Free radical generation by selenium compounds and their prooxidant toxicity

Area of Science:

• Biochemistry
• Toxicology
• Environmental Science

Background:

• Selenium (Se) is an essential nutrient but can be highly toxic.
• Selenium toxicity was first observed in livestock consuming accumulator plants.
• Plants and animals metabolize selenium into various compounds, influencing its toxicity.

Purpose of the Study:

• To explore the mechanisms of selenium toxicity and detoxification.
• To understand the role of selenium compounds in cellular processes.
• To investigate potential pharmaceutical applications of selenium.

Main Methods:

• Review of existing literature on selenium chemistry and biological effects.
• Analysis of in vitro reactions between selenium compounds and thiols (e.g., glutathione).
• Examination of methylation and reduction pathways for selenium detoxification.

Main Results:

• Certain selenium compounds (selenite, selenium dioxide) catalyze reactions with thiols, producing reactive oxygen species and causing toxicity.
• The liver is a primary target organ due to glutathione production.
• Methylation of selenium by plants and animals, and formation of elemental or heavy metal selenides, detoxify selenium.
• Non-toxic forms include selenium enzymes, selenoethers, and sequestered selenium (e.g., Ebselen).

Conclusions:

• The catalytic prooxidant activity of specific selenium compounds underlies their toxicity.
• Detoxification occurs via methylation or reduction to non-catalytic forms.
• Selenium's prooxidant effects may induce apoptosis, suggesting potential therapeutic uses (antibacterial, antiviral, antifungal, anticancer).