Earlier we have reported that thymic regulatory T cells (Treg) are resistant to in vivo glucocorticoid hormone (GC)-induced apoptosis, while the most GC-sensitive DP thymocytes died through the activation of mitochondrial apoptotic pathway. Here we analyzed the apoptosis-inducing effect of high dose (10^–6 M) in vitro dexamethasone (DX) treatment in mouse thymic- and splenic Tregs and CD4⁺ T cells. Activation of both extrinsic and intrinsic apoptotic pathways started after 2 h of DX treatment in CD4 SP thymocytes and was 3 × higher than in CD4⁺ splenocytes, while in Treg cells, weak activation of the extrinsic apoptotic pathway started only after 3 h. We also investigated the expression of 21 apoptosis-related molecules using a protein array and found higher level of both pro-and anti-apoptotic molecules in Tregs compared to CD4⁺ T cells. 4 h in vitro DX treatment induced upregulation of most apoptosis-related molecules both in Tregs and CD4⁺ T cells, except for the decrease of Bcl-2 expression in CD4⁺ T cells. We found high basal cytosolic Ca²⁺ levels in untreated Treg cells, which further increased after DX treatment, while the specific TCR-induced Ca²⁺ signal was lower in Tregs than in CD4⁺ T cells. Our results suggest that in the background of the relative apoptosis resistance of Treg cells to GCs might be their high basal cytosolic Ca²⁺ level and upregulated Bcl-2 expression. In contrast, downregulation of Bcl-2 expression in CD4⁺ T cells can explain their higher, DX-induced apoptosis sensitivity.

早些时候我们报道了胸腺调节性 T 细胞 (Treg) 对体内糖皮质激素 (GC) 诱导的细胞凋亡具有抵抗力，而对 GC 最敏感的 DP 胸腺细胞通过激活线粒体凋亡途径而死亡。在这里，我们分析了高剂量（10的凋亡诱导效果^-6  M）在体外地塞米松（DX）治疗小鼠thymic-和脾Treg细胞和CD4 ⁺ T细胞。在 DX 处理 2 小时后，CD4 SP 胸腺细胞开始激活外在和内在凋亡途径，并且比 CD4 ⁺高 3 倍脾细胞，而在 Treg 细胞中，外源性凋亡途径的弱激活仅在 3 小时后开始。我们还使用蛋白质阵列研究了 21 种凋亡相关分子的表达，发现与 CD4 ⁺ T 细胞相比，Tregs 中促凋亡和抗凋亡分子的水平更高。体外治疗DX 4小时诱导最凋亡相关分子二者中的Treg和CD4的上调⁺ T细胞，除Bcl-2表达的CD4中的降低⁺ T细胞。我们发现未处理的 Treg 细胞的基础胞质 Ca ²⁺水平较高，在 DX 处理后进一步增加，而 Treg 中特定的 TCR 诱导的 Ca ²⁺信号低于 CD4 ⁺T细胞。我们的结果表明，在 Treg 细胞对 GC 的相对凋亡抗性的背景下，可能是它们的高基础细胞溶质 Ca ²⁺水平和上调的 Bcl-2 表达。相比之下，CD4 ⁺ T 细胞中 Bcl-2 表达的下调可以解释它们更高的 DX 诱导的细胞凋亡敏感性。