ESTERIFICATION OF 12(S)-HYDROXY-5,8,10,14-EICOSATETRAENOIC ACID INTO THE PHOSPHOLIPIDS OF HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS - INHIBITION OF THE PROLIFERATIVE RESPONSE

12-hydroxy-eicosatetraenoic acid (12-HETE), the lipoxygenase metabolit e of arachidonic acid produced by activated platelets, has been shown to accumulate in peripheral blood mononuclear cells (PBMC) of elderly people. 12-HETE being antimitogenic for lymphocytes, its accumulation in blood cells might be involved in the well-known decline in immune f unction which accompanies aging. Because HETEs have been shown to be r apidly metabolized and/or incorporated into cellular lipids in a varie ty of cell types, we have investigated the uptake, metabolism, and int racellular distribution of exogenous 12-HETE by human PBMC. [H-3]-12-H ETE was dose and time dependently incorporated by PBMC and also metabo lized to more polar products. These polar metabolites were mainly rele ased extracellularly and only marginally esterfied in phospholipids. A lthough [3H]-12-HETE radiolabel was preferentially associated with pho sphatidylcholine, especially after prolonged labeling incubations or f ollowing successive short labeling pulses, a substantial amount of rad iolabel was also found associated with phosphatidylinositol (20-50% of the labeled phospholipids). The stability of 12-HETE in the phospholi pid pool was comparable to that reported for most other cell types, wi th 50% of the initial radiolabel being still present after 18 hr. Upon exposure to mitogenic activation, 12-HETE-labeled PBMC released unmod ified 12-HETE from phosphatidylinositol. In addition, 12-HETE dose dep endently inhibited the proliferative response of PBMC to Con A stimula tion. These results suggest that 12-HETE esterification in phospholipi ds might lead to the generation of unusual lipid second messengers wit h impaired capacity to transduce activation signals, thus decreasing l ymphocyte function. (C) 1995 Wiley-Liss, Inc.