Functions of neurotrophins and growth factors in neurogenesis and brain repair

The BDNF-Interactive Model for Sustainable Hippocampal Neurogenesis in Humans: Synergistic Effects of Environmentally-Mediated Physical Activity, Cognitive Stimulation, and Mindfulness

This paper bridges critical gaps through proposing a novel, environmentally mediated brain-derived neurotrophic factor (BDNF)-interactive model that promises to sustain adult hippocampal neurogenesis in humans. It explains how three environmental enrichment mechanisms (physical activity, cognitive stimulation, and mindfulness) can integratively regulate BDNF and other growth factors and neurotransmitters to support neurogenesis at various stages, and how those mechanisms can be promoted by the physical environment. The approach enables the isolation of specific environmental factors and their molecular effects to promote sustainable BDNF regulation by testing the environment's ability to increase BDNF immediately or shortly before it is consumed for muscle repair or brain update. This model offers a novel, feasible method to research environment enrichment and neurogenesis dynamics in real-world human contexts at the immediate molecular level, overcoming the confounds of complex environment settings and challenges of long-term exposure and structural plasticity changes. The model promises to advance understanding of environmental influences on the hippocampus to enhance brain health and cognition. This work bridges fundamental gaps in methodology and knowledge to facilitate more research on the enrichment-neuroplasticity interplay for humans without methodological limitations.

ATF5-mediated mitochondrial unfolded protein response protects against Pb-induced mitochondria damage in SH-SY5Y cell

Mitochondria is the primary target of lead (Pb) in neural cells, and Pb exposure can cause impairment to mitochondrial function and morphology. Recent studies have reported that a conserved cellular stress response, called mitochondrial unfolded protein response (mtUPR), is activated in response to mitochondrial dysfunction and protein misfolding and play protective roles in aging and neurodegeneration, but it's unknown whether mtUPR could protect against Pb-induced neurotoxicity. In this study, we found that sublethal level exposure of PbAc (2.5 μM) could cause mitochondria damage and then activate mtUPR by promoting the expression of mitochondrial proteases (LonP1 and ClpP), molecular chaperone (HSPA1A). ATF5 mediated mtUPR activation as knocking out ATF5 significantly inhibited Pb-induced LonP1 and ClpP expression. Moreover, ATF5 deficiency exacerbated Pb-induced mitochondrial morphological and oxidative phosphorylation (OXPHOS) functional damage, resulting in oxidative stress and ultimately promoting cell death. Conversely, overexpression of ATF5 confers protection against Pb-induced oxidative stress and cell death. Collectively, thess results highlight that mtUPR mediated by ATF5 safeguards against mitochondria damage caused by Pb exposure, providing insights into the development of new strategies for mitigating the Pb neurotoxicity.

Diversity of Microglia-Derived Molecules with Neurotrophic Properties That Support Neurons in the Central Nervous System and Other Tissues

Microglia, the brain immune cells, support neurons by producing several established neurotrophic molecules including glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF). Modern analytical techniques have identified numerous phenotypic states of microglia, each associated with the secretion of a diverse set of substances, which likely include not only canonical neurotrophic factors but also other less-studied molecules that can interact with neurons and provide trophic support. In this review, we consider the following eight such candidate cytokines: oncostatin M (OSM), leukemia inhibitory factor (LIF), activin A, colony-stimulating factor (CSF)-1, interleukin (IL)-34, growth/differentiation factor (GDF)-15, fibroblast growth factor (FGF)-2, and insulin-like growth factor (IGF)-2. The available literature provides sufficient evidence demonstrating murine cells produce these cytokines and that they exhibit neurotrophic activity in at least one neuronal model. Several distinct types of neurotrophic activity are identified that only partially overlap among the cytokines considered, reflecting either their distinct intrinsic properties or lack of comprehensive studies covering the full spectrum of neurotrophic effects. The scarcity of human-specific studies is another significant knowledge gap revealed by this review. Further studies on these potential microglia-derived neurotrophic factors are warranted since they may be used as targeted treatments for diverse neurological disorders.

Neuroprotective actions of norepinephrine in neurological diseases

Precise control of norepinephrine (NE) levels and NE-receptor interaction is crucial for proper function of the brain. Much evidence for this view comes from experimental studies that indicate an important role for NE in the pathophysiology and treatment of various conditions, including cognitive dysfunction, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and sleep disorders. NE provides neuroprotection against several types of insults in multiple ways. It abrogates oxidative stress, attenuates neuroinflammatory responses in neurons and glial cells, reduces neuronal and glial cell activity, promotes autophagy, and ameliorates apoptotic responses to a variety of insults. It is beneficial for the treatment of neurodegenerative diseases because it improves the generation of neurotrophic factors, promotes neuronal survival, and plays an important role in the regulation of adult neurogenesis. This review aims to present the evidence supporting a principal role for NE in neuroprotection, and molecular mechanisms of neuroprotection.

Ovomemolins: Egg-derived peptides that improved cognitive decline after oral administration in mice

Eggs not only contain all the molecules necessary to nurture new life but are also rich in nutrients such as high-quality protein. For example, epidemiologic studies have shown that egg intake is positively correlated with cognitive function. Thus, we specifically examined the effect of ovalbumin, a major protein present in egg whites, on cognitive function. First, we found that an orally administered enzymatic digest of ovalbumin improves cognitive function in mice fed a high-fat diet. Then, we narrowed down candidate peptides based on the prediction of peptide production according to enzyme-substrate specificity and comprehensive peptide analysis of the digest. We found that three peptides, namely ILPEY, LYRGGLEP, and ILELP, improve cognitive function after oral administration. We also showed that ILPEY, LYRGGLEP, and ILELP were present in the digest and named them ovomemolins A (OMA), B, and C, respectively. Notably, ovomemolins are the first peptides derived from egg whites that have been shown to improve cognitive function. The cognitive improvement induced by OMA, the most abundant of the peptides in the digest, was inhibited by methyllycaconitine, an antagonist of α7nAChR, which is known to be related to memory. These results suggest that OMA improves cognitive function through the acetylcholine system. After OMA administration, brain-derived neurotrophic factor (BDNF) mRNA expression and the number of 5-bromo-2'-deoxyuridine-positive cells suggested that OMA increases hippocampal BDNF expression and neurogenesis.

Prevention of colistin-induced neurotoxicity: a narrative review of preclinical data

Polymyxin E or colistin is an effective antibiotic against MDR Gram-negative bacteria. Due to unwanted side effects, the use of this antibiotic has been limited for a long time, but in recent years, the widespread of MDR Gram-negative bacteria infections has led to its reintroduction. Neurotoxicity and nephrotoxicity are the significant dose-limiting adverse effects of colistin. Several agents with anti-inflammatory and antioxidant properties have been used for the prevention of colistin-induced neurotoxicity. This study aims to review the preclinical studies in this field to prepare guidance for future human studies. The data was achieved by searching PubMed, Scopus, and Google Scholar databases. All eligible pre-clinical studies performed on neuroprotective agents against colistin-induced neurotoxicity, which were published up to September 2023, were included. Finally, 16 studies (ten in vitro and eight in vivo) are reviewed. Apoptosis (in 13 studies), inflammatory (in four studies), and oxidative stress (in 14 studies) pathways are the most commonly reported pathways involved in colistin-induced neurotoxicity. The assessed compounds include non-herbal (e.g., ascorbic acid, rapamycin, and minocycline) and herbal (e.g., curcumin, rutin, baicalein, salidroside, and ginsenoside) agents. Besides these compounds, some other measures like transplantation of mitochondria and the use of nerve growth factor and mesenchymal stem cells could be motivating subjects for future research. Based on the data from experimental (in vitro and animal) studies, a combination of colistin with neuroprotective agents could prevent or decrease colistin-induced neurotoxicity. However, well-designed randomized clinical trials and human studies are essential for demonstrating efficacy.

Stem cells in central nervous system diseases: Promising therapeutic strategies

Central nervous system (CNS) diseases are a leading cause of death and disability. Due to CNS neurons have no self-renewal and regenerative ability as they mature, their loss after injury or disease is irreversible and often leads to functional impairments. Unfortunately, therapeutic options for CNS diseases are still limited, and effective treatments for these notorious diseases are warranted to be explored. At present, stem cell therapy has emerged as a potential therapeutic strategy for improving the prognosis of CNS diseases. Accumulating preclinical and clinical evidences have demonstrated that multiple molecular mechanisms, such as cell replacement, immunoregulation and neurotrophic effect, underlie the use of stem cell therapy for CNS diseases. However, several issues have yet to be addressed to support its clinical application. Thus, this review article aims to summarize the role and underlying mechanisms of stem cell therapy in treating CNS diseases. And it is worthy of further evaluation for the potential therapeutic applications of stem cell treatment in CNS disease.

Reduction of restricted repetitive behavior by environmental enrichment: Potential neurobiological mechanisms

Restricted repetitive behaviors (RRB) are one of two diagnostic criteria for autism spectrum disorder and common in other neurodevelopmental and psychiatric disorders. The term restricted repetitive behavior refers to a wide variety of inflexible patterns of behavior including stereotypy, self-injury, restricted interests, insistence on sameness, and ritualistic and compulsive behavior. However, despite their prevalence in clinical populations, their underlying causes remain poorly understood hampering the development of effective treatments. Intriguingly, numerous animal studies have demonstrated that these behaviors are reduced by rearing in enriched environments (EE). Understanding the processes responsible for the attenuation of repetitive behaviors by EE should offer insights into potential therapeutic approaches, as well as shed light on the underlying neurobiology of repetitive behaviors. This review summarizes the current knowledge of the relationship between EE and RRB and discusses potential mechanisms for EE's attenuation of RRB based on the broader EE literature. Existing gaps in the literature and future directions are also discussed.

Collagen for neural tissue engineering: Materials, strategies, and challenges

Neural tissue engineering (NTE) has made remarkable strides in recent years and holds great promise for treating several devastating neurological disorders. Selecting optimal scaffolding material is crucial for NET design strategies that enable neural and non-neural cell differentiation and axonal growth. Collagen is extensively employed in NTE applications due to the inherent resistance of the nervous system against regeneration, functionalized with neurotrophic factors, antagonists of neural growth inhibitors, and other neural growth-promoting agents. Recent advancements in integrating collagen with manufacturing strategies, such as scaffolding, electrospinning, and 3D bioprinting, provide localized trophic support, guide cell alignment, and protect neural cells from immune activity. This review categorises and analyses collagen-based processing techniques investigated for neural-specific applications, highlighting their strengths and weaknesses in repair, regeneration, and recovery. We also evaluate the potential prospects and challenges of using collagen-based biomaterials in NTE. Overall, this review offers a comprehensive and systematic framework for the rational evaluation and applications of collagen in NTE.

Pro-neurogenic effects of Lilii Bulbus on hippocampal neurogenesis and memory

Lilii Bulbus, the bulb of tiger lily, has anti-oxidant and anti-tumorigenic properties. However, the effects of Lilii Bulbus on learning, memory, and hippocampal neurogenesis remain unknown. This study investigated whether water extract of Lilii Bulbus (WELB) affects memory ability and hippocampal neurogenesis. Behavioral analyses (Morris water maze and passive avoidance test), immunohistochemistry, cell proliferation assay, and immunoblot analysis were performed. WELB (50 and 100 mg/kg; for 14 days) enhanced memory retention and spatial memory in normal mice as well as in scopolamine-treated mice with memory deficits. Furthermore, the administration of WELB significantly increased the number of proliferating cells and surviving newborn cells in the dentate gyrus of the hippocampus in normal mice. We found that WELB has a pro-neurogenic effect by increasing the activation of brain-derived neurotrophic factor (BDNF)/cAMP response element-binding protein (CREB) and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) in the hippocampus. Moreover, we confirmed that WELB (100 and 200 μg/ml) significantly increased NE-4 C and primary embryonic NSCs proliferation. Inhibition/knockdown of MEK/ERK blocked WELB-induced MEK/ERK phosphorylation and NSCs proliferation. Hence, MEK/ERK activation was required in WELB-induced NSCs proliferation. Our study demonstrates the first evidence for WELB promoting hippocampal neurogenesis and memory; pro-neurogenic activity may enhance brain plasticity, with implications for treating neurodegenerative diseases.

Biotransformation, metabolic response, and toxicity of UV-234 and UV-326 in larval zebrafish (Danio rerio)

Benzotriazole ultraviolet stabilizers (BUVSs) are emerging pollutants that are widely detected in aquatic ecosystems. While structure-dependent effects of BUVSs are reported, the relationship between biotransformation and toxicity outcomes remains unclear. In this study, zebrafish embryos were exposed to two common BUVSs (UV-234 and UV-326) at 1, 10, and 100 µg/L for up to 7 days. Comparison of their uptake and biotransformation revealed that the bioaccumulation capacity of UV-234 was higher than that of UV-326, while UV-326 was more extensively biotransformed with additional conjugation reactions. However, UV-326 showed low metabolism due to inhibited phase II enzymes, which may result in the comparable internal concentrations of both BUVSs in larval zebrafish. Both BUVSs induced oxidative stress while decreased MDA, suggesting the disturbance of lipid metabolism. The subsequent metabolomic profiling revealed that UV-234 and UV-326 exerted different effects on arachidonic acid, lipid, and energy metabolism. However, both BUVSs negatively impacted the cyclic guanosine monophosphate / protein kinase G pathway. This converged metabolic change resulted in comparable toxicity of UV-234 and UV-326, which was confirmed by the induction of downstream apoptosis, neuroinflammation, and abnormal locomotion behavior. These data have important implications for understanding the metabolism, disposition, and toxicology of BUVSs in aquatic organisms.

Neurotrophic Factors as Regenerative Therapy for Neurodegenerative Diseases: Current Status, Challenges and Future Perspectives

Neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS), spinal cord injury (SCI), and amyotrophic lateral sclerosis (ALS), are characterized by acute or chronic progressive loss of one or several neuronal subtypes. However, despite their increasing prevalence, little progress has been made in successfully treating these diseases. Research has recently focused on neurotrophic factors (NTFs) as potential regenerative therapy for neurodegenerative diseases. Here, we discuss the current state of knowledge, challenges, and future perspectives of NTFs with a direct regenerative effect in chronic inflammatory and degenerative disorders. Various systems for delivery of NTFs, such as stem and immune cells, viral vectors, and biomaterials, have been applied to deliver exogenous NTFs to the central nervous system, with promising results. The challenges that currently need to be overcome include the amount of NTFs delivered, the invasiveness of the delivery route, the blood-brain barrier permeability, and the occurrence of side effects. Nevertheless, it is important to continue research and develop standards for clinical applications. In addition to the use of single NTFs, the complexity of chronic inflammatory and degenerative diseases may require combination therapies targeting multiple pathways or other possibilities using smaller molecules, such as NTF mimetics, for effective treatment.

Designing receptor agonists with enhanced pharmacokinetics by grafting macrocyclic peptides into fragment crystallizable regions

Short half-lives in circulation and poor transport across the blood-brain barrier limit the utility of cytokines and growth factors acting as receptor agonists. Here we show that surrogate receptor agonists with longer half-lives in circulation and enhanced transport rates across the blood-brain barrier can be generated by genetically inserting macrocyclic peptide pharmacophores into the structural loops of the fragment crystallizable (Fc) region of a human immunoglobulin. We used such 'lasso-grafting' approach, which preserves the expression levels of the Fc region and its affinity for the neonatal Fc receptor, to generate Fc-based protein scaffolds with macrocyclic peptides binding to the receptor tyrosine protein kinase Met. The Met agonists dimerized Met, inducing biological responses that were similar to those induced by its natural ligand. Moreover, lasso-grafting of the Fc region of the mouse anti-transferrin-receptor antibody with Met-binding macrocyclic peptides enhanced the accumulation of the resulting Met agonists in brain parenchyma in mice. Lasso-grafting may allow for designer protein therapeutics with enhanced stability and pharmacokinetics.

Childhood adverse events and BDNF promoter methylation in later-life

Studies have shown that the effects of early-life stress and trauma can be enduring, with long-term negative effects on health. Epigenetics, including DNA methylation, have been implicated as a potential mechanism for these effects. Brain-derived neurotropic factor (BDNF) is a neurotransmitter involved in learning and memory, and altered BDNF promoter methylation measured in peripheral tissue has been found with early-life stress. However, whether such methylation differences remain stable into later life, is unknown. This study aimed to investigate the association between childhood adversity and BDNF promoter methylation in adults aged 65 years and over. Data came from a large study of older community-dwelling individuals in France (ESPRIT). Information on three major childhood adverse events, namely abuse/maltreatment, war/natural disaster, and financial difficulties/poverty, was obtained by retrospective reporting from participants of ESPRIT study. BDNF promoter I and IV methylation was assessed in blood and buccal tissue. Linear regression analysis was performed, adjusting for age, sex, education, depression, and morbidity. Among 927 participants, there was no strong evidence that childhood abuse/maltreatment or financial difficulties/poverty were associated with BDNF methylation in older individuals. For war/natural disaster, differential methylation at four of twenty-nine CpG sites was observed, however, these would not have remained significant after correction for multiple testing. Together, these findings do not support a long-term association between adverse childhood events and BDNF methylation in older age, but further large prospective studies are needed, which do not target specific genes, but consider DNA methylation across the genome.

Early Life Stress Affects Bdnf Regulation: A Role for Exercise Interventions

Early life stress (ELS) encompasses exposure to aversive experiences during early development, such as neglect or maltreatment. Animal and human studies indicate that ELS has maladaptive effects on brain development, leaving individuals more vulnerable to developing behavioral and neuropsychiatric disorders later in life. This result occurs in part to disruptions in Brain derived neurotrophic factor (Bdnf) gene regulation, which plays a vital role in early neural programming and brain health in adulthood. A potential treatment mechanism to reverse the effects of ELS on Bdnf expression is aerobic exercise due to its neuroprotective properties and positive impact on Bdnf expression. Aerobic exercise opens the door to exciting and novel potential treatment strategies because it is a behavioral intervention readily and freely available to the public. In this review, we discuss the current literature investigating the use of exercise interventions in animal models of ELS to reverse or mitigate ELS-induced changes in Bdnf expression. We also encourage future studies to investigate sensitive periods of exercise exposure, as well as sufficient duration of exposure, on epigenetic and behavioral outcomes to help lead to standardized practices in the exercise intervention field.

Immune response treated with bone marrow mesenchymal stromal cells after stroke

Stroke is a leading cause of death and long-term disability worldwide. Tissue plasminogen activator (tPA) is an effective treatment for ischemic stroke. However, only a small part of patients could benefit from it. Therefore, finding a new treatment is necessary. Bone marrow mesenchymal stromal cells (BMSCs) provide a novel strategy for stroke patients. Now, many patients take stem cells to treat stroke. However, the researches of the precise inflammatory mechanism of cell replacement treatment are still rare. In this review, we summarize the immune response of BMSCs treated to stroke and may provide a new perspective for stem cell therapy.

Neuroprotective effects of sodium valproate on hippocampal cell and volume, and cognitive function in a rat model of focal cerebral ischemia

Valproate (VPA) as a histone deacetylase (HDAC) inhibitor has shown neuroprotective effects in neurodegenerative diseases. This study evaluated whether VPA treatment ameliorated the synaptic plasticity dysfunction, hippocampal neuronal loss, and spatial memory deficits induced by cerebral ischemia in the middle cerebral artery occlusion (MCAO) model. Thirty-two male Sprague-Dawley rats were randomly divided into 4 groups control, sham, cerebral ischemia+vehicle (MCAO+V), and MCAO+VPA. The right common carotid artery was occluded for 1 hour. VPA (300 mg/kg) or vehicles were injected intraperitoneally on days 0,1,2 and 3 of the reperfusion. After 7 days of reperfusion the Morris water maze, passive avoidance, and open field tests were performed. Hippocampal synaptic plasticity in the CA1 area was recorded by field potential recording. We used the term neuronal Input-Output (I/O) function and paired-pulse ratio (PPR) to refer to basal synaptic transmission and presynaptic neurotransmitter release probability respectively. After that, the brains were removed for assaying stereological parameters of the CA1 neurons. Our results showed the VPA administration significantly reduced the total infarct volume, improved MCAO-induced spatial learning -memory, fear memory, and anxiety compared to the MCAO+V group. In addition, the field potential recording showed that VPA significantly ameliorated the impaired the long- term potentiation (LTP) induced by MCAO, without any effects on basal synaptic transmission and neurotransmitter release probability. Therefore, it seems that a decrease in total infarct volume and induction of long-term potentiation via postsynaptic mechanisms is responsible for improving MCAO-induced cognitive impairment.

The Cross-Talks Among Bone Morphogenetic Protein (BMP) Signaling and Other Prominent Pathways Involved in Neural Differentiation

The bone morphogenetic proteins (BMPs) are a group of potent morphogens which are critical for the patterning, development, and function of the central nervous system. The appropriate function of the BMP pathway depends on its interaction with other signaling pathways involved in neural differentiation, leading to synergistic or antagonistic effects and ultimately favorable biological outcomes. These opposite or cooperative effects are observed when BMP interacts with fibroblast growth factor (FGF), cytokines, Notch, Sonic Hedgehog (Shh), and Wnt pathways to regulate the impact of BMP-induced signaling in neural differentiation. Herein, we review the cross-talk between BMP signaling and the prominent signaling pathways involved in neural differentiation, emphasizing the underlying basic molecular mechanisms regarding the process of neural differentiation. Knowing these cross-talks can help us to develop new approaches in regenerative medicine and stem cell based therapy. Recently, cell therapy has received significant attention as a promising treatment for traumatic or neurodegenerative diseases. Therefore, it is important to know the signaling pathways involved in stem cell differentiation toward neural cells. Our better insight into the cross-talk of signaling pathways during neural development would improve neural differentiation within in vitro tissue engineering approaches and pre-clinical practices and develop futuristic therapeutic strategies for patients with neurological disease.

Targeting the Erk1/2 and autophagy signaling easily improved the neurobalst differentiation and cognitive function after young transient forebrain ischemia compared to old gerbils

The hippocampal neurogenesis occurs constitutively throughout adulthood in mammalian species, but declines with age. In this study, we overtly found that the neuroblast proliferation and differentiation in the subgranular zone and the maturation into fully functional and integrated neurons in the granule-cell layer in young gerbils following cerebral ischemia/reperfusion was much more than those in old gerbils. The neurological function and cognitive and memory-function rehabilitation in the young gerbils improved faster than those in the old one. These results demonstrated that, during long term after cerebral ischemia/reperfusion, the ability of neurogenesis and recovery of nerve function in young animals were significantly higher than that in the old animals. We found that, after 14- and 28-day cerebral ischemia/reperfusion, the phosphorylation of MEK1/2, ERK1/2, p90RSK, and MSK1/2 protein levels in the hippocampus of young gerbils was significantly much higher than that of old gerbils. The levels of autophagy-related proteins, including Beclin-1, Atg3, Atg5, and LC3 in the hippocampus were effectively maintained and elevated at 28 days after cerebral ischemia/reperfusion in the young gerbils compared with those in the old gerbils. These results indicated that an increase or maintenance of the phosphorylation of ERK1/2 signal pathway and autophagy-related proteins was closely associated with the neuroblast proliferation and differentiation and the process of maturation into neurons. Further, we proved that neuroblast proliferation and differentiation in the dentate gyrus and cognitive function were significantly reversed in young cerebral ischemic gerbils by administering the ERK inhibitor (U0126) and autophagy inhibitor (3MA). In brief, following experimental young ischemic stroke, the long-term promotion of the neurogenesis in the young gerbil’s hippocampal dentate gyrus by upregulating the phosphorylation of ERK signaling pathway and maintaining autophagy-related protein levels, it overtly improved the neurological function and cognitive and memory function.

Adult Hippocampal Neurogenesis in Alzheimer’s Disease: An Overview of Human and Animal Studies with Implications for Therapeutic Perspectives Aimed at Memory Recovery

The mammalian hippocampal dentate gyrus is a niche for adult neurogenesis from neural stem cells. Newborn neurons integrate into existing neuronal networks, where they play a key role in hippocampal functions, including learning and memory. In the ageing brain, neurogenic capability progressively declines while in parallel increases the risk for developing Alzheimer's disease (AD), the main neurodegenerative disorder associated with memory loss. Numerous studies have investigated whether impaired adult neurogenesis contributes to memory decline in AD. Here, we review the literature on adult hippocampal neurogenesis (AHN) and AD by focusing on both human and mouse model studies. First, we describe key steps of AHN, report recent evidence of this phenomenon in humans, and describe the specific contribution of newborn neurons to memory, as evinced by animal studies. Next, we review articles investigating AHN in AD patients and critically examine the discrepancies among different studies over the last two decades. Also, we summarize researches investigating AHN in AD mouse models, and from these studies, we extrapolate the contribution of molecular factors linking AD-related changes to impaired neurogenesis. Lastly, we examine animal studies that link impaired neurogenesis to specific memory dysfunctions in AD and review treatments that have the potential to rescue memory capacities in AD by stimulating AHN.

Long-lasting impact of perinatal dietary supplementation of omega 3 fatty acids on mevalonate pathway: potential role on neuron trophism in male offspring hippocampal formation

Objective: We were aimed at evaluating the long-term impact of perinatal an omega-3 fatty acid-enriched diet on the mevalonate/cholesterol pathway in the brain of male offspring.Methods: Female rats were fed with standard or omega-3 fatty acid-enriched diet during pregnancy and lactation. Liver, brain and plasma were collected from infant, adolescent and adult male offspring for subsequent biochemical and morphological analyses.Results: The omega-3 enriched diet induced region-dependent changes of the 3-hydroxy 3-methylglutaryl Coenzyme A reductase in the brain and affected notably RhoA/CREB signaling and the nerve growth factor content in the hippocampus. Our data reveal a long-lasting impact of perinatal omega-3 fatty acid supplementation on hippocampal nerve growth factor levels mediated by reduced 3-hydroxy 3-methylglutaryl Coenzyme A reductase activation state and enhanced CREB signaling.Discussion: These data underline the importance of the perinatal omega-3 enriched diet for adult brain function and reveal a new pathway important for nerve growth factor regulation.

Neuro-Immune Aspects of Schizophrenia with Severe Negative Symptoms: New Diagnostic Markers of Disease Phenotype

The aim of the study was to analyze the immune-inflammatory profile of patients with paranoid schizophrenia and relate it to the severity of negative symptoms and the MRI data in order to identify biomarkers of schizophrenia severity, search for new approaches to therapy, and control its effectiveness.

Materials and Methods

The main group included 51 patients with paranoid schizophrenia, the control group - 30 healthy subjects. Patients underwent MRI scans and immunological studies, which included an assessment of natural and adaptive immunity, the systemic level of key pro-inflammatory and anti-inflammatory cytokines, and other markers of inflammation.

Results

Disorders of immunity and immunoinflammatory profile in patients with paranoid schizophrenia with severe negative symptoms were revealed for the first time: in the presence of severe negative symptoms (>15 points according to the NSA-4 scale), the levels of humoral immunity factors, cytokines IL-10 and IL-12p40 and neurotrophin NGF were increased as well as the markers of systemic inflammation. Morphometric changes in the brain, typical for patients with schizophrenia, and also specific for patients with severe negative symptoms, were determined. The data analysis revealed correlations between the immune changes with structural changes in some of the brain areas, including the frontal cortex and hippocampus. Associations were found between the levels of anti-inflammatory IL-10, IL-12p40 cytokines and morphometric parameters of the brain, specific only for schizophrenic patients with severe negative symptoms.

Conclusion

The interdisciplinary approach, combining brain morphometry with in-depth immunological and clinical studies, made it possible to determine neurobiological, immune, and neurocognitive markers of paranoid schizophrenia with severe negative symptoms. The results are important for further deciphering the pathogenesis of schizophrenia and its subtypes, as well as for the search for new approaches to the treatment of severe forms of the disease.

The neuroprotective properties and therapeutic potential of epidermal neural crest stem cells transplantation in a rat model of vascular dementia

INTRODUCTION

The incidence rate of senile dementia is rising, and there is no definite cure for it yet. Cell therapy, as a new investigational approach, has shown promising results. Hair bulges with abundant easily accessible neural stem cells permit autologous implantation in irreversible neurodegenerative disorders.

METHODS

Fifty rats were randomly divided into 5 groups of control, sham-operation, two-common carotid vessel-occlusion rats that received vehicle (2VO + V), 2VO rats that received 1 × 10⁶ epidermal stem cells (2VO + ESC1), and 2VO rats that received 2.5 × 10⁶ epidermal stem cells (2VO + ESC2) in 300 µl PBS intravenously on days 4, 9, and 14 after surgery. The epidermal neural crest stem cells (EPI-NCSCs) were isolated from hair follicles of rat whiskers. The open-field, passive avoidance, and Morris water maze were used as behavioral tests. The basal-synaptic transmission, long-term potentiation (LTP), and short-term synaptic plasticity were evaluated by field-potential recording of the CA1 hippocampal area.

RESULTS

30 days after the first transplantation in the 2VO + ESC1 group, functional recovery was prominent in anxiety and fear memory compared to the 2VO + ESC2 group, while LTP induction was recovered in both groups of grafted animals without improvement in basal synaptic transmission. These positive recoveries may be related to the release of different neurotrophic factors from grafted cells that can stimulate endogenous neurogenesis and synaptic plasticity.

CONCLUSIONS

Our results showed that EPI-NCSCs implantation could rescue LTP and cognitive disability in 2VO rats, while transplantation of 1 million cells showed better performance relative to 2.5 million cells.

Conditioned medium of E17 rat brain cells induced differentiation of primary colony of mice blastocyst into neuron-like cells

Background

Conditioned medium is the medium obtained from certain cultured cells and contained secretome from the cells. The secretome, which can be in the form of growth factors, cytokines, exosomes, or other proteins secreted by the cells, can induce the differentiation of cells that still have pluripotent or multipotent properties.

Objectives

This study examined the effects of conditioned medium derived from E17 rat brain cells on cells with pluripotent properties.

Methods

The conditioned medium used in this study originated from E17 rat brain cells. The CM was used to induce the differentiation of primary colonies of mice blastocysts. Primary colonies were stained with alkaline phosphatase to analyze the pluripotency. The morphological changes in the colonies were examined, and the colonies were stained with GFAP and Neu-N markers on days two and seven after adding the conditioned medium.

Results

The conditioned medium could differentiate the primary colony, beginning with the formation of embryoid-body-like structure; round GFAP positive cells were identified. Finally, neuron-like cells testing positive for Neu-N were observed on the seventh day after adding the conditioned medium.

Conclusions

Conditioned medium from different species, in this case, E17 rat brain cells, induced and promoted the differentiation of the primary colony from mice blastocysts into neuron-like cells. The addition of CM mediated neurite growth in the differentiation process.

The Alteration of Brain Interstitial Fluid Drainage with Myelination Development

The integrity of myelination is crucial for maintaining brain interstitial fluid (ISF) drainage in adults; however, the mechanism of ISF drainage with immature myelin in the developing brain remains unknown. In the present study, the ISF drainage from the caudate nucleus (Cn) to the ipsilateral cortex was studied at different developmental stages of the rat brain (P 10, 20, 30, 40, 60, 80, 10-80). The results show that the traced ISF drained to the cortex from Cn and to the thalamus in an opposite direction before P30. From P40, we found impeded drainage to the thalamus due to myelin maturation. This altered drainage was accompanied by enhanced cognitive and social functions, which were consistent with those in the adult rats. A significant difference in diffusion parameters was also demonstrated between the extracellular space (ECS) before and after P30. The present study revealed the alteration of ISF drainage regulated by myelin at different stages during development, indicating that a regional ISF homeostasis may be essential for mature psychological and cognitive functions.

Neuroprotective effects of ononin against the aluminium chloride-induced Alzheimer's disease in rats

Alzheimer’s disease (AD) is a chronic neurodegenerative disease categorized by the deficiency in the cognition and memory. Approximately 50 million peoples has the AD, which is categorized by the deficiency in the cognition, memory and other kinds of cognitive dissention. The present exploration was designed to unveil the ameliorative properties of ononin against the aluminium chloride (AlCl3)-provoked AD in animals via the suppression of oxidative stress and neuroinflammation. AD was provoked to the Sprague Dawley rats through administering orally with 0.5 ml/100 g b.wt. of AlCl3 25 days and then supplemented with the 30 mg/kg of ononin orally for 25th day to 36th day. The behavioural changes were examined using open field and Morris Water Maze test. The acetylcholine esterase (AChE) activity was studied by standard method. The status of Aβ1-42, MDA, SOD, total antioxidant capacity (TAC) were quantified using respective assay kits. The interleukin(IL)-1β and TNF-α, BDNF, PPAR-γ, p38MAPK, and NF-κB/p65 status was quantified using respective assay kits. Brain histology was studied using microscope. The ononin treatment effectively modulated the AlCl3-triggered behavioural alterations in the AD animals. Ononin appreciably suppressed the AChE, Aβ1-42, and MDA and improved the SOD and TAC in the brain tissues of AD animals. The status of IL-1β, TNF-α, p38MAPK, and NF-κB were suppressed and the BDNF and PPAR-γ contents were elevated in the brain tissues of AD animals. The outcomes brain histology analysis proved the attenuate role of ononin. Our findings recommended that the ononin treatment could ameliorate the cognitive impairment, suppress the neuroinflammation and oxidative stress in the AD animals.

A Novel NGF Receptor Agonist B355252 Ameliorates Neuronal Loss and Inflammatory Responses in a Rat Model of Cerebral Ischemia

Introduction

Cerebral ischemia is a leading cause of disability and death worldwide. However, an effective therapeutic approach for the condition remains undiscovered. The previously proposed growth factor-based therapy has been inefficient due to its inability to pass through the blood–brain barrier. B355252, a newly developed small molecule, exhibited a potential neuroprotective effect in vivo. However, its exact efficacy in cerebral ischemia remains unclear.

Methods

We adopt an endothelin-1 stereotaxic intracranial injection to induced cerebral ischemia in rat. We further conducted 2,3,5-triphenyltetrazolium chloride (TTC) staining, immunofluorescent staining, enzyme-linked immunosorbent assay (ELISA), and behavioral tests to evaluate the efficacy of B355252 in neuroprotection, anti-inflammation, and behavioral outcome improvements.

Results

We identified that B355252 could protect ischemic neurons from neuronal loss by attenuating DNA damage, reducing ROS production and the LDH level, and preventing neuronal apoptosis. Moreover, inflammatory responses in astrocytic and microglial gliosis, as well as IL-1β and TNF-α levels, were ameliorated. Consequently, the behavioral outcomes of ischemic rats in neurologic responses and fore paw function recovery were improved.

Discussion

Overall, our study verified the in vivo therapeutic potential of B355252. The study findings further support its application in the development of a therapeutic approach for stroke.

Brain-derived neurotrophic factor increases cell number of neural progenitor cells derived from human induced pluripotent stem cells

Background

Several pieces of evidence from in vitro studies showed that brain-derived neurotrophic factor (BDNF) promotes proliferation and differentiation of neural stem/progenitor cells (NSCs) into neurons. Moreover, the JAK2 pathway was proposed to be associated with mouse NSC proliferation. BDNF could activate the STAT-3 pathway and induce proliferation in mouse NSCs. However, its effects on proliferation are not fully understood and JAK/STAT pathway was proposed to play a role in this activity.

Methods

In the present study, the effects of BDNF on cell proliferation and neurite outgrowth of Alzheimer’s disease (AD) induced pluripotent stem cells (iPSCs)-derived human neural progenitor cells (hNPCs) were examined. Moreover, a specific signal transduction pathway important in cell proliferation was investigated using a JAK2 inhibitor (AG490) to clarify the role of that pathway.

Results

The proliferative effect of BDNF was remarkably observed as an increase in Ki-67 positive cells. The cell number of hNPCs was significantly increased after BDNF treatment represented by cellular metabolic activity of the cells measured by MTT assay. This noticeable effect was statistically shown at 20 ng/ml of BDNF treatment. BDNF, however, did not promote neurite outgrowth but increased neuronal cell number. It was found that AG490 suppressed hNPCs proliferation. However, this inhibitor partially decreased BDNF-induced hNPCs proliferation. These results demonstrated the potential role of BDNF for the amelioration of AD through the increase of AD-derived hNPCs number.

Adult hypothalamic neurogenesis and sleep-wake dysfunction in aging

In the mammalian brain, adult neurogenesis has been extensively studied in the hippocampal sub-granular zone and the sub-ventricular zone of the anterolateral ventricles. However, growing evidence suggests that new cells are not only "born" constitutively in the adult hypothalamus, but many of these cells also differentiate into neurons and glia and serve specific functions. The preoptic-hypothalamic area plays a central role in the regulation of many critical functions, including sleep-wakefulness and circadian rhythms. While a role for adult hippocampal neurogenesis in regulating hippocampus-dependent functions, including cognition, has been extensively studied, adult hypothalamic neurogenic process and its contributions to various hypothalamic functions, including sleep-wake regulation are just beginning to unravel. This review is aimed at providing the current understanding of the hypothalamic adult neurogenic processes and the extent to which it affects hypothalamic functions, including sleep-wake regulation. We propose that hypothalamic neurogenic processes are vital for maintaining the proper functioning of the hypothalamic sleep-wake and circadian systems in the face of regulatory challenges. Sleep-wake disturbance is a frequent and challenging problem of aging and age-related neurodegenerative diseases. Aging is also associated with a decline in the neurogenic process. We discuss a hypothesis that a decrease in the hypothalamic neurogenic process underlies the aging of its sleep-wake and circadian systems and associated sleep-wake disturbance. We further discuss whether neuro-regenerative approaches, including pharmacological and non-pharmacological stimulation of endogenous neural stem and progenitor cells in hypothalamic neurogenic niches, can be used for mitigating sleep-wake and other hypothalamic dysfunctions in aging.

Fndc5 knockdown significantly decreased the expression of neurotrophins and their respective receptors during neural differentiation of mouse embryonic stem cells

Fibronectin type III domain-containing-5 (Fndc5) is a trans-membrane protein which is involved in a variety of cellular events including neural differentiation of mouse embryonic stem cells (mESCs) as its knockdown and overexpression diminishes and facilitates this process, respectively. However, downstream targets of Fndc5 in neurogenesis are still unclear. Neurotrophins including NGF, BDNF, NT-3, and NT-4 are the primary regulators of neuronal survival, growth, differentiation, and repair. These biomolecules exert their actions through binding to two different receptor families, Trk and p75NTR. In this study, considering the fact that neurotrophins and their receptors play crucial roles in neural differentiation of ESCs, we sought to evaluate whether knockdown of Fndc5 decreased neural differentiation of mESCs by affecting the neurotrophins and their receptors expression. Results showed that at neural progenitor stage, the mRNA and protein levels of BDNF, Trk, and p75NTR receptors decreased following the Fndc5 knockdown. In mature neural cells, still, the expression of Trk and p75NTR receptors at mRNA and protein levels and BDNF and NGF expression only at protein levels showed a significant decrease in Fndc5 knockdown cells compared to control groups. Taken together, our results suggest that decreased efficiency of neural differentiation following the reduction of Fndc5 expression could be attributed to decreased levels of NGF and BDNF proteins in addition to their cognate receptors.

Sesame oil mitigates memory impairment, oxidative stress, and neurodegeneration in a rat model of Alzheimer's disease. A pivotal role of NF-κB/p38MAPK/BDNF/PPAR-γ pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Sesame (Sesamum indicum, L., Family: Pedaliaceae) is a notable folk medicine in Middle East, Asia and Africa. Many traditional and pharmacological studies have documented the unique nature of sesame oil (SO). SO has been reported to have many pharmacological effects related to the anti-inflammatory and antioxidant capacity of its components. Neuroinflammation and oxidative stress have been the predominant pathogenic events in Alzheimer's disease (AD) which is one of the most common neurodegenerative diseases.

AIM OF STUDY

we aimed to explore the neuroprotective effect and the probable mechanisms of SO against aluminium chloride (AlCl3)-induced AD symptoms.

MATERIALS AND METHODS

Rats were treated daily with AlCl3 (100 mg/kg/i.p.) either alone or with SO (two different doses) for six weeks. Behavioral (Open-field and Morris water maze tests), histopathological, and biochemical examinations were used to evaluate the neuroprotective effect and the underlying mechanisms of SO against AlCl3-induced AD symptoms.

RESULTS

Our results indicated that SO significantly improved learning and memory impairments induced by AlCl3. Indeed, SO treatment significantly restored the elevated level of acetylcholinesterase (AChE) and amyloid beta (Aβ) overexpression. Moreover, AlCl3 treatment afforded histopathological changes, increase the expression of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in addition to mitigation of oxidative stress status in the brain. SO abolished all these abnormalities. Meanwhile, AlCl3 induced activation of p38 mitogen-activated protein kinase (p38MAPK) and decreased brain-derived neurotrophic factor (BDNF) which were inhibited by SO. Furthermore, SO administration modulated the expression of the peroxisome proliferator-activated receptor gamma (PPAR-γ) and nuclear factor kappa B (NF-κB).

CONCLUSIONS

In conclusion, the neuroprotective effect of SO involved the modulation of different mechanisms targeting oxidative stress, neuroinflammation, and cognitive functions. SO may modulate different molecular targets involved in AD pathogenesis by alterations of NF-κB/p38MAPK/BDNF/PPAR-γ signalling and this may be attributed to the synergistic effect of their active components.

In vitro investigation of growth factors including MGF and IGF-1 in neural stem cell activation, proliferation, and migration

Neurogenesis is mainly activated after damage in adult tissues. This destruction activates the neural stem cells (NSCs) by exiting from a quiescent state and initiating proliferation, differentiation, and migration towards the damaged area. Although studies have investigated to clarify the process of NSC biology and neurogenesis, there are still significant artifacts in understanding the primary mechanism. It is known that only a small percentage of NSC become neurons and integrate into the brain tissue after this process. The significant proportion differentiates to become either astrocytes or oligodendrocytes. Furthermore, the quiescent stem cells in the niche are mainly activated by the stimuli affect. In recent years, many studies have been conducted with varying hormones, some of which might provide neuro-stimulation effect and/or involved in the regeneration of the brain tissue and/or neuroprotection from traumatic or ischemic pathologies, including Insulin-like growth factor 1 (IGF-1), Mechano Growth Factor (MGF), Basic Fibroblast Growth Factor (FGF-2), Erythropoietin (EPO), Epidermal Growth Factor (EGF), Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF). In this study, we examined the effects of FGF-2, MGF, IGF-1, EPO, EGF, NGF, and BDNF alone or with various combinations on rat hippocampal NSC by tracking the changes in the expression of Nestin, GFAP, TUBB3, and DCX genes during 24 h (h), 72 h and 168 h time frame. The apoptosis analysis revealed that FGF-2 and FGF-2 coupled growth factors effectively protect NSCs against apoptosis, whereas MGF coupled growth factors failed in this protection. The cell cycle analysis demonstrated that these growth factors had accumulated the NSCs exit from the quiescent phase to the Mitosis phase, mostly without being long in the Synthesis Phase. Neurosphere sizes were increased with MGF, signifying MGF being effective in neural progenitor cells. The combined use of MGF with FGF-2 was more effective in postmitotic neurons than MGF alone. We have comparatively demonstrated the effect of cytokines alone and combined administration on activation, proliferation, and migration of NSCs. Although many issues are still waiting to be investigated in adult neurogenesis, neural regeneration, and adult neural stem cell biology, the results provide vital resources to the researchers that are interested in the varying effect of growth factor on NSC.

Is neurotrophin-3 (NT-3): a potential therapeutic target for depression and anxiety?

Introduction: Neurotrophin-3 (NT-3) is thought to play a role in the neurobiological processes implicated in mood and anxiety disorders. NT-3 is a potential pharmacological target for mood disorders because of its effects on monoamine neurotransmitters, regulation of synaptic plasticity and neurogenesis, brain-derived neurotrophic factor (BDNF) signaling boosting, and modulation of the hypothalamic-pituitary-adrenal (HPA) axis. The mechanisms underlying NT-3 anxiolytic properties are less clear and require further exploration and definition. Areas covered: The evidence that supports NT-3 as a pharmacological target for anxiety and mood disorders is presented and this is followed by a reflection on the quandaries, stumbling blocks, and future perspectives for this novel target. Expert opinion: There is evidence for miRNAs being key post-transcriptional regulators of neurotrophin-3 receptor gene (NTRK3) in anxiety disorders; however, the anxiolytic properties of NT-3 need further examination and delineation. Moreover, NT-3 expression by non-neuronal cells and its role in brain circuits that participate in anxiety and mood disorders require further scrutiny. Further work is vital before progression into clinical trials can be realized.

Pulsed Electromagnetic Fields Stimulate HIF-1α-Independent VEGF Release in 1321N1 Human Astrocytes Protecting Neuron-Like SH-SY5Y Cells from Oxygen-Glucose Deprivation

Pulsed electromagnetic fields (PEMFs) are emerging as an innovative, non-invasive therapeutic option in different pathological conditions of the central nervous system, including cerebral ischemia. This study aimed to investigate the mechanism of action of PEMFs in an in vitro model of human astrocytes, which play a key role in the events that occur following ischemia. 1321N1 cells were exposed to PEMFs or hypoxic conditions and the release of relevant neurotrophic and angiogenic factors, such as VEGF, EPO, and TGF-β1, was evaluated by means of ELISA or AlphaLISA assays. The involvement of the transcription factor HIF-1α was studied by using the specific inhibitor chetomin and its expression was measured by flow cytometry. PEMF exposure induced a time-dependent, HIF-1α-independent release of VEGF from 1321N1 cells. Astrocyte conditioned medium derived from PEMF-exposed astrocytes significantly reduced the oxygen-glucose deprivation-induced cell proliferation and viability decrease in the neuron-like cells SH-SY5Y. These findings contribute to our understanding of PEMFs action in neuropathological conditions and further corroborate their therapeutic potential in cerebral ischemia.

CDK5 Targeting as a Therapy for Recovering Neurovascular Unit Integrity in Alzheimer's Disease

The neurovascular unit (NVU) is responsible for synchronizing the energetic demand, vasodynamic changes, and neurochemical and electrical function of the brain through a closed and interdependent interaction of cell components conforming to brain tissue. In this review, we will focus on cyclin-dependent kinase 5 (CDK5) as a molecular pivot, which plays a crucial role in the healthy function of neurons, astrocytes, and the endothelium and is implicated in the cross-talk of cellular adhesion signaling, ion transmission, and cytoskeletal remodeling, thus allowing the individual and interconnected homeostasis of cerebral parenchyma. Then, we discuss how CDK5 overactivation affects the integrity of the NVU in Alzheimer's disease (AD) and cognitive impairment; we emphasize how CDK5 is involved in the excitotoxicity spreading of glutamate and Ca2+ imbalance under acute and chronic injury. Additionally, we present pharmacological and gene therapy strategies for producing partial depletion of CDK5 activity on neurons, astrocytes, or endothelium to recover neuroplasticity and neurotransmission, suggesting that the NVU should be the targeted tissue unit in protective strategies. Finally, we conclude that CDK5 could be effective due to its intervention on astrocytes by its end feet on the endothelium and neurons, acting as an intermediary cell between systemic and central communication in the brain. This review provides integrated guidance regarding the pathogenesis of and potential repair strategies for AD.

Fingolimod increases oligodendrocytes markers expression in epidermal neural crest stem cells

Epidermal neural crest stem cells (EPI-NCSCs) are propitious candidates for cell replacement therapy and supplying neurotrophic factors in the neurological disorders. Considering the potential remyelinating and regenerative effects of fingolimod, in this study, we evaluated its effects on EPI-NCSCs viability and the expression of neurotrophic and oligodendrocyte differentiation factors. EPI-NCSCs, extracted from the bulge of rat hair follicles, were characterized and treated with fingolimod (0, 50, 100, 200, 400, 600, 1000, and 5000 nM). The cell viability was evaluated by MTT assay at 6, 24 and 72 h. The expression of neurotrophic and differentiation factors in the cells treated with 100 and 400 nM fingolimod were measured at 24 and 120 h. Fingolimod at 50-600 nM increased the cells viability after 6 h, with no change at the higher concentrations. The highest concentration (5000nM) induced toxicity at 24 and 72 h. NGF and GDNF genes expression were decreased at 120 h, but on the contrary, brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT3) were increased by both concentrations at both time points. Oligodendrocyte markers including platelet-derived growth factor receptor A (PDGFRα), neuron-glial antigen 2 (NG2) and growth associated protein 43 (GAP43) were elevated at 120 h, which was accompanied with reduce in stemness markers (Nestin and early growth response 1 (EGR1)). Fingolimod increased the expression of neurotrophic factors in EPI-NCSCs, and guided them to oligodendrocyte fate. Therefore, fingolimod in combination with EPI-NCSCs, can be considered as a promising approach for demyelinating neurological disorders.

Pro- and anti-inflammatory properties of interleukin (IL6) in vitro: relevance for major depression and for human hippocampal neurogenesis

BACKGROUND

Although the pro-inflammatory cytokine, interleukin (IL)6, has been generally regarded as "depressogenic", recent research has started to question this assumption, in light of the fact that this cytokine can also have anti-inflammatory properties. This bimodal action seems to be dependent on its concentration levels, and on the concomitant presence of other pro-inflammatory cytokines.

METHODS

We exposed a human hippocampal progenitor cell line HPC0A07/03C to cytokine levels described in depressed patients (IL6 5pg/ml with IL1β 10pg/ml or Macrophage Migration Inhibitory Factor (MIF) 300pg/ml), in healthy subjects (IL6 with IL1β, 1pg/ml or MIF 10pg/ml), as well as to the potentially anti-inflammatory, much higher concentrations of IL6 (50000pg/ml).

RESULTS

Treatment with high concentrations of IL6 with IL1β or MIF (resembling depressed patients) decreases neurogenesis when compared with low concentrations of the same cytokines (healthy subjects), and that this is mediated via production of, respectively, IL8 and IL1β in cell supernatant. Instead, treatment with the very high, anti-inflammatory concentration of IL6 (50000pg/ml) together with high IL1β or MIF prevents the decrease in neurogenesis and reduces both IL8 and IL1β. When the high concentrations of both IL1β and MIF were used in co-treatment, as a model of treatment resistant depression, we also demonstrate a reduction in neurogenesis, and that this is mediated via a decrease in IL4; moreover, co-treatment with high IL1β and MIF and the very high concentration of IL6 prevents the reduction in neurogenesis, and increases IL4.

CONCLUSIONS

Our results demonstrate that IL6 can exert both pro- and anti-inflammatory (potentially antidepressant) properties, depending on its concentrations and combinations with other inflammatory cytokines.

Deciphering the neuroprotective and neurogenic potential of soluble amyloid precursor protein alpha (sAPPα)

Amyloid precursor protein (APP) is a transmembrane protein expressed largely within the central nervous system. Upon cleavage, it does not produce the toxic amyloid peptide (Aβ) only, which is involved in neurodegenerative progressions but via a non-amyloidogenic pathway it is metabolized to produce a soluble fragment (sAPPα) through α-secretase. While a lot of studies are focusing on the role played by APP in the pathogenesis of Alzheimer's disease, sAPPα is reported to have numerous neuroprotective effects and it is being suggested as a candidate with possible therapeutic potential against Alzheimer's disease. However, the mechanisms through which sAPPα precisely works remain elusive. We have presented a comprehensive review of how sAPPα is regulating the neuroprotective effects in different biological models. Moreover, we have focused on the role of sAPPα during different developmental stages of the brain, neurogenic microenvironment in the brain and how this metabolite of APP is regulating the neurogenesis which is regarded as a compelling approach to ameliorate the impaired learning and memory deficits in dementia and diseases like Alzheimer's disease. sAPPα exerts beneficial physiological, biochemical and behavioral effects mitigating the detrimental effects of neurotoxic compounds. It has shown to increase the proliferation rate of numerous cell types and promised the synaptogenesis, neurite outgrowth, cell survival and cell adhesion. Taken together, we believe that further studies are warranted to investigate the exact mechanism of action so that sAPPα could be developed as a novel therapeutic target against neuronal deficits.

Suicide epigenetics, a review of recent progress

BACKGROUND

Suicide results in over 800,000 deaths every year, making it a major public health concern worldwide. It is highly complex, with genetic and environmental influences. Epigenetic mechanisms, including DNA methylation, miRNA, and histone modifications, could explain the complex interplay of environmental risk factors with genetic risk factors in the emergence of suicidal behavior.

METHODS

Here, we review the literature on suicide epigenetics over the past 10 years.

RESULTS

There has been significant progress in the field of suicide epigenetics, with emerging findings in the brain-derived neurotrophic factor and hypothalamic-pituitary-adrenal axis genes.

LIMITATIONS

Studying patient subgroups is needed in order to extract more comparable and reproducible epigenetic findings in suicide.

CONCLUSIONS

It is crucial to consider suicidal patients or suicide victims' distal and proximal past history e.g., early-life adversity and psychiatric disorder in epigenetic studies of suicidality.

Rapid differentiation of astrocytes from human embryonic stem cells

Astrocytes are abundant cells in the brain and have vital roles in various brain functions that include biochemical support of endothelial cells, supplying nutrients to the nervous tissue, maintaining the extracellular ion balance, etc. In developing nervous tissue, the differentiation of astrocytes occurs later compared to neurons. It takes more time and more techniques to obtain mature and pure astrocytes in vitro. In this study, a protocol was developed to culture mature and pure astrocytes from human embryonic stem cells (hESCs). To obtain a high quantity and quality of differentiated astrocytes, first, we efficiently generated neural progenitor cells (NPCs) derived from hESCs through the process of embryoid body (EB) formation by adding SB431542 and LDN193189 and neurosphere step. In the astrocyte differentiation stage, the efficiency of astrocyte differentiation was increased using progenitor medium containing EGF and heparin and astrocyte defined medium containing ciliary neurotrophic factor (CNTF). The cell properties were checked with immunocytochemistry and western blot using antibodies for astrocyte-specific marker proteins. From the FACS analysis, we found that the percentage of astrocytes among the cells differentiated from NPCs was over 80%. To validate the functional properties of the astrocytes, we checked IL-6 release from the astrocytes and support of synaptic formation in a co-culture with neurons. Taken altogether, with our protocol, we obtained mature astrocytes within 4 weeks from NPCs and 6 weeks from hESCs.

From Healthy Aging to Frailty: In Search of the Underlying Mechanisms

Population aging is accelerating rapidly worldwide, from 461 million people older than 65 years in 2004 to an estimated 2 billion people by 2050, leading to critical implications for the planning and delivery of health and social care. The most problematic expression of population aging is the clinical condition of frailty, which is a state of increased vulnerability that develops as a consequence of the accumulation of microscopic damages in many physiological systems that lead to a striking and disproportionate change in health state, even after an apparently small insult. Since little is known about the biology of frailty, an important perspective to understand this phenomenon is to establish how the alterations that physiologically occur during a condition of healthy aging may instead promote cumulative decline with subsequent depletion of homoeostatic reserve and increase the vulnerability also after minor stressor events. In this context, the present review aims to provide a description of the molecular mechanisms that, by having a critical impact on behavior and neuronal function in aging, might be relevant for the development of frailty. Moreover, since these biological systems are also involved in the coping strategies set in motion to respond to environmental challenges, we propose a role for lifestyle stress as an important player to drive frailty in aging.

Neuroanatomical distribution and functions of brain-derived neurotrophic factor in zebrafish (Danio rerio) brain

Brain-derived neurotrophic factor (BDNF) is an extensively studied protein that is evolutionarily conserved and widely distributed in the brain of vertebrates. It acts via its cognate receptors TrkB and p75^NTR and plays a central role in the developmental neurogenesis, neuronal survival, proliferation, differentiation, synaptic plasticity, learning and memory, adult hippocampal neurogenesis, and brain regeneration. BDNF has also been implicated in a plethora of neurological disorders. Hence, understanding the processes that are controlled by BDNF and their regulating mechanisms is important. Although, BDNF has been thoroughly studied in the mammalian models, contradictory effects of its functions have been reported on several occasions. These contradictory effects may be attributed to the sheer complexity of the mammalian brain. The study of BDNF and its associated functions in a simpler vertebrate model may provide some clarity about the effects of BDNF on the neurophysiology of the brain. Keeping that in mind, this review aims at summarizing the current knowledge about the distribution of BDNF and its associated functions in the zebrafish brain. The main focus of the review is to give a comparative overview of BDNF distribution and function in zebrafish and mammals with respect to distinct life stages. We have also reviewed the regulation of bdnf gene in zebrafish and discussed its role in developmental and adult neurogenesis.

[An experimental evaluation of the therapeutic window of the neuroprotective activity of a low-molecular nerve growth factor mimetic GK-2]

AIM

To identify the time interval for the preservation of the effect of GK-2 depending on the start of administration after modeling ischemic stroke by the transient occlusion of the middle cerebral artery in rats.

MATERIAL AND METHODS

The experiments were performed on 33 wild-type male rats and 81 male Wistar rats. Animals were kept in standard conditions. Ischemic stroke was modelled by thread occlusion of the middle cerebral artery.

RESULTS AND CONCLUSION

It was found that GK-2 at a daily dose of 1 mg/kg, intraperitoneally, during 7 days statistically significantly reduces brain infarct volume by 20-60% at the first injection from 4 to 24h, with the highest effect 6-8 hours after surgery. Thus, the 'therapeutic window' of GK-2 detected in the experiment is no less than 24 hours, which exceeds the existing neuroprotective agents.

Executive Dysfunction Early Postnatal Biomarkers among Children Born Extremely Preterm

We evaluated the relationship between blood levels of inflammatory and neurotrophic proteins during the first postnatal month in 692 children born before the 28th week of gestation and executive function limitations among those 10-year olds who had an IQ ≥ 70. The measures of dysfunction were Z-scores ≤ -1 on the Differential Ability Scales-II working memory (WM) assessment) (N = 164), the NEPSY-II (A Developmental NEuroPSYchological Assessment-II) Inhibition-Inhibition assessment) (N = 350), the NEPSY-II Inhibition-Switching assessment) (N = 345), as well as a Z-score ≤ -1 on all three assessments (identified as the executive dysfunction composite (N = 104). Increased risks of the executive dysfunction composite associated with high concentrations of inflammatory proteins (IL-8, TNF-α, and ICAM-1) were modulated by high concentrations of neurotrophic proteins. This pattern of modulation by neurotrophins of increased risk associated with inflammation was also seen for the working memory limitation, but only with high concentrations of IL-8 and TNF-α, and the switching limitation, but only with high concentrations of ICAM-1. We infer that among children born extremely preterm, risks of executive function limitations might be explained by perinatal systemic inflammation in the absence of adequate neurotrophic capability.

Investigation of glycosaminoglycan mimetic scaffolds for neurite growth

Spinal cord injury can lead to severe dysfunction as a result of limited nerve regeneration that is due to an inhibitory environment created at the site of injury. Neural tissue engineering using materials that closely mimic the extracellular matrix (ECM) during neural development could enhance neural regeneration. Glycosaminoglycans (GAGs), which are sulfated polysaccharides, have been shown to modulate axonal outgrowth in neural tissue depending upon the position and degree of sulfation. Cellulose sulfate (CelS), which is a GAG mimetic, was evaluated for its use in promoting neurite extension. Aligned fibrous scaffolds containing gelatin blended with 0.25% partially sulfated cellulose sulfate (pCelS), having sulfate predominantly at the 6-carbon position of the glucose monomer unit, and fully sulfated cellulose sulfate (fCelS), which is sulfated at the 2-, 3-, and 6-carbon positions of the glucose monomer unit, were fabricated using the electrospinning method. Comparisons were made with scaffolds containing native GAGs, chondroitin sulfate-A (CS-A) and chondroitin sulfate-C (CS-C), which were obtained from commercial sources. CS-A and CS-C are present in neural tissue ECM. The degree of sulfation and position of sulfate groups was determined using elemental analysis, Fourier-transform infrared spectroscopy (FTIR), Raman microspectroscopy, and ¹³C nuclear magnetic resonance (NMR). In vitro studies examined both nerve growth factor (NGF) binding on scaffolds and neurite extension by dorsal root ganglion (DRG) neurons. NGF binding was highest on scaffolds containing pCelS and fCelS. Neurite extension was greatest for scaffolds containing fCelS followed by pCelS, with the lowest outgrowth on the CS-A containing scaffolds, suggesting that the degree and position of sulfation of CelS was permissible for neurite outgrowth. This study demonstrated that cellulose sulfate, as a GAG mimetic, could be used for future neural tissue regeneration application. STATEMENT OF SIGNFICANCE: Scaffolds that closely mimic the native extracellular matrix (ECM) during development may be a promising approach to enhance neural regeneration. Here, we reported a glycosaminoglycan (GAG) mimetic derived from cellulose that promotes neurite extension over native GAGs, chondroitin sulfate-A (CS-A) and chondroitin sulfate-C (CS-C), which are present in neural ECM. Depending upon the degree and position of sulfation, the GAG mimetic can impact nerve growth factor binding and permissive neurite outgrowth.

Socioeconomic status and early blood concentrations of inflammation-related and neurotrophic proteins among extremely preterm newborns

The main objective of this study was to evaluate the relationship between mother’s socioeconomic disadvantage and blood concentrations of inflammation-related proteins among extremely preterm newborns (<28 weeks gestation), a group at heightened risk of cognitive impairment when exposed to systemic inflammation. We measured the concentrations of 27 inflammatory and neurotrophic proteins in blood specimens collected a week apart during the first postnatal month from 857 extremely preterm newborns in the United States. We classified children according to 3 indicators/correlates of socioeconomic disadvantage, mother’s eligibility for government-provided medical care insurance (Medicaid), mother’s formal education level, and mother’s IQ approximated with the Kaufman Brief Intelligence Test– 2. The risks of a top-quartile concentration of each protein on each of 5 days a week apart, on two occasions during the first two postnatal weeks, and during the next two weeks were modeled as functions of each indicator of socioeconomic disadvantage. The risks of top quartile concentrations of multiple (2–5) inflammation-related proteins on multiple days during the first two weeks were increased for each of the 3 indicators of socioeconomic disadvantage, while the risks of top quartile concentrations of selected neurotrophic proteins were reduced. Adjustment for socioeconomic disadvantage did not alter the relationships between protein concentrations and both low IQ and low working memory 10 years later. Among extremely preterm newborns, indicators of socioeconomic disadvantage are associated with modestly increased risk of systemic inflammation in postnatal blood during the first postnatal month and with a slightly reduced risk of a neurotrophic signal, but do not confound relationships between protein concentrations and outcomes.

Chronic mild hypoxia promotes hippocampal neurogenesis involving Notch1 signaling in epileptic rats

Cognitive impairment is one of the most common and disabling co-morbidities of epilepsy. It is therefore imperative to find novel treatment approaches to rescue cognitive function among epilepsy patients. Adult neurogenesis is strongly implicated in cognitive function, and mild hypoxia is known to promote the proliferation and differentiation of both embryonic and adult neural stem cells (NSCs). In the present study, we investigated the effect of mild hypoxia on cognitive function and hippocampal neurogenesis of rats with pilocarpine-induced chronic epilepsy. Chronic epilepsy induced marked spatial learning and memory deficits in the Morris water maze that were rescued by consecutively 28 days mild hypoxia exposure (6 h/d at 3000 m altitude equivalent) during the chronic phase. Moreover, mild hypoxia reversed the suppression of hippocampal neurogenesis and the downregulation of NT-3 and BDNF expression in hippocampus and cortex of epileptic rats. Mild hypoxia in vitro also promoted hippocampus-derived NSC proliferation and neuronal differentiation. In addition, mild hypoxia enhanced Notch1 and Hes1 expression, suggesting that Notch1 signaling may be involved in neuroprotection of hypoxia. Our data may help to pave the way for identifying new therapeutic targets for rescuing cognition conflicts in epileptic patients by using hypoxia to promote hippocampus neurogenesis.

P2X7 receptor signaling during adult hippocampal neurogenesis

Neurogenesis is a persistent and essential feature of the adult mammalian hippocampus. Granular neurons generated from resident pools of stem or progenitor cells provide a mechanism for the formation and consolidation of new memories. Regulation of hippocampal neurogenesis is complex and multifaceted, and numerous signaling pathways converge to modulate cell proliferation, apoptosis, and clearance of cellular debris, as well as synaptic integration of newborn immature neurons. The expression of functional P2X7 receptors in the central nervous system has attracted much interest and the regulatory role of this purinergic receptor during adult neurogenesis has only recently begun to be explored. P2X7 receptors are exceptionally versatile: in their canonical role they act as adenosine triphosphate-gated calcium channels and facilitate calcium-signaling cascades exerting control over the cell via calcium-encoded sensory proteins and transcription factor activation. P2X7 also mediates transmembrane pore formation to regulate cytokine release and facilitate extracellular communication, and when persistently stimulated by high extracellular adenosine triphosphate levels large P2X7 pores form, which induce apoptotic cell death through cytosolic ion dysregulation. Lastly, as a scavenger receptor P2X7 directly facilitates phagocytosis of the cellular debris that arises during neurogenesis, as well as during some disease states. Understanding how P2X7 receptors regulate the physiology of stem and progenitor cells in the adult hippocampus is an important step towards developing useful therapeutic models for regenerative medicine. This review considers the relevant aspects of adult hippocampal neurogenesis and explores how P2X7 receptor activity may influence the molecular physiology of the hippocampus, and neural stem and progenitor cells.