Synthesis and Agonistic Activity at the GPR35 of 5,6-Dihydroxyindole-2-carboxylic Acid Analogues

GPR35 acts a dual role and therapeutic target in inflammation

GPR35 is a G protein-coupled receptor with notable involvement in modulating inflammatory responses. Although the precise role of GPR35 in inflammation is not yet fully understood, studies have suggested that it may have both pro- and anti-inflammatory effects depending on the specific cellular environment. Some studies have shown that GPR35 activation can stimulate the production of pro-inflammatory cytokines and facilitate the movement of immune cells towards inflammatory tissues or infected areas. Conversely, other investigations have suggested that GPR35 may possess anti-inflammatory properties in the gastrointestinal tract, liver and certain other tissues by curbing the generation of inflammatory mediators and endorsing the differentiation of regulatory T cells. The intricate role of GPR35 in inflammation underscores the requirement for more in-depth research to thoroughly comprehend its functional mechanisms and its potential significance as a therapeutic target for inflammatory diseases. The purpose of this review is to concurrently investigate the pro-inflammatory and anti-inflammatory roles of GPR35, thus illuminating both facets of this complex issue.

GPR35 and mediators from platelets and mast cells in neutrophil migration and inflammation

Neutrophil recruitment from circulation to sites of inflammation is guided by multiple chemoattractant cues emanating from tissue cells, immune cells, and platelets. Here, we focus on the function of one G-protein coupled receptor, GPR35, in neutrophil recruitment. GPR35 has been challenging to study due the description of multiple ligands and G-protein couplings. Recently, we found that GPR35-expressing hematopoietic cells respond to the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). We discuss distinct response profiles of GPR35 to 5-HIAA compared to other ligands. To place the functions of 5-HIAA in context, we summarize the actions of serotonin in vascular biology and leukocyte recruitment. Important sources of serotonin and 5-HIAA are platelets and mast cells. We discuss the dynamics of cell migration into inflamed tissues and how multiple platelet and mast cell-derived mediators, including 5-HIAA, cooperate to promote neutrophil recruitment. Additional actions of GPR35 in tissue physiology are reviewed. Finally, we discuss how clinically approved drugs that modulate serotonin uptake and metabolism may influence 5-HIAA-GPR35 function, and we speculate about broader influences of the GPR35 ligand-receptor system in immunity and disease.

Studies towards the Design and Synthesis of Novel 1,5-Diaryl-1H-imidazole-4-carboxylic Acids and 1,5-Diaryl-1H-imidazole-4-carbohydrazides as Host LEDGF/p75 and HIV-1 Integrase Interaction Inhibitors

Two targeted sets of novel 1,5-diaryl-1H-imidazole-4-carboxylic acids 10 and carbohydrazides 11 were designed and synthesized from their corresponding ester intermediates 17, which were prepared via cycloaddition of ethyl isocyanoacetate 16 and diarylimidoyl chlorides 15. Evaluation of these new target scaffolds in the AlphaScreen^TM HIV-1 IN-LEDGF/p75 inhibition assay identified seventeen compounds exceeding the pre-defined 50% inhibitory threshold at 100 µM concentration. Further evaluation of these compounds in the HIV-1 IN strand transfer assay at 100 μM showed that none of the compounds (with the exception of 10a, 10l, and 11k, with marginal inhibitory percentages) were actively bound to the active site, indicating that they are selectively binding to the LEDGF/p75-binding pocket. In a cell-based HIV-1 antiviral assay, compounds 11a, 11b, 11g, and 11h exhibited moderate antiviral percentage inhibition of 33–45% with cytotoxicity (CC₅₀) values of >200 µM, 158.4 µM, >200 µM, and 50.4 µM, respectively. The antiviral inhibitory activity displayed by 11h was attributed to its toxicity. Upon further validation of their ability to induce multimerization in a Western blot gel assay, compounds 11a, 11b, and 11h appeared to increase higher-order forms of IN.

Biological activity and synthesis of 5,6-dihydroxyindole-2-carboxylic acid - biosynthetic precursor of melanins (microreview)

The microreview considers the biological activity and methods of obtaining natural melanin pigments and their biosynthetic precursor 5,6-dihydroxyindole-2-carboxylic acid. The key methods for the synthesis of 5,6-dihydroxyindole-2-carboxylic acid, published over the past 8 years (2012–2020), are presented.

Syntheses of PDE3A inhibitor ORG9935 and determination of the absolute stereochemistries of its enantiomers by X-ray crystallography

Two synthetic methods were developed for the synthesis of PDE3A inhibitor ORG9935. The first one proceeds in six steps and 34% overall yield and the second one in five steps and an overall yield of 69% starting from commercially available starting material 5,6-dimethoxybenzo[b]thiophene-2-carboxylic acid (6). The enantiomers of ORG9935 were separated by chiral column chromatography and the absolute stereochemistry of the (+)-enantiomer, ORG20865 was determined by X-ray crystallography to possess the (S)-configuration. The (-)-enantiomer, ORG20864, was therefore assigned the (R)-stereochemistry. The biologically less active (+)-isomer ORG20865 was converted to racemic ORG9935 under basic conditions, which then can be separated again into the enantiomers. The crystal structure of ORG20865 is notable for having the highest Z' for any known pharmaceutical substance.

SAR Studies of N-[2-(1H-Tetrazol-5-yl)phenyl]benzamide Derivatives as Potent G Protein-Coupled Receptor-35 Agonists

G protein-coupled receptor-35 (GPR35) has emerged as a potential target in the treatment of pain and inflammatory and metabolic diseases. We have discovered a series of potent GPR35 agonists based on a coumarin scaffold and found that the introduction of a 1H-tetrazol-5-yl group significantly increased their potency. We designed and synthesized a new series of N-[2-(1H-tetrazol-5-yl)phenyl]benzamide derivatives through a two-step synthetic approach, and characterized their agonistic activities against GPR35 using a dynamic mass redistribution (DMR) assay. N-(5-bromo-2-(1H-tetrazol-5-yl)phenyl)-4-methoxybenzamide (56) and N-(5-bromo-2-(1H-tetrazol-5-yl)phenyl)-2-fluoro-4-methoxybenzamide (63) displayed the highest agonistic potency agonist GPR35 with an EC₅₀ of 0.059 μM and 0.041 μM, respectively. The physicochemical properties of selected compounds were calculated to evaluate their druglikeness, suggesting that compounds 56 and 63 have good druglike properties. Together, N-[2-(1H-tetrazol-5-yl)phenyl]benzamide derivatives are potentially great candidates for developing potent GPR35 agonists.

Expedient synthesis of eumelanin-inspired 5,6-dihydroxyindole-2-carboxylate ethyl ester derivatives

Dihydroxyindoles such as 5,6-dihydroxyindole-2-carboxylic acid (DHICA) are the main monomer units of eumelanin, the black to brown pigment in humans, and have emerging biological roles beyond melanin. Elaboration of commercially available 5,6-dimethoxy-2-carboxylate ethyl ester provides ready access to DHICA-inspired small molecules, including 3-(hetero)aryl-indoles and 4,7-di-(hetero)aryl-indoles.

Two concise syntheses of novel aryl- and heteroaryl-substituted 5,6-dimethoxyindole-2-carboxylate ethyl esters utilizing regioselective halogenation/dehalogenation and Suzuki coupling are presented.

Label-free drug discovery

Current drug discovery is dominated by label-dependent molecular approaches, which screen drugs in the context of a predefined and target-based hypothesis in vitro. Given that target-based discovery has not transformed the industry, phenotypic screen that identifies drugs based on a specific phenotype of cells, tissues, or animals has gained renewed interest. However, owing to the intrinsic complexity in drug-target interactions, there is often a significant gap between the phenotype screened and the ultimate molecular mechanism of action sought. This paper presents a label-free strategy for early drug discovery. This strategy combines label-free cell phenotypic profiling with computational approaches, and holds promise to bridge the gap by offering a kinetic and holistic representation of the functional consequences of drugs in disease relevant cells that is amenable to mechanistic deconvolution.

The Three Catecholics Benserazide, Catechol and Pyrogallol are GPR35 Agonists

Nearly 1% of all clinically used drugs are catecholics, a family of catechol-containing compounds. Using label-free dynamic mass redistribution and Tango β-arrestin translocation assays, we show that several catecholics, including benserazide, catechol, 3-methoxycatechol, pyrogallol, (+)-taxifolin and fenoldopam, display agonistic activity against GPR35.

Benzofuran-, benzothiophene-, indazole- and benzisoxazole-quinones: excellent substrates for NAD(P)H:quinone oxidoreductase 1

A series of heterocyclic quinones based on benzofuran, benzothiophene, indazole and benzisoxazole has been synthesized, and evaluated for their ability to function as substrates for recombinant human NAD(P)H:quinone oxidoreductase (NQO1), a two-electron reductase upregulated in tumor cells. Overall, the quinones are excellent substrates for NQO1, approaching the reduction rates observed for menadione.

Troubleshooting and deconvoluting label-free cell phenotypic assays in drug discovery

INTRODUCTION

Central to drug discovery and development is to comprehend the target(s), potency, efficacy and safety of drug molecules using pharmacological assays. Owing to their ability to provide a holistic view of drug actions in native cells, label-free biosensor-enabled cell phenotypic assays have been emerging as new generation phenotypic assays for drug discovery. Despite the benefits associated with wide pathway coverage, high sensitivity, high information content, non-invasiveness and real-time kinetics, label-free cell phenotypic assays are often viewed to be a blackbox in the era of target-centric drug discovery.

METHODS

This article first reviews the biochemical and biological complexity of drug-target interactions, and then discusses the key characteristics of label-free cell phenotypic assays and presents a five-step strategy to troubleshooting and deconvoluting the label-free cell phenotypic profiles of drugs.

RESULTS

Drug-target interactions are intrinsically complicated. Label-free cell phenotypic signatures of drugs mirror the innate complexity of drug-target interactions, and can be effectively deconvoluted using the five-step strategy.

DISCUSSION

The past decades have witnessed dramatic expansion of pharmacological assays ranging from molecular to phenotypic assays, which is coincident with the realization of the innate complexity of drug-target interactions. The clinical features of a drug are defined by how it operates at the system level and by its distinct polypharmacology, ontarget, phenotypic and network pharmacology. Approaches to examine the biochemical, cellular and molecular mechanisms of action of drugs are essential to increase the efficiency of drug discovery and development. Label-free cell phenotypic assays and the troubleshooting and deconvoluting approach presented here may hold great promise in drug discovery and development.