Enzymatic mechanisms of ethanol oxidation in the brain
Enzymatic mechanisms of ethanol oxidation in the brain
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DOI：
10.1111/j.1530-0277.2006.00181.x
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发表时间：
2006-09-01
影响因子：
3.2
通讯作者：
Deitrich, Richard A.
中科院分区：
文献类型：
--
作者：
Zimatkin, Sergey M.;Pronko, Sergey P.;Deitrich, Richard A.
背景：乙醇在脑中氧化的确切酶机制尚不清楚。使用脑匀浆与过氧化氢酶抑制剂孵育，在大鼠脑中证明过氧化氢酶介导的乙醇氧化。乙醇脱氢酶（ADH）或细胞色素P450依赖性系统在这一过程中的作用是可能的，但尚未得到证实。本研究的目的是确定不同的酶途径对小鼠和大鼠脑匀浆中乙醇氧化的贡献。方法：采用三种方法研究了大鼠和小鼠脑中乙醇氧化的酶机制：（1）用乙醇代谢酶抑制剂预孵育脑匀浆（2）利用具有乙醇代谢酶（过氧化氢酶、CYP 2 E1或两种酶）遗传缺陷的小鼠;和（3）测定已知具有不同活性的乙醇代谢酶的脑亚细胞组分中的乙醇氧化。结果：过氧化氢酶抑制剂叠氮化钠（5 mM）和氨基三唑（5 mM）以及CYP 2 E1抑制剂二烯丙基硫醚（2 mM）和β-苯乙基异硫氰酸酯（0.1 mM）显著降低脑匀浆中乙醇衍生的乙醛（AC）和乙酸的积累。ADH抑制剂4-甲基吡唑（5 mM）显着降低乙酸，但不AC积累。乙醇衍生的AC在无催化酶小鼠脑匀浆中的蓄积为对照值的47%，在CYP 2 E1缺失小鼠中为91%，在双突变体（过氧化氢酶和CYP 2 E1均缺乏）中为24%。最高水平的乙醇氧化被发现在微粒体和过氧化物酶体亚细胞脑组分，CYP 2 E1和过氧化氢酶位于，分别Conclusions：过氧化氢酶是关键酶的乙醇氧化在啮齿动物的大脑：它可能是负责约60%的过程。CYP 2 E1在啮齿动物脑中乙醇氧化中起重要作用。醇脱氢酶在此过程中起次要作用（如果有的话）。乙醛脱氢酶在脑匀浆中乙醇衍生的AC的进一步氧化中起关键作用。
Background: The exact enzymatic mechanisms of ethanol oxidation in the brain are still unclear. The catalase-mediated oxidation of ethanol was demonstrated in rat brain using incubation of brain homogenates with catalase inhibitors. The role of the alcohol dehydrogenase (ADH) or cytochrome P450-dependent system in this process is possible, but has not been confirmed. The objective of the study was to determine the contribution of the different enzymatic pathways to ethanol oxidation in brain homogenates from mice and rats.Methods: Three approaches were used to investigate the enzymatic mechanisms of ethanol oxidation in the brain of rats and mice: (1) preincubation of brain homogenates with inhibitors of the ethanol-metabolizing enzymes (catalase, CYP2E1, ADH, and ALDH); (2) utilization of mice with genetic deficiency in ethanol-metabolizing enzymes (catalase, CYP2E1, or both enzymes); and (3) determination of ethanol oxidation in brain subcellular fractions known to have differential activity of ethanol-metabolizing enzymes. The ethanol-derived acetaldehyde (AC) and acetate were determined in brain samples by gas chromatography.Results: The catalase inhibitors sodium azide (5 mM) and aminotriazole (5 mM) as well as CYP2E1 inhibitors diallyl sulfide (2 mM) and beta-phenethyl isothiocyanate (0.1 mM) lowered significantly the accumulation of the ethanol-derived AC and acetate in brain homogenates. The ADH inhibitor 4-methyl pyrazole (5 mM) significantly decreased the acetate but not the AC accumulation. Ethanol-derived AC accumulation in brain homogenates of acatalasemic mice was 47% of the control value, 91% in CYP2E1-null mice, and 24% in double mutants (with deficiency of both catalase and CYP2E1). The highest levels of ethanol oxidation were found in microsomal and peroxisomal subcellular brain fractions, where CYP2E1 and catalase are located, respectively.Conclusions: Catalase is the key enzyme of ethanol oxidation in the brain of rodents: it may be responsible for about 60% of the process. CYP2E1 plays an important role in ethanol oxidation in the rodent brains. Alcohol dehydrogenase plays a minor role, if any, in this process. Aldehyde dehydrogenase plays the crucial role in the further oxidation of ethanol-derived AC in the brain homogenates.