Purification of a Human Red Blood Cell Protein Supporting the of Cultured CNS Neurons, and Its Identification as Catalase Survival

We have previously reported that red blood cells contain high levels of a protein that supports the survival of a variety of CNS neurons in vitro for 24 hr. Here we report the isolation of this trophic activity from human red blood cells. The active material, purified over lOOO-fold by ion-exchange chromatography and isoelectric focusing, has been identified as catalase based on its isoelectric point, subunit molecular weight, and ability to degrade hydrogen peroxide. Commercially produced bovine liver catalase, lactoperoxidase, HRP, and vitamin E all mimic the ability of the purified human protein to support neuronal survival in vitro. Pharmacological inhibitors of peroxidase activity inhibit the trophic effects of both commercial catalase and the purified blood-derived protein. These results suggest that peroxidase activity mediates the neuronotrophic activity of these agents. The bioassay culture medium itself generates peroxides in the absence of cells. Removal of this toxic material may be the basis for the trophic effects of catalase.