The role of pathogenic DJ-1 mutations in Parkinson's disease

Understanding role of pesticides in development of Parkinson's disease: Insights from Drosophila and rodent models

Parkinson's disease is a neurodegenerative illness linked to ageing, marked by the gradual decline of dopaminergic neurons in the midbrain. The exact aetiology of Parkinson's disease (PD) remains uncertain, with genetic predisposition and environmental variables playing significant roles in the disease's frequency. Epidemiological data indicates a possible connection between pesticide exposure and brain degeneration. Specific pesticides have been associated with important characteristics of Parkinson's disease, such as mitochondrial dysfunction, oxidative stress, and α-synuclein aggregation, which are crucial for the advancement of the disease. Recently, many animal models have been developed for Parkinson's disease study. Although these models do not perfectly replicate the disease's pathology, they provide valuable insights that improve our understanding of the condition and the limitations of current treatment methods. Drosophila, in particular, has been useful in studying Parkinson's disease induced by toxins or genetic factors. The review thoroughly analyses many animal models utilised in Parkinson's research, with an emphasis on issues including pesticides, genetic and epigenetic changes, proteasome failure, oxidative damage, α-synuclein inoculation, and mitochondrial dysfunction. The text highlights the important impact of pesticides on the onset of Parkinson's disease (PD) and stresses the need for more research on genetic and mechanistic alterations linked to the condition.

The Role of Structural Variants in the Genetic Architecture of Parkinson's Disease

Parkinson's disease (PD) significantly impacts millions of individuals worldwide. Although our understanding of the genetic foundations of PD has advanced, a substantial portion of the genetic variation contributing to disease risk remains unknown. Current PD genetic studies have primarily focused on one form of genetic variation, single nucleotide variants (SNVs), while other important forms of genetic variation, such as structural variants (SVs), are mostly ignored due to the complexity of detecting these variants with traditional sequencing methods. Yet, these forms of genetic variation play crucial roles in gene expression and regulation in the human brain and are causative of numerous neurological disorders, including forms of PD. This review aims to provide a comprehensive overview of our current understanding of the involvement of coding and noncoding SVs in the genetic architecture of PD.

Unraveling Dysregulated Cell Signaling Pathways, Genetic and Epigenetic Mysteries of Parkinson's Disease

Parkinson's disease (PD) is a prevalent and burdensome neurodegenerative disorder that has been extensively researched to understand its complex etiology, diagnosis, and treatment. The interplay between genetic and environmental factors in PD makes its pathophysiology difficult to comprehend, emphasizing the need for further investigation into genetic and epigenetic markers involved in the disease. Early diagnosis is crucial for optimal management of the disease, and the development of novel diagnostic biomarkers is ongoing. Although many efforts have been made in the field of recognition and interpretation of the mechanisms involved in the pathophysiology of the disease, the current knowledge about PD is just the tip of the iceberg. By scrutinizing genetic and epigenetic patterns underlying PD, new avenues can be opened for dissecting the pathology of the disorder, leading to more precise and efficient diagnostic and therapeutic approaches. This review emphasizes the importance of studying dysregulated cell signaling pathways and molecular processes associated with genes and epigenetic alterations in understanding PD, paving the way for the development of novel therapeutic strategies to combat this devastating disease.

Pathogenesis of DJ-1/PARK7-Mediated Parkinson's Disease

Parkinson's disease (PD) is a common movement disorder associated with the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Mutations in the PD-associated gene PARK7 alter the structure and function of the encoded protein DJ-1, and the resulting autosomal recessively inherited disease increases the risk of developing PD. DJ-1 was first discovered in 1997 as an oncogene and was associated with early-onset PD in 2003. Mutations in DJ-1 account for approximately 1% of all recessively inherited early-onset PD occurrences, and the functions of the protein have been studied extensively. In healthy subjects, DJ-1 acts as an antioxidant and oxidative stress sensor in several neuroprotective mechanisms. It is also involved in mitochondrial homeostasis, regulation of apoptosis, chaperone-mediated autophagy (CMA), and dopamine homeostasis by regulating various signaling pathways, transcription factors, and molecular chaperone functions. While DJ-1 protects neurons against damaging reactive oxygen species, neurotoxins, and mutant α-synuclein, mutations in the protein may lead to inefficient neuroprotection and the progression of PD. As current therapies treat only the symptoms of PD, the development of therapies that directly inhibit oxidative stress-induced neuronal cell death is critical. DJ-1 has been proposed as a potential therapeutic target, while oxidized DJ-1 could operate as a biomarker for PD. In this paper, we review the role of DJ-1 in the pathogenesis of PD by highlighting some of its key neuroprotective functions and the consequences of its dysfunction.

Parkinson's Disease: From Genetics and Epigenetics to Treatment, a miRNA-Based Strategy

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, characterized by an initial and progressive loss of dopaminergic neurons of the substantia nigra pars compacta via a potentially substantial contribution from protein aggregates, the Lewy bodies, mainly composed of α-Synuclein among other factors. Distinguishing symptoms of PD are bradykinesia, muscular rigidity, unstable posture and gait, hypokinetic movement disorder and resting tremor. Currently, there is no cure for PD, and palliative treatments, such as Levodopa administration, are directed to relieve the motor symptoms but induce severe side effects over time. Therefore, there is an urgency for discovering new drugs in order to design more effective therapeutic approaches. The evidence of epigenetic alterations, such as the dysregulation of different miRNAs that may stimulate many aspects of PD pathogenesis, opened a new scenario in the research for a successful treatment. Along this line, a promising strategy for PD treatment comes from the potential exploitation of modified exosomes, which can be loaded with bioactive molecules, such as therapeutic compounds and RNAs, and can allow their delivery to the appropriate location in the brain, overcoming the blood-brain barrier. In this regard, the transfer of miRNAs within Mesenchymal stem cell (MSC)-derived exosomes has yet to demonstrate successful results both in vitro and in vivo. This review, besides providing a systematic overview of both the genetic and epigenetic basis of the disease, aims to explore the exosomes/miRNAs network and its clinical potential for PD treatment.

Nuclear DJ-1 Regulates DNA Damage Repair via the Regulation of PARP1 Activity

DNA damage and defective DNA repair are extensively linked to neurodegeneration in Parkinson's disease (PD), but the underlying molecular mechanisms remain poorly understood. Here, we determined that the PD-associated protein DJ-1 plays an essential role in modulating DNA double-strand break (DSB) repair. Specifically, DJ-1 is a DNA damage response (DDR) protein that can be recruited to DNA damage sites, where it promotes DSB repair through both homologous recombination and nonhomologous end joining. Mechanistically, DJ-1 interacts directly with PARP1, a nuclear enzyme essential for genomic stability, and stimulates its enzymatic activity during DNA repair. Importantly, cells from PD patients with the DJ-1 mutation also have defective PARP1 activity and impaired repair of DSBs. In summary, our findings uncover a novel function of nuclear DJ-1 in DNA repair and genome stability maintenance, and suggest that defective DNA repair may contribute to the pathogenesis of PD linked to DJ-1 mutations.

Progressive Motor and Non-Motor Symptoms in Park7 Knockout Zebrafish

DJ-1 is a redox sensitive protein with a wide range of functions related to oxidative stress protection. Mutations in the park7 gene, which codes for DJ-1 are associated with early onset familial Parkinson’s disease and increased astrocytic DJ-1 levels are found in pathologic tissues from idiopathic Parkinson’s disease. We have previously established a DJ-1 knockout zebrafish line that developed normally, but with aging the DJ-1 null fish had a lowered level of tyrosine hydroxylase, respiratory mitochondrial failure and a lower body mass. Here we have examined the DJ-1 knockout from the early adult stage and show that loss of DJ-1 results in a progressive, age-dependent increase in both motoric and non-motoric symptoms associated to Parkinson’s disease. These changes coincide with changes in mitochondrial and mitochondrial associated proteins. Recent studies have suggested that a decline in NAD+ can contribute to Parkinson’s disease and that supplementation of NAD+ precursors may delay disease progression. We found that the brain NAD+/NADH ratio decreased in aging zebrafish but did not correlate with DJ-1 induced altered behavior. Differences were first observed at the late adult stage in which NAD+ and NADPH levels were decreased in DJ-1 knockouts. Considering the experimental power of zebrafish and the development of Parkinson’s disease-related symptoms in the DJ-1 null fish, this model can serve as a useful tool both to understand the progression of the disease and the effect of suggested treatments.

Role of α-synuclein in microglia: autophagy and phagocytosis balance neuroinflammation in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease, and is characterized by accumulation of α-synuclein (α-syn). Neuroinflammation driven by microglia is an important pathological manifestation of PD. α-Syn is a crucial marker of PD, and its accumulation leads to microglia M1-like phenotype polarization, activation of NLRP3 inflammasomes, and impaired autophagy and phagocytosis in microglia. Autophagy of microglia is related to degradation of α-syn and NLRP3 inflammasome blockage to relieve neuroinflammation. Microglial autophagy and phagocytosis of released α-syn or fragments from apoptotic neurons maintain homeostasis in the brain. A variety of PD-related genes such as LRRK2, GBA and DJ-1 also contribute to this stability process.

OBJECTIVES

Further studies are needed to determine how α-syn works in microglia.

METHODS

A keyword-based search was performed using the PubMed database for published articles.

CONCLUSION

In this review, we discuss the interaction between microglia and α-syn in PD pathogenesis and the possible mechanism of microglial autophagy and phagocytosis in α-syn clearance and inhibition of neuroinflammation. This may provide a novel insight into treatment of PD.

DJ-1 promotes energy balance by regulating both mitochondrial and autophagic homeostasis

The protein DJ-1 is mutated in rare familial forms of recessive Parkinson's disease and in parkinsonism accompanied by amyotrophic lateral sclerosis symptoms and dementia. DJ-1 is considered a multitasking protein able to confer protection under various conditions of stress. However, the precise cellular function still remains elusive. In the present work, we evaluated fruit flies lacking the expression of the DJ-1 homolog dj-1β as compared to control aged-matched individuals. Behavioral evaluations included lifespan, locomotion in an open field arena, sensitivity to oxidative insults, and resistance to starvation. Molecular analyses were carried out by analyzing the mitochondrial morphology and functionality, and the autophagic response. We demonstrated that dj-1β null mutant flies are hypoactive and display higher sensitivity to oxidative insults and food deprivation. Analysis of mitochondrial homeostasis revealed that loss of dj-1β leads to larger and more circular mitochondria, characterized by impaired complex-I-linked respiration while preserving ATP production capacity. Additionally, dj-1β null mutant flies present an impaired autophagic response, which is suppressed by treatment with the antioxidant molecule N-Acetyl-L-Cysteine. Overall, our data point to a mechanism whereby DJ-1 plays a critical role in the maintenance of energy homeostasis, by sustaining mitochondrial homeostasis and affecting the autophagic flux through the maintenance of the cellular redox state. In light of the involvement of DJ-1 in neurodegenerative diseases and considering that neurons are highly energy-demanding cells, particularly sensitive to redox stress, our study sheds light on a key role of DJ-1 in the maintenance of cellular homeostasis.

Human Induced Pluripotent Stem Cell Phenotyping and Preclinical Modeling of Familial Parkinson's Disease

Parkinson's disease (PD) is primarily idiopathic and a highly heterogenous neurodegenerative disease with patients experiencing a wide array of motor and non-motor symptoms. A major challenge for understanding susceptibility to PD is to determine the genetic and environmental factors that influence the mechanisms underlying the variations in disease-associated traits. The pathological hallmark of PD is the degeneration of dopaminergic neurons in the substantia nigra pars compacta region of the brain and post-mortem Lewy pathology, which leads to the loss of projecting axons innervating the striatum and to impaired motor and cognitive functions. While the cause of PD is still largely unknown, genome-wide association studies provide evidence that numerous polymorphic variants in various genes contribute to sporadic PD, and 10 to 15% of all cases are linked to some form of hereditary mutations, either autosomal dominant or recessive. Among the most common mutations observed in PD patients are in the genes LRRK2, SNCA, GBA1, PINK1, PRKN, and PARK7/DJ-1. In this review, we cover these PD-related mutations, the use of induced pluripotent stem cells as a disease in a dish model, and genetic animal models to better understand the diversity in the pathogenesis and long-term outcomes seen in PD patients.

CRISPR-Cas9-Based Technology and Its Relevance to Gene Editing in Parkinson's Disease

Parkinson's disease (PD) and other chronic and debilitating neurodegenerative diseases (NDs) impose a substantial medical, emotional, and financial burden on individuals and society. The origin of PD is unknown due to a complex combination of hereditary and environmental risk factors. However, over the last several decades, a significant amount of available data from clinical and experimental studies has implicated neuroinflammation, oxidative stress, dysregulated protein degradation, and mitochondrial dysfunction as the primary causes of PD neurodegeneration. The new gene-editing techniques hold great promise for research and therapy of NDs, such as PD, for which there are currently no effective disease-modifying treatments. As a result, gene therapy may offer new treatment options, transforming our ability to treat this disease. We present a detailed overview of novel gene-editing delivery vehicles, which is essential for their successful implementation in both cutting-edge research and prospective therapeutics. Moreover, we review the most recent advancements in CRISPR-based applications and gene therapies for a better understanding of treating PD. We explore the benefits and drawbacks of using them for a range of gene-editing applications in the brain, emphasizing some fascinating possibilities.

Exploring the journey of emodin as a potential neuroprotective agent: Novel therapeutic insights with molecular mechanism of action

Emodin is an anthraquinone derivative found in the roots and bark of a variety of plants, molds, and lichens. Emodin has been used as a traditional medication for more than 2000 years and is still common in numerous herbal drugs. Emodin is plentiful in the three plant families, including Polygonaceae (Rheum, Rumex, and Polygonum spp.), Fabaceae (Cassia spp.), and Rhamnaceae (Rhamnus, Frangula, and Ventilago spp.). Emerging experimental evidences indicate that emodin confers a wide range of pharmacological activities; special focus was implemented toward neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, cerebral ischemia, anxiety and depression, schizophrenia, chronic hyperglycemic peripheral neuropathy, etc. Numerous preclinical evidences were established in support of the neuroprotection of emodin. However, this review highlighted the role of emodin as a potent neurotherapeutic agent; therefore, its evidence-based functionality on neurological disorders (NDs).

α-Synuclein at the Presynaptic Axon Terminal as a Double-Edged Sword

α-synuclein (α-syn) is a presynaptic, lipid-binding protein strongly associated with the neuropathology observed in Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and Alzheimer’s Disease (AD). In normal physiology, α-syn plays a pivotal role in facilitating endocytosis and exocytosis. Interestingly, mutations and modifications of precise α-syn domains interfere with α-syn oligomerization and nucleation that negatively affect presynaptic vesicular dynamics, protein expressions, and mitochondrial profiles. Furthermore, the integration of the α-syn oligomers into the presynaptic membrane results in pore formations, ion influx, and excitotoxicity. Targeted therapies against specific domains of α-syn, including the use of small organic molecules, monoclonal antibodies, and synthetic peptides, are being screened and developed. However, the prospect of an effective α-syn targeted therapy is still plagued by low permeability across the blood–brain barrier (BBB), and poor entry into the presynaptic axon terminals. The present review proposes a modification of current strategies, which includes the use of novel encapsulation technology, such as lipid nanoparticles, to bypass the BBB and deliver such agents into the brain.

Longitudinal Assessment of Skilled Forelimb Motor Impairments in DJ-1 Knockout Rats

BACKGROUND

DJ-1 knockout (DJ-1 KO) rats exhibit a moderate parkinsonian phenotype, with gross motor deficits and ca. 50% loss of midbrain dopaminergic neurons appearing around 6-8 months of age. Fine motor impairments are often observed in Parkinson's disease (PD), but skilled motor function in recently developed transgenic rat models of PD is not well characterized.

OBJECTIVES

To assess the longitudinal performance of DJ-1 KO rats on a skilled forelimb reaching task.

METHODS

DJ-1 KO and wild-type (WT) rats were trained from 2 to 10 months of age on an isometric pullbar task designed to test forelimb strength and coordination. After 36 consecutive weeks of training (ca. 10 months old), task difficulty was then increased to challenge the motor capabilities of the DJ-1 KO rats. Throughout the study, subjects also received weekly assessments of gross locomotor activity in an open field.

RESULTS

Pull-task performance of the DJ-1 KO rats was impaired compared to WT, with deficits reaching significance around 7-9 months of age. When challenged, DJ-1 KO rats were able to exert increased force on the pullbar but continued to exhibit deficits compared to WT rats. Throughout the study, no differences in distance traveled or rearing frequency were observed in the open field, but DJ-1 KO rats were found to spend significantly more time in the center of the open field than WT rats.

CONCLUSIONS

Using a sensitive, automated assay of forelimb strength and coordination, we find that skilled forelimb motor performance is impaired in DJ-1 KO rats.

A Practical Approach to Early-Onset Parkinsonism

Early-onset parkinsonism (EO parkinsonism), defined as subjects with disease onset before the age of 40 or 50 years, can be the main clinical presentation of a variety of conditions that are important to differentiate. Although rarer than classical late-onset Parkinson’s disease (PD) and not infrequently overlapping with forms of juvenile onset PD, a correct diagnosis of the specific cause of EO parkinsonism is critical for offering appropriate counseling to patients, for family and work planning, and to select the most appropriate symptomatic or etiopathogenic treatments. Clinical features, radiological and laboratory findings are crucial for guiding the differential diagnosis. Here we summarize the most important conditions associated with primary and secondary EO parkinsonism. We also proposed a practical approach based on the current literature and expert opinion to help movement disorders specialists and neurologists navigate this complex and challenging landscape.

Effect of tacrolimus on the expression of Park7 in glomerular podocytes injured by puromycin aminonucleoside

OBJECTIVES

To study the effect of puromycin aminonucleoside (PAN) on the apoptosis of mouse podocyte clone 5 (MPC-5) and the expression of recombinant human Parkinson's disease 7 (Park7) and to study the protective mechanism of tacrolimus (FK506) against MPC-5 injury.

METHODS

MPC-5 cells were cultured in vitro and then divided into three groups: blank control (control), PAN, and FK506. The cells in the PAN group were added with PAN (with a concentration of 50 mg/L) to establish a model of MPC-5 injury, and those in the FK506 group were added with PAN (with a concentration of 50 mg/L) and FK506 (with a concentration of 5 mg/L). An inverted microscope was used to observe the morphology and structure of MPC-5 cells at 12, 24, and 48 hours after treatment. Flow cytometry was used to measure cell apoptosis rate. Quantitative real-time PCR was used to measure the mRNA expression of Park7. Western blot and immunofluorescent staining were used to measure the protein expression of Park7.

RESULTS

The control group had a large number of foot processes of the cell body at all time points, with tight connections between cells and a normal morphology. Compared with the control group, the PAN group had a significantly smaller cell volume at all time points, with loose connections between cells and the presence of ruptured cells. Compared with the PAN group, the FK506 group had an increased cell volume at all time points, with tighter connections between cells and a better morphology. The PAN group had a significantly higher apoptosis rate than the control group at all time points. Compared with the PAN group, the FK506 group had a significant reduction in the apoptosis rate at all time points (P<0.01). The PAN group had a significantly higher mRNA expression level of Park7 than the control group at all time points. Compared with the PAN group, the FK506 group had a significant reduction in the mRNA expression level of Park7 at all time points (P<0.01). Western blot showed that the PAN group had a significantly higher protein expression level of Park7 than the control group at all time points. Compared with the PAN group, the FK506 group had a significant reduction in the protein expression level of Park7 at all time points (P<0.01). Immunofluorescent staining showed that in the PAN group, there was a significantly lower expression of Park7 protein in cell membrane and cytoplasm, with a dense cluster distribution and increased fluorescence intensity. Compared with the PAN group, the FK506 group had a significant improvement in the distribution of Park7 protein.

CONCLUSIONS

PAN can act on MPC-5 cells and cause morphological and structural damage and apoptosis of MPC-5 cells, as well as upregulated mRNA and protein expression of Park7. FK506 can downregulate the mRNA and protein expression of Park7 in the model of MPC-5 injury, maintain cellular homeostasis, reduce proteinuria, and delay glomerulosclerosis.

Nanomedicine for Neurodegenerative Disorders: Focus on Alzheimer's and Parkinson's Diseases

Neurodegenerative disorders involve the slow and gradual degeneration of axons and neurons in the central nervous system (CNS), resulting in abnormalities in cellular function and eventual cellular demise. Patients with these disorders succumb to the high medical costs and the disruption of their normal lives. Current therapeutics employed for treating these diseases are deemed palliative. Hence, a treatment strategy that targets the disease's cause, not just the symptoms exhibited, is desired. The synergistic use of nanomedicine and gene therapy to effectively target the causative mutated gene/s in the CNS disease progression could provide the much-needed impetus in this battle against these diseases. This review focuses on Parkinson's and Alzheimer's diseases, the gene/s and proteins responsible for the damage and death of neurons, and the importance of nanomedicine as a potential treatment strategy. Multiple genes were identified in this regard, each presenting with various mutations. Hence, genome-wide sequencing is essential for specific treatment in patients. While a cure is yet to be achieved, genomic studies form the basis for creating a highly efficacious nanotherapeutic that can eradicate these dreaded diseases. Thus, nanomedicine can lead the way in helping millions of people worldwide to eventually lead a better life.

Clustered regularly interspaced short palindromic repeats as an advanced treatment for Parkinson's disease

Recently, genome-editing technology like clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 has improved the translational gap in the treatments mediated through gene therapy. The advantages of the CRISPR system, such as, work in the living cells and tissues, candidate this technique for the employing in experiments and the therapy of central nervous system diseases. Parkinson's disease (PD) is a widespread, disabling, neurodegenerative disease induced by dopaminergic neuron loss and linked to progressive motor impairment. Pathophysiological basis knowledge of PD has modified the PD classification model and expresses in the sporadic and familial types. Analyses of the earliest genetic linkage have shown in PD the inclusion of synuclein alpha (SNCA) genomic duplication and SNCA mutations in the familial types of PD pathogenesis. This review analyzes the structure, development, and function in genome editing regulated through the CRISPR/Cas9. Also, it explains the genes associated with PD pathogenesis and the appropriate modifications to favor PD. This study follows the direction by understanding the PD linking analyses in which the CRISPR technique is applied. Finally, this study explains the limitations and future trends of CRISPR service in relation to the genome-editing process in PD patients' induced pluripotent stem cells.

DJ-1 inhibits microglial activation and protects dopaminergic neurons in vitro and in vivo through interacting with microglial p65

Parkinson's disease (PD), one of the most common neurodegenerative disorders, is characterized by progressive neurodegeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). DJ-1 acts essential roles in neuronal protection and anti-neuroinflammatory response, and its loss of function is tightly associated with a familial recessive form of PD. However, the molecular mechanism of DJ-1 involved in neuroinflammation is largely unclear. Here, we found that wild-type DJ-1, rather than the pathogenic L166P mutant DJ-1, directly binds to the subunit p65 of nuclear factor-κB (NF-κB) in the cytoplasm, and loss of DJ-1 promotes p65 nuclear translocation by facilitating the dissociation between p65 and NF-κB inhibitor α (IκBα). DJ-1 knockout (DJ-1^-/-) mice exhibit more microglial activation compared with wild-type littermate controls, especially in response to lipopolysaccharide (LPS) treatment. In cellular models, knockdown of DJ-1 significantly upregulates the gene expression and increases the release of LPS-treated inflammatory cytokines in primary microglia and BV2 cells. Furthermore, DJ-1 deficiency in microglia significantly enhances the neuronal toxicity in response to LPS stimulus. In addition, pharmacological blockage of NF-κB nuclear translocation by SN-50 prevents microglial activation and alleviates the damage of DA neurons induced by microglial DJ-1 deficiency in vivo and in vitro. Thus, our data illustrate a novel mechanism by which DJ-1 facilitates the interaction between IκBα and p65 by binding to p65 in microglia, and thus repressing microglial activation and exhibiting the protection of DA neurons from neuroinflammation-mediated injury in PD.

Animal Models of Autosomal Recessive Parkinsonism

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder. The neuropathological hallmark of the disease is the loss of dopamine neurons of the substantia nigra pars compacta. The clinical manifestations of PD are bradykinesia, rigidity, resting tremors and postural instability. PD patients often display non-motor symptoms such as depression, anxiety, weakness, sleep disturbances and cognitive disorders. Although, in 90% of cases, PD has a sporadic onset of unknown etiology, highly penetrant rare genetic mutations in many genes have been linked with typical familial PD. Understanding the mechanisms behind the DA neuron death in these Mendelian forms may help to illuminate the pathogenesis of DA neuron degeneration in the more common forms of PD. A key step in the identification of the molecular pathways underlying DA neuron death, and in the development of therapeutic strategies, is the creation and characterization of animal models that faithfully recapitulate the human disease. In this review, we outline the current status of PD modeling using mouse, rat and non-mammalian models, focusing on animal models for autosomal recessive PD.

Parkinson's Disease Genetics and Pathophysiology

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by degeneration of the substantia nigra pars compacta and by accumulation of α-synuclein in Lewy bodies. PD is caused by a combination of environmental factors and genetic variants. These variants range from highly penetrant Mendelian alleles to alleles that only modestly increase disease risk. Here, we review what is known about the genetics of PD. We also describe how PD genetics have solidified the role of endosomal, lysosomal, and mitochondrial dysfunction in PD pathophysiology. Finally, we highlight how all three pathways are affected by α-synuclein and how this knowledge may be harnessed for the development of disease-modifying therapeutics.

DJ-1 in neurodegenerative diseases: Pathogenesis and clinical application

Neurodegenerative diseases (NDs) are one of the major health threats to human characterized by selective and progressive neuronal loss. The mechanisms of NDs are still not fully understood. The study of genetic defects and disease-related proteins offers us a window into the mystery of it, and the extension of knowledge indicates that different NDs share similar features, mechanisms, and even genetic or protein abnormalities. Among these findings, PARK7 and its production DJ-1 protein, which was initially found implicated in PD, have also been found altered in other NDs. PARK7 mutations, altered expression and posttranslational modification (PTM) cause DJ-1 abnormalities, which in turn lead to downstream mechanisms shared by most NDs, such as mitochondrial dysfunction, oxidative stress, protein aggregation, autophagy defects, and so on. The knowledge of DJ-1 derived from PD researches might apply to other NDs in both basic research and clinical application, and might yield novel insights into and alternative approaches for dealing with NDs.

Mitochondrial LonP1 protease is implicated in the degradation of unstable Parkinson's disease-associated DJ-1/PARK 7 missense mutants

DJ-1/PARK7 mutations are linked with familial forms of early-onset Parkinson's disease (PD). We have studied the degradation of untagged DJ-1 wild type (WT) and missense mutants in mouse embryonic fibroblasts obtained from DJ-1-null mice, an approach closer to the situation in patients carrying homozygous mutations. The results showed that the mutants L10P, M26I, A107P, P158Δ, L166P, E163K, and L172Q are unstable proteins, while A39S, E64D, R98Q, A104T, D149A, A171S, K175E, and A179T are as stable as DJ-1 WT. Inhibition of proteasomal and autophagic-lysosomal pathways had little effect on their degradation. Immunofluorescence and biochemical fractionation studies indicated that M26I, A107P, P158Δ, L166P, E163K, and L172Q mutants associate with mitochondria. Silencing of mitochondrial matrix protease LonP1 produced a strong reduction of the degradation of the mitochondrial-associated DJ-1 mutants A107P, P158Δ, L166P, E163K, and L172Q but not of mutant L10P. These results demonstrated a mitochondrial pathway of degradation of those DJ-1 missense mutants implicated in PD pathogenesis.

PARKIN, PINK1, and DJ1 analysis in early-onset Parkinson's disease in Ireland

BACKGROUND

Variants in PARKIN, PINK1, and DJ1 are associated with early-onset Parkinson' disease (EOPD, age-at-onset < 45). We previously reported a single PINK1 and a single DJ1 heterozygous variant carrier.

PURPOSE

We aimed to expand upon our previous EOPD studies and investigate for any genotype-phenotype correlations in Irish PD.

METHODS

Three hundred fourteen PD patients were recruited from Dublin Neurological Institute, Ireland. Genetic analysis was performed at the Mayo Clinic, Jacksonville, USA. We screened 81 patients with young-onset PD (age-at-onset < 50), of which 58 had EOPD.

RESULTS

We identified 4 patients with homozygous/compound heterozygous variants and 3 heterozygote carriers (pathogenic PINK1/DJ1 variants were not found). Expansion of one of the pedigrees showed a novel variant in exon 9, in a symptomatic patient. We identified 6.89% PARKIN variant carriers associated with EOPD.

CONCLUSION

These findings suggest that PINK1 and DJ1 are rarely associated with Irish YOPD, while PARKIN variant frequency is similar to that reported worldwide.

Mechanistic insights into the pathogenesis of neurodegenerative diseases: towards the development of effective therapy

Neurodegeneration is a prevalent and one of the emerging reasons for morbidity, mortality, and cognitive impairment in aging. Dementia is one of such conditions of neurodegeneration, partially manageable, irreversible, and worsens over time. This review is focused on biological and psychosocial risk factors associated with Alzheimer's and Parkinson's diseases, highlighting the value of cognitive decline. We further emphasized on current therapeutic strategies from pharmacological and non-pharmacological perspectives focusing on their effects on cognitive impairment, protein aggregation, tau pathology, and improving the quality of life. Deeper mechanistic insights into the multifactorial neurodegeneration could offer the design and development of promising diagnostic and therapeutic strategies.

Dj1 deficiency protects against atherosclerosis with anti-inflammatory response in macrophages

Inflammation is a key contributor to atherosclerosis with macrophages playing a pivotal role through the induction of oxidative stress and cytokine/chemokine secretion. DJ1, an anti-oxidant protein, has shown to paradoxically protect against chronic and acute inflammation. However, the role of DJ1 in atherosclerosis remains elusive. To assess the role of Dj1 in atherogenesis, we generated whole-body Dj1-deficient atherosclerosis-prone Apoe null mice (Dj1^-/-Apoe^-/-). After 21 weeks of atherogenic diet, Dj1^-/- Apoe^-/-mice were protected against atherosclerosis with significantly reduced plaque macrophage content. To assess whether haematopoietic or parenchymal Dj1 contributed to atheroprotection in Dj1-deficient mice, we performed bone-marrow (BM) transplantation and show that Dj1-deficient BM contributed to their attenuation in atherosclerosis. To assess cell-autonomous role of macrophage Dj1 in atheroprotection, BM-derived macrophages from Dj1-deficient mice and Dj1-silenced macrophages were assessed in response to oxidized low-density lipoprotein (oxLDL). In both cases, there was an enhanced anti-inflammatory response which may have contributed to atheroprotection in Dj1-deficient mice. There was also an increased trend of plasma DJ-1 levels from individuals with ischemic heart disease compared to those without. Our findings indicate an atheropromoting role of Dj1 and suggests that targeting Dj1 may provide a novel therapeutic avenue for atherosclerosis treatment or prevention.

Current Aspects of the Endocannabinoid System and Targeted THC and CBD Phytocannabinoids as Potential Therapeutics for Parkinson's and Alzheimer's Diseases: a Review

Neurodegeneration leading to Parkinson's disease (PD) and Alzheimer's disease (AD) has become a major health burden globally. Current treatments mainly target controlling symptoms and there are no therapeutics available in clinical practice to preventing the neurodegeneration or inducing neuronal repairing. Thus, the demand of novel research for the two disorders is imperative. This literature review aims to provide a collection of published work on PD and AD and current uses of endocannabinoid system (ECS) as a potential drug target for neurodegeneration. PD is frequently treated with L-DOPA and deep brain stimulation. Recent gene modification and remodelling techniques, such as CRISPR through human embryonic stem cells and induced pluripotent stem cells, have shown promising strategy for personalised medicine. AD characterised by extracellular deposits of amyloid β-senile plaques and neurofibrillary tangles of tau protein commonly uses choline acetyltransferase enhancers as therapeutics. The ECS is currently being studied as PD and AD drug targets where overexpression of ECS receptors exerted neuroprotection against PD and reduced neuroinflammation in AD. The delta-9-tetrahydrocannabinoid (Δ9-THC) and cannabidiol (CBD) cannabinoids of plant Cannabis sativa have shown neuroprotection upon PD and AD animal models yet triggered toxic effects on patients when administered directly. Therefore, understanding the precise molecular cascade following cannabinoid treatment is suggested, focusing especially on gene expression to identify drug targets for preventing and repairing neurodegeneration.

Small Substrate or Large? Debate Over the Mechanism of Glycation Adduct Repair by DJ-1

Glycation, the term for non-enzymatic covalent reactions between aldehyde metabolites and nucleophiles on biopolymers, results in deleterious cellular damage and diseases. Since Parkinsonism-associated protein DJ-1 was proposed as a novel deglycase that directly repairs glycated adducts, it has been considered a major contributor to glycation damage repair. Recently, an interesting debate over the mechanism of glycation repair by DJ-1 has emerged, focusing on whether the substrate of DJ-1 is glycated adducts or the free small aldehydes. The physiological significance of DJ-1 on glycation defense also remains in question. This debate is complicated by the fact that glycated biomolecular adducts are in rapid equilibrium with free aldehydes. Here, we summarize experimental evidence for the two possibilities, highlighting both consistencies and conflicts. We discuss the experimental complexities from a mechanistic perspective, and suggest classes of experiments that should help clarify this debate.

Association between a DJ-1 polymorphism and the risk of Parkinson's disease: a PRISMA-compliant systematic review and meta-analysis

Objective

In recent years, a number of case–control studies have focused on the association between the DJ-1 g.168_185del polymorphism and the risk of Parkinson's disease (PD). However, the results have been conflicting. To estimate the relationship between the DJ-1 g.168_185del polymorphism and PD susceptibility, a comprehensive meta-analysis was performed.

Methods

Eligible studies concerning the DJ-1 g.168_185del polymorphism and PD susceptibility were searched for in the PubMed, Web of Science, Embase, Wanfang, CNKI, and VIP databases. Odds ratios and 95% confidence intervals were calculated to estimate the strength of the associations. In total, 11 studies were included in this meta-analysis, including 13 case–control studies with 2890 cases and 3043 controls.

Results

This meta-analysis revealed that DJ-1 g.168_185del variants are associated with PD susceptibility in the non-Asian population, but not in the Asian population.

Conclusions

Our meta-analysis suggests that DJ-1 gene variants are not associated with the risk of PD in the overall population.

Impaired D2 receptor-dependent dopaminergic transmission in prefrontal cortex of awake mouse model of Parkinson's disease

The loss-of-function mutation in PARK7/DJ-1 is one of the most common causes of autosomal recessive Parkinson's disease, and patients carrying PARK7 mutations often exhibit both a progressive movement disorder and emotional impairment, such as anxiety. However, the causes of the emotional symptom accompanying PARK7-associated and other forms of Parkinson's disease remain largely unexplored. Using two-photon microscopic Ca2+ imaging in awake PARK7-/- and PARK7+/+ mice, we found that (i) PARK7-/- neurons in the frontal association cortex showed substantially higher circuit activity recorded as spontaneous somatic Ca2+ signals; (ii) both basal and evoked dopamine release remained intact, as determined by both electrochemical dopamine recordings and high performance liquid chromatography in vivo; (iii) D2 receptor expression was significantly decreased in postsynaptic frontal association cortical neurons, and the hyper-neuronal activity were rescued by D2 receptor intervention using either local pharmacology or viral D2 receptor over-expression; and (iv) PARK7-/- mice showed anxiety-like behaviours that were rescued by either local D2 receptor pharmacology or overexpression. Thus, for first time, we demonstrated a robust D2 receptor-dependent phenotype of individual neurons within the prefrontal cortex circuit in awake parkinsonian mice that linked with anxiety. Our work sheds light on early-onset phenotypes and the mechanisms underlying Parkinson's disease by imaging brain circuits in an awake mouse model.

Down-regulation of DJ-1 Augments Neuroinflammation via Nrf2/Trx1/NLRP3 Axis in MPTP-induced Parkinson's Disease Mouse Model

Microglia-mediated neuroinflammation plays a significant role in the pathogenesis of Parkinson's disease (PD). Down-regulation of DJ-1, a PD-associated protein, has been recently found to increase microglial sensitivity to lipopolysaccharides (LPS). However, the role of DJ-1 in microglia-mediated neuroinflammation in PD remains unclear. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was used to establish a PD model with mice and tyrosine hydroxylase (TH) staining was performed to validate the model. Adenovirus strategy and shRNA was employed to knockdown the expression of DJ-1 in mice and BV2 microglia, respectively. Western Blot and quantitative PCR were carried out to determine the expression of cytokines, DJ-1, Nrf2, Trx1 and NRLP3. Immunoprecipitation was used to examine the potential interaction between DJ-1 and Nrf2 or Trx1. Flow cytometry-based Annexin V/7-AAD assay were performed to evaluate cell apoptosis. We found that down-regulation of DJ-1 exacerbated neuroinflammation in PD mice. DJ-1 and Nrf2 knockdown promoted inflammation and cell apoptosis in BV2 microglia, while NLRP3 knockdown had opposite effects. Furthermore, DJ-1 regulated the expression of NLRP3 by upregulating Nrf2/Trx1 axis. Taken together, these data suggested that down-regulation of DJ-1 accelerated microglia-mediated neuroinflammation and cell apoptosis via Nrf2/Trx1/NLRP3 axis. Thus, our results demonstrated the important role of DJ-1 in PD pathogenesis and warranted further investigation of DJ-1 as a therapeutic target for PD.

Genetic perspective on the synergistic connection between vesicular transport, lysosomal and mitochondrial pathways associated with Parkinson's disease pathogenesis

Parkinson's disease (PD) and atypical parkinsonian syndromes (APS) are symptomatically characterized by parkinsonism, with the latter presenting additionally a distinctive range of atypical features. Although the majority of patients with PD and APS appear to be sporadic, genetic causes of several rare monogenic disease variants were identified. The knowledge acquired from these genetic factors indicated that defects in vesicular transport pathways, endo-lysosomal dysfunction, impaired autophagy-lysosomal protein and organelle degradation pathways, α-synuclein aggregation and mitochondrial dysfunction play key roles in PD pathogenesis. Moreover, membrane dynamics are increasingly recognized as a key player in the disease pathogenesis due lipid homeostasis alterations, associated with lysosomal dysfunction, caused by mutations in several PD and APS genes. The importance of lysosomal dysfunction and lipid homeostasis is strengthened by both genetic discoveries and clinical epidemiology of the association between parkinsonism and lysosomal storage disorders (LSDs), caused by the disruption of lysosomal biogenesis or function. A synergistic coordination between vesicular trafficking, lysosomal and mitochondria defects exist whereby mutations in PD and APS genes encoding proteins primarily involved one PD pathway are frequently associated with defects in other PD pathways as a secondary effect. Moreover, accumulating clinical and genetic observations suggest more complex inheritance patters of familial PD exist, including oligogenic and polygenic inheritance of genes in the same or interconnected PD pathways, further strengthening their synergistic connection.Here, we provide a comprehensive overview of PD and APS genes with functions in vesicular transport, lysosomal and mitochondrial pathways, and highlight functional and genetic evidence of the synergistic connection between these PD associated pathways.

CRISPR System: A High-throughput Toolbox for Research and Treatment of Parkinson's Disease

In recent years, the innovation of gene-editing tools such as the CRISPR/Cas9 system improves the translational gap of treatments mediated by gene therapy. The privileges of CRISPR/Cas9 such as working in living cells and organs candidate this technology for using in research and treatment of the central nervous system (CNS) disorders. Parkinson's disease (PD) is a common, debilitating, neurodegenerative disorder which occurs due to loss of dopaminergic neurons and is associated with progressive motor dysfunction. Knowledge about the pathophysiological basis of PD has altered the classification system of PD, which manifests in familial and sporadic forms. The first genetic linkage studies in PD demonstrated the involvement of Synuclein alpha (SNCA) mutations and SNCA genomic duplications in the pathogenesis of PD familial forms. Subsequent studies have also insinuated mutations in leucine repeat kinase-2 (LRRK2), Parkin, PTEN-induced putative kinase 1 (PINK1), as well as DJ-1 causing familial forms of PD. This review will attempt to discuss the structure, function, and development in genome editing mediated by CRISP/Cas9 system. Further, it describes the genes involved in the pathogenesis of PD and the pertinent alterations to them. We will pursue this line by delineating the PD linkage studies in which CRISPR system was employed. Finally, we will discuss the pros and cons of CRISPR employment vis-à-vis the process of genome editing in PD patients' iPSCs.

Novel Insights into PARK7 (DJ-1), a Potential Anti-Cancer Therapeutic Target, and Implications for Cancer Progression

The expression of PARK7 is upregulated in various types of cancer, suggesting its potential role as a critical regulator of the pathogenesis of cancer and in the treatment of cancer and neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease, and Huntington disease. PARK7 activates various intracellular signaling pathways that have been implicated in the induction of tumor progression, which subsequently enhances tumor initiation, continued proliferation, metastasis, recurrence, and resistance to chemotherapy. Additionally, secreted PARK7 has been identified as a high-risk factor for the pathogenesis and survival of various cancers. This review summarizes the current understanding of the correlation between the expression of PARK7 and tumor progression.

Genetic predispositions of Parkinson's disease revealed in patient-derived brain cells

Parkinson's disease (PD) is the second most prevalent neurological disorder and has been the focus of intense investigations to understand its etiology and progression, but it still lacks a cure. Modeling diseases of the central nervous system in vitro with human induced pluripotent stem cells (hiPSC) is still in its infancy but has the potential to expedite the discovery and validation of new treatments. Here, we discuss the interplay between genetic predispositions and midbrain neuronal impairments in people living with PD. We first summarize the prevalence of causal Parkinson's genes and risk factors reported in 74 epidemiological and genomic studies. We then present a meta-analysis of 385 hiPSC-derived neuronal lines from 67 recent independent original research articles, which point towards specific impairments in neurons from Parkinson's patients, within the context of genetic predispositions. Despite the heterogeneous nature of the disease, current iPSC models reveal converging molecular pathways underlying neurodegeneration in a range of familial and sporadic forms of Parkinson's disease. Altogether, consolidating our understanding of robust cellular phenotypes across genetic cohorts of Parkinson's patients may guide future personalized drug screens in preclinical research.

No Dataset Left Behind: Mechanistic Insights into Thyroid Receptor Signaling Through Transcriptomic Consensome Meta-Analysis

Background: Discovery-scale omics datasets relevant to thyroid receptors (TRs) and their physiological and synthetic bioactive small-molecule ligands allow for genome-wide interrogation of TR-regulated genes. These datasets have considerable collective value as a reference resource to allow researchers to routinely generate hypotheses addressing the mechanisms underlying the cell biology and physiology of TR signaling in normal and disease states. Methods: Here, we searched the Gene Expression Omnibus database to identify a population of publicly archived transcriptomic datasets involving genetic or pharmacological manipulation of either TR isoform in a mouse tissue or cell line. After initial quality control, samples were organized into contrasts (experiments), and transcript differential expression values and associated measures of significance were generated and committed to a consensome (for consensus omics) meta-analysis pipeline. To gain insight into tissue-selective functions of TRs, we generated liver- and central nervous system (CNS)-specific consensomes and identified evidence for genes that were selectively responsive to TR signaling in each organ. Results: The TR transcriptomic consensome ranks genes based on the frequency of their significant differential expression over the entire group of experiments. The TR consensome assigns elevated rankings both to known TR-regulated genes and to genes previously uncharacterized as TR-regulated, which shed mechanistic light on known cellular and physiological roles of TR signaling in different organs. We identify evidence for unreported genomic targets of TR signaling for which it exhibits strikingly distinct regulatory preferences in the liver and CNS. Moreover, the intersection of the TR consensome with consensomes for other cellular receptors sheds light on transcripts potentially mediating crosstalk between TRs and these other signaling paradigms. Conclusions: The mouse TR datasets and consensomes are freely available in the Signaling Pathways Project website for hypothesis generation, data validation, and modeling of novel mechanisms of TR regulation of gene expression. Our results demonstrate the insights into the mechanistic basis of thyroid hormone action that can arise from an ongoing commitment on the part of the research community to the deposition of discovery-scale datasets.

DJ-1 is indispensable for the S-nitrosylation of Parkin, which maintains function of mitochondria

The DJ-1 gene, a causative gene for familial Parkinson’s disease (PD), has been reported to have various functions, including transcriptional regulation, antioxidant response, and chaperone and protease functions; however, the molecular mechanism associated with the pathogenesis of PD remains elusive. To further explore the molecular function of DJ-1 in the pathogenesis of PD, we compared protein expression profiles in brain tissues from wild-type and DJ-1-deficient mice. Two-dimensional difference gel electrophoresis analysis and subsequent analysis using data mining methods revealed alterations in the expression of molecules associated with energy production. We demonstrated that DJ-1 deletion inhibited S-nitrosylation of endogenous Parkin as well as overexpressed Parkin in neuroblastoma cells and mouse brain tissues. Thus, we used genome editing to generate neuroblastoma cells with DJ-1 deletion or S-nitrosylated cysteine mutation in Parkin and demonstrated that these cells exhibited similar phenotypes characterized by enhancement of cell death under mitochondrial depolarization and dysfunction of mitochondria. Our data indicate that DJ-1 is required for the S-nitrosylation of Parkin, which positively affects mitochondrial function, and suggest that the denitrosylation of Parkin via DJ-1 inactivation might contribute to PD pathogenesis and act as a therapeutic target.

Pathological Influences on Clinical Heterogeneity in Lewy Body Diseases

PD, PD with dementia, and dementia with Lewy bodies are clinical syndromes characterized by the neuropathological accumulation of alpha-synuclein in the CNS that represent a clinicopathological spectrum known as Lewy body disorders. These clinical entities have marked heterogeneity of motor and nonmotor symptoms with highly variable disease progression. The biological basis for this clinical heterogeneity remains poorly understood. Previous attempts to subtype patients within the spectrum of Lewy body disorders have centered on clinical features, but converging evidence from studies of neuropathology and ante mortem biomarkers, including CSF, neuroimaging, and genetic studies, suggest that Alzheimer's disease beta-amyloid and tau copathology strongly influence clinical heterogeneity and prognosis in Lewy body disorders. Here, we review previous clinical biomarker and autopsy studies of Lewy body disorders and propose that Alzheimer's disease copathology is one of several likely pathological contributors to clinical heterogeneity of Lewy body disorders, and that such pathology can be assessed in vivo. Future work integrating harmonized assessments and genetics in PD, PD with dementia, and dementia with Lewy bodies patients followed to autopsy will be critical to further refine the classification of Lewy body disorders into biologically distinct endophenotypes. This approach will help facilitate clinical trial design for both symptomatic and disease-modifying therapies to target more homogenous subsets of Lewy body disorders patients with similar prognosis and underlying biology. © 2019 International Parkinson and Movement Disorder Society.

DJ-1 in Parkinson's Disease: Clinical Insights and Therapeutic Perspectives

Mutations in the protein DJ-1 cause autosomal recessive forms of Parkinson’s disease (PD) and oxidized DJ-1 is found in the brains of idiopathic PD individuals. While several functions have been ascribed to DJ-1 (most notably protection from oxidative stress), its contribution to PD pathogenesis is not yet clear. Here we provide an overview of the clinical research to date on DJ-1 and the current state of knowledge regarding DJ-1 characterization in the human brain. The relevance of DJ-1 as a PD biomarker is also discussed, as are studies exploring DJ-1 as a possible therapeutic target for PD and neurodegeneration.

Cistanche extracts ameliorates the neurotoxicity induced by hydrogen peroxide in new mutant DJ-1-transfected neuroblastoma cellular models

INTRODUCTION

DJ-1 mutation is a causative reason for familial Parkinson's disease (PD). Leucine166Proline (L166P) and C106S are two important DJ-1 mutations. In this study, we established hydrogen peroxide (H₂ O₂ ) induced L166P and C106S DJ-1-transfected neuroblastoma (SH-SY5Y) cellular models of PD and investigated the effects of Cistanche extracts and key bioactive compounds, including acteoside, echinacoside, caffeic acid, and Cistanche total glycosides on these two models.

METHODS

After expressing FLAG-tagged L166P and C106S DJ-1 plasmids in Escherichia coli, the expressed plasmids were collected, treated with restriction enzyme, and identified using DNA electrophoresis. After purification, the L166P DJ-1 and C106S DJ-1 plasmids were separately transfected into SH-SY5Y cells using liposomes. Transfected SH-SY5Y cells were detected by western blotting and immunocytochemistry. Cell viability was determined using MTT assay.

RESULTS

Both western blotting and immunocytochemistry showed that L166P and C106S DJ-1 were highly expressed in the transfected SH-SY5Y cells. MTT assays showed that transfection with L166P or C106S DJ-1 reduced the viability of SH-SY5Y cells exposed to H₂ O₂ , as compared to untransfected SH-SY5Y cells. In addition, Cistanche extracts and key bioactive compounds, including acteoside, echinacoside, caffeic acid, and Cistanche total glycosides, significantly inhibited the decreases of cell viability caused by H₂ O₂ in L166P and C106S DJ-1-transfected SH-SY5Y cells.

CONCLUSIONS

These findings suggest that we successfully established sensitive and stable H₂ O₂ induced L166P DJ-1- and C106S DJ-1-transfected SH-SY5Y cell models of PD and Cistanche extracts may thus be useful for treating PD.

Mutations in Parkinson's Disease Associated Protein DJ-1 Alter the Energetics of DJ-1 Dimerization

Patients suffering from familial Parkinson's disease are linked to mutated DJ-1 protein. Wild-type DJ-1 occurs as a homodimer, which appears to be crucial for its function. It has been established that mutation (L166P) in DJ-1 protein could destabilize the DJ-1 homodimer. Hence, dimerization aspect of DJ-1 is fundamentally important for understanding its link to the disease. X-ray structures of wild-type DJ-1 dimer have given an atomic insight into the interaction network at the dimer interface. However, the energetics of dimerization in the wild-type and its mutant protein is unknown. Using the X-ray structure of wild-type DJ-1 as the template, we report ∼1.55 μs of molecular dynamics simulations to quantitatively estimate the relative free energy of DJ-1 dimerization in the disease linked variant (L166P, A104T, and M26I) with respect to its wild-type analogue. The results suggest that dimerization is disfavored for L166P and A104T mutations, severely for the former. Notably, the M26I mutation does not alter the energetics of DJ-1 dimerization. The dynamics of the DJ-1 dimer is significantly altered in response to the L166P and A104T mutations, resulting in the significant loss of interactions at the dimer interface. L166P mutant showed the structural difference and increased flexibility in α6, α7, α8 regions with respect to the WT. A structural difference in the α6 region was noticeable between WT and A104T mutant of DJ-1. The interaction network in the dimer interface is identical for the wild-type protein and the M26I mutant. No significant change in secondary structural content was observed for DJ-1 mutants (L166P, A104T, M26I) with respect to its WT analogue.

Lack of Association Between DJ-1 Gene Promoter Polymorphism and the Risk of Parkinson's Disease

Low DJ-1 protein level caused by DJ-1 gene mutation leads to autosomal recessive Parkinson's disease (PD) due to impaired antioxidative activity. In sporadic PD patients, although mutations were rarely found, lower DJ-1 protein level was also reported. Dysregulation of DJ-1 gene expression might contribute to low DJ-1 protein level. Since the promoter is the most important element to initiate gene expression, whether polymorphisms in the DJ-1 promoter result in the dysregulation of gene expression, thus leading to low protein level and causing PD, is worth exploring. The DJ-1 promoter region was sequenced in a Chinese cohort to evaluate possible links between DJ-1 promoter polymorphisms, PD risk and clinical phenotypes. Dual-luciferase reporter assay was conducted to evaluate the influence of promoter polymorphisms on DJ-1 transcriptional activity. Related information in an existing genome-wide association studies (GWAS) database were looked up, meta-analysis of the present study and other previous reports was conducted, and expression quantitative trait loci (eQTL) analysis was performed to further explore the association. Three single nucleotide polymorphisms (SNPs) (rs17523802, rs226249, and rs35675666) and one 18 bp deletion (rs200968609) were observed in our cohort. However, there was no significant association between the four detected genetic variations and the risk of PD either in allelic or genotype model, in single-point analysis or haplotype analysis. This was supported by the meta-analysis of this study and previous reports as well as that of GWAS database PDGene. Dual luciferase reporter assay suggested these promoter polymorphisms had no influence on DJ-1 transcriptive activity, which is consistent with the eQTL analysis results using the data from GTEx database. Thus, DJ-1 promoter polymorphisms may play little role in the dysregulation of DJ-1 expression and PD susceptibility in sporadic PD.

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

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