Proteomic changes in the gills of wild-type and transgenic radiosensitive medaka following exposure to direct irradiation and to X-ray induced bystander signals

The directly irradiated and bystander gill proteome was examined in wild-type and radiosensitive transgenic medaka. Direct irradiation increased the expression of annexin max 3, creatine kinase (CK), and lactate dehydrogenase (LDH) in both strains and reduced annexin A4 in wild-type medaka only. In bystander fish, same strain pairings increased CK and LDH in both strains and increased annexin max 3 and annexin A4 in radiosensitive medaka. Mixed strain pairings revealed that, in bystander fish, annexin max 3 was only increased by a bystander signal originating from a radiosensitive source, annexin A4 was increased in radiosensitive bystanders irrespective of the signal source, and CK and LDH were increased if either the bystander signal origin or the recipient bystander fish was radiosensitive. Warm-temperature acclimation related 65-kDa protein (Wap65) was increased in all bystander medaka, whether they were paired with the same or opposite strain and chromosome 5 SR-like CTD-associated factor (SR = serine–argenine-rich, CTD = C-terminal domain) (SCAF) protein was increased in radiosensitive bystander medaka only. Annexin A4, CK and LDH are associated with apoptosis and mirror the increase in apoptotic bodies previously reported in irradiated and bystander medaka, whereas increased Wap65 and LDH suggest a protective response. Thus the proteomic changes reported here could indicate both immediate protection and longer term adaptation to subsequent radiation exposure. In addition this investigation provides further evidence to show that the bystander signal can override the intrinsic genetically determined response and also that signal production and response can be modulated independently.

Research Highlights
► Radiation causes apoptosis-related proteomic changes in the medaka gill.
► The bystander effect also causes a protective response.
► These responses differ depending on transgenic sensitivity to radiation.
► The bystander signal can override the genetically determined response.