Effect of folic acid on oxidative stress and behavioral changes in the animal model of schizophrenia induced by ketamine
Introduction
Folic acids one of the B complex vitamins which participates in the metabolism of one-carbon (C1) compounds (Coppen and Bolander-Gouaille, 2005, Mattson and Shea, 2003). This vitamin plays a neuro protective role against impairments in the central nervous system (CNS), and promotes neuronal growth and repair (Budni et al., 2011, Iskandar et al., 2004). Folic acid is also involved in the metabolism and functioning of compounds essential to the CNS, which includes the purines, pyrimidines, DNA, RNA, amino acids, phosphate compounds, vitamin B-12, methionine, S-adenosylmethionine, dopamine, adrenaline, noradrenaline and serotonin (Coppen and Bolander-Gouaille, 2005; Kronenberg et al., 2009; Lucock, 2011; ). Thus, alterations in the metabolism of folic acid can directly affect the CNS (Coppen and Bolander-Gouaille, 2005, Krebs et al., 2009, Miller, 2008, Stahl, 2007).
The presence of neuropsychiatric symptoms in patients with B deficiency vitamins complex and in children conceived following a short inter-pregnancy interval indicates a role for folic acid in schizophrenia. The influence of the interval between pregnancies could be explained by the reduction of the maternal reserves of folic acid when the maternal folic acid stores are still being replenished (Dogan et al., 2009).
Schizophrenia is a severe, chronic and debilitating mental disorder that affects 1% of the World’s population, and is characterized by positive (e.g. hallucinations), negative (e.g. blunted affects and social isolation) and cognitive symptoms (e.g. executive and memory dysfunction) (Larson et al., 2010). This disorder is considered to be the result of a genetic combination and environmental factors. Although its pathophysiology has not been fully determined, biological studies support that the involvement of several possible components, including altered DNA methylation, abnormal transmission of neurotransmitters, oxidative stress, folic acid deficiencies and high maternal homocysteine levels. Each of these factors has been separately explored, and they have all been found to involve C1 metabolism, which is a putative target-integrating gene–environment interactions by influencing epigenetic regulation (Krebs et al., 2009). Studies have indicated an important relationship between folic acid metabolism and schizophrenia. In this sense, these findings support the hypothesis that the deficiency of this vitamin during fetal development may be an important risking factor for schizophrenia (Gunawardana et al., 2011).
Current studies utilize pharmacological tools in evaluating the effects of new protective compounds against schizophrenia. Recent reviews have shown that ketamine is a useful tool for studying the positive, negative and cognitive symptoms observed in acute schizophrenia (Frohlich and Van Horn, 2014). This animal model of schizophrenia involves the acute or repeated administration of ketamine (Becker and Grecksch, 2004, Bubeníková-Valesová et al., 2008, Canever et al., 2010, De Oliveira et al., 2011). Ketamine is a dissociative anesthetic which acts as an NMDA receptor non competitive antagonist, and is largely used within research to create animal models of schizophrenia; since it induces schizophrenia-like symptoms (Dingledine et al., 1999). These animal models imitate the behavioral changes seen in schizophrenia such as hyperactivity, social interaction and memory deficits. Moreover, ketamine induces similar biochemical alterations that are found in schizophrenia, such NMDA receptor hypo function and oxidative stress (Chatterjee et al., 2011). Based on these previous results from our laboratory support the hypothesis that early insults interfere with the glutamatergic system, reflecting a greater sensitivity to the effects of ketamine in adulthood within an animal model of schizophrenia (Zugno et al., 2013). All these findings reinforce the validity of the ketamine model since it is capable to mimic the phenotype of schizophrenia in both, the animal behavior as well as in the biochemical alterations seen in brain.
Considering that the etiology of schizophrenia is not clear, current researches indicate that the accumulation of reactive oxygen species (ROS) is associated with the pathophysiology of the disorder (Ciobica et al., 2011, Ruiz-Litago et al., 2012, Yao and Keshavan, 2011). Oxidative stress occurs because of the increased levels of ROS, reactive nitrogen species (RNS) or by an imbalance in the activity of the endogenous antioxidant system (Berg et al., 2004, Kwon et al., 2003). As a consequence of the increased levels of ROS and the failure of the endogenous antioxidant system, damage to DNA, proteins and membrane lipids can occur (Konat, 2003, Kwon et al., 2003).
The link between schizophrenia and oxidative stress was recently demonstrated when it was shown that the activity of glutathione peroxides (GPx) decreased in both treated and untreated patients (Miljevic et al., 2010). Also, increased levels of markers for lipid per oxidation were observed in a similar population (Dadheech et al., 2008, Padurariu et al., 2010). Additionally, a study performed by our group suggested that the animal model of schizophrenia induced by ketamine showed changes in the activity of superoxide dismutase (SOD), catalase (CAT) and GPx, resulting in protein and lipid damage (De Oliveira et al., 2009).
Folic acid is involved in the metabolism of homocysteine that can be remethylated to methionine by enzymes that require folic acid, and it can also be catabolized by cystathionine-B-synthase, an enzyme dependent on the vitamin B6, that forms cysteine, a precursor of glutathione (Micle et al., 2012). It is known that hyperhomocysteinemia is directly related to oxidative stress. The autoxidation of homocysteine and other disulfides, releases oxygen (O2) and hydrogen peroxide (H2O2), both of them impair neuronal function and predispose the neuronal tissue to neurodegenerative and psychiatric disorders (White et al., 2001). Furthermore, the deficiency of folic acid induces the high levels of homocysteine and the formation of ROS that lead to decreases in both antioxidant potential and the activity of GPx, increasing oxidative tissue damage (McCully, 2009).
Although, studies have emphasized the association between folic acid deficiency and schizophrenia, few preclinical studies have been conducted to study the supplementation of this vitamin, or to evaluate its effect in an animal model of schizophrenia (Godfrey et al., 1990, Levine et al., 2006). In this sense, the aim of the study was to evaluate the effect of diet supplementation with folic acid over a period of seven or fourteen days in adult rats, and also to verify potential protective actions in an animal model of schizophrenia induced by acute or chronic administrations of ketamine on the animals behavioral and biochemical parameters.
Section snippets
Experimental procedures
The animals included in this study were handled according to the NIH Guide for the Care and Usage of Laboratory Animals, and also in accordance with the rules of the Brazilian Society for Neuroscience and Behavior (SBNeC). The experiments were performed at the Universidade do Extremo Sul Catarinense (UNESC) Brazil, in the Laboratory of Neurosciences, and in partnership with the Laboratory of Pathophysiology. All experimental procedures were performed in accordance with international
Behavioral tests
The results in Fig. 3A and B shows the effect of folic acid administration over a period of 7 and/or 14 days on the locomotor activity of rats in an animal model of schizophrenia induced by ketamine. Acute and chronic ketamine administration at a dose of 25 mg/kg increased the locomotor activity in these animals. Treatments with folic acid over a period of 7 days at doses of 5, 10 and 50 mg/kg were notable to prevent the hyper locomotor effect. In contrast, folic acid (10 and 50 mg/kg)
Discussion
In this study, ketamine administered in a single dose or over a period of 7 days increased the test animal’s levels of locomotion, corroborating previous studies proposed by Gama et al. (2012) and Zugno et al., (2013). Therefore, the administration of folic acid (5, 10 and 50 mg/kg) during a period of 7 days was unable to prevent hyperlocomotion in this experiment. It is possible that folic acid was not able to prevent the hyperlocomotion seen in this study due to the short period of time that
Role of the funding source
There are no conflict of interest. The funding agencies had no role in design and conduct of the study, the collection, management, analysis and interpretation of the data, or the preparation, review or approval of the manuscript. The authors were not paid to write this article by a pharmaceutical company or other agency.
Contributors
Drs Zugno, Budni, Quevedo and Schuck had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Zugno and Budni.
Acquisition of data:Wessler, Steckert, Mastella, De Oliveira, Damázio, Calixto, Pereira, Pedro.
Analysis and interpretation of data: Canever, Heylmann, Wessler and Pacheco.
Drafting of the manuscript: Canever and Budni.
Critical revision of the manuscript for importante
Acknowledgments
Laboratory of Neurosciences (Brazil) is one of the centers of the National Institute for Translational Medicine (INCT-TM) and one of the members of the Center of Excellence in Applied Neurosciences of Santa Catarina (NENASC). This research was supported by grants from 1 CNPq, 2 InstitutoCérebro e Mente and 3 UNESC. JQ and AIZ are CNPq fellows.
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