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PubMed1986

Studies on the derivatives of aziridine. I. synthesis and immunopharmacological analysis of amides of alpha-aziridinyl- beta-/p-chlorobenzoyl/-propionic acid.

Several new aziridinyl derivatives of beta-/p-chlorobenzoyl/propionic acid were synthesized (3, 5, 7, 14-18). The gamma-/p-chlorophenyl/-dihydrofuran-2-one 2 and beta-/p-chlorobenzoyl/acrylic acid 4 were used as the substrates. Compound 2 reacts with ethylenimine yielding aziridinylamide of beta-/p-chlorobenzoyl/-propionic acid 3. The sodium salt of acid 4 and methyl ester 6 were converted by reactions with ethylenimine into appropriate alpha-aziridinyl derivatives 5 and 7. The acid 4 in the reaction with phosphorus pentachloride gives the acid chloride 8 which is transformed under the influence of appropriate amines into corresponding amides 9-13. These amides react with ethylenimine giving the appropriate alpha-aziridinyl derivatives of beta-/p-chlorobenzoyl/-propionic acid 14-18. Pharmacological analysis revealed that the compounds studied possessed immunotropic activity; they modulate both humoral as well as cellular immune response. Their effect has been shown to be related to chemical structure and to substituents of the carboxyl group in particular.

Acrylates↗
PubMed1987

Continuous-infusion diaziquone in acute myeloid leukemia: a Southeastern Cancer Study Group trial.

Diaziquone (AZQ) is a synthetic quinone with considerable activity against L1210 leukemia and potent myelosuppressive activity in man. To test the efficacy and toxicity of AZQ administered by continuous infusion, a phase II multi-institutional trial was undertaken by the Southeastern Cancer Study Group. Eligible adults with acute myeloid leukemia (AML) received AZQ at a dose of 28 mg/m2 daily by continuous infusion for 5 days. Patients failing to achieve complete remission received a second course utilizing the same dose and schedule. Of 25 evaluable patients with relapsed or refractory AML, three achieved complete response (12%) and two achieved partial response (8%). All patients experienced marked myelosuppression. Severe or life-threatening infection was observed in 15 (56%) patients. Clinical or postmortem evidence of central nervous system hemorrhage was encountered in three (12%) patients with severe refractory thrombocytopenia. Minimal nonhematologic toxicity was observed, suggesting that further studies of this agent in combination regimens and possibly for marrow transplantation preparation in patients with acute leukemia are warranted.

Adult↗
PubMed1987

Myeloablation with diaziquone: in vitro assessment.

UNLABELLED: The promising antineoplastic agent diaziquone is associated with prolonged aplasia and rare instances of bone marrow necrosis, but only mild extramedullary toxicity. To explore the drug's potential as a myeloablative agent prior to bone marrow transplantation, we compared its effects on hematopoietic versus marrow stromal cells. After short-term (one to six hours) or prolonged (three to seven days) exposure to the drug, marrow was assayed for hematopoietic (CFU-Mix, BFU-E, CFU-GM) and stromal (CFU-F) colony-forming cells and studied in long-term marrow culture (LTMC). One- and three-hour treatments produced little cytotoxicity, even at 5000 ng/mL. After six-hour treatments with this dose, marrow was depleted of CFU-Mix, BFU-E, and CFU-GM, but produced CFU-GM in LTMCs, indicating an ongoing input of CFU-GM from a surviving pre-CFU-Mix population. In contrast, elimination of the latter may be inferred from the absence of CFU-GM in LTMCs exposed for three to seven days to diaziquone at only 150 ng/mL. Under these conditions, CFU-F recovery was 40% and adherent stromal layers in LTMCs were similar to untreated controls regarding rate of development and cellular composition. Our in vitro pre-CFU-Mix-ablative regimen correlates with clinical data that show prolonged but reversible myelosuppression at steady-state diaziquone plasma levels of 101 +/- 10 ng/mL (mean +/- standard error of mean) during 7-day constant infusions. IN CONCLUSION: hematopoietic cells are more sensitive than marrow stromal cells to the dose- and highly time-dependent cytotoxicity of diaziquone, a direct drug-induced noxious effect on the marrow microenvironment is an unlikely cause of the isolated episodes of marrow necrosis after the use of diaziquone in vivo, and prolonged infusion of diaziquone represents an attractive means for achieving myeloablation in selected clinical situations.

Aziridines↗
PubMed1987

Acetylcholinesterase from bovine caudate nucleus is attached to membranes by a novel subunit distinct from those of acetylcholinesterases in other tissues.

Acetylcholinesterase extracted with Triton X-100 from bovine brain caudate nuclei was purified by affinity chromatography to apparent homogeneity. The purified enzyme was labeled with [3H]diisopropyl fluorophosphate at the active sites and with the photoactivated reagent 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine, a compound which has been shown to be selective for the hydrophobic membrane-binding domains of several other proteins. The subunit structure was analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate before and after disulfide reduction. After reduction, a single 3H-labeled band at 70 kDa was stained by silver, but most of the 125I label corresponded to a 20-kDa species. Prior to reduction, five 3H-labeled and silver-stained bands were apparent at 70, 140, 160, 260, and greater than 360 kDa. These species were presumed to represent monomer and disulfide-linked oligomers of 70-kDa catalytic subunits. 125I label was selectively associated with the 160-, 260-, greater than 360-, and a 90-kDa species. Quantitative gel slicing of 3H- and 125I-labeled nonreduced enzyme supported a structural model in which the tetrameric enzyme is a dimer of nonidentical catalytic subunit dimers, one of which involves a direct intersubunit disulfide linkage between two 70-kDa catalytic subunit monomers and the second of which contains two disulfide linkages through an intervening 125I-labeled 20-kDa noncatalytic subunit. This 20-kDa subunit is proposed to contain the membrane attachment site. The brain enzyme did not contain components characteristic of the glycolipid anchors of erythrocyte acetylcholinesterases. However, part of the 125I label was associated with fatty acids, indicating that at least a portion of the brain enzyme membrane anchor is composed of nonamino acid components.

Acetylcholinesterase↗
PubMed1987

[Mechanism of the reaction of N,N-dimethyl-2-phenylaziridinium with acetylcholinesterase in its active site].

Effect of temperature on the rate of the bond-breaking step of acetylcholinesterase modification with N,N-dimethylaziridinium ion was studied within 8 to 45 degrees C temperature interval. For this reaction measured by irreversible inhibition of the acetylcholinesterase-catalyzed hydrolysis of acetylthiocholine the activation parameters delta H not equal to = 94 kJ/mole and delta S not equal to (25 degrees C) = -9.4 J/mol X deg were obtained. Processing of these data together with our earlier results on spontaneous solvolysis of the aziridinium ion in various water-solvent mixtures showed that all these reactions form a common isokinetic series. That gave evidence of the SN1 mechanism of the alkylation reaction occurring at the acetylcholinesterase active centre. Kinetics of spontaneous decomposition of the covalent bond between the aziridinium reagent and protein molecule was studied. This reaction followed the first-order kinetics and lead to complete liberation of the label from the enzyme, thus suggesting that a single carboxylic or amide group in the active centre was modified by the aziridinium ion.

Acetylcholinesterase↗
PubMed1987

Effects of an alkylating derivative of oxotremorine (BM 123A) on heart rate, muscarinic receptors and adenylate cyclase activity in the rabbit myocardium.

The effects of the aziridinium ion (BM 123A) of a 2-chloroethylamine derivative of oxotremorine, N-[4-(2-chloroethylmethylamino)-2-butynyl]-2-pyrrolidone (BM 123), on heart rate, muscarinic receptor binding properties and adenylate cyclase activity were investigated in the rabbit myocardium. BM 123A was a potent inhibitor of heart rate in spontaneously beating rabbit hearts. Perfusion of hearts with BM 123A for 30 min caused a lack of sensitivity of the heart to the muscarinic agonist oxotremorine-M and an 80% alkylation of muscarinic receptors as measured by the reduction in the binding capacity of N-[3H]methylscopolamine. Alkylation of muscarinic receptors in the heart with BM 123A had no significant effect on adenylate cyclase activity by itself but caused a functional blockade of muscarinic receptor-mediated inhibition of adenylate cyclase activity. The reversible binding characteristics of both BM 123 and BM 123A were investigated in competitive binding experiments with N-[3H]methylscopolamine at 0 degree C, conditions under which little or no receptor alkylation occurs. The concentration of BM 123A required for half-maximal receptor occupancy was similar to that of oxotremorine-M whereas the parent mustard (BM 123) was 200-fold less potent. GTP (10 microM) had no significant effect on the binding of N-methylscopolamine but caused a 16-fold increase in the concentration of BM 123A required for half-maximal receptor occupancy.

Adenylyl Cyclases↗
PubMedDate not supplied

Phase II study of continuous-infusion diaziquone in relapsed/refractory acute nonlymphocytic leukemia.

A total of 74 patients with relapsed/refractory acute nonlymphocytic leukemia were entered in a phase II trial of diaziquone (AZQ) administered by continuous infusion at a dose of 28 mg/m2 a day for 5 days. Complete remission (CR) was achieved in 12 of the 67 evaluable patients (18%), all occurring in relapsed patients (12 of 55, 22%). There were eight partial responders (one of whom was in the refractory group). Three of these had normal M-1 bone marrow but did not meet peripheral blood criteria for CR. The median duration of CR was 13.6 weeks (range, 4-40+). Nonhematologic toxicity was mild to moderate and easily manageable. Hematologic toxicity was severe or life threatening in all patients. This study confirms the activity of AZQ when given as a continuous infusion to patients with relapsed acute nonlymphocytic leukemia.

Acute Disease↗
PubMed1987

Effect of rigor and cycling cross-bridges on the structure of troponin C and on the Ca2+ affinity of the Ca2+-specific regulatory sites in skinned rabbit psoas fibers.

Intrinsic troponin C (TnC) was extracted from small bundles of rabbit psoas fibers and replaced with TnC labeled with dansylaziridine (5-dimethylaminonaphthalene-1-sulfonyl). The flourescence of incorporated dansylaziridine-labeled TnC was enhanced by the binding of Ca2+ to the Ca2+-specific (regulatory) sites of TnC and was measured simultaneously with force (Zot, H.G., Güth, K., and Potter, J.D. (1986) J. Biol. Chem. 261, 15883-15890). Various myosin cross-bridge states also altered the fluorescence of dansylaziridine-labeled TnC in the filament, with cycling cross-bridges having a greater effect than rigor cross-bridges; and in both cases, there was an additional effect of Ca2+. The paired fluorescence and tension data were used to calculate the apparent Ca2+ affinity of the regulatory sites in the thin filament and were shown to increase at least 10-fold during muscle activation presumably due to the interaction of cycling cross-bridges with the thin filament. The cross-bridge state responsible for this enhanced Ca2+ affinity was shown to be the myosin-ADP state present only when cross-bridges are cycling. The steepness of the pCa force curves (where pCa represents the -log of the free Ca2+ concentration) obtained in the presence of ATP at short and long sarcomere lengths was the same, suggesting that cooperative interactions between adjacent troponin-tropomyosin units may spread along much of the actin filament when cross-bridges are attached to it. In contrast to the cycling cross-bridges, rigor bridges only increased the Ca2+ affinity of the regulatory sites 2-fold. Taken together, the results presented here indicate a strong coupling between the Ca2+ regulatory sites and cross-bridge interactions with the thin filament.

Animals↗
PubMedDate not supplied

Electrochemistry of potential bioreductive alkylating quinones: its use in the development of new aziridinylquinones.

The concept of bioreductive alkylation as a mechanism of action of quinone-containing anticancer agents was investigated, using electrochemical techniques. According to this concept, an electrochemical step (reduction of the quinone ring) is followed by one or more chemical steps, leading to formation of the actual alkylating species. The proper use of electrochemical analysis of potential bioreductive alkylating quinones in the design of new analogs is limited. Up to now, the only electrochemical parameter frequently used in structure-activity relationship studies, is the half-wave potential of the quinone reduction. However, reliable information can only be obtained from the found value of this parameter when the reduction mechanism has been elucidated. Furthermore, it only gives information about the first step of the model. More detailed electrochemical analysis of potential bioreductive alkylating quinones, in combination with a biological evaluation, is required to gain more insight in their mechanism of action and to yield quantitative information about substituent effects on both the electrochemical and the chemical step(s) of the model. Results of such studies of a series of aziridinylquinones indicate, that the biological activity in vitro is correlated with the ease of protonation of the aziridines after quinone reduction, which is in accordance with the concept of bioreductive activation. No correlation with the ease of protonation of the aziridines prior to quinone reduction or with the quinone reduction step itself can be found.

Alkylating Agents↗
PubMed1986

Photosensitization of leukemia L1210 cells with diaziquone.

Exposure of leukemia L1210 cells in culture to the drug diaziquone resulted in inhibition of incorporation of labeled thymidine into nucleic acid and loss of cell viability. These effects were markedly potentiated by irradiation of cells previously exposed to diaziquone in culture. This result shows that diaziquone can catalyze phototoxicity; the action spectrum of the drug may limit clinical applications of this phenomenon.

Animals↗