•LC–MS/MS method for quantification of eight nucleotides and dFdCTP is developed.•Sample preparation time greatly reduced by excluding solid phase extraction step.•Applied to monitor dFdCTP and ...nucleotides in patients receiving gemcitabine.
Quantification of endogenous nucleotides is of interest for investigation of numerous cellular biochemical processes, such as energy metabolism and signal transduction, and may also be applied in cancer and antiretroviral therapies in which nucleoside analogues are used. For these purposes we developed and validated a sensitive and high accuracy ion-pair liquid chromatography tandem mass spectrometry (IP LC–MS/MS) method for simultaneous quantification of eight endogenous nucleotides (ATP, CTP, GTP, UTP, dATP, dCTP, dGTP, dTTP) and 2′,2′-difluoro-2′-deoxycytidine triphosphate (dFdCTP), an intracellular metabolite of the nucleoside analogue gemcitabine. The assay was validated using 200μL aliquots of peripheral blood mononuclear cell (20×106cells/ml, 4×106cells) extracts, pretreated with activated charcoal and spiked with unlabeled nucleotides, deoxynucleotides and dFdCTP. Analytes were extracted by simple precipitation with cold 60% methanol containing isotope labeled internal standards and separated on a porous graphitic carbon column. For method validation, the concentration ranges were: 0.125–20.8pmol injected for deoxynucleotides, 0.25–312.5pmol injected for dFdCTP and 5–3200pmol injected for nucleotides. The highest coefficients of variation (CV) were 12.1% for within run assay and 11.4% for between run assay, both representing the precision at the lowest analyte concentrations. The method was applied to monitor dFdCTP and changes in endogenous nucleotides in patients who were receiving gemcitabine infusions.
Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer death worldwide. Poor drug delivery to tumours is thought to limit chemotherapeutic treatment efficacy. Sonoporation combines ...ultrasound (US) and microbubbles to increase the permeability of cell membranes. We assessed gemcitabine uptake combined with sonoporation in vitro in three PDAC cell lines (BxPC-3, MIA PaCa-2 and PANC-1). Cells were cultured in hypoxic bioreactors, while gemcitabine incubation ± sonoporation was conducted in cells with operational or inhibited nucleoside membrane transporters. Intracellular active metabolite (dFdCTP), extracellular gemcitabine, and inactive metabolite (dFdU) concentrations were measured with liquid chromatography tandem mass spectrometry. Sonoporation with increasing US intensities resulted in decreasing extracellular gemcitabine concentrations in all three cell lines with inhibited membrane transporters. In cells with inhibited membrane transporters, without sonoporation, dFdCTP concentrations were reduced down to 10% of baseline. Sonoporation partially restored gemcitabine uptake in these cells, as indicated by a moderate increase in dFdCTP concentrations (up to 37% of baseline) in MIA PaCa-2 and PANC-1. In BxPC-3, gemcitabine was effectively inactivated to dFdU, which might represent a protective mechanism against dFdCTP accumulation in these cells. Intracellular dFdCTP concentrations did not change significantly following sonoporation in any of the cell lines with operational membrane transporters, indicating that the gemcitabine activation pathway may have been saturated with the drug. Sonoporation allowed a moderate increase in gemcitabine transmembrane uptake in all three cell lines, but pre-existing nucleoside transporters were the major determinants of gemcitabine uptake and retention.
Gemcitabine (2',2'-difluoro-2'-deoxycytidine, dFdC) and metabolite (2',2'-difluoro-2'-deoxyuridine, dFdU) quantification is warranted for individualized treatment strategies. Analyte stability is ...crucial for the validity of such quantification. We therefore studied the impact of the time interval from blood sampling to separation of plasma on gemcitabine stability. Blood from gemcitabine-treated patients was drawn into tetrahydrouridine (THU)-spiked heparin and ethylenediaminetetraacetic acid tubes and kept on ice until separation. Plasma was separated sequentially up to 24 h after sampling and dFdC and dFdU were quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS). The change in plasma concentrations over time was compared with the highest imprecision for concentrations above the lower limit of quantification of the LC-MS/MS method. Analyte concentrations decreased slightly over time, but for samples stored for 4 h on ice, the decline was smaller than the expected analytical imprecision. After 24 h, the maximum decline was 14.0%, which exceeded the expected analytical imprecision. dFdC and dFdU stabilities were acceptable for at least 4 h when THU-spiked whole blood samples were kept on ice. This is within the scope of routine sampling procedures. Further, variations in separation time intervals within this time frame are negligible when interpreting drug concentrations.
This review surveys the soft ionisation mass spectrometric methods that are most commonly used for the investigation of the mechanism of interaction between metallo-drugs and biomolecules. In the ...first part of the review, an overview of the applications of transition metal complexes in the therapy of various diseases (arthritis, cancer, diabetes) is given, whereas the second part focuses on the obtained results dealing with various aspects of the interaction between metal complexes and different types of biomolecules. Possibilities and limitations of each mass spectrometric method-namely, fast atom bombardment (FAB), electrospray ionisation (ESI) and matrix-assisted laser desorption and ionisation (MALDI)--are discussed in the third part of this review along with the examples of their application for the analysis of metal complexes, as well as of the products of their interaction with biomolecules.
Fructose rich diet increases hepatic triglycerides production and has deleterious cardiac effects. Estrogens are involved in regulation of lipid metabolism as well, but their effects are cardio ...beneficial. In order to study effects of fructose rich diet on the main heart fatty acid transporter CD36 and the role of estrogens, we subjected ovariectomized female rats to the standard diet or fructose rich diet, with or without estradiol (E2) replacement. The following parameters were analyzed: feeding behavior, visceral adipose tissue mass, plasma lipids, cardiac CD36 expression, localization and insulin regulation, as well as the profile of cardiac lipids. Results show that fructose rich diet significantly increased plasma triglycerides and decreased plasma free fatty acid (FFA) concentration, while E2 additionally emphasized FFA decrease. The fructose diet increased cardiac plasma membrane content of CD36 in the basal and insulin-stimulated states, and decreased its low density microsomes content. The E2 in fructose-fed rats raised the total cardiac protein content of CD36, its presence in plasma membranes and low density microsomes, and cardiac deposition of triglycerides, as well. Although E2 counteracts fructose in some aspects of lipid metabolism, and separately they have opposite cardiac effects, in combination with fructose rich diet, E2 additionally enhances CD36 presence in plasma membranes of cardiac cells and triglycerides accumulation, which paradoxically might promote deleterious effects of fructose diet on cardiac lipid metabolism. Taken together, the results presented in this work are of high importance for clinical administration of estrogens in females with a history of type 2 diabetes.
Phospholipase A2 is involved in propagation of inflammatory processes and carcinogenesis through its role in phospholipid metabolism, and release of arachidonic acid and lysophospholipids. Recent ...findings on correlation between elevated PLA2 activity and metastatic cancer render this enzyme an attractive target for cancer therapy. On the other hand, due to a broad range of oxidation states under physiological conditions and a high affinity for protein binding, platinum and ruthenium coordination complexes are promising candidates for PLA2 inhibitors. In this article, we discuss the interactions of Pt and Ru coordination complexes with PLA2 and phospholipids, as well as the application of MALDI-TOF mass spectrometry for screening PLA2 inhibitors. Owing to the ability of this technique to simultaneously detect and monitor changes in substrate and product concentrations, the inhibitor mechanisms of both Pt and Ru complexes with various ligands were determined.
Phospholipase A2 is involved in propagation of inflammatory processes and carcinogenesis through its role in phospholipid metabolism, and release of arachidonic acid and lysophospholipids. Recent ...findings on correlation between elevated PLA2 activity and metastatic cancer render this enzyme an attractive target for cancer therapy. On the other hand, due to a broad range of oxidation states under physiological conditions and a high affinity for protein binding, platinum and ruthenium coordination complexes are promising candidates for PLA2 inhibitors. In this article, we discuss the interactions of Pt and Ru coordination complexes with PLA2 and phospholipids, as well as the application of MALDI‐TOF mass spectrometry for screening PLA2 inhibitors. Owing to the ability of this technique to simultaneously detect and monitor changes in substrate and product concentrations, the inhibitor mechanisms of both Pt and Ru complexes with various ligands were determined.
This work has been focused on testing the influence of two selected Pt(II) complexes cisplatin, Pt(NH3)2Cl2, and Pt(dach)Cl2 on the activity of porcine pancreatic phospholipase A2 (PLA2). It has been ...assumed that this enzyme plays a role in carcinogenesis and that it could be a target in the tumour therapy. The results of this study show that both Pt(II) complexes inhibit the activity of the enzyme, though they bind to it in a different manner. While cisplatin interacts with the enzyme in an acompetitive manner, the stable interaction of Pt(dach)Cl2 with PLA2 could not be detected under our experimental conditions.
PDF
