Microglia are brain-resident immune cells that contribute to the maintenance of brain homeostasis.In the epileptic brain, microglia show various activation phenotypes depending on the stage of epileptogenesis.Therefor...Microglia are brain-resident immune cells that contribute to the maintenance of brain homeostasis.In the epileptic brain, microglia show various activation phenotypes depending on the stage of epileptogenesis.Therefore, it remains unclear whether microglial activation acts in a pro-epileptic or anti-epileptic manner.In mesial temporal lobe epilepsy, one of the most common form of epilepsies, microglia exhibit at least two distinct morphologies, amoeboid shape and ramified shape.Amoeboid microglia are often found in sclerotic area, whereas ramified microglia are mainly found in non-sclerotic area;however, it remains unclear whether these structurally distinct microglia share separate roles in the epileptic brain.Here, we review the roles of the two distinct microglial phenotypes, focusing on their pro-and anti-epileptic roles in terms of inflammatory response, regulation of neurogenesis and microglia-neuron interaction.展开更多
Millions of people worldwide are affected by traumatic spinal cord injury,which usually results in permanent sensorimotor disability.Damage to the spinal cord leads to a series of detrimental events including ischaemi...Millions of people worldwide are affected by traumatic spinal cord injury,which usually results in permanent sensorimotor disability.Damage to the spinal cord leads to a series of detrimental events including ischaemia,haemorrhage and neuroinflammation,which over time result in further neural tissue loss.Eventually,at chronic stages of traumatic spinal cord injury,the formation of a glial scar,cystic cavitation and the presence of numerous inhibitory molecules act as physical and chemical barriers to axonal regrowth.This is further hindered by a lack of intrinsic regrowth ability of adult neurons in the central nervous system.The intracellular signalling molecule,cyclic adenosine 3′,5′-monophosphate(cAMP),is known to play many important roles in the central nervous system,and elevating its levels as shown to improve axonal regeneration outcomes following traumatic spinal cord injury in animal models.However,therapies directly targeting cAMP have not found their way into the clinic,as cAMP is ubiquitously present in all cell types and its manipulation may have additional deleterious effects.A downstream effector of cAMP,exchange protein directly activated by cAMP 2(Epac2),is mainly expressed in the adult central nervous system,and its activation has been shown to mediate the positive effects of cAMP on axonal guidance and regeneration.Recently,using ex vivo modelling of traumatic spinal cord injury,Epac2 activation was found to profoundly modulate the post-lesion environment,such as decreasing the activation of astrocytes and microglia.Pilot data with Epac2 activation also suggested functional improvement assessed by in vivo models of traumatic spinal cord injury.Therefore,targeting Epac2 in traumatic spinal cord injury could represent a novel strategy in traumatic spinal cord injury repair,and future work is needed to fully establish its therapeutic potential.展开更多
In the central nervous system,immunologic surveillance and response are carried out,in large part,by microglia.These resident macrophages derive from myeloid precursors in the embryonic yolk sac,migrating to the brain...In the central nervous system,immunologic surveillance and response are carried out,in large part,by microglia.These resident macrophages derive from myeloid precursors in the embryonic yolk sac,migrating to the brain and eventually populating local tissue prior to blood-brain barrier formation.Preserved for the duration of lifespan,microglia serve the host as more than just a central arm of innate immunity,also contributing significantly to the development and maintenance of neurons and neural networks,as well as neuroregeneration.The critical nature of these varied functions makes the characterization of key roles played by microglia in neurodegenerative disorders,especially Alzheimer’s disease,of paramount importance.While genetic models and rudimentary pharmacologic approaches for microglial manipulation have greatly improved our understanding of central nervous system health and disease,significant advances in the selective and near complete in vitro and in vivo depletion of microglia for neuroscience application continue to push the boundaries of research.Here we discuss the research efficacy and utility of various microglial depletion strategies,including the highly effective CSF1R inhibitor models,noteworthy insights into the relationship between microglia and neurodegeneration,and the potential for therapeutic repurposing of microglial depletion and repopulation.展开更多
Microglia,which are tissue-resident macrophages in the brain,play a central role in the brain innate immunity and contribute to the maintenance of brain homeostasis.Lipopolysaccharide is a component of the outer membr...Microglia,which are tissue-resident macrophages in the brain,play a central role in the brain innate immunity and contribute to the maintenance of brain homeostasis.Lipopolysaccharide is a component of the outer membrane of gram-negative bacteria,and activates immune cells including microglia via Toll-like receptor 4 signaling.Lipopolysaccharide is generally known as an endotoxin,as administration of highdose lipopolysaccharide induces potent systemic inflammation.Also,it has long been recognized that lipopolysaccharide exacerbates neuroinflammation.In contrast,our study revealed that oral administration of lipopolysaccharide ameliorates Alzheimer’s disease pathology and suggested that neuroprotective microglia are involved in this phenomenon.Additionally,other recent studies have accumulated evidence demonstrating that controlled immune training with low-dose lipopolysaccharide prevents neuronal damage by transforming the microglia into a neuroprotective phenotype.Therefore,lipopolysaccharide may not a mere inflammatory inducer,but an immunomodulator that can lead to neuroprotective effects in the brain.In this review,we summarized current studies regarding neuroprotective microglia transformed by immune training with lipopolysaccharide.We state that microglia transformed by lipopolysaccharide preconditioning cannot simply be characterized by their general suppression of proinflammatory mediators and general promotion of anti-inflammatory mediators,but instead must be described by their complex profile comprising various molecules related to inflammatory regulation,phagocytosis,neuroprotection,anti-apoptosis,and antioxidation.In addition,microglial transformation seems to depend on the dose of lipopolysaccharide used during immune training.Immune training of neuroprotective microglia using lowdose lipopolysaccharide,especially through oral lipopolysaccharide administration,may represent an innovative prevention or treatment for neurological diseases;however more vigorous studies are still required to properly 展开更多
Several studies have confirmed that microglia are involved in neuropathic pain.Inhibition of guanosine-5′-triphosphate cyclohydrolase 1(GTPCH1)can reduce the inflammation of microglia.However,the precise mechanism by...Several studies have confirmed that microglia are involved in neuropathic pain.Inhibition of guanosine-5′-triphosphate cyclohydrolase 1(GTPCH1)can reduce the inflammation of microglia.However,the precise mechanism by which GTPCH1 regulates neuropathic pain remains unclear.In this study,BV2 microglia were transfected with adenovirus to knockdown GTPCH1 expression.High throughput sequencing analysis revealed that the mitogen-activated protein kinase(MAPK)related pathways and proteins were the most significantly downregulated molecular function.Co-expression network analysis of Mapk14 mRNA and five long noncoding RNAs(lnc RNAs)revealed their correlation.Quantitative reverse transcription-polymerase chain reaction revealed that among five lnc RNAs,ENSMUST00000205634,ENSMUST00000218450 and ENSMUST00000156079 were related to the downregulation of Mapk14 mRNA expression.These provide some new potential targets for the involvement of GTPCH1 in neuropathic pain.This study is the first to note the differential expression of lnc RNAs and mRNA in GTPCH1 knockdown BV2 microglia.Findings from this study reveal the mechanism by which GTPCH1 activates microglia and provide new potential targets for microglial activation in neuropathic pain.展开更多
We previously found that argon exerts its neuroprotective effect in part by inhibition of the toll-like receptors(TLR)2 and 4.The downstream transcription factors signal transducer and activator of transcription 3(STA...We previously found that argon exerts its neuroprotective effect in part by inhibition of the toll-like receptors(TLR)2 and 4.The downstream transcription factors signal transducer and activator of transcription 3(STAT3)and nuclear factor kappa B(NF-κB)are also affected by argon and may play a role in neuroprotection.It also has been demonstrated that argon treatment could mitigate brain damage,reduce excessive microglial activation,and subsequently attenuate brain inflammation.Despite intensive research,the further exact mechanism remains unclear.In this study,human neuroblastoma cells were damaged in vitro with rotenone over a period of 4 hours(to mimic cerebral ischemia and reperfusion damage),followed by a 2-hour post-conditioning with argon(75%).In a separate in vivo experiment,retinal ischemia/reperfusion injury was induced in rats by increasing intraocular pressure for 1 hour.Upon reperfusion,argon was administered by inhalation for 2 hours.Argon reduced the binding of the transcription factors signal transducer and activator of transcription 3,nuclear factor kappa B,activator protein 1,and nuclear factor erythroid 2-related factor 2,which are involved in regulation of neuronal damage.Flow cytometry analysis showed that argon downregulated the Fas ligand.Some transcription factors were regulated by toll-like receptors;therefore,their effects could be eliminated,at least in part,by the TLR2 and TLR4 inhibitor oxidized phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine(OxPAPC).Argon treatment reduced microglial activation after retinal ischemia/reperfusion injury.Subsequent quantitative polymerase chain reaction analysis revealed a reduction in the pro-inflammatory cytokines interleukin(IL-1α),IL-1β,IL-6,tumor necrosis factorα,and inducible nitric oxide synthase.Our results suggest that argon reduced the extent of inflammation in retinal neurons after ischemia/reperfusion injury by suppression of transcription factors crucial for microglial activation.Argon has no known side effects o展开更多
Osteopontin is a broadly expressed pleiotropic protein,and is attracting increased attention because of its role in the pathophysiology of several inflammatory,degenerative,autoimmune,and oncologic diseases.In fact,in...Osteopontin is a broadly expressed pleiotropic protein,and is attracting increased attention because of its role in the pathophysiology of several inflammatory,degenerative,autoimmune,and oncologic diseases.In fact,in the last decade,several studies have shown that osteopontin contributes to tissue damage not only by recruiting harmful inflammatory cells to the site of lesion,but also increasing their survival.The detrimental role of osteopontin has been indeed well documented in the context of different neurological conditions(i.e.,multiple sclerosis,Parkinson’s,and Alzheimer’s diseases).Intriguingly,recent findings show that osteopontin is involved not only in promoting tissue damage(the Yin),but also in repair/regenerative mechanisms(the Yang),mostly triggered by the inflammatory response.These two apparently discordant roles are partly related to the presence of different functional domains in the osteopontin molecule,which are exposed after thrombin or metalloproteases cleavages.Such functional domains may in turn activate intracellular signaling pathways and mediate cell-cell and cell-matrix interactions.This review describes the current knowledge on the Yin and Yang features of osteopontin in nervous system diseases.Understanding the mechanisms behind the Yin/Yang would be relevant to develop highly specific tools targeting this multifunctional protein.展开更多
基金supported in part by a Grant-in-Aid for Scientific Research (B)(17H03988 to RK) from JSPS and JST PRESTO (JPMJPR18H4 to RK)。
文摘Microglia are brain-resident immune cells that contribute to the maintenance of brain homeostasis.In the epileptic brain, microglia show various activation phenotypes depending on the stage of epileptogenesis.Therefore, it remains unclear whether microglial activation acts in a pro-epileptic or anti-epileptic manner.In mesial temporal lobe epilepsy, one of the most common form of epilepsies, microglia exhibit at least two distinct morphologies, amoeboid shape and ramified shape.Amoeboid microglia are often found in sclerotic area, whereas ramified microglia are mainly found in non-sclerotic area;however, it remains unclear whether these structurally distinct microglia share separate roles in the epileptic brain.Here, we review the roles of the two distinct microglial phenotypes, focusing on their pro-and anti-epileptic roles in terms of inflammatory response, regulation of neurogenesis and microglia-neuron interaction.
基金supported by Scottish Rugby Union funding to WH and DSthe NRB PhD scholarship from the International Spinal Rsesarch Trust to AGBa Hot-Start Scholarship from the University of aberdeen to DD。
文摘Millions of people worldwide are affected by traumatic spinal cord injury,which usually results in permanent sensorimotor disability.Damage to the spinal cord leads to a series of detrimental events including ischaemia,haemorrhage and neuroinflammation,which over time result in further neural tissue loss.Eventually,at chronic stages of traumatic spinal cord injury,the formation of a glial scar,cystic cavitation and the presence of numerous inhibitory molecules act as physical and chemical barriers to axonal regrowth.This is further hindered by a lack of intrinsic regrowth ability of adult neurons in the central nervous system.The intracellular signalling molecule,cyclic adenosine 3′,5′-monophosphate(cAMP),is known to play many important roles in the central nervous system,and elevating its levels as shown to improve axonal regeneration outcomes following traumatic spinal cord injury in animal models.However,therapies directly targeting cAMP have not found their way into the clinic,as cAMP is ubiquitously present in all cell types and its manipulation may have additional deleterious effects.A downstream effector of cAMP,exchange protein directly activated by cAMP 2(Epac2),is mainly expressed in the adult central nervous system,and its activation has been shown to mediate the positive effects of cAMP on axonal guidance and regeneration.Recently,using ex vivo modelling of traumatic spinal cord injury,Epac2 activation was found to profoundly modulate the post-lesion environment,such as decreasing the activation of astrocytes and microglia.Pilot data with Epac2 activation also suggested functional improvement assessed by in vivo models of traumatic spinal cord injury.Therefore,targeting Epac2 in traumatic spinal cord injury could represent a novel strategy in traumatic spinal cord injury repair,and future work is needed to fully establish its therapeutic potential.
基金This work was supported by DePaul University grant URC450622(to EC).
文摘In the central nervous system,immunologic surveillance and response are carried out,in large part,by microglia.These resident macrophages derive from myeloid precursors in the embryonic yolk sac,migrating to the brain and eventually populating local tissue prior to blood-brain barrier formation.Preserved for the duration of lifespan,microglia serve the host as more than just a central arm of innate immunity,also contributing significantly to the development and maintenance of neurons and neural networks,as well as neuroregeneration.The critical nature of these varied functions makes the characterization of key roles played by microglia in neurodegenerative disorders,especially Alzheimer’s disease,of paramount importance.While genetic models and rudimentary pharmacologic approaches for microglial manipulation have greatly improved our understanding of central nervous system health and disease,significant advances in the selective and near complete in vitro and in vivo depletion of microglia for neuroscience application continue to push the boundaries of research.Here we discuss the research efficacy and utility of various microglial depletion strategies,including the highly effective CSF1R inhibitor models,noteworthy insights into the relationship between microglia and neurodegeneration,and the potential for therapeutic repurposing of microglial depletion and repopulation.
基金This work was funded by Control of Innate Immunity Technology Research Association,a grant of Cross-ministerial Strategic Innovation Promotion Program,SIP-No.14533073(to GIS)from the Council for Science from Technology and Innovation(CSTI)in Cabinet Office of Japanese Government and the National Agriculture and Food Research Organization(NARO).
文摘Microglia,which are tissue-resident macrophages in the brain,play a central role in the brain innate immunity and contribute to the maintenance of brain homeostasis.Lipopolysaccharide is a component of the outer membrane of gram-negative bacteria,and activates immune cells including microglia via Toll-like receptor 4 signaling.Lipopolysaccharide is generally known as an endotoxin,as administration of highdose lipopolysaccharide induces potent systemic inflammation.Also,it has long been recognized that lipopolysaccharide exacerbates neuroinflammation.In contrast,our study revealed that oral administration of lipopolysaccharide ameliorates Alzheimer’s disease pathology and suggested that neuroprotective microglia are involved in this phenomenon.Additionally,other recent studies have accumulated evidence demonstrating that controlled immune training with low-dose lipopolysaccharide prevents neuronal damage by transforming the microglia into a neuroprotective phenotype.Therefore,lipopolysaccharide may not a mere inflammatory inducer,but an immunomodulator that can lead to neuroprotective effects in the brain.In this review,we summarized current studies regarding neuroprotective microglia transformed by immune training with lipopolysaccharide.We state that microglia transformed by lipopolysaccharide preconditioning cannot simply be characterized by their general suppression of proinflammatory mediators and general promotion of anti-inflammatory mediators,but instead must be described by their complex profile comprising various molecules related to inflammatory regulation,phagocytosis,neuroprotection,anti-apoptosis,and antioxidation.In addition,microglial transformation seems to depend on the dose of lipopolysaccharide used during immune training.Immune training of neuroprotective microglia using lowdose lipopolysaccharide,especially through oral lipopolysaccharide administration,may represent an innovative prevention or treatment for neurological diseases;however more vigorous studies are still required to properly
基金supported by the National Natural Science Foundation of China,Nos.81572205 and 81974345(both to CYM)。
文摘Several studies have confirmed that microglia are involved in neuropathic pain.Inhibition of guanosine-5′-triphosphate cyclohydrolase 1(GTPCH1)can reduce the inflammation of microglia.However,the precise mechanism by which GTPCH1 regulates neuropathic pain remains unclear.In this study,BV2 microglia were transfected with adenovirus to knockdown GTPCH1 expression.High throughput sequencing analysis revealed that the mitogen-activated protein kinase(MAPK)related pathways and proteins were the most significantly downregulated molecular function.Co-expression network analysis of Mapk14 mRNA and five long noncoding RNAs(lnc RNAs)revealed their correlation.Quantitative reverse transcription-polymerase chain reaction revealed that among five lnc RNAs,ENSMUST00000205634,ENSMUST00000218450 and ENSMUST00000156079 were related to the downregulation of Mapk14 mRNA expression.These provide some new potential targets for the involvement of GTPCH1 in neuropathic pain.This study is the first to note the differential expression of lnc RNAs and mRNA in GTPCH1 knockdown BV2 microglia.Findings from this study reveal the mechanism by which GTPCH1 activates microglia and provide new potential targets for microglial activation in neuropathic pain.
基金This work was financially supported by the Department of Anesthesiology and Critical Care,Medical Center-University of Freiburg,GermanyThe article processing charge was funded by the Baden-Württemberg Ministry of Science,Research and Art and the University of Freiburg in the funding programme Open Access Publishing.
文摘We previously found that argon exerts its neuroprotective effect in part by inhibition of the toll-like receptors(TLR)2 and 4.The downstream transcription factors signal transducer and activator of transcription 3(STAT3)and nuclear factor kappa B(NF-κB)are also affected by argon and may play a role in neuroprotection.It also has been demonstrated that argon treatment could mitigate brain damage,reduce excessive microglial activation,and subsequently attenuate brain inflammation.Despite intensive research,the further exact mechanism remains unclear.In this study,human neuroblastoma cells were damaged in vitro with rotenone over a period of 4 hours(to mimic cerebral ischemia and reperfusion damage),followed by a 2-hour post-conditioning with argon(75%).In a separate in vivo experiment,retinal ischemia/reperfusion injury was induced in rats by increasing intraocular pressure for 1 hour.Upon reperfusion,argon was administered by inhalation for 2 hours.Argon reduced the binding of the transcription factors signal transducer and activator of transcription 3,nuclear factor kappa B,activator protein 1,and nuclear factor erythroid 2-related factor 2,which are involved in regulation of neuronal damage.Flow cytometry analysis showed that argon downregulated the Fas ligand.Some transcription factors were regulated by toll-like receptors;therefore,their effects could be eliminated,at least in part,by the TLR2 and TLR4 inhibitor oxidized phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine(OxPAPC).Argon treatment reduced microglial activation after retinal ischemia/reperfusion injury.Subsequent quantitative polymerase chain reaction analysis revealed a reduction in the pro-inflammatory cytokines interleukin(IL-1α),IL-1β,IL-6,tumor necrosis factorα,and inducible nitric oxide synthase.Our results suggest that argon reduced the extent of inflammation in retinal neurons after ischemia/reperfusion injury by suppression of transcription factors crucial for microglial activation.Argon has no known side effects o
基金funded by the Italian Ministry of Education,University and Research(MIUR)Program“Departments of Excellence 2018-2022”,AGING and FOHN Projects,Fondazione Cariplo 2019-3277 and Associazione Ricerca sul Cancro(IG 20714,AIRC,Milano).
文摘Osteopontin is a broadly expressed pleiotropic protein,and is attracting increased attention because of its role in the pathophysiology of several inflammatory,degenerative,autoimmune,and oncologic diseases.In fact,in the last decade,several studies have shown that osteopontin contributes to tissue damage not only by recruiting harmful inflammatory cells to the site of lesion,but also increasing their survival.The detrimental role of osteopontin has been indeed well documented in the context of different neurological conditions(i.e.,multiple sclerosis,Parkinson’s,and Alzheimer’s diseases).Intriguingly,recent findings show that osteopontin is involved not only in promoting tissue damage(the Yin),but also in repair/regenerative mechanisms(the Yang),mostly triggered by the inflammatory response.These two apparently discordant roles are partly related to the presence of different functional domains in the osteopontin molecule,which are exposed after thrombin or metalloproteases cleavages.Such functional domains may in turn activate intracellular signaling pathways and mediate cell-cell and cell-matrix interactions.This review describes the current knowledge on the Yin and Yang features of osteopontin in nervous system diseases.Understanding the mechanisms behind the Yin/Yang would be relevant to develop highly specific tools targeting this multifunctional protein.