The Experts below are selected from a list of 162327 Experts worldwide ranked by ideXlab platform
Ralph Weissleder - One of the best experts on this subject based on the ideXlab platform.
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imaging of anticancer Drug Action in single cells
Nature Reviews Cancer, 2017Co-Authors: Miles A Miller, Ralph WeisslederAbstract:Imaging is widely used in anticancer Drug development, typically for whole-body tracking of labelled Drugs to different organs or to assess Drug efficacy through volumetric measurements. However, increasing attention has been drawn to pharmacology at the single-cell level. Diverse cell types, including cancer-associated immune cells, physicochemical features of the tumour microenvironment and heterogeneous cell behaviour all affect Drug delivery, response and resistance. This Review summarizes developments in the imaging of in vivo anticancer Drug Action, with a focus on microscopy approaches at the single-cell level and translational lessons for the clinic.
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single cell and subcellular pharmacokinetic imaging allows insight into Drug Action in vivo
Nature Communications, 2013Co-Authors: Greg M Thurber, Peter K Sorger, Katherine S Yang, Thomas Reiner, Rainer H Kohler, Timothy J Mitchison, Ralph WeisslederAbstract:Pharmacokinetic analysis at the organ level provides insight into how Drugs distribute throughout the body, but cannot explain how Drugs work at the cellular level. Here we demonstrate in vivo single-cell pharmacokinetic imaging of PARP-1 inhibitors and model Drug behaviour under varying conditions. We visualize intracellular kinetics of the PARP-1 inhibitor distribution in real time, showing that PARP-1 inhibitors reach their cellular target compartment, the nucleus, within minutes in vivo both in cancer and normal cells in various cancer models. We also use these data to validate predictive finite element modelling. Our theoretical and experimental data indicate that tumour cells are exposed to sufficiently high PARP-1 inhibitor concentrations in vivo and suggest that Drug inefficiency is likely related to proteomic heterogeneity or insensitivity of cancer cells to DNA-repair inhibition. This suggests that single-cell pharmacokinetic imaging and derived modelling improve our understanding of Drug Action at single-cell resolution in vivo.
Mark Von Zastrow - One of the best experts on this subject based on the ideXlab platform.
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a genetically encoded biosensor reveals location bias of opioid Drug Action
Neuron, 2018Co-Authors: Miriam Carolin Stoeber, Damien Jullie, Braden T Lobingier, Toon Laeremans, Jan Steyaert, Peter W Schiller, Aashish Manglik, Mark Von ZastrowAbstract:Opioid receptors (ORs) precisely modulate behavior when activated by native peptide ligands but distort behaviors to produce pathology when activated by non-peptide Drugs. A fundamental question is how Drugs differ from peptides in their Actions on target neurons. Here, we show that Drugs differ in the subcellular location at which they activate ORs. We develop a genetically encoded biosensor that directly detects ligand-induced activation of ORs and uncover a real-time map of the spatiotemporal organization of OR activation in living neurons. Peptide agonists produce a characteristic activation pattern initiated in the plasma membrane and propagating to endosomes after receptor internalization. Drugs produce a different activation pattern by additionally driving OR activation in the somatic Golgi apparatus and Golgi elements extending throughout the dendritic arbor. These results establish an approach to probe the cellular basis of neuromodulation and reveal that Drugs distort the spatiotemporal landscape of neuronal OR activation.
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a genetically encoded biosensor reveals location bias of opioid Drug Action
bioRxiv, 2018Co-Authors: Miriam Carolin Stoeber, Damien Jullie, Toon Laeremans, Jan Steyaert, Peter W Schiller, Aashish Manglik, Mark Von ZastrowAbstract:Opioid receptors (ORs) precisely modulate behavior when activated by native peptide ligands but distort behaviors to produce pathology when activated by non-peptide Drugs. A fundamental question is how Drugs differ from peptides in their Actions on target neurons. One way that Drugs can differ is by imposing selective effects on the conformational equilibrium of individual ORs. We wondered if Drugs can also impose selective effects on the location of OR activation in individual OR-expressing neurons. Here we develop a genetically encoded biosensor that directly localizes ligand-induced activation and deactivation of ORs in living cells, and use it to generate the first real- time map of the spatiotemporal organization of μ- and δ-OR activation in neurons. Peptide agonists produce a characteristic activation pattern initiated in the plasma membrane and propagating to endosomes after receptor internalization. Drugs produce a different activation pattern by uniquely driving OR activation in the somatic Golgi apparatus and extending throughout the dendritic arbor in Golgi outposts. These results demonstrate a new approach to probe the cellular basis of neuromodulation and reveal that Drugs profoundly distort the spatiotemporal landscape of neuronal OR activation.
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functional selectivity of gpcr directed Drug Action through location bias
Nature Chemical Biology, 2017Co-Authors: Roshanak Irannejad, Veronica Pessino, Delphine Mika, Bo Huang, Philip B Wedegaertner, Marco Conti, Mark Von ZastrowAbstract:G-protein-coupled receptors (GPCRs) are increasingly recognized to operate from intracellular membranes as well as the plasma membrane. The β2-adrenergic GPCR can activate Gs-linked cyclic AMP (Gs-cAMP) signaling from endosomes. We show here that the homologous human β1-adrenergic receptor initiates an internal Gs-cAMP signal from the Golgi apparatus. By developing a chemical method to acutely squelch G-protein coupling at defined membrane locations, we demonstrate that Golgi activation contributes significantly to the overall cellular cAMP response. Golgi signaling utilizes a preexisting receptor pool rather than receptors delivered from the cell surface, requiring separate access of extracellular ligands. Epinephrine, a hydrophilic endogenous ligand, accesses the Golgi-localized receptor pool by facilitated transport requiring the organic cation transporter 3 (OCT3), whereas Drugs can access the Golgi pool by passive diffusion according to hydrophobicity. We demonstrate marked differences, among both agonist and antagonist Drugs, in Golgi-localized receptor access and show that β-blocker Drugs currently used in the clinic differ markedly in ability to antagonize the Golgi signal. We propose 'location bias' as a new principle for achieving functional selectivity of GPCR-directed Drug Action.
Tanja Wenzler - One of the best experts on this subject based on the ideXlab platform.
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pharmacokinetics trypanosoma brucei gambiense efficacy and time of Drug Action of db829 a preclinical candidate for treatment of second stage human african trypanosomiasis
Antimicrobial Agents and Chemotherapy, 2013Co-Authors: Tanja Wenzler, Sihyung Yang, Olivier Braissant, David W Boykin, Michael Zhuo WangAbstract:Human African trypanosomiasis (HAT, also called sleeping sickness), a neglected tropical disease endemic to sub-Saharan Africa, is caused by the parasites Trypanosoma brucei gambiense and T. brucei rhodesiense. Current Drugs against this disease have significant limitations, including toxicity, increasing resistance, and/or a complicated parenteral treatment regimen. DB829 is a novel aza-diamidine that demonstrated excellent efficacy in mice infected with T. b. rhodesiense or T. b. brucei parasites. The current study examined the pharmacokinetics, in vitro and in vivo activity against T. b. gambiense, and time of Drug Action of DB829 in comparison to pentamidine. DB829 showed outstanding in vivo efficacy in mice infected with parasites of T. b. gambiense strains, despite having higher in vitro 50% inhibitory concentrations (IC50s) than against T. b. rhodesiense strain STIB900. A single dose of DB829 administered intraperitoneally (5 mg/kg of body weight) cured all mice infected with different T. b. gambiense strains. No cross-resistance was observed between DB829 and pentamidine in T. b. gambiense strains isolated from melarsoprol-refractory patients. Compared to pentamidine, DB829 showed a greater systemic exposure when administered intraperitoneally, partially contributing to its improved efficacy. Isothermal microcalorimetry and in vivo time-to-kill studies revealed that DB829 is a slower-acting trypanocidal compound than pentamidine. A single dose of DB829 (20 mg/kg) administered intraperitoneally clears parasites from mouse blood within 2 to 5 days. In summary, DB829 is a promising preclinical candidate for the treatment of first- and second-stage HAT caused by both Trypanosoma brucei subspecies.
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isothermal microcalorimetry a new tool to monitor Drug Action against trypanosoma brucei and plasmodium falciparum
PLOS Neglected Tropical Diseases, 2012Co-Authors: Reto Brun, Tanja Wenzler, Andrea Steinhuber, Sergio Wittlin, Christian Scheurer, Andrej TrampuzAbstract:Isothermal microcalorimetry is an established tool to measure heat flow of physical, chemical or biological processes. The metabolism of viable cells produces heat, and if sufficient cells are present, their heat production can be assessed by this method. In this study, we investigated the heat flow of two medically important protozoans, Trypanosoma brucei rhodesiense and Plasmodium falciparum. Heat flow signals obtained for these pathogens allowed us to monitor parasite growth on a real-time basis as the signals correlated with the number of viable cells. To showcase the potential of microcalorimetry for measuring Drug Action on pathogenic organisms, we tested the method with three antitrypanosomal Drugs, melarsoprol, suramin and pentamidine and three antiplasmodial Drugs, chloroquine, artemether and dihydroartemisinin, each at two concentrations on the respective parasite. With the real time measurement, inhibition was observed immediately by a reduced heat flow compared to that in untreated control samples. The onset of Drug Action, the degree of inhibition and the time to death of the parasite culture could conveniently be monitored over several days. Microcalorimetry is a valuable element to be added to the toolbox for Drug discovery for protozoal diseases such as human African trypanosomiasis and malaria. The method could probably be adapted to other protozoan parasites, especially those growing extracellularly.
Catherine J Harmer - One of the best experts on this subject based on the ideXlab platform.
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how do antidepressants work new perspectives for refining future treatment approaches
The Lancet Psychiatry, 2017Co-Authors: Catherine J Harmer, Ronald S Duman, P J CowenAbstract:Summary Most currently available antidepressants target monoamine neurotransmitter function. However, a purely neurotransmitter-based explanation for antidepressant Drug Action is challenged by the delayed clinical onset of most agents and the need to explain how neurochemical changes reverse the many different symptoms of depression. Novel approaches to understanding of antidepressant Drug Action include a focus on early changes in emotional and social processing and the role of neural plasticity. In this Review, we discuss the ways in which these two different theories reflect different or complementary approaches, and how they might be integrated to offer novel solutions for people with depression. We consider the predictions made by these mechanistic approaches for the stratification and development of new therapeutics for depression, and the next steps that need to be made to facilitate this translation of science to the clinic.
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testing the antidepressant properties of the peptide ara290 in a human neuropsychological model of Drug Action
European Neuropsychopharmacology, 2015Co-Authors: Hilâl Cerit, Catherine J Harmer, Ilya M Veer, Albert Dahan, Marieke Niesters, Kamilla W Miskowiak, Serge A R B Rombouts, Willem Van Der DoesAbstract:Studies on the neural effects of Erythropoietin (EPO) indicate that EPO may have antidepressant effects. Due to its hematopoietic effects, EPO may cause serious side-effects with repeated administration if patients are not monitored extensively. ARA290 is an EPO-analog peptide without such hematopoietic side-effects but may have neurotrophic and antidepressant effects. The aim of this study was to investigate the possible antidepressant effects of ARA290 in a neuropsychological model of Drug Action. Healthy participants (N=36) received ARA290 (2mg) or placebo in a double-blind, randomized, parallel-group design. Neural and cognitive effects were assessed one week after administration. Primary outcome measures were the neural processing of fearful vs happy faces and the behavioral recognition of emotional facial expressions. ARA290-treated individuals displayed lower neural responses to happy faces in the fusiform gyrus. ARA290 tended to lower the recognition of happy and disgust facial expressions. Although ARA290 was not associated with a better memory for positive words, it was associated with faster categorization of positive vs negative words. Finally, ARA290 increased attention towards positive emotional pictures. No effects were observed on mood and affective symptoms. ARA290 may modulate some aspects of emotional processing, however, the direction and the strength of its effects do not unequivocally support an antidepressant-like profile for ARA290. Future studies may investigate the effects of different timing and dose.
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a cognitive neuropsychological model of antidepressant Drug Action
Progress in Neuro-psychopharmacology & Biological Psychiatry, 2011Co-Authors: A Pringle, P J Cowen, Michael Browning, Catherine J HarmerAbstract:The psychological mechanisms by which antidepressant Drugs act to improve mood remain underspecified. In this paper we consider the evidence to suggest that early changes in emotional processing underlie subsequent mood improvement following antidepressant treatment. Negative biases in information processing are consistently found in depression, and we argue that primary mode of Action of antidepressant Drugs may be to remediate these biases providing a more positive social environment in which the patient can relearn emotional associations fostering later improvement in mood. Evidence from behavioural and functional magnetic resonance imaging studies supports this hypothesis. Experimental medicine models developed under this premise have the potential to screen for new treatments, to predict individual treatment response and to consider the effects of pharmacological vs psychological treatments.
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serotonin and emotional processing does it help explain antidepressant Drug Action
Neuropharmacology, 2008Co-Authors: Catherine J HarmerAbstract:There is growing interest in the effects of antidepressant Drug treatment on measures of emotional processing. Such Actions may help us understand the role of monoamines in emotional dysfunction in depression and how antidepressant Drug treatments work. Recent studies suggest that decreasing central serotonin function with tryptophan depletion can reinstate negative biases in recovered depressed patients, even at doses insufficient to induce changes in mood. Conversely, antidepressant Drug administration increases the processing of positive emotional information in healthy volunteers and acutely depressed patients early in treatment. This increase in positive bias may provide a platform for subsequent cognitive restructuring and learning which contributes to the evolution of symptom change in depression. Functional neuroimaging studies suggest that these early antidepressant effects involve fronto-limbic and extra-striate circuitry suggestive of Actions on both the initial appraisal and attentional processing of affective stimuli. This approach may therefore provide a framework for linking psychological and biological processes in emotional disorders and their treatment. Antidepressants may not directly modulate mood and anxiety but rather allow a different perspective for our ongoing evaluation of our self, the world and the future.
Olivier Braissant - One of the best experts on this subject based on the ideXlab platform.
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non invasive monitoring of Drug Action a new live in vitro assay design for chagas disease Drug discovery
PLOS Neglected Tropical Diseases, 2020Co-Authors: Pascal Mäser, Olivier Braissant, Anna F Fesser, Francisco Olmo, John Kelly, Marcel KaiserAbstract:New assay designs are needed to improve the predictive value of the Trypanosoma cruzi in vitro tests used as part of the Chagas' disease Drug development pipeline. Here, we employed a green fluorescent protein (eGFP)-expressing parasite line and live high-content imaging to monitor the growth of T. cruzi amastigotes in mouse embryonic fibroblasts. A novel assay design allowed us to follow parasite numbers over 6 days, in four-hour intervals, while occupying the microscope for only 24 hours per biological replicate. Dose-response curves were calculated for each time point after addition of test compounds, revealing how EC50 values first decreased over the time of Drug exposure, and then leveled off. However, we observed that parasite numbers could vary, even in the untreated controls, and at different sites in the same well, which caused variability in the EC50 values. To overcome this, we established that fold change in parasite number per hour is a more robust and informative measure of Drug activity. This was calculated based on an exponential growth model for every biological sample. The net fold change per hour is the result of parasite replication, differentiation, and death. The calculation of this fold change enabled us to determine the tipping point of Drug Action, i.e. the time point when the death rate of the parasites exceeded the growth rate and the fold change dropped below 1, depending on the Drug concentration and exposure time. This revealed specific pharmacodynamic profiles of the benchmark Drugs benznidazole and posaconazole.
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non invasive monitoring of Drug Action a new live in vitro assay design for chagas disease Drug discovery
bioRxiv, 2020Co-Authors: Pascal Mäser, Olivier Braissant, Anna F Fesser, Francisco Olmo, John Kelly, Marcel KaiserAbstract:Abstract New assay designs are needed to improve the predictive value of the Trypanosoma cruzi in vitro tests used as part of the Chagas’ disease Drug development pipeline. Here, we employed a green fluorescent protein (eGFP)-expressing parasite line and live high-content imaging to monitor the growth of T. cruzi amastigotes in mouse embryonic fibroblasts. A novel assay design allowed us to follow parasite numbers over 6 days, in four-hour intervals, while occupying the microscope for only 24 hours per biological replicate. Dose-response curves were calculated for each time point after addition of test compounds, revealing how EC50 values first decreased over the time of Drug exposure, and then leveled off. However, we observed that parasite numbers could vary, even in the untreated controls, and at different sites in the same well, which caused variability in the EC50 values. To overcome this, we established that fold change in parasite number per hour is a more robust and informative measure of Drug activity. This was calculated based on an exponential growth model for every biological sample. The net fold change per hour is the result of parasite replication, differentiation, and death. The calculation of this fold change enabled us to determine the tipping point of Drug Action, i.e. the point immediately before the fold change becomes negative, independent of the Drug concentration and exposure time. This time-to-kill over Drug concentration revealed specific pharmacodynamic profiles of the benchmark Drugs benznidazole and posaconazole. Author Summary Chagas’ disease, caused by Trypanosoma cruzi, is a chronic debilitating infection occurring mostly in Latin America. There is an urgent need for new, well tolerated Drugs. However, the latest therapeutic candidates have yielded disappointing outcomes in clinical trials, despite promising preclinical results. This demands new and more predictive in vitro assays. To address this, we have developed an assay design that enables the growth of T. cruzi intracellular forms to be monitored in real time, under Drug pressure, for 6 days post-infection. This allowed us to establish the tipping point of Drug Action, when the parasites stop multiplying and start to die. The resulting pharmacodynamics profiles can provide robust and informative details on anti-chagasic candidates, as demonstrated for the benchmark Drugs benznidazole and posaconazole.
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pharmacokinetics trypanosoma brucei gambiense efficacy and time of Drug Action of db829 a preclinical candidate for treatment of second stage human african trypanosomiasis
Antimicrobial Agents and Chemotherapy, 2013Co-Authors: Tanja Wenzler, Sihyung Yang, Olivier Braissant, David W Boykin, Michael Zhuo WangAbstract:Human African trypanosomiasis (HAT, also called sleeping sickness), a neglected tropical disease endemic to sub-Saharan Africa, is caused by the parasites Trypanosoma brucei gambiense and T. brucei rhodesiense. Current Drugs against this disease have significant limitations, including toxicity, increasing resistance, and/or a complicated parenteral treatment regimen. DB829 is a novel aza-diamidine that demonstrated excellent efficacy in mice infected with T. b. rhodesiense or T. b. brucei parasites. The current study examined the pharmacokinetics, in vitro and in vivo activity against T. b. gambiense, and time of Drug Action of DB829 in comparison to pentamidine. DB829 showed outstanding in vivo efficacy in mice infected with parasites of T. b. gambiense strains, despite having higher in vitro 50% inhibitory concentrations (IC50s) than against T. b. rhodesiense strain STIB900. A single dose of DB829 administered intraperitoneally (5 mg/kg of body weight) cured all mice infected with different T. b. gambiense strains. No cross-resistance was observed between DB829 and pentamidine in T. b. gambiense strains isolated from melarsoprol-refractory patients. Compared to pentamidine, DB829 showed a greater systemic exposure when administered intraperitoneally, partially contributing to its improved efficacy. Isothermal microcalorimetry and in vivo time-to-kill studies revealed that DB829 is a slower-acting trypanocidal compound than pentamidine. A single dose of DB829 (20 mg/kg) administered intraperitoneally clears parasites from mouse blood within 2 to 5 days. In summary, DB829 is a promising preclinical candidate for the treatment of first- and second-stage HAT caused by both Trypanosoma brucei subspecies.
