Casein Kinase 2 Interacting Protein-1 regulates M1 and M2 inflammatory macrophage polarization

The importance of macrophage plasticity, albeit being discovered recently, has been highlighted in a broad spectrum of biological processes operative in physiological and pathological environments. Macrophage polarized activation and inactivation has profound effects on immune and inflammatory responses with several major pathways being elucidated in the past few years. However, transcriptional regulation mechanisms governing macrophage polarization is still preliminary. In this study, we identify the Casein Kinase 2 Interacting Protein 1 (CKIP-1) as a molecular toggle manipulating macrophage speciation. CKIP-1 expression was strongly induced by pro-inflammatory M1 stimuli (LPS and IFN-γ) and robustly suppressed by M2 stimuli (IL-4 and IL-13) in human and murine macrophage. Gain and loss of function studies suggest that CKIP-1 is a prerequisite for optimal LPS-induced pro-inflammatory gene activation, which exhibits its roles in a NF-κB dependent manner. Furthermore, CKIP-1 inhibits anti-inflammatory gene expression by negatively regulating JAK1-STAT6 activation in macrophages. Taken together, these data integrated CKIP-1 expression and function as a novel transcriptional regulator of macrophage polarization and identified a double feedback loop consisting of CKIP-1 and the key regulators of the M1 and M2 macrophage effectors in polarization pathway. Moreover, the inhibitory roles of CKIP-1 in LPS-mediated sepsis and TPA-mediated cutaneous provide a new target for treatments of acute inflammation.