mTOR activation protects liver from ischemia/reperfusion-induced injury through NF-κB pathway

Hepatic steatosis renders liver more vulnerable to ischemia/reperfusion injury (IRI), which commonly occurs in transplantation, trauma, and liver resection. The underlying mechanism is not fully characterized. We aimed to clarify the role of mechanistic target of rapamycin (mTOR) signaling in hepatic ischemia/reperfusion injury (HIRI) in normal and steatotic liver using Alb-TSC1^-/- (AT) and Alb-mTOR^-/- (Am) transgenic mice. Steatotic liver induced by high-fat diet was more vulnerable to IRI. Activation of hepatic mTOR in AT mice decreased lipid accumulation attenuated HIRI as measured by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining, circulating levels of alanine aminotransferase and lactate dehydrogenase, and inflammatory mediators such as monocyte chemoattractant protein 1 (MCP-1), TNF-α, and IL-6 and hepatic cleaved caspase 3 in mice fed either a normal chow diet or a high-fat diet. The effects of mTOR activation on hepatic cleaved caspase 3 were reversed by rapamycin, an inhibitor of mTOR signaling. Inhibition of hepatic mTOR in Am mice increased hepatic lipid deposition and HIRI. The increment in hepatic susceptibility to IRI was significantly attenuated by pretreatment with IKKβ inhibitor. Further, suppression of mTOR facilitated nuclear translocation of NF-κB p65. In conclusion, our study suggests that mTOR activity in hepatocytes decreases hepatic vulnerability to injury through a mechanism dependent on NF-κB proinflammatory cytokine signaling pathway in both normal and steatotic liver.-Li, Z., Zhang, J., Mulholland, M., Zhang, W. mTOR activation protects liver from ischemia/reperfusion-induced injury through NF-κB pathway.