MPTP Mouse Research Articles

Analogues of desferrioxamine B designed to attenuate iron-mediated neurodegeneration: synthesis, characterisation and activity in the MPTP-mouse model of Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterised by the death of dopaminergic neurons in the substantia nigra pars compacta (SNpc) region of the brain and formation of α-synuclein-containing intracellular inclusions. Excess intraneuronal iron in the SNpc increases reactive oxygen species (ROS), which identifies removing iron as a possible therapeutic strategy. Desferrioxamine B (DFOB, 1) is an iron chelator produced by bacteria. Its high Fe(iii) affinity, water solubility and low chronic toxicity is useful in removing iron accumulated in plasma from patients with transfusion-dependent blood disorders. Here, lipophilic analogues of DFOB with increased potential to cross the blood-brain barrier (BBB) have been prepared by conjugating ancillary compounds onto the amine terminus. The ancillary compounds included the antioxidants rac-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (rac-trolox, rac-TLX (a truncated vitamin E variant)), R-TLX, S-TLX, methylated derivatives of 3-(6-hydroxy-2-methylchroman-2-yl)propionic acid (α-CEHC, γ-CEHC, δ-CEHC), or 4-(5-hydroxy-3-methyl-1H-pyrazol-1-yl)benzoic acid (carboxylic acid derivative of edaravone, EDA). Compounds 2-8 could have dual function in attenuating ROS by chelating Fe(iii) and via the antioxidant ancillary group. A conjugate between DFOB and an ancillary unit without antioxidant properties (3,5-dimethyladamantane-1-carboxylic acid (AdAdMe)) was included (9). Compounds 2-9 were more lipophilic (log P -0.05 to 3.39) than DFOB (log P -2.62) and showed an average plasma protein binding 6 times greater than DFOB. The ABTS˙+ radical assay indicated 2-8 had antioxidant activity ascribable to the ancillary fragment. Administration of 2 and 9 in the mouse model of PD using the neurotoxin prodrug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which recapitulates elevated iron of human PD, resulted in significant neuronal protection (p < 0.05; up to 89% of that in non-lesioned control animals), demonstrating the neuroprotective potential of these compounds for PD.

Vitamin D Treatment Attenuates Neuroinflammation and Dopaminergic Neurodegeneration in an Animal Model of Parkinson's Disease, Shifting M1 to M2 Microglia Responses.

Microglia-mediated neuroinflammation has been described as a common hallmark of Parkinson's disease (PD) and is believed to further exacerbate the progressive degeneration of dopaminergic neurons. Current therapies are unable to prevent the disease progression. A significant association has been demonstrated between PD and low levels of vitamin D in patients serum, and vitamin D supplement appears to have a beneficial clinical effect. Herein, we investigated whether vitamin D administered orally in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced preclinical animal model of PD protects against glia-mediated inflammation and nigrostriatal neurodegeneration. Vitamin D significantly attenuated the MPTP-induced loss of tyrosine hydrlase (TH)-positive neuronal cells, microglial cell activation (Iba1-immunoreactive), inducible nitric oxide synthase (iNOS) and TLR-4 expression, typical hallmarks of the pro-inflammatory (M1) activation of microglia. Additionally, Vitamin D was able to decrease pro-inflammatory cytokines mRNA expression in distinct brain areas of the MPTP mouse. Importantly, we also assessed the anti-inflammatory property of vitamin D in the MPTP mouse, in which it upregulated the anti-inflammatory cytokines (IL-10, IL-4 and TGF-β) mRNA expression as well as increasing the expression of CD163, CD206 and CD204, typical hallmarks of alternative activation of microglia for anti-inflammatory signalling (M2). Collectively, these results demonstrate that vitamin D exhibits substantial neuroprotective effects in this PD animal model, by attenuating pro-inflammatory and up-regulating anti-inflammatory processes.

The behavioural and neuroprotective outcomes when 670 nm and 810 nm near infrared light are applied together in MPTP-treated mice

We have shown previously that when applied separately, 670nm and 810nm near infrared light (NIr) reduces behavioural deficits and offers neuroprotection in a MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson’s disease. Here, we explored the beneficial outcomes when these NIr wavelengths were applied both together, either concurrently (at the same time) or sequentially (one after the other). Mice received MPTP injections (total of 50mg/kg) and had extracranial application of 670nm and/or 810nm NIr. Behavioural activity was tested with an open-field test and brains were processed for tyrosine hydroxylase immunohistochemistry and stereology. Our results showed that when 670nm and 810nm NIr were applied both together and sequentially, there was a greater overall beneficial outcome – increased locomotor activity and number of tyrosine hydroxylase immunoreactive cells in the substantia nigra pars compacta – than when they were applied either separately, or in particular, both together and concurrently. In summary, our findings have important implications for future use of NIr therapy in humans, that there are some combinations of wavelengths that provide more beneficial outcome than others.

402 - Thiol Oxidation Mediated Redox Signaling Triggers Specific Dopaminergic Neurodegeneration in Parkinson′s Disease

Oxidative stress has been implicated in pathogenesis of Parkinson’s disease (PD), but it is yet unclear as to how the generalized ROS generation leads to degeneration of dopaminergic neurons in substantia nigra pars compacta (SNpc). Activation of redox driven signaling pathways may contribute to the specific cell death seen in PD. Using the MPTP mouse model of PD, we have established that stress-regulated MAPK signaling, specifically p38 MAPK-dependent death signaling, is selectively activated in dopaminergic neurons, while JNK is activated in microglia. Further, we found ASK1 as an upstream MAP3K responsible for p38 activation. ASK1, in turn, was selectively activated by TNF upregulation acting through thiol oxidation of Trx1, a negative regulator of ASK1 activity. Further, we also observed inhibition of Akt-mediated cell survival pathway through cysteine oxidation in Akt. As protein thiol oxidation emerged as a major contributor towards selective cell death signaling, we developed a novel diamide-induced mouse model of PD to examine whether thiol oxidation alone, caused by diamide, could trigger PD-relevant phenotype. Stereotaxic injection of diamide into mouse brain led to extensive dopaminergic neurodegeneration, coupled with biochemical and behavioral deficits as observed in PD, and activation of ASK1-mediated cell death signaling. α-Synuclein aggregation, not often seen in other models of PD, was also reproduced in this model. Current studies are underway to investigate whether Grx1 inhibition in vivo (leading to increased glutathionylation and protein thiol oxidation), results in PD pathology. Overall, these studies demonstrate the critical role of thiol oxidation in triggering neurodegeneration in PD.

Mice lacking Faim2 show increased cell death in the MPTP mouse model of Parkinson disease.

The death receptor Fas/CD95 mediates apoptotic cell death in response to external stimuli. In neurons, Fas-induced apoptosis is prevented by Fas-apoptotic inhibitory molecule 2 (Faim2). Mice lacking Faim2 showed increased neurodegeneration in animal models of stroke and bacterial meningitis. We therefore tested the relevance of Faim2 in a classical animal model of Parkinson disease and determined the toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in Faim2-deficient mice. Without MPTP treatment, there was no difference in the dopaminergic system between Faim2-deficient mice and control mice. MPTP was applied i.p. in doses of 30mg per kg on five consecutive days. Fourteendays after the last MPTP injection, the number of dopaminergic neurons in the lateral substantia nigra, assayed by stereological counting, was reduced by 39% in control mice and 53% in Faim2-deficient mice. The density of dopaminergic fibers in the dorsal striatum was reduced by 36% in control mice and 69% in Faim2-deficient mice, in the ventral striatum 44% in control mice and 76% in Faim2-deficient mice. Fiber density recovered at 90days after MPTP with similar density in both groups. Striatal catecholamine levels were reduced by 81-84% in both groups and recovered at 90days. Faim2 expression was documented in mouse midbrain using quantitative reverse transcription-PCR (qRT-PCR) and found decreased after MPTP administration. Taken together, our findings demonstrate increased degeneration of dopaminergic neurons with Faim2 deficiency, indicating that Fas-induced apoptosis contributes to cell death in the MPTP mouse model. Along with the decreased expression of Faim2 after MPTP, this finding indicates that boosting Faim2 function might represent a therapeutic strategy for Parkinson disease.

Respiratory chain inhibition: one more feature to propose MPTP intoxication as a Leigh syndrome model.

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxicated mice have been widely used to model the loss of dopaminergic neurons. As this treatment leads to basal ganglia degeneration, it was proposed that MPTP mice could be used as a model of Leigh syndrome. However, this mitochondrial pathology is biochemically characterized by a respiratory chain dysfunction. To determine if MPTP can affect in vivo mitochondria function, we measured the activities of mitochondrial respiratory chain complexes in several tissues. Our results show that MPTP affects mainly mitochondrial respiratory chain complex IV, as found in Leigh Syndrome, confirming that acute MPTP intoxicated mice are a good model of Leigh Syndrome.

δ-Aminolevulinate Dehydratase Activity is Stimulated in a MPTP Mouse Model of Parkinson's Disease: Correlation with Myeloperoxidase Activity.

Myeloperoxidase (MPO) is an inducible heme peroxidase responsive to some stress situations. It is already known that its activity is stimulated in neurodegenerative disorders and in the animal model of parkinson's disease (PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). By contrast, the role of δ-aminolevulinate dehydratase (δ-ALA-D), an essential enzyme for heme synthesis, has not been investigated in the MPTP model. The aim of this study was to investigate the involvement of striatal δ-ALA-D activity in an acute model of PD, induced by MPTP, in C57Bl/6 mice and its correlation with MPO activity. Animals received four MPTP injections (20mg/kg, i.p.) or saline (vehicle) to induce a PD model. 7 days after MPTP administration, the motor function was evaluated through rotarod and challenging beam tests in mice. Afterward, mice were killed, and the striata were removed for biochemical analyses. MPTP-treated mice showed impairment in motor skills, such as balance and motor coordination. Furthermore, there was a reduction of tyrosine hydroxylase levels in these animals, which characterizes the dopaminergic lesion. Striatal δ-ALA-D activity was stimulated by MPTP, as well as the MPO activity, and a significant positive correlation between δ-ALA-D and MPO activities was also demonstrated. These data suggest that δ-ALA-D activity could be stimulated due to the requirement of heme groups by peroxidases. Therefore, this study demonstrated for the first time the involvement of striatal δ-ALA-D activity in the MPTP model and its correlation with the MPO activity.

Neuroprotective and immunomodulatory effects of raloxifene in the myenteric plexus of a mouse model of Parkinson's disease

Motor symptoms in Parkinson's disease (PD) are often preceded by nonmotor symptoms related to dysfunctions of the autonomic nervous system such as constipation, defecatory problems, and delayed gastric emptying. These gastrointestinal impairments are associated with the alteration of dopaminergic (DAergic) neurons in the myenteric plexus of the gut. Recently, we demonstrated the anti-inflammatory properties of estrogens to treat intestinal neurodegeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. The present study aimed to investigate the neuroprotective and anti-inflammatory roles of raloxifene, a selective estrogen receptor modulator (SERM) already commercialized for osteoporosis treatment. In MPTP-treated mice, we found that raloxifene decreased the loss of DAergic neurons and prevented the increase in proinflammatory macrophage density in the myenteric plexus. Interestingly, raloxifene activity was prevented by the G protein–coupled estrogen receptor 1 (GPER1) antagonist G15, suggesting that raloxifene effects were mainly mediated by GPER1. Moreover, monocytic cell proinflammatory polarization, nuclear factor-kappa B (NF-κB) response, nitric oxide (NO), and proinflammatory cytokines production following 1-methyl-4-phenylpyridinium (MPP+) treatment were also prevented by raloxifene in vitro. Overall, the present results suggest that raloxifene may help preventing the loss of DAergic neurons in the myenteric plexus in an MPTP mouse model of PD, at least in part through its anti-inflammatory effects. This suggests that drug repurposing of raloxifene might represent a promising therapeutic avenue to prevent systemic inflammation and peripheral neuronal dysfunction at early PD stages.

Cdk5/p25 specific inhibitory peptide TFP5 rescues the loss of dopaminergic neurons in a sub-acute MPTP induced PD mouse model

Parkinson's disease (PD) is pathologically characterized by progressively loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and the formation of Lewy bodies. In 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) induced PD mice models, the calpain- cyclin-dependent kinase 5 (Cdk5)-myocyte enhancer factor 2 (MEF2) signaling has been proven in governing dopaminergic neuronal death. Under MPTP insult, p35 is cleaved by calpain into p25, which binds to Cdk5 and exhibits hyperactivity of Cdk5/p25. Cdk5/p25 inactivates MEF2, a survivor factor, which is critical for DA neuronal death. In this study, neuroprotective effect of the Cdk5/p25 specific peptide, TFP5, was evaluated in sub-acute MPTP induced PD mouse model by intraperitoneal (i.p.) injection of MPTP for five consecutive days. The results indicated that the levels of p35 and p25, and p25/p35 ratio increased in the sub-acute MPTP mice. TFP5 broadly reached cortex neuron, hippocampus and SNpc areas after i.p. injections. Pretreatment with 45mg/kg/day TFP5, as well as 10mgkg/day Cdk5 inhibitor roscovitine, for three days significantly rescued DA neuronal loss up to 9.8% or 9.7% respectively compared to the saline treated group. Treatment of TFP5 and roscovitine reduced the levels of inactive form of MEF2 and cleaved caspase 3, thus protected apoptosis of DA neurons against MPTP insult. Our results propose that TFP5 might be a potential therapeutic candidate for PD.

Type-1 interferons contribute to the neuroinflammatory response and disease progression of the MPTP mouse model of Parkinson's disease.

Type-1 interferons (IFNs) are pleiotropic cytokines with a critical role in the initiation and regulation of the pro-inflammatory response. However, the contribution of the type-1 IFNs to CNS disorders, specifically chronic neuropathologies such as Parkinson's disease is still unknown. Here, we report increased type-1 IFN signaling in both post mortem human Parkinson's disease samples and in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mouse model. In response to MPTP, mice lacking the type-1 IFN receptor (IFNAR1(-/-) ) displayed decreased type-1 IFN signaling, an attenuated pro-inflammatory response and reduced loss of dopaminergic neurons. The neuroprotective potential of targeting the type-1 IFN pathway was confirmed by reduced neuroinflammation and DA cell death in mice treated with a blocking monoclonal IFNAR1 (MAR-1) antibody. The MPTP/MAR-1 treated mice also displayed increased striatal dopamine levels and improved behavioural outcomes compared to their MPTP/IgG controls. These data, implicate for the first time, a deleterious role for the type-1 IFNs as key modulators of the early neuroinflammatory response and therefore the neuronal cell death in Parkinson's disease. GLIA 2016;64:1590-1604.

Effect of total flavonoids from Scutellaria baicalensis on dopaminergic neurons in the substantia nigra.

The aim of the present study was to investigate the effect of Scutellaria baicalensis stem-leaf total flavonoid (SSTF) on the dopaminergic neurons in the substantia nigra in a mouse model of Parkinson's disease (PD). The mouse model was established by intravenous injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). SSTF (5 mg/kg) was administered to the mice before or after MPTP injection, and the effects of SSTF on the behavior of the mice and the dopaminergic neurons in the substantia nigra were assessed. In addition, the level of serum malondialdehyde (MDA) was measured. Following injection of MPTP, the number of dopaminergic neurons in the substantia nigra was decreased and the neurons appeared atrophic. In addition, the level of serum MDA in the MPTP mice increased. The mean behavioral scores and the number of dopaminergic neurons in the SSTF treatment groups were significantly higher than in the MPTP group (P<0.05), and the mean serum MDA levels were significantly lower (P<0.05). Thus, SSTF improves the behaviors and the numbers of dopaminergic neurons in the substantia nigra in MPTP-induced PD in mice. These beneficial effects appear to be associated with the reduction in serum MDA.

Effects of striatal transplantation of cells transfected with GDNF gene without pre- and pro-regions in mouse model of Parkinson's disease.

BackgroundPreviously, we have shown that transgenic cells bearing the GDNF gene with deleted pre- and pro-regions (mGDNF) can release transgenic GDNF. The medium conditioned by transgenic cells with mGDNF induced axonal growth in rat embryonic spinal ganglion in vitro. Here we demonstrate a neurotrophic effect of mGDNF on PC12 cells in vitro as well as its neuroprotective effect on dopaminergic neurons in the substantia nigra pars compacta in vivo as indicated by improved motor coordination and sleep-wakefulness cycle in the MPTP mouse model of Parkinson’s disease.ResultsHEK293 cells were transfected with a vector encoding an isoform of the human GDNF gene with deleted pre- and pro-regions (mGDNF). This factor in the medium conditioned by the transfected cells was shown to induce axonal growth in PC12 cells. The early Parkinson’s disease model was established by injection of the dopaminergic pro-neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into C57Bl/6 mice. Transgenic HEK293/mGDNF/GFP cells were transplanted into the striatum (caudate-putamen) of experimental mice. The sleep-wakefulness cycle was studied by continuous EEG and motor activity monitoring 1 and 2 weeks after MPTP injection. After the experiment, the motor coordination of experimental animals was evaluated in the rotarod test, and dopaminergic neurons in the substantia nigra pars compacta were counted in cross-sections of the midbrain. MPTP administration lowered the number of tyrosine hydroxylase immunopositive cells in the substantia nigra pars compacta, decreased motor coordination, and increased the total wake time during the dark period. The transplantation of HEK293/mGDNF cells into the caudate-putamen 3 days prior to MPTP injection smoothed these effects, while the control transplantation of HEK293 cells showed no notable impact.ConclusionsTransplantation of transgenic cells with the GDNF gene lacking the pre- and pro-sequences can protect dopaminergic neurons in the mouse midbrain from the subsequent administration of the pro-neurotoxin MPTP, which is confirmed by polysomnographic, behavioral and histochemical data. Hence it is released from transfected cells and preserves the differentiation activity and neuroprotective properties.

IDH2 deficiency promotes mitochondrial dysfunction and dopaminergic neurotoxicity: implications for Parkinson’s disease

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and its pathogenesis is under intense investigation. Substantial evidence indicates that mitochondrial dysfunction and oxidative stress play central roles in the pathophysiology of PD, through activation of mitochondria-dependent apoptotic molecular pathways. Several mitochondrial internal regulating factors act to maintain mitochondrial function. However, the mechanism by which these internal regulating factors contribute to mitochondrial dysfunction in PD remains elusive. One of these factors, mitochondrial NADP+-dependent isocitrate dehydrogenase (IDH2), has been implicated in the regulation of mitochondrial redox balance and reduction of oxidative stress-induced cell injury. Here we report that IDH2 regulates mitochondrial dysfunction and cell death in MPP+/MPTP-induced DA neuronal cells, and in a mouse model of PD. Down-regulation of IDH2 increased DA neuron sensitivity to MPP+; lowered IDH2 levels facilitated induction of apoptotic cell death due to elevated mitochondrial oxidative stress. Deficient IDH2 also promoted loss of DA SNpc neurons in an MPTP mouse model of PD. Interestingly, Mito-TEMPO, a mitochondrial ROS-specific scavenger, protected degeneration of SNpc DA neurons in the MPTP model of PD. These findings demonstrate that IDH2 contributes to degeneration of the DA neuron in the neurotoxin model of PD and establish IDH2 as a molecular target of potential therapeutic significance for this disabling neurological illness.

Exacerbation of MPTP induced neurodegeneration by a CD4+ effector T cell line specific for N-α-synuclein in a mouse model of Parkinson’s disease

Abstract Inflammation and oxidative stress play critical roles in PD. Moreover, T cell-mediated immunity regulates innate immunity to control or exacerbate neuroinflammation. We have previously shown in the MPTP mouse model that adoptive transfer of effector T cells (Teffs) which recognize nitrated α-synuclein (N-α-syn) as non-self exacerbates microglial-mediated neuroinflammation with amplified dopaminergic neurodegeneration. The specific mechanisms by which these Teffs modulate neurodegeneration remain enigmatic. However, increasing evidence suggests neurotoxic inflammatory activities have a profound effect on the pathogenesis of PD. Herein, we report on the generation and long-term culture of a N-α-syn specific CD4+ Teff line that induces increased production of reactive nitrogen species from microglia and also intensifies the loss of tyrosine hydroxylase+ (TH+) neurons of MPTP-intoxicated mice. Flow cytometric analysis showed the Teffs line exhibited very distinct expression of CD3 and CD4 cell surface markers and intracellular IL-17a cytokine, suggestive of characteristics consistent with a Th17 cell. Co-culture of the Teffs with a dopaminergic cell line significantly increased cell death of dopaminergic cells in comparison to controls. Lastly, adoptive transfer of the Teffs line to MPTP-intoxicated mice increased the loss of TH+ neurons. Together, these results support the notion that Teffs may play a pivotal role in the progression of neurodegeneration in PD. Further investigation of the mechanisms behind the exacerbation of neurodegeneration caused by Teffs has the potential to advance therapeutic strategies that target neurotoxic mechanisms to attenuate neuroinflammation and ameliorate neuronal loss in PD.

Gdf-15 deficiency does not alter vulnerability of nigrostriatal dopaminergic system in MPTP-intoxicated mice.

Growth/differentiation factor-15 (Gdf-15) is a member of the transforming growth factor-β (Tgf-β) superfamily and has been shown to be a potent neurotrophic factor for midbrain dopaminergic (DAergic) neurons both in vitro and in vivo. Gdf-15 has also been shown to be involved in inflammatory processes. The aim of this study was to identify the role of endogenous Gdf-15 in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson's disease (PD) by comparing Gdf-15 (+/+) and Gdf-15 (-/-) mice. At 4days and 14days post-MPTP administration, both Gdf-15 (+/+) and Gdf-15 (-/-) mice showed a similar decline in DAergic neuron numbers and in striatal dopamine (DA) levels. This was followed by a comparable restorative phase at 90days and 120days, indicating that the absence of Gdf-15 does not affect the susceptibility or the recovery capacity of the nigrostriatal system after MPTP administration. The MPTP-induced microglial and astrocytic response was not significantly altered between the two genotypes. However, pro-inflammatory and anti-inflammatory cytokine profiling revealed the differential expression of markers in Gdf-15 (+/+) and Gdf-15 (-/-) mice after MPTP administration. Thus, the MPTP mouse model fails to uncover a major role of endogenous Gdf-15 in the protection of MPTP-lesioned nigrostriatal DAergic neurons, in contrast to its capacity to protect the 6-hydroxydopamine-intoxicated nigrostriatal system.

Issue Cover (May 2016)

Front cover: The gut hormone ghrelin is neuroprotective in Parkinson's Disease. However, ghrelin exists in two distinctive isoforms (acylated and des-acylated ghrelin). This representative image shows dopamine neurons (green) and microglial activation (red) in response to the MPTP model of Parkinson's Disease. We show that acylated ghrelin is the isoform responsible for in vivo neuroprotection of ghrelin in the MPTP model of Parkinson's Disease by minimising dopamine cell loss and attenuating glial activation. Overall, we show that acylated ghrelin is an ideal therapeutic target to reduce Parkinson's Disease progression. Read the full article ‘Acylated but not des-acyl ghrelin is neuroprotective in an MPTP mouse model of Parkinson's disease’ by J. A. Bayliss, M. Lemus, V. V. Santos, M. Deo, J. D. Elsworth and Z. B. Andrews (J. Neurochem. 2016, vol. 137 (3), pp. 460-471) on doi: 10.1111/jnc.13576

Magnetic Resonance Imaging Features of the Nigrostriatal System: Biomarkers of Parkinson's Disease Stages?

IntroductionMagnetic resonance imaging (MRI) can be used to identify biomarkers in Parkinson’s disease (PD); R2* values reflect iron content related to high levels of oxidative stress, whereas volume and/or shape changes reflect neuronal death. We sought to assess iron overload in the nigrostriatal system and characterize its relationship with focal and overall atrophy of the striatum in the pivotal stages of PD.MethodsTwenty controls and 70 PD patients at different disease stages (untreated de novo patients, treated early-stage patients and advanced-stage patients with L-dopa-related motor complications) were included in the study. We determined the R2* values in the substantia nigra, putamen and caudate nucleus, together with striatal volume and shape analysis. We also measured R2* in an acute MPTP mouse model and in a longitudinal follow-up two years later in the early-stage PD patients.ResultsThe R2* values in the substantia nigra, putamen and caudate nucleus were significantly higher in de novo PD patients than in controls. Early-stage patients displayed significantly higher R2* values in the substantia nigra (with changes in striatal shape), relative to de novo patients. Measurements after a two-year follow-up in early-stage patients and characterization of the acute MPTP mouse model confirmed that R2* changed rapidly with disease progression. Advanced-stage patients displayed significant atrophy of striatum, relative to earlier disease stages.ConclusionEach pivotal stage in PD appears to be characterized by putative nigrostriatal MRI biomarkers: iron overload at the de novo stage, striatal shape changes at early-stage disease and generalized striatal atrophy at advanced disease.

Neuro-protective effects of Ligustri Fructus by suppression of oxidative stress in mouse model of Parkinson’s disease

Parkinson’s disease (PD) is a progressive degenerative disorder of the central nervous system (CNS) that leads to impairment of motor skills and speech. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes damage to the dopaminergic (DA) neurons, and 1-4-Methyl-4-phenylpyridinium (MPP+) causes cell death in differentiated PC12 cells that is similar to the degeneration that occurs in PD. Moreover, MPTP treatment increases the activity of the microglia cells that produced reactive oxygen species (ROS). We recently reported that Ligustri Fructus (LF), a widely used traditional herbal medicine, increases cell viability in a yeast model of PD. In the present study, we examined the inhibitory effect of LF (0.01, 5, 10 ug) on the neurotoxicity of MPTP in mice and on the MPP + -induced cell death in differentiated PC12 cells. In vivo experiment, MPTP injection revealed a significant loss of DA neurons in the substantia nigra, while LF (100, 200 mg/ kg) treatment dramatically reversed DA neuron loss in immunohistochemistry assay for tyrosine hydroxylase (TH). Furthermore, LF attenuated the MPP + -induced cell death, decreased the generation of ROS, and activated glutathione peroxidase in PC12 cells. These results suggest that LF may be beneficial for the treatment of neurodegenerative diseases such as PD.

Hericium erinaceus mycelium and its isolated erinacine A protection from MPTP-induced neurotoxicity through the ER stress, triggering an apoptosis cascade.

BackgroundHericium erinaceus is an edible mushroom; its various pharmacological effects which have been investigated. This study aimed to demonstrate whether efficacy of oral administration of H. erinaceus mycelium (HEM) and its isolated diterpenoid derivative, erinacine A, can act as an anti-neuroinflammatory agent to bring about neuroprotection using an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson’s disease, which results in motor disturbances, in addition to elucidating the mechanisms involved.MethodsMice were treated with and without HEM or erinacine A, after MPTP injection for brain injuries by the degeneration of dopaminergic nigrostriatal neurons. The efficacy of oral administration of HEM improved MPTP-induced loss of tyrosine hydroxylase positive neurons and brain impairment in the substantia nigra pars compacta as measured by brain histological examination.ResultsTreatment with HEM reduced MPTP-induced dopaminergic cell loss, apoptotic cell death induced by oxidative stress, as well as the level of glutathione, nitrotyrosine and 4-hydroxy-2-nonenal (4-HNE). Furthermore, HEM reversed MPTP-associated motor deficits, as revealed by the analysis of rotarod assessment. Our results demonstrated that erinacine A decreases the impairment of MPP-induced neuronal cell cytotoxicity and apoptosis, which were accompanied by ER stress-sustained activation of the IRE1α/TRAF2, JNK1/2 and p38 MAPK pathways, the expression of C/EBP homologous protein (CHOP), IKB-β and NF-κB, as well as Fas and Bax.ConclusionThese physiological and brain histological changes provide HEM neuron-protective insights into the progression of Parkinson’s disease, and this protective effect seems to exist both in vivo and in vitro.

Estrogen receptors modulate striatal metabotropic receptor type 5 in intact and MPTP male mice model of Parkinson’s disease

Glutamate is the most important brain excitatory neurotransmitter and glutamate overactivity is well documented in Parkinson’s disease (PD). Metabotropic glutamate (mGlu) receptors are reported to interact with membrane estrogen receptors (ERs) and more specifically the mGlu5 receptor subtype. 17β-estradiol and mGlu5 antagonists have neuroprotective effects in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. We previously reported that ERα and ERβ are involved in neuroprotection following MPTP toxicity. The present study investigated the implication of ERs on the mGlu5 receptor adaptive response to MPTP toxicity in the brain of wild type (WT), ER knockout (ERKO)α and ERKOβ male mice. Autoradiography of [3H]ABP688 specific binding to striatal mGlu5 receptors showed a dorsal/ventral gradient similar for WT, ERKOα and ERKOβ mice with higher values ventrally. The lateral septum had highest [3H]ABP688 specific binding that remained unchanged in all experimental groups. ERKOα and ERKOβ mice had similarly lower striatal [3H]ABP688 specific binding than WT mice as measured also by Western blots. MPTP dose-dependently decreased striatal [3H]ABP688 specific binding in WT but not in ERKOα and ERKOβ mice; this correlated positively with striatal dopamine concentrations. A 17β-estradiol treatment for 10 days left unchanged striatal [3H]ABP688 specific binding of unlesioned mice of the three genotypes. 17β-estradiol treatment for 5 days before MPTP and for 5 days after partially prevented the mGlu5 receptor decrease only in WT MPTP mice and this was associated with higher BDNF striatal contents. These results thus show that in male mice ERs affect striatal mGlu5 receptor levels and their response to MPTP.