Neutrophils infiltrating the CNS can produce proinflammatory mediators [such as interleukin (IL)-1β] and a series of destructive factors, including reactive oxygen species (ROS), neutrophil elastase, and matrix metalloproteinases 9 (MMP-9), which leads to destruction of the blood-brain barrier (BBB), further aggravating inflammatory injury after ischemia in ACI patients [12, 13]. Here, MMP9 is linked to ischemia.