The Ile35 Residue of the ALS-Associated Mutant SOD1 Plays a Crucial Role in the Intracellular Aggregation of the Molecule.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with an unknown pathogenesis. It has been reported that mutations in the gene for Cu/Zn superoxide dismutase (SOD1) cause familial ALS. Mutant SOD1 undergoes aggregation and forms amyloid more easily, and SOD1-immunopositive inclusions have been observed in the spinal cords of ALS patients. Because of this, SOD1 aggregation is thought to be related to the pathogenesis of ALS. Some core regions of amyloid have been identified, but the issue of whether these regions form aggregates in living cells remains unclear, and the mechanism responsible for intracellular SOD1 aggregation also remains unclear. The findings reported in this study indicate that the aggregation of the ALS-linked mutant SOD1-EGFP was significantly enhanced when the BioID2 gene was fused to the N-terminus of the mutant SOD1-EGFP plasmid for cellular expression. Expression of a series of BioID2-(C-terminal deletion peptides of SOD1)-EGFP permitted us to identify 1-35 as a minimal N-terminal sequence and Ile35 as an essential amino acid residue that contributes to the intracellular aggregation of SOD1. The findings also showed that an additional substitution of Ile35 with Ser into the ALS mutant SOD1 resulted in the significant suppression of aggregate formation. The fact that no Ile35 mutations have been reported to date in ALS patients indicates that all ALS mutant SOD1s contain Ile35. Taken together, we propose that Ile35 plays a pivotal role in the aggregation of the ALS-linked SOD1 and that this study will contribute to our understanding of the mechanism responsible for SOD1 aggregation.

A validated LC-MS/MS method for the determination of canagliflozin, a sodium-glucose co-transporter 2 (SGLT-2) inhibitor, in a lower volume of rat plasma: application to pharmacokinetic studies in rats.

Canagliflozin is a novel, orally selective inhibitor of sodium-dependent glucose co-transporter-2 (SGLT2) for the treatment of patients with type 2 diabetes mellitus. In this study, a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative analysis of canagliflozin in a lower volume of rat plasma (0.1 mL) was established and applied to a pharmacokinetic study in rats. Following liquid-liquid extraction by tert-butyl methyl ether, chromatographic separation of canagliflozin was performed on a Quicksorb ODS (2.1 mm i.d. × 150 mm, 5 µm size) using acetonitrile-0.1% formic acid (90:10, v/v) as the mobile phase at a flow rate of 0.2 mL/min. The detection was carried out using an API 3200 triple-quadrupole mass spectrometer operating in the positive electrospray ionization mode. Selected ion monitoring transitions of m/z = 462.0 [M + NH4 ](+) → 191.0 for canagliflozin and m/z = 451.2 [M + H](+) → 71.0 for empagliflozin (internal standard) were obtained. The validation of the method was investigated, and it was found to be of sufficient specificity, accuracy and precision. Canagliflozin in rat plasma was stable under the analytical conditions used. This validated method was successfully applied to assess the pharmacokinetics of canagliflozin in rats using 0.1 mL rat plasma. Copyright © 2016 John Wiley & Sons, Ltd.

A quantitative LC-MS/MS method for determining ipragliflozin, a sodium-glucose co-transporter 2 (SGLT-2) inhibitor, and its application to a pharmacokinetic study in rats.

Ipragliflozin is a highly potent and selective sodium-dependent glucose co-transporter-2 (SGLT2) inhibitor, a novel class of hypoglycemic agents. The aim of the present study was to establish a new highly sensitive and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative analysis of ipragliflozin in rat plasma and apply this method to a pharmacokinetic study in rats. Empagliflozin was used as an internal standard (I.S.) and liquid-liquid extraction was conducted using tert-butyl methyl ether. Chromatographic separation was accomplished on a Quicksorb ODS (2.1mm i.d.×150mm, 5µm in size) with acetonitrile/0.1% formic acid (90:10, v/v) at a flow rate of 0.2mL/min. An API 3200 triple quadrupole mass spectrometer operating in the positive electrospray ionization mode with multiple reaction monitoring was used to detect ipragliflozin and I.S. transitions: m/z 422.0 [M+NH4](+)→151.0 for ipragliflozin and m/z 451.2 [M+H](+)→71.0 for I.S. Inter- and intra-day accuracies and precisions were within ±15%. This validated method was successfully applied to a pharmacokinetic study of ipragliflozin in rats. This assay method may contribute to assessment of novel SGLT2 inhibitors using the rat as an animal model.