松果体褪黑素对大鼠胸腺CD4~+ CD25~+调节性T细胞发育及其相关基因Foxp3的影响

目的研究松果体摘除及补充褪黑素对大鼠胸腺CD4+ CD25+调节性T细胞(Treg细胞)产生、输出及其相关基因叉状头/翅膀状螺旋转录子(Foxp3)表达的影响。方法选用雄性清洁级SD大鼠120只,分为正常组、假手术组、松果体摘除组、松果体摘除+褪黑素低剂量组[腹腔注射7.5mg/(kg·d)]和松果体摘除+褪黑素高剂量组[腹腔注射15mg/(kg·d)],术后4、8周取材。应用流式细胞检测技术、RT-PCR法及免疫组织化学染色法观察并分析松果体摘除及补充外源性褪黑素后胸腺及外周血CD4、CD25双阳性细胞数量及胸腺Foxp3表达的变化。结果松果体摘除术后无论4周或者8周胸腺CD4+ CD25+ Treg细胞数量均无明显变化,补充褪黑素后双阳性细胞数量呈时间、剂量依赖性明显增加;松果体摘除术后4周外周血CD4+ CD25+ Treg细胞数量明显增加,但补充褪黑素后恢复正常,而术后8周各组之间无显著性差异;半定量RT-PCR及免疫组织化学结果显示,松果体摘除后4周大鼠胸腺Foxp3表达水平明显升高,补充高低两种剂量褪黑素后均有所下降并达到正常水平,而松果体摘除后8周各组之间Foxp3的表达无明显差异。结论松果体摘除对胸腺CD4+ CD25+ Treg细胞的产生无明显影响,但导致大鼠胸腺Foxp3的转录和翻译明显增加,胸腺CD4+ CD25+ Treg细胞的输出增加,而补充外源性褪黑素后能逆转上述异常,长时间作用则其影响逐渐消失。

Effect of pineal gland and melatonin on CD4~+CD25~+Treg cells development and Foxp3 expression of rat thymus

Objective To investigate the influence of pinealectomy(Px)and melatonin (MLT) supplementation on CD4~+CD25~+Treg cells development and Foxp3 expression in rat thymus. Methods One hundred and twenty clean-grade male SD rats were divided into five groups: normal control group, sham pinealectomized group, pinealectomized group, Px +7.5 mg/(kg·d) MLT group, Px +15 mg/(kg·d) MLT group, and the thymus were taken out at the 4th week and the 8th week;Flow cytometric analysis was used to analyse the number of double positive cells in the thymus and peripheral blood;Semiquantitative RT-PCR and immunohistochemistry were applied to analyse Foxp3 expression of rat thymus. Results There was no difference of the number of CD4~+CD25~+ Treg cells in rat thymus between Px and normal/sham group, and the number increased dependently on time and dose after MLT supplementation. In rat peripheral blood the double positive cells significantly increased in models of Px at the 4th week, and then backed to normal level after MLT supplementation. The results showed no significant changes in all groups at the 8th weeek;At the 4th weeks, Foxp3 expression increased in the thymus of Px rats compared to nomal/sham group, which returned to normal level after MLT supplementation. On the other hand, Foxp3 expression showed no significant difference in all groups at the 8th weeek.Conclusion Px made no difference between the development of CD4~+CD25~+Treg cells in rat thymus, but resulted in significant increase of thymic output and Foxp3 expression. All the effects disappeared at the 8th week. MLT supplementation could reverse the abnormity.