Protein degradation, aggregation, and misfolding

Syagrus coronata fixed oil prevents rotenone-induced movement disorders and oxidative stress in Drosophila melanogaster

One prominent aspect of Parkinson's disease (PD) is the presence of elevated levels of free radicals, including reactive oxygen species (ROS). Syagrus coronata (S. coronata), a palm tree, exhibits antioxidant activity attributed to its phytochemical composition, containing fatty acids, polyphenols, and flavonoids. The aim of this investigation was to examine the potential neuroprotective effects of S. coronata fixed oil against rotenone-induced toxicity using Drosophila melanogaster. Young Drosophila specimens (3-4 d old) were exposed to a diet supplemented with rotenone (50 µM) for 7 d with and without the inclusion of S. coronata fixed oil (0.2 mg/g diet). Data demonstrated that rotenone exposure resulted in significant locomotor impairment and increased mortality rates in flies. Further, rotenone administration reduced total thiol levels but elevated lipid peroxidation, iron (Fe) levels, and nitric oxide (NO) levels while decreasing the reduced capacity of mitochondria. Concomitant administration of S. coronata exhibited a protective effect against rotenone, as evidenced by a return to control levels of Fe, NO, and total thiols, lowered lipid peroxidation levels, reversed locomotor impairment, and enhanced % cell viability. Molecular docking of the oil lipidic components with antioxidant enzymes showed strong binding affinity to superoxide dismutase (SOD) and glutathione peroxidase (GPX1) enzymes. Overall, treatment with S. coronata fixed oil was found to prevent rotenone-induced movement disorders and oxidative stress in Drosophila melanogaster.

Exploring the Efficient Natural Products for the Therapy of Parkinson's Disease via Drosophila Melanogaster (Fruit Fly) Models

Parkinson's disease (PD) is a severe neurodegenerative disorder, partly attributed to mutations, environmental toxins, oxidative stress, abnormal protein aggregation, and mitochondrial dysfunction. However, the precise pathogenesis of PD and its treatment strategy still require investigation. Fortunately, natural products have demonstrated potential as therapeutic agents for alleviating PD symptoms due to their neuroprotective properties. To identify promising lead compounds from herbal medicines' natural products for PD management and understand their modes of action, suitable animal models are necessary. Drosophila melanogaster (fruit fly) serves as an essential model for studying genetic and cellular pathways in complex biological processes. Diverse Drosophila PD models have been extensively utilized in PD research, particularly for discovering neuroprotective natural products. This review emphasizes the research progress of natural products in PD using the fruit fly PD model, offering valuable insights into utilizing invertebrate models for developing novel anti-PD drugs.

The Beneficial and Adverse Effects of Autophagic Response to Caloric Restriction and Fasting

Each cell is equipped with a conserved housekeeping mechanism, known as autophagy, to recycle exhausted materials and dispose of injured organelles via lysosomal degradation. Autophagy is an early-stage cellular response to stress stimuli in both physiological and pathological situations. It is thought that the promotion of autophagy flux prevents host cells from subsequent injuries by removing damaged organelles and misfolded proteins. As a correlate, the modulation of autophagy is suggested as a therapeutic approach in diverse pathological conditions. Accumulated evidence suggests that intermittent fasting or calorie restriction can lead to the induction of adaptive autophagy and increase longevity of eukaryotic cells. However, prolonged calorie restriction with excessive autophagy response is harmful and can stimulate a type II autophagic cell death. Despite the existence of a close relationship between calorie deprivation and autophagic response in different cell types, the precise molecular mechanisms associated with this phenomenon remain unclear. Here, we aimed to highlight the possible effects of prolonged and short-term calorie restriction on autophagic response and cell homeostasis.

Extracellular vesicles and Alzheimer's disease in the novel era of Precision Medicine: implications for disease progression, diagnosis and treatment

Extracellular vesicles (EVs), secreted membranous nano-sized particles, are critical intercellular messengers participating in nervous system homeostasis, while recent evidence implicates EVs in Alzheimer's disease (AD) pathogenesis. Specifically, small EVs have been shown to spread toxic proteins, induce neuronal loss, and contribute to neuroinflammation and AD progression. On the other hand, EVs can reduce amyloid-beta deposition and transfer neuroprotective substances between cells, mitigating disease mechanisms. In addition to their roles in AD pathogenesis, EVs also exhibit great potential for the diagnosis and treatment of other brain disorders, representing an advantageous tool for Precision Medicine. Herein, we summarize the contribution of small EVs to AD-related mechanisms and disease progression, as well as their potential as diagnostic and therapeutic agents for AD.

Norovirus Intestinal Infection and Lewy Body Disease in an Older Patient with Acute Cognitive Impairment

We present a case report on an older woman with unspecific symptoms and predominant long-term gastrointestinal disturbances, acute overall health deterioration with loss of autonomy for daily activities, and cognitive impairment. Autopsy revealed the presence of alpha-synuclein deposits spread into intestinal mucosa lesions, enteric plexuses, pelvic and retroperitoneal nerves and ganglia, and other organs as well as Lewy pathology in the central nervous system (CNS). Moreover, we isolated norovirus from the patient, indicating active infection in the colon and detected colocalization of norovirus and alpha-synuclein in different regions of the patient’s brain. In view of this, we report a concomitant norovirus infection with synthesis of alpha-synuclein in the gastrointestinal mucosa and Lewy pathology in the CNS, which might support Braak’s hypothesis about the pathogenic mechanisms underlying synucleinopathies.

Dual Effects: Intrastriatal Injection of α-syn N103/tau N368 Preformed Fibrils Promotes Endogenous α-synuclein Aggregates in the Proximal Colon

BACKGROUND

Pathological changes in the brain can affect the gastrointestinal tract, whereas there is less evidence regarding the brain-gut axis.

OBJECTIVE

To identify whether cerebral endogenous phosphorylated α-synuclein induces gastrointestinal dysfunction via the brain-gut axis, mediated by the vagus nerve.

METHODS

α-syn N103/tau N368 preformed fibrils were injected into the dorsal lateral striatum of rodents, and the cerebral and colonic synucleinopathies and changes in the enteric nervous system were analyzed. Moreover, subdiaphragmatic vagotomy was conducted to confirm the role of the vagus nerve in brain-gut propagation.

RESULTS

An anterograde propagation of phosphorylated α-synuclein from the brain to the proximal colon mainly via the vagus nerve was observed at one month. The accumulation of phosphorylated α-synuclein was detected in the proximal colon over time, accompanied by infiltration of macrophages and eosinophils in the mucosa and submucosa. Upon injection with lower doses of preformed fibrils, the accumulation of phosphorylated α-synuclein and dopaminergic neuron loss was reduced to levels consistent with control at six months, while the expression levels of GFAP, Iba-1, and IL-6 increased. Under high preformed fibrils dose conditions, fecal traits and gastrointestinal motility were significantly reduced at six months, and aggregations of phosphorylated α-synuclein and an increasing level of IL-1β appeared.

CONCLUSION

Induced endogenous α-synuclein can quickly propagate into the proximal colon mainly via the vagus nerve. Injections of low doses of preformed fibrils can elicit recovery of the enteric nervous system and degradation of α-synuclein aggregates whereas high doses cause accumulation of pathological α-synuclein, enteric inflammation, and prominent gastrointestinal dysfunction.

MMM - The molecular model of memory

Identifying mechanisms underlying neurons ability to process information including acquisition, storage, and retrieval plays an important role in the understanding of the different types of memory, pathogenesis of many neurological diseases affecting memory and therapeutic target discovery. However, the traditional understanding of the mechanisms of memory associated with the electrical signals having a unique combination of frequency and amplitude does not answer the question how the memories can survive for life-long periods of time, while exposed to synaptic noise. Recent evidence suggests that, apart from neuronal circuits, a diversity of the molecular memory (MM) carriers, are essential for memory performance. The molecular model of memory (MMM) is proposed, according to which each item of incoming information (the elementary memory item - eMI) is encoded by both circuitries, with the unique for a given MI electrical parameters, and also the MM carriers, unique by its molecular composition. While operating as the carriers of incoming information, the MMs, are functioning within the neuron plasma membrane. Inactive (latent) initially, during acquisition each of the eMIs is activated to become a virtual copy of some real fact or events bygone. This activation is accompanied by the considerable remodeling of the MM molecule associated with the resonance effect.

Loss-of-function mutations in the co-chaperone protein BAG5 cause dilated cardiomyopathy requiring heart transplantation

Dilated cardiomyopathy (DCM) is a major cause of heart failure, characterized by ventricular dilatation and systolic dysfunction. Familial DCM is reportedly caused by mutations in more than 50 genes, requiring precise disease stratification based on genetic information. However, the underlying genetic causes of 60 to 80% of familial DCM cases remain unknown. Here, we identified that homozygous truncating mutations in the gene encoding Bcl-2-associated athanogene (BAG) co-chaperone 5 (BAG5) caused inherited DCM in five patients among four unrelated families with complete penetrance. BAG5 acts as a nucleotide exchange factor for heat shock cognate 71 kDa protein (HSC70), promoting adenosine diphosphate release and activating HSC70-mediated protein folding. Bag5 mutant knock-in mice exhibited ventricular dilatation, arrhythmogenicity, and poor prognosis under catecholamine stimulation, recapitulating the human DCM phenotype, and administration of an adeno-associated virus 9 vector carrying the wild-type BAG5 gene could fully ameliorate these DCM phenotypes. Immunocytochemical analysis revealed that BAG5 localized to junctional membrane complexes (JMCs), critical microdomains for calcium handling. Bag5-mutant mouse cardiomyocytes exhibited decreased abundance of functional JMC proteins under catecholamine stimulation, disrupted JMC structure, and calcium handling abnormalities. We also identified heterozygous truncating mutations in three patients with tachycardia-induced cardiomyopathy, a reversible DCM subtype associated with abnormal calcium homeostasis. Our study suggests that loss-of-function mutations in BAG5 can cause DCM, that BAG5 may be a target for genetic testing in cases of DCM, and that gene therapy may potentially be a treatment for this disease.

Post-Ischemic Treatment of Recombinant Human Secretory Leukocyte Protease Inhibitor (rhSLPI) Reduced Myocardial Ischemia/Reperfusion Injury

Myocardial ischemia/reperfusion (I/R) injury is a major cause of mortality and morbidity worldwide. Among factors contributing to I/R injury, proteolytic enzymes could also cause cellular injury, expand the injured area and induce inflammation, which then lead to cardiac dysfunction. Therefore, protease inhibition seems to provide therapeutic benefits. Previous studies showed the cardioprotective effect of secretory leukocyte protease inhibitor (SLPI) against myocardial I/R injury. However, the effect of a post-ischemic treatment with SLPI in an in vivo I/R model has never been investigated. In the present study, recombinant human (rh) SLPI (rhSLPI) was systemically injected during coronary artery occlusion or at the onset of reperfusion. The results show that post-ischemic treatment with rhSLPI could significantly reduce infarct size, Lactate Dehydrogenase (LDH) and Creatine kinase-MB (CK-MB) activity, inflammatory cytokines and protein carbonyl levels, as well as improving cardiac function. The cardioprotective effect of rhSLPI is associated with the attenuation of p38 MAPK phosphorylation, Bax, caspase-3 and -8 protein levels and enhancement of pro-survival kinase Akt and ERK1/2 phosphorylation. In summary, this is the first report showing the cardioprotective effects against myocardial I/R injury of post-ischemic treatments with rhSLPI in vivo. Thus, these results suggest that SLPI could be used as a novel therapeutic strategy to reduce myocardial I/R injury.

Differences in network controllability and regional gene expression underlie hallucinations in Parkinson's disease

Visual hallucinations are common in Parkinson's disease and are associated with poorer prognosis. Imaging studies show white matter loss and functional connectivity changes with Parkinson's visual hallucinations, but the biological factors underlying selective vulnerability of affected parts of the brain network are unknown. Recent models for Parkinson's disease hallucinations suggest they arise due to a shift in the relative effects of different networks. Understanding how structural connectivity affects the interplay between networks will provide important mechanistic insights. To address this, we investigated the structural connectivity changes that accompany visual hallucinations in Parkinson's disease and the organizational and gene expression characteristics of the preferentially affected areas of the network. We performed diffusion-weighted imaging in 100 patients with Parkinson's disease (81 without hallucinations, 19 with visual hallucinations) and 34 healthy age-matched controls. We used network-based statistics to identify changes in structural connectivity in Parkinson's disease patients with hallucinations and performed an analysis of controllability, an emerging technique that allows quantification of the influence a brain region has across the rest of the network. Using these techniques, we identified a subnetwork of reduced connectivity in Parkinson's disease hallucinations. We then used the Allen Institute for Brain Sciences human transcriptome atlas to identify regional gene expression patterns associated with affected areas of the network. Within this network, Parkinson's disease patients with hallucinations showed reduced controllability (less influence over other brain regions), than Parkinson's disease patients without hallucinations and controls. This subnetwork appears to be critical for overall brain integration, as even in controls, nodes with high controllability were more likely to be within the subnetwork. Gene expression analysis of gene modules related to the affected subnetwork revealed that down-weighted genes were most significantly enriched in genes related to mRNA and chromosome metabolic processes (with enrichment in oligodendrocytes) and upweighted genes to protein localization (with enrichment in neuronal cells). Our findings provide insights into how hallucinations are generated, with breakdown of a key structural subnetwork that exerts control across distributed brain regions. Expression of genes related to mRNA metabolism and membrane localization may be implicated, providing potential therapeutic targets.

Ameliorative effects of flavonoids and polyketides on the rotenone induced Drosophila model of Parkinson's disease

Parkinson's disease (PD) is a movement disorder associated with the progressive loss of dopaminergic neurons (DA). PD treatment remains unsatisfactory as the current synthetic drugs in clinical use relies on managing only motor symptoms. This study investigated antioxidant potentials of selected compounds namely, 5,6,7,4'-tetramethoxyflavone (1), 6-hydroxy-2,3,4,4'-tetramethoxychalcone (2), 6-methoxyhamiltone A (3), diosquinone (4) and toussantine D (5) against rotenone (6) induced PD in Drosophila melanogaster. Toxicity of these compounds was conducted by monitoring flies' survival for seven days and determining the lethal concentrations (LC₅₀). Whereas compound 1 had LC₅₀ value of 91.3 μM within three days, compounds 2, 3, 4, and 5 had LC₅₀ values of 87.2, 58.0, 64.0 and > 1000 μM, respectively on the seventh day of the experiment. We exposed flies (1-4 days old) to 500 μM rotenone and co-treated with different doses of the test compounds in the diet for seven days at final concentrations of 11.0, 43.6 and 87.2 μM for compounds 2 and 3. The concentrations used for compound 4 were 8.0, 32.0 and 64.0 μM, while 250, 500 and 1000 μM were used for compound 5. Rotenone fed flies showed impaired climbing ability compared to control flies, the phenotype that was rescued by the treatment of tested phytochemicals. Rotenone toxicity also increased malondialdehyde levels assayed by lipid peroxidation in the brain tissues relative to control flies. This effect was reduced in flies exposed to rotenone and co-treated with the phytochemicals. Moreover, expression levels of mRNA of antioxidant enzymes; superoxide dismutase and catalase were elevated in flies exposed to rotenone and normalized in flies that were co-treated with tested compounds. Besides compound 1, this study provides overall evidence that the tested flavonoids and polyketides ameliorated the rotenone provoked neurotoxicity in D. melanogaster by battling the induced oxidative stress in brain cells including DA neurons and hence rescue the locomotor behaviour deficits.

The contribution of Parkin, PINK1 and DJ-1 genes to selective neuronal degeneration in Parkinson's disease

Parkinson's disease (PD) is characterised by selective and severe degeneration of the substantia nigra pars compacta and the locus coeruleus (LC), which underlies the most prominent symptoms. Although α-synuclein accumulation has long been established to play a causal role in the disease, it alone cannot explain the selective degenerative pattern. Recent evidence shows that the selective vulnerability could arise due to the large presence of cytosolic catecholamines and Ca2+ ions in the substantia nigra pars compacta and LC specifically that can be aberrantly affected by α-synuclein accumulation. Moreover, each has its own toxic potential, and disturbance of one can exacerbate the toxic effects of the others. This presents a mechanism unique to these areas that can lead to a vicious degenerative cycle. Interestingly, in familial variants of PD, the exact same brain areas are affected, implying the underlying process is likely the same. However, the exact disease mechanisms of many of these genetic variants remain unclear. Here, we review the effects of the PD-related genes Parkin, PINK1 and DJ-1. We establish that these mutant varieties can set in motion the same degenerative process involving α-synuclein, cytosolic catecholamines and Ca2+ . Additionally, we show indications that model organisms might not accurately represent all components of this central mechanism, explaining why Parkin, PINK1 and DJ-1 model organisms often lack a convincing PD-like phenotype.

CRISPR/Cas9-induced vitellogenin knockout lead to incomplete embryonic development in Plutella xylostella

Vitellogenin (Vg) is important for insect egg maturation and embryo development. In the present study, we characterized the molecular structure and expression profile of Vg gene, and analyzed its reproductive functions in diamondback moth, Plutella xylostella (L.), a destructive pest of cruciferous crops, using CRISPR/Cas9 system. The P. xylostella Vg (PxVg) included all conserved domains and motifs that were commonly found in most insect Vgs except for the polyserine tract. PxVg gene was highly expressed in female pupae and adults. PxVg protein was detected in eggs and female adults. PxVg was mainly expressed in the fat body and its protein was detected in most tissues, except in the midgut. CRISPR/Cas9-induced PxVg knockout successfully constructed a homozygous mutant strain with a 5-base pair nucleotide deletion. No PxVg protein was found in the mutant individuals and in their ovaries. There were no significant differences between wild (WT) and mutant (Mut-5) types of P. xylostella in terms of ovariole length and the number of fully developed oocytes in newly emerged females. No significant difference was observed in the number of eggs laid within two days, but there was a lower egg hatchability (84% for WT vs. 47% for Mut-5). This is the first study presenting the functions of Vg in ovary development, egg maturation, oviposition and embryonic development of P. xylostella. Our results suggest that the reproductive functions of Vg may be species-specific in insects. It is possible that Vg may not be the major egg yolk protein precursor in P. xylostella. Other "functional Vgs" closely involved in the yolk formation and oogenesis would need to be further explored in P. xylostella.

Measuring biological aging in humans: A quest

The global population of individuals over the age of 65 is growing at an unprecedented rate and is expected to reach 1.6 billion by 2050. Most older individuals are affected by multiple chronic diseases, leading to complex drug treatments and increased risk of physical and cognitive disability. Improving or preserving the health and quality of life of these individuals is challenging due to a lack of well-established clinical guidelines. Physicians are often forced to engage in cycles of "trial and error" that are centered on palliative treatment of symptoms rather than the root cause, often resulting in dubious outcomes. Recently, geroscience challenged this view, proposing that the underlying biological mechanisms of aging are central to the global increase in susceptibility to disease and disability that occurs with aging. In fact, strong correlations have recently been revealed between health dimensions and phenotypes that are typical of aging, especially with autophagy, mitochondrial function, cellular senescence, and DNA methylation. Current research focuses on measuring the pace of aging to identify individuals who are "aging faster" to test and develop interventions that could prevent or delay the progression of multimorbidity and disability with aging. Understanding how the underlying biological mechanisms of aging connect to and impact longitudinal changes in health trajectories offers a unique opportunity to identify resilience mechanisms, their dynamic changes, and their impact on stress responses. Harnessing how to evoke and control resilience mechanisms in individuals with successful aging could lead to writing a new chapter in human medicine.

Role of Dynein and Dynactin (DCTN-1) in Neurodegenerative Diseases

The pathophysiology and concept of degeneration in central nervous system is very complex and overwhelming at times. There is a complex mechanism which exists among different molecules in the cytoplasm of cell bodies of neurons, antegrade and retrograde axonal transport of cargoes and accumulation of certain substances and proteins which can influence the excitatory neurotransmitter like glutamate initiating the process of neurodegeneration. Neurons have extensive processes and communication between those processes and the cell body is crucial to neuronal function, viability and survival over time with progression of age. Researchers believe neurons are uniquely dependent on microtubule-based cargo transport. There is enough evidence to support that deficits in retrograde axonal transport contribute to pathogenesis in multiple neurodegenerative diseases. Cytoplasmic dynein and its regulation by Dynactin (DCTN1) is the major molecular motor cargo involved in autophagy, mitosis and neuronal cell survival. Mutation in dynactin gene located in 2p13.1,is indeed studied very extensively and is considered to be involved directly or indirectly to various conditions like Perry syndrome, familial and sporadic Amyotrophic lateral sclerosis, Hereditary spastic paraplegia, Spinocerebellar Ataxia (SCA-5), Huntingtons disease, Alzheimers disease, Charcot marie tooth disease, Hereditary motor neuropathy 7B, prion disease, parkinsons disease, malformation of cortical development, polymicrogyria to name a few with exception of Multiple Sclerosis (MS).

Diabetes, a Contemporary Risk for Parkinson's Disease: Epidemiological and Cellular Evidences

Diabetes mellitus (DM), a group of diseases characterized by defective glucose metabolism, is the most widespread metabolic disorder affecting over 400 million adults worldwide. This pathological condition has been implicated in the pathogenesis of a number of central encephalopathies and peripheral neuropathies. In further support of this notion, recent epidemiological evidence suggests a link between DM and Parkinson’s disease (PD), with hyperglycemia emerging as one of the culprits in neurodegeneration involving the nigrostriatal pathway, the neuroanatomical substrate of the motor symptoms affecting parkinsonian patients. Indeed, dopaminergic neurons located in the mesencephalic substantia nigra appear to be particularly vulnerable to oxidative stress and degeneration, likely because of their intrinsic susceptibility to mitochondrial dysfunction, which may represent a direct consequence of hyperglycemia and hyperglycemia-induced oxidative stress. Other pathological pathways induced by increased intracellular glucose levels, including the polyol and the hexosamine pathway as well as the formation of advanced glycation end-products, may all play a pivotal role in mediating the detrimental effects of hyperglycemia on nigral dopaminergic neurons. In this review article, we will examine the epidemiological as well as the molecular and cellular clues supporting the potential susceptibility of nigrostriatal dopaminergic neurons to hyperglycemia.

Gene-environment interaction and Mendelian randomisation

Genetic factors only account for up to a third of the cases of Parkinson's disease (PD), while the remaining cases are of unknown aetiology. Environmental exposures (such as pesticides or heavy metals) and the interaction with genetic susceptibility factors (summarized in the concept of impaired xenobiotic metabolism) are believed to play a major role in the mechanisms of neurodegeneration. Beside of the classical association studies (e.g. genome-wide association studies), a novel approach to investigate environmental risk factors are Mendelian randomisation studies. This review explores the gene-environment interaction and the gain of Mendelian randomisation studies in assessing causalities of modifiable risk factors for PD.

Using proteomics to identify ubiquitin ligase-substrate pairs: how novel methods may unveil therapeutic targets for neurodegenerative diseases

Ubiquitin ligases play an integral role in fine-tuning signaling cascades necessary for normal cell function. Aberrant regulation of ubiquitin ligases has been implicated in several neurodegenerative diseases, generally, due to mutations within the E3 ligase itself. Several proteomic-based methods have recently emerged to facilitate the rapid identification of ligase-substrate pairs-a previously challenging feat due to the transient nature of ligase-substrate interactions. These novel methods complement standard immunoprecipitations (IPs) and include proximity-dependent biotin identification (BioID), ubiquitin ligase-substrate trapping, tandem ubiquitin-binding entities (TUBEs), and a molecular trapping unit known as the NEDDylator. The implementation of these techniques is expected to facilitate the rapid identification of novel substrates of E3 ubiquitin ligases, a process that is likely to enhance our understanding of neurodegenerative diseases and highlight novel therapeutic targets for the treatment of neurodegenerative diseases.

Tribolium castaneum as a whole-animal screening system for the detection and characterization of neuroprotective substances

Parkinson's disease (PD) is a movement disorder caused by the progressive loss of dopaminergic neurons. Natural antioxidants and plant extracts with neuroprotective properties offer a promising new therapeutic approach for PD patients, but a suitable large-scale screening system is required for their discovery and preclinical analysis. Here we used the red flour beetle (Tribolium castaneum ) as a whole-animal screening system for the detection and characterization of neuroprotective substances. Paraquat was added to the diet of adult beetles to induce PD-like symptoms, which were quantified using a novel positive geotaxis behavioral assay. These paraquat-induced behavioral changes were reduced in beetles fed on diets supplemented with l-dihydroxyphenylalanine, ascorbic acid, curcumin, hempseed flour, or the Chinese herb gou-teng. T. castaneum is, therefore, a valuable model for the screening of neuroprotective substances in chemical libraries and plant extracts and could be developed as a model for the preclinical testing of therapeutic candidates for the treatment of neurodegenerative diseases, such as PD.

Autoimmunity in Parkinson's Disease: The Role of α-Synuclein-Specific T Cells

Evidence from a variety of studies implicates a role for the adaptive immune system in Parkinson's disease (PD). Similar to multiple sclerosis (MS) patients who display a high number of T cells in the brain attacking oligodendrocytes, PD patients show higher numbers of T cells in the ventral midbrain than healthy, age-matched controls. Mouse models of the disease also show the presence of T cells in the brain. The role of these infiltrating T cells in the propagation of disease is controversial; however, recent studies indicate that they may be autoreactive in nature, recognizing disease-altered self-proteins as foreign antigens. T cells of PD patients can generate an autoimmune response to α-synuclein, a protein that is aggregated in PD. α-Synuclein and other proteins are post-translationally modified in an environment in which protein processing is altered, possibly leading to the generation of neo-epitopes, or self-peptides that have not been identified by the host immune system as non-foreign. Infiltrating T cells may also be responding to such modified proteins. Genome-wide association studies (GWAS) have shown associations of PD with haplotypes of major histocompatibility complex (MHC) class II genes, and a polymorphism in a non-coding region that may increase MHC class II in PD patients. We speculate that the inflammation observed in PD may play both pathogenic and protective roles. Future studies on the adaptive immune system in neurodegenerative disorders may elucidate steps in disease pathogenesis and assist with the development of both biomarkers and treatments.

Time-Resolved NMR Analysis of Proteolytic α-Synuclein Processing in vitro and in cellulo

Targeted proteolysis of the disordered Parkinson's disease protein alpha-synuclein (αSyn) constitutes an important event under physiological and pathological cell conditions. In this work, site-specific αSyn cleavage by different endopeptidases in vitro and by endogenous proteases in extracts of challenged and unchallenged cells was studied by time-resolved NMR spectroscopy. Specifically, proteolytic processing was monitored under neutral and low pH conditions and in response to Rotenone-induced oxidative stress. Further, time-dependent degradation of electroporation-delivered αSyn in intact SH-SY5Y and A2780 cells was analyzed. Results presented here delineate a general framework for NMR-based proteolysis studies in vitro and in cellulo, and confirm earlier reports pertaining to the exceptional proteolytic stability of αSyn under physiological cell conditions. However, experimental findings also reveal altered protease susceptibilities in selected mammalian cell lines and upon induced cell stress.

The effect of fasting or calorie restriction on autophagy induction: A review of the literature

Autophagy is a lysosomal degradation process and protective housekeeping mechanism to eliminate damaged organelles, long-lived misfolded proteins and invading pathogens. Autophagy functions to recycle building blocks and energy for cellular renovation and homeostasis, allowing cells to adapt to stress. Modulation of autophagy is a potential therapeutic target for a diverse range of diseases, including metabolic conditions, neurodegenerative diseases, cancers and infectious diseases. Traditionally, food deprivation and calorie restriction (CR) have been considered to slow aging and increase longevity. Since autophagy inhibition attenuates the anti-aging effects of CR, it has been proposed that autophagy plays a substantive role in CR-mediated longevity. Among several stress stimuli inducers of autophagy, fasting and CR are the most potent non-genetic autophagy stimulators, and lack the undesirable side effects associated with alternative interventions. Despite the importance of autophagy, the evidence connecting fasting or CR with autophagy promotion has not previously been reviewed. Therefore, our objective was to weigh the evidence relating the effect of CR or fasting on autophagy promotion. We conclude that both fasting and CR have a role in the upregulation of autophagy, the evidence overwhelmingly suggesting that autophagy is induced in a wide variety of tissues and organs in response to food deprivation.

Trehalose reduces retinal degeneration, neuroinflammation and storage burden caused by a lysosomal hydrolase deficiency

The accumulation of undegraded molecular material leads to progressive neurodegeneration in a number of lysosomal storage disorders (LSDs) that are caused by functional deficiencies of lysosomal hydrolases. To determine whether inducing macroautophagy/autophagy via small-molecule therapy would be effective for neuropathic LSDs due to enzyme deficiency, we treated a mouse model of mucopolysaccharidosis IIIB (MPS IIIB), a storage disorder caused by deficiency of the enzyme NAGLU (alpha-N-acetylglucosaminidase [Sanfilippo disease IIIB]), with the autophagy-inducing compound trehalose. Treated naglu^{–/ –} mice lived longer, displayed less hyperactivity and anxiety, retained their vision (and retinal photoreceptors), and showed reduced inflammation in the brain and retina. Treated mice also showed improved clearance of autophagic vacuoles in neuronal and glial cells, accompanied by activation of the TFEB transcriptional network that controls lysosomal biogenesis and autophagic flux. Therefore, small-molecule-induced autophagy enhancement can improve the neurological symptoms associated with a lysosomal enzyme deficiency and could provide a viable therapeutic approach to neuropathic LSDs.

Abbreviations: ANOVA: analysis of variance; Atg7: autophagy related 7; AV: autophagic vacuoles; CD68: cd68 antigen; ERG: electroretinogram; ERT: enzyme replacement therapy; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFAP: glial fibrillary acidic protein; GNAT2: guanine nucleotide binding protein, alpha transducing 2; HSCT: hematopoietic stem cell transplantation; INL: inner nuclear layer; LC3: microtubule-associated protein 1 light chain 3 alpha; MPS: mucopolysaccharidoses; NAGLU: alpha-N-acetylglucosaminidase (Sanfilippo disease IIIB); ONL: outer nuclear layer; PBS: phosphate-buffered saline; PRKCA/PKCα: protein kinase C, alpha; S1BF: somatosensory cortex; SQSTM1: sequestosome 1; TEM: transmission electron microscopy; TFEB: transcription factor EB; VMP/VPL: ventral posterior nuclei of the thalamus

Can Interactions Between α-Synuclein, Dopamine and Calcium Explain Selective Neurodegeneration in Parkinson's Disease?

Several lines of evidence place alpha-synuclein (aSyn) at the center of Parkinson's disease (PD) etiology, but it is still unclear why overexpression or mutated forms of this protein affect some neuronal populations more than others. Susceptible neuronal populations in PD, dopaminergic neurons of the substantia nigra pars compacta (SNpc) and the locus coeruleus (LC), are distinguished by relatively high cytoplasmic concentrations of dopamine and calcium ions. Here we review the evidence for the multi-hit hypothesis of neurodegeneration, including recent papers that demonstrate synergistic interactions between aSyn, calcium ions and dopamine that may lead to imbalanced protein turnover and selective susceptibility of these neurons. We conclude that decreasing the levels of any one of these toxicity mediators can be beneficial for the survival of SNpc and LC neurons, providing multiple opportunities for targeted drug interventions aimed at modifying the course of PD.

Proteins involved in the antioxidant and inflammatory response in rutin-treated human skin fibroblasts exposed to UVA or UVB irradiation

BACKGROUND

Rutin, due to its polyphenolic structure, has antioxidant properties and can be used as a cytoprotective compound against UV-induced effects on skin cells.

OBJECTIVE

The aim of this study was to examine the effect of rutin on proteomic profile in human skin fibroblasts irradiated with UV dose that induces apoptosis.

METHODS

Proteome analysis based on the results obtained by the QExactive OrbiTrap mass spectrometer.

RESULTS

Results show that rutin treatment more strongly protects against UVA-induced rather than UVB-induced increases in the total expression of proteins involved in antioxidant (such as SOD, TrxR, and Prxs 1/2) and inflammatory response (e.g., IL-17F, PAK2, and YWHAZ). However, in the case of UVB-irradiated cells, rutin additionally enhances the levels of disulfide-isomerase - an enzyme that is responsible for the formation and breakage of disulfide bonds. Moreover, UVB radiation promotes rutin-Keap1 adduct formation, which leads to the activation of Nrf2, a factor that is responsible for the synthesis of cytoprotective proteins. Furthermore, rutin partially prevents UV-induced apoptosis by restoring the physiological levels of p53, cytochrome c, and cell cycle and apoptosis regulator protein 2 that were increased following irradiation.

CONCLUSION

In conclusion, our results show that rutin effectively prevents UV-induced damages associated with proinflammatory and prooxidative activity and protects cells against apoptosis.

Parkinson's Disease Skin Fibroblasts Display Signature Alterations in Growth, Redox Homeostasis, Mitochondrial Function, and Autophagy

The discovery of biomarkers for Parkinson's disease (PD) is challenging due to the heterogeneous nature of this disorder, and a poor correlation between the underlying pathology and the clinically expressed phenotype. An ideal biomarker would inform on PD-relevant pathological changes via an easily assayed biological characteristic, which reliably tracks clinical symptoms. Human dermal (skin) fibroblasts are accessible peripheral cells that constitute a patient-specific system, which potentially recapitulates the PD chronological and epigenetic aging history. Here, we compared primary skin fibroblasts obtained from individuals diagnosed with late-onset sporadic PD, and healthy age-matched controls. These fibroblasts were studied from fundamental viewpoints of growth and morphology, as well as redox, mitochondrial, and autophagic function. It was observed that fibroblasts from PD subjects had higher growth rates, and appeared distinctly different in terms of morphology and spatial organization in culture, compared to control cells. It was also found that the PD fibroblasts exhibited significantly compromised mitochondrial structure and function when assessed via morphological and oxidative phosphorylation assays. Additionally, a striking increase in baseline macroautophagy levels was seen in cells from PD subjects. Exposure of the skin fibroblasts to physiologically relevant stress, specifically ultraviolet irradiation (UVA), further exaggerated the autophagic dysfunction in the PD cells. Moreover, the PD fibroblasts accumulated higher levels of reactive oxygen species (ROS) coupled with lower cell viability upon UVA treatment. In essence, these studies highlight primary skin fibroblasts as a patient-relevant model that captures fundamental PD molecular mechanisms, and supports their potential utility to develop diagnostic and prognostic biomarkers for the disease.

Novel animal model defines genetic contributions for neuron-to-neuron transfer of α-synuclein

Cell-to-cell spreading of misfolded α-synuclein (α-syn) is suggested to contribute to the progression of neuropathology in Parkinson’s disease (PD). Compelling evidence supports the hypothesis that misfolded α-syn transmits from neuron-to-neuron and seeds aggregation of the protein in the recipient cells. Furthermore, α-syn frequently appears to propagate in the brains of PD patients following a stereotypic pattern consistent with progressive spreading along anatomical pathways. We have generated a C. elegans model that mirrors this progression and allows us to monitor α-syn neuron-to-neuron transmission in a live animal over its lifespan. We found that modulation of autophagy or exo/endocytosis, affects α-syn transfer. Furthermore, we demonstrate that silencing C. elegans orthologs of PD-related genes also increases the accumulation of α-syn. This novel worm model is ideal for screening molecules and genes to identify those that modulate prion-like spreading of α-syn in order to target novel strategies for disease modification in PD and other synucleinopathies.

Colonic Oxidative and Mitochondrial Function in Parkinson's Disease and Idiopathic REM Sleep Behavior Disorder

OBJECTIVE

To determine potential mitochondrial and oxidative alterations in colon biopsies from idiopathic REM sleep behavior disorder (iRBD) and Parkinson's disease (PD) subjects.

METHODS

Colonic biopsies from 7 iRBD subjects, 9 subjects with clinically diagnosed PD, and 9 healthy controls were homogenized in 5% w/v mannitol. Citrate synthase (CS) and complex I (CI) were analyzed spectrophotometrically. Oxidative damage was assessed either by lipid peroxidation, through malondialdehyde and hydroxyalkenal content by spectrophotometry, or through antioxidant enzyme levels of superoxide dismutase-2 (SOD2), glutathione peroxidase-1 (Gpx1), and catalase (CAT) by western blot. The presence of mitochondrial DNA (mtDNA) deletions was assessed by long PCR and electrophoresis.

RESULTS

Nonsignificant trends to CI decrease in both iRBD (45.69 ± 18.15; 23% decrease) and PD patients (37.57 ± 12.41; 37% decrease) were found compared to controls (59.51 ± 12.52, p: NS). Lipid peroxidation was maintained among groups (iRBD: 27.46 ± 3.04, PD: 37.2 ± 3.92, and controls: 31.71 ± 3.94; p: NS). Antioxidant enzymes SOD2 (iRBD: 2.30 ± 0.92, PD: 1.48 ± 0.39, and controls: 1.09 ± 0.318) and Gpx1 (iRBD 0.29 ± 0.12, PD: 0.56 ± 0.33, and controls: 0.38 ± 0.16) did not show significant differences between groups. CAT was only detected in 2 controls and 1 iRBD subject. One iRBD patient presented a single mtDNA deletion.

Proteomic studies associated with Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is an insidious disorder affecting more than 1-2% of the population over the age of 65. Understanding the etiology of PD may create opportunities for developing new treatments. Genomic and transcriptomic studies are useful, but do not provide evidence for the actual status of the disease. Conversely, proteomic studies deal with proteins, which are real time players, and can hence provide information on the dynamic nature of the affected cells. The number of publications relating to the proteomics of PD is vast. Therefore, there is a need to evaluate the current proteomics literature and establish the connections between the past and the present to foresee the future. Areas covered: PubMed and Web of Science were used to retrieve the literature associated with PD proteomics. Studies using human samples, model organisms and cell lines were selected and reviewed to highlight their contributions to PD. Expert commentary: The proteomic studies associated with PD achieved only limited success in facilitating disease diagnosis, monitoring and progression. A global system biology approach using new models is needed. Future research should integrate the findings of proteomics with other omics data to facilitate both early diagnosis and the treatment of PD.

Alpha-synuclein at the intracellular and the extracellular side: functional and dysfunctional implications

Alpha-synuclein (α-syn) is an abundant neuronal protein whose physiological function, even if still not completely understood, has been consistently related to synaptic function and vesicle trafficking. A group of disorders known as synucleinopathies, among which Parkinson’s disease (PD), is deeply associated with the misfolding and aggregation of α-syn, which can give rise to proteinaceous inclusion known as Lewy bodies (LB). Proteostasis stress is a relevant aspect in these diseases and, currently, the presence of oligomeric α-syn species rather than insoluble aggregated forms, appeared to be associated with cytotoxicity. Many observations suggest that α-syn is responsible for neurodegeneration by interfering with multiple signaling pathways. α-syn protein can directly form plasma membrane channels or modify with their activity, thus altering membrane permeability to ions, abnormally associate with mitochondria and cause mitochondrial dysfunction (i.e. mitochondrial depolarization, Ca2+ dys-homeostasis, cytochrome c release) and interfere with autophagy regulation. The picture is further complicated by the fact that single point mutations, duplications and triplication in α-syn gene are linked to autosomal dominant forms of PD. In this review we discuss the multi-faced aspect of α-syn biology and address the main hypothesis at the basis of its involvement in neuronal degeneration.

Sorting out release, uptake and processing of alpha-synuclein during prion-like spread of pathology

Parkinson's disease is a progressive neurological disorder that is characterized by the formation of intracellular protein inclusion bodies composed primarily of a misfolded and aggregated form of the protein α-synuclein. There is growing evidence that supports the prion-like hypothesis of α-synuclein progression. This hypothesis postulates that α-synuclein is a prion-like pathological agent and is responsible for the progression of Parkinson pathology in the brain. Potential misfolding or aggregation of α-synuclein that might occur in the peripheral nervous system as a result of some insult, environmental or genetic (or more likely a combination of both) that might spread into the midbrain, eventually causing degeneration of the neurons in the substantia nigra. As the disease progresses further, it is likely that α-synuclein pathology continues to spread throughout the brain, including the cortex, leading to deterioration of cognition and higher brain functions. While it is unknown why α-synuclein initially misfolds and aggregates, a great deal has been learned about how the cell handles aberrant α-synuclein assemblies. In this review, we focus on these mechanisms and discuss them in an attempt to define the role that they might play in the propagation of misfolded α-synuclein from cell-to-cell. The prion-like hypothesis of α-synuclein pathology suggests a method for the transmission of misfolded α-synuclein from one neuron to another. This hypothesis postulates that misfolded α-synuclein becomes aggregation prone and when released and taken up by neighboring cells, seeds further misfolding and aggregation. In this review we examine the cellular mechanisms that are involved in the processing of α-synuclein and how these may contribute to the prion-like propagation of α-synuclein pathology. This article is part of a special issue on Parkinson disease.

Age- and Hypertension-Associated Protein Aggregates in Mouse Heart Have Similar Proteomic Profiles

Neurodegenerative diseases are largely defined by protein aggregates in affected tissues. Aggregates contain some shared components as well as proteins thought to be specific for each disease. Aggregation has not previously been reported in the normal, aging heart or the hypertensive heart. Detergent-insoluble protein aggregates were isolated from mouse heart and characterized on 2-dimensional gels. Their levels increased markedly and significantly with aging and after sustained angiotensin II-induced hypertension. Of the aggregate components identified by high-resolution proteomics, half changed in abundance with age (392/787) or with sustained hypertension (459/824), whereas 30% (273/901) changed concordantly in both, each P<0.05. One fifth of these proteins were previously associated with age-progressive neurodegenerative or cardiovascular diseases, or both (eg, ApoE, ApoJ, ApoAIV, clusterin, complement C3, and others involved in stress-response and protein-homeostasis pathways). Because fibrosis is a characteristic of both aged and hypertensive hearts, we posited that aging of fibroblasts may contribute to the aggregates observed in cardiac tissue. Indeed, as cardiac myofibroblasts "senesced" (approached their replicative limit) in vitro, they accrued aggregates with many of the same constituent proteins observed in vivo during natural aging or sustained hypertension. In summary, we have shown for the first time that compact (detergent-insoluble) protein aggregates accumulate during natural aging, chronic hypertension, and in vitro myofibroblast senescence, sharing many common proteins. Thus, aggregates that arise from disparate causes (aging, hypertension, and replicative senescence) may have common underlying mechanisms of accrual.

Overexpression of α-synuclein simultaneously increases glutamate NMDA receptor phosphorylation and reduces glucocerebrosidase activity

Progressive accumulation of α-synuclein (α-syn)-containing protein aggregates throughout the nervous system is a pathological hallmark of Parkinson's disease (PD). The mechanisms whereby α-syn exerts neurodegeneration remain to be fully understood. Here we show that overexpression of α-syn in transgenic mice leads to increased phosphorylation of glutamate NMDA receptor (NMDAR) subunits NR1 and NR2B in substantia nigra and striatum as well as reduced glucocerebrosidase (GCase) levels. Similarly, molecular studies performed in mouse N2A cells stably overexpressing human α-syn ((α-syn)N2A) showed that phosphorylation states of the same NMDAR subunits were increased, whereas GCase levels and lysosomal GCase activity were reduced. (α-syn)N2A cells showed an increased sensitivity to neurotoxicity towards 6-hydroxydopamine and NMDA. However, wildtype N2A, but not (α-syn)N2A cells, showed a further reduction in viability when co-incubated with 6-hydroxydopamine and the lysosomal inhibitors NH4Cl and leupeptin, suggesting that α-syn per se perturbs lysosomal functions. NMDA treatment reduced lysosomal GCase activity to the same extent in (α-syn)N2A cells as in wildtype N2A cells, indicating that the α-syn-dependent difference in NMDA neurotoxicity is unrelated to an altered GCase activity. Nevertheless, these data provide molecular evidence that overexpression of α-syn simultaneously induces two potential neurotoxic hits by increasing glutamate NMDA receptor phosphorylation, consistent with increased NMDA receptors functionality, and reducing GCase activity.

Comparative analysis of autophagy and tauopathy related markers in cerebral ischemia and Alzheimer's disease animal models

Alzheimer's disease (AD) and cerebral ischemia (CI) are neuropathologies that are characterized by aggregates of tau protein, a hallmark of cognitive disorder and dementia. Protein accumulation can be induced by autophagic failure. Autophagy is a metabolic pathway involved in the homeostatic recycling of cellular components. However, the role of autophagy in those tauopathies remains unclear. In this study, we performed a comparative analysis to identify autophagy related markers in tauopathy generated by AD and CI during short-term, intermediate, and long-term progression using the 3xTg-AD mouse model (aged 6,12, and 18 months) and the global CI 2-VO (2-Vessel Occlusion) rat model (1,15, and 30 days post-ischemia). Our findings confirmed neuronal loss and hyperphosphorylated tau aggregation in the somatosensory cortex (SS-Cx) of the 3xTg-AD mice in the late stage (aged 18 months), which was supported by a failure in autophagy. These results were in contrast to those obtained in the SS-Cx of the CI rats, in which we detected neuronal loss and tauopathy at 1 and 15 days post-ischemia, and this phenomenon was reversed at 30 days. We proposed that this phenomenon was associated with autophagy induction in the late stage, since the data showed a decrease in p-mTOR activity, an association of Beclin-1 and Vps34, a progressive reduction in PHF-1, an increase in LC3B puncta and autophago-lysosomes formation were observed. Furthermore, the survival pathways remained unaffected. Together, our comparative study suggest that autophagy could ameliorates tauopathy in CI but not in AD, suggesting a differential temporal approach to the induction of neuroprotection and the prevention of neurodegeneration.

Attenuation of neuromotor deficits by natural antioxidants of Decalepis hamiltonii in transgenic Drosophila model of Parkinson's disease

Oxidative stress is believed to be a major factor for the onset of Parkinson's disease (PD). In this study, we have investigated oxidative status in transgenic Drosophila model of PD. Our results revealed elevated levels of reactive oxygen species (ROS) and lipid peroxidation (LPO) in A30P and A53T α-synuclein PD model flies compared to control. We have demonstrated for the first time the ameliorating potential of natural antioxidants characterized from the roots of Dh in A30P and A53T α-synuclein PD model flies. Feeding of transgenic flies with aqueous Dh root extract for 21 days significantly improved their climbing ability and circadian rhythm of locomotor activity which was associated with reduction in levels of ROS and LPO and enhancement in the activities of catalase (CAT) and superoxide dismutase (SOD). Dh protected against paraquat (PQ) sensitivity in α-synuclein transgenic flies and delayed the onset of PD-like symptoms which appears to be mediated by suppression of oxidative stress.

Hydrodynamic size-based separation and characterization of protein aggregates from total cell lysates

Herein we describe a protocol that uses hollow-fiber flow field-flow fractionation (FFF) coupled with multiangle light scattering (MALS) for hydrodynamic size-based separation and characterization of complex protein aggregates. The fractionation method, which requires 1.5 h to run, was successfully modified from the analysis of protein aggregates, as found in simple protein mixtures, to complex aggregates, as found in total cell lysates. In contrast to other related methods (filter assay, analytical ultracentrifugation, gel electrophoresis and size-exclusion chromatography), hollow-fiber flow FFF coupled with MALS allows a flow-based fractionation of highly purified protein aggregates and simultaneous measurement of their molecular weight, r.m.s. radius and molecular conformation (e.g., round, rod-shaped, compact or relaxed). The polyethersulfone hollow fibers used, which have a 0.8-mm inner diameter, allow separation of as little as 20 μg of total cell lysates. In addition, the ability to run the samples in different denaturing and nondenaturing buffer allows defining true aggregates from artifacts, which can form during sample preparation. The protocol was set up using Paraquat-induced carbonylation, a model that induces protein aggregation in cultured cells. This technique will advance the biochemical, proteomic and biophysical characterization of molecular-weight aggregates associated with protein mutations, as found in many CNS degenerative diseases, or chronic oxidative stress, as found in aging, and chronic metabolic and inflammatory conditions.

The amazing ubiquitin-proteasome system: structural components and implication in aging

Proteome quality control (PQC) is critical for the maintenance of cellular functionality and it is assured by the curating activity of the proteostasis network (PN). PN is constituted of several complex protein machines that under conditions of proteome instability aim to, firstly identify, and then, either rescue or degrade nonnative polypeptides. Central to the PN functionality is the ubiquitin-proteasome system (UPS) which is composed from the ubiquitin-conjugating enzymes and the proteasome; the latter is a sophisticated multi-subunit molecular machine that functions in a bimodal way as it degrades both short-lived ubiquitinated normal proteins and nonfunctional polypeptides. UPS is also involved in PQC of the nucleus, the endoplasmic reticulum and the mitochondria and it also interacts with the other main cellular degradation axis, namely the autophagy-lysosome system. UPS functionality is optimum in the young organism but it is gradually compromised during aging resulting in increasing proteotoxic stress; these effects correlate not only with aging but also with most age-related diseases. Herein, we present a synopsis of the UPS components and of their functional alterations during cellular senescence or in vivo aging. We propose that mild UPS activation in the young organism will, likely, promote antiaging effects and/or suppress age-related diseases.

Ectosomes: a new mechanism for non-exosomal secretion of tau protein

Tau is a microtubule-associated protein that aggregates in neurodegenerative disorders known as tauopathies. Recently, studies have suggested that Tau may be secreted and play a role in neural network signalling. However, once deregulated, secreted Tau may also participate in the spreading of Tau pathology in hierarchical pathways of neurodegeneration. The mechanisms underlying neuron-to-neuron Tau transfer are still unknown; given the known role of extra-cellular vesicles in cell-to-cell communication, we wondered whether these vesicles could carry secreted Tau. We found, among vesicles, that Tau is predominately secreted in ectosomes, which are plasma membrane-originating vesicles, and when it accumulates, the exosomal pathway is activated.

Mitochondrial proteomics investigation of a cellular model of impaired dopamine homeostasis, an early step in Parkinson's disease pathogenesis

Impaired dopamine homeostasis is an early event in the pathogenesis of Parkinson's disease. Generation of intracellular reactive oxygen species consequent to dopamine oxidation leads to mitochondrial dysfunction and eventually cell death. Alterations in the mitochondrial proteome due to dopamine exposure were investigated in the SH-SY5Y human neuroblastoma cell line. The combination of two orthogonal proteomic approaches, two-dimensional electrophoresis and shotgun proteomics (proteomeXchange dataset PXD000838), was used to highlight the specific pathways perturbed by the increase of intracellular dopamine, in comparison with those perturbed by a specific mitochondrial toxin (4-methylphenylpyridinium, MPP(+)), a neurotoxin causing Parkinsonism-like symptoms in animal models. Proteins altered by MPP(+) did not completely overlap with those affected by dopamine treatment. In particular, the MPP(+) target complex I component NADH dehydrogenase [ubiquinone] iron-sulfur protein 3 was not affected by dopamine together with 26 other proteins. The comparison of proteomics approaches highlighted the fragmentation of some mitochondrial proteins, suggesting an alteration of the mitochondrial protease activity. Pathway and disease association analysis of the proteins affected by dopamine revealed the overrepresentation of the Parkinson's disease and the parkin-ubiquitin proteasomal system pathways and of gene ontologies associated with generation of precursor metabolites and energy, response to topologically incorrect proteins and programmed cell death. These alterations may be globally interpreted in part as the result of a direct effect of dopamine on mitochondria (e.g. alteration of the mitochondrial protease activity) and in part as the effect on mitochondria of a general activation of cellular processes (e.g. regulation of programmed cell death).

Natural compounds with anti-ageing activity

Ageing is a complex molecular process driven by diverse molecular pathways and biochemical events that are promoted by both environmental and genetic factors. Specifically, ageing is defined as a time-dependent decline of functional capacity and stress resistance, associated with increased chance of morbidity and mortality. These effects relate to age-related gradual accumulation of stressors that result in increasingly damaged biomolecules which eventually compromise cellular homeostasis. Nevertheless, the findings that genetic or diet interventions can increase lifespan in evolutionarily diverse organisms indicate that mortality can be postponed. Natural compounds represent an extraordinary inventory of high diversity structural scaffolds that can offer promising candidate chemical entities in the major healthcare challenge of increasing health span and/or delaying ageing. Herein, those natural compounds (either pure forms or extracts) that have been found to delay cellular senescence or in vivo ageing will be critically reviewed and summarized according to affected cellular signalling pathways. Moreover, the chemical structures of the identified natural compounds along with the profile of extracts related to their bioactive components will be presented and discussed. Finally, novel potential molecular targets for screening natural compounds for anti-ageing activity, as well as the idea that anti-ageing interventions represent a systemic approach that is also effective against age-related diseases will be discussed.

Characterization and regulation of mechanical loading-induced compensatory muscle hypertrophy

In mammalian systems, skeletal muscle exists in a dynamic state that monitors and regulates the physiological investment in muscle size to meet the current level of functional demand. This review attempts to consolidate current knowledge concerning development of the compensatory hypertrophy that occurs in response to a sustained increase in the mechanical loading of skeletal muscle. Topics covered include: defining and measuring compensatory hypertrophy, experimental models, loading stimulus parameters, acute responses to increased loading, hyperplasia, myofiber-type adaptations, the involvement of satellite cells, mRNA translational control, mechanotransduction, and endocrinology. The authors conclude with their impressions of current knowledge gaps in the field that are ripe for future study.

Dmp53, basket and drICE gene knockdown and polyphenol gallic acid increase life span and locomotor activity in a Drosophila Parkinson's disease model

Understanding the mechanism(s) by which dopaminergic (DAergic) neurons are eroded in Parkinson's disease (PD) is critical for effective therapeutic strategies. By using the binary tyrosine hydroxylase (TH)-Gal4/UAS-X RNAi Drosophila melanogaster system, we report that Dmp53, basket and drICE gene knockdown in dopaminergic neurons prolong life span (p < 0.05; log-rank test) and locomotor activity (p < 0.05; χ(2) test) in D. melanogaster lines chronically exposed to (1 mM) paraquat (PQ, oxidative stress (OS) generator) compared to untreated transgenic fly lines. Likewise, knockdown flies displayed higher climbing performance than control flies. Amazingly, gallic acid (GA) significantly protected DAergic neurons, ameliorated life span, and climbing abilities in knockdown fly lines treated with PQ compared to flies treated with PQ only. Therefore, silencing specific gene(s) involved in neuronal death might constitute an excellent tool to study the response of DAergic neurons to OS stimuli. We propose that a therapy with antioxidants and selectively "switching off" death genes in DAergic neurons could provide a means for pre-clinical PD individuals to significantly ameliorate their disease condition.

Overexpression of synphilin-1 promotes clearance of soluble and misfolded alpha-synuclein without restoring the motor phenotype in aged A30P transgenic mice

Lewy bodies and neurites are the pathological hallmark of Parkinson's disease. These structures are composed of fibrillized and ubiquitinated alpha-synuclein suggesting that impaired protein clearance is an important event in aggregate formation. The A30P mutation is known for its fast oligomerization, but slow fibrillization rate. Despite its toxicity to neurons, mechanisms involved in either clearance or conversion of A30P alpha-synuclein from its soluble state into insoluble fibrils and their effects in vivo are poorly understood. Synphilin-1 is present in Lewy bodies, interacting with alpha-synuclein in vivo and in vitro and promotes its sequestration into aggresomes, which are thought to act as cytoprotective agents facilitating protein degradation. We therefore crossed animals overexpressing A30P alpha-synuclein with synphilin-1 transgenic mice to analyze its impact on aggregation, protein clearance and phenotype progression. We observed that co-expression of synphilin-1 mildly delayed the motor phenotype caused by A30P alpha-synuclein. Additionally, the presence of N- and C-terminal truncated alpha-synuclein species and fibrils were strongly reduced in double-transgenic mice when compared with single-transgenic A30P mice. Insolubility of mutant A30P and formation of aggresomes was still detectable in aged double-transgenic mice, paralleled by an increase of ubiquitinated proteins and high autophagic activity. Hence, this study supports the notion that co-expression of synphilin-1 promotes formation of autophagic-susceptible aggresomes and consecutively the degradation of human A30P alpha-synuclein. Notably, although synphilin-1 overexpression significantly reduced formation of fibrils and astrogliosis in aged animals, a similar phenotype is present in single- and double-transgenic mice suggesting additional neurotoxic processes in disease progression.

SUMO and Parkinson's disease

Parkinson's disease (PD) is one of the most common degenerative disorders of the central nervous system that produces motor and non-motor symptoms. The majority of cases are idiopathic and characterized by the presence of Lewy bodies containing fibrillar α-synuclein. Small ubiquitin-related modifier (SUMO) immunoreactivity was observed among others in cases with PD. Key disease-associated proteins are SUMO-modified, linking this posttranslational modification to neurodegeneration. SUMOylation and SUMO-mediated mechanisms have been intensively studied in recent years, revealing nuclear and extranuclear functions for SUMO in a variety of cellular processes, including the regulation of transcriptional activity, modulation of signal transduction pathways, and response to cellular stress. This points to a role for SUMO more than just an antagonist to ubiquitin and proteasomal degradation. The identification of risk and age-at-onset gene loci was a breakthrough in PD and promoted the understanding of molecular mechanisms in the pathology. PD has been increasingly linked with mitochondrial dysfunction and impaired mitochondrial quality control. Interestingly, SUMO is involved in many of these processes and up-regulated in response to cellular stress, further emphasizing the importance of SUMOylation in physiology and disease.

Nucleotide excision repair in chronic neurodegenerative diseases

Impaired DNA repair involving the nucleotide excision repair (NER)/transcription-coupled repair (TCR) pathway cause human pathologies associated with severe neurological symptoms. These clinical observations suggest that defective NER/TCR might also play a critical role in chronic neurodegenerative disorders (ND), such as Alzheimer's and Parkinson's disease. Involvement of NER/TCR in these disorders is also substantiated by the evidence that aging constitutes the principal risk factor for chronic ND and that this DNA repair mechanism is very relevant for the aging process itself. Our understanding of the exact role of NER/TCR in chronic ND, however, is extremely rudimentary; while there is no doubt that defective NER/TCR can lead to neuronal death, evidence for its participation in the etiopathogenesis of ND is inconclusive thus far. Here we summarize the experimental observations supporting a role for NER/TCR in chronic ND and suggest questions and lines of investigation that might help in addressing this important issue. We also present a preliminary yet unprecedented meta-analysis on human brain microarray data to understand the expression levels of the various NER factors in the anatomical areas relevant for chronic ND pathogenesis. In summary, this review intends to highlight elements supporting a role of NER/TCR in these devastating disorders and to propose potential strategies of investigation.

The parkinson's disease-associated LRRK2 mutation R1441G inhibits neuronal differentiation of neural stem cells

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause familial as well as sporadic Parkinson's disease (PD) that is characterized by an age-dependent degeneration of dopaminergic neurons. LRRK2 is strongly expressed in neural stem cells (NSCs), but still the exact molecular function of LRRK2 in these cells remains unknown. By performing a systemic analysis of the gene expression profile of LRRK2-deficient NSCs, we found that the expression of several PD-associated genes, such as oxidation and reduction in mitochondria, are deregulated on LRRK2 absence. Our data, indeed, indicate that LRRK2 regulates the level of cellular oxidative stress and thereby influences the survival of NSCs. Furthermore, the lack of LRRK2 leads to an up-regulation of neuronal differentiation-inducing processes, including the Let-7a pathway. On the other hand, the constitutive mutant of LRRK2(R1441G), known to cause PD, leads to down-regulation of the same pathway. In agreement with the function of Let-7a during neuronal differentiation, LRRK2-deficient NSCs differentiate faster than wild-type cells, while LRRK2(R1441G)-expressing NSCs show impaired neuronal differentiation. These results might help better characterize the molecular mechanisms underlying the role of LRRK2 in NSCs and would further improve potential cell-replacement strategies as well as drug discovery approaches.