J. Biol. Chem., Vol. 262, Issue 15, 6976-6981, 05, 1987
Interactions of arterial cells. Studies on the mechanisms of endothelial cell modulation of cholesterol metabolism in co-cultured smooth muscle cells [published erratum appears in J Biol Chem 1987 Sep 15;262(26):12887]
DP Hajjar, AJ Marcus and KA Hajjar
Fluid phase interactions between arterial endothelial cells (EC) and smooth
muscle cells (SMC) have been studied in vitro to assess the regulation of
lipid metabolism in SMC (Hajjar, D. P., Falcone, D. J., Amberson, J. B.,
and Hefton, J. M. (1985) J. Lipid Res. 26, 1212-1223; Davies, P. F.,
Truskey, G. A., Warren, H. B., O'Connor, S. E., and Eisenhaure, B. H.
(1985) J. Cell Biol. 101, 871-879). To identify EC- derived agonists which
may modulate cholesterol metabolism in co- cultured SMC, we assessed the
role of EC-derived eicosanoids and platelet-derived growth factor (PDGF) in
the regulation of cholesteryl ester (CE) hydrolysis in SMC. The major
eicosanoids synthesized by EC include PGI2 and
12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) and, to a lesser
extent, prostaglandin E2. Exogenously added PGI2 and 12-HETE stimulated CE
hydrolytic activity in SMC by 49 and 35%, respectively, when co-cultured
with aspirin-treated EC. Aspirin-treated EC when co-cultured with SMC did
not stimulate CE hydrolytic activity in SMC, as was the case with
non-aspirin-treated EC, suggesting a role of eicosanoids in the regulation
of cholesterol metabolism. Other humoral agents derived from EC such as
PDGFc stimulated CE hydrolytic activity almost 2-fold in SMC cultured alone
or co-cultured with EC. Aspirin-treated EC, incubated with 10 ng/ml PDGF,
did not stimulate CE hydrolytic activity in co-cultured SMC. These results
suggest that growth factor-promoting activity may enhance CE hydrolysis via
the PGI2- cyclic AMP-CE hydrolysis cascade. This hypothesis supports our
observations that PDGF stimulates PGI2 production in SMC. Elevated PGI2, in
turn, can stimulate CE hydrolysis in these cells. Our findings suggest that
the regulation of cholesterol metabolism in SMC can involve, at least in
part, growth factors and EC-derived eicosanoids. These may play a central
role in the regulation of hemostasis and the inflammatory response.