title: Interactive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and retinoids on proliferation and differentiation in cultured human keratinocytes: quantification of cross-linked envelope formation.
abstract: Dioxins are potent inducers of chloracne in humans. This skin aberration can be interpreted as an altered differentiation pattern of acinar sebaceous base cells and a change in the rate of terminal differentiation of the keratinocytes. We measured this rate induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in primary cultures of human keratinocytes. As parameters for differentiation, we quantified the 35S-methionine incorporation into cross-linked envelopes (revealing the total CLE biomass), as well as the number of microscopically visible CLEs. It was shown that TCDD is a very potent inducer of both CLE biomass and number with a half-maximal effect concentration (EC50) of 1.4 nM. CLE biomass was maximally increased 10-fold and the number of cells in culture producing a CLE was increased from 15% in control cultures to maximally 75% of the cells in TCDD-treated cultures. Both effects were Ca(2+)-dependent and increased with elevated cell density, being optimal in post-confluent cultures. Retinoic acid dose-dependently decreased the effect of 10(-8) M TCDD, 10(-6) M having a nearly complete antagonistic action. This interaction of retinoic acid with TCDD-induced differentiation was non-competitive. Retinol was equally potent as an antagonist of the TCDD-induced elevation of CLE formation as compared with retinoic acid. Retinyl palmitate and etretinate were not very effective as TCDD antagonists. Supplementation of hydrocortisone suppressed the TCDD-induced keratinocyte differentiation. It was concluded that CLE biomass quantification provides a reliable and sensitive parameter for keratinocyte differentiation. In this in vitro system it is shown that TCDD strongly induces a switch from proliferation to terminal differentiation and that this effect can be antagonized effectively by retinoic acid and retinol.
mesh_terms: D000328:Adult; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006801:Humans; D007231:Infant, Newborn; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007641:Keratolytic Agents / Q000494:pharmacology*; D008715:Methionine / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000633:toxicity*; D012044:Regression Analysis; D012867:Skin / Q000166:cytology / Q000187:drug effects; D013237:Stereoisomerism; D014212:Tretinoin / Q000494:pharmacology*; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: D007641:Keratolytic Agents; D000072317:Polychlorinated Dibenzodioxins; D014801:Vitamin A; D014212:Tretinoin; D008715:Methionine