GATA-2 Transduces LPS-Induced il-1β Gene Expression in Macrophages via a Toll-Like Receptor 4/MD88/MAPK-Dependent Mechanism

Lipopolysaccharide (LPS) is a critical factor for inducing acute lung injury. GATA-2, a transcription factor, contributes to the control of cell activity and function. Exposure of RAW 264.7 cells to LPS induced interleukin (IL)-1β mRNA and protein expression and GATA-2 translocation from the cytoplasm to nuclei in concentration- and time-dependent manners. A bioinformatic search revealed that GATA-2-specific binding elements exist in the 5'-promoter region of the il-1β gene. LPS could enhance the transactivation activity of GATA-2 in macrophages. Knocking-down translation of GATA-2 mRNA using RNA interference significantly alleviated LPS-induced IL-1β mRNA and protein expression. As to the mechanism, transfection of toll-like receptor (TLR) 4 small interfering (si)RNA into macrophages concurrently decreased LPS-caused increases in nuclear GATA-2 levels. Sequentially, treatment with myeloid differentiation factor 88 (MyD88) siRNA decreased LPS-induced phosphorylation of mitogen-activated protein kinases (MAPKs) kinase 1/2 and subsequent translocation of GATA-2. Reducing MAPK activities using specific inhibitors simultaneously decreased GATA-2 activation. Furthermore, exposure of primary macrophages to LPS significantly increased the transactivation activities of GATA-2 and IL-1β mRNA and protein expression. Transfection of GATA-2 siRNA inhibited LPS-induced IL-1β mRNA expression. Results of this study show that LPS induction of il-1β gene expression in macrophages is mediated by GATA-2 via activation of TLR4, MyD88, and MAPKs.