Effect of subtoxic concentrations of metal ions on NFκB activation in THP-1 human monocytes

THP-1 human monocytes and human peripheral blood monocytes have altered inflammatory cytokine secretion profiles after exposure to a variety of metal ions known to be released from biornaterials. Transcriptional regulation of these cytokines often involves activation of the transcription factor NFkappaB. The present study was designed to determine whether metal ion treatment of monocytes results in changes in levels of activated NFkappaB. THP-1 cells were grown in suspension in the presence of sublethal concentrations of ions of Ag+, Co2+, Cu2+, Hg2+, Ni2+ and Pd2+. After 24 h of exposure to metal ions, the cells were harvested, counted, and the nuclear proteins extracted. Electrophoretic mobility shift assays were performed using a P-32-ATP end-labeled oligonucleotide consensus sequence for the NFkappaB transcription factor. DNA/protein complexes were quantified by phosphorimage analysis and compared by ANOVA (Tukey, alpha = 0.05). Exposure of THP-1 cells to 100 muM of Pd2+ caused a significant increase in activated NFkappaB (p < 0.05) whereas treatment with 5 muM of Ag+ resulted in significantly decreased levels of nuclear NFkappaB (p < 0.05). No other metal ions tested caused a significant change in basal levels of nuclear NFkappaB (Co2+, Hg2+, Ni2+, and Cu2+). However, exposure to 50 muM Of Cu2+ resulted in a reproducible, though not significant, increase in nuclear NFkappaB levels. These results indicate that inflammatory responses to some metal ions may be influenced by NFkappaB-mediated transcriptional regulation. (C) 2002 Wiley Periodicals, Inc.