Mechanisms of apoptosis in developing thymocytes as revealed by adenosine deaminase-deficient fetal thymic organ cultures.
Mechanisms of apoptosis in developing thymocytes as revealed by adenosine deaminase-deficient fetal thymic organ cultures.
复制标题
腺苷脱氨酶缺陷的胎儿胸腺器官培养物揭示了发育中胸腺细胞的凋亡机制。
DOI：
10.1016/s0006-2952(03)00530-6
复制
发表时间：
2003
影响因子：
5.8
通讯作者：
VanDeWiele,CJustin
中科院分区：
文献类型：
--
作者：
Thompson,LindaF;Vaughn,JamesG;Laurent,AlethaB;Blackburn,MichaelR;VanDeWiele,CJustin
腺苷脱氨酶（ADA）分别催化腺苷和脱氧腺苷转化为肌苷和脱氧肌苷。缺乏ada的个体患有严重的联合免疫缺陷，不能产生大量成熟的T淋巴细胞或B淋巴细胞。这是ADA底物或其代谢物积累的结果。dATP是一种候选的毒性代谢物，因为它在ada缺乏患者红细胞中的浓度与疾病的严重程度相关。ada缺乏条件下的小鼠胎儿胸腺器官培养（FTOC）可以作为一个模型系统来研究抑制胸腺生成的生化机制。在妊娠第15天开始的缺乏ada的FTOCs中，胸腺细胞的发育在CD4 - CD8 - CD44loCD25+向CD4 - CD8 - CD44loCD25 -转变时被阻止。细胞凋亡似乎与此有关，因为培养物可以通过泛caspase抑制剂zVADfmk、Bcl-2转基因或凋亡蛋白酶激活因子-1的缺失来拯救。与ada缺乏患者一样，在ada缺乏的FTOCs中，dATP也升高。在用腺苷激酶抑制剂（一种将脱氧腺苷磷酸化为dAMP的酶）处理的培养物中，dATP水平正常化，胸腺细胞发育得到恢复。zVADfmk还阻止了ada缺陷FTOCs中dATP的积累，这表明脱氧腺苷来源于因β选择检查点失败而经历凋亡的胸腺细胞。相比之下，在Bcl-2转基因小鼠胎儿胸腺的ada缺陷FTOCs中，dATP水平仍然升高。这些数据表明，胸腺细胞凋亡作为发育检查点失败的结果，涉及一个或多个不受Bcl-2调节的半胱天蛋白酶。
Adenosine deaminase (ADA) catalyzes the conversion of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. ADA-deficient individuals suffer from severe combined immunodeficiency and are unable to produce significant numbers of mature T or B lymphocytes. This occurs as a consequence of the accumulation of ADA substrates or their metabolites. dATP is a candidate toxic metabolite because its concentration in RBCs of ADA-deficient patients correlates with the severity of disease. Murine fetal thymic organ culture (FTOC) under ADA-deficient conditions can be used as a model system to investigate the biochemical mechanism responsible for the inhibition of thymopoiesis. In ADA-deficient FTOCs initiated at day 15 of gestation, thymocyte development was arrested at the CD4−CD8−CD44loCD25+to CD4−CD8−CD44loCD25−transition. Apoptosis appeared to be involved because the cultures could be rescued by the pan-caspase inhibitor zVADfmk, a Bcl-2 transgene, or deletion of apoptotic protease activating factor-1. As in ADA-deficient patients, dATP was also elevated in ADA-deficient FTOCs. dATP levels were normalized and thymocyte development was rescued in cultures treated with an inhibitor of adenosine kinase, the enzyme that phosphorylates deoxyadenosine to dAMP. zVADfmk also prevented the accumulation of dATP in ADA-deficient FTOCs, suggesting that deoxyadenosine was derived from thymocytes undergoing apoptosis as a consequence of failing the β selection checkpoint. In contrast, dATP levels remained elevated in ADA-deficient FTOCs with fetal thymuses from Bcl-2 transgenic mice. These data suggest that thymocyte apoptosis as a consequence of failing developmental checkpoints involves one or more caspases that are not regulated by Bcl-2.