Tetramethylpyrazine analogue T-006 promotes clearance of alpha-synuclein by enhancing proteasome activity in Parkinson disease models

OBJECTIVE To investigate the effects of T-006(tetramethylpyrazine derivative)in promotingα-Synuclein(α-Syn)degradation and evaluated the neuroprotective effects in cellular and animalα-Syn model of Parkinson disease(PD).METHODS The inducible PC12 cells overexpressingα-syn and the homozygous transgenic(Tg)mice expressing A53T humanα-syn were used to evaluate the neuroprotective effects of T-006.For cellular study,MTT,Western blotting,proteasomal activity assay and qRT-PCR were applied to analyze the pharmacological effects and underlying mecha⁃nisms.The gene knock-down and overexpression approaches were used to dissect the molecular signaling pathways.For animal study,ten-month-old homozygousα-Syn Tg mice were treated with T-006(3 mg·kg-1)daily by gavage for four weeks.The Western blotting,immunohistochemistry and behavioral tests were applied to determine the neuropatho⁃logical changes.RESULTS T-006 promoted the degradation of WT and mutantα-Syn in PC12α-Syn inducible cells via an ubiquitin-proteasome system(UPS)dependent and autophagy-lysosome pathway independent manner.The mecha⁃nism of action involved the upregulation of 20S proteasome subunit LMP7 expression,which leads to activation of the chymotrypsin-like proteasomal activity for protein degradation.Mechanistically,we demonstrated that T-006 activated PKA/Akt/mTOR pathway upstream for LMP 7 up-regulation and UPS activation.Finally,we illustrated that T-006 promoted both Triton-soluble and-insoluble forms ofα-syn and protected againstα-Syn-induced neurotoxicity in A53Tα-Syn Tg mice.CONCLUSION T-006 is a potent UPS activator which promotes the degradation of pathogenic proteinα-Syn in cellular and animal PD models.Our study thus high-lights the therapeutic potential of small molecular UPS activator like T-006 in the treatment of PD and related conditions.

Association Analysis of Proteasome Subunits and Transporter Associated with Antigen Processing on Chinese Patients with Parkinson＇s Disease

Background： Proteasome subunits （PSMB） and transporter associated with antigen processing （TAP） loci are located in the human leukocyte antigen （HLA） Class I1 region play important roles in immune response and protein degradation in neurodegenerative diseases. This study aimed to explore the association between single nucleotide polymorphisms （SNPs） of PSMB and TAP and Parkinson＇s disease （PD）. Methods： A case-control study was conducted by genotyping SNPs in PSMB8, PSMBg, TAP1, and TAP2 genes in the Chinese population. Subjects included 542 sporadic patients with PD and 674 healthy controls. Nine identified SNPs in PSMB8, PSMBg, TAP1, and TAP2 were genotyped through SNaPshot testing. Results： The stratified analysis ofrs 17587 was specially performed on gender. Data revealed that female patients carry a higher frequency of rsl7587-G/G versus （A/A ＋ G/A） compared with controls. But there was no significant difference with respect to the genotypic frequencies of the SNPs in PSMB8, TAP1, and TAP2 loci in PD patients. Conclusion： Chinese females carrying the rs 17587-G/G genotype in PSMB9 may increase a higher risk for PD, but no linkage was found between other SNPs in HLA Class II region and PD.

The autophagy-lysosome pathway:a potential target in the chemical and gene therapeutic strategies for Parkinson’s disease

Parkinson’s disease is a common neurodegenerative disease with movement disorders associated with the intracytoplasmic deposition of aggregate proteins such asα-synuclein in neurons.As one of the major intracellular degradation pathways,the autophagy-lysosome pathway plays an important role in eliminating these proteins.Accumulating evidence has shown that upregulation of the autophagy-lysosome pathway may contribute to the clearance ofα-synuclein aggregates and protect against degeneration of dopaminergic neurons in Parkinson’s disease.Moreover,multiple genes associated with the pathogenesis of Parkinson’s disease are intimately linked to alterations in the autophagy-lysosome pathway.Thus,this pathway appears to be a promising therapeutic target for treatment of Parkinson’s disease.In this review,we briefly introduce the machinery of autophagy.Then,we provide a description of the effects of Parkinson’s disease–related genes on the autophagy-lysosome pathway.Finally,we highlight the potential chemical and genetic therapeutic strategies targeting the autophagy–lysosome pathway and their applications in Parkinson’s disease.

The role of quercetin on the survival of neuron-like PC12 cells and the expression of α-synuclein

Both genetic and environmental factors are important in the pathogenesis of Parkinson＇s disease. As α-synuclein is a major constituent of Lewy bodies, a pathologic hallmark of Parkinson＇s disease, genetic aspects of α-synuclein is widely studied. However, the influence of dietary factors such as quercetin on α-synuclein was rarely studied. Herein we aimed to study the neuroprotective role of quercetin against various toxins affecting apoptosis, autophagy and aggresome, and the role of quercetin on α-synuclein expression. PC12 cells were pre-treated with quercetin（100, 500, 1,000 μM） and then together with various drugs such as 1-methyl-4-phenylpyridinium（MPP＋; a free radical generator）, 6-hydroxydopamine（6-OHDA; a free radical generator）, ammonium chloride（an autophagy inhibitor）, and nocodazole（an aggresome inhibitor）. Cell viability was determined using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltertazolium bromide（MTT） assay. Apoptosis was detected by annexin V-fluorescein isothiocyanate and propidium iodide through the use of fluorescence activated cell sorter. α-Synuclein expression was detected by western blot assay and immunohistochemistry. The role of α-synuclein was further studied by knocking out α-synuclein using RNA interference. Cell viability increased at lower concentrations（100 and 500 μM） of quercetin but decreased at higher concentration（1,000 μM）. Quercetin exerted neuroprotective effect against MPP＋, ammonium chloride and nocodazole at 100 μM. MPP＋ induced apoptosis was decreased by 100 μM quercetin. Quercetin treatment increased α-synuclein expression. However, knocking out α-synuclein exerted no significant effect on cell survival. In conclusion, quercetin is neuroprotective against toxic agents via affecting various mechanisms such as apoptosis, autophagy and aggresome. Because α-synuclein expression is increased by quercetin, the role of quercetin as an environmental factor in Parkinson＇s disease pathogenesis needs further investigation.

Triphenyltin inhibition of the proteasome activity and its influence on substrate protein levels in nerve cells

Triphenyltin (TPT) widely exists as environmental pollutant, but its toxicity towards nerve cells and the related mechanism remain unclear. In this research, SHSY-5Y cells were exposed to TPT, and the cellular proteasome activity, Iκb proteins, Bax and α-synuclein levels were investigated. The results show that TPT can inhibit the cellular proteasome activity, and result in the accumulation of ubiquitinized proteins. TPT exposure can change the protein levels of IκB, Bax, and α-synuclein, affect NFκB pathway, activate the process of cell death, and induce α-synuclein aggregation. Our results indicate that TPT exposure can lead to neuotoxicity.

Rotenone induces more serious learning and memory impairment than α-synuclein A30P does in Drosophila

Parkinson’s disease （PD） is a heterogenous disease caused by multifactorial etiology. PD is characterized by the loss of dopaminergic （DA） neurons in the substantia nigra and the accumulation of Lewy bodies. In this study, two Drosophila PD models by exposing Drosophila to rotenone （sporadic PD models） are proposed, and the human α-synuclein A30P protein （family PD models） in Drosophila is expressed respectively. Both models recapitulated the main human PD symptoms including the loss of dopaminergic neurons in the brain and severe locomotor deficits. Our study finds that Rotenone induces more serious learning and memory impairment than α-synuclein A30P does.

Effect of Alteration of Glutathione Content on Cell Viability in α-Synuclein-Transfected SH-SY5Y Cells

It is well known that α-synuclein (αS) plays an important role in the pathogenesis of Parkinson’s disease (PD). Moreover, oxidative stress is also thought to be an important factor in PD due to induction of dopaminergic neuronal cell death by free radicals and enhancement of αS fibrillation by oxidized stress. In the present study, to clarify the role of glutathione (GSH), an intracellular antioxidant, on the molecular mechanism of αS-induced cell injury, we examined the effects of L-buthionine-SR-sulfoximine (BSO), a GSH synthase inhibitor, with or without N-acetyl-L-cysteine (NAC), a source of GSH, on αS-induced cell injury in human neuroblastoma SH-SY5Y cells. Treatment with BSO significantly reduced the cell viability of both empty-vector- and αS-transfected SH-SY5Y cells in a dose-dependent manner (p < 0.01), although the ratio of αS-induced reduction of cell viability in α-syn-transfected cells was much greater than that in empty-vector-transfected cells. Moreover, BSO significantly reduced the intracellular total GSH level in both types of transformant cells. However, NAC significantly prevented BSO-induced reduction of both cell viability and GSH level in the αS-transfected cells. These findings suggest that GSH plays an important role in αS-induced cell injury by reducing cell viability.

Blocking meningeal lymphatic drainage aggravates Parkinson’s disease-like pathology in mice overexpressing mutated α-synuclein

Background:Abnormal aggregation of brainα-synuclein is a central step in the pathogenesis of Parkinson’s disease(PD),thus,it is reliable to promote the clearance ofα-synuclein to prevent and treat PD.Recent studies have revealed an essential role of glymphatic system and meningeal lymphatic vessels in the clearance of brain macromolecules,however,their pathophysiological aspects remain elusive.Method:Meningeal lymphatic drainage of 18-week-old A53T mice was blocked via ligating the deep cervical lymph nodes.Six weeks later,glymphatic functions and PD-like phenotypes were systemically analyzed.Results:Glymphatic influx of cerebrospinal fluid tracer was reduced in A53T mice,accompanied with perivascular aggregation ofα-synuclein and impaired polarization of aquaporin 4 expression in substantia nigra.Cervical lymphatic ligation aggravated glymphatic dysfunction of A53T mice,causing more severe accumulation ofα-synuclein,glial activation,inflammation,dopaminergic neuronal loss and motor deficits.Conclusion:The results suggest that brain lymphatic clearance dysfunction may be an aggravating factor in PD pathology.

Efficient RT-QuIC seeding activity for α-synuclein in olfactory mucosa samples of patients with Parkinson’s disease and multiple system atrophy

Background:Parkinson’s disease(PD)is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms.PD is characterized by intraneuronal accumulation of abnormalα-synuclein in brainstem while neurodegenerative parkinsonisms might be associated with accumulation of eitherα-synuclein,as in the case of Multiple System Atrophy(MSA)or tau,as in the case of Corticobasal Degeneration(CBD)and Progressive Supranuclear Palsy(PSP),in other disease-specific brain regions.Definite diagnosis of all these diseases can be formulated only neuropathologically by detection and localization ofα-synuclein or tau aggregates in the brain.Compelling evidence suggests that trace-amount of these proteins can appear in peripheral tissues,including receptor neurons of the olfactory mucosa(OM).Methods:We have set and standardized the experimental conditions to extend the ultrasensitive Real Time Quaking Induced Conversion(RT-QuIC)assay for OM analysis.In particular,by using human recombinantα-synuclein as substrate of reaction,we have assessed the ability of OM collected from patients with clinical diagnoses of PD and MSA to induceα-synuclein aggregation,and compared their seeding ability to that of OM samples collected from patients with clinical diagnoses of CBD and PSP.Results:Our results showed that a significant percentage of MSA and PD samples inducedα-synuclein aggregation with high efficiency,but also few samples of patients with the clinical diagnosis of CBD and PSP caused the same effect.Notably,the final RT-QuIC aggregates obtained from MSA and PD samples owned peculiar biochemical and morphological features potentially enabling their discrimination.Conclusions:Our study provide the proof-of-concept that olfactory mucosa samples collected from patients with PD and MSA possess important seeding activities forα-synuclein.Additional studies are required for(i)estimating sensitivity and specificity of the technique and for(ii)evaluating its application for the diagnosis of PD and neurodegenerative parkinsonisms.RT-QuIC analyses of OM and cerebrospinal fluid(CSF)can be combined with the aim of increasing the overall diagnostic accuracy of these diseases,especially in the early stages.

Erythrocytic α-Synuclein as a potential biomarker for Parkinson’s disease

Background:Erythrocytes are a major source of peripheralα-synuclein(α-Syn).The goal of the current investigation is to evaluate erythrocytic total,oligomeric/aggregated,and phosphorylatedα-Syn species as biomarkers of Parkinson’s disease(PD).PD and healthy control blood samples were collected along with extensive clinical history to determine whether total,phosphorylated,or aggregatedα-Syn derived from erythrocytes(the major source of bloodα-Syn)are more promising and consistent biomarkers for PD than are freeα-Syn species in serum or plasma.Methods:Using newly developed electrochemiluminescence assays,concentrations of erythrocytic total,aggregated and phosphorylated at Ser129(pS129)α-Syn,separated into membrane and cytosolic components,were measured in 225 PD patients and 133 healthy controls and analyzed with extensive clinical measures.Results:The total and aggregatedα-Syn levels were significantly higher in the membrane fraction of PD patients compared to healthy controls,but without alterations in the cytosolic component.The pS129 level was remarkably higher in PD subjects than in controls in the cytosolic fraction,and to a lesser extent,higher in the membrane fraction.Combining age,erythrocytic membrane aggregatedα-Syn,and cytosolic pS129 levels,a model generated by using logistic regression analysis was able to discriminate patients with PD from neurologically normal controls,with a sensitivity and a specificity of 72 and 68%,respectively.Conclusions:These results suggest that total,aggregated and phosphorylatedα-Syn levels are altered in PD erythrocytes and peripheral erythrocyticα-Syn is a potential PD biomarker that needs further validation.

Alpha-synuclein and Parkinson disease

OBJECTIVE： To review the recent progresses on the studies of α -synuclein in the pathogenesis of Parkinson disease （PD） and look into the perspective of α -synuclein as a new therapy target. DATA SOURCES： To search the literatures on the progresses of PD studies, especially on the structure, gene expression of α-synuclein and the pathogenesis of PD in Medline from January 1998 to February 2007. Search terms were ＂Parkinson＇s disease, α-synuclein＂ in English. STUDY SELECTION： Initial check the data and choose the original and review articles directly linked to the role of α-synuclein in PD pathogenesis and screening out indirectly discussing articles. Collect the full text and trace the quoting articles and the quoted articles. Only the latest reviews were chosen in Chinese articles. DATA EXTRACTION： There were 424 articles on α-synuclein and its role in the pathogenesis of PD and 43 articles directly related with α-synuclein were chosen among which 12 were reviews. DATA SYNTHESIS： α-synuclein is a kind of soluble protein expressed in pre-synapse in central nervous system encoded by gene in homologous chromosome 4q21. It has physiological function in modulating the stability of membrane and neural plasticity. There is a close relationship between gene mutation in α -synuclein and the pathogenesis of PD. Environmental and genetic factors can induce the misfolding of α-synuclein, and secondary structural change can result in oligomer formation which induces a series of cascade reaction to damage dopaminergic system subsequently. Cell and animal transgenic and non-transgenic models are established recently and the important role of α-synuclein in the pathogenesis both of familial and sporadic PD is confirmed. Studies reveal that inhibiting the aggregation of α-synuclein can prevent its neurotoxicity; gene parkin can intercept the cell death pathway triggered by the aggregation of α-synuclein in cytoplasm. CONCLUSION： Gene mutation ofα-synuclein and the impairment in its structure and function are important in the pathogenesis of PD. Intervention of the gene mutations and abnormal protein aggregation ofα-synuclein may be a new strategy for preventing and treating PD.

Dysfunction of two lysosome degradation pathways of α-synuclein in Parkinson's disease: potential therapeutic targets?

Parkinson＇s disease （PD） is pathologically characterized by the presence of α-synuclein （α-syn）-positive intra-cytoplasmic inclusions named Lewy bodies in the dopaminergic neurons of the substantia nigra. A series of morbid consequences are caused by pathologically high amounts or mutant forms of α-syn, such as defects of membrane trafficking and lipid metabolism. In this review, we consider evidence that both point mutation and overexpression of α-syn result in aberrant degradation in neurons and microglia, and this is associated with the autophagy-lysosome pathway and endosome-lysosome system, leading directly to pathological intracellular aggregation, abnormal externalization and re-internalization cycling （and, in turn, internalization and re-externalization）, and exocytosis. Based on these pathological changes, an increasing number of researchers have focused on these new therapeutic targets, aiming at alleviating the pathological accumulation of α-syn and re-establishing normal degradation.

Intestine-derived α-synuclein initiates and aggravates pathogenesis of Parkinson’s disease in Drosophila

Background:Aberrant aggregation ofα-synuclein(α-syn)is a key pathological feature of Parkinson’s disease(PD),but the precise role of intestinalα-syn in the progression of PD is unclear.In a number of genetic Drosophila models of PD,α-syn was frequently ectopically expressed in the neural system to investigate the pathobiology.Method:We investigated the potential role of intestinalα-syn in PD pathogenesis using a Drosophila model.Humanα-syn was overexpressed in Drosophila guts,and life span,survival,immunofluorescence and climbing were evalu-ated.Immunofluorescence,Western blotting and reactive oxygen species(ROS)staining were performed to assess the effects of intestinalα-syn on intestinal dysplasia.High‐throughput RNA and 16S rRNA gene sequencing,quantitative RT‐PCR,immunofluorescence,and ROS staining were performed to determine the underlying molecular mechanism.Results:We found that the intestinalα-syn alone recapitulated many phenotypic and pathological features of PD,including impaired life span,loss of dopaminergic neurons,and progressive motor defects.The intestine-derivedα-syn disrupted intestinal homeostasis and accelerated the onset of intestinal ageing.Moreover,intestinal expression ofα-syn induced dysbiosis,while microbiome depletion was efficient to restore intestinal homeostasis and ameliorate the progression of PD.Intestinalα-syn triggered ROS,and eventually led to the activation of the dual oxidase(DUOX)-ROS-Jun N-terminal Kinase(JNK)pathway.In addition,α-syn from both the gut and the brain synergized to accelerate the progression of PD.Conclusions:The intestinal expression ofα-syn recapitulates many phenotypic and pathologic features of PD,and induces dysbiosis that aggravates the pathology through the DUOX-ROS-JNK pathway in Drosophila.Our findings provide new insights into the role of intestinalα-syn in PD pathophysiology.

α-Synuclein pathology from the body to the brain:so many seeds so close to the central soil

α-Synuclein is a protein that mainly exists in the presynaptic terminals.Abnormal folding and accumulation of α-synuclein are found in several neurodegenerative diseases,including Parkinson’s disease.Aggregated and highly phospho rylated a-synuclein constitutes the main component of Lewy bodies in the brain,the pathological hallmark of Parkinson s disease.For decades,much attention has been focused on the accumulation of α-synuclein in the brain parenchyma rather than considering Parkinson s disease as a systemic disease.Recent evidence demonstrates that,at least in some patients,the initial α-synuclein pathology originates in the peripheral organs and spreads to the brain.Injection of α-synuclein preformed fibrils into the gastrointestinal tra ct trigge rs the gutto-brain propagation of α-synuclein pathology.However,whether α-synuclein pathology can occur spontaneously in peripheral organs independent of exogenous α-synuclein preformed fibrils or pathological α-synuclein leakage from the central nervous system remains under investigation.In this review,we aimed to summarize the role of peripheral α-synuclein pathology in the pathogenesis of Parkinson’s disease.We also discuss the pathways by which α-synuclein pathology spreads from the body to the brain.

The potential of bone morphogenetic protein 2 as a neurotrophic factor for Parkinson’s disease

Parkinson’s disease is the second most common neurodegenerative disorder;it affects 1%of the population over the age of 65.The number of people with Parkinson’s disease is set to rapidly increase due to changing demographics and there is an unmet clinical need for disease-modifying therapies.The pathological hallmarks of Parkinson’s disease are the progressive degeneration of dopaminergic neurons in the substantia nigra and their axons which project to the striatum,and the aggregation ofα-synuclein;these result in a range of debilitating motor and non-motor symptoms.The application of neurotrophic factors to protect and potentially regenerate the remaining dopaminergic neurons is a major area of research interest.However,this strategy has had limited success to date.Clinical trials of two well-known neurotrophic factors,glial cell line-derived neurotrophic factor and neurturin,have reported limited efficacy in Parkinson’s disease patients,despite these factors showing potent neurotrophic actions in animal studies.There is therefore a need to identify other neurotrophic factors that can protect againstα-synuclein-induced degeneration of dopaminergic neurons.The bone morphogenetic protein(BMP)family is the largest subgroup of the transforming growth factor-βsuperfamily of proteins.BMPs are naturally secreted proteins that play crucial roles throughout the developing nervous system.Importantly,many BMPs have been shown to be potent neurotrophic factors for dopaminergic neurons.Here we discuss recent work showing that transcripts for the BMP receptors and BMP2 are co-expressed with several key markers of dopaminergic neurons in the human substantia nigra,and evidence for downregulation of BMP2 expression at distinct stages of Parkinson’s disease.We also discuss studies that explored the effects of BMP2 treatment,in in vitro and in vivo models of Parkinson’s disease.These studies found potent effects of BMP2 on dopaminergic neurites,which is important given that axon degeneration is increasingly recognized as a key early event in Parkinson’s disease.Thus,the aim of this mini-review is to give an overview of the BMP family and the BMP-Smad signalling pathway,in addition to reviewing the available evidence demonstrating the potential of BMP2 for Parkinson’s disease therapy.

X-box-binding protein 1-modified neural stem cells for treatment of Parkinson's disease

X-box-binding protein 1-transfected neural stem cells were transplanted into the right lateral ventricles of rats with rotenone-induced Parkinson＇s disease. The survival capacities and differentiation rates of cells expressing the dopaminergic marker tyrosine hydroxylase were higher in X-box-binding protein 1-transfected neural stem cells compared to non-transfected cells. Moreover, dopamine and 3,4-dihydroxyphenylacetic acid levels in the substantia nigra were significantly increased, α-synuclein expression was decreased, and neurological behaviors were significantly ameliorated in rats following transplantation of X-box-binding protein 1-transfected neural stem cells. These results indicate that transplantation of X-box-binding protein 1-transfected neural stem cells can promote stem cell survival and differentiation into dopaminergic neurons, increase dopamine and 3,4-dihydroxyphenylacetic acid levels, reduce α-synuclein aggregation in the substantia nigra, and improve the symptoms of Parkinson＇s disease in rats.

Quantum dots protect against MPP＋-induced neurotoxicity in a cell model of Parkinson＇s disease through autophagy induction

Autophagy is a basic cellular process that decomposes damaged organelles and aberrant proteins. Dysregulation of autophagy is implicated in pathogenesis of neurodegenerative disorders, including Parkinson's disease(PD). Pharmacological compounds that stimulate autophagy can provide neuroprotection in models of PD. Nanoparticles have emerged as regulators of autophagy and have been tested in adjuvant therapy for diseases. In this present study, we explore the effects of quantum dots(QDs) that can induce autophagy in a cellular model of Parkinson's disease. Cd Te/Cd S/Zn S QDs protect differentiated rat pheochromocytoma PC12 cells from MPP+-induced cell damage, including reduced viability, apoptosis and accumulation of α-Synuclein, a characteristic protein of PD. The protective function of QDs is autophagy-dependent. In addition, we investigate the interaction between quantum dots and autophagic pathways and identify beclin1 as an essential factor for QDs-induced autophagy. Our results reveal new promise of QDs in the theranostic of neurodegenerative diseases.

Growth differentiation factor 5:a neurotrophic factor with neuroprotective potential in Parkinson’s disease

Parkinson’s disease is the most common movement disorder worldwide,affecting over 6 million people.It is an age-related disease,occurring in 1%of people over the age of 60,and 3%of the population over 80 years.The disease is characterized by the progressive loss of midbrain dopaminergic neurons from the substantia nigra,and their axons,which innervate the striatum,resulting in the characteristic motor and non-motor symptoms of Parkinson’s disease.This is paralleled by the intracellular accumulation ofα-synuclein in several regions of the nervous system.Current therapies are solely symptomatic and do not stop or slow disease progression.One promising disease-modifying strategy to arrest the loss of dopaminergic neurons is the targeted delivery of neurotrophic factors to the substantia nigra or striatum,to protect the remaining dopaminergic neurons of the nigrostriatal pathway.However,clinical trials of two well-established neurotrophic factors,glial cell line-derived neurotrophic factor and neurturin,have failed to meet their primary end-points.This failure is thought to be at least partly due to the downregulation byα-synuclein of Ret,the common co-receptor of glial cell line-derived neurorophic factor and neurturin.Growth/differentiation factor 5 is a member of the bone morphogenetic protein family of neurotrophic factors,that signals through the Ret-independent canonical Smad signaling pathway.Here,we review the evidence for the neurotrophic potential of growth/differentiation factor 5 in in vitro and in vivo models of Parkinson’s disease.We discuss new work on growth/differentiation factor 5’s mechanisms of action,as well as data showing that viral delivery of growth/differentiation factor 5 to the substantia nigra is neuroprotective in theα-synuclein rat model of Parkinson’s disease.These data highlight the potential for growth/differentiation factor 5 as a disease-modifying therapy for Parkinson’s disease.

Anchanling reduces pathology in a lactacystin-induced Parkinson's disease model

A rat model of Parkinson＇s disease was induced by injecting lactacystin stereotaxically into the left mesencephalic ventral tegmental area and substantia nigra pars compacta. After rats were intragastrically perfused with Anchanling, a Chinese medicine, mainly composed of magnolol, for 5 weeks, when compared with Parkinson’s disease model rats, tyrosine hydroxylase expression was increased, α-synuclein and ubiquitin expression was decreased, substantia nigra cell apoptosis was reduced, and apomorphine-induced rotational behavior was improved. Results suggested that Anchanling can ameliorate Parkinson＇s disease pathology possibly by enhancing degradation activity of the ubiquitin-proteasome system.

Is activation of GDNF/RET signaling the answer for successful treatment of Parkinson's disease?A discussion of data from the culture dish to the clinic

The neurotrophic signaling of glial cell line-derived neurotrophic factor(GDNF)with its canonical receptor,the receptor tyrosine kinase RET,coupled together with the GDNF family receptor alpha 1 is important for dopaminergic neuron survival and physiology in cell culture experiments and animal models.This prompted the idea to try GDNF/RET signaling as a therapeutic approach to treat Parkinson’s disease with the hallmark of dopaminergic cell death in the substantia nigra of the midbrain.Despite several clinical trials with GDNF in Parkinson’s disease patients,which mainly focused on optimizing the GDNF delivery technique,benefits were only seen in a few patients.In general,the endpoints did not show significant improvements.This suggests that it will be helpful to learn more about the basic biology of this fascinating but complicated GDNF/RET signaling system in the dopaminergic midbrain and about recent developments in the field to facilitate its use in the clinic.Here we will refer to the latest publications and point out important open questions in the field.