Formation and release of a peroxisome-dependent arachidonic acid metabolite by human skin fibroblasts.

Human skin fibroblasts labeled with [5,6,8,9,11,12,-14,15-3H]arachidonic acid produce a radioactive metabolite that has a shorter retention time on reverse-phase high-performance liquid chromatography than arachidonic acid. This product is not retained in the cells; it is released entirely into the extracellular fluid in a time-dependent manner. The metabolite does not cochromatograph with any of the eicosanoid standards, and its formation is not prevented by the addition of cyclooxygenase, lipoxygenase, or cytochrome P-450 inhibitors. The compound is not produced by fibroblasts labeled with [1-14C]arachidonic acid, suggesting that it is formed through an oxidative process. Chemical analyses indicated that the metabolite is 4,7,10-hexadecatrienoic acid (16:3). Peroxisome-deficient human skin fibroblasts did not produce 16:3, indicating that it probably is formed through peroxisomal beta-oxidation. Human umbilical vein endothelial cells and porcine pulmonary artery smooth muscle cells also release radioactive 16:3 following labeling with [3H]arachidonic acid. Therefore, the production of this metabolite is not limited only to fibroblasts. The fact that 16:3 is released into the extra-cellular fluid suggests that it may be a new type of lipid mediator derived from arachidonic acid, formed through a peroxisome-dependent oxidative process.