Activation of M1 macrophages in sepsis-induced acute kidney injury in response to heparin-binding protein

Background In the early stage of sepsis, M1 macrophages result in the production of inflammatory mediators and AKI. Heparin-binding protein (HBP) have been shown to play important roles in sepsis-induced AKI. In this study, we investigate the association of HBP with M1 macrophages in sepsis-induced AKI. Methods Male C57BL6 mice were subjected to cecal ligation and puncture (CLP) or sham surgery. Biochemical and histological renal damage was assessed. Macrophage infiltration was assessed by immunohistochemistry. RT-PCR was used to investigate the expression of heparin-binding protein (HBP), the inducible nitric oxide synthase (iNOS) and arginase 1 (Arg-1) mRNAs. Western blots were performed to assay the tissue levels of HBP, tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). Results High levels of HBP were obviously detected 24 h after sepsis-induced AKI. Heparin inhibited HBP expression during sepsis-induced AKI. The suppression of HBP expression by heparin injection after the establishment of sepsis-induced AKI resulted in a reduction in renal injury severity accompanied with a significant repression of M1 macrophage activation and expression of TNF-alpha and IL-6. Conclusions HBP plays an important role in the initial inflammatory reaction associated with sepsisinduced AKI, presumably by activating M1 macrophages and suppressing TNF-alpha and IL-6 secretion.