Neopterin as an Endogenous Antioxidant

Abstract

The in vitro antioxidative activity of neopterin and its in vivo potency to suppress gastric ischemia were investigated. The scavenging activity of the reduced form of neopterin, 5,6,7,8-tetrahydroneopterin (NPH4), against superoxide anion radicals, showed an extremely high superoxide anion radical scavenging activity in two assay systems, i.e., hypoxanthine/xanthine oxidase (HPX/XOD) and rat macrophage/ phorbol myristate acetate (Mø/PMA) radical-generating systems. The antioxidative activities against both super oxideanion and hydroxyl radicals were confirmed by spin trapping-ESR spectrometry. In contrast, the oxidized form of neopterin (NP) did not show any activity in the HPX/XOD system, but was effective in the Mø/PMA system. These data suggest that NPH4 directly scavenges superoxide anion radicals, while NP suppresses the superoxide anion generation in macrophages through its inhibitory effect on the membrane NADPH-oxidase. Furthermore, NPH4 and NP effectively suppressed the formation of gastric injury induced by ischemia and reperfusion. These results suggest that neopterin play an important role as an endogenous antioxidant.

Keywords

• keywords : neopterin
• antioxidant
• gastric ischemia
• superoxide anion
• esr sepectrometry