The involvement of DAMPs-mediated inflammation in cyclophosphamide-induced liver injury and the protection of liquiritigenin and liquiritin.

Cyclophosphamide (CPA) is a chemotherapeutic drug widely used in the treatment of breast cancer or leukemia in clinic. However, CPA was reported to have hepatotoxicity. This study aims to observe the engaged mechanism of CPA-induced liver injury in mice and the protection of liquiritin (LQ) and liquiritigenin (LG). Liver sinusoidal endothelial injury induced by CPA (20, 40 mg/kg) in mice was evidenced by the elevated hepatic metalloproteinase-9 (MMP-9) expression, and the results from liver histological evaluation and scanning electron microscope observation. CPA increased hepatic infiltration of neutrophils, liver myeloperoxidase (MPO) activity, serum interleukin-6 (IL-6) content, hepatic IL-6 mRNA expression, toll-like receptor-4 (TLR4) expression and nuclear factor κB (NFκB) activation in mice. Elevated serum contents of damage associated molecular patterns (DAMPs) including high mobility group box 1 (HMGB1), heat shock protein 60 (HSP60) and glucose-regulated protein 94 (Grp94) were found in mice treated with CPA. Liver sinusoidal endothelial injury and inflammation induced by CPA were diminished in TLR4 knock-out mice. LG and LQ (40, 80 mg/kg) both ameliorated liver sinusoidal endothelial injury, and reduced the increased hepatic infiltration of neutrophils, MPO activity, hepatic IL-6 mRNA expression and NFκB activation induced by CPA. In summary, these results indicate that TLR4-NFκB-mediated inflammatory injury initiated by DAMPs was critically involved in CPA-induced hepatotoxicity. LG and LQ alleviated CPA-induced liver sinusoidal endothelial injury and inflammatory injury in mice.