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Tauopathies exhibit a characteristic accumulation of misfolded tau aggregates in the brain. Tau pathology shows disease-specific spatiotemporal propagation through intercellular transmission, which is closely correlated with the progression of clinical manifestations. Therefore, identifying molecular mechanisms that prevent tau propagation is critical for developing therapeutic strategies for tauopathies. The various innate immune receptors, such as complement receptor 3 (CR3) and complement receptor 4 (CR4), have been reported to play a critical role in the clearance of various extracellular toxic molecules by microglia. However, their role in tau clearance has not been studied yet. In the present study, we investigated the role of CR3 and CR4 in regulating extracellular tau clearance. We found that CR4 selectively binds to tau fibrils but not to tau monomers, whereas CR3 does not bind to either of them. Inhibiting CR4, but not CR3, significantly reduces the uptake of tau fibrils by BV2 cells and primary microglia. By contrast, inhibiting CR4 has no effect on the uptake of tau monomers by BV2 cells. Furthermore, inhibiting CR4 suppresses the clearance of extracellular tau fibrils, leading to more seed-competent tau fibrils remaining in the extracellular space relative to control samples. We also provide evidence that the expression of CR4 is upregulated in the brains of human Alzheimer's disease patients and the PS19 mouse model of tauopathy. Taken together, our data strongly support that CR4 is a previously undescribed receptor for the clearance of tau fibrils in microglia and may represent a novel therapeutic target for tauopathy.
Assuntos
Microglia , Proteínas tau , Microglia/metabolismo , Microglia/patologia , Proteínas tau/metabolismo , Proteínas tau/genética , Animais , Humanos , Camundongos , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/genética , Tauopatias/metabolismo , Tauopatias/patologia , Tauopatias/genética , Antígeno de Macrófago 1/metabolismo , Antígeno de Macrófago 1/genética , Encéfalo/metabolismo , Encéfalo/patologia , MasculinoRESUMO
Parkinson's disease (PD) is the second most common neurodegenerative disease. However, no curative or modifying therapy is known. Inosine is a purine nucleoside that increases brain-derived neurotrophic factor (BDNF) expression in the brain through adenosine receptors. Herein, we investigated the neuroprotective effects of inosine and elucidated the mechanisms underlying its pharmacological action. Inosine rescued SH-SY5Y neuroblastoma cells from MPP+ injury in a dose-dependent manner. Inosine protection correlated with BDNF expression and the activation of its downstream signaling cascade, as the TrkB receptor inhibitor, K252a and siRNA against the BDNF gene remarkably reduced the protective effects of inosine. Blocking the A1 or A2A adenosine receptors diminished BDNF induction and the rescuing effect of inosine, indicating a critical role of adenosine A1 and A2A receptors in inosine-related BDNF elevation. We assessed whether the compound could protect dopaminergic neurons from MPTP-induced neuronal injury. Beam-walking and challenge beam tests revealed that inosine pretreatment for 3 weeks reduced the MPTP-induced motor function impairment. Inosine ameliorated dopaminergic neuronal loss and MPTP-mediated astrocytic and microglial activation in the substantia nigra and striatum. Inosine ameliorated the depletion of striatal dopamine and its metabolite following MPTP injection. BDNF upregulation and the activation of its downstream signaling pathway seemingly correlate with the neuroprotective effects of inosine. To our knowledge, this is the first study to demonstrate the neuroprotective effects of inosine against MPTP neurotoxicity via BDNF upregulation. These findings highlight the therapeutic potential of inosine in dopaminergic neurodegeneration in PD brains.
Assuntos
Neuroblastoma , Doenças Neurodegenerativas , Fármacos Neuroprotetores , Doença de Parkinson , Humanos , Camundongos , Animais , Dopamina/metabolismo , Fármacos Neuroprotetores/uso terapêutico , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Regulação para Cima , Doenças Neurodegenerativas/metabolismo , Doença de Parkinson/tratamento farmacológico , Neurônios Dopaminérgicos , Substância Negra , Inosina/farmacologia , Inosina/metabolismo , Inosina/uso terapêutico , Camundongos Endogâmicos C57BL , 1-Metil-4-Fenil-1,2,3,6-Tetra-Hidropiridina/metabolismoRESUMO
Amyloid generation plays essential roles in various human diseases, biological functions, and nanotechnology. However, developing efficient chemical and biological candidates for regulating amyloid fibrillation remains difficult because information on the molecular actions of modulators is insufficient. Thus, studies are needed to understand how the intermolecular physicochemical properties of the synthesised molecules and amyloid precursors influence amyloidogenesis. In this study, we synthesised a novel amphiphilic sub-nanosized material, arginine-arginine (RR)-bile acid (BA), by conjugating positively charged RR to hydrophobic BA. The effects of RR-BA on amyloid formation were investigated on α-synuclein (αSN) in Parkinson's disease and on K18 and amyloid-ß (1-42) (Aß42) in Alzheimer's disease. RR-BA showed no appreciable effect on the kinetics of K18 and Aß42 amyloid fibrillation because of their weak and non-specific interactions. However, RR-BA specifically bound to αSN with moderate binding affinity through electrostatic interactions between the positively charged RR and the negatively charged cluster in the C-terminus of αSN. In addition, hydrophobic BA in the αSN-RR-BA complex transiently condensed αSN for primary nucleation, thereby accelerating αSN amyloid fibrillation. We propose an electrostatic binding and hydrophobic condensation model of RR-BA-driven amyloid formation of αSN, which will contribute to the rational design and development of molecules for controlling amyloid aggregation in diverse fields.
Assuntos
Doença de Alzheimer , Doença de Parkinson , Humanos , alfa-Sinucleína/química , Doença de Parkinson/metabolismo , Amiloide/química , Doença de Alzheimer/metabolismo , Peptídeos beta-AmiloidesRESUMO
The neuropathological hallmark of Parkinson's disease (PD) is the preferential loss of dopaminergic neurons in the substantia nigra and presence of Lewy bodies in the dying neurons. Though specific molecular mechanisms for the neurodegeneration remains to be clarified, mitochondrial dysfunction and increased oxidative stress are major players associated with PD pathogenesis and these pathogenic mechanisms can be reproduced in cells and animals by application of various neurotoxins such as MPP+. In this study, we attempted to determine the neuroprotective effects of methylene blue (MB) against 1-methyl-4-phenylpyridinium (MPP+)-induced neurotoxicity, and to elucidate its action mechanism. We observed that MB attenuated MPP+-induced apoptotic cell death in SH-SY5Y cells and the mescencephalic dopaminergic neurons. In addition, MB protected the cells against MPP+-induced oxidative stress and mitochondrial dysfunction as evidenced by restoration of mitochondrial complex I activity and ATP levels, and attenuation of oxidative stress. Moreover, we demonstrated that MB induced antioxidant molecules, and activated Nrf2 pathway through AKT activation. These results indicate that MB protects the neurons from MPP+-induced toxicity through activation of antioxidant system, thereby reducing the oxidative stress and mitochondrial impairment, implying the potential use of MB in the treatment of neurodegenerative diseases such as PD.
Assuntos
1-Metil-4-fenilpiridínio/toxicidade , Azul de Metileno/farmacologia , Mitocôndrias/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Neuroproteção/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Antioxidantes/farmacologia , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Herbicidas/toxicidade , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/efeitos dos fármacos , Fator 2 Relacionado a NF-E2/agonistas , Neuroproteção/fisiologia , Fármacos Neuroprotetores/farmacologia , Estresse Oxidativo/fisiologiaRESUMO
Abnormal accumulation of misfolded tau aggregates is a pathological hallmark of various tauopathies including Alzheimer's disease (AD). Although tau is a cytosolic microtubule-associated protein enriched in neurons, it is also found in extracellular milieu, such as interstitial fluid, cerebrospinal fluid, and blood. Accumulating evidence showed that pathological tau spreads along anatomically connected areas in the brain through intercellular transmission and templated misfolding, thereby inducing neurodegeneration and cognitive dysfunction. In line with this, the spatiotemporal spreading of tau pathology is closely correlated with cognitive decline in AD patients. Although the secretion and uptake of tau involve multiple different pathways depending on tau species and cell types, a growing body of evidence suggested that tau is largely secreted in a vesicle-free forms. In this regard, the interaction of vesicle-free tau with membrane is gaining growing attention due to its importance for both of tau secretion and uptake as well as aggregation. Here, we review the recent literature on the mechanisms of the tau-membrane interaction and highlights the roles of lipids and proteins at the membrane in the tau-membrane interaction as well as tau aggregation.
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Transient receptor potential vanilloid subtype 1 (TRPV1) on astrocytes prevents ongoing degeneration of nigrostriatal dopamine (DA) neurons in MPP+-lesioned rats via ciliary neurotrophic factor (CNTF). The present study determined whether such a beneficial effect of astrocytic TRPV1 could be achieved after completion of injury of DA neurons, rather than ongoing injury, which seems more relevant to therapeutics. To test this, the MPP+-lesioned rat model utilized here exhibited approximately 70~80% degeneration of nigrostriatal DA neurons that was completed at 2 weeks post medial forebrain bundle injection of MPP+. TRPV1 agonist, capsaicin (CAP), was intraperitoneally administered. CNTF receptor alpha neutralizing antibody (CNTFRαNAb) was nigral injected to evaluate the role of CNTF endogenously produced by astrocyte through TRPV1 activation on DA neurons. Delayed treatment of CAP produced a significant reduction in amphetamine-induced rotational asymmetry. Accompanying this behavioral recovery, CAP treatment increased CNTF levels and tyrosine hydroxylase (TH) activity in the substantia nigra pars compacta (SNpc), and levels of DA and its metabolites in the striatum compared to controls. Interestingly, behavioral recovery and increases in biochemical indices were not reflected in trophic changes of the DA system. Instead, behavioral recovery was temporal and dependent on the continuous presence of CAP treatment. The results suggest that delayed treatment of CAP increases nigral TH enzyme activity and striatal levels of DA and its metabolites by CNTF endogenously derived from CAP-activated astrocytes through TRPV1, leading to functional recovery. Consequently, these findings may be useful in the treatment of DA imbalances associated with Parkinson's disease.
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Chronic neuroinflammation is a common feature of the aged brain, and its association with the major neurodegenerative changes involved in cognitive impairment and motor dysfunction is well established. One of the most potent antiaging interventions tested so far is dietary restriction (DR), which extends the lifespan in various organisms. Microglia and astrocytes are two major types of glial cells involved in the regulation of neuroinflammation. Accumulating evidence suggests that the age-related proinflammatory activation of astrocytes and microglia is attenuated under DR. However, the molecular mechanisms underlying DR-mediated regulation of neuroinflammation are not well understood. Here, we review the current understanding of the effects of DR on neuroinflammation and suggest an underlying mechanistic link between DR and neuroinflammation that may provide novel insights into the role of DR in aging and age-associated brain disorders.
Assuntos
Astrócitos/metabolismo , Inflamação/metabolismo , Microglia/metabolismo , Animais , Astrócitos/imunologia , Encefalopatias/imunologia , Encefalopatias/metabolismo , Restrição Calórica , Humanos , Inflamação/imunologia , Microglia/imunologiaRESUMO
We demonstrated that capsaicin (CAP), an agonist of transient receptor potential vanilloid subtype 1 (TRPV1), inhibits microglia activation and microglia-derived oxidative stress in the substantia nigra (SN) of MPPâº-lesioned rat. However, the detailed mechanisms how microglia-derived oxidative stress is regulated by CAP remain to be determined. Here we report that ciliary neurotrophic factor (CNTF) endogenously produced by CAP-activated astrocytes through TRPV1, but not microglia, inhibits microglial activation and microglia-derived oxidative stress, as assessed by OX-6 and OX-42 immunostaining and hydroethidine staining, respectively, resulting in neuroprotection. The significant increase in levels of CNTF receptor alpha (CNTFRα) expression was evident on microglia in the MPPâº-lesioned rat SN and the observed beneficial effects of CNTF was abolished by treatment with CNTF receptor neutralizing antibody. It is therefore likely that CNTF can exert its effect via CNTFRα on microglia, which rescues dopamine neurons in the SN of MPPâº-lesioned rats and ameliorates amphetamine-induced rotations. Immunohistochemical analysis revealed also a significantly increased expression of CNTFRα on microglia in the SN from human Parkinson's disease patients compared with age-matched controls, indicating that these findings may have relevance to the disease. These data suggest that CNTF originated from TRPV1 activated astrocytes may be beneficial to treat neurodegenerative disease associated with neuro-inflammation such as Parkinson's disease.
Assuntos
1-Metil-4-fenilpiridínio/toxicidade , Fator Neurotrófico Ciliar/farmacologia , Neurônios Dopaminérgicos/patologia , Microglia/patologia , Neuroproteção/efeitos dos fármacos , Síndromes Neurotóxicas/patologia , Estresse Oxidativo , Idoso , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Astrócitos/patologia , Capsaicina/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Neurônios Dopaminérgicos/efeitos dos fármacos , Neurônios Dopaminérgicos/metabolismo , Feminino , Técnicas de Silenciamento de Genes , Humanos , Masculino , Microglia/efeitos dos fármacos , Microglia/metabolismo , Modelos Biológicos , Degeneração Neural/patologia , Estresse Oxidativo/efeitos dos fármacos , RNA Interferente Pequeno/metabolismo , Ratos Sprague-Dawley , Espécies Reativas de Oxigênio/metabolismo , Receptor do Fator Neutrófico Ciliar/metabolismo , Substância Negra/efeitos dos fármacos , Substância Negra/metabolismo , Substância Negra/patologia , Canais de Cátion TRPV/metabolismoRESUMO
The present study investigated the effects of interleukin (IL)-4 on dopamine (DA) neurons in the substantia nigra (SN) in vivo of lipopolysaccharide (LPS)-treated rat. Tyrosine hydroxylase immunohistochemistry showed a significant loss of nigral DA neurons at 3 and 7 day post-LPS. In parallel, IL-4 immunoreactivity was upregulated as early as 1 day, reached a peak at 3 day and remained elevated at 7 day post-LPS. IL-4 immunoreactivity was detected exclusively in microglia. IL-4 neutralizing antibody (NA) significantly increased survival of DA neurons in LPS-treated SN in vivo by inhibiting microglial activation and production of proinflammatory mediator such as IL-1ß as assessed by immunihistochemical, RT-PCR and ELISA analysis, respectively. Accompanying neuroprotection are IL-4NA effects on decreased disruption of blood-brain barrier and astrocytes. The present data suggest that endogenously expressed IL-4 from reactive microglia may be involved in the neuropathological processes of degeneration of DA neurons occurring in Parkinson's disease.
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The present study examined the neuroprotective effects of capsaicin (CAP) and explored their underlying mechanisms in a lipopolysaccharide (LPS)-lesioned inflammatory rat model of Parkinson's dieases (PD). LPS was unilaterally injected into the substantia nigra (SN) in the absence or presence of CAP or capsazepine (CZP, a TRPV1 antagonist). The SN tissues were prepared for immunohistochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, western blot analysis, blood-brain barrier (BBB) permeability evaluation, and reactive oxygen species (ROS) detection. We found that CAP prevented the degeneration of nigral dopamine neurons in a dose-dependent manner and inhibited the expression of proinflammatory mediators in the LPS-lesioned SN. CAP shifted the proinflammatory M1 microglia/macrophage population to an anti-inflammatory M2 state as demonstrated by decreased expression of M1 markers (i.e., inducible nitric oxide synthase; iNOS and interleukin-6) and elevated expression of M2 markers (i.e., arginase 1 and CD206) in the SN. RT-PCR, western blotting, and immunohistochemical analysis demonstrated decreased iNOS expression and increased arginase 1 expression in the CAP-treated LPS-lesioned SN. Peroxynitrate production, reactive oxygen species levels and oxidative damage were reduced in the CAP-treated LPS-lesioned SN. The beneficial effects of CAP were blocked by CZP, indicating TRPV1 involvement. The present data indicate that CAP regulated the M1 and M2 activation states of microglia/macrophage in the LPS-lesioned SN, which resulted in the survival of dopamine neurons. It is therefore likely that TRPV1 activation by CAP has therapeutic potential for treating neurodegenerative diseases, that are associated with neuroinflammation and oxidative stress, such as PD.
Assuntos
Capsaicina/farmacologia , Neurônios Dopaminérgicos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Microglia/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Doença de Parkinson/metabolismo , Substância Negra/efeitos dos fármacos , Animais , Arginase/genética , Arginase/metabolismo , Diferenciação Celular , Neurônios Dopaminérgicos/metabolismo , Interleucina-6/genética , Interleucina-6/metabolismo , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Lipopolissacarídeos/toxicidade , Macrófagos/citologia , Macrófagos/metabolismo , Receptor de Manose , Lectinas de Ligação a Manose/genética , Lectinas de Ligação a Manose/metabolismo , Microglia/citologia , Microglia/metabolismo , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Estresse Oxidativo , Doença de Parkinson/etiologia , Ratos , Ratos Sprague-Dawley , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Canais de Cátion TRPV/metabolismoRESUMO
Understanding regulation of α-synuclein has long been a central focus for Parkinson's disease (PD) researchers. Accumulation of this protein in the Lewy body or neurites, mutations in the coding region of the gene and strong association of α-synuclein encoding gene multiplication (duplication/triplication) with familial form of PD have indicated the importance of this molecule in pathogenesis of the disease. Several years of research identified many potential faulty pathways associated with accumulation of α-synuclein inside dopaminergic neurons and its transmission to neighboring ones. Concurrently, an appreciable body of research is growing to understand the epigenetic and genetic deregulation of α-synuclein that might contribute to the disease pathology. Completion of the ENCODE (Encyclopedia of DNA Elements) project and recent advancement made in the epigenetic and trans factor mediated regulation of each gene, has tremendously accelerated the need to carefully understand the epigenetic structure of the gene (SNCA) encoding α-synuclein protein in order to decipher the regulation and contribution of α-synuclein to the pathogenesis of PD. We have also analyzed the detailed epigenetic structure of this gene with knowledge from ENCODE database, which may open new avenues in α-synuclein research. Interestingly, we have found that the gene contains several transcriptionally activate histone modifications and associated potential transcription factor binding sites in the non-coding areas that strongly suggest alternative regulatory pathways. Altogether this review will provide interesting insight of α-synuclein gene regulation from epigenetic, genetic and post-transcriptional perspectives and their potential implication in the PD pathogenesis.
Assuntos
Regulação da Expressão Gênica/genética , Doença de Parkinson/genética , alfa-Sinucleína/genética , Animais , Epigênese Genética/genética , Humanos , alfa-Sinucleína/biossínteseRESUMO
The effects of capsaicin (CAP), a transient receptor potential vanilloid subtype 1 (TRPV1) agonist, were determined on nigrostriatal dopamine (DA) neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD). The results showed that TRPV1 activation by CAP rescued nigrostriatal DA neurons, enhanced striatal DA functions and improved behavioral recovery in MPTP-treated mice. CAP neuroprotection was associated with reduced expression of proinflammatory cytokines (tumor necrosis factor-α and interleukin-1ß) and reactive oxygen species/reactive nitrogen species from activated microglia-derived NADPH oxidase, inducible nitric oxide synthase or reactive astrocyte-derived myeloidperoxidase. These beneficial effects of CAP were reversed by treatment with the TRPV1 antagonists capsazepine and iodo-resiniferatoxin, indicating TRPV1 involvement. This study demonstrates that TRPV1 activation by CAP protects nigrostriatal DA neurons via inhibition of glial activation-mediated oxidative stress and neuroinflammation in the MPTP mouse model of PD. These results suggest that CAP and its analogs may be beneficial therapeutic agents for the treatment of PD and other neurodegenerative disorders that are associated with neuroinflammation and glial activation-derived oxidative damage.
Assuntos
Antioxidantes/farmacologia , Capsaicina/farmacologia , Neurônios Dopaminérgicos/efeitos dos fármacos , Intoxicação por MPTP/metabolismo , Neuroglia/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Estresse Oxidativo , Animais , Antioxidantes/uso terapêutico , Capsaicina/uso terapêutico , Neurônios Dopaminérgicos/metabolismo , Intoxicação por MPTP/tratamento farmacológico , Masculino , Camundongos , Camundongos Endogâmicos C57BL , NADPH Oxidases/metabolismo , Neuroglia/metabolismo , Fármacos Neuroprotetores/uso terapêutico , Óxido Nítrico Sintase Tipo II/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Canais de Cátion TRPV/metabolismoRESUMO
Parkinson's disease (PD) is a progressive neurodegenerative disorder in which dopamine (DA) neurons in the substantia nigra pars compacta (SNpc) region are selectively destroyed. Sonic hedgehog (Shh) has been well known to play a key role in a variety of processes such as embryogenesis, cell proliferation and protection, and tissue repair during inflammation. However, the evidences for the innate role of Shh in adult brain injury are presently lacking and studies have been needed to unveil the importance of Shh in the process of neurodegeneration. Here, we investigated the role of Shh in the pathologic progress of Parkinson's disease in MPTP-induced animal model system. Interestingly, we observed that Shh expression was gradually increased in MPTP affected SNpc region. Activated microglia exclusively expressed SHH in vivo and we could recapitulate Shh induction in activated cultured primary microglia cells. Using the SHH responsive Cre-loxP binary genetic reporter transgenic mouse system, we also found that most of the cell types except for oligodendrocyte in the SNpc region reacted to the SHH by MPTP injection. Taken together, activated microglia induced Shh expression and most neural cells except oligodendrocyte responded to microglia-derived SHH in MPTP-treated SN. These results suggest that SHH in activated microglia by MPTP-injection might be involved in the innate processes of recovery from neurotoxin induced injury in the PD animal model system.
Assuntos
1-Metil-4-Fenil-1,2,3,6-Tetra-Hidropiridina , Proteínas Hedgehog/genética , Doença de Parkinson Secundária/genética , Doença de Parkinson Secundária/patologia , Substância Negra/patologia , Regulação para Cima , Animais , Células Cultivadas , Modelos Animais de Doenças , Proteínas Hedgehog/análise , Proteínas Hedgehog/imunologia , Inflamação/genética , Inflamação/imunologia , Inflamação/patologia , Lipopolissacarídeos/imunologia , Masculino , Camundongos Endogâmicos C57BL , Microglia , Doença de Parkinson Secundária/imunologia , Substância Negra/imunologia , Substância Negra/metabolismoRESUMO
Currently there is no neuroprotective or neurorestorative therapy for Parkinson's disease. Here we report that transient receptor potential vanilloid 1 (TRPV1) on astrocytes mediates endogenous production of ciliary neurotrophic factor (CNTF), which prevents the active degeneration of dopamine neurons and leads to behavioural recovery through CNTF receptor alpha (CNTFRα) on nigral dopamine neurons in both the MPP(+)-lesioned or adeno-associated virus α-synuclein rat models of Parkinson's disease. Western blot and immunohistochemical analysis of human post-mortem substantia nigra from Parkinson's disease suggests that this endogenous neuroprotective system (TRPV1 and CNTF on astrocytes, and CNTFRα on dopamine neurons) might have relevance to human Parkinson's disease. Our results suggest that activation of astrocytic TRPV1 activates endogenous neuroprotective machinery in vivo and that it is a novel therapeutic target for the treatment of Parkinson's disease.
Assuntos
Astrócitos/metabolismo , Fator Neurotrófico Ciliar/metabolismo , Neurônios Dopaminérgicos/metabolismo , Neuroproteção , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Substância Negra/metabolismo , Animais , Subunidade alfa do Receptor do Fator Neutrófico Ciliar/metabolismo , Modelos Animais de Doenças , Neurônios Dopaminérgicos/patologia , Feminino , Humanos , Regeneração Nervosa , Doença de Parkinson/fisiopatologia , Ratos , Substância Negra/citologia , Substância Negra/patologia , Canais de Cátion TRPV/metabolismoRESUMO
Abnormal autophagy may contribute to neurodegeneration in Parkinson's disease (PD). However, it is largely unknown how autophagy is dysregulated by oxidative stress (OS), one of major pathogenic causes of PD. We recently discovered the potential autophagy regulator gene family including Tnfaip8/Oxi-α, which is a mammalian target of rapamycin (mTOR) activator down-regulated by OS in dopaminergic neurons (J. Neurochem., 112, 2010, 366). Here, we demonstrate that the OS-induced Tnfaip8 l1/Oxi-ß could increase autophagy by a unique mechanism that increases the stability of tuberous sclerosis complex 2 (TSC2), a critical negative regulator of mTOR. Tnfaip8 l1/Oxi-ß and Tnfaip8/Oxi-α are the novel regulators of mTOR acting in opposition in dopaminergic (DA) neurons. Specifically, 6-hydroxydopamine (6-OHDA) treatment up-regulated Tnfaip8 l1/Oxi-ß in DA neurons, thus inducing autophagy, while knockdown of Tnfaip8 l1/Oxi-ß prevented significantly activation of autophagic markers by 6-OHDA. FBXW5 was identified as a novel binding protein for Tnfaip8 l1/Oxi-ß. FBXW5 is a TSC2 binding receptor within CUL4 E3 ligase complex, and it promotes proteasomal degradation of TSC2. Thus, Tnfaip8 l1/Oxi-ß competes with TSC2 to bind FBXW5, increasing TSC2 stability by preventing its ubiquitination. Our data show that the OS-induced Tnfaip8 l1/Oxi-ß stabilizes TSC2 protein, decreases mTOR phosphorylation, and enhances autophagy. Therefore, altered regulation of Tnfaip8 l1/Oxi-ß may contribute significantly to dysregulated autophagy observed in dopaminergic neurons under pathogenic OS condition. Dysfunctional autophagy is frequently observed in post-mortem brains of patients and animal models of Parkinson's disease. In dopaminergic neurons of the 6-hydroxydopamine (6-OHDA) model, oxidative stress induces Tnfaip8 l1/Oxi-ß, which results in increased autophagy by its exclusive binding with FBXW5 to stabilize TSC2. Thus, altered regulation of Tnfaip8 l1/Oxi-ß may contribute to dysregulated autophagy in dopaminergic neurons under pathogenic oxidative stress, implicating both Oxi-ß and FBXW5 as potential intervention targets for dysfunctional autophagy in dopaminergic neurons under oxidative stress.
Assuntos
Autofagia , Neurônios Dopaminérgicos/metabolismo , Proteínas F-Box/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Transtornos Parkinsonianos/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Animais , Western Blotting , Linhagem Celular , Modelos Animais de Doenças , Técnicas de Silenciamento de Genes , Humanos , Immunoblotting , Imuno-Histoquímica , Imunoprecipitação , Microscopia Confocal , Dados de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos , Estresse Oxidativo/fisiologia , Ligação Proteica , Ratos , Transfecção , Proteína 2 do Complexo Esclerose TuberosaRESUMO
Abnormal autophagy may contribute to neurodegeneration in Parkinson's disease (PD). However, it is largely unknown how autophagy is dysregulated by oxidative stress (OS), one of major pathogenic causes of PD. We recently discovered the potential autophagy regulator gene family including Tnfaip8/Oxi-α, which is an mTOR activator downregulated by OS in dopaminergic neurons (Choi et al., 2010). Here we demonstrate that the OS-induced Tnfaip8l1/Oxi-ß could increase autophagy by a unique mechanism that increases the stability of TSC2, a critical negative regulator of mTOR. Tnfaip8l1/Oxi-ß and Tnfaip8/Oxi-α are the novel regulators of mTOR acting in opposition in DA neurons. Specifically, 6-hydroxydopamine (6-OHDA) treatment upregulated Tnfaip8l1/Oxi-ß in DA neurons, thus inducing autophagy, while knockdown of Tnfaip8l1/Oxi-ß prevented significantly activation of autophagic markers by 6-OHDA. FBXW5 was identified as a novel binding protein for Tnfaip8l1/Oxi-ß. FBXW5 is a TSC2 binding receptor within CUL4 E3 ligase complex, and it promotes proteasomal degradation of TSC2. Thus, Tnfaip8l1/Oxi-ß competes with TSC2 to bind FBXW5, increasing TSC2 stability by preventing its ubiquitination. Our data show that the OS-induced Tnfaip8l1/Oxi-ß stabilizes TSC2 protein, decreases mTOR phosphorylation and enhances autophagy. Therefore, altered regulation of Tnfaip8l1/Oxi-ß may contribute significantly to dysregulated autophagy observed in dopaminergic neurons under pathogenic OS condition. This article is protected by copyright. All rights reserved.
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The present study examined whether matrix metalloproteinase-3 (MMP-3) participates in the loss of dopaminergic (DA) neurons in the nigrostriatal pathway in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease with blood brain barrier (BBB) damage and infiltration of peripheral immune cells. Tyrosine hydroxylase (TH) immunostaining of brain sections from MPTP-treated mice showed that MPTP induced significant degeneration of nigrostriatal DA neurons. Moreover, FITC-labeled albumin detection and immunostaining revealed that MPTP caused damage to the BBB and increased the number of ED-1- and CD-3-immunopositive cells in the substantia nigra (SN). Genetic ablation of MMP-3 reduced the nigrostriatal DA neuron loss and improved motor function. This neuroprotective effect afforded by MMP-3 deletion was associated with the suppression of BBB disruption and a decrease in the number of ED-1- and CD-3-immunopositive cells in the SN. These data suggest that MMP-3 could play a crucial role in neurodegenerative diseases such as PD in which BBB damage and neuroinflammation are implicated.
Assuntos
Barreira Hematoencefálica/patologia , Inflamação/patologia , Metaloproteinase 3 da Matriz/metabolismo , Neurônios/metabolismo , Doença de Parkinson/patologia , Substância Negra/patologia , Animais , Barreira Hematoencefálica/metabolismo , Densitometria , Modelos Animais de Doenças , Dopamina/metabolismo , Regulação da Expressão Gênica , Imuno-Histoquímica , Inflamação/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/patologia , Doença de Parkinson/metabolismo , Fagocitose , Substância Negra/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Accumulation of misfolded α-synuclein is the pathological hallmark of Parkinson's disease (PD). Nevertheless, little is known about the mechanism contributing to α-synuclein aggregation and its further toxicity to dopaminergic neurons. Since oxidative stress can increase the expression and aggregation levels of α-synuclein, NADPH oxidases (Noxs), which are responsible for reactive oxygen species generation, could be major players in α-synucleinopathy. Previously, we demonstrated that Nox1 is expressed in dopaminergic neurons of the PD animal models as well as postmortem brain tissue of PD patients, and is responsible for oxidative stress and subsequent neuronal degeneration. Here, using paraquat (PQ)-based in vitro and in vivo PD models, we show that Nox1 has a crucial role in modulating the behavior of α-synuclein expression and aggregation in dopaminergic neurons. We observed in differentiated human dopaminergic cells that Nox1 and α-synuclein expressions are increased under PQ exposure. Nox1 knockdown significantly reduced both α-synuclein expression and aggregation, supporting the role of Nox1 in this process. Furthermore, in rats exposed to PQ, the selective knockdown of Nox1 in the substantia nigra, using adeno-associated virus encoding Nox1-specific shRNA, largely attenuated the PQ-mediated increase of α-synuclein and ubiquitin expression levels as well as α-synuclein aggregates (proteinase K resistant) and A11 oligomers. Significant reductions in oxidative stress level and dopaminergic neuronal loss were also observed. Our data reveal a new mechanism by which α-synuclein becomes a neuropathologic protein through Nox1-mediated oxidative stress. This finding may be used to generate new therapeutic interventions that slower the rate of α-synuclein aggregation and the progression of PD pathogenesis.
Assuntos
NADPH Oxidases/fisiologia , Doença de Parkinson/metabolismo , alfa-Sinucleína/antagonistas & inibidores , alfa-Sinucleína/toxicidade , Animais , Linhagem Celular Transformada , Neurônios Dopaminérgicos/enzimologia , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Humanos , Masculino , NADPH Oxidase 1 , NADPH Oxidases/biossíntese , NADPH Oxidases/genética , Doença de Parkinson/enzimologia , Doença de Parkinson/patologia , Ratos , Ratos Wistar , Células-Tronco/metabolismo , Células-Tronco/patologia , alfa-Sinucleína/biossínteseRESUMO
We investigated the effects of synthetic cannabinoids, WIN55,212-2 and HU210, on LPS-injected rat substantia nigra in vivo. Intranigral injection of LPS resulted in a significant loss of nigral dopaminergic (DA) neurons, as determined by Nissl staining and TH immunohistochemistry. LPS-induced neurotoxicity was accompanied by microglial activation, as demonstrated by OX-42 immunohistochemistry. In parallel, Western blot analysis, ELISA assay and hydroethidine histochemistry revealed activation of NADPH oxidase, as demonstrated by increased translocation of the cytosolic proteins p47(phox) and p67(phox), generation of reactive oxygen species (ROS) and increased level of proinflammatory cytokines (TNF-α and IL-1ß), where degeneration of nigral DA neurons was evident. Interestingly, WIN55,212-2 and HU210 increased the survival of nigral DA neurons at 7days post-LPS treatment. Consistent with these results, cannabinoids inhibited activation of NADPH oxidase, ROS production and production of proinflammatory cytokines in the rat SN. The present data suggest that cannabinoids may be beneficial for the treatment of neurodegenerative diseases, such as PD, that are associated with microglial activation.
Assuntos
Antioxidantes/farmacologia , Canabinoides/farmacologia , Microglia/efeitos dos fármacos , NADPH Oxidases/antagonistas & inibidores , Degeneração Neural/prevenção & controle , Substância Negra/efeitos dos fármacos , Animais , Benzoxazinas/farmacologia , Dronabinol/análogos & derivados , Dronabinol/farmacologia , Lipopolissacarídeos/toxicidade , Microglia/metabolismo , Microglia/patologia , Morfolinas/farmacologia , Naftalenos/farmacologia , Degeneração Neural/induzido quimicamente , Degeneração Neural/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Estresse Oxidativo/efeitos dos fármacos , Ratos , Espécies Reativas de Oxigênio/metabolismo , Substância Negra/metabolismo , Substância Negra/patologiaRESUMO
This study examined whether the cannabinoid receptor type 1 (CB(1)) receptor contributes to the survival of nigrostriatal dopaminergic (DA) neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease. MPTP induced significant loss of nigrostriatal DA neurons and microglial activation in the substantia nigra (SN), visualized with tyrosine hydroxylase or macrophage Ag complex-1 immunohistochemistry. Real-time PCR, ELISA, Western blotting, and immunohistochemistry disclosed upregulation of proinflammatory cytokines, activation of microglial NADPH oxidase, and subsequent reactive oxygen species production and oxidative damage of DNA and proteins in MPTP-treated SN, resulting in degeneration of DA neurons. Conversely, treatment with nonselective cannabinoid receptor agonists (WIN55,212-2 and HU210) led to increased survival of DA neurons in the SN, their fibers and dopamine levels in the striatum, and improved motor function. This neuroprotection by cannabinoids was accompanied by suppression of NADPH oxidase reactive oxygen species production and reduced expression of proinflammatory cytokines from activated microglia. Interestingly, cannabinoids protected DA neurons against 1-methyl-4-phenyl-pyridinium neurotoxicity in cocultures of mesencephalic neurons and microglia, but not in neuron-enriched mesencephalic cultures devoid of microglia. The observed neuroprotection and inhibition of microglial activation were reversed upon treatment with CB(1) receptor selective antagonists AM251 and/or SR14,716A, confirming the involvement of the CB(1) receptor. The present in vivo and in vitro findings clearly indicate that the CB(1) receptor possesses anti-inflammatory properties and inhibits microglia-mediated oxidative stress. Our results collectively suggest that the cannabinoid system is beneficial for the treatment of Parkinson's disease and other disorders associated with neuroinflammation and microglia-derived oxidative damage.