Figure 2.
Effects of 60-min exposure to shear stress on neutrophils adherent to polyetherurethane urea. (A) F-actin content is modulated by shear stress. The maximum actin content detected through confocal analysis at 1.5 dynes/cm2 was significantly greater than were actin levels at 3.8, 5.6, and 11.3 dynes/cm2. ∗, P < 0.04. Additionally, static controls incubated with C5a demonstrated significant increases in F-actin content. ∗, P < 0.05 as compared with static controls without C5a or 3.8 and 5.6 dynes/cm2 shear levels. (B) Neutrophil area decreased with increasing shear stress. When compared with areas at all shear levels of 3.8 dynes/cm2 or greater, direct measurements produced significant differences in neutrophil area for static controls with and without C5a (P < 0.05) and shear levels of 0, 1, and 2 dynes/cm2 (P < 0.02). (C) Shear stress produced a rapid and synchronous progression from PS exposure to DNA fragmentation, as determined by in situ annexin V and TUNEL assays, respectively. Annexin V binding increased significantly for all shear levels at and above 3 dynes/cm2 as compared with 0, 1, and 2 dynes/cm2 (P < 0.05). Similarly, TUNEL-positive apoptosis was significantly greater at all shear levels of 4 dynes/cm2 or above when compared with 0, 1, 2, and 3 dynes/cm2 (P < 0.007). Data represent means ± SEM in A and B. Multiple experiments were completed separately for actin/area (9), annexin V (5), and TUNEL (7) studies, using neutrophils from at least three different blood donors.