"GLUCOCORTICOID-DEPENDENT DNA METHYLATION CHANGES IN THE ACQUISITION OF TOLEROGENESIS BY DENDRITIC CELLS"

ANTONIO GARCÍA-GÓMEZ; GISELA BARBISAN; OCTAVIO MORANTE-PALACIOS; CARLOS DE LA CALLE FABREGAT

Congreso; 41 Congreso de la Sociedad Española de Inmunología; 2019

Glucocorticoids (GCs) are essential stress hormones, which are ligands of the ubiquitously expressed Glucocorticoid Receptor (GR). Specifically, in dendritic cells (DC), synthetic GCs produce a tolerogenic phenotype. However, the mechanisms of that process have not been completely unraveled. Given the central role of DCs not only in innate but also in adaptative immunity and the widespread use of synthetic GCs, improving our knowledge of how that tolerogenic phenotype of DC is acquired could help to find new drug targets and understand the variability in the response to GCs. In this study, we isolated CD14+ monocytes (MOs) from peripheral blood of healthy donors and differentiated them in vitro to DCs in the presence or absence of a synthetic GC. We reproduced a tolerogenic phenotype in GC-treated DCs (tolDCs), defined by their ability to suppress the growth of T cells, reduced production of cytokines IL1β, and TNFa, enhanced production of IL-10 and upregulation of anti-inflammatory genes. We then studied the methylome and transcriptome of MO, DC and tolDCs cells. First, 1632 CpGs were found to be differentially methylated in tolDCs compared to DCs: 324 specifically hypomethylated in tolDCs compared to MOs and DCs (cluster 1), and 1308 in which MO-DC hypomethylation was specifically blocked in tolDCs (cluster 2). Second, most of the CpGs of both clusters were observed in introns and intergenic regions. Interestingly, these CpGs were specifically enriched in histone marks H3K4me1 and H3K27ac, hallmarks of active enhancers. Third, motif enrichment analyses revealed that cluster 1 was enriched in AP1 motifs and cluster 2 was enriched in GRE (Glucocorticoid Response Elements) motifs. Finally, a significant inverse Pearson correlation was detected between gene expression and DNA methylation. We are currently exploring the direct role of GR to target the aforementioned DNA methylation and expression changes to understand the GC-dependent acquisition of the tolerogenesis.