5-HT release in nucleus accumbens rescues social deficits in mouse autism model.

Dysfunction in prosocial interactions is a core symptom of autism spectrum disorder. However, the neural mechanisms that underlie sociability are poorly understood, limiting the rational development of therapies to treat social deficits. Here we show in mice that bidirectional modulation of the release of serotonin (5-HT) from dorsal raphe neurons in the nucleus accumbens bidirectionally modifies sociability. In a mouse model of a common genetic cause of autism spectrum disorder-a copy number variation on chromosome 16p11.2-genetic deletion of the syntenic region from 5-HT neurons induces deficits in social behaviour and decreases dorsal raphe 5-HT neuronal activity. These sociability deficits can be rescued by optogenetic activation of dorsal raphe 5-HT neurons, an effect requiring and mimicked by activation of 5-HT1b receptors in the nucleus accumbens. These results demonstrate an unexpected role for 5-HT action in the nucleus accumbens in social behaviours, and suggest that targeting this mechanism may prove therapeutically beneficial.

Ablation of tau causes an olfactory deficit in a murine model of Parkinson's disease.

Parkinson's disease is diagnosed upon the presentation of motor symptoms, resulting from substantial degeneration of dopaminergic neurons in the midbrain. Prior to diagnosis, there is a lengthy prodromal stage in which non-motor symptoms, including olfactory deficits (hyposmia), develop. There is limited information about non-motor impairments and there is a need for directed research into these early pathogenic cellular pathways that precede extensive dopaminergic death in the midbrain. The protein tau has been identified as a genetic risk factor in the development of sporadic PD. Tau knockout mice have been reported as an age-dependent model of PD, and this study has demonstrated that they develop motor deficits at 15-months-old. We have shown that at 7-month-old tau knockout mice present with an overt hyposmic phenotype. This olfactory deficit correlates with an accumulation of α-synuclein, as well as autophagic impairment, in the olfactory bulb. This pathological feature becomes apparent in the striatum and substantia nigra of 15-month-old tau knockout mice, suggesting the potential for a spread of disease. Initial primary cell culture experiments have demonstrated that ablation of tau results in the release of α-synuclein enriched exosomes, providing a potential mechanism for disease spread. These alterations in α-synuclein level as well as a marked autophagy impairment in the tau knockout primary cells recapitulate results seen in the animal model. These data implicate a pathological role for tau in early Parkinson's disease.

Modulating Protein Phosphatase 2A Rescues Disease Phenotype in Neurodegenerative Tauopathies.

Alzheimer's disease (AD) is the leading cause of dementia worldwide accounting for around 70% of all cases. There is currently no treatment for AD beyond symptom management and attempts at developing disease-modifying therapies have yielded very little. These strategies have traditionally targeted the peptide Aß, which is thought to drive pathology. However, the lack of clinical translation of these Aß-centric strategies underscores the need for diverse treatment strategies targeting other aspects of the disease. Metal dyshomeostasis is a common feature of several neurodegenerative diseases such as AD, Parkinson's disease, and frontotemporal dementia, and manipulation of metal homeostasis has been explored as a potential therapeutic avenue for these diseases. The copper ionophore glyoxalbis-[N4-methylthiosemicarbazonato]Cu(II) (CuII(gtsm)) has previously been shown to improve the cognitive deficits seen in an AD animal model; however, the molecular mechanism remained unclear. Here we report that the treatment of two animal tauopathy models (APP/PS1 and rTg4510) with CuII(gtsm) recovers the cognitive deficits seen in both neurodegenerative models. In both models, markers of tau pathology were significantly reduced with CuII(gtsm) treatment, and in the APP/PS1 model, the levels of Aß remained unchanged. Analysis of tau kinases (GSK3ß and CDK5) revealed no drug induced changes; however, both models exhibited a significant increase in the levels of the structural subunit of the tau phosphatase, PP2A. These findings suggest that targeting the tau phosphatase PP2A has therapeutic potential for preventing memory impairments and reducing the tau pathology seen in AD and other tauopathies.

Gating of social reward by oxytocin in the ventral tegmental area.

The reward generated by social interactions is critical for promoting prosocial behaviors. Here we present evidence that oxytocin (OXT) release in the ventral tegmental area (VTA), a key node of the brain's reward circuitry, is necessary to elicit social reward. During social interactions, activity in paraventricular nucleus (PVN) OXT neurons increased. Direct activation of these neurons in the PVN or their terminals in the VTA enhanced prosocial behaviors. Conversely, inhibition of PVN OXT axon terminals in the VTA decreased social interactions. OXT increased excitatory drive onto reward-specific VTA dopamine (DA) neurons. These results demonstrate that OXT promotes prosocial behavior through direct effects on VTA DA neurons, thus providing mechanistic insight into how social interactions can generate rewarding experiences.

Gene dysregulation is restored in the Parkinson's disease MPTP neurotoxic mice model upon treatment of the therapeutic drug Cu(II)(atsm).

The administration of MPTP selectively targets the dopaminergic system resulting in Parkinsonism-like symptoms and is commonly used as a mice model of Parkinson's disease. We previously demonstrated that the neuroprotective compound Cu(II)(atsm) rescues nigral cell loss and improves dopamine metabolism in the MPTP model. The mechanism of action of Cu(II)(atsm) needs to be further defined to understand how the compound promotes neuronal survival. Whole genome transcriptomic profiling has become a popular method to examine the relationship between gene expression and function. Substantia nigra samples from MPTP-lesioned mice were evaluated using whole transcriptome sequencing to investigate the genes altered upon Cu(II)(atsm) treatment. We identified 143 genes affected by MPTP lesioning that are associated with biological processes related to brain and cognitive development, dopamine synthesis and perturbed synaptic neurotransmission. Upon Cu(II)(atsm) treatment, the expression of 40 genes involved in promoting dopamine synthesis, calcium signaling and synaptic plasticity were restored which were validated by qRT-PCR. The study provides the first detailed whole transcriptomic analysis of pathways involved in MPTP-induced Parkinsonism. In addition, we identify key therapeutic pathways targeted by a potentially new class of neuroprotective agents which may provide therapeutic benefits for other neurodegenerative disorders.

High order W02-reactive stable oligomers of amyloid-ß are produced in vivo and in vitro via dialysis and filtration of synthetic amyloid-ß monomer.

Oligomeric forms of amyloid-ß (Aß) are thought to be responsible for the pathogenesis of Alzheimer's disease. While many oligomers of Aß are thought to be naturally occurring in the brain of humans and/or transgenic animals, it is well known that Aß oligomers are also readily produced in vitro in the laboratory. In recent studies, we discovered that synthetic monomeric Aß (4.7 kDa) could be transformed by microdialysis to higher molecular weight species (approximately 56 kDa, by western blot). Surface-enhanced laser desorption/ionization mass spectrometry and electron microscopy further identified these species' as potential Aß oligomers. The production of similar species could also be produced by centrifugal filtration and this formation was concentration and pore-size dependent. These higher order species of Aß were resistant to dissolution in NaOH, HFIP, formic acid, urea, and guanidine. We postulate that we have identified a novel way of producing a high order species of oligomeric Aß and we provide evidence to suggest that Aß oligomers can quite easily be a product of normal laboratory practices. These data suggest that the experimental detection of higher order oligomers in tissues derived from Alzheimer's disease brains or from animal models of disease could, in some cases, be a product the method of analysis.

Rhenium and technetium complexes that bind to amyloid-ß plaques.

Alzheimer's disease is associated with the presence of insoluble protein deposits in the brain called amyloid plaques. The major constituent of these deposits is aggregated amyloid-ß peptide. Technetium-99m complexes that bind to amyloid-ß plaques could provide important diagnostic information on amyloid-ß plaque burden using Single Photon Emission Computed Tomography (SPECT). Tridentate ligands with a stilbene functional group were used to form complexes with the fac-[M(I)(CO)3](+) (M = Re or (99m)Tc) core. The rhenium carbonyl complexes with tridentate co-ligands that included a stilbene functional group and a dimethylamino substituent bound to amyloid-ß present in human frontal cortex brain tissue from subjects with Alzheimer's disease. This chemistry was extended to make the analogous [(99m)Tc(I)(CO)3](+) complexes and the complexes were sufficiently stable in human serum. Whilst the lipophilicity (log D7.4) of the technetium complexes appeared ideally suited for penetration of the blood-brain barrier, preliminary biodistribution studies in an AD mouse model (APP/PS1) revealed relatively low brain uptake (0.24% ID g(-1) at 2 min post injection).

Oral treatment with Cu(II)(atsm) increases mutant SOD1 in vivo but protects motor neurons and improves the phenotype of a transgenic mouse model of amyotrophic lateral sclerosis.

Mutations in the metallo-protein Cu/Zn-superoxide dismutase (SOD1) cause amyotrophic lateral sclerosis (ALS) in humans and an expression level-dependent phenotype in transgenic rodents. We show that oral treatment with the therapeutic agent diacetyl-bis(4-methylthiosemicarbazonato)copper(II) [Cu(II)(atsm)] increased the concentration of mutant SOD1 (SOD1G37R) in ALS model mice, but paradoxically improved locomotor function and survival of the mice. To determine why the mice with increased levels of mutant SOD1 had an improved phenotype, we analyzed tissues by mass spectrometry. These analyses revealed most SOD1 in the spinal cord tissue of the SOD1G37R mice was Cu deficient. Treating with Cu(II)(atsm) decreased the pool of Cu-deficient SOD1 and increased the pool of fully metallated (holo) SOD1. Tracking isotopically enriched (65)Cu(II)(atsm) confirmed the increase in holo-SOD1 involved transfer of Cu from Cu(II)(atsm) to SOD1, suggesting the improved locomotor function and survival of the Cu(II)(atsm)-treated SOD1G37R mice involved, at least in part, the ability of the compound to improve the Cu content of the mutant SOD1. This was supported by improved survival of SOD1G37R mice that expressed the human gene for the Cu uptake protein CTR1. Improving the metal content of mutant SOD1 in vivo with Cu(II)(atsm) did not decrease levels of misfolded SOD1. These outcomes indicate the metal content of SOD1 may be a greater determinant of the toxicity of the protein in mutant SOD1-associated forms of ALS than the mutations themselves. Improving the metal content of SOD1 therefore represents a valid therapeutic strategy for treating ALS caused by SOD1.

Localized changes to glycogen synthase kinase-3 and collapsin response mediator protein-2 in the Huntington's disease affected brain.

All cases of Huntington's disease (HD) are caused by mutant huntingtin protein (mhtt), yet the molecular mechanisms that link mhtt to disease symptoms are not fully elucidated. Given glycogen synthase kinase-3 (GSK3) is implicated in several neurodegenerative diseases as a molecular mediator of neuronal decline and widely touted as a therapeutic target, we investigated GSK3 in cells expressing mhtt, brains of R6/1 HD mice and post-mortem human brain samples. Consistency in data across the two models and the human brain samples indicate decreased GSK3 signalling contributes to neuronal dysfunction in HD. Inhibitory phosphorylation of GSK3 (pGSK3) was elevated in mhtt cells and this appeared related to an overall energy metabolism deficit as the mhtt cells had less ATP and inhibiting ATP production in control cells expressing non-pathogenic htt with paraquat also increased pGSK3. pGSK3 was increased and ATP levels decreased in the frontal cortex and striatum of R6/1 mice and levels of cortical pGSK3 inversely correlated with cognitive function of the mice. Consistent with decreased GSK3 activity in the R6/1 mouse brain, ß-catenin levels were increased and phosphorylation of collapsin response mediator protein-2 (CRMP2) decreased in the frontal cortex where inhibitory phosphorylation of GSK3 was the greatest. pGSK3 was predominantly undetectable in HD and healthy control human brain samples, but levels of total GSK3 were decreased in the HD-affected frontal cortex and this correlated with decreased pCRMP2. Thus, disruptions to cortical GSK3 signalling, possibly due to localized energy metabolism deficits, appear to contribute to the cognitive symptoms of HD.

Modulating metals as a therapeutic strategy for Alzheimer's disease.

In 1906, Alois Alzheimer first characterized the disease that bears his name. Despite intensive research, which has led to a better understanding of the pathology, there is no effective treatment for this disease. Of the drugs approved by the US FDA, none are disease modifying, only symptomatic. Unfortunately, there have been a number of failed clinical trials in the past 10 years where studies show either no cognitive improvement or, worse, serious side effects associated with treatment. Hence, there is a need for the field to look at alternative approaches to therapy. In this review, we will discuss how metal dyshomeostasis occurs in aging and Alzheimer's disease. Concomitantly, we will discuss how targeting this dyshomeostasis offers an effective and novel therapeutic approach. Thus far, compounds that mediate these effects have shown great potential in both preclinical animal studies as well as in early-stage clinical trials.

The hypoxia imaging agent CuII(atsm) is neuroprotective and improves motor and cognitive functions in multiple animal models of Parkinson's disease.

Parkinson's disease (PD) is a progressive, chronic disease characterized by dyskinesia, rigidity, instability, and tremors. The disease is defined by the presence of Lewy bodies, which primarily consist of aggregated α-synuclein protein, and is accompanied by the loss of monoaminergic neurons. Current therapeutic strategies only give symptomatic relief of motor impairment and do not address the underlying neurodegeneration. Hence, we have identified Cu(II)(atsm) as a potential therapeutic for PD. Drug administration to four different animal models of PD resulted in improved motor and cognition function, rescued nigral cell loss, and improved dopamine metabolism. In vitro, this compound is able to inhibit the effects of peroxynitrite-driven toxicity, including the formation of nitrated α-synuclein oligomers. Our results show that Cu(II)(atsm) is effective in reversing parkinsonian defects in animal models and has the potential to be a successful treatment of PD.

Diacetylbis(N(4)-methylthiosemicarbazonato) copper(II) (CuII(atsm)) protects against peroxynitrite-induced nitrosative damage and prolongs survival in amyotrophic lateral sclerosis mouse model.

Amyotrophic lateral sclerosis (ALS) is a progressive paralyzing disease characterized by tissue oxidative damage and motor neuron degeneration. This study investigated the in vivo effect of diacetylbis(N(4)-methylthiosemicarbazonato) copper(II) (CuII(atsm)), which is an orally bioavailable, blood-brain barrier-permeable complex. In vitro the compound inhibits the action of peroxynitrite on Cu,Zn-superoxide dismutase (SOD1) and subsequent nitration of cellular proteins. Oral treatment of transgenic SOD1G93A mice with CuII(atsm) at presymptomatic and symptomatic ages was performed. The mice were examined for improvement in lifespan and motor function, as well as histological and biochemical changes to key disease markers. Systemic treatment of SOD1G93A mice significantly delayed onset of paralysis and prolonged lifespan, even when administered to symptomatic animals. Consistent with the properties of this compound, treated mice had reduced protein nitration and carbonylation, as well as increased antioxidant activity in spinal cord. Treatment also significantly preserved motor neurons and attenuated astrocyte and microglial activation in mice. Furthermore, CuII(atsm) prevented the accumulation of abnormally phosphorylated and fragmented TAR DNA-binding protein-43 (TDP-43) in spinal cord, a protein pivotal to the development of ALS. CuII(atsm) therefore represents a potential new class of neuroprotective agents targeting multiple major disease pathways of motor neurons with therapeutic potential for ALS.

The Alzheimer's therapeutic PBT2 promotes amyloid-ß degradation and GSK3 phosphorylation via a metal chaperone activity.

Impaired metal ion homeostasis causes synaptic dysfunction and treatments for Alzheimer's disease (AD) that target metal ions have therefore been developed. The leading compound in this class of therapeutic, PBT2, improved cognition in a clinical trial with AD patients. The aim of the present study was to examine the cellular mechanism of action for PBT2. We show PBT2 induces inhibitory phosphorylation of the α- and ß-isoforms of glycogen synthase kinase 3 and that this activity is dependent on PBT2 translocating extracellular Zn and Cu into cells. This activity is supported when Aß:Zn aggregates are the source of extracellular Zn and adding PBT2 to Aß:Zn preparations promotes Aß degradation by matrix metalloprotease 2. PBT2-induced glycogen synthase kinase 3 phosphorylation appears to involve inhibition of the phosphatase calcineurin. Consistent with this, PBT2 increased phosphorylation of other calcineurin substrates, including cAMP response element binding protein and Ca²âº/calmodulin-dependent protein kinase. These data demonstrate PBT2 can decrease Aß levels by sequestering the Zn that promotes extracellular formation of protease resistant Aß:Zn aggregates, and that subsequent intracellular translocation of the Zn by PBT2 induces cellular responses with synapto-trophic potential. Intracellular translocation of Zn and Cu via the metal chaperone activity of PBT2 may be an important mechanism by which PBT2 improves cognitive function in people with AD.