Microvascular COX-2/mPGES-1/EP-4 axis in human abdominal aortic aneurysm.

We investigated the prostaglandin (PG)E2 pathway in human abdominal aortic aneurysm (AAA) and its relationship with hypervascularization. We analyzed samples from patients undergoing AAA repair in comparison with those from healthy multiorgan donors. Patients were stratified according to maximum aortic diameter: low diameter (LD) (<55 mm), moderate diameter (MD) (55-69.9 mm), and high diameter (HD) (≥70 mm). AAA was characterized by abundant microvessels in the media and adventitia with perivascular infiltration of CD45-positive cells. Like endothelial cell markers, cyclooxygenase (COX)-2 and the microsomal isoform of prostaglandin E synthase (mPGES-1) transcripts were increased in AAA (4.4- and 1.4-fold, respectively). Both enzymes were localized in vascular cells and leukocytes, with maximal expression in the LD group, whereas leukocyte markers display a maximum in the MD group, suggesting that the upregulation of COX-2/mPGES-1 precedes maximal leukocyte infiltration. Plasma and in vitro tissue secreted levels of PGE2 metabolites were higher in AAA than in controls (plasma-controls, 19.9 ± 2.2; plasma-AAA, 38.8 ± 5.5 pg/ml; secretion-normal aorta, 16.5 ± 6.4; secretion-AAA, 72.9 ± 6.4 pg/mg; mean ± SEM). E-prostanoid receptor (EP)-2 and EP-4 were overexpressed in AAA, EP-4 being the only EP substantially expressed and colocalized with mPGES-1 in the microvasculature. Additionally, EP-4 mediated PGE2-induced angiogenesis in vitro. We provide new data concerning mPGES-1 expression in human AAA. Our findings suggest the potential relevance of the COX-2/mPGES-1/EP-4 axis in the AAA-associated hypervascularization.

Genetic determinants of 5-lipoxygenase pathway in a Spanish population and their relationship with cardiovascular risk.

OBJECTIVE: Leukotrienes (LT) play a role in inflammation, cardiovascular diseases, and cancer. Although some studies suggest that there are genes that determine variability of some LT-related phenotypes, the genetic influence on these phenotypes has not been evaluated. METHODS: The relative contributions of genetic and environmental influences to the 5-lipoxygenase pathway-related phenotypes (5-Lipoxygenase, five lipoxygenase activating protein (FLAP), LTA(4)-hydrolase and LTC(4)-synthase expression, and LTB(4)-plasma concentration and LTB(4) production by stimulated whole blood) were assessed in a sample of 934 individuals in 35 extended families. Our design is based on extended families recruited through a probands with idiopathic thrombophilia. This strategy allows us the analysis of the effects of measured covariates (such as sex, age and smoking), genes, and environmental variables shared by members of a household. RESULTS: All of these phenotypes showed significant genetic contributions, with heritabilities ranging from 0.33 to 0.51 for enzyme expression and from 0.25 to 0.50 for LTB(4) production of the residual phenotypic variance. Significant phenotypic and genetic correlation among the LT-related traits was found. More importantly, FLAP and LTA(4)-hydrolase expression exhibit significant genetic correlations with arterial thrombosis, indicating that some of the genes that influence quantitative variation in these phenotypes also influence the risk of thrombosis. CONCLUSION: This is the first study that quantifies the genetic component of 5-Lipoxygenase pathway phenotypes. The high heritability of these traits and the significant genetic correlations between arterial thrombosis and some of these phenotypes suggest that the exploitation of correlated quantitative phenotypes will aid the search for susceptibility genes.

Imidazolineoxyl N-oxide induces COX-2 in endothelial cells: role of free radicals.

cPTIO (2-[4-carboxyphenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) exerts beneficial actions on systemic inflammatory response. Besides its nitric oxide (NO) scavenging properties cPTIO could exert beneficial effects through modulation of arachidonic acid metabolism. We studied the effect of cPTIO on the biosynthesis of vasoactive prostaglandins (PG) by endothelial cells. Human cord umbilical vein endothelial cells (HUVEC) were treated with cPTIO, and expression of cycloxygenase (COX) isoenzymes in terms of mRNA and protein was determined by real-time-PCR and immunoblotting. Release of PGE2 (as index of untransformed PGH2 release) and 6-oxo-PGF1alpha (PGI2 stable metabolite) was determined by enzyme-immunoassay. cPTIO significantly increases the release of untransformed PGH2 associated to the induction of COX-2 expression. Experiments with NO-synthase inhibitors and radical scavengers showed that induction of COX-2 by cPTIO was mediated by free radical species, likely caused by the mobilization of NO from cellular stores. Finally, using specific signal-transduction inhibitors we show the involvement of Src/PI3-K/PKC pathway. Additional effects other than a direct NO scavenging activity may confer therapeutic advantages to cPTIO as compared with NO-synthase inhibitors for the treatment of systemic inflammation-associated vascular hyporeactivity.

Tumor cells induce COX-2 and mPGES-1 expression in microvascular endothelial cells mainly by means of IL-1 receptor activation.

Prostaglandin (PG) E(2) plays a key role in immune response, tumor progression and metastasis. We previously showed that macrovessel-derived endothelial cells do not produce PGE(2) enzymatically because they do not express the inducible microsomal PGE-synthase-1 (mPGES-1). Nevertheless, differences between macro- and micro-vessel-derived endothelial cells regarding arachidonic acid (AAc) metabolism profile have been reported. The present work was conducted to evaluate the expression of PGE(2)-pathway-related enzymes in human microvascular endothelial cells (HMVEC) in culture and to test the hypothesis that the tumor cell-HMVEC cross talk could increase mPGES-1 expression in HMVEC. We treated HMVEC in culture with human recombinant IL-1ß. IL-1ß induced PGE(2) release and COX-2 and mPGES-1 expression in terms of mRNA and protein, determined by real-time PCR and immunoblotting, respectively. HMVEC constitutively expressed mPGES-2 and cytosolic PGES (cPGES) and the IL-1ß treatment did not modify their expression. PGE(2) synthesized by HMVEC from exogenous AAc was linked to mPGES-1 expression. Immunohistochemistry analysis confirmed mPGES-1 expression in microvessels in vivo. COX-2 and mPGES-1 were also induced in HMVEC by the conditioned medium from two squamous head and neck carcinoma cell lines. Conditioned medium from tumor cell cultures contained several cytokines including the IL-1ß and IL-1α. Tumor cell-induced COX-2 and mPGES-1 in HMVEC was strongly inhibited by the IL-1-receptor antagonist, indicating the important implication of IL-1 in this effect. HMVEC could therefore contribute directly to PGE(2) formed in the tumor. Our findings support the concept that mPGES-1 could be a target for therapeutic intervention in patients with cancer.