Potential roles of brain barrier dysfunctions in the early stage of Alzheimer's disease.

Though Alzheimer's disease (AD) has been studied for more than a century, to date, no drug has provided a definitive cure. The slow development of the disease and the time lag between pathological changes and the appearance of symptoms make AD difficult to diagnose and result in a missed window of opportunity for effective treatment. Currently, there is still no effective treatment for the late stage of AD, though delayed onset or attenuation of symptoms is possible in the early stages of the disease. The brain barrier is composed of the blood-brain barrier and blood-CSF barrier and is a composite structure of highly selectivity permeability vessels and capillaries in the CNS. Dysfunction of the brain barrier has been confirmed in the late stage of AD; however, whether this dysfunction aggravates the development of AD in the early stage has not been investigated. In this mini-review, we review the basic structure of the brain barrier, including the various protein components and related cytokines and attempt to identify how these might potentially contribute to brain barrier dysfunction in the early stages of AD.