Cytokine Release and Cytotoxicity in Human Keratinocytes Induced by Polycyclic Aromatic Hydrocarbons (1-Methylpyrene and Perylene)

Abstract

The cytotoxic effects of two polycyclic aromatic hydrocarbons (PAH) (1-methyplyrene and perylene) were investigated on human skin keratinocytes. Normal human keratinocytes were cultured in the presence of various concentrations of 1-methylpyrene and perylene either alone or in combination. Following incubation, keratinocyte adhesion, viability, proliferation, colony-forming efficiency, and apoptosis/necrosis level were examined. The effects of PAH on wound healing were also determined in vitro using a scrape-wound healing assay on epidermis-like tissue. In addition, the inflammatory cell response to PAH insult was examined through interleukin-1 (IL-1) α and interleukin-6 (IL-6) secretion. Each individual PAH significantly decreased keratinocyte adhesion and viability in a concentration-dependent manner, which was associated with a reduced ability of keratinocytes to proliferate and form colonies. When PAH were combined, a greater effect on keratinocyte adhesion, viability, and proliferation was noted. Decreased cell proliferation/colony-forming efficiency was accompanied by increased cell apoptosis following incubation with either PAH. This effect was enhanced by the inhibitory influence on keratinocyte migration, as assessed by culture scratching. Each PAH also exerted a significant effect on keratinocyte immune functions by modulating the secretion of inflammatory mediators. Indeed, 1-methylpyrene or perylene, individually or when combined, significantly upregulated IL-1α and IL-6 secretion. This effect was greater and was concentration dependent when the PAH combination was used. Overall results indicate that 1-methylpyrene and perylene exerted a cytotoxic effect on human keratinocytes. Our findings may shed light on mechanisms underlying potential adverse effects of 1-methylpyrene and perylene on human skin.

This study was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Program. The authors thank Sèverine Curt for her technical support.