Organophosphorus compound-induced modification of SH-SY5Y human neuroblastoma mitochondrial transmembrane potential

Tributyl phosphate can inhibit the feeding behavior of rotifers by altering the axoneme structure, neuronal coordination and energy supply required for motile cilia

Organophosphorus flame retardants (OPFRs) are frequently detected in aquatic environments and can potentially amplify the food chain, posing a potential risk to organisms. Marine invertebrates have primitive nervous systems to regulate behavior, but how they respond to OPFRs that are potentially neurotoxic substances is unclear. This study assessed changes in the feeding behavior of rotifer Brachionus plicatilis exposed to alkyl OPFRs tributyl phosphate (TnBP) (0.376 nM, 3.76 and 22.53 µM) to elucidate the mechanism of behavioral toxicity. TnBP at 22.53 μM reduced the ingestion and filtration rates of rotifers for Chlorella vulgaris and Phaeocystis globosa in a 24-h test and altered rotifer-P. globosa population dynamics in 15-d coculture. Ciliary beat frequency was also reduced, and the expression of genes encoding the cilia axoneme was downregulated. TnBP could inhibit rotifer acetylcholinesterase activity by binding this protein and reduce the expression of the exocytotic membrane protein syntaxin-4, suggesting a disorder in nervous regulation of cilia beat. Moreover, TnBP induced abnormal shape and dysfunction of mitochondria, which caused insufficient energy required for ciliary movement. This study revealed diverse neurotoxicity mechanisms of TnBP, particularly as a potentially competing acetylcholinesterase ligand for aquatic invertebrates. Our research also provides a meaningful reference for OPFR-induced behavioral toxicity assessments.

Association between organophosphorus insecticides exposure and the prevalence of sleep problems in the US adults: An analysis based on the NHANES 2007-2018

OBJECTIVE

The aim of this study was to evaluate the association between organophosphorus pesticides (OPPs) exposure and sleep problems.

METHODS

In this study, data from 6295 participants aged 18 years or older were collected from the National Health and Nutrition Examination Survey (NHANES). The dialkyl phosphate compounds (DAPs) metabolites, OPPs exposure biomarker, were examined using solid phase extraction-high coupled with isotope dilution-ultrahigh performance liquid chromatography-tandem mass spectrometry. Data on short sleep duration (SSD), self-reported trouble sleeping and self-reported sleep disorder were collected from the database. Weighted generalized logistic model, weighted quantile sum (WQS) model, and quantile-based g calculation (QGC) methods were used for analyzing the collected data.

RESULTS

The prevalence of SSD, self-reported trouble sleeping and self-reported sleep disorder in this study were 28.91 % (1814/6274), 25.31 % (1593/6294), and 9.05 % (289/3195), respectively. After confounding factors adjustments, the prevalence of SDD in participants with high log-transformed DETP, DMTP, DEDTP, and DMDTP were 1.19 times (OR: 1.11-1.28, P < 0.001), 1.09 times (OR: 1.03-1.15, P = 0.003), 1.26 times (OR: 1.17-1.37, P < 0.0001), and 1.10 times (OR: 1.04-1.17, P = 0.003) than in participants with low showed, respectively. A non-linear relationship was noted between SSD with the urinary concentration of DEP (P for nonlinearity < 0.001), DMP (P for nonlinearity < 0.001), DMTP (P for nonlinearity = 0.006), and DMDTP (P for nonlinearity = 0.001). The WQS results showed that the prevalence of SDD was 1.28 times (95 % CI: 1.17-1.40, P < 0.001) higher in participants with high co-exposure to OPPs than in those with low co-exposure, with DEDTP having the enormous weights (0.50). The QGC results also revealed a significant positive association between the co-exposure of DAPs and SSD (OR: 1.08, 95 % CI:1.02-1.16, P = 0.01) with DETP having the most positive weight (0.44). As for the association between DAPs with self-report sleep disorder, only DEP was detected that it was positively associated with self-reported sleep disorder with all confounding factors adjusted (OR: 1.17; 95 % CI: 1.07-1.29, P = 0.001). However, all DAPs have not detected a significant association with the prevalence of self-reported trouble sleeping. Besides, there was no significant association between co-exposure to OPPs with self-reported trouble sleeping and self-reported sleep disorder.

CONCLUSION

The results of this study indicated that high levels of single or mixture urinary DAP, indicating for OPPs exposure, were associated with an increased prevalence of SSD in general adults, which has significant implications for preventing OPPs pollution and protecting sleep health.

Neuromodulatory effect of 4-(methylthio)butyl isothiocyanate against 3-nitropropionic acid induced oxidative impairments in human dopaminergic SH-SY5Y cells via BDNF/CREB/TrkB pathway

Mitochondrial impairment, energetic crisis and elevated oxidative stress have been demonstrated to play a pivotal role in the pathological processes of Huntington's disease (HD). 3-Nitropropionic acid (3-NPA) is a natural neurotoxin that mimics the neurological dysfunctions, mitochondrial impairments and oxidative imbalance of HD. The current investigation was undertaken to demonstrate the neuroprotective effect of 4-(methylthio)butyl isothiocyanate (4-MTBITC) against the 3-NPA induced neurotoxicity in human dopaminergic SH-SY5Y cells. The experimental evidence of oxidative DNA damage by 3-NPA was elucidated by pBR322 DNA nicking assay. In contrast, the 4-MTBITC considerably attenuated the DNA damage, suggesting its free radical scavenging action against 3-NPA and Fenton's reagent. The dose and time-dependent increase of 3-NPA revealed its neurotoxic dose as 0.5 mM after 24 h of treatment of SH-SY5Y cells in MTT assay. In order to determine the optimal dose at which 4-MTBITC protects cell death, the 3-NPA (IC₅₀) induced cells were pretreated with different concentrations of 4-MTBITC for 1 h. The neuroprotective dose of 4-MTBITC against 3-NPA was found to be 0.25 μM. Additionally, the elevated GSH levels in cells treated with 4-MTBITC indicate its propensity to eliminate reactive species generated as a result of 3-NPA-induced mitochondrial dysfunction. Likewise, it was determined through microscopic and flow cytometric experiments that 3-NPA's induced overproduction of reactive species and a decline in mitochondrial membrane potential (MMP) could be efficiently prevented by pre-treating cells with 4-MTBITC. To elucidate the underlying molecular mechanism, the RT-qPCR analysis revealed that the pre-treatment of 4-MTBITC effectively protected neuronal cells against 3-NPA-induced cell death by preventing Caspase-3 activation, Brain-derived neurotrophic factor (BDNF) upregulation, activation of cAMP response element-binding protein (CREB) and Nrf2 induction. Together, our findings lend credence to the idea that pre-treatment with 4-MTBITC reduced 3-NPA-induced neurotoxicity by lowering redox impairment, apoptotic state, and mitochondrial dysfunction. The present work, in conclusion, presented the first proof that the phytoconstituent 4-MTBITC supports the antioxidant system, BDNF/TrkB/CREB signaling, and neuronal survival in dopaminergic SH-SY5Y cells against 3-NPA-induced oxidative deficits.

Cellular and molecular responses to ethyl-parathion in undifferentiated SH-SY5Y cells provide neurotoxicity pathway indicators for organophosphorus impacts

High-fidelity nonanimal screening methods are needed that can rapidly and accurately characterize organophosphorus compound (OP)-induced neurotoxicity. Herein, the efficacy of human neuroblastoma cell line (SH-SY5Y) to provide molecular and cellular responses characteristic of the OP neurotoxicity pathway was investigated in response to the OP-model compound, ethyl-parathion. Undifferentiated SH-SY5Y cells were exposed to ethyl-parathion for 30 min at 0 (control), 0.5, 2.5, 5, 10, and 25 µg/ml. Dose-responsive reductions in cell viability were observed with significant reductions at ≥10 µg/ml. From these results, ethyl-parathion exposures of 0 (control), 5, and 10 µg/ml were selected to examine bioindicators underlying the OP neurotoxicity pathway including: reactive oxygen species (ROS), cell membrane peroxidation, mitochondrial membrane potential (MMP), and apoptosis. Ethyl-parathion elicited highly significant increases in ROS relative to controls (p < .01) at both exposure concentrations, confirmed using N-acetyl cysteine (NAC) as a ROS quencher which alleviated ROS increases. A response characteristic of increased ROS exposure, cell membrane-lipid peroxidation, significantly increased (p < .05) at the highest ethyl-parathion exposure (10 µg/ml). As a likely consequence of membrane-lipid peroxidation, ethyl-parathion-induced reductions in MMP were observed with significant effects at 10 µg/ml, reducing MMP by 58.2%. As a culmination of these cellular-damage indicators, apoptosis progression was investigated by phosphatidylserine translocation where ethyl-parathion-induced dose-responsive, highly significant (p < .01) increases at both 5 and 10 µg/ml. Overall, the mechanistic responses observed in undifferentiated SH-SY5Y cells corresponded with in vivo mammalian results demonstrating potential for this nonanimal model to provide accurate OP neurotoxicology screening.

The SH-SY5Y human neuroblastoma cell line, a relevant in vitro cell model for investigating neurotoxicology in human: focus on organic pollutants

Investigation of the toxicity triggered by chemicals on the human brain has traditionally relied on approaches using rodent in vivo models and in vitro cell models including primary neuronal cultures and cell lines from rodents. The issues of species differences between humans and rodents, the animal ethical concerns and the time and cost required for neurotoxicity studies on in vivo animal models, do limit the use of animal-based models in neurotoxicology. In this context, human cell models appear relevant in elucidating cellular and molecular impacts of neurotoxicants and facilitating prioritization of in vivo testing. The SH-SY5Y human neuroblastoma cell line (ATCC® CRL-2266^TM) is one of the most used cell lines in neurosciences, either undifferentiated or differentiated into neuron-like cells. This review presents the characteristics of the SH-SY5Y cell line and proposes the results of a systematic review of literature on the use of this in vitro cell model for neurotoxicity research by focusing on organic environmental pollutants including pesticides, 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), flame retardants, PFASs, parabens, bisphenols, phthalates, and PAHs. Organic environmental pollutants are widely present in the environment and increasingly known to cause clinical neurotoxic effects during fetal & child development and adulthood. Their effects on cultured SH-SY5Y cells include autophagy, cell death (apoptosis, pyroptosis, necroptosis, or necrosis), increased oxidative stress, mitochondrial dysfunction, disruption of neurotransmitter homeostasis, and alteration of neuritic length. Finally, the inherent advantages and limitations of the SH-SY5Y cell model are discussed in the context of chemical testing.

Mechanistic understanding of the toxicity of triphenyl phosphate (TPhP) to the marine diatom Phaeodactylum tricornutum: Targeting chloroplast and mitochondrial dysfunction

Triphenyl phosphate (TPhP) has been widely detected in various environmental media, including seawater, threatening the survival of marine organisms, especially marine planktic algae that are directly exposed to contamination. However, the hazard potential of TPhP on marine algae has not been studied thoroughly and systematically. In this study, a marine diatom, Phaeodactylum tricornutum, was treated with three concentrations of TPhP (0.08, 0.4 and 0.8 mg/L), and after 24 h of exposure, population growth, ultrastructure, physiology and transcriptome changes were investigated. The results reflected that TPhP suppressed the population growth of algae in a concentration-dependent manner, and the 24-h EC₅₀ value was 1.27 mg/L. At all test concentrations, P. tricornutum could absorb more than 70% of TPhP from seawater over 24 h. Ultrastructural observations suggested a distorted lamellar structure with higher TPhP treatments, and the contents of chlorophyll and its precursors were also altered, as were photosynthetic activities. Moreover, 0.8 mg/L TPhP decreased the mitochondrial membrane potential, induced ROS overproduction and disrupted the cell membrane permeability of algal cells. At the transcriptomic level, some differentially expressed genes were enriched in photosynthetic electron transport, carbon fixation, chlorophyll biosynthesis, the TCA cycle and mitochondrial glycolysis. Additionally, 0.8 mg/L TPhP inhibited lipid de novo biosynthesis, suggesting that it may target organelle membranes, thereby contributing to functional defects. Chloroplasts and mitochondria were interpreted to be the subcellular targets of TPhP in P. tricornutum. These data promote the understanding of the toxic action mode of TPhP toward marine diatoms.

Acute and long-term effects of VX in rat brain cell aggregate culture

The contact poison VX (O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate) is a chemical warfare agent that is one of the most toxic organophosphorus compounds known. Its primary mechanism of toxic action is through the inhibition of acetylcholinesterase and resultant respiratory paralysis. The majority of work on VX has thus concentrated on its potent anticholinesterase activity and acute toxicity, with few studies investigating potential long-term effects. In this report we describe the effects of VX in aggregating rat brain cell cultures out to 28 days post-exposure. Cholinesterase activity was rapidly inhibited (60 min IC50 = 0.73 +/- 0.27 nM), but recovered towards baseline values over the next four weeks. Apoptotic cell death, as measured using caspase-3 activity was evident only at 100 μM concentrations. Cell type specific enzymatic markers (glutamine synthase, choline acetyltransferase and 2',3'-cyclic nucleotide 3'-phosphodiesterase) showed no significant changes. Total Akt levels were unchanged, while an increased phosphorylation of this protein was noted only at the highest VX concentration on the first day post-exposure. In contrast, significant and delayed (28 days post-exposure) decreases were noted in vascular endothelial growth factor (VEGF) levels, a protein whose reduced levels are known to contribute to neurodegenerative disorders. These observations may indicate that the long-term effects noted in some survivors of nerve agent intoxication may be due to VX-induced declines in brain VEGF levels.

Dimethoate Induces DNA Damage and Mitochondrial Dysfunction Triggering Apoptosis in Rat Bone-Marrow and Peripheral Blood Cells

Dimethoate (DM) is an organophosphorus (OP) pesticide with wide use in the pest control. Its persistence in crops and soils could possibly cause adverse health consequences in humans as well as other non-target species. Since molecular studies confirming potential genotoxicity of DM have not been previously reported, the acute in vivo toxicological impact was evaluated in Wistar rats. Significant micronuclei induction and metaphase chromosome abnormalities in bone marrow cells exposed to three different DM doses (20, 40 and 60 mg/kg-bw) at multiple treatment durations (24, 48 and 72 h) indicated positive dose response relationship, confirming its genotoxic and cytotoxic potential. Significant mitotic index decrease was seen in dosed animals compared to vehicle control. The study used peripheral blood comet assay, indicating DM-mediated damage to DNA at all exposure levels in a time responsive manner. These assays were found to be an effective, precise, and fast technique with applied value in biomonitoring studies. Cell cycle and apoptosis along with mitochondrial membrane potential (MMP) in flow cytometric analyses confirmed DM exposure decreased MMP, affected the cell cycle, and inflicted DNA damage, which led to cellular apoptosis of leukocytes culminating into immunotoxic effects. The in silico experiments consequently augmented that DM showed acceptable binding energy value for Cyclin A2, suggesting that it could inhibit the cell cycle progression by inhibiting cyclin A2.

Caspase-1 has a critical role in blood-brain barrier injury and its inhibition contributes to multifaceted repair

Background

Excessive inflammation might activate and injure the blood-brain barrier (BBB), a common feature of many central nervous system (CNS) disorders. We previously developed an in vitro BBB injury model in which the organophosphate paraoxon (PX) affects the BBB endothelium by attenuating junctional protein expression leading to weakened barrier integrity. The objective of this study was to investigate the inflammatory cellular response at the BBB to elucidate critical pathways that might lead to effective treatment in CNS pathologies in which the BBB is compromised. We hypothesized that caspase-1, a core component of the inflammasome complex, might have important role in BBB function since accumulating evidence indicates its involvement in brain inflammation and pathophysiology.

Methods

An in vitro human BBB model was employed to investigate BBB functions related to inflammation, primarily adhesion and transmigration of peripheral blood mononuclear cells (PBMCs). Caspase-1 pathway was studied by measurements of its activation state and its role in PBMCs adhesion, transmigration, and BBB permeability were investigated using the specific caspase-1 inhibitor, VX-765. Expression level of adhesion and junctional molecules and the secretion of pro-inflammatory cytokines were measured in vitro and in vivo at the BBB endothelium after exposure to PX. The potential repair effect of blocking caspase-1 and downstream molecules was evaluated by immunocytochemistry, ELISA, and Nanostring technology.

Results

PX affected the BBB in vitro by elevating the expression of the adhesion molecules E-selectin and ICAM-1 leading to increased adhesion of PBMCs to endothelial monolayer, followed by elevated transendothelial-migration which was ICAM-1 and LFA-1 dependent. Blocking caspase-8 and 9 rescued the viability of the endothelial cells but not the elevated transmigration of PBMCs. Inhibition of caspase-1, on the other hand, robustly restored all of barrier insults tested including PBMCs adhesion and transmigration, permeability, and VE-cadherin protein levels. The in vitro inflammatory response induced by PX and the role of caspase-1 in BBB injury were corroborated in vivo in isolated blood vessels from hippocampi of mice exposed to PX and treated with VX-765.

Conclusions

These results shed light on the important role of caspase-1 in BBB insult in general and specifically in the inflamed endothelium, and suggest therapeutic potential for various CNS disorders, by targeting caspase-1 in the injured BBB.

Pesticides, cognitive functions and dementia: A review

Pesticides are widely-used chemicals commonly applied in agriculture for the protection of crops from pests. Depending on the class of pesticides, the specific substances may have a specific set of adverse effects on humans, especially in cases of acute poisoning. In past years, evidence regarding sequelae of chronic, low-level exposure has been accumulating. Cognitive impairment and dementia heavily affect a person's quality of life and scientific data has been hinting towards an association between them and antecedent chronic pesticide exposure. Here, we reviewed animal and human studies exploring the association between pesticide exposure, cognition and dementia. Additionally, we present potential mechanisms through which pesticides may act neurotoxically and lead to neurodegeneration. Study designs rarely presented homogeneity and the estimation of the exposure to pesticides has been most frequently performed without measuring the synergic effects and the possible interactions between the toxicants within mixtures, and also overlooking low exposures to environmental toxicants. It is possible that a Real-Life Risk Simulation approach would represent a robust alternative for future studies, so that the safe exposure limits and the net risk that pesticides confer to impaired cognitive function can be examined. Previous studies that evaluated the effect of low dose chronic exposure to mixtures of pesticides and other chemicals intending to simulate real life exposure scenarios showed that hormetic neurobehavioral effects can appear after mixture exposure at doses considered safe for individual compounds and these effects can be exacerbated by a coexistence with specific conditions such as vitamin deficiency. However, there is an overall indication, derived from both epidemiologic and laboratory evidence, supporting an association between exposure to neurotoxic pesticides and cognitive dysfunction, dementia and Alzheimer's disease.

Effect of the herbicide atrazine and its major metabolite, DACT, on bovine sperm cryotolerance

During freezing and thawing procedures, sperm are exposed to chemical and/or physical stressors that may cause adverse and harmful changes to sperm membranes. Accurate evaluation of the structural and functional integrity of fresh as well as cryopreserved sperm is highly important in predicting sperm fertilization capacity and success of artificial insemination (AI). The herbicide atrazine (ATZ) and its major metabolite, diaminochlorotriazine (DACT) are considered a ubiquitous environmental contaminants and endocrine disruptors, which deleteriously effect sperm function. Taking into consideration possible damage caused by environmental contaminants to sperm membranes, additive effects during cryopreservation cannot be ruled out. The aim of the current study was to evaluate the effect of ATZ (0.1 or 1 μM) and DACT (1 or 10 μM) exposure during or after cryopreservation on bovine sperm cryotolerance. Sperm membrane integrity and functionality were evaluated using fluorimetric probes: (1) double-stranded DNA was examined by 4',6-diamidino-2-phenylindole; (2) plasma membrane integrity was examined by propidium iodide; (3) acrosome reaction (AR) was examined by fluorescein isothiocyanate-conjugated Pisum sativum agglutinin; mitochondrial membrane potential (ΔΨm) was examined by 5,5',6,6'-tetra-chloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide fluorescent probe. The findings demonstrate, that exposure of sperm to ATZ (0.1 or 1 μM) or DACT (1 or 10 μM) during cryopreservation increased the proportion of dead sperm relative to the control (P < 0.09); exposure to DACT (1 or 10 μM) increased ΔΨm (P < 0.03). Neither ATZ nor DACT affected spontaneous AR. In contrast, the proportion of sperm with Ca⁺⁺ ionophore-induced AR was lower after exposure to 1 μM DACT (P < 0.05). Following freezing and thawing procedures, exposing sperm to 1 μM ATZ increased the proportion of dead sperm relative to the control (P < 0.05), but had no significant effect on sperm ΔΨm or AR. In conclusion, exposing sperm to endocrine-disrupting chemicals such as ATZ or DACT during cryopreservation reduces sperm cryotolerance and resistance post-thawing.

Blood-Brain Barrier Cellular Responses Toward Organophosphates: Natural Compensatory Processes and Exogenous Interventions to Rescue Barrier Properties

Organophosphorus compounds (OPs) are highly toxic chemicals widely used as pesticides (e.g., paraoxon (PX)- the active metabolite of the insecticide parathion) and as chemical warfare nerve agents. Blood-brain barrier (BBB) leakage has been shown in rodents exposed to PX, which is an organophosphate oxon. In this study, we investigated the cellular mechanisms involved in BBB reaction after acute exposure to PX in an established in vitro BBB system made of stem-cell derived, human brain-like endothelial cells (BLECs) together with brain pericytes that closely mimic the in vivo BBB. Our results show that PX directly affects the BBB in vitro both at toxic and non-toxic concentrations by attenuating tight junctional (TJ) protein expression and that only above a certain threshold the paracellular barrier integrity is compromised. Below this threshold, BLECs exhibit a morphological coping mechanism in which they enlarge their cell area thus preventing the formation of meaningful intercellular gaps and maintaining barrier integrity. Importantly, we demonstrate that reversal of the apoptotic cell death induced by PX, by a pan-caspase-inhibitor ZVAD-FMK (ZVAD) can reduce PX-induced cell death and elevate cell area but do not prevent the induced BBB permeability, implying that TJ complex functionality is hindered. This is corroborated by formation of ROS at all toxic concentrations of PX and which are even higher with ZVAD. We suggest that while lower levels of ROS can induce compensating mechanisms, higher PX-induced oxidative stress levels interfere with barrier integrity.

The link of organophosphorus pesticides with neurodegenerative and neurodevelopmental diseases based on evidence and mechanisms

Organophosphorus (OP) compounds have been known as the most widely used pesticides during the past half century and there have been a huge body of literature regarding their association with human chronic diseases. Neurodegenerative and neurodevelopmental disorders including Alzheimer, Parkinson, amyotrophic lateral sclerosis (ALS), attention deficit hyperactivity disorder (ADHD), and autism are among the afflicting neurological diseases which overshadow human life and their higher risk in relation to OP exposures have been uncovered by epidemiological studies. In addition, experimental studies exploring the underlying mechanisms have provided some evidence for involvement of cholinergic deficit, oxidative stress, neuro-inflammation, and epigenetic modifications as the processes which are common in the toxicity of the OP and pathophysiology of the mentioned diseases. In addition, genetic mutations and polymorphisms of different variants of some genes like paraoxonase have been shown to be implicated in both susceptibility to OPs toxicity and neurological diseases. In this article, we reviewed the epidemiological as well as experimental studies evidencing the association of exposure to OPs and incidence of neurodegenerative and neurodevelopmental diseases.

Melatonin inhibits rotenone-induced SH-SY5Y cell death via the downregulation of Dynamin-Related Protein 1 expression

Previous studies have shown that melatonin can protect cells against rotenone-induced cell death. Yet, the mechanism involved in this protection requires further research. In this study, we aimed to further investigate the effects of melatonin on inhibiting rotenone-induced SH-SY5Y cells and the underlying molecular mechanisms. Human neuroblastoma SH-SY5Y cells were treated with 0.3 or 1μM rotenone for 6 or 12h. Cell viability was measured with an MTS assay, the mitochondrial membrane potential was determined with a Rhodamine 123 staining assay, and the protein expression levels of the markers of autophagy, including cytochrome C release (Cyt C), light chain 3B (LC3 B) and Dynamin-Related Protein 1 (Drp1) were analyzed by western blotting. The co-localization of Drp1 and TOM20 proteins in the mitochondria of SH-SY5Y cells was measured by immunofluorescence coupled with confocal microscopy and the overexpression of the Drp1 gene was then conducted. The viability and expression levels of Cyt C and LC3 B in rotenone and melatonin + rotenone-treated Drp1-overexpressed SH-SY5Y cells were analyzed with MTS and western blotting, respectively. We found that rotenone effectively induced SH-SY5Y cell death by causing mitochondrial dysfunction and increasing Cyt C expression. Drp1 expression and its regulation of mitochondrial translocation mediated the rotenone-induced cell death and melatonin inhibited this process. Overexpression of Drp1 protein attenuated melatonin's inhibition of rotenone-induced SH-SY5Y cell death. In conclusion, melatonin effectively inhibits rotenone-induced neuronal cell death via the regulation of Drp1 expression.

Mitochondria and mitochondrial DNA as relevant targets for environmental contaminants

The mitochondrial DNA (mtDNA) is a closed circular molecule that encodes, in humans, 13 polypeptides components of the oxidative phosphorylation complexes. Integrity of the mitochondrial genome is essential for mitochondrial function and cellular homeostasis, and mutations and deletions in the mtDNA lead to oxidative stress, mitochondrial dysfunction and cell death. In vitro and in situ studies suggest that when exposed to certain genotoxins, mtDNA accumulates more damage than nuclear DNA, likely owing to its organization and localization in the mitochondrial matrix, which tends to accumulate lipophilic, positively charged molecules. In that regard, several relevant environmental and occupational contaminants have physical-chemical characteristics that indicate that they might accumulate in mitochondria and target mtDNA. Nonetheless, very little is known so far about mtDNA damage and mitochondrial dysfunction due to environmental exposure, either in model organisms or in humans. In this article, we discuss some of the characteristics of mtDNA which render it a potentially relevant target for damage by environmental contaminants, as well as possible functional consequences of damage/mutation accumulation. In addition, we review the data available in the literature focusing on mitochondrial effects of the most common classes of environmental pollutants. From that, we conclude that several lines of experimental evidence support the idea that mitochondria and mtDNA are susceptible and biologically relevant targets for pollutants, and more studies, including mechanistic ones, are needed to shed more light into the contribution of mitochondrial dysfunction to the environmental and human health effects of chemical exposure.

Real-Time Monitoring ATP in Mitochondrion of Living Cells: A Specific Fluorescent Probe for ATP by Dual Recognition Sites

Adenosine triphosphate (ATP) is mainly produced in the mitochondrion and used as a universal energy source for various cellular events. Various fluorescent probes for ATP have been established successfully, but most of them are not appropriate for monitoring the fluctuation of the mitochondrial ATP level. Herein, a fluorescent probe named Mito-Rh is first synthesized and used to recognize ATP in mitochondrion. In the probe, rhodamine, diethylenetriamine, and triphenylphosphonium are selected as fluorophore, reaction site, and mitochondrion-targeting group, respectively. Probe Mito-Rh shows high sensitivity to ATP with 81-fold fluorescence enhancement, and the detection range (0.1-10 mM) can match the concentration level of ATP in the mitochondrion. Moreover, Mito-Rh provides excellent selectivity toward ATP over other biological anions (ADP, AMP, GTP, CTP, UTP) owing to a concurrent effect of dual recognition sites (hydrogen bond and π-π stacking). In particular, the probe can localize in mitochondrion specifically and demonstrates utility in the real-time detection of mitochondrial ATP concentration changes.

Effect of oxidative phosphorylation signaling pathway on silkworm midgut following exposure to phoxim

Organophosphate pesticides are applied widely in the world for agricultural purposes, and their exposures often resulted in non-cocooning of Bombyx mori in China. Silkworm midgut is the major organ for digestion and nutrient absorption, importantly it is also a barrier against foreign substances and chemical pesticides. The purpose of this study was to determine the mechanism of oxidative injury in silkworm midgut with phoxim induction. The results showed that the transcription level of oxidative phosphorylation signaling pathway genes of midgut under phoxim stress. Digital gene expression (DGE) analysis revealed that 24 electron transport chain (ETC)-related genes were upregulated. Quantitative real time polymerase chain reaction results indicated that the ETC the genes encoding NADH-CoQ1, Succinic-Q, cyt c reductase-S, cyt c oxidase-S, cytochrome c oxidase polypeptide IV, ATP synthase, and vacuolar H+ ATP synthase were all significantly up-regulated by 1.50-, 1.31-, 1.42-, 1.44-, 1.70-, 2.03- and 1.43-fold, respectively. Phoxim induction enhanced the activity of ETC complex in mitochondria, and induced the accumulation of ROS in midgut. These results indicated that trace phoxim enhanced respiration in midgut, and the imbalance between the activity changes of ETC may led to reactive oxygen species accumulation. The ETC of mitochondria may be potential biomarkers of midgut toxicity in B. mori caused by phoxim exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 167-175, 2017.

Molecular Signatures of Reduced Nerve Toxicity by CeCl3 in Phoxim-exposed Silkworm Brains

CeCl3 can reduce the damage caused by OP pesticides, in this study we used the brain of silkworms to investigate the mechanism of CeCl3 effects on pesticide resistance. The results showed that phoxim treatments led to brain damages, swelling and death of neurons, chromatin condensation, and mitochondrial damage. Normal nerve conduction was severely affected by phoxim treatments, as revealed by: increases in the contents of neurotransmitters Glu, NO, and ACh by 63.65%, 61.14%, and 98.54%, respectively; decreases in the contents of 5-HT and DA by 53.19% and 43.71%, respectively; reductions in the activities of Na(+)/K(+)-ATPase, Ca(2+)/Mg(2+)-ATPase, and AChE by 85.27%, 85.63%, and 85.63%, respectively; and increase in the activity of TNOS by 22.33%. CeCl3 pretreatment can significantly reduce such damages. Results of DGE and qRT-PCR indicated that CeCl3 treatments significantly upregulated the expression levels of CYP4G23, cyt-b5, GSTs-σ1, ace1, esterase-FE4, and β-esterase 2. Overall, phoxim treatments cause nerve tissue lesions, neuron death, and nerve conduction hindrance, but CeCl3 pretreatments can promote the expression of phoxim resistance-related genes in silkworm brains to reduce phoxim-induced damages. Our study provides a potential new method to improve the resistance of silkworms against OP pesticides.

Molecular mechanisms of reduced nerve toxicity by titanium dioxide nanoparticles in the phoxim-exposed brain of Bombyx mori

Bombyx mori (B. mori), silkworm, is one of the most important economic insects in the world, while phoxim, an organophosphorus (OP) pesticide, impact its economic benefits seriously. Phoxim exposure can damage the brain, fatbody, midgut and haemolymph of B. mori. However the metabolism of proteins and carbohydrates in phoxim-exposed B. mori can be improved by Titanium dioxide nanoparticles (TiO2 NPs). In this study, we explored whether TiO2 NPs treatment can reduce the phoxim-induced brain damage of the 5th larval instar of B. mori. We observed that TiO2 NPs pretreatments significantly reduced the mortality of phoxim-exposed larva and relieved severe brain damage and oxidative stress under phoxim exposure in the brain. The treatments also relieved the phoxim-induced increases in the contents of acetylcholine (Ach), glutamate (Glu) and nitric oxide (NO) and the phoxim-induced decreases in the contents of norepinephrine (NE), Dopamine (DA), and 5-hydroxytryptamine (5-HT), and reduced the inhibition of acetylcholinesterase (AChE), Na+/K+-ATPase, Ca2+-ATPase, and Ca2+/Mg2+-ATPase activities and the activation of total nitric oxide synthase (TNOS) in the brain. Furthermore, digital gene expression profile (DGE) analysis and real time quantitative PCR (qRT-PCR) assay revealed that TiO2 NPs pretreatment inhibited the up-regulated expression of ace1, cytochrome c, caspase-9, caspase-3, Bm109 and down-regulated expression of BmIap caused by phoxim; these genes are involved in nerve conduction, oxidative stress and apoptosis. TiO2 NPs pretreatment also inhibited the down-regulated expression of H+ transporting ATP synthase and vacuolar ATP synthase under phoxim exposure, which are involved in ion transport and energy metabolism. These results indicate that TiO2 NPs pretreatment reduced the phoxim-induced nerve toxicity in the brain of B. mori.

The adverse effects of phoxim exposure in the midgut of silkworm, Bombyx mori

The silkworm is an important economic insect. Poisoning of silkworms by organophosphate pesticides causes tremendous loss to the sericulture. In this study, Solexa sequencing technology was performed to profile the gene expression changes in the midgut of silkworms in response to 24h of phoxim exposure and the impact on detoxification, apoptosis and immune defense were addressed. The results showed that 254 genes displayed at least 2.0-fold changes in expression levels, with 148 genes up-regulated and 106 genes down-regulated. Cytochrome P450 played an important role in detoxification. Histopathology examination and transmission electron microscope revealed swollen mitochondria and disappearance of the cristae of mitochondria, which are the important features in insect apoptotic cells. Cytochrome C release from mitochondria into the cytoplasm was confirmed. In addition, the Toll and immune deficiency (IMD) signal pathways were all inhibited using qRT-PCR. Our results could help better understand the impact of phoxim exposure on silkworm.

Oxidative stress resulting from exposure of a human salivary gland cells to paraoxon: an in vitro model for organophosphate oral exposure

Organophosphate (OP) compounds are used as insecticides, acaricides, and chemical agents and share a common neurotoxic mechanism of action. The biochemical alterations leading to many of the deleterious effects have been studied in neuronal cell lines, however, non-neuronal toxic effects of OPs are far less well characterized in vitro, and specifically in cell lines representing oral routes of exposure. To address this void, the human salivary gland (HSG) cell line, representing likely interactions in the oral cavity, was exposed to the representative OP paraoxon (PX; O,O-diethyl-p-nitrophenoxy phosphate) over a range of concentrations (0.01-100 μM) and analyzed for cytotoxicity. PX induced cytotoxicity in HSG cells at most of the exposure concentrations as revealed by MTT assay, however, the release of LDH only occurred at the highest concentration of PX tested (100 μM) at 48 h. Slight increases in cellular ATP levels were measured in PX-exposed (10 μM) HSG cells at 24 h. Exposing HSG cells to 10 μM PX also led to an increase in DNA fragmentation prior to loss of cellular membrane integrity implicating reactive oxygen species (ROS) as a trigger of toxicity. The ROS genes gss, gstm2, gstt2 and sod2 were upregulated, and the presence of superoxide following 10 μM PX exposure was determined via dihydroethidium fluorescence studies further implicating PX-induced oxidative stress in HSG cells.

A mechanistic overview of health associated effects of low levels of organochlorine and organophosphorous pesticides

Organochlorine and organophosphate pesticides are compounds that can be detected in human populations as a result of occupational or residential exposure. Despite their occurrence in considerably low levels in humans, their biological effects are hazardous since they interact with a plethora of enzymes, proteins, receptors and transcription factors. In this review we summarize the cell and molecular effects of organochlorine and organophosphate pesticides with respect to their toxicity, with particular emphasis on glucose and lipid metabolism, their interaction with some members of the nuclear receptor family of ligand-activated transcription factors, including the steroid and peroxisome proliferator activated receptors that changes the expression of genes involved in lipid metabolism and xenobiotic detoxification. More importantly, evidence regarding the metabolic degradation of pesticides and their accumulation in tissues is presented. Potential non-cholinergic mechanisms after long-term low-dose organophosphate exposure resulting in neurodevelopmental outcomes and neurodegeneration are also addressed. We conclude that the mechanism of pesticide-mediated toxicity is a combination of various enzyme-inhibitory, metabolic and transcriptional events acting at the cellular and molecular level.

Protective effects of vitamins C and E against hepatotoxicity induced by methyl parathion in rats

Male rats were given vitamins C+E, methyl parathion, or both daily via gavage for seven weeks. Body weight was decreased while liver weight increased significantly at the end of fourth and seventh weeks in the methyl parathion- and methyl parathion plus vitamin-treated groups. Serum total protein, albumin, triglyceride, low density lipoprotein-cholesterol (VLDL-cholesterol) levels decreased, and serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl-transferase (GGT), lactate dehydrogenase (LDH), and total cholesterol levels increased significantly in the methyl parathion- and the methyl parathion plus vitamin-treated rats. There was a statistically significant difference for all biochemical parameters when the methyl parathion plus vitamin-treated group was compared with methyl parathion-treated group. In electron microscopic investigation, cytopathological alterations were observed in hepatocytes of the methyl parathion- and the methyl parathion plus vitamin-treated rats. As a result, methyl parathion-induced hepatotoxicity is reduced by vitamins C+E, but vitamins C+E did not provide complete protection.

Mitochondrial membrane potential probes and the proton gradient: a practical usage guide

Fluorescent probes for monitoring mitochondrial membrane potential are frequently used for assessing mitochondrial function, particularly in the context of cell fate determination in biological and biomedical research. However, valid interpretation of results obtained with such probes requires careful consideration of numerous controls, as well as possible effects of non-protonic charges on dye behavior. In this context, we provide an overview of some of the important technical considerations, controls, and parallel complementary assays that can be employed to help ensure appropriate interpretation of results, thus providing a practical usage guide for monitoring mitochondrial membrane potentials with cationic probes. In total, this review will help illustrate both the strengths and potential pitfalls of common mitochondrial membrane potential dyes, and highlight best-usage approaches for their efficacious application in life sciences research.

Inhibition of mitochondrial respiratory chain in the brain of rats after hepatic failure induced by acetaminophen

Hepatic encephalopathy is an important cause of morbidity and mortality in patients with severe hepatic failure. This disease is clinically characterized by a large variety of symptoms including motor symptoms, cognitive deficits, as well as changes in the level of alertness up to hepatic coma. Acetaminophen is frequently used in animals to produce an experimental model to study the mechanisms involved in the progression of hepatic disease. The brain is highly dependent on ATP and most cell energy is obtained through oxidative phosphorylation, a process requiring the action of various respiratory enzyme complexes located in a special structure of the inner mitochondrial membrane. In this context, the authors evaluated the activities of mitochondrial respiratory chain complexes in the brain of rats submitted to acute administration of acetaminophen and treated with the combination of N-acetylcysteine (NAC) plus deferoxamine (DFX) or taurine. These results showed that acetaminophen administration inhibited the activities of complexes I and IV in cerebral cortex and that the treatment with NAC plus DFX or taurine was not able to reverse this inhibition. The authors did not observe any effect of acetaminophen administration on complexes II and III activities in any of the structures studied. The participation of oxidative stress has been postulated in the hepatic encephalopathy and it is well known that the electron transport chain itself is vulnerable to damage by reactive oxygen species. Since there was no effect of NAC + DFX, the effect of acetaminophen was likely to be due to something else than oxidative stress.

Paraoxon-induced protein expression changes to SH-SY5Y cells

SH-SY5Y neuroblastoma cells were examined to determine changes in protein expression following exposure to the organophosphate paraoxon (O,O-diethyl-p-nitrophenoxy phosphate). Exposure of SH-SY5Y cells to paraoxon (20 μM) for 48 h showed no significant change in cell viability as established using an MTT assay. Protein expression changes from the paraoxon-treated SH-SY5Y cells were determined using a comparative, subproteome approach by fractionation into cytosolic, membrane, nuclear, and cytoskeletal fractions. The fractionated proteins were separated by 2D-PAGE, identified by MALDI-TOF mass spectrometry, and expression changes determined by densitometry. Over 400 proteins were separated from the four fractions, and 16 proteins were identified with altered expression ≥1.3-fold including heat shock protein 90 (-1.3-fold), heterogeneous nuclear ribonucleoprotein C (+2.8-fold), and H(+) transporting ATP synthase beta chain (-3.1-fold). Western blot analysis conducted on total protein isolates confirmed the expression changes in these three proteins.

Thionate versus Oxon: comparison of stability, uptake, and cell toxicity of ((14)CH(3)O)(2)-labeled methyl parathion and methyl paraoxon with SH-SY5Y cells

The stability, hydrolysis, and uptake of the organophosphates methyl parathion and methyl paraoxon were investigated in SH-SY5Y cells. The stabilities of ((14)CH(3)O)(2)-methyl parathion ((14)C-MPS) and ((14)CH(3)O)(2)-methyl paraoxon ((14)C-MPO) at 1 microM in culture media had similar half-lives of 91.7 and 101.9 h, respectively. However, 100 microM MPO caused >95% cytotoxicity at 24 h, whereas 100 microM MPS caused 4-5% cytotoxicity at 24 h ( approximately 60% cytotoxicity at 48 h). Greater radioactivity was detected inside cells treated with MPO as compared to MPS, although >80% of the total MPO uptake was primarily dimethyl phosphate (DMP). Maximum uptake was reached after 48 h of (14)C-MPS or (14)C-MPO exposure with total uptakes of 1.19 and 1.76 nM/10(6) cells for MPS and MPO, respectively. The amounts of MPS and MPO detected in the cytosol after 48 h of exposure time were 0.54 and 0.37 nM/10(6) cells, respectively.

Calcium Signaling in Neuronal Cells Exposed to the Munitions Compound Cyclotrimethylenetrinitramine (RDX)

Cyclotrimethylenetrinitramine (RDX) has been used extensively as an explosive in military munitions. Mechanisms for seizure production, seen in past animal studies, have not been described. Increased calcium levels contribute to excitotoxicity, so in this study neuroblastoma cells are loaded with calcium-indicating dye before application of 1.5 µM to 7.5 mM RDX, with fluorescence recorded for 30 cycles of 11 seconds each. The lowest concentration of RDX increases calcium fluorescence significantly above baseline for cycles 2 to 8; millimolar concentrations increase calcium fluorescence significantly above baseline for cycles 2 to 30. Increases in calcium, like those of 200 nM carbachol, are prevented with 10 mM of calcium chelator ethylene glycol-bis(β-aminoethyl ether)-N,N,N,N tetra-acetic acid (EGTA, tetrasodium salt). Calcium channel blocker verapamil (20 μM), Ca2+-ATPase inhibitor thapsigargin (5 μM), and general membrane stabilizer lidocaine (10 mM) partially attenuate carbachol- and RDX-induced increases in calcium, suggesting that RDX transiently increases intracellular calcium by multiple mechanisms.

New extension of the Mitchell Theory for oxidative phosphorylation in mitochondria of living organisms

The Mitchell Theory implies the proton motive force Deltap across the inner mitochondrial membrane as the energy-rich intermediate of oxidative phosphorylation. Deltap is composed mainly of an electrical (DeltaPsi(m)) and a chemical part (DeltapH) and generated by the respiratory chain complexes I, III and IV. It is consumed mostly by the ATP synthase (complex V) to produce ATP. The free energy of electron transport within the proton pumps is sufficient to generate Deltap of about 240 mV. The proton permeability of biological membranes, however, increases exponentially above 130 mV leading to a waste of energy at high values (DeltaPsi(m)>140 mV). In addition, at DeltaPsi(m)>140 mV, the production of the superoxide radical anion O(2)(-) at complexes I, II and III increases exponentially with increasing DeltaPsi(m). O(2)(-) and its neutral product H(2)O(2) (=ROS, reactive oxygen species) induce oxidative stress which participates in aging and in the generation of degenerative diseases. Here we describe a new mechanism which acts independently of the Mitchell Theory and keeps DeltaPsi(m) at low values through feedback inhibition of complex IV (cytochrome c oxidase) at high ATP/ADP ratios, thus preventing the formation of ROS and maintaining high efficiency of oxidative phosphorylation.

DNA damage after acute and chronic treatment with malathion in rats

Malathion is an insecticide widely used in agriculture and in public health programs that when used indiscriminately in large amounts can cause environmental pollution and risk to human health. However, it is possible that during the metabolism of malathion, reactive oxygen species can be generated, and malathion may produce oxidative stress in intoxicated rats that can be responsible for alterations in DNA molecules related in some studies. As a result, the present study aimed to investigate the DNA damage of cerebral tissue and peripheral blood in rats after acute and chronic malathion exposure. We used single cell gel electrophoresis (Comet assay) to measure early damage in hippocampus and peripheral blood and the Micronucleus test in total erythrocytes samples. Malathion was administered intraperitoneally once a day for one day (acute) or for 28 days (chronic) protocols (in both protocols, malathion was administered at 25, 50, 100, and 150 mg/kg). Our results showed that malathion (100 and 150 mg/kg) increased the DNA damage index in the peripheral blood and in the hippocampus after both chronic and acute treatment. Malathion increased the frequency of micronuclei only in chronic treatment at 150 mg/kg dose, and induced a cytotoxic dose-dependent decrease in the frequency of polychromatic erythrocytes in the peripheral blood of rats. In conclusion, since malathion increased both the peripheral blood and hippocampus DNA damage index using the Comet assay and increased the frequency of micronuclei in the total peripheral blood, it can be regarded as a potential mutagen/carcinogenic agent.

Effects of organophosphorus pesticides and their ozonation byproducts on gap junctional intercellular communication in rat liver cell line

The effects of organophosphorus pesticides (OPs), oxons and their ozonation byproducts on gap junctional intercellular communication (GJIC) on cultured BRL cell line were investigated using scrape loading and dye transfer (SL/DT) technique. The neutral red uptake assay was used to identify the non-cytotoxic levels of diazinon, parathion and methyl-parathion applied to GJIC assay. The concentration-dependent inhibition of GJIC was observed over a range of 50-350 mg/l diazinon, parathion and methyl-parathion after 90 min incubation compared with the vehicle control. However, oxons and ozonation byproducts of OPs had no inhibition effect on GJIC at any of the concentrations tested. The inhibition of GJIC by OPs was reversible after removal of the tested pesticides followed by incubation with fresh medium. The present study suggested that the ozonation treatment could be used for the detoxification of drinking water and food crops contaminated with diazinon, parathion and methyl-parathion without formation of GJIC toxicity.

VX-induced cell death involves activation of caspase-3 in cultured rat cortical neurons

Exposure of cell cultures to organophosphorous compounds such as VX can result in cell death. However, it is not clear whether VX-induced cell death is necrotic or involves programmed cell death mechanisms. Activation of caspases, a family of cysteine proteases, is often involved in cell death, and in particular, caspase-3 activation appears to be a key event in programmed cell death processes including apoptosis. In this study, we investigated VX-induced neuronal cell death, as well as the underlying mechanism in terms of its effect on caspase-3 activity. Primary cortical neuronal cultures were prepared from gestational days 17 to 19 Sprague Dawley rat fetuses. At maturation, the cells were treated with varying concentrations of VX and cell death was evaluated by lactate dehydrogenase (LDH) release. VX induced an increase in LDH release in a concentration-dependent manner. Morphological VX-induced cell death was also characterized by using nuclear staining with propidium iodide and Hoechst 33342. VX induced a concentration- and time-dependent increase in caspase-3 activation. Caspase-3 activation was also confirmed by the proteolytic cleavage of poly(ADP-ribose)polymerase (PARP), an endogenous caspase-3 substrate. These data suggested that in rat cortical neurons, VX-induced cell death via a programmed cell death pathway that involves changes in caspase-3 protease.

Triorthocresyl phosphate-induced neuronal losses in lumbar spinal cord of hens--an immunohistochemistry and ultrastructure study

To investigate the neuronal losses of hens' spinal cords in the model of organophosphate-induced delayed neuropathy (OPIDN) and to analyze the impact of apoptosis on the pathogenesis of OPIDN. Adult hens were challenged with triorthocresyl phosphate (TOCP) at a single dose (750 mg/kg). Neuronal losses in the 3rd lumbar spinal cord (L3) were assessed by light-microscopy and electron-microscopy methods at different days post exposure, respectively. The typical OPIDN signs were seen in the TOCP-exposed hens at about 9th day. The number of large nerve cells declined gradually. And these cells were verified as neurons by immunostained with neuronal marker NeuN. The expression of FasL reached proximal at about 9th day, decreased from 14th day. Neurons in TOCP exposed groups displayed degenerative morphologies in electronic microscopy. Some neurons showed apoptotic-like ultrastructure profiles at 5th day. The nuclear membrane was complete with chromatin condensed to the margins of nuclear membrane like a crescent-shaped body. Mitochondria morphologic changes appeared early (5 d) following exposure to TOCP, and developed in a time-dependent fashion. Apoptosis might be involved in the development of OPIDN, and play a role in the pathogenesis of OPIDN.

Mitochondrial Respiratory Dysfunction and Oxidative Stress after Chronic Malathion Exposure

Malathion is a pesticide used on a large scale and with high potential risk for human exposure. However, it is reasonable to hypothesize that while the malathion is metabolizing reactive oxygen species (ROS) can be generated and subsequently there is onset of an oxidative stress in central nervous system (CNS) structures: hippocampus, cortex, striatum and cerebellum of intoxicated rats due to mitochondrial respiratory chain disfunctions. The present study was therefore undertaken to evaluate malathion-induced lipid peroxidation (LPO), superoxide production from sub-mitochondrial particles and the activity of complexes II and IV of the mitochondrial respiratory chain. Malathion was administered in doses of 25, 50, 100 and 150 mg malathion/kg. After malathion administration LPO increased in hippocampus and striatum. This was accompanied by an increase in the formation of superoxide in submitochondrial particles in the hippocampus. Complex IV suffered significant inhibition of its activity. We could demonstrate in this study that malathion induces oxidative stress and it could be due to inactivation of mitochondrial respiratory complexes.

Effect of rhodoxanthin from Potamogeton crispus L. on cell apoptosis in Hela cells

Carotenoid, a natural functional pigment, is known to have anti-carcinogenic activity. To verify the anti-cancer effects of rhodoxanthin which is a kind of carotenoids, we investigated the effects of rhodoxanthin from Potamogeton crispus L. on the proliferation rate, cell cycle distribution, apoptosis and the change in mitochondrial membrane potential in Hela cell line. The effects of rhodoxanthin were also tested on the concentration of Ca(2+) in cells. Rhodoxanthin inhibited cell proliferation in Hela cells in a dose and time-dependent manner. Rhodoxanthin induced an accumulation of cells in the S phase of the cell cycle, reduced the mitochondria transmembrane potential and increased the concentration of intracellular Ca(2+). In summary, our results suggested that rhodoxanthin-induced apoptosis in Hela cells occurred via these pathways.

Expression changes of neurofilament subunits in the central nervous system of hens treated with tri-ortho-cresyl phosphate (TOCP)

Tri-ortho-cresyl phosphate (TOCP) could induce degeneration of long, large diameter axons within the central and peripheral nervous system of susceptible species including human being and hens, which is referred to as organophosphorus-ester induced delayed neuropathy (OPIDN). The mechanisms involved are not understood. Neuropathologic observations suggested that neurofilament subunits (NFs) could be a main target of TOCP in the peripheral nervous system. Our previous study also showed that NFs in protein levels significantly decreased in sciatic nerves of hens treated with TOCP. In this study, to determine whether the decrement of NFs proteins in sciatic nerves was due to reductions in NF gene expression or protein degradation, hens were treated with a single dose of 750 mg/kg body weight TOCP by gavage, and sacrificed on 21 day post-exposure. Cerebral cortexes and spinal cords were sampled. Transcriptional changes of NFs including high molecular weight neurofilament (NF-H), middle molecular weight neurofilament (NF-M), low molecular weight neurofilament (NF-L), and glyceraldehydes-3-phoaphate dehydrogenase (GAPDH) as inner inference in cerebral cortexes and spinal cords were analyzed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Results showed that all of three NFs mRNA in cerebral cortexes down-regulated significantly. However, in spinal cords, there was only NF-M decreased, both of NF-H and NF-L kept unaffected. The protein levels of NFs in pellet and supernatant fractions of cerebral cortexes and spinal cords were also determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. We noticed that all NFs protein declined in pellet of cerebral cortexes, but NF-M reduction was not significant compared with that of control hens. NF-H and NF-M proteins in supernatant of cerebral cortexes exhibited significant increase, while NF-L level showed remarkable decline. In spinal cords, apart from NF-L in pellet were significantly increased, both of NF-H and NF-M in pellet and supernatant, as well as NF-L in supernatant fractions were manifested dramatic reduction compared with the pattern of control. The quantitative analyses revealed that the change magnitude in protein levels was much greater than that in mRNA levels in hens' central nervous system after TOCP administration. These findings suggest that the NFs disturbance in protein levels is closely associated with the decreases in sciatic nerves observed in our previous work after TOCP exposure, rather than that in mRNA levels, and the NFs alterations in protein levels may be one of the responsible factors for the OPIDN.

New insights on brain stem death: From bedside to bench

As much as brain stem death is currently the clinical definition of death in many countries and is a phenomenon of paramount medical importance, there is a dearth of information on its mechanistic underpinnings. A majority of the clinical studies are concerned only with methods to determine brain stem death. Whereas a vast amount of information is available on the cellular and molecular mechanisms of cell death, rarely are these studies directed specifically towards the understanding of brain stem death. This review presents a framework for translational research on brain stem death that is based on systematically coordinated clinical and laboratory efforts that center on this phenomenon. It begins with the identification of a novel clinical marker from patients that is related specifically to brain stem death. After realizing that this "life-and-death" signal is related to the functional integrity of the brain stem, its origin is traced to the rostral ventrolateral medulla (RVLM). Subsequent laboratory studies on this neural substrate in animal models of brain stem death provide credence to the notion that both "pro-life" and "pro-death" programs are at work during the progression towards death. Those programs (mitochondrial functions, nitric oxide, peroxynitrite, superoxide anion, coenzyme Q10, heat shock proteins and ubiquitin-proteasome system) hitherto identified from the RVLM are presented, along with their cellular and molecular mechanisms. It is proposed that outcome of the interplay between the "pro-life" and "pro-death" programs (dying) in this neural substrate determines the final fate of the individual (being dead). Thus, identification of additional programs in the RVLM and delineation of their regulatory mechanisms should shed new lights on future directions for clinical management of life-and-death.

Coenzyme q10 confers cardiovascular protection against acute mevinphos intoxication by ameliorating bioenergetic failure and hypoxia in the rostral ventrolateral medulla of the rat

Coenzyme Q10 (CoQ10, ubiquinone) is a highly mobile electron carrier in the mitochondrial respiratory chain that also acts as an antioxidant. We evaluated the cardiovascular protective efficacy of CoQ10 at the rostral ventrolateral medulla (RVLM), a medullary site where sympathetic vasomotor tone originates and where the organophosphate poison mevinphos (Mev) acts to elicit cardiovascular intoxication. Experiments were carried out in adult male Sprague-Dawley rats that were maintained under propofol anesthesia. Microinjection bilaterally of Mev (10 nmol) into the RVLM induced progressive hypotension and minor bradycardia, alongside significant depression of the activity of NADH cytochrome c reductase (enzyme marker for Complexes I and III) or cytochrome c oxidase (enzyme marker for Complex IV) in the mitochondrial respiratory chain, reduction in ATP concentration, or tissue hypoxia in the RVLM. On the other hand, the activity of succinate cytochrome c reductase (enzyme marker for Complexes II and III) remained unaltered. The Mev-induced hypotension, bioenergetic failure, or hypoxia was significantly reversed when CoQ10 (4 microg) was coadministered bilaterally into the RVLM with the organophosphate poison. We conclude that CoQ10 confers cardiovascular protection against acute Mev intoxication by acting on the RVLM, whose neuronal activity is intimately related to the "life-and-death" process. We also showed that amelioration of the selective dysfunction of respiratory enzyme Complexes I and IV in the mitochondrial respiratory chain, the reduced ATP level, and the induced tissue hypoxia in the RVLM are among some of the underlying mechanisms for the elicited protection.

Effects of organophosphorus compounds on ATP production and mitochondrial integrity in cultured cells

Recent studies in vivo and in vitro suggested that mitochondrial dysfunction follows exposure to organophosphorus (OP) esters. As mitochondrial ATP production is important for cellular integrity, ATP production in the presence of OP neurotoxicants was examined in a human neuronal cell line (SH-SY5Y neuroblastoma cells) and primary dorsal root ganglia (DRG) cells isolated from chick embryos and subsequently cultured to achieve maturation with axons. These cell culture systems were chosen to evaluate toxic effects on the mitochondrial respiratory chain associated with exposure to OP compounds that do and do not cause OP-induced delayed neuropathy (OPIDN), a disorder preceded by inhibition of neurotoxic esterase (NTE). Concentration- and time-response studies were done in neuroblastoma cells exposed to phenyl saligenin phosphate (PSP) and mipafox, both compounds that readily induce delayed neuropathy in hens, or paraoxon, which does not. Phenylmethylsulfonyl fluoride (PMSF) was included as a non-neuropathic inhibitor of NTE. Purified neuronal cultures from 9 day-old chick embryo DRG were treated for 12 h with 1 microM PSP, mipafox, or paraoxon. In situ evaluation of ATP production measured by bioluminescence assay demonstrated decreased ATP concentrations both in neuroblastoma cells and chick DRG neurons treated with PSP. Mipafox decreased ATP production in DRG but not in SH-SY5Y cells. This low energy state was present at several levels of the mitochondrial respiratory chain, including Complexes I, II, III, and IV, although Complex I was the most severely affected. Paraoxon and PMSF were not effective at all complexes, and, when effective, required higher concentrations than needed for PSP. Results suggest that mitochondria are an important early target for OP compounds, with exposure resulting in depletion of ATP production. The targeting of neuronal, rather than Schwann cell mitochondria in DRG following exposure to PSP and mipafox was verified by loss of the mitochondrial-specific dye, tetramethylrhodamine, in these cells. No such loss was seen in paraoxon exposed neurons isolated from DRG or in Schwann cells treated with any of the test compounds.

Bridging the gap between in vitro and in vivo toxicology testing

In vitro systems for neurotoxicological studies can be useful for the investigation of events associated with pertubations of cellular and molecular targets that are similar to those in the intact animal. The toxicities of organophosphorus compounds, which inhibit esterases, and 1,2,3,6-tetrahydropyridine (MPTP), which depletes dopamine, can be studied in human neuroblastoma cells.