CAPILLARY ENDOTHELIAL TUBES LOSE CELL JUNCTIONAL INTEGRITY AND APOPTOSE IN RESPONSE TO DIESEL EXHAUST PARTICLES

Abstract

Inhalation of diesel exhaust particles (DEP) is implicated in cardiovascular disease. DEP gain access to the vasculature, but how is unknown. To examine this, human umbilical vein endothelial cells in monolayer culture and in in vitro‐assembled capillary tubes, were treated with DEP sonicated to an average size of 2.5 um (PM2.5). DEP were diluted in medium to 1, 10, and 100 ug/ml for application to cells. Cell junction integrity was evaluated using confocal microscopy, and cytotoxicity was assayed to determine cell viability at 4, 24, and 48 hr after adding DEP. Z‐stack confocal images of capillary tubes incubated for 24 hr with different concentrations of DEP demonstrated that particles adhere to the surface and also gain access to the lumen. Increasing DEP concentration increases redistribution of the junctional protein, VE‐cadherin, from the cell‐cell borders to an intracellular localization. At 100 ug/ml DEP, junctions were totally disrupted. DEP at 1 ug/ml was not toxic to monolayer cultures: these cells doubled every 24 hr as did untreated controls. Cells treated with 10 ug/ml DEP doubled in 48 hr. TUNEL assays demonstrate 10 ug/ml caused some cell death. 100 ug/ml DEP was very toxic, killing 65% of cells by 24 hr. This data suggest DEP may gain access to the vasculature by causing alterations in the endothelial cell‐cell junctions and/or by killing vessel endothelia.