Increased protein expression levels of pCREB, BDNF and SDF-1/CXCR4 in the hippocampus may be associated with enhanced neurogenesis induced by environmental enrichment

Dynamic regulation of BDNF gene expression by estradiol and lncRNA HOTAIR

Brain derived neurotrophic factor (BDNF) is a major neurotransmitter that controls growth and maintenance of neurons and its misregulation is linked to neurodegeneration and human diseases. Estradiol (E2) is well-known to regulate the process of differentiation and plasticity of hippocampal neurons. Here we examined the mechanisms of BDNF gene regulation under basal conditions and under stimuli such as E2. Our results demonstrated that BDNF expression is induced by E2 in vitro in HT22 cells (hippocampal neuronal cells) and in vivo (in ovariectomized mouse brain under E2-treatment). Using chromatin immunoprecipitation assay, we demonstrated that estrogen receptors (ERα, ERβ) were enriched at the BDNF promoter in presence of E2. Additionally, ER-coregulators (e.g., CBP/p300, MLL3), histone acetylation, H3K4-trimethylation, and RNA polymerase II levels were also elevated at the BDNF promoter in an E2-dependent manner. Additionally, under the basal conditions (in the absence of E2), the long noncoding RNA HOTAIR and its interacting partners PRC2 and LSD1 complexes binds to the promoter of BDNF and represses its expression. HOTAIR knockdown -relieves the repression resulting in elevation of BDNF expression. Further, levels of HOTAIR-interacting partners, EZH2 and LSD1 were reduced at the BDNF promoter upon HOTAIR-knockdown revealing that HOTAIR plays a regulatory role in BDNF gene expression by modulating promoter histone modifications. Additionally, we showed that E2 induced-BDNF expression is mediated by the displacement of silencing factors, EZH2 and LSD1 at BDNF promoter and subsequent recruitment of active transcription machinery. These results reveal the mechanisms of BDNF gene regulation under the basal condition and in presence of a positive regulator such as E2 in neuronal cells.

Repetitive transcranial magnetic stimulation via the hippocampal brain-derived neurotrophic factor-tyrosine kinase receptor B pathway to affect sexual behavior and neuroplasticity in rapid ejaculation rats

BACKGROUND

Premature ejaculation (PE) is the most prevalent sexual dysfunction among men. Eejaculation involves a complex nervous mechanism in which the ejaculatory centers play a key role in modulating sperm emission. Although treatment possibilities span from psychotherapy to pharmacological approaches, results show inconsistent efficacy. In this context, the emergence of repetitive transcranial magnetic stimulation (rTMS) as a non-invasive neuromodulatory approach represents a compelling avenue for potential therapeutic exploration.

OBJECTIVE

To investigate whether high-frequency transcranial magnetic stimulation can modulate the ejaculatory behavior of rats with rapid ejaculation by altering neurotransmitter levels and neuroplasticity in the hippocampus.

METHODS

Rats have been screened for rapid ejaculation by observing behavioral indices of mating, and subsequently divided into two groups. The intervention group was administered with a 10 Hz rTMS stimulation, whereas the control group received a sham procedure. Upon the delivery of rTMS, we investigated ejaculation latency (EL), the hippocampal 5-hydroxytryptamine (5-HT) concentration, brain-derived neurotrophic factor (BDNF), synaptophysin (SYN), and postsynaptic density protein 95 (PSD95) expressions, as well as BDNF-receptor tyrosine kinase receptor B (TrkB) pathway upregulation.

RESULTS

After 14 days, EL was increased in the intervention group compared with the control group. 5-HT concentration in the hippocampal region was increased, and high-frequency rTMS activated the BDNF and TrkB pathways, including phosphorylation of cAMP response element-binding protein (CREB), and upregulated the transcription and protein expression of SYN, and PSD95.

CONCLUSION

RTMS upregulates BDNF, SYN, and PSD95 expression through activation of the BDNF-TrkB pathway and increases brain 5-hydroxytryptamine thereby regulating neuroplasticity and improving ejaculation.

Electroacupuncture Pretreatment Attenuates Learning Memory Impairment Induced by Repeated Propofol Exposure and Modulates Hippocampal Synaptic Plasticity in Rats

Background

Recurrent propofol anesthesia in the peak of neurodevelopment may lead to learning-memory decline. This study aimed to examine the efficacy of electroacupuncture pretreatment in ameliorating the aforementioned learning memory deficits and to explore its underlying mechanisms in a rat model of repeated propofol exposure.

Methods

10-day-old Sprague Dawley rats were randomly assigned to five groups: the control, fat emulsion, propofol, electroacupuncture pretreatment and electroacupuncture pretreatment combined with propofol groups. The electroacupuncture pretreatment involved three consecutive daily sessions, while propofol was received intraperitoneally once daily for five days. Following the modeling period, the rats' learning-memory performance was assessed using the New Novel Arm Y-maze, New Object Recognition, and Morris Water Maze. The Nissl staining method was used to observe the development of hippocampal neurons, while Golgi staining was employed to observe hippocampal synaptic development.

Results

The electroacupuncture pretreatment significantly attenuated the learning and memory impairment induced by recurring propofol exposure in rats. Additionally, it facilitated the development of hippocampal neurons and synaptic plasticity in the hippocampus. Immunofluorescence and Western Blot analyses were conducted to detect the expression of proteins related to apoptosis, learning memory, and synaptic plasticity. In the propofol group, the pro-apoptotic factors Caspase-3 and Bax was up-regulated, while the anti-apoptotic factor Bcl-2 was down-regulated, as compared to the blank group. Additionally, the phosphorylated cAMP-response element binding protein (pCREB), brain-derived neurotrophic factor (BDNF), synaptophysin, and growth associated protein-43 (GAP-43) was significantly decreased. In contrast, the electroacupuncture pretreatment combined with propofol group exhibited decreased the Caspase-3 and Bax and increased the Bcl-2, as compared to the propofol group, meanwhile, the pCREB, BDNF, Synaptophysin and GAP-43 was increased.

Conclusion

Our findings indicate that electroacupuncture pretreatment can alleviate the learning and memory impairment induced by recurring propofol exposure in rats. This is achieved by enhancing hippocampal synaptic plasticity, activating the pCREB/BDNF pathway and inhibiting neuronal apoptosis.

Environmental Enrichment Increased Bdnf Transcripts in the Prefrontal Cortex: Implications for an Epigenetically Controlled Mechanism

Environmental enrichment (EE) is a condition characterized by its complexity regarding social contact, exposure to novelty, tactile stimuli and voluntary exercise, also is considered as a eustress model. The impact of EE on brain physiology and behavioral outcomes may be at least partly underpinned by mechanisms involving the modulation of the brain-derived neurotrophic factor (BDNF), but the connection between specific Bdnf exon expression and their epigenetic regulation remain poorly understood. This study aimed to dissect the transcriptional and epigenetic regulatory effect of 54-day exposure to EE on BDNF by analysing individual BDNF exons mRNA expression and the DNA methylation profile of a key transcriptional regulator of the Bdnf gene, exon IV, in the prefrontal cortex (PFC) of C57BL/6 male mice (sample size = 33). Bdnf exons II, IV, VI and IX mRNA expression were upregulated and methylation levels at two CpG sites of exon IV were reduced in the PFC of EE mice. As deficit in exon IV expression has also been causally implicated in stress-related psychopathologies, we also assessed anxiety-like behavior and plasma corticosterone levels in these mice to determine any potential correlation. However, no changes were observed in EE mice. The findings may suggest an EE-induced epigenetic control of BDNF exon expression via a mechanism involving exon IV methylation. The findings of this study contribute to the current literature by dissecting the Bdnf gene topology in the PFC where transcriptional and epigenetic regulatory effect of EE takes place.

The Cannabinoids, CBDA and THCA, Rescue Memory Deficits and Reduce Amyloid-Beta and Tau Pathology in an Alzheimer’s Disease-like Mouse Model

Most studies related to hemp are focused on Cannabidiol (CBD) and Tetrahydrocannabinol (THC); however, up to 120 types of phytocannabinoids are present in hemp. Hemp leaves contain large amounts of Cannabidiolic acid (CBDA) and Tetrahydrocannabinolic acid (THCA), which are acidic variants of CBD and THC and account for the largest proportion of CBDA. In recent studies, CBDA exhibited anti-hyperalgesia and anti-inflammatory effects. THCA also showed anti-inflammatory and neuroprotective effects that may be beneficial for treating neurodegenerative diseases. CBDA and THCA can penetrate the blood–brain barrier (BBB) and affect the central nervous system. The purpose of this study was to determine whether CBDA and THCA ameliorate Alzheimer’s disease (AD)-like features in vitro and in vivo. The effect of CBDA and THCA was evaluated in the Aβ1–42-treated mouse model. We observed that Aβ1–42-treated mice had more hippocampal Aβ and p-tau levels, pathological markers of AD, and loss of cognitive function compared with PBS-treated mice. However, CBDA- and THCA-treated mice showed decreased hippocampal Aβ and p-tau and superior cognitive function compared with Aβ1–42-treated mice. In addition, CBDA and THCA lowered Aβ and p-tau levels, alleviated calcium dyshomeostasis, and exhibited neuroprotective effects in primary neurons. Our results suggest that CBDA and THCA have anti-AD effects and mitigate memory loss and resilience to increased hippocampal Ca2+, Aβ, and p-tau levels. Together, CBDA and THCA may be useful therapeutic agents for treating AD.

CXCR4 knockout induces neuropathological changes in the MPTP-lesioned model of Parkinson's disease

C-X-C chemokine receptor type 4 (CXCR4) is highly expressed in Parkinson's disease (PD) mice's brains and is related to astrocyte signaling and microglial activation. This makes CXCR4 related to neuroinflammation and also makes CXCR4 considered to be the PD development mechanism and possible therapeutic targets. Therefore, it is worth studying the effect of CXCR4 on neuropathological changes and its potential therapeutic value for PD. This study aimed to investigate the effect of CXCR4 knockout on neuropathological changes in the mouse model of PD and its mechanism. In this study, CXCR4-WT and CXCR4^+/- C57BL mice were used to make Parkinson's model. Behavioral experiments, dopaminergic neuron markers, neuroinflammation, and blood-brain barrier damage were detected to verify the effect of CXCR4 knockout on neuropathological changes. CXCR4 knockout improved the behavioral results and tyrosine hydroxylase (TH) expression of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mice. In the substantia nigra (SN) area of the brain of PD mouse model, the number of Iba1-positive (p = 0.0004) and GFAP-positive cells (p = 0.0349) was significantly lower in CXCR4 knockout group than CXCR4-WT group. CXCR4 knockout reduced MPTP-induced infiltration of peripheral immune cells and the expression of pro-inflammatory cytokines. CXCR4 knockout also protected blood-brain barrier (BBB) from MPTP-induced damage. In conclusion, CXCR4 knockout inhibits the degeneration of dopamine neurons, microglial and astrocyte activation, neuroinflammation, and BBB damages in the MPTP-lesioned PD mice.

Chronic haloperidol administration downregulates select BDNF transcript and protein levels in the dorsolateral prefrontal cortex of rhesus monkeys

Post-mortem studies in the prefrontal cortex and hippocampal formation from schizophrenia patients have revealed significant disruptions in the expression molecules associated with cytoarchitecture, synaptic structure, function, and plasticity, known to be regulated in part by brain derived neurotrophic factor (BDNF). Interestingly, several studies using postmortem brain tissue from individuals diagnosed with schizophrenia have revealed a significant reduction in BDNF mRNA and protein levels in the dorsolateral prefrontal cortex (DLPFC), hippocampus and related areas; however, differentiating the effects of illness from antipsychotic history has remained difficult. We hypothesized that chronic antipsychotic treatment may contribute to the altered BDNF mRNA and protein expression observed in post-mortem brains of individuals diagnosed with schizophrenia. To address the influence of antipsychotic administration on BDNF expression in the primate brain, rhesus monkeys orally administered haloperidol, clozapine, or vehicle twice daily for 180 days. We found BDNF splice variants 4 and 5 in the DLPFC and variant 2 in the EC were significantly down-regulated following chronic administration of haloperidol. In addition, proBDNF and mature BDNF expression in the DLPFC, but not the EC, were significantly reduced. Based on the known regulation of BDNF expression by BDNF-AS, we assessed the expression of this lncRNA and found expression was significantly upregulated in the DLPFC, but not EC. The results of the present study provide evidence of haloperidol-induced regulation of BDNF mRNA and protein expression in the DLFPC and suggest an important role for BDNF-AS in this regulation. Given the role of BDNF in synaptic plasticity, neuronal survival and maintenance, aberrant expression induced by haloperidol likely has significant ramifications for neuronal populations and circuits in primate cortex.

The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment (EE) is an environmental paradigm encompassing sensory, cognitive, and physical stimulation at a heightened level. Previous studies have reported the beneficial effects of EE in the brain, particularly in the hippocampus. EE improves cognitive function as well as ameliorates depressive and anxiety-like behaviors, making it a potentially effective neuroprotective strategy against neurodegenerative diseases such as Alzheimer's disease (AD). Here, we summarize the current evidence for EE as a neuroprotective strategy as well as the potential molecular pathways that can explain the effects of EE from a biochemical perspective using animal models. The effectiveness of EE in enhancing brain activity against neurodegeneration is explored with a view to differences present in early and late life EE exposure, with its potential application in human being discussed. We discuss EE as one of the non pharmacological approaches in preventing or delaying the onset of AD for future research.

BDNF and its Role in the Alcohol Abuse Initiated During Early Adolescence: Evidence from Preclinical and Clinical Studies

Brain-derived neurotrophic factor (BDNF) is a crucial brain signaling protein that is integral to many signaling pathways. This neurotrophin has shown to be highly involved in brain plastic processes such as neurogenesis, synaptic plasticity, axonal growth, and neurotransmission, among others. In the first part of this review, we revise the role of BDNF in different neuroplastic processes within the central nervous system. On the other hand, its deficiency in key neural circuits is associated with the development of psychiatric disorders, including alcohol abuse disorder. Many people begin to drink alcohol during adolescence, and it seems that changes in BDNF are evident after the adolescent regularly consumes alcohol. Therefore, the second part of this manuscript addresses the involvement of BDNF during adolescent brain maturation and how this process can be negatively affected by alcohol abuse. Finally, we propose different BNDF enhancers, both behavioral and pharmacological, which should be considered in the treatment of problematic alcohol consumption initiated during the adolescence.

The Preventive and Therapeutic Effect of Repetitive Transcranial Magnetic Stimulation on Radiation-Induced Brain Injury in Mice

PURPOSE

To clarify the preventive and therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) on brain injury induced by X-ray cranial irradiation, preliminarily identify the mechanism and provide a novel clinical approach for the prevention and treatment of radiation-induced brain injury (RBI).

MATERIALS AND METHODS

Male C57BL/6 mice were randomly divided into the sham group, large fractionated dose (5 Gy ×4 d) group, large fractionated dose + rTMS (5 Gy ×4 d + rTMS) group, conventional fractionated dose (2 Gy ×10 d) group and conventional fractionated dose + rTMS (2 Gy ×10 d + rTMS) group. After cranial irradiation and rTMS, behavioral experiments, morphological staining and molecular biology experiments were performed. We further determined the mechanism of rTMS on the prevention and treatment of RBI, including changes in hippocampal neuronal apoptosis, neural stem cell (NSC) proliferation and differentiation, and neuronal synaptic plasticity.

RESULTS

rTMS alleviated the negative effects of cranial radiation on the general health of mice and promoted their recovery. rTMS ameliorated the impairment of spatial learning and memory induced by cranial radiation, and this beneficial effect was more robust in the conventional fractionated dose group than the large fractionated dose group. Moreover, rTMS alleviated the alterations in hippocampal structure and neuronal death and had preventive and therapeutic effects against RBI. In addition, rTMS reduced hippocampal cell apoptosis, promoted NSC proliferation and differentiation in the hippocampus after cranial irradiation, and enhanced neuronal synaptic plasticity in the hippocampus. Subsequent studies showed that rTMS upregulated the expression of learning- and memory-related proteins.

CONCLUSION

rTMS could alleviate learning and memory impairment caused by RBI, and the preventive and therapeutic effects of rTMS were better for the conventional fraction radiation paradigms.

Hypobaric Hypoxia Induces Deficits in Adult Neurogenesis and Social Interaction via Cyclooxygenase-1/ EP1 Receptor Pathway Activating NLRP3 Inflammasome

Low oxygen environments, like hypobaric hypoxia (HH), are common nodes in a number of diseases characterized by neuroinflammation, which is detrimental to the structural and functional aspects of hippocampal circuitry. Hypoxic conditions lead to elevation of inflammasome-mediated inflammation that may contribute to cognitive deficits. However, a systematic investigation of the impact of inflammasome-mediated neuroinflammation on the components of neurogenic niche during HH remains to be elusive. Cerebral hypoxia was induced in adult male Sprague Dawley rats via decreasing partial pressure of oxygen. The effect of HH (1, 3, and 7 days at 25,000 ft) on social memory, anxiety, adult neurogenesis, and NLRP3- (NLR family pyrin domain containing 3) mediated neuroinflammation in the dentate gyrus (DG) was explored in detail. Furthermore, we explored the therapeutic efficacy of cyclooxygenase-1 inhibitor (valeryl salicylate, 5 mg/kg/day, i.p.) and EP1 receptor (EP1R) antagonist (SC19220, 1 mg/kg/day, i.p.) on HH-induced deficits. Seven days of HH exposure induced alteration in social and anxiety-like behavior along with perturbation in adult neurogenesis. Elevation in NLRP3, caspase-1, and IL-1β levels was observed during HH from day 1. A notable increase in the COX-1/EP1R pathway in activated glial cells in DG was evident during HH. COX-1 inhibitor and EP1R antagonist mitigated the detrimental effects of HH on social memory, adult neurogenesis via blunting NLRP3-mediated inflammation. Our data showed induction of the COX-1/EP1R pathway in the glial cells, which is detrimental to neurogenesis and social memory, opening up the possibility that the COX-1/EP1R pathway is a plausible target for inflammasome-related neurogenesis impairments.

Environmental Enrichment Effects on the Brain-Derived Neurotrophic Factor Expression in Healthy Condition, Alzheimer's Disease, and Other Neurodegenerative Disorders

Brain-derived neurotrophic factor (BDNF), a protein belonging to the neurotrophin family, is known to be heavily involved in synaptic plasticity processes that support brain development, post-lesion regeneration, and cognitive performances, such as learning and memory. Evidence indicates that BDNF expression can be epigenetically regulated by environmental stimuli and thus can mediate the experience-dependent brain plasticity. Environmental enrichment (EE), an experimental paradigm based on the exposure to complex stimulations, constitutes an efficient means to investigate the effects of high-level experience on behavior, cognitive processes, and neurobiological correlates, as the BDNF expression. In fact, BDNF exerts a key role in mediating and promoting EE-induced plastic changes and functional improvements in healthy and pathological conditions. This review is specifically aimed at providing an updated framework of the available evidence on the EE effects on brain and serum BDNF levels, by taking into account both changes in protein expression and regulation of gene expression. A further purpose of the present review is analyzing the potential of BDNF regulation in coping with neurodegenerative processes characterizing Alzheimer's disease (AD), given BDNF expression alterations are described in AD patients. Moreover, attention is also paid to EE effects on BDNF expression in other neurodegenerative disease. To investigate such a topic, evidence provided by experimental studies is considered. A deeper understanding of environmental ability in modulating BDNF expression in the brain may be fundamental in designing more tuned and effective applications of complex environmental stimulations as managing approaches to AD.

Characterization of nonmotor behavioral impairments and their neurochemical mechanisms in the MitoPark mouse model of progressive neurodegeneration in Parkinson's disease

Mitochondrial dysfunction has been implicated as a key player in the pathogenesis of Parkinson's disease (PD). The MitoPark mouse, a transgenic mitochondrial impairment model developed by specific inactivation of TFAM in dopaminergic neurons, spontaneously exhibits progressive motor deficits and neurodegeneration, recapitulating several features of PD. Since nonmotor symptoms are now recognized as important features of the prodromal stage of PD, we comprehensively assessed the clinically relevant motor and nonmotor deficiencies from ages 8-24 wk in both male and female MitoPark mice and their littermate controls. As expected, motor deficits in MitoPark mice began around 12-14 wk and became severe by 16-24 wk. Interestingly, MitoPark mice exhibited olfactory deficits in the novel and social scent tests as early as 10-12 wk as compared to age-matched littermate controls. Additionally, male MitoPark mice showed spatial memory deficits before female mice, beginning at 8 wk and becoming most severe at 16 wk, as determined by the Morris water maze. MitoPark mice between 16 and 24 wk spent more time immobile in forced swim and tail suspension tests, and made fewer entries into open arms of the elevated plus maze, indicating a depressive and anxiety-like phenotype, respectively. Importantly, depressive behavior as determined by immobility in forced swim test was reversible by antidepressant treatment with desipramine. Neurochemical and mechanistic studies revealed significant changes in CREB phosphorylation, BDNF, and catecholamine levels as well as neurogenesis in key brain regions. Collectively, our results indicate that MitoPark mice progressively exhibit deficits in olfactory discrimination, cognitive learning and memory, and anxiety- and depression-like behaviors as well as key neurochemical signaling associated with nonmotor deficits in PD. Thus, MitoPark mice can serve as an invaluable model for studying nonmotor deficits in addition to studying the motor deficits related to pathology in PD.

Downregulated GPR30 expression in the epileptogenic foci of female patients with focal cortical dysplasia type IIb and tuberous sclerosis complex is correlated with 18 F-FDG PET-CT values

Focal cortical dysplasia type IIb (FCDIIb) and tuberous sclerosis complex (TSC) are typical causes of developmental delay and refractory epilepsy. G‐protein‐coupled receptor 30 (GPR30) is a specific estrogen receptor that is critical in neurodevelopment, neuroinflammation, and neuronal excitability, suggesting that it plays a potential role in the epilepsy of patients with FCDIIb and TSC. Therefore, we investigated the role of GPR30 in patients with FCDIIb and TSC. We found that the expression of GPR30 and its downstream protein kinase A (PKA) pathway were decreased and negatively correlated with seizure frequency in female patients with FCDIIb and TSC, but not in male patients. GPR30 was widely distributed in neurons, astrocytes, and microglia, and its downregulation was especially notable in microglia. The GPR30 agonist G‐1 increased the expression of PKA and p‐PKA in cultured cortical neurons, and the GPR30 antagonist G‐15 exhibited the opposite effects of G‐1. The NF‐κB signaling pathway was also activated in the specimens of female patients with FCDIIb and TSC, and was regulated by G‐1 and G‐15 in cultured cortical neurons. We also found that GPR30 regulated cortical neuronal excitability by altering the frequency of spontaneous excitatory postsynaptic currents and the expression of NR2A/B. Further, the relationship between GPR30 and glycometabolism was evaluated by analyzing the correlations between GPR30 and ¹⁸F‐FDG PET‐CT values (standardized uptake values, SUVs). Positive correlations between GPR30 and SUVs were found in female patients, but not in male patients. Intriguingly, GPR30 expression and SUVs were significantly decreased in the epileptogenic tubers of female TSC patients, and ROC curves indicated that SUVs could predict the localization of epileptogenic tubers. Taken together, our results suggest a potential protective effect of GPR30 in the epileptogenesis of female patients with FCDIIb and TSC.

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.

CX3CL1 rs170364 gene polymorphism has a protective effect against major depression by enhancing its transcriptional activity

Studies have shown that adult hippocampal neurogenesis may be a cause of depression. CX3CL1 is a chemokine that plays an important role in adult neurogenesis. This study aimed to investigate the relationship between CX3CL1 polymorphisms (rs170364) and the risk of depression. A case-control study of 502 patients with major depression and 504 gender-matched and age-matched healthy controls was performed. All subjects were recruited from the Chinese Han population. Next-generation sequencing was used to genotype the CX3CL1 rs170364 locus. In addition, the effect of the rs170364 polymorphism on transcription of CX3CL1 was investigated through the use of luciferase reporter constructs and in vitro analysis in SH-SY5Y cells. Our results demonstrated that the T allele and GT + TT genotype of the CX3CL1 rs170364 locus were associated with a reduced risk of major depression. Subgroup analysis found that this significant association was consistently found in females but not in males. In vitro experiments found that the rs170364 mutation enhanced the transcriptional activity of CX3CL1. These results suggest that T allele and GT + TT genotypes of the CX3CL1 rs170364 locus may be a protective factor against the onset of depression in the Chinese Han population, especially in females. SNP rs170364 enhances the transcriptional activity of CX3CL1.

Neurobehavioral Effects of Restricted and Unpredictable Environmental Enrichment in Rats

To study how motivational factors modulate experience-dependent neurobehavioral plasticity, we modify a protocol of environmental enrichment (EE) in rats. We assumed that the benefits derived from EE might vary according to the level of incentive salience attributed to it. To enhance the rewarding properties of EE, access to the EE cage varied randomly from 2 to 48 h for 30 days (REE). The REE group was enriched only 50% of the time and was compared to standard housing and continuous EE (CEE) groups. As behavioral readout, we analyzed the spontaneous activity and the ultrasonic vocalizations (USVs) within the EE cage weekly, and in the open field test at the end of the experiment. In the cage, REE increased the utilization of materials, physical activity, and the rate of appetitive USVs. In the OF, the CEE-induced enhancements in novelty habituation and social signaling were equaled by the REE. At the neural level, we measured the expression of genes related to neural plasticity and epigenetic regulations in different brain regions. In the dorsal striatum and hippocampus, REE upregulated the expression of the brain-derived neurotrophic factor, its tropomyosin kinase B receptor, and the DNA methyltransferase 3A. Altogether, our results suggest that the higher activity within the cage and the augmented incentive motivation provoked by the REE boosted its neurobehavioral effects equaling or surpassing those observed in the CEE condition. As constant exposures to treatments or stimulating environments are virtually impossible for humans, restricted EE protocols would have greater translational value than traditional ones.

Interaction Between Neurogenic Stimuli and the Gene Network Controlling the Activation of Stem Cells of the Adult Neurogenic Niches, in Physiological and Pathological Conditions

In the adult mammalian brain new neurons are continuously generated throughout life in two niches, the dentate gyrus of the hippocampus and the subventricular zone. This process, called adult neurogenesis, starts from stem cells, which are activated and enter the cell cycle. The proliferative capability of stem cells progressively decreases during aging. The population of stem cells is generally quiescent, and it is not clear whether the potential for stem cells to expand is limited, or whether they can expand and then return to quiescence, remaining available for further activation. Certain conditions may deregulate stem cells quiescence and self-renewal. In fact we discuss the possibility of activation of stem cells by neurogenic stimuli as a function of the intensity of the stimulus (i.e., whether this is physiological or pathological), and of the deregulation of the system (i.e., whether the model is aged or carrying genetic mutations in the gene network controlling quiescence). It appears that when the system is aged and/or carrying mutations of quiescence-maintaining genes, preservation of the quiescent state of stem cells is more critical and stem cells can be activated by a neurogenic stimulus which is ineffective in normal conditions. Moreover, when a neurogenic stimulus is in itself a cause of brain damage (e.g., kainic acid treatment) the activation of stem cells occurs bypassing any inhibitory control. Plausibly, with strong neurogenic stimuli, such as kainic acid injected into the dentate gyrus, the self-renewal capacity of stem cells may undergo rapid exhaustion. However, the self-renewal capability of stem cells persists when normal stimuli are elicited in the presence of a mutation of one of the quiescence-maintaining genes, such as p16Ink4a, p21Cip1 or Btg1. In this case, stem cells become promptly activated by a neurogenic stimulus even during aging. This indicates that stem cells retain a high proliferative capability and plasticity, and suggests that stem cells are protected against the response to stimulus and are resilient to exhaustion. It will be interesting to assess at which functional degree of deregulation of the quiescence-maintaining system, stem cells will remain responsive to repeated neurogenic stimuli without undergoing exhaustion of their pool.

Axon regeneration induced by environmental enrichment- epigenetic mechanisms

Environmental enrichment is known to be beneficial for cognitive improvement. In many animal models of neurological disorders and brain injury, EE has also demonstrated neuroprotective benefits in neurodegenerative diseases and in improving recovery after stroke or traumatic brain injury. The exact underlying mechanism for these phenomena has been unclear. Recent findings have now indicated that neuronal activity elicited by environmental enrichment induces Ca²⁺ influx in dorsal root ganglion neurons results in lasting enhancement of CREB-binding protein-mediated histone acetylation. This, in turn, increases the expression of pro-regeneration genes and promotes axonal regeneration. This mechanism associated with neuronal activity elicited by environmental enrichment-mediated pathway is one of several epigenetic mechanisms which modulate axon regeneration upon injury that has recently come to light. The other prominent mechanisms, albeit not yet directly associated with environmental enrichment, include DNA methylation/demethylation and N⁶-methyladenosine modification of transcripts. In this brief review, I highlight recent work that has shed light on the epigenetic basis of environmental enrichment-based axon regeneration, and discuss the mechanism and pathways involved. I further speculate on the implications of the findings, in conjunction with the other epigenetic mechanisms, that could be harness to promote axon regeneration upon injury.

Effect of stromal cell-derived factor-1/CXCR4 axis in neural stem cell transplantation for Parkinson's disease

Previous studies have shown that neural stem cell transplantation has the potential to treat Parkinson's disease, but its specific mechanism of action is still unclear. Stromal cell-derived factor-1 and its receptor, chemokine receptor 4 (CXCR4), are important regulators of cell migration. We speculated that the CXCR4/stromal cell-derived factor 1 axis may be involved in the therapeutic effect of neural stem cell transplantation in the treatment of Parkinson's disease. A Parkinson's disease rat model was injected with 6-hydroxydopamine via the right ascending nigrostriatal dopaminergic pathway, and then treated with 5 μL of neural stem cell suspension (1.5 × 10⁴/L) in the right substantia nigra. Rats were intraperitoneally injected once daily for 3 days with 1.25 mL/kg of the CXCR4 antagonist AMD3100 to observe changes after neural stem cell transplantation. Parkinson-like behavior in rats was detected using apomorphine-induced rotation. Immunofluorescence staining was used to determine the immunoreactivity of tyrosine hydroxylase, CXCR4, and stromal cell-derived factor-1 in the brain. Using quantitative real-time polymerase chain reaction, the mRNA expression of stromal cell-derived factor-1 and CXCR4 in the right substantia nigra were measured. In addition, western blot assays were performed to analyze the protein expression of stromal cell-derived factor-1 and CXCR4. Our results demonstrated that neural stem cell transplantation noticeably reduced apomorphine-induced rotation, increased the mRNA and protein expression of stromal cell-derived factor-1 and CXCR4 in the right substantia nigra, and enhanced the immunoreactivity of tyrosine hydroxylase, CXCR4, and stromal cell-derived factor-1 in the brain. Injection of AMD3100 inhibited the aforementioned effects. These findings suggest that the stromal cell-derived factor-1/CXCR4 axis may play a significant role in the therapeutic effect of neural stem cell transplantation in a rat model of Parkinson's disease. This study was approved by the Animal Care and Use Committee of Kunming Medical University, China (approval No. SYXKK2015-0002) on April 1, 2014.

Effects of CXCR7-neutralizing antibody on neurogenesis in the hippocampal dentate gyrus and cognitive function in the chronic phase of cerebral ischemia

Stromal cell-derived factor-1 and its receptor CXCR4 are essential regulators of the neurogenesis that occurs in the adult hippocampal dentate gyrus. However, the effects of CXCR7, a new atypical receptor of stromal cell-derived factor-1, on hippocampal neurogenesis after a stroke remain largely unknown. Our study is the first to investigate the effect of a CXCR7-neutralizing antibody on neurogenesis in the dentate gyrus and the associated recovery of cognitive function of rats in the chronic stage of cerebral ischemia. The rats were randomly divided into sham, sham + anti-CXCR7, ischemia and ischemia + anti-CXCR7 groups. Endothelin-1 was injected in the ipsilateral motor cortex and striatum to induce focal cerebral ischemia. Sham group rats were injected with saline instead of endothelin-1 via intracranial injection. Both sham and ischemic rats were treated with intraventricular infusions of CXCR7-neutralizing antibodies for 6 days 1 week after surgery. Immunofluorescence staining with doublecortin, a marker for neuronal precursors, was performed to assess the neurogenesis in the dentate gyrus. We found that anti-CXCR7 antibody infusion enhanced the proliferation and dendritic development of doublecortin-labeled cells in the dentate gyrus in both ischemic and sham-operated rats. Spatial learning and memory functions were assessed by Morris water maze tests 30–32 days after ischemia. CXCR7-neutralizing antibody treatment significantly reduced the escape latency of the spatial navigation trial and increased the time spent in the target quadrant of spatial probe trial in animals that received ischemic insult, but not in sham operated rats. These results suggest that CXCR7-neutralizing antibody enhances the neurogenesis in the dentate gyrus and improves the cognitive function after cerebral ischemia in rats. All animal experimental protocols and procedures were approved by the Institutional Animal Care and Use Committee of China Medical University (CMU16089R) on December 8, 2016.

Therapeutic efficacy of environmental enrichment for substance use disorders

Addiction to drug and alcohol is regarded as a major health problem worldwide for which available treatments show limited effectiveness. The biggest challenge remains to enhance the capacities of interventions to reduce craving, prevent relapse and promote long-term recovery. New strategies to meet these challenges are being explored. Findings from preclinical work suggest that environmental enrichment (EE) holds therapeutic potential for the treatment of substance use disorders, as demonstrated in a number of animal models of drug abuse. The EE intervention introduced after drug exposure leads to attenuation of compulsive drug taking, attenuation of the rewarding (and reinforcing) effects of drugs, reductions in control of behavior by drug cues, and, very importantly, relapse prevention. Clinical work also suggests that multidimensional EE interventions (involving physical activity, social interaction, vocational training, recreational and community involvement) might produce similar therapeutic effects, if implemented continuously and rigorously. In this review we survey preclinical and clinical studies assessing the efficacy of EE as a behavioral intervention for substance use disorders and address related challenges. We also review work providing empirical evidence for EE-induced neuroplasticity within the mesocorticolimbic system that is believed to contribute to the seemingly therapeutic effects of EE on drug and alcohol-related behaviors.

High Frequency Repetitive Transcranial Magnetic Stimulation Alleviates Cognitive Impairment and Modulates Hippocampal Synaptic Structural Plasticity in Aged Mice

Normal aging is accompanied by hippocampus-dependent cognitive impairment, which is a risk factor of Alzheimer’s disease. This study aims to investigate the effect of high frequency-repetitive transcranial magnetic stimulation (HF-rTMS) on hippocampus-dependent learning and memory in aged mice and explore its underlying mechanisms. Forty-five male Kunming mice (15 months old) were randomly divided into three groups: aged sham, 5 Hz rTMS, and 25 Hz rTMS. Two sessions of 5 Hz or 25 Hz rTMS comprising 1,000 pulses in 10 trains were delivered once a day for 14 consecutive days. The aged sham group was treated by the reverse side of the coil. In the adult sham group, 15 male Kunming mice (3 months old) were treated the same way as the aged sham group. A Morris water maze (MWM) was conducted following the stimulation, and synaptic ultrastructure was observed through a transmission electron microscope. HF-rTMS improved spatial learning and memory impairment in the aged mice, and 5 Hz was more significant than 25 Hz. Synaptic plasticity-associated gene profiles were modified by HF-rTMS, especially neurotrophin signaling pathways and cyclic adenosine monophosphate response element binding protein (CREB) cofactors. Compared to the aged sham group, synaptic plasticity-associated proteins, i.e., synaptophysin (SYN) and postsynaptic density (PSD)-95 were increased; brain-derived neurotrophic factor (BDNF) and phosphorylated CREB (pCREB) significantly increased after the 5 Hz HF-rTMS treatment. Collectively, our results suggest that HF-rTMS ameliorated cognitive deficits in naturally aged mice. The 5 Hz rTMS treatment significantly enhanced synaptic structural plasticity and activated the BDNF/CREB pathway in the hippocampus.

The role of the GABAA receptor Alpha 1 subunit in the ventral hippocampus in stress resilience

Pre-pubertal stress increases post-traumatic stress disorder (PTSD) susceptibility. We have previously demonstrated that enriched environment (EE) intervention immediately after pre-pubertal stress protects from the effects of trauma in adulthood. Here, we examined whether exposure to EE would also be beneficial if applied after exposure to trauma in adulthood. We have recently shown that exposure to juvenile stress and under-water trauma (UWT) is associated with increased expression of GABA_A receptor subunit α1 in the ventral hippocampus. However, differentiating between affected and unaffected individuals, this increased expression was confined to stress-exposed, behaviorally unaffected individuals, suggesting upregulation of α1 expression as a potential mechanism of resilience. We now examined whether EE-induced resilience renders increased expression of α1 in the ventral hippocampus redundant when facing a trauma later in life. Adult rats were exposed to UWT, with pre-exposure to juvenile stress, and tested in the open field and elevated plus maze paradigms four weeks later. EE exposure during juvenility prevented pre-pubertal stress-induced vulnerability, but not if performed following UWT in adulthood. Furthermore, juvenile EE exposure prevented the trauma-associated increase in α1 expression levels. Our findings emphasize the importance of early interventions in order to reduce the likelihood of developing psychopathologies in adulthood.

Can the effects of environmental enrichment modulate BDNF expression in hippocampal plasticity? A systematic review of animal studies

BACKGROUND AND AIM

Environmental enrichment (EE) can be related to changes in the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus of adult rodents. Exposure to EE may also induce neurogenesis in the dentate gyrus (DG). The aim of this systematic review was to analyze the current literature on the correlation between neurogenesis and BDNF expression in the hippocampal DG region resulting from exposure to EE, which is associated with changes in memory, in rodents.

METHODS

Bibliographic searches of the Medline/PubMed and ScienceDirect databases were carried out, and 334 studies were found. A predefined protocol was used and registered on PROSPERO, and 32 studies were included for qualitative synthesis. The PRISMA was used to report this systematic review.

RESULTS

Most of the included studies showed that there is little evidence in the literature demonstrating that memory changes resulting from EE are dependent on BDNF expression and that there is an induction of neurogenesis in the hippocampal DG. However, the observed increase in molecular expression levels and cell proliferation is dependent on the age, the timing and duration of exposure to EE. Regarding the methodological quality of the studies, the majority presented a risk of bias due to the high variability in the age of the animals.

CONCLUSION

There are few studies in the literature that correlate the molecular and cellular mechanisms involved in neurogenesis in the hippocampal DG with BDNF expression in this region in rodents exposed to EE; however, there are other factors that can modulate this neurogenesis.

Coriolus versicolor biomass increases dendritic arborization of newly-generated neurons in mouse hippocampal dentate gyrus

Brain cognitive reserve refers to the ability of the brain to manage different challenges that arise throughout life, making it resilient to neuropathology. Hippocampal adult neurogenesis has been considered to be a relevant contributor for brain cognitive reserve and brain plasticity. Coriolus versicolor (CV), a common healthful mushroom, has been receiving increasing attention by its antitumoral, anti-inflammatory, antioxidant, antibacterial, and immunomodulatory properties, including in the hippocampus. Herein, we evaluated whether CV biomass oral administration for 2.5 months enhances hippocampal neurogenic reserve under normal/physiological conditions, by quantifying hippocampal dentate gyrus (DG) granular cell layer (GCL) and subgranular zone (SGZ) volumes, proliferation, number and dendritic complexity features of hippocampal newly-generated neurons. We also analyzed β-catenin levels in DG newly-generated immature neurons, because it plays a major role in neurogenesis. Although no differences were observed in the volume of GCL and SGZ layers, in proliferation and in the number of newly-generated neurons of controls and CV-administered mice, we found that CV administration promotes a significant increase in dendritic length and branching and total dendritic volume of immature neurons, suggesting a positive effect of oral CV administration in the hippocampal neurogenic reserve. We also observed that β-catenin levels are increased both in the nucleus and cytoplasm of DG immature neurons, suggesting that Wnt/β-catenin signalling may play an important role in the CV positive effect on the differentiation of these cells. These data unveil a so far unexplored neurogenic potential of CV supplementation, which emerges as a possible preventive strategy for different neurological conditions.

A Comprehensive Database and Analysis Framework To Incorporate Multiscale Data Types and Enable Integrated Analysis of Bioactive Polyphenols

The development of a given botanical preparation for eventual clinical application requires extensive, detailed characterizations of the chemical composition, as well as the biological availability, biological activity, and safety profiles of the botanical. These issues are typically addressed using diverse experimental protocols and model systems. Based on this consideration, in this study we established a comprehensive database and analysis framework for the collection, collation, and integrative analysis of diverse, multiscale data sets. Using this framework, we conducted an integrative analysis of heterogeneous data from in vivo and in vitro investigation of a complex bioactive dietary polyphenol-rich preparation (BDPP) and built an integrated network linking data sets generated from this multitude of diverse experimental paradigms. We established a comprehensive database and analysis framework as well as a systematic and logical means to catalogue and collate the diverse array of information gathered, which is securely stored and added to in a standardized manner to enable fast query. We demonstrated the utility of the database in (1) a statistical ranking scheme to prioritize response to treatments and (2) in depth reconstruction of functionality studies. By examination of these data sets, the system allows analytical querying of heterogeneous data and the access of information related to interactions, mechanism of actions, functions, etc., which ultimately provide a global overview of complex biological responses. Collectively, we present an integrative analysis framework that leads to novel insights on the biological activities of a complex botanical such as BDPP that is based on data-driven characterizations of interactions between BDPP-derived phenolic metabolites and their mechanisms of action, as well as synergism and/or potential cancellation of biological functions. Out integrative analytical approach provides novel means for a systematic integrative analysis of heterogeneous data types in the development of complex botanicals such as polyphenols for eventual clinical and translational applications.

Enriched environment improves behavioral performance and attenuates inflammatory response induced by TNF-α in healthy adult mice

Several studies have demonstrated the neuroprotective effect of enriched environment (EE) and its positive effect on cognitive performance in pathological conditions, such as neurodegenerative diseases, epilepsy, and traumatic brain injury. However, the immunomodulatory effect of EE in normal rodents is not well characterized. To assess the immunomodulatory effect of EE, we randomly assigned normal mice to EE housing or standard environmental (SE) housing for 3 weeks. Behavioral alterations were evaluated by open field, fear conditioning, and Morris water maze tests. Immunohistochemical staining was performed to assess the expression of behavioral-related proteins, and enzyme-linked immunosorbent assay (ELISA) for brain-derived neurotrophic factor (BDNF), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) was also performed. We also measured the levels of RIP1 and RIP3 proteins using western blotting. EE significantly improved the cognitive performance which was associated with the increased expressions of BDNF, ionized calcium-binding adapter molecule 1 (Iba1), and glial fibrillary acidic protein (GFAP); EE did not influence any morphological changes in the brain tissue in adult mice; however, increased resistance to inflammation induced by TNF-α was observed. These findings indicate that EE can positively influence cognitive and behavioral performance in healthy adult mice by exerting environ-immuno effect on neural function.

Environmental Enrichment Mitigates Deficits after Repetitive Mild Traumatic Brain Injury

Although environmental enrichment has been shown to improve functional and histologic outcomes in pre-clinical moderate-to-severe traumatic brain injury (TBI), there are a paucity of pre-clinical data regarding enrichment strategies in the setting of repetitive mild traumatic brain injury (rmTBI). Given the vast numbers of athletes and those in the military who sustain rmTBI, the mounting evidence of the long-term and progressive sequelae of rmTBI, and the lack of targeted therapies to mitigate these sequelae, successful enrichment interventions in rmTBI could have large public health significance. Here, we evaluated enrichment strategies in an established pre-clinical rmTBI model. Seventy-one male C57BL/6 mice were randomized to two different housing conditions, environmental enrichment (EE) or normal condition (NC), then subjected to rmTBI injury (seven injuries in 9 days) or sham injury (anesthesia only). Functional outcomes in all four groups (NC-TBI, EE-TBI, NC-sham, and EE-sham) were assessed by motor, exploratory/anxiety, and mnemonic behavioral tests. At the synaptic level, N-methyl d-aspartate receptor (NMDAR) subunit expression of phosphorylated glutamate receptor 1 (GluR1), phosphorylated Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), and calpain were evaluated by western blot. Compared to injured NC-TBI mice, EE-TBI mice had improved memory and decreased anxiety and exploratory activity post-injury. Treatment with enrichment also corresponded to normal NMDAR subunit expression, decreased GluR1 phosphorylation, decreased phosphorylated CaMKII, and normal calpain expression post-rmTBI. These data suggest that enrichment strategies may improve functional outcomes and mitigate synaptic changes post-rmTBI. Given that enrichment strategies are feasible in the clinical setting, particularly for athletes and soldiers for whom the risk of repetitive injury is greatest, these data suggest that clinical trials may be warranted.

Brain-derived neurotrophic factor promotes human granulosa-like tumor cell steroidogenesis and proliferation by activating the FSH receptor-mediated signaling pathway

Brain-derived neurotrophic factor (BDNF) and FSH receptor (FSHR) are expressed in ovarian granulosa cells, and play important roles in regulating follicle growth and oocyte maturation. Studies have linked the BDNF-associated signaling pathway to FSHR mRNA expression in the regulation of follicle development, but the mechanisms remain unknown. In the current study, we found that BDNF stimulated the secretion of estradiol and progesterone, and increased the proliferation of KGN cells (human granulosa-like tumor cell line). BDNF treatment also increased phosphorylated and ubiquitinated FSHR, and activated cAMP/PKA/CREB signaling pathway. Moreover, inhibition of BDNF expression by siRNA markedly reduced the estradiol secretion and down-regulated FSHR, aromatase and phosphorylated CREB; meanwhile, FSH treatment partly alleviated the effects of BDNF siRNA on KGN cells. These findings suggested that BDNF modulates graunlosa cell functions and the action probably mediated by FSHR-coupled signaling pathway, to affect aromatase-mediated steroidogenesis. These results provide an alternative target to optimize ovarian granulosa cell function.

The Impact of CXCR4 Blockade on the Survival of Rat Brain Cortical Neurons

BACKGROUND

Chemokine receptor type 4 (CXCR4) plays a role in neuronal survival/cell repair and also contributes to the progression of cancer and neurodegenerative diseases. Chemokine ligand 12 (CXCL12) binds to CXCR4. In this study, we have investigated whether CXCR4 blockade by AMD3100 (a CXCR4 antagonist, member of bicyclam family) may affect neuronal survival in the absence of insult. Thus, we have measured the mitochondrial membrane potential (MMP), Bax and Bcl-2 protein translocation, and cytochrome c release in AMD3100-treated brain cortical neurons at 7 DIV (days in vitro).

METHODS

For this aim, AMD3100 (200 nM) was added to cortical neurons for 24 h, and several biomarkers like cell viability, reactive oxygen species (ROS) generation, lactate dehydrogenase (LDH) release, caspase-3/9 activity, proteins Bax and Bcl-2 translocation, and cytochrome c release were analyzed by immunoblot.

RESULTS

CXCR4 blockade by AMD3100 (200 nM, 24 h) induces mitochondrial hyperpolarization and increases caspase-3/9 hyperpolarization without affecting LDH release as compared to untreated controls. AMD3100 also increases cytochrome c release and promotes Bax translocation to the mitochondria, whereas it raises cytosolic Bcl-2 levels in brain cortical neurons.

CONCLUSION

CXCR4 blockade induces cellular death via intrinsic apoptosis in rat brain cortical neurons in absence of insult.