title: Phorbol ester inhibits DNA damage-induced apoptosis in U937 cells through activation of protein kinase C.
abstract: The effects of phorbol 12-myristate 13-acetate (PMA) on DNA damage-induced apoptosis were examined in promyelocytic leukemia cells, U937, in comparison with other differentiation-inducing agents to clarify the role of protein kinase C (PKC) vis-a-vis cellular differentiation in apoptosis. The apoptosis of U937 cells was observed at as early as 1-1.5 h following UV irradiation, with most cells being in apoptotic state at 3 h. Pretreatment with PMA for as short as 5 min was sufficient to inhibit apoptosis induced by UV irradiation, whereas apparent changes in cell cycle distributions and expression of differentiation markers by PMA were not observed until 12 h and 48 h, respectively. The inhibition of apoptosis by PMA was completely abolished by the pretreatment with calphostin C, a PKC inhibitor, and 4 alpha-phorbor 12,13-didecanoate, which is unable to activate PKC, did not protect U937 cells against apoptosis induced by UV irradiation. Other differentiation inducers, such as cyclic AMP and active vitamin D3, did not affect the UV-induced apoptosis of U937 cells. Taken together, it was suggested that PMA inhibits DNA damage-induced apoptosis through the activation of PKC rather than as a result of differentiation of U937 cells.
authors.affiliation: Department of Geriatric Research, National Institute for Longevity Sciences, Obu, Aichi, Japan.
authors.forename: Y S
authors.initials: YS
authors.lastname: Kaneko
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: M
authors.initials: M
authors.lastname: Nakanishi
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D015152:Blotting, Northern; D003994:Bucladesine / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D004249:DNA Damage / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D020298:U937 Cells; D014466:Ultraviolet Rays
chemical_list: D004791:Enzyme Inhibitors; D009281:Naphthalenes; D003994:Bucladesine; D011493:Protein Kinase C; D002117:Calcitriol; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate