MMP9 and Stroke: Microglia are activated within hours and proinflammatory factors, such as TNF-α, IL-1β, IL-6, IFN-γ, chemokines, nitric oxide (NO), reactive oxygen species (ROS), and matrix metalloproteinase-9 (MMP-9) are released in response synapse loss after stroke, which aggravate neuronal death and disrupt the BBB [12, 58-60].