Biomedical subjects

R J Bergeron

Publications and source records attributed to R J Bergeron.

At least 19 recordsLinked to original sources

PubMed1999

Evaluation of the desferrithiocin pharmacophore as a vector for hydroxamates.

A series of (S)-desmethyldesferrithiocin (DMDFT, 1) hydroxamates and a bis-salicyl polyether hydroxamate are evaluated for their iron-clearing properties in rodents; some of these are further assessed in primates. These hydroxamates include (S)-desmethyldesferrithiocin, N-methylhydroxamate (2); (S)-desmethyldesferrithiocin, N-[5-(acetylhydroxyamino)pentyl]hydroxamate (3); desmethyldesferrithiocin, N-benzylhydroxamate (4); (S,S)-N(1), N(8)-bis[4,5-dihydro-2-(3-hydroxy-2-pyridinyl)-4-thiazoyl]-N(1), N(8)-dihydroxy-3,6-dioxa-1,8-octanediamine (5); and N(1), N(8)-bis(2-hydroxybenzoyl)-N(1),N(8)-dihydroxy-3,6-dioxa-1, 8-octanediamine (6). The ligands are evaluated when given both orally (po) and subcutaneously (sc) in the bile-duct-cannulated rodent model. In iron-overloaded primates, ligands 1-4 are assessed when administered po and sc. The efficiencies of the hydroxamates are shown to vary considerably; giving the compounds sc consistently resulted in greater chelating efficiency in vivo. After oral administration in the primate, compound 3, a pentacoordinate unsymmetrical dihydroxamate, produces iron excretion sufficient to warrant further preclinical evaluation both as a potential orally active iron-chelating agent and as a parenteral iron chelator. The increased iron clearance of several of these ligands when administered sc versus po also underscores the idea that parenteral administration is a reasonable alternative to a less efficient, orally active device which would require large and frequent doses.

Administration, Oral↗

PubMed1999

Effects of C-4 stereochemistry and C-4' hydroxylation on the iron clearing efficiency and toxicity of desferrithiocin analogues.

Additional structure-activity studies of desferrithiocin analogues are carried out. The effects of stereochemistry at C-4 on the ligands' iron clearing efficiency are reviewed and assessed using the enantiomers 4,5-dihydro-2-(2, 4-dihydroxyphenyl)thiazole-4(R)-carboxylic acid and 4,5-dihydro-2-(2, 4-dihydroxyphenyl)thiazole-4(S)-carboxylic acid. The utility of 4'-hydroxylation as a method of reducing the toxicity of desazadesferrithiocin analogues is also examined further with the synthesis and in vivo comparison of 4, 5-dihydro-2-(2-hydroxyphenyl)-4-methylthiazole-4(S)-carboxylic acid, which is the natural product 4-methylaeruginoic acid, and 4, 5-dihydro-2-(2,4-dihydroxyphenyl)-4-methylthiazole-4(S)-carboxylic acid. The stereochemistry at C-4 is shown to have a substantial effect on the iron clearing efficiency of desferrithiocin analogues, as does C-4'-hydroxylation on the toxicity profile. All of the compounds are evaluated in a bile-duct-cannulated rodent model to determine iron clearance efficiency and are carried forward to the iron-overloaded primate for iron clearing measurements. On the basis of the results of the present work, although 4,5-dihydro-2-(2, 4-dihydroxyphenyl)thiazole-4(S)-carboxylic acid is still the most promising candidate for clinical evaluation, 4,5-dihydro-2-(2, 4-dihydroxyphenyl)-4-methylthiazole-4(S)-carboxylic acid (4'-hydroxydesazadesferrithiocin) also merits further preclinical assessment.

Animals↗

PubMed1999

Polyamine analogue induction of the p53-p21WAF1/CIP1-Rb pathway and G1 arrest in human melanoma cells.

Although polyamines are well recognized for their critical involvement in cell growth, the cell cycle specificity of this requirement has not yet been characterized with respect to the newly delineated regulatory pathways. We recently reported that polyamine analogues having close structural and functional similarities to the natural polyamines produce a distinct G1 and G2-M cell cycle arrest in MALME-3M human melanoma cells. To determine a molecular basis for this observation, we examined the effects of N1,N11-diethylnorspermine on cell cycle regulatory proteins associated with G1 arrest. The analogue is known to deplete polyamine pools by suppressing biosynthetic enzymes and potently inducing the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase. Treatment of MALME-3M cells with 10 microM N1,N11-diethylnorspermine caused an increase in hypophosphorylated Rb, which correlated temporally with the onset of G1 arrest at 16-24 h. Rb hypophosphorylation was preceded by an increase in wild-type p53 (approximately 100-fold at maximum) and a concomitant increase in the cyclin-dependent kinase inhibitor, p21WAF1/CIP1 (p21; approximately 5-fold at maximum). Another cyclin-dependent kinase inhibitor, p27KIP1, and cyclin D increased slightly, whereas proliferating cell nuclear antigen and p130 remained unchanged. Induction of p21 protein was accompanied by an increase in p21 mRNA, whereas induction of p53 protein was not, suggesting transcriptional activation of the former and posttranscriptional regulation of the latter. SK-MEL-28 human melanoma cells, which contain a mutated p53, failed to induce p53 or p21 and did not arrest in G1. Rather, these cells rapidly underwent programmed cell death within 48 h. Overall, these findings provide the first indication of the cell cycle regulatory pathways by which polyamine antagonists such as analogues might inhibit growth in cells containing wild-type p53 and further suggest a mechanistic basis for differential cellular responses to these agents.

Antineoplastic Agents↗

PubMed1999

Desazadesmethyldesferrithiocin analogues as orally effective iron chelators.

Further structure-activity studies of desferrithiocin analogues are carried out. (S)-Desazadesmethyldesferrithiocin, 2-(2-hydroxyphenyl)-Delta2-thiazoline-4(S)-carboxylic acid, serves as the principal framework in the current paper. Desazadesmethyldesferrithiocin can be structurally altered with facility, and data are already available on its iron-clearing properties and toxicity parameters. Four different kinds of structural modifications of this framework are undertaken: introduction of hydroxy, carboxy, or methoxy groups on the aromatic ring; alteration of the thiazoline ring; increasing the distance between the ligand donor atoms; and benz-fusion of the aromatic rings. The structural modifications described are shown to have a tremendous impact on both the iron clearance and toxicity profiles of the desazadesmethyldesferrithiocin molecule. All of the compounds are assessed in a bile-duct-cannulated rodent model to determine iron clearance efficiency. Ligands which demonstrate an efficiency of greater than 2% are carried forward to the iron-overloaded primate for iron-clearing measurements. Ligands with efficiencies greater than 3% in the primate are then evaluated in a formal toxicity study in rodents. On the basis of the results of the present work, 2-(2, 4-dihydroxyphenyl)-Delta2-thiazoline-4(S)-carboxylic acid is a promising candidate for clinical evaluation.

Administration, Oral↗

PubMed1999

HBED: the continuing development of a potential alternative to deferoxamine for iron-chelating therapy.

To further examine the potential clinical usefulness of the hexadentate phenolic aminocarboxylate iron chelator N, N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) for the chronic treatment of transfusional iron overload, we performed a subchronic toxicity study of the HBED monosodium salt in rodents and have evaluated the iron excretion in primates induced by HBED. The HBED-induced iron excretion was determined for the monohydrochloride dihydrate that was first dissolved in a 0.1-mmol/L sodium phosphate buffer at pH 7.6 and administered to the primates either orally (PO) at a dose of 324 micromol/kg (149.3 mg/kg, n = 5), subcutaneously (sc) at a dose of 81 micromol/kg (37.3 mg/kg, n = 5), sc at 324 micromol/kg (n = 5), and sc at 162 micromol/kg (74.7 mg/kg) for 2 consecutive days for a total dose of 324 micromol/kg (n = 3). In addition, the monosodium salt of HBED in saline was administered to the monkeys sc at a single dose of 150 micromol/kg (64.9 mg/kg, n = 5) or at a dose of 75 micromol/kg every other day for three doses, for a total dose of 225 micromol/kg (n = 4). For comparative purposes, we have also administered deferoxamine (DFO) PO and sc in aqueous solution at a dose of 300 micromol/kg (200 mg/kg). In the iron-loaded Cebus apella monkey, whereas the PO administration of DFO or HBED even at a dose of 300 to 324 micromol/kg was ineffective, the sc injection of HBED in buffer or its monosodium salt, 75 to 324 micromol/kg, produced a net iron excretion that was nearly three times that observed after similar doses of sc DFO. In patients with transfusional iron overload, sc injections of HBED may provide a much needed alternative to the use of prolonged parenteral infusions of DFO. Note: After the publication of our previous paper (Blood, 91:1446, 1998) and the completion of the studies described here, it was discovered that the HBED obtained from Strem Chemical Co (Newburyport, MA) that was labeled and sold as a dihydrochloride dihydrate was in fact the monohydrochloride dihydrate. Therefore, the actual administered doses were 81, 162, or 324 micromol/kg; not 75, 150, or 300 micromol/kg as was previously reported. The new data have been recalculated accordingly, and the data from our earlier study, corrected where applicable, are shown in parentheses.

Administration, Oral↗

PubMed1998

Synthesis of reagents for the construction of hypusine and deoxyhypusine peptides and their application as peptidic antigens.

Two new synthetic methods which allow access to (2S)-deoxyhypusine, natural (2S,9R)-hypusine, (2S,9S)-hypusine, and deoxyhypusine- and hypusine-containing peptides are described. The methods involve both the construction of a deoxyhypusine reagent in which the alpha-nitrogen protecting group is orthogonal to the N-7 and N-12 protecting groups and an alternate synthesis of our previous hypusine reagent, a synthesis which provides for better stereochemical control at C-9. Synthetic hypusine and deoxyhypusine can be generated from these reagents. The hypusine-containing hexapeptide (Cys-Thr-Gly-Hpu-His-Gly) is conjugated to ovalbumin (OVA), keyhole limpet hemocyanin (KLH), and a bis-maleimide; KLH conjugates are also made with the deoxyhypusine- and lysine-containing hexapeptides. Monoclonal antibodies are generated to the hypusine-containing hexapeptide-OVA conjugate in mice. These are isolated and screened against the hypusine-containing hexapeptide-KLH and hypusine-containing hexapeptide-bis-maleimide conjugates, as well as against the deoxyhypusine-containing and lysine-containing hexapeptide-KLH conjugates. These antibodies may be useful in localizing intracellular hypusine-containing peptides as well as peptides containing hypusine analogues.

Animals↗

PubMed1998

Effect of polyamine analogues on hypusine content in JURKAT T-cells.

The availability of synthetic hypusine and deoxyhypusine has made it possible to develop analytical methods which allow for the measurement of these compounds in various tissues. The methods involve dansylation of extracts from the pellet remaining after perchloric acid precipitation of cell or tissue homogenates, followed by high-performance liquid chromatography. To demonstrate the utility of this approach, the impact of four polyamine analogues, N1,N11-diethylnorspermine (DENSPM), N1,N14-diethylhomospermine (DEHSPM), 1,6,12-triazadodecane [(4,5) triamine], and 1,7, 13-triazatridecane [(5,5) triamine], on hypusine levels in a human T-cell line (JURKAT) is evaluated. All four analogues are active in controlling cell growth and compete well with spermidine for the polyamine transport apparatus. After 144 h of exposure to JURKAT cells, DENSPM reduces putrescine to below detectable limits and spermidine to 10% of the level in control cells. The other three analogues diminish both putrescine and spermidine to below detectable limits. The effectiveness with which the compounds lower spermine levels is DENSPM > DEHSPM > (4,5) triamine > (5,5) triamine. The analogues decrease the activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase in a similar fashion. Of the four polyamines, DENSPM and DEHSPM are potent at lowering intracellular hypusine levels after 144 h: 59 +/- 9% and 73 +/- 12% of control levels, respectively. The other two analogues have marginal effects.

Adenosylmethionine Decarboxylase↗

PubMed1998

Lysosomal sequestration of polyamine analogues in Chinese hamster ovary cells resistant to the S-adenosylmethionine decarboxylase inhibitor, CGP-48664.

CGP-48664, an inhibitor of the polyamine biosynthetic enzyme S-adenosylmethionine decarboxylase (AdoMetDC), is presently undergoing Phase 1 clinical trials as an experimental anticancer agent. We have shown previously (D. L. Kramer et al., J. Biol. Chem., 270: 2124-2132, 1995) that Chinese hamster ovary (CHO) cells that are made resistant to the growth inhibitory effects of the drug overexpress AdoMetDC because of a stable gene amplification. Unexpectedly, these same cells (CHO/644) were found to be insensitive to the growth inhibitory effects of N1,N11-diethylnorspermine (DENSPM)-a polyamine analogue also undergoing Phase 1 clinical trials-despite accumulating approximately 5 times more analogue than parental cells. We now report that treatment of CHO/664 cells with DENSPM results in the formation of numerous large cytoplasmic vacuoles, which on the basis of electron microscopy and cytochemical staining seem to be lysosomal in origin. A series of newly established CHO cell lines made differentially resistant to 1, 3, 10, 30, and 100 microM CGP-48664 by chronic exposure were used to demonstrate that vacuole formation correlated with the accumulation of extremely high levels of DENSPM without increasing growth inhibition. These same cells were used to show that AdoMetDC gene overexpression as indicated by mRNA levels was unrelated to vacuole formation; cells resistant to 100 microM CGP-48664 displayed a 170-fold increase in AdoMetDC mRNA levels and formed vacuoles in response to DENSPM, whereas those resistant to 10 microM CGP-48664 displayed a 120-fold increase in AdoMetDC mRNA levels and failed to form vacuoles. Despite accumulating to high intracellular levels, DENSPM was much less effective than spermine at down-regulating ornithine decarboxylase and polyamine transport activities in highly resistant cells. Similarly, DENSPM was less able to induce spermidine/spermine N1-acetyltransferase activity in cells that formed vacuoles than in those that did not. Overall, natural polyamines failed to induce vacuoles and various analogues of DENSPM were used to probe the structural specificity of the effect. The data are consistent with the probability that DENSPM is sequestered to high concentrations in lysosomal vacuoles of CGP-48664-resistant cells and is, therefore, not available to interact with polyamine regulatory sites or to cytotoxically affect cell growth. In addition to implicating the lysosome as a potential new site of CGP-48664 drug action that could be involved in antitumor activity and/or host toxicities, the findings also suggest a potential mechanism of cell resistance to analogues such as DENSPM.

Adenosylmethionine Decarboxylase↗

PubMed1998

The origin of the differences in (R)- and (S)-desmethyldesferrithiocin. Iron-clearing properties.

The iron clearance properties, toxicity, and pharmacokinetics of (R)- and (S)-desmethyldesferrithiocin (DMDFT) are described. The studies were performed in rodent and primate models. While both enantiomers were found to be effective iron chelators with minimal toxicity in the rodents, only (S)-DMDFT was able to induce the clearance of any iron in the primates. In addition, two out of nine of the monkeys given (R)-DMDFT died within 24 h of drug administration. The reason for the differences in iron clearance properties and the apparent toxicity of the (R)-enantiomer in the primates is likely related to the disparities in the pharmacokinetics of the two analogues. The pharmacokinetic data suggest enantioselectivity in renal clearance of the desferrithiocins and their iron complexes with (S)-DMDFT clearance 3.5 times greater than that of (R)-DMDFT, and FeIII [(S)-DMDFT]2 clearance 6.8 times greater than that of FeIII [R-DMDFT]2. In all primates studied FeIII [(R)-DMDFT]2 in the plasma exceeded 25 mg/L (50 microM) for several hours and remained above 10 mg/L (20 microM) at 8 h while levels of FeIII [(S)-DMDFT]2 never exceeded 50 microM and were at or below the limits of detection 8 h post-injection.

Animals↗

PubMed1998

HBED: A potential alternative to deferoxamine for iron-chelating therapy.

To examine the potential clinical usefulness of the hexadentate phenolic aminocarboxylate iron chelator N, N-bis(2-hydroxybenzyl)ethylenediamine-N,N-diacetic acid (HBED) for the chronic treatment of transfusional iron overload, we compared the iron excretion induced by subcutaneous (SC) injection of HBED and deferoxamine (DFO), the reference chelator, in rodents and primates. In the non-iron-overloaded, bile-duct-cannulated rat, a single SC injection of HBED, 150 micromol/kg, resulted in a net iron excretion that was more than threefold greater than that after the same dose of DFO. In the iron-loaded Cebus apella monkey, a single SC injection of HBED, 150 micromol/kg, produced a net iron excretion that was more than twice that observed after the same dose of SC DFO. In patients with transfusional iron overload, SC injections of HBED may provide a much needed alternative to the use of prolonged parenteral infusions of DFO.

Animals↗

PubMed1998

Human prostatic carcinoma cell lines display altered regulation of polyamine transport in response to polyamine analogs and inhibitors.

BACKGROUND: The possibility was investigated that complex homeostatic mechanisms which maintain polyamine pools in prostate-derived tumors may differ from those which are typically seen in other tissues and tumors. METHODS: Growth sensitivity and various regulatory responses were investigated in three human prostate carcinoma cell lines (LNCaP, DU145, and PC-3) treated with the inhibitor of S-adenosylmethionine decarboxylase CGP-48664 or the polyamine analog N1,N11-diethylnorspermine (DENSPM), both of which are currently undergoing phase I clinical trial. RESULTS: Prostate tumor cell lines were all similarly growth-inhibited by the inhibitor CGP-48664 (IC50 values, 1-5 microM at 72 hr), but varied considerably in their sensitivity to DENSPM. The rank-order for cell-line growth inhibition by the analog was DU145 > PC-3 > LNCaP, with IC50 values of 1, 30, and 1,000 microM, respectively. Both compounds depleted intracellular polyamine pools to levels which seemed sufficient to account for inhibition of cell growth. While polyamine enzyme regulatory responses to both CGP-48664 and DENSPM were typical of those seen in other cell types, regulation of polyamine transport differed distinctly. Based on Vmax determinations, LNCaP cells failed to upregulate transport in response to CGP-48664, while PC-3 and LNCaP cells failed to downregulate transport in response to DENSPM. CONCLUSIONS: Relative to other cell lines, polyamine transport in prostate carcinoma cell lines was found to be uniquely insensitive to regulation by polyamines or analogs. Although this did not seem to correlate with growth sensitivity to polyamine analogs in vitro, it should be therapeutically exploitable in in vivo systems.

Adenosylmethionine Decarboxylase↗

PubMed1998

Polyamine analogue antiarrhythmics.

A group of polyamine analogues was assessed for their ability to prevent isoproterenol-induced ventricular fibrillation and death in a desoxycorticosterone acetate (DOCA)/saline rodent model. The compounds tested included polyamine antimetabolites and putrescine mimics. A structure-activity analysis revealed that tetraamines that are dicationic at physiological pH with their terminal nitrogens incorporated into pyridine rings are the most active analogues. It is clear from this study that there was no correlation between the compounds' ability to diminish polyamine metabolism and their effects on the electrical properties of the heart. In fact, the most potent polyamine antimetabolites were among the least effective antiarrhythmics. The most active of the compounds investigated, N1, N3-bis(4-pyridyl)-1,3-diaminopropane, PYR(3,3,3), was shown to both prevent isoproterenol-induced arrhythmias in DOCA/saline-treated rodents and reverse the progression of arrhythmic events that would otherwise culminate in ventricular fibrillation and death. Electrocardiographic tracings demonstrated that PYR(3,3,3) and propranolol both protect from and reverse the progression of arrhythmic events to ventricular fibrillation. In addition, cardiac pathologies from rats treated with both drugs are similar, but are substantially different from the control (isoproterenol)-treated animals. (c) 1998 The Italian Pharmacological Society.

Animals↗

PubMed1997

Effects of novel spermine analogues on cell cycle progression and apoptosis in MALME-3M human melanoma cells.

On the basis of encouraging preclinical findings, polyamine analogues have emerged as a novel class of experimental antitumor agents. The spermine derivative N1,N11-diethylnorspermine (DE-333, also known as DENSPM) is currently undergoing Phase I clinical trials against solid tumors. A series of systematically modified DE-333 analogues differing in intra-amine carbon distances and in N-alkyl terminal substituents (i.e., methyl, ethyl, and propyl) were evaluated in MALME-3M human melanoma cells, a cell line known to be cytotoxically affected by DE-333 and especially responsive to analogue induction of the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase. Analogues accumulated to comparable intracellular concentrations and similarly affected cell growth with IC50 values in the 0.5-1.0 microM range. During prolonged incubations, diethyl and dipropyl analogues were cytotoxic, whereas two dimethyl analogues were cytostatic. Cell cycle analysis following treatment with the cytotoxic analogues revealed a prominent G1 block apparent as an accumulation of cells in G0/G1 and depletion of S-phase cells as well as a less restrictive G2 block. By contrast, cytostatic analogues incompletely arrested cells in G1, leaving a significant number of S-phase cells. Morphological and immunocytochemical analysis of detached cells revealed a far greater proportion of apoptotic cells with cytotoxic analogues than with cytostatic analogues. Although spermidine/spermine N1-acetyltransferase activity was differentially induced by the analogues, there was no obvious correlation with cell cycle effects. Overall, these data indicate a previously unrecognized combined effect of polyamine analogues on cell cycle progression and apoptosis. On the basis of structure-function relationships, these activities may be manipulated to optimize therapeutic efficacy.

Acetyltransferases↗

PubMed1997

A comparison of structure-activity relationships between spermidine and spermine analogue antineoplastics.

A systematic investigation of the impact of spermidine analogues both in vitro and in vivo is described. The study characterizes the effects of these analogues on L1210 cell growth, polyamine pools, ornithine decarboxylase, S-adenosyl-L-methionine decarboxylase, spermidine/spermine N1-acetyltransferase, the maintenance of cellular charge, i.e., cationic equivalence associated with the polyamines and their analogues, and compares their ability to compete with spermidine for transport. The findings clearly demonstrate that the activity of the linear polyamine analogues is highly dependent on the length of the triamines and the size of the N(alpha),N(omega)-substituents. It appears that there is an optimum chain length for various activities and that the larger the N(alpha),N(omega)-alkyls, the less active the compound. Metabolic transformation including N-dealkylation of these compounds is also evaluated. While there is no monotonic relationship between chain length and the ability of the analogue to be metabolized, the dipropyl triamines are clearly more actively catabolized than the corresponding methyl and ethyl systems. A comparison of the triamines with the corresponding tetraamines is made throughout the text regarding both in vitro activity against L1210 cells and in vivo toxicity measurements, suggesting that several triamine analogues may offer therapeutic advantages over the corresponding tetraamines.

Acetyltransferases↗

PubMed1997

The influence of molecular conformation upon the self-assembly of cyclohexane diamide diacids.

BACKGROUND: Information regarding the self-association of small peptide motifs can be used in the design of peptide microstructures. Previous work in our laboratories illustrated the self-association of certain diamide diacids into microcapsules. In this report a series of cyclohexane diamide diacids are investigated. The cyclohexylene (R-C6H10-R) system (with its axial and equatorial requirements) provided an opportunity to study the influence of molecular conformation upon the self-aggregation process. RESULTS: Condensation of the respective cis- and trans-1,2-, 1,3-, and 1,4- cyclohexane dicarboxylic acid platforms with two equivalents of a L-Phe ester followed by deprotection gave the desired diamide diacids. Basic solutions of cis-1,2-, trans-1,3-, and cis-1,4-diamide diacids generated solid microspheres when acidified to pH 2.4. Molecular modeling revealed that 1,3-diaxial interactions favor a helical turn within these diamides. CONCLUSIONS: Access to 'complementary' molecular geometries is needed to self-associate into microscopic architectures.

Amides↗

PubMed1997

Structural basis for differential induction of spermidine/spermine N1-acetyltransferase activity by novel spermine analogs.

The spermine analog N1,N11-diethylnorspermine (DE-333, also known as DENSPM or BENSPM) is regarded as the most potent known inducer of the polyamine catabolic enzyme, spermidine/spermine N1-acetyltransferase (SSAT), increasing activity by more than 200- to 1000-fold in certain cell types. The relative ability of a series of eight systematically modified DE-333 analogs to affect SSAT expression was examined in Malme-3M human melanoma cells, one of several cell lines known to be especially responsive to induction of this enzyme. In particular, we examined the relative contribution of induction of enzyme mRNA and prolongation of enzyme half-life to analog-mediated increases in enzyme activity. Induction of enzyme mRNA was most influenced by intra-amine carbon distances; relative effectiveness was found to be proportional to the number of three-carbon units. Stabilization of enzyme was most determined by the terminal N-alkyl substituent size; among methyl, ethyl and propyl groups, methyl was least effective. Thus, DE-333, which most potently induces SSAT mRNA and effectively stabilizes SSAT enzyme activity, produces the greatest increase in enzyme activity. Although other contributing mechanisms may be involved, the relative abilities of the various analogs to induce enzyme activity is at least partially attributable to their combined effects on enzyme mRNA and protein half-life. These data reveal the highly sensitive structure-activity relationships that underlie and control spermine analog induction of SSAT activity. Pending further definition of the relationship between SSAT induction and antitumor growth and toxicity in vivo, these relationships may be used to optimize therapeutic efficacy.

Acetyltransferases↗

PubMed1996

Polyamine analogue regulation of NMDA MK-801 binding: a structure-activity study.

A series of analogues and homologues of spermine were synthesized, and their impact on MK-801 binding to the N-methyl-D-aspartate (NMDA) receptor was evaluated. These tetraamines encompass both linear and cyclic compounds. The linear molecules include norspermine, N1, N11-diethylnorspermine, N1,N12-bis(2,2,2-trifluoroethyl)spermine, homospermine, and N1,N14-diethylhomospermine. The cyclic tetraamines consist of the piperidine analogues N1,N3-bis(4-piperidinyl)-1,3-diaminopropane, N1,N4-bis(4-piperidinyl)-1,4-diaminobutane, N1,N4-bis(4-piperidinylmethyl)-1,4-diaminobutane, and N1,N4-bis[2-(4-piperidinyl)ethyl]-1,4-diaminobutane and the pyridine analogues N1,N3-bis(4-pyridyl)-1,3-diaminopropane, N1,N4-bis(4-pyridyl)-1,4-diaminobutane, N1,N4-bis(4-pyridylmethyl)-1,4-diaminobutane, and N1,N4-bis[2-(4-pyridyl)-ethyl]-1,4-diaminobutane. This structure-activity set makes it possible to establish the importance of charge, intercharge distance, and terminal nitrogen substitution on polyamine-regulated MK-801 binding in the NMDA channel. Four families of tetraamines are included in this set: norspermines, spermines, homospermines, and tetraazaoctadecanes. Calculations employing a SYBYL modeling program revealed that the distance between terminal nitrogens ranges between 12.62 and 19.61 A. The tetraamines are constructed such that within families cyclics and acyclics have similar lengths but different nitrogen pKa's and thus different protonation, or charge, states at physiological pH. The pKa values for all nitrogens of each molecule and its protonation state at physiological pH are described. The modifications at the terminal nitrogens include introduction of ethyl and beta,beta,beta-trifluoroethyl groups and incorporation into piperidinyl or pyridyl systems. The studies clearly indicate that polyamine length, charge, and terminal nitrogen substitution have a significant effect on how the tetraamine regulates MK-801 binding to the NMDA receptor. Thus a structure-activity basis set on which future design of MK-801 agonists and antagonists can be based is now available.

Animals↗

PubMed1996

Metabolically programmed polyamine analogue antidiarrheals.

The design, synthesis, and testing of a novel class of antidiarrheal drugs based on a tetraamine pharmacophore are reported. While N1,N14-diethylhomospermine (DEHSPM) (5 mg/kg) completely prevents diarrhea in rodents, tissue distribution studies demonstrated that the principal metabolite of DEHSPM, homospermine (HSPM), accumulates and persists in tissues for a protracted period of time. This accumulation accounts for a large part of the chronic toxicity of DEHSPM. Thus a major objective was to develop a metabolically labile analogue of DEHSPM which retained the desirable biological properties of the parent drug. Hydroxyl groups, sites vulnerable to further metabolic transformation, were introduced into the external aminobutyl segments providing N1,N14-diethyl-(3R),(12R)-dihydroxyhomospermine [(HO)2-DEHSPM]. The design concept was assisted by molecular modeling, which predicted that (HO)2DEHSPM would have a Ki for polyamine transport essentially identical with that of DEHSPM. The experimentally measured Ki and also the observed values of other biological properties of (HO)2DEHSPM were in fact identical with those of DEHSPM, including IC50 against L1210 cells, impact on the NMDA receptor, and impact on L1210 native polyamine pools. Most significantly, however, there was no accumulation of the dideethylated metabolite in tissues from mice treated chronically with (HO)2DEHSPM, and (HO)2DEHSPM was 3-fold less toxic than DEHSPM. Finally, (HO)2DEHSPM completely prevented diarrhea in the castor oil-treated rat model at a dose of 5 mg/kg, just as did DEHSPM.

Animals↗