The Kinase Fyn As a Novel Intermediate in L-DOPA-Induced Dyskinesia in Parkinson's Disease

Activation of mGlu2/3 receptors in the striatum alleviates L-DOPA-induced dyskinesia and inhibits abnormal postsynaptic molecular expression

Group II metabotropic glutamate receptors (mGlu2/3 receptors) have been regarded as promising candidates for the treatment of L-DOPA-induced dyskinesia (LID); however, confirmation is still lacking. As the hub of the basal ganglia circuit, the striatum plays a critical role in action control. Supersensitive responsiveness of glutamatergic corticostriatal input may be the key mechanism for the development of LID. In this study, we first examined the potency of LY354740 (12 mg/kg, i.p.) in modulating glutamate and dopamine release in lesioned striatum of stable LID rats. Then, we injected LY354740 (20nmoL or 40nmoL in 4 μL of sterile 0.9 % saline) directly into the lesioned striatum to verify its ability to reduce or attenuate L-DOPA-induced abnormal involuntary movements. In experiment conducted in established LID rats, after continuous injection for 4 days, we found that LY354740 significantly reduced the expression of dyskinesia. In another experiment conducted in parkinsonism rat models, we found that LY354740 attenuated the development of LID with an inverted-U dose-response curve. The role of LY354740 in modulating striatal expressions of LID-related molecular changes was also assessed after these behavioral experiments. We found that LY354740 significantly inhibited abnormal expressions of p-Fyn/p-NMDA/p-ERK1/2/p-HistoneH3/ΔFosB, which is in line with its ability to alleviate abnormal involuntary movements in both LID expression and induction phase. Our study indicates that activation of striatal mGlu2/3 receptors can attenuate the development of dyskinesia in parkinsonism rats and provide some functional improvements in LID rats by inhibiting LID-related molecular changes.

Fyn Kinase Activity and Its Role in Neurodegenerative Disease Pathology: a Potential Universal Target?

Fyn is a non-receptor tyrosine kinase belonging to the Src family of kinases (SFKs) which has been implicated in several integral functions throughout the central nervous system (CNS), including myelination and synaptic transmission. More recently, Fyn dysfunction has been associated with pathological processes observed in neurodegenerative diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD). Neurodegenerative diseases are amongst the leading cause of death and disability worldwide and, due to the ageing population, prevalence is predicted to rise in the coming years. Symptoms across neurodegenerative diseases are both debilitating and degenerative in nature and, concerningly, there are currently no disease-modifying therapies to prevent their progression. As such, it is important to identify potential new therapeutic targets. This review will outline the role of Fyn in normal/homeostatic processes, as well as degenerative/pathological mechanisms associated with neurodegenerative diseases, such as demyelination, pathological protein aggregation, neuroinflammation and cognitive dysfunction.

Fyn knockdown prevents levodopa-induced dyskinesia in a mouse model of Parkinson's disease

Dopamine replacement by levodopa is the most widely used therapy for Parkinson's disease (PD), however patients often develop side effects, known as levodopa-induced dyskinesia (LID), that usually need therapeutic intervention. There are no suitable therapeutic options for LID, except for the use of the NMDA receptor antagonist amantadine, which has limited efficacy. The NMDA receptor is indeed the most plausible target to manage LID in PD and recently the kinase Fyn- one of its key regulators- became a new putative molecular target involved in LID. The aim of this work was to reduce Fyn expression to alleviate LID in a mouse model of PD. We performed intra-striatal delivery of a designed micro-RNA against Fyn (miRNA-Fyn) in 6-OHDA-lesioned mice treated with levodopa. The miRNA-Fyn was delivered either before or after levodopa exposure to assess its ability to prevent or revert dyskinesia. Pre-administration of miRNA-Fyn reduced LID with a concomitant reduction of FosB-ΔFosB protein levels -a marker of LID- as well as decreased phosphorylation of the NR2B-NMDA subunit, which is a main target of Fyn. On the other hand, post L-DOPA delivery of miRNA-Fyn was less effective to revert already established dyskinesia, suggesting that early blocking of Fyn activity might be a more efficient therapeutic approach. Together, our results provide proof of concept about Fyn as a plausible therapeutic target to manage LID, and validate RNA silencing as a potential approach to locally reduce striatal Fyn, rising new perspectives for RNA therapy interventions in PD.Significance StatementLevodopa induced dyskinesia (LID) is an incapacitant side effect of treatment in Parkinson's disease (PD). LID is a therapeutic challenge, lacking an effective pharmacological treatment, except for the use of inhibitors of the NMDA receptor, which have limited efficacy and may trigger untoward side effects. The kinase Fyn is a key regulator of NMDA function and a potential therapeutic target to control LID. Here, we show that RNA interference therapy to reduce the amount of Fyn mRNA in the adult brain is effective to prevent LID in a mouse model of PD, setting the grounds for future biomedical interventions to manage LID in PD.

Drug repurposing approach to combating coronavirus: Potential drugs and drug targets

In the past two decades, three highly pathogenic human coronaviruses severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus, and, recently, SARS-CoV-2, have caused pandemics of severe acute respiratory diseases with alarming morbidity and mortality. Due to the lack of specific anti-CoV therapies, the ongoing pandemic of coronavirus disease 2019 (COVID-19) poses a great challenge to clinical management and highlights an urgent need for effective interventions. Drug repurposing is a rapid and feasible strategy to identify effective drugs for combating this deadly infection. In this review, we summarize the therapeutic CoV targets, focus on the existing small molecule drugs that have the potential to be repurposed for existing and emerging CoV infections of the future, and discuss the clinical progress of developing small molecule drugs for COVID-19.

Striatal Dopamine Induced ERK Phosphorylation Is Altered in Mouse Models of Monogenic Dystonia

BACKGROUND

Similar to some monogenic forms of dystonia, levodopa-induced dyskinesia is a hyperkinetic movement disorder with abnormal nigrostriatal dopaminergic neurotransmission. Molecularly, it is characterized by hyper-induction of phosphorylation of extracellular signal-related kinase in response to dopamine in medium spiny neurons of the direct pathway.

OBJECTIVES

The objective of this study was to determine if mouse models of monogenic dystonia exhibit molecular features of levodopa-induced dyskinesia.

METHODS

Western blotting and quantitative immunofluorescence was used to assay baseline and/or dopamine-induced levels of the phosphorylated kinase in the striatum in mouse models of DYT1, DYT6, and DYT25 expressing a reporter in dopamine D1 receptor-expressing projection neurons. Cyclic adenosine monophosphate (cAMP) immunoassay and adenylyl cyclase activity assays were also performed.

RESULTS

In DYT1 and DYT6 models, blocking dopamine reuptake with cocaine leads to enhanced extracellular signal-related kinase phosphorylation in dorsomedial striatal medium spiny neurons in the direct pathway, which is abolished by pretreatment with the N-methyl-d-aspartate antagonist MK-801. Phosphorylation is decreased in a model of DYT25. Levels of basal and stimulated cAMP and adenylyl cyclase activity were normal in the DYT1 and DYT6 mice and decreased in the DYT25 mice. Oxotremorine induced increased abnormal movements in the DYT1 knock-in mice.

CONCLUSIONS

The increased dopamine induction of extracellular signal-related kinase phosphorylation in 2 genetic types of dystonia, similar to what occurs in levodopa-induced dyskinesia, and its decrease in a third, suggests that abnormal signal transduction in response to dopamine in the postsynaptic nigrostriatal pathway might be a point of convergence for dystonia and other hyperkinetic movement disorders, potentially offering common therapeutic targets. © 2021 International Parkinson and Movement Disorder Society.

Inhibitors of Src Family Kinases, Inducible Nitric Oxide Synthase, and NADPH Oxidase as Potential CNS Drug Targets for Neurological Diseases

Neurological diseases share common neuroinflammatory and oxidative stress pathways. Both phenotypic and molecular changes in microglia, astrocytes, and neurons contribute to the progression of disease and present potential targets for disease modification. Src family kinases (SFKs) are present in both neurons and glial cells and are upregulated following neurological insults in both human and animal models. In neurons, SFKs interact with post-synaptic protein domains to mediate hyperexcitability and neurotoxicity. SFKs are upstream of signaling cascades that lead to the modulation of neurotransmitter receptors and the transcription of pro-inflammatory cytokines as well as producers of free radicals through the activation of glia. Inducible nitric oxide synthase (iNOS/NOS-II) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2), the major mediators of reactive nitrogen/oxygen species (RNS/ROS) production in the brain, are also upregulated along with the pro-inflammatory cytokines following neurological insult and contribute to disease progression. Persistent neuronal hyperexcitability, RNS/ROS, and cytokines can exacerbate neurodegeneration, a common pathognomonic feature of the most prevalent neurological disorders such as Alzheimer's disease, Parkinson's disease, and epilepsy. Using a wide variety of preclinical disease models, inhibitors of the SFK-iNOS-NOX2 signaling axis have been tested to cure or modify disease progression. In this review, we discuss the SFK-iNOS-NOX2 signaling pathway and their inhibitors as potential CNS targets for major neurological diseases.

Pivotal Role of Fyn Kinase in Parkinson's Disease and Levodopa-Induced Dyskinesia: a Novel Therapeutic Target?

The exact etiology of Parkinson's disease (PD) remains obscure, although many cellular mechanisms including α-synuclein aggregation, oxidative damage, excessive neuroinflammation, and dopaminergic neuronal apoptosis are implicated in its pathogenesis. There is still no disease-modifying treatment for PD and the gold standard therapy, chronic use of levodopa is usually accompanied by severe side effects, mainly levodopa-induced dyskinesia (LID). Hence, the elucidation of the precise underlying molecular mechanisms is of paramount importance. Fyn is a tyrosine phospho-transferase of the Src family nonreceptor kinases that is highly implicated in immune regulation, cell proliferation and normal brain development. Accumulating preclinical evidence highlights the emerging role of Fyn in key aspects of PD and LID pathogenesis: it may regulate α-synuclein phosphorylation, oxidative stress-induced dopaminergic neuronal death, enhanced neuroinflammation and glutamate excitotoxicity by mediating key signaling pathways, such as BDNF/TrkB, PKCδ, MAPK, AMPK, NF-κB, Nrf2, and NMDAR axes. These findings suggest that therapeutic targeting of Fyn or Fyn-related pathways may represent a novel approach in PD treatment. Saracatinib, a nonselective Fyn inhibitor, has already been tested in clinical trials for Alzheimer's disease, and novel selective Fyn inhibitors are under investigation. In this comprehensive review, we discuss recent evidence on the role of Fyn in the pathogenesis of PD and LID and provide insights on additional Fyn-related molecular mechanisms to be explored in PD and LID pathology that could aid in the development of future Fyn-targeted therapeutic approaches.

Fyn Tyrosine Kinase as Harmonizing Factor in Neuronal Functions and Dysfunctions

Fyn is a non-receptor or cytoplasmatic tyrosine kinase (TK) belonging to the Src family kinases (SFKs) involved in multiple transduction pathways in the central nervous system (CNS) including synaptic transmission, myelination, axon guidance, and oligodendrocyte formation. Almost one hundred years after the original description of Fyn, this protein continues to attract extreme interest because of its multiplicity of actions in the molecular signaling pathways underlying neurodevelopmental as well as neuropathologic events. This review highlights and summarizes the most relevant recent findings pertinent to the role that Fyn exerts in the brain, emphasizing aspects related to neurodevelopment and synaptic plasticity. Fyn is a common factor in healthy and diseased brains that targets different proteins and shapes different transduction signals according to the neurological conditions. We will primarily focus on Fyn-mediated signaling pathways involved in neuronal differentiation and plasticity that have been subjected to considerable attention lately, opening the fascinating scenario to target Fyn TK for the development of potential therapeutic interventions for the treatment of CNS injuries and certain neurodegenerative disorders like Alzheimer’s disease.

Fyn gene silencing reduces oligodendrocytes apoptosis through inhibiting ERK1/2 phosphorylation in epilepsy

This study aimed to investigate the effect of Fyn gene silencing on the apoptosis of oligodendrocytes (OLs) in epileptic model in vitro and the involved mechanism. Primary oligodendrocyte pro-genitor cells (OPCs) were separated from rats and differentiated to OLs. Immunofluorescent labeling showed positive expression of A2B5 in OPCs and Olig2 in OLs, suggesting the successful separation of OPCs and OLs. Three Fyn siRNAs (si-Fyn) and Fyn siRNA negative control (NC) were transfected into OLs. Western blot showed that among three si-Fyn groups, si-Fyn3 caused the lowest Fyn expression, so si-Fyn3 was chosen for following experiment. Cells were divided into four groups: Control, Model, NC and si-Fyn. In the Model group, cells were cultured in Mg-free extracellular fluid for 3 h. The morphology of control cells was normal. However, the migration of neurons, the aggregation of cell bodies and the "grid-like" changes of neural networks were observed in the model cells. OLs apoptosis in various groups was assessed by flow cytometry. Expression of Fyn, ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in OLs of various groups was evaluated by western blot. Compared with the Control group, the apoptotic rates, the Fyn expression and p-ERK1/2/ERK1/2 ratio in the Model and NC groups increased significantly (p < .05). However, the apoptotic rate, the Fyn expression and p-ERK1/2/ERK1/2 ratio in the si-Fyn group were remarkably smaller than those in the Model group (p < .05). In conclusion, Fyn gene silencing reduced the apoptosis of OLs through inhibiting the phosphorylation of ERK1/2 in epileptic model.

Modified Glutamatergic Postsynapse in Neurodegenerative Disorders

The postsynaptic density (PSD) is a complex subcellular domain important for postsynaptic signaling, function, and plasticity. The PSD is present at excitatory synapses and specialized to allow for precise neuron-to-neuron transmission of information. The PSD is localized immediately underneath the postsynaptic membrane forming a major protein network that regulates postsynaptic signaling and synaptic plasticity. Glutamatergic synaptic dysfunction affecting PSD morphology and signaling events have been described in many neurodegenerative disorders, either sporadic or familial forms. Thus, in this review we describe the main protein players forming the PSD and their activity, as well as relevant modifications in key components of the postsynaptic architecture occurring in Huntington's, Parkinson's and Alzheimer's diseases.

Circulating Brain-enriched MicroRNAs for detection and discrimination of idiopathic and genetic Parkinson's disease

BACKGROUND

A minimally invasive test for early detection and monitoring of Parkinson's disease (PD) is a highly unmet need for drug development and planning of patient care. Blood plasma represents an attractive source of biomarkers. MicroRNAs (miRNAs) are conserved noncoding RNA molecules that serve as posttranscriptional regulators of gene expression. As opposed to ubiquitously expressed miRNAs that control house-keeping processes, brain-enriched miRNAs regulate diverse aspects of neuron development and function. These include neuron-subtype specification, axonal growth, dendritic morphogenesis, and spine density. Backed by a large number of studies, we now know that the differential expression of neuron-enriched miRNAs leads to brain dysfunction.

OBJECTIVES

The aim was to identify subsets of brain-enriched miRNAs with diagnostic potential for familial and idiopathic PD as well as specify the molecular pathways deregulated in PD.

METHODS

Initially, brain-enriched miRNAs were selected based on literature review and validation studies in human tissues. Subsequently, real-time reverse transcription polymerase chain reaction was performed in the plasma of 100 healthy controls and 99 idiopathic and 53 genetic (26 alpha-synuclein^A53T and 27 glucocerebrosidase) patients. Statistical and bioinformatics analyses were carried out to pinpoint the diagnostic biomarkers and deregulated pathways, respectively.

RESULTS

An explicit molecular fingerprint for each of the 3 PD cohorts was generated. Although the idiopathic PD fingerprint was different from that of genetic PD, the molecular pathways deregulated converged between all PD subtypes.

CONCLUSIONS

The study provides a group of brain-enriched miRNAs that may be used for the detection and differentiation of PD subtypes. It has also identified the molecular pathways deregulated in PD. © 2019 International Parkinson and Movement Disorder Society.

Acoustic white noise ameliorates reduced regional brain expression of CaMKII and ΔFosB in the spontaneously hypertensive rat model of ADHD

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ΔFosB was reduced in the DL-PFC, DLS and nAc in SH rats.

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Acoustic noise normalized ΔFosB expression in the DL-PFC and nAc of SH rats.

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CaMKII expression was reduced in the TMN in SH rats.

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Acoustic noise increased CaMKII expression in the TMN in both strains.

Loud (≥70dBA) acoustic white noise improves cognitive performance in children with ADHD as well as skilled reach and rotarod performance in the spontaneously hypertensive (SH) rat model of ADHD. To investigate how acoustic noise influences the brain activity in the SH rat model of ADHD, immunohistochemical staining of two neuronal activity and plasticity markers, Ca²⁺/Calmodulin dependent protein kinase II (CaMKII) and ΔFosB, was evaluated in Wistar (n = 24) and SH (n = 16) rats after repeated exposure to acoustic noise or ambient silence. Other SH rats (n = 6) were treated with repeated methylphenidate (MPH). Expression of CaMKII was reduced in the tuberomammillary nucleus (TMN) of the SH rat compared to Wistar but not in the nucleus accumbens (nAc) or the dorsolateral prefrontal cortex (DL-PFC). In the TMN, the expression of CaMKII was increased by noise in both strains. ΔFosB expression was reduced in nAc, DL-PFC and the dorsolateral striatum (DLS) of the SH rat compared to Wistar. Exposure to acoustic white noise significantly increased ΔFosB expression in the nAc and DL-PFC but not in the DLS of SH rats. The results indicate that acoustic noise shifts a reduced neuronal activity in the nAc, TMN and DL-PFC in SH rats toward the normal levels of activity in outbred rats. This may explain why noise has benefit selectively in ADHD.

Tat-Src reduced NR2B tyrosine phosphorylation and its interaction with NR2B in levodopa-induced dyskinetic rats model

Augmented function of N-methyl-d-aspartate receptor subunit 2B (NR2B) and Src protein tyrosine kinase have been demonstrated to get involved in the pathological mechanisms of dyskinesia. In view of functional interactions between NR2B and Src, we investigated the effects of uncoupling NR2B and Src interactions on dyskinesia by using the Src-derived interfering peptide (Tat-Src). In the present study, valid 6-hydroxydopamine-lesioned parkinsonian rats were treated with levodopa intraperitoneally for 22 days to induce dyskinetic rats model. On day 23, dyskinetic rats received either Tat-Src or Tat-sSrc or vehicle with each levodopa dose. The data showed that in dyskinetic rats model intraperitoneal microinjection of Tat-Src improved dyskinetic behaviors and decreased NR2B tyrosine phosphorylation and the interactions of Src with NR2B induced by chronic levodopa treatment. Besides, Tat-Src also attenuated S-nitrosylation (SNO-Src) and the autophosphorylation (p-Src) of Src, which catalyzed NR2B phosphorylation. These findings suggest that targeting NR2B/Src complexes can be one potential treatment for dyskinesia in Parkinson's disease.