Therapeutic Application of Modulators of Endogenous Cannabinoid System in Parkinson's Disease

The endogenous cannabinoid system (ECS) of the brain plays an important role in the molecular pathogenesis of Parkinson's disease (PD). It is involved in the formation of numerous clinical manifestations of the disease by regulating the level of endogenous cannabinoids and changing the activation of cannabinoid receptors (CBRs). Therefore, ECS modulation with new drugs specifically designed for this purpose may be a promising strategy in the treatment of PD. However, fine regulation of the ECS is quite a complex task due to the functional diversity of CBRs in the basal ganglia and other parts of the central nervous system. In this review, the effects of ECS modulators in various experimental models of PD in vivo and in vitro, as well as in patients with PD, are analyzed. Prospects for the development of new cannabinoid drugs for the treatment of motor and non-motor symptoms in PD are presented.

Progress in the development of modulators targeting Frizzleds

The Frizzleds (FZDs) receptors on the cell surface belong to the class F of G protein-coupled receptors (GPCRs) which are the major receptors of WNT protein that mediates the classical WNT signaling pathway and other non-classical pathways. Besides, the FZDs also play a core role in tissue regeneration and tumor occurrence. With the structure and mechanism of FZDs activation becoming clearer, a series of FZDs modulators (inhibitors and agonists) have been developed, with the hope of bringing benefits to the treatment of cancer and degenerative diseases. Most of the FZDs inhibitors (small molecules, antibodies or designed protein inhibitors) block WNT signaling through binding to the cysteine-rich domain (CRD) of FZDs. Several small molecules impede FZDs activation by targeting to the third intracellular domain or the transmembrane domain of FZDs. However, three small molecules (FZM1.8, SAG1.3 and purmorphamine) activate the FZDs through direct interaction with the transmembrane domain. Another type of FZDs agonists are bivalent or tetravalent antibodies which activate the WNT signaling via inducing FZD-LRP5/6 heterodimerization. In this article, we reviewed the FZDs modulators reported in recent years, summarized the critical molecules' discovery processes and the elucidated relevant structural and pharmacological mechanisms. We believe the summaried molecular mechanisms of the relevant modulators could provide important guidance and reference for the future development of FZD modulators.

Dysregulated Wnt and NFAT signaling in a Parkinson's disease LRRK2 G2019S knock-in model

Parkinson's disease (PD) is a progressive late-onset neurodegenerative disease leading to physical and cognitive decline. Mutations of leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of PD. LRRK2 is a complex scaffolding protein with known regulatory roles in multiple molecular pathways. Two prominent examples of LRRK2-modulated pathways are Wingless/Int (Wnt) and nuclear factor of activated T-cells (NFAT) signaling. Both are well described key regulators of immune and nervous system development as well as maturation. The aim of this study was to establish the physiological and pathogenic role of LRRK2 in Wnt and NFAT signaling in the brain, as well as the potential contribution of the non-canonical Wnt/Calcium pathway. In vivo cerebral Wnt and NFATc1 signaling activity was quantified in LRRK2 G2019S mutant knock-in (KI) and LRRK2 knockout (KO) male and female mice with repeated measures over 28 weeks, employing lentiviral luciferase biosensors, and analyzed using a mixed-effect model. To establish spatial resolution, we investigated tissues, and primary neuronal cell cultures from different brain regions combining luciferase signaling activity, immunohistochemistry, qPCR and western blot assays. Results were analyzed by unpaired t-test with Welch's correction or 2-way ANOVA with post hoc corrections. In vivo Wnt signaling activity in LRRK2 KO and LRRK2 G2019S KI mice was increased significantly ~ threefold, with a more pronounced effect in males (~ fourfold) than females (~ twofold). NFATc1 signaling was reduced ~ 0.5-fold in LRRK2 G2019S KI mice. Brain tissue analysis showed region-specific expression changes in Wnt and NFAT signaling components. These effects were predominantly observed at the protein level in the striatum and cerebral cortex of LRRK2 KI mice. Primary neuronal cell culture analysis showed significant genotype-dependent alterations in Wnt and NFATc1 signaling under basal and stimulated conditions. Wnt and NFATc1 signaling was primarily dysregulated in cortical and hippocampal neurons respectively. Our study further built on knowledge of LRRK2 as a Wnt and NFAT signaling protein. We identified complex changes in neuronal models of LRRK2 PD, suggesting a role for mutant LRRK2 in the dysregulation of NFAT, and canonical and non-canonical Wnt signaling.

Unraveling Dysregulated Cell Signaling Pathways, Genetic and Epigenetic Mysteries of Parkinson's Disease

Parkinson's disease (PD) is a prevalent and burdensome neurodegenerative disorder that has been extensively researched to understand its complex etiology, diagnosis, and treatment. The interplay between genetic and environmental factors in PD makes its pathophysiology difficult to comprehend, emphasizing the need for further investigation into genetic and epigenetic markers involved in the disease. Early diagnosis is crucial for optimal management of the disease, and the development of novel diagnostic biomarkers is ongoing. Although many efforts have been made in the field of recognition and interpretation of the mechanisms involved in the pathophysiology of the disease, the current knowledge about PD is just the tip of the iceberg. By scrutinizing genetic and epigenetic patterns underlying PD, new avenues can be opened for dissecting the pathology of the disorder, leading to more precise and efficient diagnostic and therapeutic approaches. This review emphasizes the importance of studying dysregulated cell signaling pathways and molecular processes associated with genes and epigenetic alterations in understanding PD, paving the way for the development of novel therapeutic strategies to combat this devastating disease.

Exploring Heparan Sulfate Proteoglycans as Mediators of Human Mesenchymal Stem Cell Neurogenesis

Alzheimer's disease (AD) and traumatic brain injury (TBI) are major public health issues worldwide, with over 38 million people living with AD and approximately 48 million people (27-69 million) experiencing TBI annually. Neurodegenerative conditions are characterised by the accumulation of neurotoxic amyloid beta (Aβ) and microtubule-associated protein Tau (Tau) with current treatments focused on managing symptoms rather than addressing the underlying cause. Heparan sulfate proteoglycans (HSPGs) are a diverse family of macromolecules that interact with various proteins and ligands and promote neurogenesis, a process where new neural cells are formed from stem cells. The syndecan (SDC) and glypican (GPC) HSPGs have been implicated in AD pathogenesis, acting as drivers of disease, as well as potential therapeutic targets. Human mesenchymal stem cells (hMSCs) provide an attractive therapeutic option for studying and potentially treating neurodegenerative diseases due to their relative ease of isolation and subsequent extensive in vitro expansive potential. Understanding how HSPGs regulate protein aggregation, a key feature of neurodegenerative disorders, is essential to unravelling the underlying disease processes of AD and TBI, as well as any link between these two neurological disorders. Further research may validate HSPG, specifically SDCs or GPCs, use as neurodegenerative disease targets, either via driving hMSC stem cell therapy or direct targeting.

Reduced mastication during growth inhibits cognitive function by affecting trigeminal ganglia and modulating Wnt signaling pathway and ARHGAP33 molecular transmission

Binding of brain-derived neurotrophic factor (BDNF) to its receptor tyrosine kinase B (TrkB) is essential for the development of the hippocampus, which regulates memory and learning. Decreased masticatory stimulation during growth reportedly increases BDNF expression while decreasing TrkB expression in the hippocampus. Increased BDNF expression is associated with Wnt family member 3A (Wnt3a) expression and decreased expression of Rho GTPase Activating Protein 33 (ARHGAP33), which regulates intracellular transport of TrkB. TrkB expression may be decreased at the cell surface and affects the hippocampus via BDNF/TrkB signaling. Mastication affects cerebral blood flow and the neural cascade that occurs through the trigeminal nerve and hippocampus. In the current study, we hypothesized that decreased masticatory stimulation reduces memory/learning in mice due to altered Wnt3a and ARHGAP33 expression, which are related to memory/learning functions in the hippocampus. To test this hypothesis, we fed mice a powdered diet until 14 weeks of age and analyzed the BDNF and TrkB mRNA expression in the right hippocampus using real-time polymerase chain reaction and Wnt3a and ARHGAP33 levels in the left hippocampus using western blotting. Furthermore, we used staining to assess BDNF and TrkB expression in the hippocampus and the number of nerve cells, the average size of each single cell and the area of intercellular spaces of the trigeminal ganglion (TG). We found that decreased masticatory stimulation affected the expression of BDNF, Wnt3a, ARHGAP33, and TrkB proteins in the hippocampus, as well as memory/learning. The experimental group showed significantly decreased numbers of neurons and increased the area of intercellular spaces in the TG. Our findings suggest that reduced masticatory stimulation during growth induces a decline in memory/learning by modulating molecular transmission mechanisms in the hippocampus and TG.

Development of a highly potent and selective degrader of LRRK2

The discovery of disease-modifying therapies for Parkinson's Disease (PD) represents a critical need in neurodegenerative medicine. Genetic mutations in leucine-rich repeat kinase 2 (LRRK2) are risk factors for the development of PD, and some of these mutations have been linked to increased LRRK2 kinase activity and neuronal toxicity in cellular and animal models. Furthermore, LRRK2 function as a scaffolding protein in several pathways has been implicated as a plausible mechanism underlying neurodegeneration caused by LRRK2 mutations. Given that both the kinase activity and scaffolding function of LRRK2 have been linked to neurodegeneration, we developed proteolysis-targeting chimeras (PROTACs) targeting LRRK2. The degrader molecule JH-XII-03-02 (6) displayed high potency and remarkable selectivity for LRKK2 when assessed in a of 468 panel kinases and serves the dual purpose of eliminating both the kinase activity as well as the scaffolding function of LRRK2.

The Molecular Basis of Wnt/β-Catenin Signaling Pathways in Neurodegenerative Diseases

Defective Wnt signaling is found to be associated with various neurodegenerative diseases. In the canonical pathway, the Frizzled receptor (Fzd) and the lipoprotein receptor-related proteins 5/6 (LRP5/LRP6) create a seven-pass transmembrane receptor complex to which the Wnt ligands bind. This interaction causes the tumor suppressor adenomatous polyposis coli gene product (APC), casein kinase 1 (CK1), and GSK-3β (glycogen synthase kinase-3 beta) to be recruited by the scaffold protein Dishevelled (Dvl), which in turn deactivates the β-catenin destruction complex. This inactivation stops the destruction complex from phosphorylating β-catenin. As a result, β-catenin first builds up in the cytoplasm and then migrates into the nucleus, where it binds to the Lef/Tcf transcription factor to activate the transcription of more than 50 Wnt target genes, including those involved in cell growth, survival, differentiation, neurogenesis, and inflammation. The treatments that are currently available for neurodegenerative illnesses are most commonly not curative in nature but are only symptomatic. According to all available research, restoring Wnt/β-catenin signaling in the brains of patients with neurodegenerative disorders, particularly Alzheimer's and Parkinson's disease, would improve the condition of several patients with neurological disorders. The importance of Wnt activators and modulators in patients with such illnesses is to mainly restore rather than overstimulate the Wnt/β-catenin signaling, thereby reestablishing the equilibrium between Wnt-OFF and Wnt-ON states. In this review, we have tried to summarize the significance of the Wnt canonical pathway in the pathophysiology of certain neurodegenerative diseases, such as Alzheimer's disease, cerebral ischemia, Parkinson's disease, Huntington's disease, multiple sclerosis, and other similar diseases, and as to how can it be restored in these patients.

Want of Wnt in Parkinson's disease: Could sFRP disrupt interplay between Nurr1 and Wnt signaling?

Nuclear receptor related 1 (Nurr1) is a transcription factor known to regulate the development and maintenance of midbrain dopaminergic (mDA) neurons. Reports have confirmed that defect or obliteration of Nurr1 results in neurodegeneration and motor function impairment leading to Parkinson's disease (PD). Studies have also indicated that Nurr1 regulates the expression of alpha-synuclein (α-SYN) and mutations in Nurr1 cause α-SYN overexpression, thereby increasing the risk of PD. Nurr1 is modulated via various pathways including Wnt signaling pathway which is known to play an important role in neurogenesis and deregulation of it contributes to PD pathogenesis. Both Wnt/β-catenin dependent and independent pathways are implicated in the activation of Nurr1 and subsequent downregulation of α-SYN. This review highlights the interaction between Nurr1 and Wnt signaling pathways in mDA neuronal development. We further hypothesize how modulation of Wnt signaling pathway by its antagonist, secreted frizzled related proteins (sFRPs) could be a potential route to treat PD.

Genome-wide association study stratified by MAPT haplotypes identifies potential novel loci in Parkinson's disease

Objective

To identify genetic factors that may modify the effects of the MAPT locus in Parkinson's disease (PD).

Methods

We used data from the International Parkinson's Disease Genomics Consortium (IPDGC) and the UK biobank (UKBB). We stratified the IPDGC cohort for carriers of the H1/H1 genotype (PD patients n=8,492 and controls n=6,765) and carriers of the H2 haplotype (with either H1/H2 or H2/H2 genotypes, patients n=4,779 and controls n=4,849) to perform genome-wide association studies (GWASs). Then, we performed replication analyses in the UKBB data. To study the association of rare variants in the new nominated genes, we performed burden analyses in two cohorts (Accelerating Medicines Partnership - Parkinson Disease and UKBB) with a total sample size PD patients n=2,943 and controls n=18,486.

Results

We identified a novel locus associated with PD among MAPT H1/H1 carriers near EMP1 (rs56312722, OR=0.88, 95%CI= 0.84-0.92, p= 1.80E-08), and a novel locus associated with PD among MAPT H2 carriers near VANGL1 (rs11590278, OR=1.69 95%CI=1.40-2.03, p=2.72E-08). Similar analysis of the UKBB data did not replicate these results and rs11590278 near VANGL1 did have similar effect size and direction in carriers of H2 haplotype, albeit not statistically significant (OR= 1.32, 95%CI= 0.94-1.86, p=0.17). Rare EMP1 variants with high CADD scores were associated with PD in the MAPT H2 stratified analysis (p=9.46E-05), mainly driven by the p.V11G variant.

Interpretation

We identified several loci potentially associated with PD stratified by MAPT haplotype and larger replication studies are required to confirm these associations.

From protein biomarkers to proteomics in dementia with Lewy Bodies

Dementia with Lewy Bodies (DLB) is the second most common neurodegenerative dementia. Despite considerable research progress, there remain gaps in our understanding of the pathophysiology and there is no disease-modifying treatment. Proteomics is a powerful tool to elucidate complex biological pathways across heterogenous conditions. This review summarizes the widely used proteomic methods and presents evidence for protein dysregulation in the brain and peripheral tissues in DLB. Proteomics of post-mortem brain tissue shows that DLB shares common features with other dementias, such as synaptic dysfunction, but retains a unique protein signature. Promising diagnostic biomarkers are being identified in cerebrospinal fluid (CSF), blood, and peripheral tissues, such as serum Heart-type fatty acid binding protein. Research is needed to track these changes from the prodromal stage to established dementia, with standardized workflows to ensure replicability. Identifying novel protein targets in causative biological pathways could lead to the development of new targeted therapeutics or the stratification of participants for clinical trials.

Stress Triggers Expression of Bovine Herpesvirus 1 Infected Cell Protein 4 (bICP4) RNA during Early Stages of Reactivation from Latency in Pharyngeal Tonsil

Bovine herpesvirus 1 (BoHV-1), an important pathogen of cattle, establishes lifelong latency in sensory neurons within trigeminal ganglia (TG) after acute infection. The BoHV-1 latency-reactivation cycle, like other alphaherpesvirinae subfamily members, is essential for viral persistence and transmission. Notably, cells within pharyngeal tonsil (PT) also support a quiescent or latent BoHV-1 infection. The synthetic corticosteroid dexamethasone, which mimics the effects of stress, consistently induces BoHV-1 reactivation from latency allowing early stages of viral reactivation to be examined in the natural host. Based on previous studies, we hypothesized that stress-induced cellular factors trigger expression of key viral transcriptional regulatory genes. To explore this hypothesis, RNA-sequencing studies compared viral gene expression in PT during early stages of dexamethasone-induced reactivation from latency. Strikingly, RNA encoding infected cell protein 4 (bICP4), which is translated into an essential viral transcriptional regulatory protein, was detected 30 min after dexamethasone treatment. Ninety minutes after dexamethasone treatment bICP4 and, to a lesser extent, bICP0 RNA were detected in PT. All lytic cycle viral transcripts were detected within 3 h after dexamethasone treatment. Surprisingly, the latency related (LR) gene, the only viral gene abundantly expressed in latently infected TG neurons, was not detected in PT during latency. In TG neurons, bICP0 and the viral tegument protein VP16 are expressed before bICP4 during reactivation, suggesting distinct viral regulatory genes mediate reactivation from latency in PT versus TG neurons. Finally, these studies confirm PT is a biologically relevant site for BoHV-1 latency, reactivation from latency, and virus transmission. IMPORTANCE BoHV-1, a neurotropic herpesvirus, establishes, maintains, and reactivates from latency in neurons. BoHV-1 DNA is also detected in pharyngeal tonsil (PT) from latently infected calves. RNA-sequencing studies revealed the viral infected cell protein 4 (bICP4) RNA was expressed in PT of latently infected calves within 30 min after dexamethasone was used to initiate reactivation. As expected, bICP4 RNA was not detected during latency. All lytic cycle viral genes were expressed within 3 h after dexamethasone treatment. Conversely, bICP0 and the viral tegument protein VP16 are expressed prior to bICP4 in trigeminal ganglionic neurons during reactivation. The viral latency related gene, which is abundantly expressed in latently infected neurons, was not abundantly expressed in PT during latency. These studies provide new evidence PT is a biologically relevant site for BoHV-1 latency and reactivation. Finally, we predict other alphaherpesvirinae subfamily members utilize PT as a site for latency and reactivation.

Multifunctional role of natural products for the treatment of Parkinson's disease: At a glance

Natural substances originating from plants have long been used to treat neurodegenerative disorders (NDs). Parkinson's disease (PD) is a ND. The deterioration and subsequent cognitive impairments of the midbrain nigral dopaminergic neurons distinguish by this characteristic. Various pathogenic mechanisms and critical components have been reported, despite the fact that the origin is unknown, such as protein aggregation, iron buildup, mitochondrial dysfunction, neuroinflammation and oxidative stress. Anti-Parkinson drugs like dopamine (DA) agonists, levodopa, carbidopa, monoamine oxidase type B inhibitors and anticholinergics are used to replace DA in the current treatment model. Surgery is advised in cases where drug therapy is ineffective. Unfortunately, the current conventional treatments for PD have a number of harmful side effects and are expensive. As a result, new therapeutic strategies that control the mechanisms that contribute to neuronal death and dysfunction must be addressed. Natural resources have long been a useful source of possible treatments. PD can be treated with a variety of natural therapies made from medicinal herbs, fruits, and vegetables. In addition to their well-known anti-oxidative and anti-inflammatory capabilities, these natural products also play inhibitory roles in iron buildup, protein misfolding, the maintenance of proteasomal breakdown, mitochondrial homeostasis, and other neuroprotective processes. The goal of this research is to systematically characterize the currently available medications for Parkinson's and their therapeutic effects, which target diverse pathways. Overall, this analysis looks at the kinds of natural things that could be used in the future to treat PD in new ways or as supplements to existing treatments. We looked at the medicinal plants that can be used to treat PD. The use of natural remedies, especially those derived from plants, to treat PD has been on the rise. This article examines the fundamental characteristics of medicinal plants and the bioactive substances found in them that may be utilized to treat PD.

Convergence of signalling pathways in innate immune responses and genetic forms of Parkinson's disease

In recent years progress in molecular biology and genetics have advanced our understanding of neurological disorders and highlighted synergistic relationships with inflammatory and age-related processes. Parkinson's disease (PD) is a common neurodegenerative disorder that is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Increasing extensive evidence supports the contribution of genetic risk variants and inflammation in the pathobiology of this disease. Functional and genetic studies demonstrate an overlap between genes linked to increased risk for PD and autoimmune diseases. Variants identified in loci adjacent to LRRK2, GBA, and HLA establish a crosstalk between the pathobiologies of the two disease spectra. Furthermore, common signalling pathways associated with the pathogenesis of genetic PD are also relevant to inflammatory signaling include MAPK, NF-κB, Wnt and inflammasome signaling. Importantly, post-mortem analyses of brain and cerebrospinal fluid from PD patients show the accumulation of proinflammatory cytokines. In this review we will focus on the principal mechanisms of genetic, inflammatory and age-related risk that intersect in the pathogenesis of PD.

"Reframing" dopamine signaling at the intersection of glial networks in the aged Parkinsonian brain as innate Nrf2/Wnt driver: Therapeutical implications

Dopamine (DA) signaling via G protein‐coupled receptors is a multifunctional neurotransmitter and neuroendocrine–immune modulator. The DA nigrostriatal pathway, which controls the motor coordination, progressively degenerates in Parkinson's disease (PD), a most common neurodegenerative disorder (ND) characterized by a selective, age‐dependent loss of substantia nigra pars compacta (SNpc) neurons, where DA itself is a primary source of oxidative stress and mitochondrial impairment, intersecting astrocyte and microglial inflammatory networks. Importantly, glia acts as a preferential neuroendocrine–immune DA target, in turn, counter‐modulating inflammatory processes. With a major focus on DA intersection within the astrocyte–microglial inflammatory network in PD vulnerability, we herein first summarize the characteristics of DA signaling systems, the propensity of DA neurons to oxidative stress, and glial inflammatory triggers dictating the vulnerability to PD. Reciprocally, DA modulation of astrocytes and microglial reactivity, coupled to the synergic impact of gene–environment interactions, then constitute a further level of control regulating midbrain DA neuron (mDAn) survival/death. Not surprisingly, within this circuitry, DA converges to modulate nuclear factor erythroid 2‐like 2 (Nrf2), the master regulator of cellular defense against oxidative stress and inflammation, and Wingless (Wnt)/β‐catenin signaling, a key pathway for mDAn neurogenesis, neuroprotection, and immunomodulation, adding to the already complex “signaling puzzle,” a novel actor in mDAn–glial regulatory machinery. Here, we propose an autoregulatory feedback system allowing DA to act as an endogenous Nrf2/Wnt innate modulator and trace the importance of DA receptor agonists applied to the clinic as immune modifiers.

Molecular mechanisms of developmental pathways in neurological disorders: a pharmacological and therapeutic review

Developmental signalling pathways such as Wnt/β-catenin, Notch and Sonic hedgehog play a central role in nearly all the stages of neuronal development. The term 'embryonic' might appear to be a misnomer to several people because these pathways are functional during the early stages of embryonic development and adulthood, albeit to a certain degree. Therefore, any aberration in these pathways or their associated components may contribute towards a detrimental outcome in the form of neurological disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and stroke. In the last decade, researchers have extensively studied these pathways to decipher disease-related interactions, which can be used as therapeutic targets to improve outcomes in patients with neurological abnormalities. However, a lot remains to be understood in this domain. Nevertheless, there is strong evidence supporting the fact that embryonic signalling is indeed a crucial mechanism as is manifested by its role in driving memory loss, motor impairments and many other processes after brain trauma. In this review, we explore the key roles of three embryonic pathways in modulating a range of homeostatic processes such as maintaining blood-brain barrier integrity, mitochondrial dynamics and neuroinflammation. In addition, we extensively investigated the effect of these pathways in driving the pathophysiology of a range of disorders such as Alzheimer's, Parkinson's and diabetic neuropathy. The concluding section of the review is dedicated to neurotherapeutics, wherein we identify and list a range of biological molecules and compounds that have shown enormous potential in improving prognosis in patients with these disorders.

Stochastic Epigenetic Mutations Influence Parkinson's Disease Risk, Progression, and Mortality

BACKGROUND

Stochastic epigenetic mutations (SEM) reflect a deviation from normal site-specific methylation patterns. Epigenetic mutation load (EML) captures the accumulation of SEMs across an individual's genome and may reflect dysfunction of the epigenetic maintenance system in response to epigenetic challenges.

OBJECTIVE

We investigate whether EML is associated with PD risk and time to events (i.e., death and motor symptom decline).

METHODS

We employed logistic regression and Cox proportional hazards regression to assess the association between EML and several outcomes. Our analyses are based on 568 PD patients and 238 controls from the Parkinson's disease, Environment and Genes (PEG) study, for whom blood-based methylation data was available.

RESULTS

We found an association for PD onset and EML in all genes (OR = 1.90; 95%CI 1.52-2.37) and PD-related genes (OR = 1.87; 95%CI 1.50-2.32). EML was also associated with time to a minimum score of 35 points on the motor UPDRS exam (OR = 1.28; 95%CI 1.06-1.56) and time to death (OR = 1.29, 95%CI 1.11-1.49). An analysis of PD related genes only revealed five intragenic hotspots of high SEM density associated with PD risk.

CONCLUSION

Our findings suggest an enrichment of methylation dysregulation in PD patients in general and specifically in five PD related genes. EML may also be associated with time to death and motor symptom progression in PD patients.

Nasal obstruction during the growth period modulates the Wnt/β-catenin pathway and brain-derived neurotrophic factor production in association with tyrosine kinase receptor B mRNA reduction in mouse hippocampus

There is accumulating evidence that nasal obstruction induces high‐level brain dysfunction, including memory and learning deficits. We previously demonstrated that unilateral nasal obstruction (UNO) during the growth period increases the expression of brain‐derived neurotrophic factor (BDNF). The expression of BDNF is regulated by the Wnt/β‐Catenin pathway, which is linked to neuronal differentiation, proliferation, and maintenance. However, little is known about whether Wnt3a protein expression could be an index for modulations analyses in the Wnt/β‐Catenin pathway caused by UNO during the growth period. This study aimed to investigate the effects of UNO during the growth period on the Wnt/β‐Catenin pathway in the hippocampus using combined behavioural, biochemical, and histological approaches. Male BALB/C mice were randomly divided into the control (CONT; n = 6) and experimental (UNO; n = 6) groups. Blood oxygen saturation (SpO₂) levels were measured, and a passive avoidance test was performed in mice aged 15 weeks. Brain tissues were subjected to immunohistochemistry, real‐time reverse transcription‐polymerase chain reaction, and western blot analysis. Compared with control mice, UNO mice had lower SpO₂ levels and exhibited memory/learning impairments during behavioural testing. Moreover, Wnt3a protein, BDNF mRNA, and tyrosine kinase receptor B (TrkB) mRNA expression levels were significantly lower in the hippocampus in the UNO group than in the CONT group. Our findings suggested that UNO during the growth period appeared to modulate the hippocampal Wnt/β‐catenin pathway and BDNF production in association with TrkB mRNA reduction, thereby resulting in memory and learning impairments.

Deconstructing the molecular genetics behind the PINK1/Parkin axis in Parkinson’s disease using Drosophila melanogaster as a model organism

Background

Parkinson’s disease (PD) is a multifactorial neurodegenerative disorder marked by the death of nigrostriatal dopaminergic neurons in response to the compounding effects of oxidative stress, mitochondrial dysfunction and protein aggregation. Transgenic Drosophila models have been used extensively to decipher the underlying genetic interactions that exacerbate neural health in PD. Autosomal recessive forms of the disease have been linked to mutations in the serine/threonine kinase PINK1(PTEN-Induced Putative Kinase 1) and E3 ligase Parkin, which function in an axis that is conserved in flies. This review aims to probe the current understanding of PD pathogenesis via the PINK1/Parkin axis while underscoring the importance of several molecular and pharmacologic rescues brought to light through studies in Drosophila.

Main body

Mutations in PINK1 and Parkin have been shown to affect the axonal transport of mitochondria within dopaminergic neurons and perturb the balance between mitochondrial fusion/fission resulting in abnormal mitochondrial morphology. As per studies in flies, ectopic expression of Fwd kinase and Atg-1 to promote fission and mitophagy while suppressing fusion via MUL1 E3 ligase may aid to halt mitochondrial aggregation and prolong the survival of dopaminergic neurons. Furthermore, upregulation of Hsp70/Hsp90 chaperone systems (Trap1, CHIP) to target misfolded mitochondrial respiratory complexes may help to preserve their bioenergetic capacity. Accumulation of reactive oxygen species as a consequence of respiratory complex dysfunction or antioxidant enzyme deficiency further escalates neural death by inducing apoptosis, lipid peroxidation and DNA damage. Fly studies have reported the induction of canonical Wnt signalling to enhance the activity of transcriptional co-activators (PGC1α, FOXO) which induce the expression of antioxidant enzymes. Enhancing the clearance of free radicals via uncoupling proteins (UCP4) has also been reported to ameliorate oxidative stress-induced cell death in PINK1/Parkin mutants.

Conclusion

While these novel mechanisms require validation through mammalian studies, they offer several explanations for the factors propagating dopaminergic death as well as promising insights into the therapeutic importance of transgenic fly models in PD.

Association of AXIN1 With Parkinson's Disease in a Taiwanese Population

Objective

A meta-analysis of locus-based genome-wide association studies recently identified a relationship between AXIN1 and Parkinson’s disease (PD). Few studies of Asian populations, however, have reported such a genetic association. The influences of rs13337493, rs758033, and rs2361988, three PD-associated genetic variants of AXIN1, were investigated in the present study because AXIN1 is related to Wnt/β-catenin signaling.

Methods

A total of 2,418 individuals were enrolled in our Taiwanese cohort for analysis of the genotypic and allelic frequency. Polymerase chain reaction–restriction fragment length polymorphism analysis was employed for rs13337493 genotyping, and the Agena MassARRAY platform (Agena Bioscience, San Diego, CA, USA) was used for rs758033 and rs2361988 genotyping in 672 patients with PD and 392 controls. Taiwan Biobank data of another 1,354 healthy controls were subjected to whole-genome sequencing performed using Illumina platforms at approximately 30× average depth.

Results

Our results revealed that rs758033 {odds ratios [OR] (95% confidence interval [CI]) = 0.267 [0.064, 0.795], p = 0.014} was associated with the risk of PD, and there was a trend toward a protective effect of rs2361988 (OR [95% CI] = 0.296 [0.071, 0.884], p = 0.026) under the recessive model. The TT genotype of rs758033 (OR [95% CI] = 0.271 [0.065, 0.805], p = 0.015) and the CC genotype of rs2361988 (OR [95% CI] = 0.305 [0.073, 0.913], p = 0.031) were less common in the PD group than in the non-PD group.

Conclusion

Our findings indicate that the rs758033 and rs2361988 polymorphisms of AXIN1 may affect the risk of PD in the Taiwanese population.

Natriuretic peptides are neuroprotective on in vitro models of PD and promote dopaminergic differentiation of hiPSCs-derived neurons via the Wnt/β-catenin signaling

Over the last 20 years, the efforts to develop new therapies for Parkinson's disease (PD) have focused not only on the improvement of symptomatic therapy for motor and non-motor symptoms but also on the discovering of the potential causes of PD, in order to develop disease-modifying treatments. The emerging role of dysregulation of the Wnt/β-catenin signaling in the onset and progression of PD, as well as of other neurodegenerative diseases (NDs), renders the targeting of this signaling an attractive therapeutic opportunity for curing this brain disorder. The natriuretic peptides (NPs) atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP), are cardiac and vascular-derived hormones also widely expressed in mammalian CNS, where they seem to participate in numerous brain functions including neural development/differentiation and neuroprotection. We recently demonstrated that ANP affects the Wnt/β-catenin pathway possibly through a Frizzled receptor-mediated mechanism and that it acts as a neuroprotective agent in in vitro models of PD by upregulating this signaling. Here we provide further evidence supporting the therapeutic potential of this class of natriuretic hormones. Specifically, we demonstrate that all the three natriuretic peptides are neuroprotective for SHSY5Y cells and primary cultures of DA neurons from mouse brain, subjected to neurotoxin insult with 6-hydroxydopamine (6-OHDA) for mimicking the neurodegeneration of PD, and these effects are associated with the activation of the Wnt/β-catenin pathway. Moreover, ANP, BNP, CNP are able to improve and accelerate the dopaminergic differentiation and maturation of hiPSCs-derived neural population obtained from two differed healthy donors, concomitantly affecting the canonical Wnt signaling. Our results support the relevance of exogenous ANP, BNP, and CNP as attractive molecules for both neuroprotection and neurorepair in PD, and more in general, in NDs for which aberrant Wnt signaling seems to be the leading pathogenetic mechanism.

In silico comparative analysis of LRRK2 interactomes from brain, kidney and lung

Mutations in LRRK2 are the most frequent cause of familial Parkinson's disease (PD), with common LRRK2 non-coding variants also acting as risk factors for idiopathic PD. Currently, therapeutic agents targeting LRRK2 are undergoing advanced clinical trials in humans, however, it is important to understand the wider implications of LRRK2 targeted treatments given that LRRK2 is expressed in diverse tissues including the brain, kidney and lungs. This presents challenges to treatment in terms of effects on peripheral organ functioning, thus, protein interactors of LRRK2 could be targeted in lieu to optimize therapeutic effects. Herein an in-silico analysis of LRRK2 direct interactors in brain tissue from various brain regionswas conducted along with a comparative analysis of the LRRK2 interactome in the brain, kidney, and lung tissues. This was carried out based on curated protein-protein interaction (PPI) data from protein interaction databases such as HIPPIE, human gene/protein expression databases and Gene ontology (GO) enrichment analysis using Bingo. Seven targets (MAP2K6, MATK, MAPT, PAK6, SH3GL2, CDC42EP3 and CHGB) were found to be viable objectives for LRRK2 based investigations for PD that would have minimal impact on optimal functioning within peripheral organs. Specifically, MAPT, CHGB, PAK6, and SH3GL2 interacted with LRRK2 in the brain and kidney but not in lung tissue whilst LRRK2-MAP2K6 interacted only in the cerebellum and MATK-LRRK2 interaction was absent in kidney tissues. CDC42EP3 expression levels were low in brain tissues compared to kidney/lung. The results of this computational analysis suggest new avenues for experimental investigations towards LRRK2-targeted therapeutics.

Post-translational modifications: Regulators of neurodegenerative proteinopathies

One of the hallmark features in the neurodegenerative disorders (NDDs) is the accumulation of aggregated and/or non-functional protein in the cellular milieu. Post-translational modifications (PTMs) are an essential regulator of non-functional protein aggregation in the pathogenesis of NDDs. Any alteration in the post-translational mechanism and the protein quality control system, for instance, molecular chaperone, ubiquitin-proteasome system, autophagy-lysosomal degradation pathway, enhances the accumulation of misfolded protein, which causes neuronal dysfunction. Post-translational modification plays many roles in protein turnover rate, accumulation of aggregate and can also help in the degradation of disease-causing toxic metabolites. PTMs such as acetylation, glycosylation, phosphorylation, ubiquitination, palmitoylation, SUMOylation, nitration, oxidation, and many others regulate protein homeostasis, which includes protein structure, functions and aggregation propensity. Different studies demonstrated the involvement of PTMs in the regulation of signaling cascades such as PI3K/Akt/GSK3β, MAPK cascade, AMPK pathway, and Wnt signaling pathway in the pathogenesis of NDDs. Further, mounting evidence suggests that targeting different PTMs with small chemical molecules, which acts as an inhibitor or activator, reverse misfolded protein accumulation and thus enhances the neuroprotection. Herein, we briefly discuss the protein aggregation and various domain structures of different proteins involved in the NDDs, indicating critical amino acid residues where PTMs occur. We also describe the implementation and involvement of various PTMs on signaling cascade and cellular processes in NDDs. Lastly, we implement our current understanding of the therapeutic importance of PTMs in neurodegeneration, along with emerging techniques targeting various PTMs.

Expression levels of specific microRNAs are increased after exercise and are associated with cognitive improvement in Parkinson's disease

There is a consensus regarding the efficacy of physical exercise in maintaining or improving human health; however, there are few studies examining the effect of physical exercise on the expression levels of microRNAs (miRNA/miRs) in Parkinson's disease (PD). The aim of the present study was to investigate the effects of an interval training program on a cycle ergometer on the expression levels of miR‑106a‑5p, miR‑103a‑3p and miR‑29a‑3p in serum samples from men with PD. This was a quasi‑experimental study with pre‑ and post‑testing and with a non‑equivalent group design. The participants were selected based on the eligibility criteria and subsequently classified into two groups: Experimental group and control group. The evaluations were performed at the beginning of the study (week 0) and after 8 weeks of the intervention program (week 9). The interval training program was performed on a cycle ergometer for 30 min, three times a week during an 8‑week period. The expression levels of miR‑106a‑5p, miR‑103a‑3p and miR‑29a‑3p in the experimental group were increased after physical exercise and were associated with cognitive improvement in men with PD. However, further studies are required to clarify the potential use of these circulating miRNAs as markers of adaptation to physical exercise. Collectively, the present results indicated that these three miRNAs may be associated with the exercise response and cognitive improvement in men with PD.

From Channels to Canonical Wnt Signaling: A Pathological Perspective

Wnt signaling is an important pathway mainly active during embryonic development and controlling cell proliferation. This regulatory pathway is aberrantly activated in several human diseases. Ion channels are known modulators of several important cellular functions ranging from the tuning of the membrane potential to modulation of intracellular pathways, in particular the influence of ion channels in Wnt signaling regulation has been widely investigated. This review will discuss the known links between ion channels and canonical Wnt signaling, focusing on their possible roles in human metabolic diseases, neurological disorders, and cancer.

Potential role of cannabidiol in Parkinson's disease by targeting the WNT/β-catenin pathway, oxidative stress and inflammation

Parkinson's disease (PD) is a major neurodegenerative disease (ND), presenting a progressive degeneration of the nervous system characterized by a loss of dopamine in the substantia nigra pars compacta. Recent findings have shown that oxidative stress and inflammation play key roles in the development of PD. However, therapies remain uncertain and research for new treatment is of the utmost importance. This review focuses on the potential effects of using cannabidiol (CBD) as a potential therapeutic strategy for the treatment of PD and on some of the presumed mechanisms by which CBD provides its beneficial properties. CBD medication downregulates GSK-3β, the main inhibitor of the WNT/β-catenin pathway. Activation of the WNT/β-catenin could be associated with the control of oxidative stress and inflammation. Future prospective clinical trials should focus on CBD and its multiple interactions in the treatment of PD.

Parkinson's Disease: Potential Actions of Lithium by Targeting the WNT/β-Catenin Pathway, Oxidative Stress, Inflammation and Glutamatergic Pathway

Parkinson's disease (PD) is one of the major neurodegenerative diseases (ND) which presents a progressive neurodegeneration characterized by loss of dopamine in the substantia nigra pars compacta. It is well known that oxidative stress, inflammation and glutamatergic pathway play key roles in the development of PD. However, therapies remain uncertain and research for new treatment is mandatory. This review focuses on the potential effects of lithium, as a potential therapeutic strategy, on PD and some of the presumed mechanisms by which lithium provides its benefit properties. Lithium medication downregulates GSK-3beta, the main inhibitor of the WNT/β-catenin pathway. The stimulation of the WNT/β-catenin could be associated with the control of oxidative stress, inflammation, and glutamatergic pathway. Future prospective clinical trials could focus on lithium and its different and multiple interactions in PD.

Huang Lian Jie Du Tang attenuates paraquat-induced mitophagy in human SH-SY5Y cells: A traditional decoction with a novel therapeutic potential in treating Parkinson's disease

Huang Lian Jie Du Tang (HLJDT) is a traditional Chinese medical decoction for heat-fire clearing and detoxication. Theoretically, the cause of Parkinson's disease (PD) has been attributed to the dysregulations of internal wind, phlegm, fire, and stasis. Thus, HLJDT has been used to treat PD. However, the molecular mechanism is unknown. Besides, paraquat (PQ) as an herbicide has been known to impair midbrain dopaminergic neurons, resemblance to the pathology of PD. Thus, the molecular mechanism of HLJDT in treating PD and PQ-induced in vitro PD model was investigated in this study. Primarily, the dose-response of PQ (0.1∼1 mM)-induced neurotoxicity for 24 h was performed in the human neuroblastoma SH-SY5Y cells. The LD₅₀ of PQ is around 0.3 mM and was applied throughout the following experiments. The neutral red assay was used to estimate cell viability. Co-transfection of the mitochondrial marker and proapoptotic factor genes were applied to measure the release of mitochondrial proapoptotic factors during PQ intoxication and HLJDT protection. The fluorescent dyes were used to detect mitochondrial membrane potential and free radical formation. Western blot and dot-blot analysis and immunocytochemistry were used to estimate the level of proteins related to apoptosis and mitophagy. PINK1 gene silencing was used to determine the significance of mitophagy during PQ intoxication. In this study, HLJDT attenuated PQ-induced apoptosis in SH-SY5Y cells. HLJDT reversed PQ-induced decreased mitochondrial membrane potential and suppressed PQ-induced increased cytosolic and mitochondrial free radical formations and mitochondrial proapoptotic factor releases. Furthermore, HLJDT mitigated PQ-induced increases in full-length PINK1, phosphorylations of Parkin and ubiquitin, mitochondrial translocation of phosphorylated Parkin, and mitophagy. PINK1 gene silencing attenuated PQ-induced neurotoxicity. Therefore, HLJDT attenuated PQ-induced cell death by regulating mitophagy.

Role of RhoA-ROCK signaling in Parkinson's disease

Parkinson's disease (PD) is a complex and widespread neurodegenerative disease characterized by depletion of midbrain dopaminergic (DA) neurons. Key issues are the development of therapies that can stop or reverse the disease progression, identification of dependable biomarkers, and better understanding of the pathophysiological mechanisms of PD. RhoA-ROCK signals appear to have an important role in PD symptoms, making it a possible approach for PD treatment strategies. Activation of RhoA-ROCK (Rho-associated coiled-coil containing protein kinase) appears to stimulate various PD risk factors including aggregation of alpha-synuclein (αSyn), dysregulation of autophagy, and activation of apoptosis. This manuscript reviews current updates about the biology and function of the RhoA-ROCK pathway and discusses the possible role of this signaling pathway in causing the pathogenesis of PD. We conclude that inhibition of the RhoA-ROCK signaling pathway may have high translational potential and could be a promising therapeutic target in PD.

Parkinson's Disease Master Regulators on Substantia Nigra and Frontal Cortex and Their Use for Drug Repositioning

Parkinson's disease (PD) is among the most prevalent neurodegenerative diseases. Available evidences support the view of PD as a complex disease, being the outcome of interactions between genetic and environmental factors. In face of diagnosis and therapy challenges, and the elusive PD etiology, the use of alternative methodological approaches for the elucidation of the disease pathophysiological mechanisms and proposal of novel potential therapeutic interventions has become increasingly necessary. In the present study, we first reconstructed the transcriptional regulatory networks (TN), centered on transcription factors (TF), of two brain regions affected in PD, the substantia nigra pars compacta (SNc) and the frontal cortex (FCtx). Then, we used case-control studies data from these regions to identify TFs working as master regulators (MR) of the disease, based on region-specific TNs. Twenty-nine regulatory units enriched with differentially expressed genes were identified for the SNc, and twenty for the FCtx, all of which were considered MR candidates for PD. Three consensus MR candidates were found for SNc and FCtx, namely ATF2, SLC30A9, and ZFP69B. In order to search for novel potential therapeutic interventions, we used these consensus MR candidate signatures as input to the Connectivity Map (CMap), a computational drug repositioning webtool. This analysis resulted in the identification of four drugs that reverse the expression pattern of all three MR consensus simultaneously, benperidol, harmaline, tubocurarine chloride, and vorinostat, thus suggested as novel potential PD therapeutic interventions.

Nature-derived compounds modulating Wnt/ -catenin pathway: a preventive and therapeutic opportunity in neoplastic diseases

The Wnt/β-catenin signaling is a conserved pathway that has a crucial role in embryonic and adult life. Dysregulation of the Wnt/β-catenin pathway has been associated with diseases including cancer, and components of the signaling have been proposed as innovative therapeutic targets, mainly for cancer therapy. The attention of the worldwide researchers paid to this issue is increasing, also in view of the therapeutic potential of these agents in diseases, such as Parkinson's disease (PD), for which no cure is existing today. Much evidence indicates that abnormal Wnt/β-catenin signaling is involved in tumor immunology and the targeting of Wnt/β-catenin pathway has been also proposed as an attractive strategy to potentiate cancer immunotherapy. During the last decade, several products, including naturally occurring dietary agents as well as a wide variety of products from plant sources, including curcumin, quercetin, berberin, and ginsenosides, have been identified as potent modulators of the Wnt/β-catenin signaling and have gained interest as promising candidates for the development of chemopreventive or therapeutic drugs for cancer. In this review we make an overview of the nature-derived compounds reported to have antitumor activity by modulating the Wnt/β-catenin signaling, also focusing on extraction methods, chemical features, and bio-activity assays used for the screening of these compounds.

Molecular insights into therapeutic promise of targeting of Wnt/β-catenin signaling pathway in obesity

Obesity is a curable disorder which is a global health concern, linked to an excess amount of fat. It is caused by inherited and environmental factors and can be grim to maintain through dieting only. The importance of peculiar Wnt/β-catenin signaling has directed considerable efforts in the future production of therapeutic approaches in metabolic complications, including obesity. The article aims to examine the prospects of Wnt/β-catenin signaling cascade in obesity via directing effects of Wnt/β-catenin cascade in regulating appetite. A deep research on the literature available to date, for Wnt/β-catenin cascade in obesity is conducted using various medical databases like PubMed, MEDLINE from the internet. The articles published in English language were mainly preferred. Obesity has developed endemic worldwide, which initiates various obesity-related comorbidities. Obesity is implied by excessive deposition of fat primarily in the adipose tissue. Numerous studies have shown the vital impact of the Wnt/β-catenin signaling pathway in the growth of body part and biological homeostasis, while latent data illustrate the inherited variations in the Wnt/β-catenin cascade, correlating to several complications. The current article enlightens the stimulation of the Wnt/β-catenin cascade in obesity, mainly depot-explicit impact among adipose tissue during high caloric intake regulation and WAT browning event. Taken all together these data illustrate Wnt/β-catenin signaling cascade subsidizes to obesity promoted insulin resistance independent proliferation of adipose tissue.

Nrf2/Wnt resilience orchestrates rejuvenation of glia-neuron dialogue in Parkinson's disease

Oxidative stress and inflammation have long been recognized to contribute to Parkinson's disease (PD), a common movement disorder characterized by the selective loss of midbrain dopaminergic neurons (mDAn) of the substantia nigra pars compacta (SNpc). The causes and mechanisms still remain elusive, but a complex interplay between several genes and a number of interconnected environmental factors, are chiefly involved in mDAn demise, as they intersect the key cellular functions affected in PD, such as the inflammatory response, mitochondrial, lysosomal, proteosomal and autophagic functions. Nuclear factor erythroid 2 -like 2 (NFE2L2/Nrf2), the master regulator of cellular defense against oxidative stress and inflammation, and Wingless (Wnt)/β-catenin signaling cascade, a vital pathway for mDAn neurogenesis and neuroprotection, emerge as critical intertwinned actors in mDAn physiopathology, as a decline of an Nrf2/Wnt/β-catenin prosurvival axis with age underlying PD mutations and a variety of noxious environmental exposures drive PD neurodegeneration. Unexpectedly, astrocytes, the so-called "star-shaped" cells, harbouring an arsenal of "beneficial" and "harmful" molecules represent the turning point in the physiopathological and therapeutical scenario of PD. Fascinatingly, "astrocyte's fil rouge" brings back to Nrf2/Wnt resilience, as boosting the Nrf2/Wnt resilience program rejuvenates astrocytes, in turn (i) mitigating nigrostriatal degeneration of aged mice, (ii) reactivating neural stem progenitor cell proliferation and neuron differentiation in the brain and (iii) promoting a beneficial immunomodulation via bidirectional communication with mDAns. Then, through resilience of Nrf2/Wnt/β-catenin anti-ageing, prosurvival and proregenerative molecular programs, it seems possible to boost the inherent endogenous self-repair mechanisms. Here, the cellular and molecular aspects as well as the therapeutical options for rejuvenating glia-neuron dialogue will be discussed together with major glial-derived mechanisms and therapies that will be fundamental to the identification of novel diagnostic tools and treatments for neurodegenerative diseases (NDs), to fight ageing and nigrostriatal DAergic degeneration and promote functional recovery.

Protective role of anticancer drugs in neurodegenerative disorders: A drug repurposing approach

The disease heterogeneity and little therapeutic progress in neurodegenerative diseases justify the need for novel and effective drug discovery approaches. Drug repurposing is an emerging approach that reinvigorates the classical drug discovery method by divulging new therapeutic uses of existing drugs. The common biological background and inverse tuning between cancer and neurodegeneration give weight to the conceptualization of repurposing of anticancer drugs as novel therapeutics. Many studies are available in the literature, which highlights the success story of anticancer drugs as repurposed therapeutics. Among them, kinase inhibitors, developed for various oncology indications evinced notable neuroprotective effects in neurodegenerative diseases. In this review, we shed light on the salient role of multiple protein kinases in neurodegenerative disorders. We also proposed a feasible explanation of the action of kinase inhibitors in neurodegenerative disorders with more attention towards neurodegenerative disorders. The problem of neurotoxicity associated with some anticancer drugs is also highlighted. Our review encourages further research to better encode the hidden potential of anticancer drugs with the aim of developing prospective repurposed drugs with no toxicity for neurodegenerative disorders.

β-Catenin and TCFs/LEF signaling discordantly regulate IL-6 expression in astrocytes

Background

The Wnt/β-catenin signaling pathway is a prolific regulator of cell-to-cell communication and gene expression. Canonical Wnt/β-catenin signaling involves partnering of β-catenin with members of the TCF/LEF family of transcription factors (TCF1, TCF3, TCF4, LEF1) to regulate gene expression. IL-6 is a key cytokine involved in inflammation and is particularly a hallmark of inflammation in the brain. Astrocytes, specialized glial cells in the brain, secrete IL-6. How astrocytes regulate IL-6 expression is not entirely clear, although in other cells NFκB and C/EBP pathways play a role. We evaluated here the interface between β-catenin, TCFs/LEF and C/EBP and NF-κB in relation to IL-6 gene regulation in astrocytes.

Methods

We performed molecular loss and/or gain of function studies of β-catenin, TCF/LEF, NFκB, and C/EBP to assess IL-6 regulation in human astrocytes. Specifically, siRNA mediated target gene knockdown, cDNA over expression of target gene, and pharmacological agents for regulation of target proteins were used. IL-6 levels was evaluated by real time quantitative PCR and ELISA. We also cloned the IL-6 promoter under a firefly luciferase reporter and used bioinformatics, site directed mutagenesis, and chromatin immunoprecipitation to probe the interaction between β-catenin/TCFs/LEFs and IL-6 promoter activity.

Results

β-catenin binds to TCF/LEF to inhibits IL-6 while TCFs/LEF induce IL-6 transcription through interaction with ATF-2/SMADs. β-catenin independent of TCFs/LEF positively regulates C/EBP and NF-κB, which in turn activate IL-6 expression. The IL-6 promoter has two putative regions for TCFs/LEF binding, a proximal site located at -91 nt and a distal site at -948 nt from the transcription start site, both required for TCF/LEF induction of IL-6 independent of β-catenin.

Conclusion

IL-6 regulation in human astrocytes engages a discordant interaction between β-catenin and TCF/LEF. These findings are intriguing given that no role for β-catenin nor TCFs/LEF to date is associated with IL-6 regulation and suggest that β-catenin expression in astrocytes is a critical regulator of anti-inflammatory responses and its disruption can potentially mediate persistent neuroinflammation.

The Role of the Gastrointestinal Mucus System in Intestinal Homeostasis: Implications for Neurological Disorders

Mucus is integral to gut health and its properties may be affected in neurological disease. Mucus comprises a hydrated network of polymers including glycosylated mucin proteins. We propose that factors that influence the nervous system may also affect the volume, viscosity, porosity of mucus composition and subsequently, gastrointestinal (GI) microbial populations. The gut has its own intrinsic neuronal network, the enteric nervous system, which extends the length of the GI tract and innervates the mucosal epithelium. The ENS regulates gut function including mucus secretion and renewal. Both dysbiosis and gut dysfunction are commonly reported in several neurological disorders such as Parkinson's and Alzheimer's disease as well in patients with neurodevelopmental disorders including autism. Since some microbes use mucus as a prominent energy source, changes in mucus properties could alter, and even exacerbate, dysbiosis-related gut symptoms in neurological disorders. This review summarizes existing knowledge of the structure and function of the mucus of the GI tract and highlights areas to be addressed in future research to better understand how intestinal homeostasis is impacted in neurological disorders.

Targeting the Wnt/β-catenin pathway in neurodegenerative diseases: recent approaches and current challenges

INTRODUCTION

Wnt/β-catenin signaling is an evolutionarily conserved pathway having a crucial role in embryonic and adult life. Specifically, the Wnt/β-catenin axis is pivotal to the development and homeostasis of the nervous system, and its dysregulation has been associated with various neurological disorders, including neurodegenerative diseases. Therefore, this signaling pathway has been proposed as a potential therapeutic target against neurodegeneration.

AREAS COVERED

This review focuses on the role of Wnt/β-catenin pathway in the pathogenesis of neurodegenerative diseases, including Parkinson's, Alzheimer's Diseases and Amyotrophic Lateral Sclerosis. The evidence showing that defects in the signaling might be involved in the development of these diseases, and the pharmacological approaches tested so far, are discussed. The possibilities that this pathway offers in terms of new therapeutic opportunities are also considered.

EXPERT OPINION

The increasing interest paid to the role of Wnt/β-catenin pathway in the onset of neurodegenerative diseases demonstrates how targeting this signaling for therapeutic purposes could be a great opportunity for both neuroprotection and neurorepair. Without overlooking some licit concerns about drug safety and delivery to the brain, there is growing and more convincing evidence that restoring this signaling in neurodegenerative diseases may strongly increase the chance to develop disease-modifying treatments for these brain pathologies.

Glucose, glycolysis, and neurodegenerative diseases

Prolonged survival of a typical postmitotic neuron hinges on a balance between multiple processes, among these are a sustenance of ATP production and protection against reactive oxygen species. In neuropathological conditions, mitochondrial defects often lead to both a drop in ATP levels, as well as increase reactive oxygen species production from inefficient electron transport processes and NADPH-oxidases activities. The former often resulted in the phenomenon of compensatory aerobic glycolysis. The latter stretches the capacity of the cell's redox buffering capacity, and may lead to damages of key enzymes involved in energy metabolism. Several recent reports have indicated that enhancing glucose availability and uptake, as well as increasing glycolytic flux via pharmacological or genetic manipulation of glycolytic enzymes, could be protective in animal models of several major neurodegenerative diseases, including Parkinson's disease, Huntington's disease, and Amyotrophic lateral sclerosis. Activation of canonical Wnt signaling, which improves disease symptoms in mouse models of Alzheimer's disease also appears to work via an elevation of glycolytic enzymes and enhance glucose metabolism. Here, I discuss these findings and the possible underlying mechanisms of how an increase in glucose uptake and glycolysis could be neuroprotective. Increased glycolytic production of ATP would help alleviate energy deficiency, and ATP's hydrotropic effect may enhance solubility and clearance of toxic aggregates prevalent in many neurodegenerative diseases. Furthermore, channeling of glucose into the Pentose Phosphate Pathway would increase the redox buffering capacity of the cell.

Herpes simplex virus 1 regulates β-catenin expression in TG neurons during the latency-reactivation cycle

When herpes simplex virus 1 (HSV-1) infection is initiated in the ocular, nasal, or oral cavity, sensory neurons within trigeminal ganglia (TG) become infected. Following a burst of viral transcription in TG neurons, lytic cycle viral genes are suppressed and latency is established. The latency-associated transcript (LAT) is the only viral gene abundantly expressed during latency, and LAT expression is important for the latency-reactivation cycle. Reactivation from latency is required for virus transmission and recurrent disease, including encephalitis. The Wnt/β-catenin signaling pathway is differentially expressed in TG during the bovine herpesvirus 1 latency-reactivation cycle. Hence, we hypothesized HSV-1 regulates the Wnt/β-catenin pathway and promotes maintenance of latency because this pathway enhances neuronal survival and axonal repair. New studies revealed β-catenin was expressed in significantly more TG neurons during latency compared to TG from uninfected mice or mice latently infected with a LAT-/- mutant virus. When TG explants were incubated with media containing dexamethasone to stimulate reactivation, significantly fewer β-catenin+ TG neurons were detected. Conversely, TG explants from uninfected mice or mice latently infected with a LAT-/- mutant increased the number of β-catenin+ TG neurons in the presence of DEX relative to samples not treated with DEX. Impairing Wnt signaling with small molecule antagonists reduced virus shedding during explant-induced reactivation. These studies suggested β-catenin was differentially expressed during the latency-reactivation cycle, in part due to LAT expression.

Boosting Antioxidant Self-defenses by Grafting Astrocytes Rejuvenates the Aged Microenvironment and Mitigates Nigrostriatal Toxicity in Parkinsonian Brain via an Nrf2-Driven Wnt/β-Catenin Prosurvival Axis

Astrocyte (As) bidirectional dialog with neurons plays a fundamental role in major homeostatic brain functions, particularly providing metabolic support and antioxidant self-defense against reactive oxygen (ROS) and nitrogen species (RNS) via the activation of NF-E2-related factor 2 (Nrf2), a master regulator of oxidative stress. Disruption of As-neuron crosstalk is chiefly involved in neuronal degeneration observed in Parkinson's disease (PD), the most common movement disorder characterized by the selective degeneration of dopaminergic (DAergic) cell bodies of the substantia nigra (SN) pars compacta (SNpc). Ventral midbrain (VM)-As are recognized to exert an important role in DAergic neuroprotection via the expression of a variety of factors, including wingless-related MMTV integration site 1 (Wnt1), a principal player in DAergic neurogenesis. However, whether As, by themselves, might fulfill the role of chief players in DAergic neurorestoration of aged PD mice is presently unresolved. Here, we used primary postnatal mouse VM-As as a graft source for unilateral transplantation above the SN of aged 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice after the onset of motor symptoms. Spatio-temporal analyses documented that the engrafted cells promoted: (i) a time-dependent nigrostriatal rescue along with increased high-affinity synaptosomal DA uptake and counteraction of motor deficit, as compared to mock-grafted counterparts; and (ii) a restoration of the impaired microenvironment via upregulation of As antioxidant self-defense through the activation of Nrf2/Wnt/β-catenin signaling, suggesting that grafting As has the potential to switch the SN neurorescue-unfriendly environment to a beneficial antioxidant/anti-inflammatory prosurvival milieu. These findings highlight As-derived factors/mechanisms as the crucial key for successful therapeutic outcomes in PD.

LRRK2 Biology from structure to dysfunction: research progresses, but the themes remain the same

Since the discovery of leucine-rich repeat kinase 2 (LRRK2) as a protein that is likely central to the aetiology of Parkinson’s disease, a considerable amount of work has gone into uncovering its basic cellular function. This effort has led to the implication of LRRK2 in a bewildering range of cell biological processes and pathways, and probable roles in a number of seemingly unrelated medical conditions. In this review we summarise current knowledge of the basic biochemistry and cellular function of LRRK2. Topics covered include the identification of phosphorylation substrates of LRRK2 kinase activity, in particular Rab proteins, and advances in understanding the activation of LRRK2 kinase activity via dimerisation and association with membranes, especially via interaction with Rab29. We also discuss biochemical studies that shed light on the complex LRRK2 GTPase activity, evidence of roles for LRRK2 in a range of cell signalling pathways that are likely cell type specific, and studies linking LRRK2 to the cell biology of organelles. The latter includes the involvement of LRRK2 in autophagy, endocytosis, and processes at the trans-Golgi network, the endoplasmic reticulum and also key microtubule-based cellular structures. We further propose a mechanism linking LRRK2 dimerisation, GTPase function and membrane recruitment with LRRK2 kinase activation by Rab29. Together these data paint a picture of a research field that in many ways is moving forward with great momentum, but in other ways has not changed fundamentally. Many key advances have been made, but very often they seem to lead back to the same places.

Axin Family of Scaffolding Proteins in Development: Lessons from C. elegans

Scaffold proteins serve important roles in cellular signaling by integrating inputs from multiple signaling molecules to regulate downstream effectors that, in turn, carry out specific biological functions. One such protein, Axin, represents a major evolutionarily conserved scaffold protein in metazoans that participates in the WNT pathway and other pathways to regulate diverse cellular processes. This review summarizes the vast amount of literature on the regulation and functions of the Axin family of genes in eukaryotes, with a specific focus on Caenorhabditis elegans development. By combining early studies with recent findings, the review is aimed to serve as an updated reference for the roles of Axin in C. elegans and other model systems.

High lithium levels in tobacco may account for reduced incidences of both Parkinson's disease and melanoma in smokers through enhanced β-catenin-mediated activity

Parkinson's disease (PD) patients have higher rates of melanoma and vice versa, observations suggesting that the two conditions may share common pathogenic pathways. β-Catenin is a transcriptional cofactor that, when concentrated in the nucleus, upregulates the expression of canonical Wnt target genes, such as Nurr1, many of which are important for neuronal survival. β-Catenin-mediated activity is decreased in sporadic PD as well as in leucine-rich repeat kinase 2 (LRRK2) and β-glucosidase (GBA) mutation cellular models of PD, which is the most common genetic cause of and risk for PD, respectively. In addition, β-catenin expression is significantly decreased in more aggressive and metastatic melanoma. Multiple observational studies have shown smokers to have significantly lower rates of PD as well as melanoma implying that tobacco may contain one or more elements that protect against both conditions. In support, smoker's brains have significantly reduced levels of α-synuclein, a pathological intracellular protein found in PD brain and melanoma cells. Tobacco contains very high lithium levels compared to other plants. Lithium has a broad array of neuroprotective actions, including enhancing autophagy and reducing intracellular α-synuclein levels, and is effective in both neurotoxin and transgenic preclinical PD models. One of lithium's neuroprotective actions is enhancement of β-catenin-mediated activity leading to increased Nurr1 expression through its ability to inhibit glycogen synthase kinase-3 β (GSK-3β). Lithium also has anti-proliferative effects on melanoma cells and the clinical use of lithium is associated with a reduced incidence of melanoma as well as reduced melanoma-associated mortality. This is the first known report hypothesizing that inhaled lithium from smoking may account for the associated reduced rates of both PD and melanoma and that this protection may be mediated, in part, through lithium-induced GSK-3β inhibition and consequent enhanced β-catenin-mediated activity. This hypothesis could be directly tested in clinical trials assessing lithium therapy's ability to affect β-catenin-mediated activity and slow disease progression in patients with PD or melanoma.

Targeting kinases in Parkinson's disease: A mechanism shared by LRRK2, neurotrophins, exenatide, urate, nilotinib and lithium

Several kinases have been implicated in the pathogenesis of Parkinson's disease (PD), most notably leucine-rich repeat kinase 2 (LRRK2), as LRRK2 mutations are the most common genetic cause of a late-onset parkinsonism that is clinically indistinguishable from sporadic PD. More recently, several other kinases have emerged as promising disease-modifying targets in PD based on both preclinical studies and clinical reports on exenatide, the urate precursor inosine, nilotinib and lithium use in PD patients. These kinases include protein kinase B (Akt), glycogen synthase kinases-3β and -3α (GSK-3β and GSK-3α), c-Abelson kinase (c-Abl) and cyclin-dependent kinase 5 (cdk5). Activities of each of these kinases are involved either directly or indirectly in phosphorylating tau or increasing α-synuclein levels, intracellular proteins whose toxic oligomeric forms are strongly implicated in the pathogenesis of PD. GSK-3β, GSK-3α and cdk5 are the principle kinases involved in phosphorylating tau at sites critical for the formation of tau oligomers. Exenatide analogues, urate, nilotinib and lithium have been shown to affect one or more of the above kinases, actions that can decrease the formation and increase the clearance of intraneuronal phosphorylated tau and α-synuclein. Here we review the current preclinical and clinical evidence supporting kinase-targeting agents as potential disease-modifying therapies for PD patients enriched with these therapeutic targets and incorporate LRRK2 physiology into this novel model.

Silica nanoparticle-exposure during neuronal differentiation modulates dopaminergic and cholinergic phenotypes in SH-SY5Y cells

BACKGROUND

Silica-ε-polycaprolactone-nanoparticles (SiPCL-NPs) represent a promising tool for laser-tissue soldering in the brain. After release of the SiPCL-NPs in the brain, neuronal differentiation might be modulated. The present study was performed to determine effects of SiPCL-NP-exposure at different stages of neuronal differentiation in neuron-like SH-SY5Y cells. The resulting phenotypes were analyzed quantitatively and signaling pathways involved in neuronal differentiation and degeneration were studied. SH-SY5Y cells were differentiated with all-trans retinoic acid or staurosporine to obtain predominantly cholinergic or dopaminergic neurons. The resulting phenotype was analyzed at the end of differentiation with and without the SiPCL-NPs given at various times during differentiation.

RESULTS

Exposure to SiPCL-NPs before and during differentiation led to a decreased cell viability of SH-SY5Y cells depending on the differentiation protocol used. SiPCL-NPs co-localized with the neuronal marker β-3-tubulin but did not alter the morphology of these cells. A significant decrease in the number of tyrosine hydroxylase (TH) immunoreactive neurons was found in staurosporine-differentiated cells when SiPCL-NPs were added at the end of the differentiation. TH-protein expression was also significantly downregulated when SiPCL-NPs were applied in the middle of differentiation. Protein expression of the marker for the dopamine active transporter (DAT) was not affected by SiPCL-NPs. SiPCL-NP-exposure predominantly decreased the expression of the high-affinity choline transporter 1 (CHT1) when the NPs were given before the differentiation. Pathways involved in neuronal differentiation, namely Akt, MAP-K, MAP-2 and the neurodegeneration-related markers β-catenin and GSK-3β were not altered by NP-exposure.

CONCLUSIONS

The decrease in the number of dopaminergic and cholinergic cells may implicate neuronal dysfunction, but the data do not provide evidence that pathways relevant for differentiation and related to neurodegeneration are impaired.

Regulation of Wnt signaling by physical exercise in the cell biological processes of the locomotor system

In the past decade, researches on Wnt signaling in cell biology have made remarkable progress regarding our understanding of embryonic development, bone formation, muscle injury and repair, neurogenesis, and tumorigenesis. The study also showed that physical activity can reverse age-dependent decline in skeletal muscle, preventing osteoporosis, regenerative neurogenesis, hippocampal function, cognitive ability, and neuromuscular junction formation, and the age-dependent recession is highly correlated with Wnt signaling pathways. However, how the biological processes in cell and physical activity during/following exercise affect the Wnt signaling path of the locomotor system is largely unknown. In this study, we first briefly introduce the important features of the cellular biological processes of exercise in the locomotor system. Then, we discuss Wnt signaling and review the very few studies that have examined Wnt signaling pathways in cellular biological processes of the locomotor system during physical exercise.

Protective mechanism of Wnt4 gene on Parkinson's disease (PD) transgenic Drosophila

OBJECTIVE

The main pathological change of Parkinson's disease (PD) is progressive degeneration and necrosis of dopaminergic neurons in the midbrain, forming a Lewy body in many of the remaining neurons. Studies have found that in transgenic Drosophila, mutations in the PTEN-inducible kinase 1 (PINK1) gene may cause indirect flight muscle defects in Drosophila, and mitochondrial structural dysfunction as well.

METHODS

In this study, Wnt4 gene overexpression and knockdown were performed in PINK1 mutant PD transgenic Drosophila, and the protective effect of Wnt4 gene on PD transgenic Drosophila and its possible mechanism were explored. The Wnt4 gene was screened in the previous experiment; And by using the PD transgenic Drosophila model of the MHC-Gal4/UAS system, the PINK1 gene could be specifically activated in the Drosophila muscle tissue.

RESULTS

In PINK1 mutation transgenic fruit flies, the Wnt4 gene to study its implication on PD transgenic fruit flies' wing normality and flight ability. We found that overexpression of Wnt4 gene significantly reduced abnormality rate of PD transgenic Drosophila and improved its flight ability, and then, increased ATP concentration, enhanced mitochondrial membrane potential and normalized mitochondrial morphology were found. All of these findings suggested Wnt4 gene may have a protective effect on PD transgenic fruit flies. Furthermore, in Wnt4 gene overexpression PD transgenic Drosophila, down-regulation autophagy and apoptosis-related proteins Ref(2)P, Pro-Caspase3, and up-regulation of Beclin1, Atg8a, Bcl2 protein were confirmed by Western Blotting.

CONCLUSION

The results imply that the restoring of mitochondrial function though Wnt4 gene overexpression in the PINK1 mutant transgenic Drosophila may be related to autophagy and/or apoptosis.

Recent Development of Wnt Signaling Pathway Inhibitors for Cancer Therapeutics

PURPOSE OF REVIEW

Review current understanding of both canonical and non-canonical Wnt signaling in cancer and provide updated knowledge in current clinical trials of Wnt signaling drugs.

RECENT FINDINGS

Important roles of both canonical and non-canonical Wnt signaling in cancer have been increasingly recognized. Recent clinical trials of several Wnt-signaling drugs have showed promising outcomes. In addition, some drugs that were originally approved for the treatment of other diseases have been recently found to block Wnt signaling, highlighting their potential to treat Wnt-dependent cancer. Dysfunction of Wnt signaling is implicated in cancer, and targeting Wnt signaling represents a useful approach to treat cancer. Current clinical trials of Wnt signaling drugs have showed promising outcomes, and repurposing the previously approved drugs for other diseases to treat Wnt-dependent cancer requires further studies.