Brain distribution and elimination of recombinant human TIMP-1 after cerebral ischemia and reperfusion in rats

Objective: To investigate recombinant human TIMP-1 (I-125-rhTIMP-1) half-life in blood and its distribution in rat brain tissue after cerebral ischemia/reperfusion as part of a therapeutic development paradigm. Method: A suture model of the middle cerebral artery occlusion was used. I-125-labeled rhTIMP-1 at 60 mu g/kg (11.23 mu Ci/mg) was administered to rats intravenously at the beginning of reperfusion. Blood and brain tissue were collected. The radioactivity was detected with a gamma counter and analyzed by autoradiography. Results: The blood half-life T-1/2 of I-125-rhTIMP-1 was 42.2 hours. Thirty minutes after I-125-rhTIMP-1 administration, an increased accumulation of I-125-rhTIMP-1 in the ischemic hemisphere was observed. The maximum brain tissue concentration C-max was 26.1 ng/g at 1.5 hours in the striatum and 13.9 ng/g at 5 hours in the cortex when the uptake percentage of brain tissue to blood was 6.1 +/- 0.4 and 6.7 +/- 2.1%, respectively. The cortex and striatum elimination half-lives T-1/2 were 45.3 and 39.2 hours, respectively. Electrophoretic analysis of ischemic samples for I-125-rhTIMP-1 showed a clear 28 kDa band 1.5 hours after I-125-rhTIMP-1 administration in the cortex and striatum. The intensity of the 28 kDa band decreased after 3.0 hours of the administration. Some I-125-rhTIMP-1 maintained its molecular integrity for 8.5 hours in ischemic striatum after reperfusion. Discussion: I-125-labeled rhTIMP-1 was distributed quickly into ischemic brain tissue and had a slow elimination in both blood and brain tissue. These results, along with other studies suggesting therapeutic benefits, will aid in the development of TIMP-1 for protecting ischemic stroke.