Sodium arsenite influences proliferation and apoptosis in normal thyroid cells via modulation of ER-PI3K/AKT signaling pathway

Abstract

BackgroundRecent advances in understanding the toxic effects of inorganic arsenic have revealed that arsenic exposure impacts multiple endocrine organs, thereby altering their functions. However, the mechanisms underlying arsenic-induced thyroid injury remain unclear. ObjectiveTo investigate the mechanisms by which sodium arsenite (NaAsO₂) affects the proliferation and apoptosis of normal thyroid cells (Nthy-ori3-1) through the estrogen receptor (ER)-phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. MethodsNthy-ori3-1 cells were cultured in vitro and divided into the following groups: a control group (complete medium without drugs, 0 μmol·L−1), and NaAsO₂-treated groups at 1, 2, and 4 μmol·L−1. Additionally, 1 μmol·L−1 of the ER inhibitor ICI182780 was used to intervene in the NaAsO₂ exposure groups, resulting in the following combinations: 1 μmol·L−1 NaAsO₂ + ICI182780, 2 μmol·L−1 NaAsO₂ + ICI182780, and 4 μmol·L−1 NaAsO₂ + ICI182780. The median lethal concentration of NaAsO₂ was determined using cell viability assay. Cell viability was assessed at 24, 36, and 48 h using Cell Counting Kit-8 (CCK-8) assay. Colony formation ability was evaluated via plate cloning assay. Apoptosis was detected using Hoechst 33342 staining. Protein and mRNA expression levels of ERα, ERβ, c-MYC, Bax, Bcl-2, PI3K, p-PI3K, AKT, and p-AKT were measured using Western blot (WB) and real-time quantitative PCR (qRT-PCR), respectively. ResultsThe median lethal concentration of NaAsO₂ was determined to be 4.034 μmol·L−1. CCK-8 assay at 24, 36, and 48 h revealed that, compared with the control group, the 1, 2, and 4 μmol·L−1 NaAsO₂ groups significantly inhibited Nthy-ori3-1 cell proliferation (P 0.05). In the ICI182780-treated NaAsO₂ groups, the ERα, ERβ, c-MYC, Bcl-2, p-PI3K, and p-AKT protein expression increased (P 0.05) compared with the corresponding NaAsO₂-only groups. The mRNA expression patterns of ERα, ERβ, c-MYC, Bcl-2, and Bax were consistent with the WB results. ConclusionNaAsO₂ inhibits proliferation and promotes apoptosis in Nthy-ori3-1 cells in a dose-dependent manner. The underlying mechanism likely involves NaAsO₂-mediated suppression of the ER-PI3K/AKT signaling pathway, which subsequently regulates downstream proliferation- and apoptosis-related genes.

Keywords

• sodium arsenite
• estrogen effect
• estrogen receptor
• pi3k/akt signaling pathway
• proliferation
• apoptosis