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

Abstract

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 1RB3AN27. These mesencephalic cells were treated with low concentrations of sodium arsenite (0.1, 0.5, 1, 5, and 10 microM) and incubated for different periods of time (0-4 h). Arsenite was cytotoxic at 5 and 10 microM 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-kappaB) and activator protein-1 (AP-1) as shown by electro mobility shift assay. Incubation of antioxidants, either N-acetyl-L-cysteine (50 microM) or alpha-tocopherol (50 microM) with 1 microM arsenite, suppressed ROS generation. Arsenite at 1 microM concentration was sufficient for maximal activation of NF-kappaB and AP-1 activation. Time kinetics studies showed maximal activation of NF-kappaB by 1 microM concentration of arsenite was seen at 120 min and correlated with complete degradation of Ikappa Balpha at 60 min. Similarly, maximal activation of AP-1 by 1 microM concentration of arsenite occurred at 120 min. N-acetyl-L-cysteine at 50 microM 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 microM 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.

Analysis of mice with targeted deletion of AQP9 gene provides conclusive evidence for expression of AQP9 in neurons

“…A recent study has shown that As(13) and dopamine synergistically can cause enhanced toxicity in cultured neuronal cells with a dopaminergic phenotype (Shavali and Sens, 2008). Another study suggests that arsenite, at low and nontoxic concentrations, induces oxidative stress leading to activation of early transcription factors in immortalized mesencephalic neurons (Felix et al, 2005). Addition of antioxidants inhibited the activation of these factors.…”

The mechanistic basis of arsenicosis: Pathogenesis of skin cancer

“…IκK has a thiol moiety that may be modified by AsIII leading to IκK activation. However, arsenic-mediated ROS have also been found to promote NFκB-mediated apoptosis [73–75]. These opposing findings, though perplexing, may point to the importance of the dose-dependent effects of arsenic.…”

A Critical Role for IκB Kinase β in Metallothionein-1 Expression and Protection against Arsenic Toxicity

“…Cells normally respond to these changes by activating the defense mechanisms to re-establish redox homeostasis and protect from oxidative damage (15,16). We and others have previously reported the transcriptional activation by arsenite of a battery of antioxidant genes, including hemeoxygenase-1, metallothionein 1 and 2, and thioredoxin reductase 1, which may result in parallel changes in protein levels and enzyme or binding activity (17,18).…”