Orthotopic liver transplantation (OLT) is an effective therapeutic modality for the treatment of end-stage liver disease. However, ischemia/reperfusion injury (IRI), an exogenous Ag-independent component of the "harvesting" insult, remains one of the key limitations after OLT. Moreover, the quality of donor organs decreases along with the aging of general population and associated pathological conditions. This proposal is built upon the insights gained from our previous studies on a novel approach of combating organ IRI by locally inducing heme oxygenase-1 (HO-1) that protects against the severity of oxidative stress. Indeed, local HO-1 expression and functional response should be considered as a denominator of donor organ quality. We have also shown the role of innate immunity in liver IRI. Indeed, by utilizing a non-transplant mouse warm liver IRI model, we have documented that: (i) TLR4 activation mediates liver inflammation via IRF-3 pathway;(ii) CXCL10 regulates liver innate immune responses;(iii) Type-I IFN mediates synergy between Kupffer cells and hepatocytes, and (iv) endogenous TLR ligands are crucial in TLR4 activation-induced "sensoring" and IRI. To mimic the clinical scenario, we have recently developed a mouse model of prolonged liver cold preservation, followed by syngeneic OLT. We hypothesize that cross talk between the opposing pathways, i.e., HO-1 in the donor organ, and TLR4 in OLT recipients is instrumental in the mechanism of liver IRI. Our corollary hypothesis states that Nrf2, a bZIP transcriptional factor that regulates stress response/regulates cell redox balance, controls dysregulated HO-1 - TLR4 signaling during IRI.
Aim 1. To analyze mechanisms by which suboptimal HO-1 deficient liver grafts affect IRI sequel and TLR4 signaling in OLT recipients. Livers from WT, HO-1 deficient (+/-;KO) and HO-1 overexpressing (Tg) donors will be stored for 18 h at 4 C, and then transplanted to syngeneic WT mice. We will study (i) whether HO-1 expression and by which donor liver cell type affect IRI and OLT outcome, and (ii) if and how the local HO-1 expression in OLT affects host TLR4 signaling.
Aim 2. To dissect mechanisms by which modulation of recipient TLR4 signaling ameliorate IRI and improve the outcome of suboptimal OLTs. Livers from WT or HO-1 deficient (+/-;KO) donors will be stored for 18 h at 4 C, and then transplanted to syngeneic TRIF- or Type I IFN receptor (IFNAR)-KO mice. We will study (i) whether selective ablation of downstream TLR4 signaling in the host affect IRI sequel/OLT inflammation, and (ii) if HO-1- TLR4 cross talk can influence HMGB1-mediated IR inflammation and organ damage in OLT recipients.
Aim 3. To analyze mechanisms by which Nrf2 signaling influence IRI in OLT recipients. Livers from donor mice that are Nrf2-deficient or Nrf2-overexpressing (hepatocyte-specific conditional disruption of the Keap1 gene, which represses Nrf2) will be stored for 18 h at 4 C, and transplanted to WT mice. By modulating oxidant (HO-1 siRNA) and inflammatory (anti-HMGB1/rHMGB1) responses, we will study the regulatory function of Nrf2 upon (i) HO-1 vs (ii) TLR4 signaling pathways during IRI in OLT recipients.
Host sensitization remains the major problem in clinical organ transplantation. Many prospective transplant patients are sensitized following blood transfusions, pregnancies, or failed previous grafts. This project is designed to analyze cell mediated mechanisms leading to accelerated rejection of organ allografts and ultimately to design novel and much needed therapeutic approaches to ameliorate transplant rejection in sensitized patients.
|Zhang, Cheng; Zhang, Yu; Liu, Yuanxing et al. (2016) A soluble form of PSGL-1 requires Nrf2 signaling to protect liver transplant endothelial cells against ischemia-reperfusion injury. Am J Transplant :|
|Liu, Y; Ji, H; Zhang, Y et al. (2015) Negative CD4â€‰+â€‰TIM-3 signaling confers resistance against cold preservation damage in mouse liver transplantation. Am J Transplant 15:954-64|
|Liu, Yuanxing; Ji, Haofeng; Zhang, Yu et al. (2015) Recipient T cell TIM-3 and hepatocyte galectin-9 signalling protects mouse liver transplants against ischemia-reperfusion injury. J Hepatol 62:563-72|
|Huang, Jing; Yue, Shi; Ke, Bibo et al. (2014) Nuclear factor erythroid 2-related factor 2 regulates toll-like receptor 4 innate responses in mouse liver ischemia-reperfusion injury through Akt-forkhead box protein O1 signaling network. Transplantation 98:721-8|
|Huang, Jing; Shen, Xiu-Da; Yue, Shi et al. (2014) Adoptive transfer of heme oxygenase-1 (HO-1)-modified macrophages rescues the nuclear factor erythroid 2-related factor (Nrf2) antiinflammatory phenotype in liver ischemia/reperfusion injury. Mol Med 20:448-55|
|Ji, Haofeng; Liu, Yuanxing; Zhang, Yu et al. (2014) T-cell immunoglobulin and mucin domain 4 (TIM-4) signaling in innate immune-mediated liver ischemia-reperfusion injury. Hepatology 60:2052-64|
|Zhang, Y; Ji, H; Shen, X et al. (2013) Targeting TIM-1 on CD4 T cells depresses macrophage activation and overcomes ischemia-reperfusion injury in mouse orthotopic liver transplantation. Am J Transplant 13:56-66|
|Ji, Haofeng; Zhang, Yu; Liu, Yuanxing et al. (2013) Vasoactive intestinal peptide attenuates liver ischemia/reperfusion injury in mice via the cyclic adenosine monophosphate-protein kinase a pathway. Liver Transpl 19:945-56|
|Ke, Bibo; Shen, Xiu-Da; Zhang, Yu et al. (2013) KEAP1-NRF2 complex in ischemia-induced hepatocellular damage of mouse liver transplants. J Hepatol 59:1200-7|
|Ji, Haofeng; Zhang, Yu; Shen, Xiu-da et al. (2013) Neuropeptide PACAP in mouse liver ischemia and reperfusion injury: immunomodulation by the cAMP-PKA pathway. Hepatology 57:1225-37|
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