IFN-γ signaling, with the synergistic contribution of TNF-α, mediates cell specific microglial and astroglial activation in experimental models of Parkinson's disease

To through light on the mechanisms underlying the stimulation and persistence of glial cell activation in Parkinsonism, we investigate the function of IFN-γ and TNF-α in experimental models of Parkinson's disease and analyze their relation with local glial cell activation. It was found that IFN-γ and TNF-α remained higher over the years in the serum and CNS of chronic Parkinsonian macaques than in untreated animals, accompanied by sustained glial activation (microglia and astroglia) in the substantia nigra pars compacta. Importantly, Parkinsonian monkeys showed persistent and increasing levels of IFN-γR signaling in both microglial and astroglial cells. In addition, experiments performed in IFN-γ and TNF-α KO mice treated with MPTP revealed that, even before dopaminergic cell death can be observed, the presence of IFN-γ and TNF-α is crucial for microglial and astroglial activation, and, together, they have an important synergistic role. Both cytokines were necessary for the full level of activation to be attained in both microglial and astroglial cells. These results demonstrate that IFN-γ signaling, together with the contribution of TNF-α, have a critical and cell-specific role in stimulating and maintaining glial cell activation in Parkinsonism

Oxidation of DJ-1 Induced by 6-Hydroxydopamine Decreasing Intracellular Glutathione

DJ-1, the causative gene of a familial form of Parkinson's disease (PD), has been reported to undergo preferential oxidation of the cysteine residue at position 106 (Cys-106) under oxidative stress; however, details of the molecular mechanisms are not well known. In the present study, mechanisms of DJ-1 oxidation induced by 6-hydroxydopamine (6-OHDA) were investigated by using SH-SY5Y cells. The treatment of these cells with 6-OHDA caused an obvious acidic spot sift of DJ-1 due to its oxidation. However, when catalase, which is an hydrogen peroxide (H2O2)-removing enzyme, was added during the treatment, it failed to prevent the oxidation induced by 6-OHDA, suggesting that electrophilic p-quinone formed from 6-OHDA, but not H2O2, was responsible for the DJ-1 oxidation. Benzoquinone, another electrophilic p-quinone, also induced DJ-1 oxidation. The intracellular glutathione (GSH) levels were significantly decreased by 6-OHDA, irrespective of the presence or absence of catalase. The inhibition of GSH synthesis by buthionine sulfoximine resulted in a decrease in GSH levels and enhancement of DJ-1 oxidation. The pretreatment of cells with N-acetyl-cysteine prevented the loss of intracellular GSH and subsequently DJ-1 oxidation induced by 6-OHDA. Collectively, these results suggest that electrophilic p-quinone formed from 6-OHDA induces DJ-1 oxidation by decreasing intracellular GSH

Destruction of Dopaminergic Neurons in the Midbrain by 6-Hydroxydopamine Decreases Hippocampal Cell Proliferation in Rats: Reversal by Fluoxetine

Background Non-motor symptoms (e.g., depression, anxiety, and cognitive deficits) in patients with Parkinson disease (PD) precede the onset of the motor symptoms. Although these symptoms do not respond to pharmacological dopamine replacement therapy, their precise pathological mechanisms are currently unclear. The present study was undertaken to examine whether the unilateral 6-hydroxydopamine (6-OHDA) lesion to the substantia nigra pars compacta (SNc), which represents a model of long-term dopaminergic neurotoxicity, could affect cell proliferation in the adult rat brain. Furthermore, we examined the effects of the selective serotonin reuptake inhibitor (SSRI) fluoxetine and the selective noradrenaline reuptake inhibitor maprotiline on the reduction in cell proliferation in the subgranular zone (SGZ) by the unilateral 6-OHDA lesion. Methodology/Principal Findings A single unilateral injection of 6-OHDA into the rat SNc resulted in an almost complete loss of tyrosine hydroxylase (TH) immunoreactivity in the striatum and SNc, as well as in reductions of TH-positive cells and fibers in the ventral tegmental area (VTA). On the other hand, an injection of vehicle alone showed no overt change in TH immunoreactivity. A unilateral 6-OHDA lesion to SNc significantly decreased cell proliferation in the SGZ ipsilateral to the 6-OHDA lesion, but not in the contralateral SGZ or the subventricular zone (SVZ), of rats. Furthermore, subchronic (14 days) administration of fluoxetine (5 mg/kg/day), but not maprotiline significantly attenuated the reduction in cell proliferation in the SGZ by unilateral 6-OHDA lesion. Conclusions/Significance The present study suggests that cell proliferation in the SGZ of the dentate gyrus might be, in part, under dopaminergic control by SNc and VTA, and that subchronic administration of fluoxetine reversed the reduction in cell proliferation in the SGZ by 6-OHDA. Therefore, SSRIs such as fluoxetine might be potential therapeutic drugs for non-motor symptoms as well as motor symptoms in patients with PD, which might be associated with the reduction in cell proliferation in the SGZ

Modeling Parkinson’s Disease Using Induced Pluripotent Stem Cells

Our understanding of the underlying molecular mechanism of Parkinson’s disease (PD) is hampered by a lack of access to affected human dopaminergic (DA) neurons on which to base experimental research. Fortunately, the recent development of a PD disease model using induced pluripotent stem cells (iPSCs) provides access to cell types that were previously unobtainable in sufficient quantity or quality, and presents exciting promises for the elucidation of PD etiology and the development of potential therapeutics. To more effectively model PD, we generated two patient-derived iPSC lines: a line carrying a homozygous p.G2019S mutation in the leucine-rich repeat kinase 2 (LRRK2) gene and another carrying a full gene triplication of the α-synuclein encoding gene, SNCA. We demonstrated that these PD-linked pluripotent lines were able to differentiate into DA neurons and that these neurons exhibited increased expression of key oxidative stress response genes and α-synuclein protein. Moreover, when compared to wild-type DA neurons, LRRK2-G2019S iPSC-derived DA neurons were more sensitive to caspase-3 activation caused by exposure to hydrogen peroxide, MG-132, and 6-hydroxydopamine. In addition, SNCA-triplication iPSC-derived DA neurons formed early ubiquitin-positive puncta and were more sensitive to peak toxicity from hydrogen peroxide-induced stress. These aforementioned findings suggest that LRRK2-G2019S and SNCA-triplication iPSC-derived DA neurons exhibit early phenotypes linked to PD. Given the high penetrance of the homozygous LRRK2 mutation, the expression of wild-type α-synuclein protein in the SNCA-triplication line, and the clinical resemblance of patients afflicted with these familial disorders to sporadic PD patients, these iPSC-derived neurons may be unique and valuable models for disease diagnostics and development of novel pharmacological agents for alleviation of relevant disease phenotypes

Loss of thalamic serotonin transporters in early drug-naïve Parkinson’s disease patients is associated with tremor: an [123I]β-CIT SPECT study

In vitro studies revealed serotonin transporter (5-HTT) decline in Parkinson’s disease (PD). Yet, few studies investigated thalamic 5-HTT in vivo and its effect on PD heterogeneity. We analyzed thalamic [123I]β-CIT binding (mainly reflecting 5-HTT binding) in 32 drug-naïve PD patients and 13 controls with SPECT. Twenty-six patients were examined twice (17 months apart). Based on UPDRS scores, we identified subgroups of patients with moderate/severe tremor (PDT) and without tremor (PDWT) at the time of clinical diagnosis. Additionally, depressive symptoms were evaluated using the Beck Depression Inventory (BDI) at baseline. Mean thalamic specific to non-specific [123I]β-CIT binding ratio was lower in patients when compared to controls, and further decreased during follow-up. At baseline, average thalamic ratio was significantly lower in the PDT than in the PDWT subgroup. No correlation was found between BDI scores and thalamic binding ratios. Our findings show decline of [123I]β-CIT binding to thalamic 5-HTT in PD and its possible contribution to tremor onset

Complexity Variability Assessment of Nonlinear Time-Varying Cardiovascular Control

The application of complex systems theory to physiology and medicine has provided meaningful information about the nonlinear aspects underlying the dynamics of a wide range of biological processes and their disease-related aberrations. However, no studies have investigated whether meaningful information can be extracted by quantifying second-order moments of time-varying cardiovascular complexity. To this extent, we introduce a novel mathematical framework termed complexity variability, in which the variance of instantaneous Lyapunov spectra estimated over time serves as a reference quantifier. We apply the proposed methodology to four exemplary studies involving disorders which stem from cardiology, neurology and psychiatry: Congestive Heart Failure (CHF), Major Depression Disorder (MDD), Parkinson?s Disease (PD), and Post-Traumatic Stress Disorder (PTSD) patients with insomnia under a yoga training regime. We show that complexity assessments derived from simple time-averaging are not able to discern pathology-related changes in autonomic control, and we demonstrate that between-group differences in measures of complexity variability are consistent across pathologies. Pathological states such as CHF, MDD, and PD are associated with an increased complexity variability when compared to healthy controls, whereas wellbeing derived from yoga in PTSD is associated with lower time-variance of complexity

Distinct glutaminyl cyclase expression in Edinger–Westphal nucleus, locus coeruleus and nucleus basalis Meynert contributes to pGlu-Aβ pathology in Alzheimer’s disease

Glutaminyl cyclase (QC) was discovered recently as the enzyme catalyzing the pyroglutamate (pGlu or pE) modification of N-terminally truncated Alzheimer’s disease (AD) Aβ peptides in vivo. This modification confers resistance to proteolysis, rapid aggregation and neurotoxicity and can be prevented by QC inhibitors in vitro and in vivo, as shown in transgenic animal models. However, in mouse brain QC is only expressed by a relatively low proportion of neurons in most neocortical and hippocampal subregions. Here, we demonstrate that QC is highly abundant in subcortical brain nuclei severely affected in AD. In particular, QC is expressed by virtually all urocortin-1-positive, but not by cholinergic neurons of the Edinger–Westphal nucleus, by noradrenergic locus coeruleus and by cholinergic nucleus basalis magnocellularis neurons in mouse brain. In human brain, QC is expressed by both, urocortin-1 and cholinergic Edinger–Westphal neurons and by locus coeruleus and nucleus basalis Meynert neurons. In brains from AD patients, these neuronal populations displayed intraneuronal pE-Aβ immunoreactivity and morphological signs of degeneration as well as extracellular pE-Aβ deposits. Adjacent AD brain structures lacking QC expression and brains from control subjects were devoid of such aggregates. This is the first demonstration of QC expression and pE-Aβ formation in subcortical brain regions affected in AD. Our results may explain the high vulnerability of defined subcortical neuronal populations and their central target areas in AD as a consequence of QC expression and pE-Aβ formation

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 (alpha-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 alpha-Syn both in its aggregated and monomeric forms in cerebrospinal fluid and blood plasma. However, the effect of extracellular alpha-Syn on cellular activation and immune mediators, as well as the impact of familial PD-linked alpha-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 alpha-Syn variants on primary glial and microglial cell cultures. After stimulation of cells with alpha-Syn, we measured the release of Th1- and Th2-type cytokines as well as IP-10/CXCL10, RANTES/CCL5, MCP-1/CCL2 and MIP-1 alpha/CCL3 chemokines. Contrary to what had been observed using cell lines or for the case of aggregated alpha-Syn, we found strong differences in the immune response generated by wild-type alpha-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

Parkinson’s disease mouse models in translational research

Animal models with high predictive power are a prerequisite for translational research. The closer the similarity of a model to Parkinson’s disease (PD), the higher is the predictive value for clinical trials. An ideal PD model should present behavioral signs and pathology that resemble the human disease. The increasing understanding of PD stratification and etiology, however, complicates the choice of adequate animal models for preclinical studies. An ultimate mouse model, relevant to address all PD-related questions, is yet to be developed. However, many of the existing models are useful in answering specific questions. An appropriate model should be chosen after considering both the context of the research and the model properties. This review addresses the validity, strengths, and limitations of current PD mouse models for translational research