Paraoxonase 1 and cytochrome P450 polymorphisms in susceptibility to acute organophosphorus poisoning in Egyptians

Metabolic Characterization of Sarin, Cyclosarin, and Novichoks (A-230, A-232) in Human Liver Microsomes

We have assessed the human liver microsomal (HLM) metabolism of the chemical warfare nerve agents' sarin (GB), cyclosarin (GF), and the Novichok agents A-230 and A-232. In HLM, GB showed drastically decreased stability (t1/2 = 1.4 h). The addition of ethylenediaminetetraacetic acid (EDTA), which inhibits paraoxonase-1 (PON1), reduced the metabolism of GB in HLM suggesting at least a partial role in its metabolism (t1/2 = 2.6 h). The absence of NADPH (a requirement for CYP activity) had a major impact on metabolism, suggesting a role of likely CYP-mediated metabolism, which was rescued with the later addition of NADPH at 4 h. GF was also metabolized readily in HLM (Control t1/2 = 9.7 h; HLM t1/2 = 0.5 h), and this metabolism was mitigated by the addition of EDTA (t1/2 (fast) = 0.7 h, t1/2 (slow) = 4.0 h), suggesting a PON1 role in the metabolism of GF. GF in HLMs also showed a reduced metabolism without NADPH, suggesting a CYP-mediated role. We have described for the first time the clearance of A-230 in HLM (t1/2 (fast) = 0.9 h, t1/2 (slow) = 26.5 h), with a significantly decreased stability from the control (t1/2 = 48.3 h) and with the formation of the A-230 acid as the major metabolite. EDTA also reduced the metabolism of A-230 in HLMs (t1/2 (fast) = 0.8 h, t1/2 (slow) = 62 h). A-232 metabolism was also HLM-dependent (t1/2 (fast) = 1.2 h, t1/2 (slow) = 1190 h), although overall it was dramatically more stable in the control (t1/2 = 2,300 h). The metabolism of A-232 in HLMs also showed some inhibition by EDTA (t1/2 (fast) = 0.5 h, t1/2 (slow) = 1480 h).

PON-1 and PON-2 Polymorphisms and PON-1 Paraoxonase Activity in People Living with HIV-1

Antiretroviral therapy (ART) has significantly improved the life expectancy of people living with HIV-1 (PLWH). However, prolonged ART use is linked to metabolic alterations and oxidative stress. The paraoxonase (PON) enzymes, especially PON-1 and PON-2, are critical in maintaining antioxidant balance. Their activity can be influenced by polymorphisms such as Q192R and L55M in PON-1 and A148G and S311C in PON-2. This study examines the impact of these polymorphisms on paraoxonase activity, lipid metabolism, and infection markers in PLWH under various ART regimens. This is a case-control study with 525 participants, 175 healthy controls (HC) and 350 PLWH divided into subgroups: T0 (ART-naïve, n = 48), T1 (ART with reverse transcriptase inhibitors, n = 159), and T2 (ART with protease inhibitors, n = 143). Paraoxonase activity was higher in PLWH (123.0; IQR: 62.0-168.0) compared to HC (91.0; IQR: 48.0-136.0, p < 0.001) but similar between HC and T0 (p = 0.594). T1 (125.0; IQR: 65.5-166.0) and T2 (123.0; IQR: 61.0-182.0) showed higher activity than HC (p = 0.002 and 0.003). Among 61 complete genotypes, 13 were unique to PLWH and 6 to HC (p < 0.001). L55L was more frequent in HC (49.7% vs. 36.9% in PLWH), while M55M was higher in PLWH (p = 0.004). The S311C genotype was more frequent in HC (39.2%) than PLWH (24.9%) (p = 0.003). The L55L genotype conferred 59.9% protection against HIV-1 (OR: 0.401; 95% CI: 0.228-0.704), while the M allele increased susceptibility by ~69% (OR: 1.694; 95% CI: 1.173-2.446). The M55M genotype and/or M allele may be linked to HIV-1 susceptibility. Prolonged ART use elevates PON-1 activity in PLWH.

In Vitro Characterization and Rescue of VX Metabolism in Human Liver Microsomes

Venomous agent X (VX) is an organophosphate acetylcholinesterase (AChE) inhibitor, and although it is one of the most toxic AChE inhibitors known, the extent of metabolism in humans is not currently well understood. The known metabolism in humans is limited to the metabolite identification from a single victim of the Osaka poisoning in 1994, which allowed for the identification of several metabolic products. VX has been reported to be metabolized in vitro by paraoxonase-1 and phosphotriesterase, although their binding constants are many orders of magnitude above the LD50, suggesting limited physiologic relevance. Using incubation with human liver microsomes (HLMs), we have now characterized the metabolism of VX and the formation of multiple metabolites as well as identified a Food and Drug Administration-approved drug [ethylenediaminetetraacetic acid (EDTA)] that enhances the metabolic rate. HLM incubation alone shows a pronounced increase in the metabolism of VX compared with buffer, suggesting that cytochrome P450-mediated metabolism of VX is occurring. We identified a biphasic decay with two distinct rates of metabolism. The enhancement of VX metabolism in multiple buffers was assessed to attempt to mitigate the effect of hydrolysis rates. The formation of VX metabolites was shown to be shifted with HLMs, suggesting a pathway enhancement over simple hydrolysis. Additionally, our investigation of hydrolysis rates in various common buffers used in biologic assays discovered dramatic differences in VX stability. The new human in vitro VX metabolic data reported points to a potential in vivo treatment strategy (EDTA) for rescue in individuals that are poisoned though enhancement of metabolism alongside existing treatments. SIGNIFICANCE STATEMENT: Venomous agent X (VX) is a potent acetylcholinesterase inhibitor and chemical weapon. To date, we do not possess a clear understanding of its metabolism in humans that would assist us in treating those exposed to it. This study now describes the human liver microsomal metabolism of VX and identifies ethylenediaminetetraacetic acid, which appears to enhance the rate of metabolism. This may provide a potential treatment option for human VX poisoning.

The Incidence of the XRCC1 rs25487 and PON1 rs662 Polymorphisms in a Population from Central Brazil: Patterns in an Area with a High Level of Agricultural Activity

In Brazil, high levels of agricultural activity are reflected in the consumption of enormous amounts of pesticides. The production of grain in Brazil has been estimated at 289.8 million tons in the 2022 harvest, an expansion of 14.7% compared with 2021. These advances are likely associated with a progressive increase in the occupational exposure of a population to pesticides. The Paraoxonase 1 gene (PON1) is involved in liver detoxification; the rs662 variant of this gene modifies the activity of the enzyme. The repair of pesticide-induced genetic damage depends on the protein produced by the X-Ray Repair Cross-Complementing Group 1 gene (XRCC). Its function is impaired due to an rs25487 variant. The present study describes the frequencies of the rs662 and rs25487 and their haplotypes in a sample population from Goiás, Brazil. It compares the frequencies with other populations worldwide to verify the variation in the distribution of these SNPs, with 494 unrelated individuals in the state of Goiás. The A allele of the rs25487 variant had a frequency of 26% in the Goiás population, and the modified rs662 G allele had a frequency of 42.8%. Four haplotypes were recorded for the rs25487 (G > A) and rs662 (A > G) markers, with a frequency of 11.9% being recorded for the A-G haplotype (both modified alleles), 30.8% for the G-G haplotype, 14.3% for the A-A haplotype, and 42.8% for the G-A haplotype (both wild-type alleles). We demonstrated the distribution of important SNPs associated with pesticide exposure in an area with a high agricultural activity level, Central Brazil.

Explore the distribution of (rs35742686, rs3892097 and rs1065852) genetic polymorphisms of cytochrome P4502D6 gene in the Moroccan population

Background

The CYP2D6 gene encodes a crucial enzyme involved in the metabolic pathways of many commonly used drugs. It is a highly polymorphic gene inducing an interethnic and interindividual variability in disease susceptibility and treatment response. The aim of this study is to evaluate the frequency of the three CYP2D6 most investigated alleles (CYP2D6*3, CYP2D6*4, and CYP2D6*10 alleles) in Morocco compared to other populations.

This study enrolled 321 healthy Moroccan subjects. CYP2D6 genotypes and allele frequencies were assessed using a restriction fragment length polymorphism–polymerase chain reaction genotyping method. The Principal Component Analysis (PCA) and dendrogram were conducted to evaluate genetic proximity between Moroccans and other populations depending on CYP2D6 allele frequencies.

Results

According to the current study, the results observed the homozygous wild type of the three studied SNPs were predominant among the Moroccan population, while 1.4% of Moroccans carried the CYP2D6*4 allele responsible for a Poor Metabolizer phenotype and associated with low enzyme activity which may induce a treatment failure. The PCA and cluster dendrogram tools revealed genetic proximity between Moroccans and Mediterranean, European and African populations, versus a distancing from Asian populations.

Conclusion

The distribution of CYP2D6 polymorphisms within Morocco follows the patterns generally found among the Mediterranean, European and African populations. Furthermore, these results will help to lay a basis for clinical studies, aimed to introduce and optimize a personalized therapy in the Moroccan population.

Frequencies of CYP2D6 genetic polymorphisms in Arab populations

CYP2D6 is a key drug-metabolizing enzyme implicated in the biotransformation of approximately 25% of currently prescribed drugs. Interindividual and interethnic differences in CYP2D6 enzymatic activity, and hence variability in substrate drug efficacy and safety, are attributed to a highly polymorphic corresponding gene. This study aims at reviewing the frequencies of the most clinically relevant CYP2D6 alleles in the Arabs countries. Articles published before May 2021 that reported CYP2D6 genotype and allelic frequencies in the Arab populations of the Middle East and North Africa (MENA) region were retrieved from PubMed and Google Scholar databases. This review included 15 original articles encompassing 2737 individuals from 11 countries of the 22 members of the League of Arab States. Active CYP2D6 gene duplications reached the highest frequencies of 28.3% and 10.4% in Algeria and Saudi Arabia, respectively, and lowest in Egypt (2.41%) and Palestine (4.9%). Frequencies of the loss-of-function allele CYP2D6*4 ranged from 3.5% in Saudi Arabia to 18.8% in Egypt. The disparity in frequencies of the reduced-function CYP2D6*10 allele was perceptible, with the highest frequency reported in Jordan (14.8%) and the lowest in neighboring Palestine (2%), and in Algeria (0%). The reduced-function allele CYP2D6*41 was more prevalent in the Arabian Peninsula countries; Saudi Arabia (18.4%) and the United Arab Emirates (15.2%), in comparison with the Northern Arab-Levantine Syria (9.7%) and Algeria (8.3%). Our study demonstrates heterogeneity of CYP2D6 alleles among Arab populations. The incongruities of the frequencies of alleles in neighboring countries with similar demographic composition emphasize the necessity for harmonizing criteria of genotype assignment and conducting comprehensive studies on larger MENA Arab populations to determine their CYP2D6 allelic makeup and improve therapeutic outcomes of CYP2D6- metabolized drugs.

Cancer risk and nullity of Glutathione-S-transferase mu and theta 1 in occupational pesticide workers

Occupational exposure to pesticides has been associated with adverse health conditions, including genotoxicity and cancer. Nullity of GSTT1/GSTM1 increases the susceptibility of pesticide workers to these adverse health effects due to lack of efficient detoxification process created by the absence of these key xenobiotic metabolizing enzymes. However, this assertion does not seem to maintain its stance at all the time; some pesticide workers with the null genotypes do not present the susceptibility. This suggests the modulatory role of other confounding factors, genetic and environmental conditions. Pesticides, aggravated by the null GSTT1/GSTM1, cause genotoxicity and cancer through oxidative stress and miRNA dysregulation. Thus, the absence of these adverse health effects together with the presence of null GSTT1/GSTM1 genotypes demands further explanation. Also, understanding the mechanism behind the protection of cells - that are devoid of GSTT1/GSTM1 - from oxidative stress constitutes a great challenge and potential research area. Therefore, this review article highlights the recent advancements in the presence and absence of cancer risk in occupational pesticide workers with GSTT1 and GSTM1 null genotypes.

In vivo fluorescence-based characterization of cytochrome P450 activity during embryonic development of zebrafish (Danio rerio)

Zebrafish (Danio rerio) early life-stages are increasingly gaining attention as an alternative model in both human and environmental toxicology. Whereas there is amble knowledge about the transcription of various cytochrome P450 isoforms, the level of information about functional implications is still limited. This study investigated the development of CYP2-dependent 7-methoxycoumarin-O-demethylase (MCOD) activity throughout the early zebrafish development from 5 to 118 h post-fertilization (hpf) via confocal laser scanning microscopy. Results demonstrate that zebrafish embryos exhibit constitutive MCOD activity from as early as 5.5 hpf. Characteristic spatiotemporal patterns were documented with MCOD activities localized in several tissues and organs, namely the cardiovascular system, the brain, the digestive system, and the urinary tract. The study thereby contributes to a better understanding of the development and functional role of CYP enzymes in zebrafish early life-stages.

Investigation of pesticide exposure by genotoxicological, biochemical, genetic polymorphic and in silico analysis

Soybean farmers are exposed to various types of pesticides that contain in their formulations a combination of chemicals with genotoxic and mutagenic potential. Therefore, the objective of this paper was to evaluate the genetic damages caused by this pesticide exposure to soybean producers in the state of Mato Grosso (Brazil), regarding biochemical, genetic polymorphic and in silico analyses. A total of 148 individuals were evaluated, 76 of which were occupationally exposed and 72 were not exposed at all. The buccal micronucleus cytome assay (BMCyt) detected in the exposed group an increase on DNA damage and cell death. No inhibition of butyrylcholinesterase (BchE) was observed within the exposed group. The detection of inorganic elements was made through the particle-induced X-ray emission technique (PIXE), which revealed higher concentrations of Bromine (Br), Rubidium (Rb) and Lead (Pb) in rural workers. A molecular model using in silico analysis suggests how metal ions can cause both DNA damage and apoptosis in the exposed cells. Analysis of the compared effect of X-ray Repair Cross-complement Protein 1 (XRCC1) and Paraoxonase 1 (PON1) genotypes in the groups demonstrated an increase of binucleated cells (exposed group) and nuclear bud (non-exposed group) in individuals with the XRCC1 Trip/- and PON1 Arg/- genes. There was no significant difference in the telomere (TL) mean value in the exposed group in contrast to the non-exposed group. Our results showed that soybean producers showed genotoxic effect and cell death, which may have been induced by exposure to complex mixtures of agrochemicals and fertilizers. In addition, XRCC1 Arg/Arg could, in some respects, provide protection to individuals.

Distribution of CYP2D6 polymorphism in the Middle Eastern region

Cytochrome P450 2D6 (CYP2D6) is an important drug-metabolizing enzyme involved in the pharmacokinetic metabolism of drugs. CYP2D6 gene is highly polymorphic, and the combination of its different alleles yields different phenotypes including extensive metabolizer (EM), intermediate metabolizer (IM), poor metabolizer (PM), and ultrarapid metabolizer (UM). Genotyping of the important alleles for this gene in different ethnicities is of particular importance for assessing the efficacy of various drugs. In this study, we reviewed the CYP2D6 allele and phenotype frequencies predicted from the genotypes of CYP2D6 in the Middle East area. Regardless of different ethnicities, the CYP2D6*41 allele frequency was shown to be higher than that of other reduced functional alleles. In addition, CYP2D6*4 was the most frequent nonfunctional allele in all studied populations in the Middle East. Taken together, our findings illustrated that the frequencies of PM or IM alleles and different genotypes harboring these alleles are relatively high in the Middle Eastern countries. Therefore, the study of CYP2D6 alleles for each patient to detect those that are at risk is of great importance to prevent adverse drug reactions through individualization therapy.

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.

Electrochemical enzymatic fenitrothion sensor based on a tyrosinase/poly(2-hydroxybenzamide)-modified graphite electrode

This paper reports the electrosynthesis and characterisation of a polymeric film derived from 2-hydroxybenzamide over a graphite electrode and its application as an enzymatic biosensor for the determination and quantification of the pesticide fenitrothion. The material was analysed by scanning electron microscopy and its electrochemical properties characterised by cyclic voltammetry and electrochemical impedance spectroscopy. The enzyme tyrosinase was immobilised over the modified electrode by the drop and dry technique. Catechol was determined by direct reduction of biocatalytically formed o-quinone by employing the flow injection analysis technique. The analytical characteristics of the proposed sensor were optimised as follows: phosphate buffer 0.050 M at pH 6.5, flow rate 5.0 mL min^-1, sample injection volume 150 μL, catechol concentration 1.0 mM and maximum inhibition time by fenitrothion of 6 min. The biosensors showed a linear response to pesticide concentration from 0.018 to 3.60 μM. The limit of detection and limit of quantification were calculated as 4.70 nM and 15.9 nM (RSD < 2.7%), respectively. The intra- and inter-electrode RSDs were 3.35% (n = 15) and 8.70% (n = 7), respectively. In addition, water samples spiked with the pesticide showed an average recovery of 97.6% (±1.53).

The genetic association between PON1 polymorphisms and osteonecrosis of femoral head: A case-control study

The purpose of this study was to investigate the relationship between Paraoxonase-1 (PON1) gene rs662, rs854555 polymorphisms and osteonecrosis of the femoral head (ONFH) in Han population, northern China.Polymerase chain reaction-restriction fragment length polymorphism was used to determine genotypes of PON1 polymorphisms in 84 patients with ONFH and 96 healthy persons. χ test was used to compare distribution differences of genotype, allele, and haplotype between the case and control groups. The odds ratio (OR) and 95% confidence interval (CI) were calculated to reveal the effects of PON1 polymorphisms on risk of ONFH, and the results were adjusted using logistic regression analysis. The linkage disequilibrium and haplotype analysis were performed with haploview software.That people carrying AA genotype of rs662 were easier to be attacked by ONFH than GG genotype carriers (OR = 2.53, 95% CI = 1.05-6.07, P = .038). Meanwhile, the frequency of A allele in the case group was significantly higher than the controls and it was a risk factor for ONFH (OR = 1.56, 95% CI = 1.03-2.38, P = .038). The A-A haplotype frequency of rs854555-rs662 in PON1 was significantly correlated to the increased susceptibility to ONFH (OR = 2.74, 95% CI = 1.28-5.84).The rs662 polymorphism in PON1 may be associated with ONFH susceptibility, but not rs854555 in Han population, northern China. Additionally, haplotype is also a nonignorable risk factor.