Ellouk-Achard S, Martin C, Pham-Huy C, Duc H T, Thevenin M, Dutertre-Catella H, Warnet J M, Claude J R
Laboratoire de Toxicologie (EA 207), Faculté de Pharmacie, Université René-Descartes, Paris, France.
Arch Toxicol. 1997;71(7):437-42. doi: 10.1007/s002040050408.
FK506, cyclosporin A (CsA), and its structural analog cyclosporin G (CsG) are immunosuppressant drugs mainly metabolized by hepatic cytochrome P-450 3A (CYP 3A) oxygenase. FK506 metabolites exhibit greater toxicity than the parent drug, while CsA metabolites are far less toxic than CsA itself. The aim of our study was to compare the toxicity of CsG with CsA and FK506 as a function of CYP 3A induction. Hepatocytes from Wistar rats with or without dexamethasone (DEX) induction (200 mg/kg per day, p.o for 4 days) were used in primary culture. The DEX-inductive effect on CYP 3A was assessed by SDS-PAGE. After 6 h incubation with CsG, CsA or FK506 (5 to 200 microM), cell viability (expressed as IC50), intracellular calcium content and apoptosis were evaluated. Concerning cytotoxicity, IC50 values for CsG, CsA and FK506 were 75, 50 and 180 microM respectively in non-induced cultures, and 150, 120 and 25 microM in induced cultures. For intracellular calcium content, a dose-dependent increase was observed in all cultures. However this increase is more important for CsG and CsA in non-induced cultures (150%) compared to induced cultures (110%) at 150 microM. Conversely for FK506, this increase is greater in induced cultures (150%) than in non-induced cultures (127%). Estimation of the percentage of apoptotic cells shows similar variations. Our results show that the toxicity of the three drugs in rat hepatocytes is dependent on CYP 3A induction: increased for FK506, decreased for CsA and CsG. Moreover, with regard to the three tests used, the toxic effects of CsG are close to those of CsA, indicating that CsG metabolites are also less toxic than the parent drug.
FK506、环孢素A（CsA）及其结构类似物环孢素G（CsG）是主要由肝细胞色素P - 450 3A（CYP 3A）加氧酶代谢的免疫抑制药物。FK506代谢产物比母体药物表现出更大的毒性，而CsA代谢产物的毒性远低于CsA本身。我们研究的目的是比较CsG与CsA和FK506在CYP 3A诱导作用下的毒性。将有或没有地塞米松（DEX）诱导（每天200 mg/kg，口服4天）的Wistar大鼠的肝细胞用于原代培养。通过SDS - PAGE评估DEX对CYP 3A的诱导作用。在用CsG（5至200 microM）、CsA或FK506孵育6小时后，评估细胞活力（以IC50表示）、细胞内钙含量和细胞凋亡情况。关于细胞毒性，在未诱导的培养物中，CsG、CsA和FK506的IC50值分别为75 microM、50 microM和180 microM，在诱导的培养物中分别为150 microM、120 microM和25 microM。对于细胞内钙含量，在所有培养物中均观察到剂量依赖性增加。然而，在150 microM时，与诱导培养物（110%）相比，未诱导培养物中CsG和CsA的这种增加更为显著（150%）。相反，对于FK506，诱导培养物中的这种增加（150%）大于未诱导培养物（127%）。凋亡细胞百分比的估计显示出类似的变化。我们的结果表明，这三种药物在大鼠肝细胞中的毒性取决于CYP 3A的诱导：FK506的毒性增加，CsA和CsG的毒性降低。此外，就所使用的三项测试而言，CsG的毒性作用与CsA接近，表明CsG代谢产物的毒性也低于母体药物。
