In vitro metabolism of 3,4-methylenedioxymethamphetamine in human hepatocytes.

Users of the illicit drug, 3,4-methylenedioxymethamphetamine (MDMA), show signs of neurotoxicity. However, the precise mechanism of neurotoxicity caused by use of MDMA has not yet been elucidated. Synthetic glutathione (GSH) conjugates of MDMA are transported into the brain by the GSH transporter and subsequently produce neurotoxicity. The objective of this research is to show direct evidence of the formation of GSH adducts of MDMA in human hepatocytes. High-performance liquid chromatography coupled with tandem mass spectrometry was utilized to examine in vitro incubations of MDMA with cryopreserved human hepatocytes. The use of hydrophilic liquid chromatography in combination with linear ion trap mass spectrometry permitted the identification of two possible GSH metabolites. Enhanced product ion scans of m/z = 499 and 487 amu of extracts from hepatocytes treated with 1.0 mM MDMA show a distinct fragmentation pattern (m/z 194.2, 163, 135, 105), suggesting the formation of MDMA-GSH conjugate, MDMA-SG and 3,4-dihydroxymethamphetamine-SG. The formation of an MDMA-GSH conjugate was further supported by the apparent lack of the same fragmentation pattern from hepatocyte samples without MDMA treatment. The results generated from this study yield valuable qualitative and quantitative information about the neurotoxic thioether metabolites formed from MDMA in humans.

High-performance liquid chromatography coupled with tandem mass spectrometry for the detection of amyloid Beta peptide related with Alzheimer's disease.

Recent studies show that quantitative and qualitative differences in amyloid beta (Abeta ) peptides may be implicated in the development of Alzheimer's disease. New evidence seems to support the existence of a dynamic equilibrium between Abeta peptide in the brain and peripheral blood circulation. The quantitation of Abeta in the blood may allow the development of the potential value of Abeta peptides as a biomarker in the development of Alzheimer's disease. In this communication, quantitation of Abeta peptides using high-performance liquid chromatography coupled with tandem mass spectrometry in a linear ion trap mode is presented. RP-HPLC was performed using a Waters Xterra MS C8 column (3.0 mm x 150 mm). Abeta(1-40) peptide was eluted using a gradient elution program. Eluate from the RP-HPLC column was split to both the UV detector and electrospray ionization MS source. The product ion scan was performed in a linear ion trap mode utilizing the transition of a multiply charged molecular ion of Abeta(1-40) to a singly charged product ion. The detection limit of 31.25 ng in column load using a 3.0-mm-diameter conventional C8 column was achieved. The Abeta(1-40) standard calibration curves show excellent linearity from 34 ng to 2500 ng Abeta(1-40) of column sample load. The product ion scan enhances sensitivity 10 times compared with the best previously achieved by a single-quadrupole instrument in the selective ion monitoring mode. Moreover, the product ion scan of Abeta(1-40) provides superior selectivity and specificity, which is very important in the quantitation of Abeta(1-40) in a complex biological matrix.