In addition to mercury, cadmium and other metallic and organic electrophiles are neurotoxic. Although soft electrophiles were thought to cause toxicity by binding to thiols (SH groups), they irreversibly inhibit selenoenzymes and thus impair vital functions in tissues.

Protein incorporation of methionine or selenomethionine occurs non-specifically since they are not distinguished in plant or animal metabolism. Plants and animals both synthesize cysteine, but only animals make selenocysteine. Because it is so important in the healthy activities of brain and endocrine tissues, selenocysteine is made in all cells of all vertebrates.

Even during severe shortages of dietary selenium, brain and endocrine tissues are supplied with selenium and maintain their health. The only insults that can impair selenium's activities in these tissues are high exposures to mercury or other soft electrophiles.

Paradigm Change

Although it has always been clear that humanity is exposed to a multitude of potentially toxic agents from diets and their environments, toxicology has necessarily applied a reductionist approach, -examining exposures to each agent in isolation. In the absence of evidence of a shared mechanism, this approach was appropriate.

Now that we are aware that the toxic effects of mercury, cadmium, and other metallic or organic soft electrophiles share the same mechanism of toxicity involving binding reactions that impair selenium availability, their concomitant exposures and cooperative effects must be evaluated in aggregate and include consideration of the selenium status of the exposed individuals.

Our scientists provide advice on public and environmental health considerations for industry, governments, and academic research groups around the world.

References

• Soft Electrophile Inhibition of Selenoenzymes in Disease Pathologies
• Effects of Soft Electrophiles on Selenium Physiology in Free Radical Biology and Medicine
• Dr. Nick Ralston's Selenium Mercury Research
• The Career of Dr. Nick Ralston: Discovering the Connection Between Mercury and Selenium

Additional Links

ResearchGate

LinkedIn