Figure 1.

Illustration of the neurovascular unit (NVU) in the central nervous system. (A) The NVU comprises multiple cell types, including neurons, vascular smooth muscle cells, endothelial cells, astrocytes, microglia, and pericytes. Astrocytes and microglia release various factors (including TNF-α, IL-1β, IL-6, and VEGF), which act on neurons and endothelial cells. (B) Enlarged illustration of the interaction between astrocytes and endothelial cells. Under pathological conditions, several inflammatory cytokines (TNF-α, IL-1β, and IL-6) that are released by activated astrocytes may cause a positive feedback on the production of VEGF. These factors (TNF-α, IL-1β, IL-6, and VEGF) may collectively induce the proliferation of endothelial cells and lead to neurovascular abnormalities in brain disorders.