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Transforming growth factor β and tumor necrosis factor α inhibit both apoptosis and proliferation of activated rat hepatic stellate cells
Author(s) -
Saile Bernhard,
Matthes Nina,
Knittel Thomas,
Ramadori Giuliano
Publication year - 1999
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.510300144
Subject(s) - hepatic stellate cell , apoptosis , tumor necrosis factor alpha , transforming growth factor , biology , tunel assay , transforming growth factor beta , cancer research , endocrinology , microbiology and biotechnology , medicine , biochemistry
Abstract Transforming growth factor β (TGF‐β) as well as tumor necrosis factor α (TNF‐α) 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 < .01) under the influence of TGF‐β and by 28% ± 2% ( P < .05) under the influence of TNF‐α. TGF‐β and TNF‐α significantly reduced expression of CD95L in activated HSCs, whereas CD95 expression remained unchanged. Furthermore, HSC apoptosis induced by CD95‐agonistic antibodies was reduced from 96% ± 2% to 51 ± 7% ( P < .01) by TGF‐β, and from 96% ± 2% to 58 ± 2% ( P < .01) by TNF‐α, 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‐β and/or TNF‐α 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‐β and/or TNF‐α 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 .