Circulating neutrophils exhibit enhanced apoptosis associated with mitochondrial dysfunctions after surgery under general anaesthesia

Background: Evidence suggests that apoptosis plays a main role in the postoperative changes detected in the polymorphonuclear neutrophil (PMN) population. Furthermore, recent studies have demonstrated that mitochondrial alterations constitute critical events of the apoptotic cascade. In this study we investigated whether apoptosis among neutrophils taken from patients undergoing surgical trauma could be associated with perturbation of mitochondrial transmembrane potential (Delta Psi (m)) and/or exaggerated production of mitochondrial reactive oxygen species (ROS). Methods: Twenty-seven patients undergoing elective surgery under general anaesthesia were enrolled in the study. Peripheral blood samples were drawn one day before the operation and at 12 and 24 h after surgery. Apoptosis rate was assessed by staining neutrophils with 7-amino-actinomycin D (7-AAD) and by analysis by a FACScan flow cytometer. In order to evaluate Delta Psi (m), cells were exposed to 3,3-dihexyloxacarbocyanine iodide [DiOC(6)(3)]; intracellular ROS was measured by means of hydroethidine (HE) and 2,7-diclorofluorescein diacetate (DCFH-DA), followed by analysis on a cytofluorometer. Results: At 12 h following surgery we observed a significantly (P < 0.05) increased frequency of apoptotic PMNs compared to that preoperatively (30.79 +/- 3.68% vs 7.40 +/- 0.69%). At this same time-point, the rate of neutrophils stained with HE, DCFH-DA and [DiOC(6)(3)] were significantly (P < 0.05) higher compared to baseline (51.05 +/- 5.44%, 50.58 +/- 5.84% and 55.31 +/- 4.33% vs 20.17 +/- 2.38%, 19.59 +/- 2.03 and 25.43 +/- 2.71% respectively). Overall measurements returned to the preoperative values 24 h after surgery Conclusion: These data suggest that surgery under general anaesthesia triggers in the immediate postoperative period pathways of PMN accelerated apoptosis associated with significant alterations in mitochondrial function.