Propofol protects tyrosine against oxidation by peroxynitrite

A. Mouithys-Mickalad1, P.Hans2, S. Kohnen1, G.Deby-Dupont1,2, C. Deby1, M.Lamy1,2. 1Center of the Oxygen Research & Development,University of Liege  2Department of Anesthesia & IntensiveCareMedicine CHU, University Hospital, Liege, Belgium

 

Background & Goal of theStudy

Peroxynitrite (ONOO-), a product of the reaction of NO• with O2•, is considered as a powerful oxidant susceptible to react with several chemical compounds including thiols, tyrosine and a-tocopherol. While nitration of a-tocopherol by ONOO- appears as a minor reaction (1), nitration of tyrosine by ONOO- is considered as a major one. The formation of nitrotyrosine in biological system may induce the disruption of cell signalling. In this hypothesis, drugs able to hinder the oxidation of target biomolecules would appear as protective. We already demonstrated that propofol (an anesthetic agent) reacted with peroxynitrite to form a phenoxyl radical followed by ONOO- destruction (2). The purpose of this study was to assess the protective effect of propofol (2,6-diisopropylphenol) in an in vitro model of tyrosine oxidation by peroxynitrite, using High Performance Liquid Chromatography (HPLC) technique.

 

Materials & Methods

Peroxynitrite was prepared as previously described (2). All measurements were performed on HPLC with RP-C18 column eluted with phosphate buffer/methanol(92-2) and UV detection. After oxidation of tyrosine by peroxynitrite, nitrotyrosine produced was monitored taking the 3-nitrotyrosine as standard.

 

Results & Discussion

Peroxynitrite (3.5 mM) added to tyrosine (1 mM), resulted in 39.6 % nitrotyrosine and 60.4% intacttyrosine. Increasing concentrations of ONOO- induced a linear increase of nitrotyrosine production while intact tyrosine decreased until complete disappearance. The addition of 5 mM propofol to the reaction milieu restored 100 % intact tyrosine. The same assays performed with two different propofol concentrations (10-3-10-4 M) showed a protective effect against tyrosine oxidation by peroxynitrite in a dose-dependent manner.

 

Conclusion

These findings confirmed the peroxynitrite-scavenging effect of propofol as well as its biological interestin the oxidative disorders.

 

References

1.       Hogg N, Joseph J, Kalyanaraman B. Arch. Biochem. Biophys.1994;314: 153-158

2.       Mouithys-Mickalad A, Hans P, Deby-Dupont G, et al.Biochem. Biophys. Res. Commun. 1998;249: 833-837