Metabolism of 15-hydroxyeicosatetraenoic acid by Caco-2 cells

Monolayers of Caco-2 cells, a human enterocyte cell line, were incubated with [1-¹⁴C]15-hydroxyeicosatetraenoic acid (15-HETE), a lipid mediator of inflammation, and [1-¹⁴C]arachidonic acid. Both fatty acids were taken up readily and metabolized by Caco-2 cells. [1-¹⁴C]Arachidonic acid was directly esterified in cellular phospholipids and, to a lesser extent, in triglycerides. When [1-¹⁴C]15-hydroxyeicosatetraenoic acid was incubated with Caco-2 cells, about 10% was directly esterified into cellular lipids but most (55%) was β-oxidized to ketone bodies, CO₂, and acetate, with very little accumulation of shorter carbon chain products of partial β-oxidation. The radiolabeled acetate generated from β-oxidation of [1-¹⁴C]15-hydroxyeicosatetraenoic acid was incorporated into the synthesis of new fatty acids, primarily [¹⁴C]palmitate, which in turn was esterified into cellular phospholipids, with lesser amounts in triglycerides. Caco-2 cells were also incubated with [5,6,8,9,11,12,14,15-³H]15-hydroxyeicosatetraenoic acid; most of the radiolabel was recovered either in ketone bodies or in [³H]palmitate esterified in phospholipids and triglycerides, demonstrating that most of the [³H]15-hydroxyeicosatetraenoic acid underwent several cycles of β-oxidation. The binding of both 15-hydroxyeicosatetraenoic acid and arachidonic acid to hepatic fatty acid binding protein, the only fatty acid binding protein in Caco-2 cells, was measured. The K(d) (6.0 μM) for 15-HETE was three-fold higher than that for arachidonate (2.1 μM).