Heme-dependent decreases in endothelial barrier resistance are TLR4-dependent.

<p>Rat microvascular endothelial cell (RMVEC) monolayers were seeded in Electric Cell-substrate Impedance Sensing (ECIS) arrays as described in Methods. When monolayers reached the appropriate resistance, monolayers were treated with vehicle or heme (10 μM, <i>n =</i> 3) alone or in the presence of TAK-242 (150 μg/ml TAK-242 was added 30 min before administration of heme, <i>n =</i> 3) (A) or 10 μM hemopexin (<i>n =</i> 3) (B). Resistance was measured every 10 min for 8 h. Changes in resistance after 8 h were calculated and vehicle effects subtracted. Decreases (i.e., negative values) in resistance indicate increases in permeability. Data are mean ± SEM (<i>n =</i> 3), with each symbol representing an independent experiment. *<i>p =</i> 0.002 and **<i>p =</i> 0.003 relative to vehicle and ^$<i>p =</i> 0.018 and ^#<i>p =</i> 0.019 relative to heme determined by repeated measures 1-way ANOVA with Tukey post-test.