Aims: Chronic liver inflammation leads to an activation of hepatic stellate cells with
a consecutive excess of extracellular matrix proteins resulting in liver fibrosis.
However, little is known about the factors mediating the interaction between inflammatory
cells and hepatic stellate cells. We herein identify the inflammatory chemokine CCL5/RANTES
which can be targeted by the competitive CCL5 antagonist Met-CCL5 as a central mediator
of this interaction.
Methods: Liver fibrosis was induced in C57BL/6 mice by intraperitoneal injection of CCl4 (0.8mg/kg, 6 weeks). Simultaneously, mice received either Met-CCL5 (10µg i.p./day)
or sodium chloride as control. Fibrosis was assessed by staging of histology after
sirius red staining and measurement of intrahepatic hydroxyproline contents. The intrahepatic
mRNA expression of fibrosis related genes was determined by quantitative RT-PCR. Infiltration
of immune cells was quantified by FACS analysis. In vitro, chemotaxis of hepatic stellate
cells to CCL5 and its inhibition by Met-CCL5 was analyzed by Boyden chamber experiments.
Moreover, hepatic stellate cells were stimulated with conditioned media of T-cell
enriched splenocytes with or without Met-Rantes and Collagen secretion was determined
by Western blot analysis after stimulation.
Results: Met-CCL treated mice displayed a significantly reduced degree of fibrosis after CCl4 treatment compared to control mice (P <0.01) which was also reflected by a decreased expression of fibrosis related genes.
These mice showed a strong reduction of immune cells within the livers, in particular
CD8+ T-cells (P <0.0001 compared to control mice), leading to decreased stellate cell activation.
In vitro, the competitive CCL5 antagonist Met-CCL5 diminished the chemotactic effect
of CCL5 on hepatic stellate cells and almost completely inhibited the significantly
enhanced collagen secretion of stellate cells after incubation with conditioned medium
of T-cell enriched splenocytes (P<0.001).
Conclusions: We firstly show a significant reduction of liver fibrosis by a pharmacological antagonization
of a single chemokine. This provides a framework for the further evaluation of specific
CCL5 antagonistic strategies in the treatment of liver fibrosis.
