Sava V, Reunova O, Velasquez A, Harbison R, Sánchez-Ramos J
University of South Florida, Department of Neurology (MDC 55), 12901 Bruce B. Downs Blvd., Tampa, FL 33612, USA.
Neurotoxicology. 2006 Jan;27(1):82-92. doi: 10.1016/j.neuro.2005.07.004. Epub 2005 Sep 2.
Ochratoxin-A (OTA) is a fungal metabolite with potential toxic effects on the central nervous system that have not yet been fully characterized. OTA has complex mechanisms of action that include evocation of oxidative stress, bioenergetic compromise, inhibition of protein synthesis, production of DNA single-strand breaks and formation of OTA-DNA adducts. The time course of acute effects of OTA were investigated in the context of DNA damage, DNA repair and global oxidative stress across six brain regions. Oxidative DNA damage, as measured with the "comet assay", was significantly increased in the six brain regions at all time points up to 72 h, with peak effects noted at 24 h in midbrain (MB), CP (caudate/putamen) and HP (hippocampus). Oxidative DNA repair activity (oxyguanosine glycosylase or OGG1) was inhibited in all regions at 6 h, but recovered to control levels in cerebellum (CB) by 72 h, and showed a trend to recovery in other regions of brain. Other indices of oxidative stress were also elevated. Lipid peroxidation and superoxide dismutase (SOD) increased over time throughout the brain. In light of the known vulnerability of the nigro-striatal dopaminergic neurons to oxidative stress, levels of striatal dopamine (DA) and its metabolites were also measured. Administration of OTA (0-6 mg/kg i.p.) to mice resulted in a dose-dependent decrease in striatal DA content and turnover with an ED50 of 3.2 mg/kg. A single dose of 3.5 mg/kg decreased the intensity of tyrosine hydroxylase immunoreactivity (TH(+)) in fibers of striatum, TH(+) cells in substantia nigra (SN) and TH(+) cells of the locus ceruleus. TUNEL staining did not reveal apoptotic profiles in MB, CP or in other brain regions and did not alter DARPP32 immunoreactivity in striatum. In conclusion, OTA caused acute depletion of striatal DA on a background of globally increased oxidative stress and transient inhibition of oxidative DNA repair.
赭曲霉毒素A（OTA）是一种真菌代谢产物，对中枢神经系统具有潜在毒性作用，但其作用机制尚未完全明确。OTA具有复杂的作用机制，包括引发氧化应激、破坏生物能量代谢、抑制蛋白质合成、产生DNA单链断裂以及形成OTA-DNA加合物。本研究在六个脑区中，结合DNA损伤、DNA修复和整体氧化应激，对OTA急性效应的时间进程进行了研究。通过“彗星试验”检测发现，在长达72小时的所有时间点，六个脑区的氧化性DNA损伤均显著增加，中脑（MB）、尾状核/壳核（CP）和海马体（HP）在24小时时出现峰值效应。氧化性DNA修复活性（氧鸟苷糖基化酶或OGG1）在6小时时在所有脑区均受到抑制，但小脑（CB）在72小时时恢复到对照水平，其他脑区也呈现出恢复趋势。氧化应激的其他指标也有所升高。全脑脂质过氧化和超氧化物歧化酶（SOD）水平随时间增加。鉴于黑质纹状体多巴胺能神经元对氧化应激已知的易损性，还检测了纹状体多巴胺（DA）及其代谢产物的水平。给小鼠腹腔注射OTA（0 - 6 mg/kg）导致纹状体DA含量和周转率呈剂量依赖性下降，半数有效剂量（ED50）为3.2 mg/kg。单次注射3.5 mg/kg可降低纹状体纤维中酪氨酸羟化酶免疫反应性（TH(+)）、黑质（SN）中TH(+)细胞以及蓝斑中TH(+)细胞的强度。TUNEL染色未在MB、CP或其他脑区发现凋亡细胞，也未改变纹状体中DARPP32免疫反应性。总之，OTA在整体氧化应激增加和氧化性DNA修复短暂抑制的背景下，导致纹状体DA急性耗竭。
