Understanding the mechanisms that regulate blood-brain barrier (BBB) and blood-tumor barrier (BTB) permeability, and the ability to selectively modulate BTB permeability biochemically has important therapeutic implications. Leukotrienes increase vascular permeability in systemic capillaries but not normal brain capillaries. This may relate to a unique """"""""enzymatic barrier"""""""" in brain capillaries that inactivate vasoactive compounds, like leukotrienes. A significant correlation exists between increased BBB permeability by leukotrienes in ischemic brain capillaries, and the loss of gamma glutamyl transpeptidase (gammaGTP) in brain capillaries. The same correlation also exists in brain tumors. Leukotriene (LT) C4 will selectively open the BTB in experimental tumors two-fold without increasing permeability in the normal surrounding brain. Normal brain capillaries, unlike systemic capillaries, and brain tumor capillaries, have high concentrations of gammaGTP. Gamma GTP converts LTC4 to LTD4. Although inhibition of gammaGTP with acivicin will enhance BBB opening by leukotrienes in ischemic brain tissue, inhibition with acivicin alone may not result in leukotriene BBB opening in normal tissue. These findings suggest that other enzymes may also compose the """"""""enzymatic"""""""" BBB. There is a correlation between LTC4 in human brain tumors and the amount of edema surrounding tumors. Human brain tumors express arachidonate 5-lipoxygenase mRNA and the inhibition of 5-lipoxygenase will decrease BBB permeability in tumors. On the basis of these findings we have suggested that leukotrienes could allow for increased delivery of anti-tumor drugs to tumor tissue. Conversely, inhibition of 5-lipoxygenase could reduce brain tumor edema. To investigate further leukotrienes and the BBB: 1A) in rats with brain tumors, changes in cerebral blood flow and blood volume after intracarotid (IC) leukotriene infusions will be quantitated; and 1B) electron microscopy will be used to determine whether the mechanism by which LT's increase BBB permeability, is by opening tight junctions or increasing pinocytic transport. 1C) Leukotriene opening of the BTB to different size molecules will be determined. 2A) To identify another possible enzyme in the """"""""enzymatic barrier,"""""""" antiserum to dipeptidase (the enzyme that converts LTD4 to LTE4) is used to determine whether dipeptidase is present in brain capillaries, and if so, whether it is lost in brain tumors or ischemia. To further understand the """"""""enzymatic barrier,"""""""" 2B) other vasoactive compounds, bradykinin and histamine, that may also allow selective BBB opening will be infused IC alone and in combination with leukotrienes, with and without histamine H1 and H2 receptor blockers and 5-lipoxygenase inhibitors. 2C) The dose response to gammaGTP inhibition by acivicin to LTC4 opening will be determined. 3) 5-lipoxygenase transcripts will be further characterized in human brain tumors. 4) Studies will determine whether permeability to drugs is increased in experimental tumors after intracarotid infusion of leukotrienes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS032103-02
Application #
2270084
Study Section
Special Emphasis Panel (ZRG1-NEUB-1 (02))
Project Start
1993-08-01
Project End
1997-07-31
Budget Start
1994-09-15
Budget End
1995-07-31
Support Year
2
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of California Los Angeles
Department
Surgery
Type
Schools of Medicine
DUNS #
119132785
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Black, Keith L; Yin, Dali; Ong, John M et al. (2008) PDE5 inhibitors enhance tumor permeability and efficacy of chemotherapy in a rat brain tumor model. Brain Res 1230:290-302
Hu, Jinwei; Yuan, Xiangpeng; Ko, MinHee K et al. (2007) Calcium-activated potassium channels mediated blood-brain tumor barrier opening in a rat metastatic brain tumor model. Mol Cancer 6:22
Black, Keith L; Ningaraj, Nagendra S (2004) Modulation of brain tumor capillaries for enhanced drug delivery selectively to brain tumor. Cancer Control 11:165-73
Ningaraj, Nagendra S; Rao, Mamatha K; Black, Keith L (2003) Adenosine 5'-triphosphate-sensitive potassium channel-mediated blood-brain tumor barrier permeability increase in a rat brain tumor model. Cancer Res 63:8899-911
Ningaraj, Nagendra S; Rao, Mamatha; Black, Keith L (2003) Calcium-dependent potassium channels as a target protein for modulation of the blood-brain tumor barrier. Drug News Perspect 16:291-8
Asotra, Kamlesh; Ningaraj, Nagendra; Black, Keith L (2003) Measurement of blood-brain and blood-tumor barrier permeabilities with [14C]-labeled tracers. Methods Mol Med 89:177-90
Hashizume, Kazuhiro; Black, Keith L (2002) Increased endothelial vesicular transport correlates with increased blood-tumor barrier permeability induced by bradykinin and leukotriene C4. J Neuropathol Exp Neurol 61:725-35
Uchida, Mikito; Chen, Zutang; Liu, Yunhui et al. (2002) Overexpression of bradykinin type 2 receptors on glioma cells enhances bradykinin-mediated blood-brain tumor barrier permeability increase. Neurol Res 24:739-46
Ningaraj, Nagendra S; Rao, Mamatha; Hashizume, Kazuhiro et al. (2002) Regulation of blood-brain tumor barrier permeability by calcium-activated potassium channels. J Pharmacol Exp Ther 301:838-51
Liu, Y; Hashizume, K; Samoto, K et al. (2001) Repeated, short-term ischemia augments bradykinin-mediated opening of the blood-tumor barrier in rats with RG2 glioma. Neurol Res 23:631-40

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