We have shown that phosphorylation of C/EBPb-Thr21/ by Ribosomal-S6 Kinase (RSK) induces injury and inflammation but the molecular mechanisms remain unknown. Hypothesis: Phosphorylation of C/EBPb-Thr217 induces

activation of the Inflammasome in liver macrophages and the consequent liver injury. Methods: Liver macrophages were isolated from control G/EBPb-wf, and from transgenic mice expressing either a phosphorylation mimic C/EBPb-Glu2l7, or a non-phosphorylatable G/EBPb-Ala217. The inactive Inflammasome complex was identified by the presence of procaspase-1, pro-IL-1b and proIL-18, inactive NF-қB, non-signaling MyD-88 and Interferon-Regulatory Factor (IRF)−4 while the active Inflammasome complex was identified by the presence of caspase-1, IL-1b, IL-18, ITF2357 cost nuclear NF-қB, signaling MyD-88, adaptor aSg, IfR-5 and NALP-3 (Nat lmmunol. 10: 241,2009) Results: Treatment of learn more G/EBPb-wt mice with GGl4, Fas or dimethyl-nitrosamine induced C/EBPb-Thr21/ phosphorylation, which was physically associated with the activated Inflammasome complex (caspase-1, IRF-5 ASG and NALP-3) in liver macrophages. In contrast, both the G/EBPb-Ala217 mice and G/EBPb-wt mice treated with G/EBPb-Ala217 peptides were refractory to the assembly and activation of the

Inflammasome. The C/EBPbGlu217 mice were highly susceptible to hepatotoxin-induced activation of the Inflammasome, which assembled with C/EBPbGlu217. Cultured liver macrophages from G/EBPb-wt, G/EBPbAla217 and C/EBPb-Glu217 had a response to TGFa-induced C/EBPb-Thr2 17 phosphorylation and its assembly within the activated Inflammasome essentially identical to their respective in vivo animal models. Further, Fas-L induced liver macrophage activation and severe liver injury in C/EBPb-Glu21/ mice (ALT: 1//0 丨し/ml) compared to mice expressing the G/EBPb-Ala217 transgene (ALT: 182 Iし/ml; P < 0.0001). In addition, the G/EBPb-Ala21/ peptide stimulates the switch to non-inflammatory liver macrophages after acute dimethyl-nitrosamine or GGl4 administration to G/EBPb-wt mice. The peptide or transfer of myeloid cells from G/EBPb-Ala217

(but not from G/EBPbGlu2 17) mice normalized the increased Inflammasome activation and prevented liver injury (P < 0.001 for both). Conclusion: Phosphorylation PJ34 HCl of C/EBPb-Thr2 17 is required for the Inflammasome Complex assembly and activation in liver macrophages and for the consequent liver injury. The RSKG/EBPb phosphorylation pathway is a potential therapeutic target for liver injury. Disclosures: The following people have nothing to disclose: Martina Buck, Mario Chojkier Introduction: The inflammasome is a cytosolic protein complex that is central to the production of IL-1 p, and has important roles in chronic liver inflammation and fibrosis. Activation requires two signals but it is not known how inflammasome activity is sustained.