The impact of NF-κB activation on radiation sensitivity in human embryonic kidney cells

Kurzfassung

Outer space is heavily loaded with high-energetic particles contributing to high risks for space travelers, which could lead to lethal health problems. To protect astronauts from radiation-induced immediate and late effects, countermeasures need to be developed. This requires improved knowledge on damage response pathways and possible pharmacological interaction. DNA double-strand breaks are the ultimate damages caused by radiation. This stimulates the cellular response, which aims at repairing the damaged DNA and ensuring the survival of the cell. One of such cellular responses is the activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and its pathway. The role of NF-κB in cellular survival and proliferation has been well studied (Baldwin, 1996b). Recent studies also suggest a possible of role of the NF-κB activation in DNA repair (Volcic et al., 2012). Using this knowledge, the role of NF-κB in sensitizing cells by X-irradiation was studied by colony formation assay and cell cycle analysis. With the help of the reporter cell line, the NF-κB activation kinetics was clearly studied. Lastly, the role of NF-κB in X-irradiation-induced DNA damage and its repair was also investigated. The study was performed using a HEK NF-κB reporter cell line (HEK-pNFκB-DDtdtomatoC8) and HEK cells with a knockdown NF-κB subunit, RelA (HEK shRNA RelA). A pro-survival role of NF-κB in the survival of the HEK cells after X-irradiation was confirmed. The different phases of the cell cycle were analyzed after X-irradiation and it was observed that NF-κB regulates the G2/M arrest. Further, the NF-κB subunit, RelA was found to be involved in the phosphorylation of the H2AX foci, which is a known marker for DNA damage and repair (Sharma et al., 2012). This project reflects the potential of the NF-κB pathway as a target in modulating the cellular radiation response during space missions and aims at finding its role in radiosensitization of cells, which could be beneficial for medical purposes as well.