Peptides with 6-Aminohexanoic Acid: Synthesis and Evaluation as Plasmin Inhibitors.

Fifteen new peptide derivatives of ɛ-aminocaproic acid (EACA) containing the known fragment -Ala-Phe-Lys- with an affinity for plasmin were synthesised in the present study. The synthesis was carried out a solid phase. The following compounds were synthesised: H-Phe-Lys-EACA-X, H-d-Ala-Phe-Lys-EACA-X, H-Ala-Phe-Lys-EACA-X, H-d-Ala-Phe-EACA-X and H-Ala-Phe-EACA-X, where X = OH, NH2 and NH-(CH2)5-NH2. All peptides, except for those containing the sequence H-Ala-Phe-EACA-X, displayed higher inhibitory activity against plasmin than EACA. The most active and selective inhibitor of plasmin was the compound H-d-Ala-Phe-Lys-EACA-NH2 which inhibited the amidolytic activity of plasmin (IC50 = 0.02 mM), with the antifibrinolytic activity weaker than EACA. The resulting peptides did not affect the viability of fibroblast cells, colon cancer cell line DLD-1, breast MCF-7 and MDA-MB-231 cell lines.

Effect of short peptides containing lysine and epsilon-aminocaproic acid on fibrinolytic activity of plasmin and topoisomerase II action on supercoiled DNA.

Effects of eight short peptides containing lysine and epsilon-aminocaproic acid (EACA) on prolongation of the clot lysis time, as well as hemolytic and antibacterial activities were investigated. Interaction with plasmids pBR322 and pUC19 with the use of ethidium bromide assay and determination of influence on the activity of topoisomerase I and II were also tested. Examined compounds inhibited fibrinolytic activity of plasmin and five of them were more active than EACA. Amides of dipeptides were most active antifibrinolytics (IC50 < 0.2 mM). According to the obtained data, the significant inhibition of fibrinolytic activity of plasmin was not associated with hemolytic effects. Examined compounds did not show antibacterial activity (MIC > 512 mg/L). DNA binding effects determined with the use of ethidium bromide were weak for all peptides and similar to those observed with EACA. Six compounds inhibited topoisomerase II action on supercoiled DNA.

Tripeptides with non-code amino acids as potential serine proteases inhibitors.

Eight peptides of the general H-D-Ser-AA-Arg-OH formula, where AA = phenylglycine, phenylalanine, homophenylalanine, cyclohexylglycine, cyclohexylalanine, homocyclohexylalanine, α-methylphenylalanine and 1-aminocyclohexyl carboxylic acid were obtained and tested for their effect on the amidolytic activities of urokinase, thrombin, trypsin, plasmin, t-PA and kallikrein. We tested the hemolytic activity of the peptides against porcine erythrocytes and the antitumor activity against the human breast cancer cells, standard MCF-7 and estrogen-independent MDA-MB-231. The most active compounds were H-D-Ser-Chg-Arg-OH towards thrombin and H-D-Ser-Phg-Arg-OH towards plasmin with K(i) value 5.02 µM and 5.7 µM, respectively.

Amino and chlorambucil analogues of pentamidine--synthesis and biological examinations.

The amino analogues of pentamidine with a polymethylene (n = 3 - 6) chain and their chlorambucil derivatives were synthesized. The obtained compounds revealed cytotoxic effect on MCF-7 human breast cancer cell line (IC50 = 22 - 95 +/- 2 pM), mainly by the induction of apoptosis. The topoisomerase I/II inhibition assay and the ethidium displacement assay with the use of pBR322 plasmid DNA were used to the study of mechanism by which the obtained compounds could act. All the compounds are able to bind with DNA and interfere in vitro with the activity of topoisomerase (I and II). The determination of association constants with the use of calf thymus DNA, T4 coliphage DNA, poly(dA-dT)2 and poly(dG-dC)2 showed that the tested compounds bind within minor groove of B-DNA, but not selectively. The alkylating activity of chlorambucil derivatives determined in vitro using a Preussmann test was similar to the activity of chlorambucil. The influence of all the compounds on the amidolytic activity of plasmin and trypsin was also examined. The plasmin activity was inhibited by pentamidine, chlorambucil and aromatic bis-amines (IC50 = 0.1 - 8 mM), whereas the trypsin activity was influenced only by pentamidine.

Synthesis and activity of N-sulfonylamides of tripeptides as potential urokinase inhibitors.

Twelve peptides of the general X-SO(2)-D-Ser-Ala-Arg-OH formula (where X = methyl, phenyl, α-tolyl, p-tolyl, 4-methylbenzyl, 1-naphtyl, 2-naphtyl, 4-chlorophenyl, 4-bromophenyl, 2-mesityl, 2,4,6-triisopropylphenyl, 4-acetamidophenyl) were obtained and tested for their effect on the amidolytic activities of urokinase, thrombin, trypsin, plasmin, t-PA and kallikrein. 2,4,6-triisopropylphenyl-SO(2)-D-Ser-Ala-Arg-OH was the most selective inhibitor of urokinase and α-tolyl-SO(2)-D-Ser-Ala-Arg-OH was the most active inhibitor of uPA with K(i) value 24 µM. The compounds were tested for their in vitro antitumour activity in the following human breast cancer cells: standard MCF-7 and estrogen-independent MDA-MB-231. Four of the synthesized peptides showed cytotoxic effects against MDA-MB-231 cell lines in the range from 2.9 to 8.5 µM. The examined compound did not influence to MCF-7 cancer cells. The synthesized peptides were nontoxic to pig's erythrocytes.

Carbocyclic potential DNA minor groove binders and their biological evaluation.

The biological evaluation of carbocyclic minor groove binders 1-6 is described. The cytotoxicity of the obtained compounds was tested on MDA-MB-231 breast cancer cells. The mechanism of action of compounds 1-6 was studied employing the topoisomerase I/II inhibition assay and ethidium displacement assay using pBR322. Determination of association constants was done using calf thymus DNA, T4 coliphage DNA, poly(dA-dT)(2), and poly(dG-dC)(2). The effect of compounds 1-6 on the amidolytic activity of plasmin, trypsin, thrombin, and urokinase was also examined.

Cytotoxic activity of epsilon-aminocaproylamino acids in breast cancer MCF-7 and fibroblast cell lines.

The effect of H-EACA-L-Cys(S-Bzl)-OH, H-EACA-L-Leu-OH, H-EACA-L-Nle-OH and EACA on the viability of MCF-7 and fibroblast cells was examined. The antibacterial activity of these compounds was also tested. H-EACA-L-Leu-OH and H-EACA-L-Nle-OH showed cytotoxic activity against MCF-7 and fibroblast cell lines, particularly in the highest studied 20 mM concentration. None of the examined dipeptides showed antibacterial activity.

Effect of epsilon-aminocaproyl-S-benzyl-L-cysteine on the activity of plasminogen activators.

The effect of epsilon-aminocaproyl-S-benzyl-L-cysteine on the activation of plasminogen by t-PA. streptokinase and urokinase has been examined using fibrinolytic method. The obtained results have been compared with the obtained results for epsilon-aminocaproic acid and trans-4-(aminomethyl)cyclohexanecarboxylic acid. The inhibition of the plasminogen activation determined with the use of epsilon-aminocaproyl-S-benzyl-L-cysteine was weaker than the inhibition determined by using antifibrinolytic aminoacids.

Synthesis and biological evaluation of distamycin analogues - new potential anticancer agents.

Eight of analogues of distamycin, potential minor-groove binders, were synthesized and tested for in-vitro cytotoxicity towards human breast cancer cells MCF-7 and MDA-MB-231. The method of synthesis is simple and convenient. All of the compounds 1-8 showed antiproliferative and cytotoxic effects against both cell lines in the range 3.47 to 12.53 microM for MDA-MB-231 and 4.35 to 12.66 microM for MCF-7. All compounds demonstrated activity against DNA topoisomerases I and II at a concentration of 50 microM. The ethidium bromide assay showed that these compounds bind to plasmid pBR322, yet weaker than distamycin. Further investigations concerning the mechanism of cytotoxicity are now in progress, but the IC(50) values suggest that synthetic distamycin analogues with a free amino group, 3-4 and 7-8, can serve as potential carriers of strong acting elements, e. g. alkylating groups.

Analogues of distamycin--synthesis and biological evaluation of new aromatic oligopeptides, potential anticancer agents.

Six new aromatic oligopeptides were synthesized and evaluated for their activity in the standard cell line of the mammalian tumor MCF-7 as well as in a cell-free system employing the topoisomerase I/II inhibition assay.

Low molecular peptides as potential inhibitors of plasmin.

Ten peptides of the general formula A-Phe-Lys-X where A = H, H-D-Val, H-L-Val, H-D-Ala, H-L-Ala and X = OH, NH2 were obtained and tested for their antiplasmin activity with the use of amidolytic test.

Effects of epsilon-aminocaproiloaminoacids on the amidolytic activity of tissue plasminogen activator, urokinase and kallikrein.

Effect of three epsilon-aminocaproylaminoacids with a significant antifibrinolytic activity on amidolytic activity of tissue plasminogen activator (t-PA), urokinase and kallikrein was examined. epsilon-Aminocaproyl-S-benzyl)-L-cysteine and epsilon-aminocaproyl-L-norleucine were weak inhibitors of kallikrein. Weak activation of t-PA activity was observed at high concentration of the tested compounds. Only one of the examined dipeptides was a weak inhibitor of amidolytic activity of urokinase.

The effect of some epsilon-aminocaproic acid derivatives on platelet responses.

epsilon-Aminocaproic acid (EACA) is a synthetic low molecular drug with antifibrinolytic activity. However, treatment with this drug can be incidentally associated with an increased thrombotic tendency. The aim of the present work was to test synthetic EACA derivatives for their antiplatelet activities. We investigated the effect of three EACA derivatives with antifibrinolytic activity: I. epsilon-aminocaproyl-L-leucine hydrochloride (HCl*H-EACA-L-Leu-OH), II. epsilon-aminocaproyl-L-(S-benzyl)-cysteine hydrochloride (HCl*H-EACA-L-Cys(S-Bzl)-OH) and III. epsilon-aminocaproyl-L-norleucine (H-EACA-L-Nle-OH) on platelet responses (aggregation and adhesion) and on their integrity. It was found that: 1. as judged by LDH release test, none of the tested compounds, up to 20 mM, was toxic to platelets, 2. in comparison with EACA, all the synthetic derivatives inhibited much stronger the ADP- and collagen-induced aggregation of platelets suspended in plasma (platelet rich plasma) and aggregation of these cells in whole blood, 3. EACA and its derivatives exerted a similar inhibitory effect on the thrombin-induced adhesion of platelets to fibrinogen-coated surfaces. Since platelet activation and blood coagulation are tightly associated processes, the antiplatelet properties of EACA derivatives are expected to indicate reduced thrombotic properties of these derivatives compared to EACA.

Aromatic analogues of DNA minor groove binders--synthesis and biological evaluation.

Nine carbocyclic analogues of mono- and bis-lexitropsins and two analogues of pentamidine with unsubstituted N-terminal amine group were synthesized. We have investigated the cytotoxic activity of new aromatic analogues of DNA binding ligands in MCF-7 breast cancer cells and assessed their ability to act as inhibitors of topoisomerase I and II. These studies indicate that aromatic analogues of bis-netropsin contain two identical units tethered by alkyloxyl chains are a potent catalytic inhibitor of both topoisomerases and exhibit moderate cytotoxicity in MCF-7 breast cancer cells.

Synthesis and cytotoxic effect of carbocyclic potential minor groove binders.

New carbocyclic potential minor groove binders were synthesised, using 3-nitrobenzoyl chloride and aliphatic alpha,omega-diamines with three, four and five methylene fragments. The half structures, compounds IV-VI can be compared to bis-amidines, compounds X-XII to bis-netropsin. All of the compounds were investigated antiproliferative and cytotoxic effects in the standard cell line of mammalian tumour MCF-7.

Synthesis and biological activity of carbocyclic lexitropsins with a bioreductive fragment.

Carbocyclic oligopeptides containing of two, three or four aromatic rings with N,N-dimethylpropyl-1,3-diamine group as C-terminus fragment of compounds and 5-[bis(2-chloroethyl)amino]-2,4-dinitrobenzamide as N-terminal were synthesized. These lexitropsins present antitumour activity on the neoplastic cells hepatoblastoma HEP G2. These experiments were evaluated in hypoxic and oxygen conditions. Significant differences of activity in oxygen and hypoxic conditions were shown only in compound, N-(3-dimethylaminopropyl)-N'-([3-[5-bis(2-chlorethyl)amino]-2,4-dinitrobenzamide])-phenyl]urea dihydrochloride 1 (IC50 = 8545 nM in oxygen vs. IC50 = 710 nM in hypoxia). The rest of compounds (2-6) do not indicate differences of activity in oxygen and hypoxia.