New Hybrid Structures Based on Memanthine and Edaravone Molecules.

New hybrid structures based on memantine and edaravone molecules, in which the pyrazolone ring and adamantane fragments are linked by an alkyl linker, were synthesized. It was found that, in addition to the ability to block the intrachannel site of NMDA receptors, the new hybrid compounds exhibit the property of blockers of the allosteric site of NMDA receptors, which is not inherent in memantine and edaravone preparations. The most active hit compound was determined, which, along with the properties of a two-site blocker of the NMDA receptor, exhibits a pronounced activity as an inhibitor of lipid peroxidation, similarly to the drug edaravone.

Wave-Like Dose-Dependence of the Stimulating Effects of Dimebon on Cognition in a Wide Dose Range.

Comparison of the cognition-stimulating effects of Dimebon in a wide dose range revealed a non-monotonic and nontrivial wave-like dose-dependence of its activity. Positive results were obtained at low (0.02-0.05 mg/kg) or high (5-10 mg/kg) doses of Dimebon, while intermediate doses were ineffective. This type of the dose dependence of the pharmacological effect can indicate that the substance has several targets. This fact should be taken into consideration when selecting the doses and concentrations of the substance and its analogues for further studies, and for planning treatment schemes and administration doses in clinical studies.

Anticholinesterase and Antioxidant Activity of New Binary Conjugates of γ-Carbolines.

The synthesized new binary conjugates of tetrahydro-γ-carbolines, which contained ditriazole spacers of different length, exhibited considerable anticholinesterase and antioxidant activity as well as the potential ability to block the acetylcholinesterase-induced aggregation of ß-amyloid in contrast to the original prototype Dimebon. This makes the compounds promising candidates for further investigation as drugs for the treatment of Alzheimer's disease. Special attention should be given to the conjugate containing the hexamethylene intertriazole spacer, which can be considered as a leader in this series of compounds.

Influence of Al3+, Fe3+ and Zn2+ Ions on Phosphorylation of Tubulin and Microtubulo-Associated Proteins of Rat Brain.

Phosphorylation of τ-protein, a component of microtubules in brain neurons, is a key pathomorphological sign of Alzheimer's disease. The development of this intracellular defect can be promoted by Al3+, Fe3+, and Zn2+ ions. The concentrations of these ions in the brain are considerably elevated in Alzheimer's disease. We performed a comparative study of phosphorylation of microtubular proteins of rat brain in the presence of Al3+, Fe3+, and Zn2+ ions in concentrations of 10-500 µM and microtubular proteins of brain of patients with Alzheimer's disease. The most likely candidate for the role of a factor that promotes hyperphosphorylation of τ-protein is Al3+ in concentrations of 250 and 500 µM.

Antioxidant Properties of a Pharmaceutical Substance Hypocard, a Potential Drug for Ischemic Disease.

Antioxidant activity of a pharmaceutical substance hypocard was compared with activity of nitromalic acid and well-known agents nicorandil and Mexidol. The ability of these substances to inhibit spontaneous and oxidant-induced LPO process in rat brain homogenate was analyzed. The mechanisms of these effects were studied. The antioxidant properties of hypocard manifested in the inhibition of Fe(II)-induced LPO were significantly more pronounced in comparison with Mexidol and nicorandil.

Effect of Aluminum, Iron, and Zinc Ions on the Assembly of Microtubules from Brain Microtubule Proteins.

Al(3+), Fe(3+), and Zn(2+) ions can disturb microtubule assembly from tubulin and microtubuleassociated proteins in rat brain. The main structural forms of these microtubules are rings and tangled bundles. These structures are formed only in the presence of Al(3+) and Fe(3+) ions. Therefore, Zn(2+) ions can be excluded from possible causes of structural abnormalities in microtubules during Alzheimer's disease. Al(3+) ions are the most probable etiological cause of Alzheimer's disease. The concentration of Al(3+) ions affecting the structure of microtubules is one order of magnitude lower than that of Fe(3+) ions (10 and 100 µM, respectively), which corresponds to their brain concentration reported in Alzheimer's disease.

Biological Activity of Spirocyclic Hydroxamic Acids.

Iron-chelating activity of synthesized spirocyclic hydroxamic acids, their toxicity, and effects on mitochondrial function were studied using primary culture of cerebral cortical neurons from newborn rats. All tested compounds effectively chelated Fe(II) ions. Activity of spirocyclic hydroxamic acids more strictly depended on the structure their piperidine, but not imidazolidine fragment. All compounds were non-toxic for normal neuronal culture.

N,N'-Substituted Selenoureas as Polyfunctional Antioxidants.

Analysis of antioxidant activity of synthesized selenourea derivatives showed that N,N'-substituted selenoureas inhibited Fe(III)-induced LPO in rat brain homogenate. On the other hand, oxygen- and sulfur-containing analogs exhibited no antioxidant activity or even slight prooxidant activity. Intramolecular alkylation of selenium atom also led to loss of antioxidant activity. Thus, antioxidant activity of the compounds was due to the presence of a nonalkylated selenium atom in N,N'-substituted selenourea analogs.

Effects of anti-Alzheimer drugs on phosphorylation and assembly of microtubules from brain microtubular proteins.

We studied the effects of anti-Alzheimer drugs (tacrine, amiridine, and memantine) on phosphorylation of tubulin and microtubule-associated proteins isolated from rat brain, evaluated the capacity of these proteins to polymerize into microtubules after addition of study pharmacological agents, and analyzed the structure of generated microtubules. It was shown that test substances impair assembly of microtubules to a different extent. Dose-dependent effects of these agents on phosphorylation of tubulin and microtubule-associated proteins were observed. Triazolam (not approved for clinical use as anti-Alzheimer drug) in the same concentrations was used as the reference substance in the same tests. It was observed that this substance even in minimal concentration induced the most pronounced changes in microtubule structure. A direct correlation between the capacity of the test substances to modulate tubulin phosphorylation and to impair microtubule structure was found: the more the substance inhibited tubulin phosphorylation, the more it disordered microtubule structure.

Mechanisms of antioxidant effect of natural sesquiterpene lactone and alkaloid derivatives.

We performed screening of potential antioxidants among natural lactone and alkaloid derivatives and characterized their antioxidant effects. The substances exhibiting antioxidant and metal-chelating potential, in particular, tryptamine derivatives, are promising neuroprotector agents.

Antioxidative activity of ferrocenes bearing 2,6-di-tert-butylphenol moieties.

The antioxidative activity of ferrocenes bearing either 2,6-di-tert-butylphenol or phenyl groups has been compared using DPPH (1,1-diphenyl-2-picrylhydrazyl) test and in the study of the in vitro impact on lipid peroxidation in rat brain homogenate and on some characteristics of rat liver mitochondria. The results of DPPH test at 20 degrees C show that the activity depends strongly upon the presence of phenolic group but is improved by the influence of ferrocenyl fragment. The activity of N-(3,5-di-tert-butyl-4-hydroxyphenyl)iminomethylferrocene (1), for instance, was 88.4%, which was higher than the activity of a known antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) (48.5%), whereas the activity of N-phenyl-iminomethylferrocene 2 was almost negligible -2.9%. The data obtained demonstrate that the compounds with 2,6-di-tert-butylphenol moiety are significantly more active than the corresponding phenyl analogues in the in vitro study of lipid peroxidation in rat brain homogenate. Ferrocene 1 performs a promising behavior as an antioxidant and inhibits the calcium-dependent swelling of mitochondria. These results allow us to propose the potential cytoprotective (neuroprotective) effect of ditopic compounds containing antioxidant 2,6-di-tert-butylphenol group and redox active ferrocene fragment.

Synthesis and antioxidative activity of metalloporphyrins bearing 2,6-di-tert-butylphenol pendants.

The novel metalloporphyrins (M=HH, Fe, Mn, Co, Cu, Zn) bearing 2,6-di-tert-butylphenol pendants as antioxidant substituents, and a long chain hydrocarbon palmitoyl group have been synthesized. The oxidation of compounds by PbO2 leads to the formation of the corresponding 2,6-di-tert-butylphenoxyl radicals studied by EPR. The activity of porphyrins in lipid peroxidation has been examined using (1) in vitro lipid peroxidation induced by tert-butylhydroperoxide in respiring rat liver mitochondria, (2) in vitro lipid peroxidation in liver homogenates of Wistar strain rats, and (3) a model process of peroxidation of (Z)-octadec-9-enic (oleic) acid as a structural fragment of lipids. The activity of these compounds depends dramatically on the nature of metal and might be changed from antioxidative (M=HH, Mn, Cu, Zn) to indifferent (M=Co), and to pro-oxidative one (M=Fe). The anti- or pro-oxidative action of these compounds may be derived from the concurrence between the involvement of 2,6-di-tert-butylphenol pendants acting as radical scavengers and redox active metal center promoting oxidation processes. The results of this study suggest that the polytopic compounds combining in one molecule 2,6-di-tert-butylphenol pendants, metalloporphyrin moiety, and a palmitoyl group, are membrane active compounds and might be studied in an effort to find novel pharmaceutical agents.

[Tumor necrosis faсtor-alpha - potential target for neuroprotector dimebon]. / Faktor nekroza opukholei-al'fa - potentsial'naia mishen' dlia neiroprotektora dimebona.

Dimebon (Dimebolin) is an antihistamine drug which has been used in Russia since 1983. Recently Dimebolin has attracted renewed interest after being shown to have positive effects on persons suffering from Alzheimer's disease. Animal studies have shown that dimebon acts through multiple mechanisms, both blocking the action of neurotoxic beta-amyloid peptides and inhibiting L-type calcium channels, modulating the action of AMPA and NMDA glutamate receptors. Our experiments with cell culture L929 and mice have shown that dimebon may exert its neuroprotective effect by blocking cytotoxic signals induced by proinflammatory cytokines such as TNF-a which are believed to play a central role in Alzheimer's disease. Dimebon (10 mg/ml) protected mouse fibroblasts L929 against the toxic action of TNF-a. Our study included 65 male mice. TNF-a (10 mg per mouse), dimebon (0,2 mg/kg) and their combination were injected intraperitonealy. Changes in the level of molecular species of sphingomyelin and galactosyl ceramide in hippocampus, cerebellum and cerebral cortex within 30 min, 2 h, 4 h, and 24 h after injection were detected by chromato-mass-spectrometry. Maximal changes in sphingomyelin and galactosyl ceramides contents of different molecular species after single TNF-a administration were found in the hippocampus, and were less expressed in the cerebral cortex and cerebellum after 24 h. Dimebon itself did not induce changes in the sphingolipid spectrum in brain sections, but protected them against disorders induced by TNF-a in the brain. Modern strategies in the search of new therapeutic approaches are based on the multitarget properties of new drugs. According to our results TNF-a may serve as a new target for dimebon.

[Mitochondria as the target for neuroprotectors].

Contemporary methods of treatment of neurodegenerative diseases (NDs) are limited and mainly symptomatic. Despite difference in particular clinical manifestations, NDs have a number of common features, the main of which is death of certain neuron population. The authors suppose that mitochondria and the phenomenon of mitochondrial permeability transition (MPT), playing the key role in cell death, may be a perspective target for the search of drugs with a capability of delaying the neurological deficit associated with NDs. The authors have demonstrated that some neurotoxins which are widely used to model neurodegenerative conditions are able to potentiate or even induce MPT. The neuroprotective effect of widely used cognition-enhancing drugs, such as tacrin, memantine, dimebon, N-acethylserotonine, and extract of Gingko biloba), may also be a result of their interaction with mitochondria. Thus, the search of drugs capable of preventing or breaking the cascade of cell death as a result of MPT suppression and, at the same time, compensating for the impaired brain functions, is very topical.

Effect of tacrine, amiridine, akatinol memantine, and triazolam on phosphorylation, structure, and assembly of microtubules from brain microtubular proteins in Alzheimer diseases.

In in vitro experiments, amiridine in concentration of 100, 200, and 300 microM restored disturbed structure of microtubules assembled from tubulin and microtubule-associated proteins isolated from the brain of patients with Alzheimer disease. Tacrine in a concentration of 100, 250, and 500 microM inhibited phosphorylation of tubulin and microtubule-associated proteins isolated from the brain of patients with Alzheimer disease, while memantine and amiridine in the specified concentrations had no effect on phosphorylation.

Disturbed assembly of human cerebral microtubules in Alzheimer's disease.

It is shown for the first time that microtubular proteins isolated from the brain of patients with Alzheimer's disease can in vitro polymerize into microtubules with abnormal structure.

Dimebon and tacrine inhibit neurotoxic action of beta-amyloid in culture and block L-type Ca(2+) channels.

Dimebon, a Russian-made drug, inhibited toxic effects of beta -amyloid on cultured neurons. Excessive accumulation of beta-amyloid in the brain is characteristic of Alzheimer dementias. Antialzheimer preparations tacrine and dimebon improve survival of cerebellar granule cells during long-term incubation with Abeta25-35, the neurotoxic fragment of beta-amyloid. Both preparations can block potential-dependent Ca(2+) entry into neurons by about 20%, which is explained by their selective action on L-type Ca(2+) channels. It was assumed that the neuroprotective effect of dimebon and tacrine against Abeta25-35 partially depends on inhibition of potential-dependent Ca(2+) entry.