Title: Induction of the Antioxidant Response by the Transcription Factor NRF2 Increases Bioactivation of the Mutagenic Air Pollutant 3-Nitrobenzanthrone in Human Lung Cells.
Authors: Murray, Jessica R; de la Vega, Laureano; Hayes, John D; Duan, Ling; Penning, Trevor M
Published In Chem Res Toxicol, (2019 12 16)
Abstract: 3-Nitrobenzanthrone (3-NBA) is a suspected human carcinogen present in diesel exhaust. It requires metabolic activation via nitroreduction in order to form DNA adducts and promote mutagenesis. We have determined that human aldo-keto reductases (AKR1C1-1C3) and NAD(P)H:quinone oxidoreductase 1 (NQO1) contribute equally to the nitroreduction of 3-NBA in lung epithelial cell lines and collectively represent 50% of the nitroreductase activity. The genes encoding these enzymes are induced by the transcription factor NF-E2 p45-related factor 2 (NRF2), which raises the possibility that NRF2 activation exacerbates 3-NBA toxification. Since A549 cells possess constitutively active NRF2, we examined the effect of heterozygous (NRF2-Het) and homozygous NRF2 knockout (NRF2-KO) by CRISPR-Cas9 gene editing on the activation of 3-NBA. To evaluate whether NRF2-mediated gene induction increases 3-NBA activation, we examined the effects of NRF2 activators in immortalized human bronchial epithelial cells (HBEC3-KT). Changes in AKR1C1-1C3 and NQO1 expression by NRF2 knockout or use of NRF2 activators were confirmed by qPCR, immunoblots, and enzyme activity assays. We observed decreases in 3-NBA activation in the A549 NRF2 KO cell lines (53% reduction in A549 NRF2-Het cells and 82% reduction in A549 NRF2-KO cells) and 40-60% increases in 3-NBA bioactivation due to NRF2 activators in HBEC3-KT cells. Together, our data suggest that activation of the transcription factor NRF2 exacerbates carcinogen metabolism following exposure to diesel exhaust which may lead to an increase in 3-NBA-derived DNA adducts.
PubMed ID: 31746589
MeSH Terms: 20-Hydroxysteroid Dehydrogenases/genetics; A549 Cells; Activation, Metabolic; Air Pollutants/metabolism; Air Pollutants/toxicity*; Aldo-Keto Reductase Family 1 Member C3/genetics; Benz(a)Anthracenes/metabolism; Benz(a)Anthracenes/toxicity*; Bronchi/cytology; Epithelial Cells/drug effects; Gene Expression Regulation/physiology*; Gene Knockout Techniques; Humans; Hydroxysteroid Dehydrogenases/genetics; Imidazoles/pharmacology; Isothiocyanates/pharmacology; Mutagens/metabolism; Mutagens/toxicity*; NAD(P)H Dehydrogenase (Quinone)/genetics; NF-E2-Related Factor 2/agonists; NF-E2-Related Factor 2/genetics; NF-E2-Related Factor 2/metabolism*; Oleanolic Acid/analogs & derivatives; Oleanolic Acid/pharmacology; Oxidative Stress/drug effects; RNA, Messenger/genetics; RNA, Messenger/metabolism