Aripiprazole, an atypical antipsychotic drug, improves maturation and complexity of neuroblast dendrites in the mouse dentate gyrus via increasing superoxide dismutases

Schizophrenia Synaptic Pathology and Antipsychotic Treatment in the Framework of Oxidative and Mitochondrial Dysfunction: Translational Highlights for the Clinics and Treatment

Schizophrenia is a worldwide mental illness characterized by alterations at dopaminergic and glutamatergic synapses resulting in global dysconnectivity within and between brain networks. Impairments in inflammatory processes, mitochondrial functions, energy expenditure, and oxidative stress have been extensively associated with schizophrenia pathophysiology. Antipsychotics, the mainstay of schizophrenia pharmacological treatment and all sharing the common feature of dopamine D2 receptor occupancy, may affect antioxidant pathways as well as mitochondrial protein levels and gene expression. Here, we systematically reviewed the available evidence on antioxidants' mechanisms in antipsychotic action and the impact of first- and second-generation compounds on mitochondrial functions and oxidative stress. We further focused on clinical trials addressing the efficacy and tolerability of antioxidants as an augmentation strategy of antipsychotic treatment. EMBASE, Scopus, and Medline/PubMed databases were interrogated. The selection process was conducted in respect of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Several mitochondrial proteins involved in cell viability, energy metabolism, and regulation of oxidative systems were reported to be significantly modified by antipsychotic treatment with differences between first- and second-generation drugs. Finally, antioxidants may affect cognitive and psychotic symptoms in patients with schizophrenia, and although the evidence is only preliminary, the results indicate that further studies are warranted.

Lower circulating neuron-specific enolase concentrations in adults and adolescents with severe mental illness

BACKGROUND

Both neurodegenerative and neurodevelopmental abnormalities have been suggested to be part of the etiopathology of severe mental illness (SMI). Neuron-specific enolase (NSE), mainly located in the neuronal cytoplasm, may indicate the process as it is upregulated after neuronal injury while a switch from non-neuronal enolase to NSE occurs during neuronal maturation.

METHODS

We included 1132 adult patients with SMI [schizophrenia (SZ) or bipolar spectrum disorders], 903 adult healthy controls (HC), 32 adolescent patients with SMI and 67 adolescent HC. Plasma NSE concentrations were measured by enzyme immunoassay. For 842 adults and 85 adolescents, we used total grey matter volume (TGMV) based on T1-weighted magnetic resonance images processed in FreeSurfer v6.0. We explored NSE case-control differences in adults and adolescents separately. To investigate whether putative case-control differences in NSE were TGMV-dependent we controlled for TGMV.

RESULTS

We found significantly lower NSE concentrations in both adult (p < 0.001) and adolescent patients with SMI (p = 0.007) compared to HC. The results remained significant after controlling for TGMV. Among adults, both patients with SZ spectrum (p < 0.001) and bipolar spectrum disorders (p = 0.005) had lower NSE than HC. In both patient subgroups, lower NSE levels were associated with increased symptom severity. Among adults (p < 0.001) and adolescents (p = 0.040), females had lower NSE concentrations than males.

CONCLUSION

We found lower NSE concentrations in adult and adolescent patients with SMI compared to HC. The results suggest the lack of progressive neuronal injury, and may reflect abnormal neuronal maturation. This provides further support of a neurodevelopmental rather than a neurodegenerative mechanism in SMI.

Fe3O4 Nanozymes Improve Neuroblast Differentiation and Blood-Brain Barrier Integrity of the Hippocampal Dentate Gyrus in D-Galactose-Induced Aged Mice

Aging is a process associated with blood-brain barrier (BBB) damage and the reduction in neurogenesis, and is the greatest known risk factor for neurodegenerative disorders. However, the effects of Fe₃O₄ nanozymes on neurogenesis have rarely been studied. This study examined the effects of Fe₃O₄ nanozymes on neuronal differentiation in the dentate gyrus (DG) and BBB integrity of D-galactose-induced aged mice. Long-term treatment with Fe₃O₄ nanozymes (10 μg/mL diluted in ddH₂O daily) markedly increased the doublecortin (DCX) immunoreactivity and decreased BBB injury induced by D-galactose treatment. In addition, the decreases in the levels of antioxidant proteins including superoxide dismutase (SOD) and catalase as well as autophagy-related proteins such as Becin-1, LC3II/I, and Atg7 induced by D-galactose treatment were significantly ameliorated by Fe₃O₄ nanozymes in the DG of the mouse hippocampus. Furthermore, Fe₃O₄ nanozyme treatment showed an inhibitory effect against apoptosis in the hippocampus. In conclusion, Fe₃O₄ nanozymes can relieve neuroblast damage and promote neuroblast differentiation in the hippocampal DG by regulating oxidative stress, apoptosis, and autophagy.

Antioxidant Properties of Second-Generation Antipsychotics: Focus on Microglia

Recent studies suggest a primary role of oxidative stress in an early phase of the pathogenesis of schizophrenia and a strong neurobiological link has been found between dopaminergic system dysfunction, microglia overactivation, and oxidative stress. Different risk factors for schizophrenia increase oxidative stress phenomena raising the risk of developing psychosis. Oxidative stress induced by first-generation antipsychotics such as haloperidol significantly contributes to the development of extrapyramidal side effects. Haloperidol also exerts neurotoxic effects by decreasing antioxidant enzyme levels then worsening pro-oxidant events. Opposite to haloperidol, second-generation antipsychotics (or atypical antipsychotics) such as risperidone, clozapine, and olanzapine exert a strong antioxidant activity in experimental models of schizophrenia by rescuing the antioxidant system, with an increase in superoxide dismutase and glutathione (GSH) serum levels. Second-generation antipsychotics also improve the antioxidant status and reduce lipid peroxidation in schizophrenic patients. Interestingly, second-generation antipsychotics, such as risperidone, paliperidone, and in particular clozapine, reduce oxidative stress induced by microglia overactivation, decreasing the production of microglia-derived free radicals, finally protecting neurons against microglia-induced oxidative stress. Further, long-term clinical studies are needed to better understand the link between oxidative stress and the clinical response to antipsychotic drugs and the therapeutic potential of antioxidants to increase the response to antipsychotics.

Transcriptional Effects of Psychoactive Drugs on Genes Involved in Neurogenesis

Although neurogenesis is affected in several psychiatric diseases, the effects and mechanisms of action of psychoactive drugs on neurogenesis remain unknown and/or controversial. This study aims to evaluate the effects of psychoactive drugs on the expression of genes involved in neurogenesis. Neuronal-like cells (NT2-N) were treated with amisulpride (10 µM), aripiprazole (0.1 µM), clozapine (10 µM), lamotrigine (50 µM), lithium (2.5 mM), quetiapine (50 µM), risperidone (0.1 µM), or valproate (0.5 mM) for 24 h. Genome wide mRNA expression was quantified and analysed using gene set enrichment analysis, with the neurogenesis gene set retrieved from the Gene Ontology database and the Mammalian Adult Neurogenesis Gene Ontology (MANGO) database. Transcription factors that are more likely to regulate these genes were investigated to better understand the biological processes driving neurogenesis. Targeted metabolomics were performed using gas chromatography-mass spectrometry. Six of the eight drugs decreased the expression of genes involved in neurogenesis in both databases. This suggests that acute treatment with these psychoactive drugs negatively regulates the expression of genes involved in neurogenesis in vitro. SOX2 and three of its target genes (CCND1, BMP4, and DKK1) were also decreased after treatment with quetiapine. This can, at least in part, explain the mechanisms by which these drugs decrease neurogenesis at a transcriptional level in vitro. These results were supported by the finding of increased metabolite markers of mature neurons following treatment with most of the drugs tested, suggesting increased proportions of mature relative to immature neurons consistent with reduced neurogenesis.

Chronic administration of quetiapine stimulates dorsal hippocampal proliferation and immature neurons of male rats, but does not reverse psychosocial stress-induced hyponeophagic behavior

Quetiapine, an atypical antipsychotic, has been used for the treatment of several neuropsychiatric disorders. However, the underlying mechanism of the broad therapeutic range of quetiapine remains unknown. We previously reported that several aversive conditions affect dorsal/ventral hippocampal neurogenesis differentially. This study was aimed to elucidate the positive effects of chronic treatment with quetiapine on regional differences in hippocampal proliferation and immature neurons and behavioral changes under psychosocial stress using the Resident-Intruder paradigm. Twenty-three male Sprague-Dawley rats were intraperitoneally administered a vehicle or quetiapine (10 mg/kg) once daily for 28 days. Two weeks after starting the injections, animals were exposed to intermittent social defeat (four times over two weeks). The behavioral effects of stress and quetiapine were evaluated by the Novelty-Suppressed Feeding (NSF) test. The stereological quantification of hippocampal neurogenesis was estimated using immunostaining with Ki-67 and doublecortin (DCX). Chronic quetiapine treatment stimulated the Ki-67- and DCX-positive cells in the dorsal hippocampus, but not in the ventral subregion. The stress-induced changes in neurogenesis and hyponeophagic behavior were not reversed by repeated administration of quetiapine. Future study with additional behavioral tests is needed to elucidate the functional significance of the quetiapine-induced increase in dorsal hippocampal neurogenesis.

Intermittent fasting increases the expressions of SODs and catalase in granule and polymorphic cells and enhances neuroblast dendrite complexity and maturation in the adult gerbil dentate gyrus

Intermittent fasting (ImF) is known to reduce oxidative stress and affects adult neurogenesis in the hippocampal dentate gyrus. However, it is unknown how ImF affects endogenous antioxidants expressions, cell proliferation, and neuroblast differentiation and their dendrite remodeling over 3 months in the dentate gyrus of adult gerbils. The present study subjected 6‑month old male gerbils to a normal diet or alternate‑day ImF for 1, 2 and 3 months. Changes in body weight were not significantly different between gerbils fed a normal diet and on ImF. The present study also investigated the effects of ImF on antioxidant enzymes [superoxide dismutase (SOD)‑1, SOD2 and catalase] using immunohistochemistry, and endogenous cell proliferation, neuroblast differentiation and neuroblast dendrite complexity by using Ki67 (a cell proliferation marker) and doublecortin (neuroblast differentiation marker) immunohistochemistry in the dentate gyrus. SOD1, SOD2 and CAT immunoreactivities were shown in cells in the granule cell and polymorphic layers. SOD1, SOD2 and catalase immunoreactivity in the cells peaked at 2, 1 and 1 month, respectively, following ImF. Cell proliferation was ~250, 129 and 186% of the control, at 1, 2 and 3 months of ImF, respectively. Neuroblast differentiation was ~41, 32 and 12% of the control, at 1, 2 and 3 months of ImF, respectively, indicating that dendrites of neuroblasts were more arborized and developed at 3 months of ImF. Taken together, these results indicate that ImF for 3 months improves endogenous SOD1, SOD2 and catalase expressions and enhances cell proliferation, and neuroblast dendrites complexity and maturation in the adult gerbil dentate gyrus.

Melatonin Improves Cognitive Deficits via Restoration of Cholinergic Dysfunction in a Mouse Model of Scopolamine-Induced Amnesia

Melatonin is known to improve cognitive deficits, and its functions have been studied in various disease models, including Alzheimer's disease. In this study, we investigated effects of melatonin on cognition and the cholinergic system of the septum and hippocampus in a mouse model of scopolamine-induced amnesia. Scopolamine (1 mg/kg) and melatonin (10 mg/kg) were administered intraperitoneally to mice for 2 and 4 weeks. The Morris water maze and passive avoidance tests revealed that both treatments of scopolamine significantly impaired spatial learning and memory; however, 2- and 4-week melatonin treatments significantly improved spatial learning and memory. In addition, scopolamine treatments significantly decreased protein levels and immunoreactivities of choline acetyltransferase (ChAT), high-affinity choline transporter (CHT), vesicular acetylcholine transporter (VAChT), and muscarinic acetylcholine receptor M1 (M1R) in the septum and hippocampus. However, the treatments with melatonin resulted in increased ChAT-, CHT-, VAChT-, and M1R-immunoreactivities and their protein levels in the septum and hippocampus. Our results demonstrate that melatonin treatment is effective in improving the cognitive deficits via restoration of the cholinergic system in the septum and hippocampus of a mouse model of scopolamine-induced amnesia.

Aripiprazole prevents renal ischemia/reperfusion injury in rats, probably through nitric oxide involvement

Renal ischemia/reperfusion (I/R) injury is strongly related to morbidity and mortality. Oxidative stress, inflammation, and apoptosis play key roles in renal dysfunction following renal I/R. Aripiprazole is an atypical antipsychotic which used for the treatment of schizophrenia and bipolar disorder. Recent studies have reported aripiprazole as displaying certain anti-inflammatory effects. Regarding the underlying mechanisms of renal ischemia-reperfusion, therefore, nephroprotective effects might be predicted to be seen with aripiprazole. I/R injury was induced by bilateral clamping of the renal pedicles (45min) followed by reperfusion (24h). The mechanism of aripiprazole-mediated nephroprotection was explored by a combined use of aripiprazole and L-NAME (non-selective nitric oxide synthase inhibitor). Animals were given aripiprazole (2.5, 5, 10 and 20mg/kg) intraperitoneally, 30min before ischemia. L-NAME was administered before the aripiprazole injection. Serum creatinine and blood urea nitrogen were assessed after 24h of reperfusion. Serum levels of malondialdehyde (MDA), TNF-α and IL-1β were measured for rats treated with aripiprazole. The extent of necrosis was measured by the stereology method. Ischemia/reperfusion caused significant renal dysfunction and marked renal injury. Aripiprazole reduced creatinine and blood urea nitrogen. Serum levels of MDA, IL-1β and TNF-α were significantly lower in the aripiprazole group. Aripiprazole treatment also decreased the volume of kidney necrosis. The administration of L-NAME reversed the renoprotective effect of aripiprazole on BUN and creatinine, but enhanced the anti-necrotic effect of aripiprazole. The results show that a single dose of aripiprazole significantly improved renal function following ischemia/reperfusion injury - probably through the involvement of nitric oxide.

Antidepressant Effects of Aripiprazole Augmentation for Cilostazol-Treated Mice Exposed to Chronic Mild Stress after Ischemic Stroke

The aim of this study was to determine the effects and underlying mechanism of aripiprazole (APZ) augmentation for cilostazol (CLS)-treated post-ischemic stroke mice that were exposed to chronic mild stress (CMS). Compared to treatment with either APZ or CLS alone, the combined treatment resulted in a greater reduction in depressive behaviors, including anhedonia, despair-like behaviors, and memory impairments. This treatment also significantly reduced atrophic changes in the striatum, cortex, and midbrain of CMS-treated ischemic mice, and inhibited neuronal cell apoptosis, particularly in the striatum and the dentate gyrus of the hippocampus. Greater proliferation of neuronal progenitor cells was also observed in the ipsilateral striatum of the mice receiving combined treatment compared to mice receiving either drug alone. Phosphorylation of the cyclic adenosine monophosphate response element binding protein (CREB) was increased in the striatum, hippocampus, and midbrain of mice receiving combined treatment compared to treatment with either drug alone, particularly in the neurons of the striatum and hippocampus, and dopaminergic neurons of the midbrain. Our results suggest that APZ may augment the antidepressant effects of CLS via co-regulation of the CREB signaling pathway, resulting in the synergistic enhancement of their neuroprotective effects.

Tanshinone I Enhances Neurogenesis in the Mouse Hippocampal Dentate Gyrus via Increasing Wnt-3, Phosphorylated Glycogen Synthase Kinase-3β and β-Catenin Immunoreactivities

Tanshinone I (TsI), a lipophilic diterpene extracted from Danshan (Radix Salvia miltiorrhizae), exerts neuroprotection in cerebrovascular diseases including transient ischemic attack. In this study, we examined effects of TsI on cell proliferation and neuronal differentiation in the subgranular zone (SGZ) of the mouse dentate gyrus (DG) using Ki-67, BrdU and doublecortin (DCX) immunohistochemistry. Mice were treated with 1 and 2 mg/kg TsI for 28 days. In the 1 mg/kg TsI-treated-group, distribution patterns of BrdU, Ki-67 and DCX positive ((+)) cells in the SGZ were similar to those in the vehicle-treated-group. However, in the 2 mg/kg TsI-treated-group, double labeled BrdU(+)/NeuN(+) cells, which are mature neurons, as well as Ki-67(+), DCX(+) and BrdU(+) cells were significantly increased compared with those in the vehicle-treated-group. On the other hand, immunoreactivities and protein levels of Wnt-3, β-catenin and serine-9-glycogen synthase kinase-3β (p-GSK-3β), which are related with morphogenesis, were significantly increased in the granule cell layer of the DG only in the 2 mg/kg TsI-treated-group. Therefore, these findings indicate that TsI can promote neurogenesis in the mouse DG and that the neurogenesis is related with increases of Wnt-3, p-GSK-3β and β-catenin immunoreactivities.

The effect of second-generation antipsychotics on hippocampal volume in first episode of psychosis: longitudinal study

BACKGROUND

Current neuroscience literature has related treatment with aripiprazole to improved memory performance and subcellular changes in the hippocampus.

AIMS

To explore the volumetric changes in hippocampal grey matter in people with a first episode of psychosis (FEP) treated with second-generation antipsychotics.

METHOD

Baseline and 1-year follow-up magnetic resonance images were obtained. Hippocampal volumes were estimated by using FreeSurfer and MAGeT-Brain. Subgroups included: aripiprazole (n=13), olanzapine (n=12), risperidone/paliperidone (n=24), refused-antipsychotics (n=13) and controls (n=44).

RESULTS

Aripiprazole subgroup displayed significant increases in bilateral hippocampal volume compared with all other subgroups (FreeSurfer: all P's<0.012; MAGeT-Brain: all P's<0.040).

CONCLUSIONS

Aripiprazole is a first-line, second-generation treatment option that may provide an added benefit of pro-hippocampal growth. The biological underpinnings of these changes should be the focus of future investigations and may be key towards achieving a better clinical outcome for more individuals.

DECLARATION OF INTEREST

M.L. received financial assistance/compensation for research and educational events from Janssen-Ortho, Eli Lilly, Roche and Otsuka/Lundbeck Alliance. A.K.M. received financial assistance/compensation for research and educational activities from Pfizer, Janssen-Ortho, AstraZeneca and Bristol-Myers Squibb. R.J. received consultancy honorariums from Pfizer and Janssen-Ortho.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

Vanillin and 4-hydroxybenzyl alcohol promotes cell proliferation and neuroblast differentiation in the dentate gyrus of mice via the increase of brain-derived neurotrophic factor and tropomyosin-related kinase B

4-Hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxybenzyl alcohol (4-HBA) are well-known phenolic compounds, which possess various therapeutic properties and are widely found in a variety of plants. In the present study, the effects of vanillin and 4-HBA were first investigated on cell proliferation, as well as neuronal differentiation and integration of granule cells in the dentate gyrus (DG) of adolescent mice using Ki-67, doublecortin (DCX) immunohistochemistry and 5-bromo-2′-de-oxyuridine (BrdU)/feminizing Locus on X 3 (NeuN) double immunofluorescence. In both the vanillin and 4-HBA groups, the number of Ki-67⁺ cells, DCX⁺ neuroblasts and BrdU⁺/NeuN⁺ neurons were significantly increased in the subgranular zone of the DG, as compared with the vehicle group. In addition, the levels of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB), a BDNF receptor, were significantly increased in the DG in the vanillin and 4-HBA groups compared with the vehicle group. These results indicated that vanillin and 4-HBA enhanced cell proliferation, neuroblast differentiation and integration of granule cells in the DG of adolescent mice. These neurogenic effects of vanillin and 4-HBA may be closely associated with increases in BDNF and TrkB.

Ethanol extract of Oenanthe javanica increases cell proliferation and neuroblast differentiation in the adolescent rat dentate gyrus

Oenanthe javanica is an aquatic perennial herb that belongs to the Oenanthe genus in Apiaceae family, and it displays well-known medicinal properties such as protective effects against glutamate-induced neurotoxicity. However, few studies regarding effects of Oenanthe javanica on neurogenesis in the brain have been reported. In this study, we examined the effects of a normal diet and a diet containing ethanol extract of Oenanthe javanica on cell proliferation and neuroblast differentiation in the subgranular zone of the hippocampal dentate gyrus of adolescent rats using Ki-67 (an endogenous marker for cell proliferation) and doublecortin (a marker for neuroblast). Our results showed that Oenanthe javanica extract significantly increased the number of Ki-67-immunoreactive cells and doublecortin-immunoreactive neuroblasts in the subgranular zone of the dentate gyrus in the adolescent rats. In addition, the immunoreactivity of brain-derived neurotrophic factor was significantly increased in the dentate gyrus of the Oenanthe javanica extract-treated group compared with the control group. However, we did not find that vascular endothelial growth factor expression was increased in the Oenanthe javanica extract-treated group compared with the control group. These results indicate that Oenanthe javanica extract improves cell proliferation and neuroblast differentiation by increasing brain-derived neurotrophic factor immunoreactivity in the rat dentate gyrus.

Long-term administration of scopolamine interferes with nerve cell proliferation, differentiation and migration in adult mouse hippocampal dentate gyrus, but it does not induce cell death

Long-term administration of scopolamine, a muscarinic receptor antagonist, can inhibit the survival of newly generated cells, but its effect on the proliferation, differentiation and migration of nerve cells in the adult mouse hippocampal dentate gyrus remain poorly understood. In this study, we used immunohistochemistry and western blot methods to weekly detect the biological behaviors of nerve cells in the hippocampal dentate gyrus of adult mice that received intraperitoneal administration of scopolamine for 4 weeks. Expression of neuronal nuclear antigen (NeuN; a neuronal marker) and Fluoro-Jade B (a marker for the localization of neuronal degeneration) was also detected. After scopolamine treatment, mouse hippocampal neurons did not die, and Ki-67 (a marker for proliferating cells)-immunoreactive cells were reduced in number and reached the lowest level at 4 weeks. Doublecortin (DCX; a marker for newly generated neurons)-immunoreactive cells were gradually shortened in length and reduced in number with time. After scopolamine treatment for 4 weeks, nearly all of the 5-bromo-2'-deoxyuridine (BrdU)-labeled newly generated cells were located in the subgranular zone of the dentate gyrus, but they did not migrate into the granule cell layer. Few mature BrdU/NeuN double-labeled cells were seen in the subgranular zone of the dentate gyrus. These findings suggest that long-term administration of scopolamine interferes with the proliferation, differentiation and migration of nerve cells in the adult mouse hippocampal dentate gyrus, but it does not induce cell death.