Biomarkers of Blood–Brain Barrier Dysfunction

The brain is composed of certain interfaces, such as the blood–brain barrier (BBB), the blood–cerebrospinal fluid barrier (BCSFB), and the blood–spinal cord barrier. These can be collectively called blood–CNS barriers or brain barriers. The structure and function of brain barriers are very complex and maintain the neuronal microenvironment, playing pivotal roles in CNS homeostasis. The BBB is formed of extremely tight junctions offering a wide range of functions, such as transendothelial transport systems, enzymes, and regulation of leukocyte permeation, which thereby generates the transport, enzymatic, and immune regulatory functions of the BBB. Studies have also revealed important stages, cell types, and signaling pathways involved in BBB development. Under physiological conditions, the BBB regulates the exchange of nutrients, waste, and immune cells between the blood and the nervous tissue of the CNS and is the most important component in preserving CNS homeostasis and neuronal function. The brain barriers, particularly BBB, are very sensitive to the toxic insult of chemicals and biotoxins, and these barriers play pivotal roles in the initiation and progression of neurodegenerative diseases. This chapter describes in brief the structure and function of brain barriers and the biomarkers of toxic effects of metals, pesticides, mycotoxins, drugs of abuse, and some diseases involving the CNS.