In this study, murine peritoneal macrophages from naïve lavage were found to generate four
phospholipids that contain 12-hydroxyeicosatetraenoic
acid (12-HETE). They comprise three
plasmalogen and one diacyl
phosphatidylethanolamines (PEs) (16:0p, 18:1p, 18:0p, and 18:0a at sn-1) and are absent in macrophages from 12/
15-lipoxygenase (12/15-LOX)-deficient mice. They are generated acutely in response to
calcium mobilization, are primarily cell-associated, and are detected on the outside of the plasma membrane. Levels of 12-HETE-PEs in naïve lavage are in a similar range to those of free
12-HETE (5.5 +/- 0.2 ng or 18.5 +/- 1.03 ng/lavage for esterified versus free, respectively). In healthy mice, 12/15-LOX-derived 12-HETE-PEs are found in the peritoneal cavity, peritoneal membrane, lymph node, and intestine, with a similar distribution to 12/15-LOX-derived
12-HETE. In vivo generation of 12-HETE-PEs occurs in a Th2-dependent model of murine
lung inflammation associated with
interleukin-4/
interleukin-13 expression. In contrast, in Toll receptor-dependent
peritonitis mediated either by live bacteria or bacterial products, 12-HETE-PEs are rapidly cleared during the acute phase then reappear during resolution. The human homolog, 18:0a/15-
HETE-PE inhibited human monocyte generation of
cytokines in response to
lipopolysaccharide. In summary, a new family of
lipid mediators generated by murine macrophages during Th2
inflammation are identified and structurally characterized. The studies suggest a new paradigm for
lipids generated by 12/15-LOX in
inflammation involving formation of esterified
eicosanoids.