Immunohistochemical evidence for macroautophagy in neurones and endothelial cells in Alzheimer's disease

PTPRS is a novel marker for early Tau pathology and synaptic integrity in Alzheimer's disease

We examined the role of protein tyrosine phosphatase receptor sigma (PTPRS) in the context of Alzheimer's disease and synaptic integrity. Publicly available datasets (BRAINEAC, ROSMAP, ADC1) and a cohort of asymptomatic but "at risk" individuals (PREVENT-AD) were used to explore the relationship between PTPRS and various Alzheimer's disease biomarkers. We identified that PTPRS rs10415488 variant C shows features of neuroprotection against early Tau pathology and synaptic degeneration in Alzheimer's disease. This single nucleotide polymorphism correlated with higher PTPRS transcript abundance and lower p(181)Tau and GAP-43 levels in the CSF. In the brain, PTPRS protein abundance was significantly correlated with the quantity of two markers of synaptic integrity: SNAP25 and SYT-1. We also found the presence of sexual dimorphism for PTPRS, with higher CSF concentrations in males than females. Male carriers for variant C were found to have a 10-month delay in the onset of AD. We thus conclude that PTPRS acts as a neuroprotective receptor in Alzheimer's disease. Its protective effect is most important in males, in whom it postpones the age of onset of the disease.

PTPRS is a novel marker for early tau pathology and synaptic integrity in Alzheimer's disease

We examined the role of protein tyrosine phosphatase receptor sigma (PTPRS) in the context of Alzheimer's disease and synaptic integrity. Publicly available datasets (BRAINEAC, ROSMAP, ADC1) and a cohort of asymptomatic but "at risk" individuals (PREVENT-AD) were used to explore the relationship between PTPRS and various Alzheimer's disease biomarkers. We identified that PTPRS rs10415488 variant C shows features of neuroprotection against early tau pathology and synaptic degeneration in Alzheimer's disease. This single nucleotide polymorphism correlated with higher PTPRS transcript abundance and lower P-tau181 and GAP-43 levels in the CSF. In the brain, PTPRS protein abundance was significantly correlated with the quantity of two markers of synaptic integrity: SNAP25 and SYT-1. We also found the presence of sexual dimorphism for PTPRS, with higher CSF concentrations in males than females. Male carriers for variant C were found to have a 10-month delay in the onset of AD. We thus conclude that PTPRS acts as a neuroprotective receptor in Alzheimer's disease. Its protective effect is most important in males, in whom it postpones the age of onset of the disease.

The obesity-autophagy-cancer axis: Mechanistic insights and therapeutic perspectives

Autophagy, a self-degradative process vital for cellular homeostasis, plays a significant role in adipose tissue metabolism and tumorigenesis. This review aims to elucidate the complex interplay between autophagy, obesity, and cancer development, with a specific emphasis on how obesity-driven changes affect the regulation of autophagy and subsequent implications for cancer risk. The burgeoning epidemic of obesity underscores the relevance of this research, particularly given the established links between obesity, autophagy, and various cancers. Our exploration delves into hormonal influence, notably INS (insulin) and LEP (leptin), on obesity and autophagy interactions. Further, we draw attention to the latest findings on molecular factors linking obesity to cancer, including hormonal changes, altered metabolism, and secretory autophagy. We posit that targeting autophagy modulation may offer a potent therapeutic approach for obesity-associated cancer, pointing to promising advancements in nanocarrier-based targeted therapies for autophagy modulation. However, we also recognize the challenges inherent to these approaches, particularly concerning their precision, control, and the dual roles autophagy can play in cancer. Future research directions include identifying novel biomarkers, refining targeted therapies, and harmonizing these approaches with precision medicine principles, thereby contributing to a more personalized, effective treatment paradigm for obesity-mediated cancer.

The Molecular Mechanism and Therapeutic Application of Autophagy for Urological Disease

Autophagy is a lysosomal degradation process known as autophagic flux, involving the engulfment of damaged proteins and organelles by double-membrane autophagosomes. It comprises microautophagy, chaperone-mediated autophagy (CMA), and macroautophagy. Macroautophagy consists of three stages: induction, autophagosome formation, and autolysosome formation. Atg8-family proteins are valuable for tracking autophagic structures and have been widely utilized for monitoring autophagy. The conversion of LC3 to its lipidated form, LC3-II, served as an indicator of autophagy. Autophagy is implicated in human pathophysiology, such as neurodegeneration, cancer, and immune disorders. Moreover, autophagy impacts urological diseases, such as interstitial cystitis /bladder pain syndrome (IC/BPS), ketamine-induced ulcerative cystitis (KIC), chemotherapy-induced cystitis (CIC), radiation cystitis (RC), erectile dysfunction (ED), bladder outlet obstruction (BOO), prostate cancer, bladder cancer, renal cancer, testicular cancer, and penile cancer. Autophagy plays a dual role in the management of urologic diseases, and the identification of potential biomarkers associated with autophagy is a crucial step towards a deeper understanding of its role in these diseases. Methods for monitoring autophagy include TEM, Western blot, immunofluorescence, flow cytometry, and genetic tools. Autophagosome and autolysosome structures are discerned via TEM. Western blot, immunofluorescence, northern blot, and RT-PCR assess protein/mRNA levels. Luciferase assay tracks flux; GFP-LC3 transgenic mice aid study. Knockdown methods (miRNA and RNAi) offer insights. This article extensively examines autophagy's molecular mechanism, pharmacological regulation, and therapeutic application involvement in urological diseases.

Protective effect of saffron carotenoids against amyloid beta-induced neurotoxicity in differentiated PC12 cells via the unfolded protein response and autophagy

The preventive effect of saffron against Alzheimer's disease (AD) has been reported. Herein, we studied the effect of Cro and Crt, saffron carotenoids, on the cellular model of AD. The MTT assay, flow cytometry, and elevated p-JNK, p-Bcl-2, and c-PARP indicated the AβOs-induced apoptosis in differentiated PC12 cells. Then, the protective effects of Cro/Crt on dPC12 cells against AβOs were investigated in preventive and therapeutic modalities. Starvation was used as a positive control. RT-PCR and Western blot results revealed the reduced eIF2α phosphorylation and increased spliced-XBP1, Beclin1, LC3II, and p62, which indicate the AβOs-induced autophagic flux defect, autophagosome accumulation, and apoptosis. Cro and Crt inhibited the JNK-Bcl-2-Beclin1 pathway. They altered Beclin1 and LC3II and decreased p62 expressions, leading cells to survival. Cro and Crt altered the autophagic flux by different mechanisms. So, Cro increased the rate of autophagosome degradation more than Crt, while Crt increased the rate of autophagosome formation more than Cro. The application of 4μ8C and chloroquine as the inhibitors of XBP1 and autophagy, respectively, confirmed these results. So, augmentation of the survival branches of UPR and autophagy is involved and may serve as an effective strategy to prevent the progression of AβOs toxicity.

Genetic and Molecular Evaluation of SQSTM1/p62 on the Neuropathologies of Alzheimer’s Disease

Sequestosome 1 (SQSTM1)/p62 is a multifunctional scaffolding protein and plays a major role in the cellular processes of autophagy, upregulation of which has been shown in several neurodegenerative disorders, including Alzheimer’s disease (AD). To investigate its genetic effects and relationship with AD pathologies, we analyzed the genetic associations of SQSTM1 rs4935 with the risk of AD and the levels of AD biomarkers using the AD Neuroimaging Initiative (ADNI) Database. We further analyzed the distribution pattern of p62 immunoreactivity in relation to AD pathologies in the postmortem human brain tissues from AD and non-AD controls. We found that SQSTM1 rs4935 was not associated with the risk of AD, but its T allele was significantly associated with decreased β-amyloid (1–42) (Aβ₄₂) levels in the cerebral spinal fluid (CSF) of patients with AD (β = −9.336, p = 0.022). In addition, p62 immunoreactivity in AD is increased, but it shows an inverse relationship to Aβ deposition. A small proportion of senile plaques show p62 positive neurites. Our results suggest that SQSTM1/p62 may play an important role in the progression of AD via associations with Aβ₄₂ levels in CSF and Aβ deposition in the brain of patients with AD.

Graptopetalum paraguayense Extract Ameliorates Proteotoxicity in Aging and Age-Related Diseases in Model Systems

Declines in physiological functions are the predominant risk factors for age-related diseases, such as cancers and neurodegenerative diseases. Therefore, delaying the aging process is believed to be beneficial in preventing the onset of age-related diseases. Previous studies have demonstrated that Graptopetalum paraguayense (GP) extract inhibits liver cancer cell growth and reduces the pathological phenotypes of Alzheimer’s disease (AD) in patient IPS-derived neurons. Here, we show that GP extract suppresses β-amyloid pathology in SH-SYS5Y-APP₆₉₅ cells and APP/PS1 mice. Moreover, AMP-activated protein kinase (AMPK) activity is enhanced by GP extract in U87 cells and APP/PS1 mice. Intriguingly, GP extract enhances autophagy in SH-SYS5Y-APP₆₉₅ cells, U87 cells, and the nematode Caenorhabditis elegans, suggesting a conserved molecular mechanism by which GP extract might regulate autophagy. In agreement with its role as an autophagy activator, GP extract markedly diminishes mobility decline in polyglutamine Q35 mutants and aged wild-type N2 animals in C. elegans. Furthermore, GP extract significantly extends lifespan in C. elegans.

Alzheimer's Disease: A Molecular View of β-Amyloid Induced Morbific Events

Amyloid-β (Aβ) is a dynamic peptide of Alzheimer’s disease (AD) which accelerates the disease progression. At the cell membrane and cell compartments, the amyloid precursor protein (APP) undergoes amyloidogenic cleavage by β- and γ-secretases and engenders the Aβ. In addition, externally produced Aβ gets inside the cells by receptors mediated internalization. An elevated amount of Aβ yields spontaneous aggregation which causes organelles impairment. Aβ stimulates the hyperphosphorylation of tau protein via acceleration by several kinases. Aβ travels to the mitochondria and interacts with its functional complexes, which impairs the mitochondrial function leading to the activation of apoptotic signaling cascade. Aβ disrupts the Ca²⁺ and protein homeostasis of the endoplasmic reticulum (ER) and Golgi complex (GC) that promotes the organelle stress and inhibits its stress recovery machinery such as unfolded protein response (UPR) and ER-associated degradation (ERAD). At lysosome, Aβ precedes autophagy dysfunction upon interacting with autophagy molecules. Interestingly, Aβ act as a transcription regulator as well as inhibits telomerase activity. Both Aβ and p-tau interaction with neuronal and glial receptors elevate the inflammatory molecules and persuade inflammation. Here, we have expounded the Aβ mediated events in the cells and its cosmopolitan role on neurodegeneration, and the current clinical status of anti-amyloid therapy.

Autophagy in Acute Pancreatitis: Organelle Interaction and microRNA Regulation

Acute pancreatitis (AP) is a common disorder with significant hospital admission and mortality. Due to the unclarified pathological mechanism, there is still no effective and specific treatment for AP. Recently, autophagy has been found to be closely related with occurrence and development of AP, which is crucial in determining its severity and outcomes. Emerging evidence indicates that autophagy can be regulated and influenced by microRNAs and organelles, including mitochondria, endoplasmic reticulum and lysosome, through various ways in AP. Of note, the complex interplays and close relationships among autophagy, microRNA and organelles in AP are vital for figuring out pathogenesis but not clear yet. Thus, this review summarizes the role of autophagy in the pathological mechanism of AP, especially the relationship between impaired autophagy and organelles, and discusses the regulatory mechanism of microRNA on autophagy, which could offer new insights into understanding the pathogenesis of AP and developing new potential therapeutic targets against AP.

An Update on Autophagy in Prion Diseases

Autophagy is a dynamic intracellular mechanism involved in protein and organelle turnover through lysosomal degradation. When properly regulated, autophagy supports normal cellular and developmental processes, whereas defects in autophagic degradation have been associated with several pathologies, including prion diseases. Prion diseases, or transmissible spongiform encephalopathies (TSE), are a group of fatal neurodegenerative disorders characterized by the accumulation of the pathological misfolded isoform (PrP^Sc) of the physiological cellular prion protein (PrP^c) in the central nervous system. Autophagic vacuoles have been described in experimental models of TSE and in the natural disease in humans. The precise connection of this process with prion-related neuropathology, or even whether autophagy is completely beneficial or pathogenic during neurodegeneration, is poorly understood. Thus, the biological role of autophagy in these diseases is still open to debate. During the last years, researchers have used a wide range of morphological, genetic and biochemical methods to monitor and manipulate the autophagic pathway and thus determine the specific role of this process in TSE. It has been suggested that PrP^c could play a crucial role in modulating the autophagic pathway in neuronal cells, and the presence of abnormal autophagic activity has been frequently observed in several models of TSE both in vitro and in vivo, as well as in human prion diseases. Altogether, these findings suggest that autophagy is implicated in prion neuropathology and points to an impairment or failure of the process, potentially contributing to the pathogenesis of the disease. Additionally, autophagy is now emerging as a host defense response in controlling prion infection that plays a protective role by facilitating the clearance of aggregation-prone proteins accumulated within neurons. Since autophagy is one of the pathways of PrP^Sc degradation, and drug-induced stimulation of autophagic flux (the dynamic process of autophagic degradation activity) produces anti-prion effects, new treatments based on its activation have been tested to develop therapeutic strategies for prion diseases. In this review, we summarize previous and recent findings concerning the role of autophagy in TSE.

A Systematic Bioinformatics Workflow With Meta-Analytics Identified Potential Pathogenic Factors of Alzheimer's Disease

Potential pathogenic factors, other than well-known APP, APOE4, and PSEN, can be further identified from transcriptomics studies of differentially expressed genes (DEGs) that are specific for Alzheimer’s disease (AD), but findings are often inconsistent or even contradictory. Evidence corroboration by combining meta-analysis and bioinformatics methods may help to resolve existing inconsistencies and contradictions. This study aimed to demonstrate a systematic workflow for evidence synthesis of transcriptomic studies using both meta-analysis and bioinformatics methods to identify potential pathogenic factors. Transcriptomic data were assessed from GEO and ArrayExpress after systematic searches. The DEGs and their dysregulation states from both DNA microarray and RNA sequencing datasets were analyzed and corroborated by meta-analysis. Statistically significant DEGs were used for enrichment analysis based on KEGG and protein–protein interaction network (PPIN) analysis based on STRING. AD-specific modules were further determined by the DIAMOnD algorithm, which identifies significant connectivity patterns between specific disease-associated proteins and non-specific proteins. Within AD-specific modules, the nodes of highest degrees (>95th percentile) were considered as potential pathogenic factors. After systematic searches of 225 datasets, extensive meta-analyses among 25 datasets (21 DNA microarray datasets and 4 RNA sequencing datasets) identified 9,298 DEGs. The dysregulated genes and pathways in AD were associated with impaired amyloid-β (Aβ) clearance. From the AD-specific module, Fyn, and EGFR were the most statistically significant and biologically relevant. This meta-analytical study suggested that the reduced Aβ clearance in AD pathogenesis was associated with the genes encoding Fyn and EGFR, which were key receptors in Aβ downstream signaling.

Age-Associated mRNA and miRNA Expression Changes in the Blood-Brain Barrier

Functional and structural age-associated changes in the blood-brain barrier (BBB) may affect the neurovascular unit and contribute to the onset and progression of age-associated neurodegenerative pathologies, including Alzheimer’s disease. The current study interrogated the RNA profile of the BBB in an ageing human autopsy brain cohort and an ageing mouse model using combined laser capture microdissection and expression profiling. Only 12 overlapping genes were altered in the same direction in the BBB of both ageing human and mouse cohorts. These included genes with roles in regulating vascular tone, tight junction protein expression and cell adhesion, all processes prone to dysregulation with advancing age. Integrated mRNA and miRNA network and pathway enrichment analysis of the datasets identified 15 overlapping miRNAs that showed altered expression. In addition to targeting genes related to DNA binding and/or autophagy, many of the miRNAs identified play a role in age-relevant processes, including BBB dysfunction and regulating the neuroinflammatory response. Future studies have the potential to develop targeted therapeutic approaches against these candidates to prevent vascular dysfunction in the ageing brain.

Plasma ATG5 is increased in Alzheimer's disease

Alzheimer’s disease (AD) is a major cause of dementia. Growing evidence suggests that dysregulation of autophagy, a cellular mechanism essential for self-digestion of damaged proteins and organelles, is involved in neurological degenerative diseases including AD. Previously, we reported that autophagosomes are increased in the brains of AD mouse model. However, the plasma levels of autophagic markers have not yet been investigated in patients with AD. In this study, we investigated the expression of autophagy-related genes 5 and 12 (ATG5 and ATG12, respectively) in cells in vitro upon amyloid-beta (Aβ) treatment and in the plasma of AD patients. ATG5-ATG12 complex levels were increased in primary rat cortical neurons and human umbilical vein endothelial cells after Aβ treatment. Furthermore, we compared plasma from 69 patients with dementia, 82 patients with mild cognitive impairment (MCI), and 127 cognitively normal control participants. Plasma levels of ATG5 were significantly elevated in patients with dementia (149.3 ± 7.5 ng/mL) or MCI (152.9 ± 6.9 ng/mL) compared with the control subjects (129.0 ± 4.1 ng/mL) (p = 0.034, p = 0.016, respectively). Our results indicate that alterations in the plasma ATG5 levels might be a potential biomarker in patients at risk for AD.

Expression of Autophagy Signaling Molecules in the Outer Membranes of Chronic Subdural Hematomas

Chronic subdural hematoma (CSDH) is fundamentally treatable, although it sometimes recurs. We observed, however, several cases of spontaneous resolution of CSDH outer membranes, even in a trabecular type of CSDH, after a trepanation surgical procedure. In this study, we examined the expression of molecules of the autophagy signaling pathway in CSDH outer membranes. Eight patients whose outer membranes were obtained successfully during trepanation were included in this study. By Western blot analysis, we examined the expression of mammalian target of rapamycin (mTOR); GβL; UNC-51-like kinase-1 (ULK1); Beclin-1; autophagy-related genes (Atg) 3, 5, 7, 12, 13, and 16L1β,α; the autophagy marker Light Chain3A/B (LC3A/B); and β-actin, which constitute the autophagy signaling pathway. The expression levels of Beclin-1, Atg12, and LC3A/B were also examined by immunohistochemistry. Almost all of these molecules could be detected in all samples. Beclin-1, Atg12, and LC3A/B were found to be localized in the endothelial cells of vessels and fibroblasts in CSDH. We detected molecules of the autophagy signaling pathway in CSDH outer membranes. Autophagy contributes to the tissue homeostatic process, maintaining cellular integrity by clearing debris. Our data suggest that autophagy might play an important role in the spontaneous resolution of CSDH. Therefore, these molecules may be novel therapeutic targets for the treatment of those with CSDH.

Alzheimer's disease pathology and the unfolded protein response: prospective pathways and therapeutic targets

Many vital interdependent cellular functions including proteostasis, lipogenesis and Ca homeostasis are executed by the endoplasmic reticulum (ER). Exogenous insults can impair ER performance: this must be rapidly corrected or cell death will ensue. Protective adaptations can boost the functional capacity of the ER and form the basis of the unfolded protein response (UPR). Activated in response to the accumulation of misfolded proteins, the UPR can halt protein translation while increasing protein-handling chaperones and the degradation of erroneous proteins through a conserved three-tier molecular cascade. However, prolonged activation of the UPR can result in the maladaptation of the system, resulting in the activation of inflammatory and apoptotic effectors. Recently, UPR and its involvement in neurodegenerative disease has attracted much interest and numerous potentially 'drugable' points of crosstalk are now emerging. Here, we summarize the functions of the ER and UPR, and highlight evidence for its potential role in the pathogenesis of Alzheimer's disease, before discussing several key targets with therapeutic potential.

Trillium tschonoskii maxim saponin mitigates D-galactose-induced brain aging of rats through rescuing dysfunctional autophagy mediated by Rheb-mTOR signal pathway

During the expansion of aging population, the study correlated with brain aging is one of the important research topics. Developing novel and effective strategies for delaying brain aging is highly desired. Brain aging is characteristics of impaired cognitive capacity due to dysfunctional autophagy regulated by Rheb-mTOR signal pathway in hippocampal tissues. In the present study, we have established a rat model with brain aging through subcutaneous injection of D-galactose (D-gal). Upon the intervention of Trillium tschonoskii Maxim (TTM) saponin, one of bioactive components from local natural herbs in China, the learning and memory capacity of D-gal-induced aging rats was evaluated through Morris water maze test, and the regulation of Rheb-mTOR signal pathway and functional status of autophagy in hippocampal tissues of D-gal-induced aging rats was explored by Western blot. TTM saponin revealed an obvious function to improve learning and memory capacity of D-gal-induced aging rats through up-regulating Rheb and down-regulating mTOR, thereby rescuing dysfunctional autophagy to execute anti-aging role. Meanwhile, this study confirmed the function of TTM saponin for preventing and treating brain aging, and provided a reference for the development and utilization of natural products in health promotion and aging-associated disease treatment.

Design of Small Molecule Autophagy Modulators: A Promising Druggable Strategy

Autophagy is a lysosome-dependent mechanism of intracellular degradation for maintaining cellular homeostasis. Dysregulation of autophagy has been verified to be closely linked to a number of human diseases. Consequently, targeting autophagy has been highlighted as a novel therapeutic strategy for clinical utility. Mounting efforts have been done in recent years to elucidate the mechanisms of autophagy regulation and to identify potential modulators of autophagy. However, most of the compounds target complex and multifaceted pathway and proteins, which may limit the evaluation of therapeutic value and in depth studies as chemical tools. Therefore, the development of specific and active autophagy modulators becomes most desirable. Here, we briefly review the regulation of autophagy and then summarize the recent development of small molecules targeting the core autophagic machinery. Finally, we put forward our viewpoints on the current problems, with the aim to provide reference for future drug discovery and potential therapeutic perspectives on novel, potent, selective autophagy modulators.

Deregulation of autophagy in postmortem brains of Machado-Joseph disease patients

Autophagy, the major pathway for protein turnover, is critical to maintain cellular homeostasis and has been implicated in neurodegenerative diseases. The aim of this research was to analyze the expression of autophagy markers in postmortem brains from Machado-Joseph disease (MJD) patients. The expression of autophagy markers in the cerebellum and the oculomotor nucleus from MJD patients and age-matched controls with no signs of neuropathology was inspected postmortem by immunohistochemistry (IHC) and Western blot. Furthermore, autophagy was examined by means of transmission electron microscopy (TEM). Western blot and IHC revealed nuclear accumulation of misfolded ataxin-3 (ATXN3) and the presence of ubiquitin- and p62-positive aggregates in MJD patients as compared to controls. Moreover, the autophagic proteins, autophagy-related gene (Atg) protein (ATG)-7, ATG-12, ATG16L2 and autophagosomal microtubule-associated protein light chain 3 (LC3) were significantly increased in MJD brains relative to controls, while beclin-1 levels were reduced in MJD patients. Increase in the levels of lysosomal-associated membrane protein 2 (LAMP-2) and of the endosomal markers (Rab7 and Rab1A) were observed in MJD patients relatively to controls. In addition, these findings were further confirmed by TEM in brain tissue where large vesicles accumulating electron-dense materials were highly enriched in MJD patients. Postmortem brains with MJD exhibit increased markers of autophagy relative to age-matched control brains, therefore suggesting strong dysregulation of autophagy that may have an important role in the course of MJD pathogenesis.

Standard Immunohistochemical Assays to Assess Autophagy in Mammalian Tissue

Autophagy is a highly conserved lysosomal degradation pathway with major impact on diverse human pathologies. Despite the development of different methodologies to detect autophagy both in vitro and in vivo, monitoring autophagy in tissue via immunohistochemical techniques is hampered due to the lack of biomarkers. Immunohistochemical detection of a punctate pattern of ATG8/MAP1LC3 proteins is currently the most frequently used approach to detect autophagy in situ, but it depends on a highly sensitive detection method and is prone to misinterpretation. Moreover, reliable MAP1LC3 immunohistochemical staining requires correct tissue processing and high-quality, isoform-specific antibodies. Immunohistochemical analysis of other autophagy-related protein targets such as SQSTM1, ubiquitin, ATG5 or lysosomal proteins is not recommended as marker for autophagic activity in tissue for multiple reasons including aspecific labeling of cellular structures and a lack of differential protein expression during autophagy initiation. To better understand the role of autophagy in human disease, novel biomarkers for visualization of the autophagic process with standard histology techniques are urgently needed.

Autophagy in the placenta

Autophagy is an evolutionarily conserved catalytic process by which cytoplasmic components including damaged macromolecules and organelles are degraded. The role of autophagy includes adaptive responses to nutrition deprivation or intracellular stimuli. Although autophagosomes were first observed in early 1960s, it was 1990s that autophagy-related genes in yeast were identified and studied. Nowadays, the molecular machinery of autophagy and signaling pathway to various stimuli are almost outlined. Dysregulation of autophagic activity has been implicated in many human diseases including neurodegenerative diseases, infection and inflammation, and malignancies. However, since current understanding of autophagy in placenta is just at the beginning, this paper aims to provide general information on autophagy (part I) and to summarize articles on autophagy in human placenta (part II). This review article will serve as a basis for further researches on autophagy in relation to human pregnancy and its complications.

Autophagy: An overview and its roles in cancer and obesity

Autophagy is a normal physiological process necessary for cellular homeostasis to maintain adequate levels of cellular components. It is essential to stabilize the source of energy during development and nutritional stress and plays the dual role of survival or cell killing in various diseases including cancer. The selectivity of the response to removal of selected organelles may vary according to the each type. Macroautophagy forms a double-membraned autophagosome around the organelle destined for processing. Microautophagy involves direct engulfment of the cellular components by lysosomal invagination. Chaperone mediated autophagy (CMA) is highly selective and is dependent on the chaperone hsc70 for its activity. The effects of all these types are implemented by autophagy related genes. In this review, the markers, activators, inhibitors biological effects and roles of the three classes of autophagy in cancer and obesity are discussed.

TFEB Overexpression in the P301S Model of Tauopathy Mitigates Increased PHF1 Levels and Lipofuscin Puncta and Rescues Memory Deficits

Transcription factor EB (TFEB) was recently shown to be a master regulator of autophagy lysosome pathway. Here, we successfully generated and characterized transgenic mice overexpressing flag-TFEB. Enhanced autophagy in the flag-TFEB transgenic mice was confirmed by an increase in the cellular autophagy markers, as determined by both immunoblots and transmission electron microscopy. Surprisingly, in the flag-TFEB mice we observed increased activity of senescence-associated β-galactosidase by ∼66% of neurons in the cortex (p < 0.001) and 73% of neurons in the hippocampus (p < 0.001). More importantly, flag-TFEB expression remarkably reduced the levels of paired-helical filament (PHF)-tau from 372% in the P301S model of tauopathy to 171% (p < 0.001) in the cortex, and from 436% to 212% (p < 0.001) in the hippocampus. Significantly, reduced levels of NeuN in the cortex (38%, p < 0.001) and hippocampus (25%, p < 0.05) of P301S mice were almost completely restored to WT levels in the P301S/flag-TFEB double-transgenic mice. Also, levels of spinophilin in both the cortex (p < 0.001) and hippocampus (p < 0.001) were restored almost to WT levels. Most importantly, the age-associated lipofuscin granules, which are generally presumed to be nondegradable, were reduced by 57% (p < 0.001) in the cortex and by 55% (p < 0.001) in the hippocampus in the double-transgenic mice. Finally, TFEB overexpression in the P301S mice markedly reversed learning deficits in terms of spatial memory (Barnes maze), as well as working and reference memories (T maze). These data suggest that the overexpression of TFEB can reliably enhance autophagy in vivo, reduce levels of PHF-tau, and thereby reverse the deposition of lipofuscin granules and memory deficits.

Impaired Autophagy in Adult Bone Marrow CD34+ Cells of Patients with Aplastic Anemia: Possible Pathogenic Significance

Aplastic anemia (AA) is a bone marrow failure syndrome that is caused largely by profound quantitative and qualitative defects of hematopoietic stem and progenitor cells. However, the mechanisms underlying these defects remain unclear. Under conditions of stress, autophagy acts as a protective mechanism for cells. We therefore postulated that autophagy in CD34⁺ hematopoietic progenitor cells (HPCs) from AA patients might be impaired and play a role in the pathogenesis of AA. To test this hypothesis, we tested autophagy in CD34⁺ cells from AA samples and healthy controls and investigated the effect of autophagy on the survival of adult human bone marrow CD34⁺ cells. We found that the level of autophagy in CD34⁺ cells from AA patients was significantly lower than in age/sex-matched healthy controls, and lower in cases of severe AA than in those with non-severe AA. Autophagy in CD34⁺ cells improved upon amelioration of AA but, compared to healthy controls, was still significantly reduced even in AA patients who had achieved a complete, long-term response. We also showed that although the basal autophagy in CD34⁺ cells was low, the autophagic response of CD34⁺ cells to “adversity” was rapid. Finally, impaired autophagy resulted in reduced differentiation and proliferation of CD34⁺ cells and sensitized them to death and apoptosis. Thus, our results confirm that autophagy in CD34⁺ cells from AA patients is impaired, that autophagy is required for the survival of CD34⁺ cells, and that impaired autophagy in CD34⁺ HPCs may play an important role in the pathogenesis of AA.

Vascular mTOR-dependent mechanisms linking the control of aging to Alzheimer's disease

Aging is the strongest known risk factor for Alzheimer's disease (AD). With the discovery of the mechanistic target of rapamycin (mTOR) as a critical pathway controlling the rate of aging in mice, molecules at the interface between the regulation of aging and the mechanisms of specific age-associated diseases can be identified. We will review emerging evidence that mTOR-dependent brain vascular dysfunction, a universal feature of aging, may be one of the mechanisms linking the regulation of the rate of aging to the pathogenesis of Alzheimer's disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

SUMO1 promotes Aβ production via the modulation of autophagy

Autophagy is one of the main mechanisms in the pathophysiology of neurodegenerative disease. The accumulation of autophagic vacuoles (AVs) in affected neurons is responsible for amyloid-β (Aβ) production. Previously, we reported that SUMO1 (small ubiquitin-like modifier 1) increases Aβ levels. In this study, we explored the mechanisms underlying this. We investigated whether AV formation is necessary for Aβ production by SUMO1. Overexpression of SUMO1 increased autophagic activation, inducing the formation of LC3-II-positive AVs in neuroglioma H4 cells. Consistently, autophagic activation was decreased by the depletion of SUMO1 with small hairpin RNA (shRNA) in H4 cells. The SUMO1-mediated increase in Aβ was reduced by the autophagy inhibitors (3-methyladenine or wortmannin) or genetic inhibitors (siRNA targeting ATG5, ATG7, ATG12, or HIF1A), respectively. Accumulation of SUMO1, ATG12, and LC3 was seen in amyloid precursor protein transgenic mice. Our results suggest that SUMO1 accelerates the accumulation of AVs and promotes Aβ production, which is a key mechanism for understanding the AV-mediated pathophysiology of Alzheimer disease.

Alteration of Upstream Autophagy-Related Proteins (ULK1, ULK2, Beclin1, VPS34 and AMBRA1) in Lewy Body Disease

Autophagy is associated with the pathogenesis of Lewy body disease, including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). It is known that several downstream autophagosomal proteins are incorporated into Lewy bodies (LBs). We performed immunostaining and Western blot analysis using a cellular model of PD and human brain samples to investigate the involvement of upstream autophagosomal proteins (ULK1, ULK2, Beclin1, VPS34 and AMBRA1), which initiate autophagy and form autophagosomes. Time course analysis of cultured cells transfected with flag-α-synuclein and synphilin-1 revealed upregulation of these upstream proteins with accumulation of LB-like inclusions. In human specimens, only mature LBs were positive for upstream autophagosomal proteins. Western blotting of fractionated brain lysates showed that upstream autophagosomal proteins were detected in the soluble and insoluble fraction in DLB, corresponding to the bands of phosphorylated α-synuclein. However, Western blot analysis of total brain lysates in PD and DLB showed that the increase of upstream autophagosomal proteins was only partial. The quantitative, qualitative and locational alteration of upstream autophagosomal proteins in the present study indicates their involvement in the pathogenesis of LB disease. Our data also suggest that misinduction or impairment of upstream autophagy might occur in the disease process of LB disease.

The Ambiguous Relationship of Oxidative Stress, Tau Hyperphosphorylation, and Autophagy Dysfunction in Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia. The pathological hallmarks of AD are amyloid plaques [aggregates of amyloid-beta (Aβ)] and neurofibrillary tangles (aggregates of tau). Growing evidence suggests that tau accumulation is pathologically more relevant to the development of neurodegeneration and cognitive decline in AD patients than Aβ plaques. Oxidative stress is a prominent early event in the pathogenesis of AD and is therefore believed to contribute to tau hyperphosphorylation. Several studies have shown that the autophagic pathway in neurons is important under physiological and pathological conditions. Therefore, this pathway plays a crucial role for the degradation of endogenous soluble tau. However, the relationship between oxidative stress, tau protein hyperphosphorylation, autophagy dysregulation, and neuronal cell death in AD remains unclear. Here, we review the latest progress in AD, with a special emphasis on oxidative stress, tau hyperphosphorylation, and autophagy. We also discuss the relationship of these three factors in AD.

The role of autophagy in vascular biology

There is increasing interest in the role of autophagic flux in maintaining normal vessel wall biology and a growing suspicion that autophagic dysregulation may be a common pathway through which vascular aging and associated pathologies develop. Within endothelial and smooth muscle cells, diverse but important triggers that range from oxidized lipids to β-amyloid seem to stimulate autophagosome formation potently. In addition, emerging evidence links autophagy to a wide array of vascular processes ranging from angiogenesis to calcification of the vessel wall. Alterations in autophagic flux are also increasingly being implicated in disease processes that include both atherosclerosis and pulmonary hypertension. Finally, recent insights point toward an important role of autophagy in the paracrine regulation of vasoactive substances from the endothelium. Here, we review the progress in understanding how autophagy can contribute to vascular biology and the emerging strategies to target this process for therapeutic benefit.

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.

Aβ1-42 monomers or oligomers have different effects on autophagy and apoptosis

The role of autophagy and its relationship with apoptosis in Alzheimer disease (AD) pathogenesis is poorly understood. Disruption of autophagy leads to buildup of incompletely digested substrates, amyloid-β (Aβ) peptide accumulation in vacuoles and cell death. Aβ, in turn, has been found to affect autophagy. Thus, Aβ might be part of a loop in which it is both the substrate of altered autophagy and its cause. Given the relevance of different soluble forms of Aβ1-42 in AD, we have investigated whether monomers and oligomers of the peptide have a differential role in causing altered autophagy and cell death. Using differentiated SK-N-BE neuroblastoma cells, we found that monomers hamper the formation of the autophagic BCL2-BECN1/Beclin 1 complex and activate the MAPK8/JNK1-MAPK9/JNK2 pathway phosphorylating BCL2. Monomers also inhibit apoptosis and allow autophagy with intracellular accumulation of autophagosomes and elevation of levels of BECN1 and LC3-II, resulting in an inhibition of substrate degradation due to an inhibitory action on lysosomal activity. Oligomers, in turn, favor the formation of the BCL2-BECN1 complex favoring apoptosis. In addition, they cause a less profound increase in BECN1 and LC3-II levels than monomers without affecting the autophagic flux. Thus, data presented in this work show a link for autophagy and apoptosis with monomers and oligomers, respectively. These studies are likely to help the design of novel disease modifying therapies.

Evidence for autophagic gridlock in aging and neurodegeneration

Autophagy is essential to neuronal homeostasis, and its impairment is implicated in the development of neurodegenerative pathology. However, the underlying mechanisms and consequences of this phenomenon remain a matter of conjecture. We show that misexpression of human tau in Drosophila induces accumulation of autophagic intermediates with a preponderance of large vacuoles, which we term giant autophagic bodies (GABs), which are reminiscent of dysfunctional autophagic entities. Lowering basal autophagy reduces GABs, whereas increasing autophagy decreases mature autolysosomes. Induction of autophagy is also associated with rescue of the tauopathy phenotype, suggesting that formation of GABs may be a compensatory mechanism rather than a trigger of neurodegeneration. Last, we show that the peculiar Biondi bodies observed in the choroid epithelium of both elderly and Alzheimer's disease human brains express immunoreactive markers similar to those of GABs. Collectively, these data indicate that autophagic gridlock contributes to the development of pathology in aging and neurodegeneration.

mTOR-dependent abnormalities in autophagy characterize human malformations of cortical development: evidence from focal cortical dysplasia and tuberous sclerosis

Focal cortical dysplasia (FCD) is a localized malformation of cortical development and is the commonest cause of severe childhood epilepsy in surgical practice. Children with FCD are severely disabled by their epilepsy, presenting with frequent seizures early in life. The commonest form of FCD in children is characterized by the presence of an abnormal population of cells, known as balloon cells. Similar pathological changes are seen in the cortical malformations that characterize patients with tuberous sclerosis complex (TSC). However, the cellular and molecular mechanisms that underlie the malformations of FCD and TSC are not well understood. We provide evidence for a defect in autophagy in FCD and TSC. We have found that balloon cells contain vacuoles that include components of the autophagy pathway. Specifically, we show that balloon cells contain prominent lysosomes by electron microscopy, immunohistochemistry for LAMP1 and LAMP2, LysoTracker labelling and enzyme histochemistry for acid phosphatase. Furthermore, we found that balloon cells contain components of the ATG pathway and that there is cytoplasmic accumulation of the regulator of autophagy, DOR. Most importantly we found that there is abnormal accumulation of the autophagy cargo protein, p62. We show that this defect in autophagy can be, in part, reversed in vitro by inhibition of the mammalian target of rapamycin (mTOR) suggesting that abnormal activation of mTOR may contribute directly to a defect in autophagy in FCD and TSC.

Decoding Alzheimer's disease from perturbed cerebral glucose metabolism: implications for diagnostic and therapeutic strategies

Alzheimer's disease (AD) is an age-related devastating neurodegenerative disorder, which severely impacts on the global economic development and healthcare system. Though AD has been studied for more than 100 years since 1906, the exact cause(s) and pathogenic mechanism(s) remain to be clarified. Also, the efficient disease-modifying treatment and ideal diagnostic method for AD are unavailable. Perturbed cerebral glucose metabolism, an invariant pathophysiological feature of AD, may be a critical contributor to the pathogenesis of this disease. In this review, we firstly discussed the features of cerebral glucose metabolism in physiological and pathological conditions. Then, we further reviewed the contribution of glucose transportation abnormality and intracellular glucose catabolism dysfunction in AD pathophysiology, and proposed a hypothesis that multiple pathogenic cascades induced by impaired cerebral glucose metabolism could result in neuronal degeneration and consequently cognitive deficits in AD patients. Among these pathogenic processes, altered functional status of thiamine metabolism and brain insulin resistance are highly emphasized and characterized as major pathogenic mechanisms. Finally, considering the fact that AD patients exhibit cerebral glucose hypometabolism possibly due to impairments of insulin signaling and altered thiamine metabolism, we also discuss some potential possibilities to uncover diagnostic biomarkers for AD from abnormal glucose metabolism and to develop drugs targeting at repairing insulin signaling impairment and correcting thiamine metabolism abnormality. We conclude that glucose metabolism abnormality plays a critical role in AD pathophysiological alterations through the induction of multiple pathogenic factors such as oxidative stress, mitochondrial dysfunction, and so forth. To clarify the causes, pathogeneses and consequences of cerebral hypometabolism in AD will help break the bottleneck of current AD study in finding ideal diagnostic biomarker and disease-modifying therapy.

Autophagy: a critical regulator of cellular metabolism and homeostasis

Autophagy is a dynamic process by which cytosolic material, including organelles, proteins, and pathogens, are sequestered into membrane vesicles called autophagosomes, and then delivered to the lysosome for degradation. By recycling cellular components, this process provides a mechanism for adaptation to starvation. The regulation of autophagy by nutrient signals involves a complex network of proteins that include mammalian target of rapamycin, the class III phosphatidylinositol-3 kinase/Beclin 1 complex, and two ubiquitin-like conjugation systems. Additionally, autophagy, which can be induced by multiple forms of chemical and physical stress, including endoplasmic reticulum stress, and hypoxia, plays an integral role in the mammalian stress response. Recent studies indicate that, in addition to bulk assimilation of cytosol, autophagy may proceed through selective pathways that target distinct cargoes to autophagosomes. The principle homeostatic functions of autophagy include the selective clearance of aggregated protein to preserve proteostasis, and the selective removal of dysfunctional mitochondria (mitophagy). Additionally, autophagy plays a central role in innate and adaptive immunity, with diverse functions such as regulation of inflammatory responses, antigen presentation, and pathogen clearance. Autophagy can preserve cellular function in a wide variety of tissue injury and disease states, however, maladaptive or pro-pathogenic outcomes have also been described. Among the many diseases where autophagy may play a role include proteopathies which involve aberrant accumulation of proteins (e.g., neurodegenerative disorders), infectious diseases, and metabolic disorders such as diabetes and metabolic syndrome. Targeting the autophagy pathway and its regulatory components may eventually lead to the development of therapeutics.

Autophagy in axonal and dendritic degeneration

Degeneration of axons and dendrites is a common and early pathological feature of many neurodegenerative disorders, and is thought to be regulated by mechanisms distinct from those determining death of the cell body. The unique structures of axons and dendrites (collectively neurites) may cause them to be particularly vulnerable to the accumulation of protein aggregates and damaged organelles. Autophagy is a catabolic mechanism in which cells clear protein aggregates and damaged organelles. Basal autophagy occurs continuously as a housekeeping function, and can be acutely expanded in response to stress or injury. Emerging evidence shows that insufficient or excessive autophagy contributes to neuritic degeneration. Here, we review the recent progress that has begun to reveal the role of autophagy in neurite function and degeneration.

Autophagy modulation for Alzheimer's disease therapy

Autophagy is an essential and conserved lysosomal degradation pathway that controls the quality of cytoplasm by eliminating the intracellular aggregated proteins and damaged organelles. Autophagy works in mammalian target of rapamycin (mTOR)-dependent pathway or mTOR-independent pathway to keep the neuronal homeostasis. Mounting evidence has implicated the importance of defective autophagy in the pathogenesis of aging and neurodegenerative diseases, especially in Alzheimer's disease (AD). It has also demonstrated a neuroprotective role of autophagy in mediating the degradation of amyloid beta and tau which are major factors of AD. Amounts of molecules function in either mTOR-dependent pathway or mTOR-independent pathway to induce autophagy, which maybe a potential treatment for AD. In this review, we summarize the latest studies concerning the role of autophagy in AD and explore autophagy modulation as a potential therapeutic strategy for AD. However, to date, little of the researches on autophagy have been performed to investigate the modulation in AD; more investigations need to be confirmed in the future.

Mesenchymal stem cells enhance autophagy and increase β-amyloid clearance in Alzheimer disease models

Current evidence suggests a central role for autophagy in Alzheimer disease (AD), and dysfunction in the autophagic system may lead to amyloid-β (Aβ) accumulation. Using in vitro and in vivo AD models, the present study investigated whether mesenchymal stem cells (MSCs) could enhance autophagy and thus exert a neuroprotective effect through modulation of Aβ clearance In Aβ-treated neuronal cells, MSCs increased cellular viability and enhanced LC3-II expression compared with cells treated with Aβ only. Immunofluorescence revealed that MSC coculture in Aβ-treated neuronal cells increased the number of LC3-II-positive autophagosomes that were colocalized with a lysosomal marker. Ultrastructural analysis revealed that most autophagic vacuoles (AVs) in Aβ-treated cells were not fused with lysosomes, whereas a large portion of autophagosomes were conjoined with lysosomes in MSCs cocultured with Aβ-treated neuronal cells. Furthermore, MSC coculture markedly increased Aβ immunoreactivity colocalized within lysosomes and decreased intracellular Aβ levels compared with Aβ-treated cells. In Aβ-treated animals, MSC administration significantly increased autophagosome induction, final maturation of late AVs, and fusion with lysosomes. Moreover, MSC administration significantly reduced the level of Aβ in the hippocampus, which was elevated in Aβ-treated mice, concomitant with increased survival of hippocampal neurons. Finally, MSC coculture upregulated BECN1/Beclin 1 expression in AD models. These results suggest that MSCs significantly enhance autolysosome formation and clearance of Aβ in AD models, which may lead to increased neuronal survival against Aβ toxicity. Modulation of the autophagy pathway to repair the damaged AD brain using MSCs would have a significant impact on future strategies for AD treatment.

Immunohistochemical analysis of macroautophagy: recommendations and limitations

Transmission electron microscopy (TEM) is an indispensable standard method to monitor macroautophagy in tissue samples. Because TEM is time consuming and not suitable for daily routine, many groups try to identify macroautophagy in tissue by conventional immunohistochemistry. The aim of the present study was to evaluate whether immunohistochemical assessment of macroautophagy-related marker proteins such as LC3, ATG5, CTSD/cathepsin D, BECN1/Beclin 1 or SQSTM1/p62 is feasible and autophagy-specific. For this purpose, livers from starved mice were used as a model because hepatocytes are highly sensitive to autophagy induction. ATG7-deficient mouse livers served as negative control. Our findings indicate that unambiguous immunodetection of LC3 in paraffin-embedded tissue specimens was hampered due to low in situ levels of this protein. Maximum sensitivity could only be obtained using high-quality, isoform-specific antibodies, such as antibody 5F10, in combination with Envision+ signal amplification. Moreover, LC3 stains were optimal in neutral-buffered formalin-fixed tissue, immersed in citrate buffer during antigen retrieval. However, even when using this methodology, LC3 monitoring required overexpression of the protein, e.g., in GFP-LC3 transgenic mice. This was not only the case for the liver but also for other organs including heart, skeletal muscle, kidney and gut. Immunohistochemical detection of the autophagy-related proteins ATG5, CTSD or BECN1 is not recommendable for monitoring autophagy, due to lack of differential gene expression or doubtful specificity. SQSTM1 accumulated in autophagy-deficient liver, thus it is not a useful marker for tissue with autophagic activity. We conclude that TEM remains an indispensable technique for in situ evaluation of macroautophagy, particularly in clinical samples for which genetic manipulation or other in vitro techniques are not feasible.

Macroautophagy in sporadic and the genetic form of Parkinson's disease with the A53T α-synuclein mutation

Background

The A53T mutation in the α-synuclein gene causes autosomal-dominant Lewy body Parkinson's disease (PD). Cultured cell models have linked this mutation to increased cell macroautophagy, although evidence of enhanced macroautophagy in patients with this mutation has not been assessed.

Objective

To determine whether macroautophagy is increased by the A53T α-synuclein gene mutation in PD patients and cell models.

Methods

Formalin-fixed paraffin-embedded 10 μm-thick tissue sections from the substantia nigra and anterior cingulate cortex of two PD patients with the A53T α-synuclein gene mutation were compared with four sporadic PD cases and four controls obtained from the Sydney Brain Bank. Lewy bodies were isolated from frontal cortex of a case with late stage PD (recruited from South Australian Brain Bank). Immunohistochemistry was performed for α-synuclein and the macroautophagy markers autophagy-specific gene (ATG) 5, ATG6/Beclin1 and ATG8/LC3. SH-SY5Y cells were transfected with wild type or A53T mutant α-synuclein plasmids and observable changes in macroautophagy marker protein levels assessed using Western blotting.

Results

α-Synuclein immunoreactive neurites and dots were more numerous in patients with A53T mutations compared with late stage sporadic PD patients, and perinuclear cytoplasmic α-synuclein aggregates were observed in the α-synuclein A53T gene transfected SH-SY5Y cells compared to wild type transfections. All PD patients (with or without A53T mutations) had increased immunohistochemical evidence for macroautophagy compared with controls, and the levels of the ATG5 complex were equally increased in wild type and A53T α-synuclein gene transfected cells compared to controls.

Conclusion

Despite increased α-synuclein accumulation with A53T mutations, macroautophagy is not increased above that observed in sporadic patients with PD or in cells transfected with wild type α-synuclein, suggesting that mutated α-synuclein protein is not removed by macroautophagy.

Long-term oral lithium treatment attenuates motor disturbance in tauopathy model mice: implications of autophagy promotion

Lithium, a drug used to treat bipolar disorders, has a variety of neuroprotective mechanisms including inhibition of glycogen synthase kinase-3 (GSK-3), a major tau kinase. Recently, it has been shown that, in various neurodegenerative proteinopathies, lithium could induce autophagy. To analyze how lithium is therapeutically beneficial in tauopathies, transgenic mice overexpressing human mutant tau (P301L) were treated with oral lithium chloride (LiCl) for 4 months starting at the age of 5 months. At first, we examined the effects of treatment on behavior (using a battery of behavioral tests), tau phosphorylation (by biochemical assays), and number of neurofibrillary tangles (NFTs) (by immunohistopathology). In comparison with control mice, LiCl-treated mice showed a significantly better score in the sensory motor tasks, as well as decreases in tau phosphorylation, soluble tau level, and number of NFTs. Next, we examined lithium effects on autophagy using an antibody against microtubule-associated protein 1 light chain 3 (LC3) as an autophagosome marker. The number of LC3-positive autophagosome-like puncta was increased in neurons of LiCl-treated mice. Neurons containing NFTs were completely LC3-negative, whereas LC3-positive autophagosome-like puncta contained phosphorylated-tau (p-tau). The protein level of p62 was decreased in LiCl-treated mice. These data suggested that oral long-term lithium treatment could attenuate p-tau-induced motor disturbance not only by inhibiting GSK-3 but also by enhancing autophagy in tauopathy model mice.

Functional genomic screen and network analysis reveal novel modifiers of tauopathy dissociated from tau phosphorylation

A functional genetic screen using loss-of-function and gain-of-function alleles was performed to identify modifiers of tau-induced neurotoxicity using the 2N/4R (full-length) isoform of wild-type human tau expressed in the fly retina. We previously reported eye pigment mutations, which create dysfunctional lysosomes, as potent modifiers; here, we report 37 additional genes identified from ∼1900 genes screened, including the kinases shaggy/GSK-3beta, par-1/MARK, CamKI and Mekk1. Tau acts synergistically with Mekk1 and p38 to down-regulate extracellular regulated kinase activity, with a corresponding decrease in AT8 immunoreactivity (pS202/T205), suggesting that tau can participate in signaling pathways to regulate its own kinases. Modifiers showed poor correlation with tau phosphorylation (using the AT8, 12E8 and AT270 epitopes); moreover, tested suppressors of wild-type tau were equally effective in suppressing toxicity of a phosphorylation-resistant S11A tau construct, demonstrating that changes in tau phosphorylation state are not required to suppress or enhance its toxicity. Genes related to autophagy, the cell cycle, RNA-associated proteins and chromatin-binding proteins constitute a large percentage of identified modifiers. Other functional categories identified include mitochondrial proteins, lipid trafficking, Golgi proteins, kinesins and dynein and the Hsp70/Hsp90-organizing protein (Hop). Network analysis uncovered several other genes highly associated with the functional modifiers, including genes related to the PI3K, Notch, BMP/TGF-β and Hedgehog pathways, and nuclear trafficking. Activity of GSK-3β is strongly upregulated due to TDP-43 expression, and reduced GSK-3β dosage is also a common suppressor of Aβ42 and TDP-43 toxicity. These findings suggest therapeutic targets other than mitigation of tau phosphorylation.

Regulation of the ischemia-induced autophagy-lysosome processes by nitrosative stress in endothelial cells

The cellular mechanisms that underlie the diverse nitrosative stress-mediated cellular events associated with ischemic complications in endothelial cells are not yet clear. To characterize whether autophagic elements are associated with the nitrosative stress that causes endothelial damage after ischemia injury, an in vitro sustained oxygen-glucose deprivation (OGD) and an in vivo microsphere embolism model were used in the present study. Consistent with OGD-induced peroxynitrite formation, a rapid induction of microtubule-associated protein 1 light chain 3 (LC3)-I/II conversion and green fluorescent protein-LC3 puncta accumulation were observed in endothelial cells. The Western blot analyses indicated that OGD induced elevations in lysosome-associated membrane protein 2 and cathepsin B protein levels. Similar results were observed in the microvessel insult model, following occlusion of the microvessels using microsphere injections in rats. Furthermore, cultured endothelial cells treated with peroxynitrite (1-50 μm) exhibited a concentration-dependent change in the pattern of autophagy-lysosome signaling. Intriguingly, OGD-induced autophagy-lysosome processes were attenuated by PEP-19 overexpression and by a small-interfering RNA (siRNA)-mediated knockdown of eNOS. The importance of nitrosative stress in ischemia-induced autophagy-lysosome cascades is further supported by our finding that pharmacological inhibition of nitrosative stress by melatonin partially inhibits the ischemia-induced autophagy-lysosome cascade and the degradation of the tight junction proteins. Taken together, the present results demonstrate that peroxynitrite-mediated nitrosative stress at least partially potentiates autophagy-lysosome signaling during sustained ischemic insult-induced endothelial cell damage.

Granulovacuolar degeneration (GVD) bodies of Alzheimer's disease (AD) resemble late-stage autophagic organelles

AIMS

Granulovacuolar degeneration involves the accumulation of large, double membrane-bound bodies within certain neurones during the course of Alzheimer's disease (AD) and other adult-onset dementias. Because of the two-layer membrane morphology, it has been proposed that the bodies are related to autophagic organelles. The aim of this study was to test this hypothesis, and determine the approximate stage at which the pathway stalls in AD.

METHODS

Spatial colocalization of autophagic and endocytic markers with casein kinase 1 delta, a marker for granulovacuolar degeneration (GVD) bodies, was evaluated in hippocampal sections prepared from post mortem Braak stage IV and V AD cases using double-label confocal fluorescence microscopy.

RESULTS

GVD bodies colocalized weakly with early-stage autophagy markers LC3 and p62, but strongly with late-stage marker lysosome-associated membrane protein 1 (LAMP1), which decorated their surrounding membranes. GVD bodies also colocalized strongly with charged multivesicular body protein 2B (CHMP2B), which colocalized with the core granule, but less strongly with lysosomal marker cathepsin D.

CONCLUSIONS

The resultant immunohistochemical signature suggests that granulovacuolar degeneration bodies (GVBs) do contain late-stage autophagic markers, and accumulate at the nexus of autophagic and endocytic pathways. The data further suggest that failure to complete autolysosome formation may be an important correlate of GVB accumulation.