Phorbol Ester Facilitates Apoptosis in Murine Fibroblasts Pretreated by Mild Ultraviolet Radiation

• Published in: Journal of biochemistry (Tokyo) Vol. 126; no. 2; pp. 340 - 346
• Main Authors: Kimura, Hirokazu, Minakami, Hisanorl, Sekiguchi, Isao, Otsuki, Kunio, Shoji, Akira
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.08.1999
• Subjects: Animals; Apoptosis; Carcinogens - pharmacology; Caspase 1 - metabolism; Cell Cycle - drug effects; Cell Cycle - radiation effects; Cell Division - drug effects; Cell Division - radiation effects; Cell Line; DNA Fragmentation - drug effects; DNA Fragmentation - radiation effects; Dose-Response Relationship, Drug; Fas; fas Receptor - metabolism; Fas-ligand; Fibroblasts - drug effects; Fibroblasts - radiation effects; Flow Cytometry; Mice; phorbol myristate acetate; Proto-Oncogene Proteins c-bcl-2 - metabolism; Proto-Oncogene Proteins c-myc - metabolism; RNA, Messenger - analysis; Tetradecanoylphorbol Acetate - pharmacology; Time Factors; Tumor Suppressor Protein p53 - metabolism; ultraviolet; Ultraviolet Rays
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/oxfordjournals.jbchem.a022455

Although phorbol 12-myristate 13-acetate (PMA) inhibits apoptosis and promotes the growth of some types of cells, it induces apoptosis in other cells. We evaluated the apoptotic effects of PMA on murine fibroblasts (L-929) that had been exposed to ultraviolet-B (UV-B) radiation at 312 nm, which promotes tumor cell growth. Exposure to PMA alone did not induce Fas, Fas-L, or apoptosis. Cells exposed to mild UV-B irradiation (80 J/m2) alone exhibited a slight expression of Fas and Fas-L 36 to 48 h after the exposure, and exhibited apoptosis as evidenced by DNA fragmentation 72 h after exposure. The addition of PMA (0.8X10-5 to 3.2xl0-5M) to the medium 24h after the UV-B exposure markedly and dose-dependently enhanced these cell responses. Confluent untreated cells, cells cocultured with PMA, and cells cocultured with PMA for 24 h after the UV-B exposure consistently expressed mRNAs for wild-type p53, bcl-2y and ICE. Expression of c-myc mRNA was initially observed, but became undetectable in the cells cocultured for 24 h with a high concentration of PMA (3.2xl0-5M) following UV-B exposure. Such cells subsequently exhibited the maximal apoptotic response. We conclude that mild exposure to UV-B altered murine fibroblast cells in such a way as to facilitate their death by apoptosis upon addition of PMA.