iloprost and Carotid-Artery-Diseases

There is concern that cyclooxygenase (COX)-2 inhibitors may promote atherothrombosis by inhibiting vascular formation of prostacyclin (PGI2) and an increased thrombotic risk of COX-2 inhibitors has been reported. It is widely accepted that the prothrombotic effects of COX-2 inhibitors can be explained by the removal of platelet-inhibitory PGI2. Using microarray chip technology, we have previously demonstrated that thrombomodulin (TM) mRNA is upregulated in cultured human coronary artery smooth muscle cells by the stable prostacyclin mimetic iloprost. This study is the first to demonstrate a stimulation of the expression of functionally active thrombomodulin in human smooth muscle cells by prostaglandins, endogenously formed via the COX-2 pathway. Because TM is an important inhibitor of blood coagulation, these findings provide a novel platelet-independent mechanism to explain the prothrombotic effects of COX-2 inhibitors. The full text of this article is available online at http://circres.ahajournals.org.

Topics: Alprostadil; Blood Coagulation; Bucladesine; Carotid Artery Diseases; Carotid Artery, Internal; Cells, Cultured; Colforsin; Coronary Vessels; Culture Media, Serum-Free; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Diclofenac; Dinoprostone; Epoprostenol; Etoricoxib; Gene Expression Profiling; Gene Expression Regulation; Humans; Iloprost; Isoquinolines; Mammary Arteries; Membrane Proteins; Models, Biological; Myocytes, Smooth Muscle; Oligonucleotide Array Sequence Analysis; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Pyridines; Receptors, Prostaglandin; Receptors, Prostaglandin E; Receptors, Prostaglandin E, EP3 Subtype; RNA, Messenger; Saphenous Vein; Second Messenger Systems; Sulfonamides; Sulfones; Tetradecanoylphorbol Acetate; Thrombomodulin; Thrombophilia; Vasodilator Agents

Hyaluronic acid (HA) is a prominent constituent of the extracellular matrix of atherosclerotic vascular lesions in humans known to modulate vascular smooth muscle phenotype. The regulation of HA synthesis by vasodilatory prostaglandins was analyzed in human arterial smooth muscle cells (SMCs). The prostacyclin analogue, iloprost (100 nmol/L), markedly increased pericellular formation of HA coats and HA secretion into the cell culture medium in human arterial SMCs (8.7+/-1.6-fold). Expression of HA synthase 2 (HAS2) was determined by semiquantitative RT-PCR and found to be strongly upregulated at concentrations of iloprost between 1 and 100 nmol/L after 3 hours. Furthermore, endogenous cyclooxygenase-2 (COX2) activity was required for basal expression of HAS2 mRNA in SMCs in vitro. Total HA secretion in response to iloprost was markedly decreased by RNA interference (RNAi), specific for HAS2. In addition, siRNA targeting HAS2 strongly increased the spreading of human SMCs compared with mock-transfected cells. HAS2 mRNA levels were also stimulated by a selective prostacyclin receptor (IP) agonist, cicaprost (10 nmol/L), prostaglandin E(2) (10 nmol/L), and the EP(2) receptor agonist, butaprost (1 micromol/L). Induction of HAS2 mRNA and HA synthesis by prostaglandins was mimicked by stable cAMP analogues and forskolin. In human atherectomy specimens from the internal carotid artery, HA deposits and COX2 expression colocalized frequently. In addition, strong EP(2) receptor expression was detected in SMCs in HA-rich areas. Therefore, upregulation of HAS2 expression via EP(2) and IP receptors might contribute to the accumulation of HA during human atherosclerosis, thereby mediating proatherosclerotic functions of COX2.

Topics: 6-Ketoprostaglandin F1 alpha; Acetophenones; Alprostadil; Arteriosclerosis; Becaplermin; Benzopyrans; Bucladesine; Carotid Artery Diseases; Carotid Artery, Internal; Cells, Cultured; Colforsin; Cyclic AMP; Cyclooxygenase 2; Enzyme Induction; Epoprostenol; Extracellular Matrix; Glucuronosyltransferase; Humans; Hyaluronan Synthases; Hyaluronic Acid; Iloprost; Indoles; Isoenzymes; Isoquinolines; Macrophages; Maleimides; Membrane Proteins; Muscle Cells; Muscle, Smooth, Vascular; Pertussis Toxin; Platelet-Derived Growth Factor; Prostaglandin-Endoperoxide Synthases; Proto-Oncogene Proteins c-sis; Receptors, Prostaglandin E; Receptors, Prostaglandin E, EP2 Subtype; RNA, Messenger; RNA, Small Interfering; Sulfonamides; Vasodilator Agents