Polycyclic aromatic hydrocarbons (PAHs) in ambient air of Guangzhou city: Exposure levels, health effects and cytotoxicity.

Polycyclic aromatic hydrocarbons (PAHs) in PM2.5 pose potentially serious threats to human health. In this study, the distribution characteristics of 16 priority controlled, fine PM (PM2.5)-bound PAHs in the ambient air of Guangzhou city were analysed from 2016 to 2019. Four high-molecular-weight PAHs with the highest annual average concentrations were benzo[ghi]perylene (BghiP; 0.757 ng/m3), indeno(1,2,3-cd)pyrene (IcdP; 0.627 ng/m3), benzo[b]fluoranthene (BbF, 0.519 ng/m3) and 3,4-benzopyrene (BaP; 0.426 ng/m3). Increasing concentrations of BghiP, IcdP, BbF and BaP were associated with increasing numbers of outpatient visits for respiratory diseases, indicating that exposure to these PAHs potentially causes acute respiratory injury in residents. Acute exposure of the human bronchial epithelial cell line BEAS-2B cells to BghiP, IcdP, BbF and BaP in vitro resulted in acute inflammation, DNA damage and apoptosis. Further bioinformatic analysis indicated that nuclear receptor subfamily 1 group D member 1 (NR1D1) may be a key target gene involved in mediating the toxic effects of BghiP. Collectively, our results suggest that BghiP and the other PAHs represented by it can damage the respiratory system and induce lung cancer. This study provides valuable evidence regarding the potential health risks posed by local ambient PAHs pollution.

Involvement of m6A regulatory factor IGF2BP1 in malignant transformation of human bronchial epithelial Beas-2B cells induced by tobacco carcinogen NNK.

Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a Group 1 human carcinogen, as classified by the International Agency for Research of Cancer (IARC), and plays a significant role in lung carcinogenesis. However, its carcinogenic mechanism has not yet been fully elucidated. In this study, we performed colony formation assays, soft-agar assays, and tumor growth in nude mice to show that 100 mg/L NNK facilitates the malignant transformation of human bronchial epithelial Beas-2B cells. Transcriptome sequencing showed that insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), a post-transcriptional regulator, was differentially expressed in NNK-induced malignant transformed Beas-2B cells (2B-NNK cells). Small interfering RNA (SiRNA) was used to downregulate the expression of the IGF2BP1 gene. The reduction in protein expression, cell proliferation rate, and colony-forming ability and the increase in the apoptosis rate of Beas-2B cells transfected with the SiRNA indicated a role for IGF2BP1 in NNK-induced malignant transformation. IGF2BP1 is an N6-methyladenosine (m6A) regulatory factor, but it is not known whether its association with m6A mediates the malignant transformation of cells. Therefore, we measured the overall levels of m6A in Beas-2B cells. We found that the overall m6A level was lower in 2B-NNK cells, and knocking down IGF2BP1, the overall level of m6A was restored. Hence, we concluded that IGF2BP1 is involved in the NNK-induced malignant transformation of Beas-2B cells, possibly via m6A modification. This study therefore contributes novel insights into the environmental pathogenesis of lung cancer and the gene regulatory mechanisms of chemical carcinogenesis.

Identification of SRXN1 and KRT6A as Key Genes in Smoking-Related Non-Small-Cell Lung Cancer Through Bioinformatics and Functional Analyses.

BACKGROUND: Lung cancer is the leading cause of cancer-related mortality worldwide. Although cigarette smoking is an established risk factor for lung cancer, few reliable smoking-related biomarkers for non-small-cell lung cancer (NSCLC) are available. An improved understanding of these biomarkers would further the development of new biomarker-targeted therapies and lead to improvements in overall patient survival. METHODS: We performed bioinformatic analysis to screened potential target genes, then quantitative PCR, western, siRNA, CCK-8, flow cytometry, tumorigenicity assays in nude mice were performed to validated the function. RESULTS: In this study, we identified 83 smoking-related genes (SRGs) based on an integration analysis of two Gene Expression Omnibus (GEO) datasets, and 27 hub SRGs with potential carcinogenic effects by analyzing a dataset of smokers with NSCLC in The Cancer Genome Atlas (TCGA) database. A survival analysis revealed three genes with potential prognostic value, namely SRXN1, KRT6A and JAKMIP3. A univariate Cox analysis revealed significant associations of elevated SRXN1 and KRT6A expression with prognosis. A receiver operating characteristic (ROC) curve analysis indicated the high diagnostic value of SRXN1 and KRT6A for smoking and cancer. Quantitative PCR and western blotting validated the increased expression of SRXN1 and KRT6A mRNA and protein, respectively, in lung cancer cell lines and NSCLC tissues. In patients with NSCLC, SRXN1 and KRT6A expression was associated with the tumor-node-metastasis (TNM) stage, presence of metastasis, history of smoking and daily smoking consumption. Furthermore, inhibition of SRXN1 or KRT6A suppressed viability and enhanced apoptosis in the A549 human lung carcinoma cell line. Tumorigenicity assays in nude mice confirmed that the siRNA-mediated downregulation of SRXN1 and KRT6A expression inhibited tumor growth in vivo. CONCLUSIONS: In summary, SRXN1 and KRT6A act as oncogenes in NSCLC and might be potential biomarkers of smoking exposure and the early diagnosis and prognosis of NSCLC in smokers, which is vital for lung cancer therapy.

Fine particulate matter exposure induces DNA damage by downregulating Rad51 expression in human bronchial epithelial Beas-2B cells in vitro.

Although an accumulating body of evidence suggests that fine particulate matter (PM2.5) can cause lung injury and lung cancer, the underlying mechanisms are not yet clear. In this study, multiple endpoints associated with the cellular response to PM2.5 exposure, including the cell proliferation rate, cell apoptosis, malondialdehyde (MDA) content and DNA damage, were evaluated in human bronchial epithelial Beas-2B cells. The mRNA expression profile in PM2.5-treated cells was analyzed by transcriptome sequencing. The DNA repair gene Rad51 was then selected for further analysis. We found that the viability and growth of Beas-2B cells decreased while cell apoptosis increased in a dose-dependent manner after PM2.5 exposure. The comet assay showed that PM2.5 exposure induced evident DNA damage in PM2.5-treated cells. The MDA content in the treated cells was increased, indicating that PM2.5 exposure promoted lipid peroxidation. Furthermore, Rad51 expression was downregulated in PM2.5-treated cells, which may have contributed to the PM2.5-induced DNA damage in Beas-2B cells. Upregulation of Rad51 expression could rescue the negative impact of PM2.5 exposure in Beas-2B cells. Taken together, our research demonstrates that PM2.5 exposure induces DNA damage and impairs the DNA repair process by downregulating Rad51 expression in Beas-2B cells. This finding is expected to provide new insight into the genotoxicity of PM2.5 exposure.