Immunological features of alpha-synuclein in Parkinson's disease

Emerging roles of microglial activation and non-motor symptoms in Parkinson's disease

Recent data has indicated that the traditional view of Parkinson's disease (PD) as an isolated disorder of the nigrostriatal dopaminergic system alone is an oversimplification of its complex symptomatology. Aside from classical motor deficits, various non-motor symptoms including autonomic dysfunction, sensory and cognitive impairments as well as neuropsychiatric alterations and sleep disturbances are common in PD. Some of these non-motor symptoms can even antedate the motor problems. Many of them are associated with extranigral neuropathological changes, such as extensive α-synuclein pathology and also neuroinflammatory responses in specific brain regions, i.e. microglial activation, which has been implicated in several aspects of PD pathogenesis and progression. However, microglia do not represent a uniform population, but comprise a diverse group of cells with brain region-specific phenotypes that can exert beneficial or detrimental effects, depending on the local phenotype and context. Understanding how microglia can be neuroprotective in one brain region, while promoting neurotoxicity in another, will improve our understanding of the role of microglia in neurodegeneration in general, and of their role in PD pathology in particular. Since neuroinflammatory responses are in principle modifiable, such approaches could help to identify new targets or adjunctive therapies for the full spectrum of PD-related symptoms.

Proteolytic cleavage of extracellular α-synuclein by plasmin: implications for Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disease characterized by a progressive dopaminergic neuronal loss in association with Lewy body inclusions. Gathering evidence indicates that α-synuclein (α-syn), a major component of the Lewy body, plays an important role in the pathogenesis of PD. Although α-syn is considered to be a cytoplasmic protein, it has been detected in extracellular biological fluids, including human cerebrospinal fluid and blood plasma of healthy and diseased individuals. In addition, a prion-like spread of α-syn aggregates has been recently proposed to contribute to the propagation of Lewy bodies throughout the nervous system during progression of PD, suggesting that the metabolism of extracellular α-syn might play a key role in the pathogenesis of PD. In the present study, we found that plasmin cleaved and degraded extracellular α-syn specifically in a dose- and time- dependent manner. Aggregated forms of α-syn as well as monomeric α-syn were also cleaved by plasmin. Plasmin cleaved mainly the N-terminal region of α-syn and also inhibited the translocation of extracellular α-syn into the neighboring cells in addition to the activation of microglia and astrocytes by extracellular α-syn. Further, extracellular α-syn regulated the plasmin system through up-regulation of plasminogen activator inhibitor-1 (PAI-1) expression. These findings help to understand the molecular mechanism of PD and develop new therapeutic targets for PD.

The nitric oxide-cyclic GMP pathway regulates FoxO and alters dopaminergic neuron survival in Drosophila

Activation of the forkhead box transcription factor FoxO is suggested to be involved in dopaminergic (DA) neurodegeneration in a Drosophila model of Parkinson's disease (PD), in which a PD gene product LRRK2 activates FoxO through phosphorylation. In the current study that combines Drosophila genetics and biochemical analysis, we show that cyclic guanosine monophosphate (cGMP)-dependent kinase II (cGKII) also phosphorylates FoxO at the same residue as LRRK2, and Drosophila orthologues of cGKII and LRRK2, DG2/For and dLRRK, respectively, enhance the neurotoxic activity of FoxO in an additive manner. Biochemical assays using mammalian cGKII and FoxO1 reveal that cGKII enhances the transcriptional activity of FoxO1 through phosphorylation of the FoxO1 S319 site in the same manner as LRRK2. A Drosophila FoxO mutant resistant to phosphorylation by DG2 and dLRRK (dFoxO S259A corresponding to human FoxO1 S319A) suppressed the neurotoxicity and improved motor dysfunction caused by co-expression of FoxO and DG2. Nitric oxide synthase (NOS) and soluble guanylyl cyclase (sGC) also increased FoxO's activity, whereas the administration of a NOS inhibitor L-NAME suppressed the loss of DA neurons in aged flies co-expressing FoxO and DG2. These results strongly suggest that the NO-FoxO axis contributes to DA neurodegeneration in LRRK2-linked PD.

Inflammation in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease that is characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Inflammatory responses manifested by glial reactions, T cell infiltration, and increased expression of inflammatory cytokines, as well as other toxic mediators derived from activated glial cells, are currently recognized as prominent features of PD. The consistent findings obtained by various animal models of PD suggest that neuroinflammation is an important contributor to the pathogenesis of the disease and may further propel the progressive loss of nigral dopaminergic neurons. Furthermore, although it may not be the primary cause of PD, additional epidemiological, genetic, pharmacological, and imaging evidence support the proposal that inflammatory processes in this specific brain region are crucial for disease progression. Recent in vitro studies, however, have suggested that activation of microglia and subsequently astrocytes via mediators released by injured dopaminergic neurons is involved. However, additional in vivo experiments are needed for a deeper understanding of the mechanisms involved in PD pathogenesis. Further insight on the mechanisms of inflammation in PD will help to further develop alternative therapeutic strategies that will specifically and temporally target inflammatory processes without abrogating the potential benefits derived by neuroinflammation, such as tissue restoration.

The role of α-synuclein in neurodegeneration — An update

Genetic, neuropathological and biochemical evidence implicates α-synuclein, a 140 amino acid presynaptic neuronal protein, in the pathogenesis of Parkinson’s disease and other neurodegenerative disorders. The aggregated protein inclusions mainly containing aberrant α-synuclein are widely accepted as morphological hallmarks of α-synucleinopathies, but their composition and location vary between disorders along with neuronal networks affected. α-Synuclein exists physiologically in both soluble and membran-bound states, in unstructured and α-helical conformations, respectively, while posttranslational modifications due to proteostatic deficits are involved in β-pleated aggregation resulting in formation of typical inclusions. The physiological function of α-synuclein and its role linked to neurodegeneration, however, are incompletely understood. Soluble oligomeric, not fully fibrillar α-synuclein is thought to be neurotoxic, main targets might be the synapse, axons and glia. The effects of aberrant α-synuclein include alterations of calcium homeostasis, mitochondrial dysfunction, oxidative and nitric injuries, cytoskeletal effects, and neuroinflammation. Proteasomal dysfunction might be a common mechanism in the pathogenesis of neuronal degeneration in α-synucleinopathies. However, how α-synuclein induces neurodegeneration remains elusive as its physiological function. Genome wide association studies demonstrated the important role for genetic variants of the SNCA gene encoding α-synuclein in the etiology of Parkinson’s disease, possibly through effects on oxidation, mitochondria, autophagy, and lysosomal function. The neuropathology of synucleinopathies and the role of α-synuclein as a potential biomarker are briefly summarized. Although animal models provided new insights into the pathogenesis of Parkinson disease and multiple system atrophy, most of them do not adequately reproduce the cardinal features of these disorders. Emerging evidence, in addition to synergistic interactions of α-synuclein with various pathogenic proteins, suggests that prionlike induction and seeding of α-synuclein could lead to the spread of the pathology and disease progression. Intervention in the early aggregation pathway, aberrant cellular effects, or secretion of α-synuclein might be targets for neuroprotection and disease-modifying therapy.

Microglial cell origin and phenotypes in health and disease

Microglia - resident myeloid-lineage cells in the brain and the spinal cord parenchyma - function in the maintenance of normal tissue homeostasis. Microglia also act as sentinels of infection and injury, and participate in both innate and adaptive immune responses in the central nervous system. Microglia can become activated and/or dysregulated in the context of neurodegenerative disease and cancer, and thereby contribute to disease severity. Here, we discuss recent studies that provide new insights into the origin and phenotypes of microglia in health and disease.

The role of immunity in Huntington's disease

Huntington's disease (HD) is a devastating and incurable neurodegenerative disorder characterized by progressive cognitive, psychiatric and motor impairments. Although the disease has been seen as a disorder purely of the brain, there is now emerging evidence that abnormalities outside the central nervous system are commonly seen in HD. Indeed, the mutant huntingtin (mHtt) coded for by the abnormal gene in HD is found in every cell type where its presence has been sought. In particular, there are a number of recent observations in HD patients that mHtt interacts with the immune system with accumulating evidence that changes in the immune system may critically contribute to the pathology of HD. However, the nature of this contribution remains unclear, to the extent that it is not even known whether the immune system has a beneficial or detrimental role in HD patients. In this review, we attempt to bring a novel understanding to the interaction of the immune system to HD pathology, thereby shedding light on its potential pathogenic role. As part of this discussion, we revisit the clinical data on the anti-inflammatory drug trials in HD and propose new experimental approaches to interrogate the role of immunity in this currently incurable disorder.

Inflammation in the early stages of neurodegenerative pathology

Inflammation is secondary to protein accumulation in neurodegenerative diseases, including Alzheimer's, Parkinson's and Amyotrophic Lateral Sclerosis. Emerging evidence indicate sustained inflammatory responses, involving microglia and astrocytes in animal models of neurodegeneration. It is unknown whether inflammation is beneficial or detrimental to disease progression and how inflammatory responses are induced within the CNS. Persistence of an inflammatory stimulus or failure to resolve sustained inflammation can result in pathology, thus, mechanisms that counteract inflammation are indispensable. Here we review studies on inflammation mediated by innate and adaptive immunity in the early stages of neurodegeneration and highlight important areas for future investigation.

Environmental neurotoxic pesticide dieldrin activates a non receptor tyrosine kinase to promote PKCδ-mediated dopaminergic apoptosis in a dopaminergic neuronal cell model

Oxidative stress and apoptosis are two key pathophysiological mechanisms underlying dopaminergic degeneration in Parkinson's disease (PD). Recently, we identified that proteolytic activation of protein kinase C-delta (PKCδ), a member of the novel PKC family, contributes to oxidative stress-induced dopaminergic degeneration and that phosphorylation of tyrosine residue 311 (tyr311) on PKCδ is a key event preceding the PKCδ proteolytic activation during oxidative damage. Herein, we report that a non-receptor tyrosine kinase Fyn is significantly expressed in a dopaminergic neuronal N27 cell model. Exposure of N27 cells to the dopaminergic toxicant dieldrin (60 μM) rapidly activated Fyn kinase, PKCδ-tyr311 phosphorylation and proteolytic cleavage. Fyn kinase activation precedes the caspase-3-mediated proteolytic activation of PKCδ. Pre-treatment with p60-tyrosine-specific kinase inhibitor (TSKI) almost completely attenuated dieldrin-induced phosphorylation of PKCδ-tyr311 and its proteolytic activation. Additionally, TSKI almost completely blocked dieldrin-induced apoptotic cell death. To further confirm Fyn's role in the pro-apoptotic function of PKCδ, we adopted the RNAi approach. siRNA-mediated knockdown of Fyn kinase also effectively attenuated dieldrin-induced phosphorylation of PKCδ-tyr311, caspase-3-mediated PKCδ proteolytic cleavage, and DNA fragmentation, suggesting that Fyn kinase regulates the pro-apoptotic function of PKCδ. Collectively, these results demonstrate for the first time that Fyn kinase is a pro-apoptotic kinase that regulates upstream signaling of the PKCδ-mediated apoptotic cell death pathway in neurotoxicity models of pesticide exposure.

Neuroprotective effect of oral S/B remedy (Scutellaria baicalensis Georgi and Bupleurum scorzonerifolfium Willd) on iron-induced neurodegeneration in the nigrostriatal dopaminergic system of rat brain

AIM OF THE STUDY

S/B remedy prepared from Scutellaria baicalensis Georgi and Bupleurum scorzonerifolfium Willd, two herbals of Xiao-Tsai-Hu-Tang or Sho-Saiko-To (TJ-9), contains active flavonoids. In this study, the protective effect of S/B remedy on iron-induced neurodegeneration was investigated in the nigrostriatal dopaminergic system of rat brain.

MATERIALS AND METHODS

The antioxidative activity of S/B remedy was studied using brain homogenates incubated with ferrous citrate (iron, 1M), S/B remedy, Trolox and melatonin. Furthermore, a Parkinsonian animal model by an intranigral infusion of iron in the anesthetized rats was employed to investigate the protective effect of S/B remedy in the nigrostriatal dopaminergic system.

RESULTS

Our in vitro studies showed that S/B remedy was more potent than melatonin and equal to trolox in inhibiting iron-induced lipid peroxidation of brain homogenates. Our in vivo studies found that oral administration of S/B remedy dose-dependently attenuated iron-elevated lipid peroxidation in the infused substantia nigra (SN) and iron-depleted dopamine levels in the ipsilateral striatum. Furthermore, iron-induced reductions in glutathione (GSH) content and increases in GSSG (oxidized GSH)/GSH ratio in the infused SN were inhibited in S/B remedy-treated rats. Systemic S/B remedy attenuated the iron-induced increases in heme-oxygenase-1 levels and α-synuclein aggregation in the infused SN. Moreover, S/B remedy reduced iron-induced apoptosis via attenuating mitochondrial and endoplasmic reticulum stress. In addition, S/B remedy was anti-inflammatory as indicated by the attenuation of iron-induced elevations in inducible nitric oxide synthase and cyclo-oxygenase II levels as well as glial fibrillary acidic protein (a biological marker of astrocytes) and ED-1 (a protein indicative of activated microglia) levels in the infused SN of S/B remedy-treated rats.

CONCLUSIONS

These findings suggest that oral administration of S/B remedy is protective against iron-induced neurodegeneration in the nigrostriatal dopaminergic system of rat brain. Therefore, S/B remedy may be therapeutically useful for the treatment of CNS neurodegenerative diseases.

Osteopontin polymorphic susceptibility factor for Parkinson's disease among patients with Gaucher disease

BACKGROUND

There is an increased incidence of Parkinson's disease among obligate carriers of the common glucocerebrosidase mutations, and among patients with Parkinson disease there is an increased number who are carriers of glucocerebrosidase mutations. A Gaucher mutation is considered a susceptibility factor for Parkinson's disease. Osteopontin single-nucleotide polymorphism-66 is associated with Lewy body disease and considered a susceptibility factor. The aim of this study was to ascertain whether Gaucher patients with parkinsonism carry the osteopontin single-nucleotide polymorphism-66 polymorphic genotype TT to a greater extent than other Gaucher patients.

METHODS

Seventy adult patients with at least 1 allele having the common N370S Gaucher mutation including 10 patients with Parkinson's disease were included.

RESULTS

There was no statistically significant difference in incidence of the TT genotype in patients with clinically symptomatic Parkinson's disease (88.9%) and other Gaucher patients (72.1%).

CONCLUSIONS

This may partly explain the increased incidence of Parkinson's disease associated with Gaucher mutations.

Anti-inflammatory effects of pioglitazone on iron-induced oxidative injury in the nigrostriatal dopaminergic system

AIMS

Transition metals, oxidative stress and neuroinflammation have been proposed as part of a vicious cycle in central nervous system neurodegeneration. Our aim was to study the anti-inflammatory effect of pioglitazone, a peroxisome proliferative activated receptor-γ agonist, on iron-induced oxidative injury in rat brain.

METHODS

Intranigral infusion of ferrous citrate (iron) was performed on anaesthetized rats. Pioglitazone (20 mg/kg) was orally administered. Oxidative injury was investigated by measuring lipid peroxidation in the substantia nigra (SN) and dopamine content in the striatum. Western blot assay and DNA fragmentation were employed to study the involvement of α-synuclein aggregation, neuroinflammation as well as activation of endoplasmic reticulum (ER) and mitochondrial pathways in iron-induced apoptosis.

RESULTS

Intranigral infusion of iron time-dependently increased α-synuclein aggregation and haem oxygenase-1 levels. Furthermore, apoptosis was demonstrated by TUNEL-positive cells and DNA fragmentation in the iron-infused SN. Systemic pioglitazone was found to potentiate iron-induced elevation in nuclear peroxisome proliferative activated receptor-γ levels. However, pioglitazone inhibited iron-induced α-synuclein aggregation, elevations in interleukin-1β and interleukin-6 mRNA levels as well as increases in oxygenase-1, cyclo-oxygenase II, nitric oxide synthase and ED-1 protein levels, an indicator of activated microglia. Moreover, iron-induced DNA laddering as well as activation of ER and mitochondrial pathways were attenuated by pioglitazone. In addition, pioglitazone decreased iron-induced elevation in lipid peroxidation in the infused SN and depletion in striatal dopamine level.

CONCLUSIONS

Our results suggest that pioglitazone prevents iron-induced apoptosis via both ER and mitochondrial pathways. Furthermore, inhibition of α-synuclein aggregation and neuroinflammation may contribute to the pioglitazone-induced neuroprotection in central nervous system.

Prenatal LPS increases inflammation in the substantia nigra of Gdnf heterozygous mice

Prenatal systemic inflammation has been implicated in neurological diseases, but optimal animal models have not been developed. We investigated whether a partial genetic deletion of glial cell line-derived neurotrophic factor (Gdnf(+/-)) increased vulnerability of dopamine (DA) neurons to prenatal lipopolysaccharide (LPS). LPS [0.01 mg/kg intraperitoneal (i.p.)] or saline was administered to wild-type (WT) or Gdnf(+/-) pregnant mice on gestational day 9.5. Male offspring were examined at 3 weeks, 3 and 12 months of age. There was a progressive degeneration of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (SN) with age in Gdnf(+/-) but not in WT mice, with no observed effects on locus coeruleus (LC) noradrenergic neurons or DA neurons of the ventral tegmental area. Inflammatory markers were elevated in SN of LPS treated offspring, with exacerbation in Gdnf(+/-) mice. Intracellular accumulation of α-synuclein (α-syn) immunoreactivity in DA neurons of SN was observed in all groups of Gdnf(+/-) and in WT mice with prenatal LPS, with altered distribution between pars reticulata (pr) and pars compacta (pc). The findings suggest that prenatal LPS leads to accelerated neuropathology in the SN with age, and that a partial loss of GDNF exacerbates these effects, providing a novel model for age-related neuropathology of the nigrostriatal DA system.

CSF from Parkinson disease patients differentially affects cultured microglia and astrocytes

BACKGROUND

Excessive and abnormal accumulation of alpha-synuclein (α-synuclein) is a factor contributing to pathogenic cell death in Parkinson's disease. The purpose of this study, based on earlier observations of Parkinson's disease cerebrospinal fluid (PD-CSF) initiated cell death, was to determine the effects of CSF from PD patients on the functionally different microglia and astrocyte glial cell lines. Microglia cells from human glioblastoma and astrocytes from fetal brain tissue were cultured, grown to confluence, treated with fixed concentrations of PD-CSF, non-PD disease control CSF, or control no-CSF medium, then photographed and fluorescently probed for α-synuclein content by deconvolution fluorescence microscopy. Outcome measures included manually counted cell growth patterns from day 1-8; α-synuclein density and distribution by antibody tagged 3D model stacked deconvoluted fluorescent imaging.

RESULTS

After PD-CSF treatment, microglia growth was reduced extensively, and a non-confluent pattern with morphological changes developed, that was not evident in disease control CSF and no-CSF treated cultures. Astrocyte growth rates were similarly reduced by exposure to PD-CSF, but morphological changes were not consistently noted. PD-CSF treated microglia showed a significant increase in α-synuclein content by day 4 compared to other treatments (p ≤ 0.02). In microglia only, α-synuclein aggregated and redistributed to peri-nuclear locations.

CONCLUSIONS

Cultured microglia and astrocytes are differentially affected by PD-CSF exposure compared to non-PD-CSF controls. PD-CSF dramatically impacts microglia cell growth, morphology, and α-synuclein deposition compared to astrocytes, supporting the hypothesis of cell specific susceptibility to PD-CSF toxicity.

Polyphenolic compounds for treating neurodegenerative disorders involving protein misfolding

A diverse group of neurodegenerative diseases are characterized by progressive, age-dependent intracellular formation of misfolded protein aggregates. These include Alzheimer's disease, Huntington's disease, Parkinson's disease and a number of tau-mediated disorders. There is no effective treatment for any of these disorders; currently approved interventions are designed to treat disease symptoms and generally lead to modest modulation of clinical symptoms. None are known to mitigate underlying neuropathologic mechanisms and, thus, it is not unexpected that existing treatments appear ineffective in modulating disease progression. We note that these neurodegenerative disorders all share a common mechanistic theme in that depositions of misfolded protein in the brain is a key molecular feature underlying disease onset and/or progression. While previous studies have identified a number of drugs and nutraceuticals capable of interfering with the formation and/or stability of misfolded protein aggregates, none have been demonstrated to be effective in vivo for treating any of the neurodegenerative disorders. We hereby review accumulating evidence that a select nutraceutical grape-seed polyphenolic extract (GSPE) is effective in vitro and in vivo in mitigating certain misfolded protein-mediated neuropathologic and clinical phenotypes. We will also review evidence implicating bioavailability of GSPE components in the brain and the tolerability as well as safety of GSPE in animal models and in humans. Collectively, available information supports continued development of the GSPE for treating a variety of neurodegenerative disorders involving misfolded protein-mediated neuropathologic mechanisms.

Glial innate immunity generated by non-aggregated alpha-synuclein in mouse: differences between wild-type and Parkinson's disease-linked mutants

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized pathologically by the presence in the brain of intracellular protein inclusions highly enriched in aggregated alpha-synuclein (α-Syn). Although it has been established that progression of the disease is accompanied by sustained activation of microglia, the underlying molecules and factors involved in these immune-triggered mechanisms remain largely unexplored. Lately, accumulating evidence has shown the presence of extracellular α-Syn both in its aggregated and monomeric forms in cerebrospinal fluid and blood plasma. However, the effect of extracellular α-Syn on cellular activation and immune mediators, as well as the impact of familial PD-linked α-Syn mutants on this stimulation, are still largely unknown.

METHODS AND FINDINGS

In this work, we have compared the activation profiles of non-aggregated, extracellular wild-type and PD-linked mutant α-Syn variants on primary glial and microglial cell cultures. After stimulation of cells with α-Syn, we measured the release of Th1- and Th2- type cytokines as well as IP-10/CXCL10, RANTES/CCL5, MCP-1/CCL2 and MIP-1α/CCL3 chemokines. Contrary to what had been observed using cell lines or for the case of aggregated α-Syn, we found strong differences in the immune response generated by wild-type α-Syn and the familial PD mutants (A30P, E46K and A53T).

CONCLUSIONS

These findings might contribute to explain the differences in the onset and progression of this highly debilitating disease, which could be of value in the development of rational approaches towards effective control of immune responses that are associated with PD.

Granulocyte-colony stimulating factor (G-CSF) enhances recovery in mouse model of Parkinson's disease

INTRODUCTION

Granulocyte-colony stimulating factor (G-CSF) is used routinely in clinical practice for the treatment of neutropenia and to increase generation of hematopoietic stem cells in bone marrow donors. A growing body of literature on the neurotrophic effects of G-CSF has led to clinical trials in stroke, Alzheimer's disease (AD) and Parkinson's disease (PD).

OBJECTIVES

The primary objective of this study was to determine if G-CSF administration would rescue the nigro-striatal system and restore locomotor function after completion of a sub-acute course of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration (30mg/kg i.p. for 5 days) in 12 month-old mice. A secondary aim was to determine if G-CSF affects the neuro-inflammatory response by modulating microglial activation in striatum and midbrain.

RESULTS

MPTP-treated mice were impaired on the rotometer test after the last dose of the toxicant and remained impaired until euthanasia. MPTP-treated mice that were given an 8-day regimen of G-CSF starting 2 days after the last dose of toxicant enhanced motor performance compared to the MPTP alone group. MPTP treatment depleted striatal DA (DA) levels; G-CSF given after MPTP resulted in a partial, significant repletion of DA levels. Total microglial burden in the striatum was increased significantly in MPTP-treated mice and was reduced after G-CSF rescue.

CONCLUSION

G-CSF enhances recovery of DA nigro-striatal function from MPTP toxicity in part by modulating the microglial response to injury. The G-CSF receptor may provide a novel target for modifying the disease process in Parkinson's disease.

Development of a grape seed polyphenolic extract with anti-oligomeric activity as a novel treatment in progressive supranuclear palsy and other tauopathies

A diverse group of neurodegenerative diseases - including progressive supranuclear palsy (PSP), corticobasal degeneration and Alzheimer's disease among others, collectively referred to as tauopathies - are characterized by progressive, age-dependent intracellular formations of misfolded protein aggregates that play key roles in the initiation and progression of neuropathogenesis. Recent studies from our laboratory reveal that grape seed-derived polyphenolic extracts (GSPE) potently prevent tau fibrillization into neurotoxic aggregates and therapeutically promote the dissociation of preformed tau aggregates [J. Alzheimer's Dis. (2009) vol. 16, pp. 433]. Based on our extensive bioavailability, bioactivity and functional preclinical studies, combined with the safety of GSPE in laboratory animals and in humans, we initiated a series of studies exploring the role of GSPE (Meganatural-Az(®) GSPE) as a potential novel botanical drug for the treatment of certain forms of tauopathies including PSP, a neurodegenerative disorder involving the accumulation and deposition of misfolded tau proteins in the brain characterized, in part, by abnormal intracellular tau inclusions in specific anatomical areas involving astrocytes, oligodendrocytes and neurons [J. Neuropathol. Exp. Neurol. (2002) vol. 61, pp. 33]. In this mini-review article, we discuss the biochemical characterization of GSPE in our laboratory and its potential preventative and therapeutic role in model systems of abnormal tau processing pertinent to PSP and related tauopathies.

Mechanisms underlying inflammation in neurodegeneration

Inflammation is associated with many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. In this Review, we discuss inducers, sensors, transducers, and effectors of neuroinflammation that contribute to neuronal dysfunction and death. Although inducers of inflammation may be generated in a disease-specific manner, there is evidence for a remarkable convergence in the mechanisms responsible for the sensing, transduction, and amplification of inflammatory processes that result in the production of neurotoxic mediators. A major unanswered question is whether pharmacological inhibition of inflammation pathways will be able to safely reverse or slow the course of disease.

Neurodegenerative disorders and nanoformulated drug development

Degenerative and inflammatory diseases of the CNS include, but are not limited to, Alzheimer's and Parkinson's disease, amyotrophic lateral sclerosis, stroke, multiple sclerosis and HIV-1-associated neurocognitive disorders. These are common, debilitating and, unfortunately, hold few therapeutic options. In recent years, the application of nanotechnologies as commonly used or developing medicines has served to improve pharmacokinetics and drug delivery specifically to CNS-diseased areas. In addition, nanomedical advances are leading to therapies that target CNS pathobiology and as such, can interrupt disordered protein aggregation, deliver functional neuroprotective proteins and alter the oxidant state of affected neural tissues. This article focuses on the pathobiology of common neurodegenerative disorders with a view towards how nanomedicine may be used to improve the clinical course of neurodegenerative disorders.

Analysis of protein levels of 24 cytokines in scrapie agent-infected brain and glial cell cultures from mice differing in prion protein expression levels

Activation of microglia and astroglia is seen in many neurodegenerative diseases including prion diseases. Activated glial cells produce cytokines as a protective response against certain pathogens and as part of the host inflammatory response to brain damage. In addition, cytokines might also exacerbate tissue damage initiated by other processes. In the present work using multiplex assays to analyze protein levels of 24 cytokines in scrapie agent-infected C57BL/10 mouse brains, we observed elevation of CCL2, CCL5, CXCL1, CXCL10, granulocyte-macrophage colony-stimulating factor (GM-CSF), gamma interferon (IFN-gamma), interleukin 1alpha (IL-1alpha), IL-1beta, IL-6, and IL-12p40. Scrapie agent-infected wild-type mice and transgenic mice expressing anchorless prion protein (PrP) had similar cytokine responses in spite of extensive differences in neuropathology. Therefore, these responses may be primarily a reaction to brain damage induced by prion infection rather than specific inducers of a particular type of pathology. To study the roles of astroglia and microglia in these cytokine responses, primary glial cultures were exposed to scrapie agent-infected brain homogenates. Microglia produced only IL-12p40 and CXCL10, whereas astroglia produced these cytokines plus CCL2, CCL3, CCL5, CXCL1, G-CSF, IL-1beta, IL-6, IL-12p70, and IL-13. Glial cytokine responses from wild-type mice and transgenic mice expressing anchorless PrP differed only slightly, but glia from PrP-null mice produced only IL-12p40, indicating that PrP expression was required for scrapie agent induction of other cytokines detected. The difference in cytokine response between microglia and astroglia correlated with 20-fold-higher levels of PrP expression in astroglia versus microglia, suggesting that high-level PrP expression on astroglia might be important for induction of certain cytokines.

Amyloid formation by the pro-inflammatory S100A8/A9 proteins in the ageing prostate

Background

The conversion of soluble peptides and proteins into polymeric amyloid structures is a hallmark of many age-related degenerative disorders, including Alzheimer's disease, type II diabetes and a variety of systemic amyloidoses. We report here that amyloid formation is linked to another major age-related phenomenon − prostate tissue remodelling in middle-aged and elderly men.

Methodology/Principal Findings

By using multidisciplinary analysis of corpora amylacea inclusions in prostate glands of patients diagnosed with prostate cancer we have revealed that their major components are the amyloid forms of S100A8 and S100A9 proteins associated with numerous inflammatory conditions and types of cancer. In prostate protease rich environment the amyloids are stabilized by dystrophic calcification and lateral thickening. We have demonstrated that material closely resembling CA can be produced from S100A8/A9 in vitro under native and acidic conditions and shows the characters of amyloids. This process is facilitated by calcium or zinc, both of which are abundant in ex vivo inclusions. These observations were supported by computational analysis of the S100A8/A9 calcium-dependent aggregation propensity profiles. We found DNA and proteins from Escherichia coli in CA bodies, suggesting that their formation is likely to be associated with bacterial infection. CA inclusions were also accompanied by the activation of macrophages and by an increase in the concentration of S100A8/A9 in the surrounding tissues, indicating inflammatory reactions.

Conclusions/Significance

These findings, taken together, suggest a link between bacterial infection, inflammation and amyloid deposition of pro-inflammatory proteins S100A8/A9 in the prostate gland, such that a self-perpetuating cycle can be triggered and may increase the risk of malignancy in the ageing prostate. The results provide strong support for the prediction that the generic ability of polypeptide chains to convert into amyloids could lead to their involvement in an increasing number of otherwise apparently unrelated diseases, particularly those associated with ageing.

Dynamic changes in presynaptic and axonal transport proteins combined with striatal neuroinflammation precede dopaminergic neuronal loss in a rat model of AAV alpha-synucleinopathy

Little is known about key pathological events preceding overt neuronal degeneration in Parkinson's disease (PD) and alpha-synucleinopathy. Recombinant adeno-associated virus 2-mediated delivery of mutant (A53T) human alpha-synuclein into the substantia nigra (SN) under a neuron-specific synapsin promoter resulted in protracted neurodegeneration with significant dopaminergic (DA) neuron loss by 17 weeks. As early as 4 weeks, there was an increase in a dopamine metabolite, DOPAC and histologically, DA axons in the striatum were dystrophic with degenerative bulbs. Before neuronal loss, significant changes were identified in levels of proteins relevant to synaptic transmission and axonal transport in the striatum and the SN. For example, striatal levels of rabphilin 3A and syntaxin were reduced. Levels of anterograde transport motor proteins (KIF1A, KIF1B, KIF2A, and KIF3A) were decreased in the striatum, whereas retrograde motor proteins (dynein, dynamitin, and dynactin1) were increased. In contrast to reduced levels in the striatum, KIF1A and KIF2A levels were elevated in the SN. There were dramatic changes in cytoskeletal protein levels, with actin levels increased and alpha-/gamma-tubulin levels reduced. In addition to these alterations, a neuroinflammatory response was observed at 8 weeks in the striatum, but not in the SN, demonstrated by increased levels of Iba-1, activated microglia and increased levels of proinflammatory cytokines, including IL-1beta, IFN-gamma and TNF-alpha. These results demonstrate that changes in proteins relevant to synaptic transmission and axonal transport coupled with neuroinflammation, precede alpha-synuclein-mediated neuronal death. These findings can provide ideas for antecedent biomarkers and presymptomatic interventions in PD.