Over 1.5 billion people worldwide – or about 25% of the world population – suffer from brain disorders, including depression, stroke, neuro-AIDS, epilepsy, brain tumors, and Alzheimer’s disease. Despite this huge demand for treatments, delivery of drugs into the brain to treat these disorders is greatly impaired by the blood-brain barrier.

The blood-brain barrier is the interface between blood and brain that controls what goes in and comes out of the brain. Anatomically, the blood-brain barrier is made of endothelial cells forming a complex capillary network that supplies the brain with oxygen and nutrients, and disposes of carbon dioxide and wastes.

At the molecular level, three elements contribute to barrier function. First, tight junctions between endothelial cells form a physical barrier that restricts solutes from entering the brain. Second, metabolizing enzymes form a biochemical barrier by inactivating compounds in the brain. Third, transporters constitute an active barrier by facilitating uptake of nutrients as well as removing metabolic waste products and limiting toxins and a large number of therapeutic drugs from entering the brain. These three elements combined pose a huge challenge to deliver drugs into the brain for treatment.

Recent studies also show that the blood-brain barrier is affected by brain disorders and itself plays a role in causing disease. Therefore, understanding blood-brain barrier function under physiologic and pathophysiologic conditions holds the promise for new therapeutic strategies to enhance brain drug delivery, improve brain protection, and treat brain disorders.

Currently, we study the role of the blood-brain barrier in three disorders: