title: Inhibition of reactive nitrogen species in vitro and ex vivo by trypsin inhibitor from sweet potato 'Tainong 57' storage roots.
abstract: Peroxynitrite (ONOO-), formed from a reaction of superoxide and nitric oxide, is one of the most potent cytotoxic species known to oxidize cellular constituents including essential proteins, lipids, and DNA. ONOO- induces cellular and tissue injury, resulting in several human diseases such as Alzheimer's disease, atherosclerosis, and stroke. Due to the lack of endogenous enzymes responsible for ONOO- scavenging activity, finding a specific ONOO- scavenger is of considerable importance. In this study, the ability of trypsin inhibitor (TI), isolated from sweet potato storage roots (SPTI), to scavenge *ON and ONOO- was investigated. The data obtained show that TI generated a dose-dependent inhibition on production of nitrite and superoxide radicals. The IC50 value of TI on superoxide radical was 143.2 +/- 4.29 microg/mL. SOD activity staining was used to confirm SOD activity of SPTI. SPTI also caused a dose-dependent inhibition of the oxidation of dihydrorhodamine 123 (DHR) by peroxynitrite. A calculated IC50 value of 809.1 +/- 32.36 microg/mL was obtained on the inhibition of peroxynitrite radical. Spectrophotometric analyses revealed that TI suppressed the formation of ONOO--mediated tyrosine nitration through an electron donation mechanism. In further studies, TI also showed a significant ability to inhibit nitration of bovine serum albumin (BSA) in a dose-dependent manner. In vivo TI inhibited lipopolysaccharide-induced nitrite production in macrophages in a concentration-dependent manner with an IC50 value of 932.8 +/- 29.85 microg/mL. The present study suggested that TI had an efficient reactive nitrogen species scavenging ability. TI might be a potential effective NO and ONOO- scavenger useful for the prevention of NO- and ONOO--involved diseases.
authors.affiliation: Institute of Chinese Pharmaceutical Sciences and Department of Physiology, School of Medicine, China Medical University, Taichung 404, Taiwan. gjhuang@mail.cmu.edu.tw
authors.forename: Guan-Jhong
authors.initials: GJ
authors.lastname: Huang
authors.forename: Ming-Jyh
authors.initials: MJ
authors.lastname: Sheu
authors.forename: Hsien-Jung
authors.initials: HJ
authors.lastname: Chen
authors.forename: Yuan-Shiun
authors.initials: YS
authors.lastname: Chang
authors.forename: Yaw-Huei
authors.initials: YH
authors.lastname: Lin
mesh_terms: D000818:Animals; D002460:Cell Line; D016166:Free Radical Scavengers / Q000494:pharmacology; D027723:Ipomoea batatas / Q000737:chemistry*; D008264:Macrophages; D051379:Mice; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors; D018517:Plant Roots / Q000737:chemistry*; D026361:Reactive Nitrogen Species / Q000037:antagonists & inhibitors*; D014361:Trypsin Inhibitors / Q000494:pharmacology*
chemical_list: D016166:Free Radical Scavengers; D026361:Reactive Nitrogen Species; D014361:Trypsin Inhibitors; D030421:Peroxynitrous Acid