title: Nitric oxide-mediated bystander signal transduction induced by heavy-ion microbeam irradiation.
abstract: In general, a radiation-induced bystander response is known to be a cellular response induced in non-irradiated cells after receiving bystander signaling factors released from directly irradiated cells within a cell population. Bystander responses induced by high-linear energy transfer (LET) heavy ions at low fluence are an important health problem for astronauts in space. Bystander responses are mediated via physical cell-cell contact, such as gap-junction intercellular communication (GJIC) and/or diffusive factors released into the medium in cell culture conditions. Nitric oxide (NO) is a well-known major initiator/mediator of intercellular signaling within culture medium during bystander responses. In this study, we investigated the NO-mediated bystander signal transduction induced by high-LET argon (Ar)-ion microbeam irradiation of normal human fibroblasts. Foci formation by DNA double-strand break repair proteins was induced in non-irradiated cells, which were co-cultured with those irradiated by high-LET Ar-ion microbeams in the same culture plate. Foci formation was suppressed significantly by pretreatment with an NO scavenger. Furthermore, NO-mediated reproductive cell death was also induced in bystander cells. Phosphorylation of NF-κB and Akt were induced during NO-mediated bystander signaling in the irradiated and bystander cells. However, the activation of these proteins depended on the incubation time after irradiation. The accumulation of cyclooxygenase-2 (COX-2), a downstream target of NO and NF-κB, was observed in the bystander cells 6 h after irradiation but not in the directly irradiated cells. Our findings suggest that Akt- and NF-κB-dependent signaling pathways involving COX-2 play important roles in NO-mediated high-LET heavy-ion-induced bystander responses. In addition, COX-2 may be used as a molecular marker of high-LET heavy-ion-induced bystander cells to distinguish them from directly irradiated cells, although this may depend on the time after irradiation.
authors.affiliation: Radiation Safety Research Center, Central Research Institute of Electric Power Industry, 2-11-1 Iwado Kita, Komae, Tokyo 201-8511, Japan. Electronic address: mstomita@criepi.denken.or.jp.
authors.forename: Masanori
authors.initials: M
authors.lastname: Tomita
authors.affiliation: Division of Oncology, Biomedical Imaging Research Center, University of Fukui, 23-3 Matsuoka-Shimoaitsuki, Eiheiji-cho, Fukui 910-1193, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Matsumoto
authors.affiliation: Microbeam Radiation Biology Group, Radiation Biology Research Division, Quantum Beam Science Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan.
authors.forename: Tomoo
authors.initials: T
authors.lastname: Funayama
authors.affiliation: Microbeam Radiation Biology Group, Radiation Biology Research Division, Quantum Beam Science Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Yokota
authors.affiliation: Radiation Safety Research Center, Central Research Institute of Electric Power Industry, 2-11-1 Iwado Kita, Komae, Tokyo 201-8511, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Otsuka
authors.affiliation: Radiation Safety Research Center, Central Research Institute of Electric Power Industry, 2-11-1 Iwado Kita, Komae, Tokyo 201-8511, Japan; Proton Medical Research Group, Research and Development Department, The Wakasa Wan Energy Research Center, 64-52-1 Nagatani, Tsuruga-shi, Fukui 914-0192, Japan.
authors.forename: Munetoshi
authors.initials: M
authors.lastname: Maeda
authors.affiliation: Microbeam Radiation Biology Group, Radiation Biology Research Division, Quantum Beam Science Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kobayashi
mesh_terms: D001128:Argon; D018480:Astronauts; D024201:Bystander Effect / Q000528:radiation effects*; D002450:Cell Communication / Q000528:radiation effects*; D016923:Cell Death / Q000528:radiation effects*; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D018920:Coculture Techniques; D051546:Cyclooxygenase 2 / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects*; D004781:Environmental Exposure / Q000009:adverse effects; D005118:Extraterrestrial Environment; D005347:Fibroblasts / Q000528:radiation effects; D020450:Heavy Ions; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010766:Phosphorylation / Q000528:radiation effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D016328:NF-kappa B; D009569:Nitric Oxide; D001128:Argon; D051546:Cyclooxygenase 2; D051057:Proto-Oncogene Proteins c-akt
keywords: Bystander response; Heavy ion; Microbeam; Nitric oxide; Non-targeted effect