Amanda V. Steckert

Role of oxidative stress in the pathophysiology of bipolar disorder

In this work, we review the studies of oxidative stress markers, showing association with the pathophysiology of bipolar disorder (BD). BD is a prevalent, chronic and highly disabling psychiatric disorder. Several hypotheses have been postulated to explain the exact neurochemical mechanisms underlying the pathophysiology of BD, including a role for monoamines, gamma-amino butyric acid (GABA), glutamate, and second messenger singling pathways. More recently, oxidative stress has been implicated in the pathogenesis of BD. Recent studies have reported increased products of lipid peroxidation and alterations of the major antioxidants enzymes in patients with BD. It has been widely demonstrated that the generation of reactive oxygen species (ROS) plays a critical role in the pathophysiology of several neuropsychiatric disorders, such BD.

Lithium and valproate modulate antioxidant enzymes and prevent ouabain-induced oxidative damage in an animal model of mania

In this study, we assessed the oxidative stress parameters in rats submitted to an animal model of mania induced by ouabain (OUA), which included the use of lithium (Li) and valproate (VPA). Li and VPA treatment reversed and prevented the OUA-induced damage in these structures, however, this effect varies depending on the brain region and treatment regimen. Moreover, the activity of the antioxidant enzymes, namely, superoxide dismutase (SOD) and catalase (CAT) was found to be increased and decreased, respectively, in the brain of OUA-administered rats. Li and VPA modulated SOD and CAT activities in OUA-subjected rats in both experimental models. Our results support the notion that Li and VPA exert antioxidant-like properties in the brain of rats submitted to animal model of mania induced by ouabain.

Animal model of mania induced by ouabain: Evidence of oxidative stress in submitochondrial particles of the rat brain

The intracerebroventricular (ICV) administration of ouabain (a Na(+)/K(+)-ATPase inhibitor) in rats has been suggested to mimic some symptoms of human bipolar mania. Clinical studies have shown that bipolar disorder may be related to mitochondrial dysfunction. Herein, we investigated the behavioral and biochemical effects induced by the ICV administration of ouabain in rats. To achieve this aim, the effects of ouabain injection immediately after and 7 days following a single ICV administration (at concentrations of 10(-2) and 10(-3)M) on locomotion was measured using the open-field test. Additionally, thiobarbituric acid reactive substances (TBARSs) and superoxide production were measured in submitochondrial particles of the prefrontal cortex, hippocampus, striatum and amygdala. Our findings demonstrated that ouabain at 10(-2) and 10(-3)M induced hyperlocomotion in rats, and this response remained up to 7 days following a single ICV injection. In addition, we observed that the persistent increase in the rat spontaneous locomotion is associated with increased TBARS levels and superoxide generation in submitochondrial particles in the prefrontal cortex, striatum and amygdala. In conclusion, ouabain-induced mania-like behavior may provide a useful animal model to test the hypothesis of the involvement of oxidative stress in bipolar disorder.

Neuropeptide S produces hyperlocomotion and prevents oxidative stress damage in the mouse brain: a comparative study with amphetamine and diazepam.

Neuropeptide S (NPS) is a recently discovered peptide which induces hyperlocomotion, anxiolysis and wakefulness. This study aimed to compare behavioral and biochemical effects of NPS with amphetamine (AMPH), and diazepam (DZP). To this aim, the effects of NPS (0.01, 0.1 and 1 nmol, ICV), AMPH (2 mg/kg, IP) and DZP (1 mg/kg, IP) on locomotion and oxidative stress parameters were assessed in mouse brain structures. The administration of NPS and AMPH, but not DZP, increased locomotion compared to control. Biochemical analyses revealed that AMPH increased carbonylated proteins in striatum, but did not alter lipid peroxidation. DZP increased lipid peroxidation in the cortex and cerebellum, and increased protein carbonyl formation in the striatum. In contrast, NPS reduced carbonylated protein in the cerebellum and striatum, and also lipid peroxidation in the cortex. Additionally, the treatment with AMPH increased superoxide dismutase (SOD) activity in the striatum, while it did not affect catalase (CAT) activity. DZP did not alter SOD and CAT activity. NPS inhibited the increase of SOD activity in the cortex and cerebellum, but little influenced CAT activity. Altogether, this is the first evidence of a putative role of NPS in oxidative stress and brain injury.

Omega-3 prevents behavior response and brain oxidative damage in the ketamine model of schizophrenia.

Supplementation with omega-3 has been identified as an adjunctive alternative for the treatment of psychiatric disorders, in order to minimize symptoms. Considering the lack of understanding concerning the pathophysiology of schizophrenia, the present study hypothesized that omega 3 prevents the onset of symptoms similar to schizophrenia in young Wistar rats submitted to ketamine treatment. Moreover, the role of oxidative stress in this model was assessed. Omega-3 (0.8g/kg) or vehicle was given by orogastric gavage once daily. Both treatments were performed during 21days, starting at the 30th day of life in young rats. After 14days of treatment with omega-3 or vehicle, a concomitant treatment with saline or ketamine (25mg/kg ip daily) was started and maintained until the last day of the experiment. We evaluated the pre-pulse inhibition of the startle reflex, activity of antioxidant systems and damage to proteins and lipids. Our results demonstrate that supplementation of omega-3 prevented: decreased inhibition of startle reflex, damage to lipids in the hippocampus and striatum and damage to proteins in the prefrontal cortex. Furthermore, these changes are associated with decreased GPx in brain tissues evaluated. Together, our results suggest the prophylactic role of omega-3 against the outcome of symptoms associated with schizophrenia.

The role of microglia activation in the development of sepsis-induced long-term cognitive impairment

Oxidative stress and inflammation is likely to be a major step in the development of sepsis-associated encephalopathy (SAE) and long-term cognitive impairment. To date, it is not known whether brain inflammation and oxidative damage are a direct consequence of systemic inflammation or whether these events are driven by brain resident cells, such as microglia. Therefore, the aim of this study is to evaluate the effect of minocycline on behavioral and neuroinflammatory parameters in rats submitted to sepsis. Male Wistar rats were subjected to sepsis by cecal ligation and puncture (CLP). The animals were divided into sham-operated (Sham+control), sham-operated plus minocycline (sham+MIN), CLP (CLP+control) and CLP plus minocycline (CLP+MIN) (100 μg/kg, administered as a single intracerebroventricular (ICV) injection). Some animals were killed 24h after surgery to assess the breakdown of the blood brain barrier, cytokine levels, oxidative damage to lipids (TBARS) and proteins in the hippocampus. Some animals were allowed to recover for 10 days when step-down inhibitory avoidance and open-field tasks were performed. Treatment with minocycline prevented an increase in markers of oxidative damage and inflammation in the hippocampus after sepsis. This was associated with an improvement in long-term cognitive performance. In conclusion, we demonstrated that the inhibition of the microglia by an ICV injection of minocycline was able to decrease acute brain oxidative damage and inflammation as well as long-term cognitive impairment in sepsis survivors.

Effect of N-acetylcysteine and/or deferoxamine on oxidative stress and hyperactivity in an animal model of mania.

Studies have consistently reported the participation of free radicals in Bipolar Disorder. Administration of d-amphetamine (d-AMPH) is a relevant animal model of mania and it increases oxidative stress in rat brain. Evidences indicate that the antioxidants N-acetylcysteine (NAC) and Deferoxamine (DFX) exert protective effects in the brain. The present study was designed to evaluate the effects of NAC, DFX or their combination on AMPH-induced hyperactivity. The protein oxidation levels were analyzed in prefrontal cortex and hippocampus. In the first animal model (reversal treatment), adult male Wistar rats received saline or d-AMPH for 14 days, and from the 8th to the 14th day, they were treated with saline, NAC, DFX, or NAC plus DFX. In the second animal model (prevention treatment), rats were pretreated with saline or antioxidant regime, and from the 8th to the 14th day, they also received saline or d-AMPH. In the prefrontal cortex, the protein carbonyls were not affected by the treatment with antioxidants alone but it was increased by treatment with NAC plus DFX. At the same model, NAC plus DFX reversed the protein damage in the hippocampus, but NAC alone increased this damage. In the prevention treatment, it was observed that the protein damage in the prefrontal cortex was prevented by DFX or NAC plus DFX. In the hippocampus, the pretreatment with all antioxidant regime prevented protein damage induced by d-AMPH. At both treatments (reversal or prevention) the antioxidants did not present any effect against d-AMPH-induced hyperactivity. In conclusion, NAC or DFX and the combination of NAC plus DFX reverse and protect against d-AMPH-induced oxidative protein damage. Using these protocols we could not observe affects on locomotion, however this effect varies depending on the brain region and the treatment regime.

Synergist effects of n-acetylcysteine and deferoxamine treatment on behavioral and oxidative parameters induced by chronic mild stress in rats

A growing body of evidence has pointed to a relationship between oxidative stress and depression. Thus, the present study was aimed at evaluating the effects of the antioxidants n-acetylcysteine (NAC), deferoxamine (DFX) or their combination on sweet food consumption and oxidative stress parameters in rats submitted to 40days of exposure to chronic mild stress (CMS). Our results showed that in stressed rats treated with saline, there was a decrease in sweet food intake and treatment with NAC or NAC in combination with DFX reversed this effect. Treatment with NAC and DFX decreased the oxidative damage, which include superoxide and TBARS production in submitochondrial particles, and also thiobarbituric acid reactive substances (TBARS) levels and carbonyl proteins in the prefrontal cortex, amygdala and hippocampus. Treatment with NAC and DFX also increased the activity of the antioxidant enzymes, superoxide dismutase and catalase in the same brain areas. Even so, a combined treatment with NAC and DFX produced a stronger increase of antioxidant activities in the prefrontal cortex, amygdala and hippocampus. The results described here indicate that co-administration may induce a more pronounced antidepressant activity than each treatment alone. In conclusion, these results suggests that treatment with NAC or DFX alone or in combination on oxidative stress parameters could have positive effects against neuronal damage caused by oxidative stress in major depressive disorders.

Evaluation of behavioral and neurochemical changes induced by ketamine in rats: Implications as an animal model of mania

Bipolar disorder (BD) is a chronic, prevalent, and highly debilitating psychiatric illness characterized by recurrent manic and depressive episodes. Mood stabilizing agents such as lithium and valproate are two primary drugs used to treat BD. To develop a novel animal model of mania (hallmark of BD), it is important to assess the therapeutic and prophylactic effect of these mood stabilizers on the new candidate target animal model. The present work investigates the therapeutic and prophylactic value of lithium and valproate in a novel preclinical animal model of mania, induced by ketamine. In the prevention protocol, wistar rats were pretreated with lithium (47.5 mg/kg, i.p., twice a day), valproate (200 mg/kg, i.p., twice a day), or saline (i.p., twice a day) for 14 days. Between days 8 and 14, the rats were treated with ketamine (25 mg/kg, i.p.) or saline. In the reversal protocol, rats first received ketamine (25 mg/kg, i.p.) or saline. After, the administration of lithium, valproate, or saline was carried out for seven days. Our results indicated that lithium and valproate reversed and prevented ketamine-induced hyperlocomotion. Moreover, lithium and valproate reversed (prefrontal cortex, hippocampus, and striatum) and prevented (prefrontal cortex, hippocampus, striatum, and amygdala) the increase of the TBARS level induced by ketamine. The protein carbonyl formation, induced by ketamine, was reversed by lithium and valproate in the prefrontal cortex, hippocampus, and striatum, and prevented only in the amygdala. These findings support the notion that the administration of ketamine might be a promising pharmacological animal model of mania, which could play a role in the pathophysiology of BD.

Tianeptine exerts neuroprotective effects in the brain tissue of rats exposed to the chronic stress model

Animal models of chronic stress represent valuable tools by which to investigate the behavioral, endocrine and neurobiological changes underlying stress-related psychopathologies, such as major depression, and the efficacy of antidepressant therapies. The present study was aimed at investigating the neurochemical effects of the antidepressant tianeptine in rats exposed to the chronic stress model. To this aim, rats were subjected to 40days of chronic unpredictable stressful stimuli, after which the animals received saline or tianeptine (15mg/kg) once a day for 7days. Additionally, IL-6, IL-1, TNF-α levels and oxidative stress parameters were assessed in the prefrontal cortex (PFC), hippocampus (HPC), amygdala (AMY) and nucleus accumbens (NAc) in all of the experimental groups studied. The results indicated that chronic mild stress and tianeptine did not exercise any effects on cytokines in all of the structures studied; in the PFC and AMY thiobarbituric acid reactive substances (TBARS) levels were decreased in control rats treated with tianeptine in the HPC; superoxide dismutase (SOD) activity was found to have decreased in stressed rats treated with saline in the PFC, HPC, AMY and NAc, and tianeptine reversed this effect; catalase (CAT) activity was found to have decreased in the PFC, HPC and NAc of stressed rats treated with saline, but was shown to have increased in stressed rats treated with tianeptine, and tianeptine also reversed the decreases in CAT activity in stressed rats treated with saline, suggesting that tianeptine exerted antioxidant activity. In conclusion, the present findings open new vistas on the pharmacological activity of tianeptine, in particular, concerning its ability to attenuate oxidative stress.