Cytoprotection Against Oxidative Stress-Induced Damage of Astrocytes by Extracellular ATP Via P2Y 1 Receptors YOUICHI SHINOZAKI, 1,4 SCHUICHI KOIZUMI, 2 SEIICHI ISHIDA, 2 JUN-ICHI SAWADA, 3 YASUO OHNO, 2 AND KAZUHIDE INOUE 1,4 * 1 Division of Biosignaling, National Institute of Health Sciences, Setagaya, Tokyo, Japan 2 Division of Pharmacology, National Institute of Health Sciences, Setagaya, Tokyo, Japan 3 Division of Biochemistry and Immunochemistry, National Institute of Health Sciences, Setagaya, Tokyo, Japan 4 Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan KEY WORDS ATP; P2Y 1 receptors; astrocytes; oxidative stress ABSTRACT Oxidative stress is the main cause of neuronal damage in traumatic brain injury, hypoxia/reperfusion injury, and neurodegenerative disorders. Although extracellular nucleosides, especially adenosine, are well known to protect against neu- ronal damage in such pathological conditions, the effects of these nucleosides or nucle- otides on glial cell damage remain largely unknown. We report that ATP but not adenosine protects against the cell death of cultured astrocytes induced by hydrogen peroxide (H 2 O 2 ). ATP ameliorated the H 2 O 2 -induced decrease in cell viability of astro- cytes in an incubation time- and concentration-dependent fashion. Protection by ATP was inhibited by P2 receptor antagonists and was mimicked by P2Y 1 receptor agonists but not by adenosine. The expressions of P2Y 1 mRNAs and functional P2Y 1 receptors in astrocytes were confirmed. Thus, ATP, acting on P2Y 1 receptors in astrocytes, showed a protective action against H 2 O 2 . The astrocytic protection by the P2Y 1 receptor agonist 2-methylthio-ADP was inhibited by an intracellular Ca 2+ chelator and a blocker of phospholipase C, indicating the involvement of intracellular signals mediated by Gq/11- coupled P2Y 1 receptors. The ATP-induced protection was inhibited by cycloheximide, a protein synthesis inhibitor, and it took more than 12 h for the onset of the protective action. In the DNA microarray analysis, ATP induced a dramatic upregulation of various oxidoreductase genes. Taken together, ATP acts on P2Y 1 receptors coupled to Gq/11, resulting in the upregulation of oxidoreductase genes, leading to the protection of astrocytes against H 2 O 2 . © 2004 Wiley-Liss, Inc. INTRODUCTION Astrocytes are much more than merely support cells for neurons in the central nervous system (CNS). They can receive inputs, assimilate information, and send instructive chemical signals to neighboring glial cells as well as neurons (Araque et al., 1999a, b, 2001; Hay- don, 2001). Thus, communication among astrocytes would play an important role in brain function. Ini- tially, so-called gliotransmission, a glia-to-glia commu- nication or even neuron-to-glia communication, was reported to be mediated by glutamate (Cornell-Bell et al., 1990; Charles et al., 1991; Parpura et al., 1994; Innocenti et al., 2000) because astrocytes express glu- tamate receptors and release glutamate. However, re- Grant sponsor: Program for Promotion of Fundamental Studies in Health Sciences of the Organization for Pharmaceutical Safety and Research (OPSR); Grant number: MF-16; Grant number: MPJ-6; Grant sponsor: Grant-in-Aid for Scientific Research; Grant sponsor: Brain Science Foundation. *Correspondence to: Kazuhide Inoue, Division of Biosignaling, National Insti- tute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan. E-mail: inoue@nihs.go.jp Received 29 March 2004; Accepted 30 July 2004 DOI 10.1002/glia.20118 Published online 19 October 2004 in Wiley InterScience (www.interscience. wiley.com). GLIA 49:288 –300 (2005) © 2004 Wiley-Liss, Inc.