The review article presents a modern concept of the mechanism of antioxidant and antihypoxic action of the original drug mexidol (2-ethyl-6-methyl-3-hydroxypyridine succinate). The direct antioxidant activity of mexidol has been described, which consists in the ability of the drug to inactivate free radicals and increase the activity of the antioxidant enzymes glutathione peroxidase and superoxide dismutase in vitro. The results of the indirect antioxidant activity of mexidol, manifested in the increased expression under the ischemia of the transcription factor Nrf2, responsible for the cell resistance to oxidative stress are presented. The antihypoxic action of mexidol due to the presence of succinic acid in its molecule, which on the one hand supports the work of the Krebs cycle succinate oxidase under oxygen deficiency conditions, and on the other hand, binds to its specific receptors (GPR91), and starts a cascade of biochemical reactions that increases the body's resistance to lack of oxygen is discussed. The results of preclinical and clinical studies confirming the antioxidant and antihypoxic effects of mexidol are summarized.

P-glycoprotein (Pgp, ABCB1, MDR1) is an efflux transporter protein that removes molecules from the cells (outflow) into the extracellular space. Pgp plays an important role in pharmacokinetics, ensuring the absorption, distribution, and excretion of drugs and its substrates, as well as in the transport of endogenous molecules (steroid and thyroid hormones). It also contributes to tumor cell resistance to chemotherapy. In this review, we summarize the mechanisms of Pgp regulation during oxidative stress. The currently available data suggest that Pgp has a complex variety of regulatory mechanisms under oxidative stress, involving many transcription factors, the main ones being Nrf2 and Nf-kB. These factors often overlap, and some can be activated under certain conditions, such as the deposition of oxidation products, depending on the severity of oxidative stress. In most cases, the expression of Pgp increases due to increased transcription and translation, but under severe oxidative stress, it can also decrease due to the oxidation of amino acids in its molecule. At the same time, Pgp acts as a protector against oxidative stress, eliminating the causative factors and removing its by-products, as well as participating in signaling pathways.

P-Glycoprotein (P-gp) is one of the most clinically significant representatives of the ABC transporter superfamily due to its participation in the transport of biotic components and xenobiotics across the plasma membrane. It is known that various chemicals, environmental factors, and pathological processes can affect P-gp activity and expression. In this study, we investigated the role of P-gp in limiting the cell membrane permeability during oxidative stress. Human adenocarcinoma colon cells (Caco-2) overexpressing P-gp were cultured for 72 h in the medium containing hydrogen peroxide (0.1-50 µM). The transport of the P-gp substrate fexofenadine was evaluated in a special Transwell system. The amounts of P-gp and Nrf2 transcription factor were analyzed by the enzyme-linked immunosorbent assay. The concentration of SH-groups in proteins and the contents of lipid peroxidation products and protein carbonyl derivatives were determined spectrophotometrically. Hydrogen peroxide at a concentration of 0.1-5 µM did not significantly affect the studied parameters, while incubation with 10 µM H₂O₂ decreased in the level of SH groups in cell lysates and increased in the amount of Nrf2 in the cell lysates. Nrf2, in its turn, mediated an increase in the content and activity of the P-gp transporter, thus limiting the increasing permeability of the cell membrane. Hydrogen peroxide at a concentration of 50 µM promoted oxidative stress, which was manifested as a decrease in the content of SH-groups, increase in the concentration of lipid peroxidation products and protein carbonyl derivatives, and decrease in the P-gp level, which led to a significantly increased permeability of the plasma membrane. These results show that the transport and protective roles of P-gp, in particular, reduction of the cell membrane permeability, are affected by the intensity of oxidative stress and can be manifested only if the extent of membrane damage is insignificant.

Background. Glycoprotein-P (Pgp, АВСВ1) is a transporter protein participating in pharmacokinetics of medical drugs, and also in development of resistance of tumor cells to chemotherapy. Aim. To study the influence of progesterone on the activity of Pgp in vitro on a cell model of human small intestinal epithelium. Materials and Methods. The work was conducted on Caco-2 cells. The activity of Pgp was evaluated by transport of fexofenadine in a special transwell-system. Concentration of fexofenadine was analyzed by HPLC method. The amount of Pgp was determined by EIA method. Four series of experiments were conducted: control cells preincubated with clean transport medium without addition of any substances; influence of rifampicin on the activity and synthesis of Pgp in the concentration 10 mol/l in preincubation for 3 days (induction control); influence of progesterone on the activity of Pgp in concentrations 1, 10 and 100 mol/l in preincubation for 30 min; influence of progesterone on the activity and synthesis of Pgp in concentrations 1, 10 and 100 mol/l in preincubation for 3 days. Results. Progesterone in the concentrations 1 and 10 M in incubation with cells within 30 minutes did not show any reliable influence on the activity of Pgp, however, in concentration 100 M it reduced the activity of the transporter protein. In incubation of Caco-2 cells with progesterone in concentrations 1, 10 and 100 M within 3 days the activity of Pgp remained unchanged. Progesterone in concentration 100 M in incubation within 3 days significantly increased synthesis of Pgp in enterocytes by 114.3% as compared to control, and in other used concentrations (1 and 10 M) it produced no reliable effect. Conclusion. In in vitro experiments on Caco-2 cells progesterone in concentration 100 M produces a direct inhibiting effect on the activity of Pgp; however, in incubation within 3 days it increases synthesis of the transporter protein, which cancels out its inhibitory activity.

Objective. To study the effect of Mexidol on the level of factors regulating neuroregenesis. Material and methods. The study was performed on male Wistar rats. Focal cerebral ischemia was reproduced by endovascular occlusion-reperfusion of the right medial cerebral artery. The duration of occlusion was 60 min. During the beginning of reperfusion, the animals were given a single intravenous injection of saline solution or the drug Mexidol at a dose of 50 mg/kg. 4, 8 and 24 hours after the beginning of reperfusion in the ischemic hemisphere, the relative amount of molecules regulating neurogenesis was estimated by Western blot method. Additionally, 24 hours after the start of reperfusion, the size of the brain infarction was analyzed after staining with a 1% solution of 2.3,5,-triphenyltetrazolium. Results. When modeling occlusion-reperfusion of the middle cerebral artery, the volume of necrosis in the affected hemisphere of animals injected with saline was 37.75±7.46%, administration of Mexidol at a dose of 50 mg /kg led to a decrease in the volume of necrosis to 20.48±2.33% (p=0.0006). The simulation of occlusion-reperfusion of the middle cerebral artery was accompanied by activation of neurotrophic factors IGF-1, NGF and vascular factor VEGF. A single intravenous administration of Mexidol at a dose of 50 mg/kg during reperfusion increased the level of neurotrophic factors IGF-1, NGF, BDNF and VEGF in the ischemic area of the brain compared with the administration of saline, which leads to increased neuroregeneration at all follow-up periods (4, 8 and 24 hours after reperfusion), the marker of which is tubulin-3. Conclusion. The results suggest that Mexidol not only has a protective effect on neurons, but can also stimulate neuroregeneration by increasing the level of the main regulatory molecules.

INTRODUCTION: Organic anion transporting polypeptide 1B1 (OATP1B1) is a transporter protein that plays an important role in the pharmacokinetics of substances (its substrates), regulating their penetration into hepatocytes. The functional activity of this protein is evaluated by the transport of marker substrates, for example, atorvastatin, on cell lines overexpressing OATP1B1, such as HepG2 (human hepatocellular carcinoma). AIM: To develop and validate the technique of the quantitative determination of atorvastatin in HepG2 cell line using high-performance liquid chromatography (HPLC) with tandem mass spectrometry (MS/MS). MATERIALS AND METHODS: The study was performed on HPLC chromatograph with an MS/MS detector. The conditions of the chromatographic analysis were as follows: pre-column Selectra C18 Guard Cartridges SLC-18GDC46-5UM, chromatographic column UCT Selectra C18 4.6 mm 100 mm 5 m, 100 А column, flow velocity of 0.3 mL/min, and column thermostatic control of 35C. The volume of introduced samples was 2 L, and the analysis time was 10 min. Gradient elution mode was used: the ratios of 0.1% formic acid solution and acetonitrile were 35% and 65% for 0 and 0.3 min, 5% and 95% for 0.6 and 5 min, and 35% and 65% for 5.05 and 8 min, respectively. The retention time of atorvastatin was 4.53 min. Atorvastatin detection conditions were as follows: positive ionization mode; spray voltage,3500 V; detection mode, multiple reaction monitoring 559.30 m/z 466.20 m/z, 559.30 m/z 440.20 m/z; collision energy, 17 V; source fragmentation, 0; and gas pressure-inducing dissociation, 2 mTorr. RESULTS: The developed bioanalytical method was validated by the following parameters: linearity, selectivity, accuracy, precision, lower limit of quantity determination, sample transfer, sample stability, and matrix effect. The confirmed range of the technique in cell lysate was 0.5200 nmol/L. CONCLUSION: The results validated the technique for the quantitative determination of atorvastatin in the lysate of HepG2 cell line by HPLC-MS/MS.