Genetic polymorphisms and activity of PON1 in a Mexican population

Modulatory Effect of Lifestyle-Related, Environmental and Genetic Factors on Paraoxonase-1 Activity: A Review

Paraoxonase-1 (PON1) is a calcium-dependent, HDL-bound serum hydrolase active toward a wide variety of substrates. PON1 displays three types of activities, among which lactonase, paraoxonase, arylesterase and phosphotriesterase can be distinguished. Not only is this enzyme a major organophosphate compound detoxifier, but it is also an important constituent of the cellular antioxidant system and has anti-inflammatory and antiatherogenic functions. The concentration and activity of PON1 is highly variable among individuals, and these differences can be both of genetic origin and be a subject of epigenetic regulation. Owing to the fact that, in recent decades, the exposure of humans to an increasing number of different xenobiotics has been continuously rising, the issues concerning the role and activity of PON1 shall be reconsidered with particular attention to growing pharmaceuticals intake, dietary habits and environmental awareness. In the following manuscript, the current state of knowledge concerning the influence of certain modifiable and unmodifiable factors, including smoking, alcohol intake, gender, age and genotype variation on PON1 activity, along with pathways through which these could interfere with the enzyme's protective functions, is presented and discussed. Since exposure to certain xenobiotics plays a key role in PON1 activity, the influence of organophosphates, heavy metals and several pharmaceutical agents is also specified.

The Relationship between Cancer and Paraoxonase 1

Extensive research has been carried out to understand and elucidate the mechanisms of paraoxonase 1 (PON1) in the development of diseases including cancer, cardiovascular diseases, neurological diseases, and inflammatory diseases. This review focuses on the relationship between PON1 and cancer. The data suggest that PON1, oxidative stress, chronic inflammation, and cancer are closely linked. Certainly, the gene expression of PON1 will remain challenging to study. Therefore, targeting PON1, redox-sensitive pathways, and transcription factors promise prevention and therapy in the development of several diseases, including cancer.

A Systematic Review of Studies on Genotoxicity and Related Biomarkers in Populations Exposed to Pesticides in Mexico

In agricultural activities, pest control is essential, and the most effective method is the use of chemical agents that also represent an important source of exposure to potentially toxic compounds. Pesticides constitute a heterogeneous group of compounds designed specifically to control different pests. Besides measuring their levels or that of their metabolites in air, plasma, serum, blood, urine, etc., some studies reported increased DNA damage levels after occupational or environmental pesticides exposure, evidenced by several cytogenetic biomarkers such as chromosomal aberrations (CA), sister chromatid exchanges (SCE), micronuclei frequency (MN) together with other nuclear abnormalities (NA), alkaline comet assay, but also changes in oxidative stress parameters and miRNA levels. Single or combined, these techniques have also been used in genotoxic biomonitoring studies of workers occupationally exposed to pesticides in Mexico. Despite being a country with great agricultural activity and reported excessive pesticide use, genotoxic studies have been relatively few and, in some cases, contradictory. A review was made of the studies available (published until the end of 2020 on PubMed, Web of Science, Redalyc and Scielo, both in English and Spanish) in the scientific literature that evaluated occupational exposure of human samples to pesticides assessed with DNA damage and related biomarkers in Mexico.

The Role of Nutritional Habits and Moderate Red Wine Consumption in PON1 Status in Healthy Population

Paraoxonase 1 (PON1) plays a role as antioxidant on HDL. Including in diet additionally ingest of polyphenolic compounds can stimulate PON1 transcription and increase its activity. The aim of this study was to evaluate the effect of dietary intake, red wine consumption, and PON1 genotypes (Q192R, L55M and C-108T) on the specific activity of PON1 in a healthy population. A descriptive and analytical pilot study was conducted in Mexican volunteers clinically healthy (n = 45) aged from 21–59 years. Over 6 weeks, the study participants ingested 120 mL of red wine per day. PON1 concentration, PON1 activities, genetic polymorphisms and dietary intake were evaluated. The preliminary fingerprinting of the wine was determined to corroborate the presence of phenolic compounds such as tannins and gallotannins. Neither dietary intake nor PON1 genotypes showed an effect on the specific activity of PON1. However, a significant increase in specific AREase activity after red wine consumption period was observed in the study participants. Our data suggest that the moderate consumption of red wine has a beneficial effect on PON1 specific AREase activity in this healthy Mexican population.

Factors associated to serum paraoxonase 1 activity in patients with cardiovascular disease

OBJECTIVE

Paraoxonase 1 (PON1) is an enzyme that has antioxidant potential, which confers a protective effect against the atherosclerotic process. However, studies associating genetics, dietary patterns and PON1 activity in individuals with cardiovascular disease (CVD) are scarce. Thus, the aim of the current study was to evaluate the influence of dietary factors on serum PON1 in CVD patients.

METHODS

Cross-sectional, sub-study of the BALANCE Program Trial. All patients aged 45 years or older and had evidence of established atherosclerotic disease in the preceding 10 years. Body weight, height, waist circumference, blood pressure, lipid profile and fasting glucose were collected. Food intake was assessed with 24-h dietary recall. Data was analyzed using SAS University Edition and a P value ≤ 0.05 was considered statistically significant. Sample was divided into three groups, according to the PON1 T(-107)C genotype (CC, CT and TT) and serum PON1 activity (Low, Medium, High).

RESULTS

There were no genotype differences for major factors. However, the systolic blood pressure was lower for CT individuals (p<0.05). Intake of cholesterol, saturated fatty acids (SFA) and monounsaturated fatty acids (MUFAS) was higher in patients with lower PON1 activity. Lipid ingestion tended to be higher in patients with lower PON1 activity (p=0.08). In the multivariate logistic regression model, SFA intake (P=0.03), genotype (P=0.09), gender (P=0.04), age (P=0.07) and carbohydrate intake (P=0.16) contributed the most to the serum PON1 activity.

CONCLUSION

Based on these findings, nutritional guidance for these patients becomes essential, since dietary components interact with serum PON1 activity more than genotype.

Relationship between internal and external factors and the activity of PON1

Paraoxonase 1 (PON1) is an A-esterase calcium-dependent enzyme that is associated with high-density lipoprotein (HDL) and capable of hydrolyzing a wide variety of substrates, including organophosphate (OP) pesticides. The PON1 phenotype can be modulated by multiple internal and external factors, thereby affecting the catalytic capacity of the enzyme. The aim of this study was to evaluate factors that could modulate PON1 activity in a sample occupationally exposed to pesticides. A cross-sectional, descriptive, and analytical study was carried out with 240 workers. The participants were stratified according to their level of pesticide exposure as reference, moderate-exposure, and high-exposure groups. PON1 activities (arylesterase/AREase, CMPAase, and ssPONase (salt-stimulated)) were determined by spectrophotometry, and the Q192R and L55MPON1 genotypes by real-time PCR. The most frequent genotypes were heterozygous (QR) and homozygous (LL) for PON1Q192R and PON1L55M polymorphisms, respectively. The internal factors associated with the activity of PON1 were the PON1 genotypes (55 and 192) and biochemical parameters related to the lipid profile, in contrast, various external factors related to diet and harmful habits as well as with exposure to pesticides were associated with the activity of PON1. However, using a multivariate mixed ordinal regression model, we found a significant reduction of ssPONase activity in the high-exposure group compared with the reference group only in haplotypes QQLL and RRLL.

Genotypes of Common Polymorphisms in the PON1 Gene Associated with Paraoxonase Activity as Cardiovascular Risk Factor

BACKGROUND

Paraoxonase-1(PON1) exhibits hydrolytic activity and prevents the oxidation of high and low-density lipoproteins. Polymorphisms in the PON1 gene have been associated with variations in paraoxonase activity and with the risk of coronary artery disease (CAD).

AIM OF THE STUDY

This study analyzed the association between the frequencies of genotypes of the L55 M and Q192 R SNPs in the PON1 gene with the PON1 activity and with CAD risk factors.

METHODS

Women, determined by body composition, biochemical markers, and arylesterase (AREase) and paraoxonase (CMPase) activities were studied. Genotyping of L55 M and Q192 R polymorphisms was performed by TaqMan. Seventeen studies were used in the meta-analysis.

RESULTS

A significant decrease in PON1 activity in carrying the LM/MM and QQ genotypes is identified, correlations are found between the AREase activity with glucose, cholesterol and atherogenic risk index. Carriers of the LM or MM genotype were related with obesity (OR = 1.6; p = 0.039), and the MQ haplotype has an effect on the decrease in AREase (β = ‒22.4; p <0.001) and CMPase (β = ‒3.8; p <0.001). In addition, a lower proportion of Native American admixture was observed in women with LM or MM genotype, while it was higher for the European proportion compared with the LL genotype (p <0.001).

CONCLUSIONS

The LL-L55 M and QR-Q192 R genotypes are identified as the most frequently in the different states or cities of the country, and genotypic proportions are different, probably depending on the genetic structure of the populations. The association that is reported more frequently in the different studies is with enzymatic activity.

Interactions between superoxide dismutase and paraoxonase polymorphic variants in nonsyndromic cleft lip with or without cleft palate in the Brazilian population

During development, oxidative stress is hypothesized to mediate embryotoxicity, which may be intensified by exposition to environmental factors and by genetic variations in the enzymes involved in protecting cells from these damaging effects, including superoxide dismutase (SOD) and paraoxonase (PON). The aim of this study was to evaluate the influence of single-nucleotide polymorphisms (SNP) in genes associated with the neutralization of oxidative stress (SOD and PON family members) in the risk of nonsyndromic oral cleft in the Brazilian population. Initially, we tested for association between 28 SNP in SOD1, SOD2, SOD3, PON1, PON2, and PON3 among 325 nonsyndromic cleft lip with or without cleft palate (NSCL±P) case-parent trios. Multiple logistic regression analyses were used to explore gene, GxG and GxE, involving factors that induce oxidative stress accumulation during pregnancy. Signals still significant after both Bonferroni correction and in permutation test were subsequently confirmed in an ancestry-structured case-control analysis with 722 NSCL±P and 866 controls from the same population. In the trio sample, transmission disequilibrium test (TDT) (allele and haplotype) and GxE analysis showed no significant associations, but multiple pairwise GxG interactions involving 10 SNP in PON1, PON2, and PON3 were detected and further examined in the case-control sample. The PON1 rs2237583 and PON2 rs17166879 yielded significant evidence of SNP-SNP interactions after adjustment for multiple tests (both Bonferroni correction and 10,000 permutation test). The C allele and the CT genotype of PON1 rs2237583 were associated with significant protective effects against NSCL±P, while rs3917490 showed a significant association only in the sample composed of patients displaying high African ancestry. Our results reveal associations between rs2237583 and rs3917490 in PON1 and GxG interactions containing rs2237583 and rs17166879 with the susceptibility of NSCL±P in the Brazilian population. Furthermore, this study underlines the recent tendency of taking into account potential GxG interactions to clarify the underlying mechanisms associated with the etiology of this common malformation. Environ. Mol. Mutagen. 60: 185-196, 2019. © 2018 Wiley Periodicals, Inc.

Investigation of associations between exposures to pesticides and testosterone levels in Thai farmers

We conducted a cross-sectional study to assess the relationship between pesticide exposures and testosterone levels in 133 male Thai farmers. Urine and serum samples were collected concurrently from participants. Urine was analyzed for levels of specific and nonspecific metabolites of organophosphates (OPs), pyrethroids, select herbicides, and fungicides. Serum was analyzed for total and free testosterone. Linear regression analyses revealed significant negative relationships between total testosterone and the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) after controlling for covariates (eg, age, BMI, smoking status). Positive significant associations were found between some OP pesticides and total testosterone. Due to the small sample size and the observational nature of the study, future investigation is needed to confirm our results and to elucidate the biological mechanisms.

Polymorphisms of lipid metabolism enzyme-coding genes in patients with diabetic dyslipidemia

Objective:

The polymorphisms/mutations of genes encoding proteins and enzymes involved in lipoprotein metabolism play important roles in the development of diabetic dyslipidemia. The aim of our study was to investigate the effects of LPL (rs320), LIPC (rs2070895), SCARB1 (rs5888), LCAT (rs2292318), CETP (rs708272), ADIPOQ (rs1501299), RETN (rs3745367), PON1 (rs662), and MNSOD (rs4880) gene polymorphisms on lipid metabolism and diabetic dyslipidemia.

Methods:

This case-control study included 217 patients with diabetic dyslipidemia and 212 healthy age- and gender-matched individuals. Genomic DNA isolation was performed from blood samples, and genotype analysis was performed using melting curve analysis on a LightCycler^® 480 Instrument. The chi-square test was used to compare genotype distribution and allele frequencies between the groups.

Results:

Significant associations were observed between LPL (rs320) (p<0.001), LIPC (rs2070895) (p<0.001), SCARB1 (rs5888) (p<0.001), LCAT (rs2292318) (p<0.001), CETP (rs708272) (p<0.001), ADIPOQ (rs1501299) (p=0.01), RETN (rs3745367) (p<0.001), and MNSOD (rs4880) (p<0.001) polymorphisms and diabetic dyslipidemia. However, no association was observed between PON1 (rs662) polymorphisms and diabetic dyslipidemia (p=0.611).

Conclusion:

LPL (rs320), LIPC (rs2070895), SCARB1 (rs5888), LCAT (rs2292318), CETP (rs708272), ADIPOQ (rs1501299), RETN (rs3745367), and MNSOD (rs4880) polymorphisms play an important role in basic molecular metabolism in diabetic dyslipidemia. Therefore, these polymorphisms may be used as a predictive marker for diabetic dyslipidemia in high-risk patients. (Anatol J Cardiol 2017; 17: 313-21)

Distribution of genetic variants of oxidative stress metabolism genes: Paraoxonase 1 (PON1) and Glutathione S-transferase (GSTM1/GSTT1) in a population from Southeastern Mexico

BACKGROUND

Paraoxonase 1 (PON1) and glutathione S-transferases (GSTs) are involved in the biotransformation of xenobiotics. Variation in the enzyme concentration and activity suggests individual differences for the degree of protection against oxidative stress.

AIM

This study analysed the distribution of SNPs Q192R, L55M (PON1) and variants in GSTM1 and GSTT1 genes in a population from Southeastern Mexico.

SUBJECTS AND METHODS

One hundred and fifty-one Mexican Mestizo healthy volunteers were included. PON1 polymorphisms were determined by Taqman allele discrimination real time-PCR, whereas GSTM1 and GSTT1 genes were determined with a multiplex PCR-based method.

RESULTS

All genotypes were in Hardy-Weinberg equilibrium, except for GSTM1. The genotypic distributions of Q192R and L55M were 22% QQ, 48% QR, 30% RR, 62% LL, 34% LM and 4% MM, respectively, whereas the allele frequencies were 0.46 (Q), 0.54 (R), 0.79 (L) and 0.21 (M). The most frequent haplotype was R/L (46.7%). It was found that 31% and 9% of the individuals had the GSTM1 and GSTT1 null genotype, respectively. The frequency of the combined null genotype GSTM1*0/GSTT1*0 was 4.64%.

CONCLUSION

The results showed that the frequencies of polymorphisms of PON1, GSTM1 and GSTT1 in the Yucatán population differ to those observed in other ethnic groups and provide useful data for epidemiological studies.

Prenatal Exposure to Organophosphorous Pesticides and Fetal Growth: Pooled Results from Four Longitudinal Birth Cohort Studies

BACKGROUND

Organophosphorous (OP) pesticides are associated with reduced fetal growth in animals, but human studies are inconsistent.

OBJECTIVES

We pooled data from four cohorts to examine associations of prenatal OP exposure with birth weight (n = 1,169), length (n = 1,152), and head circumference (n = 1,143).

METHODS

Data were from the CHAMACOS, HOME, Columbia, and Mount Sinai birth cohorts. Concentrations of three diethyl phosphate (ΣDEP) and three dimethyl phosphate (ΣDMP) metabolites of OP pesticides [summed to six dialkyl phosphates (ΣDAPs)] were measured in maternal urine. Linear regression and mixed-effects models were used to examine associations with birth outcomes.

RESULTS

We found no significant associations of ΣDEP, ΣDMP, or ΣDAPs with birth weight, length, or head circumference overall. However, among non-Hispanic black women, increasing urinary ΣDAP and ΣDMP concentrations were associated with decreased birth length (β = -0.4 cm; 95% CI: -0.9, 0.0 and β = -0.4 cm; 95% CI: -0.8, 0.0, respectively, for each 10-fold increase in metabolite concentration). Among infants with the PON1192RR genotype, ΣDAP and ΣDMP were negatively associated with length (β = -0.4 cm; 95% CI: -0.9, 0.0 and β = -0.5 cm; 95% CI: -0.9, -0.1).

CONCLUSIONS

This study confirms previously reported associations of prenatal OP exposure among black women with decreased infant size at birth, but finds no evidence of smaller birth weight, length, or head circumference among whites or Hispanics. Contrary to our hypothesis, we found stronger inverse associations of DAPs and birth outcome in infants with the less susceptible PON1192RR genotype. The large pooled data set facilitated exploration of interactions by race/ethnicity and PON1 genotype, but was limited by differences in study populations.

CITATION

Harley KG, Engel SM, Vedar MG, Eskenazi B, Whyatt RM, Lanphear BP, Bradman A, Rauh VA, Yolton K, Hornung RW, Wetmur JG, Chen J, Holland NT, Barr DB, Perera FP, Wolff MS. 2016. Prenatal exposure to organophosphorous pesticides and fetal growth: pooled results from four longitudinal birth cohort studies. Environ Health Perspect 124:1084-1092; http://dx.doi.org/10.1289/ehp.1409362.

p.Q192R SNP of PON1 seems not to be Associated with Carotid Atherosclerosis Risk Factors in an Asymptomatic and Normolipidemic Brazilian Population Sample

BACKGROUND

Evidences suggest that paraoxonase 1 (PON1) confers important antioxidant and anti-inflammatory properties when associated with high-density lipoprotein (HDL).

OBJECTIVE

To investigate the relationships between p.Q192R SNP of PON1, biochemical parameters and carotid atherosclerosis in an asymptomatic, normolipidemic Brazilian population sample.

METHODS

We studied 584 volunteers (females n = 326, males n = 258; 19-75 years of age). Total genomic DNA was extracted and SNP was detected in the TaqMan® SNP OpenArray® genotyping platform (Applied Biosystems, Foster City, CA). Plasma lipoproteins and apolipoproteins were determined and PON1 activity was measured using paraoxon as a substrate. High-resolution β-mode ultrasonography was used to measure cIMT and the presence of carotid atherosclerotic plaques in a subgroup of individuals (n = 317).

RESULTS

The presence of p.192Q was associated with a significant increase in PON1 activity (RR = 12.30 (11.38); RQ = 46.96 (22.35); QQ = 85.35 (24.83) μmol/min; p < 0.0001), HDL-C (RR= 45 (37); RQ = 62 (39); QQ = 69 (29) mg/dL; p < 0.001) and apo A-I (RR = 140.76 ± 36.39; RQ = 147.62 ± 36.92; QQ = 147.49 ± 36.65 mg/dL; p = 0.019). Stepwise regression analysis revealed that heterozygous and p.192Q carriers influenced by 58% PON1 activity towards paraoxon. The univariate linear regression analysis demonstrated that p.Q192R SNP was not associated with mean cIMT; as a result, in the multiple regression analysis, no variables were selected with 5% significance. In logistic regression analysis, the studied parameters were not associated with the presence of carotid plaques.

CONCLUSION

In low-risk individuals, the presence of the p.192Q variant of PON1 is associated with a beneficial plasma lipid profile but not with carotid atherosclerosis.

Allele frequencies of PON1 Q192R polymorphism in four populations of India

The allelic distribution at Paraoxonase 1 (PON1) Q192R polymorphism determines differential sensitivity towards certain organophosphate pesticides. The alleles Q (Glutamine) and R (Arginine) at amino acid position 192 are responsible for the lower and higher activity of the enzyme towards paraoxon respectively, making knowledge of this distribution in different populations vital. This study reports the genotype and allele frequencies of the Gln192Arg polymorphism of PON1 in four populations of India, comprising two caste and two tribal groups hitherto unexamined for this polymorphism. The R allele frequencies in Jat, Meo, Santhal and Zeliangrong populations were found to be 0.47, 0.45, 0.54 and 0.51 respectively. The gene diversity analyses show a high genetic differentiation at this locus indicative of the role of populations' history and other evolutionary forces. A comparison with allele frequencies among 106 populations from different continents showed a concordance with their geographic distribution which will have repercussions in policies targeting pesticide usage.

Recent progress in the genetics and epigenetics of paraoxonase: why it is relevant to children's environmental health

PURPOSE OF REVIEW

Children are more susceptible to exposures in utero and during early childhood that may result in developmental problems and chronic diseases. Novel discoveries in the field of molecular epidemiology that can help explain susceptibility to exposures and disease will be demonstrated using the multifunctional enzyme paraoxonase 1 (PON1) as an example.

RECENT FINDINGS

The broad PON1 variability in humans, partly due to differences in genetics and age, can confer differential susceptibility because this enzyme can detoxify organophosphate pesticides and has antioxidant properties. Epigenetics plays a significant role in the mediation of the effects of environmental exposure on human health and is hypothesized to be a major contributing factor to the early-life origins of adult disease. Studies highlighted in this review demonstrate the relationship of PON1 polymorphisms with microRNA binding in addition to a link between DNA methylation in the transcriptional regulatory region with changes in PON1 enzyme levels. Other important methodologies such as ancestry informative markers and lactonase activity can enhance studies involving PON1.

SUMMARY

This PON1 model demonstrates that integrating genetic and epigenetic factors, as well as other novel methodologies, can improve our understanding of important susceptibility factors linked to pediatric disease.

Effects of anaerobic training on paraoxonase-1 enzyme (PON1) activities of high density lipoprotein subgroups and its relationship with PON1-Q192R phenotype

AIM

Paraoxonase-1 (PON1) is an antiatherosclerotic enzyme located on high-density lipoprotein (HDL). The effects of anaerobic exercise on PON1 activity are unknown. Here we investigated the effects of anaerobic judo training on three different activities of same PON1 enzyme (TDPON1), including basal PON1, salt-stimulated PON1 (SPON1), and arylesterase (AE) activities, of serum, HDL, and HDL subgroups (HDLs; HDL and its subgroups) and its relationship with PON1-Q192R phenotype (PON1P).

METHODS

Our study included 18 Turkish national female judoists (mean age: 17.9 ± 0.8 years). Before and after 5 months of anaerobic training, critical speed (CS), TDPON1 activities, cholesterol levels in the serum and supernatants of HDLs obtained by polyethylene glycol, and other major blood lipids and lipoproteins (BLLPs) including triglycerides were determined using blood samples taken after overnight fasting. PON1P groups (PGs) were categorized as QQ (QG; persons with low activity) and R carriers (QR + RR) (RG; persons with high activity) according to SPON1/AE activity ratios. The results were considered statistically significant at P ≤ 0.05.

RESULTS

Anaerobic training resulted in significantly increased the cholesterol levels of HDLs (except HDL2-C) in all subjects, but not HDLs-C in PGs. Anaerobic training resulted in significant increases in most TDPON1 activities of serum and HDLs in all subjects and (except AE) in PGs, whereas SPON1 and HDL2 AE activities increased only in the RG, which was related to PON1P. However, PON1P was not related to other measured markers, including basal BLLP profiles.

CONCLUSIONS

Anaerobic training improved most TDPON1 activities of serum and HDLs and HDLs -C levels (except HDL2-C) in all subjects, but not HDLs-C in PGs. The beneficial effects of anaerobic training on SPON1 and HDL2 AE activities were depend on PON1P. The lack of response of HDL2-C to anaerobic exercise will require further research.

Determination of the genotype and phenotype of serum paraoxonase 1 (PON1) status in a group of agricultural and nonagricultural workers in the Coquimbo Region, Chile

Paraoxonase 1 (PON1) is a glycosylated enzyme that is found associated with high-density lipoproteins in blood. In addition to its endogenous antioxidant role, this enzyme is also involved in hydrolysis of organophosphate (OP) pesticides in plasma. PON1 activity shows great variability in the population as a result of a polymorphism in the coding sequence that is expressed as a Glu(Q)/Arg(R) substitution at position 192 of the amino acid sequence. The aim of this study was to determine the activity levels (phenotype) and genotype of PON1 in a group of 85 agricultural workers occupationally exposed to OP pesticides and compared to 97 control subjects without occupational exposure. Allelic and genotypic frequencies of PON1Q192R polymorphism, as well as their catalytic activities, were established for the first time in a group of agricultural Chilean workers. The Q allele was more frequently represented in our studied population (approximately 60%). The Q allele is less efficient than the R allele at metabolizing chlorpyrifos (CPF), the most widely used OP pesticide in the geographical areas where samples were obtained. Further, a large interindividual variability in PON1 activity was observed, suggesting wide variation of individual susceptibility to CPF, an issue that needs to be considered in human monitoring studies.

Paraoxonase 1 and its relationship with pesticide biomarkers in indigenous Mexican farmworkers

OBJECTIVE

Biomarkers of pesticide toxicity and paraoxonase 1 (PON1) phenotype and genotypes were evaluated in indigenous Mexican farmworkers exposed mainly to organophosphate (OP) pesticides.

METHODS

Acetylcholinesterase, butyrylcholinesterase, and PON1 activities--arylesterase and CMPAase activities--were evaluated spectrophotometrically. PON1 55 and 192 polymorphisms were determined by real-time polymerase chain reaction. Hematological parameters were evaluated using a cytometer.

RESULTS

Butyrylcholinesterase and arylesterase activities were lower in farmworkers, who also showed lower levels of leukocytes but higher percentages of lymphocytes when compared with the nonexposed group. Our results showed a high frequency of OP, high hydrolysis-related PON1 alleles (LL/QR and LL/RR) in the study population. An association was observed between CMPAase activity and PON1Q192R polymorphism.

CONCLUSIONS

Our results suggest that pesticide exposure modifies biochemical and hematological biomarkers in the study population, and that the phenotype of PON1 (CMPAase) is a sensible susceptibility biomarker of OP pesticide toxicity.

Organophosphate pesticide exposure, PON1, and neurodevelopment in school-age children from the CHAMACOS study

INTRODUCTION

Organophosphate (OP) pesticides remain widely used in agriculture. Previously, we reported that PON1 genotype was directly associated with neurodevelopment at age two, and that PON1 genotype may increase susceptibility to OP exposure.

OBJECTIVES

We examined the relationships of maternal and child PON1 genotype and enzyme activity levels and neurodevelopment at school age and examined their interaction with maternal dialkyl phosphate (DAP) metabolite levels to investigate differential susceptibility to OP-related neurotoxicity.

METHODS

Participants were from the CHAMACOS longitudinal birth cohort of Latino families in an agricultural region of California. We measured DAP metabolites of OP pesticides in maternal and child urine samples, and analyzed PON1192 and PON1-108 genotypes and enzyme activity [arylesterase (ARYase), paraoxonase (POase)] in maternal and child blood. We examined their association with children׳s performance on the Conners׳ Kiddie Continuous Performance Test (K-CPT) at 5 years (n=296) and the Wechsler Intelligence Scale for Children (WISC-IV) at 7 years (n=327).

RESULTS

Maternal and child PON1 genotype was not related to performance on K-CPT or WISC, although WISC scores tended to be lowest in children and children of mothers who carried the PON-108TT genotype. Pregnancy ARYase levels were positively associated with all WISC subscales (e.g., 4.0 point increase in Full Scale IQ per standard deviation increase in ARYase, 95% CI=1.6, 6.4), while pregnancy POase levels were positively associated with WISC Processing Speed only. Maternal PON1-108 weakly modified the relationship of maternal DAPS and K-CPT scores (pinteraction=0.21) and WISC verbal IQ (pinteraction=0.71). The association between DAPs and Full-Scale IQ was strongest for children of mothers with lowest-tertile ARYase levels (pinteraction=0.27). This relationship held for both diethyl and dimethyl DAPs and for all subscales of the WISC.

CONCLUSIONS

We extend our previous findings that PON1 genotype and enzyme levels may be directly related to performance on certain domains of neurodevelopment in school-age children. Lower maternal PON1 enzyme levels during pregnancy may also increase susceptibility of children to neurotoxicity from OP pesticide exposure.

Paraoxonase 1 polymorphisms within a Mississippi USA population as possible biomarkers of enzyme activities associated with disease susceptibility

Paraoxonase (PON1) hydrolyzes paraoxon (PO) and diazoxon (DZO), active metabolites of insecticides parathion and diazinon. The PON1 gene has single nucleotide polymorphisms (SNPs) including a codon 192 arginine (R) to glutamine (Q) and methionine (M) to leucine (L) at codon 55. Hydrolysis of PO (POase), DZO (DZOase), dihydrocoumarin (lactonase), and phenyl acetate (arylesterase) were evaluated for associations with race, gender, age, and PON1 55/192 SNP genotypes. Variables were analyzed both individually and in combination. QQ individuals had higher lactonase (p < 0.001) than RR individuals. This might partially explain why predominantly RR African Americans have higher rates of coronary disease than predominantly QQ Caucasians. Significant (p < 0.001) differences in arylesterase were seen among genotypes with QQ and MM lowest whereas RR and LL were highest. This opposes the prevailing belief that arylesterase is unaffected by genotype and suggests that this activity cannot be used to quantify PON1 protein.

RETRACTED: Paraoxonase I polymorphisms and attention/hyperactivity in school-age children from Mexico City, Mexico

Globally, organophosphate (OP) pesticide usage and exposure is widespread. Studies have found that fetuses and infants are more sensitive than adults to environmental toxicants and that prenatal exposure to low levels of OPs has been associated with Attention Deficit Hyperactivity Disorder-Like Phenotypes (ADHD-LP). Paraoxonase 1 (PON1) is an enzyme involved in detoxifying some OPs and its polymorphisms influence enzyme activity and quantity. The objective of this study was to examine whether maternal and/or child PON1 genotypes (PON1R192Q and PON1L55M) were associated with ADHD-LP in a Mexico City, Mexico birth cohort. PON1R192Q and PON1L55M genotypes in mothers (PON1R192Q: N=531; PON1L55M: N=458) and children (PON1R192Q: N=532; PON1L55M: N=478) from blood DNA were determined. We assessed ADHD-LP for children between the ages of 6 and 13 using Conners' Parent Rating Scales-Revised (CRS-R), Conners' Continuous Performance Test (CPT), and the parent scores for Behavior Assessment System for Children-2 (BASC2). Multivariable linear regression models were used to test relationships between ADHD-LP and PON1 polymorphisms. In these models, significant associations were observed with maternal genotypes but not with the child genotypes. A higher DSM IV Hyperactivity/Impulsivity score (β=3.27 points; 95% CI (0.89, 5.65)) and a 2.17 higher score in child DSM IV Total (95% CI (0.05, 4.29)) were observed for maternal PON155MM in comparison to PON155LM+LL. The childattention problems score was 2.27 points higher (95% CI (0.002, 4.53) for maternal PON1192QQ in comparison to PON1192QR+RR. Because maternal PON1 polymorphisms were associated with child ADHD-LP, this may be a viable biomarker of susceptibility for ADHD-LP.

Paraoxonase activity and genetic polymorphisms in northern Han Chinese workers exposed to organophosphate pesticides

Paraoxonase (PON1) is one of the major players in the detoxification of organophosphates (OPs). This study presents our investigation into the effect of OPs on serum PON1 activity and the distribution of common PON1 polymorphisms in Han Chinese workers with repeated high exposure to OP pesticides, and the factors modulating PON1 activity. In all, 400 participants, including 180 workers exposed to OP pesticides occupationally, and 220 controls were investigated. Serum PON1 and cholinesterase (ChE) activity were measured, and genotyping was done using polymerase chain reaction-restriction fragment length polymorphism. The association between PON1 activity and PON1 polymorphisms, and the influencing factors of PON1 activity, were analyzed. The results revealed that repeated OP exposures significantly decreased serum PON1 and ChE activity (P< 0.05), although the exposed workers did not complain of health problems. Higher L and R allele frequencies for the L55M and Q192R polymorphisms of PON1 were observed. PON1 polymorphisms (especially the Q192R polymorphism) and pesticide exposures significantly affected serum PON1 activity in the study population. Therefore, the results of this investigation indicate PON1 polymorphisms and pesticide exposures may be important risk predictors for OP poisoning in the Han Chinese population, who display very high frequencies of the M allele and R allele for PON1 polymorphisms at the positions 55 and 192, respectively.

Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: a systematic review

Many studies have investigated the neurodevelopmental effects of prenatal and early childhood exposures to organophosphate (OP) pesticides among children, but they have not been collectively evaluated. The aim of the present article is to synthesize reported evidence over the last decade on OP exposure and neurodevelopmental effects in children. The Data Sources were PubMed, Web of Science, EBSCO, SciVerse Scopus, SpringerLink, SciELO and DOAJ. The eligibility criteria considered were studies assessing exposure to OP pesticides and neurodevelopmental effects in children from birth to 18 years of age, published between 2002 and 2012 in English or Spanish. Twenty-seven articles met the eligibility criteria. Studies were rated for evidential consideration as high, intermediate, or low based upon the study design, number of participants, exposure measurement, and neurodevelopmental measures. All but one of the 27 studies evaluated showed some negative effects of pesticides on neurobehavioral development. A positive dose-response relationship between OP exposure and neurodevelopmental outcomes was found in all but one of the 12 studies that assessed dose-response. In the ten longitudinal studies that assessed prenatal exposure to OPs, cognitive deficits (related to working memory) were found in children at age 7 years, behavioral deficits (related to attention) seen mainly in toddlers, and motor deficits (abnormal reflexes) seen mainly in neonates. No meta-analysis was possible due to different measurements of exposure assessment and outcomes. Eleven studies (all longitudinal) were rated high, 14 studies were rated intermediate, and two studies were rated low. Evidence of neurological deficits associated with exposure to OP pesticides in children is growing. The studies reviewed collectively support the hypothesis that exposure to OP pesticides induces neurotoxic effects. Further research is needed to understand effects associated with exposure in critical windows of development.

Associations of PON1 and genetic ancestry with obesity in early childhood

Obesity in children has become an epidemic in the U.S. and is particularly prominent in minority populations such as Mexican-Americans. In addition to physical activity and diet, genetics also plays a role in obesity etiology. A few studies in adults and adolescents suggest a link between obesity and paraoxonase 1 (PON1), a multifunctional enzyme that can metabolize organophosphate pesticides and also has antioxidant properties. We determined PON1₁₉₂ genotype and arylesterase levels (ARYase, measure of PON1 enzyme quantity), to characterize the relationship between PON1 and obesity in young Mexican-American children (n = 373) living in an agricultural community in California. Since PON1 polymorphisms and obesity both vary between ethnic groups, we estimated proportional genetic ancestry using 106 ancestral informative markers (AIMs). Among children, PON1₁₉₂ allele frequencies were 0.5 for both alleles, and the prevalence of obesity was high (15% and 33% at ages two and five, respectively). The average proportion of European, African, and Native American ancestry was 0.40, 0.09, and 0.51, yet there was wide inter-individual variation. We found a significantly higher odds of obesity (9.3 and 2.5- fold) in PON1_192QQ children compared to PON1_192RR children at ages two and five, respectively. Similar relationships were seen with BMI Z-scores at age two and waist circumference at age five. After adjusting for genetic ancestry in models of PON1 and BMI Z-score, effect estimates for PON1₁₉₂ genotype changed 15% and 9% among two and five year old children, respectively, providing evidence of genetic confounding by population stratification. However even after adjustment for genetic ancestry, the trend of increased BMI Z-scores with increased number of PON1₁₉₂ Q alleles remained. Our findings suggest that PON1 may play a role in obesity independent of genetic ancestry and that studies of PON1 and health outcomes, especially in admixed populations, should account for differences due to population stratification.

The Q192R polymorphism of the paraoxonase 1 gene is a risk factor for coronary artery disease in Saudi subjects

Paraoxonase-1 (PON1) is a HDL-bound antioxidant enzyme that protects LDL from oxidative modification. Discovery of the antioxidant properties of PON1 led to extensive research on its role in the initiation and progression of atherosclerosis. The Q192R (rs662; A/G) polymorphism, which results in the glutamine to arginine substitution at position 192, of the PON1 gene has been linked to increased atherosclerosis risk in several but not all population studies. Besides genetic factors, environmental variables and ethnicity have been implicated as factors responsible for the ambiguity in relating the PON1 gene with atherosclerotic risk. Here, we tested the association of the Q192R polymorphism with coronary artery disease (CAD) in Saudi ethnic subjects taking environmental factors into consideration. The genomic DNA samples from 121 angiographically confirmed CAD cases and 108 normal healthy control subjects were genotyped by PCR-RFLP analysis. The distribution of QQ, QR, and RR genotypes was significantly different between cases and controls (p < 0.005). The RR genotype was associated with CAD risk independently of several established risk factors including age, gender, smoking, obesity, and diabetes (OR 2.2, 1.4-7.4, p < 0.01). Genotype-based stratification of demographic and biochemical data revealed that the RR genotype has proatherogenic properties. This study, thus, identifies the Q192R polymorphism as an additional risk factor for CAD in the Saudi population and suggests that it may have prognostic value. The negative effect of this genetic variant is presumably due to the diminished ability of the RR variant genotype of PON1 to blunt LDL oxidation.

Effect of paraoxonase 1 192 Q/R polymorphism on paraoxonase and acetylcholinesterase enzyme activities in a Turkish population exposed to organophosphate

Organophosphate (OP) compounds are the most commonly used pesticide groups and they are commercially used in the market for local and industrial purposes. Paraoxonase 1 (PON1) enzyme plays an important role in biotransformation of OP compounds, which shows toxic effects via inhibiting the acetylcholinesterase (AChE). The aim of this study was to determine the effects of PON1 gene polymorphism and its effects on PON and AChE enzyme activities in individuals who were exposed to organophosphorus insecticides due to occupational reasons, and to profile the probability of susceptibility to organophosphorus compounds. For this purpose, 54 individuals who were exposed to OPs and 54 healthy unrelated controls were studied. First, PON1 and AChE enzyme activities were measured. Second, PON1 192 Q/R polymorphism was determined by standard polymerase chain reaction–restriction fragment length polymorphism technique. When the PON1 192 Q/R polymorphism was compared with PON1 enzyme activities, statistically significant association was found in both OP-exposed and control groups ( p < 0.05). PON1 192 R(+) (QR + RR genotypes) genotype carriers had higher PON1 activities than 192 R(−) (QQ) genotype carriers. On the other hand, results were statistically analyzed in terms of AChE enzyme activities and there were statistically significant differences only in the OP-exposed group ( p < 0.05). The mean AChE concentration in the OP-exposed group was determined as 33.79 ± 6.84 U/g haemoglobin (Hb) for PON1 192 R(+) carriers and 30.37 ± 7.62 U/g Hb for PON1 192 R(+) carriers. As a conclusion, PON1 and AChE activities were increasing according to the genotypes found in individuals having been exposed to OPs at a chronic level; 192 R(+) > 192 R(−), respectively.

Two- and three-locus haplotypes of the paraoxonase (PON1) gene are associated with coronary artery disease in Asian Indians

INTRODUCTION

In view of the reported association of SNPs in the paraoxonase (PON1) gene with coronary artery disease (CAD), and the absence of conclusive data from India, we investigated the relationship of three SNPs at different loci (-108C/T, L55M and Q192R) of the PON1 gene and their haplotypes with CAD among people residing in the northern plains of India.

MATERIALS AND METHODS

One hundred and seventy-eight healthy controls and two hundred and four angiographically-proven CAD patients were genotyped using PCR-RFLP.

RESULTS

Of the three SNPs, only the R allele of Q192R polymorphism was associated with CAD (p<0.05). Two locus haplotypes QT (OR 0.55, p=0.0004, 95% CI 0.39-0.77, significant) and LQ (odds ratio 0.73, p=0.03, 95% CI 0.55-0.97, trend) showed protective effects, while haplotypes MR (OR=5.36, p=0.0001, 95% CI 2.045-14.049) and MC (OR=2.71, p=0.011, 95% CI 1.221-6.046) were associated with increased risk of CAD. MRT, a minor three-locus haplotype also displayed significant association (OR 4.93, 95% CI 1.7-13.5) with the disease. Significance was assessed after applying Bonferroni's correction.

CONCLUSIONS

Our study revealed that only one SNP at a single locus but several haplotype combinations of PON1 coding and promoter-region polymorphisms were associated with the risk of or protection against CAD. Thus, haplotype analysis brought better insights into the association of PON1 gene polymorphisms with CAD in Asian Indians.

Effect of cigarette smoking on paraoxonase 1 activity according to PON1 L55M and PON1 Q192R gene polymorphisms

OBJECTIVE

This study aims to investigate the effect of cigarette smoking on paraoxonase 1 (PON1) activity according to PON1 L55M and PON1 Q192R gene polymorphisms.

MATERIALS AND METHODS

Our sample included 300 voluntary subjects: 138 nonsmokers and 162 current smokers aged 38.47 ± 21.91 and 35.55 ± 16.03 years, respectively. PON1 activity was determined by kinetic methods. L55M and Q192R gene polymorphisms of PON1 were determined by multiplex polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP).

RESULTS

We found in smokers a significant decrease of PON1 activity before and after adjustment. We noted a significant association between smoking status and lower PON1 activity [odds ratio (OR) = 3.03, confidence interval 95% = 1.5-5.9, p = 0.001]. In smokers, there was significant association between PON1 activity and PON1 L55M polymorphisms (p = 0.01). Also, the 55MM genotype presented the lowest paraoxonase activity, while the 55LL genotype showed the highest one. After adjustment for confounding variables, smokers with PON1 L55M polymorphism had the highest risk for lower PON1 activity; however, PON1 Q192R genotype might protect smokers from decrease in PON1 activity. We found significant interaction between the effect of cigarette smoking and both PON1 L55M and PON1 Q192R polymorphisms on lower PON1 activity.

CONCLUSIONS

Cigarette smoking was significantly associated with decrease in PON1 activity. Moreover, PON1 L55M polymorphism predisposes smokers to decreased PON1 activity in contrast to PON1 Q192R genotype.

Relationship between the paraoxonase (PON1) L55M and Q192R polymorphisms and obesity in a Mexican population: a pilot study

The aim of this study was to examine the relationship between the L55M and Q192R paraoxonase (PON1) polymorphisms and obesity in a population of adult Mexican workers. The study population included 127 adult individuals from the Universidad Autónoma del Estado de Morelos, ranging in age from 20 to 56 years and representing both sexes. Based on body mass index, 63 individuals were classified as obese and 64 as normal weight. The PON1-Q192R and PON1-L55M polymorphisms were determined by restriction fragment length polymorphism PCR analysis. Both arylesterase and paraoxonase activity levels were similar in both groups, whereas systolic pressure, triglyceride, total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, glucose, and insulin levels were higher in the obese group than in the normal-weight group (P < 0.05). An exception was the high-density lipoprotein cholesterol (HDL-C) levels, which were lower in the obese group (P < 0.05). Although the PON1-Q192R polymorphism was not associated with either group, the frequency of the homozygous L genotype for the PON1-L55M polymorphism was higher in the obese group than in the normal-weight group (P < 0.05). In conclusion, this study established a positive association between the PON1-L55M homozygous L genotype and obesity.

Paraoxonase 1 polymorphisms and haplotypes and the risk for having offspring affected with spina bifida in Southeast Mexico

BACKGROUND

Spina bifida (SB) is a common congenital malformation in Southeast Mexico. Parents of children with SB reside in areas with frequent pesticide spraying or have agriculture activities, suggesting potential exposure to pesticides. Paraoxonase 1 (PON1) is the responsible enzyme for deactivation of organophosphates (OP) in the central nervous system. Polymorphisms of PON1 genes influence the catalytic activity and plasma protein level of the enzyme, therefore, genotypic characterization of PON1 gene represents a potential predictor for susceptibility to OP-related effects.

METHODS

The frequency of PON1 haplotypes and polymorphisms (-108CT, L55M, and Q192R) were determined in this study. A case-control study was performed to evaluate the risk for having offspring affected by SB in 152 cases and 160 control parents. Polymorphisms were determined by PCR amplification and restriction fragment length polymorphism and Real Time-PCR. Odds ratios and confidence interval 95% were estimated.

RESULTS

Genotype frequencies for the three PON1 polymorphisms were distributed according to Hardy-Weinberg expectations (p > 0.05) and were significantly different between cases and controls (p < 0.05). The heterozygous CT genotype of -108CT polymorphism, the RR genotype of Q192R polymorphism, both LM and MM genotypes of L55M polymorphism, and the haplotypes 221 and 222 (for -108CT, L55M, and Q192R) were associated with the risk for having a child affected by SB (p < 0.02). The heterozygous -108CT genotype was associated only maternally, whereas the heterozygous L55M genotype was relevant only in the fathers. The RR homozygous genotype was relevant both in mothers and fathers, suggesting the importance of this substrate-specific polymorphism.

CONCLUSION

Results suggest that PON1 polymorphisms are relevant risk factors for having offspring affected with SB in this population from Southeast Mexico.

Effects of PON polymorphisms and haplotypes on molecular phenotype in Mexican-American mothers and children

Paraoxonase 1 (PON1) prevents oxidation of low-density lipoproteins and inactivates toxic oxon derivatives of organophosphate pesticides (OPs). More than 250 SNPs have been previously identified in the PON1 gene, yet studies of PON1 genetic variation focus primarily on a few promoter SNPs (-108, -162) and coding SNPs (192, 55). We sequenced the PON1 gene in 30 subjects from a Mexican-American birth cohort and identified 94 polymorphisms with minor allele frequencies >5%, including several novel variants (six SNPs, one insertion, and two deletions). Variants of the PON1 gene and three SNPs from PON2 and PON3 were genotyped in 700 children and mothers from the same cohort. PON1 phenotype was established using two substrate-specific assays: arylesterase (AREase) and paraoxonase (POase). Twelve PON1 and two PON2 polymorphisms were significantly associated with AREase activity, and 37 polymorphisms with POase activity; however, only nine were not in strong linkage disequilibrium (LD) with either PON1(-108) or PON1(192) (r(2) > 0.20), SNPs with known effects on PON1 quantity and substrate-specific activity. Single tagSNPs PON1(55) and PON1(192) accounted for similar ranges of AREase variation compared to haplotypes comprised of multiple SNPs within their haplotype blocks. However, PON1(55) explained 11-16% of POase activity, while six SNPs in the same haplotype block explained threefold more variance (36-56%). Although LD structure in the PON cluster seems similar between Mexicans and Caucasians, allele frequencies for many polymorphisms differed strikingly. Functional effects of PON genetic variation related to susceptibility to OPs and oxidative stress also differed by age and should be considered in protecting vulnerable subpopulations.

Frequency distribution of the single-nucleotide -108C/T polymorphism at the promoter region of the PON1 gene in Asian Indians and its relationship with coronary artery disease

A single-nucleotide promoter region polymorphism (-108C/T) of the paraoxonase (PON1) gene had been suggested to influence an individual's susceptibility to coronary artery disease (CAD). No data is available on this polymorphism from India. One hundred seventy-eight healthy individuals and 204 angiographically proven CAD patients were recruited to get baseline data on the frequency distribution of the -108C/T polymorphism in normal people of Asian Indian ethnicity and its relation with the risk of CAD. Polymerase chain reaction followed by restriction fragment length analysis was used as the method for genotyping. Blood samples were used for DNA isolation. In the normal subjects, the genotypes were distributed as CT (43.26%) > CC (30.34%), >TT (26.4%). The allele frequency of the C allele was 0.52, and that of the T allele was 0.48. The patients showed a similar pattern, but the TT genotype was about two times more frequent in the controls than in patients. Odds ratios for developing CAD for individuals with CT, TT, and CT + TT genotypes were 0.89 (0.50-1.59), 0.56 (0.27-1.08), and 0.76 (0.44-1.29), respectively (at 95% confidence interval), when compared to CC homozygous people (age- and sex-adjusted, p = 0.114, all genotypes compared). This suggested a trend for the T allele as protective against CAD. This first report on the frequency distribution of the -108C/T polymorphism in people of Asian Indian ethnicity suggests that the normal distribution is similar to that observed for the Chinese, Japanese, and Latino people, but the disease association is unique. The TT genotype and the T allele which are widely found associated with the risk of CAD showed a protective trend in this study.

Paraoxonase-1 genetic polymorphisms and susceptibility to DNA damage in workers occupationally exposed to organophosphate pesticides

Human paraoxonase 1 (PON1) is a lipoprotein-associated enzyme involved in the detoxification of organophosphate pesticides (OPs) by hydrolyzing the bioactive oxons. Polymorphisms of the PON1 gene are responsible for variation in the expression and catalytic activity of PON1 enzyme. In the present study, we have determined (a) the prevalence of two common PON1 polymorphisms, (b) the activity of PON1 and acetylcholinesterase enzymes, and (c) the influence of PON1 genotypes and phenotypes variation on DNA damage in workers exposed to OPs. We examined 230 subjects including 115 workers exposed to OPs and an equal number of normal healthy controls. The results revealed that PON1 activity toward paraoxon (179.19±39.36 vs. 241.52±42.32nmol/min/ml in controls) and phenylacetate (112.74±17.37 vs. 134.28±25.49μmol/min/ml in controls) was significantly lower in workers than in control subjects (p<0.001). No significant difference was observed in the distribution of genotypes and allelic frequencies of PON1(192)QR (Gln/Arg) and PON1(55)LM (Leu/Met) in workers and control subjects (p>0.05). The PON1 activity toward paraoxonase was found to be significantly higher in the R/R (Arg/Arg) genotypes than Q/R (Gln/Arg) and lowest in Q/Q (Gln/Gln) genotypes in both workers and control subjects (p<0.001). For PON1(55)LM (Leu/Met), PON1 activity toward paraoxonase was observed to be higher in individuals with L/L (Leu/Leu) genotypes and lowest in individuals with M/M (Met/Met) genotypes in both groups (p<0.001). No influence of PON1 genotypes and phenotypes was seen on the activity of acetylcholinesterase and arylesterase. The DNA damage was observed to be significantly higher in workers than in control subjects (p<0.05). Further, the individuals who showed least paraoxonase activity i.e., those with (Q/Q [Gln/Gln] and M/M [Met/Met]) genotypes showed significantly higher DNA damage compared to other isoforms in workers exposed to OPs (p<0.05). The results indicate that the individuals with PON1 Q/Q and M/M genotypes are more susceptible toward genotoxicity. In conclusion, the study suggests wide variation in enzyme activities and DNA damage due to polymorphisms in PON1 gene, which might have an important role in the identification of individual risk factors in workers occupationally exposed to OPs.

PON1 and neurodevelopment in children from the CHAMACOS study exposed to organophosphate pesticides in utero

BACKGROUND

Paraoxonase 1 (PON1) detoxifies oxon derivatives of some organophosphate (OP) pesticides, and its genetic polymorphisms influence enzyme activity and quantity. We previously reported that maternal urinary concentrations of dialkyl phosphate (DAP) metabolites, a marker of OP pesticide exposure, were related to poorer mental development and maternally reported symptoms consistent with pervasive developmental disorder (PDD) in 2-year-olds participating in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study.

OBJECTIVE

We determined whether PON1 genotypes and enzyme measurements were associated with child neurobehavioral development and whether PON1 modified the association of in utero exposure to OPs (as assessed by maternal DAPs) and neurobehavior.

METHODS

We measured DAP concentrations in maternal urine during pregnancy, PON1₁₉₂ and PON1₋₁₀₈ genotypes in mothers and children, and arylesterase (ARYase) and paraoxonase (POase) in maternal, cord, and 2-year-olds' blood. We assessed 353 2-year-olds on the Mental Development Index (MDI) and Psychomotor Development Index (PDI) of the Bayley Scales of Infant Development and queried their mothers on the Child Behavior Checklist to obtain a score for PDD.

RESULTS

Children with the PON1(-108T) allele had poorer MDI scores and somewhat poorer PDI scores. Children were less likely to display PDD when they or their mothers had higher ARYase activity and when their mothers had higher POase activity. The association between DAPs and MDI scores was strongest in children with PON1(-108T) allele, but this and other interactions between DAPs and PON1 polymorphisms or enzymes were not significant.

CONCLUSION

PON1 was associated with child neurobehavioral development, but additional research is needed to confirm whether it modifies the relation with in utero OP exposure.

Relationship between PON1L55M and Q192R gene polymorphisms and high APO B/APO A-I ratios

Elevated Apolipoprotein B Apolipoprotein A-I ratio is a risk factor for predicting coronary artery disease (CAD). Paraoxonase 1 (PON1) is a high density lipoprotein (HDL) associated serum enzyme. PON1 protects lowdensity lipoproteins (LDLs) from oxidative modifications and thus has a protective effect against CAD progression. There are two common polymorphisms, Q192R and L55M, in PON1 gene. There may be a relationship between these polymorphisms and elevated ApoB/ApoA-I ratios. Therefore, we decided to evaluate effect of these polymorphisms on individuals with high and normal ApoB/ApoA-I ratios. To evaluate Q192R and L55M polymorphisms in Iranian case group (n=75) with high ApoB/ApoA-I ratio, and control group (n=75) with normal ApoB/ApoA-I ratio, we carried out PCR using specific primers. Then, we digested PCR products by RFLP. ApoB and ApoA-I levels were determined by immunoturbidimetry method. Genotype frequencies for Q192R were determined: 49.3%QQ, 44%QR, 6.7%RR in case group, and 53.3%QQ, 33.3%QR, 13.4%RR in controls (P= 0.236). Genotype frequencies for L55M were determined: 21.3%LL, 68%LM, 10.7%MM in case group and 42.7%LL, 52%LM, 5.3%MM in controls (P= 0.016). A significant relationship between L55M polymorphism and familial history of cardiovascular disease was found (P= 0.011). In our study PON1L55M polymorphism was associated with high ApoB/ApoA-I ratios in case group. Thus, L55M polymorphism may be an independent risk factor for cardiovascular disease. Since L55M polymorphism was associated with familial history of cardiovascular disease, it is better to evaluate L55M polymorphism in younger ages even in the absence of high ApoB/ApoA-I ratios.

The role of paraoxonase polymorphisms in the induction of micronucleus in paraoxon-treated human lymphocytes

Human paraoxonase-1 (PON1) is a high-density lipoprotein-associated enzyme that has a role in the detoxification of organophosphorus compounds by hydrolyzing the bioactive oxons. PON1 polymorphims are responsible, at least in part, for the variation in the catalytic activity and expression of the enzyme and have been associated with susceptibility to organophosphorus pesticide toxicity, mainly neurotoxicity. The aim of this study was to determine whether paraoxon induced micronuclei and to examine the role of PON1 polymorphism in paraoxon's genotoxic potential. First, dose finding cytogenetic experiments were performed on lymphocyte cultures from three donors and a range of paraoxon concentration (1-25 microM) were tested. In a second set of experiments, 5 microM paraoxon was added to blood cultures of 11 donors with two different PON1 haplotypes (PON T(-108)M(55)Q(192) with low activity and haplotype PON C(-108)L(55) R(192) with high activity, referred to as PON1QQ and as PON1 RR, respectively). Because PON1 is present in blood, the effect of adding 5 microM paraoxon and 70 microl of autologous plasma to lymphocyte cultures also was examined. Paraoxon had no effect on cell viability, but caused a significant dose-dependent increase in MN frequency. The basal MN frequencies were similar on QQ and RR genotypes. A significant difference was observed in the MN frequency only in lymphocytes from individuals with the QQ genotype treated with 5 microM paraoxon and the autologous plasma did not modify these effects. The results obtained in this study suggest that PON1 genotype might have an important role in the identification of individuals at risk for cancer development due to occupational exposure to pesticides.

Maternal exposure to floricultural work during pregnancy, PON1 Q192R polymorphisms and the risk of low birth weight

BACKGROUND

Although there is evidence from animal studies of impaired reproductive function by exposure to organophosphates (OP), the effects on birth weight have not been sufficiently evaluated in epidemiological studies. Paraoxonase (PON1) detoxifies organophosphates by cleavage of active oxons. Some PON1 gene polymorphisms could reduce the enzyme activity and increase susceptibility to OP toxicity.

OBJECTIVE

To assess the association between maternal exposure to floriculture during pregnancy and the risk of low birth weight (<2500 g) in their offspring, as well as to evaluate the interaction between this exposure and maternal genotype for PON1 Q192R polymorphisms.

MATERIALS AND METHODS

A cross sectional study was carried out in two Mexican states (States of Mexico and Morelos) with high frequencies of greenhouse activity. We interviewed and collected blood samples from 264 females (floriculturists or partners of floricultural workers) who became pregnant during the 10 years prior to the interview. The questionnaire measured socioeconomic characteristics, tobacco and alcohol consumption, diseases and occupational and reproductive history. We also applied a food frequency questionnaire. Information was obtained pertaining to 467 pregnancies. DNA was extracted from white cells, and PON1 genotype was determined by Restriction Fragment Length Polymorphism for Q192R polymorphisms. Results were analyzed with generalized estimating equations models.

RESULTS

After adjusting for potential confounders, we detected a statistically significant interaction between maternal exposure to flower growing work during pregnancy and PON1 Q192R polymorphisms on risk of low birth weight. The risk of having a baby with LBW is nearly six times higher if a mother is a floriculture worker during pregnancy and has PON1 192RR genotype (OR 5.93, 95% CI 1.28, 27.5).

CONCLUSION

These results suggest that the interaction between maternal floriculture work during pregnancy and 192RR PON1 genotype increases the probability of having children with LBW.

Developmental changes in PON1 enzyme activity in young children and effects of PON1 polymorphisms

BACKGROUND

Paraoxonase 1 (PON1) is an enzyme that detoxifies activated organophosphorus pesticides (OPs) and is also involved in oxidative stress pathways.

OBJECTIVES

PON1 activity in newborns is lower than in adults, but the ontogeny of PON1 activity is poorly characterized in young children. We examined the effects of age and PON1 genotype on enzyme activity in a birth cohort of Mexican-American children.

METHODS

We determined three substrate-specific measures of PON1 activity in 1,143 plasma samples collected longitudinally from 458 children at five time points from birth through 7 years of age, and genotyped PON1 polymorphisms at positions 192 and -108 in these children.

RESULTS

Contrary to previous reports that PON1 activities plateau by 2 years of age, we observed an age-dependent increase in all three PON1 measures from birth through 7 years of age (p < 0.0001). The PON1(192) genotype significantly modified the effect of age on paraoxonase (POase) activity (p < 0.0001) such that increases in enzyme activity with age were influenced by the number of R alleles in a dose-dependent manner. Children with the PON1(-108CC192RR) diplotype had significantly higher mean PON1 activities and also experienced steeper increases of POase activity over time compared with children with the PON1(-108TT192QQ) diplotype.

CONCLUSIONS

Lower levels of the PON1 enzyme, which is involved in protection against OPs and oxidative stress, persist in young children past 2 years of age through at least 7 years of age. Future policies addressing pesticide exposure in children should take into account that the window of vulnerability to OPs in young children may last beyond infancy.

Paraoxonase gene polymorphism in south-western Korean population

Paraoxonase (PON) has anti-atherogenic activity. Considering the important role of polymorphism in the genetic susceptibility to cardiovascular disease and the variability of its allele frequencies in different ethnic groups, the distribution of genotypes and allele frequencies of PON1M55L, PON1Q192R, PON2A148G, and PON2S311C polymorphisms was analyzed in a total 988 South-western Koreans and determined their effects on lipid parameters. The genotype distribution of PON1 at position 55 was LL=0.886, LM=0.114; and at position 192 was QQ=0.406, QR=0.594. The frequencies of the PON1 55L allele and the PON1 192R allele were similar to those seen in Chinese populations and Western populations, respectively. The genetic distribution of PON2 at position 148 was AA=0.619, AG=0.345, GG=0.035; and at position 311 was CC=0.035, SC=0.345, SS=0.619. The frequencies of the PON2 148G and 311S alleles were similar to those seen in Chinese populations. The concentrations of LDL and ApoB were significantly different between the PON2A148G (P<0.05) and PON2 S311C polymorphisms (P<0.01). PON polymorphisms and allele frequencies were described in Koreans living south-western part of Korea. These ethnic variations are considered important in the interpretation of diseases associated with PON polymorphisms.

Genetic polymorphism in paraoxonase 1 (PON1): Population distribution of PON1 activity

Paraoxonase-1 (PON1) is a serum esterase that hydrolyzes the activated oxon form of several organophosphates. The central role of PON1 in detoxification of organophosphate (OP) pesticides was demonstrated in knockout mouse studies, suggesting that human variability in PON1 needs to be considered in health risk assessments involving exposure to these pesticides. The current analysis focused on two genetic loci in which polymorphisms demonstrated to affect PON1 activity. Detailed kinetic studies and population studies found that the *192Q (wild type) allele is more active toward some substrates (such as sarin, soman, and diazoxon) and less active toward others (such as paraoxon or chlorpyrifos) relative to the variant *192R allele. Another allele that affects activity is *55M; PON1 enzyme quantity, rather than specific activity or substrate preference, is altered. The *192R variant occurs commonly with a frequency of 25-64% across the populations analyzed. The *55M allele is less common, occurring in 5-40% of individuals depending upon the ethnic group studied. These activity and allele frequency data were incorporated into Monte Carlo simulations in which the frequency of both variant alleles was simultaneously modeled in Caucasian, African American, and Japanese populations. The resulting Monte Carlo activity distributions were bimodal for the substrate paraoxon with approximately fourfold differences between low- and high-activity modal medians. Differences in activity between total population median and 1st percentile were five- to sixfold. When sarin metabolic variability was simulated, the population distributions were unimodal. However, there was an even greater degree of interindividual variability (median to 1st percentile difference >20-fold). These results show that the combined effects of two PON1 allelic variants yielded a population distribution that is associated with a considerable degree of interindividual variability in enzyme activity. This indicates that assessments involving PON1 substrates need to evaluate polymorphism-related variability in enzyme activity to display the distribution of internal doses and adverse responses. This may best be achieved via physiologically based pharmacokinetic (PBPK) models that input PON1 activity distributions, such as those generated in this analysis, to simulate the range of oxon internal doses possible across the population.

PON1Q192R polymorphism is associated with lipid profile in Mexican men with Mayan ascendancy

Paraoxonase (PON1) enzyme is associated with high-density lipoproteins (HDL) that prevents low-density lipoprotein (LDL) oxidation. PON1Q192R polymorphism is associated with a risk of coronary heart disease and low HDL levels in case-control studies, but the issue is yet unresolved. Mexico has shown an increase in cardiovascular diseases, and some genetic factors may play a role. Our purpose was to evaluate the association between PON1Q192R and L55M polymorphisms and serum lipid profile in a healthy Mexican population. Ninety unrelated male inhabitants from southeastern Mexico with Mayan ascendancy agreed to participate. Demographic characteristics, lifestyle and medical history were obtained by questionnaire. Lipid profile was determined by enzymatic methods, PON1 activity by using paraoxon and phenylacetate and PON1 genotype by real-time PCR. HDL-cholesterol (HDL-C) levels were associated with genotype: 192RR homozygote subjects had lower HDL-C levels than 192QQ homozygotes, and individuals with 192RR and 192QR genotypes had an odds ratio (OR)=7.05 (95% confidence interval (CI)=1.29-38.34) of having HDL-C <60 mg/dL. Individuals with higher paraoxonase activity (>600.18 U/L) had a slight risk (OR=4.9, 95% CI=0.83-22.02) of having HDL-C <60 mg/dL. PON155LM polymorphism was associated with higher LDL-cholesterol. PON1Q192R polymorphism showed a role in modulating lipid profile: 192RR homozygotes showed the least favorable lipoprotein levels.

PON1Q192R genetic polymorphism modifies organophosphorous pesticide effects on semen quality and DNA integrity in agricultural workers from southern Mexico

Pesticide exposure, including organophosphorous (OP) insecticides, has been associated with poor semen quality, and paraoxonase (PON1), an enzyme involved in OP deactivation, may have a role on their susceptibility, due to PON1 polymorphisms. Our objective was to evaluate the role of PON1Q192R polymorphism on the susceptibility to OP toxicity on semen quality and DNA integrity in agricultural workers. A cross-sectional study was conducted in farmers with Mayan ascendancy from southeastern Mexico chronically exposed to pesticides; mostly OP. Fifty four agricultural workers (18-55 years old) were included, who provided semen and blood samples. Semen quality was evaluated according to WHO, sperm DNA damage by in situ-nick translation (NT-positive cells), PON1Q192R polymorphism by real-time PCR and serum PON1 activity by using phenylacetate and paraoxon. Two OP exposure indexes were created: at the month of sampling and during 3 months before sampling, representing the exposure to spermatids-spermatozoa and to cells at one spermatogenic cycle, respectively. PON1 192R and 192Q allele frequencies were 0.54 and 0.46, respectively. Significant associations were found between OP exposure at the month of sampling and NT-positive cells and sperm viability in homozygote 192RR subjects, and dose-effect relationships were observed between OP exposure during 3 months before sampling and sperm quality parameters and NT-positive cells in homozygote 192RR farmers. This suggests that cells at all stages of spermatogenesis are target of OP, and that there exists an interaction between OP exposure and PON1Q192R polymorphism on these effects; farmers featuring the 192RR genotype were more susceptible to develop reproductive toxic effects by OP exposure.