Antibodies against oxidized low-density lipoprotein in normolipidemic smokers

Immunometabolic and Vascular Health Responses among High Endurance Trained Subjects

In this study, we aimed to examine the impact of high endurance training on vascular health parameters and immune-endocrine responses against modified low-density lipoprotein (LDL) particles. This observational, cross-sectional study included high endurance-trained and healthy non-trained subjects. Vascular ultrasound was used to assess vascular health parameters based on carotid intima-media thickness and endothelial function (flow-mediated dilation). Enzyme-linked immunosorbent assays were used to measure interleukin (IL)-8 and IL-10, autoantibody isotypes anti-oxidized LDL (oxLDL) and anti-apolipoprotein B (ApoB-D) peptide. Plasma levels of the corticosterone and 17 α-hydroxyprogesterone hormones were analyzed by mass spectrometry. This study enrolled 96 subjects, of whom 44 were high endurance trained and 52 were healthy non-trained individuals. Smaller carotid intima-media thickness values were observed in the high-endurance trained than in the healthy non-trained males, while no differences were observed between female groups. Flow-mediated dilation measurements did not differ by training or sex. The humoral immune responses to IgG anti-oxLDL and IgM anti-ApoB-D autoantibodies showed an isotype imbalance between the high-endurance trained and the non-trained groups. Immunoendocrine parameters showed inverse correlations between 17 α-hydroxyprogesterone concentrations and carotid intima-media thickness measurements. Direct correlations were found between IL-10 concentrations and flow-mediated dilation measurements. Chronic high-endurance exercise modulates immune-endocrine and vascular health parameters, in a sex-dependent manner.

Correlation between Mitochondrial Reactive Oxygen and Severity of Atherosclerosis

Atherosclerosis has been associated with mitochondria dysfunction and damage. Our group demonstrated previously that hypercholesterolemic mice present increased mitochondrial reactive oxygen (mtROS) generation in several tissues and low NADPH/NADP+ ratio. Here, we investigated whether spontaneous atherosclerosis in these mice could be modulated by treatments that replenish or spare mitochondrial NADPH, named citrate supplementation, cholesterol synthesis inhibition, or both treatments simultaneously. Robust statistical analyses in pooled group data were performed in order to explain the variation of atherosclerosis lesion areas as related to the classic atherosclerosis risk factors such as plasma lipids, obesity, and oxidative stress, including liver mtROS. Using three distinct statistical tools (univariate correlation, adjusted correlation, and multiple regression) with increasing levels of stringency, we identified a novel significant association and a model that reliably predicts the extent of atherosclerosis due to variations in mtROS. Thus, results show that atherosclerosis lesion area is positively and independently correlated with liver mtROS production rates. Based on these findings, we propose that modulation of mitochondrial redox state influences the atherosclerosis extent.

Investigation of serum oxidized low-density lipoprotein IgG levels in patients with angiographically defined coronary artery disease

It has been suggested that antioxidized low-density lipoprotein (anti-oxLDL) antibodies play a role in the pathogenesis of atherosclerosis. The aim of this study was to measure serum ox-LDL IgG levels in 31 patients with angiographically defined coronary artery disease (CAD) (≥50% stenosis in at least one major coronary artery; CAD⁺ group) and compare these levels with those of 32 subjects with <50% coronary stenosis (CAD⁻ group) and 24 healthy age- and sex-matched controls using ELISA. We did not find any significant difference between CAD⁺, CAD⁻, and control groups in regard to oxLDL IgG levels (P = 0.83). Serum oxLDL IgG levels did not differ between 1VD (one vessel disease), 2VD (2 vessels disease), and 3VD (3 vessels disease) subgroups of CAD⁺ patients (P = 0.20). Serum anti-oxLDL titers were only significantly correlated with LDL-C in the CAD⁺ group (P < 0.05) and waist and hip circumference (P < 0.05 and P < 0.01, resp.) in the CAD⁻ group. In stepwise regression analysis, none of the conventional cardiovascular risk factors was associated with serum ox-LDL IgG levels. The present results suggest that serum levels of ox-LDL IgG are neither associated with the presence and severity of CAD nor with the conventional cardiovascular risk factors.

Adaptive immunity is related to coronary artery disease severity after acute coronary syndrome in subjects with metabolic syndrome

Metabolic syndrome (MetS) is an inflammatory state associated with high coronary disease risk. Inflammation and adaptive immunity modulate atherosclerosis and plaque instability. We examined early changes in anti-oxidized low-density lipoprotein (LDL) (anti-oxLDL) autoantibodies (Abs) in patients with MetS after an acute coronary syndrome (ACS). Patients of both genders (n=116) with MetS were prospectively included after an acute myocardial infarction (MI) or hospitalization due to unstable angina. Anti-oxLDL Abs (IgG class) were assayed at baseline, three and six weeks after ACS. The severity of coronary disease was evaluated by the Gensini score. We observed a decrease in anti-oxLDL Abs titers (p<0.002 vs. baseline), mainly in males (p=0.01), in those under 65 y (p=0.03), and in subjects with Gensini score above median (p=0.04). In conclusion, early decrease in circulating anti-oxLDL Abs is associated with coronary disease severity among subjects with MetS.

Smoking and atherosclerotic cardiovascular disease: part II: role of cigarette smoking in cardiovascular disease development

Potential mechanisms and biomarkers of atherosclerosis related to cigarette smoking - a modifiable risk factor for that disease - are discussed in this article. These include smoking-associated inflammatory markers, such as leukocytes, high-sensitivity C-reactive protein, serum amyloid A, ICAM-1 and IL-6. Other reviewed markers are indicative for smoking-related impairment of arterial endothelial function (transcapillary leakage of albumin, inhibition of endogenous nitric oxide synthase activity and reduced endothelium-dependent vasodilation) or point to oxidative stress caused by various chemicals (cholesterol oxidation, autoantibodies to oxidized low-density lipoprotein, plasma levels of malondialdehyde and F(2)-isoprostanes and reduced antioxidant capacity). Smoking enhances platelet aggregability, increases blood viscosity and shifts the pro- and antithrombotic balance towards increased coagulability (e.g., fibrinogen, von Willebrand factor, ICAM-1 and P-selectin). Insulin resistance is higher in smokers compared with nonsmokers, and hemoglobin A1c is dose-dependently elevated, as is homocysteine. Smoke exposure may influence the kinetics of markers with different response to transient or chronic changes in cigarette smoking behavior.

Oxidized low-density lipoprotein and ankle-brachial pressure index in patients with clinically evident peripheral arterial disease

OBJECTIVES

To investigate whether oxidized low-density lipoprotein is a suitable predictor of peripheral arterial disease severity. The role of oxidized low-density lipoprotein in the pathogenesis of atherosclerosis has already been investigated. Its relevance as a predictor of the appearance and worsening of coronary arterial disease is also well known. However, the same is not true regarding peripheral arterial disease.

METHOD

Eighty-five consecutive patients with an ankle-brachial pressure index (ABPI) < 0.9 and the presence of either intermittent claudication or critical lower leg ischemia were included. The plasma level of IgG autoantibodies against oxidized low-density lipoprotein was evaluated through an enzyme-linked immunosorbent assay. The results were categorized into quartiles according to the ankle-brachial pressure index (a marker of peripheral arterial disease severity), and significant differences were investigated with the Kruskal-Wallis test.

RESULTS

There was no significant difference between the quartiles for this population (p = 0.33). No correlation was found between the ankle-brachial pressure index and oxidized low-density lipoprotein levels in subjects with clinically evident peripheral arterial disease with a wide range of clinical manifestations.

CONCLUSIONS

Oxidized low-density lipoprotein is not a good predictor of peripheral arterial disease severity.

Postprandial LDL phenolic content and LDL oxidation are modulated by olive oil phenolic compounds in humans

Olive oil phenolic compounds are potent antioxidants in vitro, but evidence for antioxidant action in vivo is controversial. We examined the role of the phenolic compounds from olive oil on postprandial oxidative stress and LDL antioxidant content. Oral fat loads of 40 mL of similar olive oils, but with high (366 mg/kg), moderate (164 mg/kg), and low (2.7 mg/kg) phenolic content, were administered to 12 healthy male volunteers in a cross-over study design after a washout period in which a strict antioxidant diet was followed. Tyrosol and hydroxytyrosol, phenolic compounds of olive oil, were dose-dependently absorbed (p<0.001). Total phenolic compounds in LDL increased at postprandial state in a direct relationship with the phenolic compounds content of the olive oil ingested (p<0.05). Plasma concentrations of tyrosol, hydroxytyrosol, and 3-O-methyl-hydroxytyrosol directly correlated with changes in the total phenolic compounds content of the LDL after the high phenolic compounds content olive oil ingestion. A 40 mL dose of olive oil promoted a postprandial oxidative stress, the degree of LDL oxidation being lower as the phenolic content of the olive oil administered increases. In conclusion, olive oil phenolic content seems to modulate the LDL phenolic content and the postprandial oxidative stress promoted by 40 mL olive oil ingestion in humans.

Characterization of native and oxidized human low-density lipoproteins by the Z-scan technique

The nonlinear optical response of human normal and oxidized by Cu2+ low-density lipoproteins particles (LDL), were investigated by the Z-scan technique as a function of temperature and concentration of LDL particles. The Z-scan signals increase linearly with concentration of normal LDL particles, following the usual Beer-Lambert law in a broad range of concentrations. The oxidized LDL particles do not show nonlinear optical response. On the other hand, normal LDL increases its nonlinear optical response as a function of temperature. These behaviors can be attributed to an absorbing element that is modified by the oxidative process. Contrarily, changes in the physical state of the cores and conformation of the ApoB100 protein due to an increase in temperature seems to enhance their nonlinear optical properties. This tendency is not due to aggregation of particles. The main contribution to the nonlinear optical response of normal LDL particles comes from the phospholipid fraction of the particles.

The autoantibody repertoire against copper- or macrophage-modified LDL differs in normolipidemics and hypercholesterolemic patients

We have analyzed the antibody repertoire from normo- and hypercholesterolemic subjects to investigate how it can be related to macrophage-dependent modification of low-density lipoproteins, in comparison to the commonly used copper-oxidized LDL. Preexisting natural antibodies in plasma from normo- and hypercholesterolemic individuals were tested for their reactivity against copper ion oxidized LDL and LDL modified by macrophages. A crosswise comparison between these two antigen preparations demonstrated a different antibody repertoire in normo- and hypercholesterolemic patients. This study suggest that the search for antibodies that can influence the progression or regression of an atherosclerotic process has to take into account the process by which LDL is modified, and the repertoire of antibodies that is generated in the normal population, in comparison to that with, or at risk for, coronary artery diseases.

Smoking prevents the intravascular remodeling of high-density lipoprotein particles: implications for reverse cholesterol transport

Smoking is a leading cause of atherosclerosis acting trough a wide spectrum of mechanisms, notably the increase of the proatherogenic effect of dyslipidemia. However, a severe atherosclerotic disease is frequently observed in smokers who do not present an overt dyslipidemia. In the present study, we sought to determine if abnormalities in lipid metabolism occur in normolipidemic smokers, focusing especially on the components of intravascular remodeling of high-density lipoprotein (HDL) For this purpose, we measured lipid transfer proteins and enzymes involved in the reverse cholesterol transport (RCT) system in 29 adults: 15 smokers and 14 controls. The blood samples were drawn in the fasting state, immediately after the smokers smoked 1 cigarette. The composition of HDL particles was analyzed after isolation of HDL fractions by microultracentrifugation. We observed that normolipidemic smokers present higher total plasma and HDL phospholipids (PL) (P < .05), 30% lower postheparin hepatic lipase (HL) activity (P < .01), and 40% lower phospholipid transfer protein (PLTP) activity (P < .01), as compared with nonsmokers. The plasma cholesteryl ester transfer protein (CETP) mass was 17% higher in smokers as compared with controls (P < .05), but the endogenous CETP activity corrected for plasma triglycerides (TG) was in fact 57% lower in smokers than in controls (P < .01). Lipid transfer inhibitor protein activity was also similar in both groups. In conclusion, the habit of smoking induces a severe impairment of many steps of the RCT system even in the absence of overt dyslipidemia. Such an adverse effect might favor the atherogenicity of smoking.

Aberrant antibody responses to oxidized LDL and increased intimal thickening in apoE−/− mice exposed to cigarette smoke

Cigarette smoking is associated with increased atherosclerosis and intimal thickening, and has immune-suppressive effects. The immune system modulates atherosclerosis and intimal thickening. We hypothesized that detrimental effects of cigarette smoke (CS) involves modulation of the immune response to oxidized low-density lipoprotein (oxLDL). ApoE-/- mice fed Western diet were exposed to CS starting at 20 weeks of age. Control mice were exposed to air. After 5 weeks of CS, mice were subjected to carotid arterial cuffing for 21 days. Intimal thickening was significantly increased in CS mice compared to control (0.050 +/- 0.034 mm(2) versus 0.023 +/- 0.021 mm(2); P < 0.05). Spleen lymphocyte population, cytokine mRNA expression, and total IgM and IgG levels were similar. Anti-MDA oxLDL IgG was reduced by 40% (P < 0.05) in CS mice compared to control. Copper-oxidized LDL IgG antibodies remained unchanged but IgM increased in CS mice, associated with increased intimal thickening. Anti-phosphorylcholine (PC) IgM was also increased in the CS mice, associated with increased intimal thickening. Lymphocyte signaling molecule lymphotoxin beta (LTbeta) expression was significantly decreased in spleens of CS exposed mice. Our results suggest that immune modulation by CS characterized by aberrant antibody responses to oxLDL and reduced LTbeta mRNA expression is associated with increased intimal thickening after arterial cuffing.

Cardiovascular complications and increased levels of circulating modified low density lipoprotein in HIV patients and patients with lipodystrophy

The introduction of highly active antiretroviral therapy (HAART) for patients infected with HIV has significantly prolonged the life expectancy and to some extent has restored a functional immune response. However, the premature introduction of HAART has led to a significant and alarming increase in cardiovascular complications, including myocardial infarction and the appearance of abnormal distribution of body fat seen as lipodystrophy. One key element in the development of ischemic coronary artery disease is the presence of circulating and tissue-fixed modified low density lipoprotein (mLDL) that contributes to the initiation and progression of arterial lesions and to the formation of foam cells. Even though not completely elucidated, the most likely mechanism involves mLDL in the inflammatory response and the induction of a specific immune response against mLDL. Circulating antibodies against mLDL can serve as an indirect marker of the presence of circulating and vessel-fixed mLDL. In the present study, we measured antibodies to mLDL and correlated them with immune status (i.e., number of CD4+ T cells) in 59 HIV patients and with the clinical manifestation of lipodystrophy in 10 patients. We observed a significant reduction in anti-mLDL antibody levels related both to lipodystrophy and to an immunocompromised state in HIV patients. We speculate that these antibodies may explain in part the rapid development of ischemic coronary artery disease in some patients.

Antibodies to Oxidized Low-Density Lipoproteins and Angiographically Assessed Coronary Artery Disease in White Patients

Background— Low-density lipoprotein (LDL) can be oxidatively modified by reactive oxygen species, thus generating oxLDL. The latter induce formation of specific antibodies (oxLDLAb), which are detectable in patients with atherosclerosis, in which they might play a pathogenic or a protective role. Thus, we aimed to investigate the association of antibodies with oxidized LDLs (oxLDL) (oxLDLAbs) with coronary artery disease (CAD) and acute coronary syndromes.

Methods and Results— In a cross-sectional study of 529 consecutive patients undergoing quantitative coronary angiography for suspected CAD, we measured the titer of IgG oxLDLAbs by ELISA. With regression analysis techniques, we also investigated the determinants of oxLDLAb titer and the association of oxLDLAbs with CAD severity. We found no significant differences of oxLDLAb titer between groups of patients without and with different CAD severity. The oxLDLAb titer was 18.6 enzyme units (EU) (11.5 to 25.7 EU/mL) (mean, 95% CI) in patients without CAD; 16.8 EU (9.6 to 24.2 EU) in patients with stenosis <50%; and 19.9 EU (15 to 24.8 EU), 17.2 (13.8 to 20.6 EU), and 14.7 EU (12.1 to 17.3 EU) in those with in 1-, 2-, or 3-vessel ≥50% stenosis, respectively. Similarly, no differences of oxLDLAb titer between patients without and with acute coronary syndrome were found. The oxLDLAb titer correlated weakly with aging and with serum total, LDL, and HDL cholesterol and plasma homocysteine levels; however, only age and HDL cholesterol remained significant predictors of the oxLDLAb titer at a stepwise regression analysis.

Conclusions— The results of this study, which was adequately powered from the statistical standpoint, provided no evidence for an association of IgG oxLDLAb titer with angiographically assessed CAD in whites.