Liver Ischemia and Reperfusion Induce Periportal Expression of Necroptosis Executor pMLKL Which Is Associated With Early Allograft Dysfunction After Transplantation

Abstract

BackgroundEarly allograft dysfunction (EAD) following liver transplantation (LT) remains a major threat to the survival of liver grafts and recipients. In animal models, it is shown that hepatic ischemia-reperfusion injury (IRI) triggers phosphorylation of Mixed Lineage Kinase domain-like protein (pMLKL) inducing necroptotic cell death. However, the clinical implication of pMLKL-mediated cell death in human hepatic IRI remains largely unexplored. In this study, we aimed to investigate the expression of pMLKL in human liver grafts and its association with EAD after LT.MethodsThe expression of pMLKL was determined by immunohistochemistry in liver biopsies obtained from both human and rat LT. Human liver biopsies were obtained at the end of preservation (T0) and ~1 hour after reperfusion (T1). The positivity of pMLKL was quantified electronically and compared in rat and human livers and post-LT outcomes. Multiplex immunofluorescence staining was performed to characterize the pMLKL-expressing cells.ResultsIn the rat LT model, significant pMLKL expression was observed in livers after IRI as compared to livers of sham-operation animals. Similarly, the pMLKL score was highest after IRI in human liver grafts (in T1 biopsies). Both in rats and humans, the pMLKL expression is mostly observed in the portal triads. In grafts who developed EAD after LT (n=24), the pMLKL score at T1 was significantly higher as compared to non-EAD grafts (n=40). ROC curve revealed a high predictive value of pMLKL score at T1 (AUC 0.70) and the ratio of pMLKL score at T1 and T0 (pMLKL-index, AUC 0.82) for EAD. Liver grafts with a high pMLKL index (>1.64) had significantly higher levels of serum ALT, AST, and LDH 24 hours after LT compared to grafts with a low pMLKL index. Multivariate logistical regression analysis identified the pMLKL-index (Odds ratio=1.3, 95% CI 1.1-1.7) as a predictor of EAD development. Immunohistochemistry on serial sections and multiplex staining identified the periportal pMLKL-positive cells as portal fibroblasts, fibrocytes, and a minority of cholangiocytes.ConclusionPeriportal pMLKL expression increased significantly after IRI in both rat and human LT. The histological score of pMLKL is predictive of post-transplant EAD and is associated with early liver injury after LT. Periportal non-parenchymal cells (i.e. fibroblasts) appear most susceptible to pMLKL-mediated cell death during hepatic IRI.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury

“…Both apoptosis and necrosis were observed in hepatocytes after IR [ 25 ]. IR induces periportal expression of MLKL in human liver grafts, and is associated with early allograft dysfunction after transplantation [ 26 ]. Ferroptosis is induced by iron overload during liver IR injury [ 27 ].…”

Necroptosis in Organ Transplantation: Mechanisms and Potential Therapeutic Targets

“…Almost all of these studies are based on cell culture and animal models. There are only two human organ studies, one in the lung [ 40 ] and another in the liver [ 35 ]. More clinical research should be conducted to determine the significance of necroptosis in human organ transplants.…”

“…Human liver grafts with a high pMLKL index had significantly elevated serum levels of aminotransferases and lactate dehydrogenase 24 h after transplantation, signifying lytic cell death. Thus, the pMLKL index can serve as a reliable prognostic tool for the progression of EAD [ 35 ].…”

Cell Death in Liver Disease and Liver Surgery

“…Overall evidence suggests that necroptosis plays a relevant role as a form of lytic cell death in the IRI model, although some studies do not attribute any effects to necroptosis [ 208 , 209 ]. A recent study revealed the presence of activated MLKL in human liver grafts before and after reperfusion [ 210 ]. Interestingly, patients experiencing early allograft dysfunction show a significant increase in MLKL activation, which correlates with serum liver enzyme levels.…”