Differential effect of glucocorticoids on the activation of monocytes and macrophages.

Glucocorticoids (GCs) reduce the expression of many genes induced in inflammatory conditions in vivo or by pro-inflammatory stimuli in vitro acting on the Glucocorticoid receptor (GR/NR3C1). However, GCs have pleiotropic effects on the immune system. Monocytes and macrophages are important cells of the innate immune system, exhibiting complex properties with enhancing as well as suppressive effects on inflammatory processes depending on their stage of activation and differentiation. Macrophages contribute to host defense, tissue remodeling and wound healing The mechanisms of GCs actions on monocytes and macrophages and their contribution to systemic anti-inflammatory effects remain unclear. These effects on activation GCs in monocytes and macrophages were investigated using the human monocytic cell line THP-1 and differentiation protocol PMA. Monocytes-THP1 and macrophages derived-monocytes were exposed for 6 hours to 100 nM of dexamethasone (Dex) and analyzed by microarrays. In macrophages-derived monocytes with respect to monocytes-THP-1, the number of genes differentially regulated was almost twice, among these, genes related with pro-inflammatory pathways, like TNFa, CXCL1 and GZMA. Interestingly, one of the genes differentially regulated (decreased) in macrophages exposed to Dex was the GR itself. If this effect modifies the inflammatory function of macrophages derived-monocyte is a question that will be evaluated through this study. For this study, 12 samples were analyzed by NanoString: 2 experimental groups (Monocytes THP-1 and macrophages differentiated from monocytes THP-1; 2x106 cells/well); 2 treatments (vehicle and 100nM Dex); 1 time point (6 h) and x3 replicates. All samples passed nSolver’s initial QA/QC controls. One of the Mac Dex samples (Mac Dex 2) clustered with the Mac Controls and saw no increased expression of FKBP5. It was therefore excluded from further analysis. All remaining replicates were well correlated (R > 0.98).