Abstract: TH-PO642
Discrepant Toxicity Profiles of Cyclosporine A and Tacrolimus Beyond Calcineurin Inhibition
Session Information
- Transplantation: Basic
November 03, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Transplantation
- 2001 Transplantation: Basic
Authors
- Yilmaz, Duygu Elif, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany
- Kirschner, Karin Michaela, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany
- Demirci, Hasan, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany
- Himmerkus, Nina, Christian-Albrechts-Universitat zu Kiel, Kiel, Schleswig-Holstein, Germany
- Bachmann, Sebastian, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany
- Mutig, Kerim, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany
Background
Calcineurin inhibitors (CNI), cyclosporine A (CsA) or tacrolimus (Tac), belong to the first-line immunosuppressive strategies after solid organ transplantation. However, both CNI exert pronounced nephrotoxicity, which is typically stronger in patients receiving CsA. Calcineurin inhibition by CsA occurs via building complexes with cyclophilins, whereas Tac recruits FKBP12 instead. We hypothesized that suppression of cyclophilin chaperone function by CsA may induce endoplasmic reticulum (ER) stress and pro-apoptotic unfolded protein response (UPR) in kidney epithelia.
Methods
Effects of CsA vs. Tac (10 µM for 6 h) on the UPR signaling were compared in cultured human embryonic kidney cells (HEK293), human renal proximal tubular (PT) epithelial cells (HRPTEpC), and freshly isolated rat PTs using quantitative PCR, immunoblotting, and immunofluorescence staining. An established ER stress inducer, thapsigargin (Tg) served as a positive control.
Results
CsA and Tg, but not Tac, induced ER stress and pro-apoptotic UPR in HEK293 cells, as reflected by increased levels of key UPR products (BiP, CHOP, spliced XBP1, and phosphorylated IRE1α) and cleaved caspase-3 (cCas-3). Similar effects were observed in HRPTEpC cells and isolated rat PTs. Knockdown of cyclophilin A or B isoforms in HEK293 cells using siRNA aggravated CHOP and cCas-3 suggesting relevance of cyclophilin activity for intact proteostasis. Application of chemical chaperones, TUDCA or 4-PBA, alleviated the CsA-induced UPR suggesting that improved protein folding may have protective effects against CsA cytotoxicity. Along the same line, genetic suppression of UPR in HEK293 cells by CRISPR/Cas9-mediated deletion of the key ER stress sensors, PERK or ATF6, blunted the pro-apoptotic UPR in response to CsA.
Conclusion
In summary, these results suggest that nephrotoxic effects of CsA may be aggravated by suppression of cyclophilins, ER stress, and pro-apoptotic UPR. Pharmacological or genetic modulation of UPR bears the potential to alleviate CsA nephrotoxicity.
Funding
- Government Support – Non-U.S.