Monocyte chemotactic protein-1 as a chemoattractant for human hepatic stellate cells

Following liver injury, hepatic stellate cells (HSC) undergo proliferation and migrate into damaged areas in response to chemotactic factors. HSC have been shown to regulate leukocyte trafficking by secreting monocyte chemota ctic protein-1 (MCP-1), a chemokine that recruits monocytes and lymphocytes , In this study, we explored whether MCP-1 exerts biological actions on HSC . HSC were isolated from normal human livers, cultured on plastic, and stud ied in their myofibroblast-like phenotype, and three different cells lines were used. Chemotaxis was measured in modified Boyden chambers. Phosphatidy linositol 3-kinase (PI 3-K) was assayed on phosphotyrosine immunoprecipitat es, Exposure of HSC to MCP-1 stimulated migration of HSC in a dose-dependen t fashion. Maximal stimulation was obtained with 250 ng/mL MCP-1, which res ulted in a 3- to 4-fold stimulation of cell migration. Checkerboard analysi s showed that the increase in cell migration was almost completely a result of chemotaxis rather than chemokinesis. In contrast, in quiescent HSC, MCP -1 did not exert any effect on cell migration. In leukocytes, MCP-1 activat es the pertussis toxin-sensitive CCR2 receptor. However, transcripts for CC R2 could not be shown in HSC, and pertussis toxin only modestly inhibited M CP-l-induced migration. Exposure of HSC to MCP-1 was associated with an inc rease in cytosolic calcium concentration, PI 3-K activity, protein tyrosine phosphorylation, Blocking calcium influx or pretreatment of HSC with the P I 3-K inhibitor wortmannin markedly reduced cell migration. This study show s, for the first time, a potential direct profibrogenic action of MCP-1 via HSC chemotaxis, MCP-l-dependent signals in these cells are not transduced by CCR2 and may be mediated by alternative chemokine receptors.