Effects of arsenic and its metabolites on expressions of BCL-2α and BCL-2β transcripts

YAN Xingyu; QU Zihan; PU Huijie; YANG Xingquan; ZHOU Tianlin; HE Yuefeng

doi:10.11836/JEOM21101

YAN Xingyu, QU Zihan, PU Huijie, YANG Xingquan, ZHOU Tianlin, HE Yuefeng. Effects of arsenic and its metabolites on expressions of BCL-2α and BCL-2β transcripts[J]. Journal of Environmental and Occupational Medicine, 2022, 39(1): 78-84. DOI: 10.11836/JEOM21101

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Effects of arsenic and its metabolites on expressions of BCL-2α and BCL-2β transcripts

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Background Arsenic is a toxicant that can affect the expressions of the cellular anti-apoptotic gene BCL-2 and its protein, but the effects of arsenic on BCL-2α and BCL-2 \beta transcripts have not been reported.

Objective To investigate the potential effects of arsenic and its metabolites, methylarsonic acid (MMA) and dimethylarsonic acid (DMA), on BCL-2α, BCL-2 \beta , and BCL-2T (total of α and \beta transcripts) in human bronchial epithelial cells (16HBE) and human lung adenocarcinoma cells (A549).

Methods 16HBE cells and A549 cells were randomly divided into three categories of exposure after in vitro culture: single-selected arsenic compound exposure groups with isoconcentration (16HBE cells were treated with 4.5 μmol·L⁻¹ of MMA, DMA, and sodium arsenite, respectively, while A549 cells were treated with 60 μmol·L⁻¹ of MMA, DMA, and sodium arsenite, respectively), sodium arsenite exposure groups with different concentrations (16HBE cells were treated with 1.5, 3.0, and 4.5 μmol·L⁻¹ of sodium arsenite respectively, while A549 cells were treated with 20, 40, and 60 μmol·L⁻¹ of sodium arsenite respectively), and combined exposure groups (i.e. MMA+sodium arsenite, and DMA+sodium arsenite; the exposure concentrations of 16HBE cells were both 1.5 μmol·L⁻¹ and both 4.5 μmol·L⁻¹ respectively, and those of A549 cells were both 20 μmol·L⁻¹ and both 60 μmol·L⁻¹ respectively). Meanwhile, a blank control group was also set up in each exposure category. After 48 h of continuous exposure, the relative expressions of BCL-2α, BCL-2 \beta , and BCL-2T in both cells were detected by real-time PCR.

Results Regarding the single-selected arsenic compound exposure, in 16HBE cells, the expression levels of BCL-2α and BCL-2T under 4.5 μmol·L⁻¹ MMA treatment were lower than those in their control groups (q=3.27, 2.93, both P<0.05), and the expression levels ofBCL-2α, BCL-2 \beta , and BCL-2T under 4.5 μmol·L⁻¹ sodium arsenite were lower than those in their respective control groups (q=11.06, 3.65, 10.70, all P<0.05). In A549 cells, the expression level ofBCL-2T treated with 60 μmol·L⁻¹ DMA was lower than that in the control group (q=3.12, P<0.05), and the expression levels ofBCL-2α, BCL-2 \beta , and BCL-2T treated with 60 μmol·L⁻¹ sodium arsenite were lower than those in their respective control groups (q=7.59, 7.27, 8.06, all P<0.05). Regarding the sodium arsenite exposure: 16HBE cells treated with 1.5 μmol·L⁻¹ sodium arsenite had a lower expression level of BCL-2α and a higher expression level of BCL-2 \beta than those in their respective control groups (q=6.06, 11.92, both P<0.05); the expression level ofBCL-2α under 3.0 μmol·L⁻¹ sodium arsenite was lower than that in the control group (q=12.72, P<0.05); and under 4.5 μmol·L⁻¹ sodium arsenite treatment, the expression levels of BCL-2α, BCL-2 \beta , and BCL-2T were lower than those in their respective control groups (q=15.72, 6.79, 6.62, all P<0.05). The expression levels ofBCL-2α gradually decreased with increasing concentrations of sodium arsenite (F_{α trend}=144.80, P<0.001), whileBCL-2 \beta and BCL-2T decreased in a dose-dependent manner in the range of 1.5-4.5 μmol·L⁻¹ (F _\beta _trend=135.40, F_{T trend}=38.24, both P<0.001). In A549 cells, the expression levels ofBCL-2α, BCL-2 \beta , and BCL-2T under each concentration of sodium arsenite treatments were lower than those in their respective control groups (all P<0.05); the results of further trend tests showed that their expression levels gradually decreased with increasing concentrations of sodium arsenite (F_{α trend} =31.97, F _\beta _trend=549.50, F_{T trend}=252.40, all P<0.001). Regarding the combined exposure, under MMA+sodium arsenite treatment at both 60 μmol·L⁻¹, the expression levels of BCL-2α, BCL-2 \beta , and BCL-2T in A549 cells were higher than those in their respective control groups (q=6.37, 14.91, 5.33, all P<0.05); under DMA+sodium arsenite treatment at both 60 μmol·L⁻¹, their expression levels in A549 cells were also higher than those in their respective control group (q=8.60, 17.29, 6.91, all P<0.05).

Conclusion Exposure to a high concentration (16HBE: 4.5 μmol·L⁻¹, A549: 60 μmol·L⁻¹) of a single arsenic metabolite has no effect on BCL-2 transcripts in 16HBE cells and A549 cells. Exposure to a low concentration (1.5 μmol·L⁻¹) of sodium arsenite alone would decrease the expression level of BCL-2α and increase the expression level of BCL-2 \beta in 16HBE cells, and exposure to all designed concentrations of sodium arsenite alone would decrease the expressions of all transcripts in A549 cells. The combined exposure to high concentrations (both 60 μmol·L⁻¹) of MMA plus sodium arsenite or high concentrations (both 60 μmol·L⁻¹) of DMA plus sodium arsenite would increase the expressions of BCL-2α, BCL-2 \beta , and BCL-2Tin A549 cells, which are different from the effects presented by single exposure.

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