Cerebrospinal fluid flow. Part 2. Aquaporins and their role in CNS water homeostasis

Abstract

The capabilities of the central nervous system to receive, integrate and process the incoming information, as well as to ensure an adequate timely response, are directly determined by the ability to maintain the electrochemical gradient of ions, a certain concentration of organic molecules and the transport of water through the plasma membrane of nerve cells. This dynamic disequilibrium is a key mechanism in the generation and transmission of information in neuronal intercellular communication, in the activation of extracellular signaling molecules, and in the metabolic support of the neural tissue.

It is obvious that maintaining stable homeostasis in the central nervous system is strictly regulated by the mechanisms of ion transport, organic and inorganic molecules, and water. Astrocytes provided with proteins of ionic and aqueous transmembrane channels communicate with neurons and cells lining the cavities filled with fluid. So astroglia is the basic element in achieving such homeostatic regulation of the CNS.

Astroglial-mediated homeostasis is highly dynamic, and it has been proven that the disruption of surface expression and the polarization of transport proteins in astroglial cells underlies various pathological conditions.

The discovery and further investigation of functional characteristics of specialized water channels — aquaporins was one of the milestones in the study of the mechanisms for maintaining water homeostasis of CNS. The present review deals with base ideas concerning the role of aquaporins in the processes of water transport, such as regulating cell volume, controlling the size of extracellular space, production and drainage of cerebrospinal fluid. Certain pathological conditions caused by a violation of water homeostasis and the drainage system of the central nervous system are considered.