Connective tissue growth factor (CTGF) is an important profibrotic factor in kidney diseases. Blockade of endogenous CTGF ameliorates experimental renal damage and inhibits synthesis of extracellular matrix in cultured renal cells. CTGF regulates several cellular responses, including adhesion, migration, proliferation, and synthesis of proinflammatory factors. Here, we investigated whether CTGF participates in the inflammatory process in the kidney by evaluating the nuclear factor-kappa B (NF-kappa B) pathway, a key signaling system that controls inflammation and immune responses. Systemic administration of CTGF to mice for 24 In induced marked infiltration of inflammatory cells in the renal interstitium (T lymphocytes and monocytes/macrophages) and led to elevated renal NF-kappa B activity. Administration of CTGF increased renal expression of chemokines (MCP-1 and RANTES) and cytokines (INF-gamma, IL-6, and IL-4) that recruit immune cells and promote inflammation. Treatment with a NF-kappa B inhibitor, parthenolide, inhibited CTGF-induced renal inflammatory responses, including the up-regulation of chemokines and cytokines. In cultured murine tubuloepithelial cells, CTGF rapidly activated the NF-kappa B pathway and the cascade of mitogen-activated protein kinases, demonstrating crosstalk between these signaling pathways. CTGF, via mitogen-activated protein kinase and NF-kappa B activation, increased proinflammatory gene expression. These data show that in addition to its profibrotic properties, CTGF contributes to the recruitment of inflammatory cells in the kidney by activating the NF-kappa B pathway.