Abstract: SA-OR082

The Breast Cancer Type 1 Susceptibility Protein (BRCA1) Mediates Fibrotic Kidney Disease

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Akinfolarin, Akinwande A., Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Ajay, Amrendra Kumar, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Sabbisetti, Venkata, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Bonventre, Joseph V., Brigham and Women's Hospital, Boston, Massachusetts, United States
Background

Repetitive tubular injury leads to chronic fibrotic kidney disease (CKD). Chemical, ischemic and obstructive kidney injuries lead to replication fork arrest (RFA) and double strand DNA breaks (DSB), triggering the DNA damage response. BRCA1 is a breast tumor suppressor gene with a role in homologous recombination (HR) and maintenance of genome integrity by DNA repair. Here we deplete BRCA1 in the adult mouse proximal tubule (PT) to examine its effect on the development of interstitial fibrosis

Methods

SLC34A1 Cre mice were crossed to mice with floxed BRCA1 exon 11 allele yielding models of inducible PT BRCA1 gene deletion. After Tamoxifen-induced Cre activation, we subjected mice to bilateral ischemia/reperfusion (I/R), unilateral ureteric obstruction (UUO), or aristolochic acid (AA)-induced injury. Kidney extracts were evaluated by western blot, real time PCR and Masson’s trichrome (MT) and Picrosirius Red (PS) staining for markers of interstitial fibrosis. Markers of DNA damage, cell cycle arrest and senescence were examined by immunofluorescence. BRCA1 was also down regulated in PT cells using short-hairpin RNA against BRCA1 and cells were treated with AA and cisplatin to explore the relationship between injury and cell cycle stage, apoptosis and secretory senescence

Results

There was reduced kidney fibrosis in mice heterozygous (BRCA1WT/Δ11) and homozygous (BRCA1Δ11/Δ11) for PT BRCA1 deletion compared to wild type (BRCA1WT/WT+) littermate controls by MT and PS staining after I/R, UUO or AA. There was a corresponding decrease in fibrogenic factors including CTGF, COL4A1, fibronectin and ACTA2 in the BRCA1WT/Δ11 and BRCA1Δ11/Δ11 mice. There was a decrease in the markers of cell cycle arrest and senescence (p16ink4a and GATA4) and an increase in apoptosis among BRCA1WT/Δ11 or BRCA1Δ11/Δ11 mice when compared to WT mice. These murine data were supported by in vitro experiments with AA and Cisplatin after depleting BRCA1 in PT cells which caused less G2 cell cycle arrest and secretion of fewer fibrogenic factors

Conclusion

BRCA1 facilitates interstitial fibrosis following kidney tubular injury in mice through its role in DNA damage response and induction of senescence. We have thus identified a novel role of BRCA1 in non malignant pathobiology.

Funding

  • NIDDK Support