Microglia-inhibiting activity of Parkinson's disease drug amantadine

Neuroinflammation and Dyskinesia: A Possible Causative Relationship?

Levodopa (L-DOPA) treatment represents the gold standard therapy for Parkinson's disease (PD) patients. L-DOPA therapy shows many side effects, among them, L-DOPA-induced dyskinesias (LIDs) remain the most problematic. Several are the mechanisms underlying these processes: abnormal corticostriatal neurotransmission, pre- and post-synaptic neuronal events, changes in gene expression, and altered plasticity. In recent years, researchers have also suggested non-neuronal mechanisms as a possible cause for LIDs. We reviewed recent clinical and pre-clinical studies on neuroinflammation contribution to LIDs. Microglia and astrocytes seem to play a strategic role in LIDs phenomenon. In particular, their inflammatory response affects neuron-glia communication, synaptic activity and neuroplasticity, contributing to LIDs development. Finally, we describe possible new therapeutic interventions for dyskinesia prevention targeting glia cells.

Targeting Striatal Glutamate and Phosphodiesterases to Control L-DOPA-Induced Dyskinesia

A large body of work during the past several decades has been focused on therapeutic strategies to control L-DOPA-induced dyskinesias (LIDs), common motor complications of long-term L-DOPA therapy in Parkinson's disease (PD). Yet, LIDs remain a clinical challenge for the management of patients with advanced disease. Glutamatergic dysregulation of striatal projection neurons (SPNs) appears to be a key contributor to altered motor responses to L-DOPA. Targeting striatal hyperactivity at the glutamatergic neurotransmission level led to significant preclinical and clinical trials of a variety of antiglutamatergic agents. In fact, the only FDA-approved treatment for LIDs is amantadine, a drug with NMDAR antagonistic actions. Still, novel agents with improved pharmacological profiles are needed for LID therapy. Recently other therapeutic targets to reduce dysregulated SPN activity at the signal transduction level have emerged. In particular, mechanisms regulating the levels of cyclic nucleotides play a major role in the transduction of dopamine signals in SPNs. The phosphodiesterases (PDEs), a large family of enzymes that degrade cyclic nucleotides in a specific manner, are of special interest. We will review the research for antiglutamatergic and PDE inhibition strategies in view of the future development of novel LID therapies.

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

Application of Network Analysis to Uncover Variables Contributing to Functional Recovery after Stroke

To estimate network structures to discover the interrelationships among variables and distinguish the difference between networks. Three hundred and forty-eight stroke patients were enrolled in this retrospective study. A network analysis was used to investigate the association between those variables. A Network Comparison Test was performed to compare the correlation of variables between networks. Three hundred and twenty-five connections were identified, and 22 of these differed significantly between the high- and low-Functional Independence Measurement (FIM) groups. In the high-FIM network structure, brain-derived neurotrophic factor (BDNF) and length of stay (LOS) had associations with other nodes. However, there was no association with BDNF and LOS in the low-FIM network. In addition, the use of amantadine was associated with shorter LOS and lower FIM motor subscores in the high-FIM network, but there was no such connection in the low-FIM network. Centrality indices revealed that amantadine use had high centrality with others in the high-FIM network but not the low-FIM network. Coronary artery disease (CAD) had high centrality in the low-FIM network structure but not the high-FIM network. Network analysis revealed a new correlation of variables associated with stroke recovery. This approach might be a promising method to facilitate the discovery of novel factors important for stroke recovery.

Prevention of L-Dopa-Induced Dyskinesias by MPEP Blockade of Metabotropic Glutamate Receptor 5 Is Associated with Reduced Inflammation in the Brain of Parkinsonian Monkeys

Proinflammatory markers were found in brains of Parkinson’s disease (PD) patients. After years of L-Dopa symptomatic treatment, most PD patients develop dyskinesias. The relationship between inflammation and L-Dopa-induced dyskinesias (LID) is still unclear. We previously reported that MPEP (a metabotropic glutamate receptor 5 antagonist) reduced the development of LID in de novo MPTP-lesioned monkeys. We thus investigated if MPEP reduced the brain inflammatory response in these MPTP-lesioned monkeys and the relationship to LID. The panmacrophage/microglia marker Iba1, the phagocytosis-related receptor CD68, and the astroglial protein GFAP were measured by Western blots. The L-Dopa-treated dyskinetic MPTP monkeys had increased Iba1 content in the putamen, substantia nigra, and globus pallidus, which was prevented by MPEP cotreatment; similar findings were observed for CD68 contents in the putamen and globus pallidus. There was a strong positive correlation between dyskinesia scores and microglial markers in these regions. GFAP contents were elevated in MPTP + L-Dopa-treated monkeys among these brain regions and prevented by MPEP in the putamen and subthalamic nucleus. In conclusion, these results showed increased inflammatory markers in the basal ganglia associated with LID and revealed that MPEP inhibition of glutamate activity reduced LID and levels of inflammatory markers.

The DJ1-Nrf2-STING axis mediates the neuroprotective effects of Withaferin A in Parkinson's disease

The pathogenesis of Parkinson's disease (PD) remains unclear, and there is no disease-modifying agent for PD. Withaferin A (WA), a naturally occurring compound, has emerged as a neuroprotective agent. However, the mechanisms by which WA is neuroprotective in PD are unknown. Here we show that WA protected against loss of dopaminergic neurons, neuroinflammation, and motor deficits in MPTP-induced PD mouse models. Whole-genome deep sequencing analysis combined with Meta-analysis of human PD studies reveal that DJ1, Nrf2, and STING in substantia nigra pars compacta (SNc) are linked to anti-PD effect of WA. We found that WA activated DJ1 and Nrf2, and suppressed STING within SNc; and overexpression of STING in SNc dampened the effect of WA. Using genetically modified mice (DJ1-KO, Nrf2-KO, STINGgt/gt and STING-KO) and immunolabeling technique, we identified that WA targeted DJ1-Nrf2-STING pathway in dopaminergic neurons; and we demonstrate that STING might be an important factor in PD pathogenesis. In addition, WA alleviated accumulation of phosphorylated α-synuclein (p-α-syn) and insoluble α-syn within SNc in adeno-associated virus (AAV)-mediated human α-syn overexpression PD model. Our comparative analysis on whole-genome transcriptome profiles suggests that STING might be a key target of WA and amantadine in PD treatment. This study highlights a multifaceted role for WA in neuroprotection, and suggests that WA can be a potential candidate for treatment of PD.

New insights into pathogenesis of l-DOPA-induced dyskinesia

Parkinson's disease (PD) is a progressive and self-propelling neurodegenerative disorder, which is characterized by motor symptoms, such as rigidity, tremor, slowness of movement and problems with gait. These symptoms become worse over time. To date, Dopamine (DA) replacement therapy with 3, 4-dihydroxy-l-phenylalanine (L-DOPA) is still the most effective pharmacotherapy for motor symptoms of PD. Unfortunately, motor fluctuations consisting of wearing-off effect actions and dyskinesia tend to occur in a few years of starting l-DOPA. Currently, l-DOPA-induced dyskinesia (LID) is troublesome and the pathogenesis of LID requires further investigation. Importantly, a new intervention for LID is imminent. Thus, this review mainly summarized the clinical features, risk factors and pathogenesis of LID to provide updatefor the development of therapeutic targets and new approaches for the treatment of LID.

Doxycycline and its derivative, COL-3, decrease dyskinesia induced by l-DOPA in hemiparkinsonian rats

BACKGROUND AND PURPOSE

l-DOPA-induced dyskinesia is a debilitating effect of treating Parkinson's disease with this drug. New therapeutic approaches that prevent or attenuate this side effect are needed.

EXPERIMENTAL APPROACH

Wistar adult male rats submitted to 6-hydroxydopamine-induced unilateral medial forebrain bundle lesion were treated with l-DOPA (p.o. 20 mg·kg^-1 or s.c. 10 mg·kg^-1 ) once a day for 14 days. After this period, we tested if doxycycline (40 mg·kg^-1 , i.p.) and COL-3 (50 and 100 nmol, i.c.v.) could reverse l-DOPA-induced dyskinesia. In an additional experiment, doxycycline was administered together with l-DOPA to verify if it would prevent l-DOPA-induced dyskinesia development.

KEY RESULTS

A single injection of doxycycline or COL-3 attenuated l-DOPA-induced dyskinesia. Co-treatment with doxycycline from the first day of l-DOPA suppressed the onset of dyskinesia. The improved motor response after l-DOPA was not affected by doxycycline or COL-3. Doxycycline treatment was associated with decreased immunoreactivity of FosB, COX-2, the astroglial protein GFAP and the microglial protein OX-42, which were elevated in the basal ganglia of rats exhibiting dyskinesia. Doxycycline decreased metalloproteinase-2/-9 activity, metalloproteinase-3 expression and ROS production. Metalloproteinase-2/-9 activity and production of ROS in the basal ganglia of dyskinetic rats showed a significant correlation with the intensity of dyskinesia.

CONCLUSION AND IMPLICATIONS

The present study demonstrates the anti-dyskinetic potential of doxycycline and its analogue compound COL-3 in hemiparkinsonian rats. Given the long-established and safe clinical use of doxycycline, this study suggests that these drugs might be tested to reduce or prevent l-DOPA-induced dyskinesia in Parkinson's patients.

Expression of Transcription Factors in CD4 + T Cells as Potential Biomarkers of Motor Complications in Parkinson's Disease

Background:

Management of motor complications (MC) represents a major challenge in the long-term treatment of Parkinson’s disease (PD) patients. In this context, the role of peripheral adaptive immunity may provide new insights, since neuroinflammatory mechanisms have been proved crucial in the disease.

Objective:

The aim of this study was to analyze the transcription factors genes involved in CD4 + T cells development to uncover specific molecular signatures in patients with (PMC) and without (WMC) motor complications.

Methods:

mRNA levels of CD4 + T lymphocytes transcription factor genes TBX21, STAT1, STAT3, STAT4, STAT6, RORC, GATA3, FOXP3, and NR4A2 were measured from 40 PD patients, divided into two groups according to motor complications. Also, 40 age- and sex-matched healthy controls were enrolled.

Results:

WMC patients had higher levels of STAT1 and NR4A2 (p = 0.004; p = 0.003), whereas in PMC we found higher levels of STAT6 (p = 0.04). Also, a ROC curve analysis confirmed STAT1 and NR4A2 as feasible biomarkers to discriminate WMC (AUC = 0.76, 95%CI 0.59–0.92, p = 0.005; AUC = 0.75, 95%CI 0.58–0.90, p = 0.007). Similarly, STAT6 detected PMC patients (AUC = 0.69, 95%CI 0.52–0.86, p = 0.037).

Conclusion:

These results provide evidence of different molecular signatures in CD 4 + T cells of PD patients with and without MC, thus suggesting their potential as biomarkers of MC development.

Amantadine: reappraisal of the timeless diamond-target updates and novel therapeutic potentials

The aim of the current review was to provide a new, in-depth insight into possible pharmacological targets of amantadine to pave the way to extending its therapeutic use to further indications beyond Parkinson's disease symptoms and viral infections. Considering amantadine's affinities in vitro and the expected concentration at targets at therapeutic doses in humans, the following primary targets seem to be most plausible: aromatic amino acids decarboxylase, glial-cell derived neurotrophic factor, sigma-1 receptors, phosphodiesterases, and nicotinic receptors. Further three targets could play a role to a lesser extent: NMDA receptors, 5-HT3 receptors, and potassium channels. Based on published clinical studies, traumatic brain injury, fatigue [e.g., in multiple sclerosis (MS)], and chorea in Huntington's disease should be regarded potential, encouraging indications. Preclinical investigations suggest amantadine's therapeutic potential in several further indications such as: depression, recovery after spinal cord injury, neuroprotection in MS, and cutaneous pain. Query in the database http://www.clinicaltrials.gov reveals research interest in several further indications: cancer, autism, cocaine abuse, MS, diabetes, attention deficit-hyperactivity disorder, obesity, and schizophrenia.

Associations Between Amantadine Usage, Gait, and Cognition in PSP: A post-hoc Analysis of the Davunetide Trial

Introduction: Amantadine anecdotally improves gait in progressive supranuclear palsy (PSP) but definitive data is lacking. We investigated associations between amantadine usage, gait, cognition, and activities of daily living in 310 subjects with PSP using data from the davunetide trial.

Method: We compared baseline demographics, PSP Rating Scale (PSPRS), Repeat Battery for the Assessment of Neuropsychological Status (RBANS), and Schwab and England Activities of Daily Living (SEADL) scores between subjects taking vs. not taking amantadine using chi-square tests for categorical variables and independent sample t-tests for continuous variables. Using the general linear model (GLM), we tested whether group status predicted total PSPRS, PSPRS-gait and midline, total RBANS, RBANS-attention, and SEADL before and after the 52-weeks follow-up.

Results: Subjects taking vs. not taking amantadine were similar at baseline, except subjects taking amantadine had a higher Clinical Global Impression (CGI) Score (p = 0.01). However, the CGI change score did not differ between groups at week 52 (p = 0.10). Using GLM models (controlling for covariates), we found that subjects taking vs. not taking amantadine did not significantly predict total PSPRS, PSPRS-gait and midline, total RBANS, RBANS-attention, or SEADL at baseline, week 52, or the change score between baseline and week 52.

Discussion: This post-hoc analysis of the davunetide trial did not find an association between amantadine and gait or cognitive measures in PSP, but was not powered to find such a difference. Future studies should still examine amantadine for symptomatic benefit in multiple PSP subtypes.

Amantadine Alleviates Postoperative Cognitive Dysfunction Possibly by Preserving Neurotrophic Factor Expression and Dendritic Arborization in the Hippocampus of Old Rodents

Objectives

Amantadine has been shown to attenuate postoperative learning and memory dysfunction in young adult rats. However, postoperative cognitive dysfunction often occurs in elderly patients. We aimed to determine whether amantadine attenuated postoperative learning and memory dysfunction and whether these effects were associated with improved dendritic arborization in old rodents.

Methods

Eighteen-month old male C57BL/6J mice or Fischer 344 rats were subjected to right carotid artery exposure (surgery) under isoflurane anesthesia. This age represents an early old stage in rodents. Carotid artery exposure was used to simulate commonly performed carotid endarterectomy in elderly patients. Amantadine was injected intraperitoneally at 25 μg/g once a day for 3 days with the first dose at 15 min before surgery. The animals were tested by Barnes maze and fear conditioning starting one week after the surgery. Hippocampus was harvested for Western blotting and Golgi staining.

Results

Surgery and anesthesia impaired the learning and memory in old mice and rats. Surgery reduced the expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), dendritic arborization and spine density in the hippocampus of old rats. These effects were attenuated by amantadine. The effects of amantadine were blocked by intracerebroventricular injection of anti-BDNF antibody or anti-GDNF antibody.

Conclusion

Surgery and anesthesia impaired learning, memory and dendritic arborization in old rodents that are age relevant to postoperative cognitive dysfunction. These effects may be attenuated by amantadine via preserving the expression of neurotrophic factors.

Synthetic analogues of memantine as neuroprotective and influenza viral inhibitors: in vitro and physicochemical studies

Drug compounds including memantine moieties are an important group of biologically active agents for different pathologies, including the Alzheimer's disease. In the present study, a series of memantine derivatives incorporating amino acid residues have been synthesized and their neuroprotective in vitro evaluation in respect of the Alzheimer's disease, involving the effects on the resistance to Aβ toxicity, excitotoxicity, oxidative stress, hypoxia, and neuroinflammation has been studied. The cytotoxicities of the compounds were detected by CPE assay. TC₅₀ and IC₅₀ were determined using Reed and Muench method. Solubility and distribution were measured using a shake-flask method. Permeability of the compounds was studied using Franz diffusion cell and Permeapad™ barrier. These compounds displayed apparent multi-neuroprotective effects against copper-triggered Aβ toxicity, glutamate-induced excitotoxicity, and oxidative and hypoxic injuries. They also showed the ability to inhibit the inflammatory cytokine release from the activated microglia and potential anti-neuroinflammatory effects. Especially, two most promising compounds H-4-F-Phe-memantine and H-Tyr-memantine demonstrated the equivalent functional bioactivities in comparison with the positive control memantine hydrochloride. Higher solubility in muriatic buffer than in phosphate buffer was detected. The distribution coefficients showed the optimal lipophilicity for compounds. The presented results propose new class of memantine derivatives as potential drug compounds. Based on the experimental results, the correlations have been obtained between the biological, physicochemical parameters and structural descriptors. The correlation equations have been proposed to predict the properties of new memantine derivatives knowing only the structural formula.

Rho kinase inhibitor fasudil reduces l-DOPA-induced dyskinesia in a rat model of Parkinson's disease

BACKGROUND AND PURPOSE

Rho kinase (ROCK) activation is involved in neuroinflammatory processes leading to progression of neurodegenerative diseases such as Parkinson's disease. Furthermore, ROCK plays a major role in angiogenesis. Neuroinflammation and angiogenesis are mechanisms involved in developing l-DOPA-induced dyskinesias (LID). However, it is not known whether ROCK plays a role in LID and whether ROCK inhibitors may be useful against LID.

EXPERIMENTAL APPROACH

In rats, we performed short- and long-term dopaminergic lesions using 6-hydroxydopamine and developed a LID model. Effects of dopaminergic lesions and LID on the RhoA/ROCK levels were studied by western blot, real-time PCR analyses and ROCK activity assays in the substantia nigra and striatum. The effects of the ROCK inhibitor fasudil on LID were particularly investigated.

KEY RESULTS

Short-term 6-hydroxydopamine lesions increased nigrostriatal RhoA/ROCK expression, apparently related to the active neuroinflammatory process. However, long-term dopaminergic denervation (completed and stabilized lesions) led to a decrease in RhoA/ROCK levels. Rats with LID showed a significant increase of RhoA and ROCK expression. The development of LID was reduced by the ROCK inhibitor fasudil (10 and 40 mg·kg^-1 ), without interfering with the therapeutic effect of l-DOPA. Interestingly, treatment of 40 mg·kg^-1 of fasudil also induced a significant reduction of dyskinesia in rats with previously established LID.

CONCLUSION AND IMPLICATIONS

The present results suggest that ROCK is involved in the pathophysiology of LID and that ROCK inhibitors such as fasudil may be a novel target for preventing or treating LID. Furthermore, previous studies have revealed neuroprotective effects of ROCK inhibitors.

Levodopa partially rescues microglial numerical, morphological, and phagolysosomal alterations in a monkey model of Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative motor disorder. The mechanisms underlying the onset and progression of Levodopa (L-Dopa)-induced dyskinesia (LID) during PD treatment remain elusive. Emerging evidence implicates functional modification of microglia in the development of LID. Thus, understanding the link between microglia and the development of LID may provide the knowledge required to preserve or promote beneficial microglial functions, even during a prolonged L-Dopa treatment. To provide novel insights into microglial functional alterations in PD pathophysiology, we characterized their density, morphology, ultrastructure, and degradation activity in the sensorimotor functional territory of the putamen, using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) cynomolgus monkeys. A subset of MPTP monkeys was treated orally with L-Dopa and developed LID similar to PD patients. Using a combination of light, confocal and transmission electron microscopy, our quantitative analyses revealed alterations of microglial density, morphology and phagolysosomal activity following MPTP intoxication that were partially normalized with L-Dopa treatment. In particular, microglial density, cell body and arborization areas were increased in the MPTP monkeys, whereas L-Dopa-treated MPTP animals presented a microglial phenotype similar to the control animals. At the ultrastructural level, microglia did not differ between groups in their markers of cellular stress or aging. Nevertheless, microglia from the MPTP monkeys displayed reduced numbers of endosomes, compared with control animals, that remained lower after L-Dopa treatment. Microglia from MPTP monkeys treated with L-Dopa also had increased numbers of primary lysosomes compared with non-treated MPTP animals, while secondary and tertiary lysosomes remained unchanged. Moreover, a decrease microglial immunoreactivity for CD68, considered a marker of phagocytosis and lysosomal activity, was measured in the MPTP monkeys treated with L-Dopa, compared with non-treated MPTP animals. Taken together, these findings revealed significant changes in microglia during PD pathophysiology that were partially rescued by L-Dopa treatment. Albeit, this L-Dopa treatment conferred phagolysosomal insufficiency on microglia in the dyskinetic Parkinsonian monkeys.

Transcriptomic approach predicts a major role for transforming growth factor beta type 1 pathway in L-Dopa-induced dyskinesia in parkinsonian rats

Dyskinesia induced by long-term L-Dopa (LID) therapy in Parkinson disease is associated with altered striatal function whose molecular bases remain unclear. Here, a transcriptomic approach was applied for comprehensive analysis of distinctively regulated genes in striatal tissue, their specific pathways, and functional- and disease-associated networks in a rodent model of LID. This approach has identified transforming growth factor beta type 1 (TGFβ1) as a highly upregulated gene in dyskinetic animals. TGFβ1 pathway is a top aberrantly regulated pathway in the striatum following LID development based on differentially expressed genes (> 1.5 fold change and P < 0.05). The induction of TGFβ1 pathway specific genes, TGFβ1, INHBA, AMHR2 and PMEPA1 was also associated with regulation of NPTX2, PDP1, SCG2, SYNPR, TAC1, TH, TNNT1 genes. Transcriptional network and upstream regulator analyses have identified AKT-centered functional and ERK-centered disease networks revealing the association of TGFβ1, IL-1β and TNFα with LID development. Therefore, results support that TGFβ1 pathway is a major contributor to the pathogenic mechanisms of LID.

Modulation of neuroinflammation by cysteinyl leukotriene 1 and 2 receptors: implications for cerebral ischemia and neurodegenerative diseases

Neuroinflammation is a complex biological process and has been known to play an important role in age-related cerebrovascular and neurodegenerative disorders, such as cerebral ischemia, Alzheimer's disease, and Parkinson's disease. Cysteinyl leukotrienes (CysLTs) are potent inflammatory lipid mediators that exhibit actions mainly through activating type 1 and type 2 CysLT receptors (CysLT1 and CysLT2). Accumulating evidence shows that CysLT1 and CysLT2 are activated at different stages of pathological process in various cell types in the brain such as vascular endothelial cells, astrocytes, microglia, and neurons in response to insults. However, the precise roles and mechanisms of CysLT1 and CysLT2 in regulating the pathogenesis of cerebral ischemia, Alzheimer's disease, and Parkinson's disease are not fully understood. In this article, we focus on current advances that link activation of CysLT1 and CysLT2 to the pathological process during brain ischemia and neurodegeneration and discuss mechanisms by which CysLT1 and CysLT2 mediate inflammatory process and brain injury. Multitarget anti-inflammatory potentials of CysLT1 and CysLT2 antagonism for neuroinflammation and brain injury will also be reviewed.

Targeting the cannabinoid receptor CB2 in a mouse model of l-dopa induced dyskinesia

L-dopa induced dyskinesia (LID) is a debilitating side-effect of the primary treatment used in Parkinson's disease (PD), l-dopa. Here we investigate the effect of HU-308, a cannabinoid CB2 receptor agonist, on LIDs. Utilizing a mouse model of PD and LIDs, induced by 6-OHDA and subsequent l-dopa treatment, we show that HU-308 reduced LIDs as effectively as amantadine, the current frontline treatment. Furthermore, treatment with HU-308 plus amantadine resulted in a greater anti-dyskinetic effect than maximally achieved with HU-308 alone, potentially suggesting a synergistic effect of these two treatments. Lastly, we demonstrated that treatment with HU-308 and amantadine either alone, or in combination, decreased striatal neuroinflammation, a mechanism which has been suggested to contribute to LIDs. Taken together, our results suggest pharmacological treatments with CB2 agonists merit further investigation as therapies for LIDs in PD patients. Furthermore, since CB2 receptors are thought to be primarily expressed on, and signal through, glia, our data provide weight to suggestion that neuroinflammation, or more specifically, altered glial function, plays a role in development of LIDs.

Anti-inflammatory Activity of Ursolic Acid in MPTP-Induced Parkinsonian Mouse Model

Neuroinflammation plays an important role in the progression of Parkinson's disease (PD) and hence may represent a target for treatment. The drugs used currently for PD only provide symptomatic relief and have adverse effects in addition to their inability in preventing degeneration of neurons. Flavonoids show potent antioxidant and anti-inflammatory activities which is very valuable for the health of human beings. Thus, in the present study, we have tried to explore the anti-inflammatory activity of orally given ursolic acid (UA) (25 mg/kg bwt), a pentacyclic triterpenoid in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mouse model. Significant severe oxidative stress and biochemical alterations have been seen in Parkinsonian mice after MPTP intoxication. Whereas, UA administration has significantly rescued the harmful consequence of MPTP intoxication. Ionized calcium-binding adaptor molecule 1 (Iba1), tumor necrosis factor-alpha (TNF-α), and nuclear transcription factor-κB (NF-κB) were seen to be altered in the substantia nigra pars compacta (SNpc) of MPTP-intoxicated mice through immunohistochemical studies. The changes in the expression level of these parameters primarily suggest increased inflammatory responses in MPTP-intoxicated mice as compared with the control. However, UA have significantly reduced these inflammatory parameters (Iba1 and TNF-α) along with transcription factor NF-κB, which regulates these inflammatory parameters and thus have inhibited MPTP-induced neuroinflammation. The immunoreactivity of tyrosine hydroxylase (TH) was considerably increased by UA treatment in the SNpc of Parkinsonian mice. The neuroinflammation and neurodegeneration along with impairments in biochemical and behavioral parameters were found to be reversed on treatment with UA. Thus, UA has shown potent anti-inflammatory activity by preventing the degeneration of dopaminergic neurons from MPTP-induced Parkinsonian mice.

Time dependent degeneration of the nigrostriatal tract in mice with 6-OHDA lesioned medial forebrain bundle and the effect of activin A on L-Dopa induced dyskinesia

Background

Accurately assessing promising therapeutic interventions for human diseases depends, in part, on the reproducibility of preclinical disease models. With the development of transgenic mice, the rapid adaptation of a 6-OHDA mouse model of Parkinson’s disease that was originally described for the use in rats has come with a lack of a comprehensive characterization of lesion progression. In this study we therefore first characterised the time course of neurodegeneration in the substantia nigra pars compacta and striatum over a 4 week period following 6-OHDA injection into the medial forebrain bundle of mice. We then utilised the model to assess the anti-dyskinetic efficacy of recombinant activin A, a putative neuroprotectant and anti-inflammatory that is endogenously upregulated during the course of Parkinson’s disease.

Results

We found that degeneration of fibers in the striatum was fully established within 1 week following 6-OHDA administration, but that the loss of neurons continued to progress over time, becoming fully established 3 weeks after the 6-OHDA injection. In assessing the anti-dyskinetic efficacy of activin A using this model we found that treatment with activin A did not significantly reduce the severity, or delay the time-of-onset, of dyskinesia.

Conclusion

First, the current study concludes that a 3 week duration is required to establish a complete lesion of the nigrostriatal tract following 6-OHDA injection into the medial forebrain bundle of mice. Second, we found that activin A was not anti-dyskinetic in this model.

Electronic supplementary material

The online version of this article (10.1186/s12868-019-0487-7) contains supplementary material, which is available to authorized users.

Amantadine attenuates sepsis-induced cognitive dysfunction possibly not through inhibiting toll-like receptor 2

Amantadine has been shown to reduce anesthesia and surgery-induced neuroinflammation and cognitive dysfunction. It is known that sepsis can impair brain function. We determined whether amantadine-attenuated sepsis-induced neuroinflammation and dysfunction of learning and memory and whether toll-like receptors (TLRs) play a role in the effects. Six- to eight-week-old mice were subjected to cecal ligation and puncture (CLP). Amantadine at 30 mg/kg/day was injected intraperitoneally for 3 days. CU-CPT22, a TLR1/TLR2 inhibitor, at 3 mg/kg/day was injected intraperitoneally for 2 days. Mice were subjected to Barnes maze and fear conditioning tests from 1 week after CLP. CLP induced neuroinflammation and cognitive dysfunction. CLP also increased the expression of toll-like receptor 2 (TLR2), TLR4, and TLR9, three major TLRs in the brain, in CD-1 male mice. Amantadine attenuated CLP-induced neuroinflammation and dysfunction of learning and memory but did not have significant effects on the expression of TLRs. CU-CPT22 also attenuated sepsis-induced neuroinflammation and cognitive dysfunction. Similarly, sepsis induced neuroinflammation and cognitive dysfunction in the C57BL/6J mice. Interestingly, sepsis also induced neuroinflammation and cognitive dysfunction in the TLR2 knockout mice. The effects of amantadine on the neuroinflammation and cognitive dysfunction were still apparent in these knockout mice. TLR2 contributes to sepsis-induced neuroinflammation and cognitive dysfunction. However, inhibiting TLR2 may not be a major mechanism for amantadine to inhibit sepsis-induced neuroinflammation and cognitive dysfunction.

KEY MESSAGES

Sepsis induces neuroinflammation and cognitive impairment, which were attenuated by amantadine. Toll-like receptors 2 mediates these sepsis effects but may not be the major target for amantadine to reduce these effects.

Neuroinflammation in L-DOPA-induced dyskinesia: beyond the immune function

Neuroinflammation is a main component of Parkinson's disease (PD) neuropathology, where unremitting reactive microglia and microglia-secreted soluble molecules such as cytokines, contribute to the neurodegenerative process as part of an aberrant immune reaction. Besides, pro-inflammatory cytokines, predominantly TNF-α, play an important neuromodulatory role in the healthy and diseased brain, being involved in neurotransmitter metabolism, synaptic scaling and brain plasticity. Recent preclinical studies have evidenced an exacerbated neuroinflammatory reaction in the striatum of parkinsonian rats that developed dyskinetic responses following L-DOPA administration. These findings prompted investigation of non-neuronal mechanisms of L-DOPA-induced dyskinesia (LID) involving glial cells and glial-secreted soluble molecules. Hence, besides the classical mechanisms of LID that include abnormal corticostriatal neurotransmission and maladaptive changes in striatal medium spiny neurons (MSNs), here we review studies supporting a role of striatal neuroinflammation in the development of LID, with a focus on microglia and the pro-inflammatory cytokine TNF-α. Moreover, we discuss several mechanisms that have been involved in the development of LID, which are directly or indirectly under the control of TNF-α, and might be abnormally affected by its chronic overproduction and release by microglia in PD. It is proposed that TNF-α may contribute to the altered neuronal responses occurring in LID by targeting receptor trafficking and function in MSNs, but also dopamine synthesis in preserved dopaminergic terminals and serotonin metabolism in serotonergic neurons. Therapeutic approaches specifically targeting glial-secreted cytokines may represent a novel target for preventing or treating LID.

Immunomodulation of Parkinson's disease using Mucuna pruriens (Mp)

Immune control is associated with nigrostriatal neuroprotection for Parkinson's disease (PD); though its direct cause and effect relationships have not yet been realized and modulating the immune system for therapeutic gain has been openly discussed. While the pathobiology of PD remains in study, neuroinflammation is thought to speed nigrostriatal degeneration. The neuroinflammatory cascade associated with PD begins with aggregation of misfolded or post-translationally modified α-synuclein (α-syn). Such aggregation results in neuronal cell death and the presence of chronically activated glia (microglia and astroglia), leading to the production of proinflammatory cytokines like tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and enzymes such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and cyclooxygenase-2 (COX-2). These changes in the glial phenotype can affect the central nervous system (CNS) microenvironment by producing a pro-inflammatory milieu that speeds PD pathogenesis. Mucuna pruriens (Mp) is the most popular drug in Ayurveda, the Indian system of medicine. Several reports have suggested that it possesses analgesic, anti-inflammatory, anti-neoplastic, anti-epileptic and anti-microbial activities. Mp contain L-DOPA and ursolic acid which has an anti-inflammatory property. There are very few literatures which show the immunomodulatory activity of Mp in PD, several researchers have tried to work on the immunomodulatory activity of Mp in some other diseases. The results of several studies show that Mp modulate the immune components like TNF-α, IL-6, IFN-λ, IL-1β, iNOS and IL-2 in the CNS. It also modulates the activity of the transcription factor NF-kB which plays an important role in the progression of the PD. Thus, by altering these cytokines or transcription factors, Mp protects or prevents the progression of PD. Thus in this review we try to explore the immunomodulatory activity of Mp in PD.

Combination of homogenous liquid–liquid extraction and dispersive liquid–liquid microextraction for extraction and preconcentration of amantadine from biological samples followed by its indirect determination by flame atomic absorption spectrometry

A new and simple procedure has been developed for the indirect determination of amantadine in biological samples.

Transfusion of Old RBCs Induces Neuroinflammation and Cognitive Impairment

OBJECTIVES

Transfusing RBCs stored for longer than 14 days (old RBC) in humans is common. This transfusion can injure organs, such as lungs and kidneys. We determined whether transfusion with old RBC injured brain.

DESIGN

Prospective, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Six-month-old Sprague-Dawley rats lost 20% total blood volume and then received RBC prepared from equal volume of the lost blood. RBC was stored for 1 day (fresh RBC) or 7 days (old RBC, storage lesions similar to those of human RBC stored for 28 d). Some rats received IV cell-free hemoglobin. These rats were not subjected to hemorrhage and RBC transfusion.

MEASUREMENTS AND MAIN RESULTS

Rats were subjected to Barnes maze and fear conditioning tests from 1 week after blood transfusion. Rats transfused with old RBC but not fresh RBC took a longer time to identify the target hole in the Barnes maze and had less context-related fear conditioning behavior than control rats. Old RBC significantly increased interleukin 6 and ionized calcium-binding adapter molecule 1 in the hippocampus at 24 hours after the transfusion. These effects were attenuated by sulforaphane and minocycline, an antibiotic with anti-inflammatory property. Old RBC solution had a higher concentration of cell-free hemoglobin. Sulforaphane increased haptoglobin, a chelator of cell-free hemoglobin. Rats that received cell-free hemoglobin had a pattern of neuroinflammation and impairment of learning and memory similar to that of rats that received old RBC.

CONCLUSIONS

These results provide initial evidence to suggest that transfusion of old RBC induces neuroinflammation and impairment of learning and memory. These effects may be mediated by cell-free hemoglobin.

α-Asarone attenuates microglia-mediated neuroinflammation by inhibiting NF kappa B activation and mitigates MPTP-induced behavioral deficits in a mouse model of Parkinson's disease

The selective loss of dopaminergic neurons in Parkinson's disease (PD) is associated with microglial activation. Therefore, the importance of early therapeutic intervention to inhibit microglial activation would be an effective strategy to alleviate the progression of PD. α-Asarone, an active compound found in Araceae and Annonaceae plant species has been used to improve various disease conditions including central nervous system disorders. In the present study the in vitro and in vivo therapeutic effects of α-asarone isolated from the rhizome of Acorus gramineus Solander was evaluated on microglia-mediated neuroinflammation and neuroprotection. Lipopolysaccharide (LPS)-stimulated BV-2 microglial cells were used to evaluate in vitro effects. 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of PD was developed to study the neuroprotective effects of α-asarone in vivo. The results indicated that α-asarone significantly attenuated the LPS-stimulated increase in neuroinflammatory responses and suppressed pro-inflammatory cytokine production in BV-2 cells. Mechanistic study revealed that α-asarone inhibited the LPS-stimulated activation via regulation of nuclear factor kappa-B by blocking degradation of inhibitor kappa B-alpha signaling in BV-2 microglial cells. In in vivo studies, MPTP intoxication to mice resulted in brain microglial activation and significant behavioral deficits. Prophylactic treatment with α-asarone suppressed microglial activation and attenuated PD-like behavioral impairments as assessed by the Y-maze and pole tests. Taken together, these data demonstrate that α-asarone is a promising neuroprotective agent that should be further evaluated and developed for future prevention and treatment of microglia-mediated neuroinflammatory conditions including PD.

Plasma inflammatory biomarkers for Huntington's disease patients and mouse model

Huntington's disease (HD), caused by expanded CAG repeats encoding a polyglutamine tract in the huntingtin (HTT) protein, presents with a predominant degeneration of neurons in the striatum and cortex. Lines of evidence have observed neuroinflammation, particularly microglial activation, is involved in the pathogenesis of HD. Given that HTT is also expressed in peripheral inflammatory cells, it is possible that inflammatory changes detected in peripheral plasma may be biologically relevant and parallel the neuroinflammatory process of HD patients. By examining the expression levels of 13 microglia-derived inflammatory markers in the plasma of 5 PreHD carriers, 15 HD patients and 16 healthy controls, we found plasma levels of IL-6, MMP-9, VEGF and TGF-β1 were significantly increased in HD patients when compared with the controls, while plasma level of IL-18 were significantly reduced in HD patients compared with controls. Plasma level of IL-6 was reversely correlated with the UHDRS independence scale and functional capacity. To understand the temporal correlation between these inflammatory markers and HD progression, their levels were further tested in plasma from R6/2 mouse HD model at different ages. In rotarod test, R6/2 HD mice started to manifest HD phenotype at 7.5 weeks of age. Higher plasma VEGF levels of R6/2 mice than those of age-matched wild-type (WT) littermates were noted from 7 (presymptomatic stage) to 13 weeks of age (late symptomatic stage). The plasma IL-6 levels of R6/2 mice were higher than those of the WT littermates from 9 (early symptomatic stage) to 13 weeks of age. R6/2 mice demonstrated higher MMP-9 and TGF-β1 levels than their WT littermates from 11 (middle symptomatic stage) to 13 weeks of age. In contrast, the plasma IL-18 level was lower than those in WT littermates since 11 weeks of age. These altered expressions of inflammatory markers may serve as the potential biomarkers for HD onset and progression. Specific inhibition/activation of these inflammatory markers may be the targets of HD drug development.

Amantadine alleviates postoperative cognitive dysfunction possibly by increasing glial cell line-derived neurotrophic factor in rats

BACKGROUND

Postoperative cognitive dysfunction is a clinical entity that is associated with poor outcome. We determined the effectiveness of amantadine in reducing surgery-induced cognitive impairment and the role of glial cell line-derived neurotrophic factor (GDNF) in this effect.

METHODS

Four-month old male Fischer 344 rats were subjected to right carotid exposure under intravenous anesthesia. Some rats received intraperitoneal injection of 25 mg/kg/day amantadine for 3 days with the first dose at 15 min before the surgery or intracerebroventricular injection of GDNF or an anti-GDNF antibody at the end of surgery. One week later, rats were started to be tested by Barnes maze and fear conditioning. Hippocampus was harvested at 6 h, 24 h or 10 days after the surgery for biochemical analysis. C8-B4 cells, a microglial cell line, were pretreated with 1 ng/ml GDNF for 30 min before being exposed to 5 ng/ml lipopolysaccharide for 2 h.

RESULTS

Surgery increased the time to identify the target box in the Barnes maze when tested 1 day [22 (median) (11-66) (interquartile range) of control group vs. 158 (29-180) of surgery group, n = 15, P = 0.022) or 8 days after the training sessions and reduced context-related freezing behavior in the fear conditioning test. These effects were attenuated by amantadine (25 (14-90), n = 15, P = 0.029 compared with surgery group at 1 day after the training sessions in Barnes maze) and intracerebroventricular GDNF. Amantadine increased GDNF that was co-localized with glial fibrillary acidic protein, an astrocytic marker, in the hippocampus. Intracerebroventricular injection of an anti-GDNF antibody but not the denatured antibody blocked the effects of amantadine on cognition. Surgery induced neuroinflammation that was inhibited by amantadine. Lipopolysaccharide increased interleukin 1β production from C8-B4 cells. This effect was inhibited by GDNF.

CONCLUSIONS

Our results suggest that amantadine attenuated surgery-induced learning and memory impairment. This effect may be mediated by GDNF via inhibition of neuroinflammation.

Glial activation is associated with l-DOPA induced dyskinesia and blocked by a nitric oxide synthase inhibitor in a rat model of Parkinson's disease

l-3, 4-dihydroxyphenylalanine (L-DOPA) is the most effective treatment for Parkinson's disease but can induce debilitating abnormal involuntary movements (dyskinesia). Here we show that the development of L-DOPA-induced dyskinesia in the rat is accompanied by upregulation of an inflammatory cascade involving nitric oxide. Male Wistar rats sustained unilateral injections of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. After three weeks animals started to receive daily treatment with L-DOPA (30 mg/kg plus benserazide 7.5 mg/kg, for 21 days), combined with an inhibitor of neuronal NOS (7-nitroindazole, 7-NI, 30 mg/kg/day) or vehicle (saline-PEG 50%). All animals treated with L-DOPA and vehicle developed abnormal involuntary movements, and this effect was prevented by 7-NI. L-DOPA-treated dyskinetic animals exhibited an increased striatal and pallidal expression of glial fibrillary acidic protein (GFAP) in reactive astrocytes, an increased number of CD11b-positive microglial cells with activated morphology, and the rise of cells positive for inducible nitric oxide-synthase immunoreactivity (iNOS). All these indexes of glial activation were prevented by 7-NI co-administration. These findings provide evidence that the development of L-DOPA-induced dyskinesia in the rat is associated with activation of glial cells that promote inflammatory responses. The dramatic effect of 7-NI in preventing this glial response points to an involvement of nitric oxide. Moreover, the results suggest that the NOS inhibitor prevents dyskinesia at least in part via inhibition of glial cell activation and iNOS expression. Our observations indicate nitric oxide synthase inhibitors as a therapeutic strategy for preventing neuroinflammatory and glial components of dyskinesia pathogenesis in Parkinson's disease.

Preconditioning as a potential strategy for the prevention of Parkinson's disease

Parkinson's disease (PD) is a chronic neurodegenerative movement disorder characterized by the progressive and massive loss of dopaminergic neurons by neuronal apoptosis in the substantia nigra pars compacta and depletion of dopamine in the striatum, which lead to pathological and clinical abnormalities. A numerous of cellular processes including oxidative stress, mitochondrial dysfunction, and accumulation of α-synuclein aggregates are considered to contribute to the pathogenesis of Parkinson's disease. A further understanding of the cellular and molecular mechanisms involved in the pathophysiology of PD is crucial for developing effective diagnostic, preventative, and therapeutic strategies to cure this devastating disorder. Preconditioning (PC) is assumed as a natural adaptive process whereby a subthreshold stimulus can promote protection against a subsequent lethal stimulus in the brain as well as in other tissues that affords robust brain tolerance facing neurodegenerative insults. Multiple lines of evidence have demonstrated that preconditioning as a possible neuroprotective technique may reduce the neural deficits associated with neurodegenerative diseases such as PD. Throughout the last few decades, a lot of efforts have been made to discover the molecular determinants involved in preconditioning-induced protective responses; although, the accurate mechanisms underlying this "tolerance" phenomenon are not fully understood in PD. In this review, we will summarize pathophysiology and current therapeutic approaches in PD and discuss about preconditioning in PD as a potential neuroprotective strategy. Also the role of gene reprogramming and mitochondrial biogenesis involved in the preconditioning-mediated neuroprotective events will be highlighted. Preconditioning may represent a promising therapeutic weapon to combat neurodegeneration.

7-Methoxytacrine-adamantylamine heterodimers as cholinesterase inhibitors in Alzheimer's disease treatment--synthesis, biological evaluation and molecular modeling studies

A structural series of 7-MEOTA-adamantylamine thioureas was designed, synthesized and evaluated as inhibitors of human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBChE). The compounds were prepared based on the multi-target-directed ligand strategy with different linker lengths (n = 2-8) joining the well-known NMDA antagonist adamantine and the hAChE inhibitor 7-methoxytacrine (7-MEOTA). Based on in silico studies, these inhibitors proved dual binding site character capable of simultaneous interaction with the peripheral anionic site (PAS) of hAChE and the catalytic active site (CAS). Clearly, these structural derivatives exhibited very good inhibitory activity towards hBChE resulting in more selective inhibitors of this enzyme. The most potent cholinesterase inhibitor was found to be thiourea analogue 14 (with an IC₅₀ value of 0.47 µM for hAChE and an IC₅₀ value of 0.11 µM for hBChE, respectively). Molecule 14 is a suitable novel lead compound for further evaluation proving that the strategy of dual binding site inhibitors might be a promising direction for development of novel AD drugs.