title: A comparison of the genotoxicity of benzo[a]pyrene in four cell lines with differing metabolic capacity.
abstract: Benzo[a]pyrene (B[a]P) is a known genotoxin and carcinogen, yet its genotoxic response at low level exposure has not been determined. This study was conducted to examine the interplay of dose and metabolic capacity on genotoxicity of B[a]P. Investigating and better understanding the biological significance of low level chemical exposures will help improve human health risk assessments. The genotoxic and mutagenic effects of B[a]P were investigated using human cell lines (AHH-1, MCL-5, TK6 and HepG2) with differential expression of the CYP450 enzymes CYP1A1, 1B1 and1A2 involved in B[a]P metabolism. MCL-5 and HepG2 cells showed detectable basal expression and activity of CYP1A1, 1B1 and 1A2 than AHH-1 which only show CYP1A1 basal expression and activity. TK6 cells showed negligible expression levels of all three CYP450 enzymes. In vitro micronucleus and HPRT assays were conducted to determine the effect of B[a]P on chromosome damage and point mutation induction. After 24h exposure, linear increases in micronucleus (MN) frequency were observed in all cell lines except TK6. After 4h exposure, only the metabolically competent cell lines MCL-5 and HepG2 showed MN induction (with a threshold concentration at 25.5μM from MCL-5 cells) indicating the importance of exposure time for genotoxicity. The HPRT assay also displayed linear increases in mutant frequency in MCL-5 cells, after 4h and 24h treatments. Mutation spectra analysis of MCL-5 and AHH-1 HPRT mutants revealed frequent B[a]P induced G to T transversion mutations (72% and 44% of induced mutations in MCL-5 and AHH-1 respectively). This study therefore demonstrates a key link between metabolic capability, B[a]P exposure time and genotoxicity.
authors.affiliation: Institute of Life Sciences, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
authors.forename: Ume-Kulsoom
authors.initials: UK
authors.lastname: Shah
authors.affiliation: Institute of Life Sciences, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Seager
authors.affiliation: Safety & Environmental Assurance Centre (SEAC), Unilever, Bedford, MK44 1LQ, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Fowler
authors.affiliation: Institute of Life Sciences, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
authors.forename: Shareen H
authors.initials: SH
authors.lastname: Doak
authors.affiliation: Institute of Life Sciences, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
authors.forename: George E
authors.initials: GE
authors.lastname: Johnson
authors.affiliation: Safety & Environmental Assurance Centre (SEAC), Unilever, Bedford, MK44 1LQ, UK.
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Scott
authors.affiliation: Safety & Environmental Assurance Centre (SEAC), Unilever, Bedford, MK44 1LQ, UK.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Scott
authors.affiliation: Institute of Life Sciences, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK. Electronic address: G.J.Jenkins@swansea.ac.uk.
authors.forename: Gareth J S
authors.initials: GJ
authors.lastname: Jenkins
mesh_terms: D001564:Benzo(a)pyrene / Q000008:administration & dosage / Q000633:toxicity*; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D000072461:Cytochrome P450 Family 1 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004851:Epoxide Hydrolases / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics / Q000378:metabolism; D008658:Inactivation, Metabolic; D015162:Micronucleus Tests; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens / Q000008:administration & dosage / Q000633:toxicity*; D059645:Mutation Rate
chemical_list: D009153:Mutagens; D001564:Benzo(a)pyrene; C569463:CYP1A1 protein, human; D019363:Cytochrome P-450 CYP1A1; D000072461:Cytochrome P450 Family 1; D007041:Hypoxanthine Phosphoribosyltransferase; D004851:Epoxide Hydrolases
keywords: Dose-response; Genotoxicity; HPRT assay; Metabolic activation; Micronucleus assay; Mutagenicity; Threshold