Enhanced coronary vasoconstriction to oxidative stress product, 8-epi-prostaglandinF(2α), in experimental hypercholesterolemia

Objectives: The F₂-isoprostanes are a family of novel prostaglandin isomers and a stable product of in vivo oxidative stress. 8-epi-prostaglandinF(2α), a member of this isoprostane family, is a vasoconstrictor and its local release may contribute to the abnormal vasomotor tone associated with hypercholesterolemia. We therefore aimed to outline the role of 8-epi-prostaglandinF(2α) as a coronary vasoconstrictor in experimental hypercholesterolemia. Methods and results: Pigs were randomized to two experimental groups (each n=9): normal (N) and high cholesterol (HC) diet. To determine the vasoconstrictive effects of 8-epi-prostaglandinF(2α) in vitro, doses from 10^-9 to 10^-5 M were used to constrict coronary epicardial rings. Plasma total and LDL cholesterol levels were significantly higher in the HC group compared with the N group (P<0.005) as were plasma 8-epi-prostaglandinF(2α) levels (P<0.001). 8-epi-prostaglandinF(2α) immunoreactivity was present in the vessel wall in both groups. Normal vessels with intact endothelium (n=8 rings) contracted to 8-epi-prostaglandinF(2α) (maximal contraction 15.5±8.74%). In the HC group, rings with intact endothelium had a greater contractile response to 8-epi-prostaglandinF(2α) compared to normals (72.3±7.9%; n=8; P<0.0001). This was reversed by preincubation with NOR-3, a NO donor (maximal contraction 6.7±1.56%; n=5; P<0.0001). Enhanced contraction in normal vessels occurred with endothelial denudation (98.4±3.56%; n=6; P<0.0001) and with preincubation of the endothelium-intact rings with L-NMMA (N-monomethyl-L-arginine), an NO synthase inhibitor (85.5±10.3%, n=6, P<0.001). The enhanced contraction seen with hypercholesterolemia did not occur with other prostanoid vasoconstrictors. Conclusion: Experimental hypercholesterolemia leads to a significant increase in 8-epi-prostaglandinF(2α) levels in addition to enhanced 8-epi-prostaglandinF(2α)-induced coronary vasoconstriction, in vitro. These findings support a role for the F₂-isoprostanes in the regulation of coronary vasomotor tone in pathophysiologic states. Copyright (C) 1999 Elsevier Science B.V.