Gene Expression Changes during Early Reperfusion following Short or Long Hepatic Ischemia in a Rodent Model

Background In the U.S., patients on the waiting list in need of a liver transplant outnumber available donors by two‐fold. During transplantation, ischemia‐reperfusion (IR) of the donor tissue activates pathways that elicit inflammatory and sterile immune responses. However, fundamental molecular mechanisms of hepatic IR remain unclear. Understanding the response to various durations of ischemia could help identify targets for the attenuation of damage pathways during IR, increasing available donors suitable for transplant. Methods Using a rat model of 70% warm ischemia, RNA was extracted from the non‐ischemic and the ischemic‐reperfused lobes after 30 minutes of reperfusion following two durations of ischemia: 30 minutes and 60 minutes (termed short versus long IR, respectively). Using microarrays, differentially expressed genes and pathway analyses were utilized to examine potential upstream regulation. Nuclear extracts from each reperfused replicate were used for transcription factor activation profiling arrays. Western blotting to examine activation of MAPK pathways was also performed. Results Only 22 genes were found to change significantly in the short IR lobes compared to their non‐ischemic counterparts. These changes in gene expression were also seen in the long IR model. However, in the long IR group, many more genes changed significantly. Upstream analysis implicated reduced mTORC2 signaling in the regulation of these genes. Pathway analysis revealed enrichment of pathways related to mitochondrial dysfunction. Transcription factor activation profiling displayed a significant reduction in the activity of several transcription factors, including Foxf2, KLF4, Tcf/Lef, HNf1 and Oct4. Western blotting revealed a significant increase in Erk1/2 and JNK activity in the long IR model but not in the short IR model. Conclusions Changes in gene expression suggest mTORC2 as a major contributing factor during early reperfusion in the 60 minute ischemia model. Transient activation of Erk1/2 and JNK signaling may be involved in the response to IR following long periods of ischemia. Examination of simultaneous changes in mitochondria function and mTORC2 signaling and changes downstream from activated Erk1/2 and JNK signaling may reveal potential targets that will favor cell survival. Support or Funding Information VZ was a Howard Hughes Medical Institute Gilliam Fellow and is currently supported by the NSF Graduate Fellowship Program. These studies were supported by the Rhode Island Department of Pediatrics. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .