The MCP-1/CCR2 system has direct proinflammatory effects in human mesangial cells

Both inflammatory and haemodynamic factors have been implicated in the pathogenesis of diabetic and other progressive glomerulopathies. Mesangial cell exposure to mechanical stretch induces both intercellular adhesion molecule 1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) expression. CC Chemokine receptor 2 (CCR2), the cognate MCP-1 receptor, has been recently demonstrated in human mesangial cells (HMCs). We tested whether MCP-1 binding to CCR2 affects ICAM-1 expression in HMCs and, secondly, if stretch-induced ICAM-1 is mediated by MCP-1 via an autocrine mechanism. Serum-deprived HMCs were exposed to either rh-MCP-1 (0.1-1-10-50-100 ng/ml) or mechanical stretch in the presence and in the absence of RS102895, a specific CCR2 inhibitor. ICAM-1 expression was assessed both by immunofluorescence and cytofluorimetry. Monocyte-HMC interaction was tested by adhesion assay. CCR2 expression was studied by reverse transcriptase-polymerase chain reaction, immunoblotting, and flow cytometry. HMCs exposure to rh-MCP-1 induced a significant twofold increase in ICAM-1 expression at 24 h, leading to enhanced monocyte adhesion. This effect occurred via the CCR2 receptor as CCR2 was expressed in HMCs and CCR2 blockade prevented ICAM-1 upregulation. Stretch-induced ICAM-1 expression was not altered by CCR2 blockade and stretch significantly reduced CCR2 mRNA and protein expression via an MCP-1-independent mechanism. In conclusion, stretch and MCP-1 independently induce ICAM-1 expression in HMCs. Stretch-induced CCR2 downregulation may favour MCP-1 paracrine activity.