Antibodies to oxidized LDL in relation to intima-media thickness in carotid and femoral arteries in 58-year-old subjectively clinically healthy men

Immunity and Inflammation in Atherosclerosis

There is now overwhelming experimental and clinical evidence that atherosclerosis is a chronic inflammatory disease. Lessons from genome-wide association studies, advanced in vivo imaging techniques, transgenic lineage tracing mice, and clinical interventional studies have shown that both innate and adaptive immune mechanisms can accelerate or curb atherosclerosis. Here, we summarize and discuss the pathogenesis of atherosclerosis with a focus on adaptive immunity. We discuss some limitations of animal models and the need for models that are tailored to better translate to human atherosclerosis and ultimately progress in prevention and treatment.

Serum Anti-Apo B Antibody Level as Residual CVD Marker in DM Patients under Statin Treatment

AIM

In the pathogenesis of atherosclerosis, autoantibodies have two-facedness of progression and protection. Previous reports have indicated that low autoantibody levels against apolipoprotein B-100 (apo B-100) could increase the risk of atherosclerotic cardiovascular diseases (CVD) in healthy subjects. In this study, we investigated the relationship between circulating anti-apo B-100 autoantibodies and the clinical parameters in Japanese diabetic patients with or without CVD.

METHODS

We measured the serum levels of anti-apo B-100 autoantibodies against native and malondialdehyde (MDA)-modified p45 or p210 epitopes, as well as anti-apo E autoantibodies, using enzyme-linked immunosorbent assay.

RESULTS

In patients with CVD, the circulating levels of IgG against native p45, MDA-modified p45, and MDA-modified p210 (IgG_N-45, IgG_MDA-45, and IgG_MDA-210) were significantly lower than those in patients without CVD, whereas no difference was observed in anti-apo E autoantibody levels. In addition, IgM_N-45, IgM_MDA-45, and IgG_MDA-45 were negatively correlated with LDL-C levels, whereas IgG_N-45 and IgG_N-210 were positively correlated with HbA1c levels. No correlation was observed between autoantibody levels and diabetic microangiopathy. In the statin-treated subgroup, IgG_MDA-45 and IgG_MDA-210 were significantly lower in patients with CVD than in those without CVD.

CONCLUSION

Measurement of serum anti-apo B-100 autoantibodies can be useful for the evaluation of CVD risk in patients with diabetes receiving statin treatment.

Antibody to oxidized low-density lipoprotein inhibits THP1 cells from apoptosis by suppressing NF-κB pathway activation

Background

This study aimed to investigate whether the oxidized low-density lipoprotein (Ox-LDL) antibody is able to inhibit THP1 cell apoptosis by suppressing NF-κB pathway.

Methods

THP1 cells were induced to macrophages with phorbol 12-myristate 13-acetate (PMA). Macrophages were divided into control group, Ox-LDL group and antibody group, cells in which were treated with phosphate buffered saline (PBS), Ox-LDL (50 mg/mL), Ox-LDL (50 µg/mL) plus Ox-LDL antibody (100 mg/L), respectively, for 24 h. The apoptosis rate was determined by inverted microscopy and flow cytometry. The protein and mRNA expression of NF-κB (P65), caspase-3 and BCL2 was detected by Western blotting and reverse transcription polymerase chain reaction (RT-PCR), respectively.

Results

The apoptosis rate reduced significantly in antibody group as compared to Ox-LDL and control groups (P<0.05). The protein and mRNA expression of NF-κB pathway was markedly lowered in antibody group than in Ox-LDL and control groups (P<0.05), which reduced the Ox-LDL induced inflammation.

Conclusions

Ox-LDL antibody may be used to attenuate Ox-LDL induced inflammation and apoptosis, preventing atherosclerosis patients from acute coronary syndrome (ACS).

[Immunity and inflammation in atherosclerosis]

There is now overwhelming experimental and clinical evidence that arteriosclerosis is a chronic inflammatory disease. Lessons learned from genome-wide association studies, advanced in vivo imaging techniques, transgenic lineage tracing mice models and clinical interventional studies have shown that both innate and adaptive immune mechanisms can accelerate or curb arteriosclerosis. This article summarizes and discusses the pathogenesis of arteriosclerosis with a focus on the role of the adaptive immune system. Some limitations of animal models are discussed and the need for models that are tailored to better translate to human atherosclerosis and ultimately progress in prevention and treatment are emphasized.

DUSP1 Is a Potential Marker of Chronic Inflammation in Arabs with Cardiovascular Diseases

Background

Cardiovascular disease (CVD) risks persist in patients despite the use of conventional treatments. This might be due to chronic inflammation as reflected in epidemiological studies associating circulating low-grade inflammatory markers with CVD recurrent events. Here, we explored this potential link by assessing plasma dual-specificity phosphatase 1 (DUSP1) levels and comparing them to high-sensitivity CRP (hsCRP) and oxidized low-density lipoprotein (oxLDL) levels and their associations to conventional CVD risk factors in confirmed CVD patients.

Methods

Human adults with reported CVD (n = 207) and controls (n = 70) living in Kuwait were used in this study. Anthropometric and classical biochemical parameters were determined. Plasma levels of DUSP1, oxLDL, and hsCRP were measured using human enzyme-linked immunosorbent assay kits.

Results

DUSP1 and hsCRP plasma levels and their least square means were higher in CVD cases, while oxLDL plasma levels were lower (p < 0.05). Multivariate logistic regression analysis showed that DUSP1 and hsCRP are independently associated with CVD in the studied population, as reflected by 2-fold and 1.5-fold increased risks with increased levels of DUSP1 and hsCRP, respectively. In our study, DUSP1 levels were found to be associated with CVD despite statin treatment and diabetes status (p < 0.05), whereas hsCRP mainly correlated with obesity markers.

Conclusions

Circulating DUSP1 might be a predictor of chronic subclinical inflammation and residual risk in CVD patients, whereas our data suggest that the association between hsCRP and CVD is largely accounted for adiposity risk factors.

Von Willebrand Factor and Autoantibodies against Oxidized LDL in Hemodialysis Patients Treated with Vitamin E-Modified Dialyzers

Oxidant stress is a well known cause of damage in the atherosclerotic process. Vitamin E is one of the most promising natural antioxidants. In this study we investigated if a vitamin E-coated dialyzer was able to reduce the plasma levels of auto-antibodies against oxidized-LDL, von Willebrand factor (vWf) and thrombomodulin (TM) as markers of endothelial damage.

In this controlled 6-month prospective study, we investigated these markers in two matched groups (n= 16 each) of patients on regular hemodialysis not yet diagnosed for atherosclerosis cardiovascular disease (ACVD) (mean age= 58.3±7.0 yrs, mean dialysis age = 30.1±10.0 months), in which cellulosic (CLS) and vitamin E-modified dialyzers (CLE) were compared. At inclusion all the patients were treated with CLS. Then, the study group was shifted to CLE for 6 months.

At baseline the patients showed normal levels of vitamin E and high levels of oxLDL-Ab, vWf and TM compared to healthy subjects. In the CLE group oxLDL-Ab and vWf, but not TM levels, decreased progressively (from 472±287 to 264±199 mU/mL, p<0.0001 and from 101.1±7.5% to 76.7±18.5%; p<0.001, respectively), and vitamin E increased from 4.40±0.81 to 7.81±1.16 μg/mg of cholesterol. At the end of the study, 8 of the patients treated with CLE were randomly selected and went back to the membrane without Vitamin E for six months. They showed an significant increase in OxLDL-Ab and vWf levels and a significant reduction in tocoferol levels. In conclusion, CLE compared to cellulosic dialyzers can lower some indices of damage to LDL and endothelial cells.

Inflammation and the pathogenesis of atherosclerosis in systemic lupus erythematosus

Atherosclerosis is a complicated inflammatory process characterized by the interactions of numerous different moieties including lipids, enzymes, endothelial cells, cytokines, chemokines, leukocytes, adhesion molecules, complement and antibodies. As in the pathogenesis of many lupus disease processes, the increased risk of atherosclerosis seen in systemic lupus erythematosus (SLE) is likely due to the complex interplay of many of these inflammatory mediators. Expanding our understanding of the pathogenesis of atherosclerosis in SLE is critical if we are to improve the quality of care and reduce mortality in this vulnerable population.

Heterogeneity of B Cell Functions in Stroke-Related Risk, Prevention, Injury, and Repair

It is well established that post-stroke inflammation contributes to neurovascular injury, blood-brain barrier disruption, and poor functional recovery in both animal and clinical studies. However, recent studies also suggest that several leukocyte subsets, activated during the post-stroke immune response, can exhibit both pro-injury and pro-recovery phenotypes. In accordance with these findings, B lymphocytes, or B cells, play a heterogeneous role in the adaptive immune response to stroke. This review highlights what is currently understood about the various roles of B cells, with an emphasis on stroke risk factors, as well as post-stroke injury and repair. This includes an overview of B cell functions, such as antibody production, cytokine secretion, and contribution to the immune response as antigen presenting cells. Next, evidence for B cell-mediated mechanisms in stroke-related risk factors, including hypertension, diabetes, and atherosclerosis, is outlined, followed by studies that focus on B cells during endogenous protection from stroke. Subsequently, animal studies that investigate the role of B cells in post-stroke injury and repair are summarized, and the final section describes current B cell-related clinical trials for stroke, as well as other central nervous system diseases. This review reveals the complex role of B cells in stroke, with a focus on areas for potential clinical intervention for a disease that affects millions of people globally each year.

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.

Oral butyrate reduces oxidative stress in atherosclerotic lesion sites by a mechanism involving NADPH oxidase down-regulation in endothelial cells

Butyrate is a 4-carbon fatty acid that has antiinflammatory and antioxidative properties. It has been demonstrated that butyrate is able to reduce atherosclerotic development in animal models by reducing inflammatory factors. However, the contribution of its antioxidative effects of butyrate on atherogenesis has not yet been studied. We investigated the influence of butyrate on oxidative status, reactive oxygen species (ROS) release and oxidative enzymes (NADPH oxidase and iNOS) in atherosclerotic lesions of ApoE(-/-) mice and in oxLDL-stimulated peritoneal macrophages and endothelial cells (EA.hy926). The lesion area in aorta was reduced while in the aortic valve, although lesion area was unaltered, superoxide production and protein nitrosylation were reduced in butyrate-supplemented mice. Peritoneal macrophages from the butyrate group presented a lower free radical release after zymosan stimulus. When endothelial cells were pretreated with butyrate before oxLDL stimulus, the CCL-2 and superoxide ion productions and NADPH oxidase subunit p22phox were reduced. In macrophage cultures, in addition to a reduction in ROS release, nitric oxide and iNOS expression were down-regulated. The data suggest that one mechanism related to the effect of butyrate on atherosclerotic development is the reduction of oxidative stress in the lesion site. The reduction of oxidative stress related to NADPH oxidase and iNOS expression levels associated to butyrate supplementation attenuates endothelium dysfunction and macrophage migration and activation in the lesion site.

Detection of circulating IgG antibodies to apolipoprotein B100 in acute myocardial infarction

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Anti-ApoB IgG is involved in the development of acute myocardial infarction (AMI).

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We looked for biomarkers for the prediction of acute myocardial infarction.

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An ELISA antibody test was developed to detect anti-ApoB IgG.

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The test was used in clinical screening for anti-ApoB IgG in patients with AMI.

A number of studies have reported an association between increased levels of antibodies against oxidized low-density lipoprotein (oxLDL) and cardiovascular disease, but the anti-oxLDL antibody has not been confirmed to serve as an effective biomarker for prediction of acute myocardial infarction (AMI). Apolipoprotein B₁₀₀ (ApoB₁₀₀)-derived peptide fragments generated by proteolytic degradation and aldehyde modification are the major antigens in oxLDL, and so the present work was undertaken to detect circulating IgG for Apo-B₁₀₀-derived peptide antigens. An in-house enzyme-linked immunosorbent assay (ELISA) was developed with eight ApoB₁₀₀-derived peptide antigens (Ag1–Ag8) to detect circulating anti-ApoB₁₀₀ IgG levels in 267 patients with AMI and 201 control subjects. Binary logistic regression analysis revealed that circulating IgG for Ag1 was significantly higher in the patient group than the control group (P < 0.001) after adjustment for age, gender, smoking, hypertension, diabetes and circulating levels of cholesterol, HDL, LDL, ApoA and ApoB₁₀₀. None of the other seven antigens detected an increase in IgG levels in AMI patients compared with control subjects. Spearman correlation analysis showed no correlation between IgG antibody for Ag1 and clinical characteristics. In conclusion, the linear peptide antigens derived from ApoB₁₀₀ may be suitable for the development of an ELISA antibody test for prediction of AMI, although further confirmation is still needed in large-scale clinical studies.

Beyond vascular inflammation--recent advances in understanding atherosclerosis

Atherosclerosis is the most life-threatening pathology worldwide. Its major clinical complications, stroke, myocardial infarction, and heart failure, are on the rise in many regions of the world--despite considerable progress in understanding cause, progression, and consequences of atherosclerosis. Originally perceived as a lipid-storage disease of the arterial wall (Die cellularpathologie in ihrer begründung auf physiologische und pathologische gewebelehre. August Hirschwald Verlag Berlin, [1871]), atherosclerosis was recognized as a chronic inflammatory disease in 1986 (New Engl J Med 314:488-500, 1986). The presence of lymphocytes in atherosclerotic lesions suggested autoimmune processes in the vessel wall (Clin Exp Immunol 64:261-268, 1986). Since the advent of suitable mouse models of atherosclerosis (Science 258:468-471, 1992; Cell 71:343-353, 1992; J Clin Invest 92:883-893, 1993) and the development of flow cytometry to define the cellular infiltrate in atherosclerotic lesions (J Exp Med 203:1273-1282, 2006), the origin, lineage, phenotype, and function of distinct inflammatory cells that trigger or inhibit the inflammatory response in the atherosclerotic plaque have been studied. Multiphoton microscopy recently enabled direct visualization of antigen-specific interactions between T cells and antigen-presenting cells in the vessel wall (J Clin Invest 122:3114-3126, 2012). Vascular immunology is now emerging as a new field, providing evidence for protective as well as damaging autoimmune responses (Int Immunol 25:615-622, 2013). Manipulating inflammation and autoimmunity both hold promise for new therapeutic strategies in cardiovascular disease. Ongoing work (J Clin Invest 123:27-36, 2013; Front Immunol 2013; Semin Immunol 31:95-101, 2009) suggests that it may be possible to develop antigen-specific immunomodulatory prevention and therapy-a vaccine against atherosclerosis.

Anti-adipocyte antibody response in patients with non-alcoholic fatty liver disease

BACKGROUND AND AIM

A significant number of autoantibodies have been reported in patients with non-alcoholic fatty liver disease (NAFLD) patients. In the present study, our aim was to assess the role of disease and cell-specific antibodies, namely anti-adipocyte antibodies (anti-AdAb) in patients with NAFLD and non-alcoholic steatohepatitis (NASH).

METHODS

Flow cytometry was used to detect the presence of anti-AdAb (immunoglobulin M [IgM] and immunoglobulin G [IgG]) in sera from patients with biopsy-proven NAFLD (n = 98) and in controls (n = 49) without liver disease. Univariate and multivariate analysis was performed to draw associations between anti-AdAb IgM and IgG levels and the different clinical variables.

RESULTS

Patients with NAFLD had significantly higher levels of anti-AdAb IgM and significantly lower levels of AdAb IgG when compared with controls (P = 0.002 and P < 0.001, respectively). Patients with NASH had significantly higher levels of anti-AdAb IgM when compared with non-NASH NAFLD patients, P = 0.04. In multivariate analysis, anti-AdAb IgM was independently associated with a higher risk for NASH (odds ratio[OR]: 2.90 [confidence interval (CI) 1.18-7.16], P = 0.02). Anti-AdAb IgM was also found to be independently associated with portal inflammation in patients with NAFLD (OR: 3.01 [CI 1.15-7.90 P = 0.02]).

CONCLUSIONS

Anti-AdAb IgM was independently associated with NAFLD and NASH while anti-AdAb IgG was found to be protective against NAFLD. Anti-AdAb IgM was found specifically to be associated with the inflammatory processes in NAFLD. These findings indicate that the anti-AdAb IgM and IgG may play an immunomodulatory role in the pathogenesis of NAFLD and NASH.

Circulating autoantibodies against the apolipoprotein B-100 peptides p45 and p210 in relation to the occurrence of carotid plaques in 64-year-old women

Objectives

Immune responses against oxidized low density lipoprotein (LDL) play a key role in atherosclerosis. Previous studies have indicated inverse associations between autoantibodies to epitopes in oxidized LDL and cardiovascular disease. In this study we investigated the associations between autoantibodies against the apolipoprotein B-100 (apoB-100) peptides p45 and p210 and occurrence of carotid plaques.

Design

The study cohort consisted of a population-based sample of 64-year-old women with varying degrees of glucose tolerance (n=594). To identify and record the occurrence of carotid atherosclerotic plaques ultrasonography was used. Measurements of plasma IgM and IgG autoantibodies against the native and malondialdehyde (MDA)-modified apoB-100 peptides p45 and p210 were performed by ELISA.

Results

Women with carotid plaques were found to have lower levels of IgM MDA-p210 autoantibodies compared to plaque-free women. The number of carotid plaques in each subject and the total carotid plaque area correlated inversely with IgM MDA-p210 levels (r=-0.11, P=0.009 and r=-0.11, P=0.013, respectively). Furthermore, levels of IgM MDA-p210 above the lowest tertile were associated with an odds ratio of 0.55 (95% CI 0.38-0.79, P=0.001) for occurrence of carotid plaques, independently of other risk markers and statin treatment. Associations between apo-B100 peptide autoantibodies and cardiovascular risk factors were generally weak but subjects with impaired glucose tolerance had higher levels of IgM against MDA-p210.

Conclusion

The present study demonstrates that high levels of IgM against MDA-p210 are associated with less severe carotid disease in women. These findings provide additional support for a role of immune responses against oxidized LDL in cardiovascular disease.

Vaccination to modulate atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the artery wall. Adaptive immunity plays a key role in the pathogenesis of atherosclerosis. Recently, modulation of the immune response against atherosclerotic plaque antigen(s) has attracted attention as a potentially preventive and therapeutic approach. Here, we review a series of studies on immunization with various antigens targeting treatment and prevention of atherosclerosis. Atherosclerosis-related antigens include oxidized low-density lipoprotein (LDL), apolipoprotein B-100 (ApoB-100) and heat shock protein (HSP) 60/65. Accumulating evidence supports the idea that immunization with these antigenic proteins or peptides may reduce atherosclerosis. In this review, we discuss the current status of immunization studies and possible associated mechanisms of atheroprotection.

Lymphocyte migration into atherosclerotic plaque

Adaptive immunity is involved in the pathogenesis of atherosclerosis, but the recruitment of T and B lymphocytes to atherosclerotic lesions is not as well studied as that of monocytes. In this review, we summarize the current understanding of the role of lymphocyte subsets in the pathogenesis of atherosclerosis and discuss chemokines and chemokine receptors involved in lymphocyte homing to atherosclerotic lesions. We review evidence for involvement of the chemokines CCL5, CCL19, CCL21, CXCL10, and CXCL16 and macrophage migration inhibitory factor in lymphocyte homing in atherosclerosis. Also, we review the role of their receptors CCR5, CCR6, CCR7, CXCR3, CXCR6, and CXCR2/CXCR4 and the role of the L-selectin in mouse models of atherosclerosis.

Inflammation and immune system interactions in atherosclerosis

Cardiovascular disease (CVD) is the leading cause of mortality worldwide, accounting for 16.7 million deaths each year. The underlying cause of the majority of CVD is atherosclerosis. In the past, atherosclerosis was considered to be the result of passive lipid accumulation in the vessel wall. Today's picture is far more complex. Atherosclerosis is considered a chronic inflammatory disease that results in the formation of plaques in large and mid-sized arteries. Both cells of the innate and the adaptive immune system play a crucial role in its pathogenesis. By transforming immune cells into pro- and anti-inflammatory chemokine- and cytokine-producing units, and by guiding the interactions between the different immune cells, the immune system decisively influences the propensity of a given plaque to rupture and cause clinical symptoms like myocardial infarction and stroke. In this review, we give an overview on the newest insights in the role of different immune cells and subtypes in atherosclerosis.

Oxidation-specific biomarkers and risk of peripheral artery disease

OBJECTIVES

The goal of this study was to examine the prospective association between oxidation-specific biomarkers, primarily oxidized phospholipids (OxPL) on apolipoprotein B-100-containing lipoproteins (OxPL/apoB) and lipoprotein (a) [Lp(a)], and risk of peripheral artery disease (PAD). We examined, as secondary analyses, indirect measures of oxidized lipoproteins, including autoantibodies to malondialdehyde-modified low-density lipoprotein (MDA-LDL) and apolipoprotein B-100 immune complexes (ApoB-IC).

BACKGROUND

Biomarkers to predict the development of PAD are lacking. OxPL circulate in plasma, are transported by Lp(a), and deposit in the vascular wall and induce local inflammation.

METHODS

The study population included 2 parallel nested case-control studies of 143 men within the Health Professionals Follow-up Study (1994 to 2008) and 144 women within the Nurses' Health Study (1990 to 2010) with incident confirmed cases of clinically significant PAD, matched 1:3 to control subjects.

RESULTS

Levels of OxPL/apoB were positively associated with risk of PAD in men and women: pooled relative risk: 1.37, 95% confidence interval: 1.19 to 1.58 for each 1-SD increase after adjusting age, smoking, fasting status, month of blood draw, lipids, body mass index, and other cardiovascular disease risk factors. Lp(a) was similarly associated with risk of PAD (pooled adjusted relative risk: 1.36; 95% confidence interval: 1.18 to 1.57 for each 1-SD increase). Autoantibodies to MDA-LDL and ApoB-IC were not consistently associated with risk of PAD.

CONCLUSIONS

OxPL/apoB were positively associated with risk of PAD in men and women. The major lipoprotein carrier of OxPL, Lp(a), was also associated with risk of PAD, reinforcing the key role of OxPL in the pathophysiology of atherosclerosis mediated by Lp(a).

Immune response to lipoproteins in atherosclerosis

Atherosclerosis, the underlying cause of cardiovascular disease, is characterized by chronic inflammation and altered immune response. Cholesterol is a well-known risk factor associated with the development of cardiovascular diseases. Elevated serum cholesterol is unique because it can lead to development of atherosclerosis in animals and humans even in the absence of other risk factors. Modifications of low-density lipoproteins mediated by oxidation, enzymatic degradation, and aggregation result in changes in their function and activate both innate and adaptive immune system. Oxidized low-density lipoprotein (LDL) has been identified as one of the most important autoantigens in atherosclerosis. This escape from self-tolerance is dependent on the formation of oxidized phospholipids. The emerging understanding of the importance of immune responses against oxidized LDL in atherosclerosis has focused attention on the possibility of development of novel therapy for atherosclerosis. This review provides an overview of immune response to lipoproteins and the fascinating possibility of developing an immunomodulatory therapy for atherosclerosis.

Neither oxidized nor anti-oxidized low-density lipoprotein level is associated with atherosclerosis or mortality in hemodialysis patients

It is anticipated that oxidized low-density lipoprotein (oxLDL) and anti-oxLDL are associated with atherosclerosis and mortality. However, data on this issue are controversial and limited. We aimed to investigate the effect of these two markers on the extent and progression of atherosclerosis and mortality in a group of hemodialysis patients. In this prospective observational study with a follow-up of 36 months, 124 hemodialysis patients were studied. Ninety-five patients underwent carotid intima media thickness (CA-IMT) measurement by B-Mode ultrasonography both at baseline and at the end of the study. oxLDL and anti-oxLDL were measured by enzyme-linked immunosorbent assay. The extent and progression of CA-IMT, along with overall and cardiovascular mortality, were assessed. The mean age at baseline was 54.0 ± 14.8 years, 57.3% male and 20% diabetic. The mean oxLDL and anti-oxLDL levels were 8.11 ± 3.16 mU/L and 1.30 ± 0.31, respectively. Baseline mean CA-IMT was 0.82 ± 0.20 mm. Fifteen patients died during a follow-up period of 28.5 ± 6.6 months, 11 from cardiovascular causes. Only oxLDL, not anti-oxLDL, was correlated with the extent of atherosclerosis at baseline. However, both had no role in the progression of atherosclerosis. Also, in unadjusted and adjusted models, both parameters were not associated with overall or cardiovascular mortality. Neither oxLDL nor anti-oxLDL level is associated with the progression of atherosclerosis or mortality in hemodialysis patients.

Association of anti-oxidized LDL and candidate genes with severity of coronary stenosis in the Women's Ischemia Syndrome Evaluation study

Atherosclerosis is the major cause of coronary artery disease (CAD), and oxidized LDL (oxLDL) is believed to play a key role in the initiation of the atherosclerotic process. Recent studies show that inflammation and autoimmune reactions are also relevant in atherosclerosis. In this study, we examined the association of antibodies against oxLDL (anti-oxLDL) with the severity of CAD in 558 Women's Ischemia Syndrome Evaluation (WISE) study samples (465 whites; 93 blacks) determined by coronary stenosis (< 20%, 20%-49%, > 50% stenosis). We also examined the relationship of anti-oxLDL with serum lipid levels and nine candidate genes including APOE, APOH, APOA5, LPL, LRP1, HL, CETP, PON1, and OLR1. IgM anti-oxLDL levels were significantly higher in the >20% stenosis group than in the ≥ 20% stenosis group in whites (0.69 ± 0.02 vs. 0.64 ± 0.01, respectively; P = 0.02). IgM anti-oxLDL levels correlated significantly with total cholesterol (r² = 0.01; P = 0.03) and LDL cholesterol (r² = 0.017; P = 0.004) in whites. Multiple regression analysis revealed a suggestive association of LPL/S447X single-nucleotide polymorphism (SNP) with both IgG anti-oxLDL (P = 0.02) and IgM anti-oxLDL (P = 0.07), as well as between IgM anti-oxLDL and the OLR1/3'UTR SNP (P = 0.020). Our data suggest that higher IgM anti-oxLDL levels may provide protection against coronary stenosis and that genetic variation in some candidate genes are determinants of anti-oxLDL levels.

High plasma immunoglobulin (Ig) A and low IgG antibody titers to oxidized low-density lipoprotein are associated with markers of glucose metabolism

CONTEXT

Plasma oxidized low-density lipoprotein (OxLDL) is known to be associated with obesity, metabolic syndrome, and diabetes.

OBJECTIVE

The objective of the study was to investigate the association between plasma IgA, IgM, and IgG titers to OxLDL, phosphocholine (PC), and streptococcal cell wall polysaccharide (CWPS) and markers of glucose metabolism, type 2 diabetes, and liver adiposity.

SETTING AND PARTICIPANTS

A population-based cohort of middle-aged Finns (n = 1039) participated in the study.

DESIGN

Plasma IgM, IgG, and IgA to copper oxidized LDL (CuOx-LDL) and malondialdehyde-modified low-density lipoprotein (MDA-LDL), PC, and CWPS were determined with chemiluminescent ELISA and liver adiposity with ultrasonography.

RESULTS

IgA autoantibody titers to OxLDL and PC, but not CWPS, were positively associated with fasting blood glucose and plasma insulin levels and inversely with insulin sensitivity index. IgA to OxLDL was significantly higher (P = 0.013 for CuOx-LDL and P = 0.016 for MDA-LDL) and IgG to OxLDL significantly lower (P = 0.036 for CuOx-LDL and P = 0.001 for MDA-LDL) among the subjects with type 2 diabetes compared with subjects with normal or impaired glucose metabolism when adjusted for age, sex, body mass index, smoking, and alcohol consumption. Logistic regression analysis showed that high plasma IgA to OxLDL and low IgG to MDA-LDL were independent risk factors for type 2 diabetes. Plasma IgA titers to OxLDL demonstrated a significant association with liver adiposity (P = 0.012) and gamma-glutamyltransferase levels (P = 0.002).

CONCLUSIONS

Plasma IgA titers to OxLDL were positively and IgG titers negatively associated with markers of glucose metabolism. High plasma IgA and low IgG to OxLDL were independent risk factors for type 2 diabetes.

A higher level of IgM anti-oxidized LDL antibodies is associated with a lower severity of coronary atherosclerosis in patients on statins

BACKGROUND

Several studies show the association between anti-oxidized LDL antibodies and atherosclerosis. A certain association also seems to exist between the levels of these antibodies and treatment with statins. However, the clinical importance of these autoantibodies is still under discussion. The aim of this study was to determine whether levels of anti-oxidized LDL antibodies are associated with the presence of multivessel coronary artery disease according to whether statins were or were not being taken.

METHODS AND RESULTS

The study included 236 patients who underwent invasive coronary angiography with quantification of coronary atherosclerotic lesions to determine the presence of multivessel coronary artery disease. Measurements were made of IgG and IgM anti-oxidized LDL antibodies. In the group of patients who were taking statins, the percentage of patients with IgM anti-oxidized LDL antibodies below 50th percentile was significantly higher in those with multivessel coronary artery disease (57.4% vs. 37.5%, P<0.05). A logistic regression model in the patients taking statins showed that the variable significantly associated with the presence of multivessel coronary artery disease was the level of IgM anti-oxidized LDL antibodies.

CONCLUSIONS

The severity of multivessel coronary artery disease was inversely related with the levels of IgM anti-oxidized LDL antibodies, especially in the patients on statins.

Paraoxonase Genotype, LDL-oxidation and Carotid Atherosclerosis in Male Life-long Smokers

Paraoxonase (PON-1) is a high-density lipoprotein (HDL) associated enzyme that hydrolyzes lipid peroxides in vitro, which may therefore protect against the onset of atherosclerosis. Heavy smokers are more exposed to oxidative stress and hence at high-risk for oxidative modification of LDL. Our hypothesis is that the anti-oxidative properties of PON-1 inhibit LDL oxidation, especially in populations exposed to high oxidative stress. We have studied the effects of PON-1 genotype and smoking to variation in oxidative status parameters and intima-media thickness (IMT), a surrogate marker of atherosclerosis. The contribution of two common polymorphisms in the PON-1 gene (Q192R and L55M) to LDL oxidizability, autoantibodies directed against oxLDL and IMT were studied in 207 male life-long smokers. Smokers were classified into average, heavy and excessive smokers based on pack years of cigarettes smoked. PON-1 genotype was not associated with autoantibodies to oxLDL, LDL oxidizability or IMT. Smoking was associated with IMT in subgroups with the high levels of LDL, but not in the population at large. The lack of association of PON-1 genotype with oxidative status parameters and IMT suggests that PON-1 is not a major inhibitor of LDL oxidation in a population of life-long smokers.

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.

The therapeutic potential of targeting B cells and anti-oxLDL antibodies in atherosclerosis

While the involvement of T cells in atherosclerosis is nowadays well accepted, little is known about the role of B cells. Obviously, B cells as the source of antibodies, in particular antibodies to oxLDL, have gained a lot of attention in atherosclerosis. In addition, B cells do harbour other functions in adaptive immunity. In this review, we provide an overview of the current knowledge on both the role of B cells and antibodies, i.e., anti-oxLDL antibodies, in atherosclerosis. It appears that B cells and also anti-oxLDL antibodies may comprise pro- and anti-atherogenic effects. Therefore, the establishment of effective therapy, targeting B cells or anti-oxLDL antibodies, warrants further research to unravel these opposite effects.

Plasma interleukin-5 levels are related to antibodies binding to oxidized low-density lipoprotein and to decreased subclinical atherosclerosis

OBJECTIVES

This study's aim was to assess the role of interleukin (IL)-5 in modulating the levels of antibodies binding to oxidized low-density lipoprotein (OxLDL) in human atherosclerosis.

BACKGROUND

Various pro- and anti-inflammatory cytokines have been implicated in atherogenesis, and recent findings in mice indicate that the cytokine IL-5 plays a protective role in atherosclerosis in part via the induction of antibodies binding to OxLDL.

METHODS

Plasma IL-5 levels and antibody titers to 2 most commonly used models of OxLDL (copper OxLDL and malondialdehyde-modified LDL) were measured in 1,011 Finnish middle-aged subjects with chemiluminescent enzyme-linked immunosorbent assay. Intima-media thickness (IMT) was assessed ultrasonographically from the internal carotid artery, the bifurcation, and the common carotid artery.

RESULTS

There was a significant positive association between plasma IL-5 levels and antibody titers to copper OxLDL (p = 0.010 and p = 0.044, immunoglobin [Ig] M and G, respectively) and IgM to malondialdehyde-modified LDL (p < 0.001) in the association analysis performed between different IL-5 quartiles. Furthermore, plasma IL-5 levels were found to be inversely associated with bifurcational IMT, and even after adjustments for traditional risk factors of atherosclerosis (age, gender, smoking, systolic blood pressure, LDL, and body mass index), IL-5 remained an independent determinant of the mean bifurcational IMT (p = 0.010).

CONCLUSIONS

Our data demonstrate that plasma IL-5 levels are related to the plasma levels of antibodies binding to OxLDL and to decreased subclinical atherosclerosis in humans. These results are in line with earlier findings in murine atherosclerosis and indicate for the first time that IL-5 may play a role in human atherosclerosis.

Inflammatory lipids as a target for therapy in the rheumatic diseases

As patients with autoimmune rheumatic diseases live longer due to improved therapies and preventive measures, death and disability from cardiovascular events are increasing. Patients with rheumatoid arthritis and systemic lupus erythematosus have an increased risk of atherosclerosis that persists even after accounting for traditional cardiac risk factors. Recent studies strongly suggest that the mechanism is due in part to increased levels of oxidized lipids (such as oxidized low density lipoprotein and pro-inflammatory high density lipoproteins) which cause the inflammatory cascade that ultimately leads to plaque formation. The objective of this review is to discuss how inflammatory lipids contribute to the increased risk of atherosclerosis in rheumatoid arthritis and systemic lupus erythematosus, as well as to propose that these oxidized lipids are a rational target for therapeutic intervention in autoimmune diseases. Published literature was examined to review treatments for pro-inflammatory lipids in autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. In conclusion, it is possible that these oxidized lipids may also contribute to increased disease manifestations in rheumatic conditions. Several new and existing therapies, including statins and high density lipoprotein-associated protein peptide mimetics such as D-4F (apoA-1) target these oxidized lipids and may be useful in both preventing atherosclerosis and treating inflammation in patients with rheumatic diseases.

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.

Ethnic variation in levels of circulating IgG autoantibodies to oxidised low-density lipoprotein

BACKGROUND

Oxidised low-density lipoprotein (Ox-LDL) plays a key role in atherosclerosis. Our aim was to determine whether serum autoantibodies against Ox-LDL (Ab Ox-LDL) differ by ethnic group.

DESIGN AND METHODS

Soluble serum Ab Ox-LDL levels were measured in 250 white (113 females), 169 African origin (91 females) and 196 South Asian (92 females) individuals from the Wandsworth Heart and Stroke Study (WHSS) population. All were free from coronary heart disease (CHD), stroke, other cardiovascular disease, diabetes, drug therapy for hypertension or high lipids, hormone replacement therapy or oral contraceptive pill.

RESULTS

There were no sex differences in levels of Ab Ox-LDL, but levels were higher in non-smokers (430U/L [95% CI 471-596]) than in smokers (384U/L [316-468]) (p<0.009). Age- and sex-adjusted levels of Ab Ox-LDL were higher in people of African origin and South Asians compared to whites. This difference was maintained in South Asian women following adjustment for multiple risk factors (82% [21-175]; p=0.004). Ab Ox-LDL levels were negatively associated with serum triglycerides and positively associated with sVCAM-1.

CONCLUSIONS

Higher IgG Ab to Ox-LDL are associated with higher levels of sVCAM-1 and, are elevated in female South Asian individuals who have an increased risk of atherosclerosis compared to whites.

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.

Atherosclerosis and systemic lupus erythematosus: mechanistic basis of the association

As patients with Systemic Lupus Erythematosus (SLE) live longer due to improved therapies and preventive measures, death and disability from cardiovascular events are increasing. Patients with SLE have an increased risk of atherosclerosis that persists even after accounting for traditional cardiac risk factors. Recent studies strongly suggest that the mechanism is due in part to a combination of inflammatory and immune mechanisms. Contributory factors include increased levels of oxidized lipids (such as oxidized LDL and pro-inflammatory HDL), upregulation of adhesion molecules, and upregulation of cytokines such as MCP-1, TNF-alpha, IFN-gamma, IL-1, and IL-12. Autoanitbodies to oxidized lipids and immune complexes may also play a role in the development of atherosclerosis in SLE. As in the pathogenesis of many lupus disease processes, the increased risk of atherosclerosis seen in SLE is likely due to the complex interplay of many of these inflammatory and immune mediators.

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.

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.

Antibodies against beta2-glycoprotein I complexed with an oxidised lipoprotein relate to intima thickening of carotid arteries in primary antiphospholipid syndrome

To explore whether antibodies against β₂-glycoprotein I (β₂GPI) complexed to 7-ketocholesteryl-9-carboxynonanoate (oxLig-1) and to oxidised low-density lipoproteins (oxLDL) relate to paraoxonase activity (PONa) and/or intima media thickness (IMT) of carotid arteries in primary antiphospholipid syndrome (PAPS). As many as 29 thrombotic patients with PAPS, 10 subjects with idiopathic antiphospholipid antibodies (aPL) without thrombosis, 17 thrombotic patients with inherited thrombophilia and 23 healthy controls were investigated. The following were measured in all participants: β₂GPI−oxLDL complexes, IgG anti-β₂GPI−oxLig-1, IgG anti-β₂GPI−oxLDL antibodies (ELISA), PONa, (para-nitrophenol method), IMT of common carotid (CC) artery, carotid bifurcation (B), internal carotid (IC) by high resolution sonography. β₂GPI−oxLDL complex was highest in the control group (p < 0.01), whereas, IgG anti-β₂GPI−oxLig1 and IgG anti-β₂GPI−oxLDL were highest in PAPS (p < 0.0001). In healthy controls, β₂GPI−oxLDL complexes positively correlated to IMT of the IC (p = 0.007) and negatively to PONa after correction for age (p < 0.03). PONa inversely correlated with age (p = 0.008). In PAPS, IgG anti-2GPI−oxLig-1 independently predicted PONa (p = 0.02) and IMT of B (p = 0.003), CC, (p = 0.03) and of IC (p = 0.04). In PAPS, PONa inversely correlated to the IMT of B, CC and IC (p = 0.01, 0.02 and 0.003, respectively). IgG anti-2GPI−oxLig-1 may be involved in PAPS related atherogenesis via decreased PON activity.

Oxidized Phospholipids Predict the Presence and Progression of Carotid and Femoral Atherosclerosis and Symptomatic Cardiovascular Disease

OBJECTIVES

The purpose of this work was to determine the predictive value of oxidized phospholipids (OxPLs) present on apolipoprotein B-100 particles (apoB) in carotid and femoral atherosclerosis.

BACKGROUND

The OxPLs are pro-inflammatory and pro-atherogenic and may be detected using the antibody E06 (OxPL/apoB).

METHODS

The Bruneck study is a prospective population-based survey of 40- to 79-year-old men and women initiated in 1990. Plasma levels of OxPL/apoB and lipoprotein (a) [Lp(a)] were measured in 765 of 826 (92.6%) and 671 of 684 (98.1%) subjects alive in 1995 and 2000, respectively, and correlated with ultrasound measures of carotid and femoral atherosclerosis.

RESULTS

The distribution of the OxPL/apoB levels was skewed to lower levels and nearly identical to Lp(a) levels. The OxPL/apoB and Lp(a) levels were highly correlated (r = 0.87, p < 0.001), and displayed long-term stability and lacked correlations with most cardiovascular risk factors and lifestyle variables. The number of apolipoprotein (a) kringle IV-2 repeats was inversely related to Lp(a) mass (r = -0.48, p < 0.001) and OxPL/apoB levels (r = -0.46, p < 0.001). In multivariable analysis, OxPL/apoB levels were strongly and significantly associated with the presence, extent, and development (1995 to 2000) of carotid and femoral atherosclerosis and predicted the presence of symptomatic cardiovascular disease. Both OxPL/apoB and Lp(a) levels showed similar associations with atherosclerosis severity and progression, suggesting a common biological influence on atherogenesis.

CONCLUSIONS

This study suggests that pro-inflammatory oxidized phospholipids, present primarily on Lp(a), are significant predictors of the presence and extent of carotid and femoral atherosclerosis, development of new lesions, and increased risk of cardiovascular events. The OxPL biomarkers may provide valuable insights into diagnosing and monitoring cardiovascular disease.

Oxidized Low-Density Lipoprotein Autoantibodies, Chronic Infections, and Carotid Atherosclerosis in a Population-Based Study

OBJECTIVES

We investigated whether associations exist between immune reactions to oxidized low-density lipoproteins (OxLDLs), chronic infections, and carotid atherosclerosis as quantified by ultrasound.

BACKGROUND

Atherosclerosis is a chronic immuno-inflammatory disease wherein both oxidized lipids and infectious agents are incriminated as possible contributors.

METHODS

We measured immunoglobulin (Ig)G and IgM autoantibody titers to copper-oxidized-LDL and malondialdehyde-LDL (OxLDL-AB), IgG and IgM apolipoprotein B-100-immune complexes (ApoB-IC), and titers of antibodies to Escherichia coli and chlamydial lipopolysaccharide (LPS), mycobacterial heat shock protein 65 (mHSP65), Chlamydia pneumoniae, Helicobacter pylori, and cytomegalovirus and evaluated their relationship to cardiovascular risk factors, chronic infections, and incident/progressive carotid atherosclerosis in the Bruneck study.

RESULTS

The OxLDL-AB and ApoB-IC levels remained stable over time as indicated by strong correlations between 1995 and 2000 measurements (p < 0.001 each). Significant associations existed between all OxLDL markers and antibody titers to pathogens, especially to E. coli-LPS and mHSP65. Both OxLDL-AB and ApoB-IC levels showed a rise with increasing pathogen burden. Notably, OxLDL-ABs were also elevated in subjects with chronic infection as defined by clinical criteria. Titers of IgG, but not IgM, OxLDL-AB, or ApoB-IC inversely correlated with total cholesterol, LDL cholesterol, and apoB concentrations. The IgG OxLDL markers were positively and IgM markers were inversely associated with incident and progressive carotid atherosclerosis in univariate analyses but were not independent predictors in multivariate analyses.

CONCLUSIONS

Our study provides evidence for an association between human oxLDL markers and chronic infections. Moreover, in this population-based study, neither IgG nor IgM OxLDL autoantibodies were independently predictive of atherosclerosis progression in the carotid arteries.

Autoantibodies to oxidized LDL and cardiovascular risk: the Framingham Offspring Study

BACKGROUND

The relation between measures of oxidation of lipid particles and cardiovascular disease has not been extensively investigated prospectively on a population basis.

METHODS

A community cohort of 1192 men and 1427 women with measures of IgG antibodies to oxidized LDL were followed 8 years for the development of initial coronary heart disease (CHD) and cardiovascular disease (CVD) events.

RESULTS

Levels of IgG autoantibodies to a form of oxidized LDL were significantly associated with age in both sexes, positively with fibrinogen in men and negatively with HDL cholesterol in women. In sex-specific models that adjusted for age alone or those that adjusted for age, cholesterol, HDL cholesterol, smoking, and diabetes mellitus, there was no relation between level of antibodies to oxidized LDL and the development of CHD or CVD.

CONCLUSION

Autoantibodies to oxidized LDL were strongly related to age and were not related to incident CHD or CVD over 8 years of follow up.

Women and Ischemic Heart Disease

The current review highlights gender-specific issues in ischemic heart disease (IHD) presentation, evaluation, and outcomes with a special focus on the results derived from the National Institutes of Health-National Heart, Lung, and Blood Institute-sponsored Women's Ischemia Syndrome Evaluation (WISE) study. New evidence on gender-based differences in vascular wall, atherosclerotic plaque deposition, pathophysiology, and innovative cardiovascular imaging techniques are reviewed. Critical areas of further inquiry needed to advance new gender-specific IHD understanding are detailed.

Oxidized low-density lipoprotein biomarkers in atherosclerosis

The concept that the oxidation of lipoproteins is central in the pathogenesis of atherosclerosis was first reported over 25 years ago, initially by in vitro studies and subsequently through experimental models of atherosclerosis. The innate immune system plays a key role in atherogenesis as manifested by its atherosclerosis-modulating properties, the immunogenicity of oxidized low-density lipoprotein (LDL), and the presence of oxidized LDL autoantibodies in plasma and lesions of humans. In the past 10 years it has been possible to generate monoclonal antibodies to oxidized LDL to directly measure oxidized LDL in plasma. This has led to a rapidly accelerating pace of new reports on the relationship of circulating oxidized LDL and various cardiovascular pathologic processes, which are the focus of this review.

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 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.

The role of natural antibodies in atherogenesis

Atherosclerosis is now widely recognized as a chronic inflammatory disease that involves innate and adaptive immune responses. Both cellular and humoral components of the immune system have been implicated in atherogenesis. Natural antibodies can be considered humoral factors of innate immunity, and their functional role in health and disease has been reexamined in recent years. Natural antibodies exhibit a remarkably conserved repertoire that includes a broad specificity for self-antigens. For this reason, they are believed to be a product of natural selection and have been suggested to play an important role in "housekeeping" functions. Recent evidence has revealed that oxidation-specific epitopes are important and maybe immunodominant targets of natural antibodies, suggesting an important function for these antibodies in the host response to consequences of oxidative stress, for example, to the oxidative events that occur when cells undergo apoptosis. This review will focus on these recent findings and discuss the emerging evidence for an important role of natural antibodies in atherogenesis.