Will autoantibodies help to determine severity and progression of atherosclerosis?

Relationship of Autoantibodies to MDA-LDL and ApoB-Immune Complexes to Sex, Ethnicity, Subclinical Atherosclerosis, and Cardiovascular Events

OBJECTIVE

Modifications of lipid constituents within atherosclerotic lesions generate neoepitopes that activate innate and adaptive immune responses. We aimed to define the prevalence, distribution, and relationship of autoantibody titers of oxidized lipoproteins to subclinical atherosclerosis and major adverse cardiovascular events (MACE) in different ethnic groups.

APPROACH AND RESULTS

IgG and IgM autoantibodies to malondialdehyde-modified low-density lipoprotein (MDA-LDL) and apolipoprotein B-100-immune complexes were measured in 3509 individuals (1814 blacks, 1031 whites, 589 Hispanics, and 85 no race identifier) from the Dallas Heart Study with median 10.5-year follow-up. Coronary artery calcium score, abdominal aortic plaque by magnetic resonance imaging, and MACE were quantified. IgG MDA-LDL and IgG and IgM apolipoprotein B-100-immune complexes were significantly different between groups, with blacks having the highest levels of IgG MDA-LDL and IgG apolipoprotein B-100-immune complexes and Hispanics having the highest levels of IgM apolipoprotein B-100-immune complexes (P<0.001 for all). IgGs tended to be higher and IgMs lower with age for all markers. In multivariable-adjusted binary logistic regression analysis, a doubling of IgG MDA-LDL levels was associated with prevalent coronary artery calcium score >10 Agatston units (odds ratio [95% confidence interval], 1.21 [1.07-1.36]; P=0.002). Multivariable-adjusted Cox regression analysis revealed that IgG MDA-LDL was independently associated with time to incident MACE in the entire group (hazard ratio [95% confidence interval], 1.76 [1.16-2.72]; P=0.009 for fourth versus first quartile). This effect was particularly prominent in black subjects (hazard ratio [95% confidence interval], 2.52 [1.39-4.57]; P=0.002).

CONCLUSIONS

Autoantibodies to oxidized lipoproteins and immune complexes with apoB-100 lipoproteins vary significantly by sex, age, and ethnicity. Higher baseline IgG MDA-LDL titers independently associate with new MACE. These findings may contribute to the understanding of differences in ethnic-specific MACE events.

Low Levels of Apolipoprotein B-100 Autoantibodies Are Associated With Increased Risk of Coronary Events

OBJECTIVE

Previous smaller studies have indicated inverse associations between autoantibodies to oxidized low-density lipoprotein epitopes, and cardiovascular disease. The present study investigated associations between autoantibodies against the apolipoprotein B-100 peptides p45 and p210, respectively, and risk of incident cardiovascular disease in a large population-based cohort.

APPROACH AND RESULTS

Apolipoprotein B-100 autoantibodies were analyzed by ELISA in a prospective study, including 5393 individuals (aged 46-68 years) belonging to the cardiovascular arm of the Malmö Diet and Cancer study with a follow-up time of >15 years. Subjects that suffered an acute coronary event during follow-up (n=382) had lower levels at baseline of IgM autoantibodies recognizing the native and malondialdehyde-modified apolipoprotein B-100 peptides p45 and p210 and also lower IgG levels recognizing native p210, whereas no association was found with risk for stroke (n=317). Subjects in the highest compared with lowest tertile of IgM-p45MDA (hazard ratio [95% confidence interval]: 0.72 [0.55, 0.94]; P=0.017) and IgG-p210native (hazard ratio [95% confidence interval]: 0.73 [0.56, 0.97]; P=0.029) had lower risk for incident coronary events after adjustment for cardiovascular risk factors in Cox proportional hazard regression models. Moreover, subjects with high levels of IgG-p210native were less likely to have carotid plaques as assessed by ultrasonography at baseline (odds ratio=0.81, 95% confidence interval 0.70-0.95, P=0.008 after adjustment for risk factors).

CONCLUSIONS

This large prospective study demonstrates that subjects with high levels of apolipoprotein B-100 autoantibodies have a lower risk of coronary events supporting a protective role of these autoantibodies in cardiovascular disease.

Pathogenic immunity in systemic lupus erythematosus and atherosclerosis: common mechanisms and possible targets for intervention

Systemic lupus erythematosus (SLE) is an autoimmune disorder that primarily affects young women and is characterized by inflammation in several organs including kidneys, skin, joints, blood and nervous system. Abnormal immune cellular and humoral responses play important roles in the development of the disease process. Impaired clearance of apoptotic material is a key factor contributing to the activation of self-reactive immune cells. The incidence of atherosclerotic cardiovascular disease (CVD) is increased up to 50-fold in patients with SLE compared to age- and gender-matched controls, and this can only partly be explained by traditional risk factors for CVD. Currently, there is no effective treatment to prevent CVD complications in SLE. Traditional preventive CVD therapies have not been found to significantly lower the incidence of CVD in SLE; therefore, there is a need for novel treatment strategies and increased understanding of the mechanisms involved in the pathogenesis of CVD complications in SLE. The pathogenic immune responses in SLE and development of atherosclerotic plaques share some characteristics, such as impaired efferocytosis and skewed T-cell activation, suggesting the possibility of identifying novel targets for intervention. As novel immune-based therapies for CVD are being developed, it is possible that some of these may be effective for the prevention of CVD and for immunomodulation in SLE. However, further understanding of the mechanisms leading to an increased prevalence of cardiovascular events in SLE is critical for the development of such therapies.

Atheroprotective immunity and cardiovascular disease: therapeutic opportunities and challenges

Emerging knowledge of the role of atheroprotective immune responses in modulating inflammation and tissue repair in atherosclerotic lesions has provided promising opportunities to develop novel therapies directly targeting the disease process in the artery wall. Regulatory T (Treg) cells have a protective role through release of anti-inflammatory cytokines and suppression of autoreactive effector T cells. Studies in experimental animals have shown that blocking the generation or action of Treg cells is associated with more aggressive development of atherosclerosis. Conversely, cell transfer and other approaches to expand Treg cell populations in vivo result in reduced atherosclerosis. There have been relatively few clinical studies of Treg cells and cardiovascular disease, but the available evidence also supports a protective function. These observations have raised hope that it may be possible to develop therapies that act by enforcing the suppressive activities of Treg cells in atherosclerotic lesions. One approach to achieve this goal has been through development of vaccines that stimulate immunological tolerance for plaque antigens. Several pilot vaccines based on LDL-derived antigens have demonstrated promising results in preclinical testing. If such therapies can be shown to be effective also in clinical trials, this could have an important impact on cardiovascular prevention and treatment. Here, we review the current knowledge of the mode of action of atheroprotective immunity and of the ways to stimulate such pathways in experimental settings. The challenges in translating this knowledge into the clinical setting are also discussed within the perspective of the experience of introducing immune-based therapies for other chronic noninfectious diseases.

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.

A study of IgG antibodies to the ApoB protein in non-ST segment elevation acute coronary syndrome

OBJECTIVES

It has long been noted that there is an association of antibodies against oxidized low-density lipoprotein (oxLDL) with cardiovascular disease, but the anti-oxLDL antibody has not been confirmed as a biomarker for prediction of acute coronary syndrome (ACS). Apolipoprotein B (ApoB) may carry the epitopes for the immune response to oxLDL. The present work was thus undertaken to detect circulating antibodies to ApoB in non-ST segment elevation ACS (NSTE-ACS).

DESIGN

A total of 130 patients with NSTE-ACS and 201 control subjects were recruited. Six ApoB-derived peptipe antigens (Ag1-Ag6) were used to develop an in-house enzyme-linked immunosorbent assay to examine circulating anti-ApoB IgG levels.

RESULTS

The anti-Ag1 IgG level was significantly higher in the patient group than the control group (P < 0.001) and the non-ST segment elevation myocardial infarction appeared to be the main form of NSTE-ACS contributing to the increased levels of anti-Ag1 IgG (P < 0.001); there was no significant alteration in the levels of IgG to the other 5 antigens in NSTE-ACS.

CONCLUSIONS

Circulating anti-ApoB IgG test may be useful for prediction of NSTE-ACS although further confirmation is needed in large-scale clinical studies.

Definition of human apolipoprotein A-I epitopes recognized by autoantibodies present in patients with cardiovascular diseases

Autoantibodies to apolipoprotein A-I (anti-apoA-I IgG) have been shown to be both markers and mediators of cardiovascular disease, promoting atherogenesis and unstable atherosclerotic plaque. Previous studies have shown that high levels of anti-apoA-I IgGs are independently associated with major adverse cardiovascular events in patients with myocardial infarction. Autoantibody responses to apoA-I can be polyclonal and it is likely that more than one epitope may exist. To identify the specific immunoreactive peptides in apoA-I, we have developed a set of methodologies and procedures to isolate, purify, and identify novel apoA-I endogenous epitopes. First, we generated high purity apoA-I from human plasma, using thiophilic interaction chromatography followed by enzymatic digestion specifically at lysine or arginine residues. Immunoreactivity to the different peptides generated was tested by ELISA using serum obtained from patients with acute myocardial infarction and high titers of autoantibodies to native apoA-I. The immunoreactive peptides were further sequenced by mass spectrometry. Our approach successfully identified two novel immunoreactive peptides, recognized by autoantibodies from patients suffering from myocardial infarction, who contain a high titer of anti-apoA-I IgG. The discovery of these epitopes may open innovative prognostic and therapeutic opportunities potentially suitable to improve current cardiovascular risk stratification.

Free radicals and endothelial dysfunction: potential positive effects of TNF-α inhibitors

OBJECTIVES

During the last decade many new biological immune modulators have entered the market as new therapeutic principles. Tumor necrosis factor (TNF)-α is a pro-inflammatory cytokine known to a have a key role in the pathogenic mechanisms of various immune-mediated or inflammatory diseases. However, TNF-α also plays a key role in endothelial dysfunction and, thus, in the development and progression of atherosclerosis. What, then, is the potential therapeutic role of TNF-α inhibitors?

METHODS

We analysed the current literature concerning the administration of TNF-α inhibitors and their potential benefits upon endothelial function.

RESULTS

TNF-α inhibitors decrease the serum levels of inflammatory markers such as TNF-α itself, CRP, IL-6, and increased the tissue expression of endothelial NO synthase and the vasodilatory response to bradykinin.

DISCUSSION

TNF-α inhibitors may change the progression of endothelial dysfunction and, thus, slow down the atherosclerotic process.

Emerging biomarkers and intervention targets for immune-modulation of atherosclerosis - a review of the experimental evidence

The role of inflammation in atherosclerosis and plaque vulnerability is well recognized. However, it is only during recent years it has become evident that this inflammation is modulated by immune responses against plaque antigens such as oxidized LDL. Interestingly, both protective and pathogenic immune responses exist and experimental data from animal studies suggest that modulation of these immune responses represents a promising new target for treatment of cardiovascular disease. It has been proposed that during early stages of the disease, autoimmune responses against plaque antigens are controlled by regulatory T cells that inhibit the activity of auto-reactive Th1 effector T cells by release of anti-inflammatory cytokines such as IL-10 and TGF-β. As the disease progresses this control is gradually lost and immune responses towards plaque antigens switch towards activation of Th1 effector T cells and release of pro-inflammatory cytokines such as interferon-γ, TNF-α and IL-1β. Several novel immune-modulatory therapies that promote or mimic tolerogenic immune responses against plaque antigens have demonstrated athero-protective effects in experimental models and a first generation of such immune-modulatory therapies are now in early or about to enter into clinical testing. A challenge in the clinical development of these therapies is that our knowledge of the role of the immune system in atherosclerosis largely rests on data from animal models of the disease. It is therefore critical that more attention is given to the characterization and evaluation of immune biomarkers for cardiovascular risk.

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.

Endothelial dysfunction in rheumatic autoimmune diseases

Rheumatic autoimmune diseases have been associated with accelerated atherosclerosis and various types of vasculopathies. Atherosclerosis is an inflammatory condition which starts as a "response to injury" favoring endothelial dysfunction which is associated with increased expression of adhesion molecules, pro-inflammatory cytokines, pro-thrombotic factors, oxidative stress upregulation and abnormal vascular tone modulation. Endothelial dysfunction in rheumatic autoimmune diseases involves innate immune responses, including macrophages and dendritic cells expression of scavenger and toll-like receptors for modified or native LDL as well as neutrophil and complement activation, and dysregulation of adaptive immune responses, including proliferation of autoreactive T-helper-1 lymphocytes and defective function of dendritic and regulatory T cells. Specific differences for endothelial function among different disorders include: a) increased amounts of pro-atherogenic hormones, decreased amounts of anti-atherogenic hormones and increased insulin resistance in rheumatoid arthritis; b) autoantibodies production in systemic lupus erythematosus and antiphospholipid syndrome; c) smooth muscle cells proliferation, destruction of internal elastic lamina, fibrosis and coagulation and fibrinolytic system dysfunction in systemic sclerosis. Several self-antigens (i.e. high density lipoproteins, heat shock proteins, β2-glycoprotein1) and self-molecules modified by oxidative events (i.e. low density lipoproteins and oxidized hemoglobin) have been identified as targets of autoimmune responses. Endothelial dysfunction leads to accelerated atherosclerosis in rheumatoid arthritis, systemic lupus erythematosus and spondyloarthropaties whereas obliterative vasculopathy is associated with systemic sclerosis. In this paper, we will briefly review the most relevant information upon endothelial dysfunction and inflammatory mechanisms in atherosclerosis and we will summarize the similarities and differences in vascular disease patterns underlying different rheumatic autoimmune diseases.

Lymphocytes in atherosclerosis

It is well established that atherosclerosis is caused by an inflammatory process in the arterial intima. However, it is only in recent years that it has become clear that this inflammation is modulated by immune responses against plaque antigens. These antigens are primarily believed to be modified self-antigens such as oxidized LDL. The immune system is challenged to determine whether these antigens should be regarded self and tolerated or non-self and eliminated. The latter will result in plaque development while the first will be protective. T cells are key effectors of both types of responses. An activation of regulatory T cells inhibits auto-reactive T effector cells and is anti-inflammatory. In contrast, if Th1 cells become activated in the plaque this is associated with increased inflammation and disease progression. The role of B cells in atherosclerosis remains to be clarified but some species of athero-protective antibodies have been identified. The elucidation of role of immune system in atherosclerosis has revealed new targets for intervention and both vaccines and antibody-based therapies are presently in or due to enter clinical testing.

Oxidative stress in cardiovascular inflammation: its involvement in autoimmune responses

Recently, it has become clear that atherosclerosis is a chronic inflammatory disease in which inflammation and immune responses play a key role. Accelerated atherosclerosis has been reported in patients with autoimmune diseases, suggesting an involvement of autoimmune mechanisms in atherogenesis. Different self-antigens or modified self-molecules have been identified as target of humoral and cellular immune responses in patients with atherosclerotic disease. Oxidative stress, increasingly reported in these patients, is the major event causing structural modification of proteins with consequent appearance of neoepitopes. Self-molecules modified by oxidative events can become targets of autoimmune reactions, thus sustaining the inflammatory mechanisms involved in endothelial dysfunction and plaque development. In this paper, we will summarize the best characterized autoantigens in atherosclerosis and their possible role in cardiovascular inflammation.

Immunization with cationized BSA inhibits progression of disease in ApoBec-1/LDL receptor deficient mice with manifest atherosclerosis

Immune responses against modified self-antigens generated by hypercholesterolemia play an important role in atherosclerosis identifying the immune system as a possible novel target for prevention and treatment of cardiovascular disease. It has recently been shown that these immune responses can be modulated by subcutaneous injection of adjuvant. In the present study we immunized 25-week old ApoBec-1/LDL receptor deficient mice with manifest atherosclerosis with adjuvant and two different concentrations of the carrier molecule cationized BSA (cBSA). Plasma levels of Th2-induced apolipoprotein B (apoB)/IgG1 immune complexes were increased in the cBSA immunized groups verifying induction of immunity against a self-antigen. Mice were sacrificed at 36 weeks of age and atherosclerosis was monitored by en face Oil red O staining of the aorta. Immunization with 100 μg cBSA inhibited plaque progression, whereas the lower dose (50 μg) did not. In addition, the higher dose induced a more stable plaque phenotype, indicated by a higher content of collagen and less macrophages and T cells in the plaques. Moreover, there was an increased ratio of Foxp3+/Foxp3⁻ T cells in the circulation suggesting activation of a regulatory T cell response. In conclusion, we show that immunization with cBSA induces an immune response against apoB as well as an activation of Treg cells. This was associated with development of a more stable plaque phenotype and reduced atherosclerosis progression.

Should we measure routinely oxidised and atherogenic dense low-density lipoproteins in subjects with type 2 diabetes?

Beyond low-density lipoprotein (LDL)-cholesterol concentrations, in recent years, several clinical studies have shown that both oxidised and small, dense LDL have a strong predictive role for the presence of vascular atherosclerosis. These two lipid parameters seem to have a synergistic impact on cardiovascular risk, with a greater importance in patients at higher-risk, such as those with type-2 diabetes. Increased levels of oxidised and small, dense LDL levels are a feature of diabetic dyslipidaemia, and small, dense LDL have been shown to be a good predictor of future cardiovascular events, at both univariate and multivariate analyses. On the other hand, although the association of oxidised LDL with surrogate markers of atherosclerosis is consistent, the correlation with hard clinical end points seems to be smaller. Yet, measurement of these two lipid parameters has not been widely used in daily practice because of the limited availability of clinical data and methodological problems: lack of availability of easy, cheap and reproducible essays for measurement of oxidised and, particularly, small, dense LDL has reduced their assessment in large clinical end-points trials. However, on the basis of available data, the therapeutic modulation of small, dense LDL is significantly associated with reduced cardiovascular risk, even after adjustment for confounding factors. In conclusion, the routine measurement of oxidised and small, dense LDL in patients with type-2 diabetes cannot be recommended in daily clinical practice so far; yet, their measurement is strongly encouraged to better understand their role on the cardiovascular risk of patients with type-2 diabetes.

Autoimmunity in atherosclerosis: a protective response losing control?

Atherosclerosis is a chronic inflammatory disease characterized by accumulation of oxidized lipoproteins, increased cell death and hypertrophic degeneration of the arterial intima. The disease process is associated with local formation of modified self antigens that are targeted by both innate and adaptive immune responses. Although it remains to be firmly established it is likely that these autoimmune responses initially have a beneficial effect facilitating the removal of potentially harmful rest products from oxidized LDL and dying cells. However, studies performed on hypercholesterolaemic mice deficient in different components of the immune system uniformly suggest that the net effect of immune activation is pro-atherogenic and that atherosclerosis, at least to some extent, should be regarded as an autoimmune disease. These observations point to the possibility of developing new treatments for atherosclerosis based on modulation of immune responses against plaque antigens, an approach presently tested clinically for several other chronic inflammatory diseases with autoimmune components. Pilot studies in animals have provided promising results for both parental and oral vaccines based on oxidized LDL antigens. The time when this concept is ready for clinical testing is rapidly approaching but it will be important not to underestimate the difficulties that will be encountered in transferring the promising results from experimental animals into humans.

OxLDL–IgG Immune Complexes Induce Survival of Human Monocytes

OBJECTIVE

Immune complexes containing oxidatively modified low-density lipoprotein (oxLDL) particles are deposited in human atherosclerotic lesions during atherogenesis. Here we studied whether OxLDL-IgG immune complexes (OxLDL-IgG ICs) affect survival of human monocytes.

METHODS AND RESULTS

As demonstrated by light microscopy, and analysis of cell proliferation, caspase-3 activity, and DNA fragmentation, OxLDL-IgG ICs promoted survival of cultured human monocytes by decreasing their spontaneous apoptosis. OxLDL-IgG ICs induced a concentration-dependent production of the major monocyte growth factor, monocyte colony-stimulating factor (M-CSF), by the monocytes, but its inhibition was without effect on OxLDL-IgG IC-induced monocyte survival. Rather, OxLDL-IgG ICs induced rapid phosphorylation of Akt, suggesting a direct anti-apoptotic effect mediated by cross-linking of Fcgamma receptors. Experiments with receptor blocking antibodies revealed that the OxLDL-IgG IC-induced monocyte survival was mediated by Fcgamma receptor I.

CONCLUSIONS

The results show that OxLDL-IgG ICs promote survival of monocytes by cross-linking Fcgamma receptor I and activating Akt-dependent survival signaling. The results reveal a novel mechanism by which an immune reaction toward oxLDL can play a role in the accumulation of macrophages in human atherosclerotic lesions.

Circulating oxidized low density lipoprotein, autoantibodies against them and homocysteine serum levels in diagnosis and estimation of severity of coronary artery disease

The oxidative hypothesis of atherosclerosis proposes that oxidative modification of low density lipoprotein (LDL) plays a critical role in atherogenesis. The evaluation of LDL oxidation in vivo is therefore very important. However, data concerning the evaluation of the above biochemical marker is very limited in clinical practice. This study was conducted to test the hypothesis that plasma levels of ox-LDL reflect atherosclerosis and determine the clinical significance in the measurement of circulating ox-LDL and autoantibodies against them as well as their correlation with homocysteine and lipid parameters in the diagnosis and severity of coronary heart disease. A total of 273 individuals were examined: 41 suffering from unstable angina pectoris (UAP), 62 from stable angina pectoris (SAP) and 170 healthy control subjects. We used a sensitive method for detecting ox-LDL that is based on a direct sandwich technique (ELISA) in which two monoclonal antibodies are directed against separate antigenic determinants on the oxidized apolipoprotein-B molecule along with another enzyme immunoassay designed to determine human antibodies to oxidized LDL (anti-oxLDL) directly in serum. Total homocysteine (HCY) was evaluated by means of a fully automated fluorescence polarization immunoassay. Patients with UAP exhibited marked elevations in oxLDL levels as compared to patients with SAP (161.2 +/- 28.4 vs. 119.2 +/- 26.6, p < 0.001) and the control subjects (67 +/- 18.8, p < 0.001). The difference in oxLDL levels between patients with SAP and the control group was also statistically significant. Similarly, patients with UAP showed marked elevations in anti-oxLDL antibodies compared to both patients with SAP (602.2 +/- 62.2 vs. 510.8 +/- 50.3,p < 0.001) and control subjects (368 +/- 79.6, p < 0.001). The difference in anti-oxLDL levels between patients with SAP and the controls was also statistically significant. OxLDL levels were not correlated with age in any of the groups studied. Triglycerides, LDL-cholesterol and total cholesterol were elevated in patients with UAP as opposed to patients with SAP and the control subjects, while HDL levels were elevated in the control subjects when compared to patients with SAP and UAP. Homocysteine levels were elevated in patients suffering from UAP and SAP when compared to healthy subjects. Patients with UAP or SAP did not differ on homocysteine levels. Our findings demonstrate the presence of oxLDL in vivo, its strong association with coronary artery disease as well as with the severity of the clinical presentation.

Drug therapies to prevent coronary plaque rupture and erosion: present and future

Patients at high risk for coronary heart disease usually have a number of atherosclerotic plaques in their coronary arteries. Some plaques grow inward and, once they have caused a critical degree of luminal stenosis, lead to chronic anginal symptoms. Other plaques grow outward and remain silent unless they disrupt and trigger an acute coronary event. Either type of plaque may become vulnerable to rupture or erosion once they have reached an advanced stage. Typically, a highly stenotic fibrotic plaque is prone to erosion, whereas an advanced lipid-rich thin-cap fibroatheroma is prone to rupture. Because of the multitude and complex nature of the coronary lesions and our inability to detect silent rupture-prone plaques, the best practical approach to prevent acute coronary events is to treat the vulnerable patient, i.e., to eliminate the risk factors of coronary disease. Despite such preventive measures, a sizable number of patients still experience acute coronary events due to plaque erosion or rupture. Thus, there is room for new avenues to pharmacologically stabilize vulnerable plaques. The development of new noninvasive tools to detect the progression and regression of individual non-stenotic rupture-prone plaques will allow testing of such novel pharmacotherapies. Because no specific plaque-targeted therapies are available at present, we give an overview of the current pharmacotherapy to treat the vulnerable patient and also discuss potential novel therapies to prevent acute coronary events.