Repeated electroacupuncture preconditioning attenuates matrix metalloproteinase-9 expression and activity after focal cerebral ischemia in rats

This study investigates the effects of electroacupuncture (EA) preconditioning on blood-brain barrier (BBB) integrity and matrix metalloproteinase-9 (MMP-9) expression in subsequent ischemic hemisphere.Focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) in rats. Animals were randomly divided into four groups: normal, sham-operated, MCAO and EA groups. In EA group, rats received electroacupuncture stimuli at the Baihui acupoint (GV 20) 30 minutes/day for 5 days. Twenty-four hours after last treatment, the MCAO was performed. The brain water content and BBB permeability were measured 24 hours after MCAO. MMP-9 expression and activity were measured at 6, 12 and 24 hours after MCAO.The results showed that the brain water content of ischemic hemisphere was lower in EA group (81.45 +/- 1.09%) compared with MCAO group (83.98 +/- 1.30%; p0.05). Similarly, the Evans blue content in EA group (4.90 +/- 1.77 microg/g) was lower compared with MCAO group (9.41 +/- 2.87 microg/g; p0.05). The protein expression and enzyme activity of MMP-9 increased and reached maximum at 24 hours after reperfusion. However, the protein expression was lower in EA group at 12 and 24 hours after reperfusion (p0.01, versus MCAO group), and enzyme activity was lower in EA group only at 24 hours (p0.01, versus MCAO group).EA preconditioning could attenuate brain edema and BBB disruption caused by subsequent cerebral ischemia. EA preconditioning could decrease MMP-9 expression and activity, which may be an important mechanism of cerebral ischemic tolerance.