Produtos naturais como candidatos a fármacos úteis no tratamento do mal de Alzheimer

Alzheimer's disease (AD) is a progressive neurodegenerative pathology with severe economic and social impact. There is currently no cure, although cholinesterase inhibitors provide effective temporary relief of symptoms in some patients. Nowadays drug research and development are based on the cholinergic hypothesis that supports the cognition improvement by regulation of the synthesis and release of acetylcholine in the brain. There are only four commercial medicines approved for treatment of AD and natural products have played an important role in the research for new acetylcholinesterase inhibitors.

Obtenção de micro/nanopartículas poliméricas para o encapsulamento do fármaco bromidrato de galantamina

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência da neuromodulação parassimpática durante a indução da periodontite em camundongos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis, spectroscopic characterization, photochemical and photophysical properties and biological activities of ruthenium complexes with mono- and bi-dentate histamine ligand

The monodentate cis-[Ru(phen)(2)(hist)(2)](2+) 1R and the bidentate cis-[Ru(phen)(2)(hist)](2+) 2A complexes were prepared and characterized using spectroscopic (H-1, (H-1-H-1) COSY and (H-1-C-13) HSQC NMR, UV-vis, luminescence) techniques. The complexes presented absorption and emission in the visible region, as well as a tri-exponential emission decay. The complexes are soluble in aqueous and non-aqueous solution with solubility in a buffer solution of pH 7.4 of 1.14 x 10(-3) mol L-1 for (1R + 2A) and 6.43 x 10(-4) mol L-1 for 2A and lipophilicity measured in an aqueous-octanol solution of -1.14 and -0.96, respectively. Photolysis in the visible region in CH3CN converted the starting complexes into cis-[Ru(phen)(2)(CH3CN)(2)](2+). Histamine photorelease was also observed in pure water and in the presence of BSA (1.0 x 10(-6) mol L-1). The bidentate coordination of the histamine to the ruthenium center in relation to the monodentate coordination increased the photosubstitution quantum yield by a factor of 3. Pharmacological studies showed that the complexes present a moderate inhibition of AChE with an IC50 of 21 mu mol L-1 (referred to risvagtini, IC50 181 mu mol L-1 and galantamine IC50 0.006 mu mol L-1) with no appreciable cytotoxicity toward to the HeLa cells (50% cell viability at 925 mu mol L-1). Cell uptake of the complexes into HeLa cells was detected by fluorescence confocal microscopy. Overall, the observation of a luminescent complex that penetrates the cell wall and has low cytotoxicity, but is reactive photochemically, releasing histamine when irradiated with visible light, are interesting features for application of these complexes as phototherapeutic agents.

Modulation der Genexpression und des neuronalen Zelltods durch das Amyloid-Vorläufer-Protein (APP)

Das Amyloid-Vorläufer-Protein (APP) spielt eine zentrale Rolle in der Entstehung und Entwicklung von Morbus Alzheimer. Hierbei ist die proteolytische Prozessierung von APP von entscheidender Bedeutung. Das Verhältnis von neurotoxischen und neuroprotektiven Spaltprodukten, die über den amyloidogenen und nicht-amyloidogenen Weg der APP-Prozessierung gebildeten werden, ist für das Überleben von Neuronen und deren Resistenz gegen zytotoxische Stress-Stimuli von hoher Relevanz. Störungen der Calcium-Homöostase sind ein bekanntes Phänomen bei Morbus Alzheimer. Im ersten Teil der vorliegenden Arbeit wurde die Rolle von überexprimiertem APP in der Regulation des neuronalen Zelltods nach Calcium Freisetzung untersucht. Die Calcium Freisetzung aus dem endoplasmatischen Retikulum wurde durch die Inhibition der sarko- und endoplasmatischen Calcium-ATPasen (SERCA) ausgelöst. Dies führt zur Induktion der sogenannten „unfolded protein response“ (UPR) und zu einer Aktivierung von Effektor-Caspasen. Für APP-überexprimierende PC12 Zellen konnte bereits zuvor eine im Vergleich zur Kontrolle nach der durch Calcium Freisetzung-induzierten Apoptose eine erhöhte intrazelluläre Calcium Konzentration nachgewiesen werden. Über die Messung der Aktivierung von Effektor-Caspasen konnte zudem ein gesteigerter Zelltod in den APP-überexprimierenden Zellen gemessen werden. Zudem konnte gezeigt werden, dass der pro-apoptotische Transkriptionsfaktor CHOP, nicht aber die klassischen UPR-Zielgene spezifisch hochreguliert wurden. Die APP-modulierte gesteigerte Induktion von Apoptose nach Calcium Freisezung konnte durch Komplexierung der intrazellulären Calcium Ionen und durch Knockdown von CHOP im Vergleich zur Kontrolle gänzlich unterdrückt werden. Ferner bewirkte die Inhibition der Speicher-aktivierten Calcium-Kanälen (SOCC) eine signifikante Unterdrückung der beobachteten erhöhten intrazellulären Calcium Konzentration und der gesteigerten Apoptose in den APP-überexprimierenden PC12 Zellen. In diesem Teil der Arbeit konnte eindeutig gezeigt werden, dass APP in der Lage ist den durch Calcium-Freisetzung-induzierten Zelltod zu potenzieren. Diese Modulation durch APP verläuft in einer UPR-unabhängigen Reaktion über die Aktivierung von SOCC’s, einer erhöhten Aufnahme von extrazellulärem Calcium und durch erhöhte Induktion des pro-apoptotischen Transkriptionsfaktors CHOP. Im zweiten Teil dieser Arbeit wurde die sAPPα-vermittelte Neuroprotektion untersucht. Dabei handelt es sich um die N-terminale Ektodomäne von APP, die über die Aktivität der α-Sekretase prozessiert wird und anschließend extrazellulär abgegeben wird. Ziel dieser Versuchsreihe war die neuroprotektive physiologische Funktion von APP im Hinblick auf den Schutz von neuronalen Zellen vor diversen für Morbus Alzheimer relevanten Stress-Stimuli bzw. Apoptose-Stimuli zu untersuchen. Durch die Analyse der Effektor-Caspasen konnte gezeigt werden, dass sAPPα in der Lage ist PC12 Zellen potent vor oxidativem Stress, DNA-Schäden, Hypoxie, proteasomalem Stress und Calcium-Freisetzung zu schützen. Außerdem konnte gezeigt werden, dass sAPPα in der Lage ist den pro-apoptotischen Stress-induzierten JNK/Akt-Signalweg zu inhibieren. Eine Beteiligung des anti-apoptotischen PI3K/Akt-Signalwegs bei der sAPPα-vermittelten Protektion konnte über die Inhibition der PI3-Kinase ebenfalls demonstriert werden, die eine Aufhebung der sAPPα-vermittelten Neuroprotektion bewirkte. Diese Daten zeigen neue molekulare Mechanismen auf, die dem sAPPα-vermittelten Schutz vor pathophysiologisch relevanten Stress-Stimuli in neuronalen Zellen zugrunde liegen. Im letzten Teil der Arbeit wurden verschieden Gruppen von pharmakologischen Substanzen im Hinblick auf ihre neuroprotektive Wirkung untersucht und mit ihren Effekten auf den APP-Metabolismus korreliert. Die Untersuchungen ergaben, dass Galantamin, ein schwacher Acetycholinesterase Inhibitor und allosterisch potenzierender Ligand von nikotinischen Acetylcholin-Rezeptoren in der Lage war, naive, und mit noch höherer Effizienz APP-überexprimierende Zelllinien vor dem Stress-induzierten Zelltod zu schützen. Zudem bewirkte Galantamin in APP-überexprimierenden HEK293 Zellen eine rasche Erhöhung der sAPPα Sekretion, so dass hier von einer Rezeptor-vermittelten Modulation des APP Metabolismus ausgegangen werden kann. Omega-3 Fettsäuren wirken sich positiv auf die Membranfluidität von Zellen aus und es konnte bereits gezeigt werden, dass die Bildung des toxischen Aβ Peptids hierdurch vermindert wird. In Analogie zu Galantamin schützte die Omega-3 Fettsäure Docosahexaensäure (DHA) neuronale Zellen vor dem Stress-induzierten Zelltod, wobei der Schutz in APP-überexprimierenden Zellen besonders effizient war. Diese Daten legen nahe, dass die Aktivierung des antiamyloidogenen Wegs der APP-Prozessierung ein viel versprechender Ansatz für die Entwicklung neuer Therapien gegen Morbus Alzheimer sein könnte.

Treatment of dementia with neurotransmission modulation

The prevalence of dementia is growing in developed countries where elderly patients are increasing in numbers. Neurotransmission modulation is one approach to the treatment of dementia. Cholinergic precursors, anticholinesterases, nicotine receptor agonists and muscarinic M-2 receptor antagonists are agents that enhance cholinergic neurotransmission and that depend on having some intact cholinergic innervation to be effective in the treatment of dementia. The cholinergic precursor choline alfoscerate may be emerging as a potential useful drug in the treatment of dementia, with few adverse effects. Of the anticholinesterases, donepezil, in addition to having a similar efficacy to tacrine in mild-to-moderate Alzheimer's disease (AD), appears to have major advantages; its use is associated with lower drop-out rates in clinical trials, a lower incidence of cholinergic-like side effects and no liver toxicity. Rivastigmine is efficacious in the treatment in dementia with Lewy bodies, a condition in which the other anticholinesterases have not been tested extensively to date. Galantamine is an anticholinesterase and also acts as an allosteric potentiating modulator at nicotinic receptors to increase the release of acetylcholine. Pooled data from clinical trials of patients with mild-to-moderate AD suggest that the benefits and safety profile of galantamine are similar to those of the anticholinesterases. Selective nicotine receptor agonists are being developed that enhance cognitive performance without influencing autonomic and skeletal muscle function, but these have not yet entered clinical trial for dementia. Unlike the cholinergic enhancers, the M, receptor agonists do not depend upon intact cholinergic nerves but on intact M, receptors for their action, which are mainly preserved in AD and dementia with Lewy bodies. The M, receptor-selective agonists developed to date have shown limited efficacy in clinical trials and have a high incidence of side effects. A major recent advancement in the treatment of dementia is memantine, a non-competitive antagonist at NMDA receptors. Memantine is beneficial in the treatment of severe and moderate to-severe AD and may also be of some benefit in the treatment of mild-to-moderate vascular dementia. Drugs that modulate 5-HT, somatostatin and noradrenergic neurotransmission are also being considered for the treatment of dementia.

Systematic review of cholinergic drugs for neuroleptic-induced tardive dyskinesia: a meta-analysis of randomized controlled trials

The authors evaluated the efficacy of cholinergic drugs in the treatment of neuroleptic-induced tardive dyskinesia (TD) by a systematic review of the literature on the following agents: choline, lecithin, physostigmine, tacrine, 7-methoxyacridine, ipidacrine, galantamine, donepezil, rivastigmine, eptastigmine, metrifonate, arecoline, RS 86, xanomeline, cevimeline, deanol, and meclofenoxate. All relevant randomized controlled trials, without any language or year limitations, were obtained from the Cochrane Schizophrenia Group's Register of Trials. Trials were classified according to their methodological quality. For binary and continuous data, relative risks (RR) and weighted or standardized mean differences (SMD) were calculated, respectively. Eleven trials with a total of 261 randomized patients were included in the meta-analysis. Cholinergic drugs showed a minor trend for improvement of tardive dyskinesia symptoms, but results were not statistically significant (RR 0.84, 95% confidence interval (CI) 0.68 to 1.04, p=0.11). Despite an extensive search of the literature, eligible data for the meta-analysis were few and no results reached statistical significance. In conclusion, we found no evidence to support administration of the old cholinergic agents lecithin, deanol, and meclofenoxate to patients with tardive dyskinesia. In addition, two trials were found on novel cholinergic Alzheimer drugs in tardive dyskinesia, one of which was ongoing. Further investigation of the clinical effects of novel cholinergic agents in tardive dyskinesia is warranted. (C) 2004 Elsevier Inc. All rights reserved.

Impact of cholinesterase inhibitors on behavioral and psychological symptoms of Alzheimer's disease:a meta-analysis

Objective: To determine the efficacy of cholinesterase inhibitors (ChEIs) in improving the behavioral and psychological symptoms of dementia (BPSD) in patients with Alzheimer’s disease (AD). Data sources: We searched MEDLINE, Cochrane Registry, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) from 1966 to 2007. We limited our search to English Language, full text, published articles and human studies. Data extraction: We included randomized, double-blind, placebo-controlled trials evaluating the efficacy of donepezil, rivastigmine, or galantamine in managing BPSD displayed by AD patients. Using the United States Preventive Services Task Force (USPSTF) guidelines, we critically appraised all studies and included only those with an attrition rate of less than 40%, concealed measurement of the outcomes, and intention to treat analysis of the collected data. All data were imputed into pre-defined evidence based tables and were pooled using the Review Manager 4.2.1 software for data synthesis. Results: We found 12 studies that met our inclusion criteria but only nine of them provided sufficient data for the meta-analysis. Among patients with mild to severe AD and in comparison to placebo, ChEIs as a class had a beneficial effects on reducing BPSD with a standard mean difference (SMD) of -0.10 (95% confidence interval [CI]; -0.18, -0.01) and a weighted mean difference (WMD) of -1.38 neuropsychiatry inventory point (95% CI; -2.30, -0.46). In studies with mild AD patients, the WMD was -1.92 (95% CI; -3.18, -0.66); and in studies with severe AD patients, the WMD was -0.06 (95% CI; -2.12, +0.57). Conclusion: Cholinesterase inhibitors lead to a statistical significant reduction in BPSD among patients with AD, yet the clinical relevance of this effect remains unclear.

New cholinesterase inhibitors for Alzheimer's disease: Structure Activity Studies (SARs) and molecular docking of isoquinolone and azepanone derivatives

A library of isoquinolinone and azepanone derivatives were screened for both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity. The strategy adopted included (a) in vitro biological assays, against eel AChE (EeAChE) and equine serum BuChE (EqBuChE) in order to determine the compounds IC50 and their dose-response activity, consolidated by (b) molecular docking studies to evaluate the docking poses and interatomic interactions in the case of the hit compounds, validated by STD-NMR studies. Compound (1f) was identified as one of these hits with an IC50 of 89.5 mu M for EeAChE and 153.8 mu M for EqBuChE, (2a) was identified as a second hit with an IC50 of 108.4 mu M (EeAChE) and 277.8 mu M (EqBuChE). In order to gain insights into the binding mode and principle active site interactions of these molecules, (R)-(1f) along with 3 other analogues (also as the R-enantiomer) were docked into both RhAChE and hBuChE models. Galantamine was used as the benchmark. The docking study was validated by performing an STD-NMR study of (1f) with EeAChE using galantamine as the benchmark.