Neuroprotective effects of lignan 7-hydroxymatairesinol (HMR/lignan) in a rodent model of Parkinson's disease.

OBJECTIVES: Parkinson's disease (PD) is a neurodegenerative disease characterized by loss of dopaminergic neurons in the Substantia Nigra pars compacta (SNc). The proinflammatory response can occur early in the disease, contributing to nigrostriatal degeneration. Identification of the new molecules, which are able to slow down the degenerative process associated with PD, represents one of the main interests. Recently, natural polyphenols, especially lignans, have raised attention for their anti-inflammatory, antioxidant, and estrogenic activity at a peripheral level. The aim of this study was to evaluate the central effects of chronic treatment with lignan 7-hydroxymatairesinol (HMR/lignan) on neurodegenerative, neuroinflammatory processes and motor deficits induced by a unilateral intrastriatal injection of 6-hydroxydopamine (6-OHDA) in rats to evaluate the potential neuroprotective properties of this compound. METHODS: Sprague-Dawley male rats underwent lignan (10 mg/kg) or vehicle treatment (oral) for 4 wk starting from the day of 6-OHDA injection. The degree of nigrostriatal damage was evaluated by immunohistochemistry. Moreover, we performed a quantitative and qualitative assessment of neuroinflammatory process, including phenotypic polarization of microglia and astrocytes. The motor performance was assessed by behavioral tests. RESULTS: We demonstrated that chronic treatment with HMR/lignan was able to slow down the progression of degeneration of striatal dopaminergic terminals in a rat model of PD, with a consequent improvement in motor performance. Nevertheless, the anti-inflammatory effect of HMR/lignan observed in SNc was not sufficient to protect dopaminergic cells bodies. CONCLUSION: These results suggest intriguing properties of HMR/lignan at neuroprotective and symptomatic levels in the context of PD.

Development and biochemical characterization of a mouse model of Parkinson's disease bearing defective glucocerebrosidase activity.

GBA1 gene encodes for the lysosomal membrane protein glucocerebrosidase (GCase). GBA1 heterozygous mutations profoundly impair GCase activity and are currently recognized as an important risk factor for the development of Parkinson's disease (PD). Deficits in lysosomal degradation pathways may contribute to pathological α-synuclein accumulation, thereby favoring dopaminergic neuron degeneration and associated microglial activation. However, the precise mechanisms by which GCase deficiency may influence PD onset and progression remain unclear. In this work we used conduritol-ß-epoxide (CBE), a potent inhibitor of GCase, to induce a partial, systemic defect of GCase activity comparable to that associated with heterozygous GBA1 mutations, in mice. Chronic (28 days) administration of CBE (50 mg/kg, i.p.) was combined with administration of a classic PD-like inducing neurotoxin, such as MPTP (30 mg/kg, i.p. for 5 days). The aim was to investigate whether a pre-existing GCase defect may influence the effects of MPTP in terms of nigrostriatal damage, microglia activation and α-synuclein accumulation. Pre-treatment with CBE had tendency to enhance MPTP-induced neurodegeneration in striatum and caused significant increase of total α-synuclein expression in substantia nigra. Microglia was remarkably activated by CBE alone, without further increases when combined with MPTP. Overall, we propose this model as an additional tool to study pathophysiological processes of PD in the presence of GCase defects.

The Exosomal/Total α-Synuclein Ratio in Plasma Is Associated With Glucocerebrosidase Activity and Correlates With Measures of Disease Severity in PD Patients.

Intensive research efforts in the field of Parkinson's disease (PD) are focusing on identifying reliable biomarkers which possibly help physicians in predicting disease onset, diagnosis, and progression as well as evaluating the response to disease-modifying treatments. Given that abnormal alpha-synuclein (α-syn) accumulation is a primary component of PD pathology, this protein has attracted considerable interest as a potential biomarker for PD. Alpha-synuclein can be detected in several body fluids, including plasma, where it can be found as free form or in association with exosomes, small membranous vesicles secreted by virtually all cell types. Together with α-syn accumulation, lysosomal dysfunctions seem to play a central role in the pathogenesis of PD, given the crucial role of lysosomes in the α-syn degradation. In particular, heterozygous mutations in the GBA1 gene encoding lysosomal enzyme glucocerebrosidase (GCase) are currently considered as the most important risk factor for PD. Different studies have found that GCase deficiency leads to accumulation of α-syn; whereas at the same time, increased α-syn may inhibit GCase function, thus inducing a bidirectional pathogenic loop. In this study, we investigated whether changes in plasma total and exosome-associated α-syn could correlate with disease status and clinical parameters in PD and their relationship with GCase activity. We studied 39 PD patients (mean age: 65.2 ± 8.9; men: 25), without GBA1 mutations, and 33 age-matched controls (mean age: 61.9 ± 6.2; men: 15). Our results showed that exosomes from PD patients contain a greater amount of α-syn compared to healthy subjects (25.2 vs. 12.3 pg/mL, p < 0.001) whereas no differences were found in plasma total α-syn levels (15.7 vs. 14.8 ng/mL, p = 0.53). Moreover, we highlighted a significant increase of plasma exosomal α-syn/total α-syn ratio in PD patients (1.69 vs. 0.89, p < 0.001), which negatively correlates with disease severity (p = 0.014). Intriguingly, a significant inverse correlation between GCase activity and this ratio in PD subjects was found (p = 0.006). Additional and large-scale studies comparing GCase activity and pathological protein levels will be clearly needed to corroborate these data and determine whether the association between key players in the lysosomal system and α-syn can be used as diagnostic or prognostic biomarkers for PD.

Influence of Estrogen Modulation on Glia Activation in a Murine Model of Parkinson's Disease.

Epidemiological data suggest a sexual dimorphism in Parkinson disease (PD), with women showing lower risk of developing PD. Vulnerability of the nigrostriatal pathway may be influenced by exposure to estrogenic stimulation throughout fertile life. To further address this issue, we analyzed the progression of nigrostriatal damage, microglia and astrocyte activation and microglia polarization triggered by intrastriatal injection of dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) in male, female and ovariectomized (OVX) mice, as well as in OVX mice supplemented with 17ßestradiol (OVX+E). Animals were sacrificed at different time points following 6-OHDA injection and brain sections containing striatum and substantia nigra pars compacta (SNc) underwent immunohistochemistry for tyrosine hydroxylase (TH) (dopaminergic marker), immunofluorescence for IBA1 and GFAP (markers of microglia and astrocyte activation, respectively) and triple immunoflorescent to identify polarization of microglia toward the cytotoxic M1 (DAPI/IBA1/TNFα) or cytoprotective M2 (DAPI/IBA1/CD206) phenotype. SNc damage induced by 6-OHDA was significantly higher in OVX mice, as compared to all other experimental groups, at 7 and 14 days after surgery. Astrocyte activation was higher in OVX mice with respect the other experimental groups, at all time points. Microglial activation in the SNc was detected at earlier time points in male, female and OVX+E, while in OVX mice was detected at all time-points. Microglia polarization toward the M2, but not the M1, phenotype was detected in female and OVX+E mice, while the M1 phenotype was observed only in male and OVX mice. Our results support the protective effects of estrogens against nigrostriatal degeneration, suggesting that such effects may be mediated by an interaction with microglia, which tend to polarize preferentially toward an M2, cytoprotective phenotype in the presence of intense estrogenic stimulation.

Investigational drugs in Phase I and Phase II for Levodopa-induced dyskinesias.

INTRODUCTION: Prolonged treatment of Parkinson's disease (PD) with levodopa (L-DOPA) results in motor complications, including motor fluctuations and involuntary movements known as L-DOPA induced dyskinesias (LIDs). LIDs represent an additional cause of disability for PD patients and a major challenge for the clinical neurologist. Preclinical research has provided invaluable insights into the molecular and neural substrates of LIDs, identifying a number of potential targets for new anti-dyskinetic strategies. Areas covered: This review article is centered on drugs currently in Phase I and II clinical trials for LIDs and their relative pharmacological targets, which include glutamate, acetylcholine, serotonin, adrenergic receptors and additional targets of potential therapeutic interest. Expert opinion: LIDs are sustained by complex molecular and neurobiological mechanisms that are difficult to disentangle or target, unless one or more prevalent mechanisms are identified. In this context, the role of the serotonergic system and mGluR5 glutamate receptors seem to stand out. Interesting results have been obtained, for example, with partial 5-HT1A/5-HT1B receptor agonist eltoprazine and mGluR5 negative allosteric modulator dipraglurant. Confirmation of these results through large-scale, Phase III clinical trials will be needed, to obtain new pharmacological tools that may be used to optimize the treatment of PD patients with motor complications.

Complex Changes in the Innate and Adaptive Immunity Accompany Progressive Degeneration of the Nigrostriatal Pathway Induced by Intrastriatal Injection of 6-Hydroxydopamine in the Rat.

We investigated changes in innate and adaptive immunity paralleling the progressive nigrostriatal damage occurring in a neurotoxic model of Parkinson's disease (PD) based on unilateral infusion of 6-hydroxydopamine (6-OHDA) into the rat striatum. A time-course analysis was conducted to assess changes in morphology (activation) and cell density of microglia and astrocytes, microglia polarization (M1 vs. M2 phenotype), lymphocyte infiltration in the lesioned substantia nigra pars compacta (SNc), and modifications of CD8+ and subsets of CD4+ T cell in peripheral blood accompanying nigrostriatal degeneration. Confirming previous results, we observed slightly different profiles of activation for astrocytes and microglia paralleling nigral neuronal loss. For astrocytes, morphological changes and cell density increases were mostly evident at the latest time points (14 and 28 days post-surgery), while moderate microglia activation was present since the earliest time point. For the first time, in this model, we described the time-dependent profile of microglia polarization. Activated microglia clearly expressed the M2 phenotype in the earlier phase of the experiment, before cell death became manifest, gradually shifting to the M1 phenotype as SNc cell death started. In parallel, a reduction in the percentage of circulating CD4+ T regulatory (Treg) cells, starting as early as day 3 post-6-OHDA injection, was detected in 6-OHDA-injected rats. Our data show that nigrostriatal degeneration is associated with complex changes in central and peripheral immunity. Microglia activation and polarization, Treg cells, and the factors involved in their cross-talk should be further investigated as targets for the development of therapeutic strategies for disease modification in PD.

Andrographis Paniculata shows anti-nociceptive effects in an animal model of sensory hypersensitivity associated with migraine.

Administration of nitroglycerin (NTG) to rats induces a hyperalgesic condition and neuronal activation of central structures involved in migraine pain. In order to identify therapeutic strategies for migraine pain, we evaluated the anti-nociceptive activity of Andrographis Paniculata (AP), a herbaceous plant, in the hyperalgesia induced by NTG administration in the formalin test. We also analyzed mRNA expression of cytokines in specific brain areas after AP treatment. Male Sprague-Dawley rats were pre-treated with AP extract 30 minutes before NTG or vehicle injection. The data show that AP extract significantly reduced NTG-induced hyperalgesia in phase II of the test, 4 hours after NTG injection. In addition, AP extract reduced IL-6 mRNA expression in the medulla and mesencephalon and also mRNA levels of TNFalpha in the mesencephalic region. These findings suggest that AP extract may be a potential therapeutic approach in the treatment of general pain, and possibly of migraine.