Peripheral nerve and brain differ in their capacity to resolve N,N-diethyldithiocarbamate-mediated elevations in copper and oxidative injury

Abstract

Previous studies have demonstrated that N,N-diethyldithiocarbamate (DEDC) elevates copper and promotes oxidative stress within the nervous system. However, whether these effects resolve following cessation of exposure or have the potential to persist and result in cumulative injury has not been determined. In this study, an established model for DEDC myelin injury in the rat was used to determine whether copper levels, oxidative stress, and neuromuscular deficits resolve following the cessation of DEDC exposure. Rats were exposed to DEDC for 8 weeks and then either euthanized or maintained for 2, 6 or 12 weeks after cessation of exposure. At each time point copper levels were measured by inductively coupled mass spectrometry to assess the ability of sciatic nerve, brain, spinal cord and liver to eliminate excess copper post exposure. The protein expression levels of glutathione transferase alpha, heme oxygenase 1 and superoxide dismutase 1 in peripheral nerve and brain were also determined by western blot to assess levels of oxidative stress as a function of post exposure duration. As an initial assessment of the bioavailability of the excess copper in brain the protein expression levels of copper chaperone for superoxide dismutase 1, and prion protein were determined by western blot as a function of exposure and post exposure duration. Neuromuscular function in peripheral nerve was evaluated using grip strengths, nerve conduction velocities, and morphologic changes at the light microscope level. The data demonstrated that in peripheral nerve, copper levels and oxidative stress return to control levels within several weeks after cessation of exposure. Neuromuscular function also showed a trend towards pre-exposure values, although the resolution of myelin lesions was more delayed. In contrast, total copper and antioxidant enzyme levels remained significantly elevated in brain for longer post exposure periods. The persistence of effects observed in brain suggests that the central nervous system is more susceptible to long-term cumulative adverse effects from dithiocarbamates. Additionally, significant changes in expression levels of chaperone © 2010 Elsevier Ireland Ltd. All rights reserved. * Corresponding Author: Department of Pathology, C3320 MCN VUMC, Nashville, TN 37232-2561, bill.valentine@vanderbilt.edu, fax 615-343-9825, phone 615-343-5836. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conflict of interest statementThe authors declare that there are no conflicts of interest. NIH Public Access Author ManuscriptToxicology. Author manuscript; available in PM...

Dopaminergic neurotoxicity ofS‐ethylN,N‐dipropylthiocarbamate (EPTC), molinate, andS‐methyl‐N,N‐diethylthiocarbamate (MeDETC) inCaenorhabditis elegans

“…DEDC has been shown to increase lipid peroxidation and induce the antioxidant enzymes superoxide dismutase 1 (SOD1), glutathione S‐transferase–α (GST‐α), and heme oxygenase‐1 (HO‐1) in sciatic nerves of rats (Valentine et al . ). Sodium methyldithiocarbamate has been shown to deplete intracellular GSH, induce antioxidant enzymes sulfiredoxin, peroxiredoxin, and isocitrate dehydrogenase, and alter the inflammatory cytokine profile of peripheral macrophages in mice (Pruett et al .…”

Dietary Copper Reduces the Hepatotoxicity of (−)-Epigallocatechin-3-Gallate in Mice

“…However, in the present study, it was observed that EGCG toxicity was protected in mice with supra-physiological levels of Cu involving modulation of serum Cp activity and ROS generation. Not only does administration of DEDTC or disulfiram, which is metabolized to DEDTC in vivo, significantly increase hepatic Cu levels [ 36 , 39 , 40 , 41 ], it also significantly decreases Cu levels or Cp activities in blood [ 36 , 42 , 43 ]. It is possible that because of the low Cu and Cp activities, more EGCG was translated into liver and oxidized with ROS generation resulting into hepatotoxicity in vivo.…”

Ziram and Sodium N,N-Dimethyldithiocarbamate Inhibit Ubiquitin Activation through Intracellular Metal Transport and Increased Oxidative Stress in HEK293 Cells

“…While those previous proteomic studies are consistent with inhibition of E1 through electrophilic adduction, other studies report that E1 activity is dependent on the redox status of the cell, suggesting that dithiocarbamates may also inhibit E1 through elevated oxidative stress. , Dithiocarbamates form metal complexes that vary in their solubility and redox activity depending upon the polarity of the nitrogen substituents and the redox potential of the metal, respectively. , Dithiocarbamates readily bind copper and dithiocarbamates with nonpolar nitrogen substituents, including DEDC and N,N -dimethyldithiocarbamate (DMDC), form redox active copper complexes that cross cell membranes, partition into lipid compartments, and promote oxidative injury. − This property has been demonstrated in animal models through elevations of copper, lipid peroxidation, protein oxidative injury, and increased apoptosis. − In the study presented here, we investigated the relative contribution of covalent adduction and oxidative stress in the dithiocarbamate-mediated inhibition of E1 in HEK293 cells.…”

“…Earlier studies in cell models suggest that E1 activation is redox sensitive, and in vivo studies have demonstrated that dithiocarbamates complex metals and cross cell membranes, potentially increasing intracellular levels of redox active metals. 16 , 23 , 24 , 29 Thus, we reasoned that exposure to ziram and DMDC may be contributing to the observed E1 inhibition by promoting intracellular oxidation, a mechanism that could potentially be shared by many environmental agents and disease conditions. Therefore, our results prompted us to investigate this alternative mechanism.…”

“… 23 − 25 This property has been demonstrated in animal models through elevations of copper, lipid peroxidation, protein oxidative injury, and increased apoptosis. 24 − 26 In the study presented here, we investigated the relative contribution of covalent adduction and oxidative stress in the dithiocarbamate-mediated inhibition of E1 in HEK293 cells.…”