Cytochrome P450 (CYP450) play a major role in the bioactivation of procarcinogenesis in target tissue and the expression of this enzyme i san important determinant of human susceptibility to cancer. Relatively little is known about the overall role of CYP450 in the metabolism of xenobiotics or endogenous cellular compounds in the skin. The aim of this study was to analyse the expression of cytochrome enzymes in proliferanting human keratinocytes and melanocytes after exposure to UVB radiation and to three classical cytochrome inducers such as: β-naphthoflavone (BNF), 3-methylcholanthrene (MC), phenobarbital (PB). We investigated 7-ethoxyresorufìn O-deethylase (EROD) (which is CYP450 1A1 dependent) and 7-pentoxyresorufìn O-depenthylase activities (PROD) (CYP450 2B1 dependent)activities. Normal human keratinocytes were cultured with mitomycin-treated 3T3 cells in Dulbecco’s modified Eagle’s medium/Ham’s F12 or with KGM serum-free medium. Melanocytes were grown in medium 154. At confluency cells were incubated with inducers or irradiated with different doses of UVB. At different times after treatments, cells were harvested for in vitro measurement of CYP450 induction. The microsomal fraction was studied by western-blot analysis. Low, but measurable levels of CYP activity were detected in both basal and differentianting keratinocytes. The MC-induced EROD activity was up to 4 fold higher when compared with BNF induced activity. UVB exposure resulted in a dose-dependent (10-75 mJ) and time dependent (4-24 h) induction of CYP450 1A1 for keratinocytes and CYP450 2B1 for melanocytes. Immunoblotting assay showed expression for CYP450 1B1 for both keratinocytes and melanocytes. Proadifen, an inhibitor of CYP450-monooxygenase, led to a significant decrease in EROD activity. The results of the present study clearly show that irradiation with UVB is capable of modifying the activity of CYP450 isoenzymes not only in keratinocytes but also in melanocytes.These experimental findings stress the value of epidermal cell culture for pharmaco-toxicological studies of topical agents used in dermatology.
Induction of cytochrome P450 enzyme activity by UVB and xenobiotics in normal human keratinocytes and melanocytes / Benassi, Luisa; Bertazzoni, Giorgia; Magnoni, Cristina; Caselli, Monica; Seidenari, Stefania. - In: JOURNAL OF INVESTIGATIVE DERMATOLOGY. - ISSN 0022-202X. - STAMPA. - 119:(2002), pp. 715-715. (Intervento presentato al convegno 32 annual Meeting European Society for Dermatological research tenutosi a Geneva nel 19-21 september).
Induction of cytochrome P450 enzyme activity by UVB and xenobiotics in normal human keratinocytes and melanocytes
BENASSI, Luisa;BERTAZZONI, Giorgia;MAGNONI, Cristina;CASELLI, Monica;SEIDENARI, Stefania
2002
Abstract
Cytochrome P450 (CYP450) play a major role in the bioactivation of procarcinogenesis in target tissue and the expression of this enzyme i san important determinant of human susceptibility to cancer. Relatively little is known about the overall role of CYP450 in the metabolism of xenobiotics or endogenous cellular compounds in the skin. The aim of this study was to analyse the expression of cytochrome enzymes in proliferanting human keratinocytes and melanocytes after exposure to UVB radiation and to three classical cytochrome inducers such as: β-naphthoflavone (BNF), 3-methylcholanthrene (MC), phenobarbital (PB). We investigated 7-ethoxyresorufìn O-deethylase (EROD) (which is CYP450 1A1 dependent) and 7-pentoxyresorufìn O-depenthylase activities (PROD) (CYP450 2B1 dependent)activities. Normal human keratinocytes were cultured with mitomycin-treated 3T3 cells in Dulbecco’s modified Eagle’s medium/Ham’s F12 or with KGM serum-free medium. Melanocytes were grown in medium 154. At confluency cells were incubated with inducers or irradiated with different doses of UVB. At different times after treatments, cells were harvested for in vitro measurement of CYP450 induction. The microsomal fraction was studied by western-blot analysis. Low, but measurable levels of CYP activity were detected in both basal and differentianting keratinocytes. The MC-induced EROD activity was up to 4 fold higher when compared with BNF induced activity. UVB exposure resulted in a dose-dependent (10-75 mJ) and time dependent (4-24 h) induction of CYP450 1A1 for keratinocytes and CYP450 2B1 for melanocytes. Immunoblotting assay showed expression for CYP450 1B1 for both keratinocytes and melanocytes. Proadifen, an inhibitor of CYP450-monooxygenase, led to a significant decrease in EROD activity. The results of the present study clearly show that irradiation with UVB is capable of modifying the activity of CYP450 isoenzymes not only in keratinocytes but also in melanocytes.These experimental findings stress the value of epidermal cell culture for pharmaco-toxicological studies of topical agents used in dermatology.
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