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

✍ Scribed by Ahmed M. Elsharkawy; Matthew C. Wright; Ron T. Hay; Michael J. Arthur; Timothy Hughes; Matthias J. Bahr; Klaus Degitz; Derek A. Mann

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 228 KB
• Volume: 30
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.510300327

✦ Synopsis

Rat hepatic stellate cells (HSC

) cultured in serumcontaining medium underwent a rapid (3-hour) classical induction of p50:p65 and p65:p65 nuclear factor-B (NF-B) dimers. Subsequent culturing was associated with prolonged expression of active p50:p65 and persistent induction of a high-mobility NF-B 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 ␣ (TNF-␣), and was maintained at basal levels of expression by a soluble HSC-derived factor. An NF-B-responsive CAT reporter gene was highly active in early cultured HSCs but was also trans-activated at a lower but significant level in longerterm cultured cells and could be completely suppressed by expression of dominant negative IB-␣. Physiological significance of the lower persistent NF-B activities was also demonstrated by the ability of long-term cultured HSCs to support the activity of the NF-B-dependent human intercellular adhesion molecule-1 (ICAM-1) promoter. Freshly isolated HSCs expressed high levels of IB-␣ and IB-␤.

Culture activation was accompanied by a long-term reduction in levels of IB-␣ with no detectable expression in the nuclear fraction of cells, under these conditions p50:p65 was detected in the nucleus. IB-␤ expression was transiently reduced and, upon replenishment, was associated with appearance of a lower-mobility IB-␤ antibodyreactive 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-B DNA binding activity by gliotoxin was associated with increased numbers of apoptotic cells. We suggest that activation of NF-B 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.