New strategy of endothelial protection in cardiac surgery: use of enhancer of endothelial nitric oxide synthase.

Abstract

Endothelial dysfunction related to the loss of nitric oxide (NO) production remains an important issue in cardiac surgery. We examined the hypothesis that AVE3085, a novel compound that enhances eNOS transcription, may protect coronary endothelium against hypoxia-reoxygenation (H-R) injury during cardioplegic arrest and the possible mechanism by which this occurs. Porcine coronary small arteries (600-800-microm diameter) were subjected to hypoxia (PO(2) <5 mmHg) in St. Thomas cardioplegic (ST) solution with or without AVE3085 (10 microM) or L-arginine (10 mM) at either 37 or 4 degrees C for 60 min, followed by 30-min reoxygenation. Bradykinin (-10 to -6.5 LogM)-induced, endothelium-dependent relaxation was studied in a myograph in U(46619) precontraction before and after H-R. Protein expressions of eNOS and phosphorylated eNOS at Ser-1177 (p-eNOS(Ser1177)) were also determined. Exposure to ST solution with H-R at both 37 and 4 degrees C markedly reduced bradykinin-induced relaxation in coronary small arteries. Addition of AVE3085 in ST solution at 37 degrees C preserved the vasorelaxant response to bradykinin (95.7 +/- 2.1% vs. 69.2 +/- 6.6%, p < 0.01), with the protective effect comparable to that of L-arginine (96.1 +/- 3.3% vs. 70.6 +/- 8.7%, p < 0.05). eNOS and p-eNOS(Ser1177) expressions in coronary endothelial cells were significantly increased by the addition of AVE3085 in ST solution during hypoxia (p < 0.05). Protection of endothelium-dependent relaxation from H-R by AVE3085 (70.3 +/- 7.2% vs. 90.5 +/- 2.4%, p < 0.05) also reached a level similar to that by L-arginine (69.9 +/- 9.0% vs. 94.7 +/- 3.9%, p < 0.05) at 4 degrees C. We have demonstrated a new mechanism to protect coronary endothelium from H-R injury by using eNOS enhancers. This may form a new strategy in the future development of cardioplegic/preservation solutions with direct targeting of eNOS expression in coronary vasculature.