Abstract-In a previous work, we postulated that endothelial cells possess only the following 2 enzymes involved in prostanoid synthesis: cyclooxygenase and prostacyclin synthase. The present work focused on investigating the expression of prostaglandin (PG) E synthase (PGES) in vascular cells. Key Words: prostaglandin E synthase Ⅲ endothelium Ⅲ smooth muscle Ⅲ prostanoid Ⅲ cytokine T he potent relaxing and platelet antiaggregation agent prostaglandin (PG) I 2 (also termed prostacyclin) is the characteristic prostanoid released by vascular endothelial 1 and smooth muscle cells (SMCs). 2 PGE 2 is also a major prostanoid found to be produced in vitro by vascular cells in response to different agents, which include exogenously added arachidonic acid (AA) and several agonists. 1,3-5 Cyclooxygenase (COX, also termed PGH synthase) is the first enzyme in the biosynthesis of prostanoids. Two COX isoforms have been described. COX-1 is expressed in a constitutive manner, whereas COX-2 is the isoenzyme inducible by mitogens and overexpressed in inflammatory processes. 6 COX catalyzes the transformation of AA to PGH 2 , which has constricting and platelet-activating properties, because both thromboxane A 2 and PGH 2 share the same receptor. 7 Prostacyclin synthase (PGI synthase; PGIS) catalyzes the subsequent transformation of PGH 2 into PGI 2 . Isomerization of PGH 2 to PGE 2 may occur spontaneously 8 or may be enzymatically catalyzed by a PGE synthase (PGES). The enzyme responsible for this isomerization was little known until the recent report by Jakobsson et al, 9 who identified and characterized the human PGES as a membrane-bound enzyme of which the activity is glutathione-dependent and inducible by interleukin (IL)-1␤.We reported that endothelial cells released untransformed PGH 2 when COX activity increased and PGIS decreased as a result of the action of IL-1␤. 5,10 Although endothelial cells produced PGE 2 as a major prostanoid, in particular after cytokine stimulation, on the basis of indirect evidence we postulated that endothelial cells possess only 3 enzymes involved in the biosynthesis of prostanoids COX-1, COX-2, and PGIS. 5 Because expression of PGES could not only modulate synthesis of PGE 2 but could also modulate the release of untransformed PGH 2 or even PGI 2 by diverting metabolism of PGH 2 , this study was conducted to investigate the expression of PGES on vascular cells and its modulation by mitogens and cytokines.

Summary. Background: Prostaglandin (PG) E 2 induces expression of matrix metalloproteinases and angiogenic factors, thereby contributing to plaque instability. Objective: To study the influence of cyclooxygenase (COX) and PGE synthase (PGES) isoenzyme expression on PGE 2 and PGI 2 biosynthesis in vascular smooth muscle cells (VSMC) in culture. Methods: Cells were treated with human recombinant IL-1b over different periods of time. Expression of PGI synthase, and COX and PGES isoenzymes was determined by real-time reverse transcriptase polymerase chain reaction and immunoblotting. Biosynthesis of prostanoids from exogenous or endogenous substrate was analyzed by high-performance liquid chromatography or enzyme-immunoassay after incubation of cells with labeled arachidonic acid or thrombin, respectively. Results: Cytosolic PGES and microsomal PGES (mPGES) -1 and -2 were expressed in VSMC. PGES activity was mainly linked to mPGES-1. IL-1b induced COX-2 and mPGES-1 with a different time course. VSMC ability to synthesize PGE 2 and PGI 2 fitted mPGES-1 and COX-2 expression, respectively. The ability of VSMC to produce PGI 2 was downregulated by mPGES-1 expression and was restored when mPGES-1 expression was silenced. Results from COX-1 and COX-2 silencing and selective inhibition showed that both COX-1 and COX-2 were involved in the biosynthesis of PGE 2 and their relative contribution depended on the time of incubation with IL-1b. Conclusions: mPGES-1 is the main PGES responsible for PGE 2 biosynthesis by VSMC and its induction downregulates VSMC ability to produce PGI 2. These results support the concept that under inflammatory conditions VSMC could significantly contribute to plaque instability and that mPGES-1 may be a target for therapeutic intervention in patients with cardiovascular risk.

Abdominal aortic aneurysm (AAA) is a late-age onset disorder that affects a high percentage of the population in industrialized countries, and rupture of AAA is associated with high mortality rates ( 1 ). The etiology of AAA is complex with a relevant contribution of genetic factors ( 2 ). Although much effort has been made to clarify the mechanism of AAA development, currently the only effective approach to prevent aneurysm rupture is surgical repair by conventional or endovascular techniques.Evidence has been established for a relationship between atherosclerosis and AAA, both disorders being characterized by an underlying chronic infl ammation . However, there are marked differences between atherosclerotic lesions and AAA. Whereas atherosclerotic plaque is characterized by leukocyte infi ltration at the lumen site and hyperproliferation of vascular smooth muscle cells (VSMCs) causing neointimal hyperplasia, AAA is characterized by leukocyte infi ltration into adventitia and depletion of VSMCs in the media. Other relevant features of AAA are the wall tension strength breakdown caused by proteolytic enzymes progressively destructing elastic fi bers ( 3 ) and hypervascularization of aortic tissue. It has been proposed that this vascularization might contribute to the development and rupture of aneurysms ( 4, 5 ). Abstract We investigated the prostaglandin (PG)E

Abdominal aortic aneurysm (AAA) is a degenerative vascular disease with a complex aetiology that remains to be fully elucidated. Clinical management of AAA is limited to surgical repair, while an effective pharmacotherapy is still awaited. Endoplasmic reticulum (ER) stress and mitochondrial dysfunction have been involved in the pathogenesis of cardiovascular diseases (CVDs), although their contribution to AAA development is uncertain. Therefore, we aimed to determine their implication in AAA and investigated the profile of oxysterols in plasma, specifically 7-ketocholesterol (7-KC), as an ER stress inducer. In the present study, we determined aortic ER stress activation in a large cohort of AAA patients compared with healthy donors. Higher gene expression of activating transcription factor (ATF) 6 (ATF6), IRE-1, X-binding protein 1 (XBP-1), C/EBP-homologous protein (CHOP), CRELD2 and suppressor/enhancer of Lin-12-like (SEL1L) and greater protein levels of active ATF6, active XBP1 and of the pro-apoptotic protein CHOP were detected in human aneurysmatic samples. This was accompanied by an exacerbated apoptosis, higher reactive oxygen species (ROS) production and by a reduction in mitochondrial biogenesis in the vascular wall of AAA. The quantification of oxysterols, performed by liquid chromatography-(atmospheric pressure chemical ionization (APCI))-mass spectrometry, showed that levels of 7-KC were significantly higher while those of 7α-hydroxycholesterol (HC), 24-HC and 27-HC were lower in AAA patients compared with healthy donors. Interestingly, the levels of 7-KC correlate with the expression of ER stress markers. Our results evidence an induction of ER stress in the vascular wall of AAA patients associated with an increase in circulating 7-KC levels and a reduction in mitochondrial biogenesis suggesting their implication in the pathophysiology of this disease.