Trafficking of JC virus-like particles across the blood-brain barrier.

Hollow viral vectors, such as John Cunningham virus-like particles (JC VLPs), provide a unique opportunity to deliver drug cargo into targeted cells and tissue. Current understanding of the entry of JC virus in brain cells has remained insufficient. In particular, interaction of JC VLPs with the blood-brain barrier (BBB) has not been analyzed in detail. Thus, JC VLPs were produced in this study for investigating the trafficking across the BBB. We performed a carotid artery injection procedure for mouse brain to qualitatively study JC VLPs' in vivo binding and distribution and used in vitro approaches to analyze their uptake and export kinetics in brain endothelial cells. Our results show that clathrin-dependent mechanisms contributed to the entry of VLPs into brain endothelial cells, and exocytosis or transcytosis of VLPs across the BBB was observed in vitro. VLPs were found to interact with sialic acid glycans in mouse brain endothelia. The ability of JC VLPs to cross the BBB can be useful in developing a delivery system for transport of genes and small molecule cargoes to the brain.

Blinding and Randomization.

Most, if not all, guidelines, recommendations, and other texts on Good Research Practice emphasize the importance of blinding and randomization. There is, however, very limited specific guidance on when and how to apply blinding and randomization. This chapter aims to disambiguate these two terms by discussing what they mean, why they are applied, and how to conduct the acts of randomization and blinding. We discuss the use of blinding and randomization as the means against existing and potential risks of bias rather than a mandatory practice that is to be followed under all circumstances and at any cost. We argue that, in general, experiments should be blinded and randomized if (a) this is a confirmatory research that has a major impact on decision-making and that cannot be readily repeated (for ethical or resource-related reasons) and/or (b) no other measures can be applied to protect against existing and potential risks of bias.

Discovery of Novel and Highly Selective Inhibitors of Calpain for the Treatment of Alzheimer's Disease: 2-(3-Phenyl-1H-pyrazol-1-yl)-nicotinamides.

Calpain overactivation has been implicated in a variety of pathological disorders including ischemia/reperfusion injury, cataract formation, and neurodegenerative diseases such as Alzheimer's disease (AD). Herein we describe our efforts leading to the identification of ketoamide-based 2-(3-phenyl-1H-pyrazol-1-yl)nicotinamides as potent and reversible inhibitors of calpain with high selectivity versus related cysteine protease cathepsins, other proteases, and receptors. Broad efficacy in a set of preclinical models relevant to AD suggests that inhibition of calpain represents an attractive approach with potential benefit for the treatment of AD.

Measuring drug absorption improves interpretation of behavioral responses in a larval zebrafish locomotor assay for predicting seizure liability.

INTRODUCTION: Unanticipated effects on the central nervous system are a concern during new drug development. A larval zebrafish locomotor assay can reveal seizure liability of experimental molecules before testing in mammals. Relative absorption of compounds by larvae is lacking in prior reports of such assays; having those data may be valuable for interpreting seizure liability assay performance. METHODS: Twenty-eight reference drugs were tested at multiple dose levels in fish water and analyzed by a blinded investigator. Responses of larval zebrafish were quantified during a 30min dosing period. Predictive metrics were calculated by comparing fish activity to mammalian seizure liability for each drug. Drug level analysis was performed to calculate concentrations in dose solutions and larvae. Fifteen drug candidates with neuronal targets, some having preclinical convulsion findings in mammals, were tested similarly. RESULTS: The assay has good predictive value of established mammalian responses for reference drugs. Analysis of drug absorption by larval fish revealed a positive correlation between hyperactive behavior and pro-convulsive drug absorption. False negative results were associated with significantly lower compound absorption compared to true negative, or true positive results. The predictive value for preclinical toxicology findings was inferior to that suggested by reference drugs. DISCUSSION: Disproportionately low exposures in larvae giving false negative results demonstrate that drug exposure analysis can help interpret results. Due to the rigorous testing commonly performed in preclinical toxicology, predicting convulsions in those studies may be more difficult than predicting effects from marketed drugs.

Defining the brain circuits involved in psychiatric disorders: IMI-NEWMEDS.

Despite the vast amount of research on schizophrenia and depression in the past two decades, there have been few innovative drugs to treat these disorders. Precompetitive research collaborations between companies and academic groups can help tackle this innovation deficit, as illustrated by the achievements of the IMI-NEWMEDS consortium.

Investigational drugs targeting 5-HT6 receptors for the treatment of Alzheimer's disease.

INTRODUCTION: There are significant efforts invested into the discovery and development of novel treatments for Alzheimer's disease. While current discovery efforts and most scientific discussions seem to focus on disease-modifying therapy, there are several symptomatic therapy approaches that are being actively pursued. The goal of this review is to summarize the recent developments in the field of 5-HT6 receptor antagonists, a principle that has been extensively characterized preclinically and is now undergoing critical phases of clinical development. AREAS COVERED: The article covers the current status of 5-HT6 receptor antagonists in clinical development. It also discusses the underlying mechanisms for the observed procognitive effects. The article is based on a search for investigational drugs using the key words '5-HT6', 'cognition', 'dementia', 'Alzheimer's disease', 'Phase II' and 'Phase III' in various databases and from conference abstracts. EXPERT OPINION: After some period of little or no development activities, the field of 5-HT6 receptor antagonists attracted a lot of attention with three companies (GSK, Pfizer and Lundbeck) confirming aggressive development plans and initiating pivotal Phase II and III studies. These studies will be critical to prove that 5-HT6 receptor antagonists have a symptomatic efficacy profile that can be differentiated from that of currently used agents (cholinesterase inhibitors and the NMDA-antagonist memantine). Furthermore, there are several sets of data that point at a disease-modifying potential of this class of agents and these effects are likely to receive critical exploration if the ongoing symptomatic trials bring 5-HT6 antagonists closer to clinical use.

Synthetic Aß oligomers (Aß(1-42) globulomer) modulate presynaptic calcium currents: prevention of Aß-induced synaptic deficits by calcium channel blockers.

Alzheimer's disease is accompanied by increased brain levels of soluble amyloid-ß (Aß) oligomers. It has been suggested that oligomers directly impair synaptic function, thereby causing cognitive deficits in Alzheimer's disease patients. Recently, it has been shown that synthetic Aß oligomers directly modulate P/Q-type calcium channels, possibly leading to excitotoxic cascades and subsequent synaptic decline. Using whole-cell recordings we studied the modulation of recombinant presynaptic calcium channels in HEK293 cells after application of a stable Aß oligomer preparation (Aß1-42 globulomer). Aß globulomer shifted the half-activation voltage of P/Q-type and N-type calcium channels to more hyperpolarized values (by 11.5 and 7.5 mV). Application of non-aggregated Aß peptides had no effect. We then analyzed the potential of calcium channel blockers to prevent Aß globulomer-induced synaptic decline in hippocampal slice cultures. Specific block of P/Q-type or N-type calcium channels with peptide toxins completely reversed Aß globulomer-induced deficits in glutamatergic neurotransmission. Two state-dependent low molecular weight P/Q-type and N-type calcium channel blockers also protected neurons from Aß-induced alterations. On the contrary, inhibition of L-type calcium channels failed to reverse the deficit. Our data show that Aß globulomer directly modulates recombinant P/Q-type and N-type calcium channels in HEK293 cells. Block of presynaptic calcium channels with both state-dependent and state-independent modulators can reverse Aß-induced functional deficits in synaptic transmission. These findings indicate that presynaptic calcium channel blockers may be a therapeutic strategy for the treatment of Alzheimer's disease.

Establishment of a secondary screening assay for P/Q-type calcium channel blockers.

Development of calcium channel blockers is attractive, but has in the past been hampered by lack of high throughput electrophysiological technology. This limitation has been overcome by the implementation of automated patch clamp systems that allow identification of state-dependent compounds, which preferentially target pathologically overactive channels. We recently presented a fluorescence-based high-throughput screen for P/Q-type calcium channels followed by automated electrophysiology. Here, we provide a detailed description of the development of the secondary screen, and show the full analysis of the inactivation kinetics of the recombinant P/Q channel that served as a basis for the automated patch clamp protocol. Increasing the length of pre-depolarization shifted the inactivation to more hyperpolarized potentials. No steady-state inactivation was reached up to pre-depolarization durations of 3 min, while stability of the recordings progressively declined. As a compromise, a 3s pre-depolarization protocol was proposed for functional screening. In order to validate the electrophysiological screening, we compared kinetics and pharmacology of recombinant P/Q-type channels between automated and manual patch clamp measurements. Channel activation was similar under both conditions. By contrast, inactivation occurred at more hyperpolarized potentials in the automated system. Therefore, P/Q-type calcium channel inactivation is sensitive to the applied technological platform and needs to be adjusted when performing automated patch clamp recordings. Our results indicate that a thorough analysis of the inactivation kinetics is mandatory, when establishing an electrophysiological screening protocol for calcium channel blockers. As some data obtained by automated recordings may not be identical to manual patch clamp analysis, we recommend a proper initial validation of the screening assay and--if necessary--a posthoc adjustment of automated patch clamp values. The protocol presented here supports hit-to-lead and lead optimization efforts during the development of novel P/Q-type calcium channel blockers, and may be valuable for the generation of assays in other ion channel programs.

Dopamine D3 receptor antagonism--still a therapeutic option for the treatment of schizophrenia.

The potential of D(3) receptor antagonism to treat positive, negative, and cognitive symptoms of schizophrenia is reviewed on the basis of preclinical results and preliminary clinical data. Dopamine D(3) receptors are expressed in mesencephalic, limbic, and cortical areas relevant to psychotic and cognitive symptoms of schizophrenia. As expected, selective dopamine D(3) receptor antagonists are not effective in antipsychotic animal models, reflecting D(2) receptor antagonism. However, selective D(3) receptor antagonists affect electrical activity of dopamine neurons in the ventral tegmental area similar to atypical antipsychotics, counteract effects produced by NMDA glutamate receptor blockade, and enhance cortical dopamine and acetylcholine in microdialysis. In contrast to dopamine D(2) receptor antagonists, D(3) antagonists positively influence a variety of social and cognitive behaviors in rodents, including tests representing cognitive flexibility and executive function, which are both impaired in schizophrenia patients. Despite considerable affinity for D(3) receptors, the second-generation antipsychotics clozapine, risperidone, and olanzapine when administered to patients with schizophrenia seem not to occupy D(3) receptors sufficiently to derive any conclusion on a D(3)-mediated therapeutic benefit. ABT-925, the first selective D(3) receptor antagonist, was recently studied in patients with schizophrenia. It produced cognitive signals but did not achieve sufficient D(3) receptor occupancy to test the hypothesis that D(3) receptor antagonism is of therapeutic value to treat symptoms of schizophrenia. Based on mechanistic and experimental considerations and due to the fact that D(3) receptor antagonism can inhibit extrapyramidal symptoms and produce neither anhedonia nor metabolic adverse effects, the development and clinical testing of newer D(3) receptor antagonists with high potency at D(3) receptors, enabling sufficient receptor occupancy, is highly warranted.

Running wheel activity is sensitive to acute treatment with selective inhibitors for either serotonin or norepinephrine reuptake.

RATIONALE: Most antidepressants (AD) directly or indirectly enhance the serotonergic tone in the CNS. Since the serotonin system is involved in both, the modulation of mood and motor behavior, it was reasoned that these drugs might also interfere with running wheel activity (RWA), a form of positively motivated motor behavior, which might be linked to pathological states like obsessive-compulsive disorder (OCD). OBJECTIVES: We used RWA to characterize ADs from all major classes. Effects on RWA were compared to effects on general locomotor activity (LOC) to control for unspecific effects on general locomotion. METHODS: Two hours before lights-off, mice were treated with either vehicle or one of the following AD: the selective serotonin reuptake inhibitors (SSRIs) citalopram (3-10 mg/kg), paroxetine (1-10 mg/kg) and fluoxetine (2-6.6 mg/kg), the selective norepinephrine reuptake inhibitor (SNRI) reboxetine (1-10 mg/kg), the monoamine oxidase (MAO) inhibitors tranylcypromine (1-3 mg/kg) and moclobemide (3-10 mg/kg), and the tricyclic ADs desipramine and imipramine (10-30 mg/kg, each). LOC and RWA were measured after lights-off. RESULTS: At the highest dose tested, all ADs, with the exception of the MAO inhibitors, significantly reduced RWA. Both tricyclics inhibited RWA only at doses that similarly affected LOC. In contrast, all SSRI and reboxetine inhibited RWA at doses that left LOC unaffected. CONCLUSIONS: SSRI and the SNRI reboxetine inhibit RWA at doses not suppressing LOC. RWA may represent a simple behavioral readout of positively motivated behavior that merits further attention for psychopharmacology.

Inhibition of Calpain Prevents N-Methyl-D-aspartate-Induced Degeneration of the Nucleus Basalis and Associated Behavioral Dysfunction.

N-Methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity is thought to underlie a variety of neurological disorders, and inhibition of either the NMDA receptor itself, or molecules of the intracellular cascade, may attenuate neurodegeneration in these diseases. Calpain, a calcium-dependent cysteine protease, has been identified as part of such an NMDA receptor-induced excitotoxic signaling pathway. The present study addressed the question of whether inhibition of calpain can prevent neuronal cell death and associated behavioral deficits in a disease-relevant animal model, which is based on excitotoxic lesions of the cholinergic nucleus basalis magnocellularis of Meynert. Excitotoxic lesions of the nucleus basalis with NMDA induced a markedly impaired performance in the novel object recognition test. Treatment with the calpain inhibitor, N-(1-benzyl-2-carbamoyl-2-oxoethyl)-2-[E-2-(4-diethlyaminomethylphenyl) ethen-1-yl]benzamide (A-705253), dose-dependently prevented the behavioral deficit. Subsequent analysis of choline acetyltransferase in the cortical mantle of the lesioned animals revealed that application of A-705253 dose-dependently and significantly attenuated cholinergic neurodegeneration. Calpain inhibition also significantly diminished the accompanying gliosis, as determined by immunohistochemical analysis of microglia activation. Finally, inhibition of calpain by A-705253 and the peptidic calpain inhibitor N-acetyl-Leu-Leu-Nle-CHO did not impair long-term potentiation in hippocampal slices, indicating that calpain inhibition interrupts NMDA excitotoxicity pathways without interfering with NMDA receptor-mediated signaling involved in cognition. We conclude that inhibition of calpains may represent a valuable strategy for the prevention of excitotoxicity-induced neuronal decline without interfering with the physiological neuronal functions associated with learning and memory processes. Thus, calpain inhibition may be a promising and novel approach for the treatment of various neurodegenerative disorders.

Behavioral characterization of the mGlu group II/III receptor antagonist, LY-341495, in animal models of anxiety and depression.

There is a growing body of evidence indicating that stimulation of metabotropic glutamate type II receptors (mGlu2/3) reduces anxiety in laboratory animals and humans. Surprisingly, it was reported that mGlu2/3 receptor antagonists have antidepressant- and anxiolytic-like activities in laboratory animal studies as well. The present study aimed to resolve this controversy by characterizing behavioral effects of a selective mGlu2/3 receptor antagonist, LY-341495, in a variety of animal models sensitive to clinically used anxiolytic and antidepressant agents. In agreement with previous reports, LY-341495 (0.3-3 mg/kg, i.p.) reduced immobility in the mouse forced swim test. LY-341495 was also effective in the marble burying test in mice, although similar effects were observed after administration of various drugs including methamphetamine. Further, LY-341495 had no effects in the elevated plus maze and stress-induced hyperthermia tests in mice, as well as on punished drinking (Geller-Seifter's test) and differential reinforcement of low rates of responding (DRL) in rats. It is concluded that behavioral profile of mGlu2/3 receptor antagonists as represented by LY-341495 is different from that of conventional anxiolytic and antidepressant drugs.

The guinea pig forced swim test as a new behavioral despair model to characterize potential antidepressants.

RATIONALE: Behavioral despair is a model of high predictivity for antidepressant activity in murids. For some drug targets, guinea pigs exhibit a higher homology to their human counterparts compared to murids. OBJECTIVES: In this paper, we established a model of behavioral despair namely, the forced swim test (FST) in guinea pigs. MATERIALS AND METHODS: Male guinea pigs underwent the FST similar to rats. Animals received intraperitoneal injections of either vehicle or drugs 24, 4, and 0.5 h before testing. We tested the tricyclic antidepressants desipramine and amitriptyline, the monoamine oxidase inhibitor tranylcypromine, the selective serotonin reuptake inhibitors fluoxetine and paroxetine, and the neurokinin 1 (NK(1)) receptor antagonist, L-733,060, and for comparison the antipsychotic clozapine and the stimulant methamphetamine. RESULTS: Desipramine (> or =3 mg/kg) and amitriptyline (>10 mg/kg) increased the latency to immobility (LTI) to greater than 230 s, and tranylcypromine (10 mg/kg) it to greater than 190 s. Paroxetine (>0.3 mg/kg) and fluoxetine (>10 mg/kg) also increased LTI significantly but only to greater than 120 s. Methamphetamine (3 mg/kg) completely eliminated immobility, whereas clozapine (5-20 mg/kg) had no effect. L-733,060 (10 mg/kg) increased LTI to 270 s. Doses producing significant effects in FST were investigated in the open field. Antidepressants did not affect locomotion, whereas methamphetamine induced hyperlocomotion. CONCLUSIONS: We demonstrate the suitability of a modified procedure of the FST for a nonmurid species: the guinea pig. Known antidepressants showed similar effects as in rats and mice. It is interesting to note that the NK(1) antagonist L-733,060 increased forced swimming, suggesting its antidepressant potential. Thus, the guinea pig FST allows the study of antidepressant activity also in NK(1) antagonists that cannot be studied appropriately in murids.

Synthesis and SAR of highly potent dual 5-HT1A and 5-HT1B antagonists as potential antidepressant drugs.

Novel 5-HT(1) autoreceptor ligands based on the N-4-aryl-piperazinyl-N'-ethyl-5,6,7,8-tetrahydropyrido[4', 3':4,5]thieno[2,3-d]pyrimidin-4(3H)-one core are described. Aiming at antidepressants with a novel mode of action our objective was to identify potent antagonists showing balanced affinities and high selectivity for the 5-HT(1A) and 5-HT(1B) receptors. Strategies for the development of dual 5-HT(1A) and 5-HT(1B) antagonists based on 1 and 2 as leads and the corresponding results are discussed. Isoquinoline analogue 33 displayed high affinity and an antagonistic mode of action for the 5-HT(1A) and the 5-HT(1B) receptors and was characterized further with respect to selectivity, electrically stimulated [(3)H]5-HT release and in vivo efficacy.