Publikationsserver der RWTH Aachen University
Untersuchungen zur TGF-[beta]1-Expression und -Bioverfügbarkeit bei der Leberfibrogenese
Abstract
dc:descriptionTransforming growth factor-Beta (TGF-Beta) is one of the most important cytokines mediating fibrogenesis in the liver and in other organs. The major portion of it is secreted as latent molecule complexed either only with the “latency associated peptide” (LAP) or with LAP and the “latent TGF-Beta binding protein” (LTBP). Activated hepatic stellate cells (HSC) and their fully transdifferentiated phenotype, the myofibroblasts (MFB), are considered to be the major source of latent TGF-Beta during the process of liver fibrogenesis. Due to the proposed functions of LTBP and its isoforms in the regulation of TGF-Beta-bioavailability and -activity, the effects of cytokines with striking importance during inflammation and fibrosis on the expressions of TGF-Beta 1 and LTBP-1 were investigated in cirrhotic fat storing cells (CFSC). This cell line was obtained from HSC isolated from cirrhotic rat livers after spontaneous immortalization in culture. By RT-PCR we show that CFSC basely express LTBP-1 and TGF-Beta 1 and in correlation, basal promoter activities of LTBP-1 and TGF-Beta 1 were detected in reporter gene assays using luciferase-promoter-constructs. 24 h after stimulation of transfected CFSC with TGF-Beta 1, IL-6, PDGF-BB or TNF-Alpha no strong induction of the LTBP-1 promoters was found, although the mRNA transcript levels from stimulated cells increased two fold by PDGF-BB stimulation, going along with increased LTBP-1 protein amounts, as detected by Western blot analyses of conditioned medium. At the same time PDGF-BB had no effect on TGF-Beta promoter activity, mRNA expression or protein secretion. Vice versa TGF-Beta 1 treatment did not alter LTBP-1-expression while an autocrine induction (1,75-fold) of the TGF-Beta-promoter was found matching a two-fold increase in mRNA-levels. TNF-Alpha also induced expression of TGF-Beta 1 but not LTBP-1 whereas IL-6 revealed no regulatory effect. Parallel transfection studies using a luciferase construct, which contains nine copies of a TGF-Beta 1-inducible DNA element (“CAGA”), confirmed responsiveness of the cells to active TGF-Beta 1 and indicate basely synthesized TGF-Beta 1 being secreted as inactive complex which can be activated by transient acidification. Our data show that LTBP-1 and TGF-Beta 1 are differentially regulated by cytokines, that basely synthesized TGF-Beta 1 is secreted by CFSC in a latent form, possibly bound to LTBP, and that LTBP-1 but not TGF-Beta 1 is induced by PDGF-BB in these cells.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2005
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Westhoff, Jens Hendrik
- Contributors dc:contributor
-
- Gressner, Axel M.
Subjects
dc:subject × 7Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger