TLR4 and brain ischemia: For example, during cerebral ischemia-reperfusion, a substantial amount of inflammatory factors produced by the microenvironment can interact with surface receptors on BMECs, such as TNFR (tumor necrosis factor receptor) and TLR4 (toll like receptor 4), thereby triggering downstream activation involving the NFкB (nuclear factor kappa B) axis [17,18].