Effects on substrate profile by mutational substitutions at positions 164 and 179 of the class A TEM(pUC19) beta-lactamase from Escherichia coli.

We investigated the effects of mutations at positions 164 and 179 of the TEM(pUC19) beta-lactamase on turnover of substrates. The direct consequence of some mutations at these sites is that clinically important expanded-spectrum beta-lactams, such as third-generation cephalosporins, which are normally exceedingly poor substrates for class A beta-lactamases, bind the active site of these mutant enzymes more favorably. We employed site-saturation mutagenesis at both positions 164 and 179 to identify mutant variants of the parental enzyme that conferred resistance to expanded-spectrum beta-lactams by their enhanced ability to turn over these antibiotic substrates. Four of these mutant variants, Arg(164) --> Asn, Arg(164) --> Ser, Asp(179) --> Asn, and Asp(179) --> Gly, were purified and the details of their catalytic properties were examined in a series of biochemical and kinetic experiments. The effects on the kinetic parameters were such that either activity with the expanded-spectrum beta-lactams remained unchanged or, in some cases, the activity was enhanced. The affinity of the enzyme for these poorer substrates (as defined by the dissociation constant, K(s)) invariably increased. Computation of the microscopic rate constants (k(2) and k(3)) for turnover of these poorer substrates indicated either that the rate-limiting step in turnover was the deacylation step (governed by k(3)) or that neither the acylation nor deacylation became the sole rate-limiting step. In a few instances, the rate constants for both the acylation (k(2)) and deacylation (k(3)) of the extended-spectrum beta-lactamase were enhanced. These results were investigated further by molecular modeling experiments, using the crystal structure of the TEM(pUC19) beta-lactamase. Our results indicated that severe steric interactions between the large 7beta functionalities of the expanded-spectrum beta-lactams and the Omega-loop secondary structural element near the active site were at the root of the low affinity by the enzyme for these substrates. These conclusions were consistent with the proposal that the aforementioned mutations would enlarge the active site, and hence improve affinity.

Covalent modifications of aminophospholipids by 4-hydroxynonenal.

Lipid oxidation is implicated in a wide range of pathophysiological disorders, which leads to reactive compounds such as aldehydes. Among them 4-hydroxynonenal (4-HNE) reacts strongly with the NH2 groups of amino acids and forms mainly Michael adducts and minor Schiff-base adducts. Such reactions occur also with compounds containing thiol groups. No data are available describing 4-HNE interactions with amino-phospholipids. To investigate such a possibility, 4-HNE was incubated with either phosphatidylethanolamine (PE) or phosphatidylserine (PS) in an aqueous-organic biphasic system and the resulting products were identified by liquid chromatography-mass spectrometry (LC-MS). Our study points out the potential capacity of 4-HNE to react with phospholipids containing amino groups and particularly PE. The main resulting compounds found were a Michael adduct plus a minor Schiff base adduct, which was partly cyclized as a pyrrole derivative via a loss of water. Its stabilization as a pyrrole derivative allows to differentiate 4-HNE from the other aldehydes generated via lipid oxidation (e.g., malondialdehyde, 2-nonenal) that lack the 4-hydroxyl group. Their formation seems not to be affected when the pH varies from 6.5 to 8.5. Surprisingly, PS reacted poorly producing only a small amount of Michael adduct, the Schiff-base adduct being nondetectable. We conclude that such adducts, if they are formed in cell membranes, could alter the phospholipase-dependent cell signaling.

Behavioural profile of two potential antidepressant pyridazine derivatives including arylpiperazinyl moieties in their structure, in mice.

The potential antidepressant effects of two pyridazine derivatives, 5-benzyl 6-methyl 2-[4-(3-trifluoro-methyl phenyl) piperazin-1-yl] methylpyridazin-3-one (PC4) and 5-benzyl 6-methyl 2-[4-(3-chlorophenyl) piperazin-1-yl] methylpyridazin-3-one (PC13), were evaluated using classical psychopharmacological tests in mice. The intraperitoneal LD50 values of PC4 and PC13 were respectively 1125.8 and 429.6 mg kg-1. Only at intraperitoneal doses of 100 mg kg-1 did PC4 or PC13 significantly decrease locomotor activity. Both compounds (5-20 mg kg-1, i.p.) reduced the duration of immobility of mice in the forces swimming test, antagonized reserpine (2.5 mg kg-1, i.p.)-induced ptosis, and potentiated reserpine (2.5 mg kg-1, i.p.)-induced hypothermia. PC4 and PC13 (20 mg kg-1, i.p.) partly reversed hypothermia induced by low dose apomorphine (5 mg kg-1, s.c.) but were less effective for higher doses of apomorphine (16 mg kg-1, s.c.). At 200 mg kg-1, intraperitoneal PC13 enhanced the toxic effects of yohimbine (30 mg kg-1, s.c.), while PC4 was inactive. Head twitches produced either by L-5-hydroxytryptophan (4 mg kg-1, i.p.) in mice pretreated with pargyline (100 mg kg-1, i.p.) or by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (3 mg kg-1, i.p.) were antagonized by both pyridazine derivatives (20 mg kg-1, i.p.). PC4 and PC13 showed analgesic properties in the phenylbenzoquinone-induced abdominal constriction test (5.0 < ED50 < 5.5 mg kg-1, i.p.) and in the hot-plate test (10 to 37% of analgesia at 10 mg kg-1, i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and anticonvulsant properties of new benzylpyridazine derivatives.

Several 3-substituted pyridazines and a series of imidazo- and triazolopyridazines were synthesized and tested for anticonvulsant activity against maximal electroshock-induced seizures in mice. The most active derivatives, 3-ureidopyridazine 7 and triazolopyridazines 16, 18, 21, and 25 with oral ED50's that ranged from 6.2 to 22.0 mg/kg, were more extensively investigated by evaluating their ability to prevent chemically induced seizures and were compared with phenytoin, phenobarbital, sodium valproate, carbamazepine, and diazepam. 3-amino-7-(2,6-dichlorobenzyl)-6-methyltriazolo-[4,3-b]pyridazine (25) was also protective in the pentylenetetrazole-induced seizures test (ED50 = 76 mg/kg per os) and blocked strychnine-induced tonic extensor seizures (ED50 = 34.5 mg/kg per os). Furthermore, derivative 25 showed anticonvulsant effects on bicuculline- and yohimbine-induced seizures tests in mice. All these results suggest that the pharmacological activity of 25 is partly due to modifications of glycinergic and GABAergic transmission. Moreover, molecular modeling studies based on the antiepileptic drug lamotrigine and the most stable conformer of 25 show structural similarities between these two molecules. This conformer also agrees with the electronic tolerances and volume of benzodiazepine pharmacophore models.

Immunomodulatory agents: dioxothiadiazabicyclo[3.3.0]octanes and their 2-spiro derivatives.

A series of 6,8-dioxo-3-thia-1,7-diazabicyclo[3.3.0]octanes and a series of 6,8-dioxo-3-thia-1,7-diazabicyclo[3.3.0]octane 2-spiro derivatives were synthesized from L-(-)-R-cysteine ethyl ester in two steps. The synthetic route involved condensation of the amino acid with an appropriate aldehyde or ketone, then a further condensation of the resultant ethyl thiazolidine-4-carboxylate with an isocyanate or an isothiocyanate. The proliferative response to human lymphocyte mitogen (phytohemagglutinin) was used as a primary screening assay for most of the thiadiazabicyclic compounds in comparison with levamisole. Furthermore, the most active compounds were tested for ability to release soluble receptors (sRIL-2) after mitogenic stimulation of T cells and for ability to activate macrophage oxidative metabolism measured by chemiluminescence. Most compounds were active in all three tests and some showed dose-dependent activity.

Synthesis of new 5-substituted pyrazolo[1,5-d][1,2,4]-triazine derivatives and their analgesic, anti-inflammatory and antipyretic properties.

A series of 2-aryl-4-oxo-pyrazolo[1,5-d][1,2,4]triazines substituted in the 5-position by aminoalkyl or benzoyl moieties was synthesized and evaluated for analgesic activity. The structures of new triazine derivatives were confirmed by IR, 1H-NMR spectra and by elementary analysis. In the phenylbenzoquinone induced writhing test, only 3,3a-dihydropyrazolo triazines substituted by an arylpiperazinylmethyl group exhibited potent analgesic effect. In addition, these compounds possessed significant anti-inflammatory and antipyretic properties. A desaturation in 3,3a positions or other groups than arylpiperazinylmethyl moieties notably decreased analgesic effects.

Synthesis of Mannich bases of arylidenepyridazinones as analgesic agents.

A series of 5-arylidenepyridazin-3-ones substituted in the 2-position by an arylpiperazinoalkyl moiety (2-16) was synthesized and evaluated for analgesic activity. In the phenylbenzoquinone-induced writhing test, Mannich bases 2-14 were the most active compounds (6.1 < or = ED50 < or = 43.0 mg/kg, orally; ED50 is the half-maximal effective dose). Pyridazinones 8 and 9, with a 3-chlorophenylpiperazinomethyl substituent, also exhibited significant anti-inflammatory and antipyretic effects. The activities in the phenylbenzoquinone-induced writhing test were subjected to a Hansch analysis, and a significant correlation with lipophilicity and Hammett's constants was obtained.

Synthesis and aldose reductase inhibitory activity of triazine derivatives possessing acetic acid group.

N-Acetic acid derivatives of 6-aryl-pyrazolo-triazin-4-ones were synthesized for evaluation as new aldose reductase inhibitors. The intrinsic activity of each compound was assessed by measuring the inhibition of enzymatic activity in an isolated pig lens enzyme preparation. All the prepared compounds exhibited a significant in vitro aldose reductase inhibitory effect (10(-6) M less than or equal to IC50 less than or equal to 10(-4) M). Furthermore, biological activity (log 1/IC50) for most of the data sets could be correlated directly to electronic and steric parameters. Finally, spatial configuration of the most active derivative 6c (IC50 = 2 x 10(-6) M) was compared with that of tolrestat and with pharmacophor requirements of the aldose reductase inhibitor site using a molecular modeling system.

[Synthesis and pharmacology of structural analogs of tienilic acids]. / Synthèse et approche pharmacologique d'analogues structuraux de l'acide tiénilique.

Three structural analogs of tienilic acid were synthetized and evaluated for their diuretic activity in the rat. Two compounds are alpha substituted tienilic acid derivatives by an alkylated group. The third one is a conformationally restricted derivative through a cyclization process. All compounds fall to increase the urinary flow in the pharmacological assay.

Synthesis and aldose reductase inhibitory activity of pyridazine derivatives possessing acetic acid group.

N-acetic acid and S-acetic acid derivatives of 5-arylidene pyridazines were synthesized for evaluation as new aldose reductase inhibitors. Intrinsic activity for each compound was assessed by measuring inhibition of enzymatic activity in an isolated pig lens enzyme preparation. All prepared compounds exhibited a significant in vitro aldose reductase inhibitory effect (10(-5) M less than or equal IC50 less than or equal to 10(-4) M). It was found that lipophilicity was important in increasing activity. Furthermore, this activity (log 1/IC50) could be correlated directly to a lipophilic parameter (log kw) for the whole data set.

[Synthesis and evaluation of the aldose reductase inhibitory activity of new diaryl pyridazine-3-ones]. / Synthèse et évaluation de l'activité inhibitrice d'aldose réductase de nouvelles diaryl pyridazin-3-ones.

It has been possible to prepare from 4,6-diaryl pyridazinones a series of derivatives substituted in the 2-position by chains of various lengths bearing a carboxylic acid function. Pig lens aldose reductase inhibitory activity was evaluated for all compounds. N-acetic acid derivative 3c with a chlorine atom on the phenyl nucleus at the 6-position on the pyridazin ring was the most active pyridazinone with an IC50 value of 1.2 x 10(-5) M. Furthermore, it has been shown that lipophilicity and spatial configuration of the synthesized compounds took a prominent part on enzymatic activity.

Studies on immunostimulating derivatives: synthesis of some pyrrolo[1,2-c]pyrimidines.

In a search for potential immunomodulating agents novel pyrrolo[1,2-c]pyrimidines were synthesized and their structures elucidated by spectroscopic means. Unfortunately, most of them were cytotoxic and devoid of effects on T lymphocyte lymphoblastic transformation. Furthermore, they were inactive in the locomotor activity test in mice.

Anticonvulsant activity of 3-oxo-5-substituted benzylidene-6-methyl-(4H)-2-pyridazinylacetamides and 2-pyridazinylacetylhydrazides.

A series of 3-oxo-5-substituted-benzylidene-6-methyl-(4H)-2- pyridazinylacetamides and 2-pyridazinylacetylhydrazides were synthesized and evaluated for anticonvulsant activity against electrically and chemically induced seizures. In the maximal electroshock-induced seizures test, most of the derivatives showed an anticonvulsant effect better than that of sodium valproate, a commonly used anticonvulsant drug. At 100 mg/kg orally, compounds 5a and 5b respectively protected 50 and 60% of the mice against pentylentetrazole-induced seizures. In addition, these two derivatives showed significant anticonvulsant properties at doses that did not produce ataxia or sedation. The title compounds were also tested for their ability to antagonize convulsions induced by bicuculline and strychnine. Their effect on tremors induced by oxotremorine in mice was also evaluated.

Synthesis of 6-[(4-imidazol-1-yl)-phenyl]-4-phenyl 4,5-dihydro-2H-pyridazin-3-one: a potential blood platelet aggregation inhibitor.

A new 4,5 diaryl pyridazin-3-one, an analogue of imazodan and Cl-930 was prepared starting from conveniently available chalcone. The resulting derivative was tested in order to determine the area of pharmacological activity. This compound was devoid of positive inotropic effects but showed an important inhibition of PAF-acether induced blood platelet aggregation in vitro with a Cl50 value of 3,4 microM. Ex vivo, anti-aggregating effect against PAF-acether was less important with a DE50 value of 63 mg/kg per os.

Synthesis and pharmacological evaluation of 6,8-diaryl 1,2,4-triazolo [4,3,-b] and 1,2,3,4,-tetrazolo [1,5-b] pyridazines.

A series of 6,8-diaryl-1,2,4-triazolo[4,3-b] and 1,2,3,4-tetrazolo[1,5-b]pyridazines was synthesized from suitable chloropyridazines. The compounds were screened in mice for their ability to antagonize maximal electroshock-, pentylenetetrazole- and bicuculline-induced seizures; sedative effects were evaluated by a study of the spontaneous motor activity. Some of pyridazine derivatives exhibited appreciable anticonvulsant activity. Substituting the phenyl ring in the 6-position with an halogen atom led to a substantial increase of activity. Furthermore, none of the compounds was notably active in tests predictive of anxiolytic activity.

Synthesis and pharmacological evaluation of N-substituted 4,6-diaryl-3-pyridazinones as analgesic, antiinflammatory and antipyretic agents.

The synthesis and the pharmacological evaluation of 19 new 4,6-diaryl-3-pyridazinones are reported. All compounds were screened for analgesic, antiinflammatory and antipyretic activities. Introduction of an arylpiperazinomethyl moiety in the 2-position of the pyridazinone ring resulted in the most potent activities. Compounds 2a, 2b, 2h and 2i exhibited a higher analgesic activity than did aspirin or noramidopyrine in the hot plate test.

[Synthesis and antisecretory and anti-ulcer activity of new 4,6-diarylpyridazinones]. / Synthèse et activités antisécrétoire et antiulcéreuse de nouvelles N-uréidoalkyl pyridazinones.

It has been possible to prepare from 4,6-diaryl pyridazinones a series of derivatives substituted in the 2-position and having urea moiety via the addition of free amines into methylisocyanate. Their gastric anti-secretory and anti-ulcer activities were evaluated. The compounds with an N-2 ethyl chain on the pyridazinone ring (IVa, IVd, IVg) were the most active derivatives.

A selective inhibitor of thromboxane synthetase activity of rabbit heart tissue: a pyridazinic derivative.

The effects of 2-(2 dimethylaminoethyl) 5-benzylidene 6-methyl (2H,4H)-3-pyridazinone (III) were studied on the biosynthesis of TXA2 and PGI2 in vitro the TXA2 and PGI2 synthetase activity of heart tissue. Biosyntheses of TXA2 and PGI2 were carried out using arachidonic acid as a substrate and horse platelet and aorta microsomes as sources of TXA2 and PGI2 synthetases respectively. TXB2 and 6-keto PGF1 alpha were determined by RIA. III--did not significantly modify either the biosynthesis of PGI2 in vitro or the PGI2 synthetase activity of heart tissue. did not significantly inhibit TXA2 biosynthesis in vitro but markedly reduced the TXA2 synthetase activity of heart tissue: for a microsomal fraction concentration of 100 micrograms protein, the ID50 was 6.37 X 10(-5) M +/- 1.29 X 10(-8) M. Thus III behaves as a specific inhibitor of the TXA2 synthetase activity of heart tissue and could have a beneficial use in therapeutics.

[Synthesis and pharmacologic study of several spirohydantoins: relation to conformation]. / Synthèse et approche pharmacologique de quelques spirohydantoines: relation avec la conformation.

Using two routes starting from cyclanones, it has been possible to prepare two series of spirohydantoins substituted or not on the hydantoin nucleus nitrogen. These compounds exhibited low toxicity on pig lens aldose reductase (except for two compounds). A discussion is given on the steric and geometric requirements for effective enzyme inhibiting activity.