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The impact of serotonin on the development of bystander damage assessed by γ-H2AX foci analysis

Abstract Purpose: This investigation addresses the question of whether serum constituents have a modulating effect on the induction of bystander effects. It was carried out as part of an inter-laboratory comparison-exercise within the European Union-integrated project NOTE (Non-targeted effects of ionizing radiation). Serotonin is a neurotransmitter, which is present in the circulatory system and therefore in blood serum. Fetal bovine serum is an essential supplement to most cell culture media and contains different, batch-dependent concentrations of serotonin. In a recent publication, serotonin was found to have a strong modulating effect on the size of bystander effects detected using colony formation assays. Materials and methods: We tested modulatory effects on bystander response detected by γ-H2AX (phosphorylated histone H2AX) foci formation in cells exposed to media of irradiated cells. Cells were grown in serum batches with different serotonin concentrations. Results: While the data obtained with the three serum batches examined show a trend for increasing bystander response with increasing serotonin concentration, the effect failed to reach statistical significance. Conclusions: Serotonin may have a modulating effect on radiation-induced bystander effects, but more work is required to conclusively characterize this contribution.