Short- and long-term elevation of autoantibody titers against oxidized LDL in patients with acute coronary syndromes. Role of the lipoprotein-associated phospholipase A2 and the effect of atorvastatin treatment.

Oxidized low-density lipoprotein (oxLDL) is immunogenic while oxidized phospholipids (oxPL) formed on oxLDL and lysophosphatidylcholine (lyso-PC) generated during LDL oxidation through the hydrolysis of oxPL by the lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), significantly contribute to oxLDL immunogenicity. We determined the autoantibody titers against various forms of mildly oxLDL in patients with acute coronary syndromes without persistent elevation of the ST segment (NSTE-ACS) and with undetectable serum levels of lipoprotein (a). Moreover, the effect of early atorvastatin administration on these autoantibody titers was evaluated. From the 133 consecutive NSTE-ACS patients, 55 were eligible for the study. Thirty-four received atorvastatin (group A), whereas 21 did not received any hypolipidemic therapy (group B). Two forms of copper-oxidized LDL were prepared at the end of propagation or decomposition phase (oxLDL(P) or oxLDL(D), respectively). Similar types of oxLDL were prepared after previous inactivation of the endogenous Lp-PLA(2) [oxLDL(-)]. In group B, autoantibody titers of IgG class against oxLDL(P) and oxLDL(D) were elevated at 1 month of follow-up to reach the baseline values 3 months afterwards. By contrast the titers against oxLDL(-)(P) and oxLDL(-)(D) increased at 1 month of follow-up and remained elevated for up to 6 months of follow-up. Atorvastatin treatment prevented the elevation of autoantibody titers against all forms of oxidized LDL. We conclude that a short-term immune response against oxLDL(P) and oxLDL(D) (enriched in lyso-PC) and a chronic immune response against oxLDL(-)(P) and oxLDL(-)(D) (enriched in oxPL) are observed after an NSTE-ACS, suggesting an important role of the LDL-associated Lp-PLA(2) in modulating these immune responses. Early atorvastatin treatment prevents both immune responses; however, the clinical significance of this effect remains to be established.

Patients with early rheumatoid arthritis exhibit elevated autoantibody titers against mildly oxidized low-density lipoprotein and exhibit decreased activity of the lipoprotein-associated phospholipase A2.

Rheumatoid arthritis is a chronic inflammatory disease, associated with an excess of cardiovascular morbidity and mortality due to accelerated atherosclerosis. Oxidized low-density lipoprotein (oxLDL), the antibodies against oxLDL and the lipoprotein-associated phospholipase A2 (Lp-PLA2) may play important roles in inflammation and atherosclerosis. We investigated the plasma levels of oxLDL and Lp-PLA2 activity as well as the autoantibody titers against mildly oxLDL in patients with early rheumatoid arthritis (ERA). The long-term effects of immunointervention on these parameters in patients with active disease were also determined. Fifty-eight ERA patients who met the American College of Rheumatology criteria were included in the study. Patients were treated with methotrexate and prednisone. Sixty-three apparently healthy volunteers also participated in the study and served as controls. Three different types of mildly oxLDL were prepared at the end of the lag, propagation and decomposition phases of oxidation. The serum autoantibody titers of the IgG type against all types of oxLDL were determined by an ELISA method. The plasma levels of oxLDL and the Lp-PLA2 activity were determined by an ELISA method and by the trichloroacetic acid precipitation procedure, respectively. At baseline, ERA patients exhibited elevated autoantibody titers against all types of mildly oxLDL as well as low activity of the total plasma Lp-PLA2 and the Lp-PLA2 associated with the high-density lipoprotein, compared with controls. Multivariate regression analysis showed that the elevated autoantibody titers towards oxLDL at the end of the decomposition phase of oxidation and the low plasma Lp-PLA2 activity are independently associated with ERA. After immunointervention autoantibody titers against all types of oxLDL were decreased in parallel to the increase in high-density lipoprotein-cholesterol and high-density lipoprotein-Lp-PLA2 activity. We conclude that elevated autoantibody titers against oxLDL at the end of the decomposition phase of oxidation and low plasma Lp-PLA2 activity are feature characteristics of patients with ERA, suggesting an important role of these parameters in the pathophysiology of ERA as well as in the accelerated atherosclerosis observed in these patients.

Autoantibody titers against OxLDL are correlated with Achilles tendon thickness in patients with familial hypercholesterolemia.

Achilles tendon xanthomas are associated with increased cardiovascular risk in patients with familial hypercholesterolemia (FH). Oxidized low density lipoprotein (OxLDL), the antibodies against OxLDL, and the LDL-associated phospholipase A(2) (Lp-PLA(2)) may play important roles in atherogenesis. We investigated the possible association between plasma levels of OxLDL, Lp-PLA(2) activity, and autoantibody titers against various types of mildly OxLDL with Achilles tendon thickness (ATT). ATT was determined by sonography in 80 unrelated heterozygous FH patients. Three different types of mildly OxLDL were prepared: OxLDL(L), OxLDL(P), and OxLDL(D), at the end of the lag, propagation, and decomposition phases of oxidation, respectively. Similar types of OxLDL were also prepared after inactivation of the LDL-associated Lp-PLA(2). These types were denoted OxLDL(-)(L), OxLDL(-)(P), and OxLDL(-)(D). FH patients exhibited significantly higher plasma OxLDL levels and serum IgG titers against OxLDL(P) and OxLDL(D) compared with 40 normolipidemic apparently healthy controls. ATT values were positively correlated with autoantibody titers against OxLDL(P) and OxLDL(D); however, in multiple regression analysis, ATT was independently associated only with the autoantibody titers against OxLDL(D). We conclude that the IgG autoantibody titers against OxLDL(D) but not OxLDL or Lp-PLA(2) may play an important role in the pathogenesis of Achilles tendon xanthomas in FH patients.

The low-density lipoprotein (LDL)-associated PAF-acetylhydrolase activity and the extent of LDL oxidation are important determinants of the autoantibody titers against oxidized LDL in patients with coronary artery disease.

The oxidation of low-density lipoprotein (LDL) induces immunogenic epitopes, many of which are due to oxidatively modified phospholipids (oxPL). Lysophosphatidylcholine (lyso-PC) which is generated during LDL oxidation through the hydrolysis of oxPL by LDL-associated PAF-acetylhydrolase (PAF-AH) is also immunogenic. We investigated whether the LDL-associated PAF-AH and the extent of LDL oxidation influence the autoantibody titers against oxidized LDL (oxLDL) in patients with stable angina as well as in apparently healthy volunteers. Three types of copper-oxidized LDL, were prepared at the end of the lag, propagation or decomposition phase (oxLDL(L), oxLDL(P) and oxLDL(D), respectively). Similar types of oxidized LDL were prepared after previous inactivation of endogenous PAF-AH [oxLDL(-)]. All these types of oxLDL as well as malondialdehyde-modified LDL (MDA-LDL) were used as antigens. Antibody titers against the above antigens were measured with an ELISA method in the serum of 65 patients with stable angina and 47 apparently healthy volunteers. Both groups exhibited higher autoantibody titers against each type of oxLDL(-) compared to the respective type of oxLDL (P<0.00001). In both groups autoantibody titers were higher when the oxLDL(P) and oxLDL(D) or oxLDL(-)(P) and oxLDL(-)(D) were used as antigens compared to oxLDL(L) (P<0.04) or to oxLDL(-)(L), respectively (P<0.0001 for all comparisons). Patients had significantly higher titers against all types of oxLDL (enriched in lyso-PC) and oxLDL(-) (enriched in intact oxPL) compared to controls. Autoantibody titers against MDA-LDL did not differ between patients and controls. Multivariate logistic regression analysis showed that among the autoantibody titers measured only those towards oxLDL(P) are associated with a significantly higher risk for coronary artery disease. LDL-associated PAF-AH activity may play an important role in decreasing the overall immunogenicity of oxLDL, whereas the extent of LDL oxidation seems to modulate the epitopes formed on oxLDL. Lyso-PC, a major component of oxLDL(P), could be mainly responsible for the elevated autoantibody titers against oxLDL in patients with stable angina.

Atherogenic lipid profile is a feature characteristic of patients with early rheumatoid arthritis: effect of early treatment--a prospective, controlled study.

We investigated lipid profiles and lipoprotein modification after immuno-intervention in patients with early rheumatoid arthritis (ERA). Fifty-eight patients with ERA who met the American College of Rheumatology (ACR) criteria were included in the study. These patients had disease durations of less than one year and had not had prior treatment for it. Smokers or patients suffering from diabetes mellitus, hypothyroidism, liver or kidney disease, Cushing's syndrome, obesity, familiar dyslipidemia and those receiving medications affecting lipid metabolism were excluded from the study. Sixty-three healthy volunteers (controls) were also included. Patients were treated with methotrexate and prednisone. Lipid profiles, disease activity for the 28 joint indices score (DAS-28) as well as ACR 50% response criteria were determined for all patients. The mean DAS-28 at disease onset was 5.8 +/- 0.9. After a year of therapy, 53 (91.3%) patients achieved the ACR 20% response criteria, while 45 (77.6%) attained the ACR 50% criteria. In addition, a significant decrease in the DAS-28, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were observed. ERA patients exhibited higher serum levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglycerides, whereas their serum high-density lipoprotein cholesterol (HDL-C) levels were significantly lower compared to controls. As a consequence, the atherogenic ratio of TC/HDL-C as well as that of LDL-C/HDL-C was significantly higher in ERA patients compared to controls. After treatment, a significant reduction of the atherogenic ratio of TC/HDL-C as well as that of LDL-C/HDL-C was observed, a phenomenon primarily due to the increase of serum HDL-C levels. These changes were inversely correlated with laboratory changes, especially CRP and ESR. In conclusion, ERA patients are characterized by an atherogenic lipid profile, which improves after therapy. Thus, early immuno-intervention to control disease activity may reduce the risk of the atherosclerotic process and cardiovascular events in ERA patients.

Lipoprotein-associated phospholipase A2 activity is a marker of small, dense LDL particles in human plasma.

BACKGROUND: Recent clinical studies showed that lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a predictor for incident atherosclerotic disease. We have previously shown that among the LDL subfractions, Lp-PLA(2) activity is preferentially associated with the atherogenic small, dense (sdLDL) particles in vitro. We investigated whether Lp-PLA(2) could be a marker of sdLDL in human plasma. METHODS: One hundred and seventy-six individuals participated in the study. LDL subclass analysis was performed by polyacrylamide gel electrophoresis. Lp-PLA(2) activity and mass were determined in total plasma and in apolipoprotein B-depleted plasma (HDL-Lp-PLA(2)). Non-HDL-Lp-PLA(2) activity and mass were calculated by subtracting the HDL-Lp-PLA(2) from total plasma Lp-PLA(2). RESULTS: On the basis of the LDL subclass analysis, participants were categorized into phenotype A and non-A (total cholesterol mass of the sdLDL subfractions < or =0.155 and >0.155 mmol/L, respectively). Unlike total plasma Lp-PLA(2) mass, total plasma Lp-PLA(2) activity and non-HDL-Lp-PLA(2) activity and mass were significantly higher in persons with phenotype non-A compared with persons with phenotype A, whereas HDL-Lp-PLA(2) activity and mass were lower in persons with phenotype non-A compared with phenotype A. Total plasma activity and non-HDL-Lp-PLA(2) activity and mass, but not Lp-PLA(2) mass, were correlated with sdLDL-cholesterol mass, proportion, and mean LDL particle size. In multiple regression analysis, total plasma and non-HDL-Lp-PLA(2) activities were the second best predictors of the presence of sdLDL particles in human plasma after serum triglyceride concentrations. At serum triglyceride concentrations >1.356 mmol/L, total plasma and non-HDL-Lp-PLA(2) activity added significantly to the prediction of the presence of sdLDL in plasma. CONCLUSIONS: Lp-PLA(2) activity, but not the enzyme mass, is a marker of sdLDL in human plasma.

Lack of association between carotid intima-media thickness and PAF-acetylhydrolase mass and activity in patients with primary hyperlipidemia.

Carotid intima media thickness (IMT), represents an important clinical indicator of early atherosclerosis. Human plasma platelet-activating factor acetylhydrolase (PAF-AH) is an enzyme primarily associated with low-density lipoprotein (LDL) while a small proportion of enzymatic activity is also associated with high-density lipoprotein (HDL). Plasma paraoxonase 1 (PON1) is an esterase exclusively associated with HDL. The authors investigated the possible relationship between carotid IMT and the plasma levels of PAF-AH mass and activity as well as the PON1 activity in hyperlipidemic patients. One hundred unrelated patients with primary hyperlipidemia and 67 age-and sex-matched normolipidemic apparently healthy volunteers participated in the study. The PAF-AH activity in total plasma and in HDL-rich plasma (HDL-PAF-AH activity), the plasma PAF-AH mass, and the serum PON1 activities toward paraoxon and phenyl acetate were determined. The plasma PAF-AH mass and activity were higher in hyperlipidemic patients compared to controls, whereas the HDL-PAF-AH activity, as well as the serum PON1 activities were not significantly different between the studied groups. When hyperlipidemic patients were divided into 2 subgroups according to their IMT values (IMT <0.7 mm and IMT > or =0.7 mm) patients with IMT > or =0.7 mm had significantly higher age, and serum triglyceride concentrations, whereas no difference was found in the plasma PAF-AH mass and activity as well as in the HDL-PAF-AH activity between the 2 studied subgroups. The same phenomenon was observed for serum PON1 activities. In a multivariate analysis, only the age was significantly correlated with IMT values (p<0.05). Neither the total plasma PAF-AH mass and activity nor the HDL-PAF-AH activity are associated with early carotid atherosclerosis.

Reduced PAF-acetylhydrolase activity associated with Lp(a) in patients with coronary artery disease.

Lipoprotein(a) [Lp(a)] may be an independent risk factor for coronary artery disease (CAD). Lp(a) is enriched in platelet activating factor acetylhydrolase (PAF-AH), an enzyme which hydrolyzes and inactivates platelet activating factor (PAF) and oxidized phospholipids that are implicated in atherogenesis. We determined the mass and catalytic properties of the Lp(a)-associated PAF-AH in 28 CAD patients in relation to the LDL-associated enzyme ones. Results were then compared to those of 30 control subjects and 16 unrelated patients with primary hypercholesterolemia (Type IIA dyslipidemia) before and after atorvastatin therapy. The mass, the specific activity and kinetic constants of the Lp(a)-associated PAF-AH were significantly lower in CAD patients compared to those of either controls or hypercholesterolemic patients, a phenomenon not observed for LDL-associated PAF-AH. The enzyme specific activity and kinetic constants were significantly increased after removal of apo(a) from Lp(a) by reductive cleavage, which was not found in the control population, suggesting that the apo(a) moiety of Lp(a) from CAD patients may play an important role in the observed lower catalytic efficiency of PAF-AH. The reduced PAF-AH mass and specific activity on Lp(a) is a feature characteristic of this lipoprotein in CAD patients and may lead to a diminished capability of Lp(a) to degrade proinflammatory phospholipids. The consequences of this phenomenon as regards the pathophysiological role of Lp(a) in atherosclerosis remain to be established.

The PON1 M55L gene polymorphism is associated with reduced HDL-associated PAF-AH activity.

The platelet-activating factor acetylhydrolase activity associated with high density lipoprotein (HDL-PAF-AH) may substantially contribute to the antioxidant, anti-inflammatory, and overall antiatherogenic effects of HDL. Two enzymes associated with HDL express PAF-AH catalytic activity, PAF-AH itself and paraoxonase-1 (PON1). The relative contribution of these enzymes in the expression of PAF-AH activity on HDL remains to be established. We investigated whether the PON1 polymorphisms (M55L and Q192R) or the PAF-AH polymorphism V379A could affect the PAF-AH activity associated with HDL in both normolipidemic and dyslipidemic (type IIA and IIB) populations. We show for the first time that the PON1 M55L polymorphism significantly affects the HDL-PAF-AH activity in all studied groups, the PON1 L55L individuals having lower enzyme activity compared to those having 1 M and 2 M alleles. No differences in the HDL content concerning the major apolipoprotein and lipid constituents were observed between individuals carrying the PON1 L55L and those with the M55M polymorphism. Our results provide evidence that PON1 significantly contributes to the pool of HDL-PAF-AH activity in human plasma, and suggest that the low PAF-AH activity in HDL carrying the PON1 L alloenzyme may be an important factor contributing to the low efficiency of this HDL in protecting LDL against lipid peroxidation.