CXCR4 antagonist AMD3100 reverses the neurogenesis promoted by enriched environment and suppresses long-term seizure activity in adult rats of temporal lobe epilepsy

RNA Sequencing Demonstrates Ex Vivo Neocortical Transcriptomic Changes Induced by Epileptiform Activity in Male and Female Mice

Seizures are generally associated with epilepsy but may also be a symptom of many other neurological conditions. A hallmark of a seizure is the intensity of the local neuronal activation, which can drive large-scale gene transcription changes. Such changes in the transcriptional profile likely alter neuronal function, thereby contributing to the pathological process. Therefore, there is a strong clinical imperative to characterize how gene expression is changed by seizure activity. To this end, we developed a simplified ex vivo technique for studying seizure-induced transcriptional changes. We compared the RNA sequencing profile in mouse neocortical tissue with up to 3 h of epileptiform activity induced by 4-aminopyridine (4AP) relative to control brain slices not exposed to the drug. We identified over 100 genes with significantly altered expression after 4AP treatment, including multiple genes involved in MAPK, TNF, and neuroinflammatory signaling pathways, all of which have been linked to epilepsy previously. Notably, the patterns in male and female brain slices were almost identical. Various immediate early genes were among those showing the largest upregulation. The set of down-regulated genes included ones that might be expected either to increase or to decrease neuronal excitability. In summary, we found the seizure-induced transcriptional profile complex, but the changes aligned well with an analysis of published epilepsy-associated genes. We discuss how simple models may provide new angles for investigating seizure-induced transcriptional changes.

ΔFosB is part of a homeostatic mechanism that protects the epileptic brain from further deterioration

Activity induced transcription factor ΔFosB plays a key role in different CNS disorders including epilepsy, Alzheimer's disease, and addiction. Recent findings suggest that ΔFosB drives cognitive deficits in epilepsy and together with the emergence of small molecule inhibitors of ΔFosB activity makes it an interesting therapeutic target. However, whether ΔFosB contributes to pathophysiology or provides protection in drug-resistant epilepsy is still unclear. In this study, ΔFosB was specifically downregulated by delivering AAV-shRNA into the hippocampus of chronically epileptic mice using the drug-resistant pilocarpine model of mesial temporal epilepsy (mTLE). Immunohistochemistry analyses showed that prolonged downregulation of ΔFosB led to exacerbation of neuroinflammatory markers of astrogliosis and microgliosis, loss of mossy fibers, and hippocampal granule cell dispersion. Furthermore, prolonged inhibition of ΔFosB using a ΔJunD construct to block ΔFosB signaling in a mouse model of Alzheimer's disease, that exhibits spontaneous recurrent seizures, led to similar findings, with increased neuroinflammation and decreased NPY expression in mossy fibers. Together, these data suggest that seizure-induced ΔFosB, regardless of seizure-etiology, is part of a homeostatic mechanism that protects the epileptic brain from further deterioration.

Adult neurogenesis research in China

Neural stem cells are multipotent stem cells that generate functional newborn neurons through a process called neurogenesis. Neurogenesis in the adult brain is tightly regulated and plays a pivotal role in the maintenance of brain function. Disruption of adult neurogenesis impairs cognitive function and is correlated with numerous neurologic disorders. Deciphering the mechanisms underlying adult neurogenesis not only advances our understanding of how the brain functions, but also offers new insight into neurologic diseases and potentially contributes to the development of effective treatments. The field of adult neurogenesis is experiencing significant growth in China. Chinese researchers have demonstrated a multitude of factors governing adult neurogenesis and revealed the underlying mechanisms of and correlations between adult neurogenesis and neurologic disorders. Here, we provide an overview of recent advancements in the field of adult neurogenesis due to Chinese scientists.

Repeated Social Defeat Stress Induces HMGB1 Nuclear Export in Prefrontal Neurons, Leading to Social Avoidance in Mice

Inflammation has been associated with depression, and innate immune receptors, such as the Toll-like receptor (TLR) 2/4 in the medial prefrontal cortex (mPFC), are crucial for chronic stress-induced depression-related behaviors in mice. HMGB1, a putative ligand for TLR2/4, has been suggested to promote depression-related behaviors under acute stress. However, the roles of endogenous HMGB1 under chronic stress remain to be investigated. Here, we found that the cerebroventricular infusion of HMGB1 proteins blocked stress-induced social avoidance and that HMGB1-neutralizing antibodies augmented repeated social defeat stress-induced social avoidance in mice, suggesting the antidepressive-like effect of HMGB1 in the brain. By contrast, the infusion of HMGB1-neutralizing antibodies to the mPFC and HMGB1 knockout in α-CaMKII-positive forebrain neurons attenuated the social avoidance, suggesting the pro-depressive-like effect of HMGB1 released from prefrontal neurons under chronic stress. In addition, repeated social defeat stress induced HMGB1 nuclear export selectively in mPFC neurons, which was abolished in the mice lacking RAGE, one of HMGB1 receptors, suggesting the positive feedback loop of HMGB1-RAGE signaling under chronic stress. These findings pave the way for identifying multiple roles of HMGB1 in the brain for chronic stress and depression.

Non-invasive sensory neuromodulation in epilepsy: Updates and future perspectives

Epilepsy, one of the most common neurological disorders, often is not well controlled by current pharmacological and surgical treatments. Sensory neuromodulation, including multi-sensory stimulation, auditory stimulation, olfactory stimulation, is a kind of novel noninvasive mind-body intervention and receives continued attention as complementary safe treatment of epilepsy. In this review, we summarize the recent advances of sensory neuromodulation, including enriched environment therapy, music therapy, olfactory therapy, other mind-body interventions, for the treatment of epilepsy based on the evidence from both clinical and preclinical studies. We also discuss their possible anti-epileptic mechanisms on neural circuit level and propose perspectives on possible research directions for future studies.

Comprehensive investigation of molecular signatures and pathways linking Alzheimer's disease and Epilepsy via bioinformatic approaches

BACKGROUND

Epileptic activity is frequent in patients with Alzheimer's disease (AD), and this may accelerate AD progression; however, the relationship between AD and epilepsy remains unclear.

OBJECTIVE

We aimed to investigate the molecular pathways and genes linking AD and epilepsy using bioinformatics approaches.

METHODS

Gene expression profiles of AD (GSE1297) and epilepsy (GSE28674) were derived from the Gene Expression Omnibus (GEO) database. The top 50% expression variants were subjected to weighted gene co-expression network analysis (WGCNA) to identify key modules associated with these diseases. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) for the key modules were performed, and the intersected terms of functional enrichment and common genes within the key modules were selected. The overlapping genes were subjected to analyses of protein-protein interaction (PPI) network, transcription factor (TF)-mRNA network, microRNA (miRNA)-mRNA network, and drug prediction.

RESULTS

We identified 229 and 1187 genes in the AD-associated purple and epilepsy-associated blue modules, respectively. Six shared functional terms between the two modules included "calcium ion binding" and "calcium signaling pathway." According to 17 common genes discovered, 130 TF-mRNA pairs and 56 miRNA-mRNA pairs were established. The topological analyses of the constructed regulatory networks suggested that TF - FOXC1 and miRNA - hsa-mir-335-5p might be vital co-regulators of gene expression in AD and epilepsy. In addition, CXCR4 was identified as a hub gene, becoming the putative target for 20 drugs.

CONCLUSION

Our study provided novel insights into the molecular connection between AD and epilepsy, which might be beneficial for exploring shared mechanisms and designing disease-modifying therapies.

The effect of gemcitabine combined with AMD3100 applying to cholangiocarcinoma RBE cell lines to CXCR4/CXCL12 axis

PURPOSE

To evaluate the effect of AMD3100 treatment to cholangiocarcinoma by analyzing the relationship between them, and provide experimental evidence for whether AMD3100 can become a clinical treatment drug for cholangiocarcinoma.

MATERIALS AND METHODS

Cholangiocarcinoma RBE cell lines were used in this study. MTT cell proliferation test was used for evaluating the effect of gemcitabine and AMD3100 to cell. CXCR4, N-cadherin, VEGF-C and MMP-9 were detect by RT-PCR and western. Transwell was used for evaluating the invasion effect.

RESULTS

We demonstrated that as the concentration of gemcitabine increasing from 0.33, 3.33 to 33.33 uM, the cell survival rate was 76.65%, 71.40%, 52.25%, respectively. RT-PCR and Western blot that gemcitabine could affect the expression of CXCR4 protein and the level of mRNA transcription in a dose-dependent manner. N-cadherin VEGF-C, MMP-9 mRNA transcription level showed a significant upward trend in gemcitabine group. In Transwell test, the number of cells in the gemcitabine group was significantly higher than that in the no-medication group (p < .05), the AMD3100 group and the combination group of gemcitabine and AMD3100, the difference between the no-medication group and the AMD3100 monotherapy group was not significant, and the combination group was between them.

CONCLUSIONS

This study showed that gemcitabine significantly inhibited the growth of cholangiocarcinoma RBE cells in a dose-dependent manner, and gemcitabine can affect the expression of CXCR4, N-cadherin, VEGF-C, MMP-9 protein and mRNA. Cell invasion and metastasis-related factors decreased after AMD3100 combined with gemcitabine.

Chemokine signaling is required for homeostatic and injury-induced neurogenesis in the olfactory epithelium

The olfactory epithelium (OE) possesses unique lifelong neuroregenerative capacities and undergoes constitutive neurogenesis throughout mammalian lifespan. Two populations of stem cells, frequently dividing globose basal cells (GBCs) and quiescent horizontal basal cells (HBCs), readily replace olfactory neurons throughout lifetime. Although lineage commitment and neuronal differentiation of stem cells has already been described in terms of transcription factor expression, little is known about external factors balancing between differentiation and self-renewal. We show here that expression of the CXC-motif chemokine receptor 4 (CXCR4) distinguishes both types of stem cells. Extensive colocalization analysis revealed exclusive expression of CXCR4 in proliferating GBCs and their neuronal progenies. Moreover, only neuronal lineage cells were derived from CXCR4-CreER-tdTomato reporter mice in the OE. Furthermore, Cre-tdTomato mice specific for HBCs (Nestin+ and Cytokeratin14+) did not reduce CXCR4 expression when bred to mice bearing floxed CXCR4 alleles, and did not show labeling of the neuronal cells. CXCR4 and its ligand CXCL12 were markedly upregulated upon induction of GBC proliferation during injury-induced regeneration. in vivo overexpression of CXCL12 did downregulate CXCR4 levels, which results in reduced GBC maintenance and neuronal differentiation. We proved that these effects were caused by CXCR4 downregulation rather than over-activation by showing that the phenotypes of CXCL12-overexpressing mice were highly similar to the phenotypes of CXCR4 knockout mice. Our results demonstrate functional CXCR4 signaling in GBCs regulates cell cycle exit and neural differentiation. We propose that CXCR4/CXCL12 signaling is an essential regulator of olfactory neurogenesis and provide new insights into the dynamics of neurogenesis in the OE.

Involvement of Cxcl12a/Cxcr4b Chemokine System in Mediating the Stimulatory Effect of Embryonic Ethanol Exposure on Neuronal Density in Zebrafish Hypothalamus

BACKGROUND

Embryonic exposure to ethanol (EtOH) produces marked disturbances in neuronal development and alcohol-related behaviors, with low-moderate EtOH doses stimulating neurogenesis without producing apoptosis and high doses having major cytotoxic effects while causing gross morphological abnormalities. With the pro-inflammatory chemokine system, Cxcl12, and its main receptor Cxcr4, known to promote processes of neurogenesis, we examined here this neuroimmune system in the embryonic hypothalamus to test directly if it mediates the stimulatory effects low-moderate EtOH doses have on neuronal development.

METHODS

We used the zebrafish (Danio rerio) model, which develops externally and allows one to investigate the developing brain in vivo with precise control of dose and timing of EtOH delivery in the absence of maternal influence. Zebrafish were exposed to low-moderate EtOH doses (0.1, 0.25, 0.5% v/v), specifically during a period of peak hypothalamic development from 22 to 24 hours postfertilization, and in some tests were pretreated from 2 to 22 hpf with the Cxcr4 receptor antagonist, AMD3100. Measurements in the hypothalamus at 26 hpf were taken of cxcl12a and cxcr4b transcription, signaling, and neuronal density using qRT-PCR, RNAscope, and live imaging of transgenic zebrafish.

RESULTS

Embryonic EtOH exposure, particularly at the 0.5% dose, significantly increased levels of cxcl12a and cxcr4b mRNA in whole embryos, number of cxcl12a and cxcr4b transcripts in developing hypothalamus, and internalization of Cxcr4b receptors in hypothalamic cells. Embryonic EtOH also caused an increase in the number of hypothalamic neurons and coexpression of cxcl12a and cxcr4b transcripts within these neurons. Each of these stimulatory effects of EtOH in the embryo was blocked by pretreatment with the Cxcr4 antagonist AMD3100.

CONCLUSIONS

These results provide clear evidence that EtOH's stimulatory effects at low-moderate doses on the number of hypothalamic neurons early in development are mediated, in part, by increased transcription and intracellular activation of this chemokine system, likely due to autocrine signaling of Cxcl12a at its Cxcr4b receptor within the neurons.

Environmental enrichment alters neurobehavioral development following maternal immune activation in mice offspring with epilepsy

Epilepsy is a chronic brain disease affecting millions of people worldwide. Anxiety-related disorders and cognitive deficits are common in patients with epilepsy. Previous studies have shown that maternal infection/immune activation renders children more vulnerable to neurological disorders later in life. Environmental enrichment has been suggested to improve seizures, anxiety, and cognitive impairment in animal models. The present study aimed to explore the effects of environmental enrichment on seizure scores, anxiety-like behavior, and cognitive deficits following maternal immune activation in offspring with epilepsy. Pregnant mice were treated with lipopolysaccharides-(LPS) or vehicle, and offspring were housed in normal or enriched environments during early adolescence to adulthood. To induce epilepsy, adult male and female offspring were treated with Pentylenetetrazol-(PTZ), and then anxiety-like behavior and cognitive functions were assessed. Tumor-necrosis-factor (TNF)-α and interleukin (IL) 10 were measured in the hippocampus of offspring. Maternal immune activation sex-dependently increased seizure scores in PTZ-treated offspring. Significant increases in anxiety-like behavior, cognitive impairment, and hippocampal TNF-α and IL-10 were also found following maternal immune activation in PTZ-treated offspring. However, there was no sex difference in these behavioral abnormalities in offspring. Environmental enrichment reversed the effects of maternal immune activation on behavioral and inflammatory parameters in PTZ-treated offspring. Overall, the present findings highlight the adverse effects of prenatal maternal immune activation on seizure susceptibility and psychiatric comorbidities in offspring. This study suggests that environmental enrichment may be used as a potential treatment approach for behavioral abnormalities following maternal immune activation in PTZ-treated offspring.

Improvement of autophagy dysfunction as a potential mechanism for environmental enrichment to protect blood-brain barrier in rats with vascular cognitive impairment

Vascular cognitive impairment (VCI) is the second most common cause of dementia after Alzheimer's disease, and the cognitive impairment is one of the common effects of VCI. Unfortunately, it lacks effective therapeutic treatments at present. In our previous study, environmental enrichment (EE), as an early intervention for lifestyle modification, can ameliorate cognitive impairment by attenuating hippocampal blood-brain barrier (BBB) injury in chronic cerebral hypoperfusion (CCH) rats. However, the underlying mechanism remains unclear. Here, we found CCH rats in the standard environment (SE) developed cognitive impairment and BBB damage, which were significantly alleviated with the EE intervention. Meantime, EE improved the autophagy dysfunction caused by CCH in the hippocampus of rats, suggesting that the effect of EE on cognitive function and BBB may be related to the improvement of autophagy pathway.

The Clinical Effect of Electroconvulsive Therapy and Its Relationship with Serum Levels of MMP-9 and CXCL12 in Patients with Mania

INTRODUCTION

Electroconvulsive therapy (ECT) is a non-pharmacological method for the treatment of psychiatric disorders. The precise biochemical mechanism of the effects of ECT is not clear, and since the two factors including matrix metalloproteinase-9 (MMP-9) and stromal cell-derived factor-1 alpha (CXCL12) play an important role in improving nerve damage, the effects of ECT and its relation with serum levels of MMP-9 and CXCL12 in patients with mania were investigated in this study.

METHODS

In this before and after intervention study, the patients with mania, referring to the Qods Hospital in Sanandaj, were selected by the census method during the years 2015-2018. Young's test was performed 24 hrs before and after the first, third, and sixth sessions of ECT. For biochemical analysis, 3 mL of peripheral blood were taken prior to any anesthesia and 6 hrs after the first, third, and sixth sessions. Data were analyzed by two-way ANOVA and Pearson correlation coefficient by using the SPSS16 software.

RESULTS

The results showed a significant decrease in Young's test scores during the first to the sixth session of ECT (P≤0.05). Although the levels of CXCL12 were slightly increased after the sixth course of ECT, they were not significant. Moreover, there were no significant relationship between the Young's test score and the serum levels of both MMP-9 and CXCL12 (P≥0.05).

CONCLUSION

ECT improved patients clinically, but this effect was independent of serum levels of MMP-9 and CXCL12, and possibly other biochemical factors are involved in this pathway.

CXCR7 regulates epileptic seizures by controlling the synaptic activity of hippocampal granule cells

C–X–C motif chemokine receptor 7 (CXCR7), which mediates the immune response in the brain, was recently reported to regulate neurological functions. However, the role of CXCR7 in epilepsy remains unclear. Here, we found that CXCR7 was upregulated in the hippocampal dentate gyrus (DG) of mice subjected to kainic acid (KA)-induced epilepsy and in the brain tissues of patients with temporal lobe epilepsy. Silencing CXCR7 in the hippocampal DG region exerted an antiepileptic effect on the KA-induced mouse model of epilepsy, whereas CXCR7 overexpression produced a seizure-aggravating effect. Mechanistically, CXCR7 selectively regulated N-methyl-d-aspartate receptor (NMDAR)-mediated synaptic neurotransmission in hippocampal dentate granule cells by modulating the cell membrane expression of the NMDAR subunit2A, which requires the activation of extracellular signal-regulated kinase 1/2 (ERK1/2). Thus, CXCR7 may regulate epileptic seizures and represents a novel target for antiepileptic treatments.

Knockdown of the CXCL12/CXCR7 chemokine pathway results in learning deficits and neural progenitor maturation impairment in mice

In adult brain, the chemokine CXCL12 and its receptors CXCR4 and CXCR7 are expressed in neural progenitor and glial cells. Conditional Cxcl12 or Cxcr4 gene knockout in mice leads to severe alterations in neural progenitor proliferation, migration and differentiation. As adult hippocampal neurogenesis is involved in learning and memory processes, we investigated the long-term effects of reduced expression of CXCL12 or CXCR7 in heterozygous Cxcl12^+/- and Cxcr7^+/- animals (KD mice) on hippocampal neurogenesis, neuronal differentiation and memory processing. In Cxcl12 KD mice, Cxcr4 mRNA expression was reduced, whereas Cxcr7 was slightly increased. Conversely, in Cxcr7 KD mice, both Cxcr4 and Cxcl12 mRNA levels were decreased. Moreover, Cxcl12 KD animals showed marked behavioral and learning deficits that were associated with impaired neurogenesis in the hippocampus. Conversely, Cxcr7 KD animals showed mild learning deficits with normal neurogenesis, but reduced cell differentiation, measured with doublecortin immunolabeling. These findings suggested that a single Cxcl12 or Cxcr7 allele might not be sufficient to maintain the hippocampal niche functionality throughout life, and that heterozygosity might represent a susceptibility factor for memory dysfunction progression.

Identifying molecular mediators of environmentally enhanced neurogenesis

Adult hippocampal neurogenesis occurs throughout life and supports healthy brain functions. The production of new neurons decreases with age, and deficiencies in adult neurogenesis are associated with neurodevelopmental and degenerative disease. The rate of neurogenesis is dynamically sensitive to an individual's environmental conditions and experiences, and certain stimuli are known robustly to enhance neurogenesis in rodent models, including voluntary exercise, enriched environment, and electroconvulsive shock. In these models, information about an organism's environment and physiological state are relayed to neurogenic cell types within the hippocampus through a series of tissue and cellular interfaces, ultimately eliciting a neurogenic response from neural stem cells and newborn neurons. Therefore, an understanding of the way that novel genes and proteins act in specific cell types within this circuit-level context is of scientific and therapeutic value. Several well-studied neurotrophic factors have been implicated in environmentally enhanced neurogenesis. This review highlights recently discovered, novel molecular mediators of neurogenesis in response to environmental cues and summarizes the contribution of advanced, large-scale gene expression and function assessment technology to past, present, and future efforts aimed at elucidating cell-type-specific molecular mediators of environmentally enhanced neurogenesis.