Rat liver ferritin selectively inhibits the expression of [alpha]
-smooth muscle actin in cultured rat lipocytes.
Ramm, Grant A., Robert S. Britton, Rosemary O'neill, Howard D. Kohn,
and Bruce R. Bacon.
Division of Gastroenterology and Hepatology, Department of Internal
Medicine, Saint Louis University School of Medicine, St. Louis, MO
63110-0250
APStracts 2:0172G, 1995.
The role of ferritin in lipocyte activation is unknown. This study
examined the effect of rat liver ferritin (RLF), human recombinant H
-ferritin (HrHF), human recombinant L-ferritin (HrLF), apoferritin
(apo-RLF) and hemin on lipocyte activation. Lipocytes were cultured
on uncoated plastic and were incubated with these agents for 7 days,
at concentrations ranging from 10-14 to 10-7M (0.5 to 50 [mu]M for
hemin). Collagen/non-collagen protein production and lipocyte
proliferation were determined by 3H-proline and 3H-thymidine
incorporation, respectively, and the expression of [alpha]-smooth
muscle actin ([alpha]-SMA) and desmin was determined by Western blot.
RLF, at concentrations ranging from 10-10 to 10-7M, decreased
[alpha]-SMA expression by 65 to 88%. Apo-RLF and HrLF decreased
[alpha]-SMA by 17 to 45% at 10-7 and 10-8M, whereas HrHF had no
effect. 10 [mu]M and 50 [mu]M hemin inhibited [alpha]-SMA by 37% and
54%, respectively. Desmin expression was not altered by ferritin or
hemin. Collagen and non-collagen protein production were not altered
by either RLF or apo-RLF. Lipocyte proliferation was decreased by
56%, 32% and 40%, by 10-7M RLF, HrHF and HrLF, respectively, whereas
apo-RLF had no effect. Thus, RLF inhibited lipocyte [alpha]-SMA
expression, which may be due to an effect of sequestered iron, since
neither apo-RLF, HrHF, nor HrLF had a potent effect on [alpha]-SMA
expression, and all are essentially iron-free. The inhibitory effect
of iron-loaded RLF on [alpha]-SMA expression suggests that tissue
ferritin does not initiate lipocyte activation in iron overload, but
rather may have a suppressive action on this process.
Received 19 May 1995; accepted in final form 7 August 1995.
APS Manuscript Number G216-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.