To investigate the in vitro effect of tanshinone IIA on leukocyte-associated hypoxia-reoxygenation injury of human brain-blood barrier (BBB), we established the BBB model by culturing purified primary human brain microvascular endothelial cells (HBMVEC) to confluence on cell culture insert. BBB was identified by tight junction, transendothelial electrical resistance (TEER) and the permeability of BBB to horseradish peroxidase (HRP). The effect of tanshinone IIA on the permeability of BBB was tested at 2 h after hypoxia and 1 h after reoxygenation with or without the supernatants of activated leukocytes. The effect of tanshinone IIA on leukocytes activation was analyzed by detection of MMP-9, cytokines and reactive oxygen species. The results showed that BBB formed by confluent HBMVECs had no cellular gap. Immunofluorescent staining for ZO-1 confirmed that the cells were connected by tight junction. Moreover, the BBB model had a higher TEER and a lower permeability for HRP than confluent HUVECs. The permeability of BBB for HRP was enhanced by hypoxia-reoxygenation and further greatly enhanced by adding the supernatants of activated leukocytes before reoxygenation. But such an effect was reversed by addition of tanshinone IIA before hypoxia. Moreover, tanshinone IIA could decrease the levels of MMP-9, TNF-alpha, IL-1 alpha, IL-2, IFN-gamma and reactive oxygen species in leukocytes. In conclusion, tanshinone IIA can protect BBB against leukocyte-associated hypoxia-reoxygenation injury by attenuating the activation of leukocytes and inhibiting the injury effects of leukocytic products. Tanshinone IIA may be a novel therapeutic agent for cerebral ischemia-reperfusion injury. (C) 2010 Elsevier B.V. All rights reserved.