Opsonized‐zymosan induces a respiratory burst in human blood platelets

Abstract

Opsonized-zymosan-stimulated polymorphonuclear cells show a cyanide-insensitive oxygen consumption. We have investigated whether opsonized-zymosan could induce similar metabolic change in human blood platelets. Preparation of intact human blood platelets, obtained by separation through a Ficoll layer (23% w/v) were challenged with opsonized-zymosan. The polymorphonuclear cell contamination was less than 1/10(8) platelets. The opsonized-zymosan-stimulated platelets showed an increase of oxygen consumption. The mean of oxygen burst measured by a polarographic method with a Clark electrode was 11 nmole/10(9) platelets/min (S.E.M. 4; n = 15). The duration of the burst was 2 min. Unstimulated platelets did not show the oxygen burst. The inhibitors of respiratory chain and prostaglandin synthesis completely abolished the oxygen consumption by opsonized-zymosan-stimulated platelets. The simultaneous addition of NADH (1 mM) and opsonized-zymosan induced a burst of oxygen consumption, which occurred after a variable lag phase (10-12 min) from the stimulation, also in the presence of inhibitors. This burst, which lasted about 1 min, amounted to 10 nmole/10(9) platelets/min (S.E.M. 2; n = 15) and it was higher in the presence of NAN3, a catalase inhibitor. Zymosan treated with hydrazine or heated plasma (56 degrees C) did not cause increased oxygen consumption. Inulin or inulin-treated serum did not stimulate platelets. In these experimental conditions some NADH disappeared, as shown by isotachophoresis. The results demonstrated that an immunological stimulus may activate a membrane-linked cyanide-insensitive oxygen metabolizing system.

Particle‐induced myeloperoxidase release in serially diluted whole blood quantifies the number and the phagocytic activity of blood neutrophils and opsonization capacity of plasma

“…One component of blood, platelets, was not taken into consideration at all in the present work. Opsonized zymosan has also been reported to induce a respiratory burst in isolated human platelets (41). The burst lasted only 1-2 min and the oxygen consumption was 11 amol/ L/platelets/min, which was about 1/50 of that of activated neutrophils.…”

Mitochondria regulate platelet metamorphosis induced by opsonized zymosan A – activation and long‐term commitment to cell death

“…However, these changes were accompanied by an early and transient production of ROS, which probably serve, as in other cell systems, as signaling molecules of biological significance. Activation of platelets by OPZ was associated with a transient burst in ROS, which was possibly due, at least in part, to the energy metabolism [16]. Indeed, zymosan A, an activator of the alternative complement pathway, has been hypothesized to activate platelets in plasma in a complement‐ and fibrinogen‐dependent way [9,10,17].…”