Zeldin D C, Plitman J D, Kobayashi J, Miller R F, Snapper J R, Falck J R, Szarek J L, Philpot R M, Capdevila J H
Department of Medicine, Vanderbilt University Medical School, Nashville, Tennessee 37232, USA.
J Clin Invest. 1995 May;95(5):2150-60. doi: 10.1172/JCI117904.
Cytochrome P450 metabolizes arachidonic acid to several unique and biologically active compounds in rabbit liver and kidney. Microsomal fractions prepared from rabbit lung homogenates metabolized arachidonic acid through cytochrome P450 pathways, yielding cis-epoxyeicosatrienoic acids (EETs) and their hydration products, vic-dihydroxyeicosatrienoic acids, mid-chain cis-trans conjugated dienols, and 19- and 20-hydroxyeicosatetraenoic acids. Inhibition studies using polyclonal antibodies prepared against purified CYP2B4 demonstrated 100% inhibition of arachidonic acid epoxide formation. Purified CYP2B4, reconstituted in the presence of NADPH-cytochrome P450 reductase and cytochrome b5, metabolized arachidonic acid, producing primarily EETs. EETs were detected in lung homogenate using gas chromatography/mass spectroscopy, providing evidence for the in vivo pulmonary cytochrome P450 epoxidation of arachidonic acid. Chiral analysis of these lung EETs demonstrated a preference for the 14(R),15(S)-, 11(S),12(R)-, and 8(S),9(R)-EET enantiomers. Both EETs and vic-dihydroxyeicosatrienoic acids were detected in bronchoalveolar lavage fluid. At micromolar concentrations, methylated 5,6-EET and 8,9-EET significantly relaxed histamine-contracted guinea pig hilar bronchi in vitro. In contrast, 20-hydroxyeicosatetraenoic acid caused contraction to near maximal tension. We conclude that CYP2B4, an abundant rabbit lung cytochrome P450 enzyme, is the primary constitutive pulmonary arachidonic acid epoxygenase and that these locally produced, biologically active eicosanoids may be involved in maintaining homeostasis within the lung.
细胞色素P450在兔肝脏和肾脏中将花生四烯酸代谢为几种独特的生物活性化合物。从兔肺匀浆制备的微粒体组分通过细胞色素P450途径代谢花生四烯酸，生成顺式环氧二十碳三烯酸（EETs）及其水合产物、vic - 二羟基二十碳三烯酸、中链顺反共轭二烯醇以及19 - 和20 - 羟基二十碳四烯酸。使用针对纯化的CYP2B4制备的多克隆抗体进行的抑制研究表明，花生四烯酸环氧化物形成受到100%抑制。在存在NADPH - 细胞色素P450还原酶和细胞色素b5的情况下重构的纯化CYP2B4代谢花生四烯酸，主要产生EETs。使用气相色谱/质谱法在肺匀浆中检测到EETs，为花生四烯酸在体内肺细胞色素P450环氧化提供了证据。对这些肺EETs的手性分析表明，对14(R),15(S)-、11(S),12(R)-和8(S),9(R)-EET对映体具有偏好性。在支气管肺泡灌洗液中检测到了EETs和vic - 二羟基二十碳三烯酸。在微摩尔浓度下，甲基化的5,6 - EET和8,9 - EET在体外可显著舒张组胺收缩的豚鼠肺门支气管。相比之下，20 - 羟基二十碳四烯酸可引起收缩至接近最大张力。我们得出结论，CYP2B4是兔肺中一种丰富的细胞色素P450酶，是主要的组成型肺花生四烯酸环氧化酶，并且这些局部产生的生物活性类二十烷酸可能参与维持肺内的稳态。
