Modulation of erythropoiesis by novel human bone marrow cytochrome P450-
dependent metabolites of arachidonic acid
NG Abraham, E Feldman, JR Falck, JD Lutton and ML Schwartzman
Department of Medicine, New York Medical College, Valhalla 10595.
In the hematopoietic system the adherent stromal cells produce cytokines
necessary for proliferation and differentiation of hematopoietic cells. In
the present study, we showed the ability of adherent stromal cells to
generate novel metabolites of arachidonic acid via the NADPH-cytochrome
P450-dependent monooxygenase system. These metabolites were recovered in
the incubation media, suggesting their release from cells. The formation of
arachidonic acid metabolites was inhibited by 7-ethoxyresorufin and
SKF-525A, but not by indomethacin or BW-755C. By using two-step
high-pressure liquid chromatography (HPLC), bone marrow-adherent stromal
cells and incubation media showed the presence of metabolites in a peak
eluted at 19 to 20 minutes. The isolated HPLC peak was used to measure its
effect on colony-forming unit-erythroid (CFU-E) growth and compare it with
that of synthetic cytochrome P450 arachidonate metabolites, 19- and 20-
hydroxyeicosatetraenoic (HETE) acid. These bone marrow cytochrome P450
arachidonic acid metabolites at picomolar concentration potentiated
erythropoietin (Epo)-induced CFU-E growth by fourfold to sixfold. Addition
of 19- and 20-HETE to the bone marrow culture resulted in a potentiating
effect on CFU-E number in a dose-dependent manner. 20-HETE was much more
potent in stimulating CFU-E growth than 19-HETE at a similar concentration
of 10(-11) mol/L. The potentiating effect of 20- HETE resulted in a
shifting to the left of the dose-response curve to Epo. To substantiate the
finding of an active NADPH-dependent cytochrome P450-metabolizing system,
we further examined the ability of adherent cells to metabolize exogenous
pharmacologic compounds such as benzo(a)pyrene, a substrate for the
heme-cytochrome P450 system, aryl hydrocarbon hydroxylase. The adherent
stromal cytochrome P450 metabolizes benzo(a)pyrene at comparable levels to
blood vessel endothelial cells. These novel observations underscore the
importance of adherent stromal cytochrome P450 to metabolize endogenous
substrates, including arachidonic acid, to compounds that may interact in a
paracrine manner with Epodependent hematopoietic cells.
Volume 78,
Issue 6,
pp. 1461-1466,
09/15/1991
Copyright © 1991 by The American Society of Hematology
