The role of immunomodulators in the production of lipid mediators by macrophages (M phi)

There is evidence indicating that bioreactive lipid mediators, PAF-acether (platelet-activating factor: 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and arachidonic acid (AA) metabolites, are formed upon deacylation of ether lipids. M phi obtained from mice treated with the sterile irritant thioglycolate exhibited an impaired formation of PAF-acether, leucotrienes (LT) C4 and prostaglandins (PG). In order to assess whether the impaired formation in lipid mediators is a general feature of M phi found at inflammatory sites, we have compared the capacity of resident (R-M phi) and immunostimulant-activated M phi to release, upon a zymosan challenge, PAF-acether and cyclooxygenase and lipoxygenase products. Activated M phi was obtained from mice injected intraperitoneally with non-viable C74 streptococci (St-M phi), bacilli Calmette-Guerin (BCG-M phi) or trehalose dimycolate (TDM-M phi), a defined immunostimulant isolated from Mycobacterium tuberculosis. All populations were capable of releasing PAF-acether. However, the amount of cell-associated PAF-acether was reduced by 75-90% in activated M phi populations as compared to R-M phi. Although the acetyltransferase level was comparable, acetyl-CoA supplementation restored the formation of PAF-acether by activated M phi to control (R-M phi) level. The amount of 14C-AA metabolites released by St-M phi was much lower compared with TDM-M phi or R-M phi, as was the amount of LTC4 detected as SRS contractile activity after HPLC.(ABSTRACT TRUNCATED AT 250 WORDS)