Metabolism of benzo[a]pyrene and DNA adduct formation in cultured human epidermal keratinocytes

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Abstract
Cultured human epidermal cells which require no feeder layer were used to study metabolism of benzo[a]pyrene (BP) and DNA adduct formation. The cultures were prepared from a single cell suspension and maintained at a pH of 5.9–6.2. At 2 μM BP some cell toxicity was observed, and substantial cell death occurred at 4 μM BP. The metabolism and DNA binding of BP were followed from 6 to 48 h of incubation. High pressure liquid chromatography (h.p.l.c.) revealed that BP was metabolized into 9, 10-diol, 7, 8-diol, quinones, phenols and tetraols of BP. The DNA binding levels increased linearly up to 28 h of incubation. At 18 h, the level of DNA binding at 0.4 μM BP was 1.5 × 10−6 mol BP/mol DNA and increased to 6.0 × 10-6 mol BP/mol DNA at a dose of 4 μ BP. Analysis of the DNA adducts by h.p.l.c. indicates that the 2'-deoxy-N2-(7, 8, 9, 10-tetraphydro-7β-, 8α, 9α-trihydroxybenzo[a]pyrene-10-yl) guanosine was the predominant adduct formed in cells exposed to BP. The prevalence of the minor DNA adducts varies as a function of the source of the primary skin cells. These results confirm that human cells with no feeder layer metabolize BP and the resultant DNA damage is similar to that found in other mammalian systems.