Establishment of a sandwich ELISA using commercial antibody for plasma or serum 3-nitrotyrosine (3NT). Elevation in inflammatory diseases and complementary between 3NT and myeloperoxidase

Background: Amino acid tyrosine residue of a protein can be nitrated to form 3-nitrotyrosine (3NT), which is now being considered as a marker of inflammation, oxidative and nitrosative stress. Method: An in-house ELISA has been established using the same commercial antibody for both binding and detection of 3NT containing proteins. Results: The sensitivity of the in-house ELISA was 1.8 nmol/l. The imprecision was < 10% at all concentrations. The in-house assay correlates well with a commercial kit (r = 0.89). In addition to EDTA plasma, we found that both heparinized plasma and serum can also be used to quantify 3NT concentration. Using the in-house ELISA we have detected increased concentrations of 3NT in diseases known to be associated with inflammation and also in subjects with polyps. As marker of oxidative stress and inflammation, both 3NT and myeloperoxidase are complementary to each other in test sensitivity. Conclusion: This ELISA can be used in the clinical laboratories to monitor the inflammatory disease activity and assess early risks that are associated with inflammation, oxidative and nitrosative stress.