Toll-Like Receptor 4 Signaling is Involved in IgA-Stimulated Mesangial Cell Activation.
10.3349/ymj.2011.52.4.610
- Author:
Beom Jin LIM
1
;
Dahye LEE
;
Soon Won HONG
;
Hyeon Joo JEONG
Author Information
1. Department of Pathology, Yonsei University College of Medicine, Seoul, Korea. jeong10@yuhs.ac
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
IgA nephropathy;
mesangial cell;
cytokine;
toll-like receptor
- MeSH:
Animals;
Chemokine CCL2/secretion;
Enzyme-Linked Immunosorbent Assay;
Extracellular Signal-Regulated MAP Kinases/metabolism;
Fibronectins/secretion;
Glomerulonephritis, IGA/*metabolism;
I-kappa B Proteins/metabolism;
Mesangial Cells/*metabolism/secretion;
Mice;
Mice, Transgenic;
Phosphorylation;
RNA Interference;
RNA, Messenger/metabolism;
*Signal Transduction;
Toll-Like Receptor 4/antagonists & inhibitors/genetics/*metabolism
- From:Yonsei Medical Journal
2011;52(4):610-615
- CountryRepublic of Korea
- Language:English
-
Abstract:
PURPOSE: Deposition of polymeric IgA1 in the kidney mesangium is the hallmark of IgA nephropathy, but the molecular mechanisms of IgA-mediated mesangial responses and inflammatory injuries remain poorly understood. We hypothesize that Toll-like receptor 4 (TLR4) is involved in IgA-induced mesangial cell activation. MATERIALS AND METHODS: Mouse mesangial cells were stimulated with lipopolysaccharide (LPS) (1 microg/mL), IgA (20 microg/mL), or both, and TLR4 expression was measured by real time RT-PCR and Western blot. Intracellular responses to LPS or IgA were assessed by Western blot for ERK1/2, JNK, p38 MAP kinases (MAPKs), Ikappa-Balpha degradation and fibronectin secretion. MCP-1 secretion was assessed by ELISA. Small interfering RNA (siRNA) of TLR4 was used to confirm that the effects were caused by TLR4 activity. RESULTS: LPS- or IgA-treatment upregulated the levels of TLR4 mRNA and protein in cultured MMC at 24 h. LPS and IgA induced rapid phosphorylation of MAPKs, but degradation of Ikappa-Balpha was observed only in LPS-treated MMC. LPS, but not IgA, induced increased secretion of MCP-1 and fibronectin at 24 h or 48 h. Combined LPS and IgA treatment did not cause additional increases in TLR4 mRNA and protein levels or Ikappa-Balpha degradation, and MCP-1 and fibronectin secretions were less than with LPS alone. LPS- or IgA-induced TLR4 protein levels and MAPK activation were inhibited by transfection with TLR4 siRNA. CONCLUSION: These results indicate that the activation of MAPKs and MCP-1 secretion are mediated by TLR4, at least in part, in IgA-treated mesangial cells. TLR4 is involved in mesangial cell injury by induction of pro-inflammatory cytokines in IgA nephropathy.
