Leukotriene B4 type-1 receptor signaling promotes liver repair after hepatic ischemia/reperfusion injury through the enhancement of macrophage recruitment.

Recruited macrophages play a critical role in liver repair after acute liver injury. Leukotriene B4 (LTB4) is a potent chemoattractant for macrophages. In this study, we investigated the role of LTB4 receptor type 1 (BLT1) in liver repair during hepatic ischemia/reperfusion (I/R) injury. BLT1-knockout mice (BLT1(-/-)) or their wild-type counterparts (WT) were subjected to partial hepatic I/R. Compared with WT, BLT1(-/-) exhibited delayed liver repair and hepatocyte proliferation accompanied by a 70% reduction in the recruitment of macrophages and a 70-80% attenuation in hepatic expression of epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1). Disruption of BLT1 signaling also reduced the expression of EGF by 67% on recruited macrophages expressing VEGFR1 in the injured liver. Treatment of WT mice with an EGF-neutralizing antibody delayed liver repair and reduced macrophage recruitment, compared with control immunoglobulin G (IgG). BLT1 signaling enhanced the expression of VEGF, VEGFR1, and EGF in isolated peritoneal macrophages in vitro. These results indicate that BLT1 signaling plays a role in liver repair after hepatic I/R through enhanced expression of EGF in recruited macrophages and that the development of a specific agonist for BLT1 could be useful for liver recovery from acute liver injury.