Sorting through the roles of beclin 1 in microglia and neurodegeneration

Hypoxia-associated autophagy flux dysregulation in human cancers

A general feature of cancer is hypoxia, determined as low oxygen levels. Low oxygen levels may cause cells to alter in ways that contribute to tumor growth and resistance to treatment. Hypoxia leads to variations in cancer cell metabolism, angiogenesis and metastasis. Furthermore, a hypoxic tumor microenvironment might induce immunosuppression. Moreover, hypoxia has the potential to impact cellular processes, such as autophagy. Autophagy refers to the catabolic process by which damaged organelles and toxic macromolecules are broken down. The abnormal activation of autophagy has been extensively recorded in human tumors and it serves as a regulator of cell growth, spread to other parts of the body, and resistance to treatment. There is a correlation between hypoxia and autophagy in human malignancies. Hypoxia can regulate the activity of AMPK, mTOR, Beclin-1, and ATGs to govern autophagy in human malignancies. Furthermore, HIF-1α, serving as an indicator of low oxygen levels, controls the process of autophagy. Hypoxia-induced autophagy has a crucial role in regulating the growth, spread, and resistance to treatment in human malignancies. Hypoxia-induced regulation of autophagy can impact other mechanisms of cell death, such as apoptosis. Chemoresistance and radioresistance have become significant challenges in recent years. Hypoxia-mediated autophagy plays a crucial role in determining the response to these therapeutic treatments.

The nonautophagic functions of autophagy-related proteins

ABBREVIATIONS

ATG: autophagy related; BECN1: beclin 1; cAMP: cyclic adenosine monophosphate; dsDNA: double-stranded DNA; EMT: epithelial-mesenchymal transition; IFN: interferon; ISCs: intestinal stem cells; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK/JNK: mitogen-activated protein kinase/c-Jun N-terminal kinases; MTOR: mechanistic target of rapamycin kinase; STING1: stimulator of interferon response cGAMP interactor 1; UVRAG: UV radiation resistance associated; VPS: vacuolar protein sorting.

Microglial autophagy in cerebrovascular diseases

Microglia are considered core regulators for monitoring homeostasis in the brain and primary responders to central nervous system (CNS) injuries. Autophagy affects the innate immune functions of microglia. Recently some evidence suggests that microglial autophagy is closely associated with brain function in both ischemic stroke and hemorrhagic stroke. Herein, we will discuss the interaction between autophagy and other biological processes in microglia under physiological and pathological conditions and highlight the interaction between microglial metabolism and autophagy. In the end, we focus on the effect of microglial autophagy in cerebrovascular diseases.

Radiated glioblastoma cell-derived exosomal circ_0012381 induce M2 polarization of microglia to promote the growth of glioblastoma by CCL2/CCR2 axis

Background

Radiotherapy is the primary therapeutic option for glioblastoma. Some studies proved that radiotherapy increased the release of exosomes from cells. The mechanism by which these exosomes modify the phenotype of microglia in the tumor microenvironment to further determine the fate of irradiated glioblastoma cells remains to be elucidated.

Methods

We erected the co-culture system of glioblastoma cells and microglia. After radiation, we analyzing the immunophenotype of microglia and the proliferation of radiated glioblastoma cells. By whole transcriptome sequencing, we analyzed of circRNAs in exosomes from glioblastoma cells and microglia. We used some methods, which included RT-PCR, dual-luciferase reporter, et al., to identify how circ_0012381 from radiated glioblastoma cell-derived exosomes regulated the immunophenotype of microglia to further affect the proliferation of radiated glioblastoma cells.

Results

Radiated glioblastoma cell-derived exosomes markedly induced M2 microglia polarization. These M2-polarized microglia promoted the proliferation of irradiated glioblastoma cells. Circ_0012381 expression was increased in the irradiated glioblastoma cells, and circ_0012381 entered the microglia via exosomes. Circ_0012381 induced M2 microglia polarization by sponging with miR-340-5p to increase ARG1 expression. M2-polarized microglia suppressed phagocytosis and promoted the growth of the irradiated glioblastoma cells by CCL2/CCR2 axis. Compared with the effects of radiotherapy alone, the inhibition of exosomes significantly inhibited the growth of irradiated glioblastoma cells in a zebrafish model.

Conclusions

Our data suggested that the inhibition of exosome secretion might represent a potential therapeutic strategy to increase the efficacy of radiotherapy in patients with glioblastoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03607-0.

Fe3O4 Nanozymes Improve Neuroblast Differentiation and Blood-Brain Barrier Integrity of the Hippocampal Dentate Gyrus in D-Galactose-Induced Aged Mice

Aging is a process associated with blood-brain barrier (BBB) damage and the reduction in neurogenesis, and is the greatest known risk factor for neurodegenerative disorders. However, the effects of Fe₃O₄ nanozymes on neurogenesis have rarely been studied. This study examined the effects of Fe₃O₄ nanozymes on neuronal differentiation in the dentate gyrus (DG) and BBB integrity of D-galactose-induced aged mice. Long-term treatment with Fe₃O₄ nanozymes (10 μg/mL diluted in ddH₂O daily) markedly increased the doublecortin (DCX) immunoreactivity and decreased BBB injury induced by D-galactose treatment. In addition, the decreases in the levels of antioxidant proteins including superoxide dismutase (SOD) and catalase as well as autophagy-related proteins such as Becin-1, LC3II/I, and Atg7 induced by D-galactose treatment were significantly ameliorated by Fe₃O₄ nanozymes in the DG of the mouse hippocampus. Furthermore, Fe₃O₄ nanozyme treatment showed an inhibitory effect against apoptosis in the hippocampus. In conclusion, Fe₃O₄ nanozymes can relieve neuroblast damage and promote neuroblast differentiation in the hippocampal DG by regulating oxidative stress, apoptosis, and autophagy.

N-linoleyltyrosine exerts neuroprotective effects in APP/PS1 transgenic mice via cannabinoid receptor-mediated autophagy

Anandamide (AEA) analogs show fair effects in counteracting the deterioration of Alzheimer's disease (AD). Our previous studies demonstrated that AEA analog-N-linoleyltyrosine (NITyr) exerted significant activities. In our current research, the role and mechanisms of NITyr were assessed in APP/PS1 mice mimicking the AD model. NITyr improved motor coordination in the rotarod test (RRT) and ameliorated spatial memory in the Morris water maze (MWM) but did not increase spontaneous locomotor activity in the open field test (OFT). In addition, NITyr protected neurons against β-amyloid (Aβ) injury via hematoxylin-eosin (HE) and Nissl staining. Moreover, the related biochemical indexes showed that NITyr reduced the levels of Aβ40 and Aβ42 in the hippocampus but did not affect the expression of p-APP and β-secretase 1 (BACE1). Furthermore, the autophagy inhibitor 3-methyladenine (3 MA) attenuated the effect of NITyr on animal behaviors and neurons. Meanwhile, NITyr upregulated the expression levels of LC3-II and Beclin-1, which were weakened by AM630 (an antagonist of CB2 receptor and a weak partial agonist of CB1 receptors). AM630 also weakened the role of NITyr in animal behaviors. Thus, NITyr improved behavioral impairment and neural loss by inducing autophagy mainly mediated by the CB2 receptor, and weakly mediated by the CB1 receptor.

TRPV1 sustains microglial metabolic reprogramming in Alzheimer's disease

As the brain-resident innate immune cells, reactive microglia are a major pathological feature of Alzheimer's disease (AD). However, the exact role of microglia is still unclear in AD pathogenesis. Here, using metabolic profiling, we show that microglia energy metabolism is significantly suppressed during chronic Aβ-tolerant processes including oxidative phosphorylation and aerobic glycolysis via the mTOR-AKT-HIF-1α pathway. Pharmacological activation of TRPV1 rescues Aβ-tolerant microglial dysfunction, the AKT/mTOR pathway activity, and metabolic impairments and restores the immune responses including phagocytic activity and autophagy function. Amyloid pathology and memory impairment are accelerated in microglia-specific TRPV1-knockout APP/PS1 mice. Finally, we showed that metabolic boosting with TRPV1 agonist decreases amyloid pathology and reverses memory deficits in AD mice model. These results indicate that TRPV1 is an important target regulating metabolic reprogramming for microglial functions in AD treatment.

Deficiency of microglial Hv1 channel is associated with activation of autophagic pathway and ROS production in LPC-induced demyelination mouse model

BACKGROUND

Multiple sclerosis (MS) is an immune-mediated demyelinated disease of the central nervous system. Activation of microglia is involved in the pathogenesis of myelin loss.

OBJECTIVE

This study is focused on the role of Hv1 in regulating demyelination and microglial activation through reactive oxygen species (ROS) production after lysophosphatidylcholine (LPC)-mediated demyelination. We also explored autophagy in this process.

METHODS

A model of demyelination using two-point LPC injection into the corpus callosum was established. LFB staining, immunofluorescence, Western blot, and electron microscopy were used to study the severity of demyelination. Microglial phenotype and autophagy were detected by immunofluorescence and Western blot. Morris water maze was used to test spatial learning and memory ability.

RESULTS

We have identified that LPC-mediated myelin damage was reduced by Hv1 deficiency. Furthermore, we found that ROS and autophagy of microglia increased in the demyelination region, which was also inhibited by Hv1 knockout.

CONCLUSION

These results suggested that microglial Hv1 deficiency ameliorates demyelination through inhibition of ROS-mediated autophagy and microglial phenotypic transformation.

β‑asarone modulates Beclin‑1, LC3 and p62 expression to attenuate Aβ40 and Aβ42 levels in APP/PS1 transgenic mice with Alzheimer's disease

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly population. Autophagy is a well-known regulator of neurodegenerative diseases and β-asarone has been discovered to have certain neuropharmacological effects. Thus, the present study aimed to analyze the potential effects of β-asarone in AD and its possible mechanism of action in relation to autophagy. The present study investigated the effects of β-asarone on the number of senile plaques and amyloid β(Aβ)₄₀, Aβ₄₂, amyloid precursor protein (APP) and Beclin-1 mRNA levels in the hippocampus of APP/presenilin-1 (PS1) transgenic mice. The possible mechanism of β-asarone on autophagy-related proteins, including Beclin-1, light chain (LC)3A, LC3B and p62 levels, and the number of autophagosomes was also investigated. Mice were divided into a normal control group, a model group, a β-asarone-treated group, a 3-MA-treated group and a rapamycin-treated group. Treatments were continuously administered to all mice for 30 days by intragastric administration. The mice, including those in the normal and model control groups, were given equal volumes of saline. It was demonstrated that β-asarone treatment reduced the number of senile plaques and autophagosomes, and decreased Aβ₄₀, Aβ₄₂, APP and Beclin-1 expression in the hippocampus of model mice compared with untreated model mice. β-asarone also inhibited LC3A/B expression levels, but increased p62 expression. It was deduced that the neuroprotective effects of β-asarone in APP/PS1 transgenic mice resulted from its inhibition of autophagy. In conclusion, the data suggested that β-asarone should be explored further as a potential therapeutic agent in AD.

Exploring the bi-directional relationship between autophagy and Alzheimer's disease

Alzheimer's disease (AD) is characterized by β-amyloid (Aβ) deposition and Tau phosphorylation, in which its pathogenesis has not been cleared so far. The metabolism of Aβ and Tau is critically affected by the autophagy. Abnormal autophagy is thought to be involved in the pathogenesis of AD, regulating autophagy may become a new strategy for AD treatment. In the early stage of AD, the presence of Aβ and Tau can induce autophagy to promote their clearance by means of mTOR-dependent and independent manners. As AD progress, the autophagy goes aberrant. As a result, Aβ and Tau generate continually, which aggravates both autophagy dysfunction and AD. Besides, several related genes and proteins of AD can also adapt autophagy to make an effect on the AD development. There seems to be a bi-directional relationship between AD pathology and autophagy. At present, this article reviews this relationship from these aspects: (a) the signaling pathways of regulating autophagy; (b) the relationships between the autophagy and the processing of Aβ; (c) Aβ and Tau cause autophagy dysfunction; (d) normal autophagy promotes the clearance of Aβ and Tau; (e) the relationships between the autophagy and both genes and proteins related to AD: TFEB, miRNAs, Beclin-1, Presenilin, and Nrf2; and (f) the small molecules regulating autophagy on AD therapy. All of the above may help to further elucidate the pathogenesis of AD and provide a theoretical basis for clinical treatment of AD.

Differential Interactome and Innate Immune Response Activation of Two Structurally Distinct Misfolded Protein Oligomers

The formation of misfolded protein oligomers during early stages of amyloid aggregation and the activation of neuroinflammatory responses are two key events associated with neurodegenerative diseases. Although it has been established that misfolded oligomers are involved in the neuroinflammatory process, the links between their structural features and their functional effects on the immune response remain unknown. To explore such links, we took advantage of two structurally distinct soluble oligomers (type A and B) of protein HypF-N and compared the elicited microglial inflammatory responses. By using confocal microscopy, protein pull-down, and high-throughput mass spectrometry, we found that, even though both types bound to a common pool of microglial proteins, type B oligomers-with a lower solvent-exposed hydrophobicity-showed enhanced protein binding, correlating with the observed inflammatory response. Furthermore, the interactome associated with inflammatory-mediated neurodegeneration revealed previously unidentified receptors and signaling molecules likely to be involved in the oligomer-elicited innate immune response.

Platelet-Membrane-Camouflaged Black Phosphorus Quantum Dots Enhance Anticancer Effect Mediated by Apoptosis and Autophagy

Hederagenin (HED) has poor anticancer activity whose mechanism remains unclear and unsystematic. Free drugs for cancer treatment exhibit disadvantages such as poor targeting and efficacy. To address this problem, we constructed a nanoplatform of black phosphorus quantum dots (BPQDs) camouflaged with a platelet membrane (PLTm) carrying HED, termed PLT@BPQDs-HED. PLTm vesicles serve as a shell to encapsulate multiple high-efficiency drug-loaded nanocores, which can target tumor sites and significantly improve antitumor activity. Compared with free HED, this platform significantly reduced tumor cell viability and the mitochondrial membrane potential (MMP), while increasing the production of intracellular reactive oxygen species (ROS). The platform also significantly increased the amounts of terminal deoxyribonucleotide transferase mediated dUTP nick-end-labeling (TUNEL)-positive cells and decreased the number of Ki-67-positive cells. In addition, the platform upregulated proapoptotic factor Bax, downregulated the anti-apoptotic molecule Bcl-2, activated Caspase-9 and Caspase-3, and stimulated Cytochrome C release. Moreover, the platform promoted the formation of autophagosomes, upregulated Beclin-1, and promoted LC3-I conversion into LC3-II. This study demonstrated that the above platform significantly enhances tumor targeting and promotes mitochondria-mediated cell apoptosis and autophagy in tumor cells.

1,25(OH)2D3 Activates Autophagy to Protect against Oxidative Damage of INS-1 Pancreatic Beta Cells

Diabetes mellitus is a serious disease endangering human health worldwide. Vitamin D (Vit D) is a well-characterized regulator of calcium-phosphorus metabolism that also exerts other biological effects extending far beyond mineral homeostasis. Some epidemiological studies have suggested that Vit D has a role in defense against diabetes, although the mechanism remains unclear. Autophagy, an intracellular catabolic process, is necessary to maintain the normal structure and function of host cells. In our previous study, we found that Vit D could induce autophagy of pancreatic beta cells and prevent insulitis, although the underlying mechanisms remain to be fully elucidated. In this study, the protective effect of 1,25(OH)₂D₃, the physiologically active metabolite of Vit D, against streptozotocin-induced cytotoxicity in rat insulinoma cell line (INS-1) cells was explored. Cell viability and insulin secretion of INS-1 cells in response to different treatments were measured with a cell counting kit and enzyme-linked immune absorbent assay (ELISA), respectively. In addition, malondialdehyde (MDA) content and total antioxidant capacity (T-AOC) were measured by ELISA. RT-PCR and Western blot analyses were used to detect autophagy levels, reactive oxygen species (ROS) was assessed by fluorescence microscope, ultrastructure analysis was performed using transmission electron microscopy. The results demonstrated that 1,25(OH)₂D₃ could increase cell viability and insulin secretion of INS-1 cells, and protected cells from oxidative damage induced by streptozotocin (STZ) through autophagy activation. These findings shed light on mechanisms underlying the ameliorative effects of Vit D on diabetes mellitus.

LncRNA DYNLRB2-2 inhibits THP-1 macrophage foam cell formation by enhancing autophagy

The aim of this study was to investigate whether long non-coding RNA (lncRNA) DYNLRB2-2 can inhibit foam cell formation by activating autophagy. The location of DYNLRB2-2 in THP-1-derived macrophages was analyzed by fluorescence in situ hybridization (FISH). Oxidized-low-density lipoprotein (ox-LDL) was used to induce the formation of foam cells, Oil Red O (ORO) staining and high-performance liquid chromatography (HPLC) were performed to detect accumulation of lipid droplets and the level of cholesterol concentration, respectively. The mRNA and protein level of ATP-binding cassette transporter A1 (ABCA1) were examined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting. Relative protein levels of (p-) liver kinase B1 (LKB1), (p-) AMP-activated protein kinase (AMPK), (p-) the mammalian target of rapamycin (mTOR) and autophagy markers (LC3 II, Beclin-1 and p62) in THP-1 macrophage-derived foam cells were analyzed by Western blotting. The levels of inflammatory factors [tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β] in THP-1 macrophage-derived foam cells were detected by enzyme-linked immunosorbent assay (ELISA). 3-MA and compound C were used to block autophagy. Our data show that DYNLRB2-2 inhibited the formation of THP-1 macrophage-derived foam cells and promotes cholesterol efflux (CE) by activating autophagy. DYNLRB2-2 caused autophagy by activating the signaling pathway of LKB1/AMPK/mTOR in foam cells. DYNLRB2-2 activated the LKB1/AMPK/mTOR signaling pathway via the miR-298/Sirtuin 3 (SIRT3) axis. Our data indicated that DYNLRB2-2 enhanced CE by regulating the LKB1/AMPK/mTOR autophagy signaling pathway through the miR-298/SIRT3 axis, thereby blocking the formation of foam cells from THP-1 macrophages.

Loss of VAPB Regulates Autophagy in a Beclin 1-Dependent Manner

Autophagy is an evolutionarily-conserved self-degradative process that maintains cellular homeostasis by eliminating protein aggregates and damaged organelles. Recently, vesicle-associated membrane protein-associated protein B (VAPB), which is associated with the familial form of amyotrophic lateral sclerosis, has been shown to regulate autophagy. In the present study, we demonstrated that knockdown of VAPB induced the up-regulation of beclin 1 expression, which promoted LC3 (microtubule-associated protein light chain 3) conversion and the formation of LC3 puncta, whereas overexpression of VAPB inhibited these processes. The regulation of beclin 1 by VAPB was at the transcriptional level. Moreover, knockdown of VAPB increased autophagic flux, which promoted the degradation of the autophagy substrate p62 and neurodegenerative disease proteins. Our study provides evidence that the regulation of autophagy by VAPB is associated with the autophagy-initiating factor beclin 1.

The role of autophagy in pro-inflammatory responses of microglia activation via mitochondrial reactive oxygen species in vitro

Microglia over-activation contributes to neurodegenerative processes by neurotoxin factors and pro-inflammatory molecules of pro-inflammatory processes. Mitochondrial reactive oxygen species (ROS) and autophagy pathway might be involved in microglial activation, but the underlying mechanism is unclear. Here, we regulated autophagy pathway of microglia in vitro by autophagy inhibition (3-methyladenine treatment, siRNA-Beclin 1 or siRNA-ATG5 transfection) or induction (rapamycin treatment) in murine microglial BV-2 cells or cultured primary mouse microglial cells. And we found that autophagy inhibition could sensitize mitochondrial profile and microglial activation of cultured microglial cells, demonstrated by significant production of mitochondrial ROS, loss of mitochondrial membrane potential, secretion of pro-inflammatory cytokines including interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 12 (IL-12) and tumor necrosis factor α and marked activation of mitogen-activated proteinkinases (MAPKs) and nuclear factor κB (NF-κB). These effects could be blocked by specific inhibitors of MAPK and NF-κB or mitochondrial antioxidants, Mito-TEMPO. Meanwhile, induction of autophagy with rapamycin treatment could significantly suppress microglial inflammatory responses, mitochondrial ROS production, activation of MAPKs and NF-κB. Taken together, our in vitro results from primary cultured microglia and BV-2 cell lines indicated that autophagy inhibition might participate in brain macrophage or microglia over-activation and mitochondrial ROS generation might be involved in the regulatory microglial pro-inflammatory responses.

The role of autophagy in modulation of neuroinflammation in microglia

Microglia have multiple functions in regulating homeostasis in the central nervous system (CNS), and microglial inflammation is thought to play a role in the etiology of the neurodegenerative diseases. When endogenous or exogenous stimuli trigger disorders in microenvironmental homeostasis in CNS, microglia critically determine the fate of other neural cells. Recently, it was reported that autophagy might influence inflammation and activation of microglia. Though the interaction between autophagy and macrophages has been reported and reviewed in length, the role of autophagy in microglia has yet to be reviewed. Herein, we will highlight recent advances on the emerging role of autophagy in microglia, focusing on the regulation of autophagy during microglial inflammation, and the possible mechanism involved.

Inflammatory Stress on Autophagy in Peripheral Blood Mononuclear Cells from Patients with Alzheimer's Disease during 24 Months of Follow-Up

Recent findings indicate that microglia in Alzheimer's disease (AD) is senescent whereas peripheral blood mononuclear cells (PBMCs) could infiltrate the brain to phagocyte amyloid deposits. However, the molecular mechanisms involved in the amyloid peptide clearance remain unknown. Autophagy is a physiological degradation of proteins and organelles and can be controlled by pro-inflammatory cytokines. The purpose of this study was to evaluate the impact of inflammation on autophagy in PBMCs from AD patients at baseline, 12 and 24 months of follow-up. Furthermore, PBMCs from healthy patients were also included and treated with 20 μM amyloid peptide 1-42 to mimic AD environment. For each patient, PBMCs were stimulated with the mitogenic factor, phytohaemagglutin (PHA), and treated with either 1 μM C16 as an anti-inflammatory drug or its vehicle. Autophagic markers (Beclin-1, p62/sequestosome 1 and microtubule-associated protein-light chain 3: LC3) were quantified by western blot and cytokines (Interleukin (IL)-1β, Tumor necrosis Factor (TNF)-α and IL-6) by Luminex X-MAP® technology. Beclin-1 and TNF-α levels were inversely correlated in AD PBMCs at 12 months post-inclusion. In addition, Beclin-1 and p62 increased in the low inflammatory environment induced by C16. Only LC3-I levels were inversely correlated with cognitive decline at baseline. For the first time, this study describes longitudinal changes in autophagic markers in PBMCs of AD patients under an inflammatory environment. Inflammation would induce autophagy in the PBMCs of AD patients while an anti-inflammatory environment could inhibit their autophagic response. However, this positive response could be altered in a highly aggressive environment.

The potential of Beclin 1 as a therapeutic target for the treatment of breast cancer

INTRODUCTION

Beclin 1 plays a crucial role in autophagy via the Beclin 1 interactome, and is involved in various biological processes such as protein sorting, chemokinesis, and cell death. Via these biologic functions, Beclin 1 contributes to both tumor suppression and tumor progression.

AREAS COVERED

Beclin 1 plays a key biologic function on cell homeostasis and affects tumorigenesis. In this review, detailing up-to-date knowledge on the tumorigenic role of Beclin 1, its implication in breast cancer, and its utility as a breast cancer-specific drug target is discussed.

EXPERT OPINION

Because Beclin 1 is expressed in breast cancer cells, Beclin 1 could be a unique, effective drug target for the prevention and treatment of breast cancer. However, the expression of Beclin 1 varies according to cancer molecular subtypes, and Beclin 1 is involved in both breast cancer suppression and tumor progression; therefore, the decision of using a Beclin 1 inducer or inhibitor should be made based on breast cancer stage and subtype.

miR-Let7A Modulates Autophagy Induction in LPS-Activated Microglia

Microglia regulate the secretion of various immunomediators in central nervous system diseases. Microglial autophagy is the crucial process for cell's survival and cytokine productions. Recent studies have reported that several microRNAs are involved in the autophagy system. miR-Let7A is such a microRNA that plays a role in various inflammation responses, and is magnified as a key modulator particularly in the autophagy system. In present study, we investigated whether miR-Let7A is involved in autophagy in activating microglia. Overexpression of miR-Let7A in LPS-stimulated BV2 microglial cells promoted the induction of the autophagy related factors such as LC3II, Beclin1, and ATG3. Our results suggest a potential role of miR-Let7A in the autophagy process of microglia during CNS inflammation.