Title:The Physiological Characteristics and Transcytosis Mechanisms of the Blood-Brain Barrier (BBB)
Volume: 13
Issue: 12
Author(s): Elizabeth CM de Lange
Affiliation:
Keywords:
Blood-brain barrier, transcytosis, transport, endothelial cells, astroglial endfeet, physiological characteristics of the BBB, transport systems, brain tissue, luminal endothelial membrane, choroid plexus epithelium, blood vessels, endothelial cells, luminal endothelial membrane, Brain cerebral capillaries
Abstract: The blood-brain barrier (BBB) is the vessel wall made up of specialized capillary endothelial cells, surrounded
by astroglial endfeet and neurons, that govern the exchange of compounds between blood and brain. It protects the brain
from harmful compounds potentially present in blood, while it is specifically designed to supply the brain with the
required nutrients and to get rid of waste products. The BBB is structurally different from blood capillaries in other
tissues. The BBB strictly limits the paracellular exchange of compounds by the so-called tight junctions. Moreover, the
capillary endothelial cells contain metabolic enzymes that may convert a compound before entering the brain while
transcellular passage across the BBB may be limited or increased by active transport systems. Thus the BBB has an
important role in the relationship of the concentration-time profile of compounds in blood and those in the brain. The
functionality of the BBB is dynamically regulated, depending on the given conditions. Important examples are changes in
BBB functionality that may result in or are brought about by (CNS) disease conditions. All together this indicates the
importance of investigations on BBB functionality and resulting transport of compounds for the design and optimization
of therapeutic regimens. Thus, BBB investigation is an ever growing and dynamic field studied by pharmacologists,
neuroscientists, pathologists, physiologists, and clinical practitioners. This review deals with a general introduction on the
physiological characteristics of the BBB, its different transport systems, with particular emphasis on supposed transcytosis
mechanisms at the BBB. Specific and detailed information on drug delivery approaches aiming at transcytosis into the
brain will be dealt with in other parts of this special issue.
