Endotoxin-induced formation of 3-nitrotyrosine and investigation of antioxidant effect of taurine in guinea pig spleen

Nitric oxide (NO./Nitrogen monoxide) and superoxide (O2-.) radicals react each other with one of the most rapid reaction in biological systems (k:6,7.109 M-1s-1) to form peroxynitrite (ONOO-) that is far more toxic and reactive than its precursors, and is a relatively long-lived oxidant with a half-life of approximately 1.9 second. ONOO- is a potent oxidant and nitrating agent which causes modifications and reacts with numerous biomolecules including proteins, lipids, thiols, sulfhydryl groups, DNA bases and low molecular weight antioxidants. A well known reaction of ONOO- is forming 3-Nitrotyrosine (3-NT) by nitrating free or protein-bound tyrosine residues from ortho position. 3-NT, a stable and specific end product of ONOO-, is a biomarker that is used commonly for determining ONOO--mediated tissue damage in human disease and animal models. On the other hand, taurine (2-aminoethanesulfonic acid) is a free sulfhur containing b-amino acid which has antioxidant, antiinflammatory and detoxificant properties. In this study, the role of endotoxemia on ONOO- formation via 3-NT detection, and the antioxidant effect of taurine in LPS-treated guinea pigs were aimed. In this direction, guinea pigs were injected LPS (4 mg/kg), taurine (300 mg/kg) or taurine plus LPS intraperitoneally (ip), and levels of 3-NT and taurine were measured by HPLC, reactive nitrogen oxide species (NOx) which are stable end products of NO. were measured by spectrophotometer in spleen tissues. As a result, LPS administration significantly decreased the concentration of taurine whilst increased levels of 3-NT and NOx. It was determined that taurine decreased the levels of 3-NT and NOx in taurine plus LPS-treated group. The group in which taurine was administered alone, contradiction to well-known antioxidant effect, taurine caused elevated concentration of 3-NT and NOx.