The CC chemokine RANTES (CCL5) mediates liver fibrosis in mice and humans

Aims: Chemokines are inflammatory mediators during acute and chronic liver injury. The chemokine RANTES (CCL5) directs lymphocytes to inflamed tissues and directly activates hepatic stellate cells in vitro through interaction with CCR5. These functions define RANTES as an interesting target for antifibrotic therapies. We here present data defining the role of RANTES in human and murine liver fibrosis. Methods: In humans, a haplotype analysis with all tagging RANTES SNPs from the HapMap project was performed in 260 individuals with chronic hepatitis C (HCV). The mRNA expression of RANTES was analysed in HCV infected liver samples by quantitative RT-PCR and the stellate cell line LX–2 was stimulated with rhRANTES. Furthermore, we induced liver fibrosis by CCl 4 (6 weeks) and a methionine and choline deficient diet (MCD diet, 8 weeks) in RANTES -/- mice and wild-type littermates. Fibrosis was analyzed by staging of histology after sirius red staining and hydroxyproline measurement in liver samples. Additionally, the intrahepatic mRNA expression of fibrosis related genes (Collagen Ia1, TIMP–1, MMP–9) and interleukin–10 (IL–10) was determined by quantitative RT-PCR. Results: The genetic analysis revealed an association of RANTES haplotypes with the degree of liver fibrosis due to HCV (P=0.01 by permutation testing). In human HCV infected liver, RANTES mRNA expression was positively correlated with higher stages of liver fibrosis. rhRANTES induced proliferation of LX–2 cells which was associated with increased phosphorylation of ERK. Genetic deletion of RANTES in fibrosis prone mice led to a significantly reduced degree of fibrosis as assessed by liver histology and hydroxyproline content of liver samples (all P <0.05) in both murine fibrosis models. Compared to their wild-type littermates, treated RANTES -/- mice had significantly reduced mRNA expression of Collagen Ia1 (P <0.01 for both models) and a shift of the TIMP–1/MMP9 mRNA ratio towards a fibrinolytic phenotype. Interestingly, inhibition of fibrogenesis was associated with an increased mRNA expression of IL–10 in RANTES -/- mice (P=0.003). Conclusions: Our results identify the chemokine RANTES as an important mediator of liver fibrogenesis in mice and humans. The strong inhibition of fibrosis in RANTES -/- mice in different fibrosis models sets the stage for the evaluation of RANTES antagonistic strategies for the treatment of chronic liver diseases.