title: Involvement of purinergic signaling in cellular response to gamma radiation.
abstract: Recent studies have suggested a bystander effect in nonirradiated cells adjacent to irradiated cells; however, the mechanism is poorly understood. In this study, we investigated the involvement of both extracellular nucleotides and activation of P2 receptors in cellular responses to gamma radiation using human HaCaT keratinocytes. The concentration of ATP in culture medium was increased after gamma irradiation (0.1-1.0 Gy), suggesting that radiation induces ATP release from cells. Intracellular Ca(2+) concentration was elevated when conditioned medium from irradiated cells was transferred to nonirradiated cells, and this elevation was suppressed by apyrase (ecto-nucleotidase), indicating the involvement of extracellular nucleotides in this event. Further, we examined the activation of ERK1/2 by gamma radiation and nucleotides (ATP and UTP). Both gamma radiation and nucleotides induced activation of ERK1/2. Next, the effect of inhibitors of P2 receptors on radiation-induced activation of ERK1/2 was examined. The activation of ERK1/2 was blocked by suramin (P2Y inhibitor), MRS2578 (P2Y(6) antagonist) and apyrase. These results suggest that both released nucleotides and activation of P2Y receptors are involved in gamma-radiation-induced activation of ERK1/2. We conclude that ionizing radiation induces release of nucleotides from cells, leading to activation of P2Y receptors, which in turn would result in a variety of biological effects.
authors.affiliation: Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan. tsukim@rs.noda.tus.ac.jp
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Tsukimoto
authors.forename: Takujiro
authors.initials: T
authors.lastname: Homma
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ohshima
authors.forename: Shuji
authors.initials: S
authors.lastname: Kojima
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019898:Autocrine Communication / Q000528:radiation effects; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000378:metabolism; D004789:Enzyme Activation / Q000528:radiation effects; D005110:Extracellular Space / Q000378:metabolism / Q000528:radiation effects; D005720:Gamma Rays; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism / Q000528:radiation effects; D015603:Keratinocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019899:Paracrine Communication / Q000528:radiation effects; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D015398:Signal Transduction / Q000528:radiation effects*
chemical_list: D017077:Culture Media, Conditioned; D018048:Receptors, Purinergic P2; D000255:Adenosine Triphosphate; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium