gw9662 and Chemical-and-Drug-Induced-Liver-Injury

Apigenin has a protective effect on D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced mouse liver injury through the increments of hepatic nuclear factor erythroid 2-related factor 2 (Nrf-2) and peroxisome proliferator-activated receptor γ (PPARγ) expressions, but its exact mechanisms are still uncertain. This study aimed to further verify its protective effect on hepatocytes and to determine its target of action. The results showed that after treatment of D-GalN/LPS-stimulated hepatocytes with 2.5-20 μM apigenin, the supernatant alanine aminotransferase, aspartate aminotransferasein, tumor necrosis factor-α, and malondialdehyde levels and intracellular nuclear factor-κB protein expression were decreased, while the supernatant superoxide dismutase (SOD) and catalase (CAT) levels, intracellular PPARγ and inhibitor of kappa B-alpha protein expressions, and nucleus Nrf-2 protein expression were increased. After pretreatment with BML-111 or GW9662, the apigenin-induced nucleus Nrf-2 or intracellular PPARγ protein expressions were completely inhibited, respectively, but the both pretreatment differently affected the protective effect of apigenin on hepatocytes. The former completely canceled the protective effect, whereas the latter did not. These findings further demonstrate that apigenin can exert a protective effect on D-GalN/LPS-induced hepatocellular injury via the increment of Nrf-2 nucleus translocation, which may increase the SOD and CAT levels and PPARγ protein expression and subsequently inhibit the inflammatory response.

Topics: Active Transport, Cell Nucleus; Anilides; Animals; Apigenin; Cell Nucleus; Cells, Cultured; Chemical and Drug Induced Liver Injury; Galactosamine; Heptanoic Acids; Lipopolysaccharides; NF-E2-Related Factor 2; NF-kappa B; PPAR gamma; Rats

The NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes the oxidation of the 15(S)-hydroxyl group of prostaglandin E2 (PGE2), converting the pro-inflammatory PGE2 to the anti-inflammatory 15-keto-PGE2 (an endogenous ligand for peroxisome proliferator-activated receptor-gamma [PPAR-γ]). To evaluate the significance of 15-PGDH/15-keto-PGE2 cascade in liver inflammation and tissue injury, we generated transgenic mice with targeted expression of 15-PGDH in the liver (15-PGDH Tg) and the animals were subjected to lipopolysaccharide (LPS)/Galactosamine (GalN)-induced acute liver inflammation and injury. Compared to the wild type mice, the 15-PGDH Tg mice showed lower levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), less liver tissue damage, less hepatic apoptosis/necrosis, less macrophage activation, and lower inflammatory cytokine production. In cultured Kupffer cells, treatment with 15-keto-PGE2 or the conditioned medium (CM) from 15-PGDH Tg hepatocyes inhibited LPS-induced cytokine production, in vitro. Both 15-keto-PGE2 and the CM from15-PGDH Tg hepatocyes also up-regulated the expression of PPAR-γ downstream genes in Kupffer cells. In cultured hepatocytes, 15-keto-PGE2 treatment or 15-PGDH overexpression did not influence TNF-α-induced hepatocyte apoptosis. These findings suggest that 15-PGDH protects against LPS/GalN-induced liver injury and the effect is mediated via 15-keto-PGE2, which activates PPAR-γ in Kupffer cells and thus inhibits their ability to produce inflammatory cytokines. Accordingly, we observed that the PPAR-γ antagonist, GW9662, reversed the effect of 15-keto-PGE2 in Kupffer cell in vitro and restored the susceptibility of 15-PGDH Tg mice to LPS/GalN-induced acute liver injury in vivo. Collectively, our findings suggest that 15-PGDH-derived 15-keto-PGE2 from hepatocytes is able to activate PPAR-γ and inhibit inflammatory cytokine production in Kupffer cells and that this paracrine mechanism negatively regulates LPS-induced necro-inflammatory response in the liver. Therefore, induction of 15-PGDH expression or utilization of 15-keto-PGE2 analogue may have therapeutic benefits for the treatment of endotoxin-associated liver inflammation/injury.

Topics: Alanine Transaminase; Anilides; Animals; Aspartate Aminotransferases; Chemical and Drug Induced Liver Injury; Culture Media, Conditioned; Dinoprostone; Gene Expression Regulation; Hepatocytes; Humans; Hydroxyprostaglandin Dehydrogenases; Kupffer Cells; Lipopolysaccharides; Liver; Macrophage Activation; Macrophages; Mice; Mice, Transgenic; Paracrine Communication; PPAR gamma; Primary Cell Culture; Signal Transduction; Transgenes; Tumor Necrosis Factor-alpha