Résumé
Objective To investigate the roles of a epoprostenol(PGI2) analog (Iloprost) in regulating the differentiation of CD4+ T cells to Treg cells and the possible mechanism.Methods Naǐve CD4+ T cells were isolated from human peripheral blood samples by using the magnetic-activated cell sorting (MACS) and then cultured under Treg-polarizing condition.The percentages of Treg cells and the expression of Foxp3 at mRNA level were respectively measured by using flow cytometry and RT-PCR for evaluation the effects of Iloprost on the differentiation of CD4+ T cells to Treg cells.The cAMP accumulation assay was used to detect the level of intracellular cAMP.Flow cytometry analysis was performed to detect the phosphorylation of signal transducer and activator of transcription 5 (STAT5).Results lloprost decreased the percentage of Treg cells and inhibited the expression of Foxp3 at mRNA level in a dose dependent manner (P＜0.05).However,the inhibitory effects of Iloprost were weakened when IP receptors were blocked by IP antagonist (CAY10449).A six-fold increase in the levels of intracellular cAMP in Treg cells was induced by Iloprost (P＜0.05) and a similar effect could be achieved by using a cAMP agonist,db-cAMP (P＞0.05).H-89,a protein kinase A inhibitor,inhibited the Iloprost-induced expression of cAMP in Treg cells.Moreover,Iloprost inhibited the IL-2 mediated phosphorylation of STAT5 (P＜0.05) and a similar effect could be achieved by using db-cAMP (P＞0.05).The Iloprost-mediated down-regulation of pSTAT5 was blocked by using H-89.Conclusion PGI2 could activate the cAMP-PKA signaling pathway by binding to the IP receptor,resulting in inhibited phosphorylation of STAT5 and suppressed differentiation of naǐve CD4+ T cells to Treg cells.