Contents lists available at ScienceDirect Neurotoxicology and Teratology journal homepage: www.elsevier.com/locate/neutera Full length article Differential expression of glutamate transporters in cerebral cortex of paraoxon-treated rats Zohreh Zare a , Mohsen Tehrani b , Alireza Rafiei b , Reza Valadan b , Moslem Mohammadi c,⁎ a Department of Anatomical Sciences, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran b Department of Immunology, Molecular and Cell Biology Research Center, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran c Department of Physiology & Pharmacology, Molecular and Cell Biology Research Center, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran ARTICLE INFO Keywords: Cerebral cortex Paraoxon Glutamate uptake Transporter Convulsion ABSTRACT Glutamatergic system is involved in pathological effects of organophosphorus (OP) compounds. We aimed to determine in vivo effects of paraoxon, the bioactive metabolite of parathion, on the expression of glutamate transporters as well as Bax and Bcl2 in rat cerebral cortex. Male Wistar rats received an intraperitoneal (i.p.) injection of one of three doses of paraoxon (0.3, 0.7, or 1 mg/kg) or corn oil as vehicle (1 ml/kg). After 4 or 18 h, cerebral cortices were dissected out and used for quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot assays to measure mRNA and protein levels, respectively. The cortical glial gluta- mate transporters (GLAST and GLT-1) were up-regulated in animals treated with 0.7 mg/kg of paraoxon, but down-regulated in 1 mg/kg group. Neuronal glutamate transporter (EAAC1) was unchanged in 0.7 mg/kg treated rats, while reduced in 1 mg/kg group. No significant difference was found in the mRNA and protein expression of EAAC1 in animals intoxicated with 0.3 mg/kg of paraoxon. Paraoxon (1 mg/kg) resulted in an up- regulation of Bax and down-regulation of Bcl2 mRNA levels in the rat cerebral cortex. These results indicate that paraoxon can differentially regulate expression of glutamate transporters at mRNA and protein levels in the cerebral cortex. Changes in the expression of glutamate transporters are closely related to paraoxon-induced seizure activity. 1. Introduction Organophosphorus (OP) compounds refer to a large group of in- secticides or nerve agents, which act by inhibiting the enzyme acet- ylcholinesterase (AChE), the enzyme responsible for the breakdown of acetylcholine. Subsequently, accumulation of acetylcholine (ACh) leads to hyperstimulation of muscarinic and nicotinic receptors and produces a series of centrally and peripherally pathological responses, including hypersecretions, fasciculation, tremor, convulsions, respiratory distress, and death (Shih et al., 2003). Poisoning with pesticides, especially OP insecticides, is a major public-health concern worldwide (Albuquerque et al., 2006; Buckley et al., 2004). OP insecticide parathion is converted to its bioactive metabolite paraoxon by oxidative desulforation in the liver. Paraoxon is used in civilian laboratories as a surrogate nerve agent (Deshpande et al., 2014). Although the primary known mechanism of OP action is disruption in acetylcholine neurotransmission, these compounds have also been reported to interfere with other neurotransmitter systems, including GABAergic and glutamatergic systems. Current standard treatments for reducing OP-induced toxicity include anticholinergic compounds to reduce the muscarinic syndrome, oximes to reactivate inhibited AChE, and anticonvulsants to control OP-induced seizures. However, such treatments failed to prevent long-term OP-induced seizures and sub- sequent brain damages (Guo et al., 2015; Shih et al., 2003). Therefore, research efforts are necessary in order to identify more efficient drugs to provide neuroprotection against OP-induced brain damages. Modula- tion of the glutamatergic system and reduction of glutamate ex- citotoxicity appear to be one of the therapeutic strategies to prevent neuronal death and consequent cognitive impairment caused by OP- induced seizure (Myhrer et al., 2005). Glutamate is the major excitatory neurotransmitter in the mam- malian central nervous system and essential for normal brain function including cognition, memory, and learning. However, the extracellular concentration of glutamate must remain below its excitotoxic levels to limit overstimulation of glutamate receptors and prevent neuronal da- mage or death (Danbolt, 2001). In addition to the amount of glutamate released, the concentration of glutamate in the synaptic cleft is http://dx.doi.org/10.1016/j.ntt.2017.06.001 Received 6 April 2017; Received in revised form 12 May 2017; Accepted 7 June 2017 ⁎ Corresponding author at: Department of Physiology & Pharmacology, Molecular and Cell Biology Research Center, School of Medicine, KM 17 Khazarabad Road, Khazar Sq, P.O. Box 48471-91971, Sari, Iran. E-mail address: m.mohammadi@mazums.ac.ir (M. Mohammadi). Neurotoxicology and Teratology 62 (2017) 20–26 Available online 08 June 2017 0892-0362/ © 2017 Published by Elsevier Inc. MARK