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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.

We are always exposed to oxidative stress, when oxygen is used for production of energy for our daily activity. Mild to moderate oxidative stress affects intracellular signal transduction, accelerating the protective system for oxidation; thereby inflammatory cytokines are produced leading to increased levels of acute phase proteins. Vascular endothelial cells protect the vessels from oxidative stress, however, when they are damaged by shear stress to the vascular wall, oxidation spreads into the subendothelial matrix, leading to oxidation of low-density lipoproteins(LDL) accumulated there. Oxidized LDL is easily and abundantly taken up into macrophages via the scavenger receptors such as LOX-1, which leads to the formation of atherosclerosis. Markers for oxidative stress in vivo are being sought for prevention and treatment of cardiovascular diseases. There are a number of parameters as candidates, and among them, we chose biopyrrins, oxidative products of bilirubin, and have studied their role in coronary heart diseases. Urinary excretions of biopyrrins are significantly elevated in patients with coronary arterial stenosis and with ischemic changes on electrocardiogram. Similar finding have been obtained in patients with vasospastic angina. These findings suggest that markers for oxidative stress will be a good laboratory test for evaluation of coronary heart diseases.

Purpose: Molecular features of lipoprotein(a) [Lp (a)] associated with membranes of the lens were examined with respect to the pathogenesis and progression of cataract., Methods: Lenses were homogenized and separated into urea-soluble (US) and water-soluble (WS) fractions. Then low density lipoprotein (LDL) and high density lipoprotein (HDL) fractions were separated from US & WS fractions by flotation density gradient ultracentrifugation. LDL and HDL fractions were prepared from 14 and 54 lenses, respectively, of a group of diabetic patients with senile cataract (DM group) or a group of non-diabetic patients with senile cataract (non-DM group). Lp(a) in each fraction and in human aqueous humor was immunochemically assayed using the latex agglutination method. Molecular phenotypes of Lp(a) were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by western blotting., Results: Lp (a) contents in LDL fractions were significantly higher (p < 0.05) in the DM group [11.14 +/- 0.88(mean +/- standard deviation) micrograms/lens] than in the non-DM group [5.77 +/- 2.75 micrograms/lens]. Lp(a) values in HDL fractions were higher in the DM group than in the non-DM group, although the values did not differ significantly between the two groups. Lp (a) concentration in aqueous humor was slightly higher in the DM group than in the non-DM group. Lp (a) components examined by SDS-PAGE were detected only at the origin using immunoblotting., Conclusion: The Lp(a) content in cataractous lenses was higher in the DM group than in the non-DM group. In contrast to the molecular features of Lp(a) in blood, those of Lp(a) in cataractous lens seemed to be high molecular weight complexes. These results suggests that impairment of LDL receptors in DM is associated with disturbance in lipid metabolism which leads to accumulation of degenerated lipoproteins and altered membrane structure.