9 research outputs found
Pyridoxamine, an Inhibitor of Advanced Glycation Reactions, Also Inhibits Advanced Lipoxidation Reactions: Mechanism of Action of Pyridoxamine
Maillard or browning reactions lead to formation of advanced glycation end products (AGEs) on protein and contribute to the increase in chemical modification of proteins during aging and in diabetes. AGE inhibitors such as aminoguanidine and pyridoxamine (PM) have proven effective in animal model and clinical studies as inhibitors of AGE formation and development of diabetic complications. We report here that PM also inhibits the chemical modification of proteins during lipid peroxidation (lipoxidation) reactions in vitro, and we show that it traps reactive intermediates formed during lipid peroxidation. In reactions of arachidonate with the model protein RNase, PM prevented modification of lysine residues and formation of the advanced lipoxidation end products (ALEs) N(epsilon)-(carboxymethyl)lysine, N(epsilon)-(carboxyethyl)lysine, malondialdehyde-lysine, and 4-hydroxynonenal-lysine. PM also inhibited lysine modification and formation of ALEs during copper-catalyzed oxidation of low density lipoprotein. Hexanoic acid amide and nonanedioic acid monoamide derivatives of PM were identified as major products formed during oxidation of linoleic acid in the presence of PM. We propose a mechanism for formation of these products from the 9- and 13-oxo-decadienoic acid intermediates formed during peroxidation of linoleic acid. PM, as a potent inhibitor of both AGE and ALE formation, may prove useful for limiting the increased chemical modification of tissue proteins and associated pathology in aging and chronic diseases, including both diabetes and atherosclerosis
Enantioselective liquid chromatography–mass spectrometry assay for the determination of ifosfamide and identification of the N-dechloroethylated metabolites of ifosfamide in human plasma
A sensitive and specific liquid chromatography-mass spectrometry (LC-MS) method has been developed and validated for the enantioselective determination of ifosfamide [(R)-IF and (S)-IF] in human plasma and for the detection of the N-dechloroethylated metabolites of IF, 2-N-dechloroethylifosfamide [(R)-2-DCl-IF and (S)-2-DCl-IF] and 3-N-dechloroethylifosfamide [(R)-3-DCl-IF and (S)-3-DCl-IF]. IF, 2-DCl-IF and 3-DCl-IF were extracted from plasma using solid-phase extraction and resolved by liquid chromatography on a column containing a Chirabiotic T chiral stationary phase. The enantioselective separations were achieved using a mobile phase composed of 2-propanol:methanol (60:40 v/v) and a flow rate of 0.5 ml/min. The observed enantioselectivities (α) for IF, 2-DCl-IF and 3-DCl-IF were 1.20, 1.17 and 1.20, respectively. The calibration curve was linear in the concentration range of 37.50-4800 ng/ml for each ifosfamide enantiomer (r2 > 0.997). The lower limit of detection (LLOD) was 5.00 ng/ml. The inter- and intra-day precision ranged from 3.63 to 15.8 % relative standard deviation (RSD) and 10.1 to 14.3 % RSD, respectively, and the accuracy ranged from 89.2 to 101.5 % of the nominal values. The method was applied to the analysis of plasma samples obtained from a cancer patient who received 3.75 g/m2/d dose of (R,S)-ifosfamide as a 96-h continuous infusion
Selected Reaction Monitoring LC−MS Determination of Idoxifene and Its Pyrrolidinone Metabolite in Human Plasma Using Robotic High-Throughput, Sequential Sample Injection
Cell-based assay of MGAT2-driven diacylglycerol synthesis for profiling inhibitors: use of a stable isotope-labeled substrate and high-resolution LC/MS
Strategy to Improve the Quantitative LC-MS Analysis of Molecular Ions Resistant to Gas-Phase Collision Induced Dissociation: Application to Disulfide-Rich Cyclic Peptides
Due to observed collision induced
dissociation (CID) fragmentation
inefficiency, developing sensitive liquid chromatography tandem mass
spectrometry (LC-MS/MS) assays for CID resistant compounds is especially
challenging. As an alternative to traditional LC-MS/MS, we present
here a methodology that preserves the intact analyte ion for quantification
by selectively filtering ions while reducing chemical noise. Utilizing
a quadrupole-Orbitrap MS, the target ion is selectively isolated while
interfering matrix components undergo MS/MS fragmentation by CID,
allowing noise-free detection of the analyte’s surviving molecular
ion. In this manner, CID affords additional selectivity during high
resolution accurate mass analysis by elimination of isobaric interferences,
a fundamentally different concept than the traditional approach of
monitoring a target analyte’s unique fragment following CID.
This survivor-selected ion monitoring (survivor-SIM) approach has
allowed sensitive and specific detection of disulfide-rich cyclic
peptides extracted from plasma
Enantioselective liquid chromatography–mass spectrometry assay for the determination of ifosfamide and identification of the N-dechloroethylated metabolites of ifosfamide in human plasma
Discovery and structure activity relationships of 7-benzyl triazolopyridines as stable, selective, and reversible inhibitors of myeloperoxidase
PK/PD Disconnect Observed with a Reversible Endothelial Lipase Inhibitor
Screening of a small set of nonselective
lipase inhibitors against
endothelial lipase (EL) identified a potent and reversible inhibitor, <i>N</i>-(3-(3,4-dichlorophenyl)Âpropyl)-3-hydroxy-1-methyl-2-oxo-1,2-dihydropyridine-4-carboxamide
(<b>5</b>; EL IC<sub>50</sub> = 61 nM, EL<sub>HDL</sub> IC<sub>50</sub> = 454 nM). Deck mining identified a related hit, <i>N</i>-(3-(3,4-dichlorophenyl)Âpropyl)-4-hydroxy-1-methyl-5-oxo-2,5-dihydro-1<i>H</i>-pyrrole-3-carboxamide (<b>6a</b>; EL IC<sub>50</sub> = 41 nM, EL<sub>HDL</sub> IC<sub>50</sub> = 1760 nM). Both compounds
were selective against lipoprotein lipase (LPL) but nonselective versus
hepatic lipase (HL). Optimization of compound <b>6a</b> for
EL inhibition using HDL as substrate led to <i>N</i>-(4-(3,4<b>-</b>dichlorophenyl)Âbutan-2-yl)-1-ethyl-4-hydroxy-5-oxo-2,5-dihydro-1<i>H</i>-pyrrole-3-carboxamide (<b>7c</b>; EL IC<sub>50</sub> = 148 nM, EL<sub>HDL</sub> IC<sub>50</sub> = 218 nM) having improved
PK over compound <b>6a</b>, providing a tool molecule to test
for the ability to increase HDL-cholesterol (HDL-C) levels in vivo
using a reversible EL inhibitor. Compound <b>7c</b> did not
increase HDL-C in vivo despite achieving plasma exposures targeted
on the basis of enzyme activity and protein binding demonstrating
the need to develop more physiologically relevant in vitro assays
to guide compound progression for in vivo evaluation