Background GP-BAR1, a member G protein coupled receptor superfamily, is a cell surface bile acid-activated receptor highly expressed in the ileum and colon. In monocytes, ligation of GP-BAR1 by secondary bile acids results in a cAMP-dependent attenuation of cytokine generation.AimsTo investigate the role GP-BAR1 in regulating intestinal homeostasis and inflammation-driven immune dysfunction in rodent models of colitis.MethodsColitis was induced in wild type and GP-BAR1−/− mice by DSS and TNBS administration. Potential GP-BAR1 agonists were identified by in silico screening and computational docking studies.ResultsGP-BAR1−/− mice develop an abnormal morphology of colonic mucous cells and an altered molecular architecture of epithelial tight junctions with increased expression and abnormal subcellular distribution of zonulin 1 resulting in increased intestinal permeability and susceptibility to develop severe colitis in response to DSS at early stage of life. By in silico screening and docking studies we identified ciprofloxacin as a GP-BAR1 ligand. In monocytes, ciprofloxacin increases cAMP concentrations and attenuates TNFα release induced by TLR4 ligation in a GP-BAR1 dependent manner. Treating mice rendered colitic by TNBS with ciprofloxacin and oleanolic acid, a well characterized GP-BAR1 ligand, abrogates signs and symptoms of colitis. Colonic expression of GP-BAR1 mRNA increases in rodent models of colitis and tissues from Crohn's disease patients. Flow cytometry analysis demonstrates that ≈90% of CD14+ cells isolated from the lamina propria of TNBS-treated mice stained positively for GP-BAR1.ConclusionsGP-BAR1 regulates intestinal barrier structure. Its expression increases in rodent models of colitis and Crohn's disease. Ciprofloxacin is a GP-BAR1 ligand.

Silica gel column chromatography, followed by HPLC purification on the apolar fraction of the methanol extract of marine sponge Theonella swinhoei, resulted in the isolation of a library of 10 polyhydroxylated steroids which we named theonellasterols B-H (1-7) and conicasterols B-D (8-10). The structures were determined on the basis of extensive spectroscopic data (MS, (1)H and (13)C NMR, COSY, HSQC, HMBC, and ROESY) analysis, and the putative binding mode to nuclear receptors (NRs) has been obtained through docking calculations. Pharmacological and structure-activity relationship analysis demonstrate that these natural polyhydroxylated steroids are potent ligands of human nuclear pregnane receptor (PXR) and modulator of farnesoid-X-receptor (FXR). In addition, the molecular characterization of theonellasterol G allowed the identification of the first FXR modulator and PXR ligand so far identified. Exposure of liver cells to this agent resulted in potent induction of PXR-regulated genes and modulation of FXR-regulated genes, highlighting its pharmacological potential in the treatment of liver disorders.

The present microreview highlights the recent goals reached by the application of a combined approach of NMR spectroscopy and quantum chemical methods in the structural studies of natural products. In particular, different case studies are reported, showing the comparison of calculated NMR parameters at the quantum mechanical (QM) theory level with experimental data for the configurational assignment of organic compounds. Moreover, it is shown that the QM-NMR

Azumamide E, a cyclotetrapeptide isolated from the sponge Mycale izuensis, is the most powerful carboxylic acid containing natural histone deacetylase (HDAC) inhibitor known to date. In this paper, we describe design and synthesis of two stereochemical variants of the natural product. These compounds have allowed us to clarify the influence of side chain topology on the HDAC-inhibitory activity. The present contribution also reveals the identity of the recognition pattern between azumamides and the histone deacetylase-like protein (HDLP) model receptor and reports the azumamide E unprecedented isoform selectivity on histone deacetylases class subtypes. From the present studies, a plausible model for the interaction of azumamides with the receptor binding pocket is derived, providing a framework for the rational design of new cyclotetrapeptide-based HDAC inhibitors as antitumor agents.

The inhibition of NAD synthesis or salvage pathways has been proposed as a novel target for antitumoral drugs. Two molecules with this mechanism of action are at present undergoing clinical trials. In searching for similar novel molecules, we exploited copper-catalyzed [3 + 2] cycloaddition between azides and alkynes (click chemistry) to synthesize 185 novel analogues. The most promising compound displays an IC(50) for cytotoxicity in vitro of 3.8 +/- 0.3 nM and an IC(50) for NAD depletion of 3.0 +/- 0.4 nM. Herein, we strengthen previous data suggesting that this class of compounds induces autophagic cell death. In addition to characterizing this compound and providing a rationale via molecular docking, we reinforce the excellent potential of click chemistry for rapidly generating structure-activity relationships and for drug screening.

BackgroundThe farnesoid-x-receptor (FXR) is a bile acid sensor expressed in the liver and gastrointestinal tract. Despite FXR ligands are under investigation for treatment of cholestasis, a biochemical condition occurring in a number of liver diseases for which available therapies are poorly effective, mice harboring a disrupted FXR are protected against liver injury caused by bile acid overload in rodent models of cholestasis. Theonellasterol is a 4-methylene-24-ethylsteroid isolated from the marine sponge Theonella swinhoei. Here, we have characterized the activity of this theonellasterol on FXR-regulated genes and biological functions.Principal FindingsInterrogation of HepG2 cells, a human hepatocyte cell line, by microarray analysis and transactivation assay shows that theonellasterol is a selective FXR antagonist, devoid of any agonistic or antagonistic activity on a number of human nuclear receptors including the vitamin D receptor, PPARs, PXR, LXRs, progesterone, estrogen, glucorticoid and thyroid receptors, among others. Exposure of HepG2 cells to theonellasterol antagonizes the effect of natural and synthetic FXR agonists on FXR-regulated genes, including SHP, OSTα, BSEP and MRP4. A proof-of-concept study carried out to investigate whether FXR antagonism rescues mice from liver injury caused by the ligation of the common bile duct, a model of obstructive cholestasis, demonstrated that theonellasterol attenuates injury caused by bile duct ligation as measured by assessing serum alanine aminostrasferase levels and extent of liver necrosis at histopathology. Analysis of genes involved in bile acid uptake and excretion by hepatocytes revealed that theonellasterol increases the liver expression of MRP4, a basolateral transporter that is negatively regulated by FXR. Administering bile duct ligated mice with an FXR agonist failed to rescue from liver injury and downregulated the expression of MRP4.ConclusionsFXR antagonism in vivo results in a positive modulation of MRP4 expression in the liver and is a feasible strategy to target obstructive cholestasis.

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Microsomal prostaglandin E(2) synthase (mPGES)-1 catalyzes the transformation of PGH(2) to PGE(2) that is involved in several pathologies like fever, pain, and inflammatory disorders. To identify novel mPGES-1 inhibitors, we used in silico screening to rapidly direct the synthesis, based on the copper-catalyzed 3 + 2 Huisgen's reaction (click chemistry), of potential inhibitors. We designed 26 new triazole-based compounds in accordance with the pocket binding requirements of human mPGES-1. Docking results, in agreement with ligand efficiency values, suggested the synthesis of 15 compounds that at least in theory were shown to be more efficient in inhibiting mPGES-1. Biological evaluation of these selected compounds has disclosed three new potential anti-inflammatory drugs: (I) compound 4 displaying selectivity for mPGES-1 with an IC(50) value of 3.2 μM, (II) compound 20 that dually inhibits 5-lipoxygenase and mPGES-1, and (III) compound 7 apparently acting as 5-lipoxygenase-activating protein inhibitor (IC(50) = 0.4 μM).