HEME OXYGENASE-1 (HO-1) UPREGULATION DELAYS MORPHOLOGICAL AND OXIDATIVE DAMAGE INDUCED IN AN EXCITOTOXIC/PRO-OXIDANT MODEL IN THE RAT STRIATUM A. L. COLI ´ N-GONZA ´ LEZ, a  M. OROZCO-IBARRA, b M. E. CHA ´ NEZ-CA ´ RDENAS, a E. RANGEL-LO ´ PEZ, c A. SANTAMARI ´ A, c J. PEDRAZA-CHAVERRI, d D. BARRERA-OVIEDO e AND P. D. MALDONADO a * a Laboratorio de Patologı´a Vascular Cerebral, Instituto Nacional de Neurologı´a y Neurocirugı´a, Mexico City 14269, Mexico b Laboratorio de Neurobiologı´a Molecular y Celular, INNN-UNAM, Instituto Nacional de Neurologı´a y Neurocirugı´a, Mexico City 14269, Mexico c Laboratorio de Aminoa ´cidos Excitadores, Instituto Nacional de Neurologı´a y Neurocirugı´a, Mexico City 14269, Mexico d Departamento de Biologı´a, Facultad de Quı´mica, Universidad Nacional Auto ´ noma de Mexico, Mexico City, Mexico e Departamento de Farmacologı´a, Facultad de Medicina, Universidad Nacional Auto ´noma de Me ´xico, Mexico City, Mexico Abstract—Quinolinic acid (QA)-induced overactivation of N-methyl-D-aspartate receptors yields excitotoxicity, oxidative stress and mitochondrial dysfunction, which altogether con- tribute to trigger a wide variety of toxic pathways with biochem- ical, behavioral and neuropathological alterations similar to those observed in Huntington’s disease. Noteworthy, in the brains of these patients, increased expression of heme oxygen- ase-1 (HO-1) levels can be found. It has been proposed that this enzyme can exert a dual role, as it can be either protective or del- eterious to the CNS. While some evidence indicates that its overexpression affords cellular anti-oxidant protection due to decreased concentrations of its pro-oxidative substrate heme group, and increased bilirubin levels, other reports established that high HO-1 expression and activity may result in a pro- oxidizing atmosphere due to a release of Fe 2+ . In this work, we examined the temporal evolution of oxidative damage to pro- teins, HO-1 expression, immunoreactivity, total activity, and cell death after 1, 3, 5 and 7 days of an intrastriatal QA infusion (240 nmol/ll). QA was found to induce cellular degeneration, increasing carbonylated proteins and generating a transitory response in HO-1 mRNA, protein content, and immunoreactivity and activity in nerve cells. In order to study the role of HO-1 in the QA-induced cellular death, the tin protoporphyrin IX (SnPP), a well-known HO inhibitor, was administered to rats (30 lmol/kg, i.p.). The administration of SnPP to animals treated with QA inhibited the HO activation, and exacerbated the striatal cell damage induced by QA. Our findings reveal a potential modulatory role of HO-1 in the toxic paradigm evoked by QA in rats. This evidence provides a valuable tool for further approaches on HO-1 regulation in neurotoxic paradigms. Ó 2012 IBRO. Published by Elsevier Ltd. All rights reserved. Key words: excitotoxicity, oxidative stress, quinolinic acid, heme oxygenase-1, neuroprotection, redox modulation. INTRODUCTION Excitotoxicity is a toxic mechanism leading to cell death through the sustained activation of receptors for excitatory amino acids, mostly N-methyl-D-aspartate receptors (NMDAr). This persistent stimulation generates enhanced intracellular Ca 2+ levels, which in turn triggers a massive activation of several proteolytic and lipolytic enzymes and second messenger-mediated events, ultimately conducting cells to death (Kumar et al., 2010). Among the catalytic enzymes activated by increased Ca 2+ , the most prominent are proteases, phospholipases, endonucleases and nitric oxide synthase, to name a few (Hynd et al., 2004). Quinolinic acid (QA or 2,3-pyridinedicarboxylic acid) is a heterocyclic amino acid synthesized at the kynurenine pathway. QA selectively activates NMDAr, especially those containing NR2A and NR2B subunits (de Carvalho et al., 1996; Schwarcz et al., 2010). NMDAr overactivation by QA shares various typical features of excitotoxic patterns induced by other toxins, including massive Ca 2+ influx, exacerbated oxidative metabolism, oxidative stress and cell death (Beal et al., 1986; Stone, 1993; Santamarı´a et al., 1997; Aguilera et al., 2007; Ting et al., 2009; Maldonado et al., 2010). In addition, QA produces a toxic accumulation of transition metals (Cu + , Fe 2+ , and Mn 2+ ) in the brain, which in the presence of oxygen, contributes to the formation of superoxide anion, hydrogen peroxide (H 2 O 2 ) and hydroxyl radical (Shoham et al., 1992; Santamarı´a et al., 1996). This toxic metabolite also modifies endogenous anti-oxidants (decreasing reduced glutathione levels, as well as Cu–Zn superoxide dismutase and catalase activities) (Santamarı´a et al., 1999; Rodrı´guez- Martı´nez et al., 2000; Tasset et al., 2010), and affects Nrf2 nuclear levels (an orchestrator of anti-oxidant responses) (Tasset et al., 2010; Carmona-Ramı´rez et al., 0306-4522/12 $36.00 Ó 2012 IBRO. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.neuroscience.2012.11.031 * Corresponding author. Address: Laboratorio de Patologı´a Vascular Cerebral, Instituto Nacional de Neurologı´a y Neurocirugı´a, Insurgen- tes Sur 3877, Me´xico D.F. 14269, Mexico. Tel: +52-55-5606- 3822x2009. E-mail address: maldonado.perla@gmail.com (P. D. Maldonado).   Master in Biological Sciences, Universidad Nacional Auto´noma de Me´xico. CONACyT scholarship recipient 239954. Abbreviations: BSA, bovine serum albumin; CO, carbon monoxide; DNPH, 2,4-dinitrophenylhydrazine; FJ, Fluoro-jade B; GFAP, glial fibrillary acidic protein; HD, Huntington’s disease; HO, heme oxygenase; H 2 O 2 , hydrogen peroxide; NMDAr, N-methyl-D-aspartate receptor; QA, quinolinic acid; ROS, reactive oxygen species; SnPP, tin protoporphyrin IX; TCA, trichloroacetic acid. Neuroscience 231 (2013) 91–101 91