Vitamin C and E intake is associated with increased paraoxonase activity

Paraoxonase 1 (PON1) C/T-108 association with longitudinal mean arterial blood pressure

BACKGROUND

Blood pressure is a complex quantitative trait with a strong genetic component. In this study, we leveraged the Veterans Affairs electronic medical record system to explore the relationship between Paraoxonase 1 (PON1)-108 C/T (rs705379) and mean arterial blood pressure (MAP).

METHODS

Outpatient blood pressure data over an approximate 8-year period was collected from the Veterans Affairs Hypertensive Cohort (N = 1,302). Association between genotype and longitudinal MAP was further explored using a random effects model controlling for age, ancestry, renal function, and other determinants of blood pressure. To control for population stratification, principal component groupings based on ancestry informative markers in this dataset were included as covariates (in addition to self-identified ancestry). Data from the African American Study of Kidney Disease and Hypertension (AASK, N = 857) was used to confirm significant findings in an independent cohort.

RESULTS

There was a significant interaction between PON1-108 C/T genotype and follow-up age group. At a younger age (<50 years), there was an estimated 2.53 mm Hg (95% confidence interval: 1.06, 4.00) increase in MAP with each additional C-allele. At the older age groups, there were no significant associations between PON1-108 C/T genotype and MAP. Using data from the AASK trial, the C-allele at PON1-108 C/T was significantly associated with a higher MAP (P = 0.005) but only among younger participants (<54 years).

CONCLUSIONS

The PON1-108 polymorphism may be associated with MAP in an age-dependent manner.

Association of mate tea (Ilex paraguariensis) intake and dietary intervention and effects on oxidative stress biomarkers of dyslipidemic subjects

OBJECTIVE

To evaluate the effect of long-term ingestion of mate tea, with or without dietary intervention, on the markers of oxidative stress in dyslipidemic individuals.

METHODS

Seventy-four dyslipidemic volunteers participated in this randomized clinical trial. Subjects were divided into three treatment groups: mate tea (MT), dietary intervention (DI), and mate tea with dietary intervention (MD). Biochemical and dietary variables were assessed at the beginning of the study (baseline) and after 20, 40, 60, and 90 d of treatment. Participants in the MT and MD groups consumed 1 L/d of mate tea. Those in the DI and MD groups were instructed to increase their intake of fruit, legumes and vegetables and decrease their consumption of foods rich in cholesterol and saturated and trans-fatty acids. Biomarkers of oxidative stress such as antioxidant capacity of serum (ferric reducing antioxidant potential assay), uric acid, reduced glutathione, paraoxonase-1 enzyme, lipid hydroperoxide (LOOH), and protein carbonyl were analyzed.

RESULTS

Participants in the DI group showed a significant decrease in total fat and saturated fatty acid intakes. Those in the DI and MD groups presented a significant increase in vitamin C consumption. For all groups, there was a significant increase in ferric reducing antioxidant potential and reduced glutathione concentrations but no significant changes in LOOH, protein carbonyl, and paraoxonase-1 values. The reduced glutathione concentration was positively correlated with the consumption of monounsaturated fatty acids, fiber, and vitamin C, whereas levels of LOOH were inversely correlated with intakes of vitamin C and fiber. In addition, LOOH correlated positively with low-density lipoprotein cholesterol and inversely with high-density lipoprotein cholesterol, which had a positive association with paraoxonase-1.

CONCLUSION

The ingestion of mate tea independently of the dietary intervention increased plasma and blood antioxidant protection in patients with dyslipidemia.

Additional Common Polymorphisms in the PON Gene Cluster Predict PON1 Activity but Not Vascular Disease

Background. Paraoxonase 1 (PON1) enzymatic activity has been consistently predictive of cardiovascular disease, while the genotypes at the four functional polymorphisms at PON1 have not. The goal of this study was to identify additional variation at the PON gene cluster that improved prediction of PON1 activity and determine if these variants predict carotid artery disease (CAAD). Methods. We considered 1,328 males in a CAAD cohort. 51 tagging single-nucleotide polymorphisms (tag SNPs) across the PON cluster were evaluated to determine their effects on PON1 activity and CAAD status. Results. Six SNPs (four in PON1 and one each in PON2/3) predicted PON1 arylesterase (AREase) activity, in addition to the four previously known functional SNPs. In total, the 10 SNPs explained 30.1% of AREase activity, 5% of which was attributable to the six identified predictive SNPs. We replicate rs854567 prediction of 2.3% of AREase variance, the effects of rs3917510, and a PON3 haplotype that includes rs2375005. While AREase activity strongly predicted CAAD, none of the 10 SNPs predicting AREase predicted CAAD. Conclusions. This study identifies new genetic variants that predict additional PON1 AREase activity. Identification of SNPs associated with PON1 activity is required when evaluating the many phenotypes associated with genetic variation near PON1.

Paraoxonase and arylesterase activities in children with iron deficiency anemia and vitamin B12 deficiency anemia

Paraoxonase-1 is an esterase enzyme and it has 3 types of activity, namely paraoxonase, arylesterase, and diazoxonase. It has been reported that paraoxonase-1 deficiency is related to increased susceptibility to development of atherosclerosis and cardiovascular disease. The aim of this study was to investigate serum paraoxonase and arylesterase activities in children with iron deficiency anemia and vitamin B(12) deficiency anemia. Thirty children with iron deficiency anemia, 30 children with vitamin B(12) deficiency anemia, and 40 healthy children aged 6 months to 6 years were enrolled in this study. Serum paraoxonase and arylesterase activities were measured with a spectrophotometer by using commercially available kits. Mean paraoxonase and arylesterase activities in vitamin B(12) deficiency anemia group (103 ± 73 and 102 ± 41 U/L, respectively) were significantly lower than mean activities of control group (188 ± 100 and 147 ± 34 U/L, respectively; P < .001 for both) and iron deficiency anemia group (165 ± 103 and 138 ± 39 U/L, respectively; P < .05, P < .001), whereas there were no significant differences between iron deficiency anemia and control groups (P > .05). Paraoxonase and arylesterase activities significantly increased after treatment with vitamin B(12) in vitamin B(12) deficiency anemia; however, there were no significant changes in the activities of these enzymes after iron treatment in iron deficiency anemia group. Important correlations were found between vitamin B(12) levels and both paraoxonase and arylesterase activities (r = .367, P < .001; r = .445, P < .001). Our results suggest that vitamin B(12) deficiency anemia causes important reductions in paraoxonase and arylesterase activities, and after vitamin B(12) therapy the activities of these enzymes returned to near-normal levels.

Regulation of hepatic paraoxonase-1 expression

Serum paraoxonase-1 (PON1) is a member of the paraoxonases family (PON1, PON2, and PON3). PON1 is synthesized and secreted by the liver, and in circulation it is associated with HDL. PON1 has antioxidative properties, which are associated with the enzyme's capability to decrease oxidative stress in atherosclerotic lesions and to attenuate atherosclerosis development. Epidemiological evidence demonstrates that low PON1 activity is associated with increased risk of cardiovascular events and cardiovascular disease and is an independent risk factor for coronary artery disease. Therefore, pharmacological modulation of PON1 activity or PON1 gene expression could constitute a useful approach for preventing atherosclerosis. A primary determinant of serum PON1 levels is the availability of the enzyme for release by the liver, the principal site of PON1 production. Together with the enzyme secretion rate, enzymatic turnover, and protein stability, the level of PON1 gene expression is a major determinant of PON1 status. This paper summarizes recent progress in understanding the regulation of PON1 expression in hepatocytes.

The human paraoxonase gene cluster as a target in the treatment of atherosclerosis

The paraoxonase (PON) gene cluster contains three adjacent gene members, PON1, PON2, and PON3. Originating from the same fungus lactonase precursor, all of the three PON genes share high sequence identity and a similar β propeller protein structure. PON1 and PON3 are primarily expressed in the liver and secreted into the serum upon expression, whereas PON2 is ubiquitously expressed and remains inside the cell. Each PON member has high catalytic activity toward corresponding artificial organophosphate, and all exhibit activities to lactones. Therefore, all three members of the family are regarded as lactonases. Under physiological conditions, they act to degrade metabolites of polyunsaturated fatty acids and homocysteine (Hcy) thiolactone, among other compounds. By detoxifying both oxidized low-density lipoprotein and Hcy thiolactone, PONs protect against atherosclerosis and coronary artery diseases, as has been illustrated by many types of in vitro and in vivo experimental evidence. Clinical observations focusing on gene polymorphisms also indicate that PON1, PON2, and PON3 are protective against coronary artery disease. Many other conditions, such as diabetes, metabolic syndrome, and aging, have been shown to relate to PONs. The abundance and/or activity of PONs can be regulated by lipoproteins and their metabolites, biological macromolecules, pharmacological treatments, dietary factors, and lifestyle. In conclusion, both previous results and ongoing studies provide evidence, making the PON cluster a prospective target for the treatment of atherosclerosis.

Low high-density lipoprotein cholesterol is not responsible for decreased paraoxonase activity in chronic renal failure

BACKGROUND/AIMS

Human paraoxonase-1 (PON1) is responsible for the antioxidant effect of high-density lipoprotein (HDL) by inhibiting low-density lipoprotein oxidation. Previous studies discovered dyslipidemia (DL) and decreased PON1 activity in chronic renal failure (CRF). We aimed to determine PON and arylesterase activity, phenotypic distribution of the PON1 enzyme, and lipid profile in low and normal HDL cholesterol (HDL-C) patients with CRF, and renal transplant (TX), compared to primary DL.

METHODS

116 CRF (low or normal HDL-C), 52 TX (low or normal HDL-C), and 62 DL patients (low or normal HDL-C) were included. PON and arylesterase activities were measured spectrophotometrically. Phenotype was determined using the dual substrate method.

RESULTS

Aryl/HDL-C was significantly higher in low HDL-C patients. Patients with CRF had significantly lower arylesterase activity compared to DL, independent of HDL-C. PON activity and PON/HDL-C did not differ significantly in CRF compared to TX and DL. Phenotypic distribution was similar in patient groups. Low HDL-C CRF patients had significantly lower cholesterol and triglyceride than DL.

CONCLUSION

Decreased arylesterase activity, correlating with PON1 enzyme protein quantity, is not explicable by decreased HDL-C in CRF. Low HDL-C CRF patients' increased cardiovascular morbidity is not attributable to changes in PON1 activity, or phenotypic distribution.

Crossroads in the evaluation of paraoxonase 1 for protection against nerve agent and organophosphate toxicity

Human paraoxonase 1 (PON1), a 45kDa arylesterase associated with circulating high density lipoproteins (HDL), has been described as an anti-atherogenic element in cardiovascular disorders. The efficacy of PON1 as a catalytic bioscavenger against OP and CWNA toxicity has been on debate for the last few decades. Hydrolysis of various organophosphates (OPs) and chemical warfare nerve agents (CWNAs) by PON1 has been demonstrated in both in vitro and in vivo experiments. Recently, we established the protective efficacy of human and rabbit serum purified PON1 as well as human recombinant PON1 expressed in Trichoplusia ni larvae against nerve agent toxicity in guinea pigs. Exogenous administration of purified PON1 was effective in protecting against 1.2 X LCt(50) of sarin and soman administered endotracheally with microinstillation technology. However, the short half-life of exogenously administered PON1, probably due to poor association with circulating HDL, warrant alternative approaches for successful utility of PON1 in the treatment of OP/CWNA toxicity. In this mini review, we address the pros and cons of current PON1 prophylaxis and propose potential solutions for successful development of PON1 as an effective catalytic bioscavenger.

Assessment of the role of paraoxonase gene polymorphism (Q192R) and paraoxonase activity in the susceptibility to atherosclerosis among lead-exposed workers

BACKGROUND AND OBJECTIVE

Lead exposure is a well known cause of cardiovascular damage, including atherosclerosis. Paraoxonase 1 (PON1), a high-density lipoprotein-associated antioxidant enzyme, is capable of hydrolyzing oxidized lipids and thus it protects against atherosclerosis. The mechanism by which heavy metals inhibit serum PON1 activity is still not clear. Our aim was to detect the association between lead exposure and serum PON1 activity and lipid profile and also to study the polymorphism of the PON1 gene.

DESIGN AND SETTING

A case-control, cross-sectional study conducted from June 2008 until May 2009.

SUBJECTS AND METHODS

Male workers (n=100) in a lead battery manufactory were recruited for this study. They were compared with 100 male age-matched workers not exposed to lead (control group). Serum lipid profile, paraoxonase activity and lead were measured in blood samples. The DNA was extracted for detecting the Q192R polymorphism of the PON1 gene by polymerase chain reaction followed by restriction fragment length polymorphism.

RESULTS

There was significant difference in triglycerides, total cholesterol and high-density lipoprotein cholesterol (HDL-C) (P=.01, .05 and .04, respectively) between cases and controls. Multiple linear regression analysis showed that blood lead levels were significantly associated with decreased serum paraoxonase activity (P=.03) in lead workers. The paraoxonase genotype QR was the most prevalent in 34/53 subjects (64%) among the lead-exposed groups, while the genotype QQ was more prevalent in the control group, in 15/25 subjects (60%), with a significant difference between the control and other groups (P<.05).

CONCLUSION

Lead exposure is associated with increased triglycerides, total cholesterol and low-density lipoprotein cholesterol and decreased HDL-C. Because of the protective role of PON1 in the development of atherosclerosis, a decrease in serum PON1 activity due to lead exposure may render individuals more susceptible to atherosclerosis.

Relation between methylmercury exposure and plasma paraoxonase activity in inuit adults from Nunavik

BACKGROUND

Methylmercury (MeHg) exposure has been linked to an increased risk of coronary heart disease (CHD). Paraoxonase 1 (PON1), an enzyme located in the high-density-lipoprotein (HDL) fraction of blood lipids, may protect against CHD by metabolizing toxic oxidized lipids associated with low-density liproprotein and HDL. MeHg has been shown to inhibit PON1 activity in vitro, but this effect has not been studied in human populations.

OBJECTIVES

This study was conducted to determine whether blood mercury levels are linked to decreased plasma PON1 activities in Inuit people who are highly exposed to MeHg through their seafood-based diet.

METHODS

We measured plasma PON1 activity using a fluorogenic substrate and blood concentrations of mercury and selenium by inductively coupled plasma mass spectrometry in 896 Inuit adults. Sociodemographic, anthropometric, clinical, dietary, and lifestyle variables as well as PON1 gene variants (rs705379, rs662, rs854560) were considered as possible confounders or modifiers of the mercury-PON1 relation in multivariate analyses.

RESULTS

In a multiple regression model adjusted for age, HDL cholesterol levels, omega-3 fatty acid content of erythrocyte membranes, and PON1 variants, blood mercury concentrations were inversely associated with PON1 activities [β-coefficient = -0.063; 95% confidence interval (CI), -0.091 to -0.035; p < 0.001], whereas blood selenium concentrations were positively associated with PON1 activities (β-coefficient = 0.067; 95% CI, 0.045-0.088; p < 0.001). We found no interaction between blood mercury levels and PON1 genotypes.

CONCLUSIONS

Our results suggest that MeHg exposure exerts an inhibitory effect on PON1 activity, which seems to be offset by selenium intake.

Paraoxonase: Its antiatherogenic role in chronic renal failure

Paraoxonase (PON) is an aryldialkylphosphatase, which reversibly binds and hydrolyzes organophosphates. The PON family has three members (PON1, PON2 and PON3); they share structural properties and enzymatic activities. PON1 is shown to reside over high density lipoprotein (HDL) and has both antioxidant and antiatherogenic functions. Function of PON2 and PON3 are speculative and still under research. Several methodologies were developed over the years to determine the activity and mass of PON1, of which spectrophotometer-based methods using certain chemicals as substrate predominate. Several studies have shown decreased levels of PON1 in chronic renal failure (CRF) patients, particularly those on hemodialysis. The role of PON1 in development of cardiovascular disease has drawn considerable attention in recent years. Several authors have shown decreased levels of HDL and PON1 activity in CRF patients on hemodialysis and reported this to be a risk factor in the development of CVD. Enhancement or maintenance of the PON1 activity may prevent development of CVDs and its consequences in patients on hemodialysis.

Determinants of paraoxonase activity in healthy adults

SCOPE

Paraoxonase-1 (PON-1), associated with HDL, is regarded as anti-atherogenic, attributed to its ability to hydrolyze oxidized lipids. Here, the impact of PON and apolipoprotein E genotypes, age, alcohol and HDL-cholesterol (HDL-C) on PON activity is examined.

METHODS AND RESULTS

In total, 104 healthy UK adults participated in the study, with basal (PONA) and stimulated (PONB) PON-1 activities and arylesterase activity determined in these individuals. In univariate and correlation analysis age, HDL-C, alcohol intake and both PON genotypes were significantly associated with PONA and PONB activities (p<0.05). However, in the standard linear regression model, which explained 69% of the variability in both PONA (p<0.001) and PONB activities (p<0.001) only PON Q192R genotype emerged as a significant independent determinant, with four to fivefold higher levels in the RR versus wild-type QQ genotype groups. For PON arylesterase, HDL-C (p=0.030), apolipoprotein E (p=0.023) and PON Q192R (p=0.002) and PON L55M (p=0.002) genotypes collectively explained 14% of the total variability in the regression model.

CONCLUSION

Our results indicate that PON genotypes are stronger determinants of PON activity relative to the other potential modulators assessed. The relative impact of dietary components on PON activities remains to be established.

Ameliorative effect of vitamin C on alterations in thyroid hormones concentrations induced by subchronic coadministration of chlorpyrifos and lead in wistar rats

The present study evaluated the ameliorative effect of vitamin C on alteration in thyroid hormones induced by low-dose subchronic coadministration of chlorpyrifos (CPF) and lead (Pb). Forty Wistar rats were divided into 4 groups of 10 animals each. Groups I and II were administered soya oil (2 mL/kg) and vitamin C (100 mg/kg), respectively. Group III was coadministered CPF (4.25 mg/kg ~1/20th LD₅₀) and Pb (250 mg/kg ~1/20th LD₅₀), respectively. Group IV was pretreated with vitamin C (100 mg/kg) and then coadministered with CPF (4.25 mg/kg) and Pb (250 mg/kg), 30 min later. The regimens were administered by gavage for a period of 9 weeks. The marginal decrease in serum triiodothyronine and thyroxine and the significant increase in the concentrations of thyroid stimulating hormone and malonaldehyde in the group coadministered with CPF and Pb were ameliorated by vitamin C partly due to its antioxidant properties.

Decreased serum arylesterase activity in autism spectrum disorders

The PON1 gene, previously found associated with autism spectrum disorders (ASDs), encodes a serum protein responsible for the detoxification of organophosphates (OPs) and able to exert several enzymatic activities. PON1 arylesterase, but not diazoxonase activity, was significantly decreased in 174 ASD patients compared to 175 first-degree relatives and 144 controls (P=2.65×10⁻¹⁶). First degree relatives displayed intermediate activities, closer to patient than to control levels. Differences between patients, first-degree relatives and controls were especially evident among 164 Italians compared to 329 Caucasian-Americans, because arylesterase activity was significantly higher in Italian controls, compared to Caucasian-American controls (P=2.84×10⁻¹⁶). Arylesterase activity and PON protein concentrations were not significantly correlated, supporting a functional inhibition of arylesterase activity in ASD patients over quantitative changes in protein amounts. Serum arylesterase activity, in combination with PON1 genotypes at two single nucleotide polymorphisms (SNPs) known to influence protein amounts (rs705379: C-108T) and substrate specificity (rs662: Q192R), was able to discriminate ASD patients from controls with elevated sensitivity and specificity, depending on genotype and ethnic group. Serum arylesterase activity and genotyping at these two SNPs could thus represent an informative biochemical/genetic test, able to aid clinicians in estimating autism risk in ethnic groups with higher baseline arylesterase activity levels.

Pharmacological and dietary modulators of paraoxonase 1 (PON1) activity and expression: the hunt goes on

Paraoxonase 1 (PON1) is a high density lipoprotein (HDL)-associated enzyme displaying esterase and lactonase activity. PON1 hydrolyzes several organophosphorus (OP) insecticides and nerve agents, a number of exogenous and endogenous lactones, and metabolizes toxic oxidized lipids of low density lipoproteins (LDL) and HDL. As such, PON1 plays a relevant role in determining susceptibility to OP toxicity, cardiovascular diseases and several other diseases. Serum PON1 activity in a given population can vary by at least 40-fold. Most of this variation can be accounted for by genetic polymorphisms in the coding region (Q192R, L55M) and in the promoter region (T-108C). However, exogenous factors may also modulate PON1 activity and/or level of expression. This paper examines various factors that have been found to positively modulate PON1. Certain drugs (e.g. hypolipemic and anti-diabetic compounds), dietary factors (antioxidants, polyphenols), and life-style factors (moderate alcohol consumption) appear to increase PON1 activity. Given the relevance of PON1 in protecting from certain environmental exposure and from cardiovascular and other diseases, there is a need for further mechanistic, animal, and clinical research in this area, and for consideration of possible alternative strategies for increasing the levels and activity of PON1.

The three-gene paraoxonase family: physiologic roles, actions and regulation

The paraoxonase (PON) gene family is composed of three members (PON1, PON2, PON3) that share considerable structural homology and are located adjacently on chromosome 7 in humans. By far the most-studied member is PON1, a high-density lipoprotein-associated esterase/lactonase, also endowed with the capacity to hydrolyze organophosphates, but all the three proteins prevent oxidative stress and fight inflammation. They therefore seem central to a wide variety of human illnesses, including atherosclerosis, diabetes mellitus, mental disorders and inflammatory bowel disease. The major goal of this review is to highlight the regulation of each of the paraoxonase components by diverse nutritional molecules and pharmacological agents as well as a number of pathophysiological events, such as oxidative stress and inflammation. Considerable and detailed cell-based studies and animal model experiments have been provided to allow a thorough scrutiny of PON modulation, which will increase our understanding and ability to target these genes in order to efficiently increase their transcriptional activity and decrease the risks of developing different disorders.

No or only population-specific effect of PON1 on human longevity: a comprehensive meta-analysis

Paraoxonase 1 (PON1) has been suggested as a plausible candidate gene for human longevity due to its modulation of cardiovascular disease risk, by preventing oxidation of atherogenic low-density lipoprotein. The role of the PON1 192 Q/R polymorphism has been analyzed for association with survival at old age in several populations, albeit with controversial results. To reconcile the conflicting evidence, we performed a large association study with two samples of 2357 Germans and 1025 French, respectively. We combined our results with those from seven previous studies in the largest and most comprehensive meta-analysis on PON1 192 Q/R and longevity to-date, to include a total of 9580 individuals. No significant association of PON1 192 Q/R with longevity was observed, for either R allele or carriership. This finding relied on very large sample sizes, is supported by different analysis methods and is therefore considered very robust. Moreover, we have investigated a potential interaction of PON1 192 Q/R with APOE epsilon4 using data from four populations. Whereas a significant result was found in the German sample, this could not be confirmed in the other examined groups. Our large-scale meta-analysis provided no evidence that the PON1 192 Q/R polymorphism is associated with longevity, but this does not exclude the possibility of population-specific effects due to the influence of, and interaction between, different genetic and/or environmental factors (e.g. diet).

Ameliorative effects of vitamin C on short-term sensorimotor and cognitive changes induced by acute chlorpyrifos exposure in Wistar rats

Human and experimental animal studies have shown long- and short-term neurological sequelae following acute organophosphate (OP) exposure. Although the main molecular mechanism of OP neurotoxiicty involves acetylcholinesterase (AChE) inhibition, studies have also implicated the induction of oxidative stress. The present study was therefore aimed at evaluating the effect of acute chlorpyrifos (CPF) exposure on short-term sensorimotor and cognitive changes in Wistar rats, the role of brain lipoperoxidative changes and the effect of pretreatment with vitamin C. Twenty-eight rats divided into four groups of seven rats in each group served as subjects for this study. Rats in group I were given soya oil (2 ml/kg) while those in group II were dosed vitamin C (100 mg/kg). Group III were administered CPF only (42.5 mg/kg ∼50% of LD50), while group IV were pretreated with vitamin C (100 mg/kg) and then exposed to CPF (42.5 mg/kg), 30 min later. The regimens were administered once orally and the animals were examined for clinical signs, death and subjected to periodic neurobehavioral evaluation for motor strength, coordinated gait, neuromuscular coordination, learning and memory. At the end of 8 weeks of evaluation, the rats were sacrificed and the brain tissue evaluated for AChE activity and malonaldehyde (MDA) concentration, as an index of lipoperoxidative changes. The rats administered with CPF showed deficits in motor strength, coordinated gaits, neuromuscular coordination, learning and memory, slight decrease in AChE activity and an increase in brain MDA concentration. Pretreatment with vitamin C improved the neurobehavioral deficits and AChE activity, and caused a significant reduction in MDA concentration. In conclusion, the study has demonstrated that acute CPF exposure in Wistar rats caused short-term impairment in sensorimotor and cognitive functions partly due to brain lipoperoxidative changes, which were ameliorated by pretreatment with vitamin C.

Smoking and atherosclerotic cardiovascular disease: part II: role of cigarette smoking in cardiovascular disease development

Potential mechanisms and biomarkers of atherosclerosis related to cigarette smoking - a modifiable risk factor for that disease - are discussed in this article. These include smoking-associated inflammatory markers, such as leukocytes, high-sensitivity C-reactive protein, serum amyloid A, ICAM-1 and IL-6. Other reviewed markers are indicative for smoking-related impairment of arterial endothelial function (transcapillary leakage of albumin, inhibition of endogenous nitric oxide synthase activity and reduced endothelium-dependent vasodilation) or point to oxidative stress caused by various chemicals (cholesterol oxidation, autoantibodies to oxidized low-density lipoprotein, plasma levels of malondialdehyde and F(2)-isoprostanes and reduced antioxidant capacity). Smoking enhances platelet aggregability, increases blood viscosity and shifts the pro- and antithrombotic balance towards increased coagulability (e.g., fibrinogen, von Willebrand factor, ICAM-1 and P-selectin). Insulin resistance is higher in smokers compared with nonsmokers, and hemoglobin A1c is dose-dependently elevated, as is homocysteine. Smoke exposure may influence the kinetics of markers with different response to transient or chronic changes in cigarette smoking behavior.

Biomarkers of sensitivity and exposure in Washington state pesticide handlers

Organophosphate (OP) and N-methyl-carbamate (CB) insecticides are widely used in agriculture in the US and abroad. These compounds - which inhibit acetylcholinestersase (AChE) enzyme activity - continue to be responsible for a high proportion of pesticide poisonings among US agricultural workers. It is possible that some individuals may be especially susceptible to health effects related to OP/CB exposure. The paraoxonase (PON1) enzyme metabolizes the highly toxic oxon forms of some OPs, and an individual's PON1 status may be an important determinant of his or her sensitivity to these chemicals. This chapter discusses methods used to characterize the PON1 status of individuals and reviews previous epidemiologic studies that have evaluated PON1-related sensitivity to OPs in relation to various health endpoints. It also describes an ongoing longitudinal study among OP-exposed agricultural pesticide handlers who are participating in a recently implemented cholinesterase monitoring program in Washington State. This study will evaluate handlers' PON1 status as a hypothesized determinant of butyrylcholinesterase (BuChE) inhibition. Such studies will be useful to determine how regulatory risk assessments might account for differences in PON1-related OP sensitivity when characterizing inter-individual variability in risk related to OP exposure. Recent work assessing newer and more sensitive biomarkers of OP exposure is also discussed briefly in this chapter.

Paraoxonase variants relate to 10-year risk in coronary artery disease: impact of a high-density lipoprotein-bound antioxidant in secondary prevention

OBJECTIVES

We investigated the effects of paraoxonase (PON)-1 variants on long-term clinical outcome in patients with coronary artery disease (CAD).

BACKGROUND

PON-1 is a potential therapeutic target to further reduce cardiovascular risk because it is a detoxifying esterase with antioxidant properties. The PON-1 knockout models result in higher susceptibility to atherosclerosis, and PON activity contributes to cardiovascular risk in humans. Human gene variants determine PON activity; however, the impact of these variants on recurrent cardiovascular events in vascular disease is as of yet unknown.

METHODS

We conducted a 10-year follow-up study of 793 CAD patients in the REGRESS (REgression GRowth Evaluation Statin Study) trial cohort, using nationwide registries. Genotypes were obtained of 2 PON-1 isotypes (L55M, rs854560, and Q192R, rs662), which were previously associated with PON activity. Absolute and relative risks by genotype were estimated using Kaplan-Meier and proportional hazards analyses.

RESULTS

Carriership of the PON-1 glutamine isotype at codon 192 and methionine at codon 55 was associated with a higher risk of death due to ischemic heart disease. Hazard ratios per allele copy were 1.71 (95% confidence interval: 1.0 to 2.8, p=0.03) for the glutamine isotype at codon 192 and 1.56 (95% confidence interval: 1.1 to 2.3, p=0.03) for methionine at codon 55. Both isotypes had previously been related to lower PON activity. No effect was observed on all-cause mortality.

CONCLUSIONS

PON-1 gene variants influence the 10-year risk of fatal complications from CAD in male patients, despite no effect on all-cause mortality. These long-term findings confirm functional data on PON-1 activity, emphasize the relevance of this pathway in vascular disease, and enforce its putative role as a target to modify and estimate cardiovascular risk.

Paraoxonase 1 (PON1) expression in hepatocytes is upregulated by pomegranate polyphenols: a role for PPAR-gamma pathway

OBJECTIVE

Serum paraoxonase-1 (PON1) expression is regulated by polyphenols, shown to activate the peroxisome proliferator-activated receptor gamma (PPARgamma). Pomegranate juice (PJ) is a polyphenol-rich fruit. Because promoter sequence of PON1 gene indicates that it could be regulated by nuclear receptors, we investigated the effect of PJ polyphenols on PON1 gene expression in HuH7 hepatocytes.

METHODS AND RESULTS

PON1 protein or mRNA expression, determined by immunocytochemistry, or quantitative PCR, respectively, as well as PON1 gene promoter activation, was significantly increased in hepatocytes incubated with PJ or with its major polyphenols punicalagin, or gallic acid (GA). Ellagic acid (EA) elicited only modest stimulatory effect. Accordingly, PJ, punicalagin, GA, and less so EA, dose-dependently increased cell-associated and hepatocyte-secreted PON1 arylesterase activity. Functionally, the secreted PON1 exhibited biological activity by protecting LDL and HDL from oxidation. Finally, PJ polyphenols upregulated the hepatocyte PON1 expression, at least in part, via the intracellular signaling cascade PPARgamma-PKA-cAMP.

CONCLUSIONS

This study shows for the first time that PJ polyphenols have a specific transcriptional role in hepatocyte PON1 expression upregulation, and its secretion to the medium. We conclude that the anti-atherogenic characteristics of PJ polyphenols are modulated, at least in part, via hepatocyte PON1 upregulation and its subsequent release to the medium.

Serum cholinesterase inhibition in relation to paraoxonase-1 (PON1) status among organophosphate-exposed agricultural pesticide handlers

BACKGROUND

Animal studies have demonstrated that low paraoxonase-1 (PON1) status (i.e., low catalytic efficiency and/or low plasma PON1 activity) is associated with neurotoxic effects after exposure to several organophosphate (OP) insecticides. However, few human studies have investigated associations between PON1 status and intermediate end points, such as serum cholinesterase [butyrylcholinesterase (BuChE)] inhibition, among OP-exposed individuals.

OBJECTIVES

We evaluated the relation between plasma PON1 status and BuChE inhibition among OP-exposed agricultural pesticide handlers.

METHODS

Agricultural pesticide handlers in Washington State were recruited during the 2006 and 2007 spray seasons when they were seen for follow-up ChE testing by collaborating medical providers as part of a statewide monitoring program. Blood samples were collected from 163 participants and tested for PON1 status based on plasma PON1 activity [arylesterase (AREase)] and PON1 Q192R genotype. We evaluated percent change in BuChE activity from baseline level in relation to PON1 status.

RESULTS

We observed significantly greater BuChE inhibition among QQ homozygotes relative to RR homozygotes (p = 0.036). Lower levels of plasma PON1 activity were significantly associated with greater BuChE inhibition (p = 0.004). These associations remained after adjustment for year, days since baseline test, age, and OP exposure in the last 30 days.

CONCLUSIONS

We found that both low PON1 catalytic efficiency (i.e., the Q192 alloform) and low plasma PON1 activity were associated with BuChE inhibition among OP-exposed agricultural pesticide handlers. Corroborative findings from future studies with prospective collection of blood samples for PON1 testing, more sensitive markers of OP-related effects, and larger sample sizes are needed.

Both paraoxonase-1 genotype and activity do not predict the risk of future coronary artery disease; the EPIC-Norfolk Prospective Population Study

BACKGROUND

Paraoxonase-1 (PON1) is an antioxidant enzyme, that resides on high-density lipoprotein (HDL). PON1-activity, is heavily influenced by the PON1-Q192R polymorphism. PON1 is considered to protect against atherosclerosis, but it is unclear whether this relation is independent of its carrier, HDL. In order to evaluate the atheroprotective potential of PON1, we assessed the relationships among PON1-genotype, PON1-activity and risk of future coronary artery disease (CAD), in a large prospective case-control study.

METHODOLOGY/PRINCIPAL FINDINGS

Cases (n = 1138) were apparently healthy men and women aged 45-79 years who developed fatal or nonfatal CAD during a mean follow-up of 6 years. Controls (n = 2237) were matched by age, sex and enrollment time. PON1-activity was similar in cases and controls (60.7+/-45.3 versus 62.6+/-45.8 U/L, p = 0.3) and correlated with HDL-cholesterol levels (r = 0.16, p<0.0001). The PON1-Q192R polymorphism had a profound impact on PON1-activity, but did not predict CAD risk (Odds Ratio [OR] per R allele 0.98[0.84-1.15], p = 0.8). Using conditional logistic regression, quartiles of PON1-activity showed a modest inverse relation with CAD risk (OR for the highest versus the lowest quartile 0.77[0.63-0.95], p = 0.01; p-trend = 0.06). PON1-activity adjusted for Q192R polymorphism correlated better with HDL-cholesterol (r = 0.26, p<0.0001) and more linearly predicted CAD risk (0.79[0.64-0.98], p = 0.03; p-trend = 0.008). However, these relationships were abolished after adjustment for HDL (particles-cholesterol-size) and apolipoproteinA-I (0.94[0.74-1.18], p-trend = 0.3).

CONCLUSIONS/SIGNIFICANCE

This study, shows that PON1-activity inversely relates to CAD risk, but not independent of HDL, due to its close association with the HDL-particle. These data strongly suggest that a low PON1-activity is not a causal factor in atherogenesis.

Racial differences in paraoxonase-1 (PON1): a factor in the health of southerners?

BACKGROUND

The southern United States (excluding Florida) has the highest age-adjusted rate of cardiovascular disease (CVD) in the country, with African Americans having a higher prevalence of CVD than Caucasians. Paraoxonase-1 (PON1), an enzyme associated with high-density lipoprotein particles, participates both in the hydrolysis of oxidized lipids (thus protecting against atherosclerosis) and in the hydrolysis of organophosphates. Higher paraoxonase activity has been associated with lower risk of atherosclerosis.

OBJECTIVES

In this study we characterized the distribution of the functional PON1(Q192R) polymorphisms (PON status as assessed by diazoxonase to paraoxonase ratios) and the PON1 activity levels in 200 adult males and females of both races (50 in each race/sex class) from the southern United States from commercially obtained blood bank serum samples.

METHODS

We used spectrophotometric methods with serum to determine PON1 status, arylesterase activities (phenyl acetate hydrolysis), and levels of cotinine and C-reactive protein (CRP).

RESULTS

African Americans had higher paraoxonase activities but lower diazoxonase activities than did Caucasians, consistent with African Americans having a lower proportion of the functional genotype QQ (QQ 15%, QR 34%, RR 44%, 7% indeterminate), than did Caucasians (QQ 60%, QR 31%, RR 7%, 2% indeterminate). Cotinine levels indicated that all samples came from non-smokers and that CRP levels were higher in African Americans than in Caucasians and higher in females than in males. CRP levels showed no association with paraoxonase activities.

CONCLUSIONS

These data present initial observations for use in characterizing the poorer cardiovascular health status of the population in the southern United States and more specifically southern African Americans.

Variation in paraoxonase-1 activity and atherosclerosis

PURPOSE OF REVIEW

Paraoxonase-1 (PON1) is an HDL-associated protein of 354 amino acids with a molecular mass of 43 000 Da. It is synthesized in the liver, and in serum it is almost exclusively associated with HDL. PON1 has been reported to be an important contributor to the antioxidant and anti-inflammatory activities of HDL. PON1 impedes oxidative modification of LDL. PON1 serum activity is related to systemic lipid peroxidation stress and prospective cardiovascular risk. In this review, we discuss the relationship between PON1 activity and atherosclerotic diseases and various factors modulating PON1 activity including genes, age, lifestyle factors and medical conditions. Finally, evidence that pharmacological agents may affect PON1 activity is summarized.

RECENT FINDINGS

There is increasing evidence from both animal and human studies linking low PON1 activity to an increased likelihood of cardiovascular diseases. Two prospective studies reported a significantly lower incidence of major cardiovascular events in participants with the highest systemic PON1 activity, compared with those with the lowest activity.

SUMMARY

PON1 is a potentially antiatherogenic HDL-associated enzyme that protects LDL from oxidative modification. Enhancing PON1 activity could be an important target for future pharmacological agents aimed at decreasing cardiovascular risk.

The paraoxonases: role in human diseases and methodological difficulties in measurement

Research into the paraoxonase (PON) gene family has flourished over the past few years. In the 1970s and 1980s, only PON1 was known, and the investigations were conducted, essentially, by toxicologists focusing on protection against organophosphate poisoning. Since then, two new members of the family, PON2 and PON3, have been identified, both being shown to play antioxidant and anti-inflammatory roles. Evidence exists indicating that the PON family is central to a wide variety of human illnesses such as cardiovascular disease, diabetes mellitus, metabolic syndrome, obesity, non-alcoholic steatohepatitis, and several mental disorders. However, research is hampered considerably by the methods currently available to measure the activity of these enzymes. In this review, we summarize the state of knowledge on PON biochemistry and function, the influence of genetic variations, and the involvement of PON in several diseases. The problems associated with PON measurement, such as sample acquisition, lack of reference methods, and variety of substrates, will be presented. Also, we cover some of the present lines of research and propose some others for future progress in this field.

Paraoxonase 1 phenotype distribution and activity differs in subjects with newly diagnosed Type 2 diabetes (the CODAM Study)

AIMS

Paraoxonase 1 (PON1) is an antioxidant high-density lipoprotein-bound enzyme, which was recently found to be expressed in the islets of Langerhans. A substitution (Q/R) at position 192 results in enzymes with different activity. Oxidation has been implicated in the onset of diabetes, and it can be hypothesized that PON1 may have a protective effect on diabetes. Our aim was to compare PON1 activities and PON1 Q/R phenotypes in subjects with different degrees of glucose intolerance.

METHODS

We examined 566 members of the Cohort study of Diabetes and Atherosclerosis Maastricht (CoDAM), including subjects with normal glucose tolerance (NGT, n = 298), impaired glucose regulation (IGR, n = 128), newly diagnosed Type 2 diabetes (nDM, n = 78) and treated, that is to say known, Type 2 diabetes (kDM, n = 64). PON1 activity was measured in serum using paraoxon and diazoxon as substrates. The PON1 phenotype was determined using two-dimensional enzyme analysis.

RESULTS

The RR-phenotype was significantly more frequent in nDM compared with NGT subjects (14.1 vs. 6.0%, P = 0.05). Adjusted for the PON1 phenotype, subjects with nDM had significant lower PON1 activity towards paraoxon and diazoxon than subjects with NGT. Adjusted odds ratios comparing the RR-variant with the QQ-variant were 2.17 [95% confidence interval (CI): 0.90-5.24] for impaired glucose tolerance, 2.84 (95% CI: 1.03-7.83) for nDM, 2.13 (95% CI; 0.61-7.42) for kDM and 2.65 (95% CI: 1.10-6.40) for total diabetes mellitus.

CONCLUSIONS

An aberrant PON1 phenotype distribution and PON1 activity were observed in early diabetes. In addition, the higher state of oxidative stress may affect the future development of complications.

Effect of conjugated linoleic acid, vitamin E and their combination on lipid profiles and blood pressure of Iranian adults with active rheumatoid arthritis

The aim of this study was to assess the impact of conjugated linoleic acids (CLAs), vitamin E, and combination of these nutrients on serum lipid profiles and blood pressure (BP) in patients with active rheumatoid arthritis (RA). In a randomized, double-blind, placebo-controlled trial, 87 patients with active RA were divided into four groups receiving one of the following daily supplements for three months: Group C: CLAs 2.5 g equivalent to 2 g mixture of cis 9-trans 11 and trans 10-cis12 CLAs in a rate of 50/50; Group E: vitamin E: 400 mg; Group CE: CLAs and vitamin E at above doses: Group P: placebo. After supplementation, SBP levels decreased significantly in the group C in comparison with groups E and P and mean arterial pressure reduced significantly in groups C and CE. There weren't significant differences in the levels of prostaglandin E2 (PGE2), triglycerides, cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), LDL/HDL, cholesterol/HDL, fasting blood sugar, C-reactive protein (CRP), arylestrase activity, platelet count and body mass index between groups. CRP dropped nonsignificantly in groups P, C, E and CE (19%, 24%, 55%, and 39%, respectively). Erythrocytes sedimentation rate levels decreased in groups C, E and CE (P < or = 0.05, P < or = 0.05, P < or = 0.001, respectively). It is concluded that supplementation of CLAs decreased BP and vitamin E decreased CRP. Therefore co-supplementation of CLAs and vitamin E might be profitable for heart disease prevention in RA patients.

Lipid peroxidation in hemodialysis patients: effect of vitamin C supplementation

OBJECTIVES

Renal failure is associated with several metabolic disturbances and increasing evidences support a role of oxidative stress and impaired antioxidant defence in the pathologic mechanisms that may contribute to accelerated atherogenesis in these patients. Aim of the study was to further investigate the relationship between oxidative stress and chronic renal failure.

DESIGN AND METHODS

We compared the paraoxonase (PON1) activity, the levels of lipid hydroperoxides and AGE adducts in plasma of hemodialysis patients before and after intravenous administration of vitamin C.

RESULTS

An increase in lipid hydroperoxides, AGE adducts and a decrease in the activity of PON1 were observed in patients with respect to controls. The comparison before and after supplementation with vitamin C showed an increase of PON1 activity and a decrease of AGE and lipid hydroperoxides levels.

CONCLUSIONS

The results provide further evidence that lipid peroxidation and impairment of antioxidant system in plasma of patients may play a role in renal disease and suggest that evaluation of PON1 activity could represents an useful approach to monitor antioxidant treatment and new dialysis therapies.

Paraoxonase and arylesterase activities in patients with cardiac syndrome X, and their relationship with oxidative stress markers

OBJECTIVES

Paraoxonase-1 is a high-density lipoprotein-associated enzyme with three activities, which are paraoxonase, arylesterase and dyazoxonase. Paraoxonase-1 was shown to decrease in patients with cardiovascular diseases. We aimed to examine serum paraoxonase and arylesterase activities, and their relation with oxidative stress markers such as lipid hydroperoxide and total antioxidant status in patients with cardiac syndrome X.

METHODS

Forty-one consecutive patients with cardiac syndrome X (CSX group), 33 consecutive patients without cardiac syndrome X (non-cardiac syndrome X group) and 20 healthy volunteers as control group were taken into the study. Serum paraoxonase and arylesterase activities were measured spectrophotometrically. Lipid hydroperoxide levels were measured by ferrous oxidation with xylenol orange assay. Total antioxidant status was determined using an automated measurement method.

RESULTS

Basal paraoxonase, salt-stimulated paraoxonase and arylesterase activities were significantly lower in patients with cardiac syndrome X than those of the non-cardiac syndrome X and control groups (P<0.001, for both). Moreover, lipid hydroperoxide was found at high level, and total antioxidant status was found at low level in patients with cardiac syndrome X than control and non-cardiac syndrome X groups (P<0.001, for all). In patients with cardiac syndrome X, in multiple linear regression analysis, both paraoxonase and arylesterase activities were independently correlated with lipid hydroperoxide levels (P=0.001, P=0.003, respectively), and also arylesterase activity was independently correlated with magnitude of ST depression (P=0.002).

CONCLUSION

Reduced paraoxonase and arylesterase activities and total antioxidant status levels and enhanced lipid hydroperoxide levels in patients with cardiac syndrome X might indicate increased oxidative stress that can play a role in pathogenesis of cardiac syndrome X.

Atherosclerosis and oxidant stress: the end of the road for antioxidant vitamin treatment?

Extensive experimental data have revealed a central role for oxidative stress in atherogenesis and suggested a potential role for 'antioxidant' treatment in cardiovascular disease (CVD) [1-11]. Experimental data, however, have not translated into clinical benefit: most antioxidant vitamin trials have failed to reduce cardiovascular morbidity and mortality [12]. Moreover, recent clinical trials have suggested that mono-therapy with certain antioxidant vitamins like vitamin E may, in fact, be detrimental [13]. As a result of the disappointing outcome of 'antioxidant' vitamin trials, some authors have questioned both the utility of 'antioxidant' treatment in CVD and the supposedly central role of oxidative stress in atherogenesis [14-19]. Other investigators, however, sustain that the beneficial effects of lipid lowering and anti-hypertensive treatment are at least, in part, due to their 'antioxidant' properties, in addition to their specific pharmacological properties [20, 21]. Oxidant stress plays a pivotal role in atherogenesis, however, the clinical promise of antioxidant vitamins has failed to translate into clinical benefit. Increasing evidence suggests that more rigorous clinical trial designs are necessary to effectively divulge antioxidant utility and that a multifaceted antioxidant approach to atherosclerosis may yield the most clinical reward. This article reviews currently available evidence on the role of oxidant stress in atherosclerosis, analyzes the results of large anti-oxidant trials, and suggests ways to investigate the true role of antioxidant treatment in the clinical setting.

Alpha-tocopherol supplementation prevents the exercise-induced reduction of serum paraoxonase 1/arylesterase activities in healthy individuals

OBJECTIVE

To investigate PON 1/Aryl activities in basketball players with or without alpha-T supplementation pre- and post-training. Vitamin E (alpha-tocopherol, alpha-T) reduces lipid peroxidation. Paraoxonase 1/arylesterase (PON 1/Aryl) activities are closely related to oxidation and atherogenesis.

SUBJECT/METHODS

Blood was obtained from 10 players pre- (group A), post-exercise (group B) and after 1 month on alpha-T (200 mg per 24 h orally) supplementation pre- (group C) and post-exercise (group D). Lactate, pyruvate, muscle enzyme activities, creatine kinase, lactate dehydrogenase and total antioxidant status (TAS) were measured with commercial kits. Catecholamines and alpha-T were determined with high-performance liquid chromatography methods and PON 1/Aryl activities spectrophotometrically.

RESULTS

Lactate, pyruvate, muscle enzyme activities and catecholamines were increased (P<0.001) in all groups post-training. Alpha-T levels remained unaltered pre- vs post-exercise. TAS was decreased in all the groups post training. PON 1/Aryl activities were significantly decreased post-exercise (group B) (PON1: 65+/-12 U min(-1) ml(-1), Aryl: 58+/-14 KU min(-1) ml(-1)) as compared to those pre-exercise (group A) (PON1: 142+/-16 U min(-1) ml(-1), Aryl: 114+/-12 KU min(-1) ml(-1), P<0.001). In contrast, the studied enzyme activities remained practically unaltered after alpha-T supplementation pre- vs post-training. Both enzyme activities positively correlated to TAS (r=0.60, P<0.001).

CONCLUSIONS

Alpha-T supplementation may result in protection of the enzyme PON 1/Aryl activities from free radical production.

Vitamin E dietary supplementation significantly affects multiple risk factors for cardiovascular disease in baboons

BACKGROUND

Oxidative stress is a widely accepted risk factor for cardiovascular disease (CVD), but the CVD benefit of dietary antioxidants, such as vitamin E, is controversial.

OBJECTIVE

Therefore, we have investigated, in the baboon model, the effects of dietary vitamin E supplementation on risk factors for CVD.

DESIGN

Pedigreed baboons (n = 251) were fed 2 atherogenic diets, high in fat and cholesterol, that differed in vitamin E concentrations. After 7 wk on each diet, blood samples were taken, and a panel of CVD risk factor traits (ie, indicators of lipoprotein metabolism and oxidative stress) were measured.

RESULTS

Vitamin E supplementation caused significantly higher total antioxidant status (TAS) and lower oxidized LDL as expected. In addition, vitamin E caused 2 paradoxical effects on HDL metabolism: higher apolipoprotein A-I (apo A-I) concentrations and lower HDL sizes. We calculated a difference (Delta) variable for each trait as the value on the high-vitamin E diet minus that on the low-vitamin E diet and determined that several HDL concentration Delta variables were significantly correlated with Delta TAS, but only one, Delta apo A-I, was independently correlated. Genetic analyses showed that 2 Delta variables, Delta paraoxonase and Delta HDL(2), were significantly heritable, but that neither Delta TAS nor Delta apo A-I were heritable.

CONCLUSIONS

Thus, our data show that dietary vitamin E improves TAS and LDL quality. They also show 2 apparently paradoxical effects on HDL metabolism: lower HDL(2), which is mediated by genes, and higher apo A-I, which is not. These effects have contrasting associations with CVD risk and may help account for the mixed results from clinical trials of dietary vitamin E.

Paraoxonase Activity Following Exercise-Based Cardiac Rehabilitation Program

PURPOSE

The effect of gender on paraoxonase activity was determined in 37 ischemic heart disease patients who underwent a 12-week aerobic exercise training program.

METHODS

Paraoxonase activity was measured by its arylesterase activity (spectrophotometrically, at 250 degrees C, wavelength 270 nm).

RESULTS

A 16.7% increase in paraoxonase activity was found following the 12-week exercise program. In addition, there was a significant gender effect with higher mean paraoxonase levels among women during both preexercise (20.8%) and postexercise (24.2%) testing.

CONCLUSIONS

Aerobic exercise training was found to be an effective means in inducing plasma levels elevation of the antioxidative, antiatherogenic paraoxonase in patients with coronary artery disease, and particularly in female patients.

Sex-specific QTL effects on variation in paraoxonase 1 (PON1) activity in Mexican Americans

Paraoxonase 1 (PON1), a high-density lipoprotein-associated enzyme known to protect against cellular damage from toxic agents, may also have antioxidant properties. PON1 activity levels have been reported to differ by sex in human and animal studies with females exhibiting higher basal levels. We measured PON1 activity frozen serum for 1,406 individuals in over 40 extended pedigrees from the San Antonio Family Heart Study (SAFHS). We used a maximum likelihood-based, variance decomposition approach implemented in SOLAR to test for genotype-by-sex (G x S) interaction on variation in PON1 activity and to determine if any of the four PON1 quantitative trait loci (QTL) previously reported by us for this population might account for sex differences in PON1 activity levels. The residual additive genetic correlation (rho(G) = 0.82) between males and females is significantly different from 1 (P = 0.009), suggesting that some of the genes that influence PON1 activity act differently in females and males or, possibly, that a different combination of genes influences this trait in each sex. In addition to the QTL at or near the PON structural locus on 7q21-22, three other potential QTLs were evaluated for sex-specific effects: one each on chromosomes 12, 17 and 19. The QTL on chromosome 17 (LOD = 2.32, P = 0.0003; flanked by microsatellite marker loci D17S974 and D17S969) shows a significant (P = 0.005) sex-specific effect on PON1 activity; accounting for 6% of the additive genetic variance in males and 20% in females. This study represents the first formal statistical genetic test for G x S interactions on normal quantitative variation in PON1 activity in humans.

EVALUATION OF SUBCHRONIC CHLORPYRIFOS POISONING ON HEMATOLOGICAL AND SERUM BIOCHEMICAL CHANGES IN MICE AND PROTECTIVE EFFECT OF VITAMIN C

Chlorpyrifos (CPF) is one of the most widely used organophosphorous insecticides in agriculture with its attendant adverse health outcomes. This study aimed at evaluating the effect of subchronic oral CPF administration on hematological and serum biochemical indices, and the possible ameliorating effect of vitamin C on the indices in mice. Thirty mice divided into 3 groups of 10 mice each were used for this study. Mice in group I (control) were dosed with vegetable oil, while those in group II were given CPF (21.3 mg/kg~ 1/5(th) LD(50)) only. Mice in group III were pretreated with vitamin C (100 mg/kg) prior to dosing with CPF 30 min later (Vitamin C + CPF-treated group). This regime was given to each group of mice three times a week for a period of ten weeks. During the study period, mice were examined for signs of toxicity, and weight of each mouse was measured every week. At the end of the study period, blood samples were collected from the mice and analyzed for packed cell volume (PCV), total red blood cell (RBC), white blood cell (WBC) and total protein (TP). Serum obtained from the blood was analyzed for Na( +, K+ and Cl-), urea, creatinine, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP). The results showed that mice in the vitamin C + CPF-treated group exhibited milder signs of toxicity and significant increase in weight gain (p<0.01) compared to the CPF-treated group. No significant increase in weight in the CPF-treated group was observed compared to the control. There was a significant increase in PCV, RBC, Hb, TP and creatinine, but a significant decrease was obtained in WBC, ALT and AST in the CPF-treated group compared to the control. All the parameters with the exception of WBC, ALT and AST (which increased significantly), were significantly decreased in the vitamin C + CPF-treated group compared to CPF-treated group. ALP was significantly elevated in the CPF-treated group compared to both the control and vitamin C + CPF-treated group. No significant changes in urea and the measured electrolytes in all three groups, except a significant decrease in the concentration of Na(+) was observed in the CPF-treated group compared to the control. The study demonstrated that pretreatment of CPF-administered mice with vitamin C significantly altered some important hematological and serum biochemical parameters, revealing the protective action of the vitamin against some organ damage induced by CPF.

Time-dependent modulation of rat serum paraoxonase 1 activity by fasting

High-density lipoprotein-associated paraoxonase 1 (PON1) protects the endothelium from the pro-oxidant activity of oxidised low-density lipoprotein. Whereas fasting has been related to increased oxidative stress, intermittent fasting and caloric restriction are associated to increased resistance to oxidative injury. Taking into consideration that serum PON1 activity is modulated by a restriction of caloric intake and because there is no evidence regarding PON1 response to total food deprivation, we investigated whether PON1 activity is involved in the response aimed to counteract the greater oxidative stress associated to fasting and whether serum PON1 activity is altered by the length of food deprivation. Male Wistar rats were randomly divided into five groups: fed and 6-, 12-, 24- or 48-h fasted rats. Serum PON1 activity increases within the first hours of fasting, representing a prompt adaptation designed to attenuate blood lipid peroxidation that cannot be sustained when fasting is prolonged. This PON1 response to early fasting could be part of the mechanisms triggered by periodically repeated short periods of food deprivation - intermittent fasting - which result in increased resistance to stress by stimulating antioxidant defences.

The Relationship between PON1 phenotype and PON1-192 genotype in detoxification of three oxons by human liver

Phosphorothioate pesticides (OP) such as diazinon, chlorpyrifos, and parathion are activated to highly toxic oxon metabolites by the cytochromes P450 (P450s), mainly in the liver. Simultaneously, the P450s catalyze detoxification of OP to nontoxic dearylated metabolites. The oxon is then detoxified to the dearylated metabolite by PON1, an A-esterase present in the liver and blood serum. The aims of this study were to define the influence of PON1-192 genotype and phenotype on the capacity of human liver microsomes (n = 27) to detoxify the oxons diazoxon, chlorpyrifos-oxon, and paraoxon. Near physiological assay conditions were used to reflect as closely as possible metabolism in vivo and because the hydrolytic activity of the allelic variants of PON1-192 are differentially affected by a number of conditions. The rates of hydrolysis of diazoxon, chlorpyrifos-oxon, and paraoxon varied 5.7-, 16-, and 56-fold, respectively, regardless of PON1-192 genotype. Individuals with the PON1-192RR genotype preferentially hydrolyzed paraoxon (p < 0.01), and the R allele was associated with higher hydrolytic activity toward chlorpyrifos-oxon, but not diazoxon. There were strongly significant relationships between phenylacetate and paraoxon hydrolysis (p < 0.001) and phenylacetate and chlorpyrifos-oxon hydrolysis (p < 0.001), but not between phenylacetate and diazoxon hydrolysis. These data highlight the importance of PON1 phenotype for efficient hydrolysis of paraoxon and chlorpyrifos-oxon, but environmental and yet unknown genetic factors are more important than PON1-192 genotype in determining capacity to hydrolyze diazoxon.

A long and winding road: defining the biological role and clinical importance of paraoxonases

Paraoxonase-1 (PON1) is an enzyme belonging to a three-member gene family, each of which is highly conserved in mammalian evolution. Whilst there is consensus that the paraoxonase family members have a general protective influence, their precise biological role has remained elusive. A toxicological role, protecting from environmental poisoning by organophosphate derivatives, drove much of the earlier work on the enzymes. More recently, clinical interest has focused on a protective role in vascular disease via a hypothesised impact on lipoprotein lipid oxidation. Recent confirmation that the primary activity of the paraoxonases is that of a lactonase considerably expands the potential sources of biological substrates for the enzyme. Studies on such substrates may shed further light on different mechanisms by which paraoxonases beneficially influence atherosclerosis, as well as defining possible roles in limiting bacterial infection and in innate immunity.

Paraoxonase and arylesterase activities in coronary artery disease

BACKGROUND

Paraoxonase-1 is an enzyme with three activities which are inversely related to cardiovascular diseases. Accordingly, the aim of the study was to investigate the paraoxonase, arylesterase activities and oxidative/anti-oxidative status in coronary artery disease (CAD) and their correlation with the extent of CAD.

MATERIALS AND METHODS

Study populations of 193 patients with angiographically documented CAD, 83 patients with normal coronary angiograms (NCAD) and 55 healthy volunteers were included in the study. The patients with CAD were divided into three categories according to the number of diseased coronaries. Also, a Gensini score was calculated for each patient. Serum paraoxonase and arylesterase activities were measured spectrophotometrically. Oxidative and anti-oxidative status was evaluated by measuring serum lipid hydroperoxide (LOOH), total anti-oxidant status (TAS) and free sulfhydryl groups (-SH = total thiol). Lipid parameters were determined by routine laboratory methods.

RESULTS

Serum paraoxonase and arylesterase activities, TAS and -SH levels were lower in the CAD group compared with the NCAD group and control group (P < 0.05, all). Serum LOOH levels of the CAD group were greater than those in both the control and NCAD groups (P < 0.05). The major decreases in paraoxonase, arylesterase activities, -SH and TAS levels and the major increase in LOOH levels were observed in the 3-vessels disease group. In multiple linear regression analysis, the Gensini score was independently correlated with paraoxonase activity (beta = -0.469, P < 0.001), -SH levels (beta = -0.232, P < 0.001), HDL levels and history of diabetes.

CONCLUSIONS

Both paraoxonase activity and -SH levels are independently associated with the presence and extent of CAD. Reduced paraoxonase activity and -SH levels may play a role in the severity of coronary atherosclerosis.

Vitamin C preserves the cardio-protective paraoxonase activity of high-density lipoprotein during oxidant stress

HDL-associated paraoxonase (PON) antioxidant enzyme activity is cardio-protective. We investigated whether vitamin C prevented loss of PON activity from HDL during oxidant stress. HDL was incubated with either hydrophilic or lipophilic peroxyl radical initiators in the absence (control) or presence of vitamin C (50 and 100 micromol/L). Regardless of the type of radical, accumulation of lipid oxidation products in HDL was similar in incubations lacking vitamin C. Loss of PON activity was greater in HDL exposed to hydrophilic, in contrast to lipophilic, radicals, but addition of vitamin C maintained enzyme activity. Vitamin C's capacity to attenuate loss of the HDL ability to prevent atherogenic modification of LDL (assessed as electrophoretic mobility) was, however, modest, and appeared limited only to those incubations in which HDL was exposed to lipophilic radicals. Our results indicate that vitamin C may, under some conditions, prevent loss of cardio-protective function from HDL during oxidant stress.