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In search of multifunctional cholinesterase inhibitors as potential anti-Alzheimer drug candidates, tacrine-ferulic acid-NO donor trihybrids were synthesized and tested for their cholinesterase inhibitory activities, release of nitric oxide, vasodilator properties, cognition improving potency, and hepatotoxicity. All of the novel target compounds show higher in vitro cholinesterase inhibitory activity than tacrine. Three selected compounds (3a, 3f, and 3k) produce moderate vasorelaxation in vitro, which correlates with the release of nitric oxide. Compared to its non-nitrate dihybrid analogue (3u), the trihybrid 3f exhibits better performance in improving the scopolamine-induced cognition impairment (mice) and, furthermore, less hepatotoxicity than tacrine.

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder with multifactorial causes that requires multitargeted treatment. Inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) improve cholinergic signaling in the central nervous system and thus AChE inhibitors are well established in the therapy of AD to improve memory disturbances and other cognitive symptoms. On the other hand, AD patients benefit from reduction of pathologic glutamate-induced, Ca(2+)-mediated excitotoxicity by the N-methyl-d-aspartate receptor (NR) antagonist memantine. New drugs that simultaneously affect both cholinergic transmission and glutamate-induced excitotoxicity may further improve AD treatment. While connecting beta-carboline units by alkylene spacers in two different series of compounds and subsequent evaluation of their AChE/BChE-inhibitory potential, we found that several of these bivalent beta-carbolines were potent NR blockers. The most promising compound was a N(9)-homobivalent beta-carboline with a nonylene spacer, which displayed IC(50) values of 0.5 nM for AChE, 5.7 nM for BChE, and 1.4 microM for NR, respectively.

On the basis of the benz[d]indolo[2,3-g]azecine derivative 1 (LE300), structure-activity relations were investigated in order to identify the pharmacophore in this new class of ligands. Various structural modifications were performed and the inhibitory activities at human cloned D(1), D(2L), and D(5) receptors were measured by using a simple fluorescence microplate reader based calcium assay. Subsequently, the affinities of active compounds were estimated by radioligand binding experiments. Deleting one of the aromatic rings as well as replacing it by a phenyl moiety abolishes the inhibitory activities almost completely. Contraction of the 10-membered central ring decreases them significantly. The replacement of indole by thiophene or N-methylpyrrole reduces the inhibitory activity, whereas replacing the indole by benzene increases it. Finally, the hydroxylated dibenz[d,g]azecine derivative 11d (LE404) was found to be more active than the lead 1 in the functional calcium assay as well as in radioligand displacement experiments.

Background and purpose: Mitochondrial aldehyde dehydrogenase (ALDH-2) has been shown to provide a pathway for bioactivation of organic nitrates and to be prone to desensitization in response to highly potent, but not to less potent, nitrates. We therefore sought to support the hypothesis that bioactivation by ALDH-2 critically depends on the number of nitrate groups within the nitrovasodilator. Experimental approach: Nitrates with one (PEMN), two (PEDN; GDN), three (PETriN; glyceryl trinitrate, GTN) and four (pentaerithrityl tetranitrate, PETN) nitrate groups were investigated. Vasodilatory potency was measured in isometric tension studies using isolated aortic segments of wild type (WT) and ALDH-2 À/À mice. Activity of the cGMP-dependent kinase-I (reflected by levels of phosphorylated VAsodilator Stimulated Phosphoprotein, P-VASP) was quantified by Western blot analysis, mitochondrial dehydrogenase activity by HPLC. Following incubation of isolated mitochondria with PETN, PETriNchromophore and PEDN, metabolites were quantified using chemiluminescence nitrogen detection and mass spectrometry. Key results: Compared to WT, vasorelaxation in response to PETN, PETriN and GTN was attenuated about 10fold in ALDH-2 À/À mice, identical to WT vessels preincubated with inhibitors of ALDH-2. Reduced vasodilator potency correlated with reduced P-VASP formation and diminished biotransformation of the tetranitrate-and trinitrate-compounds. None of these findings were observed for PEDN, GDN and PEMN. Conclusions and implications: Our results support the crucial role of ALDH-2 in bioactivating highly reactive nitrates like GTN, PETN and PETriN. ALDH-2-mediated relaxation by organic nitrates therefore depends mainly on the number of nitrate groups. Less potent nitrates like PEDN, GDN and PEMN are apparently biotransformed by other pathways.

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Ligand binding studies reveal information about affinity to G protein—coupled receptors (GPCRs) rather than functional properties. Increase in intracellular Ca2+appears to represent a universal second messenger signal for a majority of recombinant GPCRs. Here, we exploit Ca2+signaling as a fast and sensitive functional screening method for a number of GPCRs coupled to different G proteins. Ca2+fluorescence measurements are performed using Oregon Green 488 BAPTA-1/AM and a microplate reader equipped with an injector. Buffer alone or test compounds dissolved in buffer are injected into a cell suspension, and fluorescence intensity is recorded for 30 s. Each of the GPCRs tested—Gq-coupled P2Y2, Gs-coupled dopamine D1 and D5, Gi-coupled dopamine D2L, and Gq/11-coupled muscarinic acetylcholine M1—yielded a significant rise in intracellular free [Ca2+] on agonist stimulation. Agonist stimulation was dose dependent, as shown for ATP or UTP stimulation of P2Y2receptors (EC50= 1 μM), SKF38393 stimulation of hD1 and hD5 (EC50= 18.1 nM and 2.7 nM), and quinpirole at hD2L (EC50= 6.5 nM). SCH23390 (at hD1 and hD5) and spiperone, haloperidol, and clozapine (at hD2L) competitively antagonized the Ca2+response. Furthermore, the Ca2+assay served to screen suramin analogs for antagonistic activity at P2Y2receptors. Screening at dopamine receptors revealed LE300, a new lead for a dopamine receptor antagonist. Advantages of the assay include fast and simple 96- or 384-well plate format (high-throughput screening), use of a visible light-excitable fluorescent dye, applicability to a majority of GPCRs, and simultaneous analysis of distinct Ca2+fluxes.