DOE Low Dose Radiation Research Program Workshop I Abstracts November 10-12, 1999, Washington, D.C.

25. Micronutrient Deficiency as a Radiation Mimic

Bruce N. Ames
401 Barker Hall, Dept of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202
Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr Way, Oakland, CA 94609
bnames@uclink4.berkeley.edu

Summary: Dietary micronutrient deficiencies appear to mimic radiation and we wish to compare them to radiation.

Abstract: Folate deficiency breaks chromosomes^[1] due to massive incorporation of uracil in human DNA (4 million/cell) with subsequent single strand breaks in DNA formed during base excision repair: two nearby single strand breaks on opposite strands cause the chromosome to fall apart. The level of folate where we see high uracil and breaks was present in 10% of the U.S. population and a much higher percentage of the poor. Vitamin B12 (14% elderly) and B6 (10% of U.S.) deficiencies also cause high uracil in human DNA and chromosome breaks as indicated by our new evidence and as expected from mechanistic considerations. Many micronutrient deficiencies are likely to damage DNA by the same mechanism as radiation, by causing single- and double-strand breaks, oxidative lesions, or both^[2], appear to be orders of magnitude more important, and should be compared for perspective^[1;2]. In addition, endogenous oxidative DNA damage is appreciable and increases with age^[3;4].

Our aim is to compare low dose radiation with micronutrient deficiency, and endogenous damage, by a variety of measures of DNA damage. Our assays include oxo8Gua, the comet assay, a new FacSort assay for micronuclei, a new sensitive ELISA assay for AP sites in DNA, and DNA microarrays for DNA damage and oxidative damage genes, as well as a very sensitive and specific GC-MS assay for lipid peroxidation. We plan to use IMR90 human diploid fibroblast primary cells in some of the initial work, comparing micronutrient deficient and sufficient cells, and with varying levels of radiation.

[1] Blount, B.C., Mack, M.M., Wehr, C., MacGregor, J., Hiatt, R., Wang, G.,Wickramasinghe, S.N., Everson, R.B. and Ames, B.N. (1997) Folate deficiency causes uracil misincorporation into human DNA and chromosome breakage: Implications for cancer and neuronal damage. Proc. Natl. Acad. Sci.USA 94; 3290-3295.

[2] Ames, B.N. (1998) Micronutrients prevent cancer and delay aging. Toxicol. Lett. 102-103; 5-18.

[3] Helbock, H.J., Beckman, K.B., Shigenaga, M.K., Walter, P., Woodall, A.A., Yeo, H.C. and Ames, B.N. (1998) DNA oxidation matters: The HPLC-EC assay of 8-oxo-deoxyguanosine and 8-oxo-guanine. Proc. Natl. Acad. Sci. USA 95; 288-293.

[4] Hagen, T.M., Ingersoll, R.T., Liu, J., Lykkesfeldt, J., Wehr, C.M., Vinarsky, V., Bartholomew, J.C. and Ames, B.N. (1998) (R)-a-Lipoic acid-supplemented old rats have improved mitochondrial function, decreased oxidative damage, and increased metabolic rate. FASEB J. 13; 411-418.