Abstract 15948: Effect of Remote Ischemic Preconditioning on Phosphorylated Protein Signalling in Children Undergoing Tetralogy of Fallot Repair: A Randomised Controlled Trial
Introduction: Our previous randomised controlled trial demonstrated cardio-respiratory protection by remote ischemic preconditioning (RIPC), induced by four 5-min cycles of ischemia-reperfusion of the lower limb in children prior to cardiac surgery. Hypothesis: RIPC may modify pro-survival intracellular phosphorylated protein signalling in myocardium and circulating leucocytes in patients undergoing tetralogy of Fallot (TOF) repair.
Methods: Children (n=37) undergoing elective repair of TOF were double-blind randomized to RIPC (n=18, 9 males, 9 females) or Control (Sham RIPC; n=18, 9 males, 10 females). Leukocytes were Ficoll isolated from blood sampled before cardiopulmonary bypass and at 0, 6 and 24 hours after. Resected right ventricular outflow tract (RVOT) muscle and leukocytes were processed for protein extractions for SDS PAGE and western blots for antibody-specific total and phosphorylated Akt, p38MAPK, STAT3, Connexin 43, GSK3β, and HSP27. Bax, Bcl-2, Parkin, Beclin-1 and LC3B were also assessed for protein expression.
Results: There was no difference in mean age (7.3±3.5 vs 6.8±3.6 months), weight (7.7±1.8 vs 7.5±1.9 kg), bypass or aortic cross-clamp times between the groups. No differences in RVOT protein expression were seen between the control sham and RIPC groups for any of the proteins (Akt, 0.46±0.06 vs 0.51±0.07; p38MAPK, 0.82±0.02 vs 0.78±0.02; STAT3, 0.53±0.08 vs 0.50±0.07; GSK3β, 0.45±0.08 vs 0.42±0.05; HSP27, 0.92±0.03 vs 0.90±0.02), except for Connexin 43 where the ratio of phosphorylated to total Connexin 43 was marginally higher after RIPC (0.33±0.01 vs 0.39±0.02, p=0.04). Notably in controls, for all proteins a markedly high proportion of total protein was phosphorylated. Markers associated with promotion of apoptosis (Bax, Bcl-2) and autophagy (Parkin, Beclin-1, LC3B) did not differ between the groups. In leukocytes, RIPC had no effect on mitochondrial respiration rates and neither on any of the proteins assessed.
Conclusions: In patients with cyanotic heart disease high proportions of proteins are already in phosphorylated form. RIPC in these patients may not further augment the protein signalling intermediates associated with activation of ischemic preconditioning in previous studies.
- © 2012 by American Heart Association, Inc.