Microglia are the resident macrophages of the CNS, which secrete several pro- and anti-inflammatory cyto-chemokines including interleukin-1β (IL-1β), in response to pathogenic stimuli. Once secreted, IL-1β binds to IL-1 receptor present on microglia and initiates the production of inflammatory cytokines in microglia. However, the detailed information regarding the molecular mechanisms of IL-1β triggered inflammatory pathways in microglia is lacking. Our studies focused on the role of Krüppel-like factor 4 (Klf4) in mediating the regulation of pro-inflammatory gene expression upon IL-1β stimulation in microglia. Our studies show that stimulation of microglia with IL-1β robustly induces Klf4 via PI3K/Akt pathway which positively regulates the production of endogenous IL-1β as well as other pro-inflammatory markers, cyclooxygenase-2, monocyte chemoattractant protein-1 and interleukin-6 (IL-6). In addition, we report that Klf4 negatively regulates the expression of inducible nitric oxide synthase, thereby playing a key role in regulating the immunomodulatory activities of microglia.
IL-1β is a potent pro-inflammatory cytokine which regulates inflammation in brain via activation of microglia. In this regard, we unravelled mechanisms for IL-1β mediated regulation of downstream Cox-2, iNOS (inducible nitric oxide synthase) as well as other cyto-chemokines in microglia and have established a role for Klf4 in mediating microglial activation. We further report that Klf4 mediates the production of endogenous IL-1β in response to exogenous IL-1β stimulation. We hereby propose a novel transcription factor underlying IL-1β mediated modulation of inflammation in the CNS.