出版社：American Society for Biochemistry and Molecular Biology
摘要：Biosynthesis of the prostaglandin endoperoxide by the cyclooxygenase (COX) enzymes is accompanied by formation of a small amount of 11 R -hydroxyeicosatetraenoic acid (HETE), 15 R -HETE, and 15 S -HETE as by-products. Acetylation of COX-2 by aspirin abrogates prostaglandin synthesis and triggers formation of 15 R -HETE as the sole product of oxygenation of arachidonic acid. Here, we investigated the formation of by-products of the transformation of 5 S -HETE by native COX-2 and by aspirin-acetylated COX-2 using HPLC-ultraviolet, GC-MS, and LC-MS analysis. 5 S ,15 S - dihydroxy (di)HETE, 5 S ,15 R -diHETE, and 5 S ,11 R -diHETE were identified as by-products of native COX-2, in addition to the previously described di-endoperoxide (5 S ,15 S -dihydroxy-9 S ,11 R ,8 S ,12 S -diperoxy-6 E ,13 E -eicosadienoic acid) as the major oxygenation product. 5 S ,15 R -diHETE was the only product formed by aspirin-acetylated COX-2. Both 5,15-diHETE and 5,11-diHETE were detected in CT26 mouse colon carcinoma cells as well as in lipopolysaccharide-activated RAW264.7 cells incubated with 5 S -HETE, and their formation was attenuated in the presence of the COX-2 specific inhibitor, NS-398. Aspirin-treated CT26 cells gave 5,15-diHETE as the most prominent product formed from 5 S -HETE. 5 S ,15 S -diHETE has been described as a product of the cross-over of 5-lipoxygenase (5-LOX) and 15-LOX activities in elicited rat mononuclear cells and human leukocytes, and our studies implicate cross-over of the 5-LOX and COX-2 pathways as an additional biosynthetic route.
