摘要

Background: A discontinuous dose response relationship is a major characteristic of the anti-inflammatory effects of low-dose X-irradiation therapy. Although recent data indicate an involvement of a variety of molecular mechanisms in these characteristics, the impact of reactive oxygen species (ROS) production to give rise or contribute to these phenomena in endothelial cells (EC) remains elusive. %26lt;br%26gt;Material and methods: HUVEC derived immortalized EA.hy926 cells were stimulated by tumor necrosis factor-alpha (TNF-alpha, 20 ng/ml) 4 h before irradiation with doses ranging from 0.3 to 1 Gy. To analyse DNA repair capacity, phospho-histone H2AX foci were assayed at 1 h, 4 h and 24 h after irradiation. ROS production and superoxide dismutase (SOD) activity were analysed by fluorometric 2 %26apos;,7 %26apos;-dichlorodihydrofluorescein-diacetate (H2DCFDA) and colorimetric assays. A functional impact of ROS gamma H2AX production was analysed by treatment with the scavenger N-acetyl-L-cysteine (NAC). %26lt;br%26gt;Results: Irrespective of stimulation by TNF-alpha, EA.hy926 cells revealed a linear dose response characteristic gamma H2AX foci detection at 1 h and 4 h after irradiation. By contrast, we observed a discontinuity in residual gamma H2AX foci detection at 24 h after irradiation with locally elevated values following a 0.5 Gy exposure that was abolished by inhibition of ROS by NAC. Moreover, SOD protein expression was significantly decreased at doses of 0.5 Gy and 0.7 Gy concomitant with a reduced SOD activity. %26lt;br%26gt;Conclusion: These data implicate a non-linear regulation of ROS production and SOD activity in EA.hy926 EC following irradiation with doses %26lt; 1 Gy that may contribute to a discontinuous dose-response relationship of residual gamma H2AX foci detection.

  • 出版日期2014-3-22