Submitted on August 6, 2003
Accepted on March 8, 2004
DIFFERENTIAL REQUIREMENT OF MEMBERS OF THE MAPK FAMILY FOR CCL2 EXPRESSION BY HEPATIC STELLATE CELLS
Fabio Marra1*, Wanda Delogu1, Ilaria Petrai1, Sabrina Pastacaldi1, Andrea Bonacchi1, Eva Efsen1, Sara Aleffi1, Cristiana Bertolani1, Massimo Pinzani1, and Paolo Gentilini1
1 Dipartimento di Medicina Interna, University of Florence, Florence, Italy
* To whom correspondence should be addressed. E-mail: f.marra{at}dmi.unifi.it.
Hepatic stellate cells (HSC) coordinate the liver wound-healing response through
secretion of several cytokines and chemokines, including CCL2 (formerly known as
monocyte chemoattractant protein-1). In this study, we evaluated the role of different
proteins of the MAPK family (ERK, p38MAPK, and JNK) in the regulation of CCL2
expression by HSC, as an index of their pro-inflammatory activity. Several mediators
activated all three MAPK, including TNF, IL-1 and PDGF. To assess the relative role
of the different MAPKs, specific pharmacologic inhibitors were used, namely
SB203580 (p38MAPK), SP600125 (JNK), and PD98059 (MEK/ERK). The efficacy and
specificity of the different inhibitors in our cellular system was verified analyzing the
enzymatic activity of the different MAPKs using in vitro kinase assays and/or testing
the inhibition of phosphorylation of downstream substrates. SB203580 and
SP600125 dose-dependently inhibited CCL2 secretion and gene expression induced
by IL-1 or TNF. In contrast, inhibition of ERK did not affect the up-regulation of CCL2
induced by the two cytokines. Finally, activin A was also found to stimulate CCL2
expression and to activate ERK, JNK, p38 and their downstream targets. Unlike in
cells exposed to pro-inflammatory cytokines, all three MAPKs were required to
induce CCL2 secretion in response to activin. We conclude that members of the
MAPK family differentially regulate cytokine-induced chemokine expression in human
HSC.
