Group IIA secreted/synovial phospholipase A(2) (GIIAPLA(2)) is an enzyme involved in the synthesis of eicosanoids such as prostaglandin E-2 (PGE(2)), the main eicosanoid contributing to pain and inflammation in rheumatic diseases. We designed, by molecular modeling, 7 novel analogs of 3-{4-[5(indol-1-yl)pentoxy]benzyl}-4H-1,2,4-oxadiazol-5-one, denoted C1, an inhibitor of the GIIAPLA(2) enzyme. We report the results of molecular dynamics studies of the complexes between these derivatives and GIIAPLA(2), along with their chemical synthesis and results from PLA(2) inhibition tests. Modeling predicted some derivatives to display greater GIIAPLA(2) affinities than did C1, and such predictions were confirmed by in vitro PLA(2) enzymatic tests. Compound C8, endowed with the most favorable energy balance, was shown experimentally to be the strongest GIIAPLA(2) inhibitor. Moreover, it displayed an anti-inflammatory activity on rabbit articular chondrocytes, as shown by its capacity to inhibit IL-1 beta-stimulated PGE(2) secretion in these cells. Interestingly, it did not modify the COX-1 to COX-2 ratio. C8 is therefore a potential candidate for anti-inflammatory therapy in joints.

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 (⩾10 μM) 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 (⩽10 μM), 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 μM 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.

We have recently reported the discovery of a series of specific inhibitors of human group IIA phospholipase A(2) (hGIIA PLA(2)) to display promising in vitro and in vivo properties. Here we describe the influence of different structural modifications on the specificity and potency against hGIIA PLA(2) versus porcine group IB PLA(2). The SAR results, as well as the logP and pK(a) values of oxadiazolone determined in this work, provide important information towards the comprehension of the mode of action of this kind of compounds.

In the search for highly selective and potent cholinesterase inhibitors (AChEI) being able to improve oxidative injury, PMS777, a tetrahydrofuran derivative, was designed as a novel dual PAF and acetylcholinesterase inhibitor. The aim of this study was to investigate the modulatory effects of PMS777 and galanthamine, another AChEI, on the oxidative injury induced in neuronal cells. The SK-N-SH cells stimulated with LPS + IL-1β were selected to investigate the direct inhibitory effect of PMS777 and galanthamine. LPS + IL-1β induced oxidative injury as assessed by ROS production (29%), GSH depletion (11%) and loss of mitochondrial activity (22%). GSH depletion was never decreased by either drug. In contrast, ROS production and mitochondrial activity were totally prevented by addition of PMS777 but not galanthamine. PMS777 also inhibits butylcholinesterase and it shows selectivity for acetylcholinesterase. Thus, this PAF antagonist inaugurates a new type of AChEI, able to fight oxidative injury. Therefore, PMS777 could be of interest on patients with cognitive impairments and inflammatory damage, as in AD.

3-(4-Tetradecyloxybenzyl)-4H-1,2,4-oxadiazol-5-one (PMS1062 or 1) can probably act as a PLA(2)-II inhibitor on the acute inflammation model, but its highly lipophilic character could prevent it from being biodistributed effectively. In this work, based on a molecular modeling study, we have proposed a model that may provide compounds retaining both anti-PLA(2) activity and specificity while becoming active per os. Moreover, molecular dynamics and energy minimization enabled us to characterize the lowest-energy complexes of each derivative. Energy balances taking account of the conformational energy changes of both partners, along with the drug-protein interaction, were performed, and were further completed by single-point computations of the contributions of solvation/desolvation to the binding. The ordering of the resulting energy balances was found to be fully consistent with the experimentally ascertained ordering of affinities inferred from the IC50 values. The essential role of an indole group partaking in cation-pi and hydrophobic interactions, together with the Ca-II-chelating oxadiazolone ring, was highlighted for the best binding compound. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).

Starting from 4-tetradecyloxybenzamidine (PMS815), a non-specific inhibitor of GI and GII PLA(2)s, we report in this work the discovery of the specificity through design, synthesis and structure-activity relationships studies of different kinds of PMS815 derivatives. The leading compound, 4,5-dihydro-3-(4-tetradecyloxybenzyl)-1,2,4-4H-oxadiazol-5-one (9b, PMS1062) exhibits a micromolar IC50 towards three group II PLA(2)s, while inactive towards four group I and one group III enzymes in two in vitro enzymatic assay conditions. It is also able to block the PLA(2)-II activities induced by LPS and IL-6 in HepG(2) cell line and no cytotoxicity is observed when PMS1062 is tested up to a concentration of 100 mu M in two different cell lines (A549 and LLC-PK1). (c) 2005 Elsevier SAS. All rights reserved.

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.