Developing a Gene Biomarker at the Tipping Point of Adaptive and Adverse Responses in Human Bronchial Epithelial Cells

• Published in: PloS one Vol. 11; no. 5; p. e0155875
• Main Authors: Currier, Jenna M, Cheng, Wan-Yun, Menendez, Daniel, Conolly, Rory, Chorley, Brian N
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 19.05.2016; Public Library of Science (PLoS)
• Subjects: 21st century; Activation; Apoptosis; Biocompatibility; Biology and Life Sciences; Biomarkers; Biomarkers - metabolism; Bronchi - cytology; Cell Line; Cell Survival; Cellular stress response; Cytotoxicity; DNA damage; Environmental effects; Environmental protection; Epithelial cells; Epithelial Cells - metabolism; Exposure; Gene expression; Gene Expression Profiling; Gene Expression Regulation; Genes; Genetic aspects; Genetic Markers; Genomes; Glutathione - metabolism; High-throughput screening; Homeostasis; Human behavior; Humans; Immunoassay; In vivo methods and tests; Information processing; Laboratories; Molecular modelling; NF-E2-Related Factor 2 - metabolism; Oligonucleotide Array Sequence Analysis; Oxidative Stress; p53 Protein; Physical Sciences; Physiological aspects; Principal Component Analysis; Respiratory tract; Risk Assessment; Signal Transduction; Signaling; Target recognition; Toxicity testing; Transcription factors; Tumor Suppressor Protein p53 - metabolism; Zinc; Zinc - chemistry; United States; North Carolina; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0155875

Determining mechanism-based biomarkers that distinguish adaptive and adverse cellular processes is critical to understanding the health effects of environmental exposures. Shifting from in vivo, low-throughput toxicity studies to high-throughput screening (HTS) paradigms and risk assessment based on in vitro and in silico testing requires utilizing toxicity pathway information to distinguish adverse outcomes from recoverable adaptive events. Little work has focused on oxidative stresses in human airway for the purposes of predicting adverse responses. We hypothesize that early gene expression-mediated molecular changes could be used to delineate adaptive and adverse responses to environmentally-based perturbations. Here, we examined cellular responses of the tracheobronchial airway to zinc (Zn) exposure, a model oxidant. Airway derived BEAS-2B cells exposed to 2-10 μM Zn2+ elicited concentration- and time-dependent cytotoxicity. Normal, adaptive, and cytotoxic Zn2+ exposure conditions were determined with traditional apical endpoints, and differences in global gene expression around the tipping point of the responses were used to delineate underlying molecular mechanisms. Bioinformatic analyses of differentially expressed genes indicate early enrichment of stress signaling pathways, including those mediated by the transcription factors p53 and NRF2. After 4 h, 154 genes were differentially expressed (p < 0.01) between the adaptive and cytotoxic Zn2+ concentrations. Nearly 40% of the biomarker genes were related to the p53 signaling pathway with 30 genes identified as likely direct targets using a database of p53 ChIP-seq studies. Despite similar p53 activation profiles, these data revealed widespread dampening of p53 and NRF2-related genes as early as 4 h after exposure at higher, unrecoverable Zn2+ exposures. Thus, in our model early increased activation of stress response pathways indicated a recoverable adaptive event. Overall, this study highlights the importance of characterizing molecular mechanisms around the tipping point of adverse responses to better inform HTS paradigms.