Biosynthetic Crossover of 5-Lipoxygenase and Cyclooxygenase-2 Yields 5-Hydroxy-PGE2 and 5-Hydroxy-PGD2

Biosynthetic crossover of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) enzymatic activities is a productive pathway to convert arachidonic acid into unique eicosanoids. Here we show that COX-2 catalysis with 5-LOX derived 5-hydroxy-eicosatetraenoic acid yields the endoperoxide 5-hydroxy-PGH 2 that spontaneously rearranges to 5-OH-PGE 2 and 5-OH-PGD 2 , the 5-hydroxy analogs of arachidonic acid derived PGE 2 and PGD 2 . The endoperoxide was identified via its predicted degradation product, 5,12-dihydroxy-heptadecatri-6 E ,8 E ,10 E -enoic acid, and by SnCl 2 -mediated reduction to 5-OH-PGF 2 a . Both 5-OH-PGE 2 and 5-OH-PGD 2 were unstable and degraded rapidly upon treatment with weak base. The instability hampered detection in biologic samples which was overcome by in situ reduction using NaBH 4 to yield the corresponding stable 5-OH-PGF 2 diastereomers and enabled detection of 5-OH-PGF 2 a in activated primary human leukocytes. 5-OH-PGE 2 and 5-OH-PGD 2 were unable to activate EP and DP prostanoid receptors suggesting their bioactivity is distinct from PGE 2 and PGD 2 .