POase Activity Research Articles

Why Should Psychiatrists and Neuroscientists Worry about Paraoxonase 1?

Background: Nitro-oxidative stress (NOS) has been implicated in the pathophysiology of psychiatric disorders. The activity of the polymorphic antioxidant enzyme paraoxonase 1 (PON1) is altered in diseases where NOS is involved. PON1 activity may be estimated using different substrates some of which are influenced by PON1 polymorphisms.Objectives: 1) to review the association between PON1 activities and psychiatric diseases using a standardized PON1 substrate terminology in order to offer a state-of-the-art review; and 2) to review the efficacy of different strategies (nutrition, drugs, lifestyle) to enhance PON1 activities.Methods: The PubMed database was searched using the terms paraoxonase 1 and psychiatric diseases. Moreover, the database was also searched for clinical trials investigating strategies to enhance PON1 activity.Results: The studies support decreased PON1 activity as determined using phenylacetate (i.e., arylesterase or AREase) as a substrate, in depression, bipolar disorder, generalized anxiety disorder (GAD) and schizophrenia, especially in antipsychotic-free patients. PON1 activity as determined with paraoxon (i.e., POase activity) yields more controversial results, which can be explained by the lack of adjustment for the Q192R polymorphism. The few clinical trials investigating the influence of nutritional, lifestyle and drugs on PON1 activities in the general population suggest that some polyphenols, oleic acid, Mediterranean diet, no smoking, being physically active and statins may be effective strategies that increase PON1 activity.Conclusion: Lowered PON1 activities appear to be a key component in the ongoing NOS processes that accompany affective disorders, GAD and schizophrenia. Treatments increasing attenuated PON1 activity could possibly be new drug targets for treating these disorders.

Voltammetric appraisal of PON1’s activities: a preliminary study

Introduction: The human serum paraoxonase 1 (EC. 3.1.8.1, PON1) is a high-density lipoprotein associated endogenous free-radical scavenging system with arylesterase (ARase), lactonase (LOase) and paraoxonase (POase) activities [1]. PON1 has been linked to several pathological conditions, such as atherosclerosis, cardiovascular diseases, and neurodegenerative disorders [1]. Additionally, it acts as a protective agent against xenobiotic toxicity, through its ability to hydrolyse organophosphate derivates [1]. Therefore, the monitorization of each PON1 activity is of great interest in clinical, environmental and warfare contexts. Electrochemical-based sensing methods are ideal for PON1 activity assessment since many of the involved reactants are electroactive. Furthermore, these methods are highly attractive for point-of-care testing applications and on-site analysis, due to their simplicity, low-cost, sensitivity, selectivity and a high degree of miniaturization. Previously, we reported a cyclic voltammetry assay for POase activity determination using ethyl-paraoxon as substrate [2]. We now turn to the LOase and AREase activities, using homocysteine thiolactone (HcyTl) and phenylacetate (PA) as the respective substrates [3,4], for the appraisal of PON1 status by voltammetric techniques. Materials and methods: Recombinant wild-type like PON1 (rePON1) G3C9 was expressed in E. coli BL21 and purified according to [5]. In the electrochemical assays, pyrolytic graphite, glassy carbon and screen-printed carbon electrodes were used as working electrodes in a three-electrode configuration with Ag/AgCl reference and platinum/carbon counter electrodes. Enzymatic reactions were analyzed between the potential window (−0.8; 1 V), at 50 mV s−1. Results: The hydrolysis of HcyTl in the presence of rePON1 (LOase activity) was not observed in any condition tested. In contrast, PA was found to be quickly hydrolysed, as showed by an increase in the oxidation current intensity associated to the product formation (phenol). Discussion and conclusions: These preliminary results show that in wild-type like rePON1 G3C9, the AREase activity is the one with the highest turn-over, since the hydrolysis of the PA occurred almost instantly, while the reaction with ethyl-paraoxon (POase) took a few minutes [2] to produce a measurable current signal variation, and the hydrolysis of HcyTl (LOase) was not measurable at all, over a time course of 18 hours.

Genotype-phenotype Analysis of Paraoxonase 1 in Schizophrenic Patients Treated with Atypical Antipsychotics.

ObjectiveRecent studies suggest a possible involvement of low paraoxonase 1 (PON1) enzyme activities in the association between schizophrenia, treatment with atypical antipsychotics and increased cardiovascular (CVD) risk. In the present study, we aimed at investigating the PON1 status in a group of schizophrenic patients treated with either olanzapine or other antipsychotic, as compared to a group of healthy control participants.MethodsWe assessed the arylesterase (AREase) and paraoxonase (POase) activities of PON1, as well as three common polymorphisms of PON1 gene (Q192R, L55M, −108C>T).ResultsWe found significantly lower (−13.3%) AREase activity in schizophrenic patients, along with significantly lower (−18.2%) POase activity in olanzapine-treated patients with QQ genotype. Furthermore, we found a significant difference between groups in L55M polymorphism distribution, whereas Q192R and −108C>T polymorphisms distributions were similar.ConclusionWe identified the olanzapine-treated patients with QQ genotype as having the lowest PON1 (POase) activity, providing a possible way of identifying schizophrenic patients exposed to the greatest risk of CVD.

PON1 status does not influence cholinesterase activity in Egyptian agricultural workers exposed to chlorpyrifos

Animal studies have shown that paraoxonase 1 (PON1) genotype can influence susceptibility to the organophosphorus pesticide chlorpyrifos (CPF). However, Monte Carlo analysis suggests that PON1 genotype may not affect CPF-related toxicity at low exposure conditions in humans. The current study sought to determine the influence of PON1 genotype on the activity of blood cholinesterase as well as the effect of CPF exposure on serum PON1 in workers occupationally exposed to CPF. Saliva, blood and urine were collected from agricultural workers (n=120) from Egypt's Menoufia Governorate to determine PON1 genotype, blood cholinesterase activity, serum PON1 activity towards chlorpyrifos-oxon (CPOase) and paraoxon (POase), and urinary levels of the CPF metabolite 3,5,6-trichloro-2-pyridinol (TCPy). The PON1 55 (P≤0.05) but not the PON1 192 genotype had a significant effect on CPOase activity. However, both the PON1 55 (P≤0.05) and PON1 192 (P≤0.001) genotypes had a significant effect on POase activity. Workers had significantly inhibited AChE and BuChE after CPF application; however, neither CPOase activity nor POase activity was associated with ChE depression when adjusted for CPF exposure (as determined by urinary TCPy levels) and stratified by PON1 genotype. CPOase and POase activity were also generally unaffected by CPF exposure although there were alterations in activity within specific genotype groups. Together, these results suggest that workers retained the capacity to detoxify chlorpyrifos-oxon under the exposure conditions experienced by this study population regardless of PON1 genotype and activity and that effects of CPF exposure on PON1 activity are minimal.

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.

PON1 and Neurodevelopment in Children from the CHAMACOS Study Exposed to Organophosphate Pesticides in Utero

BackgroundParaoxonase 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.ObjectiveWe 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.MethodsWe 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.ResultsChildren 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.ConclusionPON1 was associated with child neurobehavioral development, but additional research is needed to confirm whether it modifies the relation with in utero OP exposure.

PHENOTYPE PATTERN OF SINGLE NUCLEOTIDE POLYMORPHISM OF PARAOXONASE GENE (Q192RPON1) IN TYPE 2 DIABETIC PATIENTS

We studied the input of genetic and metabolic factors (PON1 gene polymorphism — Q192RPON1 genotype and glucolypotoxicity, respectively) to formation of enzyme functional characteristics in Type 2 diabetic patients (n = 31). Phenotyping of 79 blood samples was done by using PON1 rates of hydrolysis is of paraoxon (POase activity) and diazoxon (DZOase activity). POase activity was generally lower in diabetics than in control subjects. It was also found that against the background of conservation a determinant role of Q192RPON1 genotype for its phenotype the modulating impact of metabolic disturbances (a namely significant decrease in POase activity) was verified only in patients with QR genotype, which have been characterized significant more higher POase activity vs QQ genotype.On the other hand, there were diagnosed more pronounced hormonal-metabolic disturbances related to insulin resistance and oxidative stress in QQ homozygotes vs QR heterozygotes (increase in circulating leptin levels and decrease in erythocyte gluthathionperoxidase concentrations). We also confirmed that diazoxonase / paraoxonase activities index provides PON1 phenotype and genotype and an accurate inference of PON1 genotype. Both are important parameters for determining an individual’s PON1 status in Ukrainian Type 2 diabetes population.

Developmental Changes in PON1 Enzyme Activity in Young Children and Effects of PON1 Polymorphisms

BackgroundParaoxonase 1 (PON1) is an enzyme that detoxifies activated organophosphorus pesticides (OPs) and is also involved in oxidative stress pathways.ObjectivesPON1 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.MethodsWe 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.ResultsContrary 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 PON1192 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.ConclusionsLower 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.

Determination of Paraoxonase 1 Status Without the Use of Toxic Organophosphate Substrates

Paraoxonase 1 ( PON1 ) is a member of a tandem 3-gene family localized on human chromosome 7q21-22.1 High-density lipoprotein-associated PON1 2,3 and PON34,5 are synthesized primarily in the liver, whereas PON2 is ubiquitously expressed.1 PON1 was initially characterized and named for its ability to hydrolyze paraoxon, the toxic oxon metabolite of parathion.6 Although Aldridge6 proposed in 1953 that serum paraoxonase (POase) and arylesterase (AREase) activities were carried out by the same enzyme, controversy about 1 versus 2 enzymes persisted for many years, resulting in a reclassification of POase/AREase from EC 3.1.1.2 to EC 3.1.8.1 for PON1 as an example of an organophosphorus (OP) hydrolase.7 The controversy was finally settled when Sorenson et al8 demonstrated both activities in recombinant PON1 . However, the revised nomenclature remains in place. Early studies of plasma PON1 found a large variability of POase activity among different species and in different tissues.6 Serum POase activity distribution studies in human populations revealed an activity polymorphism of high versus low POase activity. Studies on the polymorphic distribution of PON1 in human populations using a variety of different assays revealed bi or trimodal distributions of plasma POase activity (reviewed in Ref. 9). Editorial see p 79 Our initial characterization of the human PON1 cDNA clones revealed 2 coding region polymorphisms Q192R and L55 M.10 Subsequently, it was shown that the Q192R polymorphism determined high versus low rates of paraoxon hydrolysis by the enzyme, with the PON1 R192 alloform specifying high activity.11,12 After the demonstration that high-density lipoprotein-associated PON1 was implicated in reducing low-density lipoprotein13 and high-density lipoprotein14 oxidation, epidemiological studies were undertaken to explore the possible role of genetic variability of PON1 in cardiovascular disease15 (reviewed in Ref. 16). Several meta-analyses of studies that examined only …

PON1 status is influenced by oxidative stress and inflammation in coronary heart disease patients

Objectives High-density lipoprotein (HDL) associated paraoxonase 1 (PON1) is an essential component of HDLs' capability to protect low-density lipoproteins (LDL) from oxidative modification and thus to limit the atherosclerotic process. The aim of the current study was to investigate the association between oxidative stress status, indices of inflammation and PON1 status parameters. Design and methods We determined the relationship between the oxidative stress status, inflammatory markers and PON1 status parameters in 261 middle-aged subjects: 156 coronary heart disease (CHD) patients and 105 CHD-free subjects (as the control group). The PON1 status involved PON1 activity measurements towards two substrates: paraoxon (POase activity) and diazoxon (DZOase activity) and subsequent PON1 Q192R activity phenotype determination. Results A statistically significant greater malondialdehyde (MDA) concentration in the RR phenotype subjects compared to QQ subjects within the CHD group was apparent ( P < 0.05). Multiple linear regression analysis revealed an independent influence of plasmatic SOD activity ( P < 0.05) on POase values and MDA ( P < 0.01) and O 2 − ( P < 0.05) on DZOase values. Involvement of inflammatory markers (fibrinogen and hsCRP) in the regression model did not hinder the influence of SOD and MDA on POase and DZOase activities, respectively. Conclusions Our CHD patients were in a state of oxidative stress, which was most evident in the RR phenotype group. The QQ phenotype group is associated with the lowest oxidative stress status level and also with a better capacity for anti-oxidative protection. Oxidative stress in CHD patients is maintained by systemic low-grade inflammation, which results in PON1 enzymatic activity exhaustion. Therefore, deeper investigation of an effective anti-oxidative and anti-inflammatory therapy should be necessary in order to increase anti-oxidative potency and improve PON1 status of CHD patients.

Paraoxonase-1 (PON1) activity, but not PON1Q192R phenotype, is a predictor of coronary artery disease in a middle-aged Serbian population

Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme that protects lipoproteins from oxidative modifications. Polymorphisms in the gene, including PON1Q192R, have been studied. However, inconsistencies regarding the above-mentioned polymorphism obscure its association with vascular disease. Using a two-substrate (paraoxon/diazoxon) activity method, we investigated the frequencies of PON1Q192R phenotypes in 261 middle-aged subjects: 156 patients with angiographically assessed coronary heart disease (CHD) and 105 CHD-free subjects as the control group. The PON1(192) phenotype was predicted from examination of the two-dimensional plot of hydrolysis rates of diazoxon vs. paraoxon and by using the antimode of the histogram of the ratio of diazoxonase/paraoxonase activity. The PON1Q192R phenotype frequencies in 113 patients with occlusion >50% (coronary artery disease-positive, CAD+ group) vs. control population were as follows: QQ (0.552 vs. 0.510), QR (0.382 vs. 0.408) and RR (0.066 vs. 0.082); chi2=0.414, p=0.813. We found lower paraoxonase (POase) and diazoxonase (DZOase) activities in the CAD+ patients when compared to the control population. According to logistic regression analysis, POase activity was a better predictor of coronary disease onset compared with DZOase activity measurements and PON1Q192R phenotyping. We conclude that enzyme activity (within a particular phenotypic group) is more important than phenotype alone in predicting susceptibility to coronary artery disease.

Loss of a prolyl oligopeptidase confers resistance to lithium by elevation of inositol (1,4,5) trisphosphate.

The therapeutic properties of lithium ions (Li+) are well known; however, the mechanism of their action remains unclear. To investigate this problem, we have isolated Li+-resistant mutants from Dictyostelium. Here, we describe the analysis of one of these mutants. This mutant lacks the Dictyostelium prolyl oligopeptidase gene (dpoA). We have examined the relationship between dpoA and the two major biological targets of lithium: glycogen synthase kinase 3 (GSK-3) and signal transduction via inositol (1,4,5) trisphosphate (IP3). We find no evidence for an interaction with GSK-3, but instead find that loss of dpoA causes an increased concentration of IP3. The same increase in IP3 is induced in wild-type cells by a prolyl oligopeptidase (POase) inhibitor. IP3 concentrations increase via an unconventional mechanism that involves enhanced dephosphorylation of inositol (1,3,4,5,6) pentakisphosphate. Loss of DpoA activity therefore counteracts the reduction in IP3 concentration caused by Li+ treatment. Abnormal POase activity is associated with both unipolar and bipolar depression; however, the function of POase in these conditions is unclear. Our results offer a novel mechanism that links POase activity to IP3 signalling and provides further clues for the action of Li+ in the treatment of depression.

Phenoloxidase activity in Coprinus cinereus due to protoplasting and insertion treatment with Pleurotus ostreatus DNA

An apparent phenoloxidase (POase) negative strain of Coprinus cinereus acquired POase activity through either protoplasting or DNA-insertion treatment. The DNA-treated C. cinereus showed an electrophoretic band with POase activity, which is similar to the Pleurotus ostreatus used for the DNA source.