Antipsychotic-induced oxidative stress in rat brain

Neurobehavioral and genotoxic parameters of antipsychotic agent aripiprazole in mice

AIM

Aripiprazole is an antipsychotic agent to treat schizophrenia, which acts through dopamine D(2) partial agonism, serotonin 5-HT(1A) partial agonism and 5-HT(2A) antagonism. This study was designed to evaluate the neurobehavioral effects and genotoxic/mutagenic activities of the agent, as well as its effects on lipoperoxidation.

METHODS

Open field and inhibitory avoidance tasks were used. Thirty min before performing the behavioral tasks, adult male CF-1 mice were administered aripiprazole (1, 3 or 10 mg/kg, ip) once for the acute treatment, or the same doses for 5 d for the subchronic treatment. Genotoxic effects were assessed using comet assay in the blood and brain tissues. Mutagenic effects were evaluated using bone marrow micronucleus test. Lipoperoxidation was assessed with thiobarbituric acid reactive substances (TBARS).

RESULTS

Acute and subchronic treatments significantly decreased the number of crossing and rearing in the open field task. Acute treatment significantly increased the step-down latency for both the short- and long-term memory in the inhibitory avoidance task. Subchronic treatments with aripiprazole (3 and 10 mg/kg) caused significant DNA strain-break damage in peripheral blood but not in the brain. Mutagenic effect was not detected in the acute and subchronic treatments. Nor TBARS levels in the liver were affected.

CONCLUSION

Aripiprazole improved memory, but could impair motor activities in mice. The drug increased DNA damage in blood, but did not show mutagenic effects, suggesting that it might affect long-term genomic stability.

Sulforaphane protects SK-N-SH cells against antipsychotic-induced oxidative stress

Adverse reactions to antipsychotic drugs (APs) have been attributed to oxidative stress. Sulforaphane (SF) is a potent antioxidant that protects against dopaminergic cell death. We examined the protective properties of SF against AP-induced oxidative stress in dopaminergic neuroblastoma cells. Human neuroblastoma SK-N-SH cells were treated with SF (0.5-5 μM), and 24 h later, haloperidol, risperidone or paliperidone (100 μM) was administered, either alone or in combination with dopamine (100 μM). To determine the antioxidant properties of SF, quinone oxidoreductase (NQO1) activity, glutathione S-transferase activity, and glutathione (GSH) levels were determined. Oxidative stress was measured by the increase in thiobarbituric acid reactive substances (TBARS) and in protein-bound quinones. Cell viability was also assessed. SF treatment increased GSH levels and induced NQO1 activity in SK-N-SH cells. Haloperidol was the only AP that increased TBARS when administered alone. When cells were cocultured with a drug in combination with dopamine, all three APs increased TBARS and protein-bound quinones and also induced neurotoxicity. In all the experimental conditions, 5 μM SF attenuated the accumulation of TBARS and protein-bound quinones and increased cell survival rates. Our results indicate that SF increases GSH levels and induces NQO1 activity and the removal of electrophilic quinones and radical oxygen species. Furthermore, SF could provide protective effects against AP-induced toxicity in dopaminergic cells.

Increased breath ethane levels in medicated patients with schizophrenia and bipolar disorder are unrelated to erythrocyte omega-3 fatty acid abundance

Oxidative stress has been reported to be elevated in mental illness. Preliminary evidence suggests this phenomenon can be assessed non-invasively by determining breath levels of the omega-3 polyunsaturated fatty acid (PUFA) oxidation product ethane. This study compares alkane levels in chronic, medicated, patients with schizophrenia or bipolar disorder with those in healthy controls. Both ethane and butane levels were significantly increased in patients with schizophrenia or bipolar disorder, although elevated butane levels were likely due to increased ambient gas concentrations. Ethane levels were not correlated with symptom severity or with erythrocyte omega-3 PUFA levels. Our results support the hypothesis that oxidative stress is elevated in patients with schizophrenia and bipolar disorder leading to increased breath ethane abundance. This does not appear to be caused by increased abundance of omega-3 PUFA, but rather is likely due to enhanced oxidative damage of these lipids. As such, breath hydrocarbon analysis may represent a simple, non-invasive means to monitor the metabolic processes occurring in these disorders.

Effects of aripiprazole and haloperidol on progression to schizophrenia-like behavioural abnormalities and apoptosis in rodents

Aripiprazole (APZ) is considered a first-line medication for treating first and multiple episodes of schizophrenia, but its effect on preventing the progressive pathophysiology of schizophrenia remains unclear. This study examined the hypothesis that APZ blocks enhanced glutamate release in the medial prefrontal cortex (mPFC) during psychotic episodes of schizophrenia, thereby preventing progression of the pathophysiology. We examined effects of APZ on methamphetamine (METH)-induced increases in glutamate levels in the mPFC, and on repeatedly administered METH-induced progression to schizophrenia-like behavioural abnormalities involving cross-sensitization to the N-methyl-d-aspartate (NMDA) receptor antagonist, MK-801, deficit of prepulse inhibition (PPI), and expression of TUNEL-positive cells. Additionally, we compared the preventive effects of APZ to those of a conventional antipsychotic: haloperidol (HPD). Results show that APZ (1.0 and 3.0 mg/kg) and HPD (0.1 mg/kg) each blocked METH (2.5 mg/kg)-induced increases in glutamate levels in the mPFC. Furthermore, APZ (3.0 mg/kg) and HPD (0.1 mg/kg), when co-administered repeatedly with METH, each prevented progression to schizophrenia-like behavioural and neuropathological abnormalities. Repeated co-administration of APZ (3.0 mg/kg) with saline did not induce apoptosis, although HPD (0.1 mg/kg) with saline did induce apoptosis. These results indicate that APZ and HPD prevented progressive pathophysiology, which is related to increased glutamate levels, and indicate that repeated administration of HPD, but not APZ, induced apoptosis under conditions without increased glutamate levels. These findings suggest the importance of using APZ and HPD in the appropriate stages of the glutamate-related pathophysiology of schizophrenia.

The genotoxic and oxidative damage potential of olanzapine in vitro

Olanzapine (OLZ) is an atypical antipsychotic drug and is commonly used for the treatment of schizophrenia and bipolar disorder (BD). However, recent reports indicated that this drug could exhibit cytotoxic effects on nervous and immune systems. To our knowledge, there is scarce data considering the genotoxic or oxidative damage potentials of OLZ on human lymphocyte culture system. Therefore, in this study, the genotoxic potential of OLZ (0 to 160 µM) have been evaluated in human whole blood cultures (WBCs) related to oxidative status. Sister-chromatid exchange (SCE) test was applied to estimate the DNA damage, and biochemical parameters (total antioxidant capacity [TAC] and total oxidative stress [TOS]) were examined to determine oxidative stress. Our results indicated that the tested antipsychotic drug did not induce SCEs in lymphocytes of treated cultures. However, the application of the highest OLZ concentration caused oxidative stress. It is concluded that the OLZ can be used safely, but it is necessary to consider the tissue damages that are likely to appear depending on the oxidative stress.

Effects of olanzapine, fluoxetine and olanzapine/fluoxetine on creatine kinase activity in rat brain

Recently, a fixed combination of the atypical antipsychotic olanzapine and the serotonin selective reuptake inhibitor (SSRI) fluoxetine has been approved in the US for the treatment of bipolar I depression. In this work, we evaluated the effect of acute and chronic administration of fluoxetine, olanzapine and the combination of fluoxetine/olanzapine on creatine kinase (CK) activity in the brain of rats. For acute treatment, adult male Wistar rats received one single injection of olanzapine (3 or 6 mg/kg) and/or fluoxetine (12.5 or 25mg/kg). For chronic treatment, adult male Wistar rats received daily injections of olanzapine (3 or 6 mg/kg) and/or fluoxetine (12.5 or 25mg/kg) for 28 days. In the present study we observed that acute administration of OLZ inhibited CK activity in cerebellum and prefrontal cortex. The acute administration of FLX inhibited creatine kinase in cerebellum, prefrontal cortex, hippocampus, striatum and cerebral cortex. In the chronic treatment, when the animals were killed 2h after the last injection a decrease in creatine kinase activity after FLX administration, alone or in combination with OLZ, in cerebellum, prefrontal cortex, hippocampus, striatum and cerebral cortex of rats occurred. However, when the animals were killed 24h after the last injection, we found no alterations in the enzyme. Although it is difficult to extrapolate our findings to the human condition, the inhibition of creatine kinase activity by these drugs may be associated to the occurrence of some side effects of OLZ and FLX.

Protective effect of cyclooxygenase (COX)-inhibitors against drug-induced catatonia and MPTP-induced striatal lesions in rats

The present study explored the involvement of cyclooxygenase (COX) in the pathophysiology of Parkinson's disease (PD). Further, the protective effect of COX-inhibitors against perphenazine-induced catatonia and 1-methyl-4-phenyl-1, 2, 3, 6-tertahydropyridine (MPTP)-induced striatal lesions in rats was evaluated. Administration of perphenazine (5 mg/kg., i.p.) produced severe catatonia (rigid behavior) in rats; the maximum score reached at 4 h (estimated as 100% AUC) and declined within 24 h. An intrastriatal injection of MPTP produced hypolocomotor activity in rats. Both perphenazine and MPTP produced oxidative stress as demonstrated by increased levels of lipid peroxides, nitrite and decreased antioxidant defense system in the whole brain and striatal region, in particular. Pretreatment with various COX-inhibitors viz. rofecoxib, celecoxib, nimesulide or naproxen offered protection against perphenazine-induced catatonia, the effect was more pronounced with rofecoxib. Rofecoxib and celecoxib (both selective COX-2 inhibitors) also reversed the perphenazine-induced oxidative stress. Further, prior treatment with rofecoxib (8 mg/kg, p.o.) reversed both the behavioral and biochemical changes induced by MPTP. These results suggest that COX-inhibitors particularly, rofecoxib offers protection against drug-induced catatonia and MPTP-induced striatal lesions possibly by modulating dopaminergic neurotransmission and/or oxidative stress.

Bipolar disorder and mechanisms of action of mood stabilizers

Bipolar disorder (BD) is a major medical and social burden, whose cause, pathophysiology and treatment are not agreed on. It is characterized by recurrent periods of mania and depression (Bipolar I) or of hypomania and depression (Bipolar II). Its inheritance is polygenic, with evidence of a neurotransmission imbalance and disease progression. Patients often take multiple agents concurrently, with incomplete therapeutic success, particularly with regard to depression. Suicide is common. Of the hypotheses regarding the action of mood stabilizers in BD, the "arachidonic acid (AA) cascade" hypothesis is presented in detail in this review. It is based on evidence that chronic administration of lithium, carbamazepine, sodium valproate, or lamotrigine to rats downregulated AA turnover in brain phospholipids, formation of prostaglandin E(2), and/or expression of AA cascade enzymes, including cytosolic phospholipase A(2), cyclooxygenase-2 and/or acyl-CoA synthetase. The changes were selective for AA, since brain docosahexaenoic or palmitic acid metabolism, when measured, was unaffected, and topiramate, ineffective in BD, did not modify the rat brain AA cascade. Downregulation of the cascade by the mood stabilizers corresponded to inhibition of AA neurotransmission via dopaminergic D(2)-like and glutamatergic NMDA receptors. Unlike the mood stabilizers, antidepressants that increase switching of bipolar depression to mania upregulated the rat brain AA cascade. These observations suggest that the brain AA cascade is a common target of mood stabilizers, and that bipolar symptoms, particularly mania, are associated with an upregulated cascade and excess AA signaling via D(2)-like and NMDA receptors. This review presents ways to test these suggestions.

Neurobiology of Schizophrenia Spectrum Disorders: The Role of Oxidative Stress

Mitochondrial dysfunction and oxidative stress are increasingly implicated in the pathophysiology of schizophrenia. The brain is the body’s highest energy consumer, and the glutathione system is the brain’s dominant free radical scavenger. In the current paper, we review the evidence of central and peripheral nervous system anomalies in the oxidative defences of individuals with schizophrenia, principally involving the glutathione system. This is reflected by evidence of the manifold consequences of oxidative stress that include lipid peroxidation, protein carboxylation, DNA damage and apoptosis – all potentially part of the process of neuroprogression in the disorder. Importantly, oxidative stress is amenable to intervention. We consider the clinical potential of some possible interventions that help reduce oxidative stress, via augmentation of the glutathione system, particularly N-acetyl cysteine. We argue that a better understanding of the mechanisms and pathways underlying oxidative stress will assist in developing the therapeutic potential of this area. Key words: Glutathione, Magnetic resonance spectroscopy, N-acetyl cysteine