Positive Effect of YB-1 and Mesenchymal Stromal Cells on Primary Hippocampal Culture under Conditions of ACE2 Receptor Blockade

Although the current COVID-19 incidence situation is not an emergency, more new strains of SARS-CoV-2 coronavirus continue to emerge worldwide, some of which are more virulent than the original virus. Studies have shown that patients with Alzheimer's disease (AD) had a high risk of severe COVID-19, but the molecular and cellular mechanism of this predisposition is not fully elucidated. In this study, we developed a cellular model of the initial stage of COVID-19 on primary hippocampal culture of 5xFAD mice, a familial AD model, using a specific ACE2 receptor inhibitor, MLN-4760. This model is based on the experimentally proven decrease in ACE2 receptor activity observed in COVID-19 patients due to internalization of the receptor inside the cell after binding to coronavirus. Using immunochemical staining with specific antibodies to detect neurons (marker MAP2) and astroglia (marker GFAP), it was found that 24 h after the addition of MLN-4760 (0.2 nmol per 1 mL of medium) to the culture medium, there was a decrease in the density of astrocytes and neurons, a change in their morphology with a sharp reduction in the length and density of neurites, which led to the death of the cell culture. The transgenic culture was more sensitive to the effect of the inhibitor compared to the control hippocampal culture of native mice. In the second part of the study the possibilities of preventing the destructive effect of MLN-4760 on the hippocampal culture condition were studied. It was shown that administration of YB-1, an endogenous polyfunctional stress protein, promoted restoration of cell culture structure and resulted in stimulation of neurite growth and astroglia activation. Introduction of multipotent mesenchymal stromal cells (MMSCs) after ACE2 blockade was also accompanied by improved culture survival, restoration of cell morphology, and increased density of astrocytes and neurons. The obtained results indicate that YB-1 and cell therapy using MMSCs are promising options for the development of new effective methods to prevent the pathological effect of the virus on brain tissue, which is an important link in the treatment of infection caused by SARS-CoV-2 virus.