Changes in growth factor and cytokine expression in biliary obstructed rat liver and their relationship with delayed liver regeneration after partial hepatectomy.
Makino Hironobu,Shimizu Hiroaki,Ito Hiroshi,Kimura Fumio,Ambiru Satoshi,Togawa Akira,Ohtsuka Masayuki,Yoshidome Hiroyuki,Kato Atsushi,Yoshitomi Hideyuki,Sawada Shigeaki,Miyazaki Masaru
World journal of gastroenterology
AIM:To study the effects of obstructive jaundice on liver regeneration after partial hepatectomy. METHODS:Hepatocyte growth factor (HGF), its receptor, c-Met, vascular endothelial growth factor (VEGF) and transforming growth factor-beta1 (TGF-beta1) mRNA expression in both liver tissue and isolated liver cells were investigated after biliary obstruction (BO) by quantitative reverse-transcription polymerase chain reaction (RT-PCR) using a LightCycler. Immunohistochemical staining for desmin and alpha-smooth muscle actin (alpha-SMA) was also studied. Regenerating liver weight and proliferating cell nuclear antigen (PCNA) labeling index, and growth factor expression were then evaluated after 70% hepatectomy with concomitant internal biliary drainage in BO rats or sham-operated rats. RESULTS:Hepatic TGF-beta1 mRNA levels increased significantly 14 days after BO, and further increased with duration of cholestasis. Meanwhile, HGF and VEGF tended to increase, but was not significant. In cell isolates, TGF-beta1 mRNA was found mainly in the hepatic stellate cell (HSC) fraction. Immunohistochemical studies revealed an increased number of HSCs (desmin-positive cells) and activated HSCs (alpha-SMA-positive cells) in portal areas after BO. In a hepatectomy model, liver regeneration was delayed in BO rats, as compared to sham-operated rats. TGF-beta1 mRNA was significantly up-regulated up to 48 h after hepatectomy, and the earlier HGF mRNA peak was lost in BO rats. CONCLUSION:BO induces HSCs proliferation and activation, leading to up-regulation of TGF-beta1 mRNA and suppression of HGF mRNA in livers. These altered expression patterns may be strongly involved in delayed liver regeneration after hepatectomy with obstructive jaundice.
IL-17A synergistically enhances bile acid-induced inflammation during obstructive cholestasis.
O'Brien Kate M,Allen Katryn M,Rockwell Cheryl E,Towery Keara,Luyendyk James P,Copple Bryan L
The American journal of pathology
During obstructive cholestasis, increased concentrations of bile acids activate ERK1/2 in hepatocytes, which up-regulates early growth response factor 1, a key regulator of proinflammatory cytokines, such as macrophage inflammatory protein 2 (MIP-2), which, in turn, exacerbates cholestatic liver injury. Recent studies have indicated that IL-17A contributes to hepatic inflammation during obstructive cholestasis, suggesting that bile acids and IL-17A may interact to regulate hepatic inflammatory responses. We treated mice with an IL-17A neutralizing antibody or control IgG and subjected them to bile duct ligation. Neutralization of IL-17A prevented up-regulation of proinflammatory cytokines, hepatic neutrophil accumulation, and liver injury, indicating an important role for IL-17A in neutrophilic inflammation during cholestasis. Treatment of primary mouse hepatocytes with taurocholic acid (TCA) increased the expression of MIP-2. Co-treatment with IL-17A synergistically enhanced up-regulation of MIP-2 by TCA. In contrast to MIP-2, IL-17A did not affect up-regulation of Egr-1 by TCA, indicating that IL-17A does not affect bile acid-induced activation of signaling pathways upstream of early growth response factor 1. In addition, bile acids increased expression of IL-23, a key regulator of IL-17A production in hepatocytes in vitro and in vivo. Collectively, these data identify bile acids as novel triggers of the IL-23/IL-17A axis and suggest that IL-17A promotes hepatic inflammation during cholestasis by synergistically enhancing bile acid-induced production of proinflammatory cytokines by hepatocytes.
FXR agonist obeticholic acid induces liver growth but exacerbates biliary injury in rats with obstructive cholestasis.
van Golen Rowan F,Olthof Pim B,Lionarons Daniël A,Reiniers Megan J,Alles Lindy K,Uz Zehra,de Haan Lianne,Ergin Bulent,de Waart Dirk R,Maas Adrie,Verheij Joanne,Jansen Peter L,Damink Steven W Olde,Schaap Frank G,van Gulik Thomas M,Heger Michal
Cholestasis impairs liver regeneration following partial liver resection (PHx). Bile acid receptor farnesoid X-receptor (FXR) is a key mediator of liver regeneration. The effects of FXR agonist obeticholic acid (OCA) on liver (re)growth were therefore studied in cholestatic rats. Animals underwent sham surgery or reversible bile duct ligation (rBDL). PHx with concurrent internal biliary drainage was performed 7 days after rBDL. Animals were untreated or received OCA (10 mg/kg/day) per oral gavage from rBDL until sacrifice. After 7 days of OCA treatment, dry liver weight increased in the rBDL + OCA group, indicating OCA-mediated liver growth. Enhanced proliferation in the rBDL + OCA group prior to PHx concurred with a rise in Ki67-positive hepatocytes, elevated hepatic Ccnd1 and Cdc25b expression, and an induction of intestinal fibroblast growth factor 15 expression. Liver regrowth after PHx was initially stagnant in the rBDL + OCA group, possibly due to hepatomegaly prior to PHx. OCA increased hepatobiliary injury markers during BDL, which was accompanied by upregulation of the bile salt export pump. There were no differences in histological liver injury. In conclusion, OCA induces liver growth in cholestatic rats prior to PHx but exacerbates biliary injury during cholestasis, likely by forced pumping of bile acids into an obstructed biliary tree.