[Causal relationship: and if "yes", and if "not"... on basis of which criterias?]

A woman was referred to us 4 days after the sudden onset of continuous rotatory vertigo. The diagnosis of a left vestibular neuronitis was made. During the investigations, a meningioma of the contralateral posterior fossa was discovered. Is there any relationship between the two disorders? The etiology of peripheral vestibular disorders remains poorly understood in most cases. Anomalies of cells surrounding the sensory organs have been demonstrated in post-mortem examination of the inner ear of patients with a vestibular deficit that could be caused by a "biological stress". Therefore there may be a link between left vestibular deficit and the mass of the right posterior fossa, considered as a fortuitous discovery, at first.

Study of PMS777, a new type of acetylcholinesterase inhibitor, in human HepG2 cells. Comparison with tacrine and galanthamine on oxidative stress and mitochondrial impairment

Acetylcholinesterase inhibitors are commonly used as cognitive enhancers for dementia in aged people. Among them, tacrine (THA) but not galanthamine, was shown to exhibit hepatotoxicity which reduces its clinical use. PMS777, both a PAF antagonist and a new potent acetylcholinesterase inhibitor was recently demonstrated to reverse scopolamine-induced amnesia in mice without toxicity. In the present study, the effects of THA, galanthamine and PMS777 were compared in HepG2 cells on the oxidative parameters involved in the reported hepatotoxicity of THA. THA (> or = 10 microM) induced an oxidative stress as shown by elevated ROS and MDA production and by a decrease in GSH level. Moreover, mitochondrial membrane potential and redox status were decreased. At low concentrations (< or =10 microM), there was no significant disturbance. None of the oxidative stress markers was affected by PMS777 up to the maximum concentration tested and it is suggested that PMS777 is not cytotoxic for HepG2 cells. Galanthamine was also without cytotoxicity. Our results suggest that the toxic effect of THA above 10 microM may be caused by drug-induced mitochondrial energization impairment and destabilisation of membrane phospholipids associated with an oxidative stress. In contrast by preventing these dysfunctions, PMS777 could be safer than THA.

Structure-activity relationships in platelet-activating factor (PAF). 11-From PAF-antagonism to phospholipase A(2) inhibition: syntheses and structure-activity relationships in 1-arylsulfamido-2-alkylpiperazines

1-Benzoyl-2-alkyl piperazines are strong inhibitors of Group I and II secreted PLA(2)s. An improvement of their activity was obtained by replacing the amide function by a sulfamide and by introduction of electrodonor substituents on the para position of the benzenesulfonyl moiety. Neither the position on one of the carbon of the piperazine ring nor the absolute configuration of this carbon have an effect on the affinity for one or the other group of PLA(2), but the lipophilicity remains for these series an essential parameter. In addition structure-activity relationships allow new hypothesis on interaction of these piperazine derivatives with the catalytic site of PLA(2)s.

PMS-601, a new platelet-activating factor receptor antagonist that inhibits human immunodeficiency virus replication and potentiates zidovudine activity in macrophages

We assessed the anti-human immunodeficiency virus (anti-HIV) activity in vitro of new platelet-activating factor (PAF) receptor antagonists, as PAF and viral replication are thought to be involved in HIV neuropathogenesis. We found that PMS-601 inhibited proinflammatory cytokine synthesis and HIV replication in macrophages and potentiated the antiretroviral activity of zidovudine. These results suggest that PMS-601 is of potential value as an adjuvant treatment for HIV infection.

Structure-activity relationships on adrenoceptors and imidazoline-preferring binding sites (I(1,2)-PBSs). Part 1: Weak intramolecular H-bond and conformational flexibility in a new I1-PBS-selective imidazoline analogue, trans1-(4',5'-dihydro-1'H-imidazol-2'-yl)methyl-2-hydroxyindane (PMS 952)

The highly selective I1-PBS imidazoline analogue PMS 952 has been selected to study the incidence of intramolecular hydrogen bond and molecular flexibility on its biological activity. On one hand, the weak energy difference between three calculated conformers does not support the stabilization of one conformer by an internal hydrogen bond. The 3-D electrostatic map confirms this feature and the solvent effect does not significantly modify the relative energy of these conformers. On the other hand, the conformational spaces of the neutral and ionized forms present a great number of equilibrium structures, in a short energetic range (20 Kcal). The results are representative of an exceptional conformational flexibility due to a cooperative effect between several parts of the molecule.

Structure-activity relationships in platelet-activating factor (PAF). 10. From PAF antagonism to inhibition of HIV-1 replication

Excessive levels of PAF and cells of macrophage lineage appear to play an important role in neuronal cell injury, inflammatory syndrome, and HIV replication in CNS resulting in AIDS dementia complex (ADC). The beneficial effects of PAF receptor antagonists are evident and give rise to expected therapeutic strategies for neurotrauma. Piperazine derivatives bearing a "cache-oreilles" (ear-muff) electronic distribution are able to inhibit in vitro PAF effects and, thus, could be used in pathologies where this mediator is involved. Therefore, their potential anti-HIV activity was investigated, and we find that (i) these PAF antagonists are effectively active in HIV-infected monocyte-derived macrophages (MDM) but there is no correlation between both anti-HIV and anti-PAF activities; (ii) the presence of a carbamate function (compounds 1a-d) is favorable to the antiviral activity; (iii) the lipophilicity of the substituent on the piperazinic cycle seems to be less important for the anti-PAF activity than for the antiviral one. Our leading compound, PMS 601 (compound 1a), presents a dual activity with IC(50) of 8 and 11 microM for anti-PAF and anti-HIV activity, respectively, without cytotoxic events at 1000 microM in MDM. Although its mode of action is not clearly defined, these data suggest that PMS 601, which displays no effect on acellular reverse transcriptase or protease tests, deserves further investigation in the treatment of HIV-1-associated dementia.

[Antiretroviral ant anti-inflammatory properties of a novel platelet activation factor antagonist, PMS-601]

The platelet-activating factor (PAF) plays a major role in neuropathogenesis associated with human immunodeficiency virus (HIV) infection by enhancing the inflammatory syndrome and viral replication, particularly in cells of the macrophage lineage, and its neurotoxic properties. We therefore evaluated the ability of PAF-R antagonists to inhibit HIV-1 replication and down-modulate the synthesis of pro-inflammatory mediators in healthy or HIV-1-infected macrophages. PMS-601 demonstrated the highest anti-HIV activity. Considering its mode of action and anti-inflammatory properties, PMS-601 interferes with early and late steps of the HIV biological cycle and decreases the synthesis of PAF, TNF-alpha, MIP-1 alpha, MIP-1 beta and RANTES. Altogether, these results suggest that PAF-receptor antagonists, and particularly PMS-601, could be of potential value as treatment adjuvants in HIV infection.

A new phospholipase A2 inhibitor, unrelated to substrate analogues: kinetic characterization of the inhibition of secretory phospholipases A2 by PMS 832

Starting from a series of compounds which were known to be PAF antagonists, we have synthesized molecules that are good inhibitors of PLA2s of groups I or II, with IC50 in the micromolar range (Binisti et al., 1997). In this report we investigate the mechanism of inhibition of bovine and porcine pancreatic phospholipases A2 (group I), and platelet lysate phospholipase A2 (group II) by one of these compounds, 1-(4'-methoxybenzoyl)-2-n-tridecylpiperazine (PMS 832). We show that PMS 832 behaves as a reversible, competitive inhibitor, with Ki values of 4.1 +/- 1.2 and 1.5 +/- 0.4 microM for porcine pancreatic phospholipase A2 and platelet lysate phospholipase A2, respectively. PMS 832 failed to inhibit platelet activation induced by several agonists and was also found to be inactive towards phospholipase C from Bacillus cereus, indicating a high specificity for phospholipase A2 inactivation. Thus, PMS 832 and its derivatives could serve as interesting tools to investigate the role of extracellular phospholipases A2 in inflammatory processes, and may be useful in the development of new anti-inflammatory agents.

Design and modeling of new platelet-activating factor antagonists. 3. Relative importance of hydrophobicity and electronic distribution in piperazinic series

Extensive analysis of results obtained in earlier publications (Lamouri et al. (1993); Tavet et al. (1996) led us to reexamine our interpretations and conclusions about hydrophobic and electronic distribution effects. In terms of hydrophobicity balance, a bilinear regression has been derived between lipophilicity of the appendix in position-2, f(Z), versus anti-aggregant activity for 45 homogeneous compounds including data from both papers (Parts 1 and 2). These features reinforce the conclusion that the kinetic phase in the experimental medium is probably determinant. Consequently, the role of electronic distribution is preponderant at the level of the receptor. Two specific studies demonstrated that decrease of negative electrostatic potential effects of the largest "cache-oreilles' system lowered the anti-aggregant activity (comparison of compounds 1f, 2, 3 and 4), on one hand and, on the other hand, the combined effect of phenyl groups created negative wells, as observed there with a diphenyl-methyl moiety, instead of an usual trimethoxybenzoyl function (comparison of compounds 8 and 10). It was clearly demonstrated that this moiety does not work by means of a hydrophobic anchorage: comparison of compounds 9, 10 and 11.

Preventive effects of two PAF-antagonists, PMS 536 and PMS 549, on cyclosporin-induced LLC-PK1 oxidative injury

The present study was undertaken to evaluate the effects of platelet activating factor (PAF) antagonists, PMS 536 and PMS 549, on LLC-PK1 toxicity induced by Cyclosporin A (CsA). The LLC-PK1 cell line was used as an in vitro model. CsA cytotoxicity was determined in relation with ATP content. Alkaline phosphatase and N-acetyl-beta-glucosaminidase activities, which are directly correlated with tubular cell damage, were used as markers for renal injury. CsA alone provoked in the LLC-PK1 cell line a marked decrease in cell viability (55%) and membrane integrity (56%), and a significant increase in AP and NAG activities and in oxidized glutathione level. The ATP decrease and the ADP increase, resulting in a decline of the ATP/ADP ratio, is indicative of an anoxic energy charge. Co-treatment with CsA plus PMS 536 or PMS 549 resulted in a minor decrease in cell viability and in significant membrane integrity recovery. Moreover, the ATP depletion and the increase in ATP metabolites, hypoxanthine and uric acid induced by CsA were strongly prevented by PAF antagonists. In contrast, GSSG level remained high as in CsA-treated cells, but GSH level was in the range of controls. Our results suggest that both PAF antagonists attenuate CsA oxidative injury and prevent energy metabolism disturbances probably by maintaining cell integrity. The lipophilicity of both molecules may be responsible for membrane stabilization and may confer the protective effects observed in energy metabolism. The results obtained with PMS 536 and PMS 549 are indicative of interactions between PAF and CsA in renal injury and suggest the therapeutic potential of these PAF-antagonists against CsA-induced nephrotoxicity.

Structure-activity relationships in platelet activating factor. 9. From PAF-antagonism to PLA2 inhibition

Many important mediators of inflammation result from the liberation of free arachidonic acid from phospholipid pools, which arise from the action of phospholipase A2 (PLA2). Therefore the inhibition of this enzyme would be an important treatment in many inflammatory disease states. Starting from a series of compounds which are known as PAF-antagonists, we have synthesized new molecules. These new compounds inhibited various secretory PLA2s, with IC50's in the mumol range. This allowed us to analyze the structure-activity relationships for PLA2 inhibition. The results showed that inhibition of secretory PLA2 depends on the length of the alkyl chain, with an optimum for 13 to 17 carbons, which is in agreement with X-ray crystallographic and nuclear magnetic resonance (NMR) studies on the active site of PLA2s, and that a free nitrogen on the piperazine ring is required to ensure a good inhibitory potency.

Design and modeling of new platelet-activating factor antagonists. 2. Synthesis and biological activity of 1,4-bis-(3',4',5'-trimethoxybenzoyl)-2-alkyl and 2-alkyloxymethylpiperazines

In the continuation of our investigations on the structure of platelet-activating factor (PAF)-receptor, 25 additional 2-substituted 1,4-bis-(poly- and mono methoxybenzoyl)-piperazines were synthesized and their in vitro biological activities measured. Substituent at position 2 is representative of the classical balance lipophilicity/hydrophilicity, i.e. alkyl, phenylalkyl, alkoxy and polyalkoxy groups. A potent PAF-induced platelet aggregation inhibitory activity measured in PRP medium is obtained with 5c, IC50 = 6 x 10(-8) M, which displaces the [3H]PAF from platelet membrane with an EC50 = 6 x 10(-8) M, and compound 4 presents an EC50 of 3 x 10(-8) M. Examination of structure-activity relationships shows that molecules bearing a hydrophilic or slightly hydrophobic appendix in position-2 are still potent; their IC50 being included between 10(-6) and 10(-7) M. After quantitative analysis, it seems that in PRP medium, the role of serum albumin must be taken into account instead of a pure hydrophobic interaction of the appendix Z into the receptor. The role of the methoxy groups in producing a potent antagonistic activity is demonstrated by syntheses of several 2-octylpiperazine analogs. These specific features will be quantitatively analysed in the following related publication (part 3).

4-Alkoxybenzamidines as new potent phospholipase A2 inhibitors

A series of 4-alkoxybenzamidines was synthesized, varying the number of carbons of the alkyl chain, and their potency as phospholipase A2 (PLA2) inhibitors was evaluated. The relationship between their capacity to inhibit PLA2 activity and their lipophilicity was examined. The optimum of the inhibitory effect against two extracellular PLA2S from rabbit platelets and bovine pancreas was observed with compounds bearing an alkyl chain of 12 and 14 carbons. These 4-dodecyl and tetradecyloxbenzamidines inhibited bovine pancreatic and rabbit platelet lysate PLA2S with IC50 values of 3 microM and 5-5.8 microM, respectively. The mechanism of inhibition was of the competitive type. In addition, 4-tetradecyloxbenzamidine was shown to exert an antiinflammatory effect in vivo on the carrageenan-induced rat paw oedema. These results show that 4-tetradecyloxybenzamidine will serve as an interesting tool to investigate the physiological role of mammalian-secreted PLA2, both in vitro and in vivo.

Design and modeling of new platelet-activating factor antagonists. 1. Synthesis and biological activity of 1,4-bis(3',4',5'-trimethoxybenzoyl)-2-[[(substituted carbonyl and carbamoyl)oxy]methyl]piperazines

To further investigate our hypothesis on the structure of the platelet-activating factor (PAF) receptor, 35 compounds derived from 1,4-bis(3',4',5'-trimethoxybenzoyl)piperazine were synthesized and their in vitro antagonistic effect was measured. Substitution of the compounds in position 2, by ester or carbamate groups, giving increased steric hindrance and hydrophobicity, increased the platelet aggregation inhibitory activity from 2 microM (without substitution, compound 2) to 0.07 microM (compound 1h) and gave a maximum displacement of [3H]PAF from platelet membrane of 0.05 microM (compound 1k). It appears that the PAF antagonistic effect is only weakly enantiospecific, as observed in many cases including antagonists structurally related or not to PAF. 3D electrostatic potential maps (calculated at -10 kcal/mol) of such compounds revealed a double "Cache-oreilles" (ear-muffs) system. One of these systems has been previously described (distance between atoms generating negative wells, 11-14 A). The second shorter "Cache-oreilles" (6-7 A) system appears to be required for increased PAF antagonistic activity. This short distance between groups generating the negative wells is present in the gingkolides, a series of naturally occurring PAF antagonists. The present study indicates that the structure of the PAF receptor may be more complicated than our initial hypothesis and may be a tetrapolarized structure, with alternants of electropositive and hydrophobic areas. This modified hypothesis is in agreement with recent publications concerning PAF antagonists bearing a cationic moiety.

Production and characterization of antibodies to platelet-activating factor

Antibodies directed against platelet-activating factor (PAF) have been raised in rabbits immunized with a novel platelet-activating factor analogue-conjugate. An analogue of PAF with a carbon double bond at the terminal end of the alkyl chain was subjected to ozonolysis and converted to the aldehyde. The aldehyde was coupled to thyroglobulin by reductive alkylation and rabbits were immunized via either intramuscular or intradermal routes in complete Freund's adjuvant. The antibodies are specific for PAF with a preference for the optically active (R)-enantiomer. There appears to be a requirement for antibody binding of an alkyl chain of up to 18 Carbon atoms at C1, and an acetyl group in the C2 position. The ability of a number of structural analogues to inhibit binding of tracer to the antibody is related to the biological activity of the analogue, and therefore may reflect the structural domains that are critical for PAF to interact with its receptor.

Structure-activity relationships in platelet-activating factor (PAF antagonists). 6. Synthesis and in vitro antagonistic activities of 2-substituted 5-oxotetrahydrofurans

The synthesis of 2,5-disubstituted tetrahedrofuran compounds as potential in vitro PAF antagonists is described. Results demonstrate that the structural requirements for potent PAF antagonist activity are: a moderate lipophilic group or a trimethoxyphenyl group in position-5, and a long aliphatic chain terminated by a cationic polar head in position-2. The cis-trans configuration does not induce any difference in biological activity. Some conformational features of the putative PAF receptor are proposed in light of the present findings.

PAF receptor structure: a hypothesis

Different hypotheses of the structure of platelet-activating factor (PAF) receptor based on structure-activity relationships of agonists and antagonists are reviewed. For an agonistic effect, strong hydrophobic interactions and an ether function are required in position-1 of the glycerol backbone; chain length limitations and steric hindrance demand a small group in position-2. The unusual structural properties of non-PAF-like antagonists required 3-D electrostatic potential calculations. This method applied to seven potent antagonists suggests a strong "Cache-orielles" (ear-muff) effect, i.e., two strong electronegative wells (isocontour at -10 Kcal/mole) are located at 180 degrees to each other and at a relatively constant distance. Initial consideration of the "Cache-oreilles" effect implied the structure of a bipolarized cylinder of 10-12 A diameter for the receptor. However, very recent results on studies with agonists and antagonists structurally similar to PAF suggest that the receptor may in fact be a multi-polarized cylinder.

PAF receptor and "Cache-oreilles" effect. Simple PAF antagonists

Nine simple and structurally flexible PAF antagonists were synthesized and their inhibitory effects on PAF induced platelet aggregation were measured. Compounds with PAF antagonistic activity exhibited a negative electrostatic potential generated by two trimethoxyphenyl groups (isocontour at -10 Kcal/mole) at various distances between the negative clouds. The optimal distance between the atoms generating the "cache-oreilles" system for exhibiting potent PAF antagonistic activity is estimated to be 11-13 A. In the flexible molecules studied, the dispersion of the electronic distribution is not necessarily favorable for anti-PAF activity. The data support the simple bipolarized model for the PAF receptor that has been proposed by the authors.

PAF-receptor. III. Conformational and electronic properties of PAF-like agonists and antagonists

In order to compare electronic and conformational properties of PAF-agonists and PAF-antagonists, 14 analogues structurally related to PAF were studied. A common conformation of the glycerol backbone was present in all agonists and all constrained or flexible antagonists. The distinction between agonists and antagonists appears to be casted on position-2 where the folded conformation of the substituent for agonists should be the most probable. In position-3 the gauche conformation can be adopted by all the analysed compounds. The electrostatic potential well at -30 kcal/mol stretches to the carbonyl group in position-2 in the folded conformation of the agonists. On the contrary, in constrained antagonists, a second negative zone appears around the carbamate group. Given the modelling results, the triethylammonium PAF analogue considered in literature as a weak agonist, was resynthesized and proved to be more potent than previously reported. These experimental results confirm our hypothesis in terms of a common conformation of agonist and antagonist PAF-like molecules.

PAF receptor. 2. Quantitative hydrophobic contribution of the agonist's etheroxid chain

In order to undertake a quantitative assessment of the contribution of the hydrophobic effect of the etheroxid chain to agonistic activity, it was necessary to include in the calculated data a highly lipophilic platelet-activating factor (PAF) analogue. The synthesis of such a compound--racemic 1-O-docosyl-2-O-acetylglycero-3-phosphocholine (C22 PAF)--is described. The regression analysis performed with data of 14 etheroxid analogues (reviewed by Godfroid et al., 1987), combined with data obtained with C22 PAF, is significant with respect to a parabolic evolution between lipophilicity of the chain and the logarithm of relative platelet stimulation. This result is characteristic of a hydrophobic interaction between the agonist and the PAF receptor.

PAF-receptor. 1. 'Cache-oreilles' effect of selected high-potency platelet-activating factor (PAF) antagonists

Three-dimensional electrostatic maps were calculated for six potent antagonists of platelet-activating factor (PAF), the antagonists being selected for their apparent structural heterogeneity. The molecules examined were the compact Ginkgolides BN 52020, BN 52021 and BN 52022 (1, 2 and 3), the semi-rigid kadsurenone (4), a flexible synthetic dinor type C furanoid lignan L-652,731 (5a) and the triazolothienobenzodiazepine WEB 2086 (7). Calculation of the electrostatic potential generated around all the above molecules showed the existence of two wells of negative potential or 'cache-oreilles' (ear-muffs), i.e., the isocontours drawn at -10 kcal/mol, located at 180 degrees from each other and separated by a maximum distance of 22-27 A. Except for the synthetic dinor type C furanoid lignan (5a), the molecules also presented a moderate hydrophobic fragment, which constitutes a third point of interaction with the high-affinity binding site in rabbit and human platelets. The findings of the present study allow speculation that this high-affinity acceptor site may be a 'polarized cylinder' with a diameter of 10-12 A.

Structure-activity relationship in PAF-acether. 4. Synthesis and biological activities of carboxylate isosteres

The synthesis and biological characterization of some 3-carboxylate isosteres of PAF-acether structurally modified in positions 1 (ether, carbamate), 2 (acetoyl, ethoxy), and 3 (chain length and polar head group) are reported. All derivatives present antagonist activities against PAF-acether-induced effects in vitro (platelet aggregation) and in vivo (bronchoconstriction and thrombocytopenia in guinea pig and, to a lesser extent, hypotension in rat). The functional modifications presented here do not modify dramatically the potency of antagonist activities, and there is no enantioselectivity. All of the isosteres are specific PAF-acether antagonists, except the 1-carbamoyl analogue, which is also potent against acetylcholine-induced hypotension and bronchoconstriction.

Alkyl analogs of diacylglycerol as activators of protein kinase C

Diacylglycerols which activate protein kinase C have the 1,2-sn configuration. Short-chain saturated fatty acids or long-chain unsaturated fatty acids are required for supporting the potency of these lipids. Using alkyl analogs such as 1-O-decyl-2-O-decanoylglycerol, 1-O-decanoyl-2-O-decylglycerol, 1,2-O-didecylglycerol, 1-O-hexadecyl-2-O-acetylglycerol and 1-O-decyl-2-O-acetylglycerol, we showed that the ether bond was consistently associated with a loss of activity to varying extents. The results suggest that the ester bond in the 1-position is a major determinant of diacylglycerol-mediated protein kinase activation.

Structure-activity relationship in PAF-acether. 3. Hydrophobic contribution to agonistic activity

The synthesis of some selected PAF-acether homologues with an alkoxy-chain length from C1 to C20 in position 1 is described. All agonist activities are closely correlated among themselves and with the calculated fatty-chain hydrophobicity. After a discussion on recent published results and comparison with our data, we conclude that the ether oxide function is absolutely essential at the glycerol 1-position for potent agonist activity and that potency correlates well with hydrophobicity parameters. We indicate the importance of steric and configurational constraints.

Effects of a new anorectic drug (PM 170) on development of gold thioglucose-induced obesity in mice

Gold thioglucose (GTG)-injected mice and lean mice were treated for 16 days with PM 170. The body weight and body fat were significantly increased by GTG injection and these increases in the GTG-obese group were reduced by PM 170. PM 170 also reduced food intake (16%), total body triacylglycerol (51%) and total body cholesterol (36%). Basal lipolysis of white adipose tissue, as measured by glycerol release, was stimulated by 150%. Compared to GTG-PM 170 mice, body weight gain was 2 times higher in GTG-pair-fed mice. Body fat and total body lipid content remained elevated.

Effects of PAF-acether and structural analogues on platelet activation and bronchoconstriction in guinea-pigs

PAF-acether (platelet-activating factor) (1-O-alkyl-2-acetyl-sn-glycerol-3-phosphorylcholine) induces platelet-dependent bronchoconstriction in the guinea-pig which correlates with its in vivo thrombocytopenic effect. We investigated the influence of modifications of the polar head group in position 3 of the glycerol skeleton of PAF-acether on guinea-pig platelet activation and bronchoconstriction. PAF-acether itself induced concentration-dependent platelet activation (EC50 for aggregation = 0.41 nM and EC20 for secretion of ATP = 0.56 nM). The 3-phosphoryl-N-methyl-morpholino ethanol analogue was slightly more active than PAF-acether and the 3-phosphoryl-N-methyl-piperidinium ethanol, 3-phopshoryl-(N-methyl-piperidino-3') methanol and 3-phosphoryl-(N-methyl-hydroxy-4') piperidine analogues were equieffective to PAF-acether in activating platelets. The 3-phosphoryl-piperidino ethanol analogue was 8 times less active than PAF-acether; the 3-phosphoryl-morpholino ethanol analogue and the 1-O-octadecyl-2-O-acetyl-3-O-[trimethyl-ammonio)-propyl) glycerol were inactive up to 1 microM. Our data show that the choline head group is not a compulsory requirement for activity. When injected i.v. to the propranolol-treated guinea-pigs, the platelet-activating analogues also induced bronchoconstriction. Two PAF-acether antagonists, compounds 48740 RP and BN 52021, inhibited PAF-acether-induced platelet activation when added to PRP at the final concentration of 0.1 mM (aggregation inhibited by 91 +/- 4 and by 94 +/- 3% respect.; secretion inhibited by 80 +/- 12 and 79 +/- 10% respectively, mean +/- S.E.M., n = 4). Both antagonists also suppressed platelet activation and in vivo bronchoconstriction, thrombocytopenia, leukopenia and hypotension induced by PAF-acether and the various analogues. Our results indicate that PAF-acether and the analogues studied trigger platelet activation and the consequent bronchoconstriction through mechanisms which share sensitivity to same antagonists.

Structure-activity relationship in PAF-acether. 2. rac-1-O-Octadecyl-2-O-acetyl-3-O-[gamma-(dimethylamino)propyl]glycerol

Two products without phosphoryl groups, 1-O-octadecyl-2-O-acetyl-3-O-[gamma-(dimethylamino)propyl]glycerol and its quaternary salt, were synthesized from 1-O-octadecyl-2-O-benzylglycerol. In comparison with PAF-acether, they lost aggregating and bronchoconstrictive activities and did not show any antagonistic effects.

Radio-labelling of 1-O-alkyl, 2-O-acetyl, sn-glycero-3-phosphorylcholine, 1-O-(9,10-di3H)-octadecyl PAF-acether

3H-labelling of 1-3H-PAF-aceter was prepared by catalytic reduction of 1-O-(9,10)-octadecenyl-2-O-benzyl-sn-glyceryl-3-phosphorylcholine and then acetylated. 5 mumoles of this dehydro derivative dissolved in methanol was treated during 4 hours with tritium gas (80 Ci) and compressed until 1.1 bar by an automatic tritium transfer unit [1]. The catalyst was removed by filtration over Millex (Millipore) and labile tritium atoms eliminated by rotatory flash evaporation. The chemical purity was checked by 3H scanning and autoradiography. It was finally recovered through preparative thin-layer chromatography and then acetylated. The specific radioactivity was found to be close to 40-50 Ci/mmole.

Biosynthesis of platelet-activating factor. I. Evidence for an acetyl-transferase activity in murine macrophages

Platelet-activating factor (PAF-acether; 1-0-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) is released from murine peritoneal adherent cells by inflammatory and non-inflammatory stimuli. We have found, in extracts from these cells, an enzyme activity that synthesizes. PAF-acether from synthetic lyso-PAF-acether by transferring the acetyl moiety of acetyl-coenzyme A onto the lyso-PAF-acether molecule. The enzyme is stabilized by 1 mM dithiothreitol, is calcium-dependent, has an apparent Km of 172 microM for acetyl-CoA and is active in a 6-8 pH range. When the acetyl-CoA substrate is replaced by propionyl-CoA, an ether lipid is produced which turns out to be as potent an aggregating agent as PAF-acether. In all cases, the products of the reaction were characterized by their behaviour in platelet-aggregation tests and their high-pressure liquid chromatography (HPLC) elution profiles. The precise definition of this acetyl-transferase is of primary importance for the development of new pharmacological agents capable of moduling a potent platelet aggregating factor.

New total synthesis and high resolution 1H NMR spectrum of platelet-activating factor, its enantiomer and racemic mixtures

A new method of synthesis of octadecyl platelet-activating factor (PAF; 1-O-octadecyl 2-O-acetyl sn-glycero-3-phosphorylcholine) is described. Its advantage is to proceed by way of the 'lyso-PAF' which may be substituted by various groups, while avoiding the inconveniences of the total synthesis already described. Moreover, the intermediates in synthesis are easier to purify, with better yields. The platelet-aggregating activity of synthetic PAF, is enantiomer (3-O-octadecyl) and racemic mixtures were 2.7 . 10(-10), 1.7 . 10(-7) and 2.2 . 10(-10) M, respectively. These results indicate the stereospecificity of platelet activation induced by PAF.

Quantitative structure-activity relationships for N-[N',N'-disubstituted-amino)acetyl]arylamines for local anesthetic activity and acute toxicity

The synthesis and physicochemical properties of a series of N-[N',N'-disubstituted-amino)acetyl]arylamines are described. A QSAR method is applied to local anesthetic activity and acute toxicity by means of a "nonclassic" substituent variation involving a modification on both aryl and amino moieties. The choice of the different parameters (partition coefficient, pKa, connectivity index, molar refraction, and molar volume) is discussed and their different methods of determination are described. Molar refraction is the parameter which explains best the variance of the local anesthetic activity, and the quadratic regression with MR leads to a "posteriori" synthesis of one compound with optimized activity. However, the partition coefficient is the most explicative parameter for intravenous toxicity.