Biosynthetic Crossover of 5-Lipoxygenase and Cyclooxygenase-2 Yields 5-Hydroxy-PGE and 5-Hydroxy-PGD.

The 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 that spontaneously rearranges to 5-OH-PGE and 5-OH-PGD, the 5-hydroxy analogs of arachidonic acid derived PGE and PGD. The endoperoxide was identified via its predicted degradation product, 5,12-dihydroxy-heptadecatri-6,8,10-enoic acid, and by SnCl-mediated reduction to 5-OH-PGF. Both 5-OH-PGE and 5-OH-PGD were unstable and degraded rapidly upon treatment with weak base. This instability hampered detection in biologic samples which was overcome by in situ reduction using NaBH to yield the corresponding stable 5-OH-PGF diastereomers and enabled detection of 5-OH-PGF in activated primary human leukocytes. 5-OH-PGE and 5-OH-PGD were unable to activate EP and DP prostanoid receptors, suggesting their bioactivity is distinct from PGE and PGD.