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ABSTRACT:The synthesis, molecular modeling, and pharmacological analysis of phenoxyalkylamino-4-phenylnicotinates (2−7), phenoxyalkoxybenzylidenemalononitriles (12, 13), pyridonepezils (14−18), and quinolinodonepezils (19−21) are described. Pyridonepezils 15−18 were found to be selective and moderately potent regarding the inhibition of hAChE, whereas quinolinodonepezils 19−21 were found to be poor inhibitors of hAChE. The most potent and selective hAChE inhibitor was ethyl 6-(4-(1-benzylpiperidin-4-yl)butylamino)-5-cyano-2-methyl-4-phenylnicotinate (18) [IC 50 (hAChE) = 0.25 ± 0.02 μM]. Pyridonepezils 15−18 and quinolinodonepezils 20−21 are more potent selective inhibitors of EeAChE than hAChE. The most potent and selective EeAChE inhibitor was ethyl 6-(2-(1-benzylpiperidin-4-yl)ethylamino)-5-cyano-2-methyl-4-phenylnicotinate (16) [IC 50 (EeAChE) = 0.0167 ± 0.0002 μM], which exhibits the same inhibitory potency as donepezil against hAChE. Compounds 2, 7, 13, 17, 18, 35, and 36 significantly prevented the decrease in cell viability caused by Aβ 1−42 . All compounds were effective in preventing the enhancement of AChE activity induced by Aβ 1−42 . Compounds 2−7 caused a significant reduction whereas pyridonepezils 17 and 18, and compound 16 also showed some activity . The pyrazolo [3,4-b]quinolines 36 and 38 also prevented the upregulation of AChE induced by Aβ 1−42 . Compounds 2, 7, 12, 13, 17, 18, and 36 may act as antagonists of voltage sensitive calcium channels, since they significantly prevented the Ca 2+ influx evoked by KCl depolarization. Docking studies show that compounds 16 and 18 adopted different orientations and conformations inside the active-site gorges of hAChE and hBuChE. The structural and energetic features of the 16-AChE and 18-AChE complexes compared to the 16-BuChE and 18-BuChE complexes account for a higher affinity of the ligand toward AChE. The present data indicate that compounds 2, 7, 17, 18, and 36 may represent attractive multipotent molecules for the potential treatment of Alzheimer's disease.

Mitochondria regulate cellular Ca(2+) oscillations, taking up Ca(2+) through its uniporter and releasing it through the mitochondrial sodium/calcium exchanger. The role of mitochondria in the regulation of Ca(2+) cycle has received much attention recently, as it is a central stage in neuronal survival and death processes. Over the last decades, the 4,1-benzothiazepine CGP37157 has been the only available blocker of the mitochondrial sodium/calcium exchanger, although it targets several other calcium transporters. We report the synthesis of 4,1-benzothiazepine derivatives with the goal of enhancing mitochondrial sodium/calcium exchanger blockade and selectivity, and the evaluation of their cytoprotective effect. The compound 4c presented an interesting neuroprotective profile in addition to an important blockade of the mitochondrial sodium/calcium exchanger. The use of this benzothiazepine could help to understand the physiological functions of the mitochondrial sodium/calcium exchanger. In addition, we hypothesize that a moderate blockade of the mitochondrial sodium/calcium exchanger would provide enhanced neuroprotection in neurons.

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in:Journal of Medicinal Chemistry 58.13 (2016)

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ITH12246 (ethyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo[b] [1,8]naphthyridine-3-carboxylate) is a 1,8-naphthyridine described to feature an interesting neuroprotective profile in in vitro models of Alzheimer's disease. These effects were proposed to be due in part to a regulatory action on protein phosphatase 2A inhibition, as it prevented binding of its inhibitor okadaic acid. We decided to investigate the pharmacological properties of ITH12246, evaluating its ability to counteract the memory impairment evoked by scopolamine, a muscarinic antagonist described to promote memory loss, as well as to reduce the infarct volume in mice suffering phototrombosis. Prior to conducting these experiments, we confirmed its in vitro neuroprotective activity against both oxidative stress and Ca 2+ overload-derived excitotoxicity, using SH-SY5Y neuroblastoma cells and rat hippocampal slices. Using a predictive model of blood-brain barrier crossing, it seems that the passage of ITH12246 is not hindered. Its potential hepatotoxicity was observed only at very high concentrations, from 0.1 mM. ITH12246, at the concentration of 10 mg/kg i.p., was able to improve the memory index of mice treated with scopolamine, from 0.22 to 0.35, in a similar fashion to the well-known Alzheimer's disease drug galantamine 2.5 mg/kg. On the other hand, ITH12246, at the concentration of 2.5 mg/kg, reduced the phototrombosis-triggered infarct volume by 67%. In the same experimental conditions, 15 mg/kg melatonin, used as control standard, reduced the infarct volume by 30%. All of these findings allow us to consider ITH12246 as a new potential drug for the treatment of neurodegenerative diseases, which would act as a multifactorial neuroprotectant.

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There is still much work to be done to validate PPP enzymes as eligible targets for the development of new drugs. The most significant barrier is likely to be persuading the majority of the scientific community that PPP enzymes are not too unspecific. Few patents disclosed the rational design of direct PPP ligands, while many inventions relied on long chain peptides-based approaches. Overall, the future of ligands for PPP enzymes as therapeutics seems both challenging and exciting.