Bylund J, Kunz T, Valmsen K, Oliw E H
Department of Pharmaceutical Biosciences, Uppsala Biomedical Center, Uppsala University, Sweden.
J Pharmacol Exp Ther. 1998 Jan;284(1):51-60.
Bisallylic carbons of polyunsaturated fatty acids can be hydroxylated in NADPH-dependent reactions in liver microsomes. Human recombinant cytochromes P450 and human and rat liver microsomes were assayed for bisallylic hydroxylation activity. CYP1A2, CYP2C8, CYP2C9, CYP2C19 and CYP3A4 converted [14C]linoleic acid to 14C-labeled 11-hydroxyoctadecadienoic acid (11-HODE), whereas [14C]arachidonic acid was oxygenated by CYP1A2 and CYP3A4 to 14C-labeled 13-hydroxyeicosatrienoic acid (13-HETE), 10-HETE and 7-HETE as determined by HPLC. Both substrates were also converted to many other metabolites. CYP2C9 appeared to form 12R-HETE and 13-HETE, whereas CYP2C8 formed 13-HETE, 11-HETE and 15-HETE as main monohydroxy metabolites. Fetal human liver microsomes metabolized linoleic acid to 11-HODE as a major hydroxy metabolite, whereas arachidonic acid appeared to be hydroxylated at C13, C20 and, to some extent, at C10, C19 and C7. Fetal liver microsomes mainly formed 13R-HETE, whereas adult human liver microsomes and CYP1A2 mainly formed 13S-HETE. 7,8-Benzoflavone (5 microM) and furafylline (20 microM), two inhibitors of CYP1A2, reduced the bisallylic hydroxylation activity of adult human liver microsomes. Treatment of rats with erythromycin or dexamethasone induced bisallylic hydroxylation of linoleic acid to 11-HODE in liver microsomes by 2- and 10-fold, respectively. The biosynthesis of 11-HODE by microsomes of dexamethasone-treated rats was inhibited by troleandomycin (ED50 = 1 microM) and by polyclonal antibodies against CYP3A1, suggesting that CYP3A1 could catalyze bisallylic hydroxylations in the dexamethasone-treated rat. We conclude from steric analysis of 13-HETE and the effects of CYP inhibitors on adult human liver microsomes that CYP1A2 might contribute to its bisallylic hydroxylation activity.
多不饱和脂肪酸的双烯丙基碳可在肝脏微粒体中依赖烟酰胺腺嘌呤二核苷酸磷酸（NADPH）的反应中发生羟基化。对人重组细胞色素P450以及人和大鼠的肝脏微粒体进行双烯丙基羟基化活性检测。细胞色素P450 1A2（CYP1A2）、细胞色素P450 2C8（CYP2C8）、细胞色素P450 2C9（CYP2C9）、细胞色素P450 2C19（CYP2C19）和细胞色素P450 3A4（CYP3A4）可将[14C]亚油酸转化为14C标记的11-羟基十八碳二烯酸（11-HODE），而[14C]花生四烯酸经CYP1A2和CYP3A4氧化生成14C标记的13-羟基二十碳三烯酸（13-HETE）、10-HETE和7-HETE，这是通过高效液相色谱法测定的。两种底物还可转化为许多其他代谢产物。CYP2C9似乎可生成12R-HETE和13-HETE，而CYP2C8生成的主要单羟基代谢产物为13-HETE、11-HETE和15-HETE。人胎儿肝脏微粒体将亚油酸代谢为主要的羟基代谢产物11-HODE，而花生四烯酸似乎在C13、C20以及在一定程度上在C10、C19和C7处发生羟基化。胎儿肝脏微粒体主要生成13R-HETE，而成人肝脏微粒体和CYP1A2主要生成13S-HETE。CYP1A2的两种抑制剂7,8-苯并黄酮（5微摩尔）和呋拉茶碱（20微摩尔）可降低成人肝脏微粒体的双烯丙基羟基化活性。用红霉素或地塞米松处理大鼠可分别使肝脏微粒体中亚油酸的双烯丙基羟基化生成11-HODE的活性提高2倍和10倍。曲古抑菌素（ED50 = 1微摩尔）和抗CYP3A1的多克隆抗体可抑制地塞米松处理大鼠的微粒体生成11-HODE，这表明CYP3A1可催化地塞米松处理大鼠体内的双烯丙基羟基化反应。我们通过对13-HETE的空间分析以及CYP抑制剂对成人肝脏微粒体的影响得出结论，CYP1A2可能有助于其双烯丙基羟基化活性。
