Development of Novel Diagnostic Agents for Atherosclerosis Using Fluorescence-labeled Peptides

The oxidative modification of low-density lipoprotein (LDL) is believed to play an important role in the pathogenesis of atherosclerosis. Therefore, probes for detection of oxidized LDL (ox-LDL) in atherosclerotic plaques and plasma are expected to be useful for the diagnosis of atherosclerosis. Recently, we found that four fluorescein isothiocyanate (FITC)-labeled heptapeptides (Lys-Trp-Tyr-Lys-Asp-Gly-Asp, KP6)-(FITC)KP6 and (FITC-AC)KP6 and then substitution with D-Lys at the N-terminus-(FITC) dKP6 and (FITC-AC) dKP6 bind with high specificity and high affinity to two oxidized forms of LDL, heavily oxidized LDL and minimally modified LDL (MM-LDL), through binding to lysophosphatidylcholine and oxidized phosphatidylcholine, present abundantly in heavily oxidized LDL and MM-LDL. Moreover, (FITC) dKP6 and (FITC-AC) dKP6 were more stable than (FITC) KP6 and (FITC-AC) KP6 in plasma in vitro. (FITC) KP6 could detect foam cells in atherosclerotic aortic plaques of apoE-knockout mice. These results suggest that four fluorescence-labeled heptapeptides could be efficient fluorescent probes for the specific detection of ox-LDL, and can therefore contribute to the identification, diagnosis, prevention, and treatment of atherosclerosis.