Lack of protection against oxidative modification of LDL by avian HDL

Human and murine high density lipoprotein (HDL) has previously been shown to decrease the accumulation of lipid peroxides on low density lipoprotein (LDL) under oxidising conditions. Several lines of evidence, including the ineffectiveness of HDL from paraoxonase knockout mice, suggest that paraoxonase (PON1) located on HDL is responsible for its protective effect against lipid peroxidation. In this report we compare the effect of HDL from chicken, turkey and ostrich with human HDL on lipid peroxidation of LDL. Avian serum lacked PON1 activity and PON1 immunoactivity was also absent by ELISA and Western blotting whereas all three techniques detected PON1 in a variety of non-avian species (cow, guinea-pig, rat, sheep, mouse, hamster, monkey and rabbit). Platelet activating factor acetyl hydrolase (PAFAH) activity was also absent from avian serum. Avian HDL isolated from plasma when incubated with human LDL was ineffective in preventing the Cu2+-induced accumulation of lipid peroxides on this lipoprotein whereas human HDL under the same conditions was highly effective in this respect. Avian LDL was much more resistant to oxidation than human LDL, perhaps explaining the lack of HDL-PON1 and PAFAH. We conclude that these findings provide further evidence than PON1 has an important role in the antiatherogenic/anti-inflammatory effects of HDL and that avian HDL can provide a valuable model which complements the use of HDL from paraoxonase knockout mice in the investigation of PON1 and PAFAH.