Cui L, Locatelli L, Xie M Y, Sommadossi J P
Department of Pharmacology and Toxicology, University of Alabama at Birmingham 35294, USA.
J Pharmacol Exp Ther. 1997 Mar;280(3):1228-34.
The effects of several anti-human immunodeficiency virus nucleoside analogs were examined on neurite regeneration and mitochondrial DNA (mtDNA) synthesis in nerve growth factor-primed PC-12 cells. Under pharmacologically relevant concentrations, the exposure of cells to 2',3'-dideoxyinosine (ddI), 2',3'-dideoxycytidine (ddC) and 2',3'-didehydro-3'-deoxythymidine (d4T) led to a marked dose-dependent inhibition of neurite regeneration with a 50% inhibitory concentration approximating 1, 5 and 15 microM, respectively. In contrast, 3'-azido-3'-deoxythymidine (AZT) and beta-L-2',3'-dideoxy-3'-thiacytidine (3TC) had no effect on neurite regeneration. Inhibition of mtDNA synthesis by ddI was dose dependent, and ddC at a concentration of 10 microM strongly reduced mtDNA content by >75%. However, no inhibition of mtDNA synthesis was detected in cells exposed to 10 microM 3TC or d4T and to 25 microM AZT, suggesting a lack of definite correlation between mtDNA depletion and blockage of neurite regeneration. High performance liquid chromatographic analysis demonstrated that AZT, ddC, 3TC and d4T were anabolized to their respective monophosphate, diphosphate and triphosphate derivatives in the PC-12 cells. In addition, d4T was phosphorylated to form its monophosphate, diphosphate and triphosphate derivatives in isolated mitochondria, whereas ddC was metabolized only to its monophosphate form and no phosphorylated metabolites of 3TC were detected under the same conditions. In summary, the peripheral neuropathy induced by ddC and ddI in patients with acquired immune deficiency syndrome may be accounted for by the depletion of mtDNA content in the neurons. As for d4T, some other mechanism(s) may be involved in its clinical neurotoxicity. Both AZT and 3TC lacked any substantial toxicity in our in vitro model, which is in agreement with the clinical action of these drugs.
研究了几种抗人类免疫缺陷病毒核苷类似物对经神经生长因子预处理的PC-12细胞神经突再生和线粒体DNA（mtDNA）合成的影响。在药理学相关浓度下，将细胞暴露于2'，3'-双脱氧肌苷（ddI）、2'，3'-双脱氧胞苷（ddC）和2'，3'-二脱氢-3'-脱氧胸苷（d4T）会导致神经突再生受到明显的剂量依赖性抑制，其50%抑制浓度分别约为1、5和15微摩尔。相比之下，3'-叠氮-3'-脱氧胸苷（AZT）和β-L-2'，3'-双脱氧-3'-硫代胞苷（3TC）对神经突再生没有影响。ddI对mtDNA合成的抑制呈剂量依赖性，10微摩尔浓度的ddC可使mtDNA含量大幅降低>75%。然而，在暴露于10微摩尔3TC或d4T以及25微摩尔AZT的细胞中未检测到mtDNA合成受到抑制，这表明mtDNA耗竭与神经突再生受阻之间缺乏明确的相关性。高效液相色谱分析表明，AZT、ddC、3TC和d4T在PC-12细胞中被代谢为各自的单磷酸、二磷酸和三磷酸衍生物。此外，d4T在分离的线粒体中被磷酸化形成其单磷酸、二磷酸和三磷酸衍生物，而ddC仅代谢为其单磷酸形式，在相同条件下未检测到3TC的磷酸化代谢产物。总之，获得性免疫缺陷综合征患者中由ddC和ddI诱导的周围神经病变可能是由于神经元中mtDNA含量的耗竭所致。至于d4T，其临床神经毒性可能涉及其他一些机制。在我们的体外模型中，AZT和3TC均未表现出任何实质性毒性，这与这些药物的临床作用一致。
