Oxidative Stress Increases Erythrocyte Sensitivity to Shear-Mediated Damage.

Patients receiving mechanical circulatory support often present with heightened inflammation and free radical production associated with pre-existing conditions in addition to that which is due to blood interactions with nonbiological surfaces. The aim of this experimental laboratory study was to assess the deformability of red blood cells (RBC) previously exposed to oxygen free radicals and determine the susceptibility of these cells to mechanical forces. In the present study, RBC from 15 healthy donors were washed and incubated for 60 min at 37°C with 50 µM phenazine methosulfate (PMS; an agent that generates superoxide within RBC). Incubated RBC and negative controls were assessed for their deformability and susceptibility to mechanical damage (using ektacytometry) prior to the application of shear stress, and also following exposure to 25 different shear conditions of varied magnitudes (shear stress 1, 4, 16, 32, 64 Pa) and durations (1, 4, 16, 32, 64 s). The salient findings demonstrate that incubation with PMS impaired important indices of RBC deformability indicating altered cell mechanics by ∼19% in all conditions (pre- and postexposure to shear stress). The typical trends in shear-mediated changes in RBC susceptibility to mechanical damage, following conditioning shear stresses, were maintained for PMS incubated and control conditions. We demonstrated that free radicals hinder the ability of RBC to deform; however, RBC retained their typical mechanical response to shear stress, albeit at a decreased level compared with control following exposure to PMS. Our findings also indicate that low shear exposure may decrease cell sensitivity to mechanical damage upon subsequent shear stress exposures. As patients receiving mechanical circulatory support have elevated exposure to free radicals (which limits RBC deformability), concomitant exposure to high shear environments needs to be minimized.