Protection of rat liver against hepatic ischemia-reperfusion injury by a novel selenocysteine-containing 7-mer peptide

Hepatic ischemia-reperfusion (I-R) injury causes acute organ damage or dysfunction, and remains a problem for liver transplantation. In the I-R phase, the generation of reactive oxygen species aggravates the injury. In the current study, a novel selenocysteine-containing 7-mer peptide (H-Arg-Sec-Gly-Arg-Asn-Ala-Gln-OH) was constructed to imitate the active site of an antioxidant enzyme, glutathione peroxidase (GPX). The 7-mer peptide which has a lower molecular weight, and improved water-solubility, higher stability and improved cell membrane permeability compared with other GPX mimics. Its GPX activity reached 13 U/µmol, which was 13 times that of ebselen (a representative GPX mimic). The effect of this GPX mimic on I-R injury of the liver was assessed in rats. The 7-mer peptide significantly inhibited the increase in serum hepatic amino-transferases, tissue malondialdehyde, nitric oxide contents, myeloperoxidase activity and decrease of GPX activity compared with I-R tissue. Following treatment with the 7-mer peptide, the expression of B-cell CLL/lymphoma-2 (Bcl-2) was significantly upregulated at the mRNA and protein level compared with the I-R group, as determined by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. By contrast, Bcl-2 associated X protein (Bax) was downregulated by the 7-mer peptide compared the I-R group. Histological and ultrastructural changes of the rat liver tissue were also compared among the experimental groups. The results of the current study suggest that the 7-mer peptide protected the liver against hepatic I-R injury via suppression of oxygen-derived free radicals and regulation of Bcl-2 and Bax expression, which are involved in the apoptosis of liver cells. The findings of the present study will further the investigation of the 7-mer peptide as an effective therapeutic agent in hepatic I-R injury.