Evaluation of an in vitro coculture model for the blood-brain barrier: Comparison of human umbilical vein endothelial cells (ECV304) and rat glioma cells (C6) from two commercial sources

Summary Cocultures of human umbilical vein endothelial cells (ECV304) and rat glioma cells (C6) from two commercial sources, American Type Culture Collection and European Collection of Animal Cell Cultures, were evaluated as an in vitro model for the blood-brain barrier. Monolayers of endothelial cells grown in the presence or absence of glial cells were examined for transendothelial electrical resistance, sucrose permeability, morphology, multidrug resistance-associated protein expression, and P-glycoprotein expression and function. Coculture of glial cells with endothelial cells increased electrical resistance and decreased sucrose permeability across European endothelial cell monolayers, but had no effect on American endothelial cells. Coculture of European glial cells with endothelial cells caused cell flattening and decreased cell stacking with both European and American endothelial cells. No P-glycoprotein or multidrug resistance-associated protein was immunodetected in endothelial cells grown in glial cell-conditioned medium. Functional P-glycoprotein was demonstrated in American endothelial cells selected in vinblastine-containing medium over eight passages, but these cells did not form a tight endothelium. In conclusion, while European glial cells confer blood-brain barrier-like morphology and barrier integrity to European endothelial cells in coculture, the European endothelial-glial cell coculture model does not express P-glycoprotein, normally found at the blood-brain barrier. Further, the response of endothelial cells to glial factors was dependent on cell source, implying heterogeneity among cell populations. On the basis of these observations, the umbilical vein endothelial cell-glial cell coculture model does not appear to be a viable model for predicting blood-brain barrier penetration of drug molecules.     

Determination of 2,4-dihydroxy-1,4(2h)-benzoxazin-3-one glucosides in corn (Zea mays L.)

A method has been developed for the determination of 2,4-dihydroxy-1,4(2H)-benzoxazin-3-ones, which occur in corn (Zea mays L.) plants as glucosides. The method involves freezing and thawing of corn tissue samples to allow enzyme-catalyzed cleavage of the glucosides, fragmentation, extraction of the released aglycons, removal of chlorophyll, conversion of the 2,4-dihydroxy-1,4(2H)-benzoxazin-3-ones to the more stable 2(3)-benzoxazolinones, extraction of the 2(3)-benzoxazolinones, and quantitative ir measurement of the 2(3)-benzoxazolinones in methylene chloride solution. The amount of 2(3)-benzoxazolinone calculated as 6-methoxybenzoxazolinone (MBOA) obtained from B37 × B14 single-cross corn was found to be $\text{1.56 mg}\text{50 g}$ fresh weight (10 samples; SD 0.16 mg). For synthetic samples, the precision of the method is that of the reproducibility of the spectrophotometer used. Depending upon the spectrophotometer used, a detection limit of $\text{0.03–0.06 mg MBOA}\text{50 g}$ fresh tissue was observed.     

On the Synthesis of 6-Methoxy-2-benzoxazolinone

6-Methoxy-2-benzoxazolinone has been synthesized by a simplified, improved procedure, the formation and reduction of 5-methoxy-2-nitrophenol and subsequent fusion of the corresponding amine hydrochloride with urea. In related work, 4-methoxy-2-(methoxymethoxy)-nitrobenzene was prepared.     

Evaluation of the Role of P-Glycoprotein in Ivermectin Uptake by Primary Cultures of Bovine Brain Microvessel Endothelial Cells

The P-glycoprotein efflux system located on the apical membrane of brain capillary endothelial cells functions as part of the blood-brain barrier. In this study, primary cultures of bovine brain microvessel endothelial cells (BMECs) were investigated for the presence of a P-glycoprotein system and its contribution in regulating ivermectin distribution across the blood-brain barrier. Results of rhodamine 123 uptake studies with cyclosporin A and verapamil as substrates indicated that a functional efflux system was present on BMECs. Immunoblot analysis with the C219 monoclonal antibody to the product of the multidrug resistant member 1(MDR1) gene also confirmed the expression of MDR1 in the BMECs. Unbound ivermectin was shown to significantly increase the uptake of rhodamine 123 in BMECs, however, the drug only modestly enhanced the transcellular passage of rhodamine. The results of these studies affirmed that unbound ivermectin is an inhibitor of the MDR1 efflux system in BMECs.