Parkinson's disease: from genetics to treatments

The Association Between Parkinson's Disease and Attention-Deficit Hyperactivity Disorder

While Parkinson’s disease (PD) and attention-deficit hyperactivity disorder (ADHD) are two distinct conditions, it has been hypothesized that they share several overlapping anatomical and neurochemical changes. In order to investigate that hypothesis, this study used claims data from Taiwan’s Longitudinal Health Insurance Database 2000 to provide the significant nationwide population-based evidence of an increased risk of PD among ADHD patients, and the connection between the two conditions was not the result of other comorbidities. Moreover, this study showed that the patients with PD were 2.8 times more likely to have a prior ADHD diagnosis compared with those without a prior history of ADHD. Furthermore, an animal model of ADHD was generated by neonatally injecting rats with 6-hydroxydopamine (6-OHDA). These rats were subjected to behavior tests and the 99mTc-TRODAT-1 brain imaging at the juvenile stage. Compared to control group rats, the 6-OHDA rats showed a significantly reduced specific uptake ratio in the striatum, indicating an underlying PD-linked pathology in the brains of these ADHD phenotype-expressing rats. Overall, these results support that ADHD shares a number of anatomical and neurochemical changes with PD. As such, improved knowledge of the neurochemical mechanisms underlying ADHD could result in improved treatments for various debilitating neurological disorders, including PD.

Applications of Genome Editing Technology in Animal Disease Modeling and Gene Therapy

Genome editing technology is a technique for targeted genetic modifications, enabling the knockout and addition of specific DNA fragments. This technology has been widely used in various types of biomedical research, clinics and agriculture. In terms of disease research, constructing appropriate animal models is necessary. Combining reproductive technology with genome editing, many animal disease models have been generated for basic and clinical research. In addition, precisely targeted modifications allow genome editing to flourish in the field of gene therapy. Many mutations refractory to traditional gene therapy could be permanently corrected at the DNA level. Thus, genome editing is undoubtedly a promising technology for gene therapy. In this review, we mainly introduce the applications of genome editing in constructing animal disease models and gene therapies, as well as its future prospects and challenges.

Simultaneous determination of FLZ and its metabolite (M1) in human plasma and urine by UHPLC-MS/MS: Application to a pharmacokinetic study

FLZ is a novel anti-Parkinson's disease candidate drug. The main active metabolite is FLZ O-dealkylation (M1) in preclinical studies. A reliable ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) quantitation method was developed for the simultaneous determination of FLZ and M1 with low limits of quantitation in human plasma (0.1 ng/mL) and urine (0.5 ng/mL). The plasma and urine samples were both purified by full-automatic solid phase extraction (SPE) method with ensured high extraction recovery and little matrix effect for both analytes, and then separated on a BEH C₁₈ column (2.1 × 50 mm, 1.7 μm). Detection and quantification were performed using an electrospray ionization (ESI) source in positive mode by multiple reaction monitoring (MRM). The precursor to product ion transitions were monitored at m/z 450.3⁺→313.2⁺ for FLZ, m/z 436.3⁺→299.1⁺ for M1, m/z 462.6⁺→142.0⁺ for [D₁₂]-FLZ (internal standard of FLZ) and m/z 447.2⁺→125.2⁺ for [D₁₁]-M1 (internal standard of M1), respectively. This method showed good linearity, accuracy, precision and stability in the range of 0.1-100 ng/mL in plasma and 0.5-500 ng/mL in urine of two analytes. Finally, the developed method was successfully applied to a pharmacokinetic research in Chinese healthy volunteers after oral administration of FLZ tablets.

Cardiac abnormalities in Parkinson's disease and Parkinsonism

OBJECTIVES

Though there is increasing evidence for primary cardiac disease in Parkinson's disease (PD) and Parkinsonism (PS), this evidence is hardly included in the general management of these patients.

METHODS

Literature review.

RESULTS

PD is one of the most common age-related neurodegenerative disorders. Epidemiological studies have shown that PD is accompanied by high rates of premature death compared with the general population. In general, death in PD/PS is usually caused by determinant factors such as pneumonia, cerebrovascular, and cardiovascular disease. There is a significant body of literature demonstrating involvement of the heart in PD/PS. Cardiac involvement in PD/PS includes cardiac autonomic dysfunction, cardiomyopathy, coronary heart disease, arrhythmias, conduction defects, and sudden cardiac death (SCD), and sudden unexpected death in Parkinson's disease (SUDPAR).

CONCLUSIONS

Cardiac abnormalities found in PD/PS are manifold but the most prominent is cardiac autonomic dysfunction. The frequency of coronary heart disease in PD is a matter of debate. Only rarely reported in PD/PS are cardiomyopathies, arrhythmias, and sudden cardiac death, and SUDPAR. It is particularly recommended that PD/PS patients are more intensively investigated cardiologically as soon as the diagnosis is established. Early recognition of cardiac involvement is important for preventing SCD and SUDPAR.

The Role of Gene Editing in Neurodegenerative Diseases

Neurodegenerative diseases (NDs), at least including Alzheimer's, Huntington's, and Parkinson's diseases, have become the most dreaded maladies because there are no precise diagnostic tools or definite treatments for these debilitating diseases. The increased prevalence and a substantial impact on the social-economic and medical care of NDs propel governments to develop policies to counteract the impact. Although the etiologies of NDs are still unknown, growing evidence suggests that genetic, cellular, and circuit alternations may cause the generation of abnormal misfolded proteins, which uncontrolledly accumulate to damage and eventually overwhelm the protein-disposal mechanisms of these neurons, leading to a common pathological feature of NDs. If the functions and the connectivity can be restored, alterations and accumulated damages may improve. The gene-editing tools including zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats-associated nucleases (CRISPR/CAS) have emerged as a novel tool not only for generating specific ND animal models for interrogating the mechanisms and screening potential drugs against NDs but also for the editing sequence-specific genes to help patients with NDs to regain function and connectivity. This review introduces the clinical manifestations of three distinct NDs and the applications of the gene-editing technology on these debilitating diseases.

Neuroprotection of Granulocyte Colony-Stimulating Factor for Early Stage Parkinson's Disease

Parkinson's disease (PD) is a slowly progressive neurodegenerative disease. Both medical and surgical choices provide symptomatic treatment. Granulocyte colony-stimulating factor (G-CSF), a conventional treatment for hematological diseases, has demonstrated its effectiveness in acute and chronic neurological diseases through its anti-inflammatory and antiapoptosis mechanisms. Based on previous in vitro and in vivo studies, we administered a lower dose (3.3 μg/kg) G-CSF injection for 5 days and six courses for 1 year in early-stage PD patients as a phase I trial. The four PD patient's mean unified PD rating scale motor scores in medication off status remained stable from 23 before the first G-CSF injection to 22 during the 2-year follow-up. 3,4-Dihydroxy-6-18F-fluoro-l-phenylalanine (18F-DOPA) positron emission tomography (PET) studies also revealed an annual 3.5% decrease in radiotracer uptake over the caudate nucleus and 7% in the putamen, both slower than those of previous reports of PD. Adverse effects included transient muscular-skeletal pain, nausea, vomiting, and elevated liver enzymes. Based on this preliminary report, G-CSF seems to alleviate disease deterioration for early stage PD patients. The effectiveness of G-CSF was possibly due to its amelioration of progressive dopaminergic neuron degeneration.

Neuroprotective Effects of Salidroside in the MPTP Mouse Model of Parkinson's Disease: Involvement of the PI3K/Akt/GSK3β Pathway

The degenerative loss through apoptosis of dopaminergic neurons in the substantia nigra pars compacta plays a primary role in the progression of Parkinson's disease (PD). Our in vitro experiments suggested that salidroside (Sal) could protect against 1-methyl-4-phenylpyridine-induced cell apoptosis in part by regulating the PI3K/Akt/GSK3β pathway. The current study aims to increase our understanding of the protective mechanisms of Sal in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropypridine- (MPTP-) induced PD mouse model. We found that pretreatment with Sal could protect against MPTP-induced increase of the time of turning downwards and climbing down to the floor. Sal also prevented MPTP-induced decrease of locomotion frequency and the increase of the immobile time. Sal provided a protection of in MPTP-induced loss of tyrosine hydroxylase-positive neurons in SNpc and the level of DA, DOPAC, and HVA in the striatum. Furthermore, Sal could increase the phosphorylation level of Akt and GSK3β, upregulate the ratio of Bcl-2/Bax, and inhibit the activation of caspase-3, caspase-6, and caspase-9. These results show that Sal prevents the loss of dopaminergic neurons and the PI3K/Akt/GSK3β pathway signaling pathway may have mediated the protection of Sal against MPTP, suggesting that Sal may be a potential candidate in neuroprotective treatment for PD.

Targeting New Candidate Genes by Small Molecules Approaching Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are among the most feared of the disorders that afflict humankind for the lack of specific diagnostic tests and effective treatments. Understanding the molecular, cellular, biochemical changes of NDs may hold therapeutic promise against debilitating central nerve system (CNS) disorders. In the present review, we summarized the clinical presentations and biology backgrounds of NDs, including Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD) and explored the role of molecular mechanisms, including dys-regulation of epigenetic control mechanisms, Ataxia-telangiectasia-mutated protein kinase (ATM), and neuroinflammation in the pathogenesis of NDs. Targeting these mechanisms may hold therapeutic promise against these devastating diseases.

Potential of Neural Stem Cell-Based Therapy for Parkinson's Disease

Neural stem cell (NSC) transplantation is an emerging strategy for restoring neuronal function in neurological disorders, such as Parkinson's disease (PD), which is characterized by a profound and selective loss of nigrostriatal dopaminergic (DA) neurons. Adult neurogenesis generates newborn neurons that can be observed at specialized niches where endothelial cells (ECs) play a significant role in regulating the behavior of NSCs, including self-renewal and differentiating into all neural lineage cells. In this minireview, we highlight the importance of establishing an appropriate microenvironment at the target site of NSC transplantation, where grafted cells integrate into the surroundings in order to enhance DA neurotransmission. Using a novel model of NSC-EC coculture, it is possible to combine ECs with NSCs, to generate such a neurovascular microenvironment. With appropriate NSCs selected, the composition of the transplant can be investigated through paracrine and juxtacrine signaling within the neurovascular unit (NVU). With target site cellular and acellular compartments of the microenvironment recognized, guided DA differentiation of NSCs can be achieved. As differentiated DA neurons integrate into the existing nigrostriatal DA pathway, the symptoms of PD can potentially be alleviated by reversing characteristic neurodegeneration.

Targeting cyclin D3/CDK6 activity for treatment of Parkinson's disease

At present, treatment for Parkinson's disease (PD) is only symptomatic; therefore, it is important to identify new targets tackling the molecular causes of the disease. We previously found that lymphoblasts from sporadic PD patients display increased activity of the cyclin D3/CDK6/pRb pathway and higher proliferation than control cells. These features were considered systemic manifestations of the disease, as aberrant activation of the cell cycle is involved in neuronal apoptosis. The main goal of this work was to elucidate whether the inhibition of cyclin D3/CDK6-associated kinase activity could be useful in PD treatment. For this purpose, we investigated the effects of two histone deacetylase (HDAC) inhibitors, suberoylanilide hydroxamic (SAHA) acid and sodium butyrate (NaB), and the m-TOR inhibitor rapamycin on cell viability and cyclin D3/CDK6 activity. Moreover, the potential neuroprotective action of these drugs was evaluated in 6-hydroxy-dopamine (6-OHDA) treated dopaminergic SH-SY5Y cells and primary rat mesencephalic cultures. Here, we report that both compounds normalized the proliferative activity of PD lymphoblasts and reduced the 6-OHDA-induced cell death in neuronal cells by preventing the over-activation of the cyclin D3/CDK6/pRb cascade. Considering that these drugs are already used in clinic for treatment of other diseases with good tolerance, it is plausible that they may serve as novel therapeutic drugs for PD. We report here that peripheral cells from Parkinson's disease (PD) patients show an enhanced proliferative activity due to the activation of cyclin D3/CDK6-mediated phosphorylation of retinoblastoma protein (pRb). Treatment of PD lymphoblasts with inhibitors of histone deacetylases like suberoylanilide hydroxamic acid (SAHA) and sodium butyrate (NaB), or with rapamycin, inhibitor of mechanistic target of rapamycin (mTOR) normalized the proliferation of PD lymphoblasts by preventing the over-activation of the cyclin D3/CDK6/pRb cascade. These drugs were shown to have neuroprotective effects in both human neuroblastoma SH-SY5Y cells and primary rat mid-brain dopaminergic neuronal cultures toxicity induced by 6-hidroxydopamine. Considering that these drugs are already used in clinic for treatment of other diseases with good tolerance, it seems reasonable to believe that the repositioning of these drugs toward PD holds promise as a novel therapeutic strategy.

Regenerative medicine for Parkinson's disease

Regenerative medicine for Parkinson’s disease (PD) is expected to develop dramatically with the advancement of biotechnology as represented by induced pluripotent stem cells. Existing therapeutic strategy for PD consists of medication using L-DOPA, surgery such as deep brain stimulation and rehabilitation. Current treatment cannot stop the progression of the disease, although there is definite therapeutic effect. True neurorestoration is strongly desired by regenerative medicine. This review article describes the historical development of regenerative medicine for PD, with a focus on fetal nigral cell transplantation and glial cell line-derived neurotrophic factor infusion. Subsequently, the current status of regenerative medicine for PD in terms of cell therapy and gene therapy are reviewed. In the end, the future direction to realize regenerative medicine for PD is discussed.

Squamosamide derivative FLZ protected tyrosine hydroxylase function in a chronic MPTP/probenecid mouse model of Parkinson's disease

Parkinson's disease (PD) is a chronic, progressive neurodegenerative disorder characterized by motor impairments and loss of dopaminergic neurons in the substantia nigra. FLZ (formulated as: N-2-(4-hydroxy-phenyl)-ethyl]-2-(2, 5-dimethoxy-phenyl)-3-(3-methoxy-4-hydroxy-phenyl)-acrylamide) is a novel synthetic derivative of squamosamide from a Chinese herb and has been proven to protect dopaminergic neurons in subacute PD models. However, whether FLZ has a neuroprotective effect on chronic PD model is still unknown. The present study was designed to verify the neuroprotection of FLZ on chronic PD mouse model induced by MPTP combined with probenecid (MPTP/p). The results showed that treatment of mice with FLZ for 9 weeks significantly improved motor behavior and dopaminergic neuronal function of mice injected with MPTP/p. The beneficial effects of FLZ attributed to the elevation of dopaminergic neuron number, dopamine level, and tyrosine hydroxylase (TH) activity, as well as decrease of α-synuclein (α-Syn) expression, α-Syn phosphorylation, nitration, and aggregation. Moreover, FLZ decreased the interaction between α-Syn and TH, which eventually improved dopaminergic neuronal function. Mechanistic study demonstrated that FLZ increased Akt and mTOR phosphorylation, suggesting that FLZ activated Akt/mTOR signaling pathway and this might be involved in the neuroprotection of FLZ. The present results provided more elaborate in vivo evidences to support the neuroprotective effect of FLZ on dopaminergic neurons of chronic PD mouse model and the potential of FLZ to be developed as new drug to treat PD.

Current proceedings of cerebral palsy

Cerebral palsy (CP) is a complicated disease with varying causes and outcomes. It has created significant burden to both affected families and societies, not to mention the quality of life of the patients themselves. There is no cure for the disease; therefore, development of effective therapeutic strategies is in great demand. Recent advances in regenerative medicine suggest that the transplantation of stem cells, including embryonic stem cells, neural stem cells, bone marrow mesenchymal stem cells, induced pluripotent stem cells, umbilical cord blood cells, and human embryonic germ cells, focusing on the root of the problem, may provide the possibility of developing a complete cure in treating CP. However, safety is the first factor to be considered because some stem cells may cause tumorigenesis. Additionally, more preclinical and clinical studies are needed to determine the type of cells, route of delivery, cell dose, timing of transplantation, and combinatorial strategies to achieve an optimal outcome.

Therapeutic strategies in Parkinson's disease: what we have learned from animal models

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by a loss of dopaminergic neurons in the substantia nigra, as well as in other brain areas. The currently available dopamine replacement therapy provides merely symptomatic benefit and is ineffective because habituation and side effects arise relatively quickly. Studying the genetic forms of PD in animal models provides novel insight that allows targeting of specific aspects of this heterogenic disease more specifically. Among others, two important cellular deficits are associated with PD; these deficits relate to (1) synaptic transmission and vesicle trafficking, and (2) mitochondrial function, relating respectively to the dominant and recessive mutations in PD-causing genes. With increased knowledge of PD, the possibility of identifying an efficient, long-lasting treatment is becoming more conceivable, but this can only be done with an increased knowledge of the specific affected cellular mechanisms. This review discusses how discoveries in animal models of PD have clarified the therapeutic potential of pathways disrupted in PD, with a specific focus on synaptic transmission, vesicle trafficking, and mitochondrial function.

Autophagy and mitophagy interplay in melanoma progression

Autophagy, or self-eating, is the most extensively studied lysosomal degradation pathway for the recycling of obsolete or damaged cytoplasmic materials, including proteins and organelles. Although this pathway was initially thought to function as trafficking system for 'in bulk' degradation by the lysosomes of cytoplasmic material, it is now widely appreciated that cargo selection by the autophagic machinery is a major process underlying the cytoprotective or--possibly--pro-death functions ascribed to this catabolic process. Indeed increasing evidence suggests that in mammalian cells the removal of dysfunctional or aged mitochondria occurs through a selective degradation pathway known as 'mitophagy'. Due to the crucial role of mitochondria in energy metabolism, redox control and cell survival/death decision, deregulated mitophagy can potentially impact a variety of crucial cell autonomous and non-autonomous processes. Accumulating evidence indicates that during malignant transformation aggressive cancers hijack autophagy to preserve energy fitness and to acquire the plasticity required to adapt to the hostile microenvironment. However, whether and how mitophagy contributes to carcinogenesis, which pathways regulate this process in the cancer cells and how cancer cell-mitophagy impacts and modifies the tumor microenvironment and therapeutic responses, remain largely unanswered issues. In this review, we discuss novel paradigms and pathways regulating mitophagy in mammalian cells and the impact this process might have on one of the most dreadful human malignancies, melanoma.