O efeito do hormônio do crescimento na transmigração de timócitos in vitro

Abstract

Transendothelial migration is a key process in lymphocyte trafficking. It is known that growth hormone (GH) modulates intrathymic T cell migration and that directly or indirectly influences the biology of endothelial cells and thymocytes. In this context, we evaluated the effect of GH on the transendothelial migration of thymocytes, in the presence or absence the chemokine CXCL12. For the study, we applied the murine thymic endothelial cell line (tEnd.1) and thymocytes freshly isolated from male C57BL/6 mice aged 4-6 weeks. Through in vitro studies of transendothelial migration of thymocytes, and analyses by flow cytometry, we observed a statistically significant reduction in the numbers of transmigrated thymocytes, mainly seen for CD4+CD8+ cells, across endothelial barriers treated with GH [100 ng/ml], for 8 h. Importantly, this effect was reverted when thymocytes were treated with GH [100 ng/ml] for 1 h. Similar effects were noted in transmigration through joint action of GH and CXCL12. Despite the fact that all the CD4/CD8-defined subsets have been affected, we observed a statistically significant increase in the number of transmigrated thymocytes, mainly of CD4+CD8+ and CD4+CD8- cells, when they were treated with GH and allowed to migrate in response to CXCL12, when compared to untreated controls in response to CXCL12. We demonstrated, by real-time PCR, that GH at 100 ng/ml did not modulate the expression of VCAM-1 and CXCL12 by tEnd.1 cells treated for 8 h. Furthermore, we found by cytofluorimetric assay that GH alone did not change the membrane expression of VLA-4 and CXCR4 receptor in transmigrated thymocytes. Through joint action of GH and CXCL12, was observed increase in expression of VLA-4 on CD4-CD8+ cells from the group of GH-treated thymocytes, when compared to groups in which endothelial cells were treated. As for expression of CXCR4, we found that the GH/CXCL12 decreased the expression of this receptor on transmigrated thymocytes, mainly in CD4+CD8+ cells from the group in which the thymocytes were treated. In conclusion, our results reinforce that GH influence the thymus physiology and modulate the biology of endothelial cells and thymocytes, with differential effects in the process of endothelial transmigration of murine thymocytes.