prostaglandin-h2 and Arteriosclerosis

A family of extremely reactive electrophiles, isolevuglandins (isoLGs), is generated in vivo by free radical-induced lipid oxidation and rearrangement of endoperoxide intermediates of the isoprostane pathway. Protein adducts of two different oxidized lipids, isoLGE(2) and iso[4]LGE(2), and the corresponding autoantibodies are present in human blood. Western blot analysis of a polyacrylamide gel electrophoresis gel detects several immunoreactive plasma proteins. Only a minor fraction of the isoLG-protein modifications is associated with low density lipoprotein since mean levels were decreased only 20-22% by immunoprecipitation of apolipoprotein B (apoB). Mean levels of both isoLGE(2) and iso[4]LGE(2)-protein adducts in plasma from patients with atherosclerosis (AS) (n=16) or end-stage renal disease (RD) (n=8) are about twice those in healthy individuals (n=25). These elevated levels are not related to variations in age, total cholesterol or apoB. A linear correlation (r=0.79) between plasma isoLGE(2) and iso[4]LGE(2)-protein adduct levels in all 49 individuals is consistent with a common free radical-induced mechanism for the production of both oxidized lipids in vivo. The correlation is even stronger (r=0.86) for patients with AS or RD. That isoLG-protein adduct levels are more strongly correlated with disease than are total cholesterol or apoB suggests an independent defect that results in an abnormally high level of oxidative injury associated with AS and RD.

Topics: Adult; Animals; Apolipoproteins B; Arteriosclerosis; Autoantibodies; Cholesterol; Fatty Acids, Unsaturated; Free Radicals; Hemocyanins; Humans; Kidney Failure, Chronic; Lipid Metabolism; Middle Aged; Molecular Structure; Oxidation-Reduction; Prostaglandin H2; Prostaglandins E; Prostaglandins H; Rabbits; Stereoisomerism

Prostacyclin (PGI2) contributes to the maintenance of a nonadhesive luminal surface in blood vessels due to its anti-platelet and vasodilatory properties. Here, we sought to determine whether peripheral blood lymphocytes (PBL) may regulate the PGI2 production of human umbilical vein endothelial cells (HUVEC). Cell-cell contact between HUVEC and lymphocytes markedly enhanced PGI2 synthesis as a function of the number of lymphocytes added. This stimulated synthesis was totally suppressed when lymphocytes and HUVEC were separated by a microporous insert. It was not due to prostaglandin H synthase up-regulation. The pretreatment of lymphocytes with the PGI2 synthase inhibitor tranylcypromine partially inhibited PGI2 synthesis (47%), suggesting a transcellular metabolism of the endothelial prostaglandin endoperoxide PGH2 by the lymphocyte PGI2 synthase. Experiments using [14C]arachidonate-labeled lymphocytes coincubated with unlabeled HUVEC, and [14C]arachidonate-labeled HUVEC coincubated with unlabeled lymphocytes showed that the arachidonic acid used for PGI2 synthesis was totally of endothelial origin. Furthermore, the PGI2 synthesis was strongly inhibited by the cytosolic phospholipase A2 inhibitor, MAFP and totally suppressed by the combination of the calcium chelators, BAPTA and EGTA. Collectively, these results suggest that lymphocytes trigger an outside-in signaling in endothelial cells involving cPLA2 activation. Overall, the switch-on for PGI2 synthesis induced by lymphocytes might serve as a protection against atherothrombogenesis.

Topics: Adult; Arachidonic Acid; Arachidonic Acids; Arteriosclerosis; Calcium; Cell Adhesion; Cells, Cultured; Chelating Agents; Coculture Techniques; Culture Media, Conditioned; Cyclooxygenase 1; Cyclooxygenase 2; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Egtazic Acid; Endothelium, Vascular; Enzyme Inhibitors; Epoprostenol; Gene Expression Regulation; Group IV Phospholipases A2; Humans; Infant, Newborn; Intramolecular Oxidoreductases; Isoenzymes; Lipopolysaccharides; Lymphocytes; Membrane Proteins; Organophosphonates; Phospholipases A; Phospholipases A2; Prostaglandin H2; Prostaglandin-Endoperoxide Synthases; Prostaglandins H; Tranylcypromine; Umbilical Veins

We examined whether prostaglandin (PG) H2, as an endothelium-dependent contracting factor, or the disturbed production of endothelium-derived relaxing factor, impairs endothelium-dependent relaxation and whether long-term inhibition of nitric oxide (NO) synthesis aggravates atherosclerosis in hypercholesterolemic rabbits. Male New Zealand White rabbits were fed one of the following diets: (1) standard chow; (2) 2% cholesterol-supplemented chow; (3) standard chow with 80 micrograms/mL N omega-nitro-L-arginine methylester (L-NAME), an NO synthetase inhibitor, in their drinking water; or (4) 2% cholesterol-supplemented chow with 80 or 160 micrograms/mL L-NAME in their drinking water. The rabbits were fed these diets for 8 or 12 weeks. Then aortic rings were obtained, and changes in isometric tension were recorded. Intimal atherosclerotic areas of the thoracic aortas were subsequently measured by planimetry. The cholesterol-supplemented diet significantly impaired endothelium-dependent aortic relaxation to acetylcholine. Pretreatment with the thromboxane A2/PGH2 receptor antagonist ONO-3708 did not reverse this impaired response. Vessels from both normocholesterolemic and hypercholesterolemic rabbits given L-NAME showed more impaired endothelium-dependent relaxation than those from their dietary counterparts not given L-NAME. Morphometric analysis revealed marked enlargement of intimal atherosclerotic areas in aortas from L-NAME-treated hypercholesterolemic rabbits compared with those from untreated hypercholesterolemic rabbits. These findings suggest that PGH2 does not contribute to impaired endothelium-dependent relaxation and that long-term administration of L-NAME promotes atherosclerosis by inhibition of NO synthesis in the hypercholesterolemic rabbit thoracic aorta.

Topics: Animals; Aorta, Thoracic; Arginine; Arteriosclerosis; Endothelium, Vascular; Hypercholesterolemia; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Prostaglandin H2; Prostaglandins H; Rabbits; Vasodilation