Protective effect of alpha-tocopherol in carrier liposomes on ultraviolet-mediated human epidermal cell damage in...

We have examined the postulated protective effect of antioxidants against ultraviolet (UV)-induced epidermal damage in an in vitro model system using either a well-differentiated human squamous cell carcinoma line SCC12F2 or human newborn keratinocytes. Cell were maintained in a serum-free defined medium only or with carrier liposomes (LPs) alone or LPs containing 1 microgram/ml alpha-tocopherol (AT/LP) or 1 microgram/ml alpha-tocopherol in oil (AT) alone. Cultures were irradiated once using a dose of solar-simulated light (25 mJ/m2, metered at 285 nm) determined in preliminary studies to decrease cell yields after 72 h by approximately 50% compared with sham-irradiated controls under basal conditions. Compared with their LP control, UV-irradiated AT/LP-treated SCC cells were significantly protected by an average of 25% against UV-mediated cell death or growth arrest as determined by the ratio of 72-h cell yields for UV-irradiated versus sham-irradiated cells. Ratios for cells treated with AT, LPs alone, or AT/LP did not differ significantly from those for untreated cells. Newborn keratinocytes had higher overall ratios of cell yields for UV-irradiated vs sham-irradiated cells, but results were otherwise similar, with AT/LP again providing significant protection, averaging 29%, compared with LP controls. UV irradiation of cells in basal medium induced the gene for heat shock protein (HSP 70), presumed to be involved in cellular response to stress; and keratinocytes treated with alpha-tocopherol in carrier liposomes showed a further increase in expression of HSP 70.(ABSTRACT TRUNCATED AT 250 WORDS)