Neuroprotective Transcription Factors in Animal Models of Parkinson Disease

FOXA1 Suppresses Endoplasmic Reticulum Stress, Oxidative Stress, and Neuronal Apoptosis in Parkinson's Disease by Activating PON2 Transcription

Endoplasmic reticulum (ER) stress and oxidative stress (OS) are often related states in pathological conditions including Parkinson's disease (PD). This study investigates the role of anti-oxidant protein paraoxonase 2 (PON2) in ER stress and OS in PD, along with its regulatory molecule. PD was induced in C57BL/6 mice using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) treatment and in SH-SY5Y cells using 1-methyl-4-phenylpyridinium. PON2 was found to be poorly expressed in the substantia nigra pars compacta (SNc) of PD mice, and its overexpression improved motor coordination of mice. Through the evaluation of tyrosine hydroxylase, dopamine transporter, reactive oxygen species (ROS), and C/EBP homologous protein (CHOP) levels and neuronal loss in mice, as well as the examination of CHOP, glucose-regulated protein 94 (GRP94), GRP78, caspase-12, sarco/endoplasmic reticulum calcium ATPase 2, malondialdehyde, and superoxide dismutase levels in SH-SY5Y cells, we observed that PON2 overexpression mitigated ER stress, OS, and neuronal apoptosis both in vivo and in vitro. Forkhead box A1 (FOXA1) was identified as a transcription factor binding to the PON2 promoter to activate its transcription. Upregulation of FOXA1 similarly protected against neuronal loss by alleviating ER stress and OS, while the protective roles were abrogated by additional PON2 silencing. In conclusion, this study demonstrates that FOXA1-mediated transcription of PON2 alleviates ER stress and OS, ultimately reducing neuronal apoptosis in PD.

STAT4 targets KISS1 to inhibit the oxidative damage, inflammation and neuronal apoptosis in experimental PD models by inactivating the MAPK pathway

BACKGROUND

Oxidative stress and neuroinflammation are proven to play critical roles in the pathogenesis of Parkinson's disease (PD). As reported, patients with PD have lower level of STAT4 compared with healthy subjects. However, the biological functions and mechanisms of STAT4 in PD pathogenesis remain uncertain. This study aimed to investigate the roles and related mechanisms of STAT4 in PD development.

METHODS

The intraperitoneal injection of MPTP (20 mg/kg) dissolved in physiological saline was performed to mimic PD-like conditions in vivo. MPP + solution was prepared for cell model of PD. Cell viability was measured by CCK-8. Griess reaction was conducted to measure NO concentrations. The mRNA and protein levels were evaluated by RT-qPCR and western blotting. ROS generation was assessed by DCFH-DA. The levels of inflammatory cytokines were measured by ELISA. Cell apoptosis was examined by flow cytometry and western blotting. Moreover, the SH-SY5Y cells were treated with conditioned medium from LPS-stimulated microglia and subjected to CCK-8 assays and ELISA. Mechanistically, CHIP assays and luciferase reporter assays were performed to verify the binding relationship between KISS1 and STAT4. For in vivo analysis, the histological changes of midbrain tissues of mice were determined by hematoxylin and eosin staining. The expression of tyrosine hydroxylase (TH) was detected by immunohistochemistry staining. Iba-1 positive microglial cells in the striatum were assessed by immunofluorescence staining.

RESULTS

For in vitro analysis, STAT4 level was downregulated after MPP+ treatment, and STAT4 upregulation inhibited the oxidative damage, inflammation and apoptosis in SH-SY5Y cells. STAT4 bound at +215-228 region of KISS1, and KISS1 upregulation counteracted the protection of STAT4 upregulation against cell damage. Moreover, STAT4 upregulation inhibited cell viability loss and inflammation induced by conditioned medium from LPS-treated microglia, whereas KISS1 upregulation had the opposite effect. For in vivo analysis, the protective effects of STAT4 upregulation against inflammatory response, oxidative stress, dopaminergic neuronal loss and microglia activation were attenuated by KISS1 upregulation. Moreover, the inactivation of MAPK pathway caused by STAT4 upregulation was reversed by KISS1 upregulation, and MAPK inhibition attenuated the MPP+-induced inflammation, oxidative stress and apoptosis in SH-SY5Y cells.

CONCLUSION

STAT4 inhibits KISS1 to attenuate the oxidative damage, inflammation and neuronal apoptosis in PD by inactivating the MAPK pathway.

Genetic analysis of transcription factors in dopaminergic neuronal development in Parkinson's disease

BACKGROUND

Genetic variants of dopaminergic transcription factor-encoding genes are suggested to be Parkinson's disease (PD) risk factors; however, no comprehensive analyses of these genes in patients with PD have been undertaken. Therefore, we aimed to genetically analyze 16 dopaminergic transcription factor genes in Chinese patients with PD.

METHODS

Whole-exome sequencing (WES) was performed using a Chinese cohort comprising 1917 unrelated patients with familial or sporadic early-onset PD and 1652 controls. Additionally, whole-genome sequencing (WGS) was performed using another Chinese cohort comprising 1962 unrelated patients with sporadic late-onset PD and 1279 controls.

RESULTS

We detected 308 rare and 208 rare protein-altering variants in the WES and WGS cohorts, respectively. Gene-based association analyses of rare variants suggested that MSX1 is enriched in sporadic late-onset PD. However, the significance did not pass the Bonferroni correction. Meanwhile, 72 and 1730 common variants were found in the WES and WGS cohorts, respectively. Unfortunately, single-variant logistic association analyses did not identify significant associations between common variants and PD.

CONCLUSIONS

Variants of 16 typical dopaminergic transcription factors might not be major genetic risk factors for PD in Chinese patients. However, we highlight the complexity of PD and the need for extensive research elucidating its etiology.

Neuroprotective role of FOXA1 in Parkinson's disease: Involvements of NF1 transcription activation and MAPK signaling pathway inhibition

Forkhead box A1 (FOXA1), a member of the forkhead family of transcription factors, plays a crucial role in the development of various organ systems and exhibits neuroprotective properties. This study aims to investigate the effect of FOXA1 on Parkinson's disease (PD) and unravel the underlying mechanism. Transcriptome analysis of PD was conducted using three GEO datasets to identify aberrantly expressed genes. A mouse model of PD was generated by injecting neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP), resulting in reduced FOXA1 expression. FOXA1 decline was also observed in 1-methyl-4-phenylpyridinium-treated SH-SY5Y cells. Artificial upregulation of FOXA1 improved motor abilities of mice according to rotarod and pole tests, and it mitigated tissue damage, cell loss, and neuronal damage in the mouse substantia nigra or in vitro. FOXA1 was found to bind to the neurofibromin 1 (NF1) promoter, thereby inducing its transcription and inactivating the mitogen-activated protein kinase (MAPK) signaling pathway. Further experimentation revealed that silencing NF1 in mice or SH-SY5Y cells counteracted the neuroprotective effects of FOXA1. In conclusion, this research suggests that FOXA1 activates NF1 transcription and inactivates the MAPK signaling pathway, ultimately ameliorating neuronal damage and motor disability in PD. The findings may offer novel ideas in the field of PD management.

The common denominators of Parkinson's disease pathogenesis and methamphetamine abuse

The pervasiveness and mortality associated with methamphetamine abuse has doubled during the past decade suggesting a possible worldwide substance use crisis. Epitomizing the pathophysiology and toxicology of methamphetamine abuse proclaims severe signs and symptoms of neurotoxic and neurobehavioral manifestations in both humans and animals. Most importantly, chronic use of this drug enhances the probability of developing neurodegenerative diseases manifolds. Parkinson's disease is one such neurological disorder, which significantly and evidently not only shares a number of toxic pathogenic mechanisms induced by methamphetamine exposure but is also interlinked both structurally andgenetically. Methamphetamine-induced neurodegeneration involves altered dopamine homeostasis that promotes the aggregation of α-synuclein protofibrils in the dopaminergic neurons and drives these neurons to make them more vulnerable to degeneration as recognized in Parkinson's disease. Moreover, the pathologic mechanisms such as mitochondrial dysfunction, oxidative stress, neuroinflammation and decreased neurogenesis detected in methamphetamine abusers dramatically resemble to what is observed in Parkinson's disease cases. Therefore, the present review comprehensively cumulates a holistic illustration of various genetic and molecular mechanisms putting across the notion of how methamphetamine administration and intoxication might lead to Parkinson's disease-like pathology and Parkinsonism.

Genes critical for development and differentiation of dopaminergic neurons are downregulated in Parkinson's disease

We performed transcriptome analysis using RNA sequencing on substantia nigra pars compacta (SNpc) from mice after acute and chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment and from Parkinson's disease (PD) patients. Acute and chronic exposure to MPTP resulted in decreased expression of genes involved in sodium channel regulation. However, upregulation of pro-inflammatory pathways was seen after single dose but not after chronic MPTP treatment. Dopamine biosynthesis and synaptic vesicle recycling pathways were downregulated in PD patients and after chronic MPTP treatment in mice. Genes essential for midbrain development and determination of dopaminergic phenotype such as, LMX1B, FOXA1, RSPO2, KLHL1, EBF3, PITX3, RGS4, ALDH1A1, RET, FOXA2, EN1, DLK1, GFRA1, LMX1A, NR4A2, GAP43, SNCA, PBX1, and GRB10 were downregulated in human PD and overexpression of GFP tagged LMX1B rescued MPP⁺ induced death in SH-SY5Y neurons. Downregulation of gene ensemble involved in development and differentiation of dopaminergic neurons indicate their potential involvement in pathogenesis and progression of human PD.

Parkinson's Disease: Overview of Transcription Factor Regulation, Genetics, and Cellular and Animal Models

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, affecting nearly 7-10 million people worldwide. Over the last decade, there has been considerable progress in our understanding of the genetic basis of PD, in the development of stem cell-based and animal models of PD, and in management of some clinical features. However, there remains little ability to change the trajectory of PD and limited knowledge of the underlying etiology of PD. The role of genetics versus environment and the underlying physiology that determines the trajectory of the disease are still debated. Moreover, even though protein aggregates such as Lewy bodies and Lewy neurites may provide diagnostic value, their physiological role remains to be fully elucidated. Finally, limitations to the model systems for probing the genetics, etiology and biology of Parkinson's disease have historically been a challenge. Here, we review highlights of the genetics of PD, advances in understanding molecular pathways and physiology, especially transcriptional factor (TF) regulators, and the development of model systems to probe etiology and potential therapeutic applications.

Roles of Transcription Factors in the Development and Reprogramming of the Dopaminergic Neurons

The meso-diencephalic dopaminergic (mdDA) neurons regulate various critical processes in the mammalian nervous system, including voluntary movement and a wide range of behaviors such as mood, reward, addiction, and stress. mdDA neuronal loss is linked with one of the most prominent human movement neurological disorders, Parkinson’s disease (PD). How these cells die and regenerate are two of the most hotly debated PD research topics. As for the latter, it has been long known that a series of transcription factors (TFs) involves the development of mdDA neurons, specifying cell types and controlling developmental patterns. In vitro and in vivo, TFs regulate the expression of tyrosine hydroxylase, a dopamine transporter, vesicular monoamine transporter 2, and L-aromatic amino acid decarboxylase, all of which are critical for dopamine synthesis and transport in dopaminergic neurons (DA neurons). In this review, we encapsulate the molecular mechanism of TFs underlying embryonic growth and maturation of mdDA neurons and update achievements on dopaminergic cell therapy dependent on knowledge of TFs in mdDA neuronal development. We believe that a deeper understanding of the extrinsic and intrinsic factors that influence DA neurons’ fate and development in the midbrain could lead to a better strategy for PD cell therapy.

Transposable elements as new players in neurodegenerative diseases

Neurodegenerative diseases (NDs), including the most prevalent Alzheimer's disease and Parkinson disease, share common pathological features. Despite decades of gene-centric approaches, the molecular mechanisms underlying these diseases remain widely elusive. In recent years, transposable elements (TEs), long considered 'junk' DNA, have gained growing interest as pathogenic players in NDs. Age is the major risk factor for most NDs, and several repressive mechanisms of TEs, such as heterochromatinization, fail with age. Indeed, heterochromatin relaxation leading to TE derepression has been reported in various models of neurodegeneration and NDs. There is also evidence that certain pathogenic proteins involved in NDs (e.g., tau, TDP-43) may control the expression of TEs. The deleterious consequences of TE activation are not well known but they could include DNA damage and genomic instability, altered host gene expression, and/or neuroinflammation, which are common hallmarks of neurodegeneration and aging. TEs might thus represent an overlooked pathogenic culprit for both brain aging and neurodegeneration. Certain pathological effects of TEs might be prevented by inhibiting their activity, pointing to TEs as novel targets for neuroprotection.

Promising drug targets and associated therapeutic interventions in Parkinson's disease

Parkinson's disease (PD) is one of the most debilitating brain diseases. Despite the availability of symptomatic treatments, response towards the health of PD patients remains scarce. To fulfil the medical needs of the PD patients, an efficacious and etiological treatment is required. In this review, we have compiled the information covering limitations of current therapeutic options in PD, novel drug targets for PD, and finally, the role of some critical beneficial natural products to control the progression of PD.

Epigenetic inactivation of the autophagy-lysosomal system in appendix in Parkinson's disease

The gastrointestinal tract may be a site of origin for α-synuclein pathology in idiopathic Parkinson's disease (PD). Disruption of the autophagy-lysosome pathway (ALP) may contribute to α-synuclein aggregation. Here we examined epigenetic alterations in the ALP in the appendix by deep sequencing DNA methylation at 521 ALP genes. We identified aberrant methylation at 928 cytosines affecting 326 ALP genes in the appendix of individuals with PD and widespread hypermethylation that is also seen in the brain of individuals with PD. In mice, we find that DNA methylation changes at ALP genes induced by chronic gut inflammation are greatly exacerbated by α-synuclein pathology. DNA methylation changes at ALP genes induced by synucleinopathy are associated with the ALP abnormalities observed in the appendix of individuals with PD specifically involving lysosomal genes. Our work identifies epigenetic dysregulation of the ALP which may suggest a potential mechanism for accumulation of α-synuclein pathology in idiopathic PD.

Perturbed DNA methylation by Gadd45b induces chromatin disorganization, DNA strand breaks and dopaminergic neuron death

Age is a major risk factor for neurodegenerative diseases like Parkinson's disease, but few studies have explored the contribution of key hallmarks of aging, namely DNA methylation changes and heterochromatin destructuration, in the neurodegenerative process. Here, we investigated the consequences of viral overexpression of Gadd45b, a multifactorial protein involved in DNA demethylation, in the mouse midbrain. Gadd45b overexpression induced global and stable changes in DNA methylation, particularly in introns of genes related to neuronal functions, as well as on LINE-1 transposable elements. This was paralleled by disorganized heterochromatin, increased DNA damage, and vulnerability to oxidative stress. LINE-1 de-repression, a potential source of DNA damage, preceded Gadd45b-induced neurodegeneration, whereas prolonged Gadd45b expression deregulated expression of genes related to heterochromatin maintenance, DNA methylation, or Parkinson's disease. Our data indicates that aging-related alterations contribute to dopaminergic neuron degeneration with potential implications for Parkinson's disease.

Neural stem cells derived from human midbrain organoids as a stable source for treating Parkinson's disease: Midbrain organoid-NSCs (Og-NSC) as a stable source for PD treatment

Successful clinical translation of stem cell-based therapy largely relies on the scalable and reproducible preparation of donor cells with potent therapeutic capacities. In this study, midbrain organoids were yielded from human pluripotent stem cells (hPSCs) to prepare cells for Parkinson's disease (PD) therapy. Neural stem/precursor cells (NSCs) isolated from midbrain organoids (Og-NSCs) expanded stably and differentiated into midbrain-type dopamine(mDA) neurons, and an unprecedentedly high proportion expressed midbrain-specific factors, with relatively low cell line and batch-to-batch variations. Single cell transcriptome analysis followed by in vitro assays indicated that the majority of cells in the Og-NSC cultures are ventral midbrain (VM)-patterned with low levels of cellular senescence/aging and mitochondrial stress, compared to those derived from 2D-culture environments. Notably, in contrast to current methods yielding mDA neurons without astrocyte differentiation, mDA neurons that differentiated from Og-NSCs were interspersed with astrocytes as in the physiologic brain environment. Thus, the Og-NSC-derived mDA neurons exhibited improved synaptic maturity, functionality, resistance to toxic insults, and faithful expressions of the midbrain-specific factors, in vitro and in vivo long after transplantation. Consequently, Og-NSC transplantation yielded potent therapeutic outcomes that are reproducible in PD model animals. Collectively, our observations demonstrate that the organoid-based method may satisfy the demands needed in the clinical setting of PD cell therapy.

Aging and pathological aging signatures of the brain: through the focusing lens of SIRT6

Brain-specific SIRT6-KO mice present increased DNA damage, learning impairments, and neurodegenerative phenotypes, placing SIRT6 as a key protein in preventing neurodegeneration. In the aging brain, SIRT6 levels/activity decline, which is accentuated in Alzheimer's patients. To understand SIRT6 roles in transcript pattern changes, we analyzed transcriptomes of young WT, old WT and young SIRT6-KO mice brains, and found changes in gene expression related to healthy and pathological aging. In addition, we traced these differences in human and mouse samples of Alzheimer's and Parkinson's diseases, healthy aging and calorie restriction (CR). Our results define four gene expression categories that change with age in a pathological or non-pathological manner, which are either reversed or not by CR. We found that each of these gene expression categories is associated with specific transcription factors, thus serving as potential candidates for their category-specific regulation. One of these candidates is YY1, which we found to act together with SIRT6 regulating specific processes. We thus argue that SIRT6 has a pivotal role in preventing age-related transcriptional changes in brains. Therefore, reduced SIRT6 activity may drive pathological age-related gene expression signatures in the brain.

When Friendship Turns Sour: Effective Communication Between Mitochondria and Intracellular Organelles in Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disease with pathological hallmarks including progressive neuronal loss from the substantia nigra pars compacta and α-synuclein intraneuronal inclusions, known as Lewy bodies. Although the etiology of PD remains elusive, mitochondrial damage has been established to take center stage in the pathogenesis of PD. Mitochondria are critical to cellular energy production, metabolism, homeostasis, and stress responses; the association with PD emphasizes the importance of maintenance of mitochondrial network integrity. To accomplish the pleiotropic functions, mitochondria are dynamic not only within their own network but also in orchestrated coordination with other organelles in the cellular community. Through physical contact sites, signal transduction, and vesicle transport, mitochondria and intracellular organelles achieve the goals of calcium homeostasis, redox homeostasis, protein homeostasis, autophagy, and apoptosis. Herein, we review the finely tuned interactions between mitochondria and surrounding intracellular organelles, with focus on the nucleus, endoplasmic reticulum, Golgi apparatus, peroxisomes, and lysosomes. Participants that may contribute to the pathogenic mechanisms of PD will be highlighted in this review.

Parkinson's Disease Master Regulators on Substantia Nigra and Frontal Cortex and Their Use for Drug Repositioning

Parkinson's disease (PD) is among the most prevalent neurodegenerative diseases. Available evidences support the view of PD as a complex disease, being the outcome of interactions between genetic and environmental factors. In face of diagnosis and therapy challenges, and the elusive PD etiology, the use of alternative methodological approaches for the elucidation of the disease pathophysiological mechanisms and proposal of novel potential therapeutic interventions has become increasingly necessary. In the present study, we first reconstructed the transcriptional regulatory networks (TN), centered on transcription factors (TF), of two brain regions affected in PD, the substantia nigra pars compacta (SNc) and the frontal cortex (FCtx). Then, we used case-control studies data from these regions to identify TFs working as master regulators (MR) of the disease, based on region-specific TNs. Twenty-nine regulatory units enriched with differentially expressed genes were identified for the SNc, and twenty for the FCtx, all of which were considered MR candidates for PD. Three consensus MR candidates were found for SNc and FCtx, namely ATF2, SLC30A9, and ZFP69B. In order to search for novel potential therapeutic interventions, we used these consensus MR candidate signatures as input to the Connectivity Map (CMap), a computational drug repositioning webtool. This analysis resulted in the identification of four drugs that reverse the expression pattern of all three MR consensus simultaneously, benperidol, harmaline, tubocurarine chloride, and vorinostat, thus suggested as novel potential PD therapeutic interventions.

Gene Expression Changes in the Ventral Tegmental Area of Male Mice with Alternative Social Behavior Experience in Chronic Agonistic Interactions

Daily agonistic interactions of mice are an effective experimental approach to elucidate the molecular mechanisms underlying the excitation of the brain neurons and the formation of alternative social behavior patterns. An RNA-Seq analysis was used to compare the ventral tegmental area (VTA) transcriptome profiles for three groups of male C57BL/6J mice: winners, a group of chronically winning mice, losers, a group of chronically defeated mice, and controls. The data obtained show that both winners and defeated mice experience stress, which however, has a more drastic effect on defeated animals causing more significant changes in the levels of gene transcription. Four genes (Nrgn, Ercc2, Otx2, and Six3) changed their VTA expression profiles in opposite directions in winners and defeated mice. It was first shown that Nrgn (neurogranin) expression was highly correlated with the expression of the genes involved in dopamine synthesis and transport (Th, Ddc, Slc6a3, and Drd2) in the VTA of defeated mice but not in winners. The obtained network of 31 coregulated genes, encoding proteins associated with nervous system development (including 24 genes associated with the generation of neurons), may be potentially useful for studying their role in the VTA dopaminergic neurons maturation under the influence of social stress.

Characterization of Age-dependent Behavior Deficits in the PGC-1α Knockout Mouse, in Relevance to the Parkinson's Disease Model

Parkinson's disease is a disorder of adult onset involving the progressive degeneration of selective portions of the central nervous system. It is known that mitochondrial dysfunction is involved in the pathogenesis of PD. Given that PGC-1α induces proliferation of mitochondria via transcription regulation, it is possible that PGC-1α pathway dysregulation is involved in PD pathogenesis. To determine how derangement of the PGC-1α pathway in age contributes to PD, in this study, we have characterized the number of dopaminergic neuron in the substantia nigra pars compacta (SNpc), motor behaviors and related expression of mitochondrial markers (CoxIV, SDHA, and Tomm20) in the ventral midbrains of PGC-1α null mice. We found an overall decrease in spontaneous, voluntary movements and severely impaired motor coordination in all age groups (10 months and 20 months) of PGC-1α null mice, while pole testing detected impaired motor activity in older PGC-1α null mice only. TH-positive neurons were significantly less in older PGC-1α null mice. Concentration of DA as well as its two metabolites reduced in an age-dependent manner in PGC-1α null mice. Expression of CoxIV, SDHA and Tomm20 also significantly decreased in the ventral midbrains of 10-month-old PGC-1α null mice. Thus, PGC-1α KO in mice induced dopaminergic neuron degeneration in the SNpc and DA deficits in the striatum in an age-dependent manner. Progressive impairment of motor coordination in an age-dependent manner was correlated to the extent of nigrostriatal dopaminergic pathway degeneration and mitochondrial dysfunction.

MiR-29c protects against inflammation and apoptosis in Parkinson's disease model in vivo and in vitro by targeting SP1

MicroRNAs (miRNAs) have been shown to have complicated implications in the pathogenesis of Parkinson's disease (PD). However, the role of miR-29c and the underlying mechanism in the development of PD remain not well understood. In this work, the MPTP-treated mice or MPP+ -intoxicated SH-SY5Y cells were established as an in vivo or in vitro PD model. Then the specific agomir of miR-29c was employed to examine its biological function on PD progress. We found that miR-29c was down-expressed but SP1 was high-expressed in substantia nigra pars compacta (SNpc) of MPTP-induced PD mice. Overexpression of miR-29c attenuated dopaminergic neuron loss and α-synuclein accumulation in SNpc of PD mice. Furthermore, the increments of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and TUNEL-positive apoptotic cells in MPTP-treated mice were ameliorated by miR-29c. Similarly, in SH-SY5Y cell models of PD, we also found that miR-29c inhibited inflammatory cytokine production, reduced apoptotic rate and suppressed pro-apoptotic regulator activity. In addition, the increased expression of SP1 in PD models was found to be inhibited by miR-29c. Luciferase reporter assay confirmed that SP1 was complementary with miR-29c. Knockdown of SP1 with siRNA restored α-synuclein accumulation, inflammation and apoptosis in MPP+ -induced SH-SY5Y cells. Collectively, this current work presents that miR-29c may directly target SP1 to protect against the neuroinflammatory and apoptotic responses in PD, providing a potential biomarker for PD diagnosis and treatment.

Parallel roles of transcription factors dFOXO and FER2 in the development and maintenance of dopaminergic neurons

Forkhead box (FOXO) proteins are evolutionarily conserved, stress-responsive transcription factors (TFs) that can promote or counteract cell death. Mutations in FOXO genes are implicated in numerous pathologies, including age-dependent neurodegenerative disorders, such as Parkinson’s disease (PD). However, the complex regulation and downstream mechanisms of FOXOs present a challenge in understanding their roles in the pathogenesis of PD. Here, we investigate the involvement of FOXO in the death of dopaminergic (DA) neurons, the key pathological feature of PD, in Drosophila. We show that dFOXO null mutants exhibit a selective loss of DA neurons in the subgroup crucial for locomotion, the protocerebral anterior medial (PAM) cluster, during development as well as in adulthood. PAM neuron-targeted adult-restricted knockdown demonstrates that dFOXO in adult PAM neurons tissue-autonomously promotes neuronal survival during aging. We further show that dFOXO and the bHLH-TF 48-related-2 (FER2) act in parallel to protect PAM neurons from different forms of cellular stress. Remarkably, however, dFOXO and FER2 share common downstream processes leading to the regulation of autophagy and mitochondrial morphology. Thus, overexpression of one can rescue the loss of function of the other. These results indicate a role of dFOXO in neuroprotection and highlight the notion that multiple genetic and environmental factors interact to increase the risk of DA neuron degeneration and the development of PD.

PD, mainly characterized by a progressive loss of dopaminergic neurons in the substantia nigra (SN), is the most prevalent neurodegenerative movement disorder affecting more than 6 million people worldwide. Despite the discovery of several genes linked to familial PD, our understanding of its pathogenesis remains limited, as approximately 90% of the PD cases are sporadic with no apparent genetic linkage. Genome-wide expression studies have implicated the stress-responsive TF FOXO in PD. However, the exact role of FOXO in the survival of DA neurons and PD pathogenesis is still poorly understood. Here, we use fruit flies to address the role of FOXO in the maintenance of DA neurons. dFOXO (Drosophila FOXO) null mutants show a progressive loss of DA neurons in the subgroup essential for locomotion, a phenotype identical to that of Fer2 mutants. Remarkably, dFOXO and FER2 act in parallel pathways to protect PAM neurons from different cellular stressors, but both pathways contribute to the regulation of autophagy and mitochondrial biology. These results demonstrate that dFOXO is required for the maintenance of DA neurons important for locomotion and shed new light on the molecular mechanisms underpinning the complex gene-environment interactions affecting DA neuron survival and PD pathogenesis.

Cografting astrocytes improves cell therapeutic outcomes in a Parkinson's disease model

Transplantation of neural progenitor cells (NPCs) is a potential therapy for treating neurodegenerative disorders, but this approach has faced many challenges and limited success, primarily because of inhospitable host brain environments that interfere with enriched neuron engraftment and function. Astrocytes play neurotrophic roles in the developing and adult brain, making them potential candidates for helping with modification of hostile brain environments. In this study, we examined whether astrocytic function could be utilized to overcome the current limitations of cell-based therapies in a murine model of Parkinson's disease (PD) that is characterized by dopamine (DA) neuron degeneration in the midbrain. We show here that cografting astrocytes, especially those derived from the midbrain, remarkably enhanced NPC-based cell therapeutic outcomes along with robust DA neuron engraftment in PD rats for at least 6 months after transplantation. We further show that engineering of donor astrocytes with Nurr1 and Foxa2, transcription factors that were recently reported to polarize harmful immunogenic glia into the neuroprotective form, further promoted the neurotrophic actions of grafted astrocytes in the cell therapeutic approach. Collectively, these findings suggest that cografting astrocytes could be a potential strategy for successful cell therapeutic outcomes in neurodegenerative disorders.

Impact of Pitx3 gene knockdown on glial cell line-derived neurotrophic factor transcriptional activity in dopaminergic neurons

Pitx3 is strongly associated with the phenotype, differentiation, and survival of dopaminergic neurons. The relationship between Pitx3 and glial cell line-derived neurotrophic factor (GDNF) in dopaminergic neurons remains poorly understood. The present investigation sought to construct and screen a lentivirus expression plasmid carrying a rat Pitx3 short hairpin (sh)RNA and to assess the impact of Pitx3 gene knockdown on GDNF transcriptional activity in MES23.5 dopaminergic neurons. Three pairs of interference sequences were designed and separately ligated into GV102 expression vectors. These recombinant plasmids were transfected into MES23.5 cells and western blot assays were performed to detect Pitx3 protein expression. Finally, the most effective Pitx3 shRNA and a dual-luciferase reporter gene plasmid carrying the GDNF promoter region (GDNF-luciferase) were cotransfected into MES23.5 cells. Sequencing showed that the synthesized sequences were identical to the three Pitx3 interference sequences. Inverted fluorescence microscopy revealed that the lentivirus expression plasmids carrying Pitx3-shRNA had 40–50% transfection efficiency. Western blot assay confirmed that the corresponding Pitx3 of the third knockdown sequence had the lowest expression level. Dual-luciferase reporter gene results showed that the GDNF transcriptional activity in dopaminergic cells cotransfected with both plasmids was decreased compared with those transfected with GDNF-luciferase alone. Together, the results showed that the designed Pitx3-shRNA interference sequence decreased Pitx3 protein expression, which decreased GDNF transcriptional activity.

Transcription Factors: Potential Cell Death Markers in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease with a long preclinical phase. The continuous loss of dopaminergic (DA) neurons is one of the pathogenic hallmarks of PD. Diagnosis largely depends on clinical observation, but motor dysfunctions do not emerge until 70%-80% of the nigrostriatal nerve terminals have been destroyed. Therefore, a biomarker that indicates the degeneration of DA neurons is urgently needed. Transcription factors are sequence-specific DNA-binding proteins that regulate RNA synthesis from a DNA template. The precise control of gene expression plays a critical role in the development, maintenance, and survival of cells, including DA neurons. Deficiency of certain transcription factors has been associated with DA neuron loss and PD. In this review, we focus on some transcription factors and discuss their structure, function, mechanisms of neuroprotection, and their potential for use as biomarkers indicating the degeneration of DA neurons.

Combining NT3-overexpressing MSCs and PLGA microcarriers for brain tissue engineering: A potential tool for treatment of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that characterized by destruction of substantia nigrostriatal pathway due to the loss of dopaminergic (DA) neurons. Regardless of substantial efforts for treatment of PD in recent years, an effective therapeutic strategy is still missing. In a multidisciplinary approach, bone marrow derived mesenchymal stem cells (BMSCs) are genetically engineered to overexpress neurotrophin-3 (nt-3 gene) that protect central nervous system tissues and stimulates neuronal-like differentiation of BMSCs. Poly(lactic-co-glycolic acid) (PLGA) microcarriers are designed as an injectable scaffold and synthesized via double emulsion method. The surface of PLGA microcarriers are functionalized by collagen as a bioadhesive agent for improved cell attachment. The results demonstrate effective overexpression of NT-3. The expression of tyrosine hydroxylase (TH) in transfected BMSCs reveal that NT-3 promotes the intracellular signaling pathway of DA neuron differentiation. It is also shown that transfected BMSCs are successfully attached to the surface of microcarriers. The presence of dopamine in peripheral media of cell/microcarrier complex reveals that BMSCs are successfully differentiated into dopaminergic neuron. Our approach that sustains presence of growth factor can be suggested as a novel complementary therapeutic strategy for treatment of Parkinson disease.