CTGF Promotes Inflammatory Cell Infiltration of the Renal Interstitium by Activating NF-κB

Abstract

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-B) pathway, a key signaling system that controls inflammation and immune responses. Systemic administration of CTGF to mice for 24 h induced marked infiltration of inflammatory cells in the renal interstitium (T lymphocytes and monocytes/macrophages) and led to elevated renal NF-B activity. Administration of CTGF increased renal expression of chemokines (MCP-1 and RANTES) and cytokines (INF-␥, IL-6, and IL-4) that recruit immune cells and promote inflammation. Treatment with a NF-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-B pathway and the cascade of mitogen-activated protein kinases, demonstrating crosstalk between these signaling pathways. CTGF, via mitogen-activated protein kinase and NF-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-B pathway.

The C-terminal module IV of connective tissue growth factor is a novel immune modulator of the Th17 response

“…We have previously observed that after 24 h, CCN2(IV) increased renal levels of IFN-g and IL-4, downregulated IL-10, and did not change IL-17A renal levels. 21 After 5 days, a slight upregulation of renal levels of all confirmed by real-time PCR (Figure 2b). These findings show that CCN2(IV) promotes a dynamic Th differentiation process in the kidney.…”

“…residues and 11 kDa; purchased from Peprotech), at the dose of 2.5 ng/g of body weight, dissolved in saline, as described previously. 21 The recombinant CCN2(IV) present endotoxin levels of o0.01, and the quality and purity was also confirmed by MALDI-TOF (data not shown). Mice were studied after 5, 10, and 15 days (n ¼ 10 mice in the 10-day group and 5 mice in the other groups).…”

“…CCN2(IV) in vivo induced an inflammatory response in the murine kidney after 24 h, 21 but there were no data at longer times. The involvement of a specific Th response activation can be determined by the evaluation of Th hallmark cytokines (Th1, Th2, Th17, and Treg cell-related cytokines: IFN-g, IL-4, IL-17A, and TGF-b1/ IL-10, respectively).…”

“…Nuclear proteins were isolated as described previously. 21 Protein concentration was determined by the BCA method (Pierce). Tissue protein extracts (30 mg/lane) were separated on 8-12% polyacrylamide-SDS gels under reducing conditions.…”

“…19 CCN2 is a chemotactic factor for immune cells, 20 has promoted cell adhesion and migration, and has upregulated proinflammatory factor production, including cytokines, chemokines, and adhesion molecules. 19 We have previously demonstrated that systemic administration of CCN2(IV) elicited the recruitment of inflammatory cells in the murine kidney after 24 h, suggesting that CCN2(IV) could induce acute inflammation in vivo, 21 but there are no data on sustained inflammation. Several studies have investigated the biological functions of CCN2 modules.…”