Prospects of using peptide drugs for the prevention and treatment of Alzheimer’s disease

BACKGROUND . Alzheimer’s disease (AD) is the most common neurodegenerative disease that causes memory loss predominantly in eldely and senile people [1]. AD is one of the most common causes of death within 5–12 years after the first detected symptoms. Modern drugs approved by the FDA (U.S. Food and Drug Administration) for the AD treatment (memantine, tacrine, rivastigmine, galantamine, donepezil) do not significantly slow down the disease progression [2] and have a wide range of side effects [3]. In view of the lack of effective treatment, the rising global prevalence of AD and significant costs of patient life support, finding effective and safe potential anti-AD drugs is becoming increasingly critical in the context of a global trend towards longer life expectancy. Peptide bioregulators are promising neuroprotectors with low immunogenicity and high physiological activity. In particular, AD therapy may benefit from studying the activity of EDR and KED short peptides obtained by analysis of amino acid composition of extracts isolated from cattle brain and vessels, respectively. AIM. To evaluate the efficacy of short peptides in in vitro and in vivo models of Alzheimer’s disease with a view to developing a drug for the treatment and prevention of this pathology. MATERIALS AND METHODS . A neuronal culture isolated from the brain of newborn wild-type mice, with the addition of synthetic oligopeptides Aβ (the amyloid synaptotoxicity model) was used as the in vitro model of AD. The study groups were as follows: Group 1: control (without Aβ); Group 2: control with the addition of Aβ; Group 3: the addition of Aβ and EDR peptide (200 ng/mL); Group 4: the addition of Aβ and KED peptide (200 ng/mL). Series of neuron microphotographs were obtained using the ThorLabs confocal microscope and ThorLabs software (USA) at the 100-fold magnification (Olympus UPlanSApo) with resolution 1024×1024, which were used for dendritic spine morphology analysis using NeuronStudio software package according to [4]. The transgenic line of 5xFAD-M mice derived by cross-breeding of 5xFAD and Thy1-GFP mice was used as an in vivo model of AD. The experimental groups were as follows: Group 1: control (a line of healthy mice, which received the injections of physiological solution); Group 2: 5xFAD-M line of mice (AD model), which received the injections of physiological solution; Group 3: 5xFAD-M line of mice (AD model), received the injections of EDR peptide; Group 4: 5xFADM line of mice (AD model), received the injections of KED peptide. Short peptides were intraperitoneally injected in mice aged from 3 to 5 months on a daily basis. At the age of 5 months, the animals underwent transcardial perfusion followed by brain extraction; fixed brain slices (40 μm thick) were prepared using a vibratome. Series of neuron microphotographs were obtained using the ThorLabs confocal microscope and ThorLabs software (USA), followed by morphometric analysis of dendritic spines. RESULTS. EDR peptide at the concentration of 200 ng/mL increased the number of the most functional mushroom spines of neurons (by 71%) to normal levels in the primary neuronal culture under amyloid synaptotoxicity conditions (in vitro AD model). KED peptide at the concentration of 200 ng/mL increased the number of mushroom spines by 20% in the AD model. Daily intraperitoneal injection of EDR and KED peptides at a concentration of 400 μg/kg to 5xFAD mice (in vivo AD model) aged from 3 to 5 months contributed to statistically significant increases in mushroom spines in the CA1 area of the hippocampus by 25% and 27%, respectively. These peptides contributed to the increase in the total dendritic density by 13% and 22%, respectively. CONCLUSIONS . The obtained results demonstrate that EDR and KED short peptides have a neuroprotective effect in the AD model, manifested by an improved functional state of neurons. Further research is needed to identify the mechanism of action of short peptides in AD in order to develop a drug for the prevention and treatment of this pathology.