Dissertation committee:
Ομότιμος Καθηγητής Χειρουργικής Γεώργιος Ανδρουλάκης,Καθηγητής Χειρουργικής Στυλιανός Κατσαραγάκης, Επίκουρος Καθηγητής Καρδιοχειρουργικής Δημήτριος Αγγουράς
Summary:
Background: Cardiac surgery under cardiopulmonary bypass (CPB) induces a major
postoperative systemic inflammatory response (SIRS) causing variations on
apoptotic potential of leukocyte subpopulations. The purpose of this study is
the qualitative and quantitative study of apoptosis in six leukocyte
subpopulations [T (CD3+/CD4+) / T (CD3+/CD8+) / Β (CD19+) / NK (CD16+/56+) /
CD14+ monocytes and CD16+ granulocytes], the study of expression of seven pro-
and anti-apoptotic genes (BCLA2A1, BCL2L1, MCL1, BAX, BID, XIAP και BIRC3), the
correlation of apoptosis with the levels of pro- and anti-inflammatory
cytokines (IL-1b, Il-6, IL-7, IL-8, IL-10, sFasL και TNFa) and its prognostic
value for the postoperative development of cardiac patients.
Methods: We studied 56 patients undergoing various cardiac surgery procedures
with cardiopulmonary bypass (CPB). Apoptotic cells were double stained with
Annexin V and propidium iodide and then analyzed by flow cytometry method.
Expression of pro- and anti-apoptotic genes was studied with microarrays’
analysis and use of quantitative RT-PCR. Serum cytokine levels were measured
using Luminex-xMap method. Blood sampling carried out at the point of
induction of anaesthesia (T0), immediately after surgery (T1), 6 h (T2), 24 h
(T3) and 48 h postoperatively (T4).
Results: Apoptosis in leukocyte subpopulations, except in the case of
B-(CD19+) lymphocytes, inhibited immediately after surgery (T1) (p < 0.001)
showing an increase at 24 hours postoperatively (T3) (p < 0.001) and a
stabilization at 48 hours postoperatively (T4) (p < 0.001). Percentage of
neutrophil apoptosis correlated negatively (Spearman’s ratio : -0,450) with its
absolute number immediately after surgery (T1). Additionaly, there was a
negative significant correlation between the percentage of neutrophil apoptosis
at induction of anaesthesia (T0) and development of postoperative atrial
fibrillation (Spearman’s ratio: - 0,469) in coronary patients. Expression of
antiapoptotic gene BCL2A1 significantly increased immediately postoperatively
(T1) in granulocytes and peripheral blood mononuclear cells (p = 0.008 and
0.021 respectively). Concentrations of inflammatory cytokines IL-6 and IL-8
showed their peak value immediately postoperatively (T1) (p < 0.001), followed
by a gradual postoperative decrease 24 h (T3) (p < 0.001) and 48h
postoperatively (T4) (p < 0.001 and p = 0.022 respectively). Concentration of
IL-10 showed its peak value 6 h postoperatively (T2) (p < 0.001), followed by a
gradual postoperative decrease 24 h (T3) (p < 0.001) and 48h postoperatively
(T4) (p < 0.001).
Conclusions: Inhibition of apoptosis immediately after surgery (T1) was
observed in the majority of leukocyte subpopulations, followed by gradual
increase 24 h (T3) and 48 h (T4) postoperatively in values similar of those at
the point of induction of anaesthesia. Preoperative percentage of neutrophil
apoptosis could be a biomarker predicting the susceptibility of patient for the
development of postoperative atrial fibrillation (POAF). Inhibition of
apoptosis immediately postoperatively (T1) seems to be expressed by
antiapoptotic gene BCL2A1. Levels of proinflammatory cytokines IL-6 and IL-8
showed their peak value immediately postoperatively (T1), while concentration
of anti-inflammatory cytokine IL-10 showed its maximum value 6 h
postoperatively (T2).
Keywords:
Cardiac surgery, Leukocyte subpopulation apoptosis, Systemic inflammatory response syndrome (SIRS), Cardiopulmonary bypass, Cytokines
