Low dose (À)deprenyl is cytoprotective: It maintains mitochondrial membrane potential and eliminates oxygen radicals L. Simon a, * , G. Szila ´gyi a , Z. Bori a , G. Telek b , K. Magyar c , Z. Nagy a a National Institute of Psychiatry and Neurology, National Stroke Center, Department of Vascular Neurology, Semmelweis University, Hu ¨vo ¨svo ¨lgyi Street 116., Budapest, H-1021 Hungary b IIIrd Department of Surgery, Semmelweis University, Budapest, Hungary c Neurochemical Research Unit of the Hungarian Academy of Sciences, Budapest, Hungary Received 2 February 2005; accepted 12 April 2005 Abstract Hypoxia leads to a collapse in mitochondrial transmembrane potential (Dw M ), a fall in the ATP/ADP ratio, and finally cell death. Since (À)deprenyl directly modulates Dw M and production of reactive oxygen species (ROS) by altering the respiratory function of mitochondria, we were interested in the dose – response relations of these effects. The changes in JC-1 red / green signal ratios {mitochondrial transmembrane potential}, and the changes in the cerium staining (intracellular ROS) in hypoxic and normoxic PC12 cell cultures were measured following 1 h of Argon hypoxia and 24 h of re-oxygenation in the absence and in the presence of various concentrations of (À)deprenyl. Dw M shifted to lower values following hypoxia/re-oxygenation and all cells had decreased and uniform Dw M levels. The amount of ROS increased. Following 24 h of treatment with various concentrations of (À)deprenyl during the re-oxygenation period, survival increased, the Dw M shift caused by oxygen deprivation was reversed and the peroxy radical levels decreased except for at 10 À 3 M. D 2005 Elsevier Inc. All rights reserved. Keywords: Mitochondrial transmembrane potential; Reactive oxygen radicals (ROS); (À)Deprenyl; JC-1; Cerium Introduction During hypoxia, the impairment of mitochondrial function, the consequent collapse in mitochondrial transmembrane potential (Dw M ), a fall in the ATP/ADP ratio, and the hypoxia-induced cytoplasmic accumulation of cytochrome c leads to cell death (Smets et al., 1994; Kroemer et al., 1997; Yermolaieva et al., 2004; Hardie, 2003; Kim et al., 2003). The outward pumping of protons across the inner mitochondrial membrane produces a proton gradient that drives the conversion of ADP to ATP and is reflected by the Dw M (Sherrat, 1991). Decreased Dw M induces opening of the mitochondrial perme- ability transition pores (PTP), which may lead to the release of mitochondrial apoptosis initiation factors (AIFs) (Marchetti et al., 1996). The loss of mitochondrial membrane potential (Dw M ) in itself may or may not lead to apoptotic cell death depending on the model system being used (Salvioli et al., 2000). An overall decrease in Dw M was reported to occur late in apoptosis, well after the release of cytochrome c from mitochondria (Yong et al., 1997). During re-oxygenization after a hypoxic period high amounts of reactive oxygen species (ROS) are generated (Yermolaieva et al., 2004). Mitochondria are the major generators of ROS. ROS production is associated with excessive oxidative stress. Membrane lipids are the primary targets of ROS, but proteins, carbohydrates and nucleic acids are also damaged, leading thus to cellular dysfunction and death. (À)Deprenyl (phenyl-isopropyl-methyl-propargylamine, selegiline) is a relatively selective, irreversible inhibitor of monoamine oxidase-B (Knoll and Magyar, 1972; Birkmayer et al., 1975; Sowa et al., 2004). Deprenyl is used in the treatment of Parkinson’s disease (Oerthel and Quinn, 1997). Since (À)deprenyl directly modulates Dw M (Wadia et al., 1998) and thus the production of reactive oxygen species (ROS) by altering the respiratory function of mitochondria in a dose- dependent fashion (Go ¨ tz et al., 1995; Thyffault et al., 1997; Wadia et al., 1998). The aim of the present study was to investigate the possible cytoprotective mechanisms of 0024-3205/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2005.04.078 * Corresponding author. Tel.: +36 6 70 319 7163; fax: +36 1 391 5440. E-mail address: simla@freemail.hu (L. Simon). Life Sciences 78 (2005) 225 – 231 www.elsevier.com/locate/lifescie