Parkinson's disease: Evidence for environmental risk factors

Post-Treatment with Erinacine A, a Derived Diterpenoid of H. erinaceus, Attenuates Neurotoxicity in MPTP Model of Parkinson's Disease

Hericium erinaceus, a valuable pharmaceutical and edible mushroom, contains potent bioactive compounds such as H. erinaceus mycelium (HEM) and its derived ethanol extraction of erinacine A, which have been found to regulate physiological functions in our previous study. However, HEM or erinacine A with post-treatment regimens also shows effects on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity, but its mechanisms remain unknown. By using annexin-V–fluorescein-isothiocyanate (FITC)/propidium iodide staining and a 2’,7’ –dichlorofluorescin diacetate (DCFDA) staining assay, the cell death, cell viability, and reactive oxygen species (ROS) of 1-methyl-4-phenylpyridinium (MMP⁺)-treated Neuro-2a (N2a) cells with or without erinacine A addition were measured, respectively. Furthermore, signaling molecules for regulating the p21/GADD45 cell death pathways and PAKalpha, p21 (RAC1) activated kinase 1 (PAK1) survival pathways were also detected in the cells treated with MPP⁺ and erinacine A by Western blots. In neurotoxic animal models of MPTP induction, the effects of HEM or erinacine A and its mechanism in vivo were determined by measuring the TH-positive cell numbers and the protein level of the substantia nigra through a brain histological examination. Our results demonstrated that post-treatment with erinacine A was capable of preventing the cytotoxicity of neuronal cells and the production of ROS in vitro and in vivo through the neuroprotective mechanism for erinacine A to rescue the neurotoxicity through the disruption of the IRE1α/TRAF2 interaction and the reduction of p21 and GADD45 expression. In addition, erinacine A treatment activated the conserved signaling pathways for neuronal survival via the phosphorylation of PAK1, AKT, LIM domain kinase 2 (LIMK2), extracellular signal-regulated kinases (ERK), and Cofilin. Similar changes in the signal molecules also were found in the substantia nigra of the MPTP, which caused TH+ neuron damage after being treated with erinacine A in the post-treatment regimens in a dose-dependent manner. Taken together, our data indicated a novel mechanism for post-treatment with erinacine A to protect from neurotoxicity through regulating neuronal survival and cell death pathways.

Association between vitamin D receptor polymorphisms and susceptibility to Parkinson's disease: An updated meta-analysis

The relationships between vitamin D receptor (VDR) gene polymorphisms, particularly ApaI, BsmI, FokI, and TaqI, and Parkinson's disease (PD) has received increasing attention in the research community. However, as the results yielded by this increased research have hitherto conflicted, we performed an updated meta-analysis of reports on the relationships between VDR polymorphisms and PD published before October 2019 that we collected from the PUBMED, EMBASE, EBSCO, China National Knowledge Infrastructure (CNKI), and Wanfang databases. The ten articles that met our screening criteria included 2782 patients and 3194 healthy controls. All the data that we received were analyzed with Stata 12.0 statistical software. The odds ratio (OR) and 95 % confidence intervals (CIs) were used to determine the relationship between VDR gene diversity and PD. While we did not find a significant correlation between the ApaI, BsmI, and TaqI polymorphisms and the risk of PD in any of the considered genetic models, we found a clear association between the FokI polymorphism and susceptibility to PD (C vs. T: OR = 1.246, 95 % CI: 1.101-1.411, P = 0; CC vs. TT: OR = 1.630, 95 % CI: 1.243-2.139, P = 0; CT vs. TT: OR = 1.382, 95 % CI: 1.059-1.804, P = 0.017; CC + CT vs. TT: OR = 1.491, 95 % CI: 1.159-1.919,P = 0.002; CC vs. CT + TT: OR = 1.261, 95 % CI: 1.062-1.496, P = 0.008). Our subgroup analysis performed according to ethnicity revealed that FokI increased the risk of PD in Asian populations (C vs. T: OR = 1.261, 95 % CI: 1.080-1.472, P = 0.003; CC vs. TT: OR = 1.664, 95 % CI: 1.189-2.330, P = 0.003; CT vs.TT: OR = 1.387, 95 % CI: 1.000-1.925, P = 0.05; CC + CT vs. TT: OR = 1.497, 95 % CI: 1.098-2.042, P = 0.011; CC vs. CT + TT: OR = 1.285, 95 % CI: 1.036-1.593, P = 0.022). Overall, the gene polymorphism of FokI only increases the risk of PD among Asian populations. Given the limited sample size of this study, the findings should be carefully explained.

Microbiome and motor neuron diseases

The microbiome is the ecological community of commensal, symbiotic, and pathogenic microorganisms that share our body space (Medical and Health Genomics, 2016, page 15-28). The human gut is the location where the maximum number of microorganisms can be found. Among the different microorganisms they can be broadly classified into two groups: the beneficial and harmful. In the human gut there is always a balance between the beneficial and the opportunistic microorganism which maintains human health. However, if the balance is not maintained and homeostasis is disturbed, with an increase in opportunistic microorganisms, it may result in various diseases like inflammatory bowel disease, irritable bowel disease, ulcerative colitis, Crohn's disease, colorectal cancer, metabolic disorders and neurodegenerative diseases including motor neuron diseases. In the present chapter we discuss the role of gut bacteria in motor neuron diseases like multiple sclerosis, Parkinson's disease and amyotrophic lateral sclerosis.

The Challenge and Opportunity to Diagnose Parkinson's Disease in Midlife

Parkinson's disease (PD) is the most common neurodegenerative movement disorder that affects extensive regions of the nervous system. Its current clinical diagnosis is based on motor symptoms that appear late during disease progression when substantial proportions of the nigrostriatal dopaminergic neuron population are lost already. Although disturbances in sleep and other biofunctions often surface years prior to motor impairments and point to a long prodromal phase, these phenotypic signs in a person's midlife lack predictive power. They do, however, signal the unfolding of the disease and suggest molecular correlates that begin deviating early on. Revealing such trajectories, hence, promises not only a better understanding of prodromal PD but may also enable a much-needed earlier diagnosis. A nexus that may harbor such molecular trajectories is the epigenome as key etiological factors of PD-genetics, age, and environment-influence this substrate. An earlier diagnosis would also allow earlier interventions and lifestyle adjustments to improve brain function and reduce symptoms. In this review, we describe the challenges of diagnosing PD early on and highlight the opportunities that may arise from steering research efforts towards comprehensive interrogations of molecular layers during the long-time neglected midlife phase. In particular, we emphasize how existing cohorts of at-risk individuals, available animal models, and suitable markers may come together and aid in revealing molecular trajectories that offer diagnostic utility for PD in its prodromal stage.

Trends in the incidence and prevalence of Parkinson's disease in Korea: a nationwide, population-based study

BACKGROUND

The lack of adequate and detailed epidemiological data of Parkinson's disease (PD), especially in Asia, is a barrier to future disease burdens and the prospect of effective public health plans. This study aimed to investigate temporal trends in the incidence and prevalence of PD in South Korea from 2010 to 2015, based on uniform diagnostic criteria.

METHODS

This study examined all PD patients registered in a South Korean national registry database of more than 50 million individuals. We analyzed the incidence and prevalence of PD according to age, gender, and region.

RESULTS

The annual incidence of PD was between 22.4-27.8 cases per 100,000 individuals. During the 6-year study period, there were 73,726 new PD patients, 42.3% of whom were men. The standardized incidence of PD increased over time in men but remained constant in women until 2013 but began to increase in 2014. The female-to-male ratio in the incidence of PD was 1.4:1 while the female-to-male ratio in the prevalence of PD was 1.6:1. The age- and gender-standardized prevalence of PD increased from 115.9 cases per 100,000 individuals in 2010 to 139.8 cases per 100,000 individuals in 2015. From 2014, the incidence and prevalence of PD peaked in individuals aged between 80 and 89 years in both men and women. Regional analysis also showed an increased prevalence of PD in all regions of Korea.

CONCLUSIONS

The incidence and prevalence of PD in Korea were higher in women and increased gradually from 2010 to 2015. The findings may contribute to epidemiological studies of PD in Asia, and may provide clues on risk factors for PD.

Nrf2-regulated miR-380-3p Blocks the Translation of Sp3 Protein and Its Mediation of Paraquat-Induced Toxicity in Mouse Neuroblastoma N2a Cells

Laboratorial and epidemiological research has established a relationship between paraquat (PQ) exposure and a risk for Parkinson's disease. Previously, we have investigated the effects of nuclear factor erythroid 2 related factor 2 (Nrf2) and microRNAs in PQ-induced neurotoxicity, addressing the function of miR-380-3p, a microRNA dysregulated by PQ, as well as Nrf2 deficiency. Nrf2 is known to mediate the expression of a variety of genes, including noncoding genes. By chromatin immunoprecipitation, we identified the relationship between Nrf2 and miR-380-3p in transcriptional regulation. qRT-PCR, Western blots, and dual-luciferase reporter gene assay showed that miR-380-3p blocked the translation of the transcription factor specificity protein-3 (Sp3) in the absence of degradation of Sp3 mRNA. Results based on cell counting analysis, annexin v-fluorescein isothiocyanate/propidium iodide double-staining assay, and propidium iodide staining showed that overexpression of miR-380-3p inhibited cell proliferation, increased the apoptotic rate, induced cell cycle arrest, and intensified the toxicity of PQ in mouse neuroblastoma (N2a [Neuro2a]) cells. Knockdown of Sp3 inhibited cell proliferation and eclipsed the alterations induced by miR-380-3p in cell proliferation. Two mediators of apoptosis and cell cycle identified in previous studies as Sp3-regulated, namely cyclin-dependent kinase inhibitor 1 (p21) and calmodulin (CaM), were dysregulated by PQ, but not Sp3 deficiency. In conclusion, Nrf2-regulated miR-380-3p inhibited cell proliferation and enhanced the PQ-induced toxicity in N2a cells potentially by blocking the translation Sp3 mRNA. We conclude that CaM and p21 were involved in PQ-induced toxicity.

Phytoconstituents in the Management of Pesticide Induced Parkinson’s Disease- A Review

Recent studies have suggested that environmental factors have a crucial role in triggering and/ or propagating the pathological changes in Parkinson’s disease (PD). Although many studies have been and being performed by utilizing MPTP like chemicals to study the effectiveness of new extracts and compounds in PD, a little focus was made on the role of pesticides. Since agricultural fields account for 37.7% of land area worldwide and the use of pesticides is an important risk factor in neurodegeneration, there is a crucial need to focus on the association between pesticides and PD. Benomyl, a benzimidazole fungicide is being widely used in India in cultivation of tropical crops. Studies prove the chronic exposure of benomyl leads to aldehyde dehydrogenase inhibition caused DOPAL toxicity, subsequently leading to dopamine degradation and Parkinson’s disease. Till date, there is no remedy for pesticide induced Parkinson’s disease. This review provides an insight of the pathophysiological aspects of pesticide induced Parkinson’s disease and also enlightens the importance of aldehyde dehydrogenase enzyme in neuroprotection.

Different Exposures to Risk Factors Do Not Explain the Inverse Relationship of Occurrence Between Cancer and Neurodegenerative Diseases: An Italian Nested Case-control Study

Several studies reported that cancer is less frequent in persons with Alzheimer's and Parkinson's Diseases (AD/PD) and vice-versa. We evaluated whether a different distribution of known nongenetic risk factors for cancer and AD/PD, might explain their inverse relationship of occurrence. We nested 2 case-control studies in a subsample of a large cohort of 1,000,000 resident in Lombardy Region in Italy (n=1515), followed-up for cancer and AD/PD occurrence since 1991 until 2012. Conditional logistic regression was performed to determine the odds ratios (OR) and 95% confidence intervals (CI) of AD/PD in subjects with and without cancer and the risk of cancer in those with and without AD/PD. A total of 54 incident cases of AD/PD and 347 cancer cases were matched with 216 and 667 controls, respectively. After controlling for low education, obesity, history of hypertension, diabetes, dyslipidemia, physical activity, smoking habit, alcohol consumption, and dietary habit, cancer was found inversely associated with the risk of AD/PD (OR, 0.66; 95% CI, 0.32-1.38), and the risk of cancer in AD/PD was similarly reduced (OR, 0.42; 95% CI, 0.20-0.91). Different exposures to nongenetic risk factors of both diseases do not explain their competitive relationship of occurrence.

The genetic architecture of Parkinson's disease

Parkinson's disease is a complex neurodegenerative disorder for which both rare and common genetic variants contribute to disease risk, onset, and progression. Mutations in more than 20 genes have been associated with the disease, most of which are highly penetrant and often cause early onset or atypical symptoms. Although our understanding of the genetic basis of Parkinson's disease has advanced considerably, much remains to be done. Further disease-related common genetic variability remains to be identified and the work in identifying rare risk alleles has only just begun. To date, genome-wide association studies have identified 90 independent risk-associated variants. However, most of them have been identified in patients of European ancestry and we know relatively little of the genetics of Parkinson's disease in other populations. We have a limited understanding of the biological functions of the risk alleles that have been identified, although Parkinson's disease risk variants appear to be in close proximity to known Parkinson's disease genes and lysosomal-related genes. In the past decade, multiple efforts have been made to investigate the genetic architecture of Parkinson's disease, and emerging technologies, such as machine learning, single-cell RNA sequencing, and high-throughput screens, will improve our understanding of genetic risk.

Acupuncture protects from 6-OHDA-induced neuronal damage by balancing the ratio of DMT1/Fpn1

Objective

Acupuncture is a commonly used method to provide motor-symptomatic relief for patients with Parkinson s disease (PD). Our objective was to evaluate protective effects of acupuncture treatment and potential underlying mechanisms according to the “gut-brain axis” theory.

Methods

We employed a 6-OHDA-induced PD rat model. The effects of acupuncture on disease development were assessed by behavioural tests and immunohistochistry (IHC). ELISA, qPCR and western blot (WB) were employed to measure inflammatory parameters and Fe metabolism in the substantia nigra (SN), striatum, duodenum and blood, respectively.

Results

Our data show that acupuncture can significantly increase the expression of tyrosine hydroxylase (TH), compared with untreated and madopa treated rats (P < 0.01 and P < 0.05, respectively). Furthermore we could observe significantly decreased levels of pro-inflammatory markers in the duodenum and serum (P < 0.05), reduced deposition of Fe in the substantia nigra (P < 0.05) and but no change in transferrin expression after acupuncture treatment. The mRNA ratio of DMT1/Fpn1 in the SN of acupuncture treated rats (1.1) was comparable to that of the sham group (1.0) which differed both significantly from the untreated and madopa treated groups (P < 0.05). Furthermore, after acupuncture expression of α-synuclein was decreased in the duodenum.

Conclusions

Acupuncture can reduce iron accumulation in the SN and protect the loss of dopamine neurons by promoting balanced expression of the iron importer DMT1 and the iron exporter Fpn1. Furthermore CNS iron homeostasis may be affected by reduced systemic and intestinal inflammation.

Mitochondrially targeted cytochrome P450 2D6 is involved in monomethylamine-induced neuronal damage in mouse models

Parkinson's disease (PD) is a major human disease associated with degeneration of the central nervous system. Evidence suggests that several endogenously formed 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mimicking chemicals that are metabolic conversion products, especially β-carbolines and isoquinolines, act as neurotoxins that induce PD or enhance progression of the disease. We have demonstrated previously that mitochondrially targeted human cytochrome P450 2D6 (CYP2D6), supported by mitochondrial adrenodoxin and adrenodoxin reductase, can efficiently catalyze the conversion of MPTP to the toxic 1-methyl-4-phenylpyridinium ion. In this study, we show that the mitochondrially targeted CYP2D6 can efficiently catalyze MPTP-mimicking compounds, i.e. 2-methyl-1,2,3,4-tetrahydroisoquinoline, 2-methyl-1,2,3,4-tetrahydro-β-carboline, and 9-methyl-norharmon, suspected to induce PD in humans. Our results reveal that activity and respiration in mouse brain mitochondrial complex I are significantly affected by these toxins in WT mice but remain unchanged in Cyp2d6 locus knockout mice, indicating a possible role of CYP2D6 in the metabolism of these compounds both in vivo and in vitro These metabolic effects were minimized in the presence of two CYP2D6 inhibitors, quinidine and ajmalicine. Neuro-2a cells stably expressing predominantly mitochondrially targeted CYP2D6 were more sensitive to toxin-mediated respiratory dysfunction and complex I inhibition than cells expressing predominantly endoplasmic reticulum-targeted CYP2D6. Exposure to these toxins also induced the autophagic marker Parkin and the mitochondrial fission marker Dynamin-related protein 1 (Drp1) in differentiated neurons expressing mitochondrial CYP2D6. Our results show that monomethylamines are converted to their toxic cationic form by mitochondrially directed CYP2D6 and result in neuronal degradation in mice.

Cannabinoid Actions on Neural Stem Cells: Implications for Pathophysiology

With the increase of life expectancy, neurodegenerative disorders are becoming not only a health but also a social burden worldwide. However, due to the multitude of pathophysiological disease states, current treatments fail to meet the desired outcomes. Therefore, there is a need for new therapeutic strategies focusing on more integrated, personalized and effective approaches. The prospect of using neural stem cells (NSC) as regenerative therapies is very promising, however several issues still need to be addressed. In particular, the potential actions of pharmacological agents used to modulate NSC activity are highly relevant. With the ongoing discussion of cannabinoid usage for medical purposes and reports drawing attention to the effects of cannabinoids on NSC regulation, there is an enormous, and yet, uncovered potential for cannabinoids as treatment options for several neurological disorders, specifically when combined with stem cell therapy. In this manuscript, we review in detail how cannabinoids act as potent regulators of NSC biology and their potential to modulate several neurogenic features in the context of pathophysiology.

The cumulative incidence and trends of rare diseases in South Korea: a nationwide study of the administrative data from the National Health Insurance Service database from 2011-2015

Background

The burden of rare diseases on society and patients’ families has increased in Korea. However, because of the infrequency of rare diseases, there is a lack of resources and information to address these cases and inadequate funding for the management of these patients. We investigated the average annual cumulative incidence of rare diseases and the trends in annual cumulative incidence from 2011 to 2015 in Korea by using nationwide administrative data from the Korean National Health Insurance Service (NHIS) database for patients registered with the co-payment assistance policy for rare and incurable diseases. Annual cumulative incidence per 10,000,000 was calculated as the total number of newly enrolled patients with the Korean Standard Classification of Diseases (KCD)-7 code in the register, divided by the number of residents with health insurance coverage during each year. We employed simple linear regression analysis to evaluate the trends in annual cumulative incidence/10,000,000 population per year for each rare disease.

Results

Overall, national support was provided for patients with 415 KCD codes listed among the targeted rare diseases. The total number of newly enrolled patients with rare diseases was 53,831 in 2011, 52,658 in 2012, 52,955 in 2013, 71,530 in 2014, and 70,559 in 2015. The number of rare diseases with an average annual cumulative incidence of 100/10,000,000 and above was 22 (5.30%), while there were 227 (54.70%) and 148 (35.66%) with an average cumulative incidence between 1/10,000,000 and 100/10,000,000 and less than 1/10,000,000, respectively. The trends in the annual cumulative incidence for 43 rare diseases were statistically significant (p-value < 0.05). The rare diseases for which the incremental trend per year was statistically significant were sarcoidosis (D86, D86.0, D86.1, D86.2, D86.3, D86.8, D86.9), Parkinson’s disease (G20), Guillain-Barré syndrome (G61.0), primary biliary cirrhosis (K74.3) and Sjogren’s syndrome (M35.0).

Conclusions

The number of rare diseases showing an increasing trend in annual cumulative incidence was higher than the number of diseases showing a decreasing trend in annual cumulative incidence. Given that the definition and diagnosis vary based on country and that there is difficulty in identifying valid cases, further detection strategies are needed to establish the incidence of each rare disease considering the importance of establishing a health policy based on the actual incidence of the targeted diseases.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1032-6) contains supplementary material, which is available to authorized users.

Association Between Parkinson's Disease and Atrial Fibrillation: A Population-Based Study

Introduction: Autonomic nervous system (ANS) dysfunction contributes to several non-motor symptoms of Parkinson's disease (PD). In addition, ANS plays a role in the genesis and maintenance of atrial fibrillation (AF). This study investigated the temporal association between PD and AF.

Methods: Data were obtained from the National Health Insurance Research Database of Taiwan. In total, 15,375 patients with newly diagnosed PD were matched with four controls each based on the propensity score. This study was bidirectional. A case-control study for the odds ratio (OR) of AF before PD and within 2 years of PD diagnosis was evaluated through conditional logistic regression. Furthermore, a cohort study on the subdistribution hazard ratio (SHR) for new-onset AF 2 years after PD diagnosis was evaluated using competing risk analysis.

Results: In the case-control study, PD was found to be significantly comorbid with AF (adjusted OR: 1.15, 95% confidence interval [CI]: 1.04–1.28). Subgroup analysis demonstrated that this association consistently presented in the absence of confounding factors of AF. In the cohort study, people with PD were found to have a lower risk of AF (adjusted SHR: 0.92, 95% CI: 0.86–0.98). However, a consistent association was not observed between the confounding factors of AF and PD during the subgroup analysis.

Conclusions: This study demonstrated that the premotor and early stages of PD were comorbid with AF, whereas the risk of AF was lower in the later stages. Thus, AF might be a premotor predictive biomarker and comorbidity of early PD.

Brain aging: A Ianus-faced player between health and neurodegeneration

Neurodegenerative diseases are incurable debilitating disorders characterized by structural and functional neuronal loss. Approximately 30 million people are affected worldwide, and this number is predicted to reach more than 150 million by 2050. Neurodegenerative disorders include Alzheimer's, Parkinson's, and prion diseases among others. These disorders are characterized by the accumulation of aggregating proteins forming amyloid, responsible for the disease-associated pathological lesions. The aggregation of amyloidogenic proteins can result either in gaining of toxic functions, derived from the damage provoked by these deposits in affected tissue, or in a loss of functions, due to the sequestration and the consequent inability of the aggregating protein to ensure its physiological role. While it is widely accepted that aging represents the main risk factor for neurodegeneration, there is still no clear cut-off line between the two conditions. Indeed, many of the pathways that are commonly altered in neurodegeneration-misfolded protein accumulation, chronic inflammation, mitochondrial dysfunction, impaired iron homeostasis, epigenetic modifications-have been often correlated also with healthy aging. This overlap could be explained by the fact that the continuous accumulation of cellular damages, together with a progressive decline in metabolic efficiency during aging, makes the neurons more vulnerable to toxic injuries. When a given threshold is exceeded, all these alterations might give rise to pathological phenotypes that ultimately lead to neurodegeneration.

The role of exposure to pesticides in the etiology of Parkinson's disease: a 18F-DOPA positron emission tomography study

Susceptibility to Parkinson's disease (PD) is believed to involve an interaction between genetic and environmental factors. The role of pesticides as a risk factor of PD and neurodegeneration remains controversial. An asymmetric decrease in ligand uptake on ¹⁸F-DOPA positron emission tomography (PET), especially in the dorsal putamen, is a sensitive marker of PD. The aim of this study was to examine the pattern of ligand uptake on ¹⁸F-DOPA PET in patients with PD exposed or not exposed to pesticides. The main sample included 26 Israeli patients with PD, 13 who were exposed to pesticides and 13 who were not, matched for age and disease duration. All underwent ¹⁸F-DOPA PET imaging, and an asymmetry index of ligand uptake between the ipsilateral and contralateral caudate, putamen, and whole striatum was calculated. No significant between-group differences were found in demographic variables, clinical asymmetry index (P = 0.15), or asymmetry index of ligand uptake in the putamen (P = 0.84), caudate (P = 0.78) and striatum (P = 0.45). Comparison of the ¹⁸F-DOPA results of the Israeli cohort with those of 17 non-pesticide-exposed patients with PD from Austria yielded no significant differences, further validating our findings. Our observations suggest that although exposure to pesticides might be a risk factor for PD, it does not have an effect on the asymmetry pattern in the nigrostriatal system over non-exposure. We assume that once the disease process is initiated in pesticide-exposed patients, the pathogenic mechanism does not differ from that of idiopathic PD.

The imbalance of serotonergic circuitry impairing the crop supercontractile muscle activity and the mitochondrial morphology of PD PINK1B9Drosophila melanogaster are rescued by Mucuna pruriens

Despite its great potentiality, little attention has been paid to modelling gastrointestinal symptoms of Parkinson's disease (PD) in Drosophila melanogaster (Dm). Our previous studies on standardized Mucuna pruriens extract (Mpe) have shown usefulness in the Drosophila model of PD. In this communication, we provide new information on the effect of Mpe on basal and serotonin treated contractions in the crop (i.e., an important and essential part of the gut) in Drosophila PD mutant for PTEN-induced putative kinase 1 (PINK1^B9) gene. The effect of Mpe on PINK1^B9 supplied with standard diet to larvae and/or adults, were assayed on 10-15 days old flies. Conversely from what we observed in the wild type flies, recordings demonstrated that exogenous applications of serotonin on crop muscles of untreated PINK1^B9 affect neither the frequency nor the amplitude of the crop contraction, while the same muscle parameters are enhanced following brain injections of serotonin, thus suggesting that PINK1^B9 mutants may likely have an impairment in the serotonergic pathways. Also, the mitochondrial morphology in the crop muscles is strongly compromised, as demonstrated by the transmission electron microscopy analysis. The Mpe treatment rescued the crop muscle parameters and also the mitochondrial morphology when supplied to both larvae and adults. Overall, this study strengthens the relevance of using PINK1^B9 Dm as a translational model to study the gastrointestinal symptoms in PD and also confirms the useful employment of M. pruriens for PD treatment.

Parkinson's Disease and Metal Storage Disorders: A Systematic Review

Metal storage disorders (MSDs) are a set of rare inherited conditions with variable clinical pictures including neurological dysfunction. The objective of this study was, through a systematic review, to identify the prevalence of Parkinsonism in patients with MSDs in order to uncover novel pathways implemented in Parkinson’s disease. Human studies describing patients of any age with an MSD diagnosis were analysed. Foreign language publications as well as animal and cellular studies were excluded. Searches were conducted through PubMed and Ovid between April and September 2018. A total of 53 publications were identified including 43 case reports, nine cross-sectional studies, and one cohort study. The publication year ranged from 1981 to 2018. The most frequently identified MSDs were Pantothenate kinase-associated neurodegeneration (PKAN) with 11 papers describing Parkinsonism, Hereditary hemochromatosis (HH) (7 papers), and Wilson’s disease (6 papers). The mean ages of onset of Parkinsonism for these MSDs were 33, 53, and 48 years old, respectively. The Parkinsonian features described in the PKAN and HH patients were invariably atypical while the majority (4/6) of the Wilson’s disease papers had a typical picture. This paper has highlighted a relationship between MSDs and Parkinsonism. However, due to the low-level evidence identified, further research is required to better define what the relationship is.

Glia Maturation Factor Dependent Inhibition of Mitochondrial PGC-1α Triggers Oxidative Stress-Mediated Apoptosis in N27 Rat Dopaminergic Neuronal Cells

Parkinson's disease (PD) is a progressive neurodegenerative disease affecting over five million individuals worldwide. The exact molecular events underlying PD pathogenesis are still not clearly known. Glia maturation factor (GMF), a neuroinflammatory protein in the brain plays an important role in the pathogenesis of PD. Mitochondrial dysfunctions and oxidative stress trigger apoptosis leading to dopaminergic neuronal degeneration in PD. Peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α or PPARGC-α) acts as a transcriptional co-regulator of mitochondrial biogenesis and energy metabolism by controlling oxidative phosphorylation, antioxidant activity, and autophagy. In this study, we found that incubation of immortalized rat dopaminergic (N27) neurons with GMF influences the expression of peroxisome PGC-1α and increases oxidative stress, mitochondrial dysfunction, and apoptotic cell death. We show that incubation with GMF reduces the expression of PGC-1α with concomitant decreases in the mitochondrial complexes. Besides, there is increased oxidative stress and depolarization of mitochondrial membrane potential (MMP) in these cells. Further, GMF reduces tyrosine hydroxylase (TH) expression and shifts Bax/Bcl-2 expression resulting in release of cytochrome-c and increased activations of effector caspase expressions. Transmission electron microscopy analyses revealed alteration in the mitochondrial architecture. Our results show that GMF acts as an important upstream regulator of PGC-1α in promoting dopaminergic neuronal death through its effect on oxidative stress-mediated apoptosis. Our current data suggest that GMF is a critical risk factor for PD and suggest that it could be explored as a potential therapeutic target to inhibit PD progression.

Computational systems biology approaches for Parkinson's disease

Parkinson's disease (PD) is a prime example of a complex and heterogeneous disorder, characterized by multifaceted and varied motor- and non-motor symptoms and different possible interplays of genetic and environmental risk factors. While investigations of individual PD-causing mutations and risk factors in isolation are providing important insights to improve our understanding of the molecular mechanisms behind PD, there is a growing consensus that a more complete understanding of these mechanisms will require an integrative modeling of multifactorial disease-associated perturbations in molecular networks. Identifying and interpreting the combinatorial effects of multiple PD-associated molecular changes may pave the way towards an earlier and reliable diagnosis and more effective therapeutic interventions. This review provides an overview of computational systems biology approaches developed in recent years to study multifactorial molecular alterations in complex disorders, with a focus on PD research applications. Strengths and weaknesses of different cellular pathway and network analyses, and multivariate machine learning techniques for investigating PD-related omics data are discussed, and strategies proposed to exploit the synergies of multiple biological knowledge and data sources. A final outlook provides an overview of specific challenges and possible next steps for translating systems biology findings in PD to new omics-based diagnostic tools and targeted, drug-based therapeutic approaches.

Associations of Spatial Disparities of Alzheimer's Disease Mortality Rates with Soil Selenium and Sulfur Concentrations and Four Common Risk Factors in the United States

BACKGROUND

Associations between environmental factors and spatial disparity of mortality rates of Alzheimer's disease (AD) in the US are not well understood.

OBJECTIVE

To find associations between 41 trace elements, four common risk factors, and AD mortality rates in the48 contiguous states.

METHODS

Isopleth maps of AD mortality rates of the 48 states and associated factors were examined. Correlations between state average AD mortality rates and concentrations of 41 soil elements, wine consumption, percentage of current smokers, obesity, and diagnosed diabetes of the 48 states between 1999 and 2014 were analyzed.

RESULTS

Among 41 elements, soil selenium concentrations have the most significant inverse correlations with AD mortality rates. Rate ratio (RR) of the 6 states with the lowest product of soil selenium and sulfur concentrations is 53% higher than the 6 states with the highest soil selenium sulfur product in the 48 states (RR = 1.53, CI95% 1.51-1.54). Soil tin concentrations have the most significant inverse correlation with AD mortality growth rates between 1999 and 2014, followed by soil sulfur concentrations. Percentages of obesity, diagnosed diabetes, smoking, and wine consumption per capita also correlate significantly with AD mortality growth rates.

CONCLUSIONS

High soil selenium and sulfur concentrations and wine consumption are associated with low AD mortality rates. Given that average soil selenium and sulfur concentrations are indicators of their intakes from food, water, and air by people in a region, long-term exposure to high soil selenium and sulfur concentrations might be beneficial to AD mortality rate reduction in a region.

Association of soil selenium, strontium, and magnesium concentrations with Parkinson's disease mortality rates in the USA

Among the 41 soil elements analyzed from 4856 sites across the contiguous 48 states, average Parkinson's disease (PD) mortality rates between 1999 and 2014 have the most significant positive correlation with the average soil strontium (Sr) concentrations (correlation r = 0.47, significance level p = 0.00), and average PD mortality rates have the most significant inverse correlation with the average soil selenium (Se) concentrations (r = -0.44, p = 0.00). Multivariate regression models indicate that soil Sr and Se concentrations can explain 35.4% of spatial disparities of the state average PD mortality rates between 1999 and 2014 (R ² = 0.354). When the five outlier states were removed from the model, concentrations of soil Sr and Se can explain 62.4% (R ² = 0.624) of the spatial disparities of PD mortality rates of the 43 remaining states. The results also indicate that high soil magnesium (Mg) concentrations suppressed the growth rate of the PD mortality rates between 1999 and 2014 in the 48 states (r = -0.42, p = 0.000). While both Se and Sr have been reported to affect the nervous system, this study is the first study that reported the statistically significant association between the PD mortality rates and soil concentrations of Se, Sr, and Mg in the 48 states. Given that soil elemental concentration in a region is broad indicator of the trace element intake from food, water, and air by people, implications of the results are that high soil Se and Mg concentrations helped reduce the PD mortality rates and benefited the PD patients in the 48 states.

Gut Microbiota Dysfunction as Reliable Non-invasive Early Diagnostic Biomarkers in the Pathophysiology of Parkinson's Disease: A Critical Review

Recent investigations suggest that gut microbiota affects the brain activity through the microbiota-gut-brain axis under both physiological and pathological disease conditions like Parkinson's disease. Further dopamine synthesis in the brain is induced by dopamine producing enzymes that are controlled by gut microbiota via the microbiota-gut-brain axis. Also alpha synuclein deposition and the associated neurodegeneration in the enteric nervous system that increase intestinal permeability, oxidative stress, and local inflammation, accounts for constipation in Parkinson's disease patients. The trigger that causes blood brain barrier leakage, immune cell activation and inflammation, and ultimately neuroinflammation in the central nervous system is believed to be due to the chronic low-grade inflammation in the gut. The non-motor symptoms that appear years before motor symptoms could be reliable early biomarkers, if they could be correlated with the established and reliable neuroimaging techniques or behavioral indices. The future directions should therefore, focus on the exploration of newer investigational techniques to identify these reliable early biomarkers and define the specific gut microbes that contribute to the development of Parkinson's disease. This ultimately should pave the way to safer and novel therapeutic approaches that avoid the complications of the drugs delivered today to the brain of Parkinson's disease patients.

At the Crossroads Between Neurodegeneration and Cancer: A Review of Overlapping Biology and Its Implications

BACKGROUND

A growing body of epidemiologic evidence suggests that neurodegenerative diseases occur less frequently in cancer survivors, and vice versa. While unusual, this inverse comorbidity is biologically plausible and could be explained, in part, by the evolutionary tradeoffs made by neurons and cycling cells to optimize the performance of their very different functions. The two cell types utilize the same proteins and pathways in different, and sometimes opposite, ways. However, cancer and neurodegeneration also share many pathophysiological features.

OBJECTIVE

In this review, we compare three overlapping aspects of neurodegeneration and cancer.

METHOD

First, we contrast the priorities and tradeoffs of dividing cells and neurons and how these manifest in disease. Second, we consider the hallmarks of biological aging that underlie both neurodegeneration and cancer. Finally, we utilize information from genetic databases to outline specific genes and pathways common to both diseases.

CONCLUSION

We argue that a detailed understanding of the biologic and genetic relationships between cancer and neurodegeneration can guide future efforts in designing disease-modifying therapeutic interventions. Lastly, strategies that target aging may prevent or delay both conditions.

Epidemiology of Parkinson's Disease-East Versus West

Background

The cause of PD at present remains unknown. A number of epidemiological studies have been conducted across the globe to ascertain the disease burden and the possible risk factors. In this review, we analyze the various studies from East and West with an aim to observe the important similarities and differences in the disease occurrence and risk factor profile.

Methods

A comprehensive search of descriptive and analytical epidemiological studies was undertaken. The descriptive studies and meta-analysis providing the standardised population rates were selected. The demographics, ethnicity and geographical differences between East and West were analysed. In analytical epidemiology, more established and well-studied non-genetic risk factors for PD were reviewed utilising the prospective cohort studies, case control studies and meta-analysis where available.

Results and Conclusion

PD is more common with increasing age and shows male predominance, which is more obvious in Western studies. The PD prevalence and incidence rates are slightly lower in the East compared to the West. Incidence studies on different ethnic populations in the same country have also found a lower occurrence of PD amongst Easterners compared to Westerners. Setting methodological differences aside, studies from East and West suggest a role for both environmental and genetic risk factors in PD causation. Smoking, caffeine intake and pesticide exposure are well-established risk factors across regions. There is a robust data for dairy product consumption, urate levels and physical activity in the West while studies on certain risk factors like head injury and alcohol show conflicting and mixed results.

Tamoxifen and the Risk of Parkinson's Disease in Female Patients with Breast Cancer in Asian People: A Nationwide Population-Based Study

Purpose

Whether tamoxifen affects the risk of neurodegenerative disease is controversial. This nationwide population-based study investigated the risk of Parkinson's disease (PD) associated with tamoxifen treatment in female patients with breast cancer using Taiwan's National Health Insurance Research Database.

Methods

A total of 5,185 and 5,592 female patients with breast cancer who did and did not, respectively, receive tamoxifen treatment between 2000 and 2009 were included in the study. Patients who subsequently developed PD were identified. A Cox proportional hazards model was used to compare the risk of PD between the aforementioned groups.

Results

Tamoxifen did not significantly increase the crude rate of developing PD in female patients with breast cancer (tamoxifen group, 16/5,169; non-tamoxifen group, 11/5,581; p=0.246). Tamoxifen did not significantly increase the adjusted hazard ratio (aHR) for subsequently developing PD (aHR, 1.310; 95% confidence interval [CI], 0.605-2.837; p=0.494). However, tamoxifen significantly increased the risk of PD among patients followed up for more than 6 years (aHR, 2.435; 95% CI, 1.008-5.882; p=0.048).

Conclusion

Tamoxifen treatment may increase the risk of PD in Taiwanese female patients with breast cancer more than 6 years after the initiation of treatment.

Outdoor Ambient Air Pollution and Neurodegenerative Diseases: the Neuroinflammation Hypothesis

PURPOSE OF REVIEW

Accumulating research indicates that ambient outdoor air pollution impacts the brain and may affect neurodegenerative diseases, yet the potential underlying mechanisms are poorly understood.

RECENT FINDINGS

The neuroinflammation hypothesis holds that elevation of cytokines and reactive oxygen species in the brain mediates the deleterious effects of urban air pollution on the central nervous system (CNS). Studies in human and animal research document that neuroinflammation occurs in response to several inhaled pollutants. Microglia are a prominent source of cytokines and reactive oxygen species in the brain, implicated in the progressive neuron damage in diverse neurodegenerative diseases, and activated by inhaled components of urban air pollution through both direct and indirect pathways. The MAC1-NOX2 pathway has been identified as a mechanism through which microglia respond to different forms of air pollution, suggesting a potential common deleterious pathway. Multiple direct and indirect pathways in response to air pollution exposure likely interact in concert to exert CNS effects.

Astrocytic Expression of GSTA4 Is Associated to Dopaminergic Neuroprotection in a Rat 6-OHDA Model of Parkinson's Disease

Idiopathic Parkinson’s disease (PD) is a complex disease caused by multiple, mainly unknown, genetic and environmental factors. The Ventral root avulsion 1 (Vra1) locus on rat chromosome 8 includes the Glutathione S-transferase alpha 4 (Gsta4) gene and has been identified in crosses between Dark Agouti (DA) and Piebald Virol Glaxo (PVG) rat strains as being associated to neurodegeneration after nerve and brain injury. The Gsta4 protein clears lipid peroxidation by-products, a process suggested to being implicated in PD. We therefore investigated whether PVG alleles in Vra1 are neuroprotective in a toxin-induced model of PD and if this effect is coupled to Gsta4. We performed unilateral 6-hydroxydopamine (6-OHDA) partial lesions in the striatum and compared the extent of neurodegeration in parental (DA) and congenic (DA.VRA1) rats. At 8 weeks after 6-OHDA lesion, DA.VRA1 rats displayed a higher density of remaining dopaminergic fibers in the dorsolateral striatum compared to DA rats (44% vs. 23%, p < 0.01), indicating that Vra1 alleles derived from the PVG strain protect dopaminergic neurons from 6-OHDA toxicity. Gsta4 gene expression levels in the striatum and midbrain were higher in DA.VRA1 congenic rats compared to DA at 2 days post-lesion (p < 0.05). The GSTA4 protein co-localized with astrocytic marker GFAP, but not with neuronal marker NeuN or microglial marker IBA1, suggesting astrocyte-specific expression. This is the first report on Vra1 protective effects on dopaminergic neurodegeneration and encourages further studies on Gsta4 in relation to PD susceptibility.

Gut microbiota: Implications in Parkinson's disease

Gut microbiota (GM) can influence various neurological outcomes, like cognition, learning, and memory. Commensal GM modulates brain development and behavior and has been implicated in several neurological disorders like Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, anxiety, stress and much more. A recent study has shown that Parkinson's disease patients suffer from GM dysbiosis, but whether it is a cause or an effect is yet to be understood. In this review, we try to connect the dots between GM and PD pathology using direct and indirect evidence.

Disease-Modifying Drugs in Parkinson's Disease

Despite an increased understanding of the pathogenesis of Parkinson's disease (PD), and a number of drugs designed to ameliorate symptoms, finding an effective neuroprotective therapy remains elusive. For decades now, several promising agents targeting different pathways have been explored as potential treatments that could help slow disease progression, but these have met with limited success. There are hurdles to overcome, particularly given that there is no exact animal model of PD and also no reliable biomarkers for PD. Without biomarkers, it is not possible to demonstrate, in the context of a clinical trial, that an intervention prevents neuronal degeneration. However, given the compelling scientific rationale of several compounds, an unrelenting pursuit continues. There have been hundreds of human studies looking at neuroprotection in PD. This article will briefly summarize several of the neuroprotective treatments that have been evaluated in large clinical trials, and will also outline some of the newer therapies that are currently being explored.

Gender differences in the adverse events' profile registered in seven observational studies of a wide gender-medicine (MetaGeM) project: the MetaGeM safety analysis

Background

MetaGeM is a wide gender-medicine project comprising post hoc and meta-analyses by gender of clinical outcomes, therapeutic approaches, and safety data from previously conducted observational studies to explore possible gender differences in real-life clinical settings. We report the results of the safety meta-analysis of seven MetaGeM studies, evaluating gender differences in adverse event (AE) incidence and severity.

Methods

Data were collected between February 2002 and July 2013. Male and female patients were compared for the main safety variables, using Student’s t-test, χ² test, or Fisher’s exact test as appropriate. As supportive analysis, a logistic regression model was estimated to evaluate associations between gender and outcome.

Results

In total, 4,870 patients (46% females, 54% males) were included in the analysis; age was higher for females (mean ± standard deviation 61.2±18.3 years) than males (56.3±16.6 years). Overall, 264 AEs were reported (59.1% in males). There were no significant gender differences in the percentage of patients with at least one AE: 3.0% for females versus 3.9% for males, χ² test P>0.05. According to the logistic regression model results, no association between gender and AEs occurrence seems to exist. A statistically significant gender difference in the percentage of drug-related AEs emerged (37.6% in females vs 20.8% in males, χ²P=0.0039). Slightly significantly more AEs in females were addressed with treatment compared with males (78.1% vs 66.7%, χ²P=0.0485). Total serious AEs (SAEs) were 47 (72% in males). The frequency of patients with ≥1 SAE was 0.6% in females versus 1.2% in males (χ² test P=0.0246).

Conclusion

This safety analysis on a large sample of almost 5,000 patients with different diseases and treated with a wide range of different drugs provides a useful overview on possible gender differences in drug tolerability, which may be helpful in more accurately designing future clinical trials from a gender-specific perspective.

Prevalence of small intestinal bacterial overgrowth in Chinese patients with Parkinson's disease

Parkinson's disease (PD) is associated with gastrointestinal motility abnormalities that could favor the occurrence of small intestinal bacterial overgrowth (SIBO). The aim of the study was to assess the prevalence of SIBO in Chinese patients with PD and the potential impact of SIBO on gastrointestinal symptoms and motor function. 182 consecutive Chinese patients with PD patients and 200 sex, age, and BMI-matched subjects without PD were included. All participants underwent the glucose breath test to assess SIBO. We examined the associations between factors and SIBO with logistic regression using SPSS. Fifty-five of the 182 PD patients were SIBO positive (30.2 %; 95 % CI 23.5-36.9 %) compared with 19 of 200 in the control group (9.5 %; 95 % CI 5.4-13.6 %); the difference was statistically significant (P < 0.0001; OR 4.13; 95 % CI 2.34-7.29). Motor fluctuations present was higher in the PD patients with SIBO than in the patients without SIBO (70.9 vs. 45.7 %; P = 0.002). Multivariate analysis showed that disease duration, Hoehn and Yahr stage, Unified PD Rating-III score, Unified PD Rating-IV score, and Non-Motor Symptoms Scale score were the factors associated with the SIBO-positive status in PD patients. SIBO was highly prevalent in PD, and nearly one-third was detected. SIBO was associated with worse gastrointestinal symptoms and worse motor function. Further studies are needed to specify the reasons underlying SIBO and worse motor function in PD.

Newly Diagnosed Anemia Increases Risk of Parkinson's disease: A Population-Based Cohort Study

Anemia and low hemoglobin have been identified to increase Parkinson’s disease (PD) risk. This population-based cohort study investigated PD risk in newly diagnosed anemic patients by using data from the Taiwan National Health Insurance Research Database. All newly diagnosed anemic patients (n = 86,334) without a history of stroke, neurodegenerative diseases, traumatic brain injury, major operations, or blood loss diseases were enrolled. A cohort of nonanemic controls, 1:1 matched with anemic patients on the basis of the demographics and pre-existing medical conditions, was also included. Competing risk analysis was used to evaluate PD risk in anemic patients compared with that in their matched controls. The adjusted hazard ratio (aHR) of PD risk in the anemic patients was 1.36 (95% confidence interval [CI]: 1.22–1.52, p < 0.001). Iron deficiency anemia (IDA) patients tended to exhibit a higher PD risk (aHR: 1.49; 95% CI: 1.24–1.79, p < 0.001). Furthermore, Iron supplement did not significantly affect the PD risk: the aHRs for PD risk were 1.32 (95% CI: 1.07–1.63, p < 0.01) and 1.86 (95% CI: 1.46–2.35, p < 0.001) in IDA patients with and without iron supplementation, respectively. The population-based cohort study indicated newly diagnosed anemia increases PD risk.

Linking Smoking, Coffee, Urate, and Parkinson's Disease - A Role for Gut Microbiota?

While the etiology and pathogenesis of Parkinson's disease (PD) is still obscure, there is evidence for lifestyle factors influencing disease risk. Best established are the inverse associations with smoking and coffee consumption. In other contexts there is evidence that health effects of lifestyle factors may depend on gut microbiome composition. Considering the gastrointestinal involvement in PD, it was recently speculated, that the associations between smoking, coffee, and PD risk could be mediated by gut microbiota. Here we review such a possible mediatory role of gut microbiota taking into account recent findings on microbiome composition in PD and extending the scope also to urate.

Sex and Gender Differences in Central Nervous System-Related Disorders

There are important sex differences in the brain that seem to arise from biology as well as psychosocial influences. Sex differences in several aspects of human behavior and cognition have been reported. Gonadal sex steroids or genes found on sex chromosomes influence sex differences in neuroanatomy, neurochemistry and neuronal structure, and connectivity. There has been some resistance to accept that sex differences in the human brain exist and have biological relevance; however, a few years ago, it has been recommended by the USA National Institute of Mental Health to incorporate sex as a variable in experimental and clinical neurological and psychiatric studies. We here review the clinical literature on sex differences in pain and neurological and psychiatric diseases, with the aim to further stimulate interest in sexual dimorphisms in the brain and brain diseases, possibly encouraging more research in the field of the implications of sex differences for treating these conditions.

Effect of heat waves on morbidity and mortality due to Parkinson's disease in Madrid: A time-series analysis

BACKGROUND

Parkinson's disease (PD) is one of the factors which are associated with a higher risk of mortality during heat waves. The use of certain neuroleptic medications to control some of this disease's complications would appear to be related to an increase in heat-related mortality.

OBJECTIVE

To analyse the relationship and quantify the short-term effect of high temperatures during heat wave episodes in Madrid on daily mortality and PD-related hospital admissions.

METHODS

We used an ecological time-series study and fit Poisson regression models. We analysed the daily number of deaths due to PD and the number of daily PD-related emergency hospital admissions in the city of Madrid, using maximum daily temperature (°C) as the main environmental variable and chemical air pollution as covariates. We controlled for trend, seasonalities, and the autoregressive nature of the series.

RESULTS

There was a maximum daily temperature of 30°C at which PD-related admissions were at a minimum. Similarly, a temperature of 34°C coincides with an increase in the number of admissions. For PD-related admissions, the Relative Risk (RR) for every increase of 1°C above the threshold temperature was 1.13 IC95%:(1.03-1.23) at lags 1 and 5; and for daily PD-related mortality, the RR was 1.14 IC95%:(1.01-1.28) at lag 3.

CONCLUSION

Our results indicate that suffering from PD is a risk factor that contributes to the excess morbidity and mortality associated with high temperatures, and is relevant from the standpoint of public health prevention plans.

Converging roles of ion channels, calcium, metabolic stress, and activity pattern of Substantia nigra dopaminergic neurons in health and Parkinson's disease

Dopamine‐releasing neurons within the Substantia nigra (SN DA) are particularly vulnerable to degeneration compared to other dopaminergic neurons. The age‐dependent, progressive loss of these neurons is a pathological hallmark of Parkinson's disease (PD), as the resulting loss of striatal dopamine causes its major movement‐related symptoms. SN DA neurons release dopamine from their axonal terminals within the dorsal striatum, and also from their cell bodies and dendrites within the midbrain in a calcium‐ and activity‐dependent manner. Their intrinsically generated and metabolically challenging activity is created and modulated by the orchestrated function of different ion channels and dopamine D2‐autoreceptors. Here, we review increasing evidence that the mechanisms that control activity patterns and calcium homeostasis of SN DA neurons are not only crucial for their dopamine release within a physiological range but also modulate their mitochondrial and lysosomal activity, their metabolic stress levels, and their vulnerability to degeneration in PD. Indeed, impaired calcium homeostasis, lysosomal and mitochondrial dysfunction, and metabolic stress in SN DA neurons represent central converging trigger factors for idiopathic and familial PD. We summarize double‐edged roles of ion channels, activity patterns, calcium homeostasis, and related feedback/feed‐forward signaling mechanisms in SN DA neurons for maintaining and modulating their physiological function, but also for contributing to their vulnerability in PD‐paradigms. We focus on the emerging roles of maintained neuronal activity and calcium homeostasis within a physiological bandwidth, and its modulation by PD‐triggers, as well as on bidirectional functions of voltage‐gated L‐type calcium channels and metabolically gated ATP‐sensitive potassium (K‐ATP) channels, and their probable interplay in health and PD.

We propose that SN DA neurons possess several feedback and feed‐forward mechanisms to protect and adapt their activity‐pattern and calcium‐homeostasis within a physiological bandwidth, and that PD‐trigger factors can narrow this bandwidth. We summarize roles of ion channels in this view, and findings documenting that both, reduced as well as elevated activity and associated calcium‐levels can trigger SN DA degeneration.

This article is part of a special issue on Parkinson disease.

Metformin, besides exhibiting strong in vivo anti-inflammatory properties, increases mptp-induced damage to the nigrostriatal dopaminergic system

Metformin is a widely used oral antidiabetic drug with known anti-inflammatory properties due to its action on AMPK protein. This drug has shown a protective effect on various tissues, including cortical neurons. The aim of this study was to determine the effect of metformin on the dopaminergic neurons of the substantia nigra of mice using the animal model of Parkinson's disease based on the injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, an inhibitor of the mitochondrial complex I. In vivo and in vitro experiments were used to study the activation of microglia and the damage of the dopaminergic neurons. Our results show that metformin reduced microglial activation measured both at cellular and molecular levels. Rather than protecting, metformin exacerbated dopaminergic damage in response to MPTP. Our data suggest that, contrary to other brain structures, metformin treatment could be deleterious for the dopaminergic system. Hence, metformin treatment may be considered as a risk factor for the development of Parkinson's disease.

Microglia-blood vessel interactions: a double-edged sword in brain pathologies

Microglia are long-living resident immune cells of the brain, which secure a stable chemical and physical microenvironment necessary for the proper functioning of the central nervous system (CNS). These highly dynamic cells continuously scan their environment for pathogens and possess the ability to react to damage-induced signals in order to protect the brain. Microglia, together with endothelial cells (ECs), pericytes and astrocytes, form the functional blood-brain barrier (BBB), a specialized endothelial structure that selectively separates the sensitive brain parenchyma from blood circulation. Microglia are in bidirectional and permanent communication with ECs and their perivascular localization enables them to survey the influx of blood-borne components into the CNS. Furthermore, they may stimulate the opening of the BBB, extravasation of leukocytes and angiogenesis. However, microglia functioning requires tight control as their dysregulation is implicated in the initiation and progression of numerous neurological diseases. Disruption of the BBB, changes in blood flow, introduction of pathogens in the sensitive CNS niche, insufficient nutrient supply, and abnormal secretion of cytokines or expression of endothelial receptors are reported to prime and attract microglia. Such reactive microglia have been reported to even escalate the damage of the brain parenchyma as is the case in ischemic injuries, brain tumors, multiple sclerosis, Alzheimer's and Parkinson's disease. In this review, we present the current state of the art of the causes and mechanisms of pathological interactions between microglia and blood vessels and explore the possibilities of targeting those dysfunctional interactions for the development of future therapeutics.

Variations in Incidence and Prevalence of Parkinson's Disease in Taiwan: A Population-Based Nationwide Study

Demographic, socioeconomic, and urbanization level variations in Parkinson's disease (PD) are rarely investigated, especially in Asia. This study describes an eight-year trend in PD incidence and prevalence in Taiwan as well as assessing the effects of sociodemographics and urbanization on the incidence and prevalence of PD. The data analyzed were acquired from the Taiwan National Health Insurance Research Database (NHIRD) entries between 2002 and 2009. The calendar year, sex, and age-specific rates were standardized, and the effects of the sociodemographics and urbanization on PD were assessed using Poisson regression analysis. PD incidence and prevalence showed a significantly increasing trend, with a greater magnitude noted for prevalence than for incidence (87.3% versus 9.2%). The PD incidence and prevalence increased with age and were slightly higher in men than in women. The people who were not under the labor force (i.e., dependents) or with lower monthly incomes were at significantly increased adjusted incidence rate ratio (1.50–1.56) and adjusted prevalence rate ratio (1.66–1.71) of PD. Moreover, significantly higher PD incidence and prevalence were noted in areas with lesser urbanization. This information emphasizes the need for preventive and clinical care strategies targeting the segment of Taiwanese population that exhibited a greater incidence and prevalence of PD.