Up-stream events in the nuclear factor κB activation cascade in response to sparsely ionizing radiation

In this work, the efficacy and cytotoxicity of four different NF-κB inhibitors, caffeic acid phenethyl ester (CAPE), capsaicin, the proteasome inhibitor MG-132, and the cell permeable peptide NF-κB SN50 were analyzed using HEK-pNF-κB-d2EGFP/Neo cells. In the recommended concentration range, only CAPE displayed considerable cytotoxicity. CAPE and capsaicin partially inhibited NF-κB activation by the cytokine tumor necrosis factor α. MG-132 completely abolished the activation and was therefore used for experiments with X-rays. NF-κB SN-50 could not reduce NF-κB dependent expression of the reporter destabilized Enhanced Green Fluorescent Protein (d2EGFP). MG-132 entirely suppressed the X-ray induced NF-κB activation in HEK-pNF-κB-d2EGFP/Neo cells. In conclusion, the degradation of the inhibitor of NF-κB (IκB) in the proteasome is essential for X-ray induced NF-κB activation, and MG-132 will be useful in studies of the NF-κB pathway involvement in the cellular response to heavy ion exposure and other space-relevant radiation qualities.