Antibodies to oxidized LDL in relation to carotid atherosclerosis, cell adhesion molecules, and phospholipase A(2)

Positive Association between Autoantibodies Against Oxidized LDL and HDL-C: A Novel Mechanism for HDL Cardioprotection?

BACKGROUND

In the atherosclerotic plaque microenvironment, oxidized phospholipids expressed in the oxidized low-density lipoprotein (oxLDL) surface bind to scavenger receptors of macrophages eliciting foam cell formation and plaque progression. Auto-antibodies against oxLDL (oxLDL-Ab) interact with oxidative epitopes leading to the formation of immune complexes that are unable to interact with macrophage receptors, thus abrogating atherogenesis. Release of oxLDL-Ab by B cells involves interleukin 5 and Th2 response, which in turn are potentiated by HDL. Thereby, we hypothesized that individuals with higher levels of HDL-C may plausibly display elevated titers of oxLDL-Ab.

OBJECTIVE

To evaluate the relationship between HDL-C and oxLDL-Ab levels.

METHODS

Asymptomatic individuals (n = 193) were grouped according to their HDL-C concentration to one of three categories: low (< 68 mg/dL), intermediate (68 to 80 mg/dL) or high (> 80 mg/dL). P values < 0.05 were considered statistically significant.

RESULTS

Our analysis included 193 individuals (mean age: 47 years; male: 26.3%). Compared to individuals in the lowest HDL-C tertile, those in the highest tertile were older (36 versus 53 years; p = 0.001) and less frequently male (42.6% versus 20.9%; p = 0.001). Mean values of oxLDL-Ab increased as the HDL-C group escalated (0.31, 0.33 and 0.43 units, respectively; p = 0.001 for trend). Simple linear regression found a significant, positive relationship between the independent variable, HDL-C, and the dependent variable, oxLDL-Ab (R = 0.293; p = 0.009). This relation remained significant (R = 0.30; p = 0.044), after adjustment by covariates. Apolipoprotein AI levels were also related to oxLDL-Ab in both simple and adjusted linear regression models.

CONCLUSION

HDL-C and oxLDL-Ab are independently related.

High Levels of (Un)Switched Memory B Cells Are Associated With Better Outcome in Patients With Advanced Atherosclerotic Disease

BACKGROUND

Atherosclerosis is an inflammatory lipid disorder and the main underlying pathology of acute ischemic events. Despite a vast amount of data from murine atherosclerosis models, evidence of B-cell involvement in human atherosclerotic disease is limited. We therefore investigated the association of circulating B-cell subtypes with the occurrence of secondary cardiovascular events in advanced atherosclerotic disease.

METHODS AND RESULTS

This cohort study consists of 168 patients who were included in the Athero-Express biobank between 2009 and 2011. Before surgery, peripheral blood mononuclear cells were isolated and stored in liquid nitrogen. After gentle thawing of the peripheral blood mononuclear cells, different B-cell subtypes including naïve, (un)switched memory, and CD27+CD43+ B1-like B cells, were analyzed by flow cytometry. Univariable and multivariable Cox proportional hazard models were used to analyze associations between B-cell subtypes, circulating antibodies and secondary cardiovascular manifestations during the 3-year follow-up period. Mean age was 70.1±9.6 years, males represented 62.8% of the population, and 54 patients had secondary manifestations during follow-up. High numbers of unswitched memory cells were protective against secondary outcome (hazard ratio, 0.30 [95% CI, 0.13-0.69]; P<0.01). Similar results were obtained for the switched memory cells that also showed to be protective against secondary outcome (hazard ratio, 0.33 [95% CI, 0.14-0.77]; P=0.01).

CONCLUSIONS

A high number of (un)switched memory B cells is associated with better outcome following carotid artery endarterectomy. These findings suggest a potential role for B-cell subsets in prediction and prevention of secondary cardiovascular events in patients with atherosclerosis.

Cardiovascular disease in systemic lupus erythematosus: A comprehensive update

Heightened rates of both cardiovascular (CV) events and subclinical atherosclerosis, documented by imaging and vascular function techniques are well established in systemic lupus erythematosus (SLE). While traditional CV factors such as smoking, dyslipidemia, diabetes mellitus (DM), hypertension, central obesity and hyperhomocysteinemia have been reported to be prevalent in lupus patients, they do not fully explain the high rates of ischemic events so far reported, implying that other factors inherent to disease itself could account for the enhanced risk, including disease duration, activity and chronicity, psychosocial factors, medications, genetic variants and altered immunological mechanisms. Though the exact pathogenesis of atherosclerosis in the setting of lupus remains ill defined, an imbalance between endothelial damage and atheroprotection seems to be a central event. Insults leading to endothelial damage in the setting of lupus include oxidized low density lipoprotein (oxLDL), autoantibodies against endothelial cells and phospholipids, type I interferons (IFN) and neutrophil extracellular traps (NETs) directly or through activation of type I IFN pathway. Increased oxidative stress, reduced levels of the normally antioxidant high density lipoprotein (HDL), increased levels of proinflammatory HDL (piHDL) and reduced paraoxonase activity have been related to increased oxLDL levels. On the other hand, impaired atheroprotective mechanisms in lupus include decreased capacity of endothelial repair-partly mediated by type I IFN- and dampened production of atheroprotective autoantibodies. In the present review, traditional and disease related risk factors for CV disease (CVD) in the setting of chronic autoimmune disorders with special focus on SLE will be discussed.

Antibodies Against Various Forms of Mildly Oxidized Low-Density Lipoprotein Are Not Associated With Carotid Intima-Media Thickness in Patients With Primary Hyperlipidemia

The carotid intima-media thickness (IMT) can reflect early atherosclerosis. Oxidative modification of low-density lipoprotein (LDL) leads to the formation of several immunogenic epitopes and different forms of antibodies against oxidized LDL (oxLDL). We investigated the possible relationship between autoantibody titers against various forms of mildly oxLDL and carotid IMT in patients (n=100) with primary hyperlipidemia. Three different types of mildly oxidized LDL—oxLDLL, oxLDLP, and oxLDLD—were prepared at the end of lag, propagation, and decomposition phases of oxidation, respectively. Similar types of oxLDL were also prepared from the same LDL preparations after inactivation of the LDL-associated platelet-activating factor acetylhydrolase (PAF-AH). These types were denoted as oxLDL(-)L, oxLDL(-)P, and oxLDL(-)D. OxLDL types are primarily enriched in lysophosphatidylcholine (lyso-PC) due to hydrolysis of oxidized phospholipids (oxPL) by PAF-AH. OxLDL(-) types are mainly enriched in intact oxPL due to the inactivation of the LDL-associated PAF-AH before oxidation. IgG autoantibodies against all types of oxLDL were determined and IMT was evaluated ultrasonographically. IMT values were significantly associated with age, systolic blood pressure and serum triglyceride levels, whereas no correlation was found between IMT values and antibody titers against all types of either oxLDL or oxLDL(-). We suggest that autoantibodies against various types of mildly oxidized LDL enriched either in lyso-PC or in oxPL are not associated with the extent of carotid atherosclerosis. This supports the concept that extensively oxidized LDL enriched in aldehydes rather than mildly oxidized LDL may play a prominent role in the early stage of atherosclerosis.

Autoantibodies to phosphorylcholine and cardiovascular outcomes in patients with acute coronary syndromes in the ATLAS ACS-TIMI 46 trial

Atherogenesis is a complex inflammatory process stemming from the accumulation and oxidation of low density lipoproteins (LDL). IgM autoantibodies against phosphorylcholine (anti-PC) bind to the PC epitope on oxidized LDL (OxLDL), inhibiting the uptake of oxLDL by macrophages in atherosclerotic lesions. Anti-PC autoantibodies have been reported to be protective against atherothrombosis. We investigated the relationship of anti-PC concentrations with cardiovascular outcomes in patients with acute coronary syndromes (ACS). We measured anti-PC levels within 7 days of an ACS in 3,356 patients enrolled in the ATLAS ACS-TIMI 46 trial, a randomized dose ranging study of rivaroxaban versus placebo. The primary endpoint was death, myocardial infarction (MI), stroke, or severe recurrent ischemia (SRI) requiring revascularization during 6 months. The median baseline anti-PC concentration was 40.9 U/mL (25th, 75th percentiles: 25.4, 67.4). There was no significant association between anti-PC levels and the primary endpoint (Q1: 6.8 %, Q2: 4.2 %, Q3: 7.8 %, Q4: 5.4 %, p-trend = 0.87), all-cause mortality (Q1: 1.4 %, Q2: 0.7 %, Q3: 2.4 %, Q4: 0.9 %, p-trend = 0. 96), or any of the other individual endpoint components (MI: p-trend = 0.87, Stroke: p-trend = 0.43, SRI: p-trend = 0.66). Using the previously reported anti-PC cutpoint of 17 U/mL did not reveal a significant relationship between anti-PC concentrations and cardiovascular outcomes (<17 U/mL: 8.1 % vs. ≥17 U/mL: 5.8 %; p = 0.11). Similarly, evaluation of anti-PC as a continuous variable did not reveal a significant association (p = 0.30). In this study of patients early after ACS undergoing intensive secondary preventive therapy, IgM anti-PC titers did not exhibit a significant relationship with cardiovascular outcomes.

LDL oxidative modification and carotid atherosclerosis: results of a multicenter study

OBJECTIVE

Serum LDL conjugated diene concentration is a marker of oxidative modification of LDL. We investigated the relationship between LDL conjugated dienes and cross-sectional subclinical atherosclerosis assessed by carotid IMT in high-risk subjects of a multicenter study.

METHODS

Serum LDL conjugated dienes and ultrasonographically assessed carotid intima-media thickness (IMT(mean), IMT(max) and IMT(mean-max)) were available for 553 subjects from Finland, France, Italy, the Netherlands, and Sweden.

RESULTS

In multivariate regression analysis, gender (p < 0.001), age (p < 0.001), systolic blood pressure (IMT(mean), p = 0.01; IMT(mean-max), p = 0.05) and serum LDL conjugated dienes (p = 0.02 for both IMT(mean) and IMT(mean-max)) were the strongest determinants of IMT variation, adjusted for study center, ultrasound videotape reader and serum LDL cholesterol. Pack-years of smoking, added into the regression model, did not destroy the significant association between increased serum LDL conjugated dienes and IMT. Ratio of LDL conjugated dienes to LDL particle cholesterol was higher in subjects of Northern recruiting centers than of Southern centers (r = 0.39, p < 0.0001).

CONCLUSIONS

There was a cross-sectional association between in vivo increased LDL oxidative modification and subclinical atherosclerosis after adjustment for traditional risk factors. The subjects in Northern countries of Europe had more oxidatively modified lipids per cholesterol in LDL particle than subjects in Southern countries.

Immunoglobulins against tyrosine-nitrated epitopes in coronary artery disease

BACKGROUND

Several lines of evidence support a pathophysiological role of immunity in atherosclerosis. Tyrosine-nitrated proteins, a footprint of oxygen- and nitrogen-derived oxidants generated by cells of the immune system, are enriched in atheromatous lesions and in circulation of patients with coronary artery disease (CAD). However, the consequences of possible immune reactions triggered by the presence of nitrated proteins in subjects with clinically documented atherosclerosis have not been explored.

METHODS AND RESULTS

Specific immunoglobulins that recognize 3-nitrotyrosine epitopes were identified in human lesions, as well as in circulation of patients with CAD. The levels of circulating immunoglobulins against 3-nitrotyrosine epitopes were quantified in patients with CAD (n=374) and subjects without CAD (non-CAD controls, n=313). A 10-fold increase in the mean level of circulating immunoglobulins against protein-bound 3-nitrotyrosine was documented in patients with CAD (3.75±1.8 μg antibody Eq/mL plasma versus 0.36±0.8 μg antibody Eq/mL plasma), and was strongly associated with angiographic evidence of significant CAD.

CONCLUSIONS

The results of this cross-sectional study suggest that posttranslational modification of proteins via nitration within atherosclerotic plaque-laden arteries and in circulation serve as neo-epitopes for the elaboration of immunoglobulins, thereby providing an association between oxidant production and the activation of the immune system in CAD.

Anti-oxidized low-density lipoprotein (oxLDL) antibody levels are not related to increasing circulating oxLDL concentrations during the course of pregnancy

PROBLEM

To address the question of whether the high levels of oxidative modified low-density lipoproteins (oxLDL) in pregnancy are opposed by an appropriate humoral autoimmune response providing anti-oxLDL autoantibodies in maternal serum of healthy women throughout gestation.

METHOD OF STUDY

Blood was taken from 33 patients at four different time points from early to late gestation and post-partum. OxLDL and anti-oxLDL concentrations were measured by enzyme-linked immunosorbent assays. ANOVA was used for statistical evaluations followed by post hoc test with Bonferoni adjustment.

RESULTS

Oxidized Low Density Lipoprotein concentrations increased while anti-oxLDL levels decreased significantly from early to late gestation. OxLDL was strongly positively correlated with LDL concentration and mildly negatively associated with anti-oxLDL levels. Estimating the status of oxidation by calculating oxLDL/LDL ratio revealed decreasing values with ongoing pregnancy. Multivariate analysis showed that anti-oxLDL levels were dependent on gestational age but neither on oxLDL levels nor on the oxLDL/LDL ratio.

CONCLUSIONS

The results indicate that normal pregnancy is a well-balanced state of oxidative and anti-oxidative processes. However, we could not confirm a dependence of anti-oxLDL autoantibodies on oxLDL concentration. Whether or not the humoral immune system is involved in oxidative defence remains to be elucidated.

Role of scavenger receptor A and CD36 in diet-induced nonalcoholic steatohepatitis in hyperlipidemic mice

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH) is a disorder that consists of steatosis and hepatic inflammation. It is not known why only some people with steatosis develop NASH. Recently, we identified dietary cholesterol as a factor that directly leads to hepatic inflammation and hepatic foam cell formation. We propose a mechanism by which Kupffer cells (KCs) take up modified cholesterol-rich lipoproteins via scavenger receptors (SRs). KCs thereby accumulate cholesterol, become activated, and may then trigger an inflammatory reaction. Scavenging of modified lipoproteins mainly depends on CD36 and macrophage scavenger receptor 1.

METHODS

To evaluate the involvement of SR-mediated uptake of modified lipoproteins by KCs in the development of diet-induced NASH, female low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice were lethally irradiated and transplanted with bone marrow from Msr1(+/+)/Cd36(+/+)or Msr1(-/-)/Cd36(-/-) mice and fed a Western diet.

RESULTS

Macrophage and neutrophil infiltration revealed that hepatic inflammation was substantially reduced by approximately 30% in Msr1(-/-)/Cd36(-/-)-transplanted mice compared with control mice. Consistent with this, the expression levels of well-known inflammatory mediators were reduced. Apoptotis and fibrosis were less pronounced in Msr1(-/-)/Cd36(-/-)-transplanted mice, in addition to the protective phenotype of natural antibodies against oxidized low-density lipoprotein in the plasma. Surprisingly, the effect on hepatic inflammation was independent of foam cell formation.

CONCLUSIONS

Targeted inactivation of SR pathways reduces the hepatic inflammation and tissue destruction associated with NASH, independent of hepatic foam cell formation.

Natural antibodies against phosphorylcholine in cardiovascular disease

Atherosclerosis is a chronic inflammatory disease characterized by the presence of activated immune-competent cells in the lesions, producing mainly proinflammatory cytokines. Atherosclerosis is the underlying cause of cardiovascular disease (CVD), to a large extent occurring after damage and/or rupture of the atherosclerotic plaques. One major factor implicated as a cause of this immune activation is modified low-density lipoproteins (LDL), especially oxidized forms (oxLDL), which are abundant in plaques, both in foam cells and in the necrotic core. The LDL-oxidation process is very complex, and the nature of the antigens has been difficult to identify. We and others have focused on the phospholipids (PL) in oxLDL, especially oxidized forms of PL, including platelet-activating factor (PAF)-like lipids and lysophosphatidylcholine (LPC), and demonstrated that these could play a major role through proinflammatory effects. One common epitope is phosphorylcholine (PC), which is also exposed on some microorganisms (including Streptococcus pneumoneae) and on apoptotic cells. Natural IgM antibodies against PC (anti-PC) have been known for a long time, but little has been reported about their role in human disease, especially in CVD. We have demonstrated that anti-PC IgM are negatively associated with atherosclerosis development in hypertensive individuals and that low levels of anti-PC independently predict development of CVD. Anti-PC IgM could, therefore, be a novel risk marker in CVD. Animal experiments indicate that both active immunization with PC and passive immunization with anti-PC ameliorate atherosclerosis development. The possibility that anti-PC could be used therapeutically in humans deserves further study.

Association of serum levels of lipid and its novel constituents with the different stages of esophageal carcinoma

BACKGROUND

The aim of the study was to evaluate the association of immunoglobulin G type of autoantibodies to oxidized low-density lipoprotein (oxLDL-lgG) and oxLDL-lgM with the progression of esophageal squamous cell carcinoma (ESSC).

METHODS

Residents from Feicheng, China aged 40 to 69 years were screened for esophageal lesions in a screening program conducted during the period of January 2008 to December 2006. There were 33 controls with normal esophageal squamous epithelium cells, 37 patients with basal cell hyperplasia, 47 with esophageal squamous cell dysplasia, and 43 with ESCC. All the participants were diagnosed by biopsy and histopathological examination. Adiponectin, oxidized low-density lipoprotein (oxLDL), autoantibodies against oxLDL (oxLDL-ab), OxLDL-lgG, and OxLDL-lgM were determined by enzyme linked immunosorbent assay (ELISA). Total cholesterol, High-density lipoprotein (HDL), triglyceride, serum albumin, and blood pressure were co-estimated. Analysis of covariance for lipid levels was used to control the influence of covariates.

RESULTS

The level of oxLDL-lgM increased gradually along with esophageal carcinoma progression. The oxLDL-lgM levels in the ESCC group were the highest after possible covariates were controlled. Binary logistic regression showed that oxLDL-lgM had a positive correlation with the development of esophageal carcinoma, while oxLDL and oxLDL-ab had a negative correlation with ESSC. No significant association between the levels of oxLDL-lgG and adiponectin and the different stages of ESSC was observed.

CONCLUSION

The present study shows that the decreased oxLDL and oxLDL-ab and the elevated oxLDL-lgM serum levels may relate to the development and progression of ESSC.

Antitreponemal antibodies leading to autoantibody production and protection from atherosclerosis in Kitavans from Papua New Guinea

The objective of our study was to determine the prevalence of anti-infectious agent antibodies and autoantibodies in a unique non-Westernized population from Kitava, Papua New Guinea (PNG), compared to Western populations. We matched 120 serum samples from Kitavans with 437 samples from four healthy control groups. Sera were tested for the presence of anti-infectious agent antibodies (treponema, toxoplsmosis, Epstein-Barr virus, cytomegalovirus, rubella) and autoantiobodies [anti-double-stranded (ds)DNA, anti-chromatin, anti-ribonucleoprotein (RNP), anti-SSB, anti-SSA, anti-Scl-70, anti-Smith, anti-centromer, anti-SmRNP, anti-Jo-1, and anti-ribosomal-P] using the Bio-Rad BioPlex 2200. Antitreponemal antibodies were detected in 87% of PNG sera versus 0-6% of controls (P < 0.0001). Anti-dsDNA antibodies were detected in 31% of PNG samples, which was significantly higher than in three of the control groups (<10%). The outstanding high rate of antitreponemal antibodies detected in Kitavans possibly represents prior yaws disease. A low prevalence of cardiovascular disease was previously documented in Kitavans and has been attributed, in addition to their diet, to the high prevalence of natural cardioprotective autoantibodies (the IgM-antiphosphorylcholine antibodies) in this population. Treponemal infection has been shown to induce the appearance of antiphosphorylcholine antibodies. These protective autoantibodies may cross-react with the pathogenic anti-dsDNA antibodies. Thus, it is suggested that infection with treponema is associated with the presence of protective as well as pathogenic autoantibodies.

Low level natural antibodies against phosphorylcholine: a novel risk marker and potential mechanism in atherosclerosis and cardiovascular disease

Atherosclerosis is an inflammatory condition characterised by an abundance of activated immunocompetent cells in plaques which cause cardiovascular disease (CVD) when they rupture. Oxidized forms of low density lipoprotein (OxLDL) are a major constituent of atherosclerotic plaques and have proinflammatory effects, making oxLDL a candidate factor promoting atherosclerosis. In previous studies we and others demonstrated that platelet-activating factor (PAF)-like lipids in oxLDL may cause oxLDL-induced immune-stimulatory effects. A common denominator is phosphorylcholine (PC), a hapten-like epitope which is exposed on OxLDL and some microorganisms. We recently demonstrated that anti-PC has anti-inflammatory properties and that low levels of anti-PC predict the development of stroke and myocardial infarction. We hypothesize that low anti-PC represents a novel paradigm as a cause of chronic inflammatory diseases such as atherosclerosis where oxidized and/or inflammatory phospholipids play a role. It is possible that anti-PC can be used as a novel diagnostic tool and therapy in atherosclerotic disease.

Clinical significance of the humoral immune response to modified LDL

Human low density lipoprotein (LDL) undergoes oxidation and glycation in vivo. By themselves, oxidized LDL (oxLDL) and AGE-LDL have proinflammatory properties and are considered atherogenic. But the atherogenicity of these lipoproteins are significantly increased as a consequence of the formation of immune complexes (IC) involving specific autoantibodies. OxLDL and AGE antibodies have been shown to be predominantly of the IgG1 and IgG3 isotypes. OxLDL antibodies are able to activate the complement system by the classical pathway and to induce FcR-mediated phagocytosis. In vitro and ex vivo studies performed with modified LDL-IC have proven their pro-inflammatory and atherogenic properties. Clinical studies have demonstrated that the levels of circulating modified LDL-IC correlate with parameters indicative of cardiovascular and renal disease in diabetic patients and other patient populations. The possibility that spontaneously formed or induced modified LDL antibodies (particularly IgM oxLDL antibodies) may have a protective effect has been suggested, but the data is unclear and needs to be further investigated.

Vaccines in development to prevent and treat atherosclerotic disease

Coronary heart disease (CHD) remains the leading cause of death in the United States. Immune mechanisms have been recently proposed to play an important role in the development of atherosclerotic plaques in CHD. Heat shock proteins and oxidized low-density lipoprotein are proinflammatory substances that have been shown to have an important role in the pathogenesis of atherosclerosis, and are now targets for clinical vaccine development. In addition, a vaccine has been developed to inhibit cholesteryl ester transfer protein. It is now recognized that many medications used to combat plaque development and rupture have significant anti-inflammatory effects and these effects are critical for drug efficacy. The influenza vaccine is associated with an atheroprotective effect. In addition, a nicotine vaccine, an antiangiotensin vaccine, and an anti-obesity vaccine may play a therapeutic role in modifying known risk factors for the development of atherosclerosis and its complications. This article reviews these vaccines as possible additions to the armamentarium of atheroprotective treatment modalities.

Distribution of IgM and IgG antibodies to oxidized LDL in immune complexes isolated from patients with type 1 diabetes and its relationship with nephropathy

Modified lipoproteins are immunogenic and play a key pathogenic role in vascular disease. Antibodies to oxidized LDL (oxLDL) are mostly of the pro-inflammatory IgG1 and IgG3 isotypes. We measured IgG and IgM oxLDL antibodies in immune complexes (IC) isolated from 36 patients with type 1 diabetes using a nested case control design. IgG antibodies predominated over IgM antibodies by an 8:1 ratio. IgG antibody concentrations were higher in the nephropathy cases compared to controls (p = 0.09), but no significant difference was observed because of two patients included in the study who had end-stage renal disease (creatinine > 5 mg/dL and glomerular filtration rate (GFR) less than 17 mL/min). After eliminating these patients from the analysis, significant positive associations of IgG antibody concentration with serum creatinine and albumin excretion rate were observed. Similarly, a negative correlation with estimated glomerular filtration rate was observed in this subsample of 34 patients. Differences in IgM antibody concentrations by nephropathy classification were not supported by the data. In conclusion, the predominance of pro-inflammatory IgG oxLDL antibodies is associated with existence of diabetic nephropathy, and a protective role of IgM antibodies could not be demonstrated.

Atherogenesis and the humoral immune response to modified lipoproteins

Modified forms of LDL are immunogenic and activate both cell-mediated and humoral immune responses. Both types of responses are pro-inflammatory and are probably primary players in the perpetuation of the chronic inflammatory reaction characteristic of atherosclerosis. The immunologic response to modified LDL can be directed to MHC-II-associated peptides in the case of T helper cells, and to a variety of epitopes-modified lysine groups, modified phospholipids, proteins that become associated with oxidized LDL (such as beta2GP1)--in the case of B cell responses. T cell activation is likely to play a major role through cross-activation of macrophages. Humoral responses to modified LDL are pathogenic as a consequence of the formation of antigen-antibody complexes containing modified LDL and IgG antibodies. Those immune complexes induce cholesterol ester accumulation in macrophages and macrophage-like cells, and induce the release of pro-inflammatory cytokines, chemokines, oxygen active radicals, and matrix metalloproteinases from those cells. There is no conclusive evidence supporting a protective role for IgM antibodies in humans, possibly because autoantibodies to modified lipoproteins are predominantly of the IgG isotype.

Gluten-free vegan diet induces decreased LDL and oxidized LDL levels and raised atheroprotective natural antibodies against phosphorylcholine in patients with rheumatoid arthritis: a randomized study

Introduction

The purpose of this study was to investigate the effects of vegan diet in patients with rheumatoid arthritis (RA) on blood lipids oxidized low-density lipoprotein (oxLDL) and natural atheroprotective antibodies against phosphorylcholine (anti-PCs).

Methods

Sixty-six patients with active RA were randomly assigned to either a vegan diet free of gluten (38 patients) or a well-balanced non-vegan diet (28 patients) for 1 year. Thirty patients in the vegan group completed more than 3 months on the diet regimen. Blood lipids were analyzed by routine methods, and oxLDL and anti-PCs were analyzed by enzyme-linked immunosorbent assay. Data and serum samples were obtained at baseline and after 3 and 12 months.

Results

Mean ages were 50.0 years for the vegan group and 50.8 years for controls. Gluten-free vegan diet induced lower body mass index (BMI) and low-density lipoprotein (LDL) and higher anti-PC IgM than control diet (p < 0.005). In the vegan group, BMI, LDL, and cholesterol decreased after both 3 and 12 months (p < 0.01) and oxLDL after 3 months (p = 0.021) and trendwise after 12 months (p = 0.090). Triglycerides and high-density lipoprotein did not change. IgA anti-PC levels increased after 3 months (p = 0.027) and IgM anti-PC levels increased trendwise after 12 months (p = 0.057). There was no difference in IgG anti-PC levels. In the control diet group, IgM anti-PC levels decreased both after 3 and 12 months (p < 0.01). When separating vegan patients into clinical responders and non-responders at 12 months, the effects on oxLDL and anti-PC IgA were seen only in responders (p < 0.05).

Conclusion

A gluten-free vegan diet in RA induces changes that are potentially atheroprotective and anti-inflammatory, including decreased LDL and oxLDL levels and raised anti-PC IgM and IgA levels.

Oxidized LDL and anti-oxLDL antibody levels in peripheral atherosclerotic disease

OBJECTIVE

Oxidative modification of LDL (oxLDL) is important in atherogenesis and is proposed as a useful marker for identifying patients with coronary artery disease. Antibody to oxLDL (oxLDL Ab) is detected in human sera, although its biological significance is not well established. We aimed to measure oxLDL and oxLDL Ab in peripheral atherosclerotic disease (PAD) patients, and to examine the relation between them in an attempt to understand the role of oxLDL Ab. Total risk of atherosclerosis was estimated using the global risk assessment score (GRAS) calculated on the basis of age, total cholesterol, HDL cholesterol (HDL-Chol), diabetes, hypertension and smoking.

MATERIAL AND METHODS

Twenty-one patients aged 63.05+/-9.13 years, diagnosed by peripheric angiography as PAD, and 21 healthy controls aged 47.67+/-13.61 years took part in the study. Total LDL and HDL cholesterol levels were determined by enzymatic methods. Levels of circulating oxLDL were measured by monoclonal antibody 4E6-based competition ELISA. IgG class oxLDL Ab titre was measured by ELISA.

RESULTS

Compared to healthy controls, PAD patients had higher levels of oxLDL (p<0.05), oxLDL Ab (p<0.05), LDL cholesterol (LDL-Chol) (p<0.05), total cholesterol (p<0.05) and lower HDL-Chol (p<0.05). OxLDL was found to be positively correlated with total cholesterol (r = 0.471, p<0.05) and LDL-Chol (r = 0.614, p<0.01) and GRAS (r = 0.435, p<0.05) and negatively with HDL-Chol (r = -0.459, p<0.05), but not with oxLDL Ab in PAD patients.

CONCLUSIONS

These findings might indicate that high LDL-Chol levels influence the oxidation of LDL and that oxLDL is a possible marker of PAD. However, the role of oxLDL Ab in atherosclerosis remains controversial.

Brachial artery intima-media thickness and echogenicity in relation to lipids and markers of oxidative stress in elderly subjects:--the prospective investigation of the vasculature in Uppsala Seniors (PIVUS) Study

The aim of the present study was to relate brachial artery intima-media thickness (IMT) and the grey scale median of the intima-media complex (IM-GSM) to traditional cardiovascular risk factors and markers of inflammation and oxidative stress. In the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS) study, a population-based study of 1016 subjects aged 70, brachial artery IMT and IM-GSM, who were evaluated by ultrasound. Lipids, thirteen markers of inflammation and nine markers of oxidative stress were measured. The Framingham risk score was related to IMT (p < 0.0001), but not to the IM-GSM. In univariate analysis, HDL-cholesterol, serum triglycerides, fasting glucose, smoking, HOMA insulin resistance index and oxidized LDL levels were related to IMT. HDL and LDL-cholesterol, triglycerides, VCAM-1, e-selectin, leukocyte count, conjugated diens, baseline conjugated diens (BCD)-LDL, antibodies to oxLDL, the GSSG/GSH glutathione ratio and homocysteine were related to IM-GSM. In multiple regression models, HDL-cholesterol, fasting glucose and oxLDL levels were the independently related to IMT (p = 0.01-0.04), while serum triglycerides, BCD-LDL and the GSSG/GSH ratio were independently related to IM-GSM (p = 0.0001-0.004). In conclusion, in addition to traditional lipid variables, markers of oxidative stress were associated with both thickness and echogenicity of the brachial artery intima-media complex. Thus, both thickness and echogenicity of the brachial artery intima-media complex might be useful biomarkers in the future.

Elevated white blood cell count, CRP and fibrinogen levels are not associated with increased anti-endothelial and anti-ox-LDL antibody, MCP-1, and RANTES levels in early onset occlusive carotid artery disease

BACKGROUND

Inflammatory processes have importance in atherosclerosis. We evaluated if subjects below 55 years of age with occlusive carotid artery disease have higher serum levels of antibodies against oxidized LDL and endothelial cells and the chemokines MCP-1 and RANTES than age matched subjects without atherosclerosis.

METHODS AND RESULTS

Sixty patients with occlusive carotid artery disease (stenosis or occlusion) and 30 age-matched controls participated in the study. We measured the degree of carotid artery stenosis and intima-media thickness (IMT) by duplex ultrasound. White blood cell count (WBC), C-reactive protein (CRP), and fibrinogen levels were significantly higher in patients (means+/-SD: 7.5+/-1.8 vs. 6.1+/-1.1 G/L, p<0.001; 7.7+/-20.7 vs. 2.5+/-1.9 mg/L, p=0.015; and 3.7+/-0.9 vs. 3.1+/-0.5 g/L, p<0.001, respectively). Antibody levels against oxidized LDL and endothelial cells (21.1+/-22.9 and 19.9+/-15.3 EU/mL, p=0.6; and 19+/-15 vs. 20+/-9 U/mL, p=0.07) and RANTES and MCP-1 levels (72.4+/-32.3 vs. 73.8+/-27.3 ng/mL, p=0.7; and 468+/-1041 vs. 318+/-131 pg/mL, p=0.7) did not differ significantly between patients and controls and did not correlate with IMT.

CONCLUSIONS

Higher levels of WBC, CRP, and fibrinogen suggest an ongoing inflammation in early-onset carotid atherosclerosis, but increased IMT is not associated by the elevation of serum levels of chemokines and antibodies evaluated in this study.

Atheroprotective natural anti-phosphorylcholine antibodies of IgM subclass are decreased in Swedish controls as compared to non-westernized individuals from New Guinea

Objective

To determine the importance of IgM antibodies against phosphorylcholine (aPC), a novel protective factor for cardiovascular disease (CVD), in a population with a non-western life style as compared with a Swedish control group.

Methods and results

Risk factors for cardiovascular disease were determined in a group of 108 individuals aged 40–86 years from New Guinea and 108 age-and sex-matched individuals from a population based study in Sweden. Antibodies were tested by ELISA. aPC IgM levels were significantly higher among New Guineans than among Swedish controls (p < 0.0001). This difference remained significant among both men and women when controlled for LDL and blood pressure which were lower and smoking which was more prevalent in New Guineans as compared to Swedish controls (p < 0.0001). aPC IgM was significantly and negatively associated with age and systolic blood pressure among Swedish controls and with waist circumference among New Guineans. aPC IgM levels were significantly higher among women than men in both groups. The proportion of the saturated fatty acid (FA) myristic acid in serum cholesterol esters was negatively but polyunsaturated eicosapentaenoic acid and also lipoprotein (a) were positively associated with aPC IgM levels.

Conclusion

IgM-antibodies against PC, which have atheroprotective properties, are higher in a population from Kitava, New Guinea with a traditional lifestyle, than in Swedish Controls, and higher among women than men in both populations tested. Such antibodies could contribute to the low incidence of cardiovascular disease reported from Kitava and could also provide an explanation as to why women have a later onset of CVD than men.

Changes in immune responses to oxidized LDL epitopes during aging in hypercholesterolemic apoE(−/−) mice

Atherosclerosis is a disease associated with aging and is subject to modulation by both the innate and adaptive immune system. The time course of age-dependent changes in immune regulation in the context of atherosclerosis has not been characterized. This study aims to describe alteration of the immune responses to oxidized LDL (oxLDL) during aging that is associated with changes in plaque size and phenotype in apoE(−/−) mice. Mice fed a Western diet were euthanized at 15–17, 36, or >52 wk of age. The descending aortas were stained for assessment of extent of atherosclerosis. Plaque lipid, macrophage, and collagen content were evaluated in aortic sinus lesions. The adaptive immune response to oxLDL was assessed using anti-malondialdehyde-oxidized LDL (MDA-LDL) and copper-oxidized LDL (Cu-oxLDL) IgG, and the innate immune response was assessed using anti-Cu-oxLDL and phosphorylcholine (PC) IgM. Aging was associated with a significant increase in plaque area and collagen content and a decrease in plaque macrophage and lipid content. MDA-LDL IgG significantly increased at 36 wk but was reduced in mice >52 wk. Cu-oxLDL IgG increased with age and IgG-apoB immune complexes were increased in the >52 wk group. Cu-oxLDL and PC IgM significantly increased with age. The expression of splenic cytokines such as IFN-γ, IL-4, and IL-10 increased with age. Our study shows a generalized increase in innate immune responses associated with progression of atherosclerosis and a less inflammatory and less lipid-containing plaque phenotype during aging. The adaptive immune response appeared to be less generalized, with a specific reduction in MDA-LDL IgG.

Distinctiveness of secretory phospholipase A2 group IIA and V suggesting unique roles in atherosclerosis

Clinical observations strongly support an association of circulating levels of secretory phospholipases A(2) (sPLA(2)) in atherosclerotic cardiovascular disease (ACVD). Two modes of action can provide causal support for these statistical correlations. One is the action of the enzymes on circulating lipoproteins and the other is direct action on the lipoproteins once in the arterial extracellular intima. In this review we discuss results suggesting a distinct profile of characteristics related to localization, action on plasma lipoproteins and interaction with arterial proteoglycans for sPLA(2)-IIA and sPLA(2)-V. The differences observed indicate that these enzymes may contribute to atherosclerosis through dissimilar pathways. Furthermore, we comment on recent animal studies from our laboratory indicating that the expression of type V enzyme is up-regulated by genetically and nutritionally-induced dyslipidemias but not the group type IIA enzyme, which is well known to be up-regulated by acute inflammation. The results suggest that if similar up-regulation occurs in humans in response to hyperlipidemia, it may create a distinctive link between the group V enzyme and the disease.

Autoantibody titers against OxLDL are correlated with Achilles tendon thickness in patients with familial hypercholesterolemia

Achilles tendon xanthomas are associated with increased cardiovascular risk in patients with familial hypercholesterolemia (FH). Oxidized low density lipoprotein (OxLDL), the antibodies against OxLDL, and the LDL-associated phospholipase A(2) (Lp-PLA(2)) may play important roles in atherogenesis. We investigated the possible association between plasma levels of OxLDL, Lp-PLA(2) activity, and autoantibody titers against various types of mildly OxLDL with Achilles tendon thickness (ATT). ATT was determined by sonography in 80 unrelated heterozygous FH patients. Three different types of mildly OxLDL were prepared: OxLDL(L), OxLDL(P), and OxLDL(D), at the end of the lag, propagation, and decomposition phases of oxidation, respectively. Similar types of OxLDL were also prepared after inactivation of the LDL-associated Lp-PLA(2). These types were denoted OxLDL(-)(L), OxLDL(-)(P), and OxLDL(-)(D). FH patients exhibited significantly higher plasma OxLDL levels and serum IgG titers against OxLDL(P) and OxLDL(D) compared with 40 normolipidemic apparently healthy controls. ATT values were positively correlated with autoantibody titers against OxLDL(P) and OxLDL(D); however, in multiple regression analysis, ATT was independently associated only with the autoantibody titers against OxLDL(D). We conclude that the IgG autoantibody titers against OxLDL(D) but not OxLDL or Lp-PLA(2) may play an important role in the pathogenesis of Achilles tendon xanthomas in FH patients.

Identification of autoantibodies in human plasma recognizing an apoB-100 LDL receptor binding site peptide

The aim of this study was to test the hypothesis that autoantibodies recognize amino acid sequences in the LDL receptor binding region of apolipoprotein B-100 (apoB-100). Autoantibodies against an unmodified or malondialdehyde (MDA)-modified LDL receptor binding site peptide were determined by ELISA in baseline plasma samples of 78 cases with coronary events and 149 matched controls recruited from the prospective Malmö Diet Cancer Study. IgG and IgM recognizing this peptide were detected in all subjects but did not differ between cases and controls. Inverse associations were observed between IgG against the native binding site and plasma oxidized LDL (r = -0.21, P < 0.005), but there were no significant associations with total or LDL cholesterol levels. In univariate analyses, inverse associations were found between baseline carotid intima-media thickness and IgG against the MDA-modified binding site (r = -0.14, P < 0.05), but this association was lost when controlling for other major cardiovascular risk factors. Specificity studies demonstrated that the binding of autoantibodies to these sequences could be inhibited by oxidized but not by native LDL. Autoantibodies recognizing the LDL receptor binding site in apoB-100 are frequently expressed. Their association with plasma oxidized LDL suggests that they have been generated in response to breakdown products of LDL oxidation, but their influence on cholesterol metabolism and the development of atherosclerosis appears limited.

OxLDL/beta2GPI complexes and autoantibodies in patients with systemic lupus erythematosus, systemic sclerosis, and antiphospholipid syndrome: pathogenic implications for vascular involvement

Oxidized low-density lipoprotein (oxLDL) interacts with beta2GPI, forming oxLDL/beta2GPI complexes. Autoimmune vascular inflammation (and oxidative stress) may promote the formation of these complexes. The coexistence of oxLDL/beta2GPI complexes with autoantibodies to these complexes suggests an active pro-atherogenic role in vascular thrombosis and atherosclerosis. Immunoglobulin G (IgG) anti-oxLDL/beta2GPI antibodies have been regarded as pro-atherogenic, whereas IgM antibodies are thought to be anti-atherogenic. For this study, oxLDL/beta2GPI complexes, IgG, and IgM anti-oxLDL/beta2GPI antibodies were measured using enzyme-linked immunosorbent assay (ELISA). Measurements were taken in two patient groups: (1) those with systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and rheumatoid arthritis (RA); and (2) those with primary and secondary antiphospholipid syndrome (APS). For oxLDL/beta2GPI complexes, SLE and SSc patients had the highest mean optical densities (ODs) (P <.001), followed by RA (P = .139) and healthy controls. IgG anti-oxLDL/beta2GPI antibody distribution followed the same pattern observed with oxLDL/beta2GPI complexes, SLE and SSc (P <.001), RA (P = .08), and controls. IgM antibodies showed a reverse pattern, with the highest mean OD in RA (P <.001), followed by SSc (P = .007) and SLE (P = 143). Both IgG and IgM anti-oxLDL/beta2GPI antibodies were significantly higher in secondary APS patients compared with SLE controls without APS. In addition, the highest mean OD and prevalence of IgG anti-oxLDL/beta2GPI antibodies were observed in APS patients with a history of arterial thrombosis. These results may reflect the widespread vascular involvement seen in SLE and SSc, in contrast to the relatively low vascular involvement in RA. In SLE and SSc, high serum levels and prevalence of circulating oxLDL/beta2GPI complexes and IgG anti-oxLDL/beta2GPI antibodies indicate significant vascular oxidative stress as well as a possible pathogenic role in autoimmune-mediated atherosclerosis.

Alcohol consumption is directly associated with circulating oxidized low-density lipoprotein

Findings on the association of alcohol consumption and oxidation of low-density lipoprotein (LDL), which is thought to play a crucial role in the generation of atherosclerotic lesion, are inconsistent. The aim of the present study was to investigate the association of total alcohol consumption and type of alcoholic beverage with circulating plasma LDL oxidation. This cross-sectional study included data of circulating oxidized LDL (ox-LDL) from a subpopulation of 587 men and women enrolled in a population-based survey conducted in 2000 in Girona (Spain). Multivariate analysis was performed to describe the independent association of alcohol consumption and ox-LDL. Increasing alcohol consumption was associated with high in vivo ox-LDL levels in the present population. The consumption of 10 g of alcohol was associated with an increase of 2.40 U/L of ox-LDL (p = 0.002). Adjustment for dietary variables, leisure-time physical activity, educational level, smoking, LDL-cholesterol, high-density lipoprotein-cholesterol, glycemia, triglycerides, diabetes, body mass index, waist circumference, and systolic and diastolic blood pressures only slightly modified this association (p = 0.003). In this full adjusted model the consumption of 10 g of alcohol per day was associated with an increase of 2.11 U/L of ox-LDL. Consumption of wine (ml/day) was associated with increasing ox-LDL levels (p = 0.029), however, attenuated after controlling for alcohol. No significant relationship of ox-LDL with alcohol-independent consumption of wine, beer, and spirits was observed. Alcohol consumption was independently and directly associated with circulating ox-LDL in the present population.

Identification of mildly oxidized low-density lipoprotein (electronegative LDL) and its auto-antibodies IgG in children and adolescents hypercholesterolemic offsprings

BACKGROUND

Oxidative modification of low-density lipoproteins (LDL) is an essential step in atherogenesis, generating minimally oxidized LDL, also called electronegative LDL [LDL(-)], which has chemotactic, cytotoxic and immunogenic properties.

METHODS AND RESULTS

Serum LDL(-) and anti-LDL(-) auto-antibodies (IgG) were evaluated in 28 children and adolescents with familial hypercholesterolemia (FH) antecedents, with or without early coronary artery disease in first-degree relatives (eCAD), hypercholesterolemic (hc) or normocholesterolemic (nc) versus a control group of normocholesterolemic children without pathologic antecedents (C). ELISA method was used for detection of LDL(-) and anti-LDL(-) IgG. LDL(-) serum levels did not differ among the four groups (FH-eCAD-hc 41.4 +/- 24.9 microg/dl; FH-hc 38.3 +/- 11.2 microg/dl; FH-nc 47.3 +/- 17.0 microg/dl and C 44.2 +/- 28.8 microg/dl, p = 0.659). However, IgG anti-LDL(-) auto-antibodies were significantly higher in the control group in comparison to the FH groups with or without eCAD, independent of hypercholesterolemia or normocholesterolemia (FH-eCAD-hc 0.825 +/- 0.289 microg/dl; FH-hc 0.667 +/- 0.307 microg/dl; FH-nc 0.763 +/- 0.204 microg/dl and C 1.105 +/- 0.233 microg/dl, p = 0.006). When the auto-antibodies of groups with FH, with or without eCAD and with or without hypercholesterolemia were compared, no differences were found (p = 0.509).

CONCLUSION

These results showed that FH and/or eCAD children and adolescents have lower titers of auto-antibodies anti-LDL(-) than children from normal families, independent of serum LDL-cholesterol or serum LDL(-).

Intravenous immunoglobulin and atherosclerosis

Several inflammatory and immunological factors have been established as important contributors to atherogenesis. Among these, oxidized low-density lipoprotein (oxLDL) play a central role in the initiation and progression of atherosclerotic lesions. In atherosclerotic lesions, oxLDL was also found to co-localize with beta2-glycoprotein I (beta2-GPI). Immunoglobulin (Ig)G autoantibodies against beta2-GPI complexed with oxLDL are pro-atherogenic because they increase uptake of the complexes by macrophages. In contrast, IgM natural anti-oxLDL antibodies derived from atherosclerosis-prone apolipoprotein E (ApoE) deficient mice reduced incidence of atherosclerosis. Such anti-oxLDL antibodies have been found in humans, and the accumulating evidences seem to support the idea that anti-oxLDL antibodies have a protective role for atherogenesis. Intravenous immunoglobulins (IVIgs) contain natural anti-oxLDL antibodies and infusion of IVIg into ApoE-deficient mice has been reported to decrease atherosclerosis. The anti-atherogenic property of IVIg may be derived from non-antigen-specific antibody binding to FCgamma receptors, which blocks foam cell formation of macrophages. Several other possible mechanisms are also discussed.

Reduction of oxidative stress and modulation of autoantibodies against modified low-density lipoprotein after rosuvastatin therapy

AIMS

To examine the effect of 24 weeks' rosuvastatin treatment on oxidative stress and changes in immune response to oxidized low-density lipoprotein (LDL).

METHODS

This was an open-label study of patients in Austria receiving 10 or 40 mg rosuvastatin daily alternately during 12 and 24 weeks. Circulating concentrations of antibodies to malondialdehyde-oxidized LDL (MDA-LDL), both IgG and IgM type, to copper-oxidized LDL (Cu-OxLDL-IgG), concentrations of oxidized LDL complexed to IgG (OxLDL-IC) and markers of oxidative stress and systemic inflammation in subjects with plasma LDL cholesterol concentrations between 130 mg dl-1 and 250 mg dl-1 and triglycerides

RESULTS

During statin therapy, plasma endogenous peroxides (POX-ACT) concentrations and peroxidase activity were significantly decreased, associated with a modest increase in total antioxidant capacity (TAC). Antibody titres to MDA-LDL-IgM, Cu-OxLDL-IgG and OxLDL-IC decreased, whereas MDA-LDL-IgG concentrations were increased after therapy. These changes were dose- and LDL-independent. POX-ACT concentrations were significantly positively correlated with inflammation markers before and after therapy and inversely with high-density lipoprotein-cholesterol concentrations after therapy.

CONCLUSION

This study provides in vivo evidence that rosuvastatin significantly reduces oxidative stress and has immunomodulatory properties in a dose- and LDL-independent manner.

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Key Words

• autoantibodies
• oxidative stress
• oxidatively modified low-density lipoprotein
• rosuvastatin

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MESH Headings

• Antioxidants/metabolism
• Autoantibodies/immunology
• Biomarkers/blood
• Copper/metabolism
• Dose-Response Relationship, Drug
• Female
• Fluorobenzenes/therapeutic use
• Humans
• Hydroxymethylglutaryl-CoA Reductase Inhibitors/therapeutic use
• Immunoglobulin G/immunology
• Immunoglobulin M/immunology
• Lipoproteins, LDL/metabolism
• Male
• Malondialdehyde/metabolism
• Middle Aged
• Oxidation-Reduction
• Oxidative Stress/drug effects
• Peroxidase/metabolism
• Peroxides/blood
• Pyrimidines/therapeutic use
• Rosuvastatin Calcium
• Sulfonamides/therapeutic use

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Grants Collapse

Affiliation(s)

Ulrike Resch Medical University of Vienna, Wilhelm Auerswald Atherosclerosis Research Group, Vienna, Austria.
Franz Tatzber
Alexandra Budinsky
Helmut Sinzinger

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Immunomodulation of atherosclerosis with a vaccine

Experimental observations have established that the innate and adaptive immune mechanisms both have roles in the modulation of atherosclerosis. The complex function that the immune system has in the pathophysiology of atherosclerosis is highlighted by the fact that both proatherogenic and atheroprotective effects of immune activation can be demonstrated. An immune response to the protein and lipid components of oxidized LDL cholesterol has been observed in experimental models, and immunization with these antigens has generally reduced atherosclerosis. The findings suggest the tantalizing possibility that an atheroprotective vaccine can be developed. Our laboratories have identified several antigenic epitopes in the human apolipoprotein B100 component of LDL cholesterol. Active immunization with some of these epitopes has reduced atherosclerosis in hyperlipidemic mice. We believe, therefore, that a vaccine based on apolipoprotein B100-related peptide could have a role in reducing atherosclerosis. In this review, we discuss the possible immunologic mechanisms by which vaccines against atherosclerosis might work and the ways in which such treatment might be most effectively administered.

Antibodies of IgM subclass to phosphorylcholine and oxidized LDL are protective factors for atherosclerosis in patients with hypertension

OBJECTIVE

To determine the importance of antibodies against phosphorylcholine (PC) and oxidized low density lipoprotein (OxLDL) for development of atherosclerosis.

METHODS AND RESULTS

Two hundred and twenty six individuals with established hypertension (diastolic pressure > 95mmHg) were from European Lacidipine Study on Atherosclerosis. Antibodies of IgG and IgM subclass were tested by ELISA against PC (aPC), cupper-oxidized (ox)- or malondialdehyde (MDA)-modified LDL. High-sensitivity C-reactive protein was measured by nephelometry. As a surrogate measure of atherosclerosis, we used the mean of the maximum intima-media thicknesses (IMT) in the far walls of common carotids and bifurcations was determined by ultrasonography at the time of enrolment, and 4 years following enrolment. aPC could be competed out by PC and OxLDL, while cardiolipin (CL) and beta2-glycoprotein I (beta2GPI) were less effective and phosphatidylserine (PS) not at all. Increases in IMT at follow-up were less common in subjects which at the time of enrolment had high IgM aPC (both 75th and 90th; odds ratios: 0.46; CI: 0.25-0.85; 0.36; CI: 0.15-0.87) and high IgM aOxLDL and aMDA-LDL (90th; odds ratios 0.27; p = 0.01; CI: 0.11-0.69 and 0.27; p = 0.01; CI: 0.11-0.69). CRP was unrelated to IMT-changes. The relationship between IgM aPC, aOxLDL and aMDA-LDL and changes in IMT was independent of age, treatment with atenolol or lacidipine, smoking and lipids. Women had higher levels of IgM antibodies tested (p < 0.05).

CONCLUSIONS

High levels of IgM-antibodies against PC and OxLDL predict a favourable outcome in the development of carotid atherosclerosis in hypertensive subjects. Whether these antibodies could be used therapeutically deserves further study.

Antibodies to oxidized LDL in atherosclerosis development--clinical and animal studies

Atherosclerotic lesions represent the principal cause of death in western industrialized countries. Immune mechanisms have been suggested to play a key role in the development of atherosclerosis. Several lines of evidence support that oxidized LDL (oxLDL) may be a key antigen in atherosclerosis. Antibodies to oxLDL have been found in human and rabbit plasma and in atherosclerotic lesions. So far, it has not been well established if the immune response is predominantly pro- or antiatherogenic. During the last decade, numerous studies have been performed investigating the relationship between circulating antibodies in plasma in relation to endothelial dysfunction, subclinical atherosclerosis and cardiovascular events in different patient categories. Taken together, these studies have shown diverging results. However, most studies have shown that elevated IgG titers to oxLDL are related to atherosclerotic disease. Even if fewer studies have investigated IgM titers, most studies seem to show an inverse relationship between IgM titers and atherosclerotic disease. In animal studies, it has been shown that immunization with oxLDL induces antibody formation (both IgG and IgM) and protects against atherosclerosis development. Furthermore, it has also been shown that immunization with Streptococcus pneumoniae induce an IgM response, which is associated with decreased atherosclerosis development, and plasma from these mice also has the ability to block uptake of oxLDL to macrophages. To conclude, antibodies to oxLDL in clinical cardiovascular disease show diverging results, while animal studies suggest that immunization may have a beneficial role in atherosclerosis development. Prospective and intervention studies, as well as mechanistic studies are clearly needed to elucidate the possible causal role of antibodies to oxLDL in man.

SLE, atherosclerosis and cardiovascular disease

Atherosclerosis is an inflammatory disease and the major cause of cardiovascular disease (CVD) in general. Atherosclerotic plaques are characterized by the presence of activated immune competent cells, but antigens and underlying mechanisms causing this immune activation are not well defined. During recent years and with improved treatment of acute disease manifestations, it has become clear that the risk of CVD is very high in a prototypic autoimmune disease, systemic lupus erythematosus (SLE). SLE-related CVD and atherosclerosis are important clinical problems but may in addition also shed light on how immune reactions are related to premature atherosclerosis and atherothrombosis. A combination of traditional and nontraditional risk factors, including dyslipidaemia (and to a varying degree hypertension, diabetes and smoking), inflammation, antiphospholipid antibodies (aPL) and lipid oxidation are related to CVD in SLE. Premature atherosclerosis in some form leading to atherothrombosis is likely to be a major underlying mechanism, though distinctive features if any, of SLE-related atherosclerosis when compared with 'normal' atherosclerosis are not clear. One interesting possibility is that factors such as inflammation or aPL make atherosclerotic lesions in autoimmune disease more prone to rupture than in 'normal' atherosclerosis. Whether premature atherosclerosis is a general feature of SLE or only affects a subgroup of patients remains to be demonstrated. Treatment of SLE patients should also include a close monitoring of traditional risk factors for CVD. In addition, attention should also be paid to nontraditional risk factors such as inflammation and SLE-related factors such as aPL. Hopefully novel therapeutic principles will be developed that target the causes of the inflammation and immune reactions present in atherosclerotic lesions.

Natural antibodies and the autoimmunity of atherosclerosis

In recent years, the subject of natural antibodies has been revisited and the immunobiological roles of these humoral factors are being better defined. These antibodies are secreted by distinct sets of innate-like B cells, B-1 cells and marginal zone B cells, which arise early in development to become the sources of "natural immune memory". Due to their interactions with a variety of self-determinants, natural antibodies have previously been postulated to play roles in the maintenance of host homeostasis. A central paradigm has recently been developed from the demonstration that oxidation derived epitopes on apoptotic cells and oxidized low-density lipoproteins are recognized by the phosphorylcholine-specific germline encoded B-1 cell natural antibody, T15, which has provided important insights into possible "house-keeping" functions under both normal and pathological conditions. In this review, the potential functions of natural antibodies in the pathogenesis and progression of the chronic inflammatory condition of atherosclerosis are discussed, as well as their capacities for apoptotic cell binding and clearance. These interactions of natural antibodies and oxidation-epitopes from phospholipids appear to provide a dynamic immunobiological connection linking host responses in infection, autoimmunity and atherosclerosis.

Differences in human antioxidized LDL autoantibodies in patients with stable and unstable angina

BACKGROUND

Autoantibodies to oxidized LDL (anti-oxLDL) have been found in the serum of patients with coronary artery disease (CAD). This study was designed to compare the differences in anti-oxLDL titers and isotypes in unstable and stable angina patients and to correlate these results with known markers of active inflammation in CAD.

METHODS

Thirty patients from a tertiary referral general hospital with documented CAD were studied. Anti-oxLDL IgG titers and its isotypes, high sensitivity C-reactive protein (hsCRP) and serum amyloid A (SAA) were measured.

RESULTS

The anti-oxLDL IgG titer was lower (p=0.03) in the unstable angina group compared to the stable angina patients (0.084+/-0.102 OD versus 0.195+/-0.149 OD, respectively). The predominant IgG isotype in both groups was IgG2. IgG4 was significantly higher (0.270+/-0.146 OD, p=0.04) in the unstable angina group versus patients with stable angina (0.198+/-0.019 OD). There was a significant inverse correlation between anti-oxLDL and hsCRP and SAA in this sample population (R=0.37, p<0.05 and R=0.36, p<0.05, respectively).

CONCLUSION

Patients with unstable angina have lower levels of anti-oxLDL IgG in the acute setting of CAD. Plaque instabilization does not seem to acutely modify the isotype subsets of anti-oxLDL IgG in these patients.

Assessment of atherosclerotic risk factors and endothelial function in children and young adults with pediatric-onset systemic lupus erythematosus

OBJECTIVE

To characterize atherosclerotic risk factors and endothelial function in pediatric-onset systemic lupus erythematosus (SLE).

METHODS

Lipoproteins, oxidized state, and autoantibodies to oxidized low-density lipoprotein (Ox-LDL) were assessed. Endothelial function was evaluated using brachial artery reactivity.

RESULTS

Thirty-three SLE patients and 30 controls were studied. SLE subjects had significantly decreased mean high-density lipoprotein (HDL) cholesterol (41 mg/dl versus 51 mg/dl; P = 0.002) and apolipoprotein A-I (97 mg/dl versus 199 mg/dl; P = 0.0004). There was no difference between groups in markers of oxidized state (including nitric oxide metabolites, isoprostanes, and Ox-LDL) or in endothelial function. However, SLE subjects had increased median anti-Ox-LDL IgG (2,480 relative light units [RLU] versus 1,567 RLU; P = 0.0007) and IgG immune complexes with LDL (4,222 RLU versus 2,868 RLU; P = 0.002).

CONCLUSION

Pediatric SLE patients had significantly decreased levels of HDL cholesterol and apolipoprotein A-I and elevated titers of autoantibodies to Ox-LDL. Despite these atherosclerotic risk factors, SLE patients had normal measures of oxidized state and endothelial function.

Relation of Secretory Phospholipase A2 and High-Sensitivity C-Reactive Protein to Chlamydia Pneumoniae Infection in Acute Coronary Syndromes

BACKGROUND

Recently it has become clear that inflammatory changes play a part in the development of atherosclerosis, including coronary artery disease, and Chlamydia pneumoniae (C. pneumoniae) is thought to be a proinflammatory factor. The plasma concentration of high-sensitive C-reactive protein (hs-CRP) is a potential predictor of outcome in atherosclerotic diseases. Recent interest has focused on secretory group IIA phospholipase A(2) (sPLA (2)) in regard to the progression of atherosclerotic disease.

METHODS AND RESULTS

The concentrations of sPLA(2), hs-CRP, and the titers of C. pneumoniae IgG and IgA antibodies were measured in blood samples. The study groups were an acute coronary syndrome (ACS) group, old myocardial infarction/angina pectoris (OMI/AP) group, and a control group. The concentrations of sPLA(2) and hs-CRP in the ACS group and the OMI/AP group were higher than in the control group. The titers of C. pneumoniae IgG and IgA were higher in the ACS group than in the control group. The sPLA(2) concentration was higher in those who were positive to C. pneumoniae IgG/IgA than in those who were negative.

CONCLUSION

Increased concentrations of sPLA(2) reflect participation in the progression of coronary artery disease. The sPLA(2) concentration was higher in patients positive for C. pneumoniae than in those negative for C. pneumoniae, so C. pneumoniae infection poses a greater risk for ACS in those individuals than in those who are free of such infection.

Augmented PLA2Activity in Pre-eclamptic Decidual Tissue—A Key Player in the Pathophysiology of ‘Acute Atherosis’ in Pre-eclampsia?

Decidual acute atherosis is associated with pre-eclampsia, but the underlying mechanism is still unclear. We have previously demonstrated elevated level of the oxidative stress marker 8-isoprostaglandin F(2 alpha)(8-isoprostane) and lipids in pre-eclamptic decidual tissue. Arachidonic acid (AA) in tissue phospholipids is a source for 8-isoprostane generation, and 8-isoprostane is liberated from tissue phospholipids by phospholipase A(2)(PLA(2)). The aims of this study were to explore whether AA content or PLA(2)expression in pre-eclamptic decidual tissue differed from controls. Decidua basalis tissues were obtained by vacuum aspiration at Caesarean delivery in pre-eclamptic and control pregnancies. We demonstrated a statistically significantly higher total PLA(2)activity in pre-eclamptic decidua compared to control tissue. On the other hand, no differences in AA content of tissue phospholipids or protein expression of secretory and cytosolic PLA(2)between pre-eclamptic and control decidual tissue were found. In conclusion, the elevated level of free 8-isoprostane in pre-eclamptic decidual tissue could be caused by augmented PLA(2)activity. We speculate that an elevated PLA(2)enzyme activity in pre-eclamptic decidual tissue could be of importance in the pathogenesis of 'acute atherosis', comparable to the atherogenesis in cardiovascular diseases.

Myeloperoxidase-derived reactive chlorinating species from human monocytes target plasmalogens in low density lipoprotein

A role for myeloperoxidase (MPO) in atherosclerosis has received considerable attention recently. To identify potential chlorinated lipid products in human low density lipoprotein (LDL), studies were designed to demonstrate that MPO-derived reactive chlorinating species (RCS) target the plasmalogen pool of LDL isolated from peripheral human blood in vitro. The vinyl ether bond of LDL plasmalogens was targeted by MPO-derived RCS, resulting in the release of the 16- and 18-carbon-containing alpha-chloro fatty aldehydes, 2-chlorohexadecanal and 2-chlorooctadecanal, respectively, from the plasmalogen glycerol backbone. Targeting of the LDL plasmalogen vinyl ether bond was dependent on the presence of MPO-derived RCS. Electrospray ionization mass spectrometric analysis of MPO-treated LDL demonstrated that a novel population of unsaturated lysophosphatidylcholine molecular species was produced by a phospholipase A2-independent mechanism. Unsaturated lysophosphatidylcholine molecular species elicited cyclic AMP response element binding protein phosphorylation in RAW 264.7 cells. Additionally, MPO-mediated targeting of both monocyte and LDL plasmalogen pools was demonstrated in phorbol myristate acetate-stimulated human monocytes, resulting in the production of both 2-chlorohexadecanal and 2-chlorooctadecanal. In contrast, alpha-chloro fatty aldehydes were not produced in phorbol myristate acetate-stimulated mouse monocytes. Collectively, the present studies demonstrate a novel MPO-specific mechanism that mediates the production of a novel group of unsaturated lysophosphatidylcholine molecular species and chlorinated aldehydes from both LDL and monocyte plasmalogen pools that may have important effects during inflammatory reactions mediated by monocytes, most notably atherosclerosis.

Phospholipase A(2) isoforms: a perspective

Several new PLA(2)s have been identified based on their nucleotide gene sequences. They were classified mainly into three groups: cytosolic PLA(2) (cPLA(2)), secretary PLA(2) (sPLA(2)), and intracellular PLA(2) (iPLA(2)). They differ from each other in terms of substrate specificity, Ca(2+) requirement and lipid modification. The questions that still remain to be addressed are the subcellular localization and differential regulation of the isoforms in various cell types and under different physiological conditions. It is required to identify the downstream events that occur upon PLA(2) activation, particularly target protein or metabolic pathway for liberated arachidonic acid or other fatty acids. Understanding the same will greatly help in the development of potent and specific pharmacological modulators that can be used for basic research and clinical applications. The information of the human and other genomes of PLA(2)s, combined with the use of proteomics and genetically manipulated mouse models of different diseases, will illuminate us about the specific and potentially overlapping roles of individual phospholipases as mediators of physiological and pathological processes. Hopefully, such understanding will enable the development of specific agents aimed at decreasing the potential contribution of individual secretary phospholipases to vascular diseases. The signaling cascades involved in the activation of cPLA(2) by mitogen activated protein kinases (MAPKs) is now evident. It has been demonstrated that p44 MAPK phosphorylates cPLA(2) and increases its activity in cells and tissues. The phosphorylation of cPLA(2) at ser505 occurs before the increase in intracellular Ca(2+) that facilitate the binding of the lipid binding domain of cPLA(2) to phospholipids, promoting its translocation to cellular membranes and AA release. Recently, a negative feed back loop for cPLA(2) activation by MAPK has been proposed. If PLA(2) activation in a given model depends on PKC, PKA, cAMP, or MAPK then inhibition of these phosphorylating enzymes may alter activities of PLA(2) isoforms during cellular injury. Understanding the signaling pathways involved in the activation/deactivation of PLA(2) during cellular injury will point to key events that can be used to prevent the cellular injury. Furthermore, to date, there is limited information available regarding the regulation of iPLA(2) or sPLA(2) by these pathways.

Oxidised LDL modulates immune-activation by an IL-12 dependent mechanism

Oxidised low density lipoprotein (oxLDL) is one factor that may cause the immune reaction in the artery wall characteristic of atherosclerosis. OxLDL can promote immune activation as determined by enhanced secretion of IFN-gamma and TNF by immune competent cells. We previously demonstrated that Platelet-activating factor (PAF)-like lipids and/or lysophosphatidylcholine (LPC) in OxLDL contribute significantly to this immune activation, but these factors may also inhibit immune activation, at higher concentrations. We here demonstrate that IL-12 induces enhanced IFN-gamma secretion in peripheral blood mononuclear cells (PBMC), with no addition of a specific antigen, as determined by ELISPOT. Antibodies to IL-12 and to MHC class II inhibited both IL-12- and oxLDL-induced IFN-gamma secretion. OxLDL induced IL-12 production in PBMC. In the presence of IL-10, a T helper 2 cytokine, oxLDL induced a decreased IFN-gamma secretion, indicating that the local cytokine-milieu may determine the immunological properties of oxLDL. IL-10 could also be induced by OxLDL. Mononuclear leukocytes were prepared directly from human atherosclerotic plaques obtained at carotid operations. OxLDL had the capacity to induce IL-12, IL-10 and TNF from plaque cells using ELISPOT. Taken together, our data indicate that oxLDL can modulate immune reactivity in atherosclerosis by a nonspecific mechanism. OxLDL can be inhibitory, especially at higher concentrations. However, oxLDL can also promote immune activation by functioning as an adjuvant, potentiating and/or modulating immune-reactions via IL-12 and other cytokines including IL-10. This suggests that a specific T cell epitope in oxLDL is not necessary for oxLDL-induced T cell activation.