Parkinsonian Rats Research Articles

Pharmacodynamic, pharmacokinetic and rat brain receptor occupancy profile of NLX-112, a highly selective 5-HT1A receptor biased agonist.

NLX-112 (i.e., F13640, befiradol) exhibits nanomolar affinity, exceptional selectivity and full agonist efficacy at serotonin 5-HT1A receptors. NLX-112 shows efficacy in rat, marmoset and macaque models of L-DOPA induced dyskinesia (LID) in Parkinson's disease and has shown clinical efficacy in a Phase 2a proof-of-concept study for this indication. Here we investigated, in rats, its pharmacodynamic, pharmacokinetic (PK) and brain 5-HT1A receptor occupancy profiles, and its PK properties in the absence and presence of L-DOPA. Total and free NLX-112 exposure in plasma, CSF and striatal ECF was dose-proportional over the range tested (0.04, 0.16 and 0.63mg/kg i.p.). NLX-112 exposure increased rapidly (Tmax 0.25-0.5h) and exhibited approximately threefold longer half-life in brain than in plasma (1.1 and 3.6h, respectively). At a pharmacologically relevant dose of 0.16 mg/kg i.p., previously shown to elicit anti-LID activity in parkinsonian rats, brain concentration of NLX-112 was 51-63 ng/g from 0.15 to 1h. In microPET imaging experiments, NLX-112 showed dose-dependent reduction of 18F-F13640 (i.e., 18F-NLX-112) brain 5-HT1A receptor labeling in cingulate cortex and striatum, regions associated with motor control and mood, with almost complete inhibition of labeling at the dose of 0.63 mg/kg i.p.. Co-administration of L-DOPA (6mg/kg s.c., a dose used to elicit LID in parkinsonian rats) together with NLX-112 (0.16mg/kg i.p.) did not modify PK parameters in rat plasma and brain of either NLX-112 or L-DOPA. Here, we demonstrate that NLX-112's profile is compatible with 'druggable' parameters for CNS indications, and the results provide measures of brain concentrations and 5-HT1A receptor binding parameters relevant to the anti-dyskinetic activity of the compound.

Subthalamic nucleus deep brain stimulation induces functional deficits in norepinephrinergic neurotransmission in a Parkinson’s disease model

BackgroundDeep brain stimulation of the subthalamic nucleus (STN-DBS) is a successful treatment option in Parkinson’s disease (PD) for different motor and non-motor symptoms, but has been linked to postoperative cognitive impairment. AimSince both dopaminergic and norepinephrinergic neurotransmissions play important roles in symptom development, we analysed STN-DBS effects on dopamine and norepinephrine availability in different brain regions and morphological alterations of catecholaminergic neurons in the 6-hydroxydopamine PD rat model. MethodsWe applied one week of continuous unilateral STN-DBS or sham stimulation, respectively, in groups of healthy and 6-hydroxydopamine-lesioned rats to quantify dopamine and norepinephrine contents in the striatum, olfactory bulb and dentate gyrus. In addition, we analysed dopaminergic cell counts in the substantia nigra pars compacta and area tegmentalis ventralis and norepinephrinergic neurons in the locus coeruleus after one and six weeks of STN-DBS. ResultsIn 6-hydroxydopamine-lesioned animals, one week of STN-DBS did not alter dopamine levels, while striatal norepinephrine levels were decreased. However, neither one nor six weeks of STN-DBS altered dopaminergic neuron numbers in the midbrain or norepinephrinergic neuron counts in the locus coeruleus. Dopaminergic fibre density in the dorsal and ventral striatum also remained unchanged after six weeks of STN-DBS. In healthy animals, one week of STN-DBS resulted in increased dopamine levels in the olfactory bulb and decreased contents in the dentate gyrus, but had no effects on norepinephrine availability. ConclusionsSTN-DBS modulates striatal norepinephrinergic neurotransmission in a PD rat model. Additional behavioural studies are required to investigate the functional impact of this finding.

The involvement of Slc7a11/xCT related iron accumulation on acupuncture intervention in 6-OHDA-induced Parkinson rat

BackgroundAcupuncture plays a critical role for the treatment of patients with Parkinson's disease (PD), which is characterized by ferroptosis of dopaminergic neurons. It has been found that acupuncture can reduce iron accumulation. However, the mechanism of acupuncture therapy against PD by inhibiting ferroptosis remains unclear. ObjectiveTo investigate the potential mechanism of acupuncture on alleviating ferroptosis in 6-OHDA-induced PD rats. MethodsMale Sprague-Dawley rats were randomly divided into sham group, acupuncture group, and PD model group, with the PD model induced by 6-OHDA. The motor function of the rats was tested by the rotation test and suspension test, respectively. Immunohistochemistry and iron staining were performed to analyze nerve damage, and the effect of acupuncture on the accumulation of iron in the substantia nigra (SN). RNA-seq analysis in the SN of rats were performed to discover ferroptosis-related genes. Differentially expressed genes (DEGs) resulted from the acupuncture treatment were identified and were used for Gene Ontology (GO) function, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. A protein–protein interaction (PPI) network was constructed, and alternative splicing (AS) analysis of the transcriptome was performed. Western blot was used to detect the protein level change of Slc7a11/xCT. ResultsRotation test and suspension test indicated a positive effect of acupuncture on body weight gain and limb function. Perl's iron staining and ELISA test detected 6-OHDA induced iron accumulation in the SN and nerve damage, which was mitigated by acupuncture treatment. Acupuncture treatment brought about the differential expression of a total of 1088 genes in the SN of rats. GO and KEGG enrichment revealed that such DEGs were mainly associated with several key biological process (BP), cellular component (CC) and molecular function (MF) terms. These terms included collagen fibril organization, extracellular matrix organization, collagen trimer, extracellular matrix components, chemokine receptor binding and cargo receptor activity, etc. Additionally, the DEGs were found to be involved in pathways such as complement and coagulation. The PPI network of DEGs suggested a critical role of Slc7a11, which was further supported by an up-regulated Slc7a11/xCT protein level in the substantia nigra (SN) tissue of rats treated with acupuncture compared to their PD model counterparts (P = 0.045). ConclusionAcupuncture may prevent ferroptosis through Slc7a11/xCT as one of the targets in 6-OHDA-induced PD model and thereby could be promising for PD treatment.

The Interactive Effects of The Aerobic Exercise and Vitamin E Supplementation on Parkinson's Rat Model.

In Parkinson's disease (PD), mitochondrial defects and oxidative stress cause an increase in free radicals and the death of dopaminergic neurons in the substantia nigra. By preventing lipid peroxidation and protecting against peroxide radicals, vitamin E is the most important antioxidant of biological membranes that can neutralize free radicals. Also, the improvement of the functional status of mitochondria can be influenced by exercise, which can be partially the result of changes in the mitochondrial mitophagy and dynamics system. This study aimed to investigate the interactive effects of six weeks of vitamin E (VE) consumption and training on the mitochondrial function [Cytochrome C (Cyt-C), Adenosine triphosphate (Atp) synthase, optical atrophy1 mitochondrial dynamics like guanosine triphosphatase (GTPase), 8-Oxodequanosin and Pten induced kinase 1 (Pink1) is a protein coding gene] in the hippocampus tissue of PD rats. In this experimental study, 4-6-month-old Sprague-Dawley rats (mean weight 250 ± 30 g) were given parkinsonism with reserpine (2 mg/kg) and were categorized into different groups, including healthy (H), PD, VE solvent+PD (Sham), aerobic exercise+PD (AE+PD), VE+PD, AE+VE+PD. The aerobic training program was carried out for six weeks and 5 sessions per week and each session lasted 15-22 minutes. VE was also taken orally at 30 mg/kg daily. A six-week regimen of VE supplement along with the AE significantly reduced the Cyt-C gene expression level, also we observed a significant increase in gene expression level of the Pink1, Atp synthase and Opa1 (P<0.05). There is no significant difference was found in the level of 8-Oxog detected in hippocampal tissue samples (P>0.05). The consumption of VE along with AE may provide therapeutic effects on mitochondrial damage in PD rats.

Tricompartmental Microcarriers with Controlled Release for Efficient Management of Parkinson's Disease.

Parkinson's is a progressive neurodegenerative disease of the nervous system. It has no cure, but its symptoms can be managed by supplying dopamine artificially to the brain.This work aims to engineer tricompartmental polymeric microcarriers by electrohydrodynamic cojetting technique to encapsulate three PD (Parkinson's disease) drugs incorporated with high encapsulation efficiency (∼100%) in a single carrier at a fixed drug ratio of 4:1:8 (Levodopa (LD): Carbidopa(CD): Entacapone (ENT)). Upon oral administration, the drug ratio needs to be maintained during subsequent release from microparticles to enhance the bioavailability of primary drug LD. This presents a notable challenge, as the three drugs vary in their aqueous solubility (LD > CD > ENT). The equilibrium of therapeutic release was achieved using a combination of FDA-approved polymers (PLA, PLGA, PCL, and PEG) and the disc shape of particles. In vitro studies demonstrated the simultaneous release of all the three therapeutics in a sustained and controlled manner. Additionally, pharmacodynamics and pharmacokinetics studies in Parkinson's disease rats induced by rotenone showed a remarkable improvement in PD conditions for the microparticles-fed rats, thereby showing a great promise toward efficient management of PD.

Extended Supplementation With B. Lactis MH-022 Mitigates Motor Impairments in 6-OHDA-Induced Parkinson's Disease Rats Through Gut Microbiota Modulation

Extended Supplementation With B. Lactis MH-022 Mitigates Motor Impairments in 6-OHDA-Induced Parkinson's Disease Rats Through Gut Microbiota Modulation

Assessment of Serum Levels of Phosphate and Corticosterone as Possible Biomarkers for Early Diagnosis of Parkinson’s Disease in Rats with 6-OHDA-Induced Parkinson

Background: Early diagnosis of Parkinson›s disease can play an important role in improving its prognosis. Due to controversies about the serum level of corticosterone and phosphate in parkinsonian rats, this study was designed to measure and evaluate the levels of corticosterone and phosphate as possible biomarkers of early diagnosis in rats with 6-OHDA-induced parkinsonism. Methods: Forty rats were divided into three groups: control (n=10), sham (n=10), and 6-OHDA (n=20). The rats in the 6-OHDA and sham groups underwent stereotaxic surgery to be injected with 6-OHDA and its carrier into their medial forebrain bundle (MFB). Apomorphine-induced rotational and cylinder tests were done to examine parkinsonism progression and sensory-motor function. Corticosterone and phosphate serum levels were measured in the serum and striatum. Results: Net contralateral rotations and asymmetry scores in the fourth, sixth, and eighth weeks after surgery compared with the second week showed a gradual increase in the 6-OHDA group. The serum levels of corticosterone were 90±13 before surgery, and they declined to 88±36 and 55±9 ng/L in the second and eighth weeks after surgery, respectively. The serum levels of phosphate were 6±0.22 before surgery, and they decreased to 5.2±0.13 and 5±0.12 mg/dl in the second and eighth weeks after surgery, respectively. The serum levels of phosphate and corticosterone remained relatively unchanged in the sham and control groups. Conclusion: In conclusion, the progressive death of dopaminergic neurons is accompanied by decreased serum corticosterone and phosphate levels. Thus, the serum level of corticosterone can be used as a biomarker in diagnosing Parkinson’s disease. In contrast, serum phosphate levels were still within the normal range and cannot be used as a biomarker.

Apilarnil exerts neuroprotective effects and alleviates motor dysfunction by rebalancing M1/M2 microglia polarization, regulating miR-155 and miR-124 expression in a rotenone-induced Parkinson’s disease rat model

Microglial activation contributes to the neuropathology of Parkinson’s disease (PD). Inhibiting M1 while simultaneously boosting M2 microglia activation may therefore be a potential treatment for PD. Apilarnil (API) is a bee product produced from drone larvae. Recent research has demonstrated the protective effects of API on multiple body systems. Nevertheless, its impact on PD or the microglial M1/M2 pathway has not yet been investigated. Thus, we intended to evaluate the dose-dependent effects of API in rotenone (ROT)-induced PD rat model and explore the role of M1/M2 in mediating its effect. Seventy-two Wistar rats were equally grouped as; control, API, ROT, and groups in which API (200, 400, and 800 mg/kg, p.o.) was given simultaneously with ROT (2 mg/kg, s.c.) for 28 days. The high dose of API (800 mg/kg) showed enhanced motor function, higher expression of tyrosine hydroxylase and dopamine levels, less dopamine turnover and α-synuclein expression, and a better histopathological picture when compared to the ROT group and the lower two doses. API’s high dose exerted its neuroprotective effects through abridging the M1 microglial activity, illustrated in the reduced expression of miR-155, Iba-1, CD36, CXCL10, and other pro-inflammatory markers’ levels. Inversely, API high dose enhanced M2 microglial activity, witnessed in the elevated expression of miR-124, CD206, Ym1, Fizz1, arginase-1, and other anti-inflammatory indices, in comparison to the diseased group. To conclude, our study revealed a novel neuroprotective impact for API against experimentally induced PD, where the high dose showed the highest protection via rebalancing M1/M2 polarization.

Antinociceptive role of the thalamic dopamine D3 receptor in descending modulation of intramuscular formalin-induced muscle nociception in a rat model of Parkinson's disease

Pain in Parkinson's disease (PD) has been validated as one of the major non-motor dysfunctions affecting the quality of life and subsequent rehabilitation. In the present study, we investigated the role of the dopamine D3 receptor in the thalamic mediodorsal (MD) and ventromedial (VM) nuclei mediated descending control of nociception and intramuscular (i.m.) 2.5% formalin-induced persistent muscle nociception. Paw withdrawal reflexes were measured in naive rats and rats subjected to PD induced by unilateral microinjection of 6 μg 6-OHDA into the rat striatum. Formalin-induced muscle nociception in phase 1, inter-phase, and phase 2 was significantly greater in PD rats compared to naive and vehicle-treated rats (P < 0.001). PD rats exhibited bilaterally mechanical hyperalgesia and heat hypoalgesia in formalin-induced muscle nociception. Microinjection of SK609, a dopamine D3 receptor agonist, at various doses (2.5–7.5 nmol/0.5 μl) into the thalamic VM nucleus dose-dependently prolonged heat-evoked paw withdrawal latencies in both naive and PD rats. Administration of SK609 to either the MD or VM nuclei had no effect on noxious mechanically evoked paw withdrawal reflexes. Pre-treatment of the thalamic MD nucleus with SK609 significantly attenuated formalin-induced nociception, and reversed mechanical hyperalgesia, but not heat hypoalgesia. Pre-treatment of the thalamic VM nucleus with SK609 inhibited formalin-induced nociception in the late phase of phase 2 (30–75 min) and heat hypoalgesia, but not mechanical hyperalgesia (P < 0.05). It is suggested that the dopamine D3 receptors in the thalamus play an antinociceptive role in the descending modulation of nociception. Activation of D3 receptors within the thalamic MD and VM nuclei attenuates descending facilitation and enhances descending inhibition in rats during PD.

Blockade of pre- and post-synaptic GABAB receptors in the anteroventral bed nucleus of stria terminalis produces anxiolytic-like and anxiety-like effects in parkinsonian rats respectively

The anteroventral bed nucleus of stria terminalis (avBNST) is a limbic forebrain region involved in the regulation of anxiety, and expresses GABAB receptors, which are located at both pre- and post-synaptic sites. However, it is unclear how blockade of these receptors affects anxiety-like behaviors, particularly in Parkinson's disease (PD)-related anxiety. In the present study, unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta in rats induced anxiety-like behaviors, and increased GABA release and decreased glutamate release in the avBNST, as well as decreased level of dopamine (DA) in the basolateral amygdala (BLA). Intra-avBNST injection of pre-synaptic GABAB receptor antagonist CGP36216 produced anxiolytic-like effects, while the injection of post-synaptic GABAB receptor antagonist CGP35348 induced anxiety-like responses in both sham and 6-OHDA rats. Intra-avBNST injection of CGP36216 inhibited the GABAergic neurons and increased GABA/glutamate ratio in the avBNST and increased levels of DA and serotonin (5-HT) in the BLA; conversely, CGP35348 produced opposite effects on the firing activity of avBNST GABAergic neurons and levels of the neurotransmitters in the avBNST and BLA. Moreover, the doses of the antagonists producing significant behavioral effects in 6-OHDA rats were lower than those in sham rats, and the duration of action of the antagonists on the firing rate of the neurons and release of the neurotransmitters was prolonged in 6-OHDA rats. Altogether, these findings suggest that pre- and post-synaptic GABAB receptors in the avBNST are implicated in PD-related anxiety-like behaviors, and degeneration of the nigrostriatal pathway enhances functions and/or upregulates expression of these receptors.

NIR-II light therapy improves cognitive performance in MPTP induced Parkinson's disease rat models: A preliminary experimental study

Cognitive impairment is an important component of non motor symptoms in Parkinson's disease (PD), and if not addressed in a timely manner, it can easily progress to dementia. However, no effective method currently exists to completely prevent or reverse cognitive impairment associated with PD. We therefore aimed to investigate the therapeutic effect of near-infrared region II light (NIR-II) region illumination on cognitive impairment in PD through behavioral experiments (water maze and rotary rod) and multiple fluorescence immunohistochemistry techniques. The 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced group was compared with the MPTP- untreated rat group, showing a significant reduction in escape latency and significant increase in the fall latency in the MPTP-treated group. The horizontal analysis results indicated that NIR-II phototherapy improved the learning and cognitive abilities as well as coordination and balance abilities of rats. Post-treatment, the MPTP rats showed significantly shortened, escape latency, prolonged target quadrant residence time, and prolonged fall latency compared with pre-treatment. The longitudinal analysis results reaffirmed that NIR-II phototherapy improved the learning and cognitive abilities as well as coordination and balance abilities of rats. The multiple fluorescence immunohistochemistry analysis trend plot showed that the activated microglia and astrocytes in the hippocampus were highest in MPTP-induced PD untreated group, moderate in MPTP-induced PD treatment group, and lowest in the control group. Our data indicates that NIR-II illumination improves learning and cognitive impairment as well as coordination and balance abilities in PD rats by downregulating the activation of microglia and astrocytes in the hippocampus.

Examining the Mechanism of Treatment for Primary Dysmenorrhea with Wenjing Huoxue Decoction based on Transcriptomics, Metabolomics, and Network Pharmacology.

Wenjing Huoxue Decoction (WJHXD) is a traditional treatment for primary dysmenorrhea (PD) that can quickly relieve various symptoms caused by PD. Previous clinical studies have shown that WJHXD has better long-term efficacy than ibuprofen in the treatment of PD and can reverse the disorder of T cell subsets. To investigate the effect of WJHXD on serum-related factors in the treatment of PD, including the identification of key targets, pathways, and active ingredients. In order to study the effects of the WJHXD intervention in Parkinson's Disease (PD) rats, we used transcriptomics and metabolomics methods to examine the differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs). We also utilized network pharmacology to predict the target and effective route of WJHXD in treating PD. Finally, we employed molecular docking (MD) technology to confirm the placement of important targets and metabolites. WJHXD has been found to be effective in prolonging the onset time and decreasing the number of writhing episodes in PD rats after oxytocin injection. It has also been observed to reduce the levels of PGF2, COX-2, AVP, and PGE2 in the serum of PD rats to different degrees. Transcriptomics analysis has revealed that the core targets of WJHXD include KRT1, KRT16, CCL5, F2, NOS2, RAC2, and others, while the core pathways are Calcium signaling and cAMP signaling. The Estrogen signaling pathway was found to be downregulated in PD rats compared to normal uterine tissue, but WJHXD was able to up-regulate the pathway. A combined transcriptomics and metabolomics analysis suggested that WJHXD may be involved in eight metabolism-related pathways, with the most reliable ones being mucin-type O-glycan biosynthesis and glycolysis or gluconeogenesis. MD has shown that Hydroxyisocaproic acid may bind to important targets such as SLC6A4, PTGER3, IGFBP3, and IGF2. In WJHXD, the most targeted herbs were Corydalis rhizoma, licorice, and Myrrha. The most targeted active ingredients include quercetin, 3'-Hydroxy-4'-O-methylglabridin, shinpterocarpin, and isorhamnetin. Potential targets include PTGS2, NOS2, AR, SCN5A, and GAS6. Analysis revealed 72 highly reliable relationships between group A and B DEGs and DEMs, with 23 positive correlations and 49 negative correlations among them. A combined analysis of transcriptomics, metabolomics, and network pharmacology was used to identify possible targets, pathways, and active ingredients of WJHXD in PD treatment, and the correlation between DEGs and DEMs was investigated. However, further research is required to confirm the relationship between active ingredients, targets, and metabolites.

Analysis of the mechanism by which ketamine affects astrocytes in Parkinsonian rats through the PI3K/AKT axis.

Parkinson's disease (PD) remains the most common neurodegenerative disease worldwide, seriously affecting the normal life of patients. Currently, there is no effective clinical cure for PD. In this study, the research team explored the effect of ketamine (KET) on PD, which can lay a reliable foundation for future KET treatment of PD. First, the research team established a PD rat model with 6-hydroxydopamine (6-OHDA). The detection showed that the maximum angle of the inclined plate stay, the number oftimes of grid crossings andstanding, and the ATPaseactivity in brain tissue were significantly lower in PD rats than in control rats, while the positive rate of α-synuclein in brain tissue was increased, showing typical pathological manifestations of PD. After using KET to intervene in PD rats, the behavioral and brain pathological changes were significantly alleviated, and the inflammation and oxidative stress damage of brain tissue were effectively reduced, suggesting the potential therapeutic effects of KET on PD. Furthermore, the use of KET inhibited the PI3K/AKT axis in the brain tissue of PD rats and promoted autophagy. Moreover, the significant suppression of the PI3K/AKT axis by KET was also demonstrated in the PD cell model established through lipopolysaccharide (LPS) inducement of astrocyte cell line HA1800. It is suggested that the mechanismof KET on PD is related to the inhibition of the PI3K/AKT axis.

Cannabidiol improves non-motor symptoms, attenuates neuroinflammation, and favours hippocampal newborn neuronal maturation in a rat model of Parkinsonism.

To investigate the effects of cannabidiol (CBD) on emotional and cognitive symptoms in rats with intra-nigral 6-hydroxydopamine (6-OHDA) lesions. Adult male Wistar rats received bilateral intranigral 6-OHDA infusions and were tested in a battery of behavioural paradigms to evaluate non-motor symptoms. The brains were obtained to evaluate the effects of CBD on hippocampal neurogenesis. 6-OHDA-lesioned rats exhibited memory impairments and despair-like behaviour in the novelty-suppressed feeding test and forced swim test, respectively. The animals also exhibited dopaminergic neuronal loss in the substantia nigra pars compacta (SNpc), striatum, and ventral tegmental area and a reduction of hippocampal neurogenesis. CBD decreased dopaminergic neuronal loss in the SNpc, reduced the mortality rate and decreased neuroinflammation in 6-OHDA-lesioned rats. In parallel, CBD prevented memory impairments and attenuated despair-like behaviour that were induced by bilateral intranigral 6-OHDA lesions. Repeated treatment with CBD favoured the neuronal maturation of newborn neurons in the hippocampus in Parkinsonian rats. The present findings suggest a potential beneficial effect of CBD on non-motor symptoms induced by intra-nigral 6-OHDA infusion in rats.

PINK1 knockout rats show premotor cognitive deficits measured through a complex maze.

Cognitive decline in Parkinson's disease (PD) is a critical premotor sign that may occur in approximately 40% of PD patients up to 10 years prior to clinical recognition and diagnosis. Delineating the mechanisms and specific behavioral signs of cognitive decline associated with PD prior to motor impairment is a critical unmet need. Rodent PD models that have an impairment in a cognitive phenotype for a time period sufficiently long enough prior to motor decline can be useful to establish viable candidate mechanisms. Arguably, the methods used to evaluate cognitive decline in rodent models should emulate methods used in the assessment of humans to optimize translation. Premotor cognitive decline in human PD can potentially be examined in the genetically altered PINK1-/- rat model, which exhibits a protracted onset of motor decline in most studies. To increase translation to cognitive assessment in human PD, we used a modified non-water multiple T-maze, which assesses attention, cognitive flexibility, and working memory similarly to the Trail Making Test (TMT) in humans. Similar to the deficiencies revealed in TMT test outcomes in human PD, 4-month-old PINK1-/- rats made more errors and took longer to complete the maze, despite a hyperkinetic phenotype, compared to wild-type rats. Thus, we have identified a potential methodological tool with cross-species translation to evaluate executive functioning in an established PD rat model.

The necessity of eliminating the interference of panaxatriol saponins to maximize the preventive effect of panaxadiol saponins against Parkinson's disease in rats

BackgroundThe effects of individual panaxadiol saponin and panaxatriol saponin on rodent models of Parkinson's disease (PD) have been recognized. However, it is not clear whether purified total ginsenosides as an entirety has effect against PD in rat model. This study compared the protective effects of a purified panaxadiol saponin fraction (PDSF), a purified panaxatriol saponin fraction (PTSF), and their mixtures against the rotenone (ROT)-induced PD in rats. MethodsPotential effects of PDSF, PTSF, and their mixtures against motor dysfunction and impairments of nigrostriatal dopaminergic neurons (DN), blood-brain barrier (BBB), cerebrovascular endothelial cells (CEC), and glial cells were measured in the models of ROT-induced PD rats and cell damage. Pro-inflammatory NF-kB p65 (p65) activation was localized in DN and other cells in the striatum. ResultsPDSF and PTSF had a dose-dependent effect against motor dysfunction with a larger effective dose range for PDSF. PDSF protected CEC, glial cells, and DN in models of PD rats and cell damage, while PTSF had no such protections. Chronic ROT exposure potently activated p65 in CEC with enhanced pro-inflammatory and decreased anti-inflammatory factors and impaired BBB in the striatum, PDSF almost completely blocked the ROT-induced p65 activation and maintained both anti- and pro-inflammatory factors at normal levels and BBB integrity, but PTSF aggravated the p65 activation with impaired BBB. Furthermore, PTSF nullified all the effects of PDSF when they were co-administrated. ConclusionPDSF had significant protective effect against the ROT-induced PD in rats by protecting CEC, glial cells, and DN, likely through inhibiting NF-κB p65 in CEC from triggering neuroinflammation, and also directly protecting glial cells and neurons against ROT-induced toxicity. PDSF has great potential for preventing and treating PD.

Lateral habenula 5-HT1B receptors are involved in regulation of anxiety-like behaviors in parkinsonian rats

Although the output of the lateral habenula (LHb) controls the activity of midbrain dopaminergic and serotonergic systems, which are implicated in the pathophysiology of anxiety, it is not clear the role of LHb 5-HT1B receptors in regulation of anxiety-like behaviors, particularly in Parkinson's disease-related anxiety. In this study, unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta in rats induced anxiety-like behaviors, led to decreased normalized δ power and increased normalized θ power in the LHb, and decreased dopamine (DA) level in the prelimbic cortex (PrL) compared with sham rats. Down-regulation of LHb 5-HT1B receptors by RNA interference produced anxiety-like effects, decreased normalized δ power and increased normalized θ power in the LHb in both sham and lesioned rats. Further, intra-LHb injection of 5-HT1B receptor agonist CP93129 induced anxiolytic-like responses, increased normalized δ power and decreased normalized θ power in the LHb, and increased DA and serotonin (5-HT) release in the PrL; conversely, 5-HT1B receptor antagonist SB216641 produced anxiety-like effects, decreased normalized δ power and increased normalized θ power in the LHb, and decreased DA and 5-HT release in the PrL in sham and lesioned rats. Additionally, effects of CP93129 and SB216641 on the behaviors, normalized δ and θ power in the LHb, and DA and 5-HT release in the PrL were decreased in lesioned rats, which were consistent with down-regulation of LHb 5-HT1B receptors after DA depletion. Collectively, these findings suggest that 5-HT1B receptors in the LHb are involved in the regulation of anxiety-like behaviors.

Non-HLA angiotensin-type-1 receptor autoantibodies mediate the long-term loss of grafted neurons in Parkinson’s disease models

BackgroundClinical trials have provided evidence that transplants of dopaminergic precursors, which may be replaced by new in vitro stem cell sources, can integrate into the host tissue, and alleviate motor symptoms in Parkinson´s disease (PD). In some patients, deterioration of graft function occurred several months after observing a graft-derived functional improvement. Rejection of peripheral organs was initially related to HLA-specific antibodies. However, the role of non-HLA antibodies is now considered also relevant for rejection. Angiotensin-II type-1 receptor autoantibodies (AT1-AA) act as agonists of the AT1 receptors. AT1-AA are the non-HLA antibodies most widely associated with graft dysfunction or rejection after transplantation of different solid organs and hematopoietic stem cells. However, it is not known about the presence and possible functional effects of AT1-AA in dopaminergic grafts, and the effects of treatment with AT1 receptor blockers (ARBs) such as candesartan on graft survival.MethodsIn a 6-hydroxydopamine PD rat model, we studied the short-term (10 days)- and long-term (3 months) effects of chronic treatment with the ARB candesartan on survival of grafted dopaminergic neurons and microglial graft infiltration, as well as the effects of dopaminergic denervation and grafting on serum and CSF AT1-AA levels. The expression of AT1 receptors in grafted neurons was determined by laser capture microdissection.ResultsAt the early period post-grafting, the number of grafted dopaminergic neurons that survived was not significantly different between treated and untreated hosts (i.e., control rats and rats treated with candesartan), probably because, just after grafting, other deleterious factors are predominant for dopaminergic cell death, such as mechanical trauma, lack of growth factors/nutrients and ischemia. However, several months post-grafting, we observed a significantly higher number of surviving dopaminergic neurons and a higher density of striatal dopaminergic terminals in the candesartan-treated group. For several months, grafted rats showed blood and cerebrospinal fluid levels of AT1-AA higher than normal controls, and also higher AT1-AA levels than non-grafted parkinsonian rats.ConclusionsThe results suggest the use of ARBs such as candesartan in PD patients, particularly before and after dopaminergic grafts, and the need to monitor AT1-AA levels in PD patients, particularly in those candidates for dopaminergic grafting.

Chamuangone-enriched rice bran oil ameliorates neurodegeneration in haloperidol-induced Parkinsonian rat model via modulation of neuro-inflammatory mediators and suppression of oxidative stress markers

A natural bioactive compound chamuangone extracted from Thai salad Garcinia cowa leaves exhibited robust medicinal properties, targeting central oxidative stress pathways, and having neuroprotective potential. Chamuangone-enriched rice bran oil (CERBO), with 1.97 mg/mL chamuangone, was obtained through green extraction. The study was designed to evaluate the anti-Parkinson’s activity of CERBO in the haloperidol- induced Parkinsonian rat model. Animals were categorized into six groups as control, disease control and treatment groups. Parkinson’s disease (PD)-like symptoms were induced by administration of haloperidol 1 mg/kg, intraperitoneally; CERBO treatment groups received 2.5, 5, and 7.5 mg/kg orally before the administration of haloperidol for 21 days. Neurobehavioral, biochemical, neurochemical, and histopathological studies along with gene expression analysis were performed at the completion of the study. CERBO markedly recover the motor and non-motor PD-like symptoms in treatment groups dose-dependently. The levels of antioxidant enzymes, such as catalase, superoxide dismutase, reduced glutathione, and glutathione peroxidase, increased, while malondialdehyde levels decreased dose-dependently in CERBO-treated groups. CERBO dose-dependent elevations were observed in neurotransmitters (dopamine, serotonin, and noradrenaline). PD-associated specific biomarker (α-synuclein) decreased dose-dependently with downregulation in messenger RNA expression of neuro-inflammatory mediators (interleukin α, interleukin 1β, and tumor necrosis factor-α). Histopathological studies revealed recovery in neuronal loss, formation of Lewy’s bodies, and neurofibrillary tangles in the treatment groups. It was concluded from the data that CERBO possessed good anti-Parkinson’s activity and could be a novel, safe, and effective remedy for the treatment of PD.

Impact of subthalamic nucleus deep brain stimulation at different frequencies on neurogenesis in a rat model of Parkinson's disease

Neurogenesis, play a vital role in neuronal plasticity of adult mammalian brains, and its dysregulation is present in the pathophysiology of Parkinson's disease (PD). While subthalamic nucleus deep brain stimulation (STN-DBS) at various frequencies has been proven effective in alleviating PD symptoms, its influence on neurogenesis remains unclear. This study aimed to investigate the effects of 1-week electrical stimulation at frequencies of 60Hz, 130Hz, and 180Hz on neurogenesis in the subventricular zone (SVZ) of PD rats. A hemiparkinsonian rat model was established using 6-hydroxydopamine and categorized into six groups: control, PD, sham stimulation, 60Hz stimulation, 130Hz stimulation, and 180Hz stimulation. Motor function was assessed using the open field test and rotarod test after one week of STN-DBS at different frequencies. Tyrosine hydroxylase (TH) expression in brain tissue was analyzed via Western blot and immunohistochemistry. Immunofluorescence analysis was conducted to evaluate the expression of BrdU/Sox2, BrdU/GFAP, Ki67/GFAP, and BrdU/DCX in bilateral SVZ and the rostral migratory stream (RMS). Our findings revealed that high-frequency STN-DBS improved motor function. Specifically, stimulation at 130Hz increased dopaminergic neuron survival in the PD rat model, while significantly enhancing the proliferation of neural stem cells (NSCs) and neuroblasts in bilateral SVZ. Moreover, this stimulation effectively facilitated the generation of new NSCs in the ipsilateral RMS and triggered the emergence of fresh neuroblasts in bilateral RMS, with notable presence within the lesioned striatum. Conversely, electrical stimulation at 60Hz and 180Hz did not exhibit comparable effects. The observed promotion of neurogenesis in PD rats following STN-DBS provides valuable insights into the mechanistic basis of this therapeutic approach for PD.