Abstract
It is now well accepted that radiation induced bystander effects can occur in cells exposed to media from irradiated cells. The aim of this study was to follow the bystander cells in real time following addition of media from irradiated cells and to determine the effect of inhibiting these signals. A human keratinocyte cell line, HaCaT cells, was irradiated (0.005, 0.05 and 0.5 Gy) with γ irradiation, conditioned medium was harvested after one hour and added to recipient bystander cells. Reactive oxygen species, nitric oxide, Glutathione levels, caspase activation, cytotoxicity and cell viability was measured after the addition of irradiated cell conditioned media to bystander cells. Reactive oxygen species and nitric oxide levels in bystander cells treated with 0.5Gy ICCM were analysed in real time using time lapse fluorescence microscopy. The levels of reactive oxygen species were also measured in real time after the addition of extracellular signal-regulated kinase and c-Jun amino-terminal kinase pathway inhibitors. ROS and glutathione levels were observed to increase after the addition of irradiated cell conditioned media (0.005, 0.05 and 0.5 Gy ICCM). Caspase activation was found to increase 4 hours after irradiated cell conditioned media treatment (0.005, 0.05 and 0.5 Gy ICCM) and this increase was observed up to 8 hours and there after a reduction in caspase activation was observed. A decrease in cell viability was observed but no major change in cytotoxicity was found in HaCaT cells after treatment with irradiated cell conditioned media (0.005, 0.05 and 0.5 Gy ICCM). This study involved the identification of key signaling molecules such as reactive oxygen species, nitric oxide, glutathione and caspases generated in bystander cells. These results suggest a clear connection between reactive oxygen species and cell survival pathways with persistent production of reactive oxygen species and nitric oxide in bystander cells following exposure to irradiated cell conditioned media.
Highlights
Radiation induced bystander effects have been observed in unirradiated cells upon receiving signals from irradiated cells [1,2,3,4,5,6]
The cells were incubated with a Jun N-terminal kinase (JNK) inhibitor (SP600125) before the addition of 0.5 Gy ICCM and these cells showed a significant increase in reactive oxygen species (ROS) production (Fig 1C) compared with 0 Gy ICCM
This study showed the production of intercellular signaling molecules such as ROS for 24 hours and nitric oxide (NO) for 4 hours after the addition of ICCM
Summary
Radiation induced bystander effects have been observed in unirradiated cells upon receiving signals from irradiated cells [1,2,3,4,5,6]. Bystander signals may be transferred to surrounding cells either by gap junctional intercellular communication or by the production of soluble extracellular factors released from irradiated cells Soluble signaling factors such as reactive oxygen species (ROS) [24,25,26,27,28,29], nitric oxide (NO) [28, 30, 31], secondary messengers like calcium [18, 27, 32, 33], cytokines such as interleukins [34,35,36], transforming growth factor (TGFβ) [29, 37, 38], tumor necrosis factor (TNFα) and (TNF)-related apoptosis-inducing ligand (TRAIL) [39, 40] have been found to play a major role in radiation-induced bystander effects. There is increasing evidence suggesting that exosomes play a potential role in transferring signals from irradiated to non-irradiated cells [41,42,43,44]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
