Antioxidants effectively prevent oxidation-induced protein damage in OLN 93 cells Andrea Ernst, a Alexandra Stolzing, a Grit Sandig, a and Tilman Grune a,b, * a Neuroscience Research Center, Medical Faculty (Charit e), Humboldt University, Berlin, Germany b Molecular Aging Research, Institute for Environmental Medical Research, Heinrich Heine University, D€ usseldorf, Germany Received 2 June 2003, and in revised form 10 September 2003 Abstract Oxidative stress is supposed to play an important role in demyelinating diseases. Oligodendrocytes are the myelin-forming cells in the brain and are highly susceptible to oxidative stress due to their low antioxidative defense systems and high metabolic rate. In the present work, we tested the response of the oligodendrocyte cell line OLN 93 to oxidative stress. OLN 93 cell cultures are char- acterized by a loss of cell viability after oxidation. This loss of cell viability is accompanied by an increase in protein oxidation and consequently an elevated overall proteolysis. To minimize the oxidative damage, we tested the effects of the antioxidants a-lipoic acid and coenzyme Q 10 . Both compounds were able to elevate cell viability and to decrease intracellular protein turnover and oxidant induced protein oxidation. Therefore, we concluded that the excessive oxidative damage of oligodendrocytes and their protein pool can be prevented by the usage of antioxidants. Ó 2003 Elsevier Inc. All rights reserved. Keywords: Oligodendrocytes; Protein oxidation; Antioxidants; Free radicals; OLN93 cells Oligodendrocytes, as the myelin-forming cells of the central nervous system, require large amounts of energy for the biosynthesis of myelin lipids. As a consequences they produce a lot of reactive oxygen species (ROS) 1 as byproduct of the mitochondrial electron transport chain [1,2]. Furthermore, large amounts of ROS are produced by macrophages and activated microglial cells in the brain, which may be involved in myelin damage or death of oligodendrocytes [3]. Oligodendrocytes, as major iron-containing cells of the brain, are highly susceptible to oxidative stress. This may be related to their high iron content and low antioxidative defense systems [4,5]. Nitric oxide and superoxide radicals are secreted by inflammatory cells during disease and are able to release iron from the ferritin pool [6]. Free iron ions are able to mediate the formation of highly reactive oxidizing spe- cies including the formation of hydroxyl radicals from hydrogen peroxide via the Fenton reaction [7]. Excessive production of ROS lead to DNA damage, lipid perox- idation, and protein oxidation [8,9]. In particular, pro- tein oxidation seems to be important in several neurodegenerative and neuroinflammatory diseases [10– 15], especially since one of the highlights of these dis- eases is the accumulation of oxidized proteins within neurons or extracellular tissue. Additionally, immuno- logical reactions towards oxidatively modified proteins seem to play an important role in the development of demyelinating diseases such as multiple sclerosis and the experimental autoimmune encephylomyelitis (EAE), an animal model of multiple sclerosis [16,17]. The oxidation of amino acid residues, the formation of protein aggregates by cross-linking and the produc- tion of protein fragments [18–20] may result in the loss of activity and inactivation of enzymes and metabolic pathways [21] and finally end up with cell death. It was shown that the proteasomal system is responsible for the degradation of oxidized proteins [22–24]. In oligodendrocytes, the amount of the mitochondrial superoxide dismutase, one of the major ROS removing * Corresponding author. Fax: +49-211-3389-222. E-mail address: tilman.grune@uni-duesseldorf.de (T. Grune). 1 Abbreviations used: Cu/ZnSOD, copper/zink superoxide dismu- tase; DMEM, DulbeccoÕs modified EagleÕs medium; FCS, fetal calf serum; MnSOD, manganese superoxide dismutase; PAGE, polyacryl gel electrophoresis; ROS, reactive oxygen species. 0003-9861/$ - see front matter Ó 2003 Elsevier Inc. All rights reserved. doi:10.1016/j.abb.2003.10.008 Archives of Biochemistry and Biophysics 421 (2004) 54–60 ABB www.elsevier.com/locate/yabbi