Formation and Metabolism of Salsolinol Enantiomers

1-甲基-4-苯基-1，2，3，6-四氢吡啶(MPTP)是一种外源性(合成)神经毒素 人类、非人类灵长类动物和大鼠中的帕金森氏症。丹参素(6，7-二羟基-1-甲基-1，2，3，4 -四氢异喹啉(四氢异喹啉，SAL)是一种MPTP样神经毒素。它的一些I相代谢物，如N-甲基- (R)-SAL，已被证明靶向和损伤黑质纹状体多巴胺能神经元诱导 帕金森症。不幸的是，SAL可以在体内由多巴胺(A)缩合而成 大脑中的神经递质)和乙醛(酒精的代谢物)。非常有趣的是，这两个人 N-甲基-SAL的对映体具有明显的神经毒理学特性。N-甲基-(R)-SAL诱导 对大鼠帕金森病有抑制作用，但N-甲基-(S)-丹参不能。然而，体内的立体化学方面 这些神经毒性对映体的形成和代谢在很大程度上仍不清楚。为 例如，关于生理体液中SAL的立体特异性出现的文献数据是 前后不一致。这项研究的目标是确定生物合成和代谢途径 萨尔对映体。为此目的，开发适用于 需要同时定量SAL及其I相代谢物的对映体。我们 建议开发一种基于毛细管高效液相色谱/串联质谱仪的手性分析方法 用于此目的的光谱分析。在分析方法到位后，将进行研究。 结果：1)测定大鼠内源性SAL及其代谢物的对映体组成 2)研究SAL在大鼠脑内的体内形成。 用~(13)C标记的乙醛和丙酮酸对大鼠进行微透析；3)分析 ~(13)C标记SAL和N-甲基SAL的I相代谢产物 对映体(如[1，m-13C2]-丹参素)；和4)评估对映体SAL的神经毒性 其在PC-12中的主要I相代谢产物为N-甲基-SA和N-甲基-4-羟基-SA 和SH-SY5Y细胞。假设是神经毒性更强的(R)对映体的外消旋 内源性SAL及其代谢产物是导致健康人排毒的主要途径 神经系统。通过使用改进的手性分析方法并结合In 活体微渗析和稳定同位素标记技术的研究将做出重大贡献 根据我们对这些神经毒素在体内形成和代谢的了解，这些毒素参与了 某些神经退行性疾病的发病机制，如帕金森氏病。从这些 随着研究的深入，我们也将在理解立体化学方面取得重大进展。 一般情况下会有神经毒性。

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is an exogenous (synthetic) neurotoxin inducing Parkinsonism in humans, non-human primates, and rats. Salsolinol (6,7-dihydroxy-1-methyl-1, 2, 3, 4 -tetrahydroisoquinoline, Sal) is an MPTP-like neurotoxin. Some of its phase I metabolites, e.g. N-methyl- (R)-Sal, have been shown to target and injure particularly dopaminergic nigrostriatal neurons inducing Parkinsonism. Unfortunately, Sal can be formed in vivo from the condensation of dopamine (a neurotransmitter in the brain) and acetaldehyde (a metabolite of alcohol). Very interestingly, the two enantiomers of N-methyl-Sal exhibit distinct neurotoxicological properties. N-methyl-(R)-Sal induces Parkinsonism in rats, but N-methyl-(S)-Sal does not. However, the stereochemical aspects of in-vivo formation and metabolism of these neurotoxic enantiomers remain largely unknown. For example, literature data on the stereospecific occurrence of Sal in physiological fluids are inconsistent. The goal of this research is to identify the biosynthetic and metabolic pathways of Sal enantiomers. To this end, the development of suitable analytical methodology for simultaneous quantification of the enantiomers of Sal and its phase I metabolites is needed. We are proposing to develop a chiral analytical method based on capillary HPLC /tandem mass spectrometry for this purpose. After the analytical methodology is in place, studies will be carried out: 1) to determine the enantiomeric compositions of endogenous Sal and its metabolites in rat brain and physiological fluids; 2) to investigate in vivo formation of Sal in rat brain using microdialysis after administering 13C labeled acetaldehyde and pyruvic acid to rats; 3) to profile the phase I metabolites of Sal and N-methyl-Sal using 13C labeled Sal or N-methyl-Sal enantiomers (e.g. [1 ,m-13C2]-salsolinol); and 4) to assess the neurotoxicity of enantiomeric Sal and its major phase I metabolites including N-methyl-Sal and N-methyl-4-hydroxyl-Sal in PC-12 and SH-SY5Y cells. The hypothesis is that racemization of the more neurotoxic (R)-enantiomers of endogenous Sal and its metabolites is a major pathway leading to detoxification in a healthy nervous system. By using the improved methodology for chiral analysis in combination with in vivo microdialysis and stable isotope labeling techniques, the research will contribute significantly to our knowledge of in vivo formation and metabolism of these neurotoxins involved in the pathogenesis of certain neurodegenerative disorders such as Parkinson's disease. From these studies, significant gains will also be made in understanding the stereochemical aspects of neurotoxicity in general.