Inhibition of reactive nitrogen species in vitro and ex vivo by thioredoxin h2 from sweet potato ‘Tainong 57’ storage roots

In this study, the ability of thioredoxin h2 (TRX h2) expressed in Escherichia coli to scavenge ON and ONOO− were investigated. The data obtained show that TRX h2 generated a dose-dependent inhibition on production of nitrite and superoxide radicals. TRX h2 also caused a dose-dependent inhibition of the oxidation of dihydrorhodamine 123 (DHR) by peroxynitrite. Spectrophotometric analyses revealed that TRX h2 suppressed the formation of ONOO−-mediated tyrosine nitration through an electron donation mechanism. In further studies, TRX h2 also showed a significant ability of inhibiting the nitration of bovine serum albumin (BSA) in a dose-dependent manner. In vivo TRX h2 inhibited LPS-induced nitrite production in macrophage in a concentration-dependent manner. The present study suggested that TRX h2 had an efficient reactive nitrogen species scavenging ability. TRX h2 might be a potential effective NO and ONOO− scavenger useful for the prevention of the NO and ONOO− involved diseases.