Defense Date


Document Type


Degree Name

Doctor of Philosophy


Molecular Biology and Genetics

First Advisor

Martin Mangino


Of the over 108,000 American awaiting a life-saving organ transplant today, over 12,000 (11%) of those need a new liver (OPTN, 2020). Last year, only 35% of patients on the waiting list for an organ were transplanted. Improving the quality of marginal organs by preventing or reversing preservation injury could vastly increase the number of transplants performed. Washout of circulating blood during liver procurement with cold University of Wisconsin solution flushes out any endogenous pro-survival signaling molecules. We investigated lysophospholipid (LPL) surface receptors (G-protein coupled receptors for lysophosphatidic acid (LPA) and sphingosine- 1-phosphate (S1P)) and their role in protecting hepatocytes against preservation injury. Using an in vitro model of organ preservation, we found that treatment with exogenous LPA during cold storage does not prevent preservation injury. However, the method of lipid delivery may be to blame. The ratio of intracellular S1P:ceramide, an indicator of cell health, is decreased in hepatocytes following cold storage. Inhibition of sphingosine kinase-2 (SK2), the enzyme responsible for much of the intracellularly acting S1P, with ABC294640 (a selective SK2 inhibitor) is devastating in rodent liver transplant, ex vivo perfusion, and in vitro models. Upon further investigation, the mechanism of ABC294640 toxicity is two-fold: this compound directly inhibits complex I of the mitochondrial electron transport chain, independent of its effects on SK2. These data clarify the detrimental phenotype associated with ABC294640 treatment of the liver during cold storage. Modulating LPL signaling pathways, upstream of mitochondrial activity and cytoskeleton conformation may improve liver graft function following preservation.


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