Influência da prolactina nos compartimentos linfoide e estromal do microambiente tímico

Abstract

Prolactin (PRL), besides its classic effects on breast development and lactation, several shreds of evidence show its actions on the immune system, including pleiotropic effects on the thymus. Therefore, this study aimed to evaluate the influence of PRL in the lymphoid and stromal comparTSCnts of the thymic microenvironment. For the study, we used the primary culture of mouse thymic stromal cells (TSC), thymic epithelial cell line (TECs) and lactating female mice. Initially, the effect of prolactin on the thymocytes viability and thymic epithelial cells was demonstrated, it was observed that PRL at all concentrations tested (10, 50, 100, 500 and 1000 ng/mL) was not capable.to decrease cell viability, based on this data the concentration of 10 ng/mL was chosen for the development of the study. The immunofluorescence showed the presence of medullary and cortical epithelial cells in the primary culture of TSC. The PRL treaTSCnt was able to increase laminin, on the other hand, did not altered fibronectin deposition in TSCs, this increase was also observed in laminin deposition in TECs. Besides, PRL also increased CXCL12 chemokine expression in TSC and TECs. Also, PRL treaTSCnt was able to alter f-actin polymerization in TSCs as the TEC began to present filopod. By flow cytometry, it was observed that PRL did not interfere in the expression of the integrins VLA-5 and VLA-6 in thymocytes. However, the treaTSCnt increased the expression of the chemokine receptor CXCR4, in total, double-positive and CD4+ thymocytes. In the cell adhesion, when TSCs were pretreated with PRL, there was an increase in the number of total thymocytes and the double-positive and CD8 + subpopulations that adhered to their surface. However, adherence was not altered when TECs were pretreated with PRL. In the transwell chamber, the thymocyte migration assay against PRL-pretreated TSC and in the presence of CXCL12 as a chemoattractant factor, it was found that PRL and chemokine CXCL12 alone or in combination increased the migration of total and the subpopulation of double-positive and CD8+ thymocytes. Finally, lactating female thymus was evaluated and was observed an increase in CXCL12 expression in the lactating thymic microenvironment. However, CXCR4 expression on the thymocyte surface was not altered. In cell migration, it was found that thymocytes of lactating females showed an increase in migratory capacity when compared to control and migration was potentiated against CXCL12. By flow cytometry, it was found that this increase occurred mainly in double-positive and CD8+ thymocytes. Together, the data obtained in the study demonstrate the effect of PRL on thymic stromal cells and thymocytes, especially in the adhesion and cell migration processes, placing this hormone as a potential regulator of thymic physiology.