Accumulation of Neurotoxic Thioether Metabolites of 3,4-(±)-Methylenedioxymethamphetamine in Rat Brain
作者:Gladys V. Erives、Serrine S. Lau、Terrence J. Monks
DOI:10.1124/jpet.107.128785
日期:2008.1
The serotonergic neurotoxicity of 3,4-(±)-methylenedioxymethamphetamine (MDMA) appears dependent upon systemic metabolism because direct injection of MDMA into the brain fails to reproduce the neurotoxicity. MDMA is demethylenated to the catechol metabolite N -methyl-α-methyldopamine ( N -Me-α-MeDA). Thioether (glutathione and N -acetylcysteine) metabolites of N -Me-α-MeDA are neurotoxic and are present in rat brain following s.c. injection of MDMA. Because multidose administration of MDMA is typical of drug intake during rave parties, the present study was designed to determine the effects of multiple doses of MDMA on the concentration of neurotoxic thioether metabolites in rat brain. Administration of MDMA (20 mg/kg s.c.) at 12-h intervals for a total of four injections led to a significant accumulation of the N -Me-α-MeDA thioether metabolites in striatal dialysate. The area under the curve (AUC)0–300 min for 5-(glutathion- S -yl)- N -Me-α-MeDA increased 33% between the first and fourth injections and essentially doubled for 2,5-bis-(glutathion- S -yl)- N -Me-α-MeDA. Likewise, accumulation of the mercapturic acid metabolites was reflected by increases in the AUC0–300 min for both 5-( N -acetylcystein- S -yl)- N -Me-α-MeDA (35%) and 2,5-bis-( N -acetylcystein- S -yl)- N -Me-α-MeDA (85%), probably because processes for their elimination become saturated. Indeed, the elimination half-life of 5-( N -acetylcystein- S -yl)- N -Me-α-MeDA and 2,5-bis-( N -acetylcystein- S -yl)- N -Me-α-MeDA increased by 53 and 28%, respectively, between the first and third doses. Finally, although the C max values for the monothioether conjugates were essentially unchanged after each injection, the values increased by 38 and ∼50% for 2,5-bis-(glutathion- S -yl)- N -Me-α-MeDA and 2,5-bis-( N -acetylcystein- S -yl)- N -Me-α-MeDA, respectively, between the first and fourth injections. The data indicate that neurotoxic metabolites of MDMA may accumulate in brain after multiple dosing.
3,4-(±)-亚甲二氧基甲基苯丙胺(MDMA)的5-羟色胺能神经毒性似乎取决于全身代谢,因为直接将MDMA注入大脑无法再现其神经毒性。亚甲二氧基甲基苯丙胺会被去甲基化为儿茶酚代谢物 N -甲基-α-甲基多巴胺(N -Me-α-MeDA)。N -Me-α-MeDA的硫醚(谷胱甘肽和N -乙酰半胱氨酸)代谢物具有神经毒性,在大鼠脑中静脉注射MDMA后会出现这种代谢物。由于多剂量服用摇头丸是狂欢派对中的典型药物摄入方式,因此本研究旨在确定多剂量服用摇头丸对大鼠大脑中神经毒性硫醚代谢物浓度的影响。每隔 12 小时注射一次亚甲二氧基甲基苯丙胺(20 毫克/千克 s.c.),共注射四次,会导致纹状体透析液中 N -Me-α-MeDA 硫醚代谢物的显著积累。5-(glutathion- S -yl)- N -Me-α-MeDA 的 0-300 分钟曲线下面积(AUC)在第一次和第四次注射之间增加了 33%,而 2,5-双-(glutathion- S -yl)- N -Me-α-MeDA 的曲线下面积则增加了一倍。同样,5-( N -乙酰基半胱氨酸-S-基)-N-Me-α-MeDA(35%)和 2,5-双-( N -乙酰基半胱氨酸-S-基)-N-Me-α-MeDA(85%)的 AUC0-300 min 增加,反映了巯基酸代谢物的积累,这可能是因为它们的消除过程已达到饱和。事实上,5-(N-乙酰基 cystein- S-基)-N-Me-α-MeDA 和 2,5-双(N-乙酰基 cystein- S-基)-N-Me-α-MeDA 的消除半衰期在第一和第三剂量之间分别增加了 53% 和 28%。最后,虽然单硫醚共轭物的最大 C 值在每次注射后基本保持不变,但 2,5-双(谷胱甘肽-S-基)-N-Me-α-MeDA 和 2,5-双(N-乙酰基半胱氨酸-S-基)-N-Me-α-MeDA 的最大 C 值在第一次和第四次注射之间分别增加了 38% 和 ∼50%。这些数据表明,多次给药后,亚甲二氧基甲基苯丙胺的神经毒性代谢物可能会在大脑中积累。