Abstract: TH-PO337

Par1b Is Protective to Cisplatin Induced Renal Tubular Injury

Session Information

Category: Acute Kidney Injury

  • 002 AKI: Repair and Regeneration

Authors

  • Pal, Abhijeet, Children's Hospital at Montefiore, Bronx, New York, United States
  • Chu, Philip, Albert Einstein College of Medicine, New York, New York, United States
  • Pullman, James M., Montefiore Medical Center, Bronx, New York, United States
  • Kaskel, Frederick J., Albert Einstein College of Medicine, Children's Hospital at Montefiore, Bronx, New York, United States
  • Reidy, Kimberly J., Children's Hospital at Montefiore/ Albert Einstein College of Medicine, Bronxville, New York, United States
Background

Nephrotoxic injury is an important contributor to childhood acute kidney injury (AKI). Partitioning defective(Par)1b is a serine threonine kinase member of Par polarity protein family. Dual loss of Par1b and its paralogue Par1a in mice leads to defects in Notch expression and glomerular and proximal tubule development. We identified increased expression of Par1b in proximal tubules in mouse models of AKI and in human kidney tissue with acute tubular necrosis(ATN). We hypothesized that Par1 proteins are protective and promote renal epithelial repair.

Methods

To test this, we used in vivo and in vitro approaches. We induced AKI in Par1b-/- (Par1b KO) mice with the proximal tubular nephrotoxin, cisplatin. In addition, loss of function was studied using primary proximal tubular cultures from Par1b KO and WT mice. For gain of function, adenoviral constructs were used to overexpress Par1b or control constructs in primary proximal tubular cultures.

Results

Par1b KO mice developed more severe ATN, with higher tubular injury scores and higher Kim-1 levels. Cytoskeletal architecture and cell-extracellular matrix structures were severely disrupted in cisplatin injected Par1b KO kidneys compared to WT as demonstrated by immunostaining of adhesion molecules (e-cadherin, β-catenin, and β1-integrin). To identify the mechanisms underlying the increased injury, we examined the effect of loss of Par1b on apoptosis and necrosis. Par1b deletion led to increased apoptosis following cisplatin treatment, as demonstrated by increased TUNEL staining in vivo and increased cleaved caspase 3 staining in vitro. Increased necroptosis was also demonstrated by increased RIP-1 levels in the Par1b KO kidneys. In WT kidneys, cisplatin exposure induced renal repair pathways, as evidenced by increased expression of Wnt4 and its effectors Axin2 and Lhx1 along with increased levels of activated cleaved Notch2 receptor and increased expression of its effectors Hes1 and Hes5. This effect was attenuated in Par1b KO kidneys. Par1b overexpression in proximal tubular cells showed increased cell viability following cisplatin treatment, demonstrating a protective role for Par1b.

Conclusion

Both in vivo and in vitro studies support the protective role for Par1b in cisplatin induced ATN. Further defining Par1b targets may lead to therapeutic options to prevent cisplatin induced AKI in the future.