Modifications of plasma platelet-activating factor (PAF)-acetylhydrolase/PAF system activity in patients with chronic hepatitis C virus infection

Lipid droplets and lipid mediators in viral infection and immunity

Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.

An insight into the role of arachidonic acid derived lipid mediators in virus associated pathogenesis and malignancies

Several studies shed light on the size and diversity of the lipidome, along with its role in physiological and pathological processes in human health. Besides that, lipids also function as important signaling mediators. This review focuses on discussing the role of arachidonic acid (AA) derived lipids as mediators in diseases with special emphasis on viral infections. Structurally, arachidonic acid derived lipids, also referred to as lipid mediators, can be classified into three specific classes: Class 1-eicosanoids derived from arachidonic acid metabolism; Class 2-lysophospholipids consisting of either a glycerol or a sphingosine backbone; Class 3-AA and ω-3 polyunsaturated fatty acid (PUFA) derivatives. Class 1 and 2 lipids are commonly referred to as pro-inflammatory molecules, which are found upregulated in diseases like cancer and viral infection. Class 3 lipids are anti-inflammatory molecules, which could be potentially used in treatment of diseases associated with inflammation. The function of each class has been elucidated as unique and contributory to an overall cellular homeostasis. Current work in this field is promising and will surely usher in a new era of lipid understanding and control not only at the molecular level, but also in terms of holistic patient care.

Lipoprotein-associated phospholipase A2 (Lp-PLA2) and tumor necrosis factor-alpha (TNF-α) and their relation to premature atherosclerosis in β-thalassemia children

BACKGROUND/OBJECTIVES

Beta (β)-thalassemia adults are prone to premature atherosclerosis but data about this complication among thalassemia children are few. Lipoprotein-associated phospholipase A2 (Lp-PLA2) and tumor necrosis factor-α (TNF-α) are inflammatory markers that could be implicated in atherosclerotic process. We investigated Lp-PLA2 and TNF-α levels in β-thalassemia children and their relation to subclinical atherosclerosis.

METHODS

Twenty-two β-thalassemia major (TM), 20 β-thalassemia intermedia children, and 30 age- and sex-matched healthy controls were included. Lipid profile (by colorimetric assay), serum ferritin, TNF-α, and plasma Lp-PLA2 levels (by enzyme-linked immunosorbent assay technique) were estimated. Carotid intima-media thickness (cIMT) was measured by high-resolution ultrasound.

RESULTS

Both patient groups exhibited anti-atherogenic lipid profile except increased serum triglycerides. They had significantly higher plasma Lp-PLA2 and serum TNF-α compared to the controls (P < 0.001). Elevated cIMT was documented in 57% of the thalassemia children and was higher among hepatitis C (HCV) positive patients. Serum ferritin, TNF-α, and plasma Lp-PLA2 levels were significantly higher in patients with premature atherosclerosis. cIMT correlated significantly with serum ferritin, TNF-α, and plasma Lp-PLA2 in both patient groups. Among TM children, serum ferritin had significant positive correlation with serum TNF-α and plasma Lp-PLA2. The elevation of both markers was not related to HCV infection.

CONCLUSIONS

Premature atherosclerosis is common among young thalassemia children. Lp-PLA2 and TNF-α are significantly increased in thalassemia children and show strong correlations with cIMT, suggesting that both of them may be appreciated as modulating factors in carotid atherosclerosis pathophysiological process among these children.

Clinical application of elevated platelet-activating factor acetylhydrolase in patients with hepatitis B

Background

The aim of this study was to investigate the variation of platelet-activating factor acetylhydrolase (PAF-AH) in patients with various stages of hepatitis B infection and evaluate the association between PAF-AH activity and chronic severe hepatitis B (CSHB) and mortality in patients with hepatitis B.

Methods

Serum PAF-AH activity was measured in 216 patients with hepatitis B and in 152 healthy controls using an automatic biochemical analysis system. Spearman correlation was used to investigate the correlation between PAF-AH activity and other biochemical indicators. The receiver operating characteristic (ROC) curve and multivariable logistic regression analysis were used to evaluate the ability of PAF-AH activity to predict CSHB and mortality in patients with hepatitis B.

Results

The PAF-AH activities in patients with CSHB (1320 ± 481 U/L) were significantly higher than those in healthy controls and in other hepatitis B groups (all P < 0.01). In patients with hepatitis B, PAF-AH activity correlated with total bilirubin (r = 0.633), total bile acid (r = 0.559), aspartate aminotransferase (r = 0.332), apolipoprotein B (r = 0.348), high-density lipoprotein cholesterol (r = −0.493), and apolipoprotein AI (r = −0.530). The areas under the ROC curves for the ability of PAF-AH activity to predict CSHB and mortality in patients with hepatitis B were 0.881 (95% confidence interval (CI): 0.824–0.937, P < 0.001) and 0.757 (95% CI: 0.677–0.837, P < 0.001), respectively. Multivariate logistic regression analysis showed PAF-AH activity to be an independent factor predicting CSHB with an odds ratio of 1.003 (95% CI: 1.002–1.005, P < 0.001).

Conclusion

Elevated PAF-AH in patients with hepatitis B was significantly associated with liver damage. Thus, serum PAF-AH could be used as a novel indicator for predicting CSHB and mortality in patients with hepatitis B. Further, PAF-AH activity was an independent factor predicting CSHB.

Pleiotropy and allelic heterogeneity in the TOMM40-APOE genomic region related to clinical and metabolic features of hepatitis C infection

Hepatitis C virus (HCV) modulates host lipid metabolism as part of its lifecycle and is dependent upon VLDL for co-assembly and secretion. HCV dyslipidemia is associated with steatosis, insulin resistance, IL28B genotype and disease progression. Apolipoprotein E (ApoE) is an important lipid transport protein, a key constituent of VLDL, and is involved in immunomodulation. Our aims were to determine the role of APOE regional polymorphisms on host lipids, IL28B genotype and disease severity in chronic HCV (CHC) patients. The study cohort included 732 CHC patients with available DNA for genotype determination of four polymorphisms in the chromosome 19 region that encompasses the TOMM40, APOE and APOC1 genes. Serum lipid analysis and apolipoproteins levels were measured using an immunoturbidimetric assay. APOE rs7412 polymorphism (capturing the ε2 isoform) was significantly associated with serum ApoE levels in both Caucasians and African-American patients (p = 2.3 × 10(-11)) and explained 7 % of variance in serum ApoE. Among IL28B-CC patients (n = 196), the rs429358 (defines ε4 isoform) and TOMM40 '523' S polymorphisms were associated with 12 % of variance in ApoB levels. Patients homozygous for the APOE ε3 isoform had a greater than twofold increased odds of F2-F4 fibrosis (p = 1.8 × 10(-5)), independent of serum lipid and lipoprotein levels. There were no associations between APOE polymorphisms and serum HDL-C, APO-CIII and triglycerides. In CHC patients, genetic heterogeneity in the APOE/TOMM40 genomic region is significantly associated with variation in serum ApoE and ApoB levels, and also with fibrosis suggesting a pleiotropic attribute of this genomic region.

Association of carotid plaque Lp-PLA(2) with macrophages and Chlamydia pneumoniae infection among patients at risk for stroke

Background

We previously showed that the burden of Chlamydia pneumoniae in carotid plaques was significantly associated with plaque interleukin (IL)-6, and serum IL-6 and C-reactive protein (CRP), suggesting that infected plaques contribute to systemic inflammatory markers in patients with stroke risk. Since lipoprotein-associated phospholipase A2 (Lp-PLA₂) mediates inflammation in atherosclerosis, we hypothesized that serum Lp-PLA₂ mass and activity levels and plaque Lp-PLA₂ may be influenced by plaque C. pneumoniae infection.

Methodology/Principal Findings

Forty-two patients underwent elective carotid endarterectomy. Tissue obtained at surgery was stained by immunohistochemistry for Lp-PLA₂ grade, macrophages, IL-6, C. pneumoniae and CD4+ and CD8+ cells. Serum Lp-PLA₂ activity and mass were measured using the colorimetric activity method (CAM™) and ELISA, respectively. Serum homocysteine levels were measured by HPLC. Eleven (26.2%) patients were symptomatic with transient ischemic attacks. There was no correlation between patient risk factors (smoking, coronary artery disease, elevated cholesterol, diabetes, obesity, hypertension and family history of genetic disorders) for atherosclerosis and serum levels or plaque grade for Lp-PLA₂. Plaque Lp-PLA₂ correlated with serum homocysteine levels (p = 0.013), plaque macrophages (p<0.01), and plaque C. pneumoniae (p<0.001), which predominantly infected macrophages, co-localizing with Lp-PLA₂.

Conclusions

The significant association of plaque Lp-PLA₂ with plaque macrophages and C. pneumoniae suggests an interactive role in accelerating inflammation in atherosclerosis. A possible mechanism for C. pneumoniae in the atherogenic process may involve infection of macrophages that induce Lp-PLA₂ production leading to upregulation of inflammatory mediators in plaque tissue. Additional in vitro and in vivo research will be needed to advance our understanding of specific C. pneumoniae and Lp-PLA₂ interactions in atherosclerosis.