Merging memantine and ferulic acid to probe connections between NMDA receptors, oxidative stress and amyloid-ß peptide in Alzheimer's disease.

N-methyl-d-aspartate receptors (NMDAR) are critically involved in the pathogenesis of Alzheimer's disease (AD). Acting as an open-channel blocker, the anti-AD drug memantine preferentially targets NMDAR overactivation, which has been proposed to trigger neurotoxic events mediated by amyloid ß peptide (Aß) and oxidative stress. In this study, we applied a multifunctional approach by conjugating memantine to ferulic acid, which is known to protect the brain from Aß neurotoxicity and neuronal death caused by ROS. The most interesting compound (7) behaved, like memantine, as a voltage-dependent antagonist of NMDAR (IC50 = 6.9 µM). In addition, at 10 µM concentration, 7 exerted antioxidant properties both directly and indirectly through the activation of the Nrf-2 pathway in SH-SY5Y cells. At the same concentration, differently from the parent compounds memantine and ferulic acid alone, it was able to modulate Aß production, as revealed by the observed increase of the non-amyloidogenic sAPPα in H4-SW cells. These findings suggest that compound 7 may represent a promising tool for investigating NMDAR-mediated neurotoxic events involving Aß burden and oxidative damage.

Modulation of Keap1/Nrf2/ARE Signaling Pathway by Curcuma- and Garlic-Derived Hybrids.

Nrf2 is a basic leucine zipper transcription factor that binds to the promoter region of the antioxidant response element (ARE), inducing the coordinated up-regulation of antioxidant and detoxification genes. We recently synthesized a set of new molecules by combining the functional moieties of curcumin and diallyl sulfide, both known to induce the expression of antioxidant phase II enzymes by activating Nrf2 pathway. The aim of the study is to investigate the ability of such compounds to activate Keap1/Nrf2/ARE cytoprotective pathway, in comparison with two reference Nrf2-activators: curcumin and dimethyl fumarate, a drug approved for the treatment of relapsing-remitting multiple sclerosis. Furthermore, since Nrf2 pathway is known to be regulated also by epigenetic modifications, including key modifications in microRNA (miRNA) expression, the effects of the hybrids on the expression levels of selected miRNAs, associated with Nrf2 signaling pathway have also been investigated. The results show that compounds exert antioxidant effect by activating Nrf2 signaling pathway and inducing the ARE-regulated expression of its downstream target genes, such as HO-1 and NQO1, with two hybrids to a higher extent than curcumin. In addition, some molecules induce changes in the expression levels of miR-125b-5p, even if to a lesser extent than curcumin. However, no changes have been observed in the expression levels of mRNA coding for glutathione synthetase, suggesting that the modulation of this mRNA is not strictly under the control of miR-125b-5p, which could be influenced by other miRNAs.

Multitarget drug design strategy in Alzheimer's disease: focus on cholinergic transmission and amyloid-ß aggregation.

AIM: Alzheimer pathogenesis has been associated with a network of processes working simultaneously and synergistically. Over time, much interest has been focused on cholinergic transmission and its mutual interconnections with other active players of the disease. Besides the cholinesterase mainstay, the multifaceted interplay between nicotinic receptors and amyloid is actually considered to have a central role in neuroprotection. Thus, the multitarget drug-design strategy has emerged as a chance to face the disease network. METHODS: By exploiting the multitarget approach, hybrid compounds have been synthesized and studied in vitro and in silico toward selected targets of the cholinergic and amyloidogenic pathways. RESULTS: The new molecules were able to target the cholinergic system, by joining direct nicotinic receptor stimulation to acetylcholinesterase inhibition, and to inhibit amyloid-ß aggregation. CONCLUSION: The compounds emerged as a suitable starting point for a further optimization process.

Targeting the Nrf2/Amyloid-Beta Liaison in Alzheimer's Disease: A Rational Approach.

Amyloid is a prominent feature of Alzheimer's disease (AD). Yet, a linear linkage between amyloid-ß peptide (Aß) and the disease onset and progression has recently been questioned. In this context, the crucial partnership between Aß and Nrf2 pathways is acquiring paramount importance, offering prospects for deciphering the Aß-centered disease network. Here, we report on a new class of antiaggregating agents rationally designed to simultaneously activate transcription-based antioxidant responses, whose lead 1 showed interesting properties in a preliminary investigation. Relying on the requirements of Aß recognition, we identified the catechol derivative 12. In SH-SY5Y neuroblastoma cells, 12 combined remarkable free radical scavenger properties to the ability to trigger the Nrf2 pathway and induce the Nrf2-dependent defensive gene NQO1 by means of electrophilic activation of the transcriptional response. Moreover, 12 prevented the formation of cytotoxic stable oligomeric intermediates, being significantly more effective, and per se less toxic, than prototype 1. More importantly, as different chemical features were exploited to regulate Nrf2 and Aß activities, the two pathways could be tuned independently. These findings point to compound 12 and its derivatives as promising tools for investigating the therapeutic potential of the Nrf2/Aß cellular network, laying foundation for generating new drug leads to confront AD.

Multitarget strategies in Alzheimer's disease: benefits and challenges on the road to therapeutics.

Alzheimer's disease is a multifactorial syndrome, for which effective cures are urgently needed. Seeking for enhanced therapeutic efficacy, multitarget drugs have been increasingly sought after over the last decades. They offer the attractive prospect of tackling intricate network effects, but with the benefits of a single-molecule therapy. Herein, we highlight relevant progress in the field, focusing on acetylcholinesterase inhibition and amyloid pathways as two pivotal features in multitarget design strategies. We also discuss the intertwined relationship between selected molecular targets and give a brief glimpse into the power of multitarget agents as pharmacological probes of Alzheimer's disease molecular mechanisms.

Nature-Inspired Multifunctional Ligands: Focusing on Amyloid-Based Molecular Mechanisms of Alzheimer's Disease.

The amyloidogenic pathway is a prominent feature of Alzheimer's disease (AD). However, growing evidence suggests that a linear disease model based on ß-amyloid peptide (Aß) alone is not likely to be realistic, which therefore calls for further investigations on the other actors involved in the play. The pro-oxidant environment induced by Aß in AD pathology is well established, and a correlation among Aß, oxidative stress, and conformational changes in p53 has been suggested. In this study, we applied a multifunctional approach to identify allyl thioesters of variously substituted trans-cinnamic acids for which the pharmacological profile was strategically tuned by hydroxy substituents on the aromatic moiety. Indeed, only catechol derivative 3 [(S)-allyl (E)-3-(3,4-dihydroxyphenyl)prop-2-enethioate] inhibited Aß fibrilization. Conversely, albeit to different extents, all compounds were able to decrease the formation of reactive oxygen species in SH-SY5Y neuroblastoma cells and to prevent alterations in the conformation of p53 and its activity mediated by soluble sub-lethal concentrations of Aß. This may support an involvement of oxidative stress in Aß function, with p53 emerging as a potential mediator of their functional interplay.

Radical trideuteromethylation with deuterated dimethyl sulfoxide in the synthesis of heterocycles and labelled building blocks.

The potential of deuterated pharmaceuticals is being widely demonstrated. Here we describe the first trideuteromethylation under radical reaction conditions using deuterated dimethyl sulfoxide as a reagent for the synthesis of labelled heterocycles and trideuteromethylated compounds. A broad scope of the developed method for the synthesis of various scaffolds was demonstrated.

In Vivo Characterization of ARN14140, a Memantine/Galantamine-Based Multi-Target Compound for Alzheimer's Disease.

Alzheimer's disease (AD) is a chronic pathological condition that leads to neurodegeneration, loss of intellectual abilities, including cognition and memory, and ultimately to death. It is widely recognized that AD is a multifactorial disease, where different pathological cascades (mainly amyloid and tau) contribute to neural death and to the clinical outcome related to the disease. The currently available drugs for AD were developed according to the one-target, one-drug paradigm. In recent times, multi-target strategies have begun to play an increasingly central role in the discovery of more efficacious candidates for complex neurological conditions, including AD. In this study, we report on the in vivo pharmacological characterization of ARN14140, a new chemical entity, which was obtained through a multi-target structure-activity relationship campaign, and which showed a balanced inhibiting profile against the acetylcholinesterase enzyme and the NMDA receptor. Based on the initial promising biochemical data, ARN14140 is here studied in mice treated with the amyloidogenic fragment 25-35 of the amyloid-ß peptide, a consolidated non-transgenic AD model. Sub-chronically treating animals with ARN14140 leads to a prevention of the cognitive impairment and of biomarker levels connected to neurodegeneration, demonstrating its neuroprotective potential as new AD agent.

Polyamine Conjugation as a Promising Strategy To Target Amyloid Aggregation in the Framework of Alzheimer's Disease.

Spermine conjugates 2-6, carrying variously decorated 3,5-dibenzylidenepiperidin-4-one as bioactive motives, were designed to direct antiaggregating properties into mitochondria, using a polyamine functionality as the vehicle tool. The study confirmed mitochondrial import of the catechol derivative 2, which displayed effective antiaggregating activity and neuroprotective effects against Aß-induced toxicity. Notably, a key functional role for the polyamine motif in Aß molecular recognition was also unraveled. This experimental readout, which was supported by in silico studies, gives important new insight into the polyamine's action. Hence, we propose polyamine conjugation as a promising strategy for the development of neuroprotectant leads that may contribute to decipher the complex picture of Aß toxicity.