p300 and C/EBPß-regulated IKKß expression are involved in thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells.

Asthma and chronic obstructive pulmonary disease (COPD) are common chronic lung inflammatory diseases. Thrombin and interleukin (IL)-8/C-X-C chemokine ligand 8 (CXCL8) play critical roles in lung inflammation. Our previous study showed that c-Src-dependent IκB kinase (IKK)/IκBα/nuclear factor (NF)-κB and mitogen-activated protein kinase kinase kinase 1 (MEKK1)/extracellular signal-regulated kinase (ERK)/ribosomal S6 protein kinase (RSK)-dependent CAAT/enhancer-binding protein ß (C/EBPß) activation are involved in thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells. In this study, we aimed to investigate the roles of p300 and C/EBPß-reliant IKKß expression in thrombin-induced IL-8/CXCL8 expression. Thrombin-induced increases in IL-8/CXCL8-luciferase activity and IL-8/CXCL8 release were inhibited by p300 small interfering (siRNA). Thrombin-caused histone H3 acetylation was attenuated by p300 siRNA. Stimulation of cells with thrombin for 12h resulted in increases in IKKß expression and phosphorylation in human lung epithelial cells. However, thrombin did not affect p65 expression. Moreover, 12h of thrombin stimulation produced increases in IKKß expression and phosphorylation, and IκBα phosphorylation, which were inhibited by C/EBPß siRNA. Finally, treatment of cells with thrombin caused increases in p300 and C/EBPß complex formation, p65 and C/EBPß complex formation, and recruitment of p300, p65, and C/EBPß to the IL-8/CXCL8 promoter. These results imply that p300-dependent histone H3 acetylation and C/EBPß-regulated IKKß expression contribute to thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells. Results of this study will help clarify C/EBPß signaling pathways involved in thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells.