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

Association between Paraoxonase-1 p.Q192R Polymorphism and Coronary Artery Disease susceptibility in the Colombian Population

Background

Paraoxonase-1 (PON1), a glycoprotein associated with serum high-density lipoprotein (HDL), has a central role in metabolizing lipid peroxides, exhibiting antiatherogenic properties. The polymorphism p.Q192R has been previously associated with coronary artery disease (CAD) susceptibility and clopidogrel response.

Purpose

We aimed at investigating the association of PON1 p.Q192R with CAD and clopidogrel response in Colombian population.

Patients and Methods

The study was conducted among 163 patients diagnosed with CAD and treated with clopidogrel. The allele frequencies for the PON1 192Q and 192R alleles were determined in cases and Latin-American controls obtained from the public database gnomAD (n = 17,711). Response to clopidogrel was determined by assessing the platelet function using the INNOVANCE PFA-200 System. We determined the association between PON1 p.Q192R polymorphism, increased susceptibility to CAD and high on-treatment platelet reactivity (HPR) by using odds ratio (OR) and 95% confidence interval (CI) on four genetic models.

Results

The allele frequencies for the PON1 192Q and 192R alleles were 0.60 and 0.40, respectively. The allele distribution was found to be statistically different from the control group and other ethnic groups. The allele 192R was positively associated with decreased susceptibility to CAD under a dominant model (OR, 0.58; 95% CI, 0.42–0.8; P < 0.01). We found no association between the polymorphism and HPR.

Conclusion

We propose that PON1 p.Q192R is a potentially useful marker for CAD susceptibility in the Colombian population and lacks association with HPR under clopidogrel treatment.

Chlorpyrifos and Δ9 Tetrahydrocannabinol exposure and effects on parameters associated with the endocannabinoid system and risk factors for obesity

Marilyn Silva. Retired from a career in toxicology and risk assessment. Increased childhood and adult obesity are associated with chlorpyrifos (CPF), an organophosphate pesticide. Cannabis (Δ9Tetrahydrocannabinol: Δ9THC) use has increased globally with legalization. CPF applications on cannabis crops lacks federally regulated tolerances and may pose health risks through exposure during development and in adulthood. Both CPF and Δ9THC affect the endocannabinoid system (eCBS), a regulator of appetite, energy balance, and gut microbiota, which, if disrupted, increases risk for obesity and related diseases. CPF inhibits eCB metabolism and Δ9THC is a partial agonist/antagonist at the cannabinoid receptor (CB1R). Effects of each on obesogenic parameters were examined via literature search. Male rodents with CPF exposure showed increased body weights, dysbiosis, inflammation and oxidative stress, potentially associated with increased eCBs acting through the gut-microbiota-adipose-brain regulatory loop. Δ9THC generally decreased body weights via partial agonism at the CB1R, lowering levels of eCBs. Dysbiosis and/or oxidative stress associated inflammation occurred with CPF, but these parameters were not tested with Δ9THC. Database deficiencies included limited endpoints to compare between chemicals/age-groups, inter-study variables (dose ranges, dosing vehicle, rodent strain, treatment duration, etc.). CPF and Δ9THC were not tested together, but human co-chemical effects would depend on exposure ratio, subject age, exposure duration, and health status, among others. An overriding concern is that both chemicals are well-documented developmental neurotoxins in addition to their low dose effects on energy balance. A co-exposure risk assessment is warranted with increased use and lack of federal CPF regulation on cannabis.

Paraoxonase 1 and Non-Alcoholic Fatty Liver Disease: A Meta-Analysis

Oxidative stress is involved in the pathophysiology of nonalcoholic fatty liver disease (NAFLD). However, reliable biomarkers of NAFLD in relation to oxidative stress are not available. While paraoxonase 1 (PON1) is an antioxidant biomarker, there appears to be mixed data on PON-1 in patients with NAFLD. The aim of this meta-analysis was to assess the current data on PON1 activity (i.e., paraoxonase and arylesterase) in patients with NAFLD. A PubMed, CENTRAL, and Embase search identified 12 eligible articles. In the meta-analysis, the paraoxonase activity was low in patients with NAFLD (mean difference (MD) −27.17 U/L; 95% confidence interval (CI) −37.31 to −17.03). No difference was noted in the arylesterase activity (MD 2.45 U/L; 95% CI −39.83 to 44.74). In a subgroup analysis, the paraoxonase activity was low in biopsy-proven nonalcoholic steatohepatitis (MD −92.11 U/L; 95% CI −115.11 to −69.11), while the activity in NAFLD as diagnosed by ultrasonography or laboratory data was similar (MD −2.91 U/L; 95% CI −11.63 to 5.80) to that of non-NAFLD. In summary, the PON1, especially paraoxonase, activity could be a useful biomarker of NAFLD. Further studies are warranted to ascertain the relevance of PON1 measurements in patients with NAFLD.

Paraoxonase 1 concerning dyslipidaemia, cardiovascular diseases, and mortality in haemodialysis patients

Paraoxonase 1 (PON1) is known for preventing atherosclerosis through lipid-modifying features, antioxidant activity, anti-inflammatory, anti-apoptosis, anti-thrombosis, and anti-adhesion properties. Uremic patients requiring haemodialysis (HD) are especially prone to atherosclerosis and its complications. We analysed the PON1 gene (PON1) polymorphisms and serum PON1 (paraoxonase) activity concerning dyslipidaemia and related cardiovascular diseases and mortality to show how they associate under uremic conditions modified by maintenance HD treatment. The rs662 AA + AG (OR 1.76, 95%CI 1.10-2.80, P = 0.018), rs854560 TT (OR 1.48, 95%CI 1.04-2.11, P = 0.031), and rs854560 AT + TT (OR 1.28, 95%CI 1.01-1.63, P = 0.040) contributed to the prevalence of atherogenic dyslipidaemia diagnosed by the triglyceride (TG)/HDL-cholesterol ratio ≥ 3.8. The normalized serum PON1 activity positively correlated with atherogenic dyslipidaemia (ẞ 0.67 ± 0.25, P = 0.008). The PON1 rs854560 allele T was involved in the higher prevalence of ischemic cerebral stroke (OR 1.38, 1.02-1.85, P = 0.034). The PON1 rs705379 TT genotype contributed to cardiovascular (HR 1.27, 95% CI 1.03-1.57, P = 0.025) and cardiac (HR 1.34, 95% CI 1.05-1.71, P = 0.018) mortality. All P-values were obtained in multiple regression analyses, including clinical variables. Multifaceted associations of PON1 with dyslipidaemia, ischemic cerebral stroke, and cardiovascular mortality in HD patients provide arguments for the consideration of PON1 and its protein product as therapeutic targets in the prevention of atherosclerosis and its complications in uremic patients.

Paraoxonase single nucleotide variants show associations with polycystic ovary syndrome: a meta-analysis

BACKGROUND

Etiology of polycystic ovary syndrome (PCOS) is attributed to genetic and environmental factors. One environmental factor is oxidative stress. Paraoxonase 1 (PON1) is an antioxidant high-density lipoprotein-associated enzyme encoded by the PON1 gene. The PON1 gene has been implicated in the risk for PCOS, the influence of which appears to come from single nucleotide variants (SNVs) at multiple genetic loci. However, association study reports have been inconsistent which compels a meta-analysis to obtain more precise estimates.

METHODS

From 12 publications, extracted genotype data were used in two genetic procedures. First, linkage disequilibrium (LD) was used to group eight PON SNVs into three: LD1, LD2 and LD3. Second, frequencies of the variant (var), wild-type (wt) and heterozygous (het) genotypes were used for genetic modeling (allele-genotype for LD1 and standard for LD2 and LD3). Risk associations were expressed in terms of pooled odds ratios (ORs), 95% confidence intervals (CIs) and P^a-values. Evidence was considered strong when significance was high (P^a < 0.0001) and heterogeneity absent (I² = 0%). Pooled effects were subjected to modifier (power), subgroup (Asian/Caucasian), outlier, sensitivity and publication bias treatments. Multiple comparisons were Bonferroni-corrected.

RESULTS

This meta-analysis generated 11 significant outcomes, five in LD1, six in LD2 and none in LD3. All six LD2 outcomes did not survive the Bonferroni-correction but two of the five in LD1 did. These two core LD1 findings conferred greater odds of PCOS to the var allele in the highly significant (P^a < 0.0001) overall (OR 1.44, 95% CI 1.24-1.67) and Asian (OR 1.41, 95% CI 1.20-1.65) outcomes. Of these two core outcomes, the Asian effect was homogeneous (I² = 0%) but not the overall (I² = 29%).

CONCLUSIONS

Of the eight PON SNVs examined, two (rs854560 and rs662) were associated with PCOS risk. These 1.4-fold increased risk effects rendered Asians susceptible to PCOS. High statistical power, high significance, zero to low-level heterogeneity, robustness and lack of bias in the core outcomes underpinned the strong evidence for association.

Paraoxonase 1 gene polymorphisms concerning non-insulin-dependent diabetes mellitus nephropathy in hemodialysis patients

AIMS

Data on involvement of paraoxonase 1 gene (PON1) in non-insulin-dependent diabetes mellitus (NIDDM) nephropathy are scarce. We investigated PON1 polymorphisms concerning end-stage NIDDM nephropathy and atherosclerotic complications in NIDDM nephropathy patients treated with hemodialysis (HD).

METHODS

In NIDDM nephropathy (n = 402) and non-diabetic (n = 998) HD subjects, we obtained PON1 polymorphisms by HRM analysis (rs662) or predesigned TaqMan SNV Genotyping Assay (rs854560, rs705379).

RESULTS

Only PON1 rs705379 was associated with end-stage NIDDM nephropathy in the recessive (OR 1.451, 95% CI 1.104-1.906, P = 0.009) and additive (OR 1.398, 95%CI 1.009-1.936, P = 0.046) inheritance modes. NIDDM nephropathy patients bearing the rs854560 T allele were at higher risk for ischemic cerebral stroke (OR 2.087, 95%CI 1.145-3.801, P = 0.016). In non-diabetic patients but not NIDDM nephropathy subjects, atherogenic dyslipidemia corresponded with PON1 rs662 A allele and PON1 rs854560 TT homozygosity.

CONCLUSIONS

In HD patients, NIDDM nephropathy correlates with the TT genotype of PON1 rs705379. The rs854560 T allele indicates a higher risk for atherosclerotic diseases in NIDDM nephropathy subjects. The T alleles of both PON1 SNVs are known as low expression variants downregulated serum PON1 activity. An increase of diminished PON1 activity may be a target in the prevention of NIDDM nephropathy and NIDDM atherosclerotic complications.

Bayesian meta-analysis of inter-phenotypic differences in human serum paraoxonase-1 activity for chemical risk assessment

Human variability in paraoxonase-1 (PON1) activities is driven by genetic polymorphisms that affect the internal dose of active oxons of organophosphorus (OP) insecticides. Here, an extensive literature search has been performed to collect human genotypic frequencies (i.e. L55M, Q192R, and C-108T) in subgroups from a range of geographical ancestry and PON1 activities in three probe substrates (paraoxon, diazoxon and phenyl acetate). Bayesian meta-analyses were performed to estimate variability distributions for PON1 activities and PON1-related uncertainty factors (UFs), while integrating quantifiable sources of inter-study, inter-phenotypic and inter-individual differences. Inter-phenotypic differences were quantified using the population with high PON1 activity as the reference group. Results from the meta-analyses provided PON1 variability distributions and these can be implemented in generic physiologically based kinetic models to develop quantitative in vitro in vivo extrapolation models. PON1-related UFs in the Caucasian population were above the default toxicokinetic UF of 3.16 for two specific genotypes namely -108CC using diazoxon as probe substrate and, -108CT, -108TT, 55MM and 192QQ using paraoxon as probe substrate. However, integration of PON1 genotypic frequencies and activity distributions showed that all UFs were within the default toxicokinetic UF. Quantitative inter-individual differences in PON1 activity are important for chemical risk assessment particularly with regards to the potential sensitivity to organophosphates' toxicity.

Biochemical and genotoxic effects in women exposed to pesticides in Southern Ecuador

Toxicity refers to the potential of a substance such as a pesticide to cause damage to the structure or functions of an exposed organism. Pesticides can lead to harmful biological effects in exposed animals and their offspring over the medium and long term. They can affect the immunological, nervous, endocrine, and reproductive systems. DNA damage has also been linked to exposure to pesticides, and this damage can cause abortions, degenerative diseases, and cancer. The aim of this work was to establish whether women who are indirectly exposed to pesticides exhibit a compromised health status, including genotoxic effect. Women exposed indirectly to pesticides in Chimchanga and Colaisaca in the south of Ecuador underwent hematological and biochemical tests and micronucleus assay in buccal cells. The subjects were also genotyped for GSTM1, GSTT1, GSTP1, and PON1 polymorphisms, which can modify an individual's capacity to metabolize pesticides and relation with damage of DNA. The study revealed hepatic toxicity in Colaisaca women (AST and ALT) and an increase in the rate of micronucleus (MN) in Colaisaca individuals. In addition, genetic polymorphisms in PON1 and GSTP1 showed effects of modulating the frequency of karyolytic cells, karyorrhectic cells, and condensed chromatin cells.

Genetic polymorphisms as determinants of pesticide toxicity: Recent advances

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Genetic polymorphisms may influence pesticides-induced oxidative damage.Pesticides modulate immune-system cells functionality, leading to the onset of a dangerous pro-inflammatory microenvironment.

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DNA repair genes, Cytochrome P450 s, PON and GST genes have a key role in the metabolism of xenobiotics.

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Many workers are professionally exposed to pesticides with potential health consequences.

Occupational and environmental exposure to pesticides may induce harmful effects on human health by promoting the development of a wide range of disorders. Some of the most recently hypothesized mechanisms are oxidative stress and epigenetic modifications, however biological effects seem to be modulated mainly by the occurrence of genetic polymorphisms. The susceptibility to exposure can be evaluated by studying the most common polymorphisms of genes involved in the metabolism of organophosphorus compounds (cytochrome P450, glutathione transferase, acetyltransferases or paraoxonase 1). The aim of this article is to review recent literature data concerning the influence of genetic polymorphisms on pesticides-induced oxidative damage.

Association of PON1 gene polymorphisms with polycystic ovarian syndrome risk: a meta-analysis of case-control studies

PURPOSE

Evidences showed that paraoxonase 1 (PON1) gene polymorphism has an impact on women's susceptibility to polycystic ovarian syndrome (PCOS) by influencing the expression and activity of PON1. However, the effects of three PON1 polymorphisms (- 108 C>T, L55M and Q192R) on the incidence of PCOS have generated inconsistent results. Here, we conducted a meta-analysis to investigate the association between PON1 polymorphisms and PCOS risk.

METHODS

All eligible trials were identified via systematic searches of multiple literature databases. Outcome data were synthesized by using crude odds ratio with 95% confidence interval. Heterogeneity was assessed with the I² test. Publication bias and subgroup analyses were also performed.

RESULTS

A total of 2449 cases and 1977 controls from nine studies were selected for analysis. The pooled results showed a significant association between PCOS risk and PON1 - 108 C/T polymorphism in the following genetic models [allelic, 0.72 (0.56-0.92); homozygote, 0.51 (0.32-0.82); heterozygote, 0.44 (0.25-0.78); and dominant 0.47 (0.29-0.77)]. For the PON1 192 Q/R polymorphism, a significant relationship was found in the allelic model [0.62 (0.41-0.93)] and recessive model [0.61 (0.37-0.98)]. PCOS risk was also linked to PON1 L55M polymorphism in the heterozygote model [0.62 (0.39-0.98)] and dominant model [0.63 (0.41-0.96)].

CONCLUSIONS

Our study has shown that PON1 - 108 C/T polymorphism might be associated with increased risk of PCOS under the allelic, homozygote, heterozygote, and dominant models. Additionally, PON1 192 Q/R and L55M polymorphisms were significantly related only in the allelic and recessive model, and in the heterozygote and dominant model, respectively.

Paraoxonase-1 genetic polymorphisms in organophosphate metabolism

Organophosphates (OPs) are a class of chemicals commonly used in agriculture as pesticides, that can often lead to severe toxicity in humans. Paraoxonase-1 (PON1) belongs to a family of A-esterases and hydrolyses several OPs while also serving other biological roles. Two main genetic polymorphisms have been shown to affect enzymatic ability; an A > G transition in the 192nd position (192 Q/R, rs662), and an A > T at codon 55 (55 M/L, rs854560). In this review, we searched PubMed for relevant articles published from its inception till June 2018 and included publications from 1996 to 2018. We aimed to address the distribution of the polymorphisms in various populations, the way they affect enzymatic activity and the possible use of PON1 as a biomarker. The polymorphisms present great heterogeneity between populations, with the data being clearer over 192 Q/R, and this heterogeneity is related to the phylogenetic origins of each population. Concerning enzymatic activity, the different genotypes react better or worse to different OP substrates, with studies presenting a variety of findings. Detecting the "paraoxonase status" of an individual -referring to PON1 function- seems to be important in predicting OP toxicity, as studies have shown that some specific-genotype individuals present symptoms of toxicity in higher rates than others. We are strongly convinced that in order for the scientific community to reach a consensus over which polymorphisms confer susceptibility to toxicity and whether PON1 can eventually be used as a biomarker, more studies need to be carried out, since the data thus far does not seem to reach a universal conclusion.

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.

Association of Paraoxonase-1 Q192R (rs662) Single Nucleotide Variation with Cardiovascular Risk in Coffee Harvesters of Central Colombia

Paraoxonase 1 (PON1), a high-density lipoprotein-associated antioxidant enzyme, hydrolyzes several organophosphate pesticides and oxidized lipids. The PON1 Q192R polymorphism affects the catalytic efficiency and is considered a risk factor for pesticide intoxication and cardiovascular disease (CVD) but the association is not consistent between individuals or populations. We aimed to study the association of PON1 Q192R polymorphism with CVD risk in coffee harvesters of central Colombia. Demographics were collected from 205 subjects via standardized questionnaires. Lipid profiles and serum butyrylcholinesterase (BChE) were measured by standard procedures. The calculated 10-year atherosclerotic CVD (ASCVD) risk was used as the cardiovascular risk estimate. Q192R genotype was determined by real-time PCR. Prevalence of hypertension, hypercholesterolemia, and the 10-year ASCVD risk was 33%, 62%, and 22%, respectively. BChE levels were no indicative of recent pesticide exposure, although a positive correlation was observed with BChE and hypercholesterolemia. The Q192R genotype frequencies were 38% (QQ), 44% (QR), and 18% (RR). We found an association of the 192Q genotype with hypertension. The results of this study signal the importance to evaluate the influence and potential interactions of BChE and PON1 192Q allele with known genetic and environmental factors implicated in the pathogenesis of CVD.

A Meta-Analysis on the Relationship of the PON Genes and Alzheimer Disease

AIM

This study aimed to evaluate the association of the paraoxonase (PON) gene variants and Alzheimer disease (AD) using meta-analysis.

METHODS

Relevant studies were identified by searching English and Chinese databases extensively. Allele and genotype frequencies for each included study were extracted. Newcastle-Ottawa Scale (NOS) was employed to assess the quality of included studies. The odds ratio (OR) with 95% confidence interval (95% CI) was calculated using a random-effects or fixed-effects model. A Q statistic was used to evaluate homogeneity, and Egger test and funnel plot were used to assess publication bias.

RESULTS

A total of 15 studies (involving 5 polymorphisms) were included and identified for the current meta-analysis. The NOS scores ranged from 7 to 8, meaning good quality of studies. It was found that the SS genotype of PON2 S311C polymorphism had an significant association with AD in the studied population (OR = 0.82, 95% CI: 0.68-0.99, P = .04), and the A allele of PON1 rs705379 polymorphism was positively related to AD in Caucasian population (OR = 1.21, 95% CI: 1.05-1.39, P = .009) as well as the GG genotype decreased AD risk significantly in Caucasians (OR = 0.7, 95% CI: 0.56-0.88, P = .002). However, there was no significant relationship between other 3 genetic variants of PON genes (L55 M, Q192 R, and -161C/T of PON1 gene) and AD.

CONCLUSION

Existing evidence indicates that the S311C polymorphism (SS genotype) and the rs705379 (the A allele and GG genotype) are associated with risk of AD in studied population. Future studies with larger sample sizes will be necessary to confirm the present results.

A framework and case studies for evaluation of enzyme ontogeny in children's health risk evaluation

Knowledge of the ontogeny of Phase I and Phase II metabolizing enzymes may be used to inform children's vulnerability based upon likely differences in internal dose from xenobiotic exposure. This might provide a qualitative assessment of toxicokinetic (TK) variability and uncertainty pertinent to early lifestages and help scope a more quantitative physiologically based toxicokinetic (PBTK) assessment. Although much is known regarding the ontogeny of metabolizing systems, this is not commonly utilized in scoping and problem formulation stage of human health risk evaluation. A framework is proposed for introducing this information into problem formulation which combines data on enzyme ontogeny and chemical-specific TK to explore potential child/adult differences in internal dose and whether such metabolic differences may be important factors in risk evaluation. The framework is illustrated with five case study chemicals, including some which are data rich and provide proof of concept, while others are data poor. Case studies for toluene and chlorpyrifos indicate potentially important child/adult TK differences while scoping for acetaminophen suggests enzyme ontogeny is unlikely to increase early-life risks. Scoping for trichloroethylene and aromatic amines indicates numerous ways that enzyme ontogeny may affect internal dose which necessitates further evaluation. PBTK modeling is a critical and feasible next step to further evaluate child-adult differences in internal dose for a number of these chemicals.

Paraoxonase and atherosclerosis-related cardiovascular diseases

In humans, three paraoxonase (PON1, PON2, and PON3) genes are clustered on chromosome 7 at a locus that spans a distance around 170 kb. These genes are highly homologous to each other and have a similar protein structural organization. PON2 is the intracellular enzyme, which is expressed in many tissues and organs, while two other members of PON gene family are produced by liver and associate with high density lipoprotein (HDL). The lactonase activity is the ancestral. Besides lactones and organic phosphates, PONs can hydrolyze and therefore detoxify oxidized low density lipoprotein and homocysteine thiolactone, i.e. two cytotoxic compounds with a strong proatherogenic action. Indeed, PONs possess numerous atheroprotective properties, which include antioxidant activity, anti-inflammatory action, preserving HDL function, stimulation of cholesterol efflux, anti-apoptosis, anti-thrombosis, and anti-adhesion. PON genetic polymorphisms contribute to susceptibility/protection from atherosclerosis-related diseases. The bright antiatherogenic activity of the PON cluster makes it a promising target for the development of new therapeutic strategies.

Associations of maternal organophosphate pesticide exposure and PON1 activity with birth outcomes in SAWASDEE birth cohort, Thailand

Prenatal organophosphate (OP) pesticide exposure has been reported to be associated with adverse birth outcomes and neurodevelopment. However, the mechanisms of toxicity of OP pesticides on human fetal development have not yet been elucidated. Our pilot study birth cohort, the Study of Asian Women and Offspring's Development and Environmental Exposures (SAWASDEE cohort) aimed to evaluate environmental chemical exposures and their relation to birth outcomes and infant neurodevelopment in 52 pregnant farmworkers in Fang district, Chiang Mai province, Thailand. A large array of data was collected multiple times during pregnancy including approximately monthly urine samples for evaluation of pesticide exposure, three blood samples for pesticide-related enzyme measurements and questionnaire data. This study investigated the changes in maternal acetylcholinesterase (AChE) and paraoxonase 1 (PON1) activities and their relation to urinary diakylphosphates (DAPs), class-related metabolites of OP pesticides, during pregnancy. Maternal AChE, butyrylcholinesterase (BChE) and PON1 activities were measured three times during pregnancy and urinary DAP concentrations were measured, on average, 8 times from enrollment during pregnancy until delivery. Among the individuals in the group with low maternal PON1 activity (n=23), newborn head circumference was negatively correlated with log10 maternal ∑DEAP and ∑DAP at enrollment (gestational age=12±3 weeks; β=-1.0 cm, p=0.03 and β=-1.8 cm, p<0.01, respectively) and at 32 weeks pregnancy (β=-1.1cm, p=0.04 and β=-2.6 cm, p=0.01, respectively). Furthermore, among these mothers, newborn birthweight was also negatively associated with log10 maternal ∑DEAP and ∑DAP at enrollment (β=-219.7 g, p=0.05 and β=-371.3g, p=0.02, respectively). Associations between maternal DAP levels and newborn outcomes were not observed in the group of participants with high maternal PON1 activity. Our results support previous findings from US birth cohort studies. This is the first study to report the associations between prenatal OP pesticide exposure and birth outcomes in Thailand.

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.

Lactonase activity and status of paraoxonase 1 in Chinese women with polycystic ovarian syndrome

OBJECTIVE

To study the relationship between the lactonase activities and status of paraoxonase 1 (PON1) and its association with the PON1 genetic polymorphisms in women with polycystic ovarian syndrome (PCOS).

DESIGN

A case-control study.

METHODS

A total of 455 PCOS patients and 441 control women were included in this study. The lactonase activities and concentrations of PON1 were assayed using 5-thiobutyl butyrolactone (TBBL) and 7-O-diethylphosphoryl-3-cyano-4-methyl-7-hydroxycoumarin (DEPCyMC) respectively. A normalized lactonase activity (NLA) was estimated based on the ratio of TBBLase:DEPCyMCase activity. The PON1 genotypes, serum malondialdehyde (MDA) levels and total antioxidant capacity were analyzed.

RESULTS

The lactonase activities and levels of PON1 were higher in PCOS patients than in the control women. However, the NLA did not significantly differ between groups. The -108C→T variation of the PON1 gene showed decreased lactonase activities and levels of PON1 in a genotype-dependent manner (CC>CT>TT); the 192Q→R variation of the PON1 gene showed increased PON1 lactonase activities and NLA; and the 55L→M variation of the PON1 gene showed decreased lactonase activities and levels of PON1 but an increased NLA. A multivariable regression analysis showed that the -108C/T, 192Q/R, and 55L/M variations of the PON1 gene, serum apolipoprotein A1, and MDA levels were significant predictors of PON1 lactonase activity, PON1 level, and NLA.

CONCLUSIONS

The serum lactonase activities and concentrations of PON1 are increased in PCOS patients. The increased oxidative stress and the -108C/T, 192Q/R, and 55L/M genetic polymorphisms of PON1 may be associated with these changes.

Association between genetic polymorphisms and carotid atherosclerosis in patients treated with radiotherapy for nasopharyngeal carcinoma

Background

Radiotherapy (RT) of the neck is commonly given to nasopharyngeal carcinoma (NPC) patients for preventing cervical lymph node metastasis. However, neck RT may induce the development of carotid atherosclerosis. The mechanisms of radiation-induced carotid atherosclerosis are still unclear and no previous study has investigated the genetic involvement of radiation-induced carotid atherosclerosis. The present study aims to determine the association between genetic polymorphisms and carotid atherosclerosis in patients treated with RT for nasopharyngeal carcinoma.

Methods

The present study recruited 128 post-RT NPC patients. Carotid plaque score was assessed using ultrasonography. Thirteen single nucleotide polymorphisms (SNPs) that affect the function of anti-atherosclerotic genes, including SOD2, SOD3, CAT, PON1, PPARG, ADIPOQ, IL10, TGFB1 and NOS3, were genotyped. Association between the 13 SNPs and carotid atherosclerosis was evaluated using multiple regression after adjustment for covariates (PLINK). Multiple testing was corrected using Benjamini-Hochberg step-up false discovery rate controlling procedure.

Results

rs662 and rs705379 of PON1 were close to be significantly associated with carotid plaque score (Corrected P value, P_cor = 0.0528 and P_cor = 0.0842). When the two SNPs were combined together, TC haplotype in rs662-rs705379 of PON1 was significantly associated with higher carotid plaque score (P_cor < 0.05). None of the other SNPs showed significant association with carotid plaque score.

Conclusions

TC haplotype in rs662-rs705379 of PON1 is likely to be a genetic risk factor of carotid plaque score. Post-RT NPC patients with the TC haplotype may need earlier and more frequent carotid ultrasound examinations for early detection of carotid atherosclerosis.

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.

PON1-108 TT and PON1-192 RR genotypes are more frequently encountered in Greek PCOS than non-PCOS women, and are associated with hyperandrogenaemia

OBJECTIVE

To investigate the frequencies of three paraoxonase (PON)1 polymorphisms in Greek polycystic ovary syndrome (PCOS) and non-PCOS women, and their genotypes association with hyperandrogenaemia and insulin resistance.

DESIGN

Case-control genetic association study.

SETTING

University Hospital Endocrine Unit.

PATIENTS

A total of 142 PCOS cases (NIH criteria) and 112 controls.

MAIN OUTCOME MEASURE

Genotyping of the c.-108C>T (PON1-108), the c.163T>A (PON1-55) and the c.575A>G (PON1-192) polymorphisms and measurement of baseline androgen and insulin resistance profile.

RESULTS

The PON1-108 TT and PON1-192 RR genotypes were more frequently encountered in the PCOS than in the control group. The PON1-192 R allele frequency was greater in the PCOS than in the control group. Comparing the PCOS and the control groups, statistical significances favoured a recessive and a dominant genetic model, respectively, for the single PON1-108 T and PON1-192 R alleles. Free Androgen Index (FAI) levels were higher in patients with PON1-108 TT, whereas Testosterone, FAI and Dehydroepiandrosterone sulphate (DHEAS) levels were higher in patients with PON1-192 RR than patients with the wild or the heterozygous genotype.

CONCLUSIONS

The decreased PON1 activity-associated PON1-108 TT and the PON1-192 RR genotypes are more frequently found in Greek PCOS women and are associated with hyperandrogenaemia. Hyperandrogenaemia must depend also on other genetic factors because the same genotypes were not associated with hyperandrogenaemia in the control group. Through identification of the involved polymorphisms, women with PCOS could potentially have a better therapeutic screening.

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.

Addressing human variability in next-generation human health risk assessments of environmental chemicals

BACKGROUND

Characterizing variability in the extent and nature of responses to environmental exposures is a critical aspect of human health risk assessment.

OBJECTIVE

Our goal was to explore how next-generation human health risk assessments may better characterize variability in the context of the conceptual framework for the source-to-outcome continuum.

METHODS

This review was informed by a National Research Council workshop titled "Biological Factors that Underlie Individual Susceptibility to Environmental Stressors and Their Implications for Decision-Making." We considered current experimental and in silico approaches, and emerging data streams (such as genetically defined human cells lines, genetically diverse rodent models, human omic profiling, and genome-wide association studies) that are providing new types of information and models relevant for assessing interindividual variability for application to human health risk assessments of environmental chemicals.

DISCUSSION

One challenge for characterizing variability is the wide range of sources of inherent biological variability (e.g., genetic and epigenetic variants) among individuals. A second challenge is that each particular pair of health outcomes and chemical exposures involves combinations of these sources, which may be further compounded by extrinsic factors (e.g., diet, psychosocial stressors, other exogenous chemical exposures). A third challenge is that different decision contexts present distinct needs regarding the identification-and extent of characterization-of interindividual variability in the human population.

CONCLUSIONS

Despite these inherent challenges, opportunities exist to incorporate evidence from emerging data streams for addressing interindividual variability in a range of decision-making contexts.

The Past and Present of Paraoxonase Enzyme: Its Role in the Cardiovascular System and Some Diseases

Although paraoxonase is synthesized in many tissues including the heart, colon, kidneys, lungs, small intestines and brain, its major locus of synthesis is the liver. PON1 is in close association with apolipoproteins and protects LDL against oxidation. It was reported that PON1 quantities dropped to 40 times lower than normal in cardiovascular diseases and diseases like diabetes, ulcerative colitis, Crohn's disease, chronic renal failure, SLE, Behcet's disease, cancer, hepatitis B, obesity, metabolic syndrome, Alzheimer's and dementia. It is speculated that the concerning decline in serum PON1 amount results from single nucleotide polymorphism in the coding (Q192R, L55M) and promoter (T-108C) sites of the PON1 gene. Additionally, circulating amounts of PON1 are affected by vitamins, antioxidants, fatty acids, dietary factors, drugs, age and lifestyle. This collection attempts to review and examine the past and present studies of paraoxonase and its relation with the cardiovascular system and some relevant diseases.

PON gene polymorphisms and ischaemic stroke: a systematic review and meta analysis

BACKGROUND

Paraoxonase is known to play an important role in the pathophysiology of atherosclerosis. Genetic variants of the paraoxonase gene have been implicated as risk factors for atherosclerotic diseases such as coronary artery disease, but individual genetic association studies examining the relationship between the paraoxonase gene polymorphisms and ischaemic stroke have yielded inconsistent results.

AIM

This study aimed to evaluate the association between the paraoxonase gene variants and ischaemic stroke using systematic review with meta-analysis.

METHODS

Relevant studies were identified by searching English and Chinese databases extensively. Allele and genotype frequencies for each included study were extracted. The odds ratio was calculated using a random-effects or fixed-effects model. A Q statistic was used to evaluate homogeneity, and Egger's test and funnel plot were used to assess publication bias.

RESULTS

A total of 28 studies were included and identified for the current meta-analysis. It was found that the R allele or RR genotype of paraoxonase 1 Q192R polymorphism had an increased risk for ischaemic stroke in the general population (192R allele: odds ratio: 1·21, 95% confidence interval: 1·08-1·35, P = 0·0009 and 192RR genotype: odds ratio: 1·25, 95% confidence interval: 1·06-1·49, P = 0·009 in general population, respectively), but there was no significant association between other genetic variants of paraoxonase gene and ischaemic stroke.

CONCLUSIONS

Existing evidence indicates that the Q192R polymorphism (the R allele and RR genotype) is associated with an increased risk of ischaemic stroke in the general population. Future studies with larger sample sizes will be necessary to confirm the present results.

Evidence for association between paraoxonase 1 gene polymorphisms and polycystic ovarian syndrome in southwest Chinese women

OBJECTIVE

The aim of this study was to investigate the relationship between 192Q/R and 55L/M polymorphisms of paraoxonase 1 (PON1) gene and polycystic ovarian syndrome (PCOS) in Chinese women.

DESIGN

A case-control study.

METHODS

A total of 1113 subjects (610 patients with PCOS and 503 control women) from a population of Chinese Han nationality in Chengdu area were included in this study. PON1 genotypes were studied using PCR and restriction fragment length polymorphism analysis. Clinical and metabolic parameters were analyzed.

RESULTS

The frequencies of PON1 192RR genotype and R allele were significantly higher in patients with PCOS than in control women (44.6 vs 36.4%, 0.667 vs 0.610 respectively). The 192RR genotype remained a significant predictor for PCOS (odds ratio (RR/QR)(+)(QQ): 1.656, 95% confidence interval: 1.156-2.371) in prognostic models including age, body mass index, insulin resistance index, triglyceride, HDL, and LDL as covariates. Compared with patients with QQ genotype, patients with RR or QR genotype had significantly higher waist circumference and fasting insulin and triglyceride levels, patients with RR genotype had significantly higher waist-to-hip ratio, and patients with QR genotype had significantly higher homeostasis model assessment of insulin resistance. Such relationships were not detected in the control women. No significant differences were found in the frequencies of PON1 55L/M genotype and allele between PCOS and control groups.

CONCLUSIONS

The 192Q/R, but not 55L/M, polymorphism in PON1 gene is associated with the risk of PCOS in south-west Chinese women.

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.

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.

Genetic variability in molecular responses to chemical exposure

Individuals differ in their response to environmental exposures. In the following, we describe examples and paradigms of studying heritable differences in response to exposure-commonly known as "gene-environment interaction" or "ecogenetics"-and their relation to disease etiology and susceptibility. Our discussion is framed in three parts. In the first, we describe replicated examples of studies that have typified the field, single genetic variant, and exposure associations to disease. Second, we describe how studies have scaled up search for interaction using genome-wide measurement modalities, bioinformatics, and model organisms. Finally, we discuss a more comprehensive representation of chemical exposures as the "envirome" and how we may use the envirome to examine interplay between genetics and the environment.

Serum PON-1 activity but not Q192R polymorphism is related to the extent of atherosclerosis

AIM

Paraoxonase-1 (PON1) is an antioxidant enzyme located in high density lipoprotein (HDL). PON1 was defined as a protective factor against atherosclerosis. The aim of this study was to investigate the possible relationship between serum paraoxonase (PONase), homocysteine thiolactonase (HTase) activities and PON1 Q192R polymorphism, and the extent and severity of atherosclerosis.

METHODS

Blood specimens were collected from 142 individuals who had no coronary artery lesions angiographically (control group) and 128 individuals who had angiographically documented coronary artery disease of several degrees (patient group). The extent and severity of arterial lesions were evaluated by the Gensini scoring system. PONase and HTase activities were measured in serum using a spectrophotometric method. PON1 Q192R polymorphism was evaluated using PCR-RFLP after DNA isolation from blood.

RESULTS

Serum PONase and HTase activities were significantly lower in the patient group than in healthy controls (135.7±56.0U/mL vs 153.8±62.0U/mL, p< 0.05; 36.0±6.1 U/mL vs 43.0±4.04 U/mL, p< 0.01; respectively). In the patient group, there was a negative correlation between PONase, HTase activities and the Gensini score (r=-0.168, p= 0.039; r=-0.164, p= 0.006, respectively). In both groups, there was no significant difference in the distribution of PON1 Q192R polymorphism. In the patient group, the distribution of Gensini scores according to genotypes was not significant.

CONCLUSION

It has been concluded that serum PONase and HTase activities might be a more relevant marker than PON1 genotype in evaluating the extent and severity of atherosclerosis.

Plasma proteomic profiles from disease-discordant monozygotic twins suggest that molecular pathways are shared in multiple systemic autoimmune diseases

Introduction

Although systemic autoimmune diseases (SAID) share many clinical and laboratory features, whether they also share some common features of pathogenesis remains unclear. We assessed plasma proteomic profiles among different SAID for evidence of common molecular pathways that could provide insights into pathogenic mechanisms shared by these diseases.

Methods

Differential quantitative proteomic analyses (one-dimensional reverse-phase liquid chromatography-mass spectrometry) were performed to assess patterns of plasma protein expression. Monozygotic twins (four pairs discordant for systemic lupus erythematosus, four pairs discordant for juvenile idiopathic arthritis and two pairs discordant for juvenile dermatomyositis) were studied to minimize polymorphic gene effects. Comparisons were also made to 10 unrelated, matched controls.

Results

Multiple plasma proteins, including acute phase reactants, structural proteins, immune response proteins, coagulation and transcriptional factors, were differentially expressed similarly among the different SAID studied. Multivariate Random Forest modeling identified seven proteins whose combined altered expression levels effectively segregated affected vs. unaffected twins. Among these seven proteins, four were also identified in univariate analyses of proteomic data (syntaxin 17, α-glucosidase, paraoxonase 1, and the sixth component of complement). Molecular pathway modeling indicated that these factors may be integrated through interactions with a candidate plasma biomarker, PON1 and the pro-inflammatory cytokine IL-6.

Conclusions

Together, these data suggest that different SAID may share common alterations of plasma protein expression and molecular pathways. An understanding of the mechanisms leading to the altered plasma proteomes common among these SAID may provide useful insights into their pathogeneses.

Influence of Physical Activity Intervention on Circulating Soluble Receptor for Advanced Glycation end Products in Elderly Subjects

Background

Inflammation, often accompanied by oxidation, caused by advanced glycation end products (AGEs) may be quenched by the soluble receptor for AGEs (sRAGE). The present study aimed to investigate the influence of physical activity on circulating sRAGE, and the association between changes of circulating sRAGE and paraoxonase1 (PON1) activity (as an antioxidative enzyme) in a physical activity intervention study on an elderly subject cohort.

Methods

Serum sRAGE, PON1 activity and cardiometabolic variables were measured in 30 community-dwelling asymptomatic Japanese volunteers (15 men/15 women, mean age 65 years) in the pre- and post-phase of a 6-month interventional program designed to increase physical activity.

Results

The body mass index and sRAGE levels (1103 ± 496 to 1030 ± 437 ng/L, P < 0.05) were significantly reduced during the intervention period. In addition, the change of sRAGE was significantly and inversely correlated with that of PON1 activity, independent of the other cardiometabolic variables (β = - 0.511, P < 0.01).

Conclusions

This study showed a reduction of sRAGE levels, and an inverse correlation between sRAGE and PON1 activity, after the intervention study increasing physical activity on an elderly population. These findings represent a modest but significant modulation of sRAGE by this type of exercise intervention, which warranted future studies on the clinical relevance of sRAGE changes in physical activity.

Keywords

AGEs; RAGE; Paraoxonase1; Exercise; Atherosclerosis

Genetic polymorphism in metabolism and host defense enzymes: implications for human health risk assessment

Genetic polymorphisms in xenobiotic metabolizing enzymes can have profound influence on enzyme function, with implications for chemical clearance and internal dose. The effects of polymorphisms have been evaluated for certain therapeutic drugs but there has been relatively little investigation with environmental toxicants. Polymorphisms can also affect the function of host defense mechanisms and thus modify the pharmacodynamic response. This review and analysis explores the feasibility of using polymorphism data in human health risk assessment for four enzymes, two involved in conjugation (uridine diphosphoglucuronosyltransferases [UGTs], sulfotransferases [SULTs]), and two involved in detoxification (microsomal epoxide hydrolase [EPHX1], NADPH quinone oxidoreductase I [NQO1]). This set of evaluations complements our previous analyses with oxidative and conjugating enzymes. Of the numerous UGT and SULT enzymes, the greatest likelihood for polymorphism effect on conjugation function are for SULT1A1 (*2 polymorphism), UGT1A1 (*6, *7, *28 polymorphisms), UGT1A7 (*3 polymorphism), UGT2B15 (*2 polymorphism), and UGT2B17 (null polymorphism). The null polymorphism in NQO1 has the potential to impair host defense. These highlighted polymorphisms are of sufficient frequency to be prioritized for consideration in chemical risk assessments. In contrast, SNPs in EPHX1 are not sufficiently influential or defined for inclusion in risk models. The current analysis is an important first step in bringing the highlighted polymorphisms into a physiologically based pharmacokinetic (PBPK) modeling framework.

Utilizing toxicogenomic data to understand chemical mechanism of action in risk assessment

The predominant role of toxicogenomic data in risk assessment, thus far, has been one of augmentation of more traditional in vitro and in vivo toxicology data. This article focuses on the current available examples of instances where toxicogenomic data has been evaluated in human health risk assessment (e.g., acetochlor and arsenicals) which have been limited to the application of toxicogenomic data to inform mechanism of action. This article reviews the regulatory policy backdrop and highlights important efforts to ultimately achieve regulatory acceptance. A number of research efforts on specific chemicals that were designed for risk assessment purposes have employed mechanism or mode of action hypothesis testing and generating strategies. The strides made by large scale efforts to utilize toxicogenomic data in screening, testing, and risk assessment are also discussed. These efforts include both the refinement of methodologies for performing toxicogenomics studies and analysis of the resultant data sets. The current issues limiting the application of toxicogenomics to define mode or mechanism of action in risk assessment are discussed together with interrelated research needs. In summary, as chemical risk assessment moves away from a single mechanism of action approach toward a toxicity pathway-based paradigm, we envision that toxicogenomic data from multiple technologies (e.g., proteomics, metabolomics, transcriptomics, supportive RT-PCR studies) can be used in conjunction with one another to understand the complexities of multiple, and possibly interacting, pathways affected by chemicals which will impact human health risk assessment.

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.

Relationship between Paraoxonase 1 (PON1) gene polymorphisms and susceptibility of stroke: a meta-analysis

Genetic variants of paraoxonase 1 (PON1) were implicated in stroke susceptibility in several case-control association studies. However, the studies have reported apparently conflicting results, rendering precise assessment of the disease risk associated with the variants difficult. A meta-analysis was therefore conducted by including the studies that examined the association between two common polymorphisms (L55M and Q192R) in the coding region of PON1 gene and the risk of stroke. Altogether 10 studies on L55M polymorphism and 11 studies on Q192R polymorphism were included in this meta-analysis. The results showed, although there was no significant association of the 55L allele with stroke [random effects OR = 1.09, 95% CI (0.93, 1.27), P = 0.29], the 192R allele conferred significant risk of stroke in the overall study population [random effects OR = 1.25, 95% CI (1.07, 1.46), P = 0.006]. Same pattern of results as both the allele contrasts was obtained for the homozygote contrasts and the dominant, recessive and additive models. Subgroup analyses for stroke type, age of patients and ethnicity revealed no association of the 55L allele with stroke, whereas the association of the 192R allele persisted significantly in the groups comprising ischemic stroke patients, stroke patients with mean age >60 years and Caucasian subjects. But no significant association of this allele with stroke susceptibility was detected in the East Asian population. Therefore, the results of this meta-analysis indicate, the Q192R polymorphism could be an important risk factor for stroke, especially in the Caucasian population.

Approaches to advancing quantitative human health risk assessment of environmental chemicals in the post-genomic era

The contribution of genomics and associated technologies to human health risk assessment for environmental chemicals has focused largely on elucidating mechanisms of toxicity, as discussed in other articles in this issue. However, there is interest in moving beyond hazard characterization to making more direct impacts on quantitative risk assessment (QRA)--i.e., the determination of toxicity values for setting exposure standards and cleanup values. We propose that the evolution of QRA of environmental chemicals in the post-genomic era will involve three, somewhat overlapping phases in which different types of approaches begin to mature. The initial focus (in Phase I) has been and continues to be on "augmentation" of weight of evidence--using genomic and related technologies qualitatively to increase the confidence in and scientific basis of the results of QRA. Efforts aimed towards "integration" of these data with traditional animal-based approaches, in particular quantitative predictors, or surrogates, for the in vivo toxicity data to which they have been anchored are just beginning to be explored now (in Phase II). In parallel, there is a recognized need for "expansion" of the use of established biomarkers of susceptibility or risk of human diseases and disorders for QRA, particularly for addressing the issues of cumulative assessment and population risk. Ultimately (in Phase III), substantial further advances could be realized by the development of novel molecular and pathway-based biomarkers and statistical and in silico models that build on anticipated progress in understanding the pathways of human diseases and disorders. Such efforts would facilitate a gradual "reorientation" of QRA towards approaches that more directly link environmental exposures to human outcomes.