A new acetylcholinesterase inhibitor with anti-PAF activity modulates oxidative stress and pro-inflammatory mediators release in stimulated RAW 264.7 macrophage cells. Comparison with tacrine.

Inflammatory injury and induction of oxidative stress have been implicated as causative factors in neurodegenerative diseases such as Alzheimer's disease (AD). Using LPS-stimulated RAW 264.7 macrophages as a model of inflammatory injury, LPS was found to stimulate ROS production (159%), GSH depletion (15%) and loss of mitochondrial activity (32%) as well as TNFalpha release (40%), and NO production (13.7 times), all parameters involved in AD. PMS777, a tetrahydrofuran derivative, designed as a dual PAF and acetylcholinesterase inhibitor, was found to decrease ROS (up to 32%) and NO production (up to 5 times), TNFalpha release (33%). PMS777 also prevents loss of mitochondrial activity, and GSH depletion. In contrast, tacrine was found to decrease ROS production (57% up to 102%) and TNFalpha level (up to 30%). It decreases NO release only at the highest concentrations without preventing loss of mitochondrial activity and GSH depletion. In this study, we show that PMS777 is strongly anti-inflammatory against LPS-induced responses in RAW 264.7. Differential effects between PMS777 and tacrine could be attributed to the anti-PAF activity of PMS777 which was able to fight inflammatory events and oxidative injury whereas tacrine only minimizes them. PMS777 could open a new approach in the treatment of AD.

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.

Synthesis and characterization of [125I]N-(2-aminoethyl)-4-iodobenzamide as a selective monoamine oxidase B inhibitor.

We described the radiosynthesis of an analog of Ro 16-6491, [125I]N-(2-aminoethyl)-4-iodobenzamide, for SPECT exploration of the monoamine oxidase B (MAO-B) in human brain. The radiolabelling was carried out by nucleophilic exchange of the brominated precursor at solid-state phase in presence of ammonium sulphate. The radiochemical purity of radioiodinated product was higher than 95%. In comparison with Ro 16-6491, the in vitro studies showed a good selectivity of stable N-(2-aminoethyl)-4-iodobenzamide for MAO-B but a slightly lower affinity. Biodistribution studies in the rat showed a high and selective uptake of this compound in the pineal gland 1 h after i.v. injection. The cerebral uptake was low, but the coupling of [125I]N-(2-aminoethyl)-4-iodobenzamide with a lipophilic radical to enhance the passage through the blood-brain barrier can be envisaged.

Iododerivative of pargyline: a potential tracer for the exploration of monoamine oxidase sites by SPECT.

Monoamine oxidases are important in the regulation of monoaminergic neurotransmission. An increase in monoamine oxidase B (MAO B) has been observed in some neurodegenerative diseases, and therefore quantification of cerebral MAO B activity by SPECT would be useful for the diagnosis and therapeutic follow-up of these disorders. We have developed an iodinated derivative of pargyline, a selective inhibitor of MAO B, in order to explore this enzyme by SPECT. Stable bromo and iodo derivatives of pargyline were synthesized and chemically characterized. The radioiodinated ligand [125I]-2-iodopargyline was obtained with high specific activity from the bromo precursor by nucleophilic exchange. Affinity and selectivity of 2-iodopargyline were tested in vitro. Biodistribution study of [125I]-2-iodopargyline was performed in rats. Radioiodinated ligand were obtained in a no-carrier-added form. 2-iodopargyline has a higher in vitro affinity for MAO B than pargyline. However, the in vitro selectivity for MAO B was better for pargyline than for 2-iodopargyline. Ex vivo autoradiographic studies and in vivo saturation studies with selective inhibitors of MAO showed that the cerebral biodistribution of [125I]-2-iodopargyline in the rat is consistent with high level binding to MAO B sites in the pineal gland and in the thalamus. In conclusion, 2-iodopargyline preferentially binds in vivo to MAO B sites with high affinity. However, its selectivity for MAO B in rats is not very high, whereas this ligand binds to a lesser extent to MAO A. It will be then of great value to evaluate the specificity of 2-iodopargyline in humans. This new ligand labeled with 123I should therefore be a suitable tool for SPECT exploration of MAO B in the human brain.

An iodinated derivative of moclobemide as potential radioligand for brain MAO-A exploration.

In vivo evaluation of MAO-A would be of great value for the diagnosis and follow-up of therapy of depression. In order to perform this exploration by SPECT, we developed an iodinated derivative of the reversible MAO-A inhibitor, moclobemide. Ro 11-9900 was synthesized and analysed by IR, NMR and HPLC. Radioiodination was carried out by nucleophilic exchange of [125I] on the brominated precursor, and yielded [125I]-Ro 11-9900 with high specific activity. In vitro experiments on rat brain homogenates showed that Ro 11-9900 had poor inhibitory activity on MAO-A, as already described for moclobemide. By contrast, in vivo biodistribution in the rat brain showed that [125I]-Ro 11-990 accumulated in a region corresponding to the localization of locus coeruleus known for its high density of MAO-A. Moreover, preinjection of the irreversible MAO-A inhibitor clorgyline (10 mg.kg-1) prevented accumulation of radioactivity by 40 to 60% and we found that the radioactivity in the brain corresponded exclusively to [125I]-Ro 11-9900 and not to a metabolite. [125I]-Ro 11-9900 was highly accumulated in the pineal gland, both on MAO-A and on MAO-B sites. We concluded that the unmetabolized iodinated derivative of moclobemide, Ro 11-9900, preferentially labeled MAO-A in vivo in the rat brain. This compound would therefore be a potential tracer for evaluation of MAO-A by SPECT.

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.