Oxidized LDL induces enhanced antibody formation and MHC class II-dependent IFN-gamma production in lymphocytes from healthy individuals

Association of lipid lowering drugs and the risk of systemic lupus erythematosus: a drug target Mendelian randomization

Background and objective: An interaction between low-density lipoprotein level, lipid-lowering drugs, and systemic lupus erythematosus (SLE) was reported by previous studies. However, whether lipid-lowering drugs provided protective effect for reducing the risk of SLE was unclear. We aimed to clarify this causal relationship through a drug-target Mendelian randomization (MR) study. Methods: Genetic instruments-single nucleotide polymorphism (SNPs)-were utilized to proxy inhibition of the three genes-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), proprotein convertase subtilisin/kexin type 9 (PCSK9), and Niemann-Pick C1-Like 1(NPC1L1), which was corresponded to three lipid-lowering drugs-statins, evolocumab, and ezetimibe. Low-density lipoprotein (LDL) cholesterol was selected as the biomarker for the measurement of the inhibitors of HMGCR, PCSK9, and NPC1L1, and the genetic data were acquired from the Global Lipids Genetics Consortium, which consisted of 1.3 million participants of European ancestry and 146.5 thousand participants of East Asian ancestry. The genetic dataset of SLE was acquired from two large-scale GWAS studies; one recruited 23,210 participants (7,219 SLE cases and 15,991 controls) of European ancestry and the other one recruited 12,653 participants (4,222 SLE cases and 8,431 controls) of Chinese ancestry. The primary analysis used the inverse variance weighted (IVW) method. Four additional sensitivity analyses, colocalization analysis, and stratification analysis were performed. Results: The primary analysis showed that inhibition of PCSK9 (evolocumab) was associated with a significantly lower risk of SLE [odds ratio (OR) 0.51, 95%CI 0.34 to 0.76, p = 0.001] in the European population. The secondary analyses had similar findings. Stratification analysis demonstrated that the preventive effect of PCSK9 inhibition for SLE was similar in both males and females. However, the results were not replicated in the East Asian population. The inhibition of HMGCR (statins) and NPC1L1 (ezetimibe) did not cause a lower risk of SLE. Conclusion: Evolocumab might provide a protective effect on the risk of SLE in the European population, but statins and ezetimibe might not have the protective effect. Further research is necessary to elucidate the specific mechanisms and potential therapeutic applications of PCSK9 inhibitors (evolocumab) in the context of SLE protection.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

Genome-Wide Identification of Associations of Circulating Molecules With Spontaneous Coronary Artery Dissection and Aortic Aneurysm and Dissection

Circulating proteins play functional roles in various biological processes and disease pathogenesis. The aim of this study was to highlight circulating proteins associated with aortic aneurysm and dissection (AAD) and spontaneous coronary artery dissection (SCAD). We examined the associations of circulating molecule levels with SCAD by integrating data from a genome-wide association study (GWAS) of CanSCAD and 7 pQTL studies. Mendelian randomization (MR) analysis was applied to examine the associations between circulating molecule levels and AAD by using data from UK Biobank GWAS and pQTL studies. The SCAD-associated SNPs in 1q21.2 were strongly associated with circulating levels of extracellular matrix protein 1 (ECM1) and 25 other proteins (encoded by CTSS, CAT, CNDP1, KNG1, SLAMF7, TIE1, CXCL1, MBL2, ESD, CXCL16, CCL14, KCNE5, CST7, PSME1, GPC3, MAP2K4, SPOCK3, LRPPRC, CLEC4M, NOG, C1QTNF9, CX3CL1, SCP2D1, SERPINF2, and FN1). These proteins were enriched in biological processes such as regulation of peptidase activity and regulation of cellular protein metabolic processes. Proteins (FGF6, FGF9, HGF, BCL2L1, and VEGFA) involved in the Ras signaling pathway were identified to be related to AAD. In addition, SCAD- and AAD-associated SNPs were associated with cytokine and lipid levels. MR analysis showed that circulating ECM1, SPOCK3 and IL1b levels were associated with AAD. Circulating levels of low-density lipoprotein cholesterol and small very-low-density lipoprotein particles were strongly associated with AAD. The present study found associations between circulating proteins and lipids and SCAD and AAD. Circulating ECM1 and low-density lipoprotein cholesterol may play a role in the pathology of SCAD and AAD.

The role of PCSK9 in inflammation, immunity, and autoimmune diseases

INTRODUCTION

Statins have pleiotropic effects, being both anti-inflammatory and immunomodulatory. Proprotein convertase subtilisin kexin 9 (PCSK9) targets the low-density lipoprotein receptor (LDLR), which increases LDL levels due to the lower expression of LDLR.

AREAS COVERED

Inhibition of PCSK9 by the use of antibodies represents a novel principle to lower LDL levels. LDL may have other properties than being a cholesterol carrier but is well established as a risk factor for cardiovascular disease and atherosclerosis. In atherosclerosis, the plaques are characterized by activated T cells and dendritic cells (DCs), dead cells, and OxLDL. The latter may be an important cause of the inflammation typical of atherosclerosis, by promoting a proinflammatory immune activation. This is inhibited by PCSK9 inhibition, and an anti-inflammatory type of immune activation is induced. OxLDL is raised in systemic lupus erythematosus (SLE), where both CVD and atherosclerosis are much increased compared to the general population. PCSK9 is reported to be associated with disease activity and complications in SLE. Also in other rheumatoid arthritis, PCSK9 may play a role.

EXPERT OPINION

PCSK9 has pleiotropic effects, being implicated in inflammation and immunity. Inhibition of PCSK9 is therefore interesting to study further as a potential therapy against inflammation and autoimmunity.

The Effect of Lipid Metabolism on CD4+ T Cells

CD4⁺ T cells play a vital role in the adaptive immune system and are involved in the pathogenesis of many diseases, including cancer, autoimmune diseases, and chronic inflammation. As an important mechanism for energy storage, a lot of researches have clarified that metabolism imbalance interacts with immune disorder, and one leads to the other. Lipid metabolism has close relationship with CD4⁺ T cells. In this review, we discuss fatty acid, cholesterol, prostaglandin, and phospholipid metabolism in CD4⁺ T cell subsets. Fatty acid β-oxidation (FAO) is activated in Th17 cell to support the proinflammatory function. Cholesterol promotes Th1, Th2, and Treg cell differentiation. In addition to glucose metabolism, lipid metabolism is also very important for immunity. Here, it is highlighted that lipid metabolism regulates CD4⁺ T cell differentiation and function and is related to diseases.

How Oxidized Low-Density Lipoprotein Activates Inflammatory Responses

Cardiovascular disease (CVD) is the number one cause of death in the United States and worldwide. The most common cause of cardiovascular disease is atherosclerosis, or formation of fatty plaques in the arteries. Low-density lipoprotein (LDL), termed "bad cholesterol", is a large molecule comprised of many proteins as well as lipids including cholesterol, phospholipids, and triglycerides. Circulating levels of LDL are directly associated with atherosclerosis disease severity. Once thought to simply be caused by passive retention of LDL in the vasculature, atherosclerosis studies over the past 40-50 years have uncovered a much more complex mechanism. It has now become well established that within the vasculature, LDL can undergo many different types of oxidative modifications such as esterification and lipid peroxidation. The resulting oxidized LDL (oxLDL) has been found to have antigenic potential and contribute heavily to atherosclerosis associated inflammation, activating both innate and adaptive immunity. This review discusses the many proposed mechanisms by which oxidized LDL modulates inflammatory responses and how this might modulate atherosclerosis.

Malondialdehyde Conjugated With Albumin Induces Pro-Inflammatory Activation of T Cells Isolated From Human Atherosclerotic Plaques Both Directly and Via Dendritic Cell-Mediated Mechanism

Human dendritic cells were differentiated from blood monocytes and treated with malondialdehyde (MDA) conjugated with human serum albumin (HSA). Autologous T cells from human plaques or blood were co-cultured with the pre-treated dendritic cells or treated directly. MDA modifications were studied by mass spectrometry. MDA-HSA induced a pro-inflammatory DC-mediated T-cell activation and also a strong direct effect on T cells, inhibited by an inhibitor of oxidative stress and antibodies against MDA. Atherogenic heat shock protein-60 was strongly induced in T cells activated by MDA-HSA. Two peptide modifications in atherosclerotic patients' HSA were similar to those present in in vitro MDA-modified HSA.

Toll-Like Receptor (TLR)4 and MyD88 are Essential for Atheroprotection by Peritoneal B1a B Cells

BACKGROUND

We previously identified peritoneal B1a cells that secrete natural IgM as a key atheroprotective B cell subset. However, the molecules that activate atheroprotective B1a cells are unknown. Here, we investigated whether Toll-like receptors (TLRs) TLR2, TLR4, and TLR9 expressed by B1a cells are required for IgM-mediated atheroprotection.

METHODS AND RESULTS

We adoptively transferred B1a cells from wild-type mice or from mice deficient in TLR2, TLR4, TLR9, or myeloid differentiation primary response 88 (MyD88) into ApoE-/- mice depleted of peritoneal B1a cells by splenectomy and fed a high-fat diet for 8 weeks. Elevations in plasma total, anti-oxLDL (oxidized low-density lipoprotein), anti-leukocyte, anti-CD3, anti-CD8, and anti-CD4 IgMs in atherosclerotic mice required B1a cells expressing TLR4 and MyD88, indicating a critical role for TLR4-MyD88 signaling for IgM secretion. Suppression of atherosclerosis was also critically dependent on B1a cells expressing TLR4-MyD88. Atherosclerosis suppression was associated not only with reductions in lesion apoptotic cells, necrotic cores, and oxLDL, but also with reduced lesion CD4+ and CD8+ T cells. Transforming growth factor beta 1 (TGF-β1) expression, including macrophages expressing TGF-β1, was increased, consistent with increased IgM-mediated phagocytosis of apoptotic cells by macrophages. Reductions in lesion inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin (IL) 1β, and IL-18 were consistent with augmented TGF-β1 expression.

CONCLUSIONS

TLR4-MyD88 expression on B1a cells is critical for their IgM-dependent atheroprotection that not only reduced lesion apoptotic cells and necrotic cores, but also decreased CD4 and CD8 T-cell infiltrates and augmented TGF-β1 expression accompanied by reduced lesion inflammatory cytokines TNF-α, IL-1β, and IL-18.

Clinical association of baseline levels of conjugated dienes in low-density lipoprotein and nitric oxide with aggressive B-cell non-Hodgkin lymphoma and their relationship with immunoglobulins and Th1-to-Th2 ratio

Objective

The aim of this study was to highlight the clinical association of baseline levels of conjugated dienes in low-density lipoprotein (LDL-BCD) and nitric oxide (NO) with immunoglobulins (Igs) and T helper (Th)1/Th2 ratio in patients with newly diagnosed B-cell non-Hodgkin lymphoma (NHL).

Patients and methods

Thirty-two newly diagnosed patients with aggressive B-cell NHL and 25 age-, sex-, and body-mass-index-matched healthy controls were randomly selected for a cross-sectional case–control study conducted at the Hematology Department of Tlemcen Medical Centre University (northwest of Algeria).

Results

Circulating levels of LDL-BCD and NO and those of IgA and IgM were significantly higher in patients than in controls. The levels of Th1/Th2 ratio and plasma total antioxidant capacity were significantly lower in patients compared with controls, while malondialdehyde and protein carbonyl levels were significantly higher in patients. B-cell NHL was significantly associated with high levels of LDL-BCD from 25th to 75th percentile (25th percentile: relative risk [RR] =2.26, 95% confidence interval [CI] 1.42–3.59, P=0.014; 50th percentile: RR =2.84, 95% CI 1.72–4.68, P<0.001; 75th percentile: RR =5.43, 95% CI 2.58–11.42, P<0.001). Similarly, the disease was significantly associated with high levels of NO production from 25th to 75th percentile (25th percentile: RR =2.07, 95% CI 1.25–3.44, P=0.024; 50th percentile: RR =2.78, 95% CI 1.63–4.72, P<0.001; 75th percentile: RR =4.68, 95% CI 2.21–9.91, P<0.001). Moreover, LDL-BCD levels were positively and significantly correlated with interferon (IFN)-γ, whereas NO levels were inversely and significantly correlated with IFN-γ and Th1/Th2 ratio.

Conclusion

LDL-BCD and NO production seem to be associated with aggressive B-cell NHL and alteration of Th1/Th2 ratio. Our results have to be examined using ex vivo mechanistic studies leading to further investigations of these parameters, with an interest in the link between Epstein–Barr virus infection and NO and immunoglobulins.

Vitamin A Decreases Cytotoxicity of Oxidized Low-Density Lipoprotein in Patients with Atherosclerosis

BACKGROUND

Oxidized low-density lipoprotein (ox-LDL) is implicated in initiation and progression of atherosclerosis. Previously, we found that ox-LDL increases vulnerability of peripheral blood mononuclear cells (PBMCs) in atherosclerotic patients compared to controls. Vitamin A induces proliferation of PBMCs. The aim of this study was to determine the effect of vitamin A supplementation on PBMC survival against LDL and different doses of ox-LDL.

METHOD

In this double-blind placebo-controlled trial, we recruited 35 atherosclerotic patients and 38 healthy controls and randomly allocated them into placebo and vitamin A groups, which received either placebo or 25,000 IU/day of vitamin A for 3 months. PBMCs were isolated, cultured, and stimulated by 1 µg/mL LDL as well as 1 µg/mL and 50 µg/mL ox-LDL. The stimulation indexes (SIs) of PBMCs were calculated to identify cell viability. Additionally, the circulating ox-LDL levels were measured by ELISA.

RESULTS

Viability of PBMCs stimulated by 50 µg/mL ox-LDL significantly increased following vitamin A supplementation in patients (p < 0.01). The levels of circulating ox-LDL were not changed by vitamin A treatment. Ox-LDL levels were strongly and positively correlated to SI of PBMCs stimulated by 1 µg/mL LDL and1 µg/mL ox-LDL in all groups.

CONCLUSION

Vitamin A decreases cytotoxicity of high-dose ox-LDL and improves PBMC viability. The protective effect of vitamin A is not mediated by an antioxidative mechanism, but may instead have been due to intracellular protection of the apoptotic machinery or induction of proliferation of the cells. Higher levels of ox-LDL increase PBMC irritability in all participants.

Animal models of surgically manipulated flow velocities to study shear stress-induced atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial tree that develops at predisposed sites, coinciding with locations that are exposed to low or oscillating shear stress. Manipulating flow velocity, and concomitantly shear stress, has proven adequate to promote endothelial activation and subsequent plaque formation in animals. In this article, we will give an overview of the animal models that have been designed to study the causal relationship between shear stress and atherosclerosis by surgically manipulating blood flow velocity profiles. These surgically manipulated models include arteriovenous fistulas, vascular grafts, arterial ligation, and perivascular devices. We review these models of manipulated blood flow velocity from an engineering and biological perspective, focusing on the shear stress profiles they induce and the vascular pathology that is observed.

The impact of rapid weight loss on oxidative stress markers and the expression of the metabolic syndrome in obese individuals

OBJECTIVE

Obesity is linked with a state of increased oxidative stress, which plays an important role in the etiology of atherosclerosis and type 2 diabetes mellitus. The aim of our study was to evaluate the effect of rapid weight loss on oxidative stress markers in obese individuals with metabolic syndrome (MetS).

DESIGN AND METHODS

We measured oxidative stress markers in 40 obese subjects with metabolic syndrome (MetS+), 40 obese subjects without metabolic syndrome (MetS-), and 20 lean controls (LC) at baseline and after three months of very low caloric diet.

RESULTS

Oxidized low density lipoprotein (ox-LDL) levels decreased by 12% in MetS+ subjects, associated with a reduction in total cholesterol (TC), even after adjustment for age and sex. Lipoprotein associated phospholipase A₂ (Lp-PLA₂) activity decreased by 4.7% in MetS+ subjects, associated with a drop in LDL-cholesterol (LDL-C), TC, and insulin levels. Multivariate logistic regression analysis showed that a model including ox-LDL, LpPLA₂ activity, and myeloperoxidase (MPO) improved prediction of MetS status among obese individuals compared to each oxidative stress marker alone.

CONCLUSIONS

Oxidative stress markers were predictive of MetS in obese subjects, suggesting a higher oxidative stress. Rapid weight loss resulted in a decline in oxidative stress markers, especially in MetS+ patients.

The Dynamics of Oxidized LDL during Atherogenesis

Accumulating evidence indicates that oxidized low-density lipoprotein (OxLDL) is a useful marker for cardiovascular disease. The uptake of OxLDL by scavenger receptors leads to the accumulation of cholesterol within the foam cells of atherosclerotic lesions. OxLDL has many stimulatory effects on vascular cells, and the presence of OxLDL in circulating blood has been established. According to the classical hypothesis, OxLDL accumulates in the atherosclerotic lesions over a long duration, leading to advanced lesions. However, recent studies on time-course changes of OxLDL in vivo raised a possibility that OxLDL can be transferred between the lesions and the circulation. In this paper, the in vivo dynamics of OxLDL are discussed.

HDL metabolism and activity in chronic kidney disease

Chronic kidney disease (CKD) is associated with development of atherosclerosis and premature death from cardiovascular disease. The predisposition of patients with CKD to atherosclerosis is driven by inflammation, oxidative stress and dyslipidemia, all of which are common features of this condition. Markers of dyslipidemia in patients with advanced CKD are impaired clearance and heightened oxidation of apolipoprotein-B-containing lipoproteins and their atherogenic remnants, and a reduction of the plasma concentration, antioxidant, and anti-inflammatory properties of high-density lipoprotein (HDL). Studies in animal models of CKD indicate that the disease promotes lipid accumulation in the artery wall and kidney, leading to atherosclerosis, glomerulosclerosis and tubulointerstitial injury. These effects seem to be mediated by an increased cellular influx of lipids, elevated cellular production and reduced cellular catabolism of fatty acids, and impaired antioxidant, anti-inflammatory and reverse lipid transport properties of HDL. Available pharmacological therapies have been largely ineffective in ameliorating oxidative stress, inflammation, HDL deficiency and/or dysfunction, and the associated atherosclerosis and cardiovascular disease in patients with end-stage renal disease. This Review aims to provide an overview of the mechanisms and consequences of CKD-induced HDL deficiency and dysfunction.

HDL-inflammatory index correlates with poor outcome in hemodialysis patients

Oxidative stress and cardiovascular disease are risk factor of patients with chronic kidney disease (CKD) on maintenance hemodialysis. We used the fluorescence of low-density lipoprotein as an index of its proinflammatory potential to examine any role that high-density lipoprotein (HDL) might have in promoting this effect. The total body fat of the patients was measured by means of near-infrared interactance and their quality of life by means of SF36 questionnaires. In 189 randomly selected patients, followed for 30 months, HDL was found to be significantly anti-inflammatory but with a large standard deviation. Fully 17% of the patients had a decidedly proinflammatory index along with inferior SF36 scores. The patients were divided into 10% increments of total body fat percentages up to 40%. HDL was found to be progressively proinflammatory the higher the body fat content. Patients with a higher HDL proinflammatory index had a higher 30-month adjusted hazard ratio for death than those whose HDL were seen to be anti-inflammatory. Our findings suggest an important role of inflammatory HDL in patients with CKD leading to poor outcome.

Atherosclerosis and the Lectin-like OXidized low-density lipoprotein scavenger receptor

The Lectin-like OXidized low-density lipoprotein scavenger receptor (LOX-1) is implicated in vascular inflammation and atherosclerotic plaque initiation, progression, and destabilization. LOX-1 levels are elevated upon recognition of oxidized low-density lipoprotein, a key pro-atherogenic substance in the vasculature. Recent evidence indicates this gene product is a biomarker of inflammation and disease status. We review and assess the role of LOX-1 in atherosclerotic plaque formation, physiologic regulation, and as a biomarker and target in cardiovascular disease diagnosis and prevention.

The expression of vascular dendritic cells in human atherosclerotic carotid plaques

Atherosclerosis is currently considered a chronic inflammatory disease, and evidence is accumulating for a role of the immune system in the progression of atherosclerosis. Dendritic cells are specialized antigen-presenting cells with the unique ability to initiate a primary immune response to certain antigens by the activation of naive T-lymphocytes. Although dendritic cells are well known to be important in the development of different diseases, studies of vascular dendritic cells in atherosclerosis are rare, and their role is not clearly understood. Therefore, we investigated the immunohistochemical expression of vascular dendritic cells in atherosclerotic plaques. Between April 2003 and December 2005, carotid endarterectomy was performed in 26 consecutive patients, and 27 carotid plaque specimens were analyzed. We investigated the immunohistochemical expression of vascular dendritic cells in human carotid plaques by measuring the signal intensity of fascin-positive cells using an image analyzer. In addition, these immunohistochemical results were related to clinical data. The highest signal intensity of dendritic cells was found in plaque shoulders, and the mean signal intensity of dendritic cells was significantly higher in complicated than in uncomplicated plaques (P = .0029). Moreover, the mean signal intensity of dendritic cells in plaques from symptomatic patients was significantly elevated compared with plaques from asymptomatic patients (P = .0004). Although atherosclerotic plaque instability is determined by multiple factors, the immune and inflammatory pathways play a particularly important role. Dendritic cells play a role in atherosclerosis, and the present study suggests that the expression of dendritic cells in human carotid arteries may be strongly associated with the occurrence of ischemic stroke.

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

Objective

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

Methods and results

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

Conclusion

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

The kidney disease wasting: Inflammation, oxidative stress, and diet-gene interaction

The 350,000 maintenance hemodialysis (MHD) patients in the United States have an unacceptably high mortality rate of >20%/year. Almost half of all deaths are assumed to be cardiovascular. Markers of kidney disease wasting (KDW) such as hypoalbuminemia, anorexia, body weight and fat loss, rather than traditional cardiovascular risk factors, appear to be the strongest predictors of early death in these patients. The KDW is closely related to oxidative stress (SOX). Such SOX markers as serum myeloperoxidase are associated with pro-inflammatory cytokines and poor survival in MHD patients. Identifying the conditions that modulate the KDW/SOX-axis may be the key to improving outcomes in MHD patients. Dysfunctional lipoproteins such as a higher ratio of the high-density lipoprotein inflammatory index (HII) may engender or aggravate the KDW, whereas functionally intact or larger lipoprotein pools, as in hypercholesterolemia and obesity, may mitigate the KDW in MHD patients. Hence, a reverse epidemiology or "bad-gone-good" phenomenon may be observed. Diet and gene and their complex interaction may lead to higher proportions of pro-inflammatory or oxidative lipoproteins such as HII, resulting in the aggravation of the SOX and inflammatory processes, endothelial dysfunction, and subsequent atherosclerotic cardiovascular disease and death in MHD patients. Understanding the factors that modulate the KDW/SOX complex and their associations with genetic polymorphism, nutrition, and outcomes in MHD patients may lead to developing more effective strategies to improve outcomes in this and the 20 to 30 million Americans with chronic disease states such as individuals with chronic heart failure, advanced age, malignancies, AIDS, or cachexia.

Antibodies against platelet-activating factor and platelet-activating factor–like lipids are raised in women with primary recurrent abortion

OBJECTIVE

The purpose of this study was to determine the antibody levels against platelet-activating factor (PAF), PAF-like lipids lysophosphatidylcholine (LPC), cardiolipin (CL), and oxidized low-density lipoprotein (LDL) in recurrent abortion.

STUDY DESIGN

Eigthy-five women with a history of at least 3 recurrent spontaneous abortions (55 women with primary abortion [31.4+/-5.1 years old]; 30 women with secondary abortion [33+/-4.5 years old]) were compared with 48 age-matched control subjects (33+/-4.4 years old) who had delivered without complications. Antibodies were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Antibodies against PAF and antibodies against oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (oxPAPC) were raised significantly in the group with primary abortion, as compared to control subjects (P<.05) and not significantly higher than in secondary abortion; antibodies against oxidized LDL, LPC, or CL levels did not differ between groups.

CONCLUSION

Antibodies against platelet-activating factor and antibodies against platelet-activating factor-like lipid oxPAPC are associated with primary recurrent abortion and may function as novel disease markers. Whether these antibodies also are pathogenic (eg, by interacting with endothelial cells in placenta or by interfering with platelet-activating factor during embryonal development) remains to be shown.

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

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

Monocytes influence the fate of T cells challenged with oxidised low density lipoproteins towards apoptosis or MHC-restricted proliferation

Atherosclerosis has been implicated in myocardial infarction, stroke and a host of cardiovascular diseases. The presence of activated T lymphocytes and macrophages, and the increased expression of HLA-DR antigen are consistent with the notion of immune activity in the atherosclerotic plaque. The nature of the causative antigen has not been established although oxidised low density lipoproteins (oxLDL) that accumulate in atherosclerotic plaques could fulfil this role. Here, we report that monocytes play a key role in influencing the fate of purified peripheral human T lymphocytes from healthy donors when the cells are exposed to LDL oxidised under the controlled conditions of water radiolysis. Our data showed that oxLDL generated under these conditions were chemoattractants for T cells. However, they induced a state of apoptosis in T lymphocytes cultured in the absence of monocytes. The extent of apoptosis was related to the degree of oxidation of LDL and the time of T cell exposure to oxLDL. OxLDL-dependent apoptosis did not involve a scavenger-like receptor. CD4(+) cells were more sensitive to the apoptotic effect of oxLDL than CD8(+) cells. OxLDL-primed (12 h) autologous monocytes triggered a robust proliferation of T lymphocytes cultured in the absence of oxLDL. The strength of T cell stimulation was related to the degree of oxidation of the LDL used in priming. Heterologous monocytes exposed to oxLDL under similar conditions induced a response that was not different than monocytes exposed to untreated LDL (natLDL) which did not induce T cell proliferation. Fucoidan did not modify the oxLDL-, monocyte-dependent T cell response to proliferation, suggesting that a scavenger-like receptor was not involved. The expression of the HLA-DR marker and the B7.2 protein were up-regulated in monocytes exposed to oxLDL but not to natLDL. The levels of B7.1 were unchanged. Our data are consistent with the notion that monocytes are critical for T cell survival in the presence of oxLDL and MHC-restricted T cell proliferative response to oxLDL.

NUTRITIONALMANAGEMENT OFMAINTENANCEDIALYSISPATIENTS: Why Aren't We Doing Better?

About 40% of patients undergoing maintenance dialysis suffer from varying degrees of protein-energy malnutrition. This is a problem of substantial importance because many measures of nutritional status correlate with the risk of morbidity and mortality. There are many causes of protein-energy malnutrition in maintenance dialysis patients. Evidence indicates that nutritional decline begins even when the reduction in glomerular filtration rate is modest, and it is likely that the observed decrease in dietary protein and energy intake plays an important role. The nutrient intake of patients receiving maintenance dialysis also is often inadequate, and several lines of evidence suggest that toxins that accumulate with renal failure suppress appetite and contribute to nutritional decline once patients are on maintenance dialysis. Recent epidemiologic studies have suggested that both increased serum levels of leptin and inflammation may reduce nutrient intake and contribute to the development of protein-energy malnutrition. It is likely that associated illnesses, which are highly prevalent, contribute to malnutrition in maintenance dialysis patients. Recent data from the United States Renal Data System registry suggest that in the United States, the mortality rate of dialysis patients is improving. However, it remains high. We offer suggestions for predialysis and dialysis care of these patients that can result in improvement in their nutritional status. Whether this improvement will result in a decrease in patient morbidity and mortality is unknown.

Induction of early atherosclerosis in CBA/J mice by combination of Trypanosoma cruzi infection and a high cholesterol diet

In addition to established factors such as hyperlipidemia, smoking and hypertension, inflammation and infection have recently been implicated as major risk factors for atherosclerotic disease. Proatherogenic effects induced by infection may be related to both systemic inflammation and to direct effects on the vascular wall. We report here that a high fat diet combined with a protozoal infection with known tropism to the heart induced early atherosclerosis and intimal inflammatory infiltrates (CD4+, CD8+ cells and macrophages) in aortas of all (n = 7) CBA/J mice investigated. These mice are normally quite resistant to atherosclerotic development and in the control group (n = 7) receiving only a fatty diet, only one mouse presented a lesion. This lesion was completely devoid of infiltrating CD8+ cells. Parasite-infected mice receiving a normal diet exhibited vasculitis, but no signs of atherosclerosis and control mice receiving normal diet, as expected, exhibited neither signs of vasculitis nor atherosclerosis. Secretion of IL-6, TNF-alpha, and IFN-gamma were demonstrated in all atherosclerotic lesions and IL-6 appeared to be the dominant cytokine, both in the lesions themselves as well as in the intimal-medial junction. There were no traces of parasites present in the artery wall, indicating that atherosclerosis was induced via an indirect route. We conclude that a high fat diet in conjunction with infection and systemic (or localized) inflammation may have a strong proatherogenic effect. Finally, we suggest that CBA/J mice infected with T. cruzi parasites and given a fatty diet could serve as a useful experimental model in the continued analysis of factors contributing to the induction of atherosclerosis.

Interferon-gamma production in response to in vitro stimulation with collagen type II in rheumatoid arthritis is associated with HLA-DRB1(*)0401 and HLA-DQ8

INTRODUCTION

Despite much work over past decades, whether antigen-specific immune reactions occur in rheumatoid arthritis (RA) and to what extent such reactions are directed towards joint-specific autoantigens is still questionable. One strong indicator for antigenic involvement in RA is the fact that certain major histocompatibility complex (MHC) class II genotypes [human leucocyte antigen (HLA)-DR4 and HLA-DR1[ predispose for the development of the disease [1]. In the present report, collagen type II (CII) was studied as a putative autoantigen on the basis of both clinical and experimental data that show an increased frequency of antibodies to CII in RA patients [2-4] and that show that CII can induce experimental arthritis [5]. It is evident from the literature that RA peripheral blood mononuclear cells (PBMCs) respond poorly to antigenic stimulation [6-8], and in particular evidence for a partial tolerization to CII has been presented [9]. The strategy of the present work has accordingly been to reinvestigate T-cell reactivity to CII in RA patients, to relate it to the response to commonly used recall antigens and to analyze interferon (IFN)-gamma responses as an alternative to proliferative responses.

AIMS

To study cellular immune reactivity to CII in patients with RA and in healthy control individuals and to correlate this reactivity to HLA class II genotypes and to the presence of antibodies to CII in serum.

METHODS

Forty-five patients who met the 1987 American college of Rheumatology classification criteria for RA [10] and 25 healthy control individuals of similar age and sex were included. Twenty-six of these patients who had low levels of anti-CII in serum were randomly chosen, whereas 19 patients with high anti-CII levels were identified by enzyme-linked immunosorbent assay (ELISA)-screening of 400 RA sera. Heparinized blood was density gradient separated and PBMCs were cultured at 1 x 10(6)/ml in RPMI-10% fetal calf serum with or without antigenic stimulation: native or denatured CII (100 microgram/ml), killed influenza virus (Vaxigrip, Pasteur Merieux, Lyon, France; diluted 1:1000) or purified protein derivative (PPD; 10 microgram/ml). CII was heat-denatured in 56 degrees C for 30 min. Cell supernatants were collected after 7 days and IFN-gamma contents were analyzed using ELISA. HLA-DR and HLA-DQ genotyping was performed utilizing a polymerase chain reaction-based technique with sequence-specific oligonucleotide probe hybridization. Nonparametric statistical analyses were utilized throughout the study.

RESULTS

PBMCs from both RA patients and healthy control individuals responded with IFN-gamma production to the same degree to stimulation with native and denatured CII (Fig. 1a), giving median stimulation indexes with native CII of 4.6 for RA patients and 5.4 for health control individuals, and with denatured CII of 2.9 for RA patients and 2.6 for healthy control individuals. RA patients with elevated levels of anti-CII had a weaker IFN-gamma response to both native and denatured CII that did healthy control individuals (P-).02 and 0.04, respectively). Stimulation with the standard recall antigens PPD and killed influenza virus yielded a median stimulation index with PPD of 10.0 for RA patients and 51.3 for healthy control individuals and with influenza of 12.3 for RA patients and 25.7 for healthy, control individuals. The RA patients displayed markedly lower responsiveness to both PPD and killed influenza virus than did healthy control individuals (Fig. 1b). IFN-gamma responses to all antigens were abrogated when coincubating with antibodies blocking MHC class II. The low response to PPD and killed influenza virus in RA patients relative to that of healthy control individuals reflects a general downregulation of antigen-induced responsiveness of T cells from RA patients [6-8]. That no difference between the RA group and the control group was recorded CII-induced IFN-gamma production therefore indicates that there may be an underlying increased responsiveness to CII in RA patients, which is obscured by the general downregulation of T-cell responsiveness in these patients. In order to address this possibility, we calculated the fraction between individual values for the CII-induced IFN-gamma production and the PPD-induced and killed influenza virus-induced IFN-gamma production and the PPD-induced and killed influenza virus-induced IFN-gamma production, and compared these fractions. A highly significant difference between the RA and health control groups was apparent after stimulation with both native CII and denatured CII when expressing the response as a fraction of that with PPD (Fig. 2a). Similar data were obtained using killed influenza virus-stimulated IFN-gamma values as the denominator (Fig. 2b).When comparing the compensated IFN-gamma response to denatured CII stimulation between RA patients with different HLA genotypes, highly significant differences were evident, with HLA-DRB1*0401 patients having greater CII responsiveness than patients who lacked this genotype (Fig. 3a). HLA-DQ8 positive patients also displayed a high responsiveness to CII as compared with HLA-DQ8 negative RA patients (Fig. 3b). These associations between the relative T-cell reactivity to denatured CII and HLA class II genotypes were not seen in healthy control individuals. Similar results were achieved using influenza as denominator (P = 0.02 for HLA-DRB1*0401 and P = 0.01 for HLA-DQ8).

DISCUSSION

No reports have previously systematically taken the general T-cell hyporesponsiveness in RA into account when investigating specific T-cell responses in this disease. In order to address this issue we used the T-cell responses to PPD and killed influenza virus as reference antigens. This was made on the assumption that exposure to these antigens is similar in age-matched and sex-matched groups of RA patients and healthy control individuals. The concept of a general hyporesponsiveness in RA T cells has been documented in several previous reports, in which both nominal antigens [6,7,8] and mitogens [11,12,13] have been used. The fact that a similar functional downregulation in RA PBMCs was obtained with both PPD and killed influenza virus as reference antigens strengthens the validity of our approach. We identified an association between the IFN-gamma response to CII and HLA-DRB1*0401 and HLA-DQ8 in the RA patient group, which is of obvious interest because both these MHC class II alleles have been associated with high responsiveness to CII in transgenic mice that express these human MHC class II molecules [14,15]. There was no association between high anti-CII levels and shared epitope (HLA-DRB1*0401 or HLA-DRB1*0404).

CONCLUSION

CII, a major autoantigen candidate in RA, can elicit an IFN-gamma response in vitro that is associated with HLA-DRB1*0401 and HLA-DQ8 in RA patients. This study, with a partly new methodological approach to a classical problem in RA, has provided some additional support to the notion that CII may be a target autoantigen of importance for a substantial group of RA patients. Continued efforts to identify mechanisms behind the general hyporesponsiveness to antigens in RA, as well as the mechanisms behind the potential partial anergy to CII, may provide us with better opportunities to study the specificity and pathophysiological relevance of anti-CII reactivity in RA.

Antibodies to platelet-activating factor are associated with borderline hypertension, early atherosclerosis and the metabolic syndrome

OBJECTIVE

Platelet-activating factor (PAF) is a phospholipid inflammatory mediator which is synthesized by a variety of cells, including monocytes and endothelial cells, and PAF can be retained in activated endothelial cell membranes. Furthermore, PAF-like lipids are produced in other phospholipid membranes as in oxidized LDL. Atherosclerosis is a chronic inflammation in the artery wall, but little is known about the role of immune reactions in the early stages of development of cardiovascular disease. In the present study we investigated if there are antibodies to PAF (aPAF) that may play a role in borderline hypertension and early atherosclerosis.

DESIGN

Seventy-three men with borderline hypertension (BHT) and 73 age-matched normotensive (NT) men (diastolic blood pressure 85-94 and <80 mmHg, respectively) were recruited from a population screening programme. Antibody levels were determined by use of ELISA. Carotid intima-media (IM)-thickness and atherosclerosis was determined by B-mode ultrasonography.

RESULTS

BHT men had 49.3% higher aPAF levels of IgG class than NT controls (P = 0.0007). Antibodies to the biologically inactive lysoPAF did not differ between BHT and NT group. aPAF levels were associated with IM-thickness in the left (P = 0.02) and right (P = 0.009) carotid artery. Furthermore, aPAF levels were enhanced in individuals with the metabolic syndrome (n = 44) as compared to those without (n = 102; P = 0.009), and also significantly associated with insulin levels (P = 0.02) and insulin resistance (P = 0.02).

CONCLUSIONS

aPAF antibodies may reflect early vascular changes and thus serve as novel markers for disease, and they may also be pathogenic, by eliciting an inflammatory reaction in the vascular wall.

Inhibition of arteriosclerosis by T-cell depletion in normocholesterolemic rabbits immunized with heat shock protein 65

Previous studies in our laboratory have shown that arteriosclerotic changes can be induced in normocholesterolemic rabbits by immunization with mycobacterial heat shock protein (hsp) 65. To further investigate the immunologic mechanisms underlying such vascular lesions, 39 male New Zealand White rabbits were treated by triple immunization with fortified Freund's complete adjuvant containing 5 mg/mL Mycobacterium tuberculosis as a source of hsp65 and simultaneous immunosuppressive therapy twice per week with either anti-CD3 monoclonal antibody (1 mg/kg) and prednisolone (1 mg/kg) or prednisolone (1 mg/kg) alone. Sixteen weeks after the first immunization the animals were killed, and as expected, severe arteriosclerotic lesions in the intima of the aortic arch were found in 9 of 10 immunized rabbits. However, only 1 of 10 rabbits immunized and immunosuppressed with the combined anti-CD3 monoclonal antibody and prednisolone treatment showed a single moderate lesion in the aorta, whereas 5 of 9 rabbits immunized and immunosuppressed by prednisolone treatment alone showed lesions, albeit mild. In conclusion, the early inflammatory stages of arteriosclerotic lesions induced by immunization with hsp65 can be inhibited by immunosuppressive therapy with anti-CD3 monoclonal antibody.

Cytokine expression in advanced human atherosclerotic plaques: dominance of pro-inflammatory (Th1) and macrophage-stimulating cytokines

The atherosclerotic lesion contains large numbers of macrophages and T lymphocytes. This suggests that a cellular immune response may take place in the lesion, and oxidized lipoproteins, heat shock proteins, and micro-organisms have been implied as candidate antigens. However, the effector mechanisms elicited by this response have been largely unclear. We have therefore analyzed endarterectomy specimens by immunohistochemistry and reverse transcription-PCR to detect immune cytokines produced by immunocompetent cells of the advanced human plaque. The pro-inflammatory T cell cytokines, interleukin-2 and interferon-7, were found in a large proportion of plaques (IL-2 in 50% and interferon-gamma in 30% of plaques by immunohistochemistry and mRNA for both cytokines in 70% of plaques by PCR). In contrast, interleukin-4 and interleukin-5 were rarely observed (both cytokines in 10% of plaques by immunohistochemistry, mRNA for interleukin-4 in 10% and for interleukin-5 in 40% by PCR). This demonstrates the presence of a predominantly pro-inflammatory, Th1-type T cell response in atherosclerosis. This conclusion was further supported by the expression of the pro-inflammatory cytokine, interleukin-1 by plaque macrophages and endothelial cells. In addition, the chemokine interleukin-8 and the macrophage differentiation-stimulating cytokine, granulocyte-monocyte colony stimulating factor, were observed in plaque tissues, suggesting that the micro-environment promotes monocyte recruitment and macrophage differentiation. Occasional eosinophils and B cells were, however observed, which is compatible with a microheterogeneity within the lesion. Finally, the anti-inflammatory and fibrogenic cytokines, transforming growth factor-beta1-3 and its carrier protein, latent TGF-beta binding protein, were found in large amounts in all plaques. Together, these results show that a pro-inflammatory, Thl type cellular immune response takes place in the atherosclerotic plaque. The balance between pro-inflammatory and anti-inflammatory cytokines may be decisive for the progression of the lesion.

Cytokine secretion profiles of cloned T cells from human aortic atherosclerotic plaques

T cells take part in the chronic inflammatory reaction in atherosclerotic plaques, but their specific role in atherosclerosis has not yet been fully elucidated. Nevertheless, one may anticipate that activated T cells may secrete cytokines capable of modulating the morphology and hence the stability of plaques by regulating cell proliferation, lipid metabolism, and extracellular matrix (ECM) synthesis and/or degradation. This study has been designed to investigate the functional properties of T cells in atherosclerotic lesions. For this purpose, T-cell clones were generated from atherosclerotic plaques isolated from human aortas obtained at autopsy from six subjects. Cloned cells were activated with PMA and OKT-3 to initiate cytokine production and cytokine profiles of CD4-positive clones were measured by ELISA. The majority of the T-cell clones (125/155, 81 per cent) produced both interferon (IFN)-gamma and interleukin (IL)-4 (type 0 cytokine profile). Moreover, the production of IFN-gamma was dominant in the majority of these clones. A type 1 cytokine profile (high levels of IFN-gamma and low levels of IL-4) was found in 17 per cent of the clones (27/155). Only three clones (2 per cent) showed a type 2 cytokine secretion pattern (high levels of IL-4 and low levels of IFN-gamma). No cytolytic activity could be established in plaque-derived T cells. Our results show that the T-cell population in atherosclerotic lesions is heterogeneous, but the most dominant T cell by far is the one with a type 0 cytokine profile. The dominant secretion of IFN-gamma by T-cell clones suggest an important role for plaque T cells in modulating the growth and differentiation of other cells, such as macrophages and smooth muscle cells in atherosclerotic plaques.

Lysophosphatidylcholine (LPC) induces proinflammatory cytokines by a platelet-activating factor (PAF) receptor-dependent mechanism

Oxidized low-density lipoprotein (oxLDL) consists of both lipid components and apoprotein B100. OxLDL has both proinflammatory and cytotoxic properties. The present study was undertaken to investigate the effects of components in the lipid moiety of oxLDL on immune activation as determined by cytokine and immunoglobulin secretion. LPC induced interferon-gamma (IFN-gamma) secretion in peripheral blood mononuclear leucocytes from healthy blood donors. The effect varied between individuals, and there were both responders and non-responders. Furthermore, LPC induced enhanced antibody production, indicating B cell activation. None of eight oxysterols, arachidonic acid (AA), or 15-lipoxygenase products of AA tested had immune stimulatory properties. We recently demonstrated that PAF and oxLDL induce IFN-gamma secretion by a common mechanism. LPC-induced IFN-gamma secretion was inhibited by a specific PAF receptor antagonist, WEB 2170, indicating that the PAF receptor is involved in LPC-induced immune activation. Both oxLDL- and LPC-induced antibody formation was inhibited by WEB 2170. Furthermore LPC also induced tumour necrosis factor-alpha secretion, and this effect was inhibited by WEB 2170. LPC is produced during lipid oxidation (as in oxLDL), but also by enzymes such as phospholipase A2. The findings indicate that LPC may play an important role in inflammatory reactions, including atherosclerosis.

Strong association between malnutrition, inflammation, and atherosclerosis in chronic renal failure

BACKGROUND

Atherosclerotic cardiovascular disease and malnutrition are widely recognized as leading causes of the increased morbidity and mortality observed in uremic patients. C-reactive protein (CRP), an acute-phase protein, is a predictor of cardiovascular mortality in nonrenal patient populations. In chronic renal failure (CRF), the prevalence of an acute-phase response has been associated with an increased mortality.

METHODS

One hundred and nine predialysis patients (age 52 +/- 1 years) with terminal CRF (glomerular filtration rate 7 +/- 1 ml/min) were studied. By using noninvasive B-mode ultrasonography, the cross-sectional carotid intima-media area was calculated, and the presence or absence of carotid plaques was determined. Nutritional status was assessed by subjective global assessment (SGA), dual-energy x-ray absorptiometry (DXA), serum albumin, serum creatinine, serum urea, and 24-hour urine urea excretion. The presence of an inflammatory reaction was assessed by CRP, fibrinogen (N = 46), and tumor necrosis factor-alpha (TNF-alpha; N = 87). Lipid parameters, including Lp(a) and apo(a)-isoforms, as well as markers of oxidative stress (autoantibodies against oxidized low-density lipoprotein and vitamin E), were also determined.

RESULTS

Compared with healthy controls, CRF patients had an increased mean carotid intima-media area (18.3 +/- 0.6 vs. 13.2 +/- 0.7 mm2, P < 0.0001) and a higher prevalence of carotid plaques (72 vs. 32%, P = 0.001). The prevalence of malnutrition (SGA 2 to 4) was 44%, and 32% of all patients had an acute-phase response (CRP > or = 10 mg/liter). Malnourished patients had higher CRP levels (23 +/- 3 vs. 13 +/- 2 mg/liter, P < 0.01), elevated calculated intima-media area (20.2 +/- 0.8 vs. 16.9 +/- 0.7 mm2, P < 0.01) and a higher prevalence of carotid plaques (90 vs. 60%, P < 0.0001) compared with well-nourished patients. During stepwise multivariate analysis adjusting for age and gender, vitamin E (P < 0.05) and CRP (P < 0.05) remained associated with an increased intima-media area. The presence of carotid plaques was significantly associated with age (P < 0.001), log oxidized low-density lipoprotein (oxLDL; P < 0.01), and small apo(a) isoform size (P < 0.05) in a multivariate logistic regression model.

CONCLUSION

These results indicate that the rapidly developing atherosclerosis in advanced CRF appears to be caused by a synergism of different mechanisms, such as malnutrition, inflammation, oxidative stress, and genetic components. Apart from classic risk factors, low vitamin E levels and elevated CRP levels are associated with an increased intima-media area, whereas small molecular weight apo(a) isoforms and increased levels of oxLDL are associated with the presence of carotid plaques.

Antibodies against lysophosphatidylcholine and oxidized LDL in patients with SLE

Lysophosphatidylcholine (LPC) is present in oxidized low density lipoprotein (oxLDL), which is implicated in atherosclerosis. Antibodies to cardiolipin (aCL) and oxLDL (aoxLDL) have been shown to crossreact. LPC is formed by hydrolysis of phosphatidylcholine (PC) in LDL and cell membranes, induced by phospholipase A2 or by oxidation. We here demonstrate the presence of enhanced antibody levels to LPC in 184 patients with SLE as compared to 85 healthy, age-matched controls. The antibody reactivity to LPC was not specifically related to oxidation of the fatty acid moiety in LPC, since LPC containing only the saturated fatty acid palmitic acid showed equivalent antibody levels as LPC containing unsaturated fatty acids. aPC were significantly lower as compared to aLPC, indicating that hydrolysis of PC at the sn-2 position increases the antigenic potential of the molecule. Beta-glycoprotein 1 was a cofactor for aCL, but not for aoxLDL or aLPC, and the antigenicity of these compounds is therefore not directly related to beta2GP1. There was a close correlation between aoxLDL, aCL and aLPC and both LPC and oxLDL competitively inhibited aCL-binding to CL. LPC, oxLDL and CL thus display a common antigenic site, which could be formed by removal of a fatty acid at the sn-2 position, possibly due to the activity to phospholipase A2 and/or oxidation. This study indicates the potential role of LDL-oxidation and phospholipase A2 in SLE.

Antibodies to adult human endothelial cells cross-react with oxidized low-density lipoprotein and beta 2-glycoprotein I (beta 2-GPI) in systemic lupus erythematosus

Cardiovascular manifestations are common in systemic lupus erythematosus (SLE). Oxidized low-density lipoprotein (oxLDL) is implicated in cardiovascular disease, especially atherosclerosis, and cross-reacts with antibodies to cardiolipin (aCL). beta 2-GPI is a plasma protein participating in the coagulating cascade, and is also cofactor for aCL, and some aCL have been shown to be directed against beta 2-GPI and/or complexes between beta 2-GPI and phospholipids. Lysophosphatidylcholine (LPC) is a phospholipid present both in oxLDL and in damaged endothelium, and we recently showed that LPC is involved in the antigenicity of oxLDL. Antibodies to endothelial cells (aEC) correlate with diseases activity in SLE and vasculitis, and we recently showed that aEC are enhanced in cardiovascular disease such as borderline hypertension and early atherosclerosis. aEC were determined using EC from adult V. Saphena Magna. Antibody levels were determined by ELISA. aEC of IgG type were enhanced in 184 patients with SLE compared with 85 healthy controls. There was a close correlation between aoxLDL, aCL, aLPC, a beta 2-GPI and aEC. Binding of sera to EC was competitively inhibited by beta 2-GPI, LPC and oxLDL. Taken together, the data indicate that EC share antigenic epitopes with beta 2-GPI and with oxLDL, especially LPC. Phospholipids in EC membranes may thus be antigenic epitopes. beta 2-GPI may bind to these phospholipids, and become an autoantigen. LPC is formed by oxidation of phospholipids and/or proinflammatory factors leading to activation of phospholipase A2, and the findings indicate the potential role of both lipid oxidation and phospholipase A2 in SLE.

Cloning of monoclonal autoantibodies to epitopes of oxidized lipoproteins from apolipoprotein E-deficient mice. Demonstration of epitopes of oxidized low density lipoprotein in human plasma

Many reactive products may be formed when LDL undergoes lipid peroxidation, which in turn can react with lipids, apoproteins, and proteins, generating immunogenic neoepitopes. Autoantibodies recognizing model epitopes of oxidized low density lipoprotein, such as malondialdehydelysine, occur in plasma and in atherosclerotic lesions of humans and animals. Because apo E-deficient mice develop particularly high titers of such autoantibodies, we used their spleens to clone 13 monoclonal antibodies to various epitopes of oxidized LDL ("E0 antibodies"). Binding and competitive RIAs demonstrated significant differences in fine specificity even between E0 antibodies initially selected for binding to the same screening antigen. For example, some E0 antibodies selected for binding to malondialdehyde-LDL also recognized copper oxidized LDL, acrolein-LDL, or LDL modified by arachidonic or linoleic acid oxidation products. Circulating IgG and IgM autoantibodies binding to copper-oxidized LDL, 4-hydroxynonenal-LDL, acrolein-LDL, and LDL modified with arachidonic or linoleic acid oxidation products were found in apo E-deficient mice, suggesting that the respective antigens are formed in vivo. Epitopes recognized by some of the E0 monoclonal antibodies were also found on human circulating LDL. Each of the E0 monoclonal antibodies immunostained rabbit and human atherosclerotic lesions, and some of them yielded distinct staining patterns in advanced lesions. Together, this suggests that the natural monoclonal antibodies recognize different epitopes of complex structures formed during oxidation of lipoproteins, or epitopes formed independently at different lesion sites. Our data demonstrate that a profound immunological response to a large number of different epitopes of oxidized lipoproteins occurs in vivo. The availability of "natural" monoclonal autoantibodies should facilitate the identification of specific epitopes inducing this response.