MADOPAR-INDUCED DYSKINESIA IN 1-METHYL-4-PHENYL-1,2,3,6-TETRAHYDROPYRIDINE (MPTP) HEMIPARKINSONIAN MONKEY MODEL

Infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into the right common carotid artery produced hemiparkinsonian syndrome on contralateral limbs in 5 rhesus monkeys. The hemiparkinsonian syndrome produced responded to madopar medication and the circling motion changed from toward the MPTP-treated side to away from the MPTP-treated side. Long term use of madopar developed a peak-dose dyskinesia of the face and limbs at the contralateral side. The toxic effect of MPTP was confirmed biochemically by reduction of nigrostriatal DA and histologically by degeneration of nigral neurons on the MPTP-treated side. It is concluded that this hemiparkinsonian monkey model will be of value in the elucidation of the neural mechanism underlying L-DOPA or DA agonists induced dyskinesia in Parkinson’s disease and in the search for newer methods of treatment which would produce less dyskinesia.

Prenatal and Postnatal Exposures to 1-Methyl-4-phenyl-1,2,3,6-tetra Hydropyridine (MPTP) Impaired Mouse Midbrain Dopamine System and May Produce a Predisposing and Inducing Model for Parkinson’s Disease

Dopamine cell bodies in the substantia nigra of the midbrain and with their terminals projecting to the neostriatum form the nigrostriatum and these dopamine neurons degenerate in Parkinson’s disease (PD). Based on metabolic and func- tional specialization of the cell bodies versus the axon terminals, the level and disposition of dopamine, its metabolites and enzymes are different in both regions and are likely to be affected differently in PD. We examined changes in the midbrain dopamine system following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), to test the hypothesis that a predisposing/sensitization stage and a inducing/precipitating stage underlie PD. Pregnant mice were treated with a low dose of MPTP during gestation days 8 - 12 to model the predisposing/sensitization stage, by interrupting the fetal mid- brain dopamine system during its neurogenesis. For the inducing/precipitating stage, the 12-weeks offspring were ad- ministered MPTP. The prenatal-MPTP offspring appear normal, but midbrain dopamine, 3,4-di-hydroxy-phenyl-acetic- acid, 3-methoxytyramine, tyrosine-hydroxylase and L-aromatic-amino-acid-decarboxylase, were reduced by 49.6%, 48%, 54%, 20.9% and 25%. Postnatal-MPTP of 10, 20, 30 mg/kg administered to the prenatal-PBS vs prenatal-MPTP offspring reduced midbrain dopamine by 43.6%, 47.2%, 70.3% vs 85.4%, 89.1%, 95.2%;tyrosine-hydroxylase by 30%, 63%, 81% vs 30.7%, 70.4%, 91.4%;L-aromatic-amino-acid-decarboxylase by 0%, 2%, 40% vs 32%, 40%, 58%. The prenatal-MPTP may render the DA system sensitive by causing sub-threshold reduction of DA, its metabolites and en- zymes, enabling postnatal-MPTP to reduce dopamine above the 70% - 80% PD-inducing threshold. Thus, the study may produce a prenatal predisposing/sensitization and postnatal inducing/precipitation model of PD. It also indicates that some cases of PD may have a fetal basis, in which sub-threshold nigrostriatal impairments occur early in life and PD-symptoms are induced during aging by further insults to the dopaminergic system that would not cause PD symptoms in normal indi-viduals.

Neurotoxic mechanism of 1-methyl-4-phenyl-1,2,3,6-tetradropyridine

BACKGROUND: To summarize the metabolic pathway of 1-methyl-4-phenyl-1,2,3,6-tetradropyridine (MPTP) and its mechanism in inducing Parkinson disease. DATA SOURCES: A computer-based online search of Medline database was undertaken to identify articles about the metabolic pathway of MPTP and its mechanism in inducing Parkinson disease published in English between January 1996 and August 2004, the were "MPTP, Parkinson disease". Meanwhile, Chinese relevant articles published between January 2000 and August 2004 were searched in Wanfang database with the keywords of "MPTP, Parkinson disease". STUDY SELECTION: More than 300 relevant literatures were retrieved, and the full-texts were further searched, those about the establishment of animal models, molecular mechanism of MPTP neurotoxicity and the metabolism were selected, and the obviously repetitive ones, case report and reviews were excluded, finally 18 of them were selected for summarization. DATA EXTRACTION: The 18 literatures were categorized according to MPTP induced animal models of Parkinson disease, mechanism of MPTP in inducing apoptosis in models of Parkinson disease, role of dopamine in the neurotoxic mechanism of MPTP, the role of reactive oxygen species and nitric oxide in the neurotoxicity of MPTP. DATA SYNTHESIS: Animal models of Parkinson disease induced by MPTP can not only produce the clinical characters of Parkinson disease, also duplicate the main biochemical and pathological changes of Parkinson disease. The metabolic pathway of MPTP and its mechanism in inducing Parkinson disease included producing free oxygen and nitric oxide, damaging mitochondrial respiratory chain, and inducing apoptosis, etc. which could all lead to the degeneration and loss of dopaminergic neurons. CONCLUSION: Although some aspects of the models of Parkinson disease are different from that in human beings, we can still know the neurodegeneration of Parkinson disease through studying the molecular mechanism of MPTP.

Effect of Zishenpingchan granule prepared from Chinese medicinal substances on the c-Jun N-terminal protein kinase pathway in mice with Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

OBJECTIVE:To investigate the regulatory mechanism of the c-Jun N-terminal protein kinase(JNK)signaling pathway in substantia nigra(SN) dopaminergic neurons inflammation and apoptosis, and the neuroprotective effect of Zishenpingchan granules in mice with Parkinson's disease(PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP).METHODS:PD model mice were established by intraperitoneally injecting MPTP.Sixty mice were divided into a model group, Traditional Chinese Medicine(TCM) group and control group.The mice of the TCM group were administered Zishenpingchan granules 7 days before PD induction.Seven days after PD induction, we examined locomotor activity,and performed the rotarod test and swimming test,to evaluate limb movement function.Furthermore,we used immunohistochemistry and western blotting to examine the expression of tyrosine hydroxylase(TH), cyclooxygenase-2(Cox-2), caspase-3 and p-JNK.The terminal deoxynucleotidyl transferase mediated d UTP nick end labeling(TUNEL) method was used to examine neuron apoptosis in the SN.RESULTS:Compared with the control group, the mean score of locomotor activity, rotarod test and swimming test was significantly lower in the model group(P < 0.05); the TH-positive neuron expression was significantly decreased in the SN pars compacta(SNpc); the protein expression levels of Cox-2,caspase-3 and p-JNK was obviously increased; and the number of TUNEL-positive neurons in the SN was increased(P < 0.01).Compared with the model group, the mean score of neurobehavioral tests in the TCM group was obviously higher, the loss of TH-positive neurons ignificantly decreased, the protein expression levels of Cox-2, caspase-3 and p-JNK obviously decreased, and the number of TUNEL-positive neurons in the SN clearly decreased(P < 0.01).CONCLUSION:The JNK pathway plays an important role in the regulation of inflammation and apoptosis in nigral cells in PD mice.TCM can suppress the over-activation of the JNK pathway in the SN, and alleviate the inflammatory response in nigral cells and dopaminergic neuron apoptosis in PD mice.

The transient receptor potential melastatin 2:a new therapeutical target for Parkinson's disease?

The transient receptor potential melastatin 2 is a calcium-permeable cation channel member of the TRP family. Also known as an oxidative stress-activated channel, the transient receptor potential melastatin 2 gating mechanism is dependent on reactive oxygen species. In pathological conditions, transient receptor potential melastatin 2 is overactivated, leading to a Ca~(2+) influx that alters cell homeostasis and promotes cell death. The role of transient receptor potential melastatin 2 in neurodegenerative diseases, including Alzheimer's disease and ischemia, has already been described and reviewed. However, data on transient receptor potential melastatin 2 involvement in Parkinson's disease pathology has emerged only in recent years and the issue lacks review studies that focus specifically on this topic. The present review aims to elucidate the role of the transient receptor potential melastatin 2 channel in Parkinson's disease by reviewing, summarizing, and discussing the in vitro, in vivo, and human studies published until August 2022. Here we describe fourteen studies that evaluated the transient receptor potential melastatin 2 channel in Parkinson's disease. The Parkinson's disease model used, transient receptor potential melastatin 2 antagonist and genetic approaches, and the main outcomes reported were discussed. The studies described transient receptor potential melastatin 2 activation and enhanced expression in different Parkinson's disease models. They also evidenced protective and restorative effects when using transient receptor potential melastatin 2 antagonists, knockout, or silencing. This review provides a literature overview and suggests where there is a need for more research. As a perspective point, this review shows evidence that supports transient receptor potential melastatin 2 as a pharmacological target for Parkinson's disease in the future.

Ginsenoside Rg1 attenuates motor impairment and neuroinflammation in the MPTP-probenecid-induced parkinsonism mouse model

OBJECTIVE To evaluate these activities of Rg1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)/probenecid(MPTP/p)-induced PD mouse model for the first time and to elucidate the underlying mechanisms.METHODS Male C57BL/6 mice were randomly assigned to six groups.One hour prior to MPTP/p injection,GroupⅢ-Ⅵmice received 10 mg·kg^(-1),20 mg·kg^(-1),or 40 mg·kg^(-1) Rg1 or 3 mg·kg^(-1) selegiline,respectively,orally from D(-3) to D49.GroupⅠ-Ⅱmice received solvent water.Subsequently,GroupⅡ-Ⅵmice received by injection MPTP-HCl(25 mg·kg^(-1) bw dissolved in0.9%saline,sc)on a 40-d schedule at intervals of 4 d between consecutive doses in combination with an adjuvant drug,probenecid(250 mg·kg^(-1) bw in 0.03 mL of DMSO,ip);GroupⅠmice were injected with saline and probenecid.Behavioral performance was assessed in the open field test,pole test and rotarod test.Neurotransmitters in the striatum were detected using HPLC.Protein levels were measured by Western blot.Pathological characteristics were examined by immunohistochemistry.Ultrastructure changes were observed by electron microscopy.RESULTS Oral treatment with Rg1 significantly attenuated the high MPTP-induced mortality,behavior defects,loss of dopamine neurons and abnormal ultrastructure changes in the SNpc.Other assays indicated that the protective effect of Rg1 may be mediated by its anti-neuroinflammatory properties.Rg1 regulated MPTP-induced reactive astrocytes and microglia and decreased the release of cytokines such as tumor necrosis factor-α(TNF-α)and interleukin-1b(IL^(-1)b)in the SNpc.Rg1 also al eviated the unusual MPTP induced increase in oligomeric,phosphorylated and disease-related a-synuclein in the SNpc.CONCLUSION Rg1 protects dopaminergic neurons,most likely by reducing aberrant a-synuclein-mediated neuroinflammation,and holds promise for Parkinson disease therapeutics.

Single-neuron neurodegeneration as a degenerative model for Parkinson’s disease

The positive effect of levodopa in the treatment of Parkinson’s disease,although it is limited in time and has severe side effects,has encouraged the scientific community to look for new drugs that can stop the neurodegenerative process or even regenerate the neuromelanin-containing dopaminergic nigrostriatal neurons.Successful preclinical studies with coenzyme Q10,mitoquinone,isradipine,nilotinib,TCH346,neurturin,zonisamide,deferiprone,prasinezumab,and cinpanemab prompted clinical trials.However,these failed and after more than 50 years levodopa continues to be the key drug in the treatment of the disease,despite its severe side effects after 4–6 years of chronic treatment.The lack of translated successful results obtained in preclinical investigations based on the use of neurotoxins that do not exist in the human body as new drugs for Parkinson’s disease treatment is a big problem.In our opinion,the cause of these failures lies in the experimental animal models involving neurotoxins that do not exist in the human body,such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 6-hydroxydopamine,that induce a very fast,massive and expansive neurodegenerative process,which contrasts with the extremely slow one of neuromelanin-containing dopaminergic neurons.The exceedingly slow progress of the neurodegenerative process of the nigrostriatal neurons in idiopathic Parkinson’s patients is due to(i)a degenerative model in which the neurotoxic effect of an endogenous neurotoxin affects a single neuron,(ii)a neurotoxic event that is not expansive and(iii)the fact that the neurotoxin that triggers the neurodegenerative process is produced inside the neuromelanin-containing dopaminergic neurons.The endogenous neurotoxin that fits this degenerative model involving one single neuron at a time is aminochrome,since it(i)is generated within neuromelanin-containing dopaminergic neurons,(ii)does not cause an expansive neurotoxic effect and(iii)triggers all the mechanisms involved in the neurodegenerative process of the nigrostriatal neurons in idiopathic Parkinson’s disease.In conclusion,based on the hypothesis that the neurodegenerative process of idiopathic Parkinson’s disease corresponds to a single-neuron neurodegeneration model,we must search for molecules that increase the expression of the neuroprotective enzymes DT-diaphorase and glutathione transferase M2-2.It has been observed that the activation of the Kelch-like ECH-associated protein 1/nuclear factor(erythroid-derived 2)-like 2 pathway is associated with the transcriptional activation of the DT-diaphorase and glutathione transferase genes.

Neuroprotective effects of Suhexiang Wan on the in vitro and in vivo models of Parkinson’s disease

OBJECTIVE:To examine the role of KSOP1009(a modified formulation of Suhexiang Wan essential oil)in an animal model of Parkinson's disease(PD)induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine(MPTP)injection.METHODS:Cell toxicity,apoptosis,and reactive oxygen species(ROS)levels were analyzed in the human neuroblastoma cell line SH-SY5 Y.After that,changes in animal behavior and tyrosine hydroxylase(TH)protein levels in the substantia nigra(SN)of MPTP-injected mice were examined.Three different doses of KSOP1009(30,100,and 300 mg/kg,n=8 for each group)were administered daily for 7 d before MPTP injection and 14 d after MPTP injection,totaling 21 d.RESULTS:MPP+,the active metabolite of MPTP,decreased the viability of SH-SY5 Y cells,whereas KSOP1009 alleviated MPP+-induced cytotoxicity.KSOP1009(10 and 50 mg/m L)reduced MPP+-induced ROS generation compared with the control group.Treatment with 1 m M MPP+increased the percentage of depolarized/live cells,whereas KSOP1009 intake at a dose of 10 mg/m L decreased the percentage of these cells.The mean latency to fall in the rotarod test was reduced in mice treated with MPTP compared with the control group.However,mice receiving three different doses of KSOP1009 performed better than MPTP-treated animals.MPTP-treated mice were more hesitant and took longer to traverse the balance beam than the control animals.In contrast,KSOP1009-treated mice performed significantly better than MPTPtreated mice.Furthermore,the KSOP1009-treated groups had a significantly higher number of TH-positive neurons in the lesioned SN and significantly higher expression of TH in the striatum than the MPTP-treated group.MPTP treatment strongly induced Jun-N-terminal kinase(JNK)activation,whereas KSOP1009 suppressed MPTP-induced JNK activation.In addition,KSOP1009 intake reversed the decrease in the phosphorylation levels of c AMP-response element-binding protein in the brain of MPTP-treated mice.KSOP1009 also restored the decrease in dopaminergic neurons and dopamine levels in the brain of MPTP-treated mice.CONCLUSION:KSOP1009 protected mice against MPTP-induced toxicity by decreasing ROS formation and restoring mitochondrial function.

Neuroprotective Effects of San-Jia-Fu-Mai Decoction: Studies on the in vitro and in vivo Models of Parkinson's Disease

Objective:The objective of this study was to investigate whether 70%aqueous ethanol extract of San-Jia-Fu-Mai decoction extract(SJFMDE)could protect against 1-methyl-4-phenylpyridinium(MPP+)-induced oxidative stress in PC12 cells and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced motor function deficits in mice.Materials and Methods:The cell viability,the levels of intracellular reactive oxygen species(ROS),malondialdehyde(MDA),and glutathione(GSH)in the MPP+-treated PC12 cells were measured.Motor function deficits and dopamine(DA)level in the brain striatum and tyrosine hydroxylase(TH)-positive cells in substantia nigra pars compacta(SNc)of the MPTP-treated mice were determined.Results:The results showed that SJFMDE could reduce cell death and the levels of ROS and MDA while increase the level of GSH in the MPP+-treated PC12 cells.In addition,in vivo studies showed that oral administration of SJFMDE(3,6,and 12 g/kg)significantly improved the motor function deficits induced by MPTP and enhanced the DA level in the striatum and TH-positive neuronal cells in SNc of the MPTP-treated mice.Conclusions:Our results revealed that SJFMDE possessed neuroprotective effects against neurotoxicity induced by MPP+and motor function deficits induced by MPTP via suppressing oxidative stress and increasing the levels of DA and TH,indicating that SJFMDE might be a promising Chinese medicine formula for the treatment of Parkinson’s disease.