Double-label expression studies of prostacyclin synthase, thromboxane synthase and COX isoforms in normal aortic endothelium.
We have performed double-label immunofluorescence microscopy studies to evaluate the extent of co-localization of prostacyclin synthase (PGIS) and thromboxane synthase (TXS) with cyclooxygenase (COX)-1 and COX-2 in normal aortic endothelium. In dogs, COX-2 expression was found to be restricted to small foci of endothelial cells while COX-1, PGIS and TXS were widely distributed throughout the endothelium. Quantification of the total cross-sectioned aortic endothelium revealed a 6- to 7-fold greater expression of COX-1 relative to COX-2 (55 vs. 8%) and greater co-distribution of PGIS with COX-1 compared to COX-2 (19 vs. 3%). These results are in contrast to the extensive co-localization of PGIS and COX-2 in bronchiolar epithelium. In rat and human aortas, immunofluorescence studies also showed significant COX-1 and PGIS co-localization in the endothelium. Only minor focal COX-2 expression was detected in rat endothelium, similar to the dog, while COX-2 was not detected in human specimens. Inhibition studies in rats showed that selective COX-1 inhibition caused a marked reduction of 6-keto-PGF(1alpha) and TXB(2) aortic tissue levels, while COX-2 inhibition had no significant effect, providing further evidence for a functionally larger contribution of COX-1 to the synthesis of prostacyclin and thromboxane in aortic tissue. The data suggest a major role for COX-1 in the production of both prostacyclin and thromboxane in normal aortic tissue. The extensive co-localization of PGIS and COX-2 in the lung also indicates significant tissue differences in the co-expression patterns of these two enzymes.
Kawka
Douglas W
DW
Departments of Immunology and Rheumatology, Merck Research Laboratories, Rahway, NJ 07065, USA.
Ouellet
Marc
M
Hétu
Pierre-Olivier
PO
Singer
Irwin I
II
Riendeau
Denis
D
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000201:enzymology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004285:Dogs; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D011464:Epoprostenol / Q000096:biosynthesis / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008168:Lung / Q000166:cytology / Q000201:enzymology; D009928:Organ Specificity; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D013045:Species Specificity; D013930:Thromboxane-A Synthase / Q000096:biosynthesis* / Q000235:genetics; D013931:Thromboxanes / Q000096:biosynthesis / Q000235:genetics
D007527:Isoenzymes; D013931:Thromboxanes; D003577:Cytochrome P-450 Enzyme System; D011464:Epoprostenol; D011451:Prostaglandin-Endoperoxide Synthases; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase; D013930:Thromboxane-A Synthase