Paraoxonase and platelet-activating factor acetylhydrolase activities in lipoproteins of beta-thalassemia/hemoglobin E patients.

BACKGROUND: Iron-induced oxidative stress may be implicated in the alteration of the lipoprotein-associated antioxidant enzymes paraoxonase 1 (PON1) and platelet-activating factor acetylhydrolase (PAF-AH), leading to atherosclerosis-related vascular complication in patients with beta-thalassemia hemoglobin E (beta-thal/Hb E). METHODS: Plasma and lipoprotein enzyme activities of PON1 and PAF-AH were studied in 13 mild to moderate and 15 severe cases of beta-thal/Hb E in comparison with 15 normal subjects. RESULTS: PON1 activity was significantly reduced in association with oxidative stress in the patients. There were significant correlations between high-density lipoprotein (HDL)-PON1 activity and oxidative stress markers, including plasma levels of alpha-tocopherol (r=0.694 p<0.001) and the ratio of cholesteryl linoleate to cholesteryl oleate (CL/CO, r=0.662, p<0.001) in HDL. On the other hand, PAF-AH activity was markedly increased in patients by approximately two-fold and three- to four-fold in plasma and lipoproteins, respectively. Significant correlations of low-density lipoprotein (LDL) and HDL-PAF-AH activity with plasma iron, alpha-tocopherol and the CL/CO ratio were also demonstrated. CONCLUSIONS: We suggest that impairment of PON1 activity may be directly caused by oxidative damage, while increased PAF-AH activity possibly results from oxidative stress-induced inflammatory response in beta-thal/Hb E patients.     

Paraoxonase inhibits high-density lipoprotein oxidation and preserves its functions. A possible peroxidative role for paraoxonase.

HDL levels are inversely related to the risk of developing atherosclerosis. In serum, paraoxonase (PON) is associated with HDL, and was shown to inhibit LDL oxidation. Whether PON also protects HDL from oxidation is unknown, and was determined in the present study. In humans, we found serum HDL PON activity and HDL susceptibility to oxidation to be inversely correlated (r2 = 0.77, n = 15). Supplementing human HDL with purified PON inhibited copper-induced HDL oxidation in a concentration-dependent manner. Adding PON to HDL prolonged the oxidation lag phase and reduced HDL peroxide and aldehyde formation by up to 95%. This inhibitory effect was most pronounced when PON was added before oxidation initiation. When purified PON was added to whole serum, essentially all of it became HDL-associated. The PON-enriched HDL was more resistant to copper ion-induced oxidation than was control HDL. Compared with control HDL, HDL from PON-treated serum showed a 66% prolongation in the lag phase of its oxidation, and up to a 40% reduction in peroxide and aldehyde content. In contrast, in the presence of various PON inhibitors, HDL oxidation induced by either copper ions or by a free radical generating system was markedly enhanced. As PON inhibited HDL oxidation, two major functions of HDL were assessed: macrophage cholesterol efflux, and LDL protection from oxidation. Compared with oxidized untreated HDL, oxidized PON-treated HDL caused a 45% increase in cellular cholesterol efflux from J-774 A.1 macrophages. Both HDL-associated PON and purified PON were potent inhibitors of LDL oxidation. Searching for a possible mechanism for PON-induced inhibition of HDL oxidation revealed PON (2 paraoxonase U/ml)-mediated hydrolysis of lipid peroxides (by 19%) and of cholesteryl linoleate hydroperoxides (by 90%) in oxidized HDL. HDL-associated PON, as well as purified PON, were also able to substantially hydrolyze (up to 25%) hydrogen peroxide (H2O2), a major reactive oxygen species produced under oxidative stress during atherogenesis. Finally, we analyzed serum PON activity in the atherosclerotic apolipoprotein E-deficient mice during aging and development of atherosclerotic lesions. With age, serum lipid peroxidation and lesion size increased, whereas serum PON activity decreased. We thus conclude that HDL-associated PON possesses peroxidase-like activity that can contribute to the protective effect of PON against lipoprotein oxidation. The presence of PON in HDL may thus be a major contributor to the antiatherogenicity of this lipoprotein.     

PON1 status in haemodialysis patients and the impact of hepatitis C infection

OBJECTIVES: Paraoxonase-1 (PON1) activity has been reported to decrease in both haemodialysis patients and patients with HCV infection. We aimed to investigate paraoxonase and arylesterase activities, and lipid hydroperoxide levels (LOOH) in haemodialysis patients with or without hepatitis C infection, and to find out whether PON1 activity is affected further by the presence of HCV infection in HD patients. DESIGN AND METHODS: Twenty HCV (+) haemodialysis patients, 26 HCV (-) haemodialysis patients, and 26 controls were enrolled. Paraoxonase and arylesterase activities were measured spectrophotometrically. LOOH levels were measured by ferrous oxidation with xylenol orange assay. RESULTS: Haemodialysis patients with or without HCV infection had lower paraoxonase and arylesterase activities than controls (all p<0.001), while higher LOOH levels (both p<0.001). Paraoxonase and arylesterase activities, and LOOH levels were comparable between haemodialysis patients with or without HCV infection (p>0.05). Significant inverse correlation was observed between paraoxonase or arylesterase activities, and LOOH levels (p<0.05, beta=-0.319 and p<0.05, beta=-0.348, respectively). CONCLUSION: We concluded that PON1 activity significantly decreases in both haemodialysis patients with or without HCV infection. Nevertheless, PON1 activity is not affected further by the presence of HCV infection in haemodialysis patients.     

Oxidative status and serum PON1 activity in beta-thalassemia minor

OBJECTIVES: Paraoxonase-1 (PON1) deficiency is related to increased susceptibility to low density lipoprotein oxidation and development of atherosclerosis. The aim of this study was to investigate paraoxonase and arylesterase activities along with oxidative status parameters, and to find out if there is any increased susceptibility to atherogenesis, which might be reflected with increased oxidative stress and decreased serum PON1 activity in beta-thalassemia minor (BTM) subjects. DESIGN AND METHODS: Thirty-two subjects with BTM and 28 healthy subjects as control were enrolled in the study. Serum paraoxonase and arylesterase activities, lipid hydroperoxide (LOOH) levels, total antioxidant capacity (TAC), total oxidant status (TOS) and oxidative stress index (OSI) were determined. RESULTS: Serum TAC, paraoxonase and arylesterase activities were significantly lower in BTM subjects than controls (for all p<0.001), while TOS, LOOH levels and OSI were significantly higher (p<0.001, p<0.05 and p<0.001; respectively). In BTM subjects, OSI, TOS, LOOH levels and TAC were significantly correlated with serum paraoxonase (r=-0.245, p<0.05; r=-0.231, p<0.05; r=-0.264, p<0.05 and, r=0.342, p<0.05, respectively) and arylesterase activities (r=-0.332, p<0.05, r=-0.308, p<0.05; r=-0.320, p<0.05 and r=0.443, p<0.05). Additionally, hemoglobin level was also correlated with serum paraoxonase (r=0.501, p<0.001) and arylesterase activities (r=0.501, p<0.001), TAC (r=0.402, p<0.05), TOS (r=-0.274, p<0.05) and OSI (r=-0.352, p<0.05). CONCLUSIONS: Oxidative stress is increased, while serum PON1 activity is decreased in BTM subjects. Decrease in PON1 activity seems to be associated with both the degree of oxidative stress and anemia. BTM subjects may be more prone to development of atherogenesis due to low serum PON1 activity.     

The effect of atorvastatin therapy on lecithin:cholesterol acyltransferase, cholesteryl ester transfer protein and the antioxidant paraoxonase

OBJECTIVES: The aim of our study was to examine the influence of atorvastatin on lipid parameters, particularly on HDL, and on the activity of LCAT and CETP and how they affect the activity of the HDL-associated antioxidant enzyme paraoxonase. DESIGN AND METHODS: Thirty-three patients with types II.a and II.b primary hyperlipoproteinemia were enrolled into our study. The patients received atorvastatin, 20 mg daily, for 3 months. We measured the serum paraoxonase activity and concentration, oxidized LDL, LCAT and CETP activities. RESULTS: Atorvastatin significantly reduced the levels of cholesterol, triglyceride, LDL-C and apoB, while it did not influence the levels of HDL-C and apo A-I. The increases in serum PON-specific activity, PON/HDL ratio and LCAT activity were significant, while oxLDL and CETP activities were significantly decreased. CONCLUSION: Atorvastatin may influence the composition and function of HDL, thereby possibly increasing the activity of paraoxonase and preventing atherosclerosis.     

Paraoxonase 1 (PON1) status in gastroesophageal malignancies and associated paraneoplastic syndromes - connection with inflammation

ObjectiveTo evaluate the status and diagnostic utility of antioxidant paraoxonase 1 (PON1) in gastroesophageal cancers.Design and methodsPON1's arylesterase/paraoxonase activities and phenotype were determined in 82 cancers and 57 controls, and related to clinicopathological features, anemia and cachexia coexistence, cholesterol levels, liver function panel, and inflammatory and angiogenic indices.ResultsPON1's activities were decreased in cancer. Arylesterase activity correlated with cancer T and N stages, being an N1-independent predictor. Both activities correlated with transferrin, albumin, CRP and inflammation-based Glasgow Prognostic Score, and arylesterase activity also with interleukin-6 and midkine. Phenotype A (Q192 homozygotes) was associated with lower transferrin and higher TNF-α concentrations. PON1's arylesterase activity reflected anemia severity, being correlated with hemoglobin, hematocrit, and iron. PON1 arylesterase activity negatively correlated with alkaline phosphatase and gamma-glutamyl transferase, but not with bilirubin, aminotransferases, HDL or LDL cholesterol. PON1 moderately indicated cancer presence and regional metastasis.ConclusionsPON1 activity decreases in gastroesophageal cancers and corresponds to inflammation severity and cancer-related anemia. PON1 decrease indicates lymph node metastasis, but its moderate predictive power does not recommend PON1 determination alone for clinical application.     

Paraoxonase and arylesterase activities in untreated dipper and non-dipper hypertensive patients

ObjectivesParaoxonase, a high density lipoprotein (HDL) associated enzyme, was shown to be reduced in patients with cardiovascular diseases. We aimed to examine serum paraoxonase and arylesterase activities, and oxidative stress markers such as lipid hydroperoxide (LOOH) and total antioxidant status (TAS) in dipper and non-dipper hypertensive patients.Design and methodsForty-six non-dipper hypertensives (NDH group), 40 dipper hypertensives (DH group) and 28 healthy control subjects were included in the study. Clinical and echocardiographic assessment and ambulatory blood pressure monitoring were performed in all subjects. Serum paraoxonase and arylesterase activities were measured spectrophotometrically. LOOH levels were measured by ferrous oxidation with xylenol orange assay. TAS was determined by using an automated measurement method.ResultsParaoxonase and arylesterase activities and TAS levels were significantly lower in patients with NDH compared to both DH and control groups (p < 0.001, for both). Also, LOOH levels were found at high level in patients with NDH compared to control and DH groups. In NDH group, both paraoxonase and arylesterase activities were independently correlated with LDL cholesterol, TAS and LOOH levels. In DH group, both paraoxonase and arylesterase activities were independently correlated with HDL cholesterol and LOOH levels.ConclusionsReduced paraoxonase and arylesterase activities in NDH might indicate increased oxidative stress, which plays an important role in the development of cardiovascular diseases. Low serum activities of paraoxonase and arylesterase might be considered as prospective prognostic markers of the development of cardiovascular diseases in dipper and non-dipper hypertensive patients.     

Serum levels of lipids, lipoproteins and paraoxonase activity in pre-eclampsia

Serum paraoxonase 1 (PON1) activity and the oxidation of lipoproteins were investigated in 35 women with pre-eclampsia and in 35 healthy control women with normal pregnancies. Blood pressure, body mass index (BMI), serum levels of total cholesterol, triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB) and lipoprotein (a) (Lp[a]), and PON1 activity were assessed. There were no significant between-group differences in subject age, gestational age at diagnosis of pre-eclampsia, BMI, serum total cholesterol, triglycerides, LDL and ApoB levels. Mean systolic and diastolic blood pressures and serum Lp(a) were significantly higher in subjects with pre-eclampsia than in controls. Mean serum HDL, ApoA1 and PON1 activity were significantly lower in subjects with pre-eclampsia compared with controls. In conclusion, lipids and oxidized lipoproteins may play important roles in the pathogenesis of pre-eclampsia.     

Serum paraoxonase activity in patients with type 1 diabetes compared to healthy controls

BACKGROUND: The oxidation of low-density lipoprotein (LDL) is central to current theories on the initiation and progression of atherosclerosis. Type 1 diabetes is associated with an increase in oxidative stress, which may be responsible for the increased susceptibility to coronary heart disease seen in type 1 diabetes. High-density lipoprotein (HDL) associated paraoxonase (PON1) can retard the oxidation of LDL. DESIGN: Paraoxonase activity, concentration and genotype were therefore investigated in 152 people with type 1 diabetes and 282 healthy controls. These parameters were also investigated in the group with type 1 diabetes in relation to the presence of diabetic complications. RESULTS: Both PON1 activity and concentration were significantly lower by 16.7% and 19.2% (both P < 0.05) in the type 1 diabetes group. These differences were independent of the PON1 coding region polymorphisms. The distribution of PON1 activity and mass were the same in both populations, i.e. for the PON1-192 polymorphism RR > RQ > QQ and for the PON1-55 polymorphism LL > LM > MM. There were no differences in either the PON1 polymorphisms, PON1 activity and concentration in people with type 1 diabetes in the presence or absence of micro and macro vascular complications of diabetes. CONCLUSIONS: Low PON1 activity may contribute to the increased atherosclerosis found in type 1 diabetes by reducing the ability of HDL to retard LDL oxidation despite the frequently-found increased HDL in type 1 diabetes when good glycaemic control is established.     

Serum lipid profile,oxidative status,and paraoxonase 1 activity in hyperemesis gravidarum

The aim of this study was to investigate lipid profile, paraoxonase 1 (PON1) activity, and oxidative stress status in the serum of hyperemesis gravidarum (HG) patients. Thirty‐six HG cases and 36 normal pregnants were included in the study. Serum total cholesterol (TC), triglyceride (TG), high‐density lipoprotein cholesterol (HDL‐C), low‐density lipoprotein cholesterol (LDL‐C), apoproteins A1 (apo A1) and B (apo B), malondialdehyde (MDA), and total antioxidant activity (TAO) values and PON1 and arylesterase activities were determined. Although serum TC, TG, LDL‐C, and apo B levels were not different among; the groups (P>0.05), HDL‐C (P=0.01) and apo A1 (P=0.007) levels were lower in HG patients than in normal pregnants. HG group had significantly lower serum PON1 (P=0.03) and arylesterase activities (P=0.03) compared with the control group. Additionally, mean TAO values were lower (P=0.01) and MDA levels were higher (P=0.02) in HG group than in the healthy pregnants. A significant negative correlation between PON1 and MDA was found in HG group (r=?0.33, P<0.05). The findings of this study have revealed that HG may be one of the conditions in which oxidant and antioxidant balance is impaired. J. Clin. Lab. Anal. 23:105–109, 2009. © 2009 Wiley‐Liss, Inc.     

Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures.

We previously reported that high density lipoprotein (HDL) protects against the oxidative modification of low density lipoprotein (LDL) induced by artery wall cells causing these cells to produce pro-inflammatory molecules. We also reported that enzyme systems associated with HDL were responsible for this anti-inflammatory property of HDL. We now report studies comparing HDL before and during an acute phase response (APR) in both humans and a croton oil rabbit model. In rabbits, from the onset of APR the protective effect of HDL progressively decreased and was completely lost by day three. As serum amyloid A (SAA) levels in acute phase HDL (AP-HDL) increased, apo A-I levels decreased 73%. Concomitantly, paraoxonase (PON) and platelet activating factor acetylhydrolase (PAF-AH) levels in HDL declined 71 and 90%, respectively, from days one to three. After day three, there was some recovery of the protective effect of HDL. AP-HDL from human patients and rabbits but not normal or control HDL (C-HDL) exhibited increases in ceruloplasmin (CP). This increase in CP was not seen in acute phase VLDL or LDL. C-HDL incubated with purified CP and re-isolated (CP-HDL), lost its ability to inhibit LDL oxidation. Northern blot analyses demonstrated enhanced expression of MCP-1 in coculture cells treated with AP-HDL and CP-HDL compared to C-HDL. Enrichment of human AP-HDL with purified PON or PAF-AH rendered AP-HDL protective against LDL modification. We conclude that under basal conditions HDL serves an anti-inflammatory role but during APR displacement and/or exchange of proteins associated with HDL results in a pro-inflammatory molecule.     

Influence of high‐density lipoprotein and paraoxonase‐1 on platelet reactivity in patients with acute coronary syndromes receiving clopidogrel therapy

Summary. Background: The paraoxonase activity of the enzyme paraoxonase‐1 (PON‐1) associated with high‐density lipoprotein (HDL) may significantly influence clopidogrel’s antiplatelet and clinical efficacy as a result of its involvement in the clopidogrel biotransformation to the pharmacologically active thiol metabolite. We evaluated the possible relationships of HDL levels as well as PON‐1 activities and the Q192R genotype with clopidogrel’s antiplatelet efficacy in acute coronary syndrome (ACS) patients. Methods and results: The platelet aggregation, P‐selectin expression and platelet/leukocyte conjugates as well as the clopidogrel response variability (evaluated by the VASP phosphorylation test and expressed as platelet reactivity index, PRI) were assessed in 74 ACS patients undergoing percutaneous coronary intervention (PCI) in relation to the PON‐1 Q192R genotype and to serum HDL‐cholesterol levels, and PON‐1 (paraoxonase and arylesterase) activities. Patients were loaded with 600 mg of clopidogrel followed by 75 mg per day. HDL‐cholesterol levels and PON‐1 activities at baseline (before clopidogrel loading) were not altered at 5‐ and 30‐day post‐clopidogrel loading, whereas baseline platelet activation parameters were significantly attenuated. At 5 days, 17 patients were clopidogrel non‐responders (PRI: 64.2 ± 11.1%). HDL‐cholesterol was inversely associated with platelet activation parameters independently on platelet response variability to clopidogrel whereas a negative association between platelet activation parameters and paraoxonase activity was observed in patients adequately responding to clopidogrel but not in clopidogrel non‐responders. Similarly, the platelet activation markers were significantly higher in PON‐1 Q192Q genotype carriers compared with those having one or two R alleles only in patients adequately responding to clopidogrel. Conclusions: PON‐1 is an important determinant of clopidogrel antiplatelet efficacy only in patients adequately responding to clopidogrel. These findings may be clinically important in ACS patients receiving clopidogrel therapy, especially the first days after the episode.     

HDL metabolic activities in a boy with lipoprotein lipase deficiency and his family

BACKGROUND: Lipoprotein lipase (LPL) deficiency is a rare autosomal recessively inherited disease characterized by elevated triglyceride, low total cholesterol and quantitative and qualitative alterations of high-density lipoprotein (HDL). The aim of the present study was to explore HDL metabolic activities in a patient with LPL deficiency and in his family (n = 11). MATERIALS AND METHODS: Subjects were divided into four groups: proband (Ser447Stop/Arg170Leu carrier), Ser447Stop carriers, Arg170Leu carriers and silent mutation/wild-type carriers (controls). Cholesterol efflux from Fu5AH cells, lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP), paraoxonase 1 (PON1) and platelet-activating factor acetylhydrolase (PAF-AH) activities were evaluated. RESULTS: Comparison between the proband and the control group revealed that the boy had significantly reduced cholesterol efflux (P < 0.001), conserved LCAT activity (P > 0.05) and increased CETP activity (P < 0.001). As regards antioxidant enzymes, while PON1 activity was higher in the proband than in the controls (P < 0.0001), PAF-AH activity was reduced (P < 0.05). The other groups did not show relevant differences in comparison with controls. CONCLUSIONS: The presence of one mutation was not enough to introduce important modifications in HDL functions. Markedly reduced HDL levels can keep certain normal enzymatic activities, which probably tend to counteract the deleterious effects of LPL deficiency.     

Maternal chronic hepatitis B virus is implicated with low neonatal paraoxonase/arylesterase activities

BACKGROUND: Paraoxonase/arylesterase activities are closely implicated with liver function and antiatherogenetic process. AIM: To evaluate whether maternal chronic hepatitis B virus, disease (HBV) affect serum neonatal paraoxonase/arylesterase activities. PATIENTS AND METHODS: 28 pregnant women with HBV and 28 healthy pregnant women (controls) in the delivery room and their newborns (cord blood) underwent laboratory examinations. Serological virus tests and liver function tests and paraoxonase (PON 1) activities were measured with the Siemens Advia 1650 Clinical Chemistry System, while total antioxidant capacity (TAC) levels and paraoxonase-arylesterase (PON-aryl) activities were measured spectrophotometrically. RESULTS: Serological HBV tests and HBV DNA showed chronic HBV (precore mutant G1896A) in the diseased mothers whereas anti-HBc and anti-HBe were detected in their neonates. Liver function parameters were found normal in controls and both groups of newborns. Moderately increased transaminase levels were measured in HBV mothers, whereas TAC levels were decreased in hepatic mothers and their newborns. Interestingly albumin levels did not differ among the studied groups. PON 1 and PON-aryl activities in the diseased mothers (148+/-14 U/mL/min, 130+/-16 KU/mL/min) and their infants (32+/-6 U/mL/min, 24+/-5 KU/mL/min) were significantly lower as compared to those of control mothers (217+/-16 U/mL/min, 196+/-14 KU/mL/min p<0.001) and their newborns (57+/-6 U/mL/min, 48+/-8 UK mL/min p<0.001). Inverse significant correlations were found between the studied enzyme activities and liver enzymes in all the groups of study except in infants born from HBV mothers and positive with TAC in all the studied groups. CONCLUSIONS: Decreased PON 1 and PON-aryl activities were measured in infants born from hepatic mothers probably as a consequence of their low TAC. Infants born from HBV mothers are at risk for developing LDL oxidation perinatally.     

Paraoxonase-1 (PON-1) genotype and activity and in vivo oxidized plasma low-density lipoprotein in Type II diabetes

The HDL (high-density lipoprotein)-associated enzyme PON (paraoxonase)-1 protects LDL (low-density lipoprotein) from oxidative modification in vitro, although it is unknown if this anti-atherogenic action occurs in vivo. In a cross-sectional study of 58 Type II diabetic subjects and 50 controls, we examined the fasting plasma LDL basal conjugated diene concentration [a direct measurement of circulating oxLDL (oxidatively modified LDL)], lipoprotein particle size by NMR spectroscopy, PON-1 polymorphisms (coding region polymorphisms Q192R and L55M, and gene promoter polymorphisms -108C/T and -162G/A), PON activity (with paraoxon or phenyl acetate as the substrates) and dietary antioxidant intake. Plasma oxLDL concentrations were higher in Type II diabetic patients (males, P = 0.048; females, P = 0.009) and unrelated to NMR lipoprotein size, PON-1 polymorphisms or PON activity (with paraoxon as the substrate) in any group. In men with Type II diabetes, however, there was a direct relationship between oxLDL concentrations and PON activity (with phenyl acetate as the substrate; r = 0.611, P = 0.0001) and an atherogenic NMR lipid profile in those who were PON-1 55LL homozygotes. Circulating oxLDL concentrations in vivo were unrelated to PON-1 genotypes or activity, except in male Type II diabetics where there was a direct association between PON activity (with phenyl acetate as the substrate) and oxLDL levels. These in vivo data contrast with in vitro data, and may be due to confounding by dietary fat intake. Male Type II diabetic subjects with PON-1 55LL homozygosity have an atherogenic NMR lipid profile independent of LDL oxidation. These data do not support an in vivo action of PON on LDL oxidation.     

Increased activity of platelet-activating factor acetylhydrolase in low-density lipoprotein subfractions induces enhanced lysophosphatidylcholine production during oxidation in patients with heterozygous familial hypercholesterolaemia

Patients with heterozygous familial hypercholesterolaemia (FH) have elevated plasma concentrations of low-density lipoprotein (LDL) and develop premature atherosclerosis. There is increasing evidence that oxidative modification of LDL is important for the pathogenesis of atherosclerosis, and the LDL-associated platelet-activating factor acetylhydrolase (PAF-AH) seems to play a key role in LDL oxidation by hydrolysing the oxidized phospholipids of phosphatidylcholine (PC) and producing lysophosphatidylcholine (lyso-PC). We measured the total serum and high-density lipoprotein (HDL) levels of PAF-AH activity and studied the distribution of PAF-AH activity among three LDL subfractions isolated by gradient ultracentrifugation in 15 patients with heterozygous FH and 13 normolipidaemic control subjects. We also determined the lyso-PC production in each LDL subfraction during Cu²⁺-induced oxidation in vitro. The total serum PAF-AH activity in heterozygous FH patients was significantly higher than in control subjects, whereas the HDL-associated PAF-AH activity, expressed as a percentage of total serum PAF-AH activity, was significantly lower in the FH patients than in control subjects (13.9 ± 6.6% vs. 30.6 ± 4.4%, P < 0.001). Among the LDL subfractions, the PAF-AH activity in both normolipidaemic control subjects and FH patients, expressed as nmol mg^?1 protein min^?1, was significantly higher in the LDL3 subfraction (33.1 ± 4.8 and 53.4 ± 11.5 respectively) than in the LDL2 (18.6 ± 5.3 and 26.8 ± 10.4 respectively, P < 0.0001 for both comparisons) and LDL1 subfractions (5.1 ± 1.5 and 7.8 ± 2.6, respectively, P < 0.0001 for both comparisons). Additionally, the enzyme activity in each LDL subfraction of the heterozygous FH patients was significantly higher than in control subjects (P < 0.02 for LDL1, P < 0.03 for LDL2 and P < 0.0001 for LDL3). No difference was observed in the susceptibility to oxidation of each LDL subfraction among the heterozygous FH patients and the normolipidaemic control subjects. During oxidation, the PAF-AH activity decreased, whereas the lyso-PC levels significantly increased in all subfractions of both groups. The lyso-PC/sphingomyelin molar ratio in each LDL subfraction of the FH patients 3 h after the onset of the oxidation was significantly higher than in control subjects [0.38 ± 0.05 and 0.27 ± 0.04, respectively, for LDL1 (P < 0.006), 0.47 ± 0.08 and 0.39 ± 0.03, respectively, for LDL2 (P < 0.04), 0.55 ± 0.11 and 0.42 ± 0.06, respectively, for LDL3 (P < 0.02)]. Our results show that heterozygous FH patients exhibit higher PAF-AH activity than control subjects in all LDL subfractions, resulting in higher lyso-PC production during oxidation, which confers on these subfractions higher biological potency. This phenomenon, in combination with the diminished anti-atherogenic and antioxidant capability of HDL in these patients due to the relatively low HDL-cholesterol levels compared with LDL-cholesterol levels and, consequently, the relatively low HDL-associated PAF-AH activity, could contribute to the higher atherogenicity and incidence of coronary artery disease observed in FH patients.     

The paraoxonase promoter polymorphism (-107)T>C is not associated with carotid intima-media thickness in Sicilian hypercholesterolemic patients

BACKGROUND AND OBJECTIVES: Increased plasma low-density lipoprotein-cholesterol (LDL-C) levels in hypercholesterolemic subjects are associated with enhanced LDL oxidation that represents an additional risk for atherosclerotic disease. Human serum paraoxonase (PON1), a high-density lipoprotein (HDL) associated enzyme, has been shown to protect LDL from oxidation, thus playing an important role in reducing the risk of atherosclerosis. PON1 gene polymorphisms have been found to be associated with the variations in serum PON1 levels and activities, and with the risk for coronary artery disease (CAD). This study was performed to evaluate the contribution of the PON1 promoter (-107)T>C and the coding region Gln 192 Arg (Q192R) and Leu 55 Met (L55M) polymorphisms to the presence of carotid atherosclerosis in 208 Sicilian subjects with primary hypercholesterolemia. METHODS: Carotid artery intima-media wall thickness (IMT) was measured as an indicator of early atherosclerotic disease. The subjects were classified according to whether they have a normal (1 mm) IMT. Subjects were also investigated for physical and biochemical parameters, including PON1 activity. RESULTS: No significant differences were detected among the PON1 genotypes with respect to age, sex, BMI, plasma lipids, systolic blood pressure in both groups of patients. There were significant differences between PON1 genotypes with respect to PON1 activity. The 192QQ, 55MM and (-107)TT genotypes showed lower PON1 activity compared to the RR, LL and CC genotypes. The PON1 (-107)T>C genotype distribution in both IMT groups showed no significant differences in percentage of TT, CT and CC genotypes. Similar results were obtained analyzing the Q192R and L55M genotype frequencies. Stepwise forward logistic regression analysis confirmed the lack of association between PON1 genotypes and carotid abnormalities. CONCLUSIONS: In conclusion, our data provided no evidence of a significant association between either PON1 promoter (-107)T>C or coding region, Q192R and L55M, polymorphisms and early carotid atherosclerosis in Sicilian hypercholesterolemic subjects.     

The function, composition, and particle size of high-density lipoprotein were severely impaired in an oliguric phase of hemorrhagic fever with renal syndrome patients

BACKGROUND: Patients suffering from hemorrhagic fever with renal syndrome (HFRS) often showed strikingly reduced high-density lipoprotein (HDL)-cholesterol levels during the oliguric phase, indicating severe alterations in lipoprotein metabolism. OBJECTIVE: To compare changes in the functions and composition of HDL, lipoprotein metabolism parameters were analyzed in the sera of HFRS patients in the oliguric phase and after recovery. METHODS: The serum cholesterol, triglyceride (TG), and lipoprotein/apolipoprotein profiles of HFRS patients in the oliguric and recovery phases were compared with those of normal reference sera. The activities of HDL-associated enzymes, lecithin:cholesterol acyltransferase (LCAT), and paraoxonase (PON) were also assessed. RESULTS: In the oliguric phase, serum cholesterol was substantially decreased and serum TG was increased. As observed by electron microscopy, the sizes of the HDL particles from the HFRS patients were smaller than those seen in the reference sera, with more heterogeneous distribution. Serum amyloid A (SAA) and apolipoprotein (apo) C-III were overexpressed in the oliguric phase, particularly in the HDL fraction. However, in immunodetection, the levels of apoA-I in the HDL(2) and HDL(3) of the HFRS patients were lower than those of the reference HDL. Serum LCAT and PON activities were reduced significantly in the oliguric phase, which is associated with a reduction in HDL-cholesterol levels and HDL particle size. CONCLUSION: Overexpression of both apoC-III and apoSAA in HDL and attenuated serum LCAT and PON activity were observed during the oliguric phase in HFRS patients. These results demonstrate that structural, functional, and compositional changes of HDL occurred to a substantial degree in the oliguric phase.     

Characterization of antioxidant/anti-inflammatory properties and apoA-I-containing subpopulations of HDL from family subjects with monogenic low HDL disorders

BackgroundGenetic factors regulate both high-density lipoprotein (HDL) levels and functionality, thus affecting HDL antiatherogenic properties. We characterized the HDL antioxidant/anti-inflammatory properties and apoA-I-containing subpopulations in families with monogenic low HDL disorders.MethodsSubjects with mutations in apolipoprotein A-I (apoA-I), ATP-binding cassette transporter A1 (ABCA1) or lecithin:cholesterol acyltransferase (LCAT) and family controls were studied. HDL antioxidant/anti-inflammatory properties were assayed by an in vitro fluorometric method and HDL-associated paraoxonase-1 (PON1), platelet activating factor-acetylhydrolase (PAF-AH), LCAT, malondialdehyde (MDA), PAF and serum amyloid A (SAA) were measured. ApoA-I-containing HDL subpopulations were analyzed by two-dimensional non-denaturing gel electrophoresis.ResultsApoA-I heterozygotes and subjects with partial or complete ABCA1 or LCAT deficiency had HDL with reduced antioxidant/anti-inflammatory properties and increased MDA levels. HDL-PON1 activity was reduced in apoA-I heterozygotes and in subjects with complete ABCA1 deficiency. HDL-PAF-AH activity was reduced in subjects with partial or complete ABCA1 deficiency or complete LCAT deficiency. HDL-LCAT activity was reduced in all LCAT mutation carriers. HDL-PAF levels were increased in apoA-I heterozygotes. HDL-SAA levels were increased in subjects with complete ABCA1 deficiency. ApoA-I, ABCA1 and LCAT heterozygotes were depleted of the large α1 HDL subpopulation. Subjects with complete LCAT deficiency showed mostly the small α4 HDL subpopulation and subjects with complete ABCA1 deficiency the α4 and preβ HDL subpopulations.ConclusionsThis study shows that mutations in apoA-I, ABCA1 and LCAT have direct effect on the antioxidant/anti-inflammatory properties of HDL. Furthermore, our study shows the effect of specific mutations on the apoA-I-containing HDL subpopulation profiles.     

PON1 activity and total oxidant status in patients with active pulmonary tuberculosis

OBJECTIVES: The aim of this study was to the investigate effect of tuberculosis infection on paraoxonase-1 (PON1) activity and oxidative status in patients with pulmonary tuberculosis (PTB). DESIGN AND METHODS: Twenty-five active PTB subjects and 33 healthy controls were included in the study. Serum PON1 activity, total oxidant status (TOS), lipid hydroperoxide (LOOH) and total free sulfydryl (-SH) groups were determined. RESULTS: Serum basal/salt-stimulated paraoxonase activities, arylesterase activity and total -SH group levels were significantly lower in patients with PTB than controls (p<0.05, p<0.05, p<0.001 and p<0.01 respectively), while TOS and LOOH levels were significantly higher (p<0.01 and p<0.05, respectively). In PTB patients, TOS, LOOH and total -SH group levels were significantly correlated with paraoxonase (r=-0.371, p<0.05; r=-0.286, p<0.05; r=0.625 p<0.01; respectively) and arylesterase (r=-0.437, p<0.01; r=-0.352, p<0.05; r=0.653, p<0.01; respectively). CONCLUSIONS: Patients with active PTB are exposed to potent oxidative stress and they have decreased PON1 activity. These predisposal factors may, in part, play a role in the pathogenesis of atherosclerosis in PTB.