THE IMPORTANCE OF TIGHT JUNCTIONS IN THE BLOOD-BRAIN BARRIER

There are two barriers in the central nervous system (CNS) responsible for maintaining the homeostatic balance of the human body's internal environment in relation to external conditions: the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). The blood-brain barrier is a physical barrier with a fixed location between the blood and the nervous tissue. Its basic structural elements include endothelial cells of the brain capillaries, astrocytes and pericytes. The blood-brain barrier is the barrier between the blood and neurons which isolates the central nervous system from the rest of the body in a unique manner. The blood-brain barrier is formed by astrocytes and pericytes in addition to the endothelium. Endothelial cells are tightly connected to each other by tight junctions. These connections are composed of a protein complex, which includes claudins, occludins and tricellulines. The dominant protein in the blood-brain barrier is Claudin-5. Physiologically, this barrier is a transport centre for many molecules between the central nervous system and blood. Active transport takes place mainly with the help of specific transport mechanisms. Disorders of the blood-brain barrier have an impact on many diseases of the central nervous system, indicating negative effects of the destruction of the blood-brain barrier on the functioning of the brain. At the same time, the barrier is an obstacle for protein-derived chemotherapeutic agents, which prevents the effective treatment of many brain tumours. Currently, there is much research into methods of controlling the permeability of this barrier. The bibliometric on BBB and BCSFB the period 2011-2021 was utilized in the study. A literature review was carried out searching through the PubMed, SCOPUS and Google scholar. The criterion of thematic classification was implemented to carry out an analysis of bibliographic data.