Ray S D, Sorge C L, Kamendulis L M, Corcoran G B
Toxicology Program, College of Pharmacy, University of New Mexico, Albuquerque 87131-1066.
J Pharmacol Exp Ther. 1992 Oct;263(1):387-94.
Several hepatotoxic agents damage Ca++ regulation and produce toxic cell death in a manner consistent with a cause-and-effect relationship; however, vital targets of Ca++ remain unidentified. Recent results show that DNA may be the chief Ca++ target during apoptosis, a form of cell death considered distinct from toxic cell death or necrosis. The present studies explored whether nuclear Ca++ regulation is lost before dimethylnitrosamine-induced necrosis, whether DNA is attacked by Ca(++)-dependent endonucleases and whether inhibitors of Ca(++)-endonuclease activity and the DNA repair enzyme poly(ADP-ribose)polymerase affect necrosis. Adult male ICR mice received 100 mg/kg of dimethylnitrosamine i.p. By 2 to 4 hr, total nuclear Ca++ reached 150 to 180% of control and DNA fragmentation was 140 to 170% of control. Electrophoresis of DNA revealed a sharp decline in genomic DNA with the appearance of DNA fragments in a ladder-like pattern. Ca++ elevation and DNA fragmentation preceded toxic cell death by 4 hr or more and reached peak values at 18 to 24 hr, coincident with maximal alanine aminotransferase leakage. Aurintricarboxylic acid, a Ca(++)-endonuclease inhibitor, reduced toxicity 67%. 3-Aminobenzamide, nicotinamide adenine dinucleotide and theophylline, inhibitors of poly(ADP-ribose)polymerase-mediated DNA repair, potentiated liver damage 2-fold. These results support the hypothesis that DNA fragmentation plays a contributing role in toxic cell death induced by dimethylnitrosamine. Furthermore, the findings suggest that new opportunities may exist to moderate the toxicity of alkylating hepatotoxins by altering DNA regulation.
几种肝毒性药物会破坏钙离子调节，并以与因果关系相符的方式导致毒性细胞死亡；然而，钙离子的关键靶点仍未明确。最近的研究结果表明，在细胞凋亡（一种被认为与毒性细胞死亡或坏死不同的细胞死亡形式）过程中，DNA可能是主要的钙离子靶点。本研究探讨了在二甲基亚硝胺诱导的坏死发生之前，细胞核钙离子调节是否丧失，DNA是否受到钙离子依赖性核酸内切酶的攻击，以及钙离子核酸内切酶活性抑制剂和DNA修复酶聚（ADP - 核糖）聚合酶是否会影响坏死。成年雄性ICR小鼠腹腔注射100mg/kg二甲基亚硝胺。在2至4小时时，细胞核总钙离子达到对照值的150%至180%，DNA片段化程度为对照值的140%至170%。DNA电泳显示基因组DNA急剧下降，并出现梯状模式的DNA片段。钙离子升高和DNA片段化比毒性细胞死亡提前4小时或更长时间出现，并在18至24小时达到峰值，与丙氨酸转氨酶最大程度泄漏同时发生。金精三羧酸，一种钙离子核酸内切酶抑制剂，使毒性降低了67%。3 - 氨基苯甲酰胺、烟酰胺腺嘌呤二核苷酸和茶碱，这些聚（ADP - 核糖）聚合酶介导的DNA修复抑制剂，使肝损伤增强了2倍。这些结果支持了DNA片段化在二甲基亚硝胺诱导的毒性细胞死亡中起作用的假说。此外，研究结果表明，通过改变DNA调节来减轻烷基化肝毒素的毒性可能存在新的机会。
