C-Reactive Protein Induces NF-κB Activation through Intracellular Calcium and ROS in Human Mesangial Cells

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Abstract
Background: C-reactive protein (CRP) is known to have a direct proinflammatory effect in endothelial cells. However, little is known about the effect of CRP in intrinsic renal cells. We investigated the effects of CRP on the nuclear factor-ĸB (NF-ĸB) activation and monocyte chemoattractant protein-1 (MCP-1) gene expression in human mesangial cells and also examined whether intracellular calcium and reactive oxygen species (ROS) were involved in the CRP- induced NF-ĸB activation. Methods: NF-ĸB binding activity and MCP-1 mRNA expression were measured by electrophoretic mobility shift assay and Northern blot analysis, respectively.Intracellular calcium was monitored by confocal microscopy using calcium sensitive dye, Fluo-3 and intracellular ROS production was determined, using 2′,7′-dichlorofluorescin diacetate. Results: CRP increased NF-ĸB binding activity in a dose-dependent manner (12.5–100 µg/ml), which was induced within 1 h after incubation and peaked around 3 h. CRP also increased the MCP-1 mRNA expression via activation of NF-ĸB. Both intracellular calcium and ROS was induced by CRP. Calcium chelator, BAPTA-AM and anti-oxidants such as N-acetylcysteine and tiron suppressed CRP-induced NF-ĸB activation. Conclusion: CRP exerted a proinflammatory effect in human mesangial cells by inducing MCP-1 gene expression via NF-ĸB activation, which was mediated, at least in part, through intracellular calcium and ROS.