Bradykinin preconditioning modulates aquaporin-4 expression after spinal cord ischemic injury in rats

The study investigated whether bradykinin (BK) preconditioning could regulate the expression of aquaporin-4 (AQP4) using an in vivo transient spinal cord ischemia model in rats. BK was infused continuously via the left femoral artery with infusion pump for 15 min (10 mu g/kg/min) then we induced ischemia for 20 min and reperfusion for 24 and 72 h respectively. The results demonstrated that the central part of the white matter exhibited loss of perivascular AQP4 and showed a partial recovery toward 72 h of reperfusion. The border zone of white matter was different from the central part of the white matter by showing no loss of perivascular AQP4 at 24 h of reperfusion but rather a slight increase. BK significantly reduced the expression level of AQP4 protein in the white matter, but it had none of this effect in the gray matter region at 72 h post-reperfusion. There was no difference in AQP4 protein levels between BK group and control group at the two above-mentioned spinal cord regions at 24 h after reperfusion. In addition, the changes in AQP4 protein induced by BK preconditioning were obvious at 72 h after reperfusion, which were accompanied by a reduction of spinal cord edema. Our results demonstrated that the expression of AQP4 protein after spinal cord ischemia/reperfusion was region-specific, time-dependent and also indicated that the attenuation of AQP4 expression induced by BK could be one of the important molecular mechanisms in physiopathology of spinal cord ischemic edema. (C) 2008 Elsevier B.V. All rights reserved.