Asiaticoside exerts neuroprotection through targeting NLRP3 inflammasome activation.

BACKGROUND: Parkinson's disease (PD), a neurodegenerative disorder, is characterized by motor symptoms due to the progressive loss of dopaminergic neurons in the substantia nigra (SN) and striatum (STR), alongside neuroinflammation. Asiaticoside (AS), a primary active component with anti-inflammatory and neuroprotective properties, is derived from Centella asiatica. However, the precise mechanisms through which AS influences PD associated with inflammation are not yet fully understood. PURPOSE: This study aimed to explore the protective mechanism of AS in PD. METHODS: Targets associated with AS and PD were identified from the Swiss Target Prediction, Similarity Ensemble Approach, PharmMapper, and GeneCards database. A protein-protein interaction (PPI) network was constructed to identify potential therapeutic targets. Concurrently, GO and KEGG analyses were performed to predict potential signaling pathways. To validate these mechanisms, the effects of AS on 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD in mice were investigated. Furthermore, neuroinflammation and the activation of the NLRP3 inflammasome were assessed to confirm the anti-inflammatory properties of AS. In vitro experiments in BV2 cells were then performed to investigate the mechanisms of AS in PD. Moreover, CETSA, molecular docking, and molecular dynamics simulations (MDs) were performed for further validation. RESULTS: Network pharmacology analysis identified 17 potential targets affected by AS in PD. GO and KEGG analyses suggested the biological roles of these targets, demonstrating that AS interacts with 149 pathways in PD. Notably, the NOD-like receptor signaling pathway was identified as a key pathway mediating AS's effect on PD. In vivo studies demonstrated that AS alleviated motor dysfunction and reduced the loss of dopaminergic neurons in MPTP-induced PD mice. In vitro experiments demonstrated that AS substantially decreased IL-1ß release in BV2 cells, attributing this to the modulation of the NLRP3 signaling pathway. CETSA and molecular docking studies indicated that AS forms a stable complex with NLRP3. MDs suggested that ARG578 played an important role in the formation of the complex. CONCLUSION: In this study, we first predicted that the potential target and pathway of AS's effect on PD could be NLRP3 protein and NOD-like receptor signaling pathway by network pharmacology analysis. Further, we demonstrated that AS could alleviate symptoms of PD induced by MPTP through its interaction with the NLRP3 protein for the first time by in vivo and in vitro experiments. By binding to NLRP3, AS effectively inhibits the assembly and activation of the inflammasome. These findings suggest that AS is a promising inhibitor for PD driven by NLRP3 overactivation.

Folic Acid Rescues Dopaminergic Neurons in MPTP-Induced Mice by Inhibiting the NLRP3 Inflammasome and Ameliorating Mitochondrial Impairment.

Parkinson's disease (PD) is marked by the degeneration of dopaminergic neurons of the substantia nigra (SN), with neuroinflammation and mitochondrial dysfunction being key contributors. The neuroprotective potential of folic acid (FA) in the dopaminergic system of PD was assessed in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model. MPTP (20 mg/kg of body weight) was administered to C57BL/6J mice to simulate PD symptoms followed by FA treatment (5 mg/kg of body weight). Behavioral tests, pole, rotarod, and open-field tests, evaluated motor function, while immunohistochemistry, ELISA, RT-qPCR, and Western blotting quantified neuroinflammation, oxidative stress markers, and mitochondrial function. FA supplementation considerably improved motor performance, reduced homocysteine levels and mitigated oxidative damage in the SN. The FA-attenuated activation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome lessened glial cell activity and reduced neuroinflammation. At the molecular level, FA reduced DNA damage, downregulated phosphorylated p53, and induced the expression of peroxisome proliferator-activated receptor α coactivator 1α (PGC-1α), enhancing mitochondrial function. Therefore, FA exerts neuroprotection in MPTP-induced PD by inhibiting neuroinflammation via NLRP3 inflammasome suppression and promoting mitochondrial integrity through the p53-PGC-1α pathway. Notable limitations of our study include its reliance on a single animal model and the incompletely elucidated mechanisms underlying the impact of FA on mitochondrial dynamics. Future investigations will explore the clinical utility of FA and its molecular mechanisms, further advancing it as a potential therapeutic for managing and delaying the progression of PD.

Human neural stem cells promote mitochondrial genesis to alleviate neuronal damage in MPTP-induced cynomolgus monkey models.

Currently, there is no effective treatment for Parkinson's disease (PD), and the regenerative treatment of neural stem cells (NSCs) is considered the most promising method. This study aimed to investigate the protective effect and mechanism of NSCs on neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced cynomolgus monkey (Macaca fascicularis) model of PD. We first found that injecting NSCs into the subarachnoid space relieved motor dysfunction in PD cynomolgus monkeys, as well as reduced dopaminergic neuron loss and neuronal damage in the substantia nigra (SN) and striatum. Besides, NSCs decreased 17-estradiol (E2) level, an estrogen, in the cerebrospinal fluid (CSF) of PD cynomolgus monkeys, which shows NSCs may provide neuro-protection by controlling estrogen levels in the CSF. Furthermore, NSCs elevated proliferator-activated receptor gamma coactivator-1 alpha (PGC-1a), mitofusin 2 (MFN2), and optic atrophy 1 (OPA1) expression, three genes mediating mitochondrial biogenesis, in the SN and striatum of PD monkeys. In addition, NSCs suppress reactive oxygen species (ROS) production caused by MPTP, as well as mitochondrial autophagy, therefore preserving dopaminergic neurons. In summary, our findings show that NSCs may preserve dopaminergic and neuronal cells in an MPTP-induced PD cynomolgus monkey model. These protective benefits might be attributed to NSCs' ability of modulating estrogen balance, increasing mitochondrial biogenesis, and limiting oxidative stress and mitochondrial autophagy. These findings add to our understanding of the mechanism of NSC treatment and shed light on further clinical treatment options.

Baicalin exerts neuroprotective actions by regulating the Nrf2-NLRP3 axis in toxin-induced models of Parkinson's disease.

Baicalin, a potent anti-oxidative and anti-inflammatory flavonoid compound derived from Scutellaria baicalensis, has emerged as a neuroprotective agent. However, the mechanisms by which baicalin is neuroprotective in Parkinson's disease (PD) remain unclear. In this research, α-syn/MPP+ and MPTP were used to establish PD models in BV2 cells and C57BL/6 mice, respectively. The effect and mechanism of action of baicalin in PD were investigated by Western blotting, RT-qPCR, ELISA, Immunohistochemistry (IHC) staining, Immunofluorescence (IF) staining, HPLC and methods. Results demonstrate that baicalin mitigates oxidative stress, microglia activation and inflammatory response caused by α-syn/MPP+ and MPTP. It protects against dopaminergic neuron loss and relieves motor deficits. Meanwhile, baicalin not only significantly up-regulates the expression of Nrf2 and its downstream antioxidant enzyme, but also suppresses the activation of NLRP3 inflammasome simultaneously. Notably, the beneficial effects of baicalin in PD treatment are blocked by Nrf2 knockdown. This research reveals that baicalin may exert neuroprotective effects in PD treatment by suppressing the activation of NLRP3 inflammasome and it is dependent on the Nrf2-mediated antioxidative response.

The gut microbiota metabolite butyrate mitigates MPTP/MPP+ -induced Parkinson's disease by inhibiting the JAK2/STAT3 signaling pathway.

Butyrate (BU), a gut microbiota-derived metabolite, has been reported to play a neuroprotective role in Parkinson's disease (PD). However, the specific molecular mechanism of BU has not been fully interpreted. This work aimed to verify the protective effects of BU against MPTP/MPP+ -induced neurotoxicity and explore the mechanisms involved. The results showed that BU protected against MPTP-induced motor dysfunction and decreased tyrosine hydroxylase (TH) and dopamine transporter (DAT) levels. Additionally, BU pretreatment improved PC12 cell viability and reduced MPP+ -induced PC12 cell apoptosis. BU treatment also attenuated MPP+ -stimulated oxidative stress and inflammatory response in PC12 cells. Furthermore, BU inhibited MPTP/MPP+ -induced hyperactivation of the JAK2/STAT3 signaling in mice and PC12 cells. Besides, a JAK2 agonist, Coumermycin A1 (C-A1), substantially reversed BU-mediated inhibition on JAK2/STAT3 phosphorylation in MPP+ -challenged PC12 cells and abated BU-induced repression on MPP+ -triggered apoptosis, oxidative stress, and inflammatory response in PC12 cells. To sum up, BU might exert neuroprotective effects against MPP+ /MPTP-induced neurotoxicity by inactivating the JAK2/STAT3 signaling.

The Transcription Factor Nrf2 Mediates the Effects of Antrodia camphorata Extract on Neuropathological Changes in a Mouse Model of Parkinson's Disease.

Parkinson's disease (PD) is a disorder that is characterized by progressive and selective neuronal injury and cell death. Recent studies have provided accumulating evidence for a significant role of the immune system and neuroinflammation in PD pathogenesis. On this basis, many scientific articles have highlighted the anti-inflammatory and neuroprotective properties of Antrodia camphorata (AC), an edible fungus containing various bioactive compounds. This study aimed to evaluate the inhibitory effect of AC administration on neuroinflammation and oxidative stress in a murine model of MPTP-induced dopaminergic degeneration. AC (10, 30, 100 mg/kg) was administered daily by oral gavage starting 24 h after the first administration of MPTP, and mice were sacrificed 7 days after MPTP induction. In this study, treatment with AC significantly reduced the alteration of PD hallmarks, increasing tyrosine hydroxylase expression and reducing the number of alpha-synuclein-positive neurons. In addition, AC treatment restored the myelination process of neurons associated with PD and attenuated the neuroinflammatory state. Furthermore, our study demonstrated that AC was able to reduce the oxidative stress induced by MPTP injection. In conclusion, this study highlighted that AC could be a potential therapeutic agent for the treatment of neurodegenerative disorders such as PD.

Orally Induced High Serum Level of Trimethylamine N-oxide Worsened Glial Reaction and Neuroinflammation on MPTP-Induced Acute Parkinson's Disease Model Mice.

Neuroinflammation mediated by brain glial cells is one of the pathological drivers of Parkinson's disease (PD). Recent studies have shown that higher circulating trimethylamine N-oxide (TMAO, a gut microbiota-derived metabolite) can induce neuroinflammation and are strongly related to a variety of central nervous system diseases and adverse brain events. Herein, we explored the effect of pre-existing higher circulating TMAO on dopamine system and neuroinflammation in acute PD model mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP). TMAO pretreatment was given by adding 3% (w/v) TMAO to drinking water of mice for 21 days to induce higher circulating TMAO status, then mice were administered with MPTP (20 mg/kg, i.p) for four times in one day to construct an acute PD model mice and treated with TMAO continuously until the end of the experiment. Results demonstrated that TMAO treatment significantly increased serum TMAO levels. Moreover, high serum TMAO significantly increased activation of microglia and astrocytes both in striatum and in substantia nigra. And strikingly, high serum TMAO significantly promoted the metabolism of striatal dopamine (DA) of PD model mice, although it had no significant effect on the number of dopaminergic neurons or the content of DA. Furthermore, immunofluorescence, ELISA, and RT-qPCR results of the hippocampus also showed that high serum TMAO significantly promoted the activation of microglia and astrocytes in the dentate gyrus, increased the levels of TNF-α and IL-1ß, and upregulated gene expression of M1 microglia-related markers (including CD16, CD32, and iNOS) and A2 astrocyte-related markers (including S100a10, Ptx3, and Emp1) in mRNA levels. In summary, we found that pre-existing high serum levels of TMAO worsened the PD-related brain pathology by promoting DA metabolism, aggravating neuroinflammation and regulating glial cell polarization.

Apoptotic Factors and Mitochondrial Complexes Assist Determination of Strain-Specific Susceptibility of Mice to Parkinsonian Neurotoxin MPTP.

Identification of genetic mutations in Parkinson's disease (PD) promulgates the genetic nature of disease susceptibility. Resilience-associated genes being unknown till date, the normal genetic makeup of an individual may be determinative too. Our earlier studies comparing the substantia nigra (SN) and striatum of C57BL/6J, CD-1 mice, and their F1-crossbreds demonstrated the neuroprotective role of admixing against the neurotoxin MPTP. Furthermore, the differences in levels of mitochondrial fission/fusion proteins in the SN of parent strains imply effects on mitochondrial biogenesis. Our present investigations suggest that the baseline levels of apoptotic factors Bcl-2, Bax, and AIF differ across the three strains and are differentially altered in SN following MPTP administration. The reduction in complex-I levels exclusively in MPTP-injected C57BL/6J reiterates mitochondrial involvement in PD pathogenesis. The MPTP-induced increase in complex-IV, in the nigra of both parent strains, may be compensatory in nature. The ultrastructural evaluation showed fairly preserved mitochondria in the dopaminergic neurons of CD-1 and F1-crossbreds. However, in CD-1, the endoplasmic reticulum demonstrated distinct luminal enlargement, bordering onto ballooning, suggesting proteinopathy as a possible initial trigger.The increase in α-synuclein in the pars reticulata of crossbreds suggests a supportive role for this output nucleus in compensating for the lost function of pars compacta. Alternatively, since α-synuclein over-expression occurs in different brain regions in PD, the α-synuclein increase here may suggest a similar pathogenic outcome. Further understanding is required to resolve this biological contraption. Nevertheless, admixing reduces the risk to MPTP by favoring anti-apoptotic consequences. Similar neuroprotection may be envisaged in the admixed populace of Anglo-Indians.

Novel FABP3 ligand, HY-11-9, ameliorates neuropathological deficits in MPTP-induced Parkinsonism in mice.

Parkinson's disease (PD) is characterized by dopaminergic (DAergic) neuronal loss in the substantia nigra pars compacta (SNpc), resulting from α-synuclein (αSyn) toxicity. We previously reported that αSyn oligomerization and toxicity are regulated by the fatty-acid binding protein 3 (FABP3), and the therapeutic effects of the FABP3 ligand, MF1, was successfully demonstrated in PD models. Here, we developed a novel and potent ligand, HY-11-9, which has a higher affinity for FABP3 (Kd = 11.7 ± 8.8) than MF1 (Kd = 302.8 ± 130.3). We also investigated whether the FABP3 ligand can ameliorate neuropathological deterioration after the onset of disease in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinsonism. Motor deficits were observed two weeks after MPTP treatment. Notably, oral administration of HY-11-9 (0.03 mg/kg) improved motor deficits in both beam-walking and rotarod tasks, whereas MF1 failed to improve the motor deficits in both tasks. Consistent with the behavioral tasks, HY-11-9 recovered dopamine neurons from MPTP toxicity in the substantia nigra and ventral tegmental areas. Furthermore, HY-11-9 reduced the accumulation of phosphorylated-serine129-α-synuclein (pS129-αSyn) and colocalization with FABP3 in tyrosine hydroxylase (TH)-positive DA neurons in the PD mouse model. Overall, HY-11-9 significantly improved MPTP-induced behavioral and neuropathological deterioration, suggesting that it may be a potential candidate for PD therapy.

Mesenchymal stem-cell-derived microvesicles ameliorate MPTP-induced neurotoxicity in mice: a role of the gut-microbiota-brain axis.

RATIONALE: Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder. Increasing evidence suggests the role of the gut-microbiota-brain axis in the pathogenesis of PD. Mesenchymal stem-cell-derived microvesicles (MSC-MVs) have emerged as a therapeutic potential for neurological disorders over the last years. OBJECTIVE: The objective of this study was to investigate whether MSC-MVs could improve PD-like neurotoxicity in mice after administration of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). RESULTS: MPTP-induced reductions in the dopamine transporter and tyrosine hydroxylase expressions in the striatum and substantia nigra (SNr) were attenuated after a subsequent single administration of MSC-MVs. Increases in the phosphorylated α-synuclein (p-α-Syn)/α-Syn ratio in the striatum, SNr, and colon after MPTP injection were also attenuated after MSC-MVs injection. Furthermore, MSC-MVs restored MPTP-induced abnormalities of the gut microbiota composition. Interestingly, positive correlations between the genus Dubosiella and the p-α-Syn/α-Syn ratio were observed in the brain and colon, suggesting their roles in the gut-microbiota-brain communication. Moreover, MSC-MVs attenuated MPTP-induced reduction of the metabolite, 3,6-dihydroxy-2-[3-methoxy-4-(sulfooxy)phenyl]-7-(sulfinooxy)-3,4-dihydro-2H-1-benzopyran-5-olate, in the blood. Interestingly, a negative correlation between this compound and the p-α-Syn/α-Syn ratio was observed in the brain and colon. CONCLUSIONS: These data suggest that MSC-MVs could ameliorate MPTP-induced neurotoxicity in the brain and colon via the gut-microbiota-brain axis. Therefore, MSC-MVs would have a new therapeutic potential for neurological disorders such as PD.

Gut Microbial Alteration in MPTP Mouse Model of Parkinson Disease is Administration Regimen Dependent.

Parkinson Disease (PD) is one of the most common neurodegenerative disorders characterized by loss of dopaminergic neurons involved in motor functions. Growing evidence indicates that gut microbiota communicates with the brain known as the gut-brain axis (GBA). Mitochondrial toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is commonly used in animal studies to investigate the GBA in PD. Various MPTP administration regimens are performed in PD mouse models involving one to multiple injections in 1 day or one injection per day for several days. The aim of this study is to investigate if the impact of MPTP on gut microbiota differs depending on the administration regimen. C57BL/6 mice were treated with acute or subchronic regimens of MPTP. Motor functions were assessed by open-field, catalepsy, and wire hanging tests. The cecum and the brain samples were obtained for microbiota and gene expression analyses, respectively. MPTP administration regimens differed in their ability to alter the gut microbiota. Firmicutes and Bacteroidota were both increased in subchronic mice while did not change and decreased, respectively, in acute mice. Verrucomicrobiota was elevated in acute MPTP mice but dropped in subchronic MPTP mice. Muribaculaceae was the predominant genus in all groups but acute mice. In acute mice, Akkermansia was increased and Colidextribacter was decreased; however, they showed an opposite trend in subchronic mice. These data suggest that MPTP mouse model cause a gut microbiota dysbiosis in an administration regimen dependent manner, and it is important to take consideration of mouse model to investigate the GBA in neurodegenerative diseases including PD.

Feruloylated oligosaccharides ameliorate MPTP-induced neurotoxicity in mice by activating ERK/CREB/BDNF/TrkB signalling pathway.

BACKGROUND: Feruloylated oligosaccharides (FOs) are natural esterification products of ferulic acid and oligosaccharides. STUDY DESIGN: In this study, we examined whether FOs contribute to the ensured survival of nigrostriatal dopamine neurons and inhibition of neuroinflammation in Parkinson's disease (PD). METHODS: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg) was injected intraperitoneally into mice to establish a Parkinson's disease (PD) mouse model. FOs (15 and 30 mg/kg) were orally administered daily to the MPTP-treated mice. The rotarod test, balance beam test, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), quantitative PCR (qPCR), and western blot analyses were performed to examine the neuroprotective effects of FOs on MPTP-treated mice. RESULTS: Our study indicated that FOs increased the survival of dopamine neurons in the substantia nigra pars compacta (SNc) of the MPTP-treated mice. The neuroprotective effects of FOs were accompanied by inhibited glial activation and reduced inflammatory cytokine production. The mechanistic experiments revealed that the neuroprotective effects of FOs might be mediated through the activation of the ERK/CREB/BDNF/TrkB signalling pathway. CONCLUSION: This study provides new insights into the mechanism underlying the anti-neuroinflammatory effect of phytochemicals and may facilitate the development of dietary supplements for PD patients. Our results indicate that FOs can be used as potential modulators for the prevention and treatment of PD.

MPTP induces neurodegeneration by modulating dopaminergic activity in catfish brain.

Tyrosine hydroxylase (Th) is an allosteric rate-limiting enzyme in catecholamine (CA) biosynthesis. The CAs, dopamine (DA), norepinephrine (NE), and epinephrine are important neurotransmitters wherein DA contributes a key role in the central nervous system of vertebrates. The present study evaluated DA and Th's significance in DA-ergic activity and neurodegeneration upon 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) exposure in catfish. Further, the expression of certain brain-and ovary-related genes measured through qPCR were downregulated upon MPTP treatment which is in accordance with the decreased levels of L-Dopa, DA, and NE levels estimated through HPLC-ECD. Additionally, TEM analysis depicted structural disarray of brain upon MPTP exposure and also decreased serum levels of testosterone, 11-ketotestosterone, and estradiol-17ß. MPTP treatment, in vitro, using primary brain cell culture resulted in diminished cell viability and increased ROS levels leading to elevated apoptotic cells significantly. Consequently, the study highlights the MPTP-induced neurodegeneration of the Th and DA-ergic activity in corroboration with female brain-related genes downregulation, also gonadal function as evidenced by depleted sex steroids level and low expression of ovary-related genes.

Protective effect of cistanoside A on dopaminergic neurons in Parkinson's disease via mitophagy.

One of the main pathological features of Parkinson's disease (PD) is the loss of dopaminergic neurons in the substantia nigra compacta (SNc). Cistanoside A (CA) has a strong neuroprotective effect in PD, but the exact mechanism is unclear. In the present study, the MPTP-stimulated mouse model of PD and MPP+ -treated PD model in the MES23.5 neuronal cell model of PD were used to investigate the neuroprotective effects of CA on PD and its potential mechanism. The in vivo experiment results indicated that CA improved the motor function in mice and increased the number of tyrosine hydroxylase positive cells in SNc. In vitro experiments showed that CA reduced the MPP+ -induced decrease in neurons and mitochondrial membrane potential and promoted the activation of autophagosomes. Furthermore, we found that CA promoted the recruitment of PINK1 and Parkin aggregation to impair mitochondrial membranes and inhibited mitochondrial damage via LC3- and p62-mediated autophagy. In conclusion, CA protects against MPTP-induced neurotoxicity in vivo and MPP+ -induced neurotoxicity in vitro, possibly by promoting the PINK1/Parkin/p62 pathway to accelerate the degradation of damaged mitochondria thereby reducing oxidative stress.

Exercise attenuates mitochondrial autophagy and neuronal degeneration in MPTP induced Parkinson's disease by regulating inflammatory pathway.

Parkinson's disease (PD) is a chronic neuronal loss of dopamine and drugs used for its management has several limitations. The present report determines the effect of exercise on mitochondrial autophagy against PD. Parkinson's disease was induced by 15 doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 30 mg/kg, i.p.) for 3 weeks, on five consecutive days in a week. Exposure of exercise was provided for 40 min for a period of 2 weeks after PD confirmation. Assessment of behaviour was performed to evaluate the effect of exercise on motor function and cognitive function in PD rats. Levels of reactive oxygen species (ROS) and inflammatory cytokines were assessed in PD rats using enzyme linked immunosorbent assay (ELISA). Expression of myocyte-specific enhancer factor 2D (MEF2D) and NADH dehydrogenase 6 (ND6) was estimated in PD rats. Exposure to exercise ameliorates the altered motor function and cognitive function in PD rats. There was a reduction in ROS and cytokine levels in the brain tissue of the exercise group compared to the negative control group. Exercise ameliorates the altered expression of apoptotic proteins and mRNA expression of MEF2D and ND6 in the brain tissue of MPTP induced PD rats. In conclusion, data of study reveal that exercise protects the mitochondrial autophagy in PD rats by reducing inflammatory cytokines and oxidative stress.

Defining Specific Cell States of MPTP-Induced Parkinson's Disease by Single-Nucleus RNA Sequencing.

Parkinson's disease (PD) is a neurodegenerative disease with an impairment of movement execution that is related to age and genetic and environmental factors. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin widely used to induce PD models, but the effect of MPTP on the cells and genes of PD has not been fully elucidated. By single-nucleus RNA sequencing, we uncovered the PD-specific cells and revealed the changes in their cellular states, including astrocytosis and endothelial cells' absence, as well as a cluster of medium spiny neuron cells unique to PD. Furthermore, trajectory analysis of astrocyte and endothelial cell populations predicted candidate target gene sets that might be associated with PD. Notably, the detailed regulatory roles of astrocyte-specific transcription factors Dbx2 and Sox13 in PD were revealed in our work. Finally, we characterized the cell-cell communications of PD-specific cells and found that the overall communication strength was enhanced in PD compared with a matched control, especially the signaling pathways of NRXN and NEGR. Our work provides an overview of the changes in cellular states of the MPTP-induced mouse brain.

GSNOR deficiency attenuates MPTP-induced neurotoxicity and autophagy by facilitating CDK5 S-nitrosation in a mouse model of Parkinson's disease.

The S-nitrosoglutathione reductase (GSNOR) is a key denitrosating enzyme that regulates protein S-nitrosation, a process which has been found to be involved in the pathogenesis of Parkinson's disease (PD). However, the physiological function of GSNOR in PD remains unknown. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model, we found that GSNOR expression was significantly increased and accompanied by autophagy mediated by MPTP-induced cyclin dependent kinase 5 (CDK5), behavioral dyskinesias and dopaminergic neuron loss. Whereas, knockout of GSNOR, or treatment with the GSNOR inhibitor N6022, alleviated MPTP-induced PD-like pathology and neurotoxicity. Mechanistically, deficiency of GSNOR inhibited MPTP-induced CDK5 kinase activity and CDK5-mediated autophagy by increasing S-nitrosation of CDK5 at Cys83. Our study indicated that GSNOR is a key regulator of CDK5 S-nitrosation and is actively involved in CDK5-mediated autophagy induced by MPTP.

Characterization of Developmental Neurobehavioral Toxicity in a Zebrafish MPTP-Induced Model: A Novel Mechanism Involving Anemia.

Zebrafish represent an economical alternative to rodents for developmental neurotoxicity (DNT) testing. Mechanistic understanding is the key to successfully translating zebrafish findings to humans. In the present study, we used a well-known dopaminergic (DA) neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a model chemical to uncover the molecular pathways for observed DNT effects. To enhance the specificity of potential molecular targets, we restricted our exposure to a concentration that is nonteratogenic yet exhibits high DNT effects and an exposure window sensitive to MPTP. Our DNT assessment based on a battery of motor and social behavioral tests revealed an effective concentration of 1 µM and a sensitive window of 48-96 h postfertilization (hpf) for MPTP-induced hypoactivity. It is worth noting that this hypoactivity persisted into later larval development until 28 dpf. We observed increased cell apoptosis, oxidative stress, and decreased ATP levels in larvae immediately after exposure at 96 hpf. Significant reductions of DA neurons were found in the retina at 72, 96, and 120 hpf. No visible deformity was found in motoneurons at 72, 96, and 120 hpf. Transcriptome analysis uncovered a novel pathway manifested by significant upregulation of genes enriched with erythropoiesis. Sensitive window exposure of MPTP and other DA neurotoxins rotenone and paraquat exhibited a concentration-dependent effect on transcriptional changes of embryonic hemoglobins and anemia. Given that anemia is a significant risk factor for Parkinson's disease and MPTP is known to cause parkinsonism in humans, we concluded that anemia resulting from dysregulation of primitive erythropoiesis during embryonic development might serve as a common mechanism underlying DA neurotoxin-induced DNT effects between zebrafish and humans.

Hyperbaric Oxygen Therapy Improves Parkinson's Disease by Promoting Mitochondrial Biogenesis via the SIRT-1/PGC-1α Pathway.

Hyperbaric oxygen therapy (HBOT) has been suggested as a potential adjunctive therapy for Parkinson's disease (PD). PD is a neurodegenerative disease characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The aim of this study was to investigate the protective mechanisms of HBOT on neurons and motor function in a 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD and 1-methyl-4-phenylpyridinium (MPP+)-mediated neurotoxicity in SH-SY5Y cells on the potential protective capability. In vivo: male C57BL/6 mice were randomly divided into three groups: control, MPTP group and MPTP+HBOT group. The MPTP-treated mice were intraperitoneally received MPTP (20 mg/kg) four times at 2 h intervals within a day. The day after MPTP treatment, MPTP+HBOT mice were exposed to hyperbaric oxygen at 2.5 atmosphere absolute (ATA) with 100% oxygen for 1 h once daily for 7 consecutive days. In vitro: retinoic acid (RA)-differentiated SH-SY5Y cells were treated with MPP+ for 1 h followed by hyperbaric oxygen at 2.5 ATA with 100% oxygen for 1 h. The results showed that MPTP induced a significant loss in tyrosine hydroxylase (TH)-positive neurons in the SNpc of mice. HBOT treatment significantly increased the number of TH-positive neurons, with enhanced neurotrophic factor BDNF, decreased apoptotic signaling and attenuated inflammatory mediators in the midbrain of MPTP-treated mice. In addition, MPTP treatment decreased the locomotor activity and grip strength of mice, and these effects were shown to improve after HBOT treatment. Furthermore, MPTP decreased mitochondrial biogenesis signaling (SIRT-1, PGC-1α and TFAM), as well as mitochondrial marker VDAC expression, while HBOT treatment was shown to upregulate protein expression. In cell experiments, MPP+ reduced neurite length, while HBOT treatment attenuated neurite retraction. Conclusions: the effects of HBOT in MPTP-treated mice might come from promoting mitochondrial biogenesis, decreasing apoptotic signaling and attenuating inflammatory mediators in the midbrain, suggesting its potential benefits in PD treatment.

Cerebroventricular Injection of Pgk1 Attenuates MPTP-Induced Neuronal Toxicity in Dopaminergic Cells in Zebrafish Brain in a Glycolysis-Independent Manner.

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons. While extracellular Pgk1 (ePgk1) is reported to promote neurite outgrowth, it remains unclear if it can affect the survival of dopaminergic cells. To address this, we employed cerebroventricular microinjection (CVMI) to deliver Pgk1 into the brain of larvae and adult zebrafish treated with methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a PD-like model. The number of dopamine-producing cells in ventral diencephalon clusters of Pgk1-injected, MPTP-treated embryos increased over that of MPTP-treated embryos. Swimming distances of Pgk1-injected, MPTP-treated larvae and adult zebrafish were much longer compared to MPTP-treated samples. The effect of injected Pgk1 on both dopamine-producing cells and locomotion was time- and dose-dependent. Indeed, injected Pgk1 could be detected, located on dopamine neurons. When the glycolytic mutant Pgk1, Pgk1-T378P, was injected into the brain of MPTP-treated zebrafish groups, the protective ability of dopaminergic neurons did not differ from that of normal Pgk1. Therefore, ePgk1 is functionally independent from intracellular Pgk1 serving as an energy supplier. Furthermore, when Pgk1 was added to the culture medium for culturing dopamine-like SH-SY5Y cells, it could reduce the ROS pathway and apoptosis caused by the neurotoxin MPP+. These results show that ePgk1 benefits the survival of dopamine-producing cells and decreases neurotoxin damage.