Original Contribution Glutathione depletion activates mitogen-activated protein kinase (MAPK) pathways that display organ-specific responses and brain protection in mice Jorge H. Limón-Pacheco a , Norma A. Hernández b , María L. Fanjul-Moles c , María E. Gonsebatt a, ⁎ a Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Distrito Federal, México b Subdirección de Investigación Clínica, Instituto Nacional de Cancerología, Av. San Fernando 22, Código Postal 14000, Tlalpan, Distrito Federal, México c Laboratorio de Neurobiología, Facultad de Ciencias, Universidad Nacional Autónoma de México, México Received 2 October 2006; revised 25 June 2007; accepted 27 June 2007 Available online 27 July 2007 Abstract Because mitogen-activated protein kinases (MAPK) are downstream effectors of antioxidant responses, changes in GSH levels in an organism might induce organ-specific responses. To test our hypothesis, mice were treated intraperitoneally with L-buthionine-S-R-sulfoximine (BSO) to inhibit GSH synthesis. A time-related GSH depletion in the liver and kidney correlated with p38 MAPK phosphorylation and induction of thioredoxin 1 (Tx-1) transcription. This positive regulation was associated with nuclear translocation of NF-κB and ATF-2 and c-Jun phos- phorylation in the liver, but only c-Jun phosphorylation in the kidney. Increased levels of GSH were observed in the brain together with extracellular regulated kinase 2 (ERK2) activation, Nrf2 nuclear accumulation, and increases in transcription of Nrf2, xCT , γ-glutamylcysteine synthetase (γGCSr), and Tx-1. Pretreatment with MAPK inhibitors SB203580 and U0126, or addition of the exogenous thiol N-acetylcysteine, abrogated both p38 MAPK and ERK2 activation as well as downstream effects on gene expression. No effect on γGCSr was observed. These results indicate that in mice, GSH depletion is associated with p38 MAPK phosphorylation in the liver and kidney and with ERK2 activation in the brain, in what could be considered part of the brain's protective response to thiol depletion. © 2007 Elsevier Inc. All rights reserved. Keywords: Mitogen-activated protein kinases; Glutathione; Organ-specific regulation; Redox environment Introduction Oxidative phosphorylation and metabolic transformations in eukaryotes are the main sources of reactive oxygen species (ROS) that cause oxidative damage in cellular DNA, lipids, and proteins. To contend with these toxic products, cells synthesize low molecular weight thiol-containing peptides such as gluta- thione (GSH; L-γ-glutamyl-L-cysteinyl-glycine). GSH consti- tutes the major intracellular redox buffer in the cells, but also functions as an antioxidant in xenobiotic metabolism and is considered a site for cysteine storage [1,2]. In recent years, a role for GSH in the modulation of signal transduction through direct interaction with key cysteines located in the active site or modulator regions of kinases, phosphatases, and transcription factors has been recognized [3–5]. GSH is synthesized in the cytosol in two steps. First, the enzyme γ-glutamylcysteine synthetase (γGCS) catalyzes the formation of L-γ-glutamyl-L- cysteine. The glycine residue of the GSH tripeptide is added in the second step by glutathione synthetase. Cellular GSH exists predominantly in a reduced form, but small amounts of the oxidized disulfide form GSSG can also be detected. The GSH/ GSSG ratio often is taken as an indicator of cellular redox Free Radical Biology & Medicine 43 (2007) 1335 – 1347 www.elsevier.com/locate/freeradbiomed Abbreviations: AP-1, activating protein 1; ARE, antioxidant response element; ATF-2, activating transcription factor 2; BSO, L-buthionine-S-R- sulfoximine; ERK, extracellular signal-regulated kinase; GAPDH, glyceralde- hyde phosphate dehydrogenase; GCS c,r , glutamylcysteine synthetase, c, catalytic subunit, r, regulatory subunit; GR, glutathione reductase; GSH, reduced glutathione; GSSG, oxidized glutathione; JNK, c-Jun amino N-terminal kinase; MAPK, mitogen-activated protein kinase; NF-kB, nuclear factor kappa B; Nrf2, nuclear factor E2 p45-related factor; p38 MAPK , p38 kinase; ROS, reactive oxygen species; xCT, subunit of cysteine transporter. ⁎ Corresponding author. Apartado Postal 70-228, 04510, Ciudad Universi- taria, Distrito Federal, México. Fax: +52 55 56229182. E-mail address: margen@servidor.unam.mx (M.E. Gonsebatt). 0891-5849/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.freeradbiomed.2007.06.028