Phenylhydrazones as Correctors of a Mutant Cystic Fibrosis Transmembrane Conductance Regulator.

The phenylhydrazone RDR-1 is endowed with moderate activity as F508del-CFTR corrector; nevertheless, its simple structure enables stimulating developments in this class of correctors. Therefore, we synthesized a number of phenylhydrazones 3 by reacting phenylhydrazine derivatives 1 with furfural derivatives 2. By the same reaction, also the pyridine derivatives 4, the thiophene derivatives 5, and the hydrazides 6 and 7 were prepared. All compounds were tested as F508del-CFTR correctors in the cystic fibrosis (CF) bronchial epithelial cell line CFBE41o-, using corr-4a and VX-809 as controls. Some of the tested compounds emerged as interesting F508del-CFTR correctors at 20 µM (3c) and 2 µM (5d). 3c and 5d administered together with VX-809 produced a satisfactory additivity of action. When the structure of 5d was overlapped with RDR-1 and five other established correctors, a shared central design was clearly visible. This fact may be of interest in the search for new F508del-CFTR correctors.

Matrine modulates HSC70 levels and rescues ΔF508-CFTR.

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent Cl(-) channel located in the plasma membrane, and its malfunction results in cystic fibrosis (CF), the most common lethal genetic disease in Caucasians. Most CF patients carry the deletion of Phe508 (ΔF508 mutation); this mutation prevents the delivery of the CFTR to its correct cellular location, the apical (lumen-facing) membrane of epithelial cells. Molecular chaperones play a central role in determining the fate of ΔF508-CFTR. In this report, we show that the Matrine, a quinolizidine alkaloid, downregulates the expression of the molecular chaperone HSC70 and increases the protein levels of ΔF508-CFTR in human alveolar basal epithelial cells (A549 cell line), stably transfected with a ΔF508-CFTR-expressing construct. Moreover, Matrine induced ΔF508-CFTR release from endoplasmic reticulum to cell cytosol and its localization on the cell membrane. Interestingly, downregulation of HSC70 resulted in increased levels of ΔF508-CFTR complexes with the co-chaperone BAG3 that in addition appeared to co-localize with the mutated protein on the cell surface. These results shed new light on ΔF508-CFTR interactions with proteins of the chaperones/co-chaperones system and could be useful in strategies for future medical treatments for CF.

Activity of Mannich bases of 7-hydroxycoumarin against Flaviviridae.

Some Mannich bases of 7-hydroxycoumarin (2) and their simple derivatives (3 and 4) were prepared and tested against viruses containing single-stranded, positive-sense RNA genomes (ssRNA(+)). This study was directed toward Flaviviridae and, in particular, HCV surrogate viruses (BVDV, YFV). The 7-hydroxy derivatives 2 were generally devoid of activity, but when position 7 was propylated, the resulting 7-propyloxy derivatives 3 were in some cases endowed with an interesting activity against BVDV. The formation of 7-benzoyl derivatives 4 gave compounds generally lacking in activity against Flaviviridae, whereas the appearance of activity against RSV has been observed. Also some unsymmetrical methylene derivatives 5-7 (namely coumarins bridged to chromones or indoles) were found moderately active in antiviral tests. Derivatives 3 were submitted to a molecular modeling study using DNA polymerase of HCV as a target. The good correlation between calculated molecular modeling IC(50) and experimental EC(50) indicates that DNA polymerase is potentially involved in the inhibition of surrogate HCV viruses.

Matrine in association with FD­2 stimulates F508del­cystic fibrosis transmembrane conductance regulator activity in the presence of corrector VX809.

Cystic fibrosis is caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and the predominant mutation is termed Phe508del (F508del). Therapy for F508del­CFTR patients is based on the use of Orkambi®, a combination of VX809 and VX770. However, though Orkambi leads to an improvement in the lung function of patients, a progressive reduction in its efficacy has been observed. In order to overcome this effect, the aim of the present study was to investigate the role of matrine and the in­house compound FD­2 in increasing the action of VX809 and VX770. Fischer rat thyroid cells overexpressing F508del­CFTR were treated with matrine, VX809 (corrector) and/or with a number of potentiators (VX770, FD­1 and FD­2). The results demonstrated that matrine was able to stimulate CFTR activity and, in association with FD­2, increased the functionality of the channel in the presence of VX809. Based on these results, it may be hypothesized that FD­2 may be a novel and more effective potentiator compared with VX770.

Sequence specific peptidomimetic molecules inhibitors of a protein-protein interaction at the helix 1 level of c-Myc.

Our work is focused in the broad area of strategies and efforts to inhibit protein-protein interactions. The possible strategies in this field are definitely much more varied than in the case of ATP-pocket inhibitors. In our previous work (10), we reported that a retro-inverso (RI) form of Helix1 (H1) of c-Myc, linked to an RI-internalization sequence arising from the third alpha-helix of Antennapedia (Int) was endowed with an antiproliferative and proapoptotic activity toward the cancer cell lines MCF-7 and HCT-116. The activity apparently was dependent upon the presence of the Myc motif. In this work, by ala-scan mapping of the H1 portion of our molecules with D-aa, we found two amino acids necessary for antiproliferative activity: D-Lys in 4 and D-Arg in 5 (numbers refer to L-forms). In the natural hetero-dimer, these two side chains project to the outside of the four alpha-helix bundle. Moreover, we were able to obtain three peptides more active than the original lead. They strongly reduced cell proliferation and survival (RI-Int-VV-H1-E2A,S6A,F8A; RI-Int-VV-H1-S6A,F8A,R11A; RI-Int-VV-H1-S6A,F8A,Q13A): after 8 days at 10 muM total cell number was approximately 1% of the number of cells initially seeded. In these more potent molecules, the ablated side chains project to the inside in the corresponding natural four alpha-helix bundle. In the present work, we also investigated the behavior of our molecules at the biochemical level. Using both a circular dichroism (CD) and a fluorescence anisotropy approach, we noted that side chains projecting at the interior of the four alpha-helix bundle are needed for inducing the partial unfolding of Myc-H2, without an opening of the leucine zipper. Side chains projecting at the outside are not required for this biochemical effect. However, antiproliferative activity had the opposite requirements: side chains projecting at the outside of the bundle were essential, and, on the contrary, ablation of one side chain at a time projecting at the inside increased rather than decreased biological activity. We conclude that our active molecules probably interfere at the level of a protein-protein interaction between Myc-Max and a third protein of the transcription complex. Finally, CD and nuclear magnetic resonance (NMR) data, plus dynamic simulations, suggest a prevalent random coil conformation of the H1 portion of our molecules, at least in diluted solutions. The introduction of a kink (substitution with proline in positions 5 or 7) led to an important reduction of biological activity. We have also synthesized a longer peptido-mimetic molecule (RI-Int-H1-S6A,F8A-loop-H2) with the intent of obtaining a wider zone of interaction and a stronger interference at the level of the higher-order structure (enhanceosome). RI-Int-H1-S6A,F8A-loop-H2 was less active rather than more active in respect to RI-Int-VV-H1-S6A,F8A, apparently because it has a clear bent to form a beta-sheet (CD and NMR data).

2-(dialkylamino)-4H-1-benzopyran-4-one derivatives modify chloride conductance in CFTR expressing cells.

Some 2-(diethylamino)-7-hydroxy-4H-1-benzopyran-4-one derivatives, potentially useful as activators of the cystic fibrosis transmembrane conductance regulator (CFTR), were prepared. The synthesized compounds were tested, together with others 2-(dialkylamino)-7-hydroxybenzopyran-4-one derivatives, by measuring their capacity to modify the kinetics of iodide influx in Fisher rat thyroid cells expressing wild type CFTR and the halide-sensitive yellow fluorescent protein. Among the tested compounds the dinitrile derivatives 8 and 9 are endowed with an activity comparable to the reference compound apigenin.

The search for a common structural moiety among selected pharmacological correctors of the mutant CFTR chloride channel.

BACKGROUND: The F508del mutation impairs the trafficking of CFTR from endoplasmic reticulum to plasma membrane and is responsible of a severe form of cystic fibrosis. Trafficking can be improved by small organic molecules called 'correctors'. MATERIALS & METHODS: By different synthetic ways, we prepared 4-chloroanisole and 2-(4-chloroanisol-2-yl)aminothiazole derivatives. Such compounds were ineffective as correctors but we could find a sign of activity in an intermediate. In the meantime, we found a common pharmacophoric moiety present in four known correctors. RESULTS: Following this structural indication, we synthesized a small set of new molecules endowed with a significant, even if not great, F508del-CFTR rescue activity. CONCLUSION: The cited structural feature seems interesting in the search of new correctors. To corroborate this observation, later on we found a new pyrazine derivative (Novartis) endowed with a potent activity as corrector and having the cited common design.

F508del-CFTR rescue: a matter of cell stress response.

Cystic fibrosis (CF) is a common inherited fatal disease affecting 70,000 people worldwide, with a median predicted age of survival of approximately 38 years. The deletion of Phenylalanine in position 508 of the Cystic Fibrosis Transmembrane conductance Regulator (F508del-CFTR) is the most common mutation in CF patients: the deleted protein, not properly folded, is degraded. To date no commercial drugs are available. Low temperature, some osmolytes and conditions able to induce heat shock protein 70 (Hsp70) expression and heat shock cognate 70 (Hsc70) inhibition result in F508del-CFTR rescue, hence restoring its physiological function: this review sheds light on the correlation between these several evidences. Interestingly, all these approaches have a role in the cell stress response (CSR), a set of cell reactions to stress. In addition, unpredictably, F508del-CFTR rescue has to be considered in the frame of CSR: entities that induce - or are induced during - the CSR are, in general, also able to correct trafficking defect of CFTR. Specifically, the low temperature induces, by definition, a CSR; osmolytes, such as glycerol and trimethylamine N-oxide (TMAO), are products of the CSR; pharmacological correctors, such as Matrine and 4-phenylbutirric acid (4PBA), down-regulate the constitutive Hsc70 in favor of an up-regulation of the inducible chaperone Hsp70, another component of the CSR. The identification of a common mechanism of action for different types of correctors could drive the discovery of new active molecules in CF, overcoming methods clinically inapplicable, such as the low temperature.

Asymmetric 4-aryl-1,4-dihydropyridines potentiate mutant cystic fibrosis transmembrane conductance regulator (CFTR).

Some of the genetic mutations that cause cystic fibrosis (CF) impair the gating of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) ion channel. This defect can be corrected with pharmacological tools (potentiators) that belong to various chemical families, including the 1,4-dihydropyridines (DHPs). A small set of asymmetric 4-aryl-DHPs was synthesized, and each racemic couple was tested in a functional assay carried out on cells expressing the G1349D, ΔF508, and G551D mutants. The most active racemates were subjected to chiral separation by HPLC, and the pure enantiomers were tested to evaluate any gains in activity. Although three enantiomers demonstrated high potency (K(d) values less than 0.09, 0.1, and 0.5 µM in G1349D, ΔF508, and G551D, respectively), in general, the screening of pure enantiomers did not produce a great diversity in potency values. It is probable that the degree of DHP asymmetry considered in our analysis is still insufficient with respect to that allowed in a putative DHP binding site in CFTR, so that the site could equally accommodate both enantiomers.

Interfering with protein-protein contact: molecular interaction maps and peptide modulators.

Protein-protein interactions (PPIs) can be useful targets for different pathologies. In fact controlling a function or attempting to repair an anomaly often means interfering with the cross-talk among different proteins. In order to have a general view of these cross-talks, Molecular Interaction Maps (MIMs) are used, organizing the enormous available information that is added every day and trying to understand the most suitable and accurate targets for any specific cell alteration. In this paper the c-Myc protein is taken as an example to explain the use of a map. The discovery of a peptidomimetic antagonist of c-Myc, active against proliferation of cancer cell lines, is reported and a possible mechanism of action is explained. To interfere with a specific protein-protein contact, a good starting point can be to consider a protein entity. Because the interaction between two proteins is normally characterized by a wide zone of contact, relative large inhibitors could be more convenient in the first approaches. Therefore, peptides mimicking the interacting zone can be considered as potential leads in the rational design of effective molecules. Here different examples of peptides as protein-protein interaction inhibitors are reported.

Antihypertensive 1,4-dihydropyridines as correctors of the cystic fibrosis transmembrane conductance regulator channel gating defect caused by cystic fibrosis mutations.

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel gene. CF mutations like deltaF508 cause both a mistrafficking of the protein and a gating defect. Other mutations, like G551D, cause only a gating defect. Our aim was to find chemical compounds able to stimulate the activity of CFTR mutant proteins by screening a library containing approved drugs. Two thousand compounds were tested on Fischer rat thyroid cells coexpressing deltaF508-CFTR and a halide-sensitive yellow fluorescent protein (YFP) after correction of the trafficking defect by low-temperature incubation. The YFP-based screening allowed the identification of the antihypertensive 1,4-dihydropyridines (DHPs) nifedipine, nicardipine, nimodipine, isradipine, nitrendipine, felodipine, and niguldipine as compounds able to activate deltaF508-CFTR. This effect was not derived from the inhibition of voltage-dependent Ca2+ channels, the pharmacological target of antihypertensive DHPs. Indeed, methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-2(trifluoromethylphenyl)pyridine-5-carboxylate (BayK-8644), a DHP that is effective as an activator of such channels, also stimulated CFTR activity. DHPs were also effective on the G551D-CFTR mutant by inducing a 16- to 45-fold increase of the CFTR Cl- currents. DHP activity was confirmed in airway epithelial cells from patients with CF. DHPs may represent a novel class of therapeutic agents able to correct the defect caused by a set of CF mutations.