Label-Free Dynamic Mass Redistribution and Bio-Impedance Methods for Drug Discovery

Detecting and measuring of GPCR signaling - comparison of human induced pluripotent stem cells and immortal cell lines

G protein-coupled receptors (GPCRs) are a large family of transmembrane proteins that play a major role in many physiological processes, and thus GPCR-targeted drug development has been widely promoted. Although research findings generated in immortal cell lines have contributed to the advancement of the GPCR field, the homogenous genetic backgrounds, and the overexpression of GPCRs in these cell lines make it difficult to correlate the results with clinical patients. Human induced pluripotent stem cells (hiPSCs) have the potential to overcome these limitations, because they contain patient specific genetic information and can differentiate into numerous cell types. To detect GPCRs in hiPSCs, highly selective labeling and sensitive imaging techniques are required. This review summarizes existing resonance energy transfer and protein complementation assay technologies, as well as existing and new labeling methods. The difficulties of extending existing detection methods to hiPSCs are discussed, as well as the potential of hiPSCs to expand GPCR research towards personalized medicine.

Parallelized label-free monitoring of cell adhesion on extracellular matrix proteins measured by single colour reflectometry

The understanding of the initial cell adhesion to biomaterials is crucial for the survival of implants. The manifold possibilities to tailor an implant surface and the diverse requirements for different implant applications necessitate a timesaving and highly parallelized analytical methodology. Due to its intrinsic advantages (label-free, time-resolved, robust against temperature fluctuations, and particularly the multiplexing possibilities), single colour reflectometry (SCORE) is used for the first time to investigate cell adhesion to different extracellular matrix protein-coated surfaces. The excellent correlation between the novel SCORE technology and well-established reference methods proves that the results obtained by using this direct optical method are able to reflect the cell binding processes at the transducer surface. Additionally, the high time resolution of SCORE revealed the differences in the adhesion behaviour of the cells on the different extracellular matrix protein-coated glass slides during the initial adsorption phase and during the spreading of the cells on the surfaces. Therefore, we conclude that SCORE is a perfectly suited methodology for studying the entire cell adsorption process, including morphological changes, and shows great potential for other cell-based sensing applications.

Methamphetamine Blocks Adenosine A2A Receptor Activation via Sigma 1 and Cannabinoid CB1 Receptors

Methamphetamine is, worldwide, one of the most consumed drugs of abuse. One important side effect is neurodegeneration leading to a decrease in life expectancy. The aim of this paper was to check whether the drug affects one of the receptors involved in neurodegeneration/neuroprotection events, namely the adenosine A2A receptor (A2AR). First, we noticed that methamphetamine does not affect A2A functionality if the receptor is expressed in a heterologous system. However, A2AR becomes sensitive to the drug upon complexes formation with the cannabinoid CB1 receptor (CB1R) and the sigma 1 receptor (σ1R). Signaling via both adenosine A2AR and cannabinoid CB1R was affected by methamphetamine in cells co-expressing the two receptors. In striatal primary cultures, the A2AR-CB1R heteromer complex was detected and methamphetamine not only altered its expression but completely blocked the A2AR- and the CB1R-mediated activation of the mitogen activated protein kinase (MAPK) pathway. In conclusion, methamphetamine, with the participation of σ1R, alters the expression and function of two interacting receptors, A2AR, which is a therapeutic target for neuroprotection, and CB1R, which is the most abundant G protein-coupled receptor (GPCR) in the brain.

Discovery of novel immunopharmacological ligands targeting the IL-17 inflammatory pathway

Interleukin 17 (IL-17) is a proinflammatory cytokine that acts as an immune checkpoint for several autoimmune diseases. Therapeutic neutralizing antibodies that target this cytokine have demonstrated clinical efficacy in psoriasis. However, biologics have limitations such as their high cost and their lack of oral bioavailability. Thus, it is necessary to expand the therapeutic options for this IL-17A/IL-17RA pathway, applying novel drug discovery methods to find effective small molecules. In this work, we combined biophysical and cell-based assays with structure-based docking to find novel ligands that target this pathway. First, a virtual screening of our chemical library of 60000 compounds was used to identify 67 potential ligands of IL-17A and IL-17RA. We developed a biophysical label-free binding assay to determine interactions with the extracellular domain of IL-17RA. Two molecules (CBG040591 and CBG060392) with quinazolinone and pyrrolidinedione chemical scaffolds, respectively, were confirmed as ligands of IL-17RA with micromolar affinity. The anti-inflammatory activity of these ligands as cytokine-release inhibitors was evaluated in human keratinocytes. Both ligands inhibited the release of chemokines mediated by IL-17A, with an IC₅₀ of 20.9 ± 12.6 μM and 23.6 ± 11.8 μM for CCL20 and an IC₅₀ of 26.7 ± 13.1 μM and 45.3 ± 13.0 μM for CXCL8. Hence, they blocked IL-17A proinflammatory activity, which is consistent with the inhibition of the signalling of the IL-17A receptor by ligand CBG060392. Therefore, we identified two novel immunopharmacological ligands targeting the IL-17A/IL-17RA pathway with antiinflammatory efficacy that can be promising tools for a drug discovery program for psoriasis.

Allosteric targeting of the FFA2 receptor (GPR43) restores responsiveness of desensitized human neutrophils

The G protein‐coupled free fatty acid receptor 2 (FFA2R) is highly expressed on neutrophils and was previously described to regulate neutrophil activation. Allosteric targeting of G protein‐coupled receptors (GPCRs) is increasingly explored to create distinct pharmacology compared to endogenous, orthosteric ligands. The consequence of allosteric versus orthosteric FFA2R activation for neutrophil response, however, is currently largely elusive. Here, different FFA2R desensitization profiles in human neutrophils following allosteric or orthosteric activation are reported. Using a set of neutrophil functional assays to measure calcium flux, pERK1/2, chemotaxis, cellular degranulation, and oxidative burst together with holistic and pathway‐unbiased whole cell sensing based on dynamic mass redistribution, it is found that the synthetic positive allosteric modulator agonist 4‐CMTB potently activates neutrophils and simultaneously alters FFA2R responsiveness toward the endogenous, orthosteric agonist propionic acid (C3) after homologous and heterologous receptor desensitization. Stimulation with C3 or the hierarchically superior chemokine receptor activator IL‐8 led to strong FFA2R desensitization and rendered neutrophils unresponsive toward repeated stimulation with C3. In contrast, stimulation with allosteric 4‐CMTB engaged a distinct composition of signaling pathways as compared to orthosteric receptor activation and was able to activate neutrophils that underwent homologous and heterologous desensitization with C3 and IL‐8, respectively. Moreover, allosteric FFA2R activation could re‐sensitize FFA2 toward the endogenous agonist C3 after homologous and heterologous desensitization. Given the fact that receptor desensitization is critical in neutrophils to sense and adapt to their current environment, these findings are expected to be useful for the discovery of novel pharmacological mechanisms to modulate neutrophil responsiveness therapeutically.

Critical assessment of relevant methods in the field of biosensors with direct optical detection based on fibers and waveguides using plasmonic, resonance, and interference effects

Direct optical detection has proven to be a highly interesting tool in biomolecular interaction analysis to be used in drug discovery, ligand/receptor interactions, environmental analysis, clinical diagnostics, screening of large data volumes in immunology, cancer therapy, or personalized medicine. In this review, the fundamental optical principles and applications are reviewed. Devices are based on concepts such as refractometry, evanescent field, waveguides modes, reflectometry, resonance and/or interference. They are realized in ring resonators; prism couplers; surface plasmon resonance; resonant mirror; Bragg grating; grating couplers; photonic crystals, Mach-Zehnder, Young, Hartman interferometers; backscattering; ellipsometry; or reflectance interferometry. The physical theories of various optical principles have already been reviewed in detail elsewhere and are therefore only cited. This review provides an overall survey on the application of these methods in direct optical biosensing. The "historical" development of the main principles is given to understand the various, and sometimes only slightly modified variations published as "new" methods or the use of a new acronym and commercialization by different companies. Improvement of optics is only one way to increase the quality of biosensors. Additional essential aspects are the surface modification of transducers, immobilization strategies, selection of recognition elements, the influence of non-specific interaction, selectivity, and sensitivity. Furthermore, papers use for reporting minimal amounts of detectable analyte terms such as value of mass, moles, grams, or mol/L which are difficult to compare. Both these essential aspects (i.e., biochemistry and the presentation of LOD values) can be discussed only in brief (but references are provided) in order to prevent the paper from becoming too long. The review will concentrate on a comparison of the optical methods, their application, and the resulting bioanalytical quality.

Pharmacological Assays for Investigating the NOP Receptor

The nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP) is a G protein-coupled receptor involved in the regulation of several physiological functions and pathological conditions. Thus, researchers from academia and industry are pursuing NOP to discover and study novel pharmacological entities. In a multidisciplinary effort of pharmacologists, medicinal chemists, and molecular and structural biologists the mechanisms of NOP activation and inhibition have been, at least partially, disentangled. Here, we review the in vitro methodologies employed, which have contributed to our understanding of this target. We hope this chapter guides the reader through the mostly established assay platforms to investigate NOP pharmacology, and gives some hints taking advantage from what has already illuminated the function of other GPCRs. We analyzed the pharmacological results obtained with a large panel of NOP ligands investigated in several assays including receptor binding, stimulation of GTPγS binding, decrease of cAMP levels, calcium flux stimulation via chimeric G proteins, NOP/G protein and NOP/β-arrestin interaction, label-free assays such as dynamic mass redistribution, and bioassays such as the electrically stimulated mouse vas deferens.

Receptor Binding Assays and Drug Discovery

Although Solomon Snyder authored hundreds of research reports and several books covering a broad range of topics in the neurosciences, he is best known by many as the person who developed neurotransmitter receptor radioligand binding assays. By demonstrating the utility of this approach for studying transmitter receptors in brain, Dr. Snyder provided the scientific community with a powerful new tool for identifying and characterizing these sites, for defining their relationship to neurological and psychiatric disorders, and their involvement in mediating the actions of psychotherapeutics. Although it was hoped the receptor binding technique could also be used as a primary screen to speed and simplify the identification of novel drug candidates, experience has taught that ligand binding is most useful for drug discovery when it is used in conjunction with functional, phenotypic assays. The incorporation of ligand binding assays into the drug discovery process played a significant role in altering the search for new therapeutics from solely an empirical undertaking to a mechanistic and hypothesis-driven enterprise. This illustrates the impact of Dr. Snyder's work, not only on neuroscience research but on the discovery, development, and characterization of drugs for treating a variety of medical conditions.