Biomedical subjects
Publications and source records attributed to J Barbe.
A novel set of acridinylidene thiazolidinediones and benzylidene thiazolidinediones was synthesized by nucleophilic addition of cyanoacrylates. Some of these compounds were evaluated for their glucose lowering capability and their effects on the triglyceride level in alloxan diabetic mice.
Synthesis and physico-chemical properties of 3-benzyl-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-ones, 5-benzylidene-3-(4-nitro-benzyl)-2-thioxo-imidazolidin-4-ones and 4-acridin-9-ylmethylene-1-benzyl-5-thioxo-imidazolidin-2-ones compounds are described. These thioxo-imidazolidine derivatives were prepared by alkylation and condensation with 4-fluoro-benzaldehyde or nucleophilic Michael addition with cyanoacrylates. The schistosomicidal activity of 3-benzyl-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-one compounds was evaluated.
Six new 9-(ethylthio)acridine derivatives were examined for antibacterial and antifungal activities with 10 bacterial and 8 yeast strains. The only active compounds were 2- and 3-amino derivatives. The observed MICs (mg/L) for 2-amino-9-(ethylthio)acridine (possessing the highest biological activity) were 12 (P. mirabilis), 30 (B. subtillis), 60 (C. freundii), 90 (E. coli), 128 (E. vulneris) and 500 (S. marcescens and S. aureus). Both amino derivatives have also lowest half-wave potential (E1/2) and field Swain-Lupton constants (describing oxidoreduction behavior) what supports the importance of acridine ion formation in the mechanism of antimicrobial action.
Enterobacter aerogenes, one of the most frequently isolated nosocomial pathogens in France, is exhibiting increasing multidrug resistance mechanisms associated with a change in membrane permeability. For drugs of the quinolone family, mutations in the target and active efflux play a prominent role in the resistance. We report here the effect of several pyridoquinoline derivatives that restore a noticeable fluoroquinolone accumulation to resistant strains that overexpress the MarA activator. Studies of the energy-dependent quinolone efflux indicate that the most efficient derivatives tested probably inhibit the resistance process by acting as substrate competitors on the pump extruding intracellular norfloxacin.
A method using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) has been developed for the characterization and determination of pyridoquinoline derivatives 4,6-bis(dimethylaminoethylamino)-2,8,10-trimethylpyrido[3,2-g]quinoline, 4,6-bis(dimethylaminoethoxy)-2,8,10-trimethylpyrido[3,2-g]quinoline and 4,6-bis[(dimethylaminoethyl)thio]-2,8,10-trimethylpyrido[3,2-g] quinoline, all with potential antitumor properties. LC separation was performed on a conventional C18 column using a binary mobile phase composed of acetonitrile and 50 mM aqueous ammonium formate at pH 3. The APCI mass spectra obtained showed that proton addition giving [M + H]+ was the common mode of ionization to the amino- and thiopyridoquinolines, whereas the alkoxypyridoquinoline was identified by the main formation of the [M - (C2H3)N(CH3)2 + H]+, followed by the [M + H]+ ion. The LC separation conditions and MS detection parameters were optimized for the determination. The analytical method was also applied to the determination of these pyridoquinoline derivatives in fetal calf serum using liquid-liquid extraction with dichloromethane. Acceptable recovery values were obtained, ranging between 45 and 98%.
The synthesis of several acridinic thioethers is described. Compounds prepared were tested in vitro as potential drugs against the opportunistic infection known as cryptosporidiosis. With a view to predict activity, the quantitative structure-activity relationships were investigated. Correlations between experimental data and either log P or pKa are discussed.
This study was designed to test the hypothesis that lipophilic cationic drugs with only roughly similar structures mediate the reversal of multidrug-resistance (MDR) by interacting with membrane phospholipids. The permeation properties of MDR-modulators and non-modulators were studied by quantifying their ability to induce the leakage of Sulphan blue through the membrane of negatively charged unilamellar liposomes. Of the 22 compounds under investigation, only those bearing a net positive electric charge per molecule (z) > or = 0.2 induced dye leakage. All these efficient drugs are well-known MDR-modulators: calcium-channel blockers (propranolol, verapamil, diltiazem and dipyridamole), calmodulin antagonists (clomipramine and thioridazine) and antiparasitic agents (mepacrine, thioacridine derivatives and quinine). The non-modulators tested, including antineoplastic agents and steroids, did not induce any membrane permeation. The permeation process was a co-operative one (1.1 < Hill coefficient < 4.1) and the permeation doses inducing 50% dye leakage (PD50) were 1.9-11.2 mM. The permeation ability of the MDR-modulators (log(1/PD50)) increased significantly with octanol-buffer distributions per unit net electric charge ((logD)/z). The results provide evidence that a complex interplay occurs between the electric charge and the lipophilicity of the MDR-modulators when a dye leakage is induced through model membranes, and probably also when the MDR is reversed in leukaemic cells.
Series of 9-amino and 9-thioacridines have been synthesized and studied as inhibitors of trypanothione reductase (TR) from Trypanosoma cruzi, the causative agent of Chagas' disease. The compounds are structural analogues of the acridine drug mepacrine (quinacrine), which is a competitive inhibitor of the parasite enzyme, but not of human glutathione reductase, the closest related host enzyme. The 9-aminoacridines yielded apparent K(i) values for competitive inhibition between 5 and 43 microM. The most effective inhibitors were those with the methoxy and chlorine substituents of mepacrine and NH(2) or NHCH(CH(3))(CH(2))(4)N(Et)(2) at C9. Detailed kinetic analyses revealed that in the case of 9-aminoacridines more than one inhibitor molecule can bind to the enzyme. In contrast, the 9-thioacridine derivatives inhibit TR with mixed-type kinetics. The kinetic data are discussed in light of the three-dimensional structure of the TR-mepacrine complex. The conclusion that structurally very similar acridine compounds can give rise to completely different inhibition patterns renders modelling studies and quantitative structure-activity relationships difficult.
Ribonucleotide reductases (RNRs) are key enzymes in living cells that provide the precursors of DNA synthesis. The three characterized classes of RNRs differ by their metal cofactor and their stable organic radical. We have purified to near homogeneity the enzymatically active Mn-containing RNR of Corynebacterium ammoniagenes, previously claimed to represent a fourth RNR class. N-terminal and internal peptide sequence analyses clearly indicate that the C. ammoniagenes RNR is a class Ib enzyme. In parallel, we have cloned a 10-kilobase pair fragment from C. ammoniagenes genomic DNA, using primers specific for the known class Ib RNR. The cloned class Ib locus contains the nrdHIEF genes typical for class Ib RNR operon. The deduced amino acid sequences of the nrdE and nrdF genes matched the peptides from the active enzyme, demonstrating that C. ammoniagenes RNR is composed of R1E and R2F components typical of class Ib. We also show that the Mn-containing RNR has a specificity for the NrdH-redoxin and a response to allosteric effectors that are typical of class Ib RNRs. Electron paramagnetic resonance and atomic absorption analyses confirm the presence of Mn as a cofactor and show, for the first time, insignificant amounts of iron and cobalt found in the other classes of RNR. Our discovery that C. ammoniagenes RNR is a class Ib enzyme and possesses all the highly conserved amino acid side chains that are known to ligate two ferric ions in other class I RNRs evokes new, challenging questions about the control of the metal site specificity in RNR. The cloning of the entire NrdHIEF locus of C. ammoniagenes will facilitate further studies along these lines.
The antibacterial activity of several new 5-aminoorotic acid derivatives considered as possible competitors of orotate towards dihydroorotase has been investigated. Products with a bromacetamido substitution demonstrated antibacterial properties. However, the paradoxical behavior of some compounds in synthetic media, opposed to the expected results obtained with an E. coli strain lacking dehydroorotic dehydrogenase, did not allow us to draw conclusions on their mechanism of action.
The promoter of the Rhizobium etli recA gene has been identified by primer extension and by making deletions affecting several regions located upstream of its coding region. A gel mobility shift assay carried out with crude extracts of cells of R. etli has been used to show that a DNA-protein complex is formed in the R. etli recA promoter region in vitro. Analysis of the minimal region of the recA promoter giving rise to this DNA-protein complex revealed the presence of an imperfect palindrome corresponding to the sequence TTGN11CAA. Site-directed mutation of both halves of this palindrome indicated that both motifs, TTG and CAA, are necessary for both normal DNA-protein complex formation in vitro and full DNA damage-mediated inducibility of the recA gene in vivo. However, the TTG motif seems to be more dispensable than the CAA one. The presence of this same palindrome upstream of the recA genes of Rhizobium meliloti and Agrobacterium tumefaciens, whose expression is also regulated in R. etli cells, suggests that this TTGN11CAA sequence may be the SOS box of at least these three members of the Rhizobiaceae.
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Salmonella typhimurium and Escherichia coli cells have two different class I ribonucleotide reductases encoded by the nrdEF and nrdAB operons. Despite the presence of one additional ribonucleotide reductase, the nrdAB-encoded enzyme is essential to the aerobic growth of the cell because nrdAB-defective mutants of both species are not viable in the presence of oxygen. Several factors controlling nrdAB gene transcription have been analysed intensively. Nothing is known about the expression of the nrdEF genes. To study this subject, and after cloning of E. coli nrdEF genes and sequencing of their 5' ends, the promoter of this operon has been identified by primer extension in both bacterial species. The +1 position was 691 bp and 692 bp upstream of the translational start points of the nrdE genes of S. typhimurium and E. coli, respectively. Downstream of the +1 position, and before the nrdE gene, two open reading frames (ORFs) of 81 and 136 amino acid residues are present in both bacteria. The synthesis of a polypeptide with a molecular mass of 9 kDa, corresponding to the first of these two ORFs, was observed by using the T7 RNA polymerase expression system. Comparison of the amino acid predicted sequence of this ORF reveals a significant similarity with glutaredoxin proteins. Competitive, reverse-transcription polymerase chain reaction experiments indicate that transcription from the nrdEF promoter normally takes place in wild-type cells. nrdEF transcription is increased by hydroxyurea, which inhibits class I ribonucleotide reductase activity, in both RecA+ and RecA- cells. nrdA(ts) mutants show a higher level of nrdEF transcription than wild-type cells at either the permissive or the restrictive temperature. nrdEF expression was unaffected by changes in DNA supercoiling whether caused by the introduction of either topA::Tn10 and hns::Tn10 mutations or by the inhibition of DNA gyrase with the antibiotic novobiocin. In contrast to the nrdAB genes, the nrdEF operon is not essential to the cells because nrdEF-defective mutants are viable under both aerobic and anaerobic conditions.
In the present work, we have assayed both the in vitro and in vivo action of two acridine compounds against Leishmania donovani. As part of this effort, we have studied the possible action mechanism of these compounds at the ultrastructural and biochemical levels and in relation to the synthesis of macromolecules. The two acridinones inhibit the in vitro growth of the promastigote forms of L. donovani at the highest concentration assayed (100 micrograms/ml). The in vivo results indicate that both compounds reduce the number of amastigotes per gram of spleen, and decrease parasitism, by more than 40%. With respect to the action mechanism, both compounds inhibit the incorporation of [3H]thymidine, inducing alterations at the ultrastructural level in the DNA and mitochondria. Alterations are also caused in the enzymes of the Krebs cycle.
A set of 9-thioalkylacridinones, has been prepared and investigated "in vitro" against T. cruzi. Structure-antiparasitic activity relationships are detailed with a view to identify the major structural parameters for the activity under consideration.
The antimicrobial activity of several new 9-acridinones and 9-thioalkylacridines towards Escherichia coli, Staphylococcus aureus, Mycobacterium smegmatis and Candida albicans was investigated. Minimal inhibitory, bactericidal and fungicidal concentrations were determined using a microplate assay which enabled inhibitory, bactericidal and fungicidal indices to be calculated. These indices facilitated structure/activity relationship studies. DNA-intercalating capability and DNA supercoiling inhibitory effects as well as inhibitory effects on macromolecular synthesis were determined. Results showed that intercalation into DNA, which is the mechanism of action usually postulated for acridines, cannot be correlated with the properties examined. However, inhibition of RNA synthesis may be involved in the antimicrobial activity of the drugs.
The immunomodulating effect of some new amino- and imino-acridine derivatives, were investigated on antibody dependent cellular cytotoxicity (ADCC) and induced-blast transformation of lymphocytes. In different concentrations (2.0 x 10(-6) M, 4.0 x 10(-8) M and 2.0 x 10(-5) M) the drugs produced a suppression of PHA and ConA induced cell proliferative response except in the case of 2b, 2d and 2g amino-acridines. The suppressive effects were dose dependent and exhibited a higher inhibitory level in the case of imino-acridines. Some drugs at low concentration exerted a little enhancing effect on ADCC reaction.
48 newly synthesized acridine derivatives of different classes were screened for antitrypanosomal activity. They showed a dose dependent effect on Trypanosoma rhodesiense and T. brucei bloodstream forms measured by the inhibition of esterase activity in a fluorescence based in vitro assay. After analysis of the IC50 and MIC values of the investigated acridines it was obvious that no new compound reached the level of the trypanocidal drugs in use (50 ng/ml). Most of the derivatives had IC50 values in the range of 1 to 10 micrograms/ml. 9 derivatives from different classes of acridines were in vitro active below 1 microgram/ml. Correlations between structure and effect on trypanosomes have been elucidated by comparing the IC50 and MIC values of these compounds, in the course of which no significant differences in the drug susceptibility between T. brucei und T. rhodesiense was noticed. The dialkylaminoalkyl derivatives among the group of the 9-thioacridines were slightly more potent than the mono-alkylated ones. 1,2,3,4-tetrahydro-9-thioacridines showed the influence of higher substituted side chains on the trypanocidal activity in the same way as 9-thioacridines. The corresponding ketones of 9-thioacridines confirmed the tendency of increasing toxicity due to the derivatisation of the dialkylaminoalkyl side chain. Within the series of the 9-aminoacridines the elongation of the side chain did not markedly change the activity, however the IC50 values are generally low between 0.13 and 1.2 micrograms/ml.(ABSTRACT TRUNCATED AT 250 WORDS)