EXCEEDTHE SPACE PROVIDED. Brain capillary endothelium, and its contiguous cells, pericytes and astrocytes, are the structural and functional components of the blood-brain barrier (BBB). Biochemical changes concomitant with modified functional attributes of capillaries in injured brain and brain tumors, are believed to compromise BBB and blood-tumor barrier(BTB) permeability, respectively. The BTB and injured BBB can be opened transiently with vasomodulators such as bradykinin and leukotrienes reproducibly for a selective drug delivery to brain tumors and sites of brain injury in vivo. In particular, our results suggest that bradykinin-mediated opening of BTB sequentially involves bradykinin type 2 (B2)receptors, nitric oxide (NO), cyclic GMP (cGMP),, and calcium-dependent potassium (Kca) channels. The cellular sites, however, where such molecules are produced or occur endogenously, and how they affect permeability characteristics of the capillaries in intact and injured brain, and in brain tumors, are unknown. This proposal seeks to obtain insights into the role of individual cell types that account for differential permeability responses in brain capillaries in vivo. A major goal is to determine precise spatio-temporal changes in structure and function of capillary components, and effector molecules, and relate these indices to permeability of the BBB and the BTB in vivo. Rat models of brain tumors and brain injury caused by short-terrn ischemia-reperfusion will be used for proposed studies. We will identify the cellular binding sites for bradykinin, and determine if the refractory response of the BTB to bradykinin and the permeability constant (Ki) for different-sized molecules are due to altered behavior or density distribution of functional B2 receptors. Biochemical, confocal microscopic, molecular, pharmacological and electron microscopic studies are focused on B2 receptors, NO, soluble guanylate cyclase, cGMP-dependent protein kinase and Kca channels. Transmission electron microscopic studies will determine if selective delivery of different sized molecules and viral particles across the normal or injured BBB and BTB occurs via tight junctions or transendothelial vesicular route(s) along a luminal-abluminal gradient or by other response(s) to vasomodulators. Permeability studies will determine if Kca channels constitute a convergence point of several biochemical modulators regulating BBB and BTB permeability. These studies will help delineate the operative mechanisms that constitute the BBB, and the mechanisms that lead to selective delivery of molecules of different size to abnormal or injured brain microvessels. The results of the proposed studies may have implications for selective and enhanced delivery of neuropharmaceutics, anti-neoplastic agents, and large viral vectors to abnormal brain regions for treating neurological diseases. PERFORMANCE SITE ========================================Section End===========================================
