title: p38 mitogen-activated protein kinase regulates a novel, caspase-independent pathway for the mitochondrial cytochrome c release in ultraviolet B radiation-induced apoptosis.
abstract: The mechanisms of UVB-induced apoptosis and the role of p38 mitogen-activated protein kinase (MAPK) were investigated in HaCaT cells. UVB doses that induced apoptosis also produced a sustained activation of p38 MAPK and mitochondrial cytochrome c release, leading to pro-caspase-3 activation. Late into the apoptotic process, UVB also induced a caspase-mediated cleavage of Bid. Caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone and benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone substantially blocked the UVB-induced apoptosis without preventing the release of mitochondrial cytochrome c and the p38 MAPK activation. The inhibition of p38 MAPK counteracted both apoptosis and cytochrome c release as well as the DEVD-amino-4-methylcoumarin cleavage activity without affecting the processing of pro-caspase-8. These results indicate that UVB induces multiple and independent apoptotic pathways, which culminate in pro-caspase-3 activation, and that the initial cytochrome c release is independent of caspase activity. Importantly, we show that a sustained p38 MAPK activation contributes to the UVB-induced apoptosis by mediating the release of mitochondrial cytochrome c into the cytosol.
authors.affiliation: Division of Biochemistry and Laboratory of Dermatology, Faculty of Medicine, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: Z
authors.initials: Z
authors.lastname: Assefa
authors.forename: A
authors.initials: A
authors.lastname: Vantieghem
authors.forename: M
authors.initials: M
authors.lastname: Garmyn
authors.forename: W
authors.initials: W
authors.lastname: Declercq
authors.forename: P
authors.initials: P
authors.lastname: Vandenabeele
authors.forename: J R
authors.initials: JR
authors.lastname: Vandenheede
authors.forename: R
authors.initials: R
authors.lastname: Bouillon
authors.forename: W
authors.initials: W
authors.lastname: Merlevede
authors.forename: P
authors.initials: P
authors.lastname: Agostinis
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D061945:Caspase Inhibitors; D002455:Cell Division / Q000187:drug effects / Q000528:radiation effects; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology / Q000502:physiology / Q000528:radiation effects; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism* / Q000528:radiation effects; D014466:Ultraviolet Rays; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D007093:Imidazoles; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C408604:2-(4-nitrophenyl)-4-(4-fluorophenyl)-5-(4-pyridinyl)-1H-imidazole