Altered expression of autophagic genes in the peripheral leukocytes of patients with sporadic Parkinson's disease

The lysosomal-associated membrane protein 2-macroautophagy pathway is involved in the regulatory effects of hippocampal aromatase on Aβ accumulation and AD-like behavior

AIMS

Hippocampal aromatase (AROM) knockdown induces Aβ accumulation and Alzheimer's disease (AD)-like spatial learning and memory impairment, and early hippocampal AROM overexpression in APP/PS1 mice prevents Aβ deposition and memory loss later in life. The aim of this study was to elucidate the underlying mechanism and provide novel prevention and treatment targets for AD.

MATERIALS AND METHODS

AROM-inhibiting viral vectors were constructed and injected into the hippocampi of adult female mice, after which label-free LC-MS/MS proteomics and bioinformatics analysis were conducted. Additional viral vectors targeting LAMP2 or LC3 were constructed and used to treat HT22 cells. LAMP2 expression was verified, and macroautophagy levels, autophagosome formation and Aβ accumulation were examined. Additionally, ovariectomy combined with the hippocampal injection of LAMP2 inhibition/overexpression viral vectors was applied, and learning and memory abilities and Aβ accumulation were examined.

KEY FINDINGS

Proteomics revealed the enrichment of CMA and autophagy, and LAMP2 was the most significantly upregulated protein. Higher LAMP2 levels were correlated with lower macroautophagy and autophagosomes levels but were correlated with higher Aβ accumulation, and vice versa. Additionally, hippocampal LAMP2 mediated the effects of ovariectomy on spatial memory and Aβ accumulation.

SIGNIFICANCE

These results demonstrated the important role of the hippocampal LAMP2-macroautophagy pathway in mediating both hippocampal and ovarian estrogen regulation of Aβ accumulation and AD-like behavior, indicating that LAMP2 might be a novel target for both hippocampal and circulating estrogen deficiency-associated memory impairments, such as AD.

Immune cell metabolic dysfunction in Parkinson's disease

Parkinson's disease (PD) is a multi-system disorder characterized histopathologically by degeneration of dopaminergic neurons in the substantia nigra pars compacta. While the etiology of PD remains multifactorial and complex, growing evidence suggests that cellular metabolic dysfunction is a critical driver of neuronal death. Defects in cellular metabolism related to energy production, oxidative stress, metabolic organelle health, and protein homeostasis have been reported in both neurons and immune cells in PD. We propose that these factors act synergistically in immune cells to drive aberrant inflammation in both the CNS and the periphery in PD, contributing to a hostile inflammatory environment which renders certain subsets of neurons vulnerable to degeneration. This review highlights the overlap between established neuronal metabolic deficits in PD with emerging findings in central and peripheral immune cells. By discussing the rapidly expanding literature on immunometabolic dysfunction in PD, we aim to draw attention to potential biomarkers and facilitate future development of immunomodulatory strategies to prevent or delay the progression of PD.

Identification of Key Active Constituents in Eucommia ulmoides Oliv. Leaves Against Parkinson's Disease and the Alleviative Effects via 4E-BP1 Up-Regulation

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder, affecting an increasing number of older adults. Despite extensive research, a definitive cure remains elusive. Eucommia ulmoides Oliv. leaves (EUOL) have been reported to exhibit protective effects on neurodegenerative diseases, however, their efficacy, key active constituents, and pharmacological mechanisms are not yet understood. This study aims to explore the optimal constituents of EUOL regarding anti-PD activity and its underlying mechanisms. Using a zebrafish PD model, we found that the 30% ethanol fraction extract (EF) of EUOL significantly relieved MPTP-induced locomotor impairments, increased the length of dopaminergic neurons, inhibited the loss of neuronal vasculature, and regulated the misexpression of autophagy-related genes (α-syn, lc3b, p62, and atg7). Assays of key regulators involved in PD further verified the potential of the 30% EF against PD in the cellular PD model. Reverse phase protein array (RPPA) analysis revealed that 30% EF exerted anti-PD activity by activating 4E-BP1, which was confirmed by Western blotting. Phytochemical analysis indicated that cryptochlorogenic acid, chlorogenic acid, asperuloside, caffeic acid, and asperulosidic acid are the main components of the 30% EF. Molecular docking and surface plasmon resonance (SPR) indicated that the main components of the 30% EF exhibited favorable binding interactions with 4E-BP1, further highlighting the roles of 4E-BP1 in this process. Accordingly, these components were observed to ameliorate PD-like behaviors in the zebrafish model. Overall, this study revealed that the 30% EF is the key active constituent of EUOL, which had considerable ameliorative effects on PD by up-regulating 4E-BP1. This suggests that EUOL could serve as a promising candidate for the development of novel functional foods aimed at supporting PD treatment.

Identifying potential genes driving ferroptosis in the substantia nigra and dopaminergic neurons in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder marked by dopaminergic (DA) neuron degeneration in the substantia nigra (SN). Conventional dopamine replacement therapies provide limited long-term efficacy and significant side effects. Emerging evidence suggests ferroptosis-a form of cell death driven by iron-dependent lipid peroxidation-contributes to PD pathology, though direct evidence linking dysregulation of ferroptosis-related genes in DA neuron loss in PD remains limited. This study explores the expression of ferroptosis-associated genes in the SN and DA neurons of PD patients, identifying potential therapeutic targets. We analyzed two independent RNA-seq datasets, GSE7621 and GSE8397 (GPL-96), from the GEO database to identify common differentially expressed ferroptosis-related genes in the SN of PD patients. We also conducted Gene Ontology and pathway enrichment analyses of these genes to explore the underlying mechanisms and constructed a protein-protein interaction network. The findings were further validated using an additional dataset, GSE49036. We further explored the dysregulation of these ferroptosis-related genes in DA neurons using RNA-seq data GSE169755, derived from DA neurons isolated from the SN of PD patients and controls. Lastly, the proposed hypothesis was experimentally validated in an in vitro PD model. This comprehensive multi-dataset analysis uncovers novel insights into the expression of ferroptosis-related genes in PD, suggesting potential biomarkers and therapeutic targets for mitigating DA neuron loss and PD progression.

Targeting the Interplay Between Autophagy and the Nrf2 Pathway in Parkinson's Disease with Potential Therapeutic Implications

Parkinson's disease (PD) is a prevalent neurodegenerative disorder marked by the progressive degeneration of midbrain dopaminergic neurons and resultant locomotor dysfunction. Despite over two centuries of recognition as a chronic disease, the exact pathogenesis of PD remains elusive. The onset and progression of PD involve multiple complex pathological processes, with dysfunctional autophagy and elevated oxidative stress serving as critical contributors. Notably, emerging research has underscored the interplay between autophagy and oxidative stress in PD pathogenesis. Given the limited efficacy of therapies targeting either autophagy dysfunction or oxidative stress, it is crucial to elucidate the intricate mechanisms governing their interplay in PD to develop more effective therapeutics. This review overviews the role of autophagy and nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal transcriptional regulator orchestrating cellular defense mechanisms against oxidative stress, and the complex interplay between these processes. By elucidating the intricate interplay between these key pathological processes in PD, this review will deepen our comprehensive understanding of the multifaceted pathological processes underlying PD and may uncover potential strategies for its prevention and treatment.

α-Synuclein in Parkinson's Disease: 12 Years Later

α-Synuclein (AS) is a small presynaptic protein that is genetically, biochemically, and neuropathologically linked to Parkinson's disease (PD) and related synucleinopathies. We present here a review of the topic of this relationship, focusing on more recent knowledge. In particular, we review the genetic evidence linking AS to familial and sporadic PD, including a number of recently identified point mutations in the SNCA gene. We briefly go over the relevant neuropathological findings, stressing the evidence indicating a correlation between aberrant AS deposition and nervous system dysfunction. We analyze the structural characteristics of the protein, in relation to both its physiologic and pathological conformations, with particular emphasis on posttranslational modifications, aggregation properties, and secreted forms. We review the interrelationship of AS with various cellular compartments and functions, with particular focus on the synapse and protein degradation systems. We finally go over the recent exciting data indicating that AS can provide the basis for novel robust biomarkers in the field of synucleinopathies, while at the same time results from the first clinical trials specifically targeting AS are being reported.

Identification of a novel aromatic-turmerone analog that activates chaperone-mediated autophagy through the persistent activation of p38

Introduction: Aromatic (Ar)-turmerone is a bioactive component of turmeric oil obtained from Curcuma longa. We recently identified a novel analog (A2) of ar-turmerone that protects dopaminergic neurons from toxic stimuli by activating nuclear factor erythroid 2-related factor 2 (Nrf2). D-cysteine increases Nrf2, leading to the activation of chaperone-mediated autophagy (CMA), a pathway in the autophagy-lysosome protein degradation system, in primary cultured cerebellar Purkinje cells. In this study, we attempted to identify novel analogs of ar-turmerone that activate Nrf2 more potently and investigated whether these analogs activate CMA. Methods: Four novel analogs (A4-A7) from A2 were synthesized. We investigated the effects of A2 and novel 4 analogs on Nrf2 expression via immunoblotting and CMA activity via fluorescence observation. Results: Although all analogs, including A2, increased Nrf2 expression, only A4 activated CMA in SH-SY5Y cells. Additionally, A4-mediated CMA activation was not reversed by Nrf2 inhibition, indicating that A4 activated CMA via mechanisms other than Nrf2 activation. We focused on p38, which participates in CMA activation. Inhibition of p38 significantly prevented A4-mediated activation of CMA. Although all novel analogs significantly increased the phosphorylation of p38 6 h after drug treatment, only A4 significantly increased phosphorylation 24 h after treatment. Finally, we revealed that A4 protected SH-SY5Y cells from the cytotoxicity of rotenone, and that this protection was reversed by inhibiting p38. Conclusion: These findings suggest that the novel ar-turmerone analog, A4, activates CMA and protects SH-SY5Y cells through the persistent activation of p38.

Neuronal Autophagy: Regulations and Implications in Health and Disease

Autophagy is a major degradative pathway that plays a key role in sustaining cell homeostasis, integrity, and physiological functions. Macroautophagy, which ensures the clearance of cytoplasmic components engulfed in a double-membrane autophagosome that fuses with lysosomes, is orchestrated by a complex cascade of events. Autophagy has a particularly strong impact on the nervous system, and mutations in core components cause numerous neurological diseases. We first review the regulation of autophagy, from autophagosome biogenesis to lysosomal degradation and associated neurodevelopmental/neurodegenerative disorders. We then describe how this process is specifically regulated in the axon and in the somatodendritic compartment and how it is altered in diseases. In particular, we present the neuronal specificities of autophagy, with the spatial control of autophagosome biogenesis, the close relationship of maturation with axonal transport, and the regulation by synaptic activity. Finally, we discuss the physiological functions of autophagy in the nervous system, during development and in adulthood.

The Consequences of GBA Deficiency in the Autophagy-Lysosome System in Parkinson's Disease Associated with GBA

GBA gene variants were the first genetic risk factor for Parkinson's disease. GBA encodes the lysosomal enzyme glucocerebrosidase (GBA), which is involved in sphingolipid metabolism. GBA exhibits a complex physiological function that includes not only the degradation of its substrate glucosylceramide but also the metabolism of other sphingolipids and additional lipids such as cholesterol, particularly when glucocerebrosidase activity is deficient. In the context of Parkinson's disease associated with GBA, the loss of GBA activity has been associated with the accumulation of α-synuclein species. In recent years, several hypotheses have proposed alternative and complementary pathological mechanisms to explain why lysosomal enzyme mutations lead to α-synuclein accumulation and become important risk factors in Parkinson's disease etiology. Classically, loss of GBA activity has been linked to a dysfunctional autophagy-lysosome system and to a subsequent decrease in autophagy-dependent α-synuclein turnover; however, several other pathological mechanisms underlying GBA-associated parkinsonism have been proposed. This review summarizes and discusses the different hypotheses with a special focus on autophagy-dependent mechanisms, as well as autophagy-independent mechanisms, where the role of other players such as sphingolipids, cholesterol and other GBA-related proteins make important contributions to Parkinson's disease pathogenesis.

From Lysosomal Storage Disorders to Parkinson's Disease - Challenges and Opportunities

Lysosomes are specialized organelles with an acidic pH that act as recycling hubs for intracellular and extracellular components. They harbour numerous different hydrolytic enzymes to degrade substrates like proteins, peptides, and glycolipids. Reduced catalytic activity of lysosomal enzymes can cause the accumulation of these substrates and loss of lysosomal integrity, resulting in lysosomal dysfunction and lysosomal storage disorders (LSDs). Post-mitotic cells, such as neurons, seem to be highly sensitive to damages induced by lysosomal dysfunction, thus LSDs often manifest with neurological symptoms. Interestingly, some LSDs and Parkinson's disease (PD) share common cellular pathomechanisms, suggesting convergence of aetiology of the two disease types. This is further underlined by genetic associations of several lysosomal genes involved in LSDs with PD. The increasing number of lysosome-associated genetic risk factors for PD makes it necessary to understand functions and interactions of lysosomal proteins/enzymes both in health and disease, thereby holding the potential to identify new therapeutic targets. In this review, we highlight genetic and mechanistic interactions between the complex lysosomal network, LSDs and PD, and elaborate on methodical challenges in lysosomal research.

Chaperone-Mediated Autophagy in Neurodegenerative Diseases: Molecular Mechanisms and Pharmacological Opportunities

Chaperone-mediated autophagy (CMA) is a protein degradation mechanism through lysosomes. By targeting the KFERQ motif of the substrate, CMA is responsible for the degradation of about 30% of cytosolic proteins, including a series of proteins associated with neurodegenerative diseases (NDs). The fact that decreased activity of CMA is observed in NDs, and ND-associated mutant proteins, including alpha-synuclein and Tau, directly impair CMA activity reveals a possible vicious cycle of CMA impairment and pathogenic protein accumulation in ND development. Given the intrinsic connection between CMA dysfunction and ND, enhancement of CMA has been regarded as a strategy to counteract ND. Indeed, genetic and pharmacological approaches to modulate CMA have been shown to promote the degradation of ND-associated proteins and alleviate ND phenotypes in multiple ND models. This review summarizes the current knowledge on the mechanism of CMA with a focus on its relationship with NDs and discusses the therapeutic potential of CMA modulation for ND.

Alterations in Proteostasis System Components in Peripheral Blood Mononuclear Cells in Parkinson Disease: Focusing on the HSP70 and p62 Levels

Parkinson disease (PD) is attributed to a proteostasis disorder mediated by α-synuclein accumulating in a specific brain region. PD manifestation is often related to extraneuronal alterations, some of which could be used as diagnostic or prognostic PD biomarkers. In this work, we studied the shifts in the expression of proteostasis-associated chaperones of the HSP70 family and autophagy-dependent p62 protein values in the peripheral blood mononuclear cells (PBMC) of mild to moderate PD patients. Although we did not detect any changes in the intracellular HSP70 protein pool in PD patients compared to non-PD controls, an increase in the transcriptional activity of the stress-associated HSPA1A/B and HSPA6 genes was observed in these cells. Basal p62 content was found to be increased in PD patients’ PBMC, similarly to the p62 level in substantia nigra neural cells in PD. Moreover, the spontaneous apoptosis level was increased among PBMC and positively correlated with the p62 intracellular level in the PD group. A combined HSPA6- and p62-based analysis among 26 PD patients and 36 age-matched non-PD controls pointed out the diagnostic significance of these markers, with intermediate sensitivity and high specificity of this combination when observing patients diagnosed with PD.

Improper Proteostasis: Can It Serve as Biomarkers for Neurodegenerative Diseases?

Cells synthesize new proteins after multiple molecular decisions. Damage of existing proteins, accumulation of abnormal proteins, and basic requirement of new proteins trigger protein quality control (PQC)-based alternative strategies to cope against proteostasis imbalance. Accumulation of misfolded proteins is linked with various neurodegenerative disorders. However, how deregulated components of this quality control system and their lack of general mechanism-based long-term changes can serve as biomarkers for neurodegeneration remains largely unexplored. Here, our article summarizes the chief findings, which may facilitate the search of novel and relevant proteostasis mechanism-based biomarkers associated with neuronal disorders. Understanding the abnormalities of PQC coupled molecules as possible biomarkers can help to determine neuronal fate and their contribution to the aetiology of several nervous system disorders.

Autophagy-Lysosomal Pathway as Potential Therapeutic Target in Parkinson's Disease

Cellular quality control systems have gained much attention in recent decades. Among these, autophagy is a natural self-preservation mechanism that continuously eliminates toxic cellular components and acts as an anti-ageing process. It is vital for cell survival and to preserve homeostasis. Several cell-type-dependent canonical or non-canonical autophagy pathways have been reported showing varying degrees of selectivity with regard to the substrates targeted. Here, we provide an updated review of the autophagy machinery and discuss the role of various forms of autophagy in neurodegenerative diseases, with a particular focus on Parkinson's disease. We describe recent findings that have led to the proposal of therapeutic strategies targeting autophagy to alter the course of Parkinson's disease progression.

Reduced Immunosenescence of Peripheral Blood T Cells in Parkinson's Disease with CMV Infection Background

Immunosenescence is a process of remodeling the immune system under the influence of chronic inflammation during aging. Parkinson’s disease (PD) is a common age-associated neurodegenerative disorder and is frequently accompanied by neuroinflammation. On the other hand, cytomegalovirus (CMV), one of the most spread infections in humans, may induce chronic inflammation which contributes to immunosenescence, differentiation and the inflation of T cells and NK cells. Currently, there is no clear understanding of immunosenescence severity in PD patients infected with CMV. In this study, we analyzed differentiation stages and immunosenescence characteristics of T cells and NK cells in 31 patients with mild and moderate PD severity, 33 age-matched and 30 young healthy donors. The PD patients were 100% CMV-seropositive compared to 76% age-matched and 73% young CMV-infected healthy donors. The proportion of effector memory T cells re-expressing CD45RA, CD57⁺CD56⁻ T cells and CD57⁺CD56⁺ T cells was significantly reduced in PD patients compared with CMV-seropositive age-matched healthy individuals. The CD57⁺CD56⁻ T cell proportion in PD patients was similar to that of CMV-seropositive young healthy donors. Thus, PD is characterized by reduced peripheral blood T cell immunosenescence, even against the background of CMV infection.

Autophagy in α-Synucleinopathies-An Overstrained System

Alpha-synucleinopathies comprise progressive neurodegenerative diseases, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). They all exhibit the same pathological hallmark, which is the formation of α-synuclein positive deposits in neuronal or glial cells. The aggregation of α-synuclein in the cell body of neurons, giving rise to the so-called Lewy bodies (LBs), is the major characteristic for PD and DLB, whereas the accumulation of α-synuclein in oligodendroglial cells, so-called glial cytoplasmic inclusions (GCIs), is the hallmark for MSA. The mechanisms involved in the intracytoplasmic inclusion formation in neuronal and oligodendroglial cells are not fully understood to date. A possible mechanism could be an impaired autophagic machinery that cannot cope with the high intracellular amount of α-synuclein. In fact, different studies showed that reduced autophagy is involved in α-synuclein aggregation. Furthermore, altered levels of different autophagy markers were reported in PD, DLB, and MSA brains. To date, the trigger point in disease initiation is not entirely clear; that is, whether autophagy dysfunction alone suffices to increase α-synuclein or whether α-synuclein is the pathogenic driver. In the current review, we discuss the involvement of defective autophagy machinery in the formation of α-synuclein aggregates, propagation of α-synuclein, and the resulting neurodegenerative processes in α-synucleinopathies.

The Emerging Roles of Autophagy in Human Diseases

Autophagy, a process of cellular self-digestion, delivers intracellular components including superfluous and dysfunctional proteins and organelles to the lysosome for degradation and recycling and is important to maintain cellular homeostasis. In recent decades, autophagy has been found to help fight against a variety of human diseases, but, at the same time, autophagy can also promote the procession of certain pathologies, which makes the connection between autophagy and diseases complex but interesting. In this review, we summarize the advances in understanding the roles of autophagy in human diseases and the therapeutic methods targeting autophagy and discuss some of the remaining questions in this field, focusing on cancer, neurodegenerative diseases, infectious diseases and metabolic disorders.

Expression of autophagy related genes in peripheral blood cells in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder and affects dopaminergic neurons. Autophagy often shows a circadian rhythm pattern under physiological conditions across 24 h. Abnormal autophagy and circadian dysfunction are two characteristics of PD. Whether the rhythm of autophagy is altered in PD has not yet been reported. Therefore, in this study, we collected peripheral blood samples at 6:00 h and 18:00 h from PD patients and age-matched controls, and analyzed the mRNA expressions of ULK1, BECN1, LAMP2, AMPK, and SNCA using real-time quantitative PCR. Blood samples analysis found that BECN1 and LAMP2 levels were decreased in patients with PD. Simultaneously, the rhythm of autophagy in PD is not consistent with that in the Control group, which may be a manifestation of the abnormal biological rhythm of PD.

An attempt to dissect a peripheral marker based on cell pathology in Parkinson's disease

Peripheral markers in Parkinson's disease (PD) represent a hot issue to provide early diagnosis and assess disease progression. The gold standard marker of PD should feature the same reliability as the pathogenic alteration, which produces the disease itself. PD is foremost a movement disorder produced by a loss of nigrostriatal dopamine innervation, in which striatal dopamine terminals are always markedly reduced in PD patients to an extent, which never overlaps with controls. Similarly, a reliable marker of PD should possess such a non-overlapping feature when compared with controls. In the present study, we provide a novel pathological hallmark, the autophagosome, which in each PD patient was always suppressed compared with each control subject. Autophagosomes were counted as microtubule-associated proteins 1A/1B light chain 3B (LC3)-positive vacuoles at ultrastructural morphometry within peripheral (blood) blood mononuclear cells (PBMC). This also provides the gold standard to assess the autophagy status. Since autophagy may play a role in the pathogenesis of PD, autophagosomes may be a disease marker, while participating in the biology of the disease. Stoichiometric measurement of α-synuclein despite significantly increased in PD patients, overlapped between PD and control patients. Although the study need to be validated in large populations, the number of autophagy vacuoles is neither related with therapy (the amount was similarly suppressed in a few de novo patients), nor the age in PD or controls.

Network-Based Analysis of Cognitive Impairment and Memory Deficits from Transcriptome Data

Aging is an inevitable process that negatively affects all living organisms and their vital functions. The brain is one of the most important organs in living beings and is primarily impacted by aging. The molecular mechanisms of learning, memory and cognition are altered over time, and the impairment in these mechanisms can lead to neurodegenerative diseases. Transcriptomics can be used to study these impairments to acquire more detailed information on the affected molecular mechanisms. Here we analyzed learning- and memory-related transcriptome data by mapping it on the organism-specific protein-protein interactome network. Subnetwork discovery algorithms were applied to discover highly dysregulated subnetworks, which were complemented with co-expression-based interactions. The functional analysis shows that the identified subnetworks are enriched with genes having roles in synaptic plasticity, gliogenesis, neurogenesis and cognition, which are reported to be related to memory and learning. With a detailed analysis, we show that the results from different subnetwork discovery algorithms or from different transcriptomic datasets can be successfully reconciled, leading to a memory-learning network that sheds light on the molecular mechanisms behind aging and memory-related impairments.

HSPA8 knock-down induces the accumulation of neurodegenerative disorder-associated proteins

Heat shock protein 70 family was demonstrated to play a critical role in protein homeostasis, a process profoundly impaired in neurodegenerative disorders. Neurodegenerative diseases are characterized by the accumulation of different kind of proteins and the formation of insoluble aggregates which are toxic for neurons. To explore the role of heat shock protein family 70 (in particular HSPA8 and HSPA1A) in the accumulation of proteins implied in neurodegeneration pathogenesis, in this study we verified in human SH-SY5Y neuroblastoma cells how HSPA8 or HSPA1A knock-down can affect protein levels of tau, superoxide dismutase 1 and α-synuclein. We found HSPA8 and HSPA1A reduction caused an increase of tau, superoxide dismutase 1 and α-synuclein protein levels. We also noticed HSPA8 knock-down increased α-synuclein oligomeric forms and mRNA expression. Our results suggest HSPA8 can play an important role in the homeostasis of tau, superoxide dismutase 1 and α-synuclein and in the balance between α-synuclein oligomeric and monomeric forms.

Metabolic determinants of leukocyte pathogenicity in neurological diseases

Neuroinflammatory and neurodegenerative diseases are characterized by the recruitment of circulating blood-borne innate and adaptive immune cells into the central nervous system (CNS). These leukocytes sustain the detrimental response in the CNS by releasing pro-inflammatory mediators that induce activation of local glial cells, blood-brain barrier (BBB) dysfunction, and neural cell death. However, infiltrating peripheral immune cells could also dampen CNS inflammation and support tissue repair. Recent advances in the field of immunometabolism demonstrate the importance of metabolic reprogramming for the activation and functionality of such innate and adaptive immune cell populations. In particular, an increasing body of evidence suggests that the activity of metabolites and metabolic enzymes could influence the pathogenic potential of immune cells during neuroinflammatory and neurodegenerative disorders. In this review, we discuss the role of intracellular metabolic cues in regulating leukocyte-mediated CNS damage in Alzheimer's and Parkinson's disease, multiple sclerosis and stroke, highlighting the therapeutic potential of drugs targeting metabolic pathways for the treatment of neurological diseases.

Autophagy in Parkinson's Disease

Impaired protein homeostasis and accumulation of damaged or abnormally modified protein are common disease mechanisms in many neurodegenerative disorders, including Parkinson's disease (PD). As one of the major degradation pathways, autophagy plays a pivotal role in maintaining effective turnover of proteins and damaged organelles in cells. Several decades of research efforts led to insights into the potential contribution of impaired autophagy machinery to α-synuclein accumulation and the degeneration of dopaminergic neurons, two major features of PD pathology. In this review, we summarize recent pathological, genetic, and mechanistic findings that link defective autophagy with PD pathogenesis in human patients, animals, and cellular models and discuss current challenges in the field.

Loss of HSPA9 induces peroxisomal degradation by increasing pexophagy

Quality control of peroxisomes is essential for cellular homeostasis. However, the mechanism underlying pexophagy is largely unknown. In this study, we identified HSPA9 as a novel pexophagy regulator. Downregulation of HSPA9 increased macroautophagy/autophagy but decreased the number of peroxisomes in vitro and in vivo. The loss of peroxisomes by HSPA9 depletion was attenuated in SQSTM1-deficient cells. In HSPA9-deficient cells, the level of peroxisomal reactive oxygen species (ROS) increased, while inhibition of ROS blocked pexophagy in HeLa and SH-SY5Y cells. Importantly, reconstitution of HSPA9 mutants found in Parkinson disease failed to rescue the loss of peroxisomes, whereas reconstitution with wild type inhibited pexophagy in HSPA9-depleted cells. Knockdown of Hsc70-5 decreased peroxisomes in Drosophila, and the HSPA9 mutants failed to rescue the loss of peroxisomes in Hsc70-5-depleted flies. Taken together, our findings suggest that the loss of HSPA9 enhances peroxisomal degradation by pexophagy.

Autophagic- and Lysosomal-Related Biomarkers for Parkinson's Disease: Lights and Shadows

Parkinson’s disease (PD) is a neurodegenerative disorder that currently affects 1% of the population over the age of 60 years, for which no disease-modifying treatments exist. This lack of effective treatments is related to the advanced stage of neurodegeneration existing at the time of diagnosis. Thus, the identification of early stage biomarkers is crucial. Biomarker discovery is often guided by the underlying molecular mechanisms leading to the pathology. One of the central pathways deregulated during PD, supported both by genetic and functional studies, is the autophagy-lysosomal pathway. Hence, this review presents different studies on the expression and activity of autophagic and lysosomal proteins, and their functional consequences, performed in peripheral human biospecimens. Although most biomarkers are inconsistent between studies, some of them, namely HSC70 levels in sporadic PD patients, and cathepsin D levels and glucocerebrosidase activity in PD patients carrying GBA mutations, seem to be consistent. Hence, evidence exists that the impairment of the autophagy-lysosomal pathway underlying PD pathophysiology can be detected in peripheral biosamples and further tested as potential biomarkers. However, longitudinal, stratified, and standardized analyses are needed to confirm their clinical validity and utility.

A Cleaning Crew: The Pursuit of Autophagy in Parkinson's Disease

Parkinson's disease (PD) is the second-most common neurodegenerative disorder, neuropathologically characterized by the aggregation of misfolded α-synuclein (α-syn) protein, which appears to be central to the onset and progression of PD pathology. Evidence from pioneering studies has highly advocated the existence of impaired autophagy pathways in the brains of PD patients. Autophagy is an evolutionarily conserved, homeostatic mechanism for minimizing abnormal protein aggregates and facilitating organelle turnover. Any aberration in constitutive autophagy activity results in the aggregation of misfolded α-syn, which, in turn, may further inhibit their own degradation-leading to a vicious cycle of neuronal death. Despite the plethora of available literature, there are still lacunas existing in our understanding of the exact cellular interplay between autophagy impairment and α-syn accumulation-mediated neurotoxicity. In this context, clearance of aggregated α-syn via up-regulation of the autophagy-lysosomal pathway could provide a pharmacologically viable approach to the treatment of PD. The present Review highlights the basics of autophagy and detrimental cross-talk between α-syn and chaperone-mediated autophagy, and α-syn and macroautophagy. It also depicts the interaction between α-syn and novel targets, LRRK2 and mTOR, followed by the role of autophagy in PD from a therapeutic perspective. More importantly, it further updates the reader's understanding of various newer therapeutic avenues that may accomplish disease modification via promoting clearance of toxic α-syn through activation of autophagy.

The coming of age of chaperone-mediated autophagy

Chaperone-mediated autophagy (CMA) was the first studied process that indicated that degradation of intracellular components by the lysosome can be selective - a concept that is now well accepted for other forms of autophagy. Lysosomes can degrade cellular cytosol in a nonspecific manner but can also discriminate what to target for degradation with the involvement of a degradation tag, a chaperone and a sophisticated mechanism to make the selected proteins cross the lysosomal membrane through a dedicated translocation complex. Recent studies modulating CMA activity in vivo using transgenic mouse models have demonstrated that selectivity confers on CMA the ability to participate in the regulation of multiple cellular functions. Timely degradation of specific cellular proteins by CMA modulates, for example, glucose and lipid metabolism, DNA repair, cellular reprograming and the cellular response to stress. These findings expand the physiological relevance of CMA beyond its originally identified role in protein quality control and reveal that CMA failure with age may aggravate diseases, such as ageing-associated neurodegeneration and cancer.

Autophagy dysfunction in peripheral blood mononuclear cells of Parkinson's disease patients

BACKGROUND

Alpha-synuclein aggregation is considered one of the main causes of Parkinson's Disease (PD). Malfunction of autophagy-lysosomal pathways is believed to be an underlying mechanism of α-synuclein aggregation. Although such malfunction has been observed in PD brains, it is unclear whether it may also occur in extraneuronal tissues.

OBJECTIVES

To assess lysosome-mediated protein degradation in cultured Peripheral Blood Mononuclear Cells (PBMCs) of PD patients and healthy controls.

METHODS

Total protein degradation in cultured PBMCs was measured by labelling the cells with ³H-leucine using pulse-chase experiments. Different inhibitors were used to measure a range of autophagic pathways.

RESULTS

Protein degradation through the main autophagic pathways is reduced in PD patients (n = 18) compared to age- and sex-matched healthy controls (n = 18), (macroautophagy, p = .018; Chaperone-Mediated autophagy, p = .04; and total lysosomal function, p = .007).

CONCLUSIONS

Lysosomal dysfunction is present in cultured PBMCs of PD patients, suggesting that it may reflect a systemic feature of the disease.

Pharmacokinetics and pharmacodynamics of a single dose Nilotinib in individuals with Parkinson's disease

Nilotinib is a broad-based tyrosine kinase inhibitor with the highest affinity to inhibit Abelson (c-Abl) and discoidin domain receptors (DDR1/2). Preclinical evidence indicates that Nilotinib reduces the level of brain alpha-synuclein and attenuates inflammation in models of Parkinson's disease (PD). We previously showed that Nilotinib penetrates the blood-brain barrier (BBB) and potentially improves clinical outcomes in individuals with PD and dementia with Lewy bodies (DLB). We performed a physiologically based population pharmacokinetic/pharmacodynamic (popPK/PD) study to determine the effects of Nilotinib in a cohort of 75 PD participants. Participants were randomized (1:1:1:1:1) into five groups (n = 15) and received open-label random single dose (RSD) 150:200:300:400 mg Nilotinib vs placebo. Plasma and cerebrospinal fluid (CSF) were collected at 1, 2, 3, and 4 hours after Nilotinib administration. The results show that Nilotinib enters the brain in a dose-independent manner and 200 mg Nilotinib increases the level of 3,4-Dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), suggesting alteration to dopamine metabolism. Nilotinib significantly reduces plasma total alpha-synuclein and appears to reduce CSF oligomeric: total alpha-synuclein ratio. Furthermore, Nilotinib significantly increases the CSF level of triggering receptors on myeloid cells (TREM)-2, suggesting an anti-inflammatory effect. Taken together, 200 mg Nilotinib appears to be an optimal single dose that concurrently reduces inflammation and engages surrogate disease biomarkers, including dopamine metabolism and alpha-synuclein.

Protein homeostasis of a metastable subproteome associated with Alzheimer's disease

Alzheimer's disease is the most common cause of dementia. A hallmark of this disease is the presence of aberrant deposits containing by the Aβ peptide (amyloid plaques) and the tau protein (neurofibrillary tangles) in the brains of affected individuals. Increasing evidence suggests that the formation of these deposits is closely associated with the age-related dysregulation of a large set of highly expressed and aggregation-prone proteins, which make up a metastable subproteome. To understand in more detail the origins of such dysregulation, we identify specific components of the protein homeostasis system associated with these metastable proteins by using a gene coexpression analysis. Our results reveal the particular importance of the protein trafficking and clearance mechanisms, including specific branches of the endosomal-lysosomal and ubiquitin-proteasome systems, in maintaining the homeostasis of the metastable subproteome associated with Alzheimer's disease.

Role of Chaperone-Mediated Autophagy Dysfunctions in the Pathogenesis of Parkinson's Disease

Chaperone-mediated autophagy (CMA) represents a selective form of autophagy involved in the degradation of specific soluble proteins containing a pentapeptide motif that is recognized by a cytosolic chaperone able to deliver proteins to the lysosomes for degradation. Physiologically, CMA contributes to maintain crucial cellular functions including energetic balance and protein quality control. Dysfunctions in CMA have been associated to the pathogenesis of several neurodegenerative diseases characterized by accumulation and aggregation of proteins identified as CMA substrates. In particular, increasing evidence highlights the existence of a strong relationship between CMA defects and Parkinson’s disease (PD). Several mutations associated with familial forms of PD (SNCA, LRRK2, UCHL1 and DJ-1) have been demonstrated to block or reduce the activity of CMA, the main catabolic pathway for alpha-synuclein (asyn). CMA dysfunctions also leads to a mislocalization and inactivation of the transcription factor MEF2D that plays a key-role in the survival of dopaminergic neurons. Furthermore, reduced levels of CMA markers have been observed in post mortem brain samples from PD patients. The aim of this review article is to provide an organic revision of evidence for the involvement of CMA dysfunctions in the pathogenesis of PD. Updated findings obtained in patient’s specimens will be resumed, and results deriving from in vivo and in vitro studies will be discussed to evidence the current knowledge on the molecular mechanisms underlying CMA alterations in PD. Finally, the possibility of up-regulating CMA pathway as promising neuroprotective strategy will be considered.

Chaperone mediated autophagy in aging: Starve to prosper

The major lysosomal proteolytic pathways essential for maintaining proper cellular homeostasis are macroautophagy, chaperone-mediated autophagy (CMA) and microautophagy. What differentiates CMA from the other types of autophagy is the fact that it does not involve vesicle formation; the unique feature of this pathway is the selective targeting of substrate proteins containing a CMA-targeting motif and the direct translocation into the lysosomal lumen, through the aid of chaperones/co-chaperones localized both at the cytosol and the lysosomes. CMA operates at basal conditions in most mammalian cell models analyzed so far, but it is mostly activated in response to stressors, such as trophic deprivation or oxidative stress. The activity of CMA has been shown to decline with age and such decline, correlating with accumulation of damaged/oxidized/aggregated proteins, may contribute to tissue dysfunction and, possibly, neurodegeneration. Herein, we review the recent knowledge regarding the molecular components, regulation and physiology of the CMA pathway, the contribution of impaired CMA activity to poor cellular homeostasis and inefficient response to stress during aging, and discuss the therapeutic opportunities offered by the restoration of CMA-dependent proteolysis in age-associated degenerative diseases.

Parkinson's disease: acid-glucocerebrosidase activity and alpha-synuclein clearance

The role of mutations in the gene GBA1 encoding the lysosomal hydrolase β-glucocerebrosidase for the development of synucleinopathies, such as Parkinson's disease and dementia with Lewy bodies, was only very recently uncovered. The knowledge obtained from the study of carriers or patients suffering from Gaucher disease (a common lysosomal storage disorder because of GBA1 mutations) is of particular importance for understanding the role of the enzyme and its catabolic pathway in the development of synucleinopathies. Decreased activity of β-glucocerebrosidase leads to lysosomal dysfunction and the accumulation of its substrate glucosylceramide and related lipid derivatives. Glucosylceramide is suggested to stabilize toxic oligomeric forms of α-synuclein that negatively influence the activity of β-glucocerebrosidase and to partially block export of newly synthesized β-glucocerebrosidase from the endoplasmic reticulum to late endocytic compartments, amplifying the pathological effects of α-synuclein and ultimately resulting in neuronal cell death. This pathogenic molecular feedback loop and most likely other factors (such as impaired endoplasmic reticulum-associated degradation, activation of the unfolded protein response and dysregulation of calcium homeostasis induced by misfolded GC mutants) are involved in shifting the cellular homeostasis from monomeric α-synuclein towards oligomeric neurotoxic and aggregated forms, which contribute to Parkinson's disease progression. From a therapeutic point of view, strategies aiming to increase either the expression, stability or delivery of the β-glucocerebrosidase to lysosomes are likely to decrease the α-synuclein burden and may be useful for an in depth evaluation at the organismal level. Lysosomes are critical for protein and lipid homeostasis. Recent research revealed that dysfunction of this organelle contributes to the development of neurodegenerative diseases such as Parkinson's disease (PD). Mutations in the lysosomal hydrolase β-glucocerebrosidase (GBA1) are a major risk factor for the development of PD and the molecular events linked to the reduced activity of GBA1 and the pathological accumulation of lipids and α-synuclein are just at the beginning to be understood. New therapeutic concepts in regards to how to increase the expression, stability, or delivery of β-glucocerebrosidase to lysosomes are currently developed. This article is part of a special issue on Parkinson disease.

Lysosomal alterations in peripheral blood mononuclear cells of Parkinson's disease patients

BACKGROUND

Reduced expression of lysosomal-associated membrane protein 2a and heatshock-cognate 70 proteins, involved in chaperone-mediated autophagy and of glucocerebrosidase, is reported in PD brains. The aim of this study was to identify systemic alterations in lysosomal-associated membrane protein 2a, heatshock cognate-70, and glucocerebrosidase levels/activity in peripheral blood mononuclear cells from PD patients.

METHODS

Protein/mRNA levels were assessed in PD patients from genetically undetermined background, alpha-synuclein (G209A/A53T), or glucocerebrosidase mutation carriers and age-/sex-matched controls.

RESULTS

Heatshock cognate 70 protein levels were reduced in all PD groups, whereas its mRNA levels were decreased only in the genetically undetermined group. Glucocerebrosidase protein levels were decreased only in the genetic PD groups, whereas increased mRNA levels and decreased activity were detected only in the glucocerebrosidase mutation group.

CONCLUSIONS

Reduced heatshock cognate-70 levels are suggestive of an apparent systemic chaperone-mediated autophagy dysfunction irrespective of genetic background. Glucocerebrosidase activity may serve as a screening tool to identify glucocerebrosidase mutation carriers with PD.

Αlpha-Synuclein as a Mediator in the Interplay between Aging and Parkinson's Disease

Accumulation and misfolding of the alpha-synuclein protein are core mechanisms in the pathogenesis of Parkinson's disease. While the normal function of alpha-synuclein is mainly related to the control of vesicular neurotransmission, its pathogenic effects are linked to various cellular functions, which include mitochondrial activity, as well as proteasome and autophagic degradation of proteins. Remarkably, these functions are also affected when the renewal of macromolecules and organelles becomes impaired during the normal aging process. As aging is considered a major risk factor for Parkinson's disease, it is critical to explore its molecular and cellular implications in the context of the alpha-synuclein pathology. Here, we discuss similarities and differences between normal brain aging and Parkinson's disease, with a particular emphasis on the nigral dopaminergic neurons, which appear to be selectively vulnerable to the combined effects of alpha-synuclein and aging.

Genes associated with Parkinson's disease: regulation of autophagy and beyond

Substantial progress has been made in the genetic basis of Parkinson's disease (PD). In particular, by identifying genes that segregate with inherited PD or show robust association with sporadic disease, and by showing the same genes are found on both lists, we have generated an outline of the cause of this condition. Here, we will discuss what those genes tell us about the underlying biology of PD. We specifically discuss the relationships between protein products of PD genes and show that common links include regulation of the autophagy-lysosome system, an important way by which cells recycle proteins and organelles. We also discuss whether all PD genes should be considered to be in the same pathway and propose that in some cases the relationships are closer, whereas in other cases the interactions are more distant and might be considered separate. Beilina and Cookson review the links between genes for Parkinson's disease (red) and the autophagy-lysosomal system. They propose the hypothesis that many of the known PD genes can be assigned to pathways that affect (I) turnover of mitochondria via mitophagy (II) turnover of several vesicular structures via macroautophagy or chaperone-mediated autophagy or (III) general lysosome function. This article is part of a special issue on Parkinson disease.

Untangling autophagy measurements: all fluxed up

Autophagy is an important physiological process in the heart, and alterations in autophagic activity can exacerbate or mitigate injury during various pathological processes. Methods to assess autophagy have changed rapidly because the field of research has expanded. As with any new field, methods and standards for data analysis and interpretation evolve as investigators acquire experience and insight. The purpose of this review is to summarize current methods to measure autophagy, selective mitochondrial autophagy (mitophagy), and autophagic flux. We will examine several published studies where confusion arose in data interpretation, to illustrate the challenges. Finally, we will discuss methods to assess autophagy in vivo and in patients.

Chaperone mediated autophagy to the rescue: A new-fangled target for the treatment of neurodegenerative diseases

One of the main pathways of lysosomal proteolysis is chaperone-mediated autophagy (CMA), which represents a selective mechanism for the degradation of specific soluble proteins within lysosomes. Along with the other two lysosomal pathways, macro- and micro-autophagy, CMA contributes to cellular quality control through the removal of damaged or malfunctioning proteins. The two intrinsic characteristics of CMA are the selective targeting and the direct translocation of substrate proteins into the lysosomal lumen, in a fine-tuned manner through the orchestrated action of a chaperone/co-chaperone complex localized both at the cytosol and the lysosomes. Even though CMA was originally identified as a stress-induced pathway, basal CMA activity is detectable in most cell types analyzed so far, including neurons. Additionally, CMA activity declines with age and this may become a major aggravating factor contributing to neurodegeneration. More specifically, it has been suggested that CMA impairment may underlie the accumulation of misfolded/aggregated proteins, such as alpha-synuclein or LRRK2, whose levels or conformations are critical to Parkinson's disease pathogenesis. On the other hand, CMA induction might accelerate clearance of pathogenic proteins and promote cell survival, suggesting that CMA represents a viable therapeutic target for the treatment of various proteinopathies. In the current review, we provide an overview of the current state of knowledge regarding the role of CMA under physiological and pathological conditions of the nervous system and discuss the implications of these findings for therapeutic interventions for Parkinson's disease and other neurodegenerative disorders. This article is part of Special Issue entitled "Neuronal Protein".

The autophagy/lysosome pathway is impaired in SCA7 patients and SCA7 knock-in mice

There is still no treatment for polyglutamine disorders, but clearance of mutant proteins might represent a potential therapeutic strategy. Autophagy, the major pathway for organelle and protein turnover, has been implicated in these diseases. To determine whether the autophagy/lysosome system contributes to the pathogenesis of spinocerebellar ataxia type 7 (SCA7), caused by expansion of a polyglutamine tract in the ataxin-7 protein, we looked for biochemical, histological and transcriptomic abnormalities in components of the autophagy/lysosome pathway in a knock-in mouse model of the disease, postmortem brain and peripheral blood mononuclear cells (PBMC) from patients. In the mouse model, mutant ataxin-7 accumulated in inclusions immunoreactive for the autophagy-associated proteins mTOR, beclin-1, p62 and ubiquitin. Atypical accumulations of the autophagosome/lysosome markers LC3, LAMP-1, LAMP2 and cathepsin-D were also found in the cerebellum of the SCA7 knock-in mice. In patients, abnormal accumulations of autophagy markers were detected in the cerebellum and cerebral cortex of patients, but not in the striatum that is spared in SCA7, suggesting that autophagy might be impaired by the selective accumulation of mutant ataxin-7. In vitro studies demonstrated that the autophagic flux was impaired in cells overexpressing full-length mutant ataxin-7. Interestingly, the expression of the early autophagy-associated gene ATG12 was increased in PBMC from SCA7 patients in correlation with disease severity. These results provide evidence that the autophagy/lysosome pathway is impaired in neurons undergoing degeneration in SCA7. Autophagy/lysosome-associated molecules might, therefore, be useful markers for monitoring the effects of potential therapeutic approaches using modulators of autophagy in SCA7 and other autophagy/lysosome-associated neurodegenerative disorders.

Chaperone-mediated autophagy: dedicated saviour and unfortunate victim in the neurodegeneration arena

The importance of cellular quality-control systems in the maintenance of neuronal homoeostasis and in the defence against neurodegeneration is well recognized. Chaperones and proteolytic systems, the main components of these cellular surveillance mechanisms, are key in the fight against the proteotoxicity that is often associated with severe neurodegenerative diseases. However, in recent years, a new theme has emerged which suggests that components of protein quality-control pathways are often targets of the toxic effects of pathogenic proteins and that their failure to function properly contributes to pathogenesis and disease progression. In the present mini-review, we describe this dual role as 'saviour' and 'victim' in the context of neurodegeneration for chaperone-mediated autophagy, a cellular pathway involved in the selective degradation of cytosolic proteins in lysosomes.

Bioenergetic and proteolytic defects in fibroblasts from patients with sporadic Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a complex disease and the current interest and focus of scientific research is both investigating the variety of causes that underlie PD pathogenesis, and identifying reliable biomarkers to diagnose and monitor the progression of pathology. Investigation on pathogenic mechanisms in peripheral cells, such as fibroblasts derived from patients with sporadic PD and age/gender matched controls, might generate deeper understanding of the deficits affecting dopaminergic neurons and, possibly, new tools applicable to clinical practice.

METHODS

Primary fibroblast cultures were established from skin biopsies. Increased susceptibility to the PD-related toxin rotenone was determined with apoptosis- and necrosis-specific cell death assays. Protein quality control was evaluated assessing the efficiency of the Ubiquitin Proteasome System (UPS) and protein levels of autophagic markers. Changes in cellular bioenergetics were monitored by measuring oxygen consumption and glycolysis-dependent medium acidification. The oxido-reductive status was determined by detecting mitochondrial superoxide production and oxidation levels in proteins and lipids.

RESULTS

PD fibroblasts showed higher vulnerability to necrotic cell death induced by complex I inhibitor rotenone, reduced UPS function and decreased maximal and rotenone-sensitive mitochondrial respiration. No changes in autophagy and redox markers were detected.

CONCLUSIONS

Our study shows that increased susceptibility to rotenone and the presence of proteolytic and bioenergetic deficits that typically sustain the neurodegenerative process of PD can be detected in fibroblasts from idiopathic PD patients. Fibroblasts might therefore represent a powerful and minimally invasive tool to investigate PD pathogenic mechanisms, which might translate into considerable advances in clinical management of the disease.

Loss of PINK1 impairs stress-induced autophagy and cell survival

The mitochondrial kinase PINK1 and the ubiquitin ligase Parkin are participating in quality control after CCCP- or ROS-induced mitochondrial damage, and their dysfunction is associated with the development and progression of Parkinson's disease. Furthermore, PINK1 expression is also induced by starvation indicating an additional role for PINK1 in stress response. Therefore, the effects of PINK1 deficiency on the autophago-lysosomal pathway during stress were investigated. Under trophic deprivation SH-SY5Y cells with stable PINK1 knockdown showed downregulation of key autophagic genes, including Beclin, LC3 and LAMP-2. In good agreement, protein levels of LC3-II and LAMP-2 but not of LAMP-1 were reduced in different cell model systems with PINK1 knockdown or knockout after addition of different stressors. This downregulation of autophagic factors caused increased apoptosis, which could be rescued by overexpression of LC3 or PINK1. Taken together, the PINK1-mediated reduction of autophagic key factors during stress resulted in increased cell death, thus defining an additional pathway that could contribute to the progression of Parkinson's disease in patients with PINK1 mutations.

Reduced expression of the chaperone-mediated autophagy carrier hsc70 protein in lymphomonocytes of patients with Parkinson's disease

Chaperone-mediated autophagy (CMA) impairment is recognized to play a pathogenetic role in Parkinson's disease (PD). A reduced expression of lysosomal-associated membrane protein (lamp) 2A and heat shock cognate (hsc) 70 protein, the two key regulators of CMA, has been reported in brains of PD patients. To verify the existence of a possible systemic CMA dysfunction in PD, in this study the expression of hsc70 and lamp2A was assessed in peripheral blood mononuclear cells (PBMC) of patients with sporadic PD and compared to healthy subjects. The expression of myocyte enhancer factor 2D (MEF2D), a transcriptional factor implicated in neuronal survival and specific substrate of CMA, was also evaluated. Protein and gene expression was assessed by Western blot and real-time PCR, respectively, in PBMC obtained from 53 sporadic PD patients and 53 healthy subjects. A significant reduction of hsc70 levels was observed in PBMC of PD patients, both under basal conditions and after autophagy induction obtained with serum deprivation. No difference emerged in lamp2A and MEF2D expression between patients and controls. No influence of the clinical characteristics of patients emerged on hsc70, lamp2A and MEF2D expression. These results, despite being not suggestive of the existence of a CMA impairment in PBMC of PD patients, identify a systemic hsc70 reduction in PD patients. Further studies on specific mechanisms and biological significance of such alteration are needed to corroborate this finding that could lead to the identification of a new trait biomarker for PD.