Au(III), Pd(II), Ni(II), and Hg(II) alter NF kappa B signaling in THP1 monocytic cells.
The transcription factor NFkappaB plays a key role in the tissue inflammatory response. Metal ions released into tissues from biomaterials (e.g., Au, Pd, Ni, Hg) are known to alter the binding of NFkappaB proteins to DNA, thereby modulating the effect of NFkappaB on gene activation and, ultimately, the tissue response to biomaterials. Little is known about the effect of these metals on key signaling steps prior to NFkappaB-DNA binding such as transcription factor activation or nuclear translocation, yet these steps are equally important to modulation of the pathway. Oxidative stress is known to alter NFkappaB proteins and is suspected to play a role in metal-induced NFkappaB signaling modulation. Our aim in the current study was to assess the effects of sublethal levels of Ni, Hg, Pd, and Au ions on NFkappaB activation and nuclear translocation in the monocyte, which is acknowledged as an important orchestrator of the biological response to materials and the pathogenesis of chronic disease. Sublethal concentrations of Au(III), Ni(II), Hg(II), and Pd(II) were added to cultures of human THP1 monocytic cells for 72 h. In parallel cultures, lipopolysaccharide (LPS) was added for the last 30 min to activate the monocytic cells. Then cellular cytoplasmic and nuclear proteins were isolated, separated by electrophoresis, and probed for IkappaBalpha degradation (activation) and NFkappaB p65 translocation. Protein levels were digitally quantified and statistically compared. The levels of reactive oxygen species (ROS) in the monocytic cells were measured as a possible mechanism of metal-induced NFkappaB modulation. Only Au(III) activated IkappaBalpha degradation by itself. Au(III) and Pd(II) enhanced LPS-induced IkappaBalpha degradation, but Hg(II) and Ni(II) suppressed it. Au(III), Ni(II), and Pd(II) activated p65 nuclear translocation without LPS, and all but Ni(II) enhanced LPS-induced translocation. Collectively, the results suggest that these metal ions alter activation and translocation of NFkappaB, each in a unique way at unique concentrations. Furthermore, even when these metals had no overt effects on signaling by themselves, all altered activation of signaling by LPS, suggesting that the biological effects of these metals on monocytic function may only be manifest upon activation. None of the metal ions elevated levels of ROS at 72 h, indicating that ROS were probably not direct modulators of the NFkappaB activation or translocation at this late time point.
School of Dentistry, Medical College of Georgia, Augusta, Georgia 30912-1126, USA.
J B
JB
Lewis
J C
JC
Wataha
V
V
McCloud
P E
PE
Lockwood
R L W
RL
Messer
W-Y
WY
Tseng
D002413:Cations, Divalent; D045744:Cell Line, Tumor; D006046:Gold / Q000502:physiology; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D015151:Immunoblotting; D008628:Mercury / Q000502:physiology; D019216:Metals, Heavy / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009532:Nickel / Q000502:physiology; D010165:Palladium / Q000502:physiology; D010766:Phosphorylation; D021381:Protein Transport / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology
D002413:Cations, Divalent; D020672:I-kappa B Proteins; D019216:Metals, Heavy; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D017382:Reactive Oxygen Species; D000072000:NF-KappaB Inhibitor alpha; D010165:Palladium; D006046:Gold; D009532:Nickel; D008628:Mercury