Wl. Ring et al., HUMAN MONOCYTES LOSE 5-LIPOXYGENASE AND FLAP AS THEY MATURE INTO MONOCYTE-DERIVED MACROPHAGES IN-VITRO, American journal of physiology. Cell physiology, 40(1), 1996, pp. 372-377
Previous studies in mononuclear phagocytes have shown that macrophages
have substantially greater 5-lipoxygenase activity than monocytes and
that this is associated with greater amounts of 5-lipoxygenase and it
s activating protein (FLAP). The aim of this study was to examine the
effect of mononuclear phagocyte maturation in vitro on 5-lipoxygenase
expression. At baseline, monocytes had significant 5-lipoxygenase acti
vity, but then lost all detectable 5-lipoxygenase activity over 7 days
. Immunoblot and Northern blot analysis revealed that immunoreactive p
rotein and mRNA for both 5-lipoxygenase and FLAP were significantly de
creased over time. These studies demonstrate that in vitro differentia
tion of monocytes into a macrophage phenotype is not accompanied by th
e enhanced expression of 5-lipoxygenase and FLAP seen in macrophages d
erived from in vivo sources. In fact, baseline expression of 5-lipoxyg
enase and FLAP by monocytes is lost in vitro. These studies have clear
implications for the use of cultured monocytes as a model of macropha
ges, and they also further our understanding of the regulation of the
5-lipoxygenase pathway.