Cross-talk between MCP-3 and TGFβ promotes fibroblast collagen biosynthesis

Recent studies have demonstrated upregulation of monocyte chemoattractant protein-3 (MCP-3/CCL7) in fibrosis and have suggested that in addition to a major role in regulating leucocyte recruitment this chemokine may also promote extracellular matrix (ECM) overproduction by fibroblasts. In the present study we explore interplay between MCP-3 and transforming growth factor beta (TGFβ), a potent profibrotic cytokine. We demonstrate that MCP-3 promotes activation of TGFβ signalling pathways leading to increased type I collagen secretion. In addition we show that MCP-3 gene expression is stimulated by recombinant TGFβ1, raising the possibility for synergy between these two mediators in the fibrotic microenvironment. Comparison of downstream signalling pathways that regulate collagen gene activation by both cytokines confirms the central role of MAPK pathway activation in mediating the effects of both factors. An additive effect of these two agonists was demonstrated by comparative microarray analysis for key TGFβ regulated transcripts including PAI-1, OSF2 and IGFBP6. Together, our results confirm cross-talk between MCP-3 and TGFβ that may be critical in the development of fibrosis.