Inhibition of SK2 and ER stress ameliorated inflammation and apoptosis in liver ischemia-reperfusion injury.

Ischemia-reperfusion injury (IRI) remains a major cause of mortality and morbidity after liver surgery. Endoplasmic reticulum (ER) stress is a critical mechanism of inflammatory injury during hepatic IRI. In this study, we investigated the effect of sphingosine kinases 2 (SK2) on ER stress and hepatic IRI. We established hepatic IRI mice and hepatocellular hypoxia/reoxygenation in vitro model. We observed the SK2 and ER stress protein IRE1α expression. Then, we used an SK2 inhibitor and knocked down IRE1α/SK2, to observe the effect of SK2 during IRI. Our results showed that the expression of ER stress and SK2 was significantly elevated during hepatic IRI. Inhibition of SK2 ameliorated liver inflammation and reduced cell apoptosis in hepatic IRI mice. Consistently, we found that the inhibition of IRE1α also downregulated SK2 expression and reduced mitochondrial membrane permeability. Furthermore, the knockdown of SK2 could also reduce cell damage and reduce the expression of inflammatory factors but did not influence ER stress-related signaling pathway. Taken together, our results suggested that ER stress and SK2 played important and regulatory roles in hepatic IRI. Inhibition of ER stress and SK2 could significantly improve liver function after hepatic IRI.