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Persistent activation of nuclear factor-kappaB in cultured rat hepatic stellate cells involves the induction of potentially novel Rel-like factors and prolonged changes in the expression of IkappaB family proteins

Lookup NU author(s): Dr Ahmed Elsharkawy, Professor Matthew Wright, Professor Derek Mann

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Abstract

Rat hepatic stellate cells (HSC) cultured in serum-containing medium underwent a rapid (3-hour) classical induction of p50:p65 and p65:p65 nuclear factor-kappaB (NF-kappaB) dimers. Subsequent culturing was associated with prolonged expression of active p50:p65 and persistent induction of a high-mobility NF-kappaB DNA binding complex consisting of potentially novel Rel-like protein(s). Formation of the latter complex was competed for by specific double-stranded oligonucleotides, was up-regulated by treatment of HSCs with tumor necrosis factor alpha (TNF-alpha), and was maintained at basal levels of expression by a soluble HSC-derived factor. An NF-kappaB-responsive CAT reporter gene was highly active in early cultured HSCs but was also trans-activated at a lower but significant level in longer-term cultured cells and could be completely suppressed by expression of dominant negative IkappaB-alpha. Physiological significance of the lower persistent NF-kappaB activities was also demonstrated by the ability of long-term cultured HSCs to support the activity of the NF-kappaB-dependent human intercellular adhesion molecule-1 (ICAM-1) promoter. Freshly isolated HSCs expressed high levels of IkappaB-alpha and IkappaB-beta. Culture activation was accompanied by a long-term reduction in levels of IkappaB-alpha with no detectable expression in the nuclear fraction of cells, under these conditions p50:p65 was detected in the nucleus. IkappaB-beta expression was transiently reduced and, upon replenishment, was associated with appearance of a lower-mobility IkappaB-beta antibody-reactive species. Bcl3 expression was absent in freshly isolated HSC but was induced during culturing and became a persistent feature of the activated HSC. Inhibition of NF-kappaB DNA binding activity by gliotoxin was associated with increased numbers of apoptotic cells. We suggest that activation of NF-kappaB in cultured HSC is required for expression of specific genes associated with the activated phenotype such as ICAM-1 and may be antiapoptotic for rat HSCs.


Publication metadata

Author(s): Wright MC; Mann DA; Elsharkawy AM; Hay RT; Arthur MJ; Hughes T; Bahr MJ; Degitz K

Publication type: Article

Publication status: Published

Journal: Hepatology

Year: 1999

Volume: 30

Issue: 3

Pages: 761-769

ISSN (print): 0270-9139

ISSN (electronic): 1527-3350

Publisher: John Wiley & Sons, Inc.

URL: http://dx.doi.org/10.1002/hep.510300327

DOI: 10.1002/hep.510300327


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