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TNF‐α Increases Expression of IL‐6 and ICAM‐1 Genes Through Activation of NF‐κB in Osteoblast‐like ROS17/2.8 Cells
Author(s) -
Kurokouchi Kazutoshi,
Kambe Fukushi,
Yasukawa Kou,
Izumi Ryutaro,
Ishiguro Naoki,
Iwata Hisashi,
Seo Hisao
Publication year - 1998
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.1998.13.8.1290
Subject(s) - tumor necrosis factor alpha , osteoblast , nfkb1 , p50 , cytosol , microbiology and biotechnology , messenger rna , electrophoretic mobility shift assay , endocrinology , signal transduction , nf κb , medicine , chemistry , western blot , gene expression , biology , transcription factor , biochemistry , gene , in vitro , enzyme
Tumor necrosis factor‐α (TNF‐α) plays a key role in inflammatory diseases such as rheumatoid arthritis and in postmenopausal osteoporosis. In various tissues, TNF‐α action is mediated by a transcription factor, nuclear factor‐kappa B (NF‐κB). However, little is known about how TNF‐α exerts its action in osteoblasts. We thus examined the effect of TNF‐α on the activation of NF‐κB in rat osteoblast‐like osteosarcoma cells (ROS17/2.8). Electrophoretic mobility shift assay revealed that the activation of the p50‐p65 heterodimer NF‐κB was induced by TNF‐α as early as 15 minutes followed by a persistent activation for 48 h. When the binding activity of NF‐κB in cytosol was examined using detergents that dissociate NF‐κB from an inhibitory protein IκB, it decreased during the initial 30 minutes and then increased to the unstimulated level. Northern blot analysis revealed a marked increase in the mRNA levels of p105, a precursor of p50, 6 h after TNF‐α and a gradual increase in p65 mRNA levels during the initial 1 h. Significant increase in both mRNA levels continued until 24 h after TNF‐α. These results suggest that the rapid activation of NF‐κB by TNF‐α is mainly due to the nuclear translocation of NF‐κB pre‐existing in cytosol, and that the subsequent increase in the expression of p50 and p65 may result in the persistent activation of NF‐κB during TNF‐α stimulation. TNF‐α also increased the mRNA levels of interleukin‐6 (IL‐6) and intercellular adhesion molecule‐1 (ICAM‐1). An antioxidant, N‐acetyl‐L‐cysteine, significantly attenuated the TNF‐α–dependent increase in these mRNAs, and simultaneously reduced the activation of NF‐κB by TNF‐α, indicating that NF‐κB mediates the TNF‐α–dependent expression of IL‐6 and ICAM‐1 in ROS17/2.8 cells. These results suggest that the activation of NF‐κB by TNF‐α may play an important role in the production of cytokines and cell adhesion molecules from osteoblasts, leading to the promotion of bone resorption and inflammation.