Int. J. Devl Neuroscience 31 (2013) 165–170 Contents lists available at SciVerse ScienceDirect International Journal of Developmental Neuroscience j our na l ho me p age: www.elsevier.com/locate/ijdevneu Lipoic acid increases glutamate uptake, glutamine synthetase activity and glutathione content in C6 astrocyte cell line Juliana Kleinkauf-Rocha a,b , Larissa Daniele Bobermin a , Priscila de Mattos Machado b , Carlos-Alberto Gonc¸ alves a , Carmem Gottfried a , André Quincozes-Santos a,∗ a Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil b Fundac¸ ão de Apoio a Pesquisa e Estudos na Área da Saúde, São Paulo, Brazil a r t i c l e i n f o Article history: Received 17 July 2012 Received in revised form 19 December 2012 Accepted 21 December 2012 Keywords: Lipoic acid C6 astrocyte cell line Reactive oxygen species Glutamate metabolism a b s t r a c t Alpha lipoic acid (LA) is a sulfhydryl compound, used as dietary supplement and to treat a variety of conditions associated to oxidative stress. Glial cells are key modulators of neuroprotection. We show here that LA modulates specific glial parameters in C6 astrocyte cell line, such as glutamate uptake, glutamine synthetase (GS) activity and glutathione content, commonly associated with the protective role of glial cells. LA (10 and 50 M) after 24 h of treatment significantly decreased the formation of reactive oxygen species (ROS) and nitric oxide (NO) levels, and increased glutamate uptake (up to 20%), GS activity (25%) and GSH content (up to 40%). LA increase glutamate uptake probably by decreasing oxidizing conditions and/or by mechanism dependent of protein kinase C (PKC). In contrast, high concentrations of LA (1000 M) decreased these glial functions. Moreover, this concentration increased ROS production and NO levels. In summary, these findings show that low doses of LA were able to modulate glial functions and it appears to have remarkable therapeutic potential in neurological diseases involving oxidative stress by improving glutamatergic metabolism. © 2012 ISDN. Published by Elsevier Ltd. All rights reserved. 1. Introduction Alpha lipoic acid (LA), also known as thioctic acid (1,2- dithiolane-3-pentanoic acid), is a naturally occurring compound with antioxidant properties used as dietary supplement (Sabharwal and May, 2008). Furthermore, LA is cofactor of mitochondrial enzyme complexes, such as pyruvate dehydrogenase and alpha- ketoglutarate dehydrogenase (Liu et al., 1995; Reed and Hackert, 1990) and presents metal chelation, anti-inflammatory activity and neuroprotective effect (Aguirre et al., 1999; Packer and Cadenas, 2011; Perera et al., 2011; Salinthone et al., 2011). LA contains two thiol (sulfur) groups, which may be reduced to dihydrolipoic acid (DHLA). The oxidized form is easily absorbed and taken by cells, being finally reduced to DHLA with participation of the system NADH (Haramaki et al., 1997). The mitochondria are the main site of DHLA antioxidant action; however, it also can act as antiox- idant and scavenger in the extracellular space, protecting cells against oxidative damage (Busse et al., 1992). In addition to their ∗ Corresponding author at: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600 anexo, 90035–003 Porto Alegre, RS, Brazil. Tel.: +55 51 33085559; fax: +55 51 3308 5535. E-mail address: andrequincozes@yahoo.com.br (A. Quincozes-Santos). direct antioxidant activity, DHLA play an important role in the non- enzymatic regeneration of glutathione (GSH), vitamin C, vitamin E and coenzyme Q 10 in vivo (Biewenga et al., 1997; Kolgazi et al., 2007). Dietary supplementation of LA also increases DHLA, which can act as a potent antioxidant, ameliorating oxidative stress in vitro and in vivo. Oxidative stress is a result of excessive production of reactive oxygen and/or nitrogen species (ROS and RNS, respectively) which can lead to lipid, protein and DNA oxidation and/or nitration, caus- ing cell damage (Gutteridge and Halliwell, 2010; Halliwell, 2001; Nakamura and Lipton, 2007). It is a common cause of cancer, aging, arteriosclerosis, diabetes, stroke and degenerative diseases, such as, Alzheimer’s and Parkinson’s diseases (Castagne et al., 1999; Halliwell, 2006). Glial cells are the most abundant cells in the human brain (Belanger et al., 2011; Wang and Bordey, 2008). Astrocytes display a wide range of adaptative functions in the mammalian nervous sys- tem. They interact with neurons, providing structural, metabolic, trophic support and antioxidant defenses, participating of the amino acids uptake metabolism (Barbeito et al., 2004). The gluta- mate is the major neurotransmitter in the central nervous system (CNS) and its accumulation is implicated in neurodegenerative dis- orders (Danbolt, 2001). Astroglial cells are responsible for major glutamate transport and regulate extracellular levels of glutamate (Hertz, 2006; Veenman et al., 2012). Moreover, astrocytes have a 0736-5748/$36.00 © 2012 ISDN. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijdevneu.2012.12.006