Protein Kinase C-β Inhibition and Survival Signaling after Simulated Cardioplegic-Ischemia/Reperfusion in Nondiabetic and Diabetic Human Coronary Arterial Endothelial Cells.

Background: Cardioplegic-ischemia/reperfusion (I/R) injury poses substantial challenges during postoperative recovery, with diabetic patients particularly susceptible to adverse events. Using a model entailing the subjection of human coronary artery endothelial cells (HCAECs) to simulated cardioplegic I/R, we investigated the potential of protein kinase C β (PKC-β) inhibition to augment cellular survival in this context.

Study design: HCAECs were isolated from harvested coronary arteries of diabetic (D) and nondiabetic (C) patients (N = 4 per group). HCAECs were either cultured under normoxic conditions without drug (D and C), subjected to hypoxia and reoxygenation alone (DH and CH), or subjected to hypoxia and reoxygenation and the PKC-β inhibitor LY333531 (DHT and CHT). Molecular signaling was assessed using immunoblotting.

Results: Simulated I/R decreased anti-apoptotic phosphorylated protein kinase b (p-Akt, p = 0.04) and p-Akt:Akt ratio (p = 0.004) in CH vs C, with PKC-β inhibition restoring expression in CHT (p ≤ 0.04). Treatment also increased the p-Akt:Akt ratio in DHT vs D (p = 0.03). Anti-apoptotic inducible nitric oxide synthase increased in CHT vs CH (p = 0.003), and the pro-apoptotic phosphorylated class O forkhead box transcription factor (p-FOXO): FOXO ratio decreased in CHT vs CH (p = 0.001). I/R elevated Bcl-2-associated agonist of cell death (BAD) in CH vs C (p = 0.01), but PKC-β inhibition increased anti-apoptotic p-BAD (p = 0.001) and p-BAD:BAD ratio (p = 0.03) in CHT. I/R also increased cleaved PARP (p < 0.001) and cleaved caspase 3 (p < 0.001) in DH vs D, both of which were reversed by treatment (p < 0.001 for DHT vs DH).

Conclusions: PKC-β inhibitor treatment increased pro-survival signaling and decreased pro-apoptotic signaling in nondiabetic and diabetic HCAECs subjected to simulated I/R, with mechanistic differences observed between these cohorts.