title: NADPH Oxidase-Mediated Superoxide Production by Intermediary Bacterial Metabolites of Dibenzofuran: A Potential Cause for Trans-Mitochondrial Membrane Potential (ΔΨm) Collapse in Human Hepatoma Cells.
abstract: Dibenzofuran is a direct precursor of extremely toxic compounds such as dioxins. It is widely distributed persistent organic pollutant in environment that potentiate oxidative stress, apoptosis, and necrosis through bioactivation in HepG2 cells. An alkalotolerent Pseudomonas strain ISTDF1 can metabolize dibenzofuran as a sole source of carbon and energy through diverse dioxygenation. However, there is a paucity of information about the potential toxic effects of the intermediary metabolites that are formed during treatment with dibenzofuran. We have assessed and discovered the potential mechanism of toxicity induced by metabolites of dibenzofuran that were formed at 18 and 36 h. Cell viability, CYP1A2 induction, ROS activity, Superoxide production, mitochondrial NADPH oxidase activity, and mitochondrial trans-membrane potential were studied using different assays such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), confocal laser scanning microscopy, and flow cytometry. Analysis revealed formation of 2-(1-carbonyl methylidine)-2,3-dihydrobenzofuranlidene after 18 h of bacterial treatment due to oxygenation at carbon (C3-C4). This compound induces higher mitochondrial NADPH oxidase-dependent superoxide production that makes it more toxic than the parent compound. It was evident that after 36 h of bacterial treatment, toxicity induced by dibenzofuran and its metabolites was completely removed. This study highlights the fact that despite of efficient biodegradation of toxicants, bioactive toxic intermediates can be formed. Therefore, it is necessary to assess the toxicity of each intermediary for complete mitigation of associated risk.
authors.affiliation: *School of Environmental Science, Jawaharlal Nehru University, New Delhi 110067, India; Department of Surgery and prashantjaiswal1@gmail.com.
authors.forename: Prashant Kumar
authors.initials: PK
authors.lastname: Jaiswal
authors.affiliation: The Research Institute, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada.
authors.forename: Jyotsana
authors.initials: J
authors.lastname: Gupta
authors.affiliation: *School of Environmental Science, Jawaharlal Nehru University, New Delhi 110067, India;Department of Surgery andThe Research Institute, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada prashantjaiswal1@gmail.com.
authors.forename: Shweta
authors.initials: S
authors.lastname: Shahni
authors.affiliation: *School of Environmental Science, Jawaharlal Nehru University, New Delhi 110067, India;Department of Surgery andThe Research Institute, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada prashantjaiswal1@gmail.com.
authors.forename: Indu Shekhar
authors.initials: IS
authors.lastname: Thakur
mesh_terms: D001572:Benzofurans / Q000378:metabolism* / Q000633:toxicity; D001673:Biodegradation, Environmental; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival; D019388:Cytochrome P-450 CYP1A2 / Q000096:biosynthesis; D056945:Hep G2 Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D011549:Pseudomonas / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: D001572:Benzofurans; D017382:Reactive Oxygen Species; D013481:Superoxides; C023614:dibenzofuran; C504573:CYP1A2 protein, human; D019388:Cytochrome P-450 CYP1A2; D019255:NADPH Oxidases
keywords: HepG2; MMP; Pseudomonas; ROS; dibenzofuran; dioxin