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.

Eicosanoids derived from polyunsaturated fatty acids are soluble mediators that exert a key role in the physiopathology of many disorders, including infl ammation, thrombosis, and cancer. Prostanoids derived from arachidonic acid (AAc) through the cyclooxygenase (COX) pathway are particularly relevant. The increasing interest in the role of prostanoids in the context of cancer originates in the large epidemiological trials that showed that COX-inhibiting nonsteroidal anti-infl ammatory drugs could be benefi cial against the development and growth of malignancies ( 1 ).Prostaglandin (PG)H 2 is the common cyclic-peroxide intermediate in the biosynthesis of prostanoids derived from AAc. The other prostanoids are formed in reactions catalyzed by specifi c synthases acting on PGH 2 ( 2 ). In contrast with the ubiquitous expression of COXs, expression of downstream synthases confers a cell-specifi c prostanoid profi le. COX-2 receives the most attention because, unlike COX-1, which is widely expressed, its expression is restricted in nonpathologic settings to a few cell types and tissues, but it is over-expressed in a wide range of cell types in tumors and infl amed tissues. COX-2 is transiently and Abstract Prostaglandin (PG)E 2 is relevant in tumor biology, and interactions between tumor and stroma cells dramatically infl uence tumor progression. We tested the hypothesis that cross-talk between head and neck squamous cell carcinoma (HNSCC) cells and fi broblasts could substantially enhance PGE 2 biosynthesis. We observed an enhanced production of PGE 2 in cocultures of HNSCC cell lines and fi broblasts, which was consistent with an upregulation of COX-2 and microsomal PGE-synthase-1 ( mPGES-1) in fi broblasts. In cultured endothelial cells, medium from fi broblasts treated with tumor cell-conditioned medium induced in vitro angiogenesis, and in tumor cell induced migration and proliferation, these effects were sensitive to PGs inhibition. Proteomic analysis shows that tumor cells released IL-1, and tumor cell-induced COX-2 and mPGES-1 were suppressed by the IL-1-receptor antagonist. IL-1 ␣ levels were higher than those of IL-1 ␤ in the tumor cell-conditioning medium and in the secretion from samples obtained from 20 patients with HNSCC. Fractionation of tumor cellconditioning media indicated that tumor cells secreted mature and unprocessed forms of IL-1. Our results support the concept that tumor-associated fi broblasts are a relevant source of PGE 2 in the tumor mass. Because mPGES-1 seems to be essential for a substantial biosynthesis of PGE 2 , these fi ndings also strengthen the concept that mPGES-1 may be \a target for therapeutic intervention in patients with HNSCC. Abbreviations: AAc, arachidonic acid; COX, cyclooxygenase; cPGES, cytosolic isoform of prostaglandin E synthase; FaDu-CM, FaDu-conditioned medium; HNSCC, head and neck squamous cell carcinoma; HUVEC, human umbilical vein endothelial cells; IL-1ra, interleukin-1 receptor antagonist; mPGES-1, microsomal prostaglandin E-synthase-1; MW, molecular weig...

Vascular endothelial growth factor (VEGF) could play a relevant role in angiogenesis associated with chronic allograft nephropathy. Interleukin-1beta (IL-1beta) has a key role in inflammatory response. It induces prostaglandin (PG) E2, which is involved in VEGF release by some normal and tumor cells. In the present work, we studied the effect of IL-1beta on VEGF release by rat mesangial cells, the transduction signal, and whether or not PGE2 is involved in this effect. IL-1beta induced a time-dependent formation of VEGF (analyzed by enzyme-linked immunosorbent assay) and PGE2 (analyzed by enzyme immunoassay). The latter correlated with microsomal-PGE-synthase (mPGES)-1 expression rather than with cyclooxygenase (COX)-2 in terms of protein, determined by Western blotting. No effect of IL-1beta on COX-1, cytosolic PGES, or mPGES-2 expression was observed. Indomethacin exerted a nonsignificant effect on IL-1beta-induced VEGF, and exogenously added PGE2 exhibited a nonsignificant stimulatory effect on VEGF formation. SB 203580, a p38 mitogen-activated protein kinase inhibitor, weakly inhibited the induction of VEGF by IL-1beta in a concentration-dependent manner, whereas LY 294002, a phosphoinoside 3-kinase (PI3-K) inhibitor, and rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, strongly inhibited both IL-1beta- and tumor necrosis factor-alpha-induced VEGF formation in a concentration-dependent manner. Rapamycin also decreased glomerular VEGF levels in the anti-Thy1.1 model of experimental glomerulonephritis. In conclusion, the PI3-K-mTOR pathway seems to be essential in cytokine-induced release of VEGF in mesangial cells.

Circulating endothelial progenitor cells (EPCs) play a key role in the maintenance of endothelial homoeostasis and promote vascular repair. They may also be of predictive value for cardiovascular events. Reduced EPC number and functional activity have been associated with several cardiovascular risk factors, but their relationship with hypertension remains unclear. The objective of this study was to investigate if number and function of circulating EPCs are reduced in patients with refractory hypertension (RHT). Circulating EPCs (CD34+ CD133+/CD45+) were isolated from peripheral blood by flow cytometry in 39 RHT and 30 normotensive controls. EPC number was also determined in vitro after 7 days in culture. After age adjustment, EPC concentration was significantly reduced in RHT as compared with controls (mean (95% CI), 33.8 (18.1-49.6) vs 69.1 (50.7-87.5) EPCs per 10(5) peripheral mononuclear cells (MNCs), respectively; P=0.014). After in vitro culture, EPCs were also reduced in patients as compared with controls (mean (95% CI), 142.3 (49.5-235.0) vs 611.0 (480.2-741.8) EPCs per field, respectively, P<0.001). In multiple linear regression analysis, circulating EPCs were significantly reduced by 56.3% in RHT as compared with control (P=0.006), independently of all other known risk factors. Moreover, RHT had a high independent predictive value for lower EPC proliferation. The number of EPCs per field was reduced by 76.7% in RHT with respect to controls (P<0.001). In summary, the number of circulating EPCs after culture is reduced in patients with RHT, which may be related to the increased rate of endothelial dysfunction, atherosclerotic disease and cardiovascular events observed in this population.

Unraveling the mechanistic details of copper-catalyzed arylation of nucleophiles (Ullmann-type couplings) is a very challenging task. It is a matter of intense debate whether it is a radical-based process or an organometallic redox-based process. The ancillary ligand choice in Ullmann-type couplings plays a key role in such transformations and can strongly influence the catalytic efficiency as well as the mechanism. Here, we show how a predesigned tridentate pincer-like catalyst undergoes a deactivation pathway through a Cu/Cu prototypical mechanism as demonstrated by helium-tagging infrared photodissociation (IRPD) spectroscopy and DFT studies, lending a strong support to the existence of an aryl-Cu species in the Ullmann couplings using this tridentate ligand.