Date: Saturday, May 30, 2020
Session Time: 3:15pm-4:00pm
Presentation Time: 3:30pm-4:00pm
*Purpose: Ischemia-reperfusion injury (IRI) represents a risk factor in liver transplantation (LT). We have shown that overexpression of heme oxygenase 1 (HO-1) mitigates hepatic IRI in LT. Here, we hypothesized that Human Antigen R (HuR), the stabilizer of AU-rich-containing mRNAs, is required for HO-1 mediated hepatoprotection in LT.
*Methods: HuR/HO-1 protein expression was examined in an in vitro inflammation-mimic model of hepatic warm IRI in primary mouse cultured hepatocytes and bone-marrow-derived macrophages (BMM). RNA interference or CMLD-2, a small molecule inhibitor, were used to silence/block HuR activity. RNA sequencing of HuR-silenced transcripts under in vitro warm IRI was used to analyze gene expression phenotype. Cold and warm hypoxia were contrasted to investigate the transcriptional regulators of HO-1 under stress. In the clinical arm, hepatic biopsies (Bx) were obtained at 2 hours after reperfusion from fifty-one human LT recipients recruited under IRB protocol. Human LT Bx split evenly into low-HuR (n=26) and high-HuR (n=25) expression groups were then retrospectively analyzed by RT-PCR (CD80/CD86/Cathepsin G/CD4/CD28/HO-1) and WB (HuR/HO-1).
*Results: In the experimental arm, HuR/HO-1 protein expression levels were correlated with hepatic IRI phenotype. HuR modulated HO-1 in primary hepatocytes, neutrophils, and macrophages under reperfusion. Induction of HuR/HO-1 led to cytoplasmic localization after cytokine preconditioning in hepatocyte cultures; while HuR silencing caused negative regulation of HO-1, followed by enhanced cytotoxicity. Using an HuR-inhibitor we showed that HuR likely regulates HO-1 via its 3’UTR and causes neutrophil activation (CD69+/Ly6G). Indeed, HuR silencing in BMM cultures decreased HO-1 expression, leading to the induction of proinflammatory cytokines/chemokines. RNA sequencing revealed regulation of novel genes THY1, ACOD1 and PTGES. HuR but not HIF-1α positively regulated HO-1 in warm but not cold hypoxia/reoxygenation conditions, which mimic donor organ ex vivo storage. Adjunctive inhibition of HuR diminished LC3B, a marker for autophagosome, under HO-1 regulation, suggesting a cytoprotective mechanism in hepatic IRI. In the clinical arm, hepatic biopsies from fifty-one LT patients were analyzed at 2h post-reperfusion. Graft HuR expression was negatively correlated with macrophage (CD80/CD86) and neutrophil (Cathepsin G) markers. Hepatic IRI increased HuR/HO-1 expression and inflammatory genes. High-HuR expressing liver grafts showed lower sALT/sAST levels and improved post-LT survival.
*Conclusions: This translational study identifies HuR as a novel regulator of HO-1-mediated cytoprotection in sterile liver inflammation and a potential biomarker of ischemic stress-resistance in LT.
To cite this abstract in AMA style:Dery KJ, Nakamura K, Kadono K, Hirao H, Kageyama S, Ito T, Kojima H, Kaldas F, Busuttil RW, Kupiec-Weglinski JW. Human Antigen R (HuR): A New Regulator of Heme Oxygenase-1 Cytoprotection in Mouse and Human Liver Transplantation [abstract]. Am J Transplant. 2020; 20 (suppl 3). https://atcmeetingabstracts.com/abstract/human-antigen-r-hur-a-new-regulator-of-heme-oxygenase-1-cytoprotection-in-mouse-and-human-liver-transplantation/. Accessed May 8, 2021.
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