氧化低密度脂蛋白干预记忆性CD8+T细胞亚群的分化

摘要

目的 探讨氧化低密度脂蛋白(ox-LDL)对CD8+记忆性T细胞亚群分化的影响及其机制.方法 将雌性10周龄未发生糖尿病NOD小鼠随机分为2组(n=5):ox-LDL组及对照组.断颈处死各组小鼠磁珠分离脾脏CD8+T细胞体外培养(IL-2),ox-LDL组加入ox-LDL 30μg/mL体外刺激24 h,ox-LDL未处理组作为对照组.24 h后分离细胞.体外实验利用流式细胞仪检测各组以下指标:胞内CD8+IFN-γ+确定胰岛β细胞特异性杀伤性CD8+T细胞的比例;细胞表面分子CD8、CD44、CD62L确定CD8+记忆性T细胞的不同亚群分化;T细胞相关转录因子TCF-1及STAT-3的活化确定关键性转录因子的作用.体内实验中,将各组CD8+记忆性T细胞通过尾静脉注射的方法移植给未发病NOD小鼠,同时设立未移植的模型对照组,每5 d检测血糖1次,监测小鼠的血糖改变及生存率.结果 相比对照组,ox-LDL(30μg/mL)作用24 h后,胰岛β细胞特异性杀伤性CD8+T细胞活化减少[(0.7±0.03)%vs(2.7±0.14)%,P<0.01],记忆性T细胞中的效应记忆性T细胞形成数目减少[(10.3±0.71)%vs(30.3±1.36)%,P<0.01],干细胞样记忆性T细胞增加[(72.3±3.8)%vs(55.1±2.61)%,P<0.05].T细胞转录因子TCF-1及p-STAT-3活化的也受到抑制[TCF-1:(14.5±0.82)%vs(34.2±1.23)%,磷酸化STAT-3:(3.3±0.12)%vs(22.1±1.1)%,P<0.01].T细胞移植给未发病NOD小鼠后,ox-LDL处理组小鼠血糖升高明显低于对照组(P<0.05),且生存率提高(P<0.05).结论 ox-LDL干扰记忆性CD8+T细胞核转录因子TCF-1活化及STAT-3的磷酸化,抑制长效杀伤作用的效应性和记忆性CD8+T细胞形成,诱导干细胞样记忆性CD8+T细胞形成,从而阻止胰岛β细胞自身免疫损伤及□型糖尿病的发生.%Objective To investigate effect of oxidized low-density lipoprotein (ox-LDL) on memory CD8+T cell subpopulation differentiation in mice with autoimmune diabetes. Methods Cultured splenic CD8 + T cells from pre-diabetic NOD mice isolated with magnetic beads were treated with 30 μg/mL ox-LDL and 10 U/mL interleukin-2 (IL-2) for 24 h and the control cells were treated with IL-2 only. Flow cytometry was used to determine the percentage of splenic CD8 +IFN-γ + T cells, expressions of CD8, CD44 and CD62L on the T cells, and the activation of T cell factor-1 (TCF-1) and STAT-3. The CD127+memory T cells were purified and transplanted into the pre-diabetic NOD mice via the tail vein, and the blood glucose was recorded weekly and survival time of the mice was monitored. Results Treatment with ox-LDL significantly reduced islet βcell-specific cytotoxic CD8+T cells as compared with the control group[(0.7±0.03)%vs (2.7±0.14)%, P<0.01]. The percentage of effector memory CD8+T cells (Tem) in the total memory CD8+T cells was reduced[(10.3 ± 0.71)%vs (30.3 ± 1.36)%, P<0.01]and that of stem cell-like memory T cells was significantly increased [(72.3 ± 3.8)% vs (55.1 ± 2.61)%, P<0.05] following ox-LDL treatment, which also resulted in significantly decreased activation of TCF-1 [(14.5 ± 0.82)% vs (34.2 ± 1.23)%, P<0.01] and pSTAT-3[(3.3 ± 0.12)% vs (22.1 ± 1.1)%, P<0.01]. Transplantation of ox-LDL-treated memory T cells in pre-diabetic NOD mice obviously inhibited the increase of blood glucose and prolonged the survival time of the mice (P<0.05). Conclusion Ox-LDL decreases the activation of transcriptional factors TCF-1 and phosphorylation of STAT-3, inhibits the formation of effector memory CD8 + T cells with long-term cytotoxicity, but promote the generation of stem cell-like memory CD8+ T cells, which result in suppression of islet β cell-specific effector cytotoxic CD8 + T cell differentiation to lessen autoimmune injury to the isletβcells.