Figure 2. MEK inhibition prevents SSRBCs from activating neutrophil adhesion.

The effect of MEK inhibitors on the ability of SSRBCs to stimulate neutrophil (PMN) adhesion to ECs was tested. A and B. SSRBCs (n = 8) were sham-treated or treated with 100 nM MEK inhibitor U0126, RDEA119, AZD6244 or trametinib. Washed treated SSRBCs were then co-incubated with ABO-matched naïve PMNs isolated from healthy donors (n = 8), prior to testing adhesion of PMNs to HUVECs (A; n = 4) and HMVECs-d (B; n = 4) in intermittent flow condition assays at different shear stresses. C. AARBCs (n = 3) were sham-treated, washed, and then co-incubated with ABO-matched naïve PMNs isolated from healthy donors (n = 3), prior to testing adhesion of PMNs to HUVECs and HMVECs-d at different shear stresses. D. Non-treated and TNFα-treated HUVECs were co-incubated with sham-treated SSRBCs, U0126-treated SSRBCs or sham-treated AARBCs. HUVECs were then washed free of non-adherent RBCs, and tested for their ability to support adhesion of PMNs (n = 3). Results are presented as % adherent PMNs at a shear stress of 1 dyne/cm². *:p<0.0001 compared to adhesion of naïve PMNs (PMNs only) to non-treated ECs; and **:p<0.0001 compared to adhesion of PMNs stimulated with SSRBCs (PMNs+SSRBCs). Error bars show SEM of 4 different experiments for A and B, and 3 different experiments for C and D.