BET proteins inhibitor JQ1 impairs GM-CSF-promoted peritoneal macrophage self-renewal and IL-4-induced alternative polarization

Peritoneal macrophages (PMs), which resided in peritoneal cavity, are crucial to maintain tissue homeostasis and immunity. Macrophage self-renewal and polarization states are critical for PM population homeostasis and function. However, the underlying molecular mechanism that regulates self-renewal and polarization of PMs is still unclear and needs to be explored. Here, we demonstrated that PMs self-renewal was stimulated by granulocyte macrophage colony-stimulating factor (GM-CSF), but not by macrophage colony-stimulating factor (M-CSF). Pharmacological inhibition of Bromodomain & Extraterminal (BET) Proteins by either JQ1 or ARV-825 significantly reduced GM-CSF-dependent peritoneal macrophage self-renewal by abrogating cell proliferation and decreasing self-renewal-related gene expression, such as MYC and Klf4, at transcriptional and protein levels. In addition, transcriptomic analysis showed that JQ1 blocked alternative PMs polarization by downregulating key transcriptional factor IRF4 expression, but not the activation of AKT or STAT6 in PMs. These findings illustrated that the significance of BET family proteins in GM-CSF-induced PMs self-renewal and IL-4-induced alternative polarization.