Abstract: TH-PO011

Role of Complement C1r and C1s Serine Proteases in Kidney Fibrosis

Session Information

Category: Cell Biology

  • 204 Extracellular Matrix Biology, Fibrosis, Cell Adhesion

Authors

  • Xavier, Sandhya, University of Virginia Health System, Charlottesville, Virginia, United States
  • Sahu, Ranjit K., University of Virginia Health System, Charlottesville, Virginia, United States
  • Landes, Susan G., University of Virginia Health System, Charlottesville, Virginia, United States
  • Megyesi, Judit, University of Arkansas for Medical Science, Little Rock, Arkansas, United States
  • Yu, Jing, University of Virginia, Charlottesville, Virginia, United States
  • Taylor, Ronald P., University of Virginia, Charlottesville, Virginia, United States
  • Portilla, Didier, University of Virginia Health System, Charlottesville, Virginia, United States
Background

Complement C1 complex consists of C1q, and proteases C1r and C1s. Our previous studies of UUO (Unilateral Ureteral Obstruction) demonstrated complement activation with increased synthesis of C1q, C1r and C1s in whole kidney tissue homogenates. To better understand the cellular processes leading to increased classical complement activation we examined the cellular localization and potential mechanisms leading to increased expression of C1r and C1s in kidney cells.

Methods

We performed real time-PCR, immunohistochemistry, in situ hybridization in wild type and in C1ra-/- mice subjected to sham or UUO injury. Cultured Raw 264.7 macrophages were treated with interferon gamma to induce C1r/C1s expression.

Results

We show increased synthesis of C1q in pericytes and CD45 positive cells, but C1r/C1s was only increased in CD45 positive and PDGFRβ negative cells during UUO. In situ hybridization and immunohistochemistry showed that C1s is induced following UUO injury in cortical thick ascending loops (cTALs) and dilated collecting ducts (CDs). C1r immunostaining was increased in cTALs, distal tubules and dilated CDs. Cultured RAW 264.7 macrophages treated with Interferon gamma had increased expression of C1r and C1s mRNA due to activation of the IFN-regulatory factor-1 (IRF-1) binding site present in the C1r promoter. Expression of C1r mRNA was absent in kidney tissue from C1ra-/- mice as compared to wildtype littermates. The ablation of C1r also leads to reduced or no expression of C1s mRNA in kidney tissue from C1ra-/- mice. Preliminary studies in these mice suggest that protection against kidney fibrosis is dependent on the expression levels of C1s and C3, and this needs to be further investigated.

Conclusion

The results support the role of complement activation with de novo increased synthesis of C1r/C1s expression by tubular epithelial and immune cells as an important mechanism leading to tubulointerstitial fibrosis.

Funding

  • NIDDK Support