Elevated protein carbonyls and lipid peroxidation products correlating with myeloperoxidase in tracheal aspirates from premature infants

The purpose of this study is to determine whether the oxidative injury mark ers, protein carbonyls and malondialdehyde (MDA), are elevated in tracheal aspirates from very low birth weight (<1500 g) infants; to determine whethe r levels correlate with myeloperoxidase as a marker of neutrophil inflammat ion; and to assess whether high levels are associated with poor respiratory outcome. Tracheal aspirates (144 samples) were collected from 86 infants < 1500 g at times of routine auctioning. Aspirates (82 samples) from 54 infan ts greater than or equal to 1500 g who required intubation for a variety of diagnoses were analyzed for comparison. Analyses were performed for protei n carbonyls by ELISA, total malondialdehyde by HPLC, and myeloperoxidase ac tivity. Respiratory outcome was assessed as oxygen requirement at 28-d or 3 6-wk postmenstrual age, and as the number of days of oxygen requirement. Pr otein carbonyls were significantly higher in infants <1500 g than larger in fants, and were highest close to birth. MDA concentrations were also higher in the earlier samples. There was a strong positive correlation between pr otein carbonyls and myeloperoxidase, suggesting a link between protein oxid ation and neutrophil activation. A similar but weaker correlation was seen for MDA. Carbonyls in samples taken after steroid administration were less than for controls with a similar age distribution. We did not see significa nt associations between oxidant marker levels and development of chronic lu ng disease. Our findings of higher amounts of protein and lipid oxidation p roducts in tracheal aspirates with high myeloperoxidase activity, taken tog ether with other studies showing a link between neutrophil accumulation and chronic lung disease, suggest a possible contribution by neutrophil-derive d reactive oxygen species to the injury.