Ac2­26 alleviates hepatic ischemia­reperfusion injury based on inhibiting the positive feedback loop of HMGB1/TLR4/NF­κB/neutrophils.

Inflammation is one of the most crucial mechanism underlying hepatic ischemia-reperfusion injury (HIRI). Several studies have shown that Ac2-26, the active N-terminal peptide of Annexin A1, could modulate anti-inflammatory processes and protect the organs from ischemia-reperfusion injury (IRI). However the effects of Ac2-26 on an HIRI model have not been reported to date. The purpose of the present study was to determine whether Ac2-26 pretreatment could protect hepatocytes against acute HIRI by inhibiting neutrophil infiltration through regulation of the high mobility group box protein 1 (HMGB1)/Toll-like receptor 4 (TLR4)/NF-κB signaling pathway. To this end, a total of 72 adult C57BL/6 mice were randomly divided into sham operation (sham), ischemia-reperfusion (I/R), I/R + Ac2-26 and Ac2-26 groups. The HIRI model was established by occluding the branch of the hepatic pedicle to the left and median liver lobes with an atraumatic vascular clamp for 45 min, followed by reperfusion for 24 h. The expression of HMGB1, TLR4, NF-κB, IκBα and lymphocyte antigen 6 complex locus G6D (Ly6G) was detected using reverse transcription-quantitative PCR, western blotting and immunohistochemical staining; serum levels of HMGB1 were evaluated using an enzyme-linked immunosorbent assay. Flow cytometry was used to detect the proportion of neutrophil. The results indicated that Ac2-26 preconditioning rescued hepatocyte dysfunctions induced by HIRI. In addition, HIRI was associated with a significant increase in HMGB1 expression and release, accompanied by increased expression of TLR4, which was significantly inhibited by Ac2-26. Furthermore, the expression of phosphorylated (p)-NF-κB and the ratio of p-NF-κB to NF-κB were markedly increased, while the expression of IκBα was decreased in the I/R group compared with those in the sham group; however, these effects were reversed by Ac2-26 administration. Additionally, Ac2-26 administration significantly inhibited neutrophil infiltration and resulted in low levels of neutrophils and Ly6G as well as reduced myeloperoxidase activity. Taken together, these results indicated that Ac2-26 pretreatment serves a protective role against HIRI by regulating the HMGB1/TLR4/NF-κB signaling pathway and inhibiting neutrophil infiltration.

Ac2-26 attenuates hepatic ischemia-reperfusion injury in mice via regulating IL-22/IL-22R1/STAT3 signaling.

Hepatic ischemia-reperfusion injury (HIRI) is one of the major sources of mortality and morbidity associated with hepatic surgery. Ac2-26, a short peptide of Annexin A1 protein, has been proved to have a protective effect against IRI. However, whether it exerts a protective effect on HIRI has not been reported. The HIRI mice model and the oxidative damage model of H2O2-induced AML12 cells were established to investigate whether Ac2-26 could alleviate HIRI by regulating the activation of IL-22/IL-22R1/STAT3 signaling. The protective effect of Ac2-26 was measured by various biochemical parameters related to liver function, apoptosis, inflammatory reaction, mitochondrial function and the expressions of IL-22, IL-22R1, p-STAT3Tyr705. We discovered that Ac2-26 reduced the Suzuki score and cell death rate, and increased the cell viability after HIRI. Moreover, we unraveled that Ac2-26 significantly decreased the number of apoptotic hepatocytes, and the expressions of cleaved-caspase-3 and Bax/Bcl-2 ratio. Furthermore, HIRI increased the contents of malondialdehyde (MDA), NADP+/NADPH ratio and reactive oxygen species (ROS), whereas Ac2-26 decreased them significantly. Additionally, Ac2-26 remarkably alleviated mitochondria dysfunction, which was represented by an increase in the adenosine triphosphate (ATP) content and mitochondrial membrane potential, a decrease in mitochondrial DNA (mtDNA) damage. Finally, we revealed that Ac2-26 pretreatment could significantly inhibit the activation of IL-22/IL22R1/STAT3 signaling. In conclusion, this work demonstrated that Ac2-26 ameliorated HIRI by reducing oxidative stress and inhibiting the mitochondrial apoptosis pathway, which might be closely related to the inhibition of the IL-22/IL22R1/STAT3 signaling pathway.

N-acetyl-L-tryptophan attenuates hepatic ischemia-reperfusion injury via regulating TLR4/NLRP3 signaling pathway in rats.

The aim of this study was to investigate the changes of TLR4/NLRP3 signal during hepatic ischemia-reperfusion injury (HIRI) and to verify whether N-acetyl-L-tryptophan (L-NAT) protected hepatocytes by regulating the activation of TLR4/NLRP3 signal. We have established the rat HIRI model and H2O2-induced cell damage model to simulate ischemia-reperfusion injury and detect the corresponding indicators. Compared with the sham group, Suzuki score and the level of serum ALT increased after HIRI, accompanied by an increased expression of NLRP3, ASC, Caspase-1, IL-1ß, TLR4, and NF-κB. While L-NAT pretreatment reversed the above-mentioned changes. Compared with the control group, cells in the H2O2 treated group became smaller in cell volume and round in shape with unclear boundaries. Similar to the phenotypes in vivo, H2O2 treatment also induced significant increase in expression of pyroptosis-related proteins (NLRP3, ASC, Caspase-1 and IL-1ß) and inflammatory factors (TLR4 and NF-κB). While L-NAT pretreatment attenuated injuries caused by H2O2. In conclusion, the present findings demonstrate that L-NAT alleviates HIRI by regulating activation of NLRP3 inflammasome, which may be related to the TLR4/NF-κB signaling pathway.