The transfection of BDNF to dopamine neurons potentiates the effect of dopamine D3 receptor agonist recovering the striatal innervation, dendritic spines and motor behavior in an aged rat model of Parkinson's disease

Unilateral rNurr1-V5 transgene expression in nigral dopaminergic neurons mitigates bilateral neuropathology and behavioral deficits in parkinsonian rats with α-synucleinopathy

JOURNAL/nrgr/04.03/01300535-202409000-00039/figure1/v/2024-01-16T170235Z/r/image-tiff Parkinsonism by unilateral, intranigral β-sitosterol β-D-glucoside administration in rats is distinguished in that the α-synuclein insult begins unilaterally but spreads bilaterally and increases in severity over time, thus replicating several clinical features of Parkinson's disease, a typical α-synucleinopathy. As Nurr1 represses α-synuclein, we evaluated whether unilateral transfected of rNurr1-V5 transgene via neurotensin-polyplex to the substantia nigra on day 30 after unilateral β-sitosterol β-D-glucoside lesion could affect bilateral neuropathology and sensorimotor deficits on day 30 post-transfection. This study found that rNurr1-V5 expression but not that of the green fluorescent protein (the negative control) reduced β-sitosterol β-D-glucoside-induced neuropathology. Accordingly, a bilateral increase in tyrosine hydroxylase-positive cells and arborization occurred in the substantia nigra and increased tyrosine hydroxylase-positive ramifications in the striatum. In addition, tyrosine hydroxylase-positive cells displayed less senescence marker β-galactosidase and more neuron-cytoskeleton marker βIII-tubulin and brain-derived neurotrophic factor. A significant decrease in activated microglia (positive to ionized calcium-binding adaptor molecule 1) and neurotoxic astrocytes (positive to glial fibrillary acidic protein and complement component 3) and increased neurotrophic astrocytes (positive to glial fibrillary acidic protein and S100 calcium-binding protein A10) also occurred in the substantia nigra. These effects followed the bilateral reduction in α-synuclein aggregates in the nigrostriatal system, improving sensorimotor behavior. Our results show that unilateral rNurr1-V5 transgene expression in nigral dopaminergic neurons mitigates bilateral neurodegeneration (senescence and loss of neuron-cytoskeleton and tyrosine hydroxylase-positive cells), neuroinflammation (activated microglia, neurotoxic astrocytes), α-synuclein aggregation, and sensorimotor deficits. Increased neurotrophic astrocytes and brain-derived neurotrophic factor can mediate the rNurr1-V5 effect, supporting its potential clinical use in the treatment of Parkinson's disease.

Novel Gene Therapy Approaches for Targeting Neurodegenerative Disorders: Focusing on Delivering Neurotrophic Genes

Neurodegenerative illnesses (NDDs) like Alzheimer's, Parkinson's, amyotrophic lateral sclerosis, spinal muscular atrophy, and Huntington's disease have demonstrated considerable potential for gene therapy as a viable therapeutic intervention. NDDs are marked by the decline of neurons, resulting in changes in both behavior and pathology within the body. Strikingly, only symptomatic management is available without a cure for the NDDs. There is an unmet need for a permanent therapeutic approach. Many studies have been going on to target the newer therapeutic molecular targets for NDDs including gene-based therapy. Gene therapy has the potential to provide therapeutic benefits to a large number of patients with NDDs by offering mechanisms including neuroprotection, neuro-restoration, and rectification of pathogenic pathways. Gene therapy is a medical approach that aims to modify the biological characteristics of living cells by controlling the expression of specific genes in certain neurological disorders. Despite being the most complex and well-protected organ in the human body, there is clinical evidence to show that it is possible to specifically target the central nervous system (CNS). This provides hope for the prospective application of gene therapy in treating NDDs in the future. There are several advanced techniques available for using viral or non-viral vectors to deliver the therapeutic gene to the afflicted region. Neurotrophic factors (NTF) in the brain are crucial for the development, differentiation, and survival of neurons in the CNS, making them important in the context of various neurological illnesses. Gene delivery of NTF has the potential to be used as a therapeutic approach for the treatment of neurological problems in the brain. This review primarily focuses on the methodologies employed for delivering the genes of different NTFs to treat neurological disorders. These techniques are currently being explored as a viable therapeutic approach for neurodegenerative diseases. The article exclusively addresses gene delivery approaches and does not cover additional therapy strategies for NDDs. Gene therapy offers a promising alternative treatment for NDDs by stimulating neuronal growth instead of solely relying on symptom relief from drugs and their associated adverse effects. It can serve as a long-lasting and advantageous treatment choice for the management of NDDs. The likelihood of developing NDDs increases with age as a result of neuronal degradation in the brain. Gene therapy is an optimal approach for promoting neuronal growth through the introduction of nerve growth factor genes.

Focused ultrasound on the substantia nigra enables safe neurotensin-polyplex nanoparticle-mediated gene delivery to dopaminergic neurons intranasally and by blood circulation

Neurotensin-polyplex nanoparticles provide efficient gene transfection of nigral dopaminergic neurons when intracerebrally injected in preclinical trials of Parkinson's disease because they do not cross the blood-brain barrier (BBB). Therefore, this study aimed to open BBB with focused ultrasound (FUS) on the substantia nigra to attain systemic and intranasal transfections and evaluate its detrimental effect in rats. Systemically injected Evans Blue showed that a two-pulse FUS opened the nigral BBB. Accordingly, 35 μL of neurotensin-polyplex nanoparticles encompassing the green fluorescent protein plasmid (79.6 nm mean size and + 1.3 mV Zeta-potential) caused its expression in tyrosine hydroxylase(+) cells (dopaminergic neurons) of both substantiae nigrae upon delivery via internal carotid artery, retro-orbital venous sinus, or nasal mucosa 30 min after FUS. The intracarotid delivery yielded the highest transgene expression, followed by intranasal and venous administration. However, FUS caused neuroinflammation displayed by infiltrated lymphocytes (positive to cluster of differentiation 45), activated microglia (positive to ionized calcium-binding adaptor molecule 1), neurotoxic A1 astrocytes (positive to glial fibrillary acidic protein and complement component 3), and neurotrophic A2 astrocytes (positive to glial fibrillary acidic protein and S100 calcium-binding protein A10), that ended 15 days after FUS. Dopaminergic neurons and axonal projections decreased but recuperated basal values on day 15 after transfection, correlating with a decrease and recovery of locomotor behavior. In conclusion, FUS caused transient neuroinflammation and reversible neuronal affection but allowed systemic and intranasal transfection of dopaminergic neurons in both substantiae nigrae. Therefore, FUS could advance neurotensin-polyplex nanotechnology to clinical trials for Parkinson's disease.

Transfection of the BDNF Gene in the Surviving Dopamine Neurons in Conjunction with Continuous Administration of Pramipexole Restores Normal Motor Behavior in a Bilateral Rat Model of Parkinson's Disease

In Parkinson's disease (PD), progressive degeneration of nigrostriatal innervation leads to atrophy and loss of dendritic spines of striatal medium spiny neurons (MSNs). The loss disrupts corticostriatal transmission, impairs motor behavior, and produces nonmotor symptoms. Nigral neurons express brain-derived neurotropic factor (BDNF) and dopamine D3 receptors, both protecting the dopamine neurons and the spines of MSNs. To restore motor and nonmotor symptoms to normality, we assessed a combined therapy in a bilateral rat Parkinson's model, with only 30% of surviving neurons. The preferential D3 agonist pramipexole (PPX) was infused for four ½ months via mini-osmotic pumps and one month after PPX initiation; the BDNF-gene was transfected into the surviving nigral cells using the nonviral transfection NTS-polyplex vector. Overexpression of the BDNF-gene associated with continuous PPX infusion restored motor coordination, balance, normal gait, and working memory. Recovery was also related to the restoration of the average number of dendritic spines of the striatal projection neurons and the number of TH-positive neurons of the substantia nigra and ventral tegmental area. These positive results could pave the way for further clinical research into this promising therapy.

Beyond animal models: revolutionizing neurodegenerative disease modeling using 3D in vitro organoids, microfluidic chips, and bioprinting

Neurodegenerative diseases (NDs) are characterized by uncontrolled loss of neuronal cells leading to a progressive deterioration of brain functions. The transition rate of numerous neuroprotective drugs against Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease, leading to FDA approval, is only 8-14% in the last two decades. Thus, in spite of encouraging preclinical results, these drugs have failed in human clinical trials, demonstrating that traditional cell cultures and animal models cannot accurately replicate human pathophysiology. Hence, in vitro three-dimensional (3D) models have been developed to bridge the gap between human and animal studies. Such technological advancements in 3D culture systems, such as human-induced pluripotent stem cell (iPSC)-derived cells/organoids, organ-on-a-chip technique, and 3D bioprinting, have aided our understanding of the pathophysiology and underlying mechanisms of human NDs. Despite these recent advances, we still lack a 3D model that recapitulates all the key aspects of NDs, thus making it difficult to study the ND's etiology in-depth. Hence in this review, we propose developing a combinatorial approach that allows the integration of patient-derived iPSCs/organoids with 3D bioprinting and organ-on-a-chip technique as it would encompass the neuronal cells along with their niche. Such a 3D combinatorial approach would characterize pathological processes thoroughly, making them better suited for high-throughput drug screening and developing effective novel therapeutics targeting NDs.

Dimethyl fumarate abrogates striatal endoplasmic reticulum stress in experimentally induced late-stage Huntington’s disease: Focus on the IRE1α/JNK and PERK/CHOP trajectories

Introduction: Dimethyl fumarate (DMF) is FDA-approved for use in patients with relapsing multiple sclerosis, and it processes neuroprotection in several experimental settings; however, its impact on combating Huntington’s disease (HD) remains elusive. This study aimed to explore the role of DMF post-treatment on HD mediated endoplasmic reticulum (ER) stress response in a selective striatal degeneration HD model.

Methods: Rats, exposed to 3-nitropropionic acid, were either left untreated or post-treated with DMF for 14 days.

Results and Discussion: DMF reduced locomotion deficits in both the open field and beam walk paradigms, boosted the striatal dopamine (DA) content, improved its architecture at the microscopic level, and hindered astrogliosis. Mechanistically, DMF limited the activation of two of the ER stress arms in the striatum by reducing p-IRE1α, p-JNK, and p-PERK protein expressions besides the CHOP/GADD153 content. Downstream from both ER stress arms’ suppression, DMF inhibited the intrinsic apoptotic pathway, as shown by the decrease in Bax and active caspase-3 while raising Bcl-2. DMF also decreased oxidative stress markers indicated by a decline in both reactive oxygen species and malondialdehyde while boosting glutathione. Meanwhile, it enhanced p-AKT to activate /phosphorylate mTOR and stimulate the CREB/BDNF/TrkB trajectory, which, in a positive feedforward loop, activates AKT again. DMF also downregulated the expression of miRNA-634, which negatively regulates AKT, to foster survival kinase activation.

Conclusion: This study features a focal novel point on the DMF therapeutic ability to reduce HD motor manifestations via its ability to enhance DA and suppress the IRE1α/JNK and PERK/CHOP/GADD153 hubs to inhibit the mitochondrial apoptotic pathway through activating the AKT/mTOR and BDNF/TrkB/AKT/CREB signaling pathways and abating miRNA-634 and oxidative stress.

Impact of chronic sleep deprivation and sleep recovery on hippocampal oligodendrocytes, anxiety-like behavior, spatial learning and memory of rats

Sleep and its quality play an important role in memory, cognition, and quality of life. Sleep deprivation-induced changes in hippocampal neurons and behavior have been studied widely, in contrast, the extent of damage to oligodendrocytes have not been fully understood. The present study aims to investigate chronic sleep deprivation (CSD) and sleep recovery-induced changes in oligodendrocytes of the hippocampus, cognition, and behavior of rats. Male Sprague-Dawley rats (n = 48) were grouped as control, sham control (SC), CSD, and CSD+sleep recovery (CSD+SR) (n = 12/group). CSD and CSD+SR group rats were sleep deprived for 21-days. After CSD, the CSD+SR group rats sleep recovered for 21-days. Oxidative markers, CNPase+ve oligodendrocytes, CNPase intensity, and CNPase gene expression were measured in the hippocampus, and the anxiety-like behavior, spatial learning, and memory were assessed. The 21-days of CSD significantly (p < 0.001) increased oxidative stress and significantly (p < 0.001) reduced the number of CNPase+ve oligodendrocytes, CNPase intensity, and CNPase gene expression when compared to controls. The increased oxidative stress was correlated with reduced CNPase+ve oligodendrocytes, CNPase intensity, and CNPase gene expression (r = -0.9). In-line with cellular changes, an increased (p < 0.01) anxiety-like behavior and impaired spatial memory were observed in the CSD group compared to controls. The 21-days of sleep recovery significantly (p < 0.01) reduced oxidative stress and anxiety-like behavior, improved spatial memory, increased CNPase intensity and CNPase gene expression, and non-significant (p > 0.05) increase in CNPase+ve oligodendrocytes compared to CSD. Overall, the 21-days of CSD reduced the number of CNPase+ve oligodendrocytes in the hippocampus, increased anxiety, and impaired spatial memory in rats. Though the 21-day sleep recovery showed an improvement in all parameters, it was not sufficient to completely reverse the CSD-induced changes to the control level.

A retrospective evaluation of the Brain and Body Fitness Studio service on functional capacity and quality of life in people with neurological disorders

Background

People with neurological disorders (ND) are less physically active than the general population due to physical, sensory, and/or cognitive impairments. These individuals often feel intimidated to join mainstream health and wellness centers due to lack of specialized support for people with ND. The Brain and Body Fitness Studio (BBFS) is one of the first Accredited Exercise Physiologist-led interprofessional services in Adelaide South Australia to provide individualized evidence-based multimodal exercise prescription and social support for this population. This comprehensive retrospective study evaluated the impact of BBFS on functional capacity (FC) determined as the 6-min walk distance (6 MWD) achieved during a 6-min walk test (6 MWT), of its members with ND.

Methods

Sixty-two BBFS members (age, 66 ± 10 years; 60% male) with ND (85% Parkinson's Disease; average time since diagnosis, 4 years [IQR, 2 to 12 years]) and complete pre- and post-6-month clinical assessment of the primary outcome of the study, the 6 MWD, were included in this retrospective analysis. A series of sub-analyses were also performed to investigate the effects of adherence to the recommended prescription of at least twice a week in the program (≥80 vs. < 80% adherence), and disease stage (time since diagnosis; ≥6 vs. < 6 years) on FC.

Results

Although there was no statistically significant change in 6 MWD from pre- to post-6-month BBFS program (+15 ± 90 m, p = 0.19), a clinically meaningful improvement of >14 m was evident. Improvement in 6 MWD was significantly greater in members who attended at least 80% of the recommended visits (≥80% visits, +37 ± 58 m; ≤ 80% visits,-1 ± 105 m, p = 0.046). We also found a 6 MWD improvement from pre- to post-6 months in those in the early years of their ND (< 6 years since diagnosis, +39 ± 76 m), but not in those in the later years of their ND (≥6 years since diagnosis, -36 ± 123 m, between group difference, p = 0.029).

Conclusion

A clinically meaningful 6 MWD improvement may be elicited by services provided by BBFS in people with ND. Overall, the benefits appear to be more evident in members who attended the BBFS for at least 80% of the recommended visits and those who were in the early stage of their ND diagnosis.

BDNF Val66Met Polymorphism: Suggested Genetic Involvement in Some Children with Learning Disorder

Brain-derived neurotrophic factor (BDNF) plays an essential role in neuronal survival, especially in areas responsible for memory and learning. The BDNF Val66Met polymorphism has been described as a cognitive modifier in people with neuropsychiatric disorders. BDNF levels have been found to be low in children with learning disorder (LD). However, Val66Met polymorphism has not been studied before in such children. The aim was to investigate the presence of BDNF val66Met polymorphism in a group of children with specific LD and to verify its impact on their cognitive abilities. The participants in this cross-sectional study (N = 111) were divided into two groups: one for children with LD and the other for neurotypical (NT) ones. Children with LD (N = 72) were diagnosed according to the DSM-5 criteria. Their abilities were evaluated using Stanford-Binet Intelligence Scale, dyslexia assessment test, Illinois Test of Psycholinguistic Abilities, and phonological awareness test. Genotyping of BDNF Val66Met polymorphism was performed for all participants. The frequency of the Met allele was 26% among children with LD (6 children had homozygous, 26 had heterozygous genotype). The percentage of participants with deficits in reading, writing, and phonemic segmentation was higher in Met allele carriers when compared to non-Met allele carriers in LD group. The frequency of Met allele among NT children was 3.85% (0 homozygous, 3 children had heterozygous genotype) (p = 0.00001). The high frequency of Val66Met polymorphism among children with LD introduces the BDNF gene as a genetic modifier of learning performance in some children who manifest specific learning disorder (developmental dyslexia).

Current Landscape and Emerging Opportunities of Gene Therapy with Non-viral Episomal Vectors

Gene therapy has proven to be extremely beneficial in the management of a wide range of genetic disorders for which there are currently no or few effective treatments. Gene transfer vectors are very significant in the field of gene therapy. It is possible to attach a non-viral attachment vector to the donor cell chromosome instead of integrating it, eliminating the negative consequences of both viral and integrated vectors. It is a safe and optimal express vector for gene therapy because it does not cause any adverse effects. However, the modest cloning rate, low expression, and low clone number make it unsuitable for use in gene therapy. Since the first generation of non-viral attachment episomal vectors was constructed, various steps have been taken to regulate their expression and stability, such as truncating the MAR element, lowering the amount of CpG motifs, choosing appropriate promoters and utilizing regulatory elements. This increases the transfection effectiveness of the non-viral attachment vector while also causing it to express at a high level and maintain a high level of stability. A vector is a genetic construct commonly employed in gene therapy to treat various systemic disorders. This article examines the progress made in the development of various optimization tactics for nonviral attachment vectors and the future applications of these vectors in gene therapy.

Alleviation of Cognitive and Physical Fatigue with Enzymatic Porcine Placenta Hydrolysate Intake through Reducing Oxidative Stress and Inflammation in Intensely Exercised Rats

Intense exercise is reported to induce physical and cognitive fatigue, but few studies have focused on treatments to alleviate fatigue. We hypothesized that the oral supplementation of enzymatic porcine placenta hydrolysate (EPPH) prepared using protease enzymes could alleviate exercise-induced fatigue in an animal model. The objectives of the study were to examine the hypothesis and the action mechanism of EPPH in relieving physical and cognitive fatigue. Fifty male Sprague−Dawley rats aged 8 weeks (body weight: 201 g) were classified into five groups, and rats in each group were given oral distilled water, EPPH (5 mg nitrogen/mL) at doses of 0.08, 0.16, or 0.31 mL/kg body weight (BW)/day, or glutathione (100 mg/kg BW/day) by a feeding needle for 5 weeks, which were named as the control, L-EPPH, M-EPPH, H-EPPH, or positive-control groups, respectively. Ten additional rats had no intense exercise with water administration and were designated as the no-exercise group. After 2 weeks, the rats were subjected to intense exercise and forced swimming trial for 30 min once per week for an additional 4 weeks. At 5 min after the intense exercise, lactate concentrations and lactate dehydrogenase (LDH) activity in the serum and the gastrocnemius muscle were higher in the control group, whereas M-EPPH and H-EPPH treatments suppressed the increase better than in the positive-control (p < 0.05). Intense exercise decreased glycogen content in the liver and gastrocnemius muscle, and M-EPPH and H-EPPH inhibited the decrement (p < 0.05). Moreover, lipid peroxide contents in the gastrocnemius muscle and liver were higher in the control group than in the M-EPPH, H-EPPH, positive-control, and no-exercise groups (p < 0.05). However, antioxidant enzyme activities such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were opposite to the lipid peroxide contents. Hypothalamic corticosterone and hippocampal mRNA expressions of tumor necrosis factor (TNF)-α and IL-1β were higher. However, hippocampal brain-derived neurotrophic factor (BDNF) mRNA expression and protein contents were lower in the control group than in the positive-control group. M-EPPH, H-EPPH, and positive-control suppressed the changes via activating hippocampal cAMP response element-binding protein phosphorylation, and H-EPPH showed better activity than in the positive-control (p < 0.05). In conclusion, EPPH (0.16−0.31 mL/kg BW) intake reduced exercise-induced physical and cognitive fatigue in rats and could potentially be developed as a therapeutic agent for relieving fatigue in humans.

BDNF Therapeutic Mechanisms in Neuropsychiatric Disorders

Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain and functions as both a primary neurotrophic signal and a neuromodulator. It serves essential roles in neuronal development, maintenance, transmission, and plasticity, thereby influencing aging, cognition, and behavior. Accumulating evidence associates reduced central and peripheral BDNF levels with various neuropsychiatric disorders, supporting its potential utilization as a biomarker of central pathologies. Subsequently, extensive research has been conducted to evaluate restoring, or otherwise augmenting, BDNF transmission as a potential therapeutic approach. Promising results were indeed observed for genetic BDNF upregulation or exogenous administration using a multitude of murine models of neurological and psychiatric diseases. However, varying mechanisms have been proposed to underlie the observed therapeutic effects, and many findings indicate the engagement of disease-specific and other non-specific mechanisms. This is because BDNF essentially affects all aspects of neuronal cellular function through tropomyosin receptor kinase B (TrkB) receptor signaling, the disruptions of which vary between brain regions across different pathologies leading to diversified consequences on cognition and behavior. Herein, we review the neurophysiology of BDNF transmission and signaling and classify the converging and diverging molecular mechanisms underlying its therapeutic potentials in neuropsychiatric disorders. These include neuroprotection, synaptic maintenance, immunomodulation, plasticity facilitation, secondary neuromodulation, and preservation of neurovascular unit integrity and cellular viability. Lastly, we discuss several findings suggesting BDNF as a common mediator of the therapeutic actions of centrally acting pharmacological agents used in the treatment of neurological and psychiatric illness.

New Frontiers in Neurodegeneration and Regeneration Associated with Brain-Derived Neurotrophic Factor and the rs6265 Single Nucleotide Polymorphism

Brain-derived neurotrophic factor is an extensively studied neurotrophin implicated in the pathology of multiple neurodegenerative and psychiatric disorders including, but not limited to, Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, traumatic brain injury, major de-pressive disorder, and schizophrenia. Here we provide a brief summary of current knowledge on the role of BDNF and the common human single nucleotide polymorphism, rs6265, in driving the pathogenesis and rehabilitation in these disorders, as well as the status of BDNF-targeted therapies. A common trend has emerged correlating low BDNF levels, either detected within the central nervous system or peripherally, to disease states, suggesting that BDNF replacement therapies may hold clinical promise. In addition, we introduce evidence for a distinct role of the BDNF pro-peptide as a biologically active ligand and the need for continuing studies on its neurological function outside of that as a molecular chaperone. Finally, we highlight the latest research describing the role of rs6265 expression in mechanisms of neurodegeneration as well as paradoxical advances in the understanding of this genetic variant in neuroregeneration. All of this is discussed in the context of personalized medicine, acknowledging there is no “one size fits all” therapy for neurodegenerative or psychiatric disorders and that continued study of the multiple BDNF isoforms and genetic variants represents an avenue for discovery ripe with therapeutic potential.

Swimming exercise prevents hippocampal dendritic spine changes and memory loss caused by aging: An application of a new semi-automated spine analysis software

Dendritic spines are small, ratchet-like protrusions on neuronal dendrites that form synapses for receiving neuronal messages. Dendritic spine morphology is associated with synapse function. If neurons degrade or are damaged, the spine morphology of neurons changes. Given that most commercially available spine analysis software is expensive and complex, this study investigated a semi-automated spine analysis software, CTSpine, and used previously published data to verify the accuracy of the analysis results of this software. We also applied CTSpine to understand whether aging causes alterations in the hippocampal spine morphology and whether physical exercise can impede dendritic spine changes in 20 male Sprague Dawley rats. The spines of pyramidal cells in the hippocampal Cornu Ammonis 1 (CA1) region in the aging group were more enriched in filopodium type pattern than those in the control group, whereas the spines of the exercised aging group showed a similar pattern to that of the control. No significant changes were observed in neuronal dendritic spines in other hippocampal regions. However, long-term hippocampal memory was considerably decreased in the aging group, which was reversed to some extent in the exercised aging group. CTSpine, a self-developed semi-automatic spine analysis software, showed results similar to those noted in published data and can be effectively applied to the study of dendritic patterns, including neurodevelopment and disease.

Impact of two different types of exercise training on AMPH addiction: Role of hippocampal neurotrophins

INTRODUCTION

Amphetamine (AMPH) abuse results in neurobehavioral alterations related to the reward circuit. The hippocampus plays a role in cognition, reward, and drug addiction. There are no pharmacological approaches to prevent AMPH relapse. Physical exercise has been studied as a non-pharmacological promising influence to attenuate reward symptoms related to addictive drugs.

OBJECTIVE

This study aimed to compare the effects of non-weight-loaded and weight-loaded physical exercise on behavioral (relapse, memory and anxiety) and hippocampal molecular parameters associated with AMPH addiction in Wistar rats.

METHODS

Male rats were subjected to the AMPH-Conditioned Place Preference (CPP) paradigm. After 8-conditioning days, they were subjected to swimming physical exercise protocol (without or with weight-load). Behavioral evaluations were performed to assess the influence of both exercise protocols in addiction parameters, including relapse after AMPH reconditioning, working memory, locomotor activity, and anxiety-like symptoms. Subsequently, protein levels of Brain-Derived Neurotrophic Factor (BDNF) and pro-BDNF ex-vivo assays were carried out in samples of the hippocampus of the animals.

RESULTS

AMPH relapse and anxiety-like behaviors were reduced only in rats subjected to non-weight-loaded exercise. Hippocampal BDNF and pro-BDNF immunoreactivity were increased in non-weight-loaded exercise rats. Behavioral and molecular analyses were not modified in rats subjected to weight-loaded exercise.

CONCLUSION

These findings demonstrate that non-weight-loaded exercise was more effective against relapse and anxiety-like behavior induced by AMPH. Non-weight-loaded exercise upregulated the hippocampal immunocontent levels in rats.

Overcoming barriers in non-viral gene delivery for neurological applications

Gene therapy for neurological disorders has attracted significant interest as a way to reverse or stop various disease pathologies. Typical gene therapies involving the central and peripheral nervous system make use of adeno-associated viral vectors whose questionable safety and limitations in manufacturing has given rise to extensive research into non-viral vectors. While early research studies have demonstrated limited efficacy with these non-viral vectors, investigation into various vector materials and functionalization methods has provided insight into ways to optimize these non-viral vectors to improve desired characteristics such as improved blood-brain barrier transcytosis, improved perfusion in brain region, enhanced cellular uptake and endosomal escape in neural cells, and nuclear transport of genetic material post- intracellular delivery. Using a combination of various strategies to enhance non-viral vectors, research groups have designed multi-functional vectors that have been successfully used in a variety of pre-clinical applications for the treatment of Parkinson's disease, brain cancers, and cellular reprogramming for neuron replacement. While more work is needed in the design of these multi-functional non-viral vectors for neural applications, much of the groundwork has been done and is reviewed here.

Application of neurotoxin- and pesticide-induced animal models of Parkinson's disease in the evaluation of new drug delivery systems

Parkinson's disease (PD) is the second most prevalent neuro-degenerative disease after Alzheimer´s disease. It is characterized by motor symptoms such as akinesia, bradykinesia, tremor, rigidity, and postural abnormalities, due to the loss of nigral dopaminergic neurons and a decrease in the dopa-mine contents of the caudate-putamen structures. To this date, there is no cure for the disease and available treatments are aimed at controlling the symptoms. Therefore, there is an unmet need for new treatments for PD. In the past decades, animal models of PD have been proven to be valuable tools in elucidating the nature of the pathogenic processes involved in the disease, and in designing new pharmacological approaches. Here, we review the use of neurotoxin-induced and pesticide-induced animal models of PD, specifically those induced by rotenone, paraquat, maneb, MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and 6-OHDA (6-hydroxydopamine), and their application in the development of new drug delivery systems for PD.

Involvement of DA D3 Receptors in Structural Neuroplasticity of Selected Limbic Brain Circuits: Possible Role in Treatment-Resistant Depression

Structural neuroplasticity in the adult brain is a process involving quantitative changes of the number and size of neurons and of their dendritic arborization, axon branching, spines, and synapses. These changes can occur in specific neural circuits as adaptive response to environmental challenges, exposure to stressors, tissue damage or degeneration. Converging studies point to evidence of structural plasticity in circuits operated by glutamate, GABA, dopamine, and serotonin neurotransmitters, in concert with neurotrophic factors such as Brain Derived Neurotrophic Factor (BDNF) or Insulin Growth Factor 1 (IGF1) and a series of modulators that include circulating hormones. Intriguingly, most of these endogenous agents trigger the activation of the PI3K/Akt/mTOR and ERK1/2 intracellular pathways that, in turn, lead to the production of growth-related structural changes, enhancing protein synthesis, metabolic enzyme functions, mitogenesis for energy, and new lipid-bilayer membrane apposition. The dopamine (DA) D3 receptor has been shown to play a specific role by inducing structural plasticity of the DAergic neurons of the nigrostriatal and mesocorticolimbic circuit, where they are expressed in rodents and humans, via activation of the mTORC1 and ERK1/2 pathways. These effects are BDNF-dependent and require the recruitment of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors to allow the structural changes. Since in mood disorders, depression and anhedonia have been proposed to be associated with impaired neuroplasticity and reduced DAergic tone in brain circuits connecting prefrontal cortex, ventral striatum, amygdala, and ventral mesencephalon, activation of D3 receptors could provide a therapeutic benefit. Sustained improvements of mood and anhedonia were observed in subjects with an unsatisfactory response to serotonin uptake inhibitors (SSRI) when treated with D3-preferential D2/D3 agonists such as pramipexole and ropinirole. The recent evidence that downstream mTOR pathway activation in human mesencephalic DA neurons is also produced by ketamine, probably the most effective antidepressant currently used in subjects with treatment-resistant depression, further supports the rationale for a D3 receptor activation in mood disorders.

Brain Derived Neurotrophic Factor and Cognitive Dysfunction in the Schizophrenia-Bipolar Spectrum: A Systematic Review and Meta-Analysis

BACKGROUND

Cognitive impairment is a core feature of disorders on the schizophrenia-bipolar spectrum, i.e., schizophrenia, bipolar disorder, and schizoaffective disorder. Brain-derived neurotrophic factor (BDNF) has been proposed to be a biomarker of cognitive impairment in these disorders as it plays a critical role in neuroplasticity and proposed to mediate some of the psychotropic effects of medication. However, despite numerous studies investigating the association between circulating BDNF and these disorders, no solid conclusions have been drawn regarding its involvement in cognitive impairment.

OBJECTIVES

The current systematic review and meta-analysis aims to examine blood BDNF levels and cognitive dysfunction in patients on the schizophrenia-bipolar spectrum as well as to evaluate whether circulating BDNF measurements can act as a biomarker for cognitive dysfunction.

METHODS

Studies were identified by searching Embase and Medline databases for English language articles published in peer-reviewed journals between 2000 January and 2021 June according to the PRISMA guidelines. A total of 815 articles were identified of which 32 met the inclusion criteria for the systematic review - reporting on comparisons between blood BDNF levels and cognitive functions of schizophrenia or bipolar disorder patients versus healthy controls (no studies involving schizoaffective patients were specifically obtained for the time being). Twenty-four of these studies (19 with schizophrenia and 5 with bipolar disorder patients) were eligible to be included in the meta-analysis.

RESULTS

Our findings indicated that circulating BDNF levels were significantly reduced in patients experiencing an acute episode of schizophrenia or bipolar disorder compared to healthy controls. Cognitive function was also found to be significantly worse in patients, however, correlations between BDNF levels and cognitive impairment were not always detected. Interventions, especially pharmacotherapy seemed to improve certain aspects of cognition and increase circulating BDNF levels.

CONCLUSION

Circulating BDNF alone does not seem to be a valid biomarker of cognitive dysfunction in patients with disorders on the schizophrenia-bipolar spectrum, owing to several confounding factors. Changes of the circulating levels of BDNF should be evaluated in a wider context of other stress-, immune-, and inflammatory-related factors.

Impact of Pharmacological and Non-Pharmacological Modulators on Dendritic Spines Structure and Functions in Brain

Dendritic spines are small, thin, hair-like protrusions found on the dendritic processes of neurons. They serve as independent compartments providing large amplitudes of Ca2+ signals to achieve synaptic plasticity, provide sites for newer synapses, facilitate learning and memory. One of the common and severe complication of neurodegenerative disease is cognitive impairment, which is said to be closely associated with spine pathologies viz., decreased in spine density, spine length, spine volume, spine size etc. Many treatments targeting neurological diseases have shown to improve the spine structure and distribution. However, concise data on the various modulators of dendritic spines are imperative and a need of the hour. Hence, in this review we made an attempt to consolidate the effects of various pharmacological (cholinergic, glutamatergic, GABAergic, serotonergic, adrenergic, and dopaminergic agents) and non-pharmacological modulators (dietary interventions, enriched environment, yoga and meditation) on dendritic spines structure and functions. These data suggest that both the pharmacological and non-pharmacological modulators produced significant improvement in dendritic spine structure and functions and in turn reversing the pathologies underlying neurodegeneration. Intriguingly, the non-pharmacological approaches have shown to improve intellectual performances both in preclinical and clinical platforms, but still more technology-based evidence needs to be studied. Thus, we conclude that a combination of pharmacological and non-pharmacological intervention may restore cognitive performance synergistically via improving dendritic spine number and functions in various neurological disorders.

Effects of exergaming on hippocampal volume and brain-derived neurotrophic factor levels in Parkinson's disease

BACKGROUND AND OBJECTIVE

Cognitive impairment is among the most burdensome non-motor symptoms in Parkinson's disease (PD) and has been associated with hippocampal atrophy. Exercise has been reported to enhance neuroplasticity in the hippocampus in correlation with an improvement of cognitive function. We present data from the Training-PD study, which was designed to evaluate effects of an "" training protocol on neuronal plasticity in PD.

METHODS

We initiated a 6-week exergaming training program, combining visually stimulating computer games with physical exercise in 17 PD patients and 18 matched healthy controls. Volumetric segmentation of hippocampal subfields on T1- and T2-weighted magnetic resonance imaging and brain-derived neurotrophic factor (BDNF) serum levels were analyzed before and after the training protocol.

RESULTS

The PD group showed a group-dependent significant volume increase of the left hippocampal subfields CA1, CA4/dentate gyrus (DG) and subiculum after the 6-week training protocol. The effect was most pronounced in the left DG of PD patients, who showed a significantly smaller percentage volume compared to healthy controls at baseline, but not at follow-up. Both groups had a significant increase in serum BDNF levels after training.

CONCLUSIONS

The results of the present study indicate that exergaming might be a suitable approach to induce hippocampal volume changes in PD patients. Further and larger studies are needed to verify our findings.

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.

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.

ERRγ ligand HPB2 upregulates BDNF-TrkB and enhances dopaminergic neuronal phenotype

Brain derived neurotrophic factor (BDNF) promotes maturation of dopaminergic (DAergic) neurons in the midbrain and positively regulates their maintenance and outgrowth. Therefore, understanding the mechanisms regulating the BDNF signaling pathway in DAergic neurons may help discover potential therapeutic strategies for neuropsychological disorders associated with dysregulation of DAergic neurotransmission. Because estrogen-related receptor gamma (ERRγ) is highly expressed in both the fetal nervous system and adult brains during DAergic neuronal differentiation, and it is involved in regulating the DAergic neuronal phenotype, we asked in this study whether ERRγ ligand regulates BDNF signaling and subsequent DAergic neuronal phenotype. Based on the X-ray crystal structures of the ligand binding domain of ERRγ, we designed and synthesized the ERRγ agonist, (E)-4-hydroxy-N'-(4-(phenylethynyl)benzylidene)benzohydrazide (HPB2) (K_d value, 8.35 μmol/L). HPB2 increased BDNF mRNA and protein levels, and enhanced the expression of the BDNF receptor tropomyosin receptor kinase B (TrkB) in human neuroblastoma SH-SY5Y, differentiated Lund human mesencephalic (LUHMES) cells, and primary ventral mesencephalic (VM) neurons. HPB2-induced upregulation of BDNF was attenuated by GSK5182, an antagonist of ERRγ, and siRNA-mediated ERRγ silencing. HPB2-induced activation of extracellular-signal-regulated kinase (ERK) and phosphorylation of cAMP-response element binding protein (CREB) was responsible for BDNF upregulation in SH-SY5Y cells. HPB2 enhanced the DAergic neuronal phenotype, namely upregulation of tyrosine hydroxylase (TH) and DA transporter (DAT) with neurite outgrowth, both in SH-SY5Y and primary VM neurons, which was interfered by the inhibition of BDNF-TrkB signaling, ERRγ knockdown, or blockade of ERK activation. HPB2 also upregulated BDNF and TH in the striatum and induced neurite elongation in the substantia nigra of mice brain. In conclusion, ERRγ activation regulated BDNF expression and the subsequent DAergic neuronal phenotype in neuronal cells. Our results might provide new insights into the mechanism underlying the regulation of BDNF expression, leading to novel therapeutic strategies for neuropsychological disorders associated with DAergic dysregulation.

Post-symptomatic Delivery of Brain-Derived Neurotrophic Factor (BDNF) Ameliorates Spinocerebellar Ataxia Type 1 (SCA1) Pathogenesis

Spinocerebellar ataxia type 1 (SCA1) is a fatal neurodegenerative disease caused by an abnormal expansion of CAG repeats in the Ataxin1 (ATXN1) gene. SCA1 is characterized by motor deficits, cerebellar neurodegeneration, and gliosis and gene expression changes. Expression of brain-derived neurotrophic factor (BDNF), growth factor important for the survival and function of cerebellar neurons, is decreased in ATXN1[82Q] mice, the Purkinje neuron specific transgenic mouse model of SCA1. As this decrease in BDNF expression may contribute to cerebellar neurodegeneration, we tested whether delivery of extrinsic human BDNF via osmotic ALZET pumps has a beneficial effect on disease severity in this mouse model of SCA1. Additionally, to test the effects of BDNF on established and progressing cerebellar pathogenesis and motor deficits, we delivered BDNF post-symptomatically. We have found that post-symptomatic delivery of extrinsic BDNF ameliorated motor deficits and cerebellar pathology (i.e., dendritic atrophy of Purkinje cells, and astrogliosis) indicating therapeutic potential of BDNF even after the onset of symptoms in SCA1. However, BDNF did not alter Purkinje cell gene expression changes indicating that certain aspects of disease pathogenesis cannot be ameliorated/slowed down with BDNF and that combinational therapies may be needed.

The Relation of the Brain-Derived Neurotrophic Factor with MicroRNAs in Neurodegenerative Diseases and Ischemic Stroke

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors that plays a crucial role in the development of the nervous system while supporting the survival of existing neurons and instigating neurogenesis. Altered levels of BDNF, both in the circulation and in the central nervous system (CNS), have been reported to be involved in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), multiple sclerosis (MS), and ischemic stroke. MicroRNAs (miRNAs) are a class of non-coding RNAs found in body fluids such as peripheral blood and cerebrospinal fluid. Several different miRNAs, and their target genes, are recognized to be involved in the pathophysiology of neurodegenerative and neurovascular diseases. Thus, they present as promising biomarkers and a novel treatment approach for CNS disorders. Currently, limited studies provide viable evidence of miRNA-mediated post-transcriptional regulation of BDNF. The aim of this review is to provide a comprehensive assessment of the current knowledge regarding the potential diagnostic and prognostic values of miRNAs affecting BDNF expression and its role as a CNS disorders and neurovascular disease biomarker. Moreover, a novel therapeutic approach in neurodegenerative diseases and ischemic stroke targeting miRNAs associated with BDNF will be discussed.

Influence of BDNF Genetic Polymorphisms in the Pathophysiology of Aging-related Diseases

For the first time in history, most of the population has a life expectancy equal or greater than 60 years. By the year 2050, it is expected that the world population in that age range will reach 2000 million, an increase of 900 million with respect to 2015, which poses new challenges for health systems. In this way, it is relevant to analyze the most common diseases associated with the aging process, namely Alzheimer´s disease, Parkinson Disease and Type II Diabetes, some of which may have a common genetic component that can be detected before manifesting, in order to delay their progress. Genetic inheritance and epigenetics are factors that could be linked in the development of these pathologies. Some researchers indicate that the BDNF gene is a common factor of these diseases, and apparently some of its polymorphisms favor the progression of them. In this regard, alterations in the level of BDNF expression and secretion, due to polymorphisms, could be linked to the development and/or progression of neurodegenerative and metabolic disorders. In this review we will deepen on the different polymorphisms in the BDNF gene and their possible association with age-related pathologies, to open the possibilities of potential therapeutic targets.

The BDNF Val66Met polymorphism (rs6265) enhances dopamine neuron graft efficacy and side-effect liability in rs6265 knock-in rats

Prevalent in approximately 20% of the worldwide human population, the rs6265 (also called ‘Val66Met’) single nucleotide polymorphism (SNP) in the gene for brain-derived neurotrophic factor (BDNF) is a common genetic variant that can alter therapeutic responses in individuals with Parkinson’s disease (PD). Possession of the variant Met allele results in decreased activity-dependent release of BDNF. Given the resurgent worldwide interest in neural transplantation for PD and the biological relevance of BDNF, the current studies examined the effects of the rs6265 SNP on therapeutic efficacy and side-effect development following primary dopamine (DA) neuron transplantation. Considering the significant reduction in BDNF release associated with rs6265, we hypothesized that rs6265-mediated dysfunctional BDNF signaling contributes to the limited clinical benefit observed in a subpopulation of PD patients despite robust survival of grafted DA neurons, and further, that this mutation contributes to the development of aberrant graft-induced dyskinesias (GID). To this end, we generated a CRISPR knock-in rat model of the rs6265 BDNF SNP to examine for the first time the influence of a common genetic polymorphism on graft survival, functional efficacy, and side-effect liability, comparing these parameters between wild-type (Val/Val) rats and those homozygous for the variant Met allele (Met/Met). Counter to our hypothesis, the current research indicates that Met/Met rats show enhanced graft-associated therapeutic efficacy and a paradoxical enhancement of graft-derived neurite outgrowth compared to wild-type rats. However, consistent with our hypothesis, we demonstrate that the rs6265 genotype in the host rat is strongly linked to development of GID, and that this behavioral phenotype is significantly correlated with neurochemical signatures of atypical glutamatergic neurotransmission by grafted DA neurons.

Adult Endogenous Dopaminergic Neuroregeneration Against Parkinson's Disease: Ideal Animal Models?

Parkinson's disease (PD) is the second most common neurodegenerative disease. The etiology of PD remains an enigma with no available disease modifying treatment or cure. Pharmacological compensation is the only quality of life improving treatments available. Endogenous dopaminergic neuroregeneration has recently been considered a plausible therapeutic strategy for PD. However, researchers have to first decipher the complexity of adult endogenous neuroregeneration. This raises the need of animal models to understand the underlying molecular basis. Mammalian models with highly conserved genetic homology might aid researchers to identify specific molecular mechanisms. However, the scarcity of adult neuroregeneration potential in mammals obfuscates such investigations. Nowadays, non-mammalian models are gaining popularity due to their explicit ability to neuroregenerate naturally without the need of external enhancements, yet these non-mammals have a much diverse gene homology that critical molecular signals might not be conserved across species. The present review highlights the advantages and disadvantages of both mammalian and non-mammalian animal models that can be essentially used to study the potential of endogenous DpN regeneration against PD.

Synthetic Monopartite Peptide That Enables the Nuclear Import of Genes Delivered by the Neurotensin-Polyplex Vector

Neurotensin (NTS)-polyplex is a multicomponent nonviral vector that enables gene delivery via internalization of the neurotensin type 1 receptor (NTSR1) to dopaminergic neurons and cancer cells. An approach to improving its therapeutic safety is replacing the viral karyophilic component (peptide KPSV40; MAPTKRKGSCPGAAPNKPK), which performs the nuclear import activity, by a shorter synthetic peptide (KPRa; KMAPKKRK). We explored this issue and the mechanism of plasmid DNA translocation through the expression of the green fluorescent protein or red fluorescent protein fused with KPRa and internalization assays and whole-cell patch-clamp configuration experiments in a single cell together with importin α/β pathway blockers. We showed that KPRa electrostatically bound to plasmid DNA increased the transgene expression compared with KPSV40 and enabled nuclear translocation of KPRa-fused red fluorescent proteins and plasmid DNA. Such translocation was blocked with ivermectin or mifepristone, suggesting importin α/β pathway mediation. KPRa also enabled NTS-polyplex-mediated expression of reporter or physiological genes such as human mesencephalic-derived neurotrophic factor (hMANF) in dopaminergic neurons in vivo. KPRa is a synthetic monopartite peptide that showed nuclear import activity in NTS-polyplex vector-mediated gene delivery. KPRa could also improve the transfection of other nonviral vectors used in gene therapy.

Exercise-Induced Neuroprotection in the 6-Hydroxydopamine Parkinson's Disease Model

Exercise exerts helpful effects in Parkinson's disease. In this study, the 6-hydroxydopamine (6-OHDA) injection was used to investigate the effect of exercise on apomorphine-induced rotation and neurorestoration. Rats (n = 32) were divided into four groups: (1) Saline+Noexercise (Sham); (2) 6-OHDA+Noexercise (6-OHDA); (3) Saline+Exercise (S+EXE), and (4) 6-OHDA+Exercise (6-OHDA+EXE). The rats were administered 8 μg 6-OHDA by injection into the right medial forebrain bundle. After 2 weeks, the exercise group was run (14 consecutive days, 30 min per day). One month after the surgery, following the injection of apomorphine, the 6-OHDA group displayed a significant increase in rotation and the 6-OHDA+EXE group showed a significant reduction of rotational asymmetry (P < 0.001). 6-OHDA injection reduced the mRNA and protein expression of the AMP-activated protein kinase, brain-derived neurotropic factor, and tyrosine hydroxylase in relation to the Sham group and exercise increased these levels. Expression of the silent information regulator 2 homolog 1 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha was unexpectedly enhanced in the 6-OHDA groups in relation to the Sham group. These findings suggest that the 6-OHDA injection increased the neurodegeneration and mitochondrial and behavioral dysfunctions and the treadmill running attenuated these disorders in the ipsilateral striatum of the 6-OHDA+EXE group.

Expression analysis of hippocampal and amygdala CREB-BDNF signaling pathway in nicotine-induced reward under stress in rats

Extensive research has shown that individuals are more sensitive to develop addiction and drug taking under stress state. The present study includes an expression analysis to identify the possible role of hippocampal and amygdala CREB (cAMP response element-binding protein) and BDNF (Brain-derived neurotrophic factor) activation in nicotine-induced conditioned place preference (CPP) under exposure to acute or sub-chronic stress. Using western-blot technique, CREB phosphorylation was shown to increase in the hippocampus and the amygdala following nicotine-induced CPP. The hippocampal level of BDNF was increased following nicotine administration and in the nicotine-treated animals exposed to acute stress. In animals exposed to acute stress, the amygdala ratios of the pCREB/CREB decreased, while pre-treatment of the animals with nicotine (0.1 mg/kg) decreased this ratio only in the hippocampus. Sub-chronic stress decreased the pCREB/CREB ratios in the hippocampus and the amygdala. Interestingly, sub-chronic stress-induced increase of nicotine reward only decreased the hippocampal pCREB/CREB ratio. The levels of BDNF in the hippocampus and the amygdala decreased under acute stress. Acute stress-induced increase of nicotine reward increased BDNF levels in the hippocampus. Moreover, the animals' exposure to the CPP apparatus without any drug administration increased the ratios of pCREB/tCREB and BDNF/β-actin in the targeted sites. In summary, the present study indicate that the alterations of the ratio of pCREB/CREB and also the level of BDNF in the hippocampus may be critical for enhancing nicotine reward under stress condition. The evidence from this study suggests the distinct roles of the hippocampus and the amygdala in mediating nicotine reward under stress.

Unilateral intranigral administration of β-sitosterol β-D-glucoside triggers pathological α-synuclein spreading and bilateral nigrostriatal dopaminergic neurodegeneration in the rat

The spreading and accumulation of α-synuclein and dopaminergic neurodegeneration, two hallmarks of Parkinson’s disease (PD), have been faithfully reproduced in rodent brains by chronic, oral administration of β-sitosterol β-D-glucoside (BSSG). We investigated whether a single injection of BSSG (6 μg BSSG/μL DMSO) in the left substantia nigra of Wistar rats causes the same effects. Mock DMSO injections and untreated rats formed control groups. We performed immunostainings against the pathological α-synuclein, the dopaminergic marker tyrosine hydroxylase (TH), the neuroskeleton marker β-III tubulin, the neurotensin receptor type 1 (NTSR1) as non-dopaminergic phenotype marker and Fluro-Jade C (F-J C) label for neurodegeneration. Using β-galactosidase (β-Gal) assay and active caspase-3 immunostaining, we assessed cell death mechanisms. Golgi-Cox staining was used to measure the density and types of dendritic spines of striatal medium spiny neurons. Motor and non-motor alterations were also evaluated. The study period comprised 15 to 120 days after the lesion. In the injured substantia nigra, BSSG caused a progressive α-synuclein aggregation and dopaminergic neurodegeneration caused by senescence and apoptosis. The α-synuclein immunoreactivity was also present within microglia cells. Decreased density of dopaminergic fibers and dendritic spines also occurred in the striatum. Remarkably, all the histopathological changes also appeared on the contralateral nigrostriatal system, and α-synuclein aggregates were present in other brain regions. Motor and non-motor behavioral alterations were progressive. Our data show that the stereotaxic BSSG administration reproduces PD α-synucleinopathy phenotype in the rat. This approach will aid in identifying the spread mechanism of α-synuclein pathology and validate anti-synucleinopathy therapies.

BDNF as a Promising Therapeutic Agent in Parkinson's Disease

Brain-derived neurotrophic factor (BDNF) promotes neuroprotection and neuroregeneration. In animal models of Parkinson’s disease (PD), BDNF enhances the survival of dopaminergic neurons, improves dopaminergic neurotransmission and motor performance. Pharmacological therapies of PD are symptom-targeting, and their effectiveness decreases with the progression of the disease; therefore, new therapeutical approaches are needed. Since, in both PD patients and animal PD models, decreased level of BDNF was found in the nigrostriatal pathway, it has been hypothesized that BDNF may serve as a therapeutic agent. Direct delivery of exogenous BDNF into the patient’s brain did not relieve the symptoms of disease, nor did attempts to enhance BDNF expression with gene therapy. Physical training was neuroprotective in animal models of PD. This effect is mediated, at least partly, by BDNF. Animal studies revealed that physical activity increases BDNF and tropomyosin receptor kinase B (TrkB) expression, leading to inhibition of neurodegeneration through induction of transcription factors and expression of genes related to neuronal proliferation, survival, and inflammatory response. This review focuses on the evidence that increasing BDNF level due to gene modulation or physical exercise has a neuroprotective effect and could be considered as adjunctive therapy in PD.

The effect of preventive exercise on the neuroprotection in 6-hydroxydopamine-lesioned rat brain

Parkinson's disease is characterized by neurodegeneration and learning deficiency. Physical exercise can alleviate these symptoms by increasing the expression of some effective and relevant factors. The preventive effect of 16-week treadmill running in a rat model of Parkinson's disease, before 6-hydroxydopamine (6-OHDA) induction, was assessed. Experimental groups consisted of sedentary (SED), SED+6-OHDA, exercised (EX), and EX+6-OHDA rats. Forty-eight hours after the last session of exercise, 6-OHDA was injected into the medial forebrain bundle (MFB). One week after the injection, behavioral tests, including spatial learning and memory, were assessed through Morris water maze (MWM) and apomorphine-induced rotation. Three weeks after the injection, mRNA expression and protein levels of the transcriptional co-activator peroxisome-proliferator-activated receptor-γ co-activator-1α (PGC-1α), fibronectin type III domain-containing protein 5 (FNDC5), brain-derived neurotrophic factor (BDNF), and tyrosine hydroxylase (TH) were measured in the striatum and the hippocampus of rats by applying real-time PCR and Western blotting. The findings indicate that exposure to 6-OHDA leads to impairments in behavioral and molecular functions. Exercise training prevents and reduces the symptoms caused by dopamine toxins. The results suggest that treadmill running can exert neuroprotective and have preventive effects to reduce Parkinson's disease symptoms. Novelty Parkinson's disease impairs spatial learning and memory. Parkinson's disease reduced levels of PGC-1α, FNDC5, and BDNF and increased neurodegeneration in the striatum and the hippocampus. Treadmill running before disease attenuated 6-OHDA-induced memory deficit and elevated neuroprotection. Exercise has multiple effects on memory and biochemical factors.

The noradrenergic system is necessary for survival of vulnerable midbrain dopaminergic neurons: implications for development and Parkinson's disease

The cause of midbrain dopaminergic (mDA) neuron loss in sporadic Parkinson's disease (PD) is multifactorial, involving cell autonomous factors, cell-cell interactions, and the effects of environmental toxins. Early loss of neurons in the locus coeruleus (LC), the main source of ascending noradrenergic (NA) projections, is an important feature of PD and other neurodegenerative disorders. We hypothesized that NA afferents provide trophic support for vulnerable mDA neurons. We demonstrate that depriving mDA neurons of NA input increases postnatal apoptosis and decreases cell survival in young adult rodents, with relative sparing of calbindin-positive subpopulations known to be resistant to degeneration in PD. As a mechanism, we propose that the neurotrophin brain-derived neurotrophic factor (BDNF) modulates anterograde survival effects of LC inputs to mDA neurons. We demonstrate that the LC is rich in BDNF mRNA in postnatal and young adult brains. Early postnatal NA denervation reduces both BDNF protein and activation of TrkB receptors in the ventral midbrain. Furthermore, overexpression of BDNF in NA afferents in transgenic mice increases mDA neuronal survival. Finally, increasing NA activity in primary cultures of mDA neurons improves survival, an effect that is additive or synergistic in the presence of different concentrations of BDNF. Taken together, our results point to a novel mechanism whereby LC afferents couple BDNF effects and NA activity to provide anterograde trophic support for vulnerable mDA neurons. Early loss of NA activity and anterograde neurotrophin support may contribute to degeneration of vulnerable neurons in PD and other neurodegenerative disorders.

Physical exercise and human adipose-derived mesenchymal stem cells ameliorate motor disturbances in a male rat model of Parkinson's disease

Parkinson's disease (PD) is a disabling and highly costly neurodegenerative condition with worldwide prevalence. Despite advances in treatments that slow progression and minimize locomotor impairments, its clinical management is still a challenge. Previous preclinical studies, using mesenchymal stem cell (MSC) transplantation and isolated physical exercise (EX), reported beneficial results for treatment of PD. Therefore, this experimental randomized study aimed to elucidate the therapeutic potential of combined therapy using adipose-derived human MSCs (ADSCs) grafted into the striatum in conjunction with aerobic treadmill training, specifically in terms of locomotor performance in a unilateral PD rat model induced by 6-hydroxydopamine (6-OHDA). Forty-one male Wistar rats were categorized into five groups in accordance with the type of treatment to which they were subjected (Sham, 6-OHDA - injury, 6-OHDA + exercise, 6-OHDA + cells, and 6-OHDA + combined). Subsequently, dopaminergic depletion was assessed by the methylphenidate challenge and the specified therapeutic intervention was conducted in each group. The foot fault task was performed at the end of the experiment to serve as an assessment of motor skills. The results showed that despite disturbances in motor balance and coordination, locomotor dysfunction was ameliorated in all treatment categories in comparison to the injury group (sign test, p < 0.001, effect size: 0.71). The exercise alone and combined groups were the categories that exhibited the best recovery in terms of movement performance (p < 0.001). Overall, this study confirms that exercise is a powerful option to improve motor function and a promising adjuvant intervention for stem cell transplantation in the treatment of PD motor symptoms. OPEN PRACTICES: This article has been awarded Open Data. All materials and data are publicly accessible at https://figshare.com/s/18a543c101a17a1d5560. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

Brain-Derived Neurotrophic Factor in Brain Disorders: Focus on Neuroinflammation

Brain-derived neurotrophic factor (BDNF) is one of the most studied neurotrophins in the healthy and diseased brain. As a result, there is a large body of evidence that associates BDNF with neuronal maintenance, neuronal survival, plasticity, and neurotransmitter regulation. Patients with psychiatric and neurodegenerative disorders often have reduced BDNF concentrations in their blood and brain. A current hypothesis suggests that these abnormal BDNF levels might be due to the chronic inflammatory state of the brain in certain disorders, as neuroinflammation is known to affect several BDNF-related signaling pathways. Activation of glia cells can induce an increase in the levels of pro- and antiinflammatory cytokines and reactive oxygen species, which can lead to the modulation of neuronal function and neurotoxicity observed in several brain pathologies. Understanding how neuroinflammation is involved in disorders of the brain, especially in the disease onset and progression, can be crucial for the development of new strategies of treatment. Despite the increasing evidence for the involvement of BDNF and neuroinflammation in brain disorders, there is scarce evidence that addresses the interaction between the neurotrophin and neuroinflammation in psychiatric and neurodegenerative diseases. This review focuses on the effect of acute and chronic inflammation on BDNF levels in the most common psychiatric and neurodegenerative disorders and aims to shed some light on the possible biological mechanisms that may influence this effect. In addition, this review will address the effect of behavior and pharmacological interventions on BDNF levels in these disorders.

Ketamine enhances structural plasticity in mouse mesencephalic and human iPSC-derived dopaminergic neurons via AMPAR-driven BDNF and mTOR signaling

Among neurobiological mechanisms underlying antidepressant properties of ketamine, structural remodeling of prefrontal and hippocampal neurons has been proposed as critical. The suggested mechanism involves downstream activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, which trigger mammalian target of rapamycin (mTOR)-dependent structural plasticity via brain-derived neurotrophic factor (BDNF) and protein neo-synthesis. We evaluated whether ketamine elicits similar molecular events in dopaminergic (DA) neurons, known to be affected in mood disorders, using a novel, translational strategy that involved mouse mesencephalic and human induced pluripotent stem cells-derived DA neurons. Sixty minutes exposure to ketamine elicited concentration-dependent increases of dendritic arborization and soma size in both mouse and human cultures as measured 72 hours after application. These structural effects were blocked by mTOR complex/signaling inhibitors like rapamycin. Direct evidence of mTOR activation by ketamine was revealed by its induction of p70S6 kinase. All effects of ketamine were abolished by AMPA receptor antagonists and mimicked by the AMPA-positive allosteric modulator CX614. Inhibition of BDNF signaling prevented induction of structural plasticity by ketamine or CX614. Furthermore, the actions of ketamine required functionally intact dopamine D3 receptors (D3R), as its effects were abolished by selective D3R antagonists and absent in D3R knockout preparations. Finally, the ketamine metabolite (2R,6R)-hydroxynorketamine mimicked ketamine effects at sub-micromolar concentrations. These data indicate that ketamine elicits structural plasticity by recruitment of AMPAR, mTOR and BDNF signaling in both mouse mesencephalic and human induced pluripotent stem cells-derived DA neurons. These observations are of likely relevance to the influence of ketamine upon mood and its other functional actions in vivo.

Exercise-induced increase in brain-derived neurotrophic factor in human Parkinson's disease: a systematic review and meta-analysis

Background

Animal models of exercise and Parkinson’s disease (PD) have found that the physiologic use of exercise may interact with the neurodegenerative disease process, likely mediated by brain derived neurotrophic factor (BDNF). No reviews so far have assessed the methodologic quality of available intervention studies or have bundled the effect sizes of individual studies on exercise-induced effects on BDNF blood levels in human PD.

Research design and methods

We searched MEDLINE, EMBASE, Cochrane Library, PsycINFO and PubMed from inception to June 2017.

Results

Data aggregated from two randomized controlled trials and four pre-experimental studies with a total of 100 ambulatory patients with idiopathic PD (Hoehn/Yahr ≤3) found improvements in BDNF blood concentration levels in all 6 studies (two RCTs and 4 pre-experimental studies). Pooled BDNF level change scores from the 2 RCTs resulted in a significant homogeneous summary effect size (Standardized Mean Difference 2.06, 95% CI 1.36 to 2.76), and a significant heterogeneous SES for the motor part of the UPDRS-III examination (MD -5.53, 95% CI -10.42 to -0.64). Clinical improvements were noted in all studies using a variety of outcome measures.

Limitations

The evidence-base consists primarily of small studies with low to moderate methodological quality.

Conclusions

This review provides preliminary evidence for the effectiveness of physical exercise treatments for persons with PD on BDNF blood levels. Further research is needed.

Electronic supplementary material

The online version of this article (10.1186/s40035-018-0112-1) contains supplementary material, which is available to authorized users.

Ropinirole and Pramipexole Promote Structural Plasticity in Human iPSC-Derived Dopaminergic Neurons via BDNF and mTOR Signaling

The antiparkinsonian ropinirole and pramipexole are D3 receptor- (D3R-) preferring dopaminergic (DA) agonists used as adjunctive therapeutics for the treatment resistant depression (TRD). While the exact antidepressant mechanism of action remains uncertain, a role for D3R in the restoration of impaired neuroplasticity occurring in TRD has been proposed. Since D3R agonists are highly expressed on DA neurons in humans, we studied the effect of ropinirole and pramipexole on structural plasticity using a translational model of human-inducible pluripotent stem cells (hiPSCs). Two hiPSC clones from healthy donors were differentiated into midbrain DA neurons. Ropinirole and pramipexole produced dose-dependent increases of dendritic arborization and soma size after 3 days of culture, effects antagonized by the selective D3R antagonists SB277011-A and S33084 and by the mTOR pathway kinase inhibitors LY294002 and rapamycin. All treatments were also effective in attenuating the D3R-dependent increase of p70S6-kinase phosphorylation. Immunoneutralisation of BDNF, inhibition of TrkB receptors, and blockade of MEK-ERK signaling likewise prevented ropinirole-induced structural plasticity, suggesting a critical interaction between BDNF and D3R signaling pathways. The highly similar profiles of data acquired with DA neurons derived from two hiPSC clones underpin their reliability for characterization of pharmacological agents acting via dopaminergic mechanisms.

Development of a Parenteral Formulation of NTS-Polyplex Nanoparticles for Clinical Purpose

Neurotensin (NTS)-polyplex is a nanoparticle system for targeted gene delivery that holds great promise for treatment of Parkinson’s disease and various types of cancer. However, the high instability in aqueous suspension of NTS-polyplex nanoparticles is a major limitation for their widespread clinical use. To overcome this obstacle, we developed a clinical formulation and a lyophilization process for NTS-polyplex nanoparticles. The reconstituted samples were compared with fresh preparations by using transmission electron microscopy, dynamic light scattering, electrophoretic mobility, circular dichroism and transfection assays in vitro and in vivo. Our formulation was able to confer lyoprotection and stability to these nanoparticles. In addition, transmission electron microscopy (TEM) and size exclusion-high performance liquid chromatography (SEC-HPLC) using a radioactive tag revealed that the interaction of reconstituted nanoparticles with fetal bovine or human serum did not alter their biophysical features. Furthermore, the formulation and the lyophilization procedure guaranteed functional NTS-polyplex nanoparticles for at least six months of storage at 25 °C and 60% relative humidity. Our results offer a pharmaceutical guide for formulation and long-term storage of NTS-polyplex nanoparticles that could be applied to other polyplexes.

Neurturin overexpression in dopaminergic neurons induces presynaptic and postsynaptic structural changes in rats with chronic 6-hydroxydopamine lesion

The structural effect of neurturin (NRTN) on the nigrostriatal dopaminergic system in animals remains unknown, although NRTN has been shown to be effective in Parkinson's disease animal models. Herein, we aimed to demonstrate that NRTN overexpression in dopaminergic neurons stimulates both neurite outgrowths in the nigrostriatal pathway and striatal dendritic spines in aging rats with chronic 6-hydroxydopamine (6-OHDA) lesion. At week 12 after lesion, pTracer-mNRTN-His or pGreenLantern-1 plasmids were intranigrally transfected using the NTS-polyplex nanoparticles system. We showed that the transgenic expression in dopaminergic neurons remained until the end of the study (12 weeks). Only animals expressing NRTN-His showed recovery of tyrosine hydroxylase (TH)+ cells (28 ± 2%), their neurites (32 ± 2%) and the neuron-specific cytoskeletal marker β-III-tubulin in the substantia nigra; striatal TH(+) fibers were also recovered (52 ± 3%), when compared to the healthy condition. Neurotensin receptor type 1 levels were also significantly recovered in the substantia nigra and striatum. Dopamine recovery was 70 ± 4% in the striatum and complete in the substantia nigra. The number of dendritic spines of striatal medium spiny neurons was also significantly increased, but the recovery was not complete. Drug-activated circling behavior decreased by 73 ± 2% (methamphetamine) and 89 ± 1% (apomorphine). Similar decrease was observed in the spontaneous motor behavior. Our results demonstrate that NRTN causes presynaptic and postsynaptic restoration of the nigrostriatal dopaminergic system after a 6-OHDA-induced chronic lesion. However, those improvements did not reach the healthy condition, suggesting that NRTN exerts lesser neurotrophic effects than other neurotrophic approaches.

Current understanding of the molecular mechanisms in Parkinson's disease: Targets for potential treatments

Gradual degeneration and loss of dopaminergic neurons in the substantia nigra, pars compacta and subsequent reduction of dopamine levels in striatum are associated with motor deficits that characterize Parkinson’s disease (PD). In addition, half of the PD patients also exhibit frontostriatal-mediated executive dysfunction, including deficits in attention, short-term working memory, speed of mental processing, and impulsivity. The most commonly used treatments for PD are only partially or transiently effective and are available or applicable to a minority of patients. Because, these therapies neither restore the lost or degenerated dopaminergic neurons, nor prevent or delay the disease progression, the need for more effective therapeutics is critical. In this review, we provide a comprehensive overview of the current understanding of the molecular signaling pathways involved in PD, particularly within the context of how genetic and environmental factors contribute to the initiation and progression of this disease. The involvement of molecular chaperones, autophagy-lysosomal pathways, and proteasome systems in PD are also highlighted. In addition, emerging therapies, including pharmacological manipulations, surgical procedures, stem cell transplantation, gene therapy, as well as complementary, supportive and rehabilitation therapies to prevent or delay the progression of this complex disease are reviewed.