Leukoregulin induces plasminogen activator inhibitor type-1 in human
orbital fibroblasts: evidence supporting heterogeneity among fibroblasts with
regard to their anatomic region of origin.
Hogg, Michael G., Charles H. Evans, and Terry J. Smith.
Division of Molecular and Cellular Medicine, Department of Medicine,
Department of Biochemistry and Molecular Biology, The Albany Medical College
and the Samuel S. Stratton Veterans Affairs Medical Center, Albany, NY 12208
and Tumor Biology Section, Division of Cancer Etiology, National Cancer
Institute, Bethesda, MD 20892.
APStracts 2:0069C, 1995.
Leukoregulin, a 50 kDa T-lymphocyte-derived cytokine, activates multiple
signal transduction pathways and exhibits striking anti-proliferative effects
in tumor cells in culture. In non-transformed human dermal fibroblasts,
leukoregulin influences the synthesis of collagenase, stromelysin-1, collagen
and hyaluronan and is thus a potentially important determinant of
extracellular matrix economy. Here we studied the effect of leukoregulin on
the expression of plasminogen activator inhibitor type-1 (PAI-1) in human
orbital and dermal fibroblasts. The lymphokine dramatically induced
expression of [35S]PAI-1 protein associated with the extracellular
matrix and present in the culture medium of orbital fibroblasts. The identity
of the 47 kDa protein as PAI-1 was confirmed by immunoprecipitation of medium
fractions with a polyclonal antibody. The effect on matrix-associated PAI-1
evolved over several hours and was maximal at 10 hrs. when levels were 75
-fold higher than controls and was transient in that levels were 50% lower
than the peak at 24 hrs.. It was dose-dependent, being maximal at a
leukoregulin concentration of 0.1 U/ml. A pulse-chase study failed to
demonstrate any differences in the rate of PAI-1 disappearance from the
extracellular matrix in leukoregulin-treated and serum-treated orbital
fibroblast cultures. Northern analysis demonstrated a substantial induction
of steady-state PAI-1 mRNA levels within 6 hrs. of treatment in orbital
cultures. In contrast, PAI-1 protein levels were reduced dramatically in
cultures derived from the skin of the abdominal wall. Leukoregulin resulted
in a 50-fold increase in prostaglandin E2 production in orbital cultures
after 24 hrs. When this increase in prostanoid production was blocked with
indomethacin, peak PAI-1 levels were maintained. Moreover, treatment of
cultures with indomethacin alone increased PAI-1 expression substantially
suggesting that prostaglandin E2 may play a role in the down-regulation of
basal PAI-1 synthesis in orbital fibroblasts. These results demonstrate the
potential role leukoregulin may play as a modulator of the pericellular
proteolytic environment of the human fibroblast. Further, it would appear
that the anatomic-site of origin is a crucial determinant of the cellular
response to inflammatory lymphokines.
Received 9 December 1994; accepted in final form 18 January 1995.
APS Manuscript Number C712-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 February 1995.