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

Role of Antibodies and Their Specificities in Atherosclerotic Cardiovascular Disease

Atherosclerosis is a lipid-driven chronic inflammatory disease that is modulated by innate and adaptive immunity including humoral immunity. Importantly, antibody alterations achieved by genetic means or active and passive immunization strategies in preclinical studies can improve or aggravate atherosclerosis. Additionally, a wide range of epidemiological data demonstrate not only an association between the total levels of different antibody isotypes but also levels of antibodies targeting specific antigens with atherosclerotic cardiovascular disease. Here, we discuss the potential role of atherogenic dyslipidemia on the antibody repertoire and review potential antibody-mediated effector mechanisms involved in atherosclerosis development highlighting the major atherosclerosis-associated antigens that trigger antibody responses.

Exploring of gut microbiota features in dyslipidemia and chronic coronary syndrome patients undergoing coronary angiography

Chronic coronary syndrome (CCS) has a high mortality rate, and dyslipidemia is a major risk factor. Atherosclerosis, a cause of CCS, is influenced by gut microbiota dysbiosis and its metabolites. The objective of this study was to study the diversity and composition of gut microbiota and related clinical parameters among CCS patients undergoing coronary angiography and dyslipidemia patients in comparison to healthy volunteers in Thailand. CCS patients had more risk factors and higher inflammatory markers, high-sensitivity C-reactive protein (hs-CRP) than others. The alpha diversity was lower in dyslipidemia and CCS patients than in the healthy group. A significant difference in the composition of gut microbiota was observed among the three groups. The relative abundance of Proteobacteria, Fusobacteria, Enterobacteriaceae, Prevotella, and Streptococcus was significantly increased while Roseburia, Ruminococcus, and Faecalibacterium were lower in CCS patients. In CCS patients, Lachnospiraceae, Peptostreptococcaceae, and Pediococcus were positively correlated with hs-CRP. In dyslipidemia patients, Megasphaera was strongly positively correlated with triglyceride (TG) level and negatively correlated with high-density lipoprotein cholesterol (HDL-C). The modification of gut microbiota was associated with changes in clinical parameters involved in the development of coronary artery disease (CAD) in CCS patients.

Antibodies against oxidized LDL and atherosclerosis in rheumatoid arthritis patients treated with biological agents: a prospective controlled study

OBJECTIVES

The aim of this study was to investigate the relation among atherosclerosis, antibodies against oxidized LDL (anti-oxLDL), and inflammation in rheumatoid arthritis (RA) patients treated with biological (b) disease-modifying anti-rheumatic drugs (DMARDs).

METHODS

Fifty-nine patients who were receiving conventional synthetic DMARDs and were eligible for treatment with a biological agent were included in the study. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and IgG antibodies against oxidized LDL (anti-oxLDL) as well as carotid intima-media thickness (cIMT) were determined before and after 6 months of treatment. Thirty-one healthy individuals were used as a control group.

RESULTS

At baseline, RA patients had lower TC and HDL-C levels and increased cIMT compared to controls. After a 6-month follow-up, the re-evaluation of carotids revealed a statistically important decrease of cIMT values. This observation was accompanied by a statistically important elevation of HDL-C levels and a reduction of the titer of anti-oxLDL antibodies regardless of the bDMARD that was administered. No statistically significant association was found between the cIMT and anti-oxLDL, HDL-C, CRP, or DAS28 score neither before nor 6 months after treatment using linear regression analyses adjusted for age and gender.

CONCLUSIONS

We provide evidence that atherogenic lipid profile and ongoing atherosclerosis which characterize RA patients appear to improve after biological therapy, and we also suggest a possible atherogenic effect of IgG anti-ox LDL antibodies.

Immunometabolism and immune response regulate macrophage function in atherosclerosis

Macrophages are crucial in the progression of atherosclerotic cardiovascular disease (ASCVD). In the atherosclerotic lesions, macrophages play a central role in maintaining inflammatory response, promoting plaque development, and facilitating thrombosis. Increasing studies indicate that metabolic reprogramming and immune response mediate macrophage functional changes in all stages of atherosclerosis. In this review article, we explain how metabolic changes in glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle, fatty acid synthesis, fatty acid oxidation, and cholesterol metabolism regulate macrophage function in atherosclerosis. We discuss how immune response to oxidized lipids regulate macrophage function in atherosclerosis. Additionally, we explore how abnormal metabolism leads to macrophage mitochondrial dysfunction in atherosclerosis.

Generation of cardio-protective antibodies after pneumococcal polysaccharide vaccine: Early results from a randomised controlled trial

BACKGROUND AND AIMS

Observational studies have demonstrated that the pneumococcal polysaccharide vaccine (PPV) is associated with reduced risk of cardiovascular events. This may be mediated through IgM antibodies to OxLDL, which have previously been associated with cardioprotective effects. The Australian Study for the Prevention through Immunisation of Cardiovascular Events (AUSPICE) is a double-blind, randomised controlled trial (RCT) of PPV in preventing ischaemic events. Participants received PPV or placebo once at baseline and are being followed-up for incident fatal and non-fatal myocardial infarction or stroke over 6 years.

METHODS

A subgroup of participants at one centre (Canberra; n = 1,001) were evaluated at 1 month and 2 years post immunisation for changes in surrogate markers of atherosclerosis, as pre-specified secondary outcomes: high-sensitive C-reactive protein (CRP), pulse wave velocity (PWV), and carotid intima-media thickness (CIMT). In addition, 100 participants were randomly selected in each of the intervention and control groups for measurement of anti-pneumococcal antibodies (IgG, IgG2, IgM) as well as anti-OxLDL antibodies (IgG and IgM to CuOxLDL, MDA-LDL, and PC-KLH).

RESULTS

Concentrations of anti-pneumococcal IgG and IgG2 increased and remained high at 2 years in the PPV group compared to the placebo group, while IgM increased and then declined, but remained detectable, at 2 years. There were statistically significant increases in all anti-OxLDL IgM antibodies at 1 month, which were no longer detectable at 2 years; there was no increase in anti-OxLDL IgG antibodies. There were no significant changes in CRP, PWV or CIMT between the treatment groups at the 2-year follow-up.

CONCLUSIONS

PPV engenders a long-lasting increase in anti-pneumococcal IgG, and to a lesser extent, IgM titres, as well as a transient increase in anti-OxLDL IgM antibodies. However, there were no detectable changes in surrogate markers of atherosclerosis at the 2-year follow-up. Long-term, prospective follow-up of clinical outcomes is continuing to assess if PPV reduces CVD events.

High levels of autoantibodies against apoB100 p210 are associated with lower incidence of atrial fibrillation in women

BACKGROUND AND OBJECTIVES

Atrial fibrillation (AF) is associated with inflammation, both systemically and in the atrial tissue. Oxidized low-density lipoprotein (LDL) is increased in patients with AF and is suggested to be one of the molecules that drives inflammation. Autoantibodies against oxidized LDL and apolipoprotein B100, the protein component of LDL, are linked to atherosclerotic disease. However, whether these autoantibodies are associated with occurrence of AF is not known. We investigated autoantibodies against oxidized apolipoprotein B100 peptides and incidence of AF in a large population-based cohort.

METHODS

IgM and IgG against native and aldehyde-modified apoB100 peptides 210 (p210) and 45 were analyzed by enzyme-linked immunosorbent assay (ELISA) in 5169 individuals from the Malmö Diet and Cancer cohort.

RESULTS

Seven hundred sixty-nine incident AF cases were recorded during a follow-up of 21.3 years. Individuals with high levels of IgM against native p210 at baseline had a lower risk of developing AF; however, the association did not remain after adjustment for age and sex. Women had higher levels of IgM against native p210 than men (0.70 ± 0.22 AU vs. 0.63 ± 0.21 AU, p < 0.001). The association of IgM against native p210 and AF was significantly different between sexes (p for interaction = 0.024), where females with high IgM against p210 had a lower risk for incidence of AF (hazard ratio [95% confidence interval] 4th versus 1st quartile: 0.67 [0.49-0.91]; p = 0.01) after adjusting for risk factors and comorbidities.

CONCLUSION

These findings support an association of humoral autoimmunity with AF.

Oxidized Lipids: Common Immunogenic Drivers of Non-Alcoholic Fatty Liver Disease and Atherosclerosis

The prevalence of non-alcoholic fatty liver disease (NAFLD), ranging from simple steatosis to inflammatory steatohepatitis (NASH) and cirrhosis, continues to rise, making it one of the major chronic liver diseases and indications for liver transplantation worldwide. The pathological processes underlying NAFLD not only affect the liver but are also likely to have systemic effects. In fact, growing evidence indicates that patients with NAFLD are at increased risk for developing atherosclerosis. Indeed, cardiovascular complications are the leading cause of mortality in NAFLD patients. Here, we aim to address common pathophysiological molecular pathways involved in chronic fatty liver disease and atherosclerosis. In particular, we focus on the role of oxidized lipids and the formation of oxidation-specific epitopes, which are important targets of host immunity. Acting as metabolic danger signals, they drive pro-inflammatory processes and thus contribute to disease progression. Finally, we summarize encouraging studies indicating that oxidized lipids are promising immunological targets to improve intervention strategies for NAFLD and potentially limit the risk of developing atherosclerosis.

Can manipulation of gut microbiota really be transformed into an intervention strategy for cardiovascular disease management?

Recent advancement in manipulation techniques of gut microbiota either ex vivo or in situ has broadened its plausible applicability for treating various diseases including cardiovascular disease. Several reports suggested that altering gut microbiota composition is an effective way to deal with issues associated with managing cardiovascular diseases. However, actual translation of gut microbiota manipulation-based techniques into cardiovascular-therapeutic approach is still questionable. This review summarized the evidence on challenges, opportunities, recent development, and future prospects of gut microbiota manipulation for targeting cardiovascular diseases. Initially, issues associated with current cardiovascular diseases treatment strategy, association of gut microbiota with cardiovascular disease, and its influence on cardiovascular drugs were discussed, followed by applicability of gut microbiota manipulation as a cardiovascular disease intervention strategy along with its challenges and future prospects. Despite the fact that the gut microbiota is rugged, interventions like probiotics, prebiotics, synbiotics, fecal microbiota transplantation, fecal virome transplantation, antibiotics, diet changes, and exercises could manipulate it. Advanced techniques like administration of engineered bacteriophages and bacteria could also be employed. Intensive exploration revealed that if sufficiently controlled approach and proper monitoring were applied, gut microbiota could provide a compelling answer for cardiovascular therapy.

An atherosclerotic plaque-targeted single-chain antibody for MR/NIR-II imaging of atherosclerosis and anti-atherosclerosis therapy

Background

Oxidation-specific epitopes (OSEs) are rich in atherosclerotic plaques. Innate and adaptive immune responses to OSEs play an important role in atherosclerosis. The purpose of this study was to develop novel human single-chain variable fragment (scFv) antibody specific to OSEs to image and inhibit atherosclerosis.

Results

Here, we screened a novel scFv antibody, named as ASA6, from phage-displayed human scFv library. ASA6 can bind to oxidized LDL (Ox-LDL) and atherosclerotic plaques. Meanwhile, ASA6 can also inhibit the uptake of Ox-LDL into macrophage to reduce macrophage apoptosis. The atherosclerotic lesion area of ApoE^−/− mice administrated with ASA6 antibody was significantly reduced. Transcriptome analysis reveals the anti-atherosclerosis effect of ASA6 is related to the regulation of fatty acid metabolism and inhibition of M1 macrophage polarization. Moreover, we conjugated ASA6 antibody to NaNdF₄@NaGdF₄ nanoparticles for noninvasive imaging of atherosclerotic plaques by magnetic resonance (MR) and near-infrared window II (NIR-II) imaging.

Conclusions

Together, these data demonstrate the potential of ASA6 antibody in targeted therapy and noninvasive imaging for atherosclerosis.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01047-4.

Humoral immunity in atherosclerosis and myocardial infarction: from B cells to antibodies

Immune mechanisms are critically involved in the pathogenesis of atherosclerosis and its clinical manifestations. Associations of specific antibody levels and defined B cell subsets with cardiovascular disease activity in humans as well as mounting evidence from preclinical models demonstrate a role of B cells and humoral immunity in atherosclerotic cardiovascular disease. These include all aspects of B cell immunity, the generation of antigen-specific antibodies, antigen presentation and co-stimulation of T cells, as well as production of cytokines. Through their impact on adaptive and innate immune responses and the regulation of many other immune cells, B cells mediate both protective and detrimental effects in cardiovascular disease. Several antigens derived from (oxidised) lipoproteins, the vascular wall and classical autoantigens have been identified. The unique antibody responses they trigger and their relationship with atherosclerotic cardiovascular disease are reviewed. In particular, we focus on the different effector functions of specific IgM, IgG, and IgE antibodies and the cellular responses they trigger and highlight potential strategies to target B cell functions for therapy.

Relationship Between Helicobacter pylori Infection and Arteriosclerosis

It is reported that Helicobacter pylori (H. pylori) infection may be linked to non-digestive tract diseases, such as arteriosclerosis including dyslipidemia, diabetes, obesity, hypertension, and cardiovascular disease. Therefore, we reviewed recent studies available in PubMed dealing with the mechanisms of arteriosclerosis due to H. pylori infection and the effects of H. pylori eradication. Conventional studies suggested that H. pylori infection may increase the risk of arteriosclerosis. A large interventional study is required to clarify the causal relationships and the effects of bacterial eradication.

Untying the correlation between apolipoproteins and rheumatoid arthritis

AIM AND OBJECTIVE

The concentration of lipoproteins and apolipoprotein are extremely low in the synovial fluid of any healthy person as compared to the concentrations in plasma. However, in the synovial fluid of any diseased patient the amount of cholesterol and lipids is sharply increased. The current review defines the role of various apolipoproteins and lipoproteins and their constituent subfractions in the synovial fluid embarking its principal role in rheumatoid arthritis. It also explains the need to define synovial fluid lipids, lipoprotein particle subfractions and their constituent apolipoproteins in synovial fluid.

MATERIALS AND METHODS

Various research and review articles highlighting the role of apolipoproteins and lipoproteins were procured from medical websites mainly Pubmed, Medline, Science Direct, etc., and studied for the writing of the review paper.

CONCLUSION

Mainly apolipoproteins A-1, B and E are prominently increased in chronic inflammatory joint disorders. Several theories have been proposed to understand the source of increase of lipids and apolipoproteins in synovial fluid of the diseased patients compared to healthy individuals, yet the precise mechanism is still not lucid. Lipoproteins are believed to play both functional role and pathological role in the synovial fluid. The activated T-lymphocytes in patients of RA lead to activation of inflammatory cytokines such as tumor necrosis factor and interleukins which embark to be the principal mechanism for induction of the disease. It can be thus concluded that the apolipoproteins prevent the activation of monocytes by blocking their contact of activation and thus play critical role in management of RA by inhibiting the production of proinflammatory cytokines.

The heart-gut axis: new target for atherosclerosis and congestive heart failure therapy

The human gut microbiota has been identified as a possible novel risk factor for cardiovascular disease. The intestinal microbiome plays a role in the pathogenesis of atherosclerosis and heart failure. Even though studies in rodents suggested that gut microbes may affect the risk of heart disease, this link has not been shown in humans. In the present study, we review several potential mechanisms by which the gut microbiome and bacterial translocation are associated with the development of cardiac disorders making them potential targets for novel therapeutic measures for these conditions. Modulation of the gut microbiota as a mechanism for altering the pathogenesis of disorders is an area of growing interest. Alteration in the gut microbiota is being explored as a method of reducing risk factors associated with cardiac diseases.

The Contribution of Autoantibodies to Inflammatory Cardiovascular Pathology

Chronic inflammation and resulting tissue damage underlie the vast majority of acquired cardiovascular disease (CVD), a general term encompassing a widely diverse array of conditions. Both innate and adaptive immune mechanisms contribute to chronic inflammation in CVD. Although maladies, such as atherosclerosis and cardiac fibrosis, are commonly conceptualized as disorders of inflammation, the cellular and molecular mechanisms that promote inflammation during the natural history of these diseases in human patients are not fully defined. Autoantibodies (AAbs) with specificity to self-derived epitopes accompany many forms of CVD in humans. Both adaptive/induced iAAbs (generated following cognate antigen encounter) and also autoantigen-reactive natural antibodies (produced independently of infection and in the absence of T cell help) have been demonstrated to modulate the natural history of multiple forms of CVD including atherosclerosis (atherosclerotic cardiovascular disease), dilated cardiomyopathy, and valvular heart disease. Despite the breadth of experimental evidence for the role of AAbs in CVD, there is a lack of consensus regarding their specific functions, primarily due to disparate conclusions reached, even when similar approaches and experimental models are used. In this review, we seek to summarize the current understanding of AAb function in CVD through critical assessment of the clinical and experimental evidence in this field. We additionally highlight the difficulty in translating observations made in animal models to human physiology and disease and provide a summary of unresolved questions that are critical to address in future studies.

Serum oxLDL-β2GPI complex reflects metabolic syndrome and inflammation in adipose tissue in obese

BACKGROUND/OBJECTIVES

OxLDL-β2GPI complex has been suggested to have a role in the development of atherosclerosis and other inflammatory diseases. The aim of this study was to investigate the possible association of circulating oxLDL-β2GPI with obesity-induced inflammatory state of adipose tissue and related comorbidities as metabolic syndrome development.

SUBJECTS/METHODS

Two cohorts of subjects were examined in the study. Cohort I: 36 women with wide range of body mass index (17-48 kg m^-2) and metabolic status (with or without metabolic syndrome (MS); cohort II: 20 obese women undergoing a dietary intervention (DI) consisting of 1-month very-low-calorie diet, and 5 months of weight-stabilization period. Serum levels of oxLDL-β2GPI were measured by enzyme-linked immunosorbent assay. Insulin sensitivity was evaluated by hyperinsulinemic-euglycemic clamp and homeostasis model assessment of insulin resistance. mRNA expression of macrophage markers was determined in both subcutaneous (SAT) and visceral (VAT) adipose tissue in cohort I and in SAT in cohort II.

RESULTS

Serum oxLDL-β2GPI levels were increased in obese subjects with MS compared to lean or obese without MS (obese with MS: 26.6±5.0 vs lean: 15.17±1.97, P<0.001; vs obese without MS: 16.36±2.89, P<0.05). Serum oxLDL-β2GPI correlated with MS indices (glucose, high-density lipoprotein, triglyceride and ureic acid) and with mRNA expression of macrophage markers in VAT. Weight-reducing DI decreased serum oxLDL-β2GPI levels together with lipid parameters and the mRNA expression of inflammatory markers in SAT.

CONCLUSIONS

OxLDL-β2GPI seems to be an important marker of visceral adipose tissue inflammation and possibly a factor contributing to insulin resistance and metabolic syndrome development in obese patients.

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.

Oxidized LDL at the crossroads of immunity in non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is viewed as the hepatic manifestation of the metabolic syndrome and is a condition hallmarked by lipid accumulation in the liver (steatosis) along with inflammation (hepatitis). Currently, the etiology and mechanisms leading to obesity-induced hepatic inflammation are not clear and, as a consequence, strategies to diagnose or treat NASH in an accurate manner do not exist. In the current review, we put forward the concept of oxidized lipids as a significant risk factor for NASH. We will focus on the contribution of the different types of oxidized lipids as part of the oxidized low-density lipoprotein (oxLDL) to the hepatic inflammatory response. Furthermore, we will elaborate on the underlying mechanisms linking oxLDL to inflammatory responses in the liver and on how these cascades can be used as therapeutic targets to combat NASH. This article is part of a Special Issue entitled: Lipid modification and lipid peroxidation products in innate immunity and inflammation edited by Christoph J. Binder.

Natural Antibodies as Rheostats for Susceptibility to Chronic Diseases in the Aged

Natural antibodies are spontaneously produced in the absence of infection or immunization, and are both anti-microbial and autoreactive. Autoreactive natural antibodies can bind noxious molecules, such as those involved in clinical situations of atherosclerosis (oxLDL), malignancy (NGcGM3), and neurodegeneration (amyloid, tau) and can affect the fate of their targets or the cells bearing them to maintain homeostasis. Clinically relevant natural antibodies have been shown to decline with advancing age in those few situations where measurements have been made. Consistent with this, human B-1 cells that are thought to be responsible for generating natural antibodies also decline with advancing age. These findings together suggest that an age-related decline in amount or efficacy of homeostatic natural antibodies is associated with relative loss of protection against molecules involved in several diseases whose incidence rises in the older age population, and that those individuals experiencing greatest loss are at greatest risk. In this view, natural antibodies act as rheostats for susceptibility to several age-related diseases. These considerations suggest that administration of natural antibodies, or of factors that maintain B-1 cells and/or enhance production of natural antibodies by B-1 cells, may serve to counteract the onset or progression of age-related chronic illness.

Oxidized Low Density Lipoprotein Among the Elderly in Qinghai-Tibet Plateau

OBJECTIVE

Several environmental factors including hypoxia have been reported to contribute to oxidative stress in individuals living in the highlands. However, little is known about the role of oxidized low-density lipoprotein (ox-LDL) among community-dwelling elderly in the Qinghai-Tibet plateau.

METHODS

The study population comprised 168 community-dwelling elderly subjects aged 60 years or older (male to female ratio, 70:98; mean age, 65.8 years) living in Haiyan County, located 3000 to 3200 m above sea level, 30 km northwest of Xining, Qinghai. The subjects were volunteers who joined a Comprehensive Geriatric Assessment. Plasma ox-LDL was measured in 168 community-dwelling elderly subjects aged 60 years or older (23 Tibetans and 145 Hans) with a monoclonal antibody-based enzyme-linked immunosorbent assay.

RESULTS

Mean ox-LDL level was higher among Tibetan elderly than Han elderly (Tibetan, 79.0 ± 29.6 U/L; Han, 62.8 ± 23.5 U/L; P = .003). Tibetan ethnicity was significantly associated with ox-LDL levels after adjusting for LDL cholesterol levels. In addition, high ox-LDL levels (≥70 U/L) were significantly associated with a homeostasis model assessment insulin resistance index of at least 1.6 (odds ratio [OR], 2.82; 95% confidence interval [95% CI], 1.11 to 7.15; P = .029) and ankle brachial pressure index of less than 1.0 (OR, 4.85; 95% CI, 1.14 to 10.00; P = .028), after adjusting for age, sex, and ethnicity.

CONCLUSIONS

Our findings support the hypothesis that ox-LDL levels are higher among Tibetan elderly highlanders compared with those among Han elderly. As ox-LDL levels can affect insulin resistance and arteriosclerosis, further research is needed to determine how oxidative stress influences the health situation among elderly individuals at high altitudes.

Lipidomics: quest for molecular lipid biomarkers in cardiovascular disease

Lipidomics is the comprehensive analysis of molecular lipid species, including their quantitation and metabolic pathways. The huge diversity of native lipids and their modifications make lipidomic analyses challenging. The method of choice for sensitive detection and quantitation of molecular lipid species is mass spectrometry, either by direct infusion (shotgun lipidomics) or coupled with liquid chromatography. Although shotgun lipidomics allows for high-throughput analysis, low-abundant lipid species are not detected. Previous separation of lipid species by liquid chromatography increases ionization efficiency and is better suited for quantifying low abundant and isomeric lipid species. In this review, we will discuss the potential of lipidomics for cardiovascular research. To date, cardiovascular research predominantly focuses on the role of lipid classes rather than molecular entities. An in-depth knowledge about the molecular lipid species that contribute to the pathophysiology of cardiovascular diseases may provide better biomarkers and novel therapeutic targets for cardiovascular disease.

Dietary cholesterol and oxidised cholesterol: effects on sperm characteristics, antioxidant status and hormonal profile in rats

Present study was designed to compare the potential effects of high serum levels of LDL and oxidised LDL (OxLDL) on spermatogenesis parameters in male Wistar rats. Animals were allocated into three groups and were fed for 14 weeks with normal, cholesterol-rich and oxidised cholesterol-rich diets. Blood lipid profile, sex hormones level, as well as sex organs weight were evaluated. The sex organs weight in oxidised cholesterol-fed group was significantly reduced (P < 0.05). Spermatozoa count in the group with high serum concentration of OxLDL (64 ± 4.2 × 10(6) ) was markedly lower (P < 0.01) than that of normal rats (87 ± 4.1 × 10(6) ) and rats with high serum level of LDL (90 ± 6.3 × 10(6) ). Similarly, the percentage of viable spermatozoa was significantly (P < 0.001) decreased from 78% to 52% by high level of OxLDL in serum. While, nonoxidised LDL did not have suppressive effects on spermatogenesis and organs weight. Consistent with these effects, the serum concentration of sex hormones including FSH (P < 0.001), LH (P < 0.001) and testosterone (P < 0.01) was significantly decreased only in rats with high level of OxLDL but not in rats with high level of nonoxidised LDL. In conclusion, high OxLDL level showed higher destructive effect on reproductive system compared to the high LDL level.

The role of oxidized low-density lipoproteins in atherosclerosis: the myths and the facts

The oxidative modification hypothesis of atherosclerosis, which assigns to oxidized low-density lipoproteins (LDLs) a crucial role in atherosclerosis initiation and progression, is still debated. This review examines the role played by oxidized LDLs in atherogenesis taking into account data derived by studies based on molecular and clinical approaches. Experimental data carried out in cellular lines and animal models of atherosclerosis support the proatherogenic role of oxidized LDLs: (a) through chemotactic and proliferating actions on monocytes/macrophages, inciting their transformation into foam cells; (b) through stimulation of smooth muscle cells (SMCs) recruitment and proliferation in the tunica intima; (c) through eliciting endothelial cells, SMCs, and macrophages apoptosis with ensuing necrotic core development. Moreover, most of the experimental data on atherosclerosis-prone animals benefiting from antioxidant treatment points towards a link between oxidative stress and atherosclerosis. The evidence coming from cohort studies demonstrating an association between oxidized LDLs and cardiovascular events, notwithstanding some discrepancies, seems to point towards a role of oxidized LDLs in atherosclerotic plaque development and destabilization. Finally, the results of randomized clinical trials employing antioxidants completed up to date, despite demonstrating no benefits in healthy populations, suggest a benefit in high-risk patients. In conclusion, available data seem to validate the oxidative modification hypothesis of atherosclerosis, although additional proofs are still needed.

Auto-antibodies as emergent prognostic markers and possible mediators of ischemic cardiovascular diseases

During the last 15 years, a growing body of evidence supported the fact that auto-antibodies represent not only emergent markers but also active mediators of cardiovascular disease (CVD), clinically represented mostly by acute coronary syndrome (ACS) and stroke. There is a contrasted relationship between auto-antibodies and CVD, some being protective, while others acting as potential risk factors. Therefore, we performed a review of the literature on the respective cardiovascular prognostic value of the most relevant auto-antibodies in ACS and stroke, and their putative pathophysiological properties in atherogenesis. This review highlights auto-antibodies as active modulators of the innate immune system in atherogenesis (either toward a pro- or anti-inflammatory response), or by affecting basal heart rate regulation (anti-apoA-1 IgG). Given their apparent prognostic independency towards traditional cardiovascular risk factors, the data available in the literature indicates that some of those auto-antibodies could be of valuable help for cardiovascular risk stratification in the future, especially because their deleterious effects have been shown to be potentially abrogated in vivo and in vitro by existing therapeutic modalities. Although evidence in humans is currently lacking, these studies may open innovative therapeutic perspectives for CVD in the future.

Pomegranate for your cardiovascular health

Pomegranate is a source of some very potent antioxidants (tannins, anthocyanins) which are considered to be also potent anti-atherogenic agents. The combination of the above unique various types of pomegranate polyphenols provides a much wider spectrum of action against several types of free radicals. Indeed, pomegranate is superior in comparison to other antioxidants in protecting low-density lipoprotein (LDL, "the bad cholesterol") and high-density lipoprotein (HDL, "the good cholesterol") from oxidation, and as a result it attenuates atherosclerosis development and its consequent cardiovascular events. Pomegranate antioxidants are not free, but are attached to the pomegranate sugars, and hence were shown to be beneficial even in diabetic patients. Furthermore, pomegranate antioxidants are unique in their ability to increase the activity of the HDL-associated paraoxonase 1 (PON1), which breaks down harmful oxidized lipids in lipoproteins, in macrophages, and in atherosclerotic plaques. Finally, unique pomegranate antioxidants beneficially decrease blood pressure. All the above beneficial characteristics make the pomegranate a uniquely healthy fruit.

Non-alcoholic steatohepatitis: the role of oxidized low-density lipoproteins

Non-alcoholic steatohepatitis (NASH) is hallmarked by lipid accumulation in the liver (steatosis) along with inflammation (hepatitis). The transition from simple steatosis towards NASH represents a key step in pathogenesis, as it will set the stage for further severe liver damage. Yet, the pathogenesis behind hepatic inflammation is still poorly understood. It is of relevance to better understand the underlying mechanisms involved in NASH in order to apply new knowledge to potential novel therapeutic approaches. In the current review, we propose oxidized cholesterol as a novel risk factor for NASH. Here, we summarize mouse and human studies that provide possible mechanisms for the involvement of oxidized low-density lipoproteins in NASH and consequent potential novel diagnostic tools and treatment strategies for hepatic inflammation.

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).

Emerging applications for zebrafish as a model organism to study oxidative mechanisms and their roles in inflammation and vascular accumulation of oxidized lipids

With the advent of genetic engineering, zebrafish (Danio rerio) were recognized as an attractive model organism to study many biological processes. Remarkably, the small size and optical transparency of zebrafish larvae enable high-resolution imaging of live animals. Zebrafish respond to various environmental and pathological factors with robust oxidative stress. In this article, we provide an overview of the molecular mechanisms involved in oxidative stress and antioxidant response in zebrafish. Existing applications of genetically encoded fluorescent sensors allow imaging, in real time, of the production of H(2)O(2) and studying its involvement in inflammatory responses, as well as activation of the oxidation-sensitive transcription factors HIF and NRF2. Oxidative stress, combined with hyperlipidemia, leads to oxidation of lipoproteins, the process that contributes significantly to the development of atherosclerosis in humans. Recent work found that feeding zebrafish a high-cholesterol diet results in hypercholesterolemia, vascular lipid accumulation, and extreme lipoprotein oxidation. Generation of a transgenic zebrafish expressing a green fluorescent protein-tagged human antibody to malondialdehyde (MDA)-modified LDL makes possible the in vivo visualization of MDA epitopes in the vascular wall and testing of the efficacy of antioxidants and dietary interventions. Thus, using zebrafish as a model organism provides important advantages in studying the roles of reactive oxygen species and lipid oxidation in basic biologic and pathologic processes.

Helicobacter pylori infection is identified as a cardiovascular risk factor in Central Africans

BACKGROUND

Helicobacter pylori is now incriminated in the pathogenesis of atherosclerosis.

OBJECTIVE

To examine the importance of H. pylori infection as a cardiovascular disease (CVD) risk factor.

METHODS

Two hundred five patients (128 with H. pylori infection [HP-seropositive] and 77 without) had a baseline assessment for other potential CVD risk factors and were followed prospectively for 10 years (1999-2008). They were assessed on a monthly basis for the outcomes of carotid plaque, angina pectoris, myocardial infarction, and stroke. In the HP-seropositive group, male sex and quartile 4 for IgG anti-H. pylori antibodies (anti-HP Ab) were correlated with traditional CVD risk factors, stroke, myocardial infarction, and angina pectoris.

RESULTS

At the baseline assessment, the levels of carotid intima-media thickness, blood fibrinogen, total cholesterol, fasting plasma glucose, and uric acid were higher in H. pylori-infected patients than in the uninfected group. Serum HDL-cholesterol was significantly lower in the HP-seropositive group. Men had higher levels of IgG anti-HP Ab, waist circumference, blood pressure, uric acid, and total cholesterol than women. Within the HP-seropositive group, individuals in quartile 4 for IgG anti-HP Ab had higher rates of elevated fibrinogen, diabetes mellitus, low high-density lipoprotein cholesterol, arterial hypertension, and high total cholesterol than those in quartile 1. After adjusting for traditional CVD risk factors, H. pylori infection was the only independent predictor of incident carotid plaque (multivariate odds ratio [OR] = 2.3, 95% confidence interval [CI]: 1.2-7.2; P < 0.0001) and incident acute stroke (multivariate OR = 3.6, 95% CI: 1.4-8.2; P < 0.0001). Within the HP-seropositive group and after adjusting for traditional CVD risk factors, male sex was the only independent predictor of incident angina pectoris (multivariate OR = 3.5, 95% CI: 1.6-16; P < 0.0001), incident acute stroke (multivariate OR = 3.2, 95% CI: 1.4-28; P < 0.0001), and acute myocardial infarction (multivariate OR = 7.2, 95% CI: 3.1-18; P < 0.0001).

CONCLUSION

Our study provides evidence for an association among known CVD risk factors, carotid plaque, stroke, and H. pylori infection. Among infected individuals, there is a significant association among severity of HP-seropositivity, male sex, and CVD. The eradication of H. pylori infection may therefore reduce the emerging burden of CVD in Africa.

Recognition of Porphyromonas gingivalis gingipain epitopes by natural IgM binding to malondialdehyde modified low-density lipoprotein

Objective

Increased risk for atherosclerosis is associated with infectious diseases including periodontitis. Natural IgM antibodies recognize pathogen-associated molecular patterns on bacteria, and oxidized lipid and protein epitopes on low-density lipoprotein (LDL) and apoptotic cells. We aimed to identify epitopes on periodontal pathogen Porphyromonas gingivalis recognized by natural IgM binding to malondialdehyde (MDA) modified LDL.

Methods and Results

Mouse monoclonal IgM (MDmAb) specific for MDA-LDL recognized epitopes on P. gingivalis on flow cytometry and chemiluminescence immunoassays. Immunization of C57BL/6 mice with P. gingivalis induced IgM, but not IgG, immune response to MDA-LDL and apoptotic cells. Immunization of LDLR^−/− mice with P. gingivalis induced IgM, but not IgG, immune response to MDA-LDL and diminished aortic lipid deposition. On Western blot MDmAb bound to P. gingivalis fragments identified as arginine-specific gingipain (Rgp) by mass spectrometry. Recombinant domains of Rgp produced in E. coli were devoid of phosphocholine epitopes but contained epitopes recognized by MDmAb and human serum IgM. Serum IgM levels to P. gingivalis were associated with anti-MDA-LDL levels in humans.

Conclusion

Gingipain of P. gingivalis is recognized by natural IgM and shares molecular identity with epitopes on MDA-LDL. These findings suggest a role for natural antibodies in the pathogenesis of two related inflammatory diseases, atherosclerosis and periodontitis.

Relationship of IgG and IgM autoantibodies and immune complexes to oxidized LDL with markers of oxidation and inflammation and cardiovascular events: results from the EPIC-Norfolk Study

Levels of IgG and IgM autoantibodies (AA) to malondialdehyde (MDA)-LDL and apoB-immune complexes (ICs) were measured in 748 cases and 1,723 controls in the EPIC-Norfolk cohort and their association to coronary artery disease (CAD) events determined. We evaluated whether AA and IC modify CAD risk associated with secretory phospholipase A(2) (sPLA(2)) type IIA mass and activity, lipoprotein-associated PLA(2) activity, lipoprotein (a) [Lp(a)], oxidized phospholipids on apoB-100 (OxPL/apoB), myeloperoxidase, and high sensitivity C-reactive protein. IgG ICs were higher in cases versus controls (P = 0.02). Elevated levels of IgM AA and IC were inversely associated with Framingham Risk Score and number of metabolic syndrome criteria (p range 0.02-0.001). In regression analyses adjusted for age, smoking, diabetes, LDL-cholesterol, HDL-cholesterol, and systolic blood pressure, the highest tertiles of IgG and IgM AA and IC were not associated with higher risk of CAD events compared with the lowest tertiles. However, elevated levels of IgM IC reduced the risk of Lp(a) (P = 0.006) and elevated IgG MDA-LDL potentiated the risk of sPLA(2) mass (P = 0.018). This epidemiological cohort of initially healthy subjects shows that IgG and IgM AA and IC are not independent predictors of CAD events but may modify CAD risk associated with elevated levels of oxidative biomarkers.

Oxidative stress biomarkers as predictors of cardiovascular disease

Evidence for the role of oxidative stress in the pathogenesis of cardiovascular disease (CVD) is primarily based on experimental and observational human studies. The aim of this review is to examine the observational longitudinal studies that have investigated the relationship between oxidative stress biomarkers and CVD. Fifty-one studies were identified with twenty-six of these measuring oxidized (Ox)-LDL, fifteen assessing myeloperoxidase, seven using lipid peroxidation measures and three quantifying protein oxidation. Results of studies using Ox-LDL have been equivocal with sixteen of the twenty-six studies reporting that this measure is predictive of cardiovascular events. These inconsistent results are not explained by differences in the study populations (primary or secondary CVD) or the type of assay used (auto or monoclonal antibodies). Six of the seven lipid peroxidation, and two of three protein oxidation studies found associations. Twelve of fifteen studies assessing the role of myeloperoxidase reported it to be predictive of CVD. However, issues surrounding the specificity of myeloperoxidase as a marker of oxidative stress and the small number of research groups reporting these results, limit this finding. In summary, the ability of oxidative stress biomarkers to predict CVD has yet to be established. Furthermore, it is important to note that the methods used to assess oxidative stress in these studies are indirect, and the evidence that the various methods actually reflect oxidative stress in vivo is limited.

Adaptive immunity in atherosclerosis: mechanisms and future therapeutic targets

Chronic inflammation drives the development of atherosclerosis, and adaptive immunity is deeply involved in this process. Initial studies attributed a pathogenic role to T cells in atherosclerosis, mainly owing to the proatherogenic role of the T-helper (T(H))-1 cell subset, whereas the influence of T(H)2 and T(H)17 subsets is still debated. Today we know that T regulatory cells play a critical role in the protection against atherosclerotic lesion development and inflammation. In contrast to T cells, B cells were initially considered to be protective in atherosclerosis, assumingly through the production of protective antibodies against oxidized LDL. This concept has now been refined and proatherogenic roles of certain mature B cell subsets have been identified. We review the current knowledge about the role of various lymphocyte subsets in the development and progression of atherosclerosis and highlight future targets for immunomodulatory therapy.

CagA-positive Helicobacter pylori strains enhanced coronary atherosclerosis by increasing serum OxLDL and HsCRP in patients with coronary heart disease

BACKGROUND

The role of infection in the pathogenesis of atherosclerosis is still a matter of debate.

AIMS

This study aimed to investigate the effect of CagA-positive Helicobacter pylori (H. pylori) strains infection on coronary atherosclerosis in patients with coronary heart disease and to elucidate how cytotoxin-associated gene A (CagA)-positive H. pylori strains infections were involved in coronary heart disease by examining the levels of serum lipid, high-sensitivity C-reactive protein (hsCRP) and oxidized low-density protein (oxLDL).

METHODS

Recruited for this study were 159 patients with coronary heart disease. The severity of coronary heart disease was estimated by calculating the Gensini score. Serum oxLDL and hsCRP were examined in all subjects. Current H. pylori infection was determined in all participants by means of a modified (13C) urea breath test (>200 dpm classified as positive). IgG antibodies against CagA protein were analyzed by enzyme immunoassays. Antibody titers against CagA (≥8 U/ml) were classified as positive. All subjects were divided into three groups, including an uninfected group (n=30), an H. pylori +CagA- group (n=69), and an H. pylori +CagA+ group (n=60).

RESULTS

Significant differences were found among the three groups in levels of total cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, serum hsCRP, oxLDL, and severity of coronary atherosclerosis (p<0.05). The levels of total cholesterol, LDL, apolipoprotein B, serum hsCRP, oxLDL were significantly elevated and the severity of coronary atherosclerosis was significantly increased in H. pylori +CagA+ group (p<0.05).

CONCLUSIONS

More serious coronary atherosclerosis was observed in CHD patients with H. pylori +CagA+ infection. H. pylori +CagA+ infection might be involved in coronary atherosclerosis by modifying serum lipids, enhancing LDL oxidation, and activating the inflammatory responses.

Plasma lipoproteins are important components of the immune system

Plasma lipoproteins (VLDL, LDL, Lp[a] and HDL) function primarily in lipid transport among tissues and organs. However, cumulative evidence suggests that lipoproteins may also prevent bacterial, viral and parasitic infections and are therefore a component of innate immunity. Lipoproteins can also detoxify lipopolysaccharide and lipoteichoic acid. Infections can induce oxidation of LDL, and oxLDL in turn plays important anti-infective roles and protects against endotoxin-induced tissue damage. There is also evidence that apo(a) is protective against pathogens. Taken together, the evidence suggests that it might be valuable to introduce the concept that plasma lipoproteins belong in the realm of host immune response.

Plasma lipoproteins are important components of the immune system

Plasma lipoproteins (VLDL, LDL, Lp[a] and HDL) function primarily in lipid transport among tissues and organs. However, cumulative evidence suggests that lipoproteins may also prevent bacterial, viral and parasitic infections and are therefore a component of innate immunity. Lipoproteins can also detoxify lipopolysaccharide and lipoteichoic acid. Infections can induce oxidation of LDL, and oxLDL in turn plays important anti-infective roles and protects against endotoxin-induced tissue damage. There is also evidence that apo(a) is protective against pathogens. Taken together, the evidence suggests that it might be valuable to introduce the concept that plasma lipoproteins belong in the realm of host immune response.

Coupling vascular and myocardial inflammatory injury into a common phenotype of cardiovascular dysfunction: systemic inflammation and aging - a mini-review

The rising epidemic of cardiovascular (CV) disease is fuelled by obesity, hypertension and diabetes and, independently and cumulatively, by an aging population. Extensive research identified immunoinflammatory mechanisms as key drivers in the initiation and progression of the disease, from early asymptomatic stages of vascular and myocardial injury leading to the clinically manifest dysfunction and remodeling in advanced stages. Underlying processes include endothelial dysfunction and extracellular matrix restructuration leading to increased vascular stiffness, as well as myocardial remodeling with dilatation and wall thinning. In this, overproduction of tumor necrosis factor-α, amongst others, contributes to generalized CV injury and dysfunction. Moreover, recent insights into the involvement of innate and adaptive immunity in atherosclerosis have shed light on many interesting parallels with chronic systemic inflammatory conditions, such as rheumatoid arthritis, with aggravated inflammation-induced vascular and myocardial injury. Besides, chronologic age has been identified as a potent, independent risk for reduced CV capacity and a plethora of heart diseases, with other modifiable risk factors acting as accelerators. We discuss the available evidence and propose that characterization of inflammatory CV responses might reveal a distinctive CV inflammatory phenotype. A comprehensive noninvasive bio-signature, comprising immunomic biomarkers and integrated noninvasive imaging, may serve as a potential tool in the early diagnosis and prognostication of CV risk.

Antibodies against oxidized low-density lipoprotein are associated with subclinical atherosclerosis in recent-onset rheumatoid arthritis

Rheumatoid arthritis (RA) patients have increased mortality largely as a result of cardiovascular diseases (CVD) that cannot be explained by traditional risk factors, suggesting that systemic inflammation may accelerate atherosclerosis. We investigated the presence of subclinical atherosclerosis in early RA (<12 months) and the possible association of RA-related risk factors. Forty patients with early RA and 40 controls matched for age, sex, and traditional risk factors for CVD were selected. Carotid US examination, assay of lipogram, C-reactive protein (CRP), and oxidized low-density lipoprotein antibodies (OxLDL-ab) were done. RA patients had significantly higher carotid intima-media thickness (cIMT) values and more plaque than the control (P<0.001 and P=0.0122, respectively). CRP and OxLDL-ab were significantly higher in RA patients than controls. Traditional risk factors and RA-related risk factors (disease duration, DAS-28, duration of treatment with steroids, erythrocyte sedimentation rate, and CRP) as well as OxLDL and cIMT were significantly higher in RA with plaques compared to those without plaques. Regression analysis identified the age of patients, CRP, and OxLDL-ab as an independent risk factor associated with the presence of atherosclerosis.

CONCLUSION

there is increased prevalence of carotid plaques in patients with recent-onset RA compared to matched controls. The accelerated atherosclerosis is predicted by age, CRP, and oxLDL-ab. The association of plaques with elevated CRP and OxLDL-ab support the hypothesis that chronic systemic autoimmune inflammatory process is probably a driving force for premature atherosclerosis.

The pro-inflammatory effect of uraemia overrules the anti-atherogenic potential of immunization with oxidized LDL in apoE-/- mice

BACKGROUND

Uraemia increases oxidative stress, plasma titres of antibodies recognizing oxidized low-density lipoprotein (oxLDL) and development of atherosclerosis. Immunization with oxLDL prevents classical, non-uraemic atherosclerosis. We have investigated whether immunization with oxLDL might also prevent uraemia-induced atherosclerosis in apolipoprotein E knockout (apoE-/-) mice.

METHODS

ApoE-/- mice were immunized with either native LDL (n = 25), Cu(2+)-oxidized LDL (n = 25), PBS (n = 25), the apolipoprotein B-derived peptide P45 (apoB-peptide P45) conjugated to bovine serum albumin (BSA) (n = 25) or BSA (n = 25) prior to induction of uraemia by 5/6 nephrectomy (NX).

RESULTS

Immunization with oxLDL increased plasma titres of immunoglobulin G (IgG) recognizing Cu(2+)-oxLDL and malondialdehyde-modified LDL (MDA-LDL). However, 5/6 NX induced a marked increase in plasma concentrations of anti-oxLDL antibodies as well as pro-atherogenic cytokines [interleukin (IL)-2 (IL-2), IL-4, IL-6 and IL-12)] in native mouse LDL (nLDL)-, oxLDL- and PBS-immunized mice. Even though nLDL- and oxLDL-immunized mice displayed higher anti-MDA-LDL IgG titres than the PBS group, aortic atherosclerosis lesion size was not affected by immunization. Immunization with the apoB-peptide P45, which consistently reduces classical atherosclerosis in non-uraemic mice, also did not reduce lesion size in uraemic apoE-/- mice.

CONCLUSION

The results suggest that the pro-inflammatory and pro-atherogenic effect of uraemia overrules the anti-atherogenic potential of oxLDL immunization in apoE-/- mice.

Proteomics, metabolomics, and immunomics on microparticles derived from human atherosclerotic plaques

BACKGROUND

Microparticles (MPs) with procoagulant activity are present in human atherosclerosis, but no detailed information is available on their composition.

METHODS AND RESULTS

To obtain insights into the role of MPs in atherogenesis, MP proteins were identified by tandem mass spectrometry, metabolite profiles were determined by high-resolution nuclear magnetic resonance spectroscopy, and antibody reactivity was assessed against combinatorial antigen libraries. Plaque MPs expressed surface antigens consistent with their leukocyte origin, including major histocompatibility complex classes I and II, and induced a dose-dependent stimulatory effect on T-cell proliferation. Notably, taurine, the most abundant free organic acid in human neutrophils, which scavenges myeloperoxidase-catalyzed free radicals, was highly enriched in plaque MPs. Moreover, fluorescent labeling of proteins on the MP surface suggested immunoglobulins to be trapped inside, which was confirmed by flow cytometry analysis on permeabilized and nonpermeabilized plaque MPs. Colabeling for CD14 and IgG established that more than 90% of the IgG containing MPs were CD14(+), indicating a macrophage origin. Screening against an antigen library revealed that the immunologic profiles of antibodies in MPs were similar to those found in plaques but differed profoundly from antibodies in plasma and unexpectedly, showed strong reactions with oligosaccharide antigens, in particular blood group antigen A.

CONCLUSIONS

This study provides the first evidence that immunoglobulins are present within MPs derived from plaque macrophages, that the portfolio of plaque antibodies is different from circulating antibodies in plasma, and that anticarbohydrate antibodies are retained in human atherosclerotic lesions.

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.

Anti-oxidized low-density lipoprotein antibody levels are associated with the development of type 2 diabetes mellitus

BACKGROUND

Anti-oxidized low-density lipoprotein (LDL) antibodies are associated with the oxidative capacity of plasma, but whether they protect or promote diabetes is unknown. We undertook a prospective study to determine the predictive capacity of anti-oxidized LDL antibodies for the onset of type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

We selected 391 non-diabetic women aged 18-65 years. The subjects were classified as being normal (oral glucose test tolerance normal, OGTT-N), or having impaired glucose tolerance (IGT), impaired fasting glucose (IFG) or T2DM according to their baseline glucose levels and after an OGTT. The same subjects were studied six years later. The levels of anti-oxidized LDL antibodies were classified as above or below the 50th percentile.

RESULTS

Of the women who were OGTT-N at the start of the study and who had anti-oxidized LDL antibody levels below the 50th percentile, only 65.1% were still OGTT-N after 6 years versus 79.5% of those who had anti-oxidized LDL antibody levels above the 50th percentile (P = 0.015). Women who had IGT or IFG at the start of the study whose anti-oxidized LDL antibody levels were below the 50th percentile had a relative risk of 9.79 (95% confidence interval, 1.40-68.45) of developing diabetes (P < 0.001). Logistic regression analysis showed that the variables predicting the development of a carbohydrate metabolism disorder in the women after 6 years were body mass index (P < 0.001) and the levels of anti-oxidized LDL antibodies (P = 0.042).

CONCLUSIONS

Levels of anti-oxidized LDL antibodies are independent predictors for the development of T2DM in women.

Respiratory infection recurrence and passive smoking in early atherosclerosis in children and adolescents with type 1 diabetes

BACKGROUND

Optimal glucose control in juvenile type 1 diabetes mellitus is necessary but not sufficient to reduce the burden of cardiovascular events in later life. This emphasizes the importance of searching for other possible risk factors associated with diabetes. We investigated whether recurrent episodes of acute respiratory infections and exposure to tobacco smoke could influence vascular phenotypes for early atherosclerosis in children and adolescents with type 1 diabetes.

MATERIALS AND METHODS

Common carotid artery elasticity and intima-media thickness along with circulating markers of lipid, inflammatory and glycaemic profiles were investigated in up to 98 children and adolescents with type 1 diabetes. The number of clinically manifest acute respiratory tract infections (RTI) during the past year, and the degree of exposure to environmental tobacco smoke (ETS), were assessed by separate questionnaires.

RESULTS

Carotid artery compliance (CAC) was decreased in patients with high (>or= 4/year; n = 22) recurrence of RTI compared to the remaining patients (n = 40; P < 0.05). In a multivariate analysis, the number of RTI during the past year and HbA(1C) were independently associated with decreased CAC (P < 0.05 for both). The inverse relationship between RTI recurrence and CAC was strengthened by frequent exposure to ETS.

CONCLUSIONS

High recurrence of respiratory infections in young type 1 diabetics is associated with increased stiffening of the carotid artery particularly in those often exposed to tobacco smoke.

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.