Identification of novel GDNF isoforms and cis-antisense GDNFOS gene and their regulation in human middle temporal gyrus of Alzheimer disease

The seeds of its regulation: Natural antisense transcripts as single-gene control switches in neurodegenerative disorders

Several proteins play critical roles in vulnerability or resistance to neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and frontotemporal dementia (FTD). Regulation of these proteins is critical to maintaining healthy neurohomeostasis. In addition to transcription factors regulating gene transcription and microRNAs regulating mRNA translation, natural antisense transcripts (NATs) regulate mRNA levels, splicing, and translation. NATs' roles are significant in regulating key protein-coding genes associated with neurodegenerative disorders. Elucidating the functions of these NATs could prove useful in treating or preventing diseases. NAT activity is not restricted to mRNA translation; it can also regulate DNA (de)methylation and other gene expression steps. NATs are noncoding RNAs (ncRNAs) encoded by DNA sequences overlapping the pertinent protein genes. These NATs have complex structures, including introns and exons, and therefore bind their target genes, precursor mRNAs (pre-mRNAs), and mature RNAs. They can occur at the 5'- or 3'-ends of a mRNA-coding sequence or internally to a parent gene. NATs can downregulate translation, e.g., microtubule-associated protein tau (MAPT) antisense-1 gene (MAPT-AS1), or upregulate translation, e.g., β-Amyloid site Cleaving Enzyme 1 (BACE1) antisense gene (BACE1-AS). Regulation of NATs can parallel pathogenesis, wherein a "pathogenic" NAT (e.g., BACE1-AS) is upregulated under pathogenic conditions, while a "protective" NAT (e.g., MAPT-AS1) is downregulated under pathogenic conditions. As a relatively underexplored endogenous control mechanism of protein expression, NATs may present novel mechanistic targets to prevent or ameliorate aging-related disorders.

The Role of Non-coding RNAs in Alzheimer's Disease: Pathogenesis, Novel Biomarkers, and Potential Therapeutic Targets

Long non-coding RNAs (IncRNAs) are regulatory RNA transcripts that have recently been associated with the onset of many neurodegenerative illnesses, including Alzheimer's disease (AD). Several IncRNAs have been found to be associated with AD pathophysiology, each with a distinct mechanism. In this review, we focused on the role of IncRNAs in the pathogenesis of AD and their potential as novel biomarkers and therapeutic targets. Searching for relevant articles was done using the PubMed and Cochrane library databases. Studies had to be published in full text in English in order to be considered. Some IncRNAs were found to be upregulated, while others were downregulated. Dysregulation of IncRNAs expression may contribute to AD pathogenesis. Their effects manifest as the synthesis of beta-amyloid (Aβ) plaques increases, thereby altering neuronal plasticity, inducing inflammation, and promoting apoptosis. Despite the need for more investigations, IncRNAs could potentially increase the sensitivity of early detection of AD. Until now, there has been no effective treatment for AD. Hence, InRNAs are promising molecules and may serve as potential therapeutic targets. Although several dysregulated AD-associated lncRNAs have been discovered, the functional characterization of most lncRNAs is still lacking.

Bidirectional Mapping with Contrastive Learning on Multimodal Neuroimaging Data

The modeling of the interaction between brain structure and function using deep learning techniques has yielded remarkable success in identifying potential biomarkers for different clinical phenotypes and brain diseases. However, most existing studies focus on one-way mapping, either projecting brain function to brain structure or inversely. This type of unidirectional mapping approach is limited by the fact that it treats the mapping as a one-way task and neglects the intrinsic unity between these two modalities. Moreover, when dealing with the same biological brain, mapping from structure to function and from function to structure yields dissimilar outcomes, highlighting the likelihood of bias in one-way mapping. To address this issue, we propose a novel bidirectional mapping model, named Bidirectional Mapping with Contrastive Learning (BMCL), to reduce the bias between these two unidirectional mappings via ROI-level contrastive learning. We evaluate our framework on clinical phenotype and neurodegenerative disease predictions using two publicly available datasets (HCP and OASIS). Our results demonstrate the superiority of BMCL compared to several state-of-the-art methods.

Neurotrophins and Other Growth Factors in the Pathogenesis of Alzheimer’s Disease

The involvement of the changed expression/function of neurotrophic factors in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD), has been suggested. AD is one of the age-related dementias, and is characterized by cognitive impairment with decreased memory function. Developing evidence demonstrates that decreased cell survival, synaptic dysfunction, and reduced neurogenesis are involved in the pathogenesis of AD. On the other hand, it is well known that neurotrophic factors, especially brain-derived neurotrophic factor (BDNF) and its high-affinity receptor TrkB, have multiple roles in the central nervous system (CNS), including neuronal maintenance, synaptic plasticity, and neurogenesis, which are closely linked to learning and memory function. Thus, many investigations regarding therapeutic approaches to AD, and/or the screening of novel drug candidates for its treatment, focus on upregulation of the BDNF/TrkB system. Furthermore, current studies also demonstrate that GDNF, IGF1, and bFGF, which play roles in neuroprotection, are associated with AD. In this review, we introduce data demonstrating close relationships between the pathogenesis of AD, neurotrophic factors, and drug candidates, including natural compounds that upregulate the BDNF-mediated neurotrophic system.

Novel Hominid-Specific IAPP Isoforms: Potential Biomarkers of Early Alzheimer's Disease and Inhibitors of Amyloid Formation

(1) Background and aims: Amyloidosis due to aggregation of amyloid-β (Aβ42) is a key pathogenic event in Alzheimer's disease (AD), whereas aggregation of mature islet amyloid polypeptide (IAPP37) in human islets leads to β-cell dysfunction. The aim of this study is to uncover potential biomarkers that might additionally point to therapy for early AD patients. (2) Methods: We used bioinformatic approach to uncover novel IAPP isoforms and developed a quantitative selective reaction monitoring (SRM) proteomic assay to measure their peptide levels in human plasma and CSF from individuals with early AD and controls, as well as postmortem cerebrum of clinical confirmed AD and controls. We used Thioflavin T amyloid reporter assay to measure the IAPP isoform fibrillation propensity and anti-amyloid potential against aggregation of Aβ42 and IAPP37. (3) Results: We uncovered hominid-specific IAPP isoforms: hIAPPβ, which encodes an elongated propeptide, and hIAPPγ, which is processed to mature IAPP25 instead of IAPP37. We found that hIAPPβ was significantly reduced in the plasma of AD patients with the accuracy of 89%. We uncovered that IAPP25 and a GDNF derived DNSP11 were nonaggregating peptides that inhibited the aggregation of IAPP37 and Aβ42. (4) Conclusions: The novel peptides derived from hIAPP isoforms have potential to serve as blood-derived biomarkers for early AD and be developed as peptide based anti-amyloid medicine.

Regulation of LncRNAs and microRNAs in neuronal development and disease

Non-coding RNAs (ncRNAs) are RNAs that do not encode proteins but play important roles in regulating cellular processes. Multiple studies over the past decade have demonstrated the role of microRNAs (miRNAs) in cancer, in which some miRNAs can act as biomarkers or provide therapy target. Accumulating evidence also points to the importance of long non-coding RNAs (lncRNAs) in regulating miRNA-mRNA networks. An increasing number of ncRNAs have been shown to be involved in the regulation of cellular processes, and dysregulation of ncRNAs often heralds disease. As the population ages, the incidence of neurodegenerative diseases is increasing, placing enormous pressure on global health systems. Given the excellent performance of ncRNAs in early cancer screening and treatment, here we attempted to aggregate and analyze the regulatory functions of ncRNAs in neuronal development and disease. In this review, we summarize current knowledge on ncRNA taxonomy, biogenesis, and function, and discuss current research progress on ncRNAs in relation to neuronal development, differentiation, and neurodegenerative diseases.

Novel Algorithm of Network Calcium Dynamics Analysis for Studying the Role of Astrocytes in Neuronal Activity in Alzheimer's Disease Models

Accumulated experimental data strongly suggest that astrocytes play an important role in the pathogenesis of neurodegeneration, including Alzheimer's disease (AD). The effect of astrocytes on the calcium activity of neuron-astroglia networks in AD modelling was the object of the present study. We have expanded and improved our approach's capabilities to analyze calcium activity. We have developed a novel algorithm to construct dynamic directed graphs of both astrocytic and neuronal networks. The proposed algorithm allows us not only to identify functional relationships between cells and determine the presence of network activity, but also to characterize the spread of the calcium signal from cell to cell. Our study showed that Alzheimer's astrocytes can change the functional pattern of the calcium activity of healthy nerve cells. When healthy nerve cells were cocultivated with astrocytes treated with Aβ42, activation of calcium signaling was found. When healthy nerve cells were cocultivated with 5xFAD astrocytes, inhibition of calcium signaling was observed. In this regard, it seems relevant to further study astrocytic-neuronal interactions as an important factor in the regulation of the functional activity of brain cells during neurodegenerative processes. The approach to the analysis of streaming imaging data developed by the authors is a promising tool for studying the collective calcium dynamics of nerve cells.

Amyloidogenesis and Neurotrophic Dysfunction in Alzheimer’s Disease: Do They have a Common Regulating Pathway?

The amyloid cascade hypothesis has predominately been used to describe the pathogenesis of Alzheimer’s disease (AD) for decades, as Aβ oligomers are thought to be the prime cause of AD. Meanwhile, the neurotrophic factor hypothesis has also been proposed for decades. Accumulating evidence states that the amyloidogenic process and neurotrophic dysfunction are mutually influenced and may coincidently cause the onset and progress of AD. Meanwhile, there are intracellular regulators participating both in the amyloidogenic process and neurotrophic pathways, which might be the common original causes of amyloidogenesis and neurotrophic dysfunction. In this review, the current understanding regarding the role of neurotrophic dysfunction and the amyloidogenic process in AD pathology is briefly summarized. The mutual influence of these two pathogenesis pathways and their potential common causal pathway are further discussed. Therapeutic strategies targeting the common pathways to simultaneously prevent amyloidogenesis and neurotrophic dysfunction might be anticipated for the disease-modifying treatment of AD.

Insights into the mechanisms of non-coding RNAs' implication in the pathogenesis of Alzheimer's disease

Non-coding RNAs including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are implicated in the regulation of gene expression at transcriptional, posttranscriptional, and epigenetic levels. Several studies in cell lines, animal models, and humans, have revealed that non-coding RNAs play crucial roles in the pathogenesis of Alzheimer's disease (AD). Detailed knowledge on their mechanism of implication in the AD pathogenesis can help to develop novel therapeutic and disease management strategies. The two main pathological hallmarks of AD are amyloid plaques resulting from the β-amyloid accumulation, and neurofibrillary tangles (NFT) due to the phosphorylated tau accumulation. Several lncRNAs and miRNAs play crucial roles in both these hallmarks of the AD pathogenesis and other AD-related pathological procedures such as neuronal and synaptic plasticity, neuroinflammation, neuronal differentiation and neuronal apoptosis. In this review, we outlined the non-coding RNAs and further discussed how they are implicated in these AD-related pathological procedures.

Roles of Long Non-coding RNAs in the Development of Aging-Related Neurodegenerative Diseases

Aging-related neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS), are gradually becoming the primary burden of society and cause significant health-care concerns. Aging is a critical independent risk factor for neurodegenerative diseases. The pathological alterations of neurodegenerative diseases are tightly associated with mitochondrial dysfunction, inflammation, and oxidative stress, which in turn stimulates the further progression of neurodegenerative diseases. Given the potential research value, lncRNAs have attracted considerable attention. LncRNAs play complex and dynamic roles in multiple signal transduction axis of neurodegeneration. Emerging evidence indicates that lncRNAs exert crucial regulatory effects in the initiation and development of aging-related neurodegenerative diseases. This review compiles the underlying pathological mechanisms of aging and related neurodegenerative diseases. Besides, we discuss the roles of lncRNAs in aging. In addition, the crosstalk and network of lncRNAs in neurodegenerative diseases are also explored.

Long Non-coding RNA: Insight Into Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD), a heterogeneous neurodegenerative disorder, is the most common cause of dementia accounting for an estimated 60–80% of cases. The pathogenesis of AD remains unclear, and no curative treatment is available so far. Increasing evidence has revealed a vital role of non-coding RNAs (ncRNAs), especially long non-coding RNAs (lncRNAs), in AD. LncRNAs contribute to the pathogenesis of AD via modulating amyloid production, Tau hyperphosphorylation, mitochondrial dysfunction, oxidative stress, synaptic impairment and neuroinflammation. This review describes the biological functions and mechanisms of lncRNAs in AD, indicating that lncRNAs may provide potential therapeutic targets for the diagnosis and treatment of AD.

Therapeutic potential of glial cell line-derived neurotrophic factor and cell reprogramming for hippocampal-related neurological disorders

Hippocampus serves as a pivotal role in cognitive and emotional processes, as well as in the regulation of the hypothalamus-pituitary axis. It is known to undergo mild neurodegenerative changes during normal aging and severe atrophy in Alzheimer’s disease. Furthermore, dysregulation in the hippocampal function leads to epilepsy and mood disorders. In the first section, we summarized the most salient knowledge on the role of glial cell-line-derived neurotrophic factor and its receptors focused on aging, cognition and neurodegenerative and hippocampal-related neurological diseases mentioned above. In the second section, we reviewed the therapeutic approaches, particularly gene therapy, using glial cell-line-derived neurotrophic factor or its gene, as a key molecule in the development of neurological disorders. In the third section, we pointed at the potential of regenerative medicine, as an emerging and less explored strategy for the treatment of hippocampal disorders. We briefly reviewed the use of partial reprogramming to restore brain functions, non-neuronal cell reprogramming to generate neural stem cells, and neural progenitor cells as source-specific neuronal types to be implanted in animal models of specific neurodegenerative disorders.

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.

Gene regulation by antisense transcription: A focus on neurological and cancer diseases

Advances in high-throughput sequencing over the past decades have led to the identification of thousands of non-coding RNAs (ncRNAs), which play a major role in regulating gene expression. One emerging class of ncRNAs is the natural antisense transcripts (NATs), the RNA molecules transcribed from the opposite strand of a protein-coding gene locus. NATs are known to concordantly and discordantly regulate gene expression in both cis and trans manners at the transcriptional, post-transcriptional, translational, and epigenetic levels. Aberrant expression of NATs can therefore cause dysregulation in many biological pathways and has been observed in many genetic diseases. This review outlines the involvements and mechanisms of NATs in the pathogenesis of various diseases, with a special emphasis on neurodegenerative diseases and cancer. We also summarize recent findings on NAT knockdown and/or overexpression experiments and discuss the potential of NATs as promising targets for future gene therapies.

A putative role for lncRNAs in epigenetic regulation of memory

The central dogma of molecular genetics is defined as encoded genetic information within DNA, transcribed into messenger RNA, which contain the instructions for protein synthesis, thus imparting cellular functionality and ultimately life. This molecular genetic theory has given birth to the field of neuroepigenetics, and it is now well established that epigenetic regulation of gene transcription is critical to the learning and memory process. In this review, we address a potential role for a relatively new player in the field of epigenetic crosstalk - long non-coding RNAs (lncRNAs). First, we briefly summarize epigenetic mechanisms in memory formation and examine what little is known about the emerging role of lncRNAs during this process. We then focus discussions on how lncRNAs interact with epigenetic mechanisms to control transcriptional programs under various conditions in the brain, and how this may be applied to regulation of gene expression necessary for memory formation. Next, we explore how epigenetic crosstalk in turn serves to regulate expression of various individual lncRNAs themselves. To highlight the importance of further exploring the role of lncRNA in epigenetic regulation of gene expression, we consider the significant relationship between lncRNA dysregulation and declining memory reserve with aging, Alzheimer's disease, and epilepsy, as well as the promise of novel therapeutic interventions. Finally, we conclude with a discussion of the critical questions that remain to be answered regarding a role for lncRNA in memory.

The Perspective of Dysregulated LncRNAs in Alzheimer's Disease: A Systematic Scoping Review

LncRNAs act as part of non-coding RNAs at high levels of complex and stimulatory configurations in basic molecular mechanisms. Their extensive regulatory activity in the CNS continues on a small scale, from the functions of synapses to large-scale neurodevelopment and cognitive functions, aging, and can be seen in both health and disease situations. One of the vast consequences of the pathological role of dysregulated lncRNAs in the CNS due to their role in a network of regulatory pathways can be manifested in Alzheimer's as a neurodegenerative disease. The disease is characterized by two main hallmarks: amyloid plaques due to the accumulation of β-amyloid components and neurofibrillary tangles (NFT) resulting from the accumulation of phosphorylated tau. Numerous studies in humans, animal models, and various cell lines have revealed the role of lncRNAs in the pathogenesis of Alzheimer's disease. This scoping review was performed with a six-step strategy and based on the Prisma guideline by systematically searching the publications of seven databases. Out of 1,591 records, 69 articles were utterly aligned with the specified inclusion criteria and were summarized in the relevant table. Most of the studies were devoted to BACE1-AS, NEAT1, MALAT1, and SNHG1 lncRNAs, respectively, and about one-third of the studies investigated a unique lncRNA. About 56% of the studies reported up-regulation, and 7% reported down-regulation of lncRNAs expressions. Overall, this study was conducted to investigate the association between lncRNAs and Alzheimer's disease to make a reputable source for further studies and find more molecular therapeutic goals for this disease.

Regulatory role of long non coding RNAs (lncRNAs) in neurological disorders: From novel biomarkers to promising therapeutic strategies

Long non coding RNAs (lncRNAs) are non-protein or low-protein coding transcripts that contain more than 200 nucleotides. They representing a large share of the cell's transcriptional output, demonstrate functional attributes viz. tissue-specific expression, determination of cell fate, controlled expression, RNA processing and editing, dosage compensation, genomic imprinting, conserved evolutionary traits etc. These long non coding variants are well associated with pathogenicity of various diseases including the neurological disorders like Alzheimer's disease, schizophrenia, Huntington's disease, Parkinson's disease etc. Neurological disorders are widespread and there knowing the underlying mechanisms become crucial. The lncRNAs take part in the pathogenesis by a plethora of mechanisms like decoy, scaffold, mi-RNA sequestrator, histone modifiers and in transcriptional interference. Detailed knowledge of the role of lncRNAs can help to use them further as novel biomarkers for therapeutic aspects. Here, in this review we discuss regulation and functional roles of lncRNAs in eight neurological diseases and psychiatric disorders, and the mechanisms by which they act. With these, we try to establish their roles as potential markers and viable diagnostic tools in these disorders.

Advances with Long Non-Coding RNAs in Alzheimer's Disease as Peripheral Biomarker

One of the most compelling needs in the study of Alzheimer’s disease (AD) is the characterization of cognitive decline peripheral biomarkers. In this context, the theme of altered RNA processing has emerged as a contributing factor to AD. In particular, the significant role of long non-coding RNAs (lncRNAs) associated to AD is opening new perspectives in AD research. This class of RNAs may offer numerous starting points for new investigations about pathogenic mechanisms and, in particular, about peripheral biomarkers. Indeed, altered lncRNA signatures are emerging as potential diagnostic biomarkers. In this review, we have collected and fully explored all the presented data about lncRNAs and AD in the peripheral system to offer an overview about this class of non-coding RNAs and their possible role in AD.

The Role of Hippo Signaling Pathway in the Development of the Nervous System

Hippo signaling pathway is a highly conserved and crucial signaling pathway that controls the size of tissues and organs by regulating the proliferation, differentiation, and apoptosis of cells. The nervous system is a complicated system that participates in information collection, integration, and procession. The balance of various aspects of the nervous system is vital for the normal regulation of physiological conditions of the body, like the population and distribution of nerve cells, nerve connections, and so on. Defects in these aspects may lead to cognitive, behavioral, and neurological dysfunction, resulting in various nervous system diseases. Recently, accumulating evidence proposes that Hippo pathway maintains numerous biological functions in the nervous system development, including modulating the proliferation and differentiation of nerve cells and promoting the development of synapse, corpus callosum, and cortex. In this review, we will summarize recent findings of Hippo pathway in the nervous system to improve our understanding on its function and to provide potential therapeutic strategies of nervous system diseases in the future.

Insights into lncRNAs in Alzheimer's disease mechanisms

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common dementia among the elderly. The pathophysiology of AD is characterized by two hallmarks: amyloid plaques, produced by amyloid β (Aβ) aggregation, and neurofibrillary tangle (NFT), produced by accumulation of phosphorylated tau. The regulatory roles of non-coding RNAs (ncRNAs), particularly long noncoding RNAs (lncRNAs), have been widely recognized in gene expression at the transcriptional and posttranscriptional levels. Mounting evidence shows that lncRNAs are aberrantly expressed in AD progression. Here, we review the lncRNAs that implicated in the regulation of Aβ peptide, tau, inflammation, cell death, and other aspects which are the main mechanisms of AD pathology. We also discuss the possible clinical or therapeutic utility of lncRNA detection or targeting to help diagnose or possibly combat AD.

Molecular landscape of long noncoding RNAs in brain disorders

According to current paradigms, various risk factors, such as genetic mutations, oxidative stress, neural network dysfunction, and abnormal protein degradation, contribute to the progression of brain disorders. Through the cooperation of gene transcripts in biological processes, the study of noncoding RNAs can lead to insights into the cause and treatment of brain disorders. Recently, long noncoding RNAs (lncRNAs) which are longer than 200 nucleotides in length have been suggested as key factors in various brain disorders. Accumulating evidence suggests the potential of lncRNAs as diagnostic or prognostic biomarkers and therapeutic targets. High-throughput screening-based sequencing has been instrumental in identification of lncRNAs that demand new approaches to understanding the progression of brain disorders. In this review, we discuss the recent progress in the study of lncRNAs, and addresses the pathogenesis of brain disorders that involve lncRNAs and describes the associations of lncRNAs with neurodegenerative disorders such as Alzheimer disease (AD), Parkinson disease (PD), and neurodevelopmental disorders. We also discuss potential targets of lncRNAs and their promise as novel therapeutics and biomarkers in brain disorders.

Failure of Glial Cell-Line Derived Neurotrophic Factor (GDNF) in Clinical Trials Orchestrated By Reduced NR4A2 (NURR1) Transcription Factor in Parkinson's Disease. A Systematic Review

Parkinson’s disease (PD) is one of the most common neurodegenerative maladies with unforeseen complex pathologies. While this neurodegenerative disorder’s neuropathology is reasonably well known, its etiology remains a mystery, making it challenging to aim therapy. Glial cell-line derived neurotrophic factor (GDNF) remains an auspicious therapeutic molecule for treating PD. Neurotrophic factor derived from glial cell lines is effective in rodents and nonhuman primates, but clinical findings have been equivocal. Laborious exertions have been made over the past few decades to improve and assess GDNF in treating PD (clinical studies). Definitive clinical trials have, however, failed to demonstrate a survival advantage. Consequently, there seemed to be a doubt as to whether GDNF has merit in the potential treatment of PD. The purpose of this cutting edge review is to speculate as to why the clinical trials have failed to meet the primary endpoint. We introduce a hypothesis, “Failure of GDNF in clinical trials succumbed by nuclear receptor-related factor 1 (Nurr1) shortfall.” We demonstrate how Nurr1 binds to GDNF to induce dopaminergic neuron synthesis. Due to its undisputable neuro-protection aptitude, we display Nurr1 (also called Nr4a2) as a promising therapeutic target for PD.

On the functional relevance of spatiotemporally-specific patterns of experience-dependent long noncoding RNA expression in the brain

The majority of transcriptionally active RNA derived from the mammalian genome does not code for protein. Long noncoding RNA (lncRNA) is the most abundant form of noncoding RNA found in the brain and is involved in many aspects of cellular metabolism. Beyond their fundamental role in the nucleus as decoys for RNA-binding proteins associated with alternative splicing or as guides for the epigenetic regulation of protein-coding gene expression, recent findings indicate that activity-induced lncRNAs also regulate neural plasticity. In this review, we discuss how lncRNAs may exert molecular control over brain function beyond their known roles in the nucleus. We propose that subcellular localization is a critical feature of experience-dependent lncRNA activity in the brain, and that lncRNA-mediated control over RNA metabolism at the synapse serves to regulate local mRNA stability and translation, thereby influencing neuronal function, learning and memory.

Enhancer II-targeted dsRNA decreases GDNF expression via histone H3K9 trimethylation to inhibit glioblastoma progression

BACKGROUND

Glial cell line-derived neurotrophic factor (GDNF) is expressed in both astrocytes and glioblastoma (GBM) cells. GDNF expression is significantly increased in GBM, and inhibiting its expression can retard GBM progression. However, there is no known method for specific inhibition of GDNF in GBM cells.

METHODS

Promoter-targeted dsRNA-induced transcriptional gene silencing or activation was recently achieved in human cells. This approach has the potential to specifically regulate gene transcription via epigenetic modifications. In this study, we designed six candidate dsRNAs targeting the enhancer or silencer in GDNF gene promoter II to check their effects on GDNF transcription and GBM progression.

RESULTS

Among these dsRNAs, enhancer II-targeted dsRNA significantly inhibited U251 GBM progression by downregulating GDNF (P < 0.05), while silencer II-targeted dsRNA exerted an opposite effect. Moreover, enhancer II-targeted dsRNA did not significantly change GDNF expression in human astrocytes (HA) and the proliferation and migration of HA cells (P > 0.05). Bisulfate PCR and chromatin immunoprecipitation analyses revealed that both DNA methylation and trimethylation of histone 3 at lysine 9 (H3K9me3) at silencer II-targeted region significantly increased, and H3K9me3 at enhancer II-targeted region significantly decreased, in U251 cells compared with HA cells in non-intervention condition (P < 0.05). Both enhancer II- and silencer II-targeted dsRNA significantly increased H3K9me3 methylation rather than DNA at the targeted site in U251 cells (P < 0.05). The expression and activity of histone methyltransferase SETDB1 increased dramatically in U251 cells compared with HA cells, and it was recruited to enhancer II targeting region after enhancer II-targeted dsRNA treatment in U251 cells (P < 0.05).

CONCLUSIONS

Our results demonstrate that a promoter-targeted dsRNA can silence or promote gene transcription depending on its targeted site in different cis-acting elements in the gene promoter. Targeted inhibition of GDNF by enhancer II-targeted dsRNA may be explored as a novel treatment for GBM.

Do serum GDNF levels correlate with severity of Alzheimer's disease?

INTRODUCTION

A growing body of evidence that glial cell line-derived neurotrophic factor (GDNF) levels are probably involved in pathogenesis and disease course of Alzheimer's disease (AD) suggested that its blood levels could potentially be used as a biomarker of AD. The aim of this study was to compare serum GDNF levels in patients with AD and age-matched controls.

METHODS

Serum concentrations of GDNF were compared in 25 AD patients and 25 healthy volunteers using a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Severity of the disease in AD patients was assessed using Functional Assessment Staging (FAST). Cognitive assessment of the patients was done using the Mini-Mental State Examination (MMSE).

RESULTS

Mean GDNF levels were found to be 2.45 ± 0.93 ng/ml in AD patients and 4.61 ± 3.39 ng/ml in age-matched controls. There was a statistically significant difference in GDNF serum levels in patients with AD compared to age-matched controls (p = 0.001). Moreover, GDNF serum levels were significantly correlated with disease severity (p < 0.001) and cognitive impairment (p < 0.001).

CONCLUSION

This study showed that serum levels of GDNF are significantly decreased in AD patients in comparison with age-matched controls, thus suggesting a potential role of GDNF as a disease biomarker. However, a comprehensive study of changes in serum levels of multiple neurotrophic factors reflective of different neurobiological pathways in large-scale population studies is recommended.

Hypoxia-inducible factor-2α is crucial for proper brain development

Sufficient tissue oxygenation is required for regular brain function; thus oxygen supply must be tightly regulated to avoid hypoxia and irreversible cell damage. If hypoxia occurs the transcription factor complex hypoxia-inducible factor (HIF) will accumulate and coordinate adaptation of cells to hypoxia. However, even under atmospheric O₂ conditions stabilized HIF-2α protein was found in brains of adult mice. Mice with a neuro-specific knockout of Hif-2α showed a reduction of pyramidal neurons in the retrosplenial cortex (RSC), a brain region responsible for a range of cognitive functions, including memory and navigation. Accordingly, behavioral studies showed disturbed cognitive abilities in these mice. In search of the underlying mechanisms for the specific loss of pyramidal cells in the RSC, we found deficits in migration in neural stem cells from Hif-2α knockout mice due to altered expression patterns of genes highly associated with neuronal migration and positioning.

Systematic analysis to identify transcriptome-wide dysregulation of Alzheimer's disease in genes and isoforms

Alzheimer's disease (AD) is one of the most common neurodegeneration diseases caused by multiple factors. The mechanistic insight of AD remains limited. To disclose molecular mechanisms of AD, many studies have been proposed from transcriptome analyses. However, no analysis across multiple levels of transcription has been conducted to discover co-expression networks of AD. We performed gene-level and isoform-level analyses of RNA sequencing (RNA-seq) data from 544 brain tissues of AD patients, mild cognitive impaired (MCI) patients, and healthy controls. Gene and isoform levels of co-expression modules were constructed by RNA-seq data. The associations of modules with AD were evaluated by integrating cognitive scores of patients, Genome-wide association studies (GWAS), alternative splicing analysis, and dementia-related genes expressed in brain tissues. Totally, 29 co-expression modules were found with expressions significantly correlated with the cognitive scores. Among them, two isoform modules were enriched with AD-associated SNPs and genes whose mRNA splicing displayed significant alteration in relation to AD disease. These two modules were further found enriched with dementia-related genes expressed in four brain regions of 125 AD patients. Analyzing expressions of these two modules revealed expressions of 39 isoforms (corresponding to 35 genes) significantly correlated with cognitive scores of AD patients, in which 38 isoforms were significantly up-regulated in AD patients comparing to controls, and 33 isoforms (corresponding to 29 genes) were not reported as AD-related previously. Employing the co-expression modules and the drug-induced gene expression data from Connectivity Map (CMAP), 12 drugs were predicted as significant in restoring the gene expression of AD patients towards health, which include nine drugs reported for relieving AD. In comparison, four of the top 12 significant drugs were known for relieving AD if the drug prediction was performed by the genes expressed significantly different in AD and healthy controls. Analysis of multiple levels of the transcriptomic organization is useful in suggesting AD-related co-expression networks and discovering drugs.

Effects of Transplanted Umbilical Cord Blood Mononuclear Cells Overexpressing GDNF on Spatial Memory and Hippocampal Synaptic Proteins in a Mouse Model of Alzheimer's Disease

BACKGROUND/OBJECTIVE

Alzheimer's disease (AD) is a progressive incurable neurodegenerative disorder. Glial cell line-derived neurotrophic factor (GDNF) is a prominent regulator of brain tissue and has an impressive potential for use in AD therapy. While its metabolism is still not fully understood, delivering neuropeptides such as GDNF via umbilical cord blood mononuclear cells (UCBMCs) to the sites of neurodegeneration is a promising approach in the development of innovative therapeutic avenues.

METHODS

UCBMCs were transduced with adenoviral vectors expressing GDNF and injected into AD transgenic mice. Various parameters including homing and survival of transplanted cells, expression of GDNF and synaptic proteins, as well as spatial memory were evaluated.

RESULTS

UCBMCs were observed in the hippocampus and cortex several weeks after transplantation, and their long-term presence was associated with improved spatial memory. Post-synaptic density protein 95 (PSD-95) and synaptophysin levels in the hippocampus were also effectively restored following the procedure in AD mice.

CONCLUSIONS

Our data indicate that gene-cell therapy with GDNF-overexpressing UCBMCs may produce long-lasting neuroprotection and stimulation of synaptogenesis. Such adenoviral constructs could potentially possess a high therapeutic potential for the treatment of AD.

GDNF/RET signaling in dopamine neurons in vivo

The glial cell line-derived neurotrophic factor (GDNF) and its canonical receptor Ret can signal both in tandem and separately to exert many vital functions in the midbrain dopamine system. It is known that Ret has effects on maintenance, physiology, protection and regeneration in the midbrain dopamine system, with the physiological functions of GDNF still somewhat unclear. Notwithstanding, Ret ligands, such as GDNF, are considered as promising candidates for neuroprotection and/or regeneration in Parkinson's disease, although data from clinical trials are so far inconclusive. In this review, we discuss the current knowledge of GDNF/Ret signaling in the dopamine system in vivo as well as crosstalk with pathology-associated proteins and their signaling in mammals.

Molecular mechanisms underlying actions of certain long noncoding RNAs in Alzheimer's disease

Long non-coding RNAs (lncRNAs) are a group of non-protein coding RNAs that have more than 200 nucleotides. LncRNAs play an important role in the regulation of protein-coding genes at the transcriptional and post-transcriptional levels. They are found in most organs, with a high prevalence in the central nervous system. Accumulating data suggests that lncRNAs are involved in various neurodegenerative disorders, including the onset and progression of Alzheimer's disease (AD). Recent insights suggest lncRNAs, such as BACE1-AS, 51A, 17A, NDM29 and AS-UCHL1, are dysregulated in AD tissues. Furthermore, there are ongoing efforts to explore the clinical usability of lncRNAs as biomarkers in the disease. In this review, we explore the mechanisms by which aberrant expressions of the most studied lncRNAs contribute to the neuropathologies associated with AD, including amyloid β plaques and neurofibrillary tangles. Understanding the molecular mechanisms of lncRNAs in patients with AD will reveal novel diagnosis strategies and more effective therapeutic targets.

Neurotrophins and glial cell line-derived neurotrophic factor in the ovary: physiological and pathophysiological implications

BACKGROUND

Neurotrophins [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4)] and glial cell line-derived neurotrophic factor (GDNF) are soluble polypeptide growth factors that are widely recognized for their roles in promoting cell growth, survival and differentiation in several classes of neurons. Outside the nervous system, neurotrophin (NT) and GDNF signaling events have substantial roles in various non-neural tissues, including the ovary.

OBJECTIVE AND RATIONALE

The molecular mechanisms that promote and regulate follicular development and oocyte maturation have been extensively investigated. However, most information has been obtained from animal models. Even though the fundamental process is highly similar across species, the paracrine regulation of ovarian function in humans remains poorly characterized. Therefore, this review aims to summarize the expression and functional roles of NTs and GDNF in human ovarian biology and disorders, and to describe and propose the development of novel strategies for diagnosing, treating and preventing related abnormalities.

SEARCH METHODS

Relevant literature in the English language from 1990 to 2018 describing the role of NTs and GDNF in mammalian ovarian biology and phenotypes was comprehensively selected using PubMed, MEDLINE and Google Scholar.

OUTCOMES

Studies have shown that the neurotrophins NGF, BDNF, NT-3 and NT-4 as well as GDNF and their functional receptors are expressed in the human ovary. Recently, gathered experimental data suggest putative roles for NT and GDNF signaling in the direct control of ovarian function, including follicle assembly, activation of the primordial follicles, follicular growth and development, oocyte maturation, steroidogenesis, ovulation and corpus luteum formation. Additionally, crosstalk occurs between these ovarian regulators and the endocrine signaling system. Dysregulation of the NT system may negatively affect ovarian function, leading to reproductive pathology (decreased ovarian reserve, polycystic ovary syndrome and endometriosis), female infertility and even epithelial ovarian cancers.

WIDER IMPLICATIONS

A comprehensive understanding of the expression, actions and underlying molecular mechanisms of the NT/GDNF system in the human ovary is essential for novel approaches to therapeutic and diagnostic interventions in ovarian diseases and to develop more safe, effective methods of inducing ovulation in ART in the treatment of female infertility.

Induction of GDNF and GFRα-1 Following AAV1-Rheb(S16H) Administration in the Hippocampus in vivo

The activation of neurotrophic signaling pathways following the upregulation of glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor-β family, has a potential neuroprotective effect in the adult brain. Herein, we report that hippocampal transduction of adeno-associated virus serotype 1 (AAV1) with a constitutively active form of ras homolog enriched in brain [Rheb(S16H)], which can stimulate the production of brain-derived neurotrophic factor (BDNF) in hippocampal neurons, induces the increases in expression of GDNF and GDNF family receptor α-1 (GFRα-1), in neurons and astrocytes in the hippocampus of rat brain in vivo. Moreover, upregulation of GDNF and GFRα-1 contributes to neuroprotection against thrombin-induced neurotoxicity in the hippocampus. These results suggest that AAV1-Rheb(S16H) transduction of hippocampal neurons, resulting in neurotrophic interactions between neurons and astrocytes, may be useful for neuroprotection in the adult hippocampus.

Osthole ameliorates cognitive impairments via augmenting neuronal population in APP / PS1 transgenic mice

Alzheimer's disease (AD) is a neurodegenerative disorder with notable factors of dysfunction in multiple neurological changes, encompassing neuronal loss in the frontal cortex and hippocampal regions. Dysfunction of proliferation and self-renewal of neural stem cells (NSCs) was observed in AD patients and animals. Thereby, mobilizing endogenous neurogenesis by pharmacological agents would provide a promising route for neurodegeneration. Osthole (Ost), a natural coumarin derivative, has been reported to exert extensive neuroprotective effects in AD. However, whether ost can facilitate endogenous neurogenesis against AD in vivo is still unknown. In this study, by using Morris water maze (MWM) test, hematoxylin-eosin (HE) staining, Nissl staining, immunofluorescence analysis and western blot, we demonstrated that oral administration of ost could improve the learning and memory function, inhibit neuronal apoptosis, elevate the expression of glial cell line derived neurotrophic factor (GDNF), synaptophysin (SYP) and postsynaptic density protein 95 (PSD95). Moreover, ost could remarkably enhance proliferation of NSCs and increase the amount of mature neurons in APP/PS1 transgenic mice. Together, our findings demonstrated that ost possessed the ability of promoting endogenous neurogenesis and ost could be served as a plausible agent to reverse or slow down the progress of AD.

Crosstalk between DNA methylation and histone acetylation triggers GDNF high transcription in glioblastoma cells

BACKGROUND

Glial cell line-derived neurotrophic factor (GDNF) is highly expressed in glioblastoma (GBM) and blocking its expression can inhibit the initiation and development of GBM. GDNF is a dual promoter gene, and the promoter II with two enhancers and two silencers plays a major role in transcription initiation. We had previously reported that histone hyperacetylation and DNA hypermethylation in GDNF promoter II region result in high transcription of GDNF in GBM cells, but the mechanism remains unclear. In this study, we investigated whether these modifications synergistically regulate high GDNF transcription in GBM.

RESULTS

Cyclic AMP response element binding protein (CREB) expression and phosphorylation at S133 were significantly increased in human GBM tissues and GBM cell lines (U251 and U343). In U251 GBM cells, high expressed CREB significantly enhanced GDNF transcription and promoter II activity. CREB regulated GDNF transcription via the cyclic AMP response elements (CREs) in enhancer II and silencer II of GDNF promoter II. However, the two CREs played opposite regulatory roles. Interestingly, hypermethylation of CRE in silencer II occurred in GBM tissues and cells which led to decreased and increased phosphorylated CREB (pCREB) binding to silencer II and enhancer II, respectively. Moreover, pCREB recruited CREB binding protein (CBP) with histone acetylase activity to the CRE of GDNF enhancer II, thereby increasing histone H3 acetylation and RNA polymerase II recruitment there and at the transcription start site (TSS), and promoted GDNF high transcription in U251 cells. The results indicated that high GDNF transcription was attributable to DNA hypermethylation in CRE of GDNF silencer II increasing pCREB binding to CRE in enhancer II, which enhanced CBP recruitment, histone H3 acetylation, and RNA polymerase II recruitment there and at the TSS.

CONCLUSIONS

Our results demonstrate that pCREB-induced crosstalk between DNA methylation and histone acetylation at the GDNF promoter II enhanced GDNF high transcription, providing a new perspective for GBM treatment.

Differential expression of glial cell line-derived neurotrophic factor splice variants in the mouse brain

Glial cell line-derived neurotrophic factor (GDNF) plays a critical role in neuronal survival and function. GDNF has two major splice variants in the brain, α-pro-GDNF and β-pro-GDNF, and both isoforms have strong neuroprotective effects on dopamine neurons. However, the expression of the GDNF splice variants in dopaminergic neurons in the brain remains unclear. Therefore, in this study, we investigated the mRNA and protein expression of α- and β-pro-GDNF in the mouse brain by real-time quantitative polymerase chain reaction, using splice variant-specific primers, and western blot analysis. At the mRNA level, β-pro-GDNF expression was significantly greater than that of α-pro-GDNF in the mouse brain. In contrast, at the protein level, α-pro-GDNF expression was markedly greater than that of β-pro-GDNF. To clarify the mechanism underlying this inverse relationship in mRNA and protein expression levels of the GDNF splice variants, we analyzed the expression of sorting protein-related receptor with A-type repeats (SorLA) by real-time quantitative polymerase chain reaction. At the mRNA level, SorLA was positively associated with β-pro-GDNF expression, but not with α-pro-GDNF expression. This suggests that the differential expression of α- and β-pro-GDNF in the mouse brain is related to SorLA expression. As a sorting protein, SorLA could contribute to the inverse relationship among the mRNA and protein levels of the GDNF isoforms. This study was approved by the Animal Ethics Committee of Xuzhou Medical University, China on July 14, 2016.

Citrus Auraptene Induces Glial Cell Line-Derived Neurotrophic Factor in C6 Cells

We previously demonstrated that auraptene (AUR), a natural coumarin derived from citrus plants, exerts anti-inflammatory effects in the brain, resulting in neuroprotection in some mouse models of brain disorders. The present study showed that treatment with AUR significantly increased the release of glial cell line-derived neurotrophic factor (GDNF), in a dose- and time-dependent manner, by rat C6 glioma cells, which release was associated with increased expression of GDNF mRNA. These results suggest that AUR acted as a neuroprotective agent in the brain via not only its anti-inflammatory action but also its induction of neurotrophic factor. We also showed that (1) the AUR-induced GDNF production was inhibited by U0126, a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) 1/2, and by H89, a specific inhibitor of protein kinase A (PKA); and (2) AUR induced the phosphorylation of cAMP response element-binding protein (CREB), a transcription factor located within the nucleus. These results suggest that AUR-stimulated gdnf gene expression was up-regulated through the PKA/ERK/CREB pathway in C6 cells.

Invited Review: Long non-coding RNAs: important regulators in the development, function and disorders of the central nervous system

Genome-wide transcriptional studies have demonstrated that tens of thousands of long non-coding RNAs (lncRNA) genes are expressed in the central nervous system (CNS) and that they exhibit tissue- and cell-type specificity. Their regulated and dynamic expression and their co-expression with protein-coding gene neighbours have led to the study of the functions of lncRNAs in CNS development and disorders. In this review, we describe the general characteristics, localization and classification of lncRNAs. We also elucidate the examples of the molecular mechanisms of nuclear and cytoplasmic lncRNA actions in the CNS and discuss common experimental approaches used to identify and unveil the functions of lncRNAs. Additionally, we provide examples of lncRNA studies of cell differentiation and CNS disorders including CNS injuries and neurodegenerative diseases. Finally, we review novel lncRNA-based therapies. Overall, this review highlights the important biological roles of lncRNAs in CNS functions and disorders.

Time course of transient expression of pre-α-pro-GDNF and pre-β-pro-GDNF transcripts, and mGDNF mRNA region in Krushinsky-Molodkina rat brain after audiogenic seizures

The expression of glial cell line-derived neurothrophic factor (GDNF) transcript forms pre-(α)pro-gdnf, pre-(β)pro-gdnf, and their common region m-gdnf in the pons as well as the inferior (IC) and superior colliculi in Krushinsky-Molodkina (KM) rats and in the strain "0" was analyzed by quantitative real-time polymerase chain reaction (PCR) in the control (unstimulated KM and "0" rats) and 1.5, 4.5, and 8 h after auditory stimulation. Such stimulation induced audiogenic seizures (AS) in KM rats. Audiogenic seizure was not observed in "0" rats, which was obtained by selection for the absence of AS in a population of F2 hybrids between KM and Wistar rats not predisposed to AS. A significant drop in the level of all transcripts was observed 1.5 h after auditory stimulation in both KM and "0" rats. In most cases, the average expression of α and β isoforms and m-region 4.5 h after stimulation was greater than those after 1.5 and 8 h. At the same time, the expression of pre-(β)pro-gdnf in the IC of KM rats 4.5 h after the stimulation was significantly lower than after 1.5 or 8 h. This work presents the first demonstration of different time courses of expression of the α and β GDNF isoforms during physiological processes in genotype-specific pathology.

Neurotrophic Factors Mediated Activation of Astrocytes Ameliorate Memory Loss by Amyloid Clearance after Transplantation of Lineage Negative Stem Cells

Alzheimer's disease (AD) is one of the untreatable neurodegenerative disorders with associated societal burden. Current therapies only provide symptomatic relief without altering the rate of disease progression as reported by Lanctot et al. (Therapeutic Advances in Neurological Disorders 2 (3):163-180, 2009). The increased number of failed clinical trials in last two decades indicates the imperative need to explore alternative therapies for AD as reported by Tuszynski et al. (Nature Medicine 11 (5):551-555, 2005) and Liyanage et al. (Alzheimer's & Dementia 4:628-635, 2005). In this study, we aimed to decipher the role of neurotrophic factors in the reversal of memory loss by transplantation of lineage negative (Lin-ve) stem cells in a male mouse model of cognitive impairment induced by intrahippocampal injection of amyloid β-42 (Aβ-42). The efficacy of human umbilical cord blood (hUCB) derived Lin-ve stem cells were analyzed by neurobehavioral parameters, i.e., Morris water maze and passive avoidance after bilateral intra-hippocampal transplantation using stereotaxic surgery. Real-time PCR and immunohistochemistry was carried out in brain tissues in order to analyze the expression of neurotrophic factors, apoptotic, astrocytic, and other neuronal cell markers. The transplantation of Lin-ve stem cells led to reversal of memory loss associated with reduction of Aβ-42 deposition from the brains. The molecular analysis revealed increase in neurotrophic factors, i.e., glial derived neurotrophic factor (GDNF), ciliary derived neurotrophic factor (CNTF), and Brain-derived neurotrophic factor (BDNF) after transplantation. The administration of ANA-12, a TrkB inhibitor, reversed the behavioral and molecular effects of stem cell transplantation suggesting involvement of BDNF-TrkB pathway in the rescue of memory loss. We believe that the amyloid clearance results from activation of astrocytes and anti-apoptotic pathways added by neurotrophic factors.

Mechanism of methylation and acetylation of high GDNF transcription in glioma cells: A review

Gliomas are the most common primary malignant tumors in the central nervous system. High expression of glial cell line-derived neurotrophic factor (GDNF) is an important prerequisite for the initiation and development of gliomas. However, the underlying transcription mechanism is poorly understood. Epigenetic alterations are common and important hallmarks of various types of tumors, and lead to abnormal expression of genes. Several recent studies have suggested that epigenetic modifications contribute to increased GDNF transcription. Specifically, aberrant DNA methylation and histone acetylation in the promoter regions of GDNF are related to high GDNF transcription in glioma cells, where transcription factors have extremely important roles. Therefore, elucidating the importance and features of this underlying molecular mechanism will enhance our understanding and provide clues for the accurate diagnosis and efficacious treatment of gliomas. This review summarizes the latest thinking on the potential epigenetic mechanisms of high expression of GDNF in glioma cells focusing primarily on DNA methylation and histone acetylation.

GDNFOS1 knockdown decreases the invasion and viability of glioblastoma cells

Glioblastoma multiforme is the most aggressive primary brain cancer in adults. Therefore, it is important to investigate the mechanisms associated with cell viability and invasion ability of the cells in glioblastoma multiforme. The opposite strand of the glial cell line-derived neurotrophic factor (GDNF) gene is used to transcribe the cis-antisense GDNF opposite strand (GDNFOS) gene, which belongs to the long noncoding RNAs. The current study assessed the effects of GDNFOS1 overexpression and interference on GDNF expression, cell viability and invasion ability in U87 and U251 MG glioblastoma cells. Overexpression and interference were performed using constructed lentiviral vectors, including long non-coding RNA GDNFOS1 overexpression vector, pL-short hairpin RNA (shRNA)-GDNFOS1-9, pL-shRNA-GDNFOS1-49, pL-shRNA-GDNFOS1-248, pL-shRNA-GDNFOS1-9+49, pL-shRNA-GDNFOS1-9+248 and pL-shRNA-GDNFOS1-49+248. Reverse transcription-quantitative PCR was used to determine the efficiency of interference and overexpression of GDNFOS1 in U87 and U251 MG cells. GDNF protein expression in U87 and U251 MG cells was detected using western blot analysis. In addition, cell viability was detected using a cell counting kit-8 assay at 24, 48 and 72 h after GDNFOS1 overexpression or interference. A transwell invasion assay was used to detect invasion ability. Different shRNA sequences were tested and the results revealed that a combination (pL-shRNA-GDNFOS1-49+248) was most effective in the knock-down GDNFOS1. Compared with the control group, GDNF expression in U87 MG cells was significantly increased in the GDNFOS1 overexpression group and decreased in the shRNA-GDNFOS1-248 group. U87 MG cell viability was significantly increased in the GDNFOS1 overexpression group at 24, 48 and 72 h compared with the negative control group. The viability of U87 MG cells was decreased in the GDNFOS1 interference group at 72 h when compared with the control group. The relative invasive ability was significantly increased in the GDNFOS1 overexpression group when compared with the negative control group. The invasive ability was significantly decreased in the GDNFOS1 interference group when compared with the negative control group. Similar results were exhibited by the U251 MG cells. Overall, GDNF expression, cell viability and invasion ability of glioblastoma cells significantly increased with GDNFOS1 overexpression and decreased with GDNFOS1 interference.

Emerging roles of long non-coding RNAs in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder and represents the most common form of senile dementia. The pathogenesis of AD is not yet completely understood and no curative treatment is currently available. With the recent advancement in transcriptome-wide profiling approach, several non-coding RNAs (ncRNAs) have been identified. Among them, long non-coding RNAs (lncRNAs), which are long transcripts without apparent protein-coding capacity, have received increasing interest for their involvement in a wide range of biological processes as regulatory molecules. Recent studies have suggested that lncRNAs play a role in AD pathogenesis, although their specific influences in the disorder remain to be largely unknown. Herein, we will summarize the biology and mechanisms of action of the best characterized dysregulated lncRNAs in AD, focusing the attention on their potential role in the disease pathogenesis. A deeper understanding of the molecular mechanisms and the complex network of interactions in which they are implicated should open the doors to new research considering lncRNAs as novel therapeutic targets and prognostic/diagnostic biomarkers.

Early Life Stress and Epigenetics in Late-onset Alzheimer's Dementia: A Systematic Review

Involvement of life stress in Late-Onset Alzheimer's Disease (LOAD) has been evinced in longitudinal cohort epidemiological studies, and endocrinologic evidence suggests involvements of catecholamine and corticosteroid systems in LOAD. Early Life Stress (ELS) rodent models have successfully demonstrated sequelae of maternal separation resulting in LOAD-analogous pathology, thereby supporting a role of insulin receptor signalling pertaining to GSK-3beta facilitated tau hyper-phosphorylation and amyloidogenic processing. Discussed are relevant ELS studies, and findings from three mitogen-activated protein kinase pathways (JNK/SAPK pathway, ERK pathway, p38/MAPK pathway) relevant for mediating environmental stresses. Further considered were the roles of autophagy impairment, neuroinflammation, and brain insulin resistance. For the meta-analytic evaluation, 224 candidate gene loci were extracted from reviews of animal studies of LOAD pathophysiological mechanisms, of which 60 had no positive results in human LOAD association studies. These loci were combined with 89 gene loci confirmed as LOAD risk genes in previous GWAS and WES. Of the 313 risk gene loci evaluated, there were 35 human reports on epigenomic modifications in terms of methylation or histone acetylation. 64 microRNA gene regulation mechanisms were published for the compiled loci. Genomic association studies support close relations of both noradrenergic and glucocorticoid systems with LOAD. For HPA involvement, a CRHR1 haplotype with MAPT was described, but further association of only HSD11B1 with LOAD found; however, association of FKBP1 and NC3R1 polymorphisms was documented in support of stress influence to LOAD. In the brain insulin system, IGF2R, INSR, INSRR, and plasticity regulator ARC, were associated with LOAD. Pertaining to compromised myelin stability in LOAD, relevant associations were found for BIN1, RELN, SORL1, SORCS1, CNP, MAG, and MOG. Regarding epigenetic modifications, both methylation variability and de-acetylation were reported for LOAD. The majority of up-to-date epigenomic findings include reported modifications in the well-known LOAD core pathology loci MAPT, BACE1, APP (with FOS, EGR1), PSEN1, PSEN2, and highlight a central role of BDNF. Pertaining to ELS, relevant loci are FKBP5, EGR1, GSK3B; critical roles of inflammation are indicated by CRP, TNFA, NFKB1 modifications; for cholesterol biosynthesis, DHCR24; for myelin stability BIN1, SORL1, CNP; pertaining to (epi)genetic mechanisms, hTERT, MBD2, DNMT1, MTHFR2. Findings on gene regulation were accumulated for BACE1, MAPK signalling, TLR4, BDNF, insulin signalling, with most reports for miR-132 and miR-27. Unclear in epigenomic studies remains the role of noradrenergic signalling, previously demonstrated by neuropathological findings of childhood nucleus caeruleus degeneration for LOAD tauopathy.

Regional glucose metabolism due to the presence of cerebral amyloidopathy in older adults with depression and mild cognitive impairment

BACKGROUND

Depression is a risk factor for mild cognitive impairment (MCI) and for the conversion from MCI to Alzheimer's disease (AD). This study investigated regional cerebral glucose metabolism (rCMglc) in older adults with depression and MCI, either with or without amyloidopathy.

METHODS

We recruited 31 older adults diagnosed with depression and MCI, and 21 older adults with normal cognition (NC). All participants completed demographic questionnaires and were examined with a standardized neuropsychological battery, F-18 fluorodeoxyglucose positron emission tomography (PET), and F-18 florbetaben PET. We classified subjects with depression and MCI into amyloid-β-positive (CDAP; n = 16) and amyloid-β-negative (CDAN; n = 15) groups. Pairwise rCMglc analyses were conducted between all three groups (CDAP vs. NC, CDAN vs. NC, and CDAP vs. CDAN).

RESULTS

In comparison with the NC group, the CDAP group showed reduced rCMglc predominantly in temporoparietal regions, whereas the CDAN group showed lower rCMglc in regions of the frontal lobe, in addition to the temporoparietal regions. The CDAN group also showed lower rCMglc in right anterior cingulate and left inferior orbitofrontal regions, in a comparison between the CDAP and CDAN groups.

LIMITATIONS

The generalizability of the findings is limited because this study has a relatively small number of participants. In addition, this study used cross-sectional design rather than longitudinal design.

CONCLUSIONS

Our findings may provide a reference to assess the risk of future cognitive deterioration. Consequently, this study is expected to contribute to prevention and early identification of dementia associated with AD.

The Role of Long Noncoding RNAs in Central Nervous System and Neurodegenerative Diseases

Long noncoding RNAs (lncRNAs) refer to a group of noncoding RNAs (ncRNAs) that has a transcript of more than 200 nucleotides in length in eukaryotic cells. The lncRNAs regulate gene expression at epigenetic, transcriptional, and post-transcriptional levels by multiple action modes. In this review, we describe the diverse roles reported for lncRNAs, and discuss how they could mechanistically be involved in the development of central nervous system (CNS) and neurodegenerative diseases. Further studies on the function of lncRNAs and their mechanism will help deepen our understanding of the development, function, and diseases of the CNS, and provide new ideas for the design and development of some therapeutic drugs.

The reversible effects of glial cell line-derived neurotrophic factor (GDNF) in the human brain

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor, and a member of the transforming growth factor β (TGF-β) superfamily acting on different neuronal activities. GDNF was originally identified as a neurotrophic factor crucially involved in the survival of dopaminergic neurons of the nigrostriatal pathway and is currently an established therapeutic target in Parkinson's disease. However, GDNF was later reported to be highly expressed in gliomas, especially in glioblastomas, and was demonstrated as a potent proliferation factor involved in the development and migration of gliomas. Here, we review our current understanding and progress made so far by researchers in our laboratories with references to relevant articles to support our discoveries. We present past and recent discoveries on the mechanisms involved in the protection of neurons by GDNF and examine its emerging roles in gliomas, as well as reasons for the abnormal expression in Glioblastoma Multiforme (GBM). Collectively, our work establishes a paradigm by which the ability of GDNF to protect dopaminergic neurons from degradation and its corresponding effects on glioma cells points to an underlying biological vulnerability in the effects of GDNF in the normal brain which can be subverted for use by cancer cells. Hence, presenting novel opportunities for intervention in glioma therapies.

Pre-α-pro-GDNF and Pre-β-pro-GDNF Isoforms Are Neuroprotective in the 6-hydroxydopamine Rat Model of Parkinson's Disease

Glial cell line-derived neurotrophic factor (GDNF) is one of the most studied neurotrophic factors. GDNF has two splice isoforms, full-length pre-α-pro-GDNF (α-GDNF) and pre-β-pro-GDNF (β-GDNF), which has a 26 amino acid deletion in the pro-region. Thus far, studies have focused solely on the α-GDNF isoform, and nothing is known about the in vivo effects of the shorter β-GDNF variant. Here we compare for the first time the effects of overexpressed α-GDNF and β-GDNF in non-lesioned rat striatum and the partial 6-hydroxydopamine lesion model of Parkinson's disease. GDNF isoforms were overexpressed with their native pre-pro-sequences in the striatum using an adeno-associated virus (AAV) vector, and the effects on motor performance and dopaminergic phenotype of the nigrostriatal pathway were assessed. In the non-lesioned striatum, both isoforms increased the density of dopamine transporter-positive fibers at 3 weeks after viral vector delivery. Although both isoforms increased the activity of the animals in cylinder assay, only α-GDNF enhanced the use of contralateral paw. Four weeks later, the striatal tyrosine hydroxylase (TH)-immunoreactivity was decreased in both α-GDNF and β-GDNF treated animals. In the neuroprotection assay, both GDNF splice isoforms increased the number of TH-immunoreactive cells in the substantia nigra but did not promote behavioral recovery based on amphetamine-induced rotation or cylinder assays. Thus, the shorter GDNF isoform, β-GDNF, and the full-length α-isoform have comparable neuroprotective efficacy on dopamine neurons of the nigrostriatal circuitry.

Epigenetic modulation by small molecule compounds for neurodegenerative disorders

The accumulation of somatic and genetic mutations which altered the structure and coding information of the DNA are the major cause of neurological disorders. However, our recent understanding of molecular mechanisms of 'epigenetic' phenomenon reveals that the modifications of chromatin play a significant role in the development and severity of neurological disorders. These epigenetic processes are dynamic and reversible as compared to genetic ablations which are stable and irreversible. Therefore, targeting these epigenetic processes through small molecule modulators are of great therapeutic potential. To date, large number of small molecule modulators have been discovered which are capable of altering the brain pathology by targeting epigenetic enzymes. In this review, we shall put forward the key studies supporting the role of altered epigenetic processes in neurological disorders with especial emphasis on neurodegenerative disorders. A few small molecule modulators which have been shown to possess promising results in the animal model system of neurological disorders will also be discussed with future perspectives.

Molecular mechanisms of long noncoding RNAs and their role in disease pathogenesis

LncRNAs are long non-coding regulatory RNAs that are longer than 200 nucleotides. One of the major functions of lncRNAs is the regulation of specific gene expression at multiple steps including, recruitment and expression of basal transcription machinery, post-transcriptional modifications and epigenetics [1]. Emerging evidence suggests that lncRNAs also play a critical role in maintaining tissue homeostasis during physiological and pathological conditions, lipid homeostasis, as well as epithelial and smooth muscle cell homeostasis, a topic that has been elegantly reviewed [2-5]. While aberrant expression of lncRNAs has been implicated in several disease conditions, there is paucity of information about their contribution to the etiology of diseases [6]. Several studies have compared the expression of lncRNAs under normal and cancerous conditions and found differential expression of several lncRNAs, suggesting thereby an involvement of lncRNAs in disease processes [7, 8]. Furthermore, the ability of lncRNAs to influence epigenetic changes also underlies their role in disease pathogenesis since epigenetic regulation is known to play a critical role in many human diseases [1]. LncRNAs thus are not only involved in homeostatic functioning but also play a vital role in the progression of many diseases, thereby underscoring their potential as novel therapeutic targets for the alleviation of a variety of human disease conditions.