Comparison of uric acid and ascorbic acid in protection against EAE.
Serum levels of uric acid (UA), an inhibitor of peroxynitrite- (ONOO-) related chemical reactions, became elevated approximately 30 million years ago in hominid evolution. During a similar time frame, higher mammals lost the ability to synthesize another important radical scavenger, ascorbic acid (AA), leading to the suggestion that UA may have replaced AA as an antioxidant. However, in vivo treatment with AA does not protect against the development of experimental allergic encephalomyelitis (EAE), a disease that has been associated with the activity of ONOO- and is inhibited by UA. When compared in vitro, UA and AA were found to have similar capacities to inhibit the nitrating properties of ONOO-. However UA and AA had different capacities to prevent ONOO- -mediated oxidation, especially in the presence of iron ion (Fe3+). While UA at physiological concentrations effectively blocked dihydrorhodamine-123 oxidation in the presence of Fe3+, AA did not, regardless of whether the source of ONOO- was synthetic ONOO-, SIN-1, or RAW 264.7 cells. AA also potentiated lipid peroxidation in vivo and in vitro. In conclusion, the superior protective properties of UA in EAE may be related to its ability to neutralize the oxidative properties of ONOO- in the presence of free iron ions.
Spitsin
Sergei V
SV
Department of Immunology and Microbiology, Thomas Jefferson University, Philadelphia, PA 19107, USA. sspitsin@mail.jci.tju.edu
Scott
Gwen S
GS
Mikheeva
Tatiana
T
Zborek
Anna
A
Kean
Rhonda B
RB
Brimer
Christine M
CM
Koprowski
Hilary
H
Hooper
D Craig
DC
D000418:Albumins / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000097:blood / Q000494:pharmacology*; D001812:Blood-Brain Barrier; D002460:Cell Line; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000517:prevention & control*; D005609:Free Radicals; D007150:Immunohistochemistry; D007501:Iron / Q000494:pharmacology; D015227:Lipid Peroxidation; D051379:Mice; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009186:Myelin Sheath / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors; D012235:Rhodamines / Q000494:pharmacology; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014527:Uric Acid / Q000097:blood / Q000494:pharmacology*
D000418:Albumins; D000975:Antioxidants; D005609:Free Radicals; D012235:Rhodamines; C058319:dihydrorhodamine 123; D030421:Peroxynitrous Acid; D014527:Uric Acid; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; C002385:linsidomine; D008981:Molsidomine; D007501:Iron; D001205:Ascorbic Acid; D010100:Oxygen