Neurotrophic factors hold promise for the future of Parkinson's disease treatment: is there a light at the end of the tunnel?

Growth Factors and Their Application in the Therapy of Hereditary Neurodegenerative Diseases

Hereditary neurodegenerative diseases (hNDDs) such as Alzheimer's, Parkinson's, Huntington's disease, and others are primarily characterized by their progressive nature, severely compromising both the cognitive and motor abilities of patients. The underlying genetic component in hNDDs contributes to disease risk, creating a complex genetic landscape. Considering the fact that growth factors play crucial roles in regulating cellular processes, such as proliferation, differentiation, and survival, they could have therapeutic potential for hNDDs, provided appropriate dosing and safe delivery approaches are ensured. This article presents a detailed overview of growth factors, and explores their therapeutic potential in treating hNDDs, emphasizing their roles in neuronal survival, growth, and synaptic plasticity. However, challenges such as proper dosing, delivery methods, and patient variability can hinder their clinical application.

Nigrostriatal Inflammation Is Associated with Nonmotor Symptoms in an Experimental Model of Prodromal Parkinson's Disease

Recent evidence has supported a pathogenic role for neuroinflammation in Parkinson's disease (PD). Inflammatory response has been associated with symptoms and subtypes of PD. However, it is unclear whether immune changes are involved in the initial pathogenesis of PD, leading to the non-motor symptoms (NMS) observed in its prodromal stage. The current study aimed to characterize the behavioral and cognitive changes in a toxin-induced model of prodromal PD-like syndrome. We also sought to investigate the role of neuroinflammation in prodromal PD-related NMS. Male mice were subjected to bilateral intranasal infusion with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or saline (control group), followed by comprehensive behavioral, pathological and neurochemical analysis. Intranasal MPTP infusion was able to cause the loss of dopaminergic neurons in the substantia nigra (SN). In parallel, it induced impairment in olfactory discrimination and social memory consolidation, compulsive and anxiety-like behaviors, but did not influence motor performance. Iba-1 and GFAP expressions were increased in the SN, suggesting an activated state of microglia and astrocytes. Consistent with this, MPTP mice had increased levels of IL-10 and IL-17A, and decreased levels of BDNF and TrkA mRNA in the SN. The striatum showed increased IL-17A, BDNF, and NFG levels compared to control mice. In conclusion, neuroinflammation may play an important role in the early stage of experimental PD-like syndrome, leading to cognitive and behavioral changes. Our results also indicate that intranasal administration of MPTP may represent a valuable mouse model for prodromal PD.

Neurotrophic factor MANF regulates autophagy and lysosome function to promote proteostasis in C. elegans

The conserved mesencephalic astrocyte-derived neurotrophic factor (MANF) protects dopaminergic neurons but also functions in several other tissues. Previously, we showed that Caenorhabditis elegans manf-1 null mutants have increased ER stress, dopaminergic neurodegeneration, protein aggregation, slower growth, and a reduced lifespan. The multiple requirements of MANF in different systems suggest its essential role in regulating cellular processes. However, how intracellular and extracellular MANF regulates broader cellular function remains unknown. Here, we report a novel mechanism of action for manf-1 that involves the autophagy transcription factor HLH-30/TFEB-mediated signaling to regulate lysosomal function and aging. We generated multiple transgenic strains overexpressing MANF-1 and found that animals had extended lifespan, reduced protein aggregation, and improved neuronal health. Using a fluorescently tagged MANF-1, we observed different tissue localization of MANF-1 depending on the ER retention signal. Further subcellular analysis showed that MANF-1 localizes within cells to the lysosomes. These findings were consistent with our transcriptomic studies and, together with analysis of autophagy regulators, demonstrate that MANF-1 regulates protein homeostasis through increased autophagy and lysosomal activity. Collectively, our findings establish MANF as a critical regulator of the stress response, proteostasis, and aging.

Stem Cell Therapy for the Treatment of Parkinson's Disease: What Promise Does it Hold?

Parkinson's disease (PD) is a common, progressive neurodegenerative disorder characterized by substantia nigra dopamine cell death and a varied clinical picture that affects older people. Although more than two centuries have passed since the earliest attempts to find a cure for PD, it remains an unresolved problem. With this in mind, cell replacement therapy is a new strategy for treating PD. This novel approach aims to replace degenerated dopaminergic (DAergic) neurons with new ones or provide a new source of cells that can differentiate into DAergic neurons. Induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), neural stem cells (NSCs), and embryonic stem cells (ESCs) are among the cells considered for transplantation therapies. Recently disease-modifying strategies like cell replacement therapies combined with other therapeutic approaches, such as utilizing natural compounds or biomaterials, are proposed to modify the underlying neurodegeneration. In the present review, we discuss the current advances in cell replacement therapy for PD and summarize the existing experimental and clinical evidence supporting this approach.

Effects of voluntary, and forced exercises on neurotrophic factors and cognitive function in animal models of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the elderly. Cognitive dysfunction represents a common and challenging non-motor symptom for people with Parkinson's disease. The number of neurotrophic proteins in the brain is critical in neurodegenerative diseases such as Parkinson's. This research aims to compare the effects of two types of exercise, forced and voluntary, on spatial memory and learning and neurochemical factors (CDNF and BDNF).

METHODS

In this research, 60 male rats were randomly divided into six groups (n = 10): the control (CTL) group without exercise, the Parkinson's groups without and with forced (FE) and voluntary (VE) exercises, and the sham groups (with voluntary and forced exercise). The animals in the forced exercise group were placed on the treadmill for four weeks (five days a week). At the same time, voluntary exercise training groups were placed in a special cage equipped with a rotating wheel. At the end of 4 weeks, learning and spatial memory were evaluated with the Morris water maze test. BDNF and CDNF protein levels in the hippocampus were measured by the ELISA method.

RESULTS

The results showed that although the PD group without exercise was at a significantly lower level than other groups in terms of cognitive function and neurochemical factors, both types of exercise, could improve these problems.

CONCLUSION

According to our results, 4 weeks of voluntary and forced exercises were all found to reverse the cognitive impairments of PD rats.

The role and potential therapeutic targets of astrocytes in central nervous system demyelinating diseases

Astrocytes play vital roles in the central nervous system, contributing significantly to both its normal functioning and pathological conditions. While their involvement in various diseases is increasingly recognized, their exact role in demyelinating lesions remains uncertain. Astrocytes have the potential to influence demyelination positively or negatively. They can produce and release inflammatory molecules that modulate the activation and movement of other immune cells. Moreover, they can aid in the clearance of myelin debris through phagocytosis and facilitate the recruitment and differentiation of oligodendrocyte precursor cells, thereby promoting axonal remyelination. However, excessive or prolonged astrocyte phagocytosis can exacerbate demyelination and lead to neurological impairments. This review provides an overview of the involvement of astrocytes in various demyelinating diseases, emphasizing the underlying mechanisms that contribute to demyelination. Additionally, we discuss the interactions between oligodendrocytes, oligodendrocyte precursor cells and astrocytes as therapeutic options to support myelin regeneration. Furthermore, we explore the role of astrocytes in repairing synaptic dysfunction, which is also a crucial pathological process in these disorders.

Evaluation of the therapeutic potential of cerebrolysin and/or lithium in the male Wistar rat model of Parkinson's disease induced by reserpine

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease worldwide and represents a challenge for clinicians. The present study aims to investigate the effects of cerebrolysin and/or lithium on the behavioral, neurochemical and histopathological alterations induced by reserpine as a model of PD. The rats were divided into control and reserpine-induced PD model groups. The model animals were further divided into four subgroups: rat PD model, rat PD model treated with cerebrolysin, rat PD model treated with lithium and rat PD model treated with a combination of cerebrolysin and lithium. Treatment with cerebrolysin and/or lithium ameliorated most of the alterations in oxidative stress parameters, acetylcholinesterase and monoamines in the striatum and midbrain of reserpine-induced PD model. It also ameliorated the changes in nuclear factor-kappa and improved the histopathological picture induced by reserpine. It could be suggested that cerebrolysin and/or lithium showed promising therapeutic potential against the variations induced in the reserpine model of PD. However, the ameliorating effects of lithium on the neurochemical, histopathological and behavioral alterations induced by reserpine were more prominent than those of cerebrolysin alone or combined with lithium. It can be concluded that the antioxidant and anti-inflammatory effects of both drugs played a significant role in their therapeutic potency.

GlyNAC (Glycine and N-Acetylcysteine) Supplementation in Old Mice Improves Brain Glutathione Deficiency, Oxidative Stress, Glucose Uptake, Mitochondrial Dysfunction, Genomic Damage, Inflammation and Neurotrophic Factors to Reverse Age-Associated Cognitive Decline: Implications for Improving Brain Health in Aging

Cognitive decline frequently occurs with increasing age, but mechanisms contributing to age-associated cognitive decline (ACD) are not well understood and solutions are lacking. Understanding and reversing mechanisms contributing to ACD are important because increased age is identified as the single most important risk factor for dementia. We reported earlier that ACD in older humans is associated with glutathione (GSH) deficiency, oxidative stress (OxS), mitochondrial dysfunction, glucose dysmetabolism and inflammation, and that supplementing GlyNAC (glycine and N-acetylcysteine) improved these defects. To test whether these defects occur in the brain in association with ACD, and could be improved/reversed with GlyNAC supplementation, we studied young (20-week) and old (90-week) C57BL/6J mice. Old mice received either regular or GlyNAC supplemented diets for 8 weeks, while young mice received the regular diet. Cognition and brain outcomes (GSH, OxS, mitochondrial energetics, autophagy/mitophagy, glucose transporters, inflammation, genomic damage and neurotrophic factors) were measured. Compared to young mice, the old-control mice had significant cognitive impairment and multiple brain defects. GlyNAC supplementation improved/corrected the brain defects and reversed ACD. This study finds that naturally-occurring ACD is associated with multiple abnormalities in the brain, and provides proof-of-concept that GlyNAC supplementation corrects these defects and improves cognitive function in aging.

Neuroprotective effect of hyperoside in MPP+/MPTP -induced dopaminergic neurodegeneration

Parkinson's disease (PD) is a neurodegenerative disease characterized by the pathological loss of nigrostriatal dopaminergic neurons, which causes an insufficient release of dopamine (DA) and then induces motor and nonmotor symptoms. Hyperoside (HYP) is a lignan component with anti-inflammatory, antioxidant, and neuroprotective effects. In this study, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its active neurotoxic metabolite 1-methyl-4-phenylpyridinium ion (MPP⁺) were used to induce dopaminergic neurodegeneration. The results showed that HYP (100 µg/mL) reduced MPTP-mediated cytotoxicity of SH-SY5Y cells in vitro, and HYP [25 mg/(kg d)] alleviated MPTP-induced motor symptoms in vivo. HYP treatment reduced the contents of nitric oxide (NO), H₂O₂, and malondialdehyde (MDA), as well as the mitochondrial damage of dopaminergic neurons, both in vitro and in vivo. Meanwhile, HYP treatment elevated the levels of neurotrophic factors such as glial cell line-derived neurotrophic factor, brain-derived neurotrophic factor, and recombinant cerebral dopamine neurotrophic factor in vivo, but not in vitro. Finally, Akt signaling was activated after the administration of HYP in MPP⁺/MPTP-induced dopaminergic neurodegeneration. However, the blockage of the Akt pathway with Akt inhibitor did not abolish the neuroprotective effect of HYP on DA neurons. These results showed that HYP protected the dopaminergic neurons from the MPP⁺- and MPTP-induced injuries, which did not rely on the Akt pathway.

Marine Natural Products from the Russian Pacific as Sources of Drugs for Neurodegenerative Diseases

Neurodegenerative diseases are growing to become one of humanity's biggest health problems, given the number of individuals affected by them. They cause enough mortalities and severe economic impact to rival cancers and infections. With the current diversity of pathophysiological mechanisms involved in neurodegenerative diseases, on the one hand, and scarcity of efficient prevention and treatment strategies, on the other, all possible sources for novel drug discovery must be employed. Marine pharmacology represents a relatively uncharted territory to seek promising compounds, despite the enormous chemodiversity it offers. The current work discusses one vast marine region-the Northwestern or Russian Pacific-as the treasure chest for marine-based drug discovery targeting neurodegenerative diseases. We overview the natural products of neurological properties already discovered from its waters and survey the existing molecular and cellular targets for pharmacological modulation of the disease. We further provide a general assessment of the drug discovery potential of the Russian Pacific in case of its systematic development to tackle neurodegenerative diseases.

Generation of glial cell-derived neurotrophic factor (gdnf) morphants in zebrafish larvae by cerebroventricular microinjection of vivo morpholino

Dopaminergic neurons in the brain are an important source of dopamine, which is a crucial neurotransmitter for wellbeing, memory, reward, and motor control. Deficiency of dopamine due to advanced age and accumulative dopaminergic neuron defects can lead to movement disorders such as Parkinson's disease. Glial cell-derived neurotrophic factor (GDNF) is one of many factors involved in dopaminergic neuron development and/or survival. However, other endogenous GDNF functions in the brain await further investigation. Zebrafish is a well-established genetic model for neurodevelopment and neurodegeneration studies. Importantly, zebrafish shares approximately 70% functional orthologs with human genes including GDNF. To gain a better understanding on the precise functional role of gdnf in dopaminergic neurons, our laboratory devised a targeted knockdown of gdnf in the zebrafish larval brain using vivo morpholino. Here, detailed protocols on the generation of gdnf morphants using vivo morpholino are outlined. This method can be applied for targeting of genes in the brain to determine specific spatiotemporal gene function in situ.

Cerebral dopamine neurotrophic factor increases proliferation, Migration and differentiation of subventricular zone neuroblasts in photothrombotic stroke model of mouse

BACKGROUND

Cerebral ischemic stroke can induce the proliferation of subventricular zone (SVZ) neural stem cells (NSCs) in the adult brain. However, this reparative process is restricted because of NSCs' death shortly after injury or disability of them to reach the infarct boundary. In the present study, we investigated the ability of cerebral dopamine neurotrophic factor (CDNF) on the attraction of SVZ-resident NSCs toward the lesioned area and neurological recovery in a photothrombotic (PT) stroke model of mice METHODS: The mice were assigned to three groups stroke, stroke+phosphate buffered saline (PBS), and stroke+CDNF. Migration of SVZ NSCs were evaluated by BrdU/doublecortin (DCX) double immunofluorescence method on days 7 and 14 and their differentiation were evaluated by BrdU/ Neuronal Nuclei (NeuN) double immunofluorescence method 28 days after intra-SVZ CDNF injection. Serial coronal sections were stained with cresyl violet to detect the infarct volume and a modified neurological severity score (mNSS) was performed to assess the neurological performance RESULTS: Injection of CDNF increased the proliferation of SVZ NSCs and the number of DCX-expressing neuroblasts migrated from the SVZ toward the ischemic site. It also enhanced the differentiation of migrated neuroblasts into the mature neurons in the lesioned site. Along with this, the infarct volume was significantly decreased and the neurological performance was improved as compared to other groups CONCLUSION: These results demonstrate that CDNF is capable of enhancing the proliferation of NSCs residing in the SVZ and their migration toward the ischemia region and finally, differentiation of them in stroke mice, concomitantly decreased infarct volume and improved neurological abilities were revealed.

Overexpression of Brain- and Glial Cell Line-Derived Neurotrophic Factors Is Neuroprotective in an Animal Model of Acute Hypobaric Hypoxia

Currently, the role of the neurotrophic factors BDNF and GDNF in maintaining the brain’s resistance to the damaging effects of hypoxia and functional recovery of neural networks after exposure to damaging factors are actively studied. The assessment of the effect of an increase in the level of these neurotrophic factors in brain tissues using genetic engineering methods on the resistance of laboratory animals to hypoxia may pave the way for the future clinical use of neurotrophic factors BDNF and GDNF in the treatment of hypoxic damage. This study aimed to evaluate the antihypoxic and neuroprotective properties of BDNF and GDNF expression level increase using adeno-associated viral vectors in modeling hypoxia in vivo. To achieve overexpression of neurotrophic factors in the central nervous system’s cells, viral constructs were injected into the brain ventricles of newborn male C57Bl6 (P0) mice. Acute hypobaric hypoxia was modeled on the 30th day after the injection of viral vectors. Survival, cognitive, and mnestic functions in the late post-hypoxic period were tested. Evaluation of growth and weight characteristics and the neurological status of animals showed that the overexpression of neurotrophic factors does not affect the development of mice. It was found that the use of adeno-associated viral vectors increased the survival rate of male mice under hypoxic conditions. The present study indicates that the neurotrophic factors’ overexpression, induced by the specially developed viral constructs carrying the BDNF and GDNF genes, is a prospective neuroprotection method, increasing the survival rate of animals after hypoxic injury.

The therapeutic benefits of intravenously administrated nanoparticles in stroke and age-related neurodegenerative diseases

The mean global lifetime risk of neurological disorders such as stroke, Alzheimer's disease (AD), and Parkinson's disease (PD) has shown a large effect on economy and society.Researchersare stillstruggling to find effective drugs to treatneurological disordersand drug delivery through the blood-brain barrier (BBB) is a major challenge to be overcome. The BBB is a specialized multicellular barrier between the peripheral blood circulation and the neural tissue. Unique and selective features of the BBB allow it to tightly control brain homeostasis as well as the movement of ions and molecules. Failure in maintaining any of these substances causes BBB breakdown and subsequently enhances neuroinflammation and neurodegeneration.BBB disruption is evident in many neurologicalconditions.Nevertheless, the majority of currently available therapies have tremendous problems for drug delivery into the impaired brain. Nanoparticle (NP)-mediated drug delivery has been considered as a profound substitute to solve this problem. NPs are colloidal systems with a size range of 1-1000 nm whichcan encapsulate therapeutic payloads, improve drug passage across the BBB, and target specific brain areas in neurodegenerative/ischemic diseases. A wide variety of NPs has been displayed for the efficient brain delivery of therapeutics via intravenous administration, especially when their surfaces are coated with targeting moieties. Here, we discuss recent advances in the development of NP-based therapeutics for the treatment of stroke, PD, and AD as well as the factors affecting their efficacy after systemic administration.

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.

Activation of Three Major Signaling Pathways After Endurance Training and Spinal Cord Injury

We aimed to investigate the effects of endurance training on expression of growth factors (GFs) and stimulation of neurotrophin-dependent signaling pathways (PI3k/Akt, PLCγ/PKC, PLCγ/CAMKII, Ras-Erk1/2 and Rac1-Cdc42) responsible for neuroplasticity, neuroregeneration, survival and growth after spinal cord injury (SCI). Wistar rats were divided into four groups: (i) intact controls; (ii) 6 weeks of endurance training; (iii) SCI; (iv) pre-training + SCI. The animals survived for 6 weeks after SCI. Firstly, endurance training markedly upregulated mRNA expression and protein levels (up to four times) of growth factors (BDNF, GDNF) and their receptors (TrkB, Gfrα) in low thoracic segments (Th8–Th10) compared to levels in untrained animals. Secondly, we found that spontaneous neuroplasticity seen in the SCI alone group was GF-specific and was activated through both PLCγ-PKC and PLC-CAMKII signaling pathways. In addition, training prior to SCI markedly increased the activity of PLCγ-PKC signaling at both transcript and protein levels at and around the lesion site. Similar effects were seen in expression of PI3k/Akt and Ras/Erk1/2 signaling responsible for cell survival and regeneration. Thirdly, rats which underwent physical activity prior to SCI were more active and had significantly better neurological scores at the 14th and 42nd days of survival. These results suggest that regular physical activity could play an important role after SCI, as it maintains increased expression of GFs in spinal cord tissue 6 weeks post-SCI. The BDNF- and/or BDNF + GDNF-dependent signaling pathways were significantly affected in pre-trained SCI animals. In contrast, GDNF-dependent Rac1-Cdc42 signaling was not involved in training-affected SCI response.

Cerebral dopamine neurotrophic factor transfection in dopamine neurons using neurotensin-polyplex nanoparticles reverses 6-hydroxydopamine-induced nigrostriatal neurodegeneration

Overexpression of neurotrophic factors in nigral dopamine neurons is a promising approach to reverse neurodegeneration of the nigrostriatal dopamine system, a hallmark in Parkinson's disease. The human cerebral dopamine neurotrophic factor (hCDNF) has recently emerged as a strong candidate for Parkinson's disease therapy. This study shows that hCDNF expression in dopamine neurons using the neurotensin-polyplex nanoparticle system reverses 6-hydroxydopamine-induced morphological, biochemical, and behavioral alterations. Three independent electron microscopy techniques showed that the neurotensin-polyplex nanoparticles containing the hCDNF gene, ranging in size from 20 to 150 nm, enabled the expression of a secretable hCDNF in vitro. Their injection in the substantia nigra compacta on day 21 after the 6-hydroxydopamine lesion resulted in detectable hCDNF in dopamine neurons, whose levels remained constant throughout the study in the substantia nigra compacta and striatum. Compared with the lesioned group, tyrosine hydroxylase-positive (TH⁺) nigral cell population and TH⁺ fiber density rose in the substantia nigra compacta and striatum after hCDNF transfection. An increase in βIII-tubulin and growth-associated protein 43 phospho-S41 (GAP43p) followed TH⁺ cell recovery, as well as dopamine and its catabolite levels. Partial reversal (80%) of drug-activated circling behavior and full recovery of spontaneous motor and non-motor behavior were achieved. Brain-derived neurotrophic factor recovery in dopamine neurons that also occurred suggests its participation in the neurotrophic effects. These findings support the potential of nanoparticle-mediated hCDNF gene delivery to develop a disease-modifying treatment against Parkinson's disease. The Institutional Animal Care and Use Committee of Centro de Investigación y de Estudios Avanzados approved our experimental procedures for animal use (authorization No. 162-15) on June 9, 2019.

Synergistic effects of combined therapy with transcranial photobiomodulation and enriched environment on depressive- and anxiety-like behaviors in a mice model of noise stress

The development of anxiety and depression due to chronic exposure to noise stress has remained as an unsolved health problem so far. Despite the studies suggesting the neuroenhancement effects of transcranial photobiomodulation (tPBM) and housing in an enriched environment (EE), the combined effects of these treatments have not been elucidated yet. Also, there is no available data on the relationship between the application of tPBM and hippocampal brain-derived neurotrophic factor (BDNF) expression in animal models of stress. The present study aims to investigate the application of the tPBM and EE (alone or in combination) on depressive- and anxiety-like behaviors in a mice model of noise stress. Mice were divided into five groups: control, noise, noise + EE, noise + tPBM, and noise + EE + tPBM. Except for the control group, other groups were subjected to 110 dB SPL white noise for 4 h/day for 14 consecutive days and received their respective treatments. Forced Swimming Test (FST) was used to evaluate depressive-like behaviors. Elevated Plus Maze (EPM) and Open Field Test (OFT) were used to evaluate anxiety-like behaviors. BDNF, tyrosine receptor kinase B (TrkB), and cAMP response element-binding (CREB) protein levels in the hippocampus were determined by the Western blot method, and also serum corticosterone levels were assessed using an ELISA kit. Exposure to noise stress significantly elevated serum corticosterone level; downregulated hippocampal BDNF, TrkB, and CREB protein expressions; and resulted in depressive- and anxiety-like behaviors. While, the application of tPBM (810 nm wavelength, 8 J/cm² fluence, 10 Hz pulsed wave mode), housing in EE, and their combination lowered corticosterone levels, upregulated the BDNF/TrkB/CREB signaling pathway in the hippocampus, and improved behavioral outcomes in noise stress subjected mice. Our finding revealed the improving effects of tPBM and EE on depressive and anxiety-like behaviors induced by noise stress, possibly by augmenting the BDNF/TrkB/CREB signaling pathway.

Mouse Embryonic Stem Cells Expressing GDNF Show Enhanced Dopaminergic Differentiation and Promote Behavioral Recovery After Grafting in Parkinsonian Rats

Parkinson's disease (PD) is characterized by the progressive loss of midbrain dopaminergic neurons (DaNs) of the substantia nigra pars compacta and the decrease of dopamine in the brain. Grafting DaN differentiated from embryonic stem cells (ESCs) has been proposed as an alternative therapy for current pharmacological treatments. Intrastriatal grafting of such DaNs differentiated from mouse or human ESCs improves motor performance, restores DA release, and suppresses dopamine receptor super-sensitivity. However, a low percentage of grafted neurons survive in the brain. Glial cell line-derived neurotrophic factor (GDNF) is a strong survival factor for DaNs. GDNF has proved to be neurotrophic for DaNs in vitro and in vivo, and induces axonal sprouting and maturation. Here, we engineered mouse ESCs to constitutively produce human GDNF, to analyze DaN differentiation and the possible neuroprotection by transgenic GDNF after toxic challenges in vitro, or after grafting differentiated DaNs into the striatum of Parkinsonian rats. GDNF overexpression throughout in vitro differentiation of mouse ESCs increases the proportion of midbrain DaNs. These transgenic cells were less sensitive than control cells to 6-hydroxydopamine in vitro. After grafting control or GDNF transgenic DaNs in hemi-Parkinsonian rats, we observed significant recoveries in both pharmacological and non-pharmacological behavioral tests, as well as increased striatal DA release, indicating that DaNs are functional in the brain. The graft volume, the number of surviving neurons, the number of DaNs present in the striatum, and the proportion of DaNs in the grafts were significantly higher in rats transplanted with GDNF-expressing cells, when compared to control cells. Interestingly, no morphological alterations in the brain of rats were found after grafting of GDNF-expressing cells. This approach is novel, because previous works have use co-grafting of DaNs with other cell types that express GDNF, or viral transduction in the host tissue before or after grafting of DaNs. In conclusion, GDNF production by mouse ESCs contributes to enhanced midbrain differentiation and permits a higher number of surviving DaNs after a 6-hydroxydopamine challenge in vitro, as well as post-grafting in the lesioned striatum. These GDNF-expressing ESCs can be useful to improve neuronal survival after transplantation.

Role of Receptor Protein Tyrosine Phosphatase β/ζ in Neuron-Microglia Communication in a Cellular Model of Parkinson's Disease

Pleiotrophin (PTN) is a neurotrophic factor that regulates glial responses in animal models of different types of central nervous system (CNS) injuries. PTN is upregulated in the brain in different pathologies characterized by exacerbated neuroinflammation, including Parkinson’s disease. PTN is an endogenous inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, which is abundantly expressed in the CNS. Using a specific inhibitor of RPTPβ/ζ (MY10), we aimed to assess whether the PTN/RPTPβ/ζ axis is involved in neuronal and glial injury induced by the toxin MPP+. Treatment with the RPTPβ/ζ inhibitor MY10 alone decreased the viability of both SH-SY5Y neuroblastoma cells and BV2 microglial cultures, suggesting that normal RPTPβ/ζ function is involved in neuronal and microglial viability. We observed that PTN partially decreased the cytotoxicity induced by MPP+ in SH-SY5Y cells underpinning the neuroprotective function of PTN. However, MY10 did not seem to modulate the SH-SY5Y cell loss induced by MPP+. Interestingly, we observed that media from SH-SY5Y cells treated with MPP+ and MY10 decreases microglial viability but may elicit a neuroprotective response of microglia by upregulating Ptn expression. The data suggest a neurotrophic role of microglia in response to neuronal injury through upregulation of Ptn levels.

p70S6K on astrocytes protects dopamine neurons from 1-methyl-4-phenylpyridinium neurotoxicity

Our recent finding has demonstrated that astrocytes confer neuroprotection by endogenously producing ciliary neurotrophic factor (CNTF) via transient receptor potential vanilloid 1 (TRPV1) in Parkinson's disease (PD). In this study, the possible molecular target for TRPV1-mediated CNTF production and its neuroprotective effects on dopamine neurons were further investigated. For comparison, glial cell-line derived neurotrophic factor (GDNF) was also examined. The results show that TRPV1-ribosomal protein 70 S6 kinase (p70S6K) signaling on astrocytes produces endogenous CNTF in the SN of MPP⁺ -lesioned rat. By marked contrast, the expression of GDNF on astrocytes is independent of TRPV1-p70S6K signaling. Administration of a TRPV1 agonist, capsaicin, increases levels of phosphorylated p70S6K (p-p70S6K; activation of p70S6K) on astrocytes, resulting in the survival of dopamine neurons and behavioral recovery through endogenous production of CNTF in the MPP⁺ -lesioned rat model of PD. Immunohistochemical analysis reveals expression of p-p70S6K on astrocytes in the SN of PD patients, indicating relevance to human PD. The present in vivo data is the first to demonstrate that astrocytic TRPV1-p70S6K signaling plays a pivotal role as endogenous neuroprotective, and it may constitute a novel therapeutic target for treating PD.

Role and Mechanism of Vitamin A Metabolism in the Pathophysiology of Parkinson's Disease

Evidence shows that altered retinoic acid signaling may contribute to the pathogenesis and pathophysiology of Parkinson's disease (PD). Retinoic acid is the bioactive derivative of the lipophilic vitamin A. Vitamin A is involved in several important homeostatic processes, such as cell differentiation, antioxidant activity, inflammation and neuronal plasticity. The role of vitamin A and its derivatives in the pathogenesis and pathophysiology of neurodegenerative diseases, and their potential as therapeutics, has drawn attention for more than 10 years. However, the literature sits in disparate fields. Vitamin A could act at the crossroad of multiple environmental and genetic factors of PD. The purpose of this review is to outline what is known about the role of vitamin A metabolism in the pathogenesis and pathophysiology of PD. We examine key biological systems and mechanisms that are under the control of vitamin A and its derivatives, which are (or could be) exploited for therapeutic potential in PD: the survival of dopaminergic neurons, oxidative stress, neuroinflammation, circadian rhythms, homeostasis of the enteric nervous system, and hormonal systems. We focus on the pivotal role of ALDH1A1, an enzyme expressed by dopaminergic neurons for the detoxification of these neurons, which is under the control of retinoic acid. By providing an integrated summary, this review will guide future studies on the potential role of vitamin A in the management of symptoms, health and wellbeing for PD patients.

Anti-depressant effect of cerebrolysin in reserpine-induced depression in rats: Behavioral, biochemical, molecular and immunohistochemical evidence

Depression is a major psychological disorder that contributes to global health problem. This study aimed to evaluate the anti-depressant effect of Cerebrolysin (CBL) in Reserpine-induced depressed rats, its effect on oxidative stress, inflammation, regulatory cyclic AMP-dependent response element binding protein (CREB)/brain derived neurotropic factor (BDNF) signaling pathways, brain monoamines and histopathological changes was assessed. Rats received either the vehicle or Reserpine (0.5 mg/kg, i.p.) for 14 days. The other three groups were pretreated with CBL (2.5, 5 ml/kg; i.p.) or fluoxetine (FLU) (5 mg/kg, p.o.), respectively for 14 days, 30 min before reserpine injection. Then analyses were conducted. CBL reversed Reserpine-induced reduction in latency to immobility and prolongation of immobility time in the forced swimming test (FST), reduced malondialdehyde (MDA), elevated reduced glutathione (GSH), reduced tumor necrosis factor-alpha (TNF-ɑ), and elevated BDNF cortical and hippocampal brain contents. CBL elevated protein kinase A (PKA) and nuclear factor kappa-B (NF-κB) cortical and hippocampal protein expressions. CBL also ameliorated alterations in mRNA expressions of protein kinase B (AKT), CREB and BDNF in the cortical and hippocampal tissues. CBL elevated nor-epinephrine (NE), serotonin (5-HT), and dopamine (DA) and reduced 5-Hydroxyindoleacetic acid (5-HTAA), 3,4-Dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) cortical and hippocampal contents. CBL effects were in parallel to those observed with the standard anti-depressant drug, FLU. This study shows that CBL exerted anti-depressant effect evidenced by attenuation of oxidative stress and inflammation as well as enhancement of neurogenesis, amelioration of monoaminergic system and histopathological changes.

Astrocytes in Parkinson's disease: from preclinical assays to in vivo imaging and therapeutic probes

Parkinson's disease (PD) is increasingly thought to be associated with glial pathology. Recently, research in neurodegenerative disorders has applied a greater focus to better understanding the role of astrocytes in the disease pathophysiology. In this article, we review results from the latest preclinical and clinical work, including functional imaging studies on astrocytes in PD and highlight key molecules that may prove valuable as biomarkers. We discuss how astrocytes may contribute to the initiation and progression of PD. We additionally present trials of investigational medicinal products and the current background for the design of future clinical trials.

Long-term post-mortem studies following neurturin gene therapy in patients with advanced Parkinson's disease

We performed post-mortem studies on two patients with advanced Parkinson’s disease 8 and10 years following AAV2-neurturin (CERE120) gene therapy, the longest post-mortem trophic factor gene therapy cases reported to date. CERE120 was delivered to the putamen bilaterally in one case (10 years post-surgery), and to the putamen plus the substantia nigra bilaterally in the second (8 years post-surgery). In both patients there was persistent, albeit limited, neurturin expression in the putamen covering ∼3–12% of the putamen. In the putamen, dense staining of tyrosine hydroxylase-positive fibres was observed in areas that contained detectable neurturin expression. In the substantia nigra, neurturin expression was detected in 9.8–18.95% and 22.02–39% of remaining melanin-containing neurons in the patient with putamenal and combined putamenal and nigral gene delivery, respectively. Melanized neurons displayed intense tyrosine hydroxylase and RET proto-oncogene expression in nigral neurons in the patient where CERE120 was directly delivered to the nigra. There was no difference in the degree of Lewy pathology in comparison to untreated control patients with Parkinson’s disease, and α-synuclein aggregates were detected in neurons that also stained for neurturin, RET, and tyrosine hydroxylase. These changes were not associated with antiparkinsonian benefits likely due to the limited neurturin expression. This study provides the longest term evidence of persistent transgene expression following gene delivery to the CNS and the first human results when targeting both the terminal fields in the putamen as well as the originating nigral neurons.

Cerebral Dopamine Neurotrophic Factor Regulates Multiple Neuronal Subtypes and Behavior

Cerebral dopamine neurotrophic factor (CDNF) protects dopaminergic neurons against toxic damage in the rodent brain and is in clinical trials to treat Parkinson's disease patients. Yet the underlying mechanism is poorly understood. To examine its significance for neural circuits and behavior, we examined the development of neurotransmitter systems from larval to male adult mutant zebrafish lacking cdnf Although a lack of cdnf did not affect overall brain dopamine levels, dopaminergic neuronal clusters showed significant abnormalities. The number of histamine neurons that surround the dopaminergic neurons was significantly reduced. Expression of tyrosine hydroxylase 2 in the brain was elevated in cdnf mutants throughout their lifespan. There were abnormally few GABA neurons in the hypothalamus in the mutant larvae, and expression of glutamate decarboxylase was reduced throughout the brain. cdnf mutant adults showed a range of behavioral phenotypes, including increased sensitivity to pentylenetetrazole-induced seizures. Shoaling behavior of mutant adults was abnormal, and they did not display social attraction to conspecifics. CDNF plays a profound role in shaping the neurotransmitter circuit structure, seizure susceptibility, and complex behaviors in zebrafish. These findings are informative for dissecting the diverse functions of this poorly understood factor in human conditions related to Parkinson's disease and complex behaviors.SIGNIFICANCE STATEMENT A zebrafish lacking cdnf grows normally and shows no overt morphologic phenotype throughout the life span. Remarkably, impaired social cohesion and increased seizure susceptibility were found in adult cdnf KO fish conceivably associated with significant changes of dopaminergic, GABAergic, and histaminergic systems in selective brain areas. These findings suggest that cdnf has broad effects on regulating neurogenesis and maturation of transmitter-specific neuronal types during development and throughout adulthood, rather than ones restricted to the dopaminergic systems.

Remodeling microglia to a protective phenotype in Parkinson's disease?

Parkinson's disease (PD) is the most widespread movement disorder with a prevalence of 1 in 1000 individuals above 60 years of age. Until now, understanding the pathological mechanisms of PD to translate them into therapy has remained a high research priority. In this review, we highlight evidence describing the involvement of microglial dysfunction in PD. Thereafter, we provide current knowledge suggesting that the substantia nigra pars compacta and putamen, compared to other brain regions, show a reduced microglial density, as well as altered morphological and functional properties in homeostatic conditions, while presenting dystrophic features associated with aging. Further, we describe that this defective microglial programing emerges as early as the second postnatal week, persists until adulthood and impacts negatively on their transcriptional pattern and provision of local trophic support. We emphasize the role of α-synuclein oligomers as a major dysfunctional signal underlining microglial-mediated phenotypic switch and adaptive response contributing to neurodegeneration. Moreover, we explore available avenues should microglia be considered as target for neuroprotective or restorative strategies including preventing the aggregation of α-synuclein protofibrils formation. However, we provide a note of caution regarding the success of microglial-targeted PD strategies, using minocycline as an example. In conclusion, we discuss putative neuroprotective agents that were unsuccessful in previous trials but could be reconsidered by focusing on the stage of microglial-dependent pathogenic events during PD in suitable cohorts of patients.

Immunotherapies in Huntington's disease and α-Synucleinopathies

Modulation of immune activation using immunotherapy has attracted considerable attention for many years as a potential therapeutic intervention for several inflammation-associated neurodegenerative diseases. However, the efficacy of single-target immunotherapy intervention has shown limited or no efficacy in alleviating disease burden and restoring functional capacity. Marked immune system activation and neuroinflammation are important features and prodromal signs in polyQ repeat disorders and α-synucleinopathies. This review describes the current status and future directions of immunotherapies in proteinopathy-induced neurodegeneration with emphasis on preclinical and clinical efficacies of several anti-inflammatory compounds and antibody-based therapies for the treatment of Huntington's disease and α-synucleinopathies. The review concludes with how disease modification and functional restoration could be achieved by using targeted multimodality therapy to target multiple factors.

Parkinson's Disease-Associated Changes in the Expression of Neurotrophic Factors and their Receptors upon Neuronal Differentiation of Human Induced Pluripotent Stem Cells

Parkinson's disease (PD) is a neurodegenerative pathology resulting from the degeneration of dopaminergic (DA) neurons in the substantia nigra (SN). Neurotrophic factors (NTFs) and their receptors are key regulators of the survival, differentiation, and development of neurons. However, the role of these factors in the pathogenesis of PD is still unclear. Here, we analyzed the expression of NTFs and their receptors in human induced pluripotent stem cells (iPSCs) derived from the fibroblasts of patients with PD and healthy donors (HDs). Four PD-derived iPSC lines with different mutations and three cell lines from HDs at different stages of neuronal differentiation were used for RT-qPCR analysis and ELISA. We found that the mRNA levels of most analyzed genes were altered in PD-derived cells compared with those in HD-derived cells at all stages. Importantly, irrespective of PD-associated mutations, the mRNA levels of the BDNF and GDNF genes were mostly increased or unchanged in predominantly DA terminally differentiated neurons (TDNs) compared with those in HD-derived cells. Strikingly, in contrast to BDNF and GDNF mRNA levels, BDNF and GDNF protein levels were lower in almost all PD-derived TDNs than in HD-derived cells, thus indicating the dysregulation of NTF expression at the post-transcriptional level. We suggest that this dysregulation is one of the important signs of PD development.

Neuroregeneration in Parkinson's Disease: From Proteins to Small Molecules

Background:

Parkinson’s disease (PD) is the second most common neurodegenerative disorder worldwide, the lifetime risk of developing this disease is 1.5%. Motor diagnostic symptoms of PD are caused by degeneration of nigrostria-tal dopamine neurons. There is no cure for PD and current therapy is limited to supportive care that partially alleviates dis-ease signs and symptoms. As diagnostic symptoms of PD result from progressive degeneration of dopamine neurons, drugs restoring these neurons may significantly improve treatment of PD.

Method:

A literature search was performed using the PubMed, Web of Science and Scopus databases to discuss the pro-gress achieved in the development of neuroregenerative agents for PD. Papers published before early 2018 were taken into account.

Results:

Here, we review several groups of potential agents capable of protecting and restoring dopamine neurons in cul-tures or animal models of PD including neurotrophic factors and small molecular weight compounds.

Conclusion:

Despite the promising results of in vitro and in vivo experiments, none of the found agents have yet shown conclusive neurorestorative properties in PD patients. Meanwhile, a few promising biologicals and small molecules have been identified. Their further clinical development can eventually give rise to disease-modifying drugs for PD. Thus, inten-sive research in the field is justified.

Hyperbaric oxygen improves functional recovery of rats after spinal cord injury via activating stromal cell-derived factor-1/CXC chemokine receptor 4 axis and promoting brain-derived neurothrophic factor expression

Background:

Spinal cord injury (SCI) is a worldwide medical concern. This study aimed to elucidate the mechanism underlying the protective effect of hyperbaric oxygen (HBO) against SCI-induced neurologic defects in rats via exploring the stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) axis and expression of brain-derived neurotrophic factor (BDNF).

Methods:

An acute SCI rat model was established in Sprague-Dawley rats using the Allen method. Sixty rats were divided into four groups (n = 15 in each group): sham-operated, SCI, SCI treated with HBO (SCI + HBO), and SCI treated with both HBO and AMD3100 (an antagonist of CXCR4; SCI + HBO + AMD) groups. The rats were treated with HBO twice a day for 3 days and thereafter once a day after the surgery for up to 28 days. Following the surgery, neurologic assessments were performed with the Basso-Bettie-Bresnahan (BBB) scoring system on postoperative day (POD) 7, 14, 21, and 28. Spinal cord tissues were harvested to assess the expression of SDF-1, CXCR4, and BDNF at mRNA and protein levels, using quantitative real-time polymerase chain reaction, Western blot analysis, and histopathologic analysis.

Results:

HBO treatment recovered SCI-induced descent of BBB scores on POD 14, (1.25 ± 0.75 vs. 1.03 ± 0.66, P < 0.05), 21 (5.27 ± 0.89 vs. 2.56 ± 1.24, P < 0.05), and 28 (11.35 ± 0.56 vs. 4.23 ± 1.20, P < 0.05) compared with the SCI group. Significant differences were found in the mRNA levels of SDF-1 (mRNA: day 21, SCI + HBO vs. SCI + HBO + AMD, 2.89 ± 1.60 vs. 1.56 ± 0.98, P < 0.05), CXCR4 (mRNA: day 7, SCI + HBO vs. SCI, 2.99 ± 1.60 vs.1.31 ± 0.98, P < 0.05; day 14, SCI + HBO vs. SCI + HBO + AMD, 4.18 ± 1.60 vs. 0.80 ± 0.34, P < 0.05; day 21, SCI + HBO vs. SCI, 2.10 ± 1.01 vs.1.15 ± 0.03, P < 0.05), and BDNF (mRNA: day 7, SCI + HBO vs. SCI, 3.04 ± 0.41 vs. 2.75 ± 0.31, P < 0.05; day 14, SCI + HBO vs. SCI, 3.88 ± 1.59 vs. 1.11 ± 0.40, P < 0.05), indicating the involvement of SDF-1/CXCR4 axis in the protective effect of HBO.

Conclusions:

HBO might promote the recovery of neurologic function after SCI in rats via activating the SDF-1/CXCR4 axis and promoting BDNF expression.

Immune system and new avenues in Parkinson’s disease research and treatment

Parkinson’s disease (PD) is a progressive neurological disorder characterized by degeneration of dopaminergic neurons in the substantia nigra. However, although 200 years have now passed since the primary clinical description of PD by James Parkinson, the etiology and mechanisms of neuronal loss in this disease are still not fully understood. In addition to genetic and environmental factors, activation of immunologic responses seems to have a crucial role in PD pathology. Intraneuronal accumulation of α-synuclein (α-Syn), as the main pathological hallmark of PD, potentially mediates initiation of the autoimmune and inflammatory events through, possibly, auto-reactive T cells. While current therapeutic regimens are mainly used to symptomatically suppress PD signs, application of the disease-modifying therapies including immunomodulatory strategies may slow down the progressive neurodegeneration process of PD. The aim of this review is to summarize knowledge regarding previous studies on the relationships between autoimmune reactions and PD pathology as well as to discuss current opportunities for immunomodulatory therapy.

Sleep deprivation disrupts striatal anti-apoptotic responses in 6-hydroxy dopamine-lesioned parkinsonian rats

Objective(s):

The present study was conducted to examine the effect of sleep deprivation (SD) on the anti-apoptotic pathways in Parkinsonian rats.

Materials and Methods:

Male Wistar rats (n = 40) were assigned to four groups (10 animals each): sham surgery (Sham), 6-hydroxydopamine (6-OHDA)-lesioned (OH), 6-OHDA-lesioned plus grid control (OH+GC), 6-OHDA-lesioned plus SD (OH+SD). Parkinson’s disease (PD) model was induced by the unilateral intra-striatal infusion of 6-OHDA (10 µg/rat). SD (4 hr/day, for 14 days) was induced using a multiple platforms water tank. On the last day of interventions, animals were subjected to open field test for horizontal motor performance assessment. Also, brain-derived neurotrophic factor (BDNF), Bcl-2 and Bax were assessed in the striatum of study groups.

Results:

SD obscured the motor deficits of PD animals observed in open field test. BDNF level and Bcl2/Bax ratio significantly increased in the OH group, and SD reduced their levels in the PD animals.

Conclusion:

SD suppressed the anti-apoptotic compensatory responses in the striatum; therefore, it may accelerate continual neuronal cell death in PD.

Outside in: Unraveling the Role of Neuroinflammation in the Progression of Parkinson's Disease

Neuroinflammation is one of the most important processes involved in the pathogenesis of Parkinson's disease (PD). The current concept of neuroinflammation comprises an inflammation process, which occurs in the central nervous system due to molecules released from brain-resident and/or blood-derived immune cells. Furthermore, the evidence of the contribution of systemic delivered molecules to the disease pathogenesis, such as the gut microbiota composition, has been increasing during the last years. Under physiological conditions, microglia and astrocytes support the well-being and well-function of the brain through diverse functions, including neurotrophic factor secretion in both intact and injured brain. On the other hand, genes that cause PD are expressed in astrocytes and microglia, shifting their neuroprotective role to a pathogenic one, contributing to disease onset and progression. In addition, growth factors are a subset of molecules that promote cellular survival, differentiation and maturation, which are critical signaling factors promoting the communication between cells, including neurons and blood-derived immune cells. We summarize the potential targeting of astrocytes and microglia and the systemic contribution of the gut microbiota in neuroinflammation process archived in PD.