Low levels of arsenite activates nuclear factor-κB and activator protein-1 in immortalized mesencephalic cells

Degeneration of dopaminergic neurons is one of the major features of Parkinson's disease. Many redox-active metals such as iron and manganese have been implicated in neuronal degeneration characterized by symptoms resembling Parkinson's disease. Even though, arsenic, which is another redox-active metal, has been shown to affect the central monoaminergic systems, but its potential in causing dopaminergic cell degeneration has not been fully known. Hence, the present study was designed to investigate arsenic signaling especially that is mediated by reactive oxygen species and its effect on early transcription factors in dopamine producing mesencephalic cell line 1RB(3)AN(27). These mesencephalic cells were treated with low concentrations of sodium arsenite (0.1, 0.5, 1, 5, and 10 mu M) and incubated for different periods of time (0-4 h). Arsenite was cytotoxic at 5 and 10 mu M concentrations only after 72-h incubation period. Arsenite, in a dose-dependent manner, induced generation of reactive oxygen species (ROS) and activation of early transcription factors such as nuclear factor-kappa B (NF-kappa B) and activator protein-1 (AP-1) as shown by electro mobility shift assay. Incubation of antioxidants, either N-acetyl-L-cysteine (50 mu M) or alpha-tocopherol (50 mu M) with 1 mu M arsenite, suppressed ROS generation. Arsenite at 1 mu M concentration was sufficient for maximal activation of NF-kappa B and AP-1 activation. Time kinetics studies showed maximal activation of NF-kappa B by 1 mu M concentration of arsenite was seen at 120 min and correlated with complete degradation of T kappa B alpha at 60 min. Similarly, maximal activation of AP-1 by 1 mu M concentration of arsenite occurred at 120 min. N-acetyl-L-cysteine at 50 mu M concentration inhibited arsenite-induced NF-kappa B and AP-1. In addition, arsenite was shown to induce phosphorylation of extracellular signal regulated kinase (ERK) 1/2 at concentrations of 1 mu M and above. These results suggest that arsenite, at low and subcytoxic concentrations, appears to induce oxidative stress leading to activation of early transcription factors whereas addition of antioxidant inhibited the activation of these factors. (c) 2005 Wiley Periodicals, Inc.