Sacral neuromodulation for Organophosphate-induced delayed neuropathy neurogenic lower urinary tract dysfunction: a case report.

BACKGROUND: Organophosphate-Induced Delayed Neuropathy (OPIDN) is a rare neurological disorder triggered by exposure to organophosphorus compounds. These compounds exert their neurotoxic effects by impacting the nervous system, leading to systemic manifestations. Urinary system symptoms are infrequently observed in clinical settings. Currently, effective therapeutic interventions for OPIDN-related urinary symptoms are lacking. Sacral nerve modulation therapy, an FDA-approved approach for managing lower urinary tract symptoms, presents as a promising option. Herein, we present a case of OPIDN-induced lower urinary tract obstruction successfully treated with sacral nerve modulation therapy, resulting in substantial symptom relief. CASE REPORT: A 27-year-old male patient presented with severe bilateral hydronephrosis, attributed to low bladder compliance and accompanied by a fever persisting for 6 days. The patient's medical history revealed accidental ingestion of organophosphate pesticide (Dimethoate) with no concomitant underlying diseases. In consideration of the potential for OPIDN, surgical intervention in the form of sacral neuromodulation (phase I) was undertaken. Subsequent evaluation one month post-surgery revealed notable improvements in both bladder compliance and bilateral hydronephrosis, necessitating sacral neuromodulation (phase II). Presently, following a 5-month follow-up period, the patient remains asymptomatic and in favorable health. CONCLUSION: This patient achieved long-term relief using sacral neuromodulation.

SARM1-mediated wallerian degeneration: A possible mechanism underlying organophosphorus-induced delayed neuropathy.

Some organophosphorus compounds (OPs) can cause a type of delayed neurotoxicity in human being, which is known as organophosphorus-induced delayed neuropathy (OPIDN). Signs and symptoms of the patients include tingling and sensory loss of the hands and feet, followed by progressive muscle weakness in the lower and upper limbs, and ataxia. Pathologically, OPIDN are characterized by distal sensorimotor axonopathy due to the distal axonal degeneration of nerve tracts located in central and peripheral nervous systems. The morphological pattern of the distal axonopathy is similar to Wallerian degeneration that occurs after nerve injury in vitro. It is generally acknowledged that inhibition and subsequent aging of neuropathy target esterase (NTE) is required for the occurrence of OPIDN. However, the underlying mechanisms through which NTE triggers axonal degeneration in OPIDN is still largely unclear. Recently, sterile alpha and toll/interleukin receptor motif-containing protein 1（SARM1) has been identified as a key player in Wallerian degeneration. In physical and chemical transection of axons, SARM1 was found to promotes axon degeneration by hydrolyzing NAD+. By contrast, SARM1 deficiency could prevent neuron degeneration in response to a wide range of insults. Furthermore, SARM1 can also translocate to mitochondria and cause mitochondrial damage, thus triggering axon degeneration and neuron death. These findings suggested the existence of a pathway in axonal degeneration that might be targeted therapeutically. Here, we hypothesize that SARM1 activation after NTE inhibition and aging might be an etiological factor in OPIDN that regulates Wallerian-like degeneration. Analysing SARM1 mediated NAD degeneration pathway and its upstream activators in OPIDN could contribute to the development of novel therapies to treat OPIDN.

Atg7 Knockout Alleviated the Axonal Injury of Neuro-2a Cells Induced by Tri-Ortho-Cresyl Phosphate.

Autophagy is believed to be essential for the maintenance of axonal homeostasis in neurons. However, whether autophagy is causally related to the axon degeneration in organophosphorus-induced delayed neuropathy (OPIDN) still remains unclear. This research was designed to investigate the role of autophagy in axon degeneration following tri-ortho-cresyl phosphate (TOCP) in an in vitro model. Differentiated wild-type and Atg7-/- neuro-2a (N2a) cells were treated with TOCP for 24 h. Axonal degeneration in N2a cells was quantitatively analyzed; the key molecules responsible for axon degeneration and its upstream signaling pathway were determined by Western blotting and real-time PCR. The results found that Atg7-/- cells exhibited a higher resistance to TOCP insult than wild-type cells. Further study revealed that TOCP caused a significant decrease in pro-survival factors NMNATs and SCG10 and a significant increase in pro-degenerative factor SARM1 in both cells. Notably, Atg7-/- cells presented a higher level of pro-survival factors and a lower level of pro-degenerative factors than wild-type cells in the same setting of TOCP administration. Moreover, DLK-MAPK pathway was activated following TOCP. Altogether, our results suggest that autophagy is able to affect TOCP-induced axonal injury via regulating the balance between pro-survival and pro-degenerative factors, providing a promising avenue for the potential therapy for OPIDN patients.

The role of protein kinase C alpha in tri-ortho-cresyl phosphate-induced autophagy in human neuroblastoma SK-N-SH cells.

As an organophosphorus ester, tri-ortho-cresyl phosphate (TOCP) has been widely used in agriculture and industry. It is reported that TOCP can induce organophosphate-induced delayed neuropathy (OPIDN) in sensitive animal and human species. However, the exact molecular mechanisms underlying TOCP-induced neurotoxicity are still unknown. In this study, we found that TOCP could induce autophagy by activating protein kinase C alpha (PKCα) signaling in neuroblastoma SK-N-SH cells. PKCα activators could positively regulate TOCP-induced autophagy by increasing the expression levels of neighbor BRCA1 gene protein 1 (NBR1), LC3 and P62 autophagic receptor protein. Furthermore, PKCα activation impaired the ubiquitin-proteasome system (UPS), resulting in inhibition of proteasome activity and accumulation of ubiquitinated proteins. UPS dysfunction could stimulate autophagy to serve as a compensatory pathway, which contributed to the accumulation of the abnormally hyperphosphorylated tau proteins and degradation of impaired proteins of the MAP 2 and NF-H families in neurodegenerative disorders.

Neuropathy target esterase (NTE/PNPLA6) and organophosphorus compound-induced delayed neurotoxicity (OPIDN).

Systemic inhibition of neuropathy target esterase (NTE) with certain organophosphorus (OP) compounds produces OP compound-induced delayed neurotoxicity (OPIDN), a distal degeneration of axons in the central nervous system (CNS) and peripheral nervous system (PNS), thereby providing a powerful model for studying a spectrum of neurodegenerative diseases. Axonopathies are important medical entities in their own right, but in addition, illnesses once considered primary neuronopathies are now thought to begin with axonal degeneration. These disorders include Alzheimer's disease, Parkinson's disease, and motor neuron diseases such as amyotrophic lateral sclerosis (ALS). Moreover, conditional knockout of NTE in the mouse CNS produces vacuolation and other degenerative changes in large neurons in the hippocampus, thalamus, and cerebellum, along with degeneration and swelling of axons in ascending and descending spinal cord tracts. In humans, NTE mutations cause a variety of neurodegenerative conditions resulting in a range of deficits including spastic paraplegia and blindness. Mutations in the Drosophila NTE orthologue SwissCheese (SWS) produce neurodegeneration characterized by vacuolization that can be partially rescued by expression of wild-type human NTE, suggesting a potential therapeutic approach for certain human neurological disorders. This chapter defines NTE and OPIDN, presents an overview of OP compounds, provides a rationale for NTE research, and traces the history of discovery of NTE and its relationship to OPIDN. It then briefly describes subsequent studies of NTE, including practical applications of the assay; aspects of its domain structure, subcellular localization, and tissue expression; abnormalities associated with NTE mutations, knockdown, and conventional or conditional knockout; and hypothetical models to help guide future research on elucidating the role of NTE in OPIDN.

Organophosphorus-Induced Toxic Myeloneuropathy: Series of Three Adolescent Patients with Short Review.

Organophosphate (OP) poisoning is the most common poisoning in India, accounting for almost half of the hospital admissions due to poisoning. Delayed neuropathy is initiated by an attack on a nervous tissue esterase. Although uncommon, delayed neurotoxicity has been consistently reported in literature. This mechanism is implicated not only in damaging peripheral nervous system but also in causing central processes leading to myelopathy. We report a series of three adolescent patients who came to our hospital with delayed neurological manifestations of organophosphorus poisoning, which came out to be OP-induced myeloneuropathy after detailed analysis and evaluation.

Activation of PINK1-Parkin-dependent mitophagy in Tri-ortho-cresyl phosphate-treated Neuro2a cells.

Tri-ortho-cresyl phosphate (TOCP) is a typical organophosphorus compound that can cause organophosphate-induced delayed neuropathy (OPIDN), which is pathologically characterized by axonal degeneration. Nowadays, mitochondrial dysfunction is regarded as a potential mechanism contributing to OPIDN progress. Mitophagy, a selective type of autophagy, is required to segregate damaged mitochondria from healthy mitochondrial networks and deliver them to lysosome for degradation. This research was designed to investigate the role of mitophagy in axon degeneration following TOCP administration in an in vitro model. Differentiated neuro2a (N2a) cells were divided into four groups and treated with 0, 5, 10, and 20 µM TOCP for 24 h, respectively. The critical proteins in PINK1-Parkin-dependent mitophagy including LC3, P62, PINK1, Parkin, mitochondrial proteins, and autophagic receptors were detected by immunoblotting and immunofluorescence. After TOCP treatment, increased level of ROS in N2a cells revealed a significant mitochondria damage. Meanwhile, it was observed that much more PINK1, Parkin, and LC3-II were translocated to the mitochondria. Furthermore, immunofluorescence analysis demonstrated that the co-localization of Parkin and LC3 was significantly increased. These results suggested that PINK1-Parkin dependent mitophagy pathway in N2a cells was activated by TOCP treatment. In addition, P62, a major autophagic receptor, was markedly accumulated on the mitochondria, which indicated that P62 might play a critical role in facilitating mitophagy under TOCP-induced axonal degeneration. Taken together, our results suggest that TOCP exposure resulted in the activation of PINK1-Parkin-dependent mitophagy in N2a cells. Mitophagy may act as a positively reactive mode in eliminating dysfunctional mitochondria and therefore protect neurons against TOCP neurotoxicity.

The Antidiabetic Drug Liraglutide Minimizes the Non-Cholinergic Neurotoxicity of the Pesticide Mipafox in SH-SY5Y Cells.

Organophosphorus (OPs) compounds have been widely used in agriculture, industry, and household, and the neurotoxicity induced by them is still a cause of concern. The main toxic mechanism of OPs is the inhibition of acetylcholinesterase (AChE); however, the delayed neuropathy induced by OPs (OPIDN) is mediated by other mechanisms such as the irreversible inhibition of 70% of NTE activity (neuropathy target esterase) that leads to axonal degeneration. Liraglutide is a long-lasting GLP-1 analog clinically used as antidiabetic. Its neurotrophic and neuroprotective effects have been demonstrated in vitro and in experimental models of neurodegenerative diseases. As in OPIDN, axonal degeneration also plays a role in neurodegenerative diseases. Therefore, this study investigated the protective potential of liraglutide against the neurotoxicity of OPs by using mipafox as a neuropathic agent (at a concentration able to inhibit and age 70% of NTE activity) and a neuronal model with SH-SY5Y neuroblastoma cells, which express both esterases. Liraglutide protected cells against the neurotoxicity of mipafox by increasing neuritogenesis, the uptake of glucose, the levels of cytoskeleton proteins, and synaptic-plasticity modulators, besides decreasing the pro-inflammatory cytokine interleukin 1ß and caspase-3 activity. This is the first study to suggest that liraglutide might induce beneficial effects against the delayed, non-cholinergic neurotoxicity of OPs.

TRPA1 channel mediates organophosphate-induced delayed neuropathy.

The organophosphate-induced delayed neuropathy (OPIDN), often leads to paresthesias, ataxia and paralysis, occurs in the late-stage of acute poisoning or after repeated exposures to organophosphate (OP) insecticides or nerve agents, and may contribute to the Gulf War Syndrome. The acute phase of OP poisoning is often attributed to acetylcholinesterase inhibition. However, the underlying mechanism for the delayed neuropathy remains unknown and no treatment is available. Here we demonstrate that TRPA1 channel (Transient receptor potential cation channel, member A1) mediates OPIDN. A variety of OPs, exemplified by malathion, activates TRPA1 but not other neuronal TRP channels. Malathion increases the intracellular calcium levels and upregulates the excitability of mouse dorsal root ganglion neurons in vitro. Mice with repeated exposures to malathion also develop local tissue nerve injuries and pain-related behaviors, which resembles OPIDN. Both the neuropathological changes and the nocifensive behaviors can be attenuated by treatment of TRPA1 antagonist HC030031 or abolished by knockout of Trpa1 gene. In the classic hens OPIDN model, malathion causes nerve injuries and ataxia to a similar level as the positive inducer tri-ortho-cresyl phosphate (TOCP), which also activates TRPA1 channel. Treatment with HC030031 reduces the damages caused by malathion or tri-ortho-cresyl phosphate. Duloxetine and Ketotifen, two commercially available drugs exhibiting TRPA1 inhibitory activity, show neuroprotective effects against OPIDN and might be used in emergency situations. The current study suggests TRPA1 is the major mediator of OPIDN and targeting TRPA1 is an effective way for the treatment of OPIDN.

High concentration of trichlorfon (1mM) disrupts axonal cytoskeleton and decreases the expression of plasticity-related proteins in SH-SY5Y cells.

Some organophosphorus compounds (OPs) induce a neurodegenerative disorder known as organophosphate-induced delayed neuropathy (OPIDN), which is related to irreversible inhibition of neuropathy target esterase (NTE) and impairment of neurite outgrowth. The present study addresses the effects of trichlorfon, mipafox (neuropathic model) and paraoxon (non-neuropathic model) on neurite outgrowth and neuroplasticity-related proteins in retinoic-acid-stimulated SH-SY5Y cells, a cellular model widely used to study the neurotoxicity of OPs. Mipafox (20µM) decreased cellular differentiation and the expression of neurofilament 200 (NF-200), growth associated- (GAP-43) and synaptic proteins (synapsin I and synaptophysin); whereas paraoxon (300µM) induced no effect on cellular differentiation, but significant decrease of NF-200, GAP-43, synapsin I and synaptophysin as compared to controls. However, the effects of paraoxon on these proteins were significantly lower than the effects of mipafox. In conclusion, axonal cytoskeletal proteins, as well as axonal plasticity-related proteins are more effectively affected by neuropathic (mipafox) than by non-neuropathic (paraoxon) OPs, suggesting that they might play a role in the mechanism of OPIDN. At high concentration (1mM), trichlorfon induced effects similar to those of the neuropathic OP, mipafox (20µM), but also caused high inhibition of AChE. Therefore, these effects are unlikely to occur in humans at non-lethal doses of trichlorfon.

Sarin (GB, O-isopropyl methylphosphonofluoridate) neurotoxicity: critical review.

Sarin (GB, O-isopropyl methylphosphonofluoridate) is a potent organophosphorus (OP) nerve agent that inhibits acetylcholinesterase (AChE) irreversibly. The subsequent build-up of acetylcholine (ACh) in the central nervous system (CNS) provokes seizures and, at sufficient doses, centrally-mediated respiratory arrest. Accumulation of ACh at peripheral autonomic synapses leads to peripheral signs of intoxication and overstimulation of the muscarinic and nicotinic receptors, which is described as "cholinergic crisis" (i.e. diarrhea, sweating, salivation, miosis, bronchoconstriction). Exposure to high doses of sarin can result in tremors, seizures, and hypothermia. More seriously, build-up of ACh at neuromuscular junctions also can cause paralysis and ultimately peripherally-mediated respiratory arrest which can lead to death via respiratory failure. In addition to its primary action on the cholinergic system, sarin possesses other indirect effects. These involve the activation of several neurotransmitters including gamma-amino-butyric acid (GABA) and the alteration of other signaling systems such as ion channels, cell adhesion molecules, and inflammatory regulators. Sarin exposure is associated with symptoms of organophosphate-induced delayed neurotoxicity (OPIDN) and organophosphate-induced chronic neurotoxicity (OPICN). Moreover, sarin has been involved in toxic and immunotoxic effects as well as organophosphate-induced endocrine disruption (OPIED). The standard treatment for sarin-like nerve agent exposure is post-exposure injection of atropine, a muscarinic receptor antagonist, accompanied by an oxime, an AChE reactivator, and diazepam.

Neuropathy target esterase in mouse whole blood as a biomarker of exposure to neuropathic organophosphorus compounds.

The adult hen is the standard animal model for testing organophosphorus (OP) compounds for organophosphorus compound-induced delayed neurotoxicity (OPIDN). Recently, we developed a mouse model for biochemical assessment of the neuropathic potential of OP compounds based on brain neuropathy target esterase (NTE) and acetylcholinesterase (AChE) inhibition. We carried out the present work to further develop the mouse model by testing the hypothesis that whole blood NTE inhibition could be used as a biochemical marker for exposure to neuropathic OP compounds. Because brain NTE and AChE inhibition are biomarkers of OPIDN and acute cholinergic toxicity, respectively, we compared NTE and AChE 20-min IC50 values as well as ED50 values 1 h after single intraperitoneal (i.p.) injections of increasing doses of two neuropathic OP compounds that differed in acute toxicity potency. We found good agreement between the brain and blood for in vitro sensitivity of each enzyme as well for the ratios IC50 (AChE)/IC50 (NTE). Both OP compounds inhibited AChE and NTE in the mouse brain and blood dose-dependently, and brain and blood inhibitions in vivo were well correlated for each enzyme. For both OP compounds, the ratio ED50 (AChE)/ED50 (NTE) in blood corresponded to that in the brain despite the somewhat higher sensitivity of blood enzymes. Thus, our results indicate that mouse blood NTE could serve as a biomarker of exposure to neuropathic OP compounds. Moreover, the data suggest that relative inhibition of blood NTE and AChE provide a way to assess the likelihood that OP compound exposure in a susceptible species would produce cholinergic and/or delayed neuropathic effects. Copyright © 2016 John Wiley & Sons, Ltd.

Restricted diffusion in the splenium of the corpus callosum in organophosphate induced delayed neuropathy: case report and review of literatures.

UNLABELLED: We described a 35 year-old female who developed organophosphate induced delayed neuropathy (OPIDN) with an unusal clinical manifestation and neuroradiological presentation. CASE REPORT: A 35-year-old woman came into contact with organophosphate pesticide by remissly inhalation. She got transient unconsciousness lasting for nearly 2 hours and developed transient hematuria and hyperhidrotic subsequently. She received atropine as treatment and got a satisfying recovery and was hospital discharged without any symptoms. But 20 days later the patient displayed symptoms including headache, vertigo, mental and memory decline, and was hospitalized again. Clinical manifestations, laboratorial findings, images data will be presented. The brain magnetic resonance imaging (MRI) showed an unusal neuroradiological presentation characterized by restricted diffusion in the splenium of the corpus callosum. The patient recovered satisfactorily after administration of corticosteroids and immunogloblin. CONCLUSION: OPIDN may develop in some susceptible individuals even by inhalation and sometimes with central nervous system involvement. Treatment with corticosteroids and intravenous immunogloblins was found to achieve good results.

In vitro study of the neuropathic potential of the organophosphorus compounds trichlorfon and acephate.

Organophosphorus-induced delayed neuropathy (OPIDN) is a central and peripheral distal axonopathy characterized by ataxia and paralysis. Trichlorfon and acephate are two organophosphorus compounds (OPs) used worldwide as insecticide and which cause serious effects to non-target species. Despite that, the neuropathic potential of these OPs remains unclear. The present study addressed the neurotoxic effects and the neuropathic potential of trichlorfon and acephate in SH-SY5Y human neuroblastoma cells, by evaluating inhibition and aging of neuropathy target esterase (NTE), inhibition of acetylcholinesterase (AChE), neurite outgrowth, cytotoxicity and intracellular calcium. Additionally, the effects observed were compared to those of two well-studied OPs: mipafox (known as neuropathic) and paraoxon (known as non-neuropathic). Trichlorfon and mipafox presented the lowest percentage of reactivation of inhibited NTE and the lowest ratio IC50 NTE/IC50 AChE. Moreover, they caused inhibition and aging of at least 70% of the activity of NTE at sub-lethal concentrations. All these effects have been associated with induction of OPIDN. When assayed at these concentrations, trichlorfon and mipafox reduced neurite outgrowth and increased intracellular calcium, events implicated in the development of OPIDN. Acephate caused effects similar to those caused by paraoxon (non-neuropathic OP) and was only able to inhibit 70% of NTE activity at lethal concentrations. These findings suggest that trichlorfon is potentially neuropathic, whereas acephate is not.

Mitochondrial complex I inhibition as a possible mechanism of chlorpyrifos induced neurotoxicity.

BACKGROUND: Organophosphates (OPs) represent the most widely used class of pesticides. Although perceived as low toxicity compounds compared to the previous organochlorines, they still possess neurotoxic effects both on acute and delayed levels. Delayed neurotoxic effects of OPs include OPIDN and OPICN. The mechanisms of these delayed effects have not been totally unraveled yet. One possible contributor for neurotoxicity is mitochondrial complex I (CI) inhibition. PURPOSE: in the present study we evaluated the contributing role of (CI) inhibition in chlorpyrifos (CPF) induced delayed neuropathy in hens. METHODS: Experimented birds received 150 mg/kg of CPF, and evaluated behaviorally and biochemically. RESULTS: CPF treated hens received 150 mg/kg and developed signs of delayed neurotoxicity, which were verified by NTE inhibition. These effects were paralleled by CI inhibition and decrease in ATP level. CONCLUSIONS: The data confirms the possible role of CI inhibition in CPF induced delayed neuropathy.

Further studies toward a mouse model for biochemical assessment of neuropathic potential of organophosphorus compounds.

Inhibition and aging of neuropathy target esterase (NTE) by neuropathic organophosphorus (OP) compounds triggers OP compound-induced delayed neuropathy (OPIDN), whereas inhibition of acetylcholinesterase (AChE) produces cholinergic toxicity. The neuropathic potential of an OP compound is defined by its relative inhibitory potency toward NTE vs. AChE assessed by enzyme assays following dosing in vivo or after incubations of direct-acting compounds or active metabolites with enzymes in vitro. The standard animal model of OPIDN is the adult hen, but its large size and high husbandry costs make this species a burdensome model for assessing neuropathic potential. Although the mouse does not readily exhibit clinical signs of OPIDN, it displays axonal lesions and expresses brain AChE and NTE. Therefore, the present research was performed as a further test of the hypothesis that inhibition of mouse brain AChE and NTE could be used to assess neuropathic potential using mouse brain preparations in vitro or employing mouse brain assays following dosing of OP compounds in vivo. Excellent correlations were obtained for inhibition kinetics in vitro of mouse brain enzymes vs. hen brain and human recombinant enzymes. Furthermore, inhibition of mouse brain AChE and NTE after dosing with OP compounds afforded ED(50) ratios that agreed with relative inhibitory potencies assessed in vitro. Taken together, results with mouse brain enzymes demonstrated consistent correspondence between in vitro and in vivo predictors of neuropathic potential, thus adding to previous studies supporting the validity of a mouse model for biochemical assessment of the ability of OP compounds to produce OPIDN.

Identification of differentially expressed proteins related to organophosphorus-induced delayed neuropathy in the brains of hens.

Some organophosphorus compounds can cause organophosphate-induced delayed neuropathy (OPIDN). Incidents have been documented for decades, however, little is known about which proteins contribute to the initiation, progression and development of OPIDN. In this study, 51 hens were divided into three groups. The tri-ortho-cresyl-phosphate (TOCP) group was treated with 1000 mg kg(-1) TOCP whereas the control group was treated with an equivalent volume of vehicle. The PMSF + TOCP group was treated subcutaneously with 40 mg kg(-1) phenylmethylsulfonyl fluoride (PMSF), followed by 1000 mg kg(-1) TOCP 24 h later. Proteins in the brains of hens were separated by two-dimensional polyacrylamide gel electrophoresis on day 5 after TOCP administration. Mass spectrometry identified eight differentially expressed proteins. Among these proteins, downregulated expression of glutamine synthetase (GS) in the brains of hens after TOCP treatment was further confirmed by real time RT-PCR and ELISA. Moreover, the brains of hens exposed to TOCP exhibited increased levels of glutamate (Glu) and cytosolic calcium concentration ([Ca(2+)](i)), and a decreased level of glutamine (Gln). However, there were no significant differences in GS expression or levels of Glu, Gln, and [Ca(2+)](i) in the brains of hens among the groups on day 21 after TOCP administration. These results indicate that TOCP exposure downregulates GS expression in the brains of hens, and that downregulation of GS is accompanied by increased levels of Glu and [Ca(2+)](i) in the early stage after TOCP administration. It is also suggested that the downregulated expression of GS might be associated with OPIDN through the disruption of homeostasis of the Glu-Gln cycle and [Ca(2+) ](i).

Involvement of autophagy in tri-ortho-cresyl phosphate- induced delayed neuropathy in hens.

Autophagy is a highly conserved cellular self-degradative process that plays a housekeeping role in removing aggregated proteins and damaged organelles. Our recent work has found that tri-ortho-cresyl phosphate (TOCP), a neuropathic organophosphate (OP), decreased the level of beclin 1 (a key molecule in the process of autophagy) in hen nerve tissues (Song et al., 2012). However, the role of autophagy in the pathogenesis of organophosphorus ester-induced delayed neuropathy (OPIDN) remains unclear. Here, we investigated whether dysfunctional autophagy was associated with the initiation and development of TOCP-induced delayed neuropathy. Adult hens were given a single dose of 750mg/kg TOCP (p.o.) and sacrificed on days 1, 5, 10, and 21 after dosing, respectively. The formation of autophagosomes in spinal cord motor neurons was observed by transmission electron microscopy, the level of autophagy-related proteins in hen spinal cords and tibial nerves was determined by Western blot analysis. The results demonstrated that the number of autophagosomes was markedly increased in the myelinated and unmyelinated axons of hen spinal cords after TOCP exposure. In the meantime, the level of two molecular markers for autophagy, microtubule-associated protein light chain-3 (LC3) and p62/SQSTM1 in hen nerve tissues was significantly decreased and increased, respectively. Furthermore, a marked reduction in autophagy-regulated proteins including ULK 1, AMBRA 1, ATG 5, ATG 7, ATG 12 and VPS34 expression was also observed. Our results suggested that the administration of TOCP resulted in a significant inhibition of autophagy activity in neurons, which might be associated with the pathogenesis of OPIDN.

A systematic review on the nerve-muscle electrophysiology in human organophosphorus pesticide exposure.

This article presents a systematic review of the recent literature on the scientific support of electromyography (EMG) and nerve conduction velocity (NCV) in diagnosing the exposure and toxicity of organophosphorus pesticides (OP). Specifically, this review focused on changes in EMG, NCV, occurrence of intermediate syndrome (IMS), and OP-induced delayed polyneuropathy (OPIDN) in human. All relevant bibliographic databases were searched for human studies using the key words "OP poisoning", "electromyography", "nerve conduction study," and "muscles disorders". IMS usually occurs after an acute cholinergic crisis, while OPIDN occurs after both acute and chronic exposures. Collection of these studies supports that IMS is a neuromuscular junction disorder and can be recorded upon the onset of respiratory failure. Due to heterogeneity of reports on outcomes of interest such as motor NCV and EMG amplitude in acute cases and inability to achieve precise estimation of effect in chronic cases meta-analysis was not helpful to this review. The OPIDN after both acute and low-level prolonged exposures develops peripheral neuropathy without preceding cholinergic toxicity and the progress of changes in EMG and NCV is parallel with the development of IMS and OPIDN. Persistent inhibition of acetylcholinesterase (AChE) is responsible for muscle weakness, but this is not the only factor involved in the incidence of this weakness in IMS or OPIDN suggestive of AChE assay not useful as an index of nerve and muscle impairment. Although several mechanisms for induction of this neurodegenerative disorder have been proposed as were reviewed for this article, among them oxidative stress and resulting apoptosis can be emphasized. Nevertheless, there is little synchronized evidence on subclinical electrophysiological findings that limit us to reach a strong conclusion on the diagnostic or prognostic use of EMG and NCV for acute and occupational exposures to OPs.

Acetylcholine esterase is a regulator of GFAP expression and a target of dichlorvos in astrocytic differentiation of rat glioma C6 cells.

The main target of neurotoxins is neurons because they comprise the main part of neural function, but glial cells may be indirect targets because they support the function of neurons. Among the glial cells, astrocytes in particular act as "nurse cells", regulating neuronal survival and functions. In the present study, to reveal whether a known neurotoxic substance, organophosphate dichlorvos (DDVP), affects the differentiation of astrocytes, we used an astrocyte differentiation model in rat glioma C6 cells. Morphological change and induction of GFAP expression in the differentiating C6 cells were suppressed by DDVP treatment. The known potential targets of DDVP are acetylcholine esterase (AChE), fatty acid amide hydrolase and methyl guanine methyl transferase. Among the specific inhibitors against these enzymes, the AChE inhibitor paraoxon successfully suppressed the cellular morphological changes and the induction of GFAP expression in differentiating C6 cells. These results indicate that DDVP inhibits differentiation in the C6 astrocyte-differentiation model, in which at least AChE inhibition is involved and that AChE is a potent regulator of the differentiation. Furthermore, considering that the main substrate of AChE is ACh, thus, ACh may act as regulators of astrocyte differentiation.