Hispidulin attenuates the social withdrawal in isolated disrupted-in-schizophrenia-1 mutant and chronic phencyclidine-treated mice.

BACKGROUND AND PURPOSE: Hispidulin is a flavonoid isolated from Clerodendrum inerme that was found to inhibit intractable motor tics. Previously, we found that hispidulin attenuates hyperlocomotion and the disrupted prepulse inhibition induced by methamphetamine and N-methyl-d-aspartate (NMDA) receptor antagonists, two phenotypes of schizophrenia resembling positive symptoms. Hispidulin can inhibit COMT, a dopamine-metabolizing enzyme in the prefrontal cortex (PFC) that is important for social interaction. Here, we investigated whether hispidulin would affect social withdrawal, one of the negative symptoms of schizophrenia. EXPERIMENTAL APPROACH: We examined whether acute administration of hispidulin would attenuate social withdrawal in two mice models, juvenile isolated disrupted-in-schizophrenia-1 mutant (mutDISC1) mice and chronic phencyclidine (PCP)-treated naïve mice. KEY RESULTS: In chronic PCP-treated mice, hispidulin (10 mg·kg-1 , i.p.) attenuated social withdrawal similar to that observed with dopamine D1 receptor antagonist (SCH-23390, 0.02 mg·kg-1 , i.p.) and was mimicked by the selective COMT inhibitor, OR-486 (10 mg·kg-1 , i.p.). Hispidulin increased extracellular dopamine levels in the PFC of chronic PCP-treated mice. In isolated mutDISC1 mice, hispidulin also reversed social withdrawal. In both models, intra-PFC microinjection of a D1 agonist (SKF-81297: 10 nmol/mouse/bilateral) reversed the impairment of Ser897 phosphorylation at the GluN1 subunit of NMDA receptors, suggesting the association between GluN1 Ser897 -phosphorylation and D1 activation in the PFC exits in both models. CONCLUSIONS AND IMPLICATIONS: Hispidulin attenuated social withdrawal by activating D1 receptors indirectly through elevated dopamine levels in the PFC by COMT inhibition. This nature of hispidulin suggests that it a potential novel therapeutic candidate for the treatment of negative symptoms in schizophrenia.

Author Correction: Proteomic analysis of lymphoblastoid cell lines from schizophrenic patients.

The original Article required a few updates; one co-author name, which was given as Hiroki Kiumura, has been updated to Hiroki Kimura. Furthermore, supplementary information has been updated, and grant numbers have been added. These updates have been made to both the PDF and HTML versions of this Article.

Proteomic analysis of lymphoblastoid cell lines from schizophrenic patients.

Although a number of studies have identified several convincing candidate genes or molecules, the pathophysiology of schizophrenia (SCZ) has not been completely elucidated. Therapeutic optimization based on pathophysiology should be performed as early as possible to improve functional outcomes and prognosis; to detect useful biomarkers for SCZ, which reflect pathophysiology and can be utilized for timely diagnosis and effective therapy. To explore biomarkers for SCZ, we employed fluorescence two-dimensional differential gel electrophoresis (2D-DIGE) of lymphoblastoid cell lines (LCLs) (1st sample set: 30 SCZ and 30 CON). Differentially expressed proteins were sequenced by liquid chromatography tandem-mass spectrometry (LC-MS/MS) and identified proteins were confirmed by western blotting (WB) (1st and 2nd sample set: 60 SCZ and 60 CON). Multivariate logistic regression analysis was performed to identify an optimal combination of biomarkers to create a prediction model for SCZ. Twenty protein spots were differentially expressed between SCZ and CON in 2D-DIGE analysis and 22 unique proteins were identified by LC-MS/MS. Differential expression of eight of 22 proteins was confirmed by WB. Among the eight candidate proteins (HSPA4L, MX1, GLRX3, UROD, MAPRE1, TBCB, IGHM, and GART), we successfully constructed logistic regression models comprised of 4- and 6-markers with good discriminative ability between SCZ and CON. In both WB and gene expression analysis of LCL, MX1 showed reproducibly significant associations. Moreover, Mx1 and its related proinflamatory genes (Mx2, Il1b, and Tnf) were also up-regulated in poly I:C-treated mice. Differentially expressed proteins might be associated with molecular pathophysiology of SCZ, including dysregulation of immunological reactions and potentially provide diagnostic and prognostic biomarkers.

Adolescent stress leads to glutamatergic disturbance through dopaminergic abnormalities in the prefrontal cortex of genetically vulnerable mice.

BACKGROUND: Stress during the adolescent period influences postnatal maturation and behavioral patterns in adulthood. Adolescent stress-induced molecular and functional changes in neurons are the key clinical features of psychiatric disorders including schizophrenia. OBJECTIVE: In the present study, we exposed genetically vulnerable mice to isolation stress to examine the molecular changes in the glutamatergic system involving N-methyl-d-aspartate (NMDA) receptors via dopaminergic disturbance in the prefrontal cortex (PFc). RESULTS: We report that late adolescent stress in combination with Disrupted-in-Schizophrenia 1 (DISC1) genetic risk elicited alterations in glutamatergic neurons in the PFc, such as increased expression of glutamate transporters, decreased extracellular levels of glutamate, decreased concentration of d-serine, and impaired activation of NMDA-Ca2+/calmodulin kinase II signaling. These changes resulted in behavioral deficits in locomotor activity, forced swim, social interaction, and novelty preference tests. The glutamatergic alterations in the PFc were prevented if the animals were treated with an atypical antipsychotic drug clozapine and a dopamine D1 agonist SKF81297, which suggests that the activation of dopaminergic neurons is involved in the regulation of the glutamatergic system. CONCLUSION: Our results suggest that adolescent stress combined with dopaminergic abnormalities in the PFc of genetically vulnerable mice induces glutamatergic disturbances, which leads to behavioral deficits in the young adult stage.

The involvement of brain-derived neurotrophic factor in 3,4-methylenedioxymethamphetamine-induced place preference and behavioral sensitization.

3,4-Methylenedioxymethamphetamine (MDMA) is known to induce dependence and psychosis in humans. Brain-derived neurotrophic factor (BDNF) is involved in the synaptic plasticity and neurotrophy in midbrain dopaminergic neurons. This study aimed to investigate the role of BDNF in MDMA-induced dependence and psychosis. A single dose of MDMA (10mg/kg) induced BDNF mRNA expression in the prefrontal cortex, nucleus accumbens, and amygdala, but not in the striatum or the hippocampus. However, repeated MDMA administration for 7 days induced BDNF mRNA expression in the striatum and hippocampus. Both precursor and mature BDNF protein expression increased in the nucleus accumbens, mainly in the neurons. Additionally, rapidly increased extracellular serotonin levels and gradually and modestly increased extracellular dopamine levels were noted within the nucleus accumbens of mice after repeated MDMA administration. Dopamine receptor antagonists attenuated the effect of repeated MDMA administration on BDNF mRNA expression in the nucleus accumbens. To examine the role of endogenous BDNF in the behavioral and neurochemical effects of MDMA, we used mice with heterozygous deletions of the BDNF gene. MDMA-induced place preference, behavioral sensitization, and an increase in the levels of extracellular serotonin and dopamine within the nucleus accumbens, were attenuated in BDNF heterozygous knockout mice. These results suggest that BDNF is implicated in MDMA-induced dependence and psychosis by activating the midbrain serotonergic and dopaminergic neurons.

Dipeptidyl peptidase-IV inhibitory activity of dimeric dihydrochalcone glycosides from flowers of Helichrysum arenarium.

A methanol extract of everlasting flowers of Helichrysum arenarium L. Moench (Asteraceae) was found to inhibit the increase in blood glucose elevation in sucrose-loaded mice at 500 mg/kg p.o. The methanol extract also inhibited the enzymatic activity against dipeptidyl peptidase-IV (DPP-IV, IC50 = 41.2 µg/ml), but did not show intestinal α-glucosidase inhibitory activities. From the extract, three new dimeric dihydrochalcone glycosides, arenariumosides V-VII (2-4), were isolated, and the stereostructures were elucidated based on their spectroscopic properties and chemical evidence. Of the constituents, several flavonoid constituents, including 2-4, were isolated, and these isolated constituents were investigated for their DPP-IV inhibitory effects. Among them, chalconaringenin 2'-O-ß-D-glucopyranoside (16, IC50 = 23.1 µM) and aureusidin 6-O-ß-D-glucopyranoside (35, 24.3 µM) showed relatively strong inhibitory activities.

Blonanserin ameliorates phencyclidine-induced visual-recognition memory deficits: the complex mechanism of blonanserin action involving D3-5-HT2A and D1-NMDA receptors in the mPFC.

Blonanserin differs from currently used serotonin 5-HT2A/dopamine-D2 receptor antagonists in that it exhibits higher affinity for dopamine-D2/3 receptors than for serotonin 5-HT2A receptors. We investigated the involvement of dopamine-D3 receptors in the effects of blonanserin on cognitive impairment in an animal model of schizophrenia. We also sought to elucidate the molecular mechanism underlying this involvement. Blonanserin, as well as olanzapine, significantly ameliorated phencyclidine (PCP)-induced impairment of visual-recognition memory, as demonstrated by the novel-object recognition test (NORT) and increased extracellular dopamine levels in the medial prefrontal cortex (mPFC). With blonanserin, both of these effects were antagonized by DOI (a serotonin 5-HT2A receptor agonist) and 7-OH-DPAT (a dopamine-D3 receptor agonist), whereas the effects of olanzapine were antagonized by DOI but not by 7-OH-DPAT. The ameliorating effect was also antagonized by SCH23390 (a dopamine-D1 receptor antagonist) and H-89 (a protein kinase A (PKA) inhibitor). Blonanserin significantly remediated the decrease in phosphorylation levels of PKA at Thr(197) and of NR1 (an essential subunit of N-methyl-D-aspartate (NMDA) receptors) at Ser(897) by PKA in the mPFC after a NORT training session in the PCP-administered mice. There were no differences in the levels of NR1 phosphorylated at Ser(896) by PKC in any group. These results suggest that the ameliorating effect of blonanserin on PCP-induced cognitive impairment is associated with indirect functional stimulation of the dopamine-D1-PKA-NMDA receptor pathway following augmentation of dopaminergic neurotransmission due to inhibition of both dopamine-D3 and serotonin 5-HT2A receptors in the mPFC.

Decreased L-tryptophan concentration in distinctive brain regions of mice treated repeatedly with phencyclidine.

It has been reported that repeated phencyclidine (PCP) treatment induces schizophrenia-like behavior in mice. L-Tryptophan (Trp) concentrations in brain tissues of control (n = 8) and PCP-treated mice (10 mg/kg/day, s.c., 14 days, n = 10) were determined using high-performance liquid chromatography (HPLC) with fluorescence detection. The HPLC method involved pre-column fluorescence derivatization with (R)-(-)-4-(N,N-dimethylaminosulfonyl)-7-(3-isothiocyanatopyrrolidin-1-yl)-2,1,3-benzoxadiazole (DBD-PyNCS). Eight different parts of the brain, namely, the frontal cortex, nucleus accumbens, striatum, hippocampus, amygdala, thalamus, hypothalamus, and cerebellum, of both groups were investigated. A significant decrease in the L-Trp concentration in the nucleus accumbens (p = 0.024) and hippocampus (p = 0.027) was observed in PCP-treated mice, suggesting that alteration of the L-Trp metabolism might occur in these brain parts.

Adolescent stress-induced epigenetic control of dopaminergic neurons via glucocorticoids.

Environmental stressors during childhood and adolescence influence postnatal brain maturation and human behavioral patterns in adulthood. Accordingly, excess stressors result in adult-onset neuropsychiatric disorders. We describe an underlying mechanism in which glucocorticoids link adolescent stressors to epigenetic controls in neurons. In a mouse model of this phenomenon, a mild isolation stress affects the mesocortical projection of dopaminergic neurons in which DNA hypermethylation of the tyrosine hydroxylase gene is elicited, but only when combined with a relevant genetic risk for neuropsychiatric disorders. These molecular changes are associated with several neurochemical and behavioral deficits that occur in this mouse model, all of which are blocked by a glucocorticoid receptor antagonist. The biology and phenotypes of the mouse models resemble those of psychotic depression, a common and debilitating psychiatric disease.

Vulnerability in early life to changes in the rearing environment plays a crucial role in the aetiopathology of psychiatric disorders.

Adverse events early in life, including maternal separation and social isolation, profoundly affect brain development and adult behaviour and may contribute to the occurrence of psychiatric disorders such as schizophrenia and mood disorders in genetically predisposed individuals. The molecular mechanisms underlying these environmentally induced developmental adaptations are unclear and best evaluated in animal paradigms with translational salience. In this study, we examined the effects in mice of maternal separation and/or social isolation for 6 h/d between postnatal days 15 and 21 on performance during adulthood in the open-field, social interaction, elevated plus-maze, forced swimming, Y-maze, novel object recognition, conditioned fear-learning, prepulse inhibition, and locomotor activity tests, to investigate whether this animal model could show the phenotypes for schizophrenia and mood disorders. The stress of maternal separation and isolation led to adult behavioural deficits, activation of the hypothalamic-pituitary-adrenal axis, and decreases in the levels of norepinephrine and dopamine in the frontal cortex and metabolites of dopamine and serotonin in the amygdala, showing the involvement of endocrine and neuronal risk in behavioural deficits. The results suggest that the frontal cortex and amygdala undergo structural remodelling induced by the stress of maternal separation and isolation, which alters behavioural and physiological responses in adulthood, including anxiety, memory and other cognitive processes. Further, social isolation enhanced the behavioural dysfunctions induced by maternal separation. These findings indicate that maternal separation and social isolation early in life can lead to long-lasting abnormal behaviour and pathophysiological impairments including schizophrenia and mood disorders.