Effects of tamoxifen on tricarboxylic acid cycle enzymes in the brain of rats submitted to an animal model of mania induced by amphetamine

Effect of blueberry extract on energetic metabolism, levels of brain-derived neurotrophic factor, and Ca2+-ATPase activity in the hippocampus and cerebral cortex of rats submitted to ketamine-induced mania-like behavior

Bipolar disorder (BD) is a psychiatric disease characterized by mood episodes. Blueberry is rich in bioactive compounds and shows excellent therapeutic potential against chronic diseases. The aim of this study was to evaluate the effects of blueberry extract on behavior, energetic metabolism, Ca²⁺-ATPase activity, and levels of brain-derived neurotrophic factor (BDNF) in the cerebral cortex and hippocampus of rats submitted to an animal model of mania induced by ketamine. Vehicle, lithium (45 mg/kg, twice a day), or blueberry extract (200 mg/kg), was orally administered to Wistar rats for 14 days. Ketamine (25 mg/kg) or vehicle was administered intraperitoneally, once a day, between the 8th and 14th day. On the 15th day, animals received ketamine or vehicle and were subjected to the open field test. Our results demonstrated that the administration of lithium and blueberry extract prevented ketamine-induced hyperlocomotion (P < 0.01). Blueberry extract attenuated the ketamine-induced reduction in the activity of complex I in the cerebral cortex (P < 0.05). Additionally, the administration of ketamine reduced the activities of complexes I and IV (P < 0.05) and citrate synthase in the hippocampus (P < 0.01). However, blueberry extract attenuated the inhibition in the activity of complex IV (P < 0.01). Furthermore, ketamine reduced the Ca²⁺-ATPase activity in the cerebral cortex and hippocampus (P < 0.05); however, blueberry extract prevented the change in the cerebral cortex (P < 0.05). There were no significant alterations in the levels of BDNF (P > 0.05). In conclusion, this suggested that the blueberry extract can serve as a potential therapeutic strategy for studies searching for novel therapeutic alternatives for BD patients.

Concepts of Neuroinflammation and Their Relationship With Impaired Mitochondrial Functions in Bipolar Disorder

Bipolar disorder (BD) is a chronic psychiatric disease, characterized by frequent behavioral episodes of depression and mania, and neurologically by dysregulated neurotransmission, neuroplasticity, growth factor signaling, and metabolism, as well as oxidative stress, and neuronal apoptosis, contributing to chronic neuroinflammation. These abnormalities result from complex interactions between multiple susceptibility genes and environmental factors such as stress. The neurocellular abnormalities of BD can result in gross morphological changes, such as reduced prefrontal and hippocampal volume, and circuit reorganization resulting in cognitive and emotional deficits. The term "neuroprogression" is used to denote the progressive changes from early to late stages, as BD severity and loss of treatment response correlate with the number of past episodes. In addition to circuit and cellular abnormalities, BD is associated with dysfunctional mitochondria, leading to severe metabolic disruption in high energy-demanding neurons and glia. Indeed, mitochondrial dysfunction involving electron transport chain (ETC) disruption is considered the primary cause of chronic oxidative stress in BD. The ensuing damage to membrane lipids, proteins, and DNA further perpetuates oxidative stress and neuroinflammation, creating a perpetuating pathogenic cycle. A deeper understanding of BD pathophysiology and identification of associated biomarkers of neuroinflammation are needed to facilitate early diagnosis and treatment of this debilitating disorder.

Tamoxifen has an anti-manic effect but not protect the brain against oxidative stress in an animal model of mania induced by ouabain

Studies have suggested the involvement of oxidative stress in the physiopathology of bipolar disorder. Preclinical data have shown that PKC inhibitors may act as mood-stabilizing agents and protect the brain in animal models of mania. The present study aimed to evaluate the effects of Lithium (Li) or tamoxifen (TMX) on behavioral changes and oxidative stress parameters in an animal model of mania induced by ouabain (OUA). Wistar rats received a single intracerebroventricular (ICV) injection of OUA or artificial cerebrospinal fluid (ACSF). From the day following ICV injection, the rats were treated for seven days with intraperitoneal injections of saline, Li or TMX twice a day. On the 7th day after OUA injection, locomotor activity was measured using the open-field test, and the oxidative stress parameters were evaluated in the hippocampus and frontal cortex of rats. The results showed that OUA induced hyperactivity in rats, which is considered a manic-like behavior. Also, OUA increased lipid peroxidation and oxidative damage to proteins, as well as causing alterations to antioxidant enzymes in the frontal cortex and hippocampus of rats. The Li or TMX treatment reversed the manic-like behavior induced by OUA. Besides, Li, but not TMX, reversed the oxidative damage caused by OUA. These results suggest that the manic-like effects induced by OUA and the antimanic effects of TMX seem not to be related to the oxidative stress.

Significance of protein kinase C in the neuropsychotoxicity induced by methamphetamine-like psychostimulants

The abuse of methamphetamine (MA), an amphetamine (AMPH)-type stimulant, has been demonstrated to be associated with various neuropsychotoxicity, including memory impairment, psychiatric morbidity, and dopaminergic toxicity. Compelling evidence from preclinical studies has indicated that protein kinase C (PKC), a large family of serine/threonine protein kinases, plays an important role in MA-induced neuropsychotoxicity. PKC-mediated N-terminal phosphorylation of dopamine transporter has been identified as one of the prerequisites for MA-induced synaptic dopamine release. Consistently, it has been shown that PKC is involved in MA (or AMPH)-induced memory impairment and mania-like behaviors as well as MA drug dependence. Direct or indirect regulation of factors related to neuronal plasticity seemed to be critical for these actions of PKC. In addition, PKC-mediated mitochondrial dysfunction, oxidative stress or impaired antioxidant defense system has been suggested to play a role in psychiatric and cognitive disturbance induced by MA (or AMPH). In MA-induced dopaminergic toxicity, particularly PKCδ has been shown to trigger oxidative stress, mitochondrial dysfunction, pro-apoptotic changes, and neuroinflammation. Importantly, PKCδ may be a key mediator in the positive feedback loop composed of these detrimental events to potentiate MA-induced dopaminergic toxicity. This review outlines the role of PKC and its individual isozymes in MA-induced neuropsychotoxicity. Better understanding on the molecular mechanism of PKCs might provide a great insight for the development of potential therapeutic or preventive candidates for MA (or AMPH)-associated neuropsychotoxicity.

HDAC1 and HDAC3 underlie dynamic H3K9 acetylation during embryonic neurogenesis and in schizophrenia-like animals

Although histone acetylation is one of the most widely studied epigenetic modifications, there is still a lack of information regarding how the acetylome is regulated during brain development and pathophysiological processes. We demonstrate that the embryonic brain (E15) is characterized by an increase in H3K9 acetylation as well as decreases in the levels of HDAC1 and HDAC3. Moreover, experimental induction of H3K9 hyperacetylation led to the overexpression of NCAM in the embryonic cortex and depletion of Sox2 in the subventricular ependyma, which mimicked the differentiation processes. Inducing differentiation in HDAC1-deficient mouse ESCs resulted in early H3K9 deacetylation, Sox2 downregulation, and enhanced astrogliogenesis, whereas neuro-differentiation was almost suppressed. Neuro-differentiation of (wt) ESCs was characterized by H3K9 hyperacetylation that was associated with HDAC1 and HDAC3 depletion. Conversely, the hippocampi of schizophrenia-like animals showed H3K9 deacetylation that was regulated by an increase in both HDAC1 and HDAC3. The hippocampi of schizophrenia-like brains that were treated with the cannabinoid receptor-1 inverse antagonist AM251 expressed H3K9ac at the level observed in normal brains. Together, the results indicate that co-regulation of H3K9ac by HDAC1 and HDAC3 is important to both embryonic brain development and neuro-differentiation as well as the pathophysiology of a schizophrenia-like phenotype.

Quercetin reduces manic-like behavior and brain oxidative stress induced by paradoxical sleep deprivation in mice

Quercetin is a known antioxidant and protein kinase C (PKC) inhibitor. Previous studies have shown that mania involves oxidative stress and an increase in PKC activity. We hypothesized that quercetin affects manic symptoms. In the present study, manic-like behavior (hyperlocomotion) and oxidative stress were induced by 24h paradoxical sleep deprivation (PSD) in male Swiss mice. Both 10 and 40mg/kg quercetin prevented PSD-induced hyperlocomotion. Quercetin reversed the PSD-induced decrease in glutathione (GSH) levels in the prefrontal cortex (PFC) and striatum. Quercetin also reversed the PSD-induced increase in lipid peroxidation (LPO) in the PFC, hippocampus, and striatum. Pearson's correlation analysis revealed a negative correlation between locomotor activity and GSH in the PFC in sleep-deprived mice and a positive correlation between locomotor activity and LPO in the PFC and striatum in sleep-deprived mice. These results suggest that quercetin exerts an antimanic-like effect at doses that do not impair spontaneous locomotor activity, and the antioxidant action of quercetin might contribute to its antimanic-like effects.

Tamoxifen and amphetamine abuse: Are there therapeutic possibilities?

Although best known as a selective estrogen receptor modulator (SERM), tamoxifen is a drug with a wide range of activities. Tamoxifen has demonstrated some efficacy has a therapeutic for bipolar mania and is believed to exert these effects through inhibition of protein kinase C (PKC). As the symptoms of amphetamine treatment in rodents are believed to mimic the symptoms of a manic episode, many of the preclinical studies for this indication have demonstrated that tamoxifen inhibits amphetamine action. The amphetamine-induced increase in extracellular dopamine which gives rise to the 'manic' effects is due to interaction of amphetamine with the dopamine transporter. We and others have demonstrated that PKC reduces amphetamine-induced reverse transport through the dopamine transporter. In this review, we will outline the actions of tamoxifen as a SERM and further detail another known action of tamoxifen-inhibition of PKC. We will summarize the literature showing how tamoxifen affects amphetamine action. Finally, we will present our hypothesis that tamoxifen, or an analog, could be used therapeutically to reduce amphetamine abuse in addition to treating mania.

Modeling mania in preclinical settings: A comprehensive review

The current pathophysiological understanding of mechanisms leading to onset and progression of bipolar manic episodes remains limited. At the same time, available animal models for mania have limited face, construct, and predictive validities. Additionally, these models fail to encompass recent pathophysiological frameworks of bipolar disorder (BD), e.g. neuroprogression. Therefore, there is a need to search for novel preclinical models for mania that could comprehensively address these limitations. Herein we review the history, validity, and caveats of currently available animal models for mania. We also review new genetic models for mania, namely knockout mice for genes involved in neurotransmission, synapse formation, and intracellular signaling pathways. Furthermore, we review recent trends in preclinical models for mania that may aid in the comprehension of mechanisms underlying the neuroprogressive and recurring nature of BD. In conclusion, the validity of animal models for mania remains limited. Nevertheless, novel (e.g. genetic) animal models as well as adaptation of existing paradigms hold promise.

Regulation of leukocyte tricarboxylic acid cycle in drug-naïve Bipolar Disorder

Several lines of evidence suggest a role for mitochondrial dysfunction in the pathophysiology of bipolar disorder (BD). The tricarboxylic acid cycle (TCA cycle) is fundamental for mitochondrial energy production and produces substrates used in oxidative phosphorylation by the mitochondrial electron transport chain. The activity of the key TCA cycle enzymes citrate synthase, malate dehydrogenase, and succinate dehydrogenase has never been evaluated in BD. In the present study, these enzymes were assayed from leukocytes of drug-naïve BD patients in a major depressive episode (n=18) and compared to 24 age-matched healthy controls. Drug-naïve BD patients did not show differences in activities of citrate synthase (p=0.79), malate dehydrogenase (p=0.17), and succinate dehydrogenase (p=0.35) compared with healthy controls. No correlation between any TCA cycle enzyme activity and severity of depressive symptoms was observed. Overall, these data suggest that the activities of the TCA cycle enzymes are not altered in major depressive episodes of recent-onset BD, which may support the concept of illness staging and neuroprogression in BD.