Signal transduction involved in CTGF-induced production of chemokines in mesangial cells.

OBJECTIVE AND
DESIGN: This study investigates the regulatory role of connective tissue growth factor (CTGF) on production of fractalkine, monocyte-chemoattractant protein-1 (MCP-1) and regulated on activation, normal T cell expressed and secreted (RANTES) in human mesangial cells, and explore the mechanisms of CTGF action.
METHODS: Cultured human mesangial cells were treated with CTGF. Expressions of mRNA and proteins of fractalkine, MCP-1 and RANTES were analyzed by real-time polymerase chain reaction (PCR) and by enzyme-linked immunosorbent assay, respectively. Expressions of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2), phosphoinositide 3-kinase (PI3-K) and protein kinase B (PKB) were assessed by Western blotting. Activities of nuclear factor-KB (NF-KB) were determined by NF-kappaB luciferase reporter assay.
RESULTS: CTGF enhanced the mRNA expressions and protein release of fractalkine, MCP-1 and RANTES, and the expressions of phosphorylated ERK1/2, PI3-K and PKB, and activities of NF-KB. Blockade of ERK1/2 inhibited the CTGF-induced expression ofphosphorylated ERK1/2 and NF-kappaB, and partially decreased the expressions of the above chemokines. PI3-K blockade downregulated the CTGF-stimulated expressions of phosphorylated PI3-K, PKB and NF-kappaB but not phosphorylated ERK1/2, partially decreased the expressions of the above chemokines. NF-kappaB blockade abrogated the CTGF-activated NF-kappaB and partially decreased the expressions of the above chemokines. Soluble heparin and K252a, an inhibitor of Trk, blocked CTGF-induced production of the above chemokines and the activation of the above signaling proteins.
CONCLUSION: These results demonstrated that CTGF induces production of fractalkine, MCP-1 and RANTES via ERK1/2 and PI3-K/PKB/NF-kappaB-dependent signal pathway mediated by cell surface heparin sulfate proteoglycans and the tyrosine kinase receptor TrkA in human mesangial cells.