Roles of peroxisome proliferator-activated receptor-α in acute liver failure and its pathogenetic mechanism in mice

Abstract

To explore the protective effects of peroxisome proliferator-activated receptor-α (PPAR α) in D-GalN/LPS-induced acute liver failure (ALF) and its pathogenetic mechanism. C57BL/6 mice were randomly divided into control, ALF, WY14643, 3-MA+WY14643, siAtg7+WY14643 and control siRNA+WY14643 groups (n = 8 each).For inducing ALF, the mice were injected intraperitoneally with D-GalN (700 mg/kg) and LPS (10 µg/kg). The selective activator of PPAR α-WY14643 (6 mg/kg) and autophagy inhibitor 3-MA (10 mg/kg) were administered via tail vein at 2 hours prior to D-GalN/LPS exposure. The autophagy inhibitor siAtg7 (50 µmol × L⁻¹ × kg⁻¹) and control siRNA (50 µmol × L⁻¹ × kg⁻¹) were dosed via tail vein at 48 hours prior to D-GalN/LPS exposure. At 6 hours after D-GalN/LPS dosing, the mice were anesthetized and blood sample collected.Liver samples were freshly harvested for preparing mRNA.Liver histology and serum levels of aminotransferase (ALT), aspartate aminotransferase (AST) were measured as markers of hepatic damage. Autophagy related genes (ATG5, ATG7, LAMP1), inflammatory cytokines (TNF-α, IL-1β, IL-6) and chemokines (CXCL-1, CXCL-10) were detected by real-time quantitative PCR. Differential protein expressions of LC3, ATG5, ATG7, LAMP1 in autophagy pathways were detected by Western blotting. Compared with the model group, the hepatic architecture of WY14643-treated mice was better preserved. And the serum levels of ALT and AST were significantly lower ((486 ± 56) vs (2 705 ± 423) U/L, (795 ± 115) vs (3 709 ± 820) U/L, both P < 0.05) while the expression of autophagy related gene LAMP1 and protein levels were significantly higher (mRNA:4.28 ± 0.57 vs 2.67 ± 0.43, P < 0.05) . As compared with WY14643-treated ALF, the mice receiving 3-MA or ATG7-specific siRNA suffered severe acute liver failure again as evidenced by worse preserved hepatic architecture, significantly higher levels of ALT and AST ((2 563 ± 576), (2 148 ± 221) U/L and (3 474 ± 858), (3 305 ± 632) U/L, all P < 0.05) and mRNA levels of proinflammatory cytokines and chemokines (all P < 0.05). PPARα-mediated induction of autophagy ameliorates liver injury in ALF by attenuating inflammatory responses. Thus it may become a potential target for ALF treatment.