Taurine chloramine: a possible oxidant reservoir.
Taurine is abundant in polymorphonuclear leukocytes (PMNs) where it reacts with PMN-derived hypochlorous acid to form taurine chloramine (Tau-NHCl), a substance that does not readily cross the cell membrane. When PMNs were stimulated in PBS lacking taurine, extracellular oxidant concentration was low, but the concentration increased 3-4 fold when 15 mM taurine was added, indicating that taurine lowers oxidant levels inside the cell. When Tau-NHCl was added to Jurkat cells in suspension, its half life was about 75 min. In contrast, membrane-permeable ammonia mono-chloramine (NH2Cl) has a half life of only 6 min. Accordingly, NH2Cl oxidizes cytosolic proteins, such as IkappaB, and inhibits NF-kappaB activation, whereas Tau-NHCl exhibits no comparable effect. However, when NH4+ was added to the medium, Tau-NHCl oxidizes IkappaB and inhibits NF-kappaB activation, probably through oxidant transfer to NH4+ leading to NH2Cl formation. These results indicate that Tau-NHCl can serve as an oxidant reservoir, exhibiting either delayed oxidant effects or acting as an oxidant at a distant site.
Ogino
Tetsuya
T
Pathology and Experimental Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. togino@lapis.plala.or.jp
Than
Tin Aung
TA
Hosako
Mutsumi
M
Ozaki
Michitaka
M
Omori
Masako
M
Okada
Shigeru
S
D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D009504:Neutrophils / Q000378:metabolism*; D016877:Oxidants / Q000097:blood*; D051381:Rats; D013654:Taurine / Q000031:analogs & derivatives* / Q000097:blood
D016877:Oxidants; D000643:Ammonium Chloride; D013654:Taurine; C043410:N-chlorotaurine