Physiology-based pharmacokinetic modeling suggests that rifabutin can out-balance P-glycoprotein (P-gp) induction by concurrent P-gp inhibition. However, clinical or experimental evidence for this Janus-faced rifabutin effect is missing. Consequently, LS180 cells were exposed to a moderately (2 µM) and strongly (10 µM) P-gp-inducing concentration of rifampicin or rifabutin for 6 days. Cellular accumulation of the fluorescent P-gp substrate rhodamine 123 was evaluated using flow cytometry, either without (induction only) or with adding rifamycin drug to the cells during the rhodamine 123 efflux phase (induction + potential inhibition). Rhodamine 123 accumulation was decreased similarly by both drugs after 6-day exposure (2 µM: 55% residual fluorescence compared to non-induced cells, P < 0.01; 10 µM: 30% residual fluorescence compared to non-induced cells, P < 0.001), indicating P-gp induction. Rhodamine 123 influx transporters mRNA expressions were not affected, excluding off-target effects. Acute re-exposure to rifabutin, however, considerably re-increased rhodamine 123 accumulation (2 µM induction: re-increase by 55%, P < 0.01; 10 µM induction: 49% re-increase, P < 0.001), suggesting P-gp inhibition. In contrast, rifampicin only had weak effects (2 µM induction: no re-increase; 10 µM induction: 16% re-increase; P < 0.05). Molecular docking analysis eventually revealed that rifabutin has a higher binding affinity to the inhibitor binding site of P-gp than rifampicin (ΔG (kcal/mol) = -11.5 vs -5.3). Together, this study demonstrates that rifabutin can at least partly mask P-gp induction by P-gp inhibition, mediated by high affinity binding to the inhibitory site of P-gp.

• Klíčová slova
• Induction, Inhibition, P-glycoprotein, Rifabutin, Rifampicin,
• MeSH
• P-glykoprotein metabolismus   MeSH
• rhodamin 123 metabolismus   MeSH
• rifabutin * farmakologie   MeSH
• rifampin * farmakologie   MeSH
• simulace molekulového dockingu MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• P-glykoprotein MeSH
• rhodamin 123 MeSH
• rifabutin * MeSH
• rifampin * MeSH

Multidrug resistance (MDR) is a common cause of failure in chemotherapy for malignant diseases. MDR is either acquired as a result of previous repeated exposure to cytostatic drugs (P388/MDR cells) or naturally, as some tumors are congenitally resistant to chemotherapy (CT26 cells). One of the most common mechanisms of MDR is upregulation of P-glycoprotein (P-gp) expression. Here, we used HPMA copolymer conjugates, whereby the cytostatic drug doxorubicin (Dox) or the derivative of the P-gp inhibitor reversin 121 (R121) or both were covalently bound through a degradable pH-sensitive hydrazone bond. We proved that R121, when bound to a polymeric carrier, is capable of inhibiting P-gp in P388/MDR cells and sensitizing them in relation to the cytostatic activity of Dox. Conjugate bearing both Dox and R121 was found to be far more potent in P388/MDR cells than conjugate bearing Dox alone or a mixture of conjugates bearing either Dox or R121 when cytostatic activity in vitro, cell cycle arrest, accumulation of Dox in cells and induction of apoptosis were determined. Importantly, conjugate bearing R121 is also effective in vivo as it inhibits P-gp in P388/MDR tumors after intraperitoneal administration, while both the conjugate bearing Dox and R121 induces apoptosis in P388/MDR tumors more effectively than conjugate bearing Dox alone. Only conjugate bearing Dox and R121 significantly inhibited P388/MDR tumor growth and led to the prolonged survival of treated mice. However, the most dramatic antitumor activity of this conjugate was found in the CT26 tumor model where it completely cured six out of eight experimental mice, while conjugate bearing Dox alone cured no mice.

• Klíčová slova
• Doxorubicin, HPMA copolymer carrier, Multidrug resistance, P-glycoprotein, Polymer-drug conjugate, Reversin 121,
• MeSH
• chemorezistence MeSH
• cytostatické látky aplikace a dávkování   MeSH
• doxorubicin aplikace a dávkování   MeSH
• experimentální nádory farmakoterapie   patologie   MeSH
• inbrední kmeny myší MeSH
• methakryláty chemie   MeSH
• mnohočetná léková rezistence MeSH
• myši nahé MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• nanokapsle aplikace a dávkování   chemie   MeSH
• nanokonjugáty aplikace a dávkování   chemie   MeSH
• oligopeptidy aplikace a dávkování   MeSH
• P-glykoprotein antagonisté a inhibitory   MeSH
• protokoly antitumorózní kombinované chemoterapie aplikace a dávkování   MeSH
• výsledek terapie MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytostatické látky MeSH
• doxorubicin MeSH
• hydroxypropyl methacrylate MeSH Prohlížeč
• methakryláty MeSH
• nanokapsle MeSH
• nanokonjugáty MeSH
• oligopeptidy MeSH
• P-glykoprotein MeSH
• reversin 121 MeSH Prohlížeč

Multidrug resistance (MDR) is a common problem when fighting cancer with chemotherapy. P-glycoprotein (P-gp, or MDR1) is an active pump responsible for the efflux of xenobiotics out of the cell, including anti-cancer drugs. It is a validated target against MDR. No crystal structure of the human P-gp is available to date, and only recently several cryo-EM structures have been solved. In this paper, we present a comprehensive computational approach that includes constructing the full-length three-dimensional structure of the human P-gp and its refinement using molecular dynamics. We assessed its flexibility and conformational diversity, compiling a dynamical ensemble that was used to dock a set of lignan compounds, previously reported as active P-gp inhibitors, and disclose their binding modes. Based on the statistical analysis of the docking results, we selected a system for performing the structure-based virtual screening of new potential P-gp inhibitors. We tested the method on a library of 87 natural flavonoids described in the literature, and 10 of those were experimentally assayed. The results reproduced the theoretical predictions only partially due to various possible factors. However, at least two of the predicted natural flavonoids were demonstrated to be effective P-gp inhibitors. They were able to increase the accumulation of doxorubicin inside the human promyelocytic leukemia HL60/MDR cells overexpressing P-gp and potentiate the antiproliferative activity of this anti-cancer drug.

• Klíčová slova
• P-glycoprotein, flavonoids, molecular docking, molecular dynamics, multidrug resistance, natural compounds, structure-based virtual screening,
• Publikační typ
• časopisecké články MeSH

Polymer prodrugs can considerably improve the treatment of tumors with multidrug resistance, often caused by overexpression of P-glycoprotein (P-gp). Here, we present the effect of the N-(2-hydroxypropyl) methacrylamide-based polymer conjugate with P-gp inhibitor ritonavir (RIT) on the increase of free doxorubicin (DOX) and polymer-bound DOX cytotoxicity in the human neuroblastoma 4 cell line and its resistant clones to different cytostatics. The increase in cytotoxicity after polymer-RIT conjugate pretreatment was higher for the lines overexpressing P-gp and less pronounced for those with decreased P-gp levels. Moreover, the effect of polymer conjugate containing inhibitor and DOX on the same polymer chain was lower than that of two individual polymer conjugates used sequentially. In conclusion, the polymer-RIT conjugate can significantly increase the cytotoxicity of free DOX and polymer-DOX conjugates in cells with various multidrug resistance origins and can thus be considered a suitable therapeutic enhancer of polymer prodrugs.

• MeSH
• akrylamidy aplikace a dávkování   farmakologie   MeSH
• chemorezistence MeSH
• doxorubicin aplikace a dávkování   farmakologie   MeSH
• léky antitumorózní - screeningové testy MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• neuroblastom farmakoterapie   metabolismus   MeSH
• P-glykoprotein antagonisté a inhibitory   biosyntéza   MeSH
• protokoly antitumorózní kombinované chemoterapie farmakologie   MeSH
• ritonavir aplikace a dávkování   farmakologie   MeSH
• synergismus léků MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• akrylamidy MeSH
• doxorubicin MeSH
• N-(2-hydroxypropyl)methacrylamide MeSH Prohlížeč
• P-glykoprotein MeSH
• ritonavir MeSH

The effect of P-glycoprotein (P-gp, ABCB1, MDR1) expression on cell resistance to nilotinib was studied in human leukaemia cells. We used K562/Dox cells overexpressing P-gp and their variants (subclones) with a gradually decreased P-gp expression. These subclones were established by stable transfection of K562/Dox cells with a plasmid vector expressing shRNA targeting the ABCB1 gene. Functional analysis of P-gp using a specific fluorescent probe indicated gradually decreased dye efflux which was proportional to the P-gp expression. We observed that K562/Dox cells overexpressing P-gp contained a significantly reduced intracellular level of nilotinib when compared to their counter partner K562 cells, which do not express P-gp. This effect was accompanied by a decreased sensitivity of the K562/Dox cells to nilotinib. Importantly, cells with downregulated expression of P-gp gradually lost their ability to decrease the intracellular level of nilotinib although they still significantly decreased the intracellular level of daunorubicin (DNR). Accordingly, cells with the reduced expression of P-gp concomitantly failed to provide resistance to nilotinib, however, they exhibited a significant resistance to DNR. Taken together, we demonstrated that the conclusion as to whether P-gp is involved in nilotinib resistance or not strongly depends on its expression at protein level.

• MeSH
• antitumorózní látky farmakologie   MeSH
• buňky K562 MeSH
• chemorezistence účinky léků   MeSH
• inhibitory proteinkinas farmakologie   MeSH
• leukemie farmakoterapie   metabolismus   MeSH
• lidé MeSH
• P-glykoprotein metabolismus   MeSH
• proliferace buněk účinky léků   MeSH
• pyrimidiny farmakologie   MeSH
• viabilita buněk účinky léků   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antitumorózní látky MeSH
• inhibitory proteinkinas MeSH
• nilotinib MeSH Prohlížeč
• P-glykoprotein MeSH
• pyrimidiny MeSH

UNLABELLED: INTRODUCTION AND OBJECTIVE: Cytochrome P450 enzymes are the major drug-metabolizing enzymes in humans and the importance of drug transport proteins, in particular P-glycoprotein, in the variability of drug response has also been highlighted. Activity of cytochrome P450 enzymes and P-glycoprotein can vary widely between individuals and genotyping and/or phenotyping can help assess their activity. Several phenotyping cocktails have been developed. The Geneva cocktail is composed of a specific probe for six different cytochrome P450 enzymes and one for P-glycoprotein and was used in the context of a research aiming at exploring genotypes and phenotypes in distinct human populations (NCT02789527). The aim of the present study is to solely report the safety results of the Geneva cocktail in the healthy volunteers of these populations. MATERIALS AND METHODS: The Geneva cocktail is composed of caffeine, bupropion, flurbiprofen, omeprazole, dextromethorphan, midazolam, and fexofenadine. The volunteers fasted and avoided drinking caffeine-containing beverages or food and grapefruit juice overnight before receiving the cocktail orally. They provided blood spots for the probes' concentrations at 2, 3, and 6 h after ingestion and were asked about adverse events. RESULTS: A total of 265 healthy adult volunteers were included from Ethiopia, Oman, and the Czech Republic. The mean plasma concentrations at the 2-h sampling time of each probe drug in the total sample were: 1663 ng/mL for caffeine, 8 ng/mL for bupropion, 789 ng/mL for flurbiprofen, 6 ng/mL for dextromethorphan, 2 ng/mL for midazolam, 35 ng/mL for fexofenadine, and 103 ng/mL for omeprazole. Four adverse events were observed representing an occurrence of 1.5%. All these events were categorized as mild to moderate, non-serious, and resolved spontaneously. A causal link with the cocktail cannot be excluded because of the temporal relationship but is at most evaluated as possible according to the World Health Organization-Uppsala Monitoring Centre causal assessment system. CONCLUSIONS: In this research, healthy volunteers from three different human populations were phenotyped with the Geneva cocktail. Four adverse events were observed, confirming the safety of this cocktail that is given at lower than clinically relevant doses and therefore results in concentrations lower than those reported to cause adverse events.

• MeSH
• dospělí MeSH
• fixní kombinace léků MeSH
• genotyp MeSH
• inhibitory cytochromu P450 MeSH
• léčivé přípravky metabolismus   MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• P-glykoprotein genetika   metabolismus   MeSH
• regulace genové exprese účinky léků   MeSH
• substrátová specifita MeSH
• systém (enzymů) cytochromů P-450 genetika   metabolismus   MeSH
• zdraví dobrovolníci pro lékařské studie MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH
• Etiopie MeSH
• Omán MeSH
• Názvy látek
• fixní kombinace léků MeSH
• inhibitory cytochromu P450 MeSH
• léčivé přípravky MeSH
• P-glykoprotein MeSH
• systém (enzymů) cytochromů P-450 MeSH

The transfer kinetics of cyclosporine across the dually perfused rat placenta in the maternal to fetal direction and a possible involvement of P-glycoprotein were investigated. The transplacental clearance of cyclosporine in the materno-fetal direction was found to be dependent on the maternal inflow concentration of cyclosporine. Coadministration of cyclosporine with an excess of quinidine or chlorpromazine into the maternal compartment revealed 1.7- and 1.9-fold increase in cyclosporine concentration in the fetal compartment. In the experiments where quinidine was present both in the maternal and fetal compartments, cyclosporine appeared in the fetal compartment significantly faster, and its amount was three times higher when compared with controls. Conversely, quinidine or chlorpromazine did not affect the transplacental passage of L-[(3)H]-glucose. The interference of quinidine with the metabolism of cyclosporine in the placenta was excluded because only traces of M-1 and M-17 metabolites were found in the fetal solutions. Sodium azide, a mitochondrial respiratory inhibitor, was found to double the rate of cyclosporine, but not L-[(3)H]-glucose, passage across the placenta. Our findings indicate that P-glycoprotein pumps cyclosporine out of the trophoblast cells of the rat placenta in the ATP-dependent manner and restricts the passage of cyclosporine across the placental barrier.

• MeSH
• azid sodný farmakologie   MeSH
• časové faktory MeSH
• chinidin farmakologie   MeSH
• chlorpromazin farmakologie   MeSH
• cyklosporiny farmakokinetika   MeSH
• glukosa farmakokinetika   MeSH
• kinetika MeSH
• krysa rodu Rattus MeSH
• maternofetální výměna látek * MeSH
• P-glykoprotein fyziologie   MeSH
• perfuze MeSH
• placenta metabolismus   MeSH
• potkani Wistar MeSH
• techniky in vitro MeSH
• těhotenství MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• azid sodný MeSH
• chinidin MeSH
• chlorpromazin MeSH
• cyklosporiny MeSH
• glukosa MeSH
• P-glykoprotein MeSH

Large series of O-alkyl derivatives (methyl and benzyl) of silybin and 2,3-dehydrosilybin was prepared. Selective alkylation of the silybin molecule was systematically investigated. For the first time we present here, for example, preparation of 19-nor-2,3-dehydrosilybin. All prepared silybin/2,3-dehydrosilybin derivatives were tested for cytotoxicity on a panel of drugs sensitive against multidrug resistant cell lines and the ability to inhibit P-glycoprotein mediated efflux activity. We have identified effective and relatively non-cytotoxic inhibitors of P-gp derived from 2,3-dehydrosilybin. Some of them were more effective inhibitors at concentrations lower than a standard P-gp efflux inhibitor cyclosporin A. Another group of 2,3-dehydrosilybin derivatives also had better inhibitory effects on P-gp efflux but a cytotoxicity comparable with that of parent 2,3-dehydrosilybin. Structural requirements for improving inhibitory activity and reducing toxicity of 2,3-dehydrosilybin were established. Effect of E-ring substitution as well as an influence of the substituent size at the C-7-OH position of A-ring on P-gp-inhibitory activity was evaluated for the first time in this study.

• MeSH
• alkylace MeSH
• chemorezistence MeSH
• léky antitumorózní - screeningové testy MeSH
• lidé MeSH
• magnetická rezonanční spektroskopie MeSH
• molekulární struktura MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• nádorové buňky kultivované MeSH
• oxidace-redukce MeSH
• P-glykoprotein antagonisté a inhibitory   MeSH
• proliferace buněk účinky léků   MeSH
• silibinin MeSH
• silymarin chemická syntéza   chemie   farmakologie   MeSH
• stereoizomerie MeSH
• viabilita buněk účinky léků   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• P-glykoprotein MeSH
• silibinin MeSH
• silymarin MeSH

Purine cyclin-dependent kinase inhibitors have been recognized as promising candidates for the treatment of various cancers; nevertheless, data regarding interaction of these substances with drug efflux transporters is still lacking. Recently, we have demonstrated inhibition of breast cancer resistance protein (ABCG2) by olomoucine II and purvalanol A and shown that these compounds are able to synergistically potentiate the antiproliferative effect of mitoxantrone, an ABCG2 substrate. In this follow up study, we investigated whether olomoucine II and purvalanol A are transported by ABCG2 and ABCB1 (P-glycoprotein). Using monolayers of MDCKII cells stably expressing human ABCB1 or ABCG2, we demonstrated that olomoucine II, but not purvalanol A, is a dual substrate of both ABCG2 and ABCB1. We, therefore, assume that pharmacokinetics of olomoucine II will be affected by both ABCB1 and ABCG2 transport proteins, which might potentially result in limited accumulation of the compound in tumor tissues or lead to drug-drug interactions. Pharmacokinetic behavior of purvalanol A, on the other hand, does not seem to be affected by either ABCG2 or ABCB1, theoretically favoring this drug in the potential treatment of efflux transporter-based multidrug resistant tumors. In addition, we observed intensive sulfatation of olomoucine II in MDCKII cell lines with subsequent active efflux of the metabolite out of the cells. Therefore, care should be taken when performing pharmacokinetic studies in MDCKII cells, especially if radiolabeled substrates are used; the generated sulfated conjugate may largely contaminate pharmacokinetic analysis and result in misleading interpretation. With regard to chemical structures of olomoucine II and purvalanol A, our data emphasize that even drugs with remarkable structure similarity may show different pharmacokinetic behavior such as interactions with ABC transporters or biotransformation enzymes.

• MeSH
• ABC transportér z rodiny G, člen 2 MeSH
• ABC transportéry metabolismus   MeSH
• biologický transport MeSH
• buněčné linie MeSH
• chemorezistence účinky léků   MeSH
• nádorové proteiny metabolismus   MeSH
• P-glykoprotein metabolismus   MeSH
• P-glykoproteiny MeSH
• psi MeSH
• puriny farmakokinetika   MeSH
• zvířata MeSH
• Check Tag
• psi MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 6-((3-chloro)anilino)-2-(isopropyl-2-hydroxyethylamino)-9-isopropylpurine MeSH Prohlížeč
• ABC transportér z rodiny G, člen 2 MeSH
• ABC transportéry MeSH
• ABCB1 protein, human MeSH Prohlížeč
• ABCG2 protein, human MeSH Prohlížeč
• nádorové proteiny MeSH
• olomoucine II MeSH Prohlížeč
• P-glykoprotein MeSH
• P-glykoproteiny MeSH
• puriny MeSH

The aim of the present study was to determine the structural requirements for dibenzocyclooctadiene lignans essential for P-glycoprotein inhibition. Altogether 15 structurally related lignans isolated from Schisandra chinensis or prepared by modification of their backbone were investigated, including three pairs of enantiomers. P-Glycoprotein inhibition was quantified using a doxorubicin accumulation assay in human promyelotic leukemia HL60/MDR cells overexpressing P-glycoprotein. A preliminary quantitative structure-activity relationship analysis revealed three main structural features involved in P-glycoprotein inhibition: a 1,2,3-trimethoxy moiety, a 6-acyloxy group, and the absence of a 7-hydroxy group. The most effective inhibitors, (-)-gomisin N (1) and (+)-deoxyschizandrin [(+)-2], were selected for further evaluation of their effects. Both these lignans restored the cytotoxic effect of doxorubicin in HL60/MDR cells and when combined with a subtoxic concentration of this compound increased the proportion of G2/M cells significantly, which is a usual response to treatment with this anticancer drug.

• MeSH
• cyklooktany * chemie   izolace a purifikace   farmakologie   MeSH
• doxorubicin farmakologie   MeSH
• kontrolní body fáze G2 buněčného cyklu účinky léků   MeSH
• kvantitativní vztahy mezi strukturou a aktivitou MeSH
• lidé MeSH
• lignany * chemie   izolace a purifikace   farmakologie   MeSH
• molekulární struktura MeSH
• P-glykoproteiny antagonisté a inhibitory   MeSH
• polycyklické sloučeniny * chemie   izolace a purifikace   farmakologie   MeSH
• Schisandra chemie   MeSH
• semena rostlinná chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Rusko MeSH
• Názvy látek
• cyklooktany * MeSH
• dibenzocyclooctadiene lignan MeSH Prohlížeč
• doxorubicin MeSH
• lignany * MeSH
• P-glykoproteiny MeSH
• polycyklické sloučeniny * MeSH
• schizandrin A MeSH Prohlížeč
• schizandrin B MeSH Prohlížeč