Viquez Olga M, Valentine Holly L, Friedman David B, Olson Sandra J, Valentine William M
Department of Pathology, Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2591, USA.
Chem Res Toxicol. 2007 Mar;20(3):370-9. doi: 10.1021/tx6003453. Epub 2007 Feb 27.
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 alpha,beta-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.
人类接触二硫代氨基甲酸盐源于其作为农药、在制造业以及作为药剂的用途。神经毒性是二硫代氨基甲酸盐接触已确定的危害，在人类和实验动物中均有观察到。先前的研究表明，某些二硫代氨基甲酸盐，包括N，N - 二乙基二硫代氨基甲酸盐（DEDC）、双硫仑和吡咯烷二硫代氨基甲酸盐的神经毒性，可表现为外周神经的原发性髓鞘病。由于外周神经中铜水平升高以及脂质过氧化产物水平升高伴随着DEDC诱导的损伤，有人提出铜稳态的破坏和氧化应激增加可能导致髓鞘损伤。为了进一步评估DEDC介导的脂质过氧化在神经中的生物学影响，确定了DEDC暴露导致的蛋白质表达水平变化。此外，还测定了外周神经中的蛋白质羰基含量，作为对DEDC神经病中蛋白质氧化损伤的初步评估。通过腹腔内渗透泵将大鼠暴露于DEDC八周，然后从暴露于DEDC的动物和未暴露的对照的坐骨神经中提取蛋白质。使用二维差异凝胶电泳比较蛋白质表达水平，结果显示56个斑点有显著变化，其中46个通过基质辅助激光解吸电离飞行时间质谱（MALDI - TOF/MS）鉴定。表达增加的蛋白质中有三种谷胱甘肽转移酶同工型，它们对于脂质过氧化产生的活性α，β - 不饱和醛的解毒很重要。使用免疫组织化学方法，其中一种同工型谷胱甘肽转移酶pi的表达增加定位于雪旺细胞的细胞质中。一项针对神经蛋白质羰基的免疫测定表明，从暴露于DEDC的大鼠中分离出的蛋白质羰基含量显著增加了约2倍。这些数据支持DEDC促进外周神经中蛋白质氧化损伤以及在髓鞘或雪旺细胞的其他成分中产生足够脂质过氧化以引发对氧化应激的保护性细胞反应的能力。
