The anti-parkinsonian drug zonisamide reduces neuroinflammation: Role of microglial Nav 1.6

The role of voltage-gated calcium channels in the pathogenesis of Parkinson's disease

Aim: Voltage-gated calcium (CaV) channels play an essential role in maintaining calcium homeostasis and regulating numerous physiological processes in neurons. Therefore, dysregulation of calcium signaling is relevant in many neurological disorders, including Parkinson's disease (PD). This review aims to introduce the role of CaV channels in PD and discuss some novel aspects of channel regulation and its impact on the molecular pathophysiology of the disease.

Methods: an exhaustive search of the literature in the field was carried out using the PubMed database of The National Center for Biotechnology Information. Systematic searches were performed from the initial date of publication to May 2022.

Results: Although α-synuclein aggregates are the main feature of PD, L-type calcium (CaV1) channels seem to play an essential role in the pathogenesis of PD. Changes in the functional expression of CaV1.3 channels alter Calcium homeostasis and contribute to the degeneration of dopaminergic neurons. Furthermore, recent studies suggest that CaV channel trafficking towards the cell membrane depends on the activity of the ubiquitin-proteasome system (UPS). In PD, there is an increase in the expression of L-type channels associated with a decrease in the expression of Parkin, an E3 enzyme of the UPS. Therefore, a link between Parkin and CaV channels could play a fundamental role in the pathogenesis of PD and, as such, could be a potentially attractive target for therapeutic intervention.

Conclusion: The study of alterations in the functional expression of CaV channels will provide a framework to understand better the neurodegenerative processes that occur in PD and a possible path toward identifying new therapeutic targets to treat this condition.

Drug repurposing screen identifies novel anti-inflammatory activity of sunitinib in macrophages

Inflammation is a driver of human disease and an unmet clinical need exists for new anti-inflammatory medicines. As a key cell type in both acute and chronic inflammatory pathologies, macrophages are an appealing therapeutic target for anti-inflammatory medicines. Drug repurposing - the use of existing medicines for novel indications - is an attractive strategy for the identification of new anti-inflammatory medicines with reduced development costs and lower failure rates than de novo drug discovery. In this study, FDA-approved medicines were screened in a murine macrophage NF-κB reporter cell line to identify potential anti-inflammatory drug repurposing candidates. The multi-tyrosine kinase inhibitor sunitinib was found to be a potent inhibitor of NF-κB activity and suppressor of inflammatory mediator production in murine bone marrow derived macrophages. Furthermore, oral treatment with sunitinib in mice was found to reduce TNFα production, inflammatory gene expression and organ damage in a model of endotoxemia via inhibition of NF-κB. Finally, we revealed sunitinib to have immunomodulatory effects in a model of chronic cardiovascular inflammation by reducing circulating TNFα. This study validates drug repurposing as a strategy for the identification of novel anti-inflammatory medicines and highlights sunitinib as a potential drug repurposing candidate for inflammatory disease via inhibition of NF-κB signalling.

Phenotypic Screening of Prospective Analgesics Among FDA-Approved Compounds using an iPSC-Based Model of Acute and Chronic Inflammatory Nociception

Classical target-based drug screening is low-throughput, largely subjective, and costly. Phenotypic screening based on in vitro models is increasingly being used to identify candidate compounds that modulate complex cell/tissue functions. Chronic inflammatory nociception, and subsequent chronic pain conditions, affect peripheral sensory neuron activity (e.g., firing of action potentials) through myriad pathways, and remain unaddressed in regard to effective, non-addictive management/treatment options. Here, a chronic inflammatory nociception model is demonstrated based on induced pluripotent stem cell (iPSC) sensory neurons and glia, co-cultured on microelectrode arrays (MEAs). iPSC sensory co-cultures exhibit coordinated spontaneous extracellular action potential (EAP) firing, reaching a stable baseline after ≈27 days in vitro (DIV). Spontaneous and evoked EAP metrics are significantly modulated by 24-h incubation with tumor necrosis factor-alpha (TNF-α), representing an inflammatory phenotype. Compared with positive controls (lidocaine), this model is identified as an "excellent" stand-alone assay based on a modified Z' assay quality metric. This model is then used to screen 15 cherry-picked, off-label, Food and Drug Administration (FDA)-approved compounds; 10 of 15 are identified as "hits". Both hits and "misses" are discussed in turn. In total, this data suggests that iPSC sensory co-cultures on MEAs may represent a moderate-to-high-throughput assay for drug discovery targeting inflammatory nociception.

Neuroinflammation following anti-parkinsonian drugs in early Parkinson's disease: a longitudinal PET study

The progression of neuroinflammation after anti-parkinsonian therapy on the Parkinson's disease (PD) brain and in vivo evidence of the therapy purporting neuroprotection remain unclear. To elucidate this, we examined changes in microglial activation, nigrostriatal degeneration, and clinical symptoms longitudinally after dopamine replacement therapy in early, optimally-controlled PD patients with and without zonisamide treatment using positron emission tomography (PET). We enrolled sixteen PD patients (Hoehn and Yahr stage 1-2), and age-matched normal subjects. PD patients were randomly divided into two groups: one (zonisamide+) that did and one (zonisamide-) that did not undergo zonisamide therapy. Annual changes in neuroinflammation ([11C]DPA713 PET), dopamine transporter availability ([11C]CFT PET) and clinical severity were examined. Voxelwise differentiations in the binding of [11C]DPA713 (BPND) and [11C]CFT (SUVR) were compared with normal data and between the zonisamide+ and zonisamide- PD groups. The cerebral [11C]DPA713 BPND increased with time predominantly over the parieto-occipital region in PD patients. Comparison of the zonisamide+ group with the zonisamide- group showed lower levels in the cerebral [11C]DPA713 BPND in the zonisamide+ group. While the striatal [11C]CFT SUVR decreased longitudinally, the [11C]CFT SUVR in the nucleus accumbens showed a higher binding in the zonisamide+ group. A significant annual increase in attention score were found in the zonisamide+ group. The current results indicate neuroinflammation proceeds to the whole brain even after anti-parkinsonian therapy, but zonisamide coadministration might have the potential to ameliorate proinflammatory responses, exerting a neuroprotective effect in more damaged nigrostriatal regions with enhanced attention in PD.

Efficacy of Adjunctive Therapy with Zonisamide Versus Increased Dose of Levodopa for Motor Symptoms in Patients with Dementia with Lewy Bodies: The Randomized, Controlled, Non-Inferiority DUEL Study

BACKGROUND

In patients with dementia with Lewy bodies (DLB), it is unknown whether adjunct zonisamide is as effective and safe as increasing levodopa dose when levodopa has inadequate efficacy on parkinsonism.

OBJECTIVE

To compare adjunct zonisamide 25 mg/day versus an increased levodopa dose (increased by 100 mg/day) in patients with DLB treated with levodopa ≤300 mg/day for parkinsonism.

METHODS

The DUEL study was a multicenter, randomized, controlled, open-label, parallel-group, interventional, non-inferiority trial. During the observation period, levodopa was administered at ≤300 mg/day for 4 weeks. Subsequently, patients were randomized to receive adjunct zonisamide 25 mg/day or levodopa increased by 100 mg/day.

RESULTS

Respective adjusted mean changes in MDS-UPDRS Part III total score at 16 and 24 weeks (primary endpoint) were -6.3 and -4.4 in the zonisamide add-on and -0.8 and 2.0 in the levodopa increase groups. The adjusted mean difference at 24 weeks was -6.4 (95% confidence interval [CI] -13.5, 0.7); the upper limit of the 95% CI (0.7) was lower than the non-inferiority margin (3.0). No significant between-group differences were observed in total scores of the MDS-UPDRS Part II, Eating Questionnaire, EuroQol-5 dimension-5 level, Zarit Caregiver Burden Interview, or other secondary endpoints. No notable between-group differences were observed in adverse event incidences.

CONCLUSION

Adjunct zonisamide 25 mg/day may yield moderate improvement in motor symptoms in patients with DLB when the levodopa effect is insufficient, but it could not be verified that the zonisamide 25 mg/day was as effective as levodopa 100 mg/day because levodopa showed no sufficient efficacy as assumed.

Deltamethrin-Evoked ER Stress Promotes Neuroinflammation in the Adult Mouse Hippocampus

Endoplasmic reticulum (ER) stress and neuroinflammation are involved in the pathogenesis of many neurodegenerative disorders. Previously, we reported that exposure to pyrethroid insecticide deltamethrin causes hippocampal ER stress apoptosis, a reduction in neurogenesis, and learning deficits in adult male mice. Recently, we found that deltamethrin exposure also increases the markers of neuroinflammation in BV2 cells. Here, we investigated the potential mechanistic link between ER stress and neuroinflammation following exposure to deltamethrin. We found that repeated oral exposure to deltamethrin (3 mg/kg) for 30 days caused microglial activation and increased gene expressions and protein levels of TNF-α, IL-1β, IL-6, gp91phox, 4HNE, and iNOS in the hippocampus. These changes were preceded by the induction of ER stress as the protein levels of CHOP, ATF-4, and GRP78 were significantly increased in the hippocampus. To determine whether induction of ER stress triggers the inflammatory response, we performed an additional experiment with mouse microglial cell (MMC) line. MMCs were treated with 0-5 µM deltamethrin for 24-48 h in the presence or absence of salubrinal, a pharmacological inhibitor of the ER stress factor eIF2α. We found that salubrinal (50 µM) prevented deltamethrin-induced ER stress, as indicated by decreased levels of CHOP and ATF-4, and attenuated the levels of GSH, 4-HNE, gp91phox, iNOS, ROS, TNF-α, IL-1β, and IL-6 in MMCs. Together, these results demonstrate that exposure to deltamethrin leads to ER stress-mediated neuroinflammation, which may subsequently contribute to neurodegeneration and cognitive impairment in mice.

Zonisamide Ameliorates Microglial Mitochondriopathy in Parkinson’s Disease Models

Mitochondrial dysfunction and exacerbated neuroinflammation are critical factors in the pathogenesis of both familial and non-familial forms of Parkinson’s disease (PD). This study aims to understand the possible ameliorative effects of zonisamide on microglial mitochondrial dysfunction in PD. We prepared 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and lipopolysaccharide (LPS) co-treated mouse models of PD to investigate the effects of zonisamide on mitochondrial reactive oxygen species generation in microglial cells. Consequently, we utilised a mouse BV2 cell line that is commonly used for microglial studies to determine whether zonisamide could ameliorate LPS-treated mitochondrial dysfunction in microglia. Flow cytometry assay indicated that zonisamide abolished microglial reactive oxygen species (ROS) generation in PD models. Extracellular flux assays showed that LPS exposure to BV2 cells at 1 μg/mL drastically reduced the mitochondrial oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Zonisamide overcame the inhibitory effects of LPS on mitochondrial OCR. Our present data provide novel evidence on the ameliorative effect of zonisamide against microglial mitochondrial dysfunction and support its clinical use as an antiparkinsonian drug.

Brain injury and inflammation genes common to a number of neurological diseases and the genes involved in the genesis of GABAnergic neurons are altered in monoamine oxidase B knockout mice

Monoamine oxidase B (MAO B) oxidizes trace amine phenylethylamine (PEA), and neurotransmitters serotonin and dopamine in the brain. We reported previously that PEA levels increased significantly in all brain regions, but serotonin and dopamine levels were unchanged in MAO B knockout (KO) mice. PEA and dopamine are both synthesized from phenylalanine by aromatic L-amino acid decarboxylase in dopaminergic neurons in the striatum. A high concentration of PEA in the striatum may cause dopaminergic neuronal death in the absence of MAO B. We isolated the RNA from brain tissue of MAO B KO mice (2-month old) and age-matched wild type (WT) male mice and analyzed the altered genes by Affymetrix microarray. Differentially expressed genes (DEGs) in MAO B KO compared to WT mice were analyzed by Partek Genomics Suite, followed by Ingenuity Pathway Analysis (IPA) to assess their functional relationships. DEGs in MAO B KO mice are involved in brain inflammation and the genesis of GABAnergic neurons. The significant DEGs include four brain injury or inflammation genes (upregulated: Ido1, TSPO, AVP, Tdo2), five gamma-aminobutyric acid (GABA) receptors (down-regulated: GABRA2, GABRA3, GABRB1, GABRB3, GABRG3), five transcription factors related to adult neurogenesis (upregulated: Wnt7b, Hes5; down-regulated: Pax6, Tcf4, Dtna). Altered brain injury and inflammation genes in MAO B knockout mice are involved in various neurological disorders: attention deficit hyperactive disorder, panic disorder, obsessive compulsive disorder, autism, amyotrophic lateral sclerosis, Parkinson's diseases, Alzheimer's disease, bipolar affective disorder. Many were commonly involved in these disorders, indicating that there are overlapping molecular pathways.

Ion-Channel Antiepileptic Drugs: An Analytical Perspective on the Therapeutic Drug Monitoring (TDM) of Ezogabine, Lacosamide, and Zonisamide

The term seizures includes a wide array of different disorders with variable etiology, which currently represent one of the most important classes of neurological illnesses. As a consequence, many different antiepileptic drugs (AEDs) are currently available, exploiting different activity mechanisms and providing different levels of performance in terms of selectivity, safety, and efficacy. AEDs are currently among the psychoactive drugs most frequently involved in therapeutic drug monitoring (TDM) practices. Thus, the plasma levels of AEDs and their metabolites are monitored and correlated to administered doses, therapeutic efficacy, side effects, and toxic effects. As for any analytical endeavour, the quality of plasma concentration data is only as good as the analytical method allows. In this review, the main techniques and methods are described, suitable for the TDM of three AEDs belonging to the class of ion channel agents: ezogabine (or retigabine), lacosamide, and zonisamide. In addition to this analytical overview, data are provided, pertaining to two of the most important use cases for the TDM of antiepileptics: drug–drug interactions and neuroprotection activity studies. This review contains 146 references.

Are ion channels potential therapeutic targets for Parkinson's disease?

Parkinson's disease (PD) is primarily associated with the progressive neurodegeneration of the dopaminergic neurons in the substantia nigra region of the brain. The resulting motor symptoms are managed with the help of dopamine replacement therapies. However, these therapeutics do not prevent the neurodegeneration underlying the disease and therefore lose their effectiveness in managing disease symptoms over time. Thus, there is an urgent need to develop newer therapeutics for the benefit of patients. The release of dopamine and the firing activity of substantia nigra neurons is regulated by several ion channels that act in concert. Dysregulations of these channels cause the aberrant movement of various ions in the intracellular milieu. This eventually leads to disruption of intracellular signalling cascades, alterations in cellular homeostasis, and bioenergetic deficits. Therefore, ion channels play a central role in driving the high vulnerability of dopaminergic neurons to degenerate during PD. Targeting ion channels offers an attractive mechanistic strategy to combat the process of neurodegeneration. In this review, we highlight the evidence pointing to the role of various ion channels in driving the PD processes. In addition, we also discuss the various drugs or compounds that target the ion channels and have shown neuroprotective potential in the in-vitro and in-vivo models of PD. We also discuss the current clinical status of various drugs targeting the ion channels in the context of PD.

Scorpion Venom Heat-Resistant Peptide Attenuates Microglia Activation and Neuroinflammation

Background: Intervention of neuroinflammation in central nervous system (CNS) represents a potential therapeutic strategy for a host of brain disorders. The scorpion Buthus martensii Karsch (BmK) and its venom have long been used in the Orient to treat inflammation-related diseases such as rhumatoid arthritis and chronic pain. Scorpion venom heat-resistant peptide (SVHRP), a component from BmK venom, has been shown to reduce seizure susceptibility in a rat epileptic model and protect against cerebral ischemia-reperfusion injury. As neuroinflammation has been implicated in chronic neuronal hyperexcitability, epileptogenesis and cerebral ischemia-reperfusion injury, the present study aimed to investigate whether SVHRP has anti-inflammatory property in brain.

Methods: An animal model of neuroinflammation induced by lipopolysacchride (LPS) injection was employed to investigate the effect of SVHRP (125 µg/kg, intraperitoneal injection) on inflammagen-induced expression of pro-inflammatory factors and microglia activation. The effect of SVHRP (2–20 μg/ml) on neuroinflammation was further investigated in primary brain cell cultures containing microglia as well as the immortalized BV₂ microglia culture stimulated with LPS. Real-time quantitative PCR were used to measure mRNA levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 in hippocampus of animals. Protein levels of TNF-α, iNOS, P65 subunit of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) were examined by ELISA or western blot. Microglia morphology in animal hippocampus or cell cultures and cellular distribution of p65 were shown by immunostaining.

Results: Morphological study demonstrated that activation of microglia, the main component that mediates the neuroinflammatory process, was inhibited by SVHRP in both LPS mouse and cellular model. Our results also showed dramatic increases in the expression of iNOS and TNF-α in hippocampus of LPS-injected mice, which was significantly attenuated by SVHRP treatment. In vitro results showed that SVHRP attenuated LPS-elicited expression of iNOS and TNF-α in different cultures without cell toxicity, which might be attributed to suppression of NF-κB and MAPK pathways by SVHRP.

Conclusion: Our study demonstrates that SVHRP is able to inhibit neuroinflammation and microglia activation, which may underlie the therapeutic effects of BmK-derived materials, suggesting that BmK venom could be a potential source for CNS drug development.

Scorpion venom heat-resistant synthesized peptide ameliorates 6-OHDA-induced neurotoxicity and neuroinflammation: likely role of Nav 1.6 inhibition in microglia

BACKGROUND AND PURPOSE

Microglia-related inflammation is associated with the pathology of Parkinson's disease. Functional voltage-gated sodium channels (VGSCs) are involved in regulating microglial function. Here, we aim to investigate the effects of scorpion venom heat-resistant synthesized peptide (SVHRSP) on 6-hydroxydopamine (6-OHDA)-induced Parkinson's disease-like mouse model and reveal its underlying mechanism.

EXPERIMENTAL APPROACH

Unilateral brain injection of 6-OHDA was performed to establish Parkinson's disease mouse model. After behaviour test, brain tissues were collected for morphological analysis and protein/gene expression examination. Primary microglia culture was used to investigate the role of sodium channel Na_v 1.6 in the regulation of microglia inflammation by SVHRSP.

KEY RESULTS

SVHRSP treatment attenuated motor deficits, dopamine neuron degeneration, activation of glial cells and expression of pro-inflammatory cytokines induced by 6-OHDA lesion. Primary microglia activation and the production of pro-inflammatory cytokines induced by lipopolysaccharide (LPS) were also suppressed by SVHRSP treatment. In addition, SVHRSP could inhibit mitogen-activated protein kinases (MAPKs) pathway, which plays pivotal roles in the pro-inflammatory response. Notably, SVHRSP treatment suppressed the overexpression of microglial Na_v 1.6 induced by 6-OHDA and LPS. Finally, it was shown that the anti-inflammatory effect of SVHRSP in microglia was Na_v 1.6 dependent and was related to suppression of sodium current and probably the consequent Na⁺ /Ca²⁺ exchange.

CONCLUSIONS AND IMPLICATIONS

SVHRSP might inhibit neuroinflammation and protect dopamine neurons via down-regulating microglial Na_v 1.6 and subsequently suppressing intracellular Ca²⁺ accumulation to attenuate the activation of MAPKs signalling pathway in microglia.

Roles of Microglial Ion Channel in Neurodegenerative Diseases

As the average age and life expectancy increases, the incidence of both acute and chronic central nervous system (CNS) pathologies will increase. Understanding mechanisms underlying neuroinflammation as the common feature of any neurodegenerative pathology, we can exploit the pharmacology of cell specific ion channels to improve the outcome of many CNS diseases. As the main cellular player of neuroinflammation, microglia play a central role in this process. Although microglia are considered non-excitable cells, they express a variety of ion channels under both physiological and pathological conditions that seem to be involved in a plethora of cellular processes. Here, we discuss the impact of modulating microglia voltage-gated, potential transient receptor, chloride and proton channels on microglial proliferation, migration, and phagocytosis in neurodegenerative diseases.

Nanopharmaceutical-based regenerative medicine: a promising therapeutic strategy for spinal cord injury

Spinal cord injury (SCI) is a neurological disorder that can lead to loss of perceptive and athletic function due to the severe nerve damage. To date, pieces of evidence detailing the precise pathological mechanisms in SCI are still unclear. Therefore, drug therapy cannot effectively alleviate the SCI symptoms and faces the limitations of systemic administration with large side effects. Thus, the development of SCI treatment strategies is urgent and valuable. Due to the application of nanotechnology in pharmaceutical research, nanopharmaceutical-based regenerative medicine will bring colossal development space for clinical medicine. These nanopharmaceuticals (i.e. nanocrystalline drugs and nanocarrier drugs) are designed using different types of materials or bioactive molecules, so as to improve the therapeutic effects, reduce side effects, and subtly deliver drugs, etc. Currently, an increasing number of nanopharmaceutical products have been approved by drug regulatory agencies, which has also prompted more researchers to focus on the potential treatment strategies of SCI. Therefore, the purpose of this review is to summarize and elaborate the research progress as well as the challenges and future of nanopharmaceuticals in the treatment of SCI, aiming to promote further research of nanopharmaceuticals in SCI.

Zonisamide for the Treatment of Parkinson Disease: A Current Update

Zonisamide has been used as an add-on treatment in order to overcome the deficiencies of the general therapies currently used to resolve the motor complications and non-motor symptoms of Parkinson disease. Various trials have been designed to investigate the mechanism of action and treatment effects of zonisamide in this condition. Most clinical trials of zonisamide in Parkinson disease were from Japan. The vast majority of studies used changes in the Unified Parkinson’s Disease Rating Scale (UPDRS) scores and daily “OFF” time as primary endpoints. Based on adequate randomized controlled trials, zonisamide is considered a safe and efficacious add-on treatment in Parkinson disease. The most convincing proof is available for a dosage of 25–50 mg, which was shown to lead to a significant reduction in the UPDRS III score and daily “OFF” time, without increasing disabling dyskinesia. Furthermore, zonisamide may play a beneficial role in improving non-motor symptoms in PD, including impulsive–compulsive disorder, rapid eye movement sleep behavior disorder, and dementia. Among the various mechanisms reported, inhibition of monoamine oxidase-B, blocking of T-type calcium channels, modulation of the levodopa–dopamine metabolism, modulation of receptor expression, and neuroprotection are the most often cited. The mechanisms underlying neuroprotection, including modulation of dopamine turnover, induction of neurotrophic factor expression, inhibition of oxidative stress and apoptosis, inhibition of neuroinflammation, modulation of synaptic transmission, and modulation of gene expression, have been most extensively studied. This review focuses on structure, pharmacokinetics, mechanisms, therapeutic effectiveness, and safety and tolerability of zonisamide in patients with Parkinson disease.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Ion channels and transporters in microglial function in physiology and brain diseases

Microglial cells interact with all components of the central nervous system (CNS) and are increasingly recognized to play essential roles during brain development, homeostasis and disease pathologies. Functions of microglia include maintaining tissue integrity, clearing cellular debris and dead neurons through the process of phagocytosis, and providing tissue repair by releasing anti-inflammatory cytokines and neurotrophic factors. Changes of microglial ionic homeostasis (Na⁺, Ca²⁺, K⁺, H⁺, Cl^-) are important for microglial activation, including proliferation, migration, cytokine release and reactive oxygen species production, etc. These are mediated by ion channels and ion transporters in microglial cells. Here, we review the current knowledge about the role of major microglial ion channels and transporters, including several types of Ca²⁺ channels (store-operated Ca²⁺ entry (SOCE) channels, transient receptor potential (TRP) channels and voltage-gated Ca²⁺ channels (VGCCs)) and Na⁺ channels (voltage-gated Na⁺ channels (Nav) and acid-sensing ion channels (ASICs)), K⁺ channels (inward rectifier K⁺ channels (K_ir), voltage-gated K⁺ channels (K_V) and calcium-activated K⁺ channels (K_Ca)), proton channels (voltage-gated proton channel (Hv1)), and Cl^- channels (volume (or swelling)-regulated Cl^- channels (VRCCs) and chloride intracellular channels (CLICs)). In addition, ion transporter proteins such as Na⁺/Ca²⁺ exchanger (NCX), Na⁺-K⁺-Cl^- cotransporter (NKCC1), and Na⁺/H⁺ exchanger (NHE1) are also involved in microglial function in physiology and brain diseases. We discussed microglial activation and neuroinflammation in relation to the ion channel/transporter stimulation under brain disease conditions and therapeutic aspects of targeting microglial ion channels/transporters for neurodegenerative disease, ischemic stroke, traumatic brain injury and neuropathic pain.

Microglia Implicated in Tauopathy in the Striatum of Neurodegenerative Disease Patients from Genotype to Phenotype

We found interactions between dopamine and oxidative damage in the striatum involved in advanced neurodegeneration, which probably change the microglial phenotype. We observed possible microglia dystrophy in the striatum of neurodegenerative brains. To investigate the interactions between oxidative damage and microglial phenotype, we quantified myeloperoxidase (MPO), poly (ADP-Ribose) (PAR), and triggering receptors expressed on myeloid cell 2 (TREM2) using enzyme-linked immunosorbent assay (ELISA). To test the correlations of microglia dystrophy and tauopathy, we quantified translocator protein (TSPO) and tau fibrils using autoradiography. We chose the caudate and putamen of Lewy body diseases (LBDs) (Parkinson’s disease, Parkinson’s disease dementia, and Dementia with Lewy body), Alzheimer’s disease (AD), and control brains and genotyped for TSPO, TREM2, and bridging integrator 1 (BIN1) genes using single nucleotide polymorphisms (SNP) assays. TREM2 gene variants were absent across all samples. However, associations between TSPO and BIN1 gene polymorphisms and TSPO, MPO, TREM2, and PAR level variations were found. PAR levels reduced significantly in the caudate of LBDs. TSPO density and tau fibrils decreased remarkably in the striatum of LBDs but increased in AD. Oxidative damage, induced by misfolded tau proteins and dopamine metabolism, causes microglia dystrophy or senescence during the late stage of LBDs. Consequently, microglia dysfunction conversely reduces tau propagation. The G allele of the BIN1 gene is a potential risk factor for tauopathy.

CDDO-Me Inhibits Microglial Activation and Monocyte Infiltration by Abrogating NFκB- and p38 MAPK-Mediated Signaling Pathways Following Status Epilepticus

Following status epilepticus (SE, a prolonged seizure activity), microglial activation, and monocyte infiltration result in the inflammatory responses in the brain that is involved in the epileptogenesis. Therefore, the regulation of microglia/monocyte-mediated neuroinflammation is one of the therapeutic strategies for avoidance of secondary brain injury induced by SE. 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid methyl ester (CDDO-Me; RTA 402) is an activator of nuclear factor-erythroid 2-related factor 2 (Nrf2), which regulates intracellular redox homeostasis. In addition, CDDO-Me has anti-inflammatory properties that suppress microglial proliferation and its activation, although the underlying mechanisms have not been clarified. In the present study, CDDO-Me ameliorated monocyte infiltration without vasogenic edema formation in the frontoparietal cortex (FPC) following SE, accompanied by abrogating monocyte chemotactic protein-1 (MCP-1)/tumor necrosis factor-α (TNF-α) expressions and p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation. Furthermore, CDDO-Me inhibited nuclear factor-κB (NFκB)-S276 phosphorylation and microglial transformation, independent of Nrf2 expression. Similar to CDDO-Me, SN50 (an NFκB inhibitor) mitigated monocyte infiltration by reducing MCP-1 and p38 MAPK phosphorylation in the FPC following SE. Therefore, these findings suggest, for the first time, that CDDO-Me may attenuate microglia/monocyte-mediated neuroinflammation via modulating NFκB- and p38 MAPK-MCP-1 signaling pathways following SE.

Pharmacological Targeting of Microglial Activation: New Therapeutic Approach

Mounting evidence suggests that neuroinflammation is not just a consequence but a vital contributor to the development and progression of Parkinson’s disease (PD). Microglia in particular, may contribute to the induction and modulation of inflammation in PD. Upon stimulation, microglia convert into activated phenotypes, which exist along a dynamic continuum and bear different immune properties depending on the disease stage and severity. Activated microglia release various factors involved in neuroinflammation, such as cytokines, chemokines, growth factors, reactive oxygen species (ROS), reactive nitrogen species (RNS), and prostaglandins (PGs). Further, activated microglia interact with other cell types (e.g., neurons, astrocytes and mast cells) and are closely associated with α-synuclein (α-syn) pathophysiology and iron homeostasis disturbance. Taken together, microglial activation and microglia-mediated inflammatory responses play essential roles in the pathogenesis of PD and elucidation of the complexity and imbalance of microglial activation may shed light on novel therapeutic approaches for PD.

Neurotoxicity of pesticides

Pesticides are unique environmental contaminants that are specifically introduced into the environment to control pests, often by killing them. Although pesticide application serves many important purposes, including protection against crop loss and against vector-borne diseases, there are significant concerns over the potential toxic effects of pesticides to non-target organisms, including humans. In many cases, the molecular target of a pesticide is shared by non-target species, leading to the potential for untoward effects. Here, we review the history of pesticide usage and the neurotoxicity of selected classes of pesticides, including insecticides, herbicides, and fungicides, to humans and experimental animals. Specific emphasis is given to linkages between exposure to pesticides and risk of neurological disease and dysfunction in humans coupled with mechanistic findings in humans and animal models. Finally, we discuss emerging techniques and strategies to improve translation from animal models to humans.

Insights From Dynamic Neuro-Immune Imaging on Murine Immune Responses to CNS Damage

Evolving technologies and increasing understanding of human physiology over the past century have afforded our ability to intervene on human diseases using implantable bio-materials. These bio-electronic devices present a unique challenge through the creation of an interface between the native tissue and implantable bio-materials: the generation of host immune response surrounding such devices. While recent developments in cancer immunology seek to stimulate the immune system against cancer, successful long-term application of implantable bio-material devices need to durably minimize reactive immune processes at involved anatomical sites. Peripheral immune system response has been studied extensively for implanted bio-materials at various body sites. Examples include tooth composites (Gitalis et al., 2019), inguinal hernia repair (Heymann et al., 2019), and cardiac stents and pacemaker leads (Slee et al., 2016). Studies have also been extended to less well-studied immune reactivity in response to CNS neural-electronic implant devices. Recent technological advances in 2-Photon Laser Scanning Microscopy (2P-LSM) have allowed novel insights into in vivo immune response in a variety of tissue microenvironments. While imaging of peripheral tissues has provided an abundance of data with regards to immune cell dynamics, central nervous system (CNS) imaging is comparatively complicated by tissue accessibility and manipulation. Despite these challenges, the results of dynamic intravital neuro-immune imaging thus far have provided foundational insights into basic CNS biology. Utilizing a combination of intravital and ex vivo 2P-LSM, we have observed novel pathways allowing immune cells, stromal cells, cancer cells and proteins to communicate between the CNS parenchyma and peripheral vasculature. Similar to what has been reported in the intestinal tract, we have visualized myeloid cells extend dendritic processes across the blood brain barrier (BBB) into pial blood vessels. Furthermore, transient vessel leaks seen during systemic inflammation provide opportunities for cellular protein to be exchanged between the periphery and CNS. These insights provide new, visual information regarding immune surveillance and antigen presentation within the CNS. Furthermore, when combining intravital 2P-LSM and microfluidic devices complexed with mathematical modeling, we are gaining new insights into the intravascular behavior of circulating immune cells. This new knowledge into the basic mechanisms by which cells migrate to and interact with the CNS provide important considerations for the design of neuro-electronic biomaterials that have the potential to connect the peripheral-neural microenvironments into a unique, artificial interface.

Metal Chelation Therapy and Parkinson's Disease: A Critical Review on the Thermodynamics of Complex Formation between Relevant Metal Ions and Promising or Established Drugs

The present review reports a list of approximately 800 compounds which have been used, tested or proposed for Parkinson’s disease (PD) therapy in the year range 2014–2019 (April): name(s), chemical structure and references are given. Among these compounds, approximately 250 have possible or established metal-chelating properties towards Cu(II), Cu(I), Fe(III), Fe(II), Mn(II), and Zn(II), which are considered to be involved in metal dyshomeostasis during PD. Speciation information regarding the complexes formed by these ions and the 250 compounds has been collected or, if not experimentally available, has been estimated from similar molecules. Stoichiometries and stability constants of the complexes have been reported; values of the cologarithm of the concentration of free metal ion at equilibrium (pM), and of the dissociation constant K_d (both computed at pH = 7.4 and at total metal and ligand concentrations of 10⁻⁶ and 10⁻⁵ mol/L, respectively), charge and stoichiometry of the most abundant metal–ligand complexes existing at physiological conditions, have been obtained. A rigorous definition of the reported amounts is given, the possible usefulness of this data is described, and the need to characterize the metal–ligand speciation of PD drugs is underlined.

Retracted Article: PKM2 overexpression protects against 6-hydroxydopamine-induced cell injury in the PC12 cell model of Parkinson's disease via regulation of the brahma-related gene 1/STAT3 pathway

According to published estimates, pyruvate kinase isoform M2 (PKM2) was expressed in low amounts in patients with Parkinson's disease (PD). However, the function and molecular mechanism of PKM2 in PD remain largely unknown. The main purpose of our study was to reveal the function and mechanism of PKM2 in the in vitro model of PD. Here, we show that PKM2 decreased in PC12 cells after 6-hydroxydopamine (6-OHDA) treatment, which inhibited PC12 cell survival and induced its apoptosis. PKM2 overexpression is required for 6-OHDA-induced PC12 cell survival. Moreover, up-regulated PKM2 expression suppressed PC12 cell apoptosis and caspase-3 activity compared with the 6-OHDA treatment alone group. Increased brahma-related gene 1 (Brg1) and p-STAT3 expression was observed in PKM2-overexpressed PC12 cells compared to those in 6-OHDA treated PC12 cells. Further studies suggested that Brg1 knockdown impeded the high expression of p-STAT3, which was induced by PKM2 overexpression. Finally, the STAT3 inhibitor reversed the effects of PKM2 on cell survival and apoptosis in 6-OHDA-induced PC12 cells. Our results suggest that PKM2 was involved in 6-OHDA-induced PC12 cell injury by mediating the Brg1/STAT3 pathway.

According to published estimates, pyruvate kinase isoform M2 (PKM2) was expressed in low amounts in patients with Parkinson's disease (PD) compared with the control health humans.

Zonisamide Administration Improves Fatty Acid β-Oxidation in Parkinson's Disease

Although many experimental studies have shown the favorable effects of zonisamide on mitochondria using models of Parkinson’s disease (PD), the influence of zonisamide on metabolism in PD patients remains unclear. To assess metabolic status under zonisamide treatment in PD, we performed a pilot study using a comprehensive metabolome analysis. Plasma samples were collected for at least one year from 30 patients with PD: 10 without zonisamide medication and 20 with zonisamide medication. We performed comprehensive metabolome analyses of plasma with capillary electrophoresis time-of-flight mass spectrometry and liquid chromatography time-of-flight mass spectrometry. We also measured disease severity using Hoehn and Yahr (H&Y) staging and the Unified Parkinson’s Disease Rating Scale (UPDRS) motor section, and analyzed blood chemistry. In PD with zonisamide treatment, 15 long-chain acylcarnitines (LCACs) tended to be increased, of which four (AC(12:0), AC(12:1)-1, AC(16:1), and AC(16:2)) showed statistical significance. Of these, two LCACs (AC(16:1) and AC(16:2)) were also identified by partial least squares analysis. There was no association of any LCAC with age, disease severity, levodopa daily dose, or levodopa equivalent dose. Because an upregulation of LCACs implies improvement of mitochondrial β-oxidation, zonisamide might be beneficial for mitochondrial β-oxidation, which is suppressed in PD.