Gallagher Evan P, Gardner James L
Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida, P.O. Box 110885, Gainesville, FL 32611-0885, USA.
Biochem Pharmacol. 2002 Jun 1;63(11):2025-36. doi: 10.1016/s0006-2952(02)01017-1.
The ability of the fetus to detoxify transplacental drugs and chemicals can be a critical determinant of teratogenesis and developmental toxicity. Developmentally regulated expression of alpha class glutathione S-transferases (GSTs) is of particular interest, since these isozymes have high activity toward peroxidative byproducts of oxidative injury that are linked to teratogenesis. The present study was initiated to examine the expression and catalytic activities of alpha class GST isozymes in human prenatal liver. Northern analysis demonstrated the presence of hGSTA1 and/or A2 (hGSTA1/2) and hGSTA4 steady-state mRNAs in second trimester prenatal livers. Western blotting of prenatal liver proteins provided corroborating evidence via detection of an hGSTA1/2-reactive protein in both cytosol and mitochondria and of hGSTA4-4-reactive protein in mitochondria alone. Catalytic studies demonstrated that prenatal liver cytosolic GSTs were active toward 1-chloro-2,4-dinitrobenzene (a general GST reference substrate), delta5-androstene-3,17-dione (relatively specific for hGSTA1-1), and 4-hydroxynonenal, a highly mutagenic alpha,beta-unsaturated aldehyde produced during oxidative damage and a substrate for hGSTA4-4. Total GSH-peroxidase and GST-dependent peroxidase activities were 9- and 18-fold higher, respectively, in adult liver than in prenatal liver. Multiple tissue array analyses demonstrated considerable tissue-specific and developmental variation in GST mRNA expression. In summary, our results demonstrate the presence of two important alpha class GSTs in second trimester human prenatal tissues, and indicate that mitochondrial targeting of GST may represent an important pathway for removal of cytotoxic products in prenatal liver. Furthermore, the relatively inefficient prenatal reduction of hydroperoxides may underlie an increased susceptibility to maternally transferred pro-oxidant drugs and chemicals.
胎儿对经胎盘转运的药物和化学物质进行解毒的能力可能是致畸作用和发育毒性的关键决定因素。α类谷胱甘肽S-转移酶（GSTs）的发育调控表达尤其令人关注，因为这些同工酶对与致畸作用相关的氧化损伤的过氧化副产物具有高活性。本研究旨在检测人产前肝脏中α类GST同工酶的表达和催化活性。Northern分析表明，孕中期产前肝脏中存在hGSTA1和/或A2（hGSTA1/2）以及hGSTA4稳态mRNA。产前肝脏蛋白质的Western印迹通过检测胞质溶胶和线粒体中的hGSTA1/2反应性蛋白以及仅线粒体中的hGSTA4-4反应性蛋白提供了确证证据。催化研究表明，产前肝脏胞质溶胶GSTs对1-氯-2,4-二硝基苯（一种通用的GST参考底物）、δ5-雄烯-3,17-二酮（对hGSTA1-1相对特异）和4-羟基壬烯醛具有活性，4-羟基壬烯醛是氧化损伤过程中产生的一种高度致突变的α,β-不饱和醛，也是hGSTA4-4的底物。总谷胱甘肽过氧化物酶和GST依赖性过氧化物酶活性在成人肝脏中分别比产前肝脏高9倍和18倍。多组织阵列分析表明，GST mRNA表达存在相当大的组织特异性和发育差异。总之，我们的结果证明了孕中期人产前组织中存在两种重要的α类GSTs，并表明GST的线粒体靶向可能是产前肝脏中清除细胞毒性产物的重要途径。此外，产前对氢过氧化物的还原效率相对较低可能是对母体转移的促氧化药物和化学物质易感性增加的基础。
