Deficient diet evokes nasty heart virus

Why Nature Chose Selenium

The authors were asked by the Editors of ACS Chemical Biology to write an article titled "Why Nature Chose Selenium" for the occasion of the upcoming bicentennial of the discovery of selenium by the Swedish chemist Jöns Jacob Berzelius in 1817 and styled after the famous work of Frank Westheimer on the biological chemistry of phosphate [Westheimer, F. H. (1987) Why Nature Chose Phosphates, Science 235, 1173-1178]. This work gives a history of the important discoveries of the biological processes that selenium participates in, and a point-by-point comparison of the chemistry of selenium with the atom it replaces in biology, sulfur. This analysis shows that redox chemistry is the largest chemical difference between the two chalcogens. This difference is very large for both one-electron and two-electron redox reactions. Much of this difference is due to the inability of selenium to form π bonds of all types. The outer valence electrons of selenium are also more loosely held than those of sulfur. As a result, selenium is a better nucleophile and will react with reactive oxygen species faster than sulfur, but the resulting lack of π-bond character in the Se-O bond means that the Se-oxide can be much more readily reduced in comparison to S-oxides. The combination of these properties means that replacement of sulfur with selenium in nature results in a selenium-containing biomolecule that resists permanent oxidation. Multiple examples of this gain of function behavior from the literature are discussed.

Interactions among infections, nutrients and xenobiotics

During recent years there have been several incidents in which symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Furthermore, outbreaks of infections in food-producing animals have attracted major attention regarding the safety of consumers, e.g., Bovine Spongiform Encephalitis (BSE) and influenza in chicken. As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and associated complications. Moreover, during ongoing infection, xenobiotic uptake and distribution are often changed resulting in increased toxic insult to the host. The interactions among infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology as well as in food-borne diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects among microorganisms, nutrients, and xenobiotics will have to be considered. Otherwise, such effects may gradually change the disease panorama in society.

Effects of selenium supplementation on virus-induced inflammatory heart disease

The effects of 10 wk of selenium (Se) supplementation (5 ppm) in drinking water on immune responses and resistance to a myocarditic Coxsackie virus B3 (CB3) infection were studied in female Balb/c mice. Se supplementation reduced CB3-induced mortality: at day 14 postinoculation, survival was 58% in the Se-treated group as compared to 25% in the untreated group. Whole-blood glutathione peroxidase (GSH-Px) activity was elevated by 68% (p < 0.001) and Se content in the liver by 24% (p < 0.001). Red (RBC) and white blood cell (WBC) counts, as well as the number of cells in the spleen and thymus, were unaffected. The cellular counts of T-lymphocytes (CD4+, CD8+) and natural killer (NK+) cells in the blood were not affected. However, the CD4+/CD8+ ratio (5.2) tended to increase after Se supplementation (5.9). The spleen lymphoproliferative response to T- and B-cell mitogens were increased by 9 and 43%, respectively (ns), in the Se-supplemented group. The total NK cell activity in blood and spleen showed minor increases, but when the activity in the blood was expressed per cell, the increase amounted to 35% (ns) with Se supplementation. The inflammatory and necrotic lesions in the ventricular myocardium at 7 and 14 d postinoculation were not significantly reduced by Se treatment, probably owing to the increased survival with Se even of mice with the most pronounced heart damage; comparable untreated mice were estimated to have died at day 14. Results indicate that modest doses of Se can improve immune function, which may increase the general resistance to this viral infection.