Neuronal Autophagy Research Articles

PI3K-AKT-mTOR signaling pathway regulates autophagy of hippocampal neurons in diabetic rats with chronic unpredictable mild stress

It is reported that the co-morbidities of diabetes and depression will be a new challenge for humanity. However, the underlying mechanism is not clear. The present study investigated the histopathology, autophagy of hippocampal neurons, and the PI3K-AKT- mTOR signaling pathway in type 2 diabetes with depression（T2DD） rats. The results showed that, the chronic unpredictable mild stress (CUMS), Type 2 diabetes mellitus (T2DM) and T2DD in rats were induced successfully. Compared with the CUMS and T2DM groups, the T2DD group performed significantly fewer autonomic activities in the open-field test, and longer immobile in the force swimming test, and increasing of Corticosterone (CORT) in blood. The number of pyknotic neurons at cornu ammonis 1 (CA1) and dentate gyrus (DG) of the hippocampus in T2DD was significantly increased compared with CUMS and T2DM groups. Moreover, compared with the CUMS and T2DM groups, the mitochondrial autophagosomes were most abundant in the T2DD group. As shown in western blot and immunofluorescence, compared with the control group, in the CUMS, T2DM and T2DD groups, significantly increased expression of Beclin-1 and LC3B and decreased P62 were detected. In the PC12 cells, the relative amount of parkin and LC3B in the CORT+HG group was significantly higher than that in the CORT and HG groups. Compared with the control group, p-AKT/AKT and p-mTOR/mTOR in CUMS, T2DM and T2DD groups were significantly decreased. Compared with the CUMS group, p-AKT/AKT, p-PI3K/PI3K and p-mTOR/mTOR in the T2DD group exhibited further decrease. Similar results were obtained in PC12 cells in vitro. It is suggests that memory and cognitive impairment in rats with co-morbidities of diabetes and depression might be related with hippocampal neuronal damage and autophagy increase, which was involved in the PI3K-AKT-mTOR signaling pathway.

Abelmoschus esculentus (Okra) Prevents Insulin Resistance and Restores Neuron Autophagy by Regulating Dipeptidyl Peptidase-4 and Thus Improving Hippocampal Function.

Diabetes is highly linked to the occurrence of Alzheimer disease (AD), which is characterized by beta amyloid peptide (Aβ) and hyperphosphorylation of tau (p-tau), and neuron damage particularly in hippocampus. Type 2 diabetes (T2D) is featured by insulin resistance, and phosphorylation of Ser307-IRS-1 is regarded as a resistance marker. Inhibitors of dipeptidyl peptidase-4 (DPP-4) are effective tools for treating T2D. Previously, we reported subfractions of Abelmoschus esculentus (AE, okra) (F1 rich in quercetin glycosides; F2 composed of polysaccharide) attenuated DPP-4 and its downstream signals of insulin resistance, thus preventing Aβ-induced neuron damage. Since autophagy could be protective, we now explore if AE works to modulate neuron autophagy by regulating DPP-4 and insulin resistance and, thus, improves the hippocampal function and behavior. We demonstrated that AE subfractions attenuate Aβ-induced insulin resistance and the expression of p-tau and normalize the autophagy and survival of hippocampal neurons. The action of AE may be attributed to the downregulation of DPP-4, which plays a critical role in mediating insulin resistance and hinders neuron autophagy. The in vivo findings reveal that the hippocampal insulin resistance appears to link with loss of memory, reduction of curiosity, and depression, whereas treatment with AE significantly improves the insulin sensitivity and hippocampal function. Noteworthy, even at only 5 μg/mL, F2 seems to exhibit a meaningful effect. In conclusion, we suggest that AE attenuates insulin resistance and recovers neuron autophagy which are regulated by DPP-4, thus preventing the damage to the hippocampus, improving recognition and emotion. AE may be an effective adjuvant or supplement to prevent insulin resistance-associated pathogenesis of AD if these results can be confirmed in human clinical trials.

ARL6IP5 Ameliorates α-Synuclein Burden by Inducing Autophagy via Preventing Ubiquitination and Degradation of ATG12.

Recent advanced studies in neurodegenerative diseases have revealed several links connecting autophagy and neurodegeneration. Autophagy is the major cellular degradation process for the removal of toxic protein aggregates responsible for neurodegenerative diseases. More than 30 autophagy-related proteins have been identified as directly participating in the autophagy process. Proteins regulating the process of autophagy are much more numerous and unknown. To address this, in our present study, we identified a novel regulator (ARL6IP5) of neuronal autophagy and showed that the level of ARL6IP5 decreases in the brain with age and in Parkinson's disease in mice and humans. Moreover, a cellular model of PD (Wild type and A53T mutant α-synuclein overexpression) has also shown decreased levels of ARL6IP5. ARL6IP5 overexpression reduces α-synuclein aggregate burden and improves cell survival in an A53T model of Parkinson's disease. Interestingly, detailed mechanistic studies revealed that ARL6IP5 is an autophagy inducer. ARL6IP5 enhances Rab1-dependent autophagosome initiation and elongation by stabilizing free ATG12. We report for the first time that α-synuclein downregulates ARL6IP5 to inhibit autophagy-dependent clearance of toxic aggregates that exacerbate neurodegeneration.

Cerebral Semaphorin3D is a novel risk factor for age-associated cognitive impairment

BackgroundWe previously reported that miR-195 exerts neuroprotection by inhibiting Sema3A and cerebral miR-195 levels decreased with age, both of which urged us to explore the role of miR-195 and miR-195-regulated Sema3 family members in age-associated dementia.MethodsmiR-195a KO mice were used to assess the effect of miR-195 on aging and cognitive functions. Sema3D was predicted as a miR-195 target by TargetScan and then verified by luciferase reporter assay, while effects of Sema3D and miR-195 on neural senescence were assessed by beta-galactosidase and dendritic spine density. Cerebral Sema3D was over-expressed by lentivirus and suppressed by si-RNA, and effects of over-expression of Sema3D and knockdown of miR-195 on cognitive functions were assessed by Morris Water Maze, Y-maze, and open field test. The effect of Sema3D on lifespan was assessed in Drosophila. Sema3D inhibitor was developed using homology modeling and virtual screening. One-way and two-way repeated measures ANOVA were applied to assess longitudinal data on mouse cognitive tests.ResultsCognitive impairment and reduced density of dendritic spine were observed in miR-195a knockout mice. Sema3D was identified to be a direct target of miR-195 and a possible contributor to age-associated neurodegeneration as Sema3D levels showed age-dependent increase in rodent brains. Injection of Sema3D-expressing lentivirus caused significant memory deficits while silencing hippocampal Sema3D improved cognition. Repeated injections of Sema3D-expressing lentivirus to elevate cerebral Sema3D for 10 weeks revealed a time-dependent decline of working memory. More importantly, analysis of the data on the Gene Expression Omnibus database showed that Sema3D levels were significantly higher in dementia patients than normal controls (p < 0.001). Over-expression of homolog Sema3D gene in the nervous system of Drosophila reduced locomotor activity and lifespan by 25%. Mechanistically, Sema3D might reduce stemness and number of neural stem cells and potentially disrupt neuronal autophagy. Rapamycin restored density of dendritic spines in the hippocampus from mice injected with Sema3D lentivirus. Our novel small molecule increased viability of Sema3D-treated neurons and might improve autophagy efficiency, which suggested Sema3D could be a potential drug target.4m2wJMd7gS24xvrSEVAZGFVideo ConclusionOur results highlight the importance of Sema3D in age-associated dementia. Sema3D could be a novel drug target for dementia treatment.

Early pheromone perception remodels neurodevelopment and accelerates neurodegeneration in adult C. elegans

Age-associated neurodegenerative disorders such as Parkinson's and Alzheimer's diseases are mainly caused by protein aggregation. The etiologies of these neurodegenerative diseases share a chemical environment. However, how chemical cues modulate neurodegeneration remains unclear. Here, we found that in Caenorhabditis elegans, exposure to pheromones in the L1 stage accelerates neurodegeneration in adults. Perception of pheromones ascr#3 and ascr#10 is mediated by chemosensory neurons ASK and ASI. ascr#3 perceived by G protein-coupled receptor (GPCR) DAF-38 in ASK activates glutamatergic transmission into AIA interneurons. ascr#10 perceived by GPCR STR-2 in ASI activates the secretion of neuropeptide NLP-1, which binds to the NPR-11 receptor in AIA. Activation of both ASI and ASK is required and sufficient to remodel neurodevelopment via AIA, which triggers insulin-like signaling and inhibits autophagy in adult neurons non-cell-autonomously. Our work reveals how pheromone perception at the early developmental stage modulates neurodegeneration in adults and provides insights into how the external environment impacts neurodegenerative diseases.

Role of lipids in the control of autophagy and primary cilium signaling in neurons.

The brain is, after the adipose tissue, the organ with the greatest amount of lipids and diversity in their composition in the human body. In neurons, lipids are involved in signaling pathways controlling autophagy, a lysosome-dependent catabolic process essential for the maintenance of neuronal homeostasis and the function of the primary cilium, a cellular antenna that acts as a communication hub that transfers extracellular signals into intracellular responses required for neurogenesis and brain development. A crosstalk between primary cilia and autophagy has been established; however, its role in the control of neuronal activity and homeostasis is barely known. In this review, we briefly discuss the current knowledge regarding the role of autophagy and the primary cilium in neurons. Then we review the recent literature about specific lipid subclasses in the regulation of autophagy, in the control of primary cilium structure and its dependent cellular signaling in physiological and pathological conditions, specifically focusing on neurons, an area of research that could have major implications in neurodevelopment, energy homeostasis, and neurodegeneration.

The Effect of Overnutrition on Mediated Collagen in Drosophila Melanogaster Physiology

Obesity affects approximately 13% of the adult population, resulting in excessive fat cell deposition and metabolic dysfunction. Collagen, a protein that supports skin regeneration, muscle building, and pain relief, is studied in Drosophila melanogaster under different diet conditions. This experiment aims to test whether overnutrition affects physiology and collagen due to any anatomical changes in Drosophila Melanogaster, more commonly known as fruit flies. The research conducted over several weeks utilizes two diets: an obesity-inducing diet containing excessive glucose and coconut oil and a traditional diet of blue food medium, yeast, and water. The study groups include a wild-type, collagen-mutated, and obesity-mutated group, with multiple assays measuring how the obesity-inducing diet affects each population and their collagen levels. The results reveal that the obese group experienced higher food consumption levels but had lower locomotive ability than the other test groups. Hydroxyproline, the building amino acid for collagen, and collagen levels were higher in the obesity mutant than in the wild-type and collagen mutated group. The study shows that anatomical changes in organisms are influenced by both diet and movement. The obesity group, on an obesity-inducing diet, experienced decreased movement related to increased food intake and decreased neural activity. The high-fat and high-sugar diet suppressed neuronal autophagy, created inaccurate hunger and satiety perceptions, and increased collagen deposition. Anatomical changes were observed in collagen-heavy tissue areas, whereas decreased neural activity and increased feeding rates were behavioral changes. The study emphasized the importance of a healthy diet and exercise in promoting overall health.

Acupuncture regulates autophagy in hippocampal neurons of cerebral ischemia/reperfusion injured rats by activating type Ⅲ PI3K/Beclin-1 pathway

To observe the effects of acupuncture on the expression of type Ⅲ phosphatidylinositol 3-hydroxykinase (PI3K) and Beclin-1 in hippocampus of rats with cerebral ischemia/reperfusion injury (CI/RI), so as to explore the mechanism of acupuncture in regulating type Ⅲ PI3K pathway to activate autophagy in the hippocampal neurons of CI/RI rats. SD rats were randomly divided into sham operation group (n=11) and operation group. Then after successful modeling, rats in the operation group were randomly divided into model, acupuncture, model+3-MA and acupuncture+3-MA groups, with 11 rats in each group. The model of CI/RI was established by occlusion of the middle cerebral artery. Rats in the model+3-MA and acupuncture+3-MA groups were injected with 3-MA (400 nmol/ 5 μL) 5 μL into the lateral ventricle 30 min before reperfusion. Rats in the acupuncture and acupuncture+3-MA groups were punctured with filiform needles at "Dazhui" (GV14), "Shuigou" (GV26) and "Baihui" (GV20) and stimulated manually once every 15 min. The acupuncture intervention was conducted for 30 min each time, once every 12 h for a total of 7 times. The degree of neurological impairment was evaluated 2 h after reperfusion and after intervention by Garcia score. After intervention, the percentage of cerebral ischemic area was observed by TTC staining, the protein expression levels of type Ⅲ PI3K, Beclin-1, microtubule-associated protein 1 light chain 3B (LC3B), lysosome associated membrane protein 2 (Lamp2) and P62 in ischemic hippocampal tissue were detected by Western blot, the ultrastructure of neurons in ischemic hippocampus was observed by transmission electron microscopy (TEM). Compared with the sham operation group, the Garcia score was decreased (P<0.01), the percentage of cerebral ischemic area was increased (P<0.01), the expression levels of type Ⅲ PI3K, Beclin-1, LC3B-Ⅱ/Ⅰ, Lamp2 proteins were decreased (P<0.01), and the expression level of P62 protein was increased (P<0.01) in ischemic hippocampal tissue in the model group. Compared with the model group, the Garcia score was increased (P<0.01), the percentage of cerebral ischemic area was decreased (P<0.01), the expression levels of type Ⅲ PI3K, Beclin-1, LC3B-Ⅱ/Ⅰ, Lamp2 proteins were increased (P<0.01, P<0.05) and the expression level of P62 was decreased (P<0.01) in ischemic hippocampal tissue in the acupuncture group； the percentage of cerebral ischemic area was increased (P<0.05), the expressions of type Ⅲ PI3K and Beclin-1 were decreased (P<0.01) and the expression level of P62 protein was increased (P<0.05) in ischemic hippocampal tissue in the mo-del+3-MA group. Compared with the model +3-MA group, the Garcia score was increased (P<0.05), the percentage of cerebral ischemic area was decreased (P<0.01), the expression levels of type Ⅲ PI3K, Beclin-1, LC3B-Ⅱ/Ⅰ in ischemic hippo-campal tissue were increased (P<0.01, P<0.05) in the acupuncture+3-MA group. Compared with the acupuncture group, the Garcia score was decreased, the percentage of cerebral ischemic area was increased (P<0.05, P<0.01), the expression levels of type Ⅲ PI3K, Beclin-1, Lamp2 proteins were decreased (P<0.01, P<0.05) and P62 protein was increased (P<0.05) in ischemic hippocampal tissue in the acupuncture+3-MA group. The results of TEM showed that the edema of neurons was heavier, and few hypolysosomes existed in the model group; there was no obvious damage to neuronal structure, intracellular matrix was abundant, and a few lysosomes existed in the acupuncture group; the neuronal cells had mild edema and primary lysosomes were present in the acupuncture +3-MA group. Acupuncture can improve the symptoms of neurological impairment and reduce the percentage of cerebral ischemic area in rats with CI/RI. The mechanism may be related to regulating type Ⅲ PI3K/Beclin-1 pathway, up-regulating the expressions of autophagy related factors LC3B-Ⅱ and Lamp2, and down-regulating the expression of P62.

The Potential of Edible and Medicinal Resource Polysaccharides for Prevention and Treatment of Neurodegenerative Diseases.

As natural medicines in complementary and alternative medicine, edible and medicinal resources are being gradually recognized throughout the world. According to statistics from the World Health Organization, about 80% of the worldwide population has used edible and medicinal resource products to prevent and treat diseases. Polysaccharides, one of the main effective components in edible and medicinal resources, are considered ideal regulators of various biological responses due to their high effectiveness and low toxicity, and they have a wide range of possible applications for the development of functional foods for the regulation of common, frequently occurring, chronic and severe diseases. Such applications include the development of polysaccharide products for the prevention and treatment of neurodegenerative diseases that are difficult to control by a single treatment, which is of great value to the aging population. Therefore, we evaluated the potential of polysaccharides to prevent neurodegeneration by their regulation of behavioral and major pathologies, including abnormal protein aggregation and neuronal damage caused by neuronal apoptosis, autophagy, oxidative damage, neuroinflammation, unbalanced neurotransmitters, and poor synaptic plasticity. This includes multi-target and multi-pathway regulation involving the mitochondrial pathway, MAPK pathway, NF-κB pathway, Nrf2 pathway, mTOR pathway, PI3K/AKT pathway, P53/P21 pathway, and BDNF/TrkB/CREB pathway. In this paper, research into edible and medicinal resource polysaccharides for neurodegenerative diseases was reviewed in order to provide a basis for the development and application of polysaccharide health products and promote the recognition of functional products of edible and medicinal resources.

Hydroxysafflor yellow a confers neuroprotection against acute traumatic brain injury by modulating neuronal autophagy to inhibit NLRP3 inflammasomes.

Hydroxysafflor yellow A (HSYA) is the principal bioactive compound isolated from the plant Carthamus tinctorius L. and has been reported to exert neuroprotective effects against various neurological diseases, including traumatic brain injury (TBI). However, the specific molecular and cellular mechanisms underlying HSYA-mediated neuroprotection against TBI are unclear. This study explored the effects of HSYA on autophagy and the NLRP3 inflammasome in mice with TBI and the related mechanisms. Mice were subjected to TBI and treated with or without HSYA. Neurological severity scoring, LDH assays and apoptosis detection were first performed to assess the effects of HSYA in mice with TBI. RNA-seq was then conducted to explore the mechanisms that contributed to HSYA-mediated neuroprotection. ELISA, western blotting, and immunofluorescence were performed to further investigate the mechanisms of neuroinflammation and autophagy. Moreover, 3-methyladenine (3-MA), an autophagy inhibitor, was applied to determine the connection between autophagy and the NLRP3 inflammasome. HSYA significantly decreased the neurological severity score, serum LDH levels and apoptosis in mice with TBI. A total of 921 differentially expressed genes were identified in the cortices of HSYA-treated mice with TBI and were significantly enriched in the inflammatory response and autophagy. Furthermore, HSYA treatment markedly reduced inflammatory cytokine levels and astrocyte activation. Importantly, HSYA suppressed neuronal NLRP3 inflammasome activation, as indicated by decreased levels of NLRP3, ASC and cleaved caspase-1 and a reduced NLRP3+ neuron number. It increased autophagy and ameliorated autophagic flux dysfunction, as evidenced by increased LC3 II/LC3 I levels and decreased P62 levels. The effects of HSYA on the NLRP3 inflammasome were abolished by 3-MA. Mechanistically, HSYA may enhance autophagy through AMPK/mTOR signalling. HSYA enhanced neuronal autophagy by triggering the AMPK/mTOR signalling pathway, leading to inhibition of the NLRP3 inflammasome to improve neurological recovery after TBI.

Novel therapeutic approaches to target neurodegeneration.

Ageing is the main risk factor common to most primary neurodegenerative disorders. Indeed, age-related brain alterations have been long considered to predispose to neurodegeneration. Although protein misfolding and the accumulation of toxic protein aggregates have been considered as causative events in neurodegeneration, several other biological pathways affected by brain ageing also contribute to pathogenesis. Here, we discuss the evidence showing the involvement of the mechanisms controlling neuronal structure, gene expression, autophagy, cell metabolism and neuroinflammation in the onset and progression of neurodegenerative disorders. Furthermore, we review the therapeutic strategies currently under development or as future approaches designed to normalize these pathways, which may then increase brain resilience to cope with toxic protein species. In addition to therapies targeting the insoluble protein aggregates specifically associated with each neurodegenerative disorder, these novel pharmacological approaches may be part of combined therapies designed to rescue brain function.

Microglial-to-neuronal CCR5 signaling regulates autophagy in neurodegeneration

In neurodegenerative diseases, microglia switch to an activated state, which results in excessive secretion of pro-inflammatory factors. Our work aims to investigate how this paracrine signaling affects neuronal function. Here, we show that activated microglia mediate non-cell-autonomous inhibition of neuronal autophagy, a degradative pathway critical for the removal of toxic, aggregate-prone proteins accumulating in neurodegenerative diseases. We found that the microglial-derived CCL-3/-4/-5 bind and activate neuronal CCR5, which in turn promotes mTORC1 activation and disrupts autophagy and aggregate-prone protein clearance. CCR5 and its cognate chemokines are upregulated in the brains of pre-manifesting mouse models for Huntington's disease (HD) and tauopathy, suggesting a pathological role of this microglia-neuronal axis in the early phases of these diseases. CCR5 upregulation is self-sustaining, as CCL5-CCR5 autophagy inhibition impairs CCR5 degradation itself. Finally, pharmacological or genetic inhibition of CCR5 rescues mTORC1 hyperactivation and autophagy dysfunction, which ameliorates HD and tau pathologies in mouse models.

Endophilin-A/SH3GL2 calcium switch for synaptic autophagy induction is impaired by a Parkinson’s risk variant

ABSTRACT At the synapse, proteins are reused several times during neuronal activity, causing a decline in protein function over time. Although emerging evidence supports a role of autophagy in synaptic function, the precise molecular mechanisms linking neuronal activity, autophagy and synaptic dysfunction are vastly unknown. We show how extracellular calcium influx in the pre-synaptic terminal constitutes the initial stimulus for autophagosome formation in response to neuronal activity. This mechanism likely acts to rapidly support synaptic homeostasis and protein quality control when intense neuronal activity challenges the synaptic proteome. We identified a residue in the flexible region of EndoA (Endophilin A) that dictates calcium-dependent EndoA mobility from the plasma membrane to the cytosol, where this protein interacts with autophagic membranes to promote autophagosome formation. We discovered that a novel Parkinson’s disease-risk mutation in SH3GL2 (SH3 domain containing GRB2 like 2, endophilin A1) disrupts the calcium sensing of SH3GL2, leading to an immobile protein that cannot respond to calcium influx and therefore disrupting autophagy induction at synapses. Our work shows how neuronal activity is connected with autophagy to maintain synaptic homeostasis and survival.

GATA6 Inhibits Neuronal Autophagy and Ferroptosis in Cerebral ischemia-reperfusion Injury Through a miR-193b/ATG7 axis-dependent Mechanism.

Ferroptosis is a newly described form of regulated necrotic cell death, which is engaged in the pathological cell death related to stroke, contributing to cerebral ischemia-reperfusion (I/R) injury. Therefore, we performed this study to clarify the role of GATA6 in neuronal autophagy and ferroptosis in cerebral I/R injury. The cerebral I/R injury-related differentially expressed genes (DEGs) as well as the downstream factors of GATA6 were predicted bioinformatically. Moreover, the relations between GATA6 and miR-193b and that between miR-193b and ATG7 were evaluated by chromatin immunoprecipitation and dual-luciferase reporter assays. Besides, neurons were treated with oxygen-glucose deprivation (OGD), followed by overexpression of GATA6, miR-193b, and ATG7 alone or in combination to assess neuronal autophagy and ferroptosis. At last, in vivo experiments were performed to explore the impacts of GATA6/miR-193b/ATG7 on neuronal autophagy and ferroptosis in a rat model of middle cerebral artery occlusion (MCAO)-stimulated cerebral I/R injury. It was found that GATA6 and miR-193b were poorly expressed in cerebral I/R injury. GATA6 transcriptionally activated miR-193b to downregulate ATG7. Additionally, GATA6-mediated miR-193b activation suppressed neuronal autophagy and ferroptosis in OGD-treated neurons by inhibiting ATG7. Furthermore, GATA6/miR-193b relieved cerebral I/R injury by restraining neuronal autophagy and ferroptosis via downregulation of ATG7 in vivo. In summary, GATA6 might prevent neuronal autophagy and ferroptosis to alleviate cerebral I/R injury via the miR-193b/ATG7 axis.

Mitochondrial pyruvate carrier 1 alleviates hypoxic-ischemic brain injury in rats

AimsMitochondrial dysfunction is a critical pathological change in cerebral ischemia. Mitochondrial pyruvate carrier 1 (MPC1) is a mitochondrial inner membrane protein carrier participating in pyruvate transport. The work is aiming to figure out the effect of MPC1 on cerebral ischemia. Main methodsBilateral internal carotid artery embolization (BICAO) model and oxygen glucose deprivation/reoxygenation (OGD/R) model were used to simulate cerebral ischemia in vivo and in vitro. The effect of MPC1 on cerebral ischemia was detected by imaging, behavioral test, immunofluorescence, flow cytometry, transmission electron microscopy, Western blot and RT-Q-PCR. RNA-sequence (RNA-seq) was applied to explore the potential molecular mechanisms underlying the role of MPC1 in cerebral ischemia. Key findingAfter BICAO or OGD/R treatment, MPC1 expression in ischemic cortical neurons was significantly decreased. And MPC1 deficiency significantly reduced cerebral blood flow, decreased locomotion activities and exacerbated neuronal injury. Moreover, MPC1 deficiency obviously aggravated oxidative stress, structural disruption and dysfunction of mitochondria, autophagy and calcium overload of ischemic cortical neurons. Interestingly, MPC1 overexpression remarkably reversed neuronal loss and persisting neuronal deficits induced by OGD. Using RNA-seq, 38 MPC1-associated differentially expressed genes were involved in oxidative stress, autophagy and calcium overload. Our results further confirmed that MPC1 could alleviate autophagy via the PI3K/Akt/mTOR pathway in the ischemic cortical neurons. SignificanceMPC1 may exert neuroprotective effects by attenuating oxidative stress, mitochondrial dysfunction, calcium overload and autophagy during cerebral ischemia. MPC1-related genes identified by RNA-seq may be a novel therapeutic target for cerebral ischemia.

Tumor necrosis factor α-induced protein 3 mediates inflammation and neuronal autophagy in Parkinson’s disease via the NFκB and mTOR pathways

This study aimed to probe the function of tumor necrosis factor α–induced protein 3 (TNFAIP3) in the pathogenesis of Parkinson disease (PD) with its association with autophagy and inflammatory response. TNFAIP3 was reduced in the SN of PD patients (the GSE54282 dataset) and mice and in the MPP+-treated SK-N-SH cells. TNFAIP3 inhibited inflammatory response and enhanced autophagy, thereby alleviating PD in mice. NFκB and mTOR pathways were activated in the SN of PD mice and MPP+-treated cells. TNFAIP3 blocked the two pathways by preventing the p65 nuclear translocation and stabilizing DEPTOR, an endogenous inhibitor of mTOR. NFκB activator LPS and mTOR activator MHY1485 reversed the effects of TNFAIP3 on mitigation of injury in PD mice and in SK-N-SH cells induced with MPP+. Altogether, TNFAIP3 played a neuroprotective role in MPTP-induced mice by restricting NFκB and mTOR pathways.

Fountain of youth-Targeting autophagy in aging.

As our society ages inexorably, geroscience and research focusing on healthy aging is becoming increasingly urgent. Macroautophagy (referred to as autophagy), a highly conserved process of cellular clearance and rejuvenation has attracted much attention due to its universal role in organismal life and death. Growing evidence points to autophagy process as being one of the key players in the determination of lifespan and health. Autophagy inducing interventions show significant improvement in organismal lifespan demonstrated in several experimental models. In line with this, preclinical models of age-related neurodegenerative diseases demonstrate pathology modulating effect of autophagy induction, implicating its potential to treat such disorders. In humans this specific process seems to be more complex. Recent clinical trials of drugs targeting autophagy point out some beneficial effects for clinical use, although with limited effectiveness, while others fail to show any significant improvement. We propose that using more human-relevant preclinical models for testing drug efficacy would significantly improve clinical trial outcomes. Lastly, the review discusses the available cellular reprogramming techniques used to model neuronal autophagy and neurodegeneration while exploring the existing evidence of autophagy's role in aging and pathogenesis in human-derived in vitro models such as embryonic stem cells (ESCs), induced pluripotent stem cell derived neurons (iPSC-neurons) or induced neurons (iNs).

Autophagy and neurodegeneration: Unraveling the role of C9ORF72 in the regulation of autophagy and its relationship to ALS-FTD pathology.

The proper functioning of the cell clearance machinery is critical for neuronal health within the central nervous system (CNS). In normal physiological conditions, the cell clearance machinery is actively involved in the elimination of misfolded and toxic proteins throughout the lifetime of an organism. The highly conserved and regulated pathway of autophagy is one of the important processes involved in preventing and neutralizing pathogenic buildup of toxic proteins that could eventually lead to the development of neurodegenerative diseases (NDs) such as Alzheimer's disease or Amyotrophic lateral sclerosis (ALS). The most common genetic cause of ALS and frontotemporal dementia (FTD) is a hexanucleotide expansion consisting of GGGGCC (G4C2) repeats in the chromosome 9 open reading frame 72 gene (C9ORF72). These abnormally expanded repeats have been implicated in leading to three main modes of disease pathology: loss of function of the C9ORF72 protein, the generation of RNA foci, and the production of dipeptide repeat proteins (DPRs). In this review, we discuss the normal physiological role of C9ORF72 in the autophagy-lysosome pathway (ALP), and present recent research deciphering how dysfunction of the ALP synergizes with C9ORF72 haploinsufficiency, which together with the gain of toxic mechanisms involving hexanucleotide repeat expansions and DPRs, drive the disease process. This review delves further into the interactions of C9ORF72 with RAB proteins involved in endosomal/lysosomal trafficking, and their role in regulating various steps in autophagy and lysosomal pathways. Lastly, the review aims to provide a framework for further investigations of neuronal autophagy in C9ORF72-linked ALS-FTD as well as other neurodegenerative diseases.

Xenon attenuates hypoxic-ischemic brain damage by inhibiting autophagy in neonatal rats.

Xenon (Xe) is an inert, colorless and odorless heavy gas and has many biological functions. However, little is known about whether and how Xe can modulate hypoxic-ischemic brain damage (HIBD) in neonatal rats. This study employed a neonatal rat model to explore the potential effect of Xe on neuron autophagy and the severity of HIBD. Neonatal Sprague-Dawley rats were subjected to HIBD, randomized and treated with Xe or mild hypothermia (at 32 °C) for 3 h. The degrees of HIBD, neuron autophagy and the neuronal functions in some neonates from each group were tested by histopathology, immunochemistry, transmission electron microscopy, western blot, open-field and Trapeze tests at 3 and 28 days post-induction of HIBD, respectively. Compared with the Sham group, hypoxic-ischemia caused larger volumes of cerebral infarction and severe brain damage, and increased autophagosome formation and Beclin-1 and microtubule-associated protein 1A/1B-light chain 3 class II (LC3-II) expression in the brain of rats, accompanied by the defect in neuronal functions. In contrast, treatment with Xe and/or hypothermia significantly reduced infarct volumes and ameliorated neurological defects in the HIBD rats, particularly for the combination of Xe and hypothermia. Xe significantly mitigated the relative levels of Beclin-1 and LC3-II expression and autophagosome formation induced by HIBD in rats. Xe acted as a neuroprotective factor against HIBD, possibly by inhibiting the hypoxia-induced neuron autophagy in rats.

Impaired Autophagic-Lysosomal Fusion in Parkinson's Patient Midbrain Neurons Occurs through Loss of ykt6 and Is Rescued by Farnesyltransferase Inhibition.

Macroautophagy is a catabolic process that coordinates with lysosomes to degrade aggregation-prone proteins and damaged organelles. Loss of macroautophagy preferentially affects neuron viability and is associated with age-related neurodegeneration. We previously found that α-synuclein (α-syn) inhibits lysosomal function by blocking ykt6, a farnesyl-regulated soluble NSF attachment protein receptor (SNARE) protein that is essential for hydrolase trafficking in midbrain neurons. Using Parkinson's disease (PD) patient iPSC-derived midbrain cultures, we find that chronic, endogenous accumulation of α-syn directly inhibits autophagosome-lysosome fusion by impairing ykt6-SNAP-29 complexes. In wild-type (WT) cultures, ykt6 depletion caused a near-complete block of autophagic flux, highlighting its critical role for autophagy in human iPSC-derived neurons. In PD, macroautophagy impairment was associated with increased farnesyltransferase (FTase) activity, and FTase inhibitors restored macroautophagic flux through promoting active forms of ykt6 in human cultures, and male and female mice. Our findings indicate that ykt6 mediates cellular clearance by coordinating autophagic-lysosomal fusion and hydrolase trafficking, and that macroautophagy impairment in PD can be rescued by FTase inhibitors.SIGNIFICANCE STATEMENT The pathogenic mechanisms that lead to the death of neurons in Parkinson's disease (PD) and Dementia with Lewy bodies (LBD) are currently unknown. Furthermore, disease modifying treatments for these diseases do not exist. Our study indicates that a cellular clearance pathway termed autophagy is impaired in patient-derived culture models of PD and in vivo We identified a novel druggable target, a soluble NSF attachment protein receptor (SNARE) protein called ykt6, that rescues autophagy in vitro and in vivo upon blocking its farnesylation. Our work suggests that farnesyltransferase (FTase) inhibitors may be useful therapies for PD and DLB through enhancing autophagic-lysosomal clearance of aggregated proteins.