Endothelial cell junctional integrity modulation by serotonin: an ultrastructural analysis.
We have reported previously that exogenous serotonin (5-hydroxytryptamine, 5-HT) alters cultured bovine aortic endothelial cell (BAEC) structural integrity by modulating the assembly of stress fibers. In the present study a 5-HT stimulus-coupled change in BAEC junctional integrity was quantitated by determining the width and percentage of intercellular openings in a monolayer. BAEC treated with 5-HT at concentrations of 10(-9) M to 10(-3) M caused a significant dose-dependent decrease in interendothelial cell junctional openings compared to controls, with the greatest reduction induced at 10(-6) M (92% from control). Treatment of BAEC with histamine (10(-4) M) increased the junctional openings by 82% when compared to controls. This change could be prevented by either pretreatment of the monolayers with 5-HT or by adding 5-HT in conjunction with the histamine. To assess a direct interaction of 5-HT with actin filaments, cultured BAEC monolayers were extracted, treated with 5-HT, and processed for immunocytochemical localization of 5-HT using the Avidin-Biotin method. Electron microscopy revealed 5-HT antibody bound to actin filaments and dense in areas of filament intersection, which implies a role for internalized 5-HT in stimulating the assembly of an actin filament network. Collectively, these results suggest that 5-HT helps to regulate the endothelial junctional barrier by promoting actin filament formation and stability, which may in turn increase the junctional apposition between endothelial cells.
Boston University, Department of Biology, MA 02215.
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Mineau-Hanschke
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Hechtman
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D000199:Actins / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D006632:Histamine / Q000494:pharmacology; D007150:Immunohistochemistry; D007365:Intercellular Junctions / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology*
D000199:Actins; D012701:Serotonin; D006632:Histamine