Amplification of the γ-irradiation-induced cell death pathway by reactive oxygen species in human U937 cells

Development and Evaluation of Therapeutics in the Setting of Radiation Injury

“…In the U937 cell line, we have shown that a radiation dose of 7 Gy is sufficient to induce apoptotic cell death under our experimental conditions. At 24 hours after IR, we were able to measure a significant increase in both Caspase-3 and apoptotic cell death (Figures 3-1, 3-3), which is different from a previously published study who did not observe significant cell death prior to 30 hours after 7 Gy RI [36]. This group did not show the apoptosis data prior to 48 hours but they did mention their findings.…”

“…We also established that although KZ-41 has no effect on Caspase-3 activation when administered prior to IR, there is a dose-dependent reduction in TNF-α 48 hours after IR (Figure 3-8). KZ-41 was also effective in reducing reactive oxygen species levels, another player in the propagation of radiation-induced injury, and possibly applicable in the bystander effect [36]. We demonstrated that a bystander effect can be elicited in the U937 cell line through soluble factors by a series of conditioned medium transfer experiments (Figure 3-10).…”

“…A bimodal increase was measured 24 and 48 hours after IR (Figure 3-1). No increase in phosphorylated histone 2A (pH2A.X) was observed in the time points that were measured (1,4,24,36, and 48 hours) (Figure 3-2). Significant apoptotic cell death was verified 24 hours post IR (Figure 3-3).…”

“…Tumor necrosis factor alpha (TNF-α) was measured in the medium as a function of time (1,4,24,36, and 48 hours) following radiation exposure. TNF-α levels are below detection at 1 hour after IR exposure, however, may be detected as early as 4 hours post exposure.…”

“…The ROS assay was carried out as previously described with minor modifications [36]. Dicholorofluorescindiacetate (DCFH-DA) dye was used for this assay.…”