Investigator: Nisanne Ghonem, University of Rhode Island

Scientific Theme: Cancer & Molecular Toxicology

Abstract: Orthotopic liver transplantation (OLT) is the only curative therapy for end-stage liver diseases. The surgical procedure inherently involves cold ischemia during graft preservation, followed by graft reperfusion, resulting in cold ischemia and reperfusion (I/R) injury. I/R injury is a major cause of liver graft failure, requiring re- transplantation, further depleting the scarce organ pool, and carrying a high mortality rate if patients are not re-transplanted immediately. The inflammatory response that occurs upon reperfusion is a primary cause of liver graft failure.  Unresolved inflammation is an underlying cause of several liver diseases, including liver cancer. No pharmacological treatment for I/R injury is available.  Endogenous prostacyclin (PGI2) has vasodilatory and anti-platelet aggregatory actions. Treprostinil (Remodulin®), an FDA-approved PGI2 analog, ameliorated I/R injury, reduced pro-inflammatory cytokine expression of TNFα, IL-1β, -6, IFN-γ, and up-regulated the anti-inflammatory cytokine IL-10 during rat OLT. The mechanisms, however, of treprostinil’s anti-inflammatory actions are unknown. The central hypothesis of this proposal is that treprostinil reduces hepatic inflammation by activating the nuclear hormone receptor peroxisome proliferator-activated receptor- alpha (PPARα) to inhibit NF-κB-mediated transactivation of pro-inflammatory cytokines. The first goal of this pilot study is to characterize the inhibitory role of treprostinil on NF-κB activity.  First, we will stimulate THP-I- differentiated macrophages with lipopolysaccharide to induce a human inflammatory response and measure effects of treprostinil treatment on cytokine concentration, mRNA and protein expression by ELISA, qPCR and western blot, respectively. The second part of this goal will test treprostinil’s inhibitory effects on NF-κB activity by measuring NF-κB p50 and p65 subunit nuclear translocation. Overall, these studies will characterize the transcription factor-mediated pathways by treprostinil, and identify a mechanism of treprostinil-mediated anti-inflammation. Successful completion of this pilot study will provide essential data to justify project expansion to examine treprostinil-mediated hepatic PPARα activation, which up-regulates the inhibitory proteins, IκBs, to block NF-κB nuclear translocation and reduce hepatic inflammation.

Human Health Relevance: This pilot project investigates the molecular mechanism of treprostinil, a prostacyclin analog, in reducing inflammation, as a novel therapeutic strategy to improve successful outcomes of liver transplantation, and reduce liver tumor growth. Collectively, this work makes significant contributions to the field of hepatology and transplant medicine and supports ongoing clinical investigation of treprostinil during adult OLT.