Behavioral and neurobiological changes in a novel mouse model of schizophrenia induced by the combination of cuprizone and MK-801

Tannic acid coated nanosuspension for oral delivery of chrysin intended for anti-schizophrenic effect in mice

Chrysin is a flavonoid drug with numerous therapeutic activities. It suffers from low intestinal absorption owing to its hydrophobicity. Therefore, the aim of this study is to exploit the efficient technique of nanosuspension (NSP) to formulate chrysin-NSP coated with tannic acid (TA) to improve the solubility and anti-schizophrenic activity of chrysin. A 23 full factorial design was constructed where the independent factors were type of polymer, surfactant concentration (0.5 or 1 %) and the aqueous phase volume (5 or 15 mL), while the dependent responses were the particle size (PS) of the obtained formulation as well as the % chrysin dissolved after 2 h (Q2h). The optimum formulation (NSP-4) composed of 1 % PEG 400 and 1 % Cremophor RH40 in 15 mL aqueous phase. It achieved a PS and Q2h values of 108.00 nm and 38.77 %, respectively. NSP-4 was then coated with TA (TA-coated NSP-4) for further enhancement of chrysin solubility. TA-coated NSP-4 revealed PS and zeta potential values of 150 ± 14 nm and -32.54 ± 2.45 mV, respectively. After 6 h, chrysin dissolved % were 53.97 and 80.22 for uncoated NSP-4 and TA-coated NSP-4, respectively, compared with only 9.47 for free chrysin. The developed formulations and free chrysin were assessed regarding their effect on schizophrenia induced in mice by cuprizone (CPZ). Treatment with the developed formulations and free chrysin ameliorated demyelination and behavioral deficit induced by CPZ via elevating MBP and PI3K/PKC activities as well as reducing GFAP expression levels. The developed formulations and free chrysin inhibited Galactin-3 and TGF-β expressions and stimulated GST antioxidant enzyme. Furthermore, they maintained the balances in glutamatergic and dopaminergic neurotransmission via modulation on neuregulin-1 and alleviated nuclear pyknosis and degeneration in the neurons. The order of activity was: TA-coated NSP-4 > NSP-4 > free chrysin.

Correlation between desynchrony of hippocampal neural activity and hyperlocomotion in the model mice of schizophrenia and therapeutic effects of aripiprazole

AIMS

The hippocampus has been reported to be morphologically and neurochemically altered in schizophrenia (SZ). Hyperlocomotion is a characteristic SZ-associated behavioral phenotype, which is associated with dysregulated dopamine system function induced by hippocampal hyperactivity. However, the neural mechanism of hippocampus underlying hyperlocomotion remains largely unclear.

METHODS

Mouse pups were injected with N-methyl-D-aspartate receptor antagonist (MK-801) or vehicle twice daily on postnatal days (PND) 7-11. In the adulthood phase, one cohort of mice underwent electrode implantation in field CA1 of the hippocampus for the recording local field potentials and spike activity. A separate cohort of mice underwent surgery to allow for calcium imaging of the hippocampus while monitoring the locomotion. Lastly, the effects of atypical antipsychotic (aripiprazole, ARI) were evaluated on hippocampal neural activity.

RESULTS

We found that the hippocampal theta oscillations were enhanced in MK-801-treated mice, but the correlation coefficient between the hippocampal spiking activity and theta oscillation was reduced. Consistently, although the rate and amplitude of calcium transients of hippocampal neurons were increased, their synchrony and correlation to locomotion speed were disrupted. ARI ameliorated perturbations produced by the postnatal MK-801 treatment.

CONCLUSIONS

These results suggest that the disruption of neural coordination may underly the neuropathological mechanism for hyperlocomotion of SZ.

Reactive Matrices for MALDI-MS of Cholesterol

Cholesterol is a critical molecule whose dysregulation in certain brain regions is related to multiple neurological disorders. It is of pathological importance to map the distribution of cholesterol in brain. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been widely used in the molecular imaging of metabolites at a high spatial resolution. However, it is challenging to analyze cholesterol by MALDI-MS due to its difficulty in ionization. Herein, we present for the first time a type of reactive matrix for MALDI-MS of cholesterol. Methylpyridinium carboxaldehydes react with cholesterol and other hydroxyl-containing sterols, which greatly enhanced both desorption and ionization and improved the limits of detection to the low μg/mL range. Compared with previous methods, our reactive matrix requires only one step of chemical derivatization and avoids time-consuming enzymatic reaction, which simplified the sample pretreatment. The reactive matrix was successfully used in mapping the distribution of cholesterol in brain tissue sections using MALDI-MS imaging. In summary, this work has provided a sensitive and simple method for the MALDI-MS analysis of cholesterol, has proposed a novel solution to visualize the distribution of sterol metabolites, and has great potential for applications in neurological and pathological studies.

Evaluating Gene Expression and Methylation Profiles of TCF4, MBP, and EGR1 in Peripheral Blood of Drug-Free Patients with Schizophrenia: Correlations with Psychopathology, Intelligence, and Cognitive Impairment

Discovery and validation of new, reliable diagnostic and predictive biomarkers for schizophrenia (SCZ) are an ongoing effort. Here, we assessed the mRNA expression and DNA methylation of the TCF4, MBP, and EGR1 genes in the blood of patients with SCZ and evaluated their relationships to psychopathology and cognitive impairments. Quantitative real-time PCR and quantitative methylation-specific PCR methods were used to assess the expression level and promoter DNA methylation status of these genes in 70 drug-free SCZ patients and 72 healthy controls. The correlation of molecular changes with psychopathology and cognitive performance of participants was evaluated. We observed downregulation of TCF4 and upregulation of MBP mRNA levels in SCZ cases, relative to controls in our study. DNA methylation status at the promoter region of TCF4 demonstrated an altered pattern in SCZ as well. Additionally, TCF4 mRNA levels were inversely correlated with PANSS and Stroop total errors and positively correlated with WAIS total score and working memory, consistent with previous studies by our group. In contrast, MBP mRNA level was significantly positively correlated with PANSS and Stroop total errors and inversely correlated with WAIS total score and working memory. These epigenetic and expression signatures can help to assemble a peripheral biomarker-based diagnostic panel for SCZ.

Inhibition of neuronal Kv7 channels ameliorates MK-801-induced cognitive dysfunction in mice via up-regulating NAMPT expression

PURPOSE

Abnormal energy metabolism affects cognitive function in schizophrenia. Nicotinamide phosphoribosyltransferase (NAMPT), as the rate-limiting enzyme of nicotinamide adenine dinucleotide (NAD+), is involved in energy metabolism by regulating the synthesis of NAD+. This study aims to clarify whether inhibition of Kv7 channels improves cognitive impairment by up-regulating NAMPT expression to increase the level of NAD+.

METHODS

The dominant negative pore mutation of KCNQ2 in transgenic mice was achieved by mutating residual 279-Gly to Ser (rQ2-G279S). A cognitive deficit model was established by injecting MK-801 into C57BL/6J mice. Y-maze and prepulse inhibition (PPI) tests were performed to evaluate cognitive ability. Gene and protein expression of NAMPT in the mouse hippocampus, cortex, and PC-12 cells were measured by qRT-PCR and Western blot. The level of NAD+ was measured by a WST-8 assay.

RESULTS

The Y-maze and PPI results showed that genetic or pharmacological inhibition of Kv7 channels by XE991 enhanced cognitive function in mice. Furthermore, inhibition of Kv7 channels increased the gene and protein expression of NAMPT and the level of NAD+ in the hippocampus and cortex of the above animal model. Similarly, XE991 treatment increased NAMPT expression and NAD+ levels in PC-12 cells. NAMPT inhibitor FK866 and Kv7 channel opener retigabine reversed the effects of XE991 in vivo and in vitro. In addition, XE991 increased pAMPK protein expression in PC-12 cells, while AMPK inhibitor Compound C counteracted the effect of XE991 on increasing NAMPT expression and NAD+ levels.

CONCLUSIONS

Suppression of Kv7 channel function improved spatial working memory and PPI impairment. This result may be achieved by activating AMPK to up-regulate NAMPT expression and thus increase NAD+ levels.

Huperzine-A Improved Animal Behavior in Cuprizone-Induced Mouse Model by Alleviating Demyelination and Neuroinflammation

Huperzine A (HupA) is a natural acetylcholinesterase inhibitor (AChEI) with the advantages of high efficiency, selectivity as well as reversibility and can exhibit significant therapeutic effects against certain neurodegenerative diseases. It is also beneficial in reducing the neurological impairment and neuroinflammation of experimental autoimmune encephalomyelitis (EAE), a classic model for multiple sclerosis (MS). However, whether HupA can directly regulate oligodendrocyte differentiation and maturation and promote remyelination has not been investigated previously. In this study, we have analyzed the potential protective effects of HupA on the demylination model of MS induced by cuprizone (CPZ). It was found that HupA significantly attenuated anxiety-like behavior, as well as augmented motor and cognitive functions in CPZ mice. It also decreased demyelination and axonal injury in CPZ mice. Moreover, in CPZ mice, HupA increased mRNA levels of the various anti-inflammatory cytokines (Arg1, CD206) while reducing the levels of different pro-inflammatory cytokines (iNOS, IL-1β, IL-18, CD16, and TNF-α). Mecamylamine, a nicotinic acetylcholinergic receptor antagonist, could effectively reverse the effects of HupA. Therefore, we concluded that HupA primarily exerts its therapeutic effects on multiple sclerosis through alleviating demyelination and neuroinflammation.

Sex Differences in the Behavioural Aspects of the Cuprizone-Induced Demyelination Model in Mice

Multiple sclerosis is an autoimmune disease characterised by demyelination in the central nervous system. The cuprizone-induced demyelination model is often used in mice to test novel treatments for multiple sclerosis. However, despite significant demyelination, behavioural deficits may be subtle or have mixed results depending on the paradigm used. Furthermore, the sex differences within the model are not well understood. In the current study, we have sought to understand the behavioural deficits associated with the cuprizone-induced demyelination model in both male and female C57BL/6J mice. Using Black gold II stain, we found that cuprizone administration over 6 weeks caused significant demyelination in the corpus callosum that was consistent across both sexes. Cuprizone administration caused increased mechanical sensitivity when measured using an electronic von Frey aesthesiometer, with no sex differences observed. However, cuprizone administration decreased motor coordination, with more severe deficits seen in males in the horizontal bar and passive wire hang tests. In contrast, female mice showed more severe deficits in the motor skill sequence test. Cuprizone administration caused more anxiety-like behaviours in males compared to females in the elevated zero maze. Therefore, this study provides a better understanding of the sex differences involved in the behavioural aspects of cuprizone-induced demyelination, which could allow for a better translation of results from the laboratory to the clinic.

DHF-7 Ameliorates Behavioral Disorders and White Matter Lesions by Regulating BDNF and Fyn in a Mouse Model of Schizophrenia Induced by Cuprizone and MK-801

BACKGROUND

Schizophrenia is a psychiatric disorder including multiple clinical symptoms such as severe psychosis and cognitive dysfunction. DHF-7 is a novel dihydroflavanone derivative that was designed and synthesized to treat schizophrenia. This study aimed to investigate the effects and mechanisms of DHF-7 in a mouse model of schizophrenia induced by a combination of cuprizone and MK-801.

METHODS

After intragastric administration of DHF-7 for 7 weeks, open field, Y-maze, and novel object recognition tests were performed to detect behavioral changes in the mouse model. White matter lesions and myelin loss were determined using transmission electron microscopy and oil red O staining. Western blotting and immunohistochemistry were used to detect the expression of the related proteins.

RESULTS

The results showed that DHF-7 treatment significantly improved cognitive impairment and positive symptoms in the model mice. Moreover, DHF-7 alleviated white matter lesions and demyelination and promoted the differentiation and maturation of oligodendrocytes for remyelination in the corpus callosum of model mice. The mechanistic study showed that DHF-7 increased the expression of brain-derived neurotrophic factor and phosphorylated Fyn, thus activating the tyrosine kinase receptor B (Trk B)/Fyn/N-methyl-D-aspartate receptor subunit 2 B (NMDAR2B) and Raf/mitogen-activated protein kinase (MEK)/ extracellular signal-related kinase (ERK) signaling pathways.

CONCLUSIONS

Our results provide an experimental basis for the development of DHF-7 as a novel therapeutic agent for schizophrenia.

Biochanin A Improves Memory Decline and Brain Pathology in Cuprizone-Induced Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system characterized by the demyelination of nerves, neural degeneration, and axonal loss. Cognitive impairment, including memory decline, is a significant feature in MS affecting up to 70% of patients. Thereby, it substantially impacts patients’ quality of life. Biochanin A (BCA) is an o-methylated isoflavone with a wide variety of pharmacological activities, including antioxidant, anti-inflammatory, and neuroprotective activities. Thus, this study aimed to investigate the possible protective effects of BCA on memory decline in the cuprizone (CPZ) model of MS. Thirty Swiss albino male mice (SWR/J) were randomly divided into three groups (n = 10): control (normal chow + i.p. 1:9 mixture of DMSO and PBS), CPZ (0.2% w/w of CPZ mixed into chow + i.p. 1:9 mixture of DMSO and PBS), and CPZ + BCA (0.2% w/w of CPZ mixed into chow + i.p. 40 mg/kg of BCA). At the last week of the study (week 5), a series of behavioral tasks were performed. A grip strength test was performed to assess muscle weakness while Y-maze, novel object recognition task (NORT), and novel arm discrimination task (NADT) were performed to assess memory. Additionally, histological examination of the hippocampus and the prefrontal cortex (PFC) were conducted. BCA administration caused a significant increase in the grip strength compared with the CPZ group. Additionally, BCA significantly improved the mice’s spatial memory in the Y-maze and recognition memory in the NORT and the NADT compared with the CPZ group. Moreover, BCA mitigated neuronal damage in the PFC and the hippocampus after five weeks of administration. In conclusion, our data demonstrates the possible protective effect of BCA against memory deterioration in mice fed with CPZ for five weeks.

CBD Effects on Motor Profile and Neurobiological Indices Related to Glutamatergic Function Induced by Repeated Ketamine Pre-Administration

Clinical evidence and experimental studies have shown the psychotomimetic properties induced by ketamine. Moreover, acute or chronic ketamine (KET) administration has been widely used for modeling schizophrenia-like symptomatology and pathophysiology. Several studies have reported the antipsychotic potential of cannabidiol (CBD), while there is limited information on the cannabidiol effect on KET-induced schizophrenia-like impairments. Therefore, the goal of the present study was to evaluate neuroplastic changes induced by repeated KET administration, which is used as an experimental model of schizophrenia—with a behavioral focus on positive-like symptomatology– and to assess the modulatory role of CBD treatment. The present findings have shown a robust increase in motor activity in KET-treated rats, following a 10-day period of chronic administration at the sub-anesthetic dose of 30 mg/kg (i.p), that was reversed to normal by subsequent chronic CBD treatment. Concerning the expression of glutamate receptors, the current findings have shown region-dependent KET-induced constitutional alterations in NMDA and AMPA receptors that were modified by subsequent CBD treatment. Additionally, repeated KET administration increased ERK1/2 phosphorylation state in all regions examined, apart from the ventral hippocampus that was modulated by subsequent CBD treatment. The present results show, for the first time, a stimulated motor output coupled with a specific glutamatergic-related status and ERK1/2 activation following chronic KET administration that were attenuated by CBD treatment, in a region-dependent manner. These findings provide novel information concerning the antipsychotic potential of CBD using a specific design of chronic KET administration, thus contributing to experimental approaches that mirror the symptomatology and pathophysiology of schizophrenia.