Gardner James L, Doi Adriana M, Pham Robert T, Huisden Christiaan M, Gallagher Evan P
Department of Physiological Sciences, Center for Environmental and Human Toxicology, P.O. Box 110885, University of Florida, Gainesville, FL 32611, USA.
Toxicol Appl Pharmacol. 2003 Sep 1;191(2):95-106. doi: 10.1016/s0041-008x(03)00220-5.
4-hydroxynonenal (4HNE) is a highly mutagenic and cytotoxic alpha,beta-unsaturated aldehyde that can be produced in utero during transplacental exposure to prooxidant compounds. Cellular protection against 4HNE injury is provided by alcohol dehydrogenases (ADH), aldehyde reductases (ALRD), aldehyde dehydrogenases (ALDH), and glutathione S-transferases (GST). In the present study, we examined the comparative detoxification of 4HNE by aldehyde-metabolizing enzymes in a panel of adult and second-trimester prenatal liver tissues and report the toxicological ramifications of ontogenic 4HNE detoxification in vitro. The initial rates of 4HNE oxidation and reduction were two- to fivefold lower in prenatal liver subcellular fractions as compared to adult liver, and the rates of GST conjugation of 4HNE were not detectable in either prenatal or adult cytosolic fractions. GSH-affinity purification of hepatic cytosol yielded detectable and roughly equivalent rates of GST-4HNE conjugation for the two age groups. Consistent with the inefficient oxidative and reductive metabolism of 4HNE in prenatal liver, cytosolic fractions prepared from prenatal liver exhibited a decreased ability to protect against 4HNE-protein adduct formation relative to adults. Prenatal liver hematopoietic stem cells (HSC), which constitute a significant percentage of prenatal liver cell populations, exhibited ALDH activities toward 4HNE, but little reductive or conjugative capacity toward 4HNE through ALRD, ADH, and GST. Cultured HSC exposed to 5 microM 4HNE exhibited a loss in viability and readily formed one or more high molecular weight 4HNE-protein adduct(s). Collectively, our results indicate that second trimester prenatal liver has a lower ability to detoxify 4HNE relative to adults, and that the inefficient detoxification of 4HNE underlies an increased susceptibility to 4HNE injury in sensitive prenatal hepatic cell targets.
4-羟基壬烯醛（4HNE）是一种具有高度致突变性和细胞毒性的α,β-不饱和醛，在子宫内经胎盘接触促氧化化合物时可产生。酒精脱氢酶（ADH）、醛还原酶（ALRD）、醛脱氢酶（ALDH）和谷胱甘肽S-转移酶（GST）可对细胞起到保护作用，使其免受4HNE损伤。在本研究中，我们检测了醛代谢酶对一组成人和孕中期产前肝脏组织中4HNE的比较解毒作用，并报告了体外个体发育过程中4HNE解毒的毒理学影响。与成人肝脏相比，产前肝脏亚细胞组分中4HNE氧化和还原的初始速率低两到五倍，在产前或成人胞质组分中均未检测到4HNE的GST结合速率。对肝细胞溶质进行谷胱甘肽亲和纯化后，两个年龄组的GST-4HNE结合速率均可检测到且大致相当。与产前肝脏中4HNE的氧化和还原代谢效率低下一致，相对于成人，产前肝脏制备的胞质组分对4HNE-蛋白质加合物形成的保护能力降低。产前肝脏造血干细胞（HSC）占产前肝脏细胞群体的很大比例，其表现出对4HNE的ALDH活性，但通过ALRD、ADH和GST对4HNE的还原或结合能力较弱。暴露于5 microM 4HNE的培养HSC活力丧失，并容易形成一种或多种高分子量4HNE-蛋白质加合物。总体而言，我们的结果表明，与成人相比，孕中期产前肝脏对4HNE的解毒能力较低，而4HNE解毒效率低下是敏感的产前肝细胞靶点对4HNE损伤易感性增加的原因。
