TNFα trafficking in cerebral vascular endothelial cells

Using small tags, we tracked the pathway of tumor necrosis factor (TNF)α across cerebral vascular endothelial cells. In cerebral microvessel derived RBE4 cells, 125I-TNFα had rapid endocytosis within the first 20 min and showed substantial exocytosis in the intact form. Biotinylated TNFα was detected at different time points after endocytosis by streptavidin-Quantum dots which showed its time-dependent colocalization with intracellular organelles. In mice, electron microscopic autoradiography after intravenous injection of 125I-TNFα showed its transcytosis, as signals emerged on the abluminal side of the endothelial cells and reached brain parenchyma. The vesicular trafficking of TNFα reflects the immunomodulatory potential of peripheral cytokines for the CNS.