Regulation of TNF-alpha-induced IL-6 production in MG-63 human osteoblast-like cells.
Tumor necrosis factor-alpha (TNF-alpha) stimulates osteoblast production of interleukin-6 (IL-6), an inflammatory cytokine implicated in osteoclastic bone resorption. Therefore, we tested the hypothesis that TNF-alpha-induced IL-6 production in MG-63 osteosarcoma cells occurs via the p38 mitogen-activated protein kinase (MAPK) pathway. TNF-alpha activated p38 MAPK and stimulated IL-6 secretion by MG-63 cells, and pre-incubation of cells with the p38 MAPK inhibitor abrogated TNF-alpha-dependent IL-6 secretion. Transfection of IL-6 full-length and 5-deletion gene promoter reporter constructs indicated that p38 MAPK activation by TNF-alpha enhanced IL-6 gene expression, and that the p38 MAPK-responsive region resided in the proximal 260-bp segment. Transfection of NFkappaB and C/EBPbeta-sensitive reporter promoter constructs demonstrated that NFkappaB activity was enhanced and that constitutive C/EBPbeta was inhibited by TNF-alpha, with both effects being p38 MAPK-dependent. In conclusion, although p38 MAPK activation by TNF-alpha stimulates IL-6 secretion by MG-63 cells, it has opposing effects on c/EBPbeta and NFkappaB activity.
Webb
S J
SJ
Dept. of Oral Biology, UNMC, Lincoln, NE 68583, USA.
McPherson
J R
JR
Pahan
K
K
Koka
S
S
D000704:Analysis of Variance; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000502:physiology; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D012516:Osteosarcoma; D011401:Promoter Regions, Genetic; D018709:Statistics, Nonparametric; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology* / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases
D022782:CCAAT-Enhancer-Binding Protein-beta; D015850:Interleukin-6; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases