BMVEC barrier function is compromised by the MPO-H₂O₂-Cl⁻ system.

<p>BMVEC were plated on gold microelectrodes and cultured to confluence. Barrier function of hydrocortisone-induced endothelial monolayers (7.5×10⁴ cells) was continuously monitored by impedance sensing at 4 kHz. (A) After stabilization of BMVEC monolayers induction medium was changed (arrow) to slightly acidic conditions (HBSS, pH 6). After a 30 min pre-conditioning period, BMVEC were incubated (arrow) with MPO (120 nM) and methionine (1; ‘Met’; 5 mM), H₂O₂ (2; 4×125 µM every 3 min), MPO and H₂O₂ (3), or MPO, H₂O₂ and Met (4). (B) Statistical evaluation of impedance values after 2 h from (A). Impedance was normalized to baseline and represents mean values ± SD of 4 independent experiments (ns = not significant; **p<0.01, ***p<0.001, one-way ANOVA). (C) After stabilization of BMVEC monolayers induction medium was changed (arrow) to slightly acidic conditions (HBSS, pH 6). After a 70 min pre-conditioning period, BMVEC were incubated (arrow) with 4-ABAH (1; 100 µM), MPO (2; 120 nM), MPO and H₂O₂ (3; 4×125 µM), or MPO, H₂O₂ and 4-ABAH (4). (D) Statistical evaluation of impedance values after 4 h from (C). Impedance was normalized to baseline and represents mean values ± SD of 4 independent experiments (**p<0.01, ***p<0.001, one-way ANOVA).