PYM50028, a novel, orally active, nonpeptide neurotrophic factor inducer, prevents and reverses neuronal damage induced by MPP+ in mesencephalic neurons and by MPTP in a mouse model of Parkinson's disease

GM1 oligosaccharide efficacy against α-synuclein aggregation and toxicity in vitro

Fibrillary aggregated α-synuclein represents the neurologic hallmark of Parkinson's disease and is considered to play a causative role in the disease. Although the causes leading to α-synuclein aggregation are not clear, the GM1 ganglioside interaction is recognized to prevent this process. How GM1 exerts these functions is not completely clear, although a primary role of its soluble oligosaccharide (GM1-OS) is emerging. Indeed, we recently identified GM1-OS as the bioactive moiety responsible for GM1 neurotrophic and neuroprotective properties, specifically reverting the parkinsonian phenotype both in in vitro and in vivo models. Here, we report on GM1-OS efficacy against the α-synuclein aggregation and toxicity in vitro. By amyloid seeding aggregation assay and NMR spectroscopy, we demonstrated that GM1-OS was able to prevent both the spontaneous and the prion-like α-synuclein aggregation. Additionally, circular dichroism spectroscopy of recombinant monomeric α-synuclein showed that GM1-OS did not induce any change in α-synuclein secondary structure. Importantly, GM1-OS significantly increased neuronal survival and preserved neurite networks of dopaminergic neurons affected by α-synuclein oligomers, together with a reduction of microglia activation. These data further demonstrate that the ganglioside GM1 acts through its oligosaccharide also in preventing the α-synuclein pathogenic aggregation in Parkinson's disease, opening a perspective window for GM1-OS as drug candidate.

GM1 Oligosaccharide Efficacy in Parkinson's Disease: Protection against MPTP

Past evidence has shown that the exogenous administration of GM1 ganglioside slowed neuronal death in preclinical models of Parkinson's disease, a neurodegenerative disorder characterized by the progressive loss of dopamine-producing neurons: however, the physical and chemical properties of GM1 (i.e., amphiphilicity) limited its clinical application, as the crossing of the blood-brain barrier is denied. Recently, we demonstrated that the GM1 oligosaccharide head group (GM1-OS) is the GM1 bioactive portion that, interacting with the TrkA-NGF complex at the membrane surface, promotes the activation of a multivariate network of intracellular events regulating neuronal differentiation, protection, and reparation. Here, we evaluated the GM1-OS neuroprotective potential against the Parkinson's disease-linked neurotoxin MPTP, which destroys dopaminergic neurons by affecting mitochondrial bioenergetics and causing ROS overproduction. In dopaminergic and glutamatergic primary cultures, GM1-OS administration significantly increased neuronal survival, preserved neurite network, and reduced mitochondrial ROS production enhancing the mTOR/Akt/GSK3β pathway. These data highlight the neuroprotective efficacy of GM1-OS in parkinsonian models through the implementation of mitochondrial function and reduction in oxidative stress.

Disease-modifying vs symptomatic treatments: Splitting over lumping

Clinical trials of putative disease-modifying therapies in neurodegeneration have obeyed the century-old principle of convergence, or lumping, whereby any feature of a clinicopathologic disease entity is considered relevant to most of those affected. While this convergent approach has resulted in important successes in trials of symptomatic therapies, largely aimed at correcting common neurotransmitter deficiencies (e.g., cholinergic deficiency in Alzheimer's disease or dopaminergic deficiency in Parkinson's disease), it has been consistently futile in trials of neuroprotective or disease-modifying interventions. As individuals affected by the same neurodegenerative disorder do not share the same biological drivers, splitting such disease into small molecular/biological subtypes, to match people to therapies most likely to benefit them, is vital in the pursuit of disease modification. We here discuss three paths toward the splitting needed for future successes in precision medicine: (1) encourage the development of aging cohorts agnostic to phenotype in order to enact a biology-to-phenotype direction of biomarker development and validate divergence biomarkers (present in some, absent in most); (2) demand bioassay-based recruitment of subjects into disease-modifying trials of putative neuroprotective interventions in order to match the right therapies to the right recipients; and (3) evaluate promising epidemiologic leads of presumed pathogenetic potential using Mendelian randomization studies before designing the corresponding clinical trials. The reconfiguration of disease-modifying efforts for patients with neurodegenerative disorders will require a paradigm shift from lumping to splitting and from proteinopathy to proteinopenia.

Design and Synthesis of Fsp3-Enriched Spirocyclic-Based Biological Screening Compound Arrays via DOS Strategies and Their NNMT Inhibition Profiling

Medicinal chemists are keen to explore tridimensional compounds, especially when it comes to small molecules. It has already been stressed that the majority of known drugs tend to be flat, whereas natural products tend to be more tridimensional and represent a good source of active compounds. 3D metrics have been implemented and computational descriptors are available to evaluate and prioritize compounds based on their 3D geometry. This is usually done by comparing the saturated carbon atoms in a molecule with the total number of its non-hydrogen atoms (the Fsp3 value). While this aspect is clear, still there are not enough synthetic tools that support the realization of novel chemotypes that conform to these criteria. Herein we describe a diversity oriented synthesis (DOS) synthetic cascade technology that starts from two simple reagents, and generates highly enriched Fsp3 novel and diverse spiro-scaffolds with pragmatic synthetic handles (points of diversity). The spiro nature of these scaffolds not only ensures high Fsp3 values but renders the compounds more rigid and therefore more effective in forming precise stereo-interactions with their potential biological targets. These compounds were also profiled for their drug-like properties and as potential modulators of the NNMT enzyme.

Alpha-Synuclein: The Spark That Flames Dopaminergic Neurons, In Vitro and In Vivo Evidence

Mitochondria, α-syn fibrils and the endo-lysosomal system are key players in the pathophysiology of Parkinson’s disease. The toxicity of α-syn is amplified by cell-to-cell transmission and aggregation of endogenous species in newly invaded neurons. Toxicity of α-syn PFF was investigated using primary cultures of dopaminergic neurons or on aged mice after infusion in the SNpc and combined with mild inhibition of GBA. In primary dopaminergic neurons, application of α-syn PFF induced a progressive cytotoxicity associated with mitochondrial dysfunction, oxidative stress, and accumulation of lysosomes suggesting that exogenous α-syn reached the lysosome (from the endosome). Counteracting the α-syn endocytosis with a clathrin inhibitor, dopaminergic neuron degeneration was prevented. In vivo, α-syn PFF induced progressive neurodegeneration of dopaminergic neurons associated with motor deficits. Histology revealed progressive aggregation of α-syn and microglial activation and accounted for the seeding role of α-syn, injection of which acted as a spark suggesting a triggering of cell-to-cell toxicity. We showed for the first time that a localized SNpc α-syn administration combined with a slight lysosomal deficiency and aging triggered a progressive lesion. The cellular and animal models described could help in the understanding of the human disease and might contribute to the development of new therapies.

Promising drug targets and associated therapeutic interventions in Parkinson's disease

Parkinson's disease (PD) is one of the most debilitating brain diseases. Despite the availability of symptomatic treatments, response towards the health of PD patients remains scarce. To fulfil the medical needs of the PD patients, an efficacious and etiological treatment is required. In this review, we have compiled the information covering limitations of current therapeutic options in PD, novel drug targets for PD, and finally, the role of some critical beneficial natural products to control the progression of PD.

Queuine, a bacterial-derived hypermodified nucleobase, shows protection in in vitro models of neurodegeneration

Growing evidence suggests that human gut bacteria, which comprise the microbiome, are linked to several neurodegenerative disorders. An imbalance in the bacterial population in the gut of Parkinson's disease (PD) and Alzheimer's disease (AD) patients has been detected in several studies. This dysbiosis very likely decreases or increases microbiome-derived molecules that are protective or detrimental, respectively, to the human body and those changes are communicated to the brain through the so-called 'gut-brain-axis'. The microbiome-derived molecule queuine is a hypermodified nucleobase enriched in the brain and is exclusively produced by bacteria and salvaged by humans through their gut epithelium. Queuine replaces guanine at the wobble position (position 34) of tRNAs with GUN anticodons and promotes efficient cytoplasmic and mitochondrial mRNA translation. Queuine depletion leads to protein misfolding and activation of the endoplasmic reticulum stress and unfolded protein response pathways in mice and human cells. Protein aggregation and mitochondrial impairment are often associated with neural dysfunction and neurodegeneration. To elucidate whether queuine could facilitate protein folding and prevent aggregation and mitochondrial defects that lead to proteinopathy, we tested the effect of chemically synthesized queuine, STL-101, in several in vitro models of neurodegeneration. After neurons were pretreated with STL-101 we observed a significant decrease in hyperphosphorylated alpha-synuclein, a marker of alpha-synuclein aggregation in a PD model of synucleinopathy, as well as a decrease in tau hyperphosphorylation in an acute and a chronic model of AD. Additionally, an associated increase in neuronal survival was found in cells pretreated with STL-101 in both AD models as well as in a neurotoxic model of PD. Measurement of queuine in the plasma of 180 neurologically healthy individuals suggests that healthy humans maintain protective levels of queuine. Our work has identified a new role for queuine in neuroprotection uncovering a therapeutic potential for STL-101 in neurological disorders.

Trans-synaptic degeneration in the visual pathway: Neural connectivity, pathophysiology, and clinical implications in neurodegenerative disorders

There is a strong interrelationship between eye and brain diseases. It has been shown that neurodegenerative changes can spread bidirectionally in the visual pathway along neuronal projections. For example, damage to retinal ganglion cells in the retina leads to degeneration of the visual cortex (anterograde degeneration) and vice versa (retrograde degeneration). The underlying mechanisms of this process, known as trans-synaptic degeneration (TSD), are unknown, but TSD contributes to the progression of numerous neurodegenerative disorders, leading to clinical and functional deterioration. The hierarchical structure of the visual system comprises of a strong topographic connectivity between the retina and the visual cortex and therefore serves as an ideal model to study the cellular effect, clinical manifestations, and deterioration extent of TSD. With this review we provide comprehensive information about the neural connectivity, synapse function, molecular changes, and pathophysiology of TSD in visual pathways. We then discuss its bidirectional nature and clinical implications in neurodegenerative diseases. A thorough understanding of TSD in the visual pathway can provide insights into progression of neurodegenerative disorders and its potential as a therapeutic target.

Phenotype-Agnostic Molecular Subtyping of Neurodegenerative Disorders: The Cincinnati Cohort Biomarker Program (CCBP)

Ongoing biomarker development programs have been designed to identify serologic or imaging signatures of clinico-pathologic entities, assuming distinct biological boundaries between them. Identified putative biomarkers have exhibited large variability and inconsistency between cohorts, and remain inadequate for selecting suitable recipients for potential disease-modifying interventions. We launched the Cincinnati Cohort Biomarker Program (CCBP) as a population-based, phenotype-agnostic longitudinal study. While patients affected by a wide range of neurodegenerative disorders will be deeply phenotyped using clinical, imaging, and mobile health technologies, analyses will not be anchored on phenotypic clusters but on bioassays of to-be-repurposed medications as well as on genomics, transcriptomics, proteomics, metabolomics, epigenomics, microbiomics, and pharmacogenomics analyses blinded to phenotypic data. Unique features of this cohort study include (1) a reverse biology-to-phenotype direction of biomarker development in which clinical, imaging, and mobile health technologies are subordinate to biological signals of interest; (2) hypothesis free, causally- and data driven-based analyses; (3) inclusive recruitment of patients with neurodegenerative disorders beyond clinical criteria-meeting patients with Parkinson's and Alzheimer's diseases, and (4) a large number of longitudinally followed participants. The parallel development of serum bioassays will be aimed at linking biologically suitable subjects to already available drugs with repurposing potential in future proof-of-concept adaptive clinical trials. Although many challenges are anticipated, including the unclear pathogenic relevance of identifiable biological signals and the possibility that some signals of importance may not yet be measurable with current technologies, this cohort study abandons the anchoring role of clinico-pathologic criteria in favor of biomarker-driven disease subtyping to facilitate future biosubtype-specific disease-modifying therapeutic efforts.

Nanocatalytic activity of clean-surfaced, faceted nanocrystalline gold enhances remyelination in animal models of multiple sclerosis

Development of pharmacotherapies that promote remyelination is a high priority for multiple sclerosis (MS), due to their potential for neuroprotection and restoration of function through repair of demyelinated lesions. A novel preparation of clean-surfaced, faceted gold nanocrystals demonstrated robust remyelinating activity in response to demyelinating agents in both chronic cuprizone and acute lysolecithin rodent animal models. Furthermore, oral delivery of gold nanocrystals improved motor functions of cuprizone-treated mice in both open field and kinematic gait studies. Gold nanocrystal treatment of oligodendrocyte precursor cells in culture resulted in oligodendrocyte maturation and expression of myelin differentiation markers. Additional in vitro data demonstrated that these gold nanocrystals act via a novel energy metabolism pathway involving the enhancement of key indicators of aerobic glycolysis. In response to gold nanocrystals, co-cultured central nervous system cells exhibited elevated levels of the redox coenzyme nicotine adenine dinucleotide (NAD+), elevated total intracellular ATP levels, and elevated extracellular lactate levels, along with upregulation of myelin-synthesis related genes, collectively resulting in functional myelin generation. Based on these preclinical studies, clean-surfaced, faceted gold nanocrystals represent a novel remyelinating therapeutic for multiple sclerosis.

Neuroprotective Effect of CR-777, a Glutathione Derivative of Withaferin A, Obtained through the Bioconversion of Withania somnifera (L.) Dunal Extract by the Fungus Beauveria bassiana

The bioconversion of Withania somnifera extract by the fungus Beauveria bassiana leads to cysteine and glutathione derivatives of withaferin A at the C-6 position. The compounds were purified and fully characterized by 1D-NMR, 2D-NMR, and HRMS analysis. The glutathione derivative CR-777 was evaluated as a neuroprotective agent from damage caused by different neurotoxins mimicking molecular symptoms in Parkinson´s disease (PD), including 1-methyl-4-phenylpyridinium (MPP+), 6-hydroxydopamine (6-OHDA), and α-synuclein (α-Syn). CR-777, at nanomolar concentrations, protected dopaminergic and cortical neurons. In 6-OHDA-treated neurons, CR-777 increased cell survival and neurite network and decreased the expression of α-Syn. Using specific inhibitors of cell toxicity signaling pathways and specific staining experiments, the observed role of CR-777 seemed to involve the PI3K/mTOR pathway. CR-777 could be considered as a protective agent against a large panel of neuronal stressors and was engaged in further therapeutic development steps.

Necrosis, apoptosis, necroptosis, three modes of action of dopaminergic neuron neurotoxins

Most of the Parkinson’s disease (PD) cases are sporadic, although several genes are directly related to PD. Several pathways are central in PD pathogenesis: protein aggregation linked to proteasomal impairments, mitochondrial dysfunctions and impairment in dopamine (DA) release. Here we studied the close crossing of mitochondrial dysfunction and aggregation of α-synuclein (α-syn) and in the extension in the dopaminergic neuronal death. Here, using rat primary cultures of mesencephalic neurons, we induced the mitochondrial impairments using “DA-toxins” (MPP⁺, 6OHDA, rotenone). We showed that the DA-Toxins induced dopaminergic cell death through different pathways: caspase-dependent cell death for 6OHDA; MPP⁺ stimulated caspase-independent cell death, and rotenone activated both pathways. In addition, a decrease in energy production and/or a development of oxidative stress were observed and were linked to α-syn aggregation with generation of Lewy body-like inclusions (found inside and outside the dopaminergic neurons). We demonstrated that any of induced mitochondrial disturbances and processes of death led to α-syn protein aggregation and finally to cell death. Our study depicts the cell death mechanisms taking place in in vitro models of Parkinson’s disease and how mitochondrial dysfunctions is at the cross road of the pathologies of this disease.

Marine-Derived Natural Compounds for the Treatment of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder caused by the loss of dopaminergic neurons, leading to the motor dysfunctions of patients. Although the etiology of PD is still unclear, the death of dopaminergic neurons during PD progress was revealed to be associated with the abnormal aggregation of α-synuclein, the elevation of oxidative stress, the dysfunction of mitochondrial functions, and the increase of neuroinflammation. However, current anti-PD therapies could only produce symptom-relieving effects, because they could not provide neuroprotective effects, stop or delay the degeneration of dopaminergic neurons. Marine-derived natural compounds, with their novel chemical structures and unique biological activities, may provide anti-PD neuroprotective effects. In this study, we have summarized anti-PD marine-derived natural products which have shown pharmacological activities by acting on various PD targets, such as α-synuclein, monoamine oxidase B, and reactive oxygen species. Moreover, marine-derived natural compounds currently evaluated in the clinical trials for the treatment of PD are also discussed.

Smilagenin Protects Dopaminergic Neurons in Chronic MPTP/Probenecid-Lesioned Parkinson's Disease Models

Current therapies for Parkinson’s disease (PD) only offer limited symptomatic alleviation but fail to hamper the progress of the disease. Thus, it is imperative to establish new approaches aiming at protecting or reversing neurodegeneration in PD. Recent work elucidates whether smilagenin (abbreviated SMI), a steroidal sapogenin from traditional Chinese medicinal herbs, can take neuroprotective effect on dopaminergic neurons in a chronic model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) conjuncted with probenecid mice. We reported for the first time that SMI significantly improved the locomotor ability of chronic MPTP/probenecid–lesioned mice. SMI increased the tyrosine hydroxylase (TH) positive and Nissl positive neuron number in the substantia nigra pars compacta (SNpc), augmented striatal DA and its metabolites concentration and elevated striatal dopamine transporter density (DAT). In addition, dopamine receptor D2R not D1R was down-regulated by MPTP/probenecid and slightly raised by SMI prevention. What’s more, we discovered that SMI markedly elevated striatal glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) protein levels in SMI prevented mice. And we found that SMI increased GDNF and BDNF mRNA level by promoting CREB phosphorylation in 1-methyl-4-phenylpyridimium (MPP⁺) treated SH-SY5Y cells. The results illustrated that SMI could prevent the impairment of dopaminergic neurons in chronic MPTP/probenecid-induced mouse model.

NCX1 and NCX3 as potential factors contributing to neurodegeneration and neuroinflammation in the A53T transgenic mouse model of Parkinson's Disease

Na⁺-Ca²⁺ exchanger (NCX) isoforms constitute the major cellular Ca²⁺ extruding system in neurons and microglia. We herein investigated the role of NCX isoforms in the pathophysiology of Parkinson's disease (PD). Their expression and activity were evaluated in neurons and glia of mice expressing the human A53T variant of α-synuclein (A53T mice), an animal model mimicking a familial form of PD. Western blotting revealed that NCX3 expression in the midbrain of 12-month old A53T mice was lower than that of wild type (WT). Conversely, NCX1 expression increased in the striatum. Immunohistochemical studies showed that glial fibrillary acidic protein (GFAP)-positive astroglial cells significantly increased in the substantia nigra pars compacta (SNc) and in the striatum. However, the number and the density of tyrosine hydroxylase (TH)-positive neurons decreased in both brain regions. Interestingly, ionized calcium binding adaptor molecule 1 (IBA-1)-positive microglial cells increased only in the striatum of A53T mice compared to WT. Double immunostaining studies showed that in A53T mice, NCX1 was exclusively co-expressed in IBA-1-positive microglial cells in the striatum, whereas NCX3 was solely co-expressed in TH-positive neurons in SNc. Beam walking and pole tests revealed a reduction in motor performance for A53T mice compared to WT. In vitro experiments in midbrain neurons from A53T and WT mice demonstrated a reduction in NCX3 expression, which was accompanied by mitochondrial overload of Ca²⁺ ions, monitored with confocal microscopy by X-Rhod-1 fluorescent dye. Collectively, in vivo and in vitro findings suggest that the reduction in NCX3 expression and activity in A53T neurons from midbrain may cause mitochondrial dysfunction and neuronal death in this brain area, whereas NCX1 overexpression in microglial cells may promote their proliferation in the striatum.

Integral Characterization of Defective BDNF/TrkB Signalling in Neurological and Psychiatric Disorders Leads the Way to New Therapies

Enhancement of brain-derived neurotrophic factor (BDNF) signalling has great potential in therapy for neurological and psychiatric disorders. This neurotrophin not only attenuates cell death but also promotes neuronal plasticity and function. However, an important challenge to this approach is the persistence of aberrant neurotrophic signalling due to a defective function of the BDNF high-affinity receptor, tropomyosin-related kinase B (TrkB), or downstream effectors. Such changes have been already described in several disorders, but their importance as pathological mechanisms has been frequently underestimated. This review highlights the relevance of an integrative characterization of aberrant BDNF/TrkB pathways for the rational design of therapies that by combining BDNF and TrkB targets could efficiently promote neurotrophic signalling.

Beta-asarone protects against MPTP-induced Parkinson's disease via regulating long non-coding RNA MALAT1 and inhibiting α-synuclein protein expression

OBJECTIVE

Numerous long non-coding RNAs (lncRNA) have been identified in neurodegenerative disorders including Parkinson's disease (PD). Emerging evidence demonstrates that β-asarone functions as neuroprotective effects in both in vitro and in vivo models. However, the role of β-asarone and its potential mechanism in PD remain not completely clear.

METHODS

MPTP-induced PD mouse model and SH-SY5Y cells subjected to MPP+ as its in vitro model were used to evaluate the effects of β-asarone on PD. LncRNA MALAT1 and α-synuclein expression were determined by real-time PCR and western blot methods.

RESULTS

β-Asarone significantly increased the TH+ cells number and decreased the expression levels of MALAT1 and α-synuclein in midbrain tissue of PD mice. RNA pull-down and immunoprecipitation assays confirmed that MALAT1 associated with α-synuclein, leading to the increased stability of α-synuclein and its expression in SH-SY5Y cells. β-asarone elevated the viability of cells exposed to MPP+. Either overexpressed MALAT1 or α-synuclein could canceled the protective effect of β-asarone on cell viability. In PD mice, pcDNA-MALAT1 also decreased the TH+ cells number and increased the α-synuclein expression in PD mice with treatment of β-asarone.

CONCLUSION

β-Asarone functions as a neuroprotective effect in both in vivo and in vitro models of PD via regulating MALAT1 and α-synuclein expression.

Combination of acamprosate and baclofen as a promising therapeutic approach for Parkinson's disease

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterised by the loss of dopaminergic nigrostriatal neurons but which involves the loss of additional neurotransmitter pathways. Mono- or polytherapeutic interventions in PD patients have declining efficacy long-term and no influence on disease progression. The systematic analysis of available genetic and functional data as well as the substantial overlap between Alzheimer’s disease (AD) and PD features led us to repurpose and explore the effectiveness of a combination therapy (ABC) with two drugs – acamprosate and baclofen – that was already effective in AD animal models, for the treatment of PD. We showed in vitro that ABC strongly and synergistically protected neuronal cells from oxidative stress in the oxygen and glucose deprivation model, as well as dopaminergic neurons from cell death in the 6-hydroxydopamine (6-OHDA) rat model. Furthermore, we showed that ABC normalised altered motor symptoms in vivo in 6-OHDA-treated rats, acting by protecting dopaminergic cell bodies and their striatal terminals. Interestingly, ABC also restored a normal behaviour pattern in lesioned rats suggesting a symptomatic effect, and did not negatively interact with L-dopa. Our results demonstrate the potential value of combining repurposed drugs as a promising new strategy to treat this debilitating disease.

Combination therapies: The next logical Step for the treatment of synucleinopathies?

Currently there are no disease-modifying alternatives for the treatment of most neurodegenerative disorders. The available therapies for diseases such as Parkinson's disease (PD), PD dementia (PDD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), in which the protein alpha-synuclein (α-Syn) accumulates within neurons and glial cells with toxic consequences, are focused on managing the disease symptoms. However, using strategic drug combinations and/or multi-target drugs might increase the treatment efficiency when compared with monotherapies. Synucleinopathies are complex disorders that progress through several stages, and toxic α-Syn aggregates exhibit prion-like behavior spreading from cell to cell. Therefore, it follows that these neurodegenerative disorders might require equally complex therapeutic approaches to obtain significant and long-lasting results. Hypothetically, therapies aimed at reducing α-Syn accumulation and cell-to-cell transfer, such as immunotherapy against α-Syn, could be combined with agents that reduce neuroinflammation with potential synergistic outcomes. Here we review the current evidence supporting this type of approach, suggesting that such rational therapy combinations, together with the use of multi-target drugs, may hold promise as the next logical step for the treatment of synucleinopathies.

Ameliorative effects of baicalein in MPTP-induced mouse model of Parkinson's disease: A microarray study

Baicalein, a flavonoid from Scutellaria baicalensis Georgi, has been shown to possess neuroprotective properties. The purpose of this study was to explore the effects of baicalein on motor behavioral deficits and gene expression in N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice model of Parkinson's disease (PD). The behavioral results showed that baicalein significantly improves the abnormal behaviors in MPTP-induced mice model of PD, as manifested by shortening the total time for climbing down the pole, prolonging the latent periods of rotarod, and increasing the vertical movements. Using cDNA microarray and subsequent bioinformatic analyses, it was found that baicalein significantly promotes the biological processes including neurogenesis, neuroblast proliferation, neurotrophin signaling pathway, walking and locomotor behaviors, and inhibits dopamine metabolic process through regulation of gene expressions. Based on analysis of gene co-expression networks, the results indicated that the regulation of genes such as LIMK1, SNCA and GLRA1 by baicalein might play central roles in the network. Our results provide experimental evidence for the potential use of baicalein in the treatment of PD, and revealed gene expression profiles, biological processes and pathways influenced by baicalein in MPTP-treated mice.

The ongoing pursuit of neuroprotective therapies in Parkinson disease

Many agents developed for neuroprotective treatment of Parkinson disease (PD) have shown great promise in the laboratory, but none have translated to positive results in patients with PD. Potential neuroprotective drugs, such as ubiquinone, creatine and PYM50028, have failed to show any clinical benefits in recent high-profile clinical trials. This 'failure to translate' is likely to be related primarily to our incomplete understanding of the pathogenic mechanisms underlying PD, and excessive reliance on data from toxin-based animal models to judge which agents should be selected for clinical trials. Restricted resources inevitably mean that difficult compromises must be made in terms of trial design, and reliable estimation of efficacy is further hampered by the absence of validated biomarkers of disease progression. Drug development in PD dementia has been mostly unsuccessful; however, emerging biochemical, genetic and pathological evidence suggests a link between tau and amyloid-β deposition and cognitive decline in PD, potentially opening up new possibilities for therapeutic intervention. This Review discusses the most important 'druggable' disease mechanisms in PD, as well as the most-promising drugs that are being evaluated for their potential efficiency in treatment of motor and cognitive impairments in PD.

Challenges and promises in the development of neurotrophic factor-based therapies for Parkinson's disease

Parkinson's disease (PD) is a chronic movement disorder typically coupled to progressive degeneration of dopaminergic neurons in the substantia nigra (SN). The treatments currently available are satisfactory for symptomatic management, but the efficacy tends to decrease as neuronal loss progresses. Neurotrophic factors (NTFs) are endogenous proteins known to promote neuronal survival, even in degenerating states. Therefore, the use of these factors is regarded as a possible therapeutic approach, which would aim to prevent PD or to even restore homeostasis in neurodegenerative disorders. Intriguingly, although favorable results in in vitro and in vivo models of the disease were attained, clinical trials using these molecules have failed to demonstrate a clear therapeutic benefit. Therefore, the development of animal models that more closely reproduce the mechanisms known to underlie PD-related neurodegeneration would be a major step towards improving the capacity to predict the clinical usefulness of a given NTF-based approach in the experimental setting. Moreover, some adjustments to the design of clinical trials ought to be considered, which include recruiting patients in the initial stages of the disease, improving the efficacy of the delivery methods, and combining synergetic NTFs or adding NTF-boosting drugs to the already available pharmacological approaches. Despite the drawbacks on the road to the use of NTFs as pharmacological tools for PD, very relevant achievements have been reached. In this article, we review the current status of the potential relevance of NTFs for treating PD, taking into consideration experimental evidence, human observational studies, and data from clinical trials.

Natural products from marine organisms with neuroprotective activity in the experimental models of Alzheimer's disease, Parkinson's disease and ischemic brain stroke: their molecular targets and action mechanisms

Continuous increases in the incidence of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and brain stroke demand the urgent development of therapeutics. Marine organisms are well-known producers of natural products with diverse structures and pharmacological activities. Therefore, researchers have endeavored to identify marine natural products with neuroprotective effects. In this regard, this review summarizes therapeutic targets for AD, PD, and ischemic brain stroke and marine natural products with pharmacological activities on the targets according to taxonomies of marine organisms. Furthermore, several marine natural products on the clinical trials for the treatment of neurological disorders are discussed.

Potential therapeutic effects of neurotrophins for acute and chronic neurological diseases

The neurotrophins (NTs) nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, and NT-4/5 are proteins that regulate cell proliferation, differentiation, and survival in both the developing and mature central nervous system (CNS) by binding to two receptor classes, Trk receptors and p75 NTR. Motivated by the broad growth- and survival-promoting effects of these proteins, numerous studies have attempted to use exogenous NTs to prevent the death of cells that are associated with neurological disease or promote the regeneration of severed axons caused by mechanical injury. Indeed, such neurotrophic effects have been repeatedly demonstrated in animal models of stroke, nerve injury, and neurodegenerative disease. However, limitations, including the short biological half-lives and poor blood-brain permeability of these proteins, prevent routine application from treating human disease. In this report, we reviewed evidence for the neuroprotective efficacy of NTs in animal models, highlighting outstanding technical challenges and discussing more recent attempts to harness the neuroprotective capacity of endogenous NTs using small molecule inducers and cell transplantation.

Neurotrophin strategies for neuroprotection: are they sufficient?

As people are living longer, the prevalance of neurodegenerative diseases continues to rise resulting in huge socio-economic consequences. Despite major advancements in studying the pathophysiology of these diseases and a large number of clinical trials currently there is no effective treatment for these illnesses. All neuroprotective strategies have either failed or have shown only a minimal effect. There has been a major shift in recent years exploring the potential of neuroregenerative approaches. While the concept of using neurotropins for therapeutic purposes has been in existence for many years, new modes of delivery and expression of this family of molecules makes this approach now feasilble. Further neurotropin mimetics and receptor agonists are also being developed. The use of small molecules to induce the expression of neurotropins including repurposing of FDA approved drugs for this approach is another strategy being pursued. In the review we examine these new developments and discuss the potential for such approaches in the context of the pathophysiology of neurodegenerative diseases.

Therapy for Parkinson's disease: what is in the pipeline?

Despite advances in the treatment of Parkinson's disease there are still many unmet needs, including neuroprotection, treatment of motor complications, treatment of dyskinesia, treatment of psychosis, and treatment of nondopaminergic symptoms. In this review, I highlight the obstacles to develop a neuroprotective drug and some of the treatment strategies recently approved or still in clinical trials designed to meet these unmet needs.

Reversal of dopamine neurons and locomotor ability degeneration in aged rats with smilagenin

The purpose of this paper is to study the effect of smilagenin (SMI) (PYM50028), a sapogenin compound originally identified from Chinese medicinal herb, on dopamine neurons and locomotor ability in aged rats. Experiments were carried out on young and aged Sprague-Dawley rats, which were daily administered with either SMI (18mg/kg/day) or vehicle (0.5% sodium carboxymethycellulose [CMCNa]). Open-field and rotarod performance tests revealed that behavioral ability was impaired in aged rats and was improved by oral administration of smilagenin. Immunohistochemical data showed that tyrosine hydroxylase (TH)-positive neuron numbers in the substantia nigra pars compacta (unbiased stereological counting) were altered with aging and were increased by smilagenin treatment. Likewise, the dopamine receptor density and the striatal dopamine transporter (DAT) density ((125)I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane [(125)I-FP-CIT] autoradiography) were significantly lowered in aged rats as compared to young rats, and treatment with smilagenin significantly elevated the dopamine receptor and DAT density in aged rats. Furthermore, smilagenin enhances glial cell-derived neurotrophic factor (GDNF) release both in the striatum and midbrain. These results indicate a possible role of smilagenin in the treatment of age-related extrapyramidal disorders.

Future treatments for Parkinson's disease: surfing the PD pipeline

Our current wish list for the treatment of Parkinson's disease (PD) includes therapies that will provide robust and sustained antiparkinsonian benefit through the day, ameliorate or prevent dyskinesia, and slow or prevent the progression of the disease. In this article, I review selected new therapies in clinical development for motor features or treatment complications of PD, and some that may slow disease progression. These include adenosine 2a (A2a) antagonists (istradefylline, preladenant, and SYN115), levodopa/carbidopa intestinal gel (LCIG), IPX066--an extended-release formulation of carbidopa/levodopa, XP21279--a sustained-release levodopa prodrug, ND0611--a carbidopa subcutaneous patch, safinamide--a mixed mechanism of action medication that may provide both MAO-B and glutamate inhibition, PMY50028--an oral neurotrophic factor inducer, antidyskinesia medications (AFQ056 and fipamezole), and gene therapies (AAV2-neurturin and glutamic acid decarboxylase gene transfer). Some of these therapies will never be proven efficacious and will not come to market while others may play a key role in the future treatment of PD.

Stem cells and regenerative therapies for Parkinson's disease

Currently the mainstay of Parkinson's disease (PD) therapy is the pharmacological replacement of the loss of the dopaminergic nigrostriatal pathway using drugs such as dopamine agonists and levodopa. Whilst these drugs effectively ameliorate some of the motor features of PD, they do not improve many of the nonmotor features that arise secondary to pathology outside of this system, nor do they slow the progressive neurodegeneration that is a characteristic of the disease. Regenerative therapies for PD seek to fill this therapeutic gap, with cell transplantation being the most explored approach to date. A number of different cell sources have been used in this therapeutic approach, but to date, the most successful has been the use of fetal ventral mesencephalic (VM) tissue that contains within it the developing nigral dopaminergic cells. Cell transplantation for PD was pioneered in the 1980-1990s, with several successful open-label trials of fetal VM transplantation in patients with relatively advanced PD. Whilst these findings were not replicated in two subsequent double-blind sham-surgery controlled trials, there were reasons to explain this outside of the one drawn at the time that these therapies are ineffective. Indeed all these studies have provided evidence that following the transplantation of fetal VM tissue, dopaminergic cells can survive long term, produce dopamine, and bring about clinical improvements in younger patients over many years. The use of fetal tissue, irrespective of its true efficacy, will never become a widely available therapy for PD for a host of practical and ethical reasons, and thus much work has been put in recently to exploring the utility of stem cells as a source of nigral dopaminergic neurons. In this respect, the advent of embryonic stem cell and induced pluripotent cells has heralded a new era in cell therapy for PD, and several groups have now demonstrated that these cells can form dopaminergic neurons which improve functional deficits in animal models of PD. Whilst encouraging, problems with respect to the immunogenicity and tumorigenicity of these cells means that they will need to be used in the clinic cautiously. Other regenerative therapies in PD have been tried over the years and include the use of trophic factors. This has primarily involved glial cell line-derived neurotrophic factor (GDNF) and again has produced mixed clinical effects, and in order to try and resolve this, a new trial of intraputamenal GDNF is now being planned. In addition, a new trial for platelet derived growth factor as a treatment for PD has just completed recruitment, and PYM50028 (Cogane) an oral agent shown in animal models to reduce the effects of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) lesioning by the induction of growth factors is currently under investigation in a multicentre Phase II trial. Overall, there are a number of promising new regenerative therapies being developed and tested in PD, although the true long-term efficacy of any of these in large numbers of patients is still not known.

Clinical utility of neuroprotective agents in neurodegenerative diseases: current status of drug development for Alzheimer's, Parkinson's and Huntington's diseases, and amyotrophic lateral sclerosis

INTRODUCTION

According to the definition of the Committee to Identify Neuroprotective Agents in Parkinson's Disease (CINAPS), "neuroprotection would be any intervention that favourably influences the disease process or underlying pathogenesis to produce enduring benefits for patients" [Meissner W, et al. Trends Pharmacol Sci 2004;25:249-253]. Preferably, neuroprotective agents should be used before or eventually during the prodromal phase of the diseases that could start decades before the appearance of symptoms. Although several symptomatic drugs are available, a disease-modifying agent is still elusive.

AREAS COVERED

The aim of the present review is to give an overview of neuroprotective agents being currently investigated for the treatment of AD, PD, HD and ALS in clinical phases.

EXPERT OPINION

Development of effective neuroprotective therapies resulting in clinically meaningful results is hampered by several factors in all research stages, both conceptual and methodological. Novel solutions might be offered by evaluation of new targets throughout clinical studies, therapies emerging from drug repositioning approaches, multi-target approaches and network pharmacology.

Animal models of Parkinson's disease: a source of novel treatments and clues to the cause of the disease

Animal models of Parkinson's disease (PD) have proved highly effective in the discovery of novel treatments for motor symptoms of PD and in the search for clues to the underlying cause of the illness. Models based on specific pathogenic mechanisms may subsequently lead to the development of neuroprotective agents for PD that stop or slow disease progression. The array of available rodent models is large and ranges from acute pharmacological models, such as the reserpine- or haloperidol-treated rats that display one or more parkinsonian signs, to models exhibiting destruction of the dopaminergic nigro-striatal pathway, such as the classical 6-hydroxydopamine (6-OHDA) rat and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models. All of these have provided test beds in which new molecules for treating the motor symptoms of PD can be assessed. In addition, the emergence of abnormal involuntary movements (AIMs) with repeated treatment of 6-OHDA-lesioned rats with L-DOPA has allowed for examination of the mechanisms responsible for treatment-related dyskinesia in PD, and the detection of molecules able to prevent or reverse their appearance. Other toxin-based models of nigro-striatal tract degeneration include the systemic administration of the pesticides rotenone and paraquat, but whilst providing clues to disease pathogenesis, these are not so commonly used for drug development. The MPTP-treated primate model of PD, which closely mimics the clinical features of PD and in which all currently used anti-parkinsonian medications have been shown to be effective, is undoubtedly the most clinically-relevant of all available models. The MPTP-treated primate develops clear dyskinesia when repeatedly exposed to L-DOPA, and these parkinsonian animals have shown responses to novel dopaminergic agents that are highly predictive of their effect in man. Whether non-dopaminergic drugs show the same degree of predictability of response is a matter of debate. As our understanding of the pathogenesis of PD has improved, so new rodent models produced by agents mimicking these mechanisms, including proteasome inhibitors such as PSI, lactacystin and epoximycin or inflammogens like lipopolysaccharide (LPS) have been developed. A further generation of models aimed at mimicking the genetic causes of PD has also sprung up. Whilst these newer models have provided further clues to the disease pathology, they have so far been less commonly used for drug development. There is little doubt that the availability of experimental animal models of PD has dramatically altered dopaminergic drug treatment of the illness and the prevention and reversal of drug-related side effects that emerge with disease progression and chronic medication. However, so far, we have made little progress in moving into other pharmacological areas for the treatment of PD, and we have not developed models that reflect the progressive nature of the illness and its complexity in terms of the extent of pathology and biochemical change. Only when this occurs are we likely to make progress in developing agents to stop or slow the disease progression. The overarching question that draws all of these models together in the quest for better drug treatments for PD is how well do they recapitulate the human condition and how predictive are they of successful translation of drugs into the clinic? This article aims to clarify the current position and highlight the strengths and weaknesses of available models.

A novel conjugated agent between dopamine and an A2A adenosine receptor antagonist as a potential anti-Parkinson multitarget approach

We propose a potential antiparkinsonian prodrug DP-L-A(2A)ANT (2) obtained by amidic conjugation of dopamine (1) via a succinic spacer to a new triazolo-triazine A(2A) adenosine receptor (AR) antagonist A(2A)ANT (3). The affinity of 2 and its hydrolysis products-1, 3, dopamine-linker DP-L (4) and A(2A)ANT-linker L-A(2A)ANT (5)-was evaluated for hA(1), hA(2A), hA(2B) and hA(3) ARs and rat striatum A(2A)ARs or D(2) receptors. The hydrolysis patterns of 2, 4 and 5 and the stabilities of 1 and 3 were evaluated by HPLC analysis in human whole blood and rat brain homogenates. High hA(2A) affinity was shown by compounds 2 (K(i) = 7.32 ± 0.65 nM), 3 (K(i) = 35 ± 3 nM) and 5 (K(i) = 72 ± 5 nM), whose affinity values were similar in rat striatum. These compounds were not able to change dopamine affinity for D(2) receptors but counteracted the CGS 21680-induced reduction of dopamine affinity. DP-L (4) was inactive on adenosine and dopaminergic receptors. As for stability studies, compounds 4 and 5 were not degraded in incubation media. In human blood, the prodrug 2 was hydrolyzed (half-life = 2.73 ± 0.23 h) mainly on the amidic bound coupling the A(2A)ANT (3), whereas in rat brain homogenates the prodrug 2 was hydrolyzed (half-life > eight hours) exclusively on the amidic bound coupling dopamine, allowing its controlled release and increasing its poor stability as characterized by half-life = 22.5 ± 1.5 min.

Cytokines as potential biomarkers for Parkinson's disease: a multiplex approach

Cytokines, which are immunological messengers facilitating both intra- and inter-system communication, are considered central players in the neuroinflammatory cascades associated with the neurodegenerative process in Parkinson's disease (PD) and other neurological disorders. They have also been implicated in depression and other cognitive (e.g., memory impairment, dementia) and affective disturbances (e.g., anxiety) that show high co-morbidity with neurodegenerative diseases. As such, cytokines may hold great promise as serological biomarkers in PD, with potential applications ranging from early diagnosis and disease staging, to prognosis, drug discovery, and tracking the response to treatment. Subclassification or risk stratification in PD could be based (among other things) on reliably determined cytokine panel profiles or "signatures" of particular co-morbid disease states or at-risk groups (e.g., PD alone, PD with depression and/or dementia). Researchers and clinicians seeking to describe cytokine variations in health vs. disease will benefit greatly from technologies that allow a high degree of multiplexing and thus permit the simultaneous determination of a large roster of cytokines in single small-volume samples. The need for such highly paralleled assays is underscored by the fact that cytokines do not act in isolation but rather against a backdrop of complementary and antagonistic cytokine effects; ascribing valence to the actions of any one cytokine thus requires specific knowledge about the larger cytokine milieu. This chapter provides a technological overview of the major cytokine multiplex assay platforms before discussing the implications of such tools for biomarker discovery and related applications in PD and its depressive and cognitive co-morbidities.

Harpagoside attenuates MPTP/MPP⁺ induced dopaminergic neurodegeneration and movement disorder via elevating glial cell line-derived neurotrophic factor

Parkinson's disease is a chronic neurodegenerative movement disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. New therapeutic approaches aiming at delaying or reversing the neurodegenerative process are under active investigations. In this work, we found that harpagoside, an iridoid purified from the Chinese medicinal herb Scrophularia ningpoensis, could not only prevent but also rescue the dopaminergic neurodegeneration in MPTP/MPP(+) intoxication with promising efficacy. Firstly, in cultured mesencephalic neurons, harpagoside significantly attenuated the loss of TH-positive neuron numbers and the shortening of axonal length. Secondly, in a chronic MPTP mouse model, harpagoside dose-dependently improved the loco-motor ability (rotarod test), increased the TH-positive neuron numbers in the substantia nigra pars compacta (unbiased stereological counting) and increased the striatal DAT density ((125) I-FP-CIT autoradiography). Thirdly, harpagoside markedly elevated the GDNF mRNA and GDNF protein levels in MPTP/MPP(+) lesioned models. However, the protecting effect of harpagoside on the dopaminergic degeneration disappeared when the intrinsic GDNF action was blocked by either the Ret inhibitor PP1 or the neutralizing anti-GDNF antibody. Taken together, we conclude that harpagoside attenuates the dopaminergic neurodegeneration and movement disorder mainly through elevating glial cell line-derived neurotrophic factor.

The preclinical discovery of amyotrophic lateral sclerosis drugs

INTRODUCTION

Amyotrophic lateral sclerosis (ALS), also referred to as Lou Gehrig's disease, is characterized by the progressive loss of cells in the brain and spinal cord that leads to debilitation and death in 3 - 5 years. Only one therapeutic drug, riluzole, has been approved for ALS and this drug improves survival by 2 - 3 months. The need for new therapeutics that can postpone or slow the progression of the motor deficits and prolong survival is still a strong unmet medical need.

AREAS COVERED

Although there are a number of drugs currently in clinical trials for ALS, this review provides an overview of the most promising biological targets and preclinical strategies that are currently being developed and deployed. The list of targets for ALS was compiled from a variety of websites including individual companies that have ALS programs and include those from the author's experience.

EXPERT OPINION

Progress is being made in the identification of possible new therapeutics for ALS with recent efforts in understanding the genetic causes of the disease, susceptibility factors and the development of additional preclinical animal models. However, many challenges remain in the identification of new ALS therapeutics including: the use of relevant biomarkers, the need for an earlier diagnosis of the disease and additional animal models. Multiple strategies need to be tested in the clinic in order to determine what will be effective in patients.

Motor neuron trophic factors: therapeutic use in ALS?

The modest effects of neurotrophic factor (NTF) treatment on lifespan in both animal models and clinical studies of Amyotropic Lateral Sclerosis (ALS) may result from any one or combination of the four following explanations: 1.) NTFs block cell death in some physiological contexts but not in ALS; 2.) NTFs do not rescue motoneurons (MNs) from death in any physiological context; 3.) NTFs block cell death in ALS but to no avail; and 4.) NTFs are physiologically effective but limited by pharmacokinetic constraints. The object of this review is to critically evaluate the role of both NTFs and the intracellular cell death pathway itself in regulating the survival of spinal and cranial (lower) MNs during development, after injury and in response to disease. Because the role of molecules mediating MN survival has been most clearly resolved by the in vivo analysis of genetically engineered mice, this review will focus on studies of such mice expressing reporter, null or other mutant alleles of NTFs, NTF receptors, cell death or ALS-associated genes.

Imipramine activates glial cell line-derived neurotrophic factor via early growth response gene 1 in astrocytes

Recent evidence has suggested that deficits in glial plasticity contribute to the pathophysiology of depressive disorders. The present study explored early growth response 1 (EGR-1) transcriptional regulation of imipramine-induced glial cell line-derived neurotrophic factor (GDNF) expression in astrocytes. After we observed the induction of GDNF mRNA expression in rat astrocytes in response to imipramine, deletion mutant studies showed that the proximal region between -493 and -114 of the GDNF promoter, which contains three binding sites for EGR-1, was essential for maximal imipramine-induced activation of GDNF promoter. The dose-dependent upregulation of EGR-1 by imipramine, the activation of GDNF by the over-expression of EGR-1 without imipramine and the reduction in the imipramine-induced GDNF mRNA expression after silencing of endogenous EGR-1 demonstrated that EGR-1 is upregulated by imipramine to activate the GDNF promoter. Furthermore, imipramine-induced GDNF mRNA expression was strongly attenuated in primary astrocytes from Egr-1(-/-) mice, and the immunoreactivity to an anti-GDNF antibody in glial fibrillary acidic protein-positive cells was lower in imipramine-treated astrocytes from Egr-1(-/-) mice than in those from Egr-1(+/-) mice. To determine whether mitogen-activated protein kinases (MAPKs) were associated with imipramine-induced EGR-1 expression, we examined the induction of MAPK phosphorylation in response to imipramine. Pretreatment of rat primary astrocytes with the MAPK kinase inhibitor U0126 or the JNK inhibitor SP600125 strongly inhibited imipramine-stimulated EGR-1 expression. In conclusion, we found that imipramine induction of EGR-1 upregulated GDNF in astrocytes in a dose-dependent manner. This upregulation may occur through the MEK/ERK and JNK MAPK pathways, which suggests a new therapeutic mechanism of action for depressive disorders.

Generation of a model of L-DOPA-induced dyskinesia in two different mouse strains

Prolonged use of the dopamine precursor L-DOPA for the treatment of Parkinson's disease commonly results in abnormal involuntary movements, which are termed L-DOPA-induced dyskinesia (LID). Over-activity at corticostriatal synapses onto neurons of the direct and indirect striatal output pathways has been implicated in the development of dyskinesia, but it has proved difficult to investigate the pathways separately due to their morphological similarities. The recent development of bacterial artificial chromosome mice that express green fluorescent protein in either the direct or indirect pathway allows visual identification of the output neurons in each pathway. Here we describe the use of two different strains of these transgenic mice (pure FVB and FVB crossed with C57BL6) in the development of mouse models of L-DOPA-induced dyskinesia. This model will allow the direct and indirect pathways to be studied individually to delineate the cellular and molecular mechanisms underlying dyskinesias. These studies demonstrate that mouse strain impacts on behavioural responses and L-DOPA sensitivity. Therefore, when generating mouse models of LID, strain must be taken into consideration when choosing the L-DOPA dosing regimen.

Transcriptional regulation of UCP4 by NF-kappaB and its role in mediating protection against MPP+ toxicity

Mitochondrial uncoupling protein-4 (UCP4) enhances neuronal cell survival in MPP(+)-induced toxicity by suppressing oxidative stress and preserving intracellular ATP and mitochondrial membrane potential. UCP4 expression is increased by MPP(+), but its regulation is unknown. Using serial human UCP4 promoter-luciferase reporter gene constructs, we identified and characterized several cis-acting elements that can regulate UCP4 expression. Core promoter activity exists within 100 bp upstream of the transcription initiation site (TIS=+1). Both CAAT box (-33/-27) and Sp1 (-62/-49) elements are crucial and act synergistically in its transcription. We identified a NF-kappaB putative binding site at -507/-495. Mutation of this site significantly decreased UCP4 promoter activity. Activation of NF-kappaB by TNFalpha or cycloheximide increased, whereas its inhibition by 4-hydroxy-2-nonenal or transfection of pIkappaBalphaM suppressed, UCP4 promoter activity. NF-kappaB inhibition significantly suppressed the MPP(+)-induced increase in UCP4 expression. MPP(+) increased specific binding of NF-kappaB protein complexes to this site in electrophoretic mobility shift assay. Both UCP4 knockdown and NF-kappaB inhibition exacerbated MPP(+)-induced cell death. We present the first direct evidence that UCP4 is regulated by NF-kappaB, mediated via a functional NF-kappaB site in its promoter region, and that UCP4 has a significant role in NF-kappaB prosurvival signaling, mediating its protection against MPP(+) toxicity.

Neurotrophic and neurorescue effects of Echinacoside in the subacute MPTP mouse model of Parkinson's disease

Many experiments support the notion that augmentation of neurotrophic factors' (NTFs) activity, especially glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) could prevent or halt the progress of neurodegeneration in Parkinson's disease (PD). However, application of NTFs as therapeutic agents for PD is hampered by the difficulty in delivering them to specific brain regions safely and effectively. Another potential strategy is to stimulate the endogenous expression of NTFs. In this study, we investigated the effects of Echinacoside (ECH), a monomer extracted from herbs, on rescuing dopaminergic function in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-lesioned mice. We found that oral administration of ECH (30 mg/kg/day for 14 days) to MPTP-treated mice, commencing after impairment of the nigrstriatal system, suppressed the reduction of nigral dopaminergic neurons, striatal fibers, dopamine and dopamine transporter to 134.24%, 203.17%, 147.25% and 154.72 of MPTP-lesioned animals respectively (p<0.05). There was a relative elevation in expression of GDNF and BDNF mRNA (2.94 and 3.75-fold) and protein (184.34% and 185.93%) in ECH treated mice compared with vehicle-treated MPTP-lesioned mice (p<0.05). In addition, the apoptosis cells and Bax/Bcl-2 ratio of mRNA and protein in MPTP-lesioned mice significantly increased, and these effects could be prevented by ECH. At the 7th and 14th days of ECH treatment, the gait disorder displayed obvious improvement (p<0.05). These findings demonstrate that ECH is probably a novel, orally active, non-peptide inducer of NTFs and inhibitor of apoptosis, and they provide preclinical support for therapeutic potential of this compound in the treatment of PD.

Catalpol attenuates MPTP induced neuronal degeneration of nigral-striatal dopaminergic pathway in mice through elevating glial cell derived neurotrophic factor in striatum

The protective effect of an iridoid catalpol extracted and purified from the traditional Chinese medicinal herb Rehmannia glutinosa on the neuronal degeneration of nigral-striatal dopaminergic pathway was studied in a chronic 1-methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP)/probenecid C57BL/6 mouse model and in 1-methyl-4-phenylpyridimium (MPP(+)) intoxicated cultured mesencephalic neurons. Rotarod performance revealed that the locomotor ability of mice was significantly impaired after completion of model production and maintained thereafter for at least 4 weeks. Catalpol orally administered for 8 weeks (starting from the second week of model production) dose dependently improved the locomotor ability. HPLC revealed that catalpol significantly elevated striatal dopamine levels without changing the metabolite/dopamine ratios. Nor did it bind to dopamine receptors. Therefore it is unlikely that catalpol resembles any of the known compounds for treating Parkinsonism. Instead, catalpol dose dependently raised the tyrosine hydroxylase (TH) neuron number in substantia nigra pars compacta (SNpc), the striatal dopamine transporter (DAT) density and the striatal glial cell derived neurotrophic factor (GDNF) protein level. Linear regression revealed that both the TH neuron number and DAT density were positively correlated to the GDNF level. In the cultured mesencephalic neurons, MPP(+) decreased the dopaminergic neuron number and shortened the neurite length, whereas catalpol showed protective effect dose dependently. Furthermore, the expression of GDNF mRNA was up-regulated by catalpol to a peak nearly double of normal control in neurons intoxicated with MPP(+) for 24 h but not in normal neurons. The GDNF receptor tyrosine kinase RET inhibitor 4-amino-5-(4-methyphenyl)-7-(t-butyl)-pyrazolo-[3,4-d]pyrimidine (PP1) abolished the protective effect of catalpol either partially (TH positive neuron number) or completely (neurite length). Taken together, catalpol improves locomotor ability by attenuating the neuronal degeneration of nigral-striatal dopaminergic pathway, and this attenuation is at least partially through elevating the striatal GDNF expression.

Regulation of brain-derived neurotrophic factor (BDNF) and cerebral dopamine neurotrophic factor (CDNF) by anti-parkinsonian drug therapy in vivo

Available treatment for Parkinson's disease (PD) is mainly symptomatic instead of halting or reversing degenerative processes affecting the disease. Research on the molecular pathogenesis of PD has suggested reduced trophic support as a possible cause or mediator of neurodegeneration. In animal models of the disease, neurotrophic factors prevent neurodegeneration and induce behavioral recovery. Some anti-Parkinsonian drugs show neuroprotective activity, but it is not known whether the drug-induced neuroprotection is mediated by neurotrophic factors. In this study, we have investigated the influence of two neuroprotective anti-Parkinsonian drugs, the monoamine oxidase B inhibitor selegiline and the adenosine A(2A) antagonist SCH 58261, on the levels of brain-derived neurotrophic factor (BDNF) and cerebral dopamine neurotrophic factor (CDNF) in the mouse brain. Protein levels of BDNF and CDNF were quantified by western blot after 2 weeks of treatment with either of the drugs or placebo. CDNF levels were not significantly influenced by selegiline or SCH 58261 in any brain area studied. Selegiline treatment significantly increased BDNF levels in the anterior cingulate cortex (1.55 +/- 0.22, P < 0.05, Student's t-test). In the striatum, selegiline increased BDNF content by 32%, but this change did not reach statistical significance (1.32 +/- 0.15, P < 0.13, Student's t-test). Our data suggest that neurotrophic factors, particularly BDNF may play a role in the neuroprotective effects of selegiline, but do not support the hypothesis that anti-Parkinsonian drugs would work by increasing the levels of CDNF in brain.