Trinuclear and tetranuclear iron(III) complexes with fenamates: Structure and biological profile.

The interaction of FeCl3 with the fenamate non-steroidal anti-inflammatory drugs has led to the formation and isolation of trinuclear iron(III) complexes, while in the presence of the nitrogen-donors 2,2'-bipyridine or pyridine tetranuclear iron(III) complexes were derived. The five resultant complexes were characterized by diverse techniques (including infrared, electronic and Mössbauer spectroscopy) and their crystal structures were determined by single-crystal X-ray crystallography. These complexes are the first structurally characterized Fe(III)-fenamato complexes. The complexes were evaluated for their ability to scavenge in vitro free radicals such as hydroxyl, 1,1-diphenyl-2-picrylhydrazyl and 2,2΄-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid). The in vitro binding affinity of the complexes to calf-thymus (CT) DNA was examined and their interaction with serum albumins was also investigated. In total, the complexes present promising activity against the radicals tested, and they may bind tightly to CT DNA possibly via intercalation and reversibly to serum albumins.

Multiple actions of fenamates and other nonsteroidal anti-inflammatory drugs on GABAA receptors.

The nonsteroidal anti-inflammatory drug (NSAID) niflumic acid, a fenamate in structure, has many molecular targets, one of them being specific subtypes of the main inhibitory ligand-gated anion channel, the GABAA receptor. Here, we report on the effects of other fenamates and other classes of NSAIDs on brain picrotoxinin-sensitive GABAA receptors, using an autoradiographic assay with [35S]TBPS as a ligand on mouse brain sections. We found that the other fenamates studied (flufenamic acid, meclofenamic acid, mefenamic acid and tolfenamic acid) affected the autoradiographic signal at low micromolar concentrations in a facilitatory-like allosteric fashion, i.e., without having affinity to the [35S]TBPS binding site. Unlike niflumic acid that shows clear preference for inhibiting cerebellar granule cell layer GABAA receptors, the other fenamates showed little brain regional selectivity, indicating that their actions are not receptor-subtype selective. Of the non-fenamate NSAIDs studied at 100 µM concentration, diclofenac induced the greatest inhibition of the binding, which is not surprising as it has close structural similarity with the potent fenamate meclofenamic acid. Using two-electrode voltage-clamp assays on Xenopus oocytes, the effect of niflumic acid was found to be dependent on the ß subunit variant and the presence of γ2 subunit in rat recombinant α1ß and α1ßγ2 GABAA receptors, with the ß1 allowing the niflumic acid inhibition and ß3 the stimulation of the receptor-mediated currents. In summary, the fenamate NSAIDs constitute an interesting class of compounds that could be used for development of potent GABAA receptor allosteric agonists with other targets to moderate inflammation, pain and associated anxiety/depression.

Redox-cycling and intercalating properties of novel mixed copper(II) complexes with non-steroidal anti-inflammatory drugs tolfenamic, mefenamic and flufenamic acids and phenanthroline functionality: Structure, SOD-mimetic activity, interaction with albumin, DNA damage study and anticancer activity.

Copper(II) complexes containing non-steroidal anti-inflammatory drugs (NSAIDs) have been the subject of many research papers and reviews. Here we report the synthesis, spectroscopic study and biological activity of novel mixed copper(II) complexes with NSAIDs: tolfenamic (tolf), mefenamic (mef) and flufenamic (fluf) acids and phenanthroline (phen): [Cu(tolf-O,O')2(phen)] (1), [Cu(mef-O,O')2(phen)] (2), [Cu(fluf-O,O')2(phen)] (3). Complexes were characterized by X-ray analysis and EPR spectroscopy. Complexes 1-3 are monomeric, six-coordinate and crystallize in a monoclinic space group. Interaction of Cu(II) complexes with DNA was studied by means of absorption titrations, viscosity measurements and gel electrophoresis. The relative ability of the complexes to cleave DNA even in the absence of hydrogen peroxide is in the order 3 > 2 > 1. Application of the reactive oxygen species (ROS) scavengers, L-histidine, DMSO and SOD confirmed that singlet oxygen, hydroxyl radicals (Fenton reaction) and superoxide radical were formed, respectively. Thus, in addition to mechanism of intercalation, redox-cycling mechanism which in turn lead to the formation of ROS contribute to DNA damage. Cu(II) complexes exhibit excellent SOD-mimetic activity in the order 3~1 > 2. The fluorescence spectroscopy revealed that albumin may act as a targeted drug delivery vehicle for Cu(II) complexes (K~106). The anticancer activities of complexes 1-3 were investigated using an MTS assay (reduction of the tetrazolium compound) against three cancer cell lines (HT-29 human colon adenocarcinoma, HeLa and T-47D breast cancer cells) and mesenchymal stromal cells (MSC). The most promising compound, from the viewpoint of its NSAID biological activity is 3, due to the presence of the three fluorine atoms participating in the formation of weak hydrogen-bonds at the DNA surface.

Fatty Acid Binding Proteins Expressed at the Human Blood-Brain Barrier Bind Drugs in an Isoform-Specific Manner.

PURPOSE: To examine the expression of fatty acid binding proteins (FABPs) at the human blood-brain barrier (BBB) and to assess their ability to bind lipophilic drugs. METHODS: mRNA and protein expression of FABP subtypes in immortalized human brain endothelial (hCMEC/D3) cells were examined by RT-qPCR and Western blot, respectively. FABPs that were found in hCMEC/D3 cells (hFABPs) were recombinantly expressed and purified from Escherichia coli C41(DE3) cells. Drug binding to these hFABPs was assessed using a fluorescence assay, which measured the ability of a panel of lipophilic drugs to displace the fluorescent probe compound 1-anilinonaphthalene-8-sulfonic acid (ANS). RESULTS: hFABP3, 4 and 5 were expressed in hCMEC/D3 cells at the mRNA and protein level. The competitive ANS displacement assay demonstrated that, in general, glitazones preferentially bound to hFABP5 (Ki: 1.0-28 µM) and fibrates and fenamates preferentially bound to hFABP4 (Ki: 0.100-17 µM). In general, lipophilic drugs appeared to show weaker affinities for hFABP3 relative to hFABP4 and hFABP5. No clear correlation was observed between the molecular structure or physicochemical properties of the drugs and their ability to displace ANS from hFABP3, 4 and 5. CONCLUSIONS: hFABP3, 4 and 5 are expressed at the human BBB and bind differentially to a diverse range of lipophilic drugs. The unique expression and binding patterns of hFABPs at the BBB may therefore influence drug disposition into the brain.

Trapping of palindromic ligands within native transthyretin prevents amyloid formation.

Transthyretin (TTR) amyloidosis is a fatal disease for which new therapeutic approaches are urgently needed. We have designed two palindromic ligands, 2,2'-(4,4'-(heptane-1,7-diylbis(oxy))bis(3,5-dichloro-4,1-phenylene)) bis(azanediyl)dibenzoic acid (mds84) and 2,2'-(4,4'-(undecane-1,11-diylbis(oxy))bis(3,5-dichloro-4,1-phenylene)) bis(azanediyl)dibenzoic acid (4ajm15), that are rapidly bound by native wild-type TTR in whole serum and even more avidly by amyloidogenic TTR variants. One to one stoichiometry, demonstrable in solution and by MS, was confirmed by X-ray crystallographic analysis showing simultaneous occupation of both T4 binding sites in each tetrameric TTR molecule by the pair of ligand head groups. Ligand binding by native TTR was irreversible under physiological conditions, and it stabilized the tetrameric assembly and inhibited amyloidogenic aggregation more potently than other known ligands. These superstabilizers are orally bioavailable and exhibit low inhibitory activity against cyclooxygenase (COX). They offer a promising platform for development of drugs to treat and prevent TTR amyloidosis.

Activation of TRPA1 channels by fenamate nonsteroidal anti-inflammatory drugs.

Transient receptor potential A1 (TRPA1) forms nonselective cation channels implicated in acute inflammatory pain and nociception. The mechanism of ligand activation of TRPA1 may involve either covalent modification of cysteine residues or conventional reversible ligand-receptor interactions. For certain electrophilic prostaglandins, covalent modification has been considered as the main mechanism involved in their stimulatory effect on TRPA1. Because some nonsteroidal anti-inflammatory drugs (NSAIDs) are structural analogs of prostaglandins, we examined several nonelectrophilic NSAIDs on TRPA1 activation using electrophysiological techniques and intracellular Ca(2+) measurements and found that a selected group of NSAIDs can act as TRPA1 agonists. Extracellularly applied flufenamic, niflumic, and mefenamic acid, as well as flurbiprofen, ketoprofen, diclofenac, and indomethacin, rapidly activated rat TRPA1 expressed in Xenopus oocytes and human TRPA1 endogenously expressed in WI-38 fibroblasts. Similarly, the NSAID ligands activated human TRPA1 inducibly expressed in HEK293 cells, but the responses were absent in uninduced and parental HEK293 cells. The response to fenamate agonists was blocked by TRPA1 antagonists, AP-18, HC-030031, and ruthenium red. At subsaturating concentrations, the fenamate NSAIDs also potentiate the activation of TRPA1 by allyl isothiocyanate, cinnamaldehyde, and cold, demonstrating positive synergistic interactions with other well-characterized TRPA1 activators. Importantly, among several thermosensitive TRP channels, the stimulatory effect is specific to TRPA1 because flufenamic acid inhibited TRPV1, TRPV3, and TRPM8. We conclude that fenamate NSAIDs are a novel class of potent and reversible direct agonists of TRPA1. This selective group of TRPA1-stimulating NSAIDs should provide a structural basis for developing novel ligands that noncovalently interact with TRPA1 channels.