Dopamine D2 receptor stimulation potentiates PolyQ-Huntingtin-induced mouse striatal neuron dysfunctions via Rho/ROCK-II activation

Neurodegenerative Disease Associated Pathways in the Brains of Triple Transgenic Alzheimer's Model Mice Are Reversed Following Two Weeks of Peripheral Administration of Fasudil

The pan Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor fasudil acts as a vasodilator and has been used as a medication for post-cerebral stroke for the past 29 years in Japan and China. More recently, based on the involvement of ROCK inhibition in synaptic function, neuronal survival, and processes associated with neuroinflammation, it has been suggested that the drug may be repurposed for neurodegenerative diseases. Indeed, fasudil has demonstrated preclinical efficacy in many neurodegenerative disease models. To facilitate an understanding of the wider biological processes at play due to ROCK inhibition in the context of neurodegeneration, we performed a global gene expression analysis on the brains of Alzheimer's disease model mice treated with fasudil via peripheral IP injection. We then performed a comparative analysis of the fasudil-driven transcriptional profile with profiles generated from a meta-analysis of multiple neurodegenerative diseases. Our results show that fasudil tends to drive gene expression in a reverse sense to that seen in brains with post-mortem neurodegenerative disease. The results are most striking in terms of pathway enrichment analysis, where pathways perturbed in Alzheimer's and Parkinson's diseases are overwhelmingly driven in the opposite direction by fasudil treatment. Thus, our results bolster the repurposing potential of fasudil by demonstrating an anti-neurodegenerative phenotype in a disease context and highlight the potential of in vivo transcriptional profiling of drug activity.

Focusing the pivotal role of nanotechnology in Huntington's disease: an insight into the recent advancements

Neurodegeneration is the loss of neuronal capacity and structure over time which causes neurodegenerative disorders like Alzheimer, amyotrophic lateral sclerosis, Parkinson, and Huntington's disease (HD). This review is primarily concerned with HD, which was fully described by George Huntington in 1872. In developed countries, HD has become another common single-gene neurological disorder. Because of its autosomal dominant inheritance, the sickness affects both individuals and their families. Huntington disease has been recognized as a disorder that affects the complete body and brain in which the mutant huntingtin polyglutamine (polyQ) sequence is extensively increased and gets correlated to CAG trinucleotide which codes for glutamine (Q). These proteins have characteristics that produce apoptosis and dysfunction. HD is a lethal condition which needs an immediate diagnosis and treatment, and therefore, nanoparticle has come into sight out as opportunistic strategies for treatment of HD. Nanostructures have great potential to cross the blood brain barrier and also prevent breakdown of active molecule and reduces the drug toxicity. This review explains the distinguishing symptoms, genetics, and stages during the development of Huntington's disease, and also provides an overview of HD with an emphasis on its epidemiology, pathogenesis, and management. This review focuses on the latest studies on nanotechnology-related technologies, i.e., magnetic nanoparticle, solid lipid nanoparticle, and polymeric nanoparticle for Huntington's disease treatment. The pioneering patents and in-progress clinical trials related to Huntington's disease has also been summarized in this review.

Huntington's Disease: A Clinical Review

The Huntington's gene on chromosome 4 has a dominantly inherited CAG trinucleotide repeat expansion, ultimately resulting in Huntington's disease (HD), a completely penetrant neurological condition. The frequency is 10-100 times higher in the population descended from Europe than in East Asia. Through various processes, including impairment of proteostasis, transcription, and cell function, as well as direct toxicity of the mutant protein, mutated huntingtin triggers neuronal malfunction and loss at the cellular level. As the disease worsens, the brain becomes affected together with the striatum's initial macroscopic alterations. Since there are presently few medications that can change the course of the disease, palliative therapy, and symptom control are the cornerstone of treatment. Studying the cellular pathology and gross structural changes to the brain which occur as the illness advances have made enormous progress in recent years. There's been a substantial increase in medical studies and possible treatment options over the past ten years. The new treatments that aim to reduce amounts of mutant huntingtin are the most optimistic. However, one strategy is antisense oligonucleotide treatment, for which clinical trials are currently being conducted. These control trials might help us get another inch ahead of managing and perhaps even eliminating this nasty disease.

Hunting for the cause: Evidence for prion-like mechanisms in Huntington’s disease

The hypothesis that pathogenic protein aggregates associated with neurodegenerative diseases spread from cell-to-cell in the brain in a manner akin to infectious prions has gained substantial momentum due to an explosion of research in the past 10–15 years. Here, we review current evidence supporting the existence of prion-like mechanisms in Huntington’s disease (HD), an autosomal dominant neurodegenerative disease caused by expansion of a CAG repeat tract in exon 1 of the huntingtin (HTT) gene. We summarize information gained from human studies and in vivo and in vitro models of HD that strongly support prion-like features of the mutant HTT (mHTT) protein, including potential involvement of molecular features of mHTT seeds, synaptic structures and connectivity, endocytic and exocytic mechanisms, tunneling nanotubes, and nonneuronal cells in mHTT propagation in the brain. We discuss mechanisms by which mHTT aggregate spreading and neurotoxicity could be causally linked and the potential benefits of targeting prion-like mechanisms in the search for new disease-modifying therapies for HD and other fatal neurodegenerative diseases.

Cytoskeleton saga: Its regulation in normal physiology and modulation in neurodegenerative disorders

Cells are fundamental units of life. To ensure the maintenance of homeostasis, integrity of structural and functional counterparts is needed to be essentially balanced. The cytoskeleton plays a vital role in regulating the cellular morphology, signalling and other factors involved in pathological conditions. Microtubules, actin (microfilaments), intermediate filaments (IF) and their interactions are required for these activities. Various proteins associated with these components are primary requirements for directing their functions. Disruption of this organization due to faulty genetics, oxidative stress or impaired transport mechanisms are the major causes of dysregulated signalling cascades leading to various pathological conditions like Alzheimer's (AD), Parkinson's (PD), Huntington's disease (HD) or amyotrophic lateral sclerosis (ALS), hereditary spastic paraplegia (HSP) or any traumatic injury like spinal cord injury (SCI). Novel or conventional therapeutic approaches may be specific or non-specific, targeting either three basic components of the cytoskeleton or various cascades that serve as a cue to numerous pathways like ROCK signalling or the GSK-3β pathway. An enormous number of drugs have been redirected for modulating the cytoskeletal dynamics and thereby may pave the way for inhibiting the progression of these diseases and their complications.

RhoA Signaling in Neurodegenerative Diseases

Ras homolog gene family member A (RhoA) is a small GTPase of the Rho family involved in regulating multiple signal transduction pathways that influence a diverse range of cellular functions. RhoA and many of its downstream effector proteins are highly expressed in the nervous system, implying an important role for RhoA signaling in neurons and glial cells. Indeed, emerging evidence points toward a role of aberrant RhoA signaling in neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. In this review, we summarize the current knowledge of RhoA regulation and downstream cellular functions with an emphasis on the role of RhoA signaling in neurodegenerative diseases and the therapeutic potential of RhoA inhibition in neurodegeneration.

Altered Cholesterol Homeostasis in Huntington’s Disease

Huntington’s disease (HD) is an autosomal dominant genetic disorder caused by an expansion of the CAG repeat in the first exon of Huntingtin’s gene. The associated neurodegeneration mainly affects the striatum and the cortex at early stages and progressively spreads to other brain structures. Targeting HD at its earlier stages is under intense investigation. Numerous drugs were tested, with a rate of success of only 3.5% approved molecules used as symptomatic treatment. The restoration of cholesterol metabolism, which is central to the brain homeostasis and strongly altered in HD, could be an interesting disease-modifying strategy. Cholesterol is an essential membrane component in the central nervous system (CNS); alterations of its homeostasis have deleterious consequences on neuronal functions. The levels of several sterols, upstream of cholesterol, are markedly decreased within the striatum of HD mouse model. Transcription of cholesterol biosynthetic genes is reduced in HD cell and mouse models as well as post-mortem striatal and cortical tissues from HD patients. Since the dynamic of brain cholesterol metabolism is complex, it is essential to establish the best method to target it in HD. Cholesterol, which does not cross the blood-brain-barrier, is locally synthesized and renewed within the brain. All cell types in the CNS synthesize cholesterol during development but as they progress through adulthood, neurons down-regulate their cholesterol synthesis and turn to astrocytes for their full supply. Cellular levels of cholesterol reflect the dynamic balance between synthesis, uptake and export, all integrated into the context of the cross talk between neurons and glial cells. In this review, we describe the latest advances regarding the role of cholesterol deregulation in neuronal functions and how this could be a determinant factor in neuronal degeneration and HD progression. The pathways and major mechanisms by which cholesterol and sterols are regulated in the CNS will be described. From this overview, we discuss the main clinical strategies for manipulating cholesterol metabolism in the CNS, and how to reinstate a proper balance in HD.

Antidepressant-like effects of water extract of Cordyceps militaris (Linn.) Link by modulation of ROCK2/PTEN/Akt signaling in an unpredictable chronic mild stress-induced animal model

ETHNOPHARMACOLOGY RELEVANCE

Cordyceps militaris (Linn.) Link (CM) is a medicinal mushroom traditionally used in tonics for treating several neurological disorders, including epilepsy and anxiety, in Asia. Reports have shown that CM has anti-inflammatory and anti-oxidative effects and may be beneficial for depression management.

AIM OF THE STUDY

This study aimed to investigate the potential of CM as an antidepressant for a long-term unpredictable chronic mild stress (UCMS) rodent models and explore its underlying mechanisms.

MATERIALS AND METHODS

Rats were orally administered with 125 (low, L), 250 (medium, M), and 500 (high, H) mg/kg bodyweight (bw) of the water extract of CM (WCM) for 35 consecutive days in the UCMS protocol. The levels of cerebral serotonin (5-HT), dopamine (DA), and metabolites in the frontal cortex of the rats were measured. Blood was collected to investigate the levels of proinflammatory cytokines, and the brain was dissected to assay the stress-associated ROCK2/PTEN/Akt signaling.

RESULTS

All doses of the WCM prevented abnormal behaviors induced by UCMS, including anhedonia and hypoactivity. The LWCM treatment reduced the turnover rate of 5-HT, and all doses of the WCM reduced the turnover rate of DA in the frontal cortex. The LWCM also attenuated the elevation of serum IL-1β induced by chronic stress. All doses of the WCM attenuated the ROCK2 protein hyperactivation, and the LWCM further increased the down-regulation of p-Akt/Akt signaling.

CONCLUSION

The WCM has antidepressant-like effects, which may result from the regulation of the stress-related ROCK2/PTEN/Akt pathway. Therefore, the WCM may be developed and used for the complementary treatment of depression.

TRP Channels Regulation of Rho GTPases in Brain Context and Diseases

Neurological and neuropsychiatric disorders are mediated by several pathophysiological mechanisms, including developmental and degenerative abnormalities caused primarily by disturbances in cell migration, structural plasticity of the synapse, and blood-vessel barrier function. In this context, critical pathways involved in the pathogenesis of these diseases are related to structural, scaffolding, and enzymatic activity-bearing proteins, which participate in Ca²⁺- and Ras Homologs (Rho) GTPases-mediated signaling. Rho GTPases are GDP/GTP binding proteins that regulate the cytoskeletal structure, cellular protrusion, and migration. These proteins cycle between GTP-bound (active) and GDP-bound (inactive) states due to their intrinsic GTPase activity and their dynamic regulation by GEFs, GAPs, and GDIs. One of the most important upstream inputs that modulate Rho GTPases activity is Ca²⁺ signaling, positioning ion channels as pivotal molecular entities for Rho GTPases regulation. Multiple non-selective cationic channels belonging to the Transient Receptor Potential (TRP) family participate in cytoskeletal-dependent processes through Ca²⁺-mediated modulation of Rho GTPases. Moreover, these ion channels have a role in several neuropathological events such as neuronal cell death, brain tumor progression and strokes. Although Rho GTPases-dependent pathways have been extensively studied, how they converge with TRP channels in the development or progression of neuropathologies is poorly understood. Herein, we review recent evidence and insights that link TRP channels activity to downstream Rho GTPase signaling or modulation. Moreover, using the TRIP database, we establish associations between possible mediators of Rho GTPase signaling with TRP ion channels. As such, we propose mechanisms that might explain the TRP-dependent modulation of Rho GTPases as possible pathways participating in the emergence or maintenance of neuropathological conditions.

Clinically Precedented Protein Kinases: Rationale for Their Use in Neurodegenerative Disease

Kinases are an intensively studied drug target class in current pharmacological research as evidenced by the large number of kinase inhibitors being assessed in clinical trials. Kinase-targeted therapies have potential for treatment of a broad array of indications including central nervous system (CNS) disorders. In addition to the many variables which contribute to identification of a successful therapeutic molecule, drug discovery for CNS-related disorders also requires significant consideration of access to the target organ and specifically crossing the blood-brain barrier (BBB). To date, only a small number of kinase inhibitors have been reported that are specifically designed to be BBB permeable, which nonetheless demonstrates the potential for success. This review considers the potential for kinase inhibitors in the context of unmet medical need for neurodegenerative disease. A subset of kinases that have been the focus of clinical investigations over a 10-year period have been identified and discussed individually. For each kinase target, the data underpinning the validity of each in the context of neurodegenerative disease is critically evaluated. Selected molecules for each kinase are identified with information on modality, binding site and CNS penetrance, if known. Current clinical development in neurodegenerative disease are summarized. Collectively, the review indicates that kinase targets with sufficient rationale warrant careful design approaches with an emphasis on improving brain penetrance and selectivity.

Dynamics of a Protein Interaction Network Associated to the Aggregation of polyQ-Expanded Ataxin-1

Background: Several experimental models of polyglutamine (polyQ) diseases have been previously developed that are useful for studying disease progression in the primarily affected central nervous system. However, there is a missing link between cellular and animal models that would indicate the molecular defects occurring in neurons and are responsible for the disease phenotype in vivo. Methods: Here, we used a computational approach to identify dysregulated pathways shared by an in vitro and an in vivo model of ATXN1(Q82) protein aggregation, the mutant protein that causes the neurodegenerative polyQ disease spinocerebellar ataxia type-1 (SCA1). Results: A set of common dysregulated pathways were identified, which were utilized to construct cerebellum-specific protein-protein interaction (PPI) networks at various time-points of protein aggregation. Analysis of a SCA1 network indicated important nodes which regulate its function and might represent potential pharmacological targets. Furthermore, a set of drugs interacting with these nodes and predicted to enter the blood–brain barrier (BBB) was identified. Conclusions: Our study points to molecular mechanisms of SCA1 linked from both cellular and animal models and suggests drugs that could be tested to determine whether they affect the aggregation of pathogenic ATXN1 and SCA1 disease progression.

Aripiprazole and haloperidol protect neurite lesions via reducing excessive D2R-DISC1 complex formation

Dopamine D2 receptor (D2R) hyperactivity causes altered brain development and later produces onset of symptoms mimicking schizophrenia. It is known that D2R interacts with disrupted in schizophrenia 1 (DISC1); however, the effect of D2R-DISC1 interaction in intracellular signalling and neurite growth has not been studied. This study investigated the effect of D2R over-activation on Akt-GSK3β signalling and neurite morphology in cortical neurons. Over-activation of D2Rs caused neurite lesions, which were associated with decreased protein kinase B (Akt) and glycogen synthase kinase 3 beta (GSK3β) phosphorylation in cortical neurons. The antipsychotic drug aripiprazole was more effective in the prevention of neurite lesions than haloperidol. Unlike haloperidol, aripiprazole prevented downregulation of phospho (p) Akt-pGSK3β induced by D2R hyperactivity, indicating involvement of different pathways. D2Rs were hyperactive in cortical neurons of mice with DISC1 mutation, which caused more severe neurite lesions in cortical neurons treated with quinpirole. Immunofluorescent staining for Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) confirmed that cortical pyramidal neurons were involved in the D2R hyperactivity-induced neurite lesions. Using the fluorescence resonance energy transfer (FRET) technique, we provide direct evidence that D2R hyperactivity led to D2R-DISC1 complex formation, which altered pGSK3β signalling. This study showed that D2R hyperactivity-induced D2R-DISC1 complex formation is associated with decreased pAkt-pGSK3β signalling and in turn, caused neurite impairment. Aripiprazole and haloperidol prevented the impairment of neurite growth but appeared to do so via different intracellular signalling pathways.

Cytoskeleton actin-binding proteins in clinical behavior of pituitary tumors

Although generally benign, pituitary tumors are frequently locally invasive, with reduced success of neurosurgery and unresponsive to pharmacological treatment with somatostatin or dopamine analogues. The molecular basis of the different biological behavior of pituitary tumors are still poorly identified, but a body of work now suggests that the activity of specific cytoskeleton proteins is a key factor regulating both the invasiveness and drug resistance of these tumors. This review recapitulates the experimental evidence supporting a role for the actin-binding protein filamin A (FLNA) in the regulation of somatostatin and dopamine receptors expression and signaling in pituitary tumors, thus in determining the responsiveness to currently used drugs, somatostatin analogues and dopamine receptor type 2 agonists. Regarding the regulation of invasive behavior of pituitary tumoral cells, we bring evidence to the role of the actin-severing protein cofilin, whose activation status may be modulated by dopaminergic and somatostatinergic drugs, through FLNA involvement. Molecular mechanisms involved in the regulation of FLNA expression and function in pituitary tumors will also be discussed.

Transfer of disrupted-in-schizophrenia 1 aggregates between neuronal-like cells occurs in tunnelling nanotubes and is promoted by dopamine

The disrupted-in-schizophrenia 1 (DISC1) gene was identified as a genetic risk factor for chronic mental illnesses (CMI) such as schizophrenia, bipolar disorder and severe recurrent depression. Insoluble aggregated DISC1 variants were found in the cingular cortex of sporadic, i.e. non-genetic, CMI patients. This suggests protein pathology as a novel, additional pathogenic mechanism, further corroborated in a recent transgenic rat model presenting DISC1 aggregates. Since the potential role of aggregation of DISC1 in sporadic CMI is unknown, we investigated whether DISC1 undergoes aggregation in cell culture and could spread between neuronal cells in a prion-like manner, as shown for amyloid proteins in neurodegenerative diseases. Co-culture experiments between donor cells forming DISC1 aggregates and acceptor cells showed that 4.5% of acceptor cells contained donor-derived DISC1 aggregates, thus indicating an efficient transfer in vitro. DISC1 aggregates were found inside tunnelling nanotubes (TNTs) and transfer was enhanced by increasing TNT formation and notably by dopamine treatment, which also induces DISC1 aggregation. These data indicate that DISC1 aggregates can propagate between cells similarly to prions, thus providing some molecular basis for the role of protein pathology in CMI.

Antisense oligonucleotides in neurological disorders

The introduction of genetics revolutionized the field of neurodegenerative and neuromuscular diseases and has provided considerable insight into the underlying pathomechanisms. Nevertheless, effective treatment options have been limited. This changed recently when antisense oligonucleotides (ASOs) could be translated from in vitro and experimental animal studies into clinical practice. In 2016, two ASOs were approved by the United States US Food and Drug Administration (FDA) and demonstrated remarkable efficacy in Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA). ASOs are synthetic single-stranded strings of nucleic acids. They selectively bind to specific premessenger ribonucleic acid (pre-mRNA)/mRNA sequences and alter protein synthesis by several mechanisms of action. Thus, apart from gene replacement, ASOs may therefore provide the most direct therapeutic strategy for influencing gene expression. In this review, we shall discuss basic mechanisms of ASO action, the role of chemical modifications needed to improve the pharmacodynamic and pharmacokinetic properties of ASOs, and we shall then focus on several ASOs developed for the treatment of neurodegenerative and neuromuscular disorders, including SMA, DMD, myotonic dystrophies, Huntington's disease, amyotrophic lateral sclerosis and Alzheimer's disease.

Proteomic mapping of differentially vulnerable pre-synaptic populations identifies regulators of neuronal stability in vivo

Synapses are an early pathological target in many neurodegenerative diseases ranging from well-known adult onset conditions such as Alzheimer and Parkinson disease to neurodegenerative conditions of childhood such as spinal muscular atrophy (SMA) and neuronal ceroid lipofuscinosis (NCLs). However, the reasons why synapses are particularly vulnerable to such a broad range of neurodegeneration inducing stimuli remains unknown. To identify molecular modulators of synaptic stability and degeneration, we have used the Cln3^−/− mouse model of a juvenile form of NCL. We profiled and compared the molecular composition of anatomically-distinct, differentially-affected pre-synaptic populations from the Cln3^−/− mouse brain using proteomics followed by bioinformatic analyses. Identified protein candidates were then tested using a Drosophila CLN3 model to study their ability to modify the CLN3-neurodegenerative phenotype in vivo. We identified differential perturbations in a range of molecular cascades correlating with synaptic vulnerability, including valine catabolism and rho signalling pathways. Genetic and pharmacological targeting of key ‘hub’ proteins in such pathways was sufficient to modulate phenotypic presentation in a Drosophila CLN3 model. We propose that such a workflow provides a target rich method for the identification of novel disease regulators which could be applicable to the study of other conditions where appropriate models exist.

White matter predicts functional connectivity in premanifest Huntington's disease

Objectives

The distribution of pathology in neurodegenerative disease can be predicted by the organizational characteristics of white matter in healthy brains. However, we have very little evidence for the impact these pathological changes have on brain function. Understanding any such link between structure and function is critical for understanding how underlying brain pathology influences the progressive behavioral changes associated with neurodegeneration. Here, we demonstrate such a link between structure and function in individuals with premanifest Huntington's.

Methods

Using diffusion tractography and resting state functional magnetic resonance imaging to characterize white matter organization and functional connectivity, we investigate whether characteristic patterns of white matter organization in the healthy human brain shape the changes in functional coupling between brain regions in premanifest Huntington's disease.

Results

We find changes in functional connectivity in premanifest Huntington's disease that link directly to underlying patterns of white matter organization in healthy brains. Specifically, brain areas with strong structural connectivity show decreases in functional connectivity in premanifest Huntington's disease relative to controls, while regions with weak structural connectivity show increases in functional connectivity. Furthermore, we identify a pattern of dissociation in the strongest functional connections between anterior and posterior brain regions such that anterior functional connectivity increases in strength in premanifest Huntington's disease, while posterior functional connectivity decreases.

Interpretation

Our findings demonstrate that organizational principles of white matter underlie changes in functional connectivity in premanifest Huntington's disease. Furthermore, we demonstrate functional antero–posterior dissociation that is in keeping with the caudo–rostral gradient of striatal pathology in HD.

Coupling of D2R Short but not D2R Long receptor isoform to the Rho/ROCK signaling pathway renders striatal neurons vulnerable to mutant huntingtin

Huntington's disease, an inherited neurodegenerative disorder, results from abnormal polyglutamine extension in the N-terminal region of the huntingtin protein. This mutation causes preferential degeneration of striatal projection neurons. We previously demonstrated, in vitro, that dopaminergic D2 receptor stimulation acted in synergy with expanded huntingtin to increase aggregates formation and striatal death through activation of the Rho/ROCK signaling pathway. In vivo, in a lentiviral-mediated model of expanded huntingtin expression in the rat striatum, we found that the D2 antagonist haloperidol protects striatal neurons against expanded huntingtin-mediated toxicity. Two variant transcripts are generated by alternative splicing of the of D2 receptor gene, the D2R-Long and the D2R-Short, which are thought to play different functional roles. We show herein that overexpression of D2R-Short, but not D2R-Long in cell lines is associated with activation of the RhoA/ROCK signaling pathway. In striatal neurons in culture, the selective D2 agonist Quinpirole triggers phosphorylation of cofilin, a downstream effector of ROCK, which is abrogated by siRNAs that knockdown both D2R-Long and D2R-Short, but not by siRNAs targeting D2R-Long alone. Aggregate formation and neuronal death induced by expanded huntingtin, were potentiated by Quinpirole. This D2 agonist-mediated effect was selectively inhibited by the siRNA targeting both D2R-Long and D2R-Short but not D2R-Long alone. Our data provide evidence for a specific coupling of D2R-Short to the RhoA/ROCK/cofilin pathway, and its involvement in striatal vulnerability to expanded huntingtin. A new route for targeting Rho-ROCK signaling in Huntington's disease is unraveled with our findings.

Umbelliferone reverses depression-like behavior in chronic unpredictable mild stress-induced rats by attenuating neuronal apoptosis via regulating ROCK/Akt pathway

There is increasing evidence that major depressive disorder (MDD) is also a progressive neurodegeneration disorder and neuronal damage is the major pathology of MDD. Umbelliferone, a coumarin derivative, was found in a range of plants with proved anti-oxidative, anti-inflammatory and neuroprotective effects. The primary purpose of this investigation was to evaluate whether umbelliferone could confer an antidepressant-like effect on the depressive model in rats developed by chronic unpredictable mild stress (CUMS) and explore the possible mechanism involved in its neuroprotective effects. We found that treatments with umbelliferone (15mg/kg, 30mg/kg) significantly ameliorated CUMS-induced depressive-like behaviors, such as decreased sucrose consumption, reduced locomotor activity and prolonged immobility time. Rats under CUMS stimulation treated with umbelliferone (15mg/kg, 30mg/kg) showed reduced neuronal apoptosis, as well as inhibited inflammatory cytokines levels by down-regulating Rho-associated protein kinase (ROCK) signaling and up-regulating protein kinase B (Akt) signaling. In conclusion, umbelliferone showed neuroprotective effects on CUMS-induced model of depression, which was associated with the inhibition of neuronal apoptosis modulated by ROCK/Akt pathway.

Dopamine receptor type 2 (DRD2) inhibits migration and invasion of human tumorous pituitary cells through ROCK-mediated cofilin inactivation

Non-functioning pituitary tumors (NFPTs) frequently present local invasiveness. Dopamine receptor 2 (DRD2) agonists are the only medical therapy that induces tumor shrinkage in some patients. Invasion requires cytoskeleton rearrangements that are tightly regulated by cofilin pathway, whose alterations correlate with invasion in different tumors. We investigated the effect of DR2D agonist on NFPT cells migration/invasion and the molecular mechanisms involved. We demonstrated that DRD2 agonist reduced migration (-44 ± 25%, p < 0.01) and invasion (-34 ± 6%, p < 0.001) and increased about 4-fold Ser3-phosphorylated inactive cofilin (P-cofilin) in NFPT cells. These effects were abolished by inhibiting ROCK, a kinase that phosphorylates cofilin. The overexpression of wild-type or phosphodeficient S3A-cofilin increased HP75 cells migration (+49 ± 6% and +57 ± 9% vs empty vector, respectively, p < 0.05), while phosphomimetic mutant had no effect. Interestingly, P-cofilin levels were lower in invasive vs non-invasive tumors by both western blot (mean P-cofilin/total cofilin ratio 0.77 and 1.93, respectively, p < 0.05) and immunohistochemistry (mean percentage of P-cofilin positive cells 17.6 and 45.7, respectively, p < 0.05). In conclusion, we showed that the invasiveness of pituitary tumors is promoted by the activation of cofilin, which can be regulated by DRD2 and might represent a novel biomarker for pituitary tumors' invasive behavior.

Involvement of inhibition of RhoA/Rho kinase signaling in simvastatin-induced amelioration of neuropathic pain

Small molecular G-protein plays a key role in several diseases. This study was designed to reveal the role of RhoA signaling in the pathophysiology of neuropathic pain in mice. Partial sciatic nerve injury caused thermal hyperalgesia, mechanical allodynia, and increased plasma membrane translocation of RhoA in the lumber spinal cord. GFAP-immunoreactivity (ir), Iba-1-ir, and Rho kinase 2 (ROCK2-ir) was also increased in the ipsilateral spinal dorsal horn of nerve-ligated mice. Moreover, partial nerve ligation increased the expression of phosphorylated myristoylated alanine-rich protein kinase C substrate (MARCKS)-ir in the ipsilateral spinal dorsal horn. Daily intrathecal administration of simvastatin, beginning 3days before nerve injury, completely blocked all these changes in nerve-ligated mice. Pharmacological inhibition of ROCK also attenuated the increased expression of GFAP-ir and phosphorylated MARCKS-ir. Together, it is suggested that astrogliosis initiated by the activation of RhoA/ROCK signaling results in MARCKS phosphorylation in nerve terminals, which leads to hyperalgesia in neuropathic pain. Furthermore, simvastatin exerts antihyperalgesic and antiallodynic effects through the inhibition of spinal RhoA activation.

The cytoskeleton as a novel therapeutic target for old neurodegenerative disorders

Cytoskeleton defects, including alterations in microtubule stability, in axonal transport as well as in actin dynamics, have been characterized in several unrelated neurodegenerative conditions. These observations suggest that defects of cytoskeleton organization may be a common feature contributing to neurodegeneration. In line with this hypothesis, drugs targeting the cytoskeleton are currently being tested in animal models and in human clinical trials, showing promising effects. Drugs that modulate microtubule stability, inhibitors of posttranslational modifications of cytoskeletal components, specifically compounds affecting the levels of tubulin acetylation, and compounds targeting signaling molecules which regulate cytoskeleton dynamics, constitute the mostly addressed therapeutic interventions aiming at preventing cytoskeleton damage in neurodegenerative disorders. In this review, we will discuss in a critical perspective the current knowledge on cytoskeleton damage pathways as well as therapeutic strategies designed to revert cytoskeleton-related defects mainly focusing on the following neurodegenerative disorders: Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis and Charcot-Marie-Tooth Disease.

CYP46A1, the rate-limiting enzyme for cholesterol degradation, is neuroprotective in Huntington's disease

Huntington’s disease is an autosomal dominant neurodegenerative disease caused by abnormal polyglutamine expansion in huntingtin (Exp-HTT) leading to degeneration of striatal neurons. Altered brain cholesterol homeostasis has been implicated in Huntington’s disease, with increased accumulation of cholesterol in striatal neurons yet reduced levels of cholesterol metabolic precursors. To elucidate these two seemingly opposing dysregulations, we investigated the expression of cholesterol 24-hydroxylase (CYP46A1), the neuronal-specific and rate-limiting enzyme for cholesterol conversion to 24S-hydroxycholesterol (24S-OHC). CYP46A1 protein levels were decreased in the putamen, but not cerebral cortex samples, of post-mortem Huntington’s disease patients when compared to controls. Cyp46A1 mRNA and CYP46A1 protein levels were also decreased in the striatum of the R6/2 Huntington’s disease mouse model and in ST hdh Q111 cell lines. In vivo , in a wild-type context, knocking down CYP46A1 expression in the striatum, via an adeno-associated virus-mediated delivery of selective shCYP46A1, reproduced the Huntington’s disease phenotype, with spontaneous striatal neuron degeneration and motor deficits, as assessed by rotarod. In vitro , CYP46A1 restoration protected ST hdh Q111 and Exp-HTT-expressing striatal neurons in culture from cell death. In the R6/2 Huntington’s disease mouse model, adeno-associated virus-mediated delivery of CYP46A1 into the striatum decreased neuronal atrophy, decreased the number, intensity level and size of Exp-HTT aggregates and improved motor deficits, as assessed by rotarod and clasping behavioural tests. Adeno-associated virus-CYP46A1 infection in R6/2 mice also restored levels of cholesterol and lanosterol and increased levels of desmosterol. In vitro , lanosterol and desmosterol were found to protect striatal neurons expressing Exp-HTT from death. We conclude that restoring CYP46A1 activity in the striatum promises a new therapeutic approach in Huntington’s disease.

Towards axonal regeneration and neuroprotection in glaucoma: Rho kinase inhibitors as promising therapeutics

Due to a prolonged life expectancy worldwide, the incidence of age-related neurodegenerative disorders such as glaucoma is increasing. Glaucoma is the second cause of blindness, resulting from a slow and progressive loss of retinal ganglion cells (RGCs) and their axons. Up to now, intraocular pressure (IOP) reduction is the only treatment modality by which ophthalmologists attempt to control disease progression. However, not all patients benefit from this therapy, and the pathophysiology of glaucoma is not always associated with an elevated IOP. These limitations, together with the multifactorial etiology of glaucoma, urge the pressing medical need for novel and alternative treatment strategies. Such new therapies should focus on preventing or retarding RGC death, but also on repair of injured axons, to ultimately preserve or improve structural and functional connectivity. In this respect, Rho-associated coiled-coil forming protein kinase (ROCK) inhibitors hold a promising potential to become very prominent drugs for future glaucoma treatment. Their field of action in the eye does not seem to be restricted to IOP reduction by targeting the trabecular meshwork or improving filtration surgery outcome. Indeed, over the past years, important progress has been made in elucidating their ability to improve ocular blood flow, to prevent RGC death/increase RGC survival and to retard axonal degeneration or induce proper axonal regeneration. Within this review, we aim to highlight the currently known capacity of ROCK inhibition to promote neuroprotection and regeneration in several in vitro, ex vivo and in vivo experimental glaucoma models.

Protective effect of a novel Rho kinase inhibitor WAR-5 in experimental autoimmune encephalomyelitis by modulating inflammatory response and neurotrophic factors

The Rho-kinase (ROCK) inhibitor Fasudil has proven beneficial in experimental autoimmune encephalomyelitis (EAE). Given the small safety window of Fasudil, we are looking for novel ROCK inhibitors, which have similar or stronger effect on EAE with greater safety. In this study, we report that WAR-5, a Y-27632 derivative, alleviates the clinical symptoms, attenuates myelin damage and reduces CNS inflammatory responses in EAE C57BL/6 mice at an extent similar to Fasudil, while exhibits less vasodilator and adverse reaction in vivo. WAR-5 inhibits ROCK activity, and selectively suppresses the expression of ROCK II in spleen, brain and spinal cord of EAE mice, especially in spinal cord, accompanied by decreased expression of Nogo. WAR-5 also regulates the imbalance of Th1/Th17 T cells and regulatory T cells, inhibits inflammatory microenvironment induced with NF-κB-IL-1β pathway. Importantly, WAR-5 converts M1 toward M2 microglia/macrophages that are positively correlated with BDNF and NT-3 production. Taken together, WAR-5 exhibits therapeutic potential in EAE by more selectively inhibits ROCK II, with a greater safety than Fasudil, and is worthy of further clinical study to clarify its clinical value.

Chatting with the neighbors: crosstalk between Rho-kinase (ROCK) and other signaling pathways for treatment of neurological disorders

ROCK inhibition has been largely applied as a strategy to treat neurodegenerative diseases (NDDs) and promising results have been obtained in the recent years. However, the underlying molecular and cellular mechanisms are not fully understood and different models have been proposed for neurodegenerative disorders. Here, we aim to review the current knowledge obtained for NDDs identifying common mechanisms as well as disease-specific models. In addition to the role of ROCK in different cell types such as neurons and microglia, we focus on the molecular signaling-pathways which mediate the beneficial effects of ROCK. Besides canonical ROCK signaling, modulation of neighboring pathways by non-canonical ROCK-crosstalk is a recurrent pattern in many NDD-model systems and has been suggested to mediate beneficial effects of ROCK-inhibition.

Corticostriatal synaptic adaptations in Huntington's disease

Huntington’s disease (HD) is a progressive neurodegenerative disorder that profoundly impairs corticostriatal information processing. While late stage pathology includes cell death, the appearance of motor symptoms parallels more subtle changes in neuronal function and synaptic integration. Because of the difficulty in modeling the disease and the complexity of the corticostriatal network, understanding the mechanisms driving pathology has been slow to develop. In recent years, advances in animal models and network analysis tools have begun to shed light on the circuit-specific deficits. These studies have revealed a progressive impairment of corticostriatal synaptic signaling in sub-populations of striatal neurons, turning classical excitotoxicity models of HD upside down. Disrupted brain derived neurotrophic factor signaling appears to be a key factor in this decline.

Axon growth inhibition by RhoA/ROCK in the central nervous system

Rho kinase (ROCK) is a serine/threonine kinase and a downstream target of the small GTPase Rho. The RhoA/ROCK pathway is associated with various neuronal functions such as migration, dendrite development, and axonal extension. Evidence from animal studies reveals that RhoA/ROCK signaling is involved in various central nervous system (CNS) diseases, including optic nerve and spinal cord injuries, stroke, and neurodegenerative diseases. Given that RhoA/ROCK plays a critical role in the pathophysiology of CNS diseases, the development of therapeutic agents targeting this pathway is expected to contribute to the treatment of CNS diseases. The RhoA/ROCK pathway mediates the effects of myelin-associated axon growth inhibitors—Nogo, myelin-associated glycoprotein (MAG), oligodendrocyte-myelin glycoprotein (OMgp), and repulsive guidance molecule (RGM). Blocking RhoA/ROCK signaling can reverse the inhibitory effects of these molecules on axon outgrowth, and promotes axonal sprouting and functional recovery in animal models of CNS injury. To date, several RhoA/ROCK inhibitors have been under development or in clinical trials as therapeutic agents for neurological disorders. In this review, we focus on the RhoA/ROCK signaling pathway in neurological disorders. We also discuss the potential therapeutic approaches of RhoA/ROCK inhibitors for various neurological disorders.

Possible involvement of self-defense mechanisms in the preferential vulnerability of the striatum in Huntington's disease

HD is caused by a mutation in the huntingtin gene that consists in a CAG repeat expansion translated into an abnormal poly-glutamine (polyQ) tract in the huntingtin (Htt) protein. The most striking neuropathological finding in HD is the atrophy of the striatum. The regional expression of mutant Htt (mHtt) is ubiquitous in the brain and cannot explain by itself the preferential vulnerability of the striatum in HD. mHtt has been shown to produce an early defect in transcription, through direct alteration of the function of key regulators of transcription and in addition, more indirectly, as a result of compensatory responses to cellular stress. In this review, we focus on gene products that are preferentially expressed in the striatum and have down- or up-regulated expression in HD and, as such, may play a crucial role in the susceptibility of the striatum to mHtt. Many of these striatal gene products are for a vast majority down-regulated and more rarely increased in HD. Recent research shows that some of these striatal markers have a pro-survival/neuroprotective role in neurons (e.g., MSK1, A2A, and CB1 receptors) whereas others enhance the susceptibility of striatal neurons to mHtt (e.g., Rhes, RGS2, D2 receptors). The down-regulation of these latter proteins may be considered as a potential self-defense mechanism to slow degeneration. For a majority of the striatal gene products that have been identified so far, their function in the striatum is unknown and their modifying effects on mHtt toxicity remain to be experimentally addressed. Focusing on these striatal markers may contribute to a better understanding of HD pathogenesis, and possibly the identification of novel therapeutic targets.

Quercetin improves behavioral deficiencies, restores astrocytes and microglia, and reduces serotonin metabolism in 3-nitropropionic acid-induced rat model of Huntington's Disease

AIM

Huntington's disease (HD) is an autosomal dominant disorder, for which clinically available drugs offer only symptomatic relief. These prescription drugs are not free of side effects, and the patients usually suffer from anxiety and depression. We investigated quercetin, a dietary flavonoid with free radical scavenging properties, for its beneficial potential if any, in 3-nitropropionic acid (3-NP)-induced HD in rats where both drugs were administered simultaneously.

METHODS

Performance of rats on beam balancing, elevated plus maze and gait traits were investigated following 3-NP and/or quercetin treatments for 4 days. Striatal biogenic amine levels and monoamine oxidase activity were assayed. Striatal sections were examined for Cd11B and glial fibrillary acidic protein immunoreactivity, and for evidences of neuronal lesion.

RESULTS

Quercetin significantly attenuated 3-NP-induced anxiety, motor coordination deficits, and gait despair. While the dopaminergic hyper-metabolism was unaffected, quercetin provided a significant reduction of 3-NP mediated increase in serotonin metabolism. Quercetin failed to affect 3-NP-induced striatal neuronal lesion, but decreased microglial proliferation, and increased astrocyte numbers in the lesion core.

CONCLUSION

These results taken together suggest that quercetin could be of potential use not only for correcting movement disturbances and anxiety in HD, but also for addressing inflammatory damages.

Advances in huntington disease drug discovery: novel approaches to model disease phenotypes

Huntington disease is a monogenic, autosomal dominant, progressive neurodegenerative disorder caused by a trinucleotide CAG repeat expansion in exon 1 of the huntingtin (HTT) gene; age of onset of clinical symptoms inversely correlates with expanded CAG repeat length. HD leads to extensive degeneration of the basal ganglia, hypothalamic nuclei, and selected cortical areas, and a wide range of molecular mechanisms have been implicated in disease pathology in animal or cellular models expressing mutated HTT (mHTT) proteins, either full-length or amino-terminal fragments. However, HD cellular models that recapitulate the slow progression of the disease have not been available due to the toxicity of overexpressed exogenous mHTT or to limitations with using primary cells for long-term studies. Most investigations of the effects of mHTT relied on cytotoxicity or aggregation end points in heterologous systems or in primary embryonic neuroglial cultures derived from HD mouse models. More innovative approaches are currently under active investigation, including screening using electrophysiological endpoints, as well as the recent use of primary blood mononuclear cells and of human embryonic stem cells derived from a variety of HD research participants. Here we describe how these cellular systems are being used to investigate HD biology as well as to identify mechanisms with therapeutic potential.

Dopamine D2 receptors regulate collateral inhibition between striatal medium spiny neurons

The principle neurons of the striatum are GABAergic medium spiny neurons (MSNs), whose collateral synapses onto neighboring neurons play critical roles in striatal function. MSNs can be divided by dopamine receptor expression into D1-class and D2-class MSNs, and alterations in D2 MSNs are associated with various pathological states. Despite overwhelming evidence for D2 receptors (D2Rs) in maintaining proper striatal function, it remains unclear how MSN collaterals are specifically altered by D2R activation. Here, we report that chronic D2R stimulation regulates MSN collaterals in vitro by presynaptic and postsynaptic mechanisms. We used corticostriatal cultures from mice in which MSN subtypes were distinguished by fluorophore expression. Quinpirole, an agonist for D2/3 receptors, was used to chronically activate D2Rs. Quinpirole increased the rate and strength of collateral formation onto D2R-containing MSNs as measured by dual whole-cell patch-clamp recordings. Additionally, these neurons were more sensitive to low concentrations of GABA and exhibited an increase in gephyrin puncta density, suggesting increased postsynaptic GABAA receptors. Last, quinpirole treatment increased presynaptic GABA release sites, as shown by increased frequency of sIPSCs and mIPSCs, correlating with increased VGAT (vesicular GABA transporter) puncta. Combined with the observation that there were no detectable differences in sensitivity to specific GABAA receptor modulators, we provide evidence that D2R activation powerfully transforms MSN collaterals via coordinated presynaptic and postsynaptic alterations. As the D2 class of MSNs is highly implicated in Parkinson's disease and other neurological disorders, our findings may contribute to understanding and treating the changes that occur in these pathological states.

ROCK-phosphorylated vimentin modifies mutant huntingtin aggregation via sequestration of IRBIT

BACKGROUND

Huntington's Disease (HD) is a fatal hereditary neurodegenerative disease caused by the accumulation of mutant huntingtin protein (Htt) containing an expanded polyglutamine (polyQ) tract. Activation of the channel responsible for the inositol-induced Ca²⁺ release from ensoplasmic reticulum (ER), was found to contribute substantially to neurodegeneration in HD. Importantly, chemical and genetic inhibition of inositol 1,4,5-trisphosphate (IP3) receptor type 1 (IP3R1) has been shown to reduce mutant Htt aggregation.

RESULTS

In this study, we propose a novel regulatory mechanism of IP3R1 activity by type III intermediate filament vimentin which sequesters the negative regulator of IP3R1, IRBIT, into perinuclear inclusions, and reduces its interaction with IP3R1 resulting in promotion of mutant Htt aggregation. Proteasome inhibitor MG132, which causes polyQ proteins accumulation and aggregation, enhanced the sequestration of IRBIT. Furthermore we found that IRBIT sequestration can be prevented by a rho kinase inhibitor, Y-27632.

CONCLUSIONS

Our results suggest that vimentin represents a novel and additional target for the therapy of polyQ diseases.

Huntington's disease and the striatal medium spiny neuron: cell-autonomous and non-cell-autonomous mechanisms of disease

Huntington's disease is an autosomal dominant disorder caused by a mutation in the gene encoding the protein huntingtin on chromosome 4. The mutation is an expanded CAG repeat in the first exon, encoding a polyglutamine tract. If the polyglutamine tract is > 40, penetrance is 100% and death is inevitable. Despite the widespread expression of huntingtin, HD has long been considered primarily as a disease of the striatum. It is characterized by selective vulnerability with dysfunction followed by death of the medium size spiny neuron. Considerable effort is being expended to determine whether striatal damage is cell-autonomous, non-cell-autonomous, requiring cell-cell and region to region communication, or both. We review data supporting both mechanisms. We also attempt to organize the data into common mechanisms that may arise outside the medium, spiny neuron, but ultimately have their greatest impact in the striatum.

Novel GαS-protein signaling associated with membrane-tethered amyloid precursor protein intracellular domain

Numerous physiological functions, including a role as a cell surface receptor, have been ascribed to Alzheimer's disease-associated amyloid precursor protein (APP). However, detailed analysis of intracellular signaling mediated by APP in neurons has been lacking. Here, we characterized intrinsic signaling associated with membrane-bound APP C-terminal fragments, which are generated following APP ectodomain release by α- or β-secretase cleavage. We found that accumulation of APP C-terminal fragments or expression of membrane-tethered APP intracellular domain results in adenylate cyclase-dependent activation of PKA (protein kinase A) and inhibition of GSK3β signaling cascades, and enhancement of axodendritic arborization in rat immortalized hippocampal neurons, mouse primary cortical neurons, and mouse neuroblastoma. We discovered an interaction between BBXXB motif of APP intracellular domain and the heterotrimeric G-protein subunit Gα(S), and demonstrate that Gα(S) coupling to adenylate cyclase mediates membrane-tethered APP intracellular domain-induced neurite outgrowth. Our study provides clear evidence that APP intracellular domain can have a nontranscriptional role in regulating neurite outgrowth through its membrane association. The novel functional coupling of membrane-bound APP C-terminal fragments with Gα(S) signaling identified in this study could impact several brain functions such as synaptic plasticity and memory formation.

Huntington's Disease and Striatal Signaling

Huntington’s Disease (HD) is the most frequent neurodegenerative disease caused by an expansion of polyglutamines (CAG). The main clinical manifestations of HD are chorea, cognitive impairment, and psychiatric disorders. The transmission of HD is autosomal dominant with a complete penetrance. HD has a single genetic cause, a well-defined neuropathology, and informative pre-manifest genetic testing of the disease is available. Striatal atrophy begins as early as 15 years before disease onset and continues throughout the period of manifest illness. Therefore, patients could theoretically benefit from therapy at early stages of the disease. One important characteristic of HD is the striatal vulnerability to neurodegeneration, despite similar expression of the protein in other brain areas. Aggregation of the mutated Huntingtin (HTT), impaired axonal transport, excitotoxicity, transcriptional dysregulation as well as mitochondrial dysfunction, and energy deficits, are all part of the cellular events that underlie neuronal dysfunction and striatal death. Among these non-exclusive mechanisms, an alteration of striatal signaling is thought to orchestrate the downstream events involved in the cascade of striatal dysfunction.

Huntington's disease and Group I metabotropic glutamate receptors

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized by involuntary body movement, cognitive impairment and psychiatric disturbance. A polyglutamine expansion in the amino-terminal region of the huntingtin (htt) protein is the genetic cause of HD. Htt protein interacts with a wide variety of proteins, and htt mutation causes cell signaling alterations in various neurotransmitter systems, including dopaminergic, glutamatergic, and cannabinoid systems, as well as trophic factor systems. This review will overview recent findings concerning htt-promoted alterations in cell signaling that involve different neurotransmitters and trophic factor systems, especially involving mGluR1/5, as glutamate plays a crucial role in neuronal cell death. The neuronal cell death that takes place in the striatum and cortex of HD patients is the most important factor underlying HD progression. Metabotropic glutamate receptors (mGluR1 and mGluR5) have a very controversial role in neuronal cell death and it is not clear whether mGluR1/5 activation either protects or exacerbates neuronal death. Thus, understanding how mutant htt protein affects glutamatergic receptor signaling will be essential to further establish a role for glutamate receptors in HD and develop therapeutic strategies to treat HD.

Fasudil protects hippocampal neurons against hypoxia-reoxygenation injury by suppressing microglial inflammatory responses in mice

Rho kinase (ROCK) may play an important role in regulating biological events of cells, including proliferation, differentiation and survival/death. Blockade of ROCK promotes axonal regeneration and neuron survival in vivo and in vitro, thereby exhibiting potential clinical applications in spinal cord damage and stroke. Our previous studies have demonstrated that Fasudil, a selective ROCK inhibitor, induced neuroprotection in vitro. Here we used an in vivo model of hypoxia/reoxygenation (H/R) injury to examine the neuroprotective effect of Fasudil, and explore its possible mechanism(s) in vivo. H/R resulted in the loss of hippocampal neurons, accompanied by increased apoptosis of neurons in hippocampus. The expression of ROCK II and activity of ROCK in the brain were increased after H/R, and located only in microglia, but not in astrocytes and neurons. The administration of Fasudil inhibited the activity of ROCK in brain tissue and cultured microglia, and protected hippocampal neurons against H/R injury. Further immunohistochemical analysis and cytokine determination revealed that Fasudil inhibited inducible nitric oxide synthase immunoreactivity in microglia and pro-inflammatory factors in brain tissue after H/R, which is consistent with the observation wherein Fasudil reduced the pro-inflammatory factors nitric oxide, IL-1β, IL-6 and TNF-, and increased anti-inflammatory factor IL-10 in cultured microglia under normoxic or hypoxic conditions. Our results indicate that inhibition of ROCK by Fasudil may represent a useful therapeutic perspective by inhibiting microglial inflammatory responses in the CNS.

Early synaptic pathophysiology in neurodegeneration: insights from Huntington's disease

Investigations of synaptic transmission and plasticity in mouse models of Huntington's disease (HD) demonstrate neuronal dysfunction long before the onset of classical disease indicators. Similarly, recent human studies reveal synaptic dysfunction decades before predicted clinical diagnosis in HD gene carriers. These studies guide premanifest tracking of disease and the development of treatment assessment tools. New discoveries of mechanisms underlying early neuronal dysfunction, including elevated pathogenic extrasynaptic NMDA receptor signaling, reduced synaptic connectivity and loss of brain-derived neurotrophic factor (BDNF) support have led to pharmacological interventions that can reverse or delay phenotype onset and disease progression in HD mice. Further understanding the primary effects of gene mutations associated with late-onset neurodegeneration should translate to novel treatments for HD families and guide therapeutic strategies for other neurodegenerative diseases.

The therapeutic potential of G-protein coupled receptors in Huntington's disease

Huntington's disease is a late-onset autosomal dominant inherited neurodegenerative disease characterised by increased symptom severity over time and ultimately premature death. An expanded CAG repeat sequence in the huntingtin gene leads to a polyglutamine expansion in the expressed protein, resulting in complex dysfunctions including cellular excitotoxicity and transcriptional dysregulation. Symptoms include cognitive deficits, psychiatric changes and a movement disorder often referred to as Huntington's chorea, which involves characteristic involuntary dance-like writhing movements. Neuropathologically Huntington's disease is characterised by neuronal dysfunction and death in the striatum and cortex with an overall decrease in cerebral volume (Ho et al., 2001). Neuronal dysfunction begins prior to symptom presentation, and cells of particular vulnerability include the striatal medium spiny neurons. Huntington's is a devastating disease for patients and their families and there is currently no cure, or even an effective therapy for disease symptoms. G-protein coupled receptors are the most abundant receptor type in the central nervous system and are linked to complex downstream pathways, manipulation of which may have therapeutic application in many neurological diseases. This review will highlight the potential of G-protein coupled receptor drug targets as emerging therapies for Huntington's disease.