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Toll-like receptor 4 signaling is involved in IgA-stimulated mesangial cell activation.

Lim BJ, Lee D, Hong SW, Jeong HJ - Yonsei Med. J. (2011)

Bottom Line: Small interfering RNA (siRNA) of TLR4 was used to confirm that the effects were caused by TLR4 activity.Combined LPS and IgA treatment did not cause additional increases in TLR4 mRNA and protein levels or Iκ-Bα degradation, and MCP-1 and fibronectin secretions were less than with LPS alone.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Yonsei University College of Medicine, 250 Seongsan-ro, Seodaemun-gu, Seoul 120-752, Korea.

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 μg/mL), IgA (20 μg/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), Iκ-Bα 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 Iκ-Bα 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 Iκ-Bα 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.

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Related in: MedlinePlus

TLR4 protein expression was increased by LPS or IgA stimulation at 24 hours and 48 hours. However, combined stimulation of LPS and IgA did not show an additive effect. *p<0.05 vs. 48 hours control, †p<0.05 vs. 24 hours control. TLR4, Toll-like receptor 4; mRNA, messenger ribonucleic acid; LPS, lipopolysaccharide.
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Figure 2: TLR4 protein expression was increased by LPS or IgA stimulation at 24 hours and 48 hours. However, combined stimulation of LPS and IgA did not show an additive effect. *p<0.05 vs. 48 hours control, †p<0.05 vs. 24 hours control. TLR4, Toll-like receptor 4; mRNA, messenger ribonucleic acid; LPS, lipopolysaccharide.

Mentions: LPS increased TLR4 mRNA levels 3.5-fold at 12 h and 3.2-fold at 24 h in MMC. TLR4 protein levels increased 2-fold by 24 h and slightly more by 48 h. IgA upregulated the level of TLR4 mRNA by 3-fold at 24 h, and the level of proteins 3.6- and 1.5b-fold at 24 h and 48 h, respectively. When MMC were stimulated with LPS and IgA together, there was no additive increase in TLR4 mRNA and protein expression at 24 h. At 12 h, the effect of LPS on TLR4 mRNA was even abrogated by IgA cotreatment to the level of IgA alone (Figs. 1 and 2).


Toll-like receptor 4 signaling is involved in IgA-stimulated mesangial cell activation.

Lim BJ, Lee D, Hong SW, Jeong HJ - Yonsei Med. J. (2011)

TLR4 protein expression was increased by LPS or IgA stimulation at 24 hours and 48 hours. However, combined stimulation of LPS and IgA did not show an additive effect. *p<0.05 vs. 48 hours control, †p<0.05 vs. 24 hours control. TLR4, Toll-like receptor 4; mRNA, messenger ribonucleic acid; LPS, lipopolysaccharide.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104456&req=5

Figure 2: TLR4 protein expression was increased by LPS or IgA stimulation at 24 hours and 48 hours. However, combined stimulation of LPS and IgA did not show an additive effect. *p<0.05 vs. 48 hours control, †p<0.05 vs. 24 hours control. TLR4, Toll-like receptor 4; mRNA, messenger ribonucleic acid; LPS, lipopolysaccharide.
Mentions: LPS increased TLR4 mRNA levels 3.5-fold at 12 h and 3.2-fold at 24 h in MMC. TLR4 protein levels increased 2-fold by 24 h and slightly more by 48 h. IgA upregulated the level of TLR4 mRNA by 3-fold at 24 h, and the level of proteins 3.6- and 1.5b-fold at 24 h and 48 h, respectively. When MMC were stimulated with LPS and IgA together, there was no additive increase in TLR4 mRNA and protein expression at 24 h. At 12 h, the effect of LPS on TLR4 mRNA was even abrogated by IgA cotreatment to the level of IgA alone (Figs. 1 and 2).

Bottom Line: Small interfering RNA (siRNA) of TLR4 was used to confirm that the effects were caused by TLR4 activity.Combined LPS and IgA treatment did not cause additional increases in TLR4 mRNA and protein levels or Iκ-Bα degradation, and MCP-1 and fibronectin secretions were less than with LPS alone.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Yonsei University College of Medicine, 250 Seongsan-ro, Seodaemun-gu, Seoul 120-752, Korea.

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 μg/mL), IgA (20 μg/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), Iκ-Bα 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 Iκ-Bα 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 Iκ-Bα 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.

Show MeSH
Related in: MedlinePlus