Jiřina Holá

Granulocyte colony-stimulating factor and drugs elevating extracellular adenosine synergize to enhance haematopoietic reconstitution in irradiated mice

Abstract: The activation of adenosine receptors has recently been demonstrated to stimulate haematopoiesis. In the present study, we investigated the ability of drugs elevating extracellular adenosine to influence curative effects of granulocyte colony‐stimulating factor (G‐CSF) in mice exposed to a sublethal dose of 4 Gy of 60Co radiation. Elevation of extracellular adenosine in mice was induced by the combined administration of dipyridamole, a drug inhibiting the cellular uptake of adenosine, and adenosine monophosphate (AMP), an adenosine prodrug. The effects of dipyridamole plus AMP, and G‐CSF, administered either alone or in combination, were evaluated. The drugs were injected to mice in a 4‐d treatment regimen starting on d 3 after irradiation and the haematopoietic response was evaluated on d 7, 10, 14, 18 and 24 after irradiation. While the effects of G–CSF on the late maturation stages of blood cells, appearing shortly after the completion of the treatment, were not influenced by dipyridamole plus AMP, positive effects of the combination therapy occurred in the post‐irradiation recovery phase which is dependent on the repopulation of haematopoietic stem cells. This was indicated by the significant elevation of counts of granulocyte‐macrophage progenitor cells (GM‐CFC) and granulocytic cells in the bone marrow (d 14), of GM‐CFC (d 14), granulocytic and erythroid cells (d 14 and 18) in the spleen, and of neutrophils (d 18), monocytes (d 14 and 18) and platelets (d 18) in the peripheral blood. These effects suggest that the repopulation potential of the combination therapy lies in a common multilineage cell population. The results of this study implicate the promising possibility to enhance the curative effects of G–CSF under conditions of myelosuppressive states induced by radiation exposure.

Drugs elevating extracellular adenosine promote regeneration of haematopoietic progenitor cells in severely myelosuppressed mice: their comparison and joint effects with the granulocyte colony-stimulating factor.

Abstract: We tested capabilities of drugs elevating extracellular adenosine and of granulocyte colony‐stimulating factor (G‐CSF) given alone or in combination to modulate regeneration from severe myelosuppression resulting from combined exposure of mice to ionizing radiation and carboplatin. Elevation of extracellular adenosine was induced by joint administration of dipyridamole (DP), a drug inhibiting the cellular uptake of adenosine, and adenosine monophosphate (AMP), serving as an adenosine prodrug. DP + AMP, G‐CSF or all these drugs in combination were administered in a 4‐d treatment regimen starting on day 3 after induction of myelosuppression. Comparable enhancements of haematopoietic regeneration due to elevation of extracellular adenosine or to action of G‐CSF were demonstrated as shown by elevated numbers of haematopoietic progenitor cells for granulocytes/macrophages (GM‐CFC) and erythrocytes (BFU‐E) in the bone marrow and spleen in early time intervals after termination of the drug treatment, i.e. on days 7 and 10 after induction of myelosuppression. Coadministration of all the drugs further potentiated the restoration of progenitor cell pools in the haematopoietic organs. The effects of the drug treatments on progenitor cells were reflected in the peripheral blood in later time intervals of days 15 and 20 after induction of myelosuppression, especially as significantly elevated numbers of granulocytes and less pronounced elevation of lymphocytes and erythrocytes. The results substantiate the potential of drugs elevating extracellular adenosine for clinical utilization in myelosuppressive states, e.g. those accompanying oncological radio‐ and chemotherapy.

Effects of Drugs Inhibiting Prostaglandin or Leukotriene Biosynthesis on Postirradiation Haematopoiesis in Mouse

Two non-steroidal anti-inflammatory drugs, i.e. indomethacin (INDO), an inhibitor of prostaglandin production, and esculetin (ESCUL), an inhibitor of leukotriene production, were tested for their ability to modify haematopoiesis in three experimental systems: (a) in vitro clonal proliferation of marrow GM-CFC from the irradiated mouse was found to be augmented by addition of INDO at a low concentration, and inhibited by ESCUL in a dose-dependent manner; (b) in the lethally irradiated and bone marrow-transplanted mice treated with the drugs in the postirradiation period, stimulatory effects of INDO on CFU-S and GM-CFC populations and an inhibitory effect of ESCUL on GM-CFC were observed; and (c) when the drugs were administered i.p. to mice 1 h before 5-Gy irradiation, INDO enhanced the postirradiation recovery of haematopoietic indices such the numbers of CFU-S, GM-CFC, peripheral blood granulocytes, and nucleated bone marrow cells, while ESCUL had no effect or even inhibited the recovery of these indices. Survival curves for CFU-S and GM-CFC showed that altered haematopoietic recovery in the INDO- and ESCUL-pretreated mice was not due to changes of intrinsic radiosensitivity of pluripotent (CFU-S) or committed (GM-CFC) stem cell populations. These results confirm earlier findings suggesting an inhibitory role of prostaglandins on haematopoiesis, and provide evidence that endogenous leukotrienes might play a positive role in the regulation of haematopoietic functions in an irradiated organism.

Meloxicam, a Cyclooxygenase 2 Inhibitor, Supports Hematopoietic Recovery in Gamma-Irradiated Mice

Abstract Hofer, M., Pospíšil, M., Znojil, V., Holá, J., Vacek, A., Weiterová, L., Štreitová, D. and Kozub;aaik, A. Meloxicam, a Cyclooxygenase 2 Inhibitor, Supports Hematopoietic Recovery in Gamma-Irradiated Mice. Radiat. Res. 166, 556–560 (2006). Meloxicam, a selective inhibitor of cyclooxygenase 2, a nonsteroidal anti-inflammatory drug with an improved side-effects profile in terms of gastrointestinal toxicity, has been found to stimulate hematopoiesis in whole-body γ-irradiated mice. A distinct corroboration of this positive action of meloxicam is an enhancement of the recovery of hematopoietic progenitor cells committed to granulocyte-macrophage and erythroid development, which has been demonstrated in sublethally irradiated animals treated with meloxicam at a dose of 20 mg/kg administered intraperitoneally either singly 1 h before irradiation or repeatedly after radiation exposure. The results suggest that meloxicam can be added to the list of biological response modifiers that can be used in the treatment of hematopoietic damage induced by ionizing radiation.

Drugs elevating extracellular adenosine enhance cell cycling of hematopoietic progenitor cells as inferred from the cytotoxic effects of 5-fluorouracil

OBJECTIVE Our previous studies showed that the combined administration of drugs elevating extracellular adenosine, i.e., dipyridamole and adenosine monophosphate (AMP), enhanced hematopoiesis in normal mice and increased hematopoietic recovery in irradiated mice. In the present study, we have examined the possibility that these effects are due to the adenosine-induced cycling of the hematopoietic progenitor cells. MATERIALS AND METHODS Experiments were performed under in vivo conditions using B10CBAF1 mice. The cycling status of hematopoietic progenitor cells (CFU-S(day 10), CFC-GM, and BFU-E) was determined on the basis of their sensitivity to 5-fluorouracil (5-FU), a cycle-specific cytotoxic agent. RESULTS Pretreatment of mice with dipyridamole + AMP enhanced the cytotoxic effects of a single bolus of 5-FU at a dose of 3 mg per mouse. Sensitizing effects of drugs occurred after a delay of several hours and attained a maximum of about 40-60% reduction of the progenitor cells surviving after 5-FU alone. The period of maximum sensitization of CFU-S by the combination of dipyridamole + AMP was shifted to later time intervals as compared with the effects on CFC-GM and BFU-E. Pretreatment of mice with the drugs also aggravated the 5-FU-induced lethality. Reduction of survival was found in mice exposed to two cycles of 3 mg of 5-FU following the pretreatment with dipyridamole + AMP at a time period characterized by the highest fraction of CFU-S in the S phase. CONCLUSIONS The results suggest that adenosine receptor signaling, induced by the administration of drugs elevating extracellular adenosine, enhances cycling of the hematopoietic progenitor cells. These effects might have pharmacological implications in the therapy of blood disorders.

Inhibition of cyclooxygenase 2 in mice increases production of g-csf and induces radioprotection.

Abstract Hofer, M., Pospíšil, M., Holá, J., Vacek, A., Štreitová, D. and Znojil, V. Inhibition of Cyclooxygenase 2 in Mice Increases Production of G-CSF and Induces Radioprotection. Radiat. Res. 170, 566–571 (2008). Meloxicam, a selective inhibitor of cyclooxygenase 2, was tested to determine its ability to modulate hematopoiesis and to influence survival of mid-lethally γ-irradiated mice. A single dose of meloxicam (20 mg/kg) administered to mice intraperitoneally 1 h before irradiation was shown to enhance serum levels of granulocyte colony-stimulating factor (G-CSF) during the first 24 h after irradiation, to elevate numbers of granulocytic precursor cells in bone marrow and granulocyte counts in peripheral blood on day 10 after irradiation, and to increase 30-day survival of these mice. The results provide new evidence for the protective ability of meloxicam administration to mice irradiated with mid-lethal doses and contribute to the understanding of the mechanisms of this meloxicam action by drawing attention to the possible role of increased endogenous G-CSF production.

Homeostatic action of adenosine A3 and A1 receptor agonists on proliferation of hematopoietic precursor cells.

Two adenosine receptor agonists, N 6-(3-iodobenzyl)adenosine-5′-N-methyluronamide (IB-MECA) and N 6-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.

Effects of postirradiation carboxymethylglucan administration in mice

The hemopoiesis-enhancing ability of a soluble glucan derivative, i.e. carboxymethylglucan (CMG), was investigated in gamma-irradiated mice. Attention was focused on the usefulness of its single or repeated postirradiation administration. CMG was administered i.p. at (a) single dose of 6 mg 2 h postirradiation, (b) four 6 mg doses in the first 4 days postirradiation, (c) four 1.5 mg doses at the same time intervals. Indices of granulopoiesis and inflammatory side effects (liver weight increase and hepatic granulomas) were investigated in mice irradiated with a sublethal dose of 7 Gy. All three CMG-treated groups of mice were found to exhibit enhanced hemopoietic recovery in comparison with the controls. Although the mice repeatedly given the 6 mg CMG doses showed the most rapid recoveries of all the evaluated parameters of granulopoiesis, the most pronounced hepatic side effects were found in these mice, too. When survival of mice was recorded in lethally (9 Gy) irradiated animals, the best protective response were obtained following the repeated administration of the 1.5 mg CMG dose, the survival by day 30 in this group being significantly higher not only in comparison with the controls but also with the mice repeatedly given the 6 mg dose of CMG. The results suggest that the postirradiation CMG administration can be useful for enhancing radiation suppressed hemopoiesis. However, repeated larger CMG doses may produce side effects which compromise the overall survival of irradiated mice.

Activation of adenosine A3 receptors supports hematopoiesis-stimulating effects of granulocyte colony-stimulating factor in sublethally irradiated mice

Purpose: Research areas of ‘post-exposure treatment’ and ‘cytokines and growth factors’ have top priority among studies aimed at radiological nuclear threat countermeasures. The experiments were aimed at testing the ability of N6-(3-iodobenzyl)adenosine-5′-N-methyluronamide (IB-MECA), an adenosine A3 receptor agonist, to modulate hematopoiesis in sublethally irradiated mice, when administered alone or in a combination with granulocyte colony-stimulating factor (G-CSF) in a two-day post-irradiation treatment regimen. Materials and methods: A complete analysis of hematopoiesis including determination of numbers of bone marrow hematopoietic progenitor and precursor cells, as well as of numbers of peripheral blood cells, was performed. The outcomes of the treatment were assessed at days 3 to 22 after irradiation. Results: IB-MECA alone has been found to induce a significant elevation of numbers of bone marrow granulocyte-macrophage progenitor cells (GM-CFC) and peripheral blood neutrophils. IB-MECA given concomitantly with G-CSF increased significantly bone marrow GM-CFC and erythroid progenitor cells (BFU-E) in comparison with the controls and with animals administered each of the drugs alone. Conclusions: The findings suggest the ability of IB-MECA to stimulate hematopoiesis and to support the hematopoiesis-stimulating effects of G-CSF in sublethally irradiated mice.

Peroral IMUNOR®, A Low-Molecular-Weight Immunomodulator Prepared from Disintegrated and Ultrafiltered Leukocytes, Enhances Recovery from Myelosuppression Induced by Cisplatin or 5-Fluorouracil

A single dose of IMUNOR®, a low-molecular-weight immunodulator prepared from disintegrated and ultrafiltered pig leukocytes, was found to enhance recovery of murine pool of hemopoietic progenitor cells for granulocytes and macrophages damaged by a single injection of cytotoxic drugs 5-fluorouracil or cisplatin. The best results were obtained after the treatment with IMUNOR® on days 3 or 4 after the injection of 5-fluorouracil or cisplatin. These results together with previous findings obtained in our laboratory suggest that IMUNOR® has the potential to become a part of treatment schemes in oncological practice aimed at alleviation of myelosuppression evoked by cytotoxic anti-tumor therapy.