Fuscoside: an anti-inflammatory marine natural product which selectively inhibits 5-lipoxygenase. Part I: Physiological and biochemical studies in murine inflammatory models.

The biological and biochemical pharmacology of fuscoside, a novel anti-inflammatory marine natural product isolated from the Caribbean gorgonian Eunicea fusca, has recently been characterized using murine (part I) and human (part II) models of inflammation. Topically applied fuscoside (FSD) effectively inhibits phorbol myristate acetate (PMA)-induced edema in mouse ears at levels comparable with indomethacin over a 3.3-hr exposure period, and is significantly more efficacious than indomethacin over 24 hr in the PMA model. Histological preparations and quantification of the neutrophil-specific marker, myeloperoxidase, demonstrate that FSD inhibits neutrophil infiltration into PMA-induced regions of edema and inflammation. In systemic studies, where FSD is injected i.p. before the topical application of PMA, negligible effects on ear inflammation are observed. FSD does not inhibit bee venom or human synovial fluid phospholipase A2 up to concentrations of 500 microM. In calcium ionophore-activated cultures of mouse peritoneal macrophages, FSD selectively and irreversibly inhibits leukotriene C4 biosynthesis (IC50 = 8 microM), yet has negligible effects on prostaglandin E2 production. FSD is also without effect on the conversion of arachidonic acid to prostaglandin E2 by ram seminal vesicle cyclooxygenase. Chromatographic and spectroscopic studies suggest that FSD is not metabolized, and that drug uptake/binding by macrophages is time dependent, saturable and independent of active transport mechanisms. These studies represent the first report of an anti-inflammatory marine natural product that selectively inhibits leukotriene biosynthesis.