title: Quercetin modulates OTA-induced oxidative stress and redox signalling in HepG2 cells - up regulation of Nrf2 expression and down regulation of NF-κB and COX-2.
abstract: BACKGROUND
  Ochratoxin A (OTA), a mycotoxin, causes extensive cell damage, affecting liver and kidney cells. OTA toxicity is fairly well characterized where oxidative stress is believed to play a role, however, the sequence of molecular events after OTA-exposure, have not been characterized in literature. Further, antidotes for alleviating the toxicity are sparsely reported. The aim of this study was to understand the sequence of some molecular mechanisms for OTA-induced toxicity and the cytoprotective effect of quercetin on OTA-induced toxicity.
  
  
  METHODS
  Time course studies to evaluate the time of intracellular calcium release and ROS induction were carried out. The time of activation and induction of two key redox- sensitive transcription factors, NF-κB and Nrf-2 were determined by nuclear localization and expression respectively. The time of expression of inflammatory marker COX-2 was determined. Oxidative DNA damage by comet assay and micronucleus formation was studied. The ameliorative effect of quercetin on OTA-induced toxicity was also determined on all the above-mentioned parameters.
  
  
  RESULTS
  OTA-induced calcium release, ROS generation and activated NF-κB nuclear translocation and expression. Pre-treatment with quercetin ameliorated ROS and calcium release as well as NF-κB induction and expression. Quercetin induced Nrf-2 nuclear translocation and expression. Quercetin's anti-inflammatory property was exhibited as it down regulated COX-2. Anti-genotoxic effect of quercetin was evident in prevention of DNA damage and micronucleus formation.
  
  
  CONCLUSIONS
  Quercetin modulated OTA-induced oxidative stress and redox-signaling in HepG2 cells.
  
  
  CONCLUSIONS
  The results of the study demonstrate for the first time that quercetin prevents OTA-induced toxicity in HepG2 cells.
authors.affiliation: Animal Tissue Culture and Molecular Genetics Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, India.
authors.forename: Periasamy
authors.initials: P
authors.lastname: Ramyaa
authors.forename: Rajashree
authors.initials: R
authors.lastname: Krishnaswamy
authors.forename: Viswanadha Vijaya
authors.initials: VV
authors.lastname: Padma
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D048749:Cytokinesis / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005978:Glutathione / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D015162:Micronucleus Tests; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009793:Ochratoxins / Q000494:pharmacology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects*; D050050:Protein Carbonylation / Q000187:drug effects; D011794:Quercetin / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002121:Calcium Channel Blockers; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; C495635:NFE2L2 protein, human; D009573:Nitrites; D009793:Ochratoxins; D017382:Reactive Oxygen Species; C025589:ochratoxin A; D011794:Quercetin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D005978:Glutathione; D002118:Calcium
keywords: 2,7-dichlorodihydrofluorescein diacetate; 2,7-dichlorofluorescein; 3,30-di-hexyloxacarbocyanine iodide; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; 4,4-diamidino-2-phenylindole; ANOVA; AO/EB; ARE; Acridine orange/ethidium bromide; Analysis of variance; Antioxidant responsive element; CAT; CBMN; CCCP; COX-2; Carbonyl cyanide m-chlorophenylhydrazone; Catalase; Cyclooxygenase-2; Cytokinesis block micronucleus assay; DAB; DAPI; DCF; DCF-DA; DMEM; DNA damage; DTT; DiOC6; Diaminobenzidine; Dithiothreitol; Dulbecco's modified Eagle's medium; EDTA; Ethylenediamine tetraacetic acid; FBS; Fetal bovine serum; GPx; GSH; GST; Glutathione; Glutathione S transferase; Glutathione peroxidase; IC20; Inducible nitric oxide synthase; Inflammation; Inhibitory concentration 20; Intracellular calcium level; LDH; LPO; LPS; Lactate dehydrogenase; Lipid peroxidation; Lipopolysaccharide; MN; MTT; Micronucleus; NF-κB; NO; Nitric oxide; Nrf-2; Nuclear factor E2 p45-related factor 2; Nuclear factor-kappa B; OPT; OTA; Ochratoxin; Ortho-phthalaldehyde; Oxidative stress; PCC; PMSF; Phenyl methyl sulfonyl fluoride; Protein carbonyl content; Quercetin; ROS; Reactive oxygen species; SOD; Superoxide dismutase; [Ca(2+)](i); iNOS