Title: Aflatoxin toxicity in cultured human epidermal cells: stimulation by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Authors: Walsh, A A; Hsieh, D P; Rice, R H

Published In Carcinogenesis, (1992 Nov)

Abstract: Aflatoxin B1 (AFB1) at 1 microgram/ml was markedly toxic to human epidermal cells grown in the Rheinwald-Green 3T3 feeder layer system. At 0.1 microgram/ml, the toxicity was barely evident, as assessed by colony expansion during a 2 week exposure, but it was dramatically stimulated by 5 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which was non-toxic alone. Neither AFB1-dihydrodiol nor AFB2 were toxic in the presence or absence of TCDD, indicating that metabolism to the 8,9-epoxide was responsible for the AFB1 toxicity. Stimulation of AFB1 epoxidation by TCDD was also indicated by the > 20-fold increase in DNA adduct formation in cultures exposed to [14C]AFB1 and TCDD for 4 days as compared to AFB1 alone. Analysis of free metabolites in culture medium by reverse-phase HPLC revealed that confluent epidermal cultures metabolized AFB1 to AFM1, AFB2a and aflatoxicol. In the presence of TCDD, the levels of AFM1 were higher (14 versus 3% of dose) as were those of AFB2a (3 versus 0.5% of dose), while aflatoxicol levels were lower (0.8 versus 2% of dose). In the absence of irradiated 3T3, the toxicities of AFB1, AFB2, AFM1 and aflatoxicol to cells in serum-free medium (0.15 mM Ca2+) were similar to those in the feeder layer system. Although this moderately low calcium concentration appeared quite satisfactory for observing toxicity, the response was attenuated at a lower calcium concentration (0.09 mM Ca2+).

PubMed ID: 1423872

MeSH Terms: Aflatoxin B1/chemistry; Aflatoxin B1/metabolism; Aflatoxin B1/toxicity*; Calcium/pharmacology; Cells, Cultured; Chromatography, High Pressure Liquid; Culture Media/pharmacology; DNA Damage; DNA/drug effects; Drug Synergism; Epidermal Cells; Epidermis/drug effects*; Humans; Molecular Structure; Polychlorinated Dibenzodioxins/toxicity*