Wang Li-Quan, James Margaret O
Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA.
Aquat Toxicol. 2007 Mar 10;81(3):286-92. doi: 10.1016/j.aquatox.2006.12.011. Epub 2007 Jan 3.
The sulfonation of 17beta-estradiol (E2) by human liver and recombinant sulfotransferases is influenced by environmental contaminants such as hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs), which are potent inhibitors, and the therapeutic drug, celecoxib, which affects positional sulfonation of E2. In some locations, the aquatic environment is contaminated by PCBs, OH-PCBs and widely used therapeutic drugs. The objectives of this study were to investigate the sulfonation kinetics of E2 in liver cytosol from channel catfish (Ictalurus punctatus); to examine the effect of OH-PCBs on E2 sulfonation; and to determine if celecoxib altered the position of E2 sulfonation, as it does with human liver cytosol. E2 was converted to both 3- and 17-sulfates by catfish liver cytosol. At E2 concentrations below 1 microM, formation of E2-3-sulfate (E2-3-S) predominated, but substrate inhibition was observed at higher concentrations. Rates of E2-3-S formation at different E2 concentrations were fit to a substrate inhibition model, with K'm and V'max values of 0.40 +/- 0.10 microM and 91.0 +/- 4.7 pmol/min/mg protein, respectively and K(i) of 1.08 +/- 0.09 microM. The formation of E2-17-S fit Michaelis-Menten kinetics over the concentration range 25 nM to 2.5 microM, with K(m) and V(max) values of 1.07 +/- 0.23 microM and 25.7 +/- 4.43 pmol/min/mg protein, respectively. The efficiency (V(max)/K(m)) of formation of E2-3-S was 9.8-fold higher than that of E2-17-S. Several OH-PCBs inhibited E2 3-sulfonation, measured at an E2 concentration of 1 nM. Of those tested, the most potent inhibitor was 4'-OH-CB79, with two chlorine atoms flanking the OH group (IC(50): 94 nM). The inhibition of estrogen sulfonation by OH-PCBs may disrupt the endocrine system and thus contribute to the known toxic effects of these compounds. Celecoxib did not stimulate E2-17-S formation, as is the case with human liver cytosol, but did inhibit the formation of E2-3-S (IC(50): 44 microM) and to a lesser extent, E2-17-S (IC(50): > 160 microM), suggesting the previously found effect of celecoxib on E2-17-S formation may be specific to human SULT2A1.
人肝脏和重组磺基转移酶对17β-雌二醇（E2）的磺化作用受到环境污染物的影响，如多氯联苯的羟基化代谢物（OH-PCBs），它们是强效抑制剂，以及治疗药物塞来昔布，其会影响E2的定位磺化。在一些地区，水生环境受到多氯联苯、OH-PCBs和广泛使用的治疗药物的污染。本研究的目的是研究斑点叉尾鮰（Ictalurus punctatus）肝脏胞质溶胶中E2的磺化动力学；研究OH-PCBs对E2磺化的影响；并确定塞来昔布是否会改变E2磺化的位置，就像它对人肝脏胞质溶胶的作用一样。斑点叉尾鮰肝脏胞质溶胶将E2转化为3-硫酸盐和17-硫酸盐。在E2浓度低于1μM时，E2-3-硫酸盐（E2-3-S）的形成占主导，但在较高浓度下观察到底物抑制。不同E2浓度下E2-3-S的形成速率符合底物抑制模型，K'm和V'max值分别为0.40±0.10μM和91.0±4.7 pmol/min/mg蛋白质，K(i)为1.08±0.09μM。在25 nM至2.5μM的浓度范围内，E2-17-S的形成符合米氏动力学，K(m)和V(max)值分别为1.07±0.23μM和25.7±4.43 pmol/min/mg蛋白质。E2-3-S形成的效率（V(max)/K(m)）比E2-17-S高9.8倍。几种OH-PCBs在E2浓度为1 nM时抑制E2的3-磺化。在测试的这些物质中，最有效的抑制剂是4'-OH-CB79，其OH基团两侧有两个氯原子（IC(50)：94 nM）。OH-PCBs对雌激素磺化的抑制可能会扰乱内分泌系统，从而导致这些化合物已知的毒性作用。与人类肝脏胞质溶胶的情况不同，塞来昔布不会刺激E2-17-S的形成，但会抑制E2-3-S的形成（IC(50)：44μM），在较小程度上也会抑制E2-17-S的形成（IC(50)：>160μM），这表明之前发现的塞来昔布对E2-17-S形成的影响可能是人SULT2A1特有的。
