Department of Pharmacodynamics and Molecular Genetics, School of Pharmacy, Iwate Medical University, Iwate, Japan.
J Toxicol Sci. 2011 Oct;36(5):613-23. doi: 10.2131/jts.36.613.
The purpose of our study was to examine the altered gene expression associated with nongenotoxic chemical-mediated liver hypertrophy and successive liver tumor promotion. Five-week-old male rats were fed a basal diet or a diet containing phenobarbital (PB) or clofibrate (CF) for 3 days, 4 weeks, and 13 weeks. Hepatic expression profiling of cell growth- and stress-related genes, as well as those involved in xenobiotic metabolism, was performed by DNA microarray and/or real time quantitative reverse transcription-polymerase chain reaction. The induction of liver hypertrophy and hepatic cytochrome P450 (CYP) isoforms (CYP2B1/2B2 for PB and CYP4A1 for CF) by PB and CF were clearly observed at all the treatment periods examined. Genes encoding DNA damage-inducible 45 (GADD45) family proteins, in particular GADD45g (GADD45 gamma) were down-regulated by treatment with either PB or CF for 4 and 13 weeks. The chemical-mediated development of liver hypertrophy, induction of hepatic CYPs, and suppression of hepatic GADD45g gene at week 13 disappeared at 4 weeks following cessation of the chemical treatment. Additionally, DNA microarray data indicated that cell cycle-related genes such as cyclins CCNB1 and CCNA2 and cyclin-dependent kinase inhibitor CDKN3 were also down-regulated by treatment with either PB or CF at 13 weeks. Since GADD45 functions as a chemical and radiation stress sensor by interacting with cyclins and cyclin-dependent kinase inhibitors, the decrease in the gene expression of GADD45g mRNA observed in this study, may be associated with nongenotoxic chemical-induced tumor promotion of hepatocarcinogenesis rather than liver hypertrophy.
我们的研究目的是研究与非遗传毒性化学物质介导的肝肥大和随后的肝肿瘤促进相关的基因表达改变。将 5 周龄雄性大鼠用基础饮食或含苯巴比妥（PB）或氯贝特（CF）的饮食喂养 3 天、4 周和 13 周。通过 DNA 微阵列和/或实时定量逆转录-聚合酶链反应进行细胞生长和应激相关基因以及参与外来生物代谢的基因的肝表达谱分析。在所有检查的治疗期，PB 和 CF 明显诱导肝肥大和肝细胞色素 P450（CYP）同工酶（PB 的 CYP2B1/2B2 和 CF 的 CYP4A1）。用 PB 或 CF 处理 4 周和 13 周，编码 DNA 损伤诱导 45（GADD45）家族蛋白的基因，特别是 GADD45g（GADD45 gamma）下调。肝肥大的化学介导发展、肝 CYP 的诱导和肝 GADD45g 基因的抑制在化学处理停止后 4 周内消失。此外，DNA 微阵列数据表明，细胞周期相关基因，如周期蛋白 CCNB1 和 CCNA2 和细胞周期蛋白依赖性激酶抑制剂 CDKN3，也在 13 周时用 PB 或 CF 处理而下调。由于 GADD45 通过与细胞周期蛋白和细胞周期蛋白依赖性激酶抑制剂相互作用作为化学和辐射应激传感器，因此本研究中观察到的 GADD45g mRNA 基因表达下降，可能与非遗传毒性化学物质诱导的肝癌发生的肿瘤促进而非肝肥大有关。
