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Contribution of the ROS/IRE1alpha Signaling Pathway to Arsenic Trioxide-Induced Apoptosis and Autophagy-Associated Responses in BEAS-2B Cells

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This in vitro mechanistic study investigated the role of the reactive oxygen species (ROS)/IRE1alpha signaling pathway in arsenic trioxide (As2O3)-induced apoptosis and autophagy in BEAS-2B human bronchial epithelial cells. The study aimed to elucidate the cytotoxicity and cellular mechanisms by which inorganic arsenic damages lung cells, with ROS identified as the primary upstream mediator.

Key numbers

  • As2O3 at 0.25-0.75 µM did not significantly alter BEAS-2B cell viability over 24 hours.
  • As2O3 at 1.0-2.0 µM significantly reduced cell viability in a dose-dependent manner (CCK-8 assay), p less than 0.01.
  • LDH release (necrosis/late apoptosis marker) was significantly elevated at 1.0 and 2.0 µM As2O3.
  • Cleaved caspase-3 protein (apoptosis executioner) was upregulated at 2.0 µM As2O3 versus control, p less than 0.01.
  • ROS levels were markedly elevated at 1.0 and 2.0 µM As2O3 versus control (fluorimetry and fluorescence microscopy).
  • GRP78 (ER chaperone/UPR marker), p-IRE1alpha, and p-eIF2alpha were significantly increased at 0.5 and 2.0 µM As2O3 versus control, p less than 0.01.
  • N-acetylcysteine (NAC, antioxidant) pretreatment (5.0 mM, 30 min) suppressed GRP78, p-IRE1alpha, and p-eIF2alpha upregulation and reduced As2O3-induced cleaved caspase-3, confirming ROS as the upstream effector.
  • LC3B-II/beta-actin ratio (autophagosome marker) was elevated at 0.5 and 2.0 µM As2O3; NAC administration markedly reduced LC3B-II levels, confirming ROS mediation of autophagy.

Methods (brief)

BEAS-2B cells (human bronchial epithelial line) exposed to As2O3 at 0.25-2.0 µM for 24 hours. Cell viability: CCK-8 assay. LDH: fluorimetric. Apoptosis nuclear morphology: Hoechst 33342 staining. Western blot: cleaved caspase-3, GRP78, p-IRE1alpha, p-eIF2alpha, LC3B-II (all normalized to beta-actin); n = 3 independent biological replicates. ROS: DCFH-DA dye (fluorimetry and fluorescence microscopy). Autophagy vacuoles: MDC fluorescent marker. NAC pretreatment as antioxidant control.

Evidence fitness

Supports: mechanistic understanding of how inorganic arsenic damages bronchial epithelial cells through oxidative stress and endoplasmic reticulum stress pathways (ROS-IRE1alpha-apoptosis/autophagy axis). Provides cellular-level evidence relevant to arsenic-induced lung injury. Limitation: in vitro only; As2O3 concentrations used (0.25-2.0 µM) are higher than typical environmental inhalation exposures; BEAS-2B is an immortalized cell line, not primary cells.

Limitations

In vitro only; no animal or human data; As2O3 concentrations may not reflect environmental or dietary inhalation doses; single cell type; BEAS-2B cells are SV40-transformed, which affects apoptotic thresholds relative to primary bronchial epithelial cells.

Update history

No substantive edit history is available in this build. The full commit record is available in git.

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