OBJECTIVETo investigate the role of the Notch signaling pathway, and the underlying mechanism, in development of acute liver failure (ALF) in a mouse model.

METHODSFor in vivo analysis of the role of Notch signaling in ALF, a mouse model of ALF was generated by intraperitoneal injection of 3.0 g/kg D-galactosamine. Histological specimens were stained by hematoxylin-eosin, and then studied microscopically.Expression level of Jaggedl, Notchl, NICD, and Hes5 was measured by western blotting (for protein) and real time-PCR (for mRNA). The level of CD68 protein was detected by immunohistochemical staining. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), IL-10, high mobility group box 1 (HMGB1) chromatin protein, and lipopolysaccharide (LPS) were measured by standard methods. For in vitro analysis of the molecular mechanism, the RAW264.7 macrophage cell line was cultured with LPS in the absence or presence of the Notch inhibitor DAPT, and the intracellular levels of Notch1, NICD, and Hes5 were measured by western blotting and real time-PCR and the extracellular levels of IL-10 and HMGB1 were detected in the supematant.

RESULTSCompared with unmodeled (normal control) mice, the ALF modeled mice showed higher levels of serum ALT (848.40+/-94.83 U/L vs. 38.99+/-9.63 U/L), AST (911.49+/-67.65 U/L vs. 55.28+/-7.50 U/L), HMGB1 (101.91+/-12.43 µg/L vs. 20.73+/-5.37 µg/L), 1L-10 (4 627.88+/-842.45 pg/mL vs. 1 064.92+/-238.46 pg/mL) and LPS (11.80+/-0.89 EU/mL vs. 0.58+/-0.12 EU/mL), as well as higher expression of Jagged1 (mRNA: 7.63+/-1.41 vs. 1.00+/-0.00; protein: 0.71+/-0.07 vs. 0.34+/-0.07), Notch1 (mRNA: 7.10+/-0.66 vs. 1.00+/-0.00; protein: 0.66+/-0.11 vs. 0.27+/-0.08), NICD (protein: 0.76+/-0.08 vs. 0.27+/-0.08), Hes5 (mRNA: 7.95+/-0.71 vs. 1.00+/-0.00; protein: 1.20+/-0.07 vs. 0.76+/-0.07), and CD68 (protein: 7 685.05+/-417.34 vs. 2 294.01+/-392.93) (all P<0.01). In vitro, LPS increased the extracellular levels of HMGB1 (7.44+/-0.63 vs. 0.21+/-0.05), IL-10 (315.19+/-79.13 vs. 59.19+/-23.30) and the intracellular expression of Notch1 (mRNA: 6.49+/-0.73 vs. 1.00+/-0.00), NICD (protein: 0.65+/-0.10 vs. 0.23+/-0.07), and Hes5 (mRNA: 7.30+/-0.85 vs. 1.00+/-0.00; protein: 0.96+/-0.10 vs. 0.54+/-0.07) (all P<0.01). DAPT treatment led to a decrease above the index serum levels of HMGB1 (6.22+/-0.71) and IL-10 (252.06+/-57.63), and of expression of Notch 1 (mRNA: 3.20+/-0.68), NICD (protein: 0.42+/-0.05), and Hes5 (mRNA: 4.72+/-0.67; protein: 0.84+/-0.09) (P<0.01 or <0.05).

CONCLUSIONThe Notch signaling pathway may plan an important role in the development of ALF upon activation of the pathway in macrophages by LPS and leading to promoted secretion of HMGB 1 and IL-10, with a greater effect on the former.