Protective effect of the multitarget compound DPH-4 on human SSAO/VAP-1-expressing hCMEC/D3 cells under oxygen-glucose deprivation conditions: an in vitro experimental model of cerebral ischaemia.

BACKGROUND AND PURPOSE: Stroke and Alzheimer's disease (AD) are related pathologies in which the cerebrovascular system is involved. Plasma levels of semicarbazide-sensitive amine oxidase/vascular adhesion protein 1 (SSAO/VAP-1, also known as Primary Amine Oxidase -PrAO) are increased in both stroke and AD patients and contribute to the vascular damage. During inflammation, its enzymatic activity mediates leukocyte recruitment to the injured tissue, inducing damage in the blood-brain barrier (BBB) and neuronal tissue. We hypothesized that by altering cerebrovascular function, SSAO/VAP-1 might play a role in the stroke-AD transition. Therefore, we evaluated the protective effect of the novel multitarget-directed ligand DPH-4, initially designed for AD therapy, on the BBB. EXPERIMENTAL APPROACH: A human microvascular brain endothelial cell line expressing human SSAO/VAP-1 was generated, as the expression of SSAO/VAP-1 is lost in cultured cells. To simulate ischaemic damage, these cells were subjected to oxygen and glucose deprivation (OGD) and re-oxygenation conditions. The protective role of DPH-4 was then evaluated in the presence of methylamine, an SSAO substrate, and/or ß-amyloid (Aß). KEY RESULTS: Under our conditions, DPH-4 protected brain endothelial cells from OGD and re-oxygenation-induced damage, and also decreased SSAO-dependent leukocyte adhesion. DPH-4 was also effective at preventing the damage induced by OGD and re-oxygenation in the presence of Aß as a model of AD pathology. CONCLUSIONS AND IMPLICATIONS: From these results, we concluded that the multitarget compound DPH-4 might be of therapeutic benefit to delay the onset and/or progression of the neurological pathologies associated with stroke and AD, which appear to be linked.

The multifactorial nature of Alzheimer's disease for developing potential therapeutics.

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder with several target proteins contributing to its aetiology. Pathological, genetic, biochemical, and modeling studies all point to a critical role of Aß aggregation in AD. Though there are still many enigmatic aspects of the Aß cascade, none of the gaps invalidate the hypothesis. The amyloid hypothesis determines that the production, aggregation and accumulation of Aß in the brain gives rise to a cascade of neurotoxic events that proceed to neuronal degeneration. Different targets of the disease include APP pathogenic cleavage, cytoskeletal destabilization, neurotransmitter and ion dyshomeostasis, metal ion accumulation, protein misfolding, oxidative stress, neuronal death and gene mutations. Thus, disease-modifying treatments for AD must interfere with the pathogenic steps responsible for the clinical symptoms: the deposition of extracellular Aß plaques, the intracellular neurofibrillary tangles, inflammation, oxidative stress, iron deregulation, among others. The observations supporting the development of multifunctional compounds in association with the perception that several dual binding site AChEIs were able to reach different targets guided the development of a new drug design strategy, the multi-target-directed-ligand (MTDL) approach. This may be regarded as the buildup of hybrid molecules composed of distinct pharmacophores of different drugs. Thus, each pharmacophore of the new hybrid drug would preserve the capacity of interacting with their specific sites on the targets and, therefore, generate multiple specific pharmacological responses which would enable the treatment of multi-factorial diseases. This review summarizes a few current therapeutic trends on MTDL strategy intended to halt or revert the progression of the disease.

A step further towards multitarget drugs for Alzheimer and neuronal vascular diseases: targeting the cholinergic system, amyloid-ß aggregation and Ca(2+) dyshomeostasis.

Alzheimer's disease (AD) is the most common neurodegenerative disease, affecting mainly elderly people. The reasons why AD occurs are complex and multifactorial and several biochemical targets are thought to play a key role in its progress and development. This fact has led to the development of a multitarget-directed ligand strategy as a logical approach for designing a suitable therapy. Currently, most prescribed drugs for treating AD are acetylcholinesterase inhibitors (AChEI), although these inhibitors represent solely palliative treatment. This account will summarize our current therapeutic approach for the design of multitarget drugs primarily aimed at inhibiting AChE using the key features of tacrine, which was the first approved drug for AD treatment. Secondly, as calcium homeostasis is directly related to the cell death-survival equilibrium, suitable therapy might include an action that regulates calcium homeostasis by means of targeting voltage dependent calcium channels. It is, therefore, hoped that targeting calcium homeostasis will lead directly to the development of potential neuroprotective agents. Thus, 1,4-dihydropyridines, well-known voltage-dependent calcium channel (VDCC) ligands, will be incorporated into the new molecules as a second structural feature in order to bring about this action. As a result of this development, herein, we describe the synthetic and pharmacological profile of new [1,8]-naphthyridine analogues, which are hybrids of tacrine and 1,4-dihydropyridines. Some of our molecules have shown improved inhibitory action against cholinesterases, whilst maintaining their VDCC modulating activity, and have good characteristics as neuroprotective agents. Based on kinetic analysis of the AChE inhibition experiments, it has been shown that many of the compounds bind at the peripheral anionic site (PAS). Since the AChE PAS is linked to ß-amyloid aggregation, this would give a third biological target for further preclinical development, making these molecules highly interesting targets in the search to obtain better treatments for AD.

DIBALH mediated reduction of the acetal moiety on perhydrofuro[2,3-b]pyran derivatives.

The reaction of DIBALH with bis(heteroannulated)-pyranosides containing the perhydrofuro[2,3-b]pyran moiety is described. The hydride attack at the anomeric carbon (C-9a) resulted in the exclusive tetrahydrofuran ring opening. The selectivity of this reaction has been evaluated as other benzylidene acetals built on these substrates remain practically or partially unaltered in these conditions depending on the steric volume of the O-protecting group located at C-4 (TBDMS vs. Me). This protocol can be considered as a new entry for the synthesis of chiral and highly functionalized cyclopentanes.

Synthesis and transformations of new annulated pyranosides using the Pauson-Khand reaction.

The synthesis and transformations of new annulated pyranosides are described. These adducts were prepared by Pauson-Khand reaction on differently functionalized prop-2-ynyl-2,3-dideoxy-alpha-D-erythro-hex-2-enopyranosides (1-8). Compound 1 with a free hydroxyl group at C-4 afforded significant amounts of the hydrogenolysis product 12 in addition to the normal adduct 13. The C-4 O-protected similar precursors (2-8) gave PK products in yields ranging from 39 to 63%. Pauson-Khand adduct 19 provided intermediate 23 after selective manipulation. The oxidation plus decarbonylation synthetic sequence applied to intermediate 23 gave a poor yield of compound 24 using Wilkinson's catalyst. The t-butyl hydroperoxide promoted decarbonylation of product 23 afforded formate 25 in a typical Baeyer-Villiger rearrangement. The Ferrier-II reaction on intermediate 45, readily available from compound 9, afforded the hydrindane-type derivative 46 in 34% yield using a Ferrier-II type reaction.

Free-radical mediated synthesis of enantiomerically pure, highly functionalized inositols from carbohydrates.

We report the synthesis, free-radical cyclization of precursors 1,2,7-trideoxy-7-iodo-3,4:5,6-di-O-isopropylidene-D-gluco-hept-1-enitol (1), methyl 7-O-acetyl-6-O-benzyl-8-bromo-2,3,8-trideoxy-4,5-O-isopropylidene-D-gluco-oct-2-enonate (2) and 5-O-acetyl-4-O-benzyl-6-bromo-6-deoxy-2,3-O-isopropylidene-D-glucose-O-benzyloxime (3), readily prepared from D-glucose, and some selected transformations of the carbocycles obtained from these intermediates. In compound 1 we have installed a terminal double bond and an iodide as radical acceptor and leaving group, respectively. Compounds 2 and 3 are epsilon-bromo aldehydes substituted with alpha,beta-unsaturated ester and oxime ether functions as radical traps, respectively. The tributyltin hydride mediated ring closure of these radical precursors have afforded a series of interesting, diverse and highly functionalized carbocycles which can be considered useful building blocks for the synthesis of branched-chain cyclitols, aminocyclitols and aminoconduritols. In these processes, a good chemical yield and high stereoselectivity has been found in the newly formed stereocenters. Particularly interesting has been the finding that the stereochemical outcome of the free-radical cyclization is independent of the ratio of isomers (E or Z) in oxime ether 3. These results show the power and the state of art of this strategy for the stereocontrolled synthesis of enantiomerically pure inositols from carbohydrates.

Free-radical cyclizations onto differently substituted 1,2,3-triazoles installed in sugar templates.

The synthesis and manipulation of differently substituted 1,2,3-triazoles (7-11 and 12-16) installed in sugar templates gave compounds 29-34 and 44-50, after reaction with tributyltin hydride or tris(trimethylsilyl)silane. Following standard procedures compound 44 was transformed into piperidinose derivative 54. These compounds are chiral, useful building blocks for the synthesis of glycosidase inhibitors of the fused-azole piperidinose type.