Cystic Fibrosis: A New Target for 4-Imidazo[2,1-b]thiazole-1,4-dihydropyridines

The pharmacology of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel has attracted significant interest in recent years with the aim to search for rational new therapies for diseases caused by CFTR malfunction. Mutations that abolish the function of CFTR cause the life-threatening genetic disease cystic fibrosis (CF). The most common cause of CF is the deletion of phenylalanine 508 (ΔF508) in the CFTR chloride channel. Felodipine, nifedipine, and other antihypertensive 1,4-dihydropyridines (1,4-DHPs) that block L-type Ca(2+) channels are also effective potentiators of CFTR gating, able to correct the defective activity of ΔF508 and other CFTR mutants ( Mol. Pharmacol. 2005 , 68 , 1736 ). For this purpose, we evaluated the ability of the previously and newly synthesized 4-imidazo[2,1-b]thiazoles-1,4-dihydropyridines without vascular activity and inotropic and/or chronotropic cardiac effects ( J. Med. Chem. 2008 , 51 , 1592 ) to enhance the activity of ΔF508-CFTR. Our studies indicate compounds 17, 18, 20, 21, 38, and 39 as 1,4-DHPs with an interesting profile of activity

Genetic Inhibition of the Ubiquitin Ligase Rnf5 Attenuates Phenotypes Associated to F508del Cystic Fibrosis Mutation

Cystic fibrosis (CF) is caused by mutations in the CFTR chloride channel. Deletion of phenylalanine 508 (F508del), the most frequent CF mutation, impairs CFTR trafficking and gating. F508del-CFTR mistrafficking may be corrected by acting directly on mutant CFTR itself or by modulating expression/activity of CFTR-interacting proteins, that may thus represent potential drug targets. To evaluate possible candidates for F508del-CFTR rescue, we screened a siRNA library targeting known CFTR interactors. Our analysis identified RNF5 as a protein whose inhibition promoted significant F508del-CFTR rescue and displayed an additive effect with the investigational drug VX-809. Significantly, RNF5 loss in F508del-CFTR transgenic animals ameliorated intestinal malabsorption and concomitantly led to an increase in CFTR activity in intestinal epithelial cells. In addition, we found that RNF5 is differentially expressed in human bronchial epithelia from CF vs. control patients. Our results identify RNF5 as a target for therapeutic modalities to antagonize mutant CFTR proteins

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Evidence against the rescue of defective ΔF508-CFTR cellular processing by curcumin in cell culture and mouse models

Curcumin, the yellow colored component of the spice turmeric, has been reported to rescue defective DeltaF508-cystic fibrosis transmembrane conductance regulator (CFTR) cellular processing in homozygous mutant mice, restoring nasal potential differences and improving survival (Egan, M. E., Pearson, M., Weiner, S. A., Rajendran, V., Rubin, D., Glockner-Pagel, J., Canny, S., Du, K., Lukacs, G. L., and Caplan, M. J. (2004) Science 304, 600-602). Because of the implied potential use of curcumin or similar compounds in the therapy of cystic fibrosis caused by the DeltaF508 mutation, we tried to reproduce and extend the pre-clinical data of Egan et al. Fluorometric measurements of iodide influx in Fischer rat thyroid cells expressing DeltaF508-CFTR showed no effect of curcumin (1-40 microm) when added for up to 24 h prior to assay in cells grown at 37 degrees C. Controls, including 27 degrees C rescue and 4 mm phenylbutyrate at 37 degrees C, were strongly positive. Also, curcumin did not increase short circuit current in primary cultures of a human airway epithelium homozygous for DeltaF508-CFTR with a 27 degrees C rescue-positive control. Nasal potential differences in mice were measured in response to topical perfusion with serial solutions containing amiloride, low Cl-, and forskolin. Robust low Cl- and forskolin-induced hyperpolarization of 22 +/- 3 mV was found in wild type mice, with 2.1 +/- 0.4 mV hyperpolarization in DeltaF508 homozygous mutant mice. No significant increase in Cl-/forskolin hyperpolarization was seen in any of the 22 DeltaF508 mice studied using different curcumin preparations and administration regimens, including that used by Egan et al. Assay of serum curcumin by ethyl acetate extraction followed by liquid chromatography/mass spectrometry indicated a maximum serum concentration of 60 nm, well below that of 5-15 microm, where cellular effects by sarcoplasmic/endoplasmic reticulum calcium pump inhibition are proposed to occur. Our results do not support further evaluation of curcumin for cystic fibrosis therapy

Phenylglycine and sulfonamide correctors of defective ΔF508 and G551D cystic fibrosis transmembrane conductance regulator chloride-channel gating

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel cause cystic fibrosis. The delta F508 mutation produces defects in channel gating and cellular processing, whereas the G551D mutation produces primarily a gating defect. To identify correctors of gating, 50,000 diverse small molecules were screened at 2.5 microM (with forskolin, 20 microM) by an iodide uptake assay in epithelial cells coexpressing delta F508-CFTR and a fluorescent halide indicator (yellow fluorescent protein-H148Q/I152L) after delta F508-CFTR rescue by 24-h culture at 27 degrees C. Secondary analysis and testing of >1000 structural analogs yielded two novel classes of correctors of defective delta F508-CFTR gating ("potentiators") with nanomolar potency that were active in human delta F508 and G551D cells. The most potent compound of the phenylglycine class, 2-[(2-1H-indol-3-yl-acetyl)-methylamino]-N-(4-isopropylphenyl)-2-phenylacetamide, reversibly activated delta F508-CFTR in the presence of forskolin with K(a) approximately 70 nM and also activated the CFTR gating mutants G551D and G1349D with K(a) values of approximately 1100 and 40 nM, respectively. The most potent sulfonamide, 6-(ethylphenylsulfamoyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid cycloheptylamide, had K(a) approximately 20 nM for activation of delta F508-CFTR. In cell-attached patch-clamp experiments, phenylglycine-01 (PG-01) and sulfonamide-01 (SF-01) increased channel open probability >5-fold by the reduction of interburst closed time. An interesting property of these compounds was their ability to act in synergy with cAMP agonists. Microsome metabolism studies and rat pharmacokinetic analysis suggested significantly more rapid metabolism of PG-01 than SF-03. Phenylglycine and sulfonamide compounds may be useful for monotherapy of cystic fibrosis caused by gating mutants and possibly for a subset of delta F508 subjects with significant delta F508-CFTR plasma-membrane expression