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

Synthesis of ether lipids: natural compounds and analogues

Ether lipids are compounds present in many living organisms including humans that feature an ether bond linkage at the sn-1 position of the glycerol. This class of lipids features singular structural roles and biological functions. Alkyl ether lipids and alkenyl ether lipids (also identified as plasmalogens) correspond to the two sub-classes of naturally occurring ether lipids. In 1979 the discovery of the structure of the platelet-activating factor (PAF) that belongs to the alkyl ether class of lipids increased the interest in these bioactive lipids and further promoted the synthesis of non-natural ether lipids that was initiated in the late 60's with the development of edelfosine (an anticancer drug). More recently, ohmline, a glyco glycero ether lipid that modulates selectively SK3 ion channels and reduces in vivo the occurrence of bone metastases, and other glyco glycero ether also identified as GAEL (glycosylated antitumor ether lipids) that exhibit promising anticancer properties renew the interest in this class of compounds. Indeed, ether lipid represent a new and promising class of compounds featuring the capacity to modulate selectively the activity of some membrane proteins or, for other compounds, feature antiproliferative properties via an original mechanism of action. The increasing interest in studying ether lipids for fundamental and applied researches invited to review the methodologies developed to prepare ether lipids. In this review we focus on the synthetic method used for the preparation of alkyl ether lipids either naturally occurring ether lipids (e.g., PAF) or synthetic derivatives that were developed to study their biological properties. The synthesis of neutral or charged ether lipids are reported with the aim to assemble in this review the most frequently used methodologies to prepare this specific class of compounds.

Rational modification, synthesis and biological evaluation of N-substituted phthalazinone derivatives designed to target interleukine-15 protein

Interleukin (IL)-15 is a pleiotropic cytokine structurally close to IL-2 and sharing with the IL-2Rβ and γc receptor (R) subunits. IL-15 plays important roles in innate and adaptative immunity, supporting the activation and proliferation of NK, NK-T, and CD8⁺ T cells. Over-expression of IL-15 has been shown to participate to the development of inflammatory and autoimmune diseases and diverse T cell malignancies. This study is in continuity of our previous work through which a family of small-molecule inhibitors impeding IL-15/IL-2Rβ interaction with sub-micromolar activity has been identified using pharmacophore-based virtual screening and hit optimization methods. With the aim to improve the efficacy and selectivity of our lead inhibitor, specific modifications have been introduced on the basis of optimized SAR and modelisation. The new series of compounds generated have been evaluated for their capacity to inhibit the proliferation as well as the down-stream signaling of IL-15-dependent cells and to bind to IL-15.

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.

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.