Tanaka Kohji, Kiyosawa Naoki, Watanabe Kyoko, Manabe Sunao
Medicinal Safety Research Labs., Sankyo Co., Ltd, Horikoshi, Fukuroi, Shizuoka, Japan.
J Toxicol Sci. 2007 May;32(2):129-34. doi: 10.2131/jts.32.129.
In our previous study, we demonstrated that the initial hepatic injury caused by bromobenzene (BB) was no longer detected in rats despite subsequent dosing, indicating that the liver acquired resistance to BB-induced hepatotoxicity. In this experiment, microarray analysis was conducted to characterize this resistance. The liver samples for the analysis utilized were obtained from previous experiments where F344 rats were treated intraperitoneally with BB (150 mg/kg). At 24 hr post-dose, hepatic injury was confirmed by monitoring the AST values and then the rats were maintained at the same dosing regimen for an additional 8 days. The gene expression profiles of the BB-treated rat livers were compared with a vehicle-treated group by Affymetrix RG_U34A arrays. As results, a decreased expression level of CYP3A9 and an increased expression level of GST Yc2 and glutathione peroxidase (GPX) were detected. These changes indicated suppression of the phase I reaction and induction of the phase II reaction (glutathione conjugation). Increased expression levels of epoxide hydrolase (EH) and NAD(P)H:quinone oxidoreductase (NQO1) also suggested the involvement of EH- and NQO1-mediated hydrolysis other than glutathione conjugation with resistance in the phase II reaction. Moreover, an increased expression level of abcc3 (multidrug resistance protein 3; Mrp3) was significantly noted. Based on the present findings, it was suggested that Mrp3 in the phase III reaction (drug elimination) contributed to the resistance to BB hepatotoxicity in addition to the suppression of the phase I reaction (metabolic activation) and the induction of the phase II reaction (detoxification). Among them, the factors which contributed most were considered to be the increased GST Yc2 and Mrp3, based on the degree of the gene expression changes.
在我们之前的研究中，我们证明，尽管后续给药，但在大鼠中不再检测到由溴苯（BB）引起的初始肝损伤，这表明肝脏获得了对BB诱导的肝毒性的抗性。在本实验中，进行了微阵列分析以表征这种抗性。用于分析的肝脏样本取自先前的实验，在该实验中，F344大鼠腹腔注射BB（150mg/kg）。给药后24小时，通过监测AST值确认肝损伤，然后将大鼠维持在相同的给药方案下另外8天。通过Affymetrix RG_U34A阵列将BB处理的大鼠肝脏的基因表达谱与载体处理组进行比较。结果，检测到CYP3A9表达水平降低，GST Yc2和谷胱甘肽过氧化物酶（GPX）表达水平升高。这些变化表明I相反应受到抑制，II相反应（谷胱甘肽结合）被诱导。环氧水解酶（EH）和NAD（P）H：醌氧化还原酶（NQO1）表达水平的增加也表明除了谷胱甘肽结合外，EH和NQO1介导的水解参与了II相反应中的抗性。此外，明显注意到abcc3（多药耐药蛋白3；Mrp3）的表达水平增加。基于目前的研究结果，表明III相反应（药物消除）中的Mrp3除了抑制I相反应（代谢活化）和诱导II相反应（解毒）外，还对BB肝毒性的抗性有贡献。其中，根据基因表达变化的程度，认为贡献最大 的因素是GST Yc2和Mrp3的增加。
