Abstract:
Objective To assess the in vitro effect and mechanism of tumor necrosis factor-α (TNF - α) expression induced by bradykinin (BK) in glioma cells on the blood-tumor barrier (BTB).
Methods A radioimmunoassay was used to dynamically monitor the TNF-α content in a nutrient fluid at 0, 5, 10, 15, 30, and 60 min time points after BK treatment of C6 cells and glial cells. An in vitro BTB model was established using a coculture of brain microvascular endothelial cells (BMEC) and C6 cells. The effect of a BK- treated C6 conditioned medium (C6CM) on the levels of nuclear transcription factor kappa B (NF - κB) mRNA was investigated by PCR. The occludin expression, as well as the transendothelial resistance (TER) and permeability of BTB, was also investigated via the immunofluorescence technique.
Results The TNF-α content in the nutrient fluid of the C6 cells clearly increased after BK treatment compared with that of the control group; however, the glial cells showed no such result. C6CM acted on BTB in vitro, resulting in the decrease in the NF - κB mRNA and occludin expression levels until the minimum was reached at 15 min. Meanwhile, the permeability of BTB increased, whereas TER decreased.
Conclusion BK induced the C6 cells to release TNF-α. TNF-α in turn inhibited NF-κB transcription and reduced the occludin expression. These mechanisms may explain the effects of TNF-α on the opening of BTB using BK.
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