Biochemical, behavioral and immunohistochemical alterations in MPTP-treated mouse model of Parkinson's disease

Therapeutic considerations of bioactive compounds in Alzheimer's disease and Parkinson's disease: Dissecting the molecular pathways

Leading neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) are characterized by the impairment of memory and motor functions, respectively. Despite several breakthroughs, there exists a lack of disease-modifying treatment strategies for these diseases, as the available drugs provide symptomatic relief and bring along side effects. Bioactive compounds are reported to bear neuroprotective properties with minimal toxicity, however, a detailed elucidation of their modes of neuroprotection is lacking. The review elucidates the neuroprotective mechanism(s) of some of the major phyto-compounds in pre-clinical and clinical studies of AD and PD to understand their potential in combating these diseases. Curcumin, eugenol, resveratrol, baicalein, sesamol and so on have proved efficient in countering the pathological hallmarks of AD and PD. Curcumin, resveratrol, caffeine and so on have reached the clinical phases of these diseases, while aromadendrin, delphinidin, cyanidin and xanthohumol are yet to be extensively explored in pre-clinical phases. The review highlights the need for extensive investigation of these compounds in the clinical stages of these diseases so as to utilize their disease-modifying abilities in the real field of treatment. Moreover, poor pharmacokinetic properties of natural compounds are constraints to their therapeutic yields and this review suggests a plausible contribution of nanotechnology in overcoming these limitations.

Combating Dopaminergic Neurodegeneration in Parkinson's Disease through Nanovesicle Technology

Parkinson's disease (PD) is characterized by dopaminergic neurodegeneration, resulting in dopamine depletion and motor behavior deficits. Since the discovery of L-DOPA, it has been the most prescribed drug for symptomatic relief in PD, whose prolonged use, however, causes undesirable motor fluctuations like dyskinesia and dystonia. Further, therapeutics targeting the pathological hallmarks of PD including α-synuclein aggregation, oxidative stress, neuroinflammation, and autophagy impairment have also been developed, yet PD treatment is a largely unmet success. The inception of the nanovesicle-based drug delivery approach over the past few decades brings add-on advantages to the therapeutic strategies for PD treatment in which nanovesicles (basically phospholipid-containing artificial structures) are used to load and deliver drugs to the target site of the body. The present review narrates the characteristic features of nanovesicles including their blood-brain barrier permeability and ability to reach dopaminergic neurons of the brain and finally discusses the current status of this technology in the treatment of PD. From the review, it becomes evident that with the assistance of nanovesicle technology, the therapeutic efficacy of anti-PD pharmaceuticals, phyto-compounds, as well as that of nucleic acids targeting α-synuclein aggregation gained a significant increment. Furthermore, owing to the multiple drug-carrying abilities of nanovesicles, combination therapy targeting multiple pathogenic events of PD has also found success in preclinical studies and will plausibly lead to effective treatment strategies in the near future.

Modeling of the Progressive Degradation of the Nigrostriatal Dopaminergic System in Mice to Study the Mechanisms of Neurodegeneration and Neuroplasticity in Parkinson's Disease

The fight against neurodegenerative diseases, including Parkinson's disease (PD), is among the global challenges of the 21st century. The low efficiency of therapy is due to the late diagnosis and treatment of PD, which take place when there is already significant degradation of the nigrostriatal dopaminergic system, a key link in the regulation of motor function. We have developed a subchronic mouse model of PD by repeatedly administering 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at gradually increasing doses with a 24 h interval between injections, a period comparable to the time of MPTP metabolism and elimination from the body. This model reproduces the main hallmarks of PD: progressive degeneration of dopaminergic neurons; the appearance of motor disorders with a 70-80% decrease in the level of dopamine in the striatum; an increase in dopamine turnover in the striatum to compensate for dopamine deficiency. When comparing the degradation of the nigrostriatal dopaminergic system and motor disorders in mice in the acute and subchronic models of PD, it has turned out that the resistance of dopaminergic neurons to MPTP increases with its repeated administration. Our subchronic model of PD opens up broad prospects for studying the molecular mechanisms of PD pathogenesis and developing technologies for early diagnosis and preventive treatment.

Insights into Manganese Superoxide Dismutase and Human Diseases

Redox equilibria and the modulation of redox signalling play crucial roles in physiological processes. Overproduction of reactive oxygen species (ROS) disrupts the body's antioxidant defence, compromising redox homeostasis and increasing oxidative stress, leading to the development of several diseases. Manganese superoxide dismutase (MnSOD) is a principal antioxidant enzyme that protects cells from oxidative damage by converting superoxide anion radicals to hydrogen peroxide and oxygen in mitochondria. Systematic studies have demonstrated that MnSOD plays an indispensable role in multiple diseases. This review focuses on preclinical evidence that describes the mechanisms of MnSOD in diseases accompanied with an imbalanced redox status, including fibrotic diseases, inflammation, diabetes, vascular diseases, neurodegenerative diseases, and cancer. The potential therapeutic effects of MnSOD activators and MnSOD mimetics are also discussed. Targeting this specific superoxide anion radical scavenger may be a clinically beneficial strategy, and understanding the therapeutic role of MnSOD may provide a positive insight into preventing and treating related diseases.

A comprehensive and mechanistic review on protective effects of kaempferol against natural and chemical toxins: Role of NF-κB inhibition and Nrf2 activation

Different toxins, including chemicals and natural, can be entered from various routes and influence human health. Herbal medicines and their active components can attenuate the toxicity of agents via multiple mechanisms. For example, kaempferol, as a flavonoid, can be found in fruits and vegetables, and has an essential role in improving disorders such as cardiovascular disorders, neurological diseases, cancer, pain, and inflammation situations. The beneficial effects of kaempferol may be related to the inhibition of oxidative stress, attenuation of inflammatory factors such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2) and nuclear factor ĸB (NF-ĸB) as well as the modulation of apoptosis and mitogen-activated protein kinase (MAPK) signaling pathways. This flavonoid boasts a wide spectrum of toxin targeting effects in tissue fibrosis, inflammation, and oxidative stress thus shows promising protective effects against natural and chemical toxin induced hepatotoxicity, nephrotoxicity, cardiotoxicity, neurotoxicity, lung, and intestinal in the in vitro and in vivo setting. The most remarkable aspect of kaempferol is that it does not focus its efforts on just one organ or one molecular pathway. Although its significance as a treatment option remains questionable and requires more clinical studies, it seems to be a low-risk therapeutic option. It is crucial to emphasize that kaempferol's poor bioavailability is a significant barrier to its use as a therapeutic option. Nanotechnology can be a promising way to overcome this challenge, reviving optimism in using kaempferol as a viable treatment agent against toxin-induced disorders.

The C-terminal domain of the heavy chain of tetanus toxin prevents the oxidative and nitrosative stress induced by acute toxicity of 1-methyl-4-phenylpyridinium, a rat model of Parkinson's disease

The recombinant carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) exerts neuroprotective and neurorestorative effects on the dopaminergic system of animal models of Parkinson's disease (PD). The present study aimed to determine the effect of the Hc-TeTx fragment on the markers of oxidative stress and nitrosative stress generated by the acute toxicity of 1-methyl-4-phenylpyridinium (MPP⁺). For this purpose, the Hc-TeTx fragment was administered once a day in three 20 μg/kg consecutive injections into the grastrocnemius muscle of the rats, with an intra-striatal unilateral injection of 1 μL of MPP⁺ [10 μg/mL] then administered in order to cause a dopaminergic lesion. The results obtained show that the rats treated with Hc-TeTx plus MPP⁺ presented an increase in the expression of tyrosine hydroxylase (TH), a significantly greater decrease in the levels of the markers of oxidative stress, nitrosative stress, and neurodegeneration than that observed for the group injured with only MPP⁺. Moreover, it was observed that total superoxide dismutase (SOD) and copper/zinc SOD activity increased with the administration of Hc-TeTx. Finally, immunoreactivity levels were observed to decrease for the levels of 3-nitrotyrosine and the glial fibrillary acidic protein in the ipsilateral striatum of the rats treated with Hc-TeTx plus MPP⁺, in contrast with those lesioned with MPP⁺ alone. Our results demonstrate that the recombinant Hc-TeTx fragment may be a potent antioxidant and, therefore, could be suggested as a therapeutic tool against the dopaminergic neuronal impairment observed in the early stages of PD.

A Mouse Model of Nigrostriatal Dopaminergic Axonal Degeneration As a Tool for Testing Neuroprotectors

Degeneration of nigrostriatal dopaminergic neurons in Parkinson's disease begins from the axonal terminals in the striatum and, then, in retrograde fashion, progresses to the cell bodies in the substantia nigra. Investigation of the dynamics of axonal terminal degeneration may help in the identification of new targets for neuroprotective treatment and be used as a tool for testing potential drugs. We have shown that the degeneration rate of dopaminergic axonal terminals changes over time, and that the striatal dopamine concentration is the most sensitive parameter to the action of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). This model was validated using neuroprotectors with well-known mechanisms of action: the dopamine transporter inhibitor nomifensine and SEMAX peptide that stimulates the secretion of endogenous neurotrophic factors or acts as an antioxidant. Nomifensine was shown to almost completely protect dopaminergic fibers from the toxic effect of MPTP and maintain the striatal dopamine concentration at the control level. However, SEMAX, slightly but reliably, increased striatal dopamine when administered before MPTP treatment, which indicates that it is more effective as an inductor of endogenous neurotrophic factor secretion rather than as an antioxidant.

Impaired autophagy in microglia aggravates dopaminergic neurodegeneration by regulating NLRP3 inflammasome activation in experimental models of Parkinson's disease

Microglia-mediated inflammation plays an important role in the pathogenesis of several neurodegenerative diseases including Parkinson's disease (PD). Recently, autophagy has been linked to the regulation of the inflammatory response. However, the potential role of microglial autophagy in the context of PD pathology has not been characterized. In the present study, we investigated whether impaired microglial autophagy would affect dopaminergic neurodegeneration and neuroinflammation both in vivo and in vitro. In vitro, BV2 microglial cells were exposed to LPS in the presence or absence of autophagy-related gene 5 (Atg5) small interference RNA (Atg5-siRNA). For in vivo study, microglial Atg5 conditional knockout (Atg5^flox/flox; CX3CR1-Cre) mice and their wild-type littermates (Atg5^flox/flox) were intraperitoneally injected with MPTP to induce experimental PD model. Our results revealed that disruption of autophagy by Atg5-siRNA aggravated LPS-induced inflammatory responses in BV2 cells and caused greater apoptosis in SH-SY5Y cells treated with BV2 conditioned medium. In mice, impaired autophagy in microglia exacerbated dopaminergic neuron loss in response to MPTP. The mechanism by which the deficiency of microglial autophagy promoted neuroinflammation and dopaminergic neurodegeneration was related to the regulation of NLRP3 inflammasome activation. These findings demonstrate that impairing microglial autophagy aggravates pro-inflammatory responses to LPS and exacerbates MPTP-induced neurodegeneration by modulating NLRP3 inflammasome responses. We anticipate that enhancing microglial autophagy may be a promising new therapeutic strategy for PD.

Therapeutic potential of mangiferin in the treatment of various neuropsychiatric and neurodegenerative disorders

Xanthones are important chemical class of bioactive products that confers therapeutic benefits. Of several xanthones, mangiferin is known to be distributed widely across several fruits, vegetables and medicinal plants. Mangiferin has been shown to exert neuroprotective effects in both in-vitro and in-vivo models. Mangiferin attenuates cerebral infarction, cerebral edema, lipid peroxidation (MDA), neuronal damage, etc. Mangiferin further potentiate levels of endogenous antioxidants to confer protection against the oxidative stress inside the neurons. Mangiferin is involved in the regulation of various signaling pathways that influences the production and levels of proinflammatory cytokines in brain. Mangiferin cosunteracted the neurotoxic effect of amyloid-beta, MPTP, rotenone, 6-OHDA etc and confer protection to neurons. These evidence suggested that the mangiferin may be a potential therapeutic strategy for the treatment of various neurological disorders. The present review demonstrated the pharmacodynamics-pharmacokinetics of mangiferin and neurotherapeutic potential in several neurological disorders with underlying mechanisms.

Neuroprotective effect of NXP031 in the MPTP-induced Parkinson's disease model

Parkinson's disease (PD) is a neurodegenerative disease characterized by the progressive degeneration of dopaminergic neurons in the substantia nigra (SN). Oxidative stress has been identified as one of the major causes of nigrostriatal degeneration in PD. Ascorbic acid plays a role as an efficient antioxidant to protect cells from free radical damage, but it is easily oxidized and loses its antioxidant activity. To overcome this limitation, we have recently developed NXP031, a single-stranded DNA aptamer that binds to ascorbic acid with excellent specificity, reducing its oxidation and increasing its efficacy. This study investigated the neuroprotective effects of NXP031 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model. Acute degeneration of nigral dopaminergic neurons was induced by four consecutive treatments of MPTP (20 mg/kg) in male C57BL/6 J mice. NXP031 (Vitamin C/Aptamin C 200 mg/4 mg/kg) was administered intraperitoneally for 5 days following MPTP. We observed that the administration of NXP031 ameliorated MPTP-induced loss of dopaminergic neurons in the SN and exhibited improvement of MPTP-mediated motor impairment. We further found that NXP031 increased plasma ascorbic acid levels and inhibited microglia activation-induced neuroinflammation in the SN, which might contribute to the protective effects of NXP031 on nigrostriatal degeneration. Our findings suggest that NXP031 could be a potential therapeutic intervention in PD.

Sensory neuropathy and nociception in rodent models of Parkinson's disease

Parkinson's disease (PD) often manifests with prodromal pain and sensory losses whose etiologies are not well understood. Multiple genetic and toxicity-based rodent models of PD partly recapitulate the histopathology and motor function deficits. Although far less studied, there is some evidence that rodents, similar to humans, develop sensory manifestations of the disease, which may precede motor disturbances and help to elucidate the underlying mechanisms of PD-associated pain at the molecular and neuron circuit levels. The present Review summarizes nociception and other sensory functions in frequently used rodent PD models within the context of the complex phenotypes. In terms of mechanisms, it appears that the acute loss of dopaminergic neurons in systemic toxicity models (MPTP, rotenone) primarily causes nociceptive hyperexcitability, presumably owing to a loss of inhibitory control, whereas genetic models primarily result in a progressive loss of heat perception, reflecting sensory fiber neuropathies. At the molecular level, neither α-synuclein deposits alone nor failure of mitophagy alone appear to be strong enough to result in axonal or synaptic pathology of nociceptive neurons that manifest at the behavioral level, and peripheral sensory loss may mask central ‘pain’ in behavioral tests. Hence, allostatic combinations or additional challenges and novel behavioral assessments are needed to better evaluate PD-associated sensory neuropathies and pain in rodents.

Summary: Rodent models of Parkinson's disease partially develop prodromal somatosensory and olfactory dysfunctions reminiscent of sensory neuropathies in patients and reveal mechanistic insight, but data are incomplete and fragmented.

Administration of tetrahydrobiopterin restored the decline of dopamine in the striatum induced by an acute action of MPTP

Parkinson's disease (PD) is the second common neurodegenerative disorder. Deficit of the nigro-striatal dopaminergic neurons causes the motor symptoms of PD. While the oxidative stress is thought to be deeply involved in the etiology of PD, molecular targets for the oxidative insults has not been fully elucidated. 6R-5,6,7,8-Tetrahydrobiopterin (BH4) is a cofactor for tyrosine hydroxylase (TH), the rate-limiting enzyme for production of dopamine, and easily oxidized to its dihydro-form. In this study, we examined the alteration in the metabolism of BH4 caused by a parkinsonian neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP reduced the dopamine content and the in vivo activity of TH in the striatum prior to degeneration of the dopaminergic neurons. We found that administration of BH4 could restore the dopamine content and in vivo TH activity in the striatum of MPTP-treated mice. Unexpectedly, when BH4 was administered with MPTP, BH4 contents in the brain were far higher than those injected without MPTP even at 23 h after the last injection. Because MPTP has been shown to increase ROS production in the dopaminergic neurons, we assumed that the increased ROS oxidizes BH4 into its dihydro-form, excreted from the dopaminergic neurons, taken-up by the neighboring cells, reduced back to BH4, and then accumulated in the brain. We also investigated the action of MPTP in mice lacking quinonoid-dihydropteridine reductase (Qdpr), an enzyme catalyzing regeneration of BH4 from quinonoid dihydrobiopterin. The dopamine depletion induced by MPTP was severer in Qdpr-deficient mice than in wild-type mice. The present data suggest that perturbation of the BH4 metabolism would be the cause of early and persistent dopamine depletion in the striatum.

TREM2 overexpression attenuates neuroinflammation and protects dopaminergic neurons in experimental models of Parkinson's disease

Triggering receptor expressed on myeloid cells-2 (TREM2) was a newly identified receptor expressed on microglia. Several observations support the hypothesis that TREM2 variation may confer susceptibility to Parkinson's disease (PD). Therefore, in this paper, we explored the role of TREM2 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Our results revealed that overexpression of TREM2 remarkably reduced MPTP-induced neuropathology including the dopaminergic neurodegeneration and neuroinflammation in vivo. Further mechanistic study revealed that TREM2 inhibited neuroinflammation by negatively regulating the TRAF6/TLR4-mediated activation of the MAPK and NF-κB signaling pathways. Taken together, our data suggest that TREM2 may have important neuroprotective effects against PD by critically modulating neuroinflammatory responses. These findings provide insights into the role of TREM2 in PD pathogenesis, and highlight TREM2 as a potential therapeutic target for this kind of disease.

Drug-induced Parkinson's disease modulates protein kinase A and Olfactory Marker Protein in the mouse olfactory bulb

Background

Olfaction is often affected in parkinsonian patients, but dopaminergic cells in the olfactory bulb are not affected by some Parkinson-inducing drugs. We investigated whether the drug MPTP produces the olfactory deficits typical of Parkinson and affects the olfactory bulb in mice.

Findings

Lesioned and control mice were tested for olfactory search, for motor and exploratory behavior. Brains and olfactory mucosa were investigated via immunohistochemistry for thyrosine hydroxylase, Olfactory Marker Protein and cyclic AMP-dependent protein kinase as an intracellular pathway involved in dopaminergic neurotransmission. MPTP induced motor impairment, but no deficit in olfactory search. Thyrosine hydroxylase did not differ in olfactory bulb, while a strong decrease was detected in substantia nigra and tegmentum of MPTP mice. Olfactory Marker Protein decreased in the olfactory bulb of MPTP mice, while a cyclic AMP-dependent protein kinase increased in the inner granular layer of MPTP mice.

Conclusions

MPTP mice do not present behavioural deficits in olfactory search, yet immunoreactivity reveals modifications in the olfactory bulb, and suggests changes in intracellular signal processing, possibly linked to neuron survival after MPTP.

TracMouse: A computer aided movement analysis script for the mouse inverted horizontal grid test

In rodents, detection and quantification of motor impairments is difficult. The traction test (inverted grid with mice clinging to the underside) currently has no objective rating system. We here developed and validated the semi-automatic MATLAB script TracMouse for unbiased detection of video-recorded movement patterns. High precision videos were analyzed by: (i) principal identification of anatomical paw details frame-by-frame by an experimentally blinded rater; (ii) automatic retrieval of proxies by TracMouse for individual paws. The basic states of Hold and Step were discriminated as duration and frequency, and these principle parameters were converted into static and dynamic endpoints and their discriminating power assessed in a dopaminergic lesion model. Relative to hind paws, forepaws performed ~4 times more steps, they were ~20% longer, and Hold duration was ~5 times shorter in normal C57Bl/6 mice. Thus, forepaw steps were classified as exploratory, hind paw movement as locomotive. Multiple novel features pertaining to paw sequence, step lengths and exploratory touches were accessible through TracMouse and revealed subtle Parkinsonian phenotypes. Novel proxies using TracMouse revealed previously unidentified features of movement and may aid the understanding of (i) brain circuits related to motor planning and execution, and (ii) phenotype detection in experimental models of movement disorders.

Medicinal plant Combretum leprosum mart ameliorates motor, biochemical and molecular alterations in a Parkinson's disease model induced by MPTP

ETHNOPHARMACOLOGICAL RELEVANCE

Combretum leprosum is a popular medicinal plant distributed in north and northeastern regions of Brazil. Many different parts of this plant are used in traditional medicine to treat several inflammatory diseases. Parkinson's disease (PD) is a disorder associated with inflammatory toxic factors and the treatments available provide merely a delay of the neurodegeneration.

AIM OF THE STUDY

We investigated the potential neuroprotective properties of the C. leprosum ethanolic extract (C.l.EE) in a murine model of PD using the toxin 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP).

MATERIALS AND METHODS

The mice were split into four groups: V/S (vehicle/saline), E/S (extract/saline), V/M (vehicle/MPTP) and E/M (extract/ MPTP). Mice received MPTP (30mg/kg, i.p.) or vehicle (10ml/kg, i.p.) once a day for 5 consecutive days and vehicle (10ml/kg) or C.l.EE (100mg/kg) orally by intra-gastric gavage (i.g.) during a 14-d period, starting 3 days before the first MPTP injection. All groups were assessed for behavioural impairments (amphetamine-induced locomotor activity and muscle strength), dopamine content in striatum using high performance liquid chromatography (HPLC), tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions using qPCR.

RESULTS

Animals were injected with d-amphetamine (2mg/kg) and the activity was recorded. Amphetamine-induced hyperlocomotion was observed in all groups; however animals treated with MPTP showed exacerbated hyperlocomotion (approximately 3 fold increase compared to control groups). By contrast, mice treated with MPTP that received C.l.EE exhibited attenuation of the hyperlocomotion and did not differ from control groups. Muscle strength test pointed that C.l.EE strongly avoided muscular deficits caused by MPTP (approximately 2 fold increase compared to V/M group). Dopamine and its metabolites were measured in the striatum. The V/M group presented a dopamine reduction of 80%. On the other hand, the E/M group exhibited an increase in dopamine and its metabolites levels (approximately 3 fold increase compared to V/M group). Tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions were significantly reduced in the V/M group (60%). Conversely, C.l.EE treatment was able to increase the mRNA levels of those genes in the E/M group (approximately 2 fold for TH and DAT).

CONCLUSIONS

These data show, for the first time, that C. leprosum ethanolic extract prevented motor and molecular changes induced by MPTP, and partially reverted dopamine deficit. Thus, our results demonstrate that C.l.EE has potential for the treatment and prevention of PD.

5-hydroxymethylcytosine is detected in RNA from mouse brain tissues

5-hydroxymethylcytosine (5hmC) is considered as a novel DNA modification and plays an important role in cancer, stem cells, and developmental diseases. In this study, we demonstrated the existence of RNA 5hmC modification in mouse brain RNA by using a dot blot analysis method. Our data indicated that 5hmC modification in RNA samples was less than that in DNA samples. Further, we optimized the conditions for 5hmC detection in RNA samples such as DNase treatment, denature reagents, denature time, sample air-dry time, and the cross-linking time between RNA and membrane. Our results demonstrated that DNase treatment and denature reagents were two important factors that affected the 5hmC detection in RNA samples. By using the optimal conditions for RNA 5hmC detection, we found that the brainstem, the hippocampus, and the cerebellum had high levels of 5hmC modification and 5mC modification in RNA. Finally, we found that RNA 5hmC modification decreased in MPTP-induced Parkinson's disease model in mice. These suggest that 5hmC modification in RNA might play an important regulative role on protein or microRNA expression in these brain tissues. Because DNA 5hmC modification plays an important role in neural differentiation and development as well as neurological diseases, the significance of 5hmC modification in RNA in different neurological diseases needs further investigation. In summary, our study demonstrated for the first time the abundance of 5hmC modification in brain RNA by using a dot blot analysis method and proved that dot blot analysis is a useful method for 5hmC detection in RNA samples.

Bee Venom Phospholipase A2, a Novel Foxp3+ Regulatory T Cell Inducer, Protects Dopaminergic Neurons by Modulating Neuroinflammatory Responses in a Mouse Model of Parkinson's Disease

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.

Identification of Neurexophilin 3 as a Novel Supportive Factor for Survival of Induced Pluripotent Stem Cell-Derived Dopaminergic Progenitors

Successful cell transplantation for Parkinson's disease (PD) depends on both an optimal host brain environment and ideal donor cells. We report that a secreted peptide, neurexophilin 3 (NXPH3), supports the survival of mouse induced pluripotent stem cell-derived (iPSC-derived) dopaminergic (DA) neurons in vitro and in vivo. We compared the gene expression profiles in the mouse striatum from two different environments: a supportive environment, which we defined as 1 week after acute administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and a nonsupportive environment, defined as 8 weeks after chronic administration of MPTP. NXPH3 expression was higher in the former condition and lower in the latter compared with untreated controls. When we injected mouse iPSC-derived neural cells along with NXPH3 into the mouse striatum, the ratio of tyrosine hydroxylase-positive DA neurons per graft volume was higher at 8 weeks compared with cell injections that excluded NXPH3. In addition, quantitative polymerase chain reaction analyses of the postmortem putamen revealed that the expression level of NXPH3 was lower in PD patients compared with normal controls. These findings will contribute to optimizing the host brain environment and patient recruitment in cell therapy for PD.

Korean Red Ginseng protects dopaminergic neurons by suppressing the cleavage of p35 to p25 in a Parkinson's disease mouse model

Background

Ginseng is known to have antiapoptotic, anti-inflammatory, and antioxidant effects. The present study investigated a possible role of Korean Red Ginseng (KRG) in suppressing dopaminergic neuronal cell death and the cleavage of p35 to p25 in the substantia nigra (SN) and striatum (ST) using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease mouse model.

Methods

Ten-week-old male C57BL/6 mice were injected intraperitoneally with 30 mg/kg of MPTP at 24-h intervals for 5 d, and then administered KRG (1 mg/kg, 10 mg/kg, or 100 mg/kg) once a day for 12 consecutive days from the first injection. Pole tests were performed to assess the motor function of the mice, dopaminergic neuronal survival in the SN and ST was evaluated using tyrosine hydroxylase-immunohistochemistry, and the expressions of cyclin-dependent kinase 5 (Cdk5), p35, and p25 in the SN and ST were measured using Western blotting.

Results

MPTP administration caused behavioral impairment, dopaminergic neuronal death, increased Cdk5 and p25 expression, and decreased p35 expression in the nigrostriatal system of mice, whereas KRG dose-dependently alleviated these MPTP-induced changes.

Conclusion

These results indicate that KRG can inhibit MPTP-induced dopaminergic neuronal death and suppress the cleavage of p35 to p25 in the SN and the ST, suggesting a possible role for KRG in the treatment of Parkinson's disease.

Mirtazapine has a therapeutic potency in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice model of Parkinson's disease

Background

Mirtazapine, a noradrenergic and specific serotonergic antidepressant (NaSSA), shows multiple pharmacological actions such as inhibiting presynaptic α₂ noradrenaline receptor (NAR) and selectively activating 5-hydroxytriptamine (5-HT) 1A receptor (5-HT_1AR). Mirtazapine was also reported to increase dopamine release in the cortical neurons with 5-HT dependent manner. To examine whether mirtazapine has a therapeutic potency in Parkinson’s disease (PD), we examined this compound in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice model of PD.

Results

Male C57BL/6 mice were subjected to MPTP treatment to establish a PD model. Mirtazapine was administered once a day for 3 days after MPTP treatment. MPTP-induced motor dysfunction, assessed by beam-walking and rota-rod tests, was significantly improved by administration of mirtazapine. Biochemical examinations by high performance liquid chromatography and western blot analysis suggested mirtazapine facilitated utilization of dopamine by increasing turnover and protein expression of transporters, without affecting on neurodegenerative process by MPTP. These therapeutic effects of mirtazapine were reduced by administration of WAY100635, an inhibitor for 5HT_1AR, or of clonidine, a selective agonist for α₂-NAR, or of prazosin, an inhibitor for α₁-NAR, respectively.

Conclusion

Our results showed mirtazapine had a therapeutic potency against PD in a mouse model. Because PD patients sometimes show depression together, it will be a useful drug for a future PD treatment.

In vivo imaging of enteric neurogenesis in the deep tissue of mouse small intestine

One of the challenges of using imaging techniques as a tool to study cellular physiology has been the inability to resolve structures that are not located near the surface of the preparation. Nonlinear optical microscopy, in particular two photon-excited fluorescence microscopy (2PM), has overcome this limitation, providing deeper optical penetration (several hundred µm) in ex vivo and in vivo preparations. We have used this approach in the gut to achieve the first in vivo imaging of enteric neurons and nerve fibers in the mucosa, submucosa, submucosal and myenteric plexuses, and circular and longitudinal muscles of the small intestine in H-line: Thy1 promoter GFP mice. Moreover, we obtained clear three-dimensional imaging of enteric neurons that were newly generated after gut transection and reanastomosis. Neurogenesis was promoted by oral application of the 5-HT₄-receptor agonist, mosapride citrate (MOS). The number of newly generated neurons observed in mice treated with MOS for one week was 421±89 per 864,900 µm² (n = 5), which was significantly greater than that observed in preparations treated with MOS plus an antagonist (113±76 per 864,900 µm²) or in 4 week vehicle controls (100±34 per 864,900 µm²) (n = 4 both). Most neurons were located within 100 µm of the surface. These results confirm that activation of enteric neural 5-HT₄-receptor by MOS promotes formation of new enteric neurons. We conclude that in vivo 2PM imaging made it possible to perform high-resolution deep imaging of the living mouse whole gut and reveal formation of new enteric neurons promoted by 5-HT₄-receptor activation.

Effects of a copper-deficient diet on the biochemistry, neural morphology and behavior of aged mice

Copper dyshomeostasis has been suggested as an aetiological risk factor for some neurodegenerative diseases, such as Alzheimer’s disease. However, the precise mechanism at the base of this involvement is still obscure. In this work, we show the effects of a copper-deficient diet in aged CD1 mice and the influence of such a diet on: a) the concentration of various metal ions (aluminium, copper, iron, calcium, zinc) in the main organs and in different brain areas; b) the alteration of metallothioneins I-II and tyrosine hydroxylase immunopositivity in the brain; c) behavioural tests (open field, pole, predatory aggression, and habituation/dishabituation smell tests). Our data suggested that the copper-deficiency was able to produce a sort of “domino effect” which altered the concentration of the other tested metal ions in the main organs as well as in the brain, without, however, significantly affecting the animal behaviour.

Reactive oxygen species regulated mitochondria-mediated apoptosis in PC12 cells exposed to chlorpyrifos

Reactive oxidative species (ROS) generated by environmental toxicants including pesticides could be one of the factors underlying the neuronal cell damage in neurodegenerative diseases. In this study we found that chlorpyrifos (CPF) induced apoptosis in dopaminergic neuronal components of PC12 cells as demonstrated by the activation of caspases and nuclear condensation. Furthermore, CPF also reduced the tyrosine hydroxylase-positive immunoreactivity in substantia nigra of the rat. In addition, CPF induced inhibition of mitochondrial complex I activity. Importantly, N-acetyl cysteine (NAC) treatment effectively blocked apoptosis via the caspase-9 and caspase-3 pathways while NAC attenuated the inhibition of mitochondrial complex I activity as well as the oxidative metabolism of dopamine (DA). These results demonstrated that CPF-induced apoptosis was involved in mitochondrial dysfunction through the production of ROS. In the response of cellular antioxidant systems to CPF, we found that CPF treatment increased HO-1 expression while the expression of CuZnSOD and MnSOD was reduced. In addition, we found that CPF treatment activated MAPK pathways, including ERK 1/2, the JNK, and the p38 MAP kinase in a time-dependent manner. NAC treatment abolished MAPK phosphorylation caused by CPF, indicating that ROS are upstream signals of MAPK. Interestingly, MAPK inhibitors abolished cytotoxicity and reduced ROS generation by CPF treatment. Our results demonstrate that CPF induced neuronal cell death in part through MAPK activation via ROS generation, suggesting its potential to generate oxidative stress via mitochondrial damage and its involvement in oxidative stress-related neurodegenerative disease.

Neuroprotective effect of kaempferol against a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease

In the present study, we investigated the neuroprotective effects of kaempferol in the mouse model of Parkinson's disease, which was induced by neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We confirmed that MPTP led to behavioral deficits, depletion of dopamine and its metabolites, reduction in superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) activity, and the elevation of malondialdehyde (MDA) levels in the substantia nigra. When administered prior to MPTP, kaempferol improved motor coordination, raised striatal dopamine and its metabolite levels, increased SOD and GSH-PX activity, and reduced the content of MDA compared with mice treated with MPTP alone. Immunohistochemical studies using anti-tyrosine hydroxylase (TH) antibody showed that medication of kaempferol could prevent the loss of TH-positive neurons induced by MPTP. Taken together, we propose that kaempferol has shown anti-parkinsonian properties in our studies. More work is needed to explore detailed mechanisms of action.

Partial dopamine depletion in MPTP-treated mice differentially altered motor skill learning and action control

Recent findings suggest that the neurotransmitter dopamine (DA) system plays a role in motor control and the acquisition of habits and skills. However, isolating DA-mediated motor learning from motor performance remains challenging as most studies include often severely DA-depleted mice. Using the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), we investigated the effect of various degrees of DA-depletion in mice on three tests of motor behaviors: the accelerating rotarod, wire suspension and pole tests. Three protocols were performed to decrease DA synthesis to various extents: 4 injections (i.p.) of 9 mg/kg in 1 day; 4 injections (i.p.) of 15 mg/kg in 1 day; or 5 injections (s.c.) of 30 mg/kg in 5 days. Severity of DA-depletion was assessed by the evaluation of tyrosine hydroxylase (TH) and dopamine transporter levels in the striatum using the Western blot technique. Mice were gathered into four different groups according their TH levels: mild, moderate, marked and severe. In these mice, the general motor abilities such as coordination, motion speed and muscular strength were relatively intact whereas impaired acquisition of skilled behavior occurred in mice with marked and severe reduction in TH levels. Marked and severely DA-depleted mice exhibited lower scores within the first trials of the first training day as well as a much slower progression in the following days on the accelerating rotarod. Based on these results, we conclude that the learning of a skilled behavior is more vulnerable to DA depletion than the DA-mediated control of motor activity.

Neuroprotection effects of retained acupuncture in neurotoxin-induced Parkinson's disease mice

The aim of this study was to investigate the role of retained acupuncture (RA) in neurotoxin-induced Parkinson's disease (PD) mice. Male C57BL/6 mice were injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to induce the PD model. The mice were divided into four groups, namely, (1) normal; (2) MPTP+retained acupuncture (RA); (3) MPTP+electroacupuncture (EA); (4) MPTP+sham acupuncture (SA). After mice being manipulated with/without acupuncture at acupoints (Daling, PC 7), groups 2-4 were injected with MPTP (15 mg/kg/d). The mice were evaluated for behavioral changes, in terms of time of landing, after acupuncture treatment. The animals were sacrificed and their brains assayed for dopamine and its metabolites and tyrosine hydroxylase (TH) expression by using HPLC and immunohistochemistry/Western blotting, respectively. [(123)I] IBZM-SPECT imaging between SA and RA groups were compared. The results showed that the time of landing of the three groups with treatment was significant longer than group 1 (normal) (4.33±0.15 s). Nonetheless, group 2 (RA) (7.13±0.20 s) had a shorter time of landing than group 4 (SA) (7.89±0.46 s). The number of TH (+) neurons and the expression of TH proteins were significantly higher in the RA group than in the SA/EA groups. RA also increased the uptake of [(123)I] IBZM into the triatum compared to the SA group. We conclude that RA possibly attenuates neuronal damage in MPTP-induced PD mice, which suggests RA may be useful as a complementary strategy when treating human PD.

Protective Role of rAAV-NDI1, Serotype 5, in an Acute MPTP Mouse Parkinson's Model

Defects in mitochondrial proton-translocating NADH-quinone oxidoreductase (complex I) have been implicated in a number of acquired and hereditary diseases including Leigh's syndrome and more recently Parkinson's disease. A limited number of strategies have been attempted to repair the damaged complex I with little or no success. We have recently shown that the non-proton-pumping, internal NADH-ubiquinone oxidoreductase (Ndi1) from Saccharomyces cerevisiae (baker's yeast) can be successfully inserted into the mitochondria of mice and rats, and the enzyme was found to be fully active. Using recombinant adenoassociated virus vectors (serotype 5) carrying our NDI1 gene, we were able to express the Ndi1 protein in the substantia nigra (SN) of C57BL/6 mice with an expression period of two months. The results show that the AAV serotype 5 was highly efficient in expressing Ndi1 in the SN, when compared to a previous model using serotype 2, which led to nearly 100% protection when using an acute MPTP model. It is conceivable that the AAV-serotype5 carrying the NDI1 gene is a powerful tool for proof-of-concept study to demonstrate complex I defects as the causable factor in diseases of the brain.

Role of glial cells in neurotoxin-induced animal models of Parkinson's disease

Dopaminergic neurons are selectively vulnerable to oxidative stress and inflammatory attack. The neuronal cell loss in the substantia nigra is associated with a glial response composed markedly of activated microglia and, to a lesser extent, of reactive astrocytes although these glial responses may be the source of neurotrophic factors and can protect against oxidative stress such as reactive oxygen species and reactive nitrogen species. However, the glial response can also mediate a variety of deleterious events related to the production of pro-inflammatory, pro-oxidant reactive species, prostaglandins, cytokines, and so on. In this review, we discuss the possible protective and deleterious effects of glial cells in the neurodegenerative diseases and examine how these factors may contribute to the pathogenesis of Parkinson's disease. This review suggests that further investigation concerning glial reaction in Parkinson's disease may lead to disease-modifying therapeutic approaches and may contribute to the pathogenesis of this disease.

GFAP expression in the rat brain following sub-chronic exposure to a 900 MHz electromagnetic field signal

PURPOSE

The rapid development and expansion of mobile communications contributes to the general debate on the effects of electromagnetic fields emitted by mobile phones on the nervous system. This study aims at measuring the glial fibrillary acidic protein (GFAP) expression in 48 rat brains to evaluate reactive astrocytosis, three and 10 days after long-term head-only sub-chronic exposure to a 900 MHz electromagnetic field (EMF) signal, in male rats.

METHODS

Sprague-Dawley rats were exposed for 45 min/day at a brain-averaged specific absorption rate (SAR) = 1.5 W/kg or 15 min/day at a SAR = 6 W/kg for five days per week during an eight-week period. GFAP expression was measured by the immunocytochemistry method in the following rat brain areas: Prefrontal cortex, cerebellar cortex, dentate gyrus of the hippocampus, lateral globus pallidus of the striatum, and the caudate putamen.

RESULTS

Compared to the sham-treated rats, those exposed to the sub-chronic GSM (Global System for mobile communications) signal at 1.5 or 6 W/kg showed an increase in GFAP levels in the different brain areas, three and ten days after treatment.

CONCLUSION

Our results show that sub-chronic exposures to a 900 MHz EMF signal for two months could adversely affect rat brain (sign of a potential gliosis).

Neuroprotective effect of long-term NDI1 gene expression in a chronic mouse model of Parkinson disorder

Previously, we showed that the internal rotenone-insensitive nicotinamide adenine dinucleotide (NADH)-quinone oxidoreductase (NDI1) gene from Saccharomyces cerevisiae (baker's yeast) can be successfully inserted into the mitochondria of mice and rats and the expressed enzyme was found to be fully functional. In this study, we investigated the ability of the Ndi1 enzyme to protect the dopaminergic neurons in a chronic mouse model of Parkinson disorder. After expression of the NDI1 gene in the unilateral substantia nigra of male C57BL/6 mice for 8 months, a chronic Parkinsonian model was created by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) with probenecid and evaluated using neurochemical and behavioral responses 1-4 weeks post-MPTP/probenecid injection. We showed that expression of Ndi1 was able to significantly prevent the loss of dopamine and tyrosine hydroxylase as well as the dopaminergic transporters in the striatum of the chronic Parkinsonian mice. Behavioral assessment based on a methamphetamine-induced rotation test and spontaneous swing test further supported neurological preservation in the NDI1-treated Parkinsonian mice. The data presented in this study demonstrate a protective effect of the NDI1 gene in dopaminergic neurons, suggesting its therapeutic potential for Parkinson-like disorders.

Activation of phosphatidylinositol-linked D1-like receptor modulates FGF-2 expression in astrocytes via IP3-dependent Ca2+ signaling

Fibroblast growth factor-2 (FGF-2) is predominantly synthesized and secreted by astrocytes in adult brain. Our previous study showed that activation of classical dopamine receptor D(1) or D(2) elicits FGF-2 biosynthesis and secretion in astrocytes. Here, we report that astrocytic FGF-2 expression is also regulated by phosphatidylinositol (PI)-linked D(1)-like receptor. SKF83959, a selective PI-linked D(1)-like receptor agonist, upregulates the levels of FGF-2 protein in striatal astrocyte cultures in classical dopamine D(1) and D(2) receptor-independent manner. The conditional medium derived from SKF83959-activated astrocytes promoted the number of TH(+) neurons in vitro. Treatment of astrocytes with SKF83959 increased intracellular calcium in two phases. Inhibition of intracellular calcium oscillation by inositol 1,4,5-triphosphate (IP3) inhibitors blocked the SKF83959-induced increase in FGF-2 expression. Moreover, intraperitoneal administration of SKF83959 reversed l-methyl-4-phenyl-l,2,3,6-tetrahydropypridine (MPTP)-induced reduction in FGF-2 expression in both the striatum and ventral midbrain and resulted in marked protection of dopaminergic neurons from MPTP-induced neurotoxicity. These results indicate that IP3/Ca(2+)/calmodulin-dependent protein kinase is an uncharted intracellular signaling pathway that is crucial for the regulation of FGF-2 synthesis in astrocytes. PI-linked D(1)-like receptor plays an important role in the regulation of astrocytic FGF-2 expression and neuroprotection which may provide a potential target for the drug discovery in Parkinson's disease.

Pyrethroid and organophosphate insecticide exposure in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson’s disease: an immunohistochemical analysis of tyrosine hydroxylase and glial fibrillary acidic protein in dorsolateral striatum

The pyrethroid insecticide permethrin and the organophosphate insecticide chlorpyrifos can experimentally produce Parkinson’s disease (PD)-associated changes in the dopaminergic nigrostriatal pathway, short of frank degeneration, although at doses considerably higher than from a likely environmental exposure. The ability of permethrin (200 mg/kg), chlorpyrifos (50 mg/kg), or combined permethrin + chlorpyrifos to facilitate nigrostriatal damage in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (30 mg/kg) C57BL/6 mouse model of PD was investigated in three separate experiments. Tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP) immunohistochemistry assessed nigrostriatal degeneration or nigrostriatal damage more subtle than frank degeneration. Four fields in the dorsolateral caudate-putamen were examined at two rostrocaudal locations. The dopaminergic neurotoxin MPTP decreased striatal TH immunopositive neuropil and increased GFAP immunopositive neuropil. Neither permethrin nor chlorpyrifos, alone or in combination, altered the effects of MPTP upon TH or GFAP immunostaining. Permethrin alone increased striatal GFAP immunopositive neuropil but not when combined with chlorpyrifos treatment. Therefore, combined administration of the two insecticides appeared to protect against an increase in a neuropathological indicator of striatal damage seen with permethrin treatment alone. Differences compared with analysis of entire striatum emphasize the value of varying the topographic focus used to assess nigrostriatal degeneration in studies of insecticides in PD.

The nigrostriatal dopamine system of aging GFRalpha-1 heterozygous mice: neurochemistry, morphology and behavior

Given the established importance of glial cell line-derived neurotrophic factor (GDNF) in maintaining dopaminergic neurotransmitter systems, the nigrostriatal system and associated behaviors of mice with genetic reduction of its high-affinity receptor, GDNF receptor (GFR)alpha-1 (GFRalpha-1(+/-)), were compared with wild-type controls. Motor activity and the stimulatory effects of a dopamine (DA) D1 receptor agonist (SKF 82958) were assessed longitudinally at 8 and 18 months of age. Monoamine concentrations and dopaminergic nerve terminals in the striatum and the number of dopaminergic neurons in the substantia nigra (SN) were assessed. The results support the importance of GFRalpha-1 in maintaining normal function of the nigrostriatal dopaminergic system, with deficits being observed for GFRalpha-1(+/-) mice at both ages. Motor activity was lower and the stimulatory effects of the DA agonist were enhanced for the older GFRalpha-1(+/-) mice. DA in the striatum was reduced in the GFRalpha-1(+/-) mice at both ages, and tyrosine hydroxylase-positive cell numbers in the SN were reduced most substantially in the older GFRalpha-1(+/-) mice. The combined behavioral, pharmacological probe, neurochemical and morphological measures provide evidence of abnormalities in GFRalpha-1(+/-) mice that are indicative of an exacerbated aging-related decline in dopaminergic system function. The noted deficiencies, in turn, suggest that GFRalpha-1 is necessary for GDNF to maintain normal function of the nigrostriatal dopaminergic system. Although the precise mechanism(s) for the aging-related changes in the dopaminergic system remain to be established, the present study clearly establishes that genetic reductions in GFRalpha-1 can contribute to the degenerative changes observed in this system during the aging process.

Expression of Cbl-interacting protein of 85 kDa in MPTP mouse model of Parkinson's disease and 1-methyl-4-phenyl-pyridinium ion-treated dopaminergic SH-SY5Y cells

The newly discovered Cbl-interacting protein of 85 kDa (CIN85) is involved in many cellular processes, but its functions in the brain and in neurodegenerative diseases remain unclear. In this paper, we investigated the distribution of CIN85 protein in different regions of adult mouse brain using Western blot analysis and immunohistochemistry, and found that CIN85 was ubiquitously expressed in mouse brain. In the striatum and substantia nigra, two regions most deeply affected in Parkinson's disease, the level of CIN85 protein was relatively high. In the MPTP mouse model of Parkinson's disease, the expression of CIN85 in the striatum and substantia nigra was complicated. But in 1-methyl-4-phenyl-pyridinium ion-treated human dopaminergic SH-SY5Y cells, the expression of CIN85 increased dramatically. Knocking down of CIN85 by short hairpin RNA reduced SH-SY5Y cell death. Therefore, CIN85 might play different roles in the dopaminergic cell line and in the nigrostriatum of mouse brain under neurotoxin challenge.

Protective action of neuronal nitric oxide synthase inhibitor in the MPTP mouse model of Parkinson's disease

We examined the effects of 7-nitroindazole on the dopaminergic system in mice after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. The mice received four intraperitoneal injections of MPTP (20 mg/kg) at 2 h-intervals. Administration of 7-nitroindazole showed dose-dependent neuroprotective effects against striatal dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) depletion 7 days after MPTP treatment. Behavioral testing showed that MPTP-treated mice exhibited motor deficits in the catalepsy test after 7 days, but 7-nitroindazole prevented the appearance of motor abnormalities in this test. The MPTP-treated mice exhibited the loss of tyrosine hydroxylase-containing dopaminergic neurons in mice after 1, 3 and 7 days, but 7-nitroindazole-treated mice showed a protective effect. GFAP (glial fibrillary acidic protein)-positive astrocytes were accumulated in the striatum 3 and 7 days and in the substantia nigra 1, 3 and 7 days after MPTP treatment. In contrast, 7-nitroindazole prevented a significant increase in the number of GFAP-positive astrocytes in the striatum and substantia nigra after MPTP treatment. The reactive astrocytes in the striatum and substantia nigra after MPTP treatment increased the production of S100beta protein, which is thought to promote neuronal damage, but 7-nitoindazole suppressed the expression of S100 beta protein. Activation of microglia, with an increase in staining intensity and morphological changes, was observed in the striatum and substantia nigra 1 and 3 days after MPTP treatment, but 7-nitroindazole prevented a significant increase in the number of isolectin B(4) positive microglia in the striatum and substantia nigra. On the other hand, nestin-immunoreactive cells were increased significantly in the striatum 3 and 7 days after MPTP treatment. 7-Nitroindazole treatment facilitated nestin expression in the striatum 7 days after MPTP treatment. Thus, nNOS inhibitor 7-nitroindazole protected dopaminergic neurons against MPTP neurotoxicity in mice and ameliorated neurological deficits. The results suggest that the neuroprotection is mediated though the modulation of glial activation, including the inhibition of S100beta synthesis and the prevention of microglial activation. These results suggest the therapeutic strategy targeted to glial modulation with 7-nitoindazole offers a great potential for the development of new neuroprotective therapies for Parkinson's disease.

Delayed treatment with arundic acid reduces the MPTP-induced neurotoxicity in mice

The authors investigated the protective effects of a novel astrocyte-modulating agent, arundic acid, in a 1-methyl-4-phenyl-1,2,3,6-tetrahyropyridine (MPTP) mouse model of Parkinson's disease. Male mice received four intraperitoneal (i.p.) injections of MPTP (20 mg/kg) at 2 h intervals. The content of dopamine and its metabolites in the striatum was reduced markedly 7 days after MPTP treatment. The delayed treatment with arundic acid (30 mg/kg, i.p.) administered 3, 4, 5 and 6 days after MPTP treatment did not affect the depletion of dopamine and its metabolites in the striatum. Our immunohistochemical study with anti-tyrosine hydroxylase antibody, anti-neuronal nuclei antibody, anti-glial fibrillary acidic protein antibody, anti-S 100beta antibody and anti-nestin antibody showed that the delayed treatment with arundic acid had a protective effect against MPTP-induced neuronal damage in the striatum and the substantia nigra of mice. Furthermore, this agent ameliorated the severe reductions in number of isolectin reactive microglia in the striatum and the substantia nigra 7 days after MPTP treatment. These results demonstrate that the inhibition of S 100beta synthesis in astrocytes may be the major component of the beneficial effect of arundic acid. Thus, our present findings provide that the therapeutic strategies targeted to astrocytic modulation with arundic acid offers a great potential for restoring the functional capacity of the surviving dopaminergic neurons in individuals affected with Parkinson's disease.

Complement 3-deficient mice are not protected against MPTP-induced dopaminergic neurotoxicity

Recent studies have invoked inflammation as a major contributor to the pathogenesis of Parkinson's disease (PD). Emerging evidence indicated that components of complement system may be involved in such disorder and contribute to its development. We thus observed the influence of deficiency of complement 3 (C3), the key component of complement system, on the death of dopaminergic neurons in substantia nigra pars compacta (SNpc) and the loss of dopaminergic fibers in striatum induced by acute or chronic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Immunohistochemical staining of dopaminergic neurons in SNpc and neurochemical analysis of dopamine and its metabolites in striata revealed that there was no significant difference between the two genotypes. Longer survival time also indicated that C3 might not mediate the spontaneous recovery of dopaminergic fibers in mouse striatum acutely challenged by MPTP. We conclude that, despite growing evidence indicating the involvement of complement system in the pathogenesis of PD, our data do not support a role for C3 in this established model of PD, as indicated by results from HPLC analysis and immunohistochemical staining.

MPTP-induced deficits in striatal synaptic plasticity are prevented by glial cell line-derived neurotrophic factor expressed via an adeno-associated viral vector

This study determined the consequences of dopamine denervation of the striatum on synaptic plasticity and prevention of these changes with gene therapy using an adeno-associated viral vector (AAV) expressing glial cell line-derived neurotrophic factor (GDNF). C57BL6/J mice were injected with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP); long-term depression (LTD) or potentiation (LTP) were measured in vitro. Fast-scan cyclic voltammetry measured electrically released dopamine from a functionally relevant pool in these same striatal slices. After MPTP, dopamine release and uptake were greatly diminished, and LTP and LTD were blocked in the striatal slices. The loss of plasticity resulted directly from the loss of dopamine since its application rescued synaptic plasticity. Striatal GDNF expression via AAV, before MPTP, significantly protected against the loss of dopamine and prevented the blockade of corticostriatal LTP. These data demonstrate that dopamine plays a role in supporting several forms of striatal plasticity and that GDNF expression via AAV prevents the loss of dopamine and striatal plasticity caused by MPTP. We propose that impairment of striatal plasticity after dopamine denervation plays a role in the symptomology of Parkinson's disease and that AAV expression of neurotrophic factors represents a tenable approach to protecting against or slowing these neurobiological deficits.

Damage to oligodendrocytes in the striatum after MPTP neurotoxicity in mice

We investigated the alteration of oligodendrocytes in comparison with that of astrocytes and microglia in the mouse striatum after MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropridine) treatment under the same conditions using Western blot analysis and Immunohistochemistry. In our Western blot analysis, four administrations of MPTP at 2-h intervals to mice produced the remarkable loss of TH (tyrosine hydroxylase) protein levels in the striatum after 3 and 7 days. In contrast, GFAP (glial fibrillary acidic protein) and Iba-1 protein in the striatum showed a significant increase of GFAP and Iba-1 protein levels 3 and 7 days after MPTP treatment. On the other hand, the levels of CNPase (2', 3'-cyclic nucleotide 3'-phosphodiesterase) protein were decreased significantly in the striatum 3 and 7 days after MPTP treatment. In our immunohistochemical study, a significant decrease in the area of expression of CNPase-positive profiles was observed in the striatum 3 and 7 days after MPTP treatment. These results demonstrate that oligodendrocytes in the striatum are damaged after MPTP treatment. Thus our present findings provide valuable information for the pathogenesis of Parkinson's disease.

Lamotrigine is neuroprotective in the energy deficiency model of MPTP intoxicated mice

The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) inhibits the mitochondrial complex I of the respiratory chain. This results in ATP and ion homeostasis disturbances, which lead to selective death of the substantia nigra dopaminergic neurons. Well known as a Parkinson's disease model, the MPTP animal model also provides a potential paradigm of the energy deficiencies found in childhood. In these conditions, anticonvulsants may provide neuroprotection by limiting cellular energy consumption. We tested valproate, topiramate and lamotrigine in the MPTP mouse model. Dopamine transporter (DAT) density was assessed by quantitative autoradiography, tyrosine hydroxylase (TH) was evaluated by immunohistochemistry and dopamine (DA) levels by HPLC-ED whereas neuronal apoptosis was monitored through active caspase-3. Expectedly, the DAT density, TH immunoreactive neurons and DA content in the MPTP group were respectively reduced to 51%, 40% and 26% versus control animals. Unlike valproate and topiramate, lamotrigine provided a significant neuroprotection against MPTP in maintaining these levels at 99%, 74% and 58% respectively and reducing the induced apoptosis. Altogether, the data indicate that lamotrigine limits dopaminergic neuronal death in the substantia nigra and promotes striatal dendrites sprouting. Lamotrigine, a widely used and well-tolerated molecule in young patients, could represent a valuable adjuvant therapy in various energy deficiency conditions during childhood.