Dual regulation of il-1b-mediated matrix metalloproteinase-9
expression in mesangial cells by nf-kb and ap-1.
Yokoo, Takashi, and Masanori Kitamura.
Department of Medicine, University College London Medical School,
The Rayne Institute, 5 University Street, London WC1E 6JJ, U.K.
APStracts 2:0131F, 1995.
Takashi Yokoo and Masanori Kitamura. Dual regulation of IL-1b-mediated
matrix metalloproteinase-9 expression in mesangial cells by NF-kB and
AP-1. Glomerular mesangial cells express matrix metalloproteinase-9
(MMP-9) in response to the proinflammatory cytokine IL-1b. To
elucidate the signal transduction systems involved, we focused on the
role of nuclear factor-kB (NF-kB) and activator protein-1 (AP-1)
since the 5'-flanking region of MMP-9 gene contains binding sequences
for these transacting molecules. In rat mesangial cells treated with
an inhibitor of NF-kB, pyrrolidine dithiocarbamate, induction of MMP
-9 by IL-1b was suppressed at both mRNA and protein levels. Mesangial
cells stably transfected with a dominant negative mutant of NF-kB
also showed blunted induction of MMP-9. Transient transfection study
with a kB reporter construct revealed that IL-1b indeed activated the
kB site and that pyrrolidine dithiocarbamate abolished this
activation. These results suggest that IL-1b induced MMP-9 via the
stimulation of NF-kB pathway. To examine whether tyrosine kinase is
involved in this pathway, mesangial cells were stimulated by IL-1b in
the presence of a tyrosine kinase inhibitor, genistein. This
inhibitor dose-dependently suppressed the expression of MMP-9 as well
as the activation of the kB site by IL-1b, indicating the involvement
of tyrosine kinase in the stimulation of NF-kB. Since mesangial cells
stimulated by IL-1b transiently expressed c-fos and c-jun mRNAs prior
to the expression of MMP-9, the role of these genes in mediating the
IL-1b response was further examined. Transfection of mesangial cells
with a c-jun antisense cDNA and treatment with a pharmacological
inhibitor of c-Jun/AP-1, curcumin revealed that the induction of c
-Jun/AP-1 is essential for the expression of MMP-9 by IL-1b. Although
protein kinase C (PKC) is regarded as a potential inducer of AP-1,
stimulation of mesangial cells with phorbol myristate acetate failed
to induce MMP-9. Similarly, depletion of intracellular PKC did not
obviously affect the induction of MMP-9 by IL-1b. These findings
demonstrate that dual-operation of tyrosine kinase-mediated NF-kB
stimulation and c-Jun/AP-1 activation is essential to the induction
of MMP-9 by IL-1b in cultured mesangial cells.
Received 15 February 1995; accepted in final form 17 July 1995.
APS Manuscript Number F55-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.