High-throughput fluorescence polarization method for identifying ligands of LOX-1

Development of an automated, high-throughput SARS-CoV-2 neutralization assay based on a pseudotyped virus using a vesicular stomatitis virus (VSV) vector

ABSTRACTThe global outbreak of COVID-19 has caused a severe threat to human health; therefore, simple, high-throughput neutralization assays are desirable for developing vaccines and drugs against COVID-19. In this study, a high-titre SARS-CoV-2 pseudovirus was successfully packaged by truncating the C-terminus of the SARS-CoV-2 spike protein by 21 amino acids and infecting 293 T cells that had been stably transfected with the angiotensin-converting enzyme 2 (ACE2) receptor and furin (named AF cells), to establish a simple, high-throughput, and automated 384-well plate neutralization assay. The method was optimized for cell amount, virus inoculation, incubation time, and detection time. The automated assay showed good sensitivity, accuracy, reproducibility, Z' factor, and a good correlation with the live virus neutralization assay. The high-throughput approach would make it available for the SARS-CoV-2 neutralization test in large-scale clinical trials and seroepidemiological surveys which would aid the accelerated vaccine development and evaluation.

Screening and Identification of HTNVpv Entry Inhibitors with High-throughput Pseudovirus-based Chemiluminescence

Hantaviruses, such as Hantaan virus (HTNV) and Seoul virus, are the causative agents of Hantavirus cardiopulmonary syndrome (HCPS) and hemorrhagic fever with renal syndrome (HFRS), and are important zoonotic pathogens. China has the highest incidence of HFRS, which is mainly caused by HTNV and Seoul virus. No approved antiviral drugs are available for these hantaviral diseases. Here, a chemiluminescence-based high-throughput-screening (HTS) assay was developed and used to screen HTNV pseudovirus (HTNV_pv) inhibitors in a library of 1813 approved drugs and 556 small-molecule compounds from traditional Chinese medicine sources. We identified six compounds with in vitro anti-HTNV_pv activities in the low-micromolar range (EC₅₀ values of 0.1–2.2 ​μmol/L; selectivity index of 40–900). Among the six selected compounds, cepharanthine not only showed good anti-HTNV_pv activity in vitro but also inhibited HTNV_pv-fluc infection in Balb/c mice 5 ​h after infection by 94% (180 ​mg/kg/d, P ​< ​0.01), 93% (90 ​mg/kg/d, P ​< ​0.01), or 92% (45 ​mg/kg/d, P ​< ​0.01), respectively, in a bioluminescent imaging mouse model. A time-of-addition analysis suggested that the antiviral mechanism of cepharanthine involves the membrane fusion and entry phases. Overall, we have established a HTS method for antiviral drugs screening, and shown that cepharanthine is a candidate for HCPS and HFRS therapy. These findings may offer a starting point for the treatment of patients infected with hantaviruses.

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A chemiluminescence-based high-throughput-screening (HTS) assay was used to screen HTNV pseudovirus (HTNV_pv) inhibitors.

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Cepharanthine showed good anti-HTNV_pv activity in vitro and in vivo.

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A time-of-addition analysis suggested that cepharanthine involves the membrane fusion and entry phases.

High-Throughput Screening and Identification of Human Adenovirus Type 5 Inhibitors

Human adenovirus infections can develop into diffuse multi-organ diseases in young children and immunocompromised patients, and severe cases can lead to death. However, there are no approved antiviral drugs available to treat adenovirus diseases. In this study, a chemiluminescence-based, high-throughput screening (HTS) assay was developed and applied to screen human adenovirus 5(HAdV5)inhibitors from 1,813 approved drug library and 556 traditional Chinese medicine-sourced small-molecule compounds. We identified three compounds with in vitro anti-HAdV5 activities in the low-micromolar range (EC50 values 0.3-4.5 μM, selectivity index values 20-300) that also showed inhibitory effects on HAdV3. Cardamomin (CDM) had good anti-HAdV5 activity in vitro. Furthermore, three dilutions of CDM (150, 75, and 37.5 mg/kg/d) administered to BALB/c mouse models inhibited HAdV5-fluc infection at 1 day post-infection by 80% (p < 0.05), 76% (p < 0.05), and 58% (p < 0.05), respectively. HE-staining of pathological tissue sections of mice infected with a wildtype adenoviral strain showed that CDM had a protective effect on tissues, especially in the liver, and greatly inhibited virus-induced necrosis of liver tissue. Thus, CDM inhibits adenovirus replication in vivo and in vitro. This study established a high-throughput screening method for anti-HAdV5 drugs and demonstrated CDM to be a candidate for HAdV5 therapy, potentially providing a new treatment for patients infected with adenoviruses.

Melatonin and regulation of autophagy: Mechanisms and therapeutic implications

Mitochondria are essential subcellular units that generate basic energy for the cell, as well as influence Ca²⁺ flux, apoptosis, and cell signaling. Mitophagy can selectively remove impaired mitochondria to preserve mitochondrial function, which is crucial for normal cellular maintenance. Mitochondrial dysfunction and mitophagy are widely reported to be linked to various pathogeneses. In addition, there is increasing evidence regarding the beneficial role of melatonin in the regulation and intervention of mitophagy progression. In this review, we focus on specific pathological conditions, including ischemia/reperfusion injury (IRI), cancer and neurodegenerative diseases, and elucidate the essential role of melatonin in the modulation of mitophagy in each of these distinct disorders.

Screening and evaluation of potential inhibitors against vaccinia virus from 767 approved drugs

The development of therapies for human smallpox is needed due to the increasing concern over the potential use of smallpox virus as a biological weapon. Here, we report a high-throughput screening for anti-smallpox virus drugs from a 767-small-molecule library, employing two vaccinia virus (VACV) strains containing firefly luciferase (VTT-Fluc and VG9-Fluc) as surrogate viruses. Using an eight-point dose response format assay, 26 compounds of different pharmacological classes were identified with in vitro anti-VACV activities. Mycophenolate mofetil (MMF) and tranilast (TRA) were detected to possess the highest anti-VACV potency (selectivity index values of >334 and >74, respectively); they could inhibit VTT-Fluc replication in nude mice at 5 days post-infection by 99% (10 mg/kg, P < .01) and 59% (45 mg/kg, P = .01), respectively, as indicated by bioluminescent intensity. In conclusion, MMF and TRA are promising anti-smallpox virus candidates for further optimization and repurposing for use in clinical practice.

Monoamines and their Derivatives on GPCRs: Potential Therapy for Alzheimer's Disease

Albeit cholinergic depletion remains the key event in Alzheimer's Disease (AD), recent information describes stronger links between monoamines (trace amines, catecholamines, histamine, serotonin, and melatonin) and AD than those known in the past century. Therefore, new drug design strategies focus efforts to translate the scope on these topics and to offer new drugs which can be applied as therapeutic tools in AD. In the present work, we reviewed the state-of-art regarding genetic, neuropathology and neurochemistry of AD involving monoamine systems. Then, we compiled the effects of monoamines found in the brain of mammals as well as the reported effects of their derivatives and some structure-activity relationships. Recent derivatives have triggered exciting effects and pharmacokinetic properties in both murine models and humans. In some cases, the mechanism of action is clear, essentially through the interaction on G-protein-coupled receptors as revised in this manuscript. Additional mechanisms are inhibition of enzymes for their biotransformation, regulation of free-radicals in the central nervous system and others for the effects on Tau phosphorylation or amyloid-beta accumulation. All these data make the monoamines and their derivatives attractive potential elements for AD therapy.

Identification of small molecule inhibitors targeting the SMARCA2 bromodomain from a high-throughput screening assay

SMARCA2 is a critical catalytic subunit of the switch/sucrose non-fermenting (SWI/SNF) chromatin remodeling complexes. Dysregulation of SMARCA2 is associated with several diseases, including some cancers. SMARCA2 is multi-domain protein containing a bromodomain (BRD) that specifically recognizes acetylated lysine residues in histone tails, thus playing an important role in chromatin remodeling. Many potent and specific inhibitors targeting other BRDs have recently been discovered and have been widely used for cancer treatments and biological research. However, hit discovery targeting SMARCA2-BRD is particularly lacking. To date, there is a paucity of reported high-throughput screening (HTS) assays targeting the SMARCA2-BRD interface. In this study, we developed an AlphaScreen HTS system for the discovery of SMARCA2-BRD inhibitors and optimized the physicochemical conditions including pH, salt concentrations and detergent levels. Through an established AlphaScreen-based high-throughput screening assay against an in-house compound library, DCSM06 was identified as a novel SMARCA2-BRD inhibitor with an IC₅₀ value of 39.9±3.0 μmol/L. Surface plasmon resonance demonstrated the binding between SMARCA2-BRD and DCSM06 (K_d=38.6 μmol/L). A similarity-based analog search led to identification of DCSM06-05 with an IC₅₀ value of 9.0±1.4 μmol/L. Molecular docking was performed to predict the binding mode of DCSM06-05 and to decipher the structural basis of the infiuence of chemical modifications on inhibitor potency. DCSM06-05 may be used as a starting point for further medicinal chemistry optimization and could function as a chemical tool for SMARCA2-related functional studies.

Development of a high-throughput fluorescence polarization assay for the discovery of EZH2-EED interaction inhibitors

Aberrant activity of enhancer of zeste homolog 2 (EZH2) is associated with a wide range of human cancers. The interaction of EZH2 with embryonic ectoderm development (EED) is required for EZH2's catalytic activity. Inhibition of the EZH2-EED complex thus represents a novel strategy for interfering with the oncogenic potentials of EZH2 by targeting both its catalytic and non-catalytic functions. To date, there have been no reported high-throughput screening (HTS) assays for inhibitors acting at the EZH2-EED interface. In this study, we developed a fluorescence polarization (FP)-based HTS system for the discovery of EZH2-EED interaction inhibitors. The tracer peptide sequences, positions of fluorescein labeling, and a variety of physicochemical conditions were optimized. The high Z' factors (>0.9) at a variety of DMSO concentrations suggested that this system is robust and suitable for HTS. The minimal sequence requirement for the EZH2-EED interaction was determined by using this system. A pilot screening of an in-house compound library containing 1600 FDA-approved drugs identified four compounds (apomorphine hydrochloride, oxyphenbutazone, nifedipine and ergonovine maleate) as potential EZH2-EED interaction inhibitors.

Influence of the Circadian System on Disease Severity

The severity of many diseases varies across the day and night. For example, adverse cardiovascular incidents peak in the morning, asthma is often worse at night and temporal lobe epileptic seizures are most prevalent in the afternoon. These patterns may be due to the day/night rhythm in environment and behavior, and/or endogenous circadian rhythms in physiology. Furthermore, chronic misalignment between the endogenous circadian timing system and the behavioral cycles could be a cause of increased risk of diabetes, obesity, cardiovascular disease and certain cancers in shift workers. Here we describe the magnitude, relevance and potential biological basis of such daily changes in disease severity and of circadian/behavioral misalignment, and present how these insights may help in the development of appropriate chronotherapy.

A high throughput fluorescence polarization assay for inhibitors of the GoLoco motif/G-alpha interaction

The GoLoco motif is a short Galpha-binding polypeptide sequence. It is often found in proteins that regulate cell-surface receptor signaling, such as RGS12, as well as in proteins that regulate mitotic spindle orientation and force generation during cell division, such as GPSM2/LGN. Here, we describe a high throughput fluorescence polarization (FP) assay using fluorophore-labeled GoLoco motif peptides for identifying inhibitors of the GoLoco motif interaction with the G-protein alpha subunit Galpha (i1). The assay exhibits considerable stability over time and is tolerant to DMSO up to 5%. The Z'-factors for robustness of the GPSM2 and RGS12 GoLoco motif assays in a 96-well plate format were determined to be 0.81 and 0.84, respectively; the latter assay was run in a 384-well plate format and produced a Z'-factor of 0.80. To determine the screening factor window (Z-factor) of the RGS12 GoLoco motif screen using a small molecule library, the NCI Diversity Set was screened. The Z-factor was determined to be 0.66, suggesting that this FP assay would perform well when developed for 1,536-well format and scaled up to larger libraries. We then miniaturized to a 4 microL final volume a pair of FP assays utilizing fluorescein- (green) and rhodamine- (red) labeled RGS12 GoLoco motif peptides. In a fully-automated run, the Sigma-Aldrich LOPAC(1280) collection was screened three times with every library compound being tested over a range of concentrations following the quantitative high throughput screening (qHTS) paradigm; excellent assay performance was noted with average Z-factors of 0.84 and 0.66 for the green- and red-label assays, respectively.

Oxidized low density lipoprotein receptor-1 mediates oxidized low density lipoprotein-induced apoptosis in human umbilical vein endothelial cells: Role of reactive oxygen species

Studies have shown that oxidized low density lipoprotein (ox-LDL) elicits both necrotic and apoptotic cell death and several mechanisms have been proposed. Ox-LDL induces reactive oxygen species (ROS), a second messenger that might be involved in apoptosis, formation in different types of cells including endothelial cells (ECs) and smooth muscle cells (SMCs). As lectin-like ox-LDL receptor-1 (LOX-1) was the main receptor for ox-LDL, this study was designed to determine whether the apoptosis induced by ox-LDL was mediated by LOX-1 in cultured human umbilical vein endothelial cells (HUVECs) and whether there is an association between LOX-1 mediated apoptosis and the production of ROS. After exposure to ox-LDL (50,100, and 150 microg/ml for 18 h), HUVECs exhibit typical apoptotic characteristics as determined by transmission electron microscopy and flow cytometry analysis in a dose-dependent pattern. Ox-LDL increases intracellular ROS formation including superoxide anion (O2-) and hydrogen peroxide (H2O2) in a dose-dependent and time-dependent manner. Pretreatment with anti-LOX-1 mAb, Vitamin C, apocynin or catalase significantly reduced ROS production and prevented ox-LDL-induced apoptosis, while indomethacin or allopurinol had no effect. These results suggest that LOX-1 mediates ox-LDL-induced apoptosis in endothelial cells and that ROS production and NADPH oxidase might play an important role in ox-LDL-induced apoptosis.