title: UV irradiation induces downregulation of bcl-2 expression in vitro and in vivo.
abstract: Recently, the proto-oncogenes bcl-2 and bax have emerged as important regulators of the apoptotic form of cell death. We examined UV irradiation-elicited apoptosis and regulation of bcl-2 and bax expression both in vivo in human skin and in vitro in HeLa cells. Using flow cytometric analysis, HeLa cells were found to undergo apoptosis at the 12-h time-point after exposure to UVB irradiation (100 mJ/cm2). The expression of bcl-2 mRNA was found to decrease after a single dose of UVB radiation (doses 10-200 mJ/cm2). In contrast, the expression of bax mRNA was not significantly changed. When human skin was irradiated with a single dose of solar-simulated radiation (40 mJ/cm2), Bcl-2-positive cells were significantly reduced in the epidermis at the 3- and 6-h time-points. Our results suggest that UV irradiation downregulates bcl-2 expression both in vitro at the mRNA level and in vivo at the protein level, and that downregulation of bcl-2 constitutes a mechanism of potential importance in UV-induced apoptosis in human epidermis.
authors.affiliation: Department of Clinical Chemistry, University of Turku, Finland. kirsi.isoherranen@huch.fi
authors.forename: K
authors.initials: K
authors.lastname: Isoherranen
authors.forename: I
authors.initials: I
authors.lastname: Sauroja
authors.forename: C
authors.initials: C
authors.lastname: Jansen
authors.forename: K
authors.initials: K
authors.lastname: Punnonen
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000528:radiation effects; D053938:DNA Fragmentation / Q000528:radiation effects; D005434:Flow Cytometry; D015870:Gene Expression / Q000528:radiation effects; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D012867:Skin / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein