Antibodies against lysophosphatidylcholine and oxidized LDL in patients with SLE

Association of angiotensin-converting enzyme (ACE) I/D variation with biochemical parameters and oxidative stress markers in systemic lupus erythematosus patients in west of Iran

PURPOSE

We aimed to study insertion/deletion (I/D) variation (rs4646994) of ACE gene in a group of SLE patients in west of Iran and its possible relationship with oxidative stress.

METHOD AND RESULTS

Genotypes and allele frequencies related to ACE (I/D) variation were determined in 108 SLE patients and 110 gender and age-matched healthy controls using PCR. Neopterin, malondialdehyde (MDA), and serum lipid concentrations were determined by HPLC and enzyme assay respectively. The overall distribution of ACE I/D genotypes in SLE patients was different from that of the control group (P = 0.005). DD genotype compared to ID genotype increased the risk of SLE (OR = 2.57, 95% CI 1.4-4.8, P = 0.003). ID genotype compared to the II genotype decreased the risk of disease (OR = 0.45, 95% CI 0.2-0.99, p = 0.042). SLE patients with DD, ID, and II genotypes had lower paraoxonase (PON) activity and higher serum levels of MDA and neopterin versus control patients. We also detected a significant protective effect against SLE in presence of ACE I alleles and lack of angiotensin II receptor, type 1 (AGTR1) A1166C (NCBI reference SNP id: rs5186), C alleles in this study (OR = 0.31, 95% CI 0.14-0.68, P = 0.002).

CONCLUSIONS

Carriers of the DD genotype of ACE gene with higher serum concentrations of neopterin and MDA, and lower PON activity had a high risk to develop SLE, while ID genotype decreased the risk of disease development by 2.22 times compared to II genotype.

Cardiovascular Involvement in Sjögren’s Syndrome

Sjögren Syndrome (SS) seems to be associated with a greater “overall risk” of cardiovascular (CV) and cerebrovascular events. Although not conventionally considered a feature of the disease, CV events represent a major burden in SS patients. CV risk is the consequence of a complex combination of multiple factors, including traditional risk factors and disease-related mechanisms. A complex relationships between disease-related features, endothelial dysfunction and traditional risk factor has been suggested. Several drugs are available for treating the systemic manifestations of SS, however they have shown positive effects on different outcomes of the disease, but until today the data on the role of these drugs on CV events are scarse. Given these data, the aim of this review was to evaluate the risk of CV risk in primary SS and the effect of the drugs on this manifestation.

Ischemic Heart Disease and Rheumatoid Arthritis-Two Conditions, the Same Background

Rheumatoid arthritis (RA) is one of the most frequent inflammatory rheumatic diseases, having a considerably increased prevalence of mortality and morbidity due to cardiovascular disease (CVD). RA patients have an augmented risk for ischemic and non-ischemic heart disease. Increased cardiovascular (CV) risk is related to disease activity and chronic inflammation. Traditional risk factors and RA-related characteristics participate in vascular involvement, inducing subclinical changes in coronary microcirculation. RA is considered an independent risk factor for coronary artery disease (CAD). Endothelial dysfunction is a precocious marker of atherosclerosis (ATS). Pro-inflammatory cytokines (such as TNFα, IL-1, and IL-6) play an important role in synovial inflammation and ATS progression. Therefore, targeting inflammation is essential to controlling RA and preventing CVD. Present guidelines emphasize the importance of disease control, but studies show that RA- treatment has a different influence on CV risk. Based on the excessive risk for CV events in RA, permanent evaluation of CVD in these patients is critical. CVD risk calculators, designed for the general population, do not use RA-related predictive determinants; also, new scores that take into account RA-derived factors have restricted validity, with none of them encompassing imaging modalities or specific biomarkers involved in RA activity.

Immune responses against oxidized LDL as possible targets for prevention of atherosclerosis in systemic lupus erythematosus

Patients suffering from systemic lupus erythematosus (SLE) are at increased risk of developing cardiovascular disease (CVD) and traditional therapies including statins provide insufficient protection. Impaired removal of apoptotic material is a common pathogenic mechanism in both SLE and atherosclerosis and is considered to be a key factor in the development of autoimmunity. Since oxidized LDL and apoptotic material bind to the same receptors, we aimed to investigate if targeting the oxidized LDL autoimmunity can affect atherosclerosis in SLE. To investigate the possible role of oxidized LDL autoimmunity in the accelerated atherosclerosis associated with SLE we used a hypercholesterolemic SLE mouse model (B6.lpr.ApoE^-/- mice). Promoting LDL tolerance through mucosal immunization with an apolipoprotein B-100 peptide p45 (amino acids 661-680) and cholera toxin B-subunit fusion protein increased regulatory T cells and B cells in mesenteric lymph nodes and reduced plaque development in the aorta by 33%. Treatment with the oxidized LDL-specific antibody Orticumab reduced aortic atherosclerosis by 43%, subvalvular plaque area by 50% and the macrophage content by 31%. The present study provides support for oxLDL as a possible target for prevention of cardiovascular complications in SLE.

Bioactive lipids, inflammation and chronic diseases

Endogenous bioactive lipids are part of a complex network that modulates a plethora of cellular and molecular processes involved in health and disease, of which inflammation represents one of the most prominent examples. Inflammation serves as a well-conserved defence mechanism, triggered in the event of chemical, mechanical or microbial damage, that is meant to eradicate the source of damage and restore tissue function. However, excessive inflammatory signals, or impairment of pro-resolving/anti-inflammatory pathways leads to chronic inflammation, which is a hallmark of chronic pathologies. All main classes of endogenous bioactive lipids - namely eicosanoids, specialized pro-resolving lipid mediators, lysoglycerophopsholipids and endocannabinoids - have been consistently involved in the chronic inflammation that characterises pathologies such as cancer, diabetes, atherosclerosis, asthma, as well as autoimmune and neurodegenerative disorders and inflammatory bowel diseases. This review gathers the current knowledge concerning the involvement of endogenous bioactive lipids in the pathogenic processes of chronic inflammatory pathologies.

Discovering new metabolite alterations in primary sjögren's syndrome in urinary and plasma samples using an HPLC-ESI-QTOF-MS methodology

Sjögren's Syndrome (SjS) is a complex autoimmune disease characterized by the affection of the exocrine glands and the involvement of multiple organs. Although a greater number of biomarker studies have been carried out in recent years, the origin and pathogenesis are not yet well known and therefore there is a need to continue studying this pathology. This work aims to find metabolic changes in biological samples (plasma and urine), which could help identify the metabolic pathways affected by the SjS pathogenesis. The samples collected from SjS patients and healthy volunteers were analyzed by a fingerprinting metabolomic approach based on HPLC-ESI-QTOF-MS methodology. After feature pre-selection by univariate statistical tests, an integrated PLS-DA model using data from urine and plasma was constructed obtaining a good classification between cases and controls (AUROC = 0.839 ± 0.021). 31 and 38 metabolites in plasma and urine, respectively, showed significant differences between healthy volunteers and SjS patients and were proposed for their identification. From them, 12 plasma and 24 urinary metabolites could be annotated. In general, the main metabolic pathways altered in SjS patients were related to the metabolism of phospholipids, fatty acids, and amino acids, specially tryptophan, proline and phenylalanine.

Atherosclerosis and autoimmunity: a growing relationship

Atherosclerosis is regarded as one of the leading causes of mortality and morbidity in the world. Nowadays, it seems that atherosclerosis cannot be defined merely through the Framingham traditional risk factors and that autoimmunity settings exert a remarkable role in its mechanobiology. Individuals with autoimmune disorders show enhanced occurrence of cardiovascular complications and subclinical atherosclerosis. The mechanisms underlying the atherosclerosis in disorders like rheumatoid arthritis, systemic lupus erythematosus, antiphospholipid syndrome, systemic sclerosis and Sjögren's syndrome, seem to be the classical risk factors. However, chronic inflammatory processes and abnormal immune function may also be involved in atherosclerosis development. Autoantigens, autoantibodies, infectious agents and pro-inflammatory mediators exert a role in that process. Being armed with the mechanisms underlying autoimmunity in the etiopathogenesis of atherosclerosis in rheumatic autoimmune disorders and the shared etiologic pathway may result in substantial developing therapeutics for these patients.

Identification of a plasma signature of psychotic disorder in children and adolescents from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort

The identification of an early biomarker of psychotic disorder is important as early treatment is associated with improved patient outcome. Metabolomic and lipidomic approaches in combination with multivariate statistical analysis were applied to identify plasma alterations in children (age 11) (38 cases vs 67 controls) and adolescents (age 18) (36 cases vs 117 controls) preceeding or coincident with the development of psychotic disorder (PD) at age 18 in the Avon Longitudinal Study of Parents and Children (ALSPAC). Overall, 179 lipids were identified at age 11, with 32 found to be significantly altered between the control and PD groups. Following correction for multiple comparisons, 8 of these lipids remained significant (lysophosphatidlycholines (LPCs) LPC(18:1), LPC(18:2), LPC(20:3); phosphatidlycholines (PCs) PC(32:2; PC(34:2), PC(36:4), PC(0-34-3) and sphingomyelin (SM) SM(d18:1/24:0)), all of which were elevated in the PD group. At age 18, 23 lipids were significantly different between the control and PD groups, although none remained significant following correction for multiple comparisons. In conclusion, the findings indicate that the lipidome is altered in the blood during childhood, long before the development of psychotic disorder. LPCs in particular are elevated in those who develop PD, indicating inflammatory abnormalities and altered phospholipid metabolism. These findings were not found at age 18, suggesting there may be ongoing alterations in the pathophysiological processes from prodrome to onset of PD.

Liposomes assembled from a dual drug-tailed phospholipid for cancer therapy

We report a novel dual drug-tailed phospholipid which can form liposomes as a combination of prodrug and drug carrier. An amphiphilic dual chlorambucil-tailed phospholipid (DCTP) was synthesized by a straightforward esterification. With two chlorambucil molecules as hydrophobic tails and one glycerophosphatidylcholine molecule as a hydrophilic head, the DCTP, a phospholipid prodrug, undergoes assembly to form a liposome without any additives by the thin lipid film technique. The DCTP liposomes, as an effective carrier of chlorambucil, exhibited a very high loading capacity and excellent stability. The liposomes had higher cytotoxic effects to cancer cell lines than free DCTP and chlorambucil. The in vivo antitumor activity assessment indicated that the DCTP liposomes could inhibit the tumor growth effectively. This novel strategy of dual drug-tailed phospholipid liposomes may be also applicable to other hydrophobic anticancer drugs which have great potential in cancer therapy.

Lysophosphatidylcholine perpetuates macrophage polarization toward classically activated phenotype in inflammation

Pro-inflammatory macrophages are involved in vascular inflammation and serve as the major effector cells in the pathophysiology of atherosclerosis. Phosphatidylcholine (PC) is a major phospholipid moiety affixed to oxidized low-density lipoprotein (oxLDL) and thought to play important roles in the development of atherosclerosis. In this study we described that a bioactive lipid derivative, lysophosphatidylcholine (lysoPC), generated from hydrolysis of the PC moiety of oxidized LDL, promoted and stabilized a strong M1 phenotype in macrophage polarization. Another derivative, 9-hydroxyoctadecadienoic acid (9-HODE), did not show the similar biological function. Blockade of G protein coupled receptor, G2A, which mediates the signal transduction of lysoPC, diminished the effects of lysoPC on the macrophage polarization toward M1 phenotype. The results provide insights into the new mechanism on how oxidized LDL participates in tissue inflammation in atherosclerosis.

Autoantibodies to posttranslational modifications in rheumatoid arthritis

Autoantibodies have been associated with human pathologies for a long time, particularly with autoimmune diseases (AIDs). Rheumatoid factor (RF) is known since the late 1930s to be associated with rheumatoid arthritis (RA). The discovery of anticitrullinated protein antibodies in the last century has changed this and other posttranslational modifications (PTM) relevant to RA have since been described. Such PTM introduce neoepitopes in proteins that can generate novel autoantibody specificities. The recent recognition of these novel specificities in RA provides a unique opportunity to understand human B-cell development in vivo. In this paper, we will review the three of the main classes of PTMs already associated with RA: citrullination, carbamylation, and oxidation. With the advancement of research methodologies it should be expected that other autoantibodies against PTM proteins could be discovered in patients with autoimmune diseases. Many of such autoantibodies may provide significant biomarker potential.

Autoimmune-mediated reduction of high-density lipoprotein-cholesterol and paraoxonase 1 activity in systemic lupus erythematosus-prone gld mice

OBJECTIVE

To characterize modifications of high-density lipoprotein (HDL) in autoimmune gld mice that may be relevant to premature atherosclerosis in systemic lupus erythematosus, and to assess their relationship to specific aspects of autoimmune disease.

METHODS

HDL cholesterol (HDL-C), apolipoprotein A-I (Apo A-I), paraoxonase 1 (PON1) activity, hepatic gene expression, and HDL biogenesis were measured in aging female gld and wild-type congenic mice. Autoantibodies, lymphoid organs, and cytokines were analyzed by enzyme-linked immunosorbent assay, flow cytometry, and multiplex assay, respectively.

RESULTS

Plasma HDL-C, HDL Apo A-I, and HDL-associated PON1 activity were reduced in aging gld mice in association with the development of autoimmunity, independent of changes in hepatic Apo A-I and PON1 expression or HDL biogenesis. Hepatic induction of the acute-phase reactant serum amyloid A1 resulted in its incorporation into HDL in gld mice. Deletion of the lipid-sensitive receptor G2A in gld mice (G2A-/- gld) attenuated reductions in HDL-C and PON1 activity without altering hepatic Apo A-I and PON1 expression, HDL biogenesis, or levels of acute-phase proinflammatory cytokines. Plasma anti-Apo A-I autoantibodies were elevated in aging gld mice commensurate with detectable increases in Apo A-I immune complexes. Autoantibody levels were lower in aging G2A-/- gld mice compared with gld mice, and anti-Apo A-I autoantibody levels were significantly related to HDL-C concentrations (r=-0.645, P<0.00004) and PON1 activity (r=-0.555, P<0.0007) among autoimmune gld and G2A-/- gld mice.

CONCLUSION

Autoantibodies against Apo A-I contribute to reducing HDL-C and PON1 activity in autoimmune gld mice independently of hepatic HDL biogenesis, suggesting that functional impairment and premature clearance of HDL immune complexes may be principal mechanisms involved.

Accumulation of VEGFR-2+/CD133+ cells and decreased number and impaired functionality of CD34+/VEGFR-2+ cells in patients with SLE

OBJECTIVE

Inflammation and atherosclerosis are the major causes of cardiovascular disease (CVD) in SLE. Both traditional and disease-specific risk factors contribute to the formation of endothelial dysfunction. Endothelial progenitor cells (EPCs) have the ability to restore endothelial integrity. The aim of this study was to determine whether the number and function of EPCs are altered in SLE.

METHODS

Nineteen patients with SLE and 19 controls were analysed. VEGF receptor-2 (VEGFR-2)(+)/CD133(+) and CD34(+)/VEGFR-2(+) cells were quantified by flow cytometry. EPC differentiation was measured by DiI-acLDL/Lectin I staining. Furthermore, apoptosis, proliferation capacity, migration capacity and clonogenic ability of EPCs were determined.

RESULTS

VEGFR-2(+)/CD133(+) cells were enhanced in SLE [215 (37) vs 122 (11) cells/1 x 10(6) lymphocytes; P = 0.029], whereas the number [106 (13) vs 215 (27) cells/1 x 10(6) lymphocytes; P = 0.002] and the proliferation rate [96% (6%) vs 143% (19%); P = 0.008] of CD34(+)/VEGFR-2(+) cells were decreased compared with controls. Additionally, EPCs in SLE showed an increased apoptosis [7% (1.4%) vs 3% (0.4%); P = 0.004], an impaired differentiation [36 (5) vs 121 (20) cells/mm(2); P < 0.001] and a reduced migratory capacity [116% (4%) vs 139% (4%); P = 0.001].

CONCLUSIONS

Our results suggest that the mobilization of progenitor cells is unaffected in SLE, but the diminished number and the altered functionality of circulating CD34(+)/VEGFR-2(+) cells reduce the ability to repair vascular damage and thus may trigger the development of atherosclerosis in SLE.

G2A and LPC: regulatory functions in immunity

The G2A receptor was originally identified by virtue of its transcriptional induction in murine B lymphoid cells in response to oncogenic transformation and treatment with various DNA-damaging agents. While preliminary characterization of cellular responses to G2A overexpression in fibroblastic cell lines suggested that this receptor may negatively regulate cell growth under conditions of proliferative and genotoxic stress, subsequent studies driven by the discovery of lysophosphatidylcholine (LPC) as a regulator of G2A signaling in immunoregulatory cells point to an important role for this receptor in innate and adaptive immunity.

The role of innate and adaptive immunity to oxidized low-density lipoprotein in the development of atherosclerosis

Atherosclerosis is a chronic inflammatory process of the arterial wall associated with systemic and local immune responses to various antigens, oxidized low-density lipoprotein (oxLDL) being the most significant. Both IgM and IgG antibodies to oxLDL are produced during atherosclerosis. Some studies have shown that elevated levels of antibody to oxLDL correlate with the degree of atherosclerosis. Other studies reported that immunization of experimental animals with oxLDL induces high levels of antibodies to oxLDL, with decreased atherosclerosis, suggesting that the immune response to oxLDL may be antiatherogenic. The accelerated development of atherosclerosis has been observed in patients with systemic autoimmune diseases. In patients with antiphospholipid syndrome (APS), beta2-glycoprotein I (beta2GPI) is a major antigenic target for anticardiolipin antibodies (aCLs). We recently reported that oxLDL interacts with beta2GPI via oxLDL-derived specific ligands, such as 7-ketocholesteryl-9-carboxynonanoate (oxLig-1) to form complexes. In vitro, anti-beta2GPI autoantibodies bind to oxLDL/beta2GPI complexes that are actively taken up by macrophages via Fcgamma receptors. Circulating oxLDL/beta2GPI complexes were detected in patients with systemic lupus erythematosus (SLE) and APS, at higher levels than in healthy individuals. Autoantibodies against these complexes were also present; however, IgG anti-oxLig-1/beta2GPI antibody levels in SLE patients with APS were significantly higher than those in SLE patients without APS and those in healthy individuals.

Quantification of lysophosphatidylcholines and phosphatidylcholines using liquid chromatography-tandem mass spectrometry in neonatal serum

We established an improved method for quantification of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) molecular species in neonatal serum using high-performance liquid chromatography coupled tandem mass spectrometry (LC-MS/MS). A multiple reaction monitoring (MRM) mode of positive ionization for MS/MS was used. The method involved purification of phospholipids by solid phase extraction (SPE) from a 20-microl minimum specimen of serum. The assayed values of authentic 16:0-LPC and 18:0-LPC showed a linear response, and our quantitative results showed high precision for the all species of PC and LPC. Then, we quantified PC and LPC in adult and neonatal serum and compared them. Day 0-1 neonatal serum 16:0-, 18:0-, 18:1-, 18:2-LPC levels were significantly lower than adult ones. All species LPC levels in the day 0-1 neonates were significantly lower than day 4-8 neonates. Day 0-1 neonatal serum 16:0/18:2-, 18:0/18:2-PC levels were significantly lower than adult ones. Our method is advantageous for precise assessments of the relationships between PCs/LPCs levels and neonatal infectious diseases.

New Facet of Antiphospholipid Antibodies

Since the aCL test was first described, several reports have described the heterogeneity of aPL, which binds to different anionic phospholipids, proteins, or to a phospholipid-protein complex. It has been recently reported that antiphospholipids (aPLs) from the sera of patients with the antiphospholipid syndrome (APS) are able to bind some newly identified antigens, the lyso(bis)phosphatidic acid (LBPA), lipid restricted to the late endosomes, and the sulfatides, acidic glycosphingolipids involved in the hemostatic process. Of interest, aLBPAs are present in the sera of a large number of patients with APS showing similar sensitivity and specificity compared to anti-beta(2) glycoprotein I antibodies (abeta(2)-GPIs) and close association with lupus anticoagulant. Moreover, beta(2)-GPI binds to sulfatides and the majority of the aPL reacting with cardiolipin-beta(2)-GPI complex also react with the sulfatide-beta(2)-GPI complex. Different mechanisms involved in the production of autoantibodies in autoimmune diseases have been proposed and, among them, apoptosis or programmed cell death seems to play a leading role. The relocation of CL and its metabolites during apoptosis may represent an in vivo trigger for the generation of aCL, and the higher reactivity of sera from APS patients to monolysocardiolipin, the immediate degradation product of mitochondrial CL validates this hypothesis. Finally, increasing evidence suggests that oxidative stress could be a pathogenic link between aPL and thrombosis, and antioxidant treatment may have some efficacy in preventing the clinical manifestations of this syndrome.

Inflammation and Accelerated Atherosclerosis: Basic Mechanisms

This article summarizes knowledge of the pathogenic mechanisms in autoimmune rheumatic diseases as risk factors for accelerated atherosclerosis. The studies described support a role for immunologic-inflammatory mechanisms in the pathogenesis of atherosclerosis. This immunologic-inflammatory state is evident in many autoimmune diseases, but also in the general population lacking an overt autoimmune disease. The ability to immunomodulate atherosclerosis (currently only experimental) should lead to future research into the mechanisms and treatment of atherosclerosis, the leading cause of death in the Western world.

Lysophosphatidylcholine induces tPA gene expression through CRE-dependent mechanism

Lysophosphatidylcholine (lysoPC) is implicated in the development of atherosclerosis and certain autoimmune diseases, and is reported to induce tissue-type plasminogen activator (tPA) at the protein level in endothelial cells. This study was designed to investigate the effect of lysoPC on tPA gene expression and the underlying molecular mechanisms in cultured endothelial cells. LysoPC transiently induced the mRNA expression of tPA in endothelial cells. LysoPC also induced the mRNA expression of urokinase-type plasminogen activator (uPA), uPA receptor, and plasminogen activator inhibitor-1, but the kinetics were different from that of tPA. Promoter analysis revealed that the cyclic AMP-responsive element of the tPA gene (tPACRE) is required for lysoPC-induced tPA expression. Furthermore, an electrophoresis mobility shift assay showed that lysoPC increased the binding activity of CRE binding protein to tPACRE. These results indicated that lysoPC transcriptionally upregulated the gene expression of tPA in endothelial cells, at least in part, via tPACRE activation.

Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in SLE patients

OBJECTIVE

Description of the various autoantibodies that can be detected in patients with systemic lupus erythematosus (SLE).

METHODS

A literature review, using the terms "autoantibody" and "systemic lupus erythematosus", was conducted to search for articles on autoantibodies in SLE, their target antigens, association with disease activity, or other clinical associations.

RESULTS

One hundred sixteen autoantibodies were described in SLE patients. These include autoantibodies that target nuclear antigens, cytoplasmic antigens, cell membrane antigens, phospholipid-associated antigens, blood cells, endothelial cells, and nervous system antigens, plasma proteins, matrix proteins, and miscellaneous antigens. The target of autoantibody, the autoantigen properties, autoantibody frequencies in SLE, as well as clinical associations, and correlation with disease activity are described for all 116 autoantibodies.

CONCLUSIONS

SLE is the autoimmune disease with the largest number of detectable autoantibodies. Their production could be antigen-driven, the result of polyclonal B cell activation, impaired apoptotic pathways, or the outcome of idiotypic network dysregulation.

Lipid peroxidation is enhanced in patients with systemic lupus erythematosus and is associated with arterial and renal disease manifestations

OBJECTIVE

Cardiovascular disease with premature atherosclerosis is common in patients with systemic lupus erythematosus (SLE). We previously identified elevated levels of oxidized low-density lipoprotein (OxLDL) together with elevated levels of autoantibodies related to OxLDL as risk factors for cardiovascular disease in female patients with SLE. Autoantibodies to OxLDL are common in SLE and cross-react with anticardiolipin antibodies (aCL). We therefore hypothesized that lipid peroxidation is enhanced in patients with SLE in general.

METHODS

One hundred forty-seven female patients with SLE and 60 age- and sex-matched controls were compared. A monoclonal antibody to oxidized phospholipids, EO6, was used to determine oxidation epitopes on LDL. Anti-OxLDL and autoantibodies to malondialdehyde (MDA)-modified LDL, cardiolipin, and oxidized aCL were determined by chemiluminescence technique.

RESULTS

As determined by binding of EO6, patients with SLE had a higher level of oxidized phospholipids on LDL (P = 0.005) compared with controls. The level of OxLDL (e.g., oxidized phospholipid/apolipoprotein B) was associated with arterial disease (P = 0.006) and renal manifestations (P = 0.04). As reported previously, levels of aCL, autoantibodies to OxLDL, and autoantibodies to MDA-modified LDL were enhanced and were closely correlated in SLE. Anticardiolipin antibodies from these SLE patients recognized mainly oxidized forms of cardiolipin, indicating that antigenic epitopes on cardiolipin are related to lipid peroxidation in patients with SLE.

CONCLUSION

In general, patients with SLE (particularly those with cardiovascular disease) had more oxidized epitopes on LDL compared with controls. Furthermore, aCL in these patients recognized epitopes generated during lipid peroxidation. Thus, "neo" self antigens on lipoproteins, generated during oxidation, are present in SLE and may be of importance for the development of premature cardiovascular disease and possibly also for other autoimmune phenomena observed in SLE.

Dyslipidemia associated with atherosclerotic disease systemically alters dendritic cell mobilization

High LDL and/or low HDL are risk factors for atherosclerosis and are also a common clinical feature in systemic lupus erythematosus, rheumatoid arthritis, and psoriasis. Here, we show that changes in lipid profiles that reflect atherosclerotic disease led to activation of skin murine dendritic cells (DCs) locally, promoted dermal inflammation, and induced lymph node hypertrophy. Paradoxically, DC migration to lymph nodes was impaired, suppressing immunologic priming. Impaired migration resulted from inhibitory signals generated by platelet-activating factor (PAF) or oxidized LDL that acts as a PAF mimetic. Normal DC migration and priming was restored by HDL or HDL-associated PAF acetylhydrolase (PAFAH), which mediates inactivation of PAF and oxidized LDL. Thus, atherosclerotic changes can sequester activated DCs in the periphery where they may aggravate local inflammation even as they poorly carry out functions that require their migration to lymph nodes. In this context, HDL and PAFAH maintain a normally functional DC compartment.

A glance at G-protein-coupled receptors for lipid mediators: a growing receptor family with remarkably diverse ligands

A plethora of lipid-like molecules known to act as intracellular second messengers are now recognized to signal cells through plasma membrane 7 transmembrane G-protein-coupled receptors (GPCRs). This has been the result of a decade-long genetic hunt for novel sequences encoding 7 transmembrane receptor proteins and the efforts to pair novel sequences with biologically active substances of (partly) unknown molecular mechanism of action. Identification of novel GPCR ligand pairs represents the first step to shed more light into the mode of action of novel cellular signaling molecules in human health and disease and might represent a fruitful source for the development of new drugs, judged on the successful history of GPCR as drug targets. Since 2000, more than 16 reports became available on lipid mediators--as diverse as lysophospholipids, arachidonic acid metabolites, short-, medium-, and long-chain fatty acids as well as steroid-like molecules--exerting their effects as extracellular mediators via rhodopsin-like family GPCRs. These reports have opened new avenues for research in human lipid receptor physiology and pharmacology. Here, the current knowledge on the recently deorphanized lipid receptors, including their isolation, expression pattern, function, and possible physiological or pathological roles will be reviewed.

Oxidative stress in systemic lupus erythematosus and antiphospholipid syndrome: a gateway to atherosclerosis

Vascular disease and atherosclerosis are significant clinical features of systemic lupus erythematosus and antiphospholipid syndrome. Oxidation is one of the major factors responsible for atheroma development in this context. Anticardiolipin antibodies seem to play an important role by inducing nitric oxide and superoxide production, resulting in enhanced levels of plasma peroxynitrite, which is a powerful pro-oxidant substance. Furthermore, direct interference of these antibodies with paraoxonase activity, a high-density lipoprotein-related anti-oxidant enzyme, would contribute to the oxidative stress found in these conditions. The accelerated process of atherogenesis found in these diseases can represent a useful model for the study of atherosclerosis in the general population.

High-Throughput Quantification of Lysophosphatidylcholine by Electrospray Ionization Tandem Mass Spectrometry

Background: Lysophosphatidylcholine (LPC) has been suggested to play a functional role in various diseases, including atherosclerosis, diabetes, and cancer mediated by LPC-specific G-protein-coupled receptors. Initial studies provided evidence for a potential use of LPC as diagnostic maker. However, existing methodologies are of limited value for a systematic evaluation of LPC species concentrations because of complicated, time-consuming procedures. We describe a methodology based on electrospray ionization tandem mass spectrometry (ESI-MS/MS) applicable for high-throughput LPC quantification.

Methods: Crude lipid extracts of EDTA-plasma samples were used for direct flow injection analysis. LPC 13:0 and LPC 19:0 were added as internal standards, and the ESI-MS/MS was operated in the parent-scan mode for m/z 184. Quantification was achieved by standard addition. Data processing was highly automated by use of the mass spectrometer software and self-programmed Excel macros.

Results: The calibrators LPC 16:0, LPC 18:0, and LPC 22:0 showed a linear response independent of sample dilution and plasma cholesterol concentration for both internal standards. The within-run imprecision (CV) was 3% for the major and 12% for the minor species, whereas the total imprecision was ∼12% for the major and 25% for the minor species. The detection limit was &lt;1 μmol/L.

Conclusion: The developed ESI-MS/MS methodology with an analysis time of 2 min/sample, simple sample preparation, and automated data analysis allows high-throughput quantification of distinct LPC species from plasma samples, which could be a valuable tool for the evaluation of LPC as diagnostic marker.

Antibodies to high-density lipoprotein and beta2-glycoprotein I are inversely correlated with paraoxonase activity in systemic lupus erythematosus and primary antiphospholipid syndrome

OBJECTIVE

To determine the prevalence of anti-high-density lipoprotein (anti-HDL) antibodies and to establish a possible relationship between anti-HDL, anticardiolipin antibodies (aCL), anti-beta(2)-glycoprotein I (anti-beta(2)GPI), and paraoxonase (PON) activity in patients with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (APS).

METHODS

Thirty-two patients with SLE and 36 with primary APS were enrolled in a cross-sectional study. Twenty age- and sex-matched healthy subjects were used as controls. Serum levels of IgG and IgM aCL, anti-beta(2)GPI, and antiprothrombin antibodies and IgG anti-HDL were measured by enzyme-linked immunosorbent assay. Total cholesterol, HDL cholesterol, HDL(2), and HDL(3) were determined by standard enzymatic techniques. PON activity was assessed by quantification of nitrophenol formation, and total antioxidant capacity (TAC) by chemiluminescence.

RESULTS

Levels of total HDL, HDL(2), and HDL(3) were reduced in patients with SLE compared with controls (mean +/- SD 0.51 +/- 0.3, 0.37 +/- 0.3, and 0.14 +/- 0.1 mmoles/liter, respectively, versus 1.42 +/- 0.9, 1.01 +/- 0.7, and 0.40 +/- 0.2). Patients with SLE and primary APS had higher titers of anti-HDL antibodies and lower PON activity than controls. In the SLE population, PON activity was inversely correlated with IgG anti-HDL titers (r = -0.48, P = 0.005) whereas in the primary APS population, IgG anti-beta(2)GPI was the only independent predictor of PON activity (r = -0.483, P = 0.003). In the SLE group, anti-HDL was inversely correlated with TAC (r = -0.40, P < 0.02), and PON activity was positively correlated with TAC (r = 0.43, P < 0.02).

CONCLUSION

IgG anti-HDL and IgG anti-beta(2)GPI antibodies are associated with reduced PON activity in patients with SLE and primary APS. Since the physiologic role of PON is to prevent low-density lipoprotein oxidation with its attendant atherogenic effects, the reported interactions may be relevant to the development of atherosclerosis in SLE and primary APS.

Lysophosphatidylcholine as a ligand for immunoregulation

Despite the recognized effects of lysophosphatidylcholine upon cells of the immune system and its association with inflammatory processes, its mechanism of action has remained poorly characterized. Our recent identification of the first lysophosphatidylcholine receptor as an immunoregulatory G protein-coupled receptor named G2A whose genetic ablation results in the development of inflammatory autoimmune disease has, therefore, provided a new perspective on the role of this lysophospholipid as a modulator of immune responses. This commentary discusses the biological properties of lysophosphatidylcholine as an immunoregulatory ligand for cells of the innate and adaptive arms of the immune system. Although we focus primarily on ligand interactions with G2A, we also discuss the issue of possible functional redundancy with other receptors with recently established ligand specificities towards phosphorylcholine-containing lysolipids including lysophosphatidylcholine.

Immune mechanisms in atherosclerosis

Atherosclerosis is an inflammatory disease. Its lesions are filled with immune cells that can orchestrate and effect inflammatory responses. In fact, the first lesions of atherosclerosis consist of macrophages and T cells. Unstable plaques are particularly rich in activated immune cells, suggesting that they may initiate plaque activation. We have seen a rapid increase in the understanding of the mechanisms that govern the recruitment, differentiation, and activation of immune cells in atherosclerosis. Experimental research has identified several candidate antigens, and there are encouraging data suggesting that immune modulation as well as immunization can reduce the progression of the disease. This review provides an overview of our current understanding of the role of immune mechanisms in atherosclerosis.

Low density lipoprotein oxidation, antioxidants, and atherosclerosis

Oxidized low density lipoproteins (LDLs) are believed to be the most atherogenic form of LDL. However, although a number of experimental data support this concept, the protective role of antioxidants that may prevent LDL oxidation in atherosclerosis is only partially confirmed by studies in humans. Observational and epidemiologic data as well as randomized trials failed to provide clear-cut indications because of mixed results on the protective role of antioxidants against cardiovascular diseases. In spite of the lack of a general consensus, recent data reinforce the concept that a regular intake of antioxidants present in food blocks the progression of atherosclerosis and that the reduced oxidisability of LDL may represent a good marker to follow the action of antioxidants. When it becomes possible to monitor the efficacy of any antioxidant therapy with validated markers of oxidation, the potential influence of vitamins and antioxidants on coronary artery disease will eventually be resolved.