cicaprost and Arteriosclerosis

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

Vascular smooth muscle is now recognized as an important site of mediator generation under inflammatory conditions. Indeed, the release of leukocyte activators, such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-8, by human arterial smooth muscle cells has recently been demonstrated. However, the potential for venous cells to release GM-CSF has not been addressed. We have shown that human vascular smooth muscle cells express the "inflammatory" form of cyclooxygenase (COX), cyclooxygenase-2 (COX-2), when stimulated with cytokines. In some nonvascular cell types, the COX activity has been shown to regulate the release of GM-CSF and IL-8, although the nature of the isoform responsible was not addressed. We show that human venous smooth muscle cells, like their arterial counterparts, release GM-CSF after stimulation with IL-1beta. Similarly, both cell types released IL-8. Under the same conditions, we found that COX-2 activity suppressed GM-CSF, but not IL-8, release by both types of human vascular cells. Moreover, the prostacyclin mimetic, cicaprost, and the cAMP analogue, dibutyryl cAMP, inhibited GM-CSF release from these cells. These observations suggest that COX-2 activity suppresses GM-CSF release via a cAMP-dependent pathway in human vascular cells and illustrates a novel mechanism by which this enzyme can modulate immune and inflammatory events.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Antineoplastic Agents; Arteriosclerosis; Aspirin; Bucladesine; Cells, Cultured; Cyclic AMP; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Dinoprostone; Epoprostenol; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Indans; Indomethacin; Interleukin-1; Interleukin-8; Isoenzymes; Mammary Arteries; Meloxicam; Membrane Proteins; Muscle, Smooth, Vascular; Neutrophils; Prostaglandin-Endoperoxide Synthases; Saphenous Vein; Sulfonamides; Thiazines; Thiazoles; Tumor Necrosis Factor-alpha

The efficacy of the oral prostacyclin mimetic cicaprost in preventing atheromatous plaque formation was studied in an in vivo model of experimental hypercholesterolemia. New Zealand white rabbits were fed either standard chow or a cholesterol-enriched (1%) diet for 12 weeks. Cicaprost was added to the drinking water in a non-hypotensive dose (5 micrograms/kg/day) and withdrawn 3 days prior to studying platelet, leukocyte and endothelial function. In cholesterol-fed rabbits, oral cicaprost reduced the aortic intimal surface covered by atheromatous lesions from 84 to 63% (P < 0.05). There was no major difference in serum lipid composition between cicaprost- and vehicle-treated animals. In hyper-cholesterolemic rabbits there was a significant impairment of endothelium-dependent relaxations. Cicaprost treatment considerably improved this endothelial function but had no effect in rabbits receiving standard diet. In addition, platelet and leukocyte hyperreactivity, as seen in hypercholesterolemic rabbits, were largely reduced by cicaprost treatment. These data are the first to demonstrate marked antiatherosclerotic effects of long-term oral prostacyclin treatment. The mechanism may be related to improved endothelial function and subsequent prevention of secondary platelet and neutrophil hyperreactivity.

Topics: Acetylcholine; Adenosine Diphosphate; Adenosine Triphosphate; Animals; Aorta; Arteriosclerosis; Blood Platelets; Endothelium, Vascular; Epoprostenol; Hypercholesterolemia; Male; Muscle Relaxation; Neutrophils; Prostaglandins, Synthetic; Rabbits

The effects of the orally active prostacyclin mimetic cicaprost on morphologic and functional alterations of rabbit aorta was investigated in experimental hypercholesterolemia. Oral cicaprost resulted in a significantly reduced aortic atheromatous plaque formation and partially prevented hypercholesterolemia-induced impairment of endothelium-dependent relaxations. It is concluded that long-term substitution with PGI2 may beneficially influence the progression of atherosclerosis.

Topics: Administration, Oral; Animals; Aorta, Thoracic; Arteriosclerosis; Blood Vessels; Epoprostenol; Hypercholesterolemia; Lipids; Muscle Relaxation; Muscle, Smooth, Vascular; Rabbits