Interleukin-17A plays a pivotal role after partial hepatectomy in mice.

Liver regeneration after partial hepatectomy (PH) is regulated by tumor necrosis factor (TNF)-α derived from the Kupffer cell. Furthermore, it was reported from our laboratory that interleukin (IL)-17A enhances the production of TNF-α by the Kupffer cell, suggesting that IL-17A may play a role in liver regeneration. The purpose was to determine the role of IL-17A and the spleen in liver regeneration after PH. Two mouse models including the wild-type (WT) mice or the IL-17A knockout (KO) mice underwent PH. Animals were killed at the designated time points; liver tissues were harvested for further investigation. Proliferation of hepatocytes was evaluated. Furthermore, the messenger RNA and protein expression of TNF-α and IL-6 were measured in the liver. In another set of experiments, the two animal models underwent splenectomy before PH. In an in vitro study, CD4-positive lymphocytes in the spleen were isolated from mice, and the number of IL-17A-positive cells was investigated. Liver regeneration was significantly impaired in the KO mice compared with the WT mice. This was associated with suppression of cell proliferation assessed by cell proliferation markers in the KO mice. In the WT mice that underwent splenectomy, liver regeneration was significantly delayed compared with animals without splenectomy. In contrast, splenectomy did not affect liver regeneration in the KO mice. IL-17A-positive lymphocytes increased significantly in the spleen in the WT mice after PH. These results indicate that IL-17A derived from CD4-positive lymphocytes in the spleen is a key regulator in liver regeneration after PH.

Furuya S ，Kono H ，Hara M ，Hirayama K ，Tsuchiya M ，Fujii H ... -  《-》

Interleukin-17A plays a pivotal role in cholestatic liver fibrosis in mice.

It was recently reported that serum interleukin (IL)-17 levels increased in liver fibrosis associated with human alcoholic liver disease. However, the role of IL-17 in liver fibrosis has not yet been elucidated. Therefore, the aim of this study was to evaluate the role of IL-17 on cholestatic liver fibrosis. IL-17A knockout (KO) and wild-type (WT) mice were subjected to bile duct ligation. Animals were sacrificed at designated times, and serum and liver tissues were collected. The mRNA expression of hepatic fibrotic markers was assessed, and distribution of activated hepatic stellate cells (HSCs) was determined by immunohistochemical staining. In an in vitro study, Kupffer cells (KCs) and HSCs were isolated from WT mice. KCs were cultured with IL-17A or IL-17F, and production of tumor necrosis factor α (TNF-α) and transforming growth factor β1 (TGF-β1) was measured. HSCs were cultured with IL-17A or IL-17F, and morphologic changes were assessed by immunohistochemical staining. Liver damage observed in the WT mice was significantly improved in the KO mice. Serum TNF-α and TGF-β1 levels were significantly decreased in the KO compared with the WT mice. The hepatic mRNA expression of TNF-α, TGF-β1, and collagen 1α1, which increased in the WT mice, also significantly decreased in the KO mice. Increased hepatic fibrosis in the WT mice was significantly improved in the KO mice. Cytokine production was increased in IL-17A-treated KCs. The most remarkable myofibroblast-like changes were observed in isolated HSCs in the presence of IL-17A. IL-17A was involved in the pathogenesis of cholestatic liver fibrosis by activation of both the KCs and HSCs.

Hara M ，Kono H ，Furuya S ，Hirayama K ，Tsuchiya M ，Fujii H ... -  《-》

Liver regeneration is impaired in macrophage colony stimulating factor deficient mice after partial hepatectomy: the role of M-CSF-induced macrophages.

Macrophage colony stimulating factor (M-CSF), which induces maturation of macrophages, is notably expressed in the liver. Thus, the specific purpose of this study was to investigate the role of M-CSF in liver regeneration after partial hepatectomy (PH). Osteopetrotic (op/op) mice, genetically lacking functional M-CSF, or their littermate mice underwent 70% PH. Animals were sacrificed at the designated time points after PH, and remnant liver tissues were harvested for further investigations. Proliferation of hepatocytes was evaluated by the expression of BrdU and the liver-body weight ratio. The mRNA expression levels of TNF-α and IL-6 and protein expression levels of phosphorylated (p) STAT3 were measured. The number of Kupffer cells (KCs) was determined by immunohistochemistry. Furthermore, KCs were isolated from op/op mice or littermate mice, and mRNA expression levels of TNF- α and IL-6 were assessed after stimulation with LPS. In littermate mice, steady liver regeneration was observed. The number of KCs reduced markedly by about 60% in the op/op mice compared with littermates as reported previously. Furthermore, these cells were morphologically small and immature. In littermate mice, the peak expression levels of TNF-α and IL-6 in the liver was observed 1h after PH, which was consistent with data in previous reports. In contrast, in op/op mice, the peak expression levels were observed 3 h after PH and were significantly lower compared with littermate mice. As a result, the proliferation of hepatocytes was significantly impaired in op/op mice. The mRNA expression level of IL-6, but not TNF-α,was significantly reduced in isolated KCs from op/op mice compared with the littermates after stimulation with LPS, suggesting that the function of KCs is different between op/op mice and littermate mice. To clarify the role of M-CSF in liver regeneration, op/op mice received intraperitoneally, mouse recombinant M-CSF 2 d before PH, and liver regeneration was also assessed. As a result, the numbers of Kupffer cells and liver regeneration were recovered in the op/op mice treated with M-CSF to a similar extent to those in their littermates. Thus, M-CSF-induced hepatic macrophages play an important role in liver regeneration after PH.

Amemiya H ，Kono H ，Fujii H 《-》

Role of IL-17A in neutrophil recruitment and hepatic injury after warm ischemia-reperfusion mice.

Kono H ，Fujii H ，Ogiku M ，Hosomura N ，Amemiya H ，Tsuchiya M ，Hara M ... -  《-》

Interleukin 17A plays a role in lipopolysaccharide/D-galactosamine-induced fulminant hepatic injury in mice.

Lipopolysaccharide/d-galactosamine (LPS/GalN)-induced hepatic injury is an experimental model of fulminant hepatic failure in which tumor necrosis factor alpha (TNF-α) plays a pivotal role. Moreover, it was reported from our laboratory that interleukin (IL) 17A enhanced production of TNF-α by the Kupffer cell. The purpose of this study was to determine the role of IL-17A in LPS/GalN-induced hepatic injury in mice. LPS/GalN was injected into three mouse models: wild-type (WT) mice, IL-17A knockout (KO) mice, or IL-17A KO mice treated with recombinant mouse (rm) IL-17A homodimer (KO + rmIL-17A). Survival was assessed for 24 h after LPS/GalN injection, and histopathologic findings were evaluated at various time points after LPS/GalN injection for neutrophil and apoptosis markers. After LPS/GalN injection, expression of the inflammatory mediators TNF-α, IL-6, monocyte chemotactic protein 1, IL-17A, high-mobility group box 1, and soluble intercellular adhesion molecule 1 was assessed in serum by enzyme-linked immunosorbent assay. Survival was higher in KO mice compared with WT mice after LPS/GalN injection. However, in KO + rmIL-17A mice, mortality was not significantly different compared to the other groups. Neutrophil infiltration and apoptosis were significantly greater in WT mice than KO mice. Furthermore, serum alanine aminotransferase, serum TNF-α, monocyte chemotactic protein 1, IL-17A, high-mobility group box 1, and soluble intercellular adhesion molecule 1 levels were also significantly greater in WT mice than KO mice. In KO + rmIL-17A mice, these levels were similar to those in WT mice. IL-17A is a key regulator in hepatic injury caused by neutrophil-induced inflammatory responses after LPS/GalN injection.

Furuya S ，Kono H ，Hara M ，Hirayama K ，Sun C ，Fujii H ... -  《-》