Protection against peroxynitrite by selenoproteins

Area of Science:

• Biochemistry
• Cellular Biology
• Oxidative Stress Research

Background:

• Excessive peroxynitrite generation causes DNA damage and disrupts protein function via 3-nitrotyrosine formation.
• Selenium-containing enzymes are implicated in peroxynitrite reduction.
• Previous studies highlighted ebselen's reaction with peroxynitrite, but GPx's efficacy was less understood.

Purpose of the Study:

• To investigate the protective role of glutathione peroxidase (GPx) against peroxynitrite-induced cellular damage.
• To compare the peroxynitrite reductase activity of GPx with other selenium compounds and ebselen.
• To elucidate the mechanism of GPx in mitigating oxidative stress caused by peroxynitrite.

Main Methods:

• Assessing the protection against dihydrorhodamine 123 (DHR) oxidation by peroxynitrite.
• Measuring the inhibition of benzoate hydroxylation under steady-state peroxynitrite conditions.
• Analyzing protein 3-nitrotyrosine formation in human fibroblast lysates using Western blots.
• Quantifying nitrite and nitrate formation from peroxynitrite.

Main Results:

• Glutathione peroxidase (GPx) demonstrated superior protection against DHR oxidation compared to ebselen.
• GPx, with glutathione (GSH), effectively inhibited peroxynitrite-induced benzoate hydroxylation, unlike GPx or GSH alone.
• GPx and selenomethionine protected human fibroblast lysates against 3-nitrotyrosine formation.
• GPx, ebselen, and selenomethionine enhanced nitrite formation from peroxynitrite, indicating its reduction.

Conclusions:

• Glutathione peroxidase (GPx) functions as a peroxynitrite reductase, offering cellular defense against oxidative damage.
• The protective mechanism involves the reduction of peroxynitrite, preventing DNA and protein modifications.
• This newly identified function of GPx may extend to other selenoproteins and potentially organotellurium compounds.