1. Inhibition of angiotensin I-converting enzyme induces radioprotection by preserving murine hematopoietic short-term reconstituting cells
Sabine Charrier, Annie Michaud, Sabrina Badaoui, Sébastien Giroux, Eric Ezan, Françoise Sainteny, Pierre Corvol, William Vainchenker Blood. 2004 Aug 15;104(4):978-85. doi: 10.1182/blood-2003-11-3828. Epub 2004 Apr 22.
Angiotensin I-converting enzyme (ACE) inhibitors can affect hematopoiesis by several mechanisms including inhibition of angiotensin II formation and increasing plasma concentrations of AcSDKP (acetyl-N-Ser-Asp-Lys-Pro), an ACE substrate and a negative regulator of hematopoiesis. We tested whether ACE inhibition could decrease the hematopoietic toxicity of lethal or sublethal irradiation protocols. In all cases, short treatment with the ACE inhibitor perindopril protected against irradiation-induced death. ACE inhibition accelerated hematopoietic recovery and led to a significant increase in platelet and red cell counts. Pretreatment with perindopril increased bone marrow cellularity and the number of hematopoietic progenitors (granulocyte macrophage colony-forming unit [CFU-GM], erythroid burst-forming unit [BFU-E], and megakaryocyte colony-forming unit [CFU-MK]) from day 7 to 28 after irradiation. Perindopril also increased the number of hematopoietic stem cells with at least a short-term reconstitutive activity in animals that recovered from irradiation. To determine the mechanism of action involved, we evaluated the effects of increasing AcSDKP plasma concentrations and of an angiotensin II type 1 (AT1) receptor antagonist (telmisartan) on radioprotection. We found that the AT1-receptor antagonism mediated similar radioprotection as the ACE inhibitor. These results suggest that ACE inhibitors and AT1-receptor antagonists could be used to decrease the hematopoietic toxicity of irradiation.
2. Captopril inhibits the proliferation of hematopoietic stem and progenitor cells in murine long-term bone marrow cultures
J E Chisi, J Wdzieczak-Bakala, J Thierry, C V Briscoe, A C Riches Stem Cells. 1999;17(6):339-44. doi: 10.1002/stem.170339.
Drugs used mainly for the treatment of hypertension, such as angiotensin I-converting enzyme (ACE) inhibitors, can cause pancytopenia. The underlying cause of this side effect remains unknown. In the present study, long-term bone marrow cultures (LTBMCs) were utilized to evaluate the role of captopril (D-3-mercapto-2-methylpropionyl-L-proline), one of the potent ACE inhibitors, in regulating hematopoietic stem/progenitor cell proliferation. Captopril (10(-6) M final concentration) was added to LTBMCs at the beginning of the culture period and at weekly intervals for six weeks. There was no toxicity to the bone marrow cells as measured by the unchanged cell number in the nonadherent layer during the whole culture period, and there was an increased cellularity of the adherent layer at the end of the six weeks of treatment. However, captopril decreased the proportion of granulocyte-macrophage colony-forming cells (GM-CFCs) in S phase at weeks 2 and 3 as well as that of high proliferative potential colony-forming cells (HPP-CFCs) at week 3 in the nonadherent layer. There was no change in the kinetics of the GM-CFCs and HPP-CFCs present in the adherent layer. These results suggest that captopril causes myelosuppression by inhibiting hematopoietic cell proliferation of progenitor and stem cells rather than depleting cells of the bone marrow microenvironment.
3. Activity of acetyl-n-ser-asp-lys-pro (AcSDKP) on hematopoietic progenitor cells in short-term and long-term murine bone marrow cultures
J D Jackson, Y Yan, C Ewel, J E Talmadge Exp Hematol. 1996 Feb;24(3):475-81.
The tetrapeptide AcSDKP is a potent inhibitor of hematopoietic stem cell proliferation. Its activity was systematically examined in murine long-term bone marrow cultures (LTBMC) and short-term liquid cultures in the presence or absence of exogenous cytokines. The effects of AcSDKP on the production of granulocyte-macrophage colony-forming cells (CFU-GM) and high proliferative potential colony-forming cells (HPP-CFC) in LTBMCs were examined. AcSDKP was added daily to LTBMCs at various concentrations (10-3--10-16M) for up to 5 weeks. AcSDKP inhibited the entry of progenitor cells into S phase as measured by 3H-thymidine suicide assay and the absolute number of progenitor cells with peak activity at 10-12 M with less activity seen at higher or lower concentrations. The number of nonadherent CFU-GM per LTBMC was unchanged from control values at 1 week of treatment with AcSDKP but was significantly depressed at weeks 3 and 5. In contrast, HPP-CFC progenitor cells were decreased throughout the treatment period, and the numbers of CFU-GM and HPP-CFC in S phase were significantly decreased throughout the treatment period. Maximum S-phase inhibitory activity was observed at 10-12 M AcSDKP. AcSDKP had no effect on the number of adherent CFU-GM or HPP-CFC, cellularity per culture or percent of adherent progenitor cells in S phase. Murine short-term bone marrow cultures were also treated with AcSDKP in the presence or absence of cytokines (interleukin-3 [LI-3], stem cell factor [SCF], or granulocyte colony-stimulating factor [G-CSF]) for various time periods. Dose-response studies showed maximum effects at 10-12 M AcSDKP when no cytokines were added and 10-14 M AcSDKP when exogenous cytokines were added. These studies indicate that the concentration of the tetrapeptide critical in obtaining an effect on hematopoietic progenitor cells, and furthermore, we report that the presence of cytokines or stromal cells also affects the response of progenitor cells to AcSDKP.
