Segreto Helena R C, Ferreira Alice T, Kimura Edna T, Franco Marcello, Egami Mizue I, Silva Maria Regina R, Segreto Roberto A
Department of Medicine-Division of Radiotherapy, Federal University of São Paulo, Rua Botucatu 740, São Paulo-SP, Brazil.
Am J Hematol. 2002 Nov;71(3):143-51. doi: 10.1002/ajh.10201.
Experiments were undertaken to assess the role of amifostine in the activation of latent TGFbeta1 and in the smad proteins cascade (smad 2/3, smad4, smad7), focusing on megakaryocytes, in the bone marrow irradiated in vivo. Non-irradiated megakaryocytes were negative for active TGFbeta1. Immunopositivity to active TGFbeta1 was detected in megakaryocytes 10 days after irradiation in amifostine- treated and untreated marrows. Smad 2/3 and smad 4 were strongly positive in the nucleus of megakaryocytes 10 days after irradiation. At the same time, a predominant hypocellular bone marrow with foci of hematopoiesis was observed with few megakaryocytes. An increase in the number of reticulin fibers was also seen. In amifostine-treated marrows, smad 2/3 and smad4 were not detected in the nucleus but were positive in the cytoplasm of megakaryocytes 10 days after irradiation. Coincidentally, bone marrows were cellular with megakaryocytes. Smad7 immunoexpression was detected in the cytoplasm of megakaryocytes in the non-irradiated, amifostine-treated and in the irradiated, amifostine-treated marrows. Data indicate that amifostine does not prevent latent TGFbeta1 activation in irradiated megakaryocytes. While TGFbeta1 signal transduction occurs in megakaryocytes in untreated bone marrows, it is inhibited in megakaryocytes in amifostine-treated marrows due to the induction of smad 7 activation. This is the first report showing smad 7 activation by amifostine. Our results also suggest a role for TGFbeta1 as an inhibitor of megakaryocytes in vivo.
开展实验以评估氨磷汀在体内照射的骨髓中对潜伏性转化生长因子β1（TGFβ1）激活以及对Smad蛋白级联反应（Smad 2/3、Smad4、Smad7）的作用，重点关注巨核细胞。未照射的巨核细胞中活性TGFβ1呈阴性。在氨磷汀处理和未处理的骨髓中，照射后10天的巨核细胞中检测到活性TGFβ1免疫阳性。照射后10天，巨核细胞核内的Smad 2/3和Smad 4呈强阳性。与此同时，观察到主要为造血灶的细胞减少的骨髓，巨核细胞很少。还可见网状纤维数量增加。在氨磷汀处理的骨髓中，照射后10天，Smad 2/3和Smad4在巨核细胞核内未检测到，但在巨核细胞胞质中呈阳性。巧合的是，骨髓细胞丰富，有巨核细胞。在未照射、氨磷汀处理的骨髓以及照射、氨磷汀处理的骨髓中的巨核细胞胞质中检测到Smad7免疫表达。数据表明氨磷汀不能阻止照射后巨核细胞中潜伏性TGFβ1的激活。虽然TGFβ1信号转导在未处理骨髓的巨核细胞中发生，但在氨磷汀处理的骨髓的巨核细胞中由于Smad 7激活的诱导而受到抑制。这是首次报道氨磷汀激活Smad 7。我们的结果还提示TGFβ1在体内作为巨核细胞抑制剂的作用。
