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Abstract: TH-OR76

Mechanism of Cold Storage-Mediated Regulation of Heat Shock Proteins in Renal Grafts After Transplantation

Session Information

Category: Transplantation

  • 2101 Transplantation: Basic

Authors

  • Lee, Seongok, University of Arkansas for Medical Sciences College of Medicine, Little Rock, Arkansas, United States
  • Parajuli, Nirmala, University of Arkansas for Medical Sciences College of Medicine, Little Rock, Arkansas, United States
Background

Ischemia-reperfusion injury associated with cold storage (CS) followed by transplantation contributes to impaired protein homeostasis leading to kidney graft injury. However, the mechanisms of impaired protein homeostasis remain elusive.

Methods

Isolated donor rat kidneys were stored in University of Wisconsin (UW) solution at 4°C for 0- or 18-hr followed by transplantation to recipient rats (CS+Tx). To simulate in vitro model of CS+Tx, rat or human proximal tubular cells (PTCs) were exposed to UW solution at 4°C followed by rewarming (RW) at 37°C (CS+RW). RNA interference, overexpression studies, and western blotting were the key assays.

Results

Using in vivo and in vitro models of transplantation, we found that the two members of 70-KDa heat shock proteins (HSPs) were dysregulated—a robust increase of Hsp72 and a decrease of Hsc70—in kidney grafts after CS+Tx. HSF1 is a stress-activated transcription factor that induces HSPs during stress. Our data show that the HSF1 was significantly increased and modified during CS in both in vitro and in vivo transplant models, but decreases after reperfusion/rewarming episodes in kidney/renal cells. To investigate the mechanisms of excessive induction of Hsp72 after CS+Tx, the protein level of Hsc70 and/or HSF1 was modulated in PTCs, followed by CS+RW. Interestingly, Hsc70 knockdown in PTCs increased Hsp72 protein but decreased HSF1 protein. Whereas HSF1 depletion increased Hsc70 protein and did not change the Hsp72 protein level in PTCs, the double knockdown of HSF1 and Hsc70 significantly increased the Hsp72 protein levels. Finally, the HSF1 knockdown in PTCs followed by CS+RW decreased Hsc70 levels but increased the Hsp72 protein.

Conclusion

These data show a reciprocal relationship between Hsc70 and Hsp72 in PTCs and that the Hsc70 negatively regulates Hsp72 protein levels. Our data also indicated that the excessive increase of Hsp72 is not regulated by the classical HSF1 pathway, and the elevated Hsp72 protein negatively regulates kidney function after CS+Tx. Together, the results suggest Hsp72 as a potential therapeutic target during CS to improve outcomes after kidney transplantation.

Funding

  • NIDDK Support