Salvianolic acid B alleviate the disruption of blood-brain barrier in rats after cerebral ischemia-reperfusion by inhibiting MAPK pathway

The aim of the study is to investigate the effect of salvianolic acid B (SalB) on blood-brain barrier (BBB) in rats after cerebral ischemia-reperfusion, and to illustrate its possible mechanisms.  Cerebral ischemia- reperfusion was induced by middle cerebral artery occlusion in rats.  The break-down of BBB was indicated by extravasations of immunoglobulin (IgG) monitored with immunohistochemistry.  The expression of MMP-9 and NOS2 in the brain was determined by immunohistochemistry, and the expression of p-p38 and p-ERK1/2 was detected by Western blotting.  It was shown that on day 2 after ischemia-reperfusion the IgG accumulated around the vascular boundary zone, suggesting the break-down of BBB, and the expression of MMP-9 and NOS2 up-regulated at the same time.  The result of Western blotting suggested that the expression of p-p38 and p-ERK1/2 increased.  On day 7 after ischemia-reperfusion the expression of MMP-9 and NOS2 was about the same level as day 2, the expression of p-p38 was higher than that on day 2 and the expression of p-ERK1/2   was slightly lower than that on day 2.  SalB (1 and 10 mg·kg⁻¹) significantly alleviated the extravasations of immunoglobulin induced by cerebral ischemia-reperfusion (P < 0.05).  On day 2 and day 7 SalB attenuated the expression of MMP-9 and NOS2 (P < 0.05).  SalB (10 mg·kg⁻¹) reduced the expression of p-p38 and p-ERK1/2 apparently on day 2 and 7 after ischemia-reperfusion (P < 0.05).  SalB (1 mg·kg⁻¹) inhibited the expression of p-p38 on day 7 after ischemia-reperfusion (P < 0.05).  The results indicate that SalB protects blood-brain barrier in rats after cerebral ischemia-reperfusion by inhibiting the MAPK pathway.