Synthesis and mutagenic risk of avanafil's potential genotoxic impurities

In the technical route for the synthesis of avanafil, 1-ethyl-(3-dimethylaminopropyl)carbamyldiimide hydrochloride (EDCI) and 1-hydroxybenzotriazole (HOBT) are used as reactive acid-amine binding agents. HOBT contains trace amounts of hydrazine residue, and there is a risk of introducing potentially mutagenic impurities with hydrazide-containing structures. The potentially genotoxic impurities E (Imp-E) and F (Imp-F) of avanafil with altering hydrazide-structure were synthesized by chemical method; subsequently, the impurities were evaluated and classified according to ICH M7 guidelines. Two complementary quantitative structure-activity relationship (QSAR) evaluation systems (Derek and Sarah) based on expert rules and statistics were used to preliminarily predict the genotoxicity of Imp-E and Imp-F, and the prediction result of E was suspected to be positive. In the Ames test of Imp-E and Imp-F, in the dose range of 62.5-1000 μg per plate, with or without the presence of metabolic activation system S9, the number of revertant colonies did not exceed 2 times the number of colonies in the solvent control group and did not show a dose-response relationship, and the test results were negative. Imp-E and Imp-F were determined to be negative for genotoxicity, which could be controlled as class 5 in ICH M7, that is, non mutagenic impurity.

Chlorpyrifos-induced suppression of the antioxidative defense system leads to cytotoxicity and genotoxicity in macrophages

Chlorpyrifos, widely used for pest control, is known to have various harmful effects, although its toxic effects in macrophages and the mechanisms underlying its toxicity remain unclear. The present study investigated the toxic effects of chlorypyrifos in a macrophage cell line. Here, we found that chlorpyrifos induced cytotoxicity and genotoxicity in RAW264.7 macrophages. Moreover, chlorpyrifos induced intracellular ROS production, subsequently leading to lipid peroxidation. Chlorpyrifos reduced the activation of antioxidative enzymes including superoxide dismutase, catalase, and glutathione peroxidase. Chlorpyrifos upregulated HO-1 expression and activated the Keap1-Nrf2 pathway, as indicated by enhanced Nrf2 phosphorylation and Keap1 degradation. Chlorpyrifos exerted effects on the following in a dose-dependent manner: cytotoxicity, genotoxicity, lipid peroxidation, intracellular ROS production, antioxidative enzyme activity reduction, HO-1 expression, Nrf2 phosphorylation, and Keap1 degradation. Notably, N-acetyl-L-cysteine successfully inhibited chlorpyrifos-induced intracellular ROS generation, cytotoxicity, and genotoxicity. Thus, chlorpyrifos may induce cytotoxicity and genotoxicity by promoting intracellular ROS production and suppressing the antioxidative defense system activation in macrophages.

Protective Effects of Dexmedetomidine Infusion on Genotoxic Potential of Isoflurane in Patients Undergoing Emergency Surgery

BACKGROUND

Isoflurane (ISO) has been extensively uses in general anesthesia and reported to cause deoxyribonucleic acid (DNA) damage in prolonged surgical procedures. Dexmedetomidine (DEX) is an adrenergic agonist and having antioxidant activity that may reduce the genotoxic potential (DNA damage) and oxidative stress induced by ISO in patients undergoing major neurosurgical procedures. Methods and Findings. Twenty-four patients of ASA (American Society of Anesthesiologists) classes I and II were randomly divided into two groups (n = 12). Group A patients received ISO, while group B patients received DEX infusion for maintenance of anesthesia. Venous blood samples were collected at different time intervals and used to evaluate the oxidative stress marker malondialdehyde (MDA) and endogenous antioxidants superoxide dismutases (SOD) and catalases (CAT). A single-cell gel electrophoresis (SCGE)-comet assay was used to investigate the genotoxic potential of ISO.

CONCLUSION

Increased level of antioxidants and decreased value of MDA and genetic damage index were seen in group B (P < 0.001) in a time-dependent manner. Genetic damage was highest at point T ₂ (0.77 vs. 1.37), and continued to decrease till T ₃ (0.42 vs. 1.19), with respect to negative controls or baseline values following DEX infusion. Significantly, higher level of MDA was recorded in serum of group A (P < 0.001) as compared to group B (1.60 ± 0.33 vs. 0.03 ± 0.001). Enzymatic activities of CAT and SOD were significantly higher in group B than group A (10.11 ± 2.18 vs. 5.71 ± 0.33), (1.04 ± 0.05 vs. 0.95 ± 0.01), respectively. It may play a contributing role in daily anesthesia practice and improve the toxic effects on patients as well as anesthesia personnel. Trial Registration. Ethical Committee of Post Graduate Medical Institute (PGMI), Lahore General Hospital approved the use of humans in this study vide human subject application number ANS-6466 dated February 04, 2019. Furthermore, as the clinical trials required registration from an appropriate registry approved by World Health Organization (WHO), this trail also retrospectively registered at Thai Clinical Trials Registry (an approved WHO registry for clinical trials registration) under reference ID TCTR20211230001 on December 30, 2021.

The effect of low doses of chlorpyrifos on blood and bone marrow cells in Wistar rats

The aim of this study was to investigate the genotoxic potential of low doses of chlorpyrifos (CPF) on blood and bone marrow cells in adult male Wistar rats. CPF was administered by oral gavage at daily doses of 0.010, 0.015, and 0.160 mg/kg of body weight (bw) for 28 consecutive days. Positive control (PC) was administered 300 mg/kg bw/day of ethyl methane sulphonate (EMS) for the final three days of the experiment. Toxic outcomes of exposure were determined with the in vivo micronucleus (MN) assay and alkaline comet assay. The 28-day exposure to the 0.015 mg/kg CPF dose, which was three times higher than the current value of acute reference dose (ARfD), reduced body weight gain in rats the most. The in vivo MN assay showed significant differences in number of reticulocytes per 1000 erythrocytes between PC and negative control (NC) and between all control groups and the groups exposed to 0.015 and 0.160 mg/kg bw/day of CPF. The number of micronucleated polychromatic erythrocytes per 2000 erythrocytes was significantly higher in the PC than the NC group or group exposed to 0.015 mg/kg bw/day of CPF. CPF treatment did not significantly increase primary DNA damage in bone marrow cells compared to the NC group. However, the damage in bone marrow cells of CPF-exposed rats was much higher than the one recorded in leukocytes, established in the previous research. Both assays proved to be successful for the assessment of CPFinduced genome instability in Wistar rats. However, the exact mechanisms of damage have to be further investigated and confirmed by other, more sensitive methods.

Chlorpyrifos Occurrence and Toxicological Risk Assessment: A Review

Chlorpyrifos (CPF) was the most frequently used pesticide in food production in the European Union (EU) until 2020. Unfortunately, this compound is still being applied in other parts of the world. National monitoring of pesticides conducted in various countries indicates the presence of CPF in soil, food, and water, which may have toxic effects on consumers, farmers, and animal health. In addition, CPF may influence changes in the population of fungi, bacteria, and actinomycete in soil and can inhibit nitrogen mineralization. The mechanisms of CPF activity are based on the inhibition of acetylcholinesterase (AChE) activity. This compound also exhibits reproductive toxicity, neurotoxicity, and genotoxicity. The problem seems to be the discrepancy between the actual observations and the final conclusions drawn for the substance's approval in reports presenting the toxic impact of CPF on human health. Therefore, this influence is still a current and important issue that requires continuous monitoring despite its withdrawal from the market in the EU. This review traces the scientific reports describing the effects of CPF resulting in changes occurring in both the environment and at the cellular and tissue level in humans and animals. It also provides an insight into the hazards and risks to human health in food consumer products in which CPF has been detected.

Enantioselective degradation of the organophosphorus insecticide isocarbophos in Cupriavidus nantongensis X1T: Characteristics, enantioselective regulation, degradation pathways, and toxicity assessment

The chiral pesticide enantiomers often show selective efficacy and non-target toxicity. In this study, the enantioselective degradation characteristics of the chiral organophosphorus insecticide isocarbophos (ICP) by Cupriavidus nantongensis X1^T were investigated systematically. Strain X1^T preferentially degraded the ICP R isomer (R-ICP) over the S isomer (S-ICP). The degradation rate constant of R-ICP was 42-fold greater than S-ICP, while the former is less bioactive against pest insects but more toxic to humans than the latter. The concentration ratio of S-ICP to R-ICP determines whether S-ICP can be degraded by strain X1^T. S-ICP started to degrade only when the ratio (C_S-ICP/C_R-ICP) was greater than 62. Divalent metal cations could improve the degradation ability of strain X1^T. The detected metabolites that were identified suggested a novel hydrolysis pathway, while the hydrolytic metabolites were less toxic to fish and green algae than those from P-O bond breakage. The crude enzyme degraded both R-ICP and S-ICP in a similar rate, indicating that enantioselective degradation was due to the transportation of strain X1^T. The strain X1^T also enantioselectively degraded the chiral organophosphorus insecticides isofenphos-methyl and profenofos. The enantioselective degradation characteristics of strain X1^T make it suitable for remediation of chiral organophosphorus insecticide contaminated soil and water.

A comprehensive review on chlorpyrifos toxicity with special reference to endocrine disruption: Evidence of mechanisms, exposures and mitigation strategies

Chlorpyrifos (CPF) is a broad-spectrum chlorinated organophosphate (OP) pesticide used for the control of a variety of insects and pathogens in crops, fruits, vegetables, as well as households, and various other locations. The toxicity of CPF has been associated with neurological dysfunctions, endocrine disruption, and cardiovascular diseases (CVDs). It can also induce developmental and behavioral anomalies, hematological malignancies, genotoxicity, histopathological aberrations, immunotoxicity, and oxidative stress as evidenced by animal modeling. Moreover, eye irritation and dermatological defects are also reported due to CPF toxicity. The mechanism of action of CPF involves blocking the active sites of the enzyme, acetylcholinesterase (AChE), thereby producing adverse nervous system effects. Although CPF has low persistence in the body, its active metabolites, 3,5,6-trichloro-2-pyridinol (TCP), and chlorpyrifos-oxon (CPO) are comparatively more persistent, albeit equally toxic, and thus produce serious health complications. The present review has been compiled taking into account the work related to CPF toxicity and provides a brief compilation of CPF-induced defects in animals and humans, emphasizing the abnormalities leading to endocrine disruption, neurotoxicity, reproductive carcinogenesis, and disruptive mammary gland functionality. Moreover, the clinical signs and symptoms associated with the CPF exposure along with the possible pharmacological treatment are reported in this treatise. Additionally, the effect of food processing methods in reducing CPF residues from different agricultural commodities and dietary interventions to curtail the toxicity of CPF has also been discussed.

Resistance development characteristics of reared German cockroach (Blattodea: Blattellidae) to chlorpyrifos

Understanding the process of resistance development of German cockroach, Blattella germanica (L.), in detail is necessary to potentially delay the development of insecticides resistance by rotation or discontinuation of insecticides at the right time. In this study, we investigated the resistance development of the reared German cockroach to chlorpyrifos (CPF) for 23 generations from susceptible cockroaches. CPF 50% lethal dose (LD₅₀) and resistance ratio of each generation cockroaches were determined. The CPF LD₅₀ to each generation cockroaches was used as the insecticide selection pressure of this generation by topical application. The resistance development curve was depicted according to the CPF LD₅₀ to all 23 generations of cockroaches. As a result, a highly resistant German cockroach cohort to CPF, which the resistance ratio was 21.63, was obtained after 23 generations’ selection. During the selection, the cockroaches developed low resistance from F1 to F5, moderate resistance from F6 to F12, and high resistance from F13 to F23. There was a rapid resistance increase every 5–7 generations. The resistance growing showed relatively slow from F1 to F11. The fastest growing phase of the resistance was from F12 to F20, in which accounted for more than 80% of the total resistance increase in 23 generations. The development of resistance to CPF tended to slow down from F21 to F23. These findings may provide a basis for the rational use of insecticides, delaying the development of resistance by rotation or discontinuation.

Evaluation of the genotoxic potential of cypermethrin, chlorpyrifos and their subsequent mixture, on cultured bovine lymphocytes

Cypermethrin (CYP) and chlorpyrifos (CPF) are insecticides/parasiticides used in the production of fruits, vegetables and beef cattle. These substances or their metabolites are frequently reported as residues in food, whose consumption in a diet implies a genotoxic risk. The potential for chronic toxicity of CYP and CPF is unclear, and only a few genotoxicological evaluations based on their mixture have been performed. The aim of this study was to evaluate the genotoxic potential of CYP, CPF and CYP + CPF in five concentrations, from 5.9 to 175 μg/mL, on bovine lymphocytes. By means of the cytokinesis-block micronucleus cytome assay, a decrease in the cell proliferation index was observed (r = -0.89 p = 0.04); and also an increase in the frequencies of binucleated cells (BN) with micronuclei (BNMn) (r = 0.93, p = 0.02) and BN with nuclear buds (BNBud) (r = 0.778 p = 0.04), depending on the concentrations of CPF. An increase in BNMn frequencies was observed as a function of CYP concentrations (r = 0.89, p = 0.04) and also of the CYP + CPF mix (r = 0.99, p = 0.008). CYP caused greater genotoxic damage (BNMn) than CPF and the mixture on bovine lymphocytes. Cells with simultaneous presentation of micronuclei and nuclear buds were detected, as well as cells with irregular nuclei, something never previously reported, whose origin and significance should be investigated. The genotoxic effect of chlorpyrifos, cypermethrin and their mixture on bovine lymphocytes was observed. We recognized the value of the use of primary bovine cultures, animal species adjacent to man in the food chain, for genotoxicity studies.

Statement on the available outcomes of the human health assessment in the context of the pesticides peer review of the active substance chlorpyrifos

In July 2019, the European Commission asked EFSA to provide a statement on the available outcomes of the human health assessment in the context of the pesticides peer review for the renewal of approval of the active substance chlorpyrifos conducted in accordance with Commission Implementing Regulation (EC) No 844/2012. The current statement contains a summary of the main findings of the assessment related to human health following the pesticides peer review expert discussions in mammalian toxicology held between 1 and 5 April 2019, as well as EFSA's additional considerations, including whether the active substance can be expected to meet the approval criteria applicable to human health as laid down in Article 4 of Regulation (EC) No 1107/2009. The identified concerns are presented as follows.

This publication is linked to the following EFSA Journal article: http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2019.5810/full

Chromosome Missegregation and Aneuploidy Induction in Human Peripheral Blood Lymphocytes In vitro by Low Concentrations of Chlorpyrifos, Imidacloprid and α-Cypermethrin

Chlorpyrifos, imidacloprid, and α-cypermethrin are some of the most widely used insecticides in contemporary agriculture. However, their low-dose, nontarget genotoxic effects have not been extensively assayed. As one of the most relevant cancer biomarkers, we aimed to assess the aneuploidy due to chromosome missegregation during mitosis. To aim it we treated human lymphocytes in vitro with three concentrations of insecticides equivalents relevant for real scenario exposure assessed by regulatory agencies. We focused on chlorpyrifos as conventional and imidacloprid and α-cypermethrin as sustainable use insecticides. Cytokinesis-blocked micronucleus assay was performed coupled with fluorescence in situ hybridization (FISH) with directly labeled pancentromeric probes for chromosomes 9, 18, X and Y. None of the insecticides induced significant secondary DNA damage in terms of micronuclei (MN), nuclear buds (NB), or nucleoplasmic bridges (NPB). However, significant disbalances in chromosomes 9, 18, X and Y, and in insecticide-treated cells has been observed. According to recent studies, these disbalances in chromosome numbers may be atributted to defect sister chromatid cohesion which contribute to the increase of chromosome missegregation but not to micronuclei incidence. We conclude that tested insecticidal active substances exert chromosome missegregation effects at low concentrations, possibly by mechanism of sister chromatid cohesion. These findings may contribute to future risk assesments and understanding of insecticide mode of action on human genome. Environ. Mol. Mutagen. 60:72-84, 2019. © 2018 Wiley Periodicals, Inc.

Short-term and persistent impacts on behaviors related to locomotion, anxiety, and startle responses of Japanese medaka (Oryzias latipes) induced by acute, sublethal exposure to chlorpyrifos

Although most exposures to chlorpyrifos (CPF) in natural flowing waters are brief and episodic, there have been a few reports of the persistence of abnormal fish behaviors caused by such acute exposure. The present study focused on the behavioral and biochemical responses of Japanese medaka (Oryzias latipes) to acute, sublethal exposure to CPF, as well as the persistence of the effects during a 3-week recovery test in CPF-free water. The medaka became hyperactive and exhibited an elevated anxiety state after a 4-day exposure to 0.024mg/L of CPF, but they recovered from these abnormal behavioral responses within 7days of recovery treatment. In contrast, persistent impacts on some startle responses to a sudden stimulation (induced by a ball drop) were observed in medaka exposed to CPF. The reaction latency did not change immediately after the 4-day exposure, but was significantly prolonged by as much as 21days after the termination of exposure. The post-stimulus swimming distance within 5s significantly decreased on the day immediately after the 4-day exposure, but it significantly increased after 7days of recovery treatment. The activity of acetylcholinesterase (AChE) in the brains of medaka was significantly inhibited on the day immediately after the 4-day exposure, but it returned to 80% and 110% of that in control fish on days 7 and 21 of the recovery period, respectively. However, AChE activities in the eyes of exposed medaka were persistently inhibited and declined to 33%, 71%, and 72% of that in control fish on days 0 (immediately after the 4-day exposure), 7, and 21 of recovery, respectively. Correlation analysis suggested that the changes of AChE activities in the brains of medaka may underlie some of the observed acute behavioral changes, and the changes of AChE activities in the eyes may contribute to the persistence of the abnormalities in the reaction latency of the startle response. Our findings suggest that medaka need a long time to recover from acute, sublethal exposure to CPF, and the persistence of the behavioral abnormalities might affect their fitness in natural habitats.

Mother gestational exposure to organophosphorus pesticide induces neuron and glia loss in daughter adult brain

Chlorpyrifos (CPF) is a widely used organophosphorus pesticide with developmental neurotoxicity such as morphogenesis toxicity. In the present study, we assessed the effects of prenatal CPF exposure on systemic parameters and cytoarchitecture of medial prefrontal cortex (mPFC) in adulthood. Gestational dams were exposed to 5mg/kg/d of CPF during gestational days 13-17, while body weight, organ coefficient, and neuron and glia counts of offspring were determined on postnatal day 60. Our results showed that CPF treatment induced little or no effects on body weight and organ coefficients. There were also no significant pathological changes in mPFC. However, neuron and glia count analysis showed that CPF treatment reduced neuron and glia counts in anterior cingulate, prelimbic, and infralimbic areas of mPFC. The CPF react pattern was similar in both sexes, and there was no statistical difference in most of the sub-regions. Thus, our results revealed an embryonic origin brain deficit induced by gestational mother pesticide exposure.

Increased Expression of P-Glycoprotein Is Associated With Chlorpyrifos Resistance in the German Cockroach (Blattodea: Blattellidae)

A principal method for control of the German cockroach, Blattella germanica (L.), is the broad-spectrum organophosphorus insecticide, chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate); however, extensive and repeated application has resulted in the development of resistance to chlorpyrifos in this insect. Evidence suggests that ATP-binding cassette protein transporters, including P-glycoprotein, are involved in insecticide resistance. However, little is known of the role of P-glycoprotein in insecticide resistance in the German cockroach. Here, we developed a chlorpyrifos-resistant strain of German cockroach and investigated the relationship between P-glycoprotein and chlorpyrifos resistance using toxicity assays; inhibition studies with two P-glycoprotein inhibitors, verapamil and quinine; P-glycoprotein-ATPase activity assays; and western blotting analysis. After 23 generations of selection from susceptible strain cockroaches, we obtained animals with high resistance to chlorpyrifos. When P-glycoprotein-ATPase activity was inhibited by verapamil and quinine, we observed enhanced susceptibility to chlorpyrifos in both control and chlorpyrifos-resistant cockroaches. No significant alterations of P-glycoprotein expression or ATPase activity were observed in cockroaches acutely exposed to LD50 doses of chlorpyrifos for 24 h, while P-glycoprotein expression and ATPase activity were clearly elevated in the chlorpyrifos-resistant cockroach strain. Thus, we conclude that P-glycoprotein is associated with chlorpyrifos resistance in the German cockroach and that elevated levels of P-glycoprotein expression and ATPase activity may be an important mechanism of chlorpyrifos resistance in the German cockroach.

Evaluation of geno-toxicity of methyl parathion and chlorpyrifos to human liver carcinoma cell line (HepG2)

Insecticides and their residues are known to cause several types of ailments in human body. An attempt had been made to assess digitally the geno-toxicity of methyl parathion (MP) and chlorpyrifos (CP) to in vitro-grown HepG2 cell line, with Hoechst 33342 staining, comet, and micronucleus assays. Additionally, "acridine orange/ethidium bromide" (AO/EB) staining was done for the determination of insecticide-induced cytotoxicity, in corollary. Hoechst 33342 staining of cells revealed a decrease in live cell counts at 8-40 mg/L MP and 15-70 mg/L CP. Moreover, nuclear fragmentations in ranges 8 to 40 mg/L MP and 15 to 70 mg/L CP were recorded dependant on individual doses, increasingly with concomitant increases in comet tail length values. DNA fragmentation index measured in comet assays was 94.3 ± 0.57 at 40 mg/L MP and 93.3 ± 2.08 at 70 mg/L CP. Average micronuclei number was 59.0 ± 2.00 at 40 mg/L MP and 62.6 ± 1.52 at 70 mg/L CP, per 1000 cell nuclei, in micronucleus assay. Minimum inhibitory concentration (MIC) values with AO/EB staining for monitoring cytotoxicity were 4 and 10 mg/L for MP and CP, respectively. Lethal concentration50 (LC50) values were 20.89 mg/L MP and 79.43 mg/L CP in AO/EB staining, for cytotoxicity with probit analyses. It was concluded that MP was comparatively more geno-toxic than CP to HepG2 cell. It was discernible that at lower levels of each insecticide, geno-toxicity was recorded in comparison to cytotoxicity.

Histopathological and genotoxic effects of chlorpyrifos in rats

This study aims to investigate the effects of chlorpyrifos's sub-acute exposure on male rats. Two groups with six animals each were orally treated, respectively, with 3.1 mg/kg b w and 6.2 mg/kg b w of chlorpyrifos during 4 weeks. The genotoxic effect of chlopyrifos was investigated using the comet assay and the micronucleus test. Some hematological and liver's histopathological changes were also evaluated. Results revealed that chlorpyrifos induced histopathological alterations in liver parenchyma. The lymphoid infiltration observed in liver sections and the increase in white blood cells parameter are signs of inflammation. A significant increase in the platelet' count and in polychromatic erythrocytes/normochromatic erythrocytes (PCE/NCE) ratio was observed in chlorpyrifos-treated groups which could be due to the stimulatory effect of chlorpyrifos on cell formation in the bone marrow at lower doses. In addition, the increase of bone marrow micronucleus percentage and the comet tail length revealed a genotoxic potential of chlorpyrifos in vivo.

Development of a freeze-dried fungal wettable powder preparation able to biodegrade chlorpyrifos on vegetables

Continuous use of the pesticide chlorpyrifos has resulted in harmful contaminations in environment and species. Based on a chlorpyrifos-degrading fungus Cladosporium cladosporioides strain Hu-01 (collection number: CCTCC M 20711), a fungal wettable powder preparation was developed aiming to efficiently remove chlorpyrifos residues from vegetables. The formula was determined to be 11.0% of carboxymethyl cellulose-Na, 9.0% of polyethylene glycol 6000, 5.0% of primary alcohol ethoxylate, 2.5% of glycine, 5.0% of fucose, 27.5% of kaolin and 40% of freeze dried fungi by response surface methodology (RSM). The results of quality inspection indicated that the fungal preparation could reach manufacturing standards. Finally, the degradation of chlorpyrifos by this fungal preparation was determined on pre-harvest cabbage. Compared to the controls without fungal preparation, the degradation of chlorpyrifos on cabbages, which was sprayed with the fungal preparation, was up to 91% after 7 d. These results suggested this freeze-dried fungal wettable powder may possess potential for biodegradation of chlorpyrifos residues on vegetables and provide a potential strategy for food and environment safety against pesticide residues.