Cold Storage-Mediated Activation of P38MAPK-MK2 Axis Induces Kidney Injury after Transplantation

Background: Most donor kidneys undergo cold storage (CS) before transplantation (Tx), but this often results in suboptimal outcomes because CS activates cellular pathways that damage kidney tissue. Previously we showed that normal proteasome function is needed to maintain kidney function and CS followed by transplantation (CS+Tx) reduces proteasome function and increases inflammation in rat renal grafts; however, the mechanisms behind the CS-mediated proteaome dysfunction and inflammation remain unclear. Methods: In vivo rat kidney CS followed by transplantation (CS+Tx) and in vitro rat renal cell CS followed by rewarming (CS+RW) models were used. Proteasome function was assessed using renal cell extract and fluorescent-based peptide substrates. Protein levels were evaluated using renal extracts and western blotting analysis. Results: CS increased phosphorylation of P38MAPK in rat renal cells in a time-dependent manner, suggesting activation of P38MAPK pathway. Inhibiting P38MAPK with a selective inhibitor, VX-745, during CS followed by rewarming restored the proteasome activity and mitigated cell injury in rat renal cells, suggesting that P38MAPK negatively regulates proteasome function in renal cells during CS+RW. We evaluated MK2, a downstream signaling molecule of P38MAPK activation that promotes inflammation in eukaryotic cells. We observed that CS+RW increased MK2 activation in rat renal cells. Finally, inhibiting P38MAPK with VX-745 during CS reduced activation of MK2 in renal cells following rewarming, suggesting that the p38PMAK could be a critical regulator of CS-mediated inflammation via MK2 pathway. Conclusion: Our data indicate that the P38MAPK is a contributor of CS-mediated proteasome dysfunction and renal injury. Similarly, P38MAPK-MK2 axis may promote inflammation in renal cells during CS+Tx and this pathway may serve as a new therapeutic target to improve the outcomes of kidney transplantation and potential clinical applications during organ transplant. Funding: NIDDK Support