Biomedical subjects

P Nickel

Publications and source records attributed to P Nickel.

At least 19 recordsLinked to original sources

PubMed2000

The suramin analogue NF279 is a novel and potent antagonist selective for the P2X(1) receptor.

The suramin analogue 8,8'-(carbonylbis(imino-4, 1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)) bis(1,3,5-naphthalenetrisul fonic acid) (NF279) was analysed with respect to its potency and P2X receptor subtype selectivity. Two-electrode voltage-clamp measurements were performed with Xenopus laevis oocytes expressing homomultimeric rat P2X(1), P2X(2), P2X(3) and human P2X(4) receptors. For the fast desensitising P2X(1) and P2X(3) receptors, IC(50) values strongly depended on whether oocytes were pre-incubated with NF279 prior to ATP superfusion or exposed to NF279 simultaneously with ATP. With a 10 s pre-incubation period of NF279, IC(50) values of 19 nM and 1.62 microM were obtained for rat P2X(1) and P2X(3), respectively. Without pre-incubation, IC(50) values amounted to 2 microM and 85.5 microM for P2X(1) and P2X(3), respectively. For the non-desensitising rat P2X(2) receptor NF279 appeared to act as a competitive antagonist with an IC(50) value of 0.76 microM and a K(B) value of 0.36 microM, as derived from Schild analysis. P2X(4) receptors were the least sensitive subtypes for NF279 (IC(50)>300 microM). The antagonism was fully reversible at all P2X subtypes analysed. Our results indicate that NF279 is a potent P2X(1) receptor-selective and reversible antagonist.

Adenosine Triphosphate↗

PubMed2000

Antagonism by the suramin analogue NF279 on human P2X(1) and P2X(7) receptors.

The effect of the suramin analogue 8,8'-(carbonylbis(imino-4, 1-phenylenecarbonylimino-4,1-phenylenecarbonylimino))bis(1,3 , 5-naphthalenetrisulfonic acid) (NF279) was analyzed on human P2X(1) and P2X(7) receptor subtypes (human P2X(1) and human P2X(7)) heterologously expressed in Xenopus oocytes using the two-microelectrode voltage-clamp technique. At activating ATP concentrations of 1 microM (human P2X(1)) and 10 microM ATP (human P2X(7)), IC(50) values of 0.05 microM and 2.8 microM were found for human P2X(1) and human P2X(7) receptors, respectively. An increase in the activating [ATP] shifted the NF279 concentration-inhibition curve rightwards for both receptors. NF279 slowed the activation of both human P2X(1) and human P2X(7) as well as the desensitization of human P2X(1). The data support a model in which desensitization of P2X(1) is dependent on preceding activation of these P2X receptors. It is concluded that NF279 acts as a competitive antagonist with much higher potency at human P2X(1) than at P2X(7) receptors. NF279 may hence be suited to discriminate between both receptors in native tissues.

Animals↗

PubMed2000

Antitumour activity of suramin analogues in human tumour cell lines and primary cultures of tumour cells from patients.

Suramin has shown promising antitumour activity against several tumour types, both in vitro and in vivo, but the clinical utility of this compound is hampered by its unfavourable toxicity profile. In the present study, the semi-automated fluorometric microculture cytotoxicity assay (FMCA) was employed for evaluation of the cytotoxicity of seven suramin analogues in vitro in a panel of human tumour cell lines and in primary cultures of tumour cells from patients. Like suramin, the analogues showed little sensitivity to resistance mechanisms involving P-glycoprotein, topoisomerase II, multidrug resistance associated protein and glutathione-mediated drug resistance. In the cell line panel, NF067 and FCE 26644 showed activity comparable with suramin. All analogues were less potent than suramin in patient cells except for FCE 26644. Correlation to suramin activity patterns in the cell line panel was highest for NF037 and low to moderate for the remaining analogues. In patient cells, high correlation coefficients were obtained for FCE 26644, NF110, NF031 and NF037. The results indicate that the cytotoxic activity of suramin on patient tumour cells is shared by the analogues with FCE 26644 being the most active. The pharmacophore for cytotoxicity in patient cells may be different from that observed in the cell lines.

Antineoplastic Agents↗

PubMed2000

The effect of P2 receptor antagonists and ATPase inhibition on sympathetic purinergic neurotransmission in the guinea-pig isolated vas deferens.

1. Intracellular microelectrodes were used to record the transmembrane potential and excitatory junction potentials (e.j.p.s) produced by sympathetic nerve stimulation (1 Hz) in smooth muscle cells of the guinea-pig isolated vas deferens. 2. The symmetrical 3'-urea of 8-(benzamido)naphthalene-1,3,5-trisulphonic acid (NF023) produced a concentration-dependent inhibition of e.j.p. magnitude (IC(50)=4. 8x10(-6) M), but had no effect on the resting membrane potential of the smooth muscle cells. 3. Pyridoxal-5-phosphate (P-5-P) also depressed e.j.p. magnitude in a concentration-dependent manner, but was less potent than NF023 (IC(50)=2.2x10(-5) M). At 10(-4) M and above P-5-P significantly depolarized the smooth muscle cells. 4. The nucleoside triphosphatase inhibitor 6-N,N-diethyl-D-beta, gamma-dibromomethyleneATP (ARL 67156) (5x10(-5) M) significantly increased e.j.p. amplitude. ARL 67156 (10(-4) M) further increased e. j.p. amplitude such that they often reached threshold for initiation of action potentials, causing muscle contraction and expulsion of the recording electrode. 5. After reduction of e.j.p.s by NF023 or P-5-P (both 10(-5) M), subsequent co-addition of ARL 67156 (10(-4) M) significantly increased their magnitude. 6. The overflow of endogenous ATP evoked by field stimulation of sympathetic nerves (8 Hz, 1 min) was measured by HPLC and flurometric detection. ARL 67156 (10(-4) M) enhanced ATP overflow by almost 700% compared to control. 7. We conclude that for electrophysiological studies NF023 is preferable to other P2X receptor antagonists such as pyridoxalphosphate -6-azophenyl-2',4'-disulphonic acid (PPADS), suramin or P-5-P. Furthermore, breakdown of endogenous ATP by nucleoside triphosphatases is an important modulator of purinergic neurotransmission in the guinea-pig vas deferens.

Adenosine Triphosphatases↗

PubMed2000

Angiostatic effects of suramin analogs in vitro.

Suramin analogs are polyanionic naphthylureas structurally related to suramin, an antitumor agent with a narrow therapeutic window. The angiostatic activities of suramin and 16 suramin analogs were investigated using an easily quantifiable in vitro angiogenesis system. In addition, the antiproliferative activities of the analogs were studied in four different human tumor cell lines and in porcine aortic endothelial cells. The suramin analogs encompassed two main structural variations, i.e. their molecular size, and the number and substitution pattern of the sulfonate groups. Some suramin analogs with a reduced number of sulfonate groups (NF062, NF289 and NF326) showed significant dose-dependent angiostatic and also antiproliferative activities. The disulfonate NF062 was superior to suramin in inhibiting HT29 and T47D tumor cells while demonstrating a similar angiostatic potential as suramin. Therefore, the sulfonate groups in the para position of the amino groups of the naphthyl residues of suramin seem to be of special importance. The very small disulfonates (NF108, NF109, NF499, NF500 and NF241) and the asymmetric compound NF520, one half of the suramin molecule, are inactive. Therefore, a minimal molecule size seems to be essential for the biological activity. Suramin is a rather rigid molecule. The highly flexible analogs (NF527, NF528 and NF529) are inactive. This indicates that the molecular rigidity is important for the biological activity.

Angiogenesis Inhibitors↗

PubMed1999

Antagonistic properties of the suramin analogue NF023 at heterologously expressed P2X receptors.

The suramin analogue 8,8'-(carbonylbis(imino-3,1-phenylene carbonylimino)bis(1,3,5-naphthalenetrisulfonic acid) (NF023) antagonizes in a competitive fashion P2X receptor-mediated responses in certain vascular and visceral smooth muscles. In the present study, the effect of NF023 on voltage-clamped Xenopus oocytes heterologously expressing homomultimeric P2X1-P2X4 as well as heteromultimeric P2X2/P2X3 receptors has been characterized. P2X1 receptors were most sensitive to inhibition by NF023 with IC50 values of 0.24 and 0.21 microM for the rat and human homologue, respectively. P2X3 receptors have an intermediate sensitivity with IC50 values of 8.5 and 28.9 microM for rat and human subtypes, respectively and P2X2 was the least sensitive subtype (IC50 > 50 microM). P2X4 receptors were insensitive to NF023 at concentrations up to 100 microM. Coexpression of rat P2X3 with rat P2X2 resulted in receptors whose sensitivity to NF023 was identical to that obtained for homomultimeric rat P2X3 receptors (alphabeta meATP as agonist; IC50 = 1.4 and 1.6 microM, respectively). NF023 inhibited P2X1 receptors in a voltage-insensitive manner. In addition, NF023 (5 and 30 microM) caused a shift of the concentration-response curve to the right without affecting the maximal response to ATP (K(B) = 1.1 +/- 0.2 microM). Our results indicate that NF023 is a subtype-selective and surmountable antagonist at P2X1 receptors heterologously expressed in Xenopus oocytes.

Adenosine Triphosphate↗

PubMed1999

Novel ligands for P2 receptor subtypes in innervated tissues.

Among suramin analogues, the properties of P2 receptor subtype blockade and ecto-nucleotidase inhibition appear to be controlled by different structural parameters (Fig. 1 and 2, Table 1; Van Rhee et al., 1994; Beukers et al., 1995; Bültmann et al., 1996; Damer et al., 1998a, 1998b; and this study): the molecular size of the compounds, the position of the sulfonic acid residues in the naphthalene rings, the substitution pattern of the benzoyl moieties and the 3'- or 4'-aminobenzoyl-linkages of the phenyl rings "1" and "2". As a result, compounds with different receptor selectivity profiles were obtained. A maximum in potency at and selectivity for P2X1 receptors is reached in NF279, which is a specific P2 receptor antagonist and the compound with the highest P2X1 vs. P2Y receptor and ecto-nucleotidase selectivity presently available.

Adenosine Triphosphate↗

PubMed1999

Suramin and suramin analogs activate skeletal muscle ryanodine receptor via a calmodulin binding site.

Contraction of skeletal muscle is triggered by the rapid release of Ca2+ from the sarcoplasmic reticulum via the ryanodine receptor/calcium-release channel. The trypanocidal drug suramin is an efficient activator of the ryanodine receptor. Here, we used high-affinity [3H]ryanodine binding to sarcoplasmic reticulum from rabbit skeletal muscle to screen for more potent analogs of suramin. This approach resulted in the identification of NF307, which accelerates the association rate of [3H]ryanodine binding with an EC50 = 91 +/- 7 microM at 0.19 microM calculated free Ca2+. In single-channel recordings with the purified ryanodine receptor, NF307 increased mean open probability at 0.6 microM Ca2+ from 0.020 +/- 0.006 to 0.53 +/- 0.07 with no effect on current amplitude and unitary conductance. Like caffeine, NF307 exerts a very pronounced Ca2+-sensitizing effect (EC50 of Ca2+ shifted approximately 10-fold by saturating NF307 concentrations). Conversely, increasing concentrations of free Ca2+ sensitized the receptor for NF307 (EC50 = 14.6 +/- 3.5 microM at 0.82 microM estimated free Ca2+). The effects of NF307 and caffeine on [3H]ryanodine binding were additive, irrespective of the Ca2+ concentration. In contrast, the effects of calmodulin, which activates and inhibits the ryanodine receptor in the absence and presence of Ca2+, respectively, and of NF307 were mutually antagonistic. If the purified ryanodine receptor was prebound to a calmodulin-Sepharose matrix, 100 microM NF307 and 300 microM suramin eluted the purified ryanodine receptor to an extent that was comparable to the effect of 10 microM calmodulin. We conclude that NF307 and suramin interact directly with a calmodulin binding domain of the ryanodine receptor. Because of its potent calcium-sensitizing effect, NF307 may represent a lead compound in the search of synthetic ryanodine receptor ligands.

Animals↗

PubMed1998

A trypanosome oligopeptidase as a target for the trypanocidal agents pentamidine, diminazene and suramin.

African trypanosomes contain a cytosolic serine oligopeptidase, called OP-Tb, that is reversibly inhibited by the active principles of three of the five most commonly used trypanocidal drugs: pentamidine, diminazene and suramin. OP-Tb was inhibited by pentamidine in a competitive manner, and by suramin in a partial, non-competitive manner. The inhibition of OP-Tb by a variety of suramin analogues correlated with the trypanocidal efficacy of these analogues (P=0.03; by paired Student's t-test). Since intracellular (therapeutic) concentrations of pentamidine and suramin are reported to reach approximately 206Ki and 15Ki respectively, we suggest that these drugs may exert part of their trypanocidal activity through the inhibition of OP-Tb.

Animals↗

PubMed1998

NF279: a novel potent and selective antagonist of P2X receptor-mediated responses.

8,8'-(Carbonylbis(imino-4, 1 -phenylenecarbonylimino-4,1-phenylenecarbonylimino))bis(1,3, 5-naphthalenetrisulfonic acid) (NF279) antagonized P2X receptor-mediated contractions in rat vas deferens, evoked by alpha,beta-methylene ATP (10 microM; pIC50=5.71) without affecting responses mediated via alpha1A-adrenoceptors, adenosine A1 and A2B receptors, histamine H1, muscarinic M3 and nicotinic receptors. The low inhibitory potency of NF279 on P2Y receptors in guinea-pig taenia coli (pA2=4.10) and at ecto-nucleotidases in folliculated Xenopus laevis oocytes (IC50 > 100 microM) indicates that NF279 is a novel specific and selective P2X receptor antagonist.

Adenosine Triphosphate↗

PubMed1998

Gsalpha-selective G protein antagonists.

Suramin acts as a G protein inhibitor because it inhibits the rate-limiting step in activation of the Galpha subunit, i.e., the exchange of GDP for GTP. Here, we have searched for analogues that are selective for Gsalpha. Two compounds have been identified: NF449 (4,4',4",4'"-[carbonyl-bis[imino-5,1,3-benzenetriyl bis-(carbonylimino)]]tetrakis-(benzene-1,3-disulfonate) and NF503 (4, 4'-[carbonylbis[imino-3,1-phenylene-(2, 5-benzimidazolylene)carbonylimino]]bis-benzenesulfonate). These compounds (i) suppress the association rate of guanosine 5'-[gamma-thio]triphosphate ([35S]GTP[gammaS]) binding to Gsalpha-s but not to Gialpha-1, (ii) inhibit stimulation of adenylyl cyclase activity in S49 cyc- membranes (deficient in endogenous Gsalpha) by exogenously added Gsalpha-s, and (iii) block the coupling of beta-adrenergic receptors to Gs with half-maximum effects in the low micromolar range. In contrast to suramin, which is not selective, NF503 and NF449 disrupt the interaction of the A1-adenosine receptor with its cognate G proteins (Gi/Go) at concentrations that are >30-fold higher than those required for uncoupling of beta-adrenergic receptor/Gs tandems; similarly, the angiotensin II type-1 receptor (a prototypical Gq-coupled receptor) is barely affected by the compounds. Thus, NF503 and NF449 fulfill essential criteria for Gsalpha-selective antagonists. The observations demonstrate the feasibility of subtype-selective G protein inhibition.

Adenylyl Cyclases↗

PubMed1998

Suramin analogues with a 2-phenylbenzimidazole moiety as partial structure; potential anti HIV- and angiostatic drugs, 2: Sulfanilic acid-, benzenedisulfonic acid-, and naphthalenetrisulfonic acid analogues.

The synthesis of suramin analogues bearing a 2-phenyl-benzimidazole moiety is described. Aminoarene sulfonic acids 2a-e are acylated with 3,4-dinitrobenzoyl chloride 3 yielding the amides 4a-e which are hydrogenated to the corresponding diamines 5a-e. These are treated with 3-nitrobenzaldehyde, yielding the azomethines 7a-e and their isomers 8a-e and 9a-e. Key step in the synthesis of the target compounds 12a-e is the oxidation of the azomethines with oxygen to the benzimidazoles 10a-e. These are hydrogenated to the amines 11a-e reacting with phosgene to yield the symmetric ureas 12a-e. Results of the anti-HIV, cytostatic, and antiangiogenic screening are presented.

Anti-HIV Agents↗

PubMed1998

Antiangiogenic and antiproliferative activity of suramin analogues.

The purpose of this study was to test the ability of 70 polyanionic analogues of suramin to inhibit angiogenesis. The ID50, the dose that produced 50% inhibition of angiogenesis, was determined for suramin and each of the analogues by measuring the ability of various amounts to inhibit angiogenesis in vivo in the chick egg chorioallantoic membrane (CAM) assay. Of the 70 analogues, 11 had antiangiogenic activities similar to suramin and an additional 7 were significantly more potent than suramin. All seven of these analogues were from the naphthalenetrisulfonic acid group and contained large urea groups. The benzene sulfonic and disulfonic acid analogues were less active inhibitors of angiogenesis than the naphthalenetrisulfonic acid analogues. Replacement of the naphthalenetrisulfonic acid groups by aliphatic carboxylic acids or benzoic acid gave analogues with very little antiangiogenic activity. In subsequent experiments, the antiproliferative activity of selected analogues on basic FGF (bFGF)-stimulated growth of immortalized human microvascular endothelial cells in vitro was determined. Analogues that inhibited angiogenesis to a greater extent than suramin in the CAM assay generally showed a greater antiproliferative effect on bFGF-induced growth of human microvascular endothelial cells. These results suggest that some of the polyanionic analogues may be potent therapeutic agents for cancers and angiogenesis-dependent diseases.

Animals↗

PubMed1998

Determination of protein binding of gyrase inhibitors by means of continuous ultrafiltration.

In order to characterize the protein binding of a drug, it is necessary to have a method which is close to in vivo conditions and fast in the course of measurement. The continuous ultrafiltration fulfils both requirements for substances with a high extent of protein binding. In this study, 18 gyrase inhibitors in clinical practice, characterized by a lower extent of protein binding, were subjected to the titration procedure of the continuous ultrafiltration using bovine and human serum albumin (BSA, HSA), and human plasma. The results of the continuous ultrafiltration were found to be similar to those obtained by means of the 'classical' discontinuous ultrafiltration using plasma (correlation between continuous and discontinuous ultrafiltration r2 = 0.87). In the cases of pipemidic acid, enoxacin and rufloxacin, the continuous method gave approximately 20% lower degrees of protein binding than the discontinuous procedure, which utilizes plasma having the full range of proteins. It is likely that these drugs bind mainly to other proteins in plasma than HSA. This finding proves that this fast method is worthwhile in the whole range of protein binding.

Animals↗

PubMed1997

[Malaria].

Explore the source record for details and available documents.

Antimalarials↗

PubMed1997

[Diagnosis of dermatomycoses with polymerase chain reaction].

A polymerase chain reaction (PCR) assay for the detection of dermatophytes was established. The primers "TR1" and "TR2" amplify a 581 bp fragment within the gene coding for the small ribosomal subunit (185 rRNA) of fungi. PCR allowed the detection of isolates of 7 common dermatophytes and in addition several yeasts and moulds. Hybridisation with specific oligonucleotides results in the identification of dermatophytes and Candida albicans. Restriction analysis of the PCR product allowed us to distinguish between dermatophytes and yeasts or moulds. The specificity of the PCR with respect to fungi was assessed by testing human DNA collected from 42 dermis and epidermis specimens as well as DNA from selected plants and animals. To evaluate the clinical relevance of the PCR assay, 69 routinely collected skin and nail specimens were examined by PCR and culture. PCR detected dermatophytes in 35 and culture in 28 of 38 specimens that were classified as positive. Sensitivity of PCR (92%) was higher than that of culture (73%). These results show that PCR has advantages over culture for the detection of dermatophytes.

Arthrodermataceae↗

PubMed1997

Vasoconstrictor responses via P2X-receptors are selectively antagonized by NF023 in rabbit isolated aorta and saphenous artery.

1. The effects of NF023, the symmetrical 3'-urea of 8-(benzamido)naphthalene-1,3,5-trisulphonic acid), and its parent compound suramin were investigated on vasoconstrictor responses to alpha, beta-methylene ATP in rabbit isolated saphenous artery and vasodilator responses to ATP in noradrenaline-precontracted rabbit isolated thoracic aorta. 2. In rabbit isolated saphenous artery, alpha, beta-methylene ATP-induced vasoconstrictor responses via P2X-receptors were concentration-dependently and competitively antagonised by NF023 (30-300 microM; pA2 = 5.69 +/- 0.04). Suramin (100-1000 microM) also competitively blocked vasoconstrictor responses to alpha, beta-methylene ATP, albeit with lower potency (pA2 = 4.79 +/- 0.05). In contrast, NF023 (100 microM) did not significantly affect contractile responses to noradrenaline or histamine in the saphenous artery. 3. In noradrenaline-precontracted rabbit isolated thoracic aorta preparations, ATP (3-3000 microM) concentration-dependently induced relaxations via endothelium-dependent or smooth muscle P2Y-receptor subtypes. NF023 (30-300 microM) failed to block relaxant responses to ATP at endothelium-dependent P2Y-receptors, whereas suramin (100-1000 microM) did antagonise endothelium-dependent vasodilator responses to ATP. Neither NF023 (100 microM) nor suramin (300 microM) influenced vasorelaxant responses to ATP via endothelium-independent P2Y-receptors. 4. In conclusion, this study outlines the selectivity of NF023 as an effective P2X-receptor antagonist in rabbit isolated blood vessels without affecting endothelium-dependent or endothelium-independent P2Y-receptor subtypes, adrenoceptors or histamine receptors.

Adenosine Triphosphate↗

PubMed1996

Rapid, highly sensitive gradient narrow-bore high-performance liquid chromatographic determination of suramin and its analogues.

A high-performance liquid chromatography (HPLC) method for the determination of suramin, its precursors and analogues in aqueous solutions and in plasma samples with advantages compared to earlier methods is described. Due to the method's high sensitivity (detection limit of suramin in plasma samples: 7 ng/ml; in aqueous solutions: 5 ng/ml) and selectivity (suramin tR: 7.05 min, precursor amine 2 tR: 4.68 min), it is possible to analyze degradation products, impurities and possible metabolites of suramin besides suramin. Tetrabutylammonium hydrogensulfate (TBAHS) (5 mM) is used as ion-pairing reagent in a mixture of 36% methanol and 0.02 M phosphate buffer pH 6.5 is used as the mobile phase. After sample injection, a linear gradient from 36 to 62.9% methanol is run. A C8 stationary phase (100 x 2.1 mm I.D.) is used and ultraviolet (UV) detection at 238 nm is applied. Plasma extraction is performed with tetrabutylammonium bromide (pH 8.0) and acetonitrile. This procedure allows the determination of suramin and its precursor amine 2 in the range of 0.05-400 micrograms/ml with high precision [relative standard deviation of peak areas at 0.05 microgram/ml: 2.10% (n = 5)] and nearly complete recovery (> 96.5%). Because of the high flexibility of the chromatographic system and subsequently the universality of the method, the analysis of a broad range of suramin analogues is possible. The result of the purity check of two suramin analogues is given.

Chromatography, High Pressure Liquid↗