Gene therapy to prevent organophosphate intoxication

Role of PON1 L55M Gene Polymorphism in Parkinson's Disease among North Indian Population

BACKGROUND AND OBJECTIVES

The role of various genetic markers including alpha synuclein, Parkin, etc., is known in the pathogenesis of Parkinson's disease (PD). Novel genetic markers including paraoxonase 1 (PON1) have also been linked to PD pathogenesis in recent studies. The PON1 L55M allele carriers may have defective clearance of environmental toxins and may result in increased susceptibility to PD. Hence, we studied the role of PON1 L55M polymorphism in PD among a North Indian population.

MATERIALS AND METHOD

Seventy-four PD patients and 74 age- and sex-matched controls were recruited in this hospital-based case-control study. Baseline characteristics were recorded using structured questionnaire. DNA was extracted from 3-4 ml of venous blood, followed by PCR and restriction digestion. PON1 L55M genotypes were visualized as bands: LL (177 bp), LM (177, 140 bp) and MM (140,44 bp) on 3% agarose gel. Mann-Whitney U test and Chi-squared test were used for comparing two groups of skewed and categorical variables, respectively. Measures of strength of association were calculated by binary regression analysis. P value < 0.05 was considered as significant.

RESULTS

Parkinson's disease patients had significantly higher exposure to pesticides (12.2%; P (organophosphate exposure) < 0.001) and well water drinking (28.4%; P = 0.006) compared to controls. Frequency distribution of LL, LM, MM genotypes was 67.5% (50/74), 28.4% (21/74), and 4.1% (3/74), respectively, for cases and 72.6% (54/74), 26% (19/74) and 1.4% (1/74), respectively, for controls. PON1 L55M genotype distribution between Parkinson's disease cases and controls was not significant (P = 0.53). PON1 L55M polymorphism was not associated with PD after adjusting for confounders by binary regression analysis.

CONCLUSION

There was no significant association between PON1 L55M polymorphism and PD. Larger population-based studies would be required from India before drawing any definite conclusions.

Serum Activities of Paraoxonase 1 (PON1) in Predicting Liver Damage Among Patients Diagnosed With Hepatocellular Carcinoma: A Case-Control Study

Introduction Hepatocellular carcinoma (HCC) is one of the most common cancers in the world and unless diagnosed timely has limited options for treatment. Paraoxonase (PON) is a glycosylated protein that has been implicated in antioxidant and other biochemical functions. Paraoxonase 1 (PON1) is an esterase associated with high-density lipoprotein (HDL) particles. The present study was carried out to assess the PON1 activity and compare it with the standard liver function tests (LFTs) in assessing the predictability of liver damage among patients diagnosed with HCC. Methods This case-control study was carried out in the Department of Biochemistry attached to Great Eastern Medical School and Hospital, Srikakulam, Andhra Pradesh. Serum PON1 activities and LFTs like total bilirubin, direct bilirubin, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), total protein, and albumin were estimated in 30 patients diagnosed with HCC and 30 healthy persons. All the parameters were estimated using standard biochemical methods. The data was analyzed using GraphPad Prism version 6.0 (GraphPad Software, Inc). A probability (p) value <0.05 was considered to be statistically significant. Receiver operating characteristic curve (ROC) analysis was performed to assess the area under the curve (AUC) for accuracy, sensitivity, specificity, and diagnostic efficiency. Results The serum activities of PON1 had identical sensitivity (70%) to albumin (70%) and were superior to other tested parameters. Additionally, PON1 activities showed lower specificity (86.67%) than the other tested parameters. ROC analysis showed increased diagnostic efficacy (DE) of PON1 (DE=78.3%; p<0.0001) when compared with total bilirubin (DE=76.6%; p=0.0039), direct bilirubin (DE=74.9%; p=0.04), ALT (DE=73.30%; p=0.0006), and total protein (DE=71.6%; p=0.0005). However, the DE of PON1 was comparable with AST (DE=81.60%; p<0.0001), ALP (DE=79.9%; p<0.0001), and albumin (DE=83.30%, p<0.0001). Conclusions Serum activities of PON1 could be used as a diagnostic marker for assessing liver damage among HCC patients.

Effective remediation and decontamination of organophosphorus compounds using enzymes: From rational design to potential applications

Organophosphorus compounds (OPs) have been widely used in agriculture for decades because of their high insecticidal efficiency, which maintains and increases crop yields worldwide. More importantly, OPs, as typical chemical warfare agents, are a serious concern and significant danger for military and civilian personnel. The widespread use of OPs, superfluous and unreasonable use, has caused great harm to the environment and food chain. Developing efficient and environmentally friendly solutions for the decontamination of OPs is a long-term challenge. Microbial enzymes show potential application as natural and green biocatalysts. Thus, utilizing OP-degrading enzymes for environmental decontamination presents significant advantages, as these enzymes can rapidly hydrolyze OPs; are environmentally friendly, nonflammable, and noncorrosive; and can be discarded safely and easily. Here, the properties, structure and catalytic mechanism of various typical OP-degrading enzymes are reviewed. The methods and effects utilized to improve the expression level, catalytic performance and stability of OP-degrading enzymes were systematically summarized. In addition, the immobilization of OP-degrading enzymes was explicated emphatically, and the latest progress of cascade reactions based on immobilized enzymes was discussed. Finally, the latest applications of OP-degrading enzymes were summarized, including biosensors, nanozyme mimics and medical detoxification. This review provides guidance for the future development of OP-degrading enzymes and promotes their application in the field of environmental bioremediation and medicine.

Migraine and thyroid dysfunction: Co-occurrence, shared genes and biological mechanisms

BACKGROUND AND PURPOSE

Migraine and thyroid dysfunction, particularly hypothyroidism, are common medical conditions and are known to have high heritability. Thyroid function measures, thyroid stimulating hormone (TSH) and free thyroxine (fT4), are also known to be genetically influenced. Although observational epidemiological studies report an increased co-occurrence of migraine and thyroid dysfunction, a clear and combined interpretation of the findings is currently lacking. A narrative review is provided of the epidemiological and genetic association evidence linking migraine, hypothyroidism, hyperthyroidism and thyroid hormones TSH and fT4.

METHODS

An extensive literature search was conducted in the PubMed database for epidemiological, candidate gene and genome-wide association studies using the terms migraine, headache, thyroid hormones, TSH, fT4, thyroid function, hypothyroidism and hyperthyroidism.

RESULTS

Epidemiological studies suggest a bidirectional relationship between migraine and thyroid dysfunction. However, the nature of the relationship remains unclear, with some studies suggesting migraine increases the risk for thyroid dysfunction whilst other studies suggest the reverse. Early candidate gene studies have provided nominal evidence for MTHFR and APOE, whilst more recently genome-wide association studies have provided robust evidence for THADA and ITPK1 being associated with both migraine and thyroid dysfunction.

CONCLUSIONS

These genetic associations improve our understanding of the genetic relationship between migraine and thyroid dysfunction, provide an opportunity to develop biomarkers to identify migraine patients most likely to benefit from thyroid hormone therapy, and indicate that further cross-trait genetic studies have excellent potential to provide biological insight into their relationship and inform clinical interventions.

Esterases as emerging biocatalysts: Mechanistic insights, genomic and metagenomic, immobilization, and biotechnological applications

Esterase enzymes are a family of hydrolases that catalyze the breakdown and formation of ester bonds. Esterases have gained a prominent position in today's world's industrial enzymes market. Due to their unique biocatalytic attributes, esterases contribute to environmentally sustainable design approaches, including biomass degradation, food and feed industry, dairy, clothing, agrochemical (herbicides, insecticides), bioremediation, biosensor development, anticancer, antitumor, gene therapy, and diagnostic purposes. Esterases can be isolated by a diverse range of mammalian tissues, animals, and microorganisms. The isolation of extremophilic esterases increases the interest of researchers in the extraction and utilization of these enzymes at the industrial level. Genomic, metagenomic, and immobilization techniques have opened innovative ways to extract esterases and utilize them for a longer time to take advantage of their beneficial activities. The current study discusses the types of esterases, metagenomic studies for exploring new esterases, and their biomedical applications in different industrial sectors.

Lupeol inhibits pesticides induced hepatotoxicity via reducing oxidative stress and inflammatory markers in the rats

The present study was aimed at investigating the toxicity of various pesticides on rat liver. It also aimed to show whether this toxicity could be avoided using lupeol. Adult male Wistars albino rats were randomly divided into nine groups. Control groups were given saline, corn oil, and lupeol; pesticide groups were given malathion, chlorpyrifos, and tebuconazole; in the other three treatments, same doses of pesticides and lupeol were given to the rats for ten days. Histopathological examination showed severe degenerative changes in the pesticide groups. Serum AChE activities, liver GSH, total antioxidant capacity levels, AChE, CAT, SOD, GPx, GR, Na⁺/K⁺-ATPase, ARE, and PON were decreased, while serum TNF-α, liver LPO, HP, NO, AOPP, total oxidant status, ROS, and oxidative stress index levels as well as AST, ALT, ALP, GST, arginase and xanthine oxidase activities were increased in the pesticides administered groups. It was observed that the PCNA levels determined by the immunohistochemical method increased in the pesticide groups. Also, the results Raman spectroscopy suggest that the technique may be used to understand/have an insight into pesticide toxicity mechanisms. The administration of lupeol demonstrated a hepatoprotective effect against pesticide-induced toxicity.

DNA damage in a Chilean population exposed to pesticides and its association with PON1 (Q192R and L55M) susceptibility biomarker

The active ingredients in pesticides are known to be genotoxic that can cause mutations, chromosomal aberrations, or other types of DNA damage. Early detection of genotoxicity reduces the risk of developing diseases such as cancer or suffering from reproductive disorders. In turn, the genotoxic risk depends on the intrinsic capability of the individual to metabolize and eliminate the xenobiotic from the organism. This study aimed to determine if two polymorphisms of paraoxonase-1 (PON1), which is involved in the metabolism of several organophosphate (OP) pesticides, are predictors of susceptibility to DNA damage in agricultural workers and inhabitants of rural areas chronically exposed to pesticides. A cross-sectional study was made considering three groups: agricultural workers (occupational exposure, OE, n = 85), rural inhabitants (environmental exposure, EE, n = 60), and an unexposed group conformed by people living far from agricultural areas (U, n = 33). The level of individual DNA damage was measured using the comet assay, and genotyping was done to determine the PON1 Q192R and L55M polymorphisms. Acetylcholinesterase and butyrilcholinesterase activities were also measured to determine exposure to OP. Individuals belonging to EE and OE groups displayed higher levels of DNA damage compared with U group (p < .001). OP exposure was the main predictor of genotoxicity (β = 16.19; 95% CI: 1.85, 30.52), instead of PON1 polymorphisms (β = -12.20; 95% CI: -27.87, 3.48). These results confirm the genotoxic effects of pesticide exposure and suggest that the catalytic efficiency of PON1 to metabolize OP pesticides becomes negligible in individuals with a history of long-term environmental or occupational exposure to these substances.

Organophosphorus poisoning in animals and enzymatic antidotes

Organophosphorus compounds (OPs) are neurotoxic molecules developed as pesticides and chemical warfare nerve agents (CWNAs). Most of them are covalent inhibitors of acetylcholinesterase (AChE), a key enzyme in nervous systems, and are therefore responsible for numerous poisonings around the world. Many animal models have been studied over the years in order to decipher the toxicity of OPs and to provide insights for therapeutic and decontamination purposes. Environmental impact on wild animal species has been analyzed to understand the consequences of OP uses in agriculture. In complement, various laboratory models, from invertebrates to aquatic organisms, rodents and primates, have been chosen to study chronic and acute toxicity as well as neurobehavioral impact, immune response, developmental disruption, and other pathological signs. Several decontamination approaches were developed to counteract the poisoning effects of OPs. Among these, enzyme-based strategies are particularly attractive as they allow efficient external decontamination without toxicity or environmental impact and may be of interest for treatment. Approaches using bioscavengers for prophylaxis, treatment, and external decontamination are emphasized and their potential is discussed in the light of toxicological observations from various animal models. The relevance of animal models, regarding their cholinergic system and the abundance of naturally protecting enzymes, is also discussed for better extrapolation of results to human.

Association between serum paraoxonase 1 activity and its polymorphisms with multiple sclerosis: a systematic review

BACKGROUND

Human serum paraoxonase (PON) is an enzyme that is synthesized by the liver and enters the bloodstream, and it is transmitted by high-density lipoproteins (HDL). Paraoxonase 1 (PON1) is a hydrolytic enzyme with a wide range of substrates and the ability to protect against lipid oxidation. In this study, due to the activity of PON1 in the brain and its antioxidant effects on the reduction of neurological disorders in the central nervous system, the role of PON1 and its polymorphisms related to multiple sclerosis has been examined to enhance treatment methods.

METHODS

This article is a systematic review. In this study, the role of PON1 and its polymorphisms in multiple sclerosis (MS) has been investigated. Articles published in Persian and international databases of SID, Google Scholar, ISI (WoS), Magiran, PubMed, Scopus, IranDoc, Science Direct, and Iran Medix were examined, using the search keywords of Paraoxonase 1, polymorphism, multiple sclerosis, and PON1.

RESULTS

PON1 is undoubtedly a potential factor in the pathogenesis of multiple sclerosis, and it plays an important role in protecting antioxidants in the blood. Oxidative stress and lipid peroxidation are factors in the pathogenesis of MS. Both inflammatory cytokines and oxidative stress have a detrimental effect on PON1. However, reducing the activity of PON1 may help to restore the pathogenesis of the disease.

CONCLUSION

Decreased PON1 activity and PON1 polymorphism are associated with several neurological diseases, including ischemic stroke, white matter lesions (WMLs), amyotrophic lateral sclerosis (ALS), dementia, and Parkinson's disease. PON1-55M alleles in Italians and PON1-192Q alleles in Poles were associated with a high risk of MS. Moreover, PON1-55 and PON1-192 polymorphisms were not associated with MS onset age, nor its evolutionary type.

Review on mechanistic strategy of gene therapy in the treatment of disease

Gene therapy has become a revolution and its breakthrough is a corner stone in modern science. This treatment has rising advantages with limited negative aspects. Gene therapy is a therapeutic method in which, transfer of DNA to an individual to manipulate a defective gene is performed and to mitigate a disease which is not responding to pharmacological therapy. The gene therapy strategies are divided into two main categories such as direct in-vivo gene delivery of manipulated viral vector vehicle into the host and ex-vivo genetically engineered stem cells. In this review, we tried to cover all aspects of gene therapy studies; starting with the concept of gene, its treatment, gene delivery system and types, clinical trial either by vitro or In-Vivo -Clinical Trials and Clinical Intoxication of Gene Therapy. Therefore, the promise of successful treatment with gene therapy could positively affect millions of lives. The main aim of this review is to address the principles of gene therapy, various methods involved in the gene therapy, clinical applications and its merits and demerits.

Developmental and social deficits and enhanced sensitivity to prenatal chlorpyrifos in PON1-/- mouse pups and adults

The levels and activity of the enzyme paraoxonase 1 affect the vulnerability to the teratogenic effects of organophosphate pesticides. Mutant mice lacking the gene for paraoxonase1 (PON1^-/-) are more susceptible to the toxic effects of chlorpyrifos, and were hypothesized to be more vulnerable to social behavior deficits induced by exposure to chlorpyrifos during gestation. Three experiments were performed comparing PON1^-/- mice to PON1^+/+ mice born to dams treated with 0.5 mg/kg chlorpyrifos or cornoil vehicle on gestational days 12–15. Chlofpyrifos-exposed male PON1^-/- mouse pups had delayed development of reflexes in in the first experiment. In the second experiment, adult male and female PON1^-/- mice and the female PON1^+/+ mice all displayed lower social preference than the male vehicle-treated PON1^+/+ mice. The PON1^-/- mice and the female PON1^+/+ mice displayed lower social preference compared to the PON1^+/+ male mice. Male adult mice that had been exposed in utero to chlorpyrifos showed less conditioned social preference regardless of genotype. In the third study, the delayed reflex development was replicated in male and female PON1^-/- mice, but chlorpyrifos did not augment this effect. Nest Odor Preference, a test of early social attachment to dam and siblings, was lower in PON1^-/- mouse pups compared to PON1^+/+ pups. This study shows for the first time that PON1^-/- mice have a behavioral phenotype that indicates impaired reflex development and social behavior. Chlorpyrifos exposure during gestation tended to augment some of these effects.

[Organophosphorus poisoning: Towards enzymatic treatments]

Organophosphorus compounds (OP) are toxic molecules developed as insecticides and chemical warfare nerve agents (CWNAs). Most OP are neurotoxic and act as nervous system disruptors by blocking cholinergic transmission. They are therefore responsible for many poisonings worldwide. OP toxicity may result either from acute or chronic exposure, and their poisoning effect were evaluated using several animal models. These latter were also used for evaluating the efficacy of antidotes. Strategies based on enzymes that can trap (stoichiometric bioscavengers) or degrade (catalytic bioscavengers) OP, were particularly studied since they allow effective decontamination, without toxicity or environmental impact. This review summarizes the results obtained in vivo with enzymes through three levels: prophylaxis, treatment and external decontamination. The efficiency of enzymatic treatments in different animal models is presented and the relevance of these models is also discussed for a better extrapolation to humans.

Redox Mechanisms in Migraine: Novel Therapeutics and Dietary Interventions

SIGNIFICANCE

Migraine represents the third most prevalent and the seventh most disabling human disorder. Approximately 30% of migraine patients experience transient, fully reversible, focal neurological symptoms (aura) preceding the attack. Recent Advances: Awareness of the hypothesis that migraine actually embodies a spectrum of illnesses-ranging from episodic to chronic forms-is progressively increasing and poses novel challenges for clarifying the underlying pathophysiological mechanisms of migraine as well as for the development of novel therapeutic interventions. Several theories have evolved to the current concept that a combination of genetic, epigenetic, and environmental factors may play a role in migraine pathogenesis, although their relative importance is still being debated.

CRITICAL ISSUES

One critical issue that deserves a particular attention is the role of oxidative stress in migraine. Indeed, potentially harmful oxidative events occur during the migraine attack and long-lasting or frequent migraine episodes may increase brain exposure to oxidative events that can lead to chronic transformation. Moreover, a wide variety of dietary, environmental, physiological, behavioral, and pharmacological migraine triggers may act through oxidative stress, with clear implications for migraine treatment and prophylaxis. Interestingly, almost all current prophylactic migraine agents exert antioxidant effects.

FUTURE DIRECTIONS

Increasing awareness of the role of oxidative stress and/or decreased antioxidant defenses in migraine pathogenesis and progression to a chronic condition lays the foundations for the design of novel prophylactic approaches, which, by reducing brain oxidative phenomena, could favorably modify the clinical course of migraine. Antioxid. Redox Signal. 28, 1144-1183.

Genetic bases of the nutritional approach to migraine

Migraine is a common multifactorial and polygenic neurological disabling disorder characterized by a genetic background and associated to environmental, hormonal and food stimulations. A large series of evidence suggest a strong correlation between nutrition and migraine and indicates several commonly foods, food additives and beverages that may be involved in the mechanisms triggering the headache attack in migraine-susceptible persons. There are foods and drinks, or ingredients of the same, that can trigger the migraine crisis as well as some foods play a protective function depending on the specific genetic sensitivity of the subject. The recent biotechnological advances have enhanced the identification of some genetic factors involved in onset diseases and the identification of sequence variants of genes responsible for the individual sensitivity to migraine trigger-foods. Therefore many studies are aimed at the analysis of polymorphisms of genes coding for the enzymes involved in the metabolism of food factors in order to clarify the different ways in which people respond to foods based on their genetic constitution. This review discusses the latest knowledge and scientific evidence of the role of gene variants and nutrients, food additives and nutraceuticals interactions in migraine.

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.

Effect of PON1 gene polymorphisms in Turkish patients with hepatocellular carcinoma

Background: Reactive oxygen species (ROS) can oxidize biological molecules that mediate carcinogenesis by causing metabolic malfunction and damage to DNA. Human serum paraoxonases (PON1, PON2 and PON3) play a role in antioxidant defense and protect the cell against ROS. PON1 polymorphisms Q192R and L55M have been shown to be associated with several human cancers, but their association with hepatocellular carcinoma (HCC) has yet to be investigated. Methods: We performed genotyping analysis using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a hospital-based case–control study of 217 confirmed HCC patients and 217 age-, gender-, smoking- and alcohol consumption-matched cancer-free controls in Turkish population. Results: Q192R and L55M polymorphisms were in significant linkage disequilibrium (LD) (D′ = 0.77). However, allele, genotype and haplotype analysis showed no significant differences between the risks of HCC and PON1 polymorphisms. Moreover, no significant differences were found between clinical findings, clinicopathological features and sex in comparison with the PON1 genotypes in HCC group. Conclusion: Our results suggest for the first time that neither the Q192R polymorphism nor the L55M polymorphism has relationship with the risk of developing HCC. Further independent studies are required to clarify the possible role of PON1 gene Q192R and L55M polymorphisms on the risk of developing HCC in a larger series and also in patients of different ethnic origins.

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Human serum paraoxonases (PON) play a key role to protect the cell against ROS.

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We analyzed for the first time the relationship between PON1 polymorphisms and HCC.

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No significant differences between HCC risk and PON1 (L55M, Q192R) polymorphisms

Paraoxonase 1 (PON1) as a genetic determinant of susceptibility to organophosphate toxicity

Paraoxonase (PON1) is an A-esterase capable of hydrolyzing the active metabolites (oxons) of a number of organophosphorus (OP) insecticides such as parathion, diazinon and chlorpyrifos. PON1 activity is highest in liver and in plasma. Human PON1 displays two polymorphisms in the coding region (Q192R and L55M) and several polymorphisms in the promoter and the 3'-UTR regions. The Q192R polymorphism imparts differential catalytic activity toward some OP substrates, while the polymorphism at position -108 (C/T) is the major contributor of differences in the levels of PON1 expression. Both contribute to determining an individual's PON1 "status". Animal studies have shown that PON1 is an important determinant of OP toxicity. Administration of exogenous PON1 to rats or mice protects them from the toxicity of specific OPs. PON1 knockout mice display a high sensitivity to the toxicity of diazoxon and chlorpyrifos oxon, but not of paraoxon. In vitro catalytic efficiencies of purified PON192 alloforms for hydrolysis of specific oxon substrates accurately predict the degree of in vivo protection afforded by each isoform. Evidence is slowly emerging that a low PON1 status may increase susceptibility to OP toxicity in humans. Low PON1 activity may also contribute to the developmental toxicity and neurotoxicity of OPs, as shown by animal and human studies.

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.

Common genetic variants in the myeloperoxidase and paraoxonase genes and the related cancer risk: a review

Modern approaches in health care are moving toward the model of "personalized medicine." Today, current research in molecular biology and medicine is focused on developing genomic markers with predictive, therapeutic, and prognostic significance. One of the most widespread and significant genomic markers is the single nucleotide polymorphism (SNP), which represents a variation in DNA sequence when a single nucleotide differs between members of a biological species or paired chromosomes in an individual. Antioxidant defense enzymes break down dangerous reactive compounds, called reactive oxygen species, and prevent DNA strand from carcinogen-specific mutations. It is well known that inherited variations in genes that encode antioxidant defense enzymes may modulate individual susceptibility to cancer. In our previous study we have determined the predictive significance of several SNPs of superoxide dismutase (SOD) and glutathione peroxidase gene families in the context of cancer risk. The present review includes a summary and discussion of the current findings evaluating the role of SNPs of the myeloperoxidase (MPO) and paraoxanase (PON) genes in cancer occurrence and development. We suggest that rs2333227 (MPO_ -463G/A) and rs854560 polymorphisms have a great predictive significance; they could probably be utilized as cancer predictors in the future. Also, we recommend further in-depth research for rs11079344 (MPO), rs8178406 (MPO), rs2243828 (MPO), rs662 (PON1), rs705379 (PON1), and PON1_304A/G polymorphisms. These SNPs may become significant cancer-associated biomarkers.

Delayed reduction of hippocampal synaptic transmission and spines following exposure to repeated subclinical doses of organophosphorus pesticide in adult mice

Agricultural and household organophosphorus (OP) pesticides inhibit acetylcholinesterase (AchE), resulting in increased acetylcholine (Ach) in the central nervous system. In adults, acute and prolonged exposure to high doses of AchE inhibitors causes severe, clinically apparent symptoms, followed by lasting memory impairments and cognitive dysfunction. The neurotoxicity of repeated environmental exposure to lower, subclinical doses of OP pesticides in adults is not as well studied. However, repeated exposure to acetylcholinesterase inhibitors, such as chlorpyrifos (CPF), pyridostigmine, and sarin nerve agent, has been epidemiologically linked to delayed onset symptoms in Gulf War Illness and may be relevant to environmental exposure in farm workers among others. We treated adult mice with a subclinical dose (5 mg/kg) of CPF for 5 consecutive days and investigated hippocampal synaptic transmission and spine density early (2-7 days) and late (3 months) after CPF administration. No signs of cholinergic toxicity were observed at any time during or after treatment. At 2-7 days after the last injection, we found increased synaptic transmission in the CA3-CA1 region of the hippocampus of CPF-treated mice compared with controls. In contrast, at 3 months after CPF administration, we observed a 50% reduction in synaptic transmission likely due to a corresponding 50% decrease in CA1 pyramidal neuron synaptic spine density. This study is the first to identify a biphasic progression of synaptic abnormalities following repeated OP exposure and suggests that even in the absence of acute cholinergic toxicity, repeated exposure to CPF causes delayed persistent damage to the adult brain in vivo.

Toxic influence of organophosphate, carbamate, and organochlorine pesticides on cellular metabolism of lipids, proteins, and carbohydrates: a systematic review

Pesticides, including organophosphate (OP), organochlorine (OC), and carbamate (CB) compounds, are widely used in agricultural and indoor purposes. OP and CB act as acetyl cholinesterase (AChE) inhibitors that affect lots of organs such as peripheral and central nervous systems, muscles, liver, pancreas, and brain, whereas OC are neurotoxic involved in alteration of ion channels. There are several reports about metabolic disorders, hyperglycemia, and also oxidative stress in acute and chronic exposures to pesticides that are linked with diabetes and other metabolic disorders. In this respect, there are several in vitro and in vivo but few clinical studies about mechanism underlying these effects. Bibliographic databases were searched for the years 1963-2010 and resulted in 1652 articles. After elimination of duplicates or irrelevant papers, 204 papers were included and reviewed. Results indicated that OP and CB impair the enzymatic pathways involved in metabolism of carbohydrates, fats and protein within cytoplasm, mitochondria, and proxisomes. It is believed that OP and CB show this effect through inhibition of AChE or affecting target organs directly. OC mostly affect lipid metabolism in the adipose tissues and change glucose pathway in other cells. As a shared mechanism, all OP, CB and OC induce cellular oxidative stress via affecting mitochondrial function and therefore disrupt neuronal and hormonal status of the body. Establishing proper epidemiological studies to explore exact relationships between exposure levels to these pesticides and rate of resulted metabolic disorders in human will be helpful.

Adenovirus-mediated human paraoxonase1 gene transfer to provide protection against the toxicity of the organophosphorus pesticide toxicant diazoxon

Human paraoxonase1 (hPON1) is a potential therapeutic against the toxicity of organophosphorus (OP) pesticides and chemical warfare nerve agents. We tested whether PON1 gene transfer using adenovirus provides protection against the toxicity of the OP diazoxon. Using an adenovirus construct containing hPON1 gene, we showed elevated levels of recombinant hPON1 in vitro in 293A cells and in vivo in mice. The recombinant enzyme was secreted by 293A cells into culture medium and into the systemic circulation of mice. Western blotting revealed that the virally expressed hPON1 had the expected molecular weight of 45 kDa. Recombinant hPON1 in mice was in complex with mouse high-density lipoprotein (HDL) and migrated more slowly than endogenous hPON1 in the human HDL complex. Mice injected with adenovirus expressed PON1 at 600-3480 U ml(-1) on day 5 post-treatment, which is 8-50-fold above endogenous. Six mice expressing hPON1 survived 2LD(50) doses of diazoxon. Four of the six mice survived a second dose of diazoxon (for a total of 4LD(50)) administered 24 h later. In contrast, none of the three mice in the control group survived one 2LD(50) dose. These results show that hPON1 in mice functions as a prophylactic and offers significant protection against lethal doses of diazoxon.

Two common nonsynonymous paraoxonase 1 (PON1) gene polymorphisms and brain astrocytoma and meningioma

BACKGROUND

Human serum paraoxonase 1 (PON1) plays a major role in the metabolism of several organophosphorus compounds. The enzyme is encoded by the polymorphic gene PON1, located on chromosome 7q21.3. Aiming to identify genetic variations related to the risk of developing brain tumors, we investigated the putative association between common nonsynonymous PON1 polymorphisms and the risk of developing astrocytoma and meningioma.

METHODS

Seventy one consecutive patients with brain tumors (43 with astrocytoma grade II/III and 28 with meningioma) with ages ranging 21 to 76 years, and 220 healthy controls subjects were analyzed for the frequency of the nonsynonymous PON1 genotypes L55M rs854560 and Q192R rs662. All participants were adult Caucasian individuals recruited in the central area of Spain.

RESULTS

The frequencies of the PON1 genotypes and allelic variants of the polymorphisms PON1 L55M and PON1 Q192R did not differ significantly between patients with astrocytoma and meningioma and controls. The minor allele frequencies were as follows: PON1 55L, 0.398, 0.328 and 0.286 for patients with astrocytoma, meningioma and control individuals, respectively; PON1 192R, 0.341, 0.362 and 0.302 for patients with astrocytoma, meningioma and control individuals, respectively. Correction for age, gender, or education, made no difference in odds ratios and the p values remained non-significant. Haplotype association analyses did not identify any significant association with the risk of developing astrocytoma or meningioma.

CONCLUSIONS

Common nonsynonymous PON1 polymorphisms are not related with the risk of developing astrocytoma and meningioma.

Paraoxonase 1 (PON1) polymorphisms and risk for essential tremor

BACKGROUND

The polymorphic enzyme human serum paraoxonase 1 (PON1), encoded by the gene PON1 (chromosome 7q21.3), plays a major role in the metabolism of organophosphorus compounds. We investigated the possible association between the PON1 genotype and allelic variants of the polymorphisms Leu55Met and Glu192Arg, and the risk for essential tremor (ET).

METHODS

We studied the frequency of the PON1 genotypes and allelic variants in 201 patients with ET and 220 healthy controls using a PCR-RLFP method.

RESULTS

The frequencies of the PON1 genotypes and allelic variants of the polymorphisms Leu55Met and Gln192Arg did not differ significantly between patients with ET and controls. These polymorphisms were unrelated with the age of onset of ET.

CONCLUSIONS

PON1 polymorphisms are not related with the risk for ET.

Paraoxonase 1 polymorphisms are not related with the risk for multiple sclerosis

It has been suggested a possible role of oxidative stress and lipid peroxidation in the inflammatory processes and in the pathogenesis of multiple sclerosis. Human serum paraoxonase 1 is a polymorphic enzyme encoded by the gene PON1, located in chromosome 7q21.3, that plays a major role in the metabolism of organophosporus compounds, and in the protection against oxidative stress. Paraoxonase-1 activity has been found decreased in the plasma of multiple sclerosis patients. An association between PON1 polymorphism and the risk of multiple sclerosis has been described in Italians. To investigate the possible association between the PON1 genotype and allelic variants of the polymorphisms L55M and Q192R and the risk for multiple sclerosis in the Spanish Caucasian population; we studied the frequency of the PON1 genotypes and allelic variants in 228 patients with multiple sclerosis and 220 healthy controls using a PCR-RLFP method. The frequencies of the PON1 genotypes and allelic variants did not differ significantly between patients and controls, and were unrelated with gender, age of onset, and course of the disease. The OR (95% confidence intervals) for the variant alleles PON1-55L and PON1-192R were 0.96 (0.73-1.26) and 1.01 (0.76-1.35), respectively. The results of the present study suggest that PON1 polymorphism is not related with the risk for multiple sclerosis in our population.

Neuroprotection from diazinon-induced toxicity in differentiating murine N2a neuroblastoma cells

In previous work, the outgrowth of axon-like processes by differentiating mouse N2a neuroblastoma cells was shown to be inhibited by exposure to 10 microM diazinon. In the present work, N2a cells were induced to differentiate for 24 h in the presence and absence of 10 microM diazinon and 20% (v/v) conditioned medium derived from differentiating rat C6 glioma cells. Cells were then stained or lysed for morphological and biochemical analyses, respectively. The data showed that co-treatment with conditioned medium prevented the neurite inhibitory effect of diazinon. Furthermore, a significant recovery was also observed in the reduced levels of neurofilament heavy chain (NFH), heat shock protein-70 (HSP-70) and growth-associated protein-43 (GAP-43) observed as a result of diazinon treatment in the absence of conditioned medium, as seen by densitometric analysis of Western blots of cell lysates probed with monoclonal antibodies N52, BRM-22 and GAP-7B10. By contrast, no significant change was noted in the reactivity of cell lysates with antibodies against alpha- and beta-tubulin under any condition tested. After pre-incubation with a polyclonal anti-glial cell line-derived neurotrophic factor (GDNF) antibody, conditioned medium derived from rat C6 glioma cells lost its ability to protect N2a cells against the neurite inhibitory effects of diazinon. In conclusion, these data demonstrate that C6 conditioned medium protects N2a cells from the neurite inhibitory effects of diazinon by blocking molecular events leading to axon damage and that GDNF is implicated in these effects.

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.

Adenovirus-mediated gene transfer of human butyrylcholinesterase results in persistent high-level transgene expression in vivo

Human serum butyrylcholinesterase (Hu BChE) is a promising therapeutic against the toxicity of chemical warfare nerve agents, pesticide intoxication, and cocaine overdose. However, its widespread application is hampered by difficulties in large-scale production of the native protein from human plasma and/or availability as a recombinant protein suitable for use in vivo. This limitation may be resolved by in vivo delivery and expression of the Hu BChE gene. In this study, recombinant (r) adenoviruses (Ads) encoding full-length and truncated rHu BChEs were tested for in vivo expression in mice. Mice injected with these rAds intraperitoneally failed to express rHu BChE. However, a single tail vein injection of both rAds resulted in persistent high serum levels of rHu BChE in BChE knockout mice, which peaked on days 4/5 at 377+/-162U/ml for full-length rHu BChE and 574+/-143U/ml for truncated rHu BChE. These activity levels are orders of magnitude higher than 1.9U/ml of mouse BChE present in wild-type mouse serum. Thereafter, rHu BChE levels dropped rapidly and very little or no activity was detected in the serum 10 days post-virus administration. In conclusion, the present study demonstrates the potential of rAd-mediated Hu BChE gene therapy to counteract multiple lethal doses of chemical warfare nerve agent toxicity.

Human paraoxonase: A promising approach for pre-treatment and therapy of organophosphorus poisoning

The limited efficiency of medical countermeasures against poisoning by nerve agent justifies efforts to find new prophylactic means and new antidotes. The concept of bioscavengers has emerged as an alternative approach to pharmacological pre- and post-exposure treatments. Catalytic scavengers are enzymes displaying a turnover with OPs as substrates, allowing rapid and efficient protection using administration of small doses. Several reasons have endorsed human paraoxonase (PON1) to be a pertinent candidate as catalytic bioscavenger. The physiological function of PON1 has not yet been unambiguously identified. Considered as a promiscuous enzyme, PON1 appears to be primarily a lactonase and also displays an anti-atherogenic activity closely linked to its localization on HDL particles. A HDL-associated phosphate transporter termed human phosphate binding protein (HPBP) was found to be a partner of natural human PON. In the absence of its natural environment (or mimicry by detergents), human PON1 is unstable and tends to aggregate. Converging data indicate that both the activity and the stability of PON1 are dramatically dependent on the HDL component molecular environment, including HPBP. Therefore, biochemical and physiological characterization of PON1-HPBP complexes, the environment allowing retaining functional enzyme state(s), and the thermal and storage stability of PON1 are mandatory. Synergistic efforts on characterization of recombinant hybrid PON1 expressed in E. coli and natural human PON1 provide information for the future rational design of stable mutants of PON1-based catalytic scavengers to be used as safe and effective countermeasures to OP intoxication.

Toxicity of chlorpyrifos and chlorpyrifos oxon in a transgenic mouse model of the human paraoxonase (PON1) Q192R polymorphism

OBJECTIVES

The Q192R polymorphism of paraoxonase (PON1) has been shown to affect hydrolysis of organophosphorus compounds. The Q192 and R192 alloforms exhibit equivalent catalytic efficiencies of hydrolysis for diazoxon, the oxon form of the pesticide (DZ). However, the R192 alloform has a higher catalytic efficiency of hydrolysis than does the Q192 alloform for chlorpyrifos oxon (CPO), the oxon form of the pesticide chlorpyrifos (CPS). The current study examined the relevance of these observations for in-vivo exposures to chlorpyrifos and chlorpyrifos oxon.

METHODS

Using a transgenic mouse model we examined the relevance of the Q192R polymorphism for exposure to CPS and CPO in vivo. Transgenic mice were generated that expressed either human PON1Q192 or PON1R192 at equivalent levels, in the absence of endogenous mouse PON1. Dose-response and time course experiments were performed on adult mice exposed dermally to CPS or CPO. Morbidity and acetylcholinesterase (AChE) activity in the brain and diaphragm were determined in the first 24 h following exposure.

RESULTS

Mice expressing PON1Q192 were significantly more sensitive to CPO, and to a lesser extent CPS, than were mice expressing PON1R192. The time course of inhibition following exposure to 1.2 mg/kg CPO revealed maximum inhibition of brain AChE at 6-12 h, with PON1R192, PON1Q192, and PON1 mice exhibiting 40, 70 and 85% inhibition, respectively, relative to control mice. The effect of PON1 removal on the dose-response curve for CPS exposure was remarkably consistent with a PBPK/PD model of CPS exposure.

CONCLUSION

These results indicate that individuals expressing only the PON1Q192 allele would be more sensitive to the adverse effects of CPO or CPS exposure, especially if they are expressing a low level of plasma PON1Q192.

Naked DNA prevents soman intoxication

Paraoxonase (Q isoenzyme, PON1) can effectively hydrolyze chlorpyrifos-oxon (CPO), soman, sarin, and other organophosphates. Previous studies had indicated that the levels of serum PON1 in gene therapy with adenoviral vector could decrease the toxicity of CPO. In our study, plasmid pcDNA/PON1 injected into the tail vein of mice gave excellent expression at 24h after delivery, and PON1 activity decreased gradually along with days. The PON1 activities of mice treated with different doses of the plasmid (150, 300, and 600 microg/mouse) indicated a very good dose-effect relationship. Toxicity study has been performed using one lethal dose of soman (200 microg/kg). The mean death latency of mice pre-treated with 150, 300, 600, and 1200 microg pcDNA/PON1 extended and the mortality decreased vs control mice received the null pcDNA. These results demonstrate that increasing serum PON1 by naked DNA can offer protection toward the acute toxicity of soman.

Further assessment of an in vitro screen that may help identify organophosphorus pesticides that are more acutely toxic to the young

Some, but not all, organophosphorus pesticides are more acutely toxic to the young as compared to adults. We have developed an in vitro assay that measures the detoxification potential (via carboxylesterase and A-esterases) of tissues. Previous results using this in vitro screen correlated with the marked in vivo sensitivity of the young to chlorpyrifos and also correlated with the equal sensitivity of the young and adult to methamidophos (Padilla et al., 2000). We have now extended these observations to two other pesticides that have already been shown in the literature to be more toxic to the young: parathion (paraoxon) and malathion (malaoxon). In our in vitro assay, liver or plasma from 7-d-old rats were much less efficacious than adult tissues at detoxification of the active metabolites of these two pesticides. Using our in vitro assay we also tested the active metabolite of diazinon, diazoxon, and again found that young liver or plasma possessed much less detoxification capability than adult tissues. From these results, we predicted that young animals would be more sensitive to diazinon, which, in fact, was the case: When postnatal day (PND) 17 or adult rats were given a dosage of 75 mg/kg diazinon, adult brain cholinesterase (ChE) was only inhibited 38%, while the brain ChE in the PND 17 animals showed much more inhibition (75%). We conclude that our in vitro screen may prove to be a useful, quick, convenient test for identifying which organophosphorus pesticides may be more acutely toxic to the young as compared to adults.

Paraoxonase 1 (PON1) gene polymorphisms and Parkinson’s disease in a Finnish population

Paraoxonase 1 (PON1) is involved in the metabolism and detoxification of insecticides and pesticides. Two polymorphisms within the gene affect the enzyme activity. One is a methionine to leucine change at position 54 (M54L) and the other is a glutamine to arginine variant at position 192 (Q192R). There are contrasting reports assessing the role of these variants in Parkinson's disease (PD). We performed a case--control association study in order to elucidate the possible contribution of variability within PON1 to the risk of sporadic PD in a Finnish population. There was no statistically significant association of the allele, genotype or haplotype distribution with PD (all P values > 0.75). Our results suggest that the M54L and Q192R polymorphisms are not major risk factors for PD in the Finnish population.

Association of paraoxonase 1 gene polymorphisms with risk of Parkinson's disease: a meta-analysis

Paraoxonase1 (PON1) gene polymorphisms were implicated as risk factors for Parkinson's disease (PD), but the results of case-control studies that investigated these associations were controversial. In order to provide an answer to these contradictory results, a meta-analysis of all available studies relating the PON1-55M/L and PON1-192Q/R polymorphisms to the risk of developing PD was conducted. The racial descent of the populations in these studies was Caucasian and Asian. The meta-analysis revealed that there was an association of the PON1-55M allele and the risk of developing PD relative to the L allele: fixed effects pooled odds ratio (OR)=1.32 [95%CI (1.10-1.59)]. In addition, there was evidence of association for the genotypic contrast PON1-55MM+LM relative to PON1-55LL: fixed effects OR=1.50 [95%CI (1.16-1.95)]. There was no significant association between PON1-192Q/R alleles and risk of developing PD: OR=1.09 [95%CI (0.93-1.26)]. There was no evidence for an association between the genotypic contrasts of PON1-192 and development of PD. The heterogeneity between studies and the publication bias were not significant ( P> or =0.10) in either polymorphism. Therefore, the pooled results of the meta-analysis supported that there was an association between PON1-55M/L polymorphism and PD and that PON1-192Q/R polymorphism was unlikely to be a major risk factor for susceptibility to PD.

Dietary polyphenols increase paraoxonase 1 gene expression by an aryl hydrocarbon receptor-dependent mechanism

Human paraoxonase 1 (PON-1) is a serum high-density lipoprotein-associated enzyme mainly secreted by the liver. It has endogenous and exogenous substrates and displays protective properties with respect to cardiovascular disease and organophosphate intoxication. In the HuH7 human hepatoma cell line, PON-1 activity and mRNA levels were increased by dietary polyphenolic compounds such as quercetin but also by toxic ligands of the aryl hydrocarbon receptor (AhR) such as 3-methylcholanthrene (3-MC). However, the 2,3,7,8-tetrachlorobenzo(p)dioxin (TCDD) was a poor inducer. Transient and stable transfection assays indicated that these compounds increased the PON-1 gene promoter activity in an AhR-dependent manner, since their effect was inhibited by 7-keto-cholesterol and AhR-directed short interfering RNA. Deletions and mutations studies showed that a xenobiotic responsive element (XRE)-like sequence within the PON-1 promoter mediated the effect of 3-MC and quercetin. In contrast with consensus XREs from the cytochrome P450 1A1 gene, the PON-1 XRE-like element mediated preferentially the effect of quercetin compared to the results seen with TCDD. Furthermore, AhR binding to this element was preferentially activated by quercetin. These observations provide a molecular mechanism for the regulation of the cardioprotective enzyme PON-1 by polyphenols. They suggest also that AhR ligands may differentially regulate gene expression depending on the DNA target sequence.

Future applications of phosphotriesterases in the prophylaxis and treatment of organophosporus insecticide and nerve agent poisonings

Organophosphorus compounds (OPs) are being used as insecticides and warfare agents. OP insecticides represent an important problem of public health, causing around 200,000 deaths annually. The World Health Organization has pointed to the necessity to introduce new medical practices that improve the results of classical treatments. Many studies have shown that the administration of phosphotriesterases (enzymes that detoxify OPs through hydrolysis) is a promising treatment of persons poisoned with OPs. Such an enzyme-based treatment might introduce important improvements in the treatment of patients having ingested large amounts of OPs. Phosphotriesterases might also be suitable for prophylactic treatment of persons at risk to be severely exposed. The new experimental treatments do not exhibit the intrinsic neurotoxicity of the classical prophylaxis based on carbamates and antimuscarinic drugs. Experimental data suggest that might be time to initiate clinical trials in order to study the efficacy of phosphotriesterases in the therapy and prophylaxis of OP intoxication.

Nerve agents: a comprehensive review

Nerve agents are perhaps the most feared of potential agents of chemical attack. The authors review the history, physical characteristics, pharmacology, clinical effects, and treatment of these agents.

Study of the mechanism ofFlavobacteriumsp. for hydrolyzing organophosphate pesticides

The biotransformation by Flavobacterium sp. of the following organophosphate pesticides was experimentally and theoretically studied: phorate, tetrachlorvinphos, methyl-parathion, terbufos, trichloronate, ethoprophos, phosphamidon, fenitrothion, dimethoate and DEF. The Flavobacterium sp. ATCC 27551 strain bearing the organophosphate-degradation gene was used. Bacteria were incubated in the presence of each pesticide for a duration of 7 days. Parent pesticides were identified and quantified by means of a gas-chromatography mass spectrum system. Activity was considered as the amount (micromol) of each pesticide degraded by Flavobacterium sp. Also, structural parameters obtained by means of the CAChe program package for biomolecules, the reactivity index of phosphorus, of oxygen at the P = O function and of sulfur at the P = S function, and lipophilicity (log Poct) (ALOGPS v. 2.0) were obtained for each pesticide. Pesticides were hydrolyzed at the bond between phosphorous and the heteroatom, producing phosphoric acid and three metabolites. Enzymatic activity was significantly explained by the following multiple linear relationship: Enzymatic activity = 162.2 - 9.5(dihedral angle energy) - 25.0(Total energy) - 0.51(Molecular weight). Finally, a mechanism of Flavobacterium sp. to hydrolyze pesticides was proposed.

Functional genomic of the paraoxonase (PON1) polymorphisms: effects on pesticide sensitivity, cardiovascular disease, and drug metabolism

This review focuses on the functional genomics of the human paraoxonase (PON1) polymorphisms. Levels and genetic variability of the PON1 position 192 isoforms (Gln/Arg) influence sensitivity to specific insecticides or nerve agents and risk for cardiovascular disease. A more recent area of investigation, the role of PON1 in drug metabolism, is also discussed. We emphasize the importance of considering both PON1 isoforms and PON1 levels in disease/sensitivity association studies.

Human serum paraoxonase (PON1) activity in acute organophosphorous insecticide poisoning

Human serum paraoxonase (PON1) and perhaps other mammalian paraoxonases catalyzes the hydrolysis of certain organophosphorus (OP) insecticides and nerve gases and so may alter significantly an individual's susceptibility to the toxicity of these chemicals. Serum PON1 exhibits a substrate dependent polymorphism and this polymorphism shows great interethnic variability. This study focused on the investigation of PON1, arylesterase and cholinesterase activities in 28 acute OP insecticide poisoning cases. Insecticide analysis were performed by GC-NPD and activities of enzymes were measured by using spectrophotometer. The activity levels for salt stimulated PON1, basal PON1 and arylesterase were found as 78.83 (35.39-186.13), 39.97 (2.49-80.43) micromol/min/l and 126.26 (36.34-288.24) mmol/min/l respectively. On the other hand the activity levels for butyrylcholinesterase (BTC) and acetylcholinesterase (AchE) were found as 797.23 (106.3-3823)U/l and 4.65 (0.21-30.29)U/ml. There was a correlation between percent stimulation of PON1 and BTC activities (r=0.446, P<0.05), but this correlation was lower than in cases who exposed to OP insecticides chronically. As a conclusion, in chronic and acute OP exposure, both PON1 level and phenotype must be taken into consideration.

Opposite regulation of the human paraoxonase-1 gene PON-1 by fenofibrate and statins

The human paraoxonase-1 (PON-1) is a serum high-density lipoprotein-associated phosphotriesterase secreted mainly by the liver. This enzyme is able to hydrolyze toxic organophosphate xenobiotics, endogenous oxidized phospholipids, and homocysteine thiolactone. Physiologically, it is thought to protect against cardiovascular diseases. The level of PON-1 gene expression is a major determinant of paraoxonase-1 status but little is known regarding the regulation of this gene. We identified several transcription start sites and characterized the regulation of its promoter by fibrates and statins. In HuH7 human hepatoma cells, the PON-1 secreted enzymatic activity and mRNA levels were increased by fenofibric acid (approximately 70%) and decreased by several statins (approximately 50%). Transient and stable transfection assays in HuH7 cells indicated that the modulation of the mRNA and enzymatic activity levels could be accounted for by the regulation of the PON-1 gene promoter activity by these drugs. These effects are probably not mediated by the PPAR alpha because over-expression of this receptor decreased the fibrate effect and did not modify statins activity. The repressive effect of statins is reversed by mevalonate and 22(R)-hydroxycholesterol, suggesting the involvement of the liver X receptor in the mechanism. The opposite effects of fenofibrate and statins could be consistent with clinical data on homocysteine levels after hypolipidemic drug treatment. Regarding the toxicological aspects, the induction achieved with fenofibric acid, although limited, could increase organophosphate metabolism and may be relevant in certain conditions for protective treatments.

Paraoxonase (PON 1) as a biomarker of susceptibility for organophosphate toxicity

Paraoxonase (PON1) is an A-esterase capable of hydrolysing the active metabolites (oxons) of a number of organophosphorus (OP) insecticides such as parathion, diazinon and chlorpyrifos. PON1 activity is highest in liver and plasma, and among animal species significant differences exist, with birds and rabbits displaying very low and high activity, respectively. Human PON1 has two polymorphisms in the coding region (Q192R and L55M) and five polymorphisms in the promoter region. The Q192R polymorphism imparts different catalytic activity toward some OP substrates, while the polymorphism at position -108 (C/T) is the major contributor to differences in the level of PON1 expression. Animal studies have shown that PON1 is an important determinant of OP toxicity, with animal species with a low PON1 activity having an increased sensitivity to OPs. Administration of exogenous PON1 to rats or mice protects them from the toxicity of OPs. PON1 knockout mice display a high sensitivity to the toxicity of diazoxon and chlorpyrifos oxon, but not paraoxon. In vitro assayed catalytic efficiencies of purified PON(192) isoforms for hydrolysis of specific oxon substrates accurately predict the degree of in vivo protection afforded by each isoform. Low PON1 activity may also contribute to the higher sensitivity of newborns to OP toxicity.

Monte Carlo analysis of the human chlorpyrifos-oxonase (PON1) polymorphism using a physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) model

Susceptibility to organophosphate (OP) insecticides, like chlorpyrifos (CPF), may result from differences in the extent of metabolic detoxification of the active metabolite, CPF-oxon. A genetic polymorphism in the arylesterase (PON1; CPF-oxonase) detoxification of OPs, results in the expression of a range of enzyme activities within humans. This study utilized Monte Carlo analysis and physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) modeling to investigate the impact of human CPF-oxonase status on the theoretical concentration of CPF-oxon in the brain. At low doses ( approximately 5 microg/kg) the model is insensitive to changes in CPF-oxonase. However, with increasing dose (>0.5 mg/kg) the model suggests a dose-dependent non-linear increase in the brain CPF-oxon concentration, which is associated with CPF-oxonase activity. Following repeated high dose exposure, the model predicted brain CPF-oxon concentration was approximately 8x higher (5 mg/kg) versus a single exposure, whereas, at low doses (5 microg/kg), the brain concentrations were comparable regardless of exposure duration. This suggests that at low environmentally relevant exposures other esterase detoxification pathways may compensate for lower CPF-oxonase activity.

Further evidence for an association of the paraoxonase 1 (PON1) Met-54 allele with Parkinson's disease

Paraoxonase1 (PON1) is an arylesterase mainly expressed in the liver that hydrolyzes organophosphates such as pesticides, reported risk factors for Parkinson's disease (PD), and other neurotoxins. A Leu-Met 54 polymorphism in the gene for PON1-affecting enzyme activity was recently shown, employing a new restriction enzyme technique, to be associated with Parkinson's disease. We examined the same polymorphism by automated capillary sequencing in a sample of Caucasian subjects from the Stockholm area in Sweden (127 healthy individuals and 114 patients with PD) and found similar distributions and a similar difference in our sample. The genotype distribution in our PD material was LL 36.0%, LM 45.6%, and MM 18.4%; in our control material, it was LL 45.7%, LM 44.1%, and MM 10.2%. Based on the previously established increase in allele frequencies of the lower-activity Met-variant of PON1, we could confirm a significant association using a one-sided chi(2) test. Results remained significant with a two-sided chi(2) test, allowing for both increases and decreases in frequencies. Our data confirm an association between the PON1 Leu-Met 54 polymorphism and PD by demonstrating a similar association. The distribution between familial and nonfamilial PD patients was equal. No other synonymous or nonsynonymous polymorphisms were found in the sequenced coding region of PON1.