It was found earlier that the synthetic fragment corresponding to the 60–76 sequence of the extracellular domain of the receptor for advanced glycation end products (RAGE) had a protective effect on animal and cellular models of Alzheimer’s disease. It was proposed that this effect was mediated via the interaction of the peptide with beta-amyloid (Aβ), which was one of the RAGE ligands, by inhibiting the formation of toxic Aβ oligomers. The aim of this study was an application of physicochemical methods to an investigation of the ability of the 60–76 peptide to prevent the Aβ40 oligomerization in solution in comparison with the nonprotective 65–76 truncated peptide. The dynamics of the formation of the Aβ40 fibrils in the presence of the peptides was evaluated using thioflavin T. The relative sizes of oligomers were determined by dynamic light scattering. The peptide binding to Aβ40 was examined by fluorescence titration. We demonstrated by the two methods that the peptide corresponding to the 60–76 sequence of RAGE considerably inhibited (by more than 90%) the formation of oligomers and fibrils of Aβ40 distinct from the 65–76 peptide. In addition, we found that the protective effect of the peptides and their ability to inhibit the Aβ40 oligomerization did not correlate with their binding to the monomeric/tetrameric Aβ40. We confirmed in vitro the hypothesis that the protective activity of the synthetic 60–76 fragment of RAGE was associated with its ability to inhibit the Aβ oligomerization.

The solid-phase synthesis and purification of the 1-40 sequence of the human beta-amyloid were optimized, resulting in a preparation of a product with a high yield and homogeneity more than 95%. The synthetic peptide is capable of forming oligomers. This fact was confirmed by electrophoresis in the polyacrylamide gel with a subsequent immunoblotting and fluorescence spectrophotometry using the thioflavin T dye. An available method for a production of the highly specific anti-beta-amyloid antibodies with a high titer was developed. These antibodies recognized both monomeric and oligomeric forms of the 1-40 peptide of beta-amyloid under the immunoblotting conditions.

The membrane receptor for advanced glycation endproducts (RAGE) is involved in the development of a number of pathological conditions, including Alzheimer’s disease (AD), in which the receptor overexpression in brain cells and its increasing activity is observed. We have previously shown that the synthetic fragment RAGE (60–76), administered intranasally, could prevent the disturbance of the spatial memory of olfactory bulbectomized mice, that develop features of AD. We suggested that N-terminal amino function of the peptide protected with acetic group and C-terminal carboxyl group replaced with amide, would increase the stability of this peptide in in vivo experiments, and this protected peptide would show higher activity compared to the original free one. In the current study the protected peptide analog Ac-(60–76)-NH 2 was synthesized. The activity of the peptide (60–76) and its protected analog has studied in transgenic 5xFAD mice, which represent a generally accepted model of AD. The memory testing was performed in the Morris water maze. It was shown that intranasal administration of these peptides to transgenic 5xFAD mice for two months preserved the spatial memory of animals, and both peptides exhibited the same ability to prevent the spatial memory. The difference in the activity of the tested peptides was revealed 7 days after drug administration had been over, and only animals, previously received the modified peptide Ac-(60–76)-NH 2 , showed the ability to find the Morris water maze learning sector. The animals received the peptide (60–76) lost their ability to find the learning sector after 7 days and were completely disoriented. The data obtained allow us to conclude that the modified fragment (60–76) with protected N- and C-terminal functional groups has a more pronounced and long lasting protective effect compared to the free peptide (60–76). Thus, Ac-(60–76)-NH 2 is a promising candidate for development of the drug for the treatment of Alzheimer’s disease.

Objectives. Therapeutic monitoring and evaluation of the efficacy of neurotrophic therapy in patients with amnestic-type mild cognitive decline syndrome (aMCI) were performed in a model using courses of cerebrolysin. Materials and methods. A total of 19 elderly patients meeting the diagnostic criteria for aMCI syndrome were studied. All patients received treatment with cerebrolysin: 20 intravenous dropwise infusions of 30 ml in 100 ml of physiological saline. Treatment efficacy was evaluated using psychometric tests and scales (CGI, MMSE, MoCA, MDRS, clock drawing test, BNT, 10-word memory test, 10-word delayed reproduction test, forward number naming test, backward number naming test) at study weeks 0, 4, 10, and 26. Levels of autoantibodies to p75 neurotrophin receptor were determined by solid-phase immnoenzyme analysis. Serum from 19 patients was studied before cerebrolysin treatment (day 0) and at weeks 10 and 26 after treatment initiation. Results and conclusions. Patients with aMCI had increased levels of autoantibodies to p75 fragment, with gradual decreases by 5.5 months of cerebrolysin treatment, indicating that this can potentially be used as a biomarker for long-term therapeutic efficacy. The modified p75 receptor fragment 155–164, assayed in patients’ serum, may provide an effective tool for monitoring and predicting the efficacy of long-term neurotrophic therapy.

Background: Alzheimer’s disease (AD) is a chronic brain disorder associated with neuronal death and beta-amyloid oligomerization. Toxic effect of beta-amyloid occurs via many receptors on the cell surface. One of them is Receptor for Advanced Glycation End-products (RAGE). RAGE activation causes brain inflammation, oxidative stress and secretion of beta-amyloid. Thus, RAGE is considered as a potential therapeutic target for AD drug development.

Six synthetic peptides overlapping a fragment 60–76 of the receptor for advanced glycation end products (RAGE) were studied on a protective effect on spatial memory of animals in the experimental model of Alzheimer’s disease. It was shown that only a peptide corresponding to the fragment 60–70 of RAGE exhibits a therapeutic activity. Intranasal administration of this peptide into bulbectomized mice, which develop neurodegenerative features of the Alzheimer type, completely protects animal memory. Thus, it was found that the N -terminal region (60–70) within the peptide sequence 60–76 of RAGE is responsible for the revealed protective effect. The synthetic peptide RAGE-(60–70) could be the basis for the development of a new drug for the treatment of Alzheimer’s disease.

The receptor for advanced glycation end products (RAGE) plays an essential role in the development of Alzheimer's disease. Activation of RAGE causes brain inflammation, oxidative stress and secretion of beta-amyloid. It is known that the soluble isoform of receptor (sRAGE), which lacks the transmembrane and cytosolic domains, binds to ligands and prevents negative effects of the receptor activation in in vivo and in vitro experiments. We proposed that peptide fragments from sRAGE would demonstrate the same biological activity. RAGE fragments were prepared with standard Fmoc/Butprotocol of solid-phase peptide synthesis. NMRI mice were used after olfactory bulbectomy (OBX) which induced behavioral, morphological and biochemical signs of the Alzheimer's type degeneration. In 2 weeks after the surgery peptides were intranasally administrated in a dose of 20 mg per mouse during 15 days. Murine memory was tested in the Morris's water maze. We used Nissl staining to observe the morphological state of neurons in the temporal cortex and areas of CA1 and CA3 of the hippocampus. We counted the neuronal density, the percentage of normal neurons and neurons with pathologies. We selected and synthesized ten peptide fragments from unstructured surface-exposed regions of RAGE. We found that after intranasal administration of peptides only fragment (60–76) effectively prevents murine memory from impairment. Six overlapping fragments of RAGE (60–76) peptide were synthesized to find a site responding for the therapeutic effect. Tests carried out with these fragments showed that only (60–70) peptide is responsible for preventing animal memory impairment. Fragments (60–76) and (60–70) block the development of neuronal pathology in OBX mice. However, some N-terminal fragments which do not have significant activity in Morris's test also improve the morpho-functional state of neurons in OBX animals, but not so efficient in several aspects. There is a correlation between memory improvement activity and maintenance of neuronal morphology on a normal level after intranasal administration of RAGE fragment. Peptides (60–76) and (60–70) are active in both tests. Several N-terminal fragments also protect morphological state of neurons, but less noticeably, which corresponds with the absence of effect in Morris's test. Supported by RFBR Grant 15–04–01360, 17–34–80016 ”moleva.

Прионный белок является одной из мембранных мишеней бета-амилоида, основного нейротоксического агента при болезни Альцгеймера. Нами был осуществлен выбор и синтез фрагментов прионного белка 17–33, 23–33, 95–110 и 101–115, ответственных за связывание с бета-амилоидом. Было изучено влияние иммунизации пептидами на развитие признаков болезни у животных с экспериментально индуцированной формой болезни Альцгеймера. Показано, что иммунизация свободным пептидом 17–33 и белковыми конъюгатами пептидов 23–33 и 101–115 приводит к восстановлению состояния пространственной памяти животных. Также показано, что иммунизация пептидом 17–33 приводит к снижению уровня мозгового бета-амилоида и восстановлению морфофункциональных показателей мозга.

The prion protein is considered as one of the membrane targets of the neurotoxic beta-amyloid during development of Alzheimer’s disease. We chose and synthesized peptide fragments that corresponded to the 17–33, 23–33, 95–110, and 101–115 sequences of the prion protein and are responsible for the betaamyloid binding. The effect of immunization with the peptides on the development of symptoms of Alzheimer’s disease was investigated on animals with an experimentally induced form of the disease. Immunization with either free 17–33 peptide or with protein conjugates of the 23–33 and 101–115 peptides was shown to restore spatial memory of the animals. Immunization with the 17–33 peptide was also shown to decrease the level of brain beta-amyloid and to recover morphofunctional parameters of the brain.

The ability of some synthetic peptides modeling the potentially important regions of four membrane proteins, known as cell targets for beta-amyloid, to restore the spatial memory of animals in an experimental model of Alzheimer’s disease has been studied. Nine fragments of the protein receptor for advanced glycation end products (RAGE), which, according to X-ray structure analysis data, repeat all its exposed nonstructural regions, have been synthesized. The effect of these peptides and of earlier synthesized immunoprotective fragments of three other proteins (alpha7-type acethylcholine receptor, the prion protein, and the neurotrophin receptor p75) has been studied on intranasal administration, which excludes the development of the immune response to the peptide. It has been shown that only one fragment, RAGE (60–76), exhibits a therapeutic activity, by restoring the spatial memory of bulbectomized mice and decreasing the level of the brain beta-amyloid.