Specific high affinity binding of lipoxygenase metabolites of arachidonic acid by liver fatty acid binding protein

Abstract

Liver fatty acid binding protein (L-FABP) binds avidly the arachidonic acid metabolites, hydroperoxyeicosatetraenoic acids (HPETEs) and hydroxyeicosatetraenoic acids (HETEs). Binding of 15-[3H]HPETE was specific, saturable, reversible, and rapid. Protein specificity was indicated by the following order: L-FABP greater than bovine serum albumin greater than ovalbumin = beta-lactoglobulin greater than ribonuclease. Ligand specificity was evidenced by the following order of apparent competition: 15-HPETE greater than or equal to 5-HETE greater than or equal to 5-HPETE = oleic acid greater than 12-HETE greater than 12-HPETE greater than or equal to 15-HETE greater than prostaglandin E1 much greater than leukotriene C4 greater than prostaglandin E2 much greater than thromboxane B2 = leukotriene B4. Once bound, 15-HPETE was reversibly displaced. Ligand was recovered from the protein complex and confirmed to be 15-[3H]HPETE by TLC. L-FABP bound HPETE with a dissociation constant of 76 nM,5-HETE at 175 nM, and 15-HETE at 1.8 microM, and the reference fatty acids oleic acid at 1.2 microM and arachidonic acid at 1.7 microM. Thus, the affinity was approximately 16-fold greater for 15-HPETE, and 7-fold higher for 5-HETE, than for oleic acid. The need exists for studies of complexes of L-FABP with the HPETEs and HETEs in hepatocytes, especially since L-FABP has previously been associated with mitosis in normal hepatocytes, and shown to be the target protein of two liver carcinogens, and these arachidonic acid metabolites have been found to be able to modulate activities related to cell growth.