ABSTRACT
At the M2 terminal of the macrophage activation spectrum, expression of genes is regulated by transcription factors that include STAT6, CREB, and C/EBPß. Signaling through ß-adrenergic receptors drives M2 activation of macrophages, but little is known about the transcription factors involved. In the present study, we found that C/EBPß regulates the signaling pathway between ß-adrenergic stimulation and expression of Arg1 and several other specific genes in the greater M2 transcriptome. ß-adrenergic signaling induced Cebpb gene expression relatively early with a peak at 1â¯h post-stimulation, followed by peak Arg1 gene expression at 8â¯h. C/EBPß transcription factor activity was elevated at the enhancer region for Arg 1 at both 4 and 8â¯h after stimulation but not near the more proximal promoter region. Knockdown of Cebpb suppressed the ß-adrenergic-induced peak in Cebpb gene expression as well as subsequent accumulation of C/EBPß protein in the nucleus, which resulted in suppression of ß-adrenergic-induced Arg1 gene expression. Analysis of genome-wide transcriptional profiles identified 20 additional M2 genes that followed the same pattern of regulation by ß-adrenergic- and C/EBPß-signaling. Promoter-based bioinformatic analysis confirmed enrichment of binding motifs for C/EBPß transcription factor across these M2 genes. These findings pinpoint a mechanism that may be targeted to redirect the deleterious influence of ß-adrenergic signaling on macrophage involvement in M2-related diseases such as cancer.
