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

[Image: see text] 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(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-6E,8E,10E-enoic acid, and by SnCl(2)-mediated reduction to 5-OH-PGF(2α). Both 5-OH-PGE(2) and 5-OH-PGD(2) 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(4) to yield the corresponding stable 5-OH-PGF(2) diastereomers and enabled detection of 5-OH-PGF(2α) 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).