Pyridoxine induces glutathione synthesis via PKM2-mediated Nrf2 transactivation and confers neuroprotection.

Oxidative stress is a major pathogenic mechanism in Parkinson's disease (PD). As an important cellular antioxidant, glutathione (GSH) balances the production and incorporation of free radicals to protect neurons from oxidative damage. GSH level is decreased in the brains of PD patients. Hence, clarifying the molecular mechanism of GSH deficiency may help deepen our knowledge of PD pathogenesis. Here we report that the astrocytic dopamine D2 receptor (DRD2) regulates GSH synthesis via PKM2-mediated Nrf2 transactivation. In addition we find that pyridoxine can dimerize PKM2 to promote GSH biosynthesis. Further experiments show that pyridoxine supplementation increases the resistance of nigral dopaminergic neurons to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in wild-type mice as well as in astrocytic Drd2 conditional knockout mice. We conclude that dimerizing PKM2 may be a potential target for PD treatment.

Neuroprotective effect of crocin on substantia nigra in MPTP-induced Parkinson's disease model of mice.

Parkinson's disease is caused by damage to substantia nigra dopaminergic neurons. Factors such as oxidative stress, inflammatory factors, and acetylcholinesterase activity may induce this disease. On the other hand, crocin-one of the active ingredients of saffron-has anti-oxidant and anti-inflammatory properties. This study was performed to evaluate the protective effect of crocin to decrease dopaminergic neuron damage and Parkinson's disease complications induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). A set of 24 male BALB/c Mice were divided randomly into four groups: (1) MPTP group receiving 30 mg/kg MPTP for 5 days; (2) MPTP + crocin group receiving 30 mg/kg MPTP for 5 days and 30 mg/kg crocin for 15 days; (3) NS group receiving normal saline for 5 days; and (4) NSIG group receiving normal saline intraperitoneally for 5 days and also normal saline by gavage for 15 days. After the treatment period, pole and hanging motor tests were performed in all groups. Then, the brains of all the animals were removed and fixed in formalin, prepared according to routine histologic methods and cut into sections of 5 µm thickness. Prepared sections were stained by immunohistochemistry techniques and toluidine blue to detect tyrosine-hydroxylase (TH)-positive neurons and dark neurons, respectively. Finally, the mean number of these cells were calculated by stereological methods and compared with the statistical tests in different groups. The results showed a significant increase in the time taken for the animal to fall from the pole in the MPTP group in comparison with other groups (P < 0.001). The time taken for them to stay on the wire in the hanging test decreased significantly in the MPTP group compared to the other groups (P < 0.001).,while in the MPTP + crocin group, the time to falling decreased (P < 0.05) and the time staying on the wire increased (P < 0.001) compared to the MPTP group. The number of TH-positive neurons in the MPTP group also decreased significantly in comparison with saline and MPTP + crocin groups (P < 0.001). The number of dark neuron sin the MPTP group increased significantly as compared with saline and the MPTP + Crocin groups (P < 0.001). Our results showed that crocin improves MPTP-induced Parkinson's disease complications and decreases cell death in the substantia nigra.

The Neuroprotective Effects of Cinnamic Aldehyde in an MPTP Mouse Model of Parkinson's Disease.

Cinnamic aldehyde (CA), a key flavor compound in cinnamon essential oil, has been identified as an anti-oxidant, anti-angiogenic, and anti-inflammatory material. Recently, the neuroprotective effects of CA have been reported in various neurodegenerative disorders, including Parkinson's disease (PD). In neurons, autophagy is tightly regulated, and consequently, the dysregulation of autophagy may induce neurodegenerative disorders. In the present study, we found that the selective dopaminergic neuronal death in the substantia nigra of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models was prevented by CA. Stimulation of microtubule-associated protein light chain 3 (LC3) puncta mediated by MPTP treatment was decreased by CA. Moreover, down-regulated p62 in the substantia nigra of MPTP mice was increased by administration of CA. Finally, we showed that blockage of autophagy using autophagy inhibitors protected the 1-methyl-4-phenylpyridinium (MPP⁺)-mediated death of BE(2)-M17 cells. Together these results suggest that CA has a neuroprotective effect in a PD model and that inhibition of autophagy might be a promising therapeutic target for PD.

Repeated manganese administration produced abnormal expression of circadian clock genes in the hypothalamus and liver of rats.

Manganese (Mn) neurotoxicity displays non-motor dysfunction and motor impairment like Parkinson's disease (PD), and is called as Manganism. Circadian disruption is a non-motor symptom found in PD and Manganism. Clock genes are essential to drive and maintain circadian rhythm, but little is known about Mn exposure on circadian clock genes expression. Both the brain and liver are targets of Mn, we hypothesize that repeated Mn administration could affect clock gene expression in the hypothalamus and livers. Male Sprague-Dawley rats were intraperitoneally injected Mn2+ 1mg and 5mg/kg as MnCl2·4H2O, every other day for 30 days. Mn neurotoxicity was evaluated by behavioral changes and loss of dopaminergic neurons via immunohistochemistry. The expression of circadian clock genes was determined via RT-qPCR. Repeated Mn administration dose-dependently retarded the body weight gain, impaired the rotarod activity, decreased the number of dopaminergic neurons in the substantia nigra, and activated microglia in the brain. Expressions of circadian core genes brain and muscle Arnt-like protein-1 (Bmal1), locomotor output cycles kaput (Clock) and neuronal PAS domain protein2 (Npas2), and clock feedback gene cryptochrome1 (Cry1), period genes (Per1 and Per2) in the hypothalamus and liver were decreased after exposure to Mn in a dose-dependent manner, while expressions of clock-targeted genes nuclear receptor Rev-Erbα (Nr1d1) and D-box-binding protein (Dbp) were increased. Peripheral clock in the liver appears to be more susceptible to Mn-induced abnormal clock gene expression. In summary, repeated Mn administration produced dysregulation of circadian clock gene expressions in both the brain and liver.

Estrogen ameliorates microglial activation by inhibiting the Kir2.1 inward-rectifier K(+) channel.

Microglial activation is implicated in the pathogenesis of Parkinson's disease (PD). Although the etiology of PD remains unclear, age and male gender are known PD risk factors. By comparing microglia and dopaminergic (DA) neurons in the substantia nigra (SN) of male and female mice of different ages, we found that the degrees of microglial activation and DA neuron loss increased with age in both genders, but were more pronounced in males, as were peripheral lipopolysaccharide (LPS)-induced microglial activation and DA neuron loss. A bilateral ovariectomy (OVX) eliminated the female-associated protection against age- and LPS-induced microglial activation, which suggests that ovary hormones are involved in gender-specific responses. Treating female mice with 17ß-estradiol supplements reduced the age-associated microglial activation in OVX mice. Moreover, pretreating mouse BV2 microglial cells with 17ß-estradiol inhibited LPS-induced elevation of Toll-like receptor 4, phosphorylated p38, and TNF-α levels. We then examined the effect of 17ß-estradiol on inward-rectifier K(+) channel Kir2.1, a known regulator of microglial activation. We found that 17ß-estradiol inhibited the Kir2.1 activity of BV2 cells by reducing the probability that the channel would be open. We conclude that age- and inflammation-associated microglial activation is attenuated by ovarian estrogen, because it inhibits Kir2.1.

Myricitrin Ameliorates 6-Hydroxydopamine-Induced Dopaminergic Neuronal Loss in the Substantia Nigra of Mouse Brain.

Parkinson's disease (PD) is a chronic and progressive movement disorder, resulting from the degeneration of the nigrostriatal dopaminergic (DA) pathway. The cause of DA neuronal loss in PD is still unclear; however, accumulating evidence suggests that treatment with certain flavonoids can induce neuroprotective properties, such as activation of mammalian target of rapamycin complex 1 (mTORC1) and anti-inflammatory activities in animal models of PD. The bioflavonoid myricitrin is well known for its anti-inflammatory and antioxidant properties. However, it is unclear whether systemic treatment with myricitrin can protect neurons against neurotoxin-induced DA degeneration in vivo via the preservation of tyrosine hydroxylase (TH) activity and the induction of mTORC1 activation. Our results found no significant neuroprotective effect of 30 mg/kg myricitrin on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in the substantia nigra (SN) of mice. However, myricitrin treatment with 60 mg/kg protected DA neurons against 6-OHDA-induced neurotoxicity. Moreover, myricitrin treatment preserved TH enzyme activity and mTORC1 activation in nigral DA neurons in the SN of 6-OHDA-treated mice, and its treatment suppressed an increase in tumor necrosis factor-α expression in activated microglia. These results suggest that myricitrin may have neuroprotective properties linked to mTORC1 activation, preservation of TH enzyme activity, and anti-neuroinflammation for preventing DA neuronal degeneration in vivo.

Increased number of TH-immunoreactive cells in the ventral tegmental area after deep brain stimulation of the anterior nucleus of the thalamus.

Dopamine (DA) has been long implicated with the processes of memory. In long-term memory, the hippocampus and ventral tegmental area (VTA) use DA to enhance long-term potentiation, while prefrontal DA D1 receptors are involved in working memory. Deep brain stimulation (DBS) of specific brain areas have been shown to affect memory impairments in animal models. Here, we tested the hypothesis that DBS could reverse memory impairments by increasing the number of dopaminergic cells in the VTA. Rats received DBS at the level of the mammillothalamic tract, the anterior nucleus of the thalamus, and entorhinal cortex before euthanasia. These regions are part of the so-called memory circuit. Brain sections were processed for c-Fos and tyrosine hydroxylase (TH) immunocytochemistry in the VTA and the substantia nigra pars compacta (SNc). c-Fos, TH and c-Fos/TH immunoreactive cells were analyzed by means of stereology and confocal microscopy. Our results showed that DBS of the anterior nucleus of the thalamus induced substantial higher numbers of TH-immunoreactive cells in the VTA, while there were no significant differences between the experimental groups in the number of TH immunoreactive cells in the SNc, c-Fos immunoreactive cells and c-Fos/TH double-labeled cells in both the SNc and VTA. Our findings suggest a phenotypic switch, or neurotransmitter respecification, of DAergic cells specifically in the VTA which may be induced by DBS in the anterior nucleus of the thalamus.

Stimulation of δ opioid receptor and blockade of nociceptin/orphanin FQ receptor synergistically attenuate parkinsonism.

δ opioid peptide (DOP) receptors are considered a therapeutic target in Parkinson's disease, although the use of DOP agonists may be limited by side effects, including convulsions. To circumvent this issue, we evaluated whether blockade of nociceptin/orphanin FQ (N/OFQ) tone potentiated the antiparkinsonian effects of DOP agonists, thus allowing for reduction of their dosage. Systemic administration of the N/OFQ receptor (NOP) antagonist J-113397 [(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H benzimidazol-2-one] and the DOP receptor agonist SNC-80 [(+)-4-[(αR)-α-(2S,5R)-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxy-benzyl]-N-N-diethylbenzamide] revealed synergistic attenuation of motor deficits in 6-hydroxydopamine hemilesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice. In this model, repeated administration of the combination produced reproducible antiparkinsonian effects and was not associated with rescued striatal dopamine terminals. Microdialysis studies revealed that either systemic administration or local intranigral perfusion of J-113397 and SNC-80 led to the enhancement of nigral GABA, reduction of nigral Glu, and reduction of thalamic GABA levels, consistent with the view that NOP receptor blockade and DOP receptor stimulation caused synergistic overinhibition of nigro-thalamic GABA neurons. Whole-cell recording of GABA neurons in nigral slices confirmed that NOP receptor blockade enhanced the DOP receptor-induced effect on IPSCs via presynaptic mechanisms. Finally, SNC-80 more potently stimulated stepping activity in mice lacking the NOP receptor than wild-type controls, confirming the in vivo occurrence of an NOP-DOP receptor interaction. We conclude that endogenous N/OFQ functionally opposes DOP transmission in substantia nigra reticulata and that NOP receptor antagonists might be used in combination with DOP receptor agonists to reduce their dosage while maintaining their full therapeutic efficacy.

[Effect of electroacupuncture intervention on levels of SOD, GSH, GSH-Px, MDA, and apoptosis of dopaminergic neurons in substantia Nigra in rats with Parkinson's disease].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on superoxide (SOD), glutathione peroxidase (GSH-Px) activity, contents of glutathione (GSH) and malondiadehyde (MDA), and expression of tyrosine hydroxylase (TH) and apoptosis of Dopaminergic (DA) neurons in Substantia Nigra of rats with Parkinson's disease (PD). METHODS: Adult male Wistar rats were randomly divided into normal (10 rats), model (11 rats), EA (11 rats) and medication (11 rats) groups. The PD model was established by i.h. of Rotenone (0.8 mg/kg) for 28 days. EA stimulation (2 Hz/80 Hz, 2 mA) was applied at "Baihui" (GV 20), "Sanyinjiao" (SP 6) and "Taichong" (LR 3) acupoints for 10 min, once per day for 14 times. For rats in the medication group, Madopar suspension fluid (1.67 mg/kg) was given by gavage for 14 days. Xanthine oxidase method and colorimetric ana- lysis method were used to examine the SOD, GSH-Px activity and contents of GSH and MDA in the Substantia Nigra tissue of the right brain, respectively. Immunohistochemical technique was used to detect the TH positive neurons and TUNEL method was used to examine the apoptosis of DA neurons of the Substantia Nigra in the left brain. RESULTS: Following the intervention, the decreased SOD and GSH-Px activity, GSH contents, and the increased MDA content of the Substantia Nigra in PD rats were obviously reversed by EA intervention (P < 0.05) but not by medication except MDA content (P > 0.05). In comparison with the model group, the decreased TH immunoactivity, and the increased numbers of apoptotic cells of DA neurons were apparently suppressed in both EA and medication groups (P < 0.05), but without significant differences between the EA and the medication groups (P > 0.05). In addition, HE stain showed that EA intervention could improve PD-induced impairment of Substantia Nigra neurons (mild swelling of neurons with large nucleus and deranged fibers). CONCLUSION: EA intervention can reduce pathological changes of Substantial Nigra in PD rats, which is probably associated with its effects in up-regulating the SOD and GSH-Px activity, GSH contents, and down-regulating MDA level, and reducing the apoptosis of DA neurons of the Substantia Nigra, suggesting an anti-oxidative stress effect of EA therapy.

In vivo electrophysiology of nigral and thalamic neurons in alpha-synuclein-overexpressing mice highlights differences from toxin-based models of parkinsonism.

Numerous studies have suggested that alpha-synuclein plays a prominent role in both familial and idiopathic Parkinson's disease (PD). Mice in which human alpha-synuclein is overexpressed (ASO) display progressive motor deficits and many nonmotor features of PD. However, it is unclear what in vivo pathophysiological mechanisms drive these motor deficits. It is also unknown whether previously proposed pathophysiological features (i.e., increased beta oscillations, bursting, and synchronization) described in toxin-based, nigrostriatal dopamine-depletion models are also present in ASO mice. To address these issues, we first confirmed that 5- to 6-mo-old ASO mice have robust motor dysfunction, despite the absence of significant nigrostriatal dopamine degeneration. In the same animals, we then recorded simultaneous single units and local field potentials (LFPs) in the substantia nigra pars reticulata (SNpr), the main basal ganglia output nucleus, and one of its main thalamic targets, the ventromedial nucleus, as well as LFPs in the primary motor cortex in anesthetized ASO mice and their age-matched, wild-type littermates. Neural activity was examined during slow wave activity and desynchronized cortical states, as previously described in 6-hydroxydopamine-lesioned rats. In contrast to toxin-based models, we found a small decrease, rather than an increase, in beta oscillations in the desynchronized state. Similarly, synchronized burst firing of nigral neurons observed in toxin-based models was not observed in ASO mice. Instead, we found more subtle changes in pauses of SNpr firing compared with wild-type control mice. Our results suggest that the pathophysiology underlying motor dysfunction in ASO mice is distinctly different from striatal dopamine-depletion models of parkinsonism.

Systemic delivery of tyrosine-mutant AAV vectors results in robust transduction of neurons in adult mice.

Recombinant adeno-associated virus (AAV) vectors are powerful tools for both basic neuroscience experiments and clinical gene therapies for neurological diseases. Intravascularly administered self-complementary AAV9 vectors can cross the blood-brain barrier. However, AAV9 vectors are of limited usefulness because they mainly transduce astrocytes in adult animal brains and have restrictions on foreign DNA package sizes. In this study, we show that intracardiac injections of tyrosine-mutant pseudotype AAV9/3 vectors resulted in extensive and widespread transgene expression in the brains and spinal cords of adult mice. Furthermore, the usage of neuron-specific promoters achieved selective transduction of neurons. These results suggest that tyrosine-mutant AAV9/3 vectors may be effective vehicles for delivery of therapeutic genes, including miRNAs, into the brain and for treating diseases that affect broad areas of the central nervous system.

Neuropathology and behavioral impairments in Wistar rats with a 6-OHDA lesion in the substantia nigra compacta and exposure to a static magnetic field.

Studies have sought to assess various potential neuroprotective therapeutics in Parkinson's disease. The aim of this study was to evaluate the effects of static magnetic field stimulation 14 days after a 6-Hydroxydopamine (6-OHDA) substantia nigra compacta (SNc) lesion on motor behavior, as assessed by the rotarod (RR) test and brain tissue morphology. Forty male Wistar rats were used and were divided into five groups: control group, sham group (SG), lesion group (LG), lesion north pole group (LNPG) and lesion south pole group (LSPG). In groups with magnetic stimulation, a 3200-gauss magnet was fixed to the skull. After the experiments, the animals were anesthetized for brain perfusion. Coronal sections of the SNc were stained with Nissl. The RR test showed a decrease in the time spent on the apparatus in the LG compared with all groups. The LNPG and LSPG had significant increases in the time spent when compared to the LG. A morphometric analysis revealed a significant reduction in the number of neurons in the LG, LNPG and LSPG in relation to the SG. There were a higher number of neurons in the LNPG and LSPG than the LG, and a higher number of neurons in the LSPG than the LNPG. We observed that the LG, LNPG and LSPG showed a higher number of glial cells than the SG, and the LNPG and LSPG showed a lower number of glial cells than the LG. Our results demonstrate a potential therapeutic use of static magnetic fields for the preservation of motor behavior and brain morphology in the SNc after 14 days with 6-OHDA lesion.

Differential regional expression patterns of α-synuclein, TNF-α, and IL-1ß; and variable status of dopaminergic neurotoxicity in mouse brain after Paraquat treatment.

BACKGROUND: Paraquat (1, 1-dimethyl-4, 4-bipyridium dichloride; PQ) causes neurotoxicity, especially dopaminergic neurotoxicity, and is a supposed risk factor for Parkinson's disease (PD). However, the cellular and molecular mechanisms of PQ-induced neurodegeneration are far from clear. Previous studies have shown that PQ induces neuroinflammation and dopaminergic cell loss, but the prime cause of those events is still in debate. METHODS: We examined the neuropathological effects of PQ not only in substantia nigra (SN) but also in frontal cortex (FC) and hippocampus of the progressive mouse (adult Swiss albino) model of PD-like neurodegeneration, using immunohistochemistry, western blots, and histological and biochemical analyses. RESULTS: PQ caused differential patterns of changes in cellular morphology and expression of proteins related to PD and neuroinflammation in the three regions examined (SN, FC and hippocampus). Coincident with behavioral impairment and brain-specific ROS generation, there was differential immunolocalization and decreased expression levels of tyrosine hydroxylase (TH) in the three regions, whereas α-synuclein immunopositivity increased in hippocampus, increased in FC and decreased in SN. PQ-induced neuroinflammation was characterized by area-specific changes in localization and appearances of microglial cells with or without activation and increment in expression patterns of tumor necrosis factor-α in the three regions of mouse brain. Expression of interleukin-1ß was increased in FC and hippocampus but not significantly changed in SN. CONCLUSION: The present study demonstrates that PQ induces ROS production and differential α-synuclein expression that promotes neuroinflammation in microglia-dependent or -independent manners, and produces different patterns of dopaminergic neurotoxicity in three different regions of mouse brain.

Phosphatidylinositol 3-kinase/Akt signaling pathway mediates acupuncture-induced dopaminergic neuron protection and motor function improvement in a mouse model of Parkinson's disease.

It has been reported that acupuncture treatment reduced dopaminergic neuron degeneration in Parkinson's disease (PD) models. However, the mechanistic pathways underlying, such neuroprotection, are poorly understood. Here, we investigated the effects and the underlying mechanism of acupuncture in a mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). First, we observed that MPTP-induced impairment of Akt activation, but not MPTP-induced c-Jun activation, was effectively restored by acupuncture treatment in the substantia nigra. Furthermore, we demonstrated for the first time that the brain-specific blockade of phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, by intranasal administration of LY294002, a specific inhibitor of PI3K/Akt signaling pathway, significantly blocked acupuncture-induced dopaminergic neuron protection and motor function improvement. Our results provide evidence that PI3K/Akt signaling pathway may play a central role in the mechanism underlying acupuncture-induced benefits in Parkinsonian mice.

Neuroprotective effects and mechanisms of exercise in a chronic mouse model of Parkinson's disease with moderate neurodegeneration.

The protective impact of exercise on neurodegenerative processes has not been confirmed, and the mechanisms underlying the benefit of exercise have not been determined in human Parkinson's disease or in chronic animal disease models. This research examined the long-term neurological, behavioral, and mechanistic consequences of endurance exercise in experimental chronic parkinsonism. We used a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease with moderate neurodegeneration and examined the effects of treadmill exercise on movement and balance coordination, changes in dopamine neuron biomarkers, mitochondrial functions, and neurotrophic factor activities in the nigrostriatal system. The exercise results were compared with those of the control and sedentary chronic parkinsonian animals. After 18 weeks of exercise training in the chronic parkinsonian mice, we observed a significant deterrence in the loss of neuronal dopamine-producing cells and other functional indicators. The impaired movement and balance incoordination in the chronic parkinsonian mice were also markedly reduced following exercise. Mechanistic investigations revealed that the neuronal and behavioral recovery produced by exercise in the chronic parkinsonian mice was associated with an improved mitochondrial function and an increase in the brain region-specific levels of brain-derived and glial cell line-derived neurotrophic factors. Our findings indicate that exercise not only produces neuronal and mitochondrial protection, it also boosts nigrostriatal neurotrophic factor levels in the chronic parkinsonian mice with moderate neurodegeneration. Therefore, modifying lifestyle with increased exercise activity would be a non-pharmacological neuroprotective approach for averting neurodegenerative processes, as demonstrated in experimental chronic parkinsonism.

Protective effect of resveratrol derived from Polygonum cuspidatum and its liposomal form on nigral cells in parkinsonian rats.

OBJECTIVE: Oxidative stress which is an important factor in the pathogenesis of Parkinson's disease (PD) leads to the selective loss of nigral dopaminergic neurons in PD. Resveratrol is a well known antioxidant that exerts extensive pharmacological effects. This study aimed to investigate the protective effect of resveratrol derived from Polygonum cuspidatum and its liposomal form on nigral cells of PD rats. METHODS: A rat PD model was established by unilateral microinjection of 6-hydroxy dopamine in the striatum. Then, P. cuspidatum and its liposomal form were intragastrically administered once daily for 2 consecutive weeks. The behaviors, tyrosine hydroxylase positive cells, apoptotic cells, ROS level and total antioxidant capacity were determined. RESULTS: Our results showed after 14 days of oral treatment with resveratrol or resveratrol liposome (20 mg/kg per day), the abnormal rotational behavior, the loss and apoptosis of nigral cells, and the levels of total reactive oxygen species were markedly decreased and the total antioxidant capability of nigral tissues significantly improved. Furthermore, resveratrol liposome showed more profound effects than free resveratrol. CONCLUSION: Resveratrol derived from P. cuspidatum and its liposomal form could protect the dopaminergic neurons in PD rats, to which their radical scavenging ability and antioxidant properties may attribute. Presumably due to the increased bioavailability, resveratrol liposome exerts more potent protection and may become a promising agent for the treatment of PD than free resveratrol.

Gypenosides protects dopaminergic neurons in primary culture against MPP(+)-induced oxidative injury.

Oxidative injury has been implicated in the etiology of Parkinson's disease (PD). Gypenosides (GPs), the saponins extract derived from the Gynostemma pentaphyllum, has various bioactivities. In this study, GPs was investigated for its neuroprotective effects on the 1-methyl-4-phenylpyridinium ion (MPP(+))-induced oxidative injury of dopaminergic neurons in primary nigral culture. It was found that GPs pretreatment, cotreatment or posttreatment significantly and dose-dependently attenuated MPP(+)-induced oxidative damage, reduction of dopamine uptake, loss of tyrosine hydrolase (TH)-immunopositive neurons and degeneration of TH-immunopositive neurites. However, the preventive effect of GPs was more potential than its therapeutical effect. Most importantly, the neuroprotective effect of GPs may be attributed to GPs-induced strengthened antioxidation as manifested by significantly increased glutathione content and enhanced activity of glutathione peroxidase, catalyze and superoxide dismutase in nigral culture. The neuroprotective effects of GPs are specific for dopaminergic neurons and it may have therapeutic potential in the treatment of PD.

Puerarin protects dopaminergic neurons against 6-hydroxydopamine neurotoxicity via inhibiting apoptosis and upregulating glial cell line-derived neurotrophic factor in a rat model of Parkinson's disease.

Neurodegeneration is one of the primary etiologies in the onset of Parkinson's disease. In the quest for a new antiparkinsonism treatment the potential benefits of puerarin from the roots of Pueraria lobata have been recognized. Thus, we examined whether puerarin is capable to protect dopaminergic neurons of the substantia nigra against 6-hydroxydopamine induced neuronal cell death. Our data showed that the intraperitoneal administration of 0.12 mg/kg/day puerarin over 10 days reduced the 6-hydroxydopamine-induced decrease of tyrosine hydroxylase-positive cell counts. Analysis of apoptosis via DNA fragmentation by the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay proved that puerarin could prevent 6-hydroxydopamine-induced apoptosis. As an additional apoptotic cell death marker, the BAX and BCL-2 expression levels were investigated using immunohistochemistry. Whereas 6-hydroxydopamine increased the level of Bax (p < 0.05), the coadministrated puerarin significantly antagonized this effect in a dose-dependent manner. Bcl-2 expression was not affected. Analysis of the dopamine, dihydroxyphenylacetic acid, and L-dihydroxy-phenyl-alanine contents of 6-hydroxydopamine-treated animals by HPLC revealed that puerarin was capable to restore the contents of dopamine and its metabolites. Moreover, the expression level of glial cell line-derived neurotrophic factor in the striatum was higher in puerarin than in rats treated with 6-hydroxydopamine alone. These results suggest that puerarin develops its neuroprotective effect against 6-hydroxydopamine-induced neurotoxicity in the substantia nigra through the inhibition of apoptotic signaling pathways and upregulation of glial cell line-derived neurotrophic factor expression in the striatum.

Dopaminergic neurons expressing Fos during waking and paradoxical sleep in the rat.

Formerly believed to contribute to behavioural waking (W) alone, dopaminergic (DA) neurons are now also known to participate in the regulation of paradoxical sleep (PS or REM) in mammals. Indeed, stimulation of postsynaptic DA1 receptors with agonists induces a reduction in the daily amount of PS. DA neurons in the ventral tegmental area were recently shown to fire in bursts during PS, but nothing is known about the activity of the other DA cell groups in relation to waking or PS. To fulfil this gap, we used a protocol in which rats were maintained in continuous W for 3h in a novel environment, or specifically deprived of PS for 3 days with some of them allowed to recover from this deprivation. A double immunohistochemical labeling with Fos and tyrosine hydroxylase was then performed. DA neurons in the substantia nigra (A9) and ventral tegmental area (A10), and its dorsocaudal extension in the periaqueductal gray (A10dc), almost never showed a Fos-immunoreactive nucleus, regardless of the experimental condition. The caudal hypothalamic (A11) group showed a moderate activation after PS deprivation and novel environment. During PS-recovery, the zona incerta (A13) group contained a significant number and percentage of double-labeled neurons. These results suggest that some DA neurons (A11) could participate in waking and/or the inhibition of PS during PS deprivation whereas others (A13) would be involved in the control of PS.

Preventive role of PD-1 on MPTP-induced dopamine depletion in mice.

Many current studies of Parkinson's disease (PD) suggest that inflammation is involved in the neurodegenerative process. PD-1, a traditional Korean medicine, used to treat various brain diseases in Korea. This study was designed to investigate the effect of PD-1 extract in the Parkinson's model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) lesioned mice. The MPTP administration caused the dopamine neuron loss in the striatum and substantia nigra pars compacta (SNpc), which was demonstrated by a depletion of tyrosine hydroxylase (TH). In addition, a reduction of bcl-2 expression with elevation of bax expression, caspase-3 activation, and release of cytochrome c into cytosol in dopaminergic neurons of SNpc were noted. Oral administration of PD-1 extract (50 and 100 mg kg(-1)) attenuated the MPTP-induced depletion of TH proteins in the striatum and SNpc and prevented the apoptotic effects. These results indicate that PD-1 extract is able to protect dopaminergic neurons from MPTP-induced neuronal death, with important implications for the treatment of PD.