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Re: Nitrative stress in the asphyxiated newborn.

Dear Editor,

The recent paper of Groenendaal et al supports the hypothesis that peroxynitrite formation and subsequent tyrosine nitration occur in the neonatal human brain after perinatal asphyxia (1). As we are currently studying the nitration of plasma proteins in the newborn (2), we would like to share our experience in this issue. Our aim was to identify plasma proteins whose nitration is increased in newborns who suffered perinatal asphyxia, as markers of increased peroxynitrite generation. Blood samples were collected from 21 asphyxiated term newborns and 35 normal term infants in EDTA containing tubes and rapidly centrifuged at 4°C. Plasma was prepared from arterial blood taken during the first hour of life and venous blood taken at days 1 and 4 of life. Nitrated plasma proteins were immunoprecipitated with an affinity- purified anti-3-nitrotyrosine antibody and subjected to SDS-PAGE. Gels were stained with colloidal Coomassie Blue revealing approximately 30 bands which were excised for identification by mass spectrometry. Among these, we identified albumin, fibrinogen, plasminogen, fibronectin precursor protein, vitamin D binding protein as well as a few erythrocyte proteins. Variations in the degree and the pattern of plasma protein nitration were observed in asphyxiated versus normal newborns. We have also developed a novel double-sandwich ELISA allowing the quantitative determination of nitrated plasma albumin (3). We observed a statistically significant increase of nitrated albumin concentration in day 1 venous blood of the 7 newborns who developed moderate or severe post-asphyxic encephalopathy as compared to the 14 newborns with a normal neurological evolution or mild encephalopathy. In conclusion, our data confirm the occurrence of nitrative stress after perinatal asphyxia. Nitrated plasma albumin concentration is currently being tested in neonatal practice as a potential marker and guidance for the management and follow-up of newborns potentially affected by nitrative stress and resulting end-organ injury. Research in this area may open new and exciting perspectives in neuroprotection.

References:

1. Groenendaal F, Lammers H, Smit D, Nikkels PGJ. Nitrityrosine in brain tissue of neonates after perinatal asphyxia. Arch Dis Child Fetal Neonatal Ed 20006;91:F429-F433.

2. Bottari S, Csibi A, Vermeylen D, Damis E, Cavedon C, Touma J, Salamé A, Wayenberg J-L. Nitration pattern of plasma proteins in newborns suffering from perpartal asphyxia: preliminary results. J Mat-Fet Neonat Med 2006;19(suppl 1):34.