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Depression occurs in around 40 % of patients with Parkinson's disease (PD) and contributes to severe disability and a poor quality of life. The underlying mechanisms and pathophysiology of depression in PD (PDD) remain obscure, due to a lack of stable animal models of PDD. In this study, we established a PDD model by inducing exposure to chronic mild (CMS) and strong stress (CSS) using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in PD mice. We detected changes in motor and non-motor symptoms, brain structure, neurotransmitters, levels of 5-HT related genes and inflammation. CMS exposed PD (PDMS) mice exhibited obviously decreased levels of neuromuscular strength and enhanced levels of inflammation, compared with that of control mice. CSS exposed MPTP (PDSS) mice exhibited the highest level of motor impairment and depression states along with the highest levels of inflammation enhancement and a decrease in the expression levels of 5-hydroxytryptamine (5-HT) related genes in all groups. Our results suggested that CSS can successfully induce stable depression like symptoms in sub-chronic MPTP PD mice and appears to be a valuable tool for investigating PDD. Furthermore, it was found that 5-HT system dysfunction may contribute to depression like symptoms in PD., (Copyright © 2020. Published by Elsevier B.V.)

Loss of dopaminergic neurons along the nigrostriatal axis, neuroinflammation, and peripheral immune dysfunction are the pathobiological hallmarks of Parkinson's disease (PD). Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been successfully tested for PD treatment. GM-CSF is a known immune modulator that induces regulatory T cells (Tregs) and serves as a neuronal protectant in a broad range of neurodegenerative diseases. Due to its short half-life, limited biodistribution, and potential adverse effects, alternative long-acting treatment schemes are of immediate need. A long-acting mouse GM-CSF (mPDM608) was developed through Calibr, a Division of Scripps Research. Following mPDM608 treatment, complete hematologic and chemistry profiles and T-cell phenotypes and functions were determined. Neuroprotective and anti-inflammatory capacities of mPDM608 were assessed in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mice that included transcriptomic immune profiles. Treatment with a single dose of mPDM608 resulted in dose-dependent spleen and white blood cell increases with parallel enhancements in Treg numbers and immunosuppressive function. A shift in CD4 + T-cell gene expression towards an anti-inflammatory phenotype corresponded with decreased microgliosis and increased dopaminergic neuronal cell survival. mPDM608 elicited a neuroprotective peripheral immune transformation. The observed phenotypic shift and neuroprotective response was greater than observed with recombinant GM-CSF (rGM-CSF) suggesting human PDM608 as a candidate for PD treatment.

Schisandrin A (Sch A) is one of the principal bioactive lignans isolated from Fructus schisandrae. In this study, we demonstrated its protective effect and biochemical mechanism of action in a 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine-induced mouse model of Parkinson's disease. Sch A significantly ameliorated behavioural abnormalities and increased the number of nigral dopaminergic neurons detected by tyrosine hydroxylase immunohistochemistry. Pre-treatment with Sch A significantly decreased the levels of the inflammatory mediators IL-6, IL-1β, and TNF-α and markedly improved antioxidant defences by inhibiting the activity of MDA and increasing that of SOD. Furthermore, Sch A activated expression of the autophagy-related proteins LC3-II, beclin1, parkin, and PINK1 and increased mTOR expression. Taken together, these findings indicate that Sch A has neuroprotective effects against the development of Parkinson's disease via regulation of brain autophagy.

Oxidative stress and neuroinflammation are the key and early events during the pathological process of Parkinson's disease (PD). Thus, therapeutic intervention to regulate oxidative stress and neuroinflammation would be an effective strategy to alleviate the progression of PD. Astragaloside IV, the main active component isolated from Astragalus membranaceus, has been shown to possess anti-inflammatory and anti-oxidant properties in neurodegeneration diseases, however, the molecular mechanisms of Astragaloside IV in the pathology of PD are still unclear. In this study, we explored the mechanisms of Astragaloside IV of PD on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice model and lipopolysaccharide (LPS)-induced BV2 microglia cells. Our results showed Astragaloside IV significantly alleviated behavioral impairments and dopaminergic neuron degeneration induced by MPTP. Also, Astragaloside IV inhibited microglia activation and reduced the oxidative stress of MPTP mouse model. In addition, Astragaloside IV significantly inhibited NFκB mediated NLRP3 inflammasome activation and activated Nrf2 both in vivo and in vitro. Furthermore, Astragaloside IV lessened reactive oxygen species (ROS) generation in LPS-induced BV2 microglia cells remarkably. These findings demonstrate that Astragaloside IV protects dopaminergic neuron from neuroinflammation and oxidative stress which are largely dependent upon activation of the Nrf2 pathways and suppression of NFκB/NLRP3 inflammasome signaling pathway. Therefore, Astragaloside IV is a promising neuroprotective agent that should be further developed for neurodegeneration diseases., (Copyright © 2019. Published by Elsevier B.V.)

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons and excessive microglial activation in the substantia nigra pars compacta (SNpc). In the present study, we aimed to demonstrate the therapeutic effectiveness of the potent sphingosine-1-phosphate receptor antagonist fingolimod (FTY720) in an animal model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and to identify the potential mechanisms underlying these therapeutic effects. C57BL/6J mice were orally administered FTY720 before subcutaneous injection of MPTP. Open-field and rotarod tests were performed to determine the therapeutic effect of FTY720. The damage to dopaminergic neurons and the production of monoamine neurotransmitters were assessed using immunohistochemistry, high-performance liquid chromatography, and flow cytometry. Immunofluorescence (CD68- positive) and enzyme-linked immunosorbent assay were used to analyze the activation of microglia, and the levels of activated signaling molecules were measured using Western blotting. Our findings indicated that FTY720 significantly attenuated MPTP-induced behavioral deficits, reduced the loss of dopaminergic neurons, and increased dopamine release. FTY720 directly inhibited MPTP-induced microglial activation in the SNpc, suppressed the production of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α in BV-2 microglial cells treated with 1-methyl-4-phenylpyridinium (MPP + ), and subsequently decreased apoptosis in SH-SY5Y neuroblastoma cells. Moreover, in MPP + -treated BV-2 cells and primary microglia, FTY720 treatment significantly attenuated the increases in the phosphorylation of PI3K/AKT/GSK-3β, reduced ROS generation and p65 activation, and also inhibited the activation of NLRP3 inflammasome and caspase-1. In conclusion, FTY720 may reduce PD progression by inhibiting NLRP3 inflammasome activation via its effects on ROS generation and p65 activation in microglia. These findings provide novel insights into the mechanisms underlying the therapeutic effects of FTY720, suggesting its potential as a novel therapeutic strategy against PD. Graphical Abstract FTY720 may reduce ROS production by inhibiting the PI3K/AKT/GSK-3β signaling pathway, while at the same time reducing p65 phosphorylation, thus decreasing NLRP3 inflammasome activation through these two pathways, ultimately reducing microglia activation-induced neuronal damage.

Autophagy is an essential cellular process concern with cellular homeostasis down-regulated by mTOR, whose activity can be modulated by rapamycin, a kind of lipophilic macrolide antibiotic, through forming a complex with immunophilin FKBP12 essential for mTOR regulation to induce autophagy. Therefore, rapamycin is normally used as a neuron protective agent. The immunophilin FKBP12 binding ligand FK506 is well known as an immunosuppressive agent by inhibiting the calcineurin expression. In this study, we synthesized a series of modified compounds based on the FKBP12 binding moiety to as same as the binding structure of rapamycin and FK506 particularly. We removed the other binding regions of the complex that has the property of immunosuppression. We found that a novel small molecule named TH2849 from these derivative compounds has a significant binding connection with mTOR by comparing to calcineurin. The effects of TH2849 on calcineurin/NFAT were not as significant as FK506, and weak effects on IL2/p34 cdc2 /cyclin signaling pathway were also found. Moreover, TH2849 also shows mitochondrial protective effect through stabilizing the mitochondrial structure and transmembrane potential (ΔΨm) and could rescue dopaminergic neurons in MPTP-treated zebrafishes as well as mice models with less immunosuppressive effect. Our present study shows that TH2849 works as a neuroprotective agent possibly by inducing autophagy and low immunosuppressive effect., (© 2018 John Wiley & Sons Ltd.)

Parkinson's disease (PD) is a progressive neurological motor control disorder. A key feature is the loss of midbrain dopaminergic neurons and the accumulation of aggregated alpha-synuclein (α-syn). No current treatment is on the market that slows or halts disease progression. Previous studies have shown that glucagon-like peptide-1 (GLP-1) receptor agonists have neuroprotective effects in animal models of PD. In addition, in a phase II clinical trial, the GLP-1 receptor agonist exendin-4 has shown good protective effects in PD patients. In the present study, we have investigated the neuroprotective effects of the GLP-1 analogues semaglutide (25 nmol/kg ip. once every two days for 30 days) and liraglutide (25 nmol/kg ip. once daily for 30 days) in the chronic MPTP mouse model of PD. Both drugs are currently on the market as a treatment for Type II diabetes. Our results show that both semaglutide and liraglutide improved MPTP-induced motor impairments. In addition, both drugs rescued the decrease of tyrosine hydroxylase (TH) levels, reduced the accumulation of α-syn, alleviated the chronic inflammation response in the brain, reduced lipid peroxidation, and inhibited the mitochondrial mitophagy signaling pathway, and furthermore increased expression of the key growth factor GDNF that protects dopaminergic neurons in the substantia nigra (SN) and striatum. Moreover, the long- acting GLP-1 analogue semaglutide was more potent compared with once daily liraglutide in most parameters measured in this study. Our results demonstrate that semaglutide may be a promising treatment for PD. A clinical trial testing semaglutide in PD patients will start shortly.

Parkinson's disease (PD) is the second most common neurodegenerative disorders. Neuroinflammation plays an important role in the pathogenesis of PD. Long noncoding RNA small nucleolar RNA host gene 1 (SNHG1) was elevated in the brain specimens of PD patients and MPP+-treated SH-SY5Y cells. The expression of mouse Snhg1 and miR-7 was firstly determined in lipopolysaccharide (LPS)-induced BV2 cells. The role and mechanism of SNHG1 in the neuroinflammation of PD were investigated using gain- and loss-of function approaches both in vitro and in vivo. Snhg1 expression was elevated, whereas miR-7 reduced in LPS-induced BV2 cells. Upregulation of Snhg1 elevated, and Snhg1 knockdown suppressed LPS-induced BV2 microglial activation and inflammation. miR-7 reversed, while anti-miR-7 further enhanced the effects of Snhg1 on BV2 cells. Furthermore, we found that Snhg1 functioned as a competing endogenous RNA for miR-7 to regulate nod-like receptor protein 3 (NLRP3) expression, leading to the activation of NLRP3 inflammasome. In the microglial culture supernatant transfer model, knockdown of Snhg1 or NLRP3 in LPS-stimulated BV2 cells inhibited primary neurons from apoptosis and elevated caspase-3 activity. Additionally, Snhg1 was increased in MPTP-induced PD mouse models. Downregulation of Snhg1 elevated miR-7 expression, suppressed the activation of microglia and NLRP3 inflammasome as well as dopaminergic neuron loss in the midbrain substantia nigra pars compacta in MPTP-treated mice. In conclusion, our study suggests that SNHG1 promotes neuroinflammation in the pathogenesis of PD via modulating miR-7/NLRP3 pathway., (Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.)

Neuroinflammation mediated by chronically activated microglia, largely caused by abnormal accumulation of misfolded α-synuclein (αSyn) protein, is known to contribute to the pathophysiology of Parkinson's disease (PD). In this work, based on the immunomodulatory activities displayed by particular heat-shock proteins (HSPs), we tested a novel vaccination strategy that used a combination of αSyn and Grp94 (HSPC4 or Gp96) chaperone and a murine PD model. We used two different procedures, first, the adoptive transfer of splenocytes from αSyn/Grp94-immunized mice to recipient animals, and second, direct immunization with αSyn/Grp94, to study the effects in a chronic mouse MPTP-model of parkinsonism. We found that both approaches promoted a distinct profile in the peripheral system-supported by humoral and cellular immunity-consisting of a Th1-shifted αSyn-specific response accompanied by an immune-regulatory/Th2-skewed general phenotype. Remarkably, this mixed profile sustained by αSyn/Grp94 immunization led to strong suppression of microglial activation in the substantia nigra and striatum, pointing to a newly described positive effect of anti-αSyn Th1-responses in the context of PD. This strategy is the first to target αSyn and report the suppression of PD-associated microgliosis. Overall, we show that the αSyn/Grp94 combination supports a distinct and long-lasting immune profile in the peripheral system, which has an impact at the CNS level by suppressing chronic microglial activation in an MPTP model of PD. Furthermore, our study demonstrates that reshaping peripheral immunity by vaccination with appropriate misfolding protein/HSP combinations could be highly beneficial as a treatment for neurodegenerative misfolding diseases., (© 2017 Wiley Periodicals, Inc.)

Although the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model is the most widely used animal model for Parkinson's disease (PD), it is known that nigrostriatal pathologies do not persist in the acute MPTP mouse model. This study highlights the importance of adaptive immunity in driving persistent and progressive disease in acute MPTP-intoxicated mice. Although marked infiltration of T cells into the nigra was found on 1 d of MPTP insult, T cell infiltration decreased afterward, becoming normal on 30 d of insult. Interestingly, twice-weekly supplementation of RANTES and eotaxin, chemokines that are involved in T cell trafficking, drove continuous T cell infiltration to the nigra and incessant glial inflammation. Supplementation of RANTES and eotaxin was also associated with the induction of nigral α-synuclein pathology, persistent loss of dopaminergic neurons and striatal neurotransmitters, and continuous impairment of motor functions in MPTP-intoxicated mice. In contrast, supplementation of TNF-α and IL-1β, widely studied proinflammatory cytokines, did not induce persistent disease in MPTP-insulted mice. Our results suggest that induction of adaptive immunity by RANTES and eotaxin could hold the key for driving persistent nigrostriatal pathologies in the MPTP mouse model, and that targeting these factors may halt disease progression in PD patients., (Copyright © 2017 by The American Association of Immunologists, Inc.)

Background: Evidence from mice suggests that brain infiltrating immune cells contribute to neurodegeneration, and we previously identified a deleterious lymphocyte infiltration in Parkinson's disease mice. However, this remains controversial for monocytes, due to artifact-prone techniques used to distinguish them from microglia. Our aim was to reassess this open question, by taking advantage of the recent recognition that chemokine receptors CCR2 and CX3CR1 can differentiate between inflammatory monocytes and microglia, enabling to test whether CCR2 + monocytes infiltrate the brain during dopaminergic (DA) neurodegeneration and whether they contribute to neuronal death. This revealed unexpected insights into possible regulation of monocyte-attracting CCL2 induction., Methods: We used acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice and assessed monocyte infiltration by combining laser microdissection-guided chemokine RNA profiling of the substantia nigra (SN) with immunohistochemistry and CCR2-GFP reporter mice. To determine contribution to neuronal loss, we used CCR2-deletion and CCL2-overexpression, to reduce and increase CCR2 + monocyte infiltration, and CX3CR1-deletion to assess a potential implication in CCL2 regulation., Results: Nigral chemokine profiling revealed early CCL2/7/12-CCR2 axis induction, suggesting monocyte infiltration in MPTP mice. CCL2 protein showed early peak induction in nigral astrocytes, while CCR2-GFP mice revealed early but limited nigral monocyte infiltration. However, blocking infiltration by CCR2 deletion did not influence DA neuronal loss. In contrast, transgenic astrocytic CCL2 over-induction increased CCR2 + monocyte infiltration and DA neuronal loss in MPTP mice. Surprisingly, CCL2 over-induction was also detected in MPTP intoxicated CX3CR1-deleted mice, which are known to present increased DA neuronal loss. Importantly, CX3CR1/CCL2 double-deletion suggested that increased neurotoxicity was driven by astrocytic CCL2 over-induction., Conclusions: We show that CCR2 + monocytes infiltrate the affected CNS, but at the level observed in acute MPTP mice, this does not contribute to DA neuronal loss. In contrast, the underlying astrocytic CCL2 induction seemed to be tightly controled, as already moderate CCL2 over-induction led to increased neurotoxicity in MPTP mice, likely due to the increased CCR2 + monocyte infiltration. Importantly, we found evidence suggesting that during DA neurodegeneration, this control was mediated by microglial CX3CR1 signaling, which protects against such neurotoxic CCL2 over-induction by astrocytes, thus hinting at an endogenous mechanism to limit neurotoxic effects of the CCL2-CCR2 axis.

Parkinson's disease (PD) is one of the main degenerative neurological disorders accompanying death of dopaminergic neurons prevalent in aged population. Endurance exercise (EE) has been suggested to confer neurogenesis and mitigate the degree of seriousness of PD. However, underlying molecular mechanisms responsible for exercise-mediated neuroprotection against PD remain largely unknown. Given the relevant interplay between elevated α-synuclein and neuroinflammation in a poor prognosis and vicious progression of PD and anti-inflammatory effects of EE, we hypothesized that EE would reverse motor dysfunction and cell death caused by PD. To this end, we chose a pharmacological model of PD (e.g., chronic injection of neurotoxin MPTP). Young adult male mice (7 weeks old) were randomly divided into three groups: sedentary control (C, n=10), MPTP (M, n=10), and MPTP + endurance exercise (ME, n=10). Our data showed that EE restored motor function impaired by MPTP in parallel with reduced cell death. Strikingly, EE exhibited a significant reduction in α-synuclein protein along with diminished pro-inflammatory cytokines (i.e., TNF-α and IL-1β). Supporting this, EE prevented activation of Toll like receptor 2 (TLR2) downstream signaling cascades such as MyD88, TRAF6 and TAK-1 incurred by in MPTP administration in the striatum. Moreover, EE reestablished tyrosine hydroxylase at levels similar to C group. Taken together, our data suggest that an EE-mediated neuroprotective mechanism against PD underlies anti-neuroinflammation conferred by reduced levels of α-synuclein. Our data provides an important insight into developing a non-pharmacological countermeasure against neuronal degeneration caused by PD., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Parkinson's disease (PD) is the second most common neurodegenerative disease and results from the loss of dopaminergic neurons of the nigrostriatal pathway. The pathogenesis of PD is poorly understood, but inflammatory processes have been implicated. Indeed increases in the number of major histocompatibility complex II (MHC II) reactive cells have long been recognised in the brains of PD patients at post-mortem. However whether cells expressing MHC II play an active role in PD pathogenesis has not been delineated. This was addressed utilising a transgenic mouse null for MHC II and the parkinsonian toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In wild-type mice MHC II levels in the ventral midbrain were upregulated 1-2 days after MPTP treatment and MHC II was localized in both astrocytes and microglia. MHC II null mice showed significant reductions in MPTP-induced dopaminergic neuron loss and a significantly reduced invasion of astrocytes and microglia in MHC II null mice receiving MPTP compared with controls. In addition, MHC II null mice failed to show increases in interferon-γ or tumour necrosis factor-α in the brain after MPTP treatment, as was found in wild-type mice. However, interleukin-1β was significantly increased in both wild-type and MHC II null mice. These data indicate that in addition to microglial cell/myeloid cell activation MHC Class II-mediated T cell activation is required for the full expression of pathology in this model of PD., (© 2015 Wiley Periodicals, Inc.)

Parkinson's disease (PD) is a neurodegenerative disease characterised by histopathological and biochemical manifestations such as loss of midbrain dopaminergic (DA) neurons and decrease in dopamine levels accompanied by a concomitant neuroinflammatory response in the affected brain regions. Over the past decades, the use of toxin-based animal models has been crucial to elucidate disease pathophysiology, and to develop therapeutic approaches aimed to alleviate its motor symptoms. Analyses of transgenic mice deficient for cytokines, chemokine as well as neurotrophic factors and their respective receptors in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD have broadened the current knowledge of neuroinflammation and neurotrophic support. Here, we provide a comprehensive review that summarises the contribution of microglia-mediated neuroinflammation in MPTP-induced neurodegeneration. Moreover, we highlight the contribution of neurotrophic factors as endogenous and/or exogenous molecules to slow the progression of midbrain dopaminergic (mDA) neurons and further discuss the potential of combined therapeutic approaches employing neuroinflammation modifying agents and neurotrophic factors.

Vasoactive intestinal peptide (VIP) mediates a broad range of biological responses by activating two related receptors, VIP receptor 1 and 2 (VIPR1 and VIPR2). Although the use of native VIP facilitates neuroprotection, clinical application of the hormone is limited due to VIP's rapid metabolism and inability to distinguish between VIPR1 and VIPR2 receptors. In addition, activation of both receptors by therapeutics may increase adverse secondary toxicities. Therefore, we developed metabolically stable and receptor-selective agonists for VIPR1 and VIPR2 to improve pharmacokinetic and pharmacodynamic therapeutic end points. Selective agonists were investigated for their abilities to protect mice against MPTP-induced neurodegeneration used to model Parkinson's disease (PD). Survival of tyrosine hydroxylase neurons in the substantia nigra was determined by stereological tests after MPTP intoxication in mice pretreated with either VIPR1 or VIPR2 agonist or after adoptive transfer of splenic cell populations from agonist-treated mice administered to MPTP-intoxicated animals. Treatment with VIPR2 agonist or splenocytes from agonist-treated mice resulted in increased neuronal sparing. Immunohistochemical tests showed that agonist-treated mice displayed reductions in microglial responses, with the most pronounced effects in VIPR2 agonist-treated, MPTP-intoxicated mice. In parallel studies, we observed reductions in proinflammatory cytokine release that included IL-17A, IL-6, and IFN-γ and increases in GM-CSF transcripts in CD4(+) T cells recovered from VIPR2 agonist-treated animals. Moreover, a phenotypic shift of effector to regulatory T cells was observed. These results support the use of VIPR2-selective agonists as neuroprotective agents for PD treatment., Significance Statement: Vasoactive intestinal peptide receptor 2 can elicit immune transformation in a model of Parkinson's disease (PD). Such immunomodulatory capabilities can lead to neuroprotection by attenuating microglial activation and by slowing degradation of neuronal cell bodies and termini in MPTP-intoxicated mice. The protective mechanism arises from altering a Th1/Th2 immune cytokine response into an anti-inflammatory and neuronal sparing profile. These results are directly applicable for the development of novel PD therapies., (Copyright © 2015 the authors 0270-6474/15/3516463-16$15.00/0.)

Foxp3-expressing CD4(+) regulatory T cells (Tregs) are vital for maintaining immune tolerance in animal models of various immune diseases. In the present study, we demonstrated that bee venom phospholipase A2 (bvPLA2) is the major BV compound capable of inducing Treg expansion and promotes the survival of dopaminergic neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease. We associated this neuroprotective effect of bvPLA2 with microglial deactivation and reduction of CD4(+) T cell infiltration. Interestingly, bvPLA2 had no effect on mice depleted of Tregs by injecting anti-CD25 Ab. This finding indicated that Treg-mediated modulation of peripheral immune tolerance is strongly involved in the neuroprotective effects of bvPLA2. Furthermore, our results showed that bvPLA2 directly bound to CD206 on dendritic cells and consequently promoted the secretion of PGE2, which resulted in Treg differentiation via PGE2 (EP2) receptor signaling in Foxp3(-)CD4(+) T cells. These observations suggest that bvPLA2-CD206-PGE2-EP2 signaling promotes immune tolerance through Treg differentiation and contributes to the prevention of various neurodegenerative diseases, including Parkinson's disease., (Copyright © 2015 by The American Association of Immunologists, Inc.)

The selective loss of dopaminergic neurons in Parkinson's disease (PD) is associated with microglial activation. Therefore, the importance of early therapeutic intervention to inhibit microglial activation would be an effective strategy to alleviate the progression of PD. α-Asarone, an active compound found in Araceae and Annonaceae plant species has been used to improve various disease conditions including central nervous system disorders. In the present study the in vitro and in vivo therapeutic effects of α-asarone isolated from the rhizome of Acorus gramineus Solander was evaluated on microglia-mediated neuroinflammation and neuroprotection. Lipopolysaccharide (LPS)-stimulated BV-2 microglial cells were used to evaluate in vitro effects. 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of PD was developed to study the neuroprotective effects of α-asarone in vivo. The results indicated that α-asarone significantly attenuated the LPS-stimulated increase in neuroinflammatory responses and suppressed pro-inflammatory cytokine production in BV-2 cells. Mechanistic study revealed that α-asarone inhibited the LPS-stimulated activation via regulation of nuclear factor kappa-B by blocking degradation of inhibitor kappa B-alpha signaling in BV-2 microglial cells. In in vivo studies, MPTP intoxication to mice resulted in brain microglial activation and significant behavioral deficits. Prophylactic treatment with α-asarone suppressed microglial activation and attenuated PD-like behavioral impairments as assessed by the Y-maze and pole tests. Taken together, these data demonstrate that α-asarone is a promising neuroprotective agent that should be further evaluated and developed for future prevention and treatment of microglia-mediated neuroinflammatory conditions including PD., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Microglia, the immune cells of the central nervous system, constantly survey the parenchyma in the healthy brain to maintain homeostasis. When a disturbance, such as cell death, results in ATP release in vivo, microglial processes respond by utilizing P2Y12 purinergic receptors to trigger extension toward the site of damage. Processes ultimately surround the injury site, preventing the spread of harmful cellular constituents and assisting with tissue repair. In contrast to the healthy brain, many neurodegenerative diseases, including Parkinson's disease, are characterized by the presence of neuroinflammation. Yet, the ability of microglia to respond to tissue damage under pro-inflammatory conditions has not been well studied. To assess the ability of microglia to respond to tissue injury and localized cell death in the context of Parkinson's disease, we performed confocal imaging of acute brain slices from mice with microglia-specific green fluorescent protein expression. Microglia in coronal slices containing the substantia nigra extend processes toward a mechanical injury in a P2Y12 receptor-dependent manner. However, microglia in mice treated for 5days with 20mg/kg/day 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) show significantly reduced process displacement toward the injury compared to microglia in control animals. Pre-treatment of slices from MPTP-injected mice with the A2A receptor-selective antagonist preladenant restores the ability of activated microglia to respond to tissue damage. These data support the hypothesis that chronic inflammation impedes microglial motility in response to further injury, such as cell death, and suggest that some aspects of the neuroprotection observed with adenosine A2A receptor antagonists may involve direct or indirect actions at microglia., (Copyright © 2014 Elsevier Inc. All rights reserved.)

In the present study we used a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse model to analyze resveratrol neuroprotective effects. The MPTP-induced PD model is characterized by chronic inflammation, oxidative stress and loss of the dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). We observed that resveratrol treatment significantly reduced glial activation, decreasing the levels of IL-1β, IL-6 and TNF-α, as well as their respective receptors in the SNpc of MPTP-treated mice, as demonstrated by Western blotting, RT-PCR and quantitative PCR analysis. This reduction is related to possible neuroprotection as we also observed that resveratrol administration limited the decline of tyrosine hydroxylase-immunoreactivity induced in the striatum and SNpc by MPTP injection. Consistent with these data, resveratrol treatment up-regulated the expression of the suppressor of cytokine signaling-1 (SOCS-1), supporting the hypothesis that resveratrol protects DA neurons of the SNpc against MPTP-induced cell loss by regulating inflammatory reactions, possibly through SOCS-1 induction.

A key regulator of inflammatory gene expression is the transcription factor NF-κB that is controlled by the IκB proteins. We used a transgenic mouse model expressing a constitutively active IκB-kinase-2 (IKK2-CA) in astrocytes under control of the human glial fibrillary acidic protein promotor (IKK2-mice) to investigate neuroinflammation, proinflammatory cytokine expression, microglial activation and a potential enhanced susceptibility to the neurotoxin MPTP (4×10 mg/kg). Readouts included the determination of cytokines, striatal dopamine (DA), nigral tyrosine hydroxylase (TH) positive neurons, microglial activation and motor activity. IKK2-CA expression in astrocytes conditionally induced by the tet-off system resulted in a widespread neuroinflammation indicated by the increased expression of inflammatory cytokines and the presence of activated microglia and astrogliosis. Additionally, striatal DA concentrations but not nigral TH-positive neurons were reduced in IKK2-mice by 20%. Motor activity of IKK2-mice was not affected. Surprisingly, there was a similar reduction in striatal DA concentrations and the number of nigral TH-positive neurons in IKK2 and control mice after MPTP treatment. In conclusion, although naïve IKK2-mice showed reduced striatal DA concentrations and an increase in inflammatory markers in the brain, a higher susceptibility to MPTP was not observed. This finding argues against a prominent role of astrocyte specific, IKK2-mediated neuroinflammation in MPTP-induced neurodegeneration., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Intravenous immunoglobulin (IVIg) is a blood-derived product, used for the treatment of immunodeficiency and autoimmune diseases. Since a range of immunotherapies have recently been proposed as a therapeutic strategy for Parkinson's disease (PD), we investigated the effects of an IVIg treatment in a neurotoxin-induced animal model of PD. Mice received four injections of MPTP (15 mg/kg) at 2-hour intervals followed by a 14-day IVIg treatment, which induced key immune-related changes such as increased regulatory T-cell population and decreased CD4(+)/CD8(+) ratio. The MPTP treatment induced significant 80% and 84% decreases of striatal dopamine concentrations (P < 0.01), as well as 33% and 40% reductions in the number of nigral dopaminergic neurons (P < 0.001) in controls and IVIg-treated mice, respectively. Two-way analyses of variance further revealed lower striatal tyrosine hydroxylase protein levels, striatal homovanillic acid concentrations and nigral dopaminergic neurons (P < 0.05) in IVIg-treated animals. Collectively, our results fail to support a neurorestorative effect of IVIg on the nigrostriatal system in the MPTP-treated mice and even suggest a trend toward a detrimental effect of IVIg on the dopaminergic system. These preclinical data underscore the need to proceed with caution before initiating clinical trials of IVIg in PD patients.

Although there is growing evidence for a role of the innate immune response in Parkinson's disease, the nature of any humoral response in dopaminergic degeneration is uncertain. Here we report on a protracted N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of dopaminergic death that potentially allows a more full adaptive humoral response to develop. Rag2 mutant mice that lack the full adaptive response (deficient in both T and B cells) are resistant to dopaminergic death and behavioral deficiencies in this model. These mice are resensitized after reconstitution with WT splenocytes. To more directly provide evidence for humoral/IgG involvement, we show that deficiency of Fcγ receptors, which are critical for activation of macrophages/microglia by binding to IgGs, is also protective in this protracted model. FcγR-deficient mice display improved behavior and impaired microglial activation. Interestingly, however, Rag2 mutant but not FcγR-deficient mice are resistant to a more standard N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine paradigm where death is more rapid. Taken together, these data indicate that, provided sufficient time, the humoral arm of the adaptive immune system can play a critical functional role in modulating the microglial response to dopaminergic degeneration and suggest that this humoral component may participate in degeneration in Parkinson's disease.

A growing body of evidence supports a role of inflammation in the loss of central nervous system neurons both to acute and chronic insults, while its contribution to the loss of neurons in the enteric nervous system remains largely uninvestigated. We have addressed this issue by exploring the role of inflammation in dopaminergic (DAergic) myenteric neuronal degeneration secondary to MPTP lesioning in mice deficient in MyD88, a protein implicated in the cascade of events leading to the innate immune response. Our results show that MPTP-treated MyD88 knock out (MyD88(-/-)) mice were protected against the toxin-induced TH-immunoreactive neuronal degeneration at the level of the myenteric plexus of the distal ileum, which causes a 50% loss of such neurons in MPTP-treated WT mice. Interestingly, the density of macrophages was the same in the MyD88(-/-) mice subjected to MPTP, as opposed to the increase in density observed in wild-type (WT) mice treated with the toxin, which was due to an infiltration of monocyte from the blood to the myenteric tissue. Furthermore, in MPTP-treated MyD88(-/-) mice, resident macrophages exhibited a predominant pro-repair phenotype, which could have contributed to the protection of DAergic neurons in the myenteric plexus. Taken together, our results suggest a critical role for the MyD88-dependent pathway in the gastrointestinal DAergic degeneration induced by MPTP., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Ketogenic diet (KD) is a high-fat, low-protein and low-carbohydrate diet. It is reported that KD can provide the neuroprotection for the neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease (PD) and amyotrophic lateral sclerosis. The main clinical symptom of PD is motor dysfunction derived from the loss of dopaminergic neurons in the substantia nigra (SN) and dopamine content in the striatum subsequently. It is well known that treatments with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice produce motor dysfunction, biochemical, and neurochemical changes remarkably similar to idiopathic PD patients. In this study, we investigated the neuroprotective and anti-inflammatory effects of KD in MPTP-treated mice. The data showed that pretreatment with KD alleviated the motor dysfunction induced by MPTP. The decrease of Nissl-staining and tyrosine hydroxylase (TH)-positive neurons induced by MPTP was inhibited in the SN. The change of dopamine was very similar to dopaminergic neurons in the SN. KD inhibited the activation of microglia induced by MPTP in the SN. The levels of proinflammatory cytokines (interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha) in the SN were also decreased and induced by MPTP. So, we concluded that KD was neuroprotective and anti-inflammatory against MPTP-neurotoxicity.

Nitrated alpha-synuclein (N-alpha-syn) immunization elicits adaptive immune responses to novel antigenic epitopes that exacerbate neuroinflammation and nigrostriatal degeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease. We show that such neuroimmune degenerative activities, in significant measure, are Th17 cell-mediated, with CD4(+)CD25(+) regulatory T cell (Treg) dysfunction seen among populations of N-alpha-syn-induced T cells. In contrast, purified vasoactive intestinal peptide induced and natural Tregs reversed N-alpha-syn T cell nigrostriatal degeneration. Combinations of adoptively transferred N-alpha-syn and vasoactive intestinal peptide immunocytes or natural Tregs administered to MPTP mice attenuated microglial inflammatory responses and led to robust nigrostriatal protection. Taken together, these results demonstrate Treg control of N-alpha-syn-induced neurodestructive immunity and, as such, provide a sound rationale for future Parkinson's disease immunization strategies.

Reduced expression of IGF-1R increases lifespan and resistance to oxidative stress in the mouse, raising the possibility that this also confers relative protection against the pro-parkinsonian neurotoxin MPTP, known to involve an oxidative stress component. We used heterozygous IGF-1R(+/-) mice and challenged them with MPTP. Interestingly, MPTP induced more severe lesions of dopaminergic neurons of the substantia nigra, in IGF-1R(+/-) mice than in wild-type animals. Using electron spin resonance, we found that free radicals were decreased in IGF-1R(+/-) mice in comparison with controls, both before and after MPTP exposure, suggesting that the increased vulnerability of dopamine neurons is not caused by oxidative stress. Importantly, we showed that IGF-1R(+/-) mice display a dramatically increased neuro-inflammatory response to MPTP that may ground the observed increase in neuronal death. Microarray analysis revealed that oxidative stress-associated genes, but also several anti-inflammatory signaling pathways were downregulated under control conditions in IGF-1R(+/-) mice compared to WT. Collectively, these data indicate that IGF signaling can reduce neuro-inflammation dependent sensitivity of neurons to MPTP.

Increasing evidence suggests a pivotal role for neuroinflammation in the pathogenesis of Parkinson disease, but whether activated microglia participate in disease progression remains unclear. To clarify this issue, we determined the numbers of activated microglial cells in the substantia nigra pars compacta and ventral tegmental area of monkeys subacutely and chronically exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Monkeys in the subacute MPTP treatment group were killed 1 week after the last MPTP injection; chronically treated monkeys were killed either 6 or 35 months after the last MPTP injection. Subacute MPTP administration induced loss of dopaminergic neurons in the substantia nigra pars compacta and ventral tegmental area and microglial activation in the same areas. Chronic MPTP treatment resulted in greater dopaminergic neuron depletion in both treatment groups. Both groups of chronic MPTP-treated monkeys showed increased numbers of activated microglial cells in the substantia nigra pars compacta that were similar to those of the subacute MPTP treatment group. These results indicate that microglial activation seems to be induced mainly by the toxic effects of MPTP and that it does not further progress once the toxin administration has been terminated. This suggests that the progressive degeneration of nigral cells in Parkinson disease may not necessarily be associated with progressively increased microglial activation.

The response of the immune system during injury of the central nervous system may play a role in protecting neurons. We have previously reported that immunization with MOG 35-55 prior to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced injury of the dopaminergic system promotes less dopamine depletion and less dopaminergic damage of neurons in mice. In this study, we evaluate the influence of MOG immunization on the inflammatory reaction that occurs at the place of injury. C57Bl male mice, 2 and 12 months old, received i.p. injections of MPTP (40 mg/kg) and some groups animals also received an additional injection with myelin oligodendrocyte glycoprotein (MOG) 35-55 in CFA 6 days before MPTP administration. MPTP caused a common inflammatory reaction characterized by microglial activation, infiltration of T cells into the substantia nigra and striatum and increased expression of mRNA encoding pro-inflammatory cytokines (IL-1 beta, TNFalpha, INF gamma) and trophic factors (TGFbeta, GDNF). MOG immunization prior to MPTP administration significantly diminished the microglial reaction and reduced the levels of infiltrating CD8+ lymphocytes. The number of CD4+ T cells remained at the same level as in the MPTP group. Expression of pro-inflammatory cytokines was diminished. The mRNA expression of GDNF was significantly higher in the MOG pretreated mice relative to the MPTP group, both in the 2 month old and 12 month old groups. Since MOG immunization prior to MPTP intoxication appears to prevent nigrostriatal injury, the observed decrease of inflammation and increase of GDNF mRNA expression in the injured areas might represent one of the mechanisms of observed neuroprotection.

The experiments on mice C57B1/6 with MPTP-induced Parkinsonian syndrome have shown that preliminary and simultaneous intranasal injection of glutamate antibodies inhibit development of the syndrome. Administration of glutamate antibodies decreased tremor, rigidity and increased horizontal locomotion, movement velocity in the open field.

Neuroinflammation may play a role in the pathogenesis of Parkinson's disease (PD). The present study questioned whether this neuroinflammatory response differs between the olfactory bulb, as an early affected region and the nigrostriatal system. Indeed, increased microgliosis was shown in post-mortem olfactory bulb of PD patients. Also in olfactory bulb of MPTP-treated mice, microgliosis and increased expression of IL-1alpha, IL-1beta and IL-1ra mRNA was observed early after treatment. These observations implicate that neuroinflammation is not restricted to the nigrostriatal system. MPTP-induced microgliosis in striatum and olfactory bulb was reduced in IL-1alpha/beta knockout mice, indicating that IL-1 affects microglia activation. Importantly, MPTP induced differential regulation of IL-1 receptors. mRNA levels of IL-1RI and, to a lesser extent, IL-1RII were increased in striatum. Interestingly, in the olfactory bulb only IL-1RII mRNA was enhanced. We suggest that differential regulation of IL-1 signaling can serve as an important mechanism to modulate neuroinflammatory activity after MPTP treatment and possibly during PD.

IL-6 is a major immunomodulatory cytokine with neuroprotective activity. The absence of interleukin-6 (IL-6) results in increased vulnerability of dopaminergic neurons to the neurotoxicant, MPTP, and a compromised reactive microgliosis. To determine how astrogliosis may contribute to nigrostriatal degeneration in IL-6 (-/-) mice, the inflammatory profiles of astrocytes of IL-6 genotype were compared. Fourteen cytokines and four chemokines were simultaneously assayed in the supernatants of LPS-stimulated primary astrocyte cultures. In a time course of 6, 18 and 48 h and LPS stimulations of 0, 0.1, 1, 10 and 100 ng/ml, IL-6 (-/-) astrocytes secreted significantly greater amounts of the pro-inflammatory cytokines IL-1alpha, IL-1beta and TNFalpha than did IL-6 (+/+) cells. Elevated levels of IL-10 and IL-12p40 were only detected at 48 h post-stimulation with greater IL-10 in IL-6 (-/-) supernatants and greater IL-12p40 in IL-6 (+/+) supernatants. IL-6 (+/+) astrocytes produced more G-CSF and GM-CSF when compared with IL-6 (-/-) astrocytes. Chemokine levels were greater in supernatants of IL-6 (+/+) astrocytes than IL-6 (-/-) cells prior to 48 h post-stimulation. At that time, higher levels of MIP-1alpha were maintained in IL-6 (+/+) supernatant, while similar levels of MCP-1 in supernatants of both IL-6 (+/+) and IL-6 (-/-) cells were measured. Additionally, LPS (100 ng/ml) resulted in greater levels of KC and Rantes in IL-6 (-/-) astrocyte supernatants compared with IL-6 (+/+) supernatants at that time. These results suggest that the autocrine modulatory activities of IL-6 affect multiple cytokine secretory pathways, which could participate in neurodegenerative processes.

Electrophysiological experiments on Wistar rats demonstrated that prior immunization of animals with conjugates of dopamine and serotonin with bovine serum albumin, as well as with bovine serum albumin alone, played a partial protective role in relation to the subsequent development in these animals of experimental MPTP-induced depressive syndrome: immunized animals showed no signs of the depressive state such as decreases in the latency of onset of REM sleep and the development of epileptiform activity in the caudate-putamen complex, though the increase in the proportion of REM sleep in the overall structure of sleep persisted. Changes in the spectral characteristics of brain electrical activity and sleep structure during the development of experimental MPTP-induced syndrome in animals immunized with conjugates of dopamine and serotonin with bovine serum albumin and with bovine serum albumin alone were antigen-specific and reflected functional shifts in the activity of those neurotransmitter systems targeted by immunization, as well as others sensitive to changes in the body's immunological status.

Immunological abnormalities have been described in idiopathic Parkinson's disease and in the mouse model of this disorder induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). This investigation was aimed to study the effect of MPTP on inflammatory response of whole blood phagocytes at different time intervals. C57BL male mice were injected intraperitoneally with either MPTP (30 mg/kg) or saline (control group) and the blood samples were collected at 4, 24 and 48 h. 50 microl of a 500-fold diluted blood sample was mixed with 150 microl of reaction mixture (0.4 mM luminol + 50 microg opsonized zymosan + 0.1% gelatin, in Hanks' balanced salt solution) and the chemiluminescence (CL) signal was measured in a luminometer at 37 degrees C. Although the CL response of the whole blood from control and MPTP groups was similar at 4 h, a significant increase in the CL signal was observed in MPTP-treated mice at 24 h post-treatment, which got subsided at 48 h. The findings of this study suggest that in an early stage a pro-inflammatory response following MPTP might trigger a chain of potentially toxic pathways mediated by reactive oxygen species, leading to progressive neuronal damage.

The pathological process of neurodegeneration is accompanied by an inflammatory reaction that is believed to contribute to the pathogenesis of neurodegenerative diseases. The aim of our study was to evaluate the influence of autoimmune reaction induced by post-traumatic vaccination with myelin self-antigen on spontaneous regeneration of dopaminergic neurons, injured with MPTP. C57BL mice were intoxicated with 40 mg/kg MPTP and seven days later immunized with MOG 35-55 peptide in CFA. On the 7th day following intoxication, the MPTP treated mice showed decrease of the dopamine level by 63% as compared to the control mice. However, starting from the 14th day following intoxication, a spectacular increase of dopamine content was observed. Immunization with MOG resulted in a statistically significant reduction of the increase in striatum as compared to non-immunized animals, and was lower by 23%, 17% and 15% on days 14, 28 and 50, respectively. Our results show suppressive influence of autoimmune reaction induced after injury on regeneration of dopamine cells intoxicated with MPTP.

To assess the involvement of the immune system in Parkinson's disease we studied the phenotype of circulating lymphocytes in 30 untreated and 34 treated patients. We found a numeric decrease in helper T cells (higher in CD4(+)CD45RA(+) than in CD4(+)CD29(+)) and B cells, and a rise in activated, CD4(+)CD25(+) lymphocytes that was correlated with lymphocyte depletion. All these alterations were independent of levodopa treatment. In addition, we performed striatal dopamine depletion in rats with either MPP(+) or 6-OHDA, showing that MPP(+) but not 6-OHDA can increase CD4(+)CD25(+) lymphocytes. Thus, mechanisms other than dopamine deficit may explain the immune activation in Parkinson's disease.