Abstract: TH-PO389

Local Inflammatory Mechanism Aggravated by Intraglomerular Crosstalk in Diabetic Kidney

Session Information

Category: Cell Biology

  • 201 Cell Signaling, Oxidative Stress

Authors

  • Umemoto, Shuro, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Kuwabara, Takashige, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Fujimoto, Daisuke, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Kanki, Tomoko, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Mizumoto, Teruhiko, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Kakizoe, Yutaka, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Izumi, Yuichiro, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
  • Mori, Kiyoshi, School of Pharmaceut Sci, University of Shizuoka, Shizuoka, Japan
  • Mukoyama, Masashi, Department of Nephrology, Kumamoto university graduate school of medical sciences, Kumamoto, Japan
Background

We previously reported that the myeloid-related protein 8 (MRP8, S100A8)/toll-like receptor 4 (TLR4) signaling activated by glucolipotoxicity-associated ER stress plays an important role in the progression of diabetic nephropathy. Although local activation of the renin-angiotensin system (RAS) in the kidney has been observed in concurrence with the MRP8/TLR4 activation in the diabetic-hyperlipidemic model mice, the relationship between these signals remains obscure.

Methods

In vivo studies were performed using diabetic-hyperlipidemic mice (by streptozotocin plus high-fat diet, STZ-HFD) and db/db mice, treated with olmesartan (Olm) and angiotensin II (AngII), respectively. In vitro experiments were done with mouse macrophages (MΦ) that were co-cultured with rat mesangial cells (MC), or stimulated by MC-conditioned media (MC-sup). Expressions of the pro-inflammatory and profibrotic genes were analyzed by qPCR. Inflammation and ER stress were evaluated using a THP1-dual reporter cell line monitoring NF-κB and IRF pathways. Effects of a TLR4 antagonist on this crosstalk were also examined.

Results

Angiotensinogen (Agt) mRNA was upregulated in the glomeruli of STZ-HFD mice. Olm effectively suppressed upregulation of glomerular MRP8/TLR4 and Agt in STZ-HFD mice, which was associated with the reduction of albuminuria. In contrast, a subpressor dose of AngII markedly worsened albuminuria and increased glomerular infiltrated MRP8-positive cells in db/db mice. Glomerular MΦ showed obviously high MRP8 positivity compared to tubulointerstitial ones, suggesting intraglomerular crosstalk. MRP8 and TNFα in MΦ were dramatically induced by co-culture with MC, which was reproduced by stimulation with MC-sup. Dual reporter assay revealed that MC-sup stimulation activated IRF, which could cause ER stress, as well as NF-κB in a concentration-dependent manner. Such induction was partially abrogated by the TLR4 antagonist.

Conclusion

RAS activation should contribute to progression of diabetic nephropathy through promoting intraglomerular crosstalk, which may trigger MRP8 production in glomerular MΦ. Humoral factors secreted from MC could contribute to the crosstalk partly in a TLR4-dependent manner, thus facilitating local inflammation and ER stress.