Effects of arsenic and its metabolites on p53 gene expression in BEAS-2B cells

Abstract

BackgroundArsenic is a human carcinogen. Arsenic and its metabolites affect the expression of p53, but whether there are any changes of p53 phosphorylation and ubiquitination levels in human bronchial epithelium cells (BEAS-2B) are not clear after exposure to arsenic and its metabolites. ObjectiveTo study the effects of arsenic and its metabolites monomethylarsic acid (MMA) and dimethylarsinic acid (DMA) on the expression of tumor suppressor gene p53 in BEAS-2B cells. MethodsDifferent concentrations of sodium arsenite (NaAsO2) were used to infect BEAS-2B cells, and the cell viability was detected with CCK-8 reagent to determine the dose and time of NaAsO2 used for the following study. Based on the results of cell viability, the cells were divided into two panels: a sodium arsenide panel and an arsenic methylation metabolite penal. The doses of sodium arsenite were 0, 2, 4, and 6 μmol·L−1 NaAsO2; the arsenic methylation metabolite panel consisted of 0 μmol·L−1 NaAsO2 group (control), 6 μmol· L−1 MMA group, 6 μmol· L−1 DMA group， and 6 μmol· L−1 NaAsO2 group. The cells were collected after 48 h treatment, and the total protein and total RNA were extracted. The relative levels of p53 mRNA expression were determined by quantitative real-time polymerase chain reaction (qRT-PCR), the relative expression levels of p53 protein, p53 Ser9 and Ser15 phosphorylated proteins were determined by Western blot, and the level of p53 ubiquitination was detected by co-immunoprecipitation (CO-IP). ResultsCompared with the control group, the cell viability rates in all BEAS-2B cells treated by NaAsO2 were significantly reduced (P<0.05), and the 50% cell viability was observed at 6 μmol·L−1. Compared with the control group, the relative expression level of p53 mRNA gradually decreased after NaAsO2 (2, 4, 6 μmol·L−1) treatment (P<0.05), the relative expression levels of p53 protein and Ser9 phosphorylated protein induced by NaAsO2 also decreased gradually (P<0.05), and the relative expression level of p53 Ser15 phosphorylated protein induced by NaAsO2 followed the same pattern, but it was only lower than that of the control group in the 6 μmol·L−1 NaAsO2 group (P<0.05). Compared with the control group, there were no significant effects on the relative expression levels of p53 mRNA, p53 protein, Ser9 and Ser15 phosphorylated proteins in the MMA group and the DMA group. Compared with the control group, the expression level of p53 ubiquitination was significantly decreased and the expression of K48 ubiquitination decreased significantly after NaAsO2 infection. ConclusionArsenic causes a decrease in the expression of the p53 protein in BEAS-2B cells, largely due to inhibition of the phosphorylated pathway and a decrease in mRNA expression, and protein changes caused by a decrease in p53 ubiquitination do not play a dominant role. MMA and DMA do not affect p53 gene expression.

Keywords

• arsenic
• p53
• monomethylarsin
• dimethylarsinic acid
• ubiquitination