Lipoxin A4 metabolism by differentiated HL-60 cells and human monocytes: Conversion to novel 15-oxo and dihydro products

Abstract

Lipoxins are tetraene-containing eicosanoids that possess biological activity in several organ systems. To determine their route of further metabolism, [11,12-3H]lipoxin A4 was prepared and incubated with human neutrophils, promyelocytic leukemia (HL-60) cells, and adherent monocytes. Intact neutrophils and undifferentiated HL-60 cells did not significantly metabolize [11,12-3H]LXA4, while HL-60 cells differentiated with PMA to monocyte/macrophage lineage rapidly (< 15 s) transformed this eicosanoid. The major radiolabeled LXA4-derived metabolites were characterized by physical methods and were shown to be 15-oxo-LXA4, 13,14-dihydro-15-oxo-LXA4, and 13,14-dihydro-LXA4. Substrate competition with cell-free supernatants from differentiated HL-60 cells suggests that lipoxins compete for 15-hydroxyprostaglandin dehydrogenase activity or an equivalent enzyme system. In addition, adherent monocytes exposed to [11,12-3H]LXA4 rapidly metabolized (> 60% within 30 s) the label to its oxo and dihydro derivatives. These results indicate that, unlike leukotrienes, LXA4 is subject to dehydrogenation and reduction of its conjugated tetraene to form triene-containing products. Moreover, they suggest that monocytes participate in lipoxin metabolism in their local milieu.

Interactions Between Lipoxin A4, the Stable Analogue 16‐phenoxy‐lipoxin A4 and Leukotriene B4 in Cytokine Generation by Human Monocytes

“…Due to dehydrogenation, native lipoxins are rapidly inactivated by 15-hydroxyprostaglandin dehydrogenase, which is present in human monocytes [25], whereas neutrophils do not express the necessary enzyme(s) [12]. We therefore used a LXA 4 -stable analogue designed to resist conversion leading to inactivation [36]. This analogue retains the biological activity in leucocyte adhesion and migration studies [11,37].…”

Infection and inflammatory mechanisms

“…The eicosanoid product, lipoxins, are receptor agonists that stimulate the resolution of inflammation and promote the restoration of tissue homeostasis by limiting PMN migration into sites of inflammation, modulating the phenotype of macrophages, stimulating the uptake of apoptotic PMN without secretion of pro-inflammatory cytokines (Serhan et al 1993, Maddox & Serhan 1996, Maddox et al 1997.…”

An Aspirin-Triggered Lipoxin A4 Stable Analog Displays a Unique Topical Anti-Inflammatory Profile

“…LXA 4 and ATLs undergo rapid metabolic inactivation by PG dehydrogenase-mediated oxidation and reduction (8,9). These metabolites have reduced affinity for ALX-R and decreased antiinflammatory potency.…”