Acute cadmium exposure enhances AP-1 DNA binding and induces cytokines expression and heat shock protein 70 in HepG2 cells

Cadmium (Cd) has been regarded as one of the inflammation-related xenobiotics. Cd has been extensively studied in many cellular systems, but a lot of parameters have been evaluated in different experimental conditions. This study was undertaken to examine the effects of low cadmium concentrations in HepG2 cells in the oxidative stress produced, the IL-1beta, tumor necrosis factor (TNF-alpha), IL-6, and IL-8 expression, production of heat shock protein 70 (Hsp70) and the activation of nuclear factors activation protein-1 (AP-1) and NF-kappaB under the same experimental conditions. Also, the participation of TNF-alpha and oxidative stress in AP-1 activation was evaluated. Lipid peroxidation damage increased 1.5 times after the first hour of Cd treatment and increased 1.9 times after 2 h. Similar values were maintained until 6 h. Reduced glutathione (GSH) diminished 65% after 6 h CdCl2 treatment. N-acetylcysteine (NAC) pre-treatment increased 332% GSH in Cd-treated cells. RNA was isolated from HepG2 cells after 0.5, 1, 3, or 6 h incubation with 1, 5, or 10 muM CdCl2. TNF-alpha and IL-1beta presented a maximum response after 1 h treatment. while IL-6 and IL-8 maximum response was after 3 h treatment. The Hsp70, determined by Western blot, was constitutively produced, and it increased after 3 h Cd treatment. NF-kappaB activation, determined by EMSA, was not increased as a result of Cd treatment. DNA binding of AP-1 was detected and increased, with time up to 4 h with an increment of 24 times control value with 5 muM CdCl2. The HepG2 cells were pretreated with anti-TNF-alpha antibody or I mM N-acetylcysteine I h before Cd treatment. Anti-TNF-alpha treatment reduced 67% AP-1 activation, while NAC 47.5%. These data indicate that, Cd-induced TNF-alpha and IL-1beta, that probably, activate AP-1 transcription factor and IL-6 and IL-8 were induced. Anti-TNF-alpha and NAC partially inhibited AP-1 activation. All imply that, a number of factors participate in AP-1 cadmium-induced activation. The Hsp70 is produced by the HepG2 cells after cadmium treatment, and probably has a role in the non-participation of NF-kappaB in the cellular response. (C) 2004 Elsevier Ireland Ltd. All rights reserved.