Selective activation of NF‐κB and E2F by low concentration of arsenite in U937 human monocytic leukemia cells

Abstract

Arsenite has been reported to exert dose-dependent dual effects: triggering apoptosis at relatively high concentrations, whereas inducing partial differentiation at low concentrations in leukemia cells. However, the relevant molecular mechanisms of its action at low and nonapoptotic concentrations remain to be elucidated. We examined the effect of arsenite on activation of key transcription factors in cultured U937 human monocytes/macrophages. Electrophoretic mobility shift assay (EMSA), protein/DNA array and luciferase reporter assay were used to analyze the effect of arsenite on the functional activities of transcription factors. Protein/DNA array analysis showed that activation of E2F was seen after 6-h exposure to 1 and 10 microM arsenite. In contrast, activation of NF-kappaB took place only at 1 microM arsenite, whereas 10 microM arsenite showed no recognizable effect on this nuclear transcription factor in the protein/DNA array analysis. EMSA using a NF-kappaB consensus probe indicates the functional activation of RelB/p50 in the presence of 1 microM arsenite, confirming the above results. Luciferase reporter assay for NF-kappaB showed activation of NF-kappaB in the presence of 1 microM arsenite. Interleukin (IL)-8 and B-cell-activating factor of the tumor necrosis factor family (BAFF) mRNA expression, which have been shown to be regulated through NF-kappaB, were activated in the presence of 1 microM arsenite. These results support the hypothesis that the primary action of nonapoptotic concentrations of arsenite in this cell line is activation of NF-kappaB, signaling as a decision maker for end results such as inflammation disease or cancer. This finding offers the possibility of providing a logical explanation for the observations made by many scientists that chronic exposure of human populations to low doses of arsenic is significantly correlated to clinical signs of inflammation in many tissues.

Arsenic treatment increase Aurora-A overexpression through E2F1 activation in bladder cells

“…Previous studies reported that E2F transcription factor is activated after arsenic treatment [21]. Here, we found that the protein level of E2F1, a member of E2F family, was increased dose dependently after arsenic treatment for 24 h (Fig.…”

“…Arsenic increases the activity of c- myc and E2F-1 [20] and selective activation of NF-kB and E2F by low concentration of arsenite in U937 human monocytic leukemia cells [21]. Aurora-A acts as a direct target of E2F3 during G2/M cell cycle progression [22].…”

Suppression of methylmercury-induced IL-6 and MCP-1 expressions by N-acetylcysteine in U-87MG human astrocytoma cells

“…PCR amplification was conducted as reported in previous studies [41,42] in a total volume of 20 μL containing cDNA and each primer (0.5 μM). Primers used of forward (F) and reverse (R) were β-actin, 5′-ACCCCGTGCTGCTGACC-3′(F) and 5′-CCAGAGGCGTACAGGGAT AGC-3′(R); IL-6, 5′-GAACTCCTTCTCCACAAGCG-3′(F) and 5′-TTTTCT GCCAGTGCCTCTTT-3′(R); and MCP-1, 5′-CAGCAGCAAGTGTCCCAA AG-3′(F) and 5′-GAGTGAGTGTTCAAGTCTTCGG-3′(R), respectively.…”

Mechanisms and Immune Dysregulation in Arsenic Skin Carcinogenesis

“…In fact, clinical studies in arsenic-induced Bowen's disease (As-BD) uncovered the correlations between increased 8-OHdG levels and the arsenic concentration in the lesional skin [26], indicating the importance of oxidative stress in arsenical skin carcinogenesis. Mechanistically, in vitro studies showed low concentrations of arsenic (< 5 µM) can generate ROS, which in term increases the transcription of the nuclear factor kappa B (NF-KB) [24,[27][28][29][30], that eventually promotes cell proliferation [31].…”