Bilgeri R, Petzer A L, Zilian U, Geisen F H, Schirmer M, Haun M, Konwalinka G
Department of Internal Medicine, University of Innsbruck, Austria.
Exp Hematol. 1993 Mar;21(3):432-7.
The cytotoxic effect of chlorodeoxyadenosine (CdA) on lymphocytes and monocytes requires phosphorylation by the enzyme deoxycytidine kinase and can be antagonized by coadministration of deoxycytidine (dCyt), a competitive substrate of deoxycytidine kinase. It has also been shown for lymphocytes that coadministration of 3-aminobenzamide (3-ABA), an inhibitor of the enzyme poly-(ADP ribose) synthetase, is activated by CdA-mediated DNA strand breaks, consumes intracellular nicotinamide-dinucleotide (NAD) and can antagonize the lethal effect of CdA. Recent in vitro studies have shown that not only growth of lymphocytes and monocytes, but also colony formation by erythroid and myeloid progenitors derived from normal human bone marrow, is inhibited by CdA in a dose-dependent manner. In this study we examined the effect of various doses of dCyt (10(-6) to 10(-3) M) on CdA-mediated growth inhibition of erythroid and myeloid progenitor cells in vitro. Our results show that colony formation by human bone marrow-derived progenitor cells--CFU-E (colony-forming unit erythroid), BFU-E (burst-forming unit erythroid) and CFU-GM (colony-forming unit granulocyte/macrophage)-in semisolid medium is protected by a high, but clinically achievable and non-toxic, concentration of dCyt (> 10(-4) M) against the inhibitory effects of coadministered high concentrations of CdA. The protective effect of dCyt was markedly different on the various subclasses of progenitor cells, however. Thus, with coadministration of 10(-4) M dCyt, the CFU-E colony formation could be restored to almost 100% despite the presence of high concentrations of CdA (160 nM) compared to control cultures, whereas the colony formation of BFU-E and CFU-GM was restored to only 50%. At a concentration of 10(-3) M dCyt, colony formation of BFU-E and CFU-GM was raised to 80% of control cultures even in the presence of high concentrations of CdA (160 nM). Further experiments in which 3-ABA was coadministered to CdA-treated cultures showed that in all concentrations tested (0.3 to 5 mM) 3-ABA was not able to prevent CdA-mediated cytotoxicity on bone marrow progenitors. Based on these studies, we suggest that the CdA toxicity on CFU-E is mainly mediated by phosphorylation by deoxycytidine kinase, whereas additional mechanisms may be operative in BFU-E and CFU-GM. Considerable biochemical differences seem to exist between hematopoietic stem cells on the one hand and lymphocytes and monocytes from peripheral blood on the other.
氯脱氧腺苷（CdA）对淋巴细胞和单核细胞的细胞毒性作用需要脱氧胞苷激酶将其磷酸化，并且可以通过同时给予脱氧胞苷（dCyt）来拮抗，脱氧胞苷是脱氧胞苷激酶的竞争性底物。对于淋巴细胞也已表明，同时给予3-氨基苯甲酰胺（3-ABA），一种聚（ADP核糖）合成酶的抑制剂，它被CdA介导的DNA链断裂激活，消耗细胞内烟酰胺-二核苷酸（NAD），并且可以拮抗CdA的致死作用。最近的体外研究表明，不仅淋巴细胞和单核细胞的生长，而且来自正常人骨髓的红系和髓系祖细胞的集落形成，也受到CdA的剂量依赖性抑制。在本研究中，我们检测了不同剂量的dCyt（10^(-6)至10^(-3)M）对体外CdA介导的红系和髓系祖细胞生长抑制的影响。我们的结果表明，在半固体培养基中，人骨髓来源的祖细胞——CFU-E（红系集落形成单位）、BFU-E（爆式红系集落形成单位）和CFU-GM（粒细胞/巨噬细胞集落形成单位）的集落形成受到高浓度但临床上可达到且无毒的dCyt（>10^(-4)M）的保护，免受同时给予的高浓度CdA的抑制作用。然而，dCyt对祖细胞的不同亚类的保护作用明显不同。因此，与对照培养相比，尽管存在高浓度的CdA（160 nM），但同时给予10^(-4)M dCyt时，CFU-E集落形成可恢复至几乎100%，而BFU-E和CFU-GM的集落形成仅恢复至50%。在dCyt浓度为10^(-3)M时，即使存在高浓度的CdA（160 nM），BFU-E和CFU-GM的集落形成也提高至对照培养的80%。在CdA处理的培养物中同时给予3-ABA的进一步实验表明，在所有测试浓度（0.3至5 mM）下，3-ABA均不能预防CdA对骨髓祖细胞的细胞毒性。基于这些研究，我们认为CdA对CFU-E的毒性主要由脱氧胞苷激酶的磷酸化介导，而在BFU-E和CFU-GM中可能存在其他作用机制。造血干细胞与外周血中的淋巴细胞和单核细胞之间似乎存在相当大的生化差异。
