Characterization of peroxynitrite-oxidized low density lipoprotein binding to human CD36

Peroxynitrite-mediated oxidation may be an important physiological mechanism for oxidation of low density lipoprotein (LDL), however, the molecular basis for the interaction of peroxynitrite oxidized LDL (OxLDL) with scavenger receptors such as CD36, has not been characterized. In this study, we compared the biochemical characteristics and receptor binding of LDL that was oxidized using: (1) Cu2+, a standard method of oxidizing LDL in vitro; and (2) 3-morpholinosydnonimine (SIN-1), a source of peroxynitrite. Both methods of oxidation caused an increase in electrophoretic migration of LDL, but greater mobility was observed with Cu2+-OxLDL. In addition, greater fragmentation of apolipoprotein B was observed following Cu2+ oxidation than after SIN-1 oxidation. The levels of lipid peroxides and thiobarbituric acid reactive substances were similar after 20 h of oxidation by both methods, although the time-course was distinct. Cu2+ and SIN-1-OxLDL bound specifically to the macrophage scavenger receptor CD36 with high affinity. Binding of the 20 h SIN-1 treated LDL to CD36 was comparable to a 4 h Cu2+ modified LDL. The binding of Cu2+ and SIN-1-OxLDL to CD36 was similar under different biochemical conditions and modifications of the receptor, suggesting that OxLDL particles, generated by either method, bind to the same domain of CD36. The results demonstrate that SIN-1 produced an oxidized LDL particle that binds specifically to CD36 and suggests that peroxynitrite OxLDL may represent a more physiologically relevant model than Cu2+-OxLDL for studying the interactions of OxLDL with cells and lipoprotein receptors in vitro.