There exists a requirement for drugs which would be useful in therapy of an acute radiation damage of a mammalian organism. The aim of the study was to evaluate survival parameters in mice exposed to a lethal γ-ray dose of 8.5 Gy and treated with single doses of an adenosine A(3) receptor agonist, IB-MECA, or a cyclooxygenase-2 (COX-2) inhibitor, meloxicam, administered alone or in a combination early after irradiation, i.e., 0.5 and 1 h post-irradiation, respectively. The assessed parameters were the mean survival time (MST) and the cumulative percentage 30-day survival (CPS). Administrations of single intraperitoneal doses of either IB-MECA 0.5 h post-irradiation or meloxicam 1 h post-irradiation resulted in statistically significant increases of MST in comparison with the control irradiated mice. Combined administration of IB-MECA and meloxicam was found to be the only treatment statistically enhancing the parameter of CPS and to lead to the most expressive increase in MST of the experimental mice. The findings add new knowledge on the action of an adenosine A3 receptor agonist and a COX-2 inhibitor in an irradiated mammalian organism and suggest the potential of both the investigated drugs in the treatment of the acute radiation damage.

• MeSH
• adenosin analogy a deriváty   farmakologie   MeSH
• agonisté adenosinového receptoru A3 farmakologie   MeSH
• časové faktory MeSH
• celotělové ozáření škodlivé účinky   MeSH
• cyklooxygenasa 2 metabolismus   MeSH
• inhibitory cyklooxygenasy 2 farmakologie   MeSH
• lékové interakce MeSH
• míra přežití MeSH
• myši MeSH
• radioprotektivní látky farmakologie   MeSH
• receptor adenosinový A3 metabolismus   MeSH
• thiaziny farmakologie   MeSH
• thiazoly farmakologie   MeSH
• záření gama škodlivé účinky   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The question as to whether A3 adenosine receptor (A3AR) agonists, N (6)-(3-iodobenzyl)-adenosine-5'-N- methyluronamide (IB-MECA) and 2-chloro-N (6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (Cl-IB-MECA), could exert cytotoxic effects at high concentrations with or without the involvement of A3AR has been a controversial issue for a long time. The initial findings suggesting that A3AR plays a crucial role in the induction of cell death upon treatment with micromolar concentrations of IB-MECA or Cl-IB-MECA were revised, however, the direct and unequivocal evidence is still missing. Therefore, the sensitivity of Chinese hamster ovary (CHO) cells transfected with human recombinant A3AR (A3-CHO) and their counter partner wild-type CHO cells, which do not express any of adenosine receptors, to micromolar concentrations of IB-MECA and Cl-IB-MECA was studied. We observed that IB-MECA and Cl-IB-MECA exhibited a strong inhibitory effect on cell proliferation due to the blockage of cell cycle progression at G1/S and G2/M transitions in both A3-CHO and CHO cells. Further analysis revealed that IB-MECA and Cl-IB-MECA attenuated the Erk1/2 signalling irrespectively to A3AR expression. In addition, Cl-IB-MECA induced massive cell death mainly with hallmarks of a necrosis in both cell lines. In contrast, IB-MECA affected cell viability only slightly independently of A3AR expression. IB-MECA induced cell death that exhibited apoptotic hallmarks. In general, the sensitivity of A3-CHO cells to micromolar concentrations of IB-MECA and Cl-IB-MECA was somewhat, but not significantly, higher than that observed in the CHO cells. These results strongly suggest that IB-MECA and Cl-IB-MECA exert cytotoxic effects at micromolar concentrations independently of A3AR expression.

• MeSH
• adenosin analogy a deriváty   farmakologie   MeSH
• agonisté adenosinového receptoru A3 farmakologie   MeSH
• CHO buňky MeSH
• Cricetulus MeSH
• cytotoxiny farmakologie   MeSH
• kontrolní body buněčného cyklu účinky léků   MeSH
• lidé MeSH
• mitogenem aktivovaná proteinkinasa 1 antagonisté a inhibitory   genetika   metabolismus   MeSH
• mitogenem aktivovaná proteinkinasa 3 antagonisté a inhibitory   genetika   metabolismus   MeSH
• proliferace buněk účinky léků   MeSH
• protoonkogenní proteiny c-akt genetika   metabolismus   MeSH
• receptor adenosinový A3 genetika   metabolismus   MeSH
• regulace genové exprese MeSH
• signální transdukce účinky léků   MeSH
• transfekce MeSH
• viabilita buněk účinky léků   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In our previous studies, IB-MECA, an adenosine A(3) receptor agonist, was found to stimulate proliferation of hematopoietic progenitor and precursor cells in mice. This property of IB-MECA was considered to be responsible for its ability to support regeneration of suppressed hematopoiesis after irradiation with sublethal doses of γ-rays when the drug was given in a post-irradiation treatment regimen. This study was aimed at assessing the ability of IB-MECA to influence a 30-day survival of lethally irradiated mice. In a series of experiments, IB-MECA was administered following various lethal radiation doses in various numbers of drug doses and various administration routes. Though in some of these experiments a moderate increase in 30-day survival was observed in IB-MECA-treated mice, the differences in comparison with the controls were not significantly different. It can be inferred from these results and those of previous studies assessing the effects of IB-MECA after sublethal radiation doses that IB-MECA can probably influence only a substantially preserved hematopoiesis like that remaining after sublethal irradiation. Future studies should be aimed at evaluation of the abilities of IB-MECA to influence post-irradiation survival when administered as a part of combined treatment regimens.

• MeSH
• adenosin aplikace a dávkování   analogy a deriváty   farmakologie   MeSH
• agonisté adenosinového receptoru A3 aplikace a dávkování   farmakologie   MeSH
• experimentální radiační poranění metabolismus   mortalita   MeSH
• hematopoéza účinky léků   účinky záření   MeSH
• inbrední kmeny myší MeSH
• myši MeSH
• receptor adenosinový A3 metabolismus   MeSH
• záření gama MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We studied effects of 2-chloro-N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (Cl-IB-MECA) on apoptosis induction in the K562/Dox cell line, which overexpressed P-glycoprotein (P-gp, ABCB1, MDR1). We found that the K562/Dox cell line was significantly more resistant to Cl-IB-MECA than the maternal cell line K562, which did not express P-gp. Although both cell lines expressed the A3 adenosine receptor (A3AR), cytotoxic effects of Cl-IB-MECA were not prevented by its selective antagonist MRS1523 (3-propyl-6-ethyl-5-[(ethylthio)carbonyl]-2 phenyl-4-propyl-3-pyridine carboxylate). Analysis of cell extracts revealed that the intracellular level of Cl-IB-MECA was significantly lower in the K562/Dox cell line than in the maternal cell line K562. The downregulation of P-gp expression using shRNA targeting ABCB1 gene led to increased intracellular level of Cl-IB-MECA and restored cell sensitivity to this drug. Similarly, valspodar (PSC-833), a specific inhibitor of P-gp, restored sensitivity of the K562/Dox cell line to Cl-IB-MECA with concomitant increase of intracellular level of Cl-IB-MECA in the resistant cell line, while it affected cytotoxicity of Cl-IB-MECA in the sensitive cell line only marginally. An enzyme based assay provided evidence for interaction of P-gp with Cl-IB-MECA. We further observed that cytotoxic effects of Cl-IB-MECA could be augmented by activation of extrinsic cell death pathway by Apo-2L (TRAIL) but not FasL or TNF-α. Our results revealed that Cl-IB-MECA induced an increase in expression of TRAIL receptors in K562 cells, which could sensitize cells to apoptosis induction via an extrinsic cell death pathway. Importantly, these effects were inversely related to P-gp expression. In addition, MRS1523 did not affect Cl-IB-MECA induced expression of TRAIL receptors.

• MeSH
• adenosin analogy a deriváty   farmakologie   MeSH
• adenosintrifosfatasy metabolismus   MeSH
• agonisté adenosinového receptoru A3 farmakologie   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• buněčná smrt MeSH
• chemorezistence fyziologie   MeSH
• leukemie farmakoterapie   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• P-glykoprotein genetika   metabolismus   MeSH
• receptor adenosinový A3 metabolismus   MeSH
• regulace genové exprese u nádorů MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Mouse hematopoiesis, suppressed by a sublethal dose of ionizing radiation, was the target for combined therapy with a cyclooxygenase-2 (COX-2) inhibitor meloxicam and an adenosine A₃ receptor agonist IB-MECA. The drugs were administered in an early postirradiation treatment regimen: meloxicam was given in a single dose 1hour after irradiation, IB-MECA in two doses 24 and 48hours after irradiation. Treatment-induced changes in several compartments of hematopoietic progenitor and precursor cells of the bone marrow were evaluated on day 3 after irradiation. Values of hematopoietic progenitor cells for granulocytes/macrophages and erythrocytes (GM-CFC and BFU-E, respectively), as well as those of proliferative granulocytic cells were found to be significantly higher in the mice treated with the drug combination in comparison to irradiated controls and attained the highest increase factors of 1.6, 1.6, and 2.6, respectively. The study emphasizes the significance of the combined treatment of suppressed hematopoiesis with more agents. Mechanisms of the action of the individual compounds of the studied drug combination and of their joint operation are discussed.

• MeSH
• adenosin aplikace a dávkování   analogy a deriváty   terapeutické užití   MeSH
• agonisté adenosinového receptoru A3 aplikace a dávkování   terapeutické užití   MeSH
• celotělové ozáření MeSH
• erytroidní prekurzorové buňky účinky léků   účinky záření   MeSH
• experimentální radiační poranění krev   farmakoterapie   patologie   MeSH
• faktor stimulující kolonie granulocytů krev   MeSH
• hematinika aplikace a dávkování   terapeutické užití   MeSH
• hematopoetické kmenové buňky účinky léků   účinky záření   MeSH
• hematopoéza účinky léků   účinky záření   MeSH
• inhibitory cyklooxygenasy 2 aplikace a dávkování   terapeutické užití   MeSH
• kombinovaná farmakoterapie MeSH
• křížení genetické MeSH
• myši inbrední CBA MeSH
• myši MeSH
• počet buněk MeSH
• prekurzorové buňky granulocytů účinky léků   účinky záření   MeSH
• thiaziny aplikace a dávkování   terapeutické užití   MeSH
• thiazoly aplikace a dávkování   terapeutické užití   MeSH
• záření gama škodlivé účinky   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

AIM: The sensitivity of cancer cells which exhibit multi-drug resistance phenotype to A3 adenosine receptor (A3AR) agonist N(6)-(3-iodobenzyl)-adenosine-5'-N-methylcarboxamide (IB-MECA) was studied. METHODS: To establish direct relationship between P-glycoprotein (P-gp, ABCB1 and MDR1) expression and IB-MECA induced cell death, a straightforward method for precise estimation of intracellular level of this A3AR agonist was developed. RESULTS: We subjected three human leukaemia cell lines HL-60, K562 and K562/HHT to treatment with micromolar concentrations of IB-MECA. Although all cell lines used expressed A3AR, there was a large difference in their sensitivity to IB-MECA. While HL-60 and K562 cells were almost equally sensitive, the K562/HHT cells, which exhibit a multi-drug resistance phenotype because of overexpression of P-gp, were significantly more resistant. We found that the intracellular level of IB-MECA in K562/HHT cells was approx. 10 times lower than those in HL-60 or K562 cells. Inhibitors of P-gp, including cyclosporine A (CsA) and verapamil (Vpa), increased the intracellular level of IB-MECA and reversed the resistance of K562/HHT cells to this drug. Accordingly, shRNA-mediated down-regulation of P-gp significantly increased the intracellular level of IB-MECA in K562/HHT cells which simultaneously exhibited reduced resistance to this A3AR agonist. In addition, an in vitro enzyme-based assay provided evidence that IB-MECA might serve as a substrate for P-gp. CONCLUSION: Our results suggest that P-gp overexpression prevents cells from IB-MECA induced apoptosis despite the A3AR expression. Pro-apoptotic effect of IB-MECA seemed to strongly depend on its intracellular accumulation rather than on its interaction with A3AR.

• MeSH
• adenosin analogy a deriváty   chemie   metabolismus   MeSH
• adenosintrifosfatasy metabolismus   MeSH
• agonisté adenosinového receptoru A3 MeSH
• apoptóza fyziologie   MeSH
• blokátory kalciových kanálů farmakologie   MeSH
• buňky K562 účinky léků   metabolismus   MeSH
• HL-60 buňky účinky léků   metabolismus   MeSH
• lidé MeSH
• mnohočetná léková rezistence fyziologie   MeSH
• P-glykoprotein antagonisté a inhibitory   genetika   metabolismus   MeSH
• signální transdukce fyziologie   MeSH
• verapamil farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Two adenosine receptor agonists, N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA) and N6-cyclopentyladenosine (CPA), which selectively activate adenosine A3 and A1 receptors, respectively, were tested for their ability to influence proliferation of granulocytic and erythroid cells in femoral bone marrow of mice using morphological criteria. Agonists were given intraperitoneally to mice in repeated isomolar doses of 200 nmol/kg. Three variants of experiments were performed to investigate the action of the agonists under normal resting state of mice and in phases of cell depletion and subsequent regeneration after treatment with the cytotoxic drug 5-fluorouracil. In the case of granulopoiesis, IB-MECA 1) increased by a moderate but significant level proliferation of cells under normal resting state; 2) strongly increased proliferation of cells in the cell depletion phase; but 3) did not influence cell proliferation in the regeneration phase. CPA did not influence cell proliferation under normal resting state and in the cell depletion phase, but strongly suppressed the overshooting cell proliferation in the regeneration phase. The stimulatory effect of IB-MECA on cell proliferation of erythroid cells was observed only when this agonist was administered during the cell depletion phase. CPA did not modulate erythroid proliferation in any of the functional states investigated, probably due to the lower demand for cell production as compared with granulopoiesis. The results indicate opposite effects of the two adenosine receptor agonists on proliferation of hematopoietic cells and suggest the plasticity and homeostatic role of the adenosine receptor expression.

• MeSH
• adenosin analogy a deriváty   farmakologie   MeSH
• agonisté adenosinového receptoru A1 MeSH
• agonisté adenosinového receptoru A3 MeSH
• buňky kostní dřeně cytologie   metabolismus   účinky léků   MeSH
• erytroidní buňky cytologie   metabolismus   účinky léků   MeSH
• financování organizované MeSH
• granulocyty cytologie   metabolismus   účinky léků   MeSH
• hematopoetické kmenové buňky cytologie   metabolismus   účinky léků   MeSH
• homeostáza fyziologie   MeSH
• myši inbrední C57BL MeSH
• myši inbrední CBA MeSH
• myši MeSH
• neurotransmiterové látky MeSH
• proliferace buněk účinky léků   MeSH
• receptor adenosinový A1 MeSH
• receptor adenosinový A3 metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH

The present study was performed to define the optimum conditions of the stimulatory action of the adenosine A(3) receptor agonist, N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA), on bone marrow hematopoiesis in mice. Effects of 2-day treatment with IB-MECA given at single doses of 200nmol/kg twice daily were investigated in normal mice and in mice whose femoral bone marrow cells were either depleted or regenerating after pretreatment with the cytotoxic drug 5-fluorouracil. Morphological criteria were used to determine the proliferation state of the granulocytic and erythroid cell systems. Significant negative correlation between the control proliferation state and the increase of cell proliferation after IB-MECA treatment irrespective of the cell lineage investigated was found. The results suggest the homeostatic character of the induced stimulatory effects and the need to respect the functional state of the target tissue when investigating effects of adenosine receptor agonists under in vivo conditions.

• MeSH
• adenosin analogy a deriváty   farmakologie   MeSH
• agonisté adenosinového receptoru A3 MeSH
• buněčný rodokmen MeSH
• buňky kostní dřeně účinky léků   MeSH
• erytroidní buňky účinky léků   MeSH
• financování organizované MeSH
• granulocyty účinky léků   MeSH
• hematopoéza účinky léků   MeSH
• homeostáza účinky léků   MeSH
• inbrední kmeny myší MeSH
• kostní dřeň fyziologie   MeSH
• myši MeSH
• proliferace buněk účinky léků   MeSH
• receptor adenosinový A3 MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH

• MeSH
• agonisté adenosinového receptoru A1 MeSH
• agonisté adenosinového receptoru A2 MeSH
• agonisté adenosinového receptoru A3 MeSH
• finanční podpora výzkumu jako téma MeSH
• fluoruracil analogy a deriváty   aplikace a dávkování   MeSH
• hematopoéza fyziologie   MeSH
• myši MeSH
• receptor adenosinový A1 fyziologie   MeSH
• receptor adenosinový A2A fyziologie   MeSH
• receptor adenosinový A3 fyziologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH