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.
Background: It is not fully understood whether intracellular calcium and/or reactive oxygen species (ROS) are involved in nuclear factor-ĸB (NF-ĸB) activation by proinflammatory cytokines. Silymarin exhibits anti-inflammatory and antioxidant effects but the effect of silymarin in human mesangial cells is largely unknown. Method: NF-ĸB binding activity was measured by electrophoretic mobility shift assay. Intracellular calcium was monitored by confocal microscopy using Fluo-3 and intracellular ROS production was determined by flow cytometry. Monocyte chemoattractant protein-1 (MCP-1) expression was measured by Northern blot analysis and ELISA. Results: NF-ĸB was activated within 30 min by tumor necrosis factor-α (TNF-α) or interleukin-1β (IL-1β). Intracellular ROS was not produced until 30 min and also antioxidants such as N-acetylcysteine and tiron had no effect on the TNF-α- or IL-1β-induced NF-ĸB activation. Intracellular calcium was increased by TNF-α and IL-1β. Furthermore, a calcium chelator, BAPTA-AM, attenuated the NF-ĸB activation. Silymarin dose-dependently inhibited the TNF-α- or IL-1β-induced NF-ĸB activation and MCP-1 expression. Silymarin also inhibited TNF-α-induced intracellular calcium. Conclusions: Induction of NF-ĸB within 30 min by TNF-α- and IL-1β was mediated through intracellular calcium but not ROS. Silymarin inhibited TNF-α-induced calcium-dependent NF-ĸB activation irrespective of its antioxidant effect.
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