9 HGFL is an 85-kDa circulating protein produced and secreted primarily by hepatocytes.10 Activation of Ron in peritoneal macrophages has been shown to stimulate macrophage shape changes,

chemotaxis, adhesion, and phagocytosis.11 Ron has also been shown in alveolar and peritoneal macrophages to limit select cytokine responses in inflammatory cells click here through attenuation of NF-κB by a mechanism that has yet to be identified.12, 13 Previous studies from our laboratory showed increased inflammatory responses and shortened survival times in mice with a deleted Ron tyrosine kinase domain (TK−/−) compared to wildtype control mice during the induction of bacterial peritonitis and in a lung injury model.14, 15 Paradoxically,

utilizing the well-characterized model of LPS/GalN induced ALF in mice, although serum levels of TNF-α were elevated, livers from TK−/− mice exhibited marked hepatocyte protection compared with controls.16 To investigate the function of Ron in regulating hepatocyte survival, purified EPZ015666 concentration populations of Kupffer cells and hepatocytes from wildtype and TK−/− mice were isolated. Utilizing purified cells, we recapitulated ex vivo the protected hepatocyte phenotype and exaggerated cytokine production observed in the TK−/− mice in vivo. Furthermore, by using mice with targeted deletions of Ron in hepatocytes and macrophages, we were able to substantiate our findings ex vivo. In total, our data suggests that Ron loss selectively in hepatocytes provides a survival benefit during ALF despite increased cytokine production by deregulated Kupffer cell activation. ActD, actinomycin D; ALF, acute liver failure; ALT, alanine aminotransferase; ELISA, enzyme-linked immunosorbent assay; GalN, D(+)-galactosamine hydrochloride; GusB, β-glucuronidase; HGFL, hepatocyte growth factor-like protein; Montelukast Sodium IL, interleukin; IL-1ra, interleukin-1 receptor antagonist; KC, keratinocyte chemoattractant; LPS, lipopolysaccharide; MCP-1, macrophage chemoattractant protein-1; MIP-2, macrophage inflammatory protein-2; NF-κB, nuclear factor-κB; TIMP-1, tissue inhibitor of metalloproteinase;

TK, tyrosine kinase; TNF-α, tumor necrosis factor alpha; TUNEL, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. Ron tyrosine kinase-deficient mice (TK−/−) and floxed Ron mice (TKfl/fl) were generated as described and were backcrossed into a C57BL/6 background.7 Age-matched male mice between 14 and 24 weeks old were used for all experiments. C57BL/6 albumin-Cre and lysozyme-Cre mice were obtained from the Jackson Laboratory (Bar Harbor, ME). Cre-expressing mice were crossed with floxed Ron (TKfl/fl) mice to create the targeted knockouts. Deletion of the Ron TK domain was determined by semiquantitative competitive polymerase chain reaction (PCR) as described.