Cinpanemab in Early Parkinson Disease: Evaluation of Biomarker Results From the Phase 2 SPARK Clinical Trial.

BACKGROUND AND OBJECTIVES: Sensitive, reliable, and scalable biomarkers are needed to accelerate the development of therapies for Parkinson disease (PD). In this study, we evaluate the biomarkers of early PD diagnosis, disease progression, and treatment effect collected in the SPARK. METHODS: Cinpanemab is a human-derived monoclonal antibody binding preferentially to aggregated forms of extracellular α-synuclein. SPARK was a randomized, double-blind, placebo-controlled, phase 2 multicenter trial evaluating 3 cinpanemab doses administered intravenously every 4 weeks for 52 weeks with an active treatment dose-blind extension period for up to 112 weeks. SPARK enrolled 357 participants diagnosed with PD within 3 years, aged 40-80 years, ≤2.5 on the modified Hoehn and Yahr scale, and with evidence of striatal dopaminergic deficit. The primary outcome was change from baseline in the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale total score. Secondary and exploratory biomarker outcomes evaluated change from baseline at week 52 relative to placebo. Dopamine transporter SPECT and MRI were used to quantify changes in the nigrostriatal dopamine pathway and regional atrophy. CSF and plasma samples were used to assess change in total α-synuclein levels, α-synuclein seeding, and neurofilament light chain levels. SPARK was conducted from January 2018 to April 2021 and terminated due to lack of efficacy. RESULTS: Approximately 3.8% (15/398) of SPECT-imaged participants did not have evidence of dopaminergic deficit and were screen-failed. Binary classification of α-synuclein seeding designated 93% (110/118) of the enrolled CSF subgroup as positive for α-synuclein seeds at baseline. Clinical disease progression was observed, with no statistically significant difference in cinpanemab groups compared with that in placebo. Ninety-nine percent of participants with positive α-synuclein seeding remained positive through week 52. No statistically significant changes from baseline were observed between treatment groups and placebo across biomarker measures. Broadly, there was minimal annual change with high interindividual variability across biomarkers-with striatal binding ratios of the ipsilateral putamen showing the greatest mean change/SD over time. DISCUSSION: Biomarker results indicated enrollment of the intended population with early PD, but there was no significant correlation with disease progression or clear evidence of a cinpanemab treatment effect on biomarker measures. Suitable biomarkers for evaluating disease severity and progression in early PD trials are still needed. TRIAL REGISTRATION INFORMATION: NCT03318523 (clinicaltrials.gov/ct2/show/NCT03318523); Submitted October 24, 2017; First patient enrolled January 2018.

Drivers of cyanotoxin and taste-and-odor compound presence within the benthic algae of human-disturbed rivers.

Freshwater benthic algae form complex mat matrices that can confer ecosystem benefits but also produce harmful cyanotoxins and nuisance taste-and-odor (T&O) compounds. Despite intensive study of the response of pelagic systems to anthropogenic change, the environmental factors controlling toxin presence in benthic mats remain uncertain. Here, we present a unique dataset from a rapidly urbanizing community (Kansas City, USA) that spans environmental, toxicological, taxonomic, and genomic indicators to identify the prevalence of three cyanotoxins (microcystin, anatoxin-a, and saxitoxin) and two T&O compounds (geosmin and 2-methylisoborneol). Thereafter, we construct a random forest model informed by game theory to assess underlying drivers. Microcystin (11.9 ± 11.6 µg/m2), a liver toxin linked to animal fatalities, and geosmin (0.67 ± 0.67 µg/m2), a costly-to-treat malodorous compound, were the most abundant compounds and were present in 100 % of samples, irrespective of land use or environmental conditions. Anatoxin-a (8.1 ± 11.6 µg/m2) and saxitoxin (0.18 ± 0.39 µg/m2), while not always detected, showed a systematic tradeoff in their relative importance with season, an observation not previously reported in the literature. Our model indicates that microcystin concentrations were greatest where microcystin-producing genes were present, whereas geosmin concentrations were high in the absence of geosmin-producing genes. Together, these results suggest that benthic mats produce microcystin in situ but that geosmin production may occur ex situ with its presence in mats attributable to adsorption by organic matter. Our study broadens the awareness of benthic cyanobacteria as a source of harmful and nuisance metabolites and highlights the importance of benthic monitoring for sustaining water quality standards in rivers.

Exploratory Tau Biomarker Results From a Multiple Ascending-Dose Study of BIIB080 in Alzheimer Disease: A Randomized Clinical Trial.

Importance: Accumulation of hyperphosphorylated, tangled microtubule-associated protein tau (MAPT) is a pathological hallmark of Alzheimer disease (AD) associated with disease progression and cognitive decline. Objective: To evaluate the effect of tau synthesis reduction on tau biomarkers in patients with mild AD. Design, Setting, and Participants: This randomized clinical trial was a double-blind, placebo-controlled 36-week multiple-ascending dose (MAD) phase 1b trial (October 2017 to September 2020), followed by a 64- or 71-week open-label long-term extension (LTE) (October 2019 to May 2022). After being assessed for eligibility at 12 sites in Canada and Europe, participants with mild AD and confirmed amyloid pathology were randomized 3:1 (BIIB080:placebo) in 4 dose cohorts. Intervention: Intrathecal administration of BIIB080, a MAPT-targeting antisense oligonucleotide, or placebo. Active dose arms included 10 mg every 4 weeks, 30 mg every 4 weeks, 60 mg every 4 weeks, and 115 mg every 12 weeks during the MAD period and 60 mg every 12 weeks or 115 mg every 12 weeks during the LTE. Main Outcome and Measures: The original primary end point was safety. Additionally, BIIB080, total tau (t-tau), and phosphorylated tau 181 (p-tau181) cerebrospinal fluid (CSF) concentrations were evaluated. Tau positron emission tomography (PET) was collected in a substudy, and standard uptake value ratios (SUVRs) were calculated in a priori-defined composite regions of interest. Results: Of 102 participants assessed for eligibility, 46 participants with mild AD were enrolled; 23 (50%) were female, and mean (SD) age was 65.8 (5.70) years. BIIB080 was generally well tolerated and was associated with a dose-dependent reduction in CSF t-tau and p-tau181 in the MAD period (56% reduction; 95% CI, 50% to 62%; and 51% reduction; 95% CI, 38% to 63%, of CSF t-tau in the 2 higher-dose cohorts) that continued and/or was maintained through quarterly dosing in the LTE. Tau PET demonstrated reduced accumulation vs placebo at week 25 (n = 13). At week 100, tau PET showed a reduction from baseline across all regions assessed (n = 12), with the largest reductions from baseline observed in the temporal composite (-0.71 SUVR; 95% CI, -1.40 to -0.02). A moderate correlation was observed between model-predicted cumulative CSF drug exposure and tau PET change. Conclusions and Relevance: In this randomized clinical trial, BIIB080 reduced tau biomarkers, including CSF t-tau, CSF p-tau181, and tau PET, which is associated with cognitive decline, in participants with mild AD. Effects of BIIB080 on biomarkers and clinical outcomes are being further evaluated in a phase 2 trial. Trial Registration: ClinicalTrials.gov Identifier: NCT03186989.

CSF biomarker concordance with amyloid PET in Phase 3 studies of aducanumab.

INTRODUCTION: We assessed the use of cerebrospinal fluid (CSF) biomarkers as an alternative to positron emission tomography (PET) for brain amyloid beta (Aß) pathology confirmation in the EMERGE and ENGAGE clinical trials. METHODS: EMERGE and ENGAGE were randomized, placebo-controlled, Phase 3 trials of aducanumab in participants with early Alzheimer's disease. Concordance between CSF biomarkers (Aß42, Aß40, phosphorylated tau 181, and total tau) and amyloid PET status (visual read) at screening was examined. RESULTS: Robust concordance between CSF biomarkers and amyloid PET visual status was observed (for Aß42/Aß40, AUC: 0.90; 95% CI: 0.83-0.97; p < 0.0001), confirming CSF biomarkers as a reliable alternative to amyloid PET in these studies. Compared with single CSF biomarkers, CSF biomarker ratios showed better agreement with amyloid PET visual reads, demonstrating high diagnostic accuracy. DISCUSSION: These analyses add to the growing body of evidence supporting CSF biomarkers as reliable alternatives to amyloid PET imaging for brain Aß pathology confirmation. HIGHLIGHTS: CSF biomarkers and amyloid PET concordance were assessed in Ph3 aducanumab trials. Robust concordance between CSF biomarkers and amyloid PET was observed. CSF biomarker ratios increased diagnostic accuracy over single CSF biomarkers. CSF Aß42/Aß40 demonstrated high concordance with amyloid PET. Results support CSF biomarker testing as a reliable alternative to amyloid PET.

A Comparison of Magnetic Resonance Imaging Methods to Assess Multiple Sclerosis Lesions: Implications for Patient Characterization and Clinical Trial Design.

Magnetic resonance imaging (MRI) is a sensitive imaging modality for identifying inflammatory and/or demyelinating lesions, which is critical for a clinical diagnosis of MS and evaluating drug responses. There are many unique means of probing brain tissue status, including conventional T1 and T2 weighted imaging (T1WI, T2WI), T2 fluid attenuated inversion recovery (FLAIR), magnetization transfer, myelin water fraction, diffusion tensor imaging (DTI), phase-sensitive inversion recovery and susceptibility weighted imaging (SWI), but no study has combined all of these modalities into a single well-controlled investigation. The goals of this study were to: compare different MRI measures for lesion visualization and quantification; evaluate the repeatability of various imaging methods in healthy controls; compare quantitative susceptibility mapping (QSM) with myelin water fraction; measure short-term longitudinal changes in the white matter of MS patients and map out the tissue properties of the white matter hyperintensities using STAGE (strategically acquired gradient echo imaging). Additionally, the outcomes of this study were anticipated to aid in the choice of an efficient imaging protocol reducing redundancy of information and alleviating patient burden. Of all the sequences used, T2 FLAIR and T2WI showed the most lesions. To differentiate the putative demyelinating lesions from inflammatory lesions, the fusion of SWI and T2 FLAIR was used. Our study suggests that a practical and efficient imaging protocol combining T2 FLAIR, T1WI and STAGE (with SWI and QSM) can be used to rapidly image MS patients to both find lesions and study the demyelinating and inflammatory characteristics of the lesions.

Longitudinal Magnetic Resonance Imaging of Cerebral Microbleeds in Multiple Sclerosis Patients.

We hypothesized that cerebral microbleeds (CMBs) in multiple sclerosis (MS) patients will be detected with higher prevalence compared to healthy controls (HC) and that quantitative susceptibility mapping (QSM) will help remove false positives seen in susceptibility weighted imaging (SWI). A cohort of 100 relapsing remitting MS subjects scanned at 3T were used to validate a set of CMB detection guidelines specifically using QSM. A second longitudinal cohort of 112 MS and 25 HCs, also acquired at 3T, was reviewed across two time points. Both cohorts were imaged with SWI and fluid attenuated inversion recovery. Fourteen subjects in the first cohort (14%, 95% CI 8-21%) and twenty-one subjects in the second cohort (18.7%, 95% CI 11-27%) had at least one CMB. The combined information from SWI and QSM allowed us to discern stable CMBs and new CMBs from potential mimics and evaluate changes over time. The longitudinal results demonstrated that longer disease duration increased the chance to develop new CMBs. Higher age was also associated with increased CMB prevalence for MS and HC. We observed that MS subjects developed new CMBs between time points, indicating the need for longitudinal quantitative imaging of CMBs.

Serotonin release measured in the human brain: a PET study with [11C]CIMBI-36 and d-amphetamine challenge.

Positron emission tomography (PET) enables non-invasive estimation of neurotransmitter fluctuations in the living human brain. While these methods have been applied to dopamine and some other transmitters, estimation of 5-hydroxytryptamine (5-HT; Serotonin) release has proved to be challenging. Here we demonstrate the utility of the novel 5-HT2A receptor agonist radioligand, [11C]CIMBI-36, and a d-amphetamine challenge to evaluate synaptic 5-HT changes in the living human brain. Seventeen healthy male volunteers received [11C]CIMBI-36 PET scans before and 3 h after an oral dose of d-amphetamine (0.5 mg/kg). Dynamic PET data were acquired over 90 min, and the total volume of distribution (VT) in the frontal cortex and the cerebellum derived from a kinetic analysis using MA1. The frontal cortex binding potential (BPNDfrontal) was calculated as (VTfrontal/VTcerebellum) - 1. ∆BPNDfrontal = 1 - (BPNDfrontal post-dose/BPNDfrontal baseline) was used as an index of 5-HT release. Statistical inference was tested by means of a paired Students t-test evaluating a reduction in post-amphetamine [11C]CIMBI-36 BPNDfrontal. Following d-amphetamine administration, [11C]CIMBI-36 BPNDfrontal was reduced by 14 ± 13% (p = 0.002). Similar effects were observed in other cortical regions examined in an exploratory analysis. [11C]CIMBI-36 binding is sensitive to synaptic serotonin release in the human brain, and when combined with a d-amphetamine challenge, the evaluation of the human brain serotonin system in neuropsychiatric disorders, such as major depression and Parkinson's disease is enabled.

Test-retest characteristic of [18F]MK-6240 quantitative outcomes in cognitively normal adults and subjects with Alzheimer's disease.

[18F]MK-6240 is a selective, high-affinity PET radiotracer for imaging neurofibrillary tangles (NFT) in Alzheimer's disease (AD). Herein, we report test-retest (T-RT) reproducibility of [18F]MK-6240 in AD and healthy volunteers (HV). Twelve subjects with AD and three cognitively normal HV were enrolled in the study and dynamically scanned for 150 min with [18F]MK-6240 under a T-RT protocol. Two radioactivity doses were investigated: 165 ± 3 MBq (n = 6) and 300 ± 40 MBq (n = 9). Serial arterial blood samples were taken for each scan to obtain metabolite-corrected input functions. Following intravenous administration of [18F]MK-6240, the tracer rapidly partitioned into the brain and its heterogenous distribution pattern was consistent with known NFT pathology in AD. In contrast, uptake in HV was low and uniform across the brain parenchyma. Across all subjects, average T-RT variabilities in NFT-rich regions were ∼21%, ∼14% and ∼6% for various quantitative metrics: total distribution volume (VT), binding potential (BPND), and standardized uptake ratio (SUVR90-120), respectively. No significant differences in SUVR T-RT variability were observed between the high and low injected radioactivity groups (5.6% and 6.1%, respectively). This work suggests [18F]MK-6240 has adequate SUVR T-RT characteristics supporting the use of this outcome in future studies.

Biogeography and co-occurrence of 16 planktonic species of Keratella Bory de St. Vincent, 1822 (Rotifera, Ploima, Brachionidae) in lakes and reservoirs of the United States.

We report current distributions of 16 species of Keratella Bory de St. Vincent, 1822 within lakes and reservoirs of the U.S. Specimens were identified from 988 lakes and reservoirs during spring and summer 2012 as part of the U.S. Environmental Protection Agency's National Lakes Assessment (NLA). We performed a co-occurrence analysis to determine correlations between species-pair occurrences and a niche-centroid analysis to predict optimal water quality conditions for each species. While a high degree of overlap in geographic range was observed among the species, distribution maps showed that K. quadrata was largely confined to more northern latitudes and K. americana was confined primarily to the eastern U.S. Other common species were either ubiquitously or sparsely distributed across ecoregions, suggesting that their distribution may be more related to inter-species competition or local water quality parameters. This study expands the limited pool of knowledge on rotifer biogeography within the U.S.

Amyloid beta-positive subjects exhibit longitudinal network-specific reductions in spontaneous brain activity.

Amyloid beta (Aß) deposition and cognitive decline are key features of Alzheimer's disease. The relationship between Aß status and changes in neuronal function over time, however, remains unclear. We evaluated the effect of baseline Aß status on reference region spontaneous brain activity (SBA-rr) using resting-state functional magnetic resonance imaging and fluorodeoxyglucose positron emission tomography in patients with mild cognitive impairment. Patients (N = 62, [43 Aß-positive]) from the Alzheimer's Disease Neuroimaging Initiative were divided into Aß-positive and Aß-negative groups via prespecified cerebrospinal fluid Aß42 or 18F-florbetapir positron emission tomography standardized uptake value ratio cutoffs measured at baseline. We analyzed interaction of biomarker-confirmed Aß status with SBA-rr change over a 2-year period using mixed-effects modeling. SBA-rr differences between Aß-positive and Aß-negative subjects increased significantly over time within subsystems of the default and visual networks. Changes exhibit an interaction with memory performance over time but were independent of glucose metabolism. Results reinforce the value of resting-state functional magnetic resonance imaging in evaluating Alzheimer''s disease progression and suggest spontaneous neuronal activity changes are concomitant with cognitive decline.

Environmental factors influencing the quantitative distribution of microcystin and common potentially toxigenic cyanobacteria in U.S. lakes and reservoirs.

Many species of cyanobacteria are capable of producing toxins and causing nuisance blooms, however response to environmental conditions is likely taxon-specific. Environmental factors influencing cyanobacterial composition and toxin production in lakes have been examined in many studies; yet are often confined to individual water bodies, or to a small number of systems within the same region. Here, data from the 2012 USEPA National Lakes Assessment are used to examine relationships between biovolume of common potentially-toxigenic cyanobacteria (Aphanizomenon spp., Cylindrospermopsis spp., Dolichospermum spp., Microcystis spp. and Planktothrix spp.) and environmental variables across the entire conterminous United States, and results are compared across nine distinct ecoregions. Total phosphorus and water clarity were identified as the most influential environmental factors correlated with phytoplankton community composition. The Northern, Southern and Temperate Plains ecoregions displayed the highest biovolumes of potentially toxigenic taxa on average, as well as highest mean concentrations of microcystin. In those three ecoregions, samples with microcystin concentrations greater than 1 ppb were primarily dominated by Planktothrix spp. while in all other ecoregions Dolichospermum spp. was the dominant genus. Canonical Correlation Analysis revealed a strong association between high microcystin concentrations and high nutrient concentrations (total nitrogen and total phosphorus), and between high microcystin concentrations and low percentage of watershed forest cover. Results from this study indicate that the likely occurrence of potentially toxigenic taxa in lakes and reservoirs is predictable on a biogeographical basis, depending on morphological and water quality characteristics. Data from this study may be useful to regional managers attempting to prevent or mitigate nuisance cyanobacterial blooms.

Distribution of six taxa in the family Bosminidae Baird (Crustacea: Branchiopoda: Anomopoda) in the plankton of lakes and reservoirs within the continental United States, including expanded range of the invasive cladoceran Bosmina (Eubosmina) coregoni Baird.

Updated range distributions in lakes and reservoirs of the continental United States are provided for six taxa in the family Bosminidae (Bosmina (Bosmina) cf. longirostris (Müller), Bosmina (Eubosmina) coregoni Baird, Bosmina cf. longispina Leydig, Bosmina (Liederobosmina) cf. tubicen Brehm, Bosmina (Liederobosmina) cf. hagmanni Stingelin, and Bosminopsis deitersi Richard), an ecologically important and taxonomically confusing group. This paper provides updated range distribution and information on the westward expansion of the invasive species Bosmina (Eubosmina) coregoni, which was first established in the Great Lakes in the late 1960's. Current survey data are compared with previous distribution records and discussed in the context of environmental variables.

A lake-centric geospatial database to guide research and inform management decisions in an Arctic watershed in northern Alaska experiencing climate and land-use changes.

Lakes are dominant and diverse landscape features in the Arctic, but conventional land cover classification schemes typically map them as a single uniform class. Here, we present a detailed lake-centric geospatial database for an Arctic watershed in northern Alaska. We developed a GIS dataset consisting of 4362 lakes that provides information on lake morphometry, hydrologic connectivity, surface area dynamics, surrounding terrestrial ecotypes, and other important conditions describing Arctic lakes. Analyzing the geospatial database relative to fish and bird survey data shows relations to lake depth and hydrologic connectivity, which are being used to guide research and aid in the management of aquatic resources in the National Petroleum Reserve in Alaska. Further development of similar geospatial databases is needed to better understand and plan for the impacts of ongoing climate and land-use changes occurring across lake-rich landscapes in the Arctic.

Molecular imaging in oncology drug development.

Tremendous breakthroughs are being made in cancer drug discovery and development. However, such breakthroughs come at a high financial cost. At a time when there is increasing pressure on drug pricing, in part because of increased life expectancy, it is more important than ever to drive new therapeutics towards patients as efficiently as possible. In this review we discuss the applications of molecular imaging in oncology drug development, with a focus on its ability to enable better early decision making, to increase efficiency and thereby to lower costs.

Determination of detection sensitivity for cerebral microbleeds using susceptibility-weighted imaging.

Cerebral microbleeds (CMBs) are small brain hemorrhages caused by the break down or structural abnormalities of small vessels of the brain. Owing to the paramagnetic properties of blood degradation products, CMBs can be detected in vivo using susceptibility-weighted imaging (SWI). SWI can be used not only to detect iron changes and CMBs, but also to differentiate them from calcifications, both of which may be important MR-based biomarkers for neurodegenerative diseases. Moreover, SWI can be used to quantify the iron in CMBs. SWI and gradient echo (GE) imaging are the two most common methods for the detection of iron deposition and CMBs. This study provides a comprehensive analysis of the number of voxels detected in the presence of a CMB on GE magnitude, phase and SWI composite images as a function of resolution, signal-to-noise ratio (SNR), TE, field strength and susceptibility using in silico experiments. Susceptibility maps were used to quantify the bias in the effective susceptibility value and to determine the optimal TE for CMB quantification. We observed a non-linear trend with susceptibility for CMB detection from the magnitude images, but a linear trend with susceptibility for CMB detection from the phase and SWI composite images. The optimal TE values for CMB quantification were found to be 3 ms at 7 T, 7 ms at 3 T and 14 ms at 1.5 T for a CMB of one voxel in diameter with an SNR of 20: 1. The simulations of signal loss and detectability were used to generate theoretical formulae for predictions. Copyright © 2016 John Wiley & Sons, Ltd.

Image quality of Zr-89 PET imaging in the Siemens microPET Focus 220 preclinical scanner.

PURPOSE: Zr-89 positron emission tomography (PET) is a valuable tool for understanding the biodistribution and pharmacokinetics of antibody-based therapeutics. We compared the image quality of Zr-89 PET and F-18 PET in the Siemens microPET Focus 220 preclinical scanner using different reconstruction methods. PROCEDURES: Image quality metrics were measured in various Zr-89 and F-18 PET phantoms, including the NEMA NU 4-2008 image quality phantom. Images were reconstructed using various algorithms. RESULTS: Zr-89 PET had greater image noise, inferior spatial resolution, and greater spillover than F-18 PET, but comparable recovery coefficients for cylinders of various diameters. Of the reconstruction methods, OSEM3D resulted in the lowest noise, highest recovery coefficients, best spatial resolution, but also the greatest spillover. Scatter correction results were found to be sensitive to varying object sizes. CONCLUSIONS: Zr-89 PET image quality was inferior to that of F-18, and no single reconstruction method was superior in all aspects of image quality.

Investigation of cross-species translatability of pharmacological MRI in awake nonhuman primate - a buprenorphine challenge study.

BACKGROUND: Pharmacological MRI (phMRI) is a neuroimaging technique where drug-induced hemodynamic responses can represent a pharmacodynamic biomarker to delineate underlying biological consequences of drug actions. In most preclinical studies, animals are anesthetized during image acquisition to minimize movement. However, it has been demonstrated anesthesia could attenuate basal neuronal activity, which can confound interpretation of drug-induced brain activation patterns. Significant efforts have been made to establish awake imaging in rodents and nonhuman primates (NHP). Whilst various platforms have been developed for imaging awake NHP, comparison and validation of phMRI data as translational biomarkers across species remain to be explored. METHODOLOGY: We have established an awake NHP imaging model that encompasses comprehensive acclimation procedures with a dedicated animal restrainer. Using a cerebral blood volume (CBV)-based phMRI approach, we have determined differential responses of brain activation elicited by the systemic administration of buprenorphine (0.03 mg/kg i.v.), a partial µ-opioid receptor agonist, in the same animal under awake and anesthetized conditions. Additionally, region-of-interest analyses were performed to determine regional drug-induced CBV time-course data and corresponding area-under-curve (AUC) values from brain areas with high density of µ-opioid receptors. PRINCIPAL FINDINGS: In awake NHPs, group-level analyses revealed buprenorphine significantly activated brain regions including, thalamus, striatum, frontal and cingulate cortices (paired t-test, versus saline vehicle, p<0.05, n = 4). This observation is strikingly consistent with µ-opioid receptor distribution depicted by [6-O-[(11)C]methyl]buprenorphine ([(11)C]BPN) positron emission tomography imaging study in baboons. Furthermore, our findings are consistent with previous buprenorphine phMRI studies in humans and conscious rats which collectively demonstrate the cross-species translatability of awake imaging. Conversely, no significant change in activated brain regions was found in the same animals imaged under the anesthetized condition. CONCLUSIONS: Our data highlight the utility and importance of awake NHP imaging as a translational imaging biomarker for drug research.

In vivo imaging of cerebral dopamine D3 receptors in alcoholism.

Animal studies support the role of the dopamine D3 receptor (DRD3) in alcohol reinforcement or liking. Sustained voluntary alcohol drinking in rats has been associated with an upregulation of striatal DRD3 gene expression and selective blockade of DRD3 reduces ethanol preference, consumption, and cue-induced reinstatement. In vivo measurement of DRD3 in the living human brain has not been possible until recently owing to a lack of suitable tools. In this study, DRD3 status was assessed for the first time in human alcohol addiction. Brain DRD3 availability was compared between 16 male abstinent alcohol-dependent patients and 13 healthy non-dependent age-matched males using the DRD3-preferring agonist positron emission tomography (PET) radioligand [(11)C]PHNO with and without blockade with a selective DRD3 antagonist (GSK598809 60 mg p.o.). In striatal regions of interest, where the [(11)C]PHNO PET signal represents primarily DRD2 binding, no differences were seen in [(11)C]PHNO binding between the groups at baseline. However, baseline [(11)C]PHNO binding was higher in alcohol-dependent patients in hypothalamus (VT: 16.5 ± 4 vs 13.7 ± 2.9, p = 0.040), a region in which the [(11)C]PHNO signal almost entirely reflects DRD3 availability. The reductions in regional receptor binding (VT) following a single oral dose of GSK598809 (60 mg) were consistent with those observed in previous studies across all regions. There were no differences in regional changes in VT following DRD3 blockade between the two groups, indicating that the regional fractions of DRD3 are similar in the two groups, and the increased [(11)C]PHNO binding in the hypothalamus in alcohol-dependent patients is explained by elevated DRD3 in this group. Although we found no difference between alcohol-dependent patients and controls in striatal DRD3 levels, increased DRD3 binding in the hypothalamus of alcohol-dependent patients was observed. This may be relevant to the development of future therapeutic strategies to treat alcohol abuse.

Novel cardiovascular gene functions revealed via systematic phenotype prediction in zebrafish.

Comprehensive functional annotation of vertebrate genomes is fundamental to biological discovery. Reverse genetic screening has been highly useful for determination of gene function, but is untenable as a systematic approach in vertebrate model organisms given the number of surveyable genes and observable phenotypes. Unbiased prediction of gene-phenotype relationships offers a strategy to direct finite experimental resources towards likely phenotypes, thus maximizing de novo discovery of gene functions. Here we prioritized genes for phenotypic assay in zebrafish through machine learning, predicting the effect of loss of function of each of 15,106 zebrafish genes on 338 distinct embryonic anatomical processes. Focusing on cardiovascular phenotypes, the learning procedure predicted known knockdown and mutant phenotypes with high precision. In proof-of-concept studies we validated 16 high-confidence cardiac predictions using targeted morpholino knockdown and initial blinded phenotyping in embryonic zebrafish, confirming a significant enrichment for cardiac phenotypes as compared with morpholino controls. Subsequent detailed analyses of cardiac function confirmed these results, identifying novel physiological defects for 11 tested genes. Among these we identified tmem88a, a recently described attenuator of Wnt signaling, as a discrete regulator of the patterning of intercellular coupling in the zebrafish cardiac epithelium. Thus, we show that systematic prioritization in zebrafish can accelerate the pace of developmental gene function discovery.

Pharmacological modulation of brain activity in a preclinical model of osteoarthritis.

The earliest stages of osteoarthritis are characterized by peripheral pathology; however, during disease progression chronic pain emerges-a major symptom of osteoarthritis linked to neuroplasticity. Recent clinical imaging studies involving chronic pain patients, including osteoarthritis patients, have demonstrated that functional properties of the brain are altered, and these functional changes are correlated with subjective behavioral pain measures. Currently, preclinical osteoarthritis studies have not assessed if functional properties of supraspinal pain circuitry are altered, and if these functional properties can be modulated by pharmacological therapy either by direct or indirect action on brain systems. In the current study, functional connectivity was first assessed in order to characterize the functional neuroplasticity occurring in the rodent medial meniscus tear (MMT) model of osteoarthritis-a surgical model of osteoarthritis possessing peripheral joint trauma and a hypersensitive pain state. In addition to knee joint trauma at week 3 post-MMT surgery, we observed that supraspinal networks have increased functional connectivity relative to sham animals. Importantly, we observed that early and sustained treatment with a novel, peripherally acting broad-spectrum matrix metalloproteinase (MMP) inhibitor (MMPi) significantly attenuates knee joint trauma (cartilage degradation) as well as supraspinal functional connectivity increases in MMT animals. At week 5 post-MMT surgery, the acute pharmacodynamic effects of celecoxib (selective cyclooxygenase-2 inhibitor) on brain function were evaluated using pharmacological magnetic resonance imaging (phMRI) and functional connectivity analysis. Celecoxib was chosen as a comparator, given its clinical efficacy for alleviating pain in osteoarthritis patients and its peripheral and central pharmacological action. Relative to the vehicle condition, acute celecoxib treatment in MMT animals yielded decreased phMRI infusion responses and decreased functional connectivity, the latter observation being similar to what was detected following chronic MMPi treatment. These findings demonstrate that an assessment of brain function may provide an objective means by which to further evaluate the pathology of an osteoarthritis state as well as measure the pharmacodynamic effects of therapies with peripheral or peripheral and central pharmacological action.