NLRP3 inflammasome and glia maturation factor coordinately regulate neuroinflammation and neuronal loss in MPTP mouse model of Parkinson’s disease

Neuroinflammation plays an active role in the pathogenesis of several neurodegenerative diseases, including Parkinson’s disease (PD). Earlier studies from this laboratory showed that glia maturation factor (GMF), a proinflammatory mediator; is up-regulated in the brain in neurodegenerative diseases and that deficiency of GMF showed decreased production of IL-1β and improved behavioral abnormalities in mouse model of PD. However, the mechanisms linking GMF and dopaminergic neuronal death have not been completely explored. In the present study, we have investigated the expression of NLRP3 inflammasome and caspase-1 in the substantia nigra (SN) of human PD and non-PD brains by immunohistochemistry. Wild-type (WT) and GMF^−/− (GMF knock-out) mice were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydro pyridine (MPTP) and the brains were isolated for neurochemical and morphological examinations. NLRP3 and caspase-1 positive cells were found significantly increased in PD when compared to non-PD control brains. Moreover, GMF co-localized with α-Synuclein within reactive astrocytes in the midbrain of PD. Mice treated with MPTP exhibit glial activation-induced inflammation, and nigrostriatal dopaminergic neurodegeneration. Interestingly, increased expression of the inflammasome components in astrocytes and microglia observed in the SN of MPTP-treated WT mice were significantly reduced in GMF^−/− mice. Additionally, we show that NLRP3 activation in microglia leads to translocation of GMF and NLRP3 to the mitochondria. We conclude that downregulation of GMF may have beneficial effects in prevention of PD by modulating the cytotoxic functions of microglia and astrocytes through reduced activation of the NLRP3 inflammasome; a major contributor of neuroinflammation in the CNS.     

Neuroprotective effect of gold nanoparticles composites in Parkinson's disease model

Parkinson’s disease (PD) is second most common neurodegenerative disorder worldwide. Although drugs and surgery can relieve the symptoms of PD, these therapies are incapable of fundamentally treating the disease. For PD patients, over-expression of α-synuclein (SNCA) leads to the death of dopaminergic neurons. This process can be prevented by suppressing SNCA over-expression through RNA interference. Here, we successfully synthesized gold nanoparticles (GNP) composites (CTS@GNP-pDNA-NGF) via the combination of electrostatic adsorption and photochemical immobilization, which could load plasmid DNA (pDNA) and target specific cell types. GNP was transfected into cells via endocytosis to inhibiting the apoptosis of PC12 cells and dopaminergic neurons. Simultaneously, GNP composites are also used in PD models in vivo, and it can successfully cross the blood-brain barrier by contents of GNP in the mice brain. In general, all the works demonstrated that GNP composites have good therapeutic effects for PD models in vitro and in vivo.     

皮下注射MPTP诱导猕猴双侧慢性帕金森病模型的制作

目的探讨猕猴双侧慢性不可逆性帕金森病（PD）模型的制作方法。方法 4只猕猴分别采用不同剂量（0.1 mg/kg/d和0.4 mg/kg/d）和不同频率（每天一次和隔天一次）及不同次数皮下注射1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）制作PD模型,注射MPTP前后观察行为学表现并进行非人类灵长类PD评分量表（PPRS）评分。结果猕猴注射MPTP一段时间后开始出现PD症状,主要表现为倦怠、迟缓;继续给药PD症状会出现进行性快速加重导致后续动物因进食困难而死亡;若过早停止给药,则导致PD模型不稳定,动物症状可自愈。采用剂量为0.1 mg/kg/d的MPTP连续皮下注射14 d后,猕猴出现中度PD症状（PPRS评分为6~8分）时,改隔日注射一次,共4次,猕猴出现不可逆性PD症状,且可自主摄食并长期存活,是一个成功的模型。结论适量皮下注射MPTP可制作猕猴慢性、不可逆性、双侧PD模型,其更接近人PD的临床特征,且无需鼻饲喂养可长期存活。     

AQW051, a novel and selective nicotinic acetylcholine receptor α7 partial agonist,reduces l-Dopa-induced dyskinesias and extends the duration of l-Dopa effects in parkinsonian monkeys

Nicotinic acetylcholine receptor (nAChR)-mediated signaling has been implicated in levodopa (l-Dopa)-induced dyskinesias (LID). This study investigated the novel selective α7 nAChR partial agonist (R)-3-(6-ρ-Tolyl-pyridin-3-yloxy)-1-aza-bicyclo(2.2.2)octane (AQW051) for its antidyskinetic activity in l-Dopa-treated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned cynomolgus monkeys. Six MPTP monkeys were repeatedly treated with l-Dopa to develop reproducible dyskinesias. AQW051 (2, 8, and 15 mg/kg) administered 1 h before l-Dopa treatment did not affect their parkinsonian scores or locomotor activity, but did significantly extend the duration of the l-Dopa antiparkinsonian response, by 30 min at the highest AQW051 dose (15 mg/kg). Dyskinesias were significantly reduced for the total period of l-Dopa effect following treatment with 15 mg/kg; achieving a reduction of 60% in median values. Significant reductions in 1 h peak dyskinesia scores and maximal dyskinesias were also observed with AQW051 (15 mg/kg). To understand the exposure–effect relationship and guide dose selection in clinical trials, plasma concentration-time data for the 15 mg/kg AQW051 dose were collected from three of the MPTP monkeys in a separate pharmacokinetic experiment. No abnormal behavioral or physiological effects were reported following AQW051 treatment. Our results show that AQW051 at a high dose can reduce LID without compromising the benefits of l-Dopa and extend the duration of the l-Dopa antiparkinsonian response in MPTP monkeys. This supports the clinical testing of α7 nAChR agonists to modulate LID and extend the duration of the therapeutic effect of l-Dopa.     

健行颗粒对3种拟帕金森病震颤模型小鼠的干预作用

目的建立肌肉震颤及线粒体功能障碍致3种拟帕金森病震颤小鼠模型,并在此3种模型上观察健行颗粒的药效学作用,探讨其可能的作用机理.方法经氧化震颤素和槟榔碱单次腹腔注射建立小鼠肌肉震颤模型;经MPTP 20mg/kg连续8天腹腔注射建立线粒体损伤致震颤小鼠模型.记录震颤素和槟榔碱模型小鼠震颤持续时间;观察MPTP模型小鼠爬杆行为及自主活动次数的改变,经高效液相色谱测定MPTP模型小鼠纹状体内多巴胺及其代谢产物含量的改变.结果模型组小鼠在给予震颤素或槟榔碱腹腔注射后出现明显震颤,健行颗粒用药组小鼠震颤持续时间较模型组明显缩短;对于MPTP小鼠模型,模型组小鼠爬杆时间延长,运动协调性降低,纹状体内多巴胺含量明显降低,健行颗粒用药组小鼠爬杆时间较模型组明显缩短,自主活动数增加,纹状体内多巴胺含量增高.结论槟榔碱及氧化震颤素均能制备良好的肌肉震颤小鼠模型,健行颗粒能明显减少模型动物肌肉震颤持续时间;对于MPTP腹腔注射拟帕金森小鼠模型,健行颗粒能明显缩短其爬杆时间,增强小鼠自主活动能力,提升小鼠脑纹状体内多巴胺及其代谢产物的含量.     

Past, present and future of A(2A) adenosine receptor antagonists in the therapy of Parkinson's disease

Several selective antagonists for adenosine A_2A receptors (A_2AR) are currently under evaluation in clinical trials (phases I to III) to treat Parkinson's disease, and they will probably soon reach the market. The usefulness of these antagonists has been deduced from studies demonstrating functional interactions between dopamine D₂ and adenosine A_2A receptors in the basal ganglia. At present it is believed that A_2AR antagonists can be used in combination with the dopamine precursor L-DOPA to minimize the motor symptoms of Parkinson's patients. However, a considerable body of data indicates that in addition to ameliorating motor symptoms, adenosine A_2AR antagonists may also prevent neurodegeneration. Despite these promising indications, one further issue must be considered in order to develop fully optimized antiparkinsonian drug therapy, namely the existence of (hetero)dimers/oligomers of G protein-coupled receptors, a topic that is currently the focus of intense debate within the scientific community. Dopamine D₂ receptors (D₂Rs) expressed in the striatum are known to form heteromers with A_2A adenosine receptors. Thus, the development of heteromer-specific A_2A receptor antagonists represents a promising strategy for the identification of more selective and safer drugs.     

老龄帕金森病模型小鼠氧化应激相关基因的表达差异

目的：探讨老龄帕金森病( PD)模型小鼠行为学改变及黑质纹状体系统氧化应激相关基因的表达差异。方法10月龄快速老化P8系( SAMP8)小鼠16只,随机均分为对照组和模型组。模型组小鼠背部皮下注射1-甲基-4-苯基-1,2,3,6-四氢吡啶( MPTP)制成急性损伤模型,对照组小鼠给予同量生理盐水。给药后72 h进行行为学测试,高效液相色谱法检测黑质多巴胺( DA)含量,PCR Array检测其纹状体氧化应激相关基因的表达。结果与对照组相比,模型组小鼠DA水平下降,行为学成绩下降,差异有统计学意义( P<0．01);环氧化酶-2、可诱导型一氧化氮合酶2、还原型烟酰胺腺嘌呤二核苷酸磷酸( NADPH)氧化酶基因表达上调;而谷胱甘肽过氧化物酶3、6、8等9种基因明显下调(改变倍数>2)。结论老龄PD模型小鼠氧化应激相关的基因发生上调或下调,导致氧化应激反应的发生。     

Silibinin prevents dopaminergic neuronal loss in a mouse model of Parkinson's disease via mitochondrial stabilization

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the selective loss of dopaminergic neurons in the nigrostriatal pathway. The lipophile 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) can cross the blood–brain barrier and is subsequently metabolized into toxic1‐methyl‐4‐phenylpyridine (MPP⁺), which causes mitochondrial dysfunction and the selective cell death of dopaminergic neurons. The present article reports the neuroprotective effects of silibinin in a murine MPTP model of PD. The flavonoid silibinin is the major active constituent of silymarin, an extract of milk thistle seeds, and is known to have hepatoprotective, anticancer, antioxidative, and neuroprotective effects. In the present study, silibinin effectively attenuated motor deficit and dopaminergic neuronal loss caused by MPTP. Furthermore, in vitro study confirmed that silibinin protects primary cultured neurons against MPP⁺‐induced cell death and mitochondrial membrane disruption. The findings of the present study indicate that silibinin has neuroprotective effects in MPTP‐induced models of PD rather than antioxidative or anti‐inflammatory effects and that the neuroprotection afforded might be mediated by the stabilization of mitochondrial membrane potential. Furthermore, these findings suggest that silibinin protects mitochondria in MPTP‐induced PD models and that it offers a starting point for the development of treatments that ameliorate the symptoms of PD. © 2015 Wiley Periodicals, Inc.     

Zingerone activates VMAT2 during MPP+‐induced Cell Death

Parkinson's disease (PD) is characterized by a progressive and selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and striatum. 1‐Methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) is used to produce an animal model for PD, and it is converted to 1‐methyl‐4‐phenylpyridine (MPP⁺) in animals. MPP⁺ accumulation leads to neuronal cell death. Vesicular monoamine transporter 2 (VMAT2) regulates the accumulation of monoamine neurotransmitters into synaptic vesicles and is involved in neuroprotection against neurotoxin‐induced cell death. Recently, zingerone has been reported to reduce oxidative stress and inhibit inflammation. Therefore, we examined the effect of zingerone on neuronal cell death in a PD model. In an MPP⁺ and MPTP‐mediated PD model, neuronal cell survival was increased by zingerone without modifying neuroinflammation or reactive oxygen species generation. Zingerone also induced ERK activation and VMAT2 expression, leading to the attenuation of MPP⁺‐induced neuronal cell death. Our current results suggest that zingerone has a neuroprotective effect in a PD model. Copyright © 2015 John Wiley & Sons, Ltd.     

Exercise modifies α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor expression in striatopallidal neurons in the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐lesioned mouse

The α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic‐acid‐type glutamate receptor (AMPAR) plays a critical role in modulating experience‐dependent neuroplasticity, and alterations in AMPAR expression may underlie synaptic dysfunction and disease pathophysiology. Using the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) mouse model of dopamine (DA) depletion, our previous work showed exercise increases total GluA2 subunit expression and the contribution of GluA2‐containing channels in MPTP mice. The purpose of this study was to determine whether exercise‐dependent changes in AMPAR expression after MPTP are specific to the striatopallidal (D₂R) or striatonigral (D₁R) medium spiny neuron (MSN) striatal projection pathways. Drd₂‐eGFP‐BAC transgenic mice were used to delineate differences in AMPAR expression between striatal D₂R‐MSNs and D₁R‐MSNs. Striatal AMPAR expression was assessed by immunohistochemical (IHC) staining, Western immunoblotting (WB) of preparations enriched for postsynaptic density (PSD), and alterations in the current–voltage relationship of MSNs. We found DA depletion results in the emergence of GluA2‐lacking AMPARs selectively in striatopallidal D₂R‐MSNs and that exercise reverses this effect in MPTP mice. Exercise‐induced changes in AMPAR channels observed after DA depletion were associated with alterations in GluA1 and GluA2 subunit expression in postsynaptic protein, D₂R‐MSN cell surface expression, and restoration of corticostriatal plasticity. Mechanisms regulating experience‐dependent changes in AMPAR expression may provide innovative therapeutic targets to increase the efficacy of treatments for basal ganglia disorders, including Parkinson's disease. © 2013 Wiley Periodicals, Inc.