Center for Pediatric Biomedical Research, Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642, USA.
Exp Hematol. 2011 Apr;39(4):434-45. doi: 10.1016/j.exphem.2011.01.010. Epub 2011 Feb 1.
Clastogenic injury of the erythroid lineage results in anemia, reticulocytopenia, and transient appearance of micronucleated reticulocytes. However, the micronucleated reticulocyte dose-response in murine models is only linear to 2 Gy total body irradiation and paradoxically decreases at higher exposures, suggesting complex radiation effects on erythroid intermediates. To better understand this phenomenon, we investigated the kinetics and apoptotic response of the erythron to sublethal radiation injury.
We analyzed the response to 1 and 4 Gy total body irradiation of erythroid progenitors and precursors using colony assays and imaging flow cytometry, respectively. We also investigated cell cycling and apoptotic gene expression of the steady-state erythron.
After 1 Gy total body irradiation, erythroid progenitors and precursors were partially depleted. In contrast, essentially all bone marrow erythroid progenitors and precursors were lost within 2 days after 4 Gy irradiation. Imaging flow cytometry analysis revealed preferential loss of phenotypic erythroid colony-forming units and proerythroblasts immediately after sublethal irradiation. Furthermore, these populations underwent radiation-induced apoptosis, without changes in steady-state cellular proliferation, at much higher frequencies than later-stage erythroid precursors. Primary erythroid precursor maturation is associated with marked Bcl-xL upregulation and Bax and Bid downregulation.
Micronucleated reticulocyte loss after higher sublethal radiation exposures results from rapid depletion of erythroid progenitors and precursors. This injury reveals that erythroid colony-forming units and proerythroblasts constitute a particularly proapoptotic compartment within the erythron. We conclude that the functional transition of primary proerythroblasts to later-stage erythroid precursors is characterized by a shift from a proapoptotic to an antiapoptotic phenotype.
红系造血前体细胞的断裂损伤可导致贫血、网织红细胞减少和一过性出现有核红细胞微核。然而，在小鼠模型中，有核红细胞微核剂量-反应曲线仅在总剂量 2 Gy 时呈线性，而在更高剂量时却呈下降趋势，这表明辐射对红系中间阶段存在复杂的影响。为了更好地理解这一现象，我们研究了亚致死辐射损伤对红细胞的动力学和凋亡反应。
我们分别使用集落分析和成像流式细胞术分析了 1 和 4 Gy 全身照射对红系造血前体细胞和祖细胞的反应。我们还研究了稳态红细胞的细胞周期和凋亡基因表达。
1 Gy 全身照射后，红系造血前体细胞和祖细胞部分耗竭。相比之下，4 Gy 全身照射后，骨髓中的几乎所有红系造血前体细胞和祖细胞在 2 天内被耗尽。成像流式细胞术分析显示，在亚致死照射后，表型性红系集落形成单位和原红细胞迅速丢失。此外，这些细胞群发生辐射诱导的凋亡，而稳态细胞增殖没有变化，其频率远高于晚期红系前体细胞。原发性红系前体细胞的成熟与 Bcl-xL 的显著上调以及 Bax 和 Bid 的下调有关。
较高的亚致死辐射暴露后出现的有核红细胞微核丢失是由于红系造血前体细胞和祖细胞的快速耗竭所致。这种损伤表明，红系集落形成单位和原红细胞构成了红细胞内一个特别容易发生凋亡的隔室。我们得出结论，原红细胞向晚期红系前体细胞的功能转化特征是从易凋亡表型向抗凋亡表型的转变。
