Neuronal Autophagy Research Articles

PI3K/AKT pathway: A potential therapeutic target in cerebral ischemia-reperfusion injury.

PI3K/AKT pathway: A potential therapeutic target in cerebral ischemia-reperfusion injury.

HDCA alleviates Parkinson's disease symptoms by promoting autophagic degradation of α-synuclein in enteric neurons.

HDCA alleviates Parkinson's disease symptoms by promoting autophagic degradation of α-synuclein in enteric neurons.

EGb761 suppressed vascular dementia via modulating Wnt/β-catenin signaling pathway-induced apoptosis and autophagy in hippocampal neuronal cells

ObjectivesThe study aimed to explore the effects of EGb761 on vascular dementia (VD) rats and the mechanisms of action.MethodsThe Morris water maze test was utilized to assess the spatial learning and memory abilities of the rats; Hematoxylin and Eosin (HE) staining and electron microscopy were used to observe changes in hippocampal neuron cells; Immunohistochemistry was performed to detect the expression of cleaved caspase-3 and microtubule-associated proteins light chain 3 (LC3-II) positive cells in hippocampal neurons; immunofluorescence staining was carried out to determine the immunofluorescence intensity of IRGM in hippocampal neurons; western blotting was used to measure the expression of related proteins.ResultsEGb761 significantly improved the cognitive function of vascular dementia rats (P < 0.01) and reduced the apoptosis of hippocampal neurons.Furthermore, EGb761 suppressed ROS, thereby promoting the expression of proteins related to the Wnt/β-catenin signaling pathway and inhibiting the expression of C-Jun N-terminal Kinase (p-JNK), c-Jun N-terminal kinase (p-c-JUN), Protein 53 (P53), immunity-related GTPase M (IRGM), Transcription Factor EB (TFEB), microtubule-associated proteins light chain 3 (LC3), Lysosomal Associated Membrane Protein 1 (LAMP1), and Sequestosome 1 (SQSTM1).ConclusionsGinkgo Biloba Extract 761 (EGb761) mediated the Wnt/β-catenin signaling pathway to inhibit apoptosis and autophagy in hippocampal neurons in VD rats.

AP2A1 activates Rab7 to promote axonal autophagosome transport and slow the progression of Alzheimer’s disease

BackgroundDysregulation retrograde axonal transport in neurons results in autophagosome accumulation, enhancing amyloid β (Aβ) production and accelerating Alzheimer’s disease (AD) progression. Ras-associated GTP-binding protein 7 (Rab7) is pivotal in autophagosome maturation and their fusion with lysosomes, as well as in bidirectional axonal transport through interactions with partner proteins. Recent studies suggest that adapter-associated protein complex 2 subunit α1 (AP2A1) modulates retrograde axonal autophagosomes transport, regulates autophagy, and influences AD progression. However, the interplay between AP2A1 and Rab7, along with the molecular mechanisms underlying their impact on neuronal autophagy in AD, remains poorly understood.MethodsWe employed N2a/APPswe cells, primary hippocampal neurons exposed to Aβ oligomers, and APP/PS1 transgenic mice as AD models. To assess the impact of AP2A1 on Rab7 activity and autophagy, we conducted Rab7 pulldown activation assay, transmission electron microscopy (TEM), western blot and immunofluorescence (IF) staining were performed. The interaction between AP2A1 and Rab7 was examined by co-immunoprecipitation (Co-IP), IF staining and molecular docking. Live-cell imaging was utilized to monitor autophagosome axonal transport in primary hippocampal neurons. Aβ levels were quantified through immunohistochemistry and ELISA. Behavioral alterations in mice were evaluated using the Morris water maze, open field test, object recognition test and Y-maze.ResultsWe observed reduced levels of AP2A1 and Rab7-GTP, accompanied by autophagosome accumulation, in AD models. Overexpression of AP2A1 restored autophagic flux in these cells. AP2A1 was found to bind and activate Rab7, facilitating the recruitment of retrograde axonal transport proteins DIC1 and RILP. Additionally, AP2A1 overexpression enhanced retrograde axonal autophagosome transport, reinstated autophagic flux, provided neuroprotection, and improved behavioral deficits in AD model mice through Rab7 activation.ConclusionsOur findings demonstrate that AP2A1 activates Rab7 to restore autophagic function and mitigate AD progression, providing novel therapeutic perspectives for autophagy-targeted interventions in AD.

Neurotrophic Factor-α1/carboxypeptidase E regulates critical protein networks to rescue neurodegeneration, defective synaptogenesis and impaired autophagy in Alzheimer's Disease mice.

The global aging population is increasingly inflicted with Alzheimer's disease (AD), but a cure is still unavailable. Neurotrophic Factor-α1/carboxypeptidase E (NF-α1/CPE) gene therapy has been shown to prevent and reverse memory loss and pathology AD mouse models However, the mechanisms of action of NF-α1/CPE are not fully understood. We investigated if a non-enzymatic form of NF-α1/CPE-E342Q is efficient in reversing AD pathology and carried out a proteomic study to uncover the mechanisms of action of NF-α1/CPE in AD mice. AAV-human NF-α1/CPE and a non-enzymatic form, NF-α1/CPE -E342Q were delivered into hippocampus of 3xTg-AD mice and effects on cognitive function, neurodegeneration, synaptogenesis and autophagy were investigated. A quantitative proteomic analysis of hippocampus of 3xTg-AD mice with and without AAV-NF-α1/CPE treatment was carried out. Hippocampal delivery of AAV-NF-α1/CPE-E342Q prevented memory loss, neurodegeneration and increase in activated microglia in 3xTg-AD mice, indicating its action is independent of its enzymatic activity. Quantitative proteomic analysis of hippocampus of 3xTg-AD mice that underwent NF-α1/CPE gene therapy revealed differential expression of >2000 proteins involving many metabolic pathways. Of these, two new proteins down-regulated by NF-α1/CPE: Nexin4 (SNX4) and Trim28 which increase Aβ production and tau levels, respectively were identified. Western blot analysis verified that they were reduced in AAV-NF-α1/CPE treated 3xTg-AD mice compared to untreated mice. Our proteomic analysis indicated synaptic organization as top signaling pathway altered as a response to CPE expression. Synaptic markers PSD95 and Synapsin1 were decreased in 3xTg-AD mice and were restored with AAV-NF-α1/CPE treatment. Proteomic analysis hypothesized involvement of autophagic signaling pathway. Indeed, multiple proteins known to be markers of autophagy were down-regulated in 3xTg-AD mice, accounting for impaired autophagy. Expression of these proteins were upregulated in 3xTg-AD mice with NF-α1/CPE gene therapy, thereby reversing autophagic impairment. This study uncovered vast actions of NF-α1/CPE in restoring expression of networks of critical proteins including those necessary for maintaining neuronal survival, synaptogenesis and autophagy, while down-regulating many proteins that promote tau and Aβ accumulation to reverse memory loss and AD pathology in 3xTg-AD mice. AAV-NF-α1/CPE gene therapy uniquely targets many metabolic levels, offering a promising holistic approach for AD treatment.

MTOR inhibition in Q175 Huntington's disease model mice facilitates neuronal autophagy and mutant huntingtin clearance.

Huntington's disease (HD) is caused by the expansion of the polyglutamine stretch in huntingtin protein (HTT) resulting in hallmark aggresomes/inclusion bodies (IBs) composed of mutant huntingtin protein (mHTT) and its fragments. Stimulating autophagy to enhance mHTT clearance is considered a potential therapeutic strategy for HD. Our recent evaluation of the autophagic-lysosomal pathway (ALP) in human HD brain reveals upregulated lysosomal biogenesis and relatively normal autophagy flux in early Vonsattel grade brains, but impaired autolysosome clearance in late grade brains, suggesting that autophagy stimulation could have therapeutic benefits as an early clinical intervention. Here, we tested this hypothesis by crossing the Q175 HD knock-in model with our autophagy reporter mouse TRGL (Thy-1-RFP-GFP-LC3) to investigate in vivo neuronal ALP dynamics. In the Q175 and/or TRGL/Q175 mice, mHTT was detected in autophagic vacuoles and also exhibited a high level of colocalization with autophagy receptors p62/SQSTM1 and ubiquitin in the IBs. Compared to the robust lysosomal pathology in late-stage human HD striatum, ALP alterations in Q175 models are also late-onset but milder, that included a lowered phospho-p70S6K level, lysosome depletion, and autolysosome elevation including more poorly acidified autolysosomes and larger-sized lipofuscin granules, reflecting impaired autophagic flux. Administration of a mTOR inhibitor to 6-mo-old TRGL/Q175 normalized lysosome number, ameliorated aggresome pathology while reducing mHTT-, p62-, and ubiquitin-immunoreactivities, suggesting the beneficial potential of autophagy modulation at early stages of disease progression.

MTOR inhibition in Q175 Huntington’s disease model mice facilitates neuronal autophagy and mutant huntingtin clearance

Huntington’s disease (HD) is caused by the expansion of the polyglutamine stretch in huntingtin protein (HTT) resulting in hallmark aggresomes/inclusion bodies (IBs) composed of mutant huntingtin protein (mHTT) and its fragments. Stimulating autophagy to enhance mHTT clearance is considered a potential therapeutic strategy for HD. Our recent evaluation of the autophagic-lysosomal pathway (ALP) in human HD brain reveals upregulated lysosomal biogenesis and relatively normal autophagy flux in early Vonsattel grade brains, but impaired autolysosome clearance in late grade brains, suggesting that autophagy stimulation could have therapeutic benefits as an early clinical intervention. Here, we tested this hypothesis by crossing the Q175 HD knock-in model with our autophagy reporter mouse TRGL (Thy-1-RFP-GFP-LC3) to investigate in vivo neuronal ALP dynamics. In the Q175 and/or TRGL/Q175 mice, mHTT was detected in autophagic vacuoles and also exhibited a high level of colocalization with autophagy receptors p62/SQSTM1 and ubiquitin in the IBs. Compared to the robust lysosomal pathology in late-stage human HD striatum, ALP alterations in Q175 models are also late-onset but milder, that included a lowered phospho-p70S6K level, lysosome depletion, and autolysosome elevation including more poorly acidified autolysosomes and larger-sized lipofuscin granules, reflecting impaired autophagic flux. Administration of a mTOR inhibitor to 6-mo-old TRGL/Q175 normalized lysosome number, ameliorated aggresome pathology while reducing mHTT-, p62-, and ubiquitin-immunoreactivities, suggesting the beneficial potential of autophagy modulation at early stages of disease progression.

Gene expression profiling in pure neural leprosy: insights into pathogenesis and diagnostic biomarkers.

Leprosy may affect skin and nerves, leading to permanent disabilities and deformities. Pure neural leprosy (PNL) lacks skin lesions, complicating diagnosis. Moreover there is no a specific treatment to control neural damage. Transcriptomic profiling may reveals unique gene expression changes in PNL nerves, shedding light on immune response and pathogenesis. These findings may guide early diagnosis and improve patient outcome. In the present study, we investigated the gene profiling of nerve samples from patients with PNL and revealed significant transcriptomic alterations compared to non-leprosy controls. Principal Component Analysis (PCA) of the 500 most differentially expressed genes separated the groups, with 1,199 genes showing differential expression (|log2FC| ≥ 1, FDR ≤ 0.1). Downregulated genes included GAS2L2, TRIM67, IL1RAPL1, MAP1LC3B2, and NTNG1, implicated in neuronal development and autophagy, while upregulated genes were linked to immune responses. Functional analyses highlighted inflammasome activation and autophagy impairment in PNL, correlating with nerve inflammation and architecture loss. We hope that our data will aid in identifying new markers, fostering strategies for early diagnosis, preventing disabilities, and improving the management of PNL patients.

Autophagy in alzheimer disease pathogenesis and its therapeutic values.

Alzheimer disease (AD) is the most common form of dementia with hallmarks of β-amyloid deposits, neurofilament tangles, synaptic loss and neuronal death in the patient's brain. AD is a heavy burden in an ageing society as there are no effective therapies in treating the causes or slowing down its progression. Autophagy is a conserved process through formation of double membrane structure, namely autophagosome which is delivered to lysosome to digest cellular disposals. Autophagy maintains homoeostasis in the brain and is generally considered to protect brain functions against ageing. The first evidence of autophagy involvement in AD is that there is decreased expression of autophagy essential genes in post-mortem AD brains. Autophagy is also believed to be protective in neurodegeneration. However, the molecular and cellular mechanisms for dysfunction of autophagy in AD are not fully understood. Recent studies of autophagy regulation in AD cover the findings not only in neurons, but also from fast growing evidence for their importance in glia and brain vascular system. Thus, this review composes pertinent information regarding the involvement of autophagy in neurons, glias (including microglia, astrocyte, and oligodendrocyte), and brain vascular cells in AD, and their unique cellular mechanisms of this connection in AD pathology. We will provide effectual insights both in investigating autophagy in AD pathological mechanisms and in establishing a strategic approach for developing autophagy-based AD therapies.

Inhibition of histone deacetylase 6 activity mitigates neurological impairment and post-hemorrhagic hydrocephalus after intraventricular hemorrhage by modulating pyroptosis and autophagy pathways

BackgroundPosthemorrhagic hydrocephalus (PHH) is a frequent and significant complication that impacts the prognosis of patients suffering from intraventricular hemorrhage (IVH). However, the underlying mechanism is uncertain. Neuronal pyroptosis is characterized by neuronal lysis and destruction, along with the release of inflammatory factors. Autophagy is known to inhibit inflammation, and histone deacetylase-6 (HDAC6) is implicated in the regulation of both autophagy and the NLRP3 inflammasome. However, the role of these proteins in the regulation of neuronal pyroptosis in an IVH model has not been determined.MethodsIn this study, an IVH mouse (6–8 weeks) model was generated via the intracerebroventricular administration of autologous blood at a volume of 40 µL/animal. After the surgical operation, we monitored the mice at various time points, assessing ventricle size via MRI. Additionally, during both the acute (3 days) and chronic (28 days) phases post-surgery, we examined neuronal cell damage and ventricular cilia, as well as neurological function, using HE staining, Nissl staining, scanning electron microscopy, and behavioral experiments such as neurological function scoring and water maze tests. Finally, we detected activation of the pyroptosis and autophagy pathway through western blotting and immunofluorescence staining.ResultsAutophagy induction attenuated cerebral neuronal pyroptosis caused by acute-phase autologous blood injection. HDAC6 was implicated in regulating pyroptosis in the acute phase IVH through its influence on the transcription of nuclear factor kappa-B (NF-κB). Furthermore, HDAC6 regulates excessive autophagic activation in neurons in the chronic phase of IVH. Treatment with ricolinostat improved neurological deficits and ventricular damage during the acute phase of IVH. Moreover, it alleviated mood, memory, and learning deficits in the chronic phase of IVH while also improving PHH.ConclusionsEnhanced autophagy attenuates activation of the NOD-like receptor protein 3 (NLRP3) inflammasome and inhibits neuronal pyroptosis in the acute phase of IVH. HDAC6 plays an important role in regulating the interaction between autophagy and pyroptosis. Ricolinostat treatment significantly attenuated the upregulation of inflammatory factors and neurological impairments induced by pyroptosis in the acute phase of IVH. In addition, ricolinostat effectively reduced excessive autophagy and apoptosis in neurons in the chronic phase and attenuated the formation of PHH.

Radix Hedysari Polysaccharides modulate the gut-brain axis and improve cognitive impairment in SAMP8 mice.

Radix Hedysari Polysaccharides modulate the gut-brain axis and improve cognitive impairment in SAMP8 mice.

Neuroprotective effects of bone marrow mesenchymal stem cells combined with mannitol on radiation-induced brain injury by regulating autophagy via the PI3K/AKT/mTOR signaling pathway.

Neuroprotective effects of bone marrow mesenchymal stem cells combined with mannitol on radiation-induced brain injury by regulating autophagy via the PI3K/AKT/mTOR signaling pathway.

Study on mechanism of naringin in alleviating cerebral ischemia/reperfusion injury based on DRP1/LRRK2/MCU axis

This study aims to investigate the molecular mechanism by which naringin alleviates cerebral ischemia/reperfusion(CI/R) injury through DRP1/LRRK2/MCU signaling axis. A total of 60 SD rats were randomly divided into the sham group, the model group, the sodium Danshensu group, and low-, medium-, and high-dose(50, 100, and 200 mg·kg~(-1)) naringin groups, with 10 rats in each group. Except for the sham group, a transient middle cerebral artery occlusion/reperfusion(tMCAO/R) model was established in SD rats using the suture method. Longa 5-point scale was used to assess neurological deficits. 2,3,5-Triphenyl tetrazolium chloride(TTC) staining was used to detect the volume percentage of cerebral infarction in rats. Hematoxylin-eosin(HE) staining and Nissl staining were employed to assess neuronal structural alterations and the number of Nissl bodies in cortex, respectively. Western blot was used to determine the protein expression levels of B-cell lymphoma-2 gene(Bcl-2), Bcl-2-associated X protein(Bax), cleaved cysteine-aspartate protease-3(cleaved caspase-3), mitochondrial calcium uniporter(MCU), microtubule-associated protein 1 light chain 3(LC3), and P62. Mitochondrial structure and autophagy in cortical neurons were observed by transmission electron microscopy. Immunofluorescence assay was used to quantify the fluorescence intensities of MCU and mitochondrial calcium ion, as well as the co-localization of dynamin-related protein 1(DRP1) with leucine-rich repeat kinase 2(LRRK2) and translocase of outer mitochondrial membrane 20(TOMM20) with LC3 in cortical mitochondria. The results showed that compared with the model group, naringin significantly decreased the volume percentage of cerebral infarction and neurological deficit score in tMCAO/R rats, alleviated the structural damage and Nissl body loss of cortical neurons in tMCAO/R rats, inhibited autophagosomes in cortical neurons, and increased the average diameter of cortical mitochondria. The Western blot results showed that compared to the sham group, the model group exhibited increased levels of cleaved caspase-3, Bax, MCU, and the LC3Ⅱ/LC3Ⅰ ratio in the cortex and reduced protein levels of Bcl-2 and P62. However, naringin down-regulated the protein expression of cleaved caspase-3, Bax, MCU and the ratio of LC3Ⅱ/LC3Ⅰ ratio and up-regulated the expression of Bcl-2 and P62 proteins in cortical area. In addition, immunofluorescence analysis showed that compared with the model group, naringin and positive drug treatments significantly decreased the fluorescence intensities of MCU and mitochondrial calcium ion. Meanwhile, the co-localization of DRP1 with LRRK2 and TOMM20 with LC3 in cortical mitochondria was also decreased significantly after the intervention. These findings suggest that naringin can alleviate cortical neuronal damage in tMCAO/R rats by inhibiting DRP1/LRRK2/MCU-mediated mitochondrial fragmentation and the resultant excessive mitophagy.

LAMP3 exacerbates autophagy-mediated neuronal damage through NF-kB in microglia.

LAMP3 exacerbates autophagy-mediated neuronal damage through NF-kB in microglia.

Berberine alleviates Alzheimer's disease by activating autophagy and inhibiting ferroptosis through the JNK-p38MAPK signaling pathway.

Berberine alleviates Alzheimer's disease by activating autophagy and inhibiting ferroptosis through the JNK-p38MAPK signaling pathway.

Melatonin ameliorates ischemic brain injury in experimental stroke by regulation of miR-221 and ATG7 axis.

Melatonin ameliorates ischemic brain injury in experimental stroke by regulation of miR-221 and ATG7 axis.

6-shogaol alleviates excessive neuronal autophagy and calcium overload following cerebral ischemia-reperfusion injury by inhibiting the expression of DAPK1.

6-shogaol alleviates excessive neuronal autophagy and calcium overload following cerebral ischemia-reperfusion injury by inhibiting the expression of DAPK1.

Hydrogen sulfide improves depression-like behaviors in CUMS-induced mice by regulating autophagy.

Hydrogen sulfide improves depression-like behaviors in CUMS-induced mice by regulating autophagy.

Research progress on the mechanisms of microglial extracellular vesicles affecting the prognosis of ischemic stroke.

Research progress on the mechanisms of microglial extracellular vesicles affecting the prognosis of ischemic stroke.

Glutamate gradually elevates [Zn2+]i via the CaM–CaMKII–NOS cascade in primary cultured rat embryonic cortical neurons

Zn2+ is essential for neuronal signaling, but imbalance cause cell death and neurodegenerative disorders. While the buffering system maintains low cytosolic Zn2+ concentration ([Zn2+]i), the details on physiological stimuli elevating [Zn2+]i for neuronal processes remain limited. Our previous reports have demonstrated that dopamine elevates [Zn2+]i through the cAMP−NO pathway, activating autophagy and inflammation in neurons. In this study, we adopted the Zn2+ imaging technique to verify how glutamate elevated [Zn2+]i in cultured cortical neurons and examined the inflammatory response. Our results showed that glutamate elevates the [Zn2+]i, by activating ionotropic glutamate receptors. Inhibitors of calmodulin (CaM), CaM-dependent protein kinase II (CaMKII), and NO synthase (NOS) blocked the glutamate-induced Zn2+ response. High-K+ buffer induced-membrane depolarization significantly elevated the intracellular Ca2+ concentration ([Ca2+]i) but only slightly increased [Zn2+]i and NO production. Glutamate also transiently increased NOS phosphorylation at Ser1417 within 15 min. The Zn2+ chelator, TPEN suppressed glutamate-induced inflammasome formation. These results indicate that glutamate-induced local increment in [Ca2+]i via the ionotropic glutamate receptors activates the CaM−CaMKII−NOS complex to produce NO and elevate [Zn2+]i. which trigger inflammation in cultured neurons. Henceforth, this novel glutamate−Zn2+ signaling pathway after glutamate depolarization elevates [Ca2+]i indicates the involvement of Zn2+ in modulating long-term neuronal activities.