Effect of disulfiram (DS) on mitochondria from rat hippocampus: metabolic compartmentation of DS neurotoxicity

Comparative effects of Mancozeb and Disulfiram-induced striated muscle myopathies in Long-Evans rats

Dithiocarbamates (DTCs) like mancozeb (MZ) and disulfiram (DS) are used throughout agriculture and medicine and have been implicated in neurotoxicity. Little research has been studied on the reported myopathies caused by these compounds. Their pathogenesis and mechanism of muscle toxicity has not been fully studied. The aim of this study is to investigate if DTCs alter striated muscle tissues in vivo. Long-Evans rats were treated with either MZ or DS followed by analysis of muscle biomarkers and metal levels. DS resulted in increases in serum lactate dehydrogenase (LDH), cardiac troponin, and myoglobin levels. Creatine kinase-MB serum levels decreased. Mancozeb only showed an increase in serum LDH. Both MZ and DS-treatment resulted in altered metal levels in the myocardium but not skeletal muscle. Ultrastructural alterations included damaged mitochondria and myofibril splitting. The presence of multivesicular bodies, and alterations of the intercalated disc were also seen.

The interactome of the copper transporter ATP7A belongs to a network of neurodevelopmental and neurodegeneration factors

Genetic and environmental factors, such as metals, interact to determine neurological traits. We reasoned that interactomes of molecules handling metals in neurons should include novel metal homeostasis pathways. We focused on copper and its transporter ATP7A because ATP7A null mutations cause neurodegeneration. We performed ATP7A immunoaffinity chromatography and identified 541 proteins co-isolating with ATP7A. The ATP7A interactome concentrated gene products implicated in neurodegeneration and neurodevelopmental disorders, including subunits of the Golgi-localized conserved oligomeric Golgi (COG) complex. COG null cells possess altered content and subcellular localization of ATP7A and CTR1 (SLC31A1), the transporter required for copper uptake, as well as decreased total cellular copper, and impaired copper-dependent metabolic responses. Changes in the expression of ATP7A and COG subunits in Drosophila neurons altered synapse development in larvae and copper-induced mortality of adult flies. We conclude that the ATP7A interactome encompasses a novel COG-dependent mechanism to specify neuronal development and survival.

Exposure of rat hippocampal astrocytes to Ziram increases oxidative stress

Pesticides have been shown in several studies to be the leading candidates of environmental toxins and may contribute to the pathogenesis of several neurodegenerative diseases. Ziram (zinc-bis(dimethyldithiocarbamate)) is an agricultural dithiocarbamate fungicide that is used to treat a variety of plant diseases. In spite of their generally acknowledged low toxicity, dithiocarbamates are known to cause a wide range of neurobehavioral effects as well as neuropathological changes in the brain. Astrocytes play a key role in normal brain physiology and in the pathology of the nervous system. This investigation studied the effects of 1.0 µM Ziram on rat hippocampal astrocytes. The thiobarbituric acid reactive substance assay performed showed a significant increase in malondialdehyde, a product of lipid peroxidation, in the Ziram-treated cells. Biochemical analysis also revealed a significant increase in the induction of 70 kDa heat shock and heme oxygenase 1 stress proteins. In addition, an increase of glutathione peroxidase (GPx) and a significant increase in oxidized glutathione (GSSG) were observed in the Ziram-treated cells. The ratio GSH to GSSG calculated from the treated cells was also decreased. Light and transmission electron microscopy supported the biochemical findings in Ziram-treated astrocytes. This data suggest that the cytotoxic effects observed with Ziram treatments may be related to the increase of oxidative stress.

Oxidative stress mediates drug-induced hepatotoxicity in rats: a possible role of DNA fragmentation

Sodium diethyldithiocarbamate, diclofenac and ketoconazol are three important chemotherapeutic agents that are commonly associated with hepatotoxicity. This study was undertaken to provide a better understanding of the mechanism through which these drugs induce hepatotoxicity. Some of the possible mechanisms underlying such modulation were investigated. The hepatotoxic activity of sodium diethyldithiocarbamate (800 mg kg(-1)); diclofenac (200 mg kg(-1)) and ketoconazol (100 mg kg(-1)) were investigated in vivo through the assessment of liver functions, lipid peroxidation and histopathological examination. It was found that all drugs have induced severe hepatic damage as evidenced by the elevation serum aminotransferase activities and confirmed by histological changes of liver. In addition, the drug-induced hepatotoxicity was also associated with massive liver DNA fragmentation and an increase in lipid peroxidation. These results strongly suggest a positive correlation between hepatotoxicity and DNA fragmentation. Moreover, this study also implicates calcium as a potential mediator of the drug-induced oxidative stress associated with hepatotoxicity.

The effects of ebselen on cisplatin and diethyldithiocarbamate (DDC) cytotoxicity in rat hippocampal astrocytes

Ebselen is a seleno-organic compound with documented cytoprotective properties. Little work has been done, however, demonstrating ebselen's cytoprotective properties in neural cell lines. In order to examine the effects of this compound and its mechanism of action, astrocytes were exposed to two known neurotoxicants, cisplatin and diethyldithiocarbamate (DDC). Cells were pretreated with 30 microM ebselen and subsequently treated with either 150 microM DDC for 1 h or 250 and 500 microM cisplatin for 24 h. Results indicate significant increases in viability in cells pretreated with ebselen and exposed to cisplatin. Ebselen pretreatment did not significantly increase viability in cells exposed to DDC. Light and scanning electron microscopy studies confirm the viability studies. Gross morphological damage was seen in cells treated with cisplatin, however, cells pretreated with ebselen and then exposed to cisplatin, appeared similar to controls. No differences were noted in cells pretreated with ebselen and then exposed to DDC or cells treated with DDC alone. In order to examine the mechanism of protection of this compound, glutathione status was examined. Results show that ebselen does not significantly increase reduced or oxidized glutathione (GSH, GSSG). All cell groups treated with cisplatin showed an increase in GSH levels. Ebselen showed protection in glutathione depleted cells at the 250 microM cisplatin dose. DDC treatment showed no significant increase in either reduced or oxidized glutathione. We conclude that ebselen significantly protects against cisplatin, but not DDC toxicity. We further conclude that this protection is not related to changes in glutathione status in the rat hippocampal cell line as has been reported in other cell types.

Oxidative stress and c-Jun-amino-terminal kinase activation involved in apoptosis of primary astrocytes induced by disulfiram-Cu(2+) complex

Disulfiram is frequently used in the treatment of alcoholism. In this study, we found that CuCl(2) (1-10 microM), but not other metal ions (Fe(2+), Zn(2+), Pb(2+)), markedly potentiated disulfiram-induced cytotoxicity by 440-fold in primary astrocytes. Thus, the molecular mechanisms of the cytotoxic effects induced by the disulfiram-Cu(2+) complex were explored. The changes in morphology (nuclear condensation and apoptotic body formation) and hypodiploidy of DNA suggested that the disulfiram-Cu(2+) complex induced an apoptotic process. Our studies of the death-signaling pathway reveal that decreased mitochondrial membrane potential, increased free radical production, and depletion of non-protein-thiols (glutathione) were involved. The disulfiram-Cu(2+) complex activated c-Jun-amino-terminal kinase (JNK) and caspase-3 followed by poly (ADP-ribose) polymerase degradation in a time-dependent manner. Moreover, the cellular Cu content was markedly increased and the copper chelator bathocuproine disulfonate abolished all of these cellular events, suggesting that Cu(2+) is essential for death signaling. The antioxidants N-acetylcysteine and vitamin C also inhibited the cytotoxic effect. Thus, we conclude that the disulfiram-Cu(2+) complex induces apoptosis and perhaps necrosis at a late stage mediated by oxidative stress followed by sequential activation of JNK, caspase-3 and poly (ADP-ribose) polymerase degradation. These findings imply that the axonal degeneration and neurotoxicity observed after the chronic administration of disulfiram are perhaps, at least in part, due to the cytotoxic effect of the disulfiram-Cu(2+) complex formed endogenously.

The protective effects of zinc on diethyldithiocarbamate cytotoxicity on rat astrocytes in vitro

The neurotoxicity of diethyldithiocarbamate (DDC) has been documented for decades. In particular, cytotoxic effects against rat astrocytes have been noted by a decrease in cell viability and numerous ultrastructural defects. This study indicates an in vitro protective effect by zinc administration prior to DDC insult. Cell groups pre-treated with 50 microM ZnCl2 prior to the addition of 35 microg/ml DDC showed significant protection when compared with cells treated with DDC alone. Zinc reduced the DDC-mediated toxicity to astrocytes as indicated by an increase in cell adherence and viability. Morphological evaluation indicated a significant decrease in ultrastructural alterations. Metallothionein (MT), a metal regulatory protein known to be induced by zinc was studied to determine its role in this mechanism of protection. Immunocytochemistry and immunoblots showed increased presence of MT in all zinc treated groups. This suggests a protective effect against DDC cytotoxicity on rat astrocytes in vitro may be associated with an increase in MT concentration.

The effects of disulfiram on the hippocampus and cerebellum of the rat brain: a study on oxidative stress

The purpose of this investigation was to study the relationship between disulfiram (DS) toxicity, lipid peroxidation, and copper in order to further elucidate the mechanisms of DS toxicity. Male Sprague-Dawley rats were dosed with either 375, 750 or 1500 mg/kg disulfiram via oral intubation for 1, 3 and 6 weeks. In the hippocampus and cerebellum, the increased accumulation of copper, increased production of malondialdehyde (MDA), increased activity of glutathione peroxidase along with alterations in glutathione and glutathione disulfide concentrations was indicative of oxidative stress. The production of MDA was directly related to the level of copper in both areas of the brain indicating that excess copper may be the primary cause of DS neurotoxicity.

Disulfiram lowers Ca2+, Mg(2+)-ATPase activity of rat brain synaptosomes

The chronic administration of disulfiram (DS) to rats resulted in significant decrease of synaptosomal Ca2+, Mg(2+)-ATPase activity. In vitro studies indicated that DS (ID50 = 20 microM) produced a dose-dependent inhibition of Ca2+, Mg(2+)-ATPase. However, diethyldithio-carbamate, a metabolite of DS, failed to modify Ca2+, Mg(2+)-ATPase activity, implying that the decrease in ATPase activity in DS administered rats was due to the effect of parent compound. The DS-mediated inhibition (48%) of ATPase activity was comparable with a similar degree of inhibition (49%) achieved by treating the synaptosomal membranes with N-ethylmaleimide (ID50 = 20 microM) in vitro. Furthermore, the inhibition by DS was neither altered by washing the membranes with EGTA nor reversed by treatment with sulfhydryl reagents such as GSH or dithiothreitol. About 74% and 68% decrease of synaptosomal Ca2+, Mg(2+)-ATPase specific activity was observed when treated with DS (30 microM) and EGTA (100 microM) respectively. The remaining 25-30% of total activity is suggested to be of Mg(2+)-dependent ATPase activity. This indicates that both these drugs may act on a common target, calmodulin component that represents 70-75% of total Ca2+, Mg(2+)-ATPase activity. Therefore, DS-mediated modulation of synaptosomal Ca2+, Mg(2+)-ATPase activity could affect its function of maintaining intracellular Ca2+ concentration. This could contribute to the deleterious effects on CNS.

Effect of disulfiram administration on glutamate uptake by synaptosomes in the rat brain

Although disulfiram used as a pharmacological agent in the treatment of alcoholism is reported to act on both peripheral and central nervous systems with several adverse effects, the neurotoxic property of the drug has not been properly elucidated. We observed that the chronic administration of the drug to rats significantly inhibited synaptosomal (Na+,K+)-ATPase and basal Mg(2+)-ATPase activities. Further, the uptake of gamma-aminobutyric acid and L-glutamate which rely on the energy provided by this system was depleted following chronic drug administration. Similar findings were observed when the isolated synaptosomes were treated with the drug in an in vitro system. Further, treatment of synaptosomes with ouabain, a known inhibitor of (Na+, K+)-ATPase resulted in significant depletion of 3H-GABA and L-[3H]glutamate uptake into synaptosomes indicating the importance of the enzyme in the uptake mechanism. However, diethyldithiocarbamate, a major metabolite of disulfiram did not elicit any change in either the enzyme activity or the uptake of these neurotransmitters. On the basis of these evidences, we suggest that the chronic disulfiram administration attenuated the neurotransmitter uptake mechanism and resulted in higher extracellular concentration of glutamate that could lead to glutamate-induced neurotoxicity.

Blockade of ovulation in the rat by the fungicide sodium N-methyldithiocarbamate: relationship between effects on the luteinizing hormone surge and alterations in hypothalamic catecholamines

Sodium N-methyldithiocarbamate (SMD), also known as metam sodium, is a commonly employed soil fungicide and nematocide. Structurally related dithiocarbamates have been found to decrease norepinephrine (NE) synthesis by suppressing the activity of dopamine-beta-hydroxylase. Because brain hypothalamic catecholamine (CA) activity is involved in generating the proestrus afternoon surge in blood luteinizing hormone (LH) which stimulates the final stages of ovulation, this study explored the effect of SMD on this hormonal trigger and its relationship to changes in hypothalamic CAs. Ovariectomized, steroid-primed Long-Evans rats showed a dose-related (25-100 mg/kg, IP) suppression of the surge and a drop in NE when SMD was given at 1100 h, a few h prior to the expected LH rise. The surge effect was reversed by the alpha-adrenergic agonist clonidine. With cycling rats, a decline with dose (50-300 mg/kg, 1300 h, proestrus) was seen in the percentage of ovulating females, with earlier injections (0900 h) being less effective at the highest dose. At all doses, low circulating levels of LH and prolactin at 1600 h suggested either a blockade in the proestrus surges of each hormone or a displacement in their time of occurrence. Anterior and posterior hypothalamic NE fell by 3 h postinjection and was accompanied by a rise in dopamine, while serotonin was unchanged. Although there was a distinct parallel between the alterations in regional CAs and the incidence of ovulation at the high doses of SMD, the relationship did not hold as the dose decreased. A similar dissociation between ovulation and CAs was seen when equimolar doses of SMD or methylisothiocyanate, a principal metabolite, were given by gavage. At the regional level of analysis employed, the data indicate that while IP injections of SMD are able to block the LH surge and ovulation in these rats, the dose-response relationship suggests that, along with induced alterations in CA metabolism, an additional factor may be involved in the observed effects.

Effects of diethyldithiocarbamate on calmodulin in neuroblastoma cells

Diethyldithiocarbamate (DDC) was used to treat the neuroblastoma cell line Neuro-2a. Cell injury caused by DDC affects the calcium-binding protein calmodulin (CaM) and alters copper homeostasis in these cells. Neuro-2a cells were treated with 1 x 10(-5) M DDC for 1 h and were harvested at various time points over a 24-h period. Light microscopy of control cells showed CaM deposited around the cell periphery and along the neuritic processes. Treated cells showed the same distribution until 3 h after treatment. Electron microscopy showed CaM deposited around the cell periphery and within the cytoplasm and nucleus of control cells. Treated cells showed a time-dependent localization of CaM in relation to cellular disorganization. Staining of electrophoretic transfers by ProtoGold showed that CaM was present in all control samples and treated samples through 6 h. Atomic absorption spectrophotometry showed no difference in calcium levels between control and treated samples, but copper levels were significantly elevated. This study indicated that degenerative changes induced by DDC altered calmodulin levels. These changes may have been caused by elevated copper content within the cells and subsequent cell injury.