NLRs in mouse hepatocytes respond to specific ligands to activate NFκB (135.78)

Abstract Hepatocytes are microbial-responsive cells that express and activate Toll like receptors (TLRs). NACHT-LRR receptors (NLRs) are a family of more recently identified intracellular pattern recognition receptors. NOD1 and NOD2 are NLRs that respond to specific microbial ligands and activate NFκB through activation of RIP2/RICK. We hypothesized that hepatocytes express and activate NOD1/NOD2 signaling pathways as part of their function to initiate and regulate the innate immune system. High levels of NOD1, NOD2, and RIP2/RICK mRNA and protein expression were detected by quantitative PCR or Western blot in untreated primary isolated C57BL/6 hepatocytes. Hepatocytes were then treated with LPS (100ng/mL), iE-DAP (100ng/mL; NOD1-ligand), or MDP (10μg/mL; NOD2-ligand) for up to 60min. NOD-ligands were endotoxin free. NFκB activation by EMSA in hepatocytes treated with iE-DAP was similar or higher than after LPS-stimulation. However there was minimal NFκB activation after NOD2-ligand (MDP). NOD1/2, RIP2 mRNA expression increased significantly by 1h after stimulation with LPS, MDP or iE-DAP and was maximal by 4h, remaining elevated at 24h of stimulation. Together these data show hepatocytes respond to microbial ligands specific for NOD1 or NOD2 and increase their expression suggesting a role for these proteins in hepatic responses to infection. Work supported in part by funding from NIH grant R01-GM-50441