Liver X receptor β regulates the development of the dentate gyrus and autistic-like behavior in the mouse

Dentate Gyrus Morphogenesis is Regulated by an Autism Risk Gene Trio Function in Granule Cells

Autism Spectrum Disorders (ASDs) are reported as a group of neurodevelopmental disorders. The structural changes of brain regions including the hippocampus were widely reported in autistic patients and mouse models with dysfunction of ASD risk genes, but the underlying mechanisms are not fully understood. Here, we report that deletion of Trio, a high-susceptibility gene of ASDs, causes a postnatal dentate gyrus (DG) hypoplasia with a zigzagged suprapyramidal blade, and the Trio-deficient mice display autism-like behaviors. The impaired morphogenesis of DG is mainly caused by disturbing the postnatal distribution of postmitotic granule cells (GCs), which further results in a migration deficit of neural progenitors. Furthermore, we reveal that Trio plays different roles in various excitatory neural cells by spatial transcriptomic sequencing, especially the role of regulating the migration of postmitotic GCs. In summary, our findings provide evidence of cellular mechanisms that Trio is involved in postnatal DG morphogenesis.

Investigation of Liver X Receptor Gene Variants and Oxysterol Dysregulation in Autism Spectrum Disorder

The NR1H2 gene produces the Liver X Receptor Beta (LXRB) protein, which is crucial for brain cholesterol metabolism and neuronal development. However, its involvement in autism spectrum disorder (ASD) remains largely unexplored, aside from animal studies. This study is the first to explore the potential link between autism and rs2695121/rs17373080 single nucleotide polymorphisms (SNPs) in the regulatory regions of NR1H2, known for their association with neuropsychiatric functions. Additionally, we assessed levels of oxysterols (24-Hydroxycholesterol, 25-Hydroxycholesterol, 27-Hydroxycholesterol), crucial ligands of LXR, and lipid profiles. Our cohort comprised 107 children with ASD and 103 healthy children aged 2-18 years. Clinical assessment tools included the Childhood Autism Rating Scale, Autistic Behavior Checklist, and Repetitive Behavior Scale-Revised. Genotyping for SNPs was conducted using PCR-RFLP. Lipid profiles were analyzed with Beckman Coulter kits, while oxysterol levels were determined through liquid chromatography-tandem mass spectrometry. Significantly higher total cholesterol (p = 0.003), LDL (p = 0.008), and triglyceride (p < 0.001) levels were observed in the ASD group. 27-Hydroxycholesterol levels were markedly lower in the ASD group (p ≤ 0.001). ROC analysis indicated the potential of 27-Hydroxycholesterol to discriminate ASD diagnosis. The SNP genotype and allele frequencies were similar in both groups (p > 0.05). Our findings suggest that disturbances in oxysterol metabolism, previously linked to neurodegeneration, may constitute a risk factor for ASD and contribute to its heterogeneous phenotype.

LXR agonism for CNS diseases: promises and challenges

The unfavorable prognosis of many neurological conditions could be attributed to limited tissue regeneration in central nervous system (CNS) and overwhelming inflammation, while liver X receptor (LXR) may regulate both processes due to its pivotal role in cholesterol metabolism and inflammatory response, and thus receives increasing attentions from neuroscientists and clinicians. Here, we summarize the signal transduction of LXR pathway, discuss the therapeutic potentials of LXR agonists based on preclinical data using different disease models, and analyze the dilemma and possible resolutions for clinical translation to encourage further investigations of LXR related therapies in CNS disorders.

The gut metabolite indole-3-propionic acid activates ERK1 to restore social function and hippocampal inhibitory synaptic transmission in a 16p11.2 microdeletion mouse model

BACKGROUND

Microdeletion of the human chromosomal region 16p11.2 (16p11.2+ / - ) is a prevalent genetic factor associated with autism spectrum disorder (ASD) and other neurodevelopmental disorders. However its pathogenic mechanism remains unclear, and effective treatments for 16p11.2+ / -  syndrome are lacking. Emerging evidence suggests that the gut microbiota and its metabolites are inextricably linked to host behavior through the gut-brain axis and are therefore implicated in ASD development. Despite this, the functional roles of microbial metabolites in the context of 16p11.2+ / -  are yet to be elucidated. This study aims to investigate the therapeutic potential of indole-3-propionic acid (IPA), a gut microbiota metabolite, in addressing behavioral and neural deficits associated with 16p11.2+ / - , as well as the underlying molecular mechanisms.

RESULTS

Mice with the 16p11.2+ / -  showed dysbiosis of the gut microbiota and a significant decrease in IPA levels in feces and blood circulation. Further, these mice exhibited significant social and cognitive memory impairments, along with hyperactivation of hippocampal dentate gyrus neurons and reduced inhibitory synaptic transmission in this region. However, oral administration of IPA effectively mitigated the histological and electrophysiological alterations, thereby ameliorating the social and cognitive deficits of the mice. Remarkably, IPA treatment significantly increased the phosphorylation level of ERK1, a protein encoded by the Mapk3 gene in the 16p11.2 region, without affecting the transcription and translation of the Mapk3 gene.

CONCLUSIONS

Our study reveals that 16p11.2+ / -  leads to a decline in gut metabolite IPA levels; however, IPA supplementation notably reverses the behavioral and neural phenotypes of 16p11.2+ / -  mice. These findings provide new insights into the critical role of gut microbial metabolites in ASD pathogenesis and present a promising treatment strategy for social and cognitive memory deficit disorders, such as 16p11.2 microdeletion syndrome. Video Abstract.

Puerarin attenuates valproate-induced features of ASD in male mice via regulating Slc7a11-dependent ferroptosis

Autism spectrum disorder (ASD) is a complicated, neurodevelopmental disorder characterized by social deficits and stereotyped behaviors. Accumulating evidence suggests that ferroptosis is involved in the development of ASD, but the underlying mechanism remains elusive. Puerarin has an anti-ferroptosis function. Here, we found that the administration of puerarin from P12 to P15 ameliorated the autism-associated behaviors in the VPA-exposed male mouse model of autism by inhibiting ferroptosis in neural stem cells of the hippocampus. We highlight the role of ferroptosis in the hippocampus neurogenesis and confirm that puerarin treatment inhibited iron overload, lipid peroxidation accumulation, and mitochondrial dysfunction, as well as enhanced the expression of ferroptosis inhibitory proteins, including Nrf2, GPX4, Slc7a11, and FTH1 in the hippocampus of VPA mouse model of autism. In addition, we confirmed that inhibition of xCT/Slc7a11-mediated ferroptosis occurring in the hippocampus is closely related to puerarin-exerted therapeutic effects. In conclusion, our study suggests that puerarin targets core symptoms and hippocampal neurogenesis reduction through ferroptosis inhibition, which might be a potential drug for autism intervention.

Synchronized LFP rhythmicity in the social brain reflects the context of social encounters

Mammalian social behavior is highly context-sensitive. Yet, little is known about the mechanisms that modulate social behavior according to its context. Recent studies have revealed a network of mostly limbic brain regions which regulates social behavior. We hypothesize that coherent theta and gamma rhythms reflect the organization of this network into functional sub-networks in a context-dependent manner. To test this concept, we simultaneously record local field potential (LFP) from multiple social brain regions in adult male mice performing three social discrimination tasks. While LFP rhythmicity across all tasks is dominated by a global internal state, the pattern of theta coherence between the various regions reflect the behavioral task more than other variables. Moreover, Granger causality analysis implicate the ventral dentate gyrus as a main player in coordinating the context-specific rhythmic activity. Thus, our results suggest that the pattern of coordinated rhythmic activity within the network reflects the subject's social context.

Characterizing the neuroimmune environment of offspring in a novel model of maternal allergic asthma and particulate matter exposure

Inflammation during pregnancy is associated with an increased risk for neurodevelopmental disorders (NDD). Increased gestational inflammation can be a result of an immune condition/disease, exposure to infection, and/or environmental factors. Epidemiology studies suggest that cases of NDD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with NDD such as autism spectrum disorders (ASD). Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were sensitized for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA to induce allergic asthma or phosphate buffered saline (PBS) for 1 h. Following the 1-h exposure, pregnant females were then exposed to UIS with a size distribution of 55 to 169 nm at an average concentration of 176 ± 45 μg/m3) (SD), or clean air for 4 h, over 8 exposure sessions. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. There was a suppressive effect of the combined MAA plus UIS on the anti-inflammatory cytokine IL-10. Potentially shifting the cytokine balance towards more neuroinflammation. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Lmx1a is a master regulator of the cortical hem

Development of the nervous system depends on signaling centers - specialized cellular populations that produce secreted molecules to regulate neurogenesis in the neighboring neuroepithelium. In some cases, signaling center cells also differentiate to produce key types of neurons. The formation of a signaling center involves its induction, the maintenance of expression of its secreted molecules, and cell differentiation and migration events. How these distinct processes are coordinated during signaling center development remains unknown. By performing studies in mice, we show that Lmx1a acts as a master regulator to orchestrate the formation and function of the cortical hem (CH), a critical signaling center that controls hippocampus development. Lmx1a co-regulates CH induction, its Wnt signaling, and the differentiation and migration of CH-derived Cajal-Retzius neurons. Combining RNAseq, genetic, and rescue experiments, we identified major downstream genes that mediate distinct Lmx1a-dependent processes. Our work revealed that signaling centers in the mammalian brain employ master regulatory genes and established a framework for analyzing signaling center development.

Minocycline improves autism-related behaviors by modulating microglia polarization in a mouse model of autism

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with few pharmacological treatments. Minocycline, a tetracycline derivative that inhibits microglial activation, has been well-identified with anti-inflammatory properties and neuroprotective effects. A growing body of research suggests that ASD is associated with neuroinflammation, abnormal neurotransmitter levels, and neurogenesis. Thus, we hypothesized that minocycline could improve autism-related behaviors by inhibiting microglia activation and altering neuroinflammation. To verify our hypothesis, we used a mouse model of autism, BTBR T + Itpr3tf/J (BTBR). As expected, minocycline administration rescued the sociability and repetitive, stereotyped behaviors of BTBR mice while having no effect in C57BL/6J mice. We also found that minocycline improved neurogenesis and inhibited microglia activation in the hippocampus of BTBR mice. In addition, minocycline treatment inhibited Erk1/2 phosphorylation in the hippocampus of BTBR mice. Our findings show that minocycline administration alleviates ASD-like behaviors in BTBR mice and improves neurogenesis, suggesting that minocycline supplementation might be a potential strategy for improving ASD symptoms.

Neonatal immune challenge poses a sex-specific risk for epigenetic microglial reprogramming and behavioral impairment

While the precise processes underlying a sex bias in the development of central nervous system (CNS) disorders are unknown, there is growing evidence that an early life immune activation can contribute to the disease pathogenesis. When we mimicked an early systemic viral infection or applied murine cytomegalovirus (MCMV) systemically in neonatal female and male mice, only male adolescent mice presented behavioral deficits, including reduced social behavior and cognition. This was paralleled by an increased amount of infiltrating T cells in the brain parenchyma, enhanced interferon-γ (IFNγ) signaling, and epigenetic reprogramming of microglial cells. These microglial cells showed increased phagocytic activity, which resulted in abnormal loss of excitatory synapses within the hippocampal brain region. None of these alterations were seen in female adolescent mice. Our findings underscore the early postnatal period's susceptibility to cause sex-dependent long-term CNS deficiencies following infections.

Gut Microbiota Analysis and In Silico Biomarker Detection of Children with Autism Spectrum Disorder across Cohorts

The study of human gut microbiota has attracted increasing interest in the fields of life science and healthcare. However, the complicated and interconnected associations between gut microbiota and human diseases are still difficult to determine in a predictive fashion. Artificial intelligence such as machine learning (ML) and deep learning can assist in processing and interpreting biological datasets. In this study, we aggregated data from different studies based on the species composition and relative abundance of gut microbiota in children with autism spectrum disorder (ASD) and typically developed (TD) individuals and analyzed the commonalities and differences of ASD-associated microbiota across cohorts. We established a predictive model using an ML algorithm to explore the diagnostic value of the gut microbiome for the children with ASD and identify potential biomarkers for ASD diagnosis. The results indicated that the Shenzhen cohort achieved a higher area under the receiver operating characteristic curve (AUROC) value of 0.984 with 97% accuracy, while the Moscow cohort achieved an AUROC value of 0.81 with 67% accuracy. For the combination of the two cohorts, the average prediction results had an AUROC of 0.86 and 80% accuracy. The results of our cross-cohort analysis suggested that a variety of influencing factors, such as population characteristics, geographical region, and dietary habits, should be taken into consideration in microbial transplantation or dietary therapy. Collectively, our prediction strategy based on gut microbiota can serve as an enhanced strategy for the clinical diagnosis of ASD and assist in providing a more complete method to assess the risk of the disorder.

Implication of Hippocampal Neurogenesis in Autism Spectrum Disorder: Pathogenesis and Therapeutic Implications

Autism spectrum disorder (ASD) is a cluster of heterogeneous neurodevelopmental conditions with atypical social communication and repetitive sensory-motor behaviors. The formation of new neurons from neural precursors in the hippocampus has been unequivocally demonstrated in the dentate gyrus of rodents and non-human primates. Accumulating evidence sheds light on how the deficits in the hippocampal neurogenesis may underlie some of the abnormal behavioral phenotypes in ASD. In this review, we describe the current evidence concerning pre-clinical and clinical studies supporting the significant role of hippocampal neurogenesis in ASD pathogenesis, discuss the possibility of improving hippocampal neurogenesis as a new strategy for treating ASD, and highlight the prospect of emerging pro-neurogenic therapies for ASD.

Liver fibrosis and retinal features in an older Mediterranean population: Results from the Salus in Apulia study

Background

Age is a leading contributor to the liver fibrosis rate and a gradual deterioration of optical function, but this association in older populations is still under-explored. The present study aimed to explore the link between vascular and neural retinal characteristics and the risk of liver fibrosis in 731 older adults from the population-based Salus in Apulia study.

Methods

Retinal features were obtained using optical coherence tomography (OCT) and OCT-angiography (OCT-A). Liver fibrosis risk was taken as the fibrosis-4 (FIB-4) score. Generalized linear models (logistic regression) were used to estimate the association effect between each unit increase of OCT and OCT-A parameters as independent variables and a FIB-4 ≥ 2.67 score as an outcome. Generalized additive models were used to assess the non-linear association between OCT-A features and the linear FIB-4 score.

Results

Increased gangliar cell complex (GCC) thickness was inversely associated with a FIB-4 score above the cut-off in both the raw model (OR: 0.98; 95% CI: 0.96-0.99; SE: 0.01) and after adjustment for age, sex, education, hypertension, diabetes, total cholesterol, and triglycerides (OR: 0.98; 95% CI: 0.97-0.99; SE: 0.01).

Conclusion

Our findings add to the growing volume of scientific literature demonstrating that liver fibrosis is associated with retinal neurodegeneration. This study raises a number of new questions, including whether OCT-A may be used to track the progression of metabolic abnormalities and define exact thresholds for predicting and classifying liver disease.

Liver X Receptor Regulation of Glial Cell Functions in the CNS

In this review, we discuss the role of liver X receptors (LXRs) in glial cells (microglia, oligodendrocytes and astrocytes) in the central nervous system (CNS). LXRs are oxysterol-activated nuclear receptors that, in adults, regulate genes involved in cholesterol homeostasis, the modulation of inflammatory responses and glutamate homeostasis. The study of LXR knockout mice has revealed that LXRβ plays a key role in maintaining the health of dopaminergic neurons in the substantia nigra, large motor neurons in the spinal cord and retinal ganglion cells in the eye. In the peripheral nervous system (PNS), LXRβ is responsible for the health of the spiral ganglion neurons (SGNs) in the cochlea. In addition, LXRs are essential for the homeostasis of the cerebrospinal fluid (CSF), and in LXRαβ^−/− mice, the lateral ventricles are empty and lined with lipid-laden cells. As LXRαβ^−/− mice age, lipid vacuoles accumulate in astrocytes surrounding blood vessels. By seven months of age, motor coordination becomes impaired, and there is a loss of motor neurons in the spinal cord of LXRβ^−/− mice. During development, migration of neurons in the cortex and cerebellum is retarded in LXRβ^−/− mice. Since LXRs are not expressed in dopaminergic or motor neurons in adult mice, the neuroprotective effects of LXRs appear to come from LXRs in glial cells where they are expressed. However, despite the numerous neurological deficits in LXR^−/− rodents, multiple sclerosis has the clear distinction of being the only human neurodegenerative disease in which defective LXR signaling has been identified. In this review, we summarize the regulation and functions of LXRs in glial cells and analyze how targeting LXRs in glial cells might, in the future, be used to treat neurodegenerative diseases and, perhaps, disorders caused by aberrant neuronal migration during development.

Ablation of Liver X receptor β in mice leads to overactive macrophages and death of spiral ganglion neurons

Age-related hearing loss is the most common type of hearing impairment, and is typically characterized by the loss of spiral ganglion neurons (SGNs). The two Liver X receptors (LXRs) are oxysterol-activated nuclear receptors which in adults, regulate genes involved in cholesterol homeostasis and modulation of macrophage activity. LXRβ plays a key role in maintenance of health of dopaminergic neurons in the substantia nigra, large motor neurons in the spinal cord, and retinal ganglion cells in adult mice. We now report that LXRβ is expressed in the SGNs of the cochlea and that loss of LXRβ leads to age-related cochlea degeneration. We found that in the cochlea of LXRβ-/- mice, there is loss of SGNs, activation of macrophages, demyelination in the spiral ganglion, decrease in glutamine synthetase (GS) expression and increase in glutamate accumulation in the cochlea. Part of the cause of damage to the SGNs might be glutamate toxicity which is known to be very toxic to these cells. Our study provides a so far unreported role of LXRβ in maintenance of SGNs whose loss is a very common cause of hearing impairment.

[Effects of CACNA1H gene knockout on autistic-like behaviors and the morphology of hippocampal neurons in mice]

OBJECTIVE

To investigate the effects of CACNA1H gene knockout (KO) on autistic-like behaviors and the morphology of hippocampal neurons in mice.

METHODS

In the study, 25 CACNA1H KO mice of 3-4 weeks old and C57BL/6 background were recruited as the experimental group, and 26 wild type (WT) mice of the same age and background were recruited as the control group. Three-chamber test and open field test were used to observe the social interaction, anxiety, and repetitive behaviors in mice. After that, their brain weight and size were measured, and the number of hippocampal neurons were observed by Nissl staining. Furthermore, the CACNA1H heterozygote mice were interbred with Thy1-GFP-O mice to generate CACNA1H^-/--Thy1⁺(KO-GFP) and CACNA1H^+/+-Thy1⁺ (WT-GFP) mice. The density and maturity of dendritic spines of hippocampal neurons were observed.

RESULTS

In the sociability test session of the three-chamber test, the KO mice spent more time in the chamber of the stranger mice than in the object one (F_{1, 14}=95.086, P < 0.05; Post-Hoc: P < 0.05), without any significant difference for the explored preference index between the two groups (t=1.044, P>0.05). However, in the social novelty recognition test session, no difference was observed between the time of the KO mice spend in the chamber of new stranger mice and the stranger one (F_{1, 14}=18.062, P < 0.05; Post-Hoc: P>0.05), and the explored preference index of the KO mice was less than that of the control group (t=2.390, P < 0.05). In the open field test, the KO mice spent less time in the center of the open field apparatus than the control group (t=2.503, P < 0.05), but the self-grooming time was significantly increased compared with the control group (t=-2.299, P < 0.05). Morphological results showed that the brain weight/body weight ratio (t=0.356, P>0.05) and brain size (t=-0.660, P>0.05) of the KO mice were not significantly different from those of the control group, but the number of neurons were significantly reduced in hippocampal dentate gyrus compared with the control group (t=2.323, P < 0.05). Moreover, the density of dendritic spine of dentate gyrus neurons in the KO-GFP mice was significantly increased compared with the control group (t=-2.374, P < 0.05), without any significant difference in spine maturity (t=-1.935, P>0.05).

CONCLUSION

CACNA1H KO mice represent autistic-like behavior, which may be related to the decrease in the number of neurons and the increase in the density of dendritic spine in the dentate gyrus.

Alteration of Gut Microbiota: New Strategy for Treating Autism Spectrum Disorder

Autism spectrum disorder (ASD) is defined as a complex heterogeneous disorder and characterized by stereotyped behavior and deficits in communication and social interactions. The emerging microbial knowledge has pointed to a potential link between gut microbiota dysbiosis and ASD. Evidence from animal and human studies showed that shifts in composition and activity of the gut microbiota may causally contribute to the etiopathogenesis of core symptoms in the ASD individuals with gastrointestinal tract disturbances and act on microbiota-gut-brain. In this review, we summarized the characterized gut bacterial composition of ASD and the involvement of gut microbiota and their metabolites in the onset and progression of ASD; the possible underlying mechanisms are also highlighted. Given this correlation, we also provide an overview of the microbial-based therapeutic interventions such as probiotics, antibiotics, fecal microbiota transplantation therapy, and dietary interventions and address their potential benefits on behavioral symptoms of ASD. The precise contribution of altering gut microbiome to treating core symptoms in the ASD needs to be further clarified. It seemed to open up promising avenues to develop microbial-based therapies in ASD.

Loss of liver X receptor β in astrocytes leads to anxiety-like behaviors via regulating synaptic transmission in the medial prefrontal cortex in mice

Astrocytes are integral components of synaptic transmission, and their dysfunction leads to neuropsychiatric disorders such as anxiety and depression. Liver X receptor β (LXRβ) is expressed in astrocytes, and LXRβ global knockout mice shows impaired synaptic formation. In order to define the role of LXRβ in astrocytes, we used a conditional Cre-loxP system to specifically remove LXRβ from astrocytes. We found that this deletion caused anxiety-like but not depressive-like behaviors in adult male mice. This behavioral phenotype could be completely reproduced by selective deletion of LXRβ in astrocytes in the medial prefrontal cortex (mPFC). Pyramidal neurons in layer V of mPFC are involved in mood behaviors. We found that there was an increased spontaneous excitatory synaptic transmission in layer V pyramidal neurons of the mPFC of these mice. This was concurrent with increased dendritic complexity, despite normal appearance and number of dendritic spines. In addition, gene ontology analysis of RNA sequencing revealed that deletion of astrocytic LXRβ led to the enrichment of the process of synaptic transmission in mPFC. Finally, we also confirmed that renormalized excitatory synaptic transmission in layer V pyramidal neurons alleviated the anxiety in mice with astrocytic LXRβ deletion in mPFC. Together, our findings reveal that astrocytic LXRβ in mPFC is critical in the regulation of synaptic transmission, and this provides a potential new target for treatment of anxiety-like behavior.

AAV Delivery of shRNA Against TRPC6 in Mouse Hippocampus Impairs Cognitive Function

Transient Receptor Potential Canonical 6 (TRPC6) has been suggested to be involved in synapse function and contribute to hippocampal-dependent cognitive processes. Gene silencing of TRPC6 was performed by injecting adeno-associated virus (AAV) expressing TRPC6-specific shRNA (shRNA-TRPC6) into the hippocampal dentate gyrus (DG). Spatial learning, working memory and social recognition memory were impaired in the shRNA-TRPC6 treated mice compared to control mice after 4 weeks. In addition, gene ontology (GO) analysis of RNA-sequencing revealed that viral intervention of TRPC6 expression in DG resulted in the enrichment of the process of synaptic transmission and cellular compartment of synaptic structure. KEGG analysis showed PI3K-Akt signaling pathway were significantly down-regulated. Furthermore, the shRNA-TRPC6 treatment reduced dendritic spines of DG granule neurons, in terms of spine loss, the thin and mushroom types predominated. Accompanying the spine loss, the levels of PSD95, pAkt and CREB in the hippocampus were decreased in the shRNA-TRPC6 treated animals. Taken together, our results suggest that knocking down TRPC6 in the DG have a disadvantageous effect on cognitive processes.

Activation of liver X receptors prevents emotional and cognitive dysfunction by suppressing microglial M1-polarization and restoring synaptic plasticity in the hippocampus of mice

Depression is a long-lasting and persistent mood disorder in which the regulatory mechanisms of neuroinflammation are thought to play a contributing role to the physiopathology of the condition. Previous studies have shown that liver X receptors (LXRs) can regulate the activation of microglia and neuroinflammation. However, the role of LXRs in depression remains to be fully understood. In this study, we hypothesized that stress impairs the function of LXRs and that the LXRs agonist GW3965 plays a potential anti-depressive role by inhibiting neuroinflammation. The anti-depressive effects of GW3965 were evaluated in both chronic unpredictable mild stress (CUMS) and lipopolysaccharide (LPS) models. The LXRs antagonist GSK2033 was also employed to block LXRs. Behavioural tests were performed to measure depression-like phenotypes and learning abilities. Electrophysiological recordings and Golgi staining were used to measure the plasticity of the dentate gyrus synapse. The expression of synapse and neuroinflammation related proteins were evaluated by Western blotting and immunofluorescence. The activation of LXRs by GW3965 prevented emotional and cognitive deficits induced by either CUMS or LPS. GW3965 prevented the decreased level of LXR-β induced by CUMS. The activation of LXRs significantly improved the impairment of synaptic plasticity, prevented the up-regulation of inflammatory factors and inhibited NF-κB phosphorylation and microglial M1-polarization in both models. The antidepressive-like effects of GW3965 were blocked by GSK2033 in the CUMS and LPS models. Our data suggest that inhibition of the LXRs signalling pathway may be a key driver in the pathogenesis of neuroinflammation during depression and that LXRs agonists have a high potential in the treatment of depression.

Female mice lacking ERβ display excitatory/inhibitory synaptic imbalance to drive the pathogenesis of temporal lobe epilepsy

Epilepsy is a highly prevalent and drug-refractory neurological disorder characterized by spontaneous recurrent seizures. Estrogen is identified to be proconvulsant and lowers the seizure threshold of female epilepsy. Estrogen receptor β (ERβ) has been proposed to mediate neuroprotection in epilepsy, although the underlying mechanism remains unknown. Rationale: In this study, we investigated the role of ERβ in the epileptogenesis of female temporal lobe epilepsy (TLE). Methods: Immunohistochemistry, immunofluorescence, western blots, Golgi staining, 1H MRS and whole-cell patch-clamp were used to evaluate ERβ expression, pathological changes, and synaptic excitation /inhibition (E/I) balance in female TLE patients and ovariectomized (OVX) chronic epileptic mice. Electroencephalogram (EEG) recordings were recorded to evaluate the epileptic susceptibility in OVX WT and ERβ-/- mice. And high-throughput RNA-sequence was performed to identify differential expression genes (DEGs) which can elucidate the potential mechanism of ERβ regulating the seizure susceptibility. Results: ERβ expression was decreased in the brains of female TLE patients and OVX chronic epileptic mice. ERβ deletion enhanced seizure susceptibility and exacerbated the imbalance of synaptic E/I in hippocampal CA1 area of OVX epileptic mice. In line with these observations, RNA-sequence data further identified glutamine ligase (GLUL) as the target of ERβ involved in regulating synaptic E/I in CA1. Furthermore, ERβ agonist WAY-200070 markedly suppressed epileptic phenotypes and normalized GLUL expression in CA1 region of kainic acid (KA) induced OVX chronic epileptic model. Conclusions: Our data provide novel insight into the pathogenesis of female TLE, and indicate ERβ provides a new therapeutic strategy for female TLE patients.

Effect of TO901317 on GF to promote the differentiation of human bone marrow mesenchymal stem cells into dopamine neurons on Parkinson's disease

Background:

Human bone marrow mesenchymal stem cells (hBMSCs) could differentiate into dopamine-producing cells and ameliorate behavioral deficits in Parkinson’s disease (PD) models. Liver X receptors (LXRs) are involved in the maintenance of the normal function of central nervous system myelin. Therefore, the previous work of our team has found the induction of cocktail-induced to dopaminergic (DA) phenotypes from adult rat BMSCs by using sonic hedgehog (SHH), fibroblast growth factor 8 (FGF8), basic fibroblast growth factor (bFGF), and TO901317 (an agonist of LXRs) with 87.42% of efficiency in a 6-day induction period. But we did not verify whether the induced cells had the corresponding neural function.

Methods:

Expressions of LXRα, LXRβ, and tyrosine hydroxylase (TH) were detected by immunofluorescence and western blot. Adenosine triphosphate-binding cassette transporter A1 (ABCA1) was detected by quantitative real-time PCR. The induced cells were transplanted into PD rats to study whether the induced cells are working.

Results:

The induced cells can release the dopamine transmitter; the maximum induction efficiency of differentiation of hBMSCs into DA neurons was 91.67% under conditions of combined use with TO901317 and growth factors (GF). When the induced-cells were transplanted into PD rats, the expression of TH in the striatum increased significantly, and the behavior of PD rats induced by apomorphine was significantly improved.

Conclusion:

The induced cells have the function of DA neurons and have the potential to treat PD. TO901317 promoted differentiation of hBMSCs into DA neurons, which may be related to activation of the LXR-ABCA1 signaling pathway.

Neonatal curcumin treatment restores hippocampal neurogenesis and improves autism-related behaviors in a mouse model of autism

RATIONALE

Autism spectrum disorders (ASDs) are highly prevalent neurodevelopmental disorders characterized by deficits in social communication and interaction, repetitive stereotyped behaviors, and cognitive impairments. Curcumin has been indicated to be neuroprotective against neurological and psychological disorders. However, the role of curcumin in autistic phenotypes remains unclear.

OBJECTIVES

In the current study, we evaluated the effects of neonatal curcumin treatment on behavior and hippocampal neurogenesis in BTBRT⁺ltpr3^tf/J (BTBR) mice, a model of autism.

METHODS

C57BL/6J (C57) and BTBR mouse pups were treated with 0.1% dimethyl sulfoxide (DMSO) or curcumin (20 mg/kg) from postnatal day 6 (P6) to P8. Neural progenitor cells (NPCs) in the hippocampal dentate gyrus (DG) were evaluated on P8, and neurogenesis was measured on P24 by immunofluorescence. A battery of behavioral tests was carried out when the mice were 8 weeks of age.

RESULTS

Neonatal curcumin treatment improved autism-related symptoms in BTBR mice, enhancing sociability, reducing repetitive behaviors, and ameliorating cognitive impairments. Furthermore, the suppression of hippocampal neurogenesis in BTBR mice was greatly rescued after neonatal curcumin treatment, leading to an increase in neurogenic processes and an increase in NPC proliferation concomitant with an expansion of the NPC pool on P8, and NPC differentiation towards the neuronal lineage was promoted in the DG of BTBR mice on P24.

CONCLUSIONS

Our findings suggest that neonatal curcumin treatment elicits a therapeutic response through the restoration of hippocampal neurogenesis in BTBR mice and thus may represent a promising novel pharmacological strategy for ASD treatment.

Characterization of an eutherian gene cluster generated after transposon domestication identifies Bex3 as relevant for advanced neurological functions

BACKGROUND

One of the most unusual sources of phylogenetically restricted genes is the molecular domestication of transposable elements into a host genome as functional genes. Although these kinds of events are sometimes at the core of key macroevolutionary changes, their origin and organismal function are generally poorly understood.

RESULTS

Here, we identify several previously unreported transposable element domestication events in the human and mouse genomes. Among them, we find a remarkable molecular domestication that gave rise to a multigenic family in placental mammals, the Bex/Tceal gene cluster. These genes, which act as hub proteins within diverse signaling pathways, have been associated with neurological features of human patients carrying genomic microdeletions in chromosome X. The Bex/Tceal genes display neural-enriched patterns and are differentially expressed in human neurological disorders, such as autism and schizophrenia. Two different murine alleles of the cluster member Bex3 display morphological and physiopathological brain modifications, such as reduced interneuron number and hippocampal electrophysiological imbalance, alterations that translate into distinct behavioral phenotypes.

CONCLUSIONS

We provide an in-depth understanding of the emergence of a gene cluster that originated by transposon domestication and gene duplication at the origin of placental mammals, an evolutionary process that transformed a non-functional transposon sequence into novel components of the eutherian genome. These genes were integrated into existing signaling pathways involved in the development, maintenance, and function of the CNS in eutherians. At least one of its members, Bex3, is relevant for higher brain functions in placental mammals and may be involved in human neurological disorders.

Inhibitors of cellular stress overcome acute effects of ethanol on hippocampal plasticity and learning

Ethanol intoxication can produce marked changes in cognitive function including states in which the ability to learn and remember new information is completely disrupted. These defects likely reflect changes in the synaptic plasticity thought to underlie memory formation. We have studied mechanisms contributing to the adverse effects of ethanol on hippocampal long-term potentiation (LTP) and provided evidence that ethanol-mediated LTP inhibition involves a form of metaplasticity resulting from local metabolism of ethanol to acetaldehyde and untimely activation of N-methyl-d-aspartate receptors (NMDARs), both of which are neuronal stressors. In the present studies, we sought to understand the role of cellular stress in LTP defects, and demonstrate that ethanol's effects on LTP in the CA1 hippocampal region are overcome by agents that inhibit cellular stress responses, including ISRIB, a specific inhibitor of integrated stress responses, and GW3965, an agonist that acts at liver X receptors (LXRs) and dampens cellular stress. The agents that alter LTP inhibition also prevent the adverse effects of acute ethanol on one trial inhibitory avoidance learning. Unexpectedly, we found that the LXR agonist but not ISRIB overcomes effects of ethanol on synaptic responses mediated by N-methyl-d-aspartate receptors (NMDARs). These results have implications for understanding the adverse effects of ethanol and possibly for identifying novel paths to treatments that can prevent or overcome ethanol-induced cognitive dysfunction.

Transcription Factor 4 Safeguards Hippocampal Dentate Gyrus Development by Regulating Neural Progenitor Migration

The dentate gyrus (DG) of the hippocampal formation plays essential roles in learning and memory. Defective DG development is associated with neurological disorders. Here, we show that transcription factor 4 (Tcf4) is essential for DG development. Tcf4 expression is elevated in neural progenitors of the dentate neuroepithelium in the developing mouse brain. We demonstrate that conditional disruption of Tcf4 in the dentate neuroepithelium leads to abnormal neural progenitor migration guided by disorganized radial glial fibers, which further leads to hypoplasia in the DG. Moreover, we reveal that Wnt7b is a key downstream effector of Tcf4 in regulating neural progenitor migration. Behavioral analysis shows that disruption of integrity of the DG impairs the social memory highlighting the importance of proper development of the DG. These results reveal a critical role for Tcf4 in regulating DG development. As mutations in TCF4 cause Pitt-Hopkins syndrome (PTHS) characterized by severe intellectual disability, our data also potentially provide insights into the basis of neurological defects linked to TCF4 mutations.

Construction of multicellular aggregate by E-cadherin coated microparticles enhancing the hepatic specific differentiation of mesenchymal stem cells

The differentiation of human mesenchymal stem cells (hMSCs) into hepatocyte-like cells in vitroprovides a promising candidate for cell therapy of liver diseases, and cell aggregates have been proposed to improve the efficiency of expansion and differentiation. Previously, we engineered multicellular aggregates incorporating human E-cadherin fusion protein (hE-cad-Fc)-coated poly(lactic-co-glycolic acid) (PLGA) microparticles (hE-cad-PLGAs), and a significant improvement was obtained in both cellular proliferation of and cytokine secretion by hMSCs. In this study, hepatic differentiation of hMSCs was induced by a biomimetic microenvironment consisting of these engineered aggregates and a cocktail of specific cytokines. The ratio of hE-cad-PLGAs to hMSCs in engineered hMSCs aggregates was optimized to 1:3 for hepatic differentiation. The expressions of hepatic-specific markers were significantly promoted, and cell polarity and activated drug metabolism enzymes were established in MSC/hE-cad-PLGA aggregates compared with MSC and MSC/PLGA aggregates. Moreover, the expressions of stemness and definitive endoderm markers confirmed effectively induced endoderm differentiation in MSC/hE-cad-PLGA aggregates, which was consistent with the pattern of embryonic development. After pre-differentiation for 1 week, the MSC/hE-cad-PLGA aggregates continuously progressed the hepatic phenotype expression in healthy rat peritoneum. Therefore, the biomimetic microenvironment constructed by hE-cad-PLGAs in engineered multicellular aggregates was able to promote the process of endoderm differentiation and the subsequent hepatic differentiation of hMSCs. It would be appropriate for applied research in hepatotoxic drug screening and cell-based treatment of liver diseases. By optimizing with other cytokine cocktail, the engineered multicellular aggregates can be applied to the construction of other endoderm-derived organs. STATEMENT OF SIGNIFICANCE: The differentiation of mesenchymal stem cells (MSCs) into hepatocyte-like cells in vitroprovides a promising for cell therapy for liver diseases, and cell aggregates have been proposed to improve the expansion and differentiation efficiency. Here, engineered multicellular aggregates were constructed by E-cadherin modified microparticles (hE-cad-PLGAs) construct a biomimetic microenvironment to promote the process of endoderm differentiation and the subsequent hepatic differentiation of hMSCs. Furthermore, after pre-differentiation for 1 week, the MSC/hE-cad-PLGA aggregates continuously progressed the hepatic phenotype expression in healthy rat peritoneum. Therefore, engineered multicellular aggregates with hE-cad-PLGAs would be appropriate for applied research in hepatotoxic drug screening and cell-based treatment of liver diseases, and provide a promising method in the construction of other endoderm-derived organs.

Lactobacillus acidophilus Exerts Neuroprotective Effects in Mice with Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) causes dysbiosis and intestinal barrier disruption, which further exacerbate brain damage via an inflammatory pathway. Gut microbiota remodeling by Lactobacillus acidophilus (LA) is a potential intervention.

OBJECTIVE

The aim of this study was to investigate the neuroprotective effects of LA in TBI and elucidated underlying mechanisms.

METHODS

C57BL/6 male mice (aged 8-9 wk) were subjected to weight-drop impact and gavaged with saline (TBI + vehicle) or LA (1 × 1010 CFU) (TBI + LA) on the day of injury and each day after for 1, 3, or 7 d. The sham + vehicle mice underwent craniotomy without brain injury and were gavaged with saline. Sensorimotor functions were determined pre-TBI and 1, 3, and 7 d postinjury. Indexes of neuroinflammation, peripheral inflammation, and intestinal barrier function were measured on days 3 and 7. Microbiota composition was measured 3 d postinjury. The data were mainly analyzed by 2-factor ANOVA.

RESULTS

Compared with sham + vehicle mice, the TBI + vehicle mice exhibited impairments in the neurological severity score (+692%, day 3; +600%, day 7) and rotarod test (-58%, day 3; -45%, day 7) (P < 0.05), which were rescued by LA. The numbers of microglia (total and activated) and astrocytes and concentrations of TNF-α and IL1-β in the perilesional cortex were elevated in the TBI + vehicle mice on day 3 or 7 compared with sham + vehicle mice (P < 0.05) and were normalized by LA. Compared with sham + vehicle mice, the TBI + vehicle mice exhibited increased serum concentrations of endotoxin and TNF-α, and intestinal barrier permeability (D-lactate) on days 3 and 7 (P < 0.05), and these changes were alleviated by LA. Three days postinjury, the microbiota composition was disrupted in the TBI + vehicle mice compared with sham + vehicle mice (P < 0.05), which was restored by LA.

CONCLUSION

Our results demonstrate that LA exerts neuroprotective effects that may be associated with gut microbiota remodeling in TBI mice.

Retinal and optic nerve degeneration in liver X receptor β knockout mice

The retina is an extension of the brain. Like the brain, neurodegeneration of the retina occurs with age and is the cause of several retinal diseases including optic neuritis, macular degeneration, and glaucoma. Liver X receptors (LXRs) are expressed in the brain where they play a key role in maintenance of cerebrospinal fluid and the health of dopaminergic neurons. Herein, we report that LXRs are expressed in the retina and optic nerve and that loss of LXRβ, but not LXRα, leads to loss of ganglion cells in the retina. In the retina of LXRβ^-/- mice, there is an increase in amyloid A4 and deposition of beta-amyloid (Aβ) aggregates but no change in the level of apoptosis or autophagy in the ganglion cells and no activation of microglia or astrocytes. However, in the optic nerve there is a loss of aquaporin 4 (AQP4) in astrocytes and an increase in activation of microglia. Since loss of AQP4 and microglial activation in the optic nerve precedes the loss of ganglion cells, and accumulation of Aβ in the retina, the cause of the neuronal loss appears to be optic nerve degeneration. In patients with optic neuritis there are frequently AQP4 autoantibodies which block the function of AQP4. LXRβ^-/- mouse is another model of optic neuritis in which AQP4 antibodies are not detectable, but AQP4 function is lost because of reduction in its expression.

Human amniotic epithelial cell transplantation promotes neurogenesis and ameliorates social deficits in BTBR mice

Background

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social interactions and communication and stereotypical patterns of behaviors, interests, or activities. Even with the increased prevalence of ASD, there is no defined standard drug treatment for ASD patients. Currently, stem cells, including human amniotic epithelial cell (hAEC) transplantation, seem to be a promising treatment for ASD, but the effectiveness needs to be verified, and the mechanism has not been clarified.

Methods

We intraventricularly transplanted hAECs into a 2-month-old BTBR T+tf/J (BTBR) mouse model of ASD. Behavior tests were detected 1 month later; hippocampal neurogenesis, neuroprogenitor cell (NPC) pool, and microglia activation were analyzed with immunohistochemistry and immunofluorescence; the levels of pro-inflammatory cytokines, brain-derived neurotrophic factor (BDNF), and TrkB in the hippocampus were determined by real-time PCR or western blotting.

Results

After intraventricular injection of hAECs into adult males, social deficits in BTBR mice were significantly ameliorated. In addition, hAEC transplantation restored the decline of neurogenesis and NPCs in the hippocampus of BTBR mice by expanding the stem cell pool, and the decreased levels of BDNF and TrkB were also rescued in the hippocampus of the hAEC-injected BTBR mice. Meanwhile, the transplantation of hAECs did not induce microglial overactivation or excessive production of pro-inflammatory cytokines in the hippocampus of BTBR mice.

Conclusions

Based on these results, we found that hAEC transplantation ameliorated social deficits and promoted hippocampal neurogenesis in BTBR mice. Our study indicates a promising therapeutic option that could be applied to ASD patients in the future.

The Liver X Receptor Agonist TO901317 Ameliorates Behavioral Deficits in Two Mouse Models of Autism

Autism spectrum disorder (ASD) is a developmental disability characterized by social deficits and repetitive stereotyped behaviors. There are currently no drugs available for the treatment of the core symptoms of ASD, suggesting an urgent need for new therapeutic strategies. The neurobiology of autism is complex, but emerging research indicates that defects in hippocampal neurogenesis are associated with ASD in both humans and mouse models of ASD, leading to the suggestion that restoring neurogenesis may be a novel therapeutic approach for ASD. Here, we found that postnatal treatment with TO901317 (TO), a potent liver X receptor (LXR) agonist, typically activated LXRβ and its target genes in the hippocampus, and alleviated the social deficits and stereotypical behaviors in BTBR T+ tf/J (BTBR) and valproic acid (VPA)-induced mouse models. In addition, we further confirmed that TO postnatal treatment also rescued the inhibition of adult hippocampal neurogenesis in these two models. In summary, our study suggests that LXR agonist targeting hippocampal neurogenesis may represent a novel potential therapy for ASD.

Gestational Exposure to Particulate Matter 2.5 (PM2.5) Leads to Spatial Memory Dysfunction and Neurodevelopmental Impairment in Hippocampus of Mice Offspring

Prenatal exposure to air pollutants has long-term impact on growth retardation of nervous system development and is related to central nervous system diseases in children. However, it is not well-characterized whether gestational exposure to air pollutants affects the development of nervous system in offspring. Here, we investigated the effects of gestational exposure to particulate matter 2.5 (PM_2.5) on hippocampus development in mice offspring, through neurobehavioral, ultrastructural, biochemical and molecular investigations. We found that spatial memory in mice offspring from PM_2.5 high-dosage group was impaired. Next, hippocampal ultrastructure of the mice offspring in puberty exhibited mitochondrial damage related to PM_2.5 exposure. Interestingly, EdU-positive cells in the subgranular zone (SGZ) of offspring from PM_2.5 high-dosage group decreased, with NeuN⁺/EdU⁺cells reduced significantly. Furthermore, the numbers of NeuN⁺/TUNEL⁺, GFAP⁺/TUNEL⁺, and Iba1⁺/TUNEL⁺ double-labeled cells increased with PM_2.5 exposure in a dosage-dependent manner. In addition, gestational exposure to PM_2.5 resulted in increased levels of both mRNAs and proteins involved in apoptosis, including caspase-3, -8, -9, p53, and c-Fos, and decreased Bcl-2/Bax ratios in the hippocampus of mice offspring. Moreover, gestational exposure to PM_2.5 was dosage-dependently associated with the increased secretions of inflammatory proteins, including NF-κB, TNF-α, and IL-1β. Collectively, our results suggest that gestational exposure to PM_2.5 leads to spatial memory dysfunction and neurodevelopmental impairment by exerting effects on apoptotic and neuroinflammatory events, as well as the neurogenesis in hippocampus of mice offspring.

Regulation of brain drug metabolizing enzymes and transporters by nuclear receptors

Nuclear receptors (NRs) belong to a family of ligand-dependent transcription factors. The target genes of NRs include many drug metabolizing enzymes and transporters. The central nervous system (CNS) bears the expression of NRs, drug metabolizing enzymes and transporters. NRs that express in the brain can be divided into three groups according to their characteristics of ligand binding: steroid hormone receptors, non-steroid hormone receptors, and orphan receptors. The NR-mediated regulation of drug metabolizing enzymes and transporters plays important roles in the metabolism and disposition of drugs in the CNS and the penetration of endogenous and exogenous substances through the blood-brain barrier (BBB). NR-mediated regulation of drug metabolizing enzymes and transporters can cause the toxicological effects of xenobiotics in the CNS and also lead to drug resistance in the centrum. The regulatory pathways of drug metabolizing enzymes and transporters can provide new strategies for selective regulation of the BBB permeability and drug metabolism in the brain. This review focuses on the importance of NR-mediated regulation of drug metabolizing enzymes and transporters in the CNS and the implications of this regulation in the therapeutic effect of CNS drugs and CNS side effects of drugs and other xenotoxicants.