Characterization and application of a disease-cell model for a neurodegenerative lysosomal disease

Disease-cell models that recapitulate specific molecular phenotypes are essential for the investigation of molecular pathogenesis of neurodegenerative diseases including lysosomal storage diseases (LSDs) with predominant neurological manifestations. Herein we report the development and characterization of a cell model for a rapid neurodegenerative LSDs, globoid-cell leukodystrophy (GLD), mostly known as Krabbe disease. GLD is caused by the deficiency of β-galactocerebrosidase (GALC), a lysosomal enzyme that hydrolyzes two glycosphingolipids, psychosine and galactosylceramide. Unfortunately, the available culture fibroblasts from GLD patients consist of a limited research tool as these cells fail to accumulate psychosine, the central pathogenic glycosphingolipid in this LSD that results in severe demyelination. Firstly, we obtained brain samples from the Twitcher (Twi) mice (GALC(twi/twi)), the natural mouse model with GALC deficiency. We immortalized the primary neuroglial cultured cells with SV40 large T antigen, generating the 145M-Twi and the 145C-Wt cell lines from the Twi and control mice, respectively. Both cell lines expressed specific oligodendrocyte markers including A2B5 and GalC. The 145M-Twi cells showed biochemical and cellular disturbances related to GLD neuropathogenesis including remarkable caspase-3 activation, release of cytochrome C into the cytosol and expansion of the lysosomal compartment. Under treatment with glycosphingolipids, 145M-Twi cells showed increased LC3B levels, a marker of autophagy. Using the LC-MS/MS method that we developed, the 145M-Twi cells showed significantly higher levels of psychosine. The 145M-Twi and 145C-Wt lines allowed the development of a robust throughput LC-MS/MS assay to measure cellular psychosine levels. In this throughput assay, l-cycloserine showed to significantly reduce the 145M-Twi cellular levels of psychosine. The established 145M-Twi cells are powerful research tools to investigate the neurologically relevant pathogenic pathways as well as to develop primary screening assays for the identification of therapeutic agents for GLD and potentially other glycosphingolipid disorders.

Validated LC-MS/MS method for the determination of 3-hydroxflavone and its glucuronide in blood and bioequivalent buffers: application to pharmacokinetic, absorption, and metabolism studies

The purpose of this study is to develop an UPLC-MS/MS method to quantify 3-hydroxyflavone (3-HF) and its metabolite, 3-hydroxyflavone-glucuronide (3-HFG) from biological samples. A Waters BEH C8 column was used with acetonitrile/0.1% formic acid in water as mobile phases. The mass analysis was performed in an API 5500 Qtrap mass spectrometer via multiple reaction monitoring (MRM) with positive scan mood. The one-step protein precipitation by acetonitrile was used to extract the analytes from blood. The results showed that the linear response range was 0.61-2500.00 nM for 3-HF and 0.31-2500.00 nM for 3-HFG. The intra-day variance is less than 16.5% and accuracy is in 77.7-90.6% for 3-HF and variance less than 15.9%, accuracy in 85.1-114.7% for 3-HFG. The inter-day variance is less than 20.2%, accuracy is in 110.6-114.2% for 3-HF and variance less than 15.6%, accuracy in 83.0-89.4% for 3-HFG. The analysis was done within 4.0 min. Only 10 μl of blood is needed due to the high sensitivity of this method. The validated method was successfully used to pharmacokinetic study in A/J mouse, transport study in the Caco-2 cell culture model, and glucuronidation study using mice liver and intestine microsomes. The applications revealed that this method can be used for 3-HF and 3-HFG analysis in blood as well as in bioequivalent buffers such HBSS and KPI.