Peripheral Nerve Protein Expression and Carbonyl Content in N,N-Diethlydithiocarbamate Myelinopathy

• Published in: Chemical research in toxicology Vol. 20; no. 3; pp. 370 - 379
• Main Authors: Viquez, Olga M, Valentine, Holly L, Friedman, David B, Olson, Sandra J, Valentine, William M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.03.2007
• Subjects: Animals; Chromatography, High Pressure Liquid; Databases, Factual; Demyelinating Diseases - chemically induced; Demyelinating Diseases - metabolism; Demyelinating Diseases - pathology; Ditiocarb - toxicity; Electrophoresis, Polyacrylamide Gel; Fluoresceins; Fluorescent Dyes; Globins - metabolism; Immunoassay; Immunohistochemistry; Male; Nerve Tissue Proteins - biosynthesis; Nerve Tissue Proteins - genetics; Neural Networks (Computer); Neural Pathways - physiology; Oxidative Stress - physiology; Peripheral Nervous System - metabolism; Peripheral Nervous System - pathology; Rats; Rats, Sprague-Dawley; Sciatic Nerve - pathology; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Weight Gain - drug effects
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx6003453

Human exposure to dithiocarbamates results from their uses as pesticides, in manufacturing, and as pharmaceutical agents. Neurotoxicity is an established hazard of dithiocarbamate exposure and has been observed in both humans and experimental animals. Previous studies have shown that the neurotoxicity of certain dithiocarbamates, including N,N-diethyldithiocarbamate (DEDC), disulfiram, and pyrrolidine dithiocarbamate, can manifest as a primary myelinopathy of peripheral nerves. Because increased levels of copper in peripheral nerves and elevated levels of lipid peroxidation products accompany DEDC-induced lesions, it has been suggested that the disruption of copper homeostasis and increased oxidative stress may contribute to myelin injury. To further assess the biological impact of DEDC-mediated lipid peroxidation in nerves, the changes in protein expression levels resulting from DEDC exposure were determined. In addition, protein carbonyl content in peripheral nerves was also determined as an initial assessment of protein oxidative damage in DEDC neuropathy. Rats were exposed to DEDC by intra-abdominal osmotic pumps for eight weeks and proteins extracted from the sciatic nerves of DEDC-exposed animals and from non-exposed controls. The comparison of protein expression levels using two-dimensional difference gel electrophoresis demonstrated significant changes in 56 spots of which 46 were identified by MALDI-TOF/MS. Among the proteins showing increased expression were three isoforms of glutathione transferase, important for the detoxification of reactive α,β-unsaturated aldehydes generated from lipid peroxidation. The increased expression of one isoform, glutathione transferase pi, was localized to the cytoplasm of Schwann cells using immunohistochemistry. An immunoassay for nerve protein carbonyls demonstrated a significant increase of approximately 2-fold for the proteins isolated from DEDC-exposed rats. These data support the ability of DEDC to promote protein oxidative damage in peripheral nerves and to produce sufficient lipid peroxidation in either myelin or another component of the Schwann cell to elicit a protective cellular response to oxidative stress.