MCP-1/CCR2 system is involved in high glucose-induced fibronectin and type IV collagen expression in cultured mesangial cells
Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that plays an important role in the recruitment of macrophages. Although previous studies have demonstrated the importance of MCP-1 in the pathogenesis of diabetic nephropathy (DN) in terms of inflammation, the role of MCP-1 and its receptor (C-C chemokine receptor 2; CCR2) in extracellular matrix (ECM) accumulation under diabetic conditions has been largely unexplored. This study was undertaken to investigate the functional role of the MCP-1/CCR2 system in high glucose-induced ECM (fibronectin and type IV collagen) protein expression in cultured mesangial cells (MCs). Mouse MCs were exposed to medium containing 5.6 mM glucose (NG), NG+24.4 mM mannitol (NG+M), or 30 mM glucose (HG) with or without mutant MCP-1 (mMCP-1), CCR2 small interfering (si)RNA, or CCR2 inhibitor (RS102895). To examine the relationship between MCP-1 and transforming growth factor (TGF)-beta1, MCs were also treated with TGF-beta1 (2 ng/ml) with or without mMCP-1 or CCR2 siRNA. Transient transfection was performed with Lipofectamine 2000 for 24 h. Cell viability was determined by an MTT assay, mouse and human MCP-1 and TGF-beta1 levels by ELISA, and CCR2 and ECM protein expression by Western blotting. Transfections of mMCP-1 and CCR2 siRNA increased human MCP-1 levels and inhibited CCR2 expression, respectively. HG-induced ECM protein expression and TGF-beta1 levels were significantly attenuated by mMCP-1, CCR2 siRNA, and RS102895 (P < 0.05). MCP-1 directly increased ECM protein expression, and this increase was inhibited by an anti-TGF-beta1 antibody. In addition, TGF-beta1-induced ECM protein expression was significantly abrogated by the inhibition of the MCP-1/CCR2 system (P < 0.05). These results suggest that an interaction between the MCP-1/CCR2 system and TGF-beta1 may contribute to ECM accumulation in DN. ; This work was supported by the BK21 (Brain Korea 21) Project for Medical Sciences, Yonsei University, a faculty research grant from Yonsei University College of Medicine for 2007 (6-2007-0174), a Korea Research Foundation Grant funded by the Korean government (MOEHRD; KRF-2007-331- E00086), and Korea Science and Engineering Foundation (KOSEF) grants funded by the Korea government (MOST; R01-2007-000-20263-0 and R13- 2002-054-04001-0).
