Untangling Alzheimer's disease from fibrous lesions of neurofibrillary tangles and senile plaques

Coumarin-piperazine derivatives as biologically active compounds

A number of psychiatric disorders, including anxiety, schizophrenia, Parkinson's disease, depression and others CNS diseases are known to induce defects in the function of neural pathways sustained by the neurotransmitters, like dopamine and serotonin. N-arylpiperazine moiety is important for CNS-activity, particularly for serotonergic and dopaminergic activity. In the scientific literature there are many examples of coumarin-piperazine derivatives, particularly with arylpiperazines linked to a coumarin system via an alkyl liner, which can modulate serotonin, dopamine and adrenergic receptors. Numerous studies have revealed that the inclusion of a piperazine moiety could occasionally provide unexpected improvements in the bioactivity of various biologically active compounds. The piperazine analogs have been shown to have a potent antimicrobial activity and they can also act as BACE-1 inhibitors. On the other hand, arylpiperazines linked to coumarin derivatives have been shown to have antiproliferative activity against leukemia, lung, colon, breast, and prostate tumors. Recently, it has been reported that coumarin-piperazine derivatives exhibit a Fneuroprotective effect by their antioxidant and anti-inflammatory activities and they also show activity as acetylcholinesterase inhibitors and antifilarial activity. In this work we provide a summary of the latest advances in coumarin-related chemistry relevant for biological activity.

Synthesis and Anti-Acetylcholinesterase Activity of N-[(indolyl)ethyl)-coumarin-yloxy)]Alkanamides

Novel coumarin–tryptamine systems attached through a linker were synthesised and evaluated in vitro against acetylcholinesterase by the classical Ellman's test.

Association study of cathepsin D gene polymorphism in Iranian patients with sporadic late-onset Alzheimer's disease

One of the most prevalent forms of dementia is Alzheimer's disease (AD). Complex inheritance and multifactorial patterns of late-onset AD (LOAD) along with its heterogeneity are due to the presence of different AD-predisposing genes with different influence on disease development among various populations. A key event in the pathogenesis of AD is the deposition of β-amyloid peptide, which is derived from the amyloid precursor protein by β- and γ-secretases. Cathepsin D (CTSD) is an acid protease with β- and γ-secretase-like features in vitro. An exonic C→T polymorphism at position 224 of the CTSD gene (rs: 17571) has been shown to be associated with the enzyme function of CTSD and with AD. Two studies in the German population reported a strong association of this polymorphism with an increased risk of developing AD, while other studies did not confirm this observation. We tested for this association in a case-control study in 100 Iranian sporadic LOAD patients based on diagnostic criteria of DSM-IV-TR and NINCDS-ADRDA and in 100 normal controls without any personal and family history of AD or other related dementias. Polymerase chain reaction-restriction fragment length polymorphism was set up to detect this polymorphism. Our study demonstrated that T-carrying genotype frequency in AD patients is significantly higher than in controls and there was a 2.5-fold increased risk for developing AD in the T-carrying genotype compared to C/C genotype (odds ratio = 2.5, p = 0.010). The odds ratio for subjects with the apolipoprotein E ε4 (APOE ε4) allele was 2.91 (p = 0.003) and carriers of the CTSD T and APOE ε4 alleles had a 6.25-fold increased risk of the disease (p = 0.0). Our results indicate that CTSD genotype is associated with the disease and a combination of the above risk factors significantly alters the risk for developing AD.

Synthesis and evaluation of 4-substituted coumarins as novel acetylcholinesterase inhibitors

A series of 4-hydroxycoumarin derivatives were designed and synthesized as new acetylcholinesterase (AChE) inhibitors which could be considered for Alzheimer's disease therapeutics. Among the 19 coumarin-derived compounds tested toward Electrophorus electricus acetylcholinesterase (eelAChE) and horse serum butyrylcholinesterase (eqBChE), N-(1-benzylpiperidin-4-yl)acetamide derivative 4m displayed highest AChE inhibitory activity (IC50 = 1.2 μM) and good selectivity (37 times). The docking study of the most potent compound 4m, indicated that Phe330 is responsible for ligand recognition and trafficking by forming π-cation interaction with benzylpiperidine moiety. Furthermore, the formation of an additional π-π interaction between coumarin moiety and Trp279 of peripheral anionic site could stabilize the ligand in the active site resulting in more potent inhibition of the enzyme.

Synthesis, in vitro assay, and molecular modeling of new piperidine derivatives having dual inhibitory potency against acetylcholinesterase and Aβ1–42 aggregation for Alzheimer’s disease therapeutics

With the goal of developing Alzheimer's disease therapeutics, we have designed and synthesized new piperidine derivatives having dual action of acetylcholinesterase (AChE) and beta-amyloid peptide (Abeta) aggregation inhibition. For binding with the catalytic site of AChE, an ester with aromatic group was designed, and for the peripheral site, another aromatic group was considered. And for intercalating amyloid-beta oligomerization, long and linear conformation with a lipophilic group was considered. The synthetic methods employed for the structure with dual action depended on alcohols with an aromatic ring and the substituted benzoic acids, which are esterificated in the last step of the synthetic pathway. We screened these new derivatives through inhibition tests of acetylcholinesterase, butyrylcholinesterase (BChE), and Abeta(1-42) peptide aggregation, AChE-induced Abeta(1-42) aggregation. Our results displayed that compound 12 showed the best inhibitory potency and selectivity of AChE, and 29 showed the highest selectivity of BChE inhibition. Compounds 15 and 12 had inhibitory activities against Abeta(1-42) aggregation and AChE-induced Abeta aggregation. In the docking model, we confirmed that 4-chlorobenzene of 12 plays the parallel pi-pi stacking against the indole ring of Trp84 in the bottom gorge of AChE. Because the benzyhydryl moiety of 12 covered the peripheral site of AChE in a funnel-like shape, 12 showed good inhibitory potency against AChE and could inhibit AChE-induced Abeta(1-42) peptide aggregation.

Causative and susceptibility genes for Alzheimer's disease: a review

Alzheimer's disease (AD) is the most common type of dementia in the elderly population. Three genes have been identified as responsible for the rare early-onset familial form of the disease: the amyloid precursor protein (APP) gene, the presenilin 1 (PSEN1) gene and the presenilin 2 (PSEN2) gene. Mutations in these genes, however, account for less than 5% of the total number of AD cases. The remaining 95% of AD patients are mostly sporadic late-onset cases, with a complex aetiology due to interactions between environmental conditions and genetic features of the individual. In this paper, we review the most important genes supposed to be involved in the pathogenesis of AD, known as susceptibility genes, in an attempt to provide a comprehensive picture of what is known about the genetic mechanisms underlying the onset and progression of AD. Hypotheses about the role of each gene in the pathogenic pathway are discussed, taking into account the functions and molecular features, if known, of the coded protein. A major susceptibility gene, the apolipoprotein E (APOE) gene, found to be associated with sporadic late-onset AD cases and the only one, whose role in AD has been confirmed in numerous studies, will be included in a specific chapter. As the results reported by association studies are conflicting, we conclude that a better understanding of the complex aetiology that underlies AD may be achieved likely through a multidisciplinary approach that combines clinical and neurophysiological characterization of AD subtypes and in vivo functional brain imaging studies with molecular investigations of genetic components.