Molecular Toxicology Laboratory, Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA.
Toxicol Mech Methods. 2003;13(3):169-79. doi: 10.1080/15376510309836.
Studies in our laboratory and others have indicated that acrylonitrile (VCN) induces acute and chronic neurotoxicity and brain tumors in animal models. Reduced glutathione (GSH) depletion was suggested as the initiator of oxidative stress in VCN-induced neurotoxicity. Astrocytes possess the majority of total brain GSH and express various immunological functions that are characteristic of the brain, including the secretion of cytokines. We hypothesized that astrocytes could be the primary target of VCN's adverse activities in the brain. Therefore, VCN-induced neurotoxicity was studied by exposing proliferating normal human astrocytes (NHAs) to various concentrations of VCN (25-400 muM). We assessed cell viability; levels of endogenous antioxidants, GSH, and catalase; levels of reactive oxygen species; and secretion of TNF- alpha, a cellular marker for oxidative stress and oxidative damage to nuclear DNA, after treatment with VCN. At VCN concentrations of 25 and 50 muM, the oxidative stress markers were unaffected and at least 85% of the cells were viable. Cell viability was significantly affected at 200 and 400 muM VCN (22-42% less than control, p <. 05). The results also indicated VCN-induced depletion of GSH and a concomitant increase in levels of oxidized GSH (GSSG). The levels of total GSH and GSSG in control and treated (400 muM VCN) cells were 37 and 2, respectively. There was a significant upregulation of catalase activity (21% more than control, p <. 05) at 100 muM of VCN and a downregulation at 400 muM (40% lower than control, p <. 05). A dose-dependent, significant increase in the formation of reactive oxygen species was observed at 200 to 400 muM of VCN. Also, an elevation (two- to three fold as compared to control, p <. 05) in oxidative damage to DNA was observed at these concentrations of VCN. Increase in TNF- alphasecretion (28% higher than control, p <. 05) was observed at 400 muM VCN. Therefore, redox imbalance in astrocytes may play a major role in VCN-induced neurotoxicity, which is indicated by compromised antioxidant defense mechanisms, such as depletion of GSH, increase in GSSG, inhibition of catalase, and increase in the formation of reactive oxygen species and TNF- alphasecretion, resulting in DNA oxidation.
在我们实验室和其他实验室的研究表明，丙烯腈（VCN）会在动物模型中引发急性和慢性神经毒性和脑肿瘤。谷胱甘肽（GSH）耗竭被认为是 VCN 诱导的神经毒性中氧化应激的启动因素。星形胶质细胞拥有大脑中大部分的总脑 GSH，并表达各种具有大脑特征的免疫功能，包括细胞因子的分泌。我们假设星形胶质细胞可能是 VCN 在大脑中不良活动的主要靶标。因此，通过将增殖的正常人星形胶质细胞（NHAs）暴露于不同浓度的 VCN（25-400 μM）来研究 VCN 诱导的神经毒性。我们评估了细胞活力；内源性抗氧化剂 GSH 和过氧化氢酶的水平；活性氧的水平；以及 TNF-α（细胞因子）的分泌，TNF-α是氧化应激和核 DNA 氧化损伤的细胞标志物，这些标志物在 VCN 处理后会发生变化。在 VCN 浓度为 25 和 50 μM 时，氧化应激标志物不受影响，至少 85%的细胞存活。当 VCN 浓度为 200 和 400 μM 时，细胞活力受到显著影响（比对照组低 22-42%，p<.05）。结果还表明 VCN 诱导 GSH 耗竭，并伴随氧化 GSH（GSSG）水平的升高。对照组和处理组（400 μM VCN）细胞中的总 GSH 和 GSSG 水平分别为 37 和 2。在 100 μM VCN 时，过氧化氢酶活性显著上调（比对照组高 21%，p<.05），而在 400 μM 时下调（比对照组低 40%，p<.05）。在 200 至 400 μM 的 VCN 时观察到活性氧形成的剂量依赖性显著增加。此外，在这些 VCN 浓度下，还观察到 DNA 氧化损伤的升高（比对照组高 2-3 倍，p<.05）。在 400 μM VCN 时观察到 TNF-α分泌增加（比对照组高 28%，p<.05）。因此，星形胶质细胞中的氧化还原失衡可能在 VCN 诱导的神经毒性中起主要作用，这表明抗氧化防御机制受损，如 GSH 耗竭、GSSG 增加、过氧化氢酶抑制以及活性氧形成和 TNF-α分泌增加，导致 DNA 氧化。
