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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

MCP-1 secretion in the culture media increased at 48 hours in LPS-treated MMC, but was significantly lower after treatment with combined LPS and IgA compared to LPS alone. *p<0.05 vs. 48 hours control, †p<0.05 vs. 48 hours LPS, ‡p<0.05 vs. 48 hours IgA. LPS, lipopolysaccharide; MMC, mouse mesangial cells.
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Figure 5: MCP-1 secretion in the culture media increased at 48 hours in LPS-treated MMC, but was significantly lower after treatment with combined LPS and IgA compared to LPS alone. *p<0.05 vs. 48 hours control, †p<0.05 vs. 48 hours LPS, ‡p<0.05 vs. 48 hours IgA. LPS, lipopolysaccharide; MMC, mouse mesangial cells.

Mentions: MCP-1 secretion in the culture media increased 1.2-fold at 48 h in LPS-treated MMC. IgA treatment caused an increase MCP-1 secretion at 6 h, but this decreased by 48 h. MCP-1 secretion at 48 h was significantly lower after combined LPS and IgA treatment than after LPS or IgA treatment alone (Fig. 5). Fibronectin secretion increased 1.7- and 1.6-fold at 24 h and 48 h, respectively, in LPS-treated MMC. IgA- and Combined IgA and LPS-treated MMC displayed less fibronectin secretion than MMC treated with LPS alone (Fig. 6).


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)

MCP-1 secretion in the culture media increased at 48 hours in LPS-treated MMC, but was significantly lower after treatment with combined LPS and IgA compared to LPS alone. *p<0.05 vs. 48 hours control, †p<0.05 vs. 48 hours LPS, ‡p<0.05 vs. 48 hours IgA. LPS, lipopolysaccharide; MMC, mouse mesangial cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: MCP-1 secretion in the culture media increased at 48 hours in LPS-treated MMC, but was significantly lower after treatment with combined LPS and IgA compared to LPS alone. *p<0.05 vs. 48 hours control, †p<0.05 vs. 48 hours LPS, ‡p<0.05 vs. 48 hours IgA. LPS, lipopolysaccharide; MMC, mouse mesangial cells.
Mentions: MCP-1 secretion in the culture media increased 1.2-fold at 48 h in LPS-treated MMC. IgA treatment caused an increase MCP-1 secretion at 6 h, but this decreased by 48 h. MCP-1 secretion at 48 h was significantly lower after combined LPS and IgA treatment than after LPS or IgA treatment alone (Fig. 5). Fibronectin secretion increased 1.7- and 1.6-fold at 24 h and 48 h, respectively, in LPS-treated MMC. IgA- and Combined IgA and LPS-treated MMC displayed less fibronectin secretion than MMC treated with LPS alone (Fig. 6).

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