Cerebrospinal fluid from Alzheimer patients affects cell-mediated nerve growth factor production and cell survival in vitro

Bridging neurotrophic factors and bioactive peptides to Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder. As the demographic shifting towards an aging population, AD has emerged as a prominent public health concern. The pathogenesis of AD is complex, and there are no effective treatment methods for AD until now. In recent years, neurotrophic factors and bioactive peptides including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), irisin, melatonin, have been discovered to exert neuroprotective functions for AD. Bioactive peptides can be divided into two categories based on their sources: endogenous and exogenous. This review briefly elaborates on the pathogenesis of AD and analyzes the regulatory effects of endogenous and exogenous peptides on the pathogenesis of AD, thereby providing new therapeutic targets for AD and a theoretical basis for the application of bioactive peptides as adjunctive therapies for AD.

Bioinformatics-based Study on the Effects of Umbilical Cord Mesenchymal Stem Cells on the Aging Retina

BACKGROUND

Retinal aging is one of the common public health problems caused by population aging and has become an important cause of acquired vision loss in adults. The aim of this study was to determine the role of human umbilical cord mesenchymal stem cells (hUCMSCs) in delaying retinal ganglion cell (RGC) aging and part of the network of molecular mechanisms involved.

METHODS

A retinal ganglion cell senescence model was established in vitro and treated with UCMSC. Successful establishment of the senescence system was demonstrated using β- galactosidase staining. The ameliorative effect of MSC on senescence was demonstrated using CCK8 cell viability and Annexin V-PI apoptosis staining. The relevant targets of RGC, MSC, and senescence were mainly obtained by searching the GeneCards database. The protein interaction network among the relevant targets was constructed using the String database and Cytoscape, and 10 key target genes were calculated based on the MCC algorithm, based on which Gene ontologies (GO) enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were performed. Changes in relevant target genes were detected using real-time fluorescence quantitative PCR and the mechanism of action of UCMSC was determined by RNA interference.

RESULTS

β-galactosidase staining showed that UCMSC significantly reduced the positive results of RGC. The retinal aging process was alleviated. The bioinformatics screen yielded 201 shared genes. 10 key genes were selected by the MCC algorithm, including vascular endothelial growth factor A (VEGFA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), albumin (ALB), interleukin- 6 (IL6), tumor necrosis factor (TNF), tumor protein P53 (TP53), insulin (INS), matrix metalloproteinase 9 (MMP9), epidermal growth factor (EGF), interleukin-1β (IL1B), and enrichment to related transferase activity and kinase activity regulated biological processes involved in oxidative stress and inflammation related pathways. In addition, PCR results showed that all the above molecules were altered in expression after UCMSC involvement.

CONCLUSION

This experiment demonstrated the role of UCMSC in delaying retinal ganglion cell senescence and further elucidated that UCMSC may be associated with the activation of VEGFA, TP53, ALB, GAPDH, IL6, IL1B, MMP9 genes and the inhibition of INS, EGF, and TNF in delaying retinal senescence.

Enhancement of neural regeneration as a therapeutic strategy for Alzheimer's disease (Review)

Alzheimer's disease (AD), the most common cause of dementia worldwide, has gradually become a global health concern for society and individuals with the process of global ageing. Although extensive research has been carried out on AD, the etiology and pathological mechanism of the disease are still unclear, and there is no specific drug to cure or delay AD progression. The exploration of enhancing nerve regeneration in AD has gradually attracted increasing attention. In the current review, the existing therapeutic strategies were summarized to induce nerve regeneration which can increase the number of neurons, and improve the survival of neurons, the plasticity of synapses and synaptic activity. The strategies include increasing neurotrophic expression (such as brain-derived neurotrophic factor and nerve growth factor), inhibiting acetylcholinesterase (such as donepezil, tacrine, rivastigmine and galanthamine), elevating histone deacetylase levels (such as RGFP-966, Tasquinimod, CM-414 and 44B), stimulating the brain by physiotherapy (such as near-infrared light, repetitive transcranial magnetic stimulation, and transcranial direct current stimulation) and transplanting exogenous neural stem cells. However, further evaluations need to be performed to determine the optimal treatment. The present study reviews recent interventions for enhancing adult neurogenesis and attempts to elucidate their mechanisms of action, which may provide a theoretical basis for inducing nerve regeneration to fight against AD.

Microglia Impairs Proliferation and Induces Senescence In-Vitro in NGF Releasing Cells Used in Encapsulated Cell Biodelivery for Alzheimer's Disease Therapy

There is no cure yet available for Alzheimer's disease (AD). We recently optimized encapsulated cell biodelivery (ECB) devices releasing human mature nerve growth factor (hmNGF), termed ECB-NGF, to the basal forebrain of AD patients. The ECB-NGF delivery resulted in increased CSF cholinergic markers, improved glucose metabolism, and positive effects on cognition in AD patients. However, some ECB-NGF implants showed altered hmNGF release post-explantation. To optimize the ECB-NGF platform for future therapeutic purposes, we initiated in-vitro optimization studies by exposing ECB-NGF devices to physiological factors present within the AD brain. We report here that microglia cells can impair hmNGF release from ECB-NGF devices in-vitro, which can be reversed by transferring the devices to fresh culture medium. Further, we exposed the hmNGF secreting human ARPE-19 cell line (NGC0211) to microglia (HMC3) conditioned medium (MCM; untreated or treated with IL-1β/IFNγ/Aβ₄₀/Aβ₄₂), and evaluated biochemical stress markers (ROS, GSH, ΔΨ_m, and Alamar Blue assay), cell death indicators (Annexin-V/PI), cell proliferation (CFSE retention and Ki67) and senescence markers (SA-β-gal) in NGC0211 cells. MCMs from activated microglia reduced cell proliferation and induced cell senescence in NGC0211 cells, which otherwise resist biochemical alterations and cell death. These data indicate a critical but reversible impact of activated microglia on NGC0211 cells.

The synapse as a treatment avenue for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder with devastating symptoms, including memory impairments and cognitive deficits. Hallmarks of AD pathology are amyloid-beta (Aβ) deposition forming neuritic plaques and neurofibrillary tangles (NFTs). For many years, AD drug development has mainly focused on directly targeting the Aβ aggregation or the formation of tau tangles, but this disease has no cure so far. Other common characteristics of AD are synaptic abnormalities and dysfunctions such as synaptic damage, synaptic loss, and structural changes in the synapse. Those anomalies happen in the early stages of the disease before behavioural symptoms have occurred. Therefore, better understanding the mechanisms underlying the synaptic dysfunction found in AD and targeting the synapse, especially using early treatment windows, can lead to finding novel and more effective treatments that could improve the lives of AD patients. Researchers have recently started developing different disease-modifying treatments targeting the synapse to rescue and prevent synaptic dysfunction in AD. The main objectives of these new strategies are to halt synaptic loss, strengthen synaptic connections, and improve synaptic density, potentially leading to the rescue or prevention of cognitive impairments. This article aims to address the mechanisms of synaptic degeneration in AD and discuss current strategies that focus on the synapse for AD therapy. Alzheimer's disease (AD) is a neurodegenerative disorder that significantly impairs memory and causes cognitive and behavioural deficits. Scientists worldwide have tried to find a treatment that can reverse or rescue AD symptoms, but there is no cure so far. One prominent characteristic of AD is the brain atrophy caused by significant synaptic loss and overall neuronal damage, which starts at the early stages of the disease before other AD hallmarks such as neuritic plaques and NFTs. The present review addresses the underlying mechanisms behind synaptic loss and dysfunction in AD and discusses potential strategies that target the synapse.

Systemic inflammasome activation and pyroptosis associate with the progression of amnestic mild cognitive impairment and Alzheimer's disease

BACKGROUND

Growing evidence indicates that inflammasome-mediated inflammation plays important roles in the pathophysiology of amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). Pyroptosis induced by inflammasome, and Gasdermin D (GSDMD) is involved in several neurodegenerative disorders. However, it is not clear whether peripheral inflammasome and pyroptosis are activated in aMCI and AD patients, influencing on neuroinflammation. The aim of this study was to examine the association between systemic inflammasome-induced pyroptosis and clinical features in aMCI and AD.

METHODS

A total of 86 participants, including 33 subjects with aMCI, 33 subjects with AD, and 20 cognitively normal controls, in this study. The Mini Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) scale were used for cognitive assessment. Levels of inflammasome-related genes/proteins in peripheral blood mononuclear cells (PBMCs) were determined using quantitative polymerase chain reaction and Western blotting. The levels of IL-1β, Aβ1-42, Aβ1-40, p-tau, and t-tau in cerebrospinal fluid (CSF), as well as the plasma IL-1β level, were measured by enzyme-linked immunosorbent assay. Finally, lipopolysaccharides (LPS) were used to investigate the effects of systemic inflammasome-induced pyroptosis in an AD mice model.

RESULTS

Several genes involved in the inflammatory response were enriched in PBMCs of AD patients. The mRNA and protein levels of NLRP3, caspase-1, GSDMD, and IL-1β were increased in PBMCs of aMCI and AD patients. The IL-1β level in plasma and CSF of aMCI and AD patients was significantly higher than that in controls and negatively correlated with the CSF Aβ1-42 level, as well as MMSE and MoCA scores. Furthermore, there was a positive correlation between the IL-1β level in plasma and CSF of aMCI or AD patients. In vivo experiments showed that systemic inflammasome-induced pyroptosis aggravated neuroinflammation in 5 × FAD mice.

CONCLUSIONS

Our findings showed that canonical inflammasome signaling and GSDMD-induced pyroptosis were activated in PBMCs of aMCI and AD patients. In addition, the proinflammatory cytokine IL-1β was strongly associated with the pathophysiology of aMCI and AD. As such, targeting inflammasome-induced pyroptosis may be a new approach to inhibit neuroinflammation in aMCI and AD patients.

Therapeutic potential of neurotrophic factors in Alzheimer's Disease

INTRODUCTION

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia among the elderly population. AD is accompanied with the dysregulation of specific neurotrophic factors (NTFs) and their receptors, which plays a critical role in neuronal degeneration. NTFs are small proteins with therapeutic potential for human neurodegenerative diseases. These growth factors are categorized into four families: neurotrophins, neurokines, the glial cell line-derived NTF family of ligands, and the newly discovered cerebral dopamine NTF/mesencephalic astrocyte-derived NTF family. NTFs are capable of preventing cell death in degenerative conditions and can increase the neuronal growth and function in these disorders. Nevertheless, the adverse side effects of NTFs delivery and poor diffusion of these factors in the brain restrict the efficacy of NTFs therapy in clinical situations.

MATERIALS AND METHODS

In this review, we focus on the current advances in the use of NTFs to treat AD and summarize previous experimental and clinical studies for supporting the protective and therapeutic effects of these factors.

CONCLUSION

Based on reports, NTFs are considered as new and promising candidates for treating AD and AD-associated cognitive impairment.

Amyloid-Beta Peptides and Activated Astroglia Impairs Proliferation of Nerve Growth Factor Releasing Cells In Vitro: Implication for Encapsulated Cell Biodelivery-Mediated AD Therapy

Alzheimer’s disease (AD) treatment is constrained due to the inability of peripherally administered therapeutic molecules to cross the blood–brain barrier. Encapsulated cell biodelivery (ECB) devices, a tissue-targeted approach for local drug release, was previously optimized for human mature nerve growth factor (hmNGF) delivery in AD patients but was found to have reduced hmNGF release over time. To understand the reason behind reduced ECB efficacy, we exposed hmNGF-releasing cells (NGC0211) in vitro to human cerebrospinal fluid (CSF) obtained from Subjective Cognitive Impairment (SCI), Lewy Body Dementia (LBD), and AD patients. Subsequently, we exposed NGC0211 cells directly to AD-related factors like amyloid-β peptides (Aβ_40/42) or activated astrocyte-conditioned medium (Aβ_40/42/IL-1β/TNFα-treated) and evaluated biochemical stress markers, cell death indicators, cell proliferation marker (Ki67), and hmNGF release. We found that all patients’ CSF significantly reduced hmNGF release from NGC0211 cells in vitro. Aβ_40/42, inflammatory molecules, and activated astrocytes significantly affected NGC0211 cell proliferation without altering hmNGF release or other parameters important for essential functions of the NGC0211 cells. Long-term constant cell proliferation within the ECB device is critically important to maintain a steady cell population needed for stable mNGF release. These data show hampered proliferation of NGC0211 cells, which may lead to a decline of the NGC0211 cell population in ECBs, thereby reducing hmNGF release. Our study highlights the need for future studies to strengthen ECB-mediated long-term drug delivery approaches.

A Review of Techniques for Biodelivery of Nerve Growth Factor (NGF) to the Brain in Relation to Alzheimer's Disease

Age-dependent progressive neurodegeneration and associated cognitive dysfunction represent a serious concern worldwide. Currently, dementia accounts for the fifth highest cause of death, among which Alzheimer's disease (AD) represents more than 60% of the cases. AD is associated with progressive cognitive dysfunction which affects daily life of the affected individual and associated family. The cognitive dysfunctions are at least partially due to the degeneration of a specific set of neurons (cholinergic neurons) whose cell bodies are situated in the basal forebrain region (basal forebrain cholinergic neurons, BFCNs) but innervate wide areas of the brain. It has been explicitly shown that the delivery of the neurotrophic protein nerve growth factor (NGF) can rescue BFCNs and restore cognitive dysfunction, making NGF interesting as a potential therapeutic substance for AD. Unfortunately, NGF cannot pass through the blood-brain barrier (BBB) and thus peripheral administration of NGF protein is not viable therapeutically. NGF must be delivered in a way which will allow its brain penetration and availability to the BFCNs to modulate BFCN activity and viability. Over the past few decades, various methodologies have been developed to deliver NGF to the brain tissue. In this chapter, NGF delivery methods are discussed in the context of AD.

Gene and cell therapy for the nucleus basalis of Meynert with NGF in Alzheimer's disease

There is currently no effective treatment for the most common of the dementia disorders, Alzheimer's disease (AD). It has been known for decades that the central cholinergic system is important for memory. The cholinergic neurons in the basal forebrain with its cortical and hippocampal projections degenerate in AD and thus contribute to the cognitive decline characteristic of AD. This knowledge led to the development of the currently approved treatment for AD, with inhibitors of acetylcholine-esterase targeting the cholinergic system with beneficial but mild effects. In recent years, other approaches to influence the degenerating cholinergic system in AD focusing on nerve growth factor (NGF) have been undertaken. NGF is required for the survival and function of the basal forebrain cholinergic neurons, the most important being the nucleus basalis of Meynert (nbM). Since there is a lack of NGF and its receptors in the AD forebrain, the hypothesis is that local delivery of NGF to the nbM could revive the cholinergic circuitry and thereby restore cognitive functions. Since NGF does not pass through the blood-brain barrier, approaches involving cerebral injections of genetically modified cells or viral vectors or implantation of encapsulated cells in the nbM in AD patients have been used. These attempts have been partially successful but also have limitations, which are presented and discussed here. In conclusion, these trials point to the importance of further development of NGF-related therapies in AD.

The low levels of nerve growth factor and its upstream regulatory kinases in prion infection is reversed by resveratrol

Resveratrol shows ability to eliminate prion replication, but the exact mechanism for prion eradication was not clear yet. Our previous studies demonstrate a downregulation of brain-derived nerve growth factor (BDNF) during prion infection, meanwhile recovery of cerebral nerve growth factor (NGF) level by resveratrol treatment has been reported in other neurodegenerative models. To obtain the possible changes of brain NGF and its upstream regulatory cascade during prion infection and after removal of prion propagation, the levels of NGF and its upstream regulatory factors in various prion-infected and prion-eradicated SMB cell lines and mice brains inoculated with various SMB cellular lysates were assessed with various methodologies. The levels of NGF were significantly decreased during prion replication, while recovered after removal of PrP^Sc by resveratrol in vitro. Morphological assays revealed that the NGF signals mainly colocalized within neurons, but not in the proliferative astrocytes and microglia. The upstream positive regulatory kinases, such as p-CREB, p-CaMKIV, CaMKK2 were decreased in the prion infected cells and mice brains, whereas the negative regulatory one, p-CaMKK2, was increased. The aberrant situations of those kinases in prion infected cell lines or mice brains could be also partially reversed by removal of prion agent. Moreover, we demonstrated that the signals of CaMKK2 and p-CaMKK2 were also distributed predominately in neurons in the brain tissues. The data illustrate a direct linkage of abnormally repressive NGF and its upstream regulatory kinases with prion infection. Resveratrol has not only the ability to inhibit prion replication, but also to improve the expression of NGF via CaMKK2/CaMKIV cascade, which might benefit the microenvironment in brains.

Innovative Therapy for Alzheimer's Disease-With Focus on Biodelivery of NGF

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with abnormal protein modification, inflammation and memory impairment. Aggregated amyloid beta (Aβ) and phosphorylated tau proteins are medical diagnostic features. Loss of memory in AD has been associated with central cholinergic dysfunction in basal forebrain, from where the cholinergic circuitry projects to cerebral cortex and hippocampus. Various reports link AD progression with declining activity of cholinergic neurons in basal forebrain. The neurotrophic molecule, nerve growth factor (NGF), plays a major role in the maintenance of cholinergic neurons integrity and function, both during development and adulthood. Numerous studies have also shown that NGF contributes to the survival and regeneration of neurons during aging and in age-related diseases such as AD. Changes in neurotrophic signaling pathways are involved in the aging process and contribute to cholinergic and cognitive decline as observed in AD. Further, gradual dysregulation of neurotrophic factors like NGF and brain derived neurotrophic factor (BDNF) have been reported during AD development thus intensifying further research in targeting these factors as disease modifying therapies against AD. Today, there is no cure available for AD and the effects of the symptomatic treatment like cholinesterase inhibitors (ChEIs) and memantine are transient and moderate. Although many AD treatment studies are being carried out, there has not been any breakthrough and new therapies are thus highly needed. Long-term effective therapy for alleviating cognitive impairment is a major unmet need. Discussion and summarizing the new advancements of using NGF as a potential therapeutic implication in AD are important. In summary, the intent of this review is describing available experimental and clinical data related to AD therapy, priming to gain additional facts associated with the importance of NGF for AD treatment, and encapsulated cell biodelivery (ECB) as an efficient tool for NGF delivery.