RNA m⁶A involves in regulation of oxidative stress and apoptosis may via NF-kB pathway in cadmium-induced lung cells

Cadmium has been identified as an environmental pollutant and a carcinogen. N⁶-methyladenosine (m⁶A) plays a crucial role in the development of lung tumors, but the mechanisms remain incompletely clarified. In present study, our data demonstrated that prolonged treatment of 1 μmol/L CdSO₄ for 40 passages in bronchial epithelial cells (Beas-2B cells) resulted in the development of a malignant phenotype, which manifested as boosted proliferation, migration and invasion capacity as well as apoptosis reduction. Proteomic assay revealed that in passage 40 cells, 350 proteins showed differentially expressed in comparison to control, and these proteins were primarily enriched in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of "pathways in cancer" and "Chemical carcinoma-reactive oxygen species". Moreover, the mRNAs of Nuclear factor kappa B (NF-κB) p65 and NAD(P)H: quinone oxidoreductase 1 (NQO1), the key signaling molecules in these two signaling pathways, were predicted to contain m⁶A modification sites with high confidence. The subsequent experimental results indicated that levels of m⁶A and Fat mass and obesity associated protein (FTO) elevated, while Alkylated DNA repair protein alkB homolog 5 (ALKBH5) and YTH Domain Containing Protein 2 (YTHDC2) reduced with the increasing of cadmium treatment generations. Furthermore, the reduction of m⁶A levels by 3-deazide adenosine (DAA, m⁶A inhibitor) was found to significantly inhibit malignant characteristics of cadmium-induced cells, activate molecules involved in the nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway, and inhibit the activity of NF-κB. It is also noteworthy that the results based on animals indicate that the relevant indicators and biological changes are partially similar to cell experiments. In detail, m⁶A modification levels in lung tissue were observed to increase while the expressions of FTO, ALKBH5 and YTHDC2 were found to drop. Additionally, immunofluorescence examination illustrated the co-localization of the m⁶A regulatory proteins FTO and YTHDC2 with NF-κB. The presented data collectively suggest that chronic cadmium treatment may impact the m⁶A level through influencing regulatory proteins, which could potentially trigger oxidative stress and apoptosis by regulating transcription factors such as NF-κB and NRF2. In conclusion, our study provides a scientific foundation for understanding cadmium toxicity and offers novel insights for treating cadmium-induced lung diseases.