Eicosanoid biosynthesis in an advanced deuterostomate invertebrate, the sea squirt (Ciona intestinalis)

The eicosanoid generating potential of tunic, branchial basket, intestine, ovary and tadpole larvae from the sea squirt, Ciona intestinalis, was exami ned using a combination of reverse phase high performance liquid chromatogr aphy, gas chromatography-mass spectrometry and enzyme immunoassay. All orga ns examined synthesized the lipoxygenase products 12-hydroxyeicosapentaenoi c acid (12-HEPE) and 8-HEPE implying that both 8- and 12-lipoxygenase activ ity are widely distributed in this species. In addition, tunic and branchia l basket generated significant amounts of 8,15-diHEPE and smaller amounts o f 8,15-dihydroxyeicosatetraenoic acid (8,15-diHETE), while tunic alone gene rated small amounts of conjugated tetraene-containing material with a UV ch romophore and mass ion characteristic of a lipoxin-like compound. The broad range lipoxygenase inhibitors, esculetin and nordihydroguaiaretic acid, bo th caused a significant dose dependent inhibition of 12-HEPE and 8,15-diHEP E biosynthesis in tunic, while the specific 5-lipoxygenase inhibitor, REV-5 901, and the specific 5-lipoxygenase activating protein inhibitor, MK-866, had no observable effect on the lipoxygenase profile of this tissue. Tunic, branchial basket, intestine and ovary all generated significant amounts of prostaglandin (PG) E and PGF immunoreactive material and smaller amounts o f thromboxane B immunoreactive material as measured by enzyme immunoassay. The non-specific cyclooxygenase (COX) inhibitor, indomethacin, the selectiv e COX-I inhibitors, resveratrol and valerylsalicylate, and the specific COX -2 inhibitors, NS-398, etolodac and DFU (5,5-dimethyl-3-(3-fluorophenyl)-4- (4-methylsulphonyl) phenyl-2(5H)-furanone) all caused a significant dose de pendent inhibition of the biosynthesis of PGE immunoreactive material. Howe ver, the specific COX-2 inhibitors were most effective, perhaps implying th at a COX-2-like enzyme may be present in this species. (C) 1999 Elsevier Sc ience B.V. All rights reserved.