Transfer of arachidonic acid from lymphocytes to macrophages

ABSTRACT

The incorporation and oxidation of arachidonic acid (AA) by rat lymphocytes (LY), the transfer of AA from LY to rat macrophages (Mö) in co-culture, and the subsequent functional impact on Mö phagocytosis were investigated. The rate of incorporation of [1-14C]AA by untreated-LY and TG (thioglycolate treated)-LY (TG-LY) was 158 ± 8 nmol/1010 LY per h for both untreated-LY and TG-LY. The oxidation of AA was 3.4-fold higher in TG-LY as compared with untreated cells. LY from TG-injected rats had a 2.5-fold increase in the oxidation of palmitic (PA), oleic (OA), and linoleic (LA) acids. After 6 h of incubation, [14C] from AA was distributed mainly into phospholipids. The rate of incorporation into total lipids was 1071 nmol/1010 cells in untreated-LY and 636 nmol/1010 cells in TG-LY. [14C]AA was transferred from LY to co-cultured Mö in substantial amounts (8.7 nmol for untreated and 15 nmol per 1010 for TG cells). Exogenously added AA, PA, OA, and LA caused a significant reduction of phagocytosis by resident cells. Mö co-cultured with AA-preloaded LY showed a significant reduction of the phagocytic capacity (about 40% at 35 ìM). LY preloaded with PA, LA, and OA also induced a reduction in phagocytic capacity of co-cultured Mö. TG treatment abolished the AA-induced inhibition of phagocytosis in Mö co-cultured with TG-LY. Therefore, the transfer of AA between leukocytes is a modulated process and may play an important role in controlling inflammatory and immune response.