Inhibition of neutrophil apoptosis after coronary bypass operation with cardiopulmonary bypass

Background. Granulocyte apoptosis is a key control process in the clearance of neutrophils from inflammatory sites, and its rate is modulated both in vitro and in vivo by a number of inflammatory mediators. In this study, we investigated the influence of cardiopulmonary bypass (CPB) on neutrophil apoptosis. Methods. Twenty patients undergoing coronary operation with CPB were studied. Patients undergoing off-pump (OP) coronary bypass and healthy subjects served respectively as stressed and normal groups. Interleukin-6 (IL-6), IL-8, and tumor necrosis factor-α were assessed on plasma collected preoperatively, at the end of CPB, and after intervals of 4, 8, 12, and 24 hours. Neutrophil apoptosis was detected by light microscopy as well as by the annexin-V assay on postoperative samples. The polymorphonuclear leukocyte (PMN) apoptotic receptors, Fas and FasL, were studied together with the activity of caspase 3 in postoperative neutrophils. Results. Spontaneous apoptosis was significantly delayed in PMNs from CPB patients when compared with either the stressed or control patients. Neutrophils were activated, as indicated by increased surface expression of CD11b. Western blot analysis showed a normal expression of the apoptotic receptors Fas and FasL. Caspase 3 activity was found to be significantly reduced in neutrophils from CPB patients after 18 and 24 hours of culture. When control neutrophils were cultured in the presence of postoperative plasma from OP and CPB patients, apoptosis was significantly delayed. Depleting surgical plasma of IL-6 and IL-8 completely abolished this antiapoptotic effect. Conclusions. Inflammatory mediators during CPB prolong the functional lifespan of neutrophils through modulation of apoptosis, and potentiate the inflammatory response observed after coronary bypass operation.