Transferrin Receptor Mediated Brain Uptake During Ischemia and Reperfusion

Abstract

Purpose. Drug delivery by transferrin receptor-mediated transport at the blood-brain barrier has shown beneficial effects in animal models of stroke, but it is unclear whether receptor mediated uptake remains functional in the ischemic tissue. The present study addressed that question in a mouse model of brain focal ischemia, permanent or transient middle cerebral artery occlusion (MCAO). Methods. Brain accumulation of ¹²⁵I-labeled 8D3, a mouse-specific transferrin receptor antibody, or of the isotype control UPC-10 used as vascular marker, was measured autoradiographically by phosphorimaging in the core ischemic region on cryostat brain sections up to 24h after ischemia or reperfusion. Cerebral blood flow was quantitatively determined in the same animals after administration of ^99mTc-ECD (Neurolite). Results. Apparent volume of distribution obtained with UPC-10 indicated no significant nonspecific leakage of the blood-brain barrier at any time point. Although brain uptake of 8D3 gradually declined compared to healthy tissue under MCAO, V_D remained significantly higher than V_D of UPC-10 up to 5h. In transient MCAO the brain uptake recovered to levels as in healthy tissue immediately after reperfusion. Conclusion. Transferrin receptor-mediated brain uptake, which is an energy dependent vesicular transport process, is sensitive to reduction in blood supply but remains partially functional for several hours after onset of ischemia. The uptake shows complete recovery after reperfusion. These results support the use of transferrin receptor-mediated brain drug delivery in the early phase of ischemia and in the phase when blood flow is restored.

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