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Transforming growth factor β and tumor necrosis factor α inhibit both apoptosis and proliferation of activated rat hepatic stellate cells

✍ Scribed by Bernhard Saile; Nina Matthes; Thomas Knittel; Giuliano Ramadori

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
244 KB
Volume
30
Category
Article
ISSN
0270-9139

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✦ Synopsis

Transforming growth factor ␤ (TGF-␤) as well as tumor necrosis factor ␣ (TNF-␣) gene expression are up-regulated in chronically inflamed liver. These cytokines were investigated for their influence on apoptosis and proliferation of activated hepatic stellate cells (HSCs). Spontaneous apoptosis in activated HSC was significantly down-regulated by 53% ؎ 8% (P F .01) under the influence of TGF-␤ and by 28% ؎ 2% (P F .05) under the influence of TNF-␣. TGF-␤ and TNF-␣ significantly reduced expression of CD95L in activated HSCs, whereas CD95 expression remained unchanged. Furthermore, HSC apoptosis induced by CD95agonistic antibodies was reduced from 96% ؎ 2% to 51 ؎ 7% (P F .01) by TGF-␤, and from 96% ؎ 2% to 58 ؎ 2% (P F .01) by TNF-␣, suggesting that intracellular antiapoptotic mechanisms may also be activated by both cytokines. During activation, HSC cultures showed a reduced portion of cells in the G 0 /G 1 phase and a strong increment of G 2 -phase cells. This increment was significantly inhibited (G 1 arrest) by administration of TGF-␤ and/or TNF-␣ to activated cells. In liver sections of chronically damaged rat liver (CCl 4 model), using desmin and CD95L as markers for activated HSC, most of these cells did not show apoptotic signs (TUNEL-negative). Taken together, these findings indicate that TGF-␤ and/or TNF-␣ both inhibit proliferation and also apoptosis in activated HSC in vitro. Both processes seem to be linked to each other, and their inhibition could represent the mechanism responsible for prolonged survival of activated HSC in chronic liver damage in vivo. (HEPATOLOGY 1999;30:196-202.) MATERIALS AND METHODS HSC Isolation, Characterization, Plating, and Culture Conditions. Wistar rats were provided by Charles River (Sulzfeld, Germany) and maintained under 12-hour light/dark cycles with food and water ad

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