Developmental toxicity assay using high content screening of zebrafish embryos

Typically, time‐consuming standard toxicological assays using the zebrafish (Danio rerio) embryo model evaluate mortality and teratogenicity after exposure during the first 2 days post‐fertilization. Here we describe an automated image‐based high content screening (HCS) assay to identify the teratogenic/embryotoxic potential of compounds in zebrafish embryos in vivo. Automated image acquisition was performed using a high content microscope system. Further automated analysis of embryo length, as a statistically quantifiable endpoint of toxicity, was performed on images post‐acquisition. The biological effects of ethanol, nicotine, ketamine, caffeine, dimethyl sulfoxide and temperature on zebrafish embryos were assessed. This automated developmental toxicity assay, based on a growth‐retardation endpoint should be suitable for evaluating the effects of potential teratogens and developmental toxicants in a high throughput manner. This approach can significantly expedite the screening of potential teratogens and developmental toxicants, thereby improving the current risk assessment process by decreasing analysis time and required resources. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

Quantitative characterization of mitosis-blocked tetraploid cells using high content analysis

A range of cellular evidence supporting a G1 tetraploidy checkpoint was obtained from different assay methods including flow cytometry, immunoblotting, and microscopy. Cancer research would benefit if these cellular properties could instead be measured by a single, quantitative, automated assay method, such as high content analysis (HCA). Thus, nocodazole-treated cells were fluorescently labeled for different cell cycle-associated properties, including DNA content, retinoblastoma (Rb) and histone H3 phosphorylation, p53 and p21(WAF1) expression, nuclear and cell sizes, and cell morphology, and automatically imaged, analyzed, and correlated using HCA. HCA verified that nocodazole-induced mitosis block resulted in tetraploid cells. Rb and histone H3 were maximally hyperphosphorylated by 24 h of nocodazole treatment, accompanied by cell and nuclear size decreases and cellular rounding. Cells remained tetraploid and mononucleated with longer treatments, but other targets reverted to G1 levels, including Rb and histone H3 dephosphorylation accompanied by cellular respreading. This was accompanied by increased p53 and p21(WAF1) expression levels. The range of effects accompanying nocodazole-induced block of mitosis and the resulting tetraploid cells' reversal to a pseudo-G1 state can be quantitatively measured by HCA in an automated manner, recommending this assay method for the large-scale biology challenges of modern cancer drug discovery.     

药物筛选技术的最新进展--高内涵筛选

化合物活性筛选是创新药物研究过程的起点和具有决定意义的关键步骤。基于细胞的高内涵药物筛选技术实现了对化合物多靶点多参数的同时检测，代表着创新药物研究技术发展的必然趋势，将在未来的新药研发过程中发挥重要作用。笔者介绍了高内涵筛选技术的概念、系统组成，分析了其优势特点，并简要讨论了其在新药研究尤其是抗肿瘤药物研究中的实际应用。     

Advances in high content screening for drug discovery

Cell-based target validation, secondary screening, lead optimization, and structure-activity relationships have been recast with the advent of HCS. Prior to HCS, a computational approach to the characterization of the functions of specific target proteins and other cellular constituents, along with whole-cell functions employing fluorescence cell-based assays and microscopy, required extensive interaction among the researcher, instrumentation, and software tools. Early HCS platforms were instrument-centric and addressed the need to interface fully automated fluorescence microscopy, plate-handling automation, and seamless image analysis. HCS has since evolved into an integrated solution for accelerated drug discovery by encompassing the workflow components of assay and reagent design, robust instrumentation for automated fixed-end-point and live cell kinetic analysis, generalized and specific BioApplication software (Cellomics, Pittsburgh, PA) modules that produce information on drug responses from cell image data, and informatics/bioinformatics solutions that build knowledge from this information while providing a means to globalize HCS throughout an entire organization. This review communicates how these recent advances are incorporated into the drug discovery workflow by presenting a real-world use case.     

From genome to phenome--RNAi library screening and hit characterization using signaling pathway analysis

Comprehensive, high-throughput analysis of gene function using RNA interference (RNAi)-based screens is emerging as a significant step forward for preliminary drug-target identification. Until quite recently drug target identification depended heavily on the analysis of changes in gene expression, which in turn needed to be correlated with gene function. The promise of obtaining preliminary 'gene to phenotype' information using a single high-throughput platform is propelling major investment in this area by biotechnology and pharmaceutical companies. This review discusses recent developments in the use of RNAi library screens, and the various assay formats and techniques currently in use for data analysis downstream of such screens.     

Systems cell biology knowledge created from high content screening

High content screening (HCS), the large-scale automated analysis of the temporal and spatial changes in cells and cell constituents in arrays of cells, has the potential to create enormous systems cell biology knowledge bases. HCS is being employed along with the continuum of the early drug discovery process, including lead optimization where new knowledge is being used to facilitate the decision-making process. We demonstrate methodology to build new systems cell biology knowledge using a multiplexed HCS assay, designed with the aid of knowledge-mining tools, to measure the phenotypic response of a panel of human tumor cell types to a panel of natural product-derived microtubule-targeted anticancer agents and their synthetic analogs. We show how this new systems cell biology knowledge can be used to design a lead compound optimization strategy for at least two members of the panel, (-)-laulimalide and (+)-discodermolide, that exploits cell killing activity while minimally perturbing the regulation of the cell cycle and the stability of microtubules. Furthermore, this methodology can also be applied to basic biomedical research on cells.     

A high content screening assay for identifying lysosomotropic compounds

Lysosomes are acidic organelles that are essential for the degradation of old organelles and engulfed microbes. Furthermore, lysosomes play a key role in cell death. Lipophilic or amphiphilic compounds with a basic moiety can become protonated and trapped within lysosomes, causing lysosomal dysfunction. Therefore, high-throughput screens to detect lysosomotropism, the accumulation of compounds in lysosomes, are desirable.Hence, we developed a 96-well format, high content screening assay that measures lysosomotropism and cytotoxicity by quantitative image analysis. Forty drugs, including antidepressants, antipsychotics, antiarrhythmics and anticancer agents, were tested for their effects on lysosomotropism and cytotoxicity in H9c2 cells. The assay correctly identified drugs known to cause lysosomotropism and revealed novel information showing that the anticancer drugs, gefitinib, lapatinib, and dasatinib, caused lysosomotropism. Although structurally and pharmacologically diverse, drugs that were lysosomotropic shared certain physicochemical properties, possessing a ClogP > 2 and a basic pKa between 6.5 and 11. In contrast, drugs which did not lie in this physicochemical property space were not lysosomotropic. The assay is a robust, rapid screen that can be used to identify lysosomotropic, as well as, cytotoxic compounds, and can be positioned within a screening paradigm to understand the role of lysosomotropism as a contributor to drug-induced toxicity.     

Investigations into the liver effects of ximelagatran using high content screening of primary human hepatocyte cultures

Background: Ximelagatran, the first oral agent in the new class of direct thrombin inhibitors, was withdrawn from the market due to increased rates of liver enzyme elevations in long-term treatments. Despite intensive pre clinical investigations the cellular mechanisms behind the observed hepatic effects remain unknown. Objective: The aim of this study was to assess drug-induced cytotoxicity in primary human hepatocyte cultures by ximelagatran and other reference pharmaceutical agents with known in vivo hepatotoxic profiles. Methods: Drugs cause liver injury by many distinct mechanisms that result in abnormal cellular functioning and different patterns of injury. To address many potential toxic mechanisms in a human-relevant model, freshly isolated human hepatocytes were used in automated imaging assays. Ximelagatran was used as a test compound to study biochemical and morphological changes in human hepatocytes. In addition, 11 control, reference and comparator compounds with known liver-toxic potential in humans were used. The response to these compounds was assessed across five different hepatocyte donor preparations. Results: Cytotoxicity induced by a number of compounds was quantitatively monitored using an automated imaging technique. A variety of morphological changes in hepatocyte cytoskeleton and mitochondrial function could be identified at sublethal doses of test compounds. Doses of ximelagatran up to 500 μM did not cause a cytotoxic response in the majority of preparations and no subcytotoxic response was observed at doses below 125 μM. Conclusions: The experiments described here demonstrate that primary human hepatocytes may be used in a medium-throughput format for screening using imaging-based assays for the identification of cellular responses. Overall, it is concluded that ximelagatran did not cause a significant decrease in cell viability when incubated for 24 h at considerably higher concentrations than are found in plasma following therapeutic dosing.     

High concordance of drug-induced human hepatotoxicity with in vitro cytotoxicity measured in a novel cell-based model using high content screening

To develop and validate a practical, in vitro, cell-based model to assess human hepatotoxicity potential of drugs, we used the new technology of high content screening (HCS) and a novel combination of critical model features, including (1) use of live, human hepatocytes with drug metabolism capability, (2) preincubation of cells for 3 days with drugs at a range of concentrations up to at least 30 times the efficacious concentration or 100 μM, (3) measurement of multiple parameters that were (4) morphological and biochemical, (5) indicative of prelethal cytotoxic effects, (6) representative of different mechanisms of toxicity, (7) at the single cell level and (8) amenable to rapid throughput. HCS is based on automated epifluorescence microscopy and image analysis of cells in a microtiter plate format. The assay was applied to HepG2 human hepatocytes cultured in 96-well plates and loaded with four fluorescent dyes for: calcium (Fluo-4 AM), mitochondrial membrane potential (TMRM), DNA content (Hoechst 33342) to determine nuclear area and cell number and plasma membrane permeability (TOTO-3). Assay results were compared with those from 7 conventional, in vitro cytotoxicity assays that were applied to 611 compounds and shown to have low sensitivity (<25%), although high specificity (∼90%) for detection of toxic drugs. For 243 drugs with varying degrees of toxicity, the HCS, sublethal, cytotoxicity assay had a sensitivity of 93% and specificity of 98%. Drugs testing positive that did not cause hepatotoxicity produced other serious, human organ toxicities. For 201 positive assay results, 86% drugs affected cell number, 70% affected nuclear area and mitochondrial membrane potential and 45% affected membrane permeability and 41% intracellular calcium concentration. Cell number was the first parameter affected for 56% of these drugs, nuclear area for 34% and mitochondrial membrane potential for 29% and membrane permeability for 7% and intracellular calcium for 10%. Hormesis occurred for 48% of all drugs with positive response, for 26% of mitochondrial and 34% nuclear area changes and 12% of cell number changes. Pattern of change was dependent on the class of drug and mechanism of toxicity. The ratio of concentrations for in vitro cytotoxicity to maximal efficaciousness in humans was not different across groups (12±22). Human toxicity potential was detected with 80% sensitivity and 90% specificity at a concentration of 30× the maximal efficacious concentration or 100 μM when efficaciousness was not considered. We conclude that human hepatotoxicity is highly concordant with in vitro cytotoxicity in this novel model and as detected by HCS.     

Transporter assays using solid supported membranes: a novel screening platform for drug discovery

Transporters are important targets in drug discovery. However, high throughput-capable assays for this class of membrane proteins are still missing. Here we present a novel drug discovery platform technology based on solid supported membranes. The functional principles of the technology are described, and a sample selection of transporter assays is discussed: the H(+)-dependent peptide transporter PepT1, the gastric proton pump, and the Na(+)/Ca(2+) exchanger. This technology promises to have an important impact on the drug discovery process.     

Application of laser-scanning fluorescence microplate cytometry in high content screening

The resolution of cell-based assays down to the cellular level has created new opportunities for the drug discovery process. Aptly named high content analysis, such an approach is enabling new methods of analysis for the broad range of therapeutic targets emerging in the post-genomics era, and offering alternative multiparametric readouts for some traditional analyses. Microplate cytometry is one of the technologies that is being applied to a broad range of assays utilizing fluorescent labeling, at throughputs compatible with primary screening campaigns. Cellular resolution is achieved using scanning laser excitation coupled to photomultiplier detection. This configuration results in area-based scanning across a large field of view, plus simultaneous detection of up to four emission colors for efficient multiplexing. Microplate cytometry is being used most extensively in the field of oncology research because of its usefulness for numerous applications, including protein kinase activity, cell cycle analysis, and cell colony formation. The review focuses on the Acumen Explorer microplate cytometer (TTP LabTech Ltd., Melbourn, Hertfordshire, UK), detailing the principal components of the instrument and providing an overview of its use in high content screening.     

Plasma membrane assays and three-compartment image cytometry for high content screening

High throughput image cytometers analyze individual cells in digital photomicrographs by first assigning pixels within each image to plasma membrane, cytoplasm, nucleus, or other regions. In this study, we report on a novel algorithm that: 1) identifies plasma membrane regions to measure changes in plasma membrane-associated proteins (protein kinase C [PKC] alpha, N-cadherin, E-cadherin, vascular endothelium [VE]-cadherin, and pan-cadherin) that regulate cell division, migration, and adhesion and 2) delineates the cell for generalized three-compartment image cytometry. Validation assays were performed for these proteins on cells cultured in 96-well plates and also for tissue sections obtained from transgenic and chemical carcinogenic models of skin cancer. The algorithm successfully quantified phorbol 12-myristate 13-acetate (PMA)-induced plasma membrane localization of PKCalpha in HeLa cells (Z' of 0.88). Additionally, PMA activated translocation to the plasma membrane at P < .01 of N-cadherin (in HeLa cells), E-cadherin (in A431 cells), and VE-cadherin (in human dermal microvascular endothelial cells), suggesting a relationship between PKCalpha activity and cadherin localization. For VE-cadherin, a Z' of 0.52 was obtained between serum-free medium, which increased VE-cadherin, and EGTA, which diminished VE-cadherin at the plasma membrane. For sections obtained from the transgenic skin cancer model, analysis of images with the plasma membrane algorithm revealed that tumor cells exhibited cadherin expression that was just 34% of that expressed by surrounding normal tissue; furthermore, tumor cells expressed elevated DNA content, consistent with development of aneuploidy. In contrast, increased DNA content did not occur for tumor cells produced by chemical carcinogenesis. The results demonstrate that this new algorithm for plasma membrane image cytometry enables statistically significant analyses in a variety of applications in both cultured cells and tissue sections.     

抗肾纤维化药物高内涵筛选模型的建立及应用

目的建立可用于高内涵分析的肾纤维化体外的细胞模型,为抗肾纤维化中药化合物的筛选和机制研究奠定基础。方法本研究通过TGF-β1诱导正常大鼠肾成纤维细胞NRK49F,以肌成纤维细胞标志α-平滑肌肌动蛋白(α-SMA)作为检测指标,通过高内涵成像分析系统对α-SMA荧光表达强度进行检测分析,并对细胞种板密度、诱导时间、诱导培养基中血清浓度等各种条件进行优化,建立稳定的肾纤维化体外模型。在此基础上以TGF-β1受体阻滞剂SB525334和姜黄素、大黄素对模型进行验证。并进一步探讨吡非尼酮是否具有抗肾纤维化功效。结果实验通过对细胞密度、诱导时间、培养基中血清浓度进行优化,确立了可用于高内涵分析的NRK49F肾纤维化体外模型的建立条件。SB525334、姜黄素、大黄素和吡非尼酮均能减少TGF-β1诱导的α-SMA过表达,抑制NRK49F的活化。结论实验建立了可用于高内涵筛选技术的肾纤维化体外模型,并能相对稳定地筛选具有抗肾纤维化作用的药物。吡非尼酮在本模型中抑制了成纤维化细胞向肌成纤维细胞转化,提示其可能具有抗肾纤维化作用,为抗肾纤维化药物初筛对象的选择提供了思路。     

基于液相色谱-二级质谱联用技术精神科药物中毒筛查平台的构建与临床应用

目的：建立精神科药物的中毒筛查平台,辅助临床精神科药物中毒病患的诊断与急救。方法：依托液相色谱串联质谱（LC-MS/MS）仪,建立目前常用精神科药物的检测方法;采集疑似精神科药物过量或中毒病患的胃液、尿液或血液,处理后采用LC-MS/MS进行快速筛查和定量,获得药物浓度,及时进行药物剂量调整及中毒抢救,并进行复查。结果：本中毒筛查平台共收到院内外急诊病例1 183例。药物过量或中毒病例中前四位氯氮平占34.09%,镇静催眠药占29.54%,喹硫平占15.91%,氨磺必利占11.36%。儿童药物中毒半数由药物误服引起,误服的药物排名前三位为：五氟利多、氟哌啶醇和氯氮平。以上患者经剂量调整或抢救结束后再次复查,血中药物降至安全范围或完全消除。结论：本平台的建立可以快速获取患者中毒药物信息,提高临床医生确诊率,减少患者在中毒剂量的暴露时间,缩短转归时间。     

A morphology- and kinetics-based cascade for human neural cell high content screening

The prospect of manipulating endogenous neural stem cells to replace damaged tissue and correct functional deficits represents a novel mechanism for treating a variety of central nervous system disorders. Using human neural precursor cultures and a variety of assays for studying stem cell behavior we have screened two libraries of commercially available compounds using an endpoint high content screening assay. We then performed detailed follow-up mechanistic studies on confirmed hits using endpoint and kinetics assays to characterize and differentiate the mechanisms of action of these compounds. The screening cascade employed successfully identified a number of active compounds with differing mechanisms of action. This approach shows how hits from a phenotypic screen can be prioritized and characterized by high content screening to identify potentially novel mechanisms and druggable targets to take forward into more conventional high-throughput screening approaches.     

Recent advances in quantitative high throughput and high content data analysis

ABSTRACT

Introduction: High throughput screening has become a basic technique with which to explore biological systems. Advances in technology, including increased screening capacity, as well as methods that generate multiparametric readouts, are driving the need for improvements in the analysis of data sets derived from such screens.

Areas covered: This article covers the recent advances in the analysis of high throughput screening data sets from arrayed samples, as well as the recent advances in the analysis of cell-by-cell data sets derived from image or flow cytometry application. Screening multiple genomic reagents targeting any given gene creates additional challenges and so methods that prioritize individual gene targets have been developed. The article reviews many of the open source data analysis methods that are now available and which are helping to define a consensus on the best practices to use when analyzing screening data.

Expert opinion: As data sets become larger, and more complex, the need for easily accessible data analysis tools will continue to grow. The presentation of such complex data sets, to facilitate quality control monitoring and interpretation of the results will require the development of novel visualizations. In addition, advanced statistical and machine learning algorithms that can help identify patterns, correlations and the best features in massive data sets will be required. The ease of use for these tools will be important, as they will need to be used iteratively by laboratory scientists to improve the outcomes of complex analyses.     

The virtual heart as a platform for screening drug cardiotoxicity

To predict the safety of a drug at an early stage in its development is a major challenge as there is a lack of in vitro heart models that correlate data from preclinical toxicity screening assays with clinical results. A biophysically detailed computer model of the heart, the virtual heart, provides a powerful tool for simulating drug–ion channel interactions and cardiac functions during normal and disease conditions and, therefore, provides a powerful platform for drug cardiotoxicity screening. In this article, we first review recent progress in the development of theory on drug–ion channel interactions and mathematical modelling. Then we propose a family of biomarkers that can quantitatively characterize the actions of a drug on the electrical activity of the heart at multi‐physical scales including cellular and tissue levels. We also conducted some simulations to demonstrate the application of the virtual heart to assess the pro‐arrhythmic effects of cisapride and amiodarone. Using the model we investigated the mechanisms responsible for the differences between the two drugs on pro‐arrhythmogenesis, even though both prolong the QT interval of ECGs. Several challenges for further development of a virtual heart as a platform for screening drug cardiotoxicity are discussed.

Linked Articles

This article is part of a themed section on Chinese Innovation in Cardiovascular Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-23

Abbreviations

AE

allosteric effector

APD

action potential duration

APD₉₀

APD at 90% repolarization

APs

action potentials

BCL

basic cycle length

CV

conduction velocity

CVR

conduction velocity restitution

ERP

effective refractory period

GR

guarded receptor

HH

Hodgkin–Huxley

I_CaL

L‐type Ca²⁺ current

I_Kr

delayed rectifier K⁺ channel current

I_Ktof

fast component of the cardiac transient outward current

I_Na

Na⁺ channel current

LQTs

long QT syndrome

MR

modulated receptor

QTc

corrected QT interval

VW

vulnerable window

WL

wavelength

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