Mansouri Abdellah, Haouzi Delphine, Descatoire Véronique, Demeilliers Christine, Sutton Angela, Vadrot Nathalie, Fromenty Bernard, Feldmann Gérard, Pessayre Dominique, Berson Alain
INSERM Unité 481, Faculté de Médecine Xavier Bichat, Paris, France.
Hepatology. 2003 Sep;38(3):715-25. doi: 10.1053/jhep.2003.50353.
After several weeks of treatment, levels of alanine aminotransferase (ALT) increase in 50% of patients treated with tacrine for Alzheimer's disease. We looked for progressive effects on DNA to explain delayed toxicity. We first studied the in vitro effects of tacrine on DNA replication and topoisomerase-mediated DNA relaxation. We then treated mice with doses of tacrine reproducing the human daily dose on a body area basis and studied the effects of tacrine administration for up to 28 days on hepatic DNA, mitochondrial function, and cell death. In vitro, tacrine impaired DNA polymerase gamma-mediated DNA replication and also poisoned topoisomerases I and II to increase the relaxation of a supercoiled plasmid. In vivo, administration of tacrine markedly decreased incorporation of [(3)H]thymidine into mitochondrial DNA (mtDNA), progressively and severely depleted mtDNA, and partly unwound supercoiled mtDNA into circular mtDNA. Incorporation of [(3)H]thymidine into nuclear DNA (nDNA) was barely decreased, and nDNA levels were unchanged. After 12 to 28 days of treatment, administration of tacrine increased p53, Bax, mitochondrial permeability transition, cytosolic cytochrome c, and caspase-3 activity and triggered hepatocyte apoptosis and/or necrosis. In conclusion, the intercalating drug tacrine poisons topoisomerases and impairs DNA synthesis. Tacrine has been shown to accumulate within mitochondria, and it particularly targets mtDNA. After several weeks of treatment, the combination of severe mtDNA depletion and a genotoxic stress enhancing p53, Bax, and permeability transition trigger hepatocyte necrosis and/or apoptosis.
在接受他克林治疗阿尔茨海默病的患者中，经过数周治疗后，50%的患者丙氨酸转氨酶（ALT）水平升高。我们寻找其对DNA的渐进性影响以解释延迟毒性。我们首先研究了他克林对DNA复制和拓扑异构酶介导的DNA松弛的体外作用。然后，我们以按体表面积计算相当于人类日剂量的他克林剂量处理小鼠，并研究了连续28天给予他克林对肝脏DNA、线粒体功能和细胞死亡的影响。在体外，他克林损害DNA聚合酶γ介导的DNA复制，还使拓扑异构酶I和II中毒，以增加超螺旋质粒的松弛。在体内，给予他克林显著降低了[³H]胸腺嘧啶核苷掺入线粒体DNA（mtDNA）的量，逐渐并严重地消耗mtDNA，并将部分超螺旋mtDNA解旋为环状mtDNA。[³H]胸腺嘧啶核苷掺入核DNA（nDNA）的量几乎没有减少，nDNA水平也未改变。治疗12至28天后，给予他克林增加了p53、Bax、线粒体通透性转换、细胞色素c和半胱天冬酶-3的活性，并引发肝细胞凋亡和/或坏死。总之，嵌入性药物他克林使拓扑异构酶中毒并损害DNA合成。已证明他克林在线粒体内蓄积，并且它特别靶向mtDNA。经过数周治疗后，严重的mtDNA消耗与增强p53、Bax和通透性转换的基因毒性应激相结合，引发肝细胞坏死和/或凋亡。
