The effect of dopamine on MPTP-induced rotarod disability

Iron-inhibited autophagy via transcription factor ZFP27 in Parkinson's disease

Parkinson's disease (PD) is a challenge because of the ageing of the population and the disease's complicated pathogenesis. Accumulating evidence showed that iron and autophagy were involved in PD. Nevertheless, the molecular mechanism and role of iron and autophagy in PD are not yet elucidated. In the present study, it was shown that PD mice had significant motor dysfunction, increased iron content, less dopamine neurons and more α-synuclein accumulation in the substantia nigra. Meanwhile, PD mice treated with deferoxamine exhibited less iron content, relieved the dyskinesia and had a significant increase in dopamine neurons and a significant decrease in α-synuclein. Autophagy induced by LC3 was inhibited in PD models with iron treatment. Following verification showed that iron aggregation restrained insulin-like growth factor 2 (IGF2) and transcription factor zinc finger protein 27 (ZFP27) in PD models. In addition, LC3-induced autophagy flux was reduced with ZFP27 knockdown. Furthermore, ZFP27 affected autophagy by regulating LC3 promoter activity. These data suggest that iron deposition inhibits IGF2 and ZFP27 to reduce LC3-induced autophagy, and ultimately decrease dopamine neurons, accelerating PD progression. Our findings provide a novel insight that ZFP27-mediated iron-related autophagy and IGF2 may activate the downstream kinase gene to trigger autophagy in the PD model.

Huperzine A injection ameliorates motor and cognitive abnormalities via regulating multiple pathways in a murine model of Parkinson's disease

As a common progressive neurodegenerative disorder, the satisfied therapies for Parkinson's disease (PD) are still unavailable. As a natural acetylcholinesterase inhibitor, the neuroprotective characteristic of Huperzine A (HupA) was supported by previous studies. However, questions remain on whether HupA injection (HAI, a main preparation of HupA) intervention conduces to PD treatment and if so, the potential molecular mechanisms. In this study, the efficacies of HAI treatment on PD-like pathological phenotypes were evaluated in a MPTP-induced PD murine model. The network pharmacology, transcriptome sequencing and experimental verification were integrated to comprehensively reveal the primary molecular mechanisms. Therapeutically, HAI intervention significantly improved the impaired locomotor behaviors as well as learning and memory abilities, and prevented the degeneration of dopaminergic neurons of PD mice. The network pharmacology analysis combined with experimental results showed that HAI treatment could effectively restore the disordered transcriptional levels of inflammatory factors and apoptosis related genes in the SNpc and striatum tissues of PD mice. Transcriptome sequencing results found that inflammation and oxidative phosphorylation served as significant functional mechanisms involved in HAI administration. The experimental verification indicated that HAI treatment effectively regulated the abnormal transcription levels of inflammation and oxidative phosphorylation related hub genes in the hippocampal samples of PD mice. In addition, molecular docking suggested strong affinity between HupA and the above core targets. Overall, this work displayed the reliable therapeutic effects of HAI on ameliorating the pathological symptoms of PD mice via modulating multiple pathways. The current findings were expected to provide a potential anti-PD agent.

Customizable Open-Source Rotating Rod (Rotarod) Enables Robust Low-Cost Assessment of Motor Performance in Mice

Reliable measurements of motor learning and coordination in mice are fundamental aspects of neuroscience research. Despite the advent of deep-learning approaches for motor assessment, performance testing on a rotating rod (rotarod) has remained a staple in the neuroscientist's toolbox. Surprisingly, commercially available rotarod instruments offer limited experimental flexibility at a relatively high cost. In order to address these concerns, we engineered a highly-customizable, low-budget rotarod device with increased functionality. Here, we present a detailed guide to assemble this rotarod using simple materials. Our apparatus incorporates a variation of interchangeable rod sizes and designs which provides for adjustable testing sensitivity. Moreover, our rotarod is driven by open-source software enabling bespoke acceleration ramps and sequences. Finally, we report the strengths and weaknesses of each rod design following multiday testing on cohorts of C57BL/6 mice. We expect explorations in deviant rod types to provide a foundation for the development of increasingly sensitive models for motor performance testing along with low-budget alternatives for the research community.

Deacetylation of ZKSCAN3 by SIRT1 induces autophagy and protects SN4741 cells against MPP+-induced oxidative stress

Mitochondrial dysfunction, oxidative stress and misfolded protein aggregation are related to autophagy-lysosomal dysregulation and contribute to the pathogenesis of Parkinson' s disease (PD). ZKSCAN3, a transcriptional repressor, plays a crucial role in autophagy and lysosomal biogenesis. However, the role and modification of ZKSCAN3 in the defection of ALP, along with the molecular mechanism involved in pathogenesis of PD, still remain unclear. In this study, we demonstrated that cellular reactive oxygen species (ROS) generated by MPP⁺ exposure and the resulting oxidative damage were counteracted by SIRT1-ZKSCAN3 pathway induction. Here we showed that nuclear ZKSCAN3 significantly increased in ventral midbrain of MPTP-treated mice and MPP⁺-treated SN4741 cells. Knockdown of ZKSCAN3 alleviated MPP⁺-induced ALP defect, Tyrosine Hydroxylase (TH) declination and neuronal death. NAC, a ROS scavenger, reduced the nuclear translocation of ZKSCAN3 and sequentially improved ALP function in MPP⁺-treated SN4741 cells. SRT2104, a SIRT1 activator, attenuated impairment of ALP in MPP⁺-treated SN47417 cells through decreasing nuclear accumulation of ZKSCAN3 and protected dopaminergic neurons from MPTP injury. Moreover, SRT2104 relieved impairment in locomotor activities and coordination skills upon treatment of MPTP in C57/BL6J mice through behavior tests including rotarod, pole climbing and grid. Furthermore, ZKSCAN3 was a novel substrate of SIRT1 which was deacetylated at lysine 148 residues by SIRT1. This subsequently facilitated the shuttling of ZKSCAN3 to the cytoplasm. Therefore, our study identifies a novel acetylation-dependent regulatory mechanism of nuclear translocation of ZKSCAN3. It results in autophagy-lysosomal dysfunction and then leads to DA neuronal death in MPTP/MPP⁺ model of PD.

MiR-30c-5p/ATG5 Axis Regulates the Progression of Parkinson's Disease

Serum miR-30c-5p correlates with Parkinson’s disease (PD), yet its role has not been illustrated. This research analyzed the function of miR-30c-5p in PD. The behavioral evaluation was performed on MPTP-treated PD mice transfected with miR-30c-5p agomiR, antagomiR, siATG5, or 3-MA (an autophagy inhibitor). Oxidative stress-related factors, miR-30c-5p, and apoptosis- and autophagy-associated proteins in brain tissues or cells were determined by molecular experiments. Tyrosine hydroxylase (TH) and dopamine metabolic markers were detected using immunofluorescence and Diode Array Detector (DAD), respectively. Effects of miR-30c-5p and its target gene Autophagy-related gene (ATG) 5 protein (ATG5) on MPP+-treated SH-SY5Y cells were determined through a series of molecular experiments. MiR-30c-5p was upregulated but ATG5 was downregulated in PD mice. MiR-30c-5p antagomiR attenuated the decrease of ATG5 in PD mice. MiR-30c-5p antagomiR partly alleviated the behavioral symptoms and inhibited the increases of malondialdehyde (MDA), catalase (CAT), and SOD in PD mice. The levels of Bcl-2, dopamine, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), TH, and LC3 II were downregulated in PD mice, while Bax, cleaved caspase-3, P62, and LC3 I were upregulated. However, miR-30c-5p antagomiR partly reversed the levels of these factors in PD mice. 3-MA could block the effects of miR-30c-5p antagomiR on PD mice. MiR-30c-5p antagomiR attenuated apoptosis and induced autophagy in brain tissues of MPTP-treated mice by targeting ATG5. In vitro assay results also showed that silence of ATG5 reduced the protective effect of miR-30c-5p downregulation on the cells. MiR-30c-5p regulates the progression of Parkinson’s disease through attenuating ATG5-inhibited apoptosis and -induced autophagy.

Acrolein scavenger dimercaprol offers neuroprotection in an animal model of Parkinson's disease: implication of acrolein and TRPA1

BACKGROUND

The mechanisms underlying lesions of dopaminergic (DA) neurons, an essential pathology of Parkinson's disease (PD), are largely unknown, although oxidative stress is recognized as a key factor. We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in PD pathology, and that acrolein scavenger hydralazine can reduce the elevated acrolein, mitigate DA neuron death, and alleviate motor deficits in a 6-hydroxydopamine (6-OHDA) rat model. As such, we hypothesize that a structurally distinct acrolein scavenger, dimercaprol (DP), can also offer neuroprotection and behavioral benefits.

METHODS

DP was used to lower the elevated levels of acrolein in the basal ganglia of 6-OHDA rats. The acrolein levels and related pathologies were measured by immunohistochemistry. Locomotor and behavioral effects of 6-OHDA injections and DP treatment were examined using the open field test and rotarod test. Pain was assessed using mechanical allodynia, cold hypersensitivity, and plantar tests. Finally, the effects of DP were assessed in vitro on SK-N-SH dopaminergic cells exposed to acrolein.

RESULTS

DP reduced acrolein and reversed the upregulation of pain-sensing transient receptor potential ankyrin 1 (TRPA1) channels in the substantia nigra, striatum, and cortex. DP also mitigated both motor and sensory deficits typical of PD. In addition, DP lowered acrolein and protected DA-like cells in vitro. Acrolein's ability to upregulate TRPA1 was also verified in vitro using cell lines.

CONCLUSIONS

These results further elucidated the acrolein-mediated pathogenesis and reinforced the critical role of acrolein in PD while providing strong arguments for anti-acrolein treatments as a novel and feasible strategy to combat neurodegeneration in PD. Considering the extensive involvement of acrolein in various nervous system illnesses and beyond, anti-acrolein strategies may have wide applications and broad impacts on human health.

Paeoniflorin and Plycyrrhetinic Acid Synergistically Alleviate MPP+/MPTP-Induced Oxidative Stress through Nrf2-Dependent Glutathione Biosynthesis Mechanisms

Recently, combination therapy has proven to be an effective strategy for treating polygenic/multifactorial/complex disorder such as Parkinson's disease (PD). Here, we hypothesized that dual up-regulation of glutamate cysteine ligase (GCL) catalytic subunit (GCLc) and GCL modifier subunit (GCLm) via nuclear factor E2-related factor (Nrf2) contribute to the antioxidant effect of paeoniflorin (PF) synergistically with glycyrrhetinic acid (GA) (henceforth called PF/GA) in the context of MPP⁺/MPTP neurotoxicity. Expectedly, CompuSyn synergism/antagonism analysis showed that PF/GA exerts synergistic neuroprotection. Moreover, the antioxidant effect of PF was significantly enhanced by the combined administration of GA, although GA alone did not confer the effect. Mechanistically, PF triggered extracellular signal-regulated kinase (ERK1/2) phosphorylation, resulting in Nrf2 nuclear translocation from cytoplasmic pool via de novo synthesis in MPP⁺-challenged SH-SY5Y cells. Concomitantly, GA activates Akt which in turn induces nuclear accumulation of Nrf2. Especially, PF/GA up-regulated glutamate-cysteine ligase catalytic subunit (Gclc) and glutamate-cysteine ligase modifier subunit (Gclm) are formed via two separate pathways. Furthermore, these results were confirmed through pathway blockade assays using PD98059 (ERK1/2 inhibitor), LY294002 (phosphatidylinositol-3-kinase inhibitor), and shRNA-induced Nrf2 knockdown. Additionally, using a mouse MPTP-induced model of PD, we demonstrated that PF/GA synergistically ameliorates both motor deficits and oxidative stress in the ventral midbrain. In parallel, PF/GA also up-regulated both GCLc and GCLm expression at levels of transcription and translation. Conversely, antiparkinsonism and antioxidant effects of PF/GA were not observed in Nrf2-knockout MPTP-mice. Collectively, these results show that ERK1/2 and Akt activation contribute to the synergistic antioxidant effect of PF/GA. Hence, PF/GA regimen warrants further preclinical and possible clinical study for PD.

Crocetin Alleviates Inflammation in MPTP-Induced Parkinson's Disease Models through Improving Mitochondrial Functions

Parkinson's disease (PD) is the second most common neurodegenerative disease. Crocetin, derived from saffron, exerts multiple pharmacological properties, such as anti-inflammatory, antioxidant, antifatigue, and anticancer effects. However, the effect of crocetin on PD remains unclear. In this study, we designed experiments to investigate the effect of crocetin against MPTP-induced PD models and the underlying mechanisms. Our results showed that crocetin treatment attenuates MPTP-induced motor deficits and protects dopaminergic neurons. Both in vivo and in vitro experiments demonstrated that crocetin treatment decreased the expression of inflammatory associated genes and inflammatory cytokines. Furthermore, crocetin treatment protected mitochondrial functions against MPP+ induced damage by regulating the mPTP (mitochondrial permeability transition pore) viability in the interaction of ANT (adenine nucleotide translocase) and Cyp D (Cyclophilin D) dependent manner. Therefore, our results demonstrate that crocetin has therapeutic potential in Parkinson's disease.

Novel mGluR4 agonist Rapitalam ameliorates motor dysfunction in mice with tau-associated neurodegeneration

Introduction: Tau protein is classically involved in the pathogenesis of a neurodegenerative processes, such as Parkinson’s disease. This study was aimed at testing the novel mGluR4 selective agonist using it in transgenic mice with tau-associated neurodegeneration.

Materials and methods: Mice with Human P301S Tau hyperexpression were divided into 3 groups: Rapitalam 6 mg/kg and 20 mg/kg by gavage 3 times a week; and Control (Sham). The motor functions of animals were evaluated at 12th, 14th, 16th, 18th, and 20th weeks of life using the grip-test, rotarod and hanging wire test. In addition, the time of symptoms onset and death was recorded.

Research results: The use of Rapitalam at a dose of 6 mg/kg and 20 mg/kg significantly restored the holding impulse on a hanging wire, increasing it from 5.06±1.25 kg×sec to 6.42±0.97 kg×sec and 8.84±1.17 kg×sec, respectively. A similar trend was observed in the grip test: Rapitalam recovered grip strength from 28.43±5.04 N in the control group to 44.27±5.54 N (6 mg/kg) and 59.53±7.95 (20 mg/kg). Finally, the two-month use of Rapitalam neither delayed the manifestation of symptoms, nor increased the survival of mice.

Discussion: The cause of the loss of nerve cells in the mouse-tau line is autophagy. Apparently, Rapitalam is not able to simulate this process by reducing excitotoxicity, but against the background of the neurodegenerative process, it increases the activity of the nerve cells.

Conclusion: Rapitalam improves motor dysfunction in mice with tauopathy, with no effect on the survival of animals.

Rg1 improves LPS-induced Parkinsonian symptoms in mice via inhibition of NF-κB signaling and modulation of M1/M2 polarization

Ginsenoside Rg1 is one of the most active ingredients in ginseng, which has been reported to protect dopaminergic neurons and improve behavioral defects in MPTP model, 6-OHDA model and rotenone model. However, it is unclear whether Rg1 exerted neuroprotection in LPS-induced sub-acute PD model. In this study, we investigated the neuroprotective effect of Rg1 in the sub-acute PD mouse model and explored the related mechanisms. Rg1 (10, 20, 40 mg·kg^-1·d^-1) was orally administered to mice for 18 days. A sub-acute PD model was established in the mice through LPS microinjection into the substantia nigra (SN) from D8 to D13. We found that Rg1 administration dose-dependently inhibited LPS-induced damage of dopaminergic neurons and activation of glial cells in the substantia nigra pars compacta (SNpc). The neuroprotective effects of Rg1 were associated with the reduction of pro-inflammatory cytokines and the improvement of anti-inflammatory cytokines and neurotrophin in the midbrain. Rg1 shifted the polarization of microglia towards the M2 phenotype from M1, evidenced by decreased M1 markers (inducible NO synthase, CD16, etc.) and increased M2 markers (arginase 1 (Arg1), CD206, etc) in the midbrain. Furthermore, Rg1 administration markedly inhibited nuclear translocation of NF-κB in midbrain microglia. In conclusion, Rg1 protects PD mice induced by continuous LPS injection by inhibiting the nuclear entry of NF-κB and regulating the polarization balance of microglia, shedding new light on a disease-modifying therapy of PD.

Lanthionine ketimine ester improves outcome in an MPTP-induced mouse model of Parkinson's disease via suppressions of CRMP2 phosphorylation and microglial activation

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc). Levodopa (L-Dopa), the current main treatment for PD, reduces PD symptoms by partially replacing dopamine, but it does not slow neurodegeneration. Recent studies have evidenced that neuroinflammatory processes contribute to the degeneration of dopaminergic neurons in the SNc under cytopathic conditions, while other lines of inquiry have implicated phosphorylation of collapsin response mediator protein 2 (CRMP2) as a causal factor in axonal retraction after neural injury. We recently reported on the therapeutic effect of lanthionine ketimine ester (LKE) which associates with CRMP2 following axonal injury in the spinal cord. In the present study, we report that LKE protects SNc dopaminergic neurons after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) challenge, a common model for PD, and reduces the number of activated microglia proximal to the damaged SNc. The results also show that MPTP-induced motor impairment was suppressed in LKE treatment. Furthermore, the results show that LKE inhibits the elevation of CRMP2 phosphorylation in dopaminergic neurons in the SNc after MPTP injection. These data suggest that modification of CRMP2 phosphorylation and suppression of microglial activation with LKE administration may represent a novel strategy for slowing progress of pathological processes in PD.

Delta- and mu-opioid pathways are involved in the analgesic effect of Ocimum basilicum L in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ocimum basilicum L. is a perennial herb that has been used in traditional Asian Indian medicine for thousands of years as a natural anti-inflammatory, antibiotic, diuretic, and analgesic.

AIM OF THE STUDY

The present study was conducted to investigate the analgesic effects of basil essential oil (BEO) in inflammatory pain models and identify underlying mechanisms. We further investigated whether BEO affects physiological pain and motor coordination.

MATERIALS AND METHODS

The analgesic effects of BEO were assessed in various mouse experimental pain models using formalin, acetic acid, heat, and carrageenan as stimuli. BEO was administered by intraperitoneal injection or inhalation. The involvement of various pathways in the analgesic effect of BEO was assessed by pretreating mice with selective pharmacological inhibitors, administered intraperitoneally. Opioid pathways were tested using the κ-opioid antagonist 5'-guanidinonaltrindole (GNTI; 0.3 mg/kg), δ-opioid antagonist naltrindole (NTD; 5 mg/kg) and μ-opioid antagonist naloxone (NAL; 8 mg/kg); nitric oxide (NO) pathways were tested using the NO synthase inhibitor N-nitro l-arginine methyl ester (L-NAME; 37.5 mg/kg) and NO precursor L-arginine (L-Arg; 600 mg/kg); and K_ATP channel pathways were tested using the ATP-sensitive K⁺ channel blocker, glibenclamide-hippuric acid (GHA, 2 mg/kg). Potential effects of BEO on motor coordination were assessed using a rotarod test.

RESULTS

BEO exerted analgesic effects in all pain models. Notably, pretreatment with naltrindole, naloxone, or L-arginine significantly reduced the analgesic effects of BEO in the formalin test. BEO increased mean withdrawal latencies in a thermal plantar test at a high dose, but not at lower doses. BEO had no effect on motor coordination.

CONCLUSIONS

Our findings indicate that the analgesic effects of BEO are primarily mediated by delta- and mu-opioid pathways and further suggest that BEO has potential for development as an analgesic agent for the relief of inflammatory pain.

Nurr1Cd11bcre conditional knockout mice display inflammatory injury to nigrostriatal dopaminergic neurons

Nuclear receptor-related 1 protein (NURR1) is essential for the development and maintenance of midbrain dopaminergic (DAergic) neurons. NURR1 also protects DAergic neurons against neuroinflammation. However, it remains to be determined to what extent does NURR1 exerts its protective function through acting autonomously in the microglia. Using Cre/lox gene targeting system, we deleted Nurr1 in the microglia of Nurr1^Cd11bcre conditional knockout (cKO) mice. The Nurr1^Cd11bcre cKO mice displayed age-dependent motor abnormalities and increased microglial activation, but with no obvious DAergic neurodegeneration. To boost the inflammatory injury, we systemically administered endotoxin lipopolysaccharide (LPS) to Nurr1^Cd11bcre mice. As expected, LPS treatment exacerbated the motor phenotypes and inflammatory reactions in Nurr1^Cd11bcre cKO mice. More importantly, LPS administration caused DAergic neuron loss and α-synuclein aggregation, two pathological hallmarks of Parkinson's disease (PD). Therefore, our findings provide in vivo evidence supporting a critical protective role of NURR1 in the microglia against inflammation-induced degeneration of DAergic neurons in PD.

Physical activity sustains memory retrieval in dopamine-depleted mice previously treated with L-Dopa

The neurodegenerative disorder Parkinson's disease affects motor abilities as well as cognition. The gold standard therapy is L-Dopa, which mainly restores motor skills. Therefore, we require additional interventions to sustain cognitive functions in Parkinson's disease. The lifestyle intervention "physical activity" improves adult hippocampal neurogenesis and memory but so far, its impact has not been investigated in rodent models for Parkinson's disease previously treated with the standard therapy. We hereby asked whether physical activity serves as a pro-neurogenic and -cognitive stimulus in dopamine-depleted mice previously treated with L-Dopa. Therefore, we injected dopamine-depleted mice with L-Dopa/Benserazide followed either by exercise or by a sedentary lifestyle. We analysed adult hippocampal neurogenesis histologically and assessed spatial memory in the Morris water maze. Furthermore, we investigated the hippocampal and striatal monoaminergic cross-talk. Physical activity prevented memory decline and was linked to a slower dopamine turnover but did not enhance neurogenesis in dopamine-depleted mice previously treated with L-Dopa. In conclusion, physical activity did not develop its full pro-neurogenic potential in mice previously treated with L-Dopa but sustained spatial cognition in Parkinson's disease.

Mangiferin ameliorates collateral neuropathy in tBHP induced apoptotic nephropathy by inflammation mediated kidney to brain crosstalk

The kidneys and brain share similarities in anatomy and vaso-regulation and exhibit clinical interactions in various diseases. To investigate the probable mechanism of kidney to brain crosstalk, we developed an in vivo model of renal injury in mice through intoxication with the oxidative stress inducer, tBHP. Proteinuria, abnormalities in the renal tubules and KIM1 activation were found in tBHP intoxicated animals. Due to this renal pathophysiology, various pro-inflammatory molecules (TNF-α, IL-1β, IL-6, ICAM-1, VCAM-1) especially TNF-α, entered into the brain from kidneys, triggering cerebral inflammatory cascades leading to behavioral anomalies in association with membrane lipid peroxidation, BBB disruption and brain morphological alterations. Moreover, increased levels of reactive oxygen species, decreased antioxidant enzyme activity and an altered GSH/GSSG ratio were found in both these organs. Here, we introduced mangiferin as a protective molecule because of its anti-inflammatory and antioxidant properties. Mangiferin via inhibition of apoptosis and activation of the PI3K/Akt pathway protected the kidneys. It restored the deleterious phenomena in the damaged brain by downregulating the JNK and p38MAPK mediated pro-apoptotic cascade and activating the intracellular antioxidant thioredoxin, thereby protecting against tBHP induced nephropathy mediated neuropathophysiology.

Smilagenin Protects Dopaminergic Neurons in Chronic MPTP/Probenecid-Lesioned Parkinson's Disease Models

Current therapies for Parkinson’s disease (PD) only offer limited symptomatic alleviation but fail to hamper the progress of the disease. Thus, it is imperative to establish new approaches aiming at protecting or reversing neurodegeneration in PD. Recent work elucidates whether smilagenin (abbreviated SMI), a steroidal sapogenin from traditional Chinese medicinal herbs, can take neuroprotective effect on dopaminergic neurons in a chronic model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) conjuncted with probenecid mice. We reported for the first time that SMI significantly improved the locomotor ability of chronic MPTP/probenecid–lesioned mice. SMI increased the tyrosine hydroxylase (TH) positive and Nissl positive neuron number in the substantia nigra pars compacta (SNpc), augmented striatal DA and its metabolites concentration and elevated striatal dopamine transporter density (DAT). In addition, dopamine receptor D2R not D1R was down-regulated by MPTP/probenecid and slightly raised by SMI prevention. What’s more, we discovered that SMI markedly elevated striatal glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) protein levels in SMI prevented mice. And we found that SMI increased GDNF and BDNF mRNA level by promoting CREB phosphorylation in 1-methyl-4-phenylpyridimium (MPP⁺) treated SH-SY5Y cells. The results illustrated that SMI could prevent the impairment of dopaminergic neurons in chronic MPTP/probenecid-induced mouse model.

TLR9 activation via microglial glucocorticoid receptors contributes to degeneration of midbrain dopamine neurons

Inflammation is a characteristic feature of Parkinson’s disease (PD). We examined the role of TLR9 and its regulation by glucocorticoid receptors (GRs) in degeneration of substantia nigra dopamine neurons (DNs). TLR9 agonist, CpG-ODN, induced DN degeneration in mice lacking GR in microglia but not in controls. TLR9 deletion reduced DN loss in neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. GR regulates TLR9 activation during MPTP neurotoxicity as TLR9 antagonist suppressed increased DN loss in microglia/macrophage GR mutant mice. GR absence in microglia enhanced TLR9 translocation to endolysosomes and facilitated its cleavage leading to pro-inflammatory gene expression. GR-dependent TLR9 activation also triggered DN loss following intranigral injection of mitochondrial DNA. Finally, microglial GR sensitivity to A53T-alpha-synuclein induced DN degeneration as well as decreased microglial GR expression observed in SN of PD brain samples, all suggest that reduced microglial GR activity in SN can stimulate TLR9 activation and DN loss in PD pathology.

Inflammation is a component of Parkinson’s disease. Here the authors show that activation of Toll-like receptor 9 controlled by microglial glucocorticoid receptor signaling, contributes to dopamine neuron loss in a model of Parkinson’s disease.

Acrolein-mediated neuronal cell death and alpha-synuclein aggregation: Implications for Parkinson's disease

Growing evidence suggests that oxidative stress plays a critical role in neuronal destruction characteristic of Parkinson's disease (PD). However, the molecular mechanisms of oxidative stress-mediated dopaminergic cell death are far from clear. In the current investigation, we tested the hypothesis that acrolein, an oxidative stress and lipid peroxidation (LPO) product, is a key factor in the pathogenesis of PD. Using a combination of in vitro, in vivo, and cell free models, coupled with anatomical, functional, and behavioral examination, we found that acrolein was elevated in 6-OHDA-injected rats, and behavioral deficits associated with 6-OHDA could be mitigated by the application of the acrolein scavenger hydralazine, and mimicked by injection of acrolein in healthy rats. Furthermore, hydralazine alleviated neuronal cell death elicited by 6-OHDA and another PD-related toxin, rotenone, in vitro. We also show that acrolein can promote the aggregation of alpha-synuclein, suggesting that alpha-synuclein self-assembly, a key pathological phenomenon in human PD, could play a role in neurotoxic effects of acrolein in PD models. These studies suggest that acrolein is involved in the pathogenesis of PD, and the administration of anti-acrolein scavengers such as hydralazine could represent a novel strategy to alleviate tissue damage and motor deficits associated with this disease.

Clioquinol Improves Cognitive, Motor Function, and Microanatomy of the Alpha-Synuclein hA53T Transgenic Mice

The abnormal accumulation of alpha-synuclein (α-syn) has been linked to a number of neurodegenerative disorders, the most noteworthy of which is Parkinson's disease. Alpha-synuclein itself is not toxic and fulfills various physiological roles in the central nervous system. However, specific types of aggregates have been shown to be toxic, and metals have been linked to the assembly of these toxic aggregates. In this paper, we have characterized a transgenic mouse that overexpresses the A53T mutation of human α-syn, specifically assessing cognition, motor performance, and subtle anatomical markers that have all been observed in synucleinopathies in humans. We hypothesized that treatment with the moderate-affinity metal chelator, clioquinol (CQ), would reduce the interaction between metals and α-syn to subsequently improve the phenotype of the A53T animal model. We showed that CQ prevents an iron-synuclein interaction, the formation of urea-soluble α-syn aggregates, α-syn-related substantia nigra pars compacta cell loss, reduction in dendritic spine density of hippocampal and caudate putamen medium spiny neurons, and the decline in motor and cognitive function. In conclusion, our data suggests that CQ is capable of mitigating the pathological metal/α-syn interactions, suggesting that the modulation of metal ions warrants further study as a therapeutic approach for the synucleinopathies.

Hyperexcitability and sensitization of sodium channels of dorsal root ganglion neurons in a rat model of lumber disc herniation

PURPOSE

Low back pain and sciatica are the most common symptoms of patients with lumbar disc herniation (LDH). The pathophysiology of lumbocrural pain and sciatica is not fully understood. The aim of the present study was to define the membrane properties and activities of voltage-gated sodium channels of dorsal root ganglion (DRG) neurons in a rat model of LDH.

METHODS

LDH was established by transplantation of autologous nucleus pulposus (NP) to lumbar 5 and 6 spinal nerves (L5-L6 DRG) of adult male rats. Mechanical paw withdrawal threshold (PWT) and thermal paw withdrawal latency (PWL) were measured 1 day before and through 35 days after transplantation of NP. Changes in expression of VGSCs were determined by western blotting. L5-L6 DRGs neurons innervating the hindpaw were labeled with DiI and acutely dissociated for measuring excitability and sodium channel currents under whole-cell patch clamp configurations.

RESULTS

NP transplantation significantly reduced the PWT and PWL in association with a significant reduction in rheobase and an increase in numbers of action potentials evoked by 2X and 3X rheobase current stimulation. Voltage-gated sodium current density was significantly enhanced in L5-L6 DRG neurons from LDH rats. The inactivation curve showed a leftward shift in LDH rats while activation curve did not significantly alter. However, NP transplantation remarkably enhanced expression of NaV1.7 and NaV1.8 in L5-L6 DRGs but not in T10-12 DRGs.

CONCLUSION

These data suggest that NP application produces pain-related behavior and potentiates sodium current density of DRG neurons, which is most likely mediated by enhanced expression of NaV1.7 and NaV1.8.

PEP-1-PEA-15 protects against toxin-induced neuronal damage in a mouse model of Parkinson's disease

BACKGROUND

PEA-15 is abundantly expressed in both neurons and astrocytes throughout the brain. It is a multifunctional protein with the ability to increase cell survival via anti-apoptotic and anti-proliferative properties. However, the function of PEA-15 in neuronal diseases such as Parkinson's disease (PD) remains unclear. In this study, we investigated the protective effects of PEA-15 on neuronal damage induced by MPP(+) in neuroblastoma SH-SY5Y and BV2 microglia cells and in a MPTP-induced PD mouse model using cell-permeable PEP-1-PEA-15.

METHODS

PEP-1-PEA-15 was purified using affinity chromatography. Cell viability and DNA fragmentation were examined by MTT assay and TUNEL staining. Dopaminergic neuronal cell death in the animal model was examined by immunohistochemistry.

RESULTS

PEP-1-PEA-15 transduced into the SH-SY5Y and BV2 cells in a time- and dose-dependent manner. Transduced PEP-1-PEA-15 protected against MPP(+)-induced toxicity by inhibiting intracellular ROS levels and DNA fragmentation. Further, it enhanced the expression levels of Bcl-2 and caspase-3 while reducing the expression levels of Bax and cleaved caspase-3. We found that PEP-1-PEA-15 transduced into the substantia nigra and prevented dopaminergic neuronal cell death in a MPTP-induced PD mouse. Also, we showed the neuroprotective effects in the model by demonstrating that treatment with PEP-1-PEA-15 ameliorated MPTP-induced behavioral dysfunctions and increased dopamine levels in the striatum.

CONCLUSIONS

PEP-1-PEA-15 can efficiently transduce into cells and protects against neurotoxin-induced neuronal cell death in vitro and in vivo.

GENERAL SIGNIFICANCE

These results demonstrate the potential for PEP-1-PEA-15 to provide a new strategy for protein therapy treatment of a variety of neurodegenerative diseases including PD.