Pluthero F G, Axelrad A A
Department of Anatomy, University of Toronto, Ontario, Canada.
Ann N Y Acad Sci. 1991;628:222-32. doi: 10.1111/j.1749-6632.1991.tb17249.x.
C57Bl/6 (B6) mice and mice of a congeneic strain, B6S, differ in the proportions of erythroid progenitor cells (BFU-E) typically seen in DNA synthesis in in vivo cell suicide assays, and bone marrow supernatants (MS) prepared from B6 mice can inhibit BFU-E cycling in vitro. Using in vitro BFU-E DNA synthesis assays and a model system of BFU-E in culture (DA-1 cells) as screening methods for the detection of inhibitors of BFU-E cycling, we have purified the protein that is apparently responsible for the inhibitory effects of MS on progenitor cells and that is also an antagonist of the stimulatory effects of interleukin-3 (IL-3) on DA-1 cell proliferation in culture. We have identified this protein as the Cu,Zn-containing form of the antioxidant enzyme superoxide dismutase (SOD), which is normally present in large amounts in erythrocytes. MS from B6S mice does not inhibit BFU-E DNA synthesis. However, measurements of SOD activity showed no differences between B6 and B6S mice; thus the difference between the effects of B6S-MS and B6-MS is not due to differences in the levels of SOD present. The inhibitory effects of SOD on BFU-E in vitro are opposed by the stimulatory effects of IL-3 in a dose-dependent manner, and similar interactions between stimulatory and inhibitory factors also appear to determine the effects of mouse-derived preparations on erythroid cells. If the interactions seen in vitro are applicable to the state in vivo, SOD may be a constitutive inhibitor of erythroid progenitor cell cycling in mice, acting in opposition to stimulatory factors whose expression varies in response to genetic and physiological influences.
C57Bl/6（B6）小鼠和同基因品系B6S小鼠在体内细胞自杀试验中，通常可见的红系祖细胞（BFU-E）DNA合成比例有所不同，并且从B6小鼠制备的骨髓上清液（MS）能够在体外抑制BFU-E的循环。利用体外BFU-E DNA合成试验以及培养的BFU-E模型系统（DA-1细胞）作为检测BFU-E循环抑制剂的筛选方法，我们纯化了一种蛋白质，该蛋白质显然是MS对祖细胞产生抑制作用的原因，并且也是白细胞介素-3（IL-3）对培养的DA-1细胞增殖的刺激作用的拮抗剂。我们已将该蛋白质鉴定为抗氧化酶超氧化物歧化酶（SOD）的含铜锌形式，其通常大量存在于红细胞中。B6S小鼠的MS不会抑制BFU-E DNA合成。然而，SOD活性的测量结果显示B6和B6S小鼠之间没有差异；因此，B6S-MS和B6-MS作用效果的差异并非由于SOD含量水平的不同。SOD对体外BFU-E的抑制作用以剂量依赖的方式被IL-3的刺激作用所抵消，并且刺激和抑制因子之间类似的相互作用似乎也决定了小鼠来源制剂对红系细胞的作用。如果体外观察到的相互作用适用于体内状态，那么SOD可能是小鼠红系祖细胞循环的组成型抑制剂，其作用与那些表达因遗传和生理影响而变化的刺激因子相反。
