Publication: Upregulation of fibronectin but not
of entactin, collagen IV and smooth muscle
actin by anaphylatoxin C5a in rat hepatic stellate cells
Authors
Schlaf, G. ; Schmitz, M. ; Heine, I. ; Demberg, T. ; Götze, O.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Rat Kupffer cells (KC), hepatic stellate cells
(HSC) and sinusoidal endothelial cells (SEC) all express
the C5a receptor (C5aR) constitutively in contrast to
hepatocytes (HC). HSC showed an unexpectedly high
level of expression of the C5aR. As these cells are
known to play a key role in the induction of liver fibrosis
we hypothesized that C5a may possibly induce
fibrogenetic proteins in these cells. HSC are known to
express the extracellular matrix (ECM) proteins collagen
IV, fibronectin, entactin and the structure protein smooth
muscle actin (SMA) which is regarded as a marker for
the fibrotic conversion of HSC to myofibroblast-like
cells. We investigated the effect of recombinant rat C5a
(rrC5a) on the upregulation of these ECM-proteins and
of SMA, all of which are known to be expressed by
HSC. The profibrotic cytokine TGF-ß1 (2 ng/ml), which
was used as a control, clearly upregulated the three
matrix proteins but not SMA. In the absence of any
stimulus HSC upregulated the three ECM-proteins as
well as SMA during their conversion into myofibroblastlike
cells. This resulted in a high stimulus-independent
plateau of the mRNA expressions for all four proteins
after four to five days of culture. Readouts were
therefore taken at 72 h after the isolation of the HSC
when the investigated mRNA levels had not yet reached
their maxima due to the conversion of the cells. The first
24 h of culture were performed without stimulus and the
following 48 h in the presence of 100 nM rrC5a (1
µg/ml) or TGF-ß1 (2 ng/ml). Only fibronectin-specific
mRNA was clearly upregulated by C5a whereas
entactin, collagen IV and SMA were not affected by
C5a. By competitive-quantitative PCR the upregulation
of fibronectin-specific mRNA was determined to be
about five-fold. As TGF-ß1 upregulated all of the three
investigated ECM-proteins but not SMA it was checked
as to whether C5a might act indirectly by upregulating
the expression of TGF-ß1 in KC and HSC, as both cell types are known to be sources of this profibrotic
cytokine. However, using RT-PCR, such an effect was
not detectable in either cell type after 3, 10 or 24 h.
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