Intracellular Metabolomics Identifies Efflux Transporter Inhibitors in a Routine Caco-2 Cell Permeability Assay-Biological Implications.

Caco-2 screens are routinely used in laboratories to measure the permeability of compounds and can identify substrates of efflux transporters. In this study, we hypothesized that efflux transporter inhibition of a compound can be predicted by an intracellular metabolic signature in Caco-2 cells in the assay used to test intestinal permeability. Using selective inhibitors and transporter knock-out (KO) cells and a targeted Liquid Chromatography tandem Mass Spectrometry (LC-MS) method, we identified 11 metabolites increased in cells with depleted P-glycoprotein (Pgp) activity. Four metabolites were altered with Breast Cancer Resistance (BCRP) inhibition and nine metabolites were identified in the Multidrug Drug Resistance Protein 2 (MRP2) signature. A scoring system was created that could discriminate among the three transporters and validated with additional inhibitors. Pgp and MRP2 substrates did not score as inhibitors. In contrast, BCRP substrates and inhibitors showed a similar intracellular metabolomic signature. Network analysis of signature metabolites led us to investigate changes of enzymes in one-carbon metabolism (folate and methionine cycles). Our data shows that methylenetetrahydrofolate reductase (MTHFR) protein levels increased with Pgp inhibition and Thymidylate synthase (TS) protein levels were reduced with Pgp and MRP2 inhibition. In addition, the methionine cycle is also affected by both Pgp and MRP2 inhibition. In summary, we demonstrated that the routine Caco-2 assay has the potential to identify efflux transporter inhibitors in parallel with substrates in the assays currently used in many DMPK laboratories and that inhibition of efflux transporters has biological consequences.

The development of automated patch clamp assays for canonical transient receptor potential channels TRPC3, 6, and 7.

The canonical transient receptor potential channel subfamily (TRPC3, TRPC6, and TRPC7) contains Ca(2+) permeable non-selective cation channels that are widely expressed in a variety of tissues. There is increasing evidence implicating TRPC channels, particularly TRPC3 and 6, in physiological and pathophysiological processes, eliciting interest in these channels as novel drug targets. Electrophysiology remains a benchmark technique for measuring ion channel function and accurately determining the pharmacological effects of compounds. In this report we describe the development of TRPC inhibitor assays on 2 automated planar patch clamp platforms-the IonWorks(®) Quattro™ and QPatch(®) systems. To enable activation of TRPC channels by carbachol, Chinese Hamster Ovary-K1 cells stably expressing the muscarinic M3 receptor were transduced with human TRPC3, TRPC6, or TRPC7 using BacMam viruses. TRPC3, 6, and 7 currents could be recorded on both platforms. However, the design of each platform limits which assay parameters can be recorded. Due to its continuous recording capabilities, the QPatch can capture both the activation and decay of the response. However, the transient nature of TRPC channels, the inability to reactivate and the large variation in peak currents limits the ability to develop assays for compound screening. The IonWorks Quattro, due to its discontinuous sampling, did not fully capture the peak of TRPC currents. However, due to the ability of the IonWorks Quattro to record from 64 cells per well, the variation from well to well was sufficiently reduced allowing for the development of medium-throughput screening assays.

Increased prokineticin 2 expression in gut inflammation: role in visceral pain and intestinal ion transport.

BACKGROUND: Prokineticin 2 (PROK2) is an inflammatory cytokine-like molecule expressed predominantly by macrophages and neutrophils infiltrating sites of tissue damage. Given the established role of prokineticin signaling on gastrointestinal function, we have explored Prok2 gene expression in inflammatory conditions of the gastrointestinal tract and assessed the possible consequences on gut physiology. METHODS: Prokineticin expression was examined in normal and colitic tissues using qPCR and immunohistochemistry. Functional responses to PROK2 were studied using calcium imaging and a novel antagonist, Compound 3, used to determine the role of PROK2 and prokineticin receptors in inflammatory visceral pain and ion transport. KEY RESULTS: Prok2 gene expression was up-regulated in biopsy samples from ulcerative colitis patients, and similar elevations were observed in rodent models of inflammatory colitis. Prokineticin receptor 1 (PKR1) was localized to the enteric neurons and extrinsic sensory neurons, whereas Pkr2 expression was restricted to sensory ganglia. In rats, PROK2-increased intracellular calcium levels in cultured enteric and dorsal root ganglia neurons, which was blocked by Compound 3. Moreover, PROK2 acting at prokineticin receptors stimulated intrinsic neuronally mediated ion transport in rat ileal mucosa. In vivo, Compound 3 reversed intracolonic mustard oil-induced referred allodynia and TNBS-induced visceral hypersensitivity, but not non-inflammatory, stress-induced visceral pain. CONCLUSIONS & INFERENCES: Elevated Prok2 levels, as a consequence of gastrointestinal tract inflammation, induce visceral pain via prokineticin receptors. This observation, together with the finding that PROK2 can modulate intestinal ion transport, raises the possibility that inhibitors of PROK2 signaling may have clinical utility in gastrointestinal disorders, such as irritable bowel syndrome and inflammatory bowel disease.

Design and synthesis of a library of chemokine antagonists.

A library of chemokine antagonists has been synthesized using a combination of solid and solution-phase chemistry. Structures of known chemokine antagonists were used to produce a pharmacophore which served to guide monomer selection. Several combinations of monomers have resulted in providing novel chemokine antagonists which in some cases display dual chemokine receptor antagonism.

Bridgehead enolates and bridgehead alkenes in a welwistatin model series.

Bridgehead metallation is possible in a ketone having the welwistatin skeleton, and this facilitates installation of the isothiocyanate function present in the natural product, and also enables synthesis of remarkable bridgehead alkenes.

Flexible strategy for the synthesis of pyrrolizidine alkaloids.

A general strategy for the production of pyrrolizidine alkaloids is described, starting from intermediate (+)-9. The key features are diastereoselective dihydroxylation, inversion at the ring junction by hydroboration of an enamine, and ring closure to form the bicyclo ring system. This route is attractive because of its brevity and versatility; four natural products were prepared with differing stereochemistry and substitution patterns. Finally, this work allowed assignment of the absolute stereochemistry of 2,3,7-triepiaustraline and hyacinthacine A 7.

2-Cycloalkyl phenoxyacetic acid CRTh2 receptor antagonists.

High throughput screening identified a phenoxyacetic acid scaffold as a novel CRTh2 receptor antagonist chemotype, which could be optimised to furnish a compound with functional potency for inhibition of human eosinophil shape change and oral bioavailability in the rat.

Potent and selective xanthine-based inhibitors of phosphodiesterase 5.

Inhibitors of PDE5 are useful therapeutic agents for treatment of erectile dysfunction. A series of novel xanthine derivatives has been identified as potent inhibitors of PDE5, with good levels of selectivity against other PDE isoforms, including PDE6. Studies in the dog indicate excellent oral bioavailability for compound 21.

An enzymatic approach to the desymmetrization of disubstituted pyrrolines.

The enzymatic desymmetrization of 2,2- and 2,5-disubstituted pyrroline compounds is reported in a procedure which gives access to both enantiomers in excellent enantiomeric excess and good yield. The enzyme reaction precursors are formed easily from two readily available substituted pyrroles using both ammonia (Na/NH3) and ammonia-free (Li/DBB) Birch reduction conditions.

Enantioselective partial reduction of 2,5-disubstituted pyrroles via a chiral protonation approach.

[reaction: see text] The partial reduction of 2,5-pyrrole diester 1 followed by enantioselective protonation in situ to furnish synthetically useful building blocks is described. An enantiomeric excess of up to 74% was achieved using (-)-ephedrine and related analogues as chiral proton sources. The pyrroline product obtained could be recrystallized to give enantiomerically pure material.

A combinatorial approach to the synthesis of cystine based organogelators.

A solid-phase approach was used to prepare 20 cystine amide derivatives with disulfide bond formation resulting from an intra-site reaction between neighbouring cysteine residues. Library members were screened as potential organogelators in a range of solvent mixtures and resulted in the identification of a potent gelator able to rigidify water/DMSO mixtures at concentrations as low as 1.3 mM.

Dyad beads and the combinatorial discovery of catalysts.

Dyad beads, bearing both a substrate and a catalyst, were prepared to enable direct split and mix bead based screening for catalysis.

Ion-extraction ladder sequencing from bead-based libraries.

Ion-extraction mass spectrometry of ladders of mixtures of isotopically labeled compounds from single beads allows the unambiguous sequencing of bead-based peptides and offers significant advantages over traditional methods of library analysis.

Mild and highly chemoselective oxidation of thioethers mediated by Sc(OTf)3.

[reaction: see text] Catalytic Sc(OTf)(3) greatly increases the efficiency of hydrogen peroxide mediated monooxidation of alkyl-aryl sulfides and methyl cysteine containing peptides. The method is high yielding, compatible with many widely used protecting groups, suitable for solid-phase applications and proceeds with minimum over-oxidation.

Recent advances in corticosteroids for the treatment of asthma.

The currently available therapy for asthma is highly effective and is able to control the disease in the majority of patients. There are two types of treatments for asthma: rapid relief of symptoms, used as needed and long-term control, used on a regular basis. Rapid relief is provided by short-acting beta2-agonists and anticholinergics. The control of asthma is achieved by treatment with inhaled corticosteroids (ICS), theophylline, long acting beta2-agonists and antileukotrienes. Beta2-agonists and corticosteroids dominate asthma therapy, with over 65% of the market share. Corticosteroids are the most effective drugs available to clinicians for the control of inflammation in patients with asthma. ICS have revolutionized the treatment of asthma and are now the first-line treatment for chronic asthma in all ages.

8-Aryl xanthines potent inhibitors of phosphodiesterase 5.

In clinical studies, several inhibitors of phosphodiesterase 5 (PDE5) have demonstrated utility in the treatment of erectile dysfunction. We describe herein a series of 8-aryl xanthine derivatives which function as potent PDE5 inhibitors with, in many cases, high levels of selectivity versus other PDE isoforms.

A solid-phase approach towards the synthesis of PDE5 inhibitors.

PDE5 inhibitors based upon the xanthine scaffold 8 have been expediently synthesized using a solid-phase route. Attachment of the xanthine scaffold 8 using the Rink chloride linker 4 and N-1 functionalization using Mitsunobu chemistry is described. A library of compounds was produced in multi-milligram quantities with excellent purities and acceptable yields. The compounds were tested for their PDE5 inhibitory activity.