Editors' ChoiceRADIATION

Not Out of the Path of Danger

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Science's STKE  11 Oct 2005:
Vol. 2005, Issue 305, pp. tw355
DOI: 10.1126/stke.3052005tw355

When ionizing radiation hits a cell, it can damage its DNA either directly or indirectly by generating free radicals from water. Intriguingly, recent data suggest that even cells that are not directly hit by radiation can suffer "bystander" damage as a result of signals conveyed through gap junctions, substances released from cells, or both (see Morgan and Sowa). Belyakov et al. generated three-dimensional cultured human skin tissue systems that resembled normal human epidermis and "full-thickness" skin. Tissue samples (cylinders 8 mm in diameter and about 75 μm thick or 700 μm thick for epidermis and full-thickness skin, respectively) were irradiated with a microbeam of α particles that bisected the sample in a vertical plane no more than two cell diameters wide. Three days after irradiation, the tissue was fixed and sectioned parallel to the plane of irradiation. The authors measured the fractions of apoptotic (assessed with TUNEL) and micronucleated cells in these sections to assay damage and determined that bystander effects were apparent up to a mm (about 50 to 75 cell diameters) from the site of irradiation. Apoptosis occurred about 2.8 times as often in bystander cells as in control cells from preparations in which the central plane was sham-irradiated, and micronuclei were formed about 1.7 times as often. Thus, bystander damage appears to occur in nonirradiated cells a substantial distance from the site of irradiation in a three-dimensional system that resembles normal human tissue, an effect that may have substantial implications for the assessment of low-dose radiation risk.

O. V. Belyakov, S. A. Mitchell, D. Parikh, G. Randers-Pehrson, S. A. Marino, S. A. Amundson, C. R. Geard, D. J. Brenner, Biological effects in unirradiated human tissue induced by radiation damage up to 1 mm away. Proc. Natl. Acad. Sci. U.S.A. 102, 14203-14208 (2005). [Abstract] [Full Text]

W. F. Morgan, M. B. Sowa, Effects of ionizing radiation in nonirradiated cells. Proc. Natl. Acad. Sci. U.S.A. 102, 14127-14128 (2005). [Full Text]

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