Assessment of neurohepatic DNA damage in male Sprague-Dawley rats exposed to organophosphates and pyrethroid insecticides

Metabolomic analysis of the serum and urine of rats exposed to diazinon, dimethoate, and cypermethrin alone or in combination

BACKGROUND

Multiple pesticides are often used in combination for plant protection and public health. Therefore, it is important to analyze the physiological changes induced by multiple pesticides exposure. The objective of this study was to investigate the combined toxicity of the widely-used organophosphorus and pyrethroid pesticides diazinon, dimethoate, and cypermethrin.

METHODS

Male Wistar rats were administrated by gavage once daily with the three pesticides individual or in combination for consecutive 28 days. The metabolic components of serum and urine samples were detected by using 1H nuclear magnetic resonance (NMR)-based metabolomics method. Histopathological examination of liver and kidneys and serum biochemical determination were also carried out.

RESULTS

The results showed that after the 28-day subacute exposure, serum glutamic transaminase and albumin were significantly increased and blood urea nitrogen was significantly decreased in the rats exposed to the mixture of the pesticides compared with the control rats, suggesting that the co-exposure impaired liver and kidney function. Metabolomics analysis indicated that the indicators 14 metabolites were statistically significant altered in the rats after the exposure of the pesticides. The increase in 3-hydroxybutyric acid in urine or decrease of lactate and N-acetyl-L-cysteine in serum could be a potentially sensitive biomarker of the subchronic combined effects of the three insecticides. The reduction level of 2-oxoglutarate and creatinine in urine may be indicative of dysfunction of liver and kidneys.

CONCLUSION

In summary, the exposure of rats to pesticides diazinon, dimethoate, and cypermethrin could cause disorder of lipid and amino acid metabolism, induction of oxidative stress, and dysfunction of liver and kidneys, which contributes to the understanding of combined toxic effects of the pesticides revealed by using the metabolomics analysis of the urine and serum profiles.

Oxidative stress and mitochondrial damage in lambda-cyhalothrin toxicity: A comprehensive review of antioxidant mechanisms

Lambda-cyhalothrin, also known as cyhalothrin, is an efficient, broad-spectrum, quick-acting pyrethroid insecticide and acaricide and the most powerful pyrethroid insecticide in the world. However, there is increasing evidence that lambda-cyhalothrin is closely related to a variety of toxicity drawbacks (hepatotoxicity, nephrotoxicity, neurotoxicity and reproductive toxicity, among others) in non-target organisms, and oxidative stress seems to be the main mechanism of toxicity. This manuscript reviews the oxidative and mitochondrial damage induced by lambda-cyhalothrin and the signalling pathways involved in this process, indicating that oxidative stress occupies an important position in lambda-cyhalothrin toxicity. The mechanism of antioxidants to alleviate the toxicity of lambda-cyhalothrin is also discussed. In addition, the metabolites of lambda-cyhalothrin and the major metabolic enzymes involved in metabolic reactions are summarized. This review article reveals a key mechanism of lambda-cyhalothrin toxicity-oxidative damage and suggests that the use of antioxidants seems to be an effective method for preventing toxicity.

Influence of chlorpyrifos exposure on UVB irradiation induced toxicity in human skin cells

BACKGROUND

Although chlorpyrifos (CPS) has been banned in many developed countries, it still remains one of the best-selling pesticides in the world. Widespread environmental and occupational exposure to CPS pose a serious risk to human health. Another environmental factor that can adversely affect human health is ultraviolet radiation B (UVB, 280-315 nm wave length). Here we attempt determine if exposure to CPS can modify toxic effects of UVB. Such situation might be a common phenomenon in agriculture workers, where exposure to both factors takes place.

METHODS

Two skin cell lines; namely human immortalized keratinocytes HaCaT and BJ human fibroblasts were used in this study. Cytotoxicity was investigated using a cell membrane damage detection assay (LDH Cytotoxicity Assay), a DNA damage detection assay (Comet Assay), an apoptosis induction detection assay (Apo-ONE Homogeneous Caspase-3/7 Assay) and a cell reactive oxygen species detection assay (ROS-Glo H2O2 assay). Cytokine IL-6 production was also measured in cells using an ELISA IL-6 Assay.

RESULTS

Pre-incubation of skin cells with CPS significantly increased UVB-induced toxicity at the highest UVB doses (15 and 20 mJ/cm2). Also pre-exposure of BJ cells to CPS significantly increased the level of DNA damage, except for 20 mJ/cm2 UVB. In contrast, pre-exposure of HaCaT cells, to CPS prior to UVB radiation did not cause any significant changes. A decrease in caspase 3/7 activity was observed in HaCaT cells pre-exposed to 250 µM CPS and 5 mJ/cm2 UVB. Meanwhile, no statistically significant changes were observed in fibroblasts. In HaCaT cells, pre-exposure to CPS resulted in a statistically significant increase in ROS production. Also, in BJ cells, similar results were obtained except for 20 mJ/cm2. Interestingly, CPS seems to inhibited IL-6 production in HaCaT and BJ cells exposed to UVB (in the case of HaCaT cells for all UVB doses, while for BJ cells only at 15 and 20 mJ/cm2).

CONCLUSIONS

In conclusion, the present study indicates that CPS may contribute to the increased UVB-induced toxicity in skin cells, which was likely due to the induction of ROS formation along with the generation of DNA damage. However, further studies are required to gain better understanding of the mechanisms involved.

Lambda-cyhalothrin enhances inflammation in nigrostriatal region in rats: Regulatory role of NF-κβ and JAK-STAT signaling

The risk to develop neurobehavioural abnormalities in humans on exposure to lambda-cyhalothrin (LCT) - a type II synthetic pyrethroid has enhanced significantly due to its extensive uses in agriculture, homes, veterinary practices and public health programs. Earlier, we found that the brain dopaminergic system is vulnerable to LCT and affects motor functions in rats. In continuation to this, the present study is focused to unravel the role of neuroinflammation in LCT-induced neurotoxicity in substantia nigra and corpus striatum in rats. Increase in the mRNA expression of proinflammatory cytokines (TNF- α, IL-1β, IL-6) and iNOS whereas decrease in anti-inflammatory cytokine (IL-10) was distinct both in substantia nigra and corpus striatum of rats treated with LCT (0.5, 1.0, 3.0 mg/kg body weight, p.o, for 45 days) as compared to control rats. Further, LCT-treated rats exhibited increased levels of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (Iba-1), the glial marker proteins both in substantia nigra and corpus striatum as compared to controls. Exposure of rats to LCT also caused alterations in the levels of heat shock protein 60 (HSP60) and mRNA expression of toll-like receptors (TLR2 and TLR4) in the substantia nigra and corpus striatum. An increase in the phosphorylation of key proteins involved in NF-kβ (P65, Iκβ, IKKα, IKKβ) and JAK/STAT (STAT1, STAT3) signaling and alteration in the protein levels of JAK1 and JAK2 was prominent in LCT-treated rats. Histological studies revealed damage of dopaminergic neurons and reactive gliosis as evidenced by the presence of darkly stained pyknotic neurons and decrease in Nissl substance and an increase in infiltration of immune cells both in substantia nigra and corpus striatum of LCT-treated rats. Presence of reactive microglia and astrocytes in LCT-treated rats was also distinct in ultrastructural studies. The results exhibit that LCT may damage dopaminergic neurons in the substantia nigra and corpus striatum by inducing inflammation as a result of stimulation of neuroglial cells involving activation of NF-κβ and JAK/STAT signaling.

Effects of pyrethroids on the cerebellum and related mechanisms: a narrative review

Pyrethroids (PYRs) are a group of synthetic organic chemicals that mimic natural pyrethrins. Due to their low toxicity and persistence in mammals, they are widely used today. PYRs exhibit higher lipophilicity than other insecticides, which allows them to easily penetrate the blood-brain barrier and directly induce toxic effects on the central nervous system. Several studies have shown that the cerebellum appears to be one of the regions with the largest changes in biomarkers. The cerebellum, which is extremely responsive to PYRs, functions as a crucial region for storing motor learning memories. Exposure to low doses of various types of PYRs during rat development resulted in diverse long-term effects on motor activity and coordination functions. Reduced motor activity may result from developmental exposure to PYRs in rats, as indicated by delayed cerebellar morphogenesis and maturation. PYRs also caused adverse histopathological and biochemical changes in the cerebellum of mothers and their offspring. By some studies, PYRs may affect granule cells and Purkinje cells, causing damage to cerebellar structures. Destruction of cerebellar structures and morphological defects in Purkinje cells are known to be directly related to functional impairment of motor coordination. Although numerous data support that PYRs cause damage to cerebellar structures, function and development, the mechanisms are not completely understood and require further in-depth studies. This paper reviews the available evidence on the relationship between the use of PYRs and cerebellar damage and discusses the mechanisms of PYRs.

Apoptosis is involved in paraoxon-induced histological changes in rat cerebellum

Acute toxicity of organophosphorus compounds is primarily caused by inhibition of acetylcholinesterase (AChE) at cholinergic synapses. The current study was designed to investigate the effects of paraoxon on histological changes as well as the role of mitochondrion-dependent apoptosis in causing this damage in the rat cerebellum. Adult male Wistar rats were intraperitoneally injected with paraoxon at 0.3, 0.7, or 1 mg/kg. Control animals were injected with corn oil as a vehicle. At 14 or 28 days after intoxication, histological changes and alterations in the expression of apoptosis-related proteins, including Bax, Bcl-2, and caspase-3, were investigated in the cerebellum using cresyl violet staining and western blotting, respectively. Findings showed the decreased thickness of both molecular and granular layers and reduction in the number of Purkinje cells in animals treated with a higher convulsive dose of paraoxon (1 mg/kg). In addition, exposure of rats to 1 mg/kg of paraoxon activated apoptosis pathway confirmed by an increase in Bax and caspase-3 and a decrease in Bcl-2 protein levels. According to our results, cerebellar histological changes and alterations in the expression of apoptosis-related proteins occur following exposure to a high convulsive dose of paraoxon and persist for a long time.

Dimethoate induces genotoxicity as a result of oxidative stress: in vivo and in vitro studies

Dimethoate ([O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate]) is an organophosphate insecticide and acaricide widely used for agricultural purposes. Genotoxicity refers to the ability of a chemical agent interact directly to DNA or act indirectly leading to DNA damage by affecting spindle apparatus or enzymes involved in DNA replication, thereby causing mutations. Taking into consideration the importance of genotoxicity induced by dimethoate, the purpose of this manuscript was to provide a mini review regarding genotoxicity induced by dimethoate as a result of oxidative stress. The present study was conducted on studies available in MEDLINE, PUBMED, EMBASE, and Google scholar for all kind of articles (all publications published until May, 2020) using the following key words: dimethoate, omethoate, DNA damage, genetic damage, oxidative stress, genotoxicity, mutation, and mutagenicity. The results showed that many studies were published in the scientific literature; the approach was clearly demonstrated in multiple tissues and organs, but few papers were designed in humans. In summary, new studies within the field are important for better understanding the pathobiological events of genotoxicity on human cells, particularly to explain what cells and/or tissues are more sensitive to genotoxic insult induced by dimethoate.

The palliative effect of camel milk on hepatic CYP1A1 gene expression and DNA damage induced by fenpropathrin oral intoxication in male rats

The present study investigated the alleviating role of camel milk (CM) in the mitigation of fenpropathrin (FNP) type II pyrethroid induced oxidative stress, alterations of hepatic (CYP1A1) mRNA expression pattern, and DNA damage using the alkaline comet assay (SCGE) in male rats. Sixty male Sprague-Dawley rats were separated into six groups (n = 10): 1st control (C), 2nd corn oil (CO), 3rd (CM): gavaged CM 2ml/rat, 4th (FNP): gavaged FNP 7.09 mg/kg body weight (BW), 5th (FNP pro/co-treated): gavaged CM firstly for 15 days, then CM + FNP by the same mentioned doses and route, 6th (FNP + CM co-treated): gavaged FNP firstly followed by CM by the same mentioned doses and route. Rats were orally gavaged three times per week, day after day for 60 days. FNP exposure significantly reduced serum glutathione (GSH) levels, but significantly increased serum levels of superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), protein carbonyl (PCO), and 8hydroxy2deoxyguanosine (8OH2dG). Additionally, FNP exposure significantly up-regulated the mRNA expression levels of hepatic CYP1A1 and increased the SCGE indices in whole blood, liver, and spleen tissues of exposed male rats. Administration of CM significantly regulated the FNP induced oxidative stress, reduced hepatic CYP1A1 mRNA expression levels and values of comet assay indices particularly in the (CM + FNP pro/co-treated) group compared to the (FNP + CM co-treated) group. In conclusion, our results indicate, for the first time, that FNP retains an in vivo genotoxic potential at a dose of (1/10 LD₅₀) and up-regulated hepatic CYP1A1 mRNA expression in male rats. Additionally, CM supplements may improve the genotoxic outcomes, oxidative stress, and altered CYP1A1 mRNA expression induced by FNP particularly in the pro/concurrent-treatment compared to the concurrent treatment alone.

Induction of DNA damage as a consequence of occupational exposure to crystalline silica: A review and meta-analysis

About 40 million workers are occupationally exposed to crystalline silica (CS) which was classified as a human carcinogen by the IARC. It is assumed that damage of the genetic material via inflammation and reactive oxygen species by CS lead to formation of malignant cells. We conducted a systematic literature search to find out if inhalation of CS containing dusts at workplaces causes damage of the genetic material. Thirteen studies were found eligible for this review, in most of them (n = 9) micronuclei (MN) which reflect structural/numerical chromosomal aberrations were monitored in lymphocytes and/or in exfoliated buccal cells. In 5 investigations DNA damage was measured in blood cells in single cell gel electrophoresis (comet) experiments. Frequently studied groups were potters, stone cutters, miners and construction workers. Results of meta-analyses show that exposure to CS causes formation of MN and DNA breaks, the overall ratio values were in exposed workers 2.06- and 1.96-fold higher than in controls, respectively. Two studies reported increased levels of oxidized guanine, and higher levels of DNA adducts with malondialdehyde indicating that exposure to CS leads to oxidative damage. The exposure of the workers to CS was quantified only in two studies, information concerning the size and chemical structures of the particles is lacking in most investigations. Therefore, it is not possible to use the results to derive occupational exposure limits of workers to CS which vary strongly in different countries. Nevertheless, the evaluation of the current state of knowledge shows that biomonitoring studies in which damage of the genetic material is measured in CS exposed workers can contribute to assess adverse health effects as consequence of DNA instability in specific occupations.

Oxidative stress and mitochondrial dysfunction in organophosphate pesticide-induced neurotoxicity and its amelioration: a review

Organophosphorus pesticides (OPs) are widely used for controlling pests worldwide. The inhibitory effects of these pesticides on acetylcholinesterase lead to neurotoxic damages. The oxidative stress is responsible for several neurological diseases, including Parkinson's disease, seizure, depression, and Alzheimer's disease. Strong evidence suggests that dysfunction of mitochondria and oxidative stress are involved in neurological diseases. OPs can disturb the function of mitochondria by inducing oxidative stress. In the present study, we tried to highlight the role of dysfunction of mitochondria and the induction of oxidative stress in the neurotoxicity induced by OPs. Additionally, the amelioration of OP-induced oxidative damage and mitochondrial dysfunctional through the chemical and natural antioxidants have been discussed.

Mechanochemical enhancement of the natural attenuation capacity of soils using two organophosphate biocides as models

Mechanochemical treatment by high energy ball milling is a promising technology to safely destroy organic pollutants in contaminated soil and allow its possible beneficial reuse. The present study investigates the mechanochemical activation of four major soil components, which induces generation of electrons on particle surfaces. Such phenomenon is demonstrated to occur on oxides by formation of trapped electrons in oxygen vacancies (following a zeroth-order kinetics), as well as on quartz and clayey materials to form fresh electron-rich surfaces by homolytic bond rapture (according to a first-order kinetics). Two toxic organophosphate biocides (i.e. chlorpyrifos and glyphosate) are used as model pollutants. Results show that the aromatic structure of chlorpyrifos determines a faster degradation rate, compared to the aliphatic one of glyphosate, because of the higher stability of generated radical intermediates. Moreover, the aromatic moiety facilitates adsorption on clays, thus temporarily sequestering the molecule and delaying its degradation. The many heteroatoms in both organophosphates have analogous fate: mineralization to inorganic form.