Uncovering malathion (an organophosphate insecticide) action on Ca2+ signal transduction and investigating the effects of BAPTA-AM (a cell-permeant Ca2+ chelator) on protective responses in glial cells

The Diverse Roles of Reactive Astrocytes in the Pathogenesis of Amyotrophic Lateral Sclerosis

Astrocytes displaying reactive phenotypes are characterized by their ability to remodel morphologically, molecularly, and functionally in response to pathological stimuli. This process results in the loss of their typical astrocyte functions and the acquisition of neurotoxic or neuroprotective roles. A growing body of research indicates that these reactive astrocytes play a pivotal role in the pathogenesis of amyotrophic lateral sclerosis (ALS), involving calcium homeostasis imbalance, mitochondrial dysfunction, abnormal lipid and lactate metabolism, glutamate excitotoxicity, etc. This review summarizes the characteristics of reactive astrocytes, their role in the pathogenesis of ALS, and recent advancements in astrocyte-targeting strategies.

An adverse outcome pathway for chemical-induced Parkinson's disease: Calcium is key

Exposure to pesticides is associated with an increased risk of developing Parkinson's disease (PD). Currently, rodent-based risk assessment studies cannot adequately capture neurodegenerative effects of pesticides due to a lack of human-relevant endpoints targeted at neurodegeneration. Thus, there is a need for improvement of the risk assessment guidelines. Specifically, a mechanistic assessment strategy, based on human physiology and (patho)biology is needed, which can be applied in next generation risk assessment. The Adverse Outcome Pathway (AOP) framework is particularly well-suited to provide the mechanistic basis for such a strategy. Here, we conducted a semi-systematic review in Embase and MEDLINE, focused on neurodegeneration and pesticides, to develop an AOP network for parkinsonian motor symptoms. Articles were labelled and included/excluded using the online platform Sysrev. Only primary articles, written in English, focused on effects of pesticides or PD model compounds in models for the brain were included. A total of 66 articles, out of the 1700 screened, was included. PD symptoms are caused by loss of function and ultimately death of dopaminergic neurons in the substantia nigra (SN). Our literature review highlights that a unique feature of these cells that increases their vulnerability is their reliance on continuous low-level influx of calcium. As such, excess intracellular calcium was identified as a central early Key Event (KE). This KE can lead to death of dopaminergic neurons of the SN, and eventually parkinsonian motor symptoms, via four distinct pathways: 1) activation of calpains, 2) endoplasmic reticulum stress, 3) impairment of protein degradation, and 4) oxidative damage. Several receptors have been identified that may serve as molecular initiating events (MIEs) to trigger one or more of these pathways. The proposed AOP network provides the biological basis that can be used to develop a mechanistic testing strategy that captures neurodegenerative effects of pesticides.

Methylated dialkylphosphate metabolites of the organophosphate pesticide malathion modify actin cytoskeleton arrangement and cell migration via activation of Rho GTPases Rac1 and Cdc42

The non-cholinergic molecular targets of organophosphate (OP) compounds have recently been investigated to explain their role in the generation of non-neurological diseases, such as immunotoxicity and cancer. Here, we evaluated the effects of malathion and its dialkylphosphate (DAP) metabolites on the cytoskeleton components and organization of RAW264.7 murine macrophages as non-cholinergic targets of OP and DAPs toxicity. All OP compounds affected actin and tubulin polymerization. Malathion, dimethyldithiophosphate (DMDTP) dimethylthiophosphate (DMTP), and dimethylphosphate (DMP) induced elongated morphologies and the formation of pseudopods rich in microtubule structures, and increased filopodia formation and general actin disorganization in RAW264.7 cells and slightly reduced stress fibers in the human fibroblasts GM03440, without significantly disrupting the tubulin or vimentin cytoskeleton. Exposure to DMTP and DMP increased cell migration in the wound healing assay but did not affect phagocytosis, indicating a very specific modification in the organization of the cytoskeleton. The induction of actin cytoskeleton rearrangement and cell migration suggested the activation of cytoskeletal regulators such as small GTPases. We found that DMP slightly reduced Ras homolog family member A activity but increased the activities of Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) from 5 min to 2 h of exposure. Chemical inhibition of Rac1 with NSC23766 reduced cell polarization and treatment with DMP enhanced cell migration, but Cdc42 inhibition by ML-141 completely inhibited the effects of DMP. These results suggest that methylated OP compounds, especially DMP, can modify macrophage cytoskeleton function and configuration via activation of Cdc42, which may represent a potential non-cholinergic molecular target for OP compounds.

Pesticides at brain borders: Impact on the blood-brain barrier, neuroinflammation, and neurological risk trajectories

Pesticides are omnipresent, and they pose significant environmental and health risks. Translational studies indicate that acute exposure to high pesticide levels is detrimental, and prolonged contact with low concentrations of pesticides, as single and cocktail, could represent a risk factor for multi-organ pathophysiology, including the brain. Within this research template, we focus on pesticides' impact on the blood-brain barrier (BBB) and neuroinflammation, physical and immunological borders for the homeostatic control of the central nervous system (CNS) neuronal networks. We examine the evidence supporting a link between pre- and postnatal pesticide exposure, neuroinflammatory responses, and time-depend vulnerability footprints in the brain. Because of the pathological influence of BBB damage and inflammation on neuronal transmission from early development, varying exposures to pesticides could represent a danger, perhaps accelerating adverse neurological trajectories during aging. Refining our understanding of how pesticides influence brain barriers and borders could enable the implementation of pesticide-specific regulatory measures directly relevant to environmental neuroethics, the exposome, and one-health frameworks.

Theoretical evaluation of the malathion and its chemical derivatives interaction with cytosolic phospholipase A2 from zebrafish

Cytosolic phospholipase A2 (cPLA2) belongs to a large family of proteins and plays a crucial role in the regulation of arachidonic acid metabolism and inflammation cascade in zebrafish (Danio rerio). This enzyme with a molecular weight of 85 kDa, has two distinct domains. One is the regulatory and calcium-dependent (Ca²⁺) domain called C2, the other is the catalytic α/β hydrolase Ca²⁺-independent domain, where serine and aspartic acid catalytic dyad residues are present. We investigated the interaction of malathion and their organophosphate metabolites in the cPLA2 using in silico tools. Molecular docking results showed hydrophobic interactions with the paraoxon and catalytic site residue (Ser 223). Malathion increases intracellular Ca²⁺ due to endoplasmic reticulum influx which in turn activities phospholipase A2 and arachidonic acid release. Molecular docking and homology modelling of proteins and ligands could be a complementary tool for ecotoxicology and environment pollution assessment.

Systematic Review of Calcium Channels and Intracellular Calcium Signaling: Relevance to Pesticide Neurotoxicity

Pesticides of different chemical classes exert their toxic effects on the nervous system by acting on the different regulatory mechanisms of calcium (Ca²⁺) homeostasis. Pesticides have been shown to alter Ca²⁺ homeostasis, mainly by increasing its intracellular concentration above physiological levels. The pesticide-induced Ca²⁺ overload occurs through two main mechanisms: the entry of Ca²⁺ from the extracellular medium through the different types of Ca²⁺ channels present in the plasma membrane or its release into the cytoplasm from intracellular stocks, mainly from the endoplasmic reticulum. It has also been observed that intracellular increases in the Ca²⁺ concentrations are maintained over time, because pesticides inhibit the enzymes involved in reducing its levels. Thus, the alteration of Ca²⁺ levels can lead to the activation of various signaling pathways that generate oxidative stress, neuroinflammation and, finally, neuronal death. In this review, we also discuss some proposed strategies to counteract the detrimental effects of pesticides on Ca²⁺ homeostasis.

Organophosphate toxicity: updates of malathion potential toxic effects in mammals and potential treatments

Organophosphorus insecticides toxicity is still considered a major global health problem. Malathion is one of the most commonly used organophosphates nowadays, as being considered to possess relatively low toxicity compared with other organophosphates. However, widespread use may lead to excessive exposure from multiple sources. Mechanisms of MAL toxicity include inhibition of acetylcholinesterase enzyme, change of oxidants/antioxidants balance, DNA damage, and facilitation of apoptotic cell damage. Exposure to malathion has been associated with different toxicities that nearly affect every single organ in our bodies, with CNS toxicity being the most well documented. Malathion toxic effects on liver, kidney, testis, ovaries, lung, pancreas, and blood were also reported. Moreover, malathion was considered as a genotoxic and carcinogenic chemical compound. Evidence exists for adverse effects associated with prenatal and postnatal exposure in both animals and humans. This review summarizes the toxic data available about malathion in mammals and discusses new potential therapeutic modalities, with the aim to highlight the importance of increasing awareness about its potential risk and reevaluation of the allowed daily exposure level.

Development of a CuFe2O4 - Reduced Graphene Oxide-Based Electrochemical Sensor for Malathion

A portable non-enzymatic electrochemical sensor for malathion detection based on CuFe2O4 and reduced graphene oxide nanocomposites was developed. CuFe2O4-rGO nanocomposites were synthesized using a facile one-pot co-precipitation method. X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy confirmed successful synthesis of the nanocomposites. Square wave voltammetry was performed using a portable potentiostat (CheapStat) and a three-electrode setup in order to determine the electrochemical behavior of the nanocomposite and its interaction with malathion. Maximum inhibition was observed at conditions corresponding to 15% rGO loading, pH 4 buffer solution, and five-minute accumulation time. Calibration of the sensor established a linear detection range of 0.5-8 ppm and a detection limit of 0.992 ± 0.007 ppm. Altogether, the performance parameters indicate good selectivity and potential applicability of the system for malathion monitoring particularly in agricultural products.