Spermidine ameliorates liver ischaemia-reperfusion injury through the regulation of autophagy by the AMPK-mTOR-ULK1 signalling pathway

BACKGROUND: Hepatic ischaemia-reperfusion (IR) injury is a common clinical challenge lacking effective therapy. The aim of this study was to investigate whether spermidine has protective effects against hepatic IR injury through autophagy(definition). METHODS: Liver ischaemia reperfusion was induced in male C57BL/6 mice. Then, liver function, histopathology, cytokine production and immunofluorescence were evaluated to assess the impact of spermidine pre-treatment on IR-induced liver injury. Autophagosome formation was observed by transmission electron microscopy. Western blotting was used to explore the underlying mechanism and its relationship with autophagy, and TUNEL staining was conducted to determine the relationship between apoptosis and autophagy in the ischaemic liver. RESULTS: The results of the transaminase assay, histopathological examination, and pro-inflammatory cytokine production and immunofluorescence evaluations demonstrated that mice pre-treated with spermidine showed significantly preserved liver function. Further experiments demonstrated that mice administered spermidine before the induction of IR exhibited increased autophagy via the AMPK-mTOR(definition)-ULK1 pathway, and TUNEL staining revealed that spermidine attenuated IR-induced apoptosis in the liver. CONCLUSIONS: Our results provide the first line of evidence that spermidine provides protection against IR-induced injury in the liver by regulating autophagy through the AMPK-mTOR-ULK1 signalling pathway. These results suggest that spermidine may be beneficial for hepatic IR injury.