The activity of recombinant human neuroglobin as an antioxidant and free radical scavenger.

Free radicals are by-products of metabolism and exist in a homeostasis between generation and scavenging in vivo. Excessive free radicals cause various diseases, including nervous system diseases. Neuroglobin (Ngb), a nervous system-specific oxygen-binding protein, has been suggested to be a potential free radical scavenger in the nervous system in vivo; however, its underlying mechanism remains unclear. In this study, we investigated the antioxidant potential and free radical scavenging properties of recombinant human Ngb (rhNgb) in vitro. Interestingly, we found that the rhNgb protein itself has a direct and distinct antioxidant capacity and can efficiently scavenge a variety of free radicals, including the [2,2'-azino-di-(3-ethyl-benzthiazoline-6-sulfonic acid)] (ABTS) cation, superoxide anion, hydrogen peroxide, and hydroxyl radical. The capacity of rhNgb to scavenge the superoxide anion and hydrogen peroxide was even comparable to that of vitamin C. In addition, rhNgb had Fe(2+) chelating activity but hemoglobin did not. In conclusion, our results indicated that the rhNgb protein itself has antioxidant and free radical scavenging activities, providing fundamental evidence for the neuroprotective function of Ngb. These data provide key information for the origin of the neuroprotective and physiological role of Ngb and will promote the treatment of reactive oxygen species (ROS)-related diseases using this novel oxygen-binding globin.