Institute of Chemical Biology and Fundamental Medicine SB RAS

In the present study, we developed and validated three liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods for quantification of the agent OL9-116, a Tdp1 inhibitor based on usnic acid, in murine lungs, liver and kidney, respectively. Additionally, a semi-quantitative method was developed for quantification of the agent in the primary tumor node of Lewis lung carcinoma. Tissue samples were prepared using ultrasonic homogenization and QuEChERS methodology. The quantification of the compound was performed using SCIEX 6500 QTRAP mass spectrometer in MRM mode following a chromatographic separation on a C8 reversed-phase column. The methods were validated in terms of selectivity, calibration curve, accuracy, precision, recovery, matrix factor and stability of the prepared sample, and subsequently applied for quantification of the agent OL9-116 in the organs of healthy and tumor-bearing mice following a single intragastric administration of the substance at a dose of 150 mg/kg. A comparison of the distribution of OL9-116 in the organs of the animals demonstrated that the presence of the tumor significantly altered the pharmacokinetics of the substance, reducing its bioavailability, which should be taken into account when developing tumor treatment strategies.

Abasic, or apurinic/apyrimidinic sites (AP sites) are among the most abundant DNA lesions, appearing in DNA both through spontaneous base loss and as intermediates of base excision DNA repair. Natural aldehydic AP sites have been known for decades and their interaction with the cellular replication, transcription and repair machinery has been investigated in detail. Oxidized AP sites, produced by free radical attack on intact nucleotides, received much attention recently due to their ability to trap DNA repair enzymes and chromatin structural proteins such as histones. In the past few years, it became clear that the reactive nature of aldehydic and oxidized AP sites produces a variety of modifications, including AP site-protein and AP site-peptide cross-links, adducts with small molecules of metabolic or xenobiotic origin, and AP site-mediated interstrand DNA cross-links. The diverse chemical nature of these common-origin lesions is reflected in the wide range of their biological consequences. In this review, we summarize the data on the mechanisms of modified AP sites generation, their abundance, the ability to block DNA polymerases or cause nucleotide misincorporation, and the pathways of their repair.

Abstract: The cationic amphiphile DL₄12, has been synthesized, possessing RNase activity (D-DABCO (1,4-diazabicyclo[2.2.2]octane); L₄ is a tetramethylene linker; 12 is a dodecyl residue) and pronounced antibacterial properties.A suspension of Salmonella enterica ATCC 14028 cells was incubated in 5 μM DL₄12 solution for 15 and 30 min or 5 μM ciprofloxacin solution (comparison drug); intact cells served as a control.Samples were fixed with 4% formaldehyde and 1% OsO₄ or by the Ryter-Kellenberger method with 1% OsO₄ post-fixed with 0.5% uranyl acetate, then dehydrated and embedded in an epoxy resin mixtureThe obtained ultrathin sections were examined in a Jem 1400 electron microscope.After 15 min of incubation with the DL₄12 compound, visible ribosomes disappeared from the entire cytoplasm of S. enterica cells.A homogeneous substance of medium electron d. appeared in the periplasmic space, capable of penetrating into the cytoplasm, in which polymorphic inclusions were formed.Pronounced ultrastructural changes were observed in the nucleoids of the bacteria: they were rounded, and the DNA strands "glued" together into bundles.The structure of the outer membrane has not change.The observed changes in the structure of S. enterica were similar when fixed by different methods and were due to a combination of RNase activity and the amphiphilic properties of DL₄12.The ultrastructural changes we identified have not been described in the scientific literature.This study is the first to visualize the effects of RNase and the amphiphilic component of the DL₄12 compound in bacterial cells.