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Microglia are widely present in the central nervous system and participate in various pathophysiological processes.They play an important role in degenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease.In recent years, the study of exosomes produced by microglia activation involved in the pathophysiological processes of various diseases has attracted extensive attention, but the role of exosomes has not been fully clarified.This article reviewed the characteristics and functions of microglia, the characteristics and functions of microglia-derived exosomes and their roles in central neurodegenerative diseases.
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Objective:To evaluate the relationship between M2-type microglia-derived exosomes (M2-exo) and neuronal oxygen-glucose deprivation and restoration (OGD/R) injury in mice.Methods:Mouse neuroblastoma cells (N2a cells) and BV2 microglia were cultured in vitro, and BV2 microglia were activated to M2 type using 20 ng/ml IL-4, and M0-type microglia-derived exosomes (M0-exo) and M2-exo were extracted.N2a cells were divided into 4 groups ( n=23 each) using the random number table method: control+ M0-exo group (C+ M0 group), control+ M2-exo group (C+ M2 group), OGD/R+ M0-exo group (O+ M0 group) and OGD/R+ M2-exo group (O+ M2 group).M0-exo and M2-exo (final concentration 100 μg/ml) were added in C+ M0 and C+ M2 groups, respectively, and the cells were incubated for 24 h. M0-exo and M2-exo (final concentration 100 μg/ml) were added at 3 h after oxygen and glucose deprivation, and then the cells were incubated for 24 h in O+ M0 and O+ M2 groups, respectively.N2a cell viability was measured by the CCK-8 method, and the severity of cell damage was assessed using the lactic dehydrogenase (LDH) release rate.The expression of Bax and Bcl-2 protein and mRNA was detected by quantitative real-time polymerase chain reaction and Western blot. Results:Compared with C+ M0 group, no significant changes were found in N2a cell viability, LDH release rate, Bax/Bcl-2 ratio and Bax mRNA/Bcl-2 mRNA ratio in C+ M2 group ( P>0.05), and N2a cell viability was significantly decreased, and the LDH release rate, Bax/Bcl-2 ratio and Bax mRNA/Bcl-2 mRNA ratio were increased in O+ M0 group ( P<0.05).Compared with C+ M2 group, the N2a cell viability was significantly decreased, and the LDH release rate, Bax/Bcl-2 ratio and Bax mRNA/Bcl-2 mRNA ratio were increased in O+ M2 group ( P<0.05).Compared with O+ M0 group, N2a cell viability was significantly increased, and LDH release rate, Bax/Bcl-2 ratio, and Bax mRNA/Bcl-2 mRNA ratio were decreased in O+ M2 group ( P<0.05). Conclusions:M2-exo exerts an endogenous protective effect during OGD/R in mouse neurons, which may be related to the inhibition of cell apoptosis.
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Objective:To investigate the effect of M1 microglia-derived exosomes (M1-exo) on neuronal injury after oxygen-glucose deprivation and restoration, and to explore its mechanism.Methods:The mouse microglia BV2 cells grown in logarithmic growth phase were added with 100 μg/L liposolysaccharide (LPS) and 20 μg/L interferon-γ (IFN-γ) to induce the polarization of microglia into M1 phenotype. M1 microglia were identified by Western blotting, quantitative real-time polymerase chain reaction (qPCR) and immunofluorescence. The supernatant of M1 microglia was collected, and exosomes were extracted by ExoQuick-TC TM kit. The morphology of exosomes were observed by transmission electron microscope and nanoparticle tracking analysis (NTA), and the expression of characteristic proteins CD9 and CD63 of exosomes were detected by Western blotting. The well-growing mouse neuroblastoma N2a cells were divided into six groups: the cells in group C were conventionally-cultured; and the cells in group O were subjected to oxygen-glucose deprivation for 3 hours followed by restoration of oxygen-glucose supply 24 hours to establish the model of oxygen-glucose deprivation and restoration injury; and the N2a cells in group E were co-cultured with M1-exo 24 hours after oxygen-glucose deprivation 3 hours; NC group, M group and I group constructed negative control, overexpression and knockdown of microRNA-20a-5p (miR-20a-5p) M1-exo, respectively. The succession of transfection was detected by qPCR and N2a cells in group NC, group M and group I were co-cultured with such transfected M1-exo for 24 hours after oxygen-glucose deprivation 3 hours. Cell viability were detected by cell counting kit-8 (CCK-8) assay, cell apoptosis were detected by flow cytometry, and the expression of miR-20a-5p were detected by qPCR. Results:Compared with M0 microglia, the fluorescence intensity and mRNA and protein expressions of CD32 and inducible nitric oxide synthase (iNOS), specific markers of M1 microglia, were increased [CD32 (fluorescence intensity): 36.919±1.541 vs. 3.533±0.351, CD32 mRNA (2 -ΔΔCt): 4.887±0.031 vs. 1.003±0.012, CD32/β-actin: 2.663±0.219 vs. 1.000±0.028; iNOS (fluorescence intensity): 29.513±1.197 vs. 7.933±0.378, iNOS mRNA (2 -ΔΔCt): 4.829±0.177 vs. 1.000±0.016, iNOS/β-actin: 1.991±0.035 vs. 1.000±0.045; all P < 0.01], indicating M1 microglia were successfully activated. Under electron microscopy, M1-exo had round or oval vesicular bodies with obvious membranous structures, with diameters ranging from 100 nm. Western blotting showed that the exosomes expressed specific CD63 and CD9 proteins. Compared with group C, the cell viability was decreased, the apoptosis rate and the expression of miR-20a-5p were significantly increased in group O [cell viability ( A value): 0.540±0.032 vs. 1.001±0.014, apoptosis rate: (19.857±0.910)% vs. (13.508±0.460)%, miR-20a-5p (2 -ΔΔCt): 5.508±0.291 vs. 1.033±0.101, all P < 0.01]. Compared with O group, cell viability was decreased, apoptosis rate and the expression of miR-20a-5p were increased in group E [cell viability ( A value): 0.412±0.029 vs. 0.540±0.032, apoptosis rate: (31.802±0.647)% vs. (19.857±0.910)%, miR-20a-5p (2 -ΔΔCt): 8.912±0.183 vs. 5.508±0.291, all P < 0.01], indicating that M1 microglia-derived exosomes further aggravated the damage of N2a cells after oxygen-glucose deprivation and restoration. Compared with group E, cell viability was decreased, apoptosis rate and the expression of miR-20a-5p were increased in group M [cell viability ( A value): 0.311±0.028 vs. 0.412±0.029, apoptosis rate: (36.343±0.761)% vs. (31.802±0.647)%, miR-20a-5p (2 -ΔΔCt): 32.348±0.348 vs. 8.912±0.183, all P < 0.01]; and the cell viability was increased, apoptosis rate and the expression of miR-20a-5p were decreased in group I [cell viability ( A value): 0.498±0.017 vs. 0.412±0.029, apoptosis rate: (26.437±0.793)% vs. (31.802±0.647)%, miR-20a-5p (2 -ΔΔCt): 6.875±0.219 vs. 8.912±0.183, all P < 0.01]. There was no significant difference in cell viability, apoptosis rate and the expression of miR-20a-5p between group E and group NC. Conclusion:M1 microglia-derived exosomes aggravate the injury of neurons after oxygen and glucose deprivation and reoxygenation, which may be related to miR-20a-5p carried by M1-exo.
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Objective:To evaluate the effect of electrical stimulation on lipopolysaccharide (LPS)-induced activation of M1 microglia.Methods:The well-growing BV2 microglia cells were divided into 3 groups ( n=18 each) using a random number table method: control group (group C), group LPS, LPS and electrical stimulation group (group LE). The cells were cultured for 24 h in normal culture atmosphere in group C. In group LPS and group LE, the LPS medium culture 100 ng/ml was added, and the cells were cultured for 24 h. In group LE, cells were stimulated with 100 mV/mm direct current for 4 h before LPS incubation.The levels of tumor necrosis factor-α (TNF-α) and leukocyte interleukin-1β (IL-1β) were determined by enzyme-linked immunosorbent assay.The expression of the M1 microglia surface markers CD32 and inducible nitric oxide synase (iNOS) was detected using immunofluorescent staining.The expression of CD32 and iNOS mRNA was detected using quantitative real-time polymerase chain reaction. Results:Compared with group C, the concentrations of TNF-α and IL-1β were significantly increased, and the expression of CD32 and iNOS protein and mRNA was up-regulated in LPS and LE groups ( P<0.05). Compared with group LPS, the concentrations of TNF-α and IL-1β were significantly decreased, and the expression of CD32 and iNOS protein and mRNA was down-regulated in group LE ( P<0.05). Conclusions:Electrical stimulation can inhibit LPS-induced activation of M1 microglia and thus alleviate the inflammatory responses.
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Objective:To evaluate the effect of hypothermia on the polarization of microglia and TLR4/NF-κB signaling pathway during oxygen-glucose deprivation/restoration (OGD/R).Methods:BV2 microglia were cultured in vitro and divided into 3 groups ( n=18 each) using the random number table method: control group (group C), group OGD/R and OGD/R plus hypothermia group (group OGD/R+ HT). Group C was cultured normally for 24 h. In group OGD/R, the cells were exposed to 5% CO 2-1% O 2 at 37 ℃ for 2 h in a glucose-free medium, followed by restoration of glucose and oxygen for 24 h. In group OGD/R+ HT, the high-glucose medium was replaced with a glucose-free medium, the cells were exposed to 5% CO 2-1% O 2 for 2 h in a 33 ℃ cryostat, followed by restoration of glucose and oxygen for 24 h. The cell survival rate was measured by CCK-8 assay.The expression of M1 microglia markers CD32 and iNOS protein and mRNA and M2 microglia markers CD206 and Arg-1 and mRNA was detected by immunofluorescence and real-time quantitative polymerase chain reaction.The expression of TLR-4 and NF-κB in cells was detected by Western blot, and the expression of TLR4 and NF-κB mRNA in cells was detected by real-time quantitative polymerase chain reaction.The concentrations of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β) and interleukin 10 (IL-10) in the cell supernatant were detected by enzyme-linked immunosorbent assay. Results:Compared with group C, the cell survival rate was significantly decreased, the expression of CD32, iNOS, CD206, Arg-1, TLR4 and NF-κB protein and mRNA was up-regulated, and the concentrations of TNF-α, IL-1β and IL-10 in supernatant were increased in OGD/R and OGD/R+ HT groups ( P<0.05). Compared with group OGD/R, the cell survival rate was significantly increased, the expression of CD32, iNOS, TLR4 and NF-κB protein and mRNA was down-regulated, the expression of CD206 and Arg-1 protein and mRNA was up-regulated, the concentrations of TNF-α and IL-1β in supernatant were decreased, and the concentration of IL-10 was increased in group OGD/R+ HT ( P<0.05). Conclusions:Hypothermia can significantly inhibit microglia polarization toward M1 phenotype, increase microglia polarization toward M2 phenotype and inhibit the development of inflammatory responses during OGD/R, and the mechanism may be related to inhibition of TLR4/NF-κB signaling pathway.
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Objective:To evaluate the role of exosomes in M2 microglia-induced reduction of oxygen-glucose deprivation and restoration (OGD/R) injury to astrocytes.Methods:The primary astrocytes were cultured in vitro to the logarithmic growth phase and divided into 5 groups ( n=14 each) using a random number table method: control group (group C), OGD/R group (group O), OGD/R+ M2 microglia group (O+ M2 group), OGD/R+ M2 microglia+ GW4869 group (O+ M2+ G group) and OGD/R+ M2 microglia-derived exosome group (O+ M2-E group). Cells in group C were cultured routinely.Cells in group O were subjected to 4 h of oxygen-glucose deprivation (OGD) and 24 h of restoration of O 2-glucose supply.In group O+ M2, cells were subjected to 4 h of OGD, and the supernatant of M2 microglia 2 ml was added to the medium during restoration of O 2-glucose supply, and the cells were cultured for 24 h. In group O+ M2+ G, cells were subjected to 4 h of OGD, and the supernatant of M2 microglia 2 ml treated with the exosome inhibitor GW4869 10 μmol/L was added to the medium during restoration of O 2-glucose supply, and the cells were cultured for 24 h. In group O+ M2-E, cells were subjected to 4 h of OGD, and the M2 microglia-derived exosome 10 μg/ml was added to the medium during restoration of O 2-glucose supply, and the cells were cultured for 24 h. The morphological changes of cells were observed with a light microscope, the cell viability was detected by CCK-8 assay, the expression of aquaporin 4 (AQP4) mRNA was detected by quantitative real-time polymerase chain reaction, and the expression of AQP4 and porimin was detected by Western blot. Results:Compared with group C, the cell viability was significantly decreased, the expression of AQP4 protein and mRNA and porimin was up-regulated ( P<0.05), and cell swelling occurred in the other four groups.Compared with group O, the cell viability was significantly increased, and the expression of AQP4 protein and mRNA and porimin was down-regulated in O+ M2 and O+ M2-E groups ( P<0.05), and no significant change was found in the parameters mentioned above ( P>0.05), and the cell viability was significantly attenuated in group O+ M2+ G.Compared with group O+ M2, the cell viability was significantly decreased, and the expression of AQP4 protein and mRNA and porimin was up-regulated in group O+ M2+ G ( P<0.05), and no significant change was found in the parameters mentioned above ( P>0.05), and the degree of cell swelling was increased in group O+ M2-E. Conclusions:M2 microglia can mitigate OGD/R injury to astrocytes through exosomes.
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Objective:To evaluate the role of miR-20a-5p in M1 microglia aggravating oxygen-glucose deprivation and restoration (OGD/R)-induced injury to neurons and the relationship with mitofusin2 (MFN2).Methods:The well-growing BV2 microglia (M0 type) were polarized into M1 phenotype by lipopolysaccharide (100 ng/ml) and IFN-γ (20 ng/ml) and identified by quantitative real-time polymerase chain reaction and immunofluorescence.The well-growing N2a cells were divided into 6 groups ( n=6 each) by the random number table method: control group (group C), OGD/R group, M0 microglia co-culture group (group M0), M1 microglia co-culture group (group M1), miR-20a-5p inhibitor transfection group (group I) and negative control group (group NC). The cells were routinely cultured in group C, and the cells were subjected to OGD for 3 h followed by restoration of oxygen-glucose supply to develop the model of OGD/R injury in group OGD/R.The cells were subjected to OGD for 3 h and were co-cultured with M0 microglia for 24 h during restoration of oxygen-glucose supply in group M0.The cells were subjected to OGD for 3 h and were co-cultured with M1 microglia for 24 h during restoration of oxygen-glucose supply in group M1.In group I and group NC, cells were transfected with miR-20a-5p inhibitor and negative control miRNA into M1 microglia, respectively, and N2a cells were subjected to OGD for 3 h and co-cultured with M1 microglia for 24 h during restoration of oxygen-glucose supply.The cell viability was determined by cell counting kit-8 assay, amount of lactate dehydrogenase (LDH) released was determined, the expression of miR-20a-5p and MFN2 mRNA was detected by quantitative real-time polymerase chain reaction, and MFN2 expression was detected by Western blot. Results:Compared with group C, the cell viability was significantly decreased, the amount of LDH released was increased, and the expression of MFN2 protein and mRNA was down-regulated in the other five groups, miR-20a-5p expression was significantly up-regulated in OGD/R, M0 and M1 groups, and miR-20a-5p expression was significantly down-regulated in group I ( P<0.05). There were no significant differences in the cell viability, amount of LDH released, and expression of miR-20a-5p, MFN2 protein and mRNA between group OGD/R and group M0 ( P>0.05). Compared with group OGD/R and group M0, the cell viability was significantly decreased, the amount of LDH released was increased, and the expression of MFN2 protein and mRNA was down-regulated, and miR-20a-5p expression was up-regulated in group M1 ( P<0.05). Compared with group M1, the cell viability was significantly increased, the amount of LDH released was decreased, the expression of MFN2 protein and mRNA was up-regulated, and miR-20a-5p expression was down-regulated in group I ( P<0.05). Conclusions:The mechanism by which M1 microglia aggravates OGD/R-induced damage to N2a cells may be related to the up-regulation of miR-20a-5p expression in M1 microglia and the inhibition of MFN2 expression in N2a cells.
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Objective:To evaluate the role of miR-205-3p in oncosis in astrocytes subjected to oxygen-glucose deprivation and restoration (OGD/R) and the relationship with aquaporin4 (AQP4).Methods:Primary astrocytes were cultured in vitro to the logarithmic growth phase and divided into 5 groups ( n=16 each) using a random number table method: control group (C group), OGD/R group (O group), OGD/R+ miR-205-3p mimic group (M group), OGD/R+ miR-205-3p inhibitor group (I group), and OGD/R+ negative control group (NC group). Cells were cultured routinely in C group.Cells were subjected to 4 h of oxygen-glucose deprivation in a 37℃ anaerobic incubator (containing 94% N 2, 1% O 2 and 5% CO 2) followed by restoration of O 2-glucose supply for 24 h in O group.Cells in M, I and NC groups were transfected with miR-205-3p mimic, miR-205-3p inhibitor and miR-205-3p negative control for 48 h, respectively, and then cells were subjected to 4 h of oxygen-glucose deprivation followed by restoration of O 2-glucose supply for 24 h. The cell viability was evaluated by CCK-8 assay, the cell injury and oncosis were analyzed by flow cytometry, the expression of AQP4 mRNA was detected by quantitative reverse transcription-polymerase chain reaction, and the expression of AQP4 and porimin was detected by Western blot. Results:Compared with C group, the expression of miR-205-3p was significantly down-regulated, the cell viability was decreased, the rates of cell injury and oncosis were increased, and the expression of AQP4 protein and mRNA and porimin was up-regulated in O group ( P<0.05). Compared with O group, the expression of miR-205-3p was significantly up-regulated, the cell viability was increased, the rates of cell injury and oncosis were decreased, and the expression of AQP4 protein and mRNA and porimin was down-regulated in M group, the expression of miR-205-3p was significantly down-regulated, the cell viability was decreased, the rates of cell injury and oncosis were increased, and the expression of AQP4 protein and mRNA and porimin was up-regulated in I group ( P<0.05), and no significant changes were found in NC group( P>0.05). Conclusions:miR-205-3p is involved in oncosis in astrocytes subjected to OGD/R, which is associated with regulation of AQP4 expression.
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Objective:To evaluate the role of exosomes in neuronal injury induced by M1 microglia.Methods:Liposolysaccharide 100 ng/ml and interferon-γ (IFN-γ)20 ng/ml were added to well-growing BV2 microglia to induce the polarization of microglia into M1 phenotype.Cell supernatant of M1 microglia was collected and M1 microglia exosomes (M1-exo) were extracted with exosome kit.The well-growing N2a cells were divided into 4 groups ( n=24 each) using a random number table method: control group (group C), M1 microglia group (group M), exosome group (group E), and exosome inhibitor+ M1 microglia group (group G+ M). The cells in group C were conventionally cultured, the cells in group M were cultured with the supernatant of M1 microglia for 24 h, and the cells in group E were cultured with M1 microglia-derived exosomes for 24 h. In G+ M group, exosome inhibitor GW4869 was added, M1 microglia were incubated for 24 h, then the supernatant was collected and added to N2a cells, and the cells were incubated for 24 h. Cell viability of N2a cells was measured by the cell counting kit 8 assay, cell apoptosis rate was determined by flow cytometry.The expression of apoptosis-related genes Bcl-2 and Bax mRNA was detected by quantitative real-time-polymerase chain reaction, and the expression of apoptosis-related genes Bcl-2 and Bax protein was detected by Western blot. Results:Compared with group C, the cell viability was significantly decreased, the apoptosis rate was increased, the expression of Bcl-2 protein and mRNA was down-regulated, and the expression of Bax protein and mRNA was up-regulated in the other three groups ( P<0.05). Compared with group M, the cell viability was significantly increased, the apoptosis rate was decreased, the expression of Bcl-2 protein and mRNA was up-regulated, and the expression of Bax protein and mRNA was down-regulated in group G+ M ( P<0.05). There was no significant difference in the above indexes between group E and group M ( P>0.05). Conclusions:M1 microglia can mediate neuronal injury via exosomes.
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Objective:To evaluate the role of hsa_circ_0025853 in hypothermia-induced reduction of oxygen-glucose deprivation and restoration (OGD/R) injury to neuroblastoma cells (SK-N-SH cells). Methods:SK-N-SH cells were cultured in vitro to the logarithmic phase and divided into 4 groups ( n=20 each) using a random number table method: control group (group C), group OGD/R, hypothermia group (group H) and hsa_circ_0025853 small interfering RNA (siRNA) plus hypothermia group (group S+ H). The cells were cultured in normal culture atmosphere in group C. The cells were subjected to OGD for 3 h followed by restoration of oxygen-glucose supply for 24 h in group OGD/R.The cells were subjected to OGD for 3 h followed by restoration of oxygen-glucose supply for 24 h at 32 ℃ in group H. The cells were transfected with siRNA at 48 h before establishing OGD/R model, and the other treatments were similar to those previously described in group H. At 24 h of restoration of oxygen-glucose, cell viability was measured by Cell Counting Kit-8, apoptosis rate were measured by flow cytometry.the expression of dynamin-related protein 1 (Drp1) mRNA and hsa_circ_0025853 was detected by quantitative real-time-polymerase chain reaction, and the expression of Drp1 protein was detected by Western blot. Results:Compared with group C, the cell viability was significantly decreased, the apoptosis rate of cells was increased, the expression of hsa_circ_0025853 was down-regulated, and the expression of Drp1 protein and mRNA was up-regulated in the other 3 groups ( P<0.05). Compared with group OGD/R, the cell viability was significantly increased, the apoptosis rate of cells was decreased, the expression of hsa_circ_0025853 was up-regulated, and the expression of Drp1 protein and mRNA was down-regulated in H and S+ H groups ( P<0.05). Compared with group H, the cell viability was significantly decreased, the apoptosis rate of cells was increased, the expression of hsa_circ_0025853 was down-regulated, and the expression of Drp1 protein and mRNA was up-regulated in group S+ H ( P<0.05). Conclusion:The mechanism by which hypothermia alleviates the OGD/R injury to SK-N-SH cells is related to the up-regulation of hsa_circ_0025853 expression, thus reducing the expression level of Drp1.