维生素E对大鼠肝星状细胞增殖及细胞外基质的影响

目的 观察维生素E（VE）对大鼠肝星状细胞（HSC）过氧化脂质和细胞外基质（ECM）产生的影响。方法 采用原位灌注方法分离大鼠HSC。结果 新分离的大鼠HC培养1w时具有增殖和ECM分泌的活性。VE可有效抑制大鼠HSC^3H-胸腺嗜啶（^3H-TdR）、^3H-脯氨酸（^3H-Pro）的掺入和Ⅲ型前胶原（PCⅢ）及透明质酸（HA）的分泌，VE作用后HSC产生丙二醛（MDA）下降，与分泌PCⅢ的抑制呈正相关。结论 VE可抑制大鼠HSC增殖和减少ECM的分泌。     

Myostatin regulates the fibrogenic phenotype of hepatic stellate cells via c-jun N-terminal kinase activation

Background & aimsMyostatin is mainly expressed in skeletal muscle, where it negatively regulates trophism. This myokine is implicated in the pathophysiology of nonalcoholic steatohepatitis, an emerging cause of liver fibrosis. In this study we explored the effects of myostatin on the biology of hepatic stellate cells.MethodsThe effects of myostatin were assessed both in LX-2 and in human primary stellate cells. Cell migration was determined in Boyden chambers. Activation of intracellular pathways was evaluated by Western blotting. Procollagen type 1 secretion was measured by enzyme immunoassay. The role of c-Jun N-terminal kinase was assessed by pharmacologic and genetic inhibition.ResultsActivin receptor-2B was up-regulated in livers of mice with experimental fibrosis, and detectable in human stellate cells. Serum myostatin levels increased in a model of acute liver injury. Myostatin reduced HSC proliferation, induced cell migration, and increased expression of procollagen type1, tissue inhibitor of metalloproteinase-1, and transforming growth factor-β1. Myostatin activated different signaling pathways, including c-Jun N-terminal kinase and Smad3. Genetic and/or pharmacologic inhibition of c-Jun N-terminal kinase activity significantly reduced cell migration and procollagen secretion in response to myostatin.ConclusionsActivation of activin receptor-2B by myostatin modulates the fibrogenic phenotype of human stellate cells, indicating that a myokine may be implicated in the pathogenesis of hepatic fibrosis.     

Intercellular communication via gap junctions in activated rat hepatic stellate cells

BACKGROUND AND AIMS: Gap junctional communication was studied in quiescent and activated hepatic stellate cells. METHODS: Connexin expression and intercellular dye transfer were studied in rat hepatic stellate cells in culture and in vivo. RESULTS: Protein expression of connexin 43 was up-regulated in activated hepatic stellate cells in vivo and in vitro and was mainly localized on the cell surface, whereas connexin 26 was found intracellularly. In contrast to hepatocytes, hepatic stellate cells do not express connexin 32. Confluent hepatic stellate cells in culture communicate via gap junctions, resulting in lucifer yellow transfer and propagation of intracellular calcium signals. Phorbol ester induces a protein kinase C-dependent hyperphosphorylation and degradation of connexin 43 and inhibits intercellular communication on a short-term time scale. At the long-term level, vitamin D(3) , lipopolysaccharide, thyroid hormone T(3), dexamethasone, platelet-derived growth factor, endothelin 1, and interleukin 1beta up-regulate connexin 43 protein and messenger RNA expression and enhance intercellular communication. Slight down-regulation of connexin 43 is observed in response to vitamin A. Connexin 43 induction by endothelin 1 is inhibited by both endothelin A and endothelin B receptor antagonists. In coculture systems, hepatic stellate cells communicate with each other, which is suggestive of a syncytial organization, but no communication was found between hepatic stellate cells and other liver cell types. As shown by immunohistochemistry and electron microscopy, gap junctions are formed between activated hepatic stellate cells in vivo. CONCLUSIONS: Gap junctional communication occurs between hepatic stellate cells, is enhanced after activation, and underlies complex regulation by cytokines, hormones, and vitamins.     

Immune stimulation of hepatic fibrogenesis by CD8 cells and attenuation by transgenic interleukin-10 from hepatocytes

BACKGROUNDS & AIMS: Immunomodulatory cytokines, including interleukin-10 (IL-10), may mediate hepatic fibrosis. METHODS: We generated transgenic (TG) mice with hepatocyte expression of rat IL-10 (rIL-10) to assess its impact on lymphocyte subsets and activation of hepatic stellate cells following liver injury from carbon tetrachloride (CCl 4 ) or thioacetamide (TAA). RESULTS: Fibrosis was reduced in the TG animals in both models, which was not explained solely by differences in liver injury. By fluorescence-activated cell sorter (FACS), there were less CD4+ T cells in naive TG mice, and, following fibrosis induction, CD4+ T cells decreased only in wild-type (WT) mice, whereas increases in CD8+ T cells seen in WT animals were significantly attenuated in TG mice. Subtotal irradiation diminished fibrosis equally in both WT and TG groups, suggesting that rIL-10's antifibrotic effect was lymphocyte mediated. To assess the role of lymphocytes on stellate cell activation, either whole splenic lymphocytes, CD4+, or CD8+ T-cell subsets from WT animals with CCl 4 fibrosis were adoptively transferred to severe combined immunodeficiency (SCID) recipients, which led to stellate cell activation and fibrogenic stimulation as assessed by expression of transforming growth factor (TGF)-beta1 and collagen I messenger RNA (mRNA) and by immunoblot of alpha-smooth muscle actin. Moreover, serum aminotransferase levels and stellate cell activation mRNA were significantly higher among the CD8+ T-cell recipients. CONCLUSIONS: Transgenic expression of rIL-10 in liver leads to reduced fibrosis and alterations in liver lymphocyte subsets both in untreated liver and following fibrosis induction. In this model, fibrosis may be a CD8+ T-cell-mediated disease that is attenuated by rIL-10.     

Pancreatic carcinoma cells induce fibrosis by stimulating proliferation and matrix synthesis of stellate cells

BACKGROUND & AIMS: Tumor desmoplasia is one of the representative histopathologic findings in ductal pancreatic adenocarcinoma. The aims of this study were to examine the cellular and molecular mechanisms of fibrogenesis associated with pancreatic adenocarcinomas. METHODS: Immunostainings were performed with human pancreatic adenocarcinomas (n = 27) and tumors induced in nude mice (n = 36) by subcutaneously injecting MiaPaCa2, Panc1, and SW850 with and without pancreatic stellate cells. Matrix-producing cells were isolated from pancreatic adenocarcinomas and compared with pancreatic stellate cells isolated from tissue of chronic pancreatitis. Paracrine stimulation of pancreatic stellate cells by carcinoma cells was studied regarding matrix synthesis (collagen and c-fibronectin on protein and messenger RNA level) and cell proliferation (bromodeoxyuridine incorporation). RESULTS: High numbers of desmin and alpha-smooth muscle actin-positive cells were detected in 26 of 27 pancreatic adenocarcinomas. Intense fibronectin and collagen stainings were associated with these cells. By using cytofilament stainings, gene expression profiling, and morphological examinations, the matrix-producing cells obtained by the outgrowth method from pancreatic adenocarcinomas were identified as pancreatic stellate cells. Supernatants of MiaPaCa2, Panc1, and SW850 cells stimulated proliferation and collagen type I and c-fibronectin synthesis of cultured pancreatic stellate cells. Preincubation of the carcinoma cell supernatants with neutralizing antibodies against fibroblast growth factor 2, transforming growth factor beta 1, and platelet-derived growth factor significantly reduced the stimulatory effects. Subcutaneous injection of carcinoma cells and pancreatic stellate cells induced fast-growing subcutaneous fibrotic tumors in nude mice. Morphometric analysis of carcinoma cells (cytokeratin stainings) showed a high density of carcinoma cells in these tumors. CONCLUSIONS: Pancreatic stellate cells strongly support tumor growth in the nude mouse model. The increased deposition of connective tissue in pancreatic carcinoma is the result of a paracrine stimulation of pancreatic stellate cells by carcinoma cells.     

Significance and therapeutic potential of endothelial progenitor cell transplantation in a cirrhotic liver rat model

BACKGROUND & AIMS: We investigated whether endothelial progenitor cell (EPC) transplantation could reduce established liver fibrosis and promote hepatic regeneration by isolating rat EPCs from bone marrow cells. METHODS: Recipient rats were injected intraperitoneally with carbon tetrachloride (CCl(4)) twice weekly for 6 weeks before initial administration of EPCs. CCl(4) was then readministered twice weekly for 4 more weeks, and EPC transplantation was carried out for these same 4 weeks. RESULTS: At 7 days in culture, the cells expressed Thy-1, CD31, CD133, Flt-1, Flk-1, and Tie-2, suggesting an immature endothelial lineage. Immunohistochemical analyses showed fluorescent-labeled, transplantation EPCs were incorporated into the portal tracts and fibrous septa. Single and multiple EPC transplantation rats had reduced liver fibrosis, with decreased alpha2-(I)-procollagen, fibronectin, transforming growth factor-beta, and alpha-smooth muscle actin-positive cells. Film in situ zymographic analysis revealed strong gelatinolytic activity in the periportal area, in accordance with EPC location. Real-time polymerase chain reaction analysis of multiple EPC-transplantation livers showed significantly increased messenger RNA levels of matrix metalloproteinase (MMP)-2, -9 and -13, whereas tissue inhibitor of metalloproteinase-1 expression was significantly reduced. Expression of hepatocyte growth factor, transforming growth factor-alpha, epidermal growth factor, and vascular endothelial growth factor was increased in multiple EPC-transplantation livers, while hepatocyte proliferation increased. Transaminase, total bilirubin, total protein, and albumin levels were maintained in EPC-transplantation rats, significantly improving survival rates. CONCLUSIONS: We conclude that single or repeated EPC transplantation halts established liver fibrosis in rats by suppressing activated hepatic stellate cells, increasing matrix metalloproteinase activity, and regulating hepatocyte proliferation.     

Tetramethylpyrazine reduces glucose and insulin-induced activation of hepatic stellate cells by inhibiting insulin receptor-mediated PI3K/AKT and ERK pathways

Hepatic stellate cell (HSC) activation is the central event during liver fibrogenesis. Metabolic syndrome characterized by hyperglycemia and hyperinsulinemia contributes to nonalcoholic steatohepatitis-associated liver fibrosis. This study was to investigate the effects of tetramethylpyrazine (TMP) on HSC activation induced by glucose and insulin (Glu/Ins) and the underlying mechanisms. Results showed that Glu/Ins significantly stimulated proliferation, invasion, adhesion, and extracellular matrix (ECM) production in HSCs. TMP inhibited HSC proliferation, invasion and adhesion, and reduced the expression of marker genes related to HSC activation in Glu/Ins-activated HSCs. Mechanistic evidence revealed that TMP reduced insulin receptor (InsR) expression and blocked the downstream phosphatidylinositol-3-kinase (PI3K)/AKT and extracellular signal-regulated kinase (ERK) cascades, which was required for TMP attenuation of HSC activation. Moreover, TMP modulated the genes relevant to ECM homeostasis favoring ECM degradation. It could be concluded that TMP inhibited Glu/Ins-stimulated HSC activation and ECM production by inhibiting InsR-mediated PI3K/AKT and ERK pathways.     

Role of tumor necrosis factor receptor 2 (TNFR2) in colonic epithelial hyperplasia and chronic intestinal inflammation in mice.

BACKGROUND & AIMS: Tumor necrosis factor (TNF) induces multiple effects including cell proliferation and death by ligation with TNF receptor type II (TNFR2). We studied the role of TNFR2 in chronic inflammation-induced colonic epithelial alteration. METHODS: TNFR2 expression in colonic epithelial cells (CECs) was assessed by ribonuclease protection assay (RPA) and immunohistochemistry (IHC) in patients with inflammatory bowel disease (IBD) and murine colitis models. TNFR2 expression was also analyzed using COLO205 cells. The role of TNFR2 in colonic epithelial homeostasis was examined by generating interleukin 6-deficient TCR alpha KO (alpha IL-6DKO) or TNFR2-deficient TCR alpha (alpha TNFR2DKO) mice. RESULTS: TNFR2 expression was up-regulated in CEC in both human ulcerative colitis and Crohn's disease. In vitro studies showed that TNFR2 expression was up-regulated by a cooperative effect of key proinflammatory cytokines. By RPA, the increased expression of TNFR2 was detectable in TCR alpha KO mice with colitis compared with TCR alpha KO mice without colitis or wild-type mice. In alpha IL-6DKO mice, TNFR2 expression, proliferation, and nuclear factor kappa B activation of CECs were markedly reduced compared with TCR alpha KO mice. alpha TNFR2 mice also showed significantly less colonic epithelial proliferation compared with TCR alpha KO mice. CONCLUSIONS: Expression of TNFR2 is consistently increased on CECs in both murine colitis models as well as patients with IBD. TNFR2 may play an important role in colonic inflammation-associated alteration in the intestinal epithelium.     

Smad7 prevents activation of hepatic stellate cells and liver fibrosis in rats

BACKGROUND & AIMS: Numerous studies implicate transforming growth factor (TGF)-beta signaling in liver fibrogenesis. To perturb the TGF-beta pathway during this process, we overexpressed Smad7, an intracellular antagonist of TGF-beta signaling, in vivo and in primary-cultured hepatic stellate cells (HSCs). METHODS: Ligation of the common bile duct (BDL) was used to induce liver fibrosis in rats. Animals received injections of an adenovirus carrying Smad7 cDNA into the portal vein during surgery and via the tail vein at later stages. The effect of Smad7 on TGF-beta signaling and activation of HSC was further analyzed in primary-cultured cells. RESULTS: Smad7-overexpressing BDL rats displayed reduced collagen and alpha-SMA expression and reduced hydroxyproline content in the liver, when compared with animals administered AdLacZ. Such a beneficial effect was also observed when Smad7 was expressed in animals with established fibrosis. Accordingly, Smad7 arrested transdifferentiation of primary-cultured HSCs. AdSmad7 infected cells remained in a quiescent stage and retained storage of vitamin A droplets. Smad7 expression totally blocked TGF-beta signal transduction, shown by inhibiting Smad2/3 phosphorylation, nuclear translocation of activated Smad complexes, and activation of (CAGA)(9)-MLP-Luc, resulting in decreased collagen I expression. Smad7 also abrogated TGF-beta-dependent proliferation inhibition of HSC. Smad7 did not decrease expression of alpha-SMA, but immunofluorescent staining with anti alpha-SMA antibodies displayed destruction of the fibrillar organization of the actin cytoskeleton. CONCLUSIONS: In summary, gene transfer of Smad7 inhibits experimental fibrogenesis in vivo. Studies with isolated HSC suggest that the underlying mechanisms involve inhibition of TGF-beta signaling and HSC transdifferentiation.     

Leptin enhances cytokine/chemokine production by normal lung fibroblasts by binding to leptin receptor

BackgroundObesity is a known risk and exacerbation factor for bronchial asthma. Leptin is an adipokine secreted by adipocytes and enhances energy consumption. Earlier studies have shown that leptin also activates inflammatory cells and structural cells, including airway epithelial cells, thereby exacerbating inflammation. However, little is known about leptin's effect on normal human lung fibroblasts (NHLFs), which are deeply involved in airway remodeling in asthma. This study aimed to elucidate the direct effect of leptin on NHLFs.MethodsNHLFs were co-cultured with leptin, and production of cytokines/chemokines was analyzed with real-time PCR and cytometric bead arrays (CBA). Expression of alpha smooth muscle actin (α-SMA) in the lysate of NHLFs stimulated with leptin was assessed by western blotting. Expression of leptin receptor (Ob-R) was analyzed by real-time PCR and flow cytometry. NHLFs were transfected with Ob-R small interference ribonucleic acid (siRNA) by electroporation and used for experiments.ResultsLeptin enhanced production of CCL11/Eotaxin, monocyte chemoattractant protein-1 (CCL2/MCP-1), CXCL8/IL-8, interferon gamma-induced protein 10 (CXCL10/IP-10) and IL-6 by NHLFs at both the protein and messenger ribonucleic acid (mRNA) levels. Leptin also slightly, but significantly, elevated expression of α-SMA. We found robust Ob-R expression on cell surfaces, and transfection with Ob-R siRNA suppressed the enhanced production of CCL11/Eotaxin, CXCL10/IP-10 and IL-6 by leptin, although not completely.ConclusionsThese findings indicate that leptin may contribute to worsening of asthma in obese patients by enhancing production of inflammatory mediators by binding to Ob-R and accelerating myofibroblast differentiation.