Lipoxygenase products regulate proliferation of granulocyte-macrophage progenitors

We studied the role of lipoxygenase products on the proliferation and recovery of granulocyte-macrophage progenitors (CFU-GM) in liquid cultures of normal human blood mononuclear cells containing physiologic or slightly higher than physiologic concentrations of hydrocortisone (HC). Lipoxygenase blockade by addition of nordihydroguaiaretic acid (NDGA) resulted in enhanced recovery of CFU-GM (mean increase of 230%). The number of CFU-GM recovered from 14-day liquid cultures containing 1.0 microM HC plus 10 microM NDGA was a mean of six times higher than the number present in the inoculum. Effects of addition of selected 5-lipoxygenase products into the culture containing a lipoxygenase blocker on the CFU-GM recovery and proliferative activity were dose- and metabolite-specific. Leukotriene (LT) B4 and 5-hydroxy-eicosatetraenoic acid (5-HETE) decreased recovery of CFU-GM while LTC4 and LTD4 had biphasic effects--lower doses decreased while higher doses had no effect on CFU-GM recovery. Lipoxygenase blockade decreased the percent of CFU-GM in DNA synthesis phase. Readdition of LTB4 did not reverse this effect while LTD4 had a biphasic effect--low concentrations increased the percent of CFU-GM in DNA synthesis phase to levels equivalent to CFU-GM in cultures without NDGA while higher concentrations had no effect. In semisolid CFU-GM assays, lipoxygenase blockade with NDGA completely prevented CFU-GM colony formation, suggesting that NDGA inhibits proliferation and/or differentiation of CFU-GM in semisolid culture assays. The results of our studies suggest that 5-lipoxygenase metabolites are physiologically important in regulating the proliferation of CFU-GM and, thus, granulopoiesis.