The pharmacological antagonist of the chemokine CCL5 (RANTES) Met-Rantes reduces experimental liver fibrosis in vivo

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.