Reactive oxygen species mediated activation of autophagy in liver sinusoidal endothelial cells is a key regulator of liver ischaemia-reperfusion injury

Background: Ischaemia-reperfusion injury (IRI) is the main cause of liver injury following transplantation. IRI damages liver parenchymal cells including liver sinusoidal endothelial cells (LSEC) and the key initiating... [ view full abstract ]

Background: Ischaemia-reperfusion injury (IRI) is the main cause of liver injury following transplantation. IRI damages liver parenchymal cells including liver sinusoidal endothelial cells (LSEC) and the key initiating event during IRI is thought to be the generation of Reactive Oxygen Species (ROS). However ROS can also protect against IRI by activating the cyto-protective cellular process of autophagy; consequently the relative contribution of ROS and/or autophagy to cellular damage of LSEC during IRI is not known. 

Methods: Isolated human LSEC were used in an in vitro model of IRI with ROS production and cell death determined by flow cytometry. Tracking the formation of LC3B puncta assessed autophagy activation. A murine model of liver IRI was used alongside our novel human normothermic machine liver perfusion (NMP-L) IRI model to determine the importance of LSEC autophagy in vivo. 

Results: LSEC demonstrated high basal levels of ROS production that remains unaffected during IRI. Inhibiting ROS generation in LSEC reduced LC3B puncta and sensitized cells to necrosis. Immunofluorescence analysis of murine tissue demonstrated that LC3B co-localised with the LSEC marker CD31 in both the uninjured liver and following IRI. A similar pattern was observed in the tissue of human livers that underwent a period of NMP-L. Increased LSEC-specific immunostaining of autophagy markers was observed in livers deemed viable according to established criteria when compared to non-viable livers (Fig1). 

Conclusion: ROS-mediated activation of autophagy in LSEC is a key regulator of hepatic IRI. Therapeutic augmentation of autophagy in LSEC could reduce IRI following liver surgery.