Annexin A1 Mimetic Peptide AC2-26 Inhibits Sepsis-induced Cardiomyocyte Apoptosis through LXA4/PI3K/AKT Signaling Pathway.

The aim of the present study was to explore the effects of annexin A1 (ANXA1) mimetic peptide AC2-26 on sepsis-induced cardiomyocyte apoptosis in vivo and in vitro and the underlying mechanisms. In the in vivo study, a rat septic model was established by the cecal ligation and puncture (CLP). The rats were divided into control group, sepsis group and AC2-26 group. The rats in the AC2-26 group were intraperitoneally injected with AC2-26 (1 mg/kg) 2 h before CLP, and those in the control group and sepsis group were injected with the same volume of normal saline. The myocardial tissue was examined by hematoxylin and eosin (HE) staining and transmission electron microscopy (TEM). Furthermore, myocardial apoptosis was measured by terminal dUTP nick end-labeling (TUNEL) assay. In the in vitro study, H9C2 cells were cultured and divided into three groups: control group, in which cells were only given the basic culture medium; LPS group, in which cells were treated with 10 μg/mL LPS; AC2-26 group, in which cells were treated with 0.5 μmol/L AC2-26 2 h before 10 μg/mL LPS was given. The apoptosis of H9C2 cells was detected by flow cytometry. The levels of lipoxin A4 receptor (LXA4), phosphoinositide-3-kinase (PI3K) and protein kinase B (PKB or AKT) protein were measured by Western blotting, the activity of NF-κB and the level of TNF-α by ELISA and the activities of caspase-3/8 by using the caspase activity kits. The in vivo study showed that the myocardial pathological damage and myocardial ultrastructural damage were significantly alleviated and the myocardial apoptosis significantly decreased in the AC2-26 group as compared with the sepsis group (P<0.05 for all). The in vivo study revealed that the apoptosis of H9C2 cells was profoundly ameliorated in the AC2-26 group relative to the sepsis group (P<0.05). The protein expression levels of LXA4 were significantly up-regulated, and those of PI3K and AKT prominently down-regulated in the AC2-26 group when compared with those in the LPS group (P<0.05 for all). The activity of NF-κB was greatly inhibited and the level of TNF-α markedly decreased in the AC2-26 group as compared with those in the LPS group (P<0.05 for all). AC2-26 treatment also significantly suppressed the activities of caspase-3/8 in H9C2 cells. In conclusion, these findings suggest that AC2-26 may alleviate the sepsis-induced cardiomyocyte apoptosis in vivo and in vivo through the LXA4/PI3K/AKT signaling pathway.