301
|
Jaster R, Lichte P, Fitzner B, Brock P, Glass A, Karopka T, Gierl L, Koczan D, Thiesen HJ, Sparmann G, Emmrich J, Liebe S. Peroxisome proliferator-activated receptor gamma overexpression inhibits pro-fibrogenic activities of immortalised rat pancreatic stellate cells. J Cell Mol Med 2005; 9:670-82. [PMID: 16202214 PMCID: PMC6741639 DOI: 10.1111/j.1582-4934.2005.tb00497.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pancreatic stellate cells (PSCs) play a key role in the development of pancreatic fibrosis, a constant feature of chronic pancreatitis and pancreatic cancer. In response to pro-fibrogenic mediators, PSCs undergo an activation process that involves proliferation, enhanced production of extracellular matrix proteins and a phenotypic transition towards myofibroblasts. Ligands of the peroxisome proliferator-activated receptor gamma (PPARgamma), such as thiazolidinediones, are potent inhibitors of stellate cell activation and fibrogenesis in pancreas and liver. The effects of PPARgamma ligands, however, are at least in part mediated through PPARgamma-independent pathways. Here, we have chosen a different approach to study regulatory functions of PPARgamma in PSCs. Using immortalised rat PSCs, we have established a model of tetracycline (tet)-regulated PPARgamma overexpression. Induction of PPARgamma expression strongly inhibited proliferation and enhanced the rate of apoptotic cell death. Furthermore, PPARgamma-overexpressing cells synthesised less collagen than controls. To monitor effects of PPARgamma on PSC gene expression, we employed Affymetrix microarray technology. Using stringent selection criteria, we identified 21 up- and 19 down-regulated genes in PPARgamma-overexpressing cells. Most of the corresponding gene products are either involved in lipid metabolism, play a role in signal transduction, or are secreted molecules that regulate cell growth and differentiation. In conclusion, our data suggest an active role of PPARgamma in the induction of a quiescent PSC phenotype. PPARgamma-regulated genes in PSCs may serve as novel targets for the development of antifibrotic therapies.
Collapse
Affiliation(s)
- Robert Jaster
- Department of Medicine, Division of Gastroenterology, Medical Faculty, University of Rostock, Rostock, 18057, Germany.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
302
|
Kim KA, Lim YS, Kim KM, Yoon JH, Lee HS. 15d-Deoxy-Delta12,14-prostaglandin J2 modulates collagen type I synthesis in human hepatic stellate cells by inducing oxidative stress. Prostaglandins Leukot Essent Fatty Acids 2005; 73:361-7. [PMID: 16098720 DOI: 10.1016/j.plefa.2005.06.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Revised: 05/24/2005] [Accepted: 06/18/2005] [Indexed: 10/25/2022]
Abstract
15 deoxy-Delta(12,14)-prostaglandin(2) (15d-PGJ(2)) is known to inhibit the proliferation of hepatic stellate cells (HSCs), major cellular components that cause hepatic fibrosis, in vitro. It also induces oxidative stress, which results in hepatic myofibroblast death. On the other hand, oxidative stress generally induces HSC proliferation and collagen synthesis in vitro, and liver fibrogenesis in vivo. In this study, we evaluated the effects of 15d-PGJ(2) at various concentrations on the viability and collagen synthesis of HSCs. 15d-PGJ(2) increased intracellular reactive oxygen species (ROS), and reduced the viability of human HSCs at concentrations 5 microM by inducing apoptotic cell death. In addition, the antioxidants alpha-tocopherol and N-acetylcysteine (NAC) blocked 15d-PGJ(2)-induced HSC death. Collagen I synthesis was increased 1.5-fold by 0.5 microM 15d-PGJ(2) treatment, but was reduced to 30% of the control level by 10 microM 15d-PGJ(2), and NAC pretreatment prevented these changes in collagen production by 15d-PGJ(2). We conclude that 15d-PGJ(2) may either induce or prevent hepatic fibrogenesis depending on its concentration.
Collapse
Affiliation(s)
- Kyung-Ah Kim
- Department of Internal Medicine and Liver Research Institute, Seoul National University Hospital, Seoul National University College of Medicine, Chongno-gu, Republic of Korea
| | | | | | | | | |
Collapse
|
303
|
Schnabl B, Hu K, Mühlbauer M, Hellerbrand C, Stefanovic B, Brenner DA, Schölmerich J. Zinc finger protein 267 is up-regulated during the activation process of human hepatic stellate cells and functions as a negative transcriptional regulator of MMP-10. Biochem Biophys Res Commun 2005; 335:87-96. [PMID: 16054593 DOI: 10.1016/j.bbrc.2005.07.043] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 07/13/2005] [Indexed: 01/06/2023]
Abstract
Activation of hepatic stellate cells (HSCs) is the central event in the development of liver fibrosis and cirrhosis. The transdifferentiation process of quiescent into activated HSCs requires a complete reprogramming in gene expression, which is governed by modulation of transcriptional activators or repressors. Using microarray analysis to identify genes differentially expressed during the activation process of human HSCs, zinc finger protein 267 (ZNF267) mRNA was up-regulated in activated HSCs and in cirrhotic human liver. ZNF267 belongs to the family of Kruppel-like zinc fingers and contains a conserved KRAB (Kruppel associated box) A and B domain in the N-terminal part outside the C-terminal region of zinc fingers. ZNF267 constructs containing enhanced cyan fluorescence protein were constitutively localized in the nucleus. When fused to GAL4 DNA binding domain, full-length ZNF267 and all constructs encompassing KRAB A domain showed transcriptional repressor activity. Microarray analysis and RNase protection assays showed that ZNF267 represses MMP-10 gene expression, which was confirmed by reporter gene assays. Furthermore, ZNF267 binds to the MMP-10 promoter region as demonstrated by chromatin immunoprecipitation assays. In conclusion, our results suggest that ZNF267 as a negative transcriptional regulator of MMP-10 might promote liver fibrogenesis through alteration of matrix degradation in vivo.
Collapse
Affiliation(s)
- Bernd Schnabl
- Department of Internal Medicine I, University of Regensburg, Regensburg, Germany.
| | | | | | | | | | | | | |
Collapse
|
304
|
Yavrom S, Chen L, Xiong S, Wang J, Rippe RA, Tsukamoto H. Peroxisome proliferator-activated receptor gamma suppresses proximal alpha1(I) collagen promoter via inhibition of p300-facilitated NF-I binding to DNA in hepatic stellate cells. J Biol Chem 2005; 280:40650-9. [PMID: 16216869 DOI: 10.1074/jbc.m510094200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Depletion of peroxisome proliferator-activated receptor gamma (PPARgamma) represents one of the key molecular changes that underlie transdifferentiation (activation) of hepatic stellate cells in the genesis of liver fibrosis (Miyahara, T., Schrum, L., Rippe, R., Xiong, S., Yee, H. F., Jr., Motomura, K., Anania, F. A., Willson, T. M., and Tsukamoto, H. (2000) J. Biol. Chem. 275, 35715-35722; Hazra, S., Xiong, S., Wang, J., Rippe, R. A., Krishna, V., Chatterjee, K., and Tsukamoto, H. (2004) J. Biol. Chem. 279, 11392-11401). In support of this notion, ectopic expression of PPARgamma suppresses hepatic stellate cells activation markers, most notably expression of alpha1(I) procollagen. However, the mechanisms underlying this antifibrotic effect are largely unknown. The present study utilized deletion-reporter gene constructs of proximal 2.2-kb alpha1(I) procollagen promoter to demonstrate that a region proximal to -133 bp is where PPARgamma exerts its inhibitory effect. Within this region, two DNase footprints with Sp1 and reverse CCAAT box sites exist. NF-I, but not CCAAT DNA-binding factor/NF-Y, binds to the proximal CCAAT box in hepatic stellate cells. A mutation of this site almost completely abrogates the promoter activity. NF-I mildly but independently stimulates the promoter activity and synergistically promotes Sp1-induced activity. PPARgamma inhibits NF-I binding to the most proximal footprint (-97/-85 bp) and inhibits its transactivity. The former effect is mediated by the ability of PPARgamma to inhibit p300-facilitated NF-I binding to DNA as demonstrated by chromatin immunoprecipitation assay.
Collapse
Affiliation(s)
- Sharon Yavrom
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033-9141, USA
| | | | | | | | | | | |
Collapse
|
305
|
Fiorucci S, Rizzo G, Antonelli E, Renga B, Mencarelli A, Riccardi L, Morelli A, Pruzanski M, Pellicciari R. Cross-talk between farnesoid-X-receptor (FXR) and peroxisome proliferator-activated receptor gamma contributes to the antifibrotic activity of FXR ligands in rodent models of liver cirrhosis. J Pharmacol Exp Ther 2005; 315:58-68. [PMID: 15980055 DOI: 10.1124/jpet.105.085597] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The nuclear receptors farnesoid X receptor (FXR) and peroxisome proliferator-activated receptor (PPAR)gamma exert counter-regulatory effects on hepatic stellate cells (HSCs) and protect against liver fibrosis development in rodents. Here, we investigated whether FXR ligands regulate PPARgamma expression in HSCs and models of liver fibrosis induced in rats by porcine serum and carbon tetrachloride administration and bile duct ligation. Our results demonstrate that HSCs trans-differentiation associated with suppression of PPARgamma mRNA expression, whereas FXR mRNA was unchanged. Exposure of cells to natural and synthetic ligands of FXR, including 6-ethyl chenodeoxycholic acid (6-ECDCA), a synthetic derivative of chenodeoxycholic acid, reversed this effect and increased PPARgamma mRNA by approximately 40-fold. Submaximally effective concentrations of FXR and PPARgamma ligands were additive in inhibiting alpha1(I) collagen mRNA accumulation induced by transforming growth factor (TGF)beta1. Administration of 6-ECDCA in rats rendered cirrhotic by porcine serum and carbon tetrachloride administration or bile duct ligation reverted down-regulation of PPARgamma mRNA expression in HSCs. Cotreatment with 6-ECDCA potentiates the antifibrotic activity of rosiglitazone, a PPARgamma ligand, in the porcine serum model as measured by morphometric analysis of liver collagen content, hydroxyproline, and liver expression of alpha1(I) collagen mRNA, alpha-smooth muscle actin, fibronectin, TGFbeta1, and tissue inhibitor of metalloprotease 1 and 2, whereas it enhanced the expression of PPARgamma and uncoupling protein 2, a PPARgamma-regulated gene, by 2-fold. In conclusion, by using an in vitro and in vivo approach, we demonstrated that FXR ligands up-regulate PPARgamma mRNA in HSCs and in rodent models of liver fibrosis. A FXR-PPARgamma cascade exerts counter-regulatory effects in HSCs activation.
Collapse
Affiliation(s)
- Stefano Fiorucci
- Dipartimento de Medicina Clinica e Sperimentale, Università degli Studi di Perugia, Italy.
| | | | | | | | | | | | | | | | | |
Collapse
|
306
|
Tsukada S, Parsons CJ, Rippe RA. Mechanisms of liver fibrosis. Clin Chim Acta 2005; 364:33-60. [PMID: 16139830 DOI: 10.1016/j.cca.2005.06.014] [Citation(s) in RCA: 275] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 06/07/2005] [Accepted: 06/08/2005] [Indexed: 01/18/2023]
Abstract
Liver fibrosis represents a significant health problem worldwide of which no acceptable therapy exists. The most characteristic feature of liver fibrosis is excess deposition of type I collagen. A great deal of research has been performed to understand the molecular mechanisms responsible for the development of liver fibrosis. The activated hepatic stellate cell (HSC) is the primary cell type responsible for the excess production of collagen. Following a fibrogenic stimulus, HSCs change from a quiescent to an activated, collagen-producing cell. Numerous changes in gene expression are associated with HSC activation including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses in understanding the molecular basis of collagen gene regulation have revealed a complex process offering the opportunity for multiple potential therapeutic strategies. However, further research is still needed to gain a better understanding of HSC activation and how this cell maintains its fibrogenic nature. In this review we describe many of the molecular events that occur following HSC activation and collagen gene regulation that contribute to the fibrogenic nature of these cells and provide a review of therapeutic strategies to treat this disease.
Collapse
Affiliation(s)
- Shigeki Tsukada
- Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina at Chapel Hill, NC 27599-7032, USA
| | | | | |
Collapse
|
307
|
Jakkaraju S, Zhe X, Pan D, Choudhury R, Schuger L. TIPs are tension-responsive proteins involved in myogenic versus adipogenic differentiation. Dev Cell 2005; 9:39-49. [PMID: 15992539 DOI: 10.1016/j.devcel.2005.04.015] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 01/11/2005] [Accepted: 04/29/2005] [Indexed: 12/30/2022]
Abstract
Stretch induces lung embryonic mesenchymal cells to follow a myogenic pathway. Using this system we identified a set of stretch-responsive factors, which we referred to as TIPs (tension-induced/inhibited proteins). TIPs displayed signature motifs characteristic of nuclear receptor coregulators and chromatin remodeling enzymes. A genomic BLAST search suggested that the three TIPs identified were isoforms originated by alternative splicing from a single gene. Functional studies revealed that TIP-1 and TIP-3 were involved in the cell's selection of the myogenic or the adipogenic pathway. TIP-1, induced by stretch, promoted myogenesis, while TIP-3, inhibited by stretch, stimulated adipogenesis. The selection involved TIP-mediated chromatin remodeling via a histone acetylation process and depended on TIP-1 and TIP-3 nuclear receptor binding boxes (NRBs). This study, therefore, suggests a new developmental mechanism linking the presence or absence of tension with divergent differentiation pathways.
Collapse
Affiliation(s)
- Sandhya Jakkaraju
- Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
| | | | | | | | | |
Collapse
|
308
|
Bataller R, Sancho-Bru P, Ginès P, Brenner DA. Liver fibrogenesis: a new role for the renin-angiotensin system. Antioxid Redox Signal 2005; 7:1346-55. [PMID: 16115040 DOI: 10.1089/ars.2005.7.1346] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Liver fibrosis is the consequence of chronic liver injury of any etiology. When advanced, fibrosis causes portal hypertension and liver insufficiency, and is a risk factor for developing hepatocellular carcinoma. In the last decade, there have been major advances in the knowledge of the pathogenesis of hepatic fibrosis. Hepatic stellate cells (HSCs) are recognized as the main collagen-producing cells in the injured liver, and key fibrogenic factors have been identified. Among these factors, the renin-angiotensin system (RAS) appears to play a major role. Angiotensin II (Ang II) mediates key biological actions involved in hepatic tissue repair, including myofibroblast proliferation, infiltration of inflammatory cells, and collagen synthesis. Activated HSCs secrete Ang II, which induces fibrogenic actions through the activation of NADPH oxidase. Importantly, the blockade of the RAS attenuates fibrosis development in different experimental models of chronic liver injury. Based on these studies, it has been proposed that the blockade of the RAS could be effective in preventing fibrosis progression in chronic liver diseases. Although no prospective studies have evaluated the antifibrotic effect of RAS inhibitors in patients with chronic liver diseases, controlled clinical trials are under way.
Collapse
Affiliation(s)
- Ramón Bataller
- Institut de Malalties Digestives i Metabòliques, Hospital Clinic, IDIBAPS, Barcelona, Catalonia, Spain.
| | | | | | | |
Collapse
|
309
|
Marra F, DeFranco R, Robino G, Novo E, Efsen E, Pastacaldi S, Zamara E, Vercelli A, Lottini B, Spirli C, Strazzabosco M, Pinzani M, Parola M. Thiazolidinedione treatment inhibits bile duct proliferation and fibrosis in a rat model of chronic cholestasis. World J Gastroenterol 2005; 11:4931-8. [PMID: 16124041 PMCID: PMC4321905 DOI: 10.3748/wjg.v11.i32.4931] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effects of troglitazone (TGZ), an anti-diabetic drug which activates peroxisome proliferator-activated receptor-γ (PPAR-γ), for liver tissue repair, and the development of ductular reaction, following common bile duct ligation (BDL) in rats.
METHODS: Rats were supplemented with TGZ (0.2% w/w in the pelleted food) for 1 wk before BDL or sham operation. Animals were killed at 1, 2, or 4 wk after surgery.
RESULTS: The development of liver fibrosis was reduced in rats receiving TGZ, as indicated by significant decreases of procollagen type I gene expression and liver hydroxy-proline levels. Accumulation of α-smooth-muscle actin (SMA)-expressing cells surrounding newly formed bile ducts following BDL, as well as total hepatic levels of SMA were partially inhibited by TGZ treatment, indicating the presence of a reduced number and/or activation of hepatic stellate cells (HSC) and myofibroblasts. Development of the ductular reaction was inhibited by TGZ, as indicated by histochemical evaluation and hepatic activity of γ-glutamyl-transferase (GGT).
CONCLUSION: Treatment with thiazolidinedione reduces ductular proliferation and fibrosis in a model of chronic cholestasis, and suggests that limiting cholangiocyte proliferation may contribute to the lower development of scarring in this system.
Collapse
Affiliation(s)
- Fabio Marra
- Dipartimento di Medicina Interna, University of Florence, Viale Morgagni 85, Florence I-50134, Italy.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
310
|
Guo YT, Leng XS, Li T, Peng JR, Song SH, Xiong LF, Qin ZZ. Effect of ligand of peroxisome proliferator-activated receptor gamma on the biological characters of hepatic stellate cells. World J Gastroenterol 2005; 11:4735-9. [PMID: 16094720 PMCID: PMC4615421 DOI: 10.3748/wjg.v11.i30.4735] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2004] [Revised: 06/23/2004] [Accepted: 06/24/2004] [Indexed: 02/06/2023] Open
Abstract
AIM To study the effect of rosiglitazone, which is a ligand of peroxisome proliferator-activated receptor gamma (PPARgamma), on the expression of PPARgamma in hepatic stellate cells (HSCs) and on the biological characteristics of HSCs. METHODS The activated HSCs were divided into three groups: control group, 3 micromol/L rosiglitazone group, and 10 micromol/L rosiglitazone group. The expression of PPARgamma, alpha-smooth muscle actin (alpha-SMA), and type I and III collagen was detected by RT-PCR, Western blot and immunocytochemical staining, respectively. Cell proliferation was determined with methylthiazolyltetrazolium (MTT) colorimetric assay. Cell apoptosis was demonstrated with flow cytometry. RESULTS The expression of PPARgamma at mRNA and protein level markedly increased in HSCs of 10 micromol/L rosiglitazone group (t value was 10.870 and 4.627 respectively, P<0.01 in both). The proliferation of HSCs in 10 micromol/L rosiglitazone group decreased significantly (t = 5.542, P<0.01), alpha-SMA expression level and type I collagen synthesis ability were also reduced vs controls (t value = 10.256 and 14.627 respectively, P<0.01 in both). The apoptotic rate of HSCs significantly increased in 10 micromol/L rosiglitazone group vs control (chi(2) = 16.682, P<0.01). CONCLUSION By increasing expression of PPARgamma in activated HSCs, rosiglitazone, an agonist of PPARgamma, decreases alpha-SMA expression and type I collagen synthesis, inhibits cell proliferation, and induces cell apoptosis.
Collapse
Affiliation(s)
- Yan-Tong Guo
- Department of General Surgery, Peking University People's Hospital, Beijing, China
| | | | | | | | | | | | | |
Collapse
|
311
|
Affiliation(s)
- Massimo Pinzani
- Dipartimento di Medicina Interna, Centro di Ricerca, Trasferimento e Alta Formazione DENOTHE, Università degli Studi di Firenze, Viale G.B. Morgagni, 85, 50134 Firenze, Italy.
| | | | | |
Collapse
|
312
|
Lotersztajn S, Julien B, Teixeira-Clerc F, Grenard P, Mallat A. Hepatic fibrosis: molecular mechanisms and drug targets. Annu Rev Pharmacol Toxicol 2005; 45:605-28. [PMID: 15471534 DOI: 10.1146/annurev.pharmtox.45.120403.095906] [Citation(s) in RCA: 235] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Liver fibrosis is the common response to chronic liver injury, ultimately leading to cirrhosis and its complications, portal hypertension, liver failure, and hepatocellular carcinoma. Efficient and well-tolerated antifibrotic drugs are currently lacking, and current treatment of hepatic fibrosis is limited to withdrawal of the noxious agent. Efforts over the past decade have mainly focused on fibrogenic cells generating the scarring response, although promising data on inhibition of parenchymal injury and/or reduction of liver inflammation have also been obtained. A large number of approaches have been validated in culture studies and in animal models, and several clinical trials are underway or anticipated for a growing number of molecules. This review highlights recent advances in the molecular mechanisms of liver fibrosis and discusses mechanistically based strategies that have recently emerged.
Collapse
|
313
|
Zheng S, Chen A. Activation of PPARgamma is required for curcumin to induce apoptosis and to inhibit the expression of extracellular matrix genes in hepatic stellate cells in vitro. Biochem J 2005; 384:149-57. [PMID: 15320868 PMCID: PMC1134098 DOI: 10.1042/bj20040928] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During liver fibrogenesis, quiescent HSC (hepatic stellate cells) become active, a transformation that is associated with enhanced cell proliferation and overproduction of ECM (extracellular matrix). Inhibition of cell proliferation and induction of apoptosis are potential strategies to block the activation of HSC for the prevention and treatment of liver fibrosis. Levels of PPARgamma (peroxisome proliferator-activated receptor gamma) are dramatically diminished in parallel with HSC activation. Stimulation of PPARgamma by its agonists inhibits HSC activation in vitro and in vivo. We demonstrated recently that curcumin, the yellow pigment in curry, inhibited HSC activation in vitro, reducing cell proliferation, inducing apoptosis and inhibiting ECM gene expression. Further studies indicated that curcumin induced the gene expression of PPARgamma and stimulated its activity in activated HSC in vitro, which was required for curcumin to inhibit HSC proliferation. The aims of the present study were to evaluate the roles of PPARgamma activation in the induction of apoptosis and suppression of ECM gene expression by curcumin in activated HSC, and to elucidate the underlying mechanisms. Our results demonstrated that blocking PPARgamma activation abrogated the effects of curcumin on the induction of apoptosis and inhibition of the expression of ECM genes in activated HSC in vitro. Further experiments demonstrated that curcumin suppressed the gene expression of TGF-beta (transforming growth factor-beta) receptors and interrupted the TGF-beta signalling pathway in activated HSC, which was mediated by PPARgamma activation. Taken together, our results demonstrate that curcumin stimulated PPARgamma activity in activated HSC in vitro, which was required for curcumin to reduce cell proliferation, induce apoptosis and suppress ECM gene expression. These results provide novel insight into the mechanisms responsible for the inhibition of HSC activation by curcumin. The characteristics of curcumin, which has no adverse health effects, make it a potential candidate for prevention and treatment of hepatic fibrosis.
Collapse
Affiliation(s)
- Shizhong Zheng
- *Department of Pathology, Louisiana State University Health Sciences Center in Shreveport, Shreveport, LA 71130, U.S.A
- †Department of Pharmacology, Nanjing Medical University, Nanjing, China
| | - Anping Chen
- *Department of Pathology, Louisiana State University Health Sciences Center in Shreveport, Shreveport, LA 71130, U.S.A
- ‡Department of Cellular Biology & Anatomy, Louisiana State University Health Sciences Center in Shreveport, Shreveport, LA 71130, U.S.A
- To whom correspondence should be addressed (email )
| |
Collapse
|
314
|
Planagumà A, Clària J, Miquel R, López-Parra M, Titos E, Masferrer JL, Arroyo V, Rodés J. The selective cyclooxygenase-2 inhibitor SC-236 reduces liver fibrosis by mechanisms involving non-parenchymal cell apoptosis and PPARgamma activation. FASEB J 2005; 19:1120-2. [PMID: 15876570 DOI: 10.1096/fj.04-2753fje] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The importance of inflammation in initiating the sequence of events that lead to liver fibrosis is increasingly recognized. In this study, we tested the effects of SC-236, a selective cyclooxygenase (COX)-2 inhibitor, in rats with carbon tetrachloride (CCl4)-induced liver fibrosis. Livers from CCl4-treated rats showed increased COX-2 expression and 15-deoxy-prostaglandin (PG)J2 (15d-PGJ2) formation, as well as decreased peroxisome proliferator-activated receptor (PPAR)gamma expression. In these animals, SC-236 reduced liver fibrosis as revealed by histological analysis and by a reduction in hepatic hydroxyproline levels, metalloproteinase-2 activity, and alpha-smooth muscle actin expression. Interestingly, SC-236 normalized 15d-PGJ2 levels and restored PPARgamma expression in the liver of CCl4-treated rats. In isolated hepatic stellate cells (HSCs)--the major player in liver fibrogenesis--and Kupffer cells--the cell type primarily responsible for increased hepatic COX-2-SC-236 exhibited remarkable pro-apoptotic and growth inhibitory properties. Of interest, SC-236 decreased HSC viability to a similar extent than the PPARgamma ligand rosiglitazone. Moreover, SC-236 significantly induced PPARgamma expression in HSCs and acted as a potent PPARgamma agonist in a luciferase-reporter trans-activation assay. These data indicate that, by mechanisms involving non-parenchymal cell apoptosis and PPARgamma activation, the selective COX-2 inhibitor SC-236 might have therapeutic potential for prevention of liver fibrosis.
Collapse
Affiliation(s)
- Anna Planagumà
- DNA Unit, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain
| | | | | | | | | | | | | | | |
Collapse
|
315
|
Hu K, Fink M, Froh M, Gäbele E, Hellerbrand C, Mühlbauer M, Wiest R, Schölmerich J, Schnabl B. Characterization of the human zinc finger protein 267 promoter: Essential role of nuclear factor Y. ACTA ACUST UNITED AC 2005; 1729:14-23. [PMID: 15814297 DOI: 10.1016/j.bbaexp.2005.03.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2004] [Revised: 02/08/2005] [Accepted: 03/03/2005] [Indexed: 11/21/2022]
Abstract
Liver fibrosis results from an excessive deposition of extracellular matrix proteins secreted by activated hepatic stellate cells (HSCs). The activation process is accompanied by an increased activity of various transcription factors, including zinc finger protein 267 (ZNF267). Recently, ZNF267 has been shown to modulate gene expression and to function as a transcriptional repressor. MMP-10 was identified as a target gene; its gene expression and promoter activity are inhibited by ZNF267, which might promote liver fibrogenesis through diminished matrix degradation. However, the transcriptional regulation of the ZNF267 gene is unknown. In the present study, we have cloned and characterized the human ZNF267 promoter containing a 1.5 kb fragment of the 5'-flanking region (-1414/+173). The ZNF267 gene has a TATA-less promoter with multiple transcription initiation sites. Analysis of serial 5'-deletions of luciferase reporter constructs revealed a minimal promoter between -72 and +173 bp. Mutational analysis of putative regulatory elements indicated that a CCAAT box within this region was essential for ZNF267 promoter activity. Electrophoretic mobility shift assays demonstrated that transcription factor nuclear factor Y (NF-Y) bound to the CCAAT box. In co-transfection experiments, NF-YA increased the promoter activity of ZNF267. In conclusion, our results suggest that the binding site for NF-Y is critical for ZNF267 gene regulation and, herewith, the activation of this transcriptional factor may play an important role in the activation process of HSCs and in liver fibrosis.
Collapse
Affiliation(s)
- Kanghong Hu
- Department of Internal Medicine I, University of Regensburg, 93042 Regensburg, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
316
|
Huang GC, Zhang JS, Tang QQ. Involvement of C/EBP-alpha gene in in vitro activation of rat hepatic stellate cells. Biochem Biophys Res Commun 2005; 324:1309-18. [PMID: 15504357 DOI: 10.1016/j.bbrc.2004.09.196] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2004] [Indexed: 02/07/2023]
Abstract
Hepatic stellate cells (HSCs) play key roles in hepatic fibrosis. One of the most striking alterations in activated HSCs is loss of cytoplasmic lipid droplets. However, the association of lipid storage with the activation of HSCs remains unclear. CCAAT/enhancer-binding proteins family (C/EBPs), especially C/EBP-alpha, controls differentiation of adipocytes. We suggested that C/EBP-alpha gene may be involved in HSCs activation. The present results showed that the expression levels of C/EBP-alpha and C/EBP-beta genes declined in activated HSCs. Over-expression of C/EBP-alpha gene in activated HSCs: (1) inhibited HSCs proliferation, extracellular matrix-producing, alpha-smooth muscle actin gene expression, and induced rebound of cytoplasmic lipid droplets; (2) reduced retinoic acid receptor-beta, C/EBP-delta and -beta gene expressions, but increased the active form C/EBP-beta PSer(105), and induced retinoid X receptor-alpha gene expression; and (3) did not affect the protein level of p16INK4a, p21Cip1/WAF1 or p27Kip1. In conclusions, C/EBP-alpha gene is involved in in vitro activation of rat HSCs.
Collapse
Affiliation(s)
- Guang-Cun Huang
- Department of Pathology, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
| | | | | |
Collapse
|
317
|
|
318
|
Abstract
The response to injury is one of wound healing and, subsequently, fibrosis. This response is generalized, occurring in diverse organ systems. Injury and wounding in the liver ultimately lead to cirrhosis in many patients (although not all patients), and are the result of many different diseases. The fact that various diseases result in cirrhosis suggests a common pathogenesis. Study over the past 2 decades has shed considerable light on the pathogenesis of fibrosis and cirrhosis. A growing body of literature indicates that the hepatic stellate cell is a central component in the fibrogenic process. Stellate cells undergo a transformation during injury that has been termed activation. Activation is complex and multifaceted, but one of its most prominent features is the synthesis of large amounts of extracellular matrix, resulting in deposition of scar or fibrous tissue. The fibrogenic process is dynamic; it is noteworthy that even advanced fibrosis (or cirrhosis) is reversible. The best antifibrotic therapy is treatment of the underlying disease. For example, eradication of hepatitis B or C virus can lead to the reversal of fibrosis. In situations in which treating the underlying process is not possible, specific antifibrotic therapy is desirable. A number of specific antifibrotic therapies have been tried, but have been met with poor or mediocre success. However, elucidation of the mechanisms responsible for fibrogenesis, with particular emphasis on stellate cell biology, has highlighted many putative novel therapies. This article emphasizes mechanisms underlying fibrogenesis, and reviews current antifibrotic therapies as well as potential future approaches.
Collapse
Affiliation(s)
- Don C Rockey
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA.
| |
Collapse
|
319
|
Abstract
Alcoholic liver disease (ALD) is characterized by accumulation of neutral lipids in hepatocytes leading to micro and macro-vesicular steatosis and balloon cell degeneration. Hypercaloric alimentation and resultant obesity also cause similar changes as evident in non-alcoholic fatty liver disease (NAFLD). Thus, accumulation of lipids in hepatocytes is a pathologic hallmark of ALD and NAFLD. In contrast, quiescent hepatic stellate cells (HSC) are characterized by the intracellular content of not only vitamin A but also triglycerides, and HSC activation is associated with depletion of these lipids. In fact, our recent work demonstrates that adipogenic/ lipogenic transcriptional regulation rendered by PPARgamma, LXRa, and SREBP-1c is essential for the maintenance of the fat-storing, quiescence phenotype of HSC. Expression of these adipogenic transcription factors is lost in activated HSC and the treatment of the cells with the adipocyte differentiation cocktail or ectopic expression of PPARgamma or SREBP-1c causes a reversal of activated cells to the quiescent phenotype. In steatotic livers from ALD and NAFLD mouse models, the expression of these adipogenic transcription factors is induced while the normal control livers lack such expression. Thus, adipogenic regulation is essential for HSC quiescence while it makes hepatocytes steatotic. Interestingly, under the adipogenic conditions of ALD and NAFLD, HSC are still activated to cause fibrosis. This fat paradox in hepatocytes and HSC highlights contrasted significance of fat in these two cell types that depend on each other for their homeostatic control. It further suggests, activated HSC in steatotic livers may have defective insulin signaling or lipogenic regulation.
Collapse
Affiliation(s)
- Hide Tsukamoto
- Department of Pathology, Keck School of Medicine of the University of Southern California and the Department of Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
| |
Collapse
|
320
|
Han S, Sidell N, Fisher PB, Roman J. Up-regulation of p21 gene expression by peroxisome proliferator-activated receptor gamma in human lung carcinoma cells. Clin Cancer Res 2004; 10:1911-9. [PMID: 15041706 DOI: 10.1158/1078-0432.ccr-03-0985] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE The peroxisome proliferator-activated receptor gamma (PPARgamma), a ligand-dependent transcription factor belonging to the family of nuclear receptors, has been implicated in the regulation of cell growth and differentiation although the exact mechanism(s) of this activity has not been elucidated. In this study, we explored the role of PPARgamma signaling on the control of gene expression of the cycle-dependent kinase inhibitor p21 in human lung carcinoma cells. EXPERIMENTAL DESIGN Using several human lung carcinoma cell lines (small and non-small carcinoma cells), we assayed for cell growth inhibition and apoptosis induction. We also assayed for p21 mRNA and protein expression by reverse transcription-PCR, real-time reverse transcription-PCR, and Western blot analysis. Nuclear protein binding activities to three response elements located in the p21 promoter [nuclear factor (NF)-kappaB, Sp1, and NF-interleukin 6 (IL6) CAAT/enhancer binding protein (C/EBP)] were measured by gel mobility shift assays. We used transient transfection assays with p21 promoter reporter gene constructs to determine the transcriptional regulation by PPARgamma ligands. Finally, by using p21 antisense oligonucleotides, we tested the link between PPARgamma activation and p21 signaling in cell growth inhibition assays and by Western blot analysis. RESULTS We showed that the PPARgamma ligands PGJ2 and ciglitazone inhibit the growth and induce the apoptosis of several human lung carcinoma cell lines, whereas the PPARalpha agonist WY14643 has little effect. Treatment of lung carcinoma cells with the PPARgamma ligands PGJ2, ciglitazone, troglizaone, and GW1929 elevated p21 mRNA and protein levels and reduced cyclin D1 mRNA levels. These results were supported by transient transfection assays, which indicated that PPARgamma ligands increased p21 gene promoter activity in human lung carcinoma cells. In addition, p21 antisense oligonucleotides inhibited PPARgamma ligand-induced p21 protein expression and significantly blocked lung carcinoma cell growth inhibition induced by PPARgamma ligands. Finally, electrophoresis mobility shift experiments demonstrated that PPARgamma ligands increased the nuclear binding activities of Sp1 and NF-IL6 (C/EBP), two transcription factors with regulatory elements in the promoter region of the p21 gene. CONCLUSION PPARgamma ligands inhibit human lung carcinoma cell growth and induce apoptosis by stimulating the cyclin-dependent kinase inhibitor p21 and by reducing cyclin D1 gene expression. The induction of p21 gene expression by PPARgamma ligands may be mediated through increased Sp1- and NF-IL6 (C/EBP)-dependent transcriptional activation. These observations unveil a mechanism for p21 gene regulation in lung carcinoma that represents a potential target for therapy.
Collapse
Affiliation(s)
- Shouwei Han
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
| | | | | | | |
Collapse
|
321
|
Friedman SL. Mechanisms of Disease: mechanisms of hepatic fibrosis and therapeutic implications. ACTA ACUST UNITED AC 2004; 1:98-105. [PMID: 16265071 DOI: 10.1038/ncpgasthep0055] [Citation(s) in RCA: 373] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Accepted: 10/25/2004] [Indexed: 02/07/2023]
Abstract
Hepatic fibrosis, or scarring of the liver, is emerging as a treatable complication of advanced liver disease, following significant progress in understanding its underlying mechanisms. Efforts have focused on the hepatic stellate cell, as these cells can undergo 'activation' into proliferative and fibrogenic myofibroblast-like cells during liver injury. Stimuli driving stellate cell activation include hepatocellular necrosis due to oxidant stress, apoptosis, and soluble growth factors. Specific lymphocyte subsets can also stimulate fibrogenesis. A cascade of signaling and transcriptional events in stellate cells underlies the fibrogenic response to liver injury, with each step in the cascade being a potential target for antifibrotic therapy. Disease-specific fibrogenic mechanisms have also been uncovered: in hepatitis C, this may include direct stimulation of stellate cell activation by viral infection; in nonalcoholic steatohepatitis, elevated levels of leptin and increased leptin signaling by stellate cells increase fibrogenesis. Determinants of fibrosis progression include both environmental and genetic factors, with ongoing efforts to define specific polymorphisms correlating with fibrosis progression rates. Human studies now indicate that fibrosis and even cirrhosis could be reversible, especially if the underlying disease is eradicated. A key challenge is to establish noninvasive means of assessing fibrosis stage and progression using either serum tests and/or imaging. In addition, endpoints of antifibrotic clinical trials need to be established so that reliable evidence of benefit can be identified. We are on the cusp of a new era in which antifibrotic therapies could become important in treating chronic fibrosing liver disease.
Collapse
Affiliation(s)
- Scott L Friedman
- Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY 10029, USA.
| |
Collapse
|
322
|
Desmet C, Warzée B, Gosset P, Mélotte D, Rongvaux A, Gillet L, Fiévez L, Seumois G, Vanderplasschen A, Staels B, Lekeux P, Bureau F. Pro-inflammatory properties for thiazolidinediones. Biochem Pharmacol 2004; 69:255-65. [PMID: 15627478 DOI: 10.1016/j.bcp.2004.09.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Accepted: 09/16/2004] [Indexed: 11/21/2022]
Abstract
Thiazolidinediones (TZDs) are pharmacological ligands of the peroxisome proliferator-activated receptor (PPAR)-gamma that are extensively used in the treatment of type II diabetes. Recently, an anti-inflammatory potential for TZDs has been suggested, based on observations that these compounds may inhibit pro-inflammatory cytokine expression in vitro and may attenuate the inflammatory response in vivo. Here, we show that the TZDs rosiglitazone (RSG) and troglitazone (TRO) do not inhibit the inflammatory response to tumor necrosis factor (TNF)-alpha in various epithelial cell types. On the contrary, both RSG and TRO significantly potentiated TNF-alpha-induced production of granulocyte/macrophage-colony-stimulating factor, interleukin (IL)-6 and/or IL-8 in these cells. This increase in pro-inflammatory cytokine expression was functionally significant as supernatants from cells co-treated with TNF-alpha and TZDs displayed increased neutrophil pro-survival activity when compared with supernatants from cells treated with TNF-alpha alone. Additionally, it was shown that TZDs enhance cytokine expression at the transcriptional level, but that the pro-inflammatory effects of TZDs are independent on PPARgamma, nuclear factor kappaB or mitogen-activated protein kinase activation. Our study shows that TZDs may potentiate the inflammatory response in epithelial cells, a previously unappreciated effect of these compounds.
Collapse
Affiliation(s)
- Christophe Desmet
- Department of Physiology, Bât. B42, Molecular and Cellular Therapy Center, University of Liège, B-4000 Liège, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
323
|
She H, Xiong S, Hazra S, Tsukamoto H. Adipogenic transcriptional regulation of hepatic stellate cells. J Biol Chem 2004; 280:4959-67. [PMID: 15537655 DOI: 10.1074/jbc.m410078200] [Citation(s) in RCA: 235] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Hepatic stellate cells (HSC) undergo transdifferentiation (activation) from lipid-storing pericytes to myofibroblastic cells to participate in liver fibrogenesis. Our recent work demonstrates that depletion of peroxisome proliferator-activated receptor gamma (PPARgamma) constitutes one of the key molecular events for HSC activation and that ectopic expression of this nuclear receptor achieves the phenotypic reversal of activated HSC to the quiescent cells. The present study extends these findings to test a novel hypothesis that adipogenic transcriptional regulation is required for the maintenance of HSC quiescence. Comparative analysis of quiescent and activated HSC in culture reveals higher expression of putative adipogenic transcription factors such as CCAAT/enhancer-binding protein (C/EBP) alpha, C/EBPbeta, C/EBPdelta, PPARgamma, liver X receptor alpha, sterol regulatory element-binding protein 1c and of adipocyte-specific genes in the quiescent cells. Conversely, activated HSC have increased expression of PPARbeta, a transcription factor known to promote fatty acid oxidation. A treatment of activated HSC with the adipocyte differentiation mixture (isobutylmethylxanthine, dexamethasone, and insulin) or ectopic expression of PPARgamma or SREBP-1c in these cells, induces a panel of adipogenic transcription factors, reduces PPARbeta, and causes the phenotypic reversal to quiescent HSC. These results support the importance of adipogenic transcriptional regulation in HSC quiescence and provide a new framework for identifying novel molecular targets for the treatment of liver cirrhosis.
Collapse
Affiliation(s)
- Hongyun She
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90033, USA
| | | | | | | |
Collapse
|
324
|
Jaster R. Molecular regulation of pancreatic stellate cell function. Mol Cancer 2004; 3:26. [PMID: 15469605 PMCID: PMC524499 DOI: 10.1186/1476-4598-3-26] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 10/06/2004] [Indexed: 12/11/2022] Open
Abstract
Until now, no specific therapies are available to inhibit pancreatic fibrosis, a constant pathological feature of chronic pancreatitis and pancreatic cancer. One major reason is the incomplete knowledge of the molecular principles underlying fibrogenesis in the pancreas. In the past few years, evidence has been accumulated that activated pancreatic stellate cells (PSCs) are the predominant source of extracellular matrix (ECM) proteins in the diseased organ. PSCs are vitamin A-storing, fibroblast-like cells with close morphological and biochemical similarities to hepatic stellate cells (also known as Ito-cells). In response to profibrogenic mediators such as various cytokines, PSCs undergo an activation process that involves proliferation, exhibition of a myofibroblastic phenotype and enhanced production of ECM proteins. The intracellular mediators of activation signals, and their antagonists, are only partially known so far. Recent data suggest an important role of enzymes of the mitogen-activated protein kinase family in PSC activation. On the other hand, ligands of the nuclear receptor PPARγ (peroxisome proliferator-activated receptor γ) stimulate maintenance of a quiescent PSC phenotype. In the future, targeting regulators of the PSC activation process might become a promising approach for the treatment of pancreatic fibrosis.
Collapse
Affiliation(s)
- Robert Jaster
- Department of Medicine, Division of Gastroenterology, Medical Faculty, University of Rostock, E,-Heydemann-Str, 6, 18057 Rostock, Germany.
| |
Collapse
|
325
|
Cheng J, Nakamura H, Imanishi H, Liu W, Morisaki T, Sugiyama T, Hada T. Peroxisome proliferator-activated receptor γ ligands, 15-deoxy-Δ12,14-prostaglandin J2, and ciglitazone, induce growth inhibition and cell cycle arrest in hepatic oval cells. Biochem Biophys Res Commun 2004; 322:458-64. [PMID: 15325252 DOI: 10.1016/j.bbrc.2004.07.133] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Indexed: 01/31/2023]
Abstract
There is growing evidence to show that hepatic oval cells contribute to liver regeneration, dysplastic nodule formation, and hepato-carcinogenesis. Peroxisome proliferator-activated receptors (PPARs) and their ligands play an important role in cell growth, inflammatory responses, and liver pathogenesis including fibrosis and cancer. However, little is known about the role of PPARgamma/its ligands in the growth and differentiation of hepatic oval cells. In this study, we found that OC15-5, a rat hepatic oval cell line, expressed PPARgamma at mRNA and protein levels, and a natural ligand for PPARgamma, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), and a synthetic ligand, ciglitazone, inhibited growth of OC15-5 cells by arresting at G1-S in a dose-dependent manner. Apoptosis was also induced in OC15-5 cells by 15d-PGJ2 treatment. In OC15-5 cells treated with 15d-PGJ2, the expression of CDK inhibitor, p27(Kip1), was up-regulated, while that of p21(WAF1/Cip1), p18(INK4C) CDK2, CDK4, and cyclin E was unchanged. In addition, delayed up-regulation of AFP expression was observed in OC15-5 cells after 15d-PGJ2 or ciglitazone treatment. This is the first report to show that the PPARgamma ligand was involved in the growth, cell cycle, and differentiation of hepatic oval cells, raising the possibility that the PPARgamma ligands may regulate liver regeneration and hepato-carcinogenesis.
Collapse
Affiliation(s)
- Jidong Cheng
- Division of Hepatobiliary and Pancreatic Disease, Department of Internal Medicine, Hyogo College of Medicine, 1-1 Mukogawacho, Nishinomiya, Hyogo 663-8501, Japan.
| | | | | | | | | | | | | |
Collapse
|
326
|
Cardoso CCA, Paviani ER, Cruz LA, Guma FCR, Borojevic R, Guaragna RM. Effect of pentoxifylline on arachidonic acid metabolism, neutral lipid synthesis and accumulation during induction of the lipocyte phenotype by retinol in murine hepatic stellate cell. Mol Cell Biochem 2004; 254:37-46. [PMID: 14674680 DOI: 10.1023/a:1027356412399] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In liver fibrosis, the quiescent hepatic stellate cells (HSC) are activated to proliferate and express the activated myofibroblast phenotype, losing fat droplets and the stored vitamin A, and depositing more extracellular matrix. Therapeutic strategies for liver fibrosis are focused on HSC. Pentoxifylline (PTF), an analog of the methylxanthine, prevents the biochemical and histological changes associated with animal liver fibrosis. The aim of the present study was to investigate the phenotypic change of myofibroblasts into quiescent lipocytes by PTF and/or retinol, using a permanent cell line GRX that represents murine HSC. We studied the action of both drugs on the synthesis of neutral lipids, activity of phospholipase A2 (PLA2), release of arachidonic acid (AA) and prostaglandins synthesis. Accumulation and synthesis of neutral lipids was dependent upon association of retinol with PTF. PTF (0.5 mg/mL) alone did not induce lipid accumulation and synthesis, but in cells induced by physiologic concentration of retinol (1-2.5 microM), it increased the quantity of stored lipids. Retinol and PTF (5 microM and 0.1 mg/mL, respectively) had a synergistic effect on neutral lipid synthesis and accumulation. In higher PTF concentrations (0.5 and 0.7 mg/ml), the synthesis was stimulated but accumulation decreased. Membrane-associated PLA2 activity decreased after PTF treatment, which increased the AA release 8 fold, and significantly increased the production of PGE2, but not of PGF2. However, when in presence of retinol, we observed a slightly higher increase in PGE2 and PGF2a production. In conclusion, PTF treatment generated an excess of free AA. We propose that retinol counteracts the action of PTF on the AA release and PGs production, even though both drugs stimulated the lipocyte induction in the HSC.
Collapse
Affiliation(s)
- Carla C A Cardoso
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil
| | | | | | | | | | | |
Collapse
|
327
|
Ohata M, Suzuki H, Sakamoto K, Hashimoto K, Nakajima H, Yamauchi M, Hokkyo K, Yamada H, Toda G. Pioglitazone Prevents Acute Liver Injury Induced by Ethanol and Lipopolysaccharide Through the Suppression of Tumor Necrosis Factor-alpha. Alcohol Clin Exp Res 2004. [DOI: 10.1111/j.1530-0277.2004.tb03232.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
328
|
Shimizu K, Shiratori K, Kobayashi M, Kawamata H. Troglitazone inhibits the progression of chronic pancreatitis and the profibrogenic activity of pancreatic stellate cells via a PPARgamma-independent mechanism. Pancreas 2004; 29:67-74. [PMID: 15211114 DOI: 10.1097/00006676-200407000-00058] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
We have previously reported that troglitazone inhibits proinflammatory cytokine production in chronic pancreatitis. In the present study, we show that troglitazone prevents the progression of chronic pancreatitis by inhibiting the proliferation of pancreatic stellate cells (PSCs) via a PPARgamma-independent mechanism. WBN/Kob rats with spontaneous chronic pancreatitis were fed troglitazone-containing rat chow for 3 or 6 months. Pancreatic fibrosis and expression of alpha-SMA were markedly attenuated by troglitazone. Rat PSCs expressed a higher level of PPARgamma1 mRNA than of PPARgamma2 mRNA. PSCs were transiently cotransfected with a dominant negative mutant PPARgamma1 and a PPAR-driven reporter gene. Troglitazone increased reporter activity and the mutant receptor abrogated wild-type receptor activity in a dose-dependent manner. Troglitazone inhibited cell proliferation by blocking cell-cycle progression beyond the G1 phase. These effects were observed in mutant receptor-transfected cells as well as cells transfected with the control vector. The effect of troglitazone on alpha1(I) procollagen mRNA and MCP-1 mRNA was unaffected by inhibition of endogenous PPARgamma1 receptor activity. These results suggest that troglitazone may serve as novel therapeutic agent for the treatment of chronic pancreatitis. The antifibrotic effect of troglitazone appears to be mediated, in part, via a PPARgamma-independent mechanism.
Collapse
Affiliation(s)
- Kyoko Shimizu
- Department of Clinical Laboratory, School of Medicine, Tokyo Women's Medical University, Tokyo, Japan.
| | | | | | | |
Collapse
|
329
|
N/A. N/A. Shijie Huaren Xiaohua Zazhi 2004; 12:1179-1183. [DOI: 10.11569/wcjd.v12.i5.1179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
|
330
|
Ghosh AK, Bhattacharyya S, Lakos G, Chen SJ, Mori Y, Varga J. Disruption of transforming growth factor beta signaling and profibrotic responses in normal skin fibroblasts by peroxisome proliferator-activated receptor gamma. ACTA ACUST UNITED AC 2004; 50:1305-18. [PMID: 15077315 DOI: 10.1002/art.20104] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE In fibroblasts, transforming growth factor beta (TGF beta) stimulates collagen synthesis and myofibroblast transdifferentiation through the Smad intracellular signal transduction pathway. TGF beta-mediated fibroblast activation is the hallmark of scleroderma and related fibrotic conditions, and disrupting the intracellular TGF beta/Smad signaling may provide a novel approach to controlling fibrosis. Because of its potential role in modulating inflammatory and fibrotic responses, we examined the expression of the nuclear hormone receptor peroxisome proliferator-activated receptor gamma (PPAR gamma) in normal skin fibroblasts and its effect on TGF beta-induced cellular responses. METHODS The expression and activity of PPAR gamma in normal dermal fibroblasts were examined by Northern and Western blot analyses, immunocytochemistry, flow cytometry, and transient transfections with reporter constructs. The same approaches were used to evaluate the effects of PPAR gamma activation by naturally occurring and synthetic ligands on collagen synthesis and alpha-smooth muscle actin (alpha-SMA) expression. Modulation of Smad-mediated transcriptional responses was examined by transient transfection assays using wild-type and dominant-negative PPAR gamma expression constructs. RESULTS The PPAR gamma receptor was expressed and fully functional in quiescent normal skin fibroblasts. Whereas ligand activation of cellular PPAR gamma resulted in modest suppression of basal collagen gene expression, it abrogated TGF beta-induced stimulation in a concentration-dependent manner. This response was mimicked by overexpressing PPAR gamma in fibroblasts, and was blocked by a selective antagonist of PPAR gamma signaling or by transfection of fibroblasts with dominant-negative PPAR gamma constructs. Furthermore, PPAR gamma ligands abrogated TGF beta-induced expression of alpha-SMA, a marker of myofibroblasts. Stimulation of Smad-dependent transcriptional responses by TGF beta was suppressed by PPAR gamma despite the absence of a consensus PPAR gamma-response element in the targeted promoters. Ligand-induced activation of fibroblast PPAR gamma had no effect on protein expression of cellular Smad3 or Smad7. CONCLUSION By abrogating of TGF beta-induced stimulation of collagen gene expression, myofibroblast transdifferentiation, and Smad-dependent promoter activity in normal fibroblasts, PPAR gamma may play a physiologic role in the regulation of the profibrotic response. Furthermore, our results suggest that PPAR gamma activation by pharmacologic agonists may represent a novel approach to the control of fibrosis in scleroderma.
Collapse
Affiliation(s)
- Asish K Ghosh
- University of Illinois at Chicago, College of Medicine, Chicago, Illinois 60607, USA
| | | | | | | | | | | |
Collapse
|
331
|
Sung CK, She H, Xiong S, Tsukamoto H. Tumor necrosis factor-alpha inhibits peroxisome proliferator-activated receptor gamma activity at a posttranslational level in hepatic stellate cells. Am J Physiol Gastrointest Liver Physiol 2004; 286:G722-9. [PMID: 14656714 DOI: 10.1152/ajpgi.00411.2003] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Diminished activity of peroxisome proliferator-activated receptor gamma (PPARgamma) is implicated in activation of hepatic stellate cells (HSC), a critical event in the development of liver fibrosis. In the present study, we investigated PPARgamma regulation by TNF-alpha in an HSC line designated as BSC. In BSC, TNF-alpha decreased both basal and ligand (GW1929)-induced PPARgamma mRNA levels without changing its protein expression. Nuclear extracts from BSC treated with TNF-alpha showed decreased binding of PPARgamma to PPAR-responsive element (PPRE) as determined by electrophoretic mobility shift assay. In BSC transiently transfected with a PPARgamma1 expression vector and a PPRE-luciferase reporter gene, TNF-alpha decreased both basal and GW1929-induced transactivation of the PPRE promoter. TNF-alpha increased activation of ERK1/2 and JNK, previously implicated in phosphorylation of Ser(82) of PPARgamma1 and resultant negative regulation of PPARgamma transactivity. In fact, TNF-alpha failed to inhibit transactivity of a Ser(82)Ala PPARgamma1 mutant in BSC. TNF-alpha-mediated inhibition of PPARgamma transactivity was not blocked with a Ser(32)Ala/Ser(36)Ala mutant of inhibitory NF-kappaBalpha (IkappaBalpha). These results suggest that TNF-alpha inhibits PPARgamma transactivity in cultured HSC, at least in part, by diminished PPARgamma-PPRE (DNA) binding and ERK1/2-mediated phosphorylation of Ser(82) of PPARgamma1, but not via the NF-kappaB pathway.
Collapse
Affiliation(s)
- Chin K Sung
- Dept. of Pathology, Keck School of Medicine of the Univ. of Southern California, 1333 San Pablo St., MMR 412, Los Angeles, CA 90089-9141, USA
| | | | | | | |
Collapse
|
332
|
Ip E, Farrell G, Hall P, Robertson G, Leclercq I. Administration of the potent PPARalpha agonist, Wy-14,643, reverses nutritional fibrosis and steatohepatitis in mice. Hepatology 2004; 39:1286-96. [PMID: 15122757 DOI: 10.1002/hep.20170] [Citation(s) in RCA: 284] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Administration of a methionine and choline deficient (MCD) diet to rodents causes progressive fibrosing steatohepatitis pathologically similar to human metabolic steatohepatitis. We have previously shown that the peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist, Wy-14,643, prevented the development of MCD diet-induced steatohepatitis. We have now tested whether Wy-14,643 ameliorates established steatohepatitis and fibrosis. Male C57BL6 mice were fed the MCD diet for 51 days to induce severe steatohepatitis. They were then treated with Wy-14,643 together with the MCD diet for 5 or 12 days; positive controls continued on the MCD diet for 5 or 12 days. After 5 days of Wy-14,643 treatment, alanine aminotransferase (ALT) levels were significantly decreased, steatohepatitis less severe, and hepatic lipoperoxides significantly reduced. After 12 days, hepatic triglycerides were normalized and there was near resolution of histological changes. MCD dietary feeding was associated with increased expression of vascular cell adhesion molecule (VCAM)-1, and increased numbers of activated macrophages in the liver. Treatment with Wy-14,643 reduced VCAM-1 expression and macrophage numbers. MCD diet-fed mice developed hepatic fibrosis with increased hepatic collagen alpha1(I), tissue inhibitor of metalloproteinases (TIMP)-1, TIMP-2, and matrix metalloproteinase (MMP)-13 mRNA levels. After treatment with Wy-14,643, expression of these genes was reduced in a manner that paralleled the reduction in activated hepatic stellate cells and near resolution of liver fibrosis. In conclusion, the present study shows that MCD diet-induced fibrosing steatohepatitis can be reversed by treatment with Wy-14,643. It is likely that activation of PPARalpha reverses fibrosis indirectly by reducing stimuli, such as lipid peroxides, and activation of cells responsible for promoting hepatic fibrosis.
Collapse
Affiliation(s)
- Emilia Ip
- Storr Liver Unit, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, NSW, Australia
| | | | | | | | | |
Collapse
|
333
|
Abstract
AIM: To investigate effects of pioglitazone on rat hepatic fibrosis and to explore its mechanism.
METHODS: Rat hepatic fibrosis was induced by carbon tetrachloride (CCl4). Forty Sprague-Dawley rats were divided randomly into 4 groups: control, model, and two treatment (PI, PII) groups. Except for rats in control group, all rats were given subcutaneous injection of 400 mL/L CCl4, twice a wk for 8 wk. Rats in PI and PII groups were also treated with pioglitazone of 3 mg/kg, daily via gastrogavage beginning on the 1st day and at the end of the 2nd week, administration of CCl4 respectively. Liver functions (ALT, AST), serum fibrotic markers (HA, LN, PCIII) and hepatic hydroxyproline (HP) concentration were determined respectively. Histochemical staining of formalin-fixed liver sections with HE, Masson-Trichrome, and immunohistochemical staining for α-smooth muscle actin (α-SMA) were performed. Modified Knodell and Chevallier semi-quantitative scoring system (SSS) was used to evaluate necroinflammatory activity and fibrosis degree.
RESULTS: Compared with model group, pioglitazone significantly reduced the serum levels of ALT, AST , HA, LN and PCIII (P < 0.05 or < 0 .01). The HP concentrations in PI (210.90 ± 24.07 μg/g), and PII (257.36 ± 30.55 μg/g) groups were also lower than those in model group (317.80 ± 36.44 μg/g) (P < 0.01). Histologic examination showed that PI and PII groups had milder hepatocellular degeneration, necrosis and infiltration of inflammatory cells, and thinner or less fibrotic septa than did model group. The scores for necroinflammation in PI (2.80 ± 1.03), and PII (3.00 ± 1.05) groups were significantly reduced as compared with model group (4.88 ± 2.30) (P < 0.05 or < 0.01); the fibrosis scores in PI (3.40 ± 1.65), and PII (4.60±1.35) groups were also markedly lower than those in model group (7.00 ± 3.21) (P < 0.05 or < 0.01). Immunohistochemical staining showed that expression of α-SMA in PI and PII groups was ameliorated dramatically compared with model group.
CONCLUSION: PPARγ agonist pioglitazone greatly retards the progression of rat hepatic fibrosis induced by CCl4 through inhibition of HSC activation and amelioration of hepatocyte necroinflammation in rats.
Collapse
Affiliation(s)
- Guang-Jin Yuan
- Department of Infectious Diseases, Renmin Hospital of Wuhan University, Wuhan 430060, Hubei Province, China.
| | | | | |
Collapse
|
334
|
Abstract
Progressive liver fibrosis is the main cause of organ failure in chronic liver diseases of any aetiology. Fibrosis develops with different spatial patterns and is a consequence of different prevalent mechanisms according to the diverse causes of parenchymal damage. Indeed, fibrosis, observed as a consequence of chronic viral infection is initially concentrated within and around the portal tract, while fibrosis secondary to toxic/metabolic damage is located mainly in the centrolobular areas. In addition, it is increasingly evident that different cell types are involved in the deposition of fibrillar extracellular matrix during active hepatic fibrogenesis: hepatic stellate cells are mainly involved when hepatocellular damage is limited or concentrated within the liver lobule, whereas portal myofibroblasts and fibroblasts provide a predominant contribution when the damage is located in the proximity of the portal tracts. In the later stages of evolution (septal fibrosis) it is likely that all extracellular matrix-producing cells contribute to fibrogenesis. Recruitment and activation of extracellular matrix-producing cells to the site of tissue damage can be due to different major mechanisms: (1) Chronic activation of the tissue repair process. In this case, as a consequence of the reiterated damage, accumulation of fibrillar extracellular matrix reflects the impossibility of an effective remodelling and regeneration. (2) Effect of oxidative stress products, including reactive oxygen intermediates and reactive aldehydes. These products, whose concentration become critical in toxic/metabolic liver injury, are able to induce the synthesis of fibrillar extracellular matrix even in the absence of significant hepatocyte damage and inflammation. (3) Derangement of normal the epithelial/mesenchymal interaction. This typically occurs in all conditions characterised by cholangiocyte damage/proliferation, where a consensual proliferation of extracellular matrix-producing cells and progressive fibrogenesis is commonly observed. A major advancement towards the understanding of the molecular mechanisms of fibrogenesis is derived from a consistent number of in vitro studies investigating the biological role of growth factors/cytokines and other soluble factors and their intracellular signalling pathways. The relevance of these factors has been confirmed by studies performed on animal models and by studies performed on pathological human liver. Along these lines, the elucidation of a consistent number of cellular and molecular mechanisms responsible for the progression of liver fibrosis has provided sound basis for the development of pharmacological strategies able to modulate this important pathophysiological process. Finally, there are several clinically relevant issues that need re-evaluation and/or further investigation, and in particular: (1) the need of an accurate and effective monitoring of the fibrotic progression of chronic liver diseases and of the effectiveness of the currently proposed treatments; (2) the identification of general or individual factors potentially relevant for a faster progression of the disease.
Collapse
Affiliation(s)
- M Pinzani
- Laboratory of Hepatology, Department of Internal Medicine, University of Florence, Viale G.B. Morgagni, 85, 50134 Florence, Italy.
| | | |
Collapse
|
335
|
Ueta M, Wakisaka M, Ago T, Kitazono T, Nakamura U, Yoshinari M, Iwase M, Iida M. PPARγ ligands attenuate mesangial contractile dysfunction in high glucose. Kidney Int 2004; 65:961-71. [PMID: 14871416 DOI: 10.1111/j.1523-1755.2004.00474.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND To elucidate the regulation of peroxisome proliferator-activated receptor gamma (PPARgamma) and its roles in mesangial cells, we examined the expression of PPARgamma1 and effects of its ligands on cell phenotypes and angiotensin II-induced contractile response in cultured rat mesangial cells under a high (20 mmol/L) glucose condition. METHODS The effects of tumor necrosis factor alpha (TNFalpha), protein kinase C (PKC) activation, antisense DNA for PPARgamma1, PPARgamma ligands and PD98059 were examined in mesangial cells cultured in either 5 mmol/L or 20 mmol/L glucose. The expressions of PPARgamma1 protein and alpha-smooth muscle actin (alphaSMA) as a marker of phenotype of cells were determined by Western blot. The expression of PPARgamma1 mRNA was determined by a reverse transcription-polymerase chain reaction method. The reduction of cell surface area in response to angiotensin II was measured by microscope to determine cellular contraction. RESULTS PKC activation, TNFalpha, and 20 mmol/L glucose decreased PPARgamma1 at both protein and mRNA levels, which was inhibited by PD98059, a specific inhibitor of mitogen-activated protein kinase (MAPK). Decreases of PPARgamma1 protein and contractile response and an increase of alphaSMA occurred simultaneously in the cells treated with 20 mmol/L glucose after 5 days, which were attenuated to the normal levels by PPARgamma ligands. The antisense DNA also induced the decrease of PPARgamma1 protein, contractile dysfunction, and increase of alphaSMA. CONCLUSION MAPK suppresses PPARgamma1 at the transcriptional level, and the reduction of PPARgamma1 in cultured rat mesangial cells under the high glucose condition induces phenotypic change and loss of contractile function. PPARgamma ligands recover both reductions of PPARgamma 1 protein and contractile response.
Collapse
Affiliation(s)
- Maki Ueta
- Department of Medicine and Clinical Science, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan
| | | | | | | | | | | | | | | |
Collapse
|
336
|
Sato T, Sato M, Miura M, Higashi N, Wang DR, Suzuki S, Imai K, Kojima N, Senoo H. Expression of the Peroxisome Proliferator-Activated Receptors (PPARs) in the Hepatic Stellate Cells. COMPARATIVE HEPATOLOGY 2004; 3 Suppl 1:S17. [PMID: 14960169 PMCID: PMC2410239 DOI: 10.1186/1476-5926-2-s1-s17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Takeya Sato
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Mitsuru Sato
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Mitsutaka Miura
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Nobuyo Higashi
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Da-Ren Wang
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Shinsuke Suzuki
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Katsuyuki Imai
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Naosuke Kojima
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| | - Haruki Senoo
- Department of Anatomy, Akita University School of Medicine, Akita, 010-8543, Japan
| |
Collapse
|
337
|
Hazra S, Miyahara T, Rippe RA, Tsukamoto H. PPAR Gamma and Hepatic Stellate Cells. COMPARATIVE HEPATOLOGY 2004; 3 Suppl 1:S7. [PMID: 14960159 PMCID: PMC2410230 DOI: 10.1186/1476-5926-2-s1-s7] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Activation of Hepatic stellate cells (HSC) in fibrogenesis involves distinct morphological and biochemical changes. This activation requires the coordinated changes in activity of several transcription factors. Peroxisome proliferator-activated receptor gamma (PPAR gamma) is one such factor whose activity is decreased in activated HSC. PPAR gamma ligands suppress several markers of HSC activation such as expression of collagen and alpha smooth muscle actin (alpha-SMA), cell proliferation and migration. Expression of PPAR gamma, per se, also inhibits HSC activation. These findings support the role of PPAR gamma in reversion of activated HSC toward their quiescent state.
Collapse
Affiliation(s)
- Saswati Hazra
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90033', USA
| | - Takeo Miyahara
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90033', USA
| | - Richard A Rippe
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7038, USA
| | - Hidekazu Tsukamoto
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90033', USA
- Greater Los Angeles VA Health Care System, Los Angeles, CA 90073, USA
| |
Collapse
|
338
|
Kawada N. Molecular mechanism of stellate cell activation and therapeutic strategy for liver fibrosis. COMPARATIVE HEPATOLOGY 2004; 3 Suppl 1:S3. [PMID: 14960155 PMCID: PMC2410226 DOI: 10.1186/1476-5926-2-s1-s3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Norifumi Kawada
- Department of Hepatology, Graduate School of Medicine, Osaka City University, Osaka 545-8585, Japan.
| |
Collapse
|
339
|
Andreola F, Calvisi DF, Elizondo G, Jakowlew SB, Mariano J, Gonzalez FJ, De Luca LM. Reversal of liver fibrosis in aryl hydrocarbon receptor null mice by dietary vitamin A depletion. Hepatology 2004; 39:157-66. [PMID: 14752834 DOI: 10.1002/hep.20004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Aryl hydrocarbon receptor (AHR)-null mice display a liver fibrosis phenotype that is associated with a concomitant increase in liver retinoid concentration, tissue transglutaminase type II (TGaseII) activity, transforming growth factor beta (TGF beta) overexpression, and accumulation of collagen. To test the hypothesis that this phenotype might be triggered by the observed increase in liver retinoid content, we induced the condition of retinoid depletion by feeding AHR-null mice a vitamin A- deficient diet with the purpose to reverse the phenotype. Liver retinoid content decreased sharply within the first few weeks on the retinoid-deficient diet. Analysis of TGF beta 1, TGF beta 2, and TGF beta 3 expression revealed a reduction to control levels in the AHR -/- mice accompanied by parallel changes in TGaseII protein levels. In addition, we observed an increase in the TGF beta receptors, TGF beta RI and TGF beta RII, as well as in Smad4, and their reduction to wild-type mouse liver levels in AHR -/- mice fed the retinoid-deficient diet. Reduction of peroxisomal proliferator-activated receptor gamma (PPAR gamma) messenger RNA (mRNA) and protein levels in AHR -/- mice was consistent with the presence of hepatic stellate cell (HSC) activation and liver fibrosis. Vitamin A deficiency normalized PPAR gamma expression in AHR -/- mice. In conclusion, livers from AHR -/- mice fed the vitamin A-deficient diet showed a decrease in collagen deposition, consistent with the absence of liver fibrosis.
Collapse
Affiliation(s)
- Fausto Andreola
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | | | | | | | | | | | | |
Collapse
|
340
|
Hazra S, Xiong S, Wang J, Rippe RA, Krishna V, Chatterjee K, Tsukamoto H. Peroxisome proliferator-activated receptor gamma induces a phenotypic switch from activated to quiescent hepatic stellate cells. J Biol Chem 2003; 279:11392-401. [PMID: 14702344 DOI: 10.1074/jbc.m310284200] [Citation(s) in RCA: 240] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Depletion of peroxisome proliferator-activated receptor gamma (PPARgamma) accompanies myofibroblastic transdifferentiation of hepatic stellate cells (HSC), the primary cellular event underlying liver fibrogenesis. The treatment of activated HSC in vitro or in vivo with synthetic PPARgamma ligands suppresses the fibrogenic activity of HSC. However, it is uncertain whether PPARgamma is indeed a molecular target of this effect, because the ligands are also known to have receptor-independent actions. To test this question, the present study examined the effects of forced expression of PPARgamma via an adenoviral vector on morphologic and biochemical features of culture-activated HSC. The vector-mediated expression of PPARgamma itself is sufficient to reverse the morphology of activated HSC to the quiescent phenotype with retracted cytoplasm, prominent dendritic processes, reduced stress fibers, and accumulation of retinyl palmitate. These effects are abrogated by concomitant expression of a dominant negative mutant of PPARgamma that prevents transactivation of but not binding to the PPAR response element. PPARgamma expression also inhibits the activation markers such as the expression of alpha-smooth muscle actin, type I collagen, and transforming growth factor beta1; DNA synthesis; and JunD binding to the activator protein-1 (AP-1) site and AP-1 promoter activity. Inhibited JunD activity by PPARgamma is not due to reduced JunD expression or JNK activity or to a competition for p300. But it is due to a JunD-PPARgamma interaction as demonstrated by co-immunoprecipitation and glutathione S-transferase pull-down analysis. Further, the use of deletion constructs reveals that the DNA binding region of PPARgamma is the JunD interaction domain. In summary, our results demonstrate that the restoration of PPARgamma reverses the activated HSC to the quiescent phenotype and suppresses AP-1 activity via a physical interaction between PPARgamma and JunD.
Collapse
Affiliation(s)
- Saswati Hazra
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90033, USA
| | | | | | | | | | | | | |
Collapse
|
341
|
Kamada Y, Tamura S, Kiso S, Matsumoto H, Saji Y, Yoshida Y, Fukui K, Maeda N, Nishizawa H, Nagaretani H, Okamoto Y, Kihara S, Miyagawa JI, Shinomura Y, Funahashi T, Matsuzawa Y. Enhanced carbon tetrachloride-induced liver fibrosis in mice lacking adiponectin. Gastroenterology 2003; 125:1796-807. [PMID: 14724832 DOI: 10.1053/j.gastro.2003.08.029] [Citation(s) in RCA: 377] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND & AIMS Obesity is one of the risk factors for liver fibrosis, in which plasma adiponectin, an adipocytokine, levels are decreased. Hepatic stellate cells play central roles in liver fibrosis. When they are activated, they undergo transformation to myofibroblast-like cells. Adiponectin suppresses the proliferation and migration of vascular smooth muscle cells, whose characteristics are similar to those of hepatic stellate cells. Adiponectin could have biological significances in liver fibrosis. METHODS The role of adiponectin on liver fibrosis induced by the administration of carbon tetrachloride twice a week for 12 weeks was tested by using adiponectin-knockout mice and an adenovirus-mediated adiponectin-expression system. We also investigated the effect of adiponectin in activated hepatic stellate cells. RESULTS When mice were administered carbon tetrachloride (300 microL/kg body weight) twice a week for 12 weeks, knockout mice showed extensive liver fibrosis with an enhanced expression of transforming growth factor-beta 1 and connective tissue growth factor compared with wild-type mice (P < 0.05). Injection of adenovirus producing adiponectin (AdADN) before carbon tetrachloride (1000 microL/kg body weight) treatment prevented liver fibrosis in wild-type mice (P < 0.001). Injection of AdADN at 6 weeks attenuated liver fibrosis even though carbon tetrachloride was given for an additional 6 weeks (total of 12 weeks). In cultured hepatic stellate cells, adiponectin suppressed platelet-derived growth factor-induced proliferation and migration and attenuated the effect of transforming growth factor-beta 1 on the gene expression of transforming growth factor-beta 1 and connective tissue growth factor and on nuclear translocation of Smad2. CONCLUSIONS The findings indicate that adiponectin attenuates liver fibrosis and could be a novel approach in its prevention.
Collapse
Affiliation(s)
- Yoshihiro Kamada
- Department of Internal Medicine and Molecular Science, Osaka University, Graduate School of Medicine, Suita, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
342
|
Zhang AS, Xiong S, Tsukamoto H, Enns CA. Localization of iron metabolism-related mRNAs in rat liver indicate that HFE is expressed predominantly in hepatocytes. Blood 2003; 103:1509-14. [PMID: 14563638 DOI: 10.1182/blood-2003-07-2378] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mRNAs of proteins involved in iron metabolism were measured in isolated hepatocytes, Kupffer cells, sinusoidal endothelial cells (SECs), and hepatic stellate cells (HSCs). Levels of type I hereditary hemochromatosis gene (HFE), transferrin, hepcidin, transferrin receptors 1 and 2 (TfR1, TfR2), ferroportin 1 (FPN1), divalent metal transporter 1 (DMT1), natural resistance-associated macrophage protein 1 (Nramp1), ceruloplasmin, hephaestin, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), were measured by quantitative reverse-transriptase polyerase chain reaction (qRT-PCR). We show that hepatocytes express almost all the iron-related genes tested, in keeping with their central role in iron metabolism. In addition, hepatocytes had 10-fold lower TfR1 mRNA levels than TfR2 and the lowest levels of TfR1 of the 4 cell types isolated. Kupffer cells, which process senescent red blood cells and recycle the iron, had high levels of ferroportin 1, ceruloplasmin, and hephaestin mRNA. Most important, of all the cell types tested, hepatocytes had the highest level of HFE mRNA, a factor of 10 higher than Kupffer cells. In situ hybridization analysis was conducted with rat liver sections. Consistent with the qRT-PCR analysis, HFE gene expression was localized mainly in hepatocytes. Western blot analysis confirmed this finding. Unexpectedly, HSCs also had high levels of DMT1 and ferroportin, implicating them in either iron sensing or iron cycling.
Collapse
Affiliation(s)
- An-Sheng Zhang
- Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, OR 97239, USA
| | | | | | | |
Collapse
|
343
|
Affiliation(s)
- Scott L Friedman
- Division of Liver Diseases, PO Box 1123, Mount Sinai School of Medicine, 1425 Madison Ave Room 1170F, New York, NY 10029, USA.
| |
Collapse
|
344
|
Mendez M, LaPointe MC. PPARgamma inhibition of cyclooxygenase-2, PGE2 synthase, and inducible nitric oxide synthase in cardiac myocytes. Hypertension 2003; 42:844-50. [PMID: 12885795 DOI: 10.1161/01.hyp.0000085332.69777.d1] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor superfamily. They regulate lipid metabolism, glucose homeostasis, cell proliferation, and differentiation and modulate inflammatory responses. We examined whether PPARgamma is functional in cultured neonatal ventricular myocytes and studied its role in inflammation. Western blots revealed PPARgamma in myocytes. When myocytes were transfected with a PPAR response element reporter plasmid (PPRE-TK-luciferase), the PPARgamma activator 15-deoxy-Delta12,14-prostaglandin J2 (15dPGJ2) increased promoter activity, whereas cotransfection of a dominant negative PPARgamma inhibited it. To determine the role of 15dPGJ2 in expression of proinflammatory genes, we tested its effect on interleukin-1beta induction of cyclooxygenase-2 (COX-2). 15dPGJ2 decreased interleukin-1beta stimulation of COX-2 by 40% and PGE2 production by 73%. We next questioned whether 15dPGJ2 was modulating the expression of inducible prostaglandin E2 synthase (PGES) and found that it completely blocked interleukin-1beta induction of PGES. Use of a second PPARgamma agonist, troglitazone, and the selective PPARgamma antagonist GW9662 demonstrated that the effects seen were PPARgamma-dependent. In addition, we found that 15dPGJ2 blocked interleukin-1beta stimulation of inducible nitric oxide synthase (iNOS). We concluded that 15dPGJ2 may play an anti-inflammatory role in a PPARgamma-dependent manner, decreasing COX-2, PGES, and PGE2 production, as well as iNOS expression.
Collapse
Affiliation(s)
- Mariela Mendez
- Hypertension and Vascular Research Division, Henry Ford Hospital, 2799 West Grand Blvd, Detroit, MI 48202-2689, USA
| | | |
Collapse
|
345
|
Neuschwander-Tetri BA, Brunt EM, Wehmeier KR, Oliver D, Bacon BR. Improved nonalcoholic steatohepatitis after 48 weeks of treatment with the PPAR-gamma ligand rosiglitazone. Hepatology 2003. [PMID: 14512888 DOI: 10.1002/hep.1840380427] [Citation(s) in RCA: 286] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Insulin resistance (IR) commonly is associated with nonalcoholic steatohepatitis (NASH). To establish whether IR causes NASH, this study was undertaken to determine if improving IR would improve the histologic features that define NASH. Thirty adults with prior biopsy evidence of NASH were enrolled to receive rosiglitazone, 4 mg twice daily for 48 weeks. All patients were overweight (body mass index [BMI] > 25 kg/m(2)) and 23% were severely obese (BMI > 35 kg/m(2)); 50% had impaired glucose tolerance or diabetes. Liver biopsy specimens were obtained before beginning treatment and at treatment completion. Twenty-six patients had posttreatment biopsies; of these, 22 had initial protocol liver biopsies that met published criteria for NASH on subsequent blinded evaluation. Within this initial NASH group, the mean global necroinflammatory score significantly improved with treatment and biopsies of 10 patients (45%) no longer met published criteria for NASH after treatment. Significant improvement in hepatocellular ballooning and zone 3 perisinusoidal fibrosis also occurred. Five patients withdrew early; the 25 patients completing 48 weeks of treatment had significantly improved insulin sensitivity and mean serum alanine aminotransferase (ALT) levels (104 initially, 42 U/L at the end of treatment). Adverse effects led to withdrawal of 3 patients (10%). Weight gain occurred in 67% of patients and the median weight increase was 7.3%. Within 6 months of completing treatment, liver enzyme levels had increased to near pretreatment levels. In conclusion, improving insulin sensitivity with rosiglitazone resulted in improved histologic markers of NASH, an observation suggesting that insulin resistance contributes to its development and that improving insulin sensitivity may be important in treating this liver disease.
Collapse
Affiliation(s)
- Brent A Neuschwander-Tetri
- University Liver Center, Department of Internal Medicine, Division of Gastroenterology and Hepatology, Saint Louis University School of Medicine, 3635 Vista Avenue, St. Louis, MO 63110, USA.
| | | | | | | | | |
Collapse
|
346
|
Bennett RG, Kharbanda KK, Tuma DJ. Inhibition of markers of hepatic stellate cell activation by the hormone relaxin. Biochem Pharmacol 2003; 66:867-74. [PMID: 12948868 DOI: 10.1016/s0006-2952(03)00403-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Hepatic fibrosis results from excess extracellular matrix produced primarily by hepatic stellate cells (HSC). In response to injury, HSC differentiate to a myofibroblastic phenotype expressing smooth muscle actin and fibrillar collagens. Relaxin is a polypeptide hormone shown to have antifibrotic effects in fibrosis models. In this study, activated HSC from rat liver were treated with relaxin to determine if relaxin can reverse markers of HSC activation. Relaxin treatment resulted in a decrease in the expression of smooth muscle actin, but had no effect on cell proliferation rate. The levels of total collagen and type I collagen were reduced, while the synthesis of new collagen was inhibited. Furthermore, relaxin caused an increase in the expression and secretion of rodent interstitial collagenase (MMP-13), but there was no effect on the gelatinases MMP-2 or MMP-9. Relaxin also increased secretion of TIMP-1 and TIMP-2. The effective concentration of relaxin to induce these effects was consistent with action through the relaxin receptor. In conclusion, relaxin reversed markers of the activated phenotype of HSC including the production of fibrillar collagen. At the same time, the activity of a fibrillar collagenase was increased. These data suggest that relaxin not only inhibits HSC properties that contribute to the progression of hepatic fibrosis, but also promotes the clearance of fibrillar collagen. Therefore, relaxin may be a useful approach in the treatment of hepatic fibrosis.
Collapse
Affiliation(s)
- Robert G Bennett
- Department of Medical Research, Veterans Affairs Medical Center, 4101 Woolworth Ave., Omaha, NE 68105, USA.
| | | | | |
Collapse
|
347
|
Li L, Grenard P, Nhieu JTV, Julien B, Mallat A, Habib A, Lotersztajn S. Heme oxygenase-1 is an antifibrogenic protein in human hepatic myofibroblasts. Gastroenterology 2003; 125:460-9. [PMID: 12891549 DOI: 10.1016/s0016-5085(03)00906-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND & AIMS Hepatic myofibroblasts play a key role in the development of liver fibrosis associated with chronic liver diseases. We have shown that oxidative stress is a messenger of 15-deoxy-delta-12,14-prostaglandin J2 (15-d-PGJ2) in human hepatic myofibroblasts. The aim of the present study was to investigate the role of a stress-inducible protein, heme oxygenase-1 (HO-1), in the action of 15-d-PGJ2. METHODS Expression of HO-1 was characterized in biopsy specimens of normal human liver and active cirrhosis by immunohistochemistry, and in cultured human hepatic myofibroblasts by Northern and Western blot analysis. Functional studies also were performed in cultured human hepatic myofibroblasts. RESULTS Immunohistochemistry showed that in biopsy specimens from normal livers, HO-1 protein expression was restricted to Kupffer cells. Biopsy specimens from cirrhotic patients displayed HO-1 protein both in macrophages and in myofibroblasts within fibrotic septa. HO-1 messenger RNA (mRNA) and protein also were detected in cultured human hepatic myofibroblasts and increased in response to 15-d-PGJ2 in a time- and dose-dependent manner. Induction of HO-1 in human hepatic myofibroblasts mediated 2 major antifibrogenic properties of 15-d-PGJ2, namely, inhibition of proliferation and of procollagen I mRNA expression. These effects were ascribed to bilirubin, one of the products of HO-1-mediated heme degradation. CONCLUSIONS This study shows that HO-1 is expressed in human hepatic myofibroblasts and induced during chronic liver injury. Moreover, these data unravel HO-1 as a major antifibrogenic pathway.
Collapse
Affiliation(s)
- Liying Li
- Unité INSERM 581, Hôpital Henri Mondor, Créteil, France
| | | | | | | | | | | | | |
Collapse
|
348
|
Xu J, Fu Y, Chen A. Activation of peroxisome proliferator-activated receptor-gamma contributes to the inhibitory effects of curcumin on rat hepatic stellate cell growth. Am J Physiol Gastrointest Liver Physiol 2003; 285:G20-30. [PMID: 12660143 DOI: 10.1152/ajpgi.00474.2002] [Citation(s) in RCA: 179] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Hepatic fibrogenesis occurs as a wound-healing process after many forms of chronic liver injury. Hepatic fibrosis ultimately leads to cirrhosis if not treated effectively. During liver injury, quiescent hepatic stellate cells (HSC), the most relevant cell type, become active and proliferative. Oxidative stress is a major and critical factor for HSC activation. Activation of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) inhibits the proliferation of nonadipocytes. The level of PPAR-gamma is dramatically diminished along with activation of HSC. Curcumin, the yellow pigment in curry, is a potent antioxidant. The aims of this study were to evaluate the effect of curcumin on HSC proliferation and to begin elucidating underlying mechanisms. It was hypothesized that curcumin might inhibit the proliferation of activated HSC by inducing PPAR-gamma gene expression and reviving PPAR-gamma activation. Our results indicated that curcumin significantly inhibited the proliferation of activated HSC and induced apoptosis in vitro. We demonstrated, for the first time, that curcumin dramatically induced the gene expression of PPAR-gamma and activated PPAR-gamma in activated HSC. Blocking its trans-activating activity by a PPAR-gamma antagonist markedly abrogated the effects of curcumin on inhibition of cell proliferation. Our results provide a novel insight into mechanisms underlying the inhibition of activated HSC growth by curcumin. The characteristics of curcumin, including antioxidant potential, reduction of activated HSC growth, and no adverse health effects, make it a potential antifibrotic candidate for prevention and treatment of hepatic fibrosis.
Collapse
Affiliation(s)
- Jianye Xu
- Dept. of Pathology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA
| | | | | |
Collapse
|
349
|
Abstract
Iron is an essential micronutrient. However, because human beings have no means to control iron excretion, excess iron, regardless of the route of entry, accumulates in parenchymal organs and threatens cell viability. Indeed, when iron-buffering capability is overwhelmed, oxidative stress-induced cell damage and fibrogenesis may arise, mainly in the liver, the main storage site for iron in the body. Results of recent studies have clearly shown that these pathologic events are induced by iron-generated reactive oxygen species and lipid peroxidation by-products. Hepatic fibrosis, characterized by excessive accumulation of extracellular matrix components in the liver, is a dynamic process, from chronic liver damage to end-stage liver cirrhosis. Iron-induced oxidant stress is involved in this process (1) as the primary cause of parenchymal cell necrosis or (2) as activator of cells that are effectors [e.g., hepatic stellate cells, (myo)fibroblasts] or key mediators (e.g., Kupffer cells) of hepatic fibrogenesis (or through both mechanisms). Beyond their effect as direct cytotoxic agents, iron and free radicals may trigger increased synthesis of collagen in myofibroblast-like cells as well as activate granulocytes and Kupffer cells, resulting in an increased formation of cytokines and eicosanoids and further reactive oxygen species. This may constitute a cascade of amplifying loops, which perpetuate the fibrogenic process. The fibrogenic potential of iron is even more dramatic when iron acts in concert with other hepatotoxins such as alcohol. In this instance, even if tissue iron levels are only slightly elevated, the toxic effect of alcohol or its metabolites may be amplified and propagated with rapid acceleration of the liver disease. At the molecular level, the presence of catalytically active "free iron" may (1) contribute directly to the hepatotoxicity of alcohol or (2) enhance the generation of cytokine and fibrogenic mediators from resident Kupffer cells (or be involved in both ways). A challenge for future research is to develop therapeutic tools able to block "redox-active" free iron in the cell.
Collapse
Affiliation(s)
- Antonello Pietrangelo
- Centre for the Study of Iron Disorders, Department of Internal Medicine, University of Modena and Reggio Emilia, Policlinico, Via del Pozzo 71, 41100 Modena, Italy.
| |
Collapse
|
350
|
Hellemans K, Rombouts K, Quartier E, Dittié AS, Knorr A, Michalik L, Rogiers V, Schuit F, Wahli W, Geerts A. PPARbeta regulates vitamin A metabolism-related gene expression in hepatic stellate cells undergoing activation. J Lipid Res 2003; 44:280-95. [PMID: 12576510 DOI: 10.1194/jlr.m200376-jlr200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Activation of cultured hepatic stellate cells correlated with an enhanced expression of proteins involved in uptake and storage of fatty acids (FA translocase CD36, Acyl-CoA synthetase 2) and retinol (cellular retinol binding protein type I, CRBP-I; lecithin:retinol acyltransferases, LRAT). The increased expression of CRBP-I and LRAT during hepatic stellate cells activation, both involved in retinol esterification, was in contrast with the simultaneous depletion of their typical lipid-vitamin A (vitA) reserves. Since hepatic stellate cells express high levels of peroxisome proliferator activated receptor beta (PPARbeta), which become further induced during transition into the activated phenotype, we investigated the potential role of PPARbeta in the regulation of these changes. Administration of L165041, a PPARbeta-specific agonist, further induced the expression of CD36, B-FABP, CRBP-I, and LRAT, whereas their expression was inhibited by antisense PPARbeta mRNA. PPARbeta-RXR dimers bound to CRBP-I promoter sequences. Our observations suggest that PPARbeta regulates the expression of these genes, and thus could play an important role in vitA storage. In vivo, we observed a striking association between the enhanced expression of PPARbeta and CRBP-I in activated myofibroblast-like hepatic stellate cells and the manifestation of vitA autofluorescent droplets in the fibrotic septa after injury with CCl4 or CCl4 in combination with retinol.
Collapse
Affiliation(s)
- Karine Hellemans
- Laboratory of Molecular Liver Cell Biology, Vrije Universiteit Brussel, 1090 Brussels, Belgium.
| | | | | | | | | | | | | | | | | | | |
Collapse
|