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

Abstract

Objective: To investigate recombinant human TIMP-1 (125I-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. 125I-labeled rhTIMP-1 at 60 μg/kg (11·23 μCi/μg) 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 T1/2 of 125I-rhTIMP-1 was 42·2 hours. Thirty minutes after 125I-rhTIMP-1 administration, an increased accumulation of 125I-rhTIMP-1 in the ischemic hemisphere was observed. The maximum brain tissue concentration Cmax 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 T1/2 were 45·3 and 39·2 hours, respectively. Electrophoretic analysis of ischemic samples for 125I-rhTIMP-1 showed a clear 28 kDa band 1·5 hours after 125I-rhTIMP-1 administration in the cortex and striatum. The intensity of the 28 kDa band decreased after 3·0 hours of the administration. Some 125I-rhTIMP-1 maintained its molecular integrity for 8·5 hours in ischemic striatum after reperfusion.Discussion: 125I-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.