A Novel High Content Angiogenesis Assay Reveals That Lacidipine, L-Type Calcium Channel Blocker, Induces In Vitro Vascular Lumen Expansion.

Angiogenesis is a critical cellular process toward establishing a functional circulatory system capable of delivering oxygen and nutrients to the tissue in demand. In vitro angiogenesis assays represent an important tool for elucidating the biology of blood vessel formation and for drug discovery applications. Herein, we developed a novel, high content 2D angiogenesis assay that captures endothelial morphogenesis's cellular processes, including lumen formation. In this assay, endothelial cells form luminized vascular-like structures in 48 h. The assay was validated for its specificity and performance. Using the optimized assay, we conducted a phenotypic screen of a library containing 150 FDA-approved cardiovascular drugs to identify modulators of lumen formation. The screening resulted in several L-type calcium channel blockers being able to expand the lumen space compared to controls. Among these blockers, Lacidipine was selected for follow-up studies. We found that the endothelial cells treated with Lacidipine showed enhanced activity of caspase-3 in the luminal space. Pharmacological inhibition of caspase activity abolished the Lacidipine-enhancing effect on lumen formation, suggesting the involvement of apoptosis. Using a Ca2+ biosensor, we found that Lacipidine reduces the intracellular Ca2+ oscillations amplitude in the endothelial cells at the early stage, whereas Lacidipine blocks these Ca2+ oscillations completely at the late stage. The inhibition of MLCK exhibits a phenotype of lumen expansion similar to that of Lacidipine. In conclusion, this study describes a novel high-throughput phenotypic assay to study angiogenesis. Our findings suggest that calcium signalling plays an essential role during lumen morphogenesis. L-type Ca2+ channel blockers could be used for more efficient angiogenesis-mediated therapies.

Antibacterial profiling of abietane-type diterpenoids.

Abietic and dehydroabietic acid are interesting diterpenes with a highly diverse repertoire of associated bioactivities. They have, among others, shown antibacterial and antifungal activity, potentially valuable in the struggle against the increasing antimicrobial resistance and imminent antibiotic shortage. In this paper, we describe the synthesis of a set of 9 abietic and dehydroabietic acid derivatives containing amino acid side chains and their in vitro antimicrobial profiling against a panel of human pathogenic microbial strains. Furthermore, their in vitro cytotoxicity against mammalian cells was evaluated. The experimental results showed that the most promising compound was 10 [methyl N-(abiet-8,11,13-trien-18-yl)-d-serinate], with an MIC90 of 60µg/mL against Staphylococcus aureus ATCC 25923, and 8µg/mL against methicillin-resistant S. aureus, Staphylococcus epidermidis and Streptococcus mitis. The IC50 value for compound 10 against Balb/c 3T3 cells was 45µg/mL.

The Retinoid Agonist Tazarotene Promotes Angiogenesis and Wound Healing.

Therapeutic angiogenesis is a major goal of regenerative medicine, but no clinically approved small molecule exists that enhances new blood vessel formation. Here we show, using a phenotype-driven high-content imaging screen of an annotated chemical library of 1,280 bioactive small molecules, that the retinoid agonist Tazarotene, enhances in vitro angiogenesis, promoting branching morphogenesis, and tubule remodeling. The proangiogenic phenotype is mediated by retinoic acid receptor but not retinoic X receptor activation, and is characterized by secretion of the proangiogenic factors hepatocyte growth factor, vascular endothelial growth factor, plasminogen activator, urokinase and placental growth factor, and reduced secretion of the antiangiogenic factor pentraxin-3 from adjacent fibroblasts. In vivo, Tazarotene enhanced the growth of mature and functional microvessels in Matrigel implants and wound healing models, and increased blood flow. Notably, in ear punch wound healing model, Tazarotene promoted tissue repair characterized by rapid ear punch closure with normal-appearing skin containing new hair follicles, and maturing collagen fibers. Our study suggests that Tazarotene, an FDA-approved small molecule, could be potentially exploited for therapeutic applications in neovascularization and wound healing.

Antimicrobial activity of the marine alkaloids, clathrodin and oroidin, and their synthetic analogues.

Marine organisms produce secondary metabolites that may be valuable for the development of novel drug leads as such and can also provide structural scaffolds for the design and synthesis of novel bioactive compounds. The marine alkaloids, clathrodin and oroidin, which were originally isolated from sponges of the genus, Agelas, were prepared and evaluated for their antimicrobial activity against three bacterial strains (Enterococcus faecalis, Staphylococcus aureus and Escherichia coli) and one fungal strain (Candida albicans), and oroidin was found to possess promising Gram-positive antibacterial activity. Using oroidin as a scaffold, 34 new analogues were designed, prepared and screened for their antimicrobial properties. Of these compounds, 12 exhibited >80% inhibition of the growth of at least one microorganism at a concentration of 50 µM. The most active derivative was found to be 4-phenyl-2-aminoimidazole 6h, which exhibited MIC90 (minimum inhibitory concentration) values of 12.5 µM against the Gram-positive bacteria and 50 µM against E. coli. The selectivity index between S. aureus and mammalian cells, which is important to consider in the evaluation of a compound's potential as an antimicrobial lead, was found to be 2.9 for compound 6h.

Bioactive cembrane derivatives from the Indian Ocean soft coral, Sinularia kavarattiensis.

Marine organisms and their metabolites represent a unique source of potential pharmaceutical substances. In this study, we examined marine-derived substances for their bioactive properties in a cell-based Chikungunya virus (CHIKV) replicon model and for in vitro anti-inflammatory activity. In the screening of a marine sample library, crude extracts from the Indian soft coral, Sinularia kavarattiensis, showed promising activity against the CHIKV replicon. Bioassay-guided chemical fractionation of S. kavarattiensis resulted in the isolation of six known norcembranoids (1-6) and one new compound, named kavaranolide (7). The structures were elucidated on the basis of NMR and MS spectroscopic data. Compounds 1-3 and 5-7 were evaluated for their replicon-inhibiting potential in the CHIKV model by using a luminescence-based detection technique and live cell imaging. Compounds 1 and 2 showed moderate inhibition of the CHIKV replicon, but imaging studies also revealed cytotoxic properties. Moreover, the effects of the isolated compounds on primary microglial cells, an experimental model for neuroinflammation, were evaluated. Compound 2 was shown to modulate the immune response in microglial cells and to possess potential anti-inflammatory properties by dose-dependently reducing the release of pro- and anti-inflammatory cytokines.

Clinical validation of optimised RT-LAMP for the diagnosis of SARS-CoV-2 infection.

We have optimised a reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the detection of SARS-CoV-2 from extracted RNA for clinical application. We improved the stability and reliability of the RT-LAMP assay by the addition of a temperature-dependent switch oligonucleotide to reduce self- or off-target amplification. We then developed freeze-dried master mix for single step RT-LAMP reaction, simplifying the operation for end users and improving long-term storage and transportation. The assay can detect as low as 13 copies of SARS-CoV2 RNA per reaction (25-µL). Cross reactivity with other human coronaviruses was not observed. We have applied the new RT-LAMP assay for testing clinical extracted RNA samples extracted from swabs of 72 patients in the UK and 126 samples from Greece and demonstrated the overall sensitivity of 90.2% (95% CI 83.8-94.7%) and specificity of 92.4% (95% CI 83.2-97.5%). Among 115 positive samples which Ct values were less than 34, the RT-LAMP assay was able to detect 110 of them with 95.6% sensitivity. The specificity was 100% when RNA elution used RNase-free water. The outcome of RT-LAMP can be reported by both colorimetric detection and quantifiable fluorescent reading. Objective measures with a digitized reading data flow would allow for the sharing of results for local or national surveillance.

Integrated in vitro-in silico screening strategy for the discovery of antibacterial compounds.

Multidrug-resistant bacterial infections are an increasing source of healthcare problems, and the research for new antibiotics is currently unable to respond to this challenge. In this work, we present a screening strategy that integrates cell-based high-throughput screening (HTS) with in silico analogue search for antimicrobial small-molecule drug discovery. We performed an HTS on a diverse chemical library by using an assay based on a bioluminescent Escherichia coli K-12 (pTetLux1) strain. The HTS yielded eight hit compounds with >50% inhibition. These hits were then used for structural similarity-based virtual screening, and of the 29 analogues selected for in vitro testing, four compounds displayed potential activity in the pTetLux1 assay. The 11 most active compounds from combined HTS and analogue search were further assessed for antimicrobial activity against clinically important strains of E. coli and Staphylococcus aureus and for in vitro cytotoxicity against human cells. Three of the compounds displayed antibacterial activity and low human cell cytotoxicity. Additionally, two compounds of the set fully inhibited S. aureus growth after 24 h, but also exhibited human cell cytotoxicity in vitro.

Screening and characterisation of antimicrobial properties of semisynthetic betulin derivatives.

Betulin (lup-20(29)-ene-3ß, 28-diol) is a naturally occurring triterpene, which is found in substantial amounts from the outer bark of birch trees. A library of 51 structurally diverse semisynthetic betulin derivatives was screened against five bacterial strains, Enterobacter aerogenes, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus and a fungal strain Candida albicans, using broth microdilution assays. Primary antimicrobial screening at 50 µM concentration led to the identification of five compounds showing antimicrobial properties (inhibition of growth by >70% against one or more microbial strains). According to the dose-response results, 28-O-(N-acetylanthraniloyl)betulin (compound 5) was the most active, showing MIC90 of 6.25 µM against two Gram-positive bacteria, E. faecalis and S. aureus. However, the activity of this compound was affected by albumin binding, which was demonstrated by the loss of activity in a host-pathogen co-culture assay as well as in the antibacterial assay in the presence of increased concentration of albumin. Furthermore, the effects on mammalian cells were evaluated by cytotoxicity assessment on hepatocyte cell culture after 24 h exposure to the compounds. Betulinic aldehyde (18), betulin-28-oxime (31) and hetero cycloadduct with acetoxy groups at carbon atoms 3 and 28 and ethyl substituent at the triazolo ring (43) displayed cytotoxicity towards hepatocytes, with IC50 values of 47, 25 and 16 µM, respectively. The IC50 value for 28-O-(N-acetylanthraniloyl)betulin (5) was 56 µM. The current study presents an insight into using betulin scaffold for developing derivatives with antibacterial potential, and furthermore the necessity of in-depth analysis of found actives through selectivity profiling and follow-up studies including in silico ADMET predictions.