Apolipoprotein A-I-mimetic peptides with antioxidant actions.

To augment antioxidant action of apolipoprotein A-I (Apo A-I)-mimetic peptide, the peptide F3,6,14,18 18A (DWFKAFYDKVAEKFKEAF) was modified by incorporating antioxidant amino acid residues. Introduction of His residue at position 2 or 3 at N-terminal of the peptide remarkably enhanced antioxidant action against Cu2+ oxidation of LDL and the capability of sequestering Cu2+. Likewise, the substitution of Ala for Cys residue at position 12 increased antioxidant action against Cu2+ oxidation of LDL. Additionally, the Cys substitution contributed to enhanced capabilities in the removal of hypochlorous acid (HOCl) and 13-hydroperoxyoctadecadienoic acid. Furthermore, the combined incorporation of His and Cys residues enhanced antioxidant actions in preventing Cu2+ oxidation and reducing HOCl and hydroperoxide levels. Separately, in solubilizing phosphatidylcholine, either peptides with His residue at N-terminal position 2 or 3, or those containing Cys residue at position 11 or 12 were equipotent to peptide F3,6,14,18 18A. Further, the lipid-solubilizing ability of those containing both His and Cys residues was comparable to that of peptide F3,6,14,18 18A. In support of this, a similar structural importance was observed with Trp fluorescence study illustrating the penetration of peptides in phosphatidylcholine liposome. Besides, the modified peptides were also comparable to peptide F3,6,14,18 18A in restoring phosphatidylserine-induced loss of PON1 activity. These results indicate that the insertion of His or Cys residue into peptide F3,6,14,18 18A at appropriate positions could lead to enhanced antioxidant action with no significant change of lipid-solubilizing action.