CHANGES IN THE ULTRASTRUCTUREAND FUNCTIONAL PROPERTIES OF LYMPHOCYTES IN OLDER ADULTSAT ACTIVATION OF THE PURINERGIC SIGNALLING SYSTEM (<i>in vitro</i>)
The purinergic signalling system plays a significant role in the functioning of the body from the early stages of embryogenesis through the postnatal period. It is known that with ageing, the expression of purine receptors in the nervous tissue and in the vascular endothelium decreases. However, the available literature data on the functioning of the purinergic receptor complex on the surface of blood cells is extremely scarce. This paper aimed to study the changes in the ultrastructure and functional properties of lymphocytes in older adults at activation of the purinergic signalling system. By means of mechanical stress in vitro , we modelled conditions close to physiological in the microvasculature. The structure and biophysical properties of the cell membrane, which determine the functioning of blood cells, were studied using an atomic force microscope. The elastic properties of the lymphocyte surface were analysed based on the Young’s modulus. The electrical properties of the plasma membrane were evaluated by measuring the surface potential in the Kelvin probe mode. The mechanisms of intercellular adhesion were analysed using force spectroscopy. We found that the mechanical stress-induced release of adenosine triphosphate (ATP) by blood cells affected the structure and biophysical parameters of the lymphocyte surface. When modelling the conditions of mechanical deformation of cells, the ATP level in the blood increased by the factor of 2.6 compared with the control. The number of morphological formations on the lymphocyte plasma membrane decreased in the presence of larger globular structures. Moreover, lymphocyte stiffness decreased, while the cell surface charge and adhesion strength between lymphocyte and erythrocyte increased. The obtained experimental data can be of great importance in the diagnosis and treatment of various pathological conditions that accompany ageing.