Diazinon and diazoxon impair the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons

Ameliorative Effect of Thymoquinone and Thymoquinone Nanoparticles against Diazinon-Induced Hepatic Injury in Rats: A Possible Protection Mechanism

The health benefits of thymoquinone (TQ) have been a significant focus of numerous studies. However, more research is needed to ascertain whether its nano-form can effectively treat or prevent chronic diseases. In this study, we investigated how thymoquinone and its nanoparticles can mitigate liver damage induced by diazinon in male Wistar rats and explored the intracellular mechanisms involved. Forty-two Wistar male rats (n = 42) were randomly allotted into seven groups. Group 1 served as the control. Group 2 (vehicle) consisted of rats that received corn oil via a gastric tube daily. In Group 3 (TQ), rats were given a daily oral administration of TQ (40 mg/kg bw). Group 4 (thymoquinone nanoparticles, NTQ) included rats that received NTQ (0.5 mg/kg bw) orally for 21 days. Group 5 (DZN) involved rats that were administered diazinon (DZN, 15 mg/kg bw) orally. In Group 6 (TQ + DZN), rats first received TQ orally, followed by DZN. Group 7 (NTQ + DZN) consisted of rats receiving NTQ orally, then DZN. After 21 days of treatment, the rats were euthanized. After oral administration of DZN, liver enzymes were significantly elevated (p < 0.05). Additionally, there were noticeable increases in oxidative injury markers, such as nitric oxide, malondialdehyde, redox oxygen radicals, and overall increases in hydrogen peroxide and liver protein carbonyl concentrations. This was accompanied by the upregulation of apoptotic markers (Bax, caspase9, caspase 3, bax/Bcl2 ratio), inflammatory cytokines (TNF-α, IL-6), and DNA damage. There was also a noteworthy decrease (p < 0.05) in the activities of antioxidant enzymes and anti-apoptotic markers. However, the oral administration of thymoquinone or its nanoparticle form mitigated these diazinon complications; our histopathological findings corroborated our biochemical and molecular observations. In conclusion, the significant antioxidant properties of thymoquinone, or its nanoparticle form, in tandem with the downregulation of apoptotic markers and inflammatory cytokines, provided a protective effect against hepatic dysfunction caused by diazinon.

The relationship between the cholinergic mechanism of toxicity and oxidative stress in rats during subacute diazinon poisoning

Diazinon is an organophosphate pesticide (OP) that has significant potential for accidental and intentional poisoning of wildlife, domestic animals and humans. The aim of the study is to investigate the correlation between cholinesterase activity and oxidative stress parameters in liver and diaphragm by continuous monitoring as a function of time during prolonged use of diazinon. Wistar rats were treated orally with diazinon (55 mg/kg/day): 7, 14, 21 and 28 days. At the end of each period, blood, liver and diaphragm were collected to examine cholinesterase activity and enzymatic/non-enzymatic oxidative stress parameters: superoxide dismutase 1 (SOD1), catalase (CAT), thiobarbituric acid substances (TBARS), protein carbonyl groups. In all four time periods, there was a significant change in acetylcholinesterase (AChE) in erythrocytes and butyrylcholinesterase (BuChE) in blood plasma, CAT in liver and diaphragm and SOD1 in diaphragm. Parameters significantly altered during the cholinergic crisis included: cholinesterases and TBARS in liver and diaphragm and partially SOD1 in liver. Protein carbonyl groups in liver and diaphragm were significantly altered outside the cholinergic crisis. In the liver, there was a very strong negative correlation between BuChE and TBARS in all four time periods and BuChE and CAT on day 7. In the diaphragm, a very strong negative correlation was found between AChE and TBARS at days 7 and 14, and a very strong positive correlation between AChE and SOD1 at days 14, 21 and 28. A better understanding of the relationship between cholinergic overstimulation and oxidative stress may help to better assess health status in prolonged OPs intoxication.

Organophosphate insecticides disturb neuronal network development and function via non-AChE mediated mechanisms

Exposure to organophosphate (OP) insecticides has been related to several adverse health effects, including neurotoxicity. The primary insecticidal mode of action of OP insecticides relies on (irreversible) binding to acetylcholine esterase (AChE), with -oxon metabolites having a much higher potency for AChE inhibition than the parent compounds. However, OP insecticides can also have non-AChE-mediated effects, including changes in gene expression, neuroendocrine effects, disruption of neurite outgrowth and disturbance of the intracellular calcium (Ca²⁺) homeostasis. Since Ca²⁺ is involved in neurotransmission and neuronal development, our research aimed to assess the effects of two widely used OP insecticides, chlorpyrifos (CPF) and diazinon (DZ) and their respective -oxon metabolites, on intracellular Ca²⁺ homeostasis in human SH-SY5Y cells and rat primary cortical cultures. Furthermore, we assessed the acute and chronic effects of exposure to these compounds on neuronal network maturation and function in rat primary cortical cultures using microelectrode array (MEA) recordings. While inhibition of AChE appears to be the primary mode of action of oxon-metabolites, our data indicate that both parent OP insecticides (CPF and DZ) inhibit depolarization-evoked Ca²⁺ influx and neuronal activity at concentrations far below their sensitivity for AChE inhibition, indicating that inhibition of voltage-gated calcium channels is a common mode of action of OP insecticides. Notably, parent compounds were more potent than their oxon metabolites, with exposure to diazinon-oxon (DZO) having no effect on both neuronal activity and Ca²⁺ influx. Human SH-SY5Y cells were more sensitive to OP-induced inhibition of depolarization-evoked Ca²⁺ influx than rat cortical cells. Acute exposure to OP insecticides had more potent effects on neuronal activity than on Ca²⁺ influx, suggesting that neuronal activity parameters are especially sensitive to OP exposure. Interestingly, the effects of DZ and chlorpyrifos-oxon (CPO) on neuronal activity lessened after 48 h of exposure, while the potency of CPF did not differ over time. This suggests that neurotoxicity after exposure to different OPs has different effects over time and occurs at levels that are close to human exposure levels. In line with these results, chronic exposure to CPF during 10 days impaired neuronal network development, illustrating the need to investigate possible links between early-life OP exposure and neurodevelopmental disorders in children and highlighting the importance of non-AChE mediated mechanisms of neurotoxicity after OP exposure.

Subchronic neurotoxicity of diazinon in albino mice: Impact of oxidative stress, AChE activity, and gene expression disturbances in the cerebral cortex and hippocampus on mood, spatial learning, and memory function

Diazinon (DZN) with prominent neurotoxic effects perturbs CNS function via multiple mechanisms. This investigation intends to explore mood, spatial learning, and memory dysfunction, acetylcholine esterase (AChE) activity, and neurodegeneration-related gene expression in the cortex and hippocampus regions of mice exposed to DZN for 63 consecutive days (subchronic exposure). Adult male albino mice were orally given sublethal DZN (DZNL = 0.1 mg/kg, DZNM = 1 mg/kg and DZNH = 10 mg/kg). All mice in the DZNH group died within 3 weeks postexposure. DZNL and DZNM caused body and brain weight loss (p < 0.05). Completing 9 weeks of DZN exposure, a marked decline in AChE activity and oxidative stress level was indicated in both brain regions (p < 0.05). Also, synaptophysin, vesicular acetylcholine transferase, and glutamate decarboxylase gene expressions were affected in both brain regions (p < 0.05). Furthermore, the present study revealed that DZN administration increased anxiety and depressive-like behaviors (p < 0.0001). Spatial learning and short- and long-memory were severely affected by DZNL and DZNM treatments (p < 0.0001). Taken together, subchronic exposure to low and medium doses of DZN can cause AChE inhibition, oxidative damage, and neurotransmitter disturbances in brain cells and induce neurodegeneration. These changes would impair mood, spatial learning, and memory function.

21-Day dermal exposure to aircraft engine oils: effects on esterase activities in brain and liver tissues, blood, plasma, and clinical chemistry parameters for Sprague Dawley rats

This dermal study tested the potential toxicity of grade 3 (G3) and 4 (G4) organophosphate-containing aircraft engine oils in both new (G3-N, G4-N) and used states (G3-U, G4-U) to alter esterase activities in blood, brain and liver tissues, clinical chemistry parameters, and electrophysiology of hippocampal neurons. A 300 µl volume of undiluted oil was applied in Hill Top Chamber Systems®, then attached to fur-free test sites on backs of male and female Sprague Dawley rats for 6 hr/day, 5 days/week for 21 days. Recovery rats received similar treatments and kept for 14 days post-exposure to screen for reversibility, persistence, or delayed occurrence of toxicity. In brain, both versions of G3 and G4 significantly decreased (32-41%) female acetylcholinesterase (AChE) activity while in males only G3-N and G4-N reduced (33%) AChE activity. Oils did not markedly affect AChE in liver, regardless of gender. In whole blood, G3-U decreased female AChE (29%) which persisted during recovery (32%). G4-N significantly lowered (29%) butyrylcholinesterase (BChE) in male plasma, but this effect was resolved during recovery. For clinical chemistry indices, only globulin levels in female plasma significantly increased following G3-N or G4-N exposure. Preliminary electrophysiology data suggested that effects of both versions of G3 and G4 on hippocampal function may be gender dependent. Aircraft maintenance workers may be at risk if precautions are not taken to minimize long-term aircraft oil exposure.

Neural stem cell-based in vitro bioassay for the assessment of neurotoxic potential of water samples

Intensive agriculture activities, industrialization and growing numbers of wastewater treatment plants along river banks collectively contribute to the elevated levels of neurotoxic pollutants in natural water reservoirs across Europe. We established an in vitro bioassay based upon neural stem cells isolated from the subventricular zone of the postnatal mouse to evaluate the neurotoxic potential of raw wastewater, treated sewage effluent, groundwater and drinking water. The toxic potential of water samples was evaluated employing viability, proliferation, differentiation and migration assays. We found that raw wastewater could reduce the viability and proliferation of neural stem cells, and decreased the neuronal and astrocyte differentiation, neuronal neurite growth, astrocyte growth and cell migration. Treated sewage water also showed inhibitory effects on cell proliferation and migration. Our results indicated that relatively high concentrations of nitrogenous substances, pesticides, mercuric compounds, bisphenol-A, and phthalates, along with some other pollutants in raw wastewater and treated sewage water, might be the reason for the neuroinhibitory effects of these water samples. Our model successfully predicted the neurotoxicity of water samples collected from different sources and also revealed that the incomplete removal of contaminants from wastewater can be problematic for the developing nervous system. The presented data also provides strong evidence that more effective treatments should be used to minimize the contamination of water before release into major water bodies which may be considered as water reservoirs for human usage in the future.

Environment permissible concentrations of glyphosate in drinking water can influence the fate of neural stem cells from the subventricular zone of the postnatal mouse

The developing nervous system is highly vulnerable to environmental toxicants especially pesticides. Glyphosate pesticide induces neurotoxicity both in humans and rodents, but so far only when exposed to higher concentrations. A few studies, however, have also reported the risk of general toxicity of glyphosate at concentrations comparable to allowable limits set up by environmental protection authorities. In vitro data regarding glyphosate neurotoxicity at concentrations comparable to maximum permissible concentrations in drinking water is lacking. In the present study, we established an in vitro assay based upon neural stem cells (NSCs) from the subventricular zone of the postnatal mouse to decipher the effects of two maximum permissible concentrations of glyphosate in drinking water on the basic neurogenesis processes. Our results demonstrated that maximum permissible concentrations of glyphosate recognized by environmental protection authorities significantly reduced the cell migration and differentiation of NSCs as demonstrated by the downregulation of the expression levels of the neuronal ß-tubulin III and the astrocytic S100B genes. The expression of the cytoprotective gene CYP1A1 was downregulated whilst the expression of oxidative stresses indicator gene SOD1 was upregulated. The concentration comparable to non-toxic human plasma concentration significantly induced cytotoxicity and activated Ca2+ signalling in the differentiated culture. Our findings demonstrated that the permissible concentrations of glyphosate in drinking water recognized by environmental protection authorities are capable of inducing neurotoxicity in the developing nervous system.

The protective role of alpha-lipoic acid on the appearance of fibronectin and laminin in renal tubules following diazinon exposure: An experimental immunohistochemical study

Extracellular matrix (ECM) exerts a major role in maintaining the structure and developmental processes of tissues. To form the tubular basement membrane in the kidney, sulfate proteoglycans, collagen, laminin, fibronectin, and other glycoproteins congregate in the ECM. As an insecticide, diazinon (DZN) may alter the proportion of ECM by cholinesterase activity inhibition and oxidative stress. The naturally, alpha-lipoic acid (ALA) plays an effective and therapeutic role in the treatment of toxicities and diseases in the body. In the current study, an attempt was made to evaluate the impacts of alpha-lipoic acid on the distribution of fibronectin and laminin in the renal tubules of male Wistar rats following exposure to diazinon. In this study, the animal groups comprised 30 adult male Wistar rats (almost three months old) randomly distributed into the following groups; control, DZN (40 mg/kg), DZN + ALA (40 mg/kg+100 mg/kg), ALA (100 mg/kg), and sham. The rats were anesthetized after six weeks. Blood sampling was performed, and kidneys were removed for immunohistochemistry study. Diazinon reduced the distribution of fibronectin and laminin and significantly inhibited cholinesterase activity in the renal tubules. Furthermore, urea and creatinine levels were higher in diazinon than in other groups. ALA in the co-treatment group enhanced cholinesterase activity and distribution of both glycoproteins in the renal tubules. Urea and creatinine levels were meaningfully diminished in the DZN + ALA group. The nephrotoxic effect of diazinon in vivo was the reduced distribution of laminin and fibronectin, probably induced by cholinesterase activity inhibition. As an antioxidant with specific properties, ALA reduces the nephrotoxic effects of diazinon by multifarious mechanisms.

Reactive oxygen species play a role in P2X7 receptor-mediated IL-6 production in spinal astrocytes

Astrocytes mediate a remarkable variety of cellular functions, including gliotransmitter release. Under pathological conditions, high concentrations of the purinergic receptor agonist adenosine triphosphate (ATP) are released into the extracellular space leading to the activation of the purinergic P2X7 receptor, which in turn can initiate signaling cascades. It is well-established that reactive oxygen species (ROS) increase in macrophages and microglia following P2X7 receptor activation. However, direct evidence that activation of P2X7 receptor leads to ROS production in astrocytes is lacking to date. While it is known that P2X7R activation induces cytokine production, the mechanism involved in this process is unclear. In the present study, we demonstrated that P2X7 receptor activation induced ROS production in spinal astrocytes in a concentration-dependent manner. We also found that P2X7R-mediated ROS production is at least partially through NADPH oxidase. In addition, our ELISA data show that P2X7R-induced IL-6 release was dependent on NADPH oxidase-mediated production of ROS. Collectively, these results reveal that activation of the P2X7 receptor on spinal astrocytes increases ROS production through NADPH oxidase, subsequently leading to IL-6 release. Our results reveal a role of ROS in the P2X7 signaling pathway in mouse spinal cord astrocytes and may indicate a potential mechanism for the astrocytic P2X7 receptor in chronic pain.

Photocatalytic Degradation of Diazinon in Aqueous Solutions Using Immobilized MgO Nanoparticles on Concrete

Photocatalytic degradation of diazinon in the aqueous solution using UV light and MgO nanoparticle (NPs) immobilized on the concrete was investigated. Prepared catalyst was characterized using TEM, XRD, SEM, and EDX techniques. The results showed that the average particle size of immobilized MgO NPs was 38.3 nm and NPs appropriately was coated on the concrete surface. The performance of degradation and mineralization of diazinon was evaluated by HPLC and TOC techniques, respectively. The effect of operational parameters including pH value, initial pesticide concentration, and contact time were studied on the removal and mineralization of diazinon by a photocatalytic process. The results showed that the MgO NPs and UV light had little effect in removing pesticide when used individually. On the other hand, diazinon can be effectively degraded by immobilized MgO NPs in the presence of UV light. Degradation products of diazinon using the proposed photocatalytic technique were identified by the GC-MS analysis. The maximum diazinon removal (99.46 %) was obtained under the conditions; pH 7, diazinon concentration of 5 mg/L, and contact time of 120 minutes. Also, the lowest energy consumption conditions were as follow; pH 7, diazinon concentration of 5 mg/L, and contact time of 30 minutes.

Glyphosate and glyphosate-based herbicide exposure during the peripartum period affects maternal brain plasticity, maternal behaviour and microbiome

Glyphosate is found in a large array of non-selective herbicides such as Roundup® (Monsanto, Creve Coeur, MO, USA) and is by far the most widely used herbicide. Recent work in rodent models suggests that glyphosate-based herbicides during development can affect neuronal communication and result in altered behaviours, albeit through undefined mechanisms of action. To our knowledge, no study has investigated the effects glyphosate or its formulation in herbicide on maternal behaviour and physiology. In the present study, relatively low doses of glyphosate (5 mg kg-1  d-1 ), Roundup® (5 mg kg-1  d-1 glyphosate equivalent), or vehicle were administered by ingestion to Sprague-Dawley rats from gestational day (GD) 10 to postpartum day (PD)22. The treatments significantly altered licking behaviour toward pups between PD2 and PD6. We also show in the dams at PD22 that Roundup exposure affected the maturation of doublecortin-immunoreactive new neurones in the dorsal dentate gyrus of the hippocampus of the mother. In addition, the expression of synaptophysin was up-regulated by glyphosate in the dorsal and ventral dentate gyrus and CA3 regions of the hippocampus, and down-regulated in the cingulate gyrus. Although a direct effect of glyphosate alone or its formulation on the central nervous system is currently not clear, we show that gut microbiota is significantly altered by the exposure to the pesticides, with significant alteration of the phyla Bacteroidetes and Firmicutes. This is the first study to provide evidence that glyphosate alone or in formulation (Roundup) differentially affects maternal behaviour and modulates neuroplasticity and gut microbiota in the mother.

The Precursor to Glutathione (GSH), γ-Glutamylcysteine (GGC), Can Ameliorate Oxidative Damage and Neuroinflammation Induced by Aβ40 Oligomers in Human Astrocytes

Glutathione (GSH) is one of the most abundant thiol antioxidants in cells. Many chronic and age-related diseases are associated with a decline in cellular GSH levels or impairment in the catalytic activity of the GSH biosynthetic enzyme glutamate cysteine ligase (GCL). γ-glutamylcysteine (GGC), a precursor to glutathione (GSH), can replenish depleted GSH levels under oxidative stress conditions, by circumventing the regulation of GSH biosynthesis and providing the limiting substrate. Soluble amyloid-β (Aβ) oligomers have been shown to induce oxidative stress, synaptic dysfunction and memory deficits which have been reported in Alzheimer’s disease (AD). Calcium ions, which are increased with age and in AD, have been previously reported to enhance the formation of Aβ₄₀ oligomers, which have been casually associated with the pathogenesis of the underlying neurodegenerative condition. In this study, we examined the potential beneficial effects of GGC against exogenous Aβ₄₀ oligomers on biomarkers of apoptosis and cell death, oxidative stress, and neuroinflammation, in human astrocytes. Treatment with Aβ₄₀ oligomers significantly reduced the cell viability and apoptosis of astrocyte brain cultures and increased oxidative modifications of DNA, lipids, and protein, enhanced pro-inflammatory cytokine release and increased the activity of the proteolytic matrix metalloproteinase enzyme, matric metalloproteinase (MMP)-2 and reduced the activity of MMP-9 after 24 h. Co-treatment of Aβ₄₀ oligomers with GGC at 200 μM increased the activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) and led to significant increases in the levels of the total antioxidant capacity (TAC) and GSH and reduced the GSSG/GSH ratio. GGC also upregulated the level of the anti-inflammatory cytokine IL-10 and reduced the levels of the pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) and attenuated the changes in metalloproteinase activity in oligomeric Aβ₄₀-treated astrocytes. Our data provides renewed insight on the beneficial effects of increased GSH levels by GGC in human astrocytes, and identifies yet another potential therapeutic strategy to attenuate the cytotoxic effects of Aβ oligomers in AD.

Phagocytosis and ROS production as biomarkers in Nile tilapia (Oreochromis niloticus) leukocytes by exposure to organophosphorus pesticides

Organophosphorus pesticides (OPs) are broad-spectrum insecticides. One of the commonly used OPs is diazinon (DZN). The aim of this study was to evaluate the immunotoxic effect of DZN on phagocytic parameters of blood leukocytes using the teleost fish Oreochromis niloticus as a study model. For this purpose, fish were exposed in vivo to 0.97, 1.95 and 3.97 mg/L of DZN for 6 and 24 h. Our results indicated that phagocytic active cells decreased in fish exposed in vivo to 0.97 and 1.95 mg/L of DZN for 6 and 24 h. Regarding ROS production, H₂O₂ and O₂^- levels were higher on fish exposed to 1.95 mg/L for 6 and 24 h, while H₂O₂ production increased at 0.97 mg/L for 24 h. From this we can conclude that phagocytic parameters are sensitive to assess the effect of acute intoxication with organophosphorus pesticides on Nile tilapia.

Modulation of immunological activity on macrophages induced by diazinon

Diazinon is an organophosphorus (OP) insecticide and is widely used not only in agriculture but also homes and garden in Japan. Diazinon has been reported to increase TNF-α production in rat serum and brain, suggesting that it can modify the proinflammatory response. In this study, we investigated the effects of diazinon on macrophage functions, such as cytokine production, reactive oxygen species (ROS) generation, cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) expressions, cell-surface molecule expressions, and phagocytosis in RAW264.7 cells. In RAW264.7 cells, diazinon induced the production of TNF-α and IL-6. Diazinon induced ROS generation and the expressions of COX-2, iNOS, and cell-surface molecules CD40, CD86, and MHC class II, but reduced phagocytic activity in RAW264.7 cells. ERK and p38, but not JNK and p65 were involved in diazinon-induced IL-6 expression in RAW264.7 cells. We also examined these proinflammatory responses in bone marrow-derived macrophages (BMDM) and bronchoalveolar lavage fluid (BALF) cells. These results suggested that diazinon can activate macrophages and enhance inflammatory responses.

Neurotoxicity in Preclinical Models of Occupational Exposure to Organophosphorus Compounds

Organophosphorus (OPs) compounds are widely used as insecticides, plasticizers, and fuel additives. These compounds potently inhibit acetylcholinesterase (AChE), the enzyme that inactivates acetylcholine at neuronal synapses, and acute exposure to high OP levels can cause cholinergic crisis in humans and animals. Evidence further suggests that repeated exposure to lower OP levels insufficient to cause cholinergic crisis, frequently encountered in the occupational setting, also pose serious risks to people. For example, multiple epidemiological studies have identified associations between occupational OP exposure and neurodegenerative disease, psychiatric illness, and sensorimotor deficits. Rigorous scientific investigation of the basic science mechanisms underlying these epidemiological findings requires valid preclinical models in which tightly-regulated exposure paradigms can be correlated with neurotoxicity. Here, we review the experimental models of occupational OP exposure currently used in the field. We found that animal studies simulating occupational OP exposures do indeed show evidence of neurotoxicity, and that utilization of these models is helping illuminate the mechanisms underlying OP-induced neurological sequelae. Still, further work is necessary to evaluate exposure levels, protection methods, and treatment strategies, which taken together could serve to modify guidelines for improving workplace conditions globally.

Organophosphate neurotoxicity to the voluntary motor system on the trail of environment-caused amyotrophic lateral sclerosis: the known, the misknown, and the unknown

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset paralytic disorder. It is characterized by progressive degeneration of the motor neurons controlling voluntary movement. The underlying mechanisms remain elusive, a fact that has precluded development of effective treatments. ALS presents as a sporadic condition 90-95% of the time, i.e., without familial history or obvious genetic mutation. This suggests that ALS has a strong environmental component. Organophosphates (OPs) are prime candidate neurotoxicants in the etiology of ALS, as exposure to OPs was linked to higher ALS incidence among farmers, soccer players, and Gulf War veterans. In addition, polymorphisms in paraoxonase 1, an enzyme that detoxifies OPs, may increase individual vulnerability both to OP poisoning and to the risk of developing ALS. Furthermore, exposure to high doses of OPs can give rise to OP-induced delayed neuropathy (OPIDN), a debilitating condition akin to ALS characterized by similar motor impairment and paralysis. The question we pose in this review is: "what can we learn from acute exposure to high doses of neurotoxicants (OPIDN) that could help our understanding of chronic diseases resulting from potentially decades of silent exposure (ALS)?" The resemblances between OPIDN and ALS are striking at the clinical, etiological, neuropathological, cellular, and potentially molecular levels. Here, we critically present available evidence, discuss current limitations, and posit future research. In the search for the environmental origin of ALS, OPIDN offers an exciting trail to follow, which can hopefully lead to the development of novel strategies to prevent and cure these dreadful disorders.

Blockage of both the extrinsic and intrinsic pathways of diazinon-induced apoptosis in PaTu cells by magnesium oxide and selenium nanoparticles

Diazinon (DZ) is an organophosphorus insecticide that acts as an acetylcholinesterase inhibitor. It is important to note that it can induce oxidative stress, lipid peroxidation, diabetic disorders, and cytotoxicity. Magnesium oxide (MgO) and selenium nanoparticles (Se NPs) showed promising protection against oxidative stress, lipid peroxidation, cytotoxicity, and diabetic disorders. Therefore, this study was conducted to explore the possible protective mechanisms of MgO and Se NPs against DZ-induced cytotoxicity in PaTu cell line. Cytotoxicity of DZ, in the presence or absence of effective doses of MgO and Se NPs, was determined in human pancreatic cancer cell line (PaTu cells) after 24 hours of exposure by using mitochondrial activity and mitochondrial membrane potential assays. Then, the insulin, proinsulin, and C-peptide release; caspase-3 and -9 activities; and total thiol molecule levels were assessed. Determination of cell viability, including apoptotic and necrotic cells, was assessed via acridine orange/ethidium bromide double staining. Furthermore, expression of 15 genes associated with cell death/apoptosis in various phenomena was examined after 24 hours of contact with DZ and NPs by using real-time polymerase chain reaction. Compared to the individual cases, the group receiving the combination of MgO and Se NPs showed more beneficial effects in reducing the toxicity of DZ. Cotreatment of PaTu cell lines with MgO and Se NPs counteracts the toxicity of DZ on insulin-producing cells.

Evaluation of PFOS-mediated neurotoxicity in rat primary neurons and astrocytes cultured separately or in co-culture

Perfluorooctane sulfonate (PFOS) is a potential neurotoxicant reported by epidemiological investigations and experimental studies, while the underlying mechanisms are still unclear. Astrocytes not only support for the construction of neurons, but also conduct neuronal functions through glutamate-glutamine cycle in astrocyte-neuron crosstalk. In the present study, the effect of PFOS exposure on rat primary hippocampal neurons or cortex astrocytes was evaluated. Then the role of the astrocytes in PFOS-induced toxic effect on neurons was explored with astrocyte-neuron co-culture system. Exposure of rat primary hippocampal neurons to PFOS has led to oxidation-antioxidation imbalance, increased apoptosis and abnormal autophagy. The adverse effect of PFOS on rat primary cortex astrocytes manifested in the form of altered extracellular glutamate and glutamine concentrations, decreased glutamine synthase activity, as well as decreased gene expression of glutamine synthase, glutamate transporters and glutamine transporters in the glutamate-glutamine cycle. Especially, the alleviation of PFOS-inhibited neurite outgrowth in neurons could be observed in astrocyte-neuron co-culture system, though the ability of astrocytes in fostering neurite outgrowth was affected by PFOS. These results indicated that both astrocytes and neurons might be the targets of PFOS-induced neurotoxicity, and astrocytes could protect against PFOS-inhibited neurite outgrowth in primary cultured neurons. Our research might render some information in explaining the mechanisms of PFOS-induced neurotoxicity.

Diverse neurotoxicants target the differentiation of embryonic neural stem cells into neuronal and glial phenotypes

The large number of compounds that needs to be tested for developmental neurotoxicity drives the need to establish in vitro models to evaluate specific neurotoxic endpoints. We used neural stem cells derived from rat neuroepithelium on embryonic day 14 to evaluate the impact of diverse toxicants on their ability to differentiate into glia and neurons: a glucocorticoid (dexamethasone), organophosphate insecticides (chlorpyrifos, diazinon, parathion), insecticides targeting the GABA_A receptor (dieldrin, fipronil), heavy metals (Ni²⁺, Ag⁺), nicotine and tobacco smoke extract. We found three broad groupings of effects. One diverse set of compounds, dexamethasone, the organophosphate pesticides, Ni²⁺ and nicotine, suppressed expression of the glial phenotype while having little or no effect on the neuronal phenotype. The second pattern was restricted to the pesticides acting on GABA_A receptors. These compounds promoted the glial phenotype and suppressed the neuronal phenotype. Notably, the actions of compounds eliciting either of these differentiation patterns were clearly unrelated to deficits in cell numbers: dexamethasone, dieldrin and fipronil all reduced cell numbers, whereas organophosphates and Ni²⁺ had no effect. The third pattern, shared by Ag⁺ and tobacco smoke extract, clearly delineated cytotoxicity, characterized by major cell loss with suppression of differentiation into both glial and neuronal phenotypes; but here again, there was some selectivity in that glia were suppressed more than neurons. Our results, from this survey with diverse compounds, point to convergence of neurotoxicant effects on a specific "decision node" that controls the emergence of neurons and glia from neural stem cells.

Fetal Alcohol Spectrum Disorders: An Overview from the Glia Perspective

Alcohol consumption during pregnancy can produce a variety of central nervous system (CNS) abnormalities in the offspring resulting in a broad spectrum of cognitive and behavioral impairments that constitute the most severe and long-lasting effects observed in fetal alcohol spectrum disorders (FASD). Alcohol-induced abnormalities in glial cells have been suspected of contributing to the adverse effects of alcohol on the developing brain for several years, although much research still needs to be done to causally link the effects of alcohol on specific brain structures and behavior to alterations in glial cell development and function. Damage to radial glia due to prenatal alcohol exposure may underlie observations of abnormal neuronal and glial migration in humans with Fetal Alcohol Syndrome (FAS), as well as primate and rodent models of FAS. A reduction in cell number and altered development has been reported for several glial cell types in animal models of FAS. In utero alcohol exposure can cause microencephaly when alcohol exposure occurs during the brain growth spurt a period characterized by rapid astrocyte proliferation and maturation; since astrocytes are the most abundant cells in the brain, microenchephaly may be caused by reduced astrocyte proliferation or survival, as observed in in vitro and in vivo studies. Delayed oligodendrocyte development and increased oligodendrocyte precursor apoptosis has also been reported in experimental models of FASD, which may be linked to altered myelination/white matter integrity found in FASD children. Children with FAS exhibit hypoplasia of the corpus callosum and anterior commissure, two areas requiring guidance from glial cells and proper maturation of oligodendrocytes. Finally, developmental alcohol exposure disrupts microglial function and induces microglial apoptosis; given the role of microglia in synaptic pruning during brain development, the effects of alcohol on microglia may be involved in the abnormal brain plasticity reported in FASD. The consequences of prenatal alcohol exposure on glial cells, including radial glia and other transient glial structures present in the developing brain, astrocytes, oligodendrocytes and their precursors, and microglia contributes to abnormal neuronal development, reduced neuron survival and disrupted brain architecture and connectivity. This review highlights the CNS structural abnormalities caused by in utero alcohol exposure and outlines which abnormalities are likely mediated by alcohol effects on glial cell development and function.

Ulinastatin suppresses lipopolysaccharide induced neuro-inflammation through the downregulation of nuclear factor-κB in SD rat hippocampal astrocyte

Astrocyte activation plays a pivotal role in neuroinflammation, which contributes to neuronal damage, so the inhibition of astrocyte activation may alleviate the progression of neurodegeneration. Recent studies have proved that urinary trypsin inhibitor ulinastatin could inhibit NF-kB activation. In our study, the inhibitory effects of ulinastatin on the production of pro-inflammatory mediators were investigated in lipopolysaccharide (LPS)-reduced primary astrocyte. Our results showed that ulinastatin significantly inhibited LPS-induced astrogliosis, which is measured by MTT and BrdU. Ulinastatin decreased the production of pro-inflammatory cytokines, such as TNF-α, IL-6, IL-1β, it significantly decreased both the mRNA and the protein levels of these pro-inflammatory cytokines and also increased the protein levels of IκB-α binded to NF-κB, which blocked NF-κB translocation to the nucleus and prevented its activity. Our results suggest that ulinastatin is able to inhibit neuroinflammation by interfering with NF-κB signaling. The study provides direct evidence of potential therapy methods of ulinastatin for the treatment of neuroinflammatory diseases.

Astrocytes protect against diazinon- and diazoxon-induced inhibition of neurite outgrowth by regulating neuronal glutathione

Evidence demonstrating that human exposure to various organophosphorus insecticides (OPs) is associated with neurobehavioral deficits in children continues to emerge. The present study focused on diazinon (DZ) and its active oxygen metabolite, diazoxon (DZO), and explored their ability to impair neurite outgrowth in rat primary hippocampal neurons as a mechanism of developmental neurotoxicity. Both DZ and DZO (0.5-10 μM) significantly inhibited neurite outgrowth in hippocampal neurons, at concentrations devoid of any cyototoxicity. These effects appeared to be mediated by oxidative stress, as they were prevented by antioxidants (melatonin, N-t-butyl-alpha-phenylnitrone, and glutathione ethyl ester). Inhibition of neurite outgrowth was observed at concentrations below those required to inhibit the catalytic activity of acetylcholinesterase. The presence of astrocytes in the culture was able to provide protection against inhibition of neurite outgrowth by DZ and DZO. Astrocytes increased neuronal glutathione (GSH) in neurons, to levels comparable to those of GSH ethyl ester. Astrocytes depleted of GSH by L-buthionine-(S,R)-sulfoximine no longer conferred protection against DZ- and DZO-induced inhibition of neurite outgrowth. The findings indicate that DZ and DZO inhibit neurite outgrowth in hippocampal neurons by mechanisms involving oxidative stress, and that these effects can be modulated by astrocytes and astrocyte-derived GSH. Oxidative stress from other chemical exposures, as well as genetic abnormalities that result in deficiencies in GSH synthesis and regulation, may render individuals more susceptible to these developmental neurotoxic effects of OPs.

Glia and neurodevelopment: focus on fetal alcohol spectrum disorders

During the last 20 years, new and exciting roles for glial cells in brain development have been described. Moreover, several recent studies implicated glial cells in the pathogenesis of neurodevelopmental disorders including Down syndrome, Fragile X syndrome, Rett Syndrome, Autism Spectrum Disorders, and Fetal Alcohol Spectrum Disorders (FASD). Abnormalities in glial cell development and proliferation and increased glial cell apoptosis contribute to the adverse effects of ethanol on the developing brain and it is becoming apparent that the effects of fetal alcohol are due, at least in part, to effects on glial cells affecting their ability to modulate neuronal development and function. The three major classes of glial cells, astrocytes, oligodendrocytes, and microglia as well as their precursors are affected by ethanol during brain development. Alterations in glial cell functions by ethanol dramatically affect neuronal development, survival, and function and ultimately impair the development of the proper brain architecture and connectivity. For instance, ethanol inhibits astrocyte-mediated neuritogenesis and oligodendrocyte development, survival and myelination; furthermore, ethanol induces microglia activation and oxidative stress leading to the exacerbation of ethanol-induced neuronal cell death. This review article describes the most significant recent findings pertaining the effects of ethanol on glial cells and their significance in the pathophysiology of FASD and other neurodevelopmental disorders.