Inhibition of human prenatal biosynthesis of all-trans-retinoic acid by ethanol, ethanol metabolites, and products of lipid peroxidation reactions -: A possible role for CYP2E1
Inhibition of human prenatal biosynthesis of all-trans-retinoic acid by ethanol, ethanol metabolites, and products of lipid peroxidation reactions -: A possible role for CYP2E1
复制标题
DOI：
10.1016/s0006-2952(98)00362-1
复制
发表时间：
1999-04-01
影响因子：
5.8
通讯作者：
Juchau, MR
中科院分区：
文献类型：
--
作者：
Khalighi, M;Brzezinski, MR;Juchau, MR
以人成年肝组织为阳性对照，用高效液相色谱法研究了人胎肝组织中全反式视黄醇(t-ROH)和全反式视黄醇(t-ral)向全汉维甲酸(t-RA)的生物转化。胎儿期人胞浆组分催化t-ROH的生物转化，导致t-Ra积聚，t-RA最小。NAD(+)和NADP(+)都支持产前胞浆催化的t-ROH氧化，但NAD(+)是一种更好的辅因子。相反，t-缩醛氧化成t-RA的催化作用似乎完全依赖于NAD(+)。T-ROH转化为t-Ral和t-Ral转化为t-RA的底物K-m值分别为82.4和65.8µM。乙醇浓度为10 mM和90 mM时，t-ROH向t-RA的转化率分别为25%和43%，但对t-ROH向t-RA的转化率无明显影响。相反，乙醛在0.1 mM和10 mM浓度下使t-缩醛向t-RA的转化率分别减少了25%和87%。已知的由过氧化脂质产生的几种醇和醛对人产前肝组织中t-RA的生物合成也有明显的抑制作用。在所测试的化合物中，4-羟基-2-壬烯醛(4-HNE)对t-缩醛转化为t-RA有很强的抑制作用。浓度仅为0.001 mM时，抑制率为20%，浓度为0.1mM时，几乎完全抑制。用高灵敏的蛋白质印迹技术氯唑沙宗6-羟化和逆转录聚合酶链式反应(RT-PCR)检测到人胚胎肝组织中均有明显的CYP2E1表达，这表明人胚胎肝组织中的脂质过氧化可通过该酶催化的乙醇氧化来启动。综上所述，这些研究表明，乙醇可能直接或间接地影响人产前肝组织t-RA的生物合成。乙醇及其主要氧化代谢产物乙醛均可抑制t-RA的生成。同时，细胞色素P450酶催化的乙醇氧化可通过产生多种自由基引发脂质过氧化。由此产生的过氧化脂质可以通过CYP2E1催化的反应进一步转化为醇和醛，包括4-HNE，它们是t-RA合成的有效抑制剂。(C)1999年爱思唯尔科学公司。
Biotransformation of all-trans-retinol (t-ROH) and all-trans-retinal (t-RAL) to all-hans-retinoic acid (t-RA) in human prenatal hepatic tissues (53-84 gestational days) was investigated with HPLC using human adult hepatic tissues as positive controls. Catalysis of the biotransformation of t-ROH by prenatal human cytosolic fractions resulted in accumulation of t-RAL with minimal t-RA. Oxidations of t-ROH catalyzed by prenatal cytosol were supported by both NAD(+) and NADP(+), although NAD(+) was a much better cofactor. In contrast, catalysis of the oxidation of t-RAL to t-RA appeared to be solely NAD(+) dependent. Substrate K-m values for conversions of t-ROH to t-RAL and of t-RAL to t-RA were 82.4 and 65.8 mu M, respectively. At concentrations of 10 and 90 mM, ethanol inhibited the conversion of t-ROH to t-RAL by 25 and 43%, respectively, but did not inhibit the conversion of t-RAL to t-RA significantly. In contrast, acetaldehyde reduced the conversion of t-RAL to t-RA by 25 and 87% at 0.1 and 10 mM respective concentrations. Several alcohols and aldehydes known to be generated from lipid peroxides also exhibited significant inhibition of t-RA biosynthesis in human prenatal hepatic tissues. Among the compounds tested, 4-hydroxy-2-nonenal (4-HNE) was highly effective in inhibiting the conversion of t-RAL to t-RA. A 20% inhibition was observed at a concentration of only 0.001 mM, and nearly complete inhibition was produced at 0.1 mM. Human fetal and embryonic hepatic tissues each exhibited significant CYP2E1 expression as assessed with chlorzoxazone 6-hydroxylation, a highly sensitive western blotting technique, and reverse transcriptase-polymerase chain reaction (PCR) (RT-PCR), suggesting that lipid peroxidation can be initiated via CYP2E1-catalyzed ethanol oxidation in human embryonic hepatic tissues. In summary, these studies suggest that ethanol may affect the biosynthesis of t-RA in human prenatal hepatic tissues directly and indirectly. Ethanol and its major oxidative metabolite, acetaldehyde, both inhibit the generation of t-RA. Concurrently, the CYP2E1-catalyzed oxidation of ethanol can initiate lipid peroxidation via generation of a variety of free radicals. The lipid peroxides thereby generated could then be further converted via CYP2E1-catalyzed reactions to alcohols and aldehydes, including 4-HNE, that act as potent inhibitors of t-RA synthesis. (C) 1999 Elsevier Science Inc.