title: Role of NF-kappaB in the apoptotic-resistant phenotype of keratinocytes.
abstract: Several studies point to a role for NF-kappaB in modulating epidermal thickness and apoptotic susceptibility of keratinocytes. When phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) are topically applied, prominent epidermal thickening occurs, and exposure to interferon (IFN)-gamma promotes increased epidermal thickness producing psoriatic lesions. While keratinocytes derived from psoriatic plaque resist apoptosis, and combination of TPA and IFN-gamma activates NF-kappaB, the molecular mechanism linking NF-kappaB activation and keratinocyte apoptosis resistance was unknown. Therefore, we examined the ability of IFN-gamma plus TPA to influence NF-kappaB activity, gene expression, and response to UV light-induced apoptosis. These responses in normal keratinocytes were compared with immortalized keratinocytes (HaCaT cells). Exposure of normal keratinocytes to IFN-gamma plus TPA produced a synergistic activation of NF-kappaB, compared with when each reagent was used individually. Normal keratinocytes when exposed to IFN-gamma plus TPA acquired a resistance to UV light-induced apoptosis, which was dependent on NF-kappaB because expression of a dominant negative form of IkappaBalpha overcame the resistance. Compared with normal keratinocytes, HaCaT cells have a dysfunctional constitutive NF-kappaB signaling pathway not induced by IFN-gamma and TPA, rendering HaCaT cells highly susceptible to UV-induced apoptosis. Thus, immortalized HaCaT cells have an abnormal constitutive and dysfunctional NF-kappaB signaling system. These results provide evidence that activation and proper regulation of NF-kappaB is essential for acquisition of an apoptotic-resistant phenotype for epidermal-derived keratinocytes.
authors.affiliation: Department of Pathology, Loyola University Medical Center, Cardinal Bernardin Cancer Center, Maywood, Illinois 60153, USA.
authors.forename: J Z
authors.initials: JZ
authors.lastname: Qin
authors.forename: V
authors.initials: V
authors.lastname: Chaturvedi
authors.forename: M F
authors.initials: MF
authors.lastname: Denning
authors.forename: D
authors.initials: D
authors.lastname: Choubey
authors.forename: M O
authors.initials: MO
authors.lastname: Diaz
authors.forename: B J
authors.initials: BJ
authors.lastname: Nickoloff
mesh_terms: D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D001483:Base Sequence; D001692:Biological Transport; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D017931:DNA Primers; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology*; D010641:Phenotype; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D017931:DNA Primers; D016328:NF-kappa B; D007371:Interferon-gamma; D004247:DNA; D013755:Tetradecanoylphorbol Acetate