Radiation-induced Bystander Effect in Starfish (Patiria pectinifera) Oocytes

Although multiple studies suggest that ionizing radiation can induce bystander effects (radiation-induced bystander effect, RIBE) in cultured cell lines, it is still unclear whether RIBE is evolutionarily conserved in invertebrates. In this study, we investigated the frequency of cell death of unirradiated starfish (Patiria pectinifera) oocytes co-cultured with oocytes irradiated with X rays (0, 2 and 4 Gy). We observed increased frequencies of cell death determined by morphological abnormality and TUNEL-positive cells in unirradiated oocytes co-cultured with oocytes irradiated with 2 Gy or 4 Gy oocytes. In addition, the seawater cultured with 4 Gy irradiated oocytes induced cell death in unirradiated oocytes, and TUNEL-positive cells were observed. Our results suggest that RIBE is evolutionarily conserved in starfish.