Heparin protection against Fe2+ -and Cu2+ -mediated oxidation of liposomes.

Heparin (HE) exhibited a protective effect on liposome peroxidation induced by Fe2+ and Cu2+, decreasing the formation of both conjugated dienes and thiobarbituric acid reactive substances (TBARS) in a dose-dependent manner. The antioxidant activity was more relevant in the oxidizing system employing Fe2+ and H2O2 and generating the highly reactive OH radical. The analysis of liposome size distribution by quasielastic laser light scattering showed that: (1) the native structure of the particles was completely lost after exposure to Fenton reagent; (2) the presence of HE in the reaction mixture completely prevented the peroxidative damage on liposomes. Thus, HE acts as an antioxidant factor on membrane lipid bilayer. This suggests that HE, released from mast-cell granules during inflammatory processes, might locally protect the cell membrane from the oxidative injuries.