EFFECT OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR ON EICOSANOID PRODUCTION BY MONONUCLEAR PHAGOCYTES

Granulocyte-macrophage CSF (GM-CSF) primes granulocytes for leukotrien e (LT) synthesis, Here, we examined the effects of CM-CSF on arachidon ic acid (AA) metabolism in rat alveolar macrophages (AM), peritoneal m acrophages, and human peripheral blood monocytes, Pretreatment of AMs with GM-CSF for 24 h significantly increased the synthesis of immunore active LTB(4) upon subsequent stimulation with calcium ionophore, Enha nced LT synthesis required a minimum of 6 h of CM-CSF pretreatment, su ggesting that protein synthesis was required for enhanced LT productio n; indeed, cycloheximide completely abolished the GM-CSF effect on LT synthesis, HPLC analysis confirmed that CM-CSF primed AMs for enhanced generation of LTB(4) as well as the 5-lipoxygenase products LTC(4) an d 5-HETE, Moreover, parallel increases in other AA metabolites and fre e AA were observed following CM-CSF pretreatment, The enhanced product ion of all AA metabolites indicated that GM-CSF up-regulated AA releas e, Consistent with this, whole cell lysates from GM-CSF-treated AMs de monstrated increased phospholipase A(2) (PLA(2)) activity, The increas ed activity was resistant to DTT, indicating the involvement of a PLA( 2) other than the 14-kDa PLA(2)s. By immunoblot analysis, GM-CSF treat ment caused an increase in the 85-kDa PLA(2) protein comparable to the observed increase in PLA(2) activity, Unlike AMs, neither peritoneal macrophages nor peripheral blood monocytes showed increased eicosanoid generation or increased expression of the 85-kDa PLA(2) protein follo wing CM-CSF pretreatment. These results indicate that GM-CSF increases the capacity of AMs, but not peritoneal macrophages or peripheral blo od monocytes, to generate eicosanoids, This effect results from increa sed PLA(2) activity, due at least in part to increased levels of the 8 5-kDa PLA(2) protein.