 588 (465-698) μg/L (P<0.001), and apoB-Lp-PLA(2) decreased from 0.276 (0.200-0.351) to 0.256 (0.189-0.328) g LDL protein/L (P=0.004) in response to the sodium challenge together with decreases in plasma total cholesterol, nonhigh-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein B and the total cholesterol/HDL cholesterol ratio (P<0.01 for all). Changes in plasma Lp-PLA(2) mass were correlated positively with changes in total cholesterol, LDL cholesterol and non-HDL cholesterol (r=0.260-0.276, P<0.05 to P<0.02), whereas changes in apoB-Lp-PLA(2) were correlated positively with changes in non-HDL cholesterol and in the total cholesterol/HDL cholesterol ratio (r=0.232-0.385, P<0.05-0.01).

CONCLUSION

Both plasma Lp-PLA(2) mass levels and apoB-Lp-PLA(2) decrease in response to a short-term oral sodium challenge.

Simvastatin but not bezafibrate decreases plasma lipoprotein-associated phospholipase A₂ mass in type 2 diabetes mellitus: relevance of high sensitive C-reactive protein, lipoprotein profile and low-density lipoprotein (LDL) electronegativity

OBJECTIVE

Plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) levels predict incident cardiovascular disease, impacting Lp-PLA(2) as an emerging therapeutic target. We determined Lp-PLA(2) responses to statin and fibrate administration in type 2 diabetes mellitus, and assessed relationships of changes in Lp-PLA(2) with subclinical inflammation and lipoprotein characteristics.

METHODS

A placebo-controlled cross-over study (three 8-week treatment periods with simvastatin (40 mg daily), bezafibrate (400mg daily) and their combination) was carried out in 14 male type 2 diabetic patients. Plasma Lp-PLA(2) mass was measured by turbidimetric immunoassay.

RESULTS

Plasma Lp-PLA(2) decreased (-21 ± 4%) in response to simvastatin (p<0.05 from baseline and placebo), but was unaffected by bezafibrate (1 ± 5%). The drop in Lp-PLA(2) during combined treatment (-17 ± 3%, p<0.05) was similar compared to that during simvastatin alone. The Lp-PLA(2) changes during the 3 active lipid lowering treatment periods were related positively to baseline levels of high sensitive C-reactive protein, non-HDL cholesterol, triglycerides, the total cholesterol/HDL cholesterol ratio and less LDL electronegativity (p<0.02 to p<0.01), and inversely to baseline Lp-PLA(2) (p<0.01). LpPLA(2) responses correlated inversely with changes in non-HDL cholesterol, triglycerides and the total cholesterol/HDL cholesterol ratio during treatment (p<0.05 to p<0.02).

CONCLUSIONS

In type 2 diabetes mellitus, plasma Lp-PLA(2) is likely to be lowered by statin treatment only. Enhanced subclinical inflammation and more severe dyslipidemia may predict diminished LpPLA(2) responses during lipid lowering treatment, which in turn appear to be quantitatively dissociated from decreases in apolipoprotein B lipoproteins. Conventional lipid lowering treatment may be insufficient for optimal LpPLA(2) lowering in diabetes mellitus.

Predicting the Risk of Cardiovascular Disease

Although an atherogenic lipoprotein phenotype has been well recognized as an important predictor of cardiovascular disease, recent studies have demonstrated a number of additional lipid-related markers as emerging biomarkers to identify patients at risk for future coronary heart disease. Among them, lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), seems to be a promising candidate that might be added to the clinical armamentarium for improved prediction of cardiovascular disease in the future. Of particular note, Lp-PLA(2) is the only enzyme that cleaves oxidized low-density lipoprotein (oxLDL) in the subendothelial space, with further generation of proinflammatory mediators such as lysophosphatidylcholine (LysoPC) and oxidized fatty acid (oxFA), thereby probably linking two important features of atherogenesis, namely oxidation of LDL and local inflammatory processes within the atherosclerotic plaque. This overview aims to summarize our current knowledge based on observations from recent experimental and clinical studies. Emphasis has been put on potential pathophysiological mechanisms of action and on the clinical relevance of Lp-PLA(2) in a wide variety of clinical settings, including apparently healthy individuals, patients with stable angina or acute coronary syndromes, after myocardial infarction, and with subclinical disease. Although a growing body of evidence from epidemiological and clinical studies suggests that Lp-PLA(2) may represent an independent and clinically relevant long-term risk marker for coronary heart disease and, probably, also for stroke, the role of this enzyme in the setting of the acute coronary syndrome remains to be established.

Mapping of clinical and expression quantitative trait loci in a sex-dependent effect of host susceptibility to mouse-adapted influenza H3N2/HK/1/68

Seasonal influenza outbreaks and recurrent influenza pandemics present major challenges to public health. By studying immunological responses to influenza in different host species, it may be possible to discover common mechanisms of susceptibility in response to various influenza strains. This could lead to novel therapeutic targets with wide clinical application. Using a mouse-adapted strain of influenza (A/HK/1/68-MA20 [H3N2]), we produced a mouse model of severe influenza that reproduces the hallmark high viral load and overexpression of cytokines associated with susceptibility to severe influenza in humans. We mapped genetic determinants of the host response using a panel of 29 closely related mouse strains (AcB/BcA panel of recombinant congenic strains) created from influenza-susceptible A/J and influenza-resistant C57BL/6J (B6) mice. Combined clinical quantitative trait loci (QTL) and lung expression QTL mapping identified candidate genes for two sex-specific QTL on chromosomes 2 and 17. The former includes the previously described Hc gene, a deficit of which is associated with the susceptibility phenotype in females. The latter includes the phospholipase gene Pla2g7 and Tnfrsf21, a member of the TNFR superfamily. Confirmation of the gene underlying the chromosome 17 QTL may reveal new strategies for influenza treatment.

The inhibition of lipoprotein-associated phospholipase A2 exerts beneficial effects against atherosclerosis in LDLR-deficient mice

AIM

To investigate the effects of darapladib, a specific inhibitor of lipoprotein-associated phospholipase A2 (lp-PLA2), on inflammation and atherosclerotic formation in the low density lipoprotein receptor (LDLR)-deficient mice.

METHODS

Six-week-old LDLR-deficient mice were fed an atherogenic high-fat diet for 17 weeks and then randomly divided into two groups. One group was administered darapladib (50 mg·kg(-1)·d(-1); po) for 6 weeks. The other group was administered saline as a control. Serum lipid levels were measured using the corresponding kits, and three inflammatory markers--interleukin-6 (IL-6), C reactive protein (hs-CRP), and platelet activating factor (PAF)--were determined using ELISA. Atherosclerotic plaque areas were stained with Sudan IV, and inflammatory gene expression at the lesions was evaluated using quantitative real-time PCR.

RESULTS

The body weight and serum lipid level between the two groups were similar at the end of the dietary period. The serum lp-PLA2 activity, hs-CRP and IL-6 levels, however, were significantly reduced in the darpladib group. The inhibition of lp-PLA2 did not alter the serum PAF level. Furthermore, the plaque area, from the aortic arch to the abdominal aorta, was significantly reduced in the darpladib group. Additionally, the expression of inflammatory genes monocyte chemotactic protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) was significantly reduced at the lesions in the darapladib group.

CONCLUSION

Inhibition of lp-PLA2 by darapladib decreases the inflammatory burden and atherosclerotic plaque formation in LDLR-deficient mice, which may be a new strategy for the treatment of atherosclerosis.

Inhibition of lipoprotein-associated phospholipase A2 ameliorates inflammation and decreases atherosclerotic plaque formation in ApoE-deficient mice

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is thought to play modulatory roles in the development of atherosclerosis. Here we evaluated the effects of a specific lp-PLA2 inhibitor on atherosclerosis in ApoE-deficient mice and its associated mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

ApoE-deficient mice fed an atherogenic high-fat diet for 17 weeks were divided into two groups. One group was administered the specific lp-PLA2 inhibitor, darapladib (50 mg/kg/day; p.o.) daily for 6 weeks, while the control group was administered saline. We observed no differences in body weight and serum lipids levels between the two groups at the end of the dietary period. Notably, serum lp-PLA2 activity as well as hs-CRP (C-reactive protein) and IL-6 (Interleukin-6) levels were significantly reduced in the darapladib group, compared with the vehicle group, while the serum PAF (platelet-activating factor) levels were similar between the two groups. Furthermore, the plaque area through the arch to the abdominal aorta was reduced in the darapladib group. Another finding of interest was that the macrophage content was decreased while collagen content was increased in atherosclerotic lesions at the aortic sinus in the darapladib group, compared with the vehicle group. Finally, quantitative RT-PCR performed to determine the expression patterns of specific inflammatory genes at atherosclerotic aortas revealed lower expression of MCP-1, VCAM-1 and TNF-α in the darapladib group.

CONCLUSIONS/SIGNIFICANCE

Inhibition of lp-PLA2 by darapladib leads to attenuation of in vivo inflammation and decreased plaque formation in ApoE-deficient mice, supporting an anti-atherogenic role during the progression of atherosclerosis.

Carotid intima media thickness is associated with plasma lipoprotein-associated phospholipase A2 mass in nondiabetic subjects but not in patients with type 2 diabetes

BACKGROUND

A recent meta-analysis showed that both plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2) ) mass and activity independently predict cardiovascular events. Notably, Lp-PLA(2) activity but not mass was found to be a determinant of cardiovascular outcome in type 2 diabetes mellitus. We questioned whether relationships of carotid intima media thickness (IMT), a measure of subclinical atherosclerosis, with Lp-PLA(2) mass differ between diabetic and nondiabetic subjects.

MATERIALS AND METHODS

Relationships of IMT with plasma Lp-PLA(2) mass (turbidimetric immunoassay) were compared in 74 patients with type 2 diabetes and in 64 nondiabetic subjects.

RESULTS

IMT was increased (P=0·016), but plasma Lp-PLA(2) mass was decreased in patients with diabetes compared to nondiabetic subjects (277±66 vs. 327±62μgL(-1) , P<0·001). In nondiabetic subjects, IMT was correlated positively with Lp-PLA(2) (r=0·325, P<0·009); multiple linear regression analysis confirmed an independent association of IMT with Lp-PLA(2) (ß=0·192, P=0·048). In contrast, IMT was unrelated to Lp-PLA(2) in patients with diabetes (r=0·021, P=0·86), and the relationship of IMT with Lp-PLA(2) was different in diabetic and control subjects (P<0·001). The relationship of Lp-PLA(2) with the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio also differed between diabetic and nondiabetic subjects (P<0·001).

CONCLUSIONS

Plasma Lp-PLA(2) may relate to early stages of atherosclerosis development. In diabetes mellitus, in contrast, the association of IMT with plasma Lp-PLA(2) mass is abolished, which could be partly ascribed to redistribution of Lp-PLA(2) mass from apolipoprotein B-containing lipoproteins towards HDL. These findings raise questions about the usefulness of plasma Lp-PLA(2) mass measurement as a marker of subclinical atherosclerosis in type 2 diabetes mellitus.

Plasma cholesteryl ester transfer, but not cholesterol esterification, is related to lipoprotein-associated phospholipase A2: possible contribution to an atherogenic lipoprotein profile

CONTEXT

Plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) predicts incident cardiovascular disease and is associated preferentially with negatively charged apolipoprotein B-containing lipoproteins. The plasma cholesteryl ester transfer (CET) process, which contributes to low high-density lipoprotein cholesterol and small, dense low-density lipoproteins, is affected by the composition and concentration of apolipoprotein B-containing cholesteryl ester acceptor lipoproteins.

OBJECTIVE

We tested relationships of CET with Lp-PLA(2) in subjects with and without metabolic syndrome (MetS).

DESIGN AND SETTING

In 68 subjects with MetS and 74 subjects without MetS, plasma Lp-PLA(2) mass, cholesterol esterification (EST), lecithin:cholesterol acyltransferase (LCAT) activity level, CET, CET protein (CETP) mass, and lipoproteins were measured.

RESULTS

EST, LCAT activity, CET (P < 0.001 for all), and CETP (P = 0.030) were increased, and Lp-PLA(2) was decreased (P = 0.043) in MetS. CET was correlated positively with Lp-PLA(2) in subjects with and without MetS (P < 0.05 for both). EST and LCAT activity were unrelated to Lp-PLA(2), despite a positive correlation between EST and CET (P < 0.001). After controlling for age, sex, and diabetes status, CET was determined by Lp-PLA(2) in the whole group (β = 0.245; P < 0.001), and in subjects with (β = 0.304; P = 0.001) and without MetS (β = 0.244; P = 0.006) separately, independently of triglycerides and CETP.

CONCLUSIONS

Plasma CET is related to Lp-PLA(2) in subjects with and without MetS. The process of CET, but not EST, may be influenced by Lp-PLA(2). These findings provide a rationale to evaluate whether maneuvers that inhibit Lp-PLA(2) will reduce CET, and vice versa to document effects of CETP inhibition on Lp-PLA(2).

Lipoprotein-associated phospholipase A2 as a biomarker of coronary heart disease and a therapeutic target

PURPOSE OF REVIEW

Lipoprotein-associated phospholipase A2 (Lp PLA2) is postulated to occupy a key position in the pathogenic sequence leading to formation of complex atherosclerotic lesions. This study reviews evidence supporting its role as a biomarker of vascular disease and as a possible therapeutic target.

RECENT FINDINGS

Evidence continues to build supporting the usefulness of Lp PLA2 as a predictor of coronary events in the general population and in those with established coronary heart disease. Elevated Lp PLA2 is also associated with stroke and heart failure. The crystal structure of Lp PLA2 is now available and offers insight into the links between structure, function and atherogenic properties. Recently completed studies on the efficacy of darapladib, a specific Lp PLA2 inhibitor, show beneficial changes in plaque morphology in animal models and in humans.

SUMMARY

Lp PLA2 is gaining acceptance as a useful biomarker of chronic inflammation and as a predictor of vascular disease. Early results with darapladib offer promise, but not definitive proof, of a potential role for Lp PLA2 inhibition in coronary heart disease prevention.

Reducing oxidized lipids to prevent cardiovascular disease

Despite significant success in reducing plasma cholesterol, especially low-density lipoprotein cholesterol, risks for cardiovascular disease (CVD) complications remain. Among these risks are circulating levels of oxidative modified lipoproteins, primarily oxidized low-density lipoproteins (oxLDL). The evidence supporting oxLDL as a potential target for therapeutic management to reduce metabolic complications and CVD events is reviewed in this report.

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

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

Phospholipase A2 inhibitors in the treatment of atherosclerosis: a new approach moves forward in the clinic

Phase II results of the trials of two phospholipase A2 inhibitors which may be of value in the treatment of atherosclerosis and cardiovascular disease have been reported in the past year. Darapladib (GlaxoSmithKline) is an inhibitor of lipoprotein-associated phospholipase A2 and varespladib (Anthera) inhibits several forms of the secreted phospholipase A2s. Despite the apparent similarity of mechanism, which is also built into the compounds' names, the role of the two types of phospholipase in atherogenesis is very different. Evidence for this comes from a range of preclinical studies and from epidemiological data which are summarised here. These data provide a basis for the Phase II studies and support decisions to move into Phase III, a decision which in the case of darapladib has been made and studies commenced (STABILITY trial). For varespladib the FRANCIS-ACS trial in acute coronary syndrome patients is in progress.

Lipoprotein-associated phospholipase A(2), inflammatory biomarkers, and risk of cardiovascular disease in the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER)

OBJECTIVE

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is an inflammatory biomarker that circulates mainly bound to LDL. We evaluated the association of Lp-PLA(2) with vascular events in the elderly where the importance of LDL is diminished as a risk factor for coronary disease.

METHODS

Mass and activity of Lp-PLA(2) were related to risk over 3.2 years for vascular events (definite or suspected death from CHD, non-fatal MI, fatal or non-fatal stroke) in the 2804 men and 3000 women age 70-82 years in the Prospective Study of Pravastatin in the Elderly (PROSPER).

RESULTS

Lp-PLA(2) showed a moderate, positive association with risk of a vascular event with hazard ratios of 1.25 (confidence interval (CI) 1.02-1.54) for mass and 1.39 (CI 1.14-1.70) for activity for top versus bottom quartile. Risk associations were attenuated when classical risk factors, lipids and inflammatory markers - C-reactive protein and white cell count - were included in the models. Lp-PLA(2) was unrelated to stroke risk. Inclusion of all three inflammatory markers in multivariate models negated the association of HDL cholesterol with risk (hazard ratio 0.98; CI 0.88-1.10) and increased prediction of coronary events; the C statistic rose from 63.2% to 64.4% (P<0.001).

CONCLUSION

In elderly people Lp-PLA(2), alongside other inflammatory indices, is a potential biomarker for vascular events, particularly CHD.

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 predicts progression of cardiac allograft vasculopathy and increased risk of cardiovascular events in heart transplant patients

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a risk factor for coronary artery disease (CAD) in nontransplant patients. We evaluated the association between Lp-PLA2, cardiac allograft vasculopathy (CAV) assessed by 3D intravascular ultrasound, and incidence of cardiac adverse events in heart transplant recipients.

MATERIALS AND METHODS

Fasting blood samples were obtained and stored from a cross-section of 112 cardiac transplant recipients attending the Mayo cardiac transplant clinic in 2000 to 2001, mean of 4.7 years after transplant. Lp-PLA2 was measured in plasma aliquots using an enzyme-linked immunoassay. Fifty-six of these patients subsequently underwent two 3D intravascular ultrasound studies in 2004 to 2006 12 months apart. Cardiovascular (CV) events included percutaneous coronary intervention, coronary artery bypass grafting (CABG), reduction in left ventricular ejection fraction (LVEF) < or =45% secondary to CAV and CV death.

RESULTS

High Lp-PLA2 level was associated with increase in plaque volume (r=0.43, P=0.0026) and percent plaque volume (r=0.45, P=0.0004). The association remained significant after adjusting for clinical and lipid variables. During follow-up of 5.1+/-1.6 years, 24 CV adverse events occurred in 15 of 112 (13%) heart transplant patients. Lp-PLA2 level>236 ng/mL (higher tertile) identified a subgroup of patients having a 2.4-fold increase of relative risk for combined endpoint of CV events (percutaneous coronary intervention, CABG, LVEF<45%, and CV death; 95% CI 1.16-5.19, P=0.012) compared with patients with Lp-PLA2< or =236 ng/mL.

CONCLUSIONS

Lp-PLA2 is independently associated with progression of CAV and predicts a higher incidence of CV events and CV death in transplant patients. This finding supports the concept that systemic inflammation is an important mediator of CAV. Lp-PLA2 may be a useful marker for risk of CAV and a therapeutic target in posttransplant patients.

Variability of Serial Lipoprotein-Associated Phospholipase A2 Measurements in Post–Myocardial Infarction Patients: Results from the AIRGENE Study Center Augsburg

Background: Of the numerous emerging biomarkers for coronary heart disease (CHD), lipoprotein-associated phospholipase A2 (Lp-PLA2), an enzyme involved in lipid metabolism and inflammatory pathways, seems to be a promising candidate. Implementation of Lp-PLA2 measurement into clinical practice, however, requires data on the reliability of such measurements.

Methods: We measured Lp-PLA2 concentrations by ELISA in blood samples drawn from 200 post–myocardial infarction patients (39–76 years) at 6 monthly intervals between May 2003 and February 2004, for a total of 1143 samples. We estimated analytical, within-individual, and between-individual variation, the critical difference, and the intraclass correlation coefficient of reliability (ICC) to assess the reliability of serial Lp-PLA2 measurements.

Results: The mean (SD) plasma Lp-PLA2 concentration for the study participants was 188.7 (41.8) μg/L, with no significant difference between men and women. The analytical CV for Lp-PLA2 was 4.4%, the within-individual biological CV was 15%, and the between-individual CV was 22%. The ICC was 0.66. An important part of the total variation in plasma Lp-PLA2 concentration was explained by the between-individual variation (as a percentage of the total variance, 66.1%), whereas the within-individual variance was 31.3%. The analytical variance was as low as 2.6%.

Conclusions: Between-individual variation in Lp-PLA2 concentration was substantially greater than within-individual variation. In general, our data demonstrate considerable stability and good reproducibility of serial Lp-PLA2 measurements, results that compared favorably with those for the more commonly measured lipid markers.

Statins and biomarkers of inflammation

Clinical and epidemiologic studies convincingly demonstrate that increased levels of low-density lipoprotein cholesterol promote premature atherosclerosis. Several large clinical trials have demonstrated that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) decrease cardiovascular events. The beneficial effects of statins may extend to mechanisms beyond cholesterol reduction. Evidence for the pleiotropic effects of statins is provided by recent clinical trials in which the benefit of statin drugs is manifest early in the course of lipid-lowering therapy, well before plaque regression could occur. Inflammation is pivotal in all stages of atherosclerosis, and C-reactive protein (CRP), the prototypic marker of inflammation, has emerged as a cardiovascular risk marker. Statins reduce CRP levels, and this reduction in most studies does not correlate to reduction in cholesterol. In addition, statins have beneficial effects on endothelial function, monocyte-macrophages, and platelets. In this review we discuss the role of inflammation in atherosclerosis, the role of CRP as a risk marker, the clinical evidence implicating the anti-inflammatory effects of statins, and the cellular and molecular basis underlying the anti-inflammatory effects of statins.

1H NMR at 800MHz facilitates detailed phospholipid follow-up during atherogenic modifications in low density lipoproteins

The structure of low density lipoprotein (LDL) particles and, particularly, the enzymatic and oxidative modifications of their surface is crucial in the initiation of atherosclerosis. Due to the structural complexity of LDL, there is a lack of suitable methods for dynamic follow-up studies of the molecular mechanisms in native and modified particles in physiological conditions. Here, we report that phosphatidylcholine (PC), lysophosphatidylcholine (lyso-PC), and sphingomyelin (SM) can all be identified and quantified in LDL particles by (1)H NMR spectroscopy at 800 MHz. The signal assignment for the lyso-PC is novel and we illustrate the applicability of the methodology in the case of lipid peroxidation that is generally considered as one of the key proatherogenic modifications of LDL. It was found, somewhat surprisingly, that the LDL-associated phospholipase A(2) is activated in the very beginning of the formation of PC-hydroperoxides. The (patho)physiological rationale of the resulting lyso-PC generation is also briefly discussed.

Molecular basis for susceptibility of plasma platelet-activating factor acetylhydrolase to oxidative inactivation

Platelet-activating factor acetylhydrolase (PAF-AH) is a phospholipase A2 that inactivates potent lipid messengers, such as PAF and modified phospholipids generated in settings of oxidant stress. The catalytic activity of PAF-AH is sensitive to oxidants, a feature that may have pathological consequences. We report that peroxynitrite, an oxidant species generated after cellular activation, mediates oxidative inactivation of PAF-AH. We found that peroxynitrite inactivated and derivatized the recombinant protein and obtained evidence supporting a role for a methionine and two tyrosine residues in this process. We employed interspecies comparisons and site-directed mutagenesis and identified a role for M-117, and a smaller contribution of Y-307 and Y-335 as targets of oxidant attack using free and lipoprotein-associated recombinant proteins. M-117 is adjacent to W-115 and L-116, which are essential for association of PAF-AH with LDL. Oxidation of LDL-associated PAF-AH partially dissociated the enzyme from the particles. Similarly, oxidation of the purified enzyme in the absence of lipoproteins prevented subsequent association with LDL. These results provide new insights into the molecular mechanisms that mediate inactivation of PAF-AH in settings of oxidant stress and the consequences of oxidation on the ability of this enzyme to associate with LDL.

Biomarkers for atherosclerosis: pathophysiological role and pharmacological modulation

PURPOSE OF REVIEW

The aim of this article is to discuss the potential value of biomarkers for atherosclerosis in the assessment of risk for cardiovascular disease, in the pathogenesis of atherosclerosis, and in the monitoring of pharmacological treatment.

RECENT FINDINGS

In an attempt to improve global cardiovascular risk prediction, considerable effort has been made in the discovery and characterization of soluble biomarkers which can go beyond the measure of total and LDL cholesterol levels. In particular, circulating molecules related to chronic inflammation have emerged as potential biomarkers for atherosclerosis. Evidence, obtained from in-vitro and in-vivo experimental models, has also documented that the majority of biomarkers play a pathological role in atherogenesis. Multiple screening of different biomarkers may therefore improve the assessment of risk, diagnosis, and prognosis for cardiovascular disease. In addition, soluble biomarkers have been shown to be modulated by hypolipidemic drugs and to be potentially useful in determining the clinical benefits of pharmacological therapies that do not alter serum lipid levels.

SUMMARY

Altered levels of soluble biomarkers are associated with cardiovascular disease, and profiling of multiple biomarkers for atherosclerosis will be a useful indicator for better risk assessment, diagnosis, and prognosis, as well as monitoring pharmacological treatments for atherosclerosis.

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.