Abstract: FR-PO847
Kynurenine 3-Monooxygenase Is a Key Mediator in the IDO Signaling Pathway for Prevention of Rejection in Experimental Kidney Transplantation
Session Information
- Transplantation: Basic
October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Transplantation
- 1801 Transplantation: Basic
Authors
- Wang, Youli, Augusta University, Evans, Colombia
- Merchen, Todd D., Medical College of Georgia at Augusta University, Augusta, Georgia, United States
- Lassiter, Randi, Augusta University, Evans, Colombia
- Fang, Xuexiu, Augusta University, Evans, Colombia
- Kleven, Daniel T., Augusta University, Evans, Colombia
- Ho, Chak-Sum, Gift of Life Michigan, Ann Arbor, Michigan, United States
- Nahman, N. Stanley, Medical College of Georgia at Augusta University, Augusta, Georgia, United States
Background
Indoleamine 2,3-dioxygenase (IDO) degrades tryptophan to kynurenine (KY), and the IDO-transprotein prevents rejection (RJX) in rat kidney transpants (KTx). KY is the substrate for KYnurinase (KYase), KYamiotransferase II (KAT), and KY 3-monooxygenase (KMO), each of which may generate immunosuppressive KYs, including the product of KMO, 3HK. Thus, in pig KTx we showed loss of graft KMO expression in RJX. 3HK is toxic to Tcells and neurons, yet tubular cells with elevated KMO appear normal, suggesting lineage specificity to 3HK toxicity. In this work, we further gauged the effect of RJX on enzymes degrading KY and studied the in vitro effects of 3HK on cultured kidney and Tcells.
Methods
Yorkshire pigs underwent allogeneic (Allo) or auto renal transplants (Auto [control for ischemia]) as we described (Trans Immun, 42:40, 2017). Allos had SLA testing and received mismatched kidneys. All pigs had R UNx before closure (control tissue). 72 hr post-op all grafts were taken and probed for IDO and tandem enzymes (qPCR, immunohistochemistry (IHC), and HPLC for IDO activity). 3HK cytotoxicity and cell proliferation was assessed using human primary kidney cortical endothelial (Endo) and epithelial (Epi) cells, and human peripheral blood Pan-T cells (Tcells).
Results
Allografts showed acute RJX (Banff 1-3), a 6X increase in IDO mRNA and 19.5X increase in IDO activity vs Auto. When compared to R UNx, KMO, KYase and KAT all showed a near 50% reduction in Autos, a change attributed to ischemia. However in rejecting Allos vs Autos, there was an over 90% reduction in KMO mRNA with no additive effect on KYase or KAT. IHC of kidney showed dramatic reductions in KMO protein in Epi and Endo cells. 3HK inhibited proliferation of active Tcells and promoted Tcell injury and death. The same and higher concentrations of 3HK had no effect on cortical Epi and Endo cells.
Conclusion
The loss of KMO, KYase and KAT from ischemia may partially explain RJX in the face of elevated IDO levels. The dramatic decline in KMO in RJX vs the other enzymes may exacerbate the process. 3HK destroys Tcells without affecting Epi or Endo cells. These data suggest that KMO is a key player mediating RJX in the IDO pathway and that the loss of 3HK from reductions in KMO may favor Tcell proliferation and promote RJX.
Funding
- Private Foundation Support