Biosynthetic Crossover of 5-Lipoxygenase and Cyclooxygenase-2 Yields 5-Hydroxy-PGE2 and 5-Hydroxy-PGD2
<p>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<sub>2</sub> that spontaneously rearranges to 5-OH-PGE<sub>2</sub> and 5-OH-PGD<sub>2</sub>, the 5-hydroxy analogs of arachidonic acid derived PGE<sub>2</sub> and PGD<sub>2</sub>. The endoperoxide was identified via its predicted degradation product, 5,12-dihydroxy-heptadecatri-6<i>E</i>,8<i>E</i>,10<i>E</i>-enoic acid, and by SnCl<sub>2</sub>-mediated reduction to 5-OH-PGF<sub>2</sub><sub>a</sub>. Both 5-OH-PGE<sub>2</sub> and 5-OH-PGD<sub>2</sub> 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<sub>4</sub> to yield the corresponding stable 5-OH-PGF<sub>2</sub> diastereomers and enabled detection of 5-OH-PGF<sub>2</sub><sub>a</sub> in activated primary human leukocytes. 5-OH-PGE<sub>2</sub> and 5-OH-PGD<sub>2</sub> were unable to activate EP and DP prostanoid receptors suggesting their bioactivity is distinct from PGE<sub>2</sub> and PGD<sub>2</sub>. </p>