Taurine Inhibition of Iron-Stimulated Catecholamine Oxidation
Taurine (2-aminoethane sulfonic acid) is a sulfur containing amino acid that is present in mammalian tissues in millimolar concentrations10. Taurine is involved in a diverse array of biological functions which include: osmoregulation, membrane stabilization, neuromodulation, bile salt conjugation, and calcium modulation10. A role for taurine in cellular antioxidant defense mechanisms has been observed under a number of conditions3,17,21,25. Although taurine appears to have little intrinsic reactivity with oxidizing species1, its high concentration may still allow it to directly scavenge free radicals. Furthermore, taurine may bind reactive quinones involved in redox cycling and indirectly inhibit free radical formation11,22. Taurine could also moderate the effects of free radical damage by blunting the ability of prooxidants to increase intracellular free calcium10. The biosynthesis of taurine generates intermediates (hypotaurine and cysteamine) that also have free radical scavenging properties1,10,25. The synthesis of taurine also utilizes cysteine which is an excitatory amino acid that undergoes autoxidation reactions13. Taurine is present in tissues that contain high concentrations of catecholamines which are known to be cytotoxic and increase oxidative stress8,9,16,20. Taurine content declines in brain and peripheral tissues in aged rodents4. The age-related decline in tissue taurine content could increase the susceptibility of cells to free radical-mediated damage. Catecholamines are known to undergo autoxidation reactions to generate free radicals (H2O2, hydroxyl, superoxide) and cytotoxic quinones8,11,22. The oxidation of catecholamines is catalyzed by metals such as iron13. Iron-stimulated autoxidation of catecholamines is thought to play a role in neurodegenerative diseases26. One study has reported that chronic treatment with l-dopa caused a 13% decline in brain taurine content23. At present, it is unclear whether taurine under in vivo conditions serves as a scavenger for reactive quinones and free radicals derived from catecholamine autoxidation.
KeywordsFerric Chloride Protein Carbonyl Carbonyl Content Protein Carbonyl Content Taurine Supplement
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