Effect of Coffee, Tobacco, and Alcohol on Parkinson’s Disease

Since the neuroprotective effects of coffee and tobacco on Parkinson’s disease have been reported more than 50 years ago, clinical studies using caffeine and nicotine that were presumed as effective components of coffee and tobacco, respectively, are being actively executed. However, most results failed to show significant differences between the tested and control groups, and some studies revealed contradictory results to the neuroprotection. The reason for this might be that the effective components are something other than nicotine or caffeine, and/or differences to design the clinical trials such as patients recruiting, prescribed amount and period, and analyzed criteria etc. The review summarizes recent results for effect of coffee, tobacco as well as alcohol, representatives of indulgent food, on Parkinson’s disease.

Ciliogenesis is Not Directly Regulated by LRRK2 Kinase Activity in Neurons

Mutations in the Leucine-rich repeat kinase 2 (LRRK2 ) gene are the most prevalent cause of familial Parkinson’s disease (PD). The increase in LRRK2 kinase activity observed in the pathogenic G2019S mutation is important for PD development. Several studies have reported that increased LRRK2 kinase activity and treatment with LRRK2 kinase inhibitors decreased and increased ciliogenesis, respectively, in mouse embryonic fibroblasts (MEFs) and retinal pigment epithelium (RPE) cells. In contrast, treatment of SH-SY5Y dopaminergic neuronal cells with PD-causing chemicals increased ciliogenesis. Because these reports were somewhat contradictory, we tested the effect of LRRK2 kinase activity on ciliogenesis in neurons. In SH-SY5Y cells, LRRK2 inhibitor treatment slightly increased ciliogenesis, but serum starvation showed no increase. In rat primary neurons, LRRK2 inhibitor treatment repeatedly showed no significant change. Little difference was observed between primary cortical neurons prepared from wild-type (WT) and G2019S +/- mice. However, a significant increase in ciliogenesis was observed in G2019S +/- compared to WT human fibroblasts, and this pattern was maintained in neural stem cells (NSCs) differentiated from the induced pluripotent stem cells (iPSCs) prepared from the same WT/G2019S fibroblast pair. NSCs differentiated from G2019S and its gene-corrected WT counterpart iPSCs were also used to test ciliogenesis in an isogenic background. The results showed no significant difference between WT and G2019S regardless of kinase inhibitor treatment and B27-deprivation-mimicking serum starvation. These results suggest that LRRK2 kinase activity may be not a direct regulator of ciliogenesis and ciliogenesis varies depending upon the cell type or genetic background.

Effect of Coffee, Tobacco, and Alcohol on Parkinson’s Disease

Since the neuroprotective effects of coffee and tobacco on Parkinson’s disease have been reported more than 50 years ago, clinical studies using caffeine and nicotine that were presumed as effective components of coffee and tobacco, respectively, are being actively executed. However, most results failed to show significant differences between the tested and control groups, and some studies revealed contradictory results to the neuroprotection. The reason for this might be that the effective components are something other than nicotine or caffeine, and/or differences to design the clinical trials such as patients recruiting, prescribed amount and period, and analyzed criteria etc. The review summarizes recent results for effect of coffee, tobacco as well as alcohol, representatives of indulgent food, on Parkinson’s disease.

Ciliogenesis is Not Directly Regulated by LRRK2 Kinase Activity in Neurons

Mutations in the Leucine-rich repeat kinase 2 (LRRK2 ) gene are the most prevalent cause of familial Parkinson’s disease (PD). The increase in LRRK2 kinase activity observed in the pathogenic G2019S mutation is important for PD development. Several studies have reported that increased LRRK2 kinase activity and treatment with LRRK2 kinase inhibitors decreased and increased ciliogenesis, respectively, in mouse embryonic fibroblasts (MEFs) and retinal pigment epithelium (RPE) cells. In contrast, treatment of SH-SY5Y dopaminergic neuronal cells with PD-causing chemicals increased ciliogenesis. Because these reports were somewhat contradictory, we tested the effect of LRRK2 kinase activity on ciliogenesis in neurons. In SH-SY5Y cells, LRRK2 inhibitor treatment slightly increased ciliogenesis, but serum starvation showed no increase. In rat primary neurons, LRRK2 inhibitor treatment repeatedly showed no significant change. Little difference was observed between primary cortical neurons prepared from wild-type (WT) and G2019S +/- mice. However, a significant increase in ciliogenesis was observed in G2019S +/- compared to WT human fibroblasts, and this pattern was maintained in neural stem cells (NSCs) differentiated from the induced pluripotent stem cells (iPSCs) prepared from the same WT/G2019S fibroblast pair. NSCs differentiated from G2019S and its gene-corrected WT counterpart iPSCs were also used to test ciliogenesis in an isogenic background. The results showed no significant difference between WT and G2019S regardless of kinase inhibitor treatment and B27-deprivation-mimicking serum starvation. These results suggest that LRRK2 kinase activity may be not a direct regulator of ciliogenesis and ciliogenesis varies depending upon the cell type or genetic background.

LRRK2 Kinase Activity Induces Mitochondrial Fission in Microglia via Drp1 and Modulates Neuroinflammation

Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common genetic cause of Parkinson's disease (PD). LRRK2 contains a functional kinase domain and G2019S, the most prevalent LRRK2 pathogenic mutation, increases its kinase activity. LRRK2 regulates mitochondria morphology and autophagy in neurons. LPS treatment increases LRRK2 protein level and mitochondrial fission in microglia, and down-regulation of LRRK2 expression or inhibition of its kinase activity attenuates microglia activation. Here, we evaluated the direct role of LRRK2 G2019S in mitochondrial dynamics in microglia. Initial observation of microglia in G2019S transgenic mice revealed a decrease in mitochondrial area and shortage of microglial processes compared with their littermates. Next, we elucidated the molecular mechanisms of these phenotypes. Treatment of BV2 cells and primary microglia with LPS enhanced mitochondrial fission and increased Drp1, a mitochondrial fission marker, as previously reported. Importantly, both phenotypes were rescued by treatment with GSK2578215A, a LRRK2 kinase inhibitor. Finally, the protein levels of CD68, an active microglia marker, Drp1 and TNF-α were significantly higher in brain lysates of G2019S transgenic mice compared with the levels in their littermates. Taken together, our data suggest that LRRK2 could promote microglial mitochondrial alteration via Drp1 in a kinase-dependent manner, resulting in stimulation of pro-inflammatory responses. This mechanism in microglia might be a potential target to develop PD therapy since neuroinflammation by active microglia is a major symptom of PD.

Extracellular Vesicles and Neurological Diseases

Extracellular vesicles (EVs) are small membranous vesicles that are secreted by various types of cells into biofluid or culture medium. EVs contain deoxyribonucleic acids, messenger ribonucleic acids (RNAs), microRNAs, lipids, and proteins derived from its cells of origin and can transfer those molecules to other targeted cells. Therefore, EVs can play important roles in intercellular communication. The findings of recent studies suggest that EVs can be used to spread protein aggregates in various neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. In addition, it has been recognized that EVs can be used as a material for detecting biomarkers for such diseases or as a therapeutic tool.

The Role of Autophagy Associated With Causative Genes for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative motor disorder, affecting approximately 1% of the population aged > or =60 years. Recent investigations have shown that in addition to motor symptoms such as bradykinesia, resting tremor, and gait instability, PD also causes non-motor symptoms such as insomnia, constipation, depression, and dementia. Most PD cases occurred sporadically, but 5-10% is inherited as familial PD, and several PD-causative genes have been identified and intensively studied. Autophagy is a self-degrading mechanism of balancing the energy source in response to nutrient shortage and various stresses, and is a tightly regulated and complicated process that generates double-membrane organelles. Autophagy failure has recently been observed in both animal PD models and human PD patients. The intention of this review is to introduce recent findings regarding the relationship between causative genetic mutations in PD and autophagy, from a clinical perspective.

LRRK2 phosphorylates Snapin and inhibits interaction of Snapin with SNAP-25

Leucine-rich repeat kinase 2 (LRRK2) is a gene that, upon mutation, causes autosomal-dominant familial Parkinson's disease (PD). Yeast two-hybrid screening revealed that Snapin, a SNAP-25 (synaptosomal-associated protein-25) interacting protein, interacts with LRRK2. An in vitro kinase assay exhibited that Snapin is phosphorylated by LRRK2. A glutathione-S-transferase (GST) pull-down assay showed that LRRK2 may interact with Snapin via its Ras-of-complex (ROC) and N-terminal domains, with no significant difference on interaction of Snapin with LRRK2 wild type (WT) or its pathogenic mutants. Further analysis by mutation study revealed that Threonine 117 of Snapin is one of the sites phosphorylated by LRRK2. Furthermore, a Snapin T117D phosphomimetic mutant decreased its interaction with SNAP-25 in the GST pull-down assay. SNAP-25 is a component of the SNARE (Soluble NSF Attachment protein REceptor) complex and is critical for the exocytosis of synaptic vesicles. Incubation of rat brain lysate with recombinant Snapin T117D, but not WT, protein caused decreased interaction of synaptotagmin with the SNARE complex based on a co-immunoprecipitation assay. We further found that LRRK2-dependent phosphorylation of Snapin in the hippocampal neurons resulted in a decrease in the number of readily releasable vesicles and the extent of exocytotic release. Combined, these data suggest that LRRK2 may regulate neurotransmitter release via control of Snapin function by inhibitory phosphorylation.

Misfolded Proteins in Neurodegenerative Dementias: Molecular Mechanisms

During recent years, there has been remarkable progress with respect to the identification of molecular mechanisms and underlying pathology of neurodegenerative dementias. The latest evidence indicates that a common cause and pathological mechanism of diverse neurodegenerative dementias can be found in the increased production, misfolding, aggregation, and accumulation of specific proteins such as beta-amyloid, tau protein, alpha-synuclein, prion protein, polyglutamine, transactive response DNA-binding protein (TARDBP or TDP-43), or fused in sarcoma (FUS). The conformational variants of these proteins range from small oligomers to the characteristic pathologic inclusions. However, it is noteworthy that a certain pathology can be a hallmark of a certain dementia, but there is a substantial overlap between different pathologies and different types of dementias. In this review, molecular mechanisms and pathologies of different neurodegenerative dementias will be summarized from the perspective of proteins rather than from the viewpoint of individual dementias. We will also review recent evidence surrounding these protein misfolding disorders, the role of toxic oligomers, cell-to-cell transmission, and the links between the misfolded proteins, along with the general therapeutic strategies for the protein misfolding disorders.

Unstable Repeat Expansion in Neurodegenerative Dementias: Mechanisms of Disease

The majority of neurodegenerative dementias are thought to result primarily from the misfolding, aggregation and accumulation of proteins which interfere with protein homeostasis in the brain. Some of them are caused by the expansion of unstable nucleotide repeats, which include Huntington's disease as a prototype. Other neurodevelopmental or neurodegenerative disorders, such as fragile X syndrome, some spinocerebellar ataxias and myotonic dystrophies exhibit cognitive or behavioral deficits as parts of their clinical manifestations. Unstable repeat expansions include trinucleotide, tetranucleotide, and pentanucleotide. Recently hexanucleotide repeat expansion in frontotemporal dementia and amyotrophic lateral sclerosis was identified. The pathogenic mechanisms for these repeat disorders include either loss of protein function or gain of function at the protein or RNA levels. The aim of this article is to review proposed mechanisms by which unstable repeat expansions give rise to degeneration of brain with the hope of understanding the diseases and providing insights into the areas of therapeutic intervention. We will review these potential mechanisms in the context of fragile X syndrome, Huntington's disease, spinocerebellar ataxias, myotonic dystrophy, and frontotemporal dementia and amyotrophic lateral sclerosis. We will also discuss the potential targets for therapeutic intervention.

Unstable Repeat Expansion in Neurodegenerative Dementias: Mechanisms of Disease

The majority of neurodegenerative dementias are thought to result primarily from the misfolding, aggregation and accumulation of proteins which interfere with protein homeostasis in the brain. Some of them are caused by the expansion of unstable nucleotide repeats, which include Huntington's disease as a prototype. Other neurodevelopmental or neurodegenerative disorders, such as fragile X syndrome, some spinocerebellar ataxias and myotonic dystrophies exhibit cognitive or behavioral deficits as parts of their clinical manifestations. Unstable repeat expansions include trinucleotide, tetranucleotide, and pentanucleotide. Recently hexanucleotide repeat expansion in frontotemporal dementia and amyotrophic lateral sclerosis was identified. The pathogenic mechanisms for these repeat disorders include either loss of protein function or gain of function at the protein or RNA levels. The aim of this article is to review proposed mechanisms by which unstable repeat expansions give rise to degeneration of brain with the hope of understanding the diseases and providing insights into the areas of therapeutic intervention. We will review these potential mechanisms in the context of fragile X syndrome, Huntington's disease, spinocerebellar ataxias, myotonic dystrophy, and frontotemporal dementia and amyotrophic lateral sclerosis. We will also discuss the potential targets for therapeutic intervention.

Coordinate Regulation of Neurite Outgrowth by LRRK2 and Its Interactor, Rab5

Neurite outgrowth and its maintenance are essential aspects of neuronal cells for their connectivity and communication with other neurons. Recent studies showed that over-expression of either leucine-rich repeat kinase 2 (LRRK2), whose mutations are associated with familial Parkinson's disease (PD), or Rab5b, an early endosomal marker protein, induces reduction in neurite length. Based on our recent findings that LRRK2 co-localizes and interacts with Rab5, we tested the hypothesis that LRRK2 and Rab5 may functionally interplay while controlling neurite outgrowth. Firstly, we confirmed previous reports that over-expression of either the LRRK2 PD-specific G2019S mutant or the Rab5 constitutively active Q79L mutant, but not of dominant negative N133I mutant, significantly reduces neurite outgrowth. Secondly, when over-expression of either LRRK2 wild type (WT) or G2019S was accompanied with over-expression of one of the Rab5 variants (WT, Q79L and N133I), or with down-regulation of Rab5, the reduction extent of its neurite length was similar to that of cells over-expressing LRRK2 alone, regardless of Rab5's status. Finally, we observed similar patterns of neurite length regulation in embryonic rat hippocampal neuron cultures. Taken together, our results suggest that LRRK2 and Rab5 functionally coordinate their regulation of neurite outgrowth and that LRRK2 is a more critical factor than Rab5.

Genes Causing Familial Parkinson's Disease / 대한정신약물학회지

Extended treatment using specific medicines for Parkinson's disease (PD) or psychotic disorders often induces symptoms related to psychotic disorders or PD, respectively. PD is the second most common neurodegenerative disease. Most cases of PD occur sporadically, but approximately 5-10% of cases are inherited as familial PD (FPD). Identification of the genes responsible for FPD, as well as their function, is essential to clarify the pathogenic mechanism of PD. Recent genomic analyses using samples obtained from patients with FPD have mapped 13 PARK loci and have identified SNCA, LRRK2, parkin, PINK1, DJ-1, ATP13A2 and UCHL1 as genes causing PD in those loci. This review discusses the results of recent studies on these PD genes.