Reactive oxygen species regulated mitochondria-mediated apoptosis in PC12 cells exposed to chlorpyrifos

Mitochondrial Dysfunction in Environmental Toxicology: Mechanisms, Impacts, and Health Implications

Mitochondria, pivotal to cellular metabolism, serve as the primary sources of biological energy and are key regulators of intracellular calcium ion storage, crucial for maintaining cellular calcium homeostasis. Dysfunction in these organelles impairs ATP synthesis, diminishing cellular functionality. Emerging evidence implicates mitochondrial dysfunction in the etiology and progression of diverse diseases. Environmental factors that induce mitochondrial dysregulation raise significant public health concerns, necessitating a nuanced comprehension and classification of mitochondrial-related hazards. This review systematically adopts a toxicological perspective to illuminate the biological functions of mitochondria, offering a comprehensive exploration of how toxicants instigate mitochondrial dysfunction. It delves into the disruption of energy metabolism, the initiation of mitochondrial fragility and autophagy, and the induction of mutations in mitochondrial DNA by mutagens. The overarching objective is to enhance our understanding of the repercussions of mitochondrial damage on human health.

Chlorpyrifos induces autophagy by suppressing the mTOR pathway in immortalized GnRH neurons

Chlorpyrifos (CPF) is a widely used pesticide inducing adverse neurodevelopmental and reproductive effects. However, knowledge of the underlying mechanisms is limited, particularly in the hypothalamus. We investigated the mode of action of CPF at human relevant concentrations (1 nM-100 nM) in immortalized mouse hypothalamic GnRH neurons (GT1-7), an elective model for studying disruption of the hypothalamus-pituitary-gonads (HPG) axis. We firstly examined cell vitality, proliferation, and apoptosis/necrosis. At not-cytotoxic concentrations, we evaluated neuron functionality, gene expression, Transmission Electron Microscopy (TEM) and proteomics profiles, validating results by immunofluorescence and western blotting (WB). CPF decreased cell vitality with a dose-response but did not affect cell proliferation. At 100 nM, CPF inhibited gene expression and secretion of GnRH; in addition, CPF reduced the immunoreactivity of the neuronal marker Map2 in a dose-dependent manner. The gene expression of Estrogen Receptor α and β (Erα, Erβ), Androgen Receptor (Ar), aromatase and oxytocin receptor was induced by CPF with different trends. Functional analysis of differentially expressed proteins identified Autophagy, mTOR signaling and Neutrophil extracellular traps (NETs) formation as significant pathways affected at all concentrations. This finding was phenotypically supported by the TEM analysis, showing marked autophagy and damage of mitochondria, as well as by protein analysis demonstrating a dose-dependent decrease of mTOR and its direct target pUlk1 (Ser 757). The bioinformatics network analysis identified a core module of interacting proteins, including Erα, Ar, mTOR and Sirt1, whose down-regulation was confirmed by WB analysis. Overall, our results demonstrate that CPF is an inhibitor of the mTOR pathway leading to autophagy in GnRH neurons; a possible involvement of the Erα/Ar signaling is also suggested. The evidence for adverse effects of CPF in the hypothalamus in the nanomolar range, as occurs in human exposure, increases concern on potential adverse outcomes induced by this pesticide on the HPG axis.

Biomarkers of mitochondrial dysfunction in autism spectrum disorder: A systematic review and meta-analysis

Autism spectrum disorder (ASD) is a neurodevelopmental disorder affecting 1 in 36 children and is associated with physiological abnormalities, most notably mitochondrial dysfunction, at least in a subset of individuals. This systematic review and meta-analysis discovered 204 relevant articles which evaluated biomarkers of mitochondrial dysfunction in ASD individuals. Significant elevations (all p < 0.01) in the prevalence of lactate (17%), pyruvate (41%), alanine (15%) and creatine kinase (9%) were found in ASD. Individuals with ASD had significant differences (all p < 0.01) with moderate to large effect sizes (Cohen's d' ≥ 0.6) compared to controls in mean pyruvate, lactate-to-pyruvate ratio, ATP, and creatine kinase. Some studies found abnormal TCA cycle metabolites associated with ASD. Thirteen controlled studies reported mitochondrial DNA (mtDNA) deletions or variations in the ASD group in blood, peripheral blood mononuclear cells, lymphocytes, leucocytes, granulocytes, and brain. Meta-analyses discovered significant differences (p < 0.01) in copy number of mtDNA overall and in ND1, ND4 and CytB genes. Four studies linked specific mtDNA haplogroups to ASD. A series of studies found a subgroup of ASD with elevated mitochondrial respiration which was associated with increased sensitivity of the mitochondria to physiological stressors and neurodevelopmental regression. Lactate, pyruvate, lactate-to-pyruvate ratio, carnitine, and acyl-carnitines were associated with clinical features such as delays in language, social interaction, cognition, motor skills, and with repetitive behaviors and gastrointestinal symptoms, although not all studies found an association. Lactate, carnitine, acyl-carnitines, ATP, CoQ10, as well as mtDNA variants, heteroplasmy, haplogroups and copy number were associated with ASD severity. Variability was found across biomarker studies primarily due to differences in collection and processing techniques as well as the intrinsic heterogeneity of the ASD population. Several studies reported alterations in mitochondrial metabolism in mothers of children with ASD and in neonates who develop ASD. Treatments targeting mitochondria, particularly carnitine and ubiquinol, appear beneficial in ASD. The link between mitochondrial dysfunction in ASD and common physiological abnormalities in individuals with ASD including gastrointestinal disorders, oxidative stress, and immune dysfunction is outlined. Several subtypes of mitochondrial dysfunction in ASD are discussed, including one related to neurodevelopmental regression, another related to alterations in microbiome metabolites, and another related to elevations in acyl-carnitines. Mechanisms linking abnormal mitochondrial function with alterations in prenatal brain development and postnatal brain function are outlined. Given the multisystem complexity of some individuals with ASD, this review presents evidence for the mitochondria being central to ASD by contributing to abnormalities in brain development, cognition, and comorbidities such as immune and gastrointestinal dysfunction as well as neurodevelopmental regression. A diagnostic approach to identify mitochondrial dysfunction in ASD is outlined. From this evidence, it is clear that many individuals with ASD have alterations in mitochondrial function which may need to be addressed in order to achieve optimal clinical outcomes. The fact that alterations in mitochondrial metabolism may be found during pregnancy and early in the life of individuals who eventually develop ASD provides promise for early life predictive biomarkers of ASD. Further studies may improve the understanding of the role of the mitochondria in ASD by better defining subgroups and understanding the molecular mechanisms driving some of the unique changes found in mitochondrial function in those with ASD.

Neurotoxicology of dopamine: Victim or assailant?

Since the identification of dopamine as a neurotransmitter in the mid-20th century, investigators have examined the regulation of dopamine homeostasis at a basic biological level and in human disorders. Genetic animal models that manipulate the expression of proteins involved in dopamine homeostasis have provided key insight into the consequences of dysregulated dopamine. As a result, we have come to understand the potential of dopamine to act as an endogenous neurotoxin through the generation of reactive oxygen species and reactive metabolites that can damage cellular macromolecules. Endogenous factors, such as genetic variation and subcellular processes, and exogenous factors, such as environmental exposures, have been identified as contributors to the dysregulation of dopamine homeostasis. Given the variety of dysregulating factors that impact dopamine homeostasis and the potential for dopamine itself to contribute to further cellular dysfunction, dopamine can be viewed as both the victim and an assailant of neurotoxicity. Parkinson's disease has emerged as the exemplar case study of dopamine dysregulation due to the genetic and environmental factors known to contribute to disease risk, and due to the evidence of dysregulated dopamine as a pathologic and pathogenic feature of the disease. This review, inspired by the talk, "Dopamine in Durham: location, location, location" presented by Dr. Miller for the Jacob Hooisma Memorial Lecture at the International Neurotoxicology Association meeting in 2023, offers a primer on dopamine toxicity covering endogenous and exogenous factors that disrupt dopamine homeostasis and the actions of dopamine as an endogenous neurotoxin.

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.

Sex-associated microRNAs potentially implicated in sporadic Alzheimer's disease (sAD)

BACKGROUND

The onset and pathology of sporadic Alzheimer's disease (sAD) seem to be affected by both sex and genetic mechanisms. Evidence supports that the high prevalence of sAD in women, worldwide, may be attributed to an interplay among aging, sex, and lifestyle, influenced by genetics, metabolic changes, and hormones. Interestingly, epigenetic mechanisms such as microRNAs (miRNAs), known as master regulators of gene expression, may contribute to this observed sexual dimorphism in sAD.

OBJECTIVES

To investigate the potential impact of sex-associated miRNAs on processes manifesting sAD pathology, as described by the Tau-driven Adverse Outcome Pathway (AOP) leading to memory loss.

METHODS

Using publicly available human miRNA datasets, sex-biased miRNAs, defined as differentially expressed by sex in tissues possibly affected by sAD pathology, were collected. In addition, sex hormone-related miRNAs were also retrieved from the literature. The compiled sex-biased and sex hormone-related miRNAs were further plugged into the dysregulated processes of the Tau-driven AOP for memory loss.

RESULTS

Several miRNAs, previously identified as sex-associated, were implicated in dysregulated processes associated with the manifestation of sAD pathology. Importantly, the described pathology processes were not confined to a particular sex. A mechanistic-based approach utilizing miRNAs was adopted in order to elucidate the link between sex and biological processes potentially involved in the development of memory loss.

CONCLUSIONS

The identification of sex-associated miRNAs involved in the early processes manifesting memory loss may shed light to the complex molecular mechanisms underlying sAD pathogenesis in a sex-specific manner.

Do the same chlorinated organophosphorus flame retardants that cause cytotoxicity and DNA damage share the same pathway?

Organophosphorus flame retardants (OPFRs) have been frequently detected with relatively high concentrations in various environmental media and are considered emerging environmental pollutants. However, their biological effect and underlying mechanism is still unclear, and whether chlorinated OPFRs (Cl-OPFRs) cause adverse outcomes with the same molecular initial events or share the same key events (KEs) remains unknown. In this study, in vitro bioassays were conducted to analyze the cytotoxicity, mitochondrial impairment, DNA damage and molecular mechanisms of two Cl-OPFRs. The results showed that these two Cl-OPFRs, which have similar structures, induced severe cellular and molecular damages via different underlying mechanisms. Both tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) (TCPP) induced oxidative stress-mediated mitochondrial impairment and DNA damage, as shown by the overproduction of intracellular reactive oxygen species (ROS) and mitochondrial superoxide. Furthermore, the DNA damage caused by TCPP resulted in p53/p21-mediated cell cycle arrest, as evidenced by flow cytometry and real-time PCR. At the cellular and molecular levels, TCPP increased the sub-G1 apoptotic peak and upregulated the p53/Bax apoptosis pathway, possibly resulted in apoptosis associated with its stronger cytotoxicity. Although structurally similar to TCPP, TCEP did not induce mitochondrial impairment and DNA damage by the same KEs. These results provide insight into the toxicity of Cl-OPFRs with similar structures but different mechanisms, which is of great significance for constructing adverse outcome pathways or determining intermediate KEs.

Grape seed extract prevents chlorpyrifos-induced toxicity in rat liver through the modulation of phase I detoxification pathway

Chlorpyrifos (CPF) poisoning is a public health problem for which there is not currently any effective prophylaxis. In this study, we investigated the protective effect of grape seed extract (GSE) against CPF-induced hepatotoxicity. Rats were daily treated either with CPF (2 mg/kg) or CPF and GSE (20 mg/kg) for 1 week, sacrificed, and their livers dissected for biochemical, molecular, and histopathological analyses. CPF generated liver dysfunction by altering carbohydrate, lipid, amino acid, ammonia and urea metabolism, and provoked mitochondrial impairment through disturbing tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), and mitochondrial viability. CPF also induced cholinergic excitotoxicity along with oxidative stress and histopathological alterations. Interestingly, treatment with GSE prevented all the detrimental effects of CPF through the regulation of cytochrome P450 (CYP450) gene expression. Molecular docking analysis indicated that GSE-containing polyphenols acted as epigenetic modulators through inhibiting DNA (cytosine-5)-methyltransferase 1 (DNMT1), thus favoring the CYP2C6 detoxification pathway. Thereby, GSE might be a promising strategy in the protection of the liver against CPF toxicity.

Implications of organophosphate pesticides on brain cells and their contribution toward progression of Alzheimer's disease

The most widespread neurodegenerative disorder, Alzheimer's disease (AD) is marked by severe behavioral abnormalities, cognitive and functional impairments. It is inextricably linked with the deposition of amyloid β (Aβ) plaques and tau protein in the brain. Loss of white matter, neurons, synapses, and reactive microgliosis are also frequently observed in patients of AD. Although the causative mechanisms behind the neuropathological alterations in AD are not fully understood, they are likely influenced by hereditary and environmental factors. The etiology and pathogenesis of AD are significantly influenced by the cells of the central nervous system, namely, glial cells and neurons, which are directly engaged in the transmission of electrical signals and the processing of information. Emerging evidence suggests that exposure to organophosphate pesticides (OPPs) can trigger inflammatory responses in glial cells, leading to various cascades of events that contribute to neuroinflammation, neuronal damage, and ultimately, AD pathogenesis. Furthermore, there are striking similarities between the biomarkers associated with AD and OPPs, including neuroinflammation, oxidative stress, dysregulation of microRNA, and accumulation of toxic protein aggregates, such as amyloid β. These shared markers suggest a potential mechanistic link between OPP exposure and AD pathology. In this review, we attempt to address the role of OPPs on altered cell physiology of the brain cells leading to neuroinflammation, mitochondrial dysfunction, and oxidative stress linked with AD pathogenesis.

Chlorpyrifos induces placental oxidative stress and barrier dysfunction by inducing mitochondrial apoptosis through the ERK/MAPK signaling pathway: In vitro and in vivo studies

Chlorpyrifos (CPF) is an organophosphorus pesticide that is widely used in agricultural production and residential environments worldwide. In this study, we determined the harmful effects and toxicological mechanism of CPF in porcine trophectoderm (pTr) cells and the placenta of female mice during pregnancy. The findings revealed that CPF significantly decreased cell viability and increased intracellular lactate dehydrogenase (LDH) release in pTr cells. Similarly, CPF induced reproductive toxicity in pregnant maternal mice, including decreased maternal, fetal, and placental weights. Moreover, following CPF treatment, pTr cells and the placenta of female mice showed significant apoptosis. JC-1 staining and flow cytometry analysis also revealed that the mitochondrial membrane potential (MMP) of pTr cells treated with CPF was significantly depolarized. Additionally, CPF can induce an increase in reactive oxygen species (ROS) and barrier dysfunction in pTr cells and the placenta of female mice. We further verified that CPF-induced mitochondrial apoptosis is mediated by the MAPK signaling pathway, as shown by using of small molecular inhibitors of related proteins. Also, CPF-induced oxidative stress, barrier dysfunction, and mitochondrial apoptosis in pTr cells were alleviated by U0126, an inhibitor of the ERK/MAPK signaling pathway. These findings suggested that exposure to CPF in early pregnancy might be a potential risk fator affecting placental formation and function in humans and animals.

The susceptibility of humans to neurodegenerative and neurodevelopmental toxicities caused by organophosphorus pesticides

The toxicology field is concerned with the impact of organophosphorus (OP) compounds on human health. These compounds have been linked to an increased risk of neurological disorders, including neurodegenerative and neurodevelopmental diseases. This article aims to review studies on the role of OP compounds in developing these neurological disorders and explore how genetic variations can affect susceptibility to the neurotoxicity of these pesticides. Studies have shown that exposure to OP compounds can lead to the development of various neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), attention deficit hyperactivity disorder (ADHD), autism, intellectual disability, and other developmental neurotoxicities. Apart from inhibiting the cholinesterase enzyme, OP compounds are believed to cause other pathological mechanisms at both the extracellular level (cholinergic, serotonergic, dopaminergic, glutamatergic, and GABAergic synapses) and the intracellular level (oxidative stress, mitochondrial dysfunction, inflammation, autophagy, and apoptosis) that contribute to these disorders. Specific genetic polymorphisms, including PON1, ABCB1, NOS, DRD4, GST, CYP, and APOE, have increased the risk of developing OP-related neurological disorders.

Exposure to Chlorpyrifos Alters Proliferation, Differentiation and Fatty Acid Uptake in 3T3-L1 Cells

Organophosphorus pesticides (OPs) are important factors in the etiology of many diseases, including obesity and type 2 diabetes mellitus. The aim of this study was to investigate the effect of a representative of OPs, chlorpyrifos (CPF), on viability, proliferation, differentiation, and fatty acid uptake in 3T3-L1 cells. The effect of CPF exposure on preadipocyte proliferation was examined by the MTT, NR, and BrdU assays. The impact of CPF exposure on the differentiation of preadipocytes into mature adipocytes was evaluated by Oil Red O staining and RT-qPCR. The effect of CPF on free fatty acid uptake in adipocytes was assessed with the fluorescent dye BODIPY. Our experiments demonstrated that exposure to CPF decreased the viability of 3T3-L1 cells; however, it was increased when the cells were exposed to low concentrations of the pesticide. Exposure to CPF inhibited the proliferation and differentiation of 3T3-L1 preadipocytes. CPF exposure resulted in decreased lipid accumulation, accompanied by down-regulation of the two key transcription factors in adipogenesis: C/EBPα and PPARγ. Exposure to CPF increased basal free fatty acid uptake in fully differentiated adipocytes but decreased this uptake when CPF was added during the differentiation process. Increased free fatty acid accumulation in fully differentiated adipocytes may suggest that CPF leads to adipocyte hypertrophy, one of the mechanisms leading to obesity, particularly in adults. It can therefore be concluded that CPF may disturb the activity of preadipocytes and adipocytes, although the role of this pesticide in the development of obesity requires further research.

Molecular interaction mechanisms and cellular response of superoxide dismutase and catalase to fluoranthene

As an important raw material and intermediate product of the petrochemical industry, fluoranthene (Fla) can be emitted with industrial activities and has become a typical polycyclic aromatic hydrocarbon enriched in the Chinese topsoil layer, posing a significant threat to sensitive soil biota. Here, multispectral tools and molecular simulation techniques were integrated to elucidate the molecular mechanism of Fla interaction with key antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) at the molecular level. Meanwhile, we further revealed the cellular responses of SOD and CAT and the associated redox states in earthworm (Eisenia fetida) coelomocytes based on the molecular-level results. Our results showed that the exposure to Fla affected the backbone structure of SOD and CAT molecules and resulted in the formation of Fla-SOD polymers as well as an overall reduction in the size of the Fla-CAT binding system. Fla altered the microenvironment around Tyr residues in the SOD molecule and quenched the endogenous fluorescence of Tyr within the CAT molecule. In earthworm coelomocytes, Fla at 60 and 80 μM resulted in a significant elevation of CAT and SOD activities by 114% (p = 0.032) and 6.09% (p = 0.013), respectively. Molecular simulation results suggested that Fla-induced changes in the structure and conformation of SOD and CAT may be the key reason for their altered activities. The related redox homeostasis detection in earthworm coelomocytes indicated that high concentrations (80 μM) of Fla led to a significant accumulation of intracellular ROS (p = 0.018) and resulted in the development of lipid peroxidation. Our work contributes to an in-depth understanding of the biological effect of Fla to sensitive soil fauna, thus providing new ideas for Fla ecological risk prevention and control.

Involvement of oxidative stress-related apoptosis in chlorpyrifos-induced cytotoxicity and the ameliorating potential of the antioxidant vitamin E in human glioblastoma cells

Organophosphate pesticides (OPs), which are among the most widely used synthetic chemicals for the control of a wide variety of pests, are however associated with various adverse reactions in animals and humans. Chlorpyrifos, an OP, has been shown to cause various health complications due to ingestion, inhalation, or skin absorption. The mechanisms underlying the adverse effect of chlorpyrifos on neurotoxicity have not been elucidated. Therefore, we aimed to determine the mechanism of chlorpyrifos-induced cytotoxicity and to examine whether the antioxidant vitamin E (VE) ameliorated these cytotoxic effects using DBTRG-05MG, a human glioblastoma cell line. The DBTRG-05MG cells were treated with chlorpyrifos, VE, or chlorpyrifos plus VE and compared with the untreated control cells. Chlorpyrifos induced a significant decrease in cell viability and caused morphological changes in treated cultures. Furthermore, chlorpyrifos led to the increased production of reactive oxygen species (ROS) accompanied by a decrease in the level of reduced glutathione. Additionally, chlorpyrifos induced apoptosis by upregulating the protein levels of Bax and cleaved caspase-9/caspase-3 and by downregulating the protein levels of Bcl-2. Moreover, chlorpyrifos modulated the antioxidant response by increasing the protein levels of Nrf2, HO-1, and NQO1. However, VE reversed the cytotoxicity and oxidative stress induced by chlorpyrifos treatment in DBTRG-05MG cells. Overall, these findings suggest that chlorpyrifos causes cytotoxicity through oxidative stress, a process that may play an important role in the development of chlorpyrifos-associated glioblastoma.

Network Toxicology and Molecular Docking to Investigate the Non-AChE Mechanisms of Organophosphate-Induced Neurodevelopmental Toxicity

Organophosphate pesticides (OPs) are toxic substances that contaminate aquatic environments, interfere with the development of the nervous system, and induce Neurodevelopmental Toxicity (NDT) in animals and humans. The canonical mechanism of OP neurotoxicity involves the inhibition of acetylcholinesterase (AChE), but other mechanisms non-AChE are also involved and not fully understood. We used network toxicology and molecular docking to identify molecular targets and toxicity mechanisms common to OPs. Targets related to diazinon-oxon, chlorpyrifos oxon, and paraoxon OPs were predicted using the Swiss Target Prediction and PharmMapper databases. Targets related to NDT were compiled from GeneCards and OMIM databases. In order to construct the protein-protein interaction (PPI) network, the common targets between OPs and NDT were imported into the STRING. Network topological analyses identified EGFR, MET, HSP90AA1, and SRC as hub nodes common to the three OPs. Using the Reactome pathway and gene ontology, we found that signal transduction, axon guidance, cellular responses to stress, and glutamatergic signaling activation play key roles in OP-induced NDT.

Neurobehavioral Responses and Toxic Brain Reactions of Juvenile Rats Exposed to Iprodione and Chlorpyrifos, Alone and in a Mixture

Herein, male juvenile rats (23th postnatal days (PND)) were exposed to chlorpyrifos (CPS) (7.5 mg/kg b.wt) and/or iprodione (IPD) (200 mg IPD /kg b.wt) until the onset of puberty (60th day PND). Our results demonstrated that IPD and/or CPS exposure considerably reduced locomotion and exploration. However, CPS single exposure induced anxiolytic effects. Yet, neither IPD nor IPD + CPS exposure significantly affected the anxiety index. Of note, IPD and/or CPS-exposed rats showed reduced swimming time. Moreover, IPD induced significant depression. Nonetheless, the CPS- and IPD + CPS-exposed rats showed reduced depression. The individual or concurrent IPD and CPS exposure significantly reduced TAC, NE, and AChE but increased MDA with the maximum alteration at the co-exposure. Moreover, many notable structural encephalopathic alterations were detected in IPD and/or CPS-exposed rat brain tissues. The IPD + CPS co-exposed rats revealed significantly more severe lesions with higher frequencies than the IPD or CPS-exposed ones. Conclusively, IPD exposure induced evident neurobehavioral alterations and toxic reactions in the brain tissues. IPD and CPS have different neurobehavioral effects, particularly regarding depression and anxiety. Hence, co-exposure to IPD and CPS resulted in fewer neurobehavioral aberrations relative to each exposure. Nevertheless, their simultaneous exposure resulted in more brain biochemistry and histological architecture disturbances.

Antiovarian cancer mechanism of esculetin: inducing G0/G1 arrest and apoptosis via JAK2/STAT3 signalling pathway

OBJECTIVES

Esculetin is a coumarin derivative, which is extracted from the dried barks of fraxinus chinensis Roxb. Although it is reported esculetin possesses multiple pharmacological activities, its associated regulatory mechanism on ovarian cancer isn't well investigated.

METHODS

Cytotoxicity is evaluated by MTT, clonogenic and living/dead cells staining assays. Migration and invasion effects are investigated by wound healing, and transwell assays. The effect of cell cycle and apoptosis are analyzed by flow cytometry and western blotting. Mitochondrial membrane potential and intracellular reactive oxygen species (ROS) is assessed by fluorescence microscope. Analysis of animal experiments are carried out by various pathological section assays.

KEY FINDINGS

Esculetin exerts an anti- ovarian cancer effect. It is found that apoptosis induction is promoted by the accumulation of excessive ROS and inhibition of JAK2/STAT3 signalling pathway. In addition, exposure to esculetin leads to the cell viability reduction, migration and invasion capability decrease and G0/G1 phase cell cycle arrest induced by down-regulating downstream targets of STAT3. In vivo experimental results also indicate esculetin can inhibit tumour growth of mice.

CONCLUSIONS

Our study provides some strong evidences to support esculetin as a potential anti-cancer agent in ovarian cancer.

Pesticides as a risk factor for cognitive impairment: Natural substances are expected to become alternative measures to prevent and improve cognitive impairment

Pesticides are the most effective way to control diseases, insects, weeds, and fungi. The central nervous system (CNS) is damaged by pesticide residues in various ways. By consulting relevant databases, the systemic relationships between the possible mechanisms of pesticides damage to the CNS causing cognitive impairment and related learning and memory pathways networks, as well as the structure-activity relationships between some natural substances (such as polyphenols and vitamins) and the improvement were summarized in this article. The mechanisms of cognitive impairment caused by pesticides are closely related. For example, oxidative stress, mitochondrial dysfunction, and neuroinflammation can constitute three feedback loops that interact and restrict each other. The mechanisms of neurotransmitter abnormalities and intestinal dysfunction also play an important role. The connection between pathways is complex. NMDAR, PI3K/Akt, MAPK, Keap1/Nrf2/ARE, and NF-κB pathways can be connected into a pathway network by targets such as Ras, Akt, and IKK. The reasons for the improvement of natural substances are related to their specific structure, such as polyphenols with different hydroxyl groups. This review's purpose is to lay a foundation for exploring and developing more natural substances that can effectively improve the cognitive impairment caused by pesticides.

Succinate prodrugs in combination with atropine and pralidoxime protect cerebral mitochondrial function in a rodent model of acute organophosphate poisoning

Pesticides account for hundreds of millions of cases of acute poisoning worldwide each year, with organophosphates (OPs) being responsible for the majority of all pesticide-related deaths. OPs inhibit the enzyme acetylcholinesterase (AChE), which leads to impairment of the central- and peripheral nervous system. Current standard of care (SOC) alleviates acute neurologic-, cardiovascular- and respiratory symptoms and reduces short term mortality. However, survivors often demonstrate significant neurologic sequelae. This highlights the critical need for further development of adjunctive therapies with novel targets. While the inhibition of AChE is thought to be the main mechanism of injury, mitochondrial dysfunction and resulting metabolic crisis may contribute to the overall toxicity of these agents. We hypothesized that the mitochondrially targeted succinate prodrug NV354 would support mitochondrial function and reduce brain injury during acute intoxication with the OP diisopropylfluorophosphate (DFP). To this end, we developed a rat model of acute DFP intoxication and evaluated the efficacy of NV354 as adjunctive therapy to SOC treatment with atropine and pralidoxime. We demonstrate that NV354, in combination with atropine and pralidoxime therapy, significantly improved cerebral mitochondrial complex IV-linked respiration and reduced signs of brain injury in a rodent model of acute DFP exposure.

Cognitive Impairment and Neurodegenerative Diseases Development Associated with Organophosphate Pesticides Exposure: a Review Study

A significant body of literature emphasizes the role of insecticide, particularly organophosphates (OPs), as the major environmental factor in the etiology of neurodegenerative diseases. This review aims to study the relationship between OP insecticide exposure, cognitive impairment, and neurodegenerative disease development. Human populations, especially in developing countries, are frequently exposed to OPs due to their extensive applications. The involvement of various signaling pathways in OP neurotoxicity are reported, but the OP-induced cognitive impairment and link between OP exposure and the pathophysiology of neurodegenerative diseases are not clearly understood. In the present review, we have therefore aimed to come to new conclusions which may help to find protective and preventive strategies against OP neurotoxicity and may establish a possible link between organophosphate exposure, cognitive impairment, and OP-induced neurotoxicity. Moreover, we discuss the findings obtained from animal and human research providing some support for OP-induced cognitive impairment and neurodegenerative disorders.

Neuroprotective efficacy of berberine following developmental exposure to chlorpyrifos in F1 generation of Wistar rats: Apoptosis-autophagy interplay

Chlorpyrifos (CPF), an organophosphate insecticide commonly used in agriculture and household applications, is considered a developmental neurotoxicant. This study aimed to explain the neuroprotective role of Berberine (BBR) against CPF-induced autophagy dysfunction and apoptotic neurodegeneration in the developing hippocampus. F1 generation of Wistar rats was exposed to CPF (3 mg/kg b.wt.) and co-treated with BBR (10 mg/kg b.wt) in two different exposure regimens, gestational (GD9-12 and GD17-21) and lactational (PND1-20). Our results demonstrated that CPF intoxication instigated cognitive and neurobehavioral impairment, oxidant-antioxidant imbalance, and histomorphological alterations in CA1, CA3, and DG regions of the offsprings. Furthermore, mRNA expression of pro-apoptotic genes (caspase3 and Bax) was upregulated, and that of anti-apoptotic BCl₂ was downregulated. In addition, exposure to CPF also activated the autophagy inhibitor (mTOR) transcription and subsequently downregulated the expression of autophagy markers beclin1 and LC3-II. In contrast, gestational and lactational co-treatment of BBR significantly upregulated the enzymatic anti-oxidant bar of the hippocampus and attenuated histological alterations. Moreover, BBR co-treatments reduced apoptotic neurodegeneration in the hippocampal region by regulating the expression of apoptotic genes and upregulated the levels of autophagy, confirmed by ultrastructural studies, decreased gene expression and immunostaining of mTOR and increased, and increased expression gene expression and immunostaining of LC3-II positive cells. Our results confirm that treatment with BBR induces autophagy, which plays a neuroprotective role in CPF-induced developmental neuronal apoptosis in the F1 generation of Wistar rats by regulating the balance between autophagy and apoptosis.

Building a Network of Adverse Outcome Pathways (AOPs) Incorporating the Tau-Driven AOP Toward Memory Loss (AOP429)

The adverse outcome pathway (AOP) concept was first proposed as a tool for chemical hazard assessment facilitating the regulatory decision-making in toxicology and was more recently recommended during the BioMed21 workshops as a tool for the characterization of crucial endpoints in the human disease development. This AOP framework represents mechanistically based approaches using existing data, more realistic and relevant to human biological systems. In principle, AOPs are described by molecular initiating events (MIEs) which induce key events (KEs) leading to adverse outcomes (AOs). In addition to the individual AOPs, the network of AOPs has been also suggested to beneficially support the understanding and prediction of adverse effects in risk assessment. The AOP-based networks can capture the complexity of biological systems described by different AOPs, in which multiple AOs diverge from a single MIE or multiple MIEs trigger a cascade of KEs that converge to a single AO. Here, an AOP network incorporating a recently proposed tau-driven AOP toward memory loss (AOP429) related to sporadic (late-onset) Alzheimer’s disease is constructed. This proposed AOP network is an attempt to extract useful information for better comprehending the interactions among existing mechanistic data linked to memory loss as an early phase of sporadic Alzheimer’s disease pathology.

Ameliorative potential of vitamin C and E against Roundup-glyphosate induced genotoxicity triggering apoptosis in caprine granulosa cells

The present study was aimed to investigate the genotoxic and apoptotic effects of glyphosate (GLP) in Roundup formulation along with mitigation of two potent antioxidants that is, vitamin C and E in caprine granulosa cells in vitro. The entire work was done in a dose and time dependent manner where different concentrations of GLP (0.1, 2.0, and 4.0 mg/ml) in Roundup and antioxidants (0.5 and 1.0 mM) were employed to culture of granulosa cells for exposure durations of 24, 48, and 72 h. Analysis of GLP-induced geno-toxicity was accomplished by using single cell gel electrophoresis (comet assay) assay. Results have shown increased incidences of DNA fragmentation, evidenced by presence of different types of comets (Type 1-Type 4) in Roundup-GLP- exposed groups in contrast to the control group (Type 0 comet). However, mitigation by both vitamin C and E was significant (p < .05) in combating the GLP-induced genotoxicity in granulosa cells in a concentration- and time-dependent manner. The results of our study provide a clear indication of the ameliorative actions of vitamin C and E against Roundup-GLP-induced genotoxicity that instigate apoptosis in ovarian granulosa cells of caprine.

Modulation of CREB and its associated upstream signaling pathways in pesticide-induced neurotoxicity

Human beings are exposed to various environmental xenobiotics throughout their life consisting of a broad range of physical and chemical agents that impart bodily harm. Among these, pesticide exposure that destroys insects mainly by damaging their central nervous system also exerts neurotoxic effects on humans and is implicated in the etiology of several degenerative disorders. The connectivity between CREB (cAMP Response Element Binding Protein) signaling activation and neuronal activity is of broad interest and has been thoroughly studied in various diseased states. Several genes, as well as protein kinases, are involved in the phosphorylation of CREB, including BDNF (Brain-derived neurotrophic factor), Pi3K (phosphoinositide 3-kinase), AKT (Protein kinase B), RAS (Rat Sarcoma), MEK (Mitogen-activated protein kinase), PLC (Phospholipase C), and PKC (Protein kinase C) that play an essential role in neuronal plasticity, long-term potentiation, neuronal survival, learning, and memory formation, cognitive function, synaptic transmission, and suppressing apoptosis. These elements, either singularly or in a cascade, can result in the modulation of CREB, making it a vulnerable target for various neurotoxic agents, including pesticides. This review provides insight into how these various intracellular signaling pathways converge to bring about CREB activation and how the activated or deactivated CREB levels can affect the gene expression of the upstream molecules. We also discuss the various target genes within the cascade vulnerable to different types of pesticides. Thus, this review will facilitate future investigations associated with pesticide neurotoxicity and identify valuable therapeutic targets.

A Pretreatment with Isoorientin Attenuates Redox Disruption, Mitochondrial Impairment, and Inflammation Caused by Chlorpyrifos in a Dopaminergic Cell Line: Involvement of the Nrf2/HO-1 Axis

The C-glucosyl flavone isoorientin (ISO) is obtained by humans from the diet and exhibits several cytoprotective effects, as demonstrated in different experimental models. However, it was not previously shown whether ISO would be able to prevent mitochondrial impairment in cells exposed to a chemical stressor. Thus, we treated the human neuroblastoma SH-SY5Y cells with ISO (0.5-20 µM) for 18 h before a challenge with chlorpyrifos (CPF) at 100 µM for additional 24 h. We observed that ISO prevented the CPF-induced lipid peroxidation and protein carbonylation and nitration in the membranes of mitochondria extracted from CPF-treated cells. ISO also attenuated the CPF-elicited increase in the production of reactive species in this experimental model. Moreover, ISO prevented the CPF-induced disruption in the activity of components of the oxidative phosphorylation (OXPHOS) system in the SH-SY5Y cells. ISO also promoted an anti-inflammatory action in the cells exposed to CPF. CPF caused a decrease in the activity of the enzyme heme oxygenase-1 (HO-1), a cytoprotective agent. On the other hand, ISO upregulated HO-1 activity in SH-SY5Y cells. Inhibition of HO-1 by zinc protoporphyrin-IX (ZnPP-IX) suppressed the cytoprotection induced by ISO in the CPF-treated cells. Besides, silencing of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) abolished the ISO-induced HO-1 upregulation and mitochondrial benefits induced by this flavone on the CPF-challenged cells. Thus, ISO protected mitochondria of the CPF-treated cells by an Nrf2/HO-1-dependent fashion in the SH-SY5Y cells.

Crocin Protects Malathion-Induced Striatal Biochemical Deficits by Inhibiting Apoptosis and Increasing α-Synuclein in Rats' Striatum

Long-term exposure to organophosphates might result in neurodegenerative diseases, comprising Parkinson's disease. Malathion is an organophosphate pesticide with high neurotoxicity. Oxidative stress, apoptosis, and α-synuclein accumulation are important underlying mechanisms in Parkinson's disease. According to studies, crocin, an active constituent of saffron, has anti-apoptotic, anti-inflammatory, and antioxidant properties. Thus, the effect of crocin on malathion-induced striatal biochemical deficits in rats was investigated in this study. Six groups of male Wistar rats were used: 1. control (normal saline); 2. malathion (100 mg/kg/day, i.p.); 3. crocin (10 mg/kg/day, i.p.) + malathion; 4. levodopa (10 mg/kg/day, i.p.) + malathion; 5. crocin (40 mg/kg/day, i.p.); and 6. polyethylene glycol (PEG) (vehicle of levodopa) groups. The drugs were administered for 28 days. The amounts of Bcl-2, Bax, and caspases 3, 8, and 9 proteins in the striatum were measured by western blotting. Also, the amounts of protein and mRNA level of the α-synuclein in striatum tissue were measured by western blotting and RT-qPCR methods. Malathion induced apoptosis by increasing the amount of Bax/Bcl2 ratio and caspases 3 and 9 proteins in rat striatum tissue. It also increased the protein and mRNA level of α-synuclein in striatal tissue. Co-administration of crocin or levodopa with malathion inhibited the toxic effects of malathion on striatal tissue. Crocin ameliorates the neurotoxic effect of malathion by its anti-apoptotic activity and regulating the expression of proteins involved in Parkinson's disease pathogenesis. As a result, crocin has the potential to be used as a treatment for malathion-induced neurotoxicity.

Ovarian Oxidative Stress Induced Follicle Depletion After Zona Pellucida 3 Vaccination Is Associated With Subfertility in BALB/c Mice

Impaired follicular development associated with autoimmune ovarian disease (AOD), is a typical side effect of ZP3 vaccine-induced subfertility and contributes to the fertility decline, but the mechanism is unknown. In this study, a AOD model was established with recombinant mouse zona pellucida 3 (mZP3) protein in the BALB/c mice, and co-administrated with 0.5 mg/kg antioxidant stress drug sodium selenite (SS), whereas intraperitoneal injection was used and the relationships among oxidant stress (OS), follicle loss and fertility were evaluated. Here we demonstrated that ZP3 vaccination elicited high antibody titers and correlated with reductions of ovarian follicle numbers in both fertile and infertile mice, whereby magnitudes of both factors were negatively correlated with litter size. Moreover, increased OS in ovaries of mZP3-immunized mice was related to high levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and is accompanied by a decrease in the total antioxidant capacity (TAC) of ovaries. Meanwhile, activation of caspase-3 and caspase-9 along with increased Bax and decreased Bcl-2 levels were observed, indicating the ongoing apoptosis of ovarian cells. Notably, inhibition of OS with SS reduced ovarian ROS and apoptosis levels, which was consisted with restoration of follicle numbers. More importantly, SS treatment when co-administered concurrently with mZP3 immunization led to significantly improved fertility (P < 0.05) and the average litter size of the mZP3-vaccinated SS-treated group increased by ~29.2% as compared with that of the vaccinated but untreated group. In conclusion, infertility caused by ZP3 vaccination was mechanistically associated with ovarian OS which triggered depletion of ovarian follicles.

A Common Feature of Pesticides: Oxidative Stress-The Role of Oxidative Stress in Pesticide-Induced Toxicity

Pesticides are important chemicals or biological agents that deter or kill pests. The use of pesticides has continued to increase as it is still considered the most effective method to reduce pests and increase crop growth. However, pesticides have other consequences, including potential toxicity to humans and wildlife. Pesticides have been associated with increased risk of cardiovascular disease, cancer, and birth defects. Labels on pesticides also suggest limiting exposure to these hazardous chemicals. Based on experimental evidence, various types of pesticides all seem to have a common effect, the induction of oxidative stress in different cell types and animal models. Pesticide-induced oxidative stress is caused by both reactive oxygen species (ROS) and reactive nitrogen species (RNS), which are associated with several diseases including cancer, inflammation, and cardiovascular and neurodegenerative diseases. ROS and RNS can activate at least five independent signaling pathways including mitochondrial-induced apoptosis. Limited in vitro studies also suggest that exogenous antioxidants can reduce or prevent the deleterious effects of pesticides.

In vitro cytotoxicity and genotoxicity of single and combined pesticides used by Bolivian farmers

We previously showed that farmers in Bolivia are exposed to many pesticides, some at elevated levels, and that this was associated with increased risk of genetic damage. To improve the understanding of possible mixture effects, the cytotoxicity and genotoxicity of pesticides were studied in vitro using human liver HepG2 cells. The studied pesticides were 2,4-D, chlorpyrifos, cypermethrin, glyphosate, methamidophos, paraquat, profenofos, and tebuconazole. Three mixtures (U1, U2, and U3) were based on profiles of urinary pesticide metabolites and one mixture on the most frequently used pesticides (S1). The results showed that paraquat and methamidophos were the most cytotoxic pesticides (EC₅₀ ≤0.3 mM). Paraquat, chlorpyrifos, tebuconazole, and the U1, U2, and U3 mixtures, which contained a large proportion of either chlorpyrifos or tebuconazole, significantly increased intracellular ROS levels. Most pesticides activated DNA damage signaling through proteins Chk1 and H2AX. Strongest responses were elicited by paraquat, profenofos, chlorpyrifos, cypermethrin, and the S1 mixture, which contained 25% paraquat. Comet assay revealed significant increases of DNA damage in response to paraquat, cypermethrin, and U2 and S1 mixtures, which contained high levels of cypermethrin and paraquat, respectively. In summary, we showed that the tested pesticides, alone or in mixtures, in general induced oxidative stress and that most pesticides, and especially paraquat and cypermethrin, were genotoxic in HepG2 cells. We could also show that mixtures dominated by these two pesticides displayed a marked genotoxic potency, which agreed with our previous population studies.

Chlorpyrifos caused necroptosis via MAPK/NF-κB/TNF-α pathway in common carp (Cyprinus carpio L.) gills

Chlorpyrifos (CPF) is an organophosphate insecticide and can cause cell death of animals. In the study, the common carp were exposed to CPF at 0 μg/L (the control group), 1.16 μg/L (the low dose group), 11.6 μg/L (the medium dose group), and 116 μg/L (the high dose group), respectively. The carp were euthanized at the 30th day and gills were collected immediately. The ultrastructural and histopathological observations showed obvious necrosis characteristics and inflammatory injury in the CPF-treated groups. CPF exposure activated the MAPK pathway, in which the mRNA and protein expressions of extracellular signal-regulated (ERK), p38 MAP kinase (p38), and c-Jun N-terminal kinase (JNK) were increased; the mRNAs and proteins of NF-κB and TNF-α were activated; and the mRNAs and proteins of necroptosis related genes were changed (the mRNA and protein expression of RIPK1, RIPK3, MLKL, and FADD were increased and caspase-8 was decreased) with concentration dependency. Taken together, we concluded that CPF exposure activated the MAPK/NF-κB/TNF-α pathway, promoted inflammatory injure and evoked necroptosis in common carp gills. In addition, CPF-induced inflammation and necroptosis was concentration dependency. The toxic effects of CPF on gills provided data for both aquaculture and toxicological studies.

3-Indolepropionic acid upturned male reproductive function by reducing oxido-inflammatory responses and apoptosis along the hypothalamic-pituitary-gonadal axis of adult rats exposed to chlorpyrifos

We examined the effect of 3-Indolepropionic acid (3-IPA), an antioxidant on the organophosphorus pesticide chlorpyrifos (CPF)-induced reproductive toxicity in rats. The five experimental rat cohorts were treated per os for 14 consecutive days as follows: Control (Corn oil 2 mL/kg body weight), CPF alone (5 mg/kg), 3-IPA alone (40 mg/kg) and the co-treated rat cohorts (CPF:5 mg/kg + 3-IPA: 20 or 40 mg/kg). Biomarkers of testicular and epididymal function, oxidative stress, myeloperoxidase (MPO) activity and the levels of nitric oxide (NO), reactive oxygen and nitrogen (RONS) species and lipid peroxidation (LPO) were assessed. Also, tumour necrosis factor-alpha (TNF-α), Bcl-2-associated X (Bax) and B cell lymphoma 2 (Bcl-2) proteins were estimated, and tissue histology was microscopically examined. CPF alone significantly (p < 0.05) increased biomarkers of reproductive toxicities were averted in rats co-treated 3-IPA. Decreases in antioxidants and increases in lipid peroxidation and reactive oxygen and nitrogen species were lessened (p < 0.05) in CPF and 3-IPA co-treated rats. CPF mediated increases in TNF-α, NO, Bax, and MPO activity was reduced (p < 0.05) in the epididymis, testes, and hypothalamus of rats co-treated with 3-IPA. In addition, Bcl-2 expression was increased in rats co-treated with 3-IPA dose-dependently. Histopathological examination revealed severe lesions induced by CPF were prevented in rats co-treated with 3-IPA. Our findings demonstrate that exogenous 3-IPA reduced CPF-induced oxidative stress, inflammation, and apoptosis in the epididymis and testes of male rats.

Oxytocin Attenuates Methamphetamine-Induced Apoptosis via Oxytocin Receptor in Rat Hippocampal Neurons

Methamphetamine (METH) is a highly neurotoxic psychoactive substance that can directly damage the central nervous system through prolonged use. Oxytocin (OT) has attracted much attention because of its neuroprotective effect. The purpose of this study was to investigate whether OT is neuroprotective against METH-induced damage in rat hippocampal neurons. Our results revealed that pre-incubation with OT significantly prevented the damage of METH to hippocampal neurons, including the decrease of mitochondrial membrane potential and the increase of ROS (reactive oxygen species). OT pre-incubation attenuated the up-regulation of Cleaved-Caspase-3 expression and the down-regulation of Bcl-2/Bax expression induced by METH. Pre-incubation with OT prevented the decrease in oxytocin receptor density and P-CREB (phosphorylation of cAMP-response element binding) expression induced by METH in rat hippocampal neurons. Moreover, Pre-incubation of atosiban (ATO) significantly prevented these changes. In conclusion, our study proved that pre-administration of OT could significantly attenuate hippocampal neuron apoptosis induced by METH. Oxytocin receptor activation is involved in the preventive effect of OT on METH-induced apoptosis in rat hippocampal neurons.

Corticosterone and chlorpyrifos oxon exposure elicits spatiotemporal MAPK phosphoprotein signaling in a mouse brain

Chlorpyrifos (CPF) is one of the most widely-used pesticides globally for agricultural purposes. Certain occupations (e.g., farmers, military) are at an increased risk for high-dose exposure to CPF, which can lead to seizures and irreversible brain injury. Workers with the highest risk of exposure typically experience increased circulating cortisol levels, which is related to physiological stress. To better represent this exposure scenario, a mouse model utilized exogenous administration of corticosterone (CORT; high physiologic stress mimic) in combination with chlorpyrifos oxon (CPO; oxon metabolite of CPF); this combination increases neuroinflammation post-exposure. In the present study adult male C57BL/6J mice were given CORT (200 μg/mL) in drinking water for seven days followed by a single intraperitoneal injection of CPO (8.0 mg/kg) on day eight, and euthanized 0.5, 2, and 24 h post-injection. Ten post-translationally modified proteins were measured in the frontal cortex and striatum to evaluate brain region-specific effects. The spatiotemporal response to CORT + CPO sequentially activated phosphoproteins (p-ERK1/2, p-MEK1/2, p-JNK) involved in mitogen-activated protein kinase (MAPK) signaling. Observed p-ZAP70 responses further integrated MAPK signaling and provided a spatiotemporal connection between protein phosphorylation and neuroinflammation. This study provides insight into the spatiotemporal cellular signaling cascade following CORT + CPO exposure that represent these vulnerable populations.

Impact of environmental toxicants on p38- and ERK-MAPK signaling pathways in the central nervous system

There are several candidate signalling pathways that mediate the response of the central nervous system (CNS) cells to environmental toxins. However, much is still to be learned on how these pathways modulate neurotoxicity. The mitogen-activated protein kinases (MAPKs) signalling pathways, which include the extracellular signal-regulated protein kinase (ERK) and the p38-MAPK, are potentially key pathways to regulate CNS responses to environmental toxins. The pathways play leading roles in the transmission of extracellular signals into the cell nucleus, leading to cell differentiation, cell growth, and apoptosis, to name a few. Moreover, exposure to environmental toxins induces p38- and ERK-MAPK activation, which leads to oxidative stress, inflammation, and apoptosis in the CNS. Here, we provide a concise review of the recent evidence demonstrating the role of p38- and ERK-MAPK signaling pathways and their downstream targets in the CNS following exposure to environmental toxicants such as metals, organophosphorus and persistent organic pollutants.

Lyciumamide A, a dimer of phenolic amide, protects against NMDA-induced neurotoxicity and potential mechanisms in vitro

Currently, the excessive activation of N-methyl-D-aspartate receptors (NMDARs) is considered to be a crucial mechanism of brain injury. Lycium barbarum A (LyA) is a dimer of phenol amides isolated from the fruit of Lycium barbarum. Our previous studies have shown that LyA has potential antioxidant activity. This study aimed to explore the neuroprotective effect of LyA and its potential mechanism. Firstly, the molecular docking was used to preliminarily explore the potential function of LyA to block NMDAR. Then, the ability of LyA was further verified by NMDA-induced human neuroblastoma SH-SY5Y cells in vivo. Treatment with LyA significantly attenuated NMDA-induced neuronal insults by increasing cell viability, reducing lactate dehydrogenase (LDH) release, and increasing cell survival. Meanwhile, LyA significantly reversed the increase in intracellular calcium and in ROS production induced by NMDA. Finally, the western blot indicated that LyA could suppress the Ca²⁺ influx and increase the p-NR2B, p-CaMKII, p-JNK, and p-p38 level induced by NMDA. These above findings provide evidence that LyA protect against brain injury, and restraining NMDARs and suppressing mitochondrial oxidative stress and inhibiting cell apoptosis may be involved in the protective mechanism.

Hormetic Effects of Binaphthyl Phosphonothioates as Pro-oxidants and Antioxidants

Organophosphorous compounds with such a wide variety in structure, application, and biochemical activities include pesticides, herbicides, nerve agents, medicines, reagents in organic chemistry, and additives for polymers. Binaphthyl phosphono-, phosphorothioates, and their derivatives, are useful chiral catalysts for various asymmetric reactions and are expected to act as heavy metal scavengers. In this study, we aimed to evaluate the neurotoxicity and biochemical properties of a new series of binaphthyl phosphonothioates called KK compounds using the mouse hippocampal HT22 cells. Despite negligible structural difference, the compounds exhibited differential general cytotoxic activity which was independent of acetylcholine esterase inhibition; on the other hand, all compounds tested prevented endogenous oxidative stress by suppressing generation of reactive oxygen species. Among them, KK397, KK387, KK410, and KK421 showed hormesis, i.e., biphasic dose responses to endogenous oxidative stress, characterized by beneficial effect at low dose and toxic effect at high dose. At cytotoxic concentrations, these compounds were potent radical generators and activated intracellular signaling molecules such as the p38 mitogen-activated protein kinase, c-Jun NH₂-terminal kinase, growth arrest- and DNA damage-inducible gene 153, X-box binding protein 1, and heme oxygenase 1, which are preferentially activated by cell stress-inducing signals, including oxidative and endoplasmic reticulum stress. These findings indicated that novel binaphthyl phosphonothioates can exhibit multiple biochemical properties, functioning as antioxidants and/or pro-oxidants, depending on the concentration, and chemical modification of binaphthyl organophosphorus compounds endowed them with unique characteristics and multiple beneficial functions.

Glutathione in Chlorpyrifos-and Chlorpyrifos-Oxon-Induced Toxicity: a Comparative Study Focused on Non-cholinergic Toxicity in HT22 Cells

Chlorpyrifos (CPF) is a neurotoxic organophosphorus (OP) insecticide widely used for agricultural purposes. CPF-mediated neurotoxicity is mainly associated with its anticholinesterase activity, which may lead to a cholinergic syndrome. CPF metabolism generates chlorpyrifos-oxon (CPF-O), which possesses higher anticholinesterase activity and, consequently, plays a major role in the cholinergic syndrome observed after CPF poisoning. Recent lines of evidence have also reported non-cholinergic endpoints of CPF- and CPF-O-induced neurotoxicities, but comparisons on the non-cholinergic toxic properties of CPF and CPF-O are lacking. In this study, we compared the non-cholinergic toxicities displayed by CPF and CPF-O in cultured neuronal cells, with a particular emphasis on their pro-oxidant properties. Using immortalized cells derived from mouse hippocampus (HT22 line, which does present detectable acetylcholinesterase activity), we observed that CPF-O was 5-fold more potent in decreasing cell viability compared with CPF. Atropine, a muscarinic acetylcholine receptor antagonist, protected against acetylcholine (ACh)-induced toxicity but failed to prevent the CPF- and CPF-O-induced cytotoxicities in HT22 cells. CPF or CPF-O exposures significantly decreased the levels of the antioxidant glutathione (GSH); this event preceded the significant decrease in cell viability. Pretreatment with N-acetylcysteine (NAC, a GSH precursor) protected against the cytotoxicity induced by both CPF and CPF-O. The present study indicates that GSH depletion is a non-cholinergic event involved in CPF and CPF-O toxicities. The study also shows that in addition of being a more potent AChE inhibitor, CPF-O is also a more potent pro-oxidant molecule when compared with CPF, highlighting the role of CPF metabolism (bioactivation to CPF-O) in the ensuing non-cholinergic toxicity.

Chlorpyrifos-induced toxicity has no gender selectivity in the early fetal brain

Organophosphorus pesticides induce gender-specific developmental neurotoxicity after birth, especially in adolescents and adults. However, whether and when the selectivity occurs in fetus remains unclear. In this study, we analyzed chlorpyrifos (CPF)-induced neurotoxicity in the early fetal brains of male and female mice. The gestational dams were administered 0, 1, 3, and 5 mg/(kg.d) CPF during gestational days (GD)7-11, and brains from the fetuses were isolated and analyzed on GD12. Fetal gender was identified by PCR technique based on male-specific Sry gene and Myog control gene. The body weight and head weight, the activity of acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and the content of malondialdehyde (MDA), as well as the oxidative stress-related gene expression were examined. Our results showed that CPF pretreatment induced AChE inhibition in GD12 fetal brain. CPF treatment activated SOD and GPX but not CAT and MDA. For oxidative stress-related gene expression, CPF pretreatment increased mRNA expression of Sod1, Cat, Gpx1, and Gpx2 in the fetal brain on GD12. The statistical analysis did not show gender-selective CPF-induced toxicity. Moreover, our results showed that although the gestational exposure to CPF could elicit abnormalities in the early fetal brain, the toxicity observed was not gender-specific.

Organophosphorus Compounds and MAPK Signaling Pathways

The molecular signaling pathways that lead to cell survival/death after exposure to organophosphate compounds (OPCs) are not yet fully understood. Mitogen-activated protein kinases (MAPKs) including the extracellular signal-regulated protein kinase (ERK), the c-Jun NH2-terminal kinase (JNK), and the p38-MAPK play the leading roles in the transmission of extracellular signals into the cell nucleus, leading to cell differentiation, cell growth, and apoptosis. Moreover, exposure to OPCs induces ERK, JNK, and p38-MAPK activation, which leads to oxidative stress and apoptosis in various tissues. However, the activation of MAPK signaling pathways may differ depending on the type of OPCs and the type of cell exposed. Finally, different cell responses can be induced by different types of MAPK signaling pathways after exposure to OPCs.

Mitochondrial respiratory chain complex I dysfunction induced by N-methyl carbamate ex vivo can be alleviated with a cell-permeable succinate prodrug

Human exposure to carbamates and organophosphates poses a serious threat to society and current pharmacological treatment is solely targeting the compounds' inhibitory effect on acetylcholinesterase. This toxicological pathway, responsible for acute symptom presentation, can be counteracted with currently available therapies such as atropine and oximes. However, there is still significant long-term morbidity and mortality. We propose mitochondrial dysfunction as an additional cellular mechanism of carbamate toxicity and suggest pharmacological targeting of mitochondria to overcome acute metabolic decompensation. Here, we investigated the effects on mitochondrial respiratory function of N-succinimidyl N-methylcarbamate (NSNM), a surrogate for carbamate insecticides, ex vivo in human platelets. Characterization of the mitochondrial toxicity of NSNM in platelets revealed a dose-dependent decrease in mitochondral oxygen consumption linked to respiratory chain complex I while the pathway through complex II was unaffected. In intact platelets, an increase in lactate production was seen, due to a compensatory shift towards anaerobic metabolism. Treatment with a cell-permeable succinate prodrug restored the NSNM-induced (100 μM) decrease in mitochondrial oxygen consumption and normalized lactate production to the level of control. We have demonstrated that carbamate-induced mitochondrial complex I dysfunction can be alleviated with a mitochondrial targeted countermeasure: a cell-permeable prodrug of the mitochondrial complex II substrate succinate.

An Overview on the Effect of Neonicotinoid Insecticides on Mammalian Cholinergic Functions through the Activation of Neuronal Nicotinic Acetylcholine Receptors

Neonicotinoid insecticides are used worldwide and have been demonstrated as toxic to beneficial insects such as honeybees. Their effectiveness is predominantly attributed to their high affinity for insect neuronal nicotinic acetylcholine receptors (nAChRs). Mammalian neuronal nAChRs are of major importance because cholinergic synaptic transmission plays a key role in rapid neurotransmission, learning and memory processes, and neurodegenerative diseases. Because of the low agonist effects of neonicotinoid insecticides on mammalian neuronal nAChRs, it has been suggested that they are relatively safe for mammals, including humans. However, several lines of evidence have demonstrated that neonicotinoid insecticides can modulate cholinergic functions through neuronal nAChRs. Major studies on the influence of neonicotinoid insecticides on cholinergic functions have been conducted using nicotine low-affinity homomeric α7 and high-affinity heteromeric α4β2 receptors, as they are the most abundant in the nervous system. It has been found that the neonicotinoids thiamethoxam and clothianidin can activate the release of dopamine in rat striatum. In some contexts, such as neurodegenerative diseases, they can disturb the neuronal distribution or induce oxidative stress, leading to neurotoxicity. This review highlights recent studies on the mode of action of neonicotinoid insecticides on mammalian neuronal nAChRs and cholinergic functions.

Croton campestris A. St.-Hill Methanolic Fraction in a Chlorpyrifos-Induced Toxicity Model in Drosophila melanogaster: Protective Role of Gallic Acid

Croton campestris A. St-Hill popularly known as "velame do campo" is a native species of the savannah from northeastern Brazil, being used in folk medicine due to its beneficial effects in the treatment of many diseases, inflammation, detoxification, gastritis, and syphilis; however, its potential use as an antidote against organophosphorus compound poisoning has not yet been shown. Here, the protective effect of the methanolic fraction of C. campestris A. St.-Hill (MFCC) in Drosophila melanogaster exposed to chlorpyrifos (CP) was investigated. Flies were exposed to CP and MFCC during 48 h through the diet. Following the treatments, parameters such as mortality, locomotor behavior, and oxidative stress markers were evaluated. Exposure of flies to CP induced significant impairments in survival and locomotor performance. In parallel, increased reactive oxygen species and lipoperoxidation occurred. In addition, the activity of acetylcholinesterase was inhibited by CP, and superoxide dismutase and glutathione S-transferase activity was induced. Treatment with MFCC resulted in a blockage of all CP-induced effects, with the exception of glutathione S-transferase. Among the major compounds found in MFCC, only gallic acid (GA) showed a protective role against CP while quercetin and caffeic acid alone were ineffective. When in combination, these compounds avoided the toxicity of CP at the same level as GA. As far as we know, this is the first study reporting the protective effect of MFCC against organophosphate toxicity in vivo and highlights the biotechnological potential of this fraction attributing a major role in mediating the observed effects to GA. Therefore, MFCC may be considered a promising source for the development of new therapeutic agents for the treatment of organophosphate intoxications.

Integrated gender-related effects of profenofos and paclobutrazol on neurotransmitters in mouse

This study investigated the effects of paclobutrazol and profenofos on six neurotransmitters and their metabolites involving in cholinergic and non-cholinergic neurotransmission systems in mouse. The results revealed that profenofos decreased the levels of 5-hydroxyindole-3-acetic acid (5-HIAA) and normetanephrine (MNE), and increased the level of dopamine (DA) in the mice after four weeks of exposure. The turnovers of serotonergic neurotransmission system (5-HIAA/5-HT) and noradrenergic neurotransmission system (MNE/NE) showed a decline under exposure of profenofos. Exposure to paclobutrazol resulted in decreases of 5-HIAA and MNE in both sexes of mice, and of 5-HT and ACh in the females. Similar to profenofos, the turnovers of serotonergic neurotransmission system and noradrenergic neurotransmission system decreased in the mice exposed to paclobutrazol. The integrated biomarker response (IBR) was introduced to comprehensively evaluate the neurotoxic effects of the two pesticides through integration of the responses of neurotransmitters. The results of IBR indicated that the overall effect of neurotransmitters increased at the beginning of exposure and then decreased in the end. It was also found that the order of neurotoxic effect for the two pesticides is as: paclobutrazol > profenofos referred to their LD50. Furthermore, the effects on neurotransmitters are higher in the males.

Nephroprotective Role of Beta vulgaris L. Root Extract against Chlorpyrifos-Induced Renal Injury in Rats

Organophosphorus pesticides (OPs) are widely used for agricultural and housekeeping purposes. Exposure to OPs is associated with the progression of several health issues. Antioxidant agents may be powerful candidates to minimise adverse reactions caused by OPs. The aim of the present study was to evaluate the nephroprotective effects of red beetroot extract (RBR) against chlorpyrifos- (CPF-) induced renal impairments. CPF induced kidney dysfunction, as demonstrated by changes in serum creatinine and urea levels. Moreover, CPF exposure induced oxidative stress in the kidneys as determined by increased malondialdehyde and nitric oxide levels, decreased glutathione content, decreased catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase activities, and decreased nuclear factor (erythroid-derived 2)-like-2 factor expression. In addition, CPF induced inflammation in renal tissue as evidenced by increased release of tumor necrosis factor-alpha and interleukin-1β and upregulation of inducible nitric oxide synthase. Furthermore, CPF promoted cell death as demonstrated by decreased Bcl-2 and increased Bax and caspase-3 levels. Treatment with RBR one hour prior to CPF treatment blocked the effects observed in response to CPF alone. Our results suggest that RBR could be used to alleviate CPF-induced nephrotoxicity through antioxidant, anti-inflammatory, and antiapoptotic activities.

Effects of chlorpyrifos on cell death and cellular phenotypic specification of human neural stem cells

Chlorpyrifos (CPF) is an organophosphate pesticide widely used in agriculture, whose traditional and well-known mechanism of action is the inhibition of the enzyme Acetylcholinesterase (AChE). Subacute exposures to CPF have been associated with alterations different from the inhibition of AChE. Because of the vulnerability of the developing nervous system, prenatal and early postnatal exposures are of special concern. Human neural stem cells (hNSC) provide the opportunity to study early stages of neural development and may be a valuable tool for developmental neurotoxicology (DNT). In the current work, the cell line hNS1 was used as a model system with the aim of validating this cell line as a reliable testing method. To evaluate the effects of CPF on early developmental stages, hNS1 cells were exposed to different concentrations of the pesticide and cell death, proliferation and cell fate specification were analyzed under differentiation conditions. Since hNS1 cells responded to CPF in a similar way to other human cell lines, we consider it may be a valid model for DNT chemical assessment. CPF induced apoptotic cell death only at the highest doses tested, suggesting that it is not toxic for the specific developmental stage here addressed under short term exposure. In addition, the higher doses of CPF promoted the generation of astroglial cells, without affecting neurogenesis.

Potential role of N-acetylcysteine on chlorpyrifos-induced neurotoxicity in rats

Chlorpyrifos (CPF) is a widely used organophosphate insecticide with several harmful effects. N-acetylcysteine (NAC) represents an ideal antixenobiotic; it can directly enter endogenous biochemical processes and is used as adjunctive treatment for psychiatric disorders. We aimed to evaluate the neuroprotective effect of NAC as an antioxidant drug against CPF-induced neurotoxicity in adult male albino rat brains. Twenty-eight male Wister rats were allocated into four groups (n = 7) and were administered the following for 28 days: group I (control group), physiological saline (0.9% NaCl); group II (CPF group), 10 mg/kg body weight (BW) CPF; group III (NAC group), 100 mg/kg BW NAC; and group VI (CPF+NAC group), NAC 1 h before CPF. CPF intoxication resulted in acetylcholinesterase inhibition, reduced glutathione content, and elevated levels of malondialdehyde and nitric oxide, which are oxidative stress biomarkers. CPF also depleted the activity of antioxidant enzymes, superoxide dismutase and catalase, and levels of inflammatory mediators, tumor necrosis factor-α, interleukin (IL)-6, and IL-1β. Levels of vascular endothelial growth factor, Bax, and the proapoptotic caspases-3 also increased, while brain-derived neurotrophic factor level decreased. Additionally, CPF significantly diminished Bcl-2 (an antiapoptotic protein) in rat brain cortical tissue. NAC treatment was found to protect brain tissue by reversing the CPF-induced neurotoxicity. Our results show the antioxidant, antiinflammatory, and antiapoptotic effects of NAC on CPF-induced neurotoxicity in rat brain tissue.

Saliva and urine metabolic profiling reveals altered amino acid and energy metabolism in male farmers exposed to pesticides in Madhya Pradesh State, India

Globally, the human population is exposed to low doses of pesticides due to its extensive use in agriculture. The chronic exposure to pesticides can lead to cancer, depression, anxiety, Parkinson's and Alzheimer's diseases etc. Here, we have made an attempt to use mass spectrometry based metabolomics to investigate the metabolic perturbations induced by the pesticides in the urine and saliva samples of farmers from the Madhya Pradesh State of India. The study was aimed to establish non-invasive matrices like urine and saliva as alternative diagnostic matrices to the occupational exposure studies. Saliva and urine samples were collected from 51 pesticides applicators and acquired metabolic profiles of urine and saliva samples using gas chromatography-mass spectrometry (GC-MS). Multivariate pattern recognition and pathway analysis were used to analyze and interpret the data. Investigation of endogenous metabolic profiles revealed remarkable discrimination in both saliva and urine samples of the exposed population strongly suggesting the changes in metabolic composition within the identified metabolites (for urine samples: accuracy 0.9766, R² = 0.9130, Q² = 0.8703; for saliva samples, an accuracy of 0.9961, R² = 0.9698, Q² = 0.9637). Thirteen metabolites of urine samples and sixteen metabolites of saliva samples were identified as differential metabolites specific to pesticide exposure. Pathway analysis of differential metabolites revealed that amino acid metabolism, energy metabolism (glycolysis and TCA cycle) and glutathione metabolism (oxidative stress) were found to affect in pesticide exposed population. The present study suggested that GC-MS based metabolomics can help to reveal the metabolic perturbations in human population after pesticides exposure.

Aryl-phosphorus-containing flame retardants induce oxidative stress, the p53-dependent DNA damage response and mitochondrial impairment in A549 cells

Aryl phosphorus-containing flame retardants (aryl-PFRs) have been frequently detected with increasingly used worldwide as one of alternatives for brominated flame retardants. However, information on their adverse effects on human health and ecosystem is insufficient, with limited study on their molecular mode of action in vitro. In this study, the cytotoxicity, DNA damage, mitochondrial impairment and the involved molecular mechanisms of certain frequently detectable aryl-PFRs, including 2-ethylhexyldiphenyl phosphate (EHDPP), methyl diphenyl phosphate (MDPP), bisphenol-A bis (diphenyl phosphate) (BDP), isodecyl diphenyl phosphate (IDPP), cresyl diphenyl phosphate (CDP) and the structurally similar and widely used organophosphorus pesticide chlorpyrifos (CPF), were evaluated in A549 cells using high-content screening (HCS) system. Aryl-PFRs showed different lethal concentration 50 (LC50) values ranging from 97.94 to 546.85 μM in A549 cells using CCK-8 assay. EHDPP, IDPP, CDP, MDPP and CPF demonstrated an ability to induce DNA damage, evidenced by increased DNA content and S phase-reducing cell cycle arrest effect using fluorophore dye cocktail assay. Additionally, the selected aryl-PFRs induced mitochondrial impairment by the increasing mitochondrial mass and decreasing mitochondrial membrane potential. Moreover, BDP, MDPP, and CDP, which contain short alkyl chains showed their potential oxidative stress with intracellular ROS and mitochondrial superoxide overproduction from an initially relatively low concentration. Additionally, based on the promotion of firefly luminescence in p53-transfected A549 cells, p53 activation was found to be involved in aryl-PFRs-induced DNA damage. Further real-time PCR results showed that all selected aryl-PFRs triggered p53/p21/gadd45β-, and p53/p21/mdm2-mediated cell cycle pathways, and the p53/bax mediated apoptosis pathway to induce DNA damage and cytotoxic effects. These results suggest that aryl-PFRs (e.g., BDP, MDPP, CDP) cause oxidative stress-mediated DNA damage and mitochondrial impairment, and p53-dependent pathway was involved in the aryl-PFRs-induced DNA damage and cell cycle arrest. In conclusion, this study improves the understanding of PFRs-induced adverse outcomes and the involved molecular mechanism.

High-potassium preconditioning enhances tolerance to focal cerebral ischemia-reperfusion injury through anti-apoptotic effects in male rats

Imbalances between cellular K⁺ efflux and influx are considered to be involved in cerebral ischemia-reperfusion (I/R) injury. High-potassium pretreatment alleviates this injury, but the underlying molecular mechanism is unclear. In this study, we sought to investigate whether high-potassium preconditioning enhances cerebral tolerance to I/R injury through an anti-apoptotic mechanism. Adult male Sprague-Dawley rats were randomly divided into four groups (n = 40/group): a sham-operated group, normal saline group (3.2 ml/kg saline, intravenous (IV)), and low-dose and high-dose potassium chloride (KCl) groups (40 and 80 mg/kg KCl solution, IV, respectively). Subsequently, the rats underwent 90 min of middle cerebral artery occlusion (MCAO) followed by 24 hr of reperfusion (MCAO/R). Neurological deficit scores, 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin and eosin staining, and TUNEL assay were used to assess neural injury. The expression of apoptotic proteins, brain potassium levels, mitochondrial function and oxidative stress were detected to explore the potential mechanism. After 24 hr of reperfusion, in both KCl treatment groups, neurological deficits and the cerebral infarct volume were reduced, and the apoptosis index of neurons was decreased. Furthermore, high-potassium preconditioning increased brain K⁺ , adenosine triphosphate (ATP), cytochrome c oxidase (COX) levels, reduced malondialdehyde level, improved Na⁺ /K⁺ -ATPase, succinic dehydrogenase and superoxide dismutase activities, upregulated anti-apoptotic protein expression, and downregulated pro-apoptotic protein expression. This study suggests that high-potassium preconditioning enhanced cerebral tolerance to I/R injury in a rat MCAO/R model. The protective mechanism may involve apoptosis inhibition via preservation of intracellular K⁺ and improvement of mitochondrial function.