Plasma proteins modified by tyrosine nitration in acute respiratory distress syndrome

Abstract

The present study identifies proteins modified by nitration in the plasma of patients with ongoing acute respiratory distress syndrome (ARDS). The proteins modified by nitration in ARDS were revealed by microsequencing and specific antibody detection to be ceruloplasmin, transferrin, α1-protease inhibitor, α1-antichymotrypsin, and β-chain fibrinogen. Exposure to nitrating agents did not deter the chymotrypsin-inhibiting activity of α1-antichymotrypsin. However, the ferroxidase activity of ceruloplasmin and the elastase-inhibiting activity of α1-protease inhibitor were reduced to 50.3 ± 1.6 and 60.3 ± 5.3% of control after exposure to the nitrating agent. In contrast, the rate of interaction of fibrinogen with thrombin was increased to 193.4 ± 8.5% of the control value after exposure of fibrinogen to nitration. Ferroxidase activity of ceruloplasmin and elastase-inhibiting activity of the α1-protease inhibitor in the ARDS patients were significantly reduced (by 81 and 44%, respectively), whereas α1-antichymotrypsin activity was not significantly altered. Posttranslational modifications of plasma proteins mediated by nitrating agents may offer a biochemical explanation for the reported diminished ferroxidase activity, elevated levels of elastase, and fibrin deposits detected in patients with ongoing ARDS.