Aim: To determine the therapeutic potential of sphingosine kinase 1 (Sphk1) inhibition and its underlying mechanism in a well-characterized mouse model of D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced acute liver failure (ALF).
Methods: Balb/c mice were randomly assigned to different groups, with ALF induced by intraperitoneal injection of D-GaIN (600 mg/kg) and LPS (10 μg/kg). The Kaplan-Meier method was used for survival analysis. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels at different time points within one week were determined using a multi-parametric analyzer. Serum high-mobility group box 1 (HMGB1), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, IL-10, and sphingosine-1-phosphate were detected by enzyme-linked immunosorbent assay. Hepatic morphological changes at 36 h after acute liver injury induction were assessed by hematoxylin and eosin staining. HMGB1 expression in hepatocytes and cytoplasmic translocation were detected by immunohistochemistry. Expression of Sphk1 in liver tissue and peripheral blood mononuclear cells (PBMCs) was analyzed by Western blot.
Results: The expression of Sphk1 in liver tissue and PBMCs was upregulated in GalN/LPS-induced ALF. Upregulated Sphk1 expression in liver tissue was mainly caused by Kupffer cells, the resident macrophages of the liver. The survival rates of mice in the N,N-dimethylsphingosine (DMS, a specific inhibitor of SphK1) treatment group were significantly higher than that of the control group (P < 0.001). DMS treatment significantly decreased the levels of serum ALT and AST at 6, 12, and 24 h compared with that of the control group (P < 0.01 for all). Serum HMGB1 levels at 6, 12, and 24 h, as well as serum TNF-α, IL-6, and IL-1β levels at 12 h, were significantly lower in the DMS treatment group than in the control group (P < 0.01 for all). Furthermore, hepatic inflammation, necrosis, and HMGB1 cytoplasm translocation in liver cells were significantly decreased in the DMS treatment group compared to the control group (43.72% ± 5.51% vs 3.57% ± 0.83%, χ(2) = 12.81, P < 0.01).
Conclusion: Inhibition of SphK1 ameliorates ALF by reducing HMGB1 cytoplasmic translocation in liver cells, and so might be a potential therapeutic strategy for this disease.
Keywords: Acute liver failure; Cytoplasmic translocation; High-mobility group box 1; Inflammatory cytokine; Sphingosine kinase 1.